Title of Invention	"DEVICE FOR OPENING OF CONTACTS OF A CIRCUIT BREAKER"
Abstract	Present invention discloses a device for opening contacts of a circuit breaker. The circuit breaker of the present invention is an electro-pneumatic system which is energy efficient and simple in construction. The present invention overcomes the drawbacks or difficulties present in the prior existing circuit breaker; particularly present invention overcome problems during the opening of contacts. The present invention uses lesser number of electrical and mechanical components as compared to the prior existing systems. Simple construction provides ease of manufacturing economical in cost and reliable operation.

Title of Invention

"DEVICE FOR OPENING OF CONTACTS OF A CIRCUIT BREAKER"

Abstract

Present invention discloses a device for opening contacts of a circuit breaker. The circuit breaker of the present invention is an electro-pneumatic system which is energy efficient and simple in construction. The present invention overcomes the drawbacks or difficulties present in the prior existing circuit breaker; particularly present invention overcome problems during the opening of contacts. The present invention uses lesser number of electrical and mechanical components as compared to the prior existing systems. Simple construction provides ease of manufacturing economical in cost and reliable operation.

Full Text	DEVICE FOR OPENING OF CONTACTS OF A CIRCUIT BREAKER Field of the Invention: The present invention relates to a device for opening of contacts of a circuit breaker. More particularly, the present invention relates to a device for opening and closing the contacts of a circuit breaker provided in an electric traction vehicle. Background and Prior Art Description: As shown in figure 1, in an electric traction vehicle (10), the current is drawn from an overhead catenary (11) via a pantograph bus bar connection (12) and consumed in propulsion of electric traction vehicle (10). For the purpose of controlling the current drawn from the overhead catenary (11), a circuit breaker (14) is included between the pantograph bus bar connection (12) and the traction transformer (13). The circuit breaker (14) thus included is preferably of a vacuum circuit breaker. The vacuum circuit breaker (VCB) (14) is a single phase 25kV AC circuit breaker and is used to protect power circuit applied on electric locomotives and electric multiple units (EMUs). In other words, the VCB (14) is used to disconnect the vehicle (10) from the overhead catenary (11) in the event of overload and short-circuit conditions or any other abnormal working conditions defined and implemented for the applications on vehicle (10). The VCB (14) is intended for installation on the roof of a traction vehicle (10) to carry current from the pantograph bus bar connection (12) to one end of a vacuum interrupter and from other end of the vacuum interrupter to a roof bushing of a loco transformer. The design and implementation of the VCB is preferably adapted to the requirements and working conditions of electric traction vehicle and service condition on Railways. The VCB utilizes vacuum to extinguish arcing when the circuit breaker is opened and to act as a dielectric to insulate the contacts after the arc is interrupted. More details regarding construction of the VCB can be found in Indian Patent Application No. 738/MAS/l 994. The vacuum circuit breaker consists of three main parts: (a) An upper part, which is a high voltage circuit (HT); (b) An intermediate part, which assures isolation from earth; and (c) A lower part having control and drive mechanism. The VCB is designed in such a way that upper part and the intermediate part are located over the roof of the traction vehicle and are exposed to the open atmosphere whereas the lower part is under the roof of the traction vehicle. With reference to figure 2, it can be noticed that the circuit breaker and more particularly the vacuum circuit breaker comprises of vacuum switch tube (28), a movable contact (29) and a fixed contact (30). For the purpose of opening and closing contacts (29 and 30) of the vacuum circuit breaker, a control and drive mechanism is used. One of the control and drive mechanism used is described in US Patent number 5,298,702 (corresponding to Indian Patent Application Number 523/MAS/1992), the contents of which are herein incorporated as reference. The diagram of the control and drive mechanism described in the aforesaid US patent is provided as figure 2 for the purpose of easy reference. The drive mechanism (20) contains a pressure medium reservoir (21), a drive piston (22) which slides in a drive cylinder (23) and acts on a mechanism (24) for displacing a movable contact (29) of the vacuum switch tube. During a first phase of operation of the drive mechanism, i.e. during the process of closing the contacts, the pressure medium contained in the pressure medium reservoir (21) is supplied to the drive cylinder (23), which displaces the drive piston (22) in an upward direction so as to move the movable contact (29) towards the fixed contact (30) and at an extreme upward location of the drive piston (22) closes the contacts. During the first phase, the pressure medium displaces the drive piston (22) against force exerted by a spring mechanism (25) and a vacuum pressure existing between the two contacts (29 and 30). Once the contacts are closed, a second phase of operation of the drive mechanism begins. In the second phase of operation of the drive mechanism, the moving contact (29) must be kept in locked state with respect to the fixed contact (30). For the purpose of keeping the contacts locked, a holding coil (26) located substantially above the drive cylinder is energized so long as contacts are to be closed and the same holds the drive piston (22) in the extreme upward location i.e. where the contacts (29 and 30) get closed. After the closing of contacts, an interposed valve (27) disposed between the pressure medium reservoir (21) and the drive cylinder (23) is actuated and the pressure medium contained in the drive cylinder (23) is released. The actuation of the interposed valve (27) and the activation of the holding coil are done by an electronic circuit (31) (shown in figure 3). A third phase of operation of the drive mechanism is actuated to interrupt the power circuit current and to open the contacts under overload or short-circuit current conditions or any other abnormal working conditions defined and implemented for the applications. The third phase of operation can also be actuated voluntarily by an operator for disconnecting the vehicle from the overhead catenary. In order to open the contacts (29 and 30) of the circuit breaker, the locking of the contacts (29 and 30) is first cancelled by de-energizing the coil (26) through the electronic circuit (31) (refer to figure 2 and 3). Once the coil is de-energized, the force of the loaded spring (25) automatically and instantaneously pushes the drive piston (22) in a downward direction from the extreme upward location to an extreme downward location. It should be noticed that the pressure medium which was contained by the drive cylinder (in the first phase of the operation) is released during the second phase of operation and hence, the drive cylinder can be assumed to contain negligible amount of pressure medium. Even the negligible amount of the pressure medium inside the drive cylinder is present at atmospheric pressure. Due to the above reasons, once the holding coil is de-energized, the force exerted by the spring and the force exerted by the vacuum (contained in the vacuum switch tube) expels the negligible amount of the pressure medium contained in the drive cylinder and the downward movement of the drive piston occurs at a very high speed. As persons skilled in the art would be aware, it is necessary to move the drive piston (and in turn the movable contact coupled to the drive piston) at a very fast speed during the third phase of operation so as to avoid sparking and charge transfer from the fixed contact to the movable contact. Thus, without limiting to any particular theory, it can be said that release of the pressure medium contained in the drive cylinder during the second phase of operation, facilitates movement of the drive piston in the downward direction (in the third phase) and more particularly, it facilitates achieving the high speed movement of the drive piston in the downward direction. However, in order to attain such a high speed during the downward movement, it was mandatory to expel the pressure medium contained in the drive cylinder in the second phase itself, due to which, during the entire second phase of operation, the holding coil (26) located substantially above the drive cylinder was kept energized. Because of negligible amount of pressure medium inside the drive cylinder, the movement of the drive piston in addition to attaining very high speed, becomes uncontrollable in many instances. More particularly, the speed at which the drive piston moves in the downward direction is such that it causes the piston to collide with wall of the drive cylinder at the extreme downward location. Due to such collision, the piston as well as the wall of the drive cylinder can be damaged. Further, such high impact collision can cause the piston to bounce back, which may result in unwanted contact re-making (or in other words contact re-closing leading to arcing). To avoid the collision of the piston with the cylinder, plurality of oil filed dampers are installed at the bottom of the pneumatic cylinder. As the piston reaches at the bottom location the dampers avoids collision of the piston with the bottom of the cylinder. The disadvantages with such kind of dampening system are as follows: (a) Balancing of plungers of oil filled dampers is difficult (b) Manufacturing of these dampers is difficult. (c) All the dampers located at the bottom of the cylinders should be loaded with equal load. It is difficult to precisely achieve this condition. (d) The location where the dampers are located at the bottom of the cylinder are required to be air tight so as to avoid leaks through the locations where the dampers are located. It is difficult to precisely achieve this condition. Thus, the operation of the above-mentioned contact breaker can be said to be based on the following principle: (a) pneumatic (air pressure) closing (b) electromagnetic (coil) holding and (c) mechanical (spring action) opening. ft can be noticed that the above-mentioned circuit breaker is operated using electro-pneumatic based drive and control system. The drive and the control system utilizes large number of components that work in the voltage range of 6V-30V DC (such as 12V DC coils, 24 V DC coils etc.), A person skilled would be aware, the battery provided in the locomotive supply energy in the form of 110V / 72V / 24V DC and hence use of the mentioned components necessitates, conditioning of locomotive battery supply, which results in complete waste of the energy. Since, the coil used for keeping the contacts in the closed state is required to be supplied the power almost during the entire operation of the circuit breaker, a large amount of energy is wasted by (a) the operation of the coil and (b) for the purpose of conditioning of the locomotive battery supply. In addition, the passive and active components used in the electronic control unit (in spite of the fact that these components had adequate margin) were prone to malfunction / failure and were the major contributor for occasional failures of the VCB. Therefore, there exists a long felt need to provide a device for opening the contact of the circuit breaker that overcomes one or more of the afore-said drawbacks and at the same time minimize the power consumption. Particularly, there exists a long felt need to provide a device for opening the contacts of a circuit breaker that achieves high speed movement of the drive piston in the downward direction and at the same time reduces the need of power conditioning, provides enhanced reliability, provides dampening and/or cushioning at the end of the opening of contacts. Objects of the Invention: The main object of the present invention is to provide a device for opening of contacts of a circuit breaker that obviates at least one of the disadvantages described in the foregoing paragraphs. Brief description of the accompanying drawings: In order that the invention may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying drawings, where like reference numerals refer to identical or functionally similar elements throughout the separate views. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present invention where: Figure 1 shows a electrical traction vehicle Figure 2 shows a circuit breaker according to the prior art Figure 3 illustrates a schematic of typical electronic control in the prior art circuit breaker Figure 4 is an exemplary illustration of a vacuum circuit breaker while contacts are at closed position, according to the present invention Figure 4(a) is an exemplary illustration of opening of contacts of a vacuum circuit breaker according to the present invention Figure 4(b) illustratively shows vacuum circuit breaker while contacts are at open position according to the present invention Figure 5 is exemplary illustration of connection circuit for control circuit of vacuum circuit breaker according to the present invention. Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. Summary of the Invention: Accordingly, the present invention provides an energy efficient device for opening contacts of a circuit breaker that is based on the principal of pneumatic closing, pneumatic holding and spring opening. Despite being based on the principal of pneumatic holding, the device achieves high speed movement of the drive piston in the downward direction and at the same time reduces the need of power conditioning, provides enhanced reliability, provides dampening and/or cushioning at the end of the opening of contacts. In addition to being energy efficient, the device of the present invention eliminates substantial number of mechanical components and also eliminates substantial active and passive components in the electronic control unit thereby improving the reliability of the operation of the device, reducing the manufacturing cost and enhancing ease of manufacturing. Statement of the Invention: Accordingly, the present invention provides a device for opening of contacts of a circuit breaker, comprising: a vacuum switch tube consisting of a fixed contact and a moving contact; a reservoir for storing compressed air; a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a driving piston, the driving piston being connected to the movable contact of the vacuum switch tube; and an exhaust region being in communication with the said pneumatic cylinder; characterized in that, the pneumatic cylinder being connected to the reservoir and the exhaust region by a common channel; the common channel comprising at least one inlet port connecting the pneumatic cylinder to the reservoir and at least one outlet port connecting the pneumatic cylinder to the exhaust region; wherein a total passage of the outlet port(s) is substantially greater than a total passage of the inlet port(s). Detailed description of the present invention: Accordingly, the present invention provides a device for opening of contacts of a circuit breaker, comprising: a vacuum switch tube consisting of a fixed contact and a moving contact; a reservoir for storing compressed air; a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a driving piston which is connected to the movable contact of the vacuum switch tube; and an exhaust region being in communication with the said pneumatic cylinder; characterized in that, the pneumatic cylinder being connected to the reservoir and the exhaust region by a common channel; the common channel comprising at least one inlet port connecting the pneumatic cylinder to the reservoir and at least one outlet port connecting the pneumatic cylinder to the exhaust region; wherein a total passage of the outlet port(s) is substantially greater than a total passage of the inlet port(s). In an embodiment of the present invention the common channel comprises a displaceable valve for controlling the flow of the compressed air through the said ports. In another embodiment of the present invention the displaceable valve comprises a first closing means displaceable with respect to the inlet port and a second closing means displaceable with respect to the outlet port. In still another embodiment of the present invention the displaceable valve is actuated by means of a motorized mechanism or electromagnetic mechanism or a spring mechanism or combinations thereof. In yet another embodiment of the present invention the first closing means and the second closing means are arranged to close the inlet port and open the outlet port synchronously and vice versa. In a further embodiment of the present invention the inlet port and the first closing means are configured such that by the operation of the said first closing means, the said reservoir is brought in fluid flow communication with the said pneumatic cylinder for supplying the compressed air to the pneumatic cylinder at a first rate. In a further more embodiment of the present the outlet port and the second closing means are configured such that by the operation of the second closing means, the pneumatic cylinder is brought in fluid flow communication with an exhaust region for expelling the compressed air from the pneumatic cylinder at a second rate. In another embodiment of the present invention the second rate is substantially greater than the first rate. In still another embodiment of the present invention the flow of air from the pneumatic cylinder to the common channel is divided into two parallel passages, a first air flow passage and a second air flow passage. In yet another embodiment of the present invention the first air flow passage provided between the pneumatic cylinder and the common channel, an air flow regulating device is provided for coarse flow regulation. In a further embodiment of the present invention the air flow regulating device comprises an orifice provided in the pneumatic cylinder at about a downward / bottom location and projection formed on the piston, insertable into the orifice. In a further more embodiment of the present invention a one-way valve is provided in the second air flow passage provided between the pneumatic cylinder and the common channel. In an embodiment of the present invention the flow of the air through the first passage is obstructed once the projection formed on the piston gets inserted into the orifice during the downward motion of the piston and the air flows through the second passage also. In another embodiment of the present invention the second air flow passage comes into operation after the first air flow passage has experienced a predetermined amount of obstruction. In one more embodiment of the present invention the one way valve is a pressure sensitive valve for fine tuning. The present invention is described with reference to the figures and specific embodiments; this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such alternative embodiments form part of the present invention. Figure 4, 4(a) and 4(b) shows various kinematics schemes of the device for opening of contacts of a circuit breaker in accordance with some of the alternative embodiments of the present invention. The device of the present invention comprises a vacuum switch tube (80) consisting of a fixed contact (90) and a movable contact (1 50) and a reservoir (100) for storing the compressed air. The reservoir may be provided with a pressure regulator with a filter (110) and a pressure switch (120) for monitoring minimum pressure. The reservoir (100) is arranged to be brought in fluid flow communication with a pneumatic cylinder (130). The pneumatic cylinder (130) houses a slidable piston (140) which is coupled to the movable contact (150) of the vacuum switch tube (80) through a drive mechanism (160). The pneumatic cylinder (130) is arranged to be brought in fluid flow communication with an exhaust region (170) which can be atmosphere or an outer space. The reservoir (100) and the exhaust region (170) are brought in flow communication with the pneumatic cylinder (130) by a common channel (180). The common channel (180) is provided with an inlet port (190) and an outlet port (200). A displaceable valve (210) is placed in the common channel for regulating the flow of the compressed air through said ports. There can be more than one inlet ports and the outlet ports. The displaceable valve (210) is actuated by an actuating mechanism (220) such as a motorized mechanism or an electromagnetic mechanism or a spring mechanism or combinations thereof. The displaceable valve (210) comprising a first closing means (230) and a second closing means (240). The first closing means (230) is displaceable with respect to the inlet port (190) and the second closing means (240) is displaceable with respect to the outlet port (200). The first closing means (230) and the second closing means (240) are arranged to close the inlet port (190) and open the outlet port (200) synchronously and vice versa. More particularly, the first closing means (230) and the second closing means (240) are arranged such that outlet port (200) remains closed till the inlet port (190) remains open and similarly, the inlet port (190) remains closed till the outlet port (200) remains open. When the current is required to be drawn from the over head catenary the contacts are closed and for closing the contacts, the displaceable valve is actuated so as to bring the reservoir (100) in fluid flow communication with the pneumatic cylinder (130). More particularly, the displaceable valve is actuated such that the second closing means closes the outlet port and the first closing means opens the inlet port, thereby bringing the pneumatic cylinder in fluid communication with the reservoir. With the closure of the contacts, the first phase of operation comes to an end and a second phase of operation begins. In the second phase of operation, the contacts must be continuously maintained in the closed state. As indicated in the prior art section, this was previously being achieved by use of a holding coil. However, in the present invention, the inventors have used the air contained in the pneumatic cylinder at the end of the first phase to hold the contacts. Thus, the second phase of operation is effected without substantial energy consumption. This is achieved by not allowing the compressed air contained in the pneumatic cylinder to escape to the exhaust region. The second phase is completed without substantial energy consumption primarily because the reservoir and the exhaust region are connected to the pneumatic cylinder by means of a common channel having the displaceable valve and more particularly because the first closing means (230) and the second closing means (240) are arranged such that outlet port (200) remains closed till the inlet port (190) remains open. Thus, the present invention eliminates the need of active and passive components in the electronic circuits to operate the holding coil by eliminating the requirement of any power conditioning, Hence, there is no wastage of energy in the active and passive components of the electronic circuits. Figure 5 illustrates circuit configuration for a circuit breaker according to the present invention. When we compare figure 3 with figure 5, the simplification attained in the circuit which controls the operation of the various components is evident. In the third phase of operation, the contacts of the circuit breaker are opened. For the purpose of opening the contacts, the pneumatic cylinder is brought in fluid flow communication the exhaust region. This is achieved by actuating the displaceable valve using the actuating mechanism (220) to open the outlet port and bring the pneumatic cylinder in fluid flow communication with the exhaust region. By activating the actuating mechanism, the first closing means (230) actuates to close the inlet port (190) of the common channel (180) and the second closing means (240) actuates to open the outlet port (200) to bring the pneumatic cylinder (130) in flow communication with exhaust region (170). It was noticed during the operation of the said device that although the device provided satisfactory performance during the first and the second phases of operation, the third phase of operation was not being effected to the satisfactory level. More particularly, it was noticed that although, after the pneumatic cylinder is brought in fluid flow communication with the exhaust region, the force of the loaded spring (270, 280) is automatically and instantaneously pushing the drive piston (140) in a downward direction from the extreme upward location, the downward movement of the drive piston may occur at a speed which is less than the desired speed. Without restricting to any particular theory, the inventors feel that the same is because of the resistance provided by the air which is to be ousted from the pneumatic cylinder. As mentioned in the prior art section, in the prior art devices, the pressure medium (air) contained in the pneumatic cylinder is exhausted prior to the beginning of the third phase (i.e. during the second phase itself). Due to the above, the downward movement of the drive piston in the prior art device occurs at a desired high speed. Thus, the invention focused on ensuring the rate at which the compressed air contained in the reservoir was communicated to the pneumatic cylinder through the common channel is different from the rate at which the compressed air contained in the pneumatic cylinder is expelled to the exhaust region through the common channel. If the rate at which air contained in the reservoir is communicated to the pneumatic cylinder is termed as a first flow rate and if the rate at which the compressed air contained in the pneumatic cylinder is expelled to the exhaust region is termed as a second flow rate, a difference between the first and the second rates was aimed. More particularly, the second rate was designed to be substantially greater than the first rate. To achieve the above difference in the first and the second rates, the size of the outlet port (200) is made larger than the size of the inlet port (190). Thus, the air contained in the pneumatic cylinder (130) is expelled to the exhaust region (170) via the common channel at the second rate which is substantially greater than the first rate. Due to the above construction, immediately after the outlet port is opened, the downward motion of the piston commences and the same is assisted by the compression springs (270, 280). The compression springs gets charged during the closing of the contacts and once the outlet port is opened, they release the energy stored therein to revert back the whele-drive mechanism (160) connected to the moving contact (150) to its initial open position. Thus, the size of the outlet port(s) in the common channel was constructed to be of a specific and substantially larger size as compared to the inlet port(s) so that the air contained in the reservoir was delivered into the pneumatic cylinder at a desired first rate (in the first phase of operation) and the air contained in the pneumatic cylinder is exhausted to the exhaust region at a desired second rate, wherein the second rate is substantially greater than the first rate. First rate and second rate being matched with the characteristics of the vacuum switch tube (80). Due to the above construction, the primary objective of attaining high speed during the downward motion of the piston is achieved and the downward movement of the drive piston occurs at a desired high speed. However, it was noticed that because of the increased size of the outlet port, the movement of the drive piston in addition to attaining very high speed during the downward movement, becomes un-controllable in many instances. More particularly, the speed at which the drive piston moves in the downward direction is such that it causes the piston to collide with wall of the drive cylinder at the extreme downward location. Due to such collision, the piston as well as the wall of the drive cylinder can be damaged. Further, such high impact collision can cause the piston to bounce back, which may result in unwanted contact re-making (or in other words contact re-closing leading to arcing). To avoid the collision of the piston with the cylinder, damping was to be provided for which a new and innovative approach was adopted in the present invention. The pneumatic cylinder is provided with a first air flow regulating device preferably in the form an orifice (250) at a bottom location of the pneumatic cylinder and the piston (140) is provided with a projection (260) for closing the orifice (250) when the piston (140) is at its lowermost location. The above construction provides an obstruction free path to the air being released through the pneumatic cylinder in the initial phase of the downward movement of the piston. However, once the projection provided on the piston comes in contact with the orifice, the flow of the air to the exhaust region is altered. Thus, velocity of motion of the piston in the downward direction is decreased prior to the piston reaching the wall of the pneumatic cylinder. It was sometimes noticed that due to the high speed of the downward motion and due to substantial restriction of the flow of the air to the exhaust region, the residual air trapped inside the pneumatic cylinder may be compressed to such an extent that it may push the piston back in the upward direction, and which may cause the piston to bounce back. As it is advisable to avoid such bouncing of the piston, to avoid any unwanted contact making (or in other words contact closing), a mechanism was developed to further enhance the operation of the device. In the developed mechanism, the flow of the air from the pneumatic cylinder to the common channel is divided into two parallel passages for avoiding the excessive pressure buildup of the residual air inside the pneumatic cylinder. The two air flow passages comprise a first air flow passage and a second air flow passage (as shown in figures 4, 4(a) and 4(b)). The first air flow passage includes the first air flow regulating device as described above, and more particularly, the first air flow regulating device comprises an orifice formed at the bottom of the pneumatic cylinder and a projection provided on the piston. Initially, when the operating mechanism is actuated to open the outlet port, air contained in the pneumatic cylinder follows the path of least resistance and start escaping through the first air flow passage at a high speed to the exhaust region. During this initial stage, the second air flow passage remains completely blocked. As the air flows out of the pneumatic cylinder, the piston moves in the downward direction at a high speed. The first air flow regulating device is configured in such a way that after a predetermined piston displacement, it obstructs the flow of air through the first air flow passage. In other words, once the piston reaches almost the bottom most portion, the projection formed on the piston enters into the orifice and obstructs the flow of air through the first air flow passage Thus, velocity of motion of the piston in the downward direction starts decreasing prior to the piston reaching the wall of the pneumatic cylinder. In order to safeguard against the bouncing back of the piston due to excessive pressure buildup by the orifice (250) and projection (260), a second air flow path is provided. The second air flow passage provides a route for the residual air trapped inside the pneumatic cylinder to follow and reach the common channel once the projection formed on the piston enters the orifice. The second air flow passage is provided with a second air flow regulating device. More particularly, the second air flow passage comprises a one way valve (290) which preferably can be a pressure sensitive valve. The second air flow regulating device is configured such that it conies into play after it experiences a predetermined amount of pressure. As described in the previous paragraphs, the bouncing back of the piston is caused because of the excessive increase in the pressure of the residual air. By providing the second air flow regulating route with a pressure sensitive valve, the excessive build up in the pressure of the residual air is checked and controlled. Thus, obstruction of the air by the first air flow regulating device provides a damping effect during the downward movement of the piston and release of residual air by the second air flow passage regulates the damping effect and avoids the bouncing of the piston. The cushioning or damping achieved in the present device is advantageous as compared to the prior existing systems or devices. The arrangement provided for cushioning and dampening overcomes all the problems with the dampening system of the prior art. We Claim: 1 A device for opening of contacts of a circuit breaker, comprising: a vacuum switch tube consisting of a fixed contact and a moving contact; a reservoir for storing compressed air; a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a driving piston which is connected to the movable contact of the vacuum switch tube; and an exhaust region being in communication with the said pneumatic cylinder; characterized in that, the pneumatic cylinder being connected to the reservoir and the exhaust region by a common channel; the common channel comprising at least one inlet port connecting the pneumatic cylinder to the reservoir and at least one outlet port connecting the pneumatic cylinder to the exhaust region; wherein a total passage of the outlet port(s) is substantially greater than a total passage of the inlet port(s). 2 The device as claimed in any one of the preceding claims 1, wherein the common channel comprises a displaceable valve for controlling the flow of the air through the said ports. 3. The device as claimed in claim 1 and 2, wherein the displaceable valve comprises a first closing means displaceable with respect to the inlet port and a second closing means displaceable with respect to the outlet port. 4. The device as claimed in any one of the preceding claims 1-3, wherein the displaceable valve is actuated by means of a motorized mechanism or electromagnetic mechanism or a spring mechanism or combinations thereof. 5. The device as claimed in any one of the preceding claims 1-4, wherein the first closing means and the second closing means are arranged to close the inlet port and open the outlet port synchronously and vice versa. 6 The device as claimed in any one of the preceding claims 1-5, wherein the inlet port(s) and the first closing means are configured such that by the operation of the said first closing means, the said reservoir is brought in fluid flow communication with the said pneumatic cylinder for supplying the compressed air to the pneumatic cylinder at a first rate. 7 The device as claimed in any one of the preceding claims 1-6, wherein the outlet port(s) and the second closing means are configured such that by the operation of the second closing means, the pneumatic cylinder is brought in fluid flow communication with an exhaust region for expelling the air from the pneumatic cylinder to the exhaust region at a second rate. 8. The device as claimed in claims 6 and 7, wherein the second rate is made different in predefined manner than the first rate. 9. The device as claimed in any one of the preceding claims 1-8, wherein the flow of air from the pneumatic cylinder to the common channel is divided into a first air flow passage and a second air flow passage and wherein the first air flow passage is functionally parallel to the second air flow passage. 10. The device as claimed in claim 9, wherein in the first air flow passage a first air flow regulating device is provided for coarse air flow regulation. 11. The device as claimed in claim 10, wherein the first air flow regulating device comprises an orifice provided in the pneumatic cylinder at about a downward location and a projection formed on the piston, the projection formed on the piston being insertable inside the orifice provided at a downward location of the pneumatic cylinder. 12. The device as claimed in claim 9, wherein in the second air flow passage a second air flow regulating device is provided for fine air flow regulation. 13. The device as claimed in any one of claims 9 to 12, wherein the flow of the air through the first passage is obstructed once the projection formed on the piston gets inserted into the orifice during the downward motion of the piston and the air flows through the second passage also. 14. The device as claimed in any one of the preceding claims 1-13, wherein the second air flow passage comes into operation after the first air flow passage has experienced a predetermined amount of obstruction. 15. The device as claimed in any of the preceding claim 1-14, wherein the one way valve is a pressure sensitive valve. 16. A device for opening of contacts of a circuit breaker substantially as herein described with reference to the accompanying drawings.

Full Text

DEVICE FOR OPENING OF CONTACTS OF A CIRCUIT
BREAKER
Field of the Invention:
The present invention relates to a device for opening of contacts of a circuit breaker. More particularly, the present invention relates to a device for opening and closing the contacts of a circuit breaker provided in an electric traction vehicle.
Background and Prior Art Description:
As shown in figure 1, in an electric traction vehicle (10), the current is drawn from an overhead catenary (11) via a pantograph bus bar connection (12) and consumed in propulsion of electric traction vehicle (10). For the purpose of controlling the current drawn from the overhead catenary (11), a circuit breaker (14) is included between the pantograph bus bar connection (12) and the traction transformer (13). The circuit breaker (14) thus included is preferably of a vacuum circuit breaker. The vacuum circuit breaker (VCB) (14) is a single phase 25kV AC circuit breaker and is used to protect power circuit applied on electric locomotives and electric multiple units (EMUs). In other words, the VCB (14) is used to disconnect the vehicle (10) from the overhead catenary (11) in the event of overload and short-circuit conditions or any other abnormal working conditions defined and implemented for the applications on vehicle (10).
The VCB (14) is intended for installation on the roof of a traction vehicle (10) to carry current from the pantograph bus bar connection (12) to one end of a vacuum interrupter and from other end of the vacuum interrupter to a roof bushing of a loco transformer. The design and implementation of the VCB is preferably adapted to the requirements and working conditions of electric traction vehicle and service condition on Railways.
The VCB utilizes vacuum to extinguish arcing when the circuit breaker is opened and to act as a dielectric to insulate the contacts after the arc is interrupted. More details regarding construction of the VCB can be found in Indian Patent Application No. 738/MAS/l 994. The vacuum circuit breaker consists of three main parts:
(a) An upper part, which is a high voltage circuit (HT);
(b) An intermediate part, which assures isolation from earth; and

(c) A lower part having control and drive mechanism.
The VCB is designed in such a way that upper part and the intermediate part are located over the roof of the traction vehicle and are exposed to the open atmosphere whereas the lower part is under the roof of the traction vehicle.
With reference to figure 2, it can be noticed that the circuit breaker and more particularly the vacuum circuit breaker comprises of vacuum switch tube (28), a movable contact (29) and a fixed contact (30). For the purpose of opening and closing contacts (29 and 30) of the vacuum circuit breaker, a control and drive mechanism is used. One of the control and drive mechanism used is described in US Patent number 5,298,702 (corresponding to Indian Patent Application Number 523/MAS/1992), the contents of which are herein incorporated as reference. The diagram of the control and drive mechanism described in the aforesaid US patent is provided as figure 2 for the purpose of easy reference.
The drive mechanism (20) contains a pressure medium reservoir (21), a drive piston (22) which slides in a drive cylinder (23) and acts on a mechanism (24) for displacing a movable contact (29) of the vacuum switch tube.
During a first phase of operation of the drive mechanism, i.e. during the process of closing the contacts, the pressure medium contained in the pressure medium reservoir (21) is supplied to the drive cylinder (23), which displaces the drive piston (22) in an upward direction so as to move the movable contact (29) towards the fixed contact (30) and at an extreme upward location of the drive piston (22) closes the contacts. During the first phase, the pressure medium displaces the drive piston (22) against force exerted by a spring mechanism (25) and a vacuum pressure existing between the two contacts (29 and 30). Once the contacts are closed, a second phase of operation of the drive mechanism begins.
In the second phase of operation of the drive mechanism, the moving contact (29) must be kept in locked state with respect to the fixed contact (30). For the purpose of keeping the contacts locked, a holding coil (26) located substantially above the drive cylinder is energized so long as contacts are to be closed and the same holds the drive piston (22) in

the extreme upward location i.e. where the contacts (29 and 30) get closed. After the closing of contacts, an interposed valve (27) disposed between the pressure medium reservoir (21) and the drive cylinder (23) is actuated and the pressure medium contained in the drive cylinder (23) is released. The actuation of the interposed valve (27) and the activation of the holding coil are done by an electronic circuit (31) (shown in figure 3).
A third phase of operation of the drive mechanism is actuated to interrupt the power circuit current and to open the contacts under overload or short-circuit current conditions or any other abnormal working conditions defined and implemented for the applications. The third phase of operation can also be actuated voluntarily by an operator for disconnecting the vehicle from the overhead catenary. In order to open the contacts (29 and 30) of the circuit breaker, the locking of the contacts (29 and 30) is first cancelled by de-energizing the coil (26) through the electronic circuit (31) (refer to figure 2 and 3). Once the coil is de-energized, the force of the loaded spring (25) automatically and instantaneously pushes the drive piston (22) in a downward direction from the extreme upward location to an extreme downward location. It should be noticed that the pressure medium which was contained by the drive cylinder (in the first phase of the operation) is released during the second phase of operation and hence, the drive cylinder can be assumed to contain negligible amount of pressure medium. Even the negligible amount of the pressure medium inside the drive cylinder is present at atmospheric pressure. Due to the above reasons, once the holding coil is de-energized, the force exerted by the spring and the force exerted by the vacuum (contained in the vacuum switch tube) expels the negligible amount of the pressure medium contained in the drive cylinder and the downward movement of the drive piston occurs at a very high speed.
As persons skilled in the art would be aware, it is necessary to move the drive piston (and in turn the movable contact coupled to the drive piston) at a very fast speed during the third phase of operation so as to avoid sparking and charge transfer from the fixed contact to the movable contact.
Thus, without limiting to any particular theory, it can be said that release of the pressure medium contained in the drive cylinder during the second phase of operation, facilitates

movement of the drive piston in the downward direction (in the third phase) and more particularly, it facilitates achieving the high speed movement of the drive piston in the downward direction.
However, in order to attain such a high speed during the downward movement, it was mandatory to expel the pressure medium contained in the drive cylinder in the second phase itself, due to which, during the entire second phase of operation, the holding coil (26) located substantially above the drive cylinder was kept energized.
Because of negligible amount of pressure medium inside the drive cylinder, the movement of the drive piston in addition to attaining very high speed, becomes uncontrollable in many instances. More particularly, the speed at which the drive piston moves in the downward direction is such that it causes the piston to collide with wall of the drive cylinder at the extreme downward location. Due to such collision, the piston as well as the wall of the drive cylinder can be damaged. Further, such high impact collision can cause the piston to bounce back, which may result in unwanted contact re-making (or in other words contact re-closing leading to arcing).
To avoid the collision of the piston with the cylinder, plurality of oil filed dampers are installed at the bottom of the pneumatic cylinder. As the piston reaches at the bottom location the dampers avoids collision of the piston with the bottom of the cylinder. The disadvantages with such kind of dampening system are as follows:
(a) Balancing of plungers of oil filled dampers is difficult
(b) Manufacturing of these dampers is difficult.
(c) All the dampers located at the bottom of the cylinders should be loaded with equal
load. It is difficult to precisely achieve this condition.
(d) The location where the dampers are located at the bottom of the cylinder are
required to be air tight so as to avoid leaks through the locations where the
dampers are located. It is difficult to precisely achieve this condition.
Thus, the operation of the above-mentioned contact breaker can be said to be based on the following principle:

(a) pneumatic (air pressure) closing
(b) electromagnetic (coil) holding and
(c) mechanical (spring action) opening.
ft can be noticed that the above-mentioned circuit breaker is operated using electro-pneumatic based drive and control system. The drive and the control system utilizes large number of components that work in the voltage range of 6V-30V DC (such as 12V DC coils, 24 V DC coils etc.), A person skilled would be aware, the battery provided in the locomotive supply energy in the form of 110V / 72V / 24V DC and hence use of the mentioned components necessitates, conditioning of locomotive battery supply, which results in complete waste of the energy. Since, the coil used for keeping the contacts in the closed state is required to be supplied the power almost during the entire operation of the circuit breaker, a large amount of energy is wasted by (a) the operation of the coil and (b) for the purpose of conditioning of the locomotive battery supply. In addition, the passive and active components used in the electronic control unit (in spite of the fact that these components had adequate margin) were prone to malfunction / failure and were the major contributor for occasional failures of the VCB.
Therefore, there exists a long felt need to provide a device for opening the contact of the circuit breaker that overcomes one or more of the afore-said drawbacks and at the same time minimize the power consumption. Particularly, there exists a long felt need to provide a device for opening the contacts of a circuit breaker that achieves high speed movement of the drive piston in the downward direction and at the same time reduces the need of power conditioning, provides enhanced reliability, provides dampening and/or cushioning at the end of the opening of contacts.
Objects of the Invention:
The main object of the present invention is to provide a device for opening of contacts of a circuit breaker that obviates at least one of the disadvantages described in the foregoing paragraphs.

Brief description of the accompanying drawings:
In order that the invention may be readily understood and put into practical effect,
reference will now be made to exemplary embodiments as illustrated with reference to
the accompanying drawings, where like reference numerals refer to identical or
functionally similar elements throughout the separate views. The figures together with a
detailed description below, are incorporated in and form part of the specification, and
serve to further illustrate the embodiments and explain various principles and advantages,
in accordance with the present invention where:
Figure 1 shows a electrical traction vehicle
Figure 2 shows a circuit breaker according to the prior art
Figure 3 illustrates a schematic of typical electronic control in the prior art circuit breaker
Figure 4 is an exemplary illustration of a vacuum circuit breaker while contacts are at
closed position, according to the present invention
Figure 4(a) is an exemplary illustration of opening of contacts of a vacuum circuit
breaker according to the present invention
Figure 4(b) illustratively shows vacuum circuit breaker while contacts are at open
position according to the present invention
Figure 5 is exemplary illustration of connection circuit for control circuit of vacuum
circuit breaker according to the present invention.
Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity
and have not necessarily been drawn to scale. For example, the dimensions of some of
the elements in the drawings may be exaggerated relative to other elements to help to
improve understanding of embodiments of the present invention.
Summary of the Invention:
Accordingly, the present invention provides an energy efficient device for opening contacts of a circuit breaker that is based on the principal of pneumatic closing, pneumatic holding and spring opening. Despite being based on the principal of pneumatic holding, the device achieves high speed movement of the drive piston in the downward direction and at the same time reduces the need of power conditioning, provides enhanced reliability, provides dampening and/or cushioning at the end of the opening of

contacts. In addition to being energy efficient, the device of the present invention eliminates substantial number of mechanical components and also eliminates substantial active and passive components in the electronic control unit thereby improving the reliability of the operation of the device, reducing the manufacturing cost and enhancing ease of manufacturing.
Statement of the Invention:
Accordingly, the present invention provides a device for opening of contacts of a circuit
breaker, comprising:
a vacuum switch tube consisting of a fixed contact and a moving contact;
a reservoir for storing compressed air;
a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a
driving piston, the driving piston being connected to the movable contact of the vacuum
switch tube; and
an exhaust region being in communication with the said pneumatic cylinder;
characterized in that,
the pneumatic cylinder being connected to the reservoir and the exhaust region by a
common channel; the common channel comprising at least one inlet port connecting the
pneumatic cylinder to the reservoir and at least one outlet port connecting the pneumatic
cylinder to the exhaust region; wherein a total passage of the outlet port(s) is substantially
greater than a total passage of the inlet port(s).
Detailed description of the present invention:
Accordingly, the present invention provides a device for opening of contacts of a circuit
breaker, comprising:
a vacuum switch tube consisting of a fixed contact and a moving contact;
a reservoir for storing compressed air;
a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a
driving piston which is connected to the movable contact of the vacuum switch tube; and
an exhaust region being in communication with the said pneumatic cylinder;
characterized in that,

the pneumatic cylinder being connected to the reservoir and the exhaust region by a common channel; the common channel comprising at least one inlet port connecting the pneumatic cylinder to the reservoir and at least one outlet port connecting the pneumatic cylinder to the exhaust region; wherein a total passage of the outlet port(s) is substantially greater than a total passage of the inlet port(s).
In an embodiment of the present invention the common channel comprises a displaceable valve for controlling the flow of the compressed air through the said ports.
In another embodiment of the present invention the displaceable valve comprises a first closing means displaceable with respect to the inlet port and a second closing means displaceable with respect to the outlet port.
In still another embodiment of the present invention the displaceable valve is actuated by means of a motorized mechanism or electromagnetic mechanism or a spring mechanism or combinations thereof.
In yet another embodiment of the present invention the first closing means and the second closing means are arranged to close the inlet port and open the outlet port synchronously and vice versa.
In a further embodiment of the present invention the inlet port and the first closing means are configured such that by the operation of the said first closing means, the said reservoir is brought in fluid flow communication with the said pneumatic cylinder for supplying the compressed air to the pneumatic cylinder at a first rate.
In a further more embodiment of the present the outlet port and the second closing means are configured such that by the operation of the second closing means, the pneumatic cylinder is brought in fluid flow communication with an exhaust region for expelling the compressed air from the pneumatic cylinder at a second rate.
In another embodiment of the present invention the second rate is substantially greater than the first rate.

In still another embodiment of the present invention the flow of air from the pneumatic cylinder to the common channel is divided into two parallel passages, a first air flow passage and a second air flow passage.
In yet another embodiment of the present invention the first air flow passage provided between the pneumatic cylinder and the common channel, an air flow regulating device is provided for coarse flow regulation.
In a further embodiment of the present invention the air flow regulating device comprises an orifice provided in the pneumatic cylinder at about a downward / bottom location and projection formed on the piston, insertable into the orifice.
In a further more embodiment of the present invention a one-way valve is provided in the second air flow passage provided between the pneumatic cylinder and the common channel.
In an embodiment of the present invention the flow of the air through the first passage is obstructed once the projection formed on the piston gets inserted into the orifice during the downward motion of the piston and the air flows through the second passage also.
In another embodiment of the present invention the second air flow passage comes into operation after the first air flow passage has experienced a predetermined amount of obstruction.
In one more embodiment of the present invention the one way valve is a pressure sensitive valve for fine tuning.
The present invention is described with reference to the figures and specific embodiments; this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such alternative embodiments form part of the present invention.

Figure 4, 4(a) and 4(b) shows various kinematics schemes of the device for opening of contacts of a circuit breaker in accordance with some of the alternative embodiments of the present invention. The device of the present invention comprises a vacuum switch tube (80) consisting of a fixed contact (90) and a movable contact (1 50) and a reservoir (100) for storing the compressed air. The reservoir may be provided with a pressure regulator with a filter (110) and a pressure switch (120) for monitoring minimum pressure. The reservoir (100) is arranged to be brought in fluid flow communication with a pneumatic cylinder (130). The pneumatic cylinder (130) houses a slidable piston (140) which is coupled to the movable contact (150) of the vacuum switch tube (80) through a drive mechanism (160). The pneumatic cylinder (130) is arranged to be brought in fluid flow communication with an exhaust region (170) which can be atmosphere or an outer space. The reservoir (100) and the exhaust region (170) are brought in flow communication with the pneumatic cylinder (130) by a common channel (180).
The common channel (180) is provided with an inlet port (190) and an outlet port (200). A displaceable valve (210) is placed in the common channel for regulating the flow of the compressed air through said ports. There can be more than one inlet ports and the outlet ports. The displaceable valve (210) is actuated by an actuating mechanism (220) such as a motorized mechanism or an electromagnetic mechanism or a spring mechanism or combinations thereof. The displaceable valve (210) comprising a first closing means (230) and a second closing means (240). The first closing means (230) is displaceable with respect to the inlet port (190) and the second closing means (240) is displaceable with respect to the outlet port (200). The first closing means (230) and the second closing means (240) are arranged to close the inlet port (190) and open the outlet port (200) synchronously and vice versa. More particularly, the first closing means (230) and the second closing means (240) are arranged such that outlet port (200) remains closed till the inlet port (190) remains open and similarly, the inlet port (190) remains closed till the outlet port (200) remains open.
When the current is required to be drawn from the over head catenary the contacts are closed and for closing the contacts, the displaceable valve is actuated so as to bring the reservoir (100) in fluid flow communication with the pneumatic cylinder (130). More

particularly, the displaceable valve is actuated such that the second closing means closes the outlet port and the first closing means opens the inlet port, thereby bringing the pneumatic cylinder in fluid communication with the reservoir. With the closure of the contacts, the first phase of operation comes to an end and a second phase of operation begins.
In the second phase of operation, the contacts must be continuously maintained in the closed state. As indicated in the prior art section, this was previously being achieved by use of a holding coil. However, in the present invention, the inventors have used the air contained in the pneumatic cylinder at the end of the first phase to hold the contacts. Thus, the second phase of operation is effected without substantial energy consumption. This is achieved by not allowing the compressed air contained in the pneumatic cylinder to escape to the exhaust region. The second phase is completed without substantial energy consumption primarily because the reservoir and the exhaust region are connected to the pneumatic cylinder by means of a common channel having the displaceable valve and more particularly because the first closing means (230) and the second closing means (240) are arranged such that outlet port (200) remains closed till the inlet port (190) remains open.
Thus, the present invention eliminates the need of active and passive components in the electronic circuits to operate the holding coil by eliminating the requirement of any power conditioning, Hence, there is no wastage of energy in the active and passive components of the electronic circuits.
Figure 5 illustrates circuit configuration for a circuit breaker according to the present invention. When we compare figure 3 with figure 5, the simplification attained in the circuit which controls the operation of the various components is evident.
In the third phase of operation, the contacts of the circuit breaker are opened. For the purpose of opening the contacts, the pneumatic cylinder is brought in fluid flow communication the exhaust region. This is achieved by actuating the displaceable valve using the actuating mechanism (220) to open the outlet port and bring the pneumatic cylinder in fluid flow communication with the exhaust region. By activating the actuating

mechanism, the first closing means (230) actuates to close the inlet port (190) of the common channel (180) and the second closing means (240) actuates to open the outlet port (200) to bring the pneumatic cylinder (130) in flow communication with exhaust region (170).
It was noticed during the operation of the said device that although the device provided satisfactory performance during the first and the second phases of operation, the third phase of operation was not being effected to the satisfactory level.
More particularly, it was noticed that although, after the pneumatic cylinder is brought in fluid flow communication with the exhaust region, the force of the loaded spring (270, 280) is automatically and instantaneously pushing the drive piston (140) in a downward direction from the extreme upward location, the downward movement of the drive piston may occur at a speed which is less than the desired speed.
Without restricting to any particular theory, the inventors feel that the same is because of the resistance provided by the air which is to be ousted from the pneumatic cylinder.
As mentioned in the prior art section, in the prior art devices, the pressure medium (air) contained in the pneumatic cylinder is exhausted prior to the beginning of the third phase (i.e. during the second phase itself). Due to the above, the downward movement of the drive piston in the prior art device occurs at a desired high speed.
Thus, the invention focused on ensuring the rate at which the compressed air contained in the reservoir was communicated to the pneumatic cylinder through the common channel is different from the rate at which the compressed air contained in the pneumatic cylinder is expelled to the exhaust region through the common channel. If the rate at which air contained in the reservoir is communicated to the pneumatic cylinder is termed as a first flow rate and if the rate at which the compressed air contained in the pneumatic cylinder is expelled to the exhaust region is termed as a second flow rate, a difference between the first and the second rates was aimed. More particularly, the second rate was designed to be substantially greater than the first rate. To achieve the above difference in the first and

the second rates, the size of the outlet port (200) is made larger than the size of the inlet port (190). Thus, the air contained in the pneumatic cylinder (130) is expelled to the exhaust region (170) via the common channel at the second rate which is substantially greater than the first rate. Due to the above construction, immediately after the outlet port is opened, the downward motion of the piston commences and the same is assisted by the compression springs (270, 280). The compression springs gets charged during the closing of the contacts and once the outlet port is opened, they release the energy stored therein to revert back the whele-drive mechanism (160) connected to the moving contact (150) to its initial open position.
Thus, the size of the outlet port(s) in the common channel was constructed to be of a specific and substantially larger size as compared to the inlet port(s) so that the air contained in the reservoir was delivered into the pneumatic cylinder at a desired first rate (in the first phase of operation) and the air contained in the pneumatic cylinder is exhausted to the exhaust region at a desired second rate, wherein the second rate is substantially greater than the first rate. First rate and second rate being matched with the characteristics of the vacuum switch tube (80). Due to the above construction, the primary objective of attaining high speed during the downward motion of the piston is achieved and the downward movement of the drive piston occurs at a desired high speed.
However, it was noticed that because of the increased size of the outlet port, the movement of the drive piston in addition to attaining very high speed during the downward movement, becomes un-controllable in many instances. More particularly, the speed at which the drive piston moves in the downward direction is such that it causes the piston to collide with wall of the drive cylinder at the extreme downward location. Due to such collision, the piston as well as the wall of the drive cylinder can be damaged. Further, such high impact collision can cause the piston to bounce back, which may result in unwanted contact re-making (or in other words contact re-closing leading to arcing).
To avoid the collision of the piston with the cylinder, damping was to be provided for which a new and innovative approach was adopted in the present invention. The pneumatic cylinder is provided with a first air flow regulating device preferably in the

form an orifice (250) at a bottom location of the pneumatic cylinder and the piston (140) is provided with a projection (260) for closing the orifice (250) when the piston (140) is at its lowermost location. The above construction provides an obstruction free path to the air being released through the pneumatic cylinder in the initial phase of the downward movement of the piston. However, once the projection provided on the piston comes in contact with the orifice, the flow of the air to the exhaust region is altered. Thus, velocity of motion of the piston in the downward direction is decreased prior to the piston reaching the wall of the pneumatic cylinder.
It was sometimes noticed that due to the high speed of the downward motion and due to substantial restriction of the flow of the air to the exhaust region, the residual air trapped inside the pneumatic cylinder may be compressed to such an extent that it may push the piston back in the upward direction, and which may cause the piston to bounce back. As it is advisable to avoid such bouncing of the piston, to avoid any unwanted contact making (or in other words contact closing), a mechanism was developed to further enhance the operation of the device.
In the developed mechanism, the flow of the air from the pneumatic cylinder to the common channel is divided into two parallel passages for avoiding the excessive pressure buildup of the residual air inside the pneumatic cylinder. The two air flow passages comprise a first air flow passage and a second air flow passage (as shown in figures 4, 4(a) and 4(b)).
The first air flow passage includes the first air flow regulating device as described above, and more particularly, the first air flow regulating device comprises an orifice formed at the bottom of the pneumatic cylinder and a projection provided on the piston.
Initially, when the operating mechanism is actuated to open the outlet port, air contained in the pneumatic cylinder follows the path of least resistance and start escaping through the first air flow passage at a high speed to the exhaust region. During this initial stage, the second air flow passage remains completely blocked. As the air flows out of the pneumatic cylinder, the piston moves in the downward direction at a high speed. The first

air flow regulating device is configured in such a way that after a predetermined piston displacement, it obstructs the flow of air through the first air flow passage. In other words, once the piston reaches almost the bottom most portion, the projection formed on the piston enters into the orifice and obstructs the flow of air through the first air flow passage Thus, velocity of motion of the piston in the downward direction starts decreasing prior to the piston reaching the wall of the pneumatic cylinder.
In order to safeguard against the bouncing back of the piston due to excessive pressure buildup by the orifice (250) and projection (260), a second air flow path is provided. The second air flow passage provides a route for the residual air trapped inside the pneumatic cylinder to follow and reach the common channel once the projection formed on the piston enters the orifice. The second air flow passage is provided with a second air flow regulating device. More particularly, the second air flow passage comprises a one way valve (290) which preferably can be a pressure sensitive valve. The second air flow regulating device is configured such that it conies into play after it experiences a predetermined amount of pressure. As described in the previous paragraphs, the bouncing back of the piston is caused because of the excessive increase in the pressure of the residual air. By providing the second air flow regulating route with a pressure sensitive valve, the excessive build up in the pressure of the residual air is checked and controlled. Thus, obstruction of the air by the first air flow regulating device provides a damping effect during the downward movement of the piston and release of residual air by the second air flow passage regulates the damping effect and avoids the bouncing of the piston.
The cushioning or damping achieved in the present device is advantageous as compared to the prior existing systems or devices. The arrangement provided for cushioning and dampening overcomes all the problems with the dampening system of the prior art.

We Claim:
1 A device for opening of contacts of a circuit breaker, comprising:
a vacuum switch tube consisting of a fixed contact and a moving contact;
a reservoir for storing compressed air;
a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder
housing a driving piston which is connected to the movable contact of the vacuum
switch tube; and
an exhaust region being in communication with the said pneumatic cylinder;
characterized in that,
the pneumatic cylinder being connected to the reservoir and the exhaust region by
a common channel; the common channel comprising at least one inlet port
connecting the pneumatic cylinder to the reservoir and at least one outlet port
connecting the pneumatic cylinder to the exhaust region; wherein a total passage
of the outlet port(s) is substantially greater than a total passage of the inlet port(s).
2 The device as claimed in any one of the preceding claims 1, wherein the common channel comprises a displaceable valve for controlling the flow of the air through the said ports.
3. The device as claimed in claim 1 and 2, wherein the displaceable valve comprises
a first closing means displaceable with respect to the inlet port and a second
closing means displaceable with respect to the outlet port.
4. The device as claimed in any one of the preceding claims 1-3, wherein the
displaceable valve is actuated by means of a motorized mechanism or
electromagnetic mechanism or a spring mechanism or combinations thereof.
5. The device as claimed in any one of the preceding claims 1-4, wherein the first
closing means and the second closing means are arranged to close the inlet port
and open the outlet port synchronously and vice versa.

6 The device as claimed in any one of the preceding claims 1-5, wherein the inlet
port(s) and the first closing means are configured such that by the operation of the
said first closing means, the said reservoir is brought in fluid flow communication
with the said pneumatic cylinder for supplying the compressed air to the
pneumatic cylinder at a first rate.
7 The device as claimed in any one of the preceding claims 1-6, wherein the outlet
port(s) and the second closing means are configured such that by the operation of
the second closing means, the pneumatic cylinder is brought in fluid flow
communication with an exhaust region for expelling the air from the pneumatic
cylinder to the exhaust region at a second rate.

8. The device as claimed in claims 6 and 7, wherein the second rate is made different
in predefined manner than the first rate.
9. The device as claimed in any one of the preceding claims 1-8, wherein the flow of
air from the pneumatic cylinder to the common channel is divided into a first air
flow passage and a second air flow passage and wherein the first air flow passage
is functionally parallel to the second air flow passage.
10. The device as claimed in claim 9, wherein in the first air flow passage a first air
flow regulating device is provided for coarse air flow regulation.
11. The device as claimed in claim 10, wherein the first air flow regulating device
comprises an orifice provided in the pneumatic cylinder at about a downward
location and a projection formed on the piston, the projection formed on the
piston being insertable inside the orifice provided at a downward location of the
pneumatic cylinder.
12. The device as claimed in claim 9, wherein in the second air flow passage a second
air flow regulating device is provided for fine air flow regulation.

13. The device as claimed in any one of claims 9 to 12, wherein the flow of the air
through the first passage is obstructed once the projection formed on the piston
gets inserted into the orifice during the downward motion of the piston and the air
flows through the second passage also.
14. The device as claimed in any one of the preceding claims 1-13, wherein the
second air flow passage comes into operation after the first air flow passage has
experienced a predetermined amount of obstruction.
15. The device as claimed in any of the preceding claim 1-14, wherein the one way
valve is a pressure sensitive valve.
16. A device for opening of contacts of a circuit breaker substantially as herein
described with reference to the accompanying drawings.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=vvkJz02aE8pJPiX7W2GtDg==&loc=+mN2fYxnTC4l0fUd8W4CAA==

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Patent Number

269448

Indian Patent Application Number

2014/DEL/2006

PG Journal Number

44/2015

Publication Date

30-Oct-2015

Grant Date

21-Oct-2015

Date of Filing

11-Sep-2006

Name of Patentee

AUTOMETERS ALLIANCE LTD.

Applicant Address

C-63, SECTOR-57, NOIDA-201307, UTTAR PRADESH, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	DIGAMBAR PRASAD BHATT	C-63, SECTOR-57, NOIDA-201307, UTTAR PRADESH, INDIA
2	RANDHIR SINGH	C-63, SECTOR-57, NOIDA-201307, UTTAR PRADESH, INDIA

PCT International Classification Number

H01H71/10

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA