Title of Invention

GEAR SHIFTING MECHANISM

Abstract

The present invention relates to a system for controlling gear shifting mechanism for an automobile with auxiliary gearbox, more specifically to electro-pneumatic gear shifting mechanism with manual override for a truck application. The system includes an electro pneumatic arrangement for shifting the gear to auxiliary application and manual mechanism for shifting manually when the electro pneumatic arrangement fails.

Full Text

FORM 2 THE PATENTS ACT 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See Section 10; rule 13) TITLE OF THE INVENTION GEAR SHIFTING MECHANISM APPLICANTS TATA MOTORS LIMITED, an Indian company having its registered office at Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001 Maharashtra, India INVENTORS Pandharinath Namdeo Khatmode and K. Thangaraj Both Indian nationals of TATA MOTORS LIMITED, an Indian company having its registered office at Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001 Maharashtra, India PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed. FIELD OF INVENTION The present invention relates to a system for controlling gear shifting mechanism for an automobile with auxiliary gearbox, more specifically to electro-pneumatic gear shifting mechanism with manual override for a truck application. BACKGROUND OF INVENTION Commercial trucks are used for different applications like fire fighter, self loading vehicle, garbage collector, recovery vehicles when in stationary mode. All these applications need a prime mover to drive them. Engine fitted on vehicle can be used as prime mover for all such applications by deploying an auxiliary gearbox just after main gearbox. An auxiliary gearbox is having two outputs one going to rear axle of vehicle and other goes to the auxiliary application. Thus engine power can be utilized either to move the vehicle or to drive auxiliary application. This requires a mechanism to select either vehicle mode or auxiliary mode by shifting gears in auxiliary gearbox. Typically, this is achieved by providing mechanical linkage from driver cabin to the auxiliary gearbox. Providing a mechanical linkage from driver cabin to auxiliary gear box, particularly when distance between driver cabin and auxiliary gearbox is more or in case of trucks fitted with tiltable cabin, requires a complex mechanical linkages. Alternately, mechanical linkages can be provided from auxiliary gear box to a suitable point on chassis. For operating such vehicles, either driver has to get down or another person has to operate the linkage to select either vehicle mode or auxiliary mode and then go to his seat and then start the engine. This activity is time consuming and cannot be afforded in applications like fire-fighting vehicles. 2 Alternately, the shifting of gears for auxiliary gearbox can be done with the help of pneumatic actuator with spring return. Supply of air to the cylinder can be controlled by either electro-pneumatic valve or a mechanical valve from driver's cabin. But in the event of air leakages in the system, supply air pressure drops below minimum pressure required to operate the pneumatic actuator. Then selecting of gears becomes impossible. Further, alternative arrangement for gear shifting of auxiliary gearbox can be the combination of mechanical linkage and electro-pneumatic system. In such combination, electro-pneumatic system can be used for regular shifting. Whenever there is air leakage, mechanical linkage can be used as an alternate option. But as pneumatic actuator shifts a shifter shaft of auxiliary gearbox, mechanical linkage attached to the same shifter shaft fork also moves; thus requiring more pneumatic force to change the gear. This results in requirement of bigger size pneumatic cylinder and high air pressure to operate it and overall system cost increases. There is need to provide a way of shifting gears of auxiliary gearbox such as to overcome or minimize the difficulties mentioned above SUMMARY OF INVENTION The object of the invention is to provide a gear shifting mechanism comprising an electro-pneumatic means including a solenoid valve, a pneumatic cylinder with cylinder rod and a return spring, a mechanical means connecting said cylinder rod to an auxiliary gear box and to a sliding tube, and a manual shifting means including a shaft with two locking means, first locking means to lock the shaft to first position such that said tube slides over said shaft, second locking means to lock shaft to second position such that said sliding tube moves along with the said shaft, and a mechanical means for moving said shaft inside said sliding tube. 3 Another object of the invention is to provide a gear shifting mechanism comprising a solenoid valve, a pneumatic cylinder with cylinder rod and a return spring, a shifter fork with first end and second end, said first end connected to said sliding tube and second end connected to shifter shaft of auxiliary gear box, a shaft with a first end having two holes and a second end, said shaft having two locking means, first locking means is a pin inserted in first hole so that said shaft slides inside the sliding tube with pin sliding inside the slotted portion of the sliding tube, second locking means is a pin inserted in both first and second holes of the said shaft such that second end of sliding tube locked in between said pins, and a mechanical means for moving shaft including a rotating handle, a transfer shaft with lever, said rotating handle connected to said transfer shaft, a locking member to hold said handle in particular position, said lever connected to second end of the said shaft. DETAILS OF DRAWINGS Embodiment of the invention will be described by way of example and with reference to the drawings in which: Figure 1 diagrammatically illustrates the vehicle layout for background application which includes the electro-pneumatic gear shifting mechanism for auxiliary gear box with manual override provision. Figure 2A is an external view of electro-pneumatic shifting mechanism with manual override by means of mechanical linkage for auxiliary gearbox with shifter shaft of the auxiliary gearbox according to the invention. Figure 2B is an exploded view of the embodiment of Figure 2 A. Figure 3 is an exploded view of the slip device of the embodiment of Figure 2A showing sliding tube with fork, pin and a shaft with fork. 4 Figure 4 is a cross-sectional view of the slip device of the embodiment of Figure 2A showing the electro-pneumatic actuator with return spring, shifter shaft of auxiliary gearbox and lever of the mechanical linkage. Figure 5 is an electro-pneumatic diagram of the preferred embodiment of Figure 2A. DETAILED DESCRIPTION OF INVENTION Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same. Figure 1 diagrammatically illustrates the vehicle layout for background application, which includes electro-pneumatic gear shifting mechanism with manual override provision (6) for auxiliary gear box (7). From auxiliary gearbox (7), drive goes to either rear axle (10) for driving the vehicle or to auxiliary application (11). An electro-pneumatic gear shifting mechanism with manual override provision (6) for auxiliary gear box (7) provides means for selecting either vehicle mode or auxiliary application mode. Figure 2A is an external view of an electro-pneumatic shifting mechanism with manual override provision with shifter shaft of the auxiliary gearbox according to the invention. Figure 2B is an exploded view of the embodiment of Figure 2A. Figure 3 is an exploded view of the slip device of the embodiment of Figure 2A showing sliding tube with fork, pin and a shaft with fork. Figure 4 adds further details for the slip provision in the mechanical linkage along-with the electro-pneumatic means for gear shifting. 5 The basic mechanism can be described as an electro-pneumatic system and a mechanical linkage. Figure 5 is an electro-pneumatic circuit diagram of the preferred embodiment of Figure 2A. An electro-pneumatic system involves single acting pneumatic cylinder (13) with solenoid valve (13b), cylinder rod (13c) which is connected to the shifting fork (14) of auxiliary gearbox (7). Pneumatic cylinder (13) with solenoid valve (13b) is mounted on vehicle chassis with suitable bracket (not shown). The said cylinder (13) is having sufficient travel to shift the shifter shaft (12) to position "II". Return spring (13a) provides a biasing means for pneumatic cylinder (13). Return spring (13a) always keeps shifter fork (12) in position "I" as a default. This means that unless there is pressurized air supply to cylinder (13), power from engine (1) will be always transferred to rear axle (10). Control of the pneumatic cylinder (13) is accomplished by the way of solenoid operated direction control valve (13b). This valve (13b) is typically 3/2 way valve (3 ports and 2 positions). Three ports are inlet port (28), exhaust port (29) and output port (30). Suitable on / off switch (31) with indicator (not shown) for controlling the position of solenoid valve (13b) is provided near to the driver. Electrical supply for operating solenoid valve (13b) is tapped from the vehicle power source (32). The said valve (13b) is having a biasing means (34) such that, in "off condition of switch (32), output port (30) is in direct communication with exhaust port (29) thus exhausting pneumatic cylinder (13) to the atmosphere. Pressurized air supply for the pneumatic actuation of the cylinder (13) is tapped from the vehicle air reservoir (33). This air connection is given to the inlet port (28) of the valve (13b). The mechanical linkage involves a slip device which includes sliding tube (15), a shaft (17) and a pin (16) as shown in figure 2A; Figure 2B and Figure 3. The sliding tube (15) is having first end with fork (15a) and the second end with slotted 6 tube (15b); slot being in the direction of axis of tube. Shaft (17) is having first end with a shaft (17a) with two holes (first hole a and second hole b) in the transverse direction to the shaft axis and the second end with fork (17b). Fork (15a) at first end of sliding tube (15) is connected to the shifting fork (14). Pin (16) is fitted in first hole "a" of shaft (17a) through a slot in the tube (15b). The construction of slip device allows it to transmit forces in pull only. In case of push, sliding tube (15) freely slides over shaft (17). Further mechanical linkage is having a lever (18) connected to fork (17b) at second end of shaft (17), a transfer shaft (19) with its supports (20 and 22), handle (27) to operate the linkage and a bracket (24) with locking provision for handle (27). Return spring (13a) provides a biasing means for mechanical linkage also by pulling shifter shaft (12) to position "I". Supports (20 and 22) are rigidly mounted on underbody of the vehicle (not shown) with the help of screws. Brass bushes (21) are provided in supports (20 and 22) to reduce the friction. Also grease nipples (23) are provided at each support for lubrication of the transfer shaft (19) - bush (21) interface area. Mechanical linkage is operated with the help of handle (27), which is mounted on transfer shaft (19) along with bend plate (26) with the help of bolt. An electrical switch (25) is suitably mounted on bracket (24). From the said switch (25), connection is given to the indicator lamp (not shown) fitted near to driver preferably on dashboard to indicate whether the mechanical linkage is in on mode or off mode. The said switch (25) is having a plunger which gets pressed against bend plate (26) whenever the handle (27) is in position "A". In this condition, this switch is in off mode. Return spring (13a) of pneumatic cylinder (13) always holds shifting fork (14) and in turn shifter shaft (12) in position "I"; thus ensuring transfer of power to rear axle (10). When handle (27) is shifted to position "B" manually, it can be locked in position by means of pin (35) which is inserted in the tube (36) provided on bracket (24). 7 For electro-pneumatic operation, as switch (31) is pressed to "on" position, electrical supply goes to the solenoid of valve (13b). Due to this, valve (13b) goes in "on" condition and port (28) is in direct communication with port (30). As pressurized air enters pneumatic cylinder (13), it pushes cylinder rod (13c) along with shifting fork (14), and a sliding tube (15). As shifting fork (14) moves, shifter shaft (12) of auxiliary gearbox (7) which is rigidly connected to it; also moves to position "II"; thus engaging the gear in auxiliary gear box (7) to transmit the power to auxiliary application (11). During this operation, the sliding tube (15) moves freely over a shaft (17) due to slot provided in the tube (15a). This prevents entire mechanical linkage getting disturbed due to actuation of pneumatic cylinder (13). It helps in reducing the force required for pneumatic actuation of the cylinder (13) to engage the gears of auxiliary gearbox (7) which in turn reduces the cost of pneumatic cylinder (13) due to requirement of smaller size cylinder and less air pressure required to operate the cylinder. Now, as soon as the switch (31) is switched off, biasing means (34) provided in valve (13b) brings it to off position. Due to this output port (30) is in direct communication with exhaust port (29) thus exhausting pneumatic cylinder (13) to the atmosphere. As a result of this, biasing means (13a) provided in pneumatic cylinder (13), pulls cylinder rod (13c) along with shifting fork (14), and sliding tube (15) to its home position. As shifting fork (14) moves, shifter shaft (12) of auxiliary gearbox (7) which is rigidly connected to it; also moves to its default position "I" engaging the gear in auxiliary gear box (7) to transfer the power to rear axle (10). In the event of non-availability of pressurized air, electro-pneumatic shifting mechanism becomes defunct. In such cases mechanical linkage is used to shift the gears of auxiliary gearbox. To engage mechanical linkage, driver has to get down. He then takes out a locking pin (35) from tube (36) and then rotates handle (27) to 8 position "B" and then inserts locking pin (35) into the other tube (37) on bracket (24). Due to this handle (27) gets locked in position "B". As handle (27) is rotated, transfer shaft (19) with lever (18) rotates in the direction of rotation of handle. This pulls a shaft (17) along with pin (16). As this pin (16) is at the end of slot of sliding tube (15), it results in movement of sliding tube (15), shifting fork (14) and in turn shifter shaft (12) to position "II". Due to this gear in the auxiliary gearbox (7) gets shifted to transmit power to auxiliary application. At the same time, cylinder rod (13c) along with spring (13a) gets pulled along with mechanical linkage. It results in continuous pull force on shifting fork (14). As handle (27) is locked in position "B" with help of pin (35) and tube (37), shifter shaft (12) remains in position "II" against the force of spring (13a). As handle (27) is rotated to position "B", bend plate (26) also rotates along with it, thus releasing the plunger of switch (25). Due to this, switch (25) goes to "on" position, thus giving signal to indicator (not shown) in driver cabin indicating that auxiliary gearbox (7) is in engaged mode for auxiliary application with the help of mechanical linkage. To disengage auxiliary application, driver has to pull pin (35) from tube (37). As continuous force is acting on shifting fork (14) due to spring (13a), it gets pulled along with entire mechanical linkage and shifter shaft (12). This brings shifter shaft (12) back to its home position "I" and the gears in auxiliary gear box (7), gets shifted to transmit power to rear axle (10). As handle (27), comes to it's home position "A", bend plate (26) again gets pressed against plunger of switch (25), thus switching off the indicator (not shown). In the event of failure of return spring (13a) of pneumatic cylinder (13) and nonavailability of pressurized air, it is necessary to shift gears in auxiliary gearbox (7) by means of mechanical linkage only. This can be accomplished by putting a pin (16') into second hole "b" in the shaft (17). This locks the slip tube (15) with shaft (17) thus making it rigid linkage. Now mechanical linkage can work both in push 9 and pull modes; enabling user to engage or disengage the gears of auxiliary gearbox (7). The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof. 10 WE CLAIM 1. A gear shifting mechanism comprising - an electro-pneumatic means including a solenoid valve, a pneumatic cylinder with cylinder rod and a return spring, a mechanical means connecting said cylinder rod to an auxiliary gear box and to a sliding tube, and - a manual shifting means including a shaft with two locking means, first locking means to lock the shaft to first position such that said sliding tube slides over said shaft, second locking means to lock the shaft to second position such that said sliding tube moves along with said shaft, and a means for moving said shaft inside said sliding tube. 2. A gear shifting mechanism as claimed in claim 1 wherein said mechanical means including a shifting fork with first end and second end, said first end connected to said sliding tube and second end connected to shifter shaft of auxiliary gear box. 3. A gear shifting mechanism as claimed in claim 1 wherein said sliding tube having a first end and second, said second end having a slot along the axis of the tube. 4. A gear shifting mechanism as claimed in claim 1 wherein said shaft having a first end and a second end, said first end having two holes in the transverse direction of axis of the shaft. 5. A gear shifting mechanism as claimed in any one of the preceding claims wherein said first locking means is a pin inserted in the first hole so that said shaft slides inside the sliding tube with pin sliding inside the slotted portion of the sliding tube. 11 6. A gear shifting mechanism as claimed in any one of the preceding claims wherein said second locking means is a pin inserted in both the first and second holes of the said shaft such that second end of sliding tube locked in between said pins. 7. A gear shifting mechanism as claimed in claim 1 wherein said means for moving shaft including a rotating handle, a transfer shaft with lever, said rotating handle connected to said transfer shaft, a locking member to hold said handle in particular position, said lever connected to second end of the said shaft. 8. A gear shifting mechanism as claimed in claim 1 wherein said electro pneumatic means push said sliding tube to slide over said shaft and said mechanical means for moving the shaft moves the shaft along with the sliding tube. 9. A gear shifting mechanism comprising a solenoid valve, a pneumatic cylinder with cylinder rod and a return spring, a shifting fork with first end and second end, said first end connected to said sliding tube and second end connected to shifter shaft of auxiliary gear box, a shaft with a first end having two holes and a second end, said shaft having two locking means, first locking means is a pin inserted in first hole so that said shaft slides inside the sliding tube with pin sliding inside the slotted portion of the sliding tube, second locking means is a pin inserted in both first and second holes of the said shaft such that second end of sliding tube locked in between said pins, and a mechanical means for moving shaft including a rotating handle, a transfer shaft with lever, said rotating handle connected to said transfer shaft, a locking member to hold said handle in particular position, said lever connected to second end of the said shaft. 12 10. A gear shifting mechanism substantially as herein described with reference to accompanying drawings. Dated this 1st day of October 2007. 13 ABSTRACT Gear Shifting Mechanism The present invention relates to a system for controlling gear shifting mechanism for an automobile with auxiliary gearbox, more specifically to electro-pneumatic gear shifting mechanism with manual override for a truck application. The system includes an electro pneumatic arrangement for shifting the gear to auxiliary application and manual mechanism for shifting manually when the electro pneumatic arrangement fails. 14 Fig2A

Documents:

1940-mum-2007-abstract.doc

1940-mum-2007-abstract.pdf

1940-MUM-2007-CLAIMS(AMENDED)-(23-11-2012).pdf

1940-MUM-2007-CLAIMS(AMENDED)-(3-1-2012).pdf

1940-mum-2007-claims.doc

1940-mum-2007-claims.pdf

1940-MUM-2007-CORRESPONDENCE(20-11-2007).pdf

1940-mum-2007-correspondence-received.pdf

1940-mum-2007-description (complete).pdf

1940-mum-2007-drawings.pdf

1940-MUM-2007-FORM 18(20-11-2007).pdf

1940-MUM-2007-FORM 8(20-11-2007).pdf

1940-MUM-2007-FORM 9(20-11-2007).pdf

1940-mum-2007-form-1.pdf

1940-mum-2007-form-2.doc

1940-mum-2007-form-2.pdf

1940-mum-2007-form-26.pdf

1940-mum-2007-form-3.pdf

1940-MUM-2007-GENERAL POWER OF ATTORNEY(23-11-2012).pdf

1940-MUM-2007-GENERAL POWER OF ATTORNEY(3-1-2012).pdf

1940-MUM-2007-MARKED COPY(3-1-2012).tif

1940-MUM-2007-REPLY TO EXAMINATION REPORT(3-1-2012).pdf

1940-MUM-2007-REPLY TO HEARING(23-11-2012).pdf

1940-MUM-2007-SPECIFICATION(AMENDED)-(23-11-2012).pdf

1940-MUM-2007-SPECIFICATION(AMENDED)-(3-1-2012).pdf

1940-MUM-2007-SPECIFICATION(MARKED COPY)-(23-11-2012).pdf

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