Title of Invention	"A HYDRAULIC SYSTEM FOR LOAD COMPENSATED CONTROL OF HITCHED AGRICULTURAL IMPLEMENTS OF A TRACTOR"
Abstract	This invention relates to a hydraulic system for load compensated control of agricultural implements hitched to a tractor, which shows the problem of non-smooth and jerky movements under varying load conditions during lowering or lifting of agricultural implements hitched to the linkage end of a tractor. This is made possible by incorporating a six-way five position spool type direction control valve, having in-built flow control facility, in the hydraulic control system resulting in a novel integrated load compensated control system capable of providing smooth and non-jerky movement in an energy efficient manner to agricultural implements hitched to a tractor.

Title of Invention

"A HYDRAULIC SYSTEM FOR LOAD COMPENSATED CONTROL OF HITCHED AGRICULTURAL IMPLEMENTS OF A TRACTOR"

Abstract

This invention relates to a hydraulic system for load compensated control of agricultural implements hitched to a tractor, which shows the problem of non-smooth and jerky movements under varying load conditions during lowering or lifting of agricultural implements hitched to the linkage end of a tractor. This is made possible by incorporating a six-way five position spool type direction control valve, having in-built flow control facility, in the hydraulic control system resulting in a novel integrated load compensated control system capable of providing smooth and non-jerky movement in an energy efficient manner to agricultural implements hitched to a tractor.

Full Text	The present invention relates to a hydraulic system for load compensated control of agricultural implements hitched to a tractor. The main usage of such hydraulic systems are in the field of agricultural and soil preparation vehicles like tractors where the agricultural implements are normally fitted at the linkage end, called, hitch, at the back of such vehicles. The agricultural implements, that is, the soil processing devices, such as plough, cutter are fitted at the hitch-end before the agricultural work is initiated in the field. According to the stage of use of such implements, the device may have to be positioned at desired levels and at varying soil conditions. The soil condition translates soil-resistance and coupled with depth of cut offers varying loads to implements and such resistance is the draft to the device. The purpose of the present invention is to solve the technical problems of position and draft control of the agricultural implements, hydraulically, and in a manner that when load at the hitch-end varies depending on the agricultural conditions, the movement of the implement with respect to the soil-level is always 'smooth', that is not jerky, that is, technically speaking, the movement of the implement is 'load compensated'. While solving the requirement of load compensation in the present invention, care has been taken, to reduce the energy loss in the form of pressurized oil. In figure 1 of the drawings accompanying this specification is shown a layout drawing of an existing hydraulic system being u:-ed in the tractors of M/S International Tractors Limited. In this hydraulic circuit the load compensation facility is not existing. The name of each component with the reference numbering, is being given below: 1. Oil Tank 2. Direction Control Valve 2a. Oil Port of 2 2b. Oil Port of 2 2c. Spool actuation lever of the direction control valve, this lever is mechanically connected with the mechanical device for operation with manual or auto mode. 2d. Oil Port of 2 2e. Oil Port of 2 3. Relief Valve 4. Cylinder/Actuator 5. Check Valve 6. Response Valve 7. Unloading Valve 7a. Pilot Port of 7 8. Relief Valve 9. Pump 10. Motor/Engine 11. Check Valve Figure 1 represents the prior art status of the relevant hydraulic control circuitry as in use in a tractor to control the working of a hitched implement. The function of the circuit is described below: During holding, that is, the neutral position or when the implement remains at rest position, the oil from pump (9) is connected to the tank (1) through the unloading valve (7) and the check valve (11), while the pilot operation of the unloading valve (7) is actuated by discharging the pilot pressure in the form of pressurized fluid to the tank (1) through the direction control valve (2). In this situation, the ports (2a) and (2e) of the direction control valve (2) are kept closed and oil is not passing through any other components (valves) of this circuit. While lifting the load the passage of energy in the form of pressurized oil is initiated at the pump (9) driven by the motor/engine (10), oil goes through the check valve (5) and finally reaches the cylinder (4). At the same time, the pressurized fluid from the pump (9) goes through the direction control valve (2) and reaches the unloading valve (7) as a pilot pressure, to close the unloading valve (7). To achieve this passage of flow, from pump (9) to the actuator (4), the ports (2b) and (2e) of the direction control valve (2) and response valve (6) are kept closed. While lowering the load and eventually engaging the soil on which the implement has to work, the passage of energy in the form of pressurized oil initiated at the pump (9) driven by the motor/engine (10), the pressurized oil moves through the unloading valve (7) and the check valve (11) to reach the tank, while the pilot operation of the unloading valve (7) is actuated by discharging the fluid through the direction control valve (2) to the tank (1). At the same time, oil from the actuator (4), from the previous state, reaches the tank (1) via response valve (6) and direction control valve (2). In this situation, the port (2a) of the directional control valve (2) is kept closed and oil is not passing through any other components (valves) of this circuit. The relief valve (8) and valve (3) at any state of operation, that is, lifting, lowering, engaging the soil and holding, protect the circuit from overpressure by releasing the oil to the tank (1). In the prior ait circuit as shown in figure i, the response valve (6) requires adjustments/readjustments from lime to time, depending upon the load and function situations. This is a drawback for this circuit, besides, in the absence of load compensation facility, energy toss, in idling as well as in control aspects, in the form of more return flow to the tank is also a drawback and as such a technical problem which needs to be solved. On a search of patent databases it is seen that: US Patent, 5577435, High flow hydraulic circuit for tractors, discloses about hydraulic aided steering facility. US Patent, 4354555, Hydraulic lifting arrangement for implements, especially on tractors, deals with automatic rapid level adjustment facility for the implement where the terrain has varied topography of the land and the purpose of the patent is different from the present technical requirements. In US Patent, 5501136, Control system for a hydraulic motor, discusses mainly about the control aspects of a hydraulic motor and not relevant to the present technical problem. In The US Patent, 5579642, Pressure compensating hydraulic control system, discloses the usability of a variable displacement pump and not related to the present problems. The main object of the present invention is to provide a hydraulic system for load compensated control of agricultural implements hitched to a tractor, which obviates the drawbacks as detailed above. Another object of the present invention is to solve the technical problem of handling the load associated with agricultural implements hitched to a tractor, in smooth and non jerky way, that is, in a manner, the load position, while changing, changes in a load compensated manner, to avoid any extra loading on the hitch point of the mechanical linkage of the tractor and the load movement is smooth. Yet another object of the present invention is to reduce the energy loss in the form of non-working pressurized fluid, which is dumped in the tank, from time to time. Still another object of the present invention is to avoid the readjustment of the response valve as in the prior art, manually, from time to time, depending on the load and function conditions. The present invention provides a hydraulic system for load compensated control of agricultural implements hitched to a tractor. This is made possible by the non-obvious inventive step of providing a direction control (dc) valve which is a six-way five position spool type valve having in-built flow control facility at both ends. The incorporation of this dc valve in the hydraulic control system results in a novel integrated load compensated control system capable of providing smooth and non-jerky movement in an energy efficient manner during lowering or lifting of an agricultural implement hitched to the linkage-end of a tractor. In figures 2, 3 and 4 of the drawings accompanying this specification is shown the layout drawing of the present invention. Figure 2, 3 and 4 represent the hydraulic control circuit of the present invention comprising of specific components as given below, in which, one component, that is, the Direction Control (dc) Valve (12), is the inventive step which solves the main technical problems of load compensation, energy saving and non-requirement of any response valve, as in the prior art and its associated adjustments. The various parts shown in figures 2 and 3 are: 1. Oil Tank (In all the drawing the oil tank is No. 1) 2c. Control lever of the direction control valve (as explained, in figure 1) 12. Direction Control Valve, Six-way five position spool type valve having in-built flow control facility at two ends. 12a. Oil port of 12 I2b. Oil port of 12 12c. Oil port of 12 12d. Oil port of 12 12e. Oil port of 12 12f. Oil port of 12 13. Relief Valve 14. Cylinder/Actuator 15. Check valve 16. Differential Pressure Sensing Valve (DPS), normally open 17. Differential Pressure Sensing Valve (DPS), normally closed 18. Relief Valve 19. Pump 20. Prime mover (Motor/Engine) 21. Pair of Check Valves Figure 4 provides details of the flow control valve (12). In figure 4(1) is shown the assembly drawing of the flow control v;ilve (12), at neutral position. In figure 4(1), the part numbers 2c and 12a to 12f are as explained earlier. The additional parts shown are: 22. Valve sleeve of the flow control valve (12). 22a. O-ring seats. 22b. Lubrication recesses. In figure 4(2), the complete valve sleeve (22) has been represented. In figure 4(3), the complete view of the valve-spool has been represented. The valve-spool actuation lever (2c) having the control lever facility at one end and having a hole (2f) at that end. Accordingly the present invention provides a hydraulic system for load compensated control of agricultural implements hitched to a tractor, which comprises a prime mover (20) such as a motor/engine connected to drive a pump (19) fitted with an oil tank (1) at its suction end and having a multi-branch delivery line, one branch of the delivery line of the pump (19) connects the tank (1) via a relief valve (18), a second branch of the delivery line from the pump (19) also connects the tank (1) via a pair of check valves (21), a third branch of the delivery line from the said pump (19) connects to a multi-port direction control (dc) valve (12) whose ports (12a) and (12c) are connected directly to the tank (1) and port (12b) is connected to the tank (1) via a normally closed differential pressure sensing valve (17), port (12e) of the dc valve (12) provides a pilot pressure connection to the said check valves (21), port (12f) of the dc valve (12) connects an actuator (14) via a check valve (15) and port (12d) of the dc valve (12) is connected to the line inter-connecting the check valve (15) and the actuator (14) via a normally open differential pressure sensing valve (16) connected to the tank (1), the said actuator (14) is connected with the said tank (1) via a relief valve (13), the said dc valve (12) is provided with spool actuation lever (2c) capable of providing connection with the hand mode or auto mode leverage. In an embodiment of the present invention the direction control valve (12) is a spool type valve having five positions of control and six ports for connections and inbuilt flow control facility at the two ends of the valve. In another embodiment of the present invention, the pilot pressure connection of port (12e) of dc valve (12) to the cheek valves (21) is capable of unloading oil to the tank (1) without actuating relief valves (13, 18). In still another embodiment of the present invention, the differential pressure sensing valves (16, 17) are capable of proportionate actuation to pass/block oil to the hydraulic system to provide pressure condition in the circuit such that there is low back pressure which facilitates saving of energy. In a feature of the present invention, the requirement of a response valve (6) as shown in figure 1 depicting the prior art, has been made redundant, that is, repeated changing of the settings of that valve with the change of load is no more required. In figures 2, 3 and 4 of the drawings details of the present invention are shown, where the valve (12) is a five position, six port direction control (dc) valve which constitutes the non-obvious inventive step resulting in the novelty of providing a solution to the specific technical problem when used in association with the supporting DPS valves (16), (17) and the two check valves (21). The technical problem as mentioned in the previous paragraph is that, while the load (implement plus soil resistance) at the end of the mechanical linkage (hitch), while being lowered or lifted, produces a requirement of load compensation in the demand pattern of the hydraulic system. Normally, in the prior art, the load compensation at the end of the hitch requires the provision of maintaining a high backpressure for proper functioning of the hydraulic system particularly for the functioning of the check valve (11), as shown in figure 1. The situation of a high back pressure in the system results in consumption of more energy as well as generates heat as a sign of lower efficiency. This problem has been solved in the present invention. Another problem is solved through the load compensation mechanism of the present invention: the requirement of repeated adjustment of the response valve (6) as shown in figure 1, according to the loading at the hitch end is not required and that makes the functioning of the system of the present invention very smooth and automatic irrespective of Ihe load (implement) to be handled at the hitch end of a tractor. The working of the system of the present invention is explained below: During holding/neutral position, the oil from the pump (19) goes to the tank (1) through Ihe pair of check valves (21). At this time, the ports (12b, I2c, 12d) and 12e) of the direction control valve (12) are kept in closed state and oil is not passing through any other components (valves) of this circuit. lifting of a load, the passage of energy in the form of pressurized oil is initiated at the pump (19) driven by the motor/engine (20). The pressurized oil is moved through direction control valve (12) and finally reaches the cylinder (14) through check valve (15). To achieve this flow passage, from pump (19) to the actuator (14), the pair of check valves (21) remain closed, DPS valve (17) remains normally closed, DPS valve (16) remains normally open and ports (12a, 12b, 12c, 12f) of direction control valve (12) are kept open. The characteristics of the valve (16) and valve (17) are such that it opens and closes gradually when the pressure situation, so demands, to transfer extra oil to the sump/tank (1). During lowering of a load and eventually engaging the soil on which the implement has to work, the passage of energy in the form of pressurized oil is initiated at the pump (19) driven by the motor/engine (20), the pressurized oil is moved through the pair of check valves (21) to reach the tank (1), while the pilot operation of the check valves (21) is actuated by receiving the pilot pressure via the direction control valve (12). At the same time oil from the actuator (14), from the previous state, reaches to the tank (1) via the DPS valve (16) and the direction control valve (12). The relief valves (13) and (18) at any state of operation, that is, lifting, lowering, engaging the soil, and holding, protect the circuit from over pressure by releasing the oil to the tank (1). The two pilot operated check valves (21) effects the unloading of the pump, that is, the oil is returning to the tank (1) when the mail! flow control valve (12) is in the neutral position (central position of the five positions) or in the lowering mode. It has been verified that the system only built up a low pressure (less than 10 bar) in such conditions, showing that the energy loss has been much reduced, in the absence of high backpressure, as in prior art circuits. The following example is given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. Example-1 1. The present invention is a hydraulic control circuit and its capability was tested by being fitted on to a tractor and used in field condition. The system was tested in this manner and was found to be satisfactory. 2. The normally open differential pressure- sensing valve (16) maintained the lowering speed of the implement irrespective of the load on the lifting arm at the hitch point. It was found that the speed of lowering was not varying with the load variation at the implement. 3. The other differential pressure sensing valve (17) which is normally closed, maintained the lifting speed irrespective of the load variation at the hitch point and there was no variation of speed with the change of the load. These observations were noted during actual trials to show conclusively that the purpose of load compensation through this invention was achieved. It was found, in both the mode of lowering and lifting of load, the speed of movement was smooth and constant. The system was also found to be stable and almost free from any oscillation. The novelty of this invention resides in providing load compensation during handling of a load by an agricultural tractor, in a manner that during lowering or during lifting, the movement of the linkage-end (hitch point) maintains constant speed with the change of load and the movement is smooth and non-jerky. The requirement of high backpressure in the system for control purpose is also not there, making the system more energy efficient. This has been achieved by the main inventive step of a directional control (dc) valve (12) having five position and six ports with built-in flow control facility at two ends of this valve. This dc valve (12) when incorporated with the components as shown in figure 2, 3 and 4, provides an integrated hydraulic system which solves the technical problen load compensation in an energy efficient manner in the case of mobile machinery, like an agricultural tractor. The main advantages of the present invention are: 1. Handling of the load/change of load by the implement of a tractor/mobile unit, in a load compensated mode, keeping the movement of the implement, non-jerky arid smooth, in constant speed. 2. For unloading the oil to the tank and for the ..-ontrol requirement, :naintaining of high back pressure has been deleted making this hydraulic circuit more energy efficient. 3. There is no requirement of changing the setting of any response valve with the change of load, making this system, automatic, if required. 4. The operation of the relief valves are made limited and effective only for sudden- safety, this reduces the possibility of bulk pressure loss through such valves. We claim, 1. A hydraulic system for load compensated control of agricultural implements hitched to a tractor, which comprises a prime mover (20) such as a motor/engine connected to and having a multi - branch delivery line, one branch of drive a pump (19) fitted with an oil tank (1) at its suction end/the delivery line of the pump (19) connects the tank (1) via a relief valve (18), a second branch of the delivery line from the pump (19) also connects the tank (1) via a pair of check valves (21), a third branch of the delivery line from the said pump (19) connects to a multi-port direction control (dc) valve (12) whose ports (12a) and (12c) are connected directly to the tank (1) and port (12b) is connected to the tank (I) via a normally closed differential pressure sensing valve (17), port (12e) of the dc valve (12) provides a pilot pressure connection to the said check valves (21), port (12f) of the dc valve (12) connects an actuator (14) via a check valve (15) and .' . port (12d) of the dc valve (12) is connected to the line inter-connecting the check valve (15) and the actuator (14) via a normally open differential pressure sensing valve ((16) connected to the tank (1), the said actuator (14) is connected with the said tank (1) via a relief valve (13), the said dc valve (12) is provided with a spool actuation lever (2c) capable of providing connection with the hand mode or auto mode leverage. 2. A hydraulic systen as claimed in claim 1, wherein the direction control valve (12) is a live control position six connection port spool type direction control valve having in-built flow control facility at its two ends. 3. A hydraulic systemftts claimed in claim1-2, wherein, Ihc pilot pressure connection of port (12e) of dc Valve (12) is capable of unloading oil to the tank (1), without activating relief valves (13, 18).. 4. A hydraulic system\|\as claimed in claim 1-3 3, wherein, the differential pressure sensing valves (16) and (17) are capable of proportionate activation to pass/block oil to the hydraulic system to provide pressing condition such that there is low hack pressure. 5. A hydraulic system for load compensated control of agricultural implements hitched to a tractor, substantially as herein described with reference to the example and figures 2 to 4 of the drawings accompanying this specification.

Full Text

The present invention relates to a hydraulic system for load compensated control of agricultural implements hitched to a tractor.
The main usage of such hydraulic systems are in the field of agricultural and soil preparation vehicles like tractors where the agricultural implements are normally fitted at the linkage end, called, hitch, at the back of such vehicles. The agricultural implements, that is, the soil processing devices, such as plough, cutter are fitted at the hitch-end before the agricultural work is initiated in the field. According to the stage of use of such implements, the device may have to be positioned at desired levels and at varying soil conditions. The soil condition translates soil-resistance and coupled with depth of cut offers varying loads to implements and such resistance is the draft to the device. The purpose of the present invention is to solve the technical problems of position and draft control of the agricultural implements, hydraulically, and in a manner that when load at the hitch-end varies depending on the agricultural conditions, the movement of the implement with respect to the soil-level is always 'smooth', that is not jerky, that is, technically speaking, the movement of the implement is 'load compensated'. While solving the requirement of load compensation in the present invention, care has been taken, to reduce the energy loss in the form of pressurized oil.
In figure 1 of the drawings accompanying this specification is shown a layout drawing of an existing hydraulic system being u:-ed in the tractors of M/S International Tractors Limited. In this hydraulic circuit the load compensation facility is not existing. The name of each component with the reference numbering, is being given below:
1. Oil Tank
2. Direction Control Valve
2a. Oil Port of 2
2b. Oil Port of 2

2c. Spool actuation lever of the direction control valve, this lever is mechanically connected with the mechanical device for operation with manual or auto mode. 2d. Oil Port of 2 2e. Oil Port of 2
3. Relief Valve
4. Cylinder/Actuator
5. Check Valve
6. Response Valve
7. Unloading Valve
7a. Pilot Port of 7
8. Relief Valve
9. Pump

10. Motor/Engine
11. Check Valve
Figure 1 represents the prior art status of the relevant hydraulic control circuitry as in use in a tractor to control the working of a hitched implement. The function of the circuit is described below:
During holding, that is, the neutral position or when the implement remains at rest position, the oil from pump (9) is connected to the tank (1) through the unloading valve (7) and the check valve (11), while the pilot operation of the unloading valve (7) is actuated by discharging the pilot pressure in the form of pressurized fluid to the tank (1) through the direction control valve (2). In this situation, the ports (2a) and (2e) of the direction control valve (2) are kept closed and oil is not passing through any other components (valves) of this circuit.

While lifting the load the passage of energy in the form of pressurized oil is initiated at the pump (9) driven by the motor/engine (10), oil goes through the check valve (5) and finally reaches the cylinder (4). At the same time, the pressurized fluid from the pump (9) goes through the direction control valve (2) and reaches the unloading valve (7) as a pilot pressure, to close the unloading valve (7). To achieve this passage of flow, from pump (9) to the actuator (4), the ports (2b) and (2e) of the direction control valve (2) and response valve (6) are kept closed.
While lowering the load and eventually engaging the soil on which the implement has to work, the passage of energy in the form of pressurized oil initiated at the pump (9) driven by the motor/engine (10), the pressurized oil moves through the unloading valve (7) and the check valve (11) to reach the tank, while the pilot operation of the unloading valve (7) is actuated by discharging the fluid through the direction control valve (2) to the tank (1). At the same time, oil from the actuator (4), from the previous state, reaches the tank (1) via response valve (6) and direction control valve (2). In this situation, the port (2a) of the directional control valve (2) is kept closed and oil is not passing through any other components (valves) of this circuit. The relief valve (8) and valve (3) at any state of operation, that is, lifting, lowering, engaging the soil and holding, protect the circuit from overpressure by releasing the oil to the tank (1).
In the prior ait circuit as shown in figure i, the response valve (6) requires adjustments/readjustments from lime to time, depending upon the load and function situations. This is a drawback for this circuit, besides, in the absence of load compensation facility, energy toss, in idling as well as in control aspects, in the form of more return flow to the tank is also a drawback and as such a technical problem which needs to be solved.

On a search of patent databases it is seen that:
US Patent, 5577435, High flow hydraulic circuit for tractors, discloses about hydraulic
aided steering facility.
US Patent, 4354555, Hydraulic lifting arrangement for implements, especially on
tractors, deals with automatic rapid level adjustment facility for the implement where the
terrain has varied topography of the land and the purpose of the patent is different from
the present technical requirements.
In US Patent, 5501136, Control system for a hydraulic motor, discusses mainly about the control aspects of a hydraulic motor and not relevant to the present technical problem.
In The US Patent, 5579642, Pressure compensating hydraulic control system, discloses the usability of a variable displacement pump and not related to the present problems. The main object of the present invention is to provide a hydraulic system for load compensated control of agricultural implements hitched to a tractor, which obviates the drawbacks as detailed above.
Another object of the present invention is to solve the technical problem of handling the load associated with agricultural implements hitched to a tractor, in smooth and non jerky way, that is, in a manner, the load position, while changing, changes in a load compensated manner, to avoid any extra loading on the hitch point of the mechanical linkage of the tractor and the load movement is smooth.
Yet another object of the present invention is to reduce the energy loss in the form of non-working pressurized fluid, which is dumped in the tank, from time to time. Still another object of the present invention is to avoid the readjustment of the response valve as in the prior art, manually, from time to time, depending on the load and function conditions.

The present invention provides a hydraulic system for load compensated control of
agricultural implements hitched to a tractor. This is made possible by the non-obvious
inventive step of providing a direction control (dc) valve which is a six-way five position
spool type valve having in-built flow control facility at both ends. The incorporation of
this dc valve in the hydraulic control system results in a novel integrated load
compensated control system capable of providing smooth and non-jerky movement in an
energy efficient manner during lowering or lifting of an agricultural implement hitched to
the linkage-end of a tractor.
In figures 2, 3 and 4 of the drawings accompanying this specification is shown the layout
drawing of the present invention.
Figure 2, 3 and 4 represent the hydraulic control circuit of the present invention
comprising of specific components as given below, in which, one component, that is, the
Direction Control (dc) Valve (12), is the inventive step which solves the main technical
problems of load compensation, energy saving and non-requirement of any response
valve, as in the prior art and its associated adjustments.
The various parts shown in figures 2 and 3 are:
1. Oil Tank (In all the drawing the oil tank is No. 1)
2c. Control lever of the direction control valve (as explained, in figure 1)
12. Direction Control Valve, Six-way five position spool type valve having in-built flow
control facility at two ends.
12a. Oil port of 12
I2b. Oil port of 12
12c. Oil port of 12
12d. Oil port of 12
12e. Oil port of 12

12f. Oil port of 12
13. Relief Valve
14. Cylinder/Actuator
15. Check valve
16. Differential Pressure Sensing Valve (DPS), normally open
17. Differential Pressure Sensing Valve (DPS), normally closed
18. Relief Valve
19. Pump
20. Prime mover (Motor/Engine)
21. Pair of Check Valves
Figure 4 provides details of the flow control valve (12). In figure 4(1) is shown the assembly drawing of the flow control v;ilve (12), at neutral position. In figure 4(1), the part numbers 2c and 12a to 12f are as explained earlier. The additional parts shown are:
22. Valve sleeve of the flow control valve (12).
22a. O-ring seats.
22b. Lubrication recesses.
In figure 4(2), the complete valve sleeve (22) has been represented. In figure 4(3), the complete view of the valve-spool has been represented. The valve-spool actuation lever (2c) having the control lever facility at one end and having a hole (2f) at that end. Accordingly the present invention provides a hydraulic system for load compensated control of agricultural implements hitched to a tractor, which comprises a prime mover (20) such as a motor/engine connected to drive a pump (19) fitted with an oil tank (1) at its suction end and having a multi-branch delivery line, one branch of the delivery line of the pump (19) connects the tank (1) via a relief valve (18), a second branch of the

delivery line from the pump (19) also connects the tank (1) via a pair of check valves (21), a third branch of the delivery line from the said pump (19) connects to a multi-port direction control (dc) valve (12) whose ports (12a) and (12c) are connected directly to the tank (1) and port (12b) is connected to the tank (1) via a normally closed differential pressure sensing valve (17), port (12e) of the dc valve (12) provides a pilot pressure connection to the said check valves (21), port (12f) of the dc valve (12) connects an actuator (14) via a check valve (15) and port (12d) of the dc valve (12) is connected to the line inter-connecting the check valve (15) and the actuator (14) via a normally open differential pressure sensing valve (16) connected to the tank (1), the said actuator (14) is connected with the said tank (1) via a relief valve (13), the said dc valve (12) is provided with spool actuation lever (2c) capable of providing connection with the hand mode or auto mode leverage.
In an embodiment of the present invention the direction control valve (12) is a spool type valve having five positions of control and six ports for connections and inbuilt flow control facility at the two ends of the valve.
In another embodiment of the present invention, the pilot pressure connection of port (12e) of dc valve (12) to the cheek valves (21) is capable of unloading oil to the tank (1) without actuating relief valves (13, 18).
In still another embodiment of the present invention, the differential pressure sensing valves (16, 17) are capable of proportionate actuation to pass/block oil to the hydraulic system to provide pressure condition in the circuit such that there is low back pressure which facilitates saving of energy.
In a feature of the present invention, the requirement of a response valve (6) as shown in figure 1 depicting the prior art, has been made redundant, that is, repeated changing of the settings of that valve with the change of load is no more required.

In figures 2, 3 and 4 of the drawings details of the present invention are shown, where the valve (12) is a five position, six port direction control (dc) valve which constitutes the non-obvious inventive step resulting in the novelty of providing a solution to the specific technical problem when used in association with the supporting DPS valves (16), (17) and the two check valves (21).
The technical problem as mentioned in the previous paragraph is that, while the load (implement plus soil resistance) at the end of the mechanical linkage (hitch), while being lowered or lifted, produces a requirement of load compensation in the demand pattern of the hydraulic system. Normally, in the prior art, the load compensation at the end of the hitch requires the provision of maintaining a high backpressure for proper functioning of the hydraulic system particularly for the functioning of the check valve (11), as shown in figure 1. The situation of a high back pressure in the system results in consumption of more energy as well as generates heat as a sign of lower efficiency. This problem has been solved in the present invention.
Another problem is solved through the load compensation mechanism of the present invention: the requirement of repeated adjustment of the response valve (6) as shown in figure 1, according to the loading at the hitch end is not required and that makes the functioning of the system of the present invention very smooth and automatic irrespective of Ihe load (implement) to be handled at the hitch end of a tractor.
The working of the system of the present invention is explained below: During holding/neutral position, the oil from the pump (19) goes to the tank (1) through Ihe pair of check valves (21). At this time, the ports (12b, I2c, 12d) and 12e) of the direction control valve (12) are kept in closed state and oil is not passing through any other components (valves) of this circuit.

lifting of a load, the passage of energy in the form of pressurized oil is initiated at the pump (19) driven by the motor/engine (20). The pressurized oil is moved through direction control valve (12) and finally reaches the cylinder (14) through check valve (15). To achieve this flow passage, from pump (19) to the actuator (14), the pair of check valves (21) remain closed, DPS valve (17) remains normally closed, DPS valve (16) remains normally open and ports (12a, 12b, 12c, 12f) of direction control valve (12) are kept open. The characteristics of the valve (16) and valve (17) are such that it opens and closes gradually when the pressure situation, so demands, to transfer extra oil to the sump/tank (1).
During lowering of a load and eventually engaging the soil on which the implement has to work, the passage of energy in the form of pressurized oil is initiated at the pump (19) driven by the motor/engine (20), the pressurized oil is moved through the pair of check valves (21) to reach the tank (1), while the pilot operation of the check valves (21) is actuated by receiving the pilot pressure via the direction control valve (12). At the same time oil from the actuator (14), from the previous state, reaches to the tank (1) via the DPS valve (16) and the direction control valve (12). The relief valves (13) and (18) at any state of operation, that is, lifting, lowering, engaging the soil, and holding, protect the circuit from over pressure by releasing the oil to the tank (1).
The two pilot operated check valves (21) effects the unloading of the pump, that is, the oil is returning to the tank (1) when the mail! flow control valve (12) is in the neutral position (central position of the five positions) or in the lowering mode. It has been verified that the system only built up a low pressure (less than 10 bar) in such conditions, showing that the energy loss has been much reduced, in the absence of high backpressure, as in prior art circuits.
The following example is given by way of illustration of the present invention and
should not be construed to limit the scope of the present invention.
Example-1
1. The present invention is a hydraulic control circuit and its capability was tested by
being fitted on to a tractor and used in field condition. The system was tested in this manner and was found to be satisfactory.
2. The normally open differential pressure- sensing valve (16) maintained the lowering
speed of the implement irrespective of the load on the lifting arm at the hitch point. It was
found that the speed of lowering was not varying with the load variation at the
implement.
3. The other differential pressure sensing valve (17) which is normally closed,
maintained the lifting speed irrespective of the load variation at the hitch point and there
was no variation of speed with the change of the load.
These observations were noted during actual trials to show conclusively that the purpose of load compensation through this invention was achieved. It was found, in both the mode of lowering and lifting of load, the speed of movement was smooth and constant. The system was also found to be stable and almost free from any oscillation. The novelty of this invention resides in providing load compensation during handling of a load by an agricultural tractor, in a manner that during lowering or during lifting, the movement of the linkage-end (hitch point) maintains constant speed with the change of load and the movement is smooth and non-jerky. The requirement of high backpressure in the system for control purpose is also not there, making the system more energy efficient.
This has been achieved by the main inventive step of a directional control (dc) valve (12) having five position and six ports with built-in flow control facility at two ends of this valve. This dc valve (12) when incorporated with the components as shown in figure 2, 3

and 4, provides an integrated hydraulic system which solves the technical problen load compensation in an energy efficient manner in the case of mobile machinery, like an agricultural tractor. The main advantages of the present invention are:
1. Handling of the load/change of load by the implement of a tractor/mobile unit, in a
load compensated mode, keeping the movement of the implement, non-jerky arid
smooth, in constant speed.
2. For unloading the oil to the tank and for the ..-ontrol requirement, :naintaining of high
back pressure has been deleted making this hydraulic circuit more energy efficient.
3. There is no requirement of changing the setting of any response valve with the change
of load, making this system, automatic, if required.
4. The operation of the relief valves are made limited and effective only for sudden-
safety, this reduces the possibility of bulk pressure loss through such valves.

We claim,
1. A hydraulic system for load compensated control of agricultural implements hitched to a tractor, which comprises a prime mover (20) such as a motor/engine connected to
and having a multi - branch delivery line, one branch of
drive a pump (19) fitted with an oil tank (1) at its suction end/the delivery line of the pump (19) connects the tank (1) via a relief valve (18), a second branch of the delivery line from the pump (19) also connects the tank (1) via a pair of check valves (21), a third branch of the delivery line from the said pump (19) connects to a multi-port direction control (dc) valve (12) whose ports (12a) and (12c) are connected directly to the tank (1) and port (12b) is connected to the tank (I) via a normally closed differential pressure sensing valve (17), port (12e) of the dc valve (12) provides a pilot pressure connection to the said check valves (21), port (12f) of the dc valve (12) connects an actuator (14) via a check valve (15) and .' . port (12d) of the dc valve (12) is connected to the line inter-connecting the check valve (15) and the actuator (14) via a normally open differential pressure sensing valve ((16) connected to the tank (1), the said actuator (14) is connected with the said tank (1) via a relief valve (13), the said dc valve (12) is provided with a spool actuation lever (2c) capable
of providing connection with the hand mode or auto mode leverage.

2. A hydraulic systen as claimed in claim 1, wherein the direction control valve (12) is
a live control position six connection port spool type direction control valve having in-built flow control facility at its two ends.
3. A hydraulic systemftts claimed in claim1-2, wherein, Ihc pilot pressure connection
of port (12e) of dc Valve (12) is capable of unloading oil to the tank (1), without
activating relief valves (13, 18)..
4. A hydraulic system|\as claimed in claim 1-3 3, wherein, the differential pressure
sensing valves (16) and (17) are capable of proportionate activation to pass/block oil
to the hydraulic system to provide pressing condition such that there is low hack pressure.
5. A hydraulic system for load compensated control of agricultural implements hitched to a tractor, substantially as herein described with reference to the example and figures 2 to 4 of the drawings accompanying this specification.

Documents:

506-del-2002-abstract.pdf

506-del-2002-claims.pdf

506-del-2002-correspondence-others.pdf

506-del-2002-correspondence-po.pdf

506-del-2002-dawings.pdf

506-del-2002-description (complete).pdf

506-del-2002-form-1.pdf

506-del-2002-form-18.pdf

506-del-2002-form-2.pdf

506-del-2002-form-3.pdf

« Previous Patent

Next Patent »

Patent Number

231646

Indian Patent Application Number

506/DEL/2002

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

07-Mar-2009

Date of Filing

30-Apr-2002

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	MIHIR KUMAR BANERJEE	CMERI, DURGAPUR, WB, INDIA. PIN-713209
2	ARUP KUMAR NANDI	CMERI, DURGAPUR, WB, INDIA. PIN-713209
3	BIBHUTI BHUSAN GHOSH	CMERI, DURGAPUR, WB, INDIA. PIN-713209

PCT International Classification Number

F15B 011/05

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA