Title of Invention

"IMPROVED HYDRAULIC SYSTEM FOR AGRICULTUAL TRACTORS"

Abstract

The present invention provides tor improved hydraulic system tor agricultural tractor. A tractor finds wide application in agriculture, utilizing various implements to work on the soil. It is necessary to control the implements to obtain desired ettect on the soil while the tractor is pulling the implement and for that a complete onboard hydraulic system is provided on the tractor, driven by the engine. The hydraulic system is designed to work in either of the two modes . 1. Position Control; or 2. Draft control It is possible to run the hydraulic system in the combined mode also. The present invention provides for improvements in the three areas namely; 1. Position Control System; 2. Draft Control System; and 3. Hydraulic Control Valve. The improvements provided by the present invention result in greater efficiency, better control, compact and rigid system, smooth & reliable spool movement and fuel savings. PRIOR ART In the presently known and conventional tractor hydraulic systems, a piston cylinder assembly generates the hydraulic thrust, which is transferred to the rockshaft through a connecting rod and an arm rigidly mounted on the rockshaft. The hydraulic cylinder is thus capable of turning the rockshaft through a preset angle. Two lift arms rigidly mounted on the rockshaft lift the implement with the above rotation. For position control in the existing hydraulic systems a lever is mounted on a pin joint provided at the upper end in front of the rockshaft. This lever carries a roller in the middle. A cam provided on the ram arm actuates the roller and effects the swinging of the lever. The lower end of the lever is connected to the middle of the position actuator, which is carried by the position setting lever pin joined to the upper end. The lower end of this actuator slides through a slot provided in the stem of the control valve.

Full Text

For draft control a spring-loaded spindle located inside a rigid tube at the rear of the tractor, is provided to sense the draft load. The forward end of the spindle is given a flat shape that bears on the end of the sensor pin. This sensor pin swings the draft link through a pin joint in the other end. The draft link is connected to the draft actuator by means of the draft coupler.. The draft coupler is provided with a slot at the actuator end. Both, the position and the draft couplers are fitted with the springs that enable the couplers to retract when the load exceeds the force set to the spring. The draft actuator is also mounted in a similar fashion as position actuator, but connected to the draft setting lever. In the conventional and presently known hydraulic systems the hydraulic circuit is housed in two separate units. The control and the unloading valve are located in a block mounted inside the tractor. The check valve and the response valve are housed in another body mounted over the rear cover of the tractor. The response valve in the presently known hydraulic systems is of rotary type. For taking hydraulic tap off for external cylinders, the lift arm movement has to be physically restricted. The known and conventional hydraulic system has its limitations which are addressed by the present invention. SUMMARY OF THE INVENTION The present invention, therefore, addresses the limitations of the presently known and conventional hydraulic systems and provides for improved hydraulic system comprising: A. POSITION CONTROL SYSTEM B. DRAFT CONTROL SYSTEM C HYDRAULIC CONTROL VALVE POSITION CONTROL SYSTEM In the present invention the position of lever in the position circuit system has been improved. The position lever has been placed behind the rock shaft which has resulted in bringing the control valve actuator and ram cylinder closer to rock shaft thereby making the system compact and hence rigid Additional support is provided in the form of a link hinged with the fixed housing which relieves the load from the control valve spool and thereby provides more smooth and reliable spool movement. The improvements provided by the present invention in Position Control System are particularly described and illustrated in Figure 1 which works as follows : The Piston assembly (2) is fitted in the Cylinder (1), which is fixed to the housing mounted at the rear of the tractor. Connecting rod (8) transmits the hydraulics thrust to the Ram Arm (9). The Lift Arm (17) is locked with the ram arm as both these are mounted the Rock Shaft (15). The Position link (11) is pivoted at the upper end A Roller (12) is provided at the upper end of the position oink. This roller is in such a position that the integral cam (16) provided on the ram arm may operate it. The position link is connected by a pin joint to the lower end of the Position Coupler (10). The position coupler is a telescopic assembly with a compression Spring (18) fitted between the two sliding parts. The upper end of the position coupler is pin jointed to the Position Actuator (7). The position actuator is supported on the Support (6) by means of a pin joint at the lower end. The support is suspended from another pin joint at the upper joint from the fixed housing. The upper end of the position actuator is connected to the Position Setting Lever (14) by means of a Short Link (13). A pin joints at the both ends connect this short link. The lower oink of the position actuator as well as its supports are connected to a Block (5) by means of the same pin joint. The block is designed to push the stem of the Control Valve (3) against a return compression Spring (4). The integral cam provided on the ram arm displaces the roller carried on the upper end of the position link in such a way that the roller is pushed away from the center of the rockshaft as the lift arm comes down. This swings the link around its pivot in the middle part. The swing of the Link affects a corresponding swing m the Actuator as the Coupler transmits the motion. However, the setting Lever is capable of swinging the Actuator through the desired angle as determined by the setting angle. In the position shown, the roller on the link is already in contact with the cam and the coupler cannot transfer the motion of the actuator to the link. Therefore, the pin joint between the Actuator and the coupler acts as the pivot for the actuator. When the Actuator swings around this pivot, it moves the block, which pushes the stemp of the valve towards "raise" position against the return spring. Therefore, the implement is raised by the system. When the implement is raised, the ram arm with the cam turns and tends to create a gap between the roller and the cam. However, the return spring then pushes the lower end of the actuator, thereby maintaining the contact between the roller and the cam through the coupler, which transfers the motion. The motion stops only when the control valve comes to neutral. The system thus, provides for maintaining the constant implement position as set by the setting lever. DRAFT CONTROL SYSTEM In the present invention the position of the draft link in the draft control system has been shifted behind the rock shaft and thus, making it compact and rigid as also in the position control system. A novel feature of a roller has been added on the draft link. This added roller makes contact with the striker of the draft sensor and transmits the displacement of the draft sensor in a positive manner, unaffected by the accuracy of the alignment. As in the position control system additional support link has also been provided to the draft actuator hinged to the fixed housing. Figure 2 particularly describes and illustrates the improvements in the Draft Control System which works as follows: The Piston Assembly (2) is fitted in the Cylinder (1), which is fixed to the housing mounted at the rear of the tractor. Connecting Rod (8) transmits the hydraulic thrust to the Ram Arm (9). The Lift Arm (17) is locked with the ram arm as both are mounted on the Rock Shaft (15). The draft load sensing system consists of Draft Spring (21) mounted inside Draft Housing Tube (16). The Draft Spindle (23) passes through the spring and carries the Striker (24) in front of the housing tube. This striker is locked by Nut (19). The Draft Link (11) is pivoted at the upper end. A Roller (12) is provided at the lower part of the draft link. This roller is in such a position that the striker may operate it. The draft link is connected by a pin joint to the lower end of the Draft Coupler (10). The draft coupler is a telescopic assembly with a compression Spring (18) fitted between the two sliding parts. The upper end of the draft coupler is provided with a slot wherein the pin fitted to Draft Actuator (7) can slide. The draft actuator is supported on the Support (6) by means of a pin joint at the lower end The support is suspended from another pin joint at the upper joint from the fixed housing. The upper end of the draft actuator is connected to the Draft Setting Lever (14) by means of a Short Link (13). This short link is connected by pin joint at the both ends. The lower link of the draft actuator as well as its support is connected to a Block (5) by means of the same pin joint. The block is designed to push the stem of the Control Varve (3) against a return compression Spring (4). The ram arm carries an integral Finger (22). The draft coupler is also fitted with an integral Pin (20). The draft load acting on the end of the Spindle compresses the draft spring in a proportionate manner. This results in a displacement of the Spindle along with the Striker and the Nut. The Striker swings the Link by thrusting on the Roller, which is free to turn on its supporting pin. The swing of the Link affects a similar swing in the Actuator as the Coupler transmits the motion. However, the setting Lever is capable of swinging the Actuator through the desired angle as determined by the setting angle. This creates the desired displacement of the pin of the Actuator in the slot of the Coupler. Thus the motion is transmitted from the Link to the Actuator only after the slot touches the pin. Therefore, the Actuator starts swinging only after the draft load as set by the setting lever is attained and the contact between the pin and the slots takes place. When the Actuator swings it moves the stem of the valve towards "raise" position against the return spring. Therefore, the implement is raised by the system when the draft load is equal to the set value. When the implement is raised the draft load begins to decrease. The system is provides to maintain the constant draft load. When the valve is in the "raise" position the Piston moves outward inside the Cylinder. The motion of the piston is transmitted through the connecting rod to the ram arm and the lift arm. However, as the outermost position of the piston is reached the finger on the ram arm actuates the pin on the coupler. This compresses the spring in the coupler and moves the slot towards the rear of the tractor. Thus, the slot loses contact with the pin of the actuator and a gap is created behind the pin. Under this condition the return spring of the valve is able to push the block and the stem back to the neutral position. This arrests the "raise" motion of the system and the motion of the piston stops at the outermost position. HYDRAULIC CONTROL VALVE The hydraulic control valve is normally in two or more separate blocks. In the present invention a composite block has been used which houses all the control valves. This avoids pipe connections and the resulting leakages, and thus ensures positive response of the hydraulic system. This composite valve block is mounted on the face of the cylinder by means of a number of screws. The oil flow to the cylinder passes directly from the composite valve block through a port protected by a face o-ring. The response valve is a spring-loaded ball and seat type of valve. The oil from the cylinder enters the ball end of the valve and closes the valve in leak proof manner. In order to affect the desired flow, the ball is displaced off the seat by a spool, which is sealed with o-rings. The movement of the spool is adjusted by means of a screw fitted with a hand knob, provided on the wall of the rear cover. The present invention also incorporated a facility to shut oil flow into the cylinder. For this purpose, a spool and a screw similar to the design described above, used for the response valve, is incorporated to close the check valve. When this valve is closed, the system may be utilized for operating an external hydraulic cylinder similar to the one used in the system. The position-setting lever may be used for operations of external cylinders. We claim I. An improved hydraulic system comprising improved position control system; draft control system and improved composite hydraulic control valves. 2 An improved hydraulic system comprising improved position control system as claimed in claim 1 wherein position link is located behind the rock shaft. 3 An improved hydraulic system comprising improved position control system as claimed in claim 1 wherein the actuator is connected to the position setting lever by a pin jointed at each end; 4. An improved hydraulic system comprising improved position control system as claimed in claim 1 wherein the actuator is supported on a supporting member by means of a pin joint. 5 An improved hydraulic system comprising improved position control system as claimed in claim 1 wherein the member supporting the actuator is connected by a pin joint to the fixed housing of the system. 6. An improved hydraulic system comprising improved draft control system as claimed in claim 1 wherein the displacement of the sensor spring is transmitted to the link by means of the free running roller. 7. An improved hydraulic system comprising improved draft control system as claimed in claim 1 wherein a stopping mechanism for the piston is actuated by a finger on the ram arm. 8. An improved hydraulic system comprising improved draft control system as claimed in claim 1 wherein the draft link is positioned between the rock shaft and the sensor spring assembly. 9. An improved hydraulic system comprising improved draft control system as claimed in claim 1 wherein the actuator is connected to the draft setting lever by a pin jointed at each end. 10. An improved hydraulic system comprising improved draft control system as claimed in claim 1 wherein the actuator is supported on a supporting member by means of a pin point. II. An improved hydraulic system comprising improved draft control system as claimed in claim 1 wherein the member supporting the actuator is connected by a pin joint to the fixed housing of the system.12.An improved hydraulic system comprising a composite valve block as claimed in claim 1 wherein all the valves needed for the tractor hydraulic system are housed 13. An improved hydraulic system comprising a composite valve block as claimed in claim 1 which is mounted on the face of the cylinder and provided with a matching port for direct passage of oil from the valve to the cylinder. 14 An improved hydraulic system comprising a composite valve block as claimed in claim 1 with a response valve of spring loaded ball and seat type where the throttling eflfect is created by the movement of the ball effected by a spool and a hand operated screw. 15. An improved hydraulic system comprising a composite valve block as claimed in claim 1 with a check valve of spring loaded ball and seat type where the passage can be shut by forcing the ball on to the valve seat by means of a spool and a hand operated screw, thereby allowing the operation of external cylinders.

Documents:

33-del-2002-abstract.pdf

33-del-2002-claims.pdf

33-del-2002-correspondence-others.pdf

33-del-2002-correspondence-po.pdf

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

33-del-2002-drawings.pdf

33-del-2002-form-2.pdf

33-del-2002-form-3.pdf

33-del-2002-gpa.pdf