FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Electromechanical hydraulic system for operating the 3-point linkage of a work vehicle
APPLICANTS
Mahindra & Mahindra Ltd., Gateway Building, Apollo Bunder, Mumbai 400001, 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
This invention relates to an electromechanical hydraulic system for operating the 3-point linkage of a work vehicle.
BACKGROUND OF INVENTION
Work vehicles or off-road vehicles are used to carry out heavy work in adverse terrains and working conditions and can be broadly classified into two categories namely heavy duty work vehicles such as agricultural tractors or earth movers used for large scale operations and light duty work vehicles such as compact tractors used for small scale operations. Work vehicles working in farm land are generally provided with a 3-point linkage/hitch at the rear end thereof for attaching various earth-working implements thereto. The earth-working implements enable the work vehicles to carry out the various field operations. The 3-point linkage and earth-working implements are operated by a hydraulic system comprising a hydraulic cylinder controlled by a hydraulic valve. The hydraulic cylinder comprises a piston reciprocating in the cylinder and operatively coupled to a rotating shaft disposed perpendicular to the piston. A pair of lift arms are mounted to the rotating shaft spaced apart from each other and are connected to the 3-point linkage. The hydraulic valve comprises a linearly adjustable spool to control hydraulic flow in the cylinder side and piston side of the hydraulic cylinder and thereby the stroke of the piston and the up and down movement of the lift arms and the 3-point linkage and earth working implements.

The hydraulic system also comprises a position control or adjustment mechanism for presetting the height and depth the 3-point linkage and the earth working implements can move up and down. Depending on the nature of the field work and field conditions such as ground contour or ground undulation or unevenness or soil conditions, the earth-working implements are preset to the height and depth they can move up and down by operating the position control mechanism by the operator or driver of the work vehicle. The position control mechanism comprises a position control lever located near the operator's seat and connected to the spool of the hydraulic valve through a mechanical linkage. The position control lever is operated by the operator to set or adjust the position of the spool and control the hydraulic flow into the cylinder so-as to limit the stroke of the piston and the up and down movements of the 3-point linkages and earth-working implements.
While operating on uneven fields or grounds and/or while encountering obstructions such as stones, rocks or hard soil on the operating fields or grounds, it is necessary to lift the 3-point linkage and earth-working implements instantly with the least delay in order to prevent damage to the implements, accidents or stalling of the vehicles. However, with the mechanical linkage, it is difficult to precisely preset and control the lifting and lowering movements of the 3-point linkage and earth-working implements. Because of the long response time of the mechanical linkage also, it is practically difficult to instantly lift the 3-point linkage and earth-moving implements. Furthermore, it is also cumbersome and difficult manually to operate the spool with the position control lever and mechanical linkage. As a result of all this, the position control mechanism is not smooth to operate and user friendly. The mechanical linkage also requires periodical servicing and maintenance. Cost of the mechanical linkage is high and reliability of the mechanical linkage is poor. There is thus need for hydraulic systems for operating the 3-

point linkage and associated earth working implements of work vehicles which can be precisely preset to control the lifting and lowering movements of the 3-point linkage and earth-working implements of work vehicles and can instantly lift and lower the 3-point linkage and earth working implements, which have increased response time, which require practically no servicing and maintenance and which are cost effective and reliable and smooth in operation and user friendly.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided an electromechanical hydraulic system (100) for operating the 3-point linkage of a work vehicle comprising a rotating shaft (116) horizontally rotatably mounted on a base (10) and having a pair of lift arms (102) mounted thereto spaced from each other and connected to the 3-point linkage, a hydraulic cylinder (128) mounted on the base and having a reciprocating piston (130) operatively coupled to the rotating shaft perpendicular thereto, a hydraulic valve (120) comprising a linearly adjustable spool (121) for controlling the hydraulic flow in the hydraulic cylinder and a position control mechanism (150) for controlling the up and down movements of the 3-point linkage and earth working implements, wherein the position control mechanism comprises a horizontally rotatably disposed lead screw (108) driven by a servo motor (106), a nut (110) linearly movably disposed over the lead screw in thread engagement therewith and a linear actuator rod (122) one end whereof is fixed to the nut and the other end whereof is adapted to abut the spool and a control panel (136) for controlling the operation of the servo motor and the linear movement of the nut and the linear actuator rod.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 of the accompanying drawings is a schematic isometric view of an electromechanical ' hydraulic system according to an embodiment of the invention without the control panel;
Fig 2 is a partial isometric view of the electromagnetic hydraulic system of Fig 1;
Fig 3 is an exploded view of the position control mechanism of the electromechanical hydraulic system of Figs 1 and 2; and
Fig 4 is a block diagram of the control panel of the position control mechanism of Fig 3.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
As illustrated in Figs 1 to 4 of the accompanying drawings, the electromechanical hydraulic system (mechatronics hydraulic system) 100 for operating the 3-point linkage (not shown) of a work vehicle (not shown) comprises a rotating shaft 116 horizontally rotatably mounted on base 10 and having a pair of lift arms 102 mounted thereto spaced from each other and connected to the 3-point linkage. 128 is a hydraulic cylinder mounted on the base and having a reciprocating piston 130 operatively coupled to the rotating shaft perpendicular thereto. The reciprocating movement of the piston in the hydraulic cylinder gives a rotary motion to the rotating shaft. As a result, the 3-point linkage and earth working implements (not shown) attached to the 3-point linkage move up and down along with the lift arms. 120 is a hydraulic valve comprising a linearly adjustable spool 121 for controlling the hydraulic flow in the hydraulic cylinder.

150 is a position control mechanism for controlling the up and down movements of the'3-point linkage and earth-working implements. The position control mechanism comprises a servomotor (reversible motor) 106 vertically disposed and mounted on a support 170 which in turn is mounted on a support plate 151. The support plate 151 is fixed to the base or integrally formed with the base. A lead screw 108 is horizontally rotatably disposed in a U-shaped slot 171 in an upright member 172 fixed on the support plate 151. One end of the lead screw is coupled to the motor shaft (not shown) through a coupling arrangement (not shown) so as to convert the rotary motion of the motor shaft in the vertical plane into rotary motion of the lead screw in the horizontal plane. The coupling arrangement is not illustrated and described in detail as it is well within the knowledge of a person skilled in the art and is not required to be illustrated to understand the invention,
A nut 110 is linearly movably disposed over the lead screw in thread engagement therewith through hole 173 in the nut. 122 is a linear actuator rod fixed to the nut at one end thereof and having a flange 152 at the other end thereof adapted to abut a corresponding flange 160 on the spool 121. 136 is a control panel for controlling the operation of the servo motor 106 and the linear movement of the nut 110 and the linear actuator rod 122. The control panel comprises a variable speed setting switch 134 connected to a DC supply 153 and an electronic control unit 154 connected to the DC supply and the variable speed setting switch and the servo motor 106. The control panel also comprises an angular sensor 112 mounted on an upright member 174 fixed on the support plate 151 and connected to the electronic control unit. The angular sensor comprises a spindle 175 extending through a hole 176 in the upright member 174 and through a hole 177 in upright member 178 fixed to the support plate. The spindle 175 is coupled to the distal end of the lead screw.

The variable speed setting switch 134 is located in the vehicle cabin (not shown) close to the operator of the work vehicle. In order to control the up and down movements of the 3-point linkage and the earth-working implements attached to the 3-point linkage, the operator has to simply select the position of the variable speed setting switch 134. The electronic control unit 154 senses the speed setting selected on the speed setting switch and controls the motor speed accordingly. Depending upon the speed of rotation of the motor, the lead screw rotates in the horizontal plane and the nut moves linearly forward and backward according to the speed and direction of rotation of the motor. As the nut moves linearly back and forth, the linear actuator rod 122 moves back and forth to adjust the position of the spool 121 and thereby the flow of hydraulic in the hydraulic cylinder 128. According to the flow of the hydraulic in the cylinder, the stroke of the piston 130 and up and down movements of the 3-point linkage and the earth-working implements are controlled. During rotation of the lead screw 108, the spindle 175 of the angular sensor 112 also rotates. As a result, the angular position of the lead screw and hence the angular position of the 3-point linkage and the earth-working implements is sensed and controlled by the electronic control unit 154.
According to the invention the position control lever and mechanical linkage have been eliminated and instead, the lifting and lowering movements of the 3-point linkage and earth working implements are precisely controlled electronically by sensing the angular position of the 3-point linkage and the earth-working implements and by controlling the operation of the motor and the position of the spool of the hydraulic valve. Being electronically operated, response time of the position control mechanism of the invention is very fast and the 3-point linkage and earth working implements are instantly lifted and lowered as and when required. As a result, the earth-working implements can be instantly lifted while operating on uneven fields or grounds or

encountering obstructions such as stones, rocks or hard soil thereby preventing damage to the implements, accidents or stalling of vehicles. Thus the operation of the 3-point linkage and earth-working implements is smoothly and precisely controlled. The position setting mechanism does not require any servicing and maintenance and is cost effective and reliable. Being electronically operated, the hydraulic system of the invention, is also easy to operate and is user friendly.

We Claim:
1. An electromechanical hydraulic system (100) for operating the 3-point linkage of a work vehicle comprising a rotating shaft (116) horizontally rotatably mounted on a base (10) and having a pair of lift arms (102) mounted thereto spaced from each other and connected to the 3-point linkage, a hydraulic cylinder (128) mounted on the base and having a reciprocating piston (130) operatively coupled to the rotating shaft perpendicular thereto, a hydraulic valve (120) comprising a linearly adjustable spool (121) for controlling the hydraulic flow in the hydraulic cylinder and a position control mechanism (150) for controlling the up and down movements of the 3-point linkage and earth working implements, wherein the position control mechanism comprises a horizontally rotatably disposed lead screw (108) driven by a servo motor (106), a nut (110) linearly movably disposed over the lead screw in thread engagement therewith and a linear actuator rod (122) one end whereof is fixed to the nut and the other end whereof is adapted to abut the spool and a control panel (136) for controlling the operation of the servo motor and the linear movement of the nut and the linear actuator rod.
2. The hydraulic system as claimed in claim 1, wherein the lead screw (108) is horizontally rotatably mounted on a support plate and the servo motor is vertically disposed and mounted on the support plate and the motor shaft is coupled to the lead screw through a coupling arrangement for converting rotary motion of the motor shaft in the vertical plane into rotary motion of the lead screw in the horizontal plane.
3. The hydraulic system as claimed in claim 1, or 2, wherein the linear actuator rod comprises a flange (152) at the other end thereof adapted to abut a corresponding flange (160) on the spool.

4. The hydraulic system as claimed in claim anyone of claims 1 to 3, wherein the control panel (136) comprises a variable speed setting switch (134) connected to a DC supply (153), an electronic control unit (154) connected to the DC supply and the variable speed setting switch and the servo motor and an angular sensor (112) connected to the electronic control unit and having a spindle (175) coupled to the distal end of the lead screw.