FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
A DRAFT SENSING, SELECTING AND INDICATING SYSTEM FOR OFF-ROAD VEHICLE SUCH AS TRACTOR
2. APPLICANT(S)
MAHINDRA & MAHINDRA LTD.
GATEWAY BUILDING, APOLLO BUNDER, MUMBAI - 400001, MAHARASHTRA, INDIAN.
The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the Invention
The present invention relates to draft sensing and indicating system for off-road vehicles such as tractors.
Background of the Invention
Farm machineries such as tractor and vehicles are conventionally provided with three point linkage mechanism to couple earth-working implements. This mechanism is disposed in the rear end of the tractor and is further linked to the hydraulic power lifting mechanism. Thus, the power produced by tractor is utilized to overcome traction and take care of the forces acting on the earth working implement in direction opposite to the travel of the tractor caused due to its insertion in soil. This resistance or pull experienced by the tractor due to the opposite forces is conventionally known as draft.
During operation in the field there is a probability that the implement encounters obstructions such as stone, rocks, hard soil. In such a situation the implement gets stuck up, that is the draft / opposite force increases to such an extent that the power produced by the tractor engine is insufficient to overcome this draft. Further, it may damage the implement. The draft or the pull of the implement varies due to varying depth of soil due to ground undulation; weight transfer and/or wheel slip etc. Hence, it is necessary to control the implement so as to avoid variations in depth (its insertion in soil) thereby avoiding damage to the implement and achieve consistent productivity.
To control the implement position it is first necessary to sense the draft force. Conventionally, a draft responsive unit is installed between the implement and hydraulic actuation system of the tractor. Setting of

draft is done manually by operators depending on their experience with respect to soil conditions, implement used and operation performed. Review of the prior art reveals following drawbacks in the systems disclosed:
√ Lack of provision to sense the draft accurately obviating the use
of mechanical linkages √ Lack of system to transmit the sensed draft signal electronically
and provide corrective response to the same from hydraulic unit
to adjust the top link position √ Lack of integration of the draft sensing means, draft indicator,
draft setting and top link actuation mechanism to achieve best
draft setting of the implement √ Lack of provision for draft setting selection √ Lack of visual indication to operator for selecting desired / best
draft setting √ Lack of flexibility of selecting draft setting from range of draft
settings
There is need to provide a system to accurately sense draft, select and indicate best draft to the operator with the aid of tailored controller yet offer flexibility to select drafts from a wide range obviating mechanical linkages for draft sensing.
Summary of the Invention
The main object of the invention is to provide a system to accurately sense draft. Further object of the invention is to set, select and indicate draft to the operator.

Yet another object of the invention is to integrate draft sensing mechanism with electronic based controller.
Yet another object of the invention is to provide facility to indicate and set best / appropriate draft.
Yet another object of the invention is to provide a visual indication to operator for selecting best draft setting.
Another object of the invention is to increase the range/capability of hydraulic draft sensing system.
Yet another object of the invention is to provide a draft sensing means to restrict undesirable deflection of spring member thereby to increase reliability of spring member as well as of hydraulic power lift system.
Yet another object of the invention is to provide a means to assistthe operator in selecting desired draft from a vast range of draft settings.
Yet another object of the invention is to obviate use of mechanical linkages for sensing the draft.
Thus in accordance with the invention the system comprising draft sensing assembly, best draft setting system comprising a control lever assembly integrated with draft setting potentiometer, a controller, valve block assembly, power train wherein,
the draft sensing assembly comprises of leaf spring, bell crank, bell crank mounting bolts, base plate mounting bolts, base plate,

adjustment bolt, linkage assembly coupled with draft sensing potentiometer wherein,
the bell crank comprises of a two substantially flat member disposed substantially in parallel with each other wherein one of the end portions of the said flat portions is joined with another substantially flat member wherein leaf spring mounting provision is fitted on the said flat portion on the surface opposite to the one on which the said flat member are joined, a cutout portion is adapted to be fitted below the said mounting provision on the said flat member are provided with one or plurality of top link mounting holes on the surface, stud is mounted on the said base plate adapted to be fitted in the said slot / cut out so as to restrain rotatable movement of the bell crank, the surface of the one of the said the flat members is operably connected to the draft sensing pot via dc linkage that comprises of at feast two link members rotatably coupled with each other wherein length of one of the link members is greater than the other, the other link member is adapted to be coupled with the second potentiometer that is configured with the said controller wherein,
one of the ends of the said leaf spring is adapted to be restrained on the said base plate and the other end is bolted on the mounting provision of the said bell crank wherein,
the said valve block assembly comprises of a draft control solenoid valve, position control solenoid valve adapted to be mounted on the valve block that is provided with interconnected passages connected to hydraulic components such as relief valve, isolating valve, lowering control valve required for functioning of hydraulic controls wherein,

the said solenoid valves are hydraulically connected to the power train
that comprises of a cylinder, rocker arm, rockshaft and lift arm wherein
the said cylinder is connected with valve block at lifting port and
lowering port,
wherein upon receiving signal from the said controller to draft control
solenoid, the hydraulic flow is diverted from valve block to lifting or
lowering port as required wherein,
the said a control lever assembly comprises of a control lever
comprising top end that is ergonomically profiled to hold the lever by
the operator wherein,
the said top end is provided with visual indicators, the bottom end of the lever is adapted to be pivotally fitted with substantially flat angle plate via mounting block, the potentiometer is mounted on the said plate wherein,
the draft setting potentiometer is calibrated to sense angular movement of the said lever around the said bottom end of the lever actuated by operator for draft sensing wherein,
the said potentiometer is configured with a microprocessor based controller that receives signal from the draft sensing means process the same to compare it with the signal received from the said potentiometer of the control lever and sends the signal to the said control lever to indicate the draft selection / setting wherein,
the implement of the off-road vehicle such as tractor is removably coupled to hydraulic lift unit through three point linkages (lower links and top link) wherein top link is mounted on the said top link mounting holes of the bell crank wherein,

upon encountering obstruction in the field, the compressive load is transferred to top link and the forces are transferred as follows to sense the draft:
√ The force due to the top link tends to push the bell crank upwards against leaf spring force;
√ It results resulting in rotation of the said bell crank against the leaf spring force;
√ this angular travel is further amplified by dc linkage and same is sensed by draft sensing potentiometer;
√ the signal from the potentiometer is sent to the controller;
√ the values of the draft sensing pot with draft setting pot are compared in the said controller, accordingly signal is sent to the said draft control solenoid to divert the flow through valve body to lifting or lowering port, thus causing the cylinder to operate and lift or lower three point linkage and implement;
√ the implement is lifted if draft force is higher than that set by the operator and implement will lower if draft force is lower than that set by the operator thereby providing a system to accurately sense draft, select and indicate best draft to the operator with the aid of tailored controller.
Description of the Invention
Features and advantages of this invention will become apparent in the
following detailed description and the preferred embodiments with reference to the accompanying drawings.
Figure 1 Schematic of the System (Sheet 1) Figure 2 Schematic of the Bell Crank (Sheet 2)

Figure 3 Schematic of the potentiometer assembly (Sheet 2) Figure 4Schematic of the best draft indicating system (Sheet 3)
As illustrated in Figure 1, the system comprises of draft sensing assembly 30, best draft setting system comprising a control lever assembly integrated with draft setting potentiometer 17, a controller 2, valve block assembly 3 and power train 5.
The draft sensing assembly 30 comprises of leaf spring 6, bell crank 7, bell crank mounting bolts 8, base plate mounting bolts 9, base plate 10, adjustment bolt 11, linkage assembly 15 coupled with draft sensing potentiometer 14.
As illustrated in Figure 2, the bell crank comprises of a two substantially flat member 31 & 32 disposed substantially in parallel with each other wherein one of the end portions of the said flat portions is joined with another substantially fiat member 33. The said leaf spring mounting provision 34 is fitted on the said flat portion 33 on the surface opposite to the one on which the said flat member 31 & 32 are joined, a cutout portion is adapted to be fitted below the said mounting provision 34, on the said flat member 31 & 32 are provided with one or plurality of top link mounting through holes 13 on the surfaces. A stud 11 is mounted on the said base plate 10 that is adapted to be fitted in the said slot / cut out so as to restrain rotatable movement of the said bell crank. The surface of the one of the said flat members 31 or 32 is operably connected to the draft sensing potentiometer 14 via linkage 15. This linkage comprises of at least two link members 35 & 36 rotatably coupled with each other wherein length of one of the link members is greater than the other. The other link member is adapted

to be coupled with the draft sensing potentiometer 14 that is configured with the said controller 2.
One of the ends of the said leaf spring 6 is adapted to be restrained on the said base plate 10 and the other end is bolted on the mounting provision 34 of the said bell crank 7. The said valve block assembly 3 comprises of a draft control solenoid va\ve 18, position control solenoid valve 19 adapted to be mounted on the valve block 20 that is provided with interconnected passages connected to hydraulic components such as relief valve, isolating valve, lowering control valve required for functioning of hydraulic controls . The said solenoid valves 18 & 19 are hydraulically connected to the power train 5 that comprises of a cylinder 22, rocker arm 23, rocker shaft 24 and lift arm 25. The cylinder 22 is connected with valve block 3 at lifting port 28 and lowering port 27. During operation, upon receiving signal from the said controller 2 to draft control solenoid 18 the hydraulic flow is diverted from valve block 20 to lifting or lowering port 27 or 28 as required.
The control lever assembly is illustrated in Figure 4. It comprises of a control lever 4 comprising top end that is ergonomically profiled to hold the lever by the operator. The said top end is provided with visual indicators 37, the bottom end of the lever is adapted to be pivotally fitted with substantially flat angle plate 38 via mounting block. The draft setting potentiometer 17 is mounted on the said plate 38. The draft setting potentiometer 17 is calibrated to sense angular movement of the said lever around the said bottom end of the lever actuated by operator. The said potentiometer 17 is configured with a microprocessor based controller 2 that receives signal from the

potentiometers 17 and 14 to process and compare the same for actuating the solenoids.
The implement (not shown) of the off-road vehicle such as tractor is removably coupled to hydraulic lift unit through three point linkages (lower links and top link). The top link is mounted on the said top link mounting holes 13 of the bell crank 7.
During operation upon encountering obstruction in the field, the compressive load is transferred to top link and the forces are transferred as follows to sense the draft:
√ The force due to the top link tends to push the bell crank 7 upwards against leaf spring 6 force;
√ it results in rotation of the said bell crank 7 against the leaf spring 6 force;
√ this angular travel is further amplified by linkage 15 and same is sensed by draft sensing potentiometer 14;
√ the signal from the potentiometer is sent to the controller 2;
√ the values of the draft sensing pot 14 with draft setting pot 17 are compared in the said controller, accordingly signal is sent to the said draft control solenoid 18 to divert the flow through valve body 20 to lifting or lowering port 27 or 28, thus causing the cylinder 22 to operate and lift or lower three point linkage and implement;
√ the implement is lifted if draft force is higher than that set by the operator and implement will lower if draft force is lower than that set by the operator thereby providing a system to accurately sense draft, select and indicate best draft to the operator with the aid of tailored controller.

It is evident from the present invention that the synergistic combination and configuration of the said draft sensing assembly, draft setting system and valve block with the control wherein the draft sensing and draft setting potentiometer governed by the microprocessor based controller work in tandem to provide signal to the solenoid so as to diver hydraulic flow to the cylinder to lift or lower the implement facilitates accurate sensing of the draft and enables the operator to set and select draft from the wide range resulting in obviating problems associated with damage of implement in varied field conditions and achieving consistent productivity.

We Claim:
1. A draft sensing and indicating system comprising draft sensing
assembly, best draft setting system comprising a control lever
assembly integrated with draft setting potentiometer (17), valve
block assembly (3), power train (5) configured with controller (2)
wherein,
the draft sensing assembly (30) comprises of leaf spring(6), bell crank (7), bell crank mounting bolts (8), base plate mounting bolts (9), base plate (10), adjustment bolt (11), linkage assembly (15) coupled with draft sensing potentiometer (14).
2. A draft sensing and indicating system as claimed in claim 1
comprising draft sensing assembly (30), best draft setting system
comprising a control lever assembly integrated with draft setting
potentiometer (17), a controller (2), valve block assembly (3),
power train (5) wherein,
the draft sensing assembly (30) comprises of leaf spring(6), bell crank(7), bell crank mounting bolts (8), base plate mounting bolts (9), base plate (10), adjustment bolt (11), linkage assembly (15) coupled with draft sensing potentiometer (14) wherein,
the bell crank comprises of a two substantially flat members (31 & 32) disposed substantially in parallel with each other wherein one of the end portions of the said flat portions is joined with another substantially flat member (33) wherein leaf spring

mounting provision (34) is fitted on the said flat portion (33) on the surface opposite to the one on which the said flat members are joined, a cutout portion is adapted to be fitted below the said mounting provision (34);
the said flat members (31 & 32) are provided with one or plurality of top link mounting holes (13) on the surface, stud (11) is mounted on the said base plate (10) adapted to be fitted in the said slot / cut out so as to restrain rotatable movement of the bell crank, the surface of the one of the said the flat members (31 or 32) is operably connected to the draft sensing potentiometer (14) via dc linkage (15) that comprises of at least two link members (35 & 36) rotatably coupled with each other wherein length of one of the link members is greater than the other, the other link member is adapted to be coupled with the second potentiometer (14) that is configured with the said controller (2) wherein,
one of the ends of the said leaf spring (6) is adapted to be restrained on the said base plate (10) and the other end is bolted on the mounting provision (34) of the said bell crank (7) wherein,
the said valve block assembly (3) comprises of a draft control solenoid valve (18), position control solenoid valve (19) adapted to be mounted on the valve block (20) that is provided with interconnected passages connected to hydraulic components such as relief valve, isolating valve, lowering control valve required for functioning of hydraulic controls wherein,
the said solenoid valves (18 & 19) are hydraulically connected to the power train (5) that comprises of a cylinder (22), rocker arm

(23), rockshaft (24) and lift arm (25) wherein the said cylinder (22) is connected with valve block (3) at lifting port (28) and lowering port (27) wherein,
upon receiving signal from the said controller to draft control solenoid (18), the hydraulic flow is diverted from valve block (20) to lifting or lowering port (17 or 28) as required.
3. A draft sensing and indicating system as claimed in claim 1 wherein the said control lever assembly comprises of a control lever (4) comprising top end that is ergonomically profiled to hold the lever by the operator wherein,
the said top end is provided with visual indicators (37), the bottom end of the lever is adapted to be pivotally fitted with substantially flat angle plate (38) via mounting block, the potentiometer (17) is mounted on the said plate wherein,
the draft setting potentiometer is calibrated to sense angular movement of the said lever around the said bottom end of the lever actuated by operator for draft sensing wherein,
the said potentiometer is configured with the said controller (2) that receives signal from potentiometers (17) and (14) to compare it with the signal received from the said potentiometer of the control lever and sends the signal to the said control lever to indicate the draft selection / setting wherein,
the implement of the off-road vehicle such as tractor is removably coupled to hydraulic lift unit through three point

linkages (lower links and top link) wherein top link is mounted on the said top link mounting holes (13) of the bell crank (7).
4. A draft sensing and indicating system as claimed in claims 1, 2
wherein the said valve block assembly (3) comprises of a draft
control solenoid valve (18), position control solenoid valve (19)
adapted to be mounted on the valve block (20) that is provided
with interconnected passages connected to hydraulic components
such as relief valve, isolating valve, lowering control valve
required for functioning of hydraulic controls wherein,
the said solenoid valves (18 & 19) are hydraulically connected to the power train (5) that comprises of a cylinder (22), rocker arm (23), rockshaft (24) and lift arm (25) wherein the said cylinder (22) is connected with valve block (3) at lifting port (28) and lowering port (27) wherein,
upon receiving signal from the said controller to draft control solenoid (18), the hydraulic flow is diverted from valve block (20) to lifting or lowering port (17 or 28) as required.
5. A draft sensing and indicating system as claimed in claims 1, 3
wherein the draft sensing assembly (30) comprises of leaf
spring(6), bell crank (7), bell crank mounting bolts (8), base
plate mounting bolts(9), base plate(lO), adjustment bolt (11),
linkage assembly (15) coupled with draft sensing potentiometer
(14) wherein,
the bell crank comprises of a two substantially flat members (31 & 32) disposed substantially in parallel with each other wherein

one of the end portions of the said flat portions is joined with another substantially flat member (33) wherein leaf spring mounting provision (34) is fitted on the said flat portion (33) on the surface opposite to the one on which the said flat members are joined, a cutout portion is adapted to be fitted below the said mounting provision (34);
the said flat members (31 & 32) are provided with one or plurality of top link mounting holes (13) on the surface, stud (11) is mounted on the said base plate (10) adapted to be fitted in the said slot / cut out so as to restrain rotatable movement of the bell crank, the surface of the one of the said the flat members (31 or 32) is operably connected to the draft sensing potentiometer (14) via dc linkage (15) that comprises of at least two link members (35 & 36) rotatably coupled with each other wherein length of one of the link members is greater than the other, the other link member is adapted to be coupled with the second potentiometer (14) that is configured with the said controller (2) wherein,
one of the ends of the said leaf spring (6) is adapted to be restrained on the said base plate (10) and the other end is bolted on the mounting provision (34) of the said bell crank (7).
6. A draft sensing and indicating system as claimed in claims 1-4 wherein the system operates upon encountering obstruction in the field wherein the compressive load is transferred to top link and the forces are transferred to sense the draft wherein,
√ the force due to the top link tends to push the bell crank (7) upwards against leaf spring (6) force;

√ it results resulting in rotation of the said bell crank (7) against the leaf spring (6) force,
√ this angular travel is further amplified by dc linkage (15) and same is sensed by draft sensing potentiometer (14);
√ the signal from the potentiometer is sent to the controller (2);
√ the values of the draft sensing pot (14) with draft setting pot (17) are compared in the said controller, accordingly signal is sent to the said draft control solenoid (18) to divert the flow through valve body (20) to lifting or lowering port (27 or 28), thus causing the cylinder (22) to operate and lift or lower three point linkage and implement;
√ the implement is lifted if draft force is higher than that set by the operator and implement will lower if draft force is lower than that set by the operator thereby providing a system to accurately sense draft, select and indicate best draft to the operator with the aid of tailored controller.
7. A draft sensing and indicating system wherein the valve block assembly (3) comprises of a draft control solenoid valve (18), position control solenoid valve (19) adapted to be mounted on the valve block (20) that is provided with interconnected passages connected to hydraulic components such as relief valve, isolating valve, lowering control valve required for functioning of hydraulic controls wherein,
the said solenoid valves (18 & 19) are hydraulicaliy connected to the power train (5) that comprises of a cylinder (22), rocker arm (23), rockshaft (24) and lift arm (25) wherein the said cylinder (22) is connected with valve block (3) at lifting port (28) and lowering port (27) wherein,

upon receiving signal from the said controller to draft control solenoid (18), the hydraulic flow is diverted from valve block (20) to lifting or lowering port (17 or 28) as required.