The present disclosure generally relates to electromechanical systems. More specifically, the present disclosure relates to an electro-mechanical system for raising or lowering a three-point linkage (TPL).
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Agricultural or industrial machinery generally operate with a three-point linkage (three-point hitch) which is used for attaching mounted implements. Typically, the three-point linkage is controlled by position and draft control levers for adjusting the position and draft of the implement respectively. Specifically, the draft control lever maintains a predetermined draft force on the three-point linkage and the position control lever maintains a predetermined height/depth of the three-point linkage. Raising and lowering of the implement is controlled through the three-point linkage by a hydraulic system which is controlled using the draft and position control levers.
During normal field operations of a machine, the draft and/or position levers are moved along its control sector to set required height and/or draft force of the implement. Currently, adjustable knobs are provided for maintaining/marking the pre-set position of the levers on the control sector so as to hold the implements at the pre-set condition. When the machine reaches the headland of the field, the operator is required to turn the machine. For safe turning of the machine, the operator lifts the implement above the ground using either of the levers. After taking turn, the operator brings the implement to the pre-set depth and/or draft by lowering the position or draft lever to its pre-set position marked by knob on the control sector. This mechanism requires the operator to repeat raising and lowering operation of the three-point linkage, by adjusting the draft or position

lever, each time he traverses the field and turns the machine at a headland. These operations are non-value-added activities in farm operation., These repeated operations become monotonous and also lead to operator fatigue. Further, during operation of the machine, the knob tends to loosen, which may cause changes in the pre-setting of the position and draft levers. In this scenario, the operator may either readjust the setting, which requires skill, experience and time or the operator may altogether avoid lifting of the implement during turning operation, which may prove hazardous for the operator and the machine.
There is, therefore, felt a need for a system for raising or lowering a three-point linkage that eliminates the above-mentioned drawbacks.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to provide an electro-mechanical system for raising or lowering a three-point linkage (TPL).
Another object of the present disclosure is to provide an electro-mechanical system for raising or lowering a TPL that facilitates easier headland turning for an operator.
Still another object of the present disclosure is to provide an electro-mechanical system for raising or lowering a TPL that reduces operator fatigue by reducing operating efforts.
Still another object of the present disclosure is to provide an electro-mechanical system for raising or lowering a TPL that reduces the time required for making a headland turn and bringing implement to a pre-set position.

Still another object of the present disclosure is to provide an electro-mechanical system which allows the operator to raise the TPL using a remote switch without changing the pre-setting of position and draft levers.
Yet another object of present disclosure is to provide a mechanical system which allows the operator to adjust maximum lifting height of TPL using the remote switch.
Still another object of the present disclosure is to provide an electro-mechanical system that allows an operator to lower the implement to a depth corresponding to the pre-setting of position and draft levers by means of the toggle switch.
Yet another object of the present disclosure is to provide a safety feature in the electro-mechanical system to protect it from sudden jerk or from manual overriding of TPL height, after pre-determined height is achieved by electro-mechanical system, by adjusting position and/or draft lever.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure envisages an electro-mechanical system for raising or lowering a three-point linkage (TPL) without operating draft and position levers. The system comprises at least one spring-centered switch, at least one actuating means, at least one lift arm, at least one cam, and at least one cam travel adjusting assembly. The spring-centered switch facilitates raising or lowering of the TPL. The actuating means is configured to be operated by the spring-centered switch to provide motion to at least one actuating mechanism for operating a spool valve. The actuating means is selected from the group consisting of a bi-directional DC motor, a pneumatic actuator, and a hydraulic actuator. The spool valve is part of a hydraulic hitch control valve. The lift arm is configured to be raised or lowered upon the operation of the spool valve of the hitch control valve through a

hydraulic power train, resulting in corresponding raising or lowering of the TPL. The cam is integrally mounted on the lift arm and configured to rotate along with the lift arm. The cam travel adjusting assembly is mounted on the lift arm at one end and connected to the cam at the other end. The cam travel adjusting assembly is configured to facilitate setting the travel of the cam to limit the maximum lifting height of the arm to a pre-determined height.
In an embodiment, the actuating mechanism comprises at least one drive means, at least one rod actuator assembly, at least one spool valve actuator, and at least one cam follower. The drive means receives motion from the actuating means. The rod actuator assembly is configured to be connected to the drive means at one end and at least one shaft actuator at the other end to transfer the received motion to the shaft actuator. The rod actuator assembly is a telescopic assembly comprising a cylinder and a sliding rod, wherein one end of the cylinder is pivotally connected to the shaft actuator, one end of the sliding rod is pivotally connected to the drive means, a resilient means is fixed between the other ends of the cylinder and the sliding rod such that the resilient means is compressed on the outward telescopic movement of the sliding rod. The spool valve actuator is rigidly connected to the shaft actuator, at a common pivot point to transfer motion received from the shaft actuator for operating the spool valve. The cam follower is mounted on the shaft actuator through a rigid linkage arm to receive the feedback of height achieved by lift arm through cam and restrain the further raising of the lift arm above the pre-determined height.
In an embodiment, the movement of the drive means is restricted between two extreme positions by means of stoppers to limit the travel of spool valve between lifting and lowering position through the rod actuator assembly and the spool valve actuator. The actuating means is configured to be stalled when the drive means reaches the extreme positions.

In an embodiment, the drive means is configured to transfer an arcuate motion of the actuating means to the shaft actuator to move it in an arcuate path through the rod actuator assembly.
In an embodiment, the actuating means is configured to move in an arcuate path
5 to provide a reverse arcuate motion to the shaft actuator, resulting in a reverse
arcuate motion of the spool valve actuator to press the spool valve for raising the lift arm. In an embodiment, the system includes a feedback mechanism comprising the cam travel adjusting assembly and the cam follower. On raising of the lift arm above the pre-determined height by the actuating means, the cam
10 presses the cam follower, causing the cam follower to exert a force on the shaft
actuator attempting to move the shaft actuator about its common pivot point in an arcuate path to release the spool valve and to bring the spool valve to a neutral position for holding the TPL at a desired height. As the drive means is already in stall condition at its stopper position, arcuate motion of the shaft actuator will
15 exert a tensile force on the rod actuator assembly. The sliding rod of the rod
actuator assembly is configured to have a telescopic movement upon the application of tensile force on its either/both sides, thereby ensuring safety of the rod actuator assembly by providing flexibility through resilient means.
In another embodiment, the actuating means is configured to move in a reverse
20 arcuate path to provide an arcuate motion to the shaft actuator, resulting in an
arcuate motion of the spool valve actuator to release the spool valve for lowering the lift arm.
In an embodiment, the cam travel adjusting assembly comprises a knob and a
connecting rod, wherein the knob is mounted on the lift arm through plate locking
25 and is free to rotate about its axis and the connecting rod is configured to connect
the knob with the cam. The retraction and extension of the connecting rod is facilitated by operating the knob, to set the travel of the cam.
6

In an embodiment, after achieving the pre-determined height, as defined by
adjustment of cam travel using the cam travel adjustment assembly, if TPL height
is further raised by adjustment of position and/or draft lever or due to jerk, the
cam follower slips over the cam profile preventing excess linkage travel and
5 breakage and thereby safeguarding the electro-mechanical system.
Advantageously, the spring-centered switch is a three position dual side momentary switch configured for raising and lowering the TPL by moving the spring-centered switch from its neutral position.
The present disclosure also envisages a method of raising or lowering a three-
10 point linkage (TPL). The method comprising the following steps:
i. setting draft and position levers to pre-determined positions;
ii. operating a spring-centered switch in one direction, upon reaching a
headland, for raising the TPL without operating the draft and position
levers; and
15 iii. operating the spring-centered switch in another direction for lowering the
TPL to bring it in a position corresponding to the setting of the draft and position levers without disturbing the levers.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
An electro-mechanical system for raising or lowering a three-point linkage (TPL)
20 of the present disclosure will now be described with the help of the accompanying
drawing, in which:
Figure 1 illustrates a side view of an electro-mechanical system for raising or lowering a three-point linkage (TPL) depicting a fully lowered lift arm; and
Figure 2 illustrates an inclined view with the system of Figure 1 with the lift arm
25 in an intermediate position;
7

Figure 3 illustrates a sectional view of a rod actuator assembly of the system of Figure 1;
Figure 4A illustrates an inclined view of the electro-mechanical system of Figure
1 depicting a fully raised lift arm with a retracted connecting rod of a cam travel
5 adjusting assembly;
Figure 4B illustrates a side view of the electro-mechanical system of Figure 1 depicting a fully raised lift arm with an elongated connected rod of the cam travel adjusting assembly;
Figure 5 illustrates a side view of tractor depicting position and draft levers of the
10 system of Figure 1; and
Figure 6 illustrates a side view of electro-mechanical system of Figure 1 depicting slipping of a cam follower over a cam profile while manually overriding position and/or draft lever to further raise TPL beyond a pre-determined height achieved by electro-mechanical system.
15 LIST OF REFERENCE NUMERALS
100 – System
1 – Actuating means
2 – Circlip
3 – Connector
20 4 – Mounting bracket
5 – Drive means
6 – Rod actuator assembly
7 – Hydraulic Hitch control Valve
8 – Control sector 25 9 – Shaft actuator
9a – Cam follower
9b – Rigid linkage arm
8

9c – Pivot point of Shaft actuator and spool valve actuator
10 – Cam
11 – Plate locking
12 – Connecting rod of cam travel adjusting assembly 5 13 – Child part of knob assembly

14 – Knob of cam travel adjusting assembly
15 – Spool valve actuator
16 – Lift arm
17 – Lift housing 10 18 – Bolt Pivot

19 – Wiring harness
20 – Spring-centered switch (Not illustrated)
21 – Cam travel adjusting assembly
22 – Spool valve 15 23 – Cylinder

24 – Sliding rod
25 – Resilient means
26 – Draft lever
27 – Position lever 20 28 – Rest plate
29 – Holding pin
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
25 Embodiments are provided so as to thoroughly and fully convey the scope of the
present disclosure to the person skilled in the art. Numerous details, are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the
9

person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
5 The terminology used, in the present disclosure, is only for the purpose of
explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises,"
10 "comprising," “including,” and “having,” are open ended transitional phrases and
therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the
15 method and process of the present disclosure is not to be construed as necessarily
requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
When an element is referred to as being "mounted on," “engaged to,” "connected
to," or "coupled to" another element, it may be directly on, engaged, connected or
20 coupled to the other element. As used herein, the term "and/or" includes any and
all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of
the present disclosure as the aforementioned terms may be only used to
distinguish one element, component, region, layer or section from another
25 component, region, layer or section. Terms such as first, second, third etc., when
used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
10

An electro-mechanical system (hereinafter referred to as “system 100”) for raising
or lowering a three-point linkage/three-point hitch (TPL), of the present
disclosure, is now being described with reference to Figure 1 through Figure 5.
Typically, three-point linkages are used for attaching implements to agricultural
5 or industrial machinery. As shown in Figure 5, a three-point linkage is controlled
by draft and position control levers (26, 27) which are moved along a control
sector 8 for setting a required height and/or draft force of the implement. The
system 100 is configured for raising or lowering the three-point linkage without
operating the draft and position control levers (26, 27). This is helpful especially
10 during turning a machine at the headland, where the implement is to be raised
without disturbing the setting of draft and position control levers (26, 27) so that after turning, it can be brought back to the pre-setting of the position or draft lever (26, 27) by operating the system of the present disclosure.
Referring to Figures 1 and 2, the system 100 comprises a spring-centered switch
15 20 (Not illustrated), an actuating means 1, a lift arm 16, a cam 10, and a cam
travel adjusting assembly 21. The spring-centered switch 20 facilitates raising or
lowering of the TPL. The actuating means 1 is configured to be operated by the
spring-centered switch 20 to provide motion to the actuating mechanism for
operating a spool valve 22. In an embodiment, the spring-centered switch 20 is
20 connected to the actuating means 1 through connector 3 with a wiring harness 19.
In another embodiment, the spring-centered switch 20 is wirelessly coupled to the
actuating means 1. The actuating means 1 may be selected from the group
consisting of, but not limited to, a bi-directional DC motor, a pneumatic actuator,
and a hydraulic actuator. Alternatively, the actuating means 1 can be a linear
25 actuator. The actuating means 1 may be mounted on a mounting bracket 4, which
is further mounted on the machine (for e.g. tractor).
The actuating mechanism comprises at least one drive means 5, at least one rod
actuator assembly 6, at least one shaft actuator 9, at least one spool valve actuator
15, and at least one cam follower 9a. The drive means 5 receives motion from the
11

actuating means 1. The rod actuator assembly 6 is configured to be connected to
the drive means 5 at one end and to the shaft actuator 9 at the other end to transfer
the received motion to the shaft actuator 9. In an embodiment, the drive means 5
is a crank. The drive means 5 is configured to transfer an arcuate motion of the
5 actuating means 1 to the shaft actuator 9 to move it in an arcuate path through the
rod actuator assembly 6. The spool valve actuator 15 is rigidly connected to the
shaft actuator 9 to transfer motion received from the shaft actuator 9 for operating
the spool valve 22 through a common pivot point 9c. The spool valve actuator 15
can be located inside the lift housing 17 of the machine. In an embodiment, the
10 spool valve 22 is a part of a hydraulic hitch control valve 7. The lift arm 16 is
configured to be raised or lowered upon the operation of the spool valve 22 of the hydraulic hitch control valve 7, through a hydraulic power train, resulting in corresponding raising or lowering of the TPL.
In an embodiment, the spring-centered switch 20 comprises of a lifting position, a
15 lowering position, and a spring-centered neutral position. When the switch 20 is
operated in the lifting position, the actuating means 1 is configured to move in an
arcuate path to provide a reverse arcuate motion to the shaft actuator 9, which
results in a reverse arcuate motion of the spool valve actuator 15 to press the spool
valve 22 for raising the lift arm 16. Similarly, when the switch 20 is operated in
20 the lowering position, the actuating means 1 is configured to move in a reverse
arcuate path to provide an arcuate motion to the shaft actuator 9, which results in an arcuate motion of the spool valve actuator 15 to release the spool valve 22 for lowering the lift arm 16.
The cam 10 is integrally mounted on the lift arm 16 and is relatively adjustable
25 with respect to the cam travel adjusting assembly 21. The cam 10 is configured to
rotate along with the lift arm 16. In an embodiment, the cam 10 is pivotally bolted
to the lift arm 16 through a bolt receiving perforation in a plate 11 by means of a
bolt pivot 18. The cam travel adjusting assembly 21 is mounted on the lift arm 16
and connected to the cam 10 through a connecting rod 12. The cam travel
12

adjusting assembly 21 is configured to facilitate setting the travel of the cam 10 to
limit the maximum lifting height of the lift arm 16 to a pre-determined height. The
cam travel adjusting assembly 21 comprises a knob 14 and the connecting rod 12.
The knob 14 and the connecting rod 12 form a pair such that rotation of the knob
5 14 results in linear motion of the connecting rod 12 to facilitate retraction and
extension of the connecting rod 12 by operating the knob 14, to set the travel of the cam 10. Alternatively, the cam adjusting assembly comprises pneumatic or electric actuator connected to the cam 10. To set the travel of cam 10, the actuator is retracted or extended. In an embodiment, the pre-determined height of the lift
10 arm 16 can be set between 50% to 95% of the maximum lifting height using the
cam travel adjusting assembly 21 by adjusting the length of the connecting rod 12. Movement of the cam 10 is restricted between two extreme positions by means of stopper 11a & 11b. The maximum lifting height of the lift arm 16 can be increased by retracting the knob 14, till the cam 10 makes contact with the stopper
15 11b as shown in Figure 4A. The retraction of the knob 14 results in an increase in
the gap between the cam 10 and the cam follower 9a, thereby increasing the cam travel (i.e. travel of the cam 10 till it reaches the cam follower 9a) and the lifting height. The maximum lifting height of the lift arm 16 can be reduced by extending the connecting rod 12 of the cam travel adjusting assembly 21, till the
20 cam 10 makes contact with the stopper 11a as shown in Figure 4B. The
extension of the connecting rod 12 of the cam travel adjusting assembly 21 results in a decrease in the gap between the cam 10 and the cam follower 9a, thereby decreasing the cam travel and the lifting height. Thus, the lifting arm of Figure 4B reaches the maximum lifting height at a height lower than that of the Figure
25 4A.
In an embodiment, the system 100 includes a feedback mechanism. The feedback mechanism comprises the cam travel adjusting assembly 21 and the cam follower 9a. The cam follower 9a is mounted on the shaft actuator 9 through a rigid linkage arm 9b to restrain the raising of the lift arm 16 above the pre-determined height
13

upon the contact of the cam 10 with the cam follower 9a. During TPL raising
operation using system 100, after achieving the pre-determined height of lift arm
16, the cam 10 makes contact with the cam follower 9a and starts pressing the
cam follower 9a. Due to the pressure of the cam 10, the cam follower 9a exerts a
5 force on the shaft actuator 9 attempting to move the shaft actuator 9 against its
original motion in reverse arcuate direction to an arcuate direction to release the
spool valve 22, eventually bringing the spool valve 22 to a neutral position for
holding the TPL at a desired height. The force experienced by shaft actuator 9
also results in a simultaneous tensile force on the rod actuator assembly 9, as the
10 drive means 5 is already in stalled condition after making contact with the stopper
4a.
To avoid sudden jerk or damage to the system 100 due to the opposing forces, the rod actuator assembly 6 is configured to have a telescopic movement. As shown in Figure 3, the rod actuator assembly 6 comprises a cylinder 23 and a sliding rod
15 24. One end of the cylinder 23 is pivotally connected to the shaft actuator 9. One
end of the sliding rod 24 is pivotally connected to the drive means 5. A resilient means 25 is fixed between the other ends of the cylinder 23 and the sliding rod 24 such that the resilient means 25 is compressed on the outward telescopic movement of the sliding rod 24. In an embodiment, the resilient means 25 is a
20 compression spring. When the shaft actuator 9 moves in an arcuate path due to the
pressure of the cam 10 and the cam follower 9a, a telescopic movement of the sliding rod 24 of the rod actuator assembly 6 with the cylinder 23 is established. The telescopic movement of the sliding rod 24 ensures safety of the rod actuator assembly 6.
25 In an embodiment, the movement of the drive means 5 is restricted between two
extreme positions by means of stoppers (4a, 4b) to restrict the raising and
lowering of the lift arm 16 between pre-determined positions. The stoppers (4a,
4b) may be mounted on a mounting bracket 4. The movement of the drive means
5 is stalled at the stoppers (4a, 4b). This, in turn, leads to the stalling of the
14

actuating means 1 as the force experience by the actuating means 1 becomes equal to the pre-set threshold resistive force. Alternatively, the actuating means 1 is electrically stalled by means of microcontrollers to restrict the movement of the drive means 5 between the extreme positions.
5 In an embodiment, after achieving the pre-determined height, as defined by adjustment of cam travel using the cam travel adjustment assembly 21, if TPL height is further raised using adjustment of position lever and/or draft lever or due to jerk on lift arm, the cam follower 9a slips over the cam profile 10 preventing excess linkage travel and breakage, and thereby safeguarding the electro-10 mechanical system 100, as shown in Figure 6.
The present disclosure also envisages a method of raising or lowering a three-
point linkage (TPL). The method is used by an operator of an agricultural machine
(for e.g. tractor) which is provided with the system 100. The method comprises
the following steps:
15 • setting draft and position levers (26, 27) to pre-determined positions;
• operating a spring-centered switch 20 in one direction, upon reaching a
headland, for raising the TPL without operating the draft and position
levers (26, 27); and
• operating the spring-centered switch 20 in another direction for lowering
20 the TPL to bring it in a position corresponding to the setting of the draft
and position levers (26, 27) without disturbing the levers (26, 27).
Advantageously, the spring-centered switch 20 is a three position dual side momentary switch configured for raising and lowering the TPL by moving the spring-centered switch 20 from its neutral position.
25 Alternatively, the spring-centered switch 20 comprises two separate spring switches, one each for either direction of rotation of the actuating means 1.
15

Advantageously, a circlip 2 may be provided to secure the drive means 5 on to the shaft.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual 5 components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCEMENTS
10 The present disclosure described herein above has several technical advantages including, but not limited to, the realization of an electro-mechanical system for raising or lowering a three-point linkage (TPL) that:
• facilitates easier headland turning for an operator;
• reduces operator fatigue;
15 • reduces the time required for making a headland turn;
• allows the operator to raise or lower the TPL using a toggle switch without changing the pre-setting of position and draft levers;
• allows an operator to lower the implement to a depth corresponding to the pre-setting of position and draft levers by means of the toggle switch; and
20 • safeguards the system when maximum height achieved by the TPL using
the system is overridden by adjusting position and draft lever.
The embodiments herein and the various features and advantageous details thereof
are explained with reference to the non-limiting embodiments in the following
description. Descriptions of well-known components and processing techniques
16

are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

WE CLAIM

An electro-mechanical system (100) for raising or lowering a three-point linkage (TPL) without operating draft and position levers (26, 27), said system (100) comprising: i. at least one spring-centered switch (20) for facilitating raising or
lowering of said TPL; ii. at least one actuating means (1) configured to be operated by said spring-centered switch (20) to provide motion to at least one actuating mechanism for operating a spool valve (22); iii. at least one lift arm (16) configured to be raised or lowered upon the operation of said spool valve (22), resulting in corresponding raising or lowering of said TPL; iv. at least one cam (10) integrally mounted on said lift arm (16), said
cam (10) configured to rotate along with said lift arm (16); and v. at least one cam travel adjusting assembly (21) mounted on said lift arm (16) and connected to said cam (10) through a connecting rod (12), said cam travel adjusting assembly (21) configured to facilitate setting the travel of said cam (10) to limit the maximum lifting height of said lift arm (16) to a pre-determined height.
The system as claimed in claim 1, wherein said actuating mechanism comprises:
a. at least one drive means (5) for receiving motion from said
actuating means (1);
b. at least one rod actuator assembly (6) configured to be connected
to said drive means (5) at one end and at least one shaft actuator (9)
at the other end to transfer said received motion to said shaft
actuator (9); and

c. at least one spool valve actuator (15) rigidly connected to said shaft
actuator (9) to transfer motion received from said shaft actuator (9)
for operating said spool valve (22); and
d. at least one cam follower (9a) mounted on said shaft actuator (9)
through a rigid linkage arm (9b) to restrain the raising of said lift
arm (16) above said pre-determined height.
The system as claimed in claim 2, wherein the movement of said drive means (5) is restricted between two extreme positions by means of stoppers (4a, 4b) to limit travel of said spool valve (22) between lifting and lowering positions through said rod actuator assembly (6) and said spool valve actuator (25).
The system as claimed in claim 3, wherein said actuating means (1) is configured to be stalled when said drive means (5) reaches said extreme positions.
The system as claimed in claim 2, wherein said drive means (5) is configured to transfer an arcuate motion of said actuating means (1) to said shaft actuator (9) to move it in an arcuate path through said rod actuator assembly (6).
The system as claimed in claim 5, wherein said actuating means (1) is configured to move in an arcuate path to provide a reverse arcuate motion to said shaft actuator (9), resulting in a reverse arcuate motion of said spool valve actuator (15) to press said spool valve (22) for raising said lift arm (16).
The system as claimed in claim 6, wherein said system consists of a feedback mechanism comprising the cam travel adjusting assembly (21) and the cam follower (9a), wherein said cam (10) is configured to press said cam follower (9a), on raising of said lift arm (16) above said pre-

determined height using said actuating means (1), causing said cam follower (9a) to exert a force on said shaft actuator (9) attempting to move said shaft actuator (9) in an arcuate path to release said spool valve (22) and to bring said spool valve (22) to a neutral position for holding said TPL at a desired height, resulting in a simultaneous tensile force on said rod actuator assembly (9), as said drive means (5) is already in stalled condition after it makes contact with said stopper (4a).
The system as claimed in claim 5, wherein said actuating means (1) is configured to move in a reverse arcuate path to provide an arcuate motion to said shaft actuator (9), resulting in arcuate motion of said spool valve actuator (15) to release said spool valve (22) for lowering said lift arm (16).
The system as claimed in claim 2, wherein said rod actuator assembly (6) is a telescopic assembly comprising a cylinder (23) and a sliding rod (24), wherein one end of said cylinder (23) is pivotally connected to said shaft actuator (9), one end of said sliding rod (24) is pivotally connected to said drive means (5), a resilient means (25) is fixed between the other ends of said cylinder (23) and said sliding rod (24) such that said resilient means (25) is compressed on the outward telescopic movement of said sliding rod (24).
The system as claimed in claims 7 and 9, wherein said sliding rod (24) of said rod actuator assembly (6) is configured to have an outward telescopic movement due to the tensile force applied on said rod actuator assembly (9) to ensure safety of said rod actuator assembly (6).
The system as claimed in claim 7, wherein said cam follower (9a) is configured to slip over said cam profile (10) after achieving the pre-determined height as defined by adjustment of cam travel using said cam travel adjustment assembly (21), if TPL height is further raised using

adjustment of said position lever (27) and/or said draft lever (26) or due to jerk, thereby preventing excess linkage travel and breakage and safeguarding said electro-mechanical system (100).
The system as claimed in claim 1, wherein said actuating means (1) is selected from the group consisting of a bi-directional DC motor, a pneumatic actuator, and a hydraulic actuator.
The system as claimed in claim 1, wherein said spool valve (22) is a part of a hydraulic hitch control valve (7).
The system as claimed in claim 1, wherein said cam travel adjusting assembly (21) comprises a knob (14) and said connecting rod (12), wherein said knob (14) and said connecting rod (12) form a pair such that rotation of said knob (14) results in linear motion of said connecting rod (12) to facilitate retraction and extension of said connecting rod (12) by operating said knob (14), to set the travel of said cam (10).
The system as claimed in claim 1, wherein said drive means (5) is a crank.
The system as claimed in claim 9, wherein said resilient means (25) is a compression spring.
The system as claimed in claim 1, wherein said spring-centered switch (20) is a three position dual side momentary switch configured for raising and lowering said TPL by moving said spring-centered switch (20) from its neutral position.
A method of raising or lowering a three-point linkage (TPL), said method comprising the following steps:
a. setting draft and position levers (26, 27) to pre-determined positions;

b. operating a spring-centered switch (20) in one direction, upon
reaching a headland, for raising said TPL without operating said
draft and position levers (26, 27); and
c. operating said spring-centered switch (20) in another direction for
lowering said TPL to bring it in a position corresponding to the
setting of said draft and position levers (26, 27) without disturbing
said levers (26, 27).
. The method as claimed in claim 17, wherein said spring-centered switch (20) is a three position dual side momentary switch configured for raising and lowering said TPL by moving said spring-centered switch (20) from its neutral position.