FIELD
The present disclosure relates to the field of agricultural vehicles.
BACKGROUND
The background information herein below relates to the present disclosure but is not
necessarily prior art.
In tractors, draft control and position control mechanisms together are utilized to
control the operating depth of an implement such as a plough attached to a three-point
linkage inside the soil against varying ground contours, softness, and so on. These
mechanisms are hydraulically operated and are controlled by the seated vehicle driver
10 using levers to him/her. A three point linkage is generally provided at the operative
rear end of the tractor. To have better productivity, improved fuel efficiency and
better power utilization, a tractor can be provided with a three-point linkage at the
operative front end as well. An automatic draft control system similar to that for the
conventional rear-side three-point linkage needs to be provided. Difficulties arise for
15 providing mechanical linkages extending upto the front side for this purpose. Hence,
a hydraulically controlled automatic draft control system can be envisaged for a frontside
three-point linkage.
Such a hydraulically controlled draft control system shall require a sensor which
senses the magnitude of the draft in the three-point linkage.
20 There is, therefore, need for a sensing mechanism for sensing magnitude of draft in a
three-point linkage.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein
satisfies, are as follows:
3
An object of the present disclosure is to provide a sensing mechanism for sensing
magnitude of draft in a three-point linkage of a tractor.
Another object of the present disclosure is to provide a sensing mechanism for
sensing magnitude of draft in a three-point linkage of a tractor, which is efficient.
Yet another object of the present disclosure is to provide a sensing mechanism 5 for
sensing magnitude of draft in a three-point linkage of a tractor, wherein the linkage is
provided in the operative front side of the tractor.
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
10 disclosure.
SUMMARY
The present disclosure envisages a hydraulic sensing mechanism for sensing a load
exerted along an elongate member. The hydraulic sensing mechanism is in fluid
communication with a hydraulic circuit. The hydraulic circuit is configured to be
15 switched between an inoperative configuration and an operative configuration in
which the hydraulic circuit permits actuation of an implement linked to the elongate
member in response to a load exerted along the elongate member.
The hydraulic sensing mechanism comprises the elongate member, a hydraulic
piston-cylinder mechanism, a resilient member. The elongate member is defined by a
20 first segment and a second segment. The hydraulic piston-cylinder mechanism is
located between the first segment and the second segment. The resilient member is
disposed within the hydraulic piston-cylinder mechanism. The hydraulic circuit is in
fluid communication with the hydraulic piston-cylinder mechanism.
4
In an embodiment, the piston of the hydraulic piston-cylinder mechanism is coupled
to one of the segments of the elongate member.
In another embodiment, the cylinder of the hydraulic piston-cylinder mechanism is
closed at both longitudinal ends. One of the segments is coupled to one longitudinal
end of the cylinder. The piston is slidably disposed inside the cylinder. The other 5 of
the segments passes through the other longitudinal end of the cylinder. A hydraulic
fluid is filled inside the cylinder. In yet another embodiment, the resilient member is
disposed between the piston and inner surface of one of the longitudinal ends of the
cylinder.
10 In still another embodiment, the cylinder is provided with an opening. The opening is
connected to one end of a hose and other end of the hose is connected to the hydraulic
circuit.
In yet another embodiment, the elongate member is a top link of a three-point linkage
of a tractor, and the hydraulic circuit is an automatic draft control circuit.
15
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
A sensing mechanism for sensing magnitude of draft in a three-point linkage of a
tractor of the present disclosure will now be described with the help of the
accompanying drawing, in which:
20 Figure 1 illustrates a sectional view of a top link with a hydraulic sensing mechanism
according to an embodiment of the present disclosure; and
Figure 2 is a schematic view of a top link of Figure 1 in fluid communication with a
hydraulic circuit.
LIST OF REFERENCE NUMERALS
25 10 elongate member
5
1 first segment of the elongate member
2 second segment of the elongate member
3 piston
4 cylinder
5a first resilient memb5 er
5b second resilient member
6 outlet
12 hydraulic circuit
14 hose
10
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the
accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the
15 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 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, well20
known apparatus structures, and well-known techniques are not described in detail.
6
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”, “comprising”, “including” a5 nd
“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
10 particular order of steps disclosed in the 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.
Providing a three-point linkage to a tractor on front as well rear sides has its own
15 advantages – better productivity, improved fuel efficiency and better power
utilization. Providing mechanical linkages extending to the front side for automatic
draft control and position control is complicated. A hydraulically operated automatic
draft control system can be envisaged.
The present disclosure provides a top link of a three-point linkage which is integrated
20 with a hydraulic piston-cylinder mechanism which reacts to the load exerted along
the top link due to an increase in magnitude of draft. The hydraulic sensing
mechanism comprises the top link 10 which is an elongate member, a hydraulic
piston-cylinder mechanism 3-4, a resilient member 5 and a hydraulic circuit 12 in
fluid communication with the top link. The top link 10 is defined by a first segment 1
25 and a second segment 2. The hydraulic piston-cylinder mechanism 3-4 is located
between the first segment 1 and the second segment 2. The resilient member 5 is
disposed within the hydraulic piston-cylinder mechanism 3-4. The hydraulic circuit
7
12 is in fluid communication particularly with the hydraulic piston-cylinder
mechanism 3-4. The hydraulic circuit 12 is configurable into a plurality of
configurations. The hydraulic sensing mechanism is configured such that a
longitudinal load exerted along the top link 10 causes switching of the hydraulic
circuit 12 from one configuration into another, and removal of the longitudinal 5 udinal load
causes switching of the circuit 12 back to the initial inoperative configuration.
The piston 3 of the hydraulic piston-cylinder mechanism is coupled to one of the
segments 1, 2 of the top link 10. The coupling is achieved by any suitable method
such as threaded joints, interference fit, welding among others, or by forming the
10 piston integral with one of the segments of the top link. The cylinder 4 is closed at
both longitudinal ends. The other of the segments 1, 2 is coupled to one longitudinal
end of the cylinder 4. The coupling can be achieved by any suitable method such as
threaded joints, interference fit, welding among others, or by forming the cylinder 4
integral with the other segment of the top link 10. The piston 3 is slidably disposed
15 inside the cylinder 3. The other of the segments passes through the other longitudinal
end of the cylinder 4. A hydraulic fluid is filled inside the cylinder 4. The end of the
cylinder 4 through which the segment coupled to the piston 3 is passed is sealed to
not allow any leakage of the hydraulic fluid. The resilient member 5 which is a
helical spring is disposed between the piston 3 and inner surface of one of the
20 longitudinal ends of the cylinder 4. In an embodiment, the resilient member 5 is a
combination of a first spring 5a and a second spring 5b with one spring disposed at
either side of the piston 3. The cylinder 4 is provided with an opening 6. The opening
6 is connected to one end of a hose 14 and other end of the hose 14 is connected to
the hydraulic circuit 12.
25 In an embodiment, the second segment 2 of the top link 10 is coupled to the piston 3.
The first segment 1 of the top link 10 is coupled to the cylinder 4, as shown in Figure
1. The opening 6 is provided in the half of the cylinder 4 adjacent to the second
8
segment 2 of the top link 10. In another embodiment which is not shown in the
drawing, the second segment 1 of the top link 10 is coupled to the piston 3. The first
segment 2 of the top link is coupled to the cylinder 4. The opening 6 is provided in
the half of the cylinder 4 adjacent to the first segment 1 of the top link 10.
The hydraulic circuit automatically controls actuation of the three-point linkage 5 in
response to the tension sensed along the top link, wherein the tension is proportional
to the magnitude of draft exerted on an implement such as a plough attached to the
three-point linkage inside the soil. As tension is exerted along the top link 10, the
piston 3, which is positioned at the centre of the cylinder 4 and is connected to one of
10 the first segment 1 and the second segment 2, gets displaced while deforming the
spring 5. The displacing cylinder 4 pushes the hydraulic fluid out of the cylinder 4
through the hose 14 and towards the hydraulic circuit 12. Consequently, a valve in the
hydraulic circuit is actuated at a threshold magnitude of fluid pressure which is
proportional to a threshold magnitude of tension along the top link 10, which is in
15 turn proportional to the predetermined threshold magnitude of draft exerted on the
implement. The actuation of the valve initiates raising of the implement coupled to
the three-point linkage of which the top link 10 is a part. The raising of the implement
can be brought about by lifting of the left and right side bottom links of the threepoint
linkage. Similarly, when the tension exerted on the top link 10 is released, the
20 piston 3 moves in the opposite direction, i.e., towards the centre of the cylinder 4 due
to the resilience of the spring 5. The hydraulic fluid gets sucked back into the cylinder
4 through the opening 6, resulting in switching of configuration of the valve in the
hydraulic circuit 12 back to the inoperative configuration. The raising or lowering
previously initiated therefore comes to a halt. In this manner, the draft control of the
25 three-point linkage is achieved.
The threshold magnitude of draft beyond which it is desired to result in raising of the
implement sunk inside the soil, can be adjusted by adjusting the threshold magnitude
of tension along the top link 10. This threshold magnitude is adjusted (or ‘tuned’) by
9
the user by a number of ways, including tightening or loosening of the spring 5,
among others.
While the above passage elaborates a mechanism for sensing tension exerted along
the top link 10, a mechanism for sensing compression can also be envisaged with a
minor modification. For this application, the outlet 6 is provided in the half of th5 e
cylinder 4 which is adjacent to segment of the top link 10 which is coupled to the
piston 3. In an embodiment, the first segment 1 is coupled to the piston 3 and the
outlet 6 is provided in the half of the cylinder 4 adjacent to the first segment 1. In
another embodiment, the second segment 2 is coupled to the piston 3 and the outlet 6
10 is provided in the half of the cylinder 4 adjacent to the second segment 2. In yet
another embodiment, a mechanism for sensing both tension and compression in the
top link 10 can be envisaged, wherein one outlet on the cylinder 4 on each side of the
piston 3 is provided, and each outlet is fluidly communicating with the same valve or
different valves in the hydraulic circuit 12.
15 The hydraulic control circuit 12 is installed in the rear portion of the tractor and
actuation of the front-side three-point linkage can be controlled by the circuit 12. The
hose 14 connecting the abovementioned opening 6 in the cylinder 4 of the top link 10
can be extended from the top link 10 of the front-side three-point linkage. Hence, a
complicated and bulky mechanical linkage for automatic draft control of the three20
point linkage is not required. Nevertheless, the hydraulic control as described above
is equally applicable for a rear-side three-point linkage by using a shorter hose.
Notwithstanding the application of the hydraulic mechanism as described above for
sensing tension or compression along a top link in a three-point linkage of a tractor,
the hydraulic sensing mechanism can be implement for any such application wherein
25 a decision needs to be made by a hydraulic circuit, say for actuating a mechanism or
any other purpose, based on crossing of threshold magnitude of the tension or
compression exerted along an elongate element.
10
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
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 5 the
present disclosure as the aforementioned terms may be only used to distinguish one
element, component, region, layer or section from another 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 Terms such as “inner”, “outer”, “beneath”, “below”, “lower”, “above”, “upper” and
the like, may be used in the present disclosure to describe relationships between
different elements as depicted from the figures.
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
15 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
20 The present disclosure described herein above has several technical advantages
including, but not limited to, the realization of a sensing mechanism for sensing
magnitude of draft in a three-point linkage of a tractor, which:
 is efficient and highly sensitive;
 eliminates need of bulky mechanical linkages extending upto a front-side
25 three-point linkage mechanism in a tractor;
11
 can be implemented for automatic hydraulic control of a three-point linkage
mechanism.
The foregoing disclosure has been described with reference to the accompanying
embodiments which do not limit the scope and ambit of the disclosure. The
description provided is purely by way of example and illustrati5 on.
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 are
omitted so as to not unnecessarily obscure the embodiments herein. The examples
10 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
15 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
20 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.
25 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.
12
Any discussion of documents, acts, materials, devices, articles or the like that has
been included in this specification is solely for the purpose of providing a context for
the disclosure. It is not to be taken as an admission that any or all of these matters
form a part of the prior art base or were common general knowledge in the field
relevant to the disclosure as it existed anywhere before the priority date of thi5 s
application.
The numerical values mentioned for the various physical parameters, dimensions or
quantities are only approximations and it is envisaged that the values higher/lower
than the numerical values assigned to the parameters, dimensions or quantities fall
10 within the scope of the disclosure, unless there is a statement in the specification
specific to the contrary.
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
15 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:
1. A hydraulic sensing mechanism for sensing a load exerted along an elongate
member (10), said hydraulic sensing mechanism being in fluid
communication with a hydraulic circuit (12), wherein said hydraulic circuit
(12) is configured to be switched between an inoperative configuration and 5 an
operative configuration in which said hydraulic circuit (12) permits actuation
of an implement linked to said elongate member (10) in response to a load
exerted along said elongate member (10).
2. The hydraulic sensing mechanism as claimed in claim 1, wherein:
10 a. said elongate member (10) is defined by a first segment (1) and a
second segment (2);
b. a hydraulic piston-cylinder mechanism (3, 4) is located between said
first segment (1) and said second segment (2);
c. a resilient member (5) is disposed within said hydraulic piston15
cylinder mechanism (3, 4); and
d. said hydraulic circuit (12) is in fluid communication with said
hydraulic piston-cylinder mechanism (3, 4).
3. The hydraulic sensing mechanism as claimed in claim 2, wherein said piston
(3) of said piston-cylinder mechanism (3, 4) is coupled to one of said segment
20 (1) and said segment (2).
4. The hydraulic sensing mechanism as claimed in claim 3, wherein said
cylinder (4) of said piston-cylinder mechanism (3, 4) is closed at both of its
longitudinal ends, wherein:
14
 one of said segment (1) and said segment (2) is coupled to one
longitudinal end of said cylinder (4);
 said piston (3) is slidably disposed inside said cylinder (4);
 the other of said segments passes through the other longitudinal end of
said cylinder (4); a5 nd
 a hydraulic fluid filled inside said cylinder (4).
5. The hydraulic sensing mechanism as claimed in claim 4, wherein said resilient
member (5) is disposed between said piston (3) and inner surface of one of
said longitudinal ends of said cylinder (4).
10 6. The hydraulic sensing mechanism as claimed in claim 5, wherein said
cylinder (4) is provided with an opening (6), wherein said opening (6) is
connected to one end of a hose (14) and other end of said hose (14) is
connected to the hydraulic circuit (12).
7. The hydraulic sensing mechanism as claimed in claim 1, wherein said
15 elongate member (10) is a top link of a three-point linkage of a tractor, and
said hydraulic circuit (12) is an automatic draft control circuit.