The present invention generally relates to mechanically controlling the
position of lower links with respect to position actuating levers in a tractor
hydraulic system. More particularly, this invention presents an implement
control system designed with a non-linear cam motion profile for controlling
lower band of operations in precision and making upper band more
responsive.
BACKGROUND OF THE INVENTION
The hydraulic hitch system is an essential component of the agricultural
tractor that maintains the depth or the height of the implement below or
above the ground level, respectively, with reference to the datum set by the
user by means of the appropriate setting lever. The setting is referenced
automatically by the implement through the hydraulic hitch system, of
which the hitch valve & and feedback mechanism is the controlling member.
The implement may be supported during its operation in association with
the agricultural tractor in any one of the following three modes:
(i) Position mode of operation: In this mode, the position of the
implement is directly set by the valve in accordance with the
setting of the position lever & position feedback mechanism on the
tractor. Then, the draft lever is withdrawn from the setting.
(ii) Draft mode of operation: In this mode, the position of the
implement is set by the valve to ensure that the draft or the force
encountered at the tip of the implement becomes proportional to
the angle set on the draft lever of the tractor. Then, the position
lever is withdrawn from the setting.
(iii) Mixed mode of operation: In this mode, both levers are set
appropriately. The depth of the implement is governed by the draft
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lever setting subject to the maximum depth obtained from the
setting of the position lever.
Thus, it would be obvious to the skilled person that the implement must
react with the soil and generate some thrust if it is required to work in either
the draft mode or the mixed mode.
Further, in most of the agricultural operations, implements position control
is important in the lower operating band (Up to 40% to 60% of initial
operating range of lower links). Position control in upper band of the
operating range is hardly used. Upper band is majorly used for
transportation only.
Furthermore, to control the position of lower links (Fig. 1) with respect to
position actuating levers, mechanical or electronic feedback mechanism
have been used conventionally. In a mechanical system, usually a camfollower
mechanism is used to get the feedback position and the control
valve unit comes to neutral. In a traditional design of all such system, cam’s
motion profile is made linear or almost linear (Fig.2) throughout the
operating range. In other conventional systems electronic position sensors
are being used. The conventional systems also use levers or knobs to control
the position of lower links.
Further, in US12/233,863 to Muzzy the patent discloses a mechanical hitch
control system for a vehicle includes a draft force sensing member, a
mechanical hitch control unit, a hitch valve actuator, and a cable
transmitting a draft force signal to the hitch control unit. A draft cam is
coupled to the draft force sensing and setting members. A position cam is
coupled to the position setting member and to a hitch position sensing
member. A draft pickup cam is coupled to the draft cam and pivotally
mounted on the hitch position setting member. At least one of the cams is
operatively engagable with the hitch valve actuator. The cams are enclosed
by housing with an opening covered by a removable side plate. The cams
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and levers are coupled to input members which are inserted through the
side plate. The assembled cams, levers and input members are then
installed into the housing through the opening. However, the
aforementioned patent although discloses hitch control but nowhere
discloses implementation of non-linear position cam to achieve the variable
lifting pattern.
Moreover, in US10/799,107 to Easton, the patent discloses a hitch control
system for controlling a vehicle hitch to which implements can be attached.
The hitch control system includes a spring-centered primary command lever
which is manually moveable from a centered position to deflected positions,
and which automatically returns to the centered position when released
from a deflected position. A control unit generates a hitch command signal
in part as a function of the lever position. The control unit has a closed-loop
control mode wherein the valve command signal is generated in response to
parameter, such as position and draft force, and the hitch command signal.
The control unit moves the hitch in a step-wise manner by a predetermined
amount in response to momentary deflection of the command lever to one of
the deflected positions, and the amount of hitch movement is independent
of an amount and duration of deflection of the command lever if the
duration is not more than a predetermined duration. Nevertheless, the
above disclosed system utilizes sensors for hitch control and is not purely
mechanical. Herein, the sensors are used to achieve the variable lifting
pattern.
Further, with the improved and precision control valve units, it is of
absolute importance to have enough range of position lever movement to
control the lower link position in the lower band of operation. Thus, there
remains a need for a system which could overcome current limitations of the
tractor hydraulic system configuration while ensuring controlling lower
band of operations with better precision and facilitating in easy and effective
control of lower link position (Fig.1).
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The present invention performs the said intended functions through an
inventive configuration of components that makes the intended function
particularly reliable, simpler, precise, better controlled and effective.
OBJECTS OF THE INVENTION
An object of the invention is to overcome the aforementioned and other
drawbacks existing in prior art tractor hydraulic system configuration.
More particularly, it is an object of the invention is to develop an implement
control system and method for mechanically controlling the position of lower
links with respect to position actuating levers in a tractor hydraulic system.
Still another object of the invention is to design an implement control
system with a non-linear cam motion profile for controlling lower band of
operations in precision.
Still another object of the invention is to design an implement control
system with a non-linear cam motion profile for controlling upper band of
operations with more responsiveness i.e. more movement of hitch point
against small rotation of position actuating lever.
Yet another object of the invention is to design a non-linear cam profile
configured to provide the feedback of the ram arm position, thereby
controlling the position of ram arm/lift arm with respect to position control
lever.
Further object of the invention is to develop an implement control system
and method for precisely controlling position of the lower links in lower
range of total operating range of the lower links.
These and other objects and advantages of the present invention will be
apparent to those skilled in the art after a consideration of the following
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detailed description taken in conjunction with the accompanying drawings
in which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION:
The present application discloses a non-linear cam follower based
implement control system for precisely controlling position of the lower links
in lower range of total operating range of the lower links and make lower
link movement more responsive at upper band of operation. Further, in an
embodiment, the system includes a response valve assembly (2) operably
connected to a control valve (9) and through an input port gallery of a
cylinder (3) to the cylinder (3). Further, in another aspect, the system
includes a position control lever (4) attached at first end of a position crank
assembly (13) and at second end of the position crank assembly (13) is
attached a position actuator (14), said position actuator (14) being
operatively engageable at first end to a non-linear cam profile (17) mounted
on one end of a ram arm (8) and at second end to spool of the control valve
(9). Further, the system includes a rockshaft (16) connecting the ram arm
(8), a first lift arm (7) and a second lift arm (7) at center, first end and
second end of the rockshaft (16) respectively.
In another aspect, the present application discloses a non-linear cam
follower based implement control method for precisely controlling position of
the lower links in lower range of total operating range of the lower links.
Further, the method includes rotating of a position control lever (4) in
clockwise direction which results in the rotation of a position crank
assembly (13). Further, in an aspect the method includes turning of a
Control valve (9) in lifting mode by pressing of a Pin control valve (10) due to
configuration of an Idler position (15) between a Ram arm (8) and a Position
actuator (14) and followed by rotating of a lift arm (7) resulting in rotation of
a Ram arm (8) which further results in a non-linear cam profile (17)
mounted on one end of a ram arm (8) to generate gap, thereby facilitating
the Pin control valve (10) to move out to bring the control valve (9) back to
neutral position.
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The above and additional advantages of the present invention will become
apparent to those skilled in the art from a reading of the following detailed
description when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The drawings refer to embodiments of the invention in which:
Fig. 1 illustrates position of implement attached in the lower link.
Fig.2 illustrates a conventional cam profile.
Fig.3 illustrates a non-linear cam profile according to an embodiment of the
invention.
Fig.4a illustrates components instrumental in effecting position feedback
mechanism according to an embodiment of the invention.
Fig.4b illustrates components instrumental in effecting position feedback
mechanism according to an embodiment of the invention.
Fig.4c illustrates components instrumental in effecting position feedback
mechanism according to an embodiment of the invention.
Fig.5 illustrates a non-linear cam profile positioned on ram arm according to
a preferred embodiment of the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Although the disclosure hereof is detailed and exact to enable those skilled
in the art to practice the invention, the physical embodiments herein
disclosed merely exemplify the invention which may be embodied in other
specific structure. While the preferred embodiment has been described, the
details may be changed without departing from the invention, which is
defined by the claims.
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It will be apparent, however, to one of ordinary skill in the art that the
present invention may be practiced without specific details of the well
known components and techniques. In other instances, well known
components or methods have not been described in detail but rather in
Figures in order to avoid unnecessarily obscuring the present invention.
Further specific numeric references should not be interpreted as a literal
sequential order. Thus, the specific details set forth are merely exemplary.
The specific details may be varied from and still be contemplated to be
within the scope of the present invention. The features discussed in an
embodiment may be implemented in another embodiment.
Moreover, occasional references to the conventional position feedback
mechanisms are made in order to better distinguish the present inventive
disclosure discussed later in greater detail. Few of the details pertaining to
the position feedback mechanism are well-known in the art, and therefore,
are described herein only in the detail required to fully disclose the present
invention.
Improving upon the conventional linear cam profile (Fig. 2) discussed at
length above (background), in the present disclosure the inventive design of
the of the cam profile as shown in Figs. 3-5 clearly makes the implement
control system as disclosed in the present application advantageous over the
existing arts as would also become clearer to the knowledgeable in the art
with the particulars of the aforesaid techniques being described below in
greater detail.
Turning now to Figures, Figs. 4-5 illustrates the various components
configuration instrumental in mechanically controlling the position of lower
links with respect to position actuating levers in a tractor hydraulic system.
The illustrated components and their working are described below:
1. Hydraulic Lift Housing (1): Hydraulic lift housing (1),
houses all the linkage components i.e. Response valve assembly
(2), cylinder (3), control valve (9) & control sector assembly (12)
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are mounted on the hydraulic lift housing (1) through screws. It
also houses Lift arm (7) & ram arm (8) through rockshaft and
end plates.
2. Response valve assembly (2): Response valve assembly is
mounted on hydraulic lift housing (1) and connected with
control valve (9). Response valve assembly and control valve
together act as a direction control valve for the hydraulic
system of tractor.
3. Cylinder (3): Cylinder is mounted on hydraulic lift
housing (1) through screws. Cylinder houses piston inside.
Cylinder’s input port gallery is also connected with response
valve assembly through hydraulic lift housing.
4. Position control lever (4): Position control lever is part of
control sector assembly (12). Position control lever is connected
with position crank (not shown) through tie-rod. Position crank
is connected to position actuator (14) through a position crank
tube. Position actuator is supported at one end by cam (17) on
Ram arm through idler position (15) and at the other end by
spool of control valve (9). By rotating the position lever about
the position crank pivot point, position actuator pushes the
spool of control valve (9), which directs the oil flow in the
cylinder and the piston pushes the connecting rod and hence
the ram arm rotates. As the position of ram arm and lift arm is
fixed with respect to each other by having a spline joint on rock
shaft. As the ram arm rotates, lift arm rotates. Due to the cam
profile on ram arm, position actuator returns back to its
original position and the flow in the cylinder stops and hence
the rotation of the lift arm. The position of lift arm and the
position control lever is fixed through the cam profile.
5. Draft control lever (5): Draft control lever is used for
controlling draft force and not have any function in position
control.
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6. Tie rod assembly (6): Tie rod assembly is used to connect
position control lever and draft control lever with position crank
and draft crank respectively.
7. Lift arm (7): Lift arm is mounted on both end of rock
shaft by splines. Lift arm position decides the position of
implement through three point linkage (not shown).
8. Ram arm (8): Ram arm is mounted on rockshaft and
connected by splines. One end of the ram arm is connected
with piston through connecting rod. Connecting rod is
connected with the ram arm (8) by a dowel pin. One end of the
ram arm is having cam profile (17). This cam profile gives the
feedback of the ram arm position and hence controls the
position of ram arm/lift arm with respect to position control
lever.
9. Control valve (9): Control valve is a directional control
valve. It is mounted inside the hydraulic lift housing and
connected to response valve assembly.
10. Pin control valve (10): Pin control valve is a part of
control valve connected with the control valve spool through a
compressed spring. This pin is in touch with position actuator.
Position actuator (14) actuates control valve through pin
control valve.
11. Draft Coupler (11): Draft coupler is a part of draft
feedback mechanism and it has no role is position control or
position feedback.
12. Control sector assembly (12): Control sector assembly is
consist of position and draft actuating levers, tie-rods, position
and draft crank, position and draft crank tube and tube
assembly. Control sector assembly is mounted on side wall of
hydraulic lift housing.
13. Position crank assembly (13): Position crank assembly
is an assembly of position crank tube and position crank. At
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end it is connected with position actuating lever through tie rod
and at other end, position actuator is connected.
14. Position actuator (14): position actuator is connected
with position crank assembly and is in touch with control valve
pin and idler position roller.
15. Idler position (15): Idler position is pivoted at the center
of position crank assembly. It is mounted on draft crank
assembly (not shown) consisting of two rollers. One roller is in
contact with position actuator and the other roller is in contact
with cam profile (17) of the ram arm (8).
16. Rockshaft (16): Rockshaft is supported in hydraulic lift
housing (1) and it holds ram arm (8) at center and two lift arms
at the both end through spline joints.
17. Non-linear cam profile (17): a non-linear cam profile
positioned on ram arm (8) facilitating in fixing of position of the
lift arm (7) and the position control lever (4).
Working of Position feedback mechanism according to a preferred
embodiment of the invention:
Position of lift arm (7) is controlled by position feedback mechanism in
tractor hydraulic hitch system. By rotating the position lever (4) in clockwise
direction, position crank assembly (13) gets rotated. As there is Idler
position (15) in between the Ram arm (8) and Position actuator (14), the Pin
control valve (10) gets pressed and turns the Control valve (9) in lifting
mode. Hydraulic oil from Pump (not shown in figs) flows through Control
valve (9) and Response valve assembly (2) to hydraulic Cylinder (3). The flow
pushes the hydraulic piston (not shown) and connecting rod which in turn
rotates the lift arm (7). Lift arm and Ram arm are mounted on a Rockshaft
(16) by spline teeth engagement. As the lift arm rotates (7), Ram arm (8) also
rotates. The cam profile on the Ram arm (8) generate gap which allows the
Pin control valve (10) to move out and which in turn bring back the control
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valve to neutral position. Thus, there is maintained a fixed relation between
position of the position control lever (4) and the lift arm (7).
The foregoing is considered as illustrative only of the principles of the
invention. Furthermore, since numerous modifications and changes will
readily occur to those skilled in the art, it is not desired to limit the
invention to the exact construction and operation shown and described.
While the preferred embodiment has been described, the details may be
changed without departing from the invention, which is defined by the
claims.

We claim:
1. In a hydraulic system for a tractor having a hitch for integrally
attaching an implement thereto, a hitch valve with upper, lower
and top links, a non-linear cam follower based implement
control system for precisely controlling position of the lower
links in lower range of total operating range of the lower links,
the implement control system comprising:
a response valve assembly (2) operably connected to a
control valve (9) and through an input port gallery of a
cylinder (3) to the cylinder (3);
a position control lever (4) attached at first end of a
position crank assembly (13) and at second end of the
position crank assembly (13) is attached a position
actuator (14), said position actuator (14) being
operatively engageable at first end to a non-linear cam
profile (17) mounted on one end of a ram arm (8) and at
second end to spool of the control valve (9);
a rockshaft (16) connecting the ram arm (8), a first lift
arm (7) and a second lift arm (7) at center, first end and
second end of the rockshaft (16) respectively.
2. The implement control system as claimed in claim 1, wherein
the first and the second lift arms (7) are connected via spline
joints.
3. The implement control system as claimed in claim 1, wherein
the position control lever (4) is attached at the first end of the
position crank assembly (13) via a tie-rod contained in a tie-rod
assembly (6), wherein the position actuator (14) is attached to
the second end of the position crank assembly (13) via a
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position crank tube, and wherein said position crank assembly
(13) mounts an idler position (15).
4. The implement control system as claimed in claim 1, further
comprising:
a hydraulic lift housing (1) enclosing the response valve
assembly (2), the cylinder (3) and the control valve (9),
via screws, said hydraulic lift housing (1) further
installing a control sector assembly (12) via a pin,
wherein the control sector assembly (12) is mounted on a
side wall of the hydraulic lift housing (1), said hydraulic
lift housing (1) further having an opening thereof and an
end plate removably attached to the hydraulic lift
housing (1) to cover said opening, the rockshaft (16)
being inserted through the side plate, thereby said
hydraulic lift housing (1) enclosing the lift rams (7) and
the Ram arm (8).
5. The implement control system as claimed in claim 2, wherein
the control sector assembly (12) comprises the position control
lever (4), the draft control lever (5), the position actuator (14), a
position crank, a draft crank, the tie-rod assembly (6), the
position crank tube, a draft crank tube and a tube assembly.
6. The implement control system as claimed in claim 1, wherein
the spool of the control valve (9) is operably connected to a pin
control valve (10) via a compressed spring.
7. The implement control system as claimed in claim 1, wherein
the non-linear cam profile (17) mounted on one end of a ram
arm (8) or mounted independently on rockshaft (16) is
configured to provide feedback of position of the ram arm (8),
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thereby controlling the position of the ram arm (8) and the lift
arm (7) with respect to the position control lever (4).
8. The implement control system as claimed in claim 1 and 4,
wherein the position actuator (14) is configured to actuate the
control valve spool (9) via the pin control valve (10).
9. The implement control system as claimed in claim 1, wherein
the position crank assembly (13) comprises a position crank
tube and position crank, and wherein the first end of the
position crank assembly (13) mounts the position rank.
10.The implement control system as claimed in claim 1, wherein
the idler position (15) comprises a first roller and a second
roller, said first roller is configured to be in contact with the
position actuator (14) and the second roller is in contact with
the cam mounted on one end of a ram arm (8).
11.The implement control system as claimed in claim 1, wherein
lateral movement of the lift arms (7) are restricted by the end
plate and plurality of bolts adapted to fix the rockshaft (16) in
the hydraulic lift housing (1).
12.The non-linear cam follower based implement control method
for precisely controlling position of the lower links in lower range
of total operating range of the lower links, the method
comprising:
rotating of a position control lever (4) in clockwise
direction, thereby resulting in the rotation of a position
crank assembly (13);
turning of a Control valve (9) in lifting mode by pressing
of a Pin control valve (10) due to configuration of an Idler
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position (15) between a Ram arm (8) and a Position
actuator (14);
rotating of a lift arm (7) resulting in rotation of a Ram
arm (8) which further results in a non-linear cam profile
(17) mounted on one end of a ram arm (8) to generate
gap, thereby facilitating the Pin control valve (10) to move
out to bring the control valve (9) back to neutral position.