Earth working – Automatic power control – Draft responsive
Reexamination Certificate
1999-08-10
2001-05-15
Novosad, Christopher J. (Department: 3671)
Earth working
Automatic power control
Draft responsive
C172S439000, C701S050000
Reexamination Certificate
active
06230817
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to work vehicle hitches including lower draft links. In particular, the present invention relates to mechanisms for adjusting the angular orientation of one draft link relative to the other draft link.
BACKGROUND OF THE INVENTION
Three-point hitches are used at the rear and at the front of work vehicles to lift, carry, push and pull various implements. Three-point hitches typically include a rocker or rocker shaft, lift links, lower or draft links, an upper or center link and rocker shaft actuators. The rocker shaft is pivotably supported by the work vehicle and includes links pivotably connected to the lift links.
The rocker shaft provides synchronized lifting of the draft links and sums the lift forces of the hydraulic lift cylinders to maintain the implement in a stable roll axis while in use or at rest. The lift links extend from the arms of the rocker shaft and are pivotably connected to the draft links. The draft links are themselves pivotably connected to the work vehicle. The actuators are pivotably coupled at one end to the work vehicle and at an opposite end to the rocker shaft to pivotably raise and lower the rocker arms. Because the arms of the rocker shaft are coupled to the lift links and thereby to the draft links, such pivotal raising and lowering of the rocker shaft arms correspondingly pivotably raises and lowers the draft links to thereby lift and lower implements mounted on the draft links.
To attach the three-point hitch to a three-point hitch implement, it is necessary to align the draft links with corresponding attachment points on the implement. However, the attachment points on the three-point hitch implement are frequently out of alignment due to the implement being parked on uneven ground or on soft ground which allows the implement to repose into an unlevel misaligned condition. As a result, the operator must realign the draft links with the attachment points of the implement.
To enable the draft links to be realigned with the attachment points of the implement, conventional lift links include mechanical length adjustment features such as turn buckles. These turn buckles enable the operator to vary the length of the lift links so as to align the end of the lift links with the attachment points of the implement.
Although commonly used in both front and rear mounted three-point hitches, the use of such turn buckles to adjust the length of the lift links and to thereby align the draft links with the implement attachment points has several drawbacks. First, adjusting such turn buckles requires that the operator stop and exit the work vehicle to access the turn buckles at the rear of the work vehicle. Second, adjustment of the turn buckles is often extremely difficult and requires additional tools. Because turn buckles typically include threaded parts, the threaded parts frequently accumulate dust, rust or other contaminants upon them making adjustment of the turn buckle difficult.
Furthermore, adjustment of the lift links, once attached to the implement, is also inconvenient and time consuming. In many situations, it is also necessary to level the draft links once they are attached to the implement due to the large loads placed upon the lift links. As a result, the operator frequently must lower the implement to reduce loads upon the lift link in order to manually adjust the turn buckle and the length of the lift link. Consequently, the operator must climb into and out of the work vehicle multiple times.
Thus, there is a continuing need for a draft link adjustment mechanism which provides for easy and inexpensive adjustment of draft links for attachment to an implement and leveling of the draft links after attachment to an implement.
SUMMARY OF THE INVENTION
According to one exemplary embodiment, the present invention provides a hitch assembly for a work vehicle. The hitch assembly includes a first draft link adapted to be pivotably coupled to the work vehicle, a second draft link adapted to be pivotably coupled to the work vehicle, a first linear actuator having a first end adapted to be pivotably coupled to the vehicle and a second end pivotably coupled to the first draft link, and a linear member having a third end adapted to be pivotably coupled to the work vehicle and a fourth end pivotably coupled to the second draft link. The first and second draft links are pivotable relative to one another. The first linear actuator is actuatable to different lengths to pivot the first draft link relative to the linear member.
According to a second embodiment, the present invention provides a hitch assembly for a work vehicle which includes a frame adapted to be stationarily coupled to the work vehicle, a first draft link adapted to be pivotably coupled to the work vehicle, a second draft link adapted to be pivotably coupled to the work vehicle, a first linear actuator having a first end adapted to be pivotably coupled to the frame and a second end pivotably coupled to the first draft link, and a second linear actuator having a third end pivotably coupled to the frame and a fourth end pivotably coupled to the second draft link. The first and second draft links are pivotable relative to one another. The first and second linear actuators are independently actuatable to a plurality of lengths to pivot the first and second draft links relative to one another.
According to a third embodiment, the present invention provides a hitch assembly for a work vehicle which includes a first draft link adapted to be pivotably coupled to the work vehicle, a second draft link adapted to be pivotably coupled to the work vehicle, at least one actuator coupled to at least one of the first and second draft links, at least one sensor configured to generate at least one position signal indicative of a position of at least of the first and second draft links and a control circuit coupled to the at least one sensor. The first and second draft links pivot relative to one another. The at least one actuator is configured to pivot at least one of the first and second draft links. The control circuit is configured to generate at least one control signal in response to the at least one position signal generated by the at least one sensor. The at least one actuator pivots one of the first and second draft links relative to the other of the first and second draft links in response to the at least one control signal.
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Case Corporation
Foley & Lardner
Novosad Christopher J.
LandOfFree
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