Land vehicles – Wheeled – Articulated vehicle
Reexamination Certificate
1999-09-03
2001-05-22
Olszewski, Robert P. (Department: 2167)
Land vehicles
Wheeled
Articulated vehicle
C280S446100
Reexamination Certificate
active
06234508
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to load sensing in work vehicles. More particularly, it relates to load sensors located between a work vehicle and a towed implement.
BACKGROUND OF THE INVENTION
Work vehicles such as tractors and backhoes, for example, tow implements using a variety of hitches to connect the vehicle and the implement. One of the most common hitches is called a “three point hitch.” It is called a three point hitch since it has three substantially parallel links or connections that extend between the vehicle (usually a tractor) and the implement. These links permit the motion between the vehicle and the implement to be constrained to relative translation, and substantially prevent relative rotation.
Many tractors or other work vehicles are able to electronically monitor and control their travel through the field, as well as control the height of and load placed upon the implement. This control is especially useful to regulate the speed of the tractor, the power output of the engine, the tractor's gear ratio and the height of the implement above or below the ground. Using various sensors on the vehicle, the tractor can raise the implement to reduce the implement load, increase the power output of the engine, down shift to a lower gear or reduce the speed of the tractor.
To sense the load placed on the tractor by the implement, a load sensor is typically provided between the implement and the tractor to sense the load placed on one or more of the links connecting the tractor to the implement. These sensors can be arranged to provide two different types of sensings: indirect and direct load sensing. Both of these methods have serious limitations. The direct method places a load sensor between the tractor and the implement that directly senses the strain applied by the implement on the tractor. As an example, a load pin is placed between one or more of the three links and the tractor or between one or more of the three links and the implement. A common direct sensing method has been to replace one or more of the pins coupling the three links of the three point hitch to the tractor or one or more of the three links connecting the three point hitch to the implement with a load sensing pin that provides an electronic signal indicative of the load applied to the pin. As the links are pulled by the tractor towing the implement, they in turn apply a force to the load pin. Load cells placed on the load pin provide an electrical signal indicative of the load on the load pin.
There are problems with the direct method. In the direct method, the pin is fixed with respect to the tractor. A bracket fixed to the tractor commonly has two ears or webs with holes through which the load pin extends. The bracket defines the axis of the load pin perpendicular to the direction of travel of the tractor, extending either vertically or horizontally, and prevents the pin from moving. Since the load sensed by the load pin typically indicates a load applied perpendicular to the load pin axis, it is responsive only to loads applied straight backward away from or forward toward the tractor. As the implement moves from side to side, however, it places a bending or torsional load on the load pin. This causes the load pin to give a false reading of the load in the link.
In the indirect method a spring member is located between the upper link and the tractor. As a load is applied to the upper link, the spring member deflects. This deflection is either sensed by a position sensor or a load sensor. While this eliminates some of the problems of the direct method, it is less accurate than the direct method.
What is needed, therefore, is an improved method and apparatus for sensing the load applied by an implement to a tractor. It is an object of this invention to provide such a method and apparatus.
SUMMARY OF THE PRESENT INVENTION
In accordance with the first embodiment of the invention an agricultural vehicle is disclosed including a tractor, an implement and a multi-point hitch connecting the tractor to the implement, the hitch including a plurality of links extending from the tractor to the implement, a swivel disposed between and coupling at least one of the links to the tractor, and a load sensor disposed between the swivel and the at least one link. The load sensor may be fixed with respect to the at least one link. The load sensor may have a primary sensing direction and that sensing direction may be fixed with respect to the at least one link. Load sensor may be a cylindrical load pin having a longitudinal cylindrical axis. The swivel may be constrained to pivot with respect to the tractor about a first pivotal axis. The at least one link may be constrained to pivot about the swivel about a second pivotal axis substantially orthogonal to the first pivotal axis. The first pivotal axis may be substantially horizontal.
In accordance with a second embodiment of the invention, a multi-point hitch for connecting a tractor to an implement is disclosed including an upper link extending from the tractor from an upper point on the tractor and couplable to an implement, two links extending from the tractor at two laterally spaced points below the upper point and couplable to an implement, a swivel coupled between the tractor and the upper link, and a load sensor coupled between the swivel and the upper link. The load sensor may have a primary sensing direction and this direction may be fixed with respect to the upper link when the upper link pivots with respect to the tractor. The load sensor may be disposed between the swivel and the upper link to transmit substantially the entire load in the upper link to the tractor. The swivel may be constrained to pivot with respect to the tractor about a first pivotal axis. The upper link may be constrained to pivot about the swivel about a second pivotal axis substantially orthogonal to the first pivotal axis. The first pivotal axis may be substantially horizontal.
In accordance with a third embodiment of the invention, an agricultural vehicle is disclosed including a tractor, and an elongate load sensing member having first and second ends and a longitudinal axis and coupled to the tractor at the first end, the member including, a first coupler disposed at the first end, a second coupler disposed at the second end and a load sensor fixed to the first coupler. The vehicle may further include a threaded cylinder disposed between and coupling the first coupler to the second coupler. The member may pivot with respect to the tractor at least about a horizontal and a vertical axis. The load sensor may pivot together with the member about the horizontal and vertical axes. The threaded cylinder may be rotatable with respect to the first and second ends to shorten or lengthen the elongate member. The first coupler may include an eye. The first coupler may also include a clevis.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.
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Schubert William L.
Stelzle Michael
Tuttle Thomas B.
Case Corporation
Cuff Michael
Foley & Lardner
Olszewski Robert P.
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