Background Art The popularity and nearly universal acceptance of rubber tired work machines over steel track in agricultural use has stemmed primarily from steel track's relatively higher noise levels, higher initial cost, lower maximum travel speed, and inability to travel on improved roads without inflicting unacceptable damage to the road's surface.

The recent advent of rubber belted track, wherein a continuous rubber belted track is entrained about a pair of wheels, has overcome a majority of the objections of steel track. Using such work machines has emphasized other problems, such as, the need for improved steering when towing an implement behind the machine for various purposes, including planting, plowing and leveling. Higher shock loading is being transmitted to the machine and the operator due to the machine's increased speed and the operation of such machines on hard surface roads, and the increasing demand for further utilization and diversification of the machine application requiring a more demanding verity of gauge adjustment.

The present invention is directed to overcome one or more of the problems as set forth above.

Disclosure of the Invention In one aspect of the invention, a work machine is comprised of a main frame including a two- piece structure defining a first structure and a second structure. The first structure is pivotally connected to the second structure. An engine is mounted near a first end portion of the first structure, and an operator's station is located near a second end portion of the first structure. A pair of endless rubber belted tracks are supported from the second structure, one of each pair of endless rubber belted tracks is positioned on an opposite side of the work machine and is powered by the engine. A suspension system is operatively interposed the first structure and the second structure.

Brief Description of the Drawings FIG. 1 is a side elevational view of the belt driven work machine embodying the present invention; and FIG. 2 is a partially sectioned elevational view of the belt driven work machine embodying the present invention Best Mode for Carrying Out the Invention Referring to FIGS. 1 and 2, a work machine 10, such as an agricultural tractor, is shown having a rubber belted track system 12. The rubber belted track system 12 utilizes a pair of endless rubber belted tracks 14, each having an inner surface 16 and a pair of sides 18. Each of the pair of endless rubber belted track is positioned on one of an opposite sides 20 of the work machine 10. The work machine 10 includes a main frame 22 having a central

axis 24 extending between the pair of endless rubber belted tracks 14. An operator's station 30 is supported on the main frame 22 and is surrounded by a cab 32, a propulsion system 34 including an engine 36 and a transmission system 38 are also supported on the main frame 22.

Attached to the main frame 22 near the rear of the work machine 10 is a hitch 50. The hitch 50 includes a 3-point configuration and is pivotally mounted to the main frame 22. For example, the hitch 50 moves through an arch on either side of the central axis 24.

Each of the pair of endless rubber belted tracks 14 is supported from the main frame 22. Each of the pair of endless rubber belted tracks 14 is powered individually by the engine 36. In this application, the transmission system 38 includes a mechanical drive system 64 utilizing a differential steering mechanism 66. As an alternative, the transmission system 38 could use a pair of motors being driven by either a conventional hydraulic arrangement or an electrical arrangement. If the hydraulic arrangement was used, either a single pump or a pair of pumps could be used. The differential steering mechanism 66 transmits power from the engine 36 to a final drive 68 supported on a roller frame 70 of each of the pair of endless belted tracks 14.

The main frame 22 in this application includes a two-piece structure being defined by a first structure 80 and a second structure 82. The first structure 80 has a first end portion 84 and a second end portion 86. The engine 36 is mounted near the first end portion 84 of the first structure 80 and the operator station 30 is located near the second end

portion 86 of the first structure 80. Located intermediate the first end portion 84 and the second end portion 86, but nearest to the second end portion 86, of the first structure 80 is a first pivot point 88 defining a first pivot axis 90 being traverse to the central axis 24. Located intermediate the first end portion 84 and the first pivot point 88 is a cylinder 92 of a suspension system 94. The suspension system 94 is operatively interposed the first structure 80 and the second structure 82. In this application, the suspension system 94 includes a pair of cylinders 92. The pair of cylinders 92 can be in communication with an accumulator 98. The pair of cylinders 92 are hydraulic cylinders 102 of a generally conventional design and includes a rod member 104 defining a rod end 106 and a piston end portion 108. The rod end 106 is attached to the first structure 80, and the piston end portion 108 is attached to the second structure 82. The suspension system 94 allows the first structure 80 to travel through an arc of about 10 degrees as shown by"A"and "A"'. As an alternative, the suspension system 94, could utilize additional passive components such as a pneumatic cylinder, an air over hydraulic cylinder, a shock absorber mechanism, coil springs or rubber springs. As a further alternative, the suspension system 94 could utilize an active system, not shown, such as a motion accelerometer being attached to the front end portion 84 of the first structure 80 sending a signal therefrom and feeding data to a controller.

Within the controller, the data would be interpreted and fluid would be directed to the cylinder 102 to compensate for the either the upward or downward motion between the first structure 80 and the second

structure 82. As a further alternative, a pair of motion accelerometers could be used. One of each of the pair of accelerometers would be attached to the front end portion 84 of the first structure 80 and to the roller frame 70 in an area generally corresponding to the front of the machine 10 or the front end portion 84 of the first structure 80. Signals or data would be sent to the controller, interpreted. Fluid would be sent to the cylinders 102 to compensated for the variation in motion and provide a suitable active suspension system 94.

The second structure 82 defines a first end portion 120 and a second end portion 122. Located intermediate the first end portion 120 and the second end portion 122, but nearest to the second end portion 122, is a second pivot point 124 being identically located with the first pivot point 88. The second pivot point 124 defines a second pivot axis 126 being identically located with that of the first pivot axis 88. The second pivot axis 126 is transverse to the central axis 24. Again, the second pivot axis 126 of the second structure 82 is symmetrical about the pivot axis 90 of the first structure 80. The piston end portion 108 of the pair of hydraulic cylinders 102 is attached to the first structure 80 on each of the opposite sides 20 of the work machine 10 near the first end portion 120. And, the rod end 106 of the pair of hydraulic cylinders 102 is attached to the second structure 82 on each of the opposite sides 20 of the work machine 10 near the first end portion 120.

The hitch 50 is attached to the second structure 82 near the second end portion 122.

Industrial Applicability In operation, the suspension system 94 when used with the work machine 10 having the rubber belted track system 12 extends the operating parameters of the work machine 10. For example, when working in a field having terraces, as the work machine 10 travels up and over a terrace, the second structure 82 and the pair of endless rubber tracks 14 follow the ground contour up the terrace. At the top of the terrace and at the point at which the center of gravity of the work machine 10 passes over the top, the second structure 82 abruptly falls to engage the downward slope of the terrace. The pair of cylinders 92 interposed the first structure 80 and the second structure 82 will cushion the impact to the engine 36 and the operator's station 30. Thus, the results of the impact will be lessened, the comfort of the operator is improved, stresses are reduced to the first structure 80 and maintenance of the first structure 80 is reduced. Increased efficiency as a result of increased travel speeds and reduced fatigue to the operator results from use of the suspension system 94.

When the suspension system 94 uses a conventional shock absorber as the pair of cylinders 92, the flexibility, variation in dampening characteristics, of the suspension system 94 is fixed and cannot be varied. As an alternative, if the pair of cylinders 92 uses a combination of a hydraulic cylinder 102 and an accumulator or another variable input, the flexibility of the suspension system 94 can be varied to match the operating conditions.

Additionally, the type of cylinders 92 could be

varied, such as a hydraulic, pneumatic or any combination thereof.

The suspension system 94 will functionally improve operations over any obstacle such as a rise or change in elevation of a road surface, plowed or disc ground and other such variables.

Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.