Motor vehicles – Special driving device – Portable track
Reexamination Certificate
2000-03-13
2001-04-24
Dickson, Paul N. (Department: 3618)
Motor vehicles
Special driving device
Portable track
C180S009380, C180S006480
Reexamination Certificate
active
06220377
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to vehicles and, more particularly, to a vehicle for use on a wide range of terrain, including uneven and/or steep terrain having a variety of soil conditions. The vehicle of the present invention offers many advantages over conventional vehicles and can replace conventional vehicles in performing a variety of tasks.
BACKGROUND AND SUMMARY OF THE INVENTION
Most conventional vehicles such as loaders or bulldozers are either driven by four wheels or by two tracks. Typical track-propelled vehicles employ a pair of spaced steel or rubber endless tracks that are driven to move the vehicle over the ground. Vehicles that are solely wheel-propelled typically include a pair of front wheels and a pair of rear wheels that are rotatably driven to propel the vehicle. The wheels of the wheel-propelled vehicles are generally large and have tread designs that aid in moving the vehicle over sand, clay and mud. These conventional vehicles, although capable of moving over terrain having a variety of soil conditions, frequently become stuck because all of the tractional forces and propelling surfaces are not always put to the ground.
Conventional four wheel vehicles and conventional two track vehicles often cause environmental damage when used in natural areas. Recently, environmental concerns have been raised about the disruption of the topsoil which occurs when conventional loader/bulldozer-type vehicles are operated on the topsoil, sand or other soft terrain of sensitive natural areas. For example, in the tree harvesting industry, construction industry and/or the agricultural industry, the operation of conventional vehicles of the type described may cause significant damage to the topsoil, which in turn may result in the formation of ruts which may lead to soil erosion.
U.S. Pat. No. 5,615,748 discloses a vehicle that has a central track and a pair of flanking wheels disposed on opposing sides of the track. The flanking wheels are mounted for pivotal movement about a pair of generally vertically extending axes.
As discussed above, the advantage of a two-track tractor vehicle over a four-wheeled tractor vehicle is its traction and stability. On the other hand, the advantage of a four-wheel tractor vehicle over a two-track tractor vehicle is in its ease of handling and maneuverability.
To a considerable extent, the tractor vehicle of my '748 patent achieves the advantages of both two track and four wheeled tractor vehicles. This is because it provides a central track for traction and stability and two outrigger wheels for ease of handling and maneuverability.
The outrigger wheels of my '748 tractor vehicle were steerable wheels of the type having an upright steering axis and a steering mechanism capable of turning both wheels generally in unison about their steering axes to effect turning movement.
It has been found that enhanced ease of handling and maneuverability can be achieved by utilizing outrigger wheels which are steered by changing the relative driving speed between the two outrigger wheels rather than by moving them in unison about upright steering axes. Further enhancement can be obtained by mounting the outrigger wheels for vertical movement and utilizing hydraulic cylinders and a control system therefor to maintain them in ground contact.
It has also been understood that the '748 tractor vehicle enhanced as aforesaid because it includes a central track and two outrigger wheels is uniquely set up to enable a substantial portion of the load support to be shifted between the central track and the outrigger wheels. For example, if the hydraulic cylinders which keep the outrigger wheels in ground contact are adjusted so that a substantially low pressure condition exists, the central track will support most of the vehicle load on the ground. As the pressure conditions in the hydraulic cylinders are increased, more and more load will be assumed by the outrigger wheels. This substantial shift in load support occurs without any shifting of the load itself or any tilting of the frame. In contrast, the only way load support can be shifted between the two tracks of a two-track tractor or the four wheels of a four-wheel tractor is to shift the load itself or tilt the frame. It has been found this unique load support shifting capability made possible by the use of hydraulic cylinders to keep the independently driving outrigger wheels on opposite sides of the central track in ground contact, enables traction and stability to be enhanced while at the same time further enhancing the ease of handling and maneuverability of the tractor vehicle.
In accordance with the principles of the present invention, the advantages discussed above are achieved by providing a vehicle comprising a main frame; an engine assembly constructed and arranged to generate power; and a driving track assembly supporting the main frame. The driving track assembly includes an endless ground engaging track. The driving track assembly is connected to the engine assembly in power supplying relation and is constructed and arranged to move the track in driving engagement with the ground using power from the engine assembly so as to move the vehicle along the ground. A pair of secondary driving and steering assemblies are mounted on opposing lateral sides of the track assembly in flanking relation. The secondary driving and steering assemblies each include a ground engaging driving and steering structure. The ground engaging driving and steering structures and the track assembly are mounted within the vehicle so as to enable the track assembly and the driving and steering structures to be moved generally vertically relative to one another to shift a distribution of vehicle weight between the driving and steering structures and the track. In the illustrated embodiments, the ground engaging driving and steering structures are moved downwardly relative to the driving track assembly, but the scope of this aspect of the invention is not limited in such a manner. The secondary driving and steering assemblies are operatively connected to the engine assembly in power supplying relation and are constructed and arranged to move the ground engaging driving and steering structures in driving engagement with the ground using power from the engine assembly so as to assist the track assembly in moving the vehicle along the ground.
The vehicle of this aspect of the invention further comprises power-operated structure operatively connected to the engine assembly in power supplying relation. The power-operated structure is constructed and arranged to affect the generally vertical relative movement between the driving and steering structures and the track assembly using power from the engine assembly to shift the distribution of the vehicle weight. An electronic controller is communicated to the power-operated structure and each of the secondary driving and steering assemblies. A steering input device is communicated to the electronic controller. The steering input device is operable to transmit a steering signal to the controller indicative of a selected angle at which the vehicle is to be steered. The controller is operable to process the steering input signal and responsively control the secondary driving and steering assemblies and the power-operated structure to affect a vehicle steering operation wherein (1) the power-operated structure affects the generally vertical relative movement between the track assembly and the driving and steering structures so as to shift the distribution of vehicle weight from the track to the driving and steering structures, thereby providing the driving and steering structures with increased traction during movement thereof in driving engagement with the ground, and (2) the secondary driving assemblies move the driving and steering structures in driving engagement with the ground to thereby steer the vehicle at the selected angle. In the preferred embodiment, the steering is affected by as a result of the movement imparted to the vehicle by one of th
Dickson Paul N.
Lansberry Tractor Company, Inc.
Lerner Avraham H.
Pillsbury & Winthrop LLP
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