Motor vehicles – Including one or more ski-like or runner members – With at least one surface-engaging propulsion element
Reexamination Certificate
2002-08-07
2004-04-06
Morris, Lesley D. (Department: 3611)
Motor vehicles
Including one or more ski-like or runner members
With at least one surface-engaging propulsion element
C180S190000, C180S009500, C305S143000
Reexamination Certificate
active
06715575
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a track tensioning system for tracked vehicles, and more particularly, to a system that uses the endless track as a spring to resist suspension displacement caused by certain types of displacement forces.
BACKGROUND OF THE INVENTION
Tracked vehicles, such as snowmobiles, have rear suspension systems generally including front and rear suspension arms pivotally mounted on a shaft rotatably connected to the frame of the tracked vehicle and a slide frame comprising a pair of laterally spaced suspension rails or longitudinal skids interconnected transversely on opposite sides of the machine. The suspension rails are in sliding contact with an endless belt that provides ice and snow surface contact and friction drive for the tracked vehicle. Where the movement of the suspension arms relative to the suspension rail is substantially limited to rotational motion, the suspension system referred to as fully coupled. As used herein, “fully coupled” means a suspension system where a displacement of any portion of the suspension rail causes immediate movement of the entire suspension rail, such as for example where the suspension forms parallelogram configuration.
In many current arrangements, a shackle or sliding block mechanism interconnects the rear suspension arm and the suspension rails to permit relative movement that includes a non-rotational component, such as a lateral or a longitudinal linear component (also referred to as lost motion). Such suspension systems are referred to as non-coupled. As used herein, “non-coupled” refers to a suspension system in which displacement of the rear suspension arm relative to a suspension rail includes a linear component.
The non-coupled configuration allows the front and rear suspension arms to operate independent of one another, which was thought advantageous in the prior art because of favorable weight transfer characteristics that enhance traction. This independence, however, was found to result in rough and unsteady rides for the rider, particularly when the rear suspension of the track encounters an elevated mound of ice or snow or the upward side of a depression. This instability detracts from the enjoyment and the utility of the vehicle since there are many areas which, when traversed, will unduly subject the rider to severe jolts and stress.
The independent movement of the front and rear suspension arms adversely affects the tracked vehicle in several ways. First, track tension is not adequately maintained when there is extreme deflection of either one of the front or rear suspension arms. Extreme variations in track tension can reduce the comfort, control, track life and ultimately the safety of the rider.
Second, independent movement of the front and rear suspension arms in a non-coupled system requires the associated springs and shock absorbers to be sprung and dampened more stiffly because each must individually support the high loads when impact occurs at either the front or rear extreme of the suspension rails. That is, the springs and shock absorbers of each suspension arm must be stiff enough to withstand and control the full impact of the bump and weight of the tracked vehicle by itself. The required stiffness of the spring and shock absorber results in a less comfortable on normal terrain.
Third, when the front suspension arm of a non-coupled suspension deflects as it contacts a bump, the front suspension arm deflects more than the rear suspension arm. This results in an angle of incidence between the suspension rails and the bump. Unless the impact is then large enough to compress the rear suspension arm spring and shock absorber assembly, thereby flattening the angle of incidence, the suspension rails will act as a ramp forcing the rear of the tracked vehicle upward. At low to moderate speeds, the suspension rails angle in an upward incline due to the greater deflection of the front suspension arm than the rear suspension arm, causing the tracked vehicle to hop over the bump, imparting a secondary jolt that increases in intensity with the speed of the tracked vehicle.
These problems were successfully addressed in by the partially coupled suspension systems disclosed in U.S. Pat. No. 5,370,198 (Karpik); U.S. Pat. No. 5,667,031 (Karpik) and U.S. Pat. No. 5,881,834 (Karpik)(hereinafter “the Karpik Patents”). The Karpik Patents disclose a coupling system that permits some independent movement of the rear suspension arm relative to the front suspension arm. Once the rear suspension arm reaches the limit of its independent motion, the system becomes fully coupled.
The coupling system can also serve as a weight transfer mechanism that transmits an increasing percentage of the tracked vehicle's weight to the front suspension arm and the forward end of the slide rail. Through the coupling system, the work of the spring and shock absorbers is shared by the front and rear suspension arms. By sharing forces acting on the suspension system generally between the front and rear suspensions arms, it is possible to use softer shock and spring calibrations than normally would be required to prevent the suspension system from bottoming out. The resulting softer shock and spring calibrations provide a more comfortable ride in normal terrain.
Assuming that the coupling system distributes forces acting on the suspension system between the front and rear suspension arms, the springs and shock absorber at the front suspension arm carries a portion of the force and the rear suspension arm carries the remainder of the force. The minimum theoretical shock and spring calibration must be set to handle the maximum anticipated force the suspension system will encounter. In order to maximize ride comfort on normal terrain, what is needed is a suspension system that reduces the shock and spring calibrations below this theoretical minimum, while still providing adequate resistance to extreme suspension displacement.
BRIEF DESCRIPTION OF THE INVENTION
The present invention relates to a system for using the endless track on a tracked vehicle as a spring to supplement the biasing force of the suspension system during certain types of loads. The resulting increase in track tension resists further increases in perimeter length, hence resisting further suspension displacement. Consequently, the spring and shock absorber calibrations can be reduced to levels not previously possible.
The suspension system for suspending an endless track beneath a tracked vehicle chassis can be a fully coupled suspension, a partially coupled suspension or a non-coupled suspension. The suspension system includes at least one elongated suspension rail having a front portion, a rear portion and a bottom track-engaging portion. At least one suspension arm has an upper end adapted for pivotal connection to the vehicle chassis and a lower end pivotally connected to the suspension rail. The upper or lower ends of the suspension arm can optionally have a displacement with a non-linear component. A biasing mechanism provides a biasing force to bias the suspension rail away from the vehicle chassis. The track tensioning system coupled to the suspension arm applies a tensioning force to the endless track in response to linear and/or rotational displacement of the suspension arm. The tensioning force generates a supplemental force transmitted by the endless track that augments the biasing force of the biasing mechanism. In a suspension system with front and rear suspension arms, the track tensioning system can be coupled to the front or rear suspension arms.
A variety of other mechanism and/or conditions can be used to cause the track tensioning system to increase track tension. In one embodiment, the track tensioning system is coupled to a coupling system. The track tensioning system applies a tensioning force to the endless track when the coupling system is activated. In another embodiment, the track tensioning system applies a tensioning force to the endless track in response to a displacement of the rear portion of the suspension r
Faegre & Benson LLP
Formula Fast Racing
Morris Lesley D.
Winner Tony
LandOfFree
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