Land vehicles – Wheeled – Running gear
Reexamination Certificate
2001-12-26
2003-11-18
Dickson, Paul N. (Department: 3616)
Land vehicles
Wheeled
Running gear
Reexamination Certificate
active
06648352
ABSTRACT:
FIELD OF THE INVENTION
The invention related generally to work vehicles, such as skid steer loaders and other skid steer vehicles. More particularly, it relates to drive and suspension systems for such vehicles.
BACKGROUND OF THE INVENTION
Skid steer vehicles such as skid steer loaders are used in a wide variety of construction environments where they are particularly suitable due to their small size and maneuverability.
Skid steer vehicles can turn with an effective turning radius of zero. They can rotate about a vertical axis extending through the center of the chassis by driving the wheels on one side of the vehicle forward and the wheels on the other side of the vehicle backwards. Since the wheels cannot be steered with respect to the chassis, this causes the wheels to skid sideways as they rotate. This is the extreme case. Even when the vehicle is moving forward or backward (i.e. the wheels on both sides of the vehicle are driven in the same direction) the vehicle still steers by skidding, albeit to a lesser degree.
Skid steer vehicles are well suited to work on construction sites and even within buildings due to this ability to skid steer. Enhancing this capability is their compact size.
Skid steer vehicles have not been provided with sprung suspensions for several reasons.
First, the addition of a suspension is difficult due to the compact size of the skid steer vehicle itself. Adding suspensions would increase the width of the vehicle and make it less suitable for the close spaces in which it is used.
Second, traditional automotive-type suspensions would cause excessive pitching of the work vehicle, given its short wheelbase (e.g. vehicles having a front-to-rear wheel spacing of less than two wheel diameters). For example, a typically automotive or truck type suspension includes a vertically oriented spring that is coupled to the chassis at its upper end. The point of coupling is typically directly above the rotational axis of the wheel supported on that suspension. As a result, whenever the wheel is forced upward, (such as when the car goes over a bump) the spring is compressed, and an upward force is applied to the chassis directly above the wheel where the spring is anchored.
For a vehicle such as a car with a large wheel-to-wheel spacing (i.e. a fore-and-aft wheel spacing of six wheel diameters or more) and a long wheelbase, this upward force does not cause significant pitching in the vehicle. For a vehicle such as a skid steer loader, with its small wheel-to-wheel spacing (i.e. a fore-and-aft wheel spacing of less than two wheel diameter) and short wheelbase, the pitching would be more severe.
What is needed therefore is a suspension system for a skid steer loader that provides springing, but avoids or reduces the pitching inherent in a short wheelbase vehicle having a spring coupled to the chassis adjacent the wheel. It is an object of this invention to provide such a vehicle.
SUMMARY OF THE INVENTION
In accordance with a first embodiment of the invention a skid steer vehicle is provided that includes a chassis having a left side and a right side; an engine fixed to the chassis; a first hydraulic fluid pump driven by the engine to provide hydraulic fluid under pressure; a second hydraulic fluid pump driven by the engine to provide hydraulic fluid under pressure; at least a first hydraulic motor in fluid communication with the first hydraulic fluid pump; at least a second hydraulic motor in fluid communication with the second hydraulic fluid pump; left front and left rear suspensions mounted in a fore-and-aft arrangement on the left side of the chassis for pivotal movement with respect thereto, each left suspension including a left ground-engaging wheel extending from the left side of the chassis and rotationally coupled to the at least a first hydraulic motor to be driven in rotation thereby, a left control arm assembly coupled to and between the left wheel and the chassis to pivot with respect to the chassis about a left control arm pivotal axis; and right front and right rear suspensions mounted in a fore-and-aft arrangement on the right side of the chassis for pivotal movement with respect thereto, each right suspension including a right ground-engaging wheel extending from the right side of the chassis and rotationally coupled to the at least a second hydraulic motor to be driven in rotation thereby, a right control arm coupled to and between the right wheel and the chassis to pivot with respect to the chassis about a right control arm pivotal axis, wherein said at least a first hydraulic motor is coupled to both of the left side suspension wheels to drive the left side wheels at the same speed, and wherein said at least a second hydraulic motor is coupled to both of the right side suspension wheels to drive the right side wheels at the same speed.
Each of the control arms of the left side suspensions and the right side suspensions may be pivotally coupled to the chassis about a pivotal axis that is disposed closer to the center of gravity of the vehicle than wheel coupled to said each control arm. The left control arm pivotal axis of the left front suspension and the right control arm pivotal axis of the right front suspension may extend laterally with respect to the chassis and may be located behind and parallel to the rotational axis of the left front and right front wheels, respectively. The left front suspension may further include a left front spring coupled to the left front control arm at the left front control arms' pivotal axis to apply a torsional force thereto, wherein the left front spring is coupled to the chassis at a position closer to the center of gravity of the vehicle than the left front control arm; and a right front spring coupled to the right front control arm at the right front control arms' pivotal axis to apply a torsional force thereto, wherein the right front spring is coupled to the chassis at a position closer to the center of gravity of the vehicle than the left front control arm. The left front spring and the right front spring may be torsion bars extending laterally with respect to the chassis and behind the rotational axes of the left front suspension wheel and the right front suspension wheel. The left rear suspension may further include a left rear spring coupled to the left rear control arm at the left rear control arms' pivotal axis to apply a torsional force thereto. The left rear spring may be coupled to the chassis at a position closer to the center of gravity of the vehicle than the left rear control arm. A right rear spring may be coupled to the right rear control arm at the right rear control arms' pivotal axis to apply a torsional force thereto. The right rear spring may be coupled to the chassis at a position closer to the center of gravity of the vehicle than the left rear control arm.
In accordance with a second embodiment of the invention, a skid steer vehicle is provided that includes a chassis having a left side and a right side; an engine mounted on the chassis; first and second hydraulic pumps driven by the engine to provide first and second sources of hydraulic fluid under pressure; four independent suspensions coupled to the chassis, each suspension including a torsion bar having a longitudinal axis, a fixed end and a free end, wherein the fixed end is fixed with respect to the chassis, a control arm having first and second ends, wherein the first end is mounted to the chassis to pivot with respect to the chassis and further wherein the free end of the torsion bar is fixed to the first end of the control arm to pivot with respect to the chassis and thereby applying a torsional load to the torsion bar, a ground-engaging wheel rotationally mounted on the second end of the control arm to rotate with respect thereto, and a hydraulic motor fixed to the second end of the control arm and also coupled to the wheel to rotate the wheel with respect to the control arm.
Two of the four suspensions may be front suspensions, disposed one on each side of the chassis. Two of the four suspensions may
Bateman Troy D.
Felsing Brian E.
Lamela Anthony J.
Case LLC
Dickson Paul N.
Fleming Faye M.
Henkel Rebecca
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