Abstract: A skid steer vehicle has a chassis with four drive wheels suspended from the chassis that are damped by four damping cylinders. An electronic controller varies the damping of the cylinders in an automatic mode, based on certain operational parameters of the vehicle, and in a manual mode in response to operator selection of a desired degree of suspension damping.

Abstract: A skid steer vehicle has a suspension that includes a control arm pivotally coupled to the vehicle chassis that is supported by a hydraulic cylinder connected to an accumulator to provide springing. A hydraulic circuit coupled to the cylinder and accumulator permit the operator to raise and lower the chassis, to lock the suspension while the vehicle is loaded, and to automatically charge or discharge the accumulator to match the cylinder pressure during loading and unloading. In this manner, when the suspension is unlocked after loading, the vehicle chassis neither rises nor falls.

Abstract: A dozer blade control system controls the position of a bulldozer blade, maintaining the blade at a constant position as the dozer travels through a worksite. The control system monitors the angle of the dozer blade with respect to the earth and when it senses that the dozer blade is tilting, it corrects the dozer blade's position by extending or retracting hydraulic cylinders that couple the dozer blade to the chassis of the crawler-tractor. When the dozer chassis pitches forwards, the blade begins to tilt forward and to drop closer to the ground. The control system senses this forward rotation of the blade and retracts the hydraulic cylinders that couple the blade to the chassis, causing the blade to return to and maintain its original position.

Abstract: A skid steer vehicle has a suspension that includes a control arm pivotally coupled to the vehicle chassis that is supported by a hydraulic cylinder connected to an accumulator to provide springing. A hydraulic circuit coupled to the cylinder and accumulator permit the operator to raise and lower the chassis, to lock the suspension while the vehicle is loaded, and to automatically charge or discharge the accumulator to match the cylinder pressure during loading and unloading. In this manner, when the suspension is unlocked after loading, the vehicle chassis neither rises nor falls.

Abstract: A work vehicle having a hydrostatic drive system provides for the recovery and reuse of the vehicle's kinetic energy by conducting pressurized hydraulic fluid out of the hydrostatic drive system into an accumulator during vehicle deceleration, and conducting the pressurized fluid back into the drive system during vehicle acceleration to assist the vehicle's engine in accelerating the vehicle.

Abstract: A work vehicle having a hydrostatic drive system provides for the recovery and reuse of the vehicle's kinetic energy by conducting pressurized hydraulic fluid out of the hydrostatic drive system into an accumulator during vehicle deceleration, and conducting the pressurized fluid back into the drive system during vehicle acceleration to assist the vehicle's engine in accelerating the vehicle.

Abstract: A skid steer vehicle has sprung suspensions, variable displacement pumps and motors connected to those pumps that drive the wheels on the vehicle as well as an electronic controller that receives signals that indicate fore-and-aft acceleration of the skid steer vehicle. Based on these signals, the controller determines whether the forward acceleration exceeds a predetermined value and locks up the rear suspensions if that value is exceeded. It also determines whether the forward deceleration exceeds a predetermined value and locks up the front suspensions if that value is exceeded. The signals can be provided by an accelerometer, a satellite receiver, wheel/motor speed sensors, sensors in the pumps that signal the specific displacement of the pumps such as their swash plate positions, or memory locations that contain previously calculated specific displacement commands that are used to drive the pumps to a particular specific displacement.

Abstract: A skid steer vehicle has sprung suspensions that can be locked to prevent vertical movement with respect to the chassis of the vehicle. The operator controls include a switch that the operator can manipulate to lock the suspensions on command. The switch is mounted on a joystick that is used to perform other vehicle functions such as moving the vehicle, raising loader arms, or tilting the bucket or other implement attached to the loader arms. The switch is located on the joystick such that the operator can manipulate the switch without having to remove his hands from the joystick.

Abstract: A skid steer vehicle has sprung suspensions, variable displacement pumps and motors connected to those pumps that drive the wheels on the vehicle as well as an electronic controller that receives signals that indicate lateral acceleration of the skid steer vehicle during turns. The controller determines whether the lateral acceleration exceeds a predetermined value, and locks up the outboard suspensions if that value is exceeded. The signals can be provided by an accelerometer, a satellite receiver, wheel/motor speed sensors, sensors in the pumps that signal the specific displacement of the pumps (such as their swash plate position, or memory locations that contain previously calculated specific displacement commands that are used to drive the pumps to a particular displacement.

Abstract: A skid steer vehicle includes a chassis mounted on four sprung suspensions that are controlled by an electronic controller. The controller monitors the speed of the vehicle and locks the suspensions when the vehicle falls below a predetermined speed.

Abstract: A skid steer vehicle has a sprung suspension system including four wheels mounted on four swing arms that are pivotally coupled to the chassis of the vehicle. An electronic controller is connected both to position sensors coupled to the swing arms to sense the position of the swing arms and wheels with respect to the chassis and also to hydraulic cylinders that control the position of the swing arms and wheels. The electronic controller determines the average position of each suspension and controls the flow of fluid to the cylinders to keep the swing arms and wheels at their proper target height when vehicle load changes.

Abstract: A skid steer vehicle has sprung suspensions that can be locked to prevent vertical movement with respect to the chassis of the vehicle. The operator controls include a switch that the operator can manipulate to lock the suspensions on command. The switch is mounted on a joystick that is used to perform other vehicle functions such as moving the vehicle, raising loader arms, or tilting the bucket or other implement attached to the loader arms. The switch is located on the joystick such that the operator can manipulate the switch without having to remove his hands from the joystick.

Abstract: A skid steer vehicle includes a chassis mounted on four sprung suspensions that are controlled by an electronic controller. The controller monitors the speed of the vehicle and locks the suspensions when the vehicle falls below a predetermined speed.

Abstract: A skid steer vehicle has sprung suspensions, variable displacement pumps and motors connected to those pumps that drive the wheels on the vehicle as well as an electronic controller that receives signals that indicate fore-and-aft acceleration of the skid steer vehicle. Based on these signals, the controller determines whether the forward acceleration exceeds a predetermined value and locks up the rear suspensions if that value is exceeded. It also determines whether the forward deceleration exceeds a predetermined value and locks up the front suspensions if that value is exceeded. The signals can be provided by an accelerometer, a satellite receiver, wheel/motor speed sensors, sensors in the pumps that signal the specific displacement of the pumps such as their swash plate positions, or memory locations that contain previously calculated specific displacement commands that are used to drive the pumps to a particular specific displacement.

Abstract: A skid steer vehicle with sprung suspensions is configured to lock the suspensions whenever the operator manipulates a manual control that generates a signal to move the loader arms or the bucket of the vehicle. The operator control, such as a joystick, sends a signal to an electronic controller indicating that the operator has moved the control and is thereby requesting the loader arms or bucket to move. The electronic controller responds to this signal by moving the loader arms or bucket and simultaneously locking the suspensions.

Abstract: A skid steer vehicle has a sprung suspension system including four wheels mounted on four swing arms that are pivotally coupled to the chassis of the vehicle. An electronic controller is connected both to position sensors coupled to the swing arms to sense the position of the swing arms and wheels with respect to the chassis and also to hydraulic cylinders that control the position of the swing arms and wheels. The electronic controller determines the average position of each suspension and controls the flow of fluid to the cylinders to keep the swing arms and wheels at their proper target height when vehicle load changes.

Abstract: A skid steer vehicle has sprung suspensions, variable displacement pumps and motors connected to those pumps that drive the wheels on the vehicle as well as an electronic controller that receives signals that indicate lateral acceleration of the skid steer vehicle during turns. The controller determines whether the lateral acceleration exceeds a predetermined value, and locks up the outboard suspensions if that value is exceeded. The signals can be provided by an accelerometer, a satellite receiver, wheel/motor speed sensors, sensors in the pumps that signal the specific displacement of the pumps (such as their swash plate position, or memory locations that contain previously calculated specific displacement commands that are used to drive the pumps to a particular displacement.

Abstract: A skid steer vehicle with sprung suspensions is configured to lock the suspensions whenever the operator manipulates a manual control that generates a signal to move the loader arms or the bucket of the vehicle. The operator control, such as a joystick, sends a signal to an electronic controller indicating that the operator has moved the control and is thereby requesting the loader arms or bucket to move. The electronic controller responds to this signal by moving the loader arms or bucket and simultaneously locking the suspensions.

Abstract: An improved mechanism is provided for controlling the relative pivoting movement of two members about a main pivot axis as effected by two hydraulic motors. Each hydraulic motor is a double-acting piston-cylinder type that is fully extended when its respective line of action intersects the main pivot axis. Each hydraulic motor has an end port at each end. Two spaced-apart intermediate ports are provided within the piston stroke length of each motor. Pilot-actuated top dead center-selector valves are provided for reversing the flow to one of the hydraulic motors in response to a pressure differential between an end port and an intermediate port of the other of the hydraulic motors. Decelerator selector valves are provided to normally direct the return flow from the hydraulic motors so as to bypass a hydraulic cushioning circuit.

Abstract: A pressure relieved piston rod seal for piston-cylinder having tandem seals around the piston rod which are subject to failure when the pressure between the seals is greater than the pressure in the cylinder chamber. The piston rod seal of this invention solves this problem by providing a unidirectional seal between the end or low pressure rod seal and the cylinder chamber which relieves the pressure between the seals while sealing the chamber. The unidirectional seal includes a fluid passage which permits fluid flow into the cylinder chamber when the pressure between the seals is greater than the pressure in the cylinder chamber and seals the cylinder bore when the pressure in the chamber is greater than the pressure between the seals.