Patent ID: 6029761
Filing Date: 2000-02-29
Classification: B60T,B62D

Abstract:
A system having a steering control valve and a fluid operated motor and adapted for use in a machine, the system comprising:a first source of pressurized fluid fluidly connected to a steering control valve and to a fluid operated motor by first and second fluid ports;a differential steer mechanism mechanically connected to the fluid operated motor;first and second drive outputs operatively connected to the differential steer mechanism;first and second fluid actuated brake mechanisms associated with the respective first and second drive outputs and being selectively operable to reduce the rotational speed of the respective associated one of the drive outputsa brake valve being connected between the first source of pressurized fluid and the first and second fluid actuated brake mechanisms, the relative speeds between the first and second drive outputs being varied in response to operation of the fluid operated steer motor;a second source of pressurized fluid operatively connected to the steering control valve and selectively operable to direct pressurized fluid to the steering control valve;a system controller operative to sense the operating pressures of the first and second sources of pressurized fluid and operable to initiate operation of the second source of pressurized fluid in the event the pressure from the first source of pressurized fluid drops below a predetermined value;an independently controlled brake actuator mechanism being disposed between the first and second fluid actuated brake mechanisms and the brake valve and fluidly connected to the steering control valve, the independently controlled brake actuator being selectively operative in response to the steering control valve to engage the appropriate one of the first and second brakes in the event the pressure from the first source of pressurized fluid drops below the predetermined value; anda shunt arrangement connected between the first and second fluid ports of the fluid operated motor and being operative to fluidly interconnect the first and second fluid ports of the fluid operated motor in response to pressurized fluid from the second source of pressurized fluid being above a predetermined level.