Single pedal braking system for crawler tractor

Claim 2

In a crawler tractor having an engine-driven transmission and a pair of tracks, a control system for steering and braking said tractor comprising: a pair of selectively operable clutches for connecting said tracks to said transmission, a pair of selectively operable clutch control valves for said pair of clutches, a pair of brakes for said tracks, a pair of hydraulic brake actuators for said pair of brakes, each brake actuator having a control element movable to operate its respective brake if fluid is being supplied to its respective actuator, a single brake pedal mechanically connected to each said control element for simultaneously operating the control elements of both of said brake actuators, a source of fluid connected to said clutch control valves, and a fluid operated shuttle valve connected between said clutch control valves and said brake actuators for controlling fluid flow from said source to said brake actuators in response to fluid flow conditions between said clutch control valves and said clutches indicative of the condition of said clutches, said shuttle valve being operable to direct fluid to both brake actuators when both clutches are operated together whereby actuation of said single brake pedal operates both brakes, said shuttle valve being further operable to direct fluid to only one brake actuator when only one clutch is operated whereby actuation of said single brake pedal operates only one brake.

Claim 3

A crawler tractor according to claim 1 wherein said one brake is the brake for that track whose clutch is disengaged.

Claim 4

A crawler tractor according to claim 1 wherein said shuttle valve comprises a shiftable control element having one position wherein it enables fluid to be directed to both brake actuators and having other positions wherein it enables fluid to be directed to only one brake actuator.

Claim 5

In a crawler tractor having an engine-driven transmission and a pair of tracks, a control system for steering and braking said tractor comprising: a source of fluid, a pair of hydraulic clutches for connecting said tracks to said transmission, a pair of selectively operable clutch control valves for said pair of clutches, each clutcH control valve being operable to direct fluid from said source to its respective clutch, each clutch control valve having a control element movable to operate its respective clutch, a pair of brakes for said tracks, a pair of hydraulic brake actuators for said pair of brakes, each brake actuator having a control element movable to operate its respective brake if fluid is being supplied to its respective actuator, a single brake pedal mechanically connected to each said control element for simultaneously operating the control elements of both of said brake actuators, and a fluid operated shuttle valve connected between said clutch control valves and said brake actuators for controlling fluid flow from said source to said brake actuators in response to the condition of said clutches, said shuttle valve comprising a control element movable in response to fluid flow between said clutch control valves and said clutches and having one position wherein it directs fluid from said source to both brake actuators when both clutches are engaged or disengaged whereby actuation of said single brake pedal operates both brakes, said shuttle valve control element being movable to another position wherein it enables fluid to be supplied to only one brake actuator in response to operation of one clutch whereby actuation of said single brake pedal operates only one brake.

Claim 6

In a crawler tractor having an engine-driven transmission and a pair of tracks, a control system for steering and braking said tractor comprising: a source of fluid, a pair of hydraulic clutches for connecting said tracks to said transmission, a pair of selectively operable clutch control valves for said pair of clutches, each clutcH control valve being operable to direct fluid from said source to its respective clutch, each clutch control valve having a control element movable to operate its respective clutch, a pair of brakes for said tracks, a pair of hydraulic brake actuators for said pair of brakes, each brake actuator having a control element movable to operate its respective brake if fluid is being supplied to its respective actuator, a single brake pedal mechanically connected to each said control element for simultaneously operating the control elements of both of said brake actuators, and a fluid operated shuttle valve connected between said clutch control valves and said brake actuators for controlling fluid flow from said source to said brake actuators in response to the condition of said clutches, said shuttle valve comprising a control element movable in response to fluid flow between said clutch control valves and said clutches and having one position wherein it directs fluid from said source to both brake actuators when both clutches are engaged or disengaged whereby actuation of said single brake pedal operates both brakes, said shuttle valve control element being movable to another position wherein it enables fluid to be supplied to only one brake actuator in response to operation of one clutch whereby actuation of said single brake pedal operates only one brake.

Claim 7

A crawler tractor according to claim 4 wherein said one brake is the brake for that track whose clutch is disengaged.

Claim 8

In a vehicle having an engine-driven transmission and right and left final drive shafts, a control system for steering and braking said vehicle comprising: a source of fluid, right and left selectively operable hydraulically controlled steering clutches for connecting said right and left final drive shafts, respectively, to said transmission, right and left steering clutch control valves for operating said right and left steering clutches, each steering clutch control valve having a control element shiftable between clutch engaged and clutch disengaged positions, each steering clutch control valve having a supply fluid port connected to said source, a clutch port connected to its respective clutch and a brake fluid port, right and left brakes operatively associated with said right and left shafts, respectively, right and left fluid operated brake actuators connected to said right and left brakes, respectively, and operable to apply its respective brake, each brake actuator having a pressure port and a control element shiftable between brake released and brake applied positions, each brake control element effecting brake application when moved to brake applied position when said pressure port is supplied with fluid, a single brake pedal, means for connecting said single brake pedal to both control elements of said brake actuator to operate both of them simultaneously, a shuttle valve responsive to the condition of said steering clutches and having a pilot pressure operated control element shiftable between a neutral position, a right brake position and a left brake position, said shuttle valve having a pair of brake actuator ports connected to said pressure ports of said brake actuators, a pair of clutch valve ports connected to said brake fluid ports of said clutch valves and a pair of pilot pressure ports connected to said clutch ports of said control valves, said shuttle valve being operable when both of said clutch fluid ports of said control valves are supplying fluid or not supplying fluid to cause the shuttle valve control element to assume its neutral position and allow fluid flow from said brake valve ports of said control valves through said shuttle valve to said pressure ports of both of said brake actuators so that actuation of said single brake pedal effects application of both brakes, said shuttle valve being further operable in response to fluid being supplied to either one of said clutch fluid ports of said clutch valves to cause said shuttle valve control element to assume onE of its other positions and allow fluid flow from said brake valve port of only one clutch valve through said shuttle valve to the pressure port of only one brake actuator so that actuation of said single brake pedal effects application of only one brake.

Claim 9

In a vehicle having an engine-driven transmission and right and left final drive shafts, a control system for steering and braking said vehicle comprising: a source of fluid, right and left selectively operable hydraulically controlled steering clutches for connecting said right and left final drive shafts, respectively, to said transmission, right and left steering clutch control valves for operating said right and left steering clutches, each steering clutch control valve having a control element shiftable between clutch engaged and clutch disengaged positions, each steering clutch control valve having a supply fluid port connected to said source, a clutch port connected to its respective clutch and a brake fluid port, right and left brakes operatively associated with said right and left shafts, respectively, right and left fluid operated brake actuators connected to said right and left brakes, respectively, and operable to apply its respective brake, each brake actuator having a pressure port and a control element shiftable between brake released and brake applied positions, each brake control element effecting brake application when moved to brake applied position when said pressure port is supplied with fluid, a single brake pedal, means for connecting said single brake pedal to both control elements of said brake actuator to operate both of them simultaneously, a shuttle valve responsive to the condition of said steering clutches and having a pilot pressure operated control element shiftable between a neutral position, a right brake position and a left brake position, said shuttle valve having a pair of brake actuator ports connected to said pressure ports of said brake actuators, a pair of clutch valve ports connected to said brake fluid ports of said clutch valves and a pair of pilot pressure ports connected to said clutch ports of said control valves, said shuttle valve being operable when both of said clutch fluid ports of said control valves are supplying fluid or not supplying fluid to cause the shuttle valve control element to assume its neutral position and allow fluid flow from said brake valve ports of said control valves through said shuttle valve to said pressure ports of both of said brake actuators so that actuation of said single brake pedal effects application of both brakes, said shuttle valve being further operable in response to fluid being supplied to either one of said clutch fluid ports of said clutch valves to cause said shuttle valve control element to assume onE of its other positions and allow fluid flow from said brake valve port of only one clutch valve through said shuttle valve to the pressure port of only one brake actuator so that actuation of said single brake pedal effects application of only one brake.