Spring applied steering brakes controlled by transmission clutch pressure

Claim 2

In a crawler tractor having a power shift transmission with forward and reverse clutches, right and left final drive sprockets connected to the transmission output through right and left hydraulically controlled steering clutches, respectively, and right and left brakes operatively associated with said right and left sprockets, respectively, hydraulic control means comprising: a first control system for said steering clutches and brakes including right and left fluid operated brake actuators connected to said right and left brakes, respectively, and operable on pressurization to disengage said brakes, a pair of springs operatively associated with said right and left brakes, respectively, urging the latter to their engaged condition, right and left clutch control valves, each having a control element shiftable between clutch engaged and clutch disengaged positions and each having a clutch port, a supply port and a brake port, a pair of passages operatively connecting said clutch ports of said right and left clutch valves to said right and left clutches, respectively, a source of fluid pressure connected to each of said supply ports, a pair of brake passages connecting said brake ports of said right and left clutch control valves to said pressure chambers of said right and left brake actuators, respectively, clutch pressure control means operatively associated with each of said clutch control valves operable when said valves are in their clutch disengaged position to permit flow from said supply port to said brake port only when the fluid pressure in said supply port is above a predetermined minimum clutch disengaging pressure, a bypass passage connected to each of said brake passages, and a brake pressure regulating valve in each of said bypass passages and including a shiftable flow control element having closed and open positions, and fluid actuator means operable on pressurization to bias said flow control elements toward their closed position, a second control system for said power shift transmission for establishing forward, reverse and neutral conditions and having a circuit with fluid at a predetermined low pressure when said transmission is in said neutral condition and at a predetermined high pressure when said transmission is in either of said forward and reverse conditions, and conduit means connecting said circuit to said fluid actuator means, whereby said brakes are engaged in said neutral condition of said transmission.

Claim 3

In a crawler tractor having a power shift transmission with forward and reverse clutches, right and left final drive sprockets connected to the transmission output through right and left hydraulically controlled steering clutches, respectively, and right and left brakes operatively associated with said right and left sprockets, respectively, hydraulic control means comprIsing: a first control system for said steering clutches and brakes including right and left fluid operated brake actuators connected to said right and left brakes, respectively, and operable on pressurization to disengage said brakes, a pair of springs operatively associated with said right and left brakes, respectively, urging the latter to their engaged condition, right and left clutch control valves, each having a control element shiftable between clutch engaged and clutch disengaged positions and each having a clutch port, a supply port and a brake port, a pair of passages operatively connecting said clutch ports of said right and left clutch valves to said right and left clutches, respectively, a source of fluid pressure connected to each of said supply ports, a pair of brake passages connecting said brake ports of said right and left clutch control valves to said pressure chambers of said right and left brake actuators, respectively, clutch pressure control means operatively associated with each of said clutch control valves operable when said valves are in their clutch disengaged position to permit flow from said supply port to said brake port only when the fluid pressure in said supply port is above a predetermined minimum clutch disengaging pressure, a bypass passage connected to each of said brake passages, and a brake pressure regulating valve in each of said bypass passages and including a shiftable flow control element having closed and open positions, and fluid actuator means operable on pressurization to bias said flow control elements toward their closed position, a second control system for said power shift transmission including fluid pump means having an output, a transmission control valve connected to said pump means output and having neutral, forward and reverse positions, forward and reverse clutch supply conduits connecting said forward and reverse clutches, respectively, to said transmission control valve, and a transmission pressure regulating valve operatively associated with the output of said fluid pump means and automatically maintaining the pump output pressure at a predetermined low level when said transmission control valve is in its neutral position and maintaining the pump output pressure at a predetermined high pressure level when said transmission control valve is in either of said forward and reverse positions, and a fluid conduit interconnecting said pump means output and said fluid actuator means, whereby said brakes are engaged when said power shift transmission is in neutral.

Claim 4

In a crawler tractor having a power shift transmission with forward and reverse clutches, right and left final drive sprockets connected to the transmission output through right and left hydraulically controlled steering clutches, respectively, and right and left brakes operatively associated with said right and left sprockets, respectively, hydraulic control means comprIsing: a first control system for said steering clutches and brakes including right and left fluid operated brake actuators connected to said right and left brakes, respectively, and operable on pressurization to disengage said brakes, a pair of springs operatively associated with said right and left brakes, respectively, urging the latter to their engaged condition, right and left clutch control valves, each having a control element shiftable between clutch engaged and clutch disengaged positions and each having a clutch port, a supply port and a brake port, a pair of passages operatively connecting said clutch ports of said right and left clutch valves to said right and left clutches, respectively, a source of fluid pressure connected to each of said supply ports, a pair of brake passages connecting said brake ports of said right and left clutch control valves to said pressure chambers of said right and left brake actuators, respectively, clutch pressure control means operatively associated with each of said clutch control valves operable when said valves are in their clutch disengaged position to permit flow from said supply port to said brake port only when the fluid pressure in said supply port is above a predetermined minimum clutch disengaging pressure, a bypass passage connected to each of said brake passages, and a brake pressure regulating valve in each of said bypass passages and including a shiftable flow control element having closed and open positions, and fluid actuator means operable on pressurization to bias said flow control elements toward their closed position, a second control system for said power shift transmission including fluid pump means having an output, a transmission control valve connected to said pump means output and having neutral, forward and reverse positions, forward and reverse clutch supply conduits connecting said forward and reverse clutches, respectively, to said transmission control valve, and a transmission pressure regulating valve operatively associated with the output of said fluid pump means and automatically maintaining the pump output pressure at a predetermined low level when said transmission control valve is in its neutral position and maintaining the pump output pressure at a predetermined high pressure level when said transmission control valve is in either of said forward and reverse positions, and a fluid conduit interconnecting said pump means output and said fluid actuator means, whereby said brakes are engaged when said power shift transmission is in neutral.

Claim 5

In a crawler tractor having a power shift transmission with forward and reverse clutches, right and left final drive sprockets connected to the transmission output through right and left hydraulically controlled steering clutches, respectively, and right and left brakes operatively associated with said right and left sprockets, respectively, hydraulic control means comprising: a first control system for said steering clutches and brakes including right and left fluid operated brake actuators connected to said right and left brakes, respectively, and operable on pressurization to disengage said brakes, a pair of springs operatively associated with said right and left brakes, respectively, urging the latter to their engaged condition, right and left clutch control valves, each having a control element shiftable between clutch engaged and clutch disengaged positions and each having a clutch port, a supply port and a brake port, a pair of passages operatively connecting said clutch ports of said right and left clutch valves to said right and left clutches, respectively, a source of fluid pressure connected to each of said supply ports, a pair of brake passages connecting said brake ports of said right and left clutch control valves to said pressure chambers of said right and left brake actuators, respectively, clutch pressure contrOl means operatively associated with each of said clutch control valves operatively associated with each of said clutch control valves operable when said valves are in their clutch disengaged position to permit flow from said supply port to said brake port only when the fluid pressure in said supply port is above a predetermined minimum clutch disengaging pressure, a bypass passage connected to each of said brake passages, and a brake pressure regulating valve in each of said bypass passages and including a shiftable flow control element having closed and open positions, and fluid actuator means operable on pressurization to bias said flow control elements toward their closed position, and a second control system for said power shift transmission including fluid pump means a transmission control valve connected to said pump means and having neutral, forward and reverse positions, and foward and reverse clutch supply conduits connecting said forward and reverse clutches, respectively, to said transmission control valve, and operating means connecting said clutch supply conduits to said fluid actuator means to pressurize the latter on delivery of pressure fluid to either of said forward and reverse clutches, said fluid actuator means being in substantially nonpressurized condition when said transmission is in neutral.

Claim 6

In a crawler tractor having a power shift transmission with forward and reverse clutches, right and left final drive sprockets connected to the transmission output through right and left hydraulically controlled steering clutches, respectively, and right and left brakes operatively associated with said right and left sprockets, respectively, hydraulic control means comprising: a first control system for said steering clutches and brakes including right and left fluid operated brake actuators connected to said right and left brakes, respectively, and operable on pressurization to disengage said brakes, a pair of springs operatively associated with said right and left brakes, respectively, urging the latter to their engaged condition, right and left clutch control valves, each having a control element shiftable between clutch engaged and clutch disengaged positions and each having a clutch port, a supply port and a brake port, a pair of passages operatively connecting said clutch ports of said right and left clutch valves to said right and left clutches, respectively, a source of fluid pressure connected to each of said supply ports, a pair of brake passages connecting said brake ports of said right and left clutch control valves to said pressure chambers of said right and left brake actuators, respectively, clutch pressure contrOl means operatively associated with each of said clutch control valves operatively associated with each of said clutch control valves operable when said valves are in their clutch disengaged position to permit flow from said supply port to said brake port only when the fluid pressure in said supply port is above a predetermined minimum clutch disengaging pressure, a bypass passage connected to each of said brake passages, and a brake pressure regulating valve in each of said bypass passages and including a shiftable flow control element having closed and open positions, and fluid actuator means operable on pressurization to bias said flow control elements toward their closed position, and a second control system for said power shift transmission including fluid pump means a transmission control valve connected to said pump means and having neutral, forward and reverse positions, and foward and reverse clutch supply conduits connecting said forward and reverse clutches, respectively, to said transmission control valve, and operating means connecting said clutch supply conduits to said fluid actuator means to pressurize the latter on delivery of pressure fluid to either of said forward and reverse clutches, said fluid actuator means being in substantially nonpressurized condition when said transmission is in neutral.

Claim 7

The control means of claim 3 wherein said operating means includes check valve means preventing flow from one clutch supply conduit to the other by way of said operating means.

Claim 8

The control means of claim 3 wherein said first control system includes a pair of manually operable brake valves operatively associated with said brake actuators, respectively.

Claim 9

The control means of claim 4 wherein said right and left brake actuators include pistons connected to said right and left brakes and wherein said brake valves include a shiftable flow control component within said pistons.