Transmission disconnect with parking brake application

Claim 1

A completely pneumatic control means for coordinated actuation of air-actuated service brake and parking brake systems with a transmission disconnect on a vehicle having a transmission and a spring-apply, pressure-release parking brake; comprising: a source of air pressure; a parking brake cylinder normally biased to apply said parking brake and connected to release said parking brake upon receiving air pressure; a parking brake valve interposed between said source and said parking brake cylinder and moveable between a release position in which pressure from said source is directed to said parking brake cylinder and an apply position in which said parking brake cylinder is exhausted to atmosphere; a pneumatic transmission disconnect cylinder having a rod connected to the transmission and first bias means urging said rod toward a position in which said transmission is operative and upon receiving air pressure moves said rod to neutralize said transmission; a transmission disconnect valve moveable between a disconnect position in which air pressure is directed from said source to said disconnect cylinder and a connect position in which said disconnect cylinder is exhausted to atmosphere; second bias means normally urging said disconnect valve to its connect position; first penumatic actuator means on said transmission disconnect valve for movement of said disconnect valve to its disconnect position in response to said first actuator means receiving air pressure; a shuttle valve having second and third pneumatic actuator means; a first conduit connecting said shuttle valve to said first actuator means; a parking brake signal valve having a fourth actuator means and a third bias means, said third bias means normally biasing said signal valve to a first position in which air pressure from said source is directed to said shuttle valve and said second actuator means to shift said shuttle valve to direct air pressure through said first conduit to said first actuator means, and when said parking brake valve is moved to its release position said fourth actuator means receiving air pressure from said source to shift said signal valve to exhaust said second actuator means to atmosphere; and second conduit means connecting said service brake system to said shuttle valve and said third actuator, air pressure in said second conduit means shifting said shuttle valve means to direct air pressure through said first conduit to said first actuator means to cause said disconnect valve to direct air pressure from said source to said disconnect cylinder.