Modulated spring brake

Claim 2

A fluid pressure brake system including a brake actuator having a service chamber and an emergency chamber, a first movable wall in said service chamber, a second movable wall in said emergency chamber, an application valve, a first conduit communicating said application valve with said service chamber on one side of said first movable wall to urge said first movable wall in brakes-on direction, a second conduit communicating said application valve with said emergency chamber on one side of said second movable wall to urge said second movable wall in brakes-on direction, a differential valve connected in said conduits downstream of said application valve and effective to open said second conduit in response to loss of pressure in said first conduit between said differential valve and said service chamber.

Claim 3

A fluid pressure brake system including a brake actuator having a service chamber and an emergency chamber, a first movable wall in said service chamber, a second movable wall in said emergency chamber, an application valve, a first conduit communicating said application valve with said service chamber on one side of said first movable wall to urge said first movable wall in brakes-on direction, a second conduit communicating said application valve with said emergency chamber on one side of said second movable wall to urge said second movable wall in brakes-on direction, a differential valve connected in said conduits downstream of said application valve and effective to open said second conduit in response to loss of pressure in said first conduit between said differential valve and said service chamber.

Claim 4

A fluid pressure brake system including a brake actuator having a service chamber and an emergency chamber, a first movable wall in said service chamber, a second movable wall in said emergency chamber, an application valve, a first conduit communicating said application valve with said service chamber on one side of said first movable wall to urge said first movable wall in brakes-on direction, a second conduit communicating said application valve with said emergency chamber on one side of said second movable wall to urge said second movable wall in brakes-on direction, a differential valve connected in said conduits downstream of said application valve and effective to open said second conduit in response to loss of pressure in said first conduit between said differential valve and said service chamber.

Claim 5

The structure of claim 1 characterized by and including automatic exhaust valve means in said second conduit and automatically openable to exhaust position in response to deactivation of said application valve.

Claim 6

A fluid pressure vehicle brake system including brake actuator means having a service chamber and an emergency chamber, a movable wall in the emergency chamber, a spring on one side of said wall in the emergency chamber urging said wall in brakes-on direction, an emergency line communicating a source of fluid pressure with said emergency on the opposite side of said wall to urge said wall in brakes-off direction, a main service pressure line communicating a source of fluid pressure with said service chamber, an auxiliary service pressure line communicating a source of fluid pressure with said emergency chamber on said one side of said wall, an application valve connected in said main and auxiliary lines for simultaneous opening and closing of said lines, and a differential valve connected in said main and auxiliary lines downstream of said application valve and effective to open said auxiliary line in response to loss of pressure in said main line.

Claim 7

A fluid pressure vehicle brake system including brake actuator means having a service chamber and an emergency chamber, a movable wall in the emergency chamber, a spring on one side of said wall in the emergency chamber urging said wall in brakes-on direction, an emergency line communicating a source of fluid pressure with said emergency on the opposite side of said wall to urge said wall in brakes-off direction, a main service pressure line communicating a source of fluid pressure with said service chamber, an auxiliary service pressure line communicating a source of fluid pressure with said emergency chamber on said one side of said wall, an application valve connected in said main and auxiliary lines for simultaneous opening and closing of said lines, and a differential valve connected in said main and auxiliary lines downstream of said application valve and effective to open said auxiliary line in response to loss of pressure in said main line.

Claim 8

For use in a vehicle fluid pressure brake system having a spring-applied, fluid pressure-retracted emergency brake actuator, a fluid pressure applied service brake actuator, an application valve and a service pressure line communicating said vale and said service brake actuator, said emergency brake actuator having an area therewith occupied by a spring, means supplying service pressure to said area in response to activation of said application valve and loss of pressure in said service line.

Claim 9

For use in a vehicle fluid pressure brake system having a spring-applied, fluid pressure-retracted emergency brake actuator, a fluid pressure applied service brake actuator, an application valve and a service pressure line communicating said vale and said service brake actuator, said emergency brake actuator having an area therewith occupied by a spring, means supplying service pressure to said area in response to activation of said application valve and loss of pressure in said service line.

Claim 10

The structure of claim 4 wherein said means includes an auxiliary service pressure line communicating said application valve with said area and a valve member connected to said first-named service and said auxiliary services lines, said valve member including means closing said auxiliary line in response to pressure in said first-named service line and opening said auxiliary line in response to loss of pressure in said first-named service line.

Claim 11

The structure of claim 5 wherein said application valve includes means for simultaneously controlling the flow of pressure in said first-named and auxiliary service lines.

Claim 12

The structure of claim 4 characterized by and including valve means for exhausting said area of said supplied pressure in response to deactivation of said application valve.

Claim 13

A fluid pressure vehicle brake system including a brake application valve, a brake actuator having a service chamber and an emergency chamber, a first movable wall in said service chamber, a second movable wall in said emergency chamber, means communicating said application valve with said service chamber on one side of said first wall, means supplying fluid pressure to said emergency chamber on one side of said second wall, a spring on the other side of said second wall and means communicating said application valve with said emergency chamber on said other side of said second wall in response to loss of fluid pressure in said service chamber.

Claim 14

A fluid pressure vehicle brake system including a brake application valve, a brake actuator having a service chamber and an emergency chamber, a first movable wall in said service chamber, a second movable wall in said emergency chamber, means communicating said application valve with said service chamber on one side of said first wall, means supplying fluid pressure to said emergency chamber on one side of said second wall, a spring on the other side of said second wall and means communicating said application valve with said emergency chamber on said other side of said second wall in response to loss of fluid pressure in said service chamber.