Automatic brake pressure control device for pneumatic anti-skid vehicle braking systems

Claim 1

Automatic brake pressure control device for anti-skid pneumatic braking systems for vehicles, said device comprising combination: a. a body having an internal cavity constituted by a first chamber, a second chamber, a third chamber and a fourth chamber arranged coaxially; b. a first free flow passage and a first restricted flow passage, both interconnecting said first and fourth chambers; c. a second free flow passage and a second restricted flow passage, both interconnecting said first and second chambers; d. a piston movable in said cavity, said piston having a head slidable fluid-tightly in said third chamber and having an inoperative position in which said piston closes said first free flow passage between the first and fourth chambers and opens said second free flow passage between the first and second chambers and having an operative position in which said piston opens said first free flow passage and closes the said second free flow passage; e. an inlet port opening into said first chamber and adapted to be connected to a source of pressure in use of the device; f. a fluid delivery port opening into said second chamber and adapted to be connected to the input of a control valve for anti-skid braking control, and g. a control passage communicating with said third chamber and adapted to be connected to the output of the said control valve, and wherein the position of the piston is controlled by the pressure difference between said third and fourth chambers to cause the piston to assume said inoperative position when the pressure in the third chamber is greater than or equal to the pressure in said fourth chamber and to assume said operative position when said pressure in the third chamber is less than the pressure in the fourth chamber.