Patent GB-303106-A (GB)
Title: Improvements in fluid pressure brake mechanism
IPC: B60T13/24
Filed: 1928-11-14
Abstract: 303,106. Bragg, C. S., and Kliesrath, V. W. Dec. 28, 1927, [Convention date]. Fluid-pressure.-In brake mechanism for vehicles comprising a main brake cylinder controlled bv main valve mechanism and one or more auxiliary brake cylinders connected with a pressure fluid operated means which on brake application operates the auxiliary brake cylinder simultaneously with the main cylinder, the pressure fluid operated means include a movable member moved by pressure variations in the main cylinder to close a space on one side of the movable member from the main cylinder and to admit pressure to this space which is connected to the auxiliary cylinder and by a return movement of the movable member this space is closed to pressure and connected to the opposite side of the movable member so as to withdraw the admitted pressure from the auxiliary cylinder. A main cylinder having the control valves in the piston hub is provided on a tractor and an auxilary cylinder on the trailer. In release position both sides of the main piston are connected to engine suction and on brake operation air is admitted to the working side, which side is connected to the pressure operated device so that this is operated to open a valve and admit air to the working side of the auxiliary cylinder the other side of which is permanently connected to suction. The pressure operated device comprises a diaphragm 91 held between two chambers 92, 93. The chamber 92 is connected to the working side of the main cylinder by. a pipe 97 and the chamber 93 to the working side of the auxiliary cylinder by a pipe 98. On releasing the brakes air is evacuated through the main cylinder from pipe 97 and chamber 92, thus moving the diaphragm 91 to open a valve 95 leading to a pipe 94b connected to engine suction which thereupon evacuates the working side of. the auxiliary cylinder through the pipe 98 and apertures 91<b> in the diaphragm. When on brake operation air is admitted to the pipe 97 and the chamber 92 from the main cylinder the diaphragm is pressed against a valve 82 to close the apertures 91<b> and open by means of a stem 80 a valve 99 which admits air by an atmospheric opening 96 to the working side of the auxiliary cylinder. When the operation of the main cylinder and the admission of air to the chamber 92 ceases the continued entrance of air by the valve 99 equalizes the pressures on opposite sides of the diaphragm 91, which closes the valve 99 and maintains the brakes applied. If the trailer breaks away from the tractor air entering the pipe 97 causes the brakes to be applied, the vacuum being maintained in the non-working side of the auxiliary, cylinder by a check valve. Provision is made for operating further auxiliary actuators. In a modification both the main and auxiliary cylinders are single acting and the vacuum valve 95 of the pressure controlled device is omitted, the air from the working side of the auxiliary cylinder being evacuated through the pipe 97. A light spring may hold the diaphragm 91 against the valve 80 in release position. The invention may be used in conjunction with apparatus in which the main control valve mechanism is arranged externallv of the main cylinder. An arrangement is described In which the valve mechanism is arranged in linkage between the foot pedal and a brake on the vehicle propellor shaft.