Patent GB-305926-A (GB)
Title: Improvements in fluid pressure servo-motors or actuators for automotive vehicles
IPC: F03D7/02
Filed: 1929-01-25
Abstract: 305,926. Bragg, C. B., and Kliesrath, V. W. Feb. 11, 1923, [Convention date]. Fluid-pressure; hand and foot actuation; force - transmitting mechanisin. - Valve mechanism for a fluid pressure actuator more particularly for operating the brakes of motor vehicles comprises a valve casing rigidly connected with and supported by a rock shaft connected with a movable member of the actuator and containing a pair of valves one or the other of which is opened according to the movement of a pedal or other operating member the arrangement being such that a valve when opened is reclosed by the follow-up movement of the casing. The front and rear brakes of a vehicle may be applied by one or a pair of connected cylinders and by continued movement of the pedal the direct effort of the operator may be applied to one pair of brakes. The brake system shown in Figs. 1 and 2 comprises a cylinder 1 rigidly mounted by arms 77 upon a rock shaft 76 connected to the rear wheel brakes 70 and having a piston 3 with a rod 5 connected by a link 78 to the rock shaft 76<a> of the front wheel brakes 70<a>. The valve mechanism comprises a pair of casing members 11, 12 clamped to the shaft 76 and each containing a valve 40, 41 adapted to be seated by a spring 26, 26<a>. The casings are closed by diaphragms 28 connected to the valve stems. The valve chamber 18<a> is connected by a pipe 65 with the intake manifold of the vehicle engine 60, the chamber 20 to the atmosphere, the chamber 21a to the chamber 21 by a pipe 30 and the chamber 21 to the cylinder 1 by pipe 23. The valves 40, 41 are operated by a lever 33 which engages the valve stems 29 and is connected by link 87 to the pedal 88. Normally the casing 11 abuts against a stop 86 and the air inlet valve 40 is held open by the pedal spring 89 so that both sides of the piston 3 are subject to atmospheric pressure. Depression of the pedal 88 permits closure of the inlet valve 40 and opens the suction valve 41 to exhaust the cylinder 1 causing it and the piston 3 to move in opposite directions to rock the shafts 76, 76a and apply the front and rear brakes with pressures determined by the leverages in the respective connections thereto. The valve casing 11. 12 by reason of its connection with the shaft 76 follows up the pedal movement and if this ceases seats the valve 41 to hold the brakes applied. By continued movement of the pedal the valve lever 33 engages the casing 12 and the effort of the operator may thus be directly applied to the rear brakes. The release position of the shafts 76, 76a is determined by stops 86, 86a. In a modification, the cylinder 1 is closed at both ends and vacuum is normally maintained on both sides of the piston. In this case the valve casing member 11 is disposed forwardly in relation to the member 12, the pipe 23 is connected to the forward piston chamber, the pipe 65 to the engine manifold as before and a branch therefrom to the rear piston chamber which is thus constantly exhausted while the forward chamber is normally exhausted by way of the open valve 41, valve chambers 21, 21<a> and pipe 23. Depression of the pedal permits closure of the valve 41 and opens the valve 40 to admit air to the forward piston chamber to apply the brakes. According to Fig. 7, the cylinder 201 is fixed and the piston operates the front and rear brakes 270, 270<a> through an equalizing lever 295 and links 278, 278<a>, the link 278a preferably being flexible. The valve casing 210 is mounted on the shaft 276 and a direct effort can be applied through it to the rear brakes by the pedal 288 as above described. In a further arrangement, Fig. 8, fixed cylinders 301, 301<a> connected by a pipe 390 are provided for operating the rear and front brakes respectively. The casing 310 of the valve mechanism which controls the pressure in both cylinders is mounted on the shaft 376. Super-atmospheric pressure may be used as the high pressure source with atmospheric or sub-atmospheric pressure as the low pressure source; in this connection reference is made in the Specification as open to inspection under Sect. 91 (3) (a), to U.S.A. Specification 682,346.