Patent GB-344671-A (GB)
IPC: B60T13/24
Filed: 1930-03-11
Abstract: 344,671. Fluid - pressure brakes. BRAGG - KLIESRATH CORPORATION. 3901, Queens Boulevard, Long Island, New York, U.S.A. March 11, 1930, No. 7939. Convention date, March 15, 1929. [Class 103 (i).] Hydraulic brake apparatus comprises in one form a pressure piston adapted first to be moved directly by a pedal and a valve which is operated by the pedal when a predetermined pressure has been applied, to cause the application of additional pressure to the pressure piston by a power piston, a further small piston slidable in the pressure piston rod being provided to exert reaction on the pedal to indicate the pressure applied to the brakes. Another device which may be entirely manually operated or be combined with a power piston comprises two pistons one of which applies hydraulic pressure to the other which in turn forces liquid into the system. As shown in Figs. 1 and 5, a hydraulic cylinder 19 fixed to a vacuum cylinder 31 and connected to brake operating cylinders by pipe 18 has slidable within it a tubular piston and piston rod 48x. A second piston 75 slidable in the piston rod 48x is connected by the rod 75a to the pedal 83. A vacuum piston 49 is slidable to a limited extent on the rod 48x against a spring 52. A valve casing 38 secured to the rod 48x comprises chambers 57, 69, 58, Fig. 5, connected by pipes 44, 37, 45 respectively to the ends of the cylinder 31 and to the suction pipe of the vehicle engine. Valves 59, 64 are actuated by an arm 72 on the spindle of a pinion 71 engaging a rack fixed to the rod 75a. The right-hand chamber of the cylinder 31 is permanently connected to atmosphere by the pipe 40. Normally the valve 59 is open and the chambers of the cylinder 31 being connected there is no pressure on the piston 49. When the pedal is depressed the piston 75 is advanced directly and the piston 48x through a spring 93 disposed between a collar on the rod 75a and the piston rod 48x, thus forcing liquid from the cylinder 19 to the brake cylinders. When sufficient pressure has developed in the system for the spring 93 to be overcome, the rod 75a moves relatively to the rod 48x and thus the valve 59 is closed and the valve 64 opened to connect the forward chamber of the cylinder 31 to suction so that the piston 49 applies further pressure to the piston 48 through the spring 52. The hydraulic pressure reacts on the pedal through the small piston 75. If the pedal movement ceases the continued forward movement of the piston 49 and rod 48x causes the suction valve 64 to close whereby the pressure is graduated. A replenishing reservoir 21 with a spring-pressed piston 24 is connected to the cylinder 19. The device shown in Fig. 7 comprises a fixed cylinder 94 connected by a pipe 143 to brake cylinders and a tubular piston rod 120 with a piston 126 slidable in this cylinder. Within the tube 120 slides a piston 121 on a rod 118 connected by a pair of rods (not shown) on either side of the cylinder 94, and a rod 105 to a pedal 112. A replenishing reservoir 136 with a spring-pressed piston 137 is connected to the cylinder 94, through pipes 132 with non-return valves at 132a, 135. When the pedal is depressed the piston 121 forces liquid into the space 131, the pressure in which acting on the piston 126 advances this piston to force liquid from the space 134 into the brake cylinders. The pressure applied to the piston 126 is multiplied by the ratio of the area of this piston to that of the piston 121. This compound cylinder device may be applied to a combined foot-and-power actuated device of the kind shown n Fig. 1. In this case, a hollow piston and piston rod 48a, 48b, Fig. 4, corresponding to the piston and rod 48x of Fig. 1, slides in a tubular piston rod 86 carrying a piston 87 slidable in the fixed cylinder 19 which is closed at one end. The pipe 92 leading to the brake cylinders is connected to the annular space between the piston-rod 86 and the cylinder 19.