Patent GB-298604-A (GB)
Title: Improvement in brake mechanism for automotive vehicles
IPC: B60T13/46
Filed: 1928-09-24
Abstract: 298,604. Bragg, C. S., and Kliesrath, V. W. Oct. 12, 1927, [Convention date]. Fluid-pressure; hand and foot actuation.- Vehicle brake mechanism comprises a fluidpressure actuator, the cylinder and piston of which are movable and connected to different brakes, the arrangement being such that the maximum pressure exerted by the actuator is insufficient to lock the wheels while additional pressure can be directly applied to the brakes connected to one element of the actuator. In one arrangement, Figs. 1 and 4, the cylinder 1 is carried by trunnions 4 on a pair of arms 77 secured to a rock shaft 76 provided with other arms 75 connected by rods 74 to the front brakes. The piston is connected by a cables 79 to an arm 77a on a rock shaft 76a having arms 75<a> connected by rods 74<a> to the rear brakes. Vacuum is normally maintained in the chambers of the cylinder on both sides of the piston and air is admitted to one chamber to apply the brakes. For this purpose, one end of the cylinder is directly connected by the pipe 132 to the induction pipe 62 of the engine of the vehicle. The other end of the cylinder is connected by the pipe 113<c> to the valve mechanism. This may be of the kind described in Specification 292,153 and comprise a casing 106 connected by a rod 82 with an arm 77<b> on the shaft 76<a> and containing air inlet and suction valves 114, 116, Fig. 5, slidably fitted on a rod 20 connected to the pedal 80 and operated by collars 120<a>, 120<b> on the rod. The valve 114 is seated by springs 125 which are just strong enough to counterbalance the pressure difference acting on the valve when the brakes are released. Normally the casing 106 abuts against a stop 84 and a spring 121 in the casing holds open the suction valve 116 as shown so that the end of the cylinder that is connected to the pipe 113<c> is connected to the suction pipe 132. When the pedal is depressed to apply the brakes, the valve 116 is seated and the inlet valve 114 is opened to admit air through a port 111<a> and the pipe 113<c> to the one end of the cylinder. The cylinder and piston are thereby both moved and the front and rear brakes simultaneously applied. If the movement of the pedal is stopped the valve 114 is seated by the movement of the casing effected by the movement of the piston and the brakes may thus be held applied. The resistance of the valve springs 125 becomes increasingly effective as the pressure difference acting on the valve 114 diminishes with increasing pressure applied to the brakes and an indication is thus given to the operator of the value of this pressure. The maximum pressure that can be applied by the cylinder and piston is arranged to be such as will not lock the wheels in normal conditions. By depressing the pedal sufficiently, however, to take up the lost motion between a collar 122 on the valve rod 20 and the valve casing the operator may transmit a direct effort through the rod 82 so as to apply additional pressure to the rear brakes or may apply such pressure alone in the event of failure of the fluid pressure. Instead of the cylinder being mounted on the rock shaft 76 it or the piston may be suspended from the chassis by a flexible link or as shown in Fig. 13 the cylinder 401 may be slidably mounted by guide members 400, 404<b> on the chassis. In this case the cylinder is connected by a rod to an arm on the rock shaft 76. The. piston may be replaced by a diaphragm. The pedal may actuate the rear brakes through the piston or cylinder. The cylinder may be of the double acting type as described in Specifications 252,333 and 262,450. Compensating for wear.-A device for adjusting the effective length of the rod 82 by which the pedal 80 actuates the rear brakes, comprises a sleeve 84 screwing on the rod and provided with a. flange 84a engaged by a collar 83a integral with a yoke 83 connected to the arm 77<b> on the rock shaft 76<a>. The parts 83<a>, 84a are provided with a recess and projection 84<c> respectively, held in engagement by a spring 85.