Patent GB-1032022-A (GB)
Title: Brake mechanism
IPC: B60T11/16
Filed: 1964-03-06
Abstract: 1,032,022. Fluid pressure brakes. BENDIX CORPORATION. March 6, 1964 [March 8, 1963], No. 9667/64. Heading F2F. In a servo-operated master cylinder assembly for pressurizing hydraulic brakes, of the kind in which a pedal-operated master cylinder generates a pressure adapted to operate a valve controlling the connection of a fluid-pressure power source with a power chamber of the servooperated master cylinder, this manually generated pressure also being adapted to operate the brakes directly on power failure, a second power chamber is provided which is permanently connected with the power source so as to hold a movable wall connected to the piston of the servo-operated master cylinder in a predetermined position against a constant, e.g. spring, force, and a latching mechanism controlled by the manually generated pressure is adapted to hold the movable wall in said position in the released brakes condition and to release the movable wall when the pedal-operated master cylinder is actuated, so that the piston is moved forward to take up slack in the hydraulic system feeding the brakes, whereby pedal travel is not appreciably increased. In one embodiment, Fig. 1, the power source is the induction manifold 40 of a vehicle engine, the vacuum being communicated at all times to power chamber 72 associated with atmosphere suspended movable wall 70, and through a control valve assembly 16 of conventional type to power chamber 30 associated with vacuum suspended movable wall 34, the chambers 74, 36 on the opposite sides of the respective movable walls 70, 34 being connected respectively with atmosphere and vacuum source, the latter through a passage in a piston 14 for operating the control valve assembly 16. Piston 14 is acted on by hydraulic pressure generated by pedal-operated master cylinder 12, this pressure also acting directly on piston 50 of the servo-operated master cylinder 51 and on a piston 98 controlling the operation of the latching mechanism. A rod 62 secured to piston 50 has a shoulder 56 for co-operation with movable wall 34 to enable power operation of piston 50, and is extended for co-operation by means of a shoulder 86 with the movable wall 70, the rearmost end being slidable in a sleeve 76 secured to the wall 70. The latching mechanism comprises a groove 78 in the sleeve 76 with which a latch 92 connected to piston 98 is normally engaged through the action of a spring 106, a sloping face of the latch and a conical end-portion 80 of the sleeve 76 facilitating such engagement. In operation, when pressure is applied manually to pedal 10 the hydraulic pressure generated acts on the piston 14 to operate the control valve 16 to admit atmospheric air to power chamber 30 and at the same time acts on piston 98 to cause it to release the latch 92. So long as vacuum is available the movable wall 70 remains, however, in its rearward position, maintaining a spring 84 compressed. If vacuum fails during such power operation, the spring 84 is enabled to expand, moving the wall 70, rod 62 and piston 50 forwardly sufficient to take up slack in the hydraulic system and draw compensating fluid from an hydraulic reservoir (not shown) through an inlet 112 past a check valve 114, so that the brakes are applied manually without travel of the pedal 10 being appreciably increased. In a second embodiment (Fig. 2, not shown), the power source is an hydraulic pump 126 which feeds a pedal-operated valve 128, also acting as a master cylinder, through check valve 130 and also the second power chamber to which it is permanently connected at 156. Valve 128 operated by pedal 132 controls the admission of hydraulic fluid from the pump to the first power chamber 144 and also to a chamber 142 where it acts on unlatching piston 178 so that a latch 174 is withdrawn from engagement with a groove 164 formed in a boss 160 secured to movable wall 154. The pressure of the pump normally retains wall 154, however, in a rearward position, compressing a spring 182. If hydraulic power fails during braking the latch 174 is again withdrawn by the pressure generated manually at 128, which closes valve 130, and spring 182 moves wall 154 forwardly, as shown, to move via rod 162, piston 148 in hydraulic cylinder 146, thereby drawing compensating fluid from a reservoir 118 via check valve 134, so that the brakes are applied manually without substantial increase of pedal travel.