Patent GB-1137901-A (GB)
Title: Improvements in or relating to fluid pressure systems for hydraulic brakes
Inventor: FARR GLYN PHILLIP REGINALD
IPC: B60T13/52
Filed: 1965-01-07
Abstract: 1,137,901. Fluid pressure brakes. GIRLING Ltd. 5 Jan., 1966 [7 Jan., 1965], No. 703/65. Heading F2F. A master cylinder unit in a fluid system for operating vehicle brakes utilizing manually and power created fluid pressure and having a differential pressure servomotor 42 controlled in dependance upon operation of the master cylinder unit comprises a master cylinder body 10 supported by a housing 52 so as to be slidably displaceable relative thereto, a radial extending annular member 11 carried by the master cylinder body and subdividing the housing into two chambers 54 and 56 which are normally interconnected by a passage 11a in said member, and a valve element 60 located in or adjacent said housing and operated by said member on relative displacement of the master cylinder and housing to isolate said chambers and establish differential pressure therein to energize the servomotor. Depression of a brake-pedal (not shown) initially moves a piston 12 in the master cylinder 10 to the left so that firstly, a recuperating valve 22 closes off a reservoir 14, and secondly, fluid is fed through line 16 to one side of a piston 30 in the bore of an auxiliary tandem master cylinder 68 having separate outlets 72 and 74 to front and rear brakes of a vehicle respectively. Said fluid passes through a port 32 in said piston directly to the front brakes and moves a floating piston to the left to apply the rear brakes. At a predetermined pressure, the pressure on the pedal moves the master cylinder 10 bodily to the left relative to the fixed motor housing 52 supporting the master cylinder. On said movement, the annular flange 11 integral with the master cylinder and dividing the housing into two chambers 54 and 58 which are connected to chambers 44 and 46 either side of a piston 40 in the sermomotor 42, said chambers being interconnected through a port 11a and connected by line 48 to a vacuum source such as an engine inlet manifold, is urged against a double headed poppet valve 60 to close port 11a and communicate chambers 54 and 46 to atmosphere. Servopiston and rod 38 are moved to the left to initially close port 32 in the auxiliary master cylinder piston and then to displace said piston to further increase the pressure to the brakes. In a simplified embodiment, Fig. 1 (not shown), the auxiliary master cylinder has a single outlet to the brakes. In a further embodiment, Fig. 3, the power booster system is wholely hydraulic, a pump 96 supplying pressurized hydraulic fluid through an accumulator 98 to a chamber 104 in a fixed motor housing 90 supporting the master cylinder 10, which chamber is sealed off, in the brake release position, by a valve 110 from chamber 92 of two chambers 92 and 94 formed in said fixed motor housing by an integral annular flange of the master cylinder. Initial movement of the master cylinder piston feeds fluid to brake lines in the same manner as previously described. At a predetermined pressure, the master cylinder moves relative to the fixed motor housing to abut said annular flange against said valve to open the same and to close a port 88 extending through the flange. Fluid then flows from chamber 104 into the chamber 92 and hence through a line 114 to a cylinder extension 116 of the auxiliary master cylinder. A piston in said extension is then urged to the left against the piston 32 of the auxiliary master cylinder to increase the brake line pressure. Alternatively, valve 110 may be open in the brake release position so that fluid is circulated by the pump through flange part 88. Fig. 4 (not shown) illustrates a further master cylinder arrangement wherein the annular flange of the master cylinder is slidable relative to the master cylinder, the movement of the master cylinder being transmitted to said flange through a resilient disc 156 which amplifies said movement, and wherein a valve disc 184 performs the function of the poppet valve of the previously described embodiment. Instead of the master cylinder moving relative to the fixed support motor housing as described, the master cylinder could remain stationary and the support motor housing could be made movable.