Patent GB-1129081-A (GB)
Title: Improvements relating to vehicle brakes
Inventor: FARR GLYN PHILLIP REGINALD
IPC: B60T8/26
Filed: 1964-08-25
Abstract: 1,129,081. Anti-skid braking system. GIRLING Ltd. 25 Nov., 1965 [25 Aug., 1964; 16 Sept., 1964; 20 May, 1965], Nos. 34838/64, 37751/64 and 21324/65. Headings F2E and F2F. An hydraulic brake pressure proportioning device comprises a body containing first and second chambers for connection respectively to a master cylinder and to at least one slave cylinder, a plunger slidable in a bore between the chambers and having opposite faces of substantially equal effective areas exposed to the chambers, and a deceleration responsive valve normally interconnecting the chambers, the deceleration responsive valve having a valve seat and an inertia member arranged to close the seat at a particular deceleration, the plunger being displaceable against a spring in a direction to decrease the volume of the second chamber with a substantially equal increase in the volume of the first chamber when the deceleration responsive valve is closed. Several embodiments of the invention are disclosed in the Specification. The device of Fig. 3 is connected at 43 to the master cylinder, at 48 to the rear brakes and by ports 51 to the front brakes. During gentle braking all brakes receive the master cylinder pressure, through passages 49, 50 to the front brakes and the passage 38 in plunger 32 to the rear brakes. At a particular deceleration valve 36 in the first chamber closes passage 38 and increasing braking pressure causes the plunger to move against spring 45 to cause the required volume changes in the first and second chambers 34, 35. When a tandem master cylinder is employed, the front brakes are connected to one chamber thereof and port 43 connected to the other, port 51 being closed off. In some other embodiments (Figs. 8-11, not shown) the plunger and the ball valve are disposed in aligned passages in the device; a by-pass valve for the ball valve may be incorporated. In the embodiment of Fig. 12, the plunger 251 disposed between the first and second chambers 268, 271 has a bore in which slides a by-pass valve 252 biased towards its closed position by a spring 303 but normally held open by piston 285 having a throttling groove 298. When slight pressure is applied to the brake pedal, fluid flows from master cylinder line port 263 to the rear brake port 276 by two routes, one past inertia valve 250 and passages 257, 298, 271; the other through passage 275, valve 252 and passages 290, 271. At a pressure of about 100 p.s.i. the spring 296 is overcome and the by-pass valve closes. The full flow now passes through chamber 250 and throttling groove 298 and develops a pressure difference across piston 285 which overcomes spring 303 and opens the by-pass valve. This reduces the pressure drop and the valve tends to close until a balance of flow is obtained. On high retardation the inertia valve closes, flow through the throttle groove ceases and the by-pass valve closes, plunger 251 now operating as before described to provide differential braking. General.-The ball valve may be, additionally, operated by jets of fluid engaging the ball when the master cylinder pedal is rapidly depressed. The helical spring controlling the plunger may be of variable rate or may be replaced by Belleville washers. In all embodiments the angular position of the inertia valve may be varied by the vehicle load. Warning devices.-Ports are provided in the devices for connection to the brake light pressure switch of a vehicle.