Patent GB-1369748-A (GB)
Title: Vehicle skid control brake system
IPC: B60T8/32
Filed: 1972-06-28
Abstract: 1369748 Anti-skid systems; modulating valves; monitoring systems; valves KELSEYHAYES CO 28 June 1972 [22 July 1971] 30294/72 Headings F2E F2F and F2V An anti-skid hydraulic brake control system for an automotive vehicle or an aircraft incorporates a modulating valve unit 24 operable in the event of a skid control signal from a module 26 to relieve braking at a wheel or wheels, the valve unit 24 incorporating a plunger 74 movable to allow a check valve assembly 88 to close to thereby cut-off communication between a line 18 to a master cylinder 20 and a line 16 to wheel brake cylinders 12, this movement of the plunger 74 following movement of a piston assembly 118 which is itself moved against a spring 140 by pressure supplied by a pump 36 as controlled by an electromagnetic control valve 46 energized by the skid control signal. As shown in Fig. 1, the unit 24 controls braking at the back wheels but it could control braking at the front wheels as well or alternatively. The pump 36 supplies pressure to the unit 24 through a line 38 and the unit 24 is connected to a return line 40 to a reservoir 42 via a line 52 to the vehicle power steering mechanism 54. As seen in Fig. 5, in the unactuated condition of the unit flow between lines 38 and 52 is via bores 48, 128, 201, 194, an opened valve 204, 208 and bores 200, 202. When skidding is sensed during a braking action the module 26 energizes a coil member 176 and a valve plate 204 of magnetic material is brought into contact with a lip 208 of a magnetic conduit member 194 to cut-off communication between bores 128 and 202. By the action of pump pressure the piston assembly 118 is now moved leftwards, allowing plunger 74 to move leftwards under the action of braking pressure and check valve 88 to close, thereby decreasing braking pressure. The head 120 of piston assembly 118 incorporates a ball valve assembly 146 and as the piston assembly 118 moves leftwards a fixed pin 158 unseats ball 148 so that fluid can flow from line 38 to line 52 via bore 128, bores 156, 154, 152 and bore 50. A throttle valve assembly 162 allows rapid communication between bores 128, 136 when the assembly is actuated, but upon ceasing of the skid control signal this valve assembly 162 acts to allow of only a slow return of piston assembly 118 and hence plunger 74 to their original positions, thereby causing a slow rise in braking pressure. The plunger 74 is slidably supported in a through bore 76 of a bearing structure 68 and an annular lip seal 78 with a seal retainer 80 provides a seal between a bore 66 of the valve housing 58 and the plunger 74. Also an annular diaphragm seal 106 between the bearing structure 68 and plunger 74 gives sealing during vacuum bleeding.  The module 26 incorporates a timing circuit 27 which gives warning to the vehicle operator if the length of each skid cycle exceeds a predetermined maximum. Initiation and termination are provided by a switch assembly 212 operated by movement of piston assembly 118: as the piston assembly 118 moves leftwards a bar 218 under the bias of a spring 226 is pivoted to engage switch 214 to initiate timing; timing is terminated when the piston assembly 118 moves rightwards again.