GB1182311A - Improvements in or relating to Hydraulic Systems - Google Patents

Abstract

1,182,311. Braking systems; valves. ALFRED TEVES G.m.b.H. 19 Jan., 1967 [26 Jan., 1966; 12 March, 1966], No. 2819/67. Headings F2F and F2V. An hydraulic system comprises two circuits, each having an independently operable pressure transmitting device (5, 6), Fig. 1 (not shown), and a pressure receiving device (1, 2) interconnected by a pressure equalizing valve (7) including two pistons 13, 14, Fig. 2, each containing a spring closed valve 22, 23 and having means for opening the valve in the other piston arranged so that when the pressure transmitting devices are independently operated the valves remain closed and the circuits remain separated and when the pressure transmitting devices are operated together the pistons are forced towards each other to unseat the valves to connect the two circuits to equalize the pressures. The pressure equalizing valve interconnects two pressure lines (3, 4) between master cylinders (5, 6) and brake cylinders (1, 2). For steering a brake pedal is operated to increase pressure in either brake circuit which forces the corresponding control piston 13, 14, Fig. 2, against the force of spring 16 or 17 to the stop 15. The other control piston 14 or 13 abuts the end cover 9 or 10 so that the exensions 30, 31 do not reach the valve members 22, 23 and the valves 20, 21 remain closed. The brake circuits remain separate and can be operated independently. If both brake pedals are depressed the control pistons 13, 14 are both moved to stop 15 so that extensions 30, 31 open the valve members 22, 23 to interconnect the brake circuits thereby equalizing the braking force applied at each wheel. In another embodiment control piston 13 or 14, Fig. 3, moves against the pressure of a spring 47 to stop 45 or 46. The resulting pressure increase in chamber 63 opens the valve member 22 or 23 of the moving control piston to allow passage of fluid from chamber 63. Fluid in chambers 59 or 60 is forced via bores 57 or 58 into an equalizing reservoir 56. The other control piston remains against its stop and its valve member remains closed so that the two brake circuits remain separated. When the circuit pressure is relieved the piston 13 or 14 returns to its inoperative position and the fluid previously forced out of chamber 63 is returned via bores 52 or 53. Simultaneous application of both right-hand and left-hand brakes causes interconnection of the brake circuits as in Fig. 2. If the two steering road wheels are braked with the driving road wheels the brake cylinders of the steering road wheels are connected to chamber 63 by a further brake connection (not shown). The steering road wheels are therefore only braked when both of the vehicle brakes are applied. When only one of the steering brakes is applied no substantial increase occurs in chamber 63. Reference has been directed by the Comptroller to Specification 983,356.