Patent GB-745875-A (GB)
Title: Hydraulic brake device for vehicles
IPC: B60T11/10
Filed: 1954-01-13
Abstract: 745,875. Hydraulic braking systems. TECNO TRADE ANSTALT. Jan. 13, 1954 [Aug. 4 1953], No. 1040/54. Class 103 (1). [Also in Groups XXXI and XXXVII] In a hydraulic braking device for vehicles, a main brake cylinder 1 operated by a brake pedal 2 is connected to the wheel brake cylinders 3 through a control cylinder 9 which may be fitted to the dashboard of the vehicle and housing a control slide 10 which may be operated by the driver in two positions to control the flow of hydraulic fluid to the wheel brake cylinders 3 from a force-storage cylinder 6 in order to replace the handbrake of conventional construction. Fig. 1 shows the system in the brake release position (only one of the four vehicle wheels being shown for simplicity). An ignition lock 11 is incorporated in the control cylinder 9 and combined with the control slide 10. The control slide 10 has at one end an operating knob 20 by means of which the control slide 10 can be pushed by the driver of the vehicle into the control cylinder 9 (Fig. 1) or pulled out of the cylinder (Fig. 2) and a keyhole 21 for an ignition key 22 by which the driver of the vehicle can turn the control slide 10, and the ignition switch 12 connected thereto, into a switched-on position A or a switched-off position O or into a second switched-off position B (Fig. 3 being a section through III-III of Fig. 2). The control cylinder 9 has three chambers 23, 24, 25 located in a row and annularly surrounding the control slide 10. The control slide 10 has a recessed portion, which, in the position shown in Fig. 1, forms a flowthrough connection for brake liquid between the chambers 23 and 24 and hence between tho main brake cylinder 1 and the wheel brake cylinders 3 and in the position shown in Fig. 2 flowthrough connection for brake liquid between the chambers 24 and 25 and hence between the pressure chamber 8 of the force-storage cylinder 6 and the wheel brake cylinders 3. Sealing sleeves 32 and 34 are provided between the chambers 23 and 24, 24 and 25 respectively, which act as non-return valves so that in the position of the control slide shown in Fig. 1, the brake liquid can flow from chamber 24 into chamber 25 and in the position of the control slide 10 shown in Fig. 2 brake liquid can flow out of chamber 23 into chamber 24 while a flow in the reverse direction is prevented. The arrangement is such that while the vehicle is travelling the key 22 is in the position A for switched-on ignition and the control slide 10 is pushed fully in (Fig. 1). The control cylinder 9 then permits a free hydraulic flow through connection between the main brake cylinder 1 and the wheel brake cylinders 3. In this position every time the brake pedal 2 is depressed, brake fluid flows from the main brake cylinder 1 into the wheel brake cylinders 3 and at the same time the pressure chamber 8 of the force-storage cylinder 6 is filled with brake fluid from the main brake cylinder 1, forcing the piston 14 back against the spring 7. If the control slide 10 is pulled by the driver by means of knob 20 to the position shown in Fig. 2, the control cylinder 9 connects the pressure chamber 8 to the wheel brake cylinders 3 to apply the wheel brakes. Thus by means of the operating knob 20 a hydraulic handbrake is thus operated by the driver of the vehicle, which when the vehicle is at rest, can be used as a parking brake and during travel can be used as an emergency brake. In case of leakage in the hydraulic system, a mechanical connection to the piston 14 is provided to mechanically apply the wheel brakes if the pressure in the pressure chamber 8 is reduced below a certain level. In the brake release position (Fig. 1) the key 22 can be drawn out of the lock 11 because pin 48 engages a corresponding notch 49 in the key. If, however, the slide has been pulled into the braking position (Fig. 2) the key 22 can be drawn out of the lock 11 because it can now push the pin 48 into a bore 50. As soon as the key 22 is withdrawn, spring 51 then pushes a pin 52 partly into slide 10 so that the latter can no longer be turned or depressed. By means of a second safety locking device 54, the ignition cannot be switched off when the slide 10 is in the brake release position (Fig. 1). This double safety locking device compels the driver of the vehicle to apply the hydraulic handbrake by pulling out the slide 10 before he removes the ignition key 22; and until the key has been turned to position B (Fig. 3) the safety locking device renders it impossible to release the hydraulic handbrake after the key 22 has been withdrawn. The position B merely serves to permit the parking of the vehicle e.g. in a garage, while the ignition is switched off. Additional braking force may be provided by use of an engine-driven oil pump to charge the force-storage means. A modification to the arrangement shown in Fig. 1 is described in which a rotary slide is incorporated in the brake device between pipes 28 and 26 and is held inoperative by a spring and brought into the open position by a member disposed beneath the brake pedal 2 so that on depression of the brake pedal 2 communication is established between the pressure chamber 8 of the force-storage means 6 and the wheel brake cylinders 3,_although the control slide 10 is in the brake-release position. The invention may also be used on a vehicle having a trailer, in which case a separate force-storage cylinder can be provided for the trailer.