Patent GB-306909-A (GB)
Title: Hydro-pneumatic brake operating apparatus for vehicles
IPC: B60T8/40
Filed: 1929-02-27
Abstract: 306,909. Compagnie Internationale des Freins Automatiques Soc. Anon. Feb. 27, 1928, [Convention date]. Fluid-pressure.-In hydraulic apparatus for actuating vehicle brakes in which liquid under the pressure of compressed gas is admitted from a storage reservoir to the brake cylinders to apply the brakes, and is returned to the reservoir in the release operation by a re-charging pump, the braking action is effected in two stages, one in which the braking pressure is provided by the storage reservoir and a second in which the brake cylinders receive an additional quantity of liquid dependent upon the speed of the vehicle. The braking pressure may also be rendered. automatically dependent upon the load of the vehicle The apparatus shown in Fig. 1 comprises a pump 5 driven from an axle of the vehicle so as normally to exhaust a discharge reservoir 3 and to charge a storage reservoir 8 containing liquid under pneumatic pressure. To obtain this condition in the first instance a quantity of liquid is placed in the closed reservoir 3 and the pump piston 5 first withdraws this liquid by way of the pipe 3<1> and suction valve 4b and delivers it through the delivery valve 4<a> and pipe 7 to the reservoir 8, air being subsequently withdrawn from the reservoir 3 and forced into the reservoir 8 until an equilibrium pressure and vacuum is reached in the two reservoirs, which is dependent upon the clearance space in the pump cylinder 4. Auxiliary hydraulic or pneumatic cylinders which may operate for example the doors of the vehicle may be supplied from the lower or upper part of the reservoir 8 and discharge into the reservoir 3, from which the fluid is again returned to the reservoir 8 by the pump 5. If the pneumatic cylinders discharge into the atmosphere the introduction of additional air into the system is provided for by the provision of a spring-loaded non-return valve 3b on the reservoir 3. Cylinders may elso be connected to the reservoir 3 for operation by-the vacuum therein. In this case the pressure in the reservoir 8 is prevented from rising above the normal by the provision of a spring-loaded valve 8<b> on the reservoir 8. The cylinder 26 which operates the brakes is connected to the reservoir 8 when it is desired to apply the brakes by de-energizing the magnet E which normally holds closed a non-return valve 8<a> thus permitting the pressure liquid to flow to the cylinder through the pipe 1 and past a non-return valve 10<a>. The valve 8<a> now acts as a suction valve to allow an additional pump piston 5b which may as shown form part of the piston 5 to draw additional liquid from the reservoir 8 and deliver it past the valve 10<a> to the brake cylinder from which it can return to the reservoir past a valve 9<a> and the pipe 7. An adjustable stop 9<k> limits the opening movement of the valve 9<a>. A braking pressure dependent upon the speed of the vehicle is thus established. In order that this pressure may also be a function of the load of the vehicle, a valve 9<b> may be provided arranged to be closed by a rod 91 to an extent dependent upon the extent of the yielding of the bearing springs. Release of the brakes is effected by energizing the magnet 3<c>, thus opening the valve 3a. Fig. 2 shows a modification in which the discharge reservoir is dispensed with and the brake piston 25 serves as the re-charging pump, being formed as the core of a solenoid whereby it is operated to return the liquid through the passage 9 to the reservoir 9 to release the brakes. In this construction the rod 91 varies the pressure of a spring acting upon the valve 9<a>. The Specification as open to inspection under Sect. 91 (3) (a) states that auxiliary cylinders may be provided for the operation off the electric motor controllers of a train of vehicles. This subject-matter does not appear in the Specification as accepted.