GB516174A - Improvements in compressors for brakes or hydraulic transmissions - Google Patents

Abstract

516,174. Hydraulic transmissions of power. SOC. ANON. DES ATELIERS GAMAIN. June 22, 1938, Nos. 18549, and 18550. Convention dates, June 23, 1937, and June 8, 1938. [Class 69 (ii)] [Also in Group XXXIV] A master cylinder for hydraulic brakes comprising coaxial high and low pressure pistons is provided with a valve adapted to connect the low pressure cylinder to the brakes, the low pressure cylinder also being connected with a space containing a piston sliding inside the low and high pressure pistons against a spring in order to vary the space so as to correspond to the pressure in the low and high pressure cylinders. Liquid is supplied to the brakes connected at 6 by both the high pressure piston 10 and the low pressure piston 9 operated by a driving member 14 until the pressures acting on the compensating pistons 26, 27 and valve 39 cause these parts to move and close the apertures 40 connecting the low pressure piston to the brakes. Liquid from the low pressure piston thus flows into the space 9<1> and the piston 27 moves in the interior of the low pressure piston 9 and fluid is forced therefrom into the reservoir connected at 7 by passages 29, 30, 31. Eventually a spring 35 engages the piston 27 causing resistance and eventually extension' 34 on the member 14 engages a cavity 33 in the piston 27. On release the pistons 9, 10 are returned by a spring 13 and the pressure of the fluid in the brakes. Fluid flows by a valve 53 from the reservoir to the low-pressure piston. The pistons are driven towards the left against the pressure of the spring 32 by the pressure of the fluid from the brakes to uncover the port 8 until this latter pressure has dissipated, when the pistons are moved to the right and port 8 closed to maintain a slight pressure on the fluid. A number of springs 35 may be provided, set back relative to one another. In a modification the communication between the low pressure and high pressure cylinders is by means of a port in the cylinder 3 in the release position and by a spring-pressed ball valve opening towards the high pressure cylinder. In a further modification, the compensating piston 27, Fig. 3, contains a valve 72 adapted to be opened by the member 14 to provide communication between the low pressure cylinder and the reservoir. The piston 27 carries a stem 37 on which is mounted a valve 61 having a packing 41 and controlling communication between the low and high pressure cylinders. When the piston 27 is moved back during brake application, liquid under pressure is released from in front of the low pressure piston into the reservoir, the piston 27 consequently returns and recloses the valve. This cycle is repeated until the pressure has attained such a value in the high pressure cylinder that the valve remains permanently open. A spring-pressed valve 81 maintains a slight pressure in the pipe lines.