GB613527A - Two-stage hydraulic master cylinder - Google Patents

Abstract

613,527. Hydraulic master cylinders. WAGNER ELECTRIC CORPORATION. Nov. 29, 1945, No. 32282. Convention date, Jan. 4. [Class 103 (i)] In a two-stage master cylinder such as described in Specification 575,417, in which the cylinder initially slides bodily to cut off communication thereof with the reservoir and the low-pressure piston is rendered ineffective at a predetermined pressure by flow through a valve-controlled passage in the high-pressure piston, this passage is restricted to provide gradual transition from the low to the high pressure stage and a passage through the low-pressure piston which byepasses the restricted passage when the pistons are retracted is closed by initial forward movement of the highpressure piston relatively to the low-pressure piston. The cylinder 14 is slidably supported within the reservoir 1 by the outlet 15 of the cylinder and the rear end thereof which respectively slide within and over members 3, 12 screwed into the reservoir. A spring 11 bearing through a washer on the inner end of the plug 3 normally holds the cylinder in the position shown in which it communicates with the reservoir through passages 16. The highpressure piston 18, 23, 30 slides in the cylinder member 12 and in the low-pressure piston 36 which normally abuts on a fixed ring 35. A passage 41 through the head 30 of the lowpressure piston 'is normally' closed by a valve 31 acted on by a spring 26 and connected to a normally unseated valve 27 to which is attached a sealing cup 28. The space at the rear of the piston 36 is normally connected to the forward cylinder chamber 14<SP>1</SP> by passages 43 in the piston. The piston 23, 30 when initially moved by the pedal carries the cylinder forward by friction to close the passages 16 and then engages the piston 36, a valve member 38 sealing off the forward chamber 14<SP>1</SP> from the space at the rear of the piston 36-which, however, receives' liquid from the reservoir through passages 14a, 17 past the sealing-cup 28 and passages 44. When the pressure in chamber 14<SP>1</SP> acting on the valve 31 against the pressure of the spring 26 is sufficient to unseat the valve, the chambers at front and rear of the piston 36 are connected together by the passage 41 and the piston thus rendered ineffective. The passage 41 is restricted to delay equalization of the pressure at the two sides of the piston 36 so that the transition from the low to the high pressure phase is rendered gradual and the change-over tends to be further delayed if the pedal is moved rapidly.