GB904737A - Improvements in or relating to air pressure braking systems - Google Patents

Abstract

904,737. Fluid-pressure brakes. CLAYTON DEWANDRE CO. Ltd. Jan. 18, 1960 [Oct. 16, 1958], No. 33073/58. Class 103 (1). A braking mechanism has a servomotor 4 disposed coaxially of and within a compressed air reservoir 1, means at one end of reservoir 1 by which manual input is transmitted mechanically to motor 4 and means extending coaxielly through the motor/ reservoir assembly for transmitting the output of the motor and the manuallyapplied effort to an hydraulic master cylinder 5 located externally of the reservoir at the other end thereof. The tandem-type master cylinder 5, the motor 4 and the end wall 3 of reservoir 1 are formed integrally, the motor 4 carrying a tubular housing 19 containing a hollow plunger 23 including a valve seat 25 normally engaged by a spring-pressed valve 27. The servo piston 31 has a stem 35 engaging the master-cylinder piston 11 and carries a control member 39 held spaced from valve 27 by a spring 40. In the release position, as shown, both sides of piston 31 are vented to atmosphere via ports 38, 41, and hollow member 39. On braking, plunger 23 is moved to engage valve 27 with member 39 and then move seat 25 from valve 27 to connect pressure reservoir 1 to the front side of piston 31 via ports 30, 28 and past seat 25, piston 31 then moving piston 11 and hence piston 12 to apply two sets of brakes via ports 9, 10. When movement of plunger 23 ceases the piston 31 and member 39 move to lap position wherein valve 27 engages seat 25 and member 39. The pressure in front of piston 31 acts via port 32 and chamber 33 on land 34 of plunger 23 to transmit " feel " to the brake pedal. When the applying force on plunger 23 is removed, spring 40 moves plunger 23 and disc 27 from member 39 to vent the servomotor, a spring 37 returning piston 31 to its inoperative position. Should the compressed air supply fail, then continued movement of plunger 23 moves pistons 31 and 11 mechanically.