Patent GB-638100-A (GB)
Title: Fluid-pressure servo-mechanism
IPC: B23Q5/36
Filed: 1947-10-03
Abstract: 638,100. Fluid-pressure servomotor-control systems valves. SMALLPEICE, C. D. P. Oct. 3, 1947, No. 26628. [Class 135] In a power assisted, manually-actuated mechanism for operating a press, brake or machine-tool slide and of the kind in which the manual control member acts on the press &c. and on the diaphragm of a pressure regulator which controls the flow of working fluid to the power means, the inlet valve which is connected to the diaphragm, is arranged to open in the same direction as that in which the fluid flows. As shown in Fig. 1, the control lever 16 is loosely pivoted to the rod 15 of the power piston 12 and fulcrumed on the end of a rod 17 passing through and secured to a diaphragm 28 forming a wall of a chamber having a compressed air inlet pipe 31, the mouth of which is controlled by a spring-loaded valve 30 actuated by the rod 17. Upon release of the hand-lever 16, the rod 17 moves down under the action of the spring 18 and opens the exhaust valve 20 to permit the escape of air from the power cylinder 11 when the piston 12 rises under the action of a spring 27 or of pressure air admitted through a pipe 26 to the space beneath a piston 24 carried by an extension of the piston rod 15. Fig. 2 shows a press operated by a hand-lever 38 connected by a link 37 to the plunger 35 of a power cylinder 34 and adjustably pivoted to the rocker 40 of a double-acting pressure regulator 42 having a compressed air inlet 43 and connected by pipes 44, 45 to the opposite ends of the power cylinder, said pipes functioning either as pressure supply or exhaust ducts. The pressure regulator comprises a body having bores 48, 49, Fig. 4, housing members 58 slidable on fixed guides 59 and secured at their upper ends to diaphragms 60 exposed to atmospheric pressure through ducts 69, 70. The members 58 are formed with bores 62, 64 connected through ports 61 with the pipes 44, 45. The upper ends of the members are closed by exhaust lift valves 65, the degree of opening of which is dependent on the positions of the studs 66, 67 in the rocker 40 and the air pressures on the undersides of the diaphragms. The admission of compressed air to the bores 48, 49 is controlled by valves 55 carried by spring-loaded arms 56 mounted on the members 58 and coacting with the open ends of ducts 53, 54 communicating with a port 52 connected to the compressed air inlet 43. Anti-clockwise movement of the rocker 40, Fig. 4, results in opening of the appropriate valve 55 to admit compressed air to the bore 49 and thence through the port 61 and pipe 44 to the upper end of the power cylinder 34, Fig. 2, to augment the downward thrust of the lever 38 on the plunger 35. Meanwhile, air pressure builds up in the bore 49 and reacting on the diaphragm 60 tends to close the valve 55. Thus, the pressure in the bore and in the pipe 45 is substantially proportional to the manual effort applied to the lever 38. During the downward movement of the plunger 35, air is exhausted from the lower end of the power cylinder through the pipe 45 to the bore 48, and thence past the lift valve 65 to the atmospheric duct 70. Specification 545,318 is referred to.