Patent GB-893294-A (GB)
Title: Hydraulic lifting gear
IPC: B66F3/30
Filed: 1959-07-06
Abstract: 893,294. Machine-tool details. SEPPELER, E. July 6, 1959 [July 4, 1958; June 25, 1959], No. 23137/59. Class 83 (3). [Also in Groups XXIII and XXX] A machine tool is provided with a verticallyadjustable work-table 47, Fig. 2, mounted on an hydraulically-operated ram 46 fitted with a locking device which comprises a split-cone 49 co-operating through interposed balls 51 with an outer coned ring 53 and is operable by actuating means arranged simultaneously to control the pressure medium in the working cylinder through either an unloading or regulating valve. The ring 53 is supported by a forked member 54 resting on a spring-loaded member 55 and a cam 65 manually controllable by a lever 64 having three control positions, namely, " neutral " (as shown), " tighten " when raised, and " lower " when moved to its lowest position. As the lever 64 is moved to the " tighten " position the top of the split cone 49 moves upward through a small clearance to bear against the downwardly-projecting end of a sleeve 60 which is spring-loaded to permit of upward movement of the split-cone until it contacts the top of the casing 48 when the cone is forced further into the ring 53 to lock the ram against further movement. As the cam 65 and lever 64 reach their fully tightened positions the forked end of the lever 54 bears downwards on the yieldable members 55. When the lever 64 is moved to the " lower " position the cam operates a release valve 70 in the hydraulic system. In a preferred embodiment, Fig. 1, in which a pedal-operated pump 25, a relief-valve 24, release valve 10, and the ram locking means 17, 18 are housed in a common casing 28, the ram 1 is telescopic, having an inner fixed portion 2 forming a piston within a cylindrical outer portion 1 which is flanged at its lower end to limit its upward movement. Fluid pumped from a reservoir 12 reaches the pressure chamber 38 above the piston through a ball-valve 31 and the piston 15. A de-aerating tube 16 depending from the closure 13 at the upper end of the cylindrical ram 1 allows occluded air to escape from the pressure chamber 38. During lowering of the ram some fluid is automatically discharged through the tube 16 and hence through an unloading valve 11 to return to the sump 12. A cam 4 is operated by the control lever 6, when in the " lowering " position, to depress the valve-actuating pin 7, the rate of lowering being adjustable by means of a sleeve 40 which varies the resistance to flow of the hydraulic fluid. A second cam 8 on a common shaft 5 with the valve-operating cam 4 raises or lowers a forked member 19 to operate the splitcone locking device, as described above. As the lever 6 is moved to the " tighten " or locking position the cam 4 is moved to the pressurerelief position, the ram 1 then being held by the locking device only, but when the lever is returned to the " neutral " position the cam 4 allows the valve 11 to close. The ram-locking device remains effective until the fluid pressure has risen sufficiently to balance the load supported by the ram; in the event of a leak in the system the load is secured by the mechanical locking device, and the contour of the cam 8 is such that the position of the forked member is unaffected when the control lever is moved from " neutral " to " lower." Fig. 3 shows a further embodiment in which the ram 74 is axially movable in a cylinder 73 formed integrally with the casing 75 and the base of a split-cone locking device 76 bears downwardly on an intermediate wall 77 of the casing. A self-locking arrestor plate 84 prevents downward movement of the ram in the event of accidental fluid pressure release from the cylinder 73. The plate 84 is supported horizontally on an abutment 85 by two loose pins 82 which are held by a weak spring in a position in which they project from the underface of the plate, the other end of the plate being supported by a leaf spring 86 which bears on a cam 93 operated by the control lever 89, causing the plate to pivot on the pins 82. When the plate is in the position shown, the ram 74 will be free to move, but when the control lever is moved to the " tighten " position the movement of the spring 86 off the cam 93 tilts the plate and thus prevents downward movement of the ram. A cam 95 operates an unloading valve 91 in the pressure pipe 92 and a cam 94 operates a forked member 80 to actuate the split-cone locking device.