Patent GB-713485-A (GB)
Title: Improvements in reversing mechanisms for the tables of machine tools
Inventor: ASBRIDGE GEORGE HERBERT
IPC: B24B47/06
Filed: 1952-02-20
Abstract: 713,485. Automatic reverse gearing; gearing for stopping and starting machinery. CHURCHILL MACHINE TOOL CO., Ltd. Feb. 19, 1953 FFeb. 20, 1952], No. 4451/52. Class 80 (2) [Also in Groups XXII, XXIII and XXIX] Driving and reversing mechanism for the reciprocatory table c of a machine tool such as grinding or planing machine comprises a hydraulically operated piston type reversing valve k, m, n, o, &c. controlled by the usual dogs a, b on the table to be reversed, the valve delivering fluid to one or other side of a piston w which controls the reversing clutch 24 in the drive to the table, the hydraulic fluid supplied to the reversing valve also passing, e.g. through a pipe 4, to a "stop" amd "start" valve which controls the supply of fluid to a piston 18 operating a clutch 19 which can put the drive to the table into action, the absence of the fluid due to failure of its supply or to manipulation of the "stop" and "start" valve (through a handle 12) causing the piston, to disconnect the drive and bring the table to rest. The dogs a, b on the reciprocating table move a bifurcated and pivoted lever f the ends of which engage plates g, q' controlling spring-urged ball valves h, i and r, s respectively. When, as shown, the plate g is depressed by rotation of the lever f, the valves h, i are opened and hydraulic fluid is supplied from a pump u through a pipe v to the centre space t between the piston-like parts m, n of the reversing valve, whence it passes through the valve i to a space p at the right-hand end of the valve and urges the piston part o, &c. leftwards to the position shown, while the space j at the left-hand side of the piston part k is open to exhaust through the valve h; the piston-parts m, n are then so positioned that hydraulic fluid is fed from the space t through a duct 27 to the left-hand side of the piston w, the right-hand side of which is open to exhaust through a duct 28, the space between the piston parts o, n and a pipe 30. When the plate q<SP>1</SP> is depressed by the lever f and the plate g correspondingly allowed to rise, the valves h, i are closed and the valves r, s opened, so that hydraulic fluid is passed to the space j, the space p is opened to exhaust, the piston valve is moved to the right thereby, and hydraulic fluid is supplied to the right-hand side of the piston w while the left-hand side thereof is opened to exhaust. The reverse valve can also be controlled by an operator, instead of automatically, by means of a handle 40. The reversing clutch 24 connects a driving shaft 2 either to a gear z or a gear y, the former meshing through an idler 26 with a gear 25, and the latter meshing directing a gear 23, both the latter being on a shaft 22 which can be connected by the clutch sleeve 19 to a shaft 20 driving the reciprocating table. The clutch sleeve 19 is maintained in the engaged position,by the admission of hydraulic fluid to a cylinder 17 through the "stop" and "start" valve, which consists of a rotatable and axially movable spindle 5 having an enlarged end 7 with ports 8, 9 therein, the port 9 allowing passage of hydraulic fluid from the pump u to the cylinder 17 in the position shown, this passage being closed and the cylinder 17 opened to exhaust through the port 8 and a passage 32 when the spindle 5 is rotated through 90 degrees to the Fig. 5 (not shown) position. The spindle 5 is turned to the position allowing hydraulic fluid to enter the cylinder 17 and engage the clutch 19 by a handle 12 against the resistance of a torsion spring 6, and is urged upwardly by a spring 10: when the pump u is functioning, the pressure of the hydraulic fluid acting in the recess 15 against the enlarged portion 7 holds the spindle 5 down against the force of the spring 10 so that the handle 12 can be engaged in a notch in the surrounding casing to hold the spindle in its rotated position and allow hydraulic fluid to pass through the port 9 to engage the clutch 19. If the supply of hydraulic fluid fails, the spring 10 moves the spindle upwardly to disengage the handle 12 from its notch, the spindle is then rotated by the torsion spring 6, the cylinder 17 opened to exhaust and the clutch 19 disengaged. The shaft 20 can alternatively be driven by hand from a shaft 35 and gears 34, 33.