Patent GB-387558-A (GB)
Title: Improvements in or relating to hydraulic actuating means for machine tool chucks
IPC: B23B31/20
Filed: 1932-05-07
Abstract: 387,558. Chucks. MILOTTA, K., 10, Sickingenstrasse, Berlin. May 7, 1932, No. 13236. [Class 83 (iii).] In a fluid-pressure-operated chuck the jaws are actuated by a draw-spindle which is moved to and from the closing position by fluid pressure acting on small annular pistons and is maintained in the closing position by the fluid acting on a large piston. A regulator is also provided for throttling the supply to the actuating pump when the pistons are stationary in the open or closed positions. In one form the jaws 6, Fig. 2, are moved radially by levers 5 rocked by a collar 7 on a hollow draw-spindle 8 which is attached to a sleeve 81. Enlargements 10, 25 on the sleeve 81 form shoulders acting as annular pistons in cylinders 12, 27 which move the draw-spindle 8 in the closing and opening directions respectively. A large piston 17 is attached to a sleeve 11 slidable on the sleeve 81 and is normally maintained in the position shown in Fig. 2 by a spring 20. In this position, passages 22 in the piston 17 allow fluid to pass freely from one side thereof to the other. In operation, fluid, preferably oil, is admitted from a constant volume pump m, Fig. 1, through a pipe e and passages 30 .. 33 in the cylinder 14 to the annular piston 10, thereby closing the chuck jaws whilst the oil in the cylinder 14 passes freely through the piston 17. When the jaws engage the neck 9, further movement of the sleeve 8<1> is prevented and the oil acting on the end of the sleeve 11 moves the piston 17 against the action of the spring 20, until a seat 23 thereon engages a seat 24 on a flange 21 formed on the sleeve 8<1>, thereby shutting off the passages 22. Pressure is then admitted to the cylinder 14 through a channel 34 in the sleeve 11 and acts on the large piston 17 to maintain the chuck closed. To release the jaws a reversing valve f, Fig. 1, is moved to connect the pipe e with an exhaust k leading to a sump i and admits oil from the pump through a pipe d to the annular cylinder 27. The spring 20 then opens the passages 22 and the oil acts on the enlargement 25 to move the sleeve 8<1> to the open position. To limit the power absorbed by the pump m when the chuck remains in the open or closed positions, a regulator o, Figs. 1 and 5, is provided having a piston 70 with an annular groove 71 normally allowing oil to pass freely from the sump to the pump through the pipes n, 73. A spring 74, adjustable by a screw 75, maintains the piston 70 in this position. When the chuck is open or closed, a rise of pressure in the supply pipe h is admitted by a pipe p above the piston 70, thereby depressing the piston and throttling the supply to the pump. In a modified construction of the piston 17, the sleeve 11 is dispensed with and the piston is moved relatively to the sleeve 8<1> by the oil acting on an annular shoulder therein. In a modified form of chuck the draw-spindle 8 is attached to a spring collet slidable in a bevelled sleeve, Fig. 4 (not shown). Spring non-return valves 35, 36, Fig. 2, are provided for relieving excess pressure in the cylinder 14.