GB848551A - Improvements in chucks for machine tools - Google Patents

Abstract

848,551. Chucks. PRECISION INDUSTRIELLE. Jan. 28, 1957 [Dec. 3, 1956], No. 3039/57. Class 83 (3). A chuck 3 for work 4 centred by other means, e.g. centres 5; 6, comprises' radially movable jaws M operated by a draw-tube 20, through means which allows the jaws to move through different individual distances in order to ensure that they apply equal gripping pressures. An odd number of carriers 11, to which the jaws are fixed by screws 10, are moved radially by levers 12, on pivots 13 and connected to the draw-tube 20 by a housing 19a, 19b. A spherical roller 16 on the lever is received in the groove of a swivelling member or (as shown), between rings 18a, 18b having spherical outer surfaces engaging spherical seatings in the housing, which is guided by a tube 3a fixed to the front of the chuck. Upon operation of the draw-tube to close the jaws on to the work, the outer surface of which is not concentric with the axis of the centres 5, 6, supporting the work, the first jaw to engage the work, and thus arrest pivotal movement of its lever 12, causes the rings 18a, 18b to swivel in the sliding housing, the swivelling movement continuing until the other jaws contact the work and end the pivotal movement of the other levers 12. To prevent bending of the work due to the jaws not engaging the work simultaneously, plungers 21, opposite the jaws in the three-jaw construction illustrated, engage and support the work before it is engaged by the jaws. The plungers are operated by projections 28, on the housing 19, which engage and move sleeves 26. The movement is transmitted, through a spring 29, to a piston rod 25 and a piston 24 having an annular groove 32 in communication with the space 22a behind the plunger 21, through passages 30, 31, and with the space 35 ahead of the piston, through a port 34 in the piston and an annular groove 33 in the sleeve 26. The spaces 35 are interconnected by passages 31, 36, to balance the forces applied by the plungers, and movement of the pistons expels liquid from the spaces 35 to the spaces 22a, through the grooves and passages 30 ... 34, thus closing the plungers 21 on to the work. The application force of the plungers increases until the spaces 22a are sealed by closure of the ports 34 upon compression of the springs 29. Instead of closing the passage 31 by a plate 40, it may be closed by the end of the machine spindle. In a modification (not shown), a single piston 24 may force liquid behind all of the plungers 21. Lathes. The live centre 5 is located in the hollow spindle 2a or, for longer work, in a tubular extension of the spindle extending out of the headstock 2. Reference has been directed by the Comptroller to Specification 824,016.