GB899753A - Improvements in and relating to indexing mechanism for machine parts - Google Patents

Abstract

899,753. Machine-tool details; indexing. FOSTER, YATES & THOM Ltd. June 3, 1960 [June 12, 1959], No. 20219/59. Class-83 (3). [Also in Group XXIX] An indexing mechanism for machine parts comprises a fluid-operated cylinder and piston arrangement, crank means operable thereby over 180 degrees through a dead-centre position for driving the part to be indexed, a directional valve arrangement for reversing the action of the cylinder and piston arrangement while the crank passes its dead-centre position and means for controlling the supply of pressure fluid to stop the crank at an indexing position. The part to be indexed is connected through a pinion 9, Fig. 1, on the indexing device and may be a rotary or reciprocating table. The pinion 9 is secured to a crank-shaft 7 which is rotated by a connecting rod 5 forming part of a double-acting piston 4 in an oscillating cylinder 6. The cylinder 6 is pivoted about trunnions 3 in bearings 4 in the indexing device. Spring-pressed relief valves 22 to relieve the pressure from either side of the piston to the other are embodied in the piston. One of the trunnions 3 is utilized as a directional valve and has passages 12, 13 communicating with the cylinder ends and with a peripheral groove 15, Fig. 4, in the trunnion. Communication between the passages 12, 13 is stopped off by two diametrically arranged plugs 20, 21 which slide around the groove 15. Supply and exhaust passages from a reversible control valve lead into the passage 15 from ports 16, 17 in the trunnion bearing. Operation. The indexed positions of the crank-shaft are at 180 degrees and at rightangles to the dead-centre position and the control valve is operated by solenoids controlled by switches on the indexed member. The piston is approximately at the mid-position when an indexed position is reached and moves away when the control valve is opened to rotate the crank. The directional valve reverses the flow of pressure liquid or air after the deadcentre position is reached and at this point the plugs 20, 21 do not completely cover the passages 16, 17 so that pressure and exhaust are connected as are the cylinder ends. A choke valve 24, Fig. 1, operated by a cam 24a may be employed to slow down the parts as an indexed position is approached. In a second embodiment, the piston-rod operating in the oscillating cylinder is provided with a central shoulder and two slidable sleeves, one each side of the shoulder, act as pistons (see Figs. 6 and 7, not shown). Specification 831,193 is referred to.