GB814622A - Improvements in or relating to indexing mechanism for the rotatable work-tables of presses and other machine tools - Google Patents

Abstract

814,622. Machine-tool details; metal-working presses. HARE Ltd., P. J., and HARE, P. J. Aug. 14, 1957 [May 17, 1956], No. 15443/56. Classes 83 (3) and 83 (4). [Also in Group XXIX] Indexing-mechanism for the rotary worktable 13 of a press or other machine-tool comprises a pawl 21 on a crank 18 turned about the axis of the table by a fluid-pressure ram-andcylinder unit 14, the moving part of which is connected to the crank by a rigid link 17. As applied to a liquid-operated press, the indexing- cylinder 16 is connected to the crank, and the ram 15 is fixed at each end to the underside of a support 24, Fig. 2, for the table. A web 25 on the crank supports the pawl 21, a spring 26 pressing the pawl into notches 22 in an indexplate 23 on the table-support shaft 19. A roller 91 on a spring-pressed lever 92 engages the notches between indexing operations. Eight indexing notches are provided, alternate ones of which are used for indexing the table in steps of 90 degrees when the crank is moved to the index starting position depicted in chaindotted lines, and rotated into the end position depicted in unbroken lines. For smaller index steps of 45 degrees, return movements of the cylinder 16 are restricted by a stop 87 (Fig. 3, not shown) spring pressed into the path of the cylinder, and which can be rocked into a retracted position by a screw. The hollow ram 11 of the press is advanced initially, against the action of its return spring 96, by liquid fed down a tube 38 into the ram. When the ram contacts the work and pressure builds up, liquid is also fed into the ram cylinder 10, behind the ram, as described below. Liquid-pressure control system.-A high-pressure pump 12 supplies the ram tube 38 through a non-return valve 40 and an adjustable needle valve 41, the cylinder space above the ram, through a valve 43 on the cylinder head, and a by-pass valve 51. A low-pressure pump 37 for the indexing mechanism is connected to a valve 33, Fig. 4, controlled by the ram 11 to admit liquid selectively to either side of the cylinder 16, through the ends of the ram 15, and allow liquid returning from the cylinder to escape through the drain ports 63, 64. During the initial down movement of the press ram 11, liquid is drawn into the cylinder space above the ram, from a reservoir, through a pipe 46 and the valve 43. Upon the build-up of pressure, the valve spool 44 is raised, against the influence of its return spring 45, by pressure beneath the valve plunger 47, closing the port to pipe 46 and allowing pressure liquid to flow to the space above the ram, through passages 49, 50. A further increase in pressure, after the ram has completed its stroke, opens a relief valve 54, in the cylinder head, through which liquid escapes to a cylinder 53 for operating the by-pass valve 51, which relieves the pressure in the cylinder 11, the ram being returned by its spring 96 at a rate controlled by the valve 41. Towards the end of the down-stroke of the ram 11, lock-nuts 79 on a shaft 75 carried by the ram move a valveoperating member 73, 74, Fig. 4, which initiates re-setting of the valve 33 and thus return of the indexing cylinder to its starting position, through a rocker 82, movement of the valve spool 56 being completed by the action of the pressure liquid admitted beneath a plunger 70 in the spool, through radial passages 68. In the valve 33, the supply from pump 37 is connected to a groove 61 which communicates selectively, through grooves 57, 58 in the spool 56, witli grooves 60, 62 connected to the indexing ram. As the ram 11 approaches the top of its stroke, lock nuts 80 on the shaft 75 raise the member 73, 74 which again initiates re-setting of the valve 33, by contact between a member 81 carried by the member 73, 74 and the valve tappet 71, the movement of the valve spool 56 again being completed by the pressure liquid acting on a plunger 69. In this setting, the valve 33 delivers pressure liquid to the righthand end of the ram to index the table. At the end of its stroke, the index cylinder 16, by means of an abutment 35, Fig. 2, opens a valve 34 connecting the low-pressure system with the bypass operating cylinder 53 and a workpiece ejector 52, thus closing the by-pass valve 51 to start another working stroke of the ram 11, and ejecting the work at a station removed 90 degrees from the ram axis 95. The Provisional Specification states also that the ram 11 may be returned by liquid pressure and that the valve 33 may be spring-pressed in one direction.