GB1506279A - Device for controlling a movable member on a machine tool - Google Patents

Abstract

1506279 Bending; shearing PROMECAM SISSON-LEHMANN 22 Dec 1975 52424/75 Headings B3E and B3W An hydraulic system for controlling the movement of the working member of a machine tool, e.g. a folding or shearing machine, comprises a single distributer including a slide valve operable either by the operative or by mechanical transmission from the working member, wherein the operative moves the slide valve to initiate the working stroke, and the valve is successively actuated by the mechanical transmission to change the speed of the working member and then to end its stroke. In the figures, the slide valve 5 has ports 31, 32, 33 co-operating with lands 35, 36 defining chambers communicating with ports 6, 10, 15. Pump 8 is connected by lines 7, 9, to port 6 and a fast speed cylinder 2. The slow speed cylinder 3 is connected to port 10 and by one-way valve 14 to reservoir 12, and port 15 is connected to reservoir 12. In the position shown, the pump is connected to reservoir and off-loaded. When the operative actuates master cylinder 21 by pedal 22, slave piston 17 moves valve 5 fully to the right, cutting off ports 31 by land 35. The pump output is thus applied to the fast cylinder 2, cylinder 3 drawing in fluid through valve 14. By controlling the degree of cut-off of ports 31, the operative can control the fast speed. A member 51, Fig. 2, moving with the working member, drives an arm 52 having cam face 57, so that at a point in the stroke determined by the setting of screw 53 roller 59 is contacted and rod 50 moved to the right. Lever 47 pivots and pushes rod 18 into the distributor 4, moving valve body 5 to a position in which the pump output is applied to both cylinders 2, 3, producing slow speed. A rise in pressure in chamber 46 caused by the working member beginning the working part of its stroke will also cause movement of the valve 5 to the slow speed position, by operating on pistons 44, annular members 43, 41, and flange 40 on the valve. At a subsequent point in the stroke determined by the resetting of screw 67, arm 60 on member 51 will further move rods 50 and 18, moving valve 5 to a position in which the pump is connected to reservoir through ports 33, which are such as to terminate the stroke while maintaining some pressure in the cylinders. On release of the operative control, the valve is returned by spring 25. The operative may actuate valve 78 to interrupt the slow movement at any time. Provision is made to avoid hunting of the valve. In another embodiment, Figs. 9 and 10 (not shown), a single cylinder is operable by two pumps for fast speed, and one pump is off-loaded for slow speed, the passages in the right hand end of the valve body and the connections to ports 6, 10 and 15 being such as to produce the same operational sequence.