GB674593A - Improvements in or relating to pressure or load control device for linkage of metal working presses - Google Patents

Abstract

674,593. Metal-working presses. CLEARING MACHINE CORPORATION. Aug. 25, 1950 [June 12, 1950], No. 21064/50. Class 83 (iv). A metal working press has a load control device associated with the mechanism for reciprocating the slide the device comprising a yieldable member mounted on the slide, a lever arm connected at one end to said yieldable member and eccentric pivot means connecting the other end of said lever arm between the slide and the said mechanism, whereby relative movement between the slide and the mechanism tending to produce an overload causes rotation of said lever arm about said eccentric pivot means against the pressure of said yieldable member. A slide 1 is reciprocated by a crank 5 on a shaft 4. The load device consists of a fluid-pressure cylinder 7 having a piston 8 attached to a rod 13, the cylinder being pivoted to a lug 11 on the slide. The rod 13 is pivotally connected to one end of a lever arm 16, the other end of which has circular side members 17 and 18 (Fig. 3), and an intermediate portion 19 partially surrounding an arcuate recess 20. The side members 17 and 18 carry an eccentric pin 22 and the lower end of a link 6 attached to the crank 5 extends into the opening 20 and surrounds the pin 22. The side members 17 and 18 of the lever are carried in bearings 24 mounted on an adjustable member 28 comprising a screw-threaded member 29 carrying a bevel gear 30 which has a flange 31 adapted to rotate in an annular recess in a sleeve 32. A stop 3 on the arm 16 limits the downward movement of the arm and the piston 8. In operation, when the load exerted by the slide multiplied by the distance between the eccentric axes 21 and 23 exceeds the fluid pressure on piston 8 multiplied by the length of lever 16 the lever rotates and raises the piston rod 13 and piston 8 so allowing the crank and link to complete their downward movement without overloading the press. The centre of the pin 22 may be on either side of the centre line passing through the crank, the screw and the lever axis 21. Also, the centre line through the crank and screws may pass through the centre of pin 22. In a double or triple-action press wherein the blank holder 34 is reciprocated by a plurality of cranks (not shown), and links 35 (Fig. 4), the lower end of the links being attached to adjustable screw members 37, the load-control device is associated with the adjustable screw members by mounting the cylinders 42 (Fig. 4) on a bar 41 secured to the screw members. The piston rods 46 are' attached to the lever arms 48 which are eccentrically mounted in bearing supports 36 as previously described. In this type of press by varying the pressure in the cylinders 42 varying pressures may be exerted at each corner of the slide. Adjustment of the press is effected manually by means of upper and lower collars 39 and 40 respectively on each adjusting screw 37, each collar abutting against a boss 38. This adjustment may be carried out mechanically by means of worm gearing and an electric motor.