Patent GB-719459-A (GB)
Title: Improvements in and relating to guards for presses
IPC: F16P3/04
Filed: 1951-01-01
Abstract: 719,459. Machinery guards. VOKES (ENGINEERING DIVISION); Ltd., G. and CHALKLEY, A. W. Jan. 1, 1952 [Jan. 1, 1951], No. 65/51. Class 80 (4) [Also in Group V] The spring-returned ram 1, Fig. 1, and guard 14 of a toggle press are reciprocated by a continuously rotating shaft 35 and means are provided to prevent the toggle from operating the ram if the guard is obstructed in its descent. The shaft 35 carries a cam 34 engaging a roller on a spring-returned forked slide 37 which moves over a guide block 38 and is pivoted on the gudgeon pin 7 of the toggle links 6, 8, so that the toggle is continuously operated. The upper pair of links 6 is pivoted by a pin 5 to an abutment 9 which is adjustable to control the pressure and carries adjustable stop rods 60 for the ram. The lower single link 8 is rigidly secured to the gudgeon 7 and at its other end has a lengthwise slot 11 with an offset portion 12 which is arcuate about the gudgeon, the forked end of the ram 1 carrying a pin 4 engaging this slot. A weight 32 is adjustable along an arm welded to a lever 15 which is clamped to the gudgeon 7 and is controlled by the guard. When the guard is open the weight 32 biases the link 8 to the position shown where the slot 11 rides over the pin 4 as the toggle is operated. the ram being held stationary in its uppermost position by the two return springs 10. The guard 14 is carried by a pair of uprights 20 slidable on guide rods 22, and is raised mechanically and closed by gravity, assisted by two light springs 23 arranged to be unstressed when the guard is closed. The uprights 20 are connected by a bar which is linked to an arm 28 fixed to a sleeve rotatable on the pin 5. An arm on the sleeve carries a roller 31 engaging the lever 15 and as the guard closes this arm is rocked to depress the lever 15 arid rotate the gudgeon 7. The link 8 is thereby rotated until the pin 4 is in the arcuate slot portion 12, thus causing the ram to be operated. The roller 31 could be mounted on the guard itself or on the bar connecting the uprights 20, but the linkage provided accelerates the movement of the roller asthe guard approaches its closed position so that the lever 15 remains inoperative until the guard is nearly closed. The shaft 35 carries a cam 50, Fig. 3, co-operating with a roller on a spring-returned lever 52 which is linked to an arm on the shaft of two sprocket wheels 58. Chains 59 connect the sprockets to the uprights 20 so that during each press cycle the guard 14 is raised by the spring 54 and is lowered by gravity and the springs 23 against the action of the weight 32. Any obstruction of the guard's descent-e.g. by an operator's fingers-prevents actuation of the lever 15 to render the ram operative. The cam 50 is so contoured and set that 'the guard remains closed during the entire downward movement of the ram 1. The continuous operation of the ram may be interrupted by moving a lever 61 into the path of a lug on one of the uprights 20 and thereby preventing the descent of the guard 14. The lever 61 is moved to its obstructing position by a pedaloperated wire 64 linked thereto, actuation of the pedal causing the press to miss one or more strokes. A spring 69 and a pedal counter-weight normally hold the lever 61 out of the path of the lug, but a hand lever 67 may be swung into the position shown to maintain the lever 61 in its obstructing position after the pedal has been released so that the machine may run without stamping. It is stated that the arm carrying the weight 32 may be fixed to the gudgeon 7 instead of to the lever 15, that the weight may be replaced by a spring, and that a pair of slotted lower toggle links may replace the single link 8 and co-operate with a single upper link.