Patent GB-749760-A (GB)
Title: Improvements in and relating to sheet feeders for die stamping or embossing presses
IPC: B65H45/12
Filed: 1953-04-15
Abstract: 749,760. Feeding sheets. VOKES (ENGINEERING DIVISION), Ltd., G., and CHALKLEY, A. W. April 14, 1954 [April 15, 1953], No. 10322/53. Class 100 (1). A sheet feeder for a stamping or embossing press comprises rotatable feed-arms having gripping means for taking a sheet removed from a stack located laterally of the press dies, and transferring the sheet to the working position and holding it securely between the dies until after the working operation when the arms return to their initial position having released the stamped sheet, means being provided for operating the gripping means to seize and release the sheets during the rotation of the arms. Sheet forwarders and detectors.-The feeder arms 1 are mounted on a vertical shaft 2 intermittently rotated through 90 degrees with a rest period between each movement by means of a Geneva stop-motion driven from a main drive shaft 3. To enable the feed arms to approach the stack in a retracted position they are slidably mounted in a capstan head 6 on the shaft 2. Each arm has a collar 7 which is engaged successively by a finger 8 actuated through a toggle link 9 engaging a cam 10 on the shaft carrying the driving member 12 of the Geneva stop motion the timing being such that the finger projects the feed arm to enable its gripper 13 to engage the top sheet of the stack 14. The four feed arms are part of two slide bars 15 arranged normal to each other so that when one feed arm is projected the diametrically opposite arm is retracted. The slide bars may be spring-loaded. The grippers 13 are adjustable on the arms and are operated by two-armed cam levers 16 the upper arms of which engage adjustable collars 17 mounted on rods 18 rotatable with and extending above the feed arms. The lower arms of the levers 16 are engaged by a finger 19 actuated by a second toggle link operated from the member 12 of the Geneva stop motion mechanism by means of an adjustable rod 21 having a lug 22 which is engaged by an eccentrically mounted roller 23 on the cam 10. The rod 21 is adjusted by a hand wheel 38 for operating on different sizes of sheets. Oil is supplied to the parts mounted on the head from a reservoir 35. The absence of a sheet in the press is detected by a lower electrical contact 41 mounted on the plate 40 and an upper contact 42 movable periodically towards the lower contact, the two only meeting in the absence of a sheet to stop the press. A recessed indexing disc 421 and a co-operating detent arm 43 ensure accurate positioning of the arms. Alternatively, the disc may consist of four V-shaped retainers pivotally and adjustably mounted on the disc, the roller of the detent engaging between the arms of the retainers. Sheet separators.-The magazine has a supporting plate 25 raised and lowered by ratchet and rack mechanism operated by a hand wheel 36, and pneumatic suckers are carried on a bar 26 to raise the top sheet of the stack to facilitate gripping of the sheet. A spring steel strip maintains the stack against the front of the magazine. The suckers are connected to a vacuum pump 29 and the sucker bar 26 is mounted on a member 27 vertically reciprocated from the shaft 3 and provides a double stage lift. A blowing device 31 operated from the pump assists in the raising of the top sheet. The reversal of the pump stroke is timed to release the vacuum on the suckers after the sheet has been engaged by the grippers.