Patent GB-325683-A (GB)
Title: Improvements relating to the bending of metal strip or sheet
IPC: B21D53/16
Filed: 1929-02-09
Abstract: 325,683. Renold, Ltd., H., and Renshaw, A. Feb. 9, 1929. Chains; tubes.-In making hollow cylindrical articles, such as the bushes for jointing the side members of sprocket-chains, from strip-metal, a blank is first cut from the strip by a punch the opposite edges of which co-operate with a die to form the two ends of the blank, the ends are then bent to wide U-sbape and the blank is finally bent round a cylindrical mandrel. The strip 20 is fed intermittently a greater distance than the length of a blank so as to overlap a die 16 and a blank is then punched out by a punch 12 and is received on a cam-operated slide 22, which transfers it along guides 28 to a bending die 18 with rounded corners, where it is bent into wide U-form by a bending punch 14 with rounded corners. The slide is provided with pins 26, 24 passing through notches in the punches 12, 14 respectively so as to strip the blanks therefrom. The blank is then transferred by the slide beneath a mandrel 30 where it is bent to cylindrical form by a pair of concave dies 40 carried by slides reciprocated in horizontal guides by racks and pinions operated by racks on vertical rams 32 and is then stripped from the mandrel by a cam-operated sleeve 48 and blown by compressed-air from a nozzle down a shoot 50. One of the dies may be formed with a central extension passing through a slot in a cam-operated clamp bar 46 and also in the cooperating die, so as to prevent bowing of the blank during bending. The clamp-bar supports the blank when the dies have been retracted. In a modification, Fig. 5, the dies are formed with full width extensions 48, 43 above and below the mandrel, the extension 43 being slotted to slide over the clamp bar 47. The dies may be cam-operated and may be moved apart sufficiently to free the blank while retaining the extension under the mandrel in which case the clamp bar is dispensed with. A vertically movable tongue may be moved in front of the blank to prevent it from being drawn back with the transfer slide. In another form the blanking and initial bending are performed by a single pair of tools in a single operation, the blanking punch 53, Fig. 10, which co-operates with the die 52 to cut out a blank, having a recess 56 co-operating with an anvil 54 with rounded corners. The die 52 is vertically adjustable by a screw-operated wedge 136, Fig. 7 and the anvil by a screw plug 144. The partly bent blank is stripped from the punch 53 by a spring-pressed pin 82, Fig. 6, carried by a transfer member 78, which transfers it along an extension of the anvil to a position above a mandrel 60, on which it is held by a plate 76. In this movement the blank passes under the rounded corners of a pair of guides 59 and engages the bevelled ends of a pair of spring- pressed plungers 63, which are retracted and then snap back behind the blanks so as to prevent them from being drawn back with the member 78. The bending is completed by a pair of concave dies 62 adjustably mounted in a pair of slides rack operated through a single ram 66 having rack teeth on each side. The mandrel, which is secured by a split chuck 86 to a sleeve 88 so that it may be reground when desired, is now retracted with the sleeve until the completed bush is removed therefrom by a stripper 90. The sleeve is connected by a lever to a spring-returned valve plunger 120, which is thus simultaneously operated so as to connect the tubes 128 and 126 and so supply compressed-air to a nozzle 96 for discharging the bush and to a nozzle 118 for ejecting the waste metal produced in the blanking operation. Such waste-metal was previously withdrawn from the vicinity of the die 52 before raising the punch 53 by a hook-ended bar carried by a slide 102 having rack teeth engaging a pinion on an axis having also a smaller pinion engaging a rack on an extension 110 of the transfer slide, so that the slide 102 moves backwards during the forward movement of the transfer slide and through a greater distance. The bushes are finished by placing them on a shouldered mandrel and pushing them through a circular die so as to render them circular and to close the joint.