Patent GB-758415-A (GB)
Title: Improvements in or relating to method of forming a door knob
IPC: B21D26/02
Filed: 1954-08-10
Abstract: 758,415. Making door knobs. TUBING SEAL CAP, Inc. Aug. 10, 1954, No. 23210/54. Classes 83 (2) and 83 (4). Stamping.-A method of forming a door knob or the like from a one-piece blank consisting of an expansible main portion with a cylindrical side wall and a bottom wall and a narrower neck portion comprises expanding the main portion of the blank into its final shape in two steps, in the first of which a plunger tightly fitting into the neck is moved inwardly therein to cause a body of liquid confined in the blank to expand said main portion to an intermediate shape whereupon in the second step the exertion of liquid pressure is continued and at the same time deforming pressure is exerted on the outer surfaces of the main portion to give its exterior the desired final shape. The bulb-shaped stamping 9 is placed in the lower die 11 of a press with its necked portion in line with a punch 12 and the upper die 13. A plunger 16 slidably mounted in the fixed platen 15 supports the lower die 11. The upper die 13 has a flared central opening 18 and is carried by a holder 20 anchored to the moving platen 23 by threaded elements 24. A die holder sleeve 22 encircles the die and holder 20. A transverse slot in the holder 20 receives the crosshead 26 carrying the punch 12. Stops 27 on the crosshead engage the lower die holder 14 at one stage of the forming operation. A retaining ring 28 is carried on a plurality of screws 29 slidably mounted in recesses 30 in the die holder sleeve 22 and a plurality of spring-loaded pins 33 on the ring 28 are received within recesses 32 in the sleeve 22. In operation as the platen 23 descends the retaining ring moves over the upper end of the blank, the punch 12 enters the necked portion of the blank and the flared end of the die 13 reduces the diameter of the necked portion. Downward movement of the crosshead 26 and punch 12 is arrested by the stop rods 27 but the upper die 13 is allowed to continue by releasing latch means 35 which enables the lower die 11 to move downwardly. The latch means consists of a pivoted spring-loaded arm 36 one end of which engages a roller 40 on a spring-loaded die supporting plunger 16 the other end being engaged by a spring-loaded tripping bar 44 adjustably secured to the moving platen 23. The necking is completed when the die 13 contacts the ring 28 and on further downward movement an ironing operation is performed by the stationary punch on the inside surface of the reduced neck portion and the wall thickness of the neck is reduced. The punch has a segmental expansion ring 58 mounted in a groove 60 below the cylindrical ironing surface 57. The segments are spring urged against a conical surface 63 so that after the ironing operation the segments expand and overlie the upper end 66 of the blank. On the return movement of the platen 23 the die 13 and the blank move with it. A spring 69 mounted on the platen 23 restrains upward movement of the crosshead 26 and so ejects the workpiece from the die 13. The blank is next placed in a die assembly for hydraulic expansion of the bulbous part 10. The assembly includes a lower die 80, and upper die 81 and a plunger 82 the end of which fits closely within the neck of the blank. The plunger is connected to a bushing 86 slidably mounted in the upper die holder 88 the downward movement of the bushing being arrested by a flange 93 on the bushing engaging a shoulder 89. An ejector 94 encircles the plunger and a plurality of ejector pins 99 extend through the moving platen 96 and the die holder 88 and rest on a flange 95 on the sleeve 94. The upper ends of the pins engage a bumper element 108 mounted on the platen 96 the upper end of which extends upwardly for contact with a stationary bar (not shown). An indenting button 112 is slidably received within a bore 110 in the lower die 80 and the lower die holder plate 114 rests on pins 122 supported by plates 119, 120 having a rubber disc 121 clamped therebetween. This arrangement allows limited downward movement of the die 80 by squeezing the rubber disc. The button 112 is supported on stationary pins 123 passing through the die holder plate and resting on an insert in the lower fixed platen 116. The upper die 81 is secured to the holder 88 by clips 146 (Fig. 25) engaging within an annular groove 147 on the die. Means for releasably locking the platens to maintain the dies in closed position comprises a series of hook elements 125 mounted on the lower platen 116. Bracket elements 129 are secured to the upper die holder 88 and pusher elements 131 are secured to the moving platen 96. A recess 135 in the upper platen receives the slidably mounted die holder 88 which is guided on pins 136. The holder is urged upwardly into the recess by spring- loaded bolt elements 137 but this action is normally prevented by locking bars 142 and rollers 143 which are interpositioned between abutments 144 and 145 on the bracket and pusher elements 129 and 131 respectively. When the cylindrical portion 83 of the plunger 82 enters the upper end of the blank 10 the rollers 143 engage within curved slots 150 in the hook elements 125 and the rollers and bars are moved laterally away from the die holder and positioned to enter the slots in the pusher elements 131. Thus the locking between the holder 88 and the platen 96 is released when the dies are closed. Further downward movement of the platen forces the plunger downwardly but the upper die and holder remain stationary with the holder entering the recess 135 in the platen. The rollers 143 move under the shoulders 152 on the hook elements and lock the dies together. In operation the blank is filled with soapy water and the length of the hexagonal end 84 of the plunger is such to trap the desired quantity of water in the blank when the plunger enters into sealing contact with the neck of the blank and expansion of the bulbous part of the blank begins before the dies 80 and 81 engage (Fig. 20). When the dies meet a locating ring 154 on the upper die 81 encircles a cylindrical surface 155 on the lower die 80 and the lock between the upper die and platen is released to enable the platen and plunger to continue their downward movement to expand the bulbous portion to conform to the die cavity 156. The shape of the button top 112 is imparted to the lower wall of the workpiece. The plunger has an adjustable spring-loaded ball relief valve 157. When the platen is retracted upwardly the lock bars 142 and rollers 143 move inwardly due to the curved portions 173 on the pusher elements 131 and free of the abutments and the dies are free to separate. Towards the end of the upward movement of the platen the bumper element 108 strikes a stationary bar (not shown) and arrests the sleeve 94 which ejects the formed blank from the upper die. In a modification the lock means are dispensed with and the rubber ring 208 (Fig. 28) is mounted between the die holder 205 and a plate 209. The plunger 212 is fixed relatively to the upper platen 217 by a fixed plate 218 and an ejector sleeve 213 surrounds the plunger. The lower die 201 is bolted to the fixed platen 202. Specification 758,414 is referred to.