Patent GB-527094-A (GB)
Title: Improvements in the manufacture of multiply metal tubing
IPC: B21C37/09
Filed: 1939-03-31
Abstract: 527,094. Making multiply tubes. GENERAL MOTORS CORPORATION. March 31, 1939, No. 10096. Convention date, April 2, 1938. [Classes 83 (ii) and 83 (iv)] In an apparatus for making multiply tubes, particularly tubes for radio-aerials on the roof of motor cars, means are provided for forming longitudinally moving strip stock into multiply tube in combination with a swager comprising a rotary head on a tubular shaft through which the formed tube passes the head carrying radially movable swaging-dies and hammers, the hammers engaging rollers in a stationary cage, and the rollers also engaging an outerrace member which is rotated in the opposite direction to the shaft so that the linear speed at which the hammer strikes a roller equals the linear speed of the roller-engaging surface of the outer rase. Two steel strips P1, P2 with scarfed edges are fed from supply reels first through a degreaser containing a cleaning vapour and then between a pair of wicks 104, Fig. 2A, dipping in vessels containing a light oil, the wicks being pressed against the strips by pads 106, 107 carried by spring-pressed plungers 110, 111 which are prevented from rotating by pins 118, 119 engaging slots in the plunger guides. The vessels may be sprung out of the way in pivots 102a, 103a, while threading in new stock. The inner surface of the inner ply and the outer surface of the outer ply are thus provided. with oil for lubricating the forming apparatus. Carburization of the surfaces due to oil vaporized when the parts are subsequently brazed in a heating furnace is prevented by the oil inside the tube combining with oxygen of the air and by the provision of a reducing atmosphere in the furnace communicating with the outside of the tube. After being oiled the strips are passed at an acute angle to each other through grooves 211, 212 in the inner faces of guides A1, A2 between which is mounted an intermediate plate A3 secured to screwadjusted base plates 201, 202. The grooves are arranged so that the strips partially overlap each other, the plates A1, A2 being vertically adjusted by wedges 205, 206, Fig. 3C, and held in adjusted position by screws 213, 214 tapped into the base plates and also by bolts 215. The wedges are held in position by washers 218 and screws 217. The strips then pass through a series of pairs of chromium-plated feed and forming rolls separated by chromium-plated guides. The rolls bend the strips successively into the forms shown in Figs. 8, 9, 16, 17, 18, 23, 24 and 29. The guides are similarly shaped so as to prevent lateral displacement of the plies. The guide immediately before the roll pass which bends the strips to the form shown in Fig. 18 carries a mandrel which extends through all the subsequent roll passes and through the dies which compact the plies. The strips in the form shown in Fig. 29 then pass through a further pair of rolls to bend the strips into the form shown in Fig. 30 and then through two further pairs of rolls, the first of which being the blank to the form shown in Fig. 31 and the second of which assists in pulling the work through the machine. Seams are between 90 degrees and 180 degrees apart. The tube so formed then passes through a rotary swaging apparatus to compact the plies on the mandrel into the form shown in Fig. 32. The tube subsequently passes through the brazing furnace which contains a bath of molten brazing material such as copper at a temperature of 2100‹ F. so as to braze the seams and plies. Excess of copper is wiped off the tube by a gas wiper and the tube is cooled first in a waterjacketed pipe containing a non-oxidizing atmosphere and then by direct contact with water and is then rolled up. The swaging apparatus consists of a pair of dies 161, each separated by a shim 160a from a hammer 160, the parts being movable radially in a guide lined with hard metal in a head 150 secured on a hollow shaft 136 which is rotated by a belt and pulley 191. The hammers are provided with lateral pins 162 engaging slots 163, 165 respectively in a plate 164 secured to the head and in the liner 156 secured to the bottom of the guide. The shaft 136 is provided with a removable liner 193 to suit the diameter of the tube and is carried by a nut 138. Escape of lubricant from the bearings is prevented at one end by a grease sealing ring 142 and at the other end by a felt washer 143 held between a metal washer 145 and a flange 144 on the head. The hammers are moved outwardly by centrifugal force when the shaft is rotated. The head is surrounded by a fixed cage 172 provided with pockets to receive rollers 170 engaged by the hammers during rotation of the shaft so as to apply pressure to the dies. The cage is provided with a cover plate 177. Surrounding the rollers is a ring 180, driven by a belt in the opposite direction to the shaft and at such a rate that the peripheral speed at the interior of the ring is equal to the peripheral speed of the hammers when striking the rollers. The rollers are thus prevented from binding in their pockets and are always free to rotate.