Patent GB-843506-A (GB)
Title: Improvements relating to the manufacture of corrugated metal tubes
Inventor: LOVE JOHN
IPC: B21D15/06
Filed: 1957-09-26
Abstract: 843,506. Making corrugated tubes. K.A.C. Ltd. Dec. 11, 1958 [Sept. 26, 1957; March 19, 1958], Nos. 30276/57 and 8874/58. Classes 83 (2) and 83 (4). A method of manufacturing corrugated metal tubes comprises applying fluid pressure internally of a length of tubing to be corrugated thereby elastically to expand the tubing radially into contact with a sleeve which surrounds part of such length to provide frictional opposition to relative axial movement between the sleeve and the tubing, and axially upsetting a free tubing portion extending from said sleeve thereby to form a corrugation having a peripheral length substantially equal to the length of such tubing portion prior to the forming thereof. Apparatus for carrying out the method comprises a sleeve 1 for slidably receiving a tube 3 accommodated in a pressure vessel 2. The bore of the sleeve is provided with rubber rings 6 to enhance the grip of the sleeve on the tube 3 when the latter is expanded by fluid pressure. A split ring-die 9 is carried by a pair of half sleeves 11a and 11b (not shown) provided internally with hard rubber corrugations 12 for supporting the formed corrugations in the tube 3. A second pressure vessel 15 communicates with a fluidpressure reservoir 16 and is provided with a valved bleed port 18. The pressure vessels 2 and 15 are reciprocated mechanically or hydraulically and the die 9, together with the half-sleeves 11a and 11b, is opened and closed by an hydraulic ram 21. In operation, the tube 3 is inserted in the sleeve so that only a short length of tube extends from the sleeve and the die parts 9 are brought together about the extending portion. The pressure vessel 15 is advanced into sealing contact with the die 9 and pressure fluid is allowed to fill the pressurevessels so that the tube 3 is expanded into tight engagement with the sleeve 1. The pressure vessel 2 is now advanced axially towards the die 9 to form a corrugation 10. After the corrugating the fluid pressure is reduced by opening valve 17 and the pressure vessel 2 is returned to its initial position. Simultaneously the pressure vessel 15 is withdrawn and the die 9 opened and the pressure vessel 2 advanced by one corrugation towards the die to advance the tubing 3 by a similar distance whereupon the die is closed to anchor the tubing whilst the pressure vessel 2 is withdrawn to its starting position for forming another corrugation (Fig. 8). To avoid loss of pressure fluid the pressure vessel 15 and the die parts 9 at least are immersed in a tank of pressure fluid. The leading end of the tube is surrounded by a collet 22 having a corrugated external configuration to engage with the rubber support corrugations of the die 9. The leading end is internally supported by a plug 22a. In a modification the pressure vessel 2 is omitted and the sleeve 1 extended to surround the tube 3 as in Fig. 8. In another modification the pressure vessel 15 is also omitted and the support corrugations of the die 9 are increased in number to support the whole of the corrugated tube against expansion under internal fluid pressure (Fig. 9). Fluid pressure is introduced into one end of the tube 3 through a flexible conduit 33 and a plug 34 seals the opposite end of the tube.