Patent GB-770428-A (GB)
Title: Apparatus for twisting tubing
IPC: B21D11/14
Filed: 1954-11-01
Abstract: 770,428. Twisting. WESTERN ELECTRIC CO., Inc. Nov. 1, 1954 [Nov. 4, 1953], No. 31500/54. Class 83 (4). [Also in Groups XXVIII and XL (b)] A twist is imparted to tubing of non-circular cross-section, particularly thin-walled rectangular tubing, e.g. an electromagnetic waveguide ; the geometrical centres of the opposite ends of the tubing may remain in alignment (" straight " twist) or may be relatively displaced laterally and/or vertically (" displaced " twist). The twisting apparatus may be an attachment to a tube-bending machine which comprises a base 12, a vertical shaft 13 rotatable by sprocket chain 15 and motor 16, a bending head 14 and a fluid-pressure cylinder 17 for reciprocably operating a mandrel shaft 18. The attachment comprises supporting members 20, 22, the member 22 being removably attached to the base 12, e.g. by bolts 21 and the member 20 supporting an apertured sleeve 23 in which is rotatably mounted a horizontal shaft 24 driven from the shaft 13 through bevel gears 19, 25. A mounting plate such as a circular disc 26 is attached, e.g. by saws 28 to the end of the shaft 24, the disc being provided with locating pins 27 ; a rotatable clamp 29 consists of a U-shaped portion 30 mounted, e.g. by welding, on the disc 26 and a yoke piece 32 removably attached to portion 30, e.g. by screws 33, the parts 30, 32 defining in their assembled position a passageway 34 of rectangular cross-section for gripping one end of a rectangular tube 35 to be twisted. Tubular slideways 36 secured to the supporting members 20, 22 extend longitudinally of the bending machine and terminate in a block 37 removably mounted on the base 12; a slide 38 longitudinally movable on the slideways comprises sections 39, 40 held in proper position on the slideways by bolts 42. The upper slide part 39 has rigidly mounted thereon a mounting block 43 on which an inverted U-shaped clamp 45 is removably secured by screws 44, the parts 43, 45 defining in their assembled position a passageway 46 of rectangular cross-section for gripping the other end of the rectangular tube 35 to be twisted. In order to effect a straight twist, the geometrical centres of the passageways 34, 46 must lie on the axis of the shaft 24. A mandrel 47 is mounted on the end of the mandrel shaft 18 and by operation of the cylinder 17 is positioned within the tube. The mandrel may be constructed as described in Specification 770,429. To effect a displaced twist in a piece of rectangular tubing, the clamp 45 is replaced by a modified clamp 48, Figs. 6, 9 and 10, comprising an upright portion 49 rigidly secured, e.g. by locating pins 50 and screws 52, to the mounting block 43 and having connected thereto by hinge pin 54 a complementary L-shaped portion 56. A bottom portion 57 is secured, by locating pins 58 and screws 59, to the mounting block 43; alternatively it may be integral with the portion 49. In the closed position, portions 49, 56, 57 define a rectangular passageway 60. Portion 49 has shoulder 62; portion 57 has shoulder 63; portion 56 has shoulders 64, 65; the shoulders project inwardly at right angles to the longitudinal axis of the passageway 60 for abutment against the extremity of a positioned tube. Portions 49, 57 have bevelled surfaces 66, 67 and portion 56 has bevelled surfaces 68, 69, portions of the bevelled surfaces being in juxtaposition when the clamp is closed so preventing relative movement of the portions of the clamp and also forming a flared guideway to aid in inserting the mandrel into the interior of the positioned tube. A locking handle is pivoted at 72 on the portion 56 and has a slot for engaging a locking pin 74 attached to the mounting block 43. The rotatable clamp 29 is replaced by a modified clamp 75, Fig. 5, comprising an L-shaped member 76 secured, by locating pins 77 and screws 78, to the disc 26 and having connected thereto by pivot pin 79 an L-shaped member 80. In the closed position, parts 76, 80 define a rectangular passageway 82 for gripping an end portion of the tube to be twisted. A locking arm 83 pivotally connected at 84 to member 80 has a slot engageable with a locking rod 86 attached to member 76. The clamp 48 is mounted upon the mounting block 43 in a position such that the horizontal and/or vertical centre lines of the closed clamp are offset from the axis of rotation of the horizontal shaft 24 by the desired amounts; the horizontal and vertical centre lines of the rotatable clamp 75 are likewise offset from the axis of rotation of the horizontal shaft 24.