Patent GB-759819-A (GB)
Title: Improvements in or relating to the manufacture of seamed tubes
IPC: B21C37/08
Filed: 1954-12-07
Abstract: 759,819. Automatic seam-straightening control systems. WESTERN ELECTRIC CO., Inc. Dec. 7, 1954 [Dec. 8, 1953], No. 35416/54. Class 38 (4). [Also in Group XXII] Apparatus for making seamed tubes includes a unit for bending a strip of material into a tube with a longitudinal seam of overlapping edges, means for advancing the strip of material through and from the bending unit in a given path, a sensing unit disposed in engagement with the tube and responsive to movement of the seam thereof out of parallel with the axis of the tube, and means responsive to the sensing unit to twist the tube in a direction to straighten the seam. A strip of metal with laterally extending corrugations is bent by a unit 10 about a cable core so that the edges overlap to form a longitudinal seam. The unit 10 has belts 14 which are driven in directions to assist in the advancement of the metal and core while they also assist in wrapping the metal about the core. The sheathed core passes through a unit 20 for soldering the overlapping edges of the sheath, the sheathed core being moved longitudinally by a capstan drive 16 towards a driven take-up reel 17 on which the sheathed core is distributed by means 18. To maintain the seam of the sheathed core substantially straight as it passes through the soldering unit 20 there are provided a sensing unit 22, a straightening unit 23 and a control unit 24. The sensing unit includes an arm 26 pivoted at 27 on a fixed support 28 so as to be movable into and out of operative position; when the arm is in the operative position, a cam 29 closes a switch 30 and wheels 31 are brought into engagement with the sheath on opposite sides of the seam. The wheels are supported by an element 32 rockably supported in a housing 33 at the forward end of the arm 26; the element 32 carries a cam 34 co-operating with normally open switches 37, 38. The sensing unit is more fully described in Specification 759,817, [Group XXII]. The straightening unit 23 includes two sets of rollers 40, 41 of resilient material mounted in holders 42, 43 actuable through racks and pinions driven by a fluid operable unit 45 which receives fluid under variable pressures from a line 46. A reversible motor drive 47 is operatively connected to a carriage 48 in which the rollers and their holders are movably mounted. The straightening unit is more fully described in Specification 759,818, [Group, XXII]. The control unit 24 includes a reversible motor 50 driving a shaft 54 through a speed-reducing unit 51 and clutch 53, 57. A spring 65 urges the clutch part 57 to disengaged position; it is moved to engaged position by a solenoid 68. A spring 74 serves to return the shaft 54 to its starting position when conditions permit. The shaft 54 carries cams 77, 78 which actuate switches 81, 82 depending on the direction of rotation of the shaft 54; the shaft 54 also carries a cam 79 which operates a valve 88 to increase the pressure of fluid passing through line 46 to the straightening unit 23. The shaft 54 also carries cams 90, 91 actuating switches 94, 95. When the sensing device 22 is moved to its operative position, the closure of switch 30 by cam 29 energizes solenoids 68, 97; solenoid 68 closes the clutch 53, 57 and solenoid 97 opens a valve 98 to allow fluid under a desired maximum pressure from a supply line 99 to pass into valve 88. The motor 47 is controlled by contacts 100, 102 of relays 101, 103 in circuit with switches 82, 81. The motor 50 is controlled by contacts 105, 107 of relays 106, 108; relay 106 is in circuit with switch 37, limit switch 94 and switch 30, while relay 108 is in circuit with switch 38, limit switch 95 and switch 30. In operation, if a condition exists tending to put a clockwise twist in the tube or sheathed core (looking in the direction of travel thereof) the consequent rocking of the sensing element 32 causes cam 34 to close 37 so energizing relay 106 to close contacts 105 so that motor 50 rotates shaft 54 counterclockwise (looking from its free end in Fig. 5). This causes cam 78 to close switch 82 so energizing relay 101 to close contacts 100 so that motor 47 rotates in counterclockwise direction (looking toward the entrance end of the straightening unit 23). Thus the straightening unit begins its rotation in a direction opposing the direction of deflection of the seam; the rollers 40, 41 of the straightening unit are forced into engagement with the tube or sheathed core under increasing pressure caused .by turning of cam 79 which gradually opens valve 88 through which fluid passes to line 46. This action continues until the seam has been straightened, whereupon the sensing unit returns to normal and cam 34 allows switch 37 to open. To control the maximum pressure applied to the rollers 40, 41 the cams 90, 91 on the shaft 54 operate singly, depending on the direction of rotation of the shaft, to open switch 94 or 95 so stopping the rotation of the motor 50. The clutch 53, 57 remains engaged due to continued energization of the solenoid 68, so that the shaft 54 remains in the position which it had reached when the motor 50 stopped, so that the straightening unit 23 continues to rotate. If the straightening unit has produced an overtwist, the sensing element 32 is rocked thereby to close switch 38 thus energizing relay 108 to close contacts 107 to cause motor 50 to drive the shaft 54 clockwise this reduces the pressure applied through the rollers to the tube or sheathed core until the sensing element 32 returns to normal.