Patent GB-741182-A (GB)
Title: Improvements in the application of sheaths to electric cables
Inventor: GRIEVE GEORGE THOMAS WILSON
IPC: H01B13/00
Filed: 1953-04-16
Abstract: 741,182. Making cables. BRITISH INSULATED CALLENDER'S CABLES, Ltd. April 15, 1954 [April 16, 1953], No. 10478/53. Class 36. [Also in Group XXX] In an apparatus for pulling a tube 7 which is to form a cable sheath from a coil over a tow-line 21 attached to a piston 25, and laying the tube out in a straight line with the tow-line inside it, a device 27 (Figs. 2 and 3) adapted to grip an end of the tube and means to close that end in a substantially air-tight manner are carried by a car 30 having means for propelling it away from the coil, and a source of compressed air is supplied which is adapted to be connected to that end of the tube 7. The car 30 preferably travels on a pair of rails 1 between which is a runway 3 consisting of a number of freely rotatable grooved rollers, and may be drawn to the rear end of the apparatus by a hawser 23 and back to the front end by a hawser 12. The tube 7 is drawn from its coil over a capstan, through a straightening device and on to the front of the runway, and its leading end is attached to the underside of the car by the device 27, the tow-line having been previously laid out on the runway and the piston 25 inserted in the leading end of the tube. The gripping device 27 comprises two cooperating semi-circular jaws 31, each of which is connected to one end of a bell-crank lever 34, the other end of which is pivotally connected to a lever 38. Each bell-crank lever 34 is rigidly connected to a vertical spindle 39 and levers 38 are pivotally connected to a draw-bar 40 to which the hawser 23 may be attached. Each vertical spindle 39 is rigidly connected to a transverse arm 42 pivoted to a lever 43, the two levers 43 being pivoted together and to a coupling member 46 to which the hawser 12 may be attached. According to one arrangement, when tension is applied to the hawser 23 the levers 38 and 34 operate to bring the jaws 31 into the gripping position and when this tension is released and tension applied to the hawser 12, the levers 43 and 34 operate to separate the jaws. Each jaw is supported on the underside of the car by a T-shaped lug 52 supported by guide-bars 53 which permit the movement of the jaws. A'metal ring 54 and rubber sealing ring 55 are placed on the leading end of the tube 7, which is then belled out. The ring 54 has two directly opposite ports 57 which open into a circumferential groove 58. Each of the jaws 31 has an inlet port (not shown) through which compressed air is supplied. When in the gripping position the jaws 31 engage the outer surface of the ring 54 and hold it on the leading end of the tube. The outer end of the gripping device 27 is closed with a rubber gland 65 which is in two halves attached respectively to each of the jaws 31. The gland 65 is apertured for the passage of tow-line 21. As the car 30 is drawn to the back of the runway, compressed air is admitted to the interior of the device 27 to hold the piston 25 stationary, thus drawing the tube 7 over the tow-line 21. The rear end of the tow-line is then released and the piston 25 is forced out of the end of tube 7 by the compressed air and removed from the tow-line. A cable core is then attached to this end of the tow-line and drawn through the tube, after which the tube and core are drawn through a sinking die to cause the tube to fit tightly on the core. Two runways 3 may be provided side-by-side so that a second length of tube may be drawn out over the tow-line while the first cable length is being completed, and in this case the car 30 is constructed so that the gripping device 27 can be moved transversely thereof to bring it over either runway (Fig. 6, not shown). The draw-bar 40 may be locked after it has brought the jaws 31 into the gripping position by a compressed air device (Fig. 10). Compressed air is admitted to the lower end of a cylinder 114 to force piston 115 upwards against the action of a tension spring 116 to cause locking pin 117 to project through a hole 118 in a horizontal bar 119 passing through the cylinder, and enter a recess 120 in the head 121 of cylinder 114. One end of bar 119 is connected to hawser 23 and the other end to draw-bar 40 (Fig. 11, not shown). When the compressed air supply to the cylinder is cut off, the pin 117 is withdrawn under the action of spring 116 to release the draw-bar 40. In an alternative arrangement the jaws 31 may be operated by compressed air which is fed into cylinder 93 (Fig. 9). The cylinder has a rear wall 96 provided with a gland 97 through which a piston-rod 95 passes, the piston-rod being connected to the draw-bar 40, and a front wall 98 having an aperture 100 for the escape of air in front of piston 94. When compressed air is introduced behind the piston 94 the jaws 31 are brought together and when the pressure is released they are opened by tension-springs 101 connected to the arms 42 and to lugs 102 on car 30. The compressors for the air may be carried by the car 30 or may be stationary at the front end of the runway, a flexible hose then being provided which is automatically paid out and taken up on a drum carried by the car as the latter travels backward and forward (see Group XXX). The car 30 may be driven along the rails by a reversible geared reduction motor 171 (Fig. 14) mounted on platform 172 carrying pulleys 182, 184, each having a number of circumferential grooves. A hawser 185 passes from one pulley to the other a number of times and the pulley 182 is driven through chain-andsprocket devices from motor 171, causing the platform 172 to move relative to the car 30 until it meets either of the two transverse members 176, when the platform and the car travel together. During the relative movement between the platform and the car the jaws 31 are opened and closed according to the direction of the movement.