Patent GB-1053763-A (GB)
IPC: D02J1/22
Abstract: 1,053,763. Hot-stretching filaments. DUNLOP RUBBER CO. Ltd. Feb. 24, 1964 [March 6, 1963], No. 8849/63. Heading B5B. [Also in Division D1] Apparatus for continuously hot-stretching a length of thermoplastic, e.g. nylon monofilament, fibre, yarn or cord comprises a framework, a vessel for containing a bed of solid particles, means for connecting the bed to a pressurized fluid for fluidizing the bed, means for heating the bed, means for supporting a continuous length of thermoplastic material during its passage through the bed, said means having separate peripheral portions rotatable at different speeds, and at least one guide member spaced-apart from the peripheral portions and having a peripheral surface for supporting the length of thermoplastic material which extends from the peripheral portions to the guide member. The apparatus also comprises tensioning means for the length of material to cause it to be stretched as it passes over the peripheral portions of the supporting means. In one embodiment (Fig. 1) a vessel 2 containing solid particles, e.g. Ballotini, fluidized by pressurized fluid source connected at 5, is heated by immersion heaters 12, 13. The supporting means for nylon filament or cord being hot stretched comprises a pulley 15 (Fig. 2, not shown) having coaxial portions 16, 19, 20 non- rotatable relative to each other each consisting of one or more annular grooves, and also a guide pulley 24, consisting of a cylinder 25 (Figs. 3 and 4, not shown) having flanged ends 26 between which extend carbide steel shafts 30, upon which the filament or cord is supported. The pulley 24 is freely rotatable about shaft 27 through which compressed air is supplied to the cage construction by pipe 32. The filament or cord is passed from driven feed rolls 35, round the supporting pulleys within the fluidized solid bed, and thence to driven take-up rolls 36 rotating at higher peripheral speed. The fluidized solid bed in vessel 2 is raised and lowered into and out of an operative position surrounding the supporting pulleys 15 and 24, by means of a pneumatic cylinder and piston assembly 7, 8. The vessel is provided with rollers 9 which run along vertical members 10 of framework 11. In operation, filament or cord from spool 44 is pretensioned at 43, hot stretched by passage over driven rolls 35, 36 and pulleys 15, 24 in the fluidized solid bed, and wound up at 46. A temperature control device (not shown) actuates electrical circuitry to cause the cylinder assembly 8 to move vessel 2 into the inoperative position when the temperature of the solid bed falls below a given point. The control device also operates heaters 12, 13, and ensures that when the vessel 2 is in the inoperative position, winding on of the filament or cord is stopped. The stretching operation may also be stopped, and vessel 2 lowered to the inoperative position by operation of switches 52 which detect breaks in the filament or cord. The part of the frame 29 whereon the pulleys are mounted is heated by coils 34 to prevent heat loss from the solid bed when raised to surround the pulleys. The pressurized air inside guide pulley 24 prevents ingress of dust thereto. In further embodiments (not shown), guide pulley 24 may be formed of three parallel plain or grooved ceramic or steel pins, or a carbide steel cylinder, or may comprise a plurality of coaxial, individually rotatable pulleys. Also, pulley 15 may comprise a plurality of coaxial pulleys of the same diameter freely rotatable relative to each other. Instead of using a pneumatic cylinder and piston, the vessel 2 containing the fluidized solid bed may be suspended over pulleys and partially balanced by counterweights. The vessel is maintained in operative position by clamping members operating on these weights. Release of these clamps, e.g. by operation of a temperature control device, causes the vessel 2 to descend under its own weight to the inoperative position.