| 摘要 |
1,250,940. Sizing extruded thermoplastics tubing. PHILIP MORRIS Inc. 20 June, 1969 [24 July, 1968], No. 31437/69. Heading B5A. [Also in Division F2] Accurate sizing of longitudinally ribbed thermoplastics tubing is effected by passing ribbed extrudate 32 from extruder. 20 into a liquid-coolant chamber 40, maintaining a pressure differential between the interior of the extrudate and the liquid such as to expand the extrudate, and confining the extrudate by a series of encircling plates 55-66. These plates each have similar central orifices shaped such that spaces 250, Fig. 6, adjacent the peaks 201 of the ribs are greater than the spaces 252 adjacent valleys 225, thereby ensuring that peaks 201 cool at a higher rate than the valleys. Further plates 110-112, Fig. 1, support the set tube. The pressure differential is obtained by applying a vacuum to chamber 40 by means of an aspirator 81 and pump 83 and venting the interior of the extrudate to atmosphere via conduit 25. Liquid is supplied to chamber 40 by a pump 88 via a spray ring 90, discharge from the ring causing turbulence in the neighbourhood of plates 55-59. Chamber 40 is sealed at each end by glands 51, liquid being pumped through conduits 53 therein to effect the seals and provide lubrication for the extrudate. Further cooling chambers may be interposed between chamber 40 and haul-off mechanism 70. Thermoplastics mentioned are polyolefins, styrenes and acetates, the preferred material being low density polyethylene to which the parameters of the description refer. The tubing is particularly intended for use in making cigarette filter tips. |
