Patent GB-800598-A (GB)
Title: Improvements in producing embossed thermoplastic film
IPC: B29C59/04
Filed: 1955-12-09
Abstract: 800,598. Embossing-machines. UNITED PLASTICS INDUSTRIES, Inc. Dec. 9, 1955 [Jan. 4, 1955], No. 35494/55. Classes 100(1) and 100(2) Apparatus for embossing thermoplastic film, wherein suction is applied to the interior of a drum having a porous embossing surface to emboss a softened thermoplastic film adapted to be passed around the drum through an extended arc, comprises means effective to prevent loss of embossing suction, along marginal portions of that portion of said film embossed by said drum, due to leakage of air into said drum through the porous material forming said embossing surface when juxtaposed to said marginal portions of said film. The film 20, Fig. 1, passes from a supply roll 21 through tensioning devices 22, 29, round heating drums 30, 32, 33, 34, having inlets and outlets for steam, hot oil or water, round an embossing drum 35, stripping roller 36, drums 38, 39 supplied with cold water, coolant removal means 40 comprising slotted tubes 108, 109 and a perforated suction roller 112, and to a take-up roll 41. During embossing, the film is cooled by sprays 42. The embossing drum 35, Figs. 1 and 2, comprises a hollow shaft 45 carrying annular spiders 48 and end-plates 47, on which is mounted an embossing sleeve 50 having aligned rows of perforations 51. The sleeve is sealed to the plates 47 by inflatable tubular members 53. The sleeve 50 is coated or covered with porous material 56 forming the embossing surface, the edges of which are protected from air entering them by impervious annular bands 57 of permanently tacky tape applied to the sleeve. Suction is applied to the shaft 45, which is provided with perforations 55, and so to the entire surface of the sleeve 50. Two endless support belts 60 are mounted to pass over a series of pulleys 72 and a weighted tensioning pulley 72a which are mounted on guide members adjustable by means of a handle towards or away from each other. Each belt 60, Figs. 1 and 6, passes round the drum 35 near one end thereof, and has stitched or otherwise secured thereto at 62 a sealing belt 61 of rubber or other flexible, impervious material, which seals off the edge of the film 20 and the part of the material 56 between the film and the band 57, thereby preventing air entering the drum. In another form, Fig. 9, a cooling belt 90 is pre-cooled by water from a roller 94 and cooled by a drum 91 supplied with water, then passing over the drum 35 along a length greater than the width of the film. At each side, the belt 90 has secured thereto a sealing belt similar to the belts 61. In another form, the sleeve 50 is provided with a greater concentration of perforations in zones at each end, underlying the spaces between the edges of the film and the bands 57, so as to give uniform embossing pressure. Feeding webs. A thermoplastic film 20, Fig. 1, is fed from a supply roll 21 to an embossing drum 35, and passes over a tensioning device 22 comprising two rods 23, the angular disposition of which controls the tension. The web then passes over an expander 25, which is a roller having a plurality of elongated slats 29 mounted circumferentially with adjacent slats displaceable longitudinally to a limited degree with respect to each other. The film is thereby expanded laterally to remove wrinkles. Specification 800,599 is referred to.