Patent GB-942214-A (GB)
IPC: B60T17/10
Filed: 1961-03-06
Abstract: 942,214. Embossing; feeding webs. M. A. CHAVANNES, and A. W. FIELDING. March 6, 1961 [March 9, 1960], No. 7998/61. Headings B6B, B6C and B6J. [Also in Division B5] An embossing roller for embossing synthetic plastic film comprises a cylindrical shell containing a chamber through which a cooling fluid may be circulated, vacuum passages being provided in the roller and communicating with surface openings in the roller. The roller 15 is mounted on a rotatable hollow shaft 100, Fig. 10, to each end of which are connected conduits 102 for the introduction and removal of a cooling liquid e.g. water. Two hubs 106, 108 are non- rotatably mounted on the shaft and have radial flanges 107 in each of which is formed a plurality of radial passages 112 closed at their outer ends by plugs 114. A steel cylindrical shell 117 has a pair of rings 118 secured to its ends which rings are in turn mounted on the hubs 106, 108. The shell 117 is secured to the flanges 107 by bolts 120 and has a cylindrical covering 128 of heat-conducting material e.g. brass or aluminium, in which are formed longitudinal passages 129 connected to the radial passages 112 by lateral holes 130 in the flanges 107. The outer surface of the covering 128 is serrated and is connected to the passages 129 by series of ports 143 (not shown). The embossing surface comprises a cylindrical grating 140 having pockets 141, mounted on the serrated surface of the covering 128 and formed of a material having low heat-conductivity e.g. a silicone, a tetrafluoroethylene, a heat-resistant rubber, an epoxy resin, an alloy of tin and bismuth. Manifolds 131, 132 are mounted on the hubs 106, 108 and are connected by conduits 138 to a source of suction, the manifolds remaining stationary while the hubs rotate in them. Each manifold has an arcuate slot 137 on its inner face with which the conduit 138 communicates and which registers with a number of holes 113 in the flanges 107 so as to connect the radial passages 112 to the source of suction. The angular extent of the slots 137, see Fig. 11, is such that suction is applied to the face of the roller only over that portion thereof which is in contact with the material to be embossed, suction being cut off from the corresponding part of the roller surface as soon as a hole 113 moves out of the range of the arcuate slot 137. Baffles 126, 127 in the shaft 100 allow cooling liquid to pass through holes 124 in the shaft, into a chamber 121 in the roller, the size of which chamber is reduced by a cylindrical structure 122 secured to the shaft, and back into the shaft through further holes 125. The serrations in the covering 128 may be replaced by a woven metal screen overlying the surface of the covering 128 or by channels on the inner face of the grating 140 connecting the pockets 141 thereof. The roller is used in a device shown in Fig. 1 for producing cushioning material having the cross-section shown in Fig. 8. A web 11 of synthetic plastic film, which may be low density polyethylene 0.001 to 0.025 inch thick, is fed from a roll 16 round heating rollers 18, 19, an expander roller 21 and further heating rollers 22, 23 to the surface of the embossing roller 15. As the web reaches the embossing roller its temperature approaches the melting point of the material and portions of the web are sucked into the pockets 141 so as to form embossments 12, Fig. 8. A second web 13 of similar material is fed from a roll 24, heated in like fashion to the web 11 and is pressed against the unembossed portions of the web 11 while the latter is still on the roller 15 by a roller 31 so that the two webs fuse together at these points and form hermetically sealed cells 14. The combined webs travel round the embossing roller 15 until they are sufficiently cooled and are then stripped off round a roller 32. If rapid cooling of the embossments 12 is desired the grating 140 may be made of a material having a higher heat conductivity than the materials previously mentioned, in which case the outer surface of the grating is coated with a heat-insulating layer e.g. of epoxy or silicone resin, so as to prevent too-rapid cooling of the unembossed portions of the film. This insulating layer may be either rigid or resilient. In another form a layer of heat conducting material is applied on top of the heat-insulating layer and is heated before the application of the web 11 to the embossing roller so as to help keep the unembossed portions of the web at a high temperature until the two webs have been joined. Cooling means may act on the outside of the combined webs as they travel round the roller 15, such means comprising either sprays of cooling liquid or an endless belt of stainless steel which travels round cooling rollers. Heat may be imparted to the webs 11, 13 after they have been brought into contact by means of a heated endless belt of a silicone-coated fabric, silicone film, or tetrafluoroethylene film. In a modification, Fig. 3 (not shown), a third web is fused to that surface of the embossed web which is not covered by web 13, thus providing cavities on both sides of web 11. In a further modification, Fig. 6 (not shown), the evacuated surface of the embossing roller cooperates with a resilient pressure roll so that the embossing is effected both by suction and mechanical pressure. Specification 942,215 is referred to. Feeding webs.-The web 11 may be guided tangentially up to the roller 15 between two manifolds 63, 64, Fig. 4, which direct blasts of heated air through nozzles 631, 64<SP>1</SP> and thereby support the web 11 between them and simultaneously heat it. Reference has been directed by the Comptroller to Specification 725,436.