GB1133338A - Plastics films perforation - Google Patents

Abstract

1,133,338. Perforating film; perforating thermoplastic sheets; laminates. BRITISH VISQUEEN Ltd. 1 Aug., 1966 [24 Aug., 1965], No. 36259/65. Headings B4B, B5A and B5N. A method of perforating two adjacent layers of plastics film by piercing the superimposed layers with at least one instrument, the tip of which passes through both layers of film, is characterized in that the instrument is caused to penetrate the film layers in an angular direction such that the angle between the path of the tip of the instrument and the interface between the two film layers does not exceed 80 degrees, and in that the film is held stationary while the instrument is inserted and withdrawn. Preferably, the angle is not less than 20 degrees. The film may be of polyolefines especially polythene and polypropylene, or of polyvinyl chloride. Apparatus for carrying out the method comprises a bar 2 provided with razor teeth across its whole width, the ends of the bar being connected with links 5, one of which is connected to an air cylinder 4, operation of which causes the-bar to move angularly parallel to itself so that the tips of the teeth penetrate the film 3 at an angle of 60 degrees to the film interface, movement of the bar being arrested by a stop 6. The teeth in the middle of the bar may be arranged to provide larger slits than those at the edges. In a modification, a perforator needle (7, Fig. 2) is operated by an air cylinder (9) so that the needle is driven through a flattened plastics sack (8) at an angle of 35 degrees to the interface between the walls of the sack.