Patent GB-978002-A (GB)
Title: Apparatus for stretching thermo-plastic film
IPC: B29C55/16
Filed: 1962-08-03
Abstract: 978,002. Film-stretching apparatus. SHIN-MITSUBISHI JUKOGYO KABUSHIKI KAISHA. Aug. 3, 1962 [Aug. 6, 1961], No. 30079/62. Heading B5B. Apparatus for longitudinal and transverse stretching of films (Figs. 1, 2, 3) comprises chain wheels 12, 13 on either side of a film 1, connected by link members 50 having gripping devices 4 for the film. The film 1 travelling into the heating chamber 25 is nipped between nipping element 6 and base 5 when the lever 7, urged upwardly by cam 23, falls by its own weight on disengagement from the cam, and moves with the links 10, 10<SP>1</SP> and 11, 11<SP>1</SP> on the base frame 3 from chain wheel 13 to chain wheel 12. Transverse stretching is effected owing to the increasing distance between the left- and right-hand base frames 3 towards the outgoing end near the cooling roll 2, while longitudinal stretching is effected by the elongation of the distances between the axles 8, 8<SP>1</SP> of successive link members 50 as the sliding elements 16, 16<SP>1</SP> progress along the guide rails 17, 17<SP>1</SP>. At the outgoing end, film 1 is released from the gripping devices 4 when the levers 7 are lifted by the cam 24, and the link members 50 are returned from chain wheel 12 to chain wheel 13 while gradually being flared, and fully opened by the guide device 22. The rate of longitudinal stretching is adjusted by rotation of handle 20, which acts on screw rod 18 and bushes 19 to vary the angle of indication of the guide rails 17, 17<SP>1</SP> to each other, the relative speeds of chain wheels 12, 13 and the speed of rotation of cooling roll 2 being correspondingly adjusted. The rate of transverse stretching is adjusted by rotation of handle 21 which alters the angle of inclination of the left- and right-hand base frames to each other. In Fig. 4 a chain of vertical link members 50a replaces the horizontal link members 50. Film 1 is engaged by pins 37 connected through levers 26, 27 to guide elements 30 which slide in guide rail 31, and to connecting pins 32 and guide strips 33 in guide rails 34 Guide strips 33 are provided to react against the tension caused by the lateral stretch of the film 1. The distance between the guide rails 34 is decreasingly tapered by the travelling direction of link members 50a, increasing the distance between adjacent connecting pins 28 with the travel of the film, thus effecting longitudinal stretching. Lateral stretching is effected as in the previous apparatus by flaring the distance between the left- and righthand base frames 3. Fig. 5 illustrates a horizontal link assembly in which the film is held by pins 37 and a sliding element 35 engaged in a groove of a guide rail 36 is provided at the bottom of the axle 8 so that the weight of the link members and the lateral stretch force are taken up by guide rail 36. In Fig. 6, the pantograph or diamond shaped link members of the previously described apparatus are replaced by a series of single link members 60 connected by junctions 61, fitted with film gripping devices, to form a variable pitch chain loop as shown. Guide rails may be used as in Fig. 1, to effect the increase of pitch. Rotating levers 37, 38 engage the links on the return run of the loop so that successive links on release from the chain wheel 12 are alternately urged in opposite lateral directions. Specification 908,191 is referred to.