Patent GB-978028-A (GB)
Title: Machines for obtaining a light-transmitting image in an opaque pressure-clearable film
IPC: G03F1/92
Filed: 1963-04-04
Abstract: 978,028. Printing apparatus. E. I. DU PONT DE NEMOURS & CO. April 4, 1963 [April 24, 1962; Feb. 5, 1963], No. 13438/63. Heading B6C. A machine for obtaining a light-transmitting image in an opaque pressure-clearable film comprises a bedplate 10, Fig. 1, adapted to support a relief printing forme 11 and an opaque, pressure-clearable film 12 in contact with the relief face, a transverse frame 17 mounted above and suspended across the bedplate, a double row of spring fingers 24 held by the frame and adapted to contact the upper surface of the film and press the latter against the relief surface of the forme and guide rails 14 slidably engaging the endplates 18 of the frame 17 for allowing relative motion between the bedplate and frame to subject the film to a stroking pressure from said fingers during the motion. The frame may be manually or mechanically reciprocated along the guide rails 14 adjustable collars 15 being secured on both rails to limit such reciprocation. A vacuum frame 50 or adhesive tape may be used to secure the film 12 over the forme 11. The fingers 24 are adjustably mounted on a supporting block 23 each end of which is fitted into a groove 22 in a bearing support 21, these supports being slidably mounted on rails 20 carried by the end plates 18. Through a collar 32 on each rail 20 and a spring 31 located between it and the adjacent support 21 the support block 23 and therefore the fingers 24 are resiliently urged to the left-hand side of the machine as viewed in Fig. 1. This side of the machine houses a ratchet and pawl mechanism whereby at the end of each stroke of the frame 17 the support block 23 and fingers 24 are moved fractionally across the bedplate towards the other side of the machine. This fractional movement is effected by cams 45 located on the headplate actuating a roller follower 44 carried by the extension 42 of a cam arm 37 which is pivotally mounted on a shaft mounting a ratchet wheel 34 located near one end of the frame 17 between an endplate 18 and a bearing support 21. The inner end of the ratchet wheel shaft is in threadable engagement with the bearing support 21. The cam arm 37 mounts a spring- loaded pawl 38 and on actuation of the roller follower 44 the pawl 38 engages and moves the wheel 34 through one tooth to thereby move the associated bearing support fractionally. The outer end of the ratchet wheel shaft mounts a handle 35 through which the position of the ratchet wheel may be initially set. If the ratchet wheel is to be actuated once per double stroke of the frame 17 then one of the cams 45 is removed. In another embodiment the frame 71, Figs. 2, 4, and associated support member 72, spring fingers 77, rails 68, supports 69, end plates 60<SP>1</SP> and ratchet mechanism 85, 86, 87, 88 are securely attached to the bedplate 60 whilst a frame 62 mounting the relief forme and film is reciprocable by hand, a handle 95 being provided for this purpose. The frame 62 runs on rollers 65 and is located relative to the bedplate 60 through a V-ridge and groove arrangement. In this embodiment the support 71 carrying the spring-fingers 77 is vertically adjustable relative to the bedplate through two screw and collar devices 74 by which the support is connected to the frame 71. In yet a further embodiment-see Figs. 9-14 (not shown)-a machine of the reciprocable frame type is provided in which the support member 23 is rockable about an axis transverse of the bedplate. In this construction the support member 23 is pivotally mounted between the supports 21 and cam and locking means are provided such that the support member 23, and hence the spring fingers, may be located within limits in any desired angular position prior to being moved over the superimposed film and forme. Figs. 7 and 8 show two forms of spring fingers the tension in the former being adjustable by vertical movement of side plates 27 whilst the tension in the latter is adjustable by the placing of shims between a mounting plate 25 and the lower surface of the support member 23. Specification 919,671 is referred to.