Patent GB-611065-A (GB)
Title: Improvements in or relating to electron discharge tube high frequency amplifiers andmodulating circuits therefor
IPC: H03C1/22
Filed: 1945-12-05
Abstract: 611,065. Photographic contact-printing apparatus. MILES AIRCRAFT, Ltd., and ROBERTS, G. Sept. 29, 1945, No. 25324. [Class 98 (ii)] Photographic contact-printing apparatus of the kind described in Specification 554,465 has (a) the thrust connection constituted by a telescopic extensible thrust link connected to the operating member and to the moving platen and capable of shortening to a predetermined length upon the operating member being moved upwards by the resilient means, thereby to thrust the moving platen upwards, and of extending freely upon downward movement of the operating member, and (b) the means urging the teeth out of engagement with the pawl constituted by spring means connecting the two parts of the elbow member to bend these parts in the disengaging direction, but yieldable to permit the elbow member straightening, upon a downward pull being applied to the lower part of the elbow member, sufficient to carry the teeth into engagement with the pawl. As shown, the apparatus comprises fixed and movable glass platens 3, 5 having therebetween a central plate fitted on either side with rubber pads 7, 8 such that by operating clasps 41, the assembly 6, 7, 8 may be secured either against the upper platen 5 for contact-printing through platen 3 by an illuminant contained within the box structure 2, or against the fixed platen 3 for reflex printing through the movable platen 5 by means of an exterior light source 9. The platen 5 is carried by a frame 4 which is vertically slidable within the cabinet 1 by means of rollers 13 and guide bars 12 and is pivoted at 18 to the telescopic extensible link 14 connected at its lower end to a lever 15 operated by a footplate 16 such that when the latter is depressed the frame 4 carrying the movable platen 5 falls under its own weight to secure the work between the rubber pads and either platen as desired. Final clamping of the work is accomplished by further depressing the footplate 16 which causes straps 34 attached thereto to exert a pull on a vertically guided cross-member 31, thereby depressing a yoke 30 to the ends of which are pivoted rods 28 comprising the lower parts of elbow members 22, the downward pull thus being transmitted to the upper parts 23 of elbow members 22 which are provided with ratchet teeth 24 engageable with pawl plates 27 attached to the frame 4, while a spring-urged catch-plate 35 co-operates with a pin 38, attached to the foot-lever 15, in order to lock the frame 4 and the members coacting therewith in the clamped position. The catch-plate 35 may be released by depressing a rod 39 which extends through the top of the cabinet and has attached thereto a knob 40. On being released, the foot-lever 15 is lifted to its uppermost position by an elastic cord 20, while the elbow members 22 are caused to disengage from the pawl plates 27 by the action of the leaf springs 28A which bear against the lower edges of the ratchet members 23. The printing apparatus and its enclosing cabinet 1 may be built into a larger cabinet 2A fitted with a box 46 for housing a film-spool, and provided with an inspection panel 50 which is illuminated from underneath by a " safe " lamp. A take-up spool 52 may be detachably secured to the side of the cabinet which is provided with cupboard space for storing the various accessories.