Patent GB-1038787-A (GB)
Title: Photographic printing apparatus
IPC: G03B27/72
Filed: 1963-11-05
Abstract: 1,038,787. Photographic printing apparatus. AGFA A. G. Nov. 5, 1963 [Nov. 9, 1962], No. 43650/63. Heading G2A. A photographic printing apparatus has a negative mask carrier adapted for interchangeable masks of different sizes, and has means separately responsive to characteristic features of individual masks to complete different electrical circuits for the control of photoelectric exposure regulating device. Fig.1. (not shown) illustrates the general aspect of the apparatus as a whole, the invention being particularly concerned with the masking means housed in a box-shaped carrier 16, which is displaceably mounted on a bracket 19 for vertical movement relative to the table-top 1a. Above the illumination source is a carrier 37 having a circular glass plate 38 whose upper surface forms a support for the film 39 which is being copied. The film is held between plate 38 and an overlying mask plate 40, its movement being guided by downwardly extending pins 41 on the mask plate. This has a central aperture 40a defining the image size. On its upper side is mounted a holding ring 48 by means of four lugs 46 which overlap a rebated rim 48b of the ring 48. The ring has two upwardly extending conical catch-pins 49 which enter and lock into aperture 50a in spring-loaded slides 50 on the carrier 16. By pressing the slides 50 inwards, the pins 49 are released so that the mask and ring, as a single unit, can be readily detached and replaced by another one. Since the ring is held in fixed position, the mask plate 40 (and hence the film) can be rotated relative to it. In the position of Fig. 3, a catch pin 53 on lug 46 enters into holding engagement with an aperture in ring 48, but plate 40 can be rotated, in either direction as limited by a stop pin 52, which allows about 8 degrees clockwise rotation and 90 degrees counter-clockwise rotation. (The position of the plate may be viewed through a window 55 in front wall of the mask carrier, normally covered by a flap 56 which can be opened by a magnet and lever arrangement.) In a partitionedoff section 16b of the carrier are arranged a series of contacts K1-K12. K12 is a working spring contact, while each of the remaining eleven corresponds to a particular size of mask. Each contact carries a pin (S1-S11) normally which rests on the top of the ring 48. Each ring has a single aperture 48a in a different position, so that one of the pins S1- S11 can enter it and so close the corresponding contact, thus setting the exposure regulating device to the appropriate value. This is an arrangement of three photo-multipliers 62, 63, 64, for the three base colours, set in a light-canalising plate 17, as described in Specification 1, 038, 786. The bracket 19 which carries the housing 16 is fixed to a bush (Fig. 2) which slides inside another bush 24. A transverse pin 26 extends across bush 23, and another transverse pin 27 extends across bush 24, passing through slots at the lower end of bush 23. A weak tension spring 28 connects pins 26 and 27, and a stronger spring 29, inside the other, is suspended from pin 26 to hang just below pin 27, so that it engages only when bush 23 is raised with respect to bush 24. A plate 30 closes the lower end of bush 23, and a projection 31a on a lever 30, which may be operated by foot or knee on a push plate 36, can abut against this plate to push bush 23 upwards. A slight push acts against spring 28 alone, and raises the mask carrier sufficiently to free the film between plate 38 and plate 40, so that it can be advanced while still held between the guiding pins 41. A stronger push has to act against both springs, and is applied when the mask carrier has to be raised sufficiently to allow the mask to be removed altogether, and replaced by one of a different size. Fig. 9 (not shown) is a circuit diagram for automatic operation and control of the apparatus.