Patent GB-802473-A (GB)
Title: Photographic printing frame and apparatus
IPC: G03B27/20
Filed: 1955-01-20
Abstract: 802,473. Photographic contact printing frame and apparatus embodying this. WOLF, J. M. E. Jan. 20, 1955 [Jan. 21, 1954], No. 1783/55. Class 98(2) The frame comprises two superposed and separable subframes adapted to form an airtight compartment between them, the lower subframe being closed by a glass plate and the upper by a flexible apron, each subframe comprising independent suction connections so that introduction of a screen between them forms two subcompartments in which any desired degree of vacuum may be established. In an example describing the apparatus as a whole, a box 1, Fig. 1, has an upper part closed off by a frame 10 and lower part provided with various sources of light on a panel 30 for which a control board 70 (detailed in Fig. 4, not shown) is provided. A gate 100 gives access to the lower part of the box 1. The frame 10 comprises the individual subframe 10<SP>1</SP> and 10<SP>2</SP>, doubly hinged to permit raising of both together or raising of 10<SP>1</SP> followed by 10<SP>2</SP>. A diffuser glass 92 may be inserted between the light sources and the frame 10. Rubber apron 13 (Fig. 9) having suction valve 16 closes upper subframe 10<SP>1</SP> and glass plate 17 having suction orifice 18 and surrounded by a rubber frame 19 closes lower sub-frame 10<SP>2</SP>, so that introduction of screen 7 forms sub-compartments 110, 112, and mechanism 50 is described (Fig. 2 not shown) to diminish the pressure of subcompartment 110 to 15 cm. mercury and subcompartment 112 to 30 cm. mercury. In use subframe 10<SP>1</SP> is swung upwards, a negative 6 is placed on the glass 17, screen 7 and then sensitive surface 5 are placed on top, subframe 10<SP>1</SP> is closed, suction is applied and exposure effected, after which suction to the lower subcompartment 112 is relieved and subframe 10<SP>1</SP> and exposure through the screen 7 is constantly pressed in contact with sensitive surface 5, enabling removal of negative 6 from glass 17, reclosing of subframe 10 1  and exposure through the screen alone with maintenance of register. The apparatus may be used without the screen 7 in position to form the two subcompartments, in which case a stopper is provided for orifice 18 in glass 17 and suction effected through valve 16 only. Two devices may be present for locating screen angles in multicolour work, the first (Fig. 6 not shown) consisting of a system of wires attached along one edge of the subframe 10<SP>2</SP> each arranged to be stretched across to the opposite edge and there retained in a recess, in alignment at a screen angle, and the second consisting of a projector 36 to produce a corresponding aerial image of lines at the level of the glass 17, each device being used in conjunction with register marks on the negative. The sources of light on the panel 30 include a fluorescent tube and a series of opal tungsten lamps for diffuse lighting, and also a point source tungsten lamp provided with rotatable colour filters operable from the board 70. Various safety lights are provided also. Timing mechanisms for exposures are described as mechanical, electrical or electronic.