Patent GB-222872-A (GB)
Title: Improvements in or relating to photomechanical processes and apparatus for carrying out the improved processes
IPC: G03F5/04
Filed: 1924-10-01
Abstract: 222,872. Precedes Bassani. Oct. 4, 1923, [Convention date]. Photo-mechanical printing-surfaces.-A photographic image for photo-mechanical use is produced in a camera by exposing a sensitive surface behind a ruled screen capable of limited disnlacement, by means operated outside the camera, in its own plane either in various directions, or in a single direction followed bv a displacement in a circular path without rotation. The effect obtained is a spreading of the light-affected elements of the sensitive surface. Fig. 3 shows the result of a first exposure yielding the black squares, and a second exposure after the screen has been slightly displaced in the direction f, yielding the shaded bands b, c. A displacement of the screen in a circular path without rotation during the second exposure would yield bands on all sides of the squares. More than two displacements followed by partial exposures may be made. Colour screens may be used, and changed for each partial exposure, to produce on a panchromatic plate monochrome tones consonant with the colours of the object. The ruled screen is supported on a reducing pantograph, the control point of which may be adjustably displaced in any direction, or caused to move in a circular path of adjustable diameter. The control point also actuates an amplifying pantograph carrying a diaphragm, of the same form as the elements of the ruled screen, which, in conjunction with a fixed sighting element, serves to indicate the displacement of the screen. In the apparatus shown, the screen 5, which consists of a single engraved glass plate having a protective coating of varnish, is supported in a carnera in a holder 8 in front of a sensitive surface. The holder is guided in a vertical plane by a frame 10 which also serves for adjusting the holder towards or away from the sensitive surface. The holder has two forks 35, each of which carries rollers 36 resting upon an extension 34 of the lowermost pivot of a reducing pantograph 27 - - 32, the middle pivot 33 of which is stationary, and the uppermost pivot 15 of which rests in a bearing 16 which is adjustable by a screw 17 in a diametral groove of a disc 12 mounted centrally on a shaft on the fixed frame 14. The discs 12 carry scales 20 and pointers 21 to permit them to be set at an angle corresponding to the direction in which it is desired that the screen 5 shall move. Displacement is then communicated to the screen by operating the screws 17 to displace the journals 16 in their grooves. To produce motion of the screen 5 in a circular path without rotation, the journals 16 are displaced in their grooves by an amount corresponding to the radius of the desired path, and the discs 12, upon which the journals 16 are now eccentrically located, are rotated by worm gearing 23, 24 from a shaft 25 manually or poweroperated. The displacements of the journals 16 are indicated by amplifying pantographs 40 - - 45 of which the middle pivots 46 are stationary Upon the outer pivot of each pantograph is suspended a strap 51 fast with a ring 50 enclosing a rotatable disc 49 carrying a diaphragm 48 of the same form as the elements of the ruled screen 5. Behind the diaphragm is a similar stationary sighting element 52, which raay be set at any angle by operating nuts 54, 55. When the elements 48, 52 have been set at an angle corresponding to the desired movement of the screen 5, a pointer 53 on the diaphragm 48 indicates to an enlarged scale the magnitude of the displacernent of the journal 16 in its groove in the disc 12. Specification 146,143 is referred to.