Patent GB-733788-A (GB)
Title: Improvements in or relating to photographic type-composing machines
IPC: B41B17/06
Filed: 1952-06-09
Abstract: 733,788. Photographic type - composing. HIGONNET, R. A. E., and MOYROUD, L. M. June 9, 1953 [June 9, 1952], No. 14518/52. Class 98 (1). In a photographic type-composing machine, a character-projection unit comprises a matrix member bearing a fount of master characters arranged in a circle and a lens associated with each master character to form an image of the character at the centre of the circle, a light source adapted to illuminate a master character on a unique radius of the circle, means for producing continuous relative rotation between the light source and the matrix member about the centre of the circle, and means for projecting the image of the illuminated character upon a lightsensitive surface. A method of manufacturing the matrix disc is also described. As shown in Fig. 5, a drum 33 carrying a number of lenses 32 is concentric with a drum 5 carrying master characters. Both drums are driven at the same speed by a motor 17. A beam of light from a lamp 24 passes through a decoder to a mirror 55 on a fixed shaft 46 and is reflected through a character and the corresponding lens 32 to a lens 35 by which an image of the character is formed on a photographic surface 7. Characters are projected only during alternate revolutions of drums 5, 33; during the intermediate revolutions light from lamp 24 is cut off by a half-revolution shutter 14 driven, at half the speed of the drums, by motor 17, and movements of a register, in which the characters of a line to be printed are stored in code form, and which controls the decoder and the surface 7, are effected. The operations are controlled in proper sequence by cams (not shown) also driven by motor 17. Light from lamp 24 is reflected along a path abcde by mirrors 50, 51, 52, 53 in a housing 69 which is rotatable so that the part bc of the path generates a cylindrical surface. This part of the light path traverses a decoder of the kind described in Specification 733,789 comprising a number of discs 61 with internal notches so arranged, that when, under the control of the code signals from the register, certain discs are rocked slightly about an axis near their edges, the light path is blocked except in one angular position corresponding to the character selected. Preferably a condenser (not shown) forms an image of the filament of lamp 24 in the plane of shutter 14. A second image is formed by a lens 49 in the middle of the set of discs 61, and a third image is formed by lens 54 at lens 32. The light is reflected by fixed mirror 55, and after passing through a slit in a stationary mask (not shown), illuminates that character 31 on drum 5 which is in position at the moment when the light path through the discs 61 is opened. The lens 32, which corresponds to the character 31, forms a virtual image thereof at the point e. An objective 35 forms a real image of the character at 36 on the photographic sheet 7. Drum 5 may be movable along shaft 46 to bring different founts of characters into use. Alternatively, the apparatus may be modified so that drum 33 is inside drum 5, and lens 32 forms a real image of the character 31 on the surface 7. In a further modification, the character drum and the lens drum are fixed inside housing 69 so as to be traversed by the part cd of the optical path. The rotation of the image is compensated by passing the light through a Dove prism rotated at half the speed of the. housing 69. Manufacture of character drum.-In order to avoid the necessity of using lenses manufactured to close tolerances, the character drum is manufactured as follows. A jig supporting a master character drawn on a sheet 100 (Fig. 8) comprises a frame 107 movable vertically by a rack and pinion 108, 109 and a bar 101 movable horizontally on the frame by a rack and pinion 103, 104. First, a sheet with cross-lines is mounted on the jig in fixed position. A drum corresponding to the character drum is mounted inside the lens drum, and a photographic film is mounted thereon to receive images of the cross-lines formed by the lenses. After development, the images are projected on to a graduated screen, and the horizontal and vertical displacements of the image are noted. Then the characters are set up on the jig and displaced by scales 111, 140 to compensate for the displacement :of the image, and projected on to a film from which the character drum is formed.