Patent GB-1293539-A (GB)
Title: Improvements relating to photo-typesetting machines
Inventor: POLLOCK GERALD
IPC: B41B17/06
Filed: 1969-03-24
Abstract: 1293539 Photographic type-composing G POLLOCK 24 June 1970 [24 March 1969] 61252/68 Heading B6W A platform 3, Figs. 1 and 4, carries support means 5 for photosensitive material, and a carriage 9, which is vertically slidable on a frame 7 by rotation of a threaded shaft 11 by an electric motor, and which supports optical projection means 13, Figs. 1 and 2, and a rotatable character matrix disc 23, Figs. 2 and 3. The projection means includes a lamp 15, condensing lens 17, filter 19 and projection lens assembly 21. The disc 23 is transparent, with two concentric rings of opaque characters, upper and lower case respectively. The disc is rotatable about a pin 31 by a motor 41 through a belt 45 when a detent 61 is disengaged by a solenoid 63 from the teeth of a wheel 49 mounted on the disc, there being one tooth for each pair of radially aligned characters, so that when the detent engages a tooth, it prevents rotation and accurately aligns a character already approximately aligned with the projection position. The pin 31 is mounted on a plate 33 slidable on the carriage 9 by means of a magnet 37 and spring 39 to bring the upper or lower case ring character into operative position. The focus is adjusted by a link 25 and cam 27 to compensate for variations in the height of the carriage, which is adjustable for optical magnification. The brightness of the lamp is adjustable by inserting into its circuit one of three variable resistors VR4, VR5, VR6 (Fig. 5, not shown) and the exposure time is varied, according to the height of the carriage, coarsely by a switch S3 (not shown) and finely by a potentiometer VR2 actuated by a cord 28. The filter is removable from the optical path by a solenoid SOL1 (not shown). The characters are selected by keys in a keyboard 64 or by a perforated or magnetic tape input. The support 5 for the photosensitive material includes a holder 87 having two sections 99, 101 for supporting a proof sheet and a work sheet, the holder being slidable between two positions to bring the desired sheet into the optical path by means of a motor 91 on a table 73 movable backwards and forwards (vertically in Fig. 4) manually by a pinion 81 on a table 71 movable to left or right manually by a pinion 75 on the platform 3. The sheet on the section 99 is coated with liquid developer so that a visible image is formed shortly after projection. In operation, the section 99 is initially in the optical path. On closing a switch S1 (not shown), voltage is applied to the electric circuits. The resistor VR4 is in circuit so that the lamp is at its lowest brightness. The filter is in operative position, passing only a small amount of red, non-actinic radiation. The image size is adjusted by setting the carriage height, thus adjusting the focus, and the brightness by varying the resistor in circuit, at this time VR4. A character-selection key is then pressed, which energizes the solenoid 63 to release the detent 61 and energize the motor 41 to rotate the font. The circuits of the motor 41 and of the solenoid 63 include the normally closed contacts of a relay RLA4 (not shown). As the disc rotates, a contact 51 rotating therewith sweeps over a series of contacts 55, each corresponding to one pair of characters, on a printed circuit board 53, and when the contact 51 engages the contact 55 corresponding to the selected character, a circuit for the relay RLA4, which circuit includes a pair of contacts closed by the key, is completed to energize the relay and stop the motor 41 and engage the detent 61. The tables 71, 73 are adjusted to locate the character image produced by the red light correctly on the proof sheet. A "start" button is then pressed, to initiate a timing sequence for a printing operation. Resistor VR5 is connected into the lamp circuit to increase the brightness, solenoid SOL1 is energized to remove the filter, and an image of the character is formed on the proof sheet. The filter is then re-inserted, and the motor 91 moves the holder 87 to bring the section 101 into the optical path, while resistor VR6 is brought into circuit, adjusting the brightness to suit the work sheet. The filter is again removed, and a character image is projected on to the work sheet. The motor 91 then returns the holder to its initial position. The disc 23 may be rotated only in one direction, or in either direction so as to move the shortest distance. The disc may be replaced by a reciprocating member. The keyboard may be replaced by a control knob which moves a contact over a second series of contacts.