Patent GB-669556-A (GB)
Title: Photographic type-composing machines
IPC: B41B17/10
Filed: 1948-10-01
Abstract: 669,556. Photo-electric control of photographic exposure. HIGONNET, R. A. E., and MOYROUD, L. M. Sept. 23, 1949 [Oct. 1, 1948], No. 25639/48. Addition to 669,531. Class 40 (iii). In a photographic typecomposing machine in which, as described in the parent Specification, a disc or cylinder bearing representations of all the types is rotated continuously, a lamp being flashed once in each revolution at a point in the cycle determined by the setting of a register so as to project a selected one of the representations on to a sensitive surface, .the precise instant of the flash is controlled by a photo-electric impulse initiated by a slit &c. in the disc &c. Three systems are described differing in the method by which the signals from the register select a type. First system, Fig. 1, in which the selection is electrically controlled. The constantly rotating disc is provided with a slot P21 for each character for the production of impulses on a photo-cell P22. These impulses are passed on to a gate valve P30 which is normally closed by reason of the ground connection to its screen grid. Relays T1 ... T7, set from the register apparatus in accordance with the type to be projected, normally provide via their back contacts and conducting portions of a commutator drum D18 shown developed in Fig. 3, circuits through which current flows in an inductor P25b, but when the position corresponding to the desired letters is reached, those brushes D1 ... D7 that are connected up by the relays, all encounter insulating portions of the drum and the resulting interruption of the circuit to the inductor produces an impulse which is applied via condenser P31 to the screen grid of the gate valve. The photo-electric impulse from the slot corresponding to the desired character is thus passed on via tubes P37 and P38 to the primary of a transformer P42, the secondary impulse enabling the projection lamp P2 to fire and print the character on the sensitive surface. The energy for the flash is obtained from a condenser P43 which is not charged again until the period after the end of the printing cycle during which the sensitive paper is moved transversely, the sequence being looked after by cam-operated contacts. This arrangement makes it possible to use a code in which with a particular setting the breaking of all the circuits of the inductor occurs at more than one point in the cycle. Modification, Fig. 4, in which register signals are decoded mechanically. The relays Tl ... T7 controlled from the register are replaced by seven magnets such as B15 which, when energized, rock arms such as B12 in which are supported discs B1 ... B7 provided with code slots and rotating continuously in synchronism with the character-bearing disc B11. When the character represented by the setting of the magnets reaches the printing position there is a continuous light-transmitting path from lamp B16 to photo-cell B17. When the path includes the accurately positioned slot in the character-bearing disc as shown, the photo-cell B17 controls printing directly and no gate valve is needed. In a modification, however, cell B17 controls the gate valve and a separate cell controlled by the slots in disc B11 controls the precise moment of printing. Modification, Fig. 6, with optical decoding. In this system, magnets MS1 ... MS7, controlled by the register, control shutters covering portions of an illuminated slit which is focused on the transparent character-bearing disc. The latter has code marks which pass the image of the slit as the disc rotates. When the desired character is in the printing position, the dark parts of the slit image correspond with the light-transmitting parts of the code marks and, as a result, light is completely cut-off from a photo-cell PC which controls the printing lamp.