Patent GB-722171-A (GB)
Title: Photographic contact-printing apparatus
IPC: G03B27/06
Filed: 1949-01-25
Abstract: 722,171. Photographic contact printing apparatus. GENERAL ANILINE & FILM CORPORATION. Jan. 25, 1949 [Feb. 26, 1948], No. 2034/49. Class 98 (2). A photographic contact printing apparatus comprises a support on which a light-sensitive sheet and an original to be copied are held stationary and in contact by pressure members housed in a carriage which is movable continuously over the support and contains a light source and mechanism whereby the pressure member occupying a position at the rear of those contacting the original is periodically lifted and then moved to a position in front of said members. In the form shown, a table 10, Fig. 1, supports the light-sensitive sheet and original and, movable thereover, is a closed carriage, the side walls 14 of which have pivoted thereto at 35 bell-crank levers 34, each pair of which supports a shaft carrying wheels, such as 16, 17. The carriage is moved over the table when an electric motor 21, Fig. 4, is energized, the drive from this motor being transmitted to the shaft carrying the wheel 16 by an endless chain and sprockets. Each bell-crank lever 34 has a pin-and-slot connection at 40 with a link 36, 37, Fig. 1, each pair of links being pivoted to one of two levers 38, rotatable by an electric motor 44 through a belt or chain drive. Energization of motor 44 thus causes the carriage and mechanism contained therein to be raised above the wheels 16, 17, for placing the original and light-sensitive material on the table 10. Rotation of the levers 38 is limited to 180 degrees of arc by pins carried by a pulley on the lever shaft and actuating switches to deenergize the motor 44. As the carriage moves over the table 10, the original and lightsensitive sheet are exposed to light from a source as of ultra-violet light which, like motors 21, 44, is energized through conductors led into the carriage by a cable 59 connected to contact strips that are mounted on the table 10 and insulated therefrom. Contact between the original and light-sensitive sheets in the printing zone is maintained-by three of four transparent pressure platens. Each platen includes a flat member 63, Fig. 12, attached to side members 64, 65; each side member has at the front end thereof a freely rotatable roller 67 and a pin 68 and includes a part having an inclined front surface 66 and a bracket -70 carrying lugs 71 secured thereto, and a rear portion on which is mounted a roller 69. The pressure platen not in contact with the original has its lugs 71 in contact with horizontal plates 72, Fig. 5, carried by the side walls of the carriage; the forward. lugs 71 are also contacted by two pins 76 carried by chains 75 entrained around sprockets, of which one pair of sprockets 79, Fig. 4, is driven by an electric motor 84 through a chain drive. When this motor is energized, the platen is moved towards the front of the carriage, which is itself moving, by the engagement of the pins 76 with the lugs 71. Such forward movement continues until the roller 67 engages a stop 87 on a cam-plate 85, Fig. 5; at this time, the rear lugs 71 pass beyond the ends of the plates 72 so that the platen pivots about the rollers 67, which are held in notches 88 in the cam-plates 85 and the rollers 69 roll down the inclined surface 66 of the pressure platen which occupies the front position of the three in contact with the original. The rollers 69 thereafter are engaged by the pins 68 on the pressure platen which is stationary, such enment causing the rollers 67 to be pulled out of the notches 88 and to roll down the inclined surfaces 89 of the plates 85 so that the platen contacts the original, as the carriage is moved forward. Immediately before the platen supported by plates 72 is moved forward by the chain, the carriage has moved forward so that a lug 71 on the rear platen of the three contacting the original engages the plunger of a normally open switch and thus closes the switch to energize the chain driving motor. The time during which this switch is closed is sufficient to move the chains 75 so that a button on one thereof moves out of contact with a normallyclosed switch for actuating the chain driving motor. Thus the plate-supported platen continues to move forward. and another pair of pins 76 engage under the front lugs 71 of the platen which was at the rear of those contacting the original and lift it so that the lugs 71 thereof run along the plates 72. The chains 75 continue to move until this platen is half-way along the plate and the former plate-supported platen is in contact with the original. Thereupon, another button on one chain opens the normally closed switch and de-energizes the chain driving motor. When the carriage reaches the end of the table, operation of the machine is stopped by the engagement of the plunger of a normally closed switch with a cam surface on the table.