Patent GB-333593-A (GB)
Title: Improvements in photographic film printers
IPC: G03B27/08
Filed: 1929-04-15
Abstract: 333,593. Thompson, F. B. April 15, 1929. Kinematograph apparatus. -In apparatus for printing positive films from a negative film having sections of varying density, a movable strip having orifices of different sizes is placed between the light source and exposure gate for controlling the intensity of the printing light. The strip is moved by mechanism controlled by the negative film, preferably by notches in the negative film. A number of printing units according to the invention may be assembled to enable a number of pecitive films to be simultaneously printed from one negative film. In the embodiment shown in Fig. 1, the negative film 7 passes from the supply reel through each unit in turn to take up reel 9, each positive film passing from one of the reels 6 through one of the printing units to its take up reel 8. The driving means 12 for feeding the films to the printing units 3 are driven by the shaft 25, the latter being geared to the motor driven shaft 21 which drives the printing unts 3. The driving means 12 comprise a feed sprocket 28, Fig. 3, mounted on the shaft 27 which is geared to the shaft 25. The films are pressed against the sprocket 28 by rollers 31 carried by a pivoted spring-urged lever 29, which can be held away from the sprocket 28 by turning the cam roller 34 through the finger 35. The shaft 27 also drives, through the friction clutch 40, a pulley 38. The latter drives the pulley 43 which is slidably keyed to the shaft 44. The shaft 44 carries the spool 48 and is adapted to be moved laterally by the link 50 and actuating rod 53 to enable the film roll to be stripped from the spool. Fig. 5 shows one of the printing units 3. The lower part 57 contains a red lamp 59 and printing lamp 60. The lamp 60 may be slid on the rod 65 by means of the cable 67 and pulley 68, the latter being turned by the crank 71 and clamped in the desired position by the lock-screw 72. The shaft 89 geared to the shaft 21 carries a gear wheel 94 and a cam 99 having two cam faces 100 and 101. A rotary shutter 98 is driven through spiral gear 96 and gear wheel 95 from the wheel 94. Adjustable spring-urged pilot pins 105 connected to a plate 110 and adapted to centre the films are intermittently permitted to project through apertures in a plate 107 at the exposure gate and through the, side perforations in the positive and negative films by the rocker arm 102 which is operated by the cam 101. Means are provided for centering the plate 107. A support 122 for a pressure plate 123 is hinged at 119 and secured in position by a latch 131, 134, 137. The pressure plate 123 is guided by pins 124 and urged by springs 125 against the films on the plate 107. The cam 100 is adapted to rock a lever 128 which pushes pins 126 through apertures in the plate 107 causing the pressure plate to be intermittently raised. In order to first contact the negative and positive films at the centre of the exposure aperture a plunger 140 is slidably mounted in the pressure plate 123 and is urged by a spring 141 between the plunger and a ruby glass observing window 138 mounted in the support 122. Means are provided for tensioning and keeping apart the two films before reaching the exposure gate. To provide an intermittent feed for the two films they are pressed, by rollers mounted on a spring urged pivoted lever, against a feed sprocket (not shown) mounted on the shaft 163, Fig. 6. The feed sprocket is intermittently rotated by a geneva star wheel 164 actuated bv a pin 165 on the disc 166, which is driven from the gear 94. Light from the lamp 60 passes through the ground glass plate 78 in the wall of the light chamber and is focussed on the exposure aperture by a lens 145 mounted in the removable slide 146. Means for regulating the intensity of the printing light comprises a film strip 147, Fig. 14, having different sized orifices 149 as described in Specification 328,423, [Class 31 (ii), Punching and perforating machines &c.]. The strip is guided immediately over the lens 145 and over a sprocket (not shown) mounted on the shaft 152, Fig. 6. The sprocket is driven through a spring urged clutch which may be withdrawn to allow the sprocket to turn freely when inserting the strip 147. The shalt 152 is adapted to be driven by the geneva star wheel 184a actuated by a pin 184 on the disc 182 which is movable transversely along the shaft 183 driven by the gear 94. Means for causing the strip 147 to move comprises a solenoid coil 176, Fig. 6, which is energized when a notch, such as 170, Fig. 14, on the negative film 7 permits a pivoted lever, having a roller permanently pressed against the edge of the film 7, to rock and close suitable contacts. The core 177 of the solenoid is adapted through a link 178 and pin 180, which engages a cam track, to move the disc 183 into engagement with the geneva star wheel 184<a>, causing the strip 147 to be moved. A further pin 186 in the link 178 is adapted to engage a flange on the disc 182 and ensure that the geneva star wheel 184<a> rotates through 180‹. A knob 197 on the solenoid core 177 enables the mechanism for driving the strip 147 to be brought into operation by hand. A further pivoted roller-carrying lever presses against the edge of the strip 147 and is adapted to break the circuit of the solenoid 176 when the negative film has run through the printer. Circuits and switches for the current supply to the motor 18, lamps 59, 60, and solenoid 176 are described. To secure a mechanical balance the printers 3, when arranged in gangs, operate with a phase difference. Kinematograph films.-In addition to the main exposure aperture the plate 107 has a slit adapted to expose the positive film along a line outside the perforations to provide a guide for the operator in projecting.