Patent GB-475208-A (GB)
Title: A device for controlling the printing light in photographic projection printing machines
IPC: G03B27/475
Filed: 1936-08-10
Abstract: 475,208. Photographic projection - printing. DALOTEL, M. A. Aug. 10, 1936, Nos. 22017 and 22018. Convention dates, Aug. 8, 1935 and July 18, 1936. [Class 98 (i)] In a machine for continuous projectionprinting of one or more negative films onto a plurality of positive films, the screens controlling the illumination through the projection windows are moved in synchronism with the unwinding of the film. The movable screens 9 in front of the window 7 are carried by rods 10 which are frictionally held between plates 4, 4<1>. The rods 10 have lateral projections 12 with spherical heads which engage in the groove 13 of a guide member 15. When a change of light occurs, the member 15 is withdrawn from the spherical heads displaced vertically by the required amount and caused to engage by its flared end 14 with the ends of the rods and so successively displace the screens. This movement is obtained by apparatus shown in Fig. 4, wherein eccentric sleeves 16 are loosely mounted on a shaft 17, each of the sleeves carrying a pinion 18 which is brought into engagement with a pinion 20 on a constantly rotating shaft 21, by the action of electromagnet 19 and clutches 22. Each sleeve has a plate 23 with two abutments which confine the rotation of the sleeves to half a revolution. A spring tends to return each sleeve to normal position. Levers 28 pivoted at 29 engage in recesses in the plates 23. On the outer sleeve 16 is mounted a pivoted fork 32 which carries the grooved member 15. The pivot pin 33 is mounted on a carriage 35. A rod 37 moves the carriage 35 on a slide 36 and carries at the opposite end a finger 38 which engage a cam groove 39 in a rotating drum 40 driven from the shaft 21 by an electromagnetically controlled clutch 45. The groove 39 has portions of different and opposite pitch 46, 47, the portion 46 causing the carriage 35 to move the guide member 15 from engagement with the spherical heads of the rods and also to cause the withdrawal of the looking levers 28. When a guide strip energizes any of the electromagnets 19 and the clutch 45, the drum 40 rotates and causes the carriage 35 and member 15 to move and release the heads 12 of the screen supports 10. The eccentric sleeves that are in engagement with the drive shaft 21 then rotate and swing the fork 32 to move the member 15 through the measured vertical distance. The spiral section 47 then returns the carriage 35 and member 15, and displaces the movable screens 9 across the windows 7. In Figs. 7 and 8, the illumination of the separate picture and sound negatives is controlled by pilot strips 51, 51<1> on which bear the tapered ends 55 of levers 56, 56<1> ... which are all pivoted on a common pin 57. At the other end are supported mercury trips 60 containing contacts 61, 62, 63 in the circuit of the electromagnets 19 and the clutch 45. A pin 58 on the mercury trip support is normally held in a raised position, but when a notch in the guide strip is opposite the nose 55, the end of the lever falls, closes the trip switch, and energizes the corresponding electromagnet 19. When the door 54 enclosing the guide strips is open, a lever 74 pivoted at 75 is swung to raise the end of the lever 56 and maintain all circuits open whilst a pivoted arm 77 actuates a fork 78 to disengage the clutch 79, 83 between a drive shaft 80 and the feed drums. When the door 54 closes it pushes a rod 70 so that the lever 74 is lowered, the clutch 83 engaged, and the pins 65, 65<1> disengaged from holes in the guide strips 51, 51<1>.