Patent GB-516014-A (GB)
Title: Improvements in or relating to photographic printing apparatus
IPC: G03F7/22
Filed: 1938-06-18
Abstract: 516,014. Photographic contact and projection printing apparatus. NICKELSBERG, P. June 18, 1938, No. 18133. Convention date, June 24, 1937. [Classes 98 (i) and 98 (ii)] A step-and-repeat printing machine comprises an upper carriage, carrying a contact or optical-projection . printing unit, driving mechanism for moving the carriage step by step to print a row of images, a lower carriage supporting a light-sensitive sheet, driving mechanism for moving this carriage transversely step by step after printing each row of images, and two actuating mechanisms driven by the driving mechanisms and co-operating with each other, comprising means which control automatically in 'sequence the entire series of operations .necessary to print a complete succession of rows of images on the sensitive sheet, and also the light exposures for the successive printings. The machine consists of an upper carriage 1, Figs. 1 and 2, supported on V-slideways on a main frame, and displaceable step by step therealong by a pair of screwed shafts 13; and a lower carriage 2 similarly supported on V-slideways at right angles to those of carriage 1, and displaceable therealong by a single screwed shaft 14. Printing devices. Carriage 1 has a light-cowl 7, and a glass negative-supporting plate 6 held in a frame 5 supported by four pistons 4 which may be moved by suction air to press the plate 6 into contact with a sensitive plate &c. held by suction means (Fig. 7, not shown) on a plate 8 of carriage 2. The cowl 7 may alternatively house an ordinary optical projection printer system producing an image on plate 8, through screens and colour filters if desired, the frame 5 and its supports being in this case dispensed with. Driving mechanism of upper carriage. The screws 13 displacing carriage 1 are driven by spur gearing 85, 86, Figs. 1 and 5, from a shaft 15 which in turn is driven from a motor-driven main shaft 17 through spur gearing 15a or 15b, a clutch 16 controlled by a lever 18 pivoted at 19 being provided which either couples the shafts via 15a for forward movement of the carriage, or via 15b for quicker return movement, or rests in a disengaged position. Fixed on shaft 15 is a locking disc 22 notched two points 23 to engage a pivoted pawl 25 operated by a rod 26, and coacting with a pivoted catch 25 operated by a rod 27. The main shaft 17 drives also, through worm gearing 28, a shaft 29 carrying cam discs 30-33, Fig. 5, for controlling various operations of the machine. Shaft 29 is in two parts adapted to .be coupled together by a clutch 34. One part further drives through spur gearing 35a a shaft 35 also in two parts adapted to be coupled together by a clutch 36, and carrying an exposure timing-disc 37 which is electrically conductive over half its periphery, the length of the conducting arc being adjustable by setting an insulating sector 38 on the rear face of which is a boss 40 co-operating with a linkage controlling the cam-shaft clutch 34. The disc 37 rubs on a fixed contact' 39, Fig. 1, to energise the printing lamp in cowl 7. To control the step-by-step displacement of carriage 1, a horizontal, graduated, toothed bar 42, Figs. 2 and 4, is mounted on the machine frame parallel,to the slideways of this carriage so that it can tilt about its own axis, and on this bar are set at predetermined distances apart a series of blocks 44. A shaft 48, connected by a crank to a control rod 50, is mounted on the machine frame parallel to the bar 42, and along it is slidable with rotation a member carrying a nose 43 adapted to engage seriatim in the blocks 44, and itself carried by a bracket 48a on or moving with the carriage 1. The faces of the blocks 44 and nose 43 are inclined so that contact of the nose with a block causes bar 42 to tilt, and the tilt is communicated by a pivoted lever 46 to an actuating rod 45 controlling the catch 25 of the locking disc 22 on shaft 15. Driving mechanism of lower carriage. The driving screw 14 of carriage 2 is driven by spur gearing 57, 58, Fig. 2, from a shaft 56 which in turn is driven from a motor-driven main shaft 60 through spur gearing 56a or 56b, a clutch 59 controlled by a lever 68 pivoted at 68a being provided which either couples the shafts via 56a for forward movement of the carriage, or via 56b for return movement, or rests in a disengaged position. Fixed on shaft 56 is a locking disc 70 notched at 71 to engage a pivoted pawl 72 operated by a rod 72a, Fig. 1, and this pawl co-operates with a pivoted catch 73 operated by a rod 54. The main shaft 60 drives also through worm gearing 61 a shaft 62 provided with a clutch 63, and carrying cam discs 74-76 for controlling various operations of the machine. Shaft 62 drives through reduction gearing 78 a further shaft 79 carrying cam discs 77, and co-operates with parts of the control mechanism of both carriages 1 and 2. The step-by-step displacement of carriage 2 is controlled in a manner similar to that of carriage 1 by the seriatim engagement of a member 51, Fig. 1, moving 'with the carriage, with a series of blocks set at predetermined distances apart on a horizontal, graduated, toothed, rocking bar 53 similar to the bar 42, and this bar co-operates in the same manner with a pivoted lever 53a linked with a rod 73a controlling the catch '73 of the locking disc 70 on shaft 56. Sequence of operations. With the negative and sensitive material in position on the plates 6, 8, for contact printing, suction is applied to the machine to hold the sensitive material on its plate and to be available for depressing the negative frame 5. The casing enclosing the apparatus is closed so that the room lights may be switched on. With the carriages 1, 2 in position for making the first print, the motors of the main shafts 17, 60 are started. Initially only the camshaft 29 with its cam-discs is driven. Cam 30 lets in suction air to pistons 4 to depress the negative frame 5 on to the sensitive material. Cam 31 lets in clutch 36 that the exposure timing-disc 37 begins to turn and switches on the printing light. Thereafter, camshaft 29 is automatically arrested until the exposure is complete, when boss 40 on rear face of timing sector 38 acts through linkage 41 to re-engage clutch 34, and re-start cam-discs 30-34. Exposure shaft 35 automatically disconnects its clutch 36 after. completing one revolution. Cam 30 releases suction air on pistons 4 so that negative frame 5 rises. Cam 32 withdraws pawl 24 from locking- disc 22 until its coil snaps under and is held by catch 25; this releases the carriage driving shaft 15. Cam 33 actuates spring plunger 21 to throw in clutch 16 to forward drive of shaft 15, so that carriage 1 begins to move, and camshaft is automatically arrested again. When carriage 1 reaches the position for the next print, nose 43 moving therewith strikes the first stop 44, tilts bar, 42 and associated lever 46, and through rods 45, 27 displaces catch 25 to release pawl 24 which thereafter engages the notch of locking disc 22 which next arrives, and locks shaft 15; simultaneously, the movement of pawl 24 through a lever not shown releases the stop 20 holding clutch 16 engaged, whereupon spring plunger 21 moves back to disengage this clutch, and motion of carriage 1 ceases. This cycle of operations continues until the first row of images has been printed, whereupon shaft 15 is again started as before to drive carriage 1 forward. Now, however, the member 48a on carriage 1 strikes a yieldable stop 64, Fig. 4, which, through linkage 66, lets in clutch 63 to start camshaft 62. Cam 75 releases the pawl 72. of the disc 70 locking drive shaft 56 of carriage 2, the tail of the pawl being held by catch 73; and simultaneously cam 74 actuates the spring plunger 21b, Fig. 2, to turn lever 68 of clutch 59 into engaged position for forward drive of carriage 2, plunger 21b being held in this position by stop 69. Shaft 56 now turns and moves carriage 2. When this has reached the position for printing the second row of images, nose 51 moving therewith engages the first block on rod 53, and tilts this rod and its associated lever 53a, which, in a manner similar to that adopted for carriage 1, throws out clutch 59 and causes pawl 72 to lock disc 70, thus arresting shaft 56 and therefore also the displacement of carriage 2. At this point, cam 76 moves clutch 16 from forward to return drive of shaft 15, so that carriage 1 returns; and cam 77, through rod 50, moves nose 43 aside so that the return of carriage 1 is unimpeded by blocks 44. Camshaft 62 is automatically disconnected and its clutch 63 is not let in again until carriage. 1 has returned to starting position, in which it is arrested by the member 48a striking a second yielding stop 65 which, through linkage 67, Figs. 1 and 4, reengages clutch 63 and re-starts camshaft 62. Cam 76 releases clutch lever 18, allowing spring plunger 21 to return clutch 16 to forward drive of carriage 1. Cam 77 restores nose 43 to normal position. Camshaft 62 is then again automatically declutched. The series of operations is now repeated until the desired number of rows has been printed, whereafter a projection on carriage 2 co-acts with a yielding stop to switch off the motors of the driving shafts 17, 60, and to actuate a warning signal. The operator then sets clutch 59 manually to return drive, manually operates means to remove nose 51 out of the path of blocks on the rod 53 on return movement of carriage 2, and starts the driving motor of shaft 60 to effect this movement, which is arrested by a second yielding stop in the same way as the forward movement was arrested. The casing may then be opened for removal of the printed sheet. Modifications of driving mechanisms. Several notches may be provided on the locking-discs 22, 70 and may be adjustable, to permit finer adjustment of the positions of the carriages during automatic actuation. For printing the second, fourth &c. rows of images, provision may be made f