Patent GB-915885-A (GB)
IPC: G03B27/22
Abstract: 915,885. Photoprinting apparatus. CHEMISCHE FABRIEK L. VAN DER GRINTEN N.V. June 13, 1961 [June 20, 1960], No. 21354/61. Class 98 (2). [Also in Group XVI] In a method of making prints from compound translucent laminar originals, each consisting of two loosely superimposed originals, one being a so-called main original and the other a so-called additional original, the main original is fed to a revolving exposure cylinder and held thereon, while the additional originals are fed in succession to be copied each in turn superimposed on the main original, and then removed, the main original being finally released from the exposure cylinder and removed. On the way to the cylinder, the originals pass a scanning device which can differentiate between main and additional originals, and sends a signal to the holding device on the exposure cylinder causing it to operate only when a main original is approaching. The apparatus as shown is composed of an exposure section A, a section B for feeding the originals into the device, and a control section C. A stack of originals is fed in between guide-plates 30, 32, from where they are led to pass between a lower roller 33 and a series of discs 38 mounted on a shaft 37. The drive to shaft 37 acts through a slipping clutch (Fig. 2, not shown) which can be adjusted to different values. As the lowermost original of the stack is taken along by roller 33, it also engages frictionally with the discs 38 above it. This friction is sufficient to drive the discs round against the action of the slip clutch, which tends to drive the discs continuously in the opposite direction. If two originals together are carried between roller 33 and the discs 38, then, since the original sheets are fairly smooth, they slide one on the other; thus the drive from roller 33 is not carried to the top original sufficiently to cause this to turn the rollers against the action of the slip clutch. Consequently, this does not slip, but continues turning the discs in the original direction, which thus rubs the top original backwards, only the bottom one proceeding forwards. This arrangement accordingly will automatically feed a stack of originals forward one at a time. The light-sensitive material is fed through the apparatus as a continuous strip 5. It is guided by a series of plates and rollers to pass round a glass exposure cylinder 3 within which is a lamp 2. A controllable pneumatic holding device for originals is fitted in the surface of cylinder 3, consisting of an air channel 4 lying along a generating line of the cylinder surface, and connected via a pipeline 72 to a valve 73. The valve can be controlled by a solenoid 74 to cause either blowing or suction through line 72. When the main original is delivered from section B, it is carried by rollers and guide-plates until its leading edge comes to abut against two spring-loaded stops 15. These are in contact with curved spring-loaded bars 12 pivoting on a shaft 13. The forward end of these bars also carry a feed roller 14. Rigidly secured to cylinder 3 is a disc having a cam projection 21, which cam closes a switch 22 once during every revolution. When this switch is actuated, a solenoid 23 causes the bars 12 to pivot downwards, so that feed roller 14 engages the original, and stops 15 are raised clear of it. The original moves on between rollers 9 and 57, to pass between the sensitive strip 5 and the exposure cylinder 3, to which it is held by suction action through pipeline 72. The following (additional) original is also fed towards the cylinder, and passes round it in superimposed contact with the main original. An exposure is now made through both originals, giving an image which is a combination of the two together. As cam 21 closes switch 22 again, a scraper bar 19 operated by an arm 25 fixed to bar 12 removes the additional original and guides it out of the apparatus on to table 65. The main original, however, remains attached to the cylinder by the suction arrangement. In this way a succession of additional originals may be passed through the apparatus, each in turn being printed in superimposition with the main original. On the way from feed section B to printing section A, the originals pass over a guide 55 below a photo-electric device 60, in which light from a lamp 62 falls on the original and is reflected back to a photo-sensitive element 63. The originals are chosen so that the main originals have a different reflecting power from the additional originals, so that the sensitive element 63 can distinguish between them. The device 60 is arranged to control the valve 73. As long as additional originals pass below the device 60, the valve 73 continues to exert a suction effect via pipeline 72, thus holding the main original continuously on cylinder 3, for the process descrideb above. When a new main original is.fed in, however, this causes the device 60 to change over the valve 73 from suction to blowing. This dislodges the main original from cylinder 3, and it is then carried out of the apparatus to make way for the new main original. Dutch Specification 66,774, Belgian Specificetion 571,684, German Specifications 671,438, 743,200, and U.S.A. Specification 2,892,629 are referred to.