Patent GB-981234-A (GB)
Title: Control device for paper webs in photographic apparatus
IPC: G03B27/58
Filed: 1962-12-31
Abstract: 981, 234. Feed control in photographic copying machines. AGFA A.G. Dec. 31, 1962 [Dec. 29,1961], No. 49168/62. Heading G2A. A control device for advancing paper webs in photographic printing apparatus comprises a webadvancing roller mounted for common rotation with a ratchet wheel, and driven by a friction coupling from a drive means, with an electromagnetically operated pawl which engages the ratchet wheel to arrest the latter and the advancing roller to terminate the web advance irrespective of continued movement of the drive means. The motive power is provided by a motor-driven chain 7 acting on a sprocket wheel 6 loosely mounted on a spindle 4. On one side of the sprocket wheel is a wheel 11 having a single tooth 11a, separated from the sprocket by a friction disc 12 and spring- urged against it. On the other side of the sprocket is a ratchet wheel 14, separated from the sprocket by a friction disc 13 and spring-urged against it. The ratchet wheel is keyed to the paper web advancing roller by pins 15. An insulating plate 20 is fixed to the wall 2 of the device, the plate carrying a circularly arranged set of contact segments 22a, b, c, d, and a contact ring 23 inside the segments. Contacts 24, 25 on wheel 11 ride on segments and ring respectively. A pawl 26 can engage both wheels 11,14 when urged downwards by a spring 27, against which it can be retracted by an electromagnet. In operation, the sprocket wheel rotates continuously. For a web-advancing movement, the electromagnet is energized to lift the pawl out of engagement with wheels 11,14, whereupon roller 17 rotates. When the magnet is deenergized, pawl 26 drops again to engage the ratchet teeth and so advance of the web is interrupted. Since wheel 11 has only one tooth, however, this rotates through a full 360 degrees before being arrested by engagement against the pawl. The advancing movement is controlled by a relay A and switch 30. A size-setting device F is provided having a distributer arm I which can be connected to one of four contacts Ia, Ib, Ic, Id, connected respectively to contact segments 22a, b, c, d. The distributer arm has a segment Is sufficiently long to leave all the previous contacts connected together as it moves over them anticlockwise. Thus as contacts 24, 25 move over ring 23 and the ring of contacts 22, through one complete revolution every time an advance movement is made, contact 24 breaks the circuit for relay A either as it leaves the end of segment 22a, or 22a + 22b &c., according to how many of these segments are connected together by the positioning of the distributer arm I. Thus four paper sizes are available. The final segment 22e ensures sufficient advance of the paper to avoid overlapping of the picture. Segment 22e also provides connection to a relay B, which operates a marking or cutting device. On the spindle of the size-setting device F is another distributer arm II, moving over contacts IIa, IIb, IIc, IId, which controls an exposure device 33, switching off the lamp when a photo-electric converter has received a predetermined amount of light, and energizes relay A to start the paper advance. On the same spindle is mounted a switch disc III, which operates when the size-setting device is changed to advance the paper so that pictures adjacent the change-over position do not overlap. The paper is similarly advanced to avoid an exposure being made where one paper web, 40, is joined to another, 40<SP>1</SP>, by providing an aperture 42 into which a finger 43 can enter, so causing contacts 37, 38 to close and operate the paper advance. A further distributer contact IV on the same spindle F moves over a series of contacts IVa &c.,which indicate how many pictures of the different sizes have been made. Fig. 4 (not shown) illustrates how the same spindle F mounts a pinion to control two size masks, and also two further distributer arm control cutting and marking devices.