Patent GB-439803-A (GB)
Title: Improvements in or relating to apparatus for use in observing moving objects, such as the web of a multi-colour or other printing machine
IPC: B41F33/02
Filed: 1934-05-16
Abstract: 439,803. Feeding webs. BOAZ, A. R., 38, York Road, Acton, London. May 16, 1934, No. 14810. [Class 100 (i)] When feeding a web in a printing - machine for multicolour or other printing, or for insetting a preprinted web, images of a succession of indexes on the travelling web are produced at a stationary point by means of a reflecting element which is mounted for pivotal movement and is rocked at a rate proportional to that of the web in one direction so as to follow a registering mark on the web and reflect an image thereof to the stationary point and is then moved in the reverse direction back into its original position to pick up and follow a succeeding mark on the web and so on, the succession of images combining to provide the effect of a single stationary image. The registering marks may be a part of the printed design or may be separate marks printed on the web with the different coloured impressions, and the web preferably travels in a rectilinear path past the observation device which comprises a casing 1, Fig. 1, having a mirror 2 pivotally mounted on a shaft 3 so that as the marks on the travelling web arrive opposite an aperture in the face 4 of the casing, they are reflected to a stationary mirror 7 and thence through a lens 8 to a viewing aperture or a screen whereby a magnified image of the marks is obtained. To the shaft 3, Fig. 2, is adjustably clamped an arm 9 having a roller 11 which is held against a cam 12 by a spring 15, the cam being driven at a speed proportional to that of the press and having such a shape that, as the cam rotates, the mirror 2 is so displaced as to produce a stationary image of the travelling registering mark at the observation point, the step 12<1> being provided to permit a quick return of the mirror to its initial position to pick up the succeeding mark on the web, the period between successive images reflected to the stationary points being within the period of persistence of human vision. Should lack of register, for example in multi-colour printing, occur, the associated marks printed by the different cylinders will not register and this will be observed in the stationary images. Correction is made either transversely or longitudinally of the web. Two or more optical systems may be provided so as to produce super-imposed images to an observer looking through the viewing lens, and these superimposed images may be arranged to overlap in time to give jointly an uninterrupted image. When more than two colour impressions are to be maintained in register, the registering marks can be either associated to form a single mark or can be arranged in groups, so that all the groups are observed together, and the depth of colour of the different impressions can also be checked in the same way. In order to provide means for regulating the angle of sweep of the mirror 2, as when using different sizes of printing cylinders, the snail cam 12 may oscillate a lever which is adjustably coupled by a link to the mirror in such a way that the displacement of the lever between the cam and the mirror can be varied.