GB904661A - Improvements in or relating to the production of continuous patterns - Google Patents

Abstract

904,661. Engraving. ELECTRIC & MUSICAL INDUSTRIES Ltd. May 14, 1959 [May 14, 1958], No. 15471/58. Class 100 (2). [Also in Groups XXXVIII and XL (b)] A method of producing a continuous pattern from a non-continuous pattern comprises deriving from portions of a non-continuous pattern which are to be joined to form said continuous pattern error information as to the mismatch between said portions, and utilizing said error information in the reproduction of said non-continuous pattern in continuous form to effect a variation of said pattern so as to produce a join between said portions which is less apparent than would be the case in the absence of said variation. The discontinuous pattern is scrutinized through an optical device giving a simultaneous view of two parts of the pattern a distance apart equal to the length of the desired pattern repeat. Two such parts are then chosen giving the least mismatching, and the error at various points across the pattern is measured by means of a rotatable periscope prism. The error is then plotted as a graph by the use of which a cam is produced having a contour representative of the error information. A sheet bearing a discontinuous pattern and with the selected repeat lines spaced 180 degrees apart is secured to a cylinder 14, Fig. 7. A carrier 17 movable axially of the cylinder by rotation of a screw 18 carries photo-electric scanning devices 19, 20 spaced apart 180 degrees round the cylinder, and an electromechanical engraving tool 21, responsive to the scanning of the pattern on the cylinder 14, to produce a continuous pattern on a cylinder 15, which is half the diameter of the cylinder 14 and rotates at the same peripheral speed. A rotary switch on the axis of the cylinder 15 effects a gradual transfer of control from one to the other of the scanners every half-revolution of the cylinder 14. In order to vary the continuous pattern produced in response to the error information so as to avoid an obvious join, the cam 25, Fig. 9, representing such information, is positioned axially of the cylinders and controls the positioning of the scanners, which are mounted so as to allow axial and circumferential movement with respect to the carrier 17. The cam transmits vertical movement to the contact 27 of a variable resistor 28 with a suitable voltage across it, so that a voltage proportional to the error is applied to a variable rotary resistor 29. A contact 30 rotating with the cylinder 15 transmits to the control units of the scanners a voltage which thus varies from zero to the voltage applied to the resistor 29, reaching the maximum as the scanning beams cross the repeat lines. The scanners are thus moved to vary the pitch of the scanning helix in such a way as to produce a gradual correction of the error. Specifications 796,994 and 866,319 are referred to.