Patent GB-419432-A (GB)
Title: Process and apparatus for the reproduction of graphical illustrations and plastic articles by cutting, engraving, profiling, photosculpture and the like
IPC: B44B1/02
Filed: 1933-02-06
Abstract: 419,432. Electrical reproducing-apparatus. BREDAEL, F., 63, Rue de Witte, Berchem, Antwerp, Belgium. Feb. 6, 1933, No. 3619. Void [Abridged as open to inspection under Sect. 91 of the Acts, Aug. 8, 1933]. [Class 40 (v).] Relates to automatic or semi-automatic apparatus for reproducing objects from a graphical representation under the control of a light sensitive element. A connection is provided between the relative movements of a tool with respect to the material to be worked and the relative movements of the light sensitive element with respect to a graphical representation of the object to be reproduced, the light sensitive element controlling the extent of the displacement, i.e. the drive, given to the tool, the stopping and return of the tool, and the displacement of the tool to an adjacent driving path on the work. The photo-electric cell 21, preferably having an adjustable diaphragm aperture is arranged to move over a picture or succession of pictures projected on to a screen 81 fixed to the carriage 20 from a projection apparatus 82, rotatably mounted about an axis 86 in a support 83 movable on a slide 84. Referring to Fig. 3, the carriage 20 will, when current is suitably supplied to the clutches 40, 41, move the cell 21 from A' to B' on the control picture and the tool from A to B on the material 7 removing therefrom a shaving of predetermined width. Upon reaching the point B' the illumination and resistance of the cell 21 is varied and the consequent variation of current is amplified and operates the clutches 40, 41, to return the tool from B to A. The carriage 20 upon completion of the return movement closes contacts reversing the operation of the clutches 40, 41 and bringing into operation the progression mechanism 23 by which the carriage 19 is stepped up to enable a shaving to be removed from a fresh adjacent portion of the material 7. In a modified working, the tool is made to follow an outline in a series of small steps by limiting the return course of the tool by time controlled mechanism or by eliminating the return course and directing the cutting course after each progression in one or other direction according as to whether the cell 21 is illuminated or not. Alternatively, the progression either rectilinear or rotary may be continuous and less than the transverse speed of the tool. In such circumstances the cell 21 moves with its aperture parlly over the clear zone of the control picture and partly over the dark zone and follows the contour with a degree of tolerance which may be controlled by adjustment of the ratio of amplification or the spring of the relay. In order to retain the cell 21 upon the outline of the control picture when the latter consists for example of a photograph in which the ratio between the densities of the dark and clear zones varies round the outline, a main light beam is projected directly to the cell through parts adjacent the outline and two or more test beams are arranged to pass respectively through the dark and clear zones on opposite sides of the outline to supplementary cells or to the same cell. In the latter case a rotary apertured shutter is arranged to permit light from the main and test beams respectively to fall upon the cell with different frequencies, so that the resultant variations of current through the cell due respectively to the main and test beams may be separated from each other. The current corresponding to the main beam is arranged to operate a relay controlling the movement of the tool and the currents corresponding to the test beams are adapted to compensate for the varying densities of the control picture by modifying the spring of the relay, the degree of amplification, or the intensity of the main beam by adjustment of a photometric wedge. If the outline in the control picture becomes badly defined owing to diffuseness, the currents arising from the test beams become of substantially equal strength and this condition may be arranged to cause a separation of the test beams until they are removed from the diffuse zone.