Patent GB-609856-A (GB)
Title: Improvements in or relating to photoelectric pick-ups or scanning devices for copying machines
IPC: G06K11/02
Filed: 1946-03-18
Abstract: 609,856. Copying machines. KAPELLA, Ltd., COOKE, E. A., and GREENHALGH, A. H. March 18, 1946, No. 8335. [Class 40 (i)] [Also in Group XL (b)] In a copying machine of the type described in Specification 570,189, [Group XXIII], wherein the carriage C, Fig. 1, carrying a workpiece and template on rotatable tables D<SP>1</SP>, El, is capable of movement in two directions, the template consists of transparent sheet on which the shaded form to be reproduced is printed and is scanned by an interrupted beam of light which after reflection from or travelling through the table E<SP>1</SP> is split into two parts, the relative sizes of which depend on the shape of the shaded template and which control by means of two photo-electric cells and two splitfield motors B<SP>8</SP>, C<SP>8</SP> the adjustment of the carriage in the two cordinate directions. The tables D<SP>1</SP>, El and a checking grid F<SP>1</SP> are connected together by flexible banding (not shown) to rotate together. Suitably mounted above the table D<SP>1</SP> is a grinding wheel G, a work microscope being provided on the bracket G<SP>3</SP> to position this wheel correctly. Specifications 588,986, [Group XXIII], and 595,204 also are referred to. Scanning arrangements-(Figs. 6, 9 and 10).- The image of a slit H<SP>6</SP> is projected on to the template K and reflected from the surface of table E<SP>1</SP>, and mirrors J<SP>1</SP>, J<SP>2</SP> to a beam-splitting mirror J3 which divides it transversely and passes one half to a photoelectric cell L<SP>1</SP> and the other to cell L<SP>2</SP>. These cells control the right and left movement of carriage C in accordance with the average illumination of bath cells and the movement towards and from the operator in accordance with the difference in illumination of the two cells. These movements thus continue until the image of the slit has its longitudinal axis tangential to the mark on the template as shown in Fig. 10. As the work proceeds the operator rotates the tables D<SP>1</SP>, E<SP>1</SP> by means of a hand-wheel E<SP>2</SP> to make a new part of the template effective. According to the Provisional Specification the cordinate movements may be controlled respectively by the cells. Circuit arrangement-(Fig. 17).-The outputs of the cells L1, L2 after amplification in tuned amplifiers are rectified at V5, V8. The difference between an adjustable fraction of the voltages of the respective load circuits R3, R4 and R5, R6 determines the voltage at the anode of a valve V10 and consequently the signal passed to the valve V11 of a pair of motor controlling valves V11, V12. An adjustable fraction of the mean of the voltage of the load circuits controls the valve V15 of a second motor controlling pair V15, V16. The pairs of motors controlling valves are such that the motor is stationary when both valves pass the same anode current and operates in one direction or the other when the valve currents are unequal. Copying solid forms.-In order to copy a solid object, a series of templates representing horizontal sections of the object to be reproduced are made, each being scanned separately and the grinding wheel being adjusted vertically for each successive scanning.