Patent GB-609155-A (GB)
Title: Improvements in and relating to printing by means of electro lines of force
IPC: B41M1/42
Filed: 1946-03-07
Abstract: 609,155. Printing. HUEBNER, W. C. March 7, 1946, No. 7108. [Class 100(ii)] [Also in Group XL(b)] In the method of printing in which ink is transferred to a moving web or sheet by the action of electromagnetic or electrostatic lines of force extending transversely to the material at the printing zone, means are provided to vary the intensity of the field of force to a predetermined extent on different areas of the web or sheet so as to produce ink deposits having varying colour shades or densities on different portions of a design. In one form, Fig. 2, a cylinder A having an inked design coacts with a cylinder B over which the web passes without contact with the cylinder A, and ink can pass from cylinder A to the paper under control of electromagnetic lines of force produced by adjustable magnetic cores 39 provided with spools 42 having right and left hand windings. A number of magnets on each cylinder are arranged side by side across the cylinders and by varying the intensities of the currents supplied to the coils the intensity of the printed impression may be varied over each line or zone of printing. Between the magnets, plates 35, 47 are provided which are connected to a source of high electrical potential to produce electrostatic lines of force as well as the electromagnetic, and either set of lines of force can be used alone or the two can be used in combination. Insulating shields 70 are arranged between the electrical discharge plates 35, 47 and the magnets which are provided with segmental field bars 44, 45. One method of controlling the intensities is shown in Figs. 5 and 7, the cylinder B being geared to a control drum 21 divided into grooves having spaced apertures 23 into which are fitted cam blocks 24 for controlling the intensity of the electro-static fields. The cams 24 control switches 26 comprising lever arms 32 having insulated conducting members adapted to connect a conductor 29 to a line 36 connected to a source of high potential through an arm 37 of a rheostat 41 or an arm of a rheostat 43, or to cut off the electrical supply. The electric circuits are completed by lines 33 connecting the discharge plates 47 to contacts 29 of the switches. The cylinder A may be a plain inked cylinder and a design produced by arrangements of cams 24. In some cases the printing-cylinder is formed of parts which are responsive and parts which are not responsive to the action of lines of force, e.g. a steel cylinder may have a design of non-magnetic metal deposited in a pattern thereon. In a further modification, Fig. 4, a design cylinder A<1> fitted with attraction plates 147 cooperates with plates 135 supplied with ink from reservoirs 125, which may be supplied with different colours for the various sections. The ink is supplied under air pressure to the plates by cocks 131, and passes over inclined plates 120 heated by electric heaters 137. The sheet 86 to be printed is carried by a band 82. In a further modification, Figs. 14, 15, a machine similar to that shown in Fig. 4, is provided with a control drum 54 fitted with an image composed of a pattern having parts of different densities, and photo-electric control devices are used to modify or produce a pattern on a web or sheet. The drum 54 rotates in unison with the cylinder A<1> and light from electric lamps 58 is projected through apertures 61 in casings 57 and is reflected from the pattern or drum 54 through apertures in similar casings upon photo-sensitive cells 60 which act to control the intensity of the fields of force directed to the different sets of plates 135, 147. A similar set of lights and cells 60a is arranged to scan the intensities of the pattern formed on the web or sheet, and these are arranged on either side of the plates 135. The electrical circuit, Fig. 15, indicates diagrammatrically how the cells 60, 60a control the strength of the electro field. If the strength of the cells 60, 60a is the same no current flows to a control valve 74 and the position of a rheostat arm 69 in the circuit of the plates 135, 147 remains constant and no variation in the printed impression occurs. If, however, one cell is stronger than the other current passes to a control valve 74 and according to which cell is of higher E.M.F. current flows from a direct current circuit 75 to one or other of two multiplying valves 76, 77, and so a current passes to an induction coil 78 or 79 to unbalance the induced voltages in the poles 80, 81 of a split-phase motor 64 which rotates the rheostat arm 69 so as to ensure equality of light intensity of the produced design and that of the control drum. In a modification the scanning of the produced pattern is dispensed with, and the action of the scanning &c. devices at the control drum controls the intensity of shade of the produced design by controlling directly a rheostat similar in function to that shown on Fig. 15.