Patent GB-737076-A (GB)
Title: Method and apparatus for reproducing images
Inventor: HUEBNER WILLIAM CARL
IPC: G03G15/34
Filed: 1953-12-14
Abstract: 737,076. Producing photographs electrically. HUEBNER CO. Dec. 14, 1953, No. 34723/53. Class 98 (2). [Also in Group XVI] A method of reproducing images directly from a copy, on print-receiving material consists of projecting light rays from the image to be copied through a lens and upon a light sensitive target to cause emission therefrom of streams of electrons in areas corresponding to the image on the copy, simultaneously positioning the print receiving material closely adjacent the electron emitting surface of the target but spaced therefrom by an air-gap and in the path of the streams of electrons, so that the electrons directly strike the print receiving material, and simultaneously introducing into the air gap printing material in the form of a cloud to be acted upon by the streams of electrons and propelled thereby to the printreceiving material to form directly on the surface thereof, adjacent to the target, the finished reproduced image. In the form of Figs. 1 and 2, the apparatus consists of a transparent cylinder 12 rotatable on a fixed axle 11 and supporting a strip 28 bearing the image to be reproduced. For use when the strip is transparent a stationary hood 14 is provided inside the cylinder enclosing an elongated lamp 17 the rays from which are directed, by a reflector 18, through a slit 16 in the hood, through the strip 28, through a lens 31 and on to the target member 42. A similar cylinder 23 rotatable on a fixed axle 53 supports a strip 29 on which the image is to be reproduced. The cylinders 12, 23 are rotated from shafts 21, 21a through skew gears 19, 20 and 26, 27. The shafts 21, 21a are connected through a change speed gear-box 22 so that the relative speeds of the cylinders can be varied. This allows the lens 33 to be adjusted along its axis in guide 32 so that the reproduction on strip 29 is the same size as, or a different size from the image on the strip 28. Both strips have marginal perforations engaged by equally spaced pins 30 on the cylinders to avoid slip during rotation of the cylinders. A hood 35 closely fitting the cylinder 23 extends across the width of the strip 29 and has a nozzle 37 adapted to direct printing material in the form of a cloud into the printing zone. The cloud of printing material is supplied through a conduit 54 which may be connected selectively with any one of conduits 57, for example supplying different colours. The cloud is charged by passing between electrode bars extending the length of the hood and mounted on brackets 55. A similar hood 36 on the other side of the printing zone has a slit 38 adapted continuously to withdraw the cloud of printing material from the air-gap. The printing zone is aligned with the slit 16 and lens 31 and is closed by a transparent plate 39 supporting a very thin transparent metallic film such as an aluminium deposit, forming the target member 42. The plate 39 is covered by a sheet of opaque material 40 having a slot extending the full width of the strip 29 allowing the light passing through the lens to fall on the target 42 and activate a layer 43 of light-sensitive material on the other side thereof. This layer 43 may be of selenium or germanium or other suitable photo-electric material. Electrons released from the light-sensitive layer by the light falling on it, are accelerated towards the copy strip 29 by the action of an electro-static field maintained in the air-gap between an electrode 47 inside the cylinder 23 and the metallic target film 42, these being connected to opposite poles of a source of high potential. The electronstream may be further guided, if necessary, by the action of a magnetic field produced by electromagnets 48, 49 clamped to axle 53. The electrons passing through the air gap and strip 29 serve to draw particles of printing medium towards the strip and so reproduce on it an image corresponding to the light image projected on to the light sensitive layer. The strip 29 is discharged before and after the printing operation by earthed rollers 69. In the case where the image bearing strip 28 is opaque light is directed on to it from the front and reflected through the lens 33. To this end, lamps 70 are provided above and below the central plane of the cylinders, the light being directed on to the strip 28 by shields 71. A switch 66 causes energization either of lamp 17 or lamps 70. The circuit supplying the lamps includes a rotating commutator adapted to switch the lamps rapidly on and off so that a pulsating light is obtained. In an alternative construction for the target 42 it consists of a fine mesh, the wires of which are coated with light-sensitive material. Multicolour printing.-The machine may be adapted for multicolour printing by using in turn a series, e.g. three image bearing strips 28 having images corresponding to the particular colour areas for the reproduction. The conduit 54 is for each such strip connected to the conduit 57 which supplies a cloud of the corresponding colour printing material.