Electric heating – Metal heating – By arc
Patent
1986-10-10
1989-02-21
Albritton, C. L.
Electric heating
Metal heating
By arc
B23K 2600
Patent
active
048067270
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase application corresponding to PCT/AT86/00009 filed Jan. 27, 1986 and based upon an Austrian application A406/85 filed Feb. 12, 1985.
FIELD OF THE INVENTION
The invention relates to a process and an apparatus for the production of a screen printing stencil.
BACKGROUND OF THE INVENTION
Screen printing stencils can be produced by galvanoplastic means or by the formation of so-called photostencils. For this purpose, an already permeable surface array, e.g. a perforated foil or a screen fabric, for cylindrical stencils in form of a cylinder, is coated with a light-sensitive lacquer. After exposure to light of the pattern through a film superimposed over the light-sensitive lacquer layer and provided with the desired pattern, and subsequent development, one obtains a photostencil whose apertures are partly closed by the hardened light-sensitive lacquer, and are partly permeable to ink.
The production of such photostencils is very laborious. For each photostencil to be produced, a color separation pattern must be drawn, from which in the production of the film a line drawing must be prepared. Then the light-sensitive lacquer can be applied to the perforated foil. The coating of the foil must be done uniformly. After coating, the photo-sensitive lacquer is dried. In the meantime, after thoroughgoing inspection and retouching, the negative is converted in a contact frame to a halftone positive which has the same size as the photostencil to be produced.
The inspection and exact cutting of the combined film in an exact height of repeat and width of master is a very significant and labor intensive procedure incidental to the production of the film.
One then stretches the completed combined film over the photostencil blank, and carry out the exposure. The exposed stencil is then developed, and subsequently placed in a fusion chamber, whereby the light-sensitive lacquer hardens.
Subsequently, the stencil is again inspected and retouches. It can be seen that this procedure is very costly.
OBJECT OF THE INVENTION
It is the task of the invention to provide an improved process and apparatus for the production of photostencils where labor and thus cost are significantly reduced, but such that the accuracy of the stencil does not suffer.
SUMMARY OF THE INVENTION
In a process for the production of a screen printing stencil, in which a foil is perforated in a regular manner, the foil is then coated so that the perforations are closed, and finally from a portion of the perforations the coating material is removed again in accordance with a desired pattern, the process of the invention provides that the coated foil is stretched, if required after drying, and a laser beam is trained as the pertinent places of the coated foil corresponding to the desired pattern to remove the coating and expose the perforations in those locations.
The apparatus for the production of a screen printing stencil, according to the invention, can comprise a stretching means for the foil and, in the plane parallel to the stretching means, guides for a laser optical system upon which a carrier carrying said laser optical system is movably disposed. A control unit for the carrier and the laser optical system is also provided.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing:
FIG. 1 shows schematically an apparatus according to the invention in isometric projection;
FIGS. 2 and 3 are elevational view of the stretch cylinder support.
SPECIFIC DESCRIPTION
On base 1 which is stiff and resistant to bending and warping, bearings 2,3 are provided for a stencil stretcher drum 4.
Parallel to the axis of stencil stretcher drum 4, parallel guides 5 are provided for a guide carriage 6.
The control switches 27 of the apparatus are only illustrated schematically.
The stencil stretcher drum 4 is a circular cylinder expandable in direction of its perimeter and running true when driven; the drum is supported only on one side during the mounting and removal of the stencils. It there
REFERENCES:
patent: 3696742 (1972-10-01), Parts et al.
patent: 3981237 (1976-09-01), Rhodes
patent: 4328410 (1982-05-01), Slivinsky et al.
patent: 4352973 (1982-10-01), Chase
Albritton C. L.
Dubno Herbert
Schablonentechnik Kufstein Gesellschaft M.B.H.
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