IES58151B2 - Process for the production of engraving transfers - Google Patents

Description

Process for the production of engraving transfers This invention relates to a process for the production of engraving transfers, for use when engraving glass, stone, tile, timber, or the like objects, hereinafter referred to collectively as a substrate except where specific reference is made to a particular type of substance, by sandblasting. By an engraving transfer is meant a mask created for each design to be engraved and comprising a pattern of open areas through which the sand passes to impinge on the substrate thereby resulting in an engraved design.

Glass engraving is carried out, for example, on flatware, holloware, barware and giftware. The actual engraving step is carried out by sandblasting using either a pressure pot blaster or a suction blaster. A transfer is applied to the object to be engraved and the rest of the object is masked off. The object is-then sandblasted and the exposed area is etched by the sand particles.

The objects may be engraved to one depth, known as single layer engraving, or to a number of depths, known as multi-layer engraving. Multi-layer engraving results in a more detailed etched image.

A process for the production of engraving transfers is known in which the transfers are produced by a silk screen method. First the artwork is drawn by hand and a paper positive is produced by camera. A negative is then made from the paper positive so produced and is placed on a silk screen coated with emulsion, which screen is then exposed to light. The unexposed areas, which were covered by the image on the negative, are then washed out. The outer edges of the screen are masked off with a paint like substance. The screen is then fitted to a screen printer such as a DEK 240 screen printer and a latexbased textile ink is applied to the screen. The image on the screen is printed onto tissue paper, which is then passed through a heater unit for curing thereof.

The resulting transfer is cut to size, a layer of glue is applied to the object to be engraved and the transfer affixed thereto. After sandblasting the transfer can be removed by steeping in warm water.

A problem with transfers made by the above process is that air bubbles can become trapped between the object and the transfer during the glueing step, such that when the object is sandblasted, the area of the transfer over an air bubble is susceptible to being blown away resulting in any unacceptable engraved piece which has to be discarded.

Another problem with these known transfers is that they cannot be used where the design requires very fine detail. An example of a finely detailed design would be a crest and/or name in small print engraved onto the base of a glass paper-weight. The engraved design must be small as it will be magnified by the paper-weight when viewed from above. Using the known transfers there can be a lack of definition and on occasions total loss of part of a'word.

It is an object of the present invention to overcome the problems of the above engraving transfers, and to produce transfers by means of which finely detailed designs can be engraved onto suitable substrates.

Accordingly, the invention provides a process for the production of engraving transfers for use in engraving a design onto a substrate, comprising applying a positive image of the design to a multi-layer liquid emulsion photosensitive film, exposing the positive image and photosensitive film to a UV light source which emits UV light in the range 370-420 nanometres, washing out the unexposed photosensitive film; and drying the resultant transfer, wherein the design is not supplied in camera ready form, and the positive image is produced by scanning the design into a computer, modifying the design using a computer aided design software package, and printing the modified design onto semi-transparent vellum paper.

The production of engraving transfers by the use of correctly exposed multi-layer liquid emulsion photosensitive film in accordance with the invention, allows for the engraving of finer detailed designs on the desired substrate than could be achieved heretofore.

Suitably photosensitive film with a thickness of about 3mm is used where shallow engraving up to 1mm in depth is required.

Suitably a photosensitive film with a thickness of about 5mm is used for deeper engraving.

Preferably, the UV light source is a 4 kilowatt metal halide bulb.

Further, preferably the positive image and the photosensitive film are placed at a distance of from 0.8 to 1 metre from the light source for an exposure time of from 60 to 300 seconds.

The exposure time is matched to the particular photosensitive film being used. As indicated above photosensitive film is available in various thicknesses, and the thicker the film the longer the required exposure time.

The computer aided design (CAD) modification includes redrawing of lines and other modifications necessary to improve definition.

By scanning the artwork into a computer equiped with CAD software, such artwork may be modified and brought to the required standard for the engraving process. The modified design may then be printed onto semi-transparent vellum paper, and the positive image produced used in the further steps of the engraving process. The printer used is preferably of laser printer quality.

The invention will be further illustrated by the following description of an embodiment thereof given by way of example.

Preparation of an engraving transfer for use in engraving onto a glass paper-weight The artwork, such as a crest with a company name in small letters - for a design to be engraved is supplied as a black and white bromide. A positive image of this artwork is created by photographic means and the resultant image is placed on a piece of 3mm thick multi-layer liquid emulsion photosensitive film. The positive image is placed emulsion side down on the photosensitive film and the assembly is placed in a vacuum frame to establish a tight contact.

The vacuum frame is then placed in a UV exposure unit which is provided with a 4 kilowatt metal halide UV light source, at a distance of 0.91 metre from the light source. The exposure unit is set for an exposure time of circa 200 seconds.

After exposure the exposed piece of film is washed out with high pressure water in a wash-out booth, using a hot/cold fed high pressure pump with a lance, fitted with a fine spray nozzle. The exposed photosensitive film is sprayed with warm water for approximately 90 seconds. This results in the unexposed film being washed away.

The film is then wiped with absorbent paper to remove excess water, and placed in a drying oven.

Adhesive is applied to the resultant engraving transfer (dried piece of photosensitive film) and/or the glass and the transfer is affixed to the base of the glass paper-weight. The unprotected area around the transfer is masked off and the piece is then transferred to a sandblasting unit. A single depth engraving to 0.8 mm in depth is produced using a suction blaster in a Hunziker ST700 cabinet, at an air pressure of between 20 and 40 pounds per square inch.

The piece is sandblasted for approximately 45 seconds and is then removed from the cabinet.

The masking material is then removed from the glass paperweight and the paper-weight placed in warm water to steep, so as to achieve removal of the transfer.

Once the transfer had become detached, the paper-weight is removed from the warm water and washed, using a detergent, and dried.

The engraved design has good definition with all the letters begin clearly legible.

In the case of multi-layer engraving the sandblasting step is carried out using a pressure blaster, at an air pressure of between 20 and 10 40 pounds per square inch.

This invention is not limited to the embodiment described above which may be modified and/or varied without departing from the scope of the invention.

Claims (3)

CLAIMS:

1. A process for the production of engraving transfers for use in engraving a design onto a substrate, comprising applying a positive image of the design to a multi-layer liquid emulsion photosensitive film, 5 exposing the positive image and photosensitive film to a UV light source which emits UV light in the range 370-420 nanometres, washing out the unexposed photosensitive film, and drying the resultant transfer, wherein the design is not supplied in camera ready form, and the positive image is produced by scanning the design into a computer, 10 modifying the design using a computer aided design software package, and printing the modified design onto semi-transparent vellum paper.

2. A process as claimed in Claim 1, wherein the UV light source is a 4 kilowatt metal halide bulb.

3. A process as claimed in Claim 1 or 2, wherein the positive 15 image and the photosensitive film are placed at a distance of from 0.8 to 1 metre from the light source for an exposure time of from 60 to 300 seconds.