Photography – Fluid-treating apparatus – Having fluid filter
Reexamination Certificate
1999-02-26
2001-05-01
Popovics, Robert J. (Department: 1723)
Photography
Fluid-treating apparatus
Having fluid filter
C396S617000, C396S626000, C396S631000, C210S744000, C210S783000, C210S805000, C210S122000, C210S167050, C210S194000, C210S248000, C210S255000, C210S387000, C210S400000, C210S456000
Reexamination Certificate
active
06224273
ABSTRACT:
The present invention relates to an improved engraving machine for manufacturing a photopolymer printing block, which is utilisable for producing printed matter by flexography, typography or dry offset; it also relates to a process for separating the constituents of the engraving both contained in said machine.
It is already known that a printing block for flexography or typography can be obtained by exposing a sensitive photopolymer plate to ultraviolet rays and interposing a negative film, which leaves the areas which need to come into relief on the finished printing block exposed to the rays, this constituting the impression stage.
The rays harden these areas, and the material of the protected surface is then removed by brushing it with planar or rotary brushes, or by using pulverisation jets; a solvent or water acts as the damping agent, and the operation is continued until the areas which have been exposed are sufficiently in relief, this constituting the so-called engraving stage.
In the course of the engraving, the water becomes laden, then saturated, with particles of polymer, dissolved and/or in suspension: therefore, it is necessary to change the engraving bath regularly.
There is a problem relating to the saturated solution, which has to be treated in a treatment device independent of the engraving machine, then thrown away. The treatment of the solution never allows the total elimination of the polymer particles, so there is a problem relating to the protection of the environment.
Known engraving tanks also have other disadvantages;
soiling of the brushes: the equipment needs to be regularly cleaned;
reduction in the volume of the bath due to evaporation: hence a faster build-up in the concentration of polymer and the need to add quantities of water; and
increase in the engraving time due to the soiling and/or evaporation of the bath.
Moreover, devices are known, for example in EP-430,233 and DE-3,338,134, having an engraving tank and a separation circuit for the constituents of the engraving bath set apart from this engraving tank, the liquid being injected back into the tank continuously after separation of the constituents.
In the document EP-430,233, the separation is achieved by decanting or filtering means, and it is impossible to replace such means in the course of engraving when they become saturated, hence the occurrence of breakdowns and the need to stop the liquid circulation in order to carry out a replacement.
In the document DE-3,238,134, the separation is achieved by a succession of decanting tanks in a complicated and cumbersome installation.
The invention seeks to find a solution to the set problem by overcoming all the above-mentioned disadvantages.
SUMMARY OF THE INVENTION
The solution according to the invention consists of a process for the manufacture of flexible printing blocks, which are utilisable for producing printed matter by flexography, typography or dry offset, of the type comprising:
a stage for polymerising areas by exposure to ultraviolet rays;
a stage for engraving non-polymerised areas by immersion and brushing in an engraving bath contained in an engraving tank, said bath becoming loaded with dissolved particles or particles in suspension during the engraving stage; and
a separation of the constituents of the engraving bath, with the liquid obtained at the time of separation being injected back into the engraving tank,
characterised in that the separation consists of filtration, during which the particles are progressively eliminated.
A device according to the invention comprises:
an engraving tank containing a bath and brushes; and
a device for separating the constituents of the bath, operating in a closed circuit, with the liquid obtained after separation of the constituents of the bath being injected back into the engraving tank,
characterised in that the separation device comprises a means of separation formed from a filter which can be replaced during the engraving as it becomes saturated.
The invention will be better understood by means of the description which follows, with reference to the single accompanying Figure.
REFERENCES:
patent: 4370406 (1983-01-01), Jones
patent: 5124736 (1992-06-01), Yamamoto et al.
patent: 5149441 (1992-09-01), Welch, II et al.
patent: 5221468 (1993-06-01), Fox et al.
Popovics Robert J.
Schnader Harrison Segal & Lewis LLP
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