Coating processes – Nonuniform coating – Striping
Patent
1987-07-15
1989-04-04
Lusignan, Michael
Coating processes
Nonuniform coating
Striping
118211, 118218, 118219, 118226, 118232, 118257, B05D 500, B05C 100, B05C 114
Patent
active
048185710
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to methods and apparatus for the coating of articles by applying a band of coating material around a recipient surface of the article, the article being of curved (circular or otherwise) cross-section and the band being at a predetermined longitudinal position on the article and of predetermined width.
The invention is especially, though not exclusively, applicable to applying coatings to articles such as hollow, rigid or semi-rigid containers, for use in packaging and made of plastics materials, the coatings being of materials for improving the barrier properties of the container. By "barrier properties" we mean partly the ability of the container to resist ingress, through its walls, of air or other gases, micro-organisms or spores of micro-organisms, the object generally being to protect a food or other product subsequently packed in the container from spoilage by oxidation or microbial action for a period sufficiently long to give the product a desired shelf-life. The term "barrier properties" equally means the ability of the container to contain products pressurised above the ambient pressure, such as carbonated beverages, or foods or drinks packed under aseptic (sterile) conditions so that the internal pressure will not be significantly reduced.
Coatings applied by the method or by the apparatus of this invention may have the further or alternative purpose of decoration, for example by providing a coloured opaque or transparent surface.
BACKGROUND ART
Our co-pending U.K. patent application No. 8614527 describes a method of applying a barrier coating, of polyvinylidene chloride (PVdC) for example, to hollow plastics containers or other articles by directing a stream of the liquid coating material against the back surface of a "curtain plate" so that it spreads over the said back surface to fall as a curtain from a lower edge of the plate on to the article to be coated. This is an effective way of coating the greater part of the external surface of the article, but generally an area at the top of the article, above the uppermost level at which the curtain contacts it, remains uncoated.
There is a need for a reliable method of applying coating material in cases where, for example, the whole of the outside surface needs to be covered. Since in general coating material should not contaminate the inside of a hollow article, such a method should apply only as much coating material as is required for the area to be coated (though the amount must be sufficient), and should be able to place it accurately and in such a manner that the material not only remains where it is placed, but is not placed anywhere except where it is required.
Known coating methods such as spray coating, powder coating and flow coating, are too inaccurate for this purpose. Known printing techniques are in general not suitable because the coating materials tend to be more viscous than printing inks and are more difficult to handle. In particular it is desirable to provide as little opportunity as possible for the material to collect on any part of the apparatus and remain there for any appreciable length of time, since is will then coagulate into a solid form difficult to remove.
Known coating materials for which the present invention is suitable include water-based synthetic compounds (now commonly referred to in the trade as "latices"), or solvent-based formulations. Typical compositions of coating materials for improving barrier properties are PVdC, mentioned above and synthetic resins based on ethylene-vinyl alcohols (EVOH).
DISCLOSURE OF INVENTION
According to the invention in a first aspect, a method of applying a band of coating material around a recipient surface of an article of curved cross-section, at a predetermined longitudinal position on the article, the band being of predetermined width, comprises the steps of:
directing a stream of liquid coating material onto a moving donor surface of an elongate donor member while moving the latter along a first path, so as to charge the do
REFERENCES:
patent: 3677801 (1972-07-01), Hardy
patent: 3695223 (1972-10-01), Dunham
patent: 3710753 (1973-01-01), Birchall et al.
patent: 4275097 (1981-06-01), Shriver
patent: 4308818 (1982-01-01), Abe et al.
patent: 4370943 (1983-02-01), Watanabe et al.
Pilley, deceased Terence J.
Pilling Fred R.
Tester Colin A.
Lusignan Michael
Metal Box Public Limited Company
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