Coating processes – Coating remains adhesive or is intended to be made adhesive – Heat sensitive adhesive
Patent
1987-03-19
1988-05-10
Pianalto, Bernard D.
Coating processes
Coating remains adhesive or is intended to be made adhesive
Heat sensitive adhesive
427348, B05D 510
Patent
active
047434694
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of applying adhesive to containers in labeling machines.
A method of this type is shown, for example, in FIG. 12a, page 20 of the September 1975 edition of "Handbuch der Etikettiertechnik" published by Hermann Kronseder, Neutraubling, German Federal Republic. In this method, a bead of hotmelt is "contactlessly" applied to a container which is to be labeled and is transported by a nozzle for hotmelt. The container is subsequently advanced from this adhesive applying station to a magazine for labels. Along such path, the container is additionally caused to rotate about its axis.
At the high speeds of advance normally employed in labeling machines today, this known method has the result that the hotmelt applied to the container is flung from the outer surface of the container due to the rotational speed of the container. In modern machines, the containers rotate at a tangential velocity of 150 to 250 meters per minute. The hotmelt, which is still in a flowable state, enters the labeling machine and causes the machine to become unusable within a very short period of time.
The speed of advance of the container must be high to insure that the heated hotmelt, which is sticky only in this condition, is capable of removing a label from the label magazine. The label is then rolled around the container due to the rotation of the container. Since it is unavoidable that the applied spot or bead of hotmelt is raised, the label is observed to have small projections in this area. These are regarded as unsightly by consumers.
The "contactless" application of the hotmelt overcomes the drawbacks which arise in those methods where the glue or hotmelt is applied to the exterior of the container via gluing rollers. The latter mode of application brings with it the danger of soiling due to contaminants on the outside of the container.
Thus, although the "contactless" glue application method has substantial advantages, it has not been possible to employ such method in practice to the satisfaction of the manufacturer of the labeling machines and of the consumer.
It is an object of the invention to further develop a method of the character described such that the "contactlessly" applied adhesive bead, or the "contactlessly" applied adhesive spot, is distributed over as large an area as possible without the fear of adhesive particles being carried into the surrounding machine components.
Spray pistols which may be used for the application of hotmelt and are capable of covering large areas with glue are known. Here, similarly to spray pistols for lacquer, the hotmelt discharged from the nozzle is atomized and brought onto the object support by a unidirectional stream of pressurized air. With this known method, particles of hotmelt cannot be prevented from entering the atmosphere and being introduced into the surrounding machine components, e.g., of labeling machines, thereby causing the machine to become unusable.
In the method of the invention, this drawback of the known method employing spray pistols is avoided by applying the pressurized air to the adhesive only after it has been deposited on the object support.
The West German Offenlegungsschrift No. 34 38 041 discloses a method which operates with a pneumatic doctor and in which flowable coating masses applied to bands of material are subjected to an aftertreatment. During normal operation, the applicator deposits an excess of the coating mass on the band and this excess is removed by the pneumatic doctor. However, even when the supply of the coating mass is adjusted in such a manner that no substantial excess of coating mass exists, the pneumatic doctor still has a favorable effect on the quality of the coating.
Advantageous embodiments of the invention are set forth in the dependent claims.
In addition to the advantages outlined previously, the method of the invention makes it possible to cool or heat hotmelt by means of the air stream so that the setting characteristics of the hotmelt can be controlled in dependence upon its chemical composit
REFERENCES:
patent: 2396946 (1946-03-01), Grupe
patent: 3953626 (1976-04-01), Suzuki et al.
patent: 4460631 (1984-07-01), Stegmeier et al.
Kontler Peter K.
Langguth GmbH & Co.
Pianalto Bernard D.
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