Coating processes – Direct application of electrical – magnetic – wave – or... – Electrostatic charge – field – or force utilized
Patent
1997-06-09
2000-02-29
Parker, Fred J.
Coating processes
Direct application of electrical, magnetic, wave, or...
Electrostatic charge, field, or force utilized
427482, 427485, 427486, 118629, 118634, B05D 104, B05B 5047
Patent
active
060306653
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The subject invention concerns a method of applying talcum powder or a powder of super-absorbent type (SAP) or the like, the latter comprising polyacrylate and/or a salt, such as a sodium salt, on a strip, e.g. a power cable.
BRIEF SUMMARY OF THE INVENTION
The main purpose of the invention is to provide a method and a device for efficient application of such powders on the strip in question.
Surprisingly, it has been found that said powders may be very efficiently applied on the strip in question, which could e.g. be a power cable, on which the talcum serves as a lubricant between two insulating layers, and a primarly purpose of the super-absorbent powder is to absorb liquid upon damages to the cable cover and on account of the swelling caused thereby to form a seal at the site of the rupture with the aid of a friction charger wherein polarizing ducts are used through which the powder material is made to pass. In this case, the ducts emanating from the friction charger debouch into a treatment chamber through which the strip to be treated is made to pass. The mouths of the ducts into the treatment chamber are distributed circumferentially with respect to said strip in such a manner that charged powder moves towards said strip from several directions simultaneously.
Further characteristics of the invention will appear from the dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will be described in the following with reference to the accompanying drawing, wherein
FIG. 1 is a schematical view of an installation in accordance with the invention, and
FIG. 2 likewise is a schematical representation in cross-sectional view of a part of the installation, viz. through the treatment chamber in which powder material is applied on a strip passing through the chamber.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1 numeral reference 1 is used to designate a movable strip being advanced in the direction of arrow 2. The advancement could be continuous or intermittent. In accordance with the embodiment illustrated the strip 1 is a metal conductor for a power cable. Numeral reference 3 designates a treatment chamber which preferably abuts tightly against the strip 1 at its two ends, for instance with the aid of bristled through-apertures. Numeral reference 4 designates a supply container holding the powder material to be applied on the strip 1. The material in question is of talcum powder type or a super-absorbent powder (SAP) or the like. The latter material contains polyacrylate and/or a salt, such as a sodium salt. The sodium salt may contain polyacrylate. Preferably, the powder is maintained in a fluidized state inside the supply container by admission of air or other gas through a perforated inner bottom wall 5. Prior to its passage through the interior bottom wall the gas is distributed via an intermediate space 6 between the interior bottom wall 5 and the outer bottom wall 7 of the container. Numeral reference 8 designates a powder pump which is connected to a friction charger 10 via a powder supply line 9. The friction charger 10, which could e.g. be configured as disclosed in Applicants' U.S. Pat. No. 4,597,534, is formed with a connection 11 for inlet of air or other propelling gas for the purpose of forcing the powder through the charging ducts provided in the friction charger. The friction charging ducts inside the friction charger 10 communicate with mouths or nozzles 13 positioned in the treatment chamber 3, by way of prolongation lines 12. The ducts inside the friction charger 10 are polarized in such a manner that they impart the desired charge to the powder material passing through the charger. When the powder is a talcum powder, the ducts preferably consist of polytetrafluoroethylene, otherwise they preferably are of nylon, but also other materials providing a negative charge, such as e.g. polyethylene plastic, are conceivable in the latter case as also other materials which like tetrafluoroethylene give a positive charge wi
REFERENCES:
patent: 2657339 (1953-10-01), Hampf
patent: 2781280 (1957-02-01), Miller
patent: 3598626 (1971-08-01), Probst et al.
patent: 4357900 (1982-11-01), Buschor
patent: 4597534 (1986-07-01), Ruud
patent: 5196456 (1993-03-01), Nguyen et al.
"The Science of Powder Coatings", Bate et al., vol. 2, pp. 69-71, 1994.
Nordson Corporation
Parker Fred J.
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