Nordson Corporation

William R Rehman

Walter H Cobbs, Jr

Harry J Lader

James C Smith

James W Messerly

Robert George Shong

Joseph G Schroeder

Gerald W Crum

Jeffrey A Perkins

Herman E Turner, Jr

Jeffrey S Noss

Michael R Sanner

James L Kennon

Jan L Shanaberger

Robert L Wacker

Dale R Juhn

Kevin C Becker

Richard C Morgan

James R Hollstein

A plurality of unconventional negative tribo-charging materials are described for use as the powder contact surfaces in tribocharging and corona powder spray guns, gun components, and powder delivery system components. The invention also provides a short barrel tribo-charging powder spray gun having an interchangeable powder contact insert and nozzle, with turbulence inducing air jets. The invention further provides novel tribocharging and corona gun designs. Improved powder coating systems are made possible wherein, for example, negative tribo guns can be utilized with negative corona guns to coat different parts of the same workpiece in a powder coating system.

Unipolarity powder coating systems including improved tribocharging and corona guns

Powder charge sleeve

A powder spray coating system includes a power source and an electrical supply line connected to the power source. A spray gun sprays powder in a spray pattern onto a part. The spray gun includes an electrode which charges powder as the powder is dispensed from the gun toward the part. The electrode is connected to the electrical supply line. A first current sensing device is located in the electrical supply line measuring gun current between the power source and the electrode. An ion collector or ABI probe is mounted with the gun for collecting free ions produced by the electrode. The collector has a forward portion positioned near the spray pattern and is spaced from the electrode. The collector is connected to a ground line. A second current sensing device is located in the ground line measuring back current between the ion collector and ground. A controller is connected between the power source and the electrode to control the gun current. The controller is also connected to the first and second current sensing devices for controlling the gun current in accordance with the difference between the measured gun current and the back current. By automatically controlling the current between the gun and the part, the present invention controls the field strength and the current between the tip of the gun and the ABI probe, making unnecessary adjustment of the position of the ABI probe in order to maximize the benefits of the probe in situations where the distance between the gun and the part changes.

Spray gun having a current monitored anti-back-ionization probe

In a triboelectric powder spray gun in which a charge is imparted to the powder triboelectrically by repeated impacts of the powder with contact surfaces, the charging effectiveness of the gun is enhanced by using an electrode to produce corona treatment of the contact surfaces. The corona treatments discharge the contact surfaces and eliminate the need for adjacent grounds with the powder flow path.

Triboelectric powder spray gun with internal discharge electrode and

An apparatus and method for utilizing and controlling finer particles in a powder coating system returns the finer particles to the spraying apparatus to be sprayed on parts by the system. Finer particles are continuously removed from the system by application onto parts, and the accumulation of fines is thereby prevented. The finer particles may be sprayed through specially adapted spray guns, which also permits the utilization of the special advantages of spraying fine powder materials. By removing fine powder particles from the system before they build up, the present invention improves the powder coating operation in various respects.

System for controlling and utilizing finer powder particles in a powder

A diaphragm assembly includes a pair of superposed flexible diaphragms adhesively secured to an annular spacer ring. The space between the diaphragms and the interior of the rings is filled preferably with de-ionized water. The resistivity of the water is monitored to detect conductivity changes upon leakage or diaphragm rupture when pumped materials or pump lubricant mix with the water. Diaphragm assembly and rupture detection methods are disclosed.

Dual diaphragm apparatus with diaphragm assembly and rupture detection

In an apparatus and method for measuring the strength of an adhesive bond, a dispenser applies adhesive to a substrate for a prescribed period of time, a conveyor moves the substrate to a compressing station within a preselected open time, after which time a compressor compresses the substrate against another substrate to form an adhesive bond therebetween, the bond being formed under a substantially constant compression force and for a preselected compression time. During the latter portion of the compression time, the bonded substrates are moved together at a substantially constant rate of speed through a transition distance, one of the substrates contacting a stop plate at the end of the compression time to prevent further movement while the other of the substrates continues at the substantially costant rate of speed to break the bond. A load cell measures the maximum pull force required to break the bond and also provides a real time analog signal for the pull force of the bond during tension, thereby to obtain an indication of the total energy expended in breaking the bond.

Method and apparatus for bond testing

A nozzle assembly adapted with an adhesive spray gun for forming a liquid adhesive/gas solution into a foam includes a nozzle formed with a chamber having a rearward end and a forward discharge orifice which is maintained at a pressure less than that required to maintain the gas in solution in the liquid. A turbulence plate having a front surface formed with a notch is mounted to the spray gun such that the notch extends within the rearward end of the chamber. The notch is formed with at least two input ends and a turbulence zone therebetween. The liquid/gas solution is conveyed to each input end of the notch where a separate stream of solution is formed. The streams move along the notch from each input end toward the turbulence zone of the notch where they impact one another within the chamber. Agitation of the liquid/gas solution caused by impacting of the separate streams, in the presence of the reduced pressure within the chamber, results in the partial or initial formation of a homogeneous, closed cell solid foam within the chamber prior to emission from the discharge orifice.

Adhesive foam generating nozzle

A foam generating nozzle is provided for converting a liquid containing a gas maintained under pressure in solution in the liquid, to a foam for application to a substrate. Complete foaming of the solution is accomplished prior to discharge from the nozzle. This assures in some applications complete atomization before contact with the substance to be coated.

Foam generating nozzle

Surface coating methods and compositions are disclosed which eliminate many of the disadvantages associated with known coating processes from pollution, equipment, materials, energy, labor and cost standpoints. According to techniques described, thermosetting liquid compositions containing film-forming solids are formulated, then conveyed in the foam state toward a surface, and upon foam disintegration, form a film of solids on the surface. The foamable thermosetting resin compositions contain a curable resin having a free hydroxyl or carboxyl group, a curing agent consisting of a lower (C.sub.1 -C.sub.4) alkoxylated amine for reaction with the resin hydroxyl or carboxyl group and a liquid blowing agent consisting of a C.sub.1 -C.sub.4 alkanol which is also a by-product of the thermosetting reaction.

Foamable thermosetting compositions and methods of coating therewith

A process for providing a substrate such as a polyethylene terephthalate container with a gas barrier coating of a copolymer of vinylidene chloride is disclosed. The process includes locating the container to be coated in close proximity to one or more airless spray nozzles and impacting the outside surface of the container with a stream of a stabilized aqueous polymer dispersion such as an aqueous polyvinylidene chloride dispersion. The impacting force of the stable polyvinylidene chloride dispersion on the surface of the container is sufficient to cause selective destabilization of the dispersion at the surface interface to form a gel layer containing the polymer in the continuous phase. This gel layer serves as an adhesive layer for an overlying layer of the aqueous polymer dispersion as a continuous uniform coating. The resulting wet coating does not sag or run off. The coating on the container is then dried in a controlled atmosphere to complete the gel formation throughout its thickness whereupon it is further dried to remove the water from the coating and to collapse the gel to form a film without distorting the container. The dried coating is smooth, uniform and uniformly transparent. In operation, the overspray can be collected and returned to achieve greater than 95% material efficiency. The process can be carried out in a continuous manner to provide a continuously moving series of containers with a uniformly transparent, gas barrier polyvinylidene chloride coating at production rates suitable for commercial applications.

Process for coating substrates with aqueous polymer dispersions

A method and apparatus for dispensing liquid compositions. The apparatus includes a reservoir for containing the liquid at a low temperature, a metering device for transferring the liquid to a circulating loop at a higher temperature, a heater/mixer for coincidentally heating and mixing the liquid in the loop and means for dispensing the liquid from the loop. The invention is particularly useful for dispensing liquid adhesive and coating compositions, including thermosetting polymers, heat sensitive polymers or plastisols and other dispersed liquid systems. In addition, mixtures of polymeric liquids with other components such as gases, solvents or liquid blowing agents may be employed with uniformity of composition for dispensing foams or atomizable paints.

Method and apparatus for dispensing liquid compositions

A process for providing a substrate such as a polyethylene terephthalate container with a gas barrier coating of a copolymer of vinylidene chloride is disclosed. The process includes locating the container to be coated in close proximity to one or more airless spray nozzles and impacting the outside surface of the container with a stream of a stabilized aqueous polymer dispersion such as an aqueous polyvinylidene chloride dispersion. The impacting force of the stable polyvinylidene chloride dispersion on the surface of the container is sufficient to cause selective destabilization of the dispersion at the surface interface to form a gel layer containing the polymer in the continuous phase. This gel layer serves as an adhesive layer for an overlying layer of the aqueous polymer dispersion as a continuous uniform coating. The resulting wet coating does not sag or run off. The coating on the container is then dried in a controlled atmosphere to complete the gel formation throughout its thickness whereupon it is further dried to remove the water from the coating and to collapse the gel to form a film without distoring the container. The dried coating is smooth, uniform and uniformly transparent. In operation, the overspray can be collected and returned to achieve greater than 95% material efficiency. The process can be carried out in a continuous manner to provide a continuously moving series of containers with a uniformly transparent, gas barrier polyvinylidene chloride coating at production rates suitable for commercial applications.

High solids coating methods and apparatus are disclosed which eliminate many of the disadvantages associated with known coating processes. The techniques disclosed require only a minor amount of a volatile solvent to achieve atomization and application of a paint or other coating material. High solids coating compositions containing about 70-99% by weight solids are atomized and coated. This method also enables polymeric compositions having high molecular weight to be employed as coating materials. According to techniques described, liquid compositions containing film-forming solids are kept under pressure with a minor amount of a highly volatile solvent of from about 1 to 30% by weight, even as low as about 1-10% by weight, at a temperature above the normal boiling point of the solvent. Such a composition is then atomized by releasing the pressure upon a stream of the composition at a temperature above the normal boiling point of the solvent and below the minimum foam temperature at atmospheric pressure for the composition. The film-forming solids are thus conveyed with or without an external atomizing means.

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Vermilion, OH, United States of America

William R Rehman