Adhesive spray gun and nozzle attachment

Abstract

An apparatus for spraying heated hot melt adhesive in elongated strands or fibers in a controlled, spiral pattern upon a substrate comprises a spray gun having a nozzle formed with an adhesive delivery passageway and an air delivery passageway both of which terminate at the base of the nozzle. A nozzle attachment in the form of an annular plate is mounted to the base of the nozzle by an end cap. The annular plate is formed with a throughbore which receives hot melt adhesive from the adhesive delivery passageway and ejects an adhesive bead through a nozzle tip formed on the plate. An annular groove formed in the plate facilitates the drilling of air jet bores therein at an angle relative to the throughbore and adhesive bead ejected therefrom. The air jet bores receive pressurized air from the air delivery passageway and direct the pressurized air substantially tangent to the adhesive bead to form elongated adhesive fibers and to impart a spiral motion to the elongated fibers so that they are formed in a compact spray pattern for deposition onto a substrate.

We claim: 
     
       1. A nozzle attachment for use in an apparatus for spraying hot melt adhesive which includes a gun body having a nozzle formed with an adhesive passageway for conveying heated hot melt adhesive and an air delivery passageway for conveying pressurized air, said nozzle attachment comprising: a one-piece annular plate formed with a first surface on one side of said plate, and a second surface on an opposite side of said plate having a nozzle tip extending outwardly therefrom;   said plate being formed with a throughbore extending between said one side and said nozzle tip, said plate being adapted to mount to said nozzle of said gun body so that said throughbore communicates with said adhesive passageway in said nozzle for receiving heated hot melt adhesive, the hot melt adhesive being ejected from said nozzle tip in said annular plate to form an adhesive bead;   said plate being formed with a substantially V-shaped annular groove forming first and second sidewalls each extending inwardly from said first surface toward said second surface and intersecting one another, said annular groove being adapted to communicate with said air delivery passageway in said nozzle of said gun body;   said plate being formed with a plurality of bores extending from said annular groove in communication with said air delivery passageway to said second surface for transmitting air therethrough, said bores each having a longitudinal axis extending substantially perpendicular to one of said first and second sidewalls of said V-shaped annular groove, said bores being formed at an angle with respect to said throughbore in said plate to direct pressurized air flowing therethrough substantially tangent to the outer periphery of said adhesive bead ejected from said nozzle tip to form said adhesive bead in elongated adhesive fibers and to impart a twisting motion to said elongated adhesive fibers to form a spiral spray pattern of elongated adhesive fibers for deposition on a substrate.   
     
     
       2. The nozzle attachment of claim 1 in which said bores in said plate are formed at an angle of about 30° relative to the longitudinal axis of said throughbore in said plate. 
     
     
       3. The nozzle attachment of claim 1 in which the longitudinal axis of each said bores forms an angle of approximately 10° relative to a vertical plane passing through the longitudinal axis of said throughbore, the pressurized air ejected from said bores thereby being directed through said bores substantially tangent to the outer periphery of said adhesive bead ejected from said nozzle tip. 
     
     
       4. The nozzle attachment of claim 1 in which the diameter of said throughbore and the diameter of said air jet bores are in the range of about 0.010 to 0.040 inches. 
     
     
       5. The nozzle attachment of claim 1 in which the diameter of said throughbore is in the range of about 0.0175 to 0.0185 inches, and the diameter of said air jet bores is in the range of about 0.017 to 0.019 inches. 
     
     
       6. Apparatus for spraying hot melt adhesive, comprising: a gun body having a nozzle formed with an adhesive passageway communicating with a source of heated hot melt adhesive and terminating in an adhesive discharge opening, said nozzle being formed with an air passageway communicating with a source of pressurized air and terminating in an air chamber;   a one-piece annular plate formed with a boss extending outwardly from a first surface of said plate and a nozzle tip extending outwardly from a second surface of said plate, said plate being formed with a throughbore extending between said boss and said nozzle tip;   said plate being formed with a substantially V-shaped annular groove forming first and second sidewalls each extending inwardly from said first surface toward said second surface thereof, and a plurality of air jet bores extending between said annular groove and said second surface at an angle relative to said throughbore, said air jet bores each having a longitudinal axis substantially perpendicular to one of said first and second sidewalls of said V-shaped annular groove;   cap means for mounting said plate to said nozzle of said gun body so that said throughbore formed between said boss and said nozzle tip communicates and said annular groove and spaced air jet bores communicate with said air chamber in said nozzle, said throughbore receiving heated hot melt adhesive from said adhesive discharge opening and ejecting the heated hot melt adhesive through said nozzle tip to form an adhesive bead, said air jet bores receiving pressurized air from said air chamber and directing the pressurized air substantially tangent to the outer periphery of said adhesive bead to form elongated adhesive fibers and to impart a twisting motion to said elongated adhesive fibers to form a spiral spray pattern of elongated adhesive fibers for deposition on a substrate.   
     
     
       7. The apparatus of claim 6 in which said nozzle of said gun body is formed with a seat which receives said boss of said plate forming a fluid-tight seal therebetween. 
     
     
       8. The apparatus of claim 6 in which a portion of said nozzle of said gun body is formed with external threads, said cap means comprising a cylindrical-shaped member formed with a throughbore defining an inner wall having threads adapted to mate with said external threads of said nozzle, said cylindrical-shaped member being formed with an annular seat which receives and supports said plate, said cylindrical-shaped member being threaded onto said nozzle to place said throughbore of said plate in communication with said adhesive discharge opening in said nozzle. .Iadd. 
     
     
       9.  A nozzle attachment for use in an apparatus for spraying hot melt adhesive which includes a gun body having a nozzle formed with an adhesive passageway for conveying heated hot melt adhesive and an air delivery passageway for conveying pressurized air, said nozzle attachment comprising: a one piece annular plate formed with a first surface on one side of said plate, and a second surface on an opposite side of said plate having a nozzle tip extending outwardly therefrom;   said plate being formed with a throughbore extending from said first surface through said nozzle tip, said throughbore having an axis, means mounting said plate to said gun of said gun body so that said throughbore communicates with said adhesive passageway in said nozzle for receiving heated hot melt adhesive, the hot melt adhesive being ejected from said nozzle tip in said annular plate to form an adhesive bead;   said plate being formed with an annular surface, said annular surface sloping relative to the axis of said throughbore;   said plate being formed with a plurality of bores extending from said annular surface through said plate, said bores being in communication with said air delivery passageway;   each of said bores having a longitudinal axis extending substantially perpendicular to said annular surface, said bores being formed at an angle with respect to said throughbore in said plate to direct pressurized air flowing therethrough substantially tangent to the outer periphery of said adhesive bead ejected from said nozzle tip to form said adhesive bead into elongated adhesive fibers and to impart a twisting motion to said elongated adhesive fibers to form a spiral spray pattern of elongated adhesive fibers for deposition on a substrate. .Iaddend. .Iadd.   
     
     
       10.  The adhesive attachment of claim 9 in which said annular surface is of frusto conical configuration. .Iaddend. .Iadd.11. The adhesive attachment of claim 9 in which said annular surface forms one wall of a groove. .Iaddend. .Iadd.12. The adhesive attachment of claim 9 in which said plate configuration provides unobstructed access to said annular surface whereby a drill bit can engage said annular surface at substantially a right angle to said surface. .Iaddend.