WO2014172352A1

WO2014172352A1 - Air cooling hot melt delivery system and method

Info

Publication number: WO2014172352A1
Application number: PCT/US2014/034168
Authority: WO
Inventors: Bryce J. Gapinski; Nicholas K. Studt; Joseph E. Tix; Daniel P. Ross; Mark T. Weinberger
Original assignee: Graco Minnesota Inc
Current assignee: Graco Minnesota Inc
Priority date: 2013-04-16
Filing date: 2014-04-15
Publication date: 2014-10-23
Anticipated expiration: 2015-10-16
Also published as: TW201501815A

Abstract

A hot melt dispensing system includes a melt system for heating adhesive pellets into liquefied adhesive pellets. The melt system includes an inlet for receiving a supply of adhesive pellets. The hot melt dispensing system further includes a feed hose for feeding adhesive pellets into the melt system and a feed inlet assembly connecting the feed hose to the melt system. The feed inlet assembly includes a venturi, a compressed air inlet for feeding compressed air into the venturi, and a venturi outlet connecting the venturi to the inlet of the melt system.

Description

AIR COOLING HOT MELT DELIVERY SYSTEM AND METHOD

CROSS-REFERENCE TO RELATED APPLICATION(S) This application claims priority from U.S. Provisional Application No. 61/812,573, filed April 16, 2013 for "AIR COOLING HOT MELT DELIVERY SYSTEM" by Bryce J. Gapinski et al.

BACKGROUND

The present disclosure relates generally to systems for dispensing hot melt adhesive. More particularly, the present disclosure relates to a system and method for cooling parts of a hot melt delivery system.

Hot melt dispensing systems are typically used in manufacturing assembly lines to automatically disperse an adhesive used in the construction of packaging materials such as boxes, cartons and the like. Hot melt dispensing systems conventionally comprise a material tank, heating elements, a pump and a dispenser. Solid polymer pellets are melted in the tank using a heating element before being supplied to the dispenser by the pump. Because the melted pellets will re-solidify into solid form if permitted to cool, the melted pellets must be maintained at temperature from the tank to the dispenser. This typically requires placement of heating elements in the tank, the pump and the dispenser, as well as heating any tubing or hoses that connect those components. Furthermore, conventional hot melt dispensing systems typically utilize tanks having large volumes so that extended periods of dispensing can occur after the pellets contained therein are melted. However, the large volume of pellets within the tank requires a lengthy period of time to completely melt, which increases start-up times for the system. For example, a typical tank includes a plurality of heating elements lining the walls of a rectangular, gravity-fed tank such that melted pellets along the walls prevents the heating elements from efficiently melting pellets in the center of the container. The extended time required to melt the pellets in these tanks increases the likelihood of "charring" or darkening of the adhesive due to prolonged heat exposure.

SUMMARY

A method of operating a hot melt dispensing system includes transporting adhesive pellets from a container through a feed hose into a venturi and flowing compressed air into the venturi through a compressed air inlet. The method further includes transporting the adhesive pellets through the venturi and into an inlet of a melt system for heating the adhesive pellets.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a system for dispensing hot melt adhesive.

FIG. 2 is a side schematic view of a melt system used in the system of FIG. 1.

FIG. 3 is a cross-sectional view of a feed inlet assembly used in the system of

FIG. 2.

DETAILED DESCRIPTION FIG. 1 is a schematic view of system 10, which is a system for dispensing hot melt adhesive. System 10 includes cold section 12, hot section 14, air source 16, air control valve 17, and controller 18. In the embodiment shown in FIG. 1, cold section 12 includes container 20 and feed assembly 22, which includes vacuum assembly 24, feed hose 26, and inlet 28. In the embodiment shown in FIG. 1, hot section 14 includes melt system 30, pump 32, and dispenser 34. Air source 16 is a source of compressed air supplied to components of system 10 in both cold section 12 and hot section 14. Air control valve 17 is connected to air source 16 via air hose 35A, and selectively controls air flow from air source 16 through air hose 35B to vacuum assembly 24 and through air hose 35C to motor 36 of pump 32. Air hose 35D connects air source 16 to dispenser 34, bypassing air control valve 17. Controller 18 is connected in communication with various components of system 10, such as air control valve 17, melt system 30, pump 32, and/or dispenser 34, for controlling operation of system 10.

Components of cold section 12 can be operated at room temperature, without being heated. Container 20 can be a hopper for containing a quantity of solid adhesive pellets for use by system 10. Suitable adhesives can include, for example, a thermoplastic polymer glue such as ethylene vinyl acetate (EVA) or metallocene. Feed assembly 22 connects container 20 to hot section 14 for delivering the solid adhesive pellets from container 20 to hot section 14. Feed assembly 22 includes vacuum assembly 24 and feed hose 26. Vacuum assembly 24 is positioned in container 20. Compressed air from air source 16 and air control valve 17 is delivered to vacuum assembly 24 to create a vacuum, inducing flow of solid adhesive pellets into inlet 28 of vacuum assembly 24 and then through feed hose 26 to hot section 14. Feed hose 26 is a tube or other passage sized with a diameter substantially larger than that of the solid adhesive pellets to allow the solid adhesive pellets to flow freely through feed hose 26. Feed hose 26 connects vacuum assembly 24 to hot section 14.

Solid adhesive pellets are delivered from feed hose 26 to melt system 30. Melt system 30 can include a container (not shown) and resistive heating elements (not shown) for melting the solid adhesive pellets to form a hot melt adhesive in liquid form. Melt system 30 can be sized to have a relatively small adhesive volume, for example about 0.5 liters, and configured to melt solid adhesive pellets in a relatively short period of time. Pump 32 is driven by motor 36 to pump hot melt adhesive from melt system 30, through supply hose 38, to dispenser 34. Motor 36 can be an air motor driven by pulses of compressed air from air source 16 and air control valve 17. Pump 32 can be a linear displacement pump driven by motor 36. In the illustrated embodiment, dispenser 34 includes manifold 40 and module 42. Hot melt adhesive from pump 32 is received in manifold 40 and dispensed via module 42. Dispenser 34 can selectively discharge hot melt adhesive whereby the hot melt adhesive is sprayed out outlet 44 of module 42 onto an object, such as a package, a case, or another object benefiting from hot melt adhesive dispensed by system 10. Module 42 can be one of multiple modules that are part of dispenser 34. In an alternative embodiment, dispenser 34 can have a different configuration, such as a handheld gun-type dispenser. Some or all of the components in hot section 14, including melt system 30, pump 32, supply hose 38, and dispenser 34, can be heated to keep the hot melt adhesive in a liquid state throughout hot section 14 during the dispensing process.

System 10 can be part of an industrial process, for example, for packaging and sealing cardboard packages and/or cases of packages. In alternative embodiments, system 10 can be modified as necessary for a particular industrial process application. For example, in one embodiment (not shown), pump 32 can be separated from melt system 30 and instead attached to dispenser 34. Supply hose 38 can then connect melt system 30 to pump 32.

FIG. 2 is a side schematic view of melt system 30. In the illustrated embodiment, melt system 30 includes melter base 46, melter 48, band heater 50, thermal break 52, feed cap 54, sensor tower 56, and level sensor 58. Melter 48 is positioned on and supported by melter base 46. Melter base 46 includes bolt holes 60 for connecting melter base 46 to pump 32 (shown in FIG. 1). Melter base 46 also includes outlet 62 to allow fluid flow of hot melt adhesive from melter 48 to pump 32. Band heater 50 is attached to melter 48 for heating melter 48. Band heater 50 is an electrically powered resistive heating element wrapped circumferentially around and in contact with melter 48 for conducting heat from band heater 50 to melter 48. Melter 48 is a container for melting adhesive pellets into a liquid state, and for holding both the adhesive pellets in a solid state and the hot melt adhesive in the liquid state. In the illustrated embodiment, melter 48 is substantially cylindrical. In alternative embodiments, melter 48 can have a different shape, such as oval, square, rectangular, or another shape suitable for the application. Thermal break 52 is a connector that connects feed cap 54 to melter 48. Thermal break 52 can be made of silicone or another material having a relatively low thermal conductivity. In alternative embodiments, thermal break 52 can be omitted and feed cap 54 can be connected to melter 48 either directly or via another suitable mechanism.

Feed cap 54 is a cover for melter 48 and melt system 30, connected to a top of melter 48. In one embodiment, feed cap 54 can be made of a polymer material. In alternative embodiments, feed cap 54 can be made of another material, such as a metal. Feed cap 54 includes cap top 64 and cap side 66. In the illustrated embodiment, cap side 66 is substantially cylindrical and cap top 64 has a substantially circular shape when viewed from above. Feed cap 54 can have a shape that is similar to that of melter 48, or can have a shape that differs from that of melter 48.

Feed inlet 68 is positioned on cap top 64 and includes inward projection 70, extending downward from cap top 64. Feed inlet 68 is a hole through cap top 64 and is connected to feed inlet assembly 71 for receiving a supply of adhesive pellets and air supplied by feed assembly 22 (shown in FIG. 1).

Feed inlet assembly 71 includes venturi outlet hose 72, venturi 74, compressed air inlet 76, and feed funnel inlet 78. A supply of adhesive pellets flows through feed hose 26 of feed assembly 22 and into feed inlet assembly 71 through feed funnel inlet 78. The supply of adhesive pellets flows out of feed inlet assembly 71 through venturi outlet hose 72 and flows into feed inlet 68.

Feed inlet assembly 71 allows the supply of adhesive pellets to be delivered to melter 48 without sticking to components of feed assembly 22. Dry adhesive pellets are typically kept at room temperature in container 20, but the adhesive pellets may come in contact with a section of feed hose 26 that is heated up due to the proximity of the section to melter 48. As a result, the adhesive pellets may begin to melt and stick to the walls of feed hose 26, which can create a restriction and plug feed hose 26, preventing the adhesive pellets from reaching melter 48. Feed inlet assembly 71 provides active cooling with venturi 74 to prevent hot melt from building up on the walls of feed hose 26.

Feed inlet assembly 71 allows adhesive pellets to flow freely from container 20 to melter 48 without creating any restrictions in tubing such as feed hose 26 near melter 48. Feed inlet assembly is located above melter 48 to counteract heat transfer from melter 48 to feed components and allow the temperature of the adhesive pellets to remain significantly below the softening point of the adhesive. This eliminates the need for maintenance of feed components, such as removing built up hot melt from feed hose 26 near melter 48.

FIG. 3 is a cross-sectional view of feed inlet assembly 71. Feed inlet assembly 71 includes venturi outlet hose or tube 72, venturi 74, compressed air inlet 76, feed funnel inlet 78, plenum 80, channels 82, feed funnel outlet 84, and o-ring 86. Feed hose 26 extends into feed funnel inlet 78. Feed funnel inlet 78 extends into venturi 74.

Adhesive pellets are fed through feed hose 26, into feed funnel inlet 78, through feed funnel outlet 84, and into venturi outlet hose 72. Adhesive pellets then flow through feed inlet 68 into melt system 30. O-ring 86 provides sealing between venturi 74 and feed funnel inlet 78. Plenum 80 is a circumferential air channel, which connects to channels 82, longitudinal, circumferentially spaced slots that form air passages in conjunction with the inner surface of venturi 74. Compressed air is fed via compressed air inlet 76 into plenum 80. The air flows through plenum 80 and into channels 82 as shown by the dotted lines and arrows in FIG. 3. Plenum 80 and channels 82 create a cone in which compressed air is blown to the center of feed funnel outlet 84 and venturi outlet hose 72, keeping adhesive pellets in the center and away from the walls of feed funnel outlet 84 and venturi outlet hose 72.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

CLAIMS:

1. A hot melt dispensing system comprising:

a melt system for heating adhesive pellets into liquefied adhesive pellets, the melt system comprising an inlet for receiving a supply of adhesive pellets; a feed hose for feeding adhesive pellets into the melt system; and

a feed inlet assembly connecting the feed hose to the melt system, the feed inlet assembly comprising:

a venturi;

a compressed air inlet for feeding compressed air into the venturi; and a venturi outlet connecting the venturi to the inlet of the melt system.

2. The hot melt dispensing system of claim 1, wherein the feed inlet assembly is located above the feed inlet of the melt system.

3. The hot melt dispensing system of claim 1, wherein the feed hose extends into the feed inlet assembly.

4. The hot melt dispensing system of claim 1, wherein the venturi outlet extends from an interior of the venturi to the inlet of the melt system.

5. The hot melt dispensing system of claim 1, the feed inlet assembly further comprising:

a feed funnel inlet for receiving the feed hose; and

a feed funnel outlet located in the venturi and connecting the feed funnel inlet to the venturi outlet.

6. The hot melt dispensing system of claim 5, the venturi further comprising:

a plenum connected to the compressed air inlet; and

a plurality of longitudinal channels fluidly connected to the plenum and

connected to the feed funnel outlet.

7. The hot melt dispensing system of claim 6, wherein the plenum is a circumferential air channel.

8. The hot melt dispensing system of claim 6, wherein the plurality of longitudinal channels is circumferentially spaced around an inner surface of the venturi to form a plurality of air passages in conjunction with the inner surface of the venturi.

9. The hot melt dispensing system of claim 6, the feed inlet assembly further comprising an o-ring for providing sealing between the venturi and the feed funnel inlet.

10. A method of operating a hot melt dispensing system, the method comprising: transporting adhesive pellets from a container through a feed hose into a venturi; flowing compressed air into the venturi through a compressed air inlet; and transporting the adhesive pellets through the venturi and into an inlet of a melt system for heating the adhesive pellets.

11. The method of claim 10, and further comprising transporting the adhesive pellets through the feed hose into a feed funnel inlet of the venturi.

12. The method of claim 11, and further comprising transporting the adhesive pellets from the feed funnel inlet of the venturi into a feed funnel outlet of the venturi prior to transporting the adhesive pellets into the inlet of the melt system.

13. The method of claim 12, and further comprising transporting the adhesive pellets from the feed funnel outlet of the venturi into a venturi outlet extending from an interior of the venturi to the inlet of the melt system.

14. The method of claim 13, wherein flowing compressed air into the venturi further comprises flowing the compressed air into a plenum of the venturi connected to the compressed air inlet.

15. The method of claim 14, and further comprising flowing the compressed air from the plenum of the venturi into a plurality of longitudinal channels fluidly connected to the plenum and connected to the feed funnel outlet.

16. The method of claim 15, wherein the plurality of longitudinal channels is circumferentially spaced around an inner surface of the venturi to form a plurality of air passages in conjunction with the inner surface of the venturi.

17. The method of claim 16, wherein the plurality of longitudinal channels and the plenum create an air cone in which the compressed air is blown to the center of the feed funnel outlet and the venturi outlet.

18. The method of claim 17, wherein the air cone prevents melting of the adhesive pellets during transportation from the container to the inlet of the melt system.