Patent Application
20130112294
The present disclosure relates generally to systems for dispensing hot melt adhesive. More particularly, the present disclosure relates to melt systems for use in systems for dispensing hot melt adhesive.
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.
According to the present invention, a hot melt dispensing system includes a hot melt tank having a tank outlet, a flow passage extending from the tank outlet, and a check valve. The flow passage includes a valve socket at a first end adjacent the tank outlet and a pump receptacle at a second end. The check valve is positioned in the valve socket.
Another embodiment is a hot melt dispensing system including a hot melt tank having a tank outlet, a flow passage extending from the tank outlet, and a check valve. The flow passage has a first end and a second end. The first end is adjacent the tank outlet. The check valve is positioned at the first end of the flow passage.
Another embodiment is an apparatus including a hot melt tank with a tank outlet and a valve housing formed as a single piece unit with the hot melt tank. The valve housing defines a flow passage extending from the tank outlet with a valve socket formed in the flow passage at the tank outlet.
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.
Hot melt tank 50 includes tank inlet 58 at a top of hot melt tank 50 and tank outlet 60 at a bottom of hot melt tank 50. Hot melt tank 50 is a container for receiving adhesive pellets from feed assembly 22 (shown in
Valve housing 52 is positioned below hot melt tank 50 and flow passage 54 extends below hot melt tank 50. Flow passage 54 has first end 62 adjacent tank outlet 60 and has second end 64. Flow passage 54 extends from tank outlet 60 such that second end 64 is distal from tank outlet 60. Valve housing 52 defines valve socket 66 at first end 62 and defines pump receptacle 68 at second end 64. Valve socket 66 is positioned below tank outlet 60. In the embodiment illustrated in
Check valve 56 includes valve body 76 and valve ball 78 positioned in valve body 76. Check valve 56 can include a spring (not shown) biasing valve ball 76 in an open or a closed position. Check valve 56 can be positioned in valve housing 52 along flow passage 54. In the illustrated embodiment, check valve 56 is positioned at first end 62 adjacent tank outlet 60. Check valve 56 is positioned in valve socket 66, which can be sized and shaped to hold check valve 56 in place. Check valve 56 can be press fit in valve socket 66 or can be threaded in valve socket 66. Check valve 56 is a one way anti-siphon valve that allows liquefied adhesive to flow from hot melt tank 50 to pump 32 but that reduces or substantially prevents flow in an opposite direction.
Pump 32 includes pump shaft 80, pump cylinder 82, piston check valve 84, seals 86, 88, and 90, and throat cartridge 92. Pump shaft 80 is a piston that is movable within pump cylinder 82. Seals 86 and 88 are v-packing seals positioned between pump shaft 80 and pump cylinder 82. Seal 90 is a throat seal between throat cartridge 92 and pump cylinder 82. Throat cartridge 92 is attached at a top of pump cylinder 82 and extends circumferentially around pump shaft 80. Pump cylinder 82 includes pump inlet 94 at its bottom and pump outlet 96 on its side.
Pump receptacle 68 is a pump connection for connecting pump 32 to valve housing 52. In the illustrated embodiment, pump receptacle 68 is connected directly to pump 32, with pump 32 positioned partially inside pump receptacle 68. Pump cylinder 82 includes threaded outer surface 98, and pump receptacle 68 includes threaded inner surface 100. Threaded outer surface 98 is engaged with threaded inner surface 100 to attach pump 32 to pump receptacle 68. In alternative embodiments, pump 32 can be connected to pump receptacle 68 via other means suitable for the application.
Pump 32 pumps liquefied adhesive from hot melt tank 50 to dispenser 34 (shown in
By forming hot melt tank 50 as a single piece with valve housing 52 or 152, melt systems 30 and 130 can have a relatively small number of machined components. Because flow passages 54 and 154 can be relatively short, a relatively small amount of material can be wasted during flushing of liquefied adhesive. By including check valve 56 at tank outlet 60, another valve need not be included at pump inlet 94. Melt systems 30 and 130 can have a relatively small footprint, which can allow for a relatively small mass requiring heating and a correspondingly small energy consumption.
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. For example, various components of system 10 can be sized, shaped, and configured differently than as illustrated as appropriate for a given application.
| Number | Date | Country | |
|---|---|---|---|
| 61556569 | Nov 2011 | US |
