US20130112312A1

US20130112312A1 - Reversible flow inducer

Info

Publication number: US20130112312A1
Application number: US13/671,237
Authority: US
Inventors: Daniel P. Ross; Paul R. Quam
Original assignee: Graco Minnesota Inc
Current assignee: Graco Minnesota Inc
Priority date: 2011-11-07
Filing date: 2012-11-07
Publication date: 2013-05-09
Also published as: WO2013070726A1; TW201341296A

Abstract

A hot melt dispensing system includes a container for storing adhesive pellets, a melt system for heating adhesive pellets into a liquid, and a feed system connecting the container to the melt system. The feed system includes a reversible flow inducer having a first position for directing air flow toward the melt system. The reversible flow inducer also has a second position for directing air flow toward the container.

Description

BACKGROUND

The present disclosure relates generally to systems for dispensing hot melt adhesive. More particularly, the present disclosure relates to feeding solid adhesive pellets in a system 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.

SUMMARY

According to the present invention, a hot melt dispensing system includes a container for storing adhesive pellets, a melt system for heating adhesive pellets into a liquid, and a feed system connecting the container to the melt system. The feed system includes a reversible flow inducer having a first position for feeding adhesive pellets from the container to the melt system. The reversible flow inducer also has a second position for returning adhesive pellets from the feed system to the container.
Another embodiment is a hot melt dispensing system including a container for storing adhesive pellets, a melt system for heating adhesive pellets into a liquid, and a feed system connecting the container to the melt system. The feed system includes a reversible flow inducer having a first position for directing air flow toward the melt system. The reversible flow inducer also has a second position for directing air flow toward the container.
Another embodiment is a method of operating a hot melt dispensing system. The method includes directing air toward a melt system via a reversible flow inducer when the reversible flow inducer is in a first position, moving the reversible flow inducer to a second position, and directing air toward a container of adhesive pellets via the reversible flow inducer when the reversible flow inducer is in the second position. The reversible flow inducer is part of a feed system connecting the container to the melt system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system for dispensing hot melt adhesive.

FIG. 2 is a side sectional view of a container and a feed assembly for use in the system of FIG. 1.

FIG. 3A is a side sectional view of a flow inducer in a first position for use in the feed assembly of FIG. 2.

FIG. 3B is a side sectional view of the flow inducer of FIG. 3A in a second position.

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. 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 sectional view of container 20 and feed assembly 22. Container 20 includes container housing 46, pellet inlet 48 at a top of container housing 46, and pellet outlet 50 at a bottom of container housing 46. Funnel 46A is a portion of container housing 46 that is substantially funnel shaped near pellet outlet 50. In the illustrated embodiment, funnel 46A is angled with respect to vertical. Container 20 is a hopper that contains a quantity of adhesive pellets 52 for use by system 10 (shown in FIG. 1).
Feed assembly 22 is a feed system fluidically connected to pellet outlet 50 of container 20 for transporting adhesive pellets 52 from container 20 to melt system 30 (shown in FIG. 1). Inlet 28 of feed assembly 22 is a pellet inlet of vacuum assembly 24. Vacuum assembly 24 is a flow inducer for inducing flow of air and adhesive pellets 52. In the illustrated embodiment, vacuum assembly 24 is a Venturi vacuum assembly having Venturi air inlet 54 and Venturi air outlet ports 56. Distribution passage 58 fluidically connects Venturi air inlet 54 to Venturi air outlet ports 56, which are angled to direct air downstream through feed assembly 22. Air from air hose 35B flows through Venturi air inlet 54, through distribution passage 58, and out at an angle through Venturi air outlet ports 56. Vacuum assembly 24 creates a vacuum in feed assembly 22 to draw adhesive pellets 52 into vacuum assembly 24, and the resulting air flow continues to push adhesive pellets 52 along through feed hose 26. The vacuum created by vacuum assembly 24 is a low pressure zone in feed assembly 22 for inducing flow of adhesive pellets 52 from container 20. In the illustrated embodiment, vacuum assembly 24 is a reversible flow inducer as further described with respect to FIGS. 3A and 3B.
FIG. 3A is a side sectional view of vacuum assembly 24 in a first position as part of feed assembly 22. Vacuum assembly 24 includes nozzle 60 and handle 62. Nozzle 60 includes nozzle body 64, which is a substantially toroidal body that defines Venturi air outlet ports 56, distribution passage 58, and pellet passage 66. Distribution passage 58 is a channel extending around nozzle body 64. Distribution passage 58 is aligned with Venturi air inlet 54 for distributing Venturi air to Venturi air outlet ports 56, which direct Venturi air flow in Vacuum assembly 24 in a selectable direction. Venturi air outlet ports 56 are positioned radially outward of and circumferentially around pellet passage 66. Pellet passage 66 includes pellet passage inlet 68 and pellet passage outlet 70. Venturi air outlet ports 56 are positioned near an end of pellet passage 66 nearest to pellet passage outlet 70. Venturi air flowing out Venturi air outlet ports 56 creates a low pressure zone in vacuum assembly 24 downstream of pellet passage outlet 70 so as to induce flow of air and adhesive pellets 52 (shown in FIG. 2) through pellet passage 66 in a a direction from pellet passage inlet 68 to pellet passage outlet 70. When vacuum assembly 24 is in the first position, vacuum assembly 24 creates a suction to draw adhesive pellets 52 from container 20 to vacuum assembly 24, and then blows adhesive pellets 52 from vacuum assembly 24 in a first direction to melt system 30 (shown in FIG. 1).
Nozzle 60 is a reversible nozzle capable of movement between first and second positions. As illustrated in FIG. 3A, nozzle 60 is in a first position for directing air flow along feed hose 26 toward melt system 30. Handle 62 is connected to nozzle 60 via shaft 72 for moving nozzle 60 between the first and second positions. Shaft 72 is supported by bearings 74 to allow handle 62, shaft 72, and nozzle 60 to pivot about an axis of shaft 72 with respect to vacuum assembly housing 76. Nozzle 60 is pivotably positioned in a pocket within vacuum assembly housing 76. In the illustrated embodiment, Venturi air inlet 54 extends into vacuum assembly housing 76 and is substantially aligned with the axis of shaft 72.
During normal operation of system 10 (shown in FIG. 1), nozzle 60 of vacuum assembly 24 can be in the first position directing air flow in the first direction. In the first position, vacuum assembly 24 can induce flow of adhesive pellets from container 20 through feed assembly 22 to melt assembly 30. After system 10 has completed a period of normal operation, system 10 can be temporarily paused or shut down. In between periods of normal operation, residual adhesive pellets 52 can remain in feed assembly 22. When system 10 is started again, those adhesive pellets 52 can be blown by vacuum assembly 24 to melt assembly 30 to be melted.
In some applications, system 10 can be used with different types of adhesive pellets 52 for different applications. Between periods of normal operation, container 20 can be disconnected and replaced with a replacement container that contains different adhesive pellets. In such circumstances, it can be desirable to remove the residual adhesive pellets 52 in feed assembly 22 so to avoid contaminating the new adhesive pellets used in the different operations.
FIG. 3B is a side sectional view of vacuum assembly 24 with nozzle 60 in the second position. In the second position, Venturi air outlet ports 56 and pellet passage 66 are pointed in a second direction toward container 20, opposite of the first direction. In the second position, Venturi air flowing out Venturi air outlet ports 56 creates a low pressure zone in vacuum assembly 24 downstream of pellet passage outlet 70 so as to induce flow of air and adhesive pellets 52 (shown in FIG. 2) through pellet passage 66 in the second direction, from feed hose 26, through pellet passage inlet 68, through pellet passage outlet 70, and into container 20. When vacuum assembly 24 is in the second position, vacuum assembly 24 creates a suction to draw adhesive pellets 52 from feed hose 26 to vacuum assembly 24, and then blows adhesive pellets 52 from vacuum assembly 24 to container 20. Vacuum assembly 24 can thus return adhesive pellets 52 from feed assembly 22 to container 20. This can be a relatively convenient way of removing adhesive pellets 52 from feed assembly 22 prior to replacing container 20. After adhesive pellets 52 are returned to container 20, container 20 can be replaced with a replacement container containing different adhesive pellets. In some embodiments, container 20 can include a shut-off valve (not shown) or other mechanism to close pellet outlet 50.
Handle 62 allows a user to manually move vacuum assembly 24 between first and second positions as necessary. In alternative embodiments, vacuum assembly 24 handle 62 can be omitted and vacuum assembly 24 can be reversed automatically or via another mechanism suitable for reversing the direction of air flow in vacuum assembly 24.
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.

Claims

1. A hot melt dispensing system comprising:

a container for storing adhesive pellets;

a melt system for heating adhesive pellets into a liquid; and

a feed system connecting the container to the melt system, the feed system comprising:

a reversible flow inducer having a first position for feeding adhesive pellets from the container to the melt system and a second position for returning adhesive pellets from the feed system to the container.

2. The hot melt dispensing system of claim 1, wherein the reversible flow inducer is a Venturi vacuum assembly that creates a vacuum in the feed system for inducing flow of adhesive pellets.

3. The hot melt dispensing system of claim 1, wherein the reversible flow inducer is connected to an outlet of the container, and wherein the feed system further comprises:

a feed hose connecting the reversible flow inducer to the melt system.

4. The hot melt dispensing system of claim 1, wherein the reversible flow inducer comprises:

a nozzle for directing air flow; and

a handle for moving the nozzle between first and second directions.

5. The hot melt dispensing system of claim 1, wherein the container comprises a hopper with a pellet inlet at a top of the hopper and a pellet outlet at a bottom of the hopper.

6. The hot melt dispensing system of claim 1, wherein a portion of the container is substantially funnel shaped.

7. A hot melt dispensing system comprising:

a container for storing adhesive pellets;

a melt system for heating adhesive pellets into a liquid; and

a reversible flow inducer having a first position for directing air flow toward the melt system and a second position for directing air flow toward the container.

8. The hot melt dispensing system of claim 7, wherein the reversible flow inducer is a Venturi vacuum assembly that creates a low pressure zone in the feed system for inducing flow of adhesive pellets.

9. The hot melt dispensing system of claim 7, wherein the reversible flow inducer is connected to an outlet of the container, and wherein the feed system further comprises:

a feed hose connecting the reversible flow inducer to the melt system.

10. The hot melt dispensing system of claim 7, wherein the reversible flow inducer comprises:

a nozzle for directing air flow; and

a handle for moving the nozzle between the first position and the second position.

11. The hot melt dispensing system of claim 10, wherein the handle pivots the nozzle between the first position and the second position.

12. The hot melt dispensing system of claim 7, wherein the reversible flow inducer comprises:

a reversible nozzle having a nozzle body defining a plurality of ports positioned circumferentially around a pellet passage.

13. The hot melt dispensing system of claim 7, wherein the reversible flow inducer comprises:

a vacuum assembly housing having a Venturi air inlet; and

a reversible nozzle having a Venturi air outlet port in fluid communication with the Venturi air inlet.

14. The hot melt dispensing system of claim 7, wherein the container comprises a hopper with a pellet inlet at a top of the hopper and a pellet outlet at a bottom of the hopper.

15. The hot melt dispensing system of claim 7, wherein the reversible flow inducer is connected to an outlet of the container.

16. A method of operating a hot melt dispensing system, the method comprising:

directing air toward a melt system via a reversible flow inducer when the reversible flow inducer is in a first position, wherein the reversible flow inducer is part of a feed system connecting a container of adhesive pellets to the melt system;

moving the reversible flow inducer to a second position; and

directing air toward the container via the reversible flow inducer when the reversible flow inducer is in the second position.

17. The method of claim 16, and further comprising:

supplying air to the reversible flow inducer to create a Venturi vacuum to induce flow of adhesive pellets.

18. The method of claim 16, wherein the reversible flow inducer creates a suction to draw adhesive pellets from the container to the reversible flow inducer and then blows the adhesive pellets from the reversible flow inducer to the melt system when the reversible flow inducer is in the first position.

19. The method of claim 16, wherein a feed hose connects the reversible flow inducer to the melt system and wherein the reversible flow inducer creates a suction to draw adhesive pellets from the feed hose to the reversible flow inducer and then blows the adhesive pellets from the reversible flow inducer to the container when the reversible flow inducer is in the second position.

20. The method of claim 16, wherein the reversible flow inducer returns adhesive pellets to the container when the reversible flow inducer is in the second position, and further comprising:

replacing the container with a replacement container after the adhesive pellets are returned to the container.