Hot melt adhesive systems and related methods

A hot melt adhesive system includes a supply container for storing adhesive particulate, a transfer pump operatively connected to the supply container, a transfer hose operatively coupled to the transfer pump, and a blocking member. The blocking member is movable between a first position in which stored adhesive particulate and air are permitted to be withdrawn from the supply container into the transfer hose, and a second position in which the stored adhesive particulate is blocked from passing through the transfer hose while air is permitted to pass therethrough to flush the transfer hose of residual adhesive particulate.

TECHNICAL FIELD

The present invention relates generally to hot melt adhesive systems. More particularly, the invention relates to systems and methods for transferring hot melt adhesive particulate from a supply container to an adhesive melter.

BACKGROUND

Thermoplastic adhesives, otherwise known as “hot melt” adhesives, have been widely used in industry for various applications. For example, thermoplastic hot melt adhesives are used for carton sealing, case sealing, tray forming, pallet stabilization, nonwoven application including diaper manufacturing, and many other applications. Hot melt adhesive, in its pre-melted state (referred to herein as “particulate” hot melt adhesive), can be provided in a variety of particulate shapes and sizes, ranging from small bb-sized pieces, to larger sized pieces including pellets and chips. Adhesive material, in the form of adhesive particulate, may be stored in an adhesive supply container and transferred to an adhesive melter, as part of an automated filling operation. At the adhesive melter, the adhesive material is then heated and melted to a desired temperature for dispensing. Hot melt adhesives are often dispensed by systems including a dispensing gun coupled via heated hoses to an adhesive melter.

In an automatic fill system, a transfer pump, such as a pneumatic pump, is connected to the adhesive container for transferring the adhesive particulate from the supply container, through a transfer hose, and to the adhesive melter. Pneumatic pumps generally rely on the suction of air located within gaps between individual pieces of adhesive particulate stored within the supply container or air otherwise disposed within the supply container. Traditionally, the adhesive particulate is fed by gravity into a lower portion of the supply container toward an inlet of the transfer pump and covers a majority of the pump inlet. At the start of a traditional fill cycle, the transfer pump generates a vacuum at the pump inlet that withdraws the adhesive particulate and air from the adhesive container. The withdrawn air and adhesive particulate then pass through the transfer hose toward the adhesive melter. In turn, the suction of the air creates a vacuum within the gaps of the adhesive particulate that withdraws additional air from a surrounding environment. The additional air from the surrounding environment continuously replaces the air within the supply container for transferring the adhesive particulate through the transfer pump.

At the end of the traditional fill cycle, the transfer pump is switched off in order to cease the transfer of air and thereby cease the transfer of adhesive particulate. Consequently, adhesive particulate that has already been withdrawn from the supply container into the transfer hose but not yet fully transferred to the adhesive melter collects and is left stranded at various low points and horizontal points within the transfer hose, unable to overcome gravitational forces. These collections of residual adhesive particulate remain within the transfer hose and are later flushed from the hose only by passing additional air through the system at the start of the next fill cycle. This characteristic limits the useful vertical transfer capability of a traditional fill system. In this regard, if a vertical section of the hose is too long, the pressure-limited pump may not be able to lift or push the particulate adhesive material through the vertical hose section during the subsequent fill cycle. Furthermore, some of the horizontal and low points at which stranded adhesive collect are located near heated components. The heat generated by these components may partially or fully melt the stranded adhesive, and lead to adhesive build-up and clogging of the transfer hose. These consequences of stranded adhesive increase the demands on transfer system components, such as the transfer pump, and reduce overall system efficiency.

There is a need, therefore, for an adhesive system and method of use that addresses the present challenges and characteristics such as those discussed above.

SUMMARY

An exemplary embodiment of a hot melt adhesive system includes a supply container for storing adhesive particulate, a transfer pump operatively connected to the supply container, a transfer hose coupled to the transfer pump, and a blocking member. The transfer pump includes a pump inlet and a pump outlet, and is operable to generate a vacuum at the pump inlet to withdraw the stored adhesive particulate and air from the supply container. The transfer hose is operatively coupled to the pump outlet for transferring the withdrawn adhesive particulate toward an adhesive melter. The blocking member is movable between a first position and a second position. In the first position, the stored adhesive particulate and air are permitted to be withdrawn from the supply container into the transfer hose. In the second position, the stored adhesive particulate is blocked from passing through the transfer hose while air is permitted to pass through the transfer hose toward the adhesive melter, thereby flushing the transfer hose of residual adhesive particulate.

In use, a method of transferring hot melt adhesive particulate includes storing adhesive particulate in a supply container and placing a blocking member in a first position in which the stored adhesive particulate and air are permitted to be withdrawn from the supply container into a transfer hose. The method further includes powering a transfer pump to generate a vacuum at a pump inlet to withdraw the stored adhesive particulate and air from the supply container into the transfer hose, and transferring the withdrawn adhesive particulate through the transfer hose toward an adhesive melter. Additionally, the method further includes moving the blocking member to a second position in which the stored adhesive particulate is blocked from passing through the transfer hose. Finally, the method includes withdrawing additional air from the supply container past the blocking member in the second position to flush the transfer hose of residual adhesive particulate.

Various additional features and advantages of the invention will become more apparent to those of ordinary skill in the art upon review of the following detailed description of the illustrative embodiments taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION

Referring to the figures, and beginning withFIG. 1, an exemplary hot melt adhesive system1includes a supply container10defining an interior space12(seeFIG. 2A) that is configured to receive and store a supply of unmelted hot melt adhesive particulate14, such as adhesive pellets and chips. According to the exemplary embodiment of the system1, the adhesive particulate is in the form of adhesive pellets. As used herein, the term “adhesive pellets” is not intended to be limiting as to any specific shape or size, so long as the adhesive pellets are suitable to be carried by a stream of forced air. As used herein, the term “air” is meant to encompass any gaseous composition. Furthermore, adhesive pellets may have regular shapes, irregular shapes, or any combination thereof, for example. Additionally, any two pellets may have distinct shapes and/or dimensions and still be jointly and generally referred to as “adhesive pellets.”

The collective adhesive particulate14stored within the supply container10includes a plurality of gaps between individual pieces of adhesive particulate14. Air is located at least within each of the gaps around the individual pieces of adhesive particulate. The system1is configured to transfer adhesive particulate14from the supply container10to an adhesive melter16, which in turn is configured to melt the particulate14and provide melted, liquid hot melt adhesive (not shown) to, for example, an adhesive dispensing module18. In particular, a transfer hose20communicates with the interior space12of the supply container10and is configured to transfer adhesive particulate14from the supply container10to the melter16. The transfer hose20may be of any desired length or diameter suitable to accommodate the adhesive dispensing requirements and the surrounding environment.

A transfer pump22is operatively connected to the supply container10and includes a pump housing24that defines a pump outlet26and a pump inlet28(seeFIG. 2A). In an exemplary embodiment, the pump inlet28extends into a lower portion of interior space12of the supply container10such that the pump inlet28and interior space12fluidly communicate (seeFIG. 2A). The transfer pump22is operable to generate pumping forces at the pump inlet28for withdrawing adhesive particulate14and air from the interior space12of the supply container10. In the exemplary embodiment, the transfer pump22creates pumping forces in the form of a venturi vacuum and uses an air source30providing an air supply (not shown), such as shop air, to create the venturi vacuum. In the exemplary embodiment, the air supplied by the air source30first enters an air filter32configured to remove impurities from the incoming air supply.

The air withdrawn by the transfer pump22from the interior space12of the supply container10includes the air that is located within the gaps created by the adhesive particulate14stored within the container10, and may further include the air that is located above the stored adhesive particulate14. For example, as the supply of adhesive particulate14depletes, the adhesive particulate14drops toward a level that may be below the pump inlet28(seeFIG. 2A). Consequently, the proportion of the withdrawn air consisting of air located above the adhesive particulate14will increase as the transfer pump22continues to withdraw adhesive particulate14.

The pump outlet26is operatively coupled to and in fluid communication with the transfer hose20, such that adhesive particulate14and air withdrawn from the container10by the transfer pump22pass into the transfer hose20. In the exemplary embodiment, the pump outlet26is located exterior to the interior space12of the supply container10.

Still referring toFIG. 1, the exemplary system1further includes a controller34mounted to a panel40that is attached to the supply container10, the controller34being powered by a power supply36. The controller34receives air supplied by the air source30, after the air passes through the air filter32, and is configured to operatively direct the air to various components of the system1. In the exemplary embodiment, the controller34directs air to the transfer pump22for creation of the venturi vacuum used to withdraw the adhesive particulate14from the supply container10. The controller34also directs air to a pneumatically operated vibrator38. The vibrator38vibrates the supply container10for reducing compaction of the stored adhesive particulate14and assisting the withdrawal of adhesive particulate14.

Referring now toFIGS. 2A and 2B, an exemplary embodiment of the system1includes a transfer gate50having an actuator52and a blocking member54coupled thereto such that the blocking member54is movable by the actuator between a first, retracted position and a second, extended position, as explained in greater detail below. The transfer gate50is positioned proximate the pump inlet28and is mounted to an interior surface42of panel40by any suitable means, such as bracket44. In alternative embodiments (not shown), the actuator52and/or the blocking member54may be positioned at various locations exterior to the interior space12of the supply container10. For example, the entire transfer gate50assembly may be positioned proximate the pump outlet26or at any preferred location downstream of the pump outlet26. As used herein, the term “downstream” references the directional flow of adhesive particulate and air from the supply container10toward the adhesive melter16. For example, the adhesive melter16is downstream of the transfer hose20.

The blocking member54includes a proximal portion56movably coupled to the actuator52, and a distal portion58extending from the proximal portion56. The distal portion58is configured to block the transfer of adhesive particulate14through the transfer hose20when the blocking member54is moved to the extended position. For example, as shown in the embodiments inFIGS. 2A and 2B, the distal portion58is configured to at least partially overlie and at least partially obstruct the pump inlet28in the extended position in order to block adhesive particulate from being withdrawn through the pump inlet28.

In exemplary embodiments shown inFIGS. 2A, 3A, and 4A-5B, the blocking member54is preferably a rod60in which the distal portion58has a smaller cross sectional area than the proximal portion56. More preferably, the proximal portion56of rod60has a generally circular cross section that tapers into a generally semi-circular cross section of distal portion58, which then terminates in a rounded tip62. As shown, this taper is such that the cross sections of the proximal portion56and the distal portion58have equal radii. Accordingly, the distal portion58of the rod60includes a planar surface64that cooperates with the pump inlet28in the extended position. Specifically, the planar surface64is adjacent to and faces the pump inlet28such that the planar surface64spans across a majority of the diameter of the pump inlet28in the extended position. The features of rod60described above advantageously facilitate the movement of the rod60past adhesive particulate14compacted in the regions surrounding the rod60, while still providing adequate obstruction of the pump inlet28in the extended position. In turn, this reduces an actuation force that the actuator52must exert on the rod60in order to effectively move the rod60from a retracted position to an extended position.

In an alternative embodiment shown inFIG. 2B, at least the distal portion58of blocking member54is in the form of a plate66. The plate66may be of any suitable shape and may be perforated (not shown) so as to allow air to freely flow through the plate66. The blocking member54is made of any suitable material, such as an aluminum alloy, plastic, or fiber-reinforced composite, for example.

The blocking member54is movable by actuator52between a first, retracted position (shown inFIGS. 2A, 2B, 4A, and 5A) and a second, extended position (shown inFIGS. 3A, 3B, 4B, and 5B). With the blocking member54in the retracted position, the stored adhesive particulate14and air are permitted to be withdrawn from the supply container10through the pump inlet28so that they may be passed into the transfer hose20(seeFIG. 1). This withdrawal of adhesive particulate14is indicated by arrows46inFIGS. 2A and 2B. When the blocking member54is actuated to the extended position (indicated inFIG. 2Aby actuation arrow48and phantom lines), the distal portion58of blocking member54overlies and substantially obstructs the pump inlet28such that the adhesive particulate14is blocked from being withdrawn through the pump inlet28, while air is still permitted to be withdrawn into the transfer hose20and toward the adhesive melter16. As a result of actuating the blocking member54to the extended position while the transfer pump22is still operating to force air through the transfer hose20, the transfer hose20is flushed of residual adhesive particulate14therein. Ideally, all adhesive particulate14is removed from the hose20during this process, however, it will be understood that removing less than all remaining adhesive particulate14will still be beneficial and within the scope of the invention. At the same time, additional adhesive particulate14is prevented from exiting the supply container10. Periodic flushing of the transfer hose20in this manner helps to prevent clogging and thereby increase the operating efficiency of the system1. For example, this may be done at the end of each particulate fill cycle for the melter16.

Persons skilled in the art will appreciate that in alternative embodiments where the transfer gate50is positioned at a location exterior to the interior space12of the supply container10, the blocking action performed by blocking member54in the extended position will occur at a location downstream of the pump inlet28. For example, where the transfer gate50is positioned downstream of the pump outlet26, the blocking member54in the extended position will permit adhesive particulate14to be withdrawn from the supply container10through the transfer pump22and into an upstream portion of a particulate transfer conduit or other structure. Upon reaching the blocking member54in the extended position, the withdrawn particulate14will be blocked from passing further downstream toward the melter16and the remainder of the transfer structure will be flushed of residual particulate14.

Referring toFIG. 3A, an exemplary blocking member54in the form of rod60is shown in the extended position in which the distal portion58overlies and substantially obstructs the pump inlet28. A gap68is thereby formed between the distal portion58and pump inlet28. The gap68is preferably sized such that it is small enough to block generally the smallest piece of adhesive particulate14from being withdrawn through the pump inlet28, yet large enough to permit sufficient withdrawal of air for effective flushing of the transfer hose20.

Referring toFIG. 3B, an alternative embodiment of the invention is shown in which the blocking member54is a plurality of rods70. A central gap72is defined between each pair of the plurality of rods70. In the extended position, the plurality of rods70overlie the pump inlet28and thereby form a plurality of gaps74similar to the gap68formed by rod60in the extended position. Accordingly, the gaps72,74are each preferably sized to be small enough to block generally the smallest piece of adhesive particulate14from being withdrawn through the pump inlet28, yet large enough to permit sufficient withdrawal of air for effective flushing of the transfer hose20.

Referring toFIGS. 4A and 4B, an exemplary embodiment of the invention is shown in which the actuator52is a pneumatic cylinder80and the blocking member54is the rod60as described above. This embodiment of the invention includes a compression spring82that overwraps the proximal portion56of the rod60and is retained by an inner surface of the cylinder80at one end and by a ring member84attached to the proximal portion56at the other end. The spring82biases the rod60toward the retracted position. The cylinder80is activated by an air source, which may be the air source30used by the transfer pump22to create pumping forces at the pump inlet28.FIG. 4Ashows the pneumatic cylinder80in an inactive state, wherein rod60is in the retracted position such that the stored adhesive particulate14and air in interior space12are permitted to be withdrawn through pump inlet28.FIG. 4Bshows the pneumatic cylinder80in an active state, achieved by forcing air into the cylinder80. The pressure of the air source applied to the cylinder80may be adjusted to extend the rod60outwardly with a force sufficient for passing through the adhesive particulate14in the region surrounding the distal portion58and the pump inlet28. The rod60is pushed outwardly toward the extended position such that the stored adhesive particulate14is blocked by distal portion58from being withdrawn through the pump inlet28, while air is still permitted to be withdrawn to thereby flush the transfer hose20of residual adhesive particulate therein. In this active state, spring82is flexed and biases the rod60toward the retracted position. The pneumatic cylinder80is deactivated by interrupting the air source, at which point the rod60snaps back to the retracted position under a spring force exerted by the spring82. Persons of ordinary skill in the art will appreciate that spring82may be substituted with any other suitable resilient means to bias the rod60toward a retracted position.

Referring toFIGS. 5A and 5B, various alternative embodiments of the invention are represented by the schematic depiction of the actuator52, which may be controlled by any suitable control device90and powered by any suitable power supply92. Whereas the actuator52is preferably powered by an air source, as embodied by the pneumatic cylinder80described above, the actuator52may alternatively be powered by an electrical source. For example, the actuator52may be a linear solenoid, a stepper motor, or similar devices, each including appropriate structure for coupling to a blocking member54. Accordingly, persons of ordinary skill in the art will appreciate that the actuator52, as depicted inFIGS. 5A and 5B, may include any pneumatically or electrically powered device capable of moving the blocking member54, such as rod60, between a retracted position and an extended position as described herein.

In another alternative embodiment of the invention (not shown), the actuator52is substituted with any suitable structure permitting the blocking member54to be moved manually between the retracted and extended positions. For example, a lever arm may be coupled at one end to the proximal portion56of rod60and extend outwardly through an aperture in the container10to form a handle, such that an operator may grip and exert a force on the handle to move the rod60between the retracted and extended positions.

While the present invention has been illustrated by the description of specific embodiments thereof, and while the embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. The various features discussed herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of the general inventive concept.