System for supplying unmelted hot melt adhesive pieces

A hot melt adhesive supply system is disclosed. The hot melt adhesive supply system includes an outer container defining an upper cavity and a lower cavity. The upper cavity includes an inner container having a top opening to receive unmelted hot melt adhesive pieces and a bottom aperture. The system also includes a dispensing mechanism between the upper cavity and the lower cavity. The dispensing mechanism regulates the dispensing of the unmelted hot melt adhesive pieces from the upper cavity to the lower cavity. The dispensing mechanism includes a base plate and one or more rotating members that rotate to move the unmelted hot melt adhesive pieces through a gap defined between the base plate and the bottom aperture. The system also includes a transfer conduit that communicates the unmelted hot melt adhesive pieces from the lower cavity to a hot melt adhesive melter.

TECHNICAL FIELD

The present disclosure generally relates to hot melt adhesive systems, and more particularly to systems for supplying hot melt adhesive melters with unmelted hot melt adhesive pieces.

BACKGROUND

Hot melt adhesive systems have many applications in manufacturing and packaging. For example, thermoplastic hot melt adhesives are used for carton sealing, case sealing, tray forming, pallet stabilization, nonwoven applications including diaper manufacturing, and many other applications. Hot melt adhesives often come in the form of pellets or particulates, which are generally referred to as pieces, and are contained in or provided from an adhesive supply, such as a tank or hopper. The hot melt adhesive pieces can be heated and melted by a melter, and liquefied hot melt adhesive can be pumped to a dispenser, such as a dispensing gun or other applicator which applies the hot melt adhesive to a substrate. Hot melt adhesive, in its pre-melted state (referred to herein as hot melt adhesive pieces, or unmelted hot melt adhesive pieces), can be provided in a variety of shapes and sizes, ranging from small bb-sized pieces, to larger sized pieces which are sometimes referred to as “chips” and still larger “pillows” that are several inches in dimension. Hot melt adhesive pieces may be moved from the adhesive supply to the melter as part of an automated filling operation.

For example, air-driven, or pneumatic, transfer systems use the force of flowing air to move hot melt adhesive pieces from an adhesive supply to a melter. In a known arrangement, a transfer conduit connects the adhesive supply with the melter, and an air pump is operated to generate an air flow that moves hot melt adhesive pieces through the transfer hose from the adhesive supply to the melter.

Environmental conditions, however, can interfere with the movement of hot melt adhesive pieces from the adhesive supply to the melter. In particular, temperature and/or the amount of time that the hot melt adhesive pieces have been in the adhesive supply may affect the movement of the hot melt adhesive pieces. For example, as the environmental temperature increases, the hot melt adhesive pieces can begin to soften and stick together to form clumps of hot melt adhesive.

Pneumatic transfer systems have a limit relative to the size and weight of the hot melt adhesive that they can transfer in a cost effective manner. Large clumps of hot melt adhesive can be too large to fit through a transfer hose and travel between the adhesive supply and the melter. Large clumps can also be too heavy to be moved by a given pneumatic transfer system. If a melter is not provided with an appropriate flow of hot melt adhesive pieces, the melter will not be able to provide liquid hot melt adhesive to a dispenser. This would cause an undesirable disruption of a dispensing operation.

In addition, as hot melt adhesive pieces begin to stick together in the adhesive supply, features can be formed in the adhesive supply that also tend to deprive an adhesive melter with an appropriate flow of hot melt adhesive pieces. For example, hot melt adhesive pieces that have stuck together can create a clump or an even larger formation in the adhesive supply. Such a formation will not be moved out of the adhesive supply by the pneumatic transfer system. In addition, the formation is likely to block the flow of hot melt adhesive pieces from the adhesive supply to the transfer conduit that connects the adhesive supply with the melter. Moreover, clumps or large formations of hot melt adhesive tend to cause nearby hot melt adhesive pieces to stick to them, and this process can lead to substantially large formations in the adhesive supply.

In addition to increased temperatures, the amount of time that hot melt adhesive pieces have been sitting still in an adhesive supply can also cause problems for moving the hot melt adhesive pieces to a melter. The longer hot melt adhesive pieces sit in the adhesive supply, they can begin to stick together, leading to similar problems as those discussed above.

Therefore, there is a need for an improved hot melt adhesive supply system that overcomes the shortcomings addressed above.

SUMMARY

Disclosed herein is a hot melt adhesive supply system. In one exemplary embodiment, a hot melt adhesive supply system includes an outer container defining an upper cavity and a lower cavity. The upper cavity includes an inner container having a top opening configured to receive unmelted hot melt adhesive pieces. The upper cavity further includes a bottom aperture. The system also includes a dispensing mechanism between the upper cavity and the lower cavity. The dispensing mechanism is configured to regulate the dispensing of the unmelted hot melt adhesive pieces from the upper cavity to the lower cavity. The dispensing mechanism includes a base plate and one or more rotating members configured to rotate to move the unmelted hot melt adhesive pieces through a gap defined between the base plate and the bottom aperture of the inner container. The system further includes a transfer conduit configured to communicate the unmelted hot melt adhesive pieces from the lower cavity to a hot melt adhesive melter.

In an aspect, the dispensing mechanism of the aforementioned system may further include a rotating shaft having a longitudinal axis and extending perpendicularly from a center of the base plate. The one of more rotating members of the dispensing mechanism may extend perpendicularly, with respect to the longitudinal axis, from the rotating shaft. The one or more rotating members may be rigid. At least one of the one or more rotating members may be curved in a direction parallel to the base plate. The rotating shaft may rotate in a direction in which a convex side of the at least one of the one or more rotating members is leading. There may be three rotating members positioned equidistantly around a circumference of the rotating shaft.

The dispensing mechanism may further include one or more upper rotating members extending perpendicularly, with respect to the longitudinal axis, from an upper portion of the rotating shaft, wherein the upper portion of the rotating shaft is situated within the inner container. At least one of the one or more upper rotating members may be flexible. At least one of the one or more upper rotating members may be tangentially, with respect to a circumference of the rotating shaft, attached to the rotating shaft. The upper rotating members may be vertically, with respect to the longitudinal axis, offset on the rotating shaft from one another. The upper rotating members may be circumferentially positioned on the rotating shaft equidistantly from one another.

In another aspect, the dispensing mechanism of the aforementioned system may further include a cylindrical gate having a diameter greater than a diameter of the base plate and movable between an open position and a closed position. In the closed position, the cylindrical gate substantially overlaps with the gap to substantially block the gap and prevent hot melt adhesive pieces from passing therethrough. In the open position, the cylindrical gate does not substantially overlap with the gap and hot melt adhesive pieces are allowed to pass therethrough. A resilient actuator may be connected to the cylindrical gate, which causes the cylindrical gate to move to the closed position when external forces are not applied to the resilient actuator. A flexible curtain may be connected to the base plate and slidingly draped over the cylindrical gate.

In yet another aspect, the inner container may include a flexible material. The aforementioned system may include a compression plate and an actuator operatively connected to the compression plate. The compression plate may be configured to manipulate the hot melt adhesive pieces in the inner container upon operation of the actuator.

In still other aspects, the height of the gap may be adjustable between, for example, a range of about 0.5 inches to about 1.5 inches. The inner container may include a grate spanning the top opening. The inner container may include a level sensor configured to detect a level of unmelted hot melt adhesive pieces in the inner container. The level sensor may be communicatively connected to an indicator disposed on the outer container. The indicator may be at least one of a light or an audio alarm. The inner container may include an inner container window, and the outer container may include an outer container window correspondingly positioned with the inner container window.

In yet other aspects, the lower cavity may include a funnel leading to a transfer mechanism, where the transfer mechanism may be configured to move the unmelted hot melt adhesive pieces through the transfer conduit. The funnel may include an air-driven vibrator. The transfer mechanism may include an eductor or an air pump to generate air flow to move the unmelted hot melt adhesive pieces through the transfer conduit. The transfer mechanism may also an exhaust conduit connected to the air-driven vibrator and supplementing the air flow. The lower cavity may include a level sensor configured to detect a level of unmelted hot melt adhesive pieces in the funnel. The level sensor may be communicatively connected to an indicator disposed on the outer container, such as a light or an audio alarm.

In yet further aspects, the dispensing mechanism may be configured to reduce a rate at which the one or more rotating members rotate or stop dispensing the unmelted hot melt adhesive pieces responsive to the level sensor detecting that the level of unmelted hot melt adhesive pieces in the funnel exceeds a pre-determined threshold.

DETAILED DESCRIPTION

FIGS. 1 and 2illustrate an exemplary hot melt adhesive supply system10(the “supply system,” hereinafter). In general, the supply system10is configured to receive a supply of hot melt adhesive pieces and provide, in a controlled manner, the hot melt adhesive pieces to an attached adhesive melter. The adhesive melter, in turn, may provide melted hot melt adhesive to an adhesive dispensing module.

The hot melt adhesive supply system10may include a rigid outer container12. In some aspects, the outer container12may be formed from a plastic bin originally intended to contain refuse. The outer container12may include an upper cavity14that initially receives the supply of hot melt adhesive pieces and a lower cavity16from which hot melt adhesive pieces are transferred, via a transfer mechanism72, to the attached adhesive melter. The upper cavity14may be defined by an upper container88. A dispensing mechanism20may be disposed between the upper cavity14and the lower cavity16to facilitate a controlled dispensing of the hot melt adhesive pieces from the upper cavity14to the lower cavity16.

An upper portion of the upper cavity14may be configured with an upper opening22through which an operator may deposit the supply of hot melt adhesive pieces into the upper cavity14. In an aspect, the upper container88may be embodied as a flexible hopper (e.g., a fabric bag). The flexible hopper may be hung from the inside of the outer container12whereby the upper opening of the flexible hopper is attached near or at the top of the outer container12. A lower portion of the upper cavity14may include a lower opening24through which the hot melt adhesive pieces may pass to the dispensing mechanism20and the lower cavity16. As can be seen inFIGS. 1and2, the upper cavity14may be configured in a gentle funnel configuration due to the upper opening22being wider than the lower opening24. Such a configuration may facilitate the downward flow of the hot melt adhesive pieces within the upper cavity14.

A grate18may span the opening of the upper cavity14to shield the operator from the moving parts within the upper cavity14. A portion of the outer container12corresponding to the upper cavity14may be configured with an upper window26to allow an operator to view the interior of the upper cavity14, such as to check on the level of hot melt adhesive pieces within the upper cavity14. The upper container88may be similarly configured with a window (not shown) corresponding to the upper window26of the outer container12. The upper cavity14may further be configured with a level sensor30to detect the vertical level of the supply of hot melt adhesive pieces within the upper cavity14, including whether the vertical level of the supply of hot melt adhesive pieces has dropped below a pre-determined threshold. The level sensor30may be positioned within the upper container88or affixed to a sidewall of the upper container88. The height at which the level sensor30is positioned relative to the upper container88may correspond with the pre-determined low-level threshold. Accordingly, the position of the level sensor30relative to the upper container88may be adjusted to thereby adjust the pre-determined low-level threshold. The level sensor30may be communicatively connected to an indicator28, such as a warning light disposed on the exterior of the outer container12or an audio alarm, to alert an operator that the upper cavity14is becoming empty or that any other problem with the supply system10has occurred.

One or more compression plates32may be operatively connected to one or more linear actuators34(e.g., pneumatic actuators). The arrangement of compression plates32and actuators34may be disposed within the outer container12but external to the upper cavity14. When the actuators34operate (e.g., the cylinders of the pneumatic actuators alternately extend and retract), the attached compression plates32perform a compressive action upon the upper cavity14to manipulate the hot melt adhesive pieces therein. The compressive action of the compression plates32may serve to break up any coalesced clumps of hot melt adhesive pieces and/or help prevent the formation of said clumps.

With additional reference toFIGS. 3A, 3B, and 4, the hot melt adhesive pieces in the upper cavity14may be dispensed to the lower cavity16via the dispensing mechanism20situated between the upper cavity14and the lower cavity16. The dispensing mechanism20may be supported by the upper cavity14or other otherwise secured within the outer container12. For example, a band clamp36may be used to affix the dispensing mechanism20to the lower opening24of the upper cavity14.

The dispensing mechanism20may include a rotating shaft38that protrudes through the lower opening24and into the upper cavity14. The rotating shaft38may be driven by an electric motor66, for example. The speed at which the rotating shaft38rotates may be varied according to the various properties of the particular type of hot melt adhesive pieces and/or the desired rate at which the supply system10is to provide the hot melt adhesive pieces to the attached adhesive melter. The rotating shaft38may comprise an upper portion40and a lower portion42. The upper portion40may be defined as the portion of the rotating shaft38that extends into the upper cavity14, inclusive of the lower opening24. The lower portion42may be defined as the portion of the rotating shaft38that is external to (e.g., below) the upper cavity14.

The upper portion40of the rotating shaft38may be configured with one or more upper members44that protrude perpendicularly, with respect to a longitudinal axis54of the rotating shaft38, from the rotating shaft38. The upper members44may be tangentially, with respect to the circumference of the rotating shaft38, attached to the rotating shaft38. In an aspect, the upper members44may be composed of a flexible material (e.g., fiberglass or rubber). As the rotating shaft38rotates, the upper members44agitate the hot melt adhesive pieces in the upper cavity14, which may help to break apart coalesced clumps and/or prevent clumping. As a further benefit, the rotation of the upper members44through the hot melt adhesive pieces operates in complement with the compressive action of the compression plates32. As the rotating shaft38rotates, the upper members44may tend to move the hot melt adhesive pieces away from the rotating shaft38and the concentric center of the upper cavity14and towards the periphery of the upper cavity14, which may create an empty area or an area less dense with hot melt adhesive pieces. As the compressive action of the compression plates32massages or manipulates the hot melt adhesive pieces, the massaged or manipulated hot melt adhesive pieces may be shifted to the empty or less dense area formed by the rotating upper members44, thus facilitating the downward movement of the hot melt adhesive pieces in the upper cavity14.

As already mentioned, the upper members44may be flexible. This flexibility may impart the added benefit that when the rotating shaft38is rotated and the flexible upper members44encounter resistance from the hot melt adhesive pieces, an inner portion (i.e., proximate to the rotating shaft38) of the upper member44may wrap around the circumference of the rotating shaft38, effectively reducing the length by which the upper member44protrudes from the rotating shaft38. When the upper member44is partially wrapped about the rotating shaft38, the upper member44encounters less resistance from the hot melt adhesive pieces agitated by the upper member44. As the partially wrapped upper member44encounters less hot melt adhesive pieces, the upper member44will correspondingly unwrap from the rotating shaft38and fully extend from the rotating shaft38. In this manner, the flexible upper members44may self-regulate the amount of torque required to rotate the rotating shaft38. Further, when encountering coalesced hot melt adhesive pieces, the flexible upper member44, by wrapping itself around the rotating shaft38, does not force but rather encourages adhesive movement. This minimizes deformation (e.g., smearing or fusing) of hot melt adhesive pieces which, if deformed, would otherwise exacerbate the problem of facilitating movement of the hot melt adhesive pieces.

The upper members44may be situated on the rotating shaft38in various configurations. In the exemplary configuration shown inFIG. 4, the rotating shaft38is configured with, for example, three pairs of upper members44: a top pair, a middle pair, and a lower pair, wherein each is vertically, with respect to the longitudinal axis54, offset from one another. The three pairs of upper members44may be equidistantly situated around the circumference of the rotating shaft38, such that the top pair is offset about 120° from the middle pair, the middle pair is offset about 120° from the lower pair, and the lower pair is offset about 120° from the top pair. It will be appreciated, however, that the rotating shaft38may be configured with any number of upper members44, in any size, and in any arrangement.

The dispensing mechanism20may include a base plate46that substantially blocks the uncontrolled free flow of hot melt adhesive pieces through the dispensing mechanism20. The rotating shaft38may be attached to the dispensing mechanism20at the center of the base plate46. The dispensing mechanism20may include a gap48(best seen inFIG. 4) formed between the base plate46and the rim of the lower opening24of the upper cavity14. In some aspects, the gap48may be defined between the base plate46and the band clamp36attaching the dispensing mechanism20to the upper cavity14. In one aspect, the gap48may be configured to be about 0.625 inches high to accommodate small, pellet-sized hot melt adhesive pieces (e.g., up to 6 mm diameter). In another aspect, the gap48may be configured to be about 1 inch to about 1.25 inches high to accommodate larger hot melt adhesive pieces (e.g., 6 mm to 12 mm diameter). In yet another aspect, the gap48may be configured to be about 1.25 inches high. In another aspect, the gap48may be configured to be about 0.5 inches to about 1.5 inches. The height of the gap48may be adjustable, such as to accommodate different sizes of hot melt adhesive pieces in separate dispensing cycles. To this end, one or more adjustable spacers56may be mounted along the periphery of the base plate46to adjust the gap48to the desired height.

One or more lower members50may be perpendicularly, with respect to the longitudinal axis54of the rotating shaft38, attached to the lower portion42of the rotating shaft38, proximate to the base plate46. In an aspect, the lower members50may be attached tangentially, with respect to the circumference of the rotating shaft38, to the rotating shaft38. The rotating shaft38may be configured with one, two, three, or more of the lower members50. In embodiments having more than one lower member50, the lower members50may be equidistantly disposed around the circumference of the rotating shaft38. In one exemplary embodiment, the rotating shaft38may be configured with three lower members50positioned equidistantly around the circumference of the rotating shaft38.

As the lower members50rotate via the rotation of the rotating shaft38, hot melt adhesive pieces, such as those in contact with the base plate46, may be moved through the gap48to fall into the lower cavity16. In various configurations, the lower members50may each be straight or curved (e.g., curved in a direction opposite the direction of rotation and parallel to the base plate46) and composed of a rigid or a flexible material. In the embodiment shown inFIGS. 3A and 3B, the lower members50are each curved and rigid and rotate in the direction indicated by arrow52. In such an embodiment, as the lower members50rotate, the convex side of each of the lower members50pushes the hot melt adhesive pieces outward from the center of the base plate46and through the gap48.

The dispensing mechanism20may further be configured with a gating mechanism58to prevent the undesired spillage of hot melt adhesive pieces from the dispensing mechanism20into the lower cavity16, such as when the operation of the supply system10is paused between dispensing cycles or while the supply system10is being moved. The gating mechanism58may include one or more actuators60, such as spring return pneumatic actuators or other type of resilient actuator, that drive a gate62up and down in directions parallel to the longitudinal axis54. The gate62may be cylindrical with an interior diameter slightly larger than the diameter of the base plate46, such that the interior of the gate62is flush or almost flush with the peripheral edge of the base plate46. As shown inFIG. 3A, when the actuators60are activated (e.g., pressurized) the gate62may be driven downward (i.e., in the direction towards the lower cavity16) to an open position wherein the gap48is substantially unobstructed by the gate62. As shown inFIG. 3B, the gate62may be moved upwards (i.e., in the direction towards the upper cavity14), such as by operation of a spring or other resilient mechanism in each of the actuators60, to a closed position. In the closed position, the gate62substantially obstructs the gap48, thereby preventing the undesired passage of hot melt adhesive pieces into the lower cavity16. When the actuators60are configured as spring return pneumatic actuators, this may impart the benefit that the gate62is automatically put in the closed position by the springs of the spring return pneumatic actuators in the event that the actuators60are depressurized, such as if the supply system10loses power.

To prevent hot melt adhesive pieces from becoming wedged between the base plate46and the gate62and interfering with the operation of the gate62, the dispensing mechanism20may be configured with a flexible curtain64, such as a fabric curtain. The curtain64may be attached to and hung from the periphery of the base plate46and draped over the gate62. As may be seen inFIGS. 3A and 3B, when the gate62is raised to the closed position, the curtain64slides over the top edge of the gate62while still remaining at least substantially draped over the gate62. In this manner, the curtain64may prevent any hot melt adhesive pieces from becoming wedged between the base plate46and the gate62and/or prevent any hot melt adhesive pieces from escaping between the base plate46and the gate62.

As the hot melt adhesive pieces are dispensed from the dispensing mechanism20, they fall into the lower cavity16. The lower cavity16may be defined at the sides by the side walls of the outer container12, at the top by the exterior of the upper cavity14and the dispensing mechanism20, and at the bottom by a funnel68. The funnel68may channel the dispensed hot melt adhesive pieces into the transfer mechanism72. The transfer mechanism72may refer generally to one or more components configured to communicate the hot melt adhesive pieces dispensed into the lower cavity16to the attached adhesive melter. The transfer mechanism72may include a transfer conduit74through which the hot melt adhesive pieces are expelled from the transfer mechanism72and the supply system10.

FIG. 5provides a close-up illustration of one exemplary embodiment of the transfer mechanism72. In this embodiment, the transfer mechanism72includes an eductor76that generates airflow90to move the hot melt adhesive pieces through and out of the transfer conduit74. A lower cavity level sensor78may be disposed at the bottom of the funnel68to detect if transfer mechanism72is overwhelmed with hot melt adhesive pieces and hot melt adhesive pieces are backing up in the bottom of the funnel68. If accumulation of hot melt adhesive pieces is detected (e.g., the level of hot melt adhesive pieces in the funnel exceeds a pre-determined threshold), the rotation rate of the lower member50of the dispensing mechanism20(to which the lower cavity level sensor78is communicatively connected) may be slowed down or stopped and/or the indicator28may be activated to notify an operator.

FIG. 6provides a close-up illustration of another exemplary embodiment of the transfer mechanism72. In this embodiment, an air pump80may be employed in the transfer mechanism72generate an airflow92to move the hot melt adhesive pieces from the bottom of the funnel68and through the transfer conduit74. The transfer mechanism72may further include a vibrator82, such as an air-driven vibrator, attached to the bottom of the funnel68. The vibration provided by the vibrator82may deter coalescing between the hot melt adhesive pieces, facilitate movement of the hot melt adhesive pieces in the funnel68and transfer mechanism72, and/or assist in aligning the hot melt adhesive pieces for movement through the transfer mechanism72. If the vibrator82is air-driven, exhaust from the vibrator82may flow via an exhaust conduit84to supplement the airflow92in the transfer mechanism72. As described above in relation toFIG. 5, the lower cavity level sensor78may also be included in the embodiment illustrated inFIG. 6.

The outer container12may be configured with a removable panel86adjacent to the lower cavity16and/or the transfer mechanism72. The removable panel86may be removed to provide physical access to the dispensing mechanism20, the lower cavity16, or the transfer mechanism72, such as to perform adjustment, maintenance, or repair. In an aspect, the removable panel86may be transparent to provide visual access to the dispensing mechanism20, the lower cavity16, or the transfer mechanism72, such as to visually evaluate if the hot melt adhesive pieces are moving properly through the transfer mechanism72or if they are building up in the funnel68.