Patent Publication Number: US-2018031163-A1

Title: Bulk adhesive transfer devices, knife gate valve devices, and related systems and methods

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/490,362, filed Sep. 18, 2014, and published as U.S. Patent App. Pub. No. 2015/0075625 on Mar. 19, 2015, which is claims the benefit of U.S. Provisional Patent App. No. 61/879,392, filed Sep. 18, 2013, the entire disclosures of which are hereby incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to melters of hot melt adhesive systems and, more particularly, to transfer devices and systems for transferring bulk amounts of unmelted hot melt adhesive particulate, such as from bulk storage to a melt section, as well as valve devices and methods used with these devices and systems. 
     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 solid or semi-solid pellets or pieces, which can be generally referred to as adhesive particulate(s). These hot melt adhesive particulates are melted into a liquid form by a melter, and the liquid hot melt adhesive is ultimately applied to an object such as a work piece, substrate or product by a dispensing device suitable to the application. 
     A supply of hot melt adhesive particulate must be maintained and delivered to the melter in order for the melter to produce the liquid hot melt adhesive used by the dispensing device. For example, it is known for a person to employ a scoop or bucket to retrieve hot melt adhesive particulates from a bulk supply, and to deliver those particulates to the melter. Typically, this involves filling a hopper or other container associated with the melter one scoop of hot melt adhesive particulate at a time. This requires the person to handle the hot melt adhesive particulate closely, which may be undesirable because hot melt adhesive dust may be stirred up during handling. In addition, transferring hot melt adhesive particulate in this manner is prone to waste caused by spillage, especially if the bulk supply is positioned away from the melter, in which case the person must hand-carry scoops of hot melt adhesive particulate from the bulk supply to the melter. 
     It is also known to use wheeled containers, such as trash can-like storage containers having two wheels at the rear thereof (referred to as totes or wheeled container), as intermediate storage containers for hot melt adhesive particulate used in the pneumatic transfer of the adhesive particulate to the melter. For example, hot melt adhesive particulate may be received from a supplier in a box, and then transferred by a person to the wheeled container. The person may then move the wheeled container to a suitable location. However, moving this type of wheeled container requires the operator to tilt the container backwardly and support the weight of the container in a balanced manner while moving. This requires that the person have sufficient strength and coordination to handle the wheeled container. Such an approach also requires a person to handle the adhesive materials closely when transferring the materials from the box to the wheeled container. This approach also has risks of waste caused by spillage, whether during the transfer into the wheeled container or when moving the container. For example, if such wheeled containers are not properly balanced during moving, the hot melt adhesive particulate contained therein could spill out. In an extreme case, such a wheeled container could tip over, causing substantial spillage of the hot melt adhesive particulate. 
     Therefore, there is a need for improvements in melters and bulk adhesive transfer devices and systems that address one or more of the drawbacks discussed above, especially those relating to handling and transferring hot melt adhesive material particulate, such as between bulk storage units and melters. 
     SUMMARY 
     Embodiments of the invention are directed to knife gate valve devices, bulk adhesive transfer devices, melters, and associated methods for controlling flow of adhesive particulates and/or supplying hot melt adhesive particulates to an adhesive melter. For example, in one embodiment a knife gate valve device is configured to be selectively operated so as to control the flow of hot melt adhesive particulate therethrough. The valve device includes a first plate having a plurality of first apertures and a second plate having a plurality of second apertures. The first and second plates are mounted for movement relative to one another so that the first and second apertures cooperate together by selectively aligning with one another to define a plurality of ports forming flow paths for the adhesive particulate through the valve device. The first and second plates move so as to sequentially open and sequentially close the plurality of ports during movement between open and closed positions. 
     The knife gate valve device in some embodiments includes first apertures each defining different opening sizes and second apertures each defining the same size, so as to enable the sequential opening and closing of the plurality of ports during relative movement of the first and second plates. The sequential opening and closing avoids multiplying the force or torque that must be applied to move the valve device between open and closed positions based on the adhesive particulate located within each of the plurality of ports. In another aspect, the second plate includes a handle so that an operator can manually rotate the second plate relative to the first plate between the open and closed positions. In some of these rotating plate embodiments of the valve, the first apertures include first aperture side edges and the second apertures include second aperture side edges angled differently than the first aperture side edges. As a result, when the first and second plates rotate relative to one another, the first and second aperture side edges pass over each other at an angle so as to define a scissor-like action for opening and closing the plurality of ports. The scissor-like opening and closing action tends to push adhesive particulate out of the way rather than pinching and splitting the adhesive particulate, which could lead to increased torque required to move the valve device between open and closed positions. The knife gate valve device may be incorporated into a bulk adhesive transfer system or a melter, in accordance with some aspects. 
     According to another embodiment of the invention, a method of controlling flow of adhesive particulate uses a knife gate valve device as described above. The method includes closing the knife gate valve device by moving the second plate relative to the first plate to a closed position in which the pluralities of first and second apertures are misaligned with one another to block flow of adhesive particulate. The knife gate valve device is opened by moving the second plate relative to the first plate to an open position in which each of the plurality of first apertures is aligned with a corresponding one of the plurality of second apertures, thereby forming a plurality of ports for adhesive particulate flow. The method also includes sequentially opening and sequentially closing the plurality of ports as the second plate moves relative to the first plate between the open and closed positions. 
     In another embodiment, a transfer device is configured to move adhesive particulate from a bulk supply to a melter. The transfer device includes a container configured to hold a supply of the adhesive particulate from the bulk supply and an outlet associated with container. The outlet is configured to be opened and closed to control flow of the adhesive particulate out of the container. A docking structure defines the outlet and is configured to selectively dock to at least one of: a part of the melter and an intermediate storage device proximate to the melter. The container and the outlet collectively define a moveable unit configured to be moved by an operator to the part of the melter or the intermediate storage device so as to selectively supply adhesive particulate to the melter, and configured to be moved away from the part of the melter or the intermediate storage device when the container is emptied of adhesive particulate by the melter. In one embodiment, the transfer device is part of the melter. 
     In one aspect, the container of the transfer device is a hopper of the melter, thereby enabling the hopper of the melter to be removed while the melter continues to operate to melt and supply liquid adhesive. It will be understood that the transfer device may be refilled at the bulk supply and re-docked to the melter after refilling, or alternatively, a different transfer device loaded with adhesive particulate may be docked in place of the original emptied transfer device. In another aspect, the transfer device also includes a framework supporting the container and including at least one wheel that enables rolling movement of the transfer device along a surface without requiring manual lifting of the adhesive particulate by the operator. This version of a transfer device collectively defines a mobile bin that may be selectively docked directly to a melter in some embodiments, and may be selectively docked to a buffer unit defining the intermediate storage device in other embodiments. Regardless of how the mobile bin is docked to structure at the melter, the mobile bin can advantageously be selectively removed for refilling or replacement while the melter continues to operate. The transfer device may be incorporated in a bulk adhesive transfer system and/or a melter. 
     In accordance with another embodiment, a melter is configured to supply liquid adhesive. The melter includes an inlet defining a docking structure configured to selectively dock to an outlet of a transfer device filled with adhesive particulate, and a melt section configured to receive adhesive particulate from the inlet. The melt section applies heat to the adhesive particulate to melt the adhesive particulate into liquid adhesive. The docking structure enables disconnection and removal of the transfer device from the inlet so that the transfer device may be replaced or refilled while the melt section continues operating. 
     Another embodiment of the invention provides a method for supplying adhesive particulate from a bulk supply to a melter using a transfer device as described above. To this end, the method includes moving the transfer device from the bulk supply towards the melter when the container is filled with adhesive particulate. The transfer device is aligned with an inlet of the melter, and the outlet is opened such that adhesive particulate is directed from the container and through the outlet towards the melter. For example, the outlet of the transfer device may be defined by a docking structure, and the alignment includes docking the transfer device to the melter. 
     According to still another embodiment of the invention, a method of providing unmelted hot melt adhesive particulates to a melter device is provided. The method includes directing unmelted hot melt adhesive particulates from a bulk supply to a mobile bin, and moving the mobile bin to a position above a buffer unit. The method further includes operating a valve on the mobile bin and allowing unmelted hot melt adhesive particulates to flow out of the mobile bin and into the buffer unit, and directing unmelted hot melt adhesive particulates from the buffer unit to the melter device. 
     According to another embodiment of the invention, a hot melt adhesive system is provided and includes a bulk supply containing a bulk amount of unmelted hot melt adhesive particulates, and a mobile bin configured to receive unmelted hot melt adhesive particulates from the bulk supply. The system further includes a buffer unit configured to receive unmelted hot melt adhesive particulates from the mobile bin and to hold a supply of unmelted hot melt adhesive particulates. The mobile bin and the buffer unit are configured such that the mobile bin is moved into position above the buffer unit to transfer unmelted hot melt adhesive particulates from the mobile bin to the buffer unit. The system further includes at least one hot melt adhesive melter device configured to melt unmelted hot melt adhesive particulates into a liquid hot melt adhesive material and being operatively coupled with the buffer unit. 
     According to another embodiment of the invention, a method of providing unmelted hot melt adhesive particulates to a melter device is provided. The method includes directing unmelted hot melt adhesive particulates from a bulk supply to a mobile bin, and moving the mobile bin to a position proximate to the melter device. The method further includes docking the mobile bin to the melter device, and directing unmelted hot melt adhesive particulates from the mobile bin to the melter device. 
     According to another embodiment of the invention, a hot melt adhesive system is provided and includes a bulk supply containing a bulk amount of unmelted hot melt adhesive particulates. The system further includes a mobile bin configured to receive unmelted hot melt adhesive particulates from the bulk supply, and at least one hot melt adhesive melter device configured to melt unmelted hot melt adhesive particulates into a liquid hot melt adhesive material. The mobile bin is further configured to be selectively docked to the melter device such that an outlet of the mobile bin is positioned proximate to an inlet of the melter device such that unmelted hot melt adhesive particulates can flow out of the outlet of the mobile bin and into the inlet of the melter device. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is an isometric environmental view showing a bulk adhesive transfer system and device according to one embodiment, with a mobile bin positioned to receive adhesive particulates from a bulk supply. 
         FIG. 2  is a further isometric environmental view of the bulk adhesive transfer system of  FIG. 1 , with the mobile bin positioned above a buffer unit for transferring adhesive particulates to the buffer unit. 
         FIG. 3  is an isometric view showing the bulk supply and mobile bin of  FIG. 1 . 
         FIG. 4  is a side elevation view showing the bulk supply and mobile bin shown in  FIG. 3  with the frame of the bulk supply shown in phantom. 
         FIG. 5  is an isometric view showing the mobile bin of  FIG. 1 . 
         FIG. 6  is an isometric view showing the mobile bin and buffer unit of  FIG. 1 . 
         FIG. 7  is a side elevation view showing the mobile bin and buffer unit of  FIG. 6 . 
         FIG. 8A  is an enlarged view of a portion of  FIG. 7 , showing the mobile bin slightly separated from the buffer unit. 
         FIG. 8B  is an enlarged view similar to  FIG. 8A , showing the mobile bin moved into contacting engagement with the buffer unit. 
         FIG. 9  is an isometric view showing features of a valve in a disassembled state. 
         FIG. 10A  is an isometric view showing the valve of  FIG. 9  in a closed configuration. 
         FIG. 10B  is an isometric view showing the valve of  FIG. 9  in a partially open configuration. 
         FIG. 11A  is a plan view showing the valve of  FIG. 9  in a first position during sequential closing of the ports of the valve (e.g., the partially open configuration of  FIG. 10B ). 
         FIG. 11B  is a plan view showing the valve of  FIG. 11A  in a second position during sequential closing of the ports of the valve. 
         FIG. 11C  is a plan view showing the valve of  FIG. 11B  in a third position during sequential closing of the ports of the valve. 
         FIG. 11D  is a plan view showing the valve of  FIG. 11C  in a fourth position during sequential closing of the ports of the valve. (e.g., the closed configuration of  FIG. 10A ). 
         FIG. 12  is an isometric view showing a mobile bin according to a further embodiment of the bulk adhesive transfer device. 
         FIG. 13  is an isometric view showing a melter including the mobile bin of  FIG. 12  docked thereto, with an enclosure in phantom. 
         FIG. 14  is an isometric view showing melter of  FIG. 13 , with an enclosure installed. 
         FIG. 15A  is a perspective view of another embodiment of a melter including a transfer device, with a container of the device shown in a removed state from a melt section, the container including a valve at the outlet thereof. 
         FIG. 15B  is a perspective view of yet another embodiment of a melter including a transfer device, with a moveable unit defined by a container and a feeder element at the outlet thereof shown in a removed state from a melt section. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 through 4 , a bulk adhesive transfer system  10  according to a first embodiment generally includes a bulk supply  12 , a mobile bin  14 , and a buffer unit  16 . The mobile bin  14  serves as a first embodiment of a (bulk adhesive) transfer device for moving adhesive particulate, with this and other embodiments of the transfer device described in greater detail below. The bulk supply  12  is configured to contain a bulk amount of unmelted hot melt adhesive pieces and/or pellets (hereinafter “adhesive particulate(s)”). The buffer unit  16  is also configured to hold a supply of adhesive particulates, this supply typically being smaller than the amount stored within the bulk supply  12 , and to supply those adhesive particulates to a hot melt adhesive melter device  18  (also referred to as a “melter,” understood to include a hopper, a heating grid, a reservoir, a manifold and a liquid pump), which is operatively coupled with the buffer unit  16  and is configured to melt the adhesive particulates into a liquid hot melt adhesive material for use in an adhesive application. The adhesive particulates may be transported pneumatically from the buffer unit  16  to the melter device  18  as described below, although other methods of transfer between the buffer unit  16  and the melter device  18  are also possible in other embodiments. Together, the bulk adhesive transfer system  10  and the melter device  18  provide a hot melt adhesive system that supplies molten hot melt adhesive to downstream devices such as dispenser guns and modules (not shown). Advantageously, the bulk adhesive transfer system  10  of this and other embodiments simplifies the task of transferring large amounts of adhesive particulate between the bulk supply  12  and the melter device  18  by avoiding the use of manual scoops and/or trash can-like wheeled storage containers that may be inefficient or subject to spills. Moreover, the bulk adhesive transfer system  10  reduces the likelihood of adhesive contamination or operator exposure to the adhesive material. 
     As shown most generally in  FIGS. 1 and 2 , the mobile bin  14  is configured to allow adhesive particulate to be transferred between the bulk supply  12  and the buffer unit  16 . For example,  FIG. 1  shows the mobile bin  14  located underneath the bulk supply  12  for receiving a supply of adhesive particulate from the bulk supply  12 , and  FIG. 2  shows the mobile bin  14  moved to the buffer unit  16  for providing the adhesive particulate to the buffer unit  16 . As shown in the FIGS. associated with this embodiment, an operator pushes or pulls the mobile bin  14  between the bulk supply  12  and the buffer unit  16 . The mobile bin  14  is more stable and less prone to spills compared to conventional trash can-like storage container designs with two wheels and manual scoops, and these advantages and the mobile bin  14  are described in further detail below. Also as described in further detail below, the transfer device defined by the mobile bin  14  may be modified in other embodiments so as to be configured for docking directly to the melter device  18  rather than docking with an intermediate storage device such as the buffer unit  16 . 
     The bulk supply  12  includes a container  20  supported by a frame  22 . The container  20  is configured to hold, or contain, a bulk amount of adhesive particulate. For example, in the embodiment shown, the container  20  is in the form of a large flexible bag, such as a Super Sack® container. Other types of storage containers may be used in alternative embodiments of the bulk supply  12 . Regardless of the type of container  20  used, the bulk supply  12  includes an outlet  24 , and the adhesive particulate may be gravity fed to the outlet  24 . Optionally, the container  20  may be reusable, and may be replenished with additional supplies of adhesive particulate, as may be required as the bulk amount of adhesive particulate therein is depleted. 
     The container  20  of the bulk supply  12  includes an outlet  24 , and a valve  26  is associated with the outlet  24 . The valve  26  is configured to selectively control the flow of adhesive particulates out of the container  20  through the outlet  24 . The bulk supply  12  may also include a tapered transfer funnel  27  as shown in  FIG. 4  configured to communicate between the valve  26  and an inlet of the mobile bin  14  as described below, although this funnel  27  may be omitted in other embodiments. The frame  22  is configured to support the container  20  in an elevated position above a surface S (such as a floor surface). In particular, the frame  22  supports the container  20  such that the mobile bin  14  can be moved into a position beneath the container  20 , as shown in  FIG. 1 . In that position, the valve  26  can be opened to allow adhesive particulates to be transferred from the container  20  to the mobile bin  14 , such as by gravity feed. 
     Optionally, an alignment guide  28  (most easily seen in  FIG. 2 ) is associated with the bulk supply  12  to aid in aligning the mobile bin  14  with respect to the outlet  24  of the container  20  and with respect to the valve  26 . While different alignment guides may be used, one example of an alignment guide  28  is shown positioned on the surface S generally beneath the outlet  24  and includes side rails  30   a ,  30   b , a stop rail  32 , and a front rail  34 . The alignment guide  28  is sized to interact with wheels  46  on the mobile bin  14  in order to guide the movement of the mobile bin  14  to the preferred location (e.g., with a top opening of the mobile bin  14  directly beneath the valve  26 ). To this end, the alignment guide  28  simplifies the positioning and operation of the mobile bin  14  and the bulk adhesive transfer system  10  for the operator. 
     In this embodiment, the mobile bin  14  is configured to receive adhesive particulate from the bulk supply  12 , and to transfer and deliver those adhesive particulate to the buffer unit  16 . Referring particularly to  FIGS. 3 through 7 , the mobile bin  14  includes a container  40  supported by a framework  42 . In the embodiment shown, the framework  42  has four legs  44 , each of which is coupled with the container  40 . Each of the legs  44  is an L-shaped bracket configured to be adhered or welded into engagement with an outer periphery of the container  40 . The framework  42  includes at least one wheel  46 , and in the embodiment shown includes four wheels  46 . More specifically, each leg  44  is associated with a wheel  46 . The wheels  46  shown in the FIGS. are caster wheels configured to roll alongside the side rails  30   a ,  30   b  of the alignment guide  28  when the mobile bin  14  is positioned at the bulk supply  12 , but other types of wheels may also be used in other embodiments. The wheels  46  allow the mobile bin  14  to be rolled on the surface S, such as between the bulk supply  12  and the buffer unit  16 . A push handle  48  is coupled with the framework  42 , and provides an ergonomic gripping point for the operator to manipulate and move the mobile bin  14  along the surface S. Therefore, as shown in  FIGS. 1 and 2  and described above, the mobile bin  14  is designed for operator movement without necessitating tipping or balancing of a load of adhesive particulate held within the container  40 . 
     The container  40  includes a body  50  having a generally drum shaped first portion  52  and a generally inwardly tapered second portion  54  extending downwardly therefrom. The drum shaped first portion  52  is generally cylindrical between an open top of the container  40  and the tapered second portion  54 . The container  40  defines an inlet  56  formed in an upper region of the first portion  52  and an outlet  58  formed in a lower region of the second portion  54 . The inlet  56  is configured to receive adhesive particulate from the bulk supply  12  and the outlet  58  is configured to communicate adhesive particulate from the container  40  to the buffer unit  16  in this embodiment. The body  50  is configured to direct adhesive particulates toward the outlet  58 . Similar to the valve  26  provided at the outlet  24  of the bulk supply  12 , a valve  60  is associated with the outlet  58  of the container  40  to selectively control the flow of adhesive particulate out of the mobile bin  14 . 
     As shown in  FIGS. 3 through 5 , the container  40  also includes a lid  62  with a port  64  formed therein (closing off a substantial portion of the open top of the container  40 ). The port  64  generally serves as the inlet  56  to the container  40  and is generally sized to match the cross-section of the tapered transfer funnel  27  extending from the valve  26  on the bulk supply  12 . Optionally, the container  40  can include one or more viewing windows  66  that allow the level or amount of adhesive particulates in the container  40  to be viewed. In this regard, the viewing windows  66  enable an operator to evaluate how much adhesive particulate is in the mobile bin  14  so that the mobile bin  14  can be moved back to the bulk supply  12  to refill the container  40 , when necessary (and so as to avoid letting the buffer unit  16  run out of adhesive particulate while the mobile bin  14  is being refilled as well). 
     Therefore, a first part of the operation of the bulk adhesive transfer system  10  is shown in  FIGS. 3 and 4 . To this end, the mobile bin  14  is moved by an operator to a position to receive adhesive particulate from the bulk supply  12 , such as when the mobile bin  14  is empty. In particular, the mobile bin  14  is positioned beneath the outlet  24  of the container  20  of the bulk supply  12 . During this movement of the mobile bin  14 , the alignment guide  28  helps align the mobile bin  14 , with the wheels  46  moving along the outermost sides of the side rails  30   a ,  30   b  until the front most of the wheels  46  contact the stop rail  32 . As will be readily understood from the view in  FIG. 4 , the stop rail  32  is specifically tailored to the mobile bin  14  being used and is positioned at a location along the surface S where the front most wheels  46  must stop in order to correctly align the port  64  of the container  40  and the outlet  24  of the bulk supply  12 . Once the mobile bin  14  is appropriately positioned, the valve  26  is opened to direct adhesive particulate from the container  20  of the bulk supply  12  into the container  40  of the mobile bin  14 . In particular, adhesive particulate are allowed to flow out of the outlet  24  of the container  20  and into the port  64  in the lid  62  of the container  40 . The valve  26  is then closed to stop the flow of adhesive particulate out of the container  20  when the mobile bin  14  has been filled with adhesive particulate. The valve  26  is preferably provided with multiple ports that sequentially open and close with a scissor-like interface at the ports to reliably ensure flow of adhesive particulate through the valve  26  when opened and to reliably cut through a column of stacked adhesive particulate without jamming or blocking during closing. One exemplary embodiment of the valve  26  and its specific operational functionality is described below in connection with  FIGS. 9 through 11D . The mobile bin  14  advantageously provides an easier and more reliable mechanism for helping an operator transfer adhesive particulate between a bulk supply  12  located remote from a melter device  18  and a buffer unit  16  located closer to the melter device  18 . 
     Now with reference to  FIGS. 6 through 8B , the buffer unit  16  is configured to receive and hold a supply of adhesive particulate from the mobile bin  14 , and to provide those adhesive particulate to the melter device  18  on demand. The buffer unit  16  includes a buffer bin  70  having an inlet  72  and at least one outlet  74 . The inlet  72  is configured to receive adhesive particulate from the mobile bin  14 , and the at least one outlet  74  is operatively coupled with the melter device  18  to provide the adhesive particulate thereto. For example, the at least one outlet  74  may be used to feed one or more melters or melter devices  18  depending on the specific installation of the adhesive dispensing/supply system incorporating the bulk adhesive transfer system  10 . In  FIG. 7 , the melter device  18  is shown as a schematic black box, although it will be understood that one example of a melter device  18  is shown in the wall-mounted melter and dispenser units MD located in close relation to the buffer unit  16  (and the at least one outlet  74  could be connected to these melter and dispenser units MD by hosing or other conduits, not shown). 
     The buffer bin  70  includes a housing  75  having a generally D-shaped cross section along its length from top to bottom, with the housing  75  supported so as to be positioned above a platform  76  situated on the surface S. The buffer bin  70  may also include a lid member  77  pivotally coupled to the housing  75  and configured to move between an open position (shown in  FIGS. 1 and 7 ) providing access into the interior of the buffer bin  70  through the open top and a closed position (not shown) which blocks access into the buffer bin  70 . Generally, when the mobile bin  14  is moved away from the buffer unit  16  as shown in  FIG. 1 , the lid member  77  will be moved to the closed position to avoid having any operator exposure to the adhesive particulate or contamination of the adhesive particulate remaining in the buffer bin  70 . 
     The buffer bin  70  is configured to be mated with the container  40  of the mobile bin  14 . To this end, the buffer bin  70  may include a lift mechanism  78  associated with the platform  76  and that is configured to move the buffer bin  70  upwardly into contacting engagement with the container  40 , as described below in connection with  FIG. 8B . In the exemplary embodiment shown, the lift mechanism  78  includes at least one compression spring  78   a  biasing the buffer bin  70  upwardly away from the platform  76  towards a raised position ( FIG. 8B ) and an air cylinder  78   b  that may be actuated to push the buffer bin  70  into the lowered position ( FIG. 8A ) against the bias of the at least one compression spring  78   a . Alternatively, the mobile bin  14  could include a mechanism for moving the container  40  downwardly into contacting engagement with the buffer bin  70  in other embodiments. Regardless of whether the buffer unit  16  or the mobile bin  14  includes the movement mechanism, the buffer bin  70  is configured to be spaced apart from the container  40  when the mobile bin  14  is moving into or out of position relative to the buffer bin  70 , and then configured to be engaged with the container  40  once these elements are aligned and properly positioned. 
     The buffer bin  70  includes a sloped internal plate  80  surrounded by the housing  75  and configured to direct adhesive particulate contained therein toward the at least one outlet  74 . Optionally, an agitation device  82  may be operatively coupled with the sloped internal plate  80  for agitating adhesive particulates thereon to cause flow of the fluidized adhesive particulate down the sloped internal plate  80  and towards the at least one outlet  74 . In some embodiments, the agitation device  82  may be configured to vibrate the sloped internal plate  80 , although other types of agitation may also be used in other embodiments of the buffer bin  70 . 
     Similar to the container  40  of the mobile bin  14 , the buffer bin  70  also includes one or more viewing windows  84  that allow the level or amount of adhesive particulate in the buffer bin  70  to be viewed. It will be understood that the buffer bin  70  may also include a level sensor (not shown) for providing an indication to the operator when the level of adhesive particulate in the buffer bin  70  is low and needs refilling. Also, the buffer bin  70  includes a flow control plate  86  (visible through the window  84  in  FIGS. 6 through 8B  and also referred to as a gate plate) which is positioned near the at least one outlet  74  to control the amount of adhesive particulate that can flow down to the space directly adjacent the at least one outlet  74 . The flow control plate  86  is moveable relative to the sloped internal plate  80  so as to adjust the gap between these elements and thereby further adjust the amount of flow permitted from the main portion of the buffer bin  70  into the space adjacent the at least one outlet  74 . Proximate to the flow control plate  86 , the sloped internal plate  80  includes a plurality of rows of pins  88  extending upwardly from the sloped internal plate  80  (three rows of pins  88  are shown of varying lengths, but it will be understood that more or fewer rows of pins  88  may be used in other embodiments and the lengths may be varied from those shown) to divide the flow of adhesive particulate as it moves towards the gap between the flow control plate  86  and the sloped internal plate  80 . This division of the flow of adhesive particulate, along with the vibration/agitation generated in the adhesive particulate, collectively encourages clumps of coalesced and/or stuck-together adhesive particulate to break apart before delivery to the at least one outlet  74 . Accordingly, only small particles (e.g., a fluidized adhesive particulate) are delivered into the at least one outlet  74  to avoid clogging of pneumatic pumps coupled to the at least one outlet  74  of the buffer bin  70  with excessive adhesive particulate in the embodiment shown. 
     Optionally, the buffer unit  16  can further include a pneumatic transfer pump  90  (or some other analogous element) configured for moving adhesive particulate from the at least one outlet  74  to the melter device  18 . In this regard, the pneumatic transfer pump  90  uses pressurized air to produce vacuum and positive pushing forces that move adhesive particulate out of a storage device (in this case, the buffer bin  70 ) and through hosing or some other conduit leading directly to the melter device  18  as well understood in the adhesive dispensing art. Also optionally, an alignment guide  92  can be associated with the buffer unit  16  to aid in aligning the mobile bin  14  with respect to the buffer bin  70 . While different alignment guides may be used, one example of an alignment guide  92  is shown positioned on the surface S generally surrounding the platform  76  and includes side rails  94   a ,  94   b , a stop rail  96 , and a front rail  98 . Therefore, the alignment guide  92  is used similarly to the alignment guide  28  described above for guiding movement of the wheels  46  on the mobile bin  14  when an operator positions the mobile bin  14  on top of the buffer unit  16 . 
     A second part of the operation of the bulk adhesive transfer system  10  is shown in  FIGS. 6 through 8B . After the mobile bin  14  has been filled at the bulk supply  12 , the mobile bin  14  is moved by an operator from the bulk supply  12  to the buffer unit  16 . In particular, the mobile bin  14  is rolled on the surface S using the wheels  46 . Because the mobile bin  14  includes four wheels  46  supporting the entire periphery of the mobile bin  14 , the operator does not need to tip the mobile bin  14  during this movement and so the risk of adhesive spills is minimized. When the mobile bin  14  approaches the buffer unit  16 , the alignment guide  92  helps align the mobile bin  14 , with the wheels  46  moving along the side rails  94   a ,  94   b  until the front most of the wheels  46  contact the stop rail  96 . As described above with the other alignment guide  28 , the stop rail  96  is positioned so that the front most wheels  46  abut the stop rail  96  when the valve  60  on the mobile bin  14  is aligned with the inlet  72  defined along the open top of the buffer bin  70 . It will be understood that the lid member  77  should be moved to the open position before rolling the mobile bin  14  in position over the buffer bin  70 . 
     Once the mobile bin  14  is appropriately positioned, the valve  60  of the mobile bin  14  is opened to direct adhesive particulate from the container  40  of the mobile bin  14  into the buffer bin  70  of the buffer unit  16 . In particular, adhesive particulate are allowed to flow by gravity feed out of the outlet  58  of the container  40  and into the inlet  72  of the buffer bin  70 . Before opening the valve  60 , the buffer bin  70  may be mated with the container  40  by moving the buffer bin  70  upwardly (e.g., disengaging the air cylinder  78   b  so as to allow the compression springs  78   a  to force the buffer bin  70  from the spaced apart configuration shown in  FIG. 8A  into contacting engagement with the container  40  as shown in  FIG. 8B . To this end, the valve  60  and bottom end of the mobile bin  14  define a docking structure for releasably attaching to the buffer bin  70 . It will be understood that “dock” or “docking” is understood in this specification to refer to releasable attachment of two elements or assemblies, such as by latching elements, clamps, locking and unlocking means, etc. 
     Once the buffer bin  70  has been substantially filled, the valve  60  may be closed so that the mobile bin  14  can be moved away to other buffer units  16  or back to the bulk supply  12  when necessary. Alternatively, the mobile bin  14  may remain in position to continue feeding adhesive particulate into the buffer unit  16  until the mobile bin  14  is emptied. The valve  60  is preferably provided with multiple ports that sequentially open and close with a scissor-like interface at the ports to reliably ensure flow of adhesive particulate through the valve  60  when opened and to reliably cut through a column of stacked adhesive particulate without jamming or blocking during closing. One exemplary embodiment of the valve  60  and its specific operational functionality is described below in connection with  FIGS. 9 through 11D . 
     After the buffer unit  16  is filled with adhesive particulate, this adhesive particulate can be directed to the melter device  18 . While the adhesive particulates are in the buffer bin  70  and before they are directed to the melter device  18 , the adhesive particulates can be agitated and/or fluidized for flow within the buffer bin  70  by the agitation device  82 . In particular, the agitation device  82  can be used to vibrate the sloped internal plate  80 , thereby agitating the adhesive particulates on and above the plate  80  as the adhesive particulates are directed toward the at least one outlet  74  of the buffer bin  70 . The vibrational energy may also be transmitted to the housing  75  of the buffer bin  70  to further encourage movement of the adhesive particulate towards the at least one outlet  74 . As described above, the gap defined by the flow control plate  86  and the vibrating/agitating plurality of pins  88  in the buffer bin  70  discourage large clumps of adhesive particulates from clogging the at least one outlet  74 . 
     The pneumatic pumps  90  are actuated on demand for more adhesive at the melter device  18 , and the adhesive particulate near the at least one outlet  74  is forced out of the buffer bin  70  and to the melter device  18  by the pneumatic pumps  90 . Although the agitation device  82  may be operated more or less frequently, in a typical operation the agitation device  82  is run concurrently with or shortly after the pneumatic pumps  90  remove adhesive particulate from the buffer bin  70 , thereby encouraging more fluidized adhesive particulate to flow into the space adjacent the at least one outlet  74 . Once the buffer bin  70  runs low on adhesive particulate, the operator may move the mobile bin  14  back into position (if it was moved away) and re-open the valve  60  to refill the buffer bin  70 . Accordingly, the melter devices  18  are reliably provided with adhesive particulate on demand by the buffer unit  16 , and the buffer unit  16  is filled by a transfer device in the form of a mobile bin  14  that removes many of the risks of spilling adhesive, contaminating adhesive, and exposing an operator to adhesive dust when transferring adhesive particulate from the bulk supply  12  to the melter devices  18 . 
     Consequently, this first embodiment of the bulk adhesive transfer system  10  enables a reliable supply of adhesive particulate to be delivered through the buffer unit  16  and to the melter device(s)  18  on demand. An operator can transfer the adhesive particulate from the bulk supply  12  to the buffer unit  16  and the melter devices  18  using the mobile bin  14 , which is configured for easy movement on wheels and spill-free use during filling at the bulk supply  12  and during emptying at the buffer unit  16 . The risks of operator exposure to adhesive dust and adhesive contamination are also minimized using this bulk adhesive transfer system  10 . It will be understood that one or more of the components of the system  10  may be modified in other embodiments, specifically the transfer device as described in connection with  FIGS. 12 through 15B  below. 
     Referring next to  FIGS. 9 through 11D , a rotary knife gate valve  110  is shown in detail, this rotary knife gate valve  110  being specifically tailored for advantageous operation as one or both of the valves  26 ,  60  described above at the outlet  24  of the bulk supply  12  and at the outlet  58  of the mobile bin  14 . The rotary knife gate valve  110  is configured to provide a plurality of ports for adhesive particulate flow out of the corresponding container (bulk supply  12  or mobile bin  14 ), thereby avoiding problems with temporary bridging or “log jamming” of adhesive across a single port. Moreover, the rotary knife gate valve  110  is designed to sequentially close the plurality of ports with a scissor-like opening action to limit jamming and blockages that would increase the resistance to closing the rotary knife gate valve  110 . These operational features of the rotary knife gate valve  110  are described in further detail below. It will be understood that the rotary knife gate valve  110  may be incorporated in multiple places in a bulk adhesive transfer system, such as system  10  described above, and in a corresponding hot melt adhesive dispensing system (e.g., the system  10  including the melter devices  18  and dispensing guns or modules). 
     With particular reference to the exploded view in  FIG. 9  and the assembled views in  FIGS. 10A and 10B , the rotary knife gate valve  110  generally includes a first plate  112  and a second plate  114  which cooperate together to define a plurality of ports that are selectively opened and closed sequentially as described in greater detail below. The second plate  114  overlies a majority of the first plate  112  and is configured to remain in abutting or contacting relation with the first plate  112 . The plates  112 ,  114  are maintained in the abutting, cooperating relationship with one another by a collar  116 , which covers only an outermost peripheral portion  112   a  of the first plate  112  and is affixed to the first plate  112  by a plurality of bolt fasteners  117  as shown. In the illustrated embodiment, the bolt fasteners  117  include a spacer  117   a  or washer that is sized to maintain a gap between the first plate  112  and the collar  116  sufficient to closely receive an outermost peripheral portion  114   a  of the second plate  114 . The spacers  117   a  may also help maintain the second plate  114  in axial alignment with the first plate  112 , although a central pivot bolt  119  may also be provided along a central axis CA of the first and second plates  112 ,  114  as shown in  FIGS. 10A and 10B . 
     Therefore, the outermost peripheral portion  114   a  of the second plate  114  is sandwiched between the collar  116  and the outermost peripheral portion  112   a  of the first plate  112 . As a result, flow of adhesive particulate through the rotary knife gate valve  110  must pass through each of the first and second plates  112 ,  114  during flow movement through the valve  110 . The second plate  114  is mounted for free rotation about the central axis CA relative to the first plate  112 , which is the movement that enables the various ports described below to be sequentially opened and closed. It will be understood that different fasteners or mechanisms may be provided to assemble the plates  112 ,  114  and collar  116  in other embodiments of the valve  110 . 
     With continued reference to  FIGS. 9 through 10B , the first plate  112  includes a plurality of first apertures designated  118   a ,  118   b ,  118   c , and  118   d . These apertures are generally radially arranged in a circular pattern around the first plate  112  and define triangular wedge shaped openings for flow through the first plate  112 , with a base of the wedge shape located proximate to the outermost peripheral portion  112   a  of the first plate  112  and a point of the wedge shape located proximate to the center of the first plate  112 . The apertures  118   a ,  118   b ,  118   c , and  118   d  in the first plate  112  are not all the same size. In particular,  118   a  is the smallest, aperture  118   b  is larger than aperture  118   a , aperture  118   c  is larger than aperture  118   b , and aperture  118   d  is larger than aperture  118   c . In this regard, the relative size of the wedge shaped apertures  118   a ,  118   b ,  118   c ,  118   d  may also be defined by the arc length or arc angle a extending/spanning between the opposing side edges  118   s  (e.g., the side edges  118   s  extending between the point of the wedge shape and the base of the wedge shape), this angle a being slightly larger in aperture  118   b  than in aperture  118   a , slightly larger in aperture  118   c  than in aperture  118   b , and slightly larger in aperture  118   d  than in aperture  118   c . This arrangement of differently sized apertures  118   a ,  118   b ,  118   c ,  118   d  in the first plate  112  helps enable the advantageous sequential opening and closing of ports as set forth below in detail. 
     The second plate  114  also includes a plurality of second apertures designated  120   a ,  120   b ,  120   c , and  120   d . These apertures are generally radially arranged in a circular pattern around the second plate  114  and have frustum shaped openings (e.g., a truncated triangular wedge shape) for flow through the second plate  114 , with a larger base of the frustum shape located proximate to the outermost peripheral portion  114   a  of the second plate  114  and a smaller base of the frustum shape located proximate to the center of the second plate  114 . The apertures  120   a ,  120   b ,  120   c , and  120   d  in the second plate  114  are all generally the same size. In this regard, the relative size of the wedge shaped apertures  120   a ,  120   b ,  120   c ,  120   d  may also be defined by the arc length or arc angle β extending/spanning between the opposing side edges  120   s  (e.g., the side edges  120   s  extending between the smaller base of the frustum shape and the larger base of the frustum shape), this angle β being identical for each of the apertures  120   a ,  120   b ,  120   c ,  120   d.    
     The apertures  118   a ,  118   b ,  118   c , and  118   d  in the first plate  112  and the apertures  120   a ,  120   b ,  120   c , and  120   d  in the second plate  114  respectively cooperate to define a plurality of ports  122   a ,  122   b ,  122   c , and  122   d . Particularly, the ports  122   a ,  122   b ,  122   c ,  122   d  are formed/opened when an aperture of the first plate  112  is aligned with an aperture of the second plate  114 , and the ports  122   a ,  122   b ,  122   c ,  122   d  are closed when the apertures of the first and second plates  112 ,  114  are misaligned. As shown in  FIG. 9 , the apertures  118   a ,  118   b ,  118   c ,  118   d  of the first plate  112  are separated by solid regions configured to align with the apertures  120   a ,  120   b ,  120   c ,  120   d  in the second plate  114  when the valve  110  is moved to the closed position. Likewise, the apertures  120   a ,  120   b ,  120   c ,  120   d  of the second plate  114  are also separated by solid regions that are configured to align with the apertures  118   a ,  118   b ,  118   c ,  118   d  of the first plate  112  when the valve  110  is moved to the closed position. Accordingly, a plurality of flow paths through the rotary knife gate valve  110  can be produced simply by rotating the second plate  114  through a relatively small angle of rotation (e.g., approximately 40-45 degrees) relative to the first plate  112  and the collar  116 . The provision of multiple flow paths or ports  122   a ,  122   b ,  122   c ,  122   d  through the valve  110  reduces the likelihood that a temporary bridging or “log jamming” of adhesive particulate across any of the ports  122   a ,  122   b ,  122   c ,  122   d  will stop flow entirely through the valve  110 , as sometimes occurs in single port valve designs, thereby enhancing the reliability of the valve  110  for use in the bulk adhesive transfer system  10 . 
     Because the apertures  118   a ,  118   b ,  118   c ,  118   d  are differently sized, as discussed above, when the first and second plates  112 ,  114  are rotated relative to each other, the ports  122   a ,  122   b ,  122   c , and  122   d  are sequentially opened or closed. For example,  FIGS. 11A through 11D  show a progression of operating positions of the rotary knife gate valve  110  during movement of the second plate  114  relative to the first plate  112  towards the closed position. It will be understood that the apertures  118   a ,  118   b ,  118   c ,  118   d  of the first plate  112  may be completely aligned with the apertures  120   a ,  120   b ,  120   c ,  120   d  in a fully opened position of the valve  110  not shown in these FIGS., and the initial position shown in  FIG. 11A  is only a partially opened position of the valve  110 . In this partially opened position shown in  FIG. 11A , all of the ports  122   a ,  122   b ,  122   c , and  122   d  are at least partially open, but the difference in sizes of the apertures  118   a ,  118   b ,  118   c ,  118   d  in the first plate  112  causes a smaller opening to be defined through port  122   a  as compared to the opening defined through port  122   b  (and smaller than the even larger openings through ports  122   c  and  122   d ). Therefore, as illustrated in the following sequence of FIGS., the continued rotation of the second plate  114  towards the closed position (counterclockwise as viewed from the top down as shown in these FIGS.) will cause the ports  122   a ,  122   b ,  122   c ,  122   d  to be closed in order of the relative sizes of the apertures  118   a ,  118   b ,  118   c ,  118   d , from smallest to largest. 
     To this end, the next position of the valve  110  during a closing operation is shown in  FIG. 11B , in which port  122   a  is closed, and ports  122   b ,  122   c , and  122   d  remain partially open. Each of the flow openings through the other ports  122   b ,  122   c ,  122   d  has become smaller as shown in  FIG. 11B  compared to the openings shown in  FIG. 11A . Likewise, the next position of the valve  110  during a closing operation is shown in  FIG. 11C , in which ports  122   a  and  122   b  are closed, and ports  122   c  and  122   d  remain partially open. Continued rotation of the second plate  114  will then result in the port  122   c  being closed (while the port  122   d  remains open) and then finally, the port  122   d  will close. This final position of the valve  110  is the closed position shown in  FIG. 11D , in which all ports  122   a ,  122   b ,  122   c , and  122   d  are closed. As a result of this sequential opening/closing design, only one of the plurality of ports  122   a ,  122   b ,  122   c ,  122   d  is being completely closed at one time. As a result, the rotational force that needs to be applied to the second plate  114  is significantly reduced compared to the alternative case where each of the ports  122   a ,  122   b ,  122   c ,  122   d  closes simultaneously (because the adhesive in the ports  122   a ,  122   b ,  122   c ,  122   d  would apply opposing torque forces at each opening being closed when done simultaneously, increasing the total resistance to closing movement by four times or more). Therefore, the rotary knife gate valve  110  is able to be easily opened and closed manually rather than requiring a high-torque motor to open and close the valve  110 . 
     Consequently, the rotary knife gate valve  110  of the illustrated embodiment also includes a handle  130  projecting radially outward beyond the outermost peripheral portion  114   a  of the second plate  114  to allow an operator to manually rotate the second plate  114  relative to the first plate  112 . In addition, the collar  116  can include a locating notch  132  that receives and retains the handle  130  when all the ports  122   a ,  122   b ,  122   c , and  122   d  are closed (e.g., when the valve  110  is in the closed position), as shown in  FIG. 11D . The handle  130  of the illustrated embodiment is configured as a squeeze handle  130  including a latching end  131  that frictionally engages the collar  116  or the notch  132 , except when the squeeze handle  130  is compressed as shown in  FIG. 10B , which causes the latching end  131  to pivot upwardly away from the collar  116 . It will be appreciated that the engagement of the latching end  131  and the notch  132  in the closed position can positively lock the handle  130  and the second plate  114  in the closed position until an intentional compression force is applied to the handle  130 , thereby ensuring that the valve  110  is not opened until the operator desires this opening. The collar  116  may also include optional visual indicia indicating the fully opened and fully closed positions as shown in  FIGS. 9 through 10B  in some embodiments. As shown in  FIGS. 9 through 11D , a couple of the bolt fasteners  117  connecting the collar  116  to the first plate  112  may optionally be removed along the arc length of travel (a partial rotation) for the handle  130  so that the handle  130  and second plate  114  can freely rotate between the open and closed positions of the valve  110 , although this removal of fasteners  117  is not required in all embodiments. 
     Also as shown by the progressive sequence of positions defined by the valve  110  during closing in  FIGS. 11A through 11D , the corresponding side edges  118   s ,  120   s  of the plurality of apertures  118 ,  120  in the first and second plates  112 ,  114  are not provided at the same angle relative to the central axis CA (e.g., the center of the first and second plates  112 ,  114 ). Instead, the side edges  118   s ,  120   s  are angled differently so that the point (radially innermost) end of the side edges  118   s  on the apertures  118   a ,  118   b ,  118   c ,  118   d  in the first plate  112  crosses underneath the corresponding side edge  120   s  on the apertures  120   a ,  120   b ,  120   c ,  120   d  before the base (radially outermost) end of the same side edges  118   s  crosses underneath the corresponding side edges  120   s . Accordingly, each of the ports  122   a ,  122   b ,  122   c ,  122   d  closes with a progressive scissor-like action rather than having the two side edges  118   s ,  120   s  close along their entire lengths simultaneously. This scissor-like action at the closing of the ports  122   a ,  122   b ,  122   c ,  122   d  tends to push adhesive particulates in the ports  122   a ,  122   b ,  122   c ,  122   d  outwardly and out of the way rather than pinching the adhesive particulates in half, as typically happens when the two side edges  118   s ,  120   s  close along their entire lengths simultaneously. This potential pinching or cutting of the adhesive particulates can jam the ports  122   a ,  122   b ,  122   c ,  122   d  and make it significantly more difficult to close the valve  110 , so the scissor-like action when closing each of the ports  122   a ,  122   b ,  122   c ,  122   d  improves the operation of the valve  110 , especially when operated manually as shown. 
     As noted above, the rotary knife gate valve  110  can be used for either or both of the valves  26 ,  60  at the bulk supply  12  and at the mobile bin  14 . Therefore, operation of those valves  26 ,  60  would include sequentially opening and sequentially closing the ports  122   a ,  122   b ,  122   c , and  122   d  with the advantageous scissor-like action described above. In some instances, for example, such a valve could be used to interrupt a moving or nonmoving amount of adhesive particulate extending through the valve  110 . For example, if the valve  110  were used on the mobile bin  14 , the valve  110  might be used to close the ports  122   a ,  122   b ,  122   c , and  122   d  before all the adhesive particulate are removed from the mobile bin  14  into the buffer unit  16 . To this end, the valve  110  shown in these FIGS. advantageously enables easy manual opening and closing operation even when the valve  110  must effectively cut through a column of stacked adhesive particulate extending between the mobile bin  14  and the buffer unit  16 , or between the bulk supply  12  and the mobile bin  14 . 
     As briefly discussed above, several alternative arrangements for transferring the adhesive particulate from a bulk supply to melt sections of melters are possible in accordance with the scope of this disclosure. To this end, the transfer device defined by the mobile bin  14  in the first embodiment of  FIGS. 1 through 8B  may be modified for the additional functionalities and benefits described below in other embodiments. Referring next to  FIGS. 12 through 14 , another embodiment of a melter  140  used with a hot melt adhesive dispensing system is shown. This embodiment of the melter  140  includes a transfer device  150  in the form of a modified mobile bin  150 , and also includes a melt section  200 . The melt section  200  includes a heating grid, reservoir, manifold and liquid adhesive pump, for example. The mobile bin  150  or transfer device of this embodiment is generally configured to receive adhesive particulate from the bulk supply  12  in a similar manner as the previously-described mobile bin  14 . Instead of being configured to dock at a buffer unit  16  as previously described, the mobile bin  150  is configured to be selectively docked to the melt section  200  of the melter  140 . In particular, the mobile bin  150  may be configured to selectively dock to the type of melt section shown in U.S. Patent Application Publication No. 2014/0102858, the content of which (relative to the melter and a feeder element described briefly below) is hereby incorporated by reference in its entirety. In this regard, the mobile bin  150  will effectively define a hopper for the melter  140 , e.g., the mobile bin  150  is a part of the melter  140 . 
     With particular reference to  FIG. 12 , the mobile bin  150  of this embodiment includes a container  152  connected to and supported by a framework  154  having at least one wheel  156 , and in the embodiment shown includes four wheels  156  on four support members defining the framework  154 . The wheels  156  enable rolling movement of the mobile bin  150  between the bulk supply  12  and the melt section  200 . The container  152  has an inlet  158  configured to receive and hold a supply of adhesive particulate from the bulk supply  12 , and an outlet  160  configured to provide adhesive particulate into an inlet defined by a feeder element  202  of the melt section  200  (shown in  FIG. 13 ). Although the inlet  158  is shown as a completely open top to the container  152  in these FIGS., it will be understood that this inlet  158  may include a lid with an inlet port sized to engage the outlet  24  of the bulk supply  12  in some embodiments, in a similar manner as the mobile bin  14  described in connection with the first embodiment. The container  152  is defined by a body  162  having a shape configured to direct adhesive particulates toward the outlet  160 , such as a generally tapered hopper shape shown in  FIGS. 12 and 13 . The mobile bin  150  is configured such that the outlet  160  may be positioned into docked engagement with the melt section  200  such that adhesive particulate can flow out of the outlet  160  of the mobile bin  150  and into the inlet of the melt section  200 . 
     Additionally, the mobile bin  150  of this embodiment includes a valve  166  located at the outlet  160  of the container  152  and configured to selectively open and close the outlet  160  to control the flow of adhesive particulate out of the container  152 . The valve  166  functions to close the outlet  160  of the mobile bin  150  whenever the mobile bin  150  is being moved, such as between the bulk supply  12  and the melt section  200 , and this closure of the outlet  160  prevents adhesive particulate from the container  152  from being spilled during the movement of the adhesive particulate in the mobile bin  150 . It will be understood that alternative mechanisms for opening and closing the outlet  160  may be provided in other embodiments of the transfer device defined by the mobile bin  150 . Optionally, the valve  166  may be configured to automatically close when the mobile bin  150  is not docked with the melt section  200 , and to automatically open when the mobile bin  150  is docked with the melt section  200 . However, the valve  166  could be configured to be manually actuated between open and closed positions as well. Advantageously, the valve  166  includes a rotary knife gate valve as described above with reference to  FIGS. 9 through 11D , thereby providing the advantageous operational benefits described above. The mobile bin  150  also includes a push handle  168  connected to the framework  154  and configured to provide a convenient ergonomic gripping point for an operator to push or pull the mobile bin  150  when moving the mobile bin  150  between the bulk supply  12  and the melt section  200 . 
     The mobile bin  150  in this embodiment of the melter  140  is used in a generally similar manner as the mobile bin  14  discussed above. Once the mobile bin  150  receives adhesive particulate from the bulk supply  12 , it is moved to a position proximate to the melt section  200 , as shown in  FIG. 13 . The mobile bin  150  is then docked to the melt section  200  (e.g., releasably attached using known means such as clamps, latches, etc., not shown in the FIGS.) by connecting the outlet  160  of the mobile bin  150  to the feeder element  202  of the melt section  200 , and adhesive particulate may then be directed from the container  152  into the melt section  200 . It will be appreciated that in some embodiments, the outlet  160  of the mobile bin  150  is merely aligned with the feeder element  202  rather than being connected or docked thereto. When the outlet  160  is docked to the melt section  200 , the valve  166  and bottom end of the container  152  effectively define the docking structure used to releasably connect to the feeder element  202  of the melt section  200 . 
     As described in U.S. Patent Application Publication No. 2014/0102858, incorporated by reference above, the feeder element  202  includes internal agitation structure (not shown) configured to agitate any flow of adhesive particulate out of the outlet  160  to force this flow to move through a projection  204  of the feeder element  202  aligned with a top opening  206  in a heated portion  208  of the melt section  200 . Also as described in detail in U.S. Publication 2014/0102858 (above), the top opening  206  includes an optional shroud  210  for guiding the flowing adhesive particulate from the projection  204  into the heated portion  208 , where a heater grid or some other known heater structures are used to apply heat and melt the adhesive particulate into liquid adhesive which is then provided to dispensing guns or other similar elements by the melt section  200 . Therefore, in the embodiments in which the mobile bin  150  is docked with the melt section  200 , the feeder element  202  defines a docking structure at an inlet of the melt section  200  so as to enable selective disconnection and removal of the mobile bin  150  from the melt section  200 . This disconnection and removal may be desired when the container  152  is emptied of adhesive particulate by the melt section  200  or even before the container  152  is emptied, if so desired. Advantageously, the melt section  200  continues operating to melt adhesive particulate and supply liquid adhesive even when the mobile bin  150  is undocked from the melt section  200 . The mobile bin  150  can be refilled or replenished with adhesive particulate at the bulk supply  12  and replaced, or a similar second mobile bin  150  filled with adhesive particulate can be docked to the melt section  200  to replace the empty initial mobile bin  150 , all without interrupting operation of the melt section  200 . 
     When the container  152  of the mobile bin  150  operates as a hopper of the melter  140  as shown in these FIGS., it will be understood that the hopper is preferably unheatred, but may be heated without departing from the functionality of this embodiment of the invention. The removable hopper concept for a melter  140  improves the functionality of this and other melters  140  by avoiding the problems with hand scoop-based manual filling of known hoppers rigidly connected to known melters while eliminating the need for pneumatic transfer or filling devices. Furthermore, the removable hopper or transfer device can be even further simplified or modified in other embodiments, such as those described below in connection with  FIGS. 15A and 15B . 
     As shown in phantom in  FIG. 13  and in solid in  FIG. 14 , the melt section  200  of this embodiment also includes an enclosure  212  that shields the heated portion  208  of the melt section  200  from operators and the outside environment, while also optionally mounting the melt section  200  on wheels. The mobile bin  150  and specifically the moveable unit defined by the container  152  and the outlet  160  are sized so as to fit completely within the enclosure  212  of the melt section  200  when the mobile bin  150  is docked with or moved into alignment with the melt section  200 . In other words,  FIGS. 13 and 14  show the mobile bin  150  moved inside the confines of the enclosure  212 . For example, part or all of the enclosure  212  may be temporarily removed when the mobile bin  150  is docked to the melt section  200 . The enclosure  212  may thereafter be reinstalled (similar to what is shown in  FIG. 14 ) to continue protecting the operator and any equipment/personnel in the area of the melt section  200  from heat energy produced by the melt section  200 . Alternatively, the mobile bin  150  can include part of an enclosure that when docked to the melt section  220  defines a part of the enclosure  212  in other embodiments. 
     In some versions of this embodiment, the container  152  (and possibly the feeder element  202  as described below) is selectively separable from the framework  154  and the remainder of the mobile bin  150 . For example, the framework  154  having wheels  156  can be used to transport the container  152  to and from the bulk supply  12 , so that adhesive particulates can be put into the container  152 . Once the container  152  are docked with the melt section  200 , the framework  154  can optionally be separated from the container  152  and moved away therefrom. In such versions of this embodiment, it is unnecessary to fit the entire framework  154  inside the enclosure  212  of the melt section  200 . In view of the simplified mechanism (e.g., the mobile bin  150 ) for transferring the adhesive particulate from the bulk supply  12  to the melt section  200 , this embodiment of the melter  140  provides the same benefits described above as the first embodiment, including but not limited to minimized risk of operator exposure to adhesive dust and minimized risk of adhesive contamination or spillage during transfer. 
     With reference to  FIG. 15A , another embodiment of a transfer device  250  defining part of a melter is shown for use with the melt section  200  of the previous embodiment. This transfer device  250  is effectively the mobile bin  150  with the framework  154  removed, as alluded to in the alternative embodiment of the previous paragraph. More particularly, the transfer device  250  includes a container  252  configured to hold a supply of the adhesive particulate from the bulk supply  12  and an outlet  260  associated with the container  252 . In order to prevent adhesive spillage during movement of the transfer device  250  between the bulk supply  12  and the melt section  200 , a valve  266  such as the knife gate valve described above is associated with the outlet  260  and controls flow of adhesive particular from the container  252  by selectively opening and closing the outlet  260 . As shown by phantom lines connecting the exploded apart structures in  FIG. 15A , the transfer device  250  is configured to be moved by an operator into alignment with the feeder element  202  of the melt section  200 , and the outlet  260  and valve  266  are understood to define docking structure for docking to the feeder element  202  in this embodiment. As with the previous embodiment, the transfer device  250  may be positioned within an enclosure  212  of the melt section  200  when these elements are docked together. Furthermore, the transfer device  250  continues to provide the advantageous benefits of a removable and refillable/replaceable hopper for the melter, the removal and replacement of the hopper being conducted while the melt section  200  continues to operate in continuous fashion. Also as with the previous embodiment, the same refilled transfer device  250  can be docked to the melt section  200  or a second replacement transfer device  250  that is already filled with adhesive particulate may be docked in place of the original transfer device  250 . As clearly evidenced in this embodiment, the container  252  and the outlet  260  collectively define a removable or moveable unit that can be moved by an operator to the melt section  200  for supplying adhesive particulate and that can be moved away from the melt section  200 , such as when the container  252  is emptied of adhesive particulate by the melt section  200 . 
     A slightly modified embodiment of the transfer device  350  defining part of a melter is shown in  FIG. 15B . The only difference in this embodiment of the transfer device  350  compared to the previous embodiment (transfer device  250 ) is that the feeder element  202  is now incorporated into the moveable unit of the transfer device  350  rather than the melt section  200 . Therefore, the inlet and/or docking structure of the melt section  200  in this embodiment is defined by the top opening  206  into the heated portion  208  and its associated optional shroud  210 . Meanwhile, the outlet  360  of the transfer device  350  is now defined by the projection  204  on the feeder element  202 . The knife gate valve device used in previous embodiments can be dispensed with between the container  352  and the feeder element  202  because the feeder element  202  controls flow through the outlet  360  (e.g., selectively opens and closes the outlet  360 ) by selectively agitating the adhesive particulate with the internal agitation elements not shown in these Figures. As with the previous embodiments, the transfer device  350  can function as a removable hopper of the melter and this removal can be conducted during continuous operation of the heated portion  208  of the melt section  200 . Likewise, the transfer device  350  is easily aligned with or docked to the inlet defined by the melt section  200 , thereby simplifying the process for refilling a hopper on the melter. 
     Consequently, in each of the embodiments of the bulk adhesive transfer system or device described above, one or more mechanisms that may be described as defining a transfer assembly are provided to help transfer and control flow of adhesive particulate between a bulk supply  12  and a melter (and indeed, may define a part of the melter). For example, the first embodiment of the transfer system  10  includes a transfer assembly having the valve  26 , the mobile bin  14 , and the buffer unit  16  in combination. Regardless of the particular structures defining the transfer assembly, these mechanisms avoid the need for an operator to manually transfer adhesive particulate from one remote location to another using manual scoops of adhesive or wheeled totes that may be difficult to control when completely filled. Accordingly, the risks of operator exposure to adhesive dust and the risks of adhesive spillage and contamination during transfer to the melter are minimized when using any of the bulk adhesive transfer systems or devices. Furthermore, the use of the removable transfer devices enables continuous operation of melter even during a refilling or replacement operation. 
     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.