Abstract:
A hot melt dispensing system comprises a container, a melter, a feed system, a dispensing system and a fluid line. The container stores hot melt pellets. The feed system transports hot melt pellets from the container to the melter. The melter is capable of heating hot melt pellets into liquid hot melt adhesive. The fluid line connects the melter and the dispensing system. The dispensing system administers liquid hot melt adhesive from the melter. The fluid line comprises a rigid segment and a heating element connected to the rigid segment. In another embodiment, the fluid line comprises first and section portions connected by an articulating joint.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is a non-provisional of U.S. Application Ser. No. 61/552,229, filed on Oct. 27, 2011. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates generally to systems for dispensing hot melt adhesive. More particularly, the present disclosure relates to heated tubing for connecting pumps with hot melt adhesive dispensers. 
         [0003]    Hot melt dispensing systems are typically used in manufacturing assembly lines to automatically disperse an adhesive used in the construction of packaging materials such as boxes, cartons and the like. Hot melt dispensing systems conventionally comprise a material tank, heating elements, a pump and a dispenser. Solid polymer pellets are melted in the tank using a heating element before being supplied to the dispenser by the pump. Because the melted pellets will re-solidify into solid form if permitted to cool, the melted pellets must be maintained at temperature from the tank to the dispenser. This typically requires placement of heating elements in the tank, the pump and the dispenser, as well as heating any tubing or hoses that connect those components. Furthermore, conventional hot melt dispensing systems typically utilize tanks having large volumes so that extended periods of dispensing can occur after the pellets contained therein are melted. However, the large volume of pellets within the tank requires a lengthy period of time to completely melt, which increases start-up times for the system. For example, a typical tank includes a plurality of heating elements lining the walls of a rectangular, gravity-fed tank such that melted pellets along the walls prevents the heating elements from efficiently melting pellets in the center of the container. The extended time required to melt the pellets in these tanks increases the likelihood of “charring” or darkening of the adhesive due to prolonged heat exposure. 
       SUMMARY 
       [0004]    According to the present invention, a hot melt dispensing system comprises a container, a melter, a feed system, a dispensing system and a fluid line. The container stores hot melt pellets. The feed system transports hot melt pellets from the container to the melter. The melter is capable of heating hot melt pellets into liquid hot melt adhesive. The fluid line connects the melter and the dispensing system. The dispensing system administers liquid hot melt adhesive from the melter. The fluid line comprises a rigid segment and a heating element connected to the rigid segment. In another embodiment, the fluid line comprises first and section portions connected by an articulating joint. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a schematic view of a system for dispensing hot melt adhesive including a hot melt dispenser. 
           [0006]      FIG. 2  is a schematic of the a melt dispensing system wherein the hot melt dispenser of  FIG. 1  is implemented within a container erector system using heated, rigid tubing connected at an articulating joint. 
           [0007]      FIG. 3  is a perspective view of a first embodiment of the articulating joint of  FIG. 2  comprising a pivoting joint connecting the heated, rigid tubing. 
           [0008]      FIG. 4  is a cross-sectional view of a second embodiment of the articulating joint of  FIG. 2  comprising a swivel joint connecting the heated, rigid tubing. 
           [0009]      FIG. 5  is a perspective view of a third embodiment of the articulating joint of  FIG. 2  comprising a flexible coupling connecting the heated, rigid tubing. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIG. 1  is a schematic view of system  10 , which is a system for dispensing hot melt adhesive. System  10  includes cold section  12 , hot section  14 , air source  16 , air control valve  17 , and controller  18 . In the embodiment shown in  FIG. 1 , cold section  12  includes container  20  and feed assembly  22 , which includes vacuum assembly  24 , feed hose  26 , and inlet  28 . In the embodiment shown in  FIG. 1 , hot section  14  includes melt system  30 , pump  32 , and dispenser  34 . Air source  16  is a source of compressed air supplied to components of system  10  in both cold section  12  and hot section  14 . Air control valve  17  is connected to air source  16  via air hose  35 A, and selectively controls air flow from air source  16  through air hose  35 B to vacuum assembly  24  and through air hose  35 C to motor  36  of pump  32 . Air hose  35 D connects air source  16  to dispenser  34 , bypassing air control valve  17 . Controller  18  is connected in communication with various components of system  10 , such as air control valve  17 , melt system  30 , pump  32 , and/or dispenser  34 , for controlling operation of system  10 . 
         [0011]    Components of cold section  12  can be operated at room temperature, without being heated. Container  20  can be a hopper for containing a quantity of solid adhesive pellets for use by system  10 . Suitable adhesives can include, for example, a thermoplastic polymer glue such as ethylene vinyl acetate (EVA) or metallocene. Feed assembly  22  connects container  20  to hot section  14  for delivering the solid adhesive pellets from container  20  to hot section  14 . Feed assembly  22  includes vacuum assembly  24  and feed hose  26 . Vacuum assembly  24  is positioned in container  20 . Compressed air from air source  16  and air control valve  17  is delivered to vacuum assembly  24  to create a vacuum, inducing flow of solid adhesive pellets into inlet  28  of vacuum assembly  24  and then through feed hose  26  to hot section  14 . Feed hose  26  is a tube or other passage sized with a diameter substantially larger than that of the solid adhesive pellets to allow the solid adhesive pellets to flow freely through feed hose  26 . Feed hose  26  connects vacuum assembly  24  to hot section  14 . 
         [0012]    Solid adhesive pellets are delivered from feed hose  26  to melt system  30 . Melt system  30  can include a container (not shown) and resistive heating elements (not shown) for melting the solid adhesive pellets to form a hot melt adhesive in liquid form. Melt system  30  can be sized to have a relatively small adhesive volume, for example about 0.5 liters, and configured to melt solid adhesive pellets in a relatively short period of time. Pump  32  is driven by motor  36  to pump hot melt adhesive from melt system  30 , through supply hose  38 , to dispenser  34 . Motor  36  can be an air motor driven by pulses of compressed air from air source  16  and air control valve  17 . Pump  32  can be a linear displacement pump driven by motor  36 . In the illustrated embodiment, dispenser  34  includes manifold  40  and module  42 . Hot melt adhesive from pump  32  is received in manifold  40  and dispensed via dispensing module  42 . Dispenser  34  can selectively discharge hot melt adhesive whereby the hot melt adhesive is sprayed out outlet  44  of module  42  onto an object, such as a package, a case, or another object benefiting from hot melt adhesive dispensed by system  10 . Module  42  can be one of multiple modules that are part of dispenser  34 . In an alternative embodiment, dispenser  34  can have a different configuration, such as a handheld gun-type dispenser. Some or all of the components in hot section  14 , including melt system  30 , pump  32 , supply hose  38 , and dispenser  34 , can be heated to keep the hot melt adhesive in a liquid state throughout hot section  14  during the dispensing process. 
         [0013]    System  10  can be part of an industrial process, for example, for packaging and sealing cardboard packages and/or cases of packages. In alternative embodiments, system  10  can be modified as necessary for a particular industrial process application. For example, in one embodiment (not shown), pump  32  can be separated from melt system  30  and instead attached to dispenser  34 . Supply hose  38  can then connect melt system  30  to pump  32 . 
         [0014]      FIG. 2  is a schematic of hot melt dispensing system  10  of  FIG. 1  wherein hot melt dispenser  34  is implemented within container erector system  46  using heated articulating tubing system  48  of the present invention. Melt system  30 , pump  32 , dispenser  34  and motor  36  are configured the same as in  FIG. 1 . However, in  FIG. 2  hose  38  is replaced by heated articulating tubing system  48 , and dispenser  34  is positioned inside container erector system  46  to apply hot melt adhesive to container  49 . The outlet of pump  32  is connected to the inlet of manifold  40  via tube sections  50 A- 50 E and joints  52 A- 52 D. Tube sections  50 A- 50 C include heating elements  54 A- 54 C, and temperature sensors  56 A- 56 C, respectively. Tube sections  50 D and  50 E may also include heating elements and temperature sensors, but they are not shown in  FIG. 2  for simplicity. 
         [0015]    Liquefied hot melt adhesive from melt system  30  is drawn into pump  32  and pumped under pressure to heated articulating tubing system  48 . Tube section  50 A extends from pump  32  to joint  52 A within container erector  46 . Joint  52 A fluidly connects tube section  50 A to tube section  50 B. Joint  52 B fluidly connects tube section  50 B to tube section  50 C within container erector  46 . Joint  52 C fluidly connects tube section  50 C to tube section  50 D within container erector  46 . Joint  52 D fluidly connects tube section  50 D to tube section  50 E within container erector  46 . Tube section  50 D fluidly connects to manifold  40  of dispenser  34 . Module  42  of dispenser  34  receives hot melt adhesive from manifold  40  such that molten hot melt adhesive from orifice  44  can be applied to container  49 . 
         [0016]    As discussed with reference to  FIG. 1 , melt system  30  converts solid hot melt adhesive pellets to a liquid hot melt adhesive. Pump  32  includes heating elements as are known in the art to maintain the hot melt adhesive in a molten state. Heating elements  54 A- 54 C maintain the hot melt adhesive in liquid form within heated articulating tubing system  48  to maintain the adhesive above its melt temperature when it arrives at dispenser  34 . Dispenser  34  may also include heating elements as needed. Heating elements  54 A- 54 C and temperature sensors  56 A- 56 C are connected to controller  18 . Controller  18  controls operation of heating elements  54 A- 54 C during all phases of operation of system  12 . For example, some or all of heating elements  54 A- 54 C may be operated at different times during start-up, operation and shut-down of system  12  to conserve energy or apply concentrated heating. Controller  18  activates heating elements  54 A- 54 C based on feedback from temperature sensors  56 A- 56 C. 
         [0017]    Container erector  46  may comprise any container erector system as is known in the art. In one embodiment, container erector  46  builds and assembles boxes from flattened pieces of cardboard. For example, U.S. Pat. Nos. 4,018,143 and 4,798,571 describe examples of container erector systems that may benefit from the present invention. In some hot melt dispensing systems, the container erector is mounted so as to be stationary with reference to the pump. Even in hot melt dispensing systems without container erectors, the dispenser can be mounted stationary with respect to the pump. Container erector systems often include tight, small, enclosed or otherwise cramped spaces where dispensers, such as dispenser  34 , need to be mounted. Thus, in conventional hot melt dispensing systems, flexible hoses are used connect the dispenser to the pump. However, for dispensers that are stationary, it is not necessary for the hoses to have flexibility after the system is installed. Furthermore, the elasticity of common flexible hoses induces low-cycle fatigue into heating elements and sensors mounted on the hoses as the pressures within the hoses change during operation of the system. Flexible hoses have an additional drawback in that hot melt adhesive can have a tendency to cake on the inside of the hoses, which leads to the adhesive charring at such locations. If the flexible hose is jostled or bent, the charred adhesive can break loose and sully the molten hot melt adhesive flowing through the hose to the dispenser. 
         [0018]    Heated articulating tubing system  48  of the present invention permits dispenser  34  to be mounted in a tight or enclosed space that is typically stationary. Tube sections  50 A- 50 D provide rigid fluid conveying bodies, such as pipes, conduits or ducts, that provide stiff platforms for mounting heating elements  54 A- 54 C and temperature sensors  56 A- 56 C. Joints  52 A- 52 D permit tube sections  50 A- 50 D to be arranged in the desired orientation with respect to each other so that dispenser  34  can be located in the desired position with respect to pump  32 . Joints  52 A- 52 D permit tube sections  50 A- 50 D to rotate, pivot or flex with respect to tube sections connected thereto. For a stationary system, once dispenser  34  is installed within container erector  46 , joints  52 A- 52 D are no longer needed to move or be articulated. For example, tube sections  50 A- 50 D can be rigidly secured to other components of system  12 , such as structural elements (e.g. conveyer belt rails or box skids) of container erector  46 , or fixed structures within the facility that system  12  is used, such as walls, ceilings or floors. Tube sections  54 A- 54 D thereby provide rigid platforms upon which heating elements  54 A- 54 C and temperature sensors  56 A- 56  can be mounted. Because tube sections  54 A- 54 C are rigid and generally inflexible, pressure changes within each tube section do not induce stress and strain in heating elements  54 A- 54 C and temperature sensors  56 A- 56  coupled thereto, thereby increasing the service life of such components. 
         [0019]      FIG. 3  is a perspective view of a first embodiment of joint  52 A connecting tube sections  50 A and  50 B in heated articulating tubing system  48  of  FIG. 2 . In the embodiment shown in  FIG. 3 , joint  52 A comprises pivot joint  58 . Tube sections  50 A and  50 B include hot melt passages  60 A and  60 B and heating element passages  62 A and  62 B, respectively. Pivot joint  58  extends into bores entering tube sections  50 A and  50 B so as to transversely intersect passages  60 A and  60 B. Heating elements  64 A and  64 B are inserted into passages  60 A and  60 B, respectively. Temperature sensor  66 A is connected to tube section  50 A. Tube section  50 B may also include a temperature sensor (not shown). Temperature sensor  66 A and heating elements  64 A and  64 B are electrically connected to or controlled by controller  18 . 
         [0020]    In the embodiment shown, tube section  50 A comprises a rectilinear pipe section having two internal passages defined by passages  60 A and  62 A. Passage  60 A comprises a blind hole that extends into tube section  50 A only as far as pivot joint  58 . However, in other embodiments, passage  60 A can extend all the way through tube section  50 A and plugs can be used at one or both ends to facilitate connection with an articulating joint if needed. Passage  62 A extends all the way through tube section  50 A so as to permit entry of heating element  64 A and to allow access for wires that connect to controller  18 . Passage  62 A and heating element  64 A may extend beyond passage  60 A and across pivot joint  58  such that heat from heating element  64 A can be applied to joint  52 A. However, in other embodiments, passage  62 A can comprise a blind hole or can utilize plugs to facilitate connection with a heating element if needed. 
         [0021]    Other than passages  60 A and  62 A and where pivot joint  58  is seated, tube section  50 A comprises a substantially solid block of material. As such, material between passages  60 A and  62 A efficiently transfers heat from heating element  64 A to passage  60 A. Passage  62 A is positioned in close proximity to passage  60 A so as to further facilitate heat transfer between the passages. Temperature sensor  66 A is positioned in close proximity to passage  60 A so as to more accurately determine the temperature of liquid hot melt adhesive within tube section  50 A. Temperature sensor  66 A can be positioned anywhere along tube section  50 A, including within passage  60 A or  62 A. Tube section  50 B is configured the same as tube section  50 B in the embodiment of  FIG. 3 . 
         [0022]    Tube sections  50 A and  50 B may be comprised of any material suitable for transporting molten hot melt adhesive. In one embodiment, tube sections  50 A and  50 B are comprised of aluminum. However, other metals, alloys or materials, such as plastics or polymers, may be used. Heating elements  54 A and  54 B may comprise any suitable heating element as is known in the industry. For example, heating elements  54 A and  54 B may comprise electrical resistance heating elements. Elongate heating cartridges, such as those described in U.S. Pat. Nos. 5,575,941 and 3,937,923, may be inserted into passages  62 A and  62 B. Alternatively, strands of wire heating elements may be strung into passages  62 A and  62 B. Temperature sensor  66 A may comprise any suitable sensor as is known in the industry, such as a thermocouple or an RTD (resistance temperature detector). 
         [0023]    Pivot joint  58  couples tube sections  50 A and  50 B together such that each is rotatable relative to the other along an axis A 1 . Pivot joint  58  permits each of tube sections  50 A and  50 B to rotate three-hundred-sixty degrees around axis A 1 . Swivel joint  58  may comprise any connector as is known in the art. In one embodiment, swivel connector comprises a connector as shown in U.S. Pat. No. 5,330,106 to Braun, Jr., which is assigned to Graco Inc. For example, pivot joint  58  comprises a fastener that extends through tube sections  50 A and  50 B that includes a passage extending along axis A 1  and a plurality of circumferential ports intersecting that passage to intersect passages  60 A and  60 B in various positions. A swivel connector having a similar construction that is suitable for use with the present invention is shown and discussed with reference to  FIG. 4 . 
         [0024]      FIG. 4  is a cross-sectional view of a second embodiment of joint  52 A connecting tube sections  50 A and  50 B in heated articulating tubing system  48  of  FIG. 2 . In the embodiment of  FIG. 4 , joint  52 A comprises swivel joint  68 , which connects rigid tube sections  70 A and  70 B. Swivel joint  68  comprises fastener  72 , swivel  74 A and swivel  74 B. Rigid tube sections  70 A and  70 B include fluid passages  76 A and  76 B, and heating element passages  78 A and  78 B, respectively. Passages  76 A,  76 B,  78 A and  78 B are configured similar to passages  60 A,  60 B,  62 A and  62 B described with reference to  FIG. 3 . Swivel  74 A comprises neck  79 A, flange  80 A, fluid passage  82 A and threaded bore  84 A. Swivel  74 B comprises neck  79 B, flange  80 B, fluid passage  82 B and swivel passage  84 B. Swivel  74 B also includes swivel socket  86  and swivel pin  88 , which includes fluid passage  89 . Fastener  72  includes passage  90 , port  92  and port  94 , and is connected to nut  96 . 
         [0025]    Tube section  70 A is coupled to flange  80 A by any suitable means or is integral with flange  80 A. Passage  76 A within tube section  70 A feeds into fluid passage  82 A. Similarly, tube section  70 B is coupled to flange  80 B such that passage  76 B feeds into fluid passage  89  of swivel pin  88 . Swivel pin  88  is inserted into swivel socket  86  of swivel  74 B. In one embodiment, swivel pin  88  is threaded into swivel socket  86  at rotatable joint  97 . In another embodiment, swivel pin  88  is rotatably connected to swivel socket  86  such as with a snap connection or some other freely rotatable joint. Swivel  74 B is positioned relative to swivel  74 A such that swivel passage  84 B aligns with threaded bore  84 A along axis A 2 . Fastener  72  is inserted into threaded bore  84 A and swivel passages  84 B to mechanically and fluidly join tube sections  70 A and  70 B. In one embodiment, fastener  72  is threaded into threaded bore  84 A while swivel passage  84 B is permitted to freely rotate about fastener  72 . Nut  96  is threaded onto fastener  72  to prevent swivels  74 A and  74 B from separating from fastener  72 . Fastener  72  includes passage  90  which extends along axis A 2 . Ports  92  and  94  are positioned along fastener  72  so as to intersect passage  90  at the level of passages  82 B and  82 A, respectively. As such, a complete fluid path is formed by passage  76 A, passage  82 A, port  94 , passage  90 , port  92 , passage  82 B, passage  89  and passage  76 B. Seals  98 A,  98 B and  98 C may be positioned around fastener  72  adjacent necks  79 A and  79 B to seal along the fluid passage route. Connected as such, necks  79 A and  79 B are configured to rotate about axis A 2  so as to allow positioning of tube sections  70 A and  70 B relative to each other at different angles, while permitting uninterrupted fluid flow. Further, tube section  70 B can rotate perpendicularly relative to axis A 2  at joint  97 . 
         [0026]      FIG. 5  is a perspective view of a third embodiment of articulating joint  52 A connecting tube sections  50 A and  50 B in heated articulating tubing system  48  of  FIG. 2 . In the embodiment of  FIG. 4 , joint  52 A comprises flexible coupling  100 , which connects tube sections  102 A and  102 B. Flexible coupling  100  is jointed to tube sections  102 A and  102 B via clamps  104 A and  104 B. Tube section  102 A is coupled to heating element  106 A and temperature sensor  108 A, which are in electronic communication with controller  18 . 
         [0027]    Tube sections  102 A and  102 B comprise hollow, cylindrical pipes formed of a rigid material, such as metal, steel aluminum or a polymer. Flexible coupling  100  comprises a length of flexible tubing of any suitable construction that permits tube section  102 B to be positioned with two degrees of freedom relative to axis A 3 . Specifically, tube section  102 B can be positioned at any angle with respect to axis A 3  and can be positioned at any circumferential position about axis A 3 . In various embodiments, flexible coupling  100  comprises a corrugated metal or plastic tubing, braided metal or plastic hose, or flexible stainless steel tubing. In other embodiments, flexible coupling  100  can be encased in a flexible sheathing to protect the enclosed fluid-conveying structure. Flexible coupling  100  is connected to tube sections  102 A and  102 B via clamps  104 A and  104 B, which may comprise any suitable connector as is known in the art. For example, clamps  104 A and  104 B may comprise hose clamps, draw latches, spring clamps or split rings. 
         [0028]    Heating element  106 A is wrapped around tube section  102 A. In one embodiment of the invention, heating element  106 A comprises a resistive heating element comprising braided wiring wrapped around tube section  102 A in a spiral fashion. However, other types of flexible, stranded heating elements as are known in the art can be used and can be arranged about tube section  102 A in other configurations. Heating element  106 A can be secured to tube section  102 A with any suitable means, such as an adhesive. The adhesive may be configured to facilitate heat transfer between heating element  106 A and tube section  102 A. Tube section  102 B may be configured with a heating element and temperature sensor similarly to tube section  102 A. If flexible coupling  100  is maintained small, or short in length, heating elements disposed on tube section  102 A and  102 B are sufficient to maintain hot melt adhesive within flexible join  100  in a molten state when traveling between tube sections  102 A and  102 B such that a separate heating element for flexible coupling  100  is not needed. However, in other embodiments of the invention, flexible coupling  100  may itself be wrapped with a heating element. 
         [0029]    Because tube sections  102 A and  102 B are rigid or otherwise resistant to flexation, heating element  106 A and sensor  108 A are not subject to stresses and strains associated with expansion or ballooning of conventional flexible hoses. As such, the service life of heating element  106 A and sensor  108 A is increased. 
         [0030]    While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.