Abstract:
A hose for transferring heated liquid, such as molten thermoplastic material. The hose includes a conduit that has an inlet end adapted to couple with a source of heated liquid, such as a heated supply tank, and a discharge end adapted to couple with a liquid dispensing apparatus, such as an applicator gun. In one embodiment, the hose may be covered by a woven outer sheath of polyamide that protects the underlying hose against abrasion damage. In another embodiment, the hose may include a hose cuff mechanically coupled with the liquid dispensing apparatus to bolster resistance to axial tensile forces and bending forces applied to the hose.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/485,456 filed on Jul. 8, 2003, and the disclosure of which is hereby incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to heated hoses and, in particular, to heated hoses for carrying molten thermoplastic material.  
       BACKGROUND OF THE INVENTION  
       [0003]     Various manufacturing processes involve the transfer of a pressurized heated liquid from a source, such as a melter tank, through heated lengths of flexible heated hose to a liquid dispensing device, such as an applicator gun or a dispenser. The liquid dispensing device dispenses heated liquid onto a target surface in the form of a continuous bead or ribbon or as intermittent beads, droplets or deposits. Among the heated liquids frequently dispensed in this manner are thermoplastic materials, such as hot melt adhesives, that may be liquid or solid at room temperature. Such thermoplastic materials are commonly pumped through a heated hose to a liquid dispensing device, such as an applicator gun. Generally, conventional heated hoses include a central conduit for conveying the heated thermoplastic material from the source to the liquid dispensing device and multiple plies of thermal and electrical insulation, heaters, and electrical wiring surrounding the central conduit.  
         [0004]     Many manufacturing processes utilize production line techniques in which the liquid dispensing device must be moved by an operator about an assembly line during application of the heated liquid to the target surface. As would be expected, the required length of hose between the source and the liquid dispensing device varies from one manufacturing process to another. In. many production line settings, the length of the heated hoses exceeds 10 feet. As the operator moves about the assembly line, the lengthy hose contacts surrounding objects, such as the article or workpiece receiving the dispensed heated liquid.  
         [0005]     Conventional heated hoses are typically covered by an outer protective covering or sheath formed from a braided polyester monofilament. In assembly line environments, these hoses may fail due to tears in the sheath resulting from chaffing, abrasion or wear resulting from intermittent contact with objects in the work environment. In rough duty assembly lines, rapid failure of the protective sheath may necessitate frequent hose replacements, which are expensive and temporarily halt the manufacturing process. One conventional solution is to design the protective sheath from a rigid corrugated plastic, such as nylon. However, the corrugations may rub and scrape against the workpiece receiving the heated liquid, which damages the workpiece.  
         [0006]     The terminal ends of conventional hoses terminate in hose fittings that facilitate fluid couplings with the heated liquid source and with the liquid dispensing device. A rigid hose cuff applied in association with the hose fitting creates a rigid interface over the region of contact between the liquid dispensing device and the hose. As the hose flexes and bends with movement about the assembly line, the hose cuffs serve to reduce hose damage by limiting flexing at the point where the hose couples to the hose fitting of the liquid dispensing device.  
         [0007]     Nonetheless, the weakest point of the flexible hose, which represents the point most susceptible to breakage of insulation or electrical wires, is at this interface between the hose cuff and the hose. Traditional hose cuffs are not directly attached to the housing of the liquid dispensing device. Instead, the hose cuff is only indirectly coupled with the liquid dispensing device by the hose fitting. As a result, abrupt tensile forces applied to the hose, such as when the hose is snagged by an obstruction in the assembly line environment, and persistent tensile forces incidental to movement about the assembly line are transmitted directly to the hose cuff and the hose fitting. The tensile forces may cause the outer protective sheath of the hose to retract and pull back from underneath the hose cuff and fret, unravel, and/or fray. Damage to the outer protective sheath may expose and/or place unexpected stresses and strains on the underlying electrical wires and potentially precipitate secondary failures, such as wire breakage and electrical shorts.  
         [0008]     In view of the deficiencies in conventional heated flexible hoses discussed above, it would be desirable to provide a heated flexible hose for coupling a source of thermoplastic material with a liquid dispensing device in which the hose has an increased durability.  
       SUMMARY OF THE INVENTION  
       [0009]     In one embodiment of the invention, an apparatus for transferring a heated liquid includes a conduit having an inlet end adapted to be coupled in fluid communication with a heated liquid source and a discharge end adapted to be coupled in fluid communication with a liquid dispensing device. Extending between the inlet end and the discharge end of the conduit are a thermal insulation layer and a heating element positioned between the thermal insulation layer and the conduit. The heating element is adapted to generate and transfer heat to the conduit. The apparatus further includes a woven outer covering extending between the inlet end and the discharge end of the hose and having a surrounding relationship with the thermal insulation layer. The woven outer covering is constructed from a plurality of braided polyamide monofilaments.  
         [0010]     The polyamide woven outer covering of the invention prevents damage to the underlying flexible hose, yet presents a smooth surface that does not damage objects in the assembly line environment, including the workpiece receiving the heated liquid. The polyamide woven outer covering also has an improved durability as compared with conventional sleeves. However, the flexibility of the polyamide woven outer covering does not hinder movement of the liquid dispensing device about the assembly line during application of heated liquid to the intended target surface.  
         [0011]     In another embodiment of the invention, an apparatus comprises a heated hose having an inlet end adapted to couple in fluid communication with a heated liquid source and a discharge end adapted to couple in fluid communication with a liquid dispensing device. Extending between the inlet end and the discharge end of the conduit are a thermal insulation layer and a heating element positioned between the thermal insulation layer and the conduit. The heating element is adapted to generate and transfer heat to the conduit. Attached to the discharge end of the hose is a hose cuff with at least one coupling element directly securing the hose cuff to the liquid dispensing device. The securement of coupling element with the liquid dispensing device prevents relative axial movement between the hose cuff and the liquid dispensing device.  
         [0012]     In accordance with another embodiment of the invention, a method of attaching a heated hose to a liquid dispensing device includes coupling a fitting at a discharge end of the hose with the liquid dispensing device and directly coupling a hose cuff at the discharge end of the hose with a portion of the liquid dispensing device. The direct coupling prevents relative axial movement between the hose cuff and the liquid dispensing device during use.  
         [0013]     A hose cuff constructed in accordance with the principles of the invention provides a more robust connection between the flexible hose and the liquid dispensing device. The hose cuff of the invention prevents, or at least reduces the incidence of, premature failure of the outer protective sheath of the flexible hose proximate to the hose cuff by reducing the effect of tensile forces and bending forces applied to the flexible hose and, in particular, to the hose&#39;s protective outer sheath during use in an assembly line environment. As a result, the insulation or electrical wires at the interface between the hose cuff and the hose are less likely to break or short.  
         [0014]     A hose constructed in accordance with the principles of the invention may replace a pre-existing conventional hose. It follows that the hose of the invention may be retrofitted in existing assembly line manufacturing processes for coupling a heated liquid source, such as a melter tank, and a liquid dispensing device, such an applicator gun or a dispenser.  
         [0015]     Various objects and advantages of the invention shall be made apparent from the accompanying drawings of the illustrative embodiments and the descriptions thereof. 
     
    
     DETAILED DESCRIPTION OF DRAWINGS  
       [0016]     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.  
         [0017]      FIG. 1  is a perspective view of the hose of the present invention connecting a supply tank to an applicator gun;  
         [0018]      FIG. 2  is an enlarged partial cross-sectional plan view of the hose of  FIG. 1 ;  
         [0019]      FIG. 3  is an exploded perspective view of the tubular body and collar portion of the hose cuff of  FIGS. 1 and 2 ;  
         [0020]      FIG. 4  is an end view of the collar portion of the hose cuff; and  
         [0021]      FIG. 5  is a cross-sectional view of an alternative embodiment of a hose cuff in accordance with the principles of the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]     With reference to  FIG. 1  and in accordance with the principles of the present invention, an adhesive dispensing apparatus  10  includes a hose  12  that connects a pump  14  of a supply tank  16  with an applicator gun  18 . Pump  14  provides a pressurized flow of the thermoplastic material, such as a hot melt adhesive, from the supply tank  16  via hose  12  to the applicator gun  18 , which selectively dispenses thermoplastic material onto a target surface. Hose  12  has a preselected length, is generally cylindrical in cross-section, and has a flexibility sufficient to permit bending as an operator moves the applicator gun  18  about the assembly line environment surrounding adhesive dispensing apparatus  10 . This allows the operator to freely position and orient the applicator gun  18  for precisely dispensing thermoplastic material onto the intended target surface. The supply tank  16  and the applicator gun  18  may be heated to maintain the thermoplastic material in flowable condition until dispensed. A suitable applicator gun  18  is described in U.S. Pat. No. 4,245,759, the disclosure of which is hereby incorporated by reference herein in its entirety.  
         [0023]     With reference to  FIGS. 1 and 2 , the hose  12  includes a central conduit or tube  22 , typically of generally circular cross-section, through which thermoplastic material can flow from the supply tank  16 . Tube  22  has an inlet end  24  equipped with a threaded hydraulic fitting  25  that connects to a complementary threaded fitting (not shown) on pump  14  and a discharge end  26  equipped with a threaded hydraulic fitting  27  that connects to a complementary threaded fitting  29  carried by the applicator gun  18 . The length of tube  22 , typically formed from a high temperature engineering polymer resin, such as polytetrafluoroethylene (PTFE), is covered by a woven metal cover  28 .  
         [0024]     Helically wrapped about the woven metal cover  28  is a layer of electrically-insulating tape  30 , preferably fiberglass electrical tape. A heating element  32  and a temperature-sensing device  34 , such as a resistance temperature detector (RTD), are each helically wound about the woven metal cover  28  along the length of the hose  12  and are separated from the woven metal cover  28  by tape  30 . The heating element  32  transfers heat through the tube  22 , metal cover  28 , and tape layer  30  to thermoplastic material resident inside tube  22 . The temperature-sensing device  34  detects the temperature of tube  22 , which is representative of the temperature of the thermoplastic material within tube  22 , and provides a signal to a controller (not shown) that regulates the power delivered to heating element  32  and/or the power delivered for heating the supply tank  16 . Of course, the heating element  32  and the temperature-sensing device  34  may be omitted from hose  12  and the supply tank  16  will not be heated for transferring certain thermoplastic materials.  
         [0025]     Multiple electrical leads  36 - 40  are likewise helically wrapped along the length of the hose  12  and separated from the heating element  32  and temperature sensing device  34  by another helically-wound layer of electrically-insulating tape  42 . The electrical leads  36 - 40  are coupled with devices (not shown), such as a heater and a temperature sensor, inside the applicator gun  18  and to establish a ground connection for the applicator gun  18 . The opposite ends of the electrical leads  36 - 40 , the heating element  32  and the temperature-sensing device  34  are operatively connected to an electrical plug  20  that is intended to couple the electrical leads  36 - 40  of the hose  12  with a control panel at the supply tank  16 . Extending along the length of the hose  12  is a metal braided cable  44  separated from the electrical leads  36 - 40  by a helically wound layer of electrically-insulating tape  46  and a thermal insulation layer  48  (e.g., Ararmid fibers). The metal braided cable  44  is used to establish an electrical ground connection with the applicator gun  18  via one of the electrical leads  36 - 40 . Covering the metal braided cable  44  is at least one thermal insulation layer  50  and a helically wound layer of tape  52  (e.g., polyethylene tape) that holds the thermal insulation layer  50  in place. Suitable hose constructions for the various layers and leads of hose  12  are described, for example, in U.S. Pat. Nos. 4,553,023 and 4,455,474, the disclosures of which are hereby incorporated by reference herein in their entirety.  
         [0026]     With continued reference to  FIGS. 1 and 2 , a braided sleeve  54  overlies tape  52  and covers the full length of hose  12  to thereby serve as a flexible, protective cover. The braided sleeve  54  is compressively attached at the opposite ends of hose  12  by metal band clamps  56 ,  58  but is otherwise unattached along its length to tape  52 . The braided sleeve  54  is formed from a monofilament of a durable thermoplastic resin, such as a nylon or polyamide (based on either polyamide 6; polyamide 6,6; polyamide 12; or polyamide alloys or blends), woven into a braided form. The invention contemplates that any other suitable polyamides formed by the condensation of dibasic organic acids and diamines may also be used. Polyamides have a greater durability than polyester, which is used in conventional protective sleeves. The braided sleeve  54  may be constructed to expand radially so that the sleeve  54  may slide over hydraulic fittings  25 ,  27  and then extend axially and contract radially to conform snugly with the exterior of hose  12 .  
         [0027]     In one specific embodiment of the invention, the braided sleeve  54  is formed from oval-shaped monofilaments (0.019″ by 0.060″) each containing one (1) fiber per monofilament, has a wall thickness between about 0.040″ and 0.050″, includes eighty (80) interlaced carriers, has an expanded outer diameter of about 2″, and has a pull-down diameter of about 1.5″. A braided sleeve particularly suitable for use as braided sleeve  54  in the invention is commercially available under the ALTA-FLEX TUFF trade name from Alta Technologies, Inc. of Pennington, N.J.  
         [0028]     The braided sleeve  54  provides continuous abrasion resistance believed to be superior to conventional outer protective sheaths typically formed from a braided polyester or polyester monofilament. As a result, the longevity of hose  12  is increased because the braided sleeve  54  is less likely to be torn, thereby exposing the underlying hose components. The braided sleeve  54  is less likely to damage the article or workpiece receiving the thermoplastic material, as compared with conventional protective sheaths of rigid corrugated plastic, because the exterior surface is relatively smooth (i.e., non-corrugated) and free of corrugations or other undulating structure. The braided sleeve  54  slides smoothly across the workpiece without causing abrasion and without snagging or tearing.  
         [0029]     With reference to  FIGS. 2-4 , placed over the respective inlet and discharge ends  24 ,  26  are respective hose cuffs  60 ,  62  that lend rigidity to these portions of hose  12 . Hose cuff  62  aids in preventing loosening of the braided sleeve  54  from compressive securement by metal band clamp  58  at the discharge end  26  of hose  12 . To that end, the hose cuff  62  applies a radial compressive force to the braided sleeve  54 , which assists a metal band clamp  58  in securing the braided sleeve  54  with the hose  12 .  
         [0030]     Cuff  62  includes a tubular body  64  having a tubular sidewall  65  of a suitable radial thickness to be structurally rigid and a two-piece collar  66  assembled from a pair of substantially identical semi-circular collar portions  66   a ,  66   b  each having an axial opening  67 ,  69 . The sidewall  65  extends between opposite open ends  87  and  89  and is centered about an axis  91 . In certain embodiments, the tubular body  64  and the collar portions  66   a ,  66   b  are molded from any suitable rigid thermoplastic resin, such as RYTON polyphenylene sulfide commercially available from Chevron Phillips Chemical Company of The Woodlands, Texas. One of a pair of tube-encased bundles  70 ,  72 , each containing a subset of electrical leads  36 - 40 , projects through a corresponding one of the axial openings  67 ,  69 . Of course, if there is only a single bundle  70 ,  72 , one of the two collar portions  66   a ,  66   b  may lack the corresponding one of the axial openings  67 ,  69 . The axial openings  67 ,  69  are depicted as circular, although the invention is not so limited as the openings  67 ,  69  may be other shapes, such as oval. The axial openings  67 ,  69  are also depicted as diametrically flanking the circular opening  74  for tube  22 , although the invention is not so limited as the axial openings  67 ,  69  may be positioned at other locations.  
         [0031]     With reference to  FIGS. 3 and 4 , each of the collar portions  66   a ,  66   b  features a corresponding one of semi-circular openings  74   a ,  74   b  ( FIG. 4 ) that, when the two collar portions  66   a ,  66   b  are assembled to form collar  66 , collectively form a substantially circular opening  74  for tube  22 . The two collar portions  66   a ,  66   b  are secured together by conventional fasteners  81  that engage registered fastener holes  75  formed in each semi-circular collar portion  66   a ,  66   b . Surrounding the outer periphery of each of the collar portions  66   a ,  66   b  is an annular lip  76  that extends radially inward toward the circular opening  74 . Lip  76  engages a circumferential groove  77  formed in the sidewall  63  of the tubular body  64  when the collar portions  66   a ,  66   b  are assembled to form collar  66  and are attached to the cuff  62 . Lip  76  is defined by a groove  79  formed in the assembled collar portions  66   a ,  66   b  that receives a radially-outward extending rim  78  defined in tubular body  64  by groove  77 . Contact between the interlocked lip  76  and rim  78  provides resistance to relative axial movement between the assembled collar portions  66   a ,  66   b  and the cuff  62 .  
         [0032]     Each of a pair of diametrically opposed keys  80  projecting from the sidewall  63  of tubular body  64  is received and captured in one of a pair of corresponding keyways  83 , which are defined as corresponding axial gaps between the lips  76  of the assembled collar portions  66   a ,  66   b . Formed on the interior of the collar portions  66   a ,  66   b  are flats  82  that mate, when the collar portions  66   a ,  66   b  are assembled and attached to the tubular body  64 , with a hexagonal-shaped shoulder  84  on hydraulic fitting  27 . Contact between the flats  82  and the shoulder  84  and contact between the keys  80  and keyways  83  collectively operate to prevent relative rotation between the tubular body  64  and the assembled collar portions  66   a ,  66   b . The arrangement and configuration of the flats  82  and the geometry of the shoulder  84  are selected to provide the requisite contribution to the rotation resistance.  
         [0033]     Slotted openings  86 ,  88  are formed in the sidewall of the tubular body  64  such that the groove  77  is positioned axially between openings  86 ,  88  and end  89  of the tubular body  64 . Each of the slotted openings  86 ,  88  extends through the sidewall thickness of the tubular body  64 , although the invention is not so limited in that the slotted openings  86 ,  88  may be recesses that do not extend through the entire thickness of the sidewall  65 . In one embodiment of the invention, each of the slotted openings  86 ,  88  has a major axis aligned substantially tangential to the circumference of the tubular body  64 .  
         [0034]     After assembly and with reference to  FIGS. 1-4 , hose cuff  62  is attached to the discharge end  26  of the hose  12 , and hydraulic fitting  27  of hose  12  is engaged with a complementary hydraulic fitting on the applicator gun  18 . The discharge end  26  of the hose  12  is positioned inside a recess defined between two assembled housing halves or shells  94 ,  96  forming a portion of the applicator gun  18 . The slotted openings  86 ,  88  engage posts  90 ,  92  used to fasten the shells  94 ,  96  together or other suitable structures inside shells  94 ,  96 . The slotted openings  86 ,  88  and the posts  90 ,  92  are constructed to provide the appropriate engagement. In, one embodiment of the invention, the posts  90 ,  92  may be oriented tangential to the circumference of tubular body  64  and parallel to the major axis of the slotted openings  86 ,  88 . The concave curvature of the slotted openings  86 ,  88  may be dimensioned and radiused similar to the convex curvature of the posts  90 ,  92 , which limits any “free play” (i.e., axial movement either inward or outward) in response to longitudinal tensile forces applied to the hose  12  when the discharge end  26  is attached to the applicator gun  18 . The mechanical engagement between the slotted openings  86 ,  88  and the posts  90 ,  92  resists axial tensile forces applied to the hose  12  so that the braided sleeve  54  is less likely to detach from hose  12 . In addition, the aforementioned mechanical engagement provides additional pull-out or pull-off resistance to the discharge end  26  of hose  12 .  
         [0035]     With reference to  FIG. 5  in which like reference numerals refer to like features in  FIGS. 1-4  and in an alternative embodiment of the invention, a single shallow groove  100  may extend circumferentially about the tubular body  64 . The groove  100  is dimensioned and configured to engage a corresponding radially-inward extending flange or necked region  102  of a pair of shells, of which shell  94   a  is shown, of an applicator gun (not shown but similar to applicator gun  18 ) to provide a locking interface between the hose  12  and the applicator gun. A person of ordinary skill in the art will appreciate that the tubular body  64  of hose cuff  62  may be modified with one or more cutouts or grooves connectable with complementary structure on a housing of an arbitrary applicator gun.  
         [0036]     While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in considerable detail in order to describe the best mode of practicing the invention, it is not the intention of applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the spirit and scope of the invention will readily appear to those skilled in the art. The invention itself should only be defined by the appended claims, wherein I claim: