Heated hose for carrying molten thermoplastic material

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

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

This invention relates to heated hoses and, in particular, to heated hoses for carrying molten thermoplastic material.

BACKGROUND OF THE INVENTION

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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'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.

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.

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

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 a perspective view of the hose of the present invention connecting a supply tank to an applicator gun;

FIG. 2 is an enlarged partial cross-sectional plan view of the hose of FIG. 1;

FIG. 3 is an exploded perspective view of the tubular body and collar portion of the hose cuff of FIGS. 1 and 2;

FIG. 4 is an end view of the collar portion of the hose cuff; and

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

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.

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.

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.

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.

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.

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.

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.

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.

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 66a, 66b 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 66a, 66b 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 66a, 66b 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.

With reference to FIGS. 3 and 4, each of the collar portions 66a, 66b features a corresponding one of semi-circular openings 74a, 74b (FIG. 4) that, when the two collar portions 66a, 66b are assembled to form collar 66, collectively form a substantially circular opening 74 for tube 22. The two collar portions 66a, 66b are secured together by conventional fasteners 81 that engage registered fastener holes 75 formed in each semi-circular collar portion 66a, 66b. Surrounding the outer periphery of each of the collar portions 66a, 66b 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 66a, 66b 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 66a, 66b 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 66a, 66b and the cuff 62.

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 66a, 66b. Formed on the interior of the collar portions 66a, 66b are flats 82 that mate, when the collar portions 66a, 66b 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 66a, 66b. 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.

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.

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.

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 94a 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.

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:

Claims

1. An apparatus for transferring a heated liquid from a heated liquid source to a liquid dispensing apparatus, comprising:

a conduit having an inlet end adapted to be coupled in fluid communication with the heated liquid source and a discharge end adapted to be coupled in fluid communication with the liquid dispensing device;

a thermal insulation layer extending between said inlet end and said discharge end of said conduit;

a heating element extending between said inlet end and said discharge end of said conduit and positioned between said thermal insulation layer and said conduit, said heating element adapted to generate and transfer heat to said conduit; and

a woven outer covering extending between said inlet end and said discharge end of said hose and having a surrounding relationship with said hose, said woven outer covering including a plurality of braided polyamide monofilaments.

2. The hose of claim 1 wherein said woven outer covering includes a plurality of oval-shaped monofilaments.

3. The hose of claim 1 wherein said woven outer covering is formed from eighty monofilament carriers.

4. The hose of claim 1 wherein said woven outer covering has an outer surface free of undulating structures.

5. The hose of claim 1 further comprising:

a hose cuff attaching said woven outer covering to said discharge end of said hose, said hose cuff including at least one coupling element for securing said hose cuff to the liquid dispensing device and preventing relative axial movement between said hose cuff and the liquid dispensing device.

6. An apparatus for transferring a heated liquid from a heated liquid source to a liquid dispensing device, comprising:

a conduit having an inlet end adapted to be coupled in fluid communication with the heated liquid source and a discharge end adapted to be coupled in fluid communication with the liquid dispensing device;

a thermal insulation layer extending between said inlet end and said discharge end of said conduit;

a heating element extending between said inlet end and said discharge end of said conduit and positioned between said thermal insulation layer and said conduit, said heating element adapted to generate and transfer heat to said conduit; and

a hose cuff attached to said discharge end of said hose, said hose cuff including at least one coupling element for directly securing said hose cuff to the liquid dispensing device and preventing relative axial movement between said hose cuff and the liquid dispensing device.

7. The hose of claim 6 wherein said hose cuff includes a sidewall, and said coupling element comprises a recess in said sidewall, said recess shaped to engage a complementary portion of the liquid dispensing device.

8. The hose of claim 7 wherein said sidewall is cylindrical, and said recess includes a major axis aligned substantially tangential to a circumference of said sidewall.

9. The hose of claim 6 wherein said hose cuff includes a sidewall and said coupling element comprises an opening extending through said sidewall, said opening shaped to engage a complementary portion of the liquid dispensing device.

10. The hose of claim 9 wherein said sidewall is cylindrical, and said opening includes a major axis aligned substantially tangential to a circumference of said sidewall.

11. The hose of claim 6 wherein said hose cuff includes a tubular body having a first open end, a second open end, and a collar covering said first open end, said tubular body is substantially centered about an axis extending between said first and second open ends, said collar includes a first opening, and said hose includes a first electrical lead projecting through said first opening.

12. The hose of claim 11 wherein said collar includes a second opening, and said hose includes a second electrical lead projecting through said second opening.

13. The hose of claim 12 wherein said collar includes a third opening substantially centered about said axis, and said hose includes a tube confining the heated liquid during transfer and projecting through said third opening, said first opening and said second opening being radially spaced from said third opening.

14. The hose of claim 13 wherein said first opening and said second opening are positioned on opposite sides of said third opening.

15. A method of attaching a hose between a liquid source and a liquid dispensing device, comprising:

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 for preventing relative axial movement between the hose cuff and the liquid dispensing device during use.

16. The method of claim 15 wherein directly coupling further comprises:

engaging the hose cuff with the liquid dispensing device.

17. The method of claim 15 wherein directly coupling further comprises:

engaging a groove on the hose cuff with a post inside a shell of the liquid dispensing device.