WO1996011356A1

WO1996011356A1 - Hot melt flexible hose with replaceable core

Info

Publication number: WO1996011356A1
Application number: PCT/US1995/013315
Authority: WO
Inventors: Martin A. Allen; John T. Fetcko
Original assignee: Exxon Chemical Patents Inc.
Priority date: 1994-10-05
Filing date: 1995-10-05
Publication date: 1996-04-18

Abstract

A flexible hose (10) for conducting polymer melt and other hot liquids comprises (a) an outer sleeve (12) assembly which includes heating elements (29) and insulation (31), and (b) a core tube (11) removably mounted in the sleeve assembly (12). Upon damage or wear to the core tube (11), it can be replaced by disconnecting and removing the worn core tube (11) from the sleeve assembly (12) and inserting a new one.

Description

HOT MELT FLEXIBLE HOSE WITH REPLACEABLE CORE

BACKGROUND

This invention relates to a flexible hose for the transfer of pressurized heated liquids. In one aspect it relates to a flexible hose for use in transf«τing pressurized molten polymers. In another aspect it relates to a flexible hose which has a replacement core in the event the hose becomes damaged, worn, or clogged during operation. There are presently a number of commercially important products that are manufactured using thermoplastic materials. Among these are polymer hot melt adhesives which are applied in molten form to substrates for bonding the substrates together. Hot melt adhesives have been used for bonding furniture parts, automotive parts, diaper backings, and the like. These adhesives exist in the solid phase at room conditions and must be heated before application to a substrate. In some manufacturing operations, a supply of the adhesive is maintained in a molten state inside a temperature controlled heating container where the adhesive temperature is typically between 250-350^°F. The molten adhesive may be applied to the substrate using either a hand operated dispensing gun or a stationary dispenser for applying adhesive to substrates on a moving conveyor line. In either case, the molten adhesive is usually transferred from the supply container to the dispenser by pumping the adhesive through a heated hose. It is necessary that the hose be heated to maintain the adhesive at the desired operating temperature and in the liquid phase as it flows through the hose. Heating is also important in the start-up operation for melting solidified adhesive which may be present in the hose from previous use. Heating is usually accomplished using electrical resistive heating elements which are incorporated into the hose as it is manufactured. In addition to being operative for heating, the hoses must have the structural integrity to withstand the high internal pressures (typically several hundred psi) at which the adhesive is pumped from the supply container to the dispenser. Another requirement for hoses used in polymer processing is flexibility to permit movement of a hand operated dispensing gun in the case where an operator may need to move the gun to apply adhesives at different points on a substrate. Flexibility also facilitates ∞nnecting a supply container to a stationary dispenser. Yet another important requirement of the hose is that it mermally insulate the heating elements and molten adhesive inside the hose from the surroundings. This is important to rninimize costly energy losses from the hose, and for safety reasons in the case where a worker contacts the outside of the hose. Another important manufacturing process is the meltblowing of polymers to produce nonwoven fabrics which have been found useful as filters, battery separators, and absorbents to name a few. In this process, hoses of the type described have been used for trarisferring a pressurized molten or semimolten polymer from an extruder apparatus to a meltblowing die where the polymer is extruded through a plurality of side-by-side orifices to form fibers. Heated air streams are made to converge onto opposite sides of the fibers to drawdown the fibers and blow the fibers onto a collector surface. The converging air streams become turbulent and induce interfiber entanglement so that as the fibers deposit on the collector a nonwoven fabric is formed. Hoses of the type described also find use in heating and transferring the hot air used in the meltblowing process.

In summary, the transfer of thermoplastics in many manufacturing processes require flexible hoses which are heated, able to withstand high internal pressures and temperatures, flexible, and uermally insulated. Such hoses typically have internal diameters in the range of 1/2 inch to S inches. A prior art hose used for transferring hot melt adhesives is described in U. S.

Patent 4,455,474. This hose is described in relation to transferring adhesives from a supply container to a hand operated dispensing gun, and is of composite design being constructed from a number of layers of different materials. The hose comprises a Teflon™ (tetrafluoroethylene fluorocarbon polymers) inner core tube with conventional hydraulic fittings at each end. The core tube is encased in a fibrous stainless steel braiding to add strength to the tube. The hose further comprises double sided tape wrapped around the braiding and adhered to the braiding. Electrical resistance heating tape is spirally wound around and adhered to the outside of the tape for heating the adhesive flowing through the inner teflon core. The remaining layers of the composite hose comprise a layer of insulating material wrapped around the heating tape, a number of electrical leads spirally wound around the insulation for carrying electrical signals between the supply container and the gun, followed by additional layers of insulation. The entire hose is encased in an outer stainless steel braiding which is held in place by hose-type clamps at either end of the hose. Molded plastic cuffs attached at each end of the hose provide support for the hydraulic fittings and have formed therein an exit conduit for the electrical heater leads and gun electrical leads. U.S. Patent 4,553,023 is a continuation-in-part of U.S. Patent 4,455,474 and teaches the use of electrical resistance heating wires in place of electrical heating tape.

A heated flexible hose for the transfer of hot melt adhesives and other polymer liquids is marketed by Furon Dekoran Unitherm Division (designated as Series 200 and 400 hoses) of Cape Coral, Florida. These hoses comprise either a teflon or convoluted stainless steel core tube having a spirally wound electrical resistance heating wire around the core, and insulating materials around the heating elements and core tube. The core, heating wire, and insulation are encased in a corrosion resistant jacket or sleeve. The convoluted steel tube is equivalent to a corrugated tube and combines good strength with some flexibility. The core tube has conventional hydraulic fittings at each end for attaching the hose. A problem encountered in the transfer of molten polymers is due to the high internal temperatures and/or pressures the transfer hoses must withstand. At the elevated temperatures of the polymer inside the hose, the polymer may experience carbonization wherein carbon residue becomes burned onto the inner walls of the flow tube. The residue may cause clogging as well as act as a containment. In prior art hoses. the occurrence of carbonization has been remedied by placing the hose in a high temperature burn-out oven to bum the residue away. Such a process is time consuming, costly, and runs the risk of damaging the various components of the hose at the high oven temperatures. The high pressures at which molten polymers are transferred give rise to the potential of rupturing the inner flow tube of the hose. In some prior art hoses the inner core of the hose consists of a teflon tube which is encased in a stainless steel braiding. The teflon tube can withstand high temperatures and provides flexibility while the braiding adds strength for withstanding high pressures. In time the braiding may fray due to corrosion or internal abrasion as the hose is flexed, thereby creating weak spots in the inner core. Rupturing of hoses belonging to the prior art would require the hose to be completely rebuilt or would render the hose useless altogether. The high temperature environment only exacerbates the rupture problem due to thermally induced stresses.

SUMMARY OF THE INVENTION The present invention is predicated on a flexible, high pressure, and electrically heated hose which has the novel feature of a replaceable core in the event the core becomes clogged, worn, or damaged. The present hose is particularly adapted for the transfer of hot meh adhesives and other molten polymers and provides an economical solution to the problems of polymer carbonization within the hose and also hose rupture. The hose is particularly adapted for the transfer of heated melts (e.g. polymers and adhesives) but may also be used to conduct other heated fluids.

The hose of the present invention is constructed in two separable main components which comprise an inner core tube and an outer sleeve assembly which receives the detachable inner core. The fluid is transferred through the inner core tube which is disposed axially within the outer sleeve assembly. The outer sleeve assembly comprises a sleeve tube, heating wire or tape wound spirally around the sleeve tube, thermal insulating material surrounding the sleeve tube and heating wire, and outer braiding surrounding the insulation. The inner core tube is slidable within the sleeve tube and is secured therein by fasteners at one or both ends of the hose. During operation heat flows from the heating wire, through the sleeve tube wall, and through the inner core tube wall to heat the fluid flowing therein. In the event a high pressure fluid ruptures the inner core tube or the inner core experiences carbonization, the inner core tube fasteners can be disengaged from the outer sleeve assembly and the inner core slidably withdrawn from the sleeve assembly while leaving the assembly intact. The inner core tube may be placed in a burnout oven for cleaning or simply replaced by inserting a new inner core tube into the outer sleeve assembly. Importantly, in the case of inner core tube rupture the sleeve tube of the assembly acts to shield the other components of the assembly from the potentially damaging fluid. The removable inner core eliminates the need for placing the entire hose into a burnout oven for cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a cross-sectional view of the inner core tube disposed within the outer sleeve assembly.

Figure 2 is a cross-sectional view of the inner core tube.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 illustrates flexible hose 1 constructed according to the present invention as comprising inner core tube 11 detachably mounted in outer sleeve assembly 12. In operation, inner tube 11 is fixed to sleeve 12 using retaining nut 13. For removing the inner core tube from the sleeve assembly, the retaining nut is disengaged and the tube is slidably withdrawn from the opposite end of the sleeve. Importantly, the components of the sleeve assembly remain intact and a replacement inner core tube may be installed in the sleeve by reversing the removal procedure.

As best seen in Figure 2 inner core tube 11 of the present invention comprises tube 14 having threaded end 16 and fitting 17 which may be a conventional hydraulic fitting. Tube 14 may be a teflon tube or more preferably a stainless steel tube of the convoluted or corrugated type to give flexibility. In the case of a corrugated tube, it may be necessary to attach straight extension tubing 18 and 19 at each end of tube 14, particularly a corrugated tube 14, for forming threads 16 and mounting fitting 17 thereon, respectively. The extensions may be formed by welding segments of pipe to tube 14. The internal threads of fitting 17 are compatible with external threads 16 so that multiple hoses may be connected in series. End 1 has threaded thereon retainer nut 13 and lock washer 22. Tubing 19 has attached thereto shoulder 23 which acts to apply a backup force as nut 13 is tightened to secure the inner core tube in the outer sleeve assembly (see Figure 1). The shoulder may be formed by welding a washer to extension 19. Stainless steel braiding 26 may be used to surround tube 14 for providing strength to the inner core tubing 14.

Referring to Figure 1 it may be seen that outer sleeve assembly 12 comprises inner sleeve tube 28, heating element 29, thermal insulation 31, and outer braiding 32. Tube 28 is preferably a teflon tube to give good flexibility; however, a convoluted steel tube may also be used. In the case of a teflon tube a steel braiding (not shown) may be placed around the tube. The braiding is optional since inner core tube 14 and inner core braiding 26 provide adequate strength for most operations. Heating element 29 may be heating wire spirally wound around tube 28. Element 29 may alternatively be heating tape. Heating element 29 will have a pair of electrical leads (not shown) which pass out of the hose through either end cap 38 or 39 for connecting the heating wire to an electrical power supply. Insulating layer 31 surrounds heating element 29 and tube 28 and acts to insulate the outside of the hose as well as to hold the heater 29 in good heat transfer relation with braiding 28. Insulation 31 may be conventional fiberglass insulation of sufficient thickness to keep the temperature of the outside of the sleeve assembly at a safe level for workers using the hose. Insulation 31 also acts to electrically insulate the outside of the sleeve assembly from electrical heating element 29. Outer braiding 32 surrounds insulation 31 and protects the internal components of the sleeve assembly as well as adding strength to the assembly. Braiding 32 also acts as a retaining jacket to maintain the components of the assembly in assembled relation, and may be made of polyester or more preferably stainless steel. In practice other layers may be provided in assembly 12. For example it is known in the art to provide a layer of vinyl electrical tape around the heating element 29 to act as a moisture barrier.

Optional messenger wire 36 and messenger wire braiding 37 may be provided between insulation 31 and outer braiding 32. Messenger wire 36 may be used to transmit electrical signals over the length of the hose as in the case where the hose may be equipped with temperature and/or pressure transducers. Messenger wire 36 may also be used to transmit signals to a dispensing unit such as a hand held gun. Multiple messenger wires may be provided.

The construction of the sleeve assembly 12 including the tube 28, heating element 29, insulation 31, messenger wire components 36 and 37, outer braiding 38, as well as the heating element electrical leads and moisture barrier tape may be in accordance with U.S. Patent 4,455,474, the disclosure of which is incorporated herein by reference.

End caps 38 and 39 are secured to each end of the sleeve assembly and act to protect the internal components of the sleeve. The end caps are held in place by a compression fit around the sleeve outer braiding 38 and act to hold the components of the assembly together. End caps 38 and 39 have center holes 41 and 42, respectively, which are sufficiently large to permit inner core tube 11 to pass therethrough. Backup washer 43 is provided between cap 39 and sleeve assembly 12. Inner core tube 11 is installed in sleeve assembly 12 by first inserting threaded end 16 into the sleeve through end cap hole 42. The inner core is pushed through the outer assembly until end 16 protrudes through opposing end cap hole 41 and core tube shoulder 23 contacts washer 43. A small amount of clearance is provided between inner sleeve tube 28 and inner core tube braiding 26 so that the inner core tube may be slidably inserted without damaging or disrupting braiding 26. Washer 22 seats onto end cap 44 and retainer nut 13 is threaded onto end 16 and tightened for securing the inner core tube 11 in sleeve assembly 12 for operation. End cap 44 and backup washer 43 are provided to protect end caps 38 and 39 from wear over the multiplicity of times the inner core may be replaced. End cap 44 and washer 43 are optional and retaining nut 13 may seat directly onto end cap 38 and shoulder 23 may be sized to seat onto end cap 39. In operation, either hose end 16 or fitting 17 would be connected to a supply of molten polymer and the other end connected to a polymer dispensing unit such as a hot melt adhesive gun or other dispenser, or a meltblowing die. The polymer entering the hose is conducted through inner tube 14 and delivered to the dispensing unit. The electrical heating wire 29 would be energized prior to introducing the polymer into the hose.

Importantly, sleeve assembly tube 28, inner core braiding 26, and inner tube 14 are in good heat transfer relation and therefore offer little resistance to the flow of heat from the heating wire to the molten polymer flowing through the inner core tube. While a small air gap may exist between braiding 26 and sleeve tube 28 to allow the inner core to be slidable within the sleeve, it should be realized that the heat dissipated by the heating wire 29 will still tend to flow radically inward since the resistance to heat flow in the radically outward direction is far greater due to thermal insulation 31. In the event that inner core tube 14 becomes clogged or damaged, the inner core may be easily removed from sleeve assembly 12 by reversing the above installation procedure. It is important to note in Figure 1 that if the inner core 11 ruptures or leaks, sleeve tube 28 acts as a shield which protects heating wire 29 and the other components of the outer assembly. In this situation, inner core 11 may be withdrawn and replaced while leaving sleeve assembly 12 intact. Thus, the design of the present invention offers an economical alternative to replacing an entire hole which has become clogged or damaged. The hose of the present invention is applicable to virtually any of the polymers or copolymers presently in use in manufacturing operations and includes polypropylene, low and high density polyethylene, ethylene, coporymers (including EVA copolymer), nylon, polyamide, polyesters, polystyrene, poly-4-methyl-pentene, polymethylethacry- ate, polytrifluorochloroethylene, polyurethanes, poly-carbonates, silicones, and blends of these. The present hose is equally applicable to the transfer of high temperature and pressurized gases such as the heated air used in meltblowing. The term fluid hereinafter is understood to refer to both liquids and gases.

Dimensions and operating conditions of the present hoses will vary from application to application. The clearance between the inner core tube 11 and the outer sleeve assembly 12 should be sufficient to allow the former to be inserted and withdrawn from the latter. Clearance of 0.01 to 0.1 inches should be sufficient. The outside diameter of the sleeve assembly 12, inner diameter of the inner core tube 11, and hose length will be similar to those presently in use (e.g. 1.5 to 6.0 inches O.D., 0.25 to 5.0 inches I.D., and 5.0 to 25.0 feet in length). The operating temperature and pressure similarly will be in the range of those presently in use (e.g. 100 to 700^°F and

100 to 2500 psig). The flexibility of the present hose will depend on the diameter of the hose with minimum bend radius increasing with diameter. For the range of sizes cited above the minimum bend radius will typically be between 8.0 to 30.0 inches.

Variations in the design of the present hose are possible without deviating from the inventive concept directed to an economical solution to the problems of clogging, wear, and leakage using a replaceable core. There are undoubtedly alternative ways for securing the inner core in the outer assembly as would be apparent to one of ordinary skill in the pertinent art.

Claims

CLAIMS We Claim:

1. A flexible hose for transferring pressurized fluids, comprising: (a) an outer sleeve assembly having

(i) an inner sleeve tube,

(ii) a heating element positioned adjacent said sleeve tube, (iϋ) insulation surrounding said sleeve tube and heating element, (iv) a retainer jacket surrounding said sleeve tube, heating element, and insulation, and

(v) means for ma taining said sleeve tube, heating element, insulation, and retaining jacket in assembled relation; and (b) an inner core tube extending substantially through said inner sleeve tube and positioned in heat transfer relation therewith, said inner core tube being detachably mounted in said sleeve assembly to permit removal therefrom without a disassembly of said sleeve assembly.

2. The hose of Claim 1 wherein said inner core tube is a convoluted steel tube and said inner sleeve tube is a teflon tube, and further comprising a stainless steel braiding around said inner core tube, said inner core tube and braiding being slidably disposed within said inner sleeve tube.

3. A flexible hose having a replaceable core for transferring a pressurized fluid, comprising:

(a) an outer sleeve assembly having (i) an inner sleeve tube,

(ii) a heating element positioned adjacent said inner sleeve tube, (iϋ) insulating material surrounding said heating element and inner sleeve tube, (rv) a retaining jacket surrounding said insulating material, and (v) an end cap around said retaining jacket at each end of said assembly, said end caps having a central hole concentric with said inner sleeve tube, said end caps imparting a radially compressive force for mamtaining the components of said sleeve assembly in assembled relation; (b) an inner core tube being slidably disposed within said inner sleeve tube and in heat transfer relation with said inner sleeve tube and heating element; and (c) means for securing said inner core tube in said sleeve assembly, whereby disengaging said securing means permits said inner core tube to be slidably withdrawn from said assembly while said assembly remains assembled.

4. The hose of Claim 3 wherein said inner core tube is a convoluted steel tube and said inner sleeve tube is a teflon tube, and further comprising a stainless steel braiding around said convoluted tube, said convoluted tube and braiding being slidably disposed within said teflon tube.

5. The hose of Claim 3 wherein said inner core tube is a convoluted steel tube and said inner sleeve tube is a convoluted steel tube, and further comprising a stainless steel braiding around said inner core tube, said inner core tube and braiding being slidably disposed within said inner sleeve tube.

6. The hose of Claim 3 wherein said inner core tube further has screw threads on one end and a shoulder element on the other end, said securing means comprising a retaining nut threaded onto said threads whereby tightening said nut causes the nut to contact one of said end caps and said shoulder element to contact the other end cap.

7. The hose of Claims 1 or 3 wherein said fluid to be transferred is a molten polymer having a temperature between 100 and 650^°F and a pressure between 100 and 2500 psig.

8. The hose of Claims 1 or 3 wherein said fluid to be transferred is a gas having a temperature in the range of 100 to 650^°F and a pressure between 100 and 2500 psig.

9. The hose of Claim 3 wherein said heating element comprises one of electrical heating wire wrapped around said inner sleeve tube or electrical heating tape wrapped around said inner sleeve tube.

10. The hose of Claim 3 further comprising an electrical wire disposed between said insulating material and said retaining jacket for transmitting electric signals along the length of the hose.

11. In a hose construction having a sleeve assembly comprising a sleeve tube, a heating element wound around the sleeve tube, an insulation layer surrounding the sleeve tube with the heating element wound therearound, a retainer sleeve surrounding the insulation layer end first and second caps mounted on opposite ends of the retaining sleeve to maintain the sleeve assembly together, each end cap having an opening formed thereon, characterized in that:

(a) a removable core tube positioned concentrically in the sleeve tube and having (i) a first end extending axially outwardly from the sleeve tube through the opening of the first end cap, and (ii) a second end extending axially outwardly from the sleeve tube through the opening of the second end cap;

(b) a first tubing connector and a shoulder secured to the first end of the core tube, the shoulder being sized to engage an end portion of the sleeve assembly; and (c) a second tubing connector threadedly connected to the second end of the core tube, said connector in assembled condition being sized to engage the second end cap whereby the end caps are rnaintained in assembled relation between the shoulder on the first end of the core tube and the second connector on the second end of the core tube, the core tube being removable by disconnecting the second tubing connector and withdrawing the core tube axially outwardly from the sleeve through the opening of the first end cap.