WO2011139898A1

WO2011139898A1 - Electrically-heatable tubing and fitting assembly for selective catalytic reduction (scr) systems

Info

Publication number: WO2011139898A1
Application number: PCT/US2011/034585
Authority: WO
Inventors: Steven M. Powell; Paul C. Menmuir; Ty A. Henry
Original assignee: Parker-Hannifin Corporation
Priority date: 2010-04-29
Filing date: 2011-04-29
Publication date: 2011-11-10

Abstract

Electrically-heatable tubing and fitting assembly. The assembly includes a tube having a tube end and an exterior surface. Radially spaced-part first and second electrical conductors (30) are disposed on the tube exterior surface. A fitting (60) is connected to the tube end as having a tubular body with a first fitting end portion (64) received within the tube end and a second fitting end portion (66) extending beyond the tube end. A resistive heating element (70) surrounds the fitting second end portion (66). The heating element (70) has a pair of leads (72 a-b) extending axially therefrom, each of the leads having a first lead end electrically connected to a corresponding one of the conductors (30 a-b).

Description

4-

ELECTRIC ALL Y- HEAT ABLE TUBING AND FITTING

ASSEMBLY FOR SELECTIVE CATALYTIC REDUCTION (SCR) SYSTEMS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of the filing date of U.S. Provisional Application Serial No. 61/329,222, filed April 29, 2010, and of U.S. Provisional Application Serial No. 61/411,545, filed November 9, 2010, the disclosure of each of which is expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates broadly to an electrically-heatable tubing and fitting assembly, and more particularly to such an assembly for use in transferring a urea, i.e., carbamide, solution in a diesel engine emissions after-treatment system.

[0003] Selective catalytic reduction (SCR) is a method of converting nitrogen oxides (NO_x) into diatomic nitrogen (N₂0) and water with the aid of an emission reduction reagent such as urea. SCR is used to reduce emissions in diesel engines such as for ships, locomotives, gas turbines, and trucks.

[0004 [ SCR systems inject a liquid urea solution or other catalyst into a stream or flue of exhaust gas. The exhaust gas is absorbed into the urea solution w ereupon the nitrogen oxides (NO_x) in the gas are converted into diatomic nitrogen by means of a chemical reaction

[0005] The basic components of a urea-based SCR system, such as may be used on a heavy duty truck for example, are a urea solution tank, pressure regulators, a control unit, temperature sensors, a dosing module, and a pump. To link these components for the purpose of transferring urea through the system, flexible hose assemblies are employed. Many of these assemblies use plastic-bodied quick-connect fittings, such as specified in Society of Automotive Engineers (SAE) Standard J2044, to allow for the assembly and disassembly of the system components.

[0006] A common problem of urea-based SCR systems is the relatively high freezing point of the urea solution. The freezing temperature of urea is about +13°F (-10.6°C). When freezing occurs, the SCR system is rendered non-operational because the urea catalyst solidifies and cannot be pumped through the hose assemblies into the exhaust stream. Since it is not unusual to encounter temperatures of +13°F (-10.6°C) and below in many northern climes, urea-based SCR systems typically are designed with heated hoses and other types of heaters to maintain the temperature of the urea solution above +13F. SCR systems and components are further described, for example, in commonly- assigned International Patent Application No. PCT/US 11/20452, titled "Electrically- Heated Hose Assembly For Selective Catalytic Reduction (SCR) Systems," filed January 7, 2011, and in the following publications: U.S. Patent Nos. 7,578,321 ; 5,976,475; EP 1,937,946; WO 2010/057819; 2010/02907642008/005829; 2007/032033; and U.S. Pub. No. 2010/0263740. Heated hoses of general types are shown, for example, in U.S. Patent Nos. 7,120,354; 6,738,566; 6,727,481; 5,910,266; 5,791,377; 5,511,530; 5,428,706; 4,815,769; 4,553,023; 4,455,474; 4,372,279; 4,038,519; 3,355,572; and 3,522,413.

[0007] As applications for urea-based SCR systems continue to increase, it is believed that improvements in electrically-heated hose and fitting assembly constructions would be well-received. Especially desired would be a construction which is flexible and lightweight, and which is economical to manufacture.

BROAD STATEMENT OF THE INVENTION

[0008] The present invention is directed to an electrically-heatable tubing, i.e., hose, and fitting assembly. More particularly, the invention is directed to such an assembly for use in transferring a urea, i.e., carbamide, solution in a diesel engine emissions after- treatment system.

[0009] The assembly includes a length of tubing which may be constructed of inner tube or core formed of one or more polymeric layers, with at least one pair of electrical wires, conductive strips, or other electrical conductors being spiral wound around or laid in parallel along the core. The electrical conductors, in turn, optionally may be surrounded by an outermost jacket formed of one or more polymeric layers. With the tubing so constructed being cut or otherwise sectioned to length, a barbed or other nipple end of a push-in type fitting may be inserted into one or each end of the length of tubing. A heating element having a pair of connection leads, such as in the form of an electrically-conductive cage or a flexible film heater strip, then may be applied over the body of the fitting as it protrudes from the end of the hose. With each of the leads of the heater element being connected to a corresponding one of the electrical conductors of the tubing, a plastic sleeve may be overmolded or otherwise formed over the fitting body to encapsulate the heater element.

[0010] The present invention, accordingly, comprises the design, fabrication, construction, combination of elements, and/or arrangement of parts and steps which are exemplified in the detailed disclosure to follow. Advantageously, through the use of the heating element which is applied overt the fitting body, conventional push-in fitting types, such as SAE J2044, may be heated without the necessity and expense of having to provide specially-designed heated fittings. These and other advantages will be readily apparent to those skilled in the art based upon the disclosure contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

[0012] Fig. 1 is a perspective view of a representative electrically-heatable tubing and fitting assembly according to the present invention;

[0013] Fig. 2 is a perspective view of the tubing of the assembly of Fig. 1 ;

[0014] Fig. 3 is a cross -sectional view of the tubing of Fig. 2 taken through line 3-3 of

Fig. 2; [0015] Fig. 4 is a side view of the resistive element of the assembly of Fig. 1, such element being in the form of a cage;

[0016] Fig. 5 is a front view of the cage of Fig. 4;

[0017] Fig. 6 is a top view of the cage of Fig. 4;

[0018] Fig. 7 is a perspective view of an alternative heating element for the assembly of Fig. 1 , such element being in the form of a flexible film heat; and

[0019[ Fig. 8 is a perspective view of the flexible film heater of Fig. 7 as applied to the body of a fitting of the assembly of Fig. 1.

[0020] The drawings will be described further in connection with the following Detailed Description of the Invention.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Certain terminology may be employed in the following description for convenience rather than for any limiting purpose. For example, the terms "forward" and "rearward," "front" and "rear," "right" and "left," "upper" and "lower," and "top" and "bottom" designate directions in the drawings to which reference is made, wi : the terms "inward," "inner," "interior," or "inboard" and "outward," "outer," "exterior," or "outboard" referring, respectively, to directions toward and away from the center of the referenced element, the terms "radial" or "horizontal" and "axial" or "vertical" referring, respectively, to directions or planes which are perpendicular, in the case of radial or horizontal, or parallel, in the case of axial or vertical, to the longitudinal central axis of the referenced element, and the terms "downstream" and "upstream" referring, respectively, to directions in and opposite that of fluid flow. Terminology of similar import other than the words specifically mentioned above likewise is to be considered as being used for purposes of convenience rather than in any limiting sense. In certain views of the figures, the axial direction may be shown by an arrow labeled "A," and the radial direction may be shown by an arrow labeled "R." The terms "tubing" and "hose" may be used interchangeably. [0022] In the igures, elements having an alphanumeric designation may he referenced herein collectively or in the alternative, as will be apparent from context, by the numeric portion of the designation only. Further, the constituent parts of various elements in the figures may be designated with separate reference numerals which shall be understood to refer to that constituent part of the element and not the element as a whole. General references, along with references to spaces, surfaces, dimensions, and extents, may be designated with arrows. Angles may be designated as "included" as measured relative to surfaces or axes of an element and as defining a space bounded internally within such element therebetween, or otherwise without such designation as being measured relative to surfaces or axes of an element and as defining a space bounded externally by or outside of such element therebetween. Generally, the measures of the angles stated are as determined relative to a common axis, which axis may be transposed in the figures for purposes of convenience in projecting the vertex of an angle defined between the axis and a surface which otherwise does not extend to the axis. The term "axis" may refer to a line or to a transverse plane through such line as will be apparent from context.

[0023] For illustrative purposes, the precepts of the electrically-heatable tubing and fitting assembly construction herein involved are described in connection with its configuration as particularly adapted for use in conveying a urea solution in an SCR system or other diesel engine or vehicular emissions after-treatment system. It will be appreciated, however, that aspects of the present invention may find use in other fluid transfer applications requiring heating and/or temperature maintenance such as may be found in the chemical, oil and gas, food processing, medical device, construction and power generation industries. Use within those such other applications therefore should be considered to be expressly within the scope of the present invention.

[0024] Referring then to the figures wherein corresponding reference characters are used to designate corresponding elements throughout the several views with equivalent elements being referenced with prime or sequential alphanumeric designations, a representative electrically-heatable tubing and fitting construction according to the present invention is shown generally at 10 in the perspective view of Fig. 1. In basic construction, assembly 10 includes a tube, referenced at 12, which extends axially along a central longitudinal axis, 14, to a predetermined length, referenced at "L," between a first tube end, 16, and a second tube end, referenced in phantom at 18. The length L of tube 12 may range, for example, from about 0.2 m to about 10 m or more.

[0025] With additional reference to the perspective and cross-sectional views of tube 12 depicted in Figs. 2 and 3, it may be seen that tube 12, which may be as shown of a single, layer construction, or alternatively of a multi-layer construction, has a circumferential exterior surface, 22, and a circumferential interior surface, 24, which defines the inner diameter, referenced at D; (Fig. 3), of tube 12. Tube 12 may be provided as molded, extruded or otherwise formed of a polymeric material such as a polyamide, polyester, polyacetal, ethylene vinyl alcohol, polyoxymethylene, polyolefin, silicone, fluoropolymer, polyvinyl chloride, polyurethane, thermoplastic elastomer, EPDM, natural or synthetic rubber, or a copolymer or blend thereof. In the case of tube 12 being formed of two or more layers, each of such layers may be independently formed of such a polymeric material.

[0026] Depending upon the amount of heat input required, at least a pair of electrical conductors, referenced generally at 30a-b, are disposed on the tube exterior surface 22. In the illustrated embodiment of Figs. 1-3, conductors 30 are provided as electrically conductive, i.e., resistive, strips or stripes, 32a-b, which extend lengthwise along the tube exterior surface 22 in parallel, such as helically or, as shown, linearly on opposite sides of tube 12. In a unitary construction of tube 12, such stripes 32 may be embedded into the tube exterior surface 22, such as by being co-extruded or co-molded with the remainder of tube 12. Stripes 32 may be formed of an inherently-conductive polymer or of a polymeric material, which may be the same as or different than the polymeric material forming the remainder of tube 12, which is rendered electrically-conductive, such as having a resistant of between about 0.1-20 ohms per foot, by virtue of being filled with metal or metal-coated particles or other electrically-conductive filler.

[0027] As is shown in phantom in Fig. 2 at 34a, such conductors 30 alternatively may be provided as electrical wires formed of copper, aluminum, a stainless or carbon steel alloy, or another metal or metal alloy, and may be sheathed within a plastic or other polymeric coating to provide corrosion resistance and electrical isolation. Wires 34 may be spiral, i.e., helically, wound in parallel pairs around the tube exterior surface 22, or alternatively laid linearly in parallel on opposite sides of tube 12. In the case of a helical winding, wires 34 may be wound at a uniform pitch and pitch angle to ensure a uniform spacing between the turns for more even heat distribution. It will be appreciated that by varying the number of stripe 32 or wire 34 pairs, or by changing the pitch or pitch angle, and/or the stripe width or thickness, or the wire gauge or type, or otherwise the resistance per foot of the conductors 30, the amount of heat input into the tube may be adjusted to provide a specified watts per meter rating and/or thaw time.

[0028] Also, wires 34 alternatively may be interposed between o layers of a conductive, positive temperature coefficient (PTC) polymer so as to function as buss wires in supplying current to the PTC layers in a self-regulating, parallel heating circuit wherein heating output is reduced automatically and proportionately with increasing temperature. Wires 34 and stripes 32 themselves may be formed of PTC materials so as to be self-regulating.

[0029] Tube 12 optionally may be sheathed within one or more layers of a coaxially- surrounding protective cover or jacket, referenced in phantom at 40 in Fig. 3. Depending upon its construction, jacket 40 may be spray-applied, dip coated, cross-head or co- extruded, or otherwise conventionally extruded, spiral or longitudinally, i.e., "cigarette," wrapped, or braided over the wires 40 to both protect the wire and to mechanically lock them in place. Each of the layers forming jacket 40 may be formed, independently, of a polymeric material such as a polyamide, polyester, polyacetal, ethylene vinyl alcohol, polyoxymethylene, polyolefin, silicone, fluoropolymer, polyvinyl chloride, polyurethanes, thermoplastic elastomer, EPDM, natural or synthetic rubber, or a copolymer or and blend thereof.

[0030] However, and as may be considered advantageous in the case of the illustrated integral conductive stripe construction, tube exterior surface 22 may itself be used as the outermost layer in the assembly 10. In this regard, as compared to a construction utilizing heating wires, such striped construction may have a reduced weight and raw material content, provide more efficient and faster heat transfer with reduced thaw times and power input need, offer a smaller tube diameter and overall assembly profile, and exhibit improved flexibility and corrosion and fatigue resistance.

[0031[ Separate reinforcement, electrically-conductive fiber, or additional resin layers (not shown) which, depending on the layer, may be wound, wrapped, or braided, also may be included in the construction of tube 12 as disposed between tube 12 and jacket 40. The entire tube 12 may be sheathed within a wire-loop or corrugated plastic or other guard (not shown) as an added protective layer.

[0032] Looking again to Fig. 1, a first and a second fitting, 60a-b, each is connected to a corresponding end 16 or 18, respectively, of tube 12. Each of the fittings 60 may be straight, as shown, or angled, and independently, may be of an SAE J2044 push-in style as shown or other quick-connect or other type such as compression or crimped, and may include metal or polymeric seals. As may be seen with momentary reference to Fig. 8, each of the fittings 60 may have a generally tubular body, 62, which may be formed of a plastic, having a first end portion, 64, and an opposite second end portion, 66. First end portion 64, which may be a barb, nipple, or other male end-form, is inserted into the inner diameter D; of tube 12 (Fig. 3) at a corresponding one of the first or second tube ends 16 or 18 (Fig. 2). Returning to Fig. 1 , fitting second end portion 66, in turn, extends axially beyond the corresponding one of the tube ends 16 or 18. A terminus, 68, adjacent second end portion 66 may be of a female coupler end-form for a snap-to-co meet or other push- in connection with an associated nipple connector (not shown).

[0033] As may be seen in Fig. 1 for fitting 60a, a resistive heating element, referenced generally at 70, is provided to surround the fitting second end portion 66. As provided, element 70 has a pair of electrical leads, 72a-b, extending axially therefrom. Each of the leads 72a-b has a corresponding distal or terminal first lead end, 74a-b, electrically connected to a corresponding one of the conductors 30a-b, such as the illustrated stripes 32a-b, and an opposite, proximal, second lead end, 76a-b. [0034] In the illustrated embodiment of assembly 10 in Fig. 1, heating element 70 is constructed as generally tubular cage, 80, formed of an electrically-conductive, i.e., resistive, material such as a metal or an inherently-conductive or conductively-filled plastic. With additional reference to the several views of Figs. 4-6, cage 80 may be constructed as being stamped, molded, or otherwise formed as length of an elongate member, 82. Such member 82 may be shaped in the form of the cage 80 as having a forward ring portion, 84, which as shown in Fig. 1 is disposable around the fitting second end portion 66, as a series of semicircular ribs, 86a-d. Such ribs 86 may be connected in pairs 86a-b and 86c-d by cross pieces, commonly referenced at 88, and may be separated on at least one side of the ring portion by a transverse gap, referenced at 90. So shaped, ring portion 84 thus may be expandable circumferentially through gap 90 so as to be receivable around the fitting second end portion 66 either before or after the fitting first end 64 is inserted into the tube end 16 or 18.

[0035] Ring portion 84 further is shaped as having a pair of legs, 92a-b, each extending transversely from an opposite side of the ring portion 84 with, as shown in Fig. 1, the tube 12 being received therebetween. Each of the legs 92a-b defines a corresponding one of the leads 72 and has a leg end, 94a-b, defining a corresponding one of the first lead ends 74a-b. With ring portion 84 being received about the fitting second end portion 66 prior to or following the fitting first end portion is 64 being inserted into a respective tube end 16 or 18, leg ends 94a-b may be electrically connected to a corresponding one of the stripes 32a-b such as being embedded therein or otherwise as being bonded thereto via ultrasonic, thermal, fusion, or RF welding, or using a conductive adhesive. Thereafter, and is depicted for fitting 60b, each fitting 60 and cage 80 may be encased within a plastic overmolding or other type sleeve or cover, 100, which may be formed of the same or different polymeric material as tube 12. Assembly 10 thereupon may be connected to a power supply to provide the power to resistively heat the assembly 10.

[0036] Turning now to Fig. 7, an alternative form of heating element 70 is provided as a flexible film heater, 110. In basic construction, such heater 110 includes a band, 112, formed of a resistive foil circuit, 113, laminated between two sheets, 114a-b, of a polyimide or other polymeric film. A pair of lead wires, 116a-b, each defining a corresponding one of the leads 72a-b (Fig. 1), extend from band 112 as having a first wire end, 1 18a-b, each defining a corresponding one of the first lead ends 74a-b, and a second wire end, 120a-b, each being soldered, bonded, or otherwise electrically connected to opposite ends of the circuit 113.

[0037] As shown in Fig. 8, band 1 12 may be bonded, such as by means of a pressure- sensitive adhesive applied to the outside of one of the sheets 114a-b, or otherwise affixed around the fitting second end portion 66 prior to or following the fitting first end portion 64 being inserted into a respective tube end 16 or 18. Thereafter such insertion, each of the first wire ends 118a-b may be electrically connected to a corresponding one of the conductors 30a-b (Fig. 1). A cover 100 (Fig. 1) then may be overmolded or otherwise formed over the fitting second end portion 66 to therein encase the heater band 112 and lead wires 116. Flexible film heaters of the type herein involved are further described, for example, in U.S. Pat. No. 3,584,198, and are available commercially from Tempco Electric Heater Corporation, Wood Dale, IL (www.tempco.com); thermo Heating Elements LLC, Piedmont, South Carolina (www.thermo-llc.com); Minco, Minneapolis, MN (www.minco.com) and OMEGA Engineering, Inc., Stamford, CT ( www.omega. com).

[0038] Thus, an electrically-heatable tubing and fitting assembly is described which is economical to manufacture and which may be easily adapted to meet a variety of heat input specifications.

[0039] As it is anticipated that certain changes may be made in the present invention without departing from the precepts herein involved, it is intended that all matter contained in the foregoing description shall be interpreted as illustrative and not in a limiting sense. All references including any priority documents cited herein are expressly incorporated by reference.

Claims

CLAIMS What is claimed is:

1. An electrically-heatable tubing and fitting assembly comprising:

a tube extending lengthwise along a longitudinal axis to at least one tube end, the tube having an exterior surface and being formed of one or more layers of one or more polymeric materials;

radially spaced-part first and second electrical conductors disposed on the tube exterior surface, the conductors extending lengthwise along the tube exterior surface; a fitting connected to the tube end comprising a generally tubular body having a first fitting end portion received within the tube end and a second fitting end portion extending beyond the tube end; and

a resistive heating element surrounding the fitting second end portion, the heating element having a pair of leads extending axially therefrom, each of the leads having a first lead end electrically connected to a corresponding one of the conductors.

2. The assembly of claim 1 wherein the heating element comprises a cage, the cage having a ring portion disposed around the fitting second end portion and pair of legs each extending transversely from an opposite side of the ring portion with the tube being received therebetween, each of the legs defining a corresponding one of the leads and having a leg end defining a corresponding first lead end.

3. The assembly of claim 2 wherein the cage is formed as a length of an elongate member, the member being configured to define a series of semicircular ribs comprising the ring portion, the ribs being connected in pairs by cross pieces and being separated on one side of the ring portion by a transverse gap, the ring portion being circumf erenti ally expandable through the gap to be receivable around the fitting second end portion.

4. The assembly of claim 3 wherein the member is formed of a resistive metal or plastic.

5. The assembly of claim 1 where in the heating element comprises a band formed of a resistive foil circuit laminated between two sheets of a polymeric film, the band being affixed around the fitting second end portion with each of the leads having a second lead end electrically connected to an opposite end of the foil circuit.

6. The assembly of any of the preceding claims wherein the first and second electrical conductors each is formed as a resistive stripe embedded in the tube exterior surface.

7. The assembly of claim 6 wherein each stripe is formed of a resistive polymeric material.

8. The assembly of any of the preceding claims further comprising a cover surrounding the heating element

9. The assembly of claim 8 wherein the cover is formed of a plastic material.

10. The assembly of any of the preceding claims wherein the polymeric materials forming each of the tube layers is selected, independently, from the group consisting of polyamides, polyesters, polyacetals, ethylene vinyl alcohol, polyoxymethylene, polyolefins, silicones, fluoropolymers, polyvinyl chlorides, polyurethanes, thermoplastic elastomers, EPDM, natural and synthetic rubbers, and copolymers and blends thereof.

1 1. A method of making an electrically-heatable tubing and fitting assembly, the method comprising the steps of:

-12- (a) providing a tube extending lengthwise along a longitudinal axis to at least one tube end, the tube having an exterior surface and being formed of one or more layers of one or more polymeric materials, and the tube having radially spaced-part first and second electrical conductors disposed on the tube exterior surface, the conductors extending lengthwise along the tube exterior surface;

(b) connecting a fitting to the tube end, the fitting comprising a generally tubular body having a first fitting end portion received within the tube end and a second fitting end portion extending beyond the tube end;

(c) prior to or following step (b), surrounding the fitting second end portion with a resistive heating element, the heating element having a pair of leads extending axially therefrom, each of the leads having a first lead end; and

(d) electrically connecting each of the first lead ends to a corresponding one of the conductors.

12. The method of claim 11 wherein the heating element comprises a cage, the cage having a ring portion disposed around the fitting second end portion and pair of legs each extending transversely from an opposite side of the ring portion with the tube being received therebetween, each of the legs defining a corresponding one of the leads and having a leg end defining a corresponding first lead end.

13. The method of claim 12 wherein the cage is formed as a length of an elongate member, the member being configured to define a series of semicircular ribs comprising the ring portion, the ribs being connected in pairs by cross pieces and being separated on one side of the ring portion by a transverse gap, the ring portion being circumferentially expandable through the gap to be receivable around the fitting second end portion.

14. The method of claim 13 wherein the member is formed of a resistive metal or plastic.

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15. The method of claim 1 1 where in the heating element comprises a band formed of a resistive foil circuit laminated between two sheets of a polymeric film, the band being affixed around the fitting second end portion with each of the leads having a second lead end electrically connected to an opposite end of the foil circuit.

16. The method of any of the preceding claims wherein the first and second electrical conductors each is formed as a resistive stripe embedded in the tube exterior surface.

17. The method of claim 16 wherein each stripe is formed of a resistive polymeric material.

18. The method of any of the preceding claims further comprising the additional step of:

(e) forming a cover around the heating element.

19. The method of claim 18 wherein the cover is formed of a plastic material.

20. The method of any of the preceding claims wherein the polymeric materials forming each of the tube layers is selected, independently, from the group consisting of polyamides, polyesters, polyacetals, ethylene vinyl alcohol, polyoxymethylene, polyolefins, silicones, fluoropolymers, polyvinyl chlorides, polyurethanes, thermoplastic elastomers, EPDM, natural and synthetic rubbers, and copolymers and blends thereof.

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