Abstract:
A hose assembly for coupling a plurality of components in fluid connection and a method for making same. According to a first aspect of the invention, the hose assembly includes at least one rigid portion and at least one flexible portion which cooperate to permit the shape and size of the hose assembly to be easily modified so that the components may be coupled to one another. A second aspect of the invention provides a method for reinforcing a flexible portion of the hose assembly to prevent the flexible portion from kinking when the flexible portion is bent. A third aspect of the invention provides a support collar for use in reinforcing an intersection between a pair of duct sections wherein at least one of the duct sections is moveable relative to the other duct section. The support collar reinforces the intersection and helps to render this section less susceptible to tearing. A fourth aspect of the invention provides a hose assembly having a sleeve member which covers at least a portion of a duct member so as to provide the duct member with a predetermined characteristic, such as abrasion, tear or puncture resistance.

Description:
TECHNICAL FIELD 
     The present invention relates generally to the forming of duct assemblies and more particularly to a duct assembly having an end or intermediate portion which is specifically tailored to the needs of a particular application. The end or intermediate portion may be relatively more flexible and self-forming than the adjoining portion or may have a protective covering to provide the hose assembly with a predetermined characteristic such as abrasion, tear or puncture resistance in a desired area. 
     BACKGROUND OF THE INVENTION 
     Background Art 
     In the aircraft industry, complex ducts are frequently required for the routing of pressurized fluids, including air, throughout the aircraft. These ducts are often times fabricated in from metal or other rigid materials in several long sections, with each section having numerous branches for coupling various components to the duct. An illustrative duct section constructed in this manner is illustrated in FIG.  1 . 
     Duct section  10  includes a body portion  12  and a plurality of branch portions  14 . Body portion  12  and branch portions  14  are formed with relatively expensive tools and equipment according to a design model. The design model typically employs the nominal positions or 3-dimensional location  16  of the components  18  that are to be coupled to the duct section  10 , as well as the structure of the device into which duct section  10  is attached, to determine the geometry of the body portion  12  and each of the branch portions  14 . In a typical situation, the design data for the duct section  10  that is developed from the design model is quite complex, with many curves, bends and branch portions  14  being formed in the duct section  10  throughout its length. 
     The configuration of the duct section  10  frequently necessitates that it be fabricated in several component parts which are then coupled together via specialized fittings, clamps or welding. Those skilled in the art will readily understand that due to part-to-part variation between the component parts, as well as the variation in which they are assembled, the configuration of duct section  10  can vary widely from the design model. Complicating matters is that the actual positions  20  of the components  18  that are to be coupled to the duct section  10  frequently vary from their nominal position  16 . 
     If the variance between the actual position  20  of the components  18  and the associated connection point of the duct section  10  are severely mis-aligned, it is necessary to take corrective action, such as modifying the tooling on which the component parts of the duct section  10  are fabricated, modifying the design positions of the components  18  which are connected to duct section  10 , and/or reworking duct section  10  to tailor it to the particular application. These corrective actions are frequently expensive and time consuming as it is usually quite difficult to identify and quantify each of the variations from the design model. Often times, the corrective action is iterative in nature, with small improvements being made over an extended period of time. 
     While the amount of time that is expended to achieve a finalized design is one drawback of an iterative design approach, another concerns the proliferation of components that result from the release of “intermediate” versions into production. As each version may have unique servicing and maintenance requirements, thereby increasing the complexity of a servicing program. Furthermore, stocking of several “intermediate” versions may be necessary to ensure that all previously produced products may be timely serviced. 
     One solution that has been proposed is to break the duct section  10  into a plurality of even shorter sub-sections which are coupled together during the installation of duct section  10  into a particular application. One drawback of the use of multiple duct sub-sections is that depending on the particular application, it can be difficult to couple the sub-sections together if the duct sub-sections are relatively inaccessible for servicing after they are located into the application. This solution is also relatively expensive, can adversely affect the overall reliability of the duct section, increase the frequency with which it must be serviced and add considerable weight to the duct section. 
     These drawbacks are particularly true where relatively long flexible hoses are employed, as these sub-sections tend to move relative to their associated duct-subsections due to vibrations that are generated in the application and transmitted through the duct. This relative motion renders the intersection between the duct sub-sections more susceptible to failure due to the stresses, strain and/or shear forces that are typically created in that region from the clamping device which secures the hose to its associated duct sub-section and/or abrading on another portion of the application (e.g., the structure to which the duct is coupled). 
     Accordingly, there remains a need in the art for a duct that is relatively easy and inexpensive to fabricate regardless of the complexity of its configuration. The duct should be easy to install and readily accommodate the variation that occurs from part-to-part and application-to-application. Furthermore, the duct should be easily tailored to the unique needs of an application. 
     SUMMARY OF THE INVENTION 
     In one preferred form, the present invention provides a duct assembly for coupling a pair of components in fluid connection. The duct assembly includes a first portion, a second portion and a support collar. The second portion is relatively more flexible than the first portion and in fluid connection with the first portion. The support collar is coupled to an outer perimeter of the second portion and abuts the first portion. The support collar is sized to prevent the formation of a stress riser at an intersection between the first and second portions to thereby render the intersection less susceptible to tearing in response to repeated flexing of the second portion. 
     In another preferred form, the present invention provides a duct assembly for coupling a pair of components in fluid connection. The duct assembly includes a duct portion and a sleeve portion. The sleeve portion is bonded to an exterior perimeter of the duct portion in a predetermined area of the duct portion and provides the predetermined area of the duct portion with a predetermined characteristic, such as abrasion and tear resistance. 
     In another preferred form, the present invention provides a method for forming a reinforced flexible duct assembly. The method includes the steps of providing a duct member, determining a diameter of the duct member, selecting a reinforcement member and a reinforcement pitch based on the diameter of the duct member, and bonding the reinforcement member to an exterior surface of the duct member in a helix such that a pitch of the helix is equal to the reinforcement pitch. 
     In another preferred form, the present invention provides a method for forming a hose assembly for coupling a plurality of components in fluid connection. The method includes the steps of forming a rigid duct structure and a flexible duct structure; and bonding the flexible duct structure to an end of the rigid duct structure to produce a clampless flexible joint which permits an end of the flexible duct structure opposite the rigid duct structure to be moved relative to the rigid duct structure. 
     In another preferred form, the present invention provides a method for forming a hose assembly for coupling a plurality of components in fluid connection. The method comprising the steps of forming a flexible duct structure from an elastomeric material; forming first and second rigid duct structures, the first and second rigid duct structures being formed to be relatively more rigid than the flexible duct structure; coupling the first rigid duct structure to a first end of the flexible duct structure; and coupling the second rigid duct structure to a second end of the flexible duct structure such that the flexible duct structure permits the first and second rigid duct structures to be moved relative to one another. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a plan view of a conventional prior art duct assembly; 
     FIG. 2 is a plan view of a duct assembly constructed in accordance with several aspects of the present invention, the duct assembly being shown in an installed condition; 
     FIG. 3 is a cross-sectional view taken along the line  3 — 3  of FIG. 2; 
     FIGS. 4 a ,  4   b ,  4   c ,  4   d ,  4   e  &amp;  4   f  are cross-sectional views of different helix members; 
     FIG. 5 is an enlarged view of a portion of FIG. 3 illustrating a bent portion of the intersection between the rigid and flexible duct structures when a positive pressure load is applied to the interior of the duct assembly; 
     FIG. 6 is a view similar to that of FIG. 6 but illustrating a bent portion of the intersection between the rigid and flexible duct structures when a negative pressure load is applied to the interior of the duct assembly; 
     FIG. 7 is a cross-sectional view taken along the line  7 — 7  of FIG. 2; 
     FIG. 8 is a plan view of a duct assembly similar to that of FIG. 2 but illustrating a first alternate construction; 
     FIG. 9 is a plan view of a duct assembly constructed in accordance with another aspect of the present invention; 
     FIG. 10 is a plan view of a duct assembly similar to that of FIG. 9 but illustrating an alternate construction. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 2 of the drawings, a duct assembly constructed in accordance with the teachings of the present invention is generally indicated by reference numeral  10 . Duct assembly  50  is shown to include a plurality of rigid duct structures  52 , a plurality of flexible duct structures  54  and a plurality of elastomeric attachment sleeves  56 . Each of the rigid duct structures  52  is formed from a material which is relatively more rigid than the flexible duct structure  54  to which it is adjacent. For example, rigid duct structures  52   a  and  52   b  are relatively more rigid than flexible duct structure  54   a . In the particular embodiment illustrated, each of the rigid duct structures  52  are fabricated from metals, such as steel and aluminum, plastics and composites such as fiberglass, carbon, KEVLAR® and NEXTEL®. 
     Each of the flexible duct structures  54  is positioned between an associated pair of rigid duct structures  52  to permit the shape of duct assembly  50  to be easily tailored to the needs of a particular application. The flexible duct structures  54  are illustrated to be bonded to one or more associated rigid duct structures  52  to produce a clampless flexible joint that joins the opposite ends of each of the flexible duct structures  54  to an associated one of the rigid duct structures  52 . In the particular embodiment illustrated, flexible duct structures  54   b ,  54   c  and  54   d  are helix reinforced structures  60  and flexible duct structures  54   a  and  54   e  are convoluted bellows structures  62 . 
     A detailed description of helix reinforced structure  60  is beyond the scope of the present invention and need not be provided herein. Briefly, and with additional reference to FIGS. 3 through 6, each of the helix reinforced structures  60  is shown to include an inner liner or member  66 , a reinforcing helix  68  and an outer member  70 . In the example provided, inner member  66  and outer member  70  are formed from conventional elastomeric duct materials (i.e., uncured elastomeric impregnated composite fabrics), such as rubber, silicone, nitrile, butyl, ethylene propylene, neoprene, polyurethane, fluoro silicone and fluoro elastomers and reinforcing helix  68  is fabricated from a thermoplastic material such as polyetherimide, polyphenisulfbne or polyarylsulfone. 
     Reinforcing helix  68  is bonded between inner and outer members  66  and  70 , thereby reinforcing inner member  66  to guard against bursting, collapsing or kinking. The cross-section of reinforcing helix  68  preferably includes a flat base  72  as shown in FIGS. 4 a  through  4   d  but other shapes, such as those shown in FIGS. 4 e  and  4   f  may also be used. Reinforcing helix  68  may also have one or more hollow cavities  74  as illustrated in FIGS. 4 c ,  4   d  and  4   f  to reduce the weight and stiffness of duct assembly  50 . Helix reinforced structure  60  is otherwise discussed in greater detail in commonly assigned U.S. Pat. No. 6,000,435, the disclosure of which is hereby incorporated by reference as if fully set forth herein. 
     In fabricating duct assembly  50 , the inner member  66  of flexible duct structure  54   b  is positioned to extend into the ends  78  and bonded to the inner walls  80  of rigid duct structures  52   b  and  52   c . An adhesive material is applied to the exterior surface  82  of inner member  66  and/or to reinforcing helix  68  and reinforcing helix  68  is applied to the portion of the inner member  66  between rigid duct structures  52   b  and  52   c . Preferably, the size of the material forming reinforcing helix  68  (i.e., the reinforcement member  84 ) as well as the pitch “p” of reinforcing helix  68  are related to the size of the flexible duct structure  54  in accordance with a second aspect of the present invention as shown, for example, in the table set forth below. Sizing reinforcement member  84  and setting the pitch “p” of reinforcing helix  68  to the reinforcement pitch set forth in the table, below, permits flexible duct structure  54  to achieve a good balance of strength and flexibility without the need for experimentation to empirically derive the size of the material and pitch of the helix. Proper selection of the material which forms reinforcing helix  68  and the pitch “p” of reinforcing helix  68  permits flexible duct structure  54  to be bent with a relatively tight bending radius without kinking (illustrated by reference letter “k” in phantom in FIG.  2 ). 
     
       
         
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                   
                 Dimension of 
                   
               
               
                   
                 Polyetherimide 
                   
               
               
                   
                 Reinforcing 
                   
               
               
                   
                 Helix 
                   
               
               
                 Diameter (d) 
                 Material* 
                 Reinforcement 
               
               
                 of Flexible 
                 (inches) 
                 Pitch 
               
             
          
           
               
                 Duct 
                 Solid 
                 Hollow- 
                 Solid 
                 Hollow- 
               
               
                 Structure 
                 Cross- 
                 Cross 
                 Cross- 
                 Cross 
               
               
                 (inches) 
                 Section 
                 Section 
                 Section 
                 Section 
               
               
                   
               
               
                 d &gt; 7½ 
                 0.15 
                 0.15 
                 ¾ 
                 ¾ 
               
               
                 7½ ≧ d &gt; 5½ 
                 ⅛ 
                 ⅛ 
                 ¾ 
                 ¾ 
               
               
                 5½ ≧ d &gt; 4 
                 0.10 
                 0.10 
                 ⅞ 
                 ⅞ 
               
               
                 4 ≧ d &gt; 3½ 
                 0.10 
                 0.10 
                 ¾ 
                 ¾ 
               
               
                 3½ ≧ d &gt; 2½ 
                 {fraction (3/32)} 
                 {fraction (3/32)} 
                 ¾ 
                 ¾ 
               
               
                 2½ ≧ d &gt; 1¾ 
                 {fraction (3/32)} 
                 {fraction (3/32)} 
                 ⅝ 
                 ⅝ 
               
               
                 1¾ ≧ d &gt; 1¼ 
                 {fraction (5/64)} 
                 {fraction (5/64)} 
                 ½ 
                 ½ 
               
               
                 1¼ ≧ d &gt; 1 
                 {fraction (1/16)} 
                 — 
                 {fraction (7/16)} 
                 — 
               
               
                 1 ≧ d 
                 {fraction (1/16)} 
                 — 
                 ⅜ 
                 — 
               
               
                   
               
               
                 *The term “dimension” is employed to describe the largest cross-sectional width dimension (e.g., diameter) of the reinforcing helix material.  
               
             
          
         
       
     
     Additional adhesive material may be applied to the inner surface  86  of outer member  70  before outer member  70  is overlaid onto the reinforcing helix  68  and inner member  66  to complete the lay-up of this portion of duct assembly  50 . Preferably, however, the lay-up also includes a pair of support collars  90  constructed in accordance with a third aspect of the present invention. Support collars  90  are disposed between reinforcing helix  68  and each of the rigid duct structures  52   b  and  52   c  and coupled to the exterior surface  94  of the outer member  70 . 
     Each of the support collars  90  are preferably fabricated from a thermoplastic material such as polyetherimide, polyphenisulfone or polyarylsulfone. The cross-section of the support collars  90  may be solid or hollow and may be identical in configuration to reinforcing helix  68 . It is preferred, however, that each of the support collars  90  have a cross-section with a rounded top  96  and a flat base  72 , such as the cross-sections shown in FIGS. 4 b  and  4   c . It is also preferred that the ends  78  of the rigid duct structures  52  include an end portion  100  which is smaller in diameter than a body portion  102  of the rigid duct structure  52 . End portion  100  preferably has a height which is equal to the height of support collar  90  and a length which is equal to the pitch “p” of reinforcing helix  68 . 
     In operation, support collar  90  is operable for distributing loads associated with the movement of flexible duct structure  54  relative to rigid duct structure  52 , whether the movement be caused from the bending of flexible duct structure  54  or exposure to a fluid pressure differential. In FIG. 5, the interior  106  of duct assembly  50  is exposed to a pressurized fluid, causing flexible duct structure  54  to bulge in an outward direction. Support collar  90  limits the amount by which the wall  108  of flexible duct structure  54  may rotate relative to rigid duct structure  52  and helps to spread the tensile and compressive forces associated with the bulging of the flexible duct structure  54  over a relatively larger area. Support collar  90  is therefore sized to prevent the formation of a stress riser at the intersection  110  between rigid duct structure  52  and flexible duct structure  54  to thereby render the intersection  110  less susceptible to tearing or shearing in response to repeated flexing of the flexible duct structure  54 . 
     A similar condition is illustrated in FIG. 6 wherein the interior  106  of duct assembly  50  is exposed to vacuum pressure, causing flexible duct structure  54  to bulge in an inward direction. Like the situation illustrated in FIG. 5, support collar  90  limits the amount by which the wall  108  of flexible duct structure  54  may rotate relative to rigid duct structure  52  and helps to spread the tensile and compressive forces associated with the bulging of the flexible duct structure  54  over a relatively larger area. A similar condition is also experienced by flexible duct structure  54  when flexible duct structure  54  is bent relative to the longitudinal axis of rigid duct structure  52 . Accordingly, support collar  90  is operable for rendering intersection  110  less susceptible to failures from the deformation of flexible duct structure  54  as a result of a differential fluid pressure as well as rendering intersection  110  less susceptible to failures from the movement or flexure of flexible duct structure  54  relative to rigid duct structure  52 . 
     Returning to FIG.  2  and with additional reference to FIG. 7, each of the convoluted bellows structures  62  is shown to include a plurality of elastomeric convolutions  120 , a pair of end portions  122  and a pair of external plies  124 . Convoluted bellows structure  62  is formed from a suitable elastomer, such as silicone, viton, flourosilicone, nitrile or neoprene. The elastomeric material may also be coated or impregnated over a fabric such as fiberglass or kevlar, depending on various design criteria. 
     Each of the end portions  122  is illustrated to be generally cylindrical in shape and sized to engage the end sections  128  of the rigid duct structures  52   a  and  52   b . External plies  124  may be formed from a material such as fiberglass reinforced silicone and are sized to overlap a portion of one of the end portions  122  and portion of an associated one of the end sections  128 , permitting the external plies  124  to secure the convoluted bellows structure  62  to an associated pair of rigid duct structures  52 . 
     The plurality of elastomeric convolutions  120  couple the end portions  122  together and are resilient enough to permit relative axial movement between rigid duct structures  52   a  and  52   b . The convoluted bellows structures  62  are generally employed in relatively short lengths and are generally more flexible than the helix reinforced structures  60 . Convoluted bellows structures  62  are typically employed to correct misalignment between the duct assembly  50  and another device (not shown), and/or to permit the length of the duct assembly  50  to be varied and/or to dampen vibrations which are transmitted through duct assembly  50 . The number, shape and height of the convolutions  120  and length of the convoluted bellows structure  62  is dependent on various design criteria, such as the anticipated misalignment or desired variation in the length of duct assembly  50 . 
     Depending on the differential fluid pressure, the fluid (e.g., air) in duct assembly  50  may exert a load on convoluted bellows structure  62  which causes the convolutions  120  to expand outwardly, possibly restricting the flow of fluid through duct assembly  50  and/or permitting the convoluted bellows structure  62  to rub and abrade on another component and in severe cases, rupture. Accordingly, a reinforcing material, such as a plurality of thermoplastic or metal reinforcing collars  132 , may be incorporated into convoluted bellows structure  62  to locally control the expansion of the convolutions  120 . 
     Returning to FIG. 2, each of the attachment sleeves  56  is illustrated to be bonded to an associated one of the rigid duct structures  52  and is employed where additional stiffness is required, as for example where the ends  150  of duct assembly  50  are clamped to another device. Each of the attachment sleeves  56  is fabricated in a multi-ply manner wherein one or more rigid layers  200  are wrapped around an inner flexible layer  202 . 
     The rigid layers  200  may be formed from a polyester impregnated fiberglass, for example, and the inner flexible layer  202  may be formed from an elastomeric material such as silicone. In the particular example provided, the silicone inner flexible layer  202  is heat resistant and operable for forming a gasket that contains pressurized fluids within duct assembly  50 , while the polyester impregnated fiberglass rigid layers  200  is suitable for withstanding the dynamic loading and motions that are transmitted through attachment sleeve  56 . 
     In forming duct assembly  50 , it is preferred that a lay-up of the entire duct assembly  50  (i.e., the rigid duct structures  52  be coupled to their respective flexible duct structures  54  and attachment sleeves  56 ) and duct assembly  50  be co-cured in an oven or autoclave in a single cycle. However, those skilled in the art will also understand that each of the flexible duct structures  54  and attachment sleeves  56  may be pre-cured as necessary and subsequently bonded to one or more of the associated rigid duct structures  52 . 
     Forming duct assembly  50  with flexible duct structures  54  and attachment sleeves  56  is highly advantageous as compared with the duct structures of the prior art because the flexible duct structures  54  permit the rigid duct structures  52  to be fabricated in relatively straight sections, thereby reducing tooling and labor costs associated with the fabrication of duct assembly  50 . Furthermore, as flexible duct structures  54  provide a comparatively large degree of latitude in the position of the ends  150  of duct assembly  50 , the process of installing duct assembly  50  into an application is considerably easier and faster. 
     In FIG. 8, duct assembly  50   a  is illustrated to be similar to duct assembly  50  in that it includes a flexible duct structure  54  and a plurality of rigid duct structures  52 . However, duct assembly  50   a  includes a plurality of attachment sleeves  56   a  which have a beaded end portion  220  that is operable for engaging the inner diameter  222  of a coupling hose  224 . A retaining ring  226  is slid along the outer surface  228  of coupling hose  224  until it passes over beaded end portion  220 . 
     The geometry of retaining ring  226  provides anti-slip resistance to coupling hose  224 , preventing coupling hose  224  from detaching from the beaded end portion  220  of hose assembly  50   a . Pressurized fluid introduced into duct assembly  50   a  generates a detaching force causing coupling hose  224  and retaining ring  226  to separate from duct assembly  50   a  until a curved portion  230  of retaining ring  226  makes contact with beaded end portion  220 . Additional detaching force then acts to squeeze retaining ring  226  and coupling hose  224  against beaded end portion  220 , thereby creating a seal between coupling hose  224  and duct assembly  50   a . Beaded end portion  220  and retaining ring  226  are discussed in greater detail in above-referenced U.S. Pat. No. 6,000,435. 
     In FIG. 9, a portion of a duct assembly constructed in accordance with the teachings of a fourth aspect of the present invention is generally indicated by reference numeral  50   b . Duct assembly  50   b  is shown to include a duct structure  250  and a sleeve member  252 . In the particular embodiment illustrated, duct structure  250  is a helix reinforced structure  60  constructed in the manner discussed above and not necessarily coupled to a rigid duct structure  52 . However, those skilled in the art will understand that the teachings of this aspect of the present invention may be applied to other types of duct structures including rigid duct structures  52 . As such, the scope of this aspect of the present invention will not be limited to duct structures having a helix reinforced structure  60 . 
     Sleeve member  252  includes a hollow central cavity (not specifically shown) which is sized to receive helix reinforced structure  60 . Sleeve member  252  is slid over duct structure  250  to a predetermined area of helix reinforced structure  60  and bonded to the exterior perimeter  256  of helix reinforced structure  60 . The ends  258  of sleeve member  252  may be secured to a lay-up of helix reinforced structure  60  via several plies of material  260  that are bonded to sleeve member  252  and helix reinforced structure  60 . Thereafter, hose assembly  50   b  is placed in an oven at an elevated temperature to permit the adhesive that bonds helix reinforced structure  60  together as well as adhesive that bonds sleeve member  252  to helix reinforced structure  60  to be simultaneously cured. 
     Sleeve member  252  is operable for providing the portion of duct structure  250  to which it is coupled a predetermined one or more predetermined characteristics, such as abrasion resistance, puncture resistance or additional strength. If abrasion resistance is required, sleeve member  252  may be formed from a material such as polyester or KEVLAR®. If puncture resistance or additional strength is required, sleeve member  252  may be formed from a woven material, such as steel wire, carbon graphite or KEVLAR® or from a material such as NEXTEL®. If heat resistance or containment is required, sleeve member  252  may be formed from a material such as NEXTEL®. 
     In FIG. 10, an alternative method for constructing hose assembly  50   b  is illustrated wherein helix reinforced structure  60  is be pre-formed and cured prior to the application of sleeve member  252  to helix reinforced structure  60  and the curing of adhesive  270  which couples sleeve member  252  to helix reinforced structure  60 . This situation is most likely to arise when duct structure  250  is in need of repair or reworking. In such situations, the repair/rework operation is frequently performed when the duct assembly  50   b  is partially installed in its operating environment and as such, it is frequently not possible to cure the adhesive in an oven. Accordingly, a silicone adhesive, such as a room-temperature vulcanizing (RTV) silicone adhesive, may be employed to bond sleeve member  252  to duct structure  250 . 
     While the invention has been described in the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.