Abstract:
A sealing assembly is equipped with life-sensing means in terms of wear ( 12   a,    12   b ), thermal degradation, physical damage, chemical incompatibility and structural breakdowns within the sealing assembly, and means ( 22   a, b ) for transmitting an output of the sensing means to detect a change in the sealing environment or an impending seal failure.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/233,530 filed on Aug. 13, 2009 and to U.S. Provisional Patent Application No. 61/329,640 filed on Apr. 30, 2010, the entire disclosures of which are hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    The invention relates generally to a sealing assembly, and more particularly to a sealing assembly that is equipped with life-sensing means in terms of wear, thermal degradation, physical damage, chemical incompatibility and structural breakdowns within the sealing assembly, and means for transmitting an output of the sensing means to detect a change in the sealing environment or an impending seal failure. 
       BACKGROUND 
       [0003]    Providing a seal between adjacent surfaces of an assembly is necessary to prevent a leak when the hardware and its mating part are conducting or containing media. Such seals are typically made of, but not limited to, thermosetting or thermoplastic polymer materials, which are relatively resilient and deformable. The seal is generally annular and has a circular cross-section, but could also include any other engineered shape configured for sealing. The hardware may have a groove in its front face for receiving the seal, or the seal may be overmolded directly onto the hardware. When the hardware is properly connected to its mating part, the seal is compressed by the adjacent face surface of the mating part. A seal may be housed in the hardware for extended periods of time. 
         [0004]    The seal assembly may be used in a hostile environment where the seal is subjected to aggressive chemicals, extreme temperatures, and/or high pressure. Such conditions may cause the seal to deteriorate. In addition, the seal may be improperly installed or may be physically damaged which may cause the seal to malfunction. 
         [0005]    Seal malfunction can cause both minor and catastrophic equipment failures. Down time, maintenance and repair costs could be minimized by the ability to sense impaired operational performance or impending failure in an elastomeric seal. 
       SUMMARY 
       [0006]    The present invention is directed to sealing assemblies, and particularly to a sealing assembly with integrated life-sensing capability for detecting structural breakdowns and environmental changes within the sealing assembly. Such sealing assembly may find particular use in applications from the automotive, heavy duty, general industrial, consumer products, fluid power, aerospace, microelectronics, energy systems, oil and gas, life sciences and chemical processing markets. 
         [0007]    In an illustrative embodiment of the invention, a sealing assembly with integrated sensing capability includes a seal member that includes first and second conductive layers and an intermediate layer therebetween, the intermediate layer being formed of a dielectric material such that the first, second and intermediate layers form in combination a capacitive element having a capacitance associated therewith. The sealing assembly also includes a first electrical contact to the first conductive member, a second electrical contact to the second conductive member, and an insulator between the first and second electrical contacts. The sealing assembly of this embodiment further includes a first plate having first central passage therethrough and a first inner sealing contact surface; and a second plate having a second central passage therethrough and a second inner sealing contact surface; the seal member located between the first plate and the second plate to form a seal therebetween. 
         [0008]    In one embodiment, the seal member may further include a second dielectric layer and a third conductive layer between the first and second conductive layers to form a capacitive element having alternating conductive and dielectric layers. 
         [0009]    The conductive layers of the seal member may be constructed of a thermosetting or thermoplastic polymer material and electrically conductive filler. The dielectric layer of the seal member may be constructed of a thermosetting or thermoplastic polymer. The polymer of the dielectric layer may also include electrically insulating filler. The first and second plates may be constructed of an electrically insulating polymeric material. 
         [0010]    In one aspect of the invention, the first plate of the sealing assembly has a first conductive element on the first inner sealing contact surface and the second plate has a second conductive element on the second inner sealing contact surface, the first conductive layer of the seal member electrically contacting the first conductive element of the first plate and the second conductive layer of the seal member electrically contacting the second conductive element of the second plate. 
         [0011]    The conductive elements of the first and second plates may be inlaid into the inner sealing surface of the first and second plates, respectively. In another embodiment, the conductive element of the first and second plates is a conductive film deposited on the inner sealing surface of the first and second plates, respectively. 
         [0012]    In one embodiment, the insulator between the first and second electrical contacts is a spacer having a central bore into which the seal member is seated, the spacer positioned between the first and second plates. 
         [0013]    In another aspect of the invention, the first conductive layer of the seal member includes an outwardly extending first tab for making electrical contact with the first conductive layer, and the second conductive layer of the seal member includes an outwardly extending second tab for making electrical contact with the second conductive layer. The sealing assembly may further include an insulating spacer into which the seal member is seated, the spacer having a channel therein, the channel having a first side and a second side and a girder between the first and second sides, the girder positioned between the first tab and the second tab of the seal member. 
         [0014]    In another illustrative embodiment of the invention, a sealing assembly with integrated sensing capability includes a seal member including first and second conductive layers and an intermediate layer therebetween, the intermediate layer being formed of a dielectric material such that the first, second and intermediate layers form in combination a capacitive element having a capacitance associated therewith. The first conductive layer of the seal member may include an outwardly extending first tab for making electrical contact with the first conductive layer, and the second conductive layer of the seal member may include an outwardly extending second tab for making electrical contact with the second conductive layer. The sealing assembly may further include an electrically insulating frame into which the seal member is seated, the frame having a channel therein, the channel having a first side and a second side and a girder between the first and second sides, the girder positioned between the first tab and the second tab of the seal member. The sealing assembly of this embodiment is configured to provide a seal between a non-conductive hardware component and a second non-conductive mating component. 
         [0015]    The capacitive element of the sealing assembly may be electrically connected to means for sensing changes in the capacitance presented by the seal member between the first conductive element and the second conductive element. 
         [0016]    In one embodiment, the capacitive element is configured to sense at least one of load conditions, wear, thermal degradation, physical damage and chemical incompatibility, and is coupled to data processing circuitry adapted to signal that a structural failure of the seal is impending. 
         [0017]    The foregoing and other features of the invention are hereinafter described in greater detail in accordance with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a top view of a capacitor seal ring in accordance with the present invention. 
           [0019]      FIG. 2  is a cross-sectional view of an exemplary embodiment of the capacitor seal ring of  FIG. 1 , wherein the seal ring has a three-layer structure. 
           [0020]      FIG. 2A  is an end view of the seal ring of  FIG. 2 . 
           [0021]      FIG. 3  is a cross-sectional view of an exemplary embodiment of the capacitor seal ring of the present invention wherein the seal ring has a five-layer structure. 
           [0022]      FIG. 3A  is an end view of the seal ring of  FIG. 3 . 
           [0023]      FIG. 4  is a perspective exploded view of an exemplary embodiment of a sealing assembly incorporating a conductive inlay and the capacitor seal ring in accordance with the present invention. 
           [0024]      FIG. 5  is an assembled view of the sealing assembly of  FIG. 4 . 
           [0025]      FIG. 6  is a perspective exploded view of another exemplary embodiment of a sealing assembly incorporating a plated conductive layer and the capacitor seal ring in accordance with the present invention. 
           [0026]      FIG. 7  is an assembled view of the sealing assembly of  FIG. 6 . 
           [0027]      FIG. 8  is a perspective exploded view of another exemplary embodiment of a sealing assembly of the present invention that conforms with a standard code  61 / 62  style flange assembly. 
           [0028]      FIG. 9  is an assembled view of the sealing assembly of  FIG. 8 . 
           [0029]      FIGS. 10A-10C  are perspective, top and cross-sectional views, respectively, of another exemplary embodiment of a capacitor seal ring having integral connection points. 
           [0030]      FIG. 11  is a perspective view of an exemplary seal assembly incorporating the capacitor seal ring of  FIGS. 10A-10C . 
           [0031]      FIG. 12  is an exploded view of the seal assembly of  FIG. 11 . 
           [0032]      FIG. 13  is an exploded view of an exemplary seal assembly for use with conductive mating hardware, and which incorporates the capacitor seal ring of  FIGS. 10A-10C . 
           [0033]      FIG. 14  is an assembled view of the sealing assembly of  FIG. 13 . 
           [0034]      FIG. 15  shows an embodiment of the sealing assembly as connected to a monitoring system. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    The present invention is directed to a sealing assembly having an integral sensor that is capable of capturing and responding to physical and chemical changes within the seal assembly. The seal within the sealing assembly functions as its own heath and life sensor. The seal includes conductive layers separated by dielectric layers to form one or more capacitive elements by which changes in capacitance can be sensed. As the seal wears, changes in the dielectric constant can occur, as do the physical properties of the conductive and dielectric layers that can also affect the capacitance of the seal. The layers of the seal are configured to enable sensing of load conditions, damage to the seal, chemical incompatibility within the seal environment and improper mounting conditions. The layers of seal can be coupled to data processing circuitry capable of predicting when a structural failure of the seal will occur, so that the seal can be safely used for its full life and then replaced before any damage occurs to any system containing the seal or to any objects surrounding the sealing assembly. Referring to the drawings, and initially to  FIGS. 1 to 2A , a capacitor seal ring  10  has a three layer laminate structure that includes a pair of conductive layers  12   a  and  12   b  separated by an intermediate dielectric layer  14 . The three layers in combination form an electrical element, namely, a capacitive element. 
         [0036]    The dielectric layer  14  may be constructed of a thermosetting elastomer, such as, for example, acrylonitrile butadiene (NBR); fluoroelastomers (FKM) including hexafluoropropylene, vinylidenefluoride, tetrafluoroethylene and perfluoromethylvinylether copolymers; hydrogenated copolymers of acrylonitrile and butadiene monomers (HNBR); silicone rubber (VMQ), including dimethylpolysiloxane; or fluorinated silicone rubber (FVMQ), including analogs of dimethylpolysiloxane. The dielectric layer  14  may also be constructed of a thermoplastic elastomer, such as, for example, styrenic block copolymers, polyolefinic blends, elastomeric alloys, polyurethanes, copolyesters and polyamides. 
         [0037]    The dielectric layer  14  may be compounded with any one of the thermosetting or thermoplastic elastomers into a suitable formulation by the addition of process aids, curatives and fillers to reinforce or otherwise modify the properties of the compound. Illustrative examples of suitable fillers for obtaining the desired dielectric properties include barium sulfate, clays, fume process silicas, and combinations of one or more thereof. Preferably, the compound used to form the dielectric layer  14  has a dielectric constant of at least 5.0 at 1 kHz. More preferably, the compound of the dielectric layer  14  has a dielectric constant of at least 10.0 at 1 kHz. 
         [0038]    The conductive layers  12   a  and  12   b  may be constructed of a thermosetting elastomer, such as, for example, acrylonitrile butadiene (NBR); fluoroelastomers (FKM) including hexafluoropropylene, vinylidenefluoride, tetrafluoroethylene and perfluoromethylvinylether copolymers; hydrogenated copolymers of acrylonitrile and butadiene monomers (HNBR); silicone rubber (VMQ), including dimethylpolysiloxane; fluorinated silicone rubber (FVMQ), including analogs of dimethylpolysiloxane; or terpolymers of ethylene propylene diene monomers (EPDM). The conductive layers may also be constructed of a thermoplastic elastomer, such as those listed above. The conductive layers  12   a  and  12   b  are compounded with one or more of the foregoing elastomers into a usable formulation by the addition of process aids, curatives and fillers to reinforce or otherwise modify the properties of the compound. Examples of suitable fillers for obtaining the desired conductive properties include carbon black, indium tin oxide, carbon nano-tubes, and graphite. In one embodiment, the volume resistivity of the compound is in the range of about 10 5  ohm-cm to about 10 8  ohm-cm. 
         [0039]    Referring to  FIGS. 3 and 3A , the capacitor seal ring  10   a  has a five-layer laminate structure that includes conductive layers  12   a,    12   b  and  12   c,  separated by dielectric layers  14   a  and  14   b.  The materials used to construct the three conductive layers and two dielectric layers may include those materials listed above with regard to the three-layer assembly. 
         [0040]    The capacitor seal ring may be constructed by cold molding the dielectric and conductive layers independently of one another. The cold molding process involves heating the respective material to a temperature that is high enough to enable the material to flow, yet not high enough to initiate the curing process. The cold molded dielectric and conductive layers are assembled in an alternating arrangement and then subjected to a curing process to form the laminate elastomeric seal. 
         [0041]    The performance and condition of the seal ring  10  can be monitored by positioning the seal ring  10  within a seal assembly and applying an electric current to one of the conductive layers to measure changes in capacitance. Electrical connection to the conductive layers  12   a  and  12   b  of the seal may be made through flanges configured specifically for this purpose. 
         [0042]    Referring to  FIGS. 4 and 5 , a seal assembly  30  includes an electrically insulating upper plate  16 , an electrically insulating lower plate  18  and a spacer  20  positioned between the upper plate  16  and the lower plate  18 . Each of the upper plate  16 , lower plate  18  and spacer  20  has a central passage therethrough. The capacitor seal ring  10  is seated within the central opening of the spacer  20 . Conductive inlay  21   b  fits within a complementary recess  24  in lower plate  18  that surrounds the central passage, and makes direct electrical contact with the second conductive layer  12   b  of seal ring  10 . Conductive inlay  21   b  includes a lead  22   b  for making electrical contact with a sensor circuit (not shown). Upper plate  16  also includes a complementary recess (not visible in figure view) that surrounds the central passage of upper plate  16  into which conductive inlay  21   a  fits to make direct electrical contact with the first conductive layer  12   a  of seal ring  10 . Conductive inlay  21   a  includes a lead  22   a  for making electrical contact with the sensor circuit. 
         [0043]    The upper plate  16 , lower plate  18 , and spacer  20  may be independently constructed from an insulating material such as plastic. Non-limiting examples of such insulating plastics include polyoxymethylene (Delrin® available from DuPont); polyether ether ketone (PEEK); polytetrafluoroethylene (PTFE); VESPEL® polyimide available from DuPont; RULON® polytetrafluoroethylene-based resins available from Saint-Gobain; and KAPTON® polyimide available from DuPont. 
         [0044]    Conductive inlays  21   a  and  21   b  may be constructive from a conductive metal or metal alloy, such as, for example, copper, brass, bronze, or stainless steel. Conductive inlays  21   a  and  21   b  are appropriately shaped based on the geometry of the seal, each with a stem-like extension  22   a,    22   b  that serves as the connection point to a circuit for measuring the capacitance and capacitance changes of the seal ring  10 . Electrical connection to the conductive inlays may be permanent, such as by soldering, or may be achieved by temporary or removable means, such as by a clip or fastener type connection. 
         [0045]    In  FIGS. 6 and 7 , another embodiment of a seal assembly is shown as  32 , which is similar to seal assembly  30 , with the exception that a conductive film  25  is deposited onto the inner surface of lower plate  18   a  to make electrical contact with seal ring  10 , rather than a conductive inlay. The conductive film  25  is generally ring shaped with a stem-like extension  26  that serves as the connection point to a circuit for measuring the capacitance and capacitance changes of the seal ring  10 . Upper plate  16   a  also includes a conductive film deposited onto the inner surface of upper plate  16   a  (not visible in figure view) for making electrical contact with seal ring  10 . Upper plate  16   a  may include a groove  28  on its outer surface, into which a seal may be seated. This additional groove may be incorporated into any of the embodiments described herein as necessary to the requirements of the application in which the sealing assembly is to be used. 
         [0046]    In  FIGS. 8 and 9 , another embodiment of a seal assembly is shown as  42 , which is similar to seal assembly  32 , with the exception that the overall shape of the assembly is not annular. Instead, the seal assembly  42  has a shape that conforms with a standard code  61 / 62  style flange assembly. Seal assembly  42  includes an electrically insulating upper plate  16   b,  an electrically insulating lower plate  18   b  and a spacer  20   a  positioned between the upper plate  16   b  and the lower plate  18   b.  The capacitor seal ring  10  is seated within the central opening of the spacer  20   a.    
         [0047]    Referring to  FIGS. 10A-10C , another embodiment of the capacitor seal is illustrated. Capacitor seal  10   b  has a three layer laminate structure that includes a pair of conductive layers  44   a  and  44   b  separated by an intermediate dielectric layer  46 . Each of the conductive layers  44   a  and  44   b  is molded with a tab  48   a,    48   b,  respectively, extending outwardly from the main body of the ring that serves as the connection point to a circuit for measuring the capacitance and capacitance changes of the seal ring  10   b.  By forming the electrical connection from the material of the conductive layers, separate conductive pathway(s) in the seal assembly (as embodied by inlays  21   a  and  21   b  in  FIG. 4 , and conductive film  25  in  FIG. 6 ) may not be required. While the tabs  48   a  and  48   b  are shown as having a rectangular shape, the tabs are not limited in shape and may be any shape suitable for making electrical connection to the ring  10   b.    
         [0048]    In  FIGS. 11 and 12 , seal assembly  50 , incorporating seal  10   b,  illustrates a simplified assembly for use with mating hardware that is non-conductive. Seal assembly  50  includes insulating spacer  52  having a central opening into which seal  10   b  is seated, such that spacer  52  frames seal  10   b.  Spacer  52  includes a bridged channel that forms an H-shaped girder  54 . Non-conductive girder  54  is positioned between tab  48   a  and  48   b  when the seal  10   b  is seated in the spacer  52  to provide access to the tabs and enable electrical connections to be made to the tabs. 
         [0049]    Referring to  FIGS. 13 and 14 , another embodiment of a seal assembly is shown as  56 . The overall shape of seal assembly  56  is not annular and the shape of the capacitor seal  10   c  is not annular. Although illustrated here as having a trapezoidal shaped cross-section, seal  10   c  may have any shape suitable for providing sealing in the particular application in which it is used. Seal assembly  56  includes an electrically insulating upper plate  16   c,  an electrically insulating lower plate  18   c  and a spacer  20   b  positioned between the upper plate  16   c  and the lower plate  18   c.  The capacitor seal  10   c  is similar to capacitor seal  10   b  in that it includes integrated tabs  48   a  and  48   b  extending from the main body of the seal. Seal  10   c  is seated within the inner bore of the spacer  20   b.  Spacer  20   b  includes a bridged channel that forms an H-shaped girder  54   a.  Non-conductive girder  54   a  is positioned between tabs  48   a  and  48   b  when the seal  10   c  is seated in the spacer  20   b  to provide access to the tabs and enable electrical connections to be made to the tabs. 
         [0050]    The sealing assembly is electrically connected to a circuit for sensing changes in the capacitance associated with the seal  10  resulting from distortion or damage to the seal. According to one aspect of the invention, an acceptable range is established for the capacitance and a signal is generated that a structural failure of the seal is impending in response to the capacitance deviating outside the acceptable range. The electrical monitoring of the condition of the seal, and in particular, monitoring the electrical capacitance with respect to a pre-established acceptable range enables accurate predictions of seal failure or environmental changes. 
         [0051]    Referring to  FIG. 15 , a sealing assembly  30  includes electrical leads  22   a  and  22   b,  which are electrically connected to the outer conductive layers of seal  10  (not visible in figure view). An acceptable range for the electrical capacitance of the capacitive coupling (e.g., based on an initial capacitance reading obtained from the seal) is first determined. By providing a suitably configured monitor  36 , changes in the electrical capacitance of the capacitive seal  10  (formed by the conductive layer  12   a,  the dielectric layer  14  and the conductive layer  12   b ) can therefore be sensed. Monitor  36  may sense changes in capacitance by including the capacitance presented by the seal as part of a resonant circuit and detecting variations in the frequency to determine changes in capacitance. A system for predicting the malfunction or deterioration of the seal includes controller  38  programmed to carry out the operations described herein. Display  40  can display a signal that structural failure of the seal  10  is impending in view of the capacitive value deviating outside the acceptable range. 
         [0052]    Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.