Patent Publication Number: US-2011049874-A1

Title: Polymeric pipe fitting and gasket assembly and sealed polymeric pipe apparatus formed therewith

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to polymeric plastic pipes and fittings and means and methods for sealed joinder thereof and, more particularly, to structures and systems for joining plastic pipes and fittings via an elastomeric gasket therebetween. 
     Polymeric plastic pipes and fittings find applications in numerous and diverse environments and uses, ranging from plumbing installations wherein the pipes and fittings serve as conduits for fresh potable water, wastewater/sewage, chemicals and/or other liquids or fluids, to electrical installations in which the pipes and fittings serve to enclose and direct electrical wiring, cables and the like. In substantially all such installations, it is desirable if not necessary that a sealed joinder be provided between connecting pipes and fittings to prevent leakage of materials from the piping system and/or to prevent infiltration of contaminants from outside the piping system. 
     Such plastic pipes and fittings offer cost, production and other advantages over cast iron, copper and other metals, but a disadvantage is that most plastic pipes and fittings present environmental concerns, particularly resulting from the requirement that hazardous adhesive compounds must typically be used to bond pipes and fittings together in a sealed manner. Governmental and other regulations are becoming increasingly strict in imposing limitations and controls over the formulation of plastic pipe and fitting compounds and the use of plastic pipe bonding adhesives. 
     Accordingly, while adhesive bonding of plastic pipe and fittings remains the currently most reliable means of sealed joinder between these components in the present state of the art, there is a growing recognized need and desire within the relevant industry for alternative devices and methods of sealing plastic pipes and fittings together, without the use of environmentally hazardous chemicals. 
     SUMMARY OF THE INVENTION 
     Briefly summarized, the present invention seeks to address the foregoing need in the industry by providing a novel tubular polymeric pipe fitting assembly which is adapted for sealed joinder with a tubular polymeric pipe section without the use of adhesives or other bonding chemicals. According to one aspect of the invention, the present pipe fitting assembly comprises a polymeric fitting and an elastomeric gasket assembled as a unit, preferably by integrally molding these elements together. 
     In the present pipe fitting assembly, the fitting basically has a tubular main body portion and an annular pipe-receiving socket portion at one end of the main body portion collectively defining interiorly therethrough a passageway. The elastomeric gasket has a first tubular axial portion in intimate sealed annular surface engagement with an interior annular wall surface of the socket portion and a second tubular axial portion integral with the first axial portion and projecting axially outwardly from the socket portion. The first and second axial portions of the gasket collectively form a continuous interior annular wall surface adapted for receiving a tubular polymeric pipe section in peripheral annular surface contact with an exterior annular surface of the pipe section. The second axial portion of the gasket is adapted to be exteriorly encircled by a clamping device for exerting a mechanical force for sealing the second axial portion of the gasket against the exterior annular surface of the pipe section. 
     Thus, a further aspect of the present invention is the provision of a sealed tubular polymeric pipe apparatus comprising the polymeric fitting and elastomeric gasket assembly, with a tubular polymeric pipe section received interiorly within the gasket with the interior annular wall surface of the gasket in peripheral annular surface contact with an exterior annular surface of the pipe section and with the clamping device exteriorly encircling the second axial portion of the gasket for exerting a mechanical force sealing the second axial portion of the gasket against the exterior annular surface of the pipe section. 
     According to one preferred feature of the invention, the first axial portion of the gasket is molded in intimate sealed annular surface engagement with the interior annular wall surface of the socket portion. It is further preferred that a mechanical interconnection is also provided between the first axial portion of the gasket and the socket portion of the fitting. For example, one form of the mechanical interconnection may comprise a surface depression formed into the interior annular wall surface of the socket portion into which the first axial portion of the gasket is molded. In a more specific such example, the surface depression may comprise a radial opening formed into the interior annular wall surface of the socket portion and a stub portion protruding from the first axial portion of the gasket into the radial opening. 
     Various forms of clamping devices may be utilized in the present invention. For example, one type of clamp that may be advantageously used in the present invention is a band-type clamp, such as commonly equipped with a worm gear-actuated means for tightening and loosening the clamp. An alternative form of clamping device may comprise an annular collar attachable to the socket portion of the fitting in compressive engagement annularly with the second axial portion of the gasket. For example, the socket portion of the fitting may have a spiral thread formed in an exterior annular wall surface of the socket portion and the annular collar may have a mating spiral thread for rotational threaded engagement between the socket portion of the fitting and the collar. In such a clamping device, the collar and the second axial portion of the gasket may be compatibly configured for axial and radial compression of the second axial portion of the gasket by the collar, e.g., via mating tapered surfaces disposed for engagement with one another. 
     The fitting may be formed of various polymeric materials, e.g., polypropylenes, polyethylenes, acrylonitrile-butadiene-styrenes, other styrenes, and chlorinated polyvinyl chlorides, and other polyvinyl chlorides. A random copolymer of an impact grade of polypropylene is presently contemplated to be preferred. Also, it is contemplated that the fitting may be made of a multi-layer construction, e.g. with outer and inner layers of a solid polymeric material between which is contained a polymeric foam layer, which could achieve weight reduction and attendant reduction in cost. Various filler materials, e.g., calcium carbonate, magnesium hydroxide, ammonium octamolybdate, alumina trihydrate, and barium sulfate, could be included as additives to the polymeric material for the fitting to impart enhanced properties such as flame resistance, flame retardancy, smoke suppression, added density, sound deadening, impact resistance, added stiffness, and/or other properties. Likewise, the gasket may be formed of various elastomers, e.g., thermoplastic vulcanizates, flexible polyvinyl chlorides, thermoplastic olefins, thermoplastic elastomers, synthetic rubbers, and natural rubbers. In one contemplated embodiment, the gasket may be formed of a first elastomer for promoting adhesion between the first axial portion of the gasket and the interior annular wall surface of the socket portion and a second elastomer for promoting sealing contact between the gasket and the exterior annular surface of the pipe section. 
     In one possible embodiment of the invention, the fitting may include a socket configured as an enlarged bell-shaped hub-like tubular socket, wherein the passageway through the tubular main body portion of the fitting is of a nominal internal cross-sectional dimension while the passageway through the annular socket portion is of an internal cross-sectional dimension greater than the nominal internal cross-sectional dimension of the passageway. In other embodiments, the fitting may include a main body and a socket formed in cylindrical coaxial alignment with one another, i.e., without an enlargement of the socket relative to the main body. 
     According to another feature of the present invention, the fitting may further include a retaining element projecting interiorly within the fitting radially inwardly into the passageway to engage the outer circumferential surface of the inserted end of a straight pipe section, thereby providing a supplementary means of mechanical engagement with the pipe section assisting the clamping device. 
     These and other aspects, features and advantages of the present invention will become more apparent from the following disclosure and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of a pipe apparatus in accordance with one contemplated embodiment of the present invention; 
         FIG. 2  is a rear perspective view of the pipe apparatus of  FIG. 1 ; 
         FIG. 3  is a lengthwise cross-sectional view of the pipe apparatus of  FIG. 1 , taken along the line  3 - 3  thereof; 
         FIG. 4  is an enlargement in cross-section of the area  4  of the pipe apparatus of  FIG. 3 ; 
         FIG. 5  in another enlarged cross-section, similar to  FIG. 4 , showing an alternative embodiment of the pipe apparatus; 
         FIG. 6  is a side elevational view of a pipe apparatus in accordance with another contemplated embodiment of the present invention; and 
         FIG. 7  is a lengthwise cross-sectional view of the pipe apparatus of  FIG. 6 , taken along line  6 - 6  thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the accompanying drawings and initially to  FIGS. 1 and 2 , a tubular pipe apparatus according to one embodiment of the present invention is indicated generally at  10  and basically comprises a tubular fitting assembly  12  joining and forming a sealed connection with two tubular straight pipe sections  14 ,  16  via clamping devices  18  retaining the elements of the pipe apparatus  10  securely together. The pipe apparatus  10  of the present invention is characterized by the absence of any required adhesive, chemical, or other potentially hazardous bonding agent or composition for sealing the fitting assembly  12  and the pipe sections  14 ,  16  to one another. 
     The pipe apparatus  10  and fitting assembly  12  of the present invention are particularly adapted and intended for use in joining pipe sections made of polymeric materials, commonly referred to in the trade collectively and generically as plastic pipe. Such plastic pipes are well-known and in common use. The pipe sections  14 ,  16  shown in the accompanying drawings and as described herein may be of any such known construction and/or configuration. Thus, as illustrated in the drawings and as described herein, the pipe sections  14 ,  16  are depicted merely as common representative cylindrical straight pipe sections, each of a uniform annular wall thickness defined between inner and outer cylindrical wall surfaces, and defining through the length of each pipe section an open passageway. However, those persons skilled in the art will also recognize that the pipe apparatus  10  and fitting assembly  12  of the present invention are equally well adapted for use with other plastic pipes, e.g., of a novel or specialized polymeric composition or physical structure or construction, whether currently known or yet to be developed. Accordingly, the present invention is not intended and should not be construed to exclude the use and application of the present invention in other embodiments with other plastic pipes. 
     With additional reference to  FIGS. 3 and 4 , the fitting assembly  12  basically comprises a tubular fitting  20  equipped at its opposite ends with integral gaskets  22 . The fitting  20  in this representative embodiment is of an elbow-type pipe fitting construction having a tubular main body  24  extending in an elongated arc of substantially ninety degrees (90°) with enlarged bell-shaped hub-like tubular sockets  26  integrally formed with the main body  24  at its opposite ends. The tubular main body  24  is formed by a continuous annular wall  28  of an essentially uniform wall thickness between inner and outer annular wall surfaces  28 A,  28 B, and preferably is of a substantially circular cross-section defining an open interior passageway  30  of an essentially uniform nominal cross-sectional dimension diametrically transverse to the interior surface  28 A through the length of the main body  24 . Each socket  26  has an annular stub wall  32  also of an essentially uniform wall thickness between inner and outer annular stub wall surfaces  32 A,  32 B, and preferably is similarly of a substantially circular transverse diametric cross-section but of a larger cross-sectional diametric dimension than the nominal cross-section of the main body  24 . The stub wall  32  of each socket  26  is joined coaxially to one respective end of the annular wall  28  via an angled annular connecting bridge wall section  34 , thereby forming an undercut shoulder  36  interiorly of the fitting  20  surrounding and radially outward of the adjacent end of the annular interior wall surface  28 A. 
     Each gasket  22  is in the form of a generally cylindrical annular sleeve preferably made of a compressibly resilient elastomeric material. More specifically, each gasket  22  is of an axial length greater than that of the interior wall surface  32 A of the respective stub wall  32 . Each gasket  22  has a cylindrical interior wall surface  38  of a circular cross-sectional diametric dimension substantially uniform along the full length of the gasket  22 , matched to or slightly smaller than the outer cross-sectional dimension of the respectively associated straight pipe section  14  or  16 . The cylindrical exterior wall surface  40  of each gasket  22  comprises a first axial portion  42  whose axial extent essentially corresponds to the axial length of the associated interior stub wall surface  32 A and whose outer cross-sectional diametric dimension matches that of the inner cross-sectional diametric dimension of such associated interior stub wall surface  32 A. The cylindrical exterior wall surface  40  of each gasket  22  further comprises a second axial portion  44  of an axial extent projecting axially outwardly beyond the terminal axial end edge of the associated stub wall  32  and having an outer cross-sectional diametric dimension greater than that of the first axial portion  42  forming a radial shoulder  46  therebetween. Each gasket  22  is integrally secured sealably within the stub wall  32  of the associated socket  26 , with the first axial gasket portion  42  in sealed intimate continuous annular surface engagement with the interior stub wall surface  32 A along and about the full axial and circumferential extent thereof and with the radial shoulder  46  therebetween abutted against the axial end face of the stub wall  32 . 
     In accordance with the present invention, the fitting  20  in any given embodiment will typically be made of a polymeric material compatible with, and often corresponding to, the polymeric material of the plastic pipes with which the fitting  20  is intended to be used. Those persons skilled in the art will recognize and understand that an extensive and diverse range of polymeric compositions and formulations are available from which the fitting  20  may be fabricated. The selection of the polymeric material will, in many if not most cases, be determined in relation to the intended end use of the pipe apparatus, e.g., according to whether the pipe apparatus may be intended for a plumbing application handling water or water-borne liquids, chemical materials, gases or other fluids, whether the pipe apparatus may be intended for underground or aboveground installations, etc. It is contemplated that the present invention may be applicable to any such embodiments and uses and it is not intended nor to be construed that the present invention is limited to fittings made of any particular polymeric material. For sake of representative illustration, but without limitation, it is contemplated that the fittings of the present invention may be made of polypropylenes, polyethylenes, acrylonitrile-butadiene-styrenes (commonly known as ABS), other styrenes, chlorinate polyvinyl chlorides, and/or other polyvinyl chlorides. A random copolymer of an impact grade of polypropylene is presently contemplated to be preferred. Also, it is contemplated that the fitting may be made of a multi-layer construction, e.g. with outer and inner layers of a solid polymeric material between which is contained a polymeric foam layer, which could achieve weight reduction and enhanced impact resistance and stiffness. Various filler materials, e.g., calcium carbonate, magnesium hydroxide, ammonium octamolybdate, alumina trihydrate, and barium sulfate, could be included as additives to the polymeric material for the fitting to impart enhanced properties such as flame resistance, flame retardancy, smoke suppression, added density, sound deadening, impact resistance, added stiffness, and/or other properties. Preferably, the fitting  20  of the present invention will be produced by an injection molding or another form of molding process and, accordingly, polymeric materials for the present fitting will typically be selected to be suitable for use in such molding operations. 
     As noted above, the gaskets  22  are made preferably of an elastomeric material providing resilient compressibility for conformance and sealing to the surfaces of the stub walls  32  of the fitting  20  and to the peripheral surfaces of the straight pipe sections  14 ,  16 . In embodiments wherein the fitting  20  will be injection molded, it is contemplated to be preferable that the elastomeric material for the gaskets  22  also be selected from appropriate materials suitable for injection molding. In this manner, the fitting  20  and the gaskets  22  could be fabricated in a common molding apparatus via a multi-step molding process known and commonly referred to in the injection molding art as a multi-shot injection process. Persons skilled in the art will recognize and understand that differing mold inserts or other mold elements of differing configurations would typically be required for the separate steps of first molding the fitting  20  and then molding the gaskets  22  into the fitting  20 , but the design of such mold elements is within the ordinary skill of persons knowledgeable and experienced in the injection molding art and therefore need not be described in detail herein. Advantageously, such a multi-shot injection process is effective to form the gaskets  22  in intimate continuous sealed surface engagement with the interior wall surfaces  32 A of the stub walls  32  of the sockets  26  to provide optimal securement and sealing therebetween. Alternative, it is contemplated and is to be understood that the gasket  22  may be joined sealably to the fitting  20  by other means, e.g., gas plate welding, hot plate joining, adhesive bonding, ultrasonic joining, or laser welding, whereby the present invention is not limited to any particular manner of joinder between the fitting and the gaskets. For sake of representative illustration, but without limitation, it is contemplated that the gaskets used in the present fitting assembly could be made from thermoplastic vulcanizates, flexible polyvinyl chlorides, thermoplastic olefins, thermoplastic elastomers, synthetic rubbers, and/or natural rubbers. These and similar elastomeric materials are known to be suitable for injection molding. 
     It is preferred that the molded surface interconnection of the gaskets  22  within the fitting  20  be supplemented by a mechanical interconnection between the first axial portion  42  of each gasket  22  and the socket portions  26  of the fitting  20 . For example, the interior wall surface  32 A of each stub wall  32  may be formed with one or more depressions, such as teeth, ridges, ribs, threads, perforations, holes or any other manner of surfacing configuration or texture to the wall surface  32 A forming one or more depressions therein into which the polymeric material of the first axial portion  42  of the gasket  22  will flow during molding. In one advantageous embodiment, a radial opening  45  may be formed through the stub wall  32  of the socket  26  thereby to serve as an injection point through which the molding material for the gasket  22  may be introduced into the fitting  20  after it has first been molded. The gasket material, when cured, thereby forms a stub portion  23  protruding from the first axial portion  42  of the gasket  22  into the radial opening  45 , to provide the desired mechanical connection of the gasket  22  to the fitting  20 . 
     It is also contemplated that the injection of the gasket material can be carried out in two steps via a multi-shot molding process using two different polymeric materials, a first elastomer injected in a first molding “shot” forming a radially outwardmost gasket layer in direct surface contact with the interior wall surface  32 A of the stub wall  32  and a second elastomer injected in a second molding “shot” forming a radially inwardmost gasket layer. The first elastomer would be selected to be of a composition optimally suitable for promoting bonding adhesion between the first axial portion  42  of the gasket  22  and the stub wall surface  32 A of the stub wall  32  of each socket  26 . The second elastomer would in turn be selected to be of a composition optimally suitable for promoting sealing contact between the interior wall surface  38  of the gasket  22  and the exterior annular surface of the pipe section  14  or  16 . The interior wall surface  38  of the gasket  22  may be formed with one or more annular ribs, teeth, ridges or other protrusions to provide enhanced frictional engagement against a pipe section inserted into the gasket (as described below) and for added resistance against withdrawal of the pipe section from the gasket. 
     The clamping devices  18  in the illustrated embodiment of  FIGS. 1-4  are common band-type clamps having an elongate toothed metal band with a screw-actuated worm gear device secured to one end which also receives the other end of the band, thereby to form the band into a ring-like annular configuration and to enable the band to be tightened into a progressively decreasing circumference by the screw actuation of the worm gear device. Such clamping devices  18  offer the advantage of ready availability, inexpensive cost and reliable operation. However, the present invention is not limited to the use of such band clamps. Rather, it is contemplated that any other form of annular clamping device could be equally well employed in the present invention, as for example is represented in the embodiment of  FIGS. 6 and 7  described hereinafter. 
     As best seen in  FIGS. 3 and 4 , each plastic pipe section  14 ,  16  has one end inserted fully into a respective one of the sockets  26  of the fitting  20  until the inserted end of the pipe abuts the interior undercut shoulder  36  within the respective socket  26 . The interior wall surface  38  of each gasket  22  fully encircles the respective pipe section  14 ,  16 , in substantially continuous annular sealing surface engagement with the outer circumferential wall surface of the pipe. The clamping devices  18  encircle the outwardly projecting second axial portion  44  of each gasket  22  and are tightened into continuous circumferential clamping engagement thereabout, exerting a mechanical force against the axial portion  44  and, in turn, against the outer wall surface of the pipe. In this manner, the clamping devices  18  supplement and secure the sealing contact between each gasket  22  and the respective pipe sections  14 ,  16  and also serve to retain each pipe section  14 ,  16  against withdrawal from the respective sockets  26 . 
     An alternative embodiment of the present pipe apparatus is indicated generally at  110  in  FIG. 5 , wherein elements of the pipe apparatus corresponding to the elements of the apparatus of  FIGS. 1-4  are identified by corresponding reference numerals in the  100  series. The pipe apparatus  110  basically comprises a tubular fitting assembly  112  which is substantially similar in structure and application as the fitting assembly  12  of  FIGS. 1-4 , except that the fitting assembly  112  additionally includes an annular retaining element  48  interiorly within the stub wall  132  between the undercut shoulder  136  and the gasket  122 . The retaining element  48  may be fabricated of a metallic material, and is preferably molded into disposition by insertion into the polymeric material of the fitting element  120  during or immediately after the molding thereof, and prior to the secondary molding of the gasket  122 . The retaining element  48  may include a circumferentially outward flange  48 A to embed within and be secured by the polymeric material of the fitting element  120 , and a circumferentially inward flange  48 B to project radially inwardly beyond the interior wall surface  132 A of the stub wall  132  into the passageway  130  in the direction toward the main body  124 . In this molded disposition, the inward flange  48 B encircles the passageway  130  to engage the outer circumferential surface of the inserted end of a straight pipe section  114 . Any force exerted against the straight pipe section tending to withdraw the pipe section out of the sockets  126  is resisted by the impingement of the retaining element  48  into the pipe, thereby providing a supplementary means of mechanical engagement with the pipe section assisting the clamping device  118 . 
       FIGS. 6 and 7  depict a further embodiment of the present pipe apparatus, indicated overall at  210 , wherein elements of the pipe apparatus corresponding to the elements of the apparatus of  FIGS. 1-4  are identified by corresponding reference numerals in the  200  series. The pipe apparatus  210  utilizes a clamping device  218  in the form of an annular collar, indicated at  250 , instead of the band-type clamps  18  of the embodiments of  FIGS. 1-4  and  5 . In this embodiment, the fitting assembly  212  utilizes a fitting  220  having a main body  224  and a socket  226  formed essentially in cylindrical co-axial alignment with one another, i.e., without any bell-shaped enlargement of the socket relative to the main body. The main body  224  and the socket  226  are separated interiorly by a radially inwardly projecting flange-like shoulder  236 . The socket portion  226  is formed at its axially outwardmost end with a recessed annular interior wall surface  232 A. The fitting assembly  212  includes an annular gasket  222  having a first axial portion  242  molded in intimate sealed annular surface engagement with the recessed wall surface  232 A and a second axial portion  244  projecting outwardly beyond the annular end edge of the socket portion  226 . The first and second axial portions  242 ,  244  of the gasket  222  form a continuous cylindrical interior gasket wall surface  238 , while the outer annular surface of the second axial portion  244  is enlarged relative to the first axial portion  242  and tapers narrowingly inwardly in the direction away from the socket  226 . The exterior annular surface of the socket portion  226  is formed adjacent its axial end edge with a spiral screw thread  252 . The collar  250  is correspondingly formed interiorly at one axial end with a correspondingly spiral screw thread  254  and the interior wall surface of the collar  250  tapers axially therefrom toward the opposite axial end of the collar  250  correspondingly to the tapering of the second axial portion  244  of the gasket  222 . 
     In use, as depicted in  FIGS. 6 and 7 , a straight plastic pipe section, e.g., pipe section  214 , has one end inserted fully into the socket  226  into abutment with the shoulder  236 , with the annular interior wall surface  238  of the gasket  222  fully encircling the pipe section in continuous annular sealing surface engagement with the outer circumferential wall surface of the pipe. The collar  250  is placed around the outer exterior of the pipe section with the axial end having the spiral thread  252  facing the socket  226 , and is then rotated to threadedly engage the corresponding thread  254  of the collar  250 . Continued rotation of the collar  250  tightens the engagement of the threads  252 ,  254  and, in turn, results in progressive engagement of the tapered interior of the collar  250  against the tapered exterior of the second axial gasket portion  244  to axially and radially compress the gasket portion  244  against the exterior annular surface of the pipe. Thus, as in the embodiments of the  FIGS. 1-4  and  5 , the collar  250  serves as a clamping device which supplements and secures the sealing contact between the gasket  222  and the pipe section  214  to resist withdrawal of the pipe section from the socket portion  226  of the fitting element  220 . 
     It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.