Patent Publication Number: US-2006001259-A1

Title: Mechanical and coil fusion combination seal

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of U.S. Provisional Patent Application No. 60/571,826, filed May 17, 2004, entitled “Mechanical and Coil Fusion Combination Seal”, the disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to coupling of plastic pipes and, more particularly, to coupling of plastic pipes by a fusion seal and/or a mechanical seal.  
      2. Description of Related Art  
      Prior to the advent of plastic pipe, most piping was made out of metal, such as copper, stainless steel, or iron. The particular metal used for the piping was dependent upon the application. For example, water could be transported through copper and/or cast-iron pipes. However, acids had to be transported in stainless steel pipe. Some of the metal pipe, such as copper and stainless steel, was expensive to manufacture and install. Typically, the pipe was either brazed or welded together. In some instances, mechanical type joints were provided for pipe connections. In today&#39;s market, all of these arrangements are expensive to manufacture and install.  
      Plastic pipe overcomes many of the expenses associated with metal pipe. Plastic pipe is inexpensive to manufacture and relatively easy and inexpensive to connect together. In the case of thermoplastic materials, such as polypropylene, the pipe can be welded together by providing a polypropylene sleeve with electrical heating elements embedded therein. This process is known as fusion welding. Fusion welded pipe is particularly applicable in situations where acid passes through the plastic pipe. Polypropylene pipes can be secured to each other through mechanical seals. In some applications, mechanical seals are preferable to the fusion welding.  
      In the past, different pipes and/or pipe couplings were provided for fusion sealing and mechanical sealing, such as those disclosed in U.S. Pat. Nos. 6,250,686 and 6,450,544, both to Becker et al., which are hereby incorporated by reference. This resulted in an increase in inventory required by the installer, such as the mechanical contractor or plumber, since different pipes were required to be used in different applications.  
      Accordingly, a need exists for a seal incorporating both a mechanical seal and a fusion seal that is able to provide a permanent fusion seal as well as provide an initial mechanical seal before the fusion process has been completed.  
     SUMMARY OF THE INVENTION  
      The present invention is drawn to a combination mechanical and fusion seal for use with a pipe. The combination mechanical and fusion seal includes a thermoplastic sleeve, wherein the thermoplastic sleeve includes a first portion constructed of a first material and a second portion constructed of a second material, wherein the first material has a lesser density and/or durometer than the density and/or durometer of the second material. The seal also includes an electrical resistive wire embedded within the second material and at least one exposed lead attached to the resistive wire. Desirably, the first material is polyethylene and the second material is polypropylene and the electrical resistive wire is constructed of one of a nickel-chrome wire and a normal heating wire with nickel plate.  
      The first portion of the thermoplastic sleeve can include a first outer surface portion tapering outwardly with a frustum conical shape and a second outer surface portion that is cylindrically shaped and flat. The second portion of the thermoplastic sleeve can include a smooth and cylindrically shaped outer portion. Furthermore, the first portion of the thermoplastic sleeve also has an inner and outer diameter that is greater than the inner and outer diameter of the second portion of the thermoplastic sleeve.  
      Additionally, the present invention is drawn to piping system utilizing the aforementioned combination mechanical and fusion seal. The piping system includes a first pipe having a first end, a second end, an outer surface, and an inner surface, wherein the inner surface defines a passageway and a receiving profile at the first end, and further wherein a combination mechanical and fusion seal is secured within the receiving profile; and a second pipe having a first end and a second end, wherein the first end of the second pipe is received by the seal of the first pipe. Desirably, the first and second pipes are constructed of a thermoplastic material, such as polypropylene.  
      The outer surface of the first end of the first pipe can include a threaded portion defined thereon. The piping system can also include a nut threaded upon the threaded portion of the first pipe for securing the first end of the second pipe within the receiving profile of the first pipe. The second end of the first pipe can also be adapted to receive a third pipe and the second end of the second pipe can be adapted to receive a fourth pipe.  
      Finally, a method of joining two thermoplastic pieces of pipe is also disclosed. The method includes the steps of: providing a first pipe having a first end, a second end, an outer surface, and an inner surface, wherein the inner surface defines a passageway and a receiving profile at the first end, and further wherein a combination mechanical and fusion seal is secured within the receiving profile; providing a second pipe having a first end and a second end; and inserting the first end of the second pipe into the sleeve of the first pipe. The outer surface of the first end of the first pipe can include a threaded portion defined thereon and the method can further include the step of threading a nut upon the threaded portion of the first pipe. The nut provides a compressive force on the first end of the first pipe to secure the first end of the second pipe within the receiving profile of the first pipe. The method can further include the step of transmitting an electrical charge to the seal through the at least one exposed lead. The electrical charge melts the seal, melts a portion of the first end of the first pipe, and melts a portion of the first end of the second pipe to form a fluid-tight seal therebetween.  
      By providing a seal incorporating both a mechanical seal and a fusion seal, pipes within the piping system may be temporarily or permanently connected efficiently, without requiring application specific inventory or hardware.  
      Further details and advantages of the present invention will become apparent upon reading the following detailed description in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an elevational view of a combination mechanical and fusion seal, partially in section, with a partial exploded view thereof, in accordance with the present invention;  
       FIG. 2  is an elevational view, partially in section, of a first pipe incorporating the combination mechanical and fusion seal of  FIG. 1 , in accordance with the present invention;  
       FIG. 3  is an elevational view, partially in section, of a second pipe used in conjunction with the first pipe of  FIG. 2 ;  
       FIG. 4  is an elevational view of a nut for threading onto the first pipe of  FIG. 2 ;  
       FIG. 5  is an elevational view, partially in section, of the first pipe securing the second pipe therein by utilizing the mechanical seal of the combination mechanical and fusion seal with the nut;  
       FIG. 6  is an elevational view, partially in section, of two combination mechanical and fusion seals configured to serve as a coupling; and  
       FIG. 7  is an elevational view, partially in section, of the first pipe securing the second pipe therein by utilizing the fusion seal of the combination mechanical and fusion seal. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The present invention will be described with reference to the accompanying figures, wherein like reference numbers correspond to like elements throughout.  
      With reference to  FIG. 1 , a combination mechanical and fusion seal  10  is a unitary seal that includes a circumferential-looped electrical resistive wire  12  embedded within a cylindrical thermoplastic sleeve  14 . Desirably, the electrical resistive wire  12  or heating element is constructed of nickel-chrome or a normal heating wire with nickel plate. Desirably, the electrical resistive wire  12  is made of eighteen (18) gauge wire and has a resistance measured in ohms per inch. The resistance of the electrical resistive wire  12  varies depending on the application. Optionally, exposed electrical resistive wire leads  16   a  and  16   b  may be attached to respective exposed portions of the electrical resistive wire  12 . The thermoplastic sleeve  14  includes a uniform body that is constructed of at least two materials.  
      Specifically, the two materials form a first portion  18  attached to a second portion  20  of the thermoplastic sleeve  14  at respective ends A and B, as shown in the exploded view of  FIG. 1 . Desirably, ends A and B are fused to each other. Generally, the first thermoplastic material has a lesser density and/or durometer than the density and/or durometer of the second material. The first thermoplastic material may have a durometer range of 50 to 89 A ASTM-D2240 and a density range of 0.919 g/cc (±15%), whereas the second thermoplastic material may have a durometer range of 70-80 R Rockwell Hardness ASTM-D785 and a density range of 0.902 g/cc (±15%). For example, although both the first material and the second material are thermoplastic materials, desirably, the first material is a soft flexible material similar to low-density polyethylene material such as Mobilbrand LQA-006 low-density polyethylene manufactured by Mobil Polymers, 2195 Lincoln Highway, Edison, N.J. 08818 or the like, whereas the second material is ProFax 8723 polypropylene manufactured by Basell North America Inc., 912 Appleton Road, Elkton, Md. 21921.  
      In addition to being constructed of a flexible material, the inside of the first portion  18  of the thermoplastic sleeve  14 , as shown in greater detail in the exploded view of  FIG. 1 , is shaped so as to provide a compression fit for any pipe that may be inserted therein. Hence, the first portion  18  of the thermoplastic sleeve  14  may be considered the mechanical seal portion of the combination mechanical and fusion seal  10 . The second portion  20  of the thermoplastic sleeve  14  includes the electrical resistive wire  12  embedded in the first portion  18  and the second portion  20  and may therefore be considered the fusion seal portion of the combination mechanical and fusion seal  10 . As can be seen in  FIG. 1 , an outer surface C and inner surface D of second portion  20  are smooth and cylindrically shaped. An outer surface portion E of the first portion  18  tapers outwardly and is frustum conical shaped, and an outer surface portion F of the first portion  18  is cylindrically shaped and flat, an inner surface G of the first surface includes a plurality of sections and varies in diameter. A diameter d 1  of the first portion  18  is greater than an inner diameter d 1 ′ of the second portion  20  and an outer diameter d 2  of the first portion  18  is greater than a second diameter d 2 ′ of the second portion  20 .  
      With reference to  FIG. 2 , and with continuing reference to  FIG. 1 , a first pipe  22  incorporating the combination mechanical and fusion seal  10  includes a body  24  that is desirably constructed of a thermoplastic material, such as polypropylene. Body  24  includes a first end  26 , a second end  28 , an outer surface  30 , and an inner surface  32 . A passageway  34  is defined by inner surface  32  of body  24 . Generally speaking, body  24  is substantially cylindrical in shape, although body  24  may assume other shapes that may be conducive to either flow of material within body  24  or other application specific purposes. Therefore, passageway  34  may also be substantially cylindrical in shape. However, it is to be understood that passageway  34  defined within body  24  may assume other forms including, but not limited to, square, rectangular, or triangular, even if the external shape of body  24  is different. Passageway  34  extends from the first end  26  to the second end  28  of body  24 . The inner surface  32  of body  24  defines a receiving profile  36  at the first end  26  of body  24 . The receiving profile  36  is sized to accommodate an end of another pipe or some other connection end, such as an inlet/outlet. Desirably, the receiving profile  36  is of unitary construction with body  24 , although, as shown in  FIG. 1 , the first end  26  may have a greater circumference than any other circumferential portion of body  24  due to the location of the receiving profile  36 . It is to be understood that the outer surface  30  and the inner surface  32  of body  24  may encompass the respective outer and inner surfaces of the receiving profile  36 . A threaded portion  38  may be defined on the outer surface  30  around the first end  26  of the body  24 . Desirably, threaded portion  38  is situated along the outer surface  30  of the receiving profile  36 . Threaded portion  38  includes one or more molded threads  40  that are preferably unitary with body  24 . Alternatively, threaded portion  38  may be a separate threaded piece (not shown) that is affixed around the first end  26 . Although it is preferred that the threads  40  are situated around the entire circumference of the first end  26 , it is to be understood that the threads  40  may be situated only partially around the circumference. Furthermore, threaded portion  38  and/or the threads  40  may be substituted with a clamping or tension locking mechanism that performs a function equivalent to that of the threads  40 .  
      As shown in  FIG. 2 , the combination mechanical and fusion seal  10  is seated within first pipe  22  and, more specifically, within the interior of the receiving profile  36  of first pipe  22 . Desirably, the inner diameter of thermoplastic sleeve  14  is slightly larger than the inner diameter of the receiving profile  36  so that a friction and pressed fit is formed when the combination mechanical and fusion seal  10  is secured within the receiving profile  36 .  
      It is to be understood that the second end  28  of body  24  of the combination mechanical and fusion seal  10  may be of the same diameter as body  24 , excluding the increase of the diameter due to the receiving profile  36 . This allows the second end  28  to be inserted into another receiving profile of another pipe, similar in construction to the receiving profile  36  of the first end  26 .  
      With reference to  FIGS. 3-5 , and with continuing reference to  FIGS. 1 and 2 , a piping system  42  may be formed by using the combination mechanical and fusion seal  10  in the first pipe  22  in conjunction with at least one other pipe, such as a connecting pipe  44 . Specifically, as depicted in  FIG. 3 , the connecting pipe  44  includes an outer surface  46 , a passageway  48 , and an end  50  for insertion into the first pipe  22 . The connecting pipe  44  may be of any dimension as long as the end  50  is adapted to be received by the combination mechanical and fusion seal  10  of the receiving profile  36  of the first pipe  22 . Desirably, the outside diameter of the end  50  is sized so as to create a friction fit between connecting pipe  44  and the combination mechanical and fusion seal  10 . Thus, the first portion  18  of the combination mechanical and fusion seal  10  is utilized to create a mechanical seal between the first pipe  22  and the connecting pipe  44 . The mechanical seal provides leak resistance and the ability to quickly and easily loosen a connection between pipes  22  and  44 . Thus, the piping system  42  may then be utilized in any application where a mechanical seal is sufficient, such as a test run of water or flow of a non-hazardous substance. The mechanical seal may be undone by simply moving the connecting pipe  44  away from the first pipe  22 . The mechanical seal may be strengthened by utilizing a nut  52 , as shown in  FIG. 5 . The nut  52  is threaded so that the nut  52  may threadably engage the threaded portion  38  of the body  24  of the first pipe  22 . The nut  52  may be constructed of the same material as the body  24 . Axially extending ribs  54  are positioned about an outer surface of the nut  52 . It is to be understood that if the resistive wire leads  16   a  and  16   b  are bent in an outward-angled position, they may be easily bent toward each other (as shown in phantom) to create sufficient clearance for the nut  52  to pass over the resistive wire leads  16   a  and  16   b  in order to threadingly engage the body  24 . Typically, as the nut  52  is tighter, it contracts end H of the first portion  18  of the combination mechanical and fusion seal  10  forcing the surface G against the outer surface of pipe  44 , and forcing at least portions of surfaces E and F against the inner surface of pipe  22 , thereby forcing a liquid tight seal. Thereafter, the resistive wire leads  16   a  and  16   b  may be bent back to their original outward-angled position.  
      With reference to  FIG. 6 , and with continuing reference to  FIGS. 1-5 , the combination mechanical and fusion seal may be used as part of a pipe coupling system. When used in a coupling system, the second end  28  of body  24  is of similar construction to the first end  26  of body  24 . Specifically, the second end  28  may also include none, one, or all of the following: another receiving profile, another threaded portion, and another combination mechanical and fusion seal  10 ′. By utilizing all three of these elements, a coupling is formed that is adapted to join two pipes having a congruous diameter. U.S. Pat. No. 6,450,544 to Becker et al., which is hereby incorporated herein by reference, discloses the use of a coupling to couple a thermoplastic pipe having a fusion seal on its outer surface to another pipe. Thus, the present invention may also be utilized to perform such a coupling function.  
      With reference to  FIG. 7  and with continuing references to  FIGS. 1-5 , the method of fusion sealing the connecting pipe  44  to the first pipe  22  will now be described. Initially, the end  50  of connecting pipe  44  is inserted into the receiving profile  36  of the first pipe  22 . Thus, the passageway  48  of the connecting pipe  44  is in fluid communication with the passageway  34  of the first pipe  22 . Forming the fusion seal, as shown in  FIG. 6 , involves passing an electric current having a voltage of typically 120 volt AC, through the electrical resistive wire  12  via the resistive wire leads  16   a  and  16   b . The electric current causes the electrical resistive wire  12  to heat, thereby causing the thermoplastic sleeve  14  and adjacent portions of the outer surface  46  of the connecting pipe  44  and the inner surface  32  of the receiving profile  36  to melt. A clamp, such as a hose clamp (not shown), may be used to squeeze the pipes  22  and  44  adjacent the second portion  20 , as indicated at arrow I. Alternatively, the nut  52  may be used for this purpose. After a period of time, the electric current is stopped from passing through the electrical resistive wire  12 . The first pipe  22  and the connecting pipe  44  are permitted to cool and harden, thereby forming a fluid-tight seal therebetween. The exposed resistive wire leads  16   a  and  16   b  and the respective exposed portions of the electrical resistive wire  12  may then be cut and removed from the thermoplastic sleeve  14 . Alternatively, the exposed resistive wire leads  16   a  and  16   b  may be left alone for future heating and melting of the thermoplastic sleeve  14 , should a leak develop or any of the pipes  22  and  44  have a need to be replaced. Once a fusion connection is established, additional leak resistance is introduced to the piping system  42  as well as a more permanent bond between pipes  22  and  44 . Thus, an exemplary use of the piping system  42  when using the fusion seal may be in a polypropylene chemical drainage system.  
      It is to be understood that the pipes  22  and  44  may be both mechanically sealed and fusion sealed. For example, during the initial installation of the piping system  42 , the pipes  22  and  44  may be mechanically sealed to secure the pipes while laying out or arranging the piping system  42 . Thereafter, when the arrangement of pipes  22  and  44  has been finalized, the pipes  22  and  44  may be fusion sealed. The nut  52  may remain on the first pipe  22  even after the first pipe  22  and the connecting pipe  44  have been fusion sealed. It is also to be understood that, although thermoplastic is the preferable material for the components making up the invention, it is contemplated that other plastic materials or copolymers can be used.  
      The present invention has been described with reference to the preferred embodiments. Obvious modifications, combinations, and alterations will occur to others upon reading the preceding detailed description. It is intended that the invention be construed as including all such modifications, combinations, and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.