Abstract:
A system is provided for the sealing of a thermoplastic weld, the system comprising: a first and second thermoplastic components; a channel disposed in opposing faces of the first and second thermoplastic components; a sealing member disposed within the channel sealing a joint between the opposing faces; and at least one thermoplastic weld joining the opposing faces proximate to the sealing member.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/512019, filed Jul. 27, 2011. This application is herein incorporated by reference in its entirety for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to thermoplastic welds, and more particularly, to a storage tank sealed with an interstitial seal between surfaces of thermoplastic members joined by welds. 
       BACKGROUND OF THE INVENTION 
       [0003]    Known tank fabrication relies on various plastic welding techniques including the provision of heated weld rods on interior and exterior surfaces of a welded joint, effectively sealing the joint, but leaving a void between the two seals. If the interior weld is compromised fluid within the tank may travel in the void until it finds an outlet in the exterior weld, resulting in a leak, the source of which may be at a significant distance from the outlet. This makes finding the source difficult, complicating repair. 
         [0004]    What is needed, therefore, are techniques for preventing fluid from traveling through the weld void. 
       SUMMARY OF THE INVENTION 
       [0005]    One embodiment of the present invention provides a system for the sealing of a thermoplastic weld, the system comprising: a first and second thermoplastic components; a channel disposed in opposing faces of the first and second thermoplastic components; a sealing member disposed within the channel sealing a joint between the opposing faces; and at least one thermoplastic weld joining the opposing faces proximate to the sealing member. 
         [0006]    Another embodiment of the present invention provides such a system wherein the sealing member comprises a polymer selected from the group of polymers consisting of polyolefins, polyamides, and polychloropenes. 
         [0007]    A further embodiment of the present invention provides such a system wherein the channel has a grooved cross section, the grooved cross section being selected from the group of grooved cross sections consisting of rectangular cross section, semicircular cross section, triganal cross section, and asymmetric cross sections. 
         [0008]    Yet another embodiment of the present invention provides such a system wherein the sealing member is a tape. 
         [0009]    A yet further embodiment of the present invention provides such a system wherein at least one thermoplastic weld comprises first and second welds disposed on interior and exterior surfaces of the opposing faces. 
         [0010]    Still another embodiment of the present invention provides such a system wherein the first and second thermoplastic components are walls of a fluid storage tank. 
         [0011]    One embodiment of the present invention provides a tank, the tank comprising: a plurality of tank members; at least one joint disposed between first and second tank members; the joint comprising a first weld, a first sealant channel, and a sealant, the first sealant channel being disposed within the joint, the sealant being disposed within the first sealant channel and the weld holding the joint secure; the sealant configured to prevent leakage of a content of the tank through the joint. 
         [0012]    Another embodiment of the present invention provides such a tank wherein the tank members are panels. 
         [0013]    A further embodiment of the present invention provides such a tank wherein the tank members are plastic. 
         [0014]    Yet another embodiment of the present invention provides such a tank further comprising a second sealant channel disposed opposite to the first sealant channel. 
         [0015]    A yet further embodiment of the present invention provides such a tank wherein the sealant is disposed between the first and the second sealant channels. 
         [0016]    Even another embodiment of the present invention provides such a tank wherein the sealant channel comprises a chamfer disposed on a corner of a first tank member. 
         [0017]    An even further embodiment of the present invention provides such a tank wherein the chamfer is disposed in a rabbet in a second tank member defining the joint. 
         [0018]    The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an elevation view illustrating a weld seal configured in accordance with one embodiment of the present invention. 
           [0020]      FIG. 2  is an elevation view illustrating a weld seal configured in accordance with an alternative embodiment of the present invention. 
           [0021]      FIG. 3  is an elevation view illustrating a weld seal configured according to an alternative embodiment of the present invention. 
           [0022]      FIG. 4A  is an expanded elevation view illustrating the assembly method of a weld seal configured according to an alternative embodiment of the present invention. 
           [0023]      FIG. 4B  is an elevation view illustrating the assembly method of a weld seal configured according to the embodiment of the present invention illustrated in  FIG. 4A . 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    One embodiment of the present invention provides a “plastic” sheet  12  having a sealing slot cut  14  in the edge of the sheet adjacent to where a weld  16  will occur. A sealant  18  is placed inside the sealing slot  14  prior to welding the sheet thereby allowing the sealant  18  to act as a barrier to prevent the loss of the liquid being stored in the liquid storage vessel. 
         [0025]    The sealant material, of one embodiment, prevents any liquid from passing through a void on the first (interior or sealing) weld thus avoiding leaks from occurring in the event of a void or breakage of the second (exterior or structural weld) weld. In many cases where no sealant is provided, when a first weld fails, liquids will travel along the space behind the weld until it finds an outlet unless prevented by a barrier. In known systems where a single weld is typically relied upon for sealing containers, in the absence of barriers behind the weld there would be no barrier to leakage. In some systems a second or structural weld, may be provided, and while not intended to provide sealing, if there is no barrier, this second weld would be sole means of preventing leaks. The addition of the sealant  18  material prevents the liquid from reaching that second weld, if there is a second weld. According to one embodiment of the present invention, the provision of a sealant barrier  18  between the first  16  and second welds  15  allows the welds to be used primarily in a manner to structurally join the sheets, but only secondarily as a liquid sealing element. 
         [0026]    The sealant  18  of one embodiment of the present invention will be contained in a sealing slot or channel  14  between the two sheets of “plastic”  12 ,  20  being joined and act as a barrier to prevent liquid from passing through a weldment void. In one embodiment, the sealing slot or channel  14  may be disposed in one of the two sheets  12 , while in other embodiments, slots or channels  14  may be provided in both sheets and the sealant disposed partially in both slots, as illustrated in  FIG. 1 . In embodiments where a single slot  14  is used, as illustrated in  FIG. 2 , the sealant may be adhesive and adhere to the surface of the non-slotted sheet. In such embodiments, when a failure occurs in an interior weld that allows the liquid to seep into the voided area where the two sheets are joined by contact (past the weld), the sealant will act as a barrier and not permit the liquid to pass and come in contact with the exterior weld. In cases where only one weld is applied, a sealant barrier configured in accord with the embodiments of the present invention, will prevent loss of the stored liquid. 
         [0027]    As illustrated in  FIG. 3 , the channel  14  may be disposed in a side of one panel  12  while the end of a second panel  20  is butted against the channeled section and welded. An alternative corner connection is illustrated in  FIGS. 4A and 4B  where an L shaped shoulder or rabbet  30  is formed in the end of one panel  12  with a chamfer  32  on a corresponding edge. Connection of the rabbet  30  with the chamfer  32  creates a space in which the sealant  18  is disposed. 
         [0028]    One embodiment of the present invention can be used on any plastic material that is welded and used to contain a liquid or solid that may leak or seep if a weld seam were to fail. One skilled in the art will appreciated that the sealant material itself may be a compressible or conformable material, or an adhesive material having suitable sealing characteristics and resistant to the liquid or solid contained in the storage tank. 
         [0029]    In one embodiment of the present invention, the sealing material is pliable and selected to adhere to the thermoplastic sheets. The sealing material is selected so as to resist migration from the sealant channel or slot, as such migration would compromise the structural integrity of the plastic welds. 
         [0030]    One embodiment of the present invention comprises a process providing a precise width and depth for the channel or slot for the proper positioning of the sealant. As such, the sealant and spline may be adjusted based on the dimensions of the joint, the liquid or solid contained by the tank, and other characteristics understood by those skilled in the art. In addition, the sealant material may be provided with selected properties that allow it to reside in the track for extended time without degrading and be able to resist liquids should they enter the track. Sealants which may be employed include, but are not limited to polyolefins, polyamides, polychloropenes, butyl tapes, vinyl tapes, polyamide tapes, polychloropene tapes, nitrate polymer tapes. Examples of such sealants include those sold under the respective trade names CRL Sealant tape; ST 132×14, ST 18×34 sealant tape, ST18×1 sealant tape and ST132×12 sealant tape; CRL 213212 (1/32″×½″) form mounting tape; deVan 578.12 Orange Butyl tape (⅛″×¼″); deVan 581.12 Gray Butyl tape ( 3/32″ diameter); Phifer Screening spline (⅛″ diameter; 3M Weatherban Sealant tape -Butyl; 3M adhesives with either a neoprene or nitrate based gasket; Tremco Butyl Glazing tapes; Tremco Butyl Sealant; Denso Butyl rubber Adhesive tape 
         [0031]    In one embodiment of the present invention, the sealant material is installed in the channel or slot in such a way as both the sealant and the channel or slot are substantially free of dust, debris, moisture, grease or other contaminants. Installation may be made at temperatures suitable for the sealant selected, in most instances ambient temperature is desirable. 
         [0032]    In one embodiment of the present invention, the sealant material is provided in a continuous seal at all joints thus configured. Where joints intersect, the sealant material may be adhered to itself, forming a continuous barrier. 
         [0033]    In one embodiment of the present invention, the sealing material is used in the process of joining together body components such as compartments, fenders, walls, and doors, to act as a barrier to prevent the contamination of the contents of the compartments from outside dirt and moisture to preserve the contents from corrosive effects. Further, the sealant material ensures that over the life of the vehicle body components, any weld separation that might occur due to extended vehicle use will not cause contamination of the contents of the compartment and will provide secondary seal capability to all body components. 
         [0034]    The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. Each and every page of this submission, and all contents thereon, however characterized, identified, or numbered, is considered a substantive part of this application for all purposes, irrespective of form or placement within the application. This specification is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure.