Abstract:
An improved Rieber type seal having an annular extending profile composed of a first thermoplastic material exhibiting a first rigidity and a second thermoplastic material having a second lesser rigidity is applied over the first material such that at least one surface of the first material is exposed upon installing within a first pipe section and contacts an inserting end of a second pipe section. The first material can include a glass filled polymer reinforced or other thermo rigid material, whereas the second material may include a softer thermoplastic backing material injected around the first material in a solidifying stage or may be one selected from the group including a thermoplastic vulcanite (TPV), thermoplastic urethane (TPU) or styrene ethylene butylene styrene (SEBS).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Provisional Patent Application No. 61/431,970 filed Jan. 12, 2011. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention discloses an improved two shot thermoformed seal for incorporation into such as a Rieber type belling process for use in interconnecting PVC piping sections. More specifically, the present invention discloses an improved elastomeric seal joint exhibiting an improved cross sectional profile established between a first shot of such as a glass filled polymer reinforced or other thermo rigid material and a second shot of a softer backing material including such as a thermoplastic vulcanite (TPV), thermoplastic urethane (TPU) or styrene ethylene butylene styrene (SEBS). An angular rib configuration associated with the cross sectional profile of the first surface contacting glass filled polymer allows for the seal to expand and contract along with environmentally induced temperature variations. The two shot forming process further establishes a high bond line strength between the first and second thermoformed materials (often exceeding the tear strength of the plastic). An optional third shot of a slip on the install surface of the ring seal further provides additional gripping and sealing characteristics. 
       BACKGROUND OF THE RELEVANT ART 
       [0003]    The prior art is documented with examples of reinforced rubber gaskets such as interposed between interconnecting end to end connected sections of PVC pipe fittings and the like. An example of such a type of gaskets is generally known as a Rieber seal (see for example U.S. Pat. No. 4,368,894 to Parmann) and which was developed in order to address certain problems, including such as the dislodging of a homogeneous and non-reinforced elastomeric gasket from an associated inner annular bell groove during insertion into the bell of an engaging spigot end of a succeeding PVC pipe section, this compromising the sealing characteristics of the joint. 
         [0004]    Conventional Rieber seals include such a steel wire or flattened band which is either externally or internally bonded, such as proximate the exterior perimeter of the annular extending elastomer body and is locked into place within the bell groove due to pre-stressing of the elastomer against the inner annular wall of the pipe, with the additional advantage of such anchoring of the gasket preventing the penetration of soil and other foreign particles into the sealing zone established between the outer walls of the gasket and the internal walls of the bell where the gasket is seated. In this fashion, the steel ring operates to hold open the seal for subsequent inter-assembly and during the initial belling process. 
         [0005]    More recent examples of two part gaskets for pipe-to-pipe connections include such as disclosed in Happel, U.S. Pat. No. 7,252,293 and which teaches a two part body having a substantially rectangular profile and including a relatively rigid component joined to a relatively resilient component. The resilient component includes a radially inwardly projecting sealing lobe for providing a compressive seal with the spigot end of a pipe, a reinforcement portion of the rigid component being disposed between the sealing lobe and the pipe bell end to provide a radially non-compressive reaction surface against which the sealing lobe is compressed. The rigid component further includes a tapered leading edge portion for aligning and centering the spigot end of a pipe upon insertion within the gasket, the leading edge portion being reinforced by a plurality of circumferentially spaced ribs. 
       SUMMARY OF THE PRESENT INVENTION 
       [0006]    The present invention discloses an improved Rieber type seal in which a first thermoplastic material having a first rigidity exhibits an annular extending profile with a cross sectional profile and a second thermoplastic material having a second lesser rigidity is applied over the first material such that at least one surface of the first material is exposed and, upon installing within a first pipe section, contacts an inserting end of a second pipe section. The first material can include a glass filled polymer reinforced or other thermo rigid material exhibiting a “V” profile. 
         [0007]    The second material may further include a softer thermoplastic backing material injected around the first material in a solidifying stage or may be one selected from the group including a thermoplastic vulcanite (TPV), thermoplastic urethane (TPU) or styrene ethylene butylene styrene (SEBS). The second material may further terminate in an outer lip edge as well as an opposite/inner biasing lobe edge. The invention further contemplates a third shot slipcoat applied over the exposed surface of the first material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Reference will now be made to the attached drawings, when read in combination with the following detailed description, wherein like reference numerals refer to like parts throughout the several views, and in which: 
           [0009]      FIG. 1  is an assembled lengthwise cutaway of the improved Rieber type seal according to one non-limiting example of the present invention installed between end-to-end engaging locations of first and second lengths of pipe; 
           [0010]      FIG. 2  is a first cutaway perspective illustrating a first example of an interface profile established between first and second polymer based materials produced according to a generally Rieber belling seal process and such as according to that previously depicted in  FIG. 1 ; 
           [0011]      FIG. 3  is an end view of the ring profile established by the first and second materials illustrated in  FIG. 2 ; 
           [0012]      FIG. 4  is a cutaway perspective similar to  FIG. 2  and of a second example of a ring profile; 
           [0013]      FIG. 5  is a cutaway perspective of a third example of a ring profile; and 
           [0014]      FIGS. 6A-6C  illustrate, in succession, examples of prior art, V4D and V5D sections taken from selected ring profiles and further including the optional addition of a third shot slipcoat surface. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    As previously described, the present invention discloses an improved two shot thermoformed seal for incorporation into such as a Rieber type belling process for use in interconnecting PVC piping sections and which addresses deficiencies associated with installation of prior Rieber type seal designs, in particular during the belling process associated with such initial gasket or seal assembly within a widened receiving (female) end of a pipe section and prior to end to end engaged assembly of pipe sections in the field. As is known, the Rieber ring is a locked in/fixed elastomeric ring seal utilized in pressurized PVC piping. 
         [0016]    Specifically, the conventional Rieber ring design is steel reinforced and is incorporated into the pipe-end socket during the manufacturing process, thus rendering the seal an integral (or locked in) part of the pipe which is ideally suited for water pressure and sewer/drainage pipes. As is further known, the outwardly facing steel ring component holds the seal open for the belling process and to ensure the seal is open for assembly in the field. Problems associated with such conventional seal designs further include mechanical fracture, including delamination from the backing thermo layer, as well as corrosion of the steel ring. 
         [0017]    Referring initially to  FIG. 1 , reduced length and interconnecting end sections are shown in lengthwise cutaway of a first length of pipe  1  exhibiting an annularly enlarged female receiving (or spigot) end  2  which contains a pre-installed seal  10  and into which is installed an inserting, or male end  3  of a further pipe section  4 . As previously described, the end to end connected pipes  1  and  4  can include, without limitation, a PVC (polyvinyl chloride) material however are further understood to not be limited in either construction or configuration. 
         [0018]    Also depicted in the lengthwise cutaway of  FIG. 1  is the lead-in angle associated with the spigot end  2  of the receiving pipe  1  and which includes a first outwardly angled surface  5  and a succeeding and communicating inward reverse angle  6  (this defining the annular extending bell profile associated with the spigot and which is understood in the art to correspond to the belling or pre-installation process for mounting the gasket  10  within the open end of the pipe  1  prior to subsequent end to end pipe installation in the field). The first pipe  1  as further shown terminates, at open end profile  7 , in a leveled end profile defining the inserting cavity for receiving the end  3  of pipe  4 . The inserting end  3  of pipe  4  further exhibits a tapered outer diameter notch, see at  8 , this facilitating assembly within the spigot  2  of receiving pipe  1  with the seal  10  pre-installed in place. 
         [0019]    Referring now to  FIG. 2 , in combination with the environmental installation of  FIG. 1 , the cutaway perspective generally at  10  is again depicted illustrating a first example of an interface profile established between first and second polymer based materials produced according to a generally Rieber belling seal process and according to the present invention. The Rieber type seal defined by the present invention improves upon existing seal designs constructed of first and second injection molded thermo-based materials, such as in particular regards to the angular rib configuration established between the harder “first shot” material and the softer “second shot” material as typically occurring during an associated injection molding operation in which the seal is produced. 
         [0020]    As depicted in each of  FIGS. 1 and 2 , a first shot (defined to include injection molding or any other suitable forming process) material  12  is provided of a higher resilient thermo polymer material which substitutes for the outer annular steel ring positioned along a lead-in surface associated with prior art belled Rieber pipe ring seal designs. The first shot  12  includes such as a glass filled polymer reinforced or other thermo rigid material and, in the illustrated variant, exhibits a sharp “V” profile with an outer turned edge  13  (as well as an outwardly stepped or projecting profile  13 ′) and which, upon installing the ring within the accessible spigot end  2  of the first PVC pipe section  1 , defines an annularly accessible pocket or seat for receiving an inserting edge profile of the succeeding PVC or like pipe section  4 . 
         [0021]    During initial seal manufacture, a second shot of a softer thermoplastic backing material  14  is injected around the solidifying first shot  12  (such as to enhance the line bonding strength established between the materials) and includes such as a thermoplastic vulcanite (TPV), thermoplastic urethane (TPU) or styrene ethylene butylene styrene (SEBS). The softer backing material  14  as depicted in cutaway exhibits a similar sharpened V-profile, see including inner pointed base edge  15  which corresponds to a similar edge  15 ′ defining the inner harder material  12 , and further so that edge extending boundaries  16  and  17  are established between the outer facing angled sides of the inner harder material  12  and mating inner facing angled sides of the outer softer backing material  14 . 
         [0022]    As further depicted in each of  FIGS. 1 and 2 , the outer material  14  terminates in an outer lip edge  18  which is additionally retained in place along its underside extending surface by the projecting profile  13 ′ associated with the harder material  12 . As shown in  FIG. 1 , the outer lip edge  18  seats against the inner angled edge of the spigot  2  defining its greatest diameter dimension and which is again located at the lead in angle defining surfaces  5  and  6  associated with the spigot  2  of the first PVC pipe section  1 . An opposite/inner biasing lobe edge  19  extending from the backing material  14  defines a generally abutment end stop with the inserting profile edge  3  of the second pipe section  4  and shown in  FIG. 1 . 
         [0023]    Although not shown, a separate brush or spray on lubricant material can be used during field installation of the pipe sections and such as to facilitate mating engagement of the inserting edge  3  of the succeeding pipe section  4  in proper annular seating and engaging fashion with the inner profile edges of the seal  10  which has again been previously mounted within the belled location of the initial pipe section  1  associated with its receiving spigot  2 . Without limitation, the lubricant can be applied to either or both the inserting portion  3  of the pipe  4 , as well as to the inner spigot  2  and/or seal  10  defining surfaces against which the outer profile of the pipe  4  seats or abuts. 
         [0024]    The angled cross sectional configuration of the first material  12  as described and further such as is additionally shown in succeeding variants is selected so as to increase both bonding surface area with the backing material  14  as well as to enhance the strength and performance characteristics of both materials  12  and  14 . As further illustrated in the end view of  FIG. 3 , an angular rib configuration, see at  19 ′, is associated with the cross sectional profile of the first surface contacting glass filled polymer (first material  12 ) and allows for the seal  10  to expand and contract along with environmentally induced temperature variations. As previously noted, the two shot forming process establishes high bond line strength between the first and second thermoformed materials (often exceeding the tear strength of the plastic). 
         [0025]    Referring now to  FIG. 4 , a cutaway is generally shown at  20  shown in perspective, similar to  FIG. 1 , and of a second example of a seal exhibiting a ring profile in which a first shot thermo material  22  exhibits an alternatively curved outer profile (see further at  24 ), combined with a pair of lengthwise extending and spaced apart support ribs  26  and  28  and a further extending edge  30  (similar to that depicted at  13  in  FIG. 1  and again including a projecting edge location). The second shot material is further shown at  32 , similar in composition to that described in  FIG. 1 , and which is again formed around and over the first shot thermo material  22 , with corresponding and opposingly seating ribs  27  and  29 , such that both materials  22  and  32  set simultaneously in order to facilitate increased bond line strength associated with a correspondingly increased bond line area resulting from the plural and overlapping profile associated with the multiple ribs  26  &amp;  28  and  27  &amp;  29 . 
         [0026]    The cross sectional profile of the second shot  32 , generally similar to that identified at  14  in  FIG. 1 , includes both an edge extending portion  34  which can engage the inner lead in angled edge of the spigot  2  in similar fashion as the lip edge  18 , as well as an inner ribbed support  36  (this corresponding to the lobe edge  19  in  FIG. 1 ) which is application-ally similar to that depicted at  19  in the seal  10  installed in  FIG. 1  to provide an abutment stop to the inserting end profile of the succeeding pipe section  4 . Otherwise, the seal  20  installs and functions in a similar fashion as that previously described and depicted at  10  in  FIGS. 1 and 2  in relation to the pipe architecture described. 
         [0027]      FIG. 5  presents a further cutaway perspective, generally at  38 , of a third example of a seal exhibiting a ring profile which is similar to that depicted in  FIG. 1  and includes a first shot  40  again including such as a glass filled polymer reinforced or other thermo rigid material and, in the illustrated variant, exhibits another example of a sharp “V” profile with an outer turned edge  42  and which, upon installing the ring within an accessible end of a first PVC pipe section, defines an annularly accessible pocket or seat for receiving an inserting edge profile of a succeeding PVC pipe section. A second shot of a softer thermoplastic backing material  44  is injected around the solidifying first shot  40  and surrounds the annular extending first shot  40  and further, as depicted in  FIG. 1 , terminates in an outer, generally flush, edge  46  (this again seating against the annular inner surface of the first PVC pipe section), as well as an opposite/inner biasing lobe edge  48 , such as again in use defining an abutment stop for seating an inserting end of a male pipe section  4  such as depicted in  FIG. 1 . 
         [0028]    Referring finally to  FIGS. 6A-6C  illustrated in succession are examples of each of prior art (at  50  in  FIG. 6A ), V4D (at  52  in  FIG. 6B ) and V5D (at  54  in  FIG. 6C ) sections taken from selected ring profiles. The 4D ( FIG. 6B ) and 5D ( FIG. 6C ) sections, given the location of the first shot of material in similar respects to those previously depicted in the variants of  FIGS. 1-4 , have been found to be more prone to delaminating during the final install and due to the first shot of rigid material (depicted in section at  56  in  FIG. 6B  and further at  58  in  FIG. 6C ) not fully encapsulated (unlike that generally shown again at  50  in  FIG. 6A ) within the softer second shot material (further at  60  in  FIG. 6B and 62  in  FIG. 6C ). Consequently, a further desired component contemplates the optional addition of a third shot slipcoat surface material (such as exhibiting any type of thermoplastic resin exhibiting selected deforming and/or frictionally resistive properties) applied onto the install surface of the ring seal, and which by non-limiting example is depicted by third shot slipcoat surface  49  in  FIG. 5 , this in order to provide additional gripping and sealing characteristics. 
         [0029]    Accordingly, the present invention discloses a lighter weight thermo based ring seal as compared to existing Rieber type seals while also overcoming many of the afore mentioned problems ascribed to the steel ring component associated with such prior art seals, these again including corrosion and mechanical fracture/delamination. The use of a two shot polymer based application for creating the ring seal further eliminates production steps leading to lower manufacturing cost. 
         [0030]    Having described our invention, other and additional preferred embodiments will become apparent to those skilled in the art to which it pertains and without deviating from the scope of the appended claims.