Abstract:
A method of forming a liner for a passage such as a sewer includes forming panels composing the liner using a neat resin of a first viscosity and a polymer concrete of a second, high viscosity. The neat resin is inserted into a mold cavity before the polymer concrete and is displaced upwardly by the polymer concrete pour to impregnate a fiber layer disposed along the periphery of the mold cavity. Resulting panels preferably have an offset joint to increase the joint strength between upper and lower panels forming the liner.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    None.  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable.  
         REFERENCE TO MICROFICHE APPENDIX  
         [0003]    Not Applicable.  
         BACKGROUND OF THE INVENTION  
         [0004]    This invention relates to the lining of sewers, water mains, culverts, tunnels, conduits, pipes, and other passageways (generically referred to herein as passages), and especially but not exclusively to the lining of underground passages. Lining in this context is intended to include both original lining and relining. It is anticipated that the process will be used mainly for the relining, particularly the relining of sewers.  
           [0005]    As sewers and other passages age, they deteriorate in many ways. Cracks appear and joints separate. Infiltration through these cracks and joints creates external voids, accelerates structural deterioration and can overload collection systems and treatment plants. Many passages can be successfully rehabilitated using what is called the soft-lining or cured in place method. This method is illustrated in U.S. Pat. Nos. 4,009,063 and 4,064,211. Most deteriorating sewers can be rehabilitated economically in this way.  
           [0006]    Other rehabilitation projects, particularly those involving larger passages, may require a different method, one using a hard liner inside the existing passage. Inserting a hard liner in an existing passage poses several problems. Typically, there is a limited amount of space available in such passages, so manipulating the liner to place it in the passage and/or assemble it in place can be difficult. Moreover, the lining of such passages should not excessively reduce the cross-sectional area of the passage, since otherwise the flow rate through the passage will be unduly restricted.  
           [0007]    Hard liners typically are formed from a polymer concrete, which in turn is composed of a suitable resin and approximately 70% by weight filler (such as sand). Frequently, one or more fiberglass layers are included adjacent the inner and outer surfaces of the liner. However, the manner in which fiberglass layers are used can result in problems, since the polymer concrete may not readily permeate the fiberglass, resulting in exposed fiberglass on either the inner or outer surface of the liner. This condition adversely affects the physical properties of the resulting laminate part, such as strength and modulus. It can also result in a loss of corrosion resistance, increased friction between the fluid and the liner, and reduced flow rate of the fluid through the passage.  
         SUMMARY OF THE INVENTION  
         [0008]    Among the various objects and features of the present invention is the provision of an improved passage liner.  
           [0009]    Another object is the provision of such a liner that facilitates the placement and assembly of the liner in a passage.  
           [0010]    A third object is the provision of such a liner that does not unduly restrict the flow of fluid through the passage.  
           [0011]    A fourth object is the provision of a method of making such a liner with improved impregnating of the fiberglass layer.  
           [0012]    A fifth object is the provision of such a method that it is relatively simple and inexpensive.  
           [0013]    Other objects and features will be in part apparent and in part pointed out hereinafter.  
           [0014]    In one aspect of the present invention, a method of making a panel for a passage liner of the present invention includes the steps of obtaining dimensions of a passage to be lined, selecting a panel having a shape suitable for use in the passage to be lined, and molding the panel in a mold cavity having a periphery. The molding step including the steps of disposing a fiber layer around at least a portion of the periphery, introducing a layer of neat resin in the mold cavity, and subsequently introducing a polymer concrete in the mold cavity such that the neat resin floats above the polymer concrete and impregnates said fiber layer as said polymer concrete is introduced.  
           [0015]    In a second aspect of the present invention, the method of making a panel for a passage liner of the present invention includes the steps of providing a mold having a mold cavity selected to form a shape corresponding to a desired shape of a panel to be inserted in a passage to be lined, and disposing a fiber layer around at least a portion of the periphery of the mold cavity, said fiber layer having openings therein so as to allow the passage of at least some fluids from the interior of the mold space to the periphery of the mold cavity. After inserting the fiber layer, neat resin of a predetermined density is inserted into the mold cavity. The mold cavity has a top and a bottom so that the neat resin becomes disposed in the bottom of the mold cavity. A flowable, curable polymer concrete is inserted into the mold cavity after the neat resin is inserted, the polymer concrete having a density greater than the density of the neat resin so that the polymer concrete displaces neat resin from the bottom of the mold cavity toward the top of the mold cavity. The neat resin flows through the openings in the fiberglass layer to impregnate the fiber layer as the neat resin is displaced toward the top of the mold cavity. The neat resin and the polymer concrete are cured to form a panel of the desired shape.  
           [0016]    In a third aspect of the present invention, a passage liner segment of the present invention includes at least first and second panels sized and shaped to jointly fit a passage to be lined. The first panel has a panel body and at least first and second prongs projecting from the panel body, the first and second prongs having substantially different lengths. The second panel has first and second mating surfaces for receiving the prongs, the first and second mating surfaces being offset circumferentially (measured in the direction along the perimeter of the liner) and radially (measured along the direction from the inside to the outside of the liner) from one another. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a cross-sectional view of a passage with a passage liner of the present invention;  
         [0018]    [0018]FIG. 2 is a side elevation of a portion of an assembled passage liner made in accordance with the present invention;  
         [0019]    [0019]FIG. 3 is a cross-sectional view of one of the joints of the liner, as assembled;  
         [0020]    [0020]FIG. 4 is a cross-sectional view of one of the joints of the liner, illustrating assembly of the liner;  
         [0021]    [0021]FIG. 5 is an elevation of an alternative construction of the liner joint used in the present invention;  
         [0022]    [0022]FIG. 6 is a flow chart illustrating the method of the present invention; and  
         [0023]    [0023]FIG. 7 is a schematic illustrating part of the method of the present invention; 
     
    
       [0024]    Similar reference characters indicate similar parts throughout the several views of the drawings.  
       DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    Turning to the drawings, FIG. 1 illustrates a passage liner  11  of the present invention. Liner  11  is composed of upper and lower panels  13  and  15 . (It should be appreciated that the invention also includes liners formed from more than two panels. It could be desirable, for example, to use more than two panels to form a single segment when dealing with larger sized passages.)  
         [0026]    As can be seen more clearly in FIG. 2, liner  11  is formed in segments  11 A,  11 B,  11 C, etc., each of which has upper and lower panels  13 ,  15 . It should be understood that each segment is formed with suitable mating surfaces (not shown and not forming part of the present invention) so that the segments are securely and smoothly joined to each other. It is preferred (although not a requirement of the present invention) that each segment be affixed to its neighbors by a suitable water resistant adhesive, such as an epoxy or polyurethane adhesive capable of setting in the presence of water.  
         [0027]    Liner  11  is disposed in a desired passage, such as the sewer  17  shown in FIG. 1. Sewer  17  is shown by way of illustration only. It should be understood that the present invention may be used with a passage of any type. Furthermore, the passage may be either an existing structure to be rehabilitated by liner  11 , or new construction. In either event, the particular size and shape of liner  11  (and hence of panels  13 ,  15 ) is selected to fit the specific passage  17  being lined. Passage  17  is, of course, surrounded by existing solid or semi-solid material  18  such as rock, pre-existing pipe, compacted soil, or the like. After liner  11  is placed in passage  17 , a suitable grout  19  is inserted between the walls of passage  17  and the exterior of liner  11 . Such grouts are well-known in the industry and form no part of the present invention. It is preferred that wooden spacer blocks  20 A- 20 D be inserted in the passage  17  to support liner  11  prior to grouting. The particular number and size of spacer blocks does not form part of the present invention. Blocks  20 A and  20 B are laid in the passage before panel  15  is placed. Blocks  20 C and  20 D are inserted along the outside of the liner after panel  13  is put into place.  
         [0028]    Lower panel  15  has a generally U-shaped panel body  15 A terminating, at the ends of each leg, in first and second prongs  21 ,  23 . (Although the panel bodies shown are generally U-shaped, the particular shape of the panel bodies do not form a part of the present invention). Prong  21  is substantially longer than prong  23 , with the result that the joint between the upper and lower panels  13 ,  15  is strengthened substantially against lateral forces. It is preferred that the difference in length between the two prongs be at least ¼″ and preferably longer. The joint between panels  13  and  15  is best illustrated in FIG. 3.  
         [0029]    Similarly, upper panel  13  has a generally U-shaped panel body  13 A (although the particular shape of the panel body forms no part of the present invention), terminating at each end in first and second mating surfaces  25 ,  27  (see FIG. 3 for a depiction of the mating surfaces along the left-hand side of the liner) for receiving prongs  21 ,  23 . Note that first and second mating surfaces  25 ,  27  are offset circumferentially and radially from one another. The circumferential offset is preferably at least ¼″ and, like the different lengths of prongs  21 ,  23 , results in a stronger joint between upper and lower panels  13 ,  15 .  
         [0030]    Also shown in FIG. 3 is a prong or protrusion  29  disposed between mating surfaces  25 ,  27  and extending from the body  13 A of upper panel  13 . Prong  29  is sized and shaped to matingly fit between the first and second prongs  21 ,  23  of the lower panel  15 . Of course the other leg of body  13 A includes a second such prong  29 . Upper panel prongs  29  facilitate the assembly of liner  11  from panels  13 ,  15  by guiding the upper panel  13  into place above lower panel  15  as indicated in FIG. 4. The prongs also serve to strengthen the joint between the panels. It is preferred, although not required by the present invention, that upper and lower panels  13 ,  15  be secured to each other by a suitable adhesive such as a water resistant epoxy or polyurethane.  
         [0031]    It is preferred, although not required by the broadest form of the present invention, that the upper and lower panels  13 ,  15  have matching profiles where the panels join so that the interior and exterior surfaces of the passage liner  11  where the panels join are relatively smooth. This feature is illustrated in FIG. 3.  
         [0032]    As an alternative to the construction shown in FIGS. 1, 3, and  4 , protrusion  29  of the upper panel  13  may be replaced by a third part, a spline  31  (see FIG. 5). Spline  31 , like the prongs and mating surfaces, extends substantially the length of the panels. In this particular construction upper panel  13  has (on each side) two prongs projecting from the body of the panel. The ends of those prongs form the first and second mating surfaces  25 ,  27 . Although not a part of the present invention, it is preferred that spline  29  be secured in place (upon assembly of the panels) with a suitable adhesive to form a substantially fixed joint between the upper and lower panels.  
         [0033]    Before the proper sized and shaped panels  13 ,  15  can be selected to line a passage, it is first necessary to obtain the dimensions of the passage to be lined. Panels  13 ,  15  appropriate for that passage are then selected. At some point, whether before or after the passage dimensions are obtained, the required panels are molded in a mold  33  having a mold cavity (or cavities)  35  (see FIG. 7 for an illustrative mold  33  and mold cavity  35 ). The particular form and type of the mold and mold cavity do not form part of the present invention. The mold cavity shape and size are selected to form a molded panel corresponding to the desired shape and size of panel to be inserted in a passage to be lined. Upper and lower panels require different molds, and differently shaped panels would require different molds as well. Mold  33  shown is a generic mold chosen to illustrate the features of the present invention. It is preferred, but not required, that the mold cavity be open to the atmosphere.  
         [0034]    Mold  33  has inner and outer walls  37 ,  39  defining the inner and outer walls of the panel being molded. Mold  33  has a base  41  that may either be a permanent part of the mold or that may be formed in place by a suitable inexpensive material. The mold may be made of any suitable material such as resin impregnated fiberglass, steel, or any other known mold material. The particular mold material does not constitute any part of the present invention.  
         [0035]    The molding process itself is outlined in FIG. 6. If desired, the mold cavity may first be sprayed with a thermosetting resin gel-coat layer, thereby forming the first layer of the molded panel, although the gel-coat layer does not form any part of the present invention. Then an optional veil layer of fine fiberglass material is inserted into the mold. The veil layer, if desired, provides additional environmental resistance.  
         [0036]    The term “neat resin” (as used in the various components of the molded part as described below) is preferably a thermosetting resin, such as a polyester resin, a vinyl ester resin, or a DCPD (dicyclopentadiene) resin, or a blend of any two of the foregoing resins. Alternatively, the neat resin could be a polyurethane resin. The following resins are examples of such resins suitable for use in the present invention:  
                                                   Resin Type   Composition                           Polyester   isophthalic propylene glycol, styrene monomer           Vinyl Ester   bisphenol A, styrene monomer           DCPD   dicyclopentadiene, styrene monomer           Polyurethane   polyisocyanates &amp; polyols                      
 
         [0037]    Moreover, the “neat resin” as that term is used throughout this specification and the claims, may have a feldspar filler of up to 23% by weight of the resin. It is preferred that the feldspar filler be of grade Minspar 4. Thus, it can be seen that neat resin, as used herein, refers to a lightly filled or non-filled resin. As will appear, it is also required that the neat resin have a density less than that of the flowable, curable polymer concrete described below.  
         [0038]    After the gel-coat and veil layer (if any) are inserted into the mold cavity  35 , a layer of woven bi-directional fiber  45  is inserted along the periphery of the cavity. (Although the present invention is described in terms of fiberglass, it should be understood that other fibers such as carbon fibers and aramid fibers may be used instead and fall within the scope of the present invention.) It is preferred that the fiberglass layer substantially cover at least what will become the interior and exterior surfaces of the resulting molded panel. The fiberglass is preferably a biaxial woven fiberglass fabric with a minimum weight of approximately 26 ounces per square yard per layer. It should be understood that the particular weight of the fabric does not form a part of the present invention. It is also preferred, but not required, that a majority of the strands of the fiberglass fabric run in the hoop direction around the pipe liner. Fiberglass layer  45  has openings therein so as to allow the passage of at least some neat resin, as described below, from the interior of the mold space to the periphery of the mold cavity.  
         [0039]    After the fiberglass layer is inserted in the mold cavity, an initial pour of neat resin is introduced into the mold cavity. That initial pour is indicated by the liquid  49  disposed in the bottom of mold  33 . By way of example and not by way of limitation, the initial pour of neat resin could form a four inch thick layer of resin in the bottom of the mold. After the initial pour of neat resin, a flowable, curable polymer concrete (indicated by arrow  51 ) is introduced into the mold cavity. The polymer concrete is preferably composed of neat resin with, by way of example, 70% by weight sand or glass filler. The sand is preferably grade 60 silica sand.  
         [0040]    The polymer concrete has a density and a viscosity substantially greater than the density and viscosity of the neat resin. For example, typical values of density and viscosity are as follows:  
                                                       Material   Density   Viscosity                           Neat Resin   1.05-1.36 g/cc         250-1100 cps           Polymer Concrete   1.70-2.00 g/cc   100,000-1,000,000 cps                      
 
         [0041]    Because of these differences in the physical properties of the neat resin and the polymer concrete, the neat resin  49  floats above the polymer concrete  51  and impregnates fiberglass layer  45  as polymer concrete  51  is introduced into the mold cavity. The polymer concrete, on the other hand, being of higher viscosity is unable to substantially penetrate the fiberglass layer, so that the fiberglass layer becomes permeated almost exclusively with neat resin. Of course, neat resin and polymer concrete having densities and viscosities outside the above ranges could be used as well, so long as the density of the polymer concrete substantially exceeds the density of the neat resin being used.  
         [0042]    It is preferred, but not required, that the neat resin level in the mold be monitored as the polymer concrete is poured, so that the neat resin can be replenished as needed. In this case, the neat resin layer may, if desired, be maintained at a predetermined thickness such as 3-4″. The neat resin and the polymer concrete are then cured to form a panel of the desired shape.  
         [0043]    It is preferred, but not required, that the polymer concrete (upon completion of the pour) basically fill the part from bottom to top. Of course, excess neat resin may remain atop the polymer concrete after the pour is completed. Such resin, if necessary, may be removed before curing or, alternatively, cured in place and trimmed off after curing.  
         [0044]    In view of the above, it will be seen that all the objects and features of the present invention are achieved, and other advantageous results obtained. The description of the invention contained herein is illustrative only, and is not intended in a limiting sense.