Lightweight vault cover

Abstract

Disclosed is a cover for a utility vault and a method for making such covers. The cover is formed from fiberglass reinforcement layers and a polymer mix matrix. The reinforcement layers include a bottom reinforcement layer, one or more edge reinforcement layers, and a top reinforcement layer. A first portion of the edge reinforcement layer overlaps a portion of the bottom reinforcement layer and a second portion of the edge reinforcement layer overlaps a portion of the top reinforcement layer. The reinforcement layers are formed from fiberglass fabric and may include fiberglass layers whose fibers are oriented quadraxially. The polymer mix impregnates the fabric layers and forms the bulk of the cover. The polymer matrix bonds the reinforcement layers so that forces applied across the top and bottom layers are communicated to the edge reinforcement layer. The polymer matrix includes a thermoset polymer resin and an expanded glass bead filler.

We claim: 
     
         1 . A method for forming a vault cover comprising the steps of:
 providing a mold cavity;   placing a top reinforcement layer along a bottom surface of the mold cavity;   placing an edge reinforcement along at least one edge of the mold cavity, wherein a first portion of the edge reinforcement overlaps a portion of the top reinforcement and second portion of the edge reinforcement extends out of the mold cavity;   substantially filling a space within the edge reinforcement and above the top reinforcement with one or more components of a matrix material;   placing a bottom reinforcement layer on top of the at least one component of the matrix material; and   folding the second portion of the edge reinforcement over the bottom reinforcement layer.   
     
     
         2 . The method of  claim 1 , wherein the at least one component of the matrix material is a filler and further comprising the step of introducing a second component of the matrix material into the mold cavity, wherein the second component is a polymer resin that infiltrates the interstitial spaces of the filler material and the top, edge, and bottom reinforcements. 
     
     
         3 . The method of  claim 2 , wherein the step of introducing is performed using injection molding. 
     
     
         4 . The method of  claim 1 , wherein the one or more components of the matrix material comprise a mixture of a polymer cement and a filler, wherein the step of substantially filling comprises infiltrating the mixture into the top and edge reinforcements with a first portion of the mixture and, following the step of folding, further comprises pouring a second portion of the mixture into the mold cavity and infiltrating the mixture into the bottom reinforcement. 
     
     
         5 . The method of  claim 1 , wherein one or more of the top reinforcement layer, the bottom reinforcement layer and the edge reinforcement layer are a fiberglass fabric. 
     
     
         6 . The method of  claim 5  wherein the fiberglass fabric comprises a quadraxial fabric. 
     
     
         7 . The method of  claim 1 , wherein the one or more components of the matrix material comprise one or more of glass beads, expanded glass beads, limestone aggregate, silica sand, chopped fiberglass fibers, polymer fibers, metallic fibers, fly ash, expanded ceramic spheres and ceramic particles. 
     
     
         8 . The method of  claim 3 , further comprising the steps of:
 placing a top lid over the mold cavity;   applying a negative pressing to the cavity through an outlet port; and   injecting the resin into the cavity via an inlet port.   
     
     
         9 . The method of  claim 2 , wherein the resin comprises one or more of an unsaturated polyester resin, a methacrylate, a vinyl ester, and an epoxy. 
     
     
         10 . The method of  claim 1 , wherein a feature is provided on an interior surface of the mold cavity, wherein the feature forms one of more of a slot, a bolt hole, a textured surface, and an indicia. 
     
     
         11 . The method of  claim 1 , wherein an edge of the vault cover has a curvilinear shape, the method further comprising the steps of
 notching the edge reinforcement; and   fitting the notched edge reinforcement into the mold cavity to conform to the curvilinear shape.   
     
     
         12 . The method of  claim 1 , further comprising embedding one or more of a RFID device, an electronic sensor, and an induction coil embedded in the matrix.