Tank assembly and related method of manufacture

Abstract

A tank assembly having an elongated plastic tubular pipe structure and at least one end wall attached to the plastic tubular pipe structure and sized to cover a cross-sectional area defined by the plastic tubular pipe structure. The end wall is a composite unit including a first plastic sheet member having an edge portion and a second plastic sheet member bonded with the edge portion of the first plastic sheet member. The first plastic sheet member is located inward of the second plastic sheet member, the second plastic sheet member having a body portion with an outwardly domed shape to define an internal space between the body portion and a body portion of the first plastic sheet member. A structural foam is disposed in the internal space to provide continuity between the first plastic sheet member and the second plastic sheet member.

What is claimed is: 
     
         1 . A tank assembly, comprising:
 an elongated plastic tubular pipe structure;   at least one end wall attached to the plastic tubular pipe structure and sized to cover a cross-sectional area defined by the plastic tubular pipe structure, the end wall comprising a composite unit formed by:
 a first plastic sheet member having an edge portion; 
 a second plastic sheet member bonded with the edge portion of the first plastic sheet member, the first plastic sheet member located inward of the second plastic sheet member, the second plastic sheet member having a body portion with an outwardly domed shape to define an internal space between the body portion and a body portion of the first plastic sheet member; 
 a structural foam disposed in the internal space to provide continuity between the first plastic sheet member and the second plastic sheet member. 
   
     
     
         2 . The tank assembly of  claim 1  wherein the second plastic sheet member has an edge portion, and the edge portion of the second plastic sheet member is bonded with the edge portion of the first plastic sheet member 
     
     
         3 . The tank assembly of  claim 1  wherein:
 the elongated tubular pipe structure comprises an HDPE pipe; 
 the first plastic sheet member is formed of HDPE material; 
 the second plastic sheet member is formed of HDPE material; and 
 the structural foam is an expanding foam urethane material. 
 
     
     
         4 . The tank assembly of  claim 1  wherein:
 a thickness of the first plastic sheet member is between about 30 mils and 1,000 mils; 
 a thickness of the second plastic sheet member is between about 30 mils and 1,000 mils; 
 an a thickness of the structural foam measured along a central longitudinal axis of the plastic tubular pipe structure is between about 1,000 mils and about 45,000 mils. 
 
     
     
         5 . The tank assembly of  claim 4  wherein the second plastic sheet member is welded to the edge portion of the first plastic sheet member, and the end wall is welded to the plastic tubular pipe structure. 
     
     
         6 . The tank assembly of  claim 1  wherein:
 a thickness of the first plastic sheet member is between about 150 mils and 800 mils; 
 a thickness of the second plastic sheet member is between about 150 mils and 800 mils; 
 an a thickness of the structural foam measured along a central longitudinal axis of the plastic tubular pipe structure is between about 5,000 mils and about 30,000 mils. 
 
     
     
         7 . A tank assembly, comprising:
 an elongated plastic tubular pipe structure;   at least one end wall attached to the plastic tubular pipe structure, the end wall comprising a composite unit formed by:
 a first plastic sheet member sized to cover a cross-sectional area defined by the plastic tubular pipe structure, the first plastic sheet member bonded to the plastic tubular pipe structure; 
 a second plastic sheet member sized to cover the cross-sectional area and spaced apart from the first plastic sheet member to define a space therebetween, the second plastic sheet member bonded to the plastic tubular pipe structure; 
 a structural foam disposed in the space to provide continuity between the first plastic sheet member and the second plastic sheet member. 
   
     
     
         8 . The tank assembly of  claim 7  wherein the edge portion of the first plastic sheet member is welded to plastic pipe structure, and the edge portion of the second plastic sheet member is welded to the plastic pipe structure. 
     
     
         9 . The tank assembly of  claim 7  wherein the end wall defines an end of the tank assembly. 
     
     
         10 . The tank assembly of  claim 7  wherein the end wall defines an internal wall of the tank assembly to divide the elongated plastic tubular pipe structure into distinct internal volumes. 
     
     
         11 . A method of manufacturing a tank assembly, the method comprising:
 joining an edge portion of a first plastic sheet member to a second plastic sheet member, where the second plastic sheet member includes a body portion that is domed outwardly away from a body portion of the first plastic sheet member to define an internal space therebetween;   injecting an expanding structural foam into the internal space to fill the internal space once cured and provide continuity between the first plastic sheet member and the second plastic sheet member;   attaching the joined first plastic sheet member and second plastic sheet member to a tubular plastic pipe structure to block a passage through the tubular plastic pipe structure.   
     
     
         12 . The method of  claim 11  wherein the joining step involves joining the edge portion of the first plastic sheet member to an edge portion of the second plastic sheet member. 
     
     
         13 . The method of  claim 11  wherein the injecting step takes place prior to the attaching step. 
     
     
         14 . The method of  claim 11  wherein the joining step involves electrofusion welding the edge portion of the first plastic sheet member to the second plastic sheet member. 
     
     
         15 . The method of  claim 14  wherein the attaching step involves electrofusion welding the joined first plastic sheet member and second plastic sheet member to the plastic tubular pipe. 
     
     
         16 . The method of  claim 14  wherein the joining step involves placing electrofusion cord in contact with both the first plastic sheet member and the second plastic sheet member, and passing electrical current through the electrofusion cord to fusion weld plastic of the first plastic sheet member to plastic of the second plastic sheet member. 
     
     
         17 . The method of  claim 11  wherein the joining step involves utilizing heat to weld the plastic sheet members together. 
     
     
         18 . A method of manufacturing a tank assembly, the method comprising:
 joining an edge portion of a first plastic sheet member to a plastic tubular pipe structure to block a passage through the plastic tubular pipe structure;   joining an edge portion of a second plastic sheet member to the plastic tubular pipe structure to block the passage through the plastic tubular pipe structure, the second plastic sheet member spaced from the first plastic sheet member to define a space therebetween;   injecting an expanding structural foam into the space to fill the space once cured and provide continuity between the first plastic sheet member and the second plastic sheet member.   
     
     
         19 . The method of  claim 18  wherein the joining steps involve welding. 
     
     
         20 . The method of  claim 19  wherein the welding involves one of electrofusion welding or heat welding.