Expansion tank with improved single diaphragm

Abstract

An improved expansion tank is provided for at least temporarily storing a pumped liquid under pressure, the expansion tank comprising a thin walled outer shell formed of two substantially hemispherical domes joined together, either directly or at the two ends of a central, substantially cylindrical section, and a flexible diaphragm located internally of the tank and secured to the inner surface of the shell of the tank to divide the internal volume of the tank into a fluid-tight section holding a gas under pressure and a fluid-tight section for holding an aqueous liquid under pressure. The improvement comprising diaphragm coupling ring formed as a discrete part of the diaphragm tank that can be fabricated independent of the domes and any cylinder. The diaphragm coupling ring provides a robust, leak-proof seal with the diaphragm, so that it can be connected onto an inner surface of an expansion tank in a separate, secondary operation.

What is claimed is: 
     
         1 . In an expansion tank for at least temporarily storing a pumped liquid under pressure, the expansion tank comprising a thin walled outer shell and a diaphragm located internally of the tank and secured to the inner surface of the shell of the tank to divide the internal volume of the tank into a fluid-tight section for holding a gas under pressure and a fluid-tight section for holding a liquid under pressure; the improvement comprising a diaphragm coupling ring fabricated independent of the tank segments and a diaphragm separating the inner volume of the tank into mutually fluid tight volumes, the coupling ring being sealingly, circumferentially connected between the inner circumferential surface of the tank wall and the peripheral edge of the diaphragm, wherein the completed tank was formed by first connecting the coupling ring to the diaphragm, then connecting the coupling ring to the inner wall surface of one of the tank segments, and then finally assembling the tank segments such that the diaphragm is sealed within the tank walls and the diaphragm divides the interior volume of the tank into two mutually fluid tight volumes that can be rendered fluid tight with respect to the space outside of the tank walls. 
     
     
         2 . The expansion tank of  claim 1  wherein the coupling ring comprises a substantially level surface connected to a circumferential wall of a tank segment and the opposing face comprises a pair of lips forming a mouth for holding in a sealing connection the peripheral edge of the diaphragm. 
     
     
         3 . The expansion tank of  claim 2 , further comprising a circumferentially extending clinch ring shaped so as to fit within the mouth of the coupling ring to tightly hold the peripheral edge of the diaphragm sealingly in place. 
     
     
         4 . The expansion tank of  claim 1  formed with a central cylindrical section and substantially hemispherically shaped end dome sections. 
     
     
         5 . The expansion tank of  claim 1 , wherein the shape of the thin walled tank is such as to be efficiently prepared for isotensoidal reinforcement by wrapping with equally stressed filaments. 
     
     
         6 . A method for forming the expansion tank of  claim 1 , the method comprising forming the central and end segments separately for forming an enclosed tank for holding a fluid and a gas in fluid-tight separation; forming a circumferential coupling ring sized to fit within and be tightly secured to the interior wall surface of a segment of the tank, the inner circumferential edge of the coupling ring formed into a mouth, and a diaphragm having a circumferentially extending peripheral edge sized to sealingly fit within the mouth of the coupling ring; securing to the inner surface of a tank segment the outer circumferential surface of the coupling ring, opposite the mouth portion holding the diaphragm edge; and combining the tank segments to form a thin-walled tank wherein the diaphragm is sealingly located internally of the tank walls to separate the inner tank volume into two mutually fluid-tight volumes for holding a liquid and a gas, respectively under pressure. 
     
     
         7 . The method of  claim 6  wherein the diaphragm and the coupling ring are separately formed and the circumferential, peripheral edge of the diaphragm is then sealingly secured in the mouth of the coupling ring. 
     
     
         8 . The method of  claim 6  wherein the diaphragm is separately formed and the and the coupling ring is then formed around circumferential, peripheral edge of the diaphragm so as to sealingly secure the circumferential, peripheral edge of the diaphragm in the mouth of the coupling ring. 
     
     
         9 . In an expansion tank for at least temporarily storing a pumped liquid under pressure, the expansion tank comprising a thin walled outer shell and a diaphragm located internally of the tank and secured to the inner surface of the shell of the tank to divide the internal volume of the tank into a fluid-tight section for holding a gas under pressure and a fluid-tight section for holding a liquid under pressure; the improvement comprising sealably securing the peripheral edge of the diaphragm to an internal, circumferential wall of a segment of the tank utilizing a tie layer that is mutually compatible with the material from which the inner circumferential surfaces of the tank segments are fabricated and with the material forming at least an outer surface of the peripheral edge of a diaphragm, the diaphragm being sealed in place so as to separate the inner volume of the tank into mutually fluid tight volumes, wherein the completed tank was formed by first connecting the diaphragm, to the inner wall surface of one of the tank segments utilizing the tie-layer, and then finally assembling the tank segments such that the diaphragm is sealed within the tank walls and the diaphragm divides the interior volume of the tank into two mutually fluid tight volumes that can be rendered fluid tight with respect to the space outside of the tank walls. 
     
     
         10 . The expansion tank of  claim 9  wherein the tie-layer is placed between the peripheral edge of a diaphragm and the wall of a tank segment such that the material compatible with the peripheral edge of the diaphragm is in contact with the diaphragm and the opposing face compatible with the tank segment inner wall surface is in contact with the wall. 
     
     
         11 . The expansion tank of  claim 9  formed with a central cylindrical section and a substantially hemispherically shaped end dome section. 
     
     
         12 . The expansion tank of  claim 9 , wherein the shape of the thin walled tank is such as to be efficiently prepared for isotensoidal reinforcement by wrapping with equally stressed filaments. 
     
     
         13 . The expansion tank of  claim 9 , wherein the tie layer is selected from the group consisting of acid-modified alkylene polymer, a NUCREL ethylene-acid copolymers, a terpolymer of ethylene/methacrylic acid/acrylic acid, modified acid olefinic polymers, acrylic acid- or anhydride grafted- olefinic polymers, DuPont's Bynel, Nucrel, and Fusabond grades, anhydride-grafted PE/PP copolymers, 
     
     
         14 . The expansion tank of  claim 9 , wherein the tie layer comprises two mutually compatible layers of material one of which is compatible with the material from which the inner circumferential surfaces of the tank segments are fabricated and the other of which is compatible with the material forming at least an outer surface of the peripheral edge of a diaphragm, or with the outer surface of a clinch ring gripping the peripheral edge of a diaphragm.