Expansion tank with a piston

Abstract

The herein described apparatus is a novel expansion tank and method for use with a water system. The housing of the expansion tank contains a spring biased piston. When the water pressure of the system is sufficient to overcome the spring's resistance, the piston will be compressed against the spring allowing water to flow into the expansion chamber. As the water pressure of the system decreases, the spring will bias the piston towards its rest position and force water from the expansion tank. By using a piston in place of the prior art rubber diaphragm a more robust mechanism to contain water resulting from thermal expansion is provided.

1 : An expansion tank for use with a fluid system having variable pressures and a predetermined safe upper-limit pressure, said expansion tank comprising:
 a housing defining a port, an internal side wall, an external wall, an upper internal space, and a lower internal space, wherein said port is in fluid communication with the fluid system and said lower internal space;   a piston slidably carried within said housing having a top surface, a bottom surface and an annular side wall;   means for urging said piston toward said lower internal space;   wherein when the predetermined safe upper-limit pressure is reached or exceeded within the fluid system, fluid flows through said port into said lower internal space thus urging against said piston and causing said piston to be displaced thereby reducing the pressure within the fluid system.   
     
     
         2 : The expansion tank of  claim 1 , wherein said piston defines said upper internal space and said lower internal space, and wherein said upper internal space is fluidly sealed from said lower internal space; 
     
     
         3 : The expansion tank of  claim 2 , further comprising at least one o-ring positioned on said annular side wall of said piston. 
     
     
         4 : The expansion tank of  claim 1 , wherein said piston has a quasi-crescent shaped bottom surface. 
     
     
         5 : The expansion tank of  claim 1 , wherein said means for urging said piston is a spring. 
     
     
         6 : The expansion tank of  claim 5 , wherein said spring is positioned on said top surface of said piston within said upper internal space. 
     
     
         7 : The expansion tank of  claim 1 , further comprising means for testing the pressure within said expansion tank. 
     
     
         8 : An expansion tank for use with a water heater (tank type) having variable pressures and a predetermined safe upper-limit pressure, said expansion tank comprising:
 a housing defining a port, an internal side wall, an external wall, an upper internal space, and a lower internal space, wherein said port is in fluid communication with the water heater tank and said lower internal space;   a piston slidably carried within said housing having a top surface, a bottom surface and an annular side wall;   a spring carried on said top surface of said piston within said upper internal space for urging said piston toward said lower internal space;   
       wherein when the predetermined safe upper-limit pressure is reached or exceeded within the water heater, fluid flows through said port into said lower internal space thus urging against said piston and causing said piston to be displaced thereby reducing the pressure within the water heater. 
     
     
         9 : The expansion tank of  claim 8 , wherein said piston face has a concave depression 
     
     
         10 : The expansion tank of  claim 8 , further comprising at least one o-ring positioned on said annular side wall of said piston wherein said upper internal space is sealed from said lower internal space. 
     
     
         11 : The expansion tank of  claim 8 , further comprising means for testing the pressure within said expansion tank. 
     
     
         12 : A method of reducing the pressure within a fluid system, comprising the steps of:
 a) obtaining an expansion tank comprising:   a housing defining a port, an internal side wall, an external wall, an upper internal space, and a lower internal space, wherein said port is in fluid communication with the fluid system and said lower internal space;   a piston slidably carried within said housing having a top surface, a bottom surface and an annular side wall;   means for urging said piston toward said lower internal space;   wherein when the predetermined safe upper-limit pressure is reached or exceeded within the fluid system, fluid flows through said port into said lower internal space thus urging against said piston and causing said piston to be displaced thereby reducing the pressure within the fluid system; and   b) attaching said expansion tank to be in fluid communication with said fluid system via said port.   
     
     
         13 : The method of  claim 12  further comprising the step of coating at least a portion of the interior walls of said housing that may come into operational contact with said piston with an insoluble lubricant. 
     
     
         14 : The method of  claim 12  further comprising the step of vacuum sealing at least a portion of said housing.