Patent Application
20130228579
This invention relates generally to water systems and more particularly to a water system expansion tank and method for use with a hot water heater.
Modern indoor plumping generally has a backflow preventer installed at or near the water meter to prevent water from a structure's water system from flowing out. The presence of a backflow preventer creates a closed system within the structure where the water system exists. Most interior water systems rely on a hot water heater to provide hot water to the structure. As the water continues to be warmed its density decreases and its volume increases, thereby generating pressure within the hot water heater's tank. To alleviate some of this pressure an expansion tank is made apart of the system thus providing more volume to contain the heated water. Without the expansion tank, pressure within the hot water heater can increases until the structural integrity of the heater is compromised. If the hot water heater becomes structurally compromised then severe water leakage can occur. Thus, the need for an expansion tank on closed water systems is known in the prior art.
An expansion tank is typically linked by a pipe to the hot water heater. The expansion tank is designed to contain excess water which is the result of thermal expansion. Thermal expansion occurs as a result of water being heated in the tank of the hot water heater. A prior art expansion tank typically uses a rubber diaphragm to divide the tank. One side of the tank is designed to receive expanding water from the water system to which it is attached. The other side of the diaphragm contains air under pressure. Water is not compressible, while air is. When heated water enters the expansion tank due to the resulting increase of water pressure it causes the diaphragm to flex against and compress the air cushion thereby allowing water to enter the tank. When the water system is opened through the use of a faucet or similar device, or the water cools, water leaves the tank and returns to the water system at large. This cycle occurs at a minimum, as frequently as the burner of the hot water heater is activated. As the rubber diaphragm flexes repeatedly under routine use it eventually tears or is otherwise compromised. Once the diaphragm wears out or ruptures the system fails resulting in pressurized water being expelled from the system into the surrounding area. The water leak could result in expensive water damage being caused to both the dwelling and other property contained therein. The cost of repair for such damage can range from $5,000-$70,000, or even more, with the average claim for water damage being $15,000 according to State Farm Insurance. As such the need for an expansion tank with a more robust means of receiving and releasing pressurized water exist.
An object of the present invention is to provide an expansion tank which overcomes the deficiencies found in the prior-art rubber diaphragm with a more robust spring-operated piston mechanism to regulate the flow of water into and out of the expansion tank.
The preferred embodiment of the present invention consists of a cylindrical housing which has an extension at one end that is configured to be connected to a water system. The interior of the cylindrical housing contains an aluminum piston which is in contact with the interior walls of the housing, effectively dividing the housing into two separate areas. The piston has two o-rings that occupy parallel planes about its periphery. The o-rings serve the purpose of preventing water from seeping around the face of the piston and collecting behind it, within the spring compartment. The walls of the housing are lubricated with an insoluble lubricant. The piston is acted on by a spring thereby pressing the piston towards the extension located at the bottom of the housing. The area between the back of the piston and the interior of the cylindrical housing contains the spring and is vacuum sealed. This area is generally referred to as the spring compartment. The piston face has a quasi-crescent shape which creates an air gap between itself and the water system. As expanding water enters through the provided opening into the interior of the cylindrical housing, the piston and spring are compressed thereby allowing the water to occupy the interior volume of the provided tank. When the system is opened, or the water cools, pressure within the system is thereby reduced. Water is expelled from the expansion tank once the force of the spring on the piston exceeds the force exerted by the water on the piston. Through the use of a spring powered aluminum piston the inherent weakness of a flexible rubber diaphragm are over come.
The foregoing it a broad outline of the significant features of the present invention, more pertinent and specific details of these features are discussed in the detailed description of the invention that follows. It should be understood by those skilled in the art that the disclosed preferred embodiment may be modified or used as a basis for designing other methods of constructing a similar device which is capable of fulfilling the same purpose. Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
The following detailed description of preferred and alternative embodiments is better understood when read in conjunction with the appended drawings. For the purposes of illustration, there is shown in the drawings exemplary embodiments; however, the subject matter is not limited to the specific elements and instrumentalities disclosed. In describing the preferred and selected alternate embodiments of the present invention, as illustrated in the Figures, specific terminology is employed for the sake of clarity. The invention, however, is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish similar functions.
It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended to define the limits of the invention.
Turning now to the figures in which like reference characters indicate corresponding elements throughout the several views, there is shown an expansion tank, generally designated by reference numeral 10, which consists of a cylindrically shaped housing, generally designated by reference numeral 20, that contains a piston 30 which is biased into position by a spring 50. The expansion tank is configured to be connected to a water system 60 through a threaded extension 28. As used herein, the word “bottom” corresponds to the portion of the housing 20 where the threaded extension 28 is located as shown in
Shown in
The spring 50 used with the preferred embodiment expansion tank 10 has a max load of 80 lbs and is manufacture from a stainless steel. It should be understood that any material suitable for use as a spring may be substituted. Further, the load weight of the spring may be selected based on the pressure generated by the water system 60 to which the expansion tank 10 is being incorporated.
The expansion tank 10 is assembled as follows. The bottom tank portion 46 and the top tank portion 44 are lubricated with an insoluble lubricant. An o-ring 38 of appropriate size is selected and placed into the o-ring grooves 36 present about the exterior side wall of the piston 30. Next, the piston 30 is placed into the interior of the bottom tank portion 46 and oriented such that its face 32 is oriented towards the bottom. The area between the face 32 of the piston 30 and the threaded extension 28 of the bottom tank portion 44 is generally referred to as the water pocket 24. A spring 50 is placed on top of the piston 30 and then covered by the top tank portion 44. Where the top tank portion 44 and the bottom tank portion 46 meet a seam is formed. At the seam the two tanks portions 44, 46 are welded together to form the housing 20 of the expansion tank 10. The area between the backside 40 of the piston 30 and the interior of the housing 20 is generally referred to as the spring compartment 22. Through the use of the port 42 located on the top tank portion 44 of the housing 20 the spring compartment 22 is vacuum sealed. It is to be understood that the spring compartment 22 does not have to be vacuumed sealed during assembly. Other ways of vacating air from the spring compartment 22 which are within the scope of the present invention are described in, but not limited to, those methods outlined in the alternate embodiments below.
In operation the housing 20 is threadedly secured to the water system 60 by the threaded extension 28, but other method routinely used to secure pipes together offer acceptable alternatives. After initial installation, water faucets may be opened to allow for air trapped in the water pocket 24 of the housing's 20 interior to be released from the water system 60 as a whole. The hot water heater has a thermostat which automatically activates a burner or series of burners to heat water contained within a tank. As the water heats it gradually expands through a phenomenon known as thermal expansion. This expansion of the water increases the internal pressure of the water system 60 as a whole and results in water being forced through the opening of the threaded extension 28 and into the interior of the housing 20. Initially the piston 30 is biased into its first position by the spring 50, shown in
The foregoing description and drawings comprise illustrative preferred and alternate embodiments of the present invention. Having thus described exemplary embodiments of the present invention, it should be noted by those skilled in the art that the within disclosures are exemplary only, and that various other alternatives, adaption's, and modifications may be made within the scope of the present invention. Merely listing the steps of the method in a certain order does not necessarily constitute any limitation on the order of the steps of the method. Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing description and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of I imitation. Accordingly, the present invention is not limited to the specific embodiments illustrated herein, but is limited only by the following claims.
