Abstract:
A water supply shut off system includes a water pressure delay device which delays the transmission of any apparent change in water pressure between the input and the output side of the valve to the control input of the valve. This delay allows the input and output pressures to have a chance to generally equalize without falsely tripping the device. The water supply shut off system can also include a thermal expansion/contraction device that allows thermal expansion and contraction of a fluid medium, such as water, when the shut off device is used with a device to be protected such as a hot water heater.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application Ser. No. 60/267,273 filed Feb. 8, 2001, which is fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to devices, such as valves, which shut off a supply of water or other fluid in the case of an unwanted leak or the like. 
     BACKGROUND INFORMATION 
     There are several known devices that attempt to shut off the flow of water to a device that may potentially leak, such as a hot water heater. The purpose of these devices is to ensure that the supply of water is provided to such devices only in the case of a legitimate demand from the user. These devices also prevent or stop the flow of water in the event of a leak, so that there will be no new water introduced into the system to feed the leaking device. 
     An example of such a device is applicant&#39;s own device disclosed in U.S. Pat. No. 6,021,808, which is fully incorporated herein by reference. Experimentation with such devices, however, has led to the discovery that there may be one or more instances when an unintentional “tripping” of the valve can occur even though there is not a true “fault” condition. Such a situation is often termed a “nuisance call” in the industry. 
     One manner in which such an unwanted fault can occur is when there is a significant pressure difference between the input and the output side of the valve. This can occur due to many reasons. For example, it may occur due to the fact that the output of the device, that is the side on the hot water tank, was filled during a time when the inlet water pressure was substantially lower. If the inlet water pressure rises some 10, 20 or more pounds above the output pressure, this can trick the valve into believing that there is a fault condition, thereby maintaining the valve closed, until reset manually. 
     A similar condition can occur in homes or businesses using private water supplies from wells or pumps. It is well known that water systems with wells or pump water experience significant fluctuations in water pressure. These fluctuations are due to the fact that the water pressure must drop low enough to trigger the pump to run long enough to fully pressurize or charge the water system. In either case, with several of the presently designed valves, the difference in the water pressure reaches the valve control line faster then the water pressure can equalize between the input and the output sides of the valve, causing a false triggering or tripping of the valve. 
     Accordingly, what is needed is a system, including one or more elements that can delay or slow down the system or drawn down water pressure from reaching the control line of such devices. This delay allows the water pressures to equalize between the input and output side of the valve, essentially eliminating false trigger conditions. 
     An additional concern with such devices is the thermal expansion and contraction, which occurs as a device to be protected, such as a water heater, heats water and shuts off. As is well known, heated water expands, while water contracts as it cools. Without a mechanism to control or account for the expansion and contraction of water, a device meant to prevent excess water leakage due to an unwanted event such as a leak will not work consistently well. Accordingly, another aspect of the present invention is to provide for and allow thermal expansion and contraction of water when used with a heating device such as hot water heater. 
     SUMMARY 
     In accordance with one aspect of the present invention, a fluid supply shut off valve system is used with a device to be protected. The system comprises a fluid monitoring device including a shut off valve, a main input, a main output, and a pressure sensor line. The shut off valve is in a normally closed position and opens to supply fluid from the main input to the main output in response to a drop in pressure sensed by the pressure sensor line on an output side of the device to be protected. The fluid monitoring device monitors a pressure differential between the main input and the main output and causes the shut off valve to remain closed when the pressure differential reaches a predetermined amount. The system also includes a delay device coupled to the pressure sensor line. The delay device delays the response to an increase in pressure at the output side of the device to be protected. 
     In accordance with another aspect of the present invention, the fluid supply shut off valve system comprises the fluid monitoring device and a thermal expansion/contraction device coupled between the pressure sensor line and the output side of the device to be protected. The thermal expansion/contraction device allows contracting fluid to be drawn back into the device to be protected. 
     According to a further aspect of the present invention, the fluid supply shut off valve system comprises the fluid monitoring device, the delay device and the thermal expansion/contraction device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein: 
     FIG. 1 is a schematic diagram of a valve incorporating the delay and expansion lines, according to one embodiment of the present invention; and 
     FIGS. 2 and 3 are schematic diagrams of a hot water system incorporating the valve, thermal expansion/contraction device and pressure delay device, according to one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In accordance with the teachings of the present invention, a fluid supply shut off valve system  100 , FIG. 1, is shown. The system  100  incorporates a supply pressure sensor line delay and a device allowing for the thermal expansion and contraction of water when used with a fluid monitoring device  10 . The fluid monitoring device  10  includes a main input or supply of water  12  and a main output  14  that flows to a device to be protected  16  such as a hot water heater. Although a hot water heater is utilized for exemplary purposes only, this is not a limitation of the present invention. 
     The fluid monitoring device  10  includes a supply pressure sensor line  18 , which senses the fluid or water pressure on the supply or output side  20  of the device  16  to be protected. One feature of the present invention is the incorporation of a water pressure delay device  22  in series with the supply pressure sensor line  18  and the output side  20  of the device to be protected  16 . The provision of the delay device  22  allows any pressure difference between the main input  12  (PI) and the main output  14  (P 2 ) to more closely equalize before the fluid pressure on the output side  20  of the device  16  is measured at point P 3  on the fluid monitoring device  10  as supplied by the supply pressure sensor line  18 . 
     The delay device  22  can be implemented in any number of fashions. The function of the delay device  22  is to delay any instantaneous change in pressure on the supply or output side  20  of the device being to be protected  16  from reaching the supply pressure sensor line  18  at point P 3  on the fluid monitoring device  10 . The delay device  22  can include one or more of the following: air bladders; water bladders; and “drippers” which may include pressure and non-pressure compensating devices which provide a reduced constant or non-constant flow of water or other fluid and act as a labyrinth which causes the water or other fluid medium to travel through a maze or series of channels within the drippers. Such drippers or labyrinths may be used alone or in combination with other devices including an air bladder or water bladder to help effectuate the delay. In addition, other items may be utilized to achieve the same purpose. 
     It should also be understood that the delay device(s) may be provided as separate elements that is, separate and apart from a fluid monitoring device  10 . Alternatively, one or more of the delay devices may be incorporated into and formed as an integral part of the fluid monitoring device  10 . 
     An additional feature of the present invention is a thermal expansion/contraction device  24 , which, in one embodiment, may be provided on the supply or output side  20  of the device to be protected  16 . Normally, the supply side  20  of the device to be protected includes one or more check valves  26  which prevents contracting water from being drawn back into the device to be protected  20 . By providing the thermal expansion/contraction device  24 , contracting water may be drawn back into the device to be protected  16  through the supply side  20 , as will be explained in greater detail below in connection with FIG.  2 . 
     Alternatively, a thermal expansion/contraction device  42  can be coupled to the fluid monitoring device  10 . The thermal expansion/contraction device  42  is provided in a thermal expansion route or line  40 , which is coupled to a supply line  28 . The thermal expansion takes place up through the main output  14 , the thermal expansion/contraction device  42 , and the thermal expansion line  40 . One embodiment of the thermal expansion/contraction device  42  is a labyrinth. In this embodiment, a thermal expansion shut off mechanism  44  is coupled to the shut off mechanism in the fluid monitoring device  10 . When the fluid monitoring device  10  closes, the shut off mechanism  44  shuts off to prevent water from the thermal expansion/contraction device  42  from trickling back into the device to be protected  16 . This shut off mechanism  44  works similar to and in conjunction with the shut off mechanism used in the fluid monitoring device  10 . 
     FIG. 2 shows one embodiment and implementation of the supply pressure sensor line delay device  22  and the thermal expansion/contraction device  24  according to one embodiment of the present invention. As is shown, the device to be protected  16  is shown as a hot water tank, for exemplary purposes only. The fluid monitoring device  10  is installed in the cold water supply line  12 / 14  to the device to be protected  16 . 
     As shown, the delay device  22  comprises of one or more devices such as a labyrinth or dripper  30  and a water hammer or other similar device  32 , such as the type manufactured by Zilmet or Amtrol. A supply line  28  taken from the fluid monitoring device  10  is provided for several reasons. The first reason is to ensure that the pressure of P 1  from the main input  12  can be provided to the control input P 3  of the fluid monitoring device  10  through the delay device  22 . It also allows for thermal contraction of heated water. Lastly, it allows for leaking faucets and compensates for any pressure lost through leaking faucets to be sure that the monitoring device  10  will still operate properly. 
     As previously mentioned, another feature of the present invention is the provision of the thermal expansion/contraction device  24  to compensate for thermal contraction. In the preferred embodiment, the thermal expansion/contraction device  24  includes a water expansion tank, which allows heated water to expand into the device  24 . The expansion/contraction device  24  can also be a labyrinth. Once the water cools, the thermal expansion/contraction device  24  allows the same water to flow back as shown by arrows  34  into the device to be protected  16 , e.g., the hot water tank or other device. 
     In another embodiment shown in FIG. 3, the delay device  22  includes a labyrinth  52  and a buffer or bladder device  54 . The labyrinth  52  ensures less flow and the bladder device  54  ensures that the supply pressure sensor line  18  does not fill too quickly. This provides the proper amount of pressure between the check valves  26   a ,  26   b.    
     Accordingly, the fluid supply shut off valve system of the present invention provides a delay to allow water pressure to equalize between the input and output side of the shut off valve, thereby preventing false triggers. The fluid supply shut off valve system of the present invention also accounts for the thermal expansion and contraction of water. 
     Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.