Abstract:
A flood prevention system includes a double-latching solenoid valve that shuts off a water supply line in response to a moisture sensor detecting a leak in a plumbing system. The double-latching feature provides the solenoid&#39;s plunger with two positions of equilibrium. This minimizes electrical power consumption so that the flood prevention system can be battery operated. To minimize a buildup of hard water deposits, the valve includes a flexible diaphragm and is cycled periodically regardless of whether flooding occurs. The sensor includes multiple methods of mounting to a floor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention generally pertains to water control valves and more specifically to a system for automatically closing a valve in response to sensing a flooding condition. 
     2. Description of Related Art 
     Various systems have been developed to prevent flooding caused by a leak in a building&#39;s plumbing system. Without flood protection, even a small leak in a water line, water heater, or washing machine can cause substantial damage to a home if the leak occurs while the family is gone on vacation or if the house is left vacant for another reason. Thus, flood prevention systems preferably operate reliably and without attendance 24 hours a day, seven days a week for months or even years. 
     If a normally open valve is used to shutoff the water supply in response to a leak, it may be years before the valve is ever energized. During the extended period of inactivity, working members of the valve may deteriorate or become jammed with hard water deposits, and the problem may not be discovered until flooding occurs. 
     If a normally closed valve is used, the valve may need to be kept energized continuously for years, which could make a battery-operated system impractical. If a power failure occurs, the valve may close and leave a family without water as well. 
     If a flood prevention system includes a moisture sensor, the method of mounting such a sensor can be important. If the sensor is simply placed on the floor, the sensor may get washed away or otherwise dislodged. On the other hand, if the sensor is permanently attached to the floor, routine mopping of the floor may trigger the system, and the sensor may be difficult to dry until the floor dries. 
     SUMMARY OF THE INVENTION 
     To provide an improved flood prevention system, an object of some embodiments is to minimize the power consumption of the overall system. 
     Another object of some embodiments is to use a shutoff valve with a solenoid having two equilibrium positions, whereby the valve can maintain its open and closed positions without electrical current. 
     Another object of some embodiments is to provide a flood prevention system that uses such a minimal amount of current that the system can be battery operated. 
     Another object of some embodiments is to use a touch-and-hold fastener for removably attaching a moisture sensor to a floor. 
     Another object of some embodiments is to use an adhesive to hold a portion of the touch-and-hold fastener to the floor. 
     Another object of some embodiments is to provide a moisture sensor with a screw-receiving hole that offers second choice of attaching the sensor to the floor. 
     Another object of some embodiments is to periodically cycle the shutoff valve of a flood prevention system to help clear the valve of any hard water deposits. 
     Another object of some embodiments is to open and close a solenoid valve by simply reversing the polarity of the voltage used for actuating valve. 
     Another object of some embodiments is to minimize the electrical power required to actuate a valve by using a valve that is pilot operated. 
     Another object of some embodiments is use a valve having a diaphragm that is more flexible than hard water deposits, whereby the hard water deposits may tend to break off and separate from the diaphragm. 
     One or more of these and other objects of the invention are provided by a flood prevention system that includes double-latching shutoff valve that responds to a moisture sensor. To minimize a buildup of hard water deposits, the valve includes a flexible diaphragm and is cycled periodically. The sensor includes multiple methods of mounting to a floor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic diagram of an automatic flood prevention system. 
     FIG. 2 is a cross-sectional view of a shutoff valve in an open position. 
     FIG. 3 is the same as FIG. 2 but with the valve closed. 
     FIG. 4 is a perspective view of a moisture sensor. 
     FIG. 5 is a control algorithm of a controller used in the system of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1-5, a plumbing system  10  is provided with a flood prevention system  12  that helps prevent a leak in plumbing system  10  from flooding a floor  14 . Plumbing system  10  can be any network of pipes that includes a water supply line  16  that feeds various water-handling appliances such as a water heater  18 , clothes washer, dishwasher, water softener, toilet, bathtub, shower, sink, etc. Flood prevention system  12  comprises a shutoff valve  20  connected to supply line  16 , a moisture sensor  22  for detecting water on floor  14 , and a controller  24  that controls the operation of valve  20  in response to moisture sensor  22  and a manual reset  26 . 
     Controller  24  is schematically illustrated to represent any logic device adapted to provide one or more outputs in response to one or more inputs. Examples of controller  24  include, but are not limited to, a computer, microcomputer, microprocessor, PLC (programmable logic controller), dedicated analog or digital circuit, and various combinations thereof In some embodiments of the invention, controller  24  includes a PIC16C711-04/P-ND programmable chip by Microchip of Chandler, Ariz. Controller  24  is shown connected to an electrical power source  28 , which in some embodiments is a battery or an electrical outlet. 
     Moisture sensor  22  includes two or more spaced-apart, electrically conductive surfaces  30  and  32  that overlay a relatively nonconductive base plate  34 . Two wires  36  and  38  connect surfaces  30  and  32  to an input  40  of controller  24 . To detect moisture, controller  24  determines whether the electrical resistance across surfaces  30  and  32  has dropped to a predetermined limit (e.g., 40 kohms), which would indicate that sufficient moisture exists to create a conductive path between surfaces  30  and  32 . 
     To install sensor  22 , a touch-and-hold fastener  42 , such as VELCRO, is attached to the underside of base plate  34 . An upper portion of fastener  42  is bonded to the underside of plate  34 , while a mating lower portion of fastener  42  has an adhesive  44  for bonding to floor  14 . As with conventional touch-and-hold fasteners, the two portions of fastener  42  releasably engage each other, which allows base plate  34  to be removably attached to floor  14 . Base plate  34  also includes a screw-receiving hole  46  that allows a screw, nail, or other type of fastener to mount sensor  22  more securely to floor  14 . 
     To minimize electrical power consumption, shutoff valve  20  is a pilot-operated valve actuated by a double-latching solenoid  48 . The term, “double-latching” refers to a solenoid with a plunger  50  having two positions of equilibrium. That is, electrical power is used to move plunger  50  between its two positions; however, electrical power is not needed to hold plunger  50  at either of its two positions. In some embodiments, a positive voltage pulse retracts plunger  50  to open valve  20 , and a negative voltage pulse extends plunger  50  to close the valve. An example of such a solenoid can be found on a Series-993 solenoid valve provided by Evolutionary Concepts, Inc., of San Dimas, Calif. The valve portion without the solenoid can be provided by the B &amp; C Valve Company, International, of Shawnee Mission, Kans. 
     Valve  20  comprises a valve body  52  having a water inlet  54  and a water outlet  56 . To selectively open and close the passageway between inlet  54  and outlet  56 , valve  20  includes a valve seat  58  with an adjacent diaphragm  60  that can move between an open position (FIG. 2) and a closed position (FIG.  3 ). Diaphragm  60  includes two orifices  62  and  64 , which help determine the pilot pressure that pushes down against diaphragm  60 . Orifice  62 , being open to inlet  54 , tends to feed the pilot pressure. Orifice  64 , on the other hand, tends to bleed off the pilot pressure when orifice  64  is open. When plunger  50  retracts, as shown in FIG. 2, orifice  64  is open to reduce the pilot pressure, whereby the water pressure underneath diaphragm  60  is sufficient to hold the diaphragm up and away from valve seat  58 . When plunger  50  extends, as shown in FIG. 3, it closes orifice  64 . However, since orifice  62  still remains open, pilot pressure builds up across substantially the entire upper surface of diaphragm  60 , which pushes diaphragm  60  down against valve seat  58 . By using water pressure to open and close valve  20 , less electrical power is needed, so a battery-operated system becomes more feasible. 
     Valve  20  is schematically illustrated in FIG. 1, wherein valve  66  represents the opening and closing of diaphragm  62  relative to valve seat  58 , item  68  represents the pilot pressure that pushes downward against diaphragm  60 , item  70  represents the pilot pressure that pushes upward against diaphragm  62 , valve  72  represents plunger  50  opening and closing orifice  64 , and detents  74  represent the two equilibrium positions of the solenoid&#39;s plunger  50 . 
     To control the operation of system  12 , controller  24  may follow the algorithm of FIG.  5 . The process begins with block  76  starting a timer and block  78  opening valve  20 . To open valve  20 , controller  24  provides at output  80  a momentary valve-opening signal, such as 50-msec 12-volt positive voltage pulse. Wires  82  then convey the voltage pulse to solenoid  48  to retract plunger  50 . In some embodiments, controller  24  provides a brief negative voltage pulse immediately preceding the positive pulse. The brief negative pulse helps initiate movement of plunger  50 ; however, the positive pulse is still used to fully retract the plunger. 
     Next, logic block  84  determines whether the timer has reached a predetermined limit (e.g., a 20-day period). If so, block  86  cycles valve  20  a few times to help clear the valve of any hard water deposits. Block  88  then resets the timer to start another 20-day period, and the logic returns to block  78  to ensure that valve  20  is open after the cycling process. 
     If the timer has not expired, decision block  90  determines whether the electrical resistance of sensor  22  is less than a predetermined limit (e.g., 40 kilo-ohms). If sensor  22  is dry, the logic returns to block  84 . If, however, sensor  22  is wet and its electrical resistance is below the predetermined limit, block  92  closes valve  20  by providing a momentary valve-closing signal at output  80 . The valve-closing signal may be a 50-msec 12-volt negative voltage pulse, which extends plunger  50 , as shown in FIG.  3 . In addition, block  94  energizes an audible and/or visual alarm. Valve  20  remains closed and the alarm remains on until block  96  determines that reset  26  has been actuated. Reset  26  can simply be a manually operated electrical switch that is wired to an input  98  of controller  24 . Once reset, block  100  de-energizes the alarm, and the logic returns to block  78 . Block  78  then reopens valve  20  to restart the flood monitoring process. 
     Pipe threads  102  and  104  of FIG. 2 illustrate connecting double-latching solenoid valve  20  to water supply line  16 ; block  78  of FIG. 5 illustrates opening the double-latching solenoid valve by providing a first momentary voltage signal thereto; leaving block  78  illustrates discontinuing the first momentary voltage signal while leaving the double-latching solenoid valve open; block  90  illustrates sensing moisture adjacent to the floor; in response to sensing moisture on the floor, block  92  following block  90  illustrates closing the double-latching solenoid valve by providing a second momentary voltage signal thereto; leaving block  92  illustrates discontinuing the second momentary voltage signal while leaving the double-latching solenoid valve closed; and block  86  illustrates periodically cycling the double-latching solenoid valve during a period when substantially no moisture is sensed. 
     Although the invention is described with reference to a preferred embodiment, it should be appreciated by those skilled in the art that various modifications are well within the scope of the invention. For example, the illustrated algorithm is just one of many control schemes that can be used, and various other algorithms can be readily applied by those skilled in the art. Therefore, the scope of the invention is to be determined by reference to the claims that follow.