Abstract:
A water sensor and activation assembly including a paper element to sense the presence of water leaks from appliances such as clothes washing machines, refrigerator ice makers and the like, and to cause an associated water shutoff valve to turn off the source of water leakage. The water sensor, in conjunction with the shutoff valve, operates without any electrical power requirement. The design allows the water sensor to operate in a high humidity environment.

Description:
FIELD OF INVENTION 
     This invention relates to a water sensor that, when coupled with an appropriate water shutoff valve, forms a reliable safety shutoff system to protect against property damage due to water leaks. The function of the water sensor is to detect the presence of water leaking from an appliance such as a toilet tank, clothes washing machine, refrigerator ice maker, or the like, and to activate a shutoff valve. Because such water leaks often result in great property damage, it is of the utmost importance to have a leak detection system that is reliable and requires little maintenance. Most existing water sensors in the above applications utilize electronics to accomplish the water detection and activation. This sensor design, in conjunction with my previously patented shutoff valve, accomplishes the design goal without requiring electrical power. 
     DESCRIPTION OF PRIOR ART 
     Numerous patents have been issued dealing with water detectors that function over a wide variety of applications, such as life preserver activators and leak detection and water shutoff devices. The water sensor and activation mechanism to be described in this invention was developed as an improvement to the leak detector and shutoff valve systems of my previous Franklin patents, U.S. Pat. No. 6,792,967 and U.S. Pat. No. 7,082,959. These two patents describe water shutoff valve systems in which a water sensor, when exposed to water, releases a spring loaded mechanism that shuts off water flow through an associated water valve. The primary objective of these inventions was to provide a leak detection and shutoff system that did not require electrical power to operate, thus avoiding the associated complication and cost of such devices. 
     During the development process of the above two patented devices it was always the goal to explore other water sensors that would be improvements to the existing design. The Franklin patents described the use of sugar, salt, or other such substances that would dissolve when exposed to water. One design consideration that has been of concern when using any of the above water soluble elements has been the accumulation of moisture over a long period of time. It can be especially problematic in high humidity environments. Water soluble elements such as sugar or salt will tend to absorb moisture and change their physical structure, often by taking on a hardened crystalline form that requires long periods of time to dissolve when exposed to water. With this in mind, the development of a paper based system was explored. The paper used in the above applications has the property of losing its physical strength by yielding to a tension force when exposed to water. 
     SUMMARY OF INVENTION 
     The development of a satisfactory and reliable paper based water sensor to be used in conjunction with the above mentioned Franklin patents required a device that would fulfill at least two basic design requirements. First, the paper element, when subjected to spring tension, must not yield appreciably when placed in a high humidity environment, on the order of ninety-five percent relative humidity. Second, the springs used to exert pressure on the paper element must be of sufficient strength to overcome any static or dynamic friction exhibited by the cable and cable housing used to couple the water sensor to the shutoff valve. In addition, the spring force must be adequate to activate the trigger mechanism located in the shutoff valve. 
     The development process revealed that the spring force necessary to overcome the typical cable friction and trigger mechanism requirements, when applied to the water absorbent paper element, causes the paper element to elongate and often yield to the point of failure when subjected to high humidity conditions. Therefore, it became necessary to revise the design in a manner that would reduce the force on the paper element to an acceptable level, and yet retain the spring force necessary to overcome the friction forces and to activate the shutoff valve. 
     It was determined that the best way to accomplish the design requirements and still retain a simple yet reliable design was to split the spring force vectors necessary to, first, place tension on the paper element and, second, to activate the shutoff valve. It will be shown in the following description how that was accomplished. 
     SUMMARY OF INVENTION 
     The present invention utilizes two springs to exert force against a common bar structure hereinafter referred to as the force bar. Two other structures are integral parts of the force bar and extend in opposite directions from the midpoint of the force bar. One of these structures contains an inset pocket to accommodate the terminating clamp end of the activating cable that attaches to the water shutoff valve. The other structure extends in the opposite direction and has a wedge shaped end that fits into the matching wedge shape ends of two half sections of the sensor holder assembly. The two half section sensor holder elements are held together by multiple turns of a paper strip that is wrapped tightly around the sensor holders. The paper strip is typically one quarter inch wide with the external terminal end fastened with adhesive to keep the paper strip from unraveling. The opposite ends of the two sensor holder elements are likewise shaped to form a wedge configuration and mate with the corresponding angle of another pointed element that forms part of the water sensor body. It will be seen that this configuration allows the force of the two springs to act in a manner that not only exerts an axial force against the sensor holder elements but also applies a right angle, lateral force that attempts to pry the two sensor holder elements apart. The amount of exerted lateral force is a function of the wedge angle. The overall wedge angle determined to be optimum in this application is about one hundred twenty degrees, however it should be understood that other angles may provide satisfactory operation. From an intuitive standpoint, it can be seen that if the wedge angles were increased to nearly one hundred eighty degrees, there would be very little lateral force attempting to pry the two sensor holder half sections apart. Most of the force would be axial in direction. On the other hand, if the wedge angles were decreased to say, twenty degrees, the dominant force would be trying to pry the sensor holder half sections apart. Thus it can be seen that the outward force that tries to separate the sensor holders can be adjusted by varying the wedge angle, yet still retaining the primary spring force necessary to activate the shutoff valve via the interconnecting cable when the paper element yields and disintegrates under exposure to water. Calculations indicate that the use of a one hundred twenty degree wedge angle results in only about forty percent of the primary spring force being applied toward separation of the sensor holder halves. This reduced force allows the paper element to remain intact in a high relative humidity environment, yet disintegrate when directly exposed to water. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a bottom view of the water sensor assembly of the present invention with the bottom cover removed to display the inner structures of the sensor prior to being exposed to water. 
         FIG. 2A  shows an enlarged perspective view of the sensor holders of the present invention prior to being moved together in position for installation of the paper used as a water sensor material. 
         FIG. 2B  shows an enlarged perspective view of the sensor holders of the present invention to aid in explaining the method of attaching and wrapping the beginning end of the paper sensor material. 
         FIG. 2C  shows an enlarged perspective view of the sensor holders of the present invention to aid in explaining the method of wrapping and attaching the terminating end of the paper sensor material. 
         FIG. 2D  shows an enlarged cross sectional drawing of the two sensor holders of the present invention to display how the paper sensor material is wrapped around the two water sensor holders and fastened thereon. 
         FIG. 3  shows a bottom view of the water sensor assembly of the present invention with the bottom cover removed to display the inner structures of the sensor after the assembly has been exposed to water. 
         FIG. 4  shows a cross-sectional side view of the water sensor assembly of the present invention. 
         FIG. 5A  shows a top view of the water sensor assembly of the present invention to display the window used to indicate if the water sensor assembly has been activated. 
         FIG. 5B  shows a cutaway view of the top view of the water sensor assembly of the present invention to facilitate explaining the location of the indicating means used to indicate if the water sensor assembly has been activated. 
         FIG. 6A  shows a portion of  FIG. 1  pertaining to the sensor holder and the associated force exerted on same. 
         FIG. 6B  shows a section of  FIG. 6A  for the purpose of describing the independent forces exerted on each half of the sensor holder. 
         FIG. 6C  shows a set of force vectors applied to the surface of the sensor holder of the present invention for the purpose of describing the forces and associated equations used to determine the effect of the sensor holder surface angle on the lateral force exerted on same. 
         FIG. 7  shows the water sensor assembly of the present invention connected to a shutoff valve via an interconnecting cable. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows the bottom view of the water sensor assembly of the present invention, generally indicated  8 , with the bottom cover removed to expose the internal structures of the water sensor and activation mechanism. Outer enclosure  9  of the water sensor body serves to house both the water absorbing material and the spring mechanism. Springs  10  and  11  are shown in compression and exert pressure at points  12   a  and  12   b  of the force bar  12 . The selected dimensions and material composition of springs  10  and  11  were largely empirically determined. The spring material used is typically stainless steel because of the moist environment where the water sensor assembly  8  might be located, thereby reducing, the possibility of rust. The springs  10  and  11  are compressed during assembly of the water sensor assembly  8  to a length that produces the desired force yet does not exceed the maximum deflection allowed by the manufacturer&#39;s specifications. The force bar  12  has two structures extending to the right, and left from its midpoint  12   c . The right hand structure  12   d  includes a section of force bar  12  that contains an inset pocket  13  used to contain a terminating clamp  14  that is fastened to cable  15 . Cable  15  exits the sensor assembly via cable adapter  16 . The cable  15  is housed in a tubular encasement  17 . The cable  15  and tubular so encasement  17  are used as connecting means between the water sensor assembly  8  and the water shutoff valve to be described later. 
     The left hand structure  12   e  of the force bar  12  has a tip  19  that is wedge shaped to make direct contact with surfaces  19   a  and  19   b  of the sensor holders  21  and  22  respectively. The wedge shaped surfaces  20   a  and  20   b  on the left end of the sensor holder sections  21  and  22  make contact with the mating, pointed surfaces of pressure point  24  that is an integral part of the outer enclosure  9 . Multiple layers of paper  23  are tightly wrapped around the two sensor holder sections  21  and  22 . The external, terminal end of the paper  23  is glued in place to prevent the paper layers from unraveling as will be explained later. 
     From the above description it can be seen that the force exerted by springs  10  and  11  on the force bar  12 , and hence on the force bar extension  12   e , will attempt to separate the two sensor holders  21  and  22 . The paper  2 . 3  restrains the lateral movement of the two sensor holders  21  and  22 . It should also be noted that the wedge angle formed on both the left and right hand surfaces  19   a ,  19   b ,  20   a  and  20   b  of the sensor holders  21  and  22  acts to determine the percentage of total force exerted by springs  10  and  11  that will actually try to force the sensor holders  21  and  22  apart. In this manner, by changing the wedge angle, one can control the tension force exerted on the paper  23 , with a larger wedge angle resulting in a reduced, lateral separating force. 
       FIG. 2A  is an enlarged view of the sensor holders  21  and  22  separated from each other to show their relative position and shape before being moved together in position for installation of the water sensor paper to be shown later as item  23 . It should be noted that both sensor holders  21  and  22  are identical in shape and size. This not only facilitates assembly but reduces parts cost. 
       FIG. 2B  is an enlarged view of the separate sensor holders  21  and  22  to better display how the paper  23 , used as a water sensor, is wrapped around and fastened to the sensor holders  21  and  22 . An appropriate adhesive material such as commercially available instant glue is applied at the start end  23   a  of the water sensor paper  23  to prevent the paper from slipping during the wrapping procedure. 
       FIG. 2C  is a duplication of  FIG. 2B  to show how the water sensor paper  23  is wrapped around the sensor holders  21  and  22  and fastened by gluing at location  23   b , thereby preventing the paper from unraveling. The number of layers of sensor paper  23  wrapped around the sensor holders  21  and  22  is arbitrarily determined, and dependent upon the type of paper used and the desired time between exposure to water and sufficient disintegration of the paper material to cause triggering of the associated water shutoff valve to be described later. The type of paper used during the development of water sensor assembly  8  was standard twenty-four pound inkjet copier paper. Three layers of the copier paper provided an acceptable trigger time of between five and fifteen, seconds when, exposed to water. 
       FIG. 2D  shows an enlarged cross sectional view of the two sensor holders  21  and  22  as viewed relative to the sectional line  30  shown in  FIG. 2C . It can be seen in  FIG. 2A ,  FIG. 2B , and  FIG. 2C  that the sensor paper  23  is wrapped in horizontal guide area  31  and vertical guide area  32  and around the perimeter of sensor holders  21  and  22  to hold them together. The protruding areas  33  and  34  at the bottom of the sensor holders extends the position of the sensor paper at point  23   c . As will be seen later, when the sensor holders are installed in the water sensor assembly  8 , this provision allows the sensor paper at point  23   c  to be located in closer proximity to the floor surface where any leaking water will accumulate. To simplify the drawing, only one layer of paper  23  is shown wrapped around the perimeter of the sensor holders  21  and  22 . It should be understood that additional layers of paper  23  could be used. Point  23   a  represents the location for the initial gluing of the sensor paper  23  and point  23   b  represents the terminating glue point as previously described. 
       FIG. 3  again shows the bottom view of the water sensor assembly  8  with the bottom cover removed, but now displaying the condition in which water has caused the paper element  23  to partially disintegrate, thereby allowing the sensor holders  21  and  22  to separate. This permits the pointed end  19  of force bar extension  12   e  to move in a leftward direction due to the force of springs  10  and  11 . This leftward movement of force bar  12  also causes the terminating clamp  14 , and hence the cable  15 , to be pulled in tension to the left in such a manner as to activate the shutoff mechanism of the associated water valve to be explained later. 
       FIG. 4  is a cross-sectional view of the water sensor assembly  8  as viewed upward from the sectioning line  18  of  FIG. 3 , and displays the orientation of the spring.  11  and other internal structures relative to the outer enclosure  9  and the bottom cover  25 . In the condition shown, the paper element  23  has not been exposed to water. The bottom edges of the sensor holders  21  and  22  are shaped in such a manner as to allow the water sensing surface  23   c  of paper element  23  to protrude slightly into the opening  26  of bottom cover  25  as previously described in  FIG. 2D . This arrangement allows the water sensing surface  23   c  to be in closer proximity to the floor surface  29 . The protrusions  30   a  and  30   b  of the outer enclosure  9  provide spacing between the bottom cover  25  and the floor surface  29 , thereby facilitating water flow toward the paper element  23 . If desired, the vertical thickness of the force bar  12   e  can be approximately the same as the vertical dimension of the sensor holders  21  and  22 , thereby optimally distributing the force exerted by the force bar  12   e  upon the sensor holder surfaces  19   a  and  19   b  as shown in  FIG. 1 . 
       FIG. 5A  is the top view of the generally indicated water sensor assembly  8 . A viewing port  27  in the outer enclosure  9  provides a means of determining if the water sensor has been activated. For example, in the normal, standby condition, the color exposed through the viewing port  27  would be green colored. If the water sensor assembly  8  was exposed to water and the water sensor paper  23  disintegrated sufficiently to trigger the associated water shutoff valve to a closed condition, the color displayed in viewing port  27  would change to red, for example. Since the water sensor assembly  8  is often positioned in locations that are visible, but not readily accessible, the ability to easily view the status of the water sensor assembly  8  is important. 
       FIG. 5B  again shows the top view of water sensor assembly  8 , but now provides a cutaway view of the underside area  12   d  of the previously described force bar  12 . The underside of the right structure  12   d  of force bar  12  of  FIG. 1 , contains two colored surface sections  28   a  and  28   b . In the normal, non-activated condition of the water sensor a green color  28   a , for example, would be visible through the viewing port  27 . Again for example, when the water sensor assembly  8  has been exposed to water and the paper element  23  has partially or totally disintegrated, allowing the force bar  12  to move to the left, a red color  28   b  would be visible through the viewing port  27  shown overlaid on  28   a.    
     In the event a water leak is detected and the water sensor assembly  8  activates the water shutoff valve, there must be a provision to reset the system once the source of the water leak has been repaired and any resulting water has been removed. In such an event, there are two obvious solutions, the first being to simply remove and replace the entire water sensor assembly  8  by disconnecting it from the cable attachment. The second solution is to provide a design in which the sensor holder half sections  21  and  22 , along with the paper  23  form a replaceable assembly (not shown). 
       FIG. 6A  shows a portion of  FIG. 1  that includes the sensor holder sections  21  and  22 , and an associated force vector F 1 . Force vector F 1  exerts a force leftward against the wedged shaped surface of the sensor holder sections  21  and  22 , and results from the total force exerted by the springs  10  and  11  shown in  FIG. 1 . 
       FIG. 6B  further enlarges the wedged shaped surfaces  19   a  and  19   b  of the sensor holder sections  21  and  22  respectively to demonstrate that the force vector F 1 , shown in  FIG. 6A , can actually be divide into two separate vectors, each with a magnitude of one-half of the force of force vector F 1 . The purpose in doing this is to facilitate calculating the lateral force exerted against the surface  19   b . Once that, is determined, then the total lateral force attempting to separate the two halves of the sensor holder sections  21  and  22  is simply twice the calculated value. 
     Next,  FIG. 6C  shows the isolated surface  19   b  of the lower sensor holder section  22 . The first calculation functions to determine what portion, of force vector F 1 / 2  is perpendicular to surface  19   b , namely, what is the value of F 2 . This is accomplished via Equation 1 of  FIG. 6C . Next, using Equation 2, one can determine the value of force vector F 3 , which will represent one half of the total lateral force exerted by force vector F 1 , and which is attempting to force the two sensor holder sections apart. 
     As an example, using a total wedge angle between the two sensor holder sections  21  and  22  of 90 degrees, that is a 45 degree surface angle θ, the effective lateral force exerted to separate the two sensor holders would be one half, or fifty percent of the force vector F 1 . As another example, using a total wedge angle of 120 degrees, that is a 60 degree angle θ, the effective lateral separation force vector F 1  would be approximately 0.43, or 43 percent of the force vector F 1 . Although the effect, of changing the wedge angle should be intuitive, these calculations will mathematically substantiate the results. In actual testing it was found that a wedge angle of 120 degrees proved satisfactory, however it should be understood that other angles may also function satisfactorily. 
       FIG. 7  shows the water sensor assembly, generally indicated  8 , attached to a water valve assembly, generally indicated  35 , via interconnecting cable assembly, generally indicated  53 , which houses internal cable  15  and its tubular encasement  17  as described and shown in  FIG. 1 . 
     The water valve assembly  35  is shown as an example of how the water sensor assembly  8  interacts with a water shutoff valve  36 . The water valve assembly  35  has a main shutoff valve body  36  with a water inlet port  37  and the water flow direction indicated by arrow  38 . Likewise there is an output port  39  with a water flow direction indicated by arrow  40 . 
     The water valve configuration show in  FIG. 7  is based on a modified version of the shutoff valve described in my previous Franklin patent U.S. Pat. No. 7,082,959. As shown in that patent, magnet holder  41  contains two magnets  42  and  43  that are used to control the position of an internal magnet (not shown) that is housed within column  44 . The internal magnet functions to open and close a pilot aperture that determines whether the valve is open or closed to fluid flow. Magnet holder  41  slides up and down on column  44 , and in its shown position allows the internal magnet, contained within column  44 , to open the shutoff valve  36  to fluid flow. Magnet holder  41  is fastened to a reset shaft  45  at location  46 . Reset shaft  45  is spring loaded in a downward direction by reset spring  51 . Reset button  52  is threaded onto the lower end of the reset shaft  45 . Slide latch  48  has a latch point  49  that is shown inserted into recessed area  47  of reset shaft  45 . This restricts the downward movement of reset shaft  45 . 
     When the water sensor assembly  8  is exposed to water, and its internal activation mechanism is triggered as previously explained, it pulls on the cable  15  of the cable assembly  53 . The end of cable  15 , located within the shutoff valve  36  and shown attached to the clamp  50 , is pulled in a rightward direction thereby causing slide latch  48  to move rightward and disengages latch point  49  from the recessed area  47  of the reset shaft  45 . Reset spring  51  now forces the reset shaft  45  and hence the magnet holder  41  in a downward direction. This movement causes the previously described internal magnet to move in a manner to close the internal pilot valve aperture and causes the valve  36  to close itself to fluid flow. 
     As previously described, once the water sensor assembly  8  is exposed to water and the water shutoff valve  36  is activated via interconnecting cable assembly, generally indicated  53 , there is a need to restore the system to a normal condition. Once the source of the water leak has been repaired, and the wet area dried, the water sensor assembly  8  would be replaced by attaching a new assembly  9  at the end of the cable assembly  53 . The water shutoff valve  36  must also now be reset to restore water flow. This is accomplished by moving the reset button  52  in an upward direction, allowing the slide latch  48  and latch point  49 , to return to their locking position. The magnet holder  41 , being restored to its upward position, will cause the internal pilot valve aperture to open, thereby restoring water flow through the valve. 
     In summary, the foregoing disclosure describes a novel water sensing assembly that when exposed to a fluid, such as wafer, causes the tensile strength of the paper element to decrease to the point where the layer or layers of paper separate and unravel. The separation and unraveling of the paper element occurs as a result of the lateral force exerted on the paper holders, and hence the paper element, by a wedge shaped structure whose source of axial motion is provided by one or more springs normally held in compression. Other possible configurations could allow the source of axial motion to be produced by a spring or springs in tension. The axial motion of the aforementioned wedge shaped structure also provides the force necessary to activate an associated water shutoff valve via a cable arrangement. The incorporated wedge shaped structure reduces the force exerted on the paper element to a level that allows the paper to tolerate a high humidity environment without disintegrating. This reduced tension is accomplished without reducing the primary spring tension required to activate the associated water shutoff valve. Another feature of this invention is that it provides an inexpensive means of activating a water shutoff valve without the use of electrical power. It should be understood that anyone skilled in the art might use a switching means to detect when the water valve has been shut off to activate an audible and/or visual alarm. The description of this invention is illustrative and not limiting; further modifications will be apparent to one skilled in the art, in the light of this disclosure and the appended claims.