Abstract:
Valve for the periodic and cyclic or otherwise intermittent release of a fluid is described along with an irrigation sprinkler incorporating the valve. The valve opens when a critical pressure level is reached in a reservoir attached to the valve, thereby permitting a portion of the fluid contained within the reservoir to be released through the valve. As the fluid is released, the pressure in the reservoir decreases. The valve does not close until the pressure level in the reservoir reaches a second pressure level that is below the critical pressure level. When the reservoir is refilled from a pressurized source at a controlled rate that is less the rate at which the fluid is expelled through the valve when open, the valve will cycle repetitively.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is related to U.S. patent application Ser. No. 10/824,171, entitled “Apparatus for Intermittent Liquid Dispersal” filed on Apr. 13, 2004 now U.S. Pat. No. 6,981,654, which claims priority from U.S. patent application Ser. No. 09/885,378, entitled “Apparatus for Intermittent Liquid Dispersal” filed on Jun. 19, 2001 now U.S. Pat. No. 6,732,947, which claims priority from U.S. Provisional Patent Application No. 60/212,896, entitled “Apparatus for Periodic Liquid Dispersal” filed on Jun. 20, 2000; the disclosures of each of these applications are hereby incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The disclosure herein relates generally to intermittent liquid dispersal and more particularly to intermittent liquid dispersal for irrigation and pest control. 
       BACKGROUND 
       [0003]    A wide variety of irrigation systems are commercially available for use in watering crops, plants, and lawns. Sprinkler-based systems are generally the most popular, although systems that deposit water directly on the ground are also utilized, such as drip systems. In either case these systems are often automated so that they irrigate an associated area on a periodic basis without substantial human intervention. 
         [0004]    Automated systems typically comprise an electronic controller and solenoid valve electrically coupled to the controller. The solenoid valve is typically located inline with a pressurized source of water. In operation, the valve opens to allow water to flow from the source, through a conduit, and out one or more sprinkler heads or drip emitters. When the cycle is complete, the controller signals the solenoid valve to close. Typically, these systems operate no more than a few times in day. A typical watering cycle may last anywhere from a few minutes to more than an hour. 
         [0005]    After a watering cycle has been completed, it is not uncommon for the ground to be soaked and saturated. In the intervening period between cycles, the soil can become arid, especially in hot and dry climates. Both saturated and arid ground conditions can be damaging to certain types of plants. For instance, a seedling without a developed root system can be dislodged from the soil if enough water is added to the ground to cause puddling. Additionally, if the ground around a seedling is allowed to dry completely for even a short period of time the seedling can quickly dehydrate and die. Furthermore, there are types of plants that have root systems that are very intolerant of saturated soil conditions and can be damaged if exposed to saturated soil on a regular basis. 
         [0006]    Ideally, it would be desirable to maintain soil at a predetermined and constant moisture level that is ideal for the plants growing therein. Increasing the frequency of irrigation cycles while reducing the time there between helps to maintain the soil at a more constant moisture level, but most electronic controllers are designed only to open an associated solenoid at most a few times every day. Even if controllers were available that allowed frequent watering cycles of short duration, the electronic solenoids generally available for use in sprinkler systems are not designed for continuous repetitive duty. 
         [0007]    Another drawback of electronic systems is that they require coupling to an electrical power source that may not be conveniently available. Additionally, the conduits of electrical current, such as the wires between the solenoid and the controller, must be protected from moisture and other potential sources of damage. These requirements of traditional automatic systems make them complicated and consequently difficult and expensive to install. Another problem that traditionally affects farmers and home gardeners alike is damage done to plants and crops by animals. It can be appreciated that animals in general will not bother plants or crops while a sprinkler is in operation because either they do not like the water or they are scared by sprinkler noise. Traditional sprinklers are relatively effective in deterring animals from entering an area being irrigated. Unfortunately, traditional sprinklers cannot be left on continuously for extended periods of time because of the amount of water used and the potential saturation of the underlying soil. Other objects, such as scarecrows, have very little effect on most animals. There are solutions that can be applied to the surfaces of plants that make them undesirable to animals, although the nature of the solutions often preclude there use on crops that are to be consumed by humans. 
       SUMMARY 
       [0008]    According to the present disclosure there is, therefore, provided an intermittent liquid dispersal device as described in the specification and accompanying claims. 
         [0009]    In an example of the present disclosure, a device for the intermittent dispersal of a fluid may include a housing with an inlet, to receive a fluid placed under increasing pressure. The housing may have an outlet to disperse the fluid. The housing may include a longitudinal bore extending through the housing and intersecting with a transverse bore forming the outlet. The longitudinal bore may have a first diameter and a second diameter in fluid communication with the inlet. The device may include a piston head at least partially contained within the longitudinal bore of the housing. The piston head may be movable (i) from a closed position to an open position when the fluid pressure equals or exceeds a first pressure level, and (ii) from an open position to a closed position when the pressure is less than or equal to a second pressure level. The second pressure level may be lower than the first pressure level. The piston head may include a first seal which obstructs the flow of the fluid from the inlet to the outlet in response to the piston head being in the closed position. The piston head may permit the flow of fluid from the inlet to the outlet in response to the piston head being in the open position. The first seal may contact the first bore diameter in the closed position. The first seal may move out of the first bore diameter in the open position. 
         [0010]    In accordance with various embodiments, the first diameter of the longitudinal bore is smaller than the second diameter of the longitudinal bore. The piston head may further include a second seal in contact with the second diameter of the longitudinal bore. The second seal may maintain contact with the second diameter of the longitudinal bore in both the open position and closed position thereby obstructing fluid from flowing out of the longitudinal bore. The first seal may have less contact with the longitudinal bore in the open position than in the closed position thereby reducing friction between the first seal and the longitudinal bore in the open position. 
         [0011]    In accordance with various embodiments, the first diameter of the longitudinal bore and the second diameter of the longitudinal bore may meet at a transition located between the inlet and the transverse bore. The transition may be a surface connecting a wall defining the first diameter of the longitudinal bore and a wall defining the second diameter of the longitudinal bore. The transition surface may be approximately 45 degrees from a plane perpendicular to the longitudinal bore. 
         [0012]    In accordance with various embodiments, the first seal may be located within a first groove around the piston head with the first groove having a first diameter. The second seal may be located within a second groove around the piston head with the second groove having a second diameter. The second groove may be larger in diameter than the first groove thereby causing an outer circumference of the second seal to extend farther from the axis of the piston head than an outer circumference of the first seal. This difference in circumferences between seals may cause the second seal to have tighter fit in the second diameter of the longitudinal bore than the fit of the first seal. 
         [0013]    In accordance with various embodiments, the device may include a valve stem connected to the piston head and extending out of the housing opposite the inlet and along the longitudinal bore. The valve stem may pass through a first magnet assembly and connect to a second magnet assembly such that the second magnet assembly moves in relation to the valve stem which in turn moves the piston head. The device may include a cap which attaches to a top portion of the housing located opposite the inlet. The first magnet assembly may be sandwiched between the cap and the housing. The attraction between the first magnet assembly and the second magnet assembly forms at least a portion of a retention force to hold the piston head in the closed position against the fluid under increasing pressure. The piston head may move toward the open position when the retention force is met. The device may include a reservoir in fluid communication with the inlet. The reservoir may be adapted to contain a compressible medium and to receive a fluid providing an increasing pressure in the reservoir. The reservoir may supply the fluid placed under increasing pressure received by the inlet. The compressible medium and the fluid may be separated by an expandable bladder  1114  which limits the fluid from absorbing the compressible medium. The reservoir may be a tank positioned vertically such that the bladder  1114  uniformly expands within the tank without being substantially biased in one direction due to gravity. 
         [0014]    In an example of the present disclosure, a device for the intermittent dispersal of a fluid may include a housing with an inlet, to receive a fluid placed under increasing pressure. The device may have an outlet to disperse the fluid. The housing may include a longitudinal bore extending through the housing and intersecting a transverse bore forming the outlet. The device may include a piston head at least partially contained within the longitudinal bore of the housing. The piston head may be movable (i) from a closed position to an open position when the fluid pressure equals or exceeds a first pressure level, and (ii) from an open position to a closed position when the pressure is less than or equal to a second pressure level. The second pressure level may be lower than the first pressure level. The piston head may include a first seal and a second seal. The first seal may be seated more tightly in the longitudinal bore in response to the piston head being in the closed position than compared to the seating of the first seal in the longitudinal bore in response to the piston head being in the open position. The second seal may maintain substantially the same fit within the longitudinal bore regardless of whether the piston head is in the closed position or the open position. 
         [0015]    In accordance with various embodiments, the longitudinal bore may include a first diameter and a second diameter with the first diameter being smaller than the second diameter. The first seal may obstruct the flow of the fluid from the inlet to the outlet in response to the piston head being in the closed position. The first seal may permit the flow of fluid from the inlet to the outlet in response to the piston being in the open position. The first seal may contact the first bore diameter in the closed position. The first seal may move out of the first bore diameter in the open position. The first seal may have less contact with the longitudinal bore in the open position than in the closed position. The piston head may include a second seal in contact with the second diameter of the longitudinal bore. The second seal may maintain contact with the second diameter of the longitudinal bore in both the open position and closed position thereby obstructing fluid from flowing out of the longitudinal bore. 
         [0016]    In accordance with various embodiments, the first diameter of the longitudinal bore and the second diameter of the longitudinal bore may meet at a transition located between the inlet and the transverse bore. The transition may be a surface connecting a wall defining the first diameter of the longitudinal bore and a wall defining the second diameter of the longitudinal bore. The transition surface is approximately 45 degrees from a plane perpendicular to the longitudinal bore. 
         [0017]    In accordance with various embodiments, the first seal may be located within a first groove around the piston head. The second seal may be located within a second groove around the piston head with the first groove having a first diameter and the second groove having a second diameter. The second groove may be larger in diameter than the first groove thereby causing an outer circumference of the second seal to extend farther from the axis of the piston head than an outer circumference of the first seal. This difference in outer circumference may cause the second seal to have tighter fit in the second diameter of the longitudinal bore than the fit of the first seal within the second diameter of the longitudinal bore. 
         [0018]    This summary of the disclosure is given to aid understanding, and one of skill in the art will understand that each of the various aspects and features of the disclosure may advantageously be used separately in some instances, or in combination with other aspects and features of the disclosure in other instances. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present disclosure will now be described by way of example only with reference to the following figures in which: 
           [0020]      FIG. 1  is an isometric view of an embodiment of a pressure-activated magnetic valve. 
           [0021]      FIG. 2  is an exploded isometric view of the embodiment of a pressure-activated magnetic valve illustrated in  FIG. 1 . 
           [0022]      FIG. 3A  is an isometric view of an embodiment of a valve housing. 
           [0023]      FIG. 3B  is a top view of an embodiment of a valve housing. 
           [0024]      FIG. 4  is an isometric view of an embodiment of a valve stem. 
           [0025]      FIG. 5  is an isometric view of an embodiment of a piston. 
           [0026]      FIG. 6A  is an isometric view of an embodiment of a magnet cap. 
           [0027]      FIG. 6B  is a top view of an embodiment of a magnet cap. 
           [0028]      FIG. 7A  is a cross-sectional view of the pressure-activated magnetic valve of  FIG. 1  taken along line A-A illustrating the valve in the closed position. 
           [0029]      FIG. 7B  is a cross-sectional view of the pressure-activated magnetic valve of  FIG. 1  taken along line A-A illustrating the valve in the open position. 
           [0030]      FIG. 8  is a cross-sectional view of an embodiment of the reservoir of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    The disclosure herein relates generally to intermittent liquid dispersal and more particularly to intermittent liquid dispersal for irrigation and pest control. The device includes a valve that is actuated by an actuation force (A) that is the result of a pressure buildup in the incoming fluid. The pressure buildup surpasses a retention force (R) created by two opposing magnetic assemblies, thereby causing the valve to open. This subject matter is related to U.S. Pat. No. 6,981,654 and U.S. Pat. No. 6,732,947, which are incorporated herein by reference. These patents may form a background and foundation to the disclosure discussed herein. The various aspects, embodiments, examples, structures, and configurations discussed herein may be applicable and/or interchangeable with the embodiments or disclosure presented in these related patents. 
         [0032]      FIG. 1  illustrates a perspective view of a pressure-activated magnetic valve (“valve”)  1010 . The valve  1010  is operable as an intermittent liquid emitter valve. The valve  1010  is supported by a base  1014 . The base  1014  may be any support that is operable to suspend other components off the ground. For example, the base  1014  may suspend a mounting platform  1015 . The base  1014  may form a wide support structure under the mounting platform  1015 . A wide support structure may be operable to keep the mounting platform  1015  from tipping over due to pressure fluctuations in the attached flow channels discussed in more detail below. In one example, base  1014  may include a plurality of support columns  1014   a - d . The support columns  1014   a - d  may be positioned around the perimeter of the mounting platform  1015 . 
         [0033]    The valve  1010  may also include a valve housing  1020 . The platform  1015  may support and elevate valve housing  1020 . For example, platform  1015  and support columns  1014   a - d  may elevate valve housing  1020  off the ground such that a fluid flow Y can enter the valve  1010  without significant interference from the ground or similar obstacles. 
         [0034]    The valve housing  1020  may be connected to one or more fluid outlets. For example, a fluid outlet  1022   a  and a fluid outlet  1022   b  may exit the valve housing  1020  on radially opposing sides. The one or more fluid outlets may direct a fluid flow X out of the valve housing  1020  into fluid channels extending to a fluid dispersion system (e.g. a sprinkler system). 
         [0035]    The valve  1010  may also include a valve stem  1032  which extends through the valve housing  1020 . A first magnet assembly  1058  may be aligned over the valve stem  1032 . The magnet assembly  1058  may be positioned between the platform  1014  and a cap  1044 . A second magnet assembly  1060  may be positioned adjacent the first magnet assembly  1058 . The second magnet assembly  1060  may also be positioned on the valve stem  1032 . In various embodiments the second magnetic assembly  1060  may be fixed relative to the valve stem  1032  and the first magnetic assembly  1058  may be fixed relative to the valve housing  1020 . For example, clamp  1093  may inhibit the second magnetic assembly  1060  from being removed from the valve stem  1032 . The valve stem  1032  may be movable relative to the valve housing  1020 . The first magnetic assembly  1058  and the second magnetic assembly  1060  may be positioned to provide a force between themselves which limits the movement of the valve stem  1032  from moving upwardly until the force between the two magnetic assemblies  1058 , 1060  is overcome. 
         [0036]    The valve housing  1020  may be in fluid communication with a reservoir  1112  via the fluid line  1147 . The fluid line  1147  may provide a fluid under increasing and decreasing pressure to the valve housing  1020  at the bottom portion  1026 . The reservoir may be operable to provide the increase and decrease in pressures which actuates the valve. 
         [0037]      FIG. 2  is an exploded isometric view of the embodiment of a pressure-activated magnetic valve  1010  illustrated in  FIG. 1 . The valve  1010  may include the valve housing  1020 . The valve housing  1020  may be connected to inlet channel  1012  and fittings  1022   a,b . The valve housing  1020  may be mounted to platform  1015  which may be elevated by base supports  1014   a - d . A locking threadable nut  1125  may be threaded onto the valve housing  1020 . The nut  1125  may restrain the housing  1020  while assembling the magnetic assembly  1058  over the valve housing  1020 . The nut  1125  may be position between the magnetic assembly  1058  and the valve housing  1020 . 
         [0038]    Fittings  1022   a,b  may be connected to liquid distribution channels  1023   a,b . The valve stem  1032  by be located through valve housing  1020 . A piston head  1090  may be located on the first end of the valve stem  1032 . A first seal  1050  (e.g. an o-ring) may be located around the piston head  1090  in a first groove  1095 . A seal  1052  may be located around the piston head  1090  in a second groove  1094 . 
         [0039]    An elastomer tube  1098  may be positioned adjacent to the piston head  1090  at the connection between the piston head  1090  and the valve stem  1032 . The valve stem  1032  may axially align with the cap  1044 . The cap  1044  may center the first magnet assembly  1058  in axial alignment with the valve housing  1020 . The first magnet assembly  1058  may include one or more magnets (e.g.  1058   a - f ). The valve stem  1032  and piston head  1090  may articulate relative to the first magnet assembly  1058 . The valve stem  1032  may axially align with a second magnet assembly  1060  fixedly connected thereto. The second magnet assembly  1060  may include one or more magnets (e.g.  1060   a - f ). Any number of magnets may be used or any size of magnets may be used. Modifying the size, number, or strength of the magnets may adjust the force between the first magnet assembly  1058  and the second magnet assembly  1060 . The magnets may be any shape and side and connect to the valve stem  1032  in any way. The magnets may have apertures. If larger than the valve stem  1032 , the magnet apertures may utilize additional hardware (e.g. washers) to adapt the large apertures to the valve stem  1032 . The connection may occur by restraining the second magnet assembly  1060  on the valve stem  1032  by placing clamps  1093 ,  1092  above and below the second magnet assembly  1060 . The clamp  1092  below the second magnet assembly  1060  may be position on an elastomer tube  1091  located around a groove (See  FIG. 3  groove  1035 ) cut in the valve stem  1032 . The clamp  1093  above the magnet assembly  1060  may realize lower forces than the clamp  1092  below the magnet assembly  1060 . As such, a clamp  1093  alone may be position above the second magnet assembly  1060  to keep it in place relative to the valve stem  1032 . Although a similar configuration to the clamp, tube and groove ( 1092 ,  1091 , and  1035  respectively) from below the second magnet assembly  1060  may be likewise applied above as well. Elastomer tubes  1091  and  1098  provide a cushion as the valves articulate since the elastomer tubes  1091  and  1098  contact the cap  1044  when the piston head  1090  articulates in one direction or the other. Elastomer tube  1098  limits the travel by contacting the cap  1044  in the upward direction. Elastomer tube  1091  limits the travel by contacting the cap  1044  in the downward direction. 
         [0040]    In accordance with various embodiments, a liquid distribution channel  1023   a  may axially align with a male pipe coupling  22   a . Likewise, a liquid distribution channel  1023   b  may axially align with a male pipe coupling  22   b . These connections may be accomplished by any variety of hydraulic connections, including for example threaded fittings. The liquid distribution channel  1023   a,b  or conduit may be fluidly coupled with the outlet port  1022   a,b . In one example, the channels  1023   a,b  may be defined by a polyethylene tubing, which may be bent, such as through use of a heat gun, into a variety of distribution patterns according to the needs of a particular user. It is envisioned that other conduits, such as stainless steel, rubber hose, pre-formed tubing, adjustable tubing, ball-and-socket piping, and the like may be used. In the various embodiments, the channels  1023   a,b  may extend transversely from the valve  1010  and then bend upwardly and substantially vertically, with the end of the channel  1023   a,b  generally above the valve  1010  so as to allow unimpeded liquid distribution from a sprinkler head such as those discussed in related embodiments. 
         [0041]      FIG. 3A  is an isometric view of an embodiment of a valve housing  1020 . As discussed above, the valve  1010  includes a valve housing  1020 . The valve housing  1020  may be any shape operable to flow a fluid through one or more channels. In various examples the valve housing  1020  may be an elongated cylindrical shape formed about a longitudinal axis. The valve housing  1020  may include a top surface  1029 . The valve housing  1020  may include a longitudinal bore  1030 . In various examples, the longitudinal bore  1030  may be formed along the longitudinal axis of the cylindrical shape. In various examples, the longitudinal bore  1030  may be any channel passing through the valve housing  1020  that is operable to receive the valve stem  1032  and/or the piston head  1090 . The valve housing  1020  may include at least one outlet port  1022   a . In various examples, the valve housing  1020  may include diametrically-opposing outlet ports  1022   a ,  1022   b  defined by walls  1056   a ,  1056   b  (shown in  FIG. 3B ). The outlet ports may be a transverse bore passing through the longitudinal bore  1030  in a substantially perpendicular orientation. In various embodiments the transverse bore may be at an angle to the longitudinal bore  1030 . In various embodiments, the transverse bore may not extend linearly through but the bore defined by wall  1056   a  may be an angle to the bore defined by wall  1056   b . In various embodiments, the valve housing  1020  may include any number of outlet ports  1022   a,b  required to facilitate a particular fluid distribution pattern. The outlet ports  1022   a,b  are located above the bottom threaded portion  1026  of the valve housing  1020 . Generally, the outlet ports  1022  are perpendicular to the longitudinal bore  1030  and the sidewall  1028  and form an aperture there between. Each outlet port  1022   a ,  1022   b  may have any diameter suitable to connection with plumbing and/or hydraulic fixtures such as the male pipe coupling  22   a ,  22   b . In various examples, each outlet port  1022   a ,  1022   b  may have diameter of suitable size to receive a barbed or threaded male coupling. 
         [0042]    The valve housing  1020  may include a top portion  1024  and a bottom portion  1026 . In various examples the top and bottom portions  1024 ,  1026  may be threaded. A sidewall  1028  may extend between the top portion  1024  and the bottom portion  1026 . In various examples, the side wall  1028  may be larger in diameter than the top portion  1024  and/or the bottom portion  1026 . The sidewall  1028  outer circumference and the top portion  1024  outer circumference may be connected by a flat surface  1027  forming a top to the sidewall  1028 . The top portion  1024  and bottom portion  1026  may be operable to receive any mechanical fitting including, for example, hydraulic fittings. The top portion  1024  may be sized to receive the cap  1044 . In various examples, the top portion  1024  may include a first set of threads that extend down a first distance from the top of the valve as shown in  FIG. 3A  and then a second set of threads that extend the remainder of the length of the top portion  1024 . The first set of threads may be 1 inch NPT tapered threads and the second set of threads may be 1 inch NPT straight threads. A similar configuration may be applied to the bottom portion  1026  or in accordance with various examples the bottom portion may have a single thread set such as NPT tapered threads extending the length of the bottom portion  1026 . The top portion and the bottom portion may extend the same length from the side wall  1028 . Alternatively, the two portions  1024 ,  1026  may be different lengths. The length of bottom portion  1026  may be minimized to decrease the length that valve housing  1020  extends below the support (e.g. platform  1015 ), but still be sufficiently long to receive a fitting such as the end of fluid supply conduit  1012 . The length of top portion  1024  on the other hand may be suitable to extend a portion of the distance through the first magnet assembly  1058  and receive the cap  1044  from the opposite side of the first magnet assembly  1058 . The cap  1044  may be threaded onto the top portion  1024  and sandwich the first magnet assembly  1058  and/or platform  1015  there between. 
         [0043]    As illustrated in  FIG. 3A , the longitudinal cylindrical longitudinal bore  1030  extends through the valve housing  1020  between the top portion  1024  and the bottom portion  1026 . The longitudinal bore  1030  is adapted to receive a valve stem  1032 . The longitudinal bore  1030  may be comprised of two bores  1030   a  and  1030   b . Stated another way, the longitudinal bore  1030  may have a first bore diameter  1030   a  and a second bore diameter  1030   b .  FIG. 3B  is a top view of an embodiment of the valve housing  1020  showing a first internal wall  1053  and a second internal wall  1057 . The first internal wall  1053  may define the first bore  1030   a . The second internal wall  1057  may define the second bore  1030   b . The first internal wall  1053  may have a larger diameter than the second internal wall  1057 . The first bore  1030   a  (and the corresponding first internal wall  1053 ) may meet and transition  1055  to the second bore  1030   b  (and the corresponding second internal wall  1057 ) at the transition  1055 . The transition  1055  may form a surface that connects the first diameter and the second diameter. In various embodiments the transition may be a surface at a 45 degree angle to an axis/plane that passes perpendicular to the longitudinal bore  1030 . The valve housing  1020  is typically fabricated from a polymeric material having a low coefficient of friction, such as Teflon™. 
         [0044]      FIG. 4  illustrates an isometric view of an embodiment of a valve stem  1032 . The valve stem  1032  may include an elongated cylindrical body  1033 . The valve stem  1032  may have a threaded end  1037  operable to engage a piston head  1090 . Intermediately along the body  1033 , the valve stem  1032  may include an annular groove  1035  operable to aid in positioning the second magnetic assembly  1060  above the groove  1035 . For example, a portion of tubing  1091  may be positioned over the groove  1035  and secured in place within the groove with a clamp  1092  (e.g. Oetiker clamp). The tube  1091  and the clamp  1092  may then support the magnet assembly  1060  above the groove. 
         [0045]    The valve stem  1032  may be fabricated from a rigid material that is resistant to corrosion from whatever fluid that is to be distributed from the valve  1010 . In one example, the valve stem  1032  may be made of stainless steel. The surface of the valve stem  1032  may be typically smooth to reduce its coefficient of friction, which provides smooth movement of the valve stem  1032  within the longitudinal bore  1030  and/or within the cap  1044 . The longitudinal bore  1030  may be an aperture with a diameter that is larger than the diameter of the valve stem  1032 , which substantially reduces or prevents any contact between the valve stem  1032  and the longitudinal bore  1030 . 
         [0046]      FIG. 5  is an isometric view of an embodiment of a piston head  1090 . The piston head  1090  may include an elongated cylindrical body  1096 . On a first end, the piston head  1090  may have a threaded aperture  1039  operable to engage the threaded end  1037  of valve stem  1032 . Intermediately along the body  1096 , the piston head  1090  may include a first annular groove  1095  operable to position first seal  1050  proximate the end of the piston head which is distal to the threaded aperture  1039 . In various examples, first seal  1050  may be an o-ring operable to seat and form a liquid tight seal within the second bore  1030   b . It may be noted that other seals such as a u-cup type seal may also be applicable. Intermediately along the body  1096 , the piston head  1090  may include a second annular groove  1094  operable to position the second seal  1052  proximate the threaded aperture  1039 . In various examples, the second seal  1052  may be a U-Cup type seal operable to seat and form a liquid tight seal within the first bore  1030   a . It may be noted that other seals such as an o-ring type seal may also be applicable. The first annular groove  1095  may be smaller in diameter than the second annular groove  1094 . The decrease in diameter may be directly related and/or proportional to the decrease in size between the first bore  1030   a  and the second bore  1030   b.    
         [0047]    In accordance with various embodiments, the piston head  1090  and the valve stem  1032  are separate devices that are merely able to connect to one another. The two devices may have different material properties. In accordance with various embodiments, the piston head  1090  and the valve stem  1032  are one contiguous device manufactured together such as being machined out of one piece of stock material. 
         [0048]      FIG. 6A  is an isometric view of an embodiment of a cap  1044 . The cap  1044  may include a bore  1031  which aligns with the longitudinal bore  1030  of valve housing  1020 . The bore  1031  may extend through a cap upper surface  1049 . A cap body  1041  may extend down from the upper cap surface  1049 . A cap lower portion  1043  may extend down from cap body  1041 . The cap body  1041  and cap lower portion  1043  may be different diameters. For example, the cap body  1041  may be larger in diameter than the cap lower portion  1043 . A lower exterior surface  1045  may connect the cap body  1041  and the cap lower portion  1043 . The lower exterior surface  1045  may be substantially parallel to the cap upper surface  1049 .  FIG. 6B  is a top view of an embodiment of a cap  1044 . The cap lower portion  1043  may be tubular aligned on the same axis of bore  1031 . The cap lower portion  1043  may have an interior wall  1042  that defines the interior cavity of the tubular nature of the cap lower portion. Interior wall  1042  may be threaded and operable to receive the top portion of valve housing  1020 , whereas the exterior surface of the lower cap portion  1043  may be operable to be inserted into the first magnetic assembly  1058 . The exterior surface of the cap lower portion  1043  may restrain the first magnetic assembly  1058  by engaging with their inner surface. The cap  1044  may have an interior surface  1047  which surrounds the bore  1031  on the inside of interior wall  1042 . Interior surface  1047  may be operable to engage the piston head  1090  on the end of valve stem  1032  and limiting the range of travel of the piston head  1090 . This limit to the range of travel may prevent or limit the piston head  1090  from being pushed out of the longitudinal bore  1030  by the fluid pressure within the valve housing  1020 . The valve stem  1032  may pass through bore  1031  which may be aligned with the longitudinal bore  1030 . In various examples, at least one magnet (e.g.  10580  may be attached to the cap  1044 , such as by a fastener (e.g. adhesive). Like the cap  1044 , the first magnet assembly  1058  and the second magnet assembly  1060  define an aperture in alignment with the cap bore  1031  that allows the valve stem  1032  to pass there through. 
         [0049]      FIG. 7A  illustrates a cross-sectional view of the pressure activated magnetic valve  1010  of  FIG. 1  taken along line A-A illustrating the valve  1010  in the closed position. As shown, the valve stem  1032  may project upwardly through the valve housing  1020 . The top portion of valve stem  1032  may pass through and/or be adjacent the top portion  1024  of the valve housing  1020 . The lower portion of the valve stem  1032  is adjacent the bottom portion  1026  of the valve housing  1020 . The piston head  1090  is connected to the threaded end  1037  of the valve stem  1032 . The first seal  1050  is secured around the first annular groove  1095  on the piston head  1090 . (In one example, the first seal  1050  may be a 50 durometer 0-ring with a high lubricity coating and/or a high lubricity Buna formulation). The first seal  1050  is positioned so that the first seal  1050  is located below the outlet ports  1022   a,b  when the valve stem  1032  is in the closed position as shown in  FIG. 7A . The first seal  1050  is positioned between the piston head  1090  and the second internal wall  1057  of valve housing  1020 . The first seal  1050  spans the gap between the outside diameter of the piston head  1090  and the inside diameter of the second internal wall  1057 . The first seal  1050  prevents fluid from flowing through the valve  1010  until the retention force (R) is met or exceeded by the activation force (A). To do this, the first seal  1050  blocks the portion of the bore above the first seal  1050  from fluid located below the first seal  1050 , to thereby prevent fluid from flowing through the valve  1010  until the A≧R. Since the first seal  1050  slides in the longitudinal bore  1030  with the piston head  1090 , a lubricant such as SuperLube™ by Synco Chemical Corp., may be applied to the first seal  1050  to facilitate smooth movement in the longitudinal bore  1030  and to help break in the first seal  1050 . Generally, the sealed or closed position of the valve  1010  (wherein water is not flowing through the outlet ports) is maintained while the retention force exceeds the pressure in the reservoir. 
         [0050]    The second seal  1052  is secured around the second annular groove  1094  on the piston head  1090 . The second seal  1052  is positioned so that the second seal  1052  is located above the outlet ports  1022   a,b  whether the valve stem  1032  is in the closed position as shown in  FIG. 7A  or in the open position as shown in  FIG. 7B . The second seal  1052  is positioned between the piston head  1090  and the valve housing  1020  the first internal wall  1053 . The second seal  1052  spans the gap between the outside diameter of the piston head  1090  and the inside diameter of the wall  1053 . By spanning this gap, the second seal  1052  better limits the intrusion of liquid out of the top of valve housing  1020 , which is generally an undesirable path for the liquid. As mentioned above, the second annular groove  1094  may be larger in diameter than the first annular groove  1095 . Additionally, as noted above, the first bore  1030   a  is larger in diameter than the second bore  1030   b . The effect is that, the second seal  1052  located over the second annular groove  1094  is forced into a larger external circumference by the larger diameter of the second annular groove  1094 . Forcing the second seal  1052  into a slightly larger external circumference enables the second seal  1052  to better engage the larger diameter of the longitudinal bore  1030   a . The first annular groove  1095  may be smaller in diameter than the second annular groove  1094 . As such, the first seal  1050  fitted into first annular groove  1095  may have a smaller exterior circumference which better fits within the second bore  1030   b.    
         [0051]      FIG. 7B  illustrates a cross-sectional view of the pressure activated magnetic valve  1010  of  FIG. 1  taken along line A-A illustrating the valve  1010  in the open position. In this open position, the piston head  1090  is above the fluid outlets  1022   a,b , allowing the fluid to flow in the direction X. In this position the A≧R causing the valve  1010  to open. The second seal  1052  maintains the same contact with first bore  1030   a  as it would in the valve closed position. The first seal  1050 , which is located around the smaller diameter of the first annular groove  1095  is positioned within first bore  1030   a  (i.e. the larger bore diameter). In this position the first seal  1050  makes less contact with the first internal wall  1053  of first bore  1030   a  than with the second internal wall  1057  of the second bore  1030   b , thus reducing the friction on the first seal  1050 . By reducing the friction on the first seal  1050  due to the larger diameter first bore  1030   a , wear is reduced prolonging the life of the first seal  1050 . Sealing against liquids passing out of the top of the valve housing  1020  is still provided because the second seal  1052  is in similar contact with first bore  1030   a  preventing the bypass of liquids. Additionally, the pressure differential between the pressure required to open the vale  1010  (i.e. A&gt;R) and the pressure required to close the valve (i.e. R&gt;A) is narrowed, because the reduction in friction within the valve reduces the force requirements to open and close the valve. Stated another way, the fluid pressure holding the valve open does not have to be reduced as much, due to less friction, in order to close the valve once it is open. 
         [0052]      FIG. 8  illustrates a cross section of a reservoir  1112 . An inlet valve allows fluid, such as water, to flow into the reservoir  1112  from a source of fluid, such as a standard garden hose fluidly connected with a domestic water tap. As discussed herein and in related embodiments, the liquid is prevented from flowing out of the outlet of the reservoir  1112  until a retention force (R) is met or exceeded by the pressure in the reservoir, which acts as an activation force (A) on the bottom of the valve stem  1032 . In the open position the R is lessened due to the distance between the magnets and may be references as RF. In the first embodiment, a partially elastic bladder  1114  within reservoir  1112  expands volumetrically when pressurized by fluid B. When the valve  1010  is opened, the elastic walls of bladder  1114  contract and force the water contained therein into the longitudinal bore  1030  as the walls contract into their nominal position. The contraction of the walls of bladder  1114  is aided by the compression of a compressible fluid A (e.g. air) within the reservoir  1112 . Accordingly, the reservoir  1112  contains a greater volume of water at the pressure when the valve opens than it holds at the pressure level at which the valve  1010  closes. It is generally the difference in these volumes that is expelled from the reservoir  1112  during each operational cycle of the valve  1010 . If a substantially rigid reservoir  1112  were utilized, very little water, perhaps a negligible amount, would be expelled from the rigid reservoir  1112  before the pressure therein dropped below the level at which the valve  1010  would close, since liquids are incompressible fluids. In embodiments of the invention adapted for use with compressible gaseous fluids, a rigid reservoir  1112  can be used since the expansion of the gas would act to maintain pressure therein. Furthermore, a rigid reservoir  1112  can be utilized with a liquid, if a portion of the reservoir  1112  contains a gas or other compressible medium, which expands as the liquid contained therein is expelled. In various embodiments, a clamp  1122  may attached the reservoir  1112  to the fluid line  1147 . 
         [0053]    The reservoir  1112  may be positioned in an upright position such that as the bladder  1114  expands it is not biased against the side walls of the reservoir  1112  by gravity. Avoiding bias against the sidewalls may extend the life of the bladder  1114  by reducing constant friction against the side walls during the constant expansion and retraction of the bladder  1114  during cycling of the system. In various embodiments, the reservoir  1112  may include a valve. In various examples, the valve  1123  may be positioned at the highest point on the reservoir  1112 . The valve  1123  may be a suitable valve to add air to the system. For example, the valve may be a Schrader valve which is operable to receive compressed air. 
         [0054]    Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example, and changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims. 
         [0055]    Many of the specific components utilized in the described embodiments are merely exemplary and other components may be substituted for them without deviating from the scope of the invention. For instance, the 0-ring seal can be replaced with any suitable type of sealing element that would prevent the fluid contained in the reservoir  1112  from flowing past it when the valve is in its closed position. Additionally, the materials that comprise the various components may vary. The valve housing which is made of Teflon™ in the embodiments described herein could be comprised of another polymeric material, such as ultra high-density polyethylene, or it could be comprised of a metallic material, such as brass. Likewise, the valve stem could be fabricated from a plastic or composite material instead of stainless steel. 
         [0056]    The valve is described above primarily in terms of a sprinkler system for the irrigation of lawns, plants, and/or crops. In addition to serving this purpose, alternative embodiments of the sprinkler system may be utilized to scare away critters and varmints that might disturb plants and crops in the area surrounding the sprinkler. It can be appreciated that the noise emanating from the valve as it opens and closes may be relatively loud depending on how the valve is designed and that this noise can be used to startle animals. If additional noise is desired, other noisemakers, such as bells, may be affixed to the valve stem to create additional noise as the valve is actuated. In other embodiments, the valve may be used for purposes unrelated to sprinkler systems or irrigation. It is contemplated that the valve may be utilized in any number of applications where a periodic controlled release of fluid is required from a pressurized source. The fluid may be either liquid or gaseous or a combination thereof. 
         [0057]    In one sense, the present invention is a valve for releasing a fluid from a pressurized source starting when the pressure in the reservoir  1112  reaches a first critical level and ending when the pressure of the fluid from its source drops below the critical level. The valve assemblies described above provide exemplary means for accomplishing the periodic release of a fluid from a pressurized source utilizing forces provided by weights and magnets. Other mechanisms, such as springs, electromagnetic, and the like, in lieu of magnets and weights are contemplated for providing a valve with similar functionality. The present invention although described in an upright position wherein the valve stem moves up and down in the barrel may also be oriented in other positions. The principles described herein will work in a similar manner. The magnetic force, however, might require adjustment to account for differences in gravitational effect. The present invention is useful where any periodic liquid dispersal is desired.