Abstract:
The present invention illustrates an irrigation valve that operates at low flows by providing a guide washer of the valve assembly that prevents diaphragm extrusion. Specifically, the circular channel area of a guide washer of the valve includes spoke-like fins. These fins keep the diaphragm from extruding into the open channel over time, while allowing for easy guide washer manufacturing.

Description:
FIELD OF THE INVENTION 
   This invention relates to an irrigation valve for controlling the flow of water through piping of an irrigation system. More particularly, this invention relates to an irrigation valve with improved operation at low water flows. 
   BACKGROUND OF THE INVENTION 
   Flow control valves are a well known and integral part of most irrigation systems. A typical example can be seen in U.S. Pat. No. 6,394,413 to Lohde, et al, herein incorporated by reference. 
   These valves control the flow of water through an upstream pipe and thereby turn sprinklers fed by the pipe on and off. Such valves are usually remotely actuated by control signals sent from an automated irrigation controller. Often, these control signals are electric impulses sent from the controller to a solenoid in the valve which ultimately controls whether the valve is open or closed. 
   Pilot-activated diaphragm-operated valves for use in irrigation systems are well known. One example can be seen in U.S. Pat. No. 3,336,843, herein incorporated by reference. 
   This style of valve has a closure member with a sealing surface which moves against or away from an annular seat to close or open the valve, respectively. Integral to the closure member is a diaphragm positioned to seal off an upper portion of the valve. When the valve is to be opened, the fluid pressure is relieved by bleeding fluid out of the diaphragm chamber through a manual valve or a remotely operated solenoid valve. Relieving this pressure allows the closure member to move upwards as water passes through the valve. 
   To save on manufacturing expenses and also to avoid the negative effects of material warpage and deformation, the closure member must be molded in such a way that it has a constant wall thickness, resulting in open channels or spaces, commonly called “material savers.” What has been discovered, however, is that over time, the diaphragm may extrude into these channels or spaces. This extrusion increases tension on the diaphragm, preventing valve closure at low water flows. 
   Some prior art valves available on the market today prevent the diaphragm extrusion into the closure member by providing a separate plastic insert into the inner channel of the guide washer. While this method prevents diaphragm extrusion, it presents increased manufacturing expense and difficulties by presenting another plastic part to design and injection mold. Further, the manufacturing conditions for both the closure member and the insert must be highly controlled and precise, otherwise the insert will fit poorly within the closure member, risking inefficient or faulty valve operation. 
   Therefore, what is needed is a single piece closure member that is easily manufactured, yet also prevents diaphragm extrusion within the closure member. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an improved valve that closes properly under low flow water conditions. 
   It is a further object of the present invention to provide an improved valve that continues to close at low water flows over an extended period of time. 
   The present invention seeks to address the above described problems and others not specifically enumerated here by providing a valve having an improved closure member, the preferred embodiment of which are described below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross sectional view of an irrigation valve of the prior art; 
       FIG. 2  is a cross sectional view of an irrigation valve as shown in  FIG. 1  with a diaphragm extruded into a closure member; 
       FIG. 3  is a cross sectional view of one embodiment of the present invention; 
       FIG. 4  is a plan view of a valve diaphragm of the prior art; 
       FIG. 5  is a plan view of a typical valve diaphragm assembly of the prior art; and 
       FIG. 6  is a plan view of one embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  illustrate a prior art irrigation valve  100  in the closed position. This irrigation valve  100  includes a water inlet port  114 , a water outlet port  115 , and a guide washer  102  that includes a sealing surface  103 . Typically the sealing surface  103  is made from a rubber or other resilient material. 
   The valve is actuated by a solenoid  112  that is connected to a solenoid plunger  108  which controls the opening and closing of a discharge port  107 . In the closed position, the solenoid plunger  108  blocks a passage  150  that otherwise connects a diaphragm chamber  109  (located above a diaphragm  101 ) to the discharge port  107  and to the valve water outlet port  115 . 
   The valve assembly  120  seals off the diaphragm chamber  109  from the lower portion of the valve. As seen in  FIG. 5 , the valve assembly  120  is made up of a diaphragm retaining cap  117  which sits over a diaphragm  101 . Beneath the diaphragm sits a guide washer  102  having an inner circular channel  110 . Retained in the guide washer  102  is a sealing surface  103 . The sealing surface  103  is secured to the guide washer  102  with a valve washer  118  and metering insert  106 . 
   The diaphragm  101  is typically composed of a semi elastic material such as rubber. Such elastic material allows the diaphragm to flex as the valve assembly  120  rises up to an open position and down to a closed position. The diaphragm is secured in the valve  100  between the upper portion  205  of the valve  100  and the lower portion  207  of the valve  100 . These two halves are secured together with screws (not shown). As seen in  FIGS. 1 and 2 , a properly secured diaphragm creates the upper diaphragm chamber  109 . 
   As best seen in  FIGS. 1 and 2 , metering pin  105  is located within the center of valve assembly  120 . The clearance  104  between the metering insert  106  and metering pin  105  allows water to enter into the diaphragm chamber  109 . The diameter of the metering pin  105  may be changed to let varying amounts of water into the diaphragm chamber  109 , thus controlling the pressure within the diaphragm chamber  104 . 
   In the closed position, the water pressure in the diaphragm chamber  109  is equal to the water pressure in the valve through water inlet port  114 . In contrast, the water pressure of diaphragm chamber  109  is much less than the pressure of water entering through the water inlet port  114  when the valve is set to the open position as discussed below. The pressure is lower due to the pressure drop that occurs when the water flows through the clearance  104 . 
   In operation, a water supply is connected to water inlet port  114 , and further portions of an irrigation system are connected to water outlet port  115 . When the solenoid  112  is un-energized, the solenoid plunger  108  is biased to cover and seal the discharge port  107 . As water enters from the water inlet port  114 , it travels through the clearance  104  of the metering insert  106 , into the diaphragm chamber  109 . Simultaneously, due to losses resulting from flow of water, the pressure of the inlet port  114  drops while passing between the seal surface  103  and valve seat  121 , causing an annular area of low pressure  152 , which helps the diaphragm assembly  120  to move downwards. Pressure builds within the diaphragm chamber  109  until it approaches equalization with the water pressure coming in from water inlet port  114 . Typical inlet pressure is about 60 psi. With the help of the spring  111 , the diaphragm assembly continues downwards until the sealing surface  103  makes contact with the valve seat  121 . 
   In the shut position, the pressure within the diaphragm chamber  109  is equal to the pressure of the inlet  114 , but the overall force on the diaphragm assembly  120  is downwards. This is due to the fact that the pressure in the diaphragm chamber  109  is exerting its effect over a larger surface area of the diaphragm assembly  120 , than the pressure in the inlet  114 . This downward resultant force prevents the diaphragm assembly  120  from being pushed up from the water pressure of the inlet  114 . As a result, the sealing surface  103  of the diaphragm assembly  120  remains seated on the valve seat  121 , preventing passage of the inlet water through the valve. 
   When the solenoid  112  is energized, the solenoid plunger  108  lifts and thus allows water from the diaphragm chamber  109  to pass through the discharge port  107  and out to the water outlet port  115 . The open discharge port  107  thus causes pressure in the diaphragm chamber  109  to drop. As a result, the water from the water inlet port  114  pushes up on the valve assembly  120 , which compresses valve spring  111  and unseats the sealing surface  103  from the valve seat  121 . With the valve pushed upwards, away from its valve seat  121 , water may freely pass from the water inlet port  114 , through valve  100 , and out water outlet port  115 . 
     FIG. 2  illustrates a problem common to prior art irrigation valves. To improve manufacturability and reduce costs, guide washer  102  is formed with an inner circular channel  110 . This inner circular channel  110  is covered by diaphragm  101 . Due to factory manufacturing conditions, air is often trapped between the diaphragm  101  and this inner circular channel  110 . 
   When the valve  100  is in the closed position, pressure builds in the diaphragm chamber  109 . Since air compresses under pressure, unlike water, a portion of the diaphragm  101   a  is thus pushed or extruded into the circular channel  110 . Consequently, the peripheral edges of the diaphragm  101  become stretched and taut, making it more difficult for the valve to close. 
   When flow into the valve  100  is medium to high (typically about 5–30 gallons per minute), the additional closing force generated by the low pressure region in the annular space  152  required to seat the valve seal  103  is available, in spite of the extruded diaphragm, and the valve assembly  120  properly closes. But when flow into the valve  100  is low (typically less than about 5 gallons per minute), the resulting low pressure region generated in the annular space  152  is insufficiently low enough to fully seat the sealing surface  103  onto the valve seat  121 . 
   In some circumstances, the faulty valve assembly  120  remains open about 0.02–0.05 inches, which is enough for the valve  100  to flow 1–4 gallons per minute, never fully shutting off. And, over time, the diaphragm  101  becomes increasingly stretched, as greater portions  101   a  of the diaphragm  101  extrude into the circular channel  110 . 
   The present invention seeks to avoid the above problem by presenting a guide washer  201  which prevents extrusion of the diaphragm  101  into the circular channel  110 . 
     FIG. 6  illustrates one embodiment of a valve assembly  202  containing a spoked guide washer  201 . The spoked guide washer  201  is circular in shape, having an inner circular channel interrupted by multiple fins  203 . Each fin  203  extends to the bottom of the inner channel and is level with the surface of the spoked guide washer  201 . 
   The positioning and the numbering of fins  203  are such that they prevent the diaphragm  101  from extruding into the gaps of the inner channel of the spoked guide washer  201 . Although air may be present in gaps of the inner channel, the spokes maintain the relative position of the diaphragm  101  and thus better ensure the valve functionality (e.g. closure) at low water flows. 
     FIG. 3  illustrates the spoked guide washer&#39;s  201  positioning within the improved valve  200 . With higher reliability, the improved valve  200  may be used for a wider variety of irrigation uses, such as drip irrigation. 
   It is known in the art that an injection molding process is best used when the design of the molded part ensures that even cooling of the molten plastic occurs. If cooling differentials occur, then the molded plastic article will likely encounter sink problems that distort or warp the molded article shape from it&#39;s intended original form. 
   The design of spoked guide washer  201  allows the article to cool evenly by virtue of the spaces between fins  203 , thus ensuring that the guide washer  201  maintains its original intended shape. 
   In a preferred embodiment, the present invention prevents diaphragm extrusion with a spoked guide washer  201 , keeping design and manufacturing costs low, while also reducing possible complication associated with additional parts. 
   An alternative embodiment of the present invention (not pictured) includes spoked bars within the guide washer wherein the bars are, radially positioned and flush with the upper surface. Like the previous embodiment&#39;s fins, the bars help support the diaphragm while preventing extrusion into the inner channel of the guide washer. Unlike the fins, the bars do not extend downward to the bottom of the inner channel, yet still provide the same extrusion resistant benefits. 
   Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.