Patent Abstract:
A flush valve has a valve body having an inlet and an outlet. A piston is disposed in the valve body between the inlet and the outlet. A piston cap is disposed within the valve body and has a wall along which the piston is guided. A groove is disposed in the piston cap wall for equalizing pressure on sides of the piston translating therein. The groove has a shallow, semicircular shape whereby a possibility that fluid flow therethrough is diminished is minimized.

Full Description:
RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 61/314,744, which was filed on Mar. 17, 2010. 
    
    
     BACKGROUND OF THE INVENTION 
     Flush valves may have a handle that, when manipulated, pushes an actuator which, in turn, opens a bypass valve within a piston in the flush valve. By opening the bypass valve, pressure above the piston drops and allows line pressure to lift the piston from its seat within the flush valve and channel water to flush a toilet, urinal or the like. While the toilet or urinal fixture is being flushed, line pressure is also directed above the piston increasing the pressure in this area. As the pressure equalizes the piston seats itself within the flush valve and stops flow therethrough. 
     Commercial flush valves sometimes experience problems such as water hammer and failure to shut off. Water hammer may occur if water in motion is forced to stop or change direction suddenly. This rapid change in momentum creates a surge in pressure and results in shock waves that propagate through the piping making noise. Some plumbing codes require flush valves to have anti-backflow devices like a vacuum breaker to prevent fouling of the potable water supply in the event of backflow from the toilet or urinal fixture into the valve and the related water supply. 
     SUMMARY OF THE INVENTION 
     A flush valve has a valve body having an inlet and an outlet. A piston is disposed in the valve body between the inlet and the outlet. A piston cap is disposed within the valve body and has a wall along which the piston is guided. A groove is disposed in the piston cap wall for equalizing pressure on sides of the piston translating therein. The groove has a shallow, semicircular shape whereby a possibility that fluid flow therethrough is diminished is minimized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective cutaway view of the flush valve of the invention. 
         FIG. 2  is a perspective view of the valve of  FIG. 1 . 
         FIG. 3  is a side view of the piston body of  FIG. 2 . 
         FIG. 4  is a perspective view of the piston cap of  FIG. 2 . 
         FIG. 4   a  is a top view of the piston cap of  FIG. 4 . 
         FIG. 5  is a perspective view of the anti-backflow prevention device of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , the flush valve  10  of the invention is shown. The flush valve  10  has a valve assembly  15 , an actuator assembly  20  (as in known in the art), an anti-back flow cartridge  30  and a discharge tube  35  that disgorges water into a toilet or urinal (not shown) or the like. 
     Referring now to  FIGS. 2 and 3 , the valve assembly  15  has an inlet  40  disposed in a valve body  45 , a piston  50  operating in the valve body  45 , a piston cap  55  and an outlet  60  disposed in the valve body. The piston  50  comprises a piston guide  65 , a piston body  70 , an o-ring  75 , a bypass seal  80 , an actuator  85 , a collar  90 , a bypass valve  95 , a spring  100 , a cap  105 , and a wiper seal  110 . 
     The piston guide  65  has a tapered interior  115 , a circular cutout  120  for holding the o-ring  75 , a shoulder  125  for mounting the bypass seal  80  and threads  130  for mating with the threaded piston body interior  135 . An extended portion  142  of the piston guide  65  extends beyond a tapered portion  140  of the valve body  45  if the piston  50  is seated. 
     The piston body  70  has a lower cutout  145  for holding the o-ring  75  and an interior ledge  150  for holding the bypass seal  80 . The shoulder  125  of the piston guide  65  and the interior ledge  150  of the piston body  70  position the bypass seal therebetween  80 . Similarly, the circular cutout  120  of the piston guide  65  and the lower cutout  145  of the piston body trap the o-ring  75  therebetween. 
     The o-ring  75  seats the piston  50  on the tapered portion  140  of the valve body  45 . In this embodiment, the tapered portion of the seal has a length of 0.125 inches and is disposed at an angle of 20° relative to the outlet, though other angles and lengths are possible for other valves. 
     The bypass valve  95 , which seats on the bypass seal  80 , has a threaded interior  155  for receiving the threaded portion  160  of the actuator  85 . The actuator is attached to the collar  90  that interacts with the actuator assembly  20  (see also  FIG. 1 ) to move/tilt the bypass valve  95  off of the bypass seal  80  as will be discussed herein. 
     The cap  105 , which is circular, has a central opening  165  therein, and a set of downwardly depending threads  170  that attach to interior threads  175  in the piston body  70 . The cap  105  seats the spring  100  between it and the bypass valve  95 . The cap also fixes the wiper seal  110  between it and an outer ledge  180  in the piston body. 
     The piston  50  moves upwardly and downwardly within the valve body  45  and within the piston cap  55 , which is conventionally fixed for easy access within the valve body  45 . An area  185  for holding fluid is defined in the piston cap  55  above the piston  50 . The wiper seal  110  extends beyond the edges of the valve to form an interference fit with an interior wall  190  of the guide (see also  FIG. 4 ) as will be discussed herein. 
     Referring to  FIG. 3 , the piston body  70  is shown. The piston body has a neck  200 , a body portion  205  having a larger perimeter than the neck, and a shoulder  210  having a rounded portion  220  and a larger perimeter than the neck. The body portion has a taper  225  therein that slopes inwardly towards the neck  200 . In the embodiment shown herein, the taper is disposed at an angle of approximately 20° relative to the shoulder and has a length of approximately 0.168 inches. The rounded portion  220  of the shoulder  210  has a radius of approximately 0.04 inches. Other combinations and permutations of radius, angle and length may be used in other valves if they provide the benefits of this invention. 
     Referring to  FIGS. 4 and 4   a , the piston cap  55  is shown having, in the embodiment shown, a groove  230  having a depth of approximately 0.006 inches and a Ø of about 0.040inches disposed in the inner wall  190 . The groove extends from a bottom  235  of the piston cap  55  to a top  240  thereof to communicate fluid from the valve inlet  40  to the area above the valve  185 . The shape of the groove  230  minimizes a possibility that debris (not shown) might get stuck in or clog the groove. The groove is further sized to allow fluid to equalize above the piston  50  to seat the piston as will be discussed herein while allowing enough fluid to pass by the wiper seal  110  to achieve an adequate flushing function. If the groove is too small in area, the valve will be open too long and if too large in area, too short. 
     Before the valve  15  is operated, pressure is equalized between the area  185  within the piston cap  55  above the piston  50  and line pressure in the plumbing system (not shown) within the inlet  40 . Pressure in the outlet  60  is low as fluid has been disgorged therethrough. During operation of the piston  50 , if the actuator assembly  20  is manipulated, the collar  90  is tilted and the actuator  85  attached thereto tips the bypass valve  95  off the bypass seal  80  against the force of the spring  100  to allow fluid to flow from the area  185  above the piston thereby lowering the pressure therein. Line pressure in the inlet  40  therefore pushes the valve  50  off its seat  140  within the valve body  45  to allow fluid to flow past the neck  200  of the piston body  70 , the o-ring  75 , the extended portion  142  of the piston guide  65 , the rounded portion  220  of the broach body shoulder  210 , and the piston body taper  225  that slopes inwardly towards the neck  200 , to exit the valve. 
     As the valve  50  operates, inlet fluid flows through the groove  230 , bypassing the wiper seal  110 , gradually allowing pressure in the area  185  above the piston  50  to equalize with the line pressure thereby gradually moving the piston  50  down along the inner wall  190  of the piston cap  55  until o-ring  75  seals against the tapered portion  140  of the valve body  45 . As the valve moves, the wiper seal  110  tends to remove debris that might clog or block fluid from flowing in the groove in the piston cap  55 . 
     The extended portion  142  of the piston guide  65 , in conjunction with the o-ring  75  and the tapered portion  140  of the valve body  45 , helps to create a funnel to minimize turbulent flow from the valve  50  as the valve seats on the tapered portion  140  of the housing  45  thereby minimizing water hammer. Similarly, the tapered portion  225  and the rounded portion  220  of the broach body  70 , collectively and individually, smooth flow around the piston body also minimizing the effects of water hammer in the valve. Additionally, the neck portion  200  of the broach body  70  allows inlet pressure to be more equally distributed therearound thereby centering the valve more efficiently thereby easing translation of the valve in the piston cap  55  and extending valve life. 
     Referring now to  FIGS. 1 ,  5 , and  5   a , the anti-backflow cartridge  30  is shown. The cartridge has a tubular housing  250  that slips into the discharge tube  35 . The tubular housing has a lip  255  that prevents the housing from slipping down into the discharge tube thereby giving a user easy access to the cartridge if maintenance is required. A pair of anti-backflow check valves  260 , manufactured by Neoperl, are arranged in series in the tubular housing and each are held therein the tubular housing  250 . The anti-backflow valves provide enough resistance to minimize backflow while allowing enough flow to maximize the use of the toilet or urinal. The o-rings  265  also prevent fluid from flowing around each anti-backflow check valve back to the valve assembly  10 . A flange  280  may depend inwardly at a bottom of said tubular housing  250 . 
     In an alternative embodiment shown in  FIG. 1 , the cartridge  250  is the discharge tube and if the cartridge needs replacement, the discharge tube is replaced therewith. The discharge tube  35  has a set of threads  255  therearound for mating with the threads  285  of the valve body  45 . 
     Each anti-backflow valve  260  prevents fluid from flowing up from the toilet or urinal (not shown) so that neither the water supply nor the valve assembly  15  is contaminated by the fluid. The anti-backflow valves replace vacuum breakers (not shown) and also have a much longer life than a typical prior art vacuum breaker. 
     The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. For instance, one of ordinary skill in the art will recognize that other designs such as objects, abstracts, architectural features may be substituted for the designs shown herein. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.

Technology Classification (CPC): 5