HK1179678B - Piston cap with center vent - Google Patents

Abstract

A flushometer having a cap with a substantially central exhaust passage adapted to remove air from the control chamber. The exhaust passage provides for communication between an upper pressure chamber and an interior piston chamber wherein during a flush cycle a portion of the contents of the upper pressure chamber is evacuated through the exhaust passage into the interior piston chamber and ultimately through the outlet of the flushometer.

Description

Piston cap with central bore

Cross reference to related patent applications

This application claims priority to U.S. provisional patent application 61/320,630, filed 4/2/2010, the entire contents of which are incorporated herein by reference.

Technical Field

The present invention relates generally to diaphragm or piston type flush valves used in urinals, water closets, and the like. More particularly, the present invention relates to a flush valve having a mechanism for venting air from the control chamber of the flush valve.

Background

Piston-type flush valves having bypass orifices are well known, such as the flush valve shown in U.S. patent No. 4,261,545, which is hereby incorporated by reference. Diaphragm flush valves also have a bypass orifice, such as the flush valve shown in U.S. Pat. No. 6,616,119, which is incorporated herein by reference. Another type of piston-type flushometer is taught, for example, in U.S. patent No. 6,913,239, which includes a dome-shaped inner cover that defines the top of the control chamber. Piston valves of this type have become popular in the market due to the advantages set forth in U.S. patent No. 6,913,239, namely that the inner cover allows the outer cover to be made of a wider range of materials and also provides improved reliability in the operation of the flush valve.

Typically, a flush valve includes a valve (piston or diaphragm type) that seals the water inlet and isolates it from the outlet of the valve body. The valve is controlled at least partially by using a pressure difference using a control chamber located in the uppermost layer inside the valve body. The function of the control chamber is to reposition the control valve on the valve seat. An auxiliary valve controllably seals the control chamber from the outlet and a bypass provides metered control flow from the inlet to the control chamber. Thus, by communication through the bypass, the control chamber may be substantially pressurized to the pressure of the inlet. The valve remains closed at equal pressures because the line pressure in the control chamber acts on a larger top side area of the piston or diaphragm than the inlet line pressure acts on a smaller bottom side area of the piston. When the auxiliary valve is opened, the control chamber becomes exposed to a lower pressure (typically atmospheric pressure), i.e. a smaller force, and the contents of the control chamber are discharged into the outlet to reduce the force exerted on the piston and allow the piston to rise away from the main seat to form an opening so that water can flow from the inlet to the outlet. The control chamber is pressurized again by the bypass, and the valve closes when the force in the control chamber on top of the piston increases to exceed the force exerted on the underside of the piston body.

In ideal operation, the flush valve includes only water flow in the inlet, valve and control chamber, i.e. there is no air in the flush valve, so that the water completely fills the volume. However, in certain situations, such as when the valve assembly is first installed after maintenance, or where the feed water contains too much dissolved gas (e.g., air), gas may be present in the valve assembly. More specifically, the gas will typically be located inside the uppermost layer of the valve assembly, which is typically (see fig. 1A and 1B) the control chamber, which is in fluid communication with the inlet. Specifically, for a commercially available flush valve utilizing a domed inner cover as taught in U.S. Pat. No. 6,913,239, the gas will have a tendency to be positioned on top of the domed inner cover. Thus, in this case, gas may be present in the control chamber.

When air (gas) is present in the control room, the number of Gallons Per Flush (GPF) will be different from the GPF when only water is present in the control room. Compressible flowing air combines with incompressible flowing water, resulting in an unstable volume in the critical control chamber. A certain amount of air will dissolve in the water and be expelled with the water during repeated rinsing cycles over time. In prior art devices, this phenomenon results in a small amount of air being expelled per flush cycle, thus the air expulsion (and return to the normal GPF of a water-only control room) is achieved over a large number of flush cycles, exceeding 50 cycles for some devices.

Disclosure of Invention

One embodiment of the present invention is directed to a flush valve having a cap with a substantially central vent passage configured to vent air from an upper pressure chamber.

In one embodiment, the present invention relates to a flush valve system. The flush valve system includes a hollow valve body having an inlet, an outlet, and a valve seat between the inlet and the outlet. The system also includes a piston assembly movable within the hollow valve body and configured to seat on the valve seat to seal the inlet from the outlet. An upper pressure chamber is located within the hollow valve body and above the valve member. The piston assembly includes: a piston having a piston inner chamber; and a cap having a cylindrical body with a cylindrical lip at the top, the cylindrical lip having a larger diameter. The cap includes a vent passage through the lip and the body to provide communication between the upper pressure chamber and the piston inner chamber, the vent passage being located substantially centrally of the cap.

In one embodiment, the present invention relates to a piston cap for a piston-type flushometer. The piston cap has a cylindrical body with an externally threaded sidewall and a lip. The lip portion has a larger diameter than the body and is disposed at a top portion of the cylindrical body. The cap includes a vent passage therethrough, an upper pressure chamber opening, and a piston inner chamber opening. The discharge passage is substantially centered on a central axis of the cap. At least one recessed area is located between upper annular projections of the body that define at least a portion of the discharge passage. The upper pressure chamber opening is larger than the lower piston inner chamber opening.

In one embodiment, the present invention relates to a method of venting gas, such as air, from a control chamber of a piston valve. The piston valve has a piston assembly adapted for reciprocal movement within the body of the flush valve, the piston assembly further including a generally cylindrical hollow piston defining a piston interior chamber sealed from the outlet by a relief valve, the piston assembly further having a control chamber above the piston valve. The method includes providing a piston cap having a centrally located vent passage providing fluid communication between the control chamber and the piston interior chamber. A safety valve is actuated to place the piston interior chamber in fluid communication with the outlet. A low pressure location is formed at a location within the vent passage. Moving the piston assembly upward to reduce the volume of the control chamber. Moving gas in the control chamber to the low pressure position. Gas is exhausted from the control chamber through the exhaust passage. Moving water in the control chamber to the low pressure position. Draining water from the control chamber through the drain passage, and closing the safety valve. The control chamber is again filled with water from the inlet and contains substantially less air than before the gas is exhausted.

The above summary is merely illustrative and is not intended to be limiting in any way. In addition to the exemplary aspects, embodiments and features described above, further aspects, embodiments and features will become apparent by reference to the following drawings and detailed description.

Drawings

The above features and other features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings.

FIG. 1A is a longitudinal section of a flush valve showing a prior art piston design; FIG. 1B is a longitudinal section of another prior art piston-type flushometer comprising a control chamber with a domed inner cover;

FIG. 2A is a side view of a piston of the prior art device of FIG. 1A; FIG. 2B is a longitudinal section along line B-B of the piston of FIG. 2A;

FIG. 3A shows a dome-shaped inner cover disposed between a cover of the valve body and an outer cover of the valve body; FIG. 3B is a longitudinal section of the dome of FIG. 3A;

FIG. 4A is a longitudinal section of a piston-type flushometer according to one embodiment of the present invention; FIG. 4B is a longitudinal section of a piston assembly according to one embodiment of the present invention;

FIG. 5A is a top view of one embodiment of a piston cap of the present invention; FIG. 5B shows a side view of the cover;

FIGS. 6A-6F illustrate longitudinal sections of various embodiments of piston caps; FIG. 6A has a relatively shallow groove; FIG. 6B has a relatively deep groove; FIG. 6C is without grooves; FIG. 6D has the vent passage terminating at a position below the upper surface of the cap; FIG. 6E has the vent passage terminating at a position above the upper surface of the cap; FIG. 6F has a substantially cylindrical discharge passage, i.e., with substantially parallel side walls, such that the cap opening of the control chamber is substantially the same size as the cap opening of the piston inner chamber; FIG. 6G has a vent passage with non-parallel sides such that the cap opening of the control chamber is smaller than the cap opening of the piston inner chamber;

FIG. 7A shows the interior of a piston valve with a central vent passage just prior to actuation; FIG. 7B shows the interior of the piston valve just after the relief valve tips and the piston begins to rise; FIG. 7C shows the interior of the piston valve at full stroke with full flow and excess air being expelled from the control chamber;

FIG. 8A shows the interior of a piston valve without a central vent passage just prior to actuation; FIG. 8B shows the interior of the piston valve just after the relief valve tips and the piston begins to rise; fig. 8C shows the interior of the piston valve at full stroke with full flow and excess air restricted in the control chamber.

Detailed Description

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, like reference numerals generally refer to like parts throughout the various views unless the context dictates otherwise. The exemplary embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present invention, as generally described and illustrated in the figures herein, could be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and are part of this invention.

Generally, the piston assembly 34 of the present invention is used with a flush valve assembly for urinals or water closets. The flush valve piston 34 is designed to control the flow of water through the flush valve to provide a fixed amount of water for each flush operation, with the water flowing through the flush valve at a high flow rate even when the water pressure is at the lower end of the range of water pressures typically found in U.S. commercially available fixtures. While the invention will be described with the desired amount of 1.6 gallons or 6 liters per flush, it will be appreciated that the size of the various components, such as the bypass, may be modified to provide different amounts of flushes per time.

Fig. 1A and 1B generally illustrate the structure of a prior art piston-type flushometer, while fig. 4A illustrates the piston-type flushometer of the present invention. The illustrated flush valve has a generally hollow valve body 10, the valve body 10 including an inlet connection 12, an outlet connection 14, and a handle coupling connection 16. The top of the valve body 10 is closed by a cover 18 and may have a sealing element 19 between the cover and the valve body. In another embodiment, as shown in FIG. 1B, a dome shaped inner shroud 82 is provided between the shroud 18 and the cap 56. A main valve seat 20 is formed on the inner wall of the valve body 10. The valve is actuated by an operating handle 22, which operating handle 22 is fastened to the valve body 10 by means of a coupling nut 24. The handle 22 is connected to a plunger 26, which plunger 26 extends into the interior of the valve body 10. The plunger 26 is guided and supported by a bushing 28, and the plunger 26 is reset by a spring 30. A rubber gasket 32 snaps over the end of bushing 28 and prevents leakage outward from handle opening 23 due to sliding plunger 26. The valve as shown in fig. 1A has a manual handle 22 for operation. The present invention is also suitable for automated operation, for example using an automated actuation mechanism 21, one embodiment of which is shown in FIG. 1B.

With continued reference to fig. 1A, 1B, and 4A, the piston assembly 34 is adapted for reciprocal movement within the valve body 10. The piston assembly 34 includes a hollow, generally cylindrical piston 36. The piston 36 has a lower cylindrical extension 38, the extension 38 being directly adjacent a piston seating area 39, the piston seating area 39 normally seating on a sealing member 41 to close the main valve seat 20 to control the flow of water through the flush valve.

Referring to fig. 2A and 2B, piston 36 is shown. The piston 36 has a pair of bypass ports 40 (alternatively, only one bypass or more than two bypasses may be employed), the bypass ports 40 being usable in combination with a filter ring 43 (fig. 1A), the filter ring 43 being adapted to provide additional anti-clogging properties in accordance with known principles (see, for example, U.S. patent No. 4,261,545). The piston inner chamber 42 of the piston 36 has an annular flange 44 that supports a seal 46. The flange and seal are located at the top of a central passage 48, which central passage 48 connects the piston interior chamber 42 with the outlet side of the flush valve at the outlet connection 14.

The piston assembly 34 also includes a relief valve 50 that normally closes the passage 48 of the piston 36. The relief valve has a collar 49, which collar 49 engages the seal 46 on the annular flange of the piston. The operating rod 52 is slidable in the central hollow portion of the relief valve 50 and extends to a position adjacent the plunger 26. Spring 54 helps to hold relief valve 50 in its proper position to close and seal piston interior chamber 42.

The piston assembly 34 also includes a cap 56, the cap 56 being threadably engaged with the upper wall of the piston 36. One end of spring 54 abuts cap 56 and abuts collar 49. A lip seal 64, held between the cap 56 and the piston 36, provides a slidable seal separating the pressure chamber 62 from the inlet water pressure.

The piston 36 has a cylindrical wall 70, preferably the cylindrical wall 70 is smooth and unobstructed. The tapered piston area 72 is directly adjacent the cylindrical wall 70 and the tapered piston area 72 may have a taper of about 10 degrees, the slope effectively providing a clear flow path around the piston when the piston is in the raised position away from the valve seat 20. The piston seating area 39 is immediately adjacent to the conical piston area 72 and when the valve is in the closed position, the piston seating area 39 will close on the main valve seat 20. Immediately downstream of the piston seating area 39 is a ring 74, which ring 74 has an outer diameter slightly smaller than the diameter of the valve outlet adjacent the valve seat 20, so that when the piston is closed, the ring area 74 will be located inside the valve seat. Since the ring 74 primarily reduces flow through the valve outlet prior to completing valve closure, the ring 74 acts as a throttling feature.

The lower cylindrical portion 38 of the piston 36 is directly adjacent the throttle ring 74 and has a plurality of radially and axially extending ribs 76, which in one embodiment are generally circumferentially evenly spaced ribs. The rib has an outer diameter smaller than the wall 70 and just slightly smaller than the passage through the valve seat 20. The ribs are therefore located inside the main part of the piston so as not to restrict the flow. In a preferred embodiment, five ribs 76 are provided to maximize stability and guidance of the piston without adversely blocking water flow past the piston when the piston is in the valve open position. In one embodiment, the ribs 76 define a fixed flow area as the ribs 76 move across the piston seating area 39 when closed, converting water flow from a main flow to a low flow. At the lower end of each axially extending rib there is a chamfered area 78 which facilitates assembly of the piston within the flush valve assembly.

The area between each rib 76 is closed by a skirt 80. As shown, skirt 80 has a radius slightly smaller than the outer surface of rib 76. The function of the skirt panels 80 is to close the area between the ribs to provide control of the water flow past the piston, which in turn will provide more coordinated operation of the flush valve. The skirt 80 improves the flow path by maintaining the flow path in an axial direction and generally circumferentially around the lower cylindrical portion 38. By preventing water flow into the water passage 48, the skirt 80 also helps prevent any back pressure that might interfere with the closure of the relief valve. The skirt region 80 terminates short of the downstream end of each rib 76.

As described above, in certain embodiments, a dome-shaped shroud 82 is provided to define the upper pressure chamber 62. Fig. 3A and 3B illustrate an embodiment of a dome-shaped cover 82. As can be seen in fig. 3B, the dome 82 may include a dome inner chamber 83, the dome inner chamber 83 defining a volume at the top of the upper pressure chamber 62 and opening into the upper pressure chamber 62. The dome 82 structure may provide additional strength against forces, as described in the 6,913,239 patent. It should be understood that while some of the figures illustrate embodiments of a flush valve having a dome-shaped cover 82 including an inner chamber 83, such a configuration is not necessary for a central exhaust passage for exhausting air as described herein.

In one embodiment, the present invention provides a cover 56, the cover 56 configured to allow fluid to pass from the upper pressure chamber 62. The cap 56 also interacts with a dome-shaped cap 82, or valve body 10 in a configuration such as that shown in fig. 1A, to control movement of the piston assembly 34 and in some embodiments to retain the spring 54 that biases the relief valve 50. The previous cover 56 includes a plurality of circumferential openings 60 disposed around the inner edge of the cover 56. The arrangement of the holes provides a uniform pressure gradient as the pressure exerts a force on the upper surface of the piston. Fig. 4A-7 illustrate various embodiments of the cover 56 of the present invention. Referring to fig. 4A and 4B, cap 56 is configured to engage the piston such that a portion of cap 56 is disposed within piston 36, a portion remains outside of piston 36, and substantially covers the upper surface of the piston. Cap 56 includes a body portion 84, a first periphery of which may be disposed within piston 36, and in one embodiment, body portion 84 includes a threaded sidewall 86 for engaging threads on the interior of cylindrical wall 70 of piston 36. As best seen in fig. 4B, 5A and 5B, cap 56 also includes a lip 88, with lip 88 having a perimeter that is greater than the perimeter of body 84 and substantially forms a top side 102 of piston 36. The cap 56 also includes a vent passage 92 defining a passage through the cap 56 having an upper pressure chamber opening 94 and a piston inner chamber opening 96. A vent passage 92 provides fluid communication between the piston inner chamber 42 and the upper pressure chamber 62. In one embodiment, the lip perimeter 90 includes a plurality of straight segments configured to provide a support function for the lid in relation to the interaction with the dome 82.

In one embodiment, the cap 56 includes a recessed area 98 defining the discharge passage 92 and extending from the lip portion 88 into the body portion 84. The recessed region 98 may not continuously surround the discharge passage 92. For example, in one non-limiting embodiment, the pocket 98 is interrupted by four walls 95, the four walls 95 connecting the vent passage 92 to a portion of the cap 56 (best shown in fig. 6C and 6G). These walls act as drive lugs for twisting the cap onto the piston body. The presence or absence of the recessed areas 98 and the depth of the recessed areas 98 may vary without departing from the spirit and scope of the present invention. Although the figures generally illustrate a recessed area 98 extending substantially through the cover 56, fig. 6A illustrates an embodiment having a shallow recessed area 98, fig. 6B illustrates an embodiment having a deep recessed area 98, and fig. 6C illustrates an embodiment without the recessed area 98.

In such an embodiment, as shown in fig. 6A and 6B, the vent passage 92 includes an upper annular projection 104, the projection 104 extending from within the recessed area 98 of the cap 56 toward the top side 102 of the cap 56. In one embodiment, as can be seen in fig. 6A, upper protrusion 104 extends substantially to the plane defined by top side 102. In another embodiment shown in fig. 6D, upper protrusion 104 extends from recessed area 98, but does not extend sufficiently beyond top side 102, such that the entire upper protrusion 104 is disposed within recessed area 98. In another embodiment shown in fig. 6E, such as for a flush valve with a shorter stroke that does not place the cap 56 immediately adjacent the top interior portion, the protrusion extends beyond the plane of the upper side of the cap 56. In one embodiment, the upper protrusion 104 may include one or more separate structures that are provided for extending the protrusion beyond the top side of the cover 56. Alternatively, upper projection 104 may be a single component, including a component integral with cover 56, such as where the entire structure is a single molded structure.

In one embodiment, as shown in fig. 6A, the discharge passage 92 extends into the piston inner chamber 42 to form a lower annular protrusion on the bottom of the cap 56. The lower annular projection 100 may be configured to retain the spring 54, for example, by extending into the piston inner chamber 42 such that the lower annular projection 100 is partially disposed within the upper portion of the spring. In this embodiment, the lower annular projection 100 acts as a spring guide. In another embodiment shown in fig. 6C, an annular groove 106 is provided on the bottom surface 103 of the cap 56, the annular groove 106 being configured to receive a portion of a spring.

The vent passage 92 may comprise a symmetrical shape, such as a cylinder, in which the piston inner chamber opening 96 and the upper pressure chamber opening 94 are substantially the same size, as shown in fig. 6F. In another embodiment, one of the piston inner chamber opening 96 and the upper pressure chamber opening 94 is larger than the other and the passage between the two tapers to form a truncated cone. Fig. 6A shows an embodiment in which the upper pressure chamber opening 94 has a larger perimeter than the piston inner chamber opening 96. Due to the shape of the vent passage 92, the location of the lowest pressure in the passage is adjacent the piston inner chamber opening 96 during a flushing event. It will be appreciated that the contents of the upper pressure chamber 62, and in particular the air, will move to a low pressure position. In another embodiment shown in fig. 6G, the upper pressure chamber opening 94 has a circumference that is less than the circumference of the piston inner chamber opening 96. This embodiment results in the lowest pressure location being adjacent the upper pressure chamber opening 94.

During operation of the flush cycle, when the safety valve 50 is opened by actuating the flush valve handle 22, the central vent passage 92 of the piston cap 56 is at the same pressure as the valve body outlet 14, typically atmospheric pressure (zero PSI). The air above the piston assembly 34 is still compressed to the static water pressure of the inlet feed water. The compressed gas bag rapidly expands toward the central discharge passage 92, which central discharge passage 92 has a pressure lower than the pressure of the gas bag and the water in the upper pressure chamber 62. The compressed gas pocket is rapidly forced through the momentarily opened auxiliary valve and out through the valve body outlet 14. Then, when the upper pressure chamber 62 is refilled by means of the bypass 40 in the piston 36, the water replaces the volume previously occupied by the displaced air. Fig. 7 shows the described movement of the air pocket. It can be seen that the air pocket moves toward the low pressure direction of the discharge passage 92. At the same time, the entire piston assembly 34 moves upward, thereby reducing the overall volume of the upper pressure chamber 62. This, together with the low pressure of the discharge passage 92, causes the water to move within the upper pressure chamber 62. Thus, in certain embodiments, as the air bag deforms toward the discharge passage 92, water rises around the periphery of the upper pressure chamber 62. The location of the air passage projection on the top side of the cover 56 allows the air bag to reach the vent passage 92 before water passes over the air bag to prevent the air bag from venting.

In contrast, fig. 8 shows a prior art piston valve without the described discharge passage 92. Although the air bag is slightly deformed, the air bag does not make contact within the recessed area 98 of the cover 56. Thus, the air pocket is not evacuated as described.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. Various singular/plural combinations are explicitly described herein for clarity.

The foregoing description of the exemplary embodiments has been presented for the purposes of illustration and description. The exact forms disclosed are not intended to be exhaustive or limiting, but rather may be modified and varied in light of the above teachings or may be learned by the practice of the disclosed embodiments. It is intended that the claims appended hereto and their equivalents define the scope of the invention.

Claims (21)

1. A flush valve system, the flush valve system comprising:

a hollow valve body having an inlet, an outlet, and a valve seat between the inlet and the outlet;

a piston assembly movable within the hollow valve body and configured to seat on the valve seat to seal the inlet from the outlet;

an upper pressure chamber within the hollow valve body and above the valve member;

the piston assembly includes: a piston having a piston inner chamber; and a cap having a cylindrical body with a cylindrical lip atop, the cylindrical lip having a larger diameter, the cap including a vent passage through the lip and the body to provide communication between the upper pressure chamber and the piston inner chamber, the vent passage being located substantially centrally of the cap.

2. The flush valve system of claim 1, wherein the discharge passage has an upper pressure chamber opening and a piston inner chamber opening.

3. The flush valve system of claim 2, wherein the upper pressure chamber opening is larger than the piston inner chamber opening.

4. The flush valve system of claim 2, wherein the piston interior chamber opening is larger than the upper pressure chamber opening.

5. The flush valve system of claim 2, wherein the piston interior chamber opening is the same size as the upper pressure chamber opening.

6. The flush valve system of claim 1, wherein the cap further comprises a groove in the top side, the groove disposed around the discharge passage.

7. The flush valve system of claim 6, wherein an upper annular projection defines a portion of the discharge passage and isolates the discharge passage from the recess.

8. The flush valve system of claim 1, wherein the exhaust passage extends above a plane defined by a top side of the cap.

9. The flush valve system of claim 1, wherein the discharge passage extends below a plane defined by an underside of the cap.

10. The flush valve system of claim 1, wherein the exhaust passage terminates below a plane defined by a top side of the cap.

11. The flush valve system of claim 1, wherein the cap includes a groove on a bottom surface, the groove surrounding the discharge passage.

12. The flush valve system of claim 6, wherein the groove extends the thickness of the lip.

13. The flush valve system of claim 6, wherein the recess extends substantially into the body.

14. A piston cap for a piston-type flushometer, the piston cap comprising:

a cylindrical body having an externally threaded sidewall; and a lip portion having a diameter greater than the diameter of the body and located on top of the cylindrical body;

the piston cap includes a discharge passage therethrough having an upper pressure chamber opening and a piston inner chamber opening, the discharge passage being substantially centered on a central axis of the piston cap;

at least one recessed area located between upper annular projections of the body, the upper annular projections defining at least a portion of the discharge passage;

wherein the upper pressure chamber opening is larger than the lower piston inner chamber opening.

15. The piston cap of claim 14, wherein the upper annular protrusion extends above a plane defined by the lip portion.

16. The piston cap of claim 14, further comprising a lower annular protrusion extending from the body and defining at least a portion of the discharge passage and the piston inner chamber opening.

17. The piston cap of claim 16, wherein the lower annular protrusion extends below a plane defined by a bottom surface of the body.

18. The piston cap of claim 17, further comprising an annular groove on a bottom surface of the body, wherein the annular groove is configured to receive a portion of a spring.

19. The piston cap of claim 18, wherein the annular groove surrounds the lower annular protrusion.

20. A method of venting gas from a control chamber of a piston valve having a piston assembly adapted for reciprocal movement within a body of a flush valve and further including a cylindrical hollow piston defining a piston interior chamber sealed from an outlet by a relief valve, the piston assembly further having a control chamber above the piston valve, the method comprising:

providing a piston cap having a centrally located vent passage providing fluid communication between the control chamber and the piston interior chamber;

actuating the safety valve to place the piston interior chamber in fluid communication with the outlet;

forming a low pressure location at a location within the discharge passage;

moving the piston assembly upward to reduce the volume of the control chamber;

moving gas in the control chamber to the low pressure position;

venting gas from the control chamber through the vent passage;

moving water in the control chamber to the low pressure position;

draining water from the control chamber through the drain passage; and

closing the safety valve;

wherein the control chamber is refilled with water from the inlet and contains less air than before the gas is exhausted.

21. The method of claim 20, wherein the gas is air.