GB2104195A

GB2104195A - Check valve assembly

Info

Publication number: GB2104195A
Application number: GB8216023A
Authority: GB
Inventors: David Edward Griswold
Original assignee: Griswold Controls LLC
Current assignee: Griswold Controls LLC
Priority date: 1978-06-23
Filing date: 1982-06-02
Publication date: 1983-03-02
Also published as: MX150564A; GB2102918A; GB2108241B; GB2104195B; DE2925179A1; GB2023776B; GB2101716A; CA1101303A; JPS5527576A; GB2023776A; GB2101716B; GB2108241A; GB2102918B

Abstract

A check valve assembly comprising a stationary valve seat 25, a stationary barrel 21 positioned coaxially of said valve seat, a removable cover 23 secured relative to said barrel, a valve poppet 28 guided for movement in said barrel toward and away from said valve seat, a spring 33 acting to move said valve poppet into sealing contact with said valve seat, means cooperating with said barrel and said cover and said valve poppet to define a spring chamber 53 remote from said valve seat and enclosing said spring, said valve on poppet having a central axial stem 39 fixed thereto, a spring retainer 36 positioned within a portion of said spring and having a central opening for sliding contact with said stem, said valve poppet, stem, spring and retainer being axially insertable into said barrel as a unitary assembly in the absence of said removable cover, and aspirator means 44 receiving fluid flow from said barrel when said valve poppet has separated from said valve seat, said aspirator means communicating with said spring chamber so that relatively rapid fluid flow through said aspirator means causes a reduction in fluid pressure in said spring chamber to oppose the action of said spring and thereby reduce the pressure drop across the check valve assembly. <IMAGE>

Description

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GB 2 104 195 A

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SPECIFICATION

Check valve assembly

5 This invention, whose subject matter has been divided from Patent Application No. 8132470, itself divided from Application No. 2023776, relates to a check valve assembly for use in backflow prevention apparatus to be installed between a supply pipe and 10 a discharge pipe. Such devices are commonly used in water supply systems in order to insure that polluted water in a discharge pipe cannot flow in a reverse direction into a supply pipe.

According to the invention there is provided a 15 check valve assembly comprising a stationary valve seat, a stationary barrel positoned coaxially of said valve seat, a removable cover secured relative to said barrel, a valve poppet guided for movement in said barrel toward and away from said valve seat, a 20 spring acting to move said valve poppet into sealing contact with said valve seat, means cooperating with said barrel and said cover and said valve poppet to define a spring chamber remote from said valve seat and enclosing said spring, said valve poppet having 25 a central axial stem fixed thereto, a spring retainer positioned within a portion of said spring and having a central opening for sliding contact with said stem, said valve poppet, stem, spring and retainer being axially insertable into said barrel as a unitary assem-30 bly in the absence of said removable cover, and aspirator means receiving fluid flow from said barrel when saicfvalve poppet has separated from said valve seat, said aspirator means communicating with said spring chamber so that relatively rapid 35 fluid flow through said aspirator means causes a reduction in fluid pressure in said spring chamber to oppose the action of said spring and thereby reduce the pressure drop across the check valve assembly.

An embodiment of the invention will now be 40 described by way of example and with reference to the accompanying drawings, in which:—

Figure 1 is a side elevation showing backflow prevention apparatus incorporating a check valve according to this invention;

45 Figure 2 is a sectional elevation showing a portion of Figure 1;

Figure 3 is a perspective view showing the valve poppet employed in the upstream check valve assembly;

50 Figure 4 is a transverse sectional view of the valve poppet shown in Figure 3, taken substantially on the lines 4-4 as shown in Figure 2.

Referring to the drawings, the backflow prevention device generally designated 10 is positioned bet-55 ween two conventional gate valves 11 and 12. The gate valve 11 forms a part of a water supply pipe, and the gate valve 12 forms a part of a water discharge pipe. The device 10 prevents flow of water from the discharge pipe back into the supply pipe. 60 As shown in Figure 2, the device 10 includes an upstream check valve assembly generally designated 13 and embodying the present invention, and a downstream check valve assembly generally designated 14 having a zone 15 between them. A 65 relief valve assembly generally designated 16 vents the zone 15 to atmosphere whenever the pressure in zone 15 and chamber 53 approaches the pressure in the inlet passage 17, within predetermined limits. The relief valve 16 is described in detail in the aforementioned Patent Application No. 2 023 776 and in Patent Application No. 8 132 471 which is another divisional of the same application. The passages 17 and 18 and the zone 15 are all formed within the integral body 19. The upstream check valve assembly 13 and the downstream check valve assembly 14are mounted on the body 19 at right angles to each other, and each is positioned at an angle of 45 degrees to the aligned axes of the inlet and outlet passages 17 and 18.

The upstream check valve assembly 13 includes a stationary barrel 21 mounted within the body 19 and having a flange 22 clamped between the body 19 and the stationary cover 23. An alignment pin 20 assures the proper orientation of the barrel 21 within the body 19. One end of the barrel 21 has a circular opening 24 defined within a stationary annular seat 25. The barrel 21 has a side window 26 communicating with the zone 15.

A valve poppet 28 is slidably mounted in the barrel 21 for movement toward and away from the stationary seat 25. The valve poppet 28 is provided with an annular resilient disk 29 which cooperates with the seat 25toform a bubble tight seal. A retainer plate 31 hoFdstFte resHient disk in position and is itself fixed to the valve poppet 28 by means of the screw 32. A coil compression spring 33 has one end seated against the internal shoulder 34 of the valve poppet 28 and the other end engaging an end flange 35 on the spring retainer 36. The spring 33 encircles the tapering portion 36a of the retainer. A key 37 prevents turning of the retainer within the cover 23, which cover is secured to the body 13 by means of threaded fastenings 38, as shown in Figure 1. A central non-circular tubular stem 39 is secured to the valve poppet 28 by means of the threaded element 41 and washer 42, and slides through a notching non-circular opening 43 in the radial portion 36b of the spring retainer 36. The stem 39 is received into a matching recess 40 in the valve poppet 28. The valve poppet 28, stem 39, element 41, washer 42, retainer 36 and spring 33 constitute a unitary assembly for installation into position, in the absence of the cover 23. For safety reasons a special tool is required to engage the threaded element 41. The assembly of cover 23 causes the spring to be further compressed beyond its relaxed position.

An ejector nozzle 44 is mounted on the valve poppet 28 and has a relatively large entrance opening 45 communicating with the space 46 defined between the valve poppet 28 and the barrel 21 and between the ribs 47 and 48. The discharge opening 49 is smaller and is directed toward a discharge passage 51 in the valve poppet 28 but which is separated therefrom by the space 52. The space 52 communicates with a reduced pressure chamber 53 containing the spring 33. This chamber 53 extends into the upper portion of the barrel 21 and into the cover 23 both inside and outside of the spring retainer 36.

A circumferential groove 54 is formed in the outer cylindrical surface of the valve poppet 28, and this

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groove 54 is interrupted at two locations to communicate with the arcuate spaces 55 and 56 formed in the outersurface of the valve poppet 28 and bounded by the interior surface 57 of the stationary 5 barrel 21. The arcuate space 55 extends from the rib 48 to the rib 58, and the arcuate space 56 extends from the rib 47 to the rib 59. Both of these arcuate spaces 55 and 56 communicate with the window opening 26 in the barrel 21. As best shown in Figure 10 4, the transverse passage 51 in the valve poppet 28 discharges through the center of the window opening 26 in the stationary barrel 21.

In the check valve 13 the space 46, the chamber 53 and the window 26 constitute respectively the first, 15 second and third chambers referred to elsewhere in this specification.

The downstream check valve assembly 14 is simi-larto the upstream check valve assembly 13 in many respects except that it does not have an ejector noz-20 zle 44 or a transverse passage 51. The stationary barrel 61 carries the stationary annular seat 62 which is engaged by the resilient disk 63 carried on the valve poppet 64. The coil compression spring 65 engages the cover 66 at one end and engages the valve pop-25 pet 64 at the other end. The cover 66 and the barrel 61 are secured to the body and aligned in the man-nerdescribed in connection with the upstream check valve assembly 13:

In the operation of the backflow prevention device 30 the pressume of water in the upstream gate valve 11 acts through the inlet passage 17 and against the exposed portion of the upstream check valve assembly 13 within the annular stationary seat 25. This pressure tends to open the valve in opposition 35 to the force of the spring 33. When the upstream pressure has reached a sufficient intensity to move the valve disk 29 away from the seat 25, the pressure acts over a larger cross-sectional area of the valve poppet 28 and the additional force increases the 40 opening movement of the valve disk 29 away from the stationary seat 25. Water flows into the arcuate space 46 between the shoulders 47 and 48 and passes through the ejector nozzle 44 and into the flared entrance opening 50 of the transverse passage 51. 45 The rapid flow from the small discharge end of the ejector nozzle 44 reduces the pressure of liquid in the chamber 53 by an aspiration effect. Water is discharged from the transverse passage 51 through the zone 15 and its velocity head acts directly on the 50 exposed surface of the valve poppet 64 in the downstream check valve assembly 14. Water is discharged through the window 60 in the wall of the barrel 61 and passes into the discharge passage 18 in the body 19.

55 The configuration of the ribs and spaces on the outersurface of the valve poppet 28 in the upstream check valve assembly 13 has the following beneficial effect: theflow from the inlet passage 17 is shielded from any substantial communication directly with 60 the zone 15, and instead the flow from the inlet passage 17 is directed toward the arcuate space 46 which is defined between the inclined ribs 47 and 48 and which space 46 feeds the ejector nozzle 44. The spaces or pockets 55 and 56 on the other side of 65 these barrel-containing ribs 47 and 48 are in direct open communication with the side window 26 in the stationary barrel 21, and hence are in communication with the zone 15. The circumferential cross flow on the periphery of the valve poppet 28 through the groove 54, pockets 55 and 56 and side window 26 serves as a barrier to leakage from the inlet 17 axially along the cylindrical surface of the valve poppet 28 into the aspirated chamber 53.

Check valve 13 is designed to maintain a specified minimum pressure differential and cooperates with the relief valve assembly 16 to insure that no reverse flow could ever occur. If for any reason the pressure differential reflected to the assembly falls below a prescribed level, the relief valve assembly will open and vent the zone 15 to atmosphere as a means of maintaining this required differential. The second check valve 14 normally will also maintain a lesser pressure differential; however, it is subject to system pressure conditions wherein the pressure in discharge chamber 18 can exceed the normal supply pressure in chamber 17. Underthese conditions the function of check valve 14 is to remain closed and isolate zone 15 from the higher backflow pressures. If the second check valve 14 should leak, this reverse flow would tend to equalize the pressure differential maintained across the first check valve 13 and consequently the relief valve assembly 16 would be caused to open and vent the-zone 15 to atmosphere and dissipate the reverse flow leakage, as particularly described in the aforementioned Patent Applications.

Check vafve 13 functions to maintain a high initial pressure differential as a backflow protection margin of safety, and to resist initial flow through the check valve. However, as normal flow is established and increases, the initial pressure differential across its seat is reflected against the larger area of the valve poppet 28 and is applied across the ejector 44 which in turn aspirates the chamber 53. This combined effect causes the check valve 13 to provide a substantially reduced pressure differential under flowing conditions. This substantially reduced pressure differential is actually less than the initial pressure differential required under a no flow condition. The manner in which this lowerthan normal pressure differential is prevented from causing the differential relief valve 16 to open is fully described in the aforementioned Patent Applications.

The device shown in the drawings and described above has been found to have exceptional operating characteristics. The pressure required for initial opening of the upstream check valve 13 is relatively high, and yet the pressure drop from the inlet passage 17 to the outlet passage 18 is exceptionally low during normal flow conditions.

Claims

1. A check valve assembly comprising a stationary valve seat, a stationary barrel positioned coaxi-ally of said valve seat, a removable cover secured relative to said barrel, a valve poppet guided for movement in said barrel toward and away from said valve seat, a spring acting to move said valve poppet into sealing contact with said valve seat, means cooperating with said barrel and said cover and said valve poppet to define a spring chamber remote

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from said valve seat and enclosing said spring, said valve poppet having a central axial stem fixed thereto, a spring retainer positioned within a portion of said spring and having a central opening for slid-5 ing contact with said stem, said valve poppet, stem, spring and retainer being axially insertable into said barrel as a unitary assembly in the absence of said removable cover, and aspirator means receiving fluid flow from said barrel when said valve poppet 10 has separated from said valve seat, said aspirator means communicating with said spring chamber so that relatively rapid fluid flow through said aspirator means causes a reduction in fluid pressure in said spring chamber to oppose the action of said spring 15 and thereby reduce the pressure drop across the check valve assembly.

2. A check valve assembly as claimed in claim 1, further comprising a stationary body, the said stationary barrel being positioned within the body 20 and having said valve seat thereon, and the said valve poppet, stem, spring, retainer, barrel and seat being axially insertable into said body as said unitary assembly in the absence of said removable cover.

25 New claims or amendments to claims filed on 22 Oct. 1982.

Superseded claims 1

1. A check valve assembly comprising a statio-30 nary valve seat, a stationary barrel positioned coaxi-ally of said valve seat, a removable cover secured relative to said barrel, a valve poppet guided for movement in said barrel toward and away from said valve seat, a spring acting to move said valve poppet 35 into sealing contact with said valve seat, sard barrel and said cover and said valve poppet defining a spring chamber remote from said valve seat and enclosing said spring, said valve poppet having a central axial stem fixed thereto, a spring retainer 40 positioned within a portion of said spring and having a central opening for sliding contact with said stem, said valve poppet, stem, spring and retainer being axially insertable into said barrel as a unitary assembly in the absence of said removable cover, and 45 aspirator means receiving fluid flow from said barrel when said valve poppet has separated from said valve seat, said aspirator means communicating with said spring chamber so that relatively rapid fluid flow through said aspirator means causes a 50 reduction in fluid pressure in said spring chamberto oppose the action of said spring and thereby reduce the pressure drop across the check valve assembly.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd., Berwick-upon-Tweed, 1983.

Published at the Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.