GB2222663A - Valve assembly - Google Patents

Abstract

A valve assembly 1 comprises a valve closure member or saddle 2 extending into a fluid flow bore 3, the valve closure member 2 having a peripheral annular flange 4, to abut against a cooperating face 5 extending around the end of the bore 3, and an annular shoulder 6 provided with a circumferential recess 7 locating a fluid sealing O-ring 9. An edge 10 of the recess 7 extends to the approximate mid-point of the O-ring 9, and the flow bore 3 has a frusto-conical valve seat 11 with which valve seat 11 an outer part 13 of the O-ring 9 is adapted to make fluid sealing contact. The junction between the frusto-conical valve seat 11 and the bore 12 is at a diameter 14 greater than the diameter 15 at the extremity of the recess 7 for the O-ring 9, and less than the outer diameter 16 of the O-ring 9. <IMAGE>

Description

VALVE ASSEMBLY ETC.

This invention relates to a valve assembly, particularly, but not necessarily exclusively, for sprinkler heads for discharging a fire quenching fluid; to a sprinkler head provided with such a valve assembly; and to a system for fire protection incorporating a plurality of such sprinkler heads.

It is already known to provide a sprinkler head formed by a sprinkler head frame having at one end a threaded stem for engagement with a pressurised fluid conduit, through which stem extends a fluid flow bore, with the flow bore terminating in a frusto-conical valve seat. Within the flow bore lies a valve closure member or saddle, having an external flange, from which extends an annular shoulder, the flange and shoulder of the saddle and the frusto-conical valve seat of the flow bore, combining to form a chamber containing a fluid sealing O-ring.Located between the saddle and a collar at the end of the sprinkler head frame remote from the threaded stem is a frangible bulb, there being a set screw extending through the collar to load the bulb against the saddle to a predetermined degree, sufficient to hold the saddle in place against the fluid pressure existing in the conduit, and compressing the sealing O-ring in the chamber.

When brought into use in the event of a fire, the frangible bulb fractures, allowing the fluid pressure in the conduit to force the saddle out of the flow bore, and to allow fluid to issue from the conduit to impinge on a deflector plate secured to the collar at the end of the sprinkler head frame, and hence provide a spray of fluid in the vicinity of the fire.

As will readily be understood, such sprinkler heads are generally expected to withstand long periods of non-use, and what has been found in practise is that compression of the O-ring over long periods causes the O-ring to adhere to the frusto-conical valve seat, causing either a delay in the ejection of the saddle or the prevention of the ejection of the saddle, even when the O-ring is formed from e.g. Teflon (Registered Trade Mark) and the saddle and frusto-conical valve seat coated with such materials.Before any sprinkler can be installed there is a mandatory requirement that its valve assembly must meet the standards laid down by approval authorities such as the Loss Prevention-Council in Great Britain, and it is essential that the valve assembly is subjected to an accelerated ageing test by holding the assembly at high ambient temperature for 9 days, after which the valve closure member or saddle must be capable of being ejected at the low pressure of .35 bar (5 psi).

An object of the present invention is to provide a valve assembly, spinkler head, and sprinkler system that avoid the problem mentioned above, and is able to meet approval authority requirements.

According to a first aspect of the present invention, there is provided a valve assembly comprising a valve closure member or saddle extending into a fluid flow bore, the valve closure member having a peripheral annular flange to abut against a co-operating face extending around the end of the bore, a fluid sealing O-ring carried by the valve closure member, and the bore having a frusto-conical valve seat, with which an outer part of the '0'-ring is adapted to make fluid sealing contact, the minimum diameter of the frusto-conical valve seat terminating between the outer diameter and the inner diameter of the 0-ring.

According to a second aspect of the present invention there is provided a sprinkler head incorporating a valve assembly as defined above.

According to a third aspect of the present invention there is provided a sprinkler system for fire protection incorporating a plurality of sprinkler heads as defined above.

Thus, with the valve closure member held within the bore with its peripheral flange in contact with the cooperating face at the end of the bore, the flange and shoulder and the frusto-conical valve seat form a chamber for the 0ring, in which chamber the O-ring is compressed against what is in effect a shortened valve seat, compared with conventional arrangements, to achieve both reduced surface contact with the frusto-conical valve seat and contact of a part of the O-ring with the fluid flow bore, whereby an effective seal is provided, and as a result of the reduced surface contact, reduced "stiction" between the O-ring and its seat upon separation of the O-ring from its seat.When the flow of fluid is required, the means holding the valve closure member in place is removed, and pressure of fluid in the conduit acting on the valve closure member results in the immediate release of the 0being from the valve seat.

Preferably, one end of the frusto-conical valve seat merges into the bore at a radius, to avoid any burr which might resist departure of the O-ring from its seat, and furthermore the frusto-conical valve seat preferably extends to an outlet from the bore which is flared or angled e.g., at 150 so as to assist in preventing the O-ring from binding on the wall of the bore as the valve closure member or saddle is ejected.

In its application to a sprinkler head of the type above defined, the reduced surface contact between the valve seat and the O-ring, that combine in their effect as has been mentioned above, has the result that the sprinkler head can be subjected to long periods of non-use, with the substantial certainty that the instant the heat sensitive element, such as a frangible bulb, is activated in the event of a fire, the valve closure member or saddle is instantly ejected from the bore to permit the flow of water.

With such items as sprinkler heads, a variety of bore diameters need to be available to provide for a greater or lesser volume of fluid to issue to suit a particular location.

With conventional sprinkler heads, the valve assembly is purpose built to suit a particular bore diameter, and the smaller the valve closure member or saddle, the greater is the tendency for it to stick over prolonged periods of non-use.

With the valve assembly according to the invention, a number of bore diameters can advantageously be accommodated up to the maximum for which the same O-ring is suited, thereby providing a degree of standardisation. Thus, for a bore diameter smaller than the permitted maximum, a bore of the required smaller diameter is formed, which is enlarged to the diameter of the maximum bore (to reduce the length of the valve seat and hence the contact area) at a point spaced from the frustoconical valve seat, and which continues at the maximum diameter to the radiussed corner at the junction of the enlarged bore with the valve seat. Consequently, a valve closure member or saddle for example, designed to suit a 3/4" (13.4 mm) diameter bore can be used in conjunction with a bore diameter down to 3/8" (9.5 mm).

The invention will now be described, in greater detail, by way- of example only, with reference to the accompanying drawings, in which: Figure 1 is a part schematic sectional side elevation of a valve assembly; and Figure 2 is a part sectional view through a sprinkler head.

In the drawings, a valve assembly 1 comprises a valve closure member or saddle 2 extending into a fluid flow bore 3.

The valve closure member 2 has a peripheral annular flange 4 to abut against a co-operating face 5 extending around the end of the bore 3, there being directly adjacent the annular flange an annular shoulder 6 provided with a circumferential recess 7 in which is located an inner part 8 of a fluid sealing 0-ring 9. An edge 18 of the recess 7 remote from the annular flange 4 extends to the approximate mid-point across the width of the O-ring 9 so as to captivate the O-ring. The flow bore 3 has a frusto-conical valve seat 11 merging at one end thereof with the bore 3 at a radius 12, with which valve seat 11 an outer part 13 of the O-ring 9 is adapted to make fluid sealing contact. The bore 3 may have a maximum diameter 14 greater than the diameter 15 at the extremity of the recess 7 for the O-ring 9, and less than the outer diameter 16 of the O-ring 9. At its other end, the frust-conical valve seat 11 extends to a flared or angled outlet 17 from the bore 3, which may require for the particular operational function in question, a minimum or reduced bore diameter 18 which is enlarged to the diameter 14 at a point 19 spaced from the radius 12.

Claims (9)

1. A valve assembly comprising a valve closure member or saddle extending into a fluid flow bore, the valve closure member having a peripheral annular flange to abut against a co-operating face extending around the end of the bore, a fluid sealing O-ring carried by the valve closure member, and the bore having a frusto-conical valve seat with which an outer part of the O-ring is adapted to make fluid sealing contact, the minimum diameter of the frusto-conical valve seat terminating between the outer diameter and the inner diameter of the O-ring.

2. A valve assembly as claimed in Claim 1, wherein the valve closure member is provided with a circumferential recess, with an inner part of the O-ring engaging the recess, so that the O-ring is retained on the valve closure member.

3. A valve assembly as claimed in Claim 1 or Claim 2, wherein one end of the frusto-conical valve seat merges into the bore at a radius.

4. A valve assembly as claimed in any preceding Claim, wherein the frusto-conical valve seat extends to a flared or angled outlet from the bore.

5. A valve assembly as claimed in Claim 4, wherein the outlet is flared or angled at 150.

6. A valve assembly as claimed in any preceding Claim, wherein, for a bore diameter smaller than a maximum diameter, a bore of the required smaller diameter is formed and is enlarged to the diameter of the maximum bore at a point spaced from the frusto-conical valve seat, and which continues at the maximum diameter to the junction with the valve seat.

7. A valve assembly substantially as hereinbefore described with reference to the accompanying drawing.

8. A sprinkler head provided with a valve assembly as defined in any one of Claims 1 to 7.

9. A sprinkler system provided with a plurality of sprinkler heads as defined in Claim 8.