PRESSURE CONTROL VALVE
Technical Field
This invention relates to pressure control valves. In particular, this invention relates to self regulating pressure control valves suited to high inlet pressures and low outlet pressures, for example, such as that found in domestic water reticulation systems.
The main purpose of a pressure control valve is to reduce an incoming mains supply pressure or inlet pressure to an acceptable user pressure or outlet pressure. This purpose is usually achieved by balancing the force exerted by the outlet pressure against a control mechanism.
Background Art
One type of such pressure control valve includes a valve body having a flow path defined therethrough from an upstream or inlet opening high pressure side to an eventual downstream or outlet opening low pressure side, the valve body being provided with a seat for sealingly seating a displaceable seal which is located on a spindle in the flow path, to which spindle a spring is operatively connected so as to urge the displaceable seal in a first direction while a diaphragm, also operatively connected to the spindle, acts in sympathy with the outlet pressure to counteract the urging of the spring in order to attain a pre-set outlet pressure. The spring may be settable to exert a desired urging force on the spindle resulting in a desired outlet pressure. In presently available pressure control valves the diaphragm tends to be selected to have a larger diameter than the inlet of the pressure control valve.
Presently available pressure control valve suffer from problems including: pressure creep, which is the gradual increase in the outlet pressure beyond the pre-set value during the operating cycle; low through flowrates for any given size; where the setting results in a high differential between the inlet and the outlet pressures the operation thereof may be noisy; the seat-seal configuration which is used to avoid noise is susceptible to dirt and surface flaws preventing proper operation; the response to inlet pressure fluctuation is slow; and slow reaction to rapid changes in the outlet pressure, for example, where a vessel which is being supplied from the outlet undergoes pressure fluctuations.
Presently known pressure control valves may include a seat portion having an arcuate seat face in the shape of a shallow radius in order to reduce noise over the seat. Usually such a seat is in the form of a sunken seat having a sealing seat surface shy of the bulk of the seat surface. This is however believed to promote pressure creep for such valves. Thus it may be generally stated that with conventional pressure control valves the reduction in operating noise goes hand in hand with increased pressure creep characteristics.
Typically, presently available pressure control valves are less prone to the above problems when the required outlet pressure is relatively high, for example, 400 kPa.
Disclosure of the Invention
The present invention attempts to provide a pressure control valve which suffers less from at least some of the problems described above. In some configurations, the invention provides for a substantially pressure creepless, quite pressure control valve.
Thus, according to a first aspect of the invention, there is provided a pressure control valve of the type described above, the pressure control valve additionally including turbulence reduction means located proximally the outlet opening and the seat.
The turbulence reduction means may be in the form of a sheet having one or more apertures or notches provided therein, in use, the one or more apertures or notches being at least partially located in the flow path.
In this specification, unless the context clearly indicates to the contrary, the words "aperture" and "apertures" are used to indicate an opening in a sheet or a sleeve, not necessarily delimited along the entire aperture perimeter by the sleeve or sheet, such as for example, a notch or cut away portion.
A portion of the sheet may define at least part of the seat of the pressure control valve.
The sheet may be a sleeve fittable into the valve body. The sleeve may act as an alignment means for aligning the displaceable seal and the seat for efficient sealing.
Typically, the one or more apertures are sized and dimensioned to provide backpressure onto the seat and displaceable seal thereby to reduce the turbulence caused by high velocities due to large pressure drops over the seat and displaceable seal. It is believed that the one or more apertures provide a staged pressure drop thereby providing a staged increase in velocity over the flow path, thereby contributing to reduction in noise under high pressure drop conditions.
The one or more apertures may have one or more straight sides.
Typically the one or more apertures are square, rectangular, trapezoidal, or the like.
If desired, and to further reduce noise, the surface finish of the aperture edges may be to a high level, for example, mirror polish or electroplated.
The aperture edges may be chamfered.
According to a second aspect of the invention, there is provided a pressure control valve of the type described above, the pressure control valve being characterised in that the seat includes a raised seat portion having a minor chamfer on its high pressure side, said seat being sized and dimensioned to, in use, sealingly-seat the displaceable seat thereon.
Typically, the seat facing surface of the displaceable seal is chamfered complementarily to the chamfer of said seat.
In an advantageous embodiment the chamfer is polished to reduce friction over the seat thereby reducing noise from the valve.
In this specification, the term "raised seat" refers to a seat configuration wherein the seal receiving portion of the seat is displaced from the body of the seat, an example of which is shown in the accompanying diagrammatic drawings.
In one embodiment, for a pressure control valve sized to reduce an incoming pressure of up to 2000 kPa to a relatively low outlet pressure of below 400 kPa, typically below 200 kPa or even 100 kPa, the chamfering of the raised seat portion may be at an angle of 30° from the horizontal. The chamfer being about 0.4 mm on a nominally 20 mm pressure control valve.
According to a third aspect of the invention there is provided a pressure control valve including both the turbulence reduction means and the chamfered raised seat portion, substantially as described above.
The valve may be made of any suitable material but typically such valves are made from brass.
Likewise, the sleeve may be made from any suitable material, however, typically the sleeve is made from a plastics material, such as PVC or polypropylene, or the like.
Brief Description of the Drawings
The invention will now be described, by way of non-limiting example only, with reference to the accompanying diagrammatic drawings.
In the drawings,
Figure 1 shows, schematic representation, in sectional side view, a pressure control valve in accordance with the invention; and
Figure 2 shows, a sleeve having a rectangular aperture and a chamfered raised seat provided thereon.
In Figure 1 , reference numeral 10 generally indicates a pressure control valve for a domestic water reticulation system, broadly in accordance with the invention.
The pressure control valve 10 includes a valve body 12 having a flow path 14 defined therethrough from an upstream or inlet opening 16 high pressure side to an eventual downstream or outlet opening 18 low pressure side, the valve body 12 being provided with a sleeve 40 having a seat 20 for sealingly seating a displaceable seal 22 which is located on a hollow spindle 24 in the flow path 14. A spring 26 is operatively connected to the spindle 24 so as to urge the spindle 24, and thus the displaceable seal 22, downwards 28 in an outlet pressure increasing direction while a diaphragm 30, also operatively connected to the spindle 24 and in flow communication with the outlet opening via the hollow spindle centre 25, acts in sympathy with the outlet pressure to counteract the urging of the spring 26 in order to attain a pre-set outlet pressure at the outlet opening 18. A notch 42 in the sleeve 40 is positioned in the flow path 14 directly opposite the outlet opening 18, between the spindle 24 axis and the outlet opening 18.
The spring 26 is settable by means of a set screw 27 to exert a desired urging force on the spindle 24 resulting in a desired outlet pressure.
In a valve 10 which is nominally 20 mm, the diaphragm 30 is similar in diameter to the inlet opening 16 diameter. This configuration leads to cost advantages in the manufacturing process since a smaller diameter diaphragm 30 allows for a smaller valve body bore 13, thereby requiring less materials, in this case brass. It also permits easier working of the valve body 12 by smaller machines. However, for other valve 10 sizes the diaphragm 30 diameter may be different in size to the inlet opening 16 diameter.
Furthermore, the smaller diameter diaphragm 30 also allows the valve body 12 to be forged rather than cast, thereby to obtain a stronger valve body 12 with thinner valve body walls 1 1 , leading to even further materials savings.
In use, the spring 26 is pre-set for a desired outlet water (or other fluid) pressure, say 100 kPa. The high pressure water (or other fluid), at pressures of up to 2000 kPa, or even more, is permitted to enter the pressure control valve 10 at inlet opening 16. The high pressure water passes along the flow path 14 into the valve body 12 where displaceable seal 22 has been lifted from its seat 20 under the urging of the spring 26 on the end of spindle 24. The water passes the seat 20 and while most of the water leaves the valve via outlet opening 18, some water passes up the hollow spindle centre 25, which acts as a pressure equalising conduit between the underside of diaphragm 30 and the outlet preset pressure at the outlet 18. The water which has passed through the hollow spindle centre 25 exerts a pressure on the diaphragm 30 which in turn urges the spindle 24, and thus the displaceable seal 22, towards a closed position, in which the flow of water through the valve body 12 is restricted, thereby balancing the spring 26 against the outlet pressure to achieve the desired outlet water pressure. A seal 41 acts to otherwise, except for the hollow spindle centre 25, keep the underside of the diaphragm 30 isolated from the inlet pressure at inlet 16.
In Figure 2, reference numeral 40 indicates the same sleeve as sleeve 40 of Figure 1 .
The sleeve 40 is fittable into the valve body 12 of Figure 1 , as shown in Figure 1 . The sleeve 40 acts also as an alignment means for aligning the displaceable seal 22 and the seat 20 for efficient sealing.
As described above for Figure 1 , the sleeve 40 has a generally rectangular notch 42 sized and dimensioned to provide backpressure onto the seat 20 and displaceable seal 22 thereby to reduce the turbulence and noise caused by high velocities, due to the large pressure drops, over the seat 20 and displaceable seal 22, as well as over the valve body generally. It is believed that this configuration provides a staged pressure drop over the flow path 14, thereby providing a staged increase in velocity over the flow path 14, and contributing to reduction in operating noise under high pressure drop conditions.
Also on the sleeve 40 is provided the seat 20. The seat 20 is in the form of a raised seat portion 21 , which is believed to eliminate creep, having a minor chamfer 23 on its high pressure side, which is believed to reduce the noise normally associated with raised seats, said seat being sized and dimensioned to, in use, sealingly-seat the displaceable seat 22 thereon.
Typically, the seat facing surface 19 of the displaceable seal 22 is chamfered complementarily to the chamfer 23 of said seat 20.
In an advantageous embodiment the chamfer 23 is polished to reduce friction over the seat 20 thereby further reducing noise from the valve.
In the embodiment shown, for a pressure control valve 10 sized to reduce an incoming pressure of up to 2000 kPa, or even more, to a relatively low outlet pressure of below 400 kPa, typically below 200 kPa or even 100 kPa, the chamfering of the raised seat portion 21 may be at an angle of 30° from the horizontal. The chamfer 23 being about 0.4 mm on a nominally 20 mm pressure control valve.