GB2201488A - Stop tap - Google Patents

Abstract

In a stop tap (10) for a water supply system and comprising a closure member 14 and a check valve (18) at least within inlet port 11 for avoiding pollution or contamination of the piping system upstream from the tap, a device for compensating the excess pressure which builds up at the closure within the tap (10) comprises a resiliently yielding member (21) defining a closed space within a chamber (20) connected to the inlet port (11). The member (21) may include a membrane, a hollow body, a bellows, or a piston. <IMAGE>

Description

STOP TAP This invention concerns a tap for water (or other liquid) with check valves provided in the inlet and outlet ports in order to avoid possible pollution or contamination caused by the passage into the piping system situated upstream of the tap of even a few drops of water from the piping.systen downstream from the tap, and the tap is also provided with an internal pressure compensating device which compensates the excess pressure- which builds up upon closing of the tap closing member, such excess pressure causing the bleeding: of the fluid, or the rupture of the check valve situated on the inlet port.

Increasingly severe standards require the adoption. in appropriate cases of stop taps of this anti-pollution type in order to prevent the water downsteam from the tap from accidentally backflowing and polluting, even with only a few drops, the water upstream from the tap. Such taps may be used, for example, to isolate the water plant in a building from the mains, or more specifically the piping system of a plot of land from that of the building on it, or to-isolate single sanitation systems from the piping system of an apartment.The use of check valves incorporated in the water inlet and outlet ports of a stop tap would of itself be expected to solve the problem satisfactorily, however,'when a non-return valve is provided in the tap, particularly in the inlet port, the danger exists that a few drops of water nevertheless be drawn downstream due to poor sealing-of the valve under pressures higher than those encountered in normal operating conditions, or more precisely because of the breaking of the check valve due to the excess pressure which builds up within the tap at the moment of its closure. Such excess pressure builds up because the tap-closing member tends to move or displace a certain - volume or amount of water towards the inlet port as it moves towards the closed position, said displacement being prevented by the same check valve.No suitable means are currently known for remedying the above problem. Thus the aim of the present invention is to provide a tap for the use foreshadowed which, other than being provided with suitable non-return or check valves in the fluid inlet and outlet ports, includes adequate pressure compensating means for compensating or reducing the excess pressures that builds up within the tap at the moment it is closed. The tap may be of any type or provided with any type of closing member, such a plug or ball members for example, the check valves being so arranged as to prevent any back-flow of liquid.

According to the present invention, a stop tap comprises a hollow-body having respective liquid inlet and outlet ports which open towards an intermediate chamber, and a closing member in the said chamber, the closing member being movable between an open position, in which communication between the inlet and outlet ports is allowed, and a closed position against a seat or sealing surface, in which the inlet port is closed towards the intermediate chamber, and a check valve at least within the inlet port, the tap also being provided with a pressure compensating device comprising a compensating chamber connected to the tap inlet port, and a resiliently yielding counter-pressure member defining a closed space in the compensating chamber.

The counter-pressure member may be variously made; it must nevertheless be such as to constitute a water-tight division into two parts of the compensating chamber volume in such a way that upon moving of the closing member to closed position, the displacement of even small quantities of liquid which remain trapped between the check valve in the inlet port and the tap closing member brings about an increase in the volume of that part of the chamber in communication with the inet port, set against a corresponding reduction in volume of the remaining part of said chamber, which is sealingly separated from the former through said counter pressure member or its resiliently yielding portion.

For the purposes of this description, by "resiliently yielding member" is meant any member capable of elastic deformation, whether totally or partially, or alternatively a member capable of movement against the action of a thrust biasing means, according to the needs or uses in each particular application. For example, the counter-pressure member of the compensating chamber may be in the form of a flexible membrane, which may be flat or convex, sealingly disposed within the compensating chamber, or a belllows-like folding element, or it may be a tightly sliding piston within the chamber with spring biassing means, or yet again said counter-pressure member can be in the form of an internally hollow body, such as a ball, a cylinder or the like, made of elastomeric material.

Some examples of tap realisations according to the invention will be described below, with reference to the accompanying drawings, in which: Figure 1 is a section through a tap with an axially movable plug-like closing member and provided with a pressure compensating device according to this invention; Figure 2 its a section through a tap with a rotary ball-like closing member and provided with a pressure compensating device according to this invention; Figures 3 to 6 are fragmentary sections showing alternative embodiments of pressure compensating device.

In Figure 1 is shown a water or other fluid tap having a body 1 comprising an inlet port 11 and an outlet port 12 which open into an intermediate chamber 13, also referred to as the closing member chamber, in which a plug-like closing member 14 is provided, carried by a drive shaft 15, operated by way of a hand-knob 16. The closing member 14 is movable between an open position set back with respect to the surface of a seating 17 at the end of the inlet port 11 or of its extension, and a closed position, shown in Figure 1, in which the closing member 14 presses against the annular surface of the seating 17.

References 18 and 19 in Figure 1 indicate check valves located in the inlet and outlet ports 11 and 12 respectively.

The check valves 11 and 12 are oriented so as to allow the flow of liquid from the inelt port 11 to the outlet port 12, but preventing any flow in the opposite direction. The use of such valves or corresponding checking elements is suggested in order to prevent possible pollution of the upstream fluid by the fluid downstream from the tap, even if through the passage of only a few drops.

Nevertheless the risk exists that because of the deformation which the closing member or its seal undergo through time, the volume of water or of liquid which remains trapped between the closing member in closed position and the upstream check valve 18 may force the liquid upstream, beyond valve 18,- because of the excess pressure generated by the movement or displacement of the small quanti.ty of incompressible liquid remaining in the tap, with the risk of detrimentally damaging the check valve during prolonged use in time.

In order to obviate the above difficulty, the tap has been furnished with a pressure compensating device capable of absorbing the excess pressure which would tend to build up within the tap upon closure. Such device comprises a pressure compensating chamber 2 which communicates with the port 11 at a location between the closing member chamber 13 and the respective check valve 18. Inside the compensating chamber 2 is an elastically yielding member 21, in the sense defined above which member 21 seals off a certain volume 2a of the compensating chamber 2 in which air is either at atmospheric pressure or at another and pre-determined pressure to which it is loaded, in such a way as to allow elastic deformation and create a counter-thrust such that for every variation of volume on one side of the member 21, caused by a movement or displacement of the liquid due to closing movement of the closing member 14, there will be a complementary variation in volume, inverse to the way just described on the opposite side.In the case of Figure 1, the elastically yielding element 21 is represented in the form of a bell shaped membrane, the edge 22 of which is an annular flange sealed against the rim of the chamber 2 through a screw-on, removable closing cap 23.

Figure 2 of the attached drawings shows an identical solution only this time applied to a tap with a rotary balllike closing member. In Figure 2 the same references as in Figure 1 have been used in order to indicate the same or equivalent parts.

The tap in Figure 2 differs from that in Figure 1 only for the fact that in Figure 2 the ball-like closing member 14a forms a seal against two lateral rings 17a and 17b in a way which is per se known.

In Figure 3 a first alternative solution regarding the pressure compensating device is shown; in this case the compensating chamber 2 comprises surface means adapted to receive and support an elastically yielding member 24 in the form of a hollow ball 24. The ball 24 must contain sufficient volume 2a of air at atmospheric pressure or at greater pressure in order to stand up to the normal feeding pressure of the liquid through the tap 1. Obviously it is possible to adapt or modify the characteristics of the device, for example, by varying the type of material used, or its thickness, in order to give a counter-thrust or a counterpressure of the preferred degree upon closure.

A second alternative embodiment is shown in Figure 4; in this case the pressure compensating chamber 2 has been modified to receive a counter-pressure member 25 of closed hollow cylindrical form in order to provide a variable volume closed portion 2a within the compensating chamber.

Alternatively, the cylindrical member 25 may present on its bottom an annular flange to seal against the rim 26 of the chamber 2 and the closing cap 23.

Figure 5 shows a fourth embodiment in which the counter-pressure member 27 has a bellows-like folded wall capable of yielding elastically.

Finally, Figure 6 shows a fifth embodiment in which the counter-pressure member of the pressure compensating device is in the form of a piston 28, with a sealing ring which tightly slides along a cylindrical wall of the chamber 2, and a thrust spring 29 biassing the piston.

Claims (1)

1. A stop tap comprising a hollow-body having respective liquid inlet and outlet ports which open towards an intermediate chamber, and a closing member in the said chamber, said closing member being movable between an open position, in which communication between the inlet and outlet ports is allowed, and a closed position against a seat or sealing surface, in which the inlet port is closed towards the intermediate chamber, and a check valve at least within the inlet port, the tap also being provided with a pressure compensating device comprising a compensating chamber connected to the tap inlet port, and a resiliently yielding counter-pressure member defining a closed space in the compensating chamber.

2. A tap according to Claim 1, in which the resiliently yielding member is in the form of a flexible membrane sealingly disposed within the compensating chamber.

3. A tap according to Claim 2, in which the membrane is bell-shaped.

4. A tap according to Claim 2 or Claim 3 in which the edge of the membrane is an annular flange sealingly pressed between the rim of the compensating chamber and a screw on removable closing cap.

5. A tap according to Claim 1, in which the resiliently yielding member is in the form of an elastically yielding hollow body.

6. A tap according to Claim 5, in which the compensating chamber comprises surface means for receiving and supporting the yielding pressure compensating member.

7. A tap according to Claim 5, in which the elastically yielding member is in the form of a cylindrical or spherical hollow body.

8. A tap according to Claim 5, in which the elastically yielding member is in the form of a hollow body having-a bellows-like folded wall.

9. A tap according to Claim 1, in which the pressure compensating device comprises a cylindrical chamber, a tightly sliding piston in the chamber, and spring means biasing the piston against the liquid pressure in the tap.

18. A stop tap substantially as hereinbefore described with reference to Figure 1 or Figure 2, or either as modified in accordance with any one of Figures 3 to 6 of the accompanying drawings.