GB2088023A - Anti-syphon valves - Google Patents

Abstract

An anti-syphon valve unit is provided as a separate unit adapted to be incorporated into a waste water piping system, rather than providing a water seal trap with integral anti- syphon device. The valve unit includes one or more valve members arranged to provide a seal against egress of water or gases under positive or nil pressure and to admit air into the system under negative pressure within the system. The or each valve member may comprise a resilient diaphragm 37 cooperating with a valve seat portion of the unit to seal off at least one vent hole 34 in the seat portion. A projecting ring 36 may be provided to form the actual valve seat. Alternatively, the valve member may be a frustoconical plug in a corresponding aperture in a body portion of the valve unit, the plug lifting to permit air to enter the piping system under negative pressure, the lifting movement being limited by a abutment in the valve unit. Alternatively again, the unit may have a plate-like valve member together with biassing means therefore to seal off one or more vent holes. <IMAGE>

Description

SPECIFICATION Anti-syphon valves This invention relates to the prevention of syphoning in a drainage system and more specifically to valve units for incorporation into a drainage system for this purpose.

It has been known for many years that offensive smells from sewers can be excluded by the use of a water seal such as a bottle trap or a trap of U formation, but the water seal can be lost either by the phenomenon of self-syphonage by which a sanitary fitting such as a wash basin empties with such velocity that all the water passes away including that water which should remain in the trap, or by induced syphonage when negative pressure, in the pipework system downstream of the trap, caused by some alternative phenomenon causes withdrawal of the water seal from the trap.

Traps with integral anti-syphon valve units have been manufactured but tend to be bulky and/or complicated to mould. One such trap incorporates in an outlet arm thereof a machined brass weight arranged to seat against a frustoconical seating and to lift from the seating, thus to permit ingress of air, when negative pressures occur within the trap which could precipitate syphoning. This requires the use of expensive materials which must be accurately machined and further is of limited usefulness and reliability.

According to the present invention there is provided a separate anti-syphon valve unit adapted to be incorporated into a waste-water piping system, which valve unit includes at least one valve member arranged to provide a seal against egress of water or gases under positive or nil pressure and to admit air into the system under negative pressure within the system.

Very preferably the valve member comprises a resilient diaphragm arranged to seal off at least one vent-hole in the valve unit; alternatively a plate-like valve member may be employed together with biassing means to seal off one or more vent holes except when under negative pressure. It is also possible to use a frustoconical valve member in conjunction with a corresponding frustoconical seating thereof, but this may be less desireable for reasons as outlined above.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig 1 is a vertical cross section through a first valve unit embodying the present invention; Figs 2 and 3 are respectively a vertical cross section and a plan of a modification of the valve unit of Fig. 1:Figs 4, 5 and 6 are respectively a plan and vertical cross sections along planes A-A and B-B in Fig 4 of a second valve unit embodying the present invention; Fig 7 is a vertical cross section of a third valve unit embodying the present invention; Fig 8 is a vertical cross section through a fourth valve unit embodying the present invention; Fig 9 is a vertical cross section through the valve part of a fifth valve unit embodying the present invention; Fig 10 is a vertical cross section through the valve body (but not showing the valve diaphragms) of a multiple valve unit incorporating a plurality of valves such as that of Fig 9; and Fig 11 is an underneath plan view of the valve seat portion of a four-valve unit incorporating a body such as that of Fig 10 with valves such as that of Fig 9.

Referring firstly to Fig. 1 of the drawings there is shown a valve unit 1 comprising a generally cylindrical valve body 2 having an integral convexly dished top 3 provided with a plurality of symmetrically spaced apertures 4 and a centrally disposed downwardly projecting peg 5. The valve body 2 is threaded at 6 for fitting it to a conventional T-piece or any other suitable connector for incorporation into a piping system and is provided with peripheral means 7 adjacent its top 3 for receiving a cap 8. The peripheral means 7 in this embodiment comprises a projecting flange over which the cap 8 is adapted to snap into position but may comprise other suitable inter-engagement means, for example a corresponding peripheral recess for cooperation with a peripheral flange on the cap 8, a bayonet fitting, or a screw thread.It is to be noted that in each case the cap 8 is so fitted on the valve body 2 as to permit air to reach the apertures 4 and to shield the apertures 4 from accidental obstruction.

On the peg 5 is mounted, by means of a togglering, circlip or other suitable device 9, a circular resilient diaphragm 10.

The diaphragm 10 is made of any suitable elastomeric material such as rubber, neoprene or EPDM while the valve body 2 and the cap 8 are likewise made of any suitable material such as polypropylene, polyethylene, an ABS plastic, polyvinyl chloride, nylon or poíybutylene.

The embodiment shown in Figs. 2 and 3 is similar to that of Fig. 1 with the difference that the valve body 2 is adapted to be solvent-welded to an appropriate connector such as a T-piece, and as such is not provided with the screw threading 6.

In use and under positive or nil pressure within the piping system the resilient diaphragm 10 will seal the apertures 4 against the egress of water or gases from the piping system but under a negative pressure such as might otherwise cause syphoning to occur within the piping system, the diaphragm 10 will move to open the apertures 4 and admit air into the piping system until the internal and external pressures are equilibrated.

The working pressure under which the diaphragm 10 will open can be determined by appropriate choice of resiliency of the diaphragm, thickness thereof, number and/or dimensions of apertures 4 and/or by selecting a different radius of curvature for the convex top 3.

In the embodiment of Figs. 4 to 6 the valve body 2, which in this case is of the solventweldable variety, is provided with a frustoconical valve member 11 which is received in a frustoconical seating 12 made of a suitable, preferably, resilient material. The seating 1 2 is in the form of a grommet adapted to fit in an aperture 13 located centrally within the valve body 2 and connecting the interior 14 of the valve body 2with a passage 1 5 arranged transversely in the valve body 2 and in communication with the exterior of the valve body 2. A depending (downwardly projecting) member 16, formed in a threaded cap 17, provides an abutment to prevent the valve member 11 from being entirely displaced from its seating 12 whilst permitting such limited movement as will admit air into the piping system.

Thus under negative pressure within the piping system the valve member 11 will lift and permit air to enter the valve via the passage 1 5 and aperture 1 3. It is a feature of this embodiment that a standard valve body can be employed, variations - in operating pressure being achieved by adoption of valve members 11 of different weights and/or diameters and of seatings 12 of various different internal diameters but of the same external diameter.

In the embodiment of Fig. 7 the valve member 11 comprises an annular plate arranged to seal a plurality of apertures 4 and biased to a sealing position by means of a coil spring 1 8. A seal 1 9 of, for example, oiled paper, may be provided to ensure air-tightness as required and a threaded cap 20 is provided on the valve unit to retain the spring 19 and to facilitate dismantling for inspection purposes.

It will be observed that the air-inlet apertures of the embodiments of Figs. 5 to 7 are so located as to render unnecessary the provision of a cap or other means to shield the apertures from accidental obstruction and that in all cases the units may be dismantled for cleaning, maintenance or inspection.

The embodiment of Fig. 8 is somewhat similar to those of Fig. 1 and Figs 2 and 3 but incorporates certain improvements. The valve body, instead of being formed integrally, comprises a stub pipe 30 which is adapted to be solvent-welded to an appropriate connector (as in the case of the embodiment of Figs. 2 and 3) and has an externally screw threaded end 31 onto which a retaining ring 32 is screwed. This ring holds in place a slightly domed and peripherally flanged valve seat portion 33 having a plurality of apertures 34 for the admission of air to the cylindrical portion 30. A rubber seal washer for other resilient sealing ring 35 is interposed between the periphery of the valve seat portion 33 and the adjacent end of the stub pipe 30.

The surface of the valve seat portion 33 facing towards the stub pipe 30 is formed with a projecting ring 36 which constitutes the actual valve seat, on which the diaphragm 37 bears to form the seal, surrounding the apertures 34. The diaphragm is similar to that of the embodiments of Fig. 1 and Figs. 2 and 3 and is similarly secured to a central peg 38 formed on the valve seat portion 33.

The valve unit is covered by a snap-on cap 40 which engages with the retaining ring 32. The ring has a chamfered surface 41 and air ways 42 for venting as indicated by a line terminating in an arrow head 43.

Such a valve seat and diaphragm combination is also employed in the embodiment of Fig. 9 which shows these parts in greater detail. Here, the valve seat portion 50 is only domed on its sealing surface (adjacent to the diaphragm 51) over an area which includes the projecting ring 52 on which the diaphragm 51 forms the seal, the other surface 53 of the valve seat portion being fiat. This drawing also shows that the diaphragm 51 can be secured to the peg 54 by means of a spire nut 55.

Fig. 10 shows the valve body of a multiple valve unit incorporating a plurality of valves as shown in Fig. 9, the diaphragm (not shown in Fig. 10) being secured to the pegs 54 of the multiple valve seat portion 50'. The construction of this unit is otherwise generally similar to that of Fig. 8 with screwed on retaining ring 56, resilient sealing ring 58 and snap-on cap 60 which in this case is slightly domed. The snap-on and holding-down arrangements of this cap comprise a peripheral series of inwardly projecting ribs 62, and the venting air enters the cap through the spaces between these ribs.

The provision of a multiple valve unit such as that of Fig. 10 is intended to overcome the problem that there is a limit to the extent to which a single valve unit can be scaled up to enable larger bore pipes to be vented adequately. This limit is possibly due to the fact that the weight of the diaphragm, acting downwards, counteracts its resilient, upward, sealing action. This problem is overcome by incorporating a plurality of small valve units into one moulding (50'). The valve unit as a whole could be provided with any number of individual valves to suit the requirement. Two such units are shown in Fig. 10 and four in Fig. 11 which also shows each valve seat portion having four venting apertures 64 of arcuate form.This four-valve arrangement has been designed for 4 inch pipe, but in designing a valve unit for 1 10 millimetre pipe it has been found preferable to provide a three-valve unit incorporating three small valves with their seat parts formed in one moulding. It will be appreciated, therefore, that by altering the number of individual valves provided, pipes of any size could theoretically be vented.

Thus by means of the present invention there is provided a separate anti-syphon valve unit which is easily incorporated at any desired place in a piping system; of course, more than one such valve unit may be employed if so wished.

Moreover, the use of such a valve unit may enable the user to dispense with the traditional upstanding soil pipe. Valve units embodying the present invention are cheap to manufacture, quiet in use, easy to assemble and install and reliable to use.

Claims (14)

1. A separate anti-syphon valve unit adapted to be incorporated into a waste water piping system, which valve unit includes at least one valve member arranged to provide a seal against egress of water or gases under positive or nil pressure and to admit air into the system under negative pressure within the system.

2. A valve unit according to claim 1, wherein the valve unit has at least one vent hole through which the air is admitted and the valve member comprises a resilient diaphragm arranged to seal off said vent hole when the diaphragm is under positive pressure and to open said vent hole under negative pressure.

3. A valve unit according to claim 2, including a seat portion with which the resilient diaphragm cooperates and in which said vent hole is formed.

4. A valve unit according to claim 3, wherein the seat portion has a projecting ring with which the diaphragm cooperates.

5. A valve unit according to claim 3 or claim 4, wherein seat portion is formed with a peg to which the diaphragm is secured.

6. A valve unit according to any one of claims 3 to 5, including a plurality of individual valves constituted by respective resilient diaphragms and seat portions.

7. A valve unit according to claim 6, wherein the plurality of seat portions are formed integrally as a multiple valve seat portion.

8. A valve unit according to any one of claims 3 to 7, including a stub pipe and a clamping ring to secure the seat portion to one end of the stub pipe.

9. A valve unit according to claim 8, wherein the clamping ring has air ways for the admission of venting air to the or each valve.

10. A valve unit according to claim 8, including a snap-on cap which engages the clamping ring by means of inwardly projecting ribs between which the venting air can enter the unit.

11. A valve unit according to claim 1, wherein the valve member comprises a frustoconical plug seated in a corresponding aperture and arranged to lift under negative pressure in the piping system, the lifting being limited by abutment means in the valve unit.

12. A valve unit according to claim 1 1, wherein the abutment means comprises an inwardly projecting portion of a cap of the unit.

13. A valve unit according to claim 11 or claim 12, wherein a transverse channel for the admission of venting air is provided in a body portion of the unit in which the valve seat is formed.

14. A valve according to claim 1, wherein a plate-like valve member is employed together with biassing means therefor to seal off one or more vent holes when the valve member is under positive pressure or nil pressure and to open the vent holes under negative pressure.

1 5. A valve unit substantially as hereinbefore described with reference to Fig. 1; Figs. 2 and 3; Figs. 4, 5 and 6; Fig. 7; Fig. 8; Fig. 9; Fig. 10; or Fig. 11 of the accompanying drawings.