GB2205595A

GB2205595A - W.C. cistern

Info

Publication number: GB2205595A
Application number: GB08713565A
Authority: GB
Inventors: Alan David Somerfield
Original assignee: Nat Research & Dev Corp
Current assignee: Nat Research & Dev Corp
Priority date: 1987-06-10
Filing date: 1987-06-10
Publication date: 1988-12-14
Anticipated expiration: 2007-06-10
Also published as: GB2205595B; GB8713565D0

Abstract

A WC cistern comprises a vessel (1) containing a fluid conduit of sinuous shape (10, 11 - 14). When the cistern is charged, discharge is prevented by pressurised air locked in part of the conduit (including 15) by a column of liquid (b) located downstream of it within the conduit. A venting tube (25) is operable to connect the air lock region (15) of the conduit with a more downstream region (17) at ambient pressure, and operates thus when a bulb (32) is squeezed to expel liquid from the tube, so initiating a discharge of the cistern. The vent tube (25) may also have a branch limb (50) having an open end (52) located only slightly below the normal full liquid level (6) within the cistern; this feature can operate to prevent initiating a discharge of the cistern by operation of the bulb (32) unless the cistern is at least nearly full. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO CISTERNS This invention relates to cisterns for water closets or the like, of the kind comprising vessels which are adapted to be repeatedly filled with liquid to a predetermined high level, and then caused to discharge by the action of a human operator or automatic mechanism.

Standard requirements set by the United Kingdom and many other nations require that the discharge of such cisterns shall be due, at least in the later stages of each discharge, to syphonic action. The advantage of such action is that no moving parts are needed to sustain it and that the discharge ceases reliably - again without the need for any moving parts - when the liquid in the cistern falls below a certain level, allowing air to enter a hitherto unbroken column of the discharging liquid so as to break the syphon.

For some known designs of WC cistern, syphonic action is necessary for the whole of each discharge operation; for other designs, simple gravity action is at least partly responsible for the beginning of each discharge operation, wholly syphonic action only taking over once the liquid level within the cistern has fallen somewhat. With all designs, some work has to be done to cause a discharge to begin. With most known designs of cistern this work involves the relative movement of associated and rigid mechanical components, such as the opening of a valve, the raising of a bell or the stroke of a piston in a cylinder. Such moveable components are inherently capable of breakage or other malfunction, and the effort required to move them, whether supplied by a human operator or by an automatic mechanism, can be inconveniently high.

The present invention arises from appreciating that a cistern with the required degree of syphonic action can be made without such mechanical components, and so that an operator or equivalent mechanism need only perform very little work to initiate a discharge, because much of the work necessary not only to fill the cistern but also to bring it to the point of discharge has already been performed by the water supply system to which the cistern is connected. According to the invention a cistern for a water closet or the like comprises a vessel adapted to be filled with a liquid to a predetermined high level, and a fluid conduit of sinuous shape arranged with its inlet arranged at low level within the vessel and its outlet directed towards a point of use.The curves of the conduit are arranged so that discharge from the vessel through the conduit is prevented by a pressurised air lock supported by a column of liquid located downstream of it within the conduit, a first vent tube connects the region of the air lock within the conduit to a zone of ambient pressure, that vent tube is located so as to fill with liquid as the vessel discharges and to retain at least some of that liquid as the vessel next fills, and there are operating means operable to discharge the retained liquid from that vent tube so venting the air lock and initiating a discharge of the vessel.

The first vent tube may be in the form of a by-pass of smaller section than the conduit and connecting the air lock region with a second region of the conduit, the second region lying downstream of the pressure-supporting liquid column.

The sinuous shape of the conduit may comprise first, second, third and fourth substantially vertical limbs arranged in succession, so that the first and second limbs are joined to form an inverted "U"-bend, the second and third limbs are joined to form a "U"-bend and the third and fourth limbs are joined to form an inverted "U'-bend, and so that the second and third limbs are adapted to contain the pressure-supporting liquid column, and the by-pass tube connects the top ends of the second and third limbs.

The by-pass tube may be of "U"-shape, comprising fifth and sixth substantially vertical limbs connected at their bottom ends by a "U"-bend, the second limb may be of substantially larger section than the third limb, and the fifth limb of substantially larger section than the sixth limb.

The operating means for removing contained liquid from the first vent tube may comprise an air tube connected to it, and mechanism to vary the air pressure within the air tube. The mechanism may comprise a squeeze bulb or the like.

A second vent tube may be operable to terminate discharge from the vessel when the liquid level within the vessel falls to a predetermined low level. The inlet to the second vent tube may be connected to the conduit downstream of the region in which the pressure supporting column is contained, and the outlet of the second vent tube may be located close to the predetermined low level within the vessel. The outlet of the second vent tube may be located higher, within the vessel, than the inlet to the fluid conduit. The air tube may include an open-ended branch limb, the open end of this branch being located within the vessel but at such a level that it is only within liquid when the vessel is at least substantially full, whereby to prevent initiating a discharge of the vessel by operation of the operating means unless the vessel is at least substantially full.

The invention will now be described, by way of example, with reference to the accompanying drawing, which shows a cistern diagrammatically in vertical section.

A watertight vessel 1 is connected by way of inlet means 2 to a water supply 3. The inlet means include a conventional silencer tube 4 and are associated with a conventional ball valve 5, adjusted so as to set the normal full water level 6 as shown.

The spillover level 7 registers with an overflow outlet 8.

Within the vessel 1 is mounted a hollow conduit 10 which is of sinuous shape and comprises four successive vertical limbs 11, 12, 13 and 14. The top ends of limbs 11 and 12 are linked by a horizontal section 15 of the conduit, so that together they form an inverted "U", the bottom ends of limbs 12 and 13 are similarly joined by a horizontal section 16 so that together they form a "U", and the top ends of limbs 13 and 14 are joined by a horizontal section 17 so that together they form an inverted "U". The end 78 of limb 11 is open, is situated close to the base 19 of vessel 1, and constitutes the inlet to the conduit 10.The outer wall of limb 14 passes through a hole 20 in the base 19, where a gasket 21 prevents leakage, and the free end 22 of limb 14 constitutes the outlet of conduit 10 and will be directed towards a chosen point of use, for instance a water closet.

Sections 15 and 17 of conduit 10 are connected not only by the "U"-formation 12-16-13, but also by a vent or by-pass tube 25, also of "U"-shape and comprising two vertical limbs 26, 27 joined at their bottom ends by a horizontal section 28. One end of an air tube 29 is connected to section 28; tube 29 includes a plenum 30, and the other end of tube 29 is connected by way of a flexible tube 31 to a squeeze bulb 32. One end of a further tube 33, of inverted "U-shape, is connected to section 17 of conduit 10, and the other and open end 34 of this vent tube is located at the level 35 at which the surface of the liquid is intended to stand when the vessel is empty, that is to say as a discharge of the vessel comes to an end.

The pipework of conduit 10 and of the rest of the tubing shown, particularly tubes 25 and 33, can in principle be of a variety of sections. Typically it will be of generally circular section with the diameters of conduit 10 and tube 25 changing along their length of course.

A cycle of operation of the cistern will now be described, beginning with the vessel 1 full of water to the normal level 6 and therefore ready for a discharge to begin. In this state limb 14 will contain only air, and the level 40 of the water in tube 33 will coincide with level 6. In limbs 11, 12, 13, 26 and 27 the water levels will typically stand at 41, 42, 43, 44 and 45.

The reason for such levels will become apparent as description of the complete cycle continues : it need only now be noted that to achieve the necessary hydrostatic stability which the cistern must have when full, the vertical distances (a) between levels 6 and 41, (b) between levels 43 and 42 and (c) between levels 45 and 44 must all be equal. The water level 46 within air tube 29 will be just below level 45. While the air in section 17 and limb 14 is at ambient pressure, as the differences between levels 43, 42 and 45, 44 clearly indicate, the air in section 15 and the upper parts of limbs 12 and 26 is under pressure, and is acting as an air lock preventing the hydrostatic head of water within the vessel from driving water through conduit 10 from inlet 18 to outlet 22 under simple gravitational action, and so starting a discharge of the cistern.

Limbs 12 and 13 are of considerable internal diameter, for instance 40mm and 30mm respectively, while limbs 26 and 27 are of much smaller section, for instance lOmm and 6mm internal diameter. If bulb 32 is squeezed and then released, the effect will first be a depression of level 46, and some accompanying change to levels 44 and 45. The suddenness of the change will inevitably introduce instability in the system by altering dimension (c), even if only slightly. A consequence of this instability is that the succeeding rise of the level in tube 29, following release of bulb 32, will tend greatly to overshoot level 46, so drawing liquid into tube 29 out of limbs 26 and 27.

Due to the low height of level 44 within limb 26, this will permit air under pressure from section 15 to enter section 28 and escape to ambient-pressure section 17 by rising up limb 27, driving out the water from that limb at the same time. The whole of tube 25 is therefore rapidly cleared of water, so that the tube acts so as to vent section 15 to ambient pressure. The hydrostatic head of water within the vessel (represented by dimension (a)) therefore drives water forward through conduit 10 so that levels 41, 42 meet, and level 43 advances through region 17 and down limb 14, so that a discharge begins and a solid column of water begins to move with increasing velocity through conduit 10 from inlet 18 to outlet 22. In the course of this movement of water, by-pass tube 25 is refilled.In the steady state flow condition the liquid level 47 in sections 15 and 17 will typically be roughly as shown, so that a small air gap is left between these levels and the highest point of the internal wall of these parts of conduit 10, and the level 47 will be reflected in tube 33 also. However the level 47 could in practice be even higher than shown, so that the flowing water substantially fills sections 17 and 18. Once the water level in vessel 1 falls below level 47, there is of course no longer any hydrostatic head within the vessel to support the discharge by gravity, and syphonic action alone is responsible for the discharge continuing.

When the liquid level in vessel 1 falls to 35, allowing air to enter tube 33 by inlet 34, that air quickly reaches section 17 and breaks the syphon. For a very short time the momentum of the water within conduit 10 will continue to cause flow through section 17 and down limb 14, but once that momentum has disappeared the discharge of the cistern is over. Before a stable condition is established, the descent of water under gravity out of limb 11 (due to the comparatively low level 35 of water in the vessel 1 outside it) will tend to create a low-pressure air space in section 15, so inducing water to flow from limb 13 to limb 12, and from limb 27 to limb 26. However, as has already been stated, limbs 12 and 26 are of larger section than limbs 13 and 27 respectively, which helps to prevent both of the "U"-shaped parts 12-16-13 and 25 from becoming unduly starved of water.As the cistern now fills through tube 4, due to the falling of ball 5, the water level within vessel 1 rises gradually from 35 to 6. As it does so the level in limb 11 tends to rise but is resisted by increasing pressure in section 15 and the upper half of limb 12, supported by an increasing height difference between levels 43 and 42, 45 and 44.

Because the power necessary to raise water to level 6 comes from the supply 3, and that level lies wholly above conduit 10 and so provides a gravitational force to assist the start of each discharge, it will be appreciated that the work required of an operator or of equivalent automatic mechanism (in squeezing and releasing the flexible bulb 32) will typically be less than the work required to move substantial and rigid components to initiate the discharge of many conventional cisterns.

The purpose of plenum 30 is to limit the height to which level 46 can rise up tube 29 when bulb 32 is released.

The drawing also shows a side limb 50 which branches off tube 29 at 51 and terminates in a downwardly-facing open end 52, located slightly below level 6. The action of this limb is to prevent a discharge of vessel 1 being started by an operator squeezing and releasing bulb 32 before the vessel has completely filled again following its previous discharge. If bulb 32 is squeezed before end 52 is covered by water, air is simply expelled from tube 29 through limb 50 without any effect on level 46. To prevent end 52 becoming uncovered as the water level in vessel 1 falls during a discharge, and so possibly breaking the syphonic action by admitting air to the conduit 10, end 52 may be surrounded by a trap in the form of an open-topped pot 53 having a small orifice 54 in its base. The orifice 54 can be dimensioned so that as the level in vessel 1 falls rapidly during a discharge, the level within pot 53 falls less quickly and does not uncover outlet 52 until the discharge is over. It will also be apparent that when bulb 32 is squeezed to initiate a discharge, some air will typically escape from tube 50 as pressure builds up within tube 29 to depress level 46.

Claims

1. A cistern for a water closet or the like, comprising a vessel adapted to be filled with liquid to a predetermined high level, and a fluid conduit of sinuous shape arranged with its inlet arranged at low level within the vessel and its outlet directed towards a point of use, in which the curves of the conduit are arranged so that discharge from the vessel through the conduit is prevented by a pressurised air lock supported by a column of liquid located downstream of it within the conduit, in which a first vent tube connects the region of the air lock within the conduit to a zone of ambient pressure, in which that vent tube is located so as to fill with liquid as the vessel discharges and to retain at least some of that liquid as the vessel next fills, and in which there are operating means operable to discharge the retained liquid from that vent tube so venting the air lock and initiating a discharge of the vessel.

2. A cistern according to Claim 1 in which the first vent tube is in the form of a by-pass of smaller section than the conduit and connecting the air lock region with a second region of the conduit, the second region lying downstream of the pressure-supporting liquid column.

3. A cistern according to Claim 2 in which the sinuous shape of the conduit comprises first, second, third and fourth substantially vertical limbs arranged in succession, in which the first and second limbs are joined to form an inverted "U"-bend, in which the second and third limbs are joined to form a "U"-bend and in which the third and fourth limbs are joined to form an inverted "U"-bend, in which the second and third limbs are adapted to contain the pressure-supporting liquid column, and in which the by-pass tube connects the top ends of the second and third limbs.

4. A cistern according to Claim 3 in which the by-pass tube is of "U"-shape, comprising fifth and sixth substantially vertical limbs connected at their bottom ends by a U-bend.

5. A cistern according to Claim 4 in which the second limb is of substantially larger section than the third limb, and the fifth limb is of substantially larger section than the sixth limb.

6. A cistern according to any of the preceding Claims in which the operating means for removing contained liquid from the first vent tube comprise an air tube connected to it, and mechanism to vary the air pressure within that air tube.

7. A cistern according to Claim 6 in which the mechanism comprises a squeeze bulb or the like.

8. A cistern according to Claim 1 including a second vent tube operable to terminate discharge from the vessel when the liquid level within the vessel falls to a predetermined low level, in which the inlet to the second vent tube is connected to the conduit downstream of the region in which the pressure supporting column is contained, and the outlet of the second vent tube is located close to the predetermined low level within the vessel.

9. A cistern according to Claim 8 in which the outlet of the second vent tube is located higher, withih the vessel, than the inlet to the fluid conduit.

10. A cistern according to Claim 6 in which the air tube includes an open-ended branch limb, the open end of this branch being located within the vessel but at such a level that it is only within liquid when the vessel is at least substantially full, whereby to prevent initiating a discharge of the vessel by operation of the operating means unless the vessel is at least substantially full.

Amendments to the claims have been filed as follows 4. A cistern according to Claim 3 in which the by-pass tube is of "U"-shape, comprising fifth and sixth substantially vertical limbs connected at their bottom ends by a U"-bend.

9. A cistern according to Claim 8 in which the outlet of the second vent tube is located higher, within the vessel, than the inlet to the fluid conduit.

11. A cistern according to Claim 1, substantially as described with reference to the accompanying drawings.