The present invention relates to improvements in and relating to water closet cisterns.

In the vast majority of older cisterns operation of the control handle or button primes a syphon which continues to operate until the water level within the cistern sinks to a pre-determined level at which time the syphon is broken. Priming of the syphon is normally accomplished by the upward motion of a piston which urges water over the arch of the syphon and initiates siphonic flow. Conventional flushing cisterns are designed to dispense a standerd volume of water which is considered necessary to flush a toilet under maximum requirement conditions.

Accordingly, one way to save water is to terminate the flush before the maximum dose of water has been dispen¬ sed. In known apparatus, proposals have been made for the premature termination of the siphonic action. One such system is disclosed in GB 1151220, in this, and in other such systems, the introduction of air into the arch of the syphon breaks the syphon.

In more recent cisterns a bell-like member is employed. This member comprises a hollow stem co-axial with the outlet of the cistern and provided with a valve means to close the outlet when the stem is in a lower posi¬ tion. Operation of the control handle or button causes the stem to be displaced upwardly allowing the discharge of water from the cistern. When sufficient water has been discharged the stem sinks under its own weight and closes the valve. Various mechanical means have been proposed to cause premature sinking of the bell so as to regulate the quantity of water discharged from the cistern. In general such mechanical means have been co - plexe and prown to brakedown.

A hybrid system is disclosed in DE 3410140. In this sys¬ tem, water flows from the cistern, through a flexible pipe into the upper part of a partially immersed bell. Water ceases to flow when the free end of the pipe is exposed above the water level, causing the syphon to be broken and the bell to sink to its original position. The depth of the free end of the pipe is controlled by a rope and pulley mechanism.

Despite the above— entioned developments there remains a need for a simple means of terminating the flush ac¬ tion of a watercloset cistern, so as to enable a 'low- flush' to be performed. The criteria which such a flush mechanism should meet are that it should be mechanically

— _

simple and contain few moving parts. Failure of the mechanism should not disable the cisterns normal ' full- flush' function. Moreover, the mechanism should be rea¬ dily adjustable so as to enable the discharge of a πiini- mum quantity of water given variations in cistern size and shape. An important practical consideration, given that most modern cisterns are constructed from plastic materials, is that exessive modification of known cis¬ tern design should be avoided, so as to enable most of the original mouldings to be employed.

An improved system is described in US 4135263. In that device an inverted cup—shaped float is loosely mounted on the stem of the flow—controlling valve— eans. The upper portion (base) of the inverted cup is provided with a port to admit air. By placing a plug in the port the flow of air can be controlled to as to cause either a slow or rapid fall of water level in the float, thereby causing slow or rapid sinking of the float and either terminating the flow after the normal, i.e. maxi¬ mum discharge or after a partial discharge. The above described device can be set to low flush in periods of drought so as to conserve water: the effect being some¬ what similar to the ancient technique of placing a brick in the cistern.

There are a number of disadvantages inherent in the apparatus disclosed in US 4135263. First, calcinareous deposits are apt to restrain or block the sliding ac- tion of the cup upon the valve stem, causing a failure of function. Second, the device may only switched be¬ tween a full and partial flush mode by removal and re¬ positioning of the plug. This requires dismantling of the cistern and makes the device completely unsuitable for many applications.

According -to the present invention there is provided a flush mechanism for a cistern of the type comprising a vertically mounted and movable stem with valve means at the lower end thereof, wherein a bell having an open lower end is fixed co—axially on the stem below the high water level in the cistern and means are provided for the optional introduction of air into the upper part of the bell so as to allow water to drain from the mouth of the bell as the water level in the cistern falls, the arrangement being such that when air is not introduced into the bell, the mass of water retained within the bell is sufficient to displace the stem downwards and cause closure of the valve means prior to discharge of the entire water content of the cistern.

By use of such a fixed bell as a variable weight on the stem, it is possible to ensure that the stem is urged downwards as the water level in the cistern falls below

thβ bell, or optionally when the bell is allowed to drain, to ensure that the complete contents of the cis¬ tern is discharged before the stem sinks to its original position. A fixed bell has the particular advantage that it cannot fail due to the formation of calcinareous de¬ posits which restrain the sliding action.

Typically, the bell fixed relative to the stem in use but is secured in such a manner that its position may be adjusted on longitudinally of the stem. This enables the quantity of water which will be discharged before the mass of the bell urges the stem downwards to be varied, thereby accommodating variations in the shape and size of cisterns, without requiring the bell to slide during use.

Preferably, the means provided for the optional intro¬ duction of air into the upper part of the bell comprise a conduit communicating with the ambient and with the upper part of the bell and an externally operable air- valve in the conduit to selectively admit or exclude a flow of air from passing along the conduit and entering the bell. The feature of having an externally controllable air- valve located in the conduit is an important feature of a preferred embodiment of the present invention. It is particularly advantageous for said air-valve to be ope¬ rable without dismantling of the cistern, as the appara- tus may then be switched from low flush to full flush mode with ease.

It xs preferable that the air-valve is contructed to fail in an open position. By use of such a valve it is possible to ensure that valve faillure will leave the mechanism in a state where it is inoperative and opera¬ tion of the flush mechanism results in a 'full-flush' .

It will be noted that as the water level in the cistern rises after discharge, air will be traped in the bell, and this air must be discharged from the bell to reset the mechanism into a state ready for a further operating cycle. Although it is possible for this air to be dis¬ charged via the conduit mentioned above, it is also pos- sible to provide a blow-valve in the upper part of the bell so as to allow this air to be released.

In an embodiment of the invention, the blow valve com¬ prises an open pore in the upper part of the bell and a water trap above the pore. It is envisaged that ball- valves and other valve means may be employed as a blow valve.

In an alternative embodiment of the invention, air is

-A-

discharged from the bell via the conduit.

In a particular embodiment of the invention the bell is provided with a float attached to an upper portion thereof. This is useful in maintain a continuous flush/ fill cycle for those applications where users of the water-closet are either incapable of operating or forget to operate the flush mechanism. This is particularly suitable for installation on premises licensed to sell alcoholic beverages. In such an embodiment a small flow of water into the cistern, eventually causes the float to lift the stem and discharge the contents of the cistern. In order that the invention may be further understood it will be explained by way of example and with reference to the accompanying single figure wherein is shown, in schematic form, a vertical cross—section through a water—closet cistern embodying the present invention.

Turning to the figure there is shown a flush mechanism for a cistern (1) of the type comprising a vertically mounted and movable stem (2) with valve means (3) at the lower end thereof, and actuating means (4) at the upper end thereof.

A bell (5) having an open lower end is fixed co-axially on the stem (2) below the high water level (6) in the cistern (1). The bell (5) is mounted adjustably on the stem (2) by means of a snug—fitting collar (7) so as to enable the bell to be moved longitudinally of the stem. Various modifications of this clamping mechanism can be envisaged. Valve means (8) are provided for the optional introduction of air into the upper part of the bell (5) through a flexible conduit (9) communicating with the ambient and with the upper part of the bell.

The air-valve (8) comprises a valve seat (8a), a valve member (8b) and a spring (8c). The spring (8c) and the valve member (8b) are so arranged as to form an 'over- centre' locking assembly. It should be noted that the valve member is formed with counterweight (8d) such that failure of the spring will cause the valve to fail in open position. By use of such a valve it is possible to ensure that valve failure will leave the mechanism in a state where it is inoperative and operation of the flush mechanism results in a 'full-flush' , as is described in more detail below. In the embodiment shown the bell is also provided with blow valve (10) comprising an open pore (11) in the upper part of the bell (5) and a water trap (12) above the pore. As mentioned above, it is envisaged that ball- valves and other valve means may be employed as a blow

valve for the pore. In an alternative embodiment, the pore can be located in the wall of the conduit (9), pre¬ ferably close to the valve seat (8a) . In a yet further embodiment the pore can be located in the valve member (8b).

In operation the invention functions as follows;

At the start of the 'full-flush' operating cycle, the cistern (1) is filled with water to the high water level (6). The bell (5) is filled with water and submerged, on operation of the actuating means (4) , the stem (2) is displaced towards the top of the figure and water begins to flow through valve means (3) causing the water level in the cistern to fall. In 'full-flush' mode, as shown in the figure, a relatively large volume of air flows allong the conduit (9) and enters the upper part of the bell. The introduction of air into the upper part of the bell allows the water to drain from the mouth of the bell as the water level in the cistern falls. Under these circumstances a relatively small amount of water is retained within the bell, and the bell stem combina¬ tion is of low mass. When the cistern is empty,, the stem settles in the conventional way and closes valve means (3). The cistern is re-filled in the conventional man¬ ner. As the water level rises within the bell (5) air escapes from the bell both through the conduit (9) and the blow-valve (10). In 'low-flush' mode, the air-valve (8) is completely closed or sufficiently closed to -restrict air flow into conduit (9). On operation of the actuating means (4), the stem (2), as before, is displaced towards the top of the figure and water again begins to flow through valve means (3) causing the water level in the cistern to fall. With valve (8) in the closed position, little or no air flows along the conduit (9) into the upper part of the bell. Under these circumstances, when air is not introduced into the bell, the mass of water retained within the bell is sufficient to displace the stem down¬ wards and cause closure of the valve means (3) prior to discharge of the entire water content of the cistern.

CLAIMS

1) A flush mechanism for a cistern of the type compri¬ sing a vertically mounted and movable stem with valve means at the lower end thereof, wherein a bell having an open lower end is fixed co-axially on the stem below the high water level in the cistern and means are provided for the optional introduction of air into the upper part of the bell so as to allow water to drain from the mouth of the bell as the water level in the cistern falls, the arrangement being such that when air is not introduced into the bell, the mass of water retained within the bell is sufficient to displace the stem downwards and cause closure of the valve means prior to discharge of the entire water content of the cistern. 2) A flush mecahnism according to claim 1, wherein the bell is releasably secured to the stem so as to enable the bell to be released for adjustment longitudinally of the stem. 3) A flush mechanism according to claim 1, wherein the means provided for the optional introduction of air into the upper part of the bell comprise a conduit communica¬ ting with the ambient and with the upper part of the bell and an air-valve in the conduit to selectively ad- it or exclude a flow of air from passing along the con¬ duit and entering the bell.

4) A flush mechanism according "to claim 3, wherein said air—valve is operable from outside the cistern.

5) A flush mechanism according to claim 4, wherein the air-valve is constructed to fail in open position.

6) A flush mechanism according to claim 1 , wherein a blow— alve is provided in the upper part of the bell so as to allow air to be released from the bell.

7) A flush mechanism according to claim 6, wherein the blow—valve comprises an open pore in the upper part of the bell and a water trap above the pore.

8) A flush mechanism according to claim 1 , wherein the bell is provided with a float attached to an upper poi— tion thereof.

9) A flush mechanism for a cistern of the type compri¬ sing a vertically mounted and movable stem with water- valve means at the lower end thereof, wherein a bell having an open lower end is fixed co—axially on the stem below the high water level in the cistern and a flexible conduit comprising externally operable air-valve means