IL114956A - Toilet flushing system - Google Patents

Description

114956/2 Toilet Flushing System Lipski Plastic Industries (1990) Ltd. (1990) >VViS tWVVt pX>a C. 97599 FIELD OF THE INVENTION This invention relates to a flush valve mechanism for controlling the flushing action of water through the water outlet of a flush cistern, and particularly to dual flush cisterns.

BACKGROUND OF THE INVENTION Flush valve mechanisms for dual flush cisterns having two operating levers for selecting full or half flushes are well known. Israel Patent Nos. 55874 and 58496 both in the name of Zeev Raz describe such a flush valve mechanisms for controlling the flushing action of water through the water outlet of a flush cistern comprising a water outlet valve liftable off the water outlet to effect the flushing action. A buoyant, valve-engaging assembly is adapted to move independently of the water outlet valve by virtue of its buoyancy, and the water outlet valve has an effective negative overall buoyancy when the cistern is at least partially full. The valve-engaging assembly comprises a pivotably mounted buoyant lever having at least one arm with a buoyant means attached at one end thereof adjacent the bottom of the cistern and provided with means at its other end for selectively engaging the valve.

A restraining means on the valve-engaging assembly is displace-able between a first position and a second position, such that in the first position the restraining means normally engages and restrains the buoyant lever with the buoyant means in close proximity to said cistern bottom and the engaging means in disengaged relationship to the valve. In the second position, the restraining means releases the buoyant lever allowing it to engage and to exert a maintaining force on the water outlet valve at the completion of the lifting thereof to overcome its negative buoyancy and to hold it open until the completion of the flushing action.

In Israel Patent No. 58496 there is disclosed a further feature of the valve-engaging mechanism whereby frictional contact with the valve is avoided. This is distinguished from South African Patent No. 7604749 in the name of Hugo Beck filed on May 12, 1978 and published in the South African Patent Journal the following month. In this patent, there is disclosed a cistern outlet valve assembly comprising a body defining an outlet and a valve seat therefor, a closure member a pivotally mounted float arm having a formation for frictionally engaging the valve stem to hold it open when the float is urged upwardly by liquid in the cistern. In fact, even these features are acknowledged as "known" since they are recited in the pre-characterizing portion of the claim and the claimed novelty resides in the provision of means in association with the float arm to enable a selection to be made of the height at which the float is located when the valve stem is disengaged by the formation. This, in turn, allows the volume of water released by a single flush to be adjusted.

In both of the above-mentioned Israel patents the restraining means serves to restrain the valve-engaging assembly from engaging the valve until the valve stem is lifted off the valve seating. Furthermore, when a partial flush only is employed, the restraining means serves the additional function of totally restraining the valve-engaging assembly so. that it cannot function. In this case, a float attached approximately midway to the valve stem maintains the valve stem in a lifted position until the water level in the cistern falls below the level of the float, whereupon the valve stem falls under its own weight, closing the valve. Whilst this happens, the valve-engaging assembly must be prevented from operating because if it were allowed to operate and engage the valve stem, then the valve stem would be maintained in a lifted disposition until the water level in the cistern fell below the level of the valve-engaging assembly. Thus, the restraining means allows for the provision of a partial flush.

Even in the particular case where only a single-volume, i.e. complete, flush is provided, a restraining means is provided, albeit of slightly different construction. In such case, the restraining means is released by the valve stem as it is lifted, allowing the valve-engaging assembly to engage the valve stem and maintain it in a lifted position until the water level in the cistern falls below the level of the valve-engaging assembly.

The restraining means provided in the above-mentioned Israel patents suffers from several drawbacks. In the case of a dual-volume flush cistern having respective first and second operating levers for partial and full flushes, the restraining means is a mechanical lever articulatedly coupled to the second operating lever which is pulled when a full flush is required. Since, as explained above, operation of the restraining means must be prevented for a partial flush, whilst the valve stem must be lifted by both operating levers, the first operating lever lifts the valve stem only, but not the restraining means, whilst operation of the second operating lever lifts both the first operating lever and with it the valve stem, and also lifts the restraining means. The resulting mechanism is complicated and relatively expensive. - 4 - 114956/2 Israel Patent No. 58496 addresses the drawbacks associated with frictional contact between the valve-engaging assembly and the valve stem, leading to surface abrasion and wear and tear. However, the resulting mechanism is comphcated, again requiring, in the case of a dual-volume flush cistern, a mechanical lever articulatedly coupled to one of the operating levers, as described above. Alternatively, for a single-volume flush cistern, the mechanical lever is dispensed with at the expense of providing a complicated mechanism formed of several discrete molded parts which interact to prevent rotation of the pivotably mounted valve-engaging assembly until the valve stem is lifted from the valve seating.

In both cases, the provision of a restraining means as described renders the valve more prone to failure, as well as increasing the overall cost of the valve.

It will be apparent from the foregoing that in all known controlled flush systems, some sort of float member is mounted on the valve stem so that the valve is maintained in an open position by means of the buoyancy afforded by the float member. By the same token, the valve closes when the water level falls beneath the lower level of the float such that the buoyancy afforded by the float is nullified, where upon the valve stem falls under its own weight.

The use of a float on the valve stem itself gives rise to various drawbacks which will now be elaborated. Thus, in prior art systems employing buoyant valve stems, there are associated three different forces which require careful balancing in order for the flush system to operate correctly. These three counteracting forces are as follows: (1) the buoyancy afforded by the valve float; (2) the weight of the valve stem; and (3) a reactive force produced by the flow of water through the valve outlet. - 4a - 114956/1 The weight of the valve stem acts downward and is compensated for by an upward force afforded by the buoyancy of the float and by the reactive force of the water which flows through the valve outlet. So far as the latter is concerned, this arises from the flow of fluid through the annular gap between the valve seating and the seal. Since water flowing through this annular gap fills the gap, it exerts a downward force on the valve seating and a corresponding reactive upward force which tends to urge the valve stem in an open position. The upward reactive force applied by the water as it flows through the annular gap is, in accordance with Bernouilli's Principle, a function of the speed with which the water flows through the valve outlet. Specifically, as the speed, or flow, of water increases, the water pressure decreases and so too does the force exerted thereby. This means that if a valve outlet of greater diameter is employed such that the water flow consequent to a flushing action is increased, then the upward reactive force exerted thereby o the valve stem is correspondingly lowered. If, to the contrary, the diameter of the valve outlet is decreased so that the water flow therethrough is correspondingly lower, then the upper reactive force applied by the water on the valve stem is greater and this, in term, adds to the buoyancy of the valve stem afforded by the float.

It is apparent from the foregoing explanations that the buoyancy afforded by the float must be very carefully adjusted according to the upward reactive force afforded by the water flushing through the valve outlet so that the combined upward force adequately compensates for the downward force due to the weight of the valve stem. Without such adjustment there exists the danger that the downward force due to the weight of the valve stem may exceed the combined upward force of the float and the upper reactive force of the flushing water. In such case, the flushing system will not work and the valve stem will simply drop under its own weight as soon as hand pressure is removed from the operating handle. This is not only unacceptable from an operational point of view but, in fact, contravenes the relevant standards. These standards are - 4b - 114956/1 designed to ensure that once momentary hand pressure is applied to the operating handle, the flushing valve will operate effectively for either a full or half flush (as required) even when the operating handle is subsequently released.

These factors are particularly significant in view of the fact that the relevant standards are also designed to ensure that a sufficient volume of water per second flushes through the valve in order properly to flush solid matter in the toilet bowl. In order to ensure an adequate flow of water in such manner, it is known to increase the diameter of the valve outlet. This ensures that more water flushes through the valve outlet per unit time. However, the very increase in water flow, decreases the upward reactive pressure produced thereby in accordance with Bernoulli's Principle as noted above. Therefore, a valve of the kind described in the prior art references discussed above which is based on the buoyancy of the valve stem and which is designed for a flush system having a valve outlet of conventional diameter, will not operate if employed in a cistern having a valve outlet of increased diameter. One ad hoc solution to this problem has simply been to retrofit a washer or gasket around the valve seating so as thereby effectively to reduce its diameter. Whilst this does allow the flush system to work properly, it does so at the expense of reducing the flushing force. This is clearly undesirable and may even contravene the relevant Standards.

SUMMARY OF THE I VENTION It is an object of the invention to" provide a flush valve mechanism in which the drawbacks associated with hitherto proposed such mechanisms are significantly reduced or eliminated.

According to the invention there is provided a flush valve mechanism for controlling the flushing action of water through a water outlet of a flush cistern, said flush valve mechanism comprising: - 4c - 114956/1 a water outlet valve liftable off the water outlet for effecting said flushing action and including a stem portion having a sealing member at a lower end thereof for sealingly engaging the water outlet, the stem portion being articulatedly coupled to at least one operating lever at an upper end thereof for Hfting the stem through a respective predetermined height such that on releasing the operating lever the stem portion falls under gravity, and said stem portion having intermediate said lower and upper ends an outwardly extending stop portion for engaging a valve-retaining assembly when the stem portion falls so as to be retained by said valve-retaining assembly thereby mamtaining the water outlet valve in an unsealed position; and said valve-retaining assembly being adapted to move independently of the water outlet valve and comprising at least one pivotably mounted lever having a first end which is unrestrained and is responsive to an operating force for engaging the stop portion when a water level in the cistern exceeds a preset height and being responsive to the water level in the cistern falling below said preset height for allowing the lever to rotate so as to disengage the stop portion, thereby causing the stem portion to fall under gravity so that the sealing member sealingly engages the water outlet.

Preferably, the flush valve mechanism is used with a dual-volume flush cistern, wherein there are provided two operating levers each for raising the stem portion through a respective predetermined height and two valve-retaining assemblies each for retaining the stop portion on the stem at a respective preset height so that the valve-retaining assemblies rotate away from their respective operative positions when the water level in the cistern falls below a respective height.

In such a dual-volume cistern, the respective preset heights of the valve-retaining assemblies may be preadjusted to provide approximately complete and half flushes of the cistern. - 5 - 114956/2 It will be apparent that the invention obviates the need for a mechanical lever to articulate motion of the operating lever to the restraining means associated with the valve-engaging mechanism in order to engage the valve stem at the end of its lift. In the invention, the valve stem can only operably engage the valve-engaging mechanism during its downward stroke whereupon further downward motion of the valve stem is prevented, until the water level in the cistern falls below the level of the valve-engaging mechanism.

The flush mechanism according to the present invention thus operates neither on the principle of the buoyancy of the valve stem nor on the balance of forces associated with prior art valve systems; and is therefore not subject to the drawbacks associated therewith as outlined above. Specifically, the invention includes at least one stop portion extending outwardly from the valve stem for engaging a valve-retaining assembly so as to be retained thereby, thus mamtaining the water outlet valve in an open, unsealed position. This situation is maintained regardless of the rate at which water flushes through the valve outlet and is thus entirely independent of the upward reactive force produced thereby on the valve stem. As a result, the invention is not subject to the drawbacks associated with hitherto proposed valve systems and operates effectively regardless of the diameter of the valve outlet and does not require either special adjustment or retrofitting for different flush cisterns.

According to a preferred embodiment of the invention, the stop portion comprises a bevelled edge for slidably engaging a corresponding bevelled end on the first end of the lever of said at least one valve-retaining assembly thereby rotating the at least one valve-retaining assembly away from its respective operative position against the operating force so as to allow the stop portion to clear the first end of the lever when the stem portion is lifted, whereupon the lever returns to its operative position under the action of the operating force and retains a lower surface of the stop portion in a rack and pawl type action. In such a mechanism, no attempt is made to avoid frictional contact between the valve-retaining assembly and the valve stem during actual operation of the valve mechanism, but the use of modern injection-molded plastics ensures that such frictional contact is minimal so as not to cause serious abrasion of the valve mechanism throughout its useful lifetime.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, there will now be described some preferred embodiments of a flush valve mechanism for a dual-volume cistern, by way of non-limiting example only, with reference to accompanying drawings, in which: Fig. 1 shows schematically a flush valve cistern according to a first embodiment of the invention with the cistern full and the valve closed; Fig. 2 shows schematically the flush valve cistern shown in Fig. 1 with the cistern full and the valve open; Fig. 3 shows schematically the flush valve cistern shown in Fig. 1 with the cistern empty and the. valve about to close; Fig. 4 shows schematically a flush valve cistern according to a second embodiment of the invention with the cistern full and the valve closed; - 7 - I Fig. 5 shows schematically the flush valve cistern shown in Fig. 4 with the cistern full and the valve open; and Fig. 6 shows schematically the flush valve cistern shown in Fig. 4 with the cistern empty and the valve about to close.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to Figs. 1 to 3, there is shown a detail of a valve 10 for I dual-volume flush cistern 11 having a water outlet 12. The valve 10 comprises a valve stem 13 (constituting a stem portion) which is liftable through first and second vertical displacements by means of corresponding first and second operating levers 14 and 15, respectively. The first and second operating means 14 and 15 are articulately coupled to an upper end 16 of the valve stem 13, in known manner, so as to lift the valve stem 13 through the required first and second displacements such that the first displacement, corresponding to a partial flush, is somewhat smaller than the second displacement, corresponding to a full flush.

At a lower end 17 of the valve stem 13 there is provided a rubber gasket 18 (constituting a sealing member) for sealingly engaging the water outlet 12 when the valve stem 13 is in its rest position, prior to pulling on either of the operating levers 14 or 15.

Also provided are a pair of valve-retaining assemblies depicted generally as 19 which are adapted to move independently of the valve 10 and comprise respective first and second levers 20 and 21 which are pivotably mounted to the valve 10 by means of a common pivot 22.

Respective first ends 23 and 24 of the levers 20 and 21 are bevelled for allowing sliding contact with a similarly bevelled edge of a stop portion 25 extending outwardly from the valve stem 13 intermediate the first and second ends 16 and 17, thereof.

First and second floats 26 and 27 are adjustably fixed to respective second ends of the first and second levers 20 and 21, opposite the first ends thereof, so as to allow for the respective heights of the floats 26 and 27 within the cistern 11 to be adjusted within predetermined limits. When the water within the cistern 11 is above the floats 26 and 27, the water exerts an operating force against the floats 26 and 27 which causes the respective first and second levers 20 and 21 to be rotated in a counterclockwise direction about their common pivot 22.

When the first operating lever 14 is pulled downwards, the valve stem 13 is lifted through the first vertical displacement whereupon the bevelled stop portion 25 on the valve stem 13 makes sliding contact with the bevelled end 23 on the first lever 20 of the valve-retaining assembly 19 so as to rotate the first lever 20 in a clockwise direction against the natural buoyancy of the float 26. The sliding contact between the stop portion 25 and the bevelled end 23 of the first lever 20 continues until a lower surface 28 of the stop portion 25 completely clears the bevelled end 23 of the first lever 20. There is now no further resistance to the natural buoyancy of the float 26 which allows for unimpeded rotation in a counter-clockwise direction of the first lever 20 about the pivot 22, so that when the valve stem 13 now falls under its own weight after releasing the first operating lever 14, the lower surface 28 of the stop portion 25 engages an upper surface of the lever 20 and is retained thereby. In this condition, the sealing member 18 is clear of the water outlet 12 and water thus flushes out of the cistern 11. The flushing action continues until the water level falls below the level of the float 26, whereupon the float 26 is no longer buoyed up by the water and so falls under its own weight together with the first lever 20. Consequently, the bevelled end 23 clears the stop portion 25 on the valve stem 13 which is thus free to fall under its own weight, thereby sealing the water outlet 12.

When a full flush is required, the second operating lever 15 is pulled downwards so as to lift the valve stem 13 through the required second vertical displacement, causing the stop portion 25 on the valve stem 13 completely to clear the bevelled end 23 of the first lever 20, initiate sliding contact with the bevelled end 24 on the second lever 21 and rotate the second lever 21 in a clockwise direction against the natural buoyancy of the float 27, until the lower surface 28 of the stop portion 25 completely clears the bevelled end 24 of the second lever 21, allowing the latter to rotate in a counter-clockwise direction on account of the natural buoyancy of the float 27. When the second operating lever 15 is now released, the valve stem 13 falls under its own weight until the lower surface 28 of the stop portion 25 meets an upper surface of the second lever 21 and is retained thereby. Water now flushes through the water outlet 12 until the water level in the cistern 11 falls below the level of the float 27, whereupon the float 27 falls under its own weight, releasing the second lever 21 from the stop portion 25 and allowing the valve stem 13 to fall under its own weight, thereby sealing the water outlet 12.

The first and second floats 26 and 27 are adjusted so that the first float 26 has a lower level which is substantially equal to half the cistern height, whilst the second float 27 has a lower level very near the bottom of the cistern 11. By such means, the first operating lever 14 produces a half flush whilst the second operating lever produces a full flush. However, as noted above, the exact vertical positions of the first and second floats 26 and 27 can be slightly adjusted so as to regulate the corresponding volumes of water which are released from the cistern 11 during a desired flushing action.

It will thus be noted that each of the valve-retaining assemblies retains the stop portion 25 on the valve stem 13 by means of a rack and pawl-type action such that the stop portion 25 is retained by the valve- - 10 - retaining assemblies during the downward stroke of the valve stem 13 after releasing the corresponding operating levers 14 and 15. On account of such a rack and pawl-type mechanism, the valve stem 13 can be lifted without any special provision being taken to prevent engagement of the valve-retaining assemblies with the stop portion 25. Indeed, as soon as the stop portion 25 makes contact with either of the bevelled ends 23 and 24 of the respective operating levers 20 and 21, there will be a slight frictional force between the stop portion 25 and the corresponding valve retaining assembly 19. However, this frictional force is not responsible for retaining the valve stem 13 and does not unduly impede its upward travel. Furthermore, the rack and pawl-type action which ensures that the valve stem 13 is retained during the subsequent downward stroke of the valve stem 13, obviates the need for any restraining means for restraining movement of the operating levers 20 and 21. This is contrast to hitherto-proposed valves as discussed above wherein a side-wall of the valve stem is frictionally retained so as to maintain the valve stem lifted, and thus the valve-retaining assembly relating to a full-flush must be restrained from operating when only a partial flush is required.

Referring now to Figs. 4 to 6 there is shown a second embodiment of the invention having an identical operating principle to the first embodiment described above and, consequently, like reference numerals will be used, where possible, for describing components which are common to both embodiments.

In this embodiment, only the valve-retaining assemblies 19 are of modified construction, the remaining features of the valve 10 being identical to the first embodiment, there being no need, therefore, to describe them again. Each of the valve-retaining assemblies 19 comprises a similar lever arm 20 and 21 having similarly bevelled ends 23 and 24 for interacting with the bevelled stop portion 25 in a rack and pawl-type action, as - 11 - described above. However, instead of providing floats at the free ends of the operating levers 20 and 21 there are provided open hollow chambers 30 and 31 adapted for slight vertical adjustment within the respective operating levers 20 and 21. The open hollow chambers 30 and 31 become filled with water when the water level in the cistern 11 is higher than the open surface of the chambers 30 and 31. Consequently, when the chambers 30 and 31 are totally immersed in water, their weight is almost exactly compensated for by the weight of the water displaced by the chambers 30 and 31, the only difference being any slight weight of the chambers themselves which is negligible. However, when the water level in the cistern 11 falls beneath the chambers 30 and 31, the latter become weighty tending to rotate the corresponding lever arms 20 and 21 in a clockwise direction about the pivot 22.

Respective compressive springs 32 and 33 are fixed between the valve 10 and the lever arms 20 and 21 such that the compressive force exerted by the springs 32 and 33 exerts a net counter-clockwise torque to the lever arms 20 and 21 for so long as the water level in the cistern 11 is higher than the hollow chambers 30 and 31.

Pulling down on the first operating lever 14 lifts the valve stem 13 past the bevelled end 23 which is then free to rotate in a counterclockwise direction under the action of the operating force provided by the compressive spring 32. When this happens, the weight of the water within the hollow chamber 30 is almost exactly compensated for by the water in the cistern 11 in accordance with Archimedes' principle so that the only net operating force on the lever arm 20 is that provided by the compressive spring 32. This situation continues, until the water level in the cistern 11 falls below the level of the hollow chamber 30, whereupon the weight of the water within the hollow chamber 30 is no longer compensated for and thus overcomes the compressive force of the spring 32, causing the lever arm 20 - 12 - to rotate in a clockwise direction, thereby releasing the stop portion 25 in a manner similar to that of the first embodiment described with reference to Figs. 1 to 3 above.

In a similar manner, pulling down on the second operating lever 15, causes the valve stem 13 to be displaced vertically through a greater height until the stop portion 25 clears the bevelled end 24 on the second lever arm 21, whereupon the lever arm 21 rotates in a counterclockwise direction under the influence of the compressive spring 33 since the weight of the water within the second hollow chamber 31 is almost exactly compensated for by water within the cistern 11. When the water level in the cistern 11 falls beneath the level of the hollow chamber 31, the weight of the water in the hollow chamber 31 is no longer compensated for and thus overcomes the operating force provided by the second compressive spring 33. Thus the second lever arm 21 rotates in a clockwise direction, releasing the stop portion 25 on the valve stem 13 and allowing the latter to fall under its own weight so as to seal the water outlet 12.

In both embodiments there is no need for a retaining means to prevent frictional contact of either of the valve-retaining assemblies 19 prior to their operation. There is also no need to restrain operation of the valve-retaining assembly associated with the complete flush when only a partial flush is required, because it is the vertical displacement of the valve stem which determines which of the two valve-retaining assemblies is operational. This, in turn, is determined by which of the two operating levers is pulled.

Whilst the invention has been described with particular reference to a dual-volume flush cistern, it will of course be appreciated that the principle of the invention is equally suitable for a single-volume flush cistern wherein only one valve-retaining assembly is provided, so adjusted that the stop portion on the valve stem is retained until the cistern is - 13 - substantially empty. By the same token, more than two valve-retaining assemblies could be provided, if desired, each for retaining the stop portion 25 at a different respective height and a like plurality of operating levers could be provided for lifting the valve stem through a desired height in order to engage a respective one of the valve-retaining assemblies, whereby multiple-volume flushes could be provided for.

Claims (9)

- 14 - CLAIMS:

1. A flush valve mechanism for controlling the flushing action of water through a water outlet of a flush cistern, said flush valve mechanism comprising: a water outlet valve liftable off the water outlet for effecting said flushing action and including a stem portion having a sealing member at a lower end thereof for sealingly engaging the water outlet, the stem portion being articulatedly coupled to at least one operating lever at an upper end thereof for lifting the stem through a respective predetermined height such that on releasing the operating lever the stem portion falls under gravity, and said stem portion having intermediate said lower and upper ends an outwardly extending stop portion for engaging a valve-retaining assembly when the stem portion falls so as to be retained by said valve-retaining assembly thereby maintaining the water outlet valve in an unsealed position; and said valve-retaining assembly being adapted to move independently of the water outlet valve and comprising at least one pivotably mounted lever having a first end which is unrestrained and is responsive to an operating force for engaging the stop portion when a water level in the cistern exceeds a preset height and being responsive to the water level in the cistern falling below said preset height for allowing the lever to rotate so as to disengage the stop portion, thereby causing the stem portion to fall under gravity so that the sealing member sealingly engages the water outlet.

2. The flush valve mechanism according to Claim 1, wherein the lever of said valve-retaining assembly has a float at a second end thereof, remote from said first end, so that when the water level in the cistern exceeds said preset height said operating force is applied by the water to the float so as to rotate the lever of the valve-retaining assembly into an i - 15 - I operative position wherein the stop portion is retained by the first end of the lever.

3. ^ 3. The flush valve mechanism according to Claim 1, wherein the lever of said valve-retaining assembly has a weight at a second end thereof, remote from said first end, which is counteracted by a compression spring which applies said operating force to the lever so as to maintain the valve- retaining assembly in an operative position wherein the weight is located at said preset height and the valve-retaining assembly retains the stop portion until the water level in the cistern falls below the weight, whereupon the weight overcomes the operating force so as to rotate the valve-retaining assembly away from said operative position.

4. The flush valve mechanism according to any one of the preceding claims, wherein the preset height is adjustable.

5. The flush valve mechanism according to Claim 2, wherein the height of the float is adjustable.

6. The flush valve mechanism according to Claim 3, wherein the height of the weight is adjustable.

7. The flush valve mechanism according to any one of the preceding claims for use with a dual-volume flush cistern, wherein there are provided two operating levers each for raising the stem portion through a respective predetermined height and two valve-retaining assemblies each for retaining the stop portion on the stem at a respective preset height so that the valve- retaining assemblies rotate away from their respective operative positions when the water level in the cistern falls below a respective height.

8. The flush valve mechanism according to any one of the preceding claims, wherein the stop portion comprises a bevelled edge for slidably engaging a corresponding bevelled end on the first end of the lever of said at least one valve-retaining assembly thereby rotating the at least one valve- retaining assembly away from its respective operative position against the - 16 - operating force so as to allow the stop portion to clear the first end of the lever when the stem portion is lifted, whereupon the lever returns to its operative position under the action of the operating force and retains a lower surface of the stop portion in a rack and pawl type action.

9. The flush valve mechanism according to Claim 7 or 8, wherein the respective preset heights of the valve-retaining assemblies are preadjust-ed to provide approximately complete and half flushes of the cistern. For the Applicants, DR. REINHOLD COHN AND PARTNERS 97599spc.JJT/jjt,prg:3.8.1995