WO1996010118A1

WO1996010118A1 - Vacuum assisted toilet flushing system

Info

Publication number: WO1996010118A1
Application number: PCT/GB1995/002305
Authority: WO
Inventors: Ian Francis Phillips; Christopher John Richmond
Original assignee: Medway Engineering Limited
Priority date: 1994-09-28
Filing date: 1995-09-28
Publication date: 1996-04-04

Abstract

A toilet flushing system comprises a water reservoir (1) provided with a water inlet and a water outlet (9) for directing water into or towards a toilet bowl (2), the discharge chamber (16) connected to the discharge outlet of the toilet bowl (2), the discharge chamber (16) having a closure valve flap at a downstream location thereof, an air conduit (4) extending between an upper end (10) of the water reservoir and the discharge chamber (16) such that a reduction in air pressure within the upper end (10) of the water reservoir caused by a fall in level in the water the reservoir is transmitted to the discharge chamber to produce a partial vacuum therein thereby to draw water from the toilet bowl into the discharge chamber, the valve flap (5) and/or the discharge chamber (16) are so constructed that, as water flows from the toilet bowl (2) into the discharge chamber (16) and the closure flap (5) opens to permit the discharge of the water, the closure flap (5) maintains a substantial gas seal with the discharge chamber whereby no air may flow back into the discharge chamber and a partial vacuum is maintained in the discharge chamber during substantially the entire duration of the flushing operation.

Description

VACUUM ASSISTED TOILET FLUSHING SYSTEM

The invention relates to a vacuum assisted toilet flushing system and is concerned with that type of system which comprises a water reservoir provided with a water inlet and a water outlet for directing water into or towards an associated toilet bowl, a discharge chamber connected to the discharge outlet of the toilet bowl, the discharge chamber having a mechanical closure valve at a downstream location thereof, an air conduit extending between an upper end of the water reservoir and the discharge chamber such that a reduction in air pressure within the upper end of the water reservoir caused by a fall in level in the water reservoir is transmitted to the discharge chamber to produce a partial vacuum therein thereby to draw water from the toilet bowl into the discharge chamber.

Toilet flushing systems are well known and generally have either a wash down or vacuum assisted mode of operation.

A typical wash down toilet flushing system comprises a water reservoir or cistern and a toilet pan or bowl with a discharge outlet connected to a waste pipe. A problem with such systems currently available is that relatively large volumes of water are required to flush the toilet bowl effectively. In recognition of this problem, regulations in the United Kingdom have been recently revised whereby all new toilet flushing systems should be adapted such that the maximum volume of water utilised in a single flushing operation is reduced from 9 litres to 7.5 litres. However, this is still a large volume of water and there remains a need for toilet flushing systems which flush effectively whilst utilising still smaller volumes of flushing water.

Various vacuum assisted toilet flushing systems are known. They are generally more efficient than simple wash down systems and usually provide the advantage of a larger water surface area in the toilet bowl. Vacuum assisted systems usually require a sealing valve, typically in the form of a second water trap, located behind the main water trap at the base of the toilet bowl. The two water traps define a discharge chamber and the reduction in air pressure, during flushing, in the discharge chamber assists the flushing action. Twin trap systems work very well but a problem is that twin trap toilet bowls are expensive and difficult to manufacture.

A vacuum assisted flushing system of the type referred to above is disclosed in WO94/02690. This prior document discloses a system with two water traps and also a system in which the downstream sealing or closure valve is constituted by a mechanical valve. The valve described is a simple flap valve which opens during flushing to allow pan discharge.

More specifically, the flap valve embodiment in the prior document operates as follows: Immediately flushing is initiated, the toilet bowl water content is rapidly drawn into the discharge chamber between the valve and the outlet of the water trap under the action of the partial vacuum which is generated in the flushing cistern by the discharge of the water and is transmitted to the discharge chamber through an air conduit. The discharge chamber fills rapidly and once the partial vacuum within it can no longer hold the valve closed, the valve opens allowing water to discharge into the waste pipe. Due to the fact that the valve is a generally circular valve flap cooperating with the generally circular internal surface of the discharge chamber, the valve not only permits the outflow of water but also permits air to enter the discharge chamber as soon as the valve opens. This allows air to enter the vacuum generating compartment within the cistern (from which the flushing water is originating) , thereby relieving the partial vacuum in the system and allowing flushing to continue. The vacuum action is therefore not substantially re¬ established during the remainder of the flushing operation.

The valve in the prior document thus inherently results in the partial vacuum in the discharge chamber being destroyed at a relatively early stage in the flushing process and thus being able to contribute to the flushing efficiency only for a short period of time. Furthermore, the use of this valve necessitates the use of a high vacuum generation cistern, which is complex and expensive, and the valve is found to be unsatisfactory when used with more simple, low vacuum generation cisterns which do not generate a sufficient level of partial vacuum to allow effective operation if substantial quantities of air are allowed to enter via the valve, once water discharge has commenced.

It is therefore the object of the present invention to provide a vacuum assisted flushing system whose operation emulates that of a twin water trap system and thus maintains a partial vacuum in the discharge chamber over substantially the entire duration of the flushing operation but from which the expensive second water trap is omitted.

According to the present invention, a toilet flushing system of the type referred to above is characterised in that the closure valve and/or the discharge chamber are so constructed that, as water flows from the toilet bowl into the discharge chamber and the closure valve opens to permit the discharge of the water, the closure valve maintains a substantial gas seal with the discharge chamber whereby no air may flow back into the discharge chamber and a partial vacuum is maintained in the discharge chamber during substantially the entire duration of the flushing operation. Thus the flushing system in accordance with the present invention has a certain similarity to the valve embodiment of the flushing system disclosed in WO94/02690 but the valve is so constructed that it will open to permit the discharge of water in the usual manner but when it does so it does not permit the backflow of air from the waste pipe into the discharge system, whereby the partial vacuum assists the flushing operation over substantially its entire duration.

It is preferred that the closure valve comprises a valve flap of which at least a portion is arranged to move pivotally with respect to the discharge chamber to permit the discharge of water whilst maintaining a substantial gas seal. The valve flap may comprise two or more substantially rigid portions, e.g. of plastics material, connected to pivot with respect to each other about substantially horizontal axes, e.g. by hinges, such as integral plastics film hinges or plastics hinges of a different flexible material, such as expanded neoprene. It is preferred that the stiffness of the hinges increases progressively in the upward direction, that is to say that each hinge provides a greater resistance to pivotal movement than the hinge below it. Alternatively, the valve flap may comprise flexible material which may flex about a plurality or an infinite number of horizontal axes to permit water to flow out of the discharge chamber whilst still maintaining a seal with the wall of the discharge chamber over the upper portions of its periphery. It is preferred that the bending stiffness of the flexible valve flap about vertical axes is greater than that about horizontal axes. This may be achieved by making the valve flap of flexible material, e.g. polymeric material, in which a plurality of horizontally extending stiffening members are embedded. It is preferred also that the bending stiffness of the valve flap about horizontal axes increases in the upward direction and this may conveniently be achieved by providing the valve flap with a thickness which increases incrementally or progressively in the upward direction.

Alternatively, the valve flap may constitute a single rigid member, preferably with a seal around its outer edge, which is of rectangular shape, the internal surface of the discharge chamber with which it is in sealing engagement being of substantially rectangular shape also. It will be appreciated that with such a construction of the valve flap the upper portions of its outer edge will remain in sealing contact with the discharge chamber at all positions of the valve flap and thus that such a valve flap may open sufficiently to permit the flow of water through it in one direction whilst nevertheless preventing the flow of gas through it in the other direction. In order to ensure that the valve flap maintains a reliable gas seal with the discharge chamber, it is preferred that it is biassed into the closed position. This may be effected by the resilience of the valve flap itself and/or of the hinges connecting its constituent portions and/or by the provision of one or more return springs.

It is preferred that the reservoir is divided into a primary compartment, in which the flushing mechanism is located, and a secondary compartment, which communicates with the primary compartment at its lower end. It is preferred also that, in distinction to the constructions illustrated in WO94/02690, the air conduit communicates with the secondary compartment and not with the primary compartment. The reason for this is that it has been found that it is very much easier to maintain the secondary compartment reliably sealed rather than the primary compartment into which the water is supplied and in which the flushing mechanism and its actuating mechanism are provided, whereby the partial vacuum developed in the secondary compartment is reliably transmitted to the discharge chamber and is not impaired by the leakage of air from the atmosphere.

It is preferred that the flushing mechanism, e.g. the lower edge of the syphon bell, if the cistern is of siphonic type, is situated at a higher level than the communication between the primary and secondary compartments, whereby air is not permitted to flow from the primary compartment to the secondary compartment at any time.

It is preferred that the primary and second compartments are so dimensioned that the volume of water released by the secondary compartment during flushing exceeds that released by the primary compartment, whereby a larger proportion of the total flushing water volume originates from the secondary compartment which results in a higher level of partial vacuum being transmitted to the discharge chamber. The ratio of the volumes of the secondary and primary compartments is conveniently between 5 :3 and 5:2.

The mechanical closure valve provided in accordance with the invention substantially contains and maintains the vacuum effect in the discharge chamber during flushing. A lower level of cistern-generated vacuum is therefore required to achieve effective flushing, thus enabling a simple and inexpensive cistern to be used.

It has been found, particularly with toilet bowls in which the water trap has a large visible surface area of the water, to be of no advantage to create a partial vacuum that results in the water level in the toilet bowl being lowered too rapidly because this can result in a large quantity of air being drawn into the system from the bowl, whereby the partial vacuum effect will be substantially reduced or destroyed before the bowl is completely cleared. It is therefore preferred that a relatively low vacuum cistern be used and that the toilet bowl has a large water surface area. The construction in accordance with the invention inherently results in the partial vacuum effect continuing until substantially the end of the flushing process, whereby the bowl is cleared effectively. It is preferred that the partial vacuum effect increases during flushing and that the water level in the bowl is seen to lower progressively during flushing. At the end of the flushing process, the partial vacuum in the discharge chamber is relieved, usually by air drawn in from the bowl due to the reduction or elimination of the water seal provided by the trap. Thus virtually all the air drawn into the cistern is fresh air drawn in from the toilet bowl close to the end of the flushing process. This air is expelled through the flap valve into the drainage system during refilling of the cistern.

In tests, the continuous action of the vacuum in the discharge chamber of the flushing system in accordance with the present invention enabled the flushing action to compare very favourably with the system disclosed in WO94/02690 with regard to the effectiveness of flushing and the low volume of water used, despite a lower level of vacuum being generated within the cistern, very effective flushing being achieved with less than 5 litres of flushing water.

Certain specific embodiments of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which:

Figure 1 is a part-cross-sectional view of a toilet flushing system in accordance with the invention in combination with a toilet bowl;

Figure 2 is a view similar to Figure 1 showing the toilet flushing system whilst flushing;

Figures 3a to 3c are diagrammatic side views on an enlarged scale of the valve flap shown in Figures 1 and 2 in the closed, partially open and fully open positions, respectively;

Figures 4a to 4c are views similar to Figures 3a to 3c, respectively, of a second type of valve flap; and

Figures 5a and 5b are graphical representations of the flushing action of the valve embodiment of the flushing system disclosed in WO94/02690 and the construction in accordance with the present invention, respectively, the level of vacuum generation being shown in each case with a solid line and the flushing water flow rate being shown in each case with a chain line.

Figures 1 and 2 show a flushing system connected to a toilet bowl or pan 2. The flushing system comprises a cistern 1 fitted with a standard float controlled water supply pipe and an overflow pipe, which are both of conventional construction and are thus not shown in the drawings. The cistern is divided into two communicating portions, namely a primary or main compartment 20, in which the flushing mechanism, in this case a syphon 6 connected to an actuating handle 11, is located and a secondary compartment 3, which communicates at its upper portion 10 with an air conduit 4. The two compartments are separated by a partition 18, in the lower end of which an aperture 18 is formed, in this case a rectangular opening 150 mm and 35 mm high, through which the compartments communicate. The lower end of the syphon mechanism 6 communicates with an outlet or downpipe 9 whose lower end communicates with a distribution chamber forming part of the toilet bowl. The distribution chamber communicates with a plurality of apertures 19 formed in the rim of the bowl in the conventional manner. At the lower end of the toilet bowl 2 is a generally part-circular depression or well which, in use, is full of water and into which extends a web 21 from above to form a water trap 7. The outlet end of the water trap communicates with a discharge chamber 16 which is defined in part by a passage forming an integral portion of the toilet bowl 2 and in part by a connector 15 which is connected thereto. The connector 15 is connected to a waste pipe 13. At the downstream end of the connector 15 is a mechanical flap valve 5, which is shown in more detail in Figure 3.

The valve flap 5, which is preferably of rectangular shape but may also have other shapes, comprises a lower rigid rectangular plastic plate 22 abutting an upper rigid rectangular plastic plate 23 and connected thereto by a rectangular strip of flexible polymeric material 24, e.g. of expanded neoprene, which may be connected to the plates 22, 23 by adhesive and acts as a resilient hinge. The upper plate 23 is connected to the upper surface of the connector 15 by means of a further and thicker rectangular strip of polymeric material 25, which may again be made of neoprene. In the closed position of the valve flap 5 shown in Figure 3a, the plates 22 and 23 are coplanar and are maintained in the closed position by the resilience of the polymeric strips 24, 25, and optionally also by a return spring (not shown) , whereby the valve flap maintains a substantial gas seal with the internal surface of the connector 15.

Flushing of the cistern is initiated by rotating the flushing lever 11 and this results in initiation of siphonic action of the syphon 6 in the usual manner. Water flows down through the downpipe 9 into the toilet bowl. As the water level in the primary compartment 20 falls, the water level in the secondary compartment 3 falls also due to the fact that the two compartments communicate through the opening 8. The secondary compartment 3 is sealed from the atmosphere and this results in the production of a partial vacuum in the upper portion 10 of the secondary compartment. This partial vacuum is transmitted via the air conduit 4 to the discharge chamber 16. The combination of an increased volume of water in the water trap 7 and the application of a reduced pressure to the downstream side of the water trap 7 results in the toilet bowl being rapidly and effectively cleared. The valve flap 5 is initially retained in the closed position by the sub- atmospheric pressure in the chamber 16 but after a relatively short period of time the weight of water acting against its upstream side is sufficient to overcome the reduced pressure and the valve flap 5 opens to permit discharge of the water into the waste pipe 13. The opening of the valve 5 may comprise pivotal movement only of the rectangular plate 22 with respect to the plate 23 about the hinge constituted by the polymeric strip 24, as shown in Figure 3b, or such movement may be coupled also with pivotal movement of the plate 23 about its upper end, as shown in Figure 2 though in practice the increased thickness of the polymeric strip 25 as compared to that of the polymeric strip 24 may prevent this from occurring. In any event, the valve flap 5 opens only to the extent necessary to permit water to flow out into the waste pipe 13 and no gap is left between the edge of the flap 5 and the internal surface of the connector 15, whereby no air is permitted to flow back into the discharge chamber 16. The partial vacuum in the chamber 16 is thus retained substantially throughout the flushing process and this will assist in holding the valve flap 5 closed as much as is possible, that is to say open only to the extent necessary to discharge the water.

If the flow of water should temporarily cease during the flushing process, for instance if the water trap 7 is obstructed, the valve flap 5 closes completely, thus resulting in the level of vacuum in the discharge chamber 16 increasing in response to the continued fall of the water level in the cistern. This increased level of vacuum will assist in removal of the blockage. If there is a large flow of water, for instance during the peak flow of the flushing cycle, or in the event that a blockage reaches the valve flap 5, the upper section or sections of the valve flap open in response to the pressure applied by the increased water level, thereby permitting the additional water or the blockage to be discharged. The valve flap will however close immediately after the blockage or increased flow has passed under the action of the resilience of the polymeric hinges and/or the return spring. Only a very small proportion of the partial vacuum is lost when this occurs but the slight reduction in the vacuum level causes a corresponding reduction of the water level in the secondary compartment 3, which is normally at a higher level than that in the primary compartment 20 during flushing, due to the vacuum effect. The result of this is that the cistern automatically dispenses more flushing water when blockages occur, and this is of course highly beneficial.

Referring now to Figure 5, the X axis in the graphs represents time, that is to say the duration of the flushing process, and the Y axis represents the vacuum level which is generated in connection with the solid line and the flushing water flow rate in relation to the chain line. It will be seen from Figure 5b that the flushing system in accordance with the present invention produces a level of partial vacuum which increases progressively for a significant portion of the flushing process and decays relatively rapidly at the end of the flushing process whilst the flushing water flow rate increases rapidly to a maximum value and remains there for much of the flushing process and then decays rapidly at the end of the flushing process . This is in sharp contrast to the characteristics, illustrated in Figure 5a, of the valve embodiment disclosed in WO94/02690 in which the vacuum level initially rises very rapidly and then decays to a very low value only about half way through the flushing process, whereby the vacuum is of little or no assistance to the flushing process in the latter portion thereof, and the flushing water volume increases progressively to its maximum value which is reached only in the second half of the flushing process.

Figure 4 shows a modified construction of valve flap 5 which comprises a single flexible flap whose thickness and thus stiffness increases progressively in the upward direction. Any convenient flexible polymeric material may be used for the valve flap but expanded neoprene may again be convenient. The valve flap is constructed to be capable of bending readily about any one of a plurality or an infinite number of horizontal axes but is relatively stiff about the vertical axes. This is achieved by embedding a plurality of elongate, substantially rigid components, e.g. stainless steel wires 26 in the valve flap. If the water flow rate is relatively low, the lower portion of the valve flap will pivot outwardly, as shown in Figure 4b, to permit the water to flow past it whilst maintaining a substantial gas seal with the connector 15. If there should be a larger water flow rate or if an obstruction should come into contact with the valve flap, a larger portion of it will pivot outwardly for a brief period of time, as shown in Figure 4c, to permit the water or obstruction to pass, whereafter the valve flap will then close again to a position sufficient to enable the current water flow rate to pass but nevertheless to maintain a substantial gas seal.

It is desirable that no air is permitted to flow from the primary compartment 20 of the cistern into the secondary compartment 3 at any time and this is ensured in the illustrated embodiment by providing the lower edge of the syphon 6 at a level above the upper edge of the opening 8 in the partition 18. However, if this were not the case, the flow of air between the two compartments could be prevented by providing a U bend or water trap construction and this can be readily provided by the provision of a partition 14, as shown in Figure 1, which extends along and is sealed to the bottom of the primary compartment 20 and whose upper edge is situated above the upper edge of the opening 8. If the cistern is of the type which incorporates a lifting flushing actuating valve as opposed to a siphonic mechanism, the seal between the two compartments of the cistern can be ensured by positioning the cistern outlet pipe higher than the upper edge of the opening 8. In this event, the secondary compartment 3 can be constituted by an open bottomed tank or compartment which is provided within the primary compartment 20. The open bottomed tank can thus be fitted within the cistern with its lower edge 20 mm or so away from the bottom of the cistern.

In some cases, for example when the flushing system is adapted for use with open rim toilet bowls, a lowering of the water level in the bowl can sometimes be experienced after flushing has terminated. This is caused by a slight residual vacuum effect continuing while the water levels are settling in the bowl after flushing. This problem can be easily overcome in a number of ways. For example, a small gallery can be provided within the bowl which holds back a small quantity of water during flushing but which allows, e.g. by means of a restricted diameter opening, such as the opening 17 shown in Figure 1, a small flow of water into the water trap 7 for a few seconds after the flush has terminated, thereby replacing any slight shortfall in the water volume in the trap 7 that may occur immediately after flushing.

It is preferred that the variable discharge valve flap is fitted to, or manufactured as part of, the toilet bowl connector 15, as illustrated. However, the invention can readily be adapted for use with bottom outlet bowls. For example, the valve flap can be fitted in a lower portion of the bowl as part of a complete assembly which can be installed into the bowl outlet prior to fitting. The lower section of the bowl outlet pipe is best configured so that as water flows out of the water trap it tends to run onto the lower section of the valve flap thereby ensuring that the whole valve is not immediately opened which would of course result in loss of the partial vacuum.

In tests, excellent results have been achieved with bottom outlet toilet bowls in which the usually round downpipe of the bowl, through which the bowl discharges into the drainage system, is replaced by a rectangular conduit. Positioned within the conduit is a single rectangular valve flap which is preferably biassed into the closed position by a spring or the like. During flushing, water runs onto the valve flap which opens or closes in response to varying water flow rates under the control of the spring or the like. Because the valve flap and conduit are rectangular and close fitting, the partial vacuum can be contained by such a valve in a manner analogous to the multi-part or flexible valve flap described above.

It will be apparent that numerous other modifications may be effected to the constructions described above and it is intended that all such modifications be embraced by the claims.

Claims

1. A toilet flushing system comprising a water reservoir (1) provided with a water inlet and a water outlet for directing water into or towards an associated toilet bowl (2) , a discharge chamber (16) connected to the discharge outlet of the toilet bowl (2) , the discharge chamber (16) having a mechanical closure valve (5) at a downstream location thereof, an air conduit (4) extending between an upper end (10) of the water reservoir and the discharge chamber (16) such that a reduction in air pressure within the upper end (10) of the water reservoir caused by a fall in level in the water reservoir is transmitted to the discharge chamber to produce a partial vacuum therein thereby to draw water from the toilet bowl into the discharge chamber, characterised in that the closure valve (5) and/or the discharge chamber (16) are so constructed that, as water flows from the toilet bowl (2) into the discharge chamber (16) and the closure valve (5) opens to permit the discharge of the water, the closure valve (5) maintains a substantial gas seal with the discharge chamber whereby no air may flow back into the discharge chamber and a partial vacuum is maintained in the discharge chamber during substantially the entire duration of the flushing operation.

2. A system as claimed in Claim 1 in which the closure valve comprises a valve flap (5) of which at least a portion is arranged to move pivotally with respect to the discharge chamber (16) to permit the discharge of water whilst maintaining a substantial gas seal.

3. A system as claimed in Claim 2 in which the valve flap (5) comprises two or more substantially rigid portions connected to pivot with respect to each other about substantially horizontal axes.

4. A system as claimed in Claim 2 in which the valve flap (5) comprises flexible material, preferably with a bending stiffness about vertical axes which is greater than that about horizontal axes.

5. A system as claimed in any one of Claims 2 to 4 in which the valve flap (5) and the internal surface of the discharge chamber with which it is in sealing engagement are substantially rectangular.

6. A system as claimed in any one of Claims 2 to 5 in which the valve flap (5) is biassed into the closed position, e.g. by a spring.

7. A system as claimed in any one of the preceding claims in which the reservoir (1) is divided into a primary compartment (20) , in which the flushing mechanism

(6) is located, and a secondary compartment (3) , which communicates with the primary compartment (20) at its lower end and with the air conduit (4) .

8. A system as claimed in Claim 7 in which the water inlet to the flushing mechanism (6) is situated at a higher level than the communication (8) between the primary and second compartments (20, 3) .

9. A system as claimed in Claim 7 or 8 in which the primary and second compartments (20, 3) are so dimensioned that the volume of water released by the secondary compartment (3) during flushing exceeds that released by the primary compartment (20) .

10. A toilet comprising a toilet bowl (2) in combination with a flushing system as claimed in any one of the preceding claims, the water outlet of the reservoir (1) being connected to a water inlet of the toilet bowl.