Syphon

Abstract

The invention relates to a syphon (1, 101, 201, 301, 401, 501, 601) for discharging water from a cistern. The syphon includes a downleg (2, 102, 202, 302, 402, 502, 602) with an outlet for connection with the base of a cistern, an upleg (3, 103, 203, 303, 403, 503, 603) surrounding the downleg, priming means (4, 104, 204, 304, 404, 504, 604) associated with the open end of the upleg and a spillover (5, 105, 205, 305, 405, 505, 605) between the upleg and the downleg. The spillover is movable, in use, with the upleg relative to the downleg to a flush position, whereby the priming means causes or encourages a water level between the upleg and downleg to rise and flow over the spillover to initiate a syphonic action..

Description

[0001] SYPHON

[0002] This invention relates to syphons for evacuating water from a cistern. More specifically, although not exclusively, this invention relates to a syphon incorporating a piston that is operated by an actuator for initiating the syphonic action.

[0003] Typical cistern draining syphons include an inverted generally II shaped duct having an upleg, a downleg and a spillover portion describing the bight of the II. The upleg includes an enlarged chamber having a lower end open to the interior of the cistern in use. The downleg generally forms or is connected to an outlet of the cistern in use for delivery of flushing water to an associated toilet pan or the like.

[0004] Within the chamber is located a vertically displaceable piston, which normally includes holes through its thickness and a flexible diaphragm secured along one of its edges to the top of the piston to act as a one way valve. When the piston is raised, the flexible diaphragm is forced against the piston by the weight of the water above it, thereby covering the holes and preventing water from passing therethrough. Once the syphonic flushing action is initiated, the flexible diaphragm is pushed away from the piston by water being drawn through the holes of the piston, thereby discharging water from the cistern in operation.

[0005] Draining syphons of this kind are also generally operated by a lever whose end is connected to a piston rod attached to the piston such that actuation of the lever raises the piston. This raises the level of water within the syphon over the bight of the II and primes the syphon to initiate the syphonic action. Actuation of the piston requires a significant amount of force, as it involves displacing a considerable volume of water at a rate sufficient to initiate the syphonic action.

[0006] The piston rod passes through the top wall of the enlarged chamber, which also requires a sliding engagement therebetween that is sealed to a sufficient extent to avoid substantial ingress of air that would otherwise interrupt the syphonic action. It is known to make use of this potential interruption of the syphonic action by including recesses in the outer surface of a lower portion of the piston rod, which allows air to pass therethrough when the water level reaches the top of the enlarged chamber to provide a partial flush.

[0007] Actuation of the piston requires a significant amount of force, as it involves displacing a considerable volume of water at a rate sufficient to initiate the syphonic action. It is a first non-exclusive object of the invention to provide a syphon for discharging water from a cistern that requires less force. It is a further non-exclusive object of the invention to provide a simpler and more reliable syphon.

[0008] According to one aspect of the invention, there is provided a syphon for discharging water from a cistern, the syphon comprising a downleg and an upleg surrounding the downleg, wherein the upleg is movable, in use, relative to the downleg to cause water therebetween to flow into the downleg and / or over a spillover to initiate a syphonic action.

[0009] The invention therefore eliminates the need for a piston rod, and can be configured to provide a smaller footprint since the downleg is received within the upleg.

[0010] The syphon may comprise a stop for limiting movement of the upleg relative to the downleg. This can ensure that the travel of the upleg is consistent, which improves the reliability of the syphonic action.

[0011] The stop may be removable or movable to a release position, for example to enable the upleg to be withdrawn, in use, from the downleg.

[0012] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising a downleg, an upleg surrounding the downleg and movable relative thereto for initiating a syphonic action and a stop for limiting movement of the upleg relative to the downleg, wherein the stop is removable or movable to a release position to enable the upleg to be withdrawn, in use, from the downleg.

[0013] The provision of a removable or retractable stop enables the upleg to be removed from the downleg whilst the syphon is installed, in use, in a cistern without the need to drain the cistern to service the internal components of the syphon.

[0014] The upleg may be movable, in use, relative to the downleg to cause a water level therebetween to rise. The upleg may be movable, in use, relative to the downleg to a flush position, e.g. to cause a water level therebetween to rise and flow into the downleg and / or over a spillover to initiate a syphonic action. The upleg may be movable, in use, relative to the downleg from a pre-flush position to the flush position. The upleg may be movable, in use, relative to the downleg between a preflush position to the flush position.

[0015] The stop may be for limiting movement of the upleg relative to the downleg when the upleg is in the pre-flush position. The syphon may comprise a return means, e.g. for returning the upleg to the pre-flush position. The stop may act, in use, against the return means, for example when the upleg reaches and / or is at its pre-flush position. The return means may be operable or configured to urge the upleg toward its pre-flush position until the stop is engaged.

[0016] This can ensure that the upleg returns to its pre-flush position consistently.

[0017] The return means may comprise a buoyancy means and / or resilient biasing means. The buoyancy means and / or the resilient biasing means may be for urging the upleg away from flush position and / or toward a pre-flush position. The resilient biasing means may act between part of the downleg and part of the upleg. The buoyancy means may comprise a float. The resilient biasing means may comprise one or more resilient biasers, members or mechanisms. The resilient biasing means may comprise one or more springs.

[0018] The stop may be movable or operable from above or from an intended upper side of the upleg. The stop may be movable between an engaged position, which may comprise a deployed position, and the release position, which may comprise a retracted position. The stop may be rotatable, for example between the engaged and release positions.

[0019] The stop may comprise a drive feature, such as a slot, socket, projection, knob or dial. The drive feature may be operable or configured to move, e.g. rotate, the stop between the engaged and release positions. The drive feature may be operable from above or from an intended upper side of the upleg.

[0020] The stop may comprise an abutment. The abutment may engage the downleg (e.g. directly or indirectly), for example when the upleg is in the pre-flush position. The stop or abutment may be for limiting upward movement of the upleg relative to the downleg, for example when the upleg is in the pre-flush position. The abutment may be in a deployed position, for example when the stop is in the engaged position. The abutment may be in a retracted position, for example when the stop is in the release position.

[0021] The abutment may engage the downleg (e.g. directly or indirectly) and / or limit upward movement of the upleg relative to the downleg, for example when it is in the deployed position and / or when the stop is in the engaged position. The abutment may be disengaged from the downleg and / or allow upward movement of the upleg relative to the downleg, for example when it is in the retracted position and / or when the stop is in the release position.

[0022] The downleg may comprise an outlet, e.g. for connection with the base of a cistern. The upleg may comprise an open end, e.g. for receiving a flow of water into a space between the upleg and the downleg. The upleg may comprise a closed end, e.g. for redirecting the flow of water into the downleg.

[0023] The syphon may comprise priming means. The priming means may be associated and / or cooperate with the open end of the upleg. The priming means may cause or encourage a water level between the upleg and the downleg to rise and flow over the spillover to initiate a syphonic action.

[0024] The syphon may comprise a spillover between the upleg and the downleg, e.g. for introducing into the downleg the flow of water redirected from the closed end of the upleg. The spillover may be movable, in use, relative to the downleg to a flush position. The spillover may be movable, in use, with the upleg. The spillover may be movable, in use, with the upleg relative to the downleg to a flush position or to their respective flush positions.

[0025] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg surrounding the downleg and having: an open end for receiving a flow of water into a space between the upleg and the downleg; and a closed end for redirecting the flow of water into the downleg; a spillover between the upleg and the downleg for introducing into the downleg the flow of water redirected from the closed end of the upleg; and priming means associated with the open end of the upleg; wherein the spillover is movable, in use, preferably with the upleg, relative to the downleg to a flush position, whereby the priming means causes or encourages a water level between the upleg and downleg to rise and flow over the spillover to initiate a syphonic action. The provision of a moving spillover in combination with priming means reduces substantially the extent to which the upleg must be moved relative to the downleg to initiate the syphonic action. As such, the syphon can be installed with the spillover above, at or at least adjacent to the fill level when it is in the flush position. This means that water is inhibited from being discharged from the cistern if the upleg fails to return to the pre-flush position. Other advantages will also be appreciated by the skilled person, in light of the disclosure below.

[0026] The syphon may comprise an interface, e.g. between the spillover and the downleg. The spillover and / or upleg may be movable, in use, relative to the downleg between a pre-flush position and a flush position. The interface may describe an undulating path or gap when the spillover and / or upleg is or are in the pre-flush position. The undulating path or gap may create an airlock. The undulating path or gap or the airlock may inhibit water from within the cistern from passing between the spillover and the downleg. The interface may describe an airlock, e.g. for inhibiting water from passing between the spillover and the downleg when the spillover and / or upleg is or are in the pre-flush position. The undulating path or gap or the airlock may be least partially evacuated when the spillover and / or upleg is or are in the flush position.

[0027] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg surrounding the downleg and having: an open end for receiving a flow of water into a space between the upleg and the downleg; and a closed end for redirecting the flow of water into the downleg; a spillover between the upleg and the downleg for introducing into the downleg the flow of water redirected from the closed end of the upleg; and an interface between the spillover and the downleg; wherein the spillover is movable, in use, preferably with the upleg, relative to the downleg from a pre-flush position, in which the interface describes an airlock for inhibiting water from passing between the spillover and the downleg, toward a flush position, in which a water level between the upleg and downleg flows over the spillover for initiating a syphonic action and in which the airlock described by the interface is least partially evacuated.

[0028] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg surrounding the downleg and having: an open end for receiving a flow of water into a space between the upleg and the downleg; and a closed end for redirecting the flow of water into the downleg; a spillover between the upleg and the downleg for introducing into the downleg the flow of water redirected from the closed end of the upleg; and an interface between the spillover and the downleg; wherein the spillover is movable, in use, preferably with the upleg, relative to the downleg from a pre-flush position, in which the interface describes an undulating path or gap for inhibiting water from passing between the spillover and the downleg, toward a flush position, in which a water level between the upleg and downleg flows over the spillover for initiating a syphonic action and in which the undulating path or gap described by the interface is least partially evacuated.

[0029] This arrangement can encourage the proper functioning of the airlock by resetting it on every flush.

[0030] In the flush position, the water level between the upleg and downleg may rise and flow over the spillover. The spillover or interface may comprise a ring, annulus or wall. The ring, annulus or wall may be annular. The ring, annulus or wall may depend from the spillover. The ring, annulus or wall may be received or receivable within a depression or recess of the interface or downleg, which may also be annular. At least part of the undulating path or gap may be described by the ring, annulus or wall and the depression or recess.

[0031] The interface may comprise a pre-flush condition, e.g. when the spillover and / or upleg is or are in the pre-flush position. The ring, annulus or wall may have a first and / or pre-flush position, e.g. which may correspond to the pre-flush position of the spillover and / or upleg and / or to the pre-flush condition of the interface. In the pre-flush position, conical surfaces of the ring, annulus or wall and the depression or recess may be spaced, for example to describe an undulating path or gap or an airlock therebetween that may be for inhibiting water from passing therebetween.

[0032] The interface may comprise a flush condition, e.g. when the spillover and / or upleg is or are in the flush position. The ring, annulus or wall may have a second and / or flush position, e.g. which may correspond to the flush position of the spillover and / or upleg and / or to the flush condition of the interface. In the flush position, the conical surfaces may be adjacent or abut one another, for example to at least partially evacuate the undulating path or gap or the airlock when the spillover is in its flush position. Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg surrounding the downleg and having: an open end for receiving a flow of water into a space between the upleg and the downleg; and a closed end for redirecting the flow of water into the downleg; and a spillover between the upleg and the downleg for introducing into the downleg the flow of water redirected from the closed end of the upleg, the spillover comprising an annular wall depending therefrom which is receivable within an annular recess of the downleg; wherein the spillover is movable, in use, preferably with the upleg, relative to the downleg from a pre-flush position, in which conical surfaces of the wall and recess are spaced to describe an undulating path or gap or an airlock therebetween for inhibiting water from passing between the spillover and the downleg, toward a flush position, in which a water level between the upleg and downleg flows over the spillover for initiating a syphonic action and in which the conical surfaces are adjacent or abut one another to at least partially evacuate the undulating path or gap or the airlock when the spillover is in its flush position.

[0033] In the flush position, the water level between the upleg and downleg may rise and flow over the spillover. The interface may comprise cooperating surfaces, e.g. annular surfaces, of the spillover and downleg. The cooperating surfaces may surround at least part of the ring, annulus or wall. The cooperating surfaces may have a smaller cone angle than that of the conical surfaces. This may encourage air to be drawn, in use, into the undulating path or gap or the airlock from the downleg.

[0034] The spillover may comprise one or more shrouds, for example an inner shroud and an outer shroud. The shroud or the inner shroud may be received within the downleg, for example within a flow conduit of the downleg, when the spillover is in its flush position. The shroud or the inner shroud may be received within the downleg for shielding the flow of water from an upper end of the downleg or flow conduit. Movement of the spillover, in use, to the flush position may cause the water level between the upleg and downleg to rise and flow over the spillover whilst being shielded from an upper end of the flow conduit of the downleg by at least one or the or each shroud and then to flow into the flow conduit to initiate a syphonic action.

[0035] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg surrounding the downleg and having: an open end for receiving a flow of water into a space between the upleg and the downleg; and a closed end for redirecting the flow of water into the downleg; and a spillover between the upleg and the downleg and comprising a shroud for introducing into the downleg the flow of water redirected from the closed end of the upleg; wherein the spillover is movable, in use, preferably with the upleg, relative to the downleg to a flush position, in which the shroud is received within a flow conduit of the downleg, whereby a water level between the upleg and downleg flows over the spillover and is shielded from an upper end of the flow conduit of the downleg by the shroud and flows into the flow conduit to initiate a syphonic action.

[0036] This arrangement can provide improved flow characteristics, particularly on initiation of the syphonic action.

[0037] In the flush position, the water level between the upleg and downleg may rise and flow over the spillover. The shroud or one of the shrouds, e.g. the inner shroud, may be nested within the ring, annulus or wall. The shroud or one of the shrouds, e.g. the outer shroud, may surround the ring, annulus or wall. At least one or the or each shroud may describe part of the undulating path or gap or the airlock.

[0038] The shroud, e.g. the inner shroud, may include an outer conical surface. The outer conical surface of the shroud may cooperate with a facing inner conical surface of the downleg or flow conduit thereof. These inner and outer conical surfaces may be spaced when the spillover is in the pre-flush position. The inner and outer conical surfaces may be adjacent or may abut one another when the spillover is in its flush position.

[0039] The shroud, e.g. the outer shroud, may include an inner conical surface. The inner conical surface of the shroud may cooperate with a facing outer conical surface of the downleg. These inner and outer conical surfaces may be spaced when the spillover is in the pre-flush position. These inner and outer conical surfaces may be adjacent or may abut one another when the spillover is in its flush position.

[0040] The spillover may have an inner periphery. The spillover may have an outer periphery. The outer periphery may be more aggressive than the inner periphery Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg surrounding the downleg and having: an open end for receiving a flow of water into a space between the upleg and the downleg; and a closed end for redirecting the flow of water into the downleg; and a spillover between the upleg and the downleg for introducing into the downleg the flow of water redirected from the closed end of the upleg, the spillover having an inner periphery and an outer periphery that is more aggressive than the inner periphery; wherein the spillover is movable, in use, preferably with the upleg, relative to the downleg to a flush position such that a water level between the upleg and downleg flows over the spillover into the downleg to initiate a syphonic action.

[0041] This geometry can provide improved flow characteristics, particularly on initiation of the syphonic action.

[0042] In the flush position, the water level between the upleg and downleg may rise and flow over the spillover. The spillover or inner periphery thereof may have an inner surface. The inner surface may be substantially toroidal. The spillover or outer periphery thereof may have an outer edge, e.g. an outer sharp edge. Alternatively, the spillover or outer periphery thereof may have an outer surface, which may be substantially toroidal. The outer periphery or surface may have a smaller radius, e.g. poloidal radius, than the inner periphery or surface.

[0043] The priming means may comprise a priming assembly. The priming means may comprise a piston. The piston may have openings therethrough. The priming means may comprise a cover. The cover may be configured to cover, in use, the openings of the piston, for example to inhibit water from flowing out of the open end of the upleg as the upleg is moved toward the flush position. The cover may be configured to move away from the openings, for example to allow water to flow into the upleg from the open end after initiation of the syphonic action.

[0044] The piston may comprise a recess. The cover may be received within the recess, for example so as to provide one or more sides. The one or more sides may at least partially surround a periphery of the cover.

[0045] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg fluidly connected to the downleg and having an open end for receiving a flow of water; a spillover between the upleg and the downleg for introducing into the downleg the flow of water received through the open end of the upleg; and priming means within the open end of the upleg, the priming means comprising a piston having a recess, openings in the recess which extend through the thickness of the piston and a cover secured to the piston within the recess so as to provide one or more sides that at least partially surround a periphery of the cover, wherein the cover is configured, upon relative movement between the piston and the upleg in a first direction, to be urged into the recess and to cover the openings, thereby to inhibit water from flowing out of the open end of the upleg for initiating a syphonic action, and to move away from the openings to allow water to flow into the upleg from the open end after initiation of the syphonic action.

[0046] It will be appreciated by those skilled in the art that such a recessed piston may be provided in a conventional syphon, for example one which includes any one or more features of the prior art described in the background above.

[0047] The recess may be for providing or may provide, in use, a shallow reservoir above the cover for receiving and / or holding water. Thus, the use of a recess can reduce the effect of a cover that is not perfectly flat.

[0048] The piston may surround the downleg. At least part of the piston may slope, for example from its periphery toward its centre or toward the downleg. The piston may have an upper surface that may slope, for example from its periphery toward its centre or toward the downleg. The cover may lie on the upper surface.

[0049] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg fluidly connected to the downleg and having an open end for receiving a flow of water; a spillover between the upleg and the downleg for introducing into the downleg the flow of water received through the open end of the upleg; and priming means within the open end of the upleg, the priming means comprising a piston having a sloping upper surface, openings in the sloping upper surface which extend through the thickness of the piston and a cover secured to the piston on the sloping upper surface, wherein the cover is configured, upon relative movement between the piston and the upleg in a first direction, to be urged against the sloping upper surface and to cover the openings, thereby to inhibit water from flowing out of the open end of the upleg for initiating a syphonic action, and to move away from the openings to allow water to flow into the upleg from the open end after initiation of the syphonic action.

[0050] The provision of a sloping piston can, in certain circumstances, improve the flow characteristics of the water passing through the openings of the piston.

[0051] The open end of the upleg may, but need not, be enlarged. The upleg may comprise a chamber, which may be enlarged. The upleg may, but need not, be substantially bell shaped. In some examples, the cross-section, e.g. transverse cross-section, of the upleg may be substantially constant. The cross-section of the upleg may be substantially constant from the open end to the spillover or to a location adjacent the spillover. The chamber may extend from the open end of the upleg, e.g. toward the closed end of the upleg. The closed end of the upleg may be round and / or may be smaller, e.g. have a smaller area, than the open end of the upleg.

[0052] The closed end of the upleg may, but need not, be substantially flat.

[0053] The upleg may comprise a conduit or conduit portion, which may extend from the closed end of the upleg, e.g. toward the chamber. The conduit or conduit portion may have a dimension, e.g. a diameter. The dimension or diameter may be within 10%, for example within 5%, of the minor dimension of the open end. The inventors have found that a nonround open end with a minor dimension that is similar or substantially the same as the dimension or diameter of the closed end can improve the performance of the syphon, particularly at the point of initiation of the flush. This is believed to relate to the differential dynamic pressures created around the downleg as the water is forced upward by the movement of the upleg.

[0054] In some examples, the closed end of the upleg may be domed or conical. The closed end may comprise a central apex, which may be further from the downleg than a radially outer portion of the closed end.

[0055] The closed end of the upleg may comprise one or more flow altering features, such as projections or fins. At least some of the flow altering features may be above the spillover. At least some of the flow altering features may be above an inner portion of the spillover. At least some of the flow altering features may be above a portion of the spillover that is inboard of an apex of the spillover. The flow altering features may be distributed about the cap, for example so as to redirect some of a flow of water passing over the spillover. The flow altering features may be spaced from one another, for example such that some of a flow of water passing over the spillover bypasses the fins.

[0056] The upleg may comprise a transition, e.g. between the open end and the closed end. The transition of the upleg may be between the chamber and the closed end. The transition of the upleg may be between the conduit or conduit portion and the open end. The transition of the upleg may be between the chamber and the conduit or conduit portion. The open end or chamber may have a larger cross-sectional area than the closed end or conduit or conduit portion. The transition may taper, e.g. between the open end and the closed end. The transition of the upleg may have a cross-sectional area that reduces, e.g. from the chamber to the closed end. At least part of the transition may form part of the chamber. At least part of the transition may form part of the conduit or conduit portion.

[0057] The chamber may comprise a first portion, which may have a constant or substantially constant cross-section or cross-sectional area. The chamber may comprise a roof or second portion, which may comprise a transition portion. The roof or second portion may be domed and / or curved. The roof or second portion may curve along the minor dimension. The roof or second portion may curve along the major dimension.

[0058] The piston may be received within the chamber of the upleg. The piston may have a complementary shape to an inner surface of the chamber of the upleg.

[0059] The syphon or priming means may comprise a sealing means or diaphragm. The sealing means or diaphragm may connect the priming means to the upleg. The sealing means or diaphragm may be for inhibiting water from leaking between priming means, e.g. the piston, and the upleg or the chamber thereof.

[0060] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg fluidly connected to the downleg and having an open end for receiving a flow of water; a spillover between the upleg and the downleg for introducing into the downleg the flow of water received through the open end of the upleg; and priming means connected to the upleg by a diaphragm for inhibiting water from leaking between priming means and the upleg, wherein the priming means is operable, in use, to cause or encourage a water level within the upleg to rise and flow over the spillover to initiate a syphonic action.

[0061] The priming means of the immediately preceding aspect of the invention may include any one or more features of the priming means described above. It will be appreciated by those skilled in the art that such a diaphragm may be provided in a conventional syphon, for example one which includes any one or more features of the prior art described in the background above.

[0062] The sealing means or diaphragm may connect the piston, e.g. a periphery thereof, to the upleg or the chamber thereof, e.g. a periphery of the upleg or chamber.

[0063] The syphon or priming means may comprise one or more walls. The wall(s) may extend from a periphery of the piston. The wall(s) may describe an upleg receptacle. The upleg, e.g. the open end thereof, may be received and / or moveable within the upleg receptacle, for example to initiate a syphonic action.

[0064] The sealing means or diaphragm may connect the wall(s) to the open end of the upleg, e.g. to a periphery of the open end. The sealing means or diaphragm may connect the piston to the chamber of the upleg via the wall(s).

[0065] The priming means or piston may comprise a cowl. The cowl may cover or partially cover the or a transition, e.g. the or a tapering transition, between the open end and the closed end. The cowl may inhibit, or may be for inhibiting, water from leaking between the piston and the upleg, e.g. when the upleg is moved from the or a pre-flush position toward the flush position.

[0066] The cowl may project from the wall(s) or upleg receptacle. The cowl may project upwardly and / or inwardly from the wall(s) or upleg receptacle. The shape of the cowl may correspond substantially to, or match or be similar to that of, the transition. The transition or cowl may taper or converge. The transition and / or the cowl may have a cross-sectional area that varies or tapers or converges. The cross-sectional area of the transition may reduce from the or an enlarged chamber, e.g. that describes the open end, to the closed end. The cross- sectional area of the cowl may reduce from the wall toward the closed end of the upleg. The priming means, e.g. the piston, may be fixed relative to the downleg. The priming means or piston and the downleg may be included in a stationary unit. The syphon may comprise a stationary unit, which may comprise the downleg and / or at least part of the priming means, for example the piston.

[0067] The stop may be for limiting movement of the upleg relative to the stationary unit. The stop may be removable or movable to a release position, for example to enable the upleg to be withdrawn, in use, from the stationary unit.

[0068] Another aspect of the invention provides a syphon for discharging water from a cistern, the syphon comprising a downleg, an upleg surrounding the downleg and movable relative thereto for causing water therebetween to flow into the downleg and / or over a spillover to initiate a syphonic action, wherein the downleg forms part of a stationary unit configured to be secured to the base of a cistern and the stop is removable or movable to a release position to enable the upleg to be withdrawn, in use, from the stationary unit.

[0069] The stop may comprise an abutment. The abutment may engage the stationary unit, e.g. the priming means or piston, for example when the upleg is in the pre-flush position. The stop or abutment may be for limiting upward movement of the upleg relative to the stationary unit, for example when the upleg is in the pre-flush position.

[0070] The abutment may engage the stationary unit, priming means or piston and / or limit upward movement of the upleg relative to the stationary unit, priming means or piston, for example when it is in the deployed position and / or when the stop is in the engaged position. The abutment may be disengaged from the stationary unit, priming means or piston and / or allow upward movement of the upleg relative to the stationary unit, priming means or piston, for example when it is in the retracted position and / or when the stop is in the release position.

[0071] The piston may be connected to the upleg by one or more resilient biasing means. The resilient biasing means connecting the piston to the upleg may be configured to urge the upleg away from flush position and / or toward a pre-flush position. The resilient biasing means connecting the piston to the upleg may be configured to urge the upleg away from the piston. The syphon may comprise an axial clearance. The axial clearance may be between the closed end of the upleg and the spillover. The axial clearance may be between 110% and 140% of a radial clearance between the spillover and a surrounding portion of the upleg, for example when the spillover is in the flush position.

[0072] The syphon may comprise a radial flow area. The radial flow area may be between the closed end of the upleg and the spillover. The radial flow area may be between 80% and 110% of an axial flow area between the spillover and a surrounding portion of the upleg, for example when the spillover is in the flush position.

[0073] The inventors have determined that the reliability of initiation of the syphon can be improved by ensuring that the axial and radial clearances between the upleg and downleg fall within the ranges above at the end of the syphon’s travel.

[0074] In fact, the inventors have found that the reliability can be improved further by ensuring that the clearance between the closed end of the upleg and the spillover or downleg inlet is between 115% and 135% of the clearance between the spillover or downleg inlet and the surrounding portion of the upleg in the flush position or predetermined flush position. Similarly, improved reliability was found to be associated with a flow area between the closed end of the upleg and the spillover or downleg inlet between 85% and 105% of the flow area between the spillover or downleg inlet and the surrounding portion of the upleg in the flush position or predetermined flush position.

[0075] The open end of the upleg may be non-round, for example substantially elliptical, oval, rectangular or obround. The open end of the upleg may have an aspect ratio of at least 2:1 . The open end of the upleg may have an aspect ratio of at least 2.5:1. The open end of the upleg may have an aspect ratio of 3:1 or less. The open end of the upleg may have an aspect ratio of 2.7:1. The inventors have found an aspect ratio of 2.5:1 to 3:1 for the open end of the upleg performs particularly well. The open end of the upleg may comprise a major dimension and a minor dimension. The aspect ratio may be the ratio of the major dimension to the minor dimension.

[0076] The stop may be one of two or more stops. The upleg and downleg may comprise cooperating stops. The cooperating stops of the upleg and downleg may be configured to engage when the spillover and / or upleg is or are in the pre-flush position. Further cooperating stops may be configured to engage when the spillover and / or upleg is or are in the flush position.

[0077] The space between the upleg and downleg may comprise an annulus or an annular flow path or passageway. The upleg may be telescopically movable, in use, relative to the downleg. The flush position may comprise predetermined flush position.

[0078] The spillover may comprise an apex. The syphon may be configured to be installed, in use, within a cistern such that the apex of the spillover is above, at or at least adjacent a fill level of the cistern when the spillover is in the flush position, e.g. for inhibiting water from being discharged from the cistern if the upleg fails to return to a pre-flush position.

[0079] Another aspect of the invention provides a toilet cistern, which may comprise a syphon as described above.

[0080] The cistern may comprise an inlet valve, e.g. for filling the cistern to a fill level. The apex of the spillover may be above, at or at least adjacent to the fill level when it is in the flush position, e.g. for inhibiting water from being discharged from the cistern if the upleg fails to return to a pre-flush position.

[0081] Another aspect of the invention provides a toilet comprising a toilet cistern as described above.

[0082] Another aspect of the invention provides a method of operating a syphon to discharge water from a cistern.

[0083] The method may comprise forcing an upleg into a body of water within a cistern. The upleg may be forced into the body of water such that it moves relative to a downleg within the upleg that has an outlet connected with a base of the cistern. The method may comprise forcing a spillover into a body of water within a cistern. The spillover may be forced into the body of water such that it moves relative to a downleg within the upleg that has an outlet connected with a base of the cistern.

[0084] The method may comprise forcing, e.g. simultaneously or together, an upleg and a spillover into a body of water within a cistern. The spillover and upleg may be forced into the body of water such that the upleg and spillover both move relative to a downleg within the upleg that has an outlet connected with a base of the cistern.

[0085] Water from the body of water may be forced or encouraged, e.g. by priming means, to enter an open end of the upleg. Water entering the open end of the upleg may flow between the upleg and downleg until it reaches and is redirected by a closed end of the upleg. Water redirected by the closed end may flow over the spillover and into the downleg and out through the outlet of the downleg to initiate a syphonic action.

[0086] Another aspect of the invention provides a method of operating a syphon to discharge water from a cistern, the method comprising forcing an upleg and a spillover into a body of water within a cistern such that the upleg and spillover both move relative to a downleg within the upleg that has an outlet connected with a base of the cistern, whereby water from the body of water is forced or encouraged by priming means to enter an open end of the upleg, flow between the upleg and downleg until it reaches and is redirected by a closed end of the upleg and flows over the spillover and into the downleg and out through the outlet of the downleg to initiate a syphonic action.

[0087] For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention. For example, the syphon, cistern or toilet may comprise any one or more features or steps of the method relevant thereto and / or the method may comprise any one or more features or steps relevant to one or more features of the syphon, cistern or toilet.

[0088] Another aspect of the invention provides a computer program element comprising and / or describing and / or defining a three-dimensional design, e.g. of the syphon described above or an embodiment or one of the components thereof. The three-dimensional design may be for use with a simulation means or an additive or subtractive manufacturing means, system or device.

[0089] The computer program element may be for causing, or operable or configured to cause, an additive or subtractive manufacturing means, system or device to manufacture the syphon described above or an embodiment or one of the components thereof. The computer program element may comprise computer readable program code means for causing an additive or subtractive manufacturing means, system or device to execute a procedure to manufacture the syphon described above or an embodiment or one of the components thereof.

[0090] A further aspect of the invention provides a computer program element comprising computer readable program code means for causing a processor to execute a procedure to implement one or more steps of the aforementioned method.

[0091] A yet further aspect of the invention provides the computer program element embodied on a computer readable medium.

[0092] Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible.

[0093] For the avoidance of doubt, the terms “may”, “and / or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so- described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0094] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0095] Figure 1 is a perspective view of a syphon according to an embodiment of the invention shown in a raised, pre-flush position;

[0096] Figure 2 is a perspective view of the syphon of Figure 1 from below;

[0097] Figure 3 is a side view of the cistern of Figure 1 ; Figure 4 is a section view along line A-A of Figure 3;

[0098] Figure 5 is a section view similar to that of Figure 4, but with the syphon shown in a lowered, flush position;

[0099] Figure 6 is a front view of the syphon of Figure 1 ;

[0100] Figure 7 is a section view along line B-B of Figure 6, showing the return springs;

[0101] Figure 8 is a perspective section view of the upleg part of the syphon of Figure 1 , taken along line A-A of Figure 3;

[0102] Figure 9 is a perspective section view of the downleg part of the syphon of Figure 1 , taken along line A-A of Figure 3;

[0103] Figure 10 is a perspective view of the piston assembly of the syphon of Figure 1 ;

[0104] Figure 11 is a perspective view of an alternative piston assembly for use in the syphon of Figure 1 ;

[0105] Figure 12 is a perspective view of the piston assembly of Figure 11 shown from below;

[0106] Figure 13 is a similar view to Figure 1 with the stop members shown in a release position to enable the removal of the upleg from the stationary unit;

[0107] Figure 14 is a similar view to Figure 2 with the stop members shown in the release position;

[0108] Figure 15 is a perspective view of the syphon of Figures 1 to 14 showing the upleg being removed from the stationary unit;

[0109] Figure 16 is a section view of part of a syphon according to another example shown in a pre-flush position; Figure 17 is a similar view to Figure 16 with the syphon shown in a flush position;

[0110] Figure 18 is a section view of part of a syphon according to another example shown in a pre-flush position;

[0111] Figure 19 is a similar view to Figure 18 with the syphon shown in a flush position;

[0112] Figure 20 is a section view of part of a syphon according to another example shown in a pre-flush position;

[0113] Figure 21 is a similar view to Figure 20 with the syphon shown in a flush position;

[0114] Figure 22 is a section view of part of a syphon according to another example shown in a pre-flush position;

[0115] Figure 23 is a similar view to Figure 22 with the syphon shown in a flush position;

[0116] Figure 24 is a perspective view of a syphon according to another embodiment of the invention shown in a raised, pre-flush position;

[0117] Figure 25 is a perspective view of the syphon of Figure 24 from below;

[0118] Figure 26 is a section view through the syphon of Figures 24 and 25;

[0119] Figure 27 is a perspective view of the inside of the end cap of the upleg part of the syphon of Figures 24 to 26

[0120] Figure 28 is a similar view to Figure 24 with the stop members shown in a release position to enable the removal of the upleg from the stationary unit;

[0121] Figure 29 is a perspective view of the syphon of Figures 24 to 28 showing the upleg being removed from the stationary unit;

[0122] Figure 30 is a perspective view of the stationary unit of the syphon of Figures 24 to 29 illustrating the removal of one of the rails securing the cover to the piston plate; Figure 31 is a similar view to Figure 30 illustrating the rail and the cover removed from the stationary unit;

[0123] Figure 32 is a perspective view of the underside of the rail shown in Figure 31 ;

[0124] Figure 33 is a perspective view of a syphon according to another embodiment of the invention shown in a raised, pre-flush position; and

[0125] Figure 34 is a section view through the syphon of Figure 33.

[0126] Referring now to Figures 1 to 10, there is shown a syphon 1 for discharging water from a cistern, which includes a downleg part 2, an upleg part 3 surrounding the downleg part 2 and a priming assembly 4 secured to the downleg part 2 to form a stationary unit 10. The upleg part 3 is movable, in use, relative to the downleg part 3 to cause a water level therebetween to rise and flow into the downleg part 2 to initiate a syphonic action.

[0127] The downleg part 2 includes a flow conduit 20, an outlet 21 and a threaded portion 22 with a flange 23 for connecting the outlet 21 with the base of a cistern (not shown) in the usual way using a threaded nut (not shown). The downleg part 2 also includes four equally spaced fins 24, 24a extending radially from and axially along an outer surface 25 of the downleg part 2, from the flange 23 toward its upper end and an intermediate flange 26 with a pair of opposed tabs 26a projecting radially therefrom. An opposed pair 24a of the radial fins 24, 24a includes a sprung arm 24b described therein, which extends toward and terminates adjacent to, but spaced from, the intermediate flange 26.

[0128] The downleg part 2 also includes an interface portion 27. The interface portion 27 includes an annular recess 28 having a pair of conical surfaces 28a, 28b describing opposed sides thereof, which converge along its depth. The outermost conical surface 28b includes a step adjacent its upper end, which delineates an annular surface 28c having a smaller cone angle than that of the outermost conical surface 28b. An upper portion of the flow conduit 20 also includes a recess 20a, which provides a conical surface 20b. The downleg part 2 also includes an upper, outer periphery 29, which includes a conical outer surface 29a. The upleg part 3 includes a non-round, enlarged open end 30 for receiving a flow of water into a space between the upleg part 3 and the downleg part 2. The upleg part 3 also includes a substantially flat closed end 31 for redirecting the flow Fw of water into the downleg part 2. A chamber 32 extends from the open end 30, a conduit portion 33 extends from the closed end 31 and a transition 34 joins the chamber 32 to the conduit portion 33. A lower portion of the chamber 32 has a substantially constant cross-section corresponding to the open end 30, along which the piston plate 40 is able to travel. The chamber 32 also includes a domed roof 34a forming part of the transition 34.

[0129] The conduit portion 33 has a substantially constant cross-section corresponding to the closed end 31 . When the upleg part 3 is mounted to the downleg part 2, the fins 24 of the downleg part 2 engage the inner surface of the conduit portion 33 of the upleg part 3 and guide its telescopic movement. The fins 24 also segment the annular space between the outer surface 25 of the downleg part 2 and the conduit portion 33 to provide a segmented annular flow path for water. The flow conduit 20 tapers inwardly to a necked diameter, and tapers back outwardly from the necked diameter to an end diameter at the outlet 21 of the downleg part 2.

[0130] In this example, the open end 30 of the upleg part 3 is rectangular with rounded corners, which has an aspect ratio in this case is approximately 2.7:1. The constant cross-section portion of the chamber 32 is also rectangular with the same aspect ratio as the open end 30. A radial flow area AR is described between the closed end 31 of the upleg part 3 and the apex of the spillover 5. This radial flow area AR corresponds to the area of flow in the radial direction, across the apex of the spillover. An axial flow area AA is described between an outer diameter of the spillover 5 and a surrounding portion of the upleg part 3. This axial flow area AA corresponds to the area of annular flow of water Fw in an axial direction, before being redirected by the closed end 31 of the upleg part 3.

[0131] Each corner of the chamber 32 includes an open-bottom cylinder 35 and each short side of the chamber 32 includes a stopper sleeve 36 within which a stop member 37 is rotatably received. Each rotatable stop member 37 is in the form of an elongate, tapered cylinder with a pair of opposed sprung arms 37a at its top end and a crescent shaped flange 37b projecting radially from its bottom end. The stop member 37 is inserted into the stopper sleeve 36, which forces the sprung arms 37a into a hole 36a at the top of the stopper sleeve 36 until radial recesses (not shown) in the sprung arms 37a align with the hole 36a, at which point the sprung arms 37a snap out into engagement within the hole 36a. The space between the sprung arms 37a is configured to receive a tool (e.g. a screwdriver) to enable the stop member 37 to be rotated between an engaged or deployed position, which is shown in Figures 1 and 2, and a release or retracted position, which is shown in Figures 13 and 14.

[0132] The priming assembly 4 is secured to the downleg part 2 and is associated with the open end 30 of the upleg part 3. In this example, the priming assembly 4 is located between the upleg part 3 and the downleg part 2. The priming assembly 4 is secured to the downleg part 2 and includes a piston plate 40 with a lattice structure that describes a plurality of openings 40a through its thickness and a cover 41 removably secured along each outer, minor edge of the piston plate 40 by a rail 42. The piston plate 40 is received within, and has a complementary shape to, an inner surface of the chamber 32.

[0133] The piston plate 40 slopes from its outer, minor edges toward a mounting ring 43 at its centre and has a pair of walls 44 extending along its outer, major edges. The mounting ring

[0134] 43 projects upwardly from the sloped piston plate 40 such that it describes with the walls

[0135] 44 a recess 45 that surrounds the periphery of the cover 41 at close proximity thereto. This creates a shallow reservoir above the cover 41 , which inhibits water from passing between upturned edges of the cover 41 and the piston plate 40.

[0136] As such, this arrangement reduces the effect of a cover 41 that is not perfectly flat. The sloping piston plate 40 also provides a more rigid construction, which inhibits bending under the hydrostatic force exerted on it during initiation of a flush.

[0137] The covers 41 are formed of a flexible material, i.e. a flexible diaphragm material, and selectively cover the openings 40a through the plate 40 to provide a one-way valve that functions in a similar way to the diaphragm on the piston of a conventional syphon. More specifically and as shown in Figure 5, the covers 41 deform about the rails 42. The deformation shown is illustrative only, and should not be considered representative of the form it takes when the siphonic action has commenced.

[0138] The mounting ring 43 includes a flange 43a projecting radially inwardly and a pair of opposed radial recesses 43b on the sides corresponding to the outer major edges of the piston plate. To secure the piston plate 40 to the downleg part 3, the upper end of the downleg part 3 is inserted into the mounting ring 43 of the piston plate 40. The piston plate 40 is then forced downwardly to urge the sprung arm 24b of the radial fins 24a of the downleg part 2 inwardly, until the flange 43a aligns with the space between the intermediate flange 26 and the sprung arm 24b. At this position, the sprung arms 24b return to their rest position and the flange 43a is captivated between the intermediate flange 26 and the sprung arm 24b and is retained on the downleg part 2.

[0139] Each corner of the piston plate 40 also includes an open-top cylinder 46 secured thereto. As illustrated in Figure 7, when the upleg part 3 is mounted over the downleg part 2, each open-bottom cylinder 35 of the upleg part 3 is received within one of the open-top cylinders 46 of the piston plate 40. A spring S is captivated between each open-bottom and open top cylinder pair 35, 46, such that the upleg part 3 is urged away from the piston 40 to a preflush position, shown in Figures 1-4 and 6.

[0140] As is clear from Figure 7, the crescent shaped flange 37b of the stop member 37 abuts a lower surface of the piston plate 40, thereby providing a stop acting against the spring S when the upleg part 3 is in the pre-flush position shown in Figure 4. Similarly, the lower edges of the open-bottom cylinders 35 of the upleg part 3 cooperate with the closed bottoms of the open-top cylinders 46 of the piston plate 40 to provide a stop, which limits the downward movement of the upleg part 3 in the flush position shown in Figure 5.

[0141] The syphon 1 also includes a spillover 5 between the upleg part 3 and the downleg part 2 for introducing into the downleg part 2 the flow of water that rises therebetween. In this example, the spillover 5 is secured within the upleg part 3 by four radial webs 50 connected to the conduit portion 33, such that the spillover 5 moves with the upleg part 3 relative to the downleg part 2.

[0142] The spillover 5 has an annular flow surface 51 that includes an inner periphery 52 and an outer periphery 53 that is more aggressive, or sharper, than the inner periphery 52. In this example, the peripheries 52, 53 are rounded, being provided by respective substantially toroidal surfaces each having a respective radius of curvature, or poloidal radius Ri, R2. The poloidal radius R1 of the inner periphery 52 is substantially larger than the poloidal radius R2 of the outer periphery 53. This has been found to improve significantly the performance of the syphon, especially in conjunction with additional features that will be described below.

[0143] The spillover 5 also includes an interface portion 54, which includes an annular wall 55 depending from the spillover 5 which is receivable within the annular recess 27a of the downleg part 2. The annular wall 55 includes a pair of conical surfaces 55a, 55b describing opposed sides thereof, which converge along its depth and which cooperate with the conical surfaces 28a, 28b of the recess 28 of the downleg part 2. The outermost conical surface 55b includes a step adjacent its upper end, which delineates an annular surface 55c having a smaller cone angle than that of the outer conical surface 55b. This annular surface 55c cooperates with the annular surface 28c delineated in the outermost conical surface 28b of the recess 28 of the interface 27 of the downleg part 2.

[0144] The interface portion 54 of the spillover 5 also includes a depending inner shroud 56 nested within the annular wall 55 and a depending outer shroud 57 surrounding the annular wall 55. The inner shroud 56 includes an outer conical surface 56a and describes the innermost portion of the inner periphery 52 of the annular flow surface 51 . The outer conical surface 56a of the inner shroud 56 cooperates with the conical surface 20b in the recess 20a in the upper portion of the flow conduit 20. The outer shroud 57 includes an inner conical surface 57a, which cooperates with the conical outer surface 29a of the upper, outer periphery 29 of the downleg part 2.

[0145] In use and when the upleg part 3 is in the pre-flush position shown in Figure 4, actuation means, such as lever or other mechanism (not shown), is operated to urge the upleg part 3 downward, toward the flush position shown in Figure 5. In doing so, downward pressure is exerted on the water within the chamber 32, which forces the cover 41 against the piston 40 and prevents water from escaping through the openings 40a. The water level between the downleg part 2 and the conduit portion 33 of the upleg part 3 rises as indicated by the flow arrows Fw, is redirected by the closed end 31 and flows over the spillover 5 to initiate a syphonic action. This causes the cover 41 to move away from the piston 40 to allow water to flow from the cistern through the openings 40a and out of the downleg part 2.

[0146] As illustrated by Figure 4, the interface portions 27, 54 of the downleg part and spillover 5 are spaced in the pre-flush position. The undulating form of the resulting gap G between the interface portions 27, 54 creates an airlock that inhibits water from within the cistern from passing between the spillover 5 and the downleg part 2. As illustrated by Figure 5, the interface portions 27, 54 of the downleg part and spillover 5 abut or are at least in close proximity to one another in the pre-flush position. This closes the undulating gap G between the interface portions 27, 54, thereby substantially evacuating the airlock.

[0147] Moreover, the cooperating annular surfaces of the interfaces 27, 54 of the downleg part 2 and the spillover 5, which surround the annular wall 55 and which have a smaller cone angle than that of the conical surfaces 55a, 55b, 56a encourage air to be drawn into the undulating gap G from the downleg part 2 when the upleg part 3 is returned to the pre-flush position shown in Figure 4. This is because the gap between these surfaces increases slower than the gap G between the other conical surfaces 55a, 55b, 56a.

[0148] As a result, the airlock is reset on every flush. This could be important in instances where irregular manipulation of the actuation mechanism might cause an ingress of water into the undulating gap G and inhibit proper operation of the syphon 1.

[0149] The inventors have determined that there are certain characteristics that are important for ensuring that the syphonic action to be initiated reliably. The provision of a non-round open end 30 in combination with a substantially flat closed end 31 have been found to be particularly effective. An aspect ratio of at least 2:1 was found to perform well, with 2.5:1 to 3:1 being ideal.

[0150] Surprisingly, the relationship between the axial clearance between the closed end of the upleg and the spillover and the radial clearance between the spillover and a surrounding portion of the upleg when the spillover is in the flush position and their associated flow areas were also found to be quite important.

[0151] More particularly, it was determined that an axial clearance between 110% and 140% of the radial clearance CR performed well, as did the corresponding relationship between the radial flow area AR and the axial flow area AA when the radial flow area AR was between 80% and 110% of the axial flow area AA.

[0152] Turning now to Figures 11 and 12, there is shown a piston plate 40’ according to another example, similar to the piston plate 40 shown in Figure 10, wherein like features are depicted by like references with the addition of a ‘. The piston plate 40’ according to this example differs from that of Figure 1 in that the sloping portion is replaced with a flat, recessed base 45a’. This creates a further wall 44a’ along each short side of the piston plate 40’, to describe, with the mounting ring 43’ and the walls 44’ extending along its outer, major edges, the recess 45’.

[0153] Referring now to Figures 13 to 15, the stop members 37 of the syphon 1 are rotated using a tool (not shown) from the engaged position, shown in Figures 1 and 2, to the release position in order to enable the upleg part 3 to be removed from the stationary unit 10. The upleg part 3 is then lifted off the stationary unit 10, which remains within the cistern (not shown).

[0154] The skilled person will appreciate that this is advantageous as it enables the internal components of the syphon 1 to be accessed and serviced without the need for turning off the water source and draining the cistern. This enables the rails 42 to be removed and the covers 41 to be replaced when they are worn.

[0155] Figures 16 and 17 show a syphon 101 according to another example, similar to the syphon 1 of Figure 1 , wherein like features are depicted by like references incremented by 100. The syphon 101 according to this example differs from that of Figure 1 in that it includes a diaphragm 105 between the piston plate 140 to the open end 130 of the upleg part 103. The diaphragm 105 connects a periphery of the open end 130 of the upleg part 103 to the piston plate 140 about its periphery, thereby to provide a membrane which prevents water from leaking out of the chamber 132 from between the outer peripheral edge of the piston plate 140 and the inner surface of the chamber 132 of the upleg part 103.

[0156] In this example, the diaphragm 105 is secured to the piston plate 140 by a retainer 150. The retainer 150 is in the form of a ring that corresponds substantially to a peripheral portion of the piston plate 140. The retainer 150 is secured to a lower side of the piston plate 140 and the diaphragm 105 extends from an inner edge of the retainer 150.

[0157] Similarly, the diaphragm 105 is secured to the open end 130 of the upleg part 103 by a retainer 137, which is also in the form of a ring that corresponds to a peripheral portion of the open end 130. In this case, the retainer 137 projects inwardly and replaces the crescent shaped flange 37b to provide a stop with which the piston plate 140, more specifically the retainer 150 mounted to the piston plate 140, cooperates to limit upward movement of the upleg part 103. In this example, the diaphragm 105 is sandwiched between the retainer 137 and a further ring-shaped retainer 151 . The membrane 105 also extends from an inner edge of the further retainer 151 .

[0158] When the upleg part 103 is in a pre-flush position, as shown in Figure 16, the diaphragm 105 depends below the open end 130 of the upleg part 103, with a substantially U-shaped cross-section and the cooperating second stops 150, 137 engage. When the upleg part 3 is in the flush position, as shown in Figure 17, the diaphragm 105 is stretched fully and the lower edges of the open-bottom cylinders 135 of the upleg part 3 engage the closed bottom of the open-top cylinders 146 of the piston plate 140.

[0159] In use, when the upleg part 103 is moved from the pre-flush position (shown in Figure 16) to the flush position (shown in Figure 17), the diaphragm 105 inhibits leakage between the piston plate 140 and the surrounding chamber 132 of the upleg part 103. Whilst some water may leak between the piston plate 140 and the chamber 132, this remains within the space defined between the diaphragm 105, the piston plate 140 and the surrounding chamber 132.

[0160] Without wishing to be bound by any particular theory, it is believed that excess water causes the diaphragm 105 to expand, creating a positive pressure within the space and effectively resisting further leakage of the water in subsequent flushes. Experiments suggest that this diaphragm can improve substantively the performance of the syphon 101.

[0161] Turning now to Figures 18 and 19, there is shown a syphon 201 according to another example, similar to the syphon 101 of Figures 16 and 17, wherein like features are depicted by like references incremented by 100. The syphon 201 according to this example differs from that of Figures 16 and 17 in that the periphery of the piston plate 240 is spaced from the inner surface of the chamber 232 of the upleg part 103 and the retainer 137a is omitted, such that the stops 137, 150 are also omitted. A chamber extension 232a, whose inner surface is substantially contiguous with that of the chamber 232, also replaces the further retainer 151. As a result, the diaphragm 205 is secured at an intermediate position of the chamber 232, 232a.

[0162] The omission of the stops 137, 150 provides flexibility in the raised position of the upleg part 203. As such, the syphon 201 can accommodate some variation in water level without the need for adjustment. The springs S (not shown in this example, but shown in Figure 7) ensures that the upleg part 203 moves to the appropriate pre-flush position, shown in Figure 18.

[0163] The space between the piston plate 240 and the chamber 232 enables water to pass freely therebetween. However, as the upleg part 203 is moved from the pre-flush position, shown in Figure 18, to the flush position, shown in Figure 19, the diaphragm 205 works with the covers 241 to prevent any water from entering the cistern and to initiate the syphonic action. The configuration of the diaphragm 205 is selected so that its resilience when stretched ensures that an appropriate pressure is created to ensure smooth initiation of the syphonic action.

[0164] In use, the syphon 201 according to this example functions in a similar way to the syphon 101 of Figures 16 and 17.

[0165] Turning now to Figures 20 and 21 , there is shown a syphon 301 according to another example, similar to the syphon 201 of Figures 18 and 19, wherein like features are depicted by like references incremented by 100. The syphon 301 according to this example differs from that of Figures 18 and 19 in that the chamber 232 is provided almost entirely by the chamber extension 232a, such that the diaphragm 305 is secured to an upper end portion of the chamber 232. The periphery of the piston plate 340 also corresponds substantially t the inner surface of the chamber extension 232a.

[0166] As a result, the diaphragm 305 is stretched substantively when the syphon 301 is in the pre-flush position, shown in Figure 20, and is collapsed and nearly folded inwardly when the syphon 301 is in the flush position, shown in Figure 21 . In use, the syphon 301 according to this example functions in a similar way to the syphon 101 of Figures 16 and 17 and the syphon 201 of Figures 18 and 19.

[0167] Turning now to Figures 22 and 23, there is shown a syphon 401 according to another example, similar to the syphon 301 of Figures 20 and 21 , wherein like features are depicted by like references incremented by 100. The syphon 401 according to this example differs from that of Figures 20 and 21 in that the piston plate 440 includes an upstanding peripheral wall 444 that describes an upleg receptacle within which the upleg part 403 is moveable to initiate the syphonic action, and a diaphragm 405 secured to the upstanding peripheral wall 444.

[0168] The peripheral wall 444 has a size and shape that is complementary and matches substantially an outer surface of the chamber 432 of the upleg part 403, thereby to minimise the clearance and to inhibit water from passing therebetween.

[0169] The diaphragm 405 is secured to an upper edge of the peripheral wall 444 by a ring-shaped retainer 450 that matches substantively the shape of its upper edge. More specifically, the diaphragm 405 is sandwiched between the retainer 450 and the upper edge of the peripheral wall 444. The diaphragm 405 extends upwardly from the peripheral wall 444 and the retainer 450 forming a U-shape when the syphon 401 is in the pre-flush position, shown in Figure 22, and is stretched substantively when the syphon 401 is in the flush position, shown in Figure 23.

[0170] In use, when the upleg part 403 is moved from the pre-flush position, shown in Figure 22, to the flush position, shown in Figure 23, syphonic action is initiated in a similar manner to that described above in relation to Figure 1. Any leakage between the upleg part 403 and the peripheral wall 444 remains within the space defined between the diaphragm 405, the upleg part 403 and the surrounding peripheral wall 444.

[0171] Figures 24 to 32 show a syphon 501 according to another example, similar to the syphon 1 of Figure 1 , wherein like features are depicted by like references incremented by 500. The syphon 501 according to this example differs from that of Figure 1 primarily in that it includes variations on the closed end 531 of the upleg part 3, the configuration of springs S that urge the upleg part 503 toward its pre-flush position, the rail 542 for securing the covers 541 to the piston plate 540 and the rotatable stop members 537 of the upleg part 503.

[0172] The closed end 531 is domed, or conical in this example, instead of flat. The closed end 531 also includes a plurality of fins 506, six in this example, depending from its conical inner surface 531a. Each fin 506 has a quasi-spherical outer, flow-contacting surface 560 and tapers to a sharp free edge above the spillover 505. The fins 506 are distributed about a circle having a diameter that is smaller than the outer portion of the spillover 505 and slightly greater than that of the inner portion thereof. As such, the fins 506 are over the inner periphery 552 of the spillover 505 and interrupt the flow Fw of water after it passes over the apex of the spillover 505.

[0173] Without wishing to be bound by any particular theory, it is believed that each fin 506 redirects a portion of the flow Fw of water down an radially outer portion of the downleg part 502. It is also believed that some of the flow passes between the fins 506, up toward the apex of the conical surface 531a and collides with the other fin bypassing portions of the annular flow front and falls down a radially inner portion of the downleg part 502. This is believed to improve syphonic performance.

[0174] In this example, the syphon 501 includes only two springs S biasing the upleg part 503 toward its pre-flush position. The springs S and the stop members 537 of the upleg part 3 are both offset on opposite sides of the centrally located, so as to provide a staggered arrangement. The springs S are installed over and retained on a pair of cruciform lugs 535 depending within the chamber 532 of the upleg part 3. The other end of each spring S is received within a respective open-top cylinder 546 of the piston plate 540.

[0175] In this example, the rotatable stop members 537 each include a knob or dial 537a instead of the spaced sprung arms 37a. The dial 537 has a flat head with concave blended sides to facilitate manual gripping and rotation of the stop member 537 from above the syphon 501 . The flange 537b is also straight with a reinforcing rib instead of crescent shaped in this example.

[0176] The piston plate 540 is secured to the downleg by an extension 524 of each of the opposed intermediate flange tabs 526a. Each intermediate flange tab extension 524 is engagingly received within a respective slot 543a in an adjacent side of the recess 543b of the piston plate 540.

[0177] The rail 542 includes a pair of depending pins 542a that are inserted through respective holes 541a of the cover 541 and respective holes 540b through the piston plate 540. The rail 542 also includes a depending resilient securing arm 542b with a barb 542c at its free end for releasably securing the rail 542 to the piston plate 540. A slot 542d extends through the rail 542, and is aligned with the securing arm 542b to provide sufficient flexibility to enable the resilient securing arm 542b to be manipulated out of engagement with the piston plate 540. To remove the rail 542 from the piston plate 540, the resilient securing arm 542b is manipulated, or bent, as shown by arrow B in Figure 30 to release the barb 542c from the piston plate 540. The rail 542 is then lifted off the piston plate 540 as illustrated by arrow L to remove the pins 542a from the holes 541a, 540b of the cover 541 and piston plate 540. The cover 541 can then be replaced.

[0178] Figures 33 and 34 show a syphon 601 according to another example, similar to the syphon 401 of Figures 22 and 23, wherein like features are depicted by like references incremented by 200. The syphon 601 according to this example differs from that of Figures 22 and 23 in that the diaphragm 405 is replaced with a cowl 605, which is secured to an upper edge of the peripheral wall 644.

[0179] The cowl 605 surrounds and has a similar shape to the tapering transition 634 of the upleg part 603. As such, the cowl 605 partially covers the transition 634 when the upleg part 603 is in the pre-flush position.

[0180] In use, the upleg part 603 is moved away from the pre-flush position, shown in Figure 33, for initiating syphonic action in a similar manner to that described above in relation to Figures 22 and 23. In the initial stage of this movement, leakage between the upleg part 403 and the peripheral wall 444 is inhibited in a similar manner to that which is described above in relation to the syphon 401 of Figures 22 and 23.

[0181] It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and / or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

CLAIMS1 . A syphon for discharging water from a cistern, the syphon comprising: a downleg with an outlet for connection with the base of a cistern; an upleg surrounding the downleg and having: an open end for receiving a flow of water into a space between the upleg and the downleg; and a closed end for redirecting the flow of water into the downleg; a spillover between the upleg and the downleg for introducing into the downleg the flow of water redirected from the closed end of the upleg; and priming means associated with the open end of the upleg; wherein the spillover is movable, in use, with the upleg relative to the downleg to a flush position, whereby the priming means causes or encourages a water level between the upleg and downleg to rise and flow over the spillover to initiate a syphonic action.

2. The syphon of claim 1 comprising an interface between the spillover and the downleg, wherein the spillover is movable, in use, with the upleg relative to the downleg between a pre-flush position, in which the interface describes an airlock for inhibiting water from passing between the spillover and the downleg, and the flush position, in which the airlock described by the interface is least partially evacuated.

3. The syphon of claim 2, wherein the interface comprises an annular wall depending from the spillover which is receivable within an annular recess of the downleg, the wall and recess having conical surfaces, which are spaced to describe an airlock therebetween for inhibiting water from passing therebetween when the spillover is in the pre-flush position, and which are adjacent or abut one another to at least partially evacuate the airlock when the spillover is in its flush position.

4. The syphon of claim 2 or claim 3, wherein the interface comprises cooperating annular surfaces of the spillover and downleg which surround at least part of the annular wall and which have a smaller cone angle than that of the conical surfaces, thereby to encourage air to be drawn, in use, into the airlock from the downleg.

5. The syphon of any preceding claim, wherein the spillover comprises a shroud received within a flow conduit of the downleg when the spillover is in its flush position for shielding the flow of water from an upper end of the flow conduit.

6. The syphon of claim 5 when dependent upon claim 3 or claim 4, wherein the shroud is nested within the annular wall and includes an outer conical surface that cooperates with a facing inner conical surface of the flow conduit of the downleg, which inner and outer conical surfaces are spaced when the spillover is in the pre-flush position and which are adjacent or abutting one another when the spillover is in its flush position.

7. The syphon of any preceding claim, wherein the spillover has an inner substantially toroidal surface and an outer edge or substantially toroidal surface having a smaller poloidal radius than the inner substantially toroidal surface.

8. The syphon of any preceding claim, wherein the priming means comprises a piston with openings therethrough and a cover configured to cover, in use, the openings to inhibit water from flowing out of the open end of the upleg as the upleg is moved toward the flush position, and to move away from the openings to allow water to flow into the upleg from the open end after initiation of the syphonic action.

9. The syphon of claim 8, wherein the piston comprises a recess within which the cover is received so as to provide one or more sides that at least partially surround a periphery of the cover.

10. The syphon of claim 8 or claim 9, wherein the piston surrounds the downleg and at least part of the piston slopes from its periphery toward the downleg.

11. The syphon of any one of claims 8 to 10, wherein the piston is received within an enlarged chamber of the upleg that extends from the open end toward the closed end and has a complementary shape to an inner surface of the enlarged chamber of the upleg.

12. The syphon of claim 11 comprising a diaphragm which connects a periphery of the piston to a periphery of the enlarged chamber of the upleg for inhibiting water from leaking between the piston and the enlarged chamber13. The syphon of any one of claims 8 to 10, wherein the priming means comprises a wall extending from a periphery of the piston to describe an upleg receptacle within which the open end of the upleg is moveable to initiate a syphonic action.

14. The syphon of claim 13 comprising a cowl projecting from the wall, wherein the upleg comprises a tapering transition between the upleg and the downleg which is partially covered by the cowl for inhibiting water from leaking between the piston and the upleg when the upleg is moved from the or a pre-flush position toward the flush position.

15. The syphon of claim 13 comprising a diaphragm which connects the wall to a periphery of the open end of the upleg for inhibiting water from leaking between the piston and the upleg.

16. The syphon of any preceding claim comprising a stop for limiting movement of the upleg relative to the downleg, wherein the stop is removable or movable to a release position to enable the upleg to be withdrawn, in use, from the downleg.

17. The syphon of any preceding claim comprising resilient biasing means for urging the upleg away from flush position and toward a pre-flush position.

18. The syphon of any one of claims 8 to 16, wherein the piston is fixed relative to the downleg and is connected to the upleg by one or more resilient biasing means configured to urge the upleg away from flush position and toward a pre-flush position.

19. The syphon of any preceding claim comprising an axial clearance between the closed end of the upleg and the spillover which is between 110% and 140% of a radial clearance between the spillover and a surrounding portion of the upleg when the spillover is in the flush position.

20. The syphon of any preceding claim comprising a radial flow area between the closed end of the upleg and the spillover which is between 80% and 110% of an axial flow area between the spillover and a surrounding portion of the upleg when the spillover is in the flush position.

21. The syphon of any preceding claim, wherein the closed end of the upleg is substantially round and the open end of the upleg is substantially elliptical, oval, rectangular or obround.

22. The syphon of any preceding claim, wherein the upleg and downleg comprise cooperating stops configured to engage when the spillover is in the flush position.

23. A toilet cistern comprising a syphon according to any preceding claim comprising an inlet valve for filling the cistern to a fill level.

24. A toilet cistern according to claim 23, wherein an apex of the spillover is above, at or at least adjacent to the fill level when it is in the flush position for inhibiting water from being discharged from the cistern if the upleg fails to return to a pre-flush position.

25. A method of operating a syphon to discharge water from a cistern, the method comprising forcing an upleg and a spillover into a body of water within a cistern such that the upleg and spillover both move relative to a downleg within the upleg that has an outlet connected with a base of the cistern, whereby water from the body of water is forced or encouraged by priming means to enter an open end of the upleg, flow between the upleg and downleg until it reaches and is redirected by a closed end of the upleg and flows over the spillover and into the downleg and out through the outlet of the downleg to initiate a syphonic action.

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