GB2547257A - Improved syphon - Google Patents

Abstract

The syphon 100 comprises an outlet tube 20 for sealed engagement with a cistern outlet, and an overflow tube 12 having an end face 14 for telescopic insertion into the outlet tube, wherein an outer surface of the overflow tube meets the end face at the end of the overflow tube, and a distal portion of the overflow tube which is inserted furthest into the outlet tube defines a cutaway when viewed from the side. A proximal portion of the defined cutaway may be higher than the distal portion when the overflow tube is inserted in the outlet to encourage air towards the proximal portion during syphoning. The distance between the proximal and distal portions may be greater than the thickness of the overflow tube. The cutaway may define a flat angled surface. Also claimed is an overflow tube for the syphon.

Description

Improved Syphon

FIELD

[01] The disclosure relates to an improved syphon, particularly, although not exclusively to syphons for cisterns.

BACKGROUND

[02] In recent years, syphons have become more versatile. Modern syphons are capable of being manipulated to provide different flushing volumes and height adjustments for particular applications. Furthermore, modern cisterns are provided with different internal dimensions, which affect the internal volume and working characteristics. These factors give rise to the need for customisation. To meet this need, height adjustable syphons have been developed. Height adjustable syphons offer improved system matching whilst maintaining overall efficiency.

[03] Typically, a height adjustable syphon is varied in overall height by moving the apex of the top section (the inverted u-shaped tube used to create the overflow) with respect to the bell housing (containing the diaphragm) and outlet down leg (the tube connected to the cistern outlet). The top section remains fluidly connected to the bell housing and outlet down leg by telescopic movement of an outlet tube (engageable with the outlet down leg) and an inlet tube (engageable with the bell housing). Typically, the outlet tube of the top section is inserted into the outlet down leg. During the flushing action (i.e. the syphoning event, also known as syphonic action), the water is drawn from the bell housing to the apex of the top section and flows through the outlet tube of the top section in order to exit the syphon through the outlet tube fixed to the cistern.

[04] As shown in Figures 1 and 2, a top section 10 (otherwise known as an overflow tube) and a cistern outlet tube 20 of a syphon 100 is shown. The top section 10 comprises an outlet tube 12 having an end face 14 that is typically a square profile (i.e. when viewed in the radial direction, the end 14 of the outlet tube 12 is substantially orthogonal to the longitudinal axis X). During the flushing action, any air within the syphon 100 is mostly replaced by water. However, as the water flows through the tubes 12,20, air present within the tubes prior to water can become trapped within the tubes 12,20. This phenomenon is more prominent in the outlet due to reduced localised pressures caused by the suction of water. The entrapped air is commonly known as air breakout. This effect is promoted by the square profile and stepped bore and associated pressure transition of the end 14, which prevents the trapped air from dissipating. Typically, to overcome this problem, the tubes 12,20 are telescopically inserted using a low tolerance fit. However, pockets of air Y1 immediately downstream of the top section outlet tube 12 are still able to form around the perimeter of the squared end 14. Any remaining air adversely affects the flow profile and reduces the outlet flow rate Z because full bore flow does not always develop. This affects the efficiency of the syphon 100 because the trapped air Y1 reduces the available bore space for the water to flow through, which reduces the overall volume and velocity of the flush delivered to the water closet (WC) pan.

[05] It is an aim of the present disclosure to improve the efficiency of the flushing action in a syphon. It is desirable to minimise or eliminate the effects of air entrapment in a syphon, particularly at the interface between the outlet down leg and overflow outlet in order to improve the volume and/or strength of flow. A further aim is to improve the flow performance of the syphon without impacting manufacturing complexity. A more efficient syphon may assist with providing reduced syphonic activation forces and/or shorter syphonic activation strokes, which may be advantageous for persons with a physical disability who may require light touch operation.

SUMMARY

[06] According to the present invention there is provided a syphon as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

[07] According to the disclosure, an overflow tube for a syphon is provided. The overflow tube comprises an outlet having respective low and high points configured to encourage trapped air bubbles away from the low point and toward the high point. As such, the outlet may have a sloped end face. The slope is configured to circumferentially move the trapped air bubbles such that the air bubbles congregate at the high point. Therefore, the slope of the end face may be more than a chamfered or rounded edge. Advantageously, the control of air bubble movement helps to improve the outlet flow rate because water flowing out of the outlet during syphoning action can follow the internal surfaces of the tubes more closely without being forced away by the air bubbles. Furthermore, abrupt pressure transitions in the outlet flow are smoothed and air breakout effects are eliminated resulting in full bore outlet flow. Overall, a more efficient system is produced.

[08] According to the disclosure, an overflow tube for a syphon is provided. The overflow tube comprises an outlet that is insertable within an outlet of a cistern. When inserted into the cistern outlet, the overflow tube overlaps with the cistern outlet such that the overlap various around the perimeter of the tube to form relative low and high points. In use, air bubbles become trapped and gather at the end of the overlap around the edge of the end face of the overflow tube. However, the bubbles migrate towards the high point due to the buoyancy effect which helps to minimise flow restriction.

[09] According to an exemplary embodiment, a syphon fora cistern is provided. The syphon comprises an outlet tube for sealed engagement with a cistern outlet. That is, the outlet tube and cistern outlet are configured to prevent water from exiting between the outlet and the outlet tube. The syphon further includes an overflow tube that may be configured as a u-shaped tube. The overflow tube having an open end, whereby the open end has an end face. The overflow tube is arranged for telescopic insertion into the outlet tube by inserting the end face and open end into an inlet of the outlet tube. The overflow tube has an outer surface that is arranged to unite with the end face at what is defined as a longitudinal extent of the overflow tube. The outer surface is arranged to face an inner surface of the outlet tube once the overflow tube is inserted in the outlet tube.

[10] The term longitudinal extent is not used to define a geometric dimension but instead is used to define the furthest circumferential points at the meeting point of the outer surface and the end face. Whereas the end face typically bridges the inner and outer surfaces of the overflow tube and is related to the thickness, the longitudinal extent may be delineated by an outer perimeter edge of the overflow tube.

[11] The longitudinal extent comprises a distal portion that is arranged to protrude into the outlet tube the most. The radial plane passing through the distal portion is defined as the distal radial plane. The overflow tube is further defined in that the longitudinal extent is configured to deviate away from the distal radial plane such that part of the longitudinal extent and/or the end face does not exist on the distal radial plane. The effect of this configuration is that the open end of the overflow tube defines a cutaway when viewed from the side.

[12] Advantageously, the efficiency of fluid flow can be improved. The deviation of the longitudinal extent from the distal radial plane reduces the tendency of the entrapped air to exist around the entire perimeter of the end face region. This allows a full bore of flow to be achieved which helps to pass more fluid through the overflow tube and initiate a syphon action quicker. Entrapped air is forced towards the cutaway when the cutaway is arranged in the most vertical position due to gravity. This allows the entrapped air or breakout to impact the flow on a smaller scale so that the flow of water is maximised.

[13] The longitudinal extent of the syphon may further comprise a proximal portion. The proximal portion defines a portion of the longitudinal extent that deviates the furthest away from the distal radial plane. When the overflow tube is arranged in the outlet tube, the syphon is configured such that the proximal portion is arranged to be vertically higher than the distal portion. The relative positioning of the distal and proximal portions are designed to encourage any entrapped air towards the proximal portion during syphoning action. This helps to increase the outlet flow rate and efficiency of the syphon. In addition, the effect of water flow passing from a smaller overflow tube bore into a larger outlet tube bore experiences an abrupt “stepped” pressure transition, whereas in this disclosure the pressure transition experienced by water flow passing from the overflow tube into the outlet tube becomes a less abrupt, phased pressure transition and breakout effects are eliminated. Therefore, a better syphon can be provided.

[14] The proximal and distal points may define a longitudinal distance between them in the direction of the longitudinal axis of the overflow tube that is greater than the thickness of the overflow tube. The longitudinal extent may be linear. The longitudinal extent may be inclined with respect to the radial and longitudinal planes of the overflow tube. Therefore, the overflow tube may be delimited with an angled profile. The longitudinal extent may be aligned along a single plane that is inclined in a linear manner, said plane having an inclination angle with respect to the distal radial plane. The inclination angle may be at least 5 degrees. Preferably, the inclination angle is at least 10 degrees. Most preferably, the inclination angle is substantially between 10 and 60 degrees. Alternatively, the longitudinal extent may be curved, i.e. arcuate. The curvature may be substantially concave or convex when viewed end on.

[15] Advantageously, the inclination angle encourages trapped air towards the highest point on the longitudinal extent in order to help maximise fluid flow by reducing the detrimental impact of entrapped air on the fluid flow. This allows fuller flow to be provided so that the syphon is more efficient. Furthermore, the pressure transition caused by the flow of water from the smaller diameter overflow tube into the larger diameter outlet tube becomes less abrupt and more phased (i.e. more gradual or smooth) because the air breakout effects are much reduced or even eliminated. The smoothing of the transition increases the efficiency of the water flow and allows higher flow rates to be achieved because the flow of water does not have to work against the more buoyant air breakout. This allows full bore flow to be achieved, which helps to provide shorter flush times. Furthermore, less work is required to establish syphoning action because of the reduced drag caused by the air breakout. Overall, a more efficient syphon can be provided.

BRIEF DESCRIPTION OF DRAWINGS

[16] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: [17] Figure 1 shows a typical syphon arrangement between cistern and overflow outlet; [18] Figure 2 shows a typical syphon arrangement (made of transparent material for experimental testing) showing the air entrapment problem; [19] Figure 3 shows an improved syphon arrangement (made of transparent material for experimental testing) wherein the overflow end face is sloped; [20] Figure 4 shows the improved syphon arrangement; and

[21] Figure 5 shows the improved overflow tube arrangement having a sloped overflow face. DESCRIPTION OF EMBODIMENTS

[22] Figures 3 to 5 show an overflow tube 10 having an outlet tube 12 inserted (e.g. telescopically) into a cistern outlet tube 20 (known as a downleg) connected to a cistern outlet. The overflow tube 12 also comprises a corresponding inlet tube that is insertable into a bell housing 30. In Figure 4, the outlet tube 12 is shown to extend longitudinally further from an apex of the overflow tube 10 than the inlet tube.

[23] The outlet tube 12 is shown with an end face 14 generally angled to the horizontal, or more specifically, angled to the radial direction of the outlet tube 12. During a flush (i.e. when a diaphragm (within a bell housing 30 fluidly connected to the overflow tube 10) is moved (by an actuating means such as an actuating stem, rod or button, any of which may be electronically controllable) to cause the syphoning action), the water passing through the overflow tube 10 and the outlet tube 12 (shown by arrow F in Figure 4) causes air to be drawn through the gap 16 between the tubes 12,20. Any trapped air tends to form air pockets Y2,Y3 that exist around the perimeter of the overflow tube 10. However, due to the inclined end surface 14 of the outlet tube 12, any air bubbles or pockets formed at a lower point Y2 will move towards a higher point Y3 due to the buoyancy of the air. As the air pocket is forced towards a predetermined location (i.e. the higher point Y3), the air pocket diminishes. This reduction in air pocket size helps to increase syphon flow so that a greater volume of water can flowthrough the outlet tube 12 fora given time.

[24] The inclination of the end face 14 causes a pinching (i.e. reduction) of the air pocket Y2,Y3, which improves flow efficiency and helps to provide full bore flow, i.e. a diameter of water flow that closely matches the internal diameter of the pipe/tube. Experimental data has shown that favourable results occur when the angle of inclination A with respect to the radial direction R of the outlet tube axis X is around 10-60 degrees. Greater inclination angles A tend to accelerate the movement of the air pockets Y2,Y3 toward the predetermined location.

[25] The end face 14 is arranged such that the wall surface of the outlet tube 12 is also aligned on the inclination angle A. This allows the outlet tube 12 to be easily cut to the desired profile if required. Advantageously, the sloped end face 14 helps to avoid the need for precision fit tubes in order to reduce the manufacturing complexity. The arrangement is particularly advantageous in a height adjustable syphon because the reduced need for high precision fits allows the telescopic tubes 12,20 to be moved (i.e. slid) relative to one another more easily. Furthermore, the improved arrangement helps to increase the outlet flow rate Z due to the reduction and/or possible elimination of the entrapped air pockets Y2,Y3, together with reduced air breakout effects from the improved pressure transition between the overflow tube and the outlet tube bores.

[26] As shown in Figures 4 and 5, the thickness of the overflow tube 12 wall may vary towards the extent or tip of the overflow tube 12. For example, the wall thickness may decrease towards the furthest longitudinal extent. This allows the impact of air bubbles to be further reduced because at least part of the wall of the overflow tube 12 tapers inwardly towards the inner wall of the cistern outlet tube 20 (i.e. downleg). The tapering helps to gradually widen the bore so that a smoother transition between the bore of the overflow tube 12 and bore of the cistern outlet tube 20 is achieved. The effect of air breakout can be further reduced or eliminated in the region of the wall tapering as shown in Figure 5.

[27] Although not shown, the overflow tube may have flow conditioners such as blades. Although these blades as such are known, the blades can help to further improve flow performance and efficiency.

[28] Although preferred embodiments) of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made without departing from the scope of the invention as defined in the claims.

Claims (10)

1. A syphon for a cistern, the syphon comprising: an outlet tube for sealed engagement with a cistern outlet; and an overflow tube having an end face at an open end arranged for telescopic insertion into the outlet tube; wherein an outer surface of the overflow tube meets the end face at a longitudinal extent; wherein a distal portion of the longitudinal extent that is configured to be inserted the furthest into the outlet tube defines a distal radial plane, such that the longitudinal extent deviates away from the distal radial plane to define a cutaway when viewed from the side.

2. The syphon according to claim 1, wherein a proximal portion of the longitudinal extent that defines the portion of the longitudinal extent that deviates the furthest from the distal radial plane is arranged to be vertically higher than the distal portion when the overflow tube is inserted into the outlet tube to thereby encourage air towards the proximal portion during syphoning action.

3. The syphon according to claim 2, wherein the longitudinal distance between the proximal and distal portions is greater than the thickness of the overflow tube.

4. The syphon according to any preceding claim, wherein the longitudinal extent is linear.

5. The syphon according to any preceding claim, wherein the longitudinal extent is inclined with respect to the radial and longitudinal planes.

6. The syphon according to claim 5, wherein the longitudinal extent is aligned along a single linear inclined plane, having an inclination angle with respect to the distal radial plane.

7. The syphon according to claim 6, wherein the inclination angle is at least 10 degrees.

8. The syphon according to claim 6, wherein the inclination angle is between 10 and 60 degrees.

9. An overflow tube for a syphon as claimed in any preceding claim.

10. A syphon for a cistern comprising an overflow tube as hereinbefore defined in any one of the Figures.