GB2420595A - A roof drainage siphon device. - Google Patents

Abstract

A siphon system which utilises a secondary flow to activate the siphon to drain a pool of water 9 comprises three distinct lengths of tubing, the feeding section 2, the drawing section 3 and the siphon section 1, arranged within a vertical plane and connected at a common hub 5. The head 7 of the siphon tube is placed near the lowest point of the pool and the tail of the siphon is connected to the hub. The drawing section extends downwards from the hub and has its lower end open to the air. The feeding section extends upwards from the hub with its upper end connected to a funnel 6. The funnel collects the secondary flow from a suitable source 10 so that it flows down the feeding section, through the hub and into the drawing section, where it accelerates towards the lower end of the drawing section sucking water into the siphon section thus priming the siphon. Once primed the siphon operates independently of the secondary flow. The syphon can be used to drain rainwater from a flat roof.

Description

* 2420595 Title Roof Drainage Syphon Device

Prior Art

Existing technology identified as relating to automatically activated syphons, particularly in the area relating to flat roof pond drainage, employs a combination of valves, water traps, residual pools at the syphon head, floats, moving parts, auxiliary pumps, pressure lines and transducers with control units to initiate the syphon action.

Methods that require a residual pool to be maintained at the head of the syphon such as US5343888 (1994) and FR2690955 (1993) cannot, by definition, empty the pool at the syphon head. This can be a major disadvantage where the retained water can cause excessive damage as in the case of pondmg on flat roofs.

A method that does not require a residual pool at the syphon head is described by patent GB2393222 (2004) which utilises a system employing an auxiliary electrical pump together with a transducer and control unit to activate the priming circuit. Potentially there is significant cost associated with the manufacture, installation and maintenance of such an arrangement and additionally a possible nuisance of noise associated with the intermittent pump operation. Other patents that employ an auxiliary power supply to initiate a syphon action include Patent US3692040 (1972) and Patent US5063959 (1991), where the standard water service is utilised to prime the syphon action.

Patent GB389645 (1933) sets forth an invention for draining a pool of water by a syphon action, which is self priming. The method consists of a main syphon tube and a parallel auxiliary syphon tube, each shaped as an inverted J' and connected to each other by a small bore hole positioned towards, but not at, their downstream ends. The downstream end of the main tube contains a U' bend to create a water trap that seals the tube against air intake. Both the main syphon tube and the auxiliary syphon tube have their upstream ends submerged in the pool of liquid to be drained. The auxiliary tube draws liquid from the pooi by means of capillary action. This flow accelerates down the vertical section of the auxiliary tube, which results in air being drawn from the main tube thus causing a column of liquid to be drawn into the syphon. This action will also incidentally draw liquid from the water trap at the down stream end of the main tube. After sufficient flow has passed through the auxiliary tube the main tube should be primed so that the main syphon will then operate.

Potential drawbacks identified with this system described by patent GB389645 are as follows: The auxiliary flow is slow by virtue of the limits of capillary action. Therefore the rate at which the main syphon can be primed is seriously restricted. A problem that is compounded as the volume of the main syphon tube increases; * To encourage the capillary action, the auxiliary tube will be of a small cross-section and thus liable to blockage. Such a threat maybe countered by the use of extremely fine filters, but these would then be liable to clog; * The water trap at the downstream end of the main tube can potentially dry out, and is also a potential site at which debris can accumulate thus leading to blockages; * The system requires a residual pond at the head of the syphon to be maintained for a protracted period of time to allow sufficient flow to pass through the auxiliary tube and so prime the main syphon. This can be a major disadvantage where the pool of water causes excessive damage to occur, such as could be the case for a flat roof; * As stated in the patent description (toward the end of the preferred embodiment) the auxiliary syphon needs to be wet to facilitate the capillary action. It is therefore possible that the auxiliary tube can dry out if the system is not used for a protracted period of time preventing the automatic activation of the syphon.

Patent US4 171709 (1979) sets forth an invention for draining a flat roof by which a chamber is positioned part way down a drain pipe with the intention of collecting and storing a proportion of the down pipe flow in readiness to prime a syphon when the main runoff ceases.

Potential drawbacks identified with this system described by patent US4 171709 are as follows: * The unit will only begin to accumulate water when the nmoff flow rate exceeds a given threshold; * The unit will only remain full provided the runoff flow rate exceeds a given threshold. Therefore, even if the unit did become charged with water, if the rainfall reduces gradually, the unit may not be charged at the crucial moment when the rainfall ceases; * For all but the heaviest of rainfalls, water tends to descend the down pipe as a film of water attached to the internal walls. The unit will therefore be extremely inefficient at collecting water so that the minimum threshold flow rate, required to charge the unit, is likely to be a deluge; * Positioning the unit in the down pipe is liable to result in a blockage caused by sediment being washed off the roof.

Patent US4406300 (1983) sets forth an invention for draining a flat roof, which utilises a secondary source to prime the main syphon. The secondary source is gravity fed having been collected from precipitation by a dedicated reservoir. This particular patent describes a variety of embodiments, in which it is averred that a process of aspiration draws water into the main syphon tube, thus initiating a syphon action.

In the first embodiment the secondary source is collected in a reservoir before being rapidly dumped into the downstream end of the syphon tube. A valve then closes to seal the syphon tube from the reservoir. The action of the dumped water as it flows through the syphon is to draw water from the pond by way of aspiration. Crucially, the operation by which the valve seals off the reservoir prevents further water or air from being drawn in at this point, thus forcing water to be drawn from the pond.

In the second embodiment the secondary source is again collected in a reservoir before being rapidly dumped into a tray. The tray is connected to the syphon at a selected position below the ponding level, via a length of tube, which is dropped in the vertical plane. It is averred that the water flowing from the tray into the syphon tube via the connecting tube will invoke a process of aspiration to draw water into the syphon head from the pond.

Potential drawbacks identified with this system described by patent US4406300 are as follows: * The secondary flow is dispensed in batch form from a reservoir using a variety of valves, reservoirs, and carefully balanced tipping buckets that all add to the complexity of the installation; * The use of a dedicated reservoir seriously restricts the flow available to prime the syphon; * Crucial to the operation of the second embodiment; The relative attributes pertaining to the secondary flow upstream and downstream of the syphon discharge are not controlled in a manner conducive to efficient aspiration of the syphon tube. Without control of such parameters the operation of the syphon becomes problematic. The type and role of these crucial attributes in respect of the current invention, are discussed later in the section headed Essential and Important Features.

Patents that disclose a syphon head for the purpose of drawing water from a shallow pond include US5063959 (1991) and GB2393222 (2004) which consists of a disc resting on the ponding surface.

The underside of the disc contains radial grooves to channel water to the syphon tube inlet. The footprint of the pad can be of appreciable size to reduce liability of blocking. Potential problems associated with such a configuration are as follows: * The pad will inhibit evaporation of any residual water that is trapped under the head once the syphon action has ceased; * The efficiency of the head would be compromised by discontinuities, such as ridges, that may be present at the lowest point of the ponding surface.

The current invention presents a series of modifications to the existing system described in the 2m1 embodiment of Patent US4406300 (1983), which improve the efficiency and reliability at which the secondary flow primes the syphon, and also increases the potential catchment area when sourcing the secondary flow from rainfall. In addition a syphon head suitable for draining a pond on a flat surface is disclosed.

The resulting system consists of the following: * A simple configuration of tubing which does not employ any moving parts, valves, pumps, auxiliary power supplies or sensors and the like, nor does it require any residual pools, or rely on capillary action to initiate a flow. The system can be configured to achieve both an efficient and rapid priming rate with respect to the volume and rate of the secondary flow; which is a particularly important attribute when the syphon head is some distance from the point at which the tail end of the main syphon tube can be dropped; * A funnel device in place of the reservoir that is suitable for collecting water from a gutter down pipe, which potentially drains water from a large area. The funnel device makes minimal impact on the aperture of the down pipe and is resilient to blockage whilst protecting against ingress of oversized debris into the secondary circuit; * A syphon head that is suitable for draining a pond to a negligible level whilst allowing timely evaporation of residual water in the region of the head, once the syphon action has ceased. The device can cope with discontinuities within the ponding region, whilst being resilient to blockage and protecting against ingress of oversized debris into the syphon system.

As a result the current invention addresses those potential problems identified against the current technology both in terms of the function and of the costs associated with manufacture, installation and maintenance.

Description

A syphon system that can be automatically activated by the action of a secondary flow.

Background

A suitable application for the invention is for draining water pools that accumulate on flat roofs. The invention utilises a secondary flow to activate a syphon that can then drain a pool of water. The secondary flow can be gravity fed from a run-off, preferably from a sizable region of the roof outside the area of ponding, so that the syphon is automatically activated whenever there is a rainfall. The point at which the secondary flow is fed into the system maybe higher or lower than the syphon head.

In its fundamental form the system consists of three distinct lengths of tubing: the feeding section, the drawing section and the syphon section, arranged within the vertical plane and connected at a common point termed the hub. The head of the syphon tube is placed at or towards the lowest position at which the water pool accumulates on the roof. The tail end of the syphon is connected to the hub, which is in turn connected to both the lower end of the feeding length and the upper end of the drawing length.

The drawing length extends downward from the hub and has its lower end open to air. The feeding length extends upwards from the hub with its upper end connected to a funnel.

The secondary flow is fed into the funnel from a suitable source so that it flows down the feeding length, through the hub and into the drawing section, where it then accelerates towards the exit at the lower end. Provided the attributes of the three main sections are suitably balanced, the consequence of the water accelerating down through the drawing tube will be to suck water into the syphon section thus priming the syphon. Once primed the syphon can operate independently of the secondary flow.

Essential and Important Features Essential to the system's function is the balance of the parameters, which contribute to the hydraulic pressure, flow resistance and terminal flow rate, in each of the three main sections of tubing. The following considerations define the particular attributes required of each section.

If, after being primed, the syphon is to continue to operate when the secondary flow ceases, the vertical projection of the syphon tube, which runs between the pond and hub, must be of sufficient length to generate a hydraulic head that can drain the pond. If, however, it is desirable for the syphon tube to be controlled so that it only operates when the secondary flow is active, then the vertical projection of the syphon tube should be reduced to a value that is unable to sustain the syphon by itself. In the latter case the syphon action will be sustained by the additional pressure provided by the action of the secondary flow accelerating down the drawing tube.

The secondary flow rate in the feeding length must be less than the terminal flow rate in the drawing tube, whilst also being sufficient to seal the feeding tube against air intake and produce an acceptable priming rate in the syphon tube. This is achieved by limiting the pressure drop across the feeding length and/or increasing the resistance to flow in the feeding length. It is crucial that the flow resistance offered by the feeding length is comparable or preferably greater than the flow resistance offered by the syphon length. This ensures that water entering the volume vacated by the secondary flow as it accelerates down the drawing tube, enters along the syphon length rather than the feeding length. In so doing the syphon length is primed.

The terminal flow rate in the drawing tube should be sufficient as to draw water into the syphon tube at an acceptable rate whilst maintaining an adequate air seal within the drawing tube. The terminal flow rate is increased by reducing the resistance to flow and/or increasing the vertical drop across the tube length. Optimal acceleration characteristics of the flow within the drawing tube might be achieved by use of a diverging cross section along the axis of the flow.

To take advantage of a secondary source that might reduce to a trickle, the water in the feeding tube can be encouraged to flow as a series of globules, punctuated with air pockets, by selecting a suitably small enough bore. Such a flow will seal the primary length, and consequently the drawing length, for a fraction of the water volume required for a continuous flow, but still prime the syphon. To take maximum advantage of such a flow the primary length should be long enough to contain a significant number of such globules to maintain a continuous seal of the primary section.

Whilst it is expected that the source for the secondary flow is likely to be a continuous stream or trickle, particularly if taken from a runoff, the circuit configuration can equally cope with a supply that is a intermittent, periodic, constant or manual in nature.

Introduction to Drawin2s

In order that the invention be more readily understood the following references describe the accompanying drawings: Fig. 1 is a schematic of the syphon system, illustrating the connectivity of the three sections of tubing in respect of a potential application to drain ponds on a flat roof.

Fig. 2 is a drawing of a syphon head for the purpose of draining ponds to a negligible level and then allowing evaporation of the residual water in the region of the syphon head.

Fig. 3 is a drawing of a funnel used to gather water from a gutter down pipe to supply the secondary circuit. The syphon and secondary circuit being mounted externally with respect to the gutter conduit.

Fig. 4 is a drawing of a funnel used to gather water from a gutter down pipe to supply the secondary circuit. The syphon and secondary circuit being mounted internally with respect to the gutter conduit.

Fig. 5 is a schematic of the syphon system depicted in fig. 1, but with multiple syphon lengths connected to the central hub via parallel and series connections.

Fig. 6 is a schematic of the syphon system depicted in fig. 1, but where the syphon tube is replaced with an alternative section configured so as not to produce a syphon action.

Fig. 7 is a schematic of two syphon systems depicted in fig. 1, connected in series so that the discharge of the first unit provides a secondary flow for the second unit.

With reference to fig. I location 9 illustrates a dished region of a flat roof in which water accumulates.

The syphon head 7 is placed at or towards the lowest position of the dished region 9.

The syphon tube 1 is then run to the edge of the roof 8, where the tail of the syphon tube 4 can be dropped to a level below that of the syphon head. The syphon tube 4 is connected via the hub 5 to the drawing section 3.

The drawing section 3 is a straight length of tube, which extends vertically downwards so as to maximise the gravitational potential across its length.

The feeding section 2 is connected to the hub 5 at its lower end, and to the funnel 6 at its upper end.

The feeding section 2 is configured as a compact helix and has a cross section smaller than that of the other two lengths of tube; namely the syphon length 1 & 4, and the drawing length 3. This arrangement provides the necessary attributes for the feeding section 2, specifically a small pressure drop across the tube length coupled with a relatively high resistance to flow.

The funnel 6 is used to collect the secondary flow from a suitable source 10, such as runoff channeled from a sizable area of roof outside the ponding region into a gutter down pipe.

During rainfall, water collects in the pool at 9 and also flows into the funnel at 6. The water entering the funnel 6, termed the secondary flow, passes down through the feeding length 2, under the action of gravity, into the drawing section 3, via the hub 5. The flow then accelerates, still under the action of gravity, along the drawing tube 3, to exit at the lower end. The drawing tube 3 is sized to produce sufficient acceleration without breaking the air seal created by the secondary flow. The accelerating flow expands the volume of air contained in the syphon tube 1 & 4, resulting in a reduction in air pressure contained therein. The reduced pressure draws fluid from the feeding section 2, and the pond 9. By incorporating sufficient flow resistance in the feeding section 2, water is drawn from the pond 9 into the syphon tube 1 & 4, thus priming the syphon. The vertical drop of the syphon tail section 4 is sufficient to sustain the syphon action, so that once primed the syphon can operate independently of the secondary flow. Hence, after being activated, the syphon will continue to operate until the pond has drained to a level below the syphon inlet.

Fig. 2 illustrates a syphon head, which is suited for the purpose of draining a pool of water to a negligible level. The head consists of a block housing 11 & 12, locating a tube 1 relative to the ponding surface 9. The tube and housing are wrapped in filter material 13 to protect against the ingress of foreign matter at the syphon head.

The block housing 11 & 12 is made from concrete so that it locates the syphon head in position by virtue of its own mass. The main body of the block housing 11, is supported above the pondmg surface 9 by three or more legs 12 with the body 11 and legs 12 providing a rigid framework to support the filter material 13. The legs 12 are spread over a suitably large area appropriate to the environment in which it is to operate, considering that a large filter area results in negligible flow resistance and has a high degree of tolerance to clogging of the filter 13. The spacings 16 between the legs 12 and the raised body 11 are configured to achieve good ventilation of the area under the head. The ventilation encourages timely evaporation of any residual water that remains in the region of the syphon head once the syphon action has ceased.

The longitudinal axis of the syphon tube I is located within a borehole in the main body 11, which is nominally aligned normal to the pond surface 9. The bore hole is of a size that results in a transition fit with the tube I so that the tube may be axially adjusted in order to abut the tip 15 against the roof surface 8. The tip 15 has a thin outer ring, which slots onto the end of the tube 1. An array of three or more radial arms project inward and downward from the outer ring of the tip 15, to regulate a small gap between the roof surface 8, and the tube 1, that will not choke the flow into the syphon. The inlet of the tube 1 being tapered 14 and the elements of the tip 15, being thin, so as to ameliorate flow resistance at the tube intake, so allowing a smaller gap than would otherwise be the case.

Fig. 3 illustrates a funnel arrangement for tapping a secondary flow from a gutter down pipe.

The funnel is integrated into a short length of pipe 18 that can easily be inserted into a convenient section of down pipe 21. The point at which the secondary flow is fed into the system maybe higher or lower than the syphon head. Flow is collected from the pipe walls by means of an annular trough 22, mounted inside the pipe 18. The feeding tube 2 is tapped into the base of the trough 22, and is configured with a short initial vertical drop, so as to generate sufficient pressure to overcome static friction, followed by a helix, created by wrapping the tube around the outside of the pipe 18. The downstream end of the feeding tube 2 is connected to the exit end of the syphon tube 4 and the entry end of the drawing tube 3 via a Tee connector 5, termed the hub. The drawing tube 3 extends downwards to discharge flow at its lower end.

The length of pipe 18, containing the trough 22, is lined with filter material 19 to prevent oversized debris entering the feeding tube. The filter material includes optional lobes 17 that drape into the trough to act as an inverted wick, helping to guide the flow down into the trough.

Fig. 4 illustrates an alternative configuration whereby all the elements described in figure 3, are contained within the gutter down pipe.

Figures 5 to 7 illustrate further embodiments to which the syphon system may be applied as described below: * Fig. 5 is a schematic of the syphon system depicted in fig. 1, but with multiple syphon lengths connected to the central hub via parallel and series connections; * Fig. 6 is a schematic of the syphon system depicted in fig. 1, but where the syphon tube is replaced with an alternative section configured so as not to produce a syphon action; * Fig. 7 is a schematic of two syphon systems depicted in fig. 1, connected in series such that the discharge of the first unit provides a secondary flow for the second unit.

Claims (1)

1. Claims Claim 1: A syphon system of a kind whereby the discharge end of a

   syphon conduit is connected to a secondary circuit configured with an upstream feeding section, which acts to restrict the flow therein whilst conveying liquid to a downstream drawing section, serving to accelerate the flow therein; the flow rate in the feeding section being less that the terminal flow rate in the drawing section; the flow in the secondary circuit serving to seal the secondary circuit and the discharge end of the syphon conduit against intake of air, so forcing liquid to be drawn in at the syphon head, thus priming the syphon.

   Claim 2: A system according to claim 1, containing one or more syphon conduits each connected to the secondary circuit either directly or via a common conduit.

   Claim 3: A system according to claim 1 or 2, whereby a syphon conduit is replaced with an alternative section configured so as not to produce a syphon action, the flow therein only resulting when a flow exists in the secondary circuit.

   Claim 4: A system according to claim 1, 2 or 3, whereby a syphon head consists of a housing, which locates a tipped conduit aligned with its longitudinal axis normal to the pond surface, the conduit being capable of axial movement relative to the housing and the conduit having a tapered inlet converging along the direction of flow; the tip having radial projections extending beyond the syphon conduit intake to create a slotted aperture regulating the gap between the conduit intake and the ponding surface; the body of the housing being raised off the ponding surface by three or more supporting legs and maintained in position by virtue of its own mass; the housing incorporating openings that allow ventilation of the area under the syphon head, and the syphon head being wrapped in filter material.

   Claim 5: A system according to claim 1, 2, 3 or 4 whereby a funnel system of a kind collects liquid from the walls of a guttering conduit which is then fed, using gravitational potential, into a feeding conduit configured with an initial short length of conduit dropped vertically down, followed by a long length of conduit arranged in a spiral.

   Claim 6: A system according to claim 1, 2, 3, 4 or 5 whereby flow in the secondary circuit is taken from rainfall runoff or an alternative supply which is of an intermittent, periodic, constant or manual source.

   Claim 7: A system according to claim 1, 2, 3, 4, 5 or 6 whereby the drawing conduit section is of a graduated section to facilitate optimum acceleration of the flow therein.

   Claim 8: A system according to claim 1, 2, 3, 4, 5, 6, or 7 whereby a set of two or more syphon systems are configured such that a proportion of the syphon systems have a secondary source supplied from the discharge of one or more of the syphons within the set.

   Claim 9: A system according to claim 1, 2, 3, 4, 5, 6, 7, or 8 whereby the bore of the feeding length is sized to achieve a piecewise continuous flow consisting of globules of liquid punctuated by pockets of gas.

   Claim 10: A system according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9 whereby a set of two or more syphon systems are configured with multiple syphon lengths connected to the central hub via parallel and series connections.

   Claim 11: A system according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 which is used to depond a flat roof.

   Claim 12: A syphon constructed and operating substantially as herein described.