AU667227B2

AU667227B2 - Drain outlet

Info

Publication number: AU667227B2
Application number: AU44387/93A
Authority: AU
Inventors: John Anthony Smith
Original assignee: FULLFLOW SYSTEMS Ltd
Current assignee: FULLFLOW Ltd
Priority date: 1992-08-07
Filing date: 1993-08-03
Publication date: 1996-03-14
Anticipated expiration: 2013-08-03
Also published as: GB9216827D0; AU4438793A

Description

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AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): FULLFLOW SYSTEMS LIMITED Invention Title: DRAIN OUTLET The following statement is a full description of this invention, including the best method of performing it known to me/us: t1

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C C I t C i 1- 'Ilr~~.lli-- j4I~~1- I___XII-LI DRAIN OUTLET This invention relates to a drain outlet suitable for use with drainage systems known as syphonic or full flowing systems. Syphonic systems find application in the context of roof drainage, though other applications are possible.

Syphonic drainage systems are used on buildings requiring water removal from their roofs during precipitation typically within gutters or from roof surfaces directly. Generally, rain water runs off the roofs and down a number of outlets provided on the roof.

The outlets channel the water into the drainage system comprising one or more horizontal or near-horizontal pipes and a downpipe. Typically a plurality of outlets may feed a common horizon~tl pipe which extends within the building. A number of such horizontal pipes may feed a common downpipe. To enable maintenance of a suction effect throughout the system due to the falling mass of water in the downpipes drawing the water along the horizontal pipes and through the cutlets, the diameters of these various pipes and the bends in the pipework, are 2 carefully chosen. For example, the diameter of the horizontal pipe which is fed by a number of outlets, may change by a calculated amount at the position at which ,he tail-pipe from a further outlet connects to the horizontal pipe.

In designing syphonic systems, an aim is to reduce the amount of air eqtering the pipework with the water, thereby increasing the amount of water the pipework can take. One important way in which the air ingress may be reduced, is by preventing the formation of a vortex at the drain outlet into the pipework.

"Ci -2- In an ideal syphonic drainage system, the outlet is designed such that the water leaving thba drain outlet and entering the downstream pipework contains no air. In this ideal system, the water, as it flows within the pipework, exerts a negative pressure upstream of it, which draws further water along the pipework. Although the term "syphonic" is used in the art, and so is used in this specification, it may be more accurate to describe such systems as full-flowing drainage systems. In practice the ideal may never be achieved, but it is believed that the suction effect is found so long as the water/air mix exceeds about 60/40. In contrast, in conventional drainage systems which rely purely on gravity, the typical wnrer/air mix would be between 20/80 and 30/70.

The present invention relates to a novel type of drain outlet suitable for use with the so-called syphonic drainage systems, which is of simple form but which tests have shown to be particularly efficient.

In accordance with the present invention there is provided a roof drain outlet comprising: a drainage bowl which has an upper portion of relatively large cross section and which is upwardly open to receive a liquid, the upper portion having a peripheral Supper rim, and a lower outlet portion of relatively small cross section through which the liquid is drained, there being a smoothly curving contour to the lower outlet portion, to encourage smooth acceleration of the liquid out of the bowl in a direction towards a central axis of the bowl; and a baffle member positioned in the bowl between the outlet of the bowl and the peripheral upper rim, for

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1.~ 3 inhibiting flow of air directly into the outlet portion of the bowl in a direction axially of the bowl.

Preferably, the roof drain outlet comprises a side wall extending downwardly from the upper rim, the side wall tapering in a downward direction, and at a lower end of the side wall a corner region of gentle curvature leading to a horizontal wall portion, the horizontal wall portion leading to a second corner region of gentle curvature, leading to the outlet portion.

Preferably, the outlet portion tapers in a downward direction.

Preferably, the roof drain outlet comprises means located within the bowl for substantially preventing the vortexing of liquid within the bowl, said means comprising one or more outwardly extending divider limbs, dividing at least a lower region of the upper portion of the bowl, and/or the outlet portion into a plurality of distinct flow passages.

This may have an advantage that the liquid cannot c circulate around the bowl in a circumferential direction 0° 25 to form a vortex, and may reduce turbulence and ingress of 0o air which is associated with the vortex.

0 0 0 o.o Promoting a non-turbulent flow early on in a syphonic drain system, ie. in the drai,.age bowl, increases the °ooe syphonic effect in the drainage system.

ot Preferably said limbs are so arranged as to substantially prevent the vortexing of liquid both in at least a lower region of the upper portion and in the outlet portion.

0000 0000 _j 4 Preferably, said divider limbs extend radially outwards, from a central axis of the drainage bowl.

Preferably, said limbs comprise divider walls arranged substantially in a vertical plane.

Preferably, the lower edges of said limbs conform to the inner surface of the bowl or at least to the lower region of the inner surface.

Preferably, said limbs extend from a lowermost position within the outlet portion, substantially corresponding to a lowermost position of the outlet portion.

Preferably, the limbs diverge in an upward and outward direction and extend to an uppermost position within the upper portion of the bowl, corresponding to an intermediate height within the upper portion of the bowl.

The limbs may extend upwardly and outwardly to the periphery of the upper portion of the bowl.

Preferably, said divider limbs are arranged to substantially prevent vortexing of the liquid at all positions within the bowl, beneath the baffle plate.

Preferably, said limb(s) comprise(s) a support which supports the baffle plate above the outlet portion.

Preferably, the plurality of limbs extend outwardly from a node and arranged substantially in a vertical plane between the inner surface of the bowl and the under surface of the baffle plate.

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5 Preferably, the upper edges of said limbs or sections of the upper edges, conform to the under surface of the baffle plate, thereby forming a cradle for the baffle plate.

Preferably, the baffle plate is located above the outlet portion in spaced relation thereto.

Preferably, the outlet portion of the bowl is narrower than the baffle plate, such that liquid cannot flow from the upper portion of the bowl to the outlet porion by direct axial movement therebetween.

Preferably, the upper portion of the bowl is wider than the baffle plate, so that a space is defined between the periphery of the baffle plate and the upper portion of the bowl for the passage of liquid.

Preferably, the arrangement is such that the liquid must pass through the space between the periphery of the baffle plate and the upper portion of the bowl and then follow an inwardly directed flow pathway leading into the outlet portion, where it once again flows axially.

4 1 25 Preferably, the cross-sectional area of the flow pathway in a direction transverse to the direction of liquid flow is at all positions greater than the crosssectional area of the outlet portion.

Preferably, the baffle plate is formed with a central cusp facing the outlet, a region between the cusp and the periphery of the baffle plate being concave.

Preferably, an inner surface of the bowl which opposes the concave region of the Daffle plate is convex.

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lr 6 The positioning of the baffle plate may reduce the flow of air into the outlet portion, whilst allowing optimum rate of liquid flow into the outlet portion. The lower portion of the bowl, and the baffle are deep enough to reduce air intake into the outlet portion when liquid flowrates are low and liquid levels in the gutter are low.

In a syphonic drainage system, this encourages the pipes to fill with water containing a low proportion of air and encourages the syphonic action to initiate at lower flowrates than would otherwise occur.

Preferably, the upper portion of the bowl is circular in horizontal cross-section and tapers inwards in a downward direction, the outlet portion is circular in horizontal cross-section and tapers inwards to its lower end, and between the outlet portion and the upper portion, there is provided a substantially horizontal wall portion and joining thi horizontal wall portion to the upper portion and the outlet portion are regions of gentle curvature, arranged so as not to disturb the flow of liquid.

Preferably, the bowl is of metal and formed by a spinning process.

4 C 44% The bowl may be formed by a pressing process.

Preferably the drain outlet further comprises a cover grill, the grill being engageable with the bowl, and the grill having a lower downwardly inwardly tapering depending skirt which engages within a flared portion of the bowl.

't t r i One or other or both of the skirt and the flared portion of the bowl may be roughened to improve the grip therebetween.

The grill, the baffle plate, and the support may form a unit removably engageable with the bowl.

The above combination of features may advantageously provide smooth acceleration of water in the bowl, reducing turbulence in the flow of water, and reducing vortexing of water and reducing the amount of air entrained with the water.

When incorporated into a syphonic drainage system, it has been experimentally observed that a drain outlet according to the above aspects enables a syphonic action in the drainage system to occur with lower rates of incoming liquid flow than would be present if other prior art designs of drain outlet were used in the same syphonic drainage system. Where a syphonic drainage system is designed such that syphonic action appears at a specified SO. water flowrate (the "Design Flowrate"), using prior art drain outlets, it has been found experimentally, that use of a drain outlet according to the present invention, when substituted for the prior art drain outlets in the same drainage system, gives rise to syphonic action at lower 4444 flowrates than the design flowrate, and when relatively low incoming levels of water are present.

30 The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Fig. 1 shows a drain outlet in side elevation; i |i i I I I 8 Fig. 2 shows the drain outlet of Fig. 1 in plan view; Fig. 3 shows, in an exploded side elevation, a cover grille, baffle plate and support used in the drain outlet of Figs. 1 and 2; Fig. 4 shows the baffle plate in vertical crosssection; Fig. 5 shows the drain outlet of Fig. 1 in a partial cross-section along the line A-A shown in Fig. 2; and Fig. 6 shows the drain outlet in the plan view of Fig. 2, but with the cover grille removed.

The drain outlet shown in the drawings has a drainage bowl 2, an upper cover grille 4 and, located between the bowl 2 and the cover grille 4, a flow control means comprising a baffle plate 6 and a support 8.

The bowl 2 comprises an upper portion 10 of relatively large cross-section and a lower, central, outlet portion 12 of relatively small cross-section. The upper portion 10 has an upper annular horizontal rim 14.

Extending downwardly from the inner periphery of the rim 14 is a side wall 16 which is circular in cross-section and which tapers slightly in a downward direction. At an intermediate position of the side wall, there is an inward step 18. At the lower end of the side wall 16 is a corner region 20 of gentle curvature, leading to a horizontal wall portion 22. This leads in turn, via a corner region 24 of still gentler curvature, to the outlet portion 12.

The outlet portion 12 tapers slightly in a downward direction.

-9- The support 8 comprises three vane-like limbs 26, arranged at 1200 to each other, each being of a rigid thinwalled material, each in a vertical plane. The lower portions 28 of the limbs 26 are joined to each other at a node 29 and the upper portions 30 of the limbs diverge from each other. As shown in Fig. 5 the lower portions 28 locate snugly within the outlet portion 12 of the bowl, the lower edges of the limbs conforming to the inner surface of the bowl. The vane-like limbs extend radially outwardly from a central axis of the bowl, and divide the lower region of the bowl and the outlet portion into three distinct flow passages.

The upper edges of the divergent portions 30 of the limbs are shaped to serve as a cradle to receive the baffle plate 6. The baffle plate 6 is a disc-like member formed with a cusp, with the apex 32 of the cusp facing downwards. Thus, the baffle plate 6 has, between its central cusp 32 and a small convex peripheral region 34, a generally concave region 36. The baffle plate is located in the bowl at a position lower than the upper horizontal rim 14 of the bowl.

As will be seen in Fig. 5, when the baffle plate 6 is engaged upon the support 8, there is defined, between the baffle plate and the lower region of the bowl, three substantially independent flow passages. The limbs 26 act as a physical barrier preventing water from vortexing in the entire region between the top of the baffle plate 6 and the bottom of the outlet portion 12.

As the baffle plate is set within the bowl at a position lower than the upper rim 14 of the bowl, the o influx of air into the outlet portion from vertically above the outlet portion is restricted, as the baffle I 10 plate restricts the flow of air into the outlet. The position of the baffle plate in the bowl is selected so as to reduce air flow into the outlet, whilst allowing the optimum rate of flow of water through the flow passages.

This helps to prevent local vortexes within each of the independent flow passages.

The outlet portion is of considerably narrower crosssection than the transverse cross-section of the flow pathway defined by the three passages, mentioned above.

The cover grille 4 has an array of vertical and circumferential ribs between which water may flow. It has a downwardly depending skirt 38, which has a slight taper in the downward direction. The skirt 38 is roughened for frictional purposes. The skirt is for engagement with the flared portion, above the step 18, of the upper region of the bowl member, with the periphery of the skirt resting on the step 18.

In this embodiment, the cover grille, baffle plate and support are secured together by means of a bolt but other methods of securing are equally possible. The head of the bolt presses a washer against the cover grille 38 and the shank of the bolt passes through an aperture 42 at the cusp 32 of the baffle plate, and is screwed into a tapered hole within the support 8. In other embodiments, these three parts need not be secured together.

As shown in Fig. 2, the cover grille has a top wall with a central wall portion 44 not formed with ribs and apertures (since these would not serve any function, in that location). Instead, the central wall portion 44 is fornmd with finger holes 46 to aid removal.

on behalf of the Applicant

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4 xl In this embodiment the bowl is of a plastics material, and vacuum moulded, or of a metallic material, and formed by spinning or pressing.. The grille is of a plastics material and injection moulded. The baffle plate is of a plastics material, and injection moulded. The support may be of a plastics material, and injection moulded or formed by welding together the three limbs.

In use, the drain outlet is located on a roof, with the rim 14 located externally, against a substantially horizontal panel within a gutter or directly to a roof and with the bowl extending downwardly. To prevent condensation forming on the under surface of the bowl, a foam jacket (not shown) conforming to the shape of the bowl, may be located on the under surface of the bowl.

The outlet portion 28 is connected to a tail-pipe (not shown). In accordance with standard practice the tailpipe may be connected to a horizontal or near horizontal pipe. A number of tail-pipes fed by respective outlets may be fed to the horizontal or near horizontal pipe, whose diameter may change as further tailpipes are fed to J' it. The pipe diameters are carefully calculated so that water flow by a suction mechanism is likely to be achieved, even on precipitation below the design flowrate.

When precipitation is moderate, flow of water into the outlet may still be rapid because of the very large roof area which feeds it. Water will flow along the gutter or roof surfaco, then over the rim 14 and into the bowl. It will pass along the flow passages defined between the baffle plate 6 and the inner facing surface of the bowl. Initially it will flow substantially vertically, and it will then be directed inwardly, to follow a transverse flowpath before entering the outlet rtr on behalf of the applicant L- "Y IQ rC I I

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IIII-_l IMi*D~~Li~il i* ii.~ ~i~ 12 portion, where it once again flows substantially vertically.

In practice the outlet portion will fill with water under quite low rates of precipitation. It will be apparent that the nature of the limbs is such as to prevent the vortexing of water both in the region between the baffle plate and the bowl and within the outlet portion. Because of the lack of vortexing, air ingress is minimised and it is believed that the water flowing within the outlet portion draws further water into the outlet portion by a suction effect.

When there is heavy precipitation, water may rise within the gutter or on the roof surface, to be above the rim 14. Once this happens, it appears that the drain outlet works still more efficiently. Air ingress appears to be minimipad further. This is thought to be because the water no longer falls into the bowl over the inner edge of the rim 14. Thus, not only does the increased head of water increase flowrate, but the water appears to a o contain less air, so enabling faster water removal. The suction effect then promotes the rapid drawing of water from the gutter or roof surface, into the outlet.

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Claims

2. A roof drain outlet acc.ording to claim 1, comprising a side wall extending downwardly from the upper rim, the t side wall tapering in a downward direction, and at a lower end of the side wall a corner region of gentle curvature i leading to a horizontal wall portion, the horizontal wall portion leading to a second corner region of gentle curvature, leading to the outlet portion.
3. A roof drain outlet according to claim 1 or 2, in which the outlet portion tapers in a downward direction.
4. A roof drain outlet according to any one of the preceding claims, comprising means located within the bowl for substar ally preventing the vortexing of liquid within the wl, said means comprising one or more outwardly extending divider limbs, dividing at least a 14 lower region of the upper portion of the bowl, and/or the outlet portion into a plurality of distinct flow passages. A drain outlet according to claim 4, wherein said limbs are so arranged as to substantially prevent the vortexing of liquid both in e ast a lower region of the upper portion and in the out.Let portion.
6. A drain outlet according to claim 4 or 5 wherein said divider lim!s extend radially outwards, from a central axis of the drainage bowl.
7. A drain outlet according to any one of cla 'ms 4 to 6, wherein said limbs comprise divider walls arranged substantially in a vertical plane.
8. A drain outlet according to any one of claims 4 to 7, wherein the lower edges of said limbs conform to the inner surface of the bowl or at least to the lower region of the inner surface.
9. A drain outlet according to any one of claims 4 to 8, wherein said limbs extend from a lowermost position within the outlet portion, substantially corresponding to a lowermost position of the outlet portion. A drain outlet according to any one of claims 4 to 9, in which the limbs diverge in an upward and outward direction and extend to an uppermost position within the upper portion of the bowl, corresponding to an intermediate height within the upper portion of the bowl.
11. A drain outlet according to any one of claims 4 to in which the limbs extend upwardly and outwardly to the periphery of the upper portion of the bowl.
12. A drain outlet according to any one of claims 4 to 11, wherein said divider limbs are arranged to substantially prevent vortexing of the liquid at all positions within the bowl, beneath the baffle plate.
13. A drain outlet according to any one of claims 4 to 12, wherein said limb(s) comprise(s) a support which supports the baffle plate above the outlet portion.
14. A drain outlet according to claim 13 wherein the support has a plurality of limbs extending outwardly from a node and arranged substantially in a vertical plane between the inner surface of the bowl and the under surface of the baffle plate. A drain outlet according to claim 14, in which the upper edges of said limbs or sections of the upper edges, conform to the under surface of the baffle plate, thereby forming a cradle for the baffle plate.
16. A drain outlet according to any one of the preceding claims wherein the baffle plate is located above the outlet portion in spaced relation thereto. S 25 17. A drain outlet according to any one of the preceding claims, in which the outlet portion of the bowl is narrower than the baffle plate, such that liquid cannot flow from the upper portion of the bowl to the outlet portion by direct axial movement therebetween. S
18. A drain outlet according to any one of the preceding claims, wherein the upper portion of the bowl is wider than the baffle plate, so that a space is defined between the periphery of the baffle plate and the upper portion of iw o the bowl for the passage of liquid. a iaLi-L miRuiner posirTlonet in tle bowl between the outlet of the bowl and the peripheral upper rim, for I ii 16
19. A drain outlet according to claim 18, in which the arrangement is such that the liquid must pass through the space between the periphery of the baffle plate and the upper portion of the bowl and then follow an inwardly directed flow pathway leading into the outlet portion, where it once again flows axially. A drain outlet according to claim 18 or 19, in which the cross-sectional area of the flow pathway in a direction transverse to the direction of liquid flow is at all positions greater than the cross-sectional area of the outlet portion.
21. A drain outlet according to any one of the preceding claims, wherein the baffle plate is formed with a central cusp facing the outlet, a region between the cusp and the periphery of the baffle plate being concave.
22. A drain outlet according to claim 21, wherein an inner surface of the bowl which opposes the concave region of the baffle plate is convex. 'I
23. A drain outlet according to any one of the preceding claims, in which the upper portion of the bowl is circular in horizontal cross-section and tapers inwards in a downward direction, the outlet portion is circular in horizontal cross-section and tapers inwards to its lower end, and between the outlet portion and the upper portion, there is provided a substantially horizontal wall portion and joining this horizontal wall portion to the upper portion and the outlet portion are regions of gentle curvature, arranged so as not to disturb the flow of liquid. L i i -17
24. A drain outlet according to any one of the preceding claims, in which the bowl is of metal and formed by a spinning process.
25. A drain outlet according to any of claims 1 to 23, in which the bowl is of metal and formed by a pressing process.
26. A drain outlet according to any one of the preceding claims, further comprising a cover grill, the grill being engageable with the bowl, and the grill having a lower downwardly inwardly tapering depending skirt which engages within a flared portion of the bowl.
27. A drain outlet according to claim 26, as appendant on claim 13, in which the grill, the baffle plate, and the support forms a unit removably engageable with the bowl.
28. A drain outlet substantially as herein described with reference to the accompanying drawings. Si 7 i ouLLtau ou tne Darrie plate. tCI ABSTRACT DRAIN OUTLET The present invention relates to drain outlets, especially for use in full-flowing (syphonic) drainage systems. A drain outlet comprises a bowl 2 for the collection of water, the bowl having a grill 4 and a set of vanes 28, for preventing vortexing of the water in the bowl. A baffle 6 provided at above the outlet of the bowl prevents the ingress of air in with the water flow. 15 The drain outlet virtually eliminates air from water entering a full-flowing drainage system at the design flowrate and reduces the amount of air entering at flows below the design flowrate. o2o (Figure I.