GB2308169A

GB2308169A - Device for coupling a rainwater drainage outlet metal stub to plastics piping

Info

Publication number: GB2308169A
Application number: GB9624884A
Authority: GB
Inventors: John Anthony Smith; John Anthony Slater
Original assignee: FULLFLOW Ltd
Current assignee: FULLFLOW Ltd
Priority date: 1995-12-06
Filing date: 1996-11-29
Publication date: 1997-06-18
Also published as: GB9624884D0

Description

Coupling Device The present invention relates to a coupling device for coupling metal piping to plastics piping.

Water outlets such as syphonic rainwater drainage outlets used for roof drainage are normally made of metal whilst the pipework to which they are connected is normally of plastics material such as high density polyethylene (HDPE). This makes it difficult to provide a secure and watertight connection between the two since plastics materials such as HDPE creep under pressure. Thus, where an outlet pipe of a rainwater outlet is inserted into an HDPE pipe and secured by means of a metal clamping band, although the band may be fully tightened initially, after a short while the "creep" effect of the HDPE will result in a relaxing of the joint, allowing it to leak.

The present invention seeks to provide an improved coupling device Accordingly, the present invention provides a coupling device for coupling a rainwater drainage outlet metal stub to plastics piping, the coupling device comprising: a tubular body having a wall with a first, female wall end portion for telescopically engaging over said metal stub, and a second wall end portion for engaging said plastics piping; a plurality of bearing members inserted in and extending radially through said first, female wall end portion; and clamping means having: a metal clamping band extending around said first wall end portion; and means for tightening said metal clamping band against said wall end portion thereby to grip said bearing members between said metal band and said metal stub securely to engage said coupling device on said metal stub.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view showing partly in section a preferred form of coupling device according to the present invention; Figure 2 is a longitudinal section through a wall of the coupling device of Figure 1 showing its connection to an outlet pipe stub of a rainwater drainage outlet; Figure 3 is an enlarged view of a portion of the section of Figure 2; Figure 4 is a view similar to that of Figure 1 of a second embodiment of coupling device according to the present invention; Figure 5 is a view similar to that of Figure 2 of the device of Figure 4; Figure 6 is a view similar to that of Figure 3 of the device of Figure 4; Figure 7 is a view similar to that of Figure 1 of a third embodiment of coupling device according to the present invention;; Figure 8 is a view similar to that of Figure 2 of the device of Figure 7; and Figure 9 is a view similar to that of Figure 3 of the device of Figure 7.

Referring firstly to Figure 1, this shows a coupling device 10 which has a body 11 of circular cross section, having a generally cylindrical form. The body has a wall 12 formed by upper and lower end portions 14, 16. The upper end portion 14 is of a smaller diameter than the lower end portion 16, resulting in a step or shoulder 18 being formed between the two, thus fowling outer and inner steps or shoulders 20, 22.

The upper, free end 24 of the upper end portion 14 has radial flange means in the form of three radially outwardly extending lugs 26 which serve to retain a metal clamping band or strap 28 around the upper end portion 14 between the lugs 26 and the outer shoulder 20.

Although three lugs 26 are shown, it will be appreciated that this number may be greater or less. The lugs may be positioned at or adjacent to the free end 24.

A number of axially extending slots 30 are also provided in the upper wall end portion 14, extending axially from the free end 24. Normally, six such slots 30 would be provided although this number may be varied as required. An annular groove 32 is formed in the inner surface of the upper wall portion 14 and retains an O ring seal 34. This is positioned closer to the shoulder 20 than to the free end 24 and the slots 30 extend towards but do not meet the groove 32.

The slots 30 enable the coupling device to be used with rainwater outlets having outlet pipe stubs of differing diameters since tightening of the clamping band 28 causes the portions of the upper wall end portion 14 which extend beneath the slots 30 to resile inwardly as the slots 30 narrow.

As is best seen in figure 3, the groove 32 has upper and lower sides which taper towards one another from the base of the groove. This serves to trap and retain the seal 34 in the groove, preventing the seal from becoming detached from the groove during handling of the coupling device. Only one of the side walls need taper inwardly.

In order to connect the coupling device 10 to an outlet stub 35 of a rainwater drainage outlet, the upper wall end portion 14 is axially slipped over the outlet stub and the clamping band 28 is tightened to clamp the wall end portion 14 against the outlet stub.

The body of the coupling device is usually made of plastics material such as HDPE for compatibility with the piping to which the rainwater outlet is to be connected. HDPE has a particularly low co-efficient of friction and has time dependent properties which result in creeping ie. relaxation of stresses set up in the material by tightening of the clamping band 28. In order to resolve this difficulty, a number of bearing members 36 are located in through-holes 38 in the upper wall portion 14. An effective form of bearing member is a knurled point grub screw. The bearing members are preferably equi-angularly spaced and ideally there are at least three although a preferred number is six.

When the clamping band 28 is tightened around the upper wall portion 14 it clamps the bearing members between the band 28 and the rainwater outlet stub 35 such that the bearing members are retained in contact with both the clamping band 28 and the rainwater outlet stub 35. Thus the clamping band 28 grips the rainwater outlet stub with a high co-efficient of friction which is highly effective in ensuring retention of the coupling device 10 on the rainwater outlet stub.

The nominal length of each bearing member is the same as the thickness of the upper wall portion 14 although slight variations in the length of the bearing members can still provide an effective and secure contact. The bearing members are conveniently of metal although any suitable material which is sufficiently hard may be used.

In the embodiment of Figures 4 to 6, the upper wall portion 14 of the body has locating means in the form of an annular rib 40 formed on the inner surface. The rib locates in a corresponding annular groove or recess 42 formed in the rainwater outlet pipe stub. This forms a positive key assisting retention of the coupling device on the pipe stub.

As can be seen from Figure 4, the annular rib 40 is located near the upper end 24 of the body and is intersected by the axial slots 30.

Figures 7 to 9 show a further embodiment of a coupling device 10, similar to that of Figures 1 to 3. However, the lower wall portion 16' is of a shorter axial length and a further step or shoulder 50 is provided in the inner surface of the upper wall portion 14 by an increased diameter portion of the wall end portion 14.

The step or shoulder 18', which is equivalent to the shoulder 18 in Figure 1, has an inner shoulder 52 which is much sharper, typically at 90% to the wall surface, than the relatively shallow angle of the shoulder 22 of the device of Figure 1. The shoulder 52 serves to locate a correspondingly shaped tubular member 54 which is a press fit within the lower wall portion 16 and which serves to trap the 0 ring seal 34 between its axially inner edge 56 and the shoulder 50. The member 54 can be secured in position with a suitable adhesive.

The lugs 26 ofthe device of Figure 1 are also replaced by an annular flange 58 which extends radially outwardly around the upper edge 24 and is intersected by the axial slots 30.

An annular groove 60 is formed in the outer surface of the upper wall portion 14. This is positioned closer to the shoulder 50 than the free end 24 and coincides with the termination of slots 30. The combination of the slots 30 and the annular groove 60 enable the coupling device to be used with rainwater outlets having outlet pipe stubs of differing diameters since tightening of the clamping band 28 causes the portions of the upper wall portion 14 which extend beneath the slots 30 to resile inwardly as the slots narrow. Annular groove 60 adds extra flexibility to the upper wall 14 and counteracts the increased stiffness of upper wall 14 introduced by the annular flange 58.

Claims

1. A coupling device for coupling a rainwater drainage outlet metal stub to plastics piping, the coupling device comprising: a tubular body having a wall with a first, female wall end portion for telescopically engaging over said metal stub, and a second wall end portion for engaging said plastics piping; a plurality of bearing members inserted in and extending radially through said first, female wall end portion; and clamping means having: a metal clamping band extending around said first wall end portion; and means for tightening said metal clamping band against said wall end portion thereby to grip said bearing members between said metal band and said metal stub securely to engage said coupling device on said metal stub.

2. A coupling device as claimed in claim 1 wherein said bearing members are metal.

3. A coupling device as claimed in claim 1 or 2 wherein: at least three bearing members are provided; and said bearing members are equi-angularly spaced around said wall end portion.

4. A coupling device as claimed in any of the preceding claims wherein each said bearing member comprises a grub screw.

5. A coupling device as claimed in claim 4 wherein each said bearing member is a knurled point grub screw.

6. A coupling device as claimed in any of claims 1 to 5 wherein said first, female wall end portion has a plurality of slots extending axially from a free end of said first wall end portion into said wall to facilitate flexing of said wall end portion radially inwardly and outwardly of said body.

7. A coupling device as claimed in any of the preceding claims wherein said first wall end portion has locating means for engaging with cooperating locating means in said outlet stub.

8. A coupling device as claimed in claim 7 wherein said locating means on said first wall end portion project radially inwardly of the wall end portion for locating in correspondingly shaped recesses in said outlet stub.

9. A coupling device as claimed in claim 7 or 8 wherein said locating means comprises an annular rib formed on an inner surface of said first wall end portion.

10. A coupling device as claimed in claim 9 when appendant to claim 6 wherein said slots intersect said annular rib.

11. A coupling device as claimed in claim in any of the preceding claims further comprising an annular sealing member located in a groove in an inner surface of said first, female wall end portion for enabling sealing engagement with said metal stub.

12. A coupling device as claimed in claim 11 wherein said groove has a base wall and side walls; and wherein at least one of said side walls tapers inwardly towards the other in a direction away from said base wall.

13. A coupling device as claimed in claim 11 or 12 wherein said bearing members are positioned axially between said sealing member and a free axial end of said first wall end portion.

14. A coupling device as claimed in claim 11, 12 or 13 further comprising a tubular member engageable in a press fit manner in said second wall end portion; and wherein said tubular member has an axial end edge co-operable with an opposing shoulder in said first wall end portion when said tubular member is engaged in said second wall end portion, thereby to form said groove.

15. A coupling device as claimed in claim 14 wherein said tubular member and said second wall end portion have co-operating locating means for accurately locating said tubular member axially within said second wall end portion.

16. A coupling device as claimed in any of the preceding claims wherein: said first, female wall end portion has a smaller diameter than said second wall end portion thereby forming radially outer and inner shoulders between said wall end portions; said first, female wall end portion has radially outwardly extending flange means at or adjacent a free axial end of said first wall end portion; and wherein said outer shoulder and said flange means serve to locate said clamping means on said first wall end portion.

17. A coupling device as claimed in claim 10 wherein said flange means comprises at least three radially outwardly extending lugs.

18. A coupling device as claimed in any of the preceding claims wherein said tubular body is cylindrical in cross section.

19. A coupling device for coupling a rainwater drainage outlet metal stub to plastics piping, the coupling being substantially as hereinbefore described with reference to Figures 1 to 3 or figures 4 to 6 or Figures 7 to 9 of the accompanying drawings.