GB2281602A - Testing plug - Google Patents

Abstract

A plastics testing plug includes a bottom plate (4) which is integral with, and moulded homogeneously with, an upstanding nipple (5). It also includes a top plate (6) which has a central orifice (7) for receiving the free end of the nipple therethrough. The top and bottom plates are adapted to receive and locate an intermediate seal (8). A wing-nut (10) is used to draw the top plate towards the bottom plate, thereby squeezing the seal such that it bulges outwardly. <IMAGE>

Description

TESTING PLUG This invention relates to testing plugs. In particular, but not exclusively, it relates to testing plugs for testing pipes or drains for leaks.

It is often necessary and sometimes required by regulations, to test drains or pipework for water-, airor gas-tightness. This is generally done for air by blocking both ends of the pipe or drain and pumping in air until a certain pressure is indicated. By measuring the air pressure, leaks will be noted if the air pressure drops. Water-tightness may be measured by filling a pipe with water, blocking both ends and by adding water at regular intervals and noticing the quantity required to maintain the original water. In a typical test, defined by British Code of Practice CP20005:1968 Sewerage; a system is filled with water and loss of water over a period of thirty minutes is measured by adding water from a measuring vessel at regular intervals of ten minutes.

The quantity required to maintain the original water is then noted. To pass the test, the average quantity added for pipes up to 18 inch (460 mm) diameter should not exceed one litre per hour per linear metre per metre of nominal diameter.

The ends of the pipe or drain can be sealed by means such as an inflatable drain bag or a testing plug.

Typical testing plugs comprise a bottom plate, which is normally circular, of outside diameter slightly less than the internal diameter of the pipe to be tested to allow the testing plug to be easily inserted into the pipe; a top plate which is normally the same outside diameter as the bottom plate; a hollow shaft, commonly termed a nipple, which is attached to the bottom plate and is upstanding therefrom so that the top plate is free floating upon it; a seal, which is generally either a molding or formed of an extrusion which is cut and joined together, the seal being held in use between the top and bottom plates; and a means such as a wing-nut which is used to tighten the top plate by drawing it towards the bottom plate and thus to squeeze the seal and cause a portion of it which is intermediate the bottom and top plates to bulge outwards and thus to grip against the inside wall of the pipe to seal the pipe. The end of the nipple remote the bottom plate is then either blanked off by a blanking cap or is provided with a nipple cap to allow water, air or another medium to be introduced into the pipes.

A problem with this type of testing plug is in guaranteeing airtight seals, particularly between the bottom plate and the nipple. Various attempts have been made to achieve an airtight seal, amongst these are the use of welding, friction welding or glueing to secure the nipple to the bottom plate. Other techniques involve inserting the nipple into a die and molding the bottom plate around the nipple or of screwing the two together by using a locking member such as lock nuts or '0' rings.

All of these techniques are unsatisfactory for various reasons.

According to the present invention there is provided a moulded plastics testing plug comprising: a bottom plate having a central orifice and an upstanding hollow shaft surrounding the central orifice and extending from the plate on one side thereof and forming an integral and homogeneous moulding with the plate; a top plate having a central orifice dimensioned to allow the hollow shaft to pass therethrough; means formed on the top and bottom plates for receiving and locating an intermediate annular seal; and means for drawing the top and bottom plates together to squeeze the seal therebetween and cause it to bulge outwardly.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which; Figure 1 shows schematically a drainage system being tested for water fastness; Figure 2 is a sectional view of a testing plug; Figure 3 shows the bottom plate of the testing plug; Figure 4 is an axial cross-section of the bottom plate; Figure 5 is an underplan view of the bottom plate, and Figure 6 is an axial cross-section of a further embodiment of a bottom plate.

Figure 1 shows schematically an underground pipe system including a pipe 1 extending between two manholes 2. In order to test the water- or air-tightness of pipe 1 both ends of it are blocked, as shown, by plugs 3. Water or air may then be added by attaching a water or air supply to one of the plugs while the other plug remains sealed. By measuring pressures or the amount of fluid needed to replenish the fluid in the pipe, the rate of leakage of the pipe can be determined.

Figure 2 shows a testing plug. The plug comprises a bottom plate 4 having a central orifice 17 and an upstanding hollow shaft 5 surrounding the orifice and extending from the plate on one side thereof. The shaft 5 and plate 4 are moulded in a single operation to form an integral and homogeneous moulding with each other. The shaft 5 is provided with an external screw thread 9. A top plate 6 has a central orifice 7 dimensional to allow the shaft 5 to pass therethrough. The top plate is of the same outer diameter as the bottom plate. A generally annular seal 8 is mounted between seal receiving portions on the top and bottom plates as shown. The seal is of a resilient material such as a commercial grade of rubber but may be of other materials such as plastics materials.

A wing-nut 10 is also located upon shaft 5 for drawing the top and bottom plates together and thus cause the seal to properly seal against the top and bottom plates and to bulge outwardly so as to contact the sides of a pipe in which the plug is inserted. An optional washer (not shown) may be applied between the wing-nut and the top plate. A cap 11 is applied over the free end of shaft 5.

The cap may either be a blanking cap or may be provided with, for example, a nipple (not shown) to allow water, air or other medium to be introduced into the pipe through the plug.

Figures 3 to 5 show the bottom plate in more detail. In a preferred embodiment, the top plate is identical or similar to the bottom plate but without the attached shaft.

The plates (and also preferably the wing-nut) are made of a plastics material of the type which is mouldable yet rigid and relatively inert after moulding to withstand the pressures and substances involved in drains testing. Typical examples are polyolefins, eg polypropylene, or polyamides, eg nylon 6 or 6 6, or polyvinyl chloride. Another example which is appropriate for the wing-nut, and also the plates, is acetal.

The bottom plate is circular, of preferred outer diameter slightly less than the internal diameter of the pipe the plug is intended to test so that the plug can easily be inserted into the pipe. As is shown most clearly in Figure 4, the base plate 4 includes a peripheral annular ring portion 12. The inner edge of this is joined by an annular shoulder 13 to an intermediate annular portion 14. Shoulder 13 may be parallel to the axis of nipple 5 but as shown, shoulder 13 lies at an angle o to this axis so that it tapers radially inwardly towards the top (in the disposition shown in Figure 4). It is this shoulder 13 that receives the edge of a rubber seal 8 and the tapered, frusto-conical, nature of the shoulder enables the seal to be easily located by simple placement. Angle a may for example be between 0 and 450, typically between 100 and 300 in embodiments of the invention, although other angles may be used. As the seal is compressed it is forced downwards and creates a seal against the edge of shoulder 13 and ring portion 12.

The intermediate portion 14 includes a slightly thicker inner part 15 extending to a central strengthening hub portion 16. Hub 16 surrounds the orifice 17 which is also defined by the internal surface of the shaft 5. The shaft 5, which is integral and moulded with the remainder of bottom plate 4 includes a first unthreaded tubular portion 18 extending perpendicularly from base 4. Above tubular portion 18 is a screw threaded portion 19.

As shown in the underplan view of Figure 5, the bottom plate 4 is provided with radially extending strengthening ribs 20 between the hub 16 and the underside of shoulder 13. In the embodiment shown, four ribs 20 are provided at 900 intervals but other configurations may be chosen.

Figure 6 shows a modified embodiment of a bottom plate. In use, when the wing-nut is tightened a considerable force may be applied to the peripheral annular portion of the bottom plate by the seal. This causes considerable bending forces to be exerted at the junction between the shaft 5 and the bottom plate. Thus, it may be desirable to strengthen this area. In the example shown in figure 6, this area is strengthened by providing a radiussed area at 200. Radiussing may also or alternatively be provided on the underside of the plate.

Other strengthening methods may be used.

The top plate 6 is similar to the bottom plate except that it is not formed with an upstanding shaft.

The central orifice 7 of the top plate will of course need to be larger than orifice 17 such that the shaft 5 fits axially within it so that the top plate floats upon the shaft.

An annual shoulder is also formed on the top plate to co-operate with the shoulder on the bottom plate.

In use, the shoulders taper radially inwards towards one another.

The top and bottom plates of the plug may be moulded by any convenient method, such as by using a high pressure plastic moulding machine.

Claims (6)

1. A moulded plastics testing plug comprising: a bottom plate having a central orifice and an upstanding hollow shaft surrounding the central orifice and extending from the plate on one side thereof and forming an integral and homogeneous moulding with the plate; a top plate having a central orifice dimensioned to allow the hollow shaft to pass therethrough; means formed on the top and bottom plates for receiving and locating an intermediate annular seal; and means for drawing the top and bottom plates together to squeeze the seal therebetween and cause it to bulge outwardly.

2. A testing plug as claimed in Claim 1, wherein the means for receiving and locating the intermediate seal comprises frustoconical annular shoulders formed on each of the plates on those sides of the plates which face one another in use; the frustoconical surfaces tapering radially inwardly towards one another.

3. A testing plug as claimed in Claim 1 or Claim 2, wherein the bottom plate includes a central strengthening hub surrounding the central orifice therein on the side of the plate opposite the hollow shaft.

4. A testing plug as claimed in Claim 3, wherein strengthening ribs extend radially outwardly from the hub.

5. A plastics testing plug as claimed in any preceding claim, wherein the junction between the hollow shaft and the bottom plate is formed with a radius to reinforce the junction.

6. A moulded plastics testing plug substantially as described herein with reference to the accompanying drawings.