GB2231448A

GB2231448A - A detectable warning tape

Info

Publication number: GB2231448A
Application number: GB9005186A
Authority: GB
Inventors: Robin Michael Boddington
Original assignee: BODDINGTONS Ltd
Current assignee: BODDINGTONS Ltd
Priority date: 1989-03-08
Filing date: 1990-03-08
Publication date: 1990-11-14
Anticipated expiration: 2010-03-08
Also published as: GB2231448B; GB9005186D0

Abstract

A detectable warning tape (4) for use with buried cables or pipes comprises a layer of an electrically conducting material (12) e.g. Al or Cu which is sandwiched between layers (14, 16) of an insulating plastics material e.g. polyethylene or polypropylene. Further layers of plastics material may be provided. One more of the layers of plastics material may be transparent. The tape may be reinforced and bear printed warnings. <IMAGE>

Description

A DETECTABLE WARNING TAPE This invention relates to a detectable warning tape.

It is often necessary to know the exact position of buried underground pipes or cables. When these pipes or cables are made of a non-metallic material, they cannot easily be detected. The result may be that workmen digging holes in the ground may inadvertently break the pipes or cables and may thus disrupt water, gas, electrical or fibre optic services.

In order to overcome the above mentioned problem, it is known to use a detectable warning tape to indicate the presence of buried non-metallic pipes and/or cables.

The detectable warning tape has electrically conducting material which is used to carry a signal to indicate the position of the buried pipes and/or cables. The known detectable warning tape is often such that it delaminates during use and thus becomes defective.

It is an aim of the present invention to provide a detectable warning tape which does not suffer from the problem of delamination.

Accordingly, this invention provides a detectable warning tape comprising a layer of an electrically conducting material which is sandwiched between first and second layers of an insulating plastics material, the first and the second layers of the insulating plastics material being joined to each other along side edge portions which extend beyond the electrically conducting material whereby the electrically conducting material is encased in a sheath of the insulating plastics material.

Preferably, the electrically conducting material is less than half the width of the first and the second layers. More preferably, the electrically conducting material is only approximately one half to one quarter of the width of the first and the second layers. Such a construction minimises on the use of the electrically conducting material and thus minimises on manufacturing costs, whilst still enabling good detectability to be achieved.

The detectable warning tape may be one in which the first layer is a base carrier layer, in which the second layer is a top cover layer, and in which the first layer is thicker than the second layer.

Advantageously, the first layer may be 0.1 - 18.0 mm thick, and the second layer may be 0.05 - 2.0mm thick.

The first layer may extend up along the sides of the electrically conducting material whereby the detectable warning tape is such that the electrically conducting material is located in a groove in the first layer.

In one embodiment of the invention, the electrically conducting material makes direct contact with the first and the second layers.

In another embodiment of the invention, the electrically conducting material is covered with third and fourth layers of an insulating plastics material before being sandwiched between the first and the second layers.

The third and the fourth layers of the insulating material are preferably the same as the plastics material that is used for the first and the second layers.

Different plastics materials may however be used if desired.

The third and the fourth layers of the insulating material give especially good sealing of the electrically conducting material.

Preferably, the plastics material is polyethylene.

Other plastics materials may however be employed including polypropylene.

Usually, the electrically conducting material and the various layers of the plastics material will be heat bonded together. This may be effected during extrusion of the plastics material.

The electrically conducting material is preferably a metal foil. A preferred metal foil is aluminium. The electrically conducting material may be other metals such for example as copper. The electrically conducting material may also be in the form of one or more wires if desired.

The detectable warning tape may include reinforcing material if desired.

The detectable warning tape will usually include a printed warning in order that workmen digging holes in the ground may see the printed warning and thus be warned that there is a pipe and/or cable below. The printed warning may be such as to indicate the precise service being detected. The detectable warning tape may also be provided with the name of the tape and/or the name of the manufacturer.

Some contractors laying the detectable warning tape may have doubts that the detectable warning tape actually operates such that the electrically conducting material can be used to carry a signal to indicate the position of buried underground pipes or cables.

In order to allay the fears of such contractors, the detectable warning tape may be such that at least one of the first and the second layers has at least a portion which is transparent and which enables the electrically conducting material to be seen.

Usually, only the second layer, which will be the top layer when the detectable warning tape is laid, will be provided with the transparent portion. If desired, however both the first and the second layers may be provided with the transparent portion.

The entire first and/or second layers may be transparent. Preferably, the layer or layers chosen to have the transparent portion will be made to be opaque and only a portion of the layer will be rendered transparent. The transparent portion may be in the form of a window at the start of the tape or it may be in the form of a plurality of spaced apart windows along the length of the tape. Still further, a narrow transparent strip could be provided along the entire length of the tape.

Where the detectable warning tape has the transparent portion and where the third and the fourth layers are employed, then the third and/or the fourth layers will normally be provided with the transparent portion in the same manner as the first and/or the second portions. The various transparent portions in the first and/or the second layers on the one hand, and in the third and/or the fourth layers on the other hand should coincide in order that the sandwiched electrically conducting material can be seen.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a first detectable warning tape in use; Figure 2 is a cross section through the first detectable warning tape; Figure 3 is a cross section through part of a second detectable warning tape; and Figure 4 shows part of a third detectable warning tape.

Referring to Figure 1, there is shown a roll 2 of detectable warning tape 4 above a pipe 6 which is buried in the ground 8. The pipe 6 may include a buried water, gas, fibre optic or other service. The detectable warning tape 4 is laid lengthwise above the top of the pipe 6. The position of the pipe 6 in the ground 8 can then accurately be determined. An electrical detection signal can be fed into the detectable warning tape 4 either by direct connection, or by induction. If induction is to be used, then a signal generator 10 is used.

The detectable warning tape 4 is simply joined by overlapping the tape for an appropriate distance which may be approximately 12" (30cm).

As can be seen, the detectable warning tape 4 is provided with its trade mark DETECTATAPE and with a printed warning which is "caution-water main below".

The detectable warning tape 4 can be provided in rolls 2 which may be of any desired length, for example 250 metres. The detectable warning tape 4 can be provided in any desired width, for example up to 500mum The detectable warning tape 4 can be attached to a pipe laying machine and it can be fed in as the pipe 6 is being laid. If the detectable warning tape 4 should become broken by other contractors, then a signal can still be induced into unbroken lengths of the detectable warning tape 4. If it is desired to feed the output from the signal generator directly into the detectable warning tape 4, then direct connection can be effected using an appropriate connector clamp. Feeding in the signal by direct connection will generally provide a stronger signal than by induction.If the detectable warning tape should become broken as mentioned, or the point at which direct access to the detectable warning tape 4 is too far away, then the signal can be induced into the detectable warning tape 4 by placing the signal generator 10 over the detectable warning tape 4 as shown in Figure 1 and inducing the signal in the same way as for a buried steel pipe.

The detectable warning tape 4 can be made in various desired and suitable appropriate thicknesses.

Referring to Figure 2, there is shown detectable warning tape 4 comprising a layer of electrically conducting material in the form of a layer 12 of aluminium foil. This layer 12 is sandwiched as shown between a first layer 14 and a second layer 16 of an insulating plastics material which is formed of polyethylene. The first and the second layers 14, 16 are joined to each other along side edge portions 18,20 which extend as shown beyond the layer 12 whereby the layer 12 is enclosed in a sheath of the insulating plastics material formed by the layers 14, 16.

The first layer 14 forms a base layer, and the second layer 16 forms a top cover layer. As shown in Figure 2, the first layer 14 is thicker than the second layer 16. The first layer 14 is 0.1 - 18.0mm thick, and the second layer 16 is 0.05 - 2.0mm thick.

As shown, the first layer 14 extends up along the sides of the layer 12 so that the detectable warning tape 4 is such that the layer 12 is located in a groove 22 in the first layer 14.

As can be seen from Figure 2, the layer 12 is less than half the width of the first and the second layers 14, 16. More specifically, the layer 12 is only approximately one sixth of the width of the layers 14, 16.

As can also be seen from Figure 2, the layer 12 makes direct contact with the first and the second layers 14, 16.

In Figure 3, there is shown part of second detectable warning tape 4 in which the layer 12 is covered with a third layer 24 and a fourth layer 26.

The third and fourth layers 24, 26 are of an electrically insulating plastics material. They will usually be made of the same plastics material as that employed for the first and the second layers 14, 16, so that the layers 24, 26 are preferably made of polyethylene. The layer 12 of the aluminium foil is covered with the layers 24,26 before it is provided with the layers 14, 16. This assists in giving very good sealing of the layer 12.

The various illustrated types of detectable warning tapes 4 may be produced by laminating the various layers together during a plastics material extrusion process.

Preferably, the layer 12 (with or without the layers 24, 26) is laminated to the first layer 14 during extrusion of the first layer 14. The second layer 16 is then laid across the whole of the formed material so as totally to seal the layer 12 to provide a totally closed sealed envelope, coupled with a mechanically strong warning tape.

The printed warning message or other information will normally be applied prior to lamination of the first layer 16.

Lamination will usually be by means of a heat bond of melted plastics material, for example melted polyethylene when this is the plastics material employed.

The melting will usually be effected as part of the extrusion process.

As mentioned above, the layer 12 is much narrower than the layers 16, 18. This saves on the cost of the aluminium foil forming the layer 12. Thus the overall detectable warning tape 4 can be produced economically at a minimum manufacturing cost whilst still giving a good visual warning coupled with good detectability via the signal generator 10 or other apparatus employed.

The good visual warning is required so that contractors can see the detectable warning tape 4 when they actually dig through the ground 8.

Referring now to Figure 4, there is shown a detectable warning tape 32 comprising a layer of an electrically conducting material 34 which is sandwiched between a first layer 36 and a second layer 38. The first and the second layers 36, 38 are of insulating plastics material in the form of polyethylene. The layer of the electrically conducting material 34 is an aluminium foil detectable laminate which is O.lmm thick. The first layer 36 forms a base layer which is 0.5mm thick. The second layer forms a sealing layer which is printed with a warning message. The second layer 38 is O.lmm thick.

The second layer 38 is provided with a transparent window 40 so that the layer 34 of the electrically conducting material can be seen. The window 40 can be repeated at intervals along the length. of the detectable warning tape 2.

The detectable warning tape 4, 32 can be laid on or above any desired and appropriate non-metallic surface installation such for example as plastics and ceramic pipes containing water or gas, or on or above fibre optic cables or other cables. Preferably, the detectable warning tapes 4, 32 are appropriately spaced apart from the installation for which they are to provide a warning 4, in order to reduce the likelihood of persons seeing the detectable warning tape 4, 32 too late and thus still fracturing the installation.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example, the layer 12 may be formed of a metal other than aluminium. Similarly, the layers 14, 16, 24, 26 may be formed of a plastics material other than polyethylene.

The detectable warning tape 4, 32 may be reinforced with a separate layer of reinforcing material (not shown) if desired. The layer 34 of the electrically conducting material may be encased in third and fourth layers of plastics material such for example as polyethylene. The detectable warning tape of the invention is preferably produced by heat bonding the separate layers together to form a complete water-tight seal but other methods may be employed for securing the separate layers together in the detectable warning tape.

Claims

1. A detectable warning tape comprising a layer of an electrically conducting material which is sandwiched between first and second layers of an insulating plastics material, the first and the second layers of the insulating plastics material being joined to each other along side edge portions which extend beyond the electrically conducting material whereby the electrically conducting material is encased in a sheet of the insulating plastics material.

2. A detectable warning tape according to claim 1 in which the electrically conducting material is less than half the width of the first and the second layers.

3. A detectable warning tape according to claim 2 in which the electrically conducting material is approximately one half to one quarter of the width of the first and the second layers.

4. A detectable warning tape according to any one of the preceding claims in which the first layer is a base carrier layer, in which the second layer is a top cover layer, and in which the first layer is thicker than the second layer.

5. A detectable warning tape according to claim 4 in which the first layer is 0.1 - 18.0mm thick, and the second layer is 0.05-2.Omm thick.

6. A detectable warning tape according to any one of the preceding claims in which the first layer extends up along the sides of the electrically conducting material whereby the detectable warning tape is such that the electrically conducting material is located in a groove in the first layer.

7. A detectable warning tape according to any one of the preceding claims in which the electrically conducting material makes direct contact with the first and the second layers.

8. A detectable warning tape according to any one of claims 1 to 6 in which the electrically conducting material is covered with third and fourth layers of an insulating plastics material before being sandwiched between the first and the second layers.

9. A detectable warning tape according to claim 8 in which the third and the fourth layers of the insulating material are the same as the plastics material that is used for the first and the second layers.

10. A detectable warning tape according to any one of the preceding claims in which the electrically conducting material is a metal foil.

11. A detectable warning tape according to claim 10 in which the metal foil is an aluminium metal foil.

12. A detectable warning tape according to any one of the preceding claims and including reinforcing material.

13. A detectable warning tape according to any one of the preceding claims and including a printed warning.

14. A detectable warning tape according to any one of the preceding claims in which at least one of the first and the second layers has at least a portion which is transparent and which enables the electrically conducting material to be seen.

15. A detectable warning tape according to claim 14 in which only the second layer is provided with the transparent portion.

16. A detectable warning tape according to claim 14 or claim 15 in which the or each transparent portion is in the form of a window at the start of the tape.

17. A detectable warning tape according to claim 14 or claim 15 in which the or each transparent portion is in the form of a plurality of spaced apart windows along the length of the detectable warning tape.

18. A detectable warning tape according to claim 14 or claim 15 in which the or each transparent portion is in the form of a narrow transparent strip provided along the entire length of the detectable warning tape.

19. A detectable warning tape substantially as herein described with reference to the accompanying drawings.