IE990565A1 - A device for detecting the proximity of an underground cable during digging - Google Patents

Abstract

A device for detecting the proximity of an underground cable conduit during digging, comprises a microphone 10 locatable within a conduit 11, within a conduit access chamber 12. The microphone 10 is in communication, through a radio transmitter unit 13, with a detector unit 19 located in a digging machine 20. In use, a sound picked up by the microphone 10 due to digging adjacent the conduit 11 is converted into a warning signal detected by a machine operator 22, located in the digging machine 20. As soon as the warning signal is detected the digging operator can be halting thus avoiding damage to the underground cable.

Description

ievice for detecting the proximity of an underground cable during digging \ I * y 1ifS.« gC ' SKs^1*'·’ -IBS ' .. -s^T ru>** _£> <5 σ ό' l»^ae^jacTO35strRie-fteef?'jg 5 o Ό 3 Ζ Ό W c c & Z 03 o :o ss This invention relates to a device for detecting the proximity of an underground cable during digging and in particular to the detection of I mderground cables in conduits, when using mechanical diggers, so as o avoid damage thereto.

Before commencing digging at a site where underground cables ire present it is necessary to mark out their location. Site maps, drawn to Cd g aap when a cable was originally installed may be available, but are not co j θ m plways accurate. Telecommunication cables are typically installed in g conduits, usually of plastics material, with personnel access chambers 2 located at regular intervals along the conduits. However, one cannot assume that a conduit will take a straight line course between adjacent chambers, as the line taken by the conduit will depend on the soil structure and on any obstructions in the path between the access chambers.

Where the telecommunication cables are of the optic fibre type, accidental severing of one of these cables can be very costly as it will disrupt communication along the cable. This results in costs being incurred by the companies using the cable which can result in compensation claims. For this reason cables are heavily insured.

Devices are available for tracking underground cables, prior to digging, by employing metal detectors. The line of the cable is marked out on the surface of the ground. However, these devices are subject to inaccuracies, particularly in the measurement of the depth of the cables underground. It will be understood that a number of conduits may be layed between adjacent chambers and they will not all travel the same path or be at the same depth below ground.

Other systems employ conductive lines associated with the conduits through which a current may be passed which in tum is detected at the surface. Again such systems are subject to inaccuracies in measurement and can only be used where the conductive lines were layed with the conduits from the outset.

Patent Publication DE A 19614707 describes a system which employs an auxiliary conductor in close proximity to the cables or pipes to be protected. The conductor is activated by low power RF energy at e.g. 10 kHz which is radiated through the intervening ground to a machine equipped with a receiver and suitable warning instruments. Thus, when the machine comes close enough to the cable the receiver will pick up the signal from the auxiliary conductor and provide a warning to the machine operator.

However, again this system requires the laying of the auxiliary conductor along with the cables from the outset and is therefore of limited usefulness.

Thus, what is required is a device for detecting the proximity of underground cables during digging which overcomes the disadvantages of the devices and methods described above.

Thus, the invention provides a device for detecting the proximity of an underground cable conduit during digging .comprising a microphone suitable for locating in the conduit access chamber, the microphone being in communication with a detector unit, and means within the detector unit for converting a sound picked up by the microphone due to digging adjacent to the conduit into a warning signal detectable by the person engaged in the digging.

The device in accordance with the invention is typically used where digging is taking place with a mechanical digging machine or digger in an area where underground cables have been layed in conduits provided with personnel access chambers at regular intervals along the line of the conduit. A microphone is placed in the conduit at an access chamber ahead of the digging and movement of the digger bucket close to the conduit will be detected by the microphone resulting in a warning signal being generated.

The person operating the digging machine would have a rough idea of the position of the cables and would be on the alert for any warning signal generated by the device. As soon as a warning signal is detected digging can be stopped, before any damage is caused to the cable, and the actual position of the cable can be noted. Thus, use of the device reduces the risk of damaging a cable and also stress on the person operating the digging machine resulting from the fear of causing some damage.

Preferably, the warning signal is visual.

Thus, the warning signal can take the form of a warning light which will be seen by either the operator of the digging machine or by a banksman. A banksman is a person who overseas the digging operation by standing next to the area being dug.

Further, preferably, the warning signal is in the form of a flashing light.

Provision of a flashing light increases the probability of notice being taken of the warning signal as early as possible.

Alternatively, the warning signal is audible.

The warning signal could take the form of a loud siren which would be audible over the noise of the digging machine.

Preferably, the warning signal is both visual and audible.

Having both a visual and audible signal results in a more efficient device. Where either the visual signal is obscured or the audible signal is missed due to other interfering noises in the site, the complimentary signal should work and thus alert the operators.

In one embodiment of the invention, the detection unit is locatable adjacent to the conduit access chamber.

Such a device would be located within an access chamber with a warning signal being provided by either a light visible above ground or a sound generated also above ground. Such a device would be relatively simple in construction.

In a further embodiment of the invention, the detection unit is locatable at a place remote from the conduit access chamber.

The advantage of such a device is that the detection unit could be placed in the cab of the digging machine close to the operator. Thus, any warning signal would be immediately detected by the operator, who would then stop digging.

Alternatively, the detection unit could be carried by the banksman who would relay any warning to the operator. In certain situations the banksman could probe the area for digging ahead of the digger and any sound transmitted to the microphone by such probing would be detected by the banksman or operator, and the exact location of the cable could be established.

Preferably, the microphone is connected to a radio transmitter unit and the detection unit has means for receiving a signal from the transmitter unit.

A radio transmitter and receiver provide a convenient method for transferring the warning signal to a location remote from the conduit access chamber.

Advantageously, the device has a plurality of microphones in communication with the detector unit.

Thus, in situations where a number of conduits have been laid between access chambers, each conduit can be monitored using an individual, microphone. Movement near any of the conduits will then activate the device to provide a warning signal to the operator.

The invention will be further illustrated by the following description of an embodiment thereof, given by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a schematic representation of a device according to the invention.

Fig. 2 is a schematic representation of the transmitter unit of the device of Fig. 1; and Fig. 3 is a schematic representation of the detection unit of the device of Fig. 1.

Referring to Fig. 1, there is illustrated a device according to the 15 invention for detecting the proximity of an underground cable conduit during digging, comprising four microphones 10 located within conduits 11, within a conduit access chamber 12. The microphones 10 are connected to a radio transmitter unit 13 by cables 14. An antenna 15 is connected to the radio transmitter unit 13 by a cable 16. The antenna is provided with a spike 17 for fixing the antenna 15 in the ground 18. The microphones 10 are in communication, through the radio transmitter unit 13, with a detector unit 19 located in a digging machine shown generally at 20. The detector unit 19 is located in the cab 21 of the digging machine 20. The digging machine operator 22, located in cab 21 of the digging machine 20, is provided with a headset 23 which is connected by a cable 24 to the detection unit 19. A receiving antenna 25 is connected to the detector unit 19 by a cable 26 (see Fig. 3).

In operation, when the bucket 27 of the digging machine 20 is operated in close proximity to one of the conduits 11, a sound wave is transmitted therethrough and is picked up by the corresponding microphone 10. A signal from the microphone 10 is converted in the radio transmission unit 13 into a radio signal which is transmitted, via the antenna 15, and is picked up by the receiving antenna 25. The signal is then converted in the detector unit 19 into an audible signal detectable on the headset 23 and a visual display (not shown) located on the detector unit 19.

Referring to Fig. 2, the radio transmitter unit 13 of the device according to the invention is illustrated in more detail.

The radio transmitter unit 13 comprises a housing 30 having connectors 31 mounted on a surface 32 thereof, and to which the microphones 10 are connected via cables 14. An on/off switch 33 is mounted on the surface 32 together with an associated indicator light 34 and a fuse 35.

A connector 36 on the surface 32 receives the cable 16 of the antenna 15. A battery 37 is connected via a cable 38 to the housing 30 at a connector 39.

Each microphone 10 is partially surrounded by sound-proofing material 40 to cut down on any interference due to background noise.

The radio frequency used by the radio transmitter unit is 28 mHz. When a number of devices in accordance with the invention are being used on the same site separate frequencies can be used to avoid confusion.

Referring to Fig. 3, the detector unit 19 of the device according to the invention is illustrated in more detail.

The detector unit 19 comprises a housing 41 having an on/off switch 42 mounted on a surface 43 thereof, together with an associated indicator light 44 and a fuse 45.

The antenna 25 is connected via the cable 26 to the housing 41 by a connector 46 on the surface 43. A battery 47 is connected to the housing 41 at a point 48 on the surface 43 via a cable 49. The headset 23 is connected via the cable 24 to the surface 43 at a connector 50. The cable 41 includes a volume control 51.

A visual display unit 52 is connected via a cable 53 to the housing 41 at a point 54 on the surface 43. The visual display unit 51 includes an array of indicator lights 55 which progressively light up, in use, depending on the level of the warning signal. A suction cup 56 is attached to the visual display unit 51 and is used for mounting the visual display unit 51 on an internal surface of the cab 21 within view of the operator 22.

Claims (10)

1. Claims: 1. A device for detecting the proximity of an underground cable conduit during digging, comprising a microphone suitable for locating in the conduit at a conduit access chamber, the microphone

2. A device according to Claim 1, wherein the warning signal 10 is visual.

3. A device according to Claim 2, wherein the warning signal is in the form of a flashing light.

4. A device according to Claim 1, wherein the warning signal is audible. 15 5. A device according to Claim 1, wherein the warning signal is both visual and audible.

5. Plurality of microphones are in communication with the detector unit. 5 being in communication with a detector unit, and means within the detector unit for converting a sound picked up by the microphone due to digging adjacent the conduit into a warning signal detectable by a person engaged in the digging.

6. A device according to any preceding claim, wherein the detection unit is locatable adjacent the conduit access chamber.

7. A device according to any of claims 1 to 5, wherein the 20 detection unit is locatable at a place remote from the conduit access chamber. ίο

8. A device according to Claim 7, wherein the microphone is connected to a radio transmitter unit and the detection unit has means for receiving a signal from the transmitter unit.

9. A device according to any preceding claim, wherein a

10. A device substantially as hereinbefore described with particular reference to and as illustrated in the accompanying drawings.