GB2102565A - Surface inspection - Google Patents

Abstract

A surface, particularly the inner surface (3) of a pipe (2) is inspected to enable surface interruptions caused by faults or joints or junctions to be detected and located, by means of a wheeled body (1) which is driven along the surface. The wheeled body is a remote controlled electric motor-driven construction having peripheral scanners (9, 10) which examine the surface (3) with infra-red radiation, and transmit data back to an interpretive control system. A number of separate scanners (9, 10) are disposed at different angular orientations around the direction of movement of the body so that information can be obtained as to the orientation of a detected surface interruption. A toothed wheel rotating in synchronism with the motor produces pulses to indicate the distance travelled. A light source 11 and detectors 12 respond to obstructions to stop the body. <IMAGE>

Description

SPECIFICATION Surface inspection This invention relates to the inspection of surfaces and is particularly concerned with the inspection of internal surfaces of passageways, such as pipes, ducts and machined bores, with a view to detecting faults, such as cracks, holes, eroded pits and burrs, orforthe purpose of locating intended surface interruptions provided by joints, junctions, and the like.

In the case where a branch pipe is to be connected to a laid sewage drain, existing joints and junctions are required to be located to assist in planning the necessary excavation work. Conventionally this is done relying on surface measurements but this can be complicated, inconvenient and unreliable. Having regard to the limited accessibility of laid sewage drains difficulties can also arise with regard to their inspection for the purpose of identifying inner surface faults.

An object of the present invention is to provide apparatus which can be used to inspect internal surfaces of passageways which are of appreciable length and/or which are fixed underground or otherwise mounted at onsite locations of limited accessibility, in a simple and convenient yet reliable manner.

According to the invention therefore there is provided apparatus for inspecting a surface comprising a body, drive means for driving said body along a path relative to said surface, scanning means mounted on said body operable to scan said surface so as to produce an electrical signal which varies in correspondence with changes in physical properties of said surface along said path, location means on said body operable to produce an electrical signal dependent on the location of the body relative to said surface along said path, and interpretation means operable to interpret said electrical signals so as to produce an output capable of identifying the occurrence and location of predetermined said changes iri physical properties of said surface.

With this invention reliable surface inspection can be effected in a particularly simple and convenient manner in so far as this requires only the driving of the body along the surface and the interpretation, electrically, of signals derived therefrom.

It is visualised that the invention will find particular application in the context of the inspection of generally smooth cylindrical inner surfaces of passageways for the purpose of detecting surface irregularities or discontinuities caused for example by faults orjoints or junctions. It is however to be understood that the invention is not intended to be restricted to this field of application and the apparatus thereof may be used for any suitable purpose any suitable context.

With regard to the said body, this may take the form of a structure mounted on rotatable friction members such as wheels and/or tracks or the like, and the said drive may comprise an electric motor arranged to drive one or more of said members if desired via an appropriate gear arrangement.

The said scanning means may comprise radiation scanning means (particularly infra-red) and this may involve a transmitting device operable to direct a beam of radiation at the surface and a receiving device operable to receive radiation by reflection from the surface. Infra-red is particularly useful in this context where irregularities or discontinuities such as cracks, gaps, holes, depressions and the like are to be detected in so far as these would tend to severely curtain the intensity of the received radiation.The arrangement may be such that the surface is constantly irradiated and the receiving device produces a correspondingly constant signal output (with the assistance if necessary of a filter or the like for example to eliminate noise) except when a surface irregularity or discontinuity occurs in which case the signal output fluctuates sharply (and which fluctuation may be modified if desired to give a pulse or pulses of desired shape). Alternatively, the surface may be exposed to pulses of radiation such that irregularities or discontinuities in the surface effect modification of a pulse train produced by the receiving device (as for example by omission of one or more pulses).

In a particularly preferred embodiment there are multiple scanning means disposed at different locations on thePody, particularly at different positions transversely of the said path of movement (e.g. at different angular locations disposed circumferentially around the axis of movement), whereby different portions of the said surface can be inspected with the apparatus.

Said location means may be operable to identify the location of a change in surface physical characteristics in terms of the distance along said path of movement and/or in terms of the orientation transversely of said path. Where distance along the path is to be identified, the said body may have mounted thereon a device which generates distance related data simultaneously with scanning of the surface, for example, a device which generates a pulse train having a pulse frequency directly related to the speed of body movement so that distance can be measured by counting pulses and the location of a change in physical characteristics can be determined by identifying the pulse count when the change is detected.Where the body has wheels orthe like driven by an electric motor, the pulses may be generated by a device driven in synchronism with the motor for example by interrupting transmission of radiation (e.g. visible light or infra-red) between a transmitter and an electrical detector with a toothed wheel or other member drivably connected to the motor.

Where orientation is to be identified, this may be effected conveniently using multiple transversely disposed scanning means as mentioned above, said location means acting to discriminate between the signals produced by the different scanning means so that an indication can be obtained as to the location of a detected physical characteristics change as between the different said surface portions being scanned. In addition to identifying orientation, multiple scanning means can also give information as to the size and/or shape of an interruption in so far as interruption-identifying signals are produced by two or more different said scanning means.

Especially in the case where orientation of a surface interruption is to be identified as mentioned above it may be desirable to monitor the orientation of the body and with this aim, one or more orientation switches, e.g. mercury switches, may be provided on the body so as to produce signals should be body tilt away from a predetermined attitude. Multiple switches (e.g. left and right switches) may be provided to give indication of the sense of any tilt.

With regard to the said interpretation means this may take any suitable form. For example, the interpretation means may comprise one or more digital counters, and/or one or more sets of indicator lamps and!or graphical display equipment capable of producing a visual display which identifies at least one parameter of the location of a detected change.

The identification of the pertinent change-indicating display with such a visual display device may be effected as a consequence of automatic actuation of the device only to produce such display and/or by automatic recordal of the pertaining display. Alternatively or additionally an alarm indicator of an audible and/or visual nature may be actuated when a change in physical characteristics is detected thereby to draw attention thereto and to the associated location identifying display (or displays).

The said interpretation means may be located remote from the said body and connected thereto via a cable link. Similarly other devices e.g. a power source for electrical components on the body, may be connected thereto remotely via a cable link.

Means may be provided for automatically stopping the movable body for example when an obstruction in the said path is detected andior when a change in physical characteristics of the said surface is detected.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Figure lisa diagrammatic side view of the movable body of one form of apparatus according to the invention in use within a pipe: Figures 2 and 3 are end views respectively on the sectional lines 2-2 and 3-3 of Figure 1; and Figure 4 is a circuit diagram of the apparatus incorporating the body of Figure 1.

Figure 1 shows a wheeled body 1 movable within and along a passageway 2 having a generally smooth cylindrical inner surface 3, such as a large ceramic underground sewage drain pipe, the body 1 being constructed so as to be specially suited for use with the pipe in question in that the body has an outer surface in close proximity to the said inner surface 3 and the wheels are arranged for smooth running along a straight line path along the pipe, as described in more detail below.

The body 1 comprises a generally cylindrical front portion 4, a generally rectangular rear housing 5, and a generally cylindrical middle portion 6 of smaller diameter than the front portion 4. Two wheels 7 are mounted on the front of the front portion so as to be freely rotatable about inclined axes. These wheels 7 have median planes which extend radially of the front portion 4 and the wheel outer peripheries have cylindrical surfaces coaxial with the wheel axes. As shown in Figure 2 the wheel peripheries run flat on the pipe inner surface 3 and hold the front portion 4 in coaxial disposition relative to the pipe axis such that a narrow annular gap is defined between the inner surface 3 of the pipe and the outer surface of the portion 4. Two wheels 8 are rotatably mounted on opposite sides of the rear portion 5 on a common horizontal axis.These wheels 8 have tyres with peripheries which are shaped, as shown in Figure 3, to conform to the curvature of the inner surface 3 of the pipe 2.

Within the end portion 5 there is a 24V d.c. electric motor which is drivably connected (via gears if desired) to the wheels 8. The motor is also connected to a toothed wheel rotatably mounted within the body, the purpose of which is described hereinafter. Around the periphery of the front end portion 4 adjacent the central portion 6 there are nine infra-red scanners lying in a common plane perpendicular to the axis of the front portion 4; namely: a central scanner 9 at the uppermost part of the portion 4 and eight side scanners 10 arranged four on each side of the central scanner 9 at equally circumferentially spaced positions. Each scanner 9, 10 comprises an electrical infra-red emitter arranged to direct a beam of infra-red at the adjacent part of the inner surface 3 and an electrical infra-red detector arranged to receive such radiation reflected back from the surface.

At the front end of the front portion 4 there is a central forwardly directed electrical light source 11 (visible or infra-red) and three peripheral equally spaced forwardly directed electrical light sensors 12.

If the body 1 is confronted with an obstruction, light will be reflected back to one or more of the sensors 12.

At the back end of the end portion 5 there is a multi-lead cable 13 which is connected within the body 1 to the motor, the light source and sensors, the scanners, and to other electrical components as shown in the box 14 at the right of FigurB 4 and as described in more detail hereinafter. The cable 13 extends along the pipe 2 behind the wheeled body 1 to a remote control system externally of the pipe and as shown in the box 15 at the left of Figure 4.

The control system comprises a power supply 16 and first and second electrical signal interpretation arrangements 17, 17a.

The power supply 16 is connected to a.c. mains and produces therefrom 24V and 12V d.c. outputs regulated respectively at 3 amps and 1.5 amps.

These outputs (and a zero terminal) are connected directly to respective leads 18, 19,20 of the cable 13.

Additionally the 24V output is connected to further leads 21, 22 via a motor control circuit 23 comprising a diode 24, an on/off switch 25, a commutator reversing switch 26, and contacts 27 of a switching relay.

The first interpretation device 17 comprises an electronic counter 28 connected to a digital display 29 (LCD or LED) and having a re-set switch 30 and a count direction reversing switch 31 ganged to the commutator 26. The counter input is connected to a respective lead 32 of the cable.

The second interpretation device 17a comprises an electronic (de-multiplexing) driving circuit 33 having an input data bus 34 connected to a respective lead 35 of the cable 13 and multiple outputs which are connected respectively to a bank of nine LEDs 36, two bleepers 37,38 and the winding 39 of the relay having the above-mentioned contacts 27.

The driving circuit 33 also has an input connected to a clock oscillator 40 (which is also connected to a respective cable lead 41) and two re-set switches 42, 43.

As shown at the right of Figure 4 the motor has field and armature windings 44,45 which are connected in series with each other and with the leads 21, 22. A commutator 46 defined by relay contacts is inserted before the field winding 44 and the winding 47 of the relay is connected in series with a diode 47a across the leads 21,22.

The lamp 11 and sensors 12 are connected to the leads 18,20 and the scanners 9, 10 are connected to the leads 19,20 to receive power therefrom. Outputs of the sensors 12 and scanners 9, 10 are connected to a multiplexer device 48 which has a data bus output 49 connected to the lead 35. The multiplexer 48 has a clock input 50 connected to lead 41 and further inputs which are connected to left hand and right hand mercury switches 51,52 mounted within the body at opposite sides thereof. The multiplexer 48 is also connected to the leads 19, 20 to receive power therefrom.

The leads 19,20 are further connected to a pulse generating circuit 53 comprising a light-emitting diode 54 and an adjacent light-sensitive transistor 55 having an output 56 connected to the lead 32. The abovementioned toothed wheel 57 drivably connected to the motor is positioned such that light transmission from the diode 54 to the transistor 55 is interrupted every time a tooth on the wheel passes between same.

In use, when the switch 25 is closed, power is supplied via the leads 21,22 to the motorwindings 44,45 and the body 1 is thereby driven along the pipe 2. The toothed wheel 57 rotates in synchronism with the motor and pulses are transmitted to the counter 28. The total number of pulses continuously updated is shown on the display 29 from a predetermined starting point at which the counter is set to zero with the switch 30. If desired the motor can be reversed to drive the body backwards by manual operation of the commutator 26 which causes the relay 46,47 to be operated to reverse the connection of the motor field winding 44 and which also operates the switch 31 to reverse the action of the counter 28.

As the body 1 advances the scanners 9, 10 scan the inner surface of the pipe and output signals are fed to the multiplexer 48. Where the surface 3 is smooth and without interruption there is no change in the nature of the output signals. Where the surface has an irregularity or discontinuity the output signal of the appropriate scanner or scanners 9, 10 will change to produce a pulse which is transmitted along the lead 35 to the driving circuit.That is, where an irregularity or discontinuity is encounted which involves an appreciable increase or decrease in the distance travelled between the transmitter and re ceiver of a scanner (as would be the case where the surface 3 is depressed or pitted or cracked or has a projection thereon) or which involves elimination or appreciable reduction of the reflected radiation (as would be the case where the surface has a hole or gap or infra-red absorbing patch due for example to erosion or corrosion), a corresponding impulse is produced derived from the change in intensity of the received reflected radiation and/or due to a detected change in the timing of a received radiation impulse compared with the expected timing based on the timing of transmitted pulses.The inputs to the multiplexer 48 and the outputs to the LEDs 36 are activated sequentially in synchronism with each other whereby the production of a pulse by one scanner 9, 10 effects illumination of a correspond ingly identified one of the LEDs. At the same time the bleeper 37 is actuated to give warning of the occurrence of the surface interruption. Thus, when the bleeper 37 sounds the location of a surface interruption can be determined by observation of the numerical value on the digital display 29 (which may represent the actual distance along the pipe in predetermined units) and by observation of which of the LEDs 36 is illuminated which indicates the scanner which has detected the interruption and consequently the orientation thereof. In this way surface interruptions can be detected and accurately located easily and conveniently.The use of infra-red for scanning purposes advantageously gives accurate detection even through pipe linings.

It is to be understood that more than an interruption may be large enough to be detected by a plurality of scanners simultaneously and/or successively and this will cause corresponding simultaneous and/or successive actuation of a plurality of the LEDs 36. In this way an indication of the shape and size of the interruption can be given.

The orientation of a surface interruption can only be accurately identified as described above if the wheeled body 1 remains vertically upright. If the body tilts slightly to one side or the other the respective mercury switch 51, 52 will be actuated and this causes the bleeper 38 to sound via data transmitted along the lead 35. The driving circuit 36 can be reset subsequently with the switch 42.

In the event that an obstruction is detected in front of the body 1 a signal is transmitted from one or more of the sensors 12 to the driving circuit 33 via the lead 35 and this also causes the bleeper 38 to sound. At the same time the relay winding 39 is actuated and the contacts 27 open thereby to stop the motor. Subsequently the driving circuit 33 can be re-set with the switch 43.

The apparatus described above can be used for detection of faults in the inner surface 3 or for the location ofjoints or junctions in the pipe. In the latter case, the apparatus can be used to identify a joint or junction prior to excavating for the purpose of fitting a branch pipe. The apparatus can however also be used for other purposes.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only.

Claims (19)

1. Apparatus for inspecting a surface comprising a body, drive means for driving said body along a path relative to said surface, scanning means mounted on said body operable to scan said surface so as to produce an electrical signal which varies in correspondence with changes in physical properties of said surface along said path, location means on said body operable to produce an electrical signal dependent on the location of the body relative to said surface along said path and interpretations means operable to interpret said electrical signals so as to produce an output capable of identifying the occurrence and location of predetermined said changes in physical properties of said surface.

2. Apparatus according to claim 1, wherein said body comprises a structure mounted on rotatable friction members.

3. Apparatus according to claim 2, wherein siad drive means comprises an electric motor arranged to drive one or more said friction members.

4. Apparatus according to any one of claims 1 to 3, wherein said scanning means comprises a radiation scanning means having a transmitting device operable to direct a beam of radiation at the surface and a receiving device operable to receive radiation by reflection from the surface.

5. Apparatus according to claim 4, wherein said radiation is infra-red radiation.

6. Apparatus according to any one of claims 1 to 4, wherein there are multiple scanning means arranged at different positions transversely of said path.

7. Apparatus according to claim 6, wherein said scanning means are arranged at different angular locations disposed circumferentially around the axis of movement of the body.

8. Apparatus according to any one of claims 1 to 7, wherein said location means is operable to identify the location of a change in surface physical characteristics in terms of the distance along said path of movement.

9. Apparatus according to claim 8, wherein said location means comprises a device which generates a pulse train having a pulse frequency directly related to the speed of body movement.

10. Apparatus according to any one of claims 1 to 9, wherein said location means is operable to identify the location of a change in surface physical characteristics in terms of the orientation transversely of said path.

11. Apparatus according to claim 10 when dependent on claim 6 or 7, wherein said location means comprises means operable to discriminate between the signals produced by the different scanning means.

12. Apparatus according to any one of claims 1 to 11, including one or more switches for monitoring the orientation of the body.

13. Apparatus according to any one of claims to 12, wherein said interpretation means comprises one or more digital counters.

14. Apparatus according to any one of claims 1 to 13, wherein said interpretation means comprises one or more sets of indicator lamps.

15. Apparatus according to any one of claims 1 to 14, wherein said interpretation means is disposed remotely from said body and is connected thereto via a multilead cable.

16. Apparatus according to any one of claims 1 to 15, wherein a power source for electrical components on said body is disposed remotely from said body and is connected thereto via a multi-lead cable.

17. Apparatus according to any one of claims 1 to 16, including means for effecting automatic stopping of the movable body when its path is obstructed.

18. Apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

19. Apparatus according to any one of claims 1 to 18, when used to inspect the inner surface of a passageway.