US20040099175A1 - Robot vehicle adapted to operate in pipelines and other narrow passages - Google Patents

Abstract

The train (1) of modules (2to6) that forms the robot comprises springs (38) to connect the successive modules together enabling curvature of the train in the bends of a pipe. However, cables (41) bring the modules together by compressing the springs when they are pulled, until the conical end faces (39, 40) are engaged in each other; the train is made rigid and can be immobilised inside the pipe to perform different types of machining operations, including welding or cutting joints between successive pipes in the pipework.

Description

• This application claims priority based on International Patent Application No. PCT/FR01/02324, entitled “Mobile Robot That Can Operate In Pipes Or Other Narrow Passages” by Yann Perrot, Olivier David and Jean Lehu, which claims priority of French application no. 00/09387, filed on Jul. 18, 2000, and which was not published in English.”[0001]
DESCRIPTION
• The domain of the invention is mobile robots for work, inspection or generally displacement inside pipework or other narrow passages.[0002]
• Robots composed of a small vehicle or an inert module pushed from behind are known, for penetration into pipes and to carry out specific work or inspections in pipes. However, it may be difficult when these robots have to go round bends in the pipework, since they cannot be very long otherwise they would get jammed. One possible solution is to construct a robot consisting of a train of modules formed to be flexible, but it then becomes difficult to stop and hold the robot at a specific place in the pipework and even more difficult to fix it such that it remains immobile despite large forces that it may transmit to the pipework, and despite large reaction forces that may be applied to it during specific work such as machining of the inside of the pipework.[0003]
• The invention offers a solution to this problem; it relates to a robot free to move by sliding in pipework or in another narrow passage, composed of a train of modules connected by flexible links and characterised in that it comprises means of fixing the modules together.[0004]
• Thus, the robot is flexible so that it can go around bends in pipes, but becomes rigid when required and is then capable of being fixed firmly in the pipework and supplying good resistance. Above all, the inhibition of flexible links stiffens the train to resist bending.[0005]
• Some favourable implementations of the invention make it possible to hold the robot at a chosen location in the pipework, by controlling appropriate mechanisms. It then becomes possible and beneficial to provide the robot with manual release mechanisms so that retraction of the holding mechanisms can be controlled manually so that the robot can be made free to move again even if direct control of the holding mechanism motors fail.[0006]
• A particular operation consists of assembling segments of pipework put end to end in sequence; the robot according to the invention can do this operation if it is built such that two portions of an anterior module can be brought towards each other, one of these portions being held in place on the free segment and the other being fixed to the previously assembled length of the pipework.[0007]
• Other important elements of the invention, and particularly specific means of performing the functions described above, will be described in detail with reference to the following figures:[0008]
• FIG. 1 is an overview of the robot,[0009]
• FIG. 2 is a view of a propulsion module,[0010]
• FIG. 3 is a view of a holding module,[0011]
• FIG. 4 shows the train stiffening system,[0012]
• FIG. 5 is a view of an anterior module,[0013]
• FIG. 6 illustrates the anterior module immobilised in the pipework,[0014]
• FIG. 7 illustrates the forced release mechanism of the anterior module,[0015]
• FIG. 8 shows another holding means for a module,[0016]
• FIG. 9 illustrates a train composed of such modules,[0017]
• FIG. 10 illustrates a case in which the invention is used,[0018]
• FIGS. 11A and 11B show a module carrying a machining tool.[0019]
• The embodiment of the invention as shown in FIG. 1 in a pipe bend comprises five modules numbered from[0020]2 to6 from the head to the tail; the head or anterior module is analignment module2 that therobot1 uses to form a path in the pipework; the next module is atool module3 carrying a working tool; the next module is apower module4 supplying energy to the previous module; the fourth module is anauxiliary functions module5; the tail or posterior module in this embodiment is animmobilisation module6. Neither the number nor the function of the modules characterise the robot according to the invention or restricts its scope, since it is obvious that the invention could be implemented with different robots. In particular, a propulsion module that will be described a little later could be added at the tail. In this embodiment, it would be superfluous becauserobot1 is designed to be pushed inside the pipework by means of aflexible rod7 attached to the rear of the tail module through crimping8. Therod7 is flexible at bends in the pipe, but it transmits all longitudinal forces imposed on it and therefore pushes therobot1 forwards. It tends to deform at the largest possible angle of curvature in a bend, separating from the extrados as shown in the diagram in the right part of FIG. 1, at location9. Therefore, it is fairly easy to calculate the penetration of therobot1 as a function of the length of the rod that has penetrated into the pipework.
• FIG. 2 shows a[0021]standalone propulsion module10. Itsenclosure11 contains amotor12 on which theshaft13 is a screw driving threetoothed wheels14. Each of them drives apulley15 that is coaxial with it, and anotherpulley17 fixed to aroller18 through abelt16. Therollers18 are distributed at 120° around a rear circumference of theenclosure11 and are placed at the end oflevers19 hinged about anaxis20 at their opposite end and mutually separated bysprings21, so as to withdrawrollers18 away from theenclosure11 until they are pressed into contact on the wall of the pipework. Another similar expandable roller system, globally referenced22, is placed in front of thepropulsion module10, except that these rollers are not driving and therefore they simply complement centring of themodule10 in the pipework. A doubleuniversal joint23 connects themodule10 to the back of theimmobilisation module6 so that a radial alignment fault can be accepted between them. Since themotor12 is fairly long and thin, theenclosure11 has a recessed shape at the centre so that it can pass through the tightest bends despite its length.
• At least two modules have an immobilisation or holding system in the pipework that will be described below; one of them is the[0022]immobilisation module6 fully illustrated in FIG. 3; itsenclosure25 is perforated by three concentric holes through which divergingpins26 can pass, and finishing at the pipework on abearing surface27. Theenclosure25 surrounds threemotors28 fixed to acommon support plate29 and that rotate thescrews30 designed to move the threadedcams31 forwards, thesurfaces32 of which push on theback faces33 of thepins26. Thecam surfaces32 are not simple wedge surfaces, but comprise at least two slopes, the first34 being steeper so that thepins26 can be pushed more quickly while theother surface35 is shallower and adjusts the pressure force of thepins26 on the pipework. The rotations ofmotors28 are synchronised using abelt36 tensioned in a triangular arrangement around threegears37 at the ends of thescrews30 at the other end of themotors28. As a variant, it would be possible to have a single motor to control the threescrews30 at the same time, using separate transmission means.
• We will now describe an essential aspect of the invention with reference to this FIG. 3, and FIG. 4; they are means of physical and electrical connections of[0023]modules2 to6 in the train that comprisehelical springs38 fixed between two consecutive modules, and an outside conicalmale face39 on the enclosure of each module at the back and an internal femaleconical face40 at the front. The only exception is thealignment module2, which is specially shaped at the front so that therobot1 can easily form its path. Thesprings38 are associated withstiffening cables41 that pass through allmodules2 to6 and extend as far as thealignment module2, behind which they are connected. In fact, there are threestiffening cables41 distributed uniformly around the circumference for a balanced transmission of the force. Thestiffening cables41 slide inducts42 behind theimmobilisation module6, extending as far as atension mechanism43 comprising adistribution plate44 to which the stripped ends of thestiffening cables41 are attached, ascrew45 at the end of which thedistribution plate44 is fixed, anut46 fitted on thescrew45 and amotor47 making thenut46 turn driven by a pulley andbelt transmission48; thescrew45 slides pulling thedistribution plate44 with it so as to pull thealignment module2 backwards. But if theimmobilisation module6 is held on the pipe by the expandedpins26, it will remain immobile, theother modules2 to5 will move closer to it and the train will contract, until the maleconical surfaces39 penetrate into the femaleconical surfaces40 such that theconsecutive modules2 to6 join together forming a single compact high strength robot element, particularly incapable of bending. When thestiffening cables41 are released, thesprings38 can relax and the train then becomes flexible once again. In a variant not shown, a cable tensioning device is installed onboard.
• We will now describe FIG. 5 and the[0024]alignment module2 of therobot1 in the pipework. It comprises aconical head50 at the front connected to amain body51 through abellows52 and containing amotor53, theshaft54 of which rotates aball screw55 housed in themain body51 through a doubleuniversal joint56 that surrounds thebellows52. Anut49 driven by theball screw55 on the centre line of the ball screw drives a complex shapedcam57 that occupies most of themain body51. It comprises mainoblique tracks58 to control the expansion of theclamping pins59 similar to the pins (26) described for theimmobilisation module6, secondaryoblique tracks60 to control the expansion ofconnection pins61 to thenext module3, and ashoulder62 at the back to control the backwards displacement of anenclosure skin63 carryingpins59 along themain body51. This displacement is directed againstsprings64 fixed to amain enclosure65 of themain body51 and that push theenclosure skin63 forwards; as a reminder, note theother springs66 and67 that pullpins59 and61 towards the inside of themain body51 and aspring68 that pulls thecam57 forwards. The advantage of this innovative assembly can easily be understood with reference to FIG. 6; thepins59 expand and enter into a groove R around the edge of a forward portion A of the pipework. This groove R marks the progress ofrobot1 in the pipework, indicating a stop position at which work can be done. However, the front portion A is not necessarily joined to the rear portion B of the pipework if the work to be done is to weld the joint J between them.
• Therefore, the first effect of a displacement of the[0025]cam57 is to immobilise themain body5 of thealignment module2 in the forward portion A of the pipework and on thetool module3 by extending thepins59 and61; theshoulder stop62 on theenclosure skin63 then pushes the enclosure skin, thepins59 and finally the front portion A until it touches the rear portion B. The joint J is then formed in front of thetool module3 that can begin to work. Therobot1 can thus be used to assemble a complete line of pipes from the inside. The bellows52 and the ball joint56 are sufficiently flexible so that theconical head50 can be engaged in the badly positioned forward pipework A, that can then be straightened by thecam57 mechanism.
• In other applications, the[0026]pins59 are only used to immobilise the train ofmodules2 to6 inside the pipework, and themodule3 tool may be a grinding wheel or a knife or a sensor to perform various types of inspections or machining on the joint J, or to cut it; thealignment module2 then holds the forward portion of the pipework A on the other side of the cut; normally, there is no need to worry about a misalignment in the pipework due to internal stresses at the cut at joint J, since the stiffness of the assembly of the train ofmodules3 and their fixity is not sufficient to prevent all deformation of therobot1.
• Another aspect of the invention, also present on the[0027]alignment module2, will now be described with reference to FIG. 7. This aspect relates to the need to control loosening ofpins59 and61 even if there is a failure in thecontrol motor53 of thecam57, or for any other reason. A manual command using acable70 parallel to thestiffening cables41 is then provided, this cable projecting backwards from the pipework like the stiffening cables. The end of thecable70 is wound in aloop71 around asafety ring72 that holds amobile ring77 in place close to ashoulder73 at the end of themain body51, despite the action ofsprings78 compressed between theshoulder73 and themobile ring77.
• However, a fairly strong tension on the[0028]cable70 is sufficient to tear thesafety ring72 out of the groove of themain body51 that held it in place, which releases themobile ring77 that thesprings78 push backwards. It releases apin75 that fixes a fixedring74 attached to the ball screw in rotation to the output shaft from universal joint56; aspring76 ejects thepin75 and breaks the connection between theball screw55 of themotor53; thespring68 can then expand and push thecam57 forwards due to the reversibility of the transmission between theball screw55 and thenut56; and thesprings66 and67 make thepins59 and61 retract.
• A similar device is provided for the other tightening pins. Returning to FIG. 3, it can be seen that there is one for the[0029]immobilisation module6; acable78 similar tocable70 terminates in aloop79 around asafety ring80 so that the safety ring is torn off when it is pulled, which releases thesupport plate29 carrying themotors28 from anose81 fixed to theenclosure25 of the module.Springs83, previously compressed between thecarrier plate29 and thedistribution plates84 fixed to theenclosure25, then expand to push thesupport plate29 backwards so as to make thecams31 withdraw. The relaxation ofsprings82 placed between theenclosure25 and thepins26 retracts the pins and releases the robot.
• FIGS. 8 and 9 show that other immobilisation means for the modules could be used, and particularly[0030]shape memory pads85 that can be in the form of discontinuous hoops around the different modules. A shape memory alloy part has the special feature that it can take on two different shapes by changing its metallurgical structure at a transition temperature, and return to the shape that was imposed on it when its temperature increases to above the transition temperature in a preliminary manufacturing step. In this case, thepads85 tend to straighten above the transition temperature, and their ends are trapped in contact with the inside face of the pipework. At the same time, their ends remain in thegrooves86 in the modules, which holds them firmly in place. Electrical power supplies, not shown, increase the temperature of thepads85. This system has the advantage that cutting off the electrical current necessarily brings thepads85 back to their initial shape and releases the module train, and the release cable systems described with reference to FIG. 7 become unnecessary. However, FIG. 9 suggests that it is useful to hold the immobilisation pins59 of thealignment module2 that are also useful as positioning references in the groove R of the pipework for all tasks in which the robot has to be stopped at a specific location.
• Obviously, all types of tools can be used; the robot was developed specifically to be capable of performing processes that involve five operations on the pipework, namely cutting, knurling, spot welding, welding and ultrasound inspection. Five similar module trains can advantageously be used, in which the[0031]tool module3 is different in each train. As can be seen in FIG. 10, thetrains1ato1emay be suspended in a circle from adrum86 byindependent advance mechanisms87 lowered in sequence into the line of pipework to be treated after rotation of thedrum86 that rotates on abase88. For example, it would be possible to treat several lines in nuclear power station steam generators that comprise a large number of parallel pipework lines to be treated, with a phase offset for each line, and pushing several module trains into different lines simultaneously.
• FIGS. 11A and 11B show that the[0032]tool modules3 usually include twomotors91 and92 on each side of a tool93 (in this case a cutter that could be replaced by a circular grinding wheel); the first of these motors rotates thetool93 around its axis through auniversal joint94, and the second makes acylindrical casing95 rotate outside aslit96 from which thetool93 projects, about its axis by agear97. Thetool93 is at the end of alever98 that pivots about aneccentric axis99 in thecasing95 and that is pushed by alinkage mechanism100 withscrew control101 activated by athird motor102 and a connectinggear103, and arocker arm104, the opposite ends of which are articulated to thelever98 and to agland105 engaged in thescrew101; furthermore, thescrew101 reaches theshaft99. Therefore, movements of the motor change the distance between thegland105 and theshaft99 and the angle of thelever98 and therocker arm104, which makes the rocker arm rotate and extend and retracttool93 before and after its work on a pipework joint.
• Circular joints can be machined by a combination of the rotation movement of the[0033]tool93, the exit movement of thetool93 and the rotation movement of thecasing95. We will not discuss these machines for machining inside a pipework any further, some of which have already been designed, but we will simply mention once again that thecasing95 extends between two half-enclosures106 and107 of thetool module3, which come closer to each other when thesprings38 are compressed until they come into contact with thecasing95 while allowing the casing to rotate.Complementary springs108 separate the two half-enclosures106 and107 when thesprings38 are released.

Claims (12)

1. Robot free to slide inside pipework or another narrow passage, composed of a train of modules (2 to6,10) connected by flexible links (38), characterised in that it comprises means of fixing (41) modules to each other to stiffen the train.

2. Mobile robot according toclaim 1, characterised in that at least some of the modules comprise means (26,59,85) of achieving fixity in the passage.

3. Mobile robot according toclaim 2, characterised in that the immobilisation means consist of the pins activated by sloping cam surfaces (57) sliding axially in the modules.

4. Mobile robot according toclaim 3, characterised in that the cam surfaces have two different slopes including a first steeper slope (34) acting firstly on the pins, and a second shallower slope (35).

5. Mobile robot according toclaim 2, characterised in that it comprises positioning means (59) in a groove in the passage.

6. Mobile robot according toclaim 5, characterised in that one of the modules is provided with means (59,62,63,66) of fixing two consecutive portions of pipework.

7. Mobile robot according toclaim 6, characterised in that the positioning means and the fixing means comprise one of the immobilisation means (59) fitted on an axially mobile portion (63) of the module, and in that the fixing means also comprise a cam surface (62) pushing the axially mobile portion.

8. Mobile robot according toclaim 2, characterised in that the immobilisation means comprise shape memory pads (85).

9. Mobile robot according toclaim 1, characterised in that the module fixing means comprise at least one pulling cable (41), attached to one of the head modules (2), and opposing propulsion means (7,10) located on one of the tail modules (6,10).

10. Mobile robot according toclaim 1, characterised in that the modules are connected together by springs (38) compressed by the fixing means (41).

11. Mobile robot according toclaim 1, characterised in that the modules are provided with complementary conical engagement surfaces (39,40).

12. Mobile robot according toclaim 2, characterised in that it comprises manual safety mechanisms to release the immobilisation means, comprising an activation cable and return springs acting on the immobilisation means.

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