LU85509A1 - SELF-CENTERING DEVICE FOR GUIDING A MEASURING INSTRUMENT OR A TOOL RELATING TO AN OBLONG OBJECT - Google Patents

Abstract

1. A self-centring device for guiding a measuring instrument or a tool relative to an elongated object, the device being designed in such a manner that the axis of orientation (11) of said instrument or tool is disposed horizontally and perpendicularly to the axis (8) of the object (1) referred to, which is also horizontal, and comprising : - four tracers (14, 15, 20, 25) which bear pairwise at either side upon said object, the two first tracers (14 and 15) being aligned with the axis of orientation (11) and the two second tracers (20 and 25) being aligned with a vertical axis (12) intersecting the axis of orientation, the device being characterized in that : - the two first tracers (14 and 15) are coupled to a deformable rhombic frame (18) and to a slide-way platform (19) adapted to ensure the lateral guidance of the second tracers (20 and 25), such that the vertical axis (12) intersects the axis of orientation (11) mid-way between the two contact points of the first two tracers (14 and 15), - and that the second two tracers (20 and 25) are coupled via an assembly comprising a pinion, a rack and a slide-way (22, 23, 24) on the one hand, and a similar assembly (28, 30, 34) on the other hand to an oscillating bench (13) adapted to support the first two tracers (14 and 15) as well as the measuring instrument or the tool respectively, such that the axis of orientation (11) intersects the vertical axis (12) mid-way between the contact points of the two second tracers (20 and 25).

Description

f i w ι7 δ ί ‘1/2119 Lx EUROPEAN ATOMIC ENERGY COMMUNITY (EURATOM)

Jean Monnet building, Plateau du Kirchberg} 'B.P. 1907 L - 1019 LUXEMBOURG

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I SELF-CENTERING DEVICE FOR THE

| . GUIDANCE OF A MEASURING INSTRUMENT OR A

S ‘TOOL RELATING TO AN OBLONG OBJECT

I The invention relates to a self-centering device for guiding I of a measuring instrument or a tool relating to an oblong object, fi device designed so that the measurement axis is horizontal and fi perpendicular to the also horizontal axis of the object in question.

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a Such a mechanism is for example applicable, but not exclusively,? ’J to the radiography of tubes whose inside is in charge of inlays it | irregular, in order to restore an image of the internal geometry. These tubes are originally clamped between two points, one of which, driving,

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; allows their rotation. A measuring installation, supported on a trolley,;! moves along a generatrix of the tube. A slow rotation of this s! tube, attached to a correction along a vertical plane of the axis of the • j measuring instrument, allows exploration of the tube to be measured, even * if it has deformations.

i · 'i-:. v ’p In practice, in fact, the tube to be studied does not have an ideal geometry. We can observe, for example, sinusoidal curvatures! along the axis of rotation, joined to deformations of the different i.

f * 1 - sections along a transverse plane. Such irregularities are for | effect of distorting the measurement because, in the absence of adequate corrections, r ~ the axis of the tube, deformed, does not necessarily coincide with the axis of the gamma-ray measuring installation.

- 2 - The invention therefore aims to design a device allowing the axis of the measuring instrument to follow as closely as possible the axis of symmetry. of the tube to be explored, even if it has geometrical deformations compared to an ideal configuration.

This object is achieved, according to the invention, by a device as specified above, which is characterized in that - four probes bear in pairs on either side of said object, the first two of these probes being aligned along the measurement axis and the two seconds being aligned along a vertical axis coinciding with the measurement axis, - the first two feelers are coupled to a deformable diamond and to a slide plate ensuring the lateral guidance of the second feelers of such so that the vertical axis intersects the measurement axis halfway between the two contact points of the two probes, - and that the two second probes are coupled via a pinion-rack-and-runner assembly on the one hand, and a similar assembly on the other hand to an oscillating bench supporting the first two probes as well as the measuring instrument, so that the measuring axis intersects the vertical axis halfway between the points of contact of the two probes.

Thanks to the invention, the measurement axis continuously adjusts to the center of the section being explored, even if the axis of the tube is deformed and even if its sections are irregular in shape.

* Preferably, said assembly is composed of two vertical racks each of which follows the vertical movement of the probe which is coupled to it, and of two pinions each of which meshes with the rack which is relative to it, the axes of the pinions being integral with the oscillating bench and coupled in rotation.

In this case, it is advantageous if the pinion coupling is carried out by means of a toothed belt.

In a preferred embodiment of the invention, the feelers are supported in contact with the periphery of said object by means of jacks - 3 - "·

Preferably, said oscillating bench is supported by pneumatic cylinders balancing the total mass of said bench increased by all * elements which form the whole while allowing its vertical displacement due to the oscillations of the racks.

The invention will be described below in more detail, using the attached drawing.

FIG. 1 represents a schematic view in vertical section of the device according to the invention.

FIG. 2 represents a detail of the device according to FIG. 1 seen according to section A-A of FIG. I. The virtual path of the tube to be explored has been shown there in broken broken lines, since it is not normally visible in this section.

The object to be explored here is a tube 1, the thickness of incrustation 2 of which we want to know by gamma-ray evaluation. This tube is fixed between a driving point 3 ensuring its rotation around the axis 5 and a tailstock 4, the axis 5 constituting the line of conjunction between the points 3 and 4.

The tube 1 is mounted horizontally on a bench on which a longitudinal exploration carriage 10 is supported, supporting an oscillating bench 13 itself secured to the measuring instrument.

The mass of the entire measuring device is balanced by means of mobile supports 6 and 7 (fig. Î).

The oscillating bench 13 can move parallel along the longitudinal axis 5.

In the drawings, there is shown the tube affected by regular bending between these points 3 and 4. For a section considered, such as that visible in FIG. 1, the axis 5 is eccentric relative to the center o of the tube. When the tube is in rotation, the center 8 of the section considered in the tube describes a circc-nférentietle trajectory 9 author eu f {i i [! î | Still referring to Figure 1, we can see a base plate | 10 depicting the carriage of a machine moving parallel to the | »Line between points 3 and 4. This carriage supports the oscillating bench 13, integral with the measuring instrument and horizontal probes 14 and 15.

| In order not to overload the drawing, the measuring instrument was not; represented. We can however consider, by analogy, the axis of this; instrument in coincidence with the axis of the horizontal probes 14 and 15.

It is composed of a gamma source, located in the same alignment as the probe 15, and a gamma developer located in the same alignment as the probe 14. These two probes and, from there, the gamma-ray measurement axis 11, are located along an axis parallel and immutable to the platform of the oscillating bench 13. As described above, the bench! oscillating 13 itself follows the movement of the movable center 8 in its vertical stroke relative to the axis 5.

The two feelers 14 and 15 remain permanently in contact with the genera-ies of the tube 1 by means of a slight pneumatic pressure exerted in two jacks 16 and 17. These two feelers are coupled to a deformable diamond 18, located according to a plane parallel to the oscillating bench 13 and below the latter.

l ·! i '| j The transverse axis of this deformable rhombus provided with slides, guides one! tray 19 comprising openwork of the “Maltese cross” type. This plate I comprises vertical slides allowing the vertical displacement of | ·; two probes 20 and 25, all er. ensuring the simultaneous translation of these.

The schematic representation makes ar-r-arsître the probes 14 and 15. according to their extreme position of offset to the left yes constitutes i i · - the maximum possible travel offered by the machine.

l · |! The probe 20 can move vertically up to the limit generated by contact with the lower generator of the tube, this by pneumatic pushing of a jack 21.

! ! ·! ! - 5 - * 1 Λ \ 'This cylinder, with a similar function for the probe 20 to that of the cylinder 16 for the probe 14, is integral with the carriage 10. Its piston is * secured to a rack 22, the part of which lower extends from a slide 23 engaged at the base of the probe 20. In this way, the latter is supported in its vertical axis 12 by this slide, while being able to move transversely by means of the deformable diamond 18.

The rack 22 meshes with a pinion 24 whose axis is integral with the oscillating bench 13.

By the same means, the probe 25 slides vertically in the slide plate 19, and in alignment with the probe 20 along the vertical axis 12, in permanent contact with the upper generator of the tube 1. The bearing force is generated by an actuator 26 whose function is exactly similar to that of the actuator 21 with respect to the probe 20, but in the opposite direction.

The piston of the jack 26 is integral with a second rack 27 whose lower extension, constituted by a slide 34, secures it with a column 28 responsible for transmitting the vertical movement of the probe 25.

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This column slides vertically in the slide plate 19 which, by means of the deformable diamond 18, allows it to move in translation simultaneously with the probe 20.

î * r t ’ë [i A cylinder 29 is intended to retract the probe 25 in order to release H the central part of the bench, thus allowing the loading and unloading operations of the tube 1.

I.

'The rack 27 meshes with a pinion 30 whose axis is integral Γ with the oscillating bench 13. The two pinions 24 and 30 are coupled by means of a toothed belt 31. Thus, the slightest rotational movement of one of these two gables is immediately transmitted to each other.

i ~ 6 -! | *! Cylinders 32 and 33, mounted on the longitudinal exploration trolley j 10, balance the mass of the whole of the oscillating bench 13 whose vertical movement is subject to the vertical movement of the feelers! 20 and 25.

i f j This device is described below in detail, considering the I three main cases, namely an ideal tube, a curved tube and a tube of deformed section.

In the case of an ideal tube, axis 5 coincides with axis 8. The bench! oscillating 13 adjusts to a level such that the measurement axis 11 intersects the vertical axis 12 midway between the contact points of the feelers 20 and 25 with their respective generatrices on the tube 1, the feelers; 14 and 15 centering the two vertical probes. The four probes are moved by means of the pneumatic cylinders 16, 17, 21 and 26. There can then be seen no displacement of the probes when the tube 1 of ideal geometry rotates around its axis 8 and the carriage 10 moves together. and the bench 13 along the longitudinal axis 5 of the tube 1. The measurement axis 11 always intersects in perfect conditions the axis 8 and the axis 12 between the probes 20 and 25.

In the case of a bent tube, which is shown in the drawings, the rotation of the tube 1 around its end points 3 and 4 means that the center 8 of the tube 1 describes a circumferential trajectory 9 around the axis 5.

! The four probes 14, 15, 20 and 25, which are based on the genera; . trices of the tube, are thus brought to traverse an oscillating movement.

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If we first consider the probes 14 and 15, arranged on - the measurement axis 11, we can see that their movement through the deformable diamond 18 and the guide plate 19 leads the probes 20 and 25 to a position such as the vertical axis 12 of the latter. always intersects the measuring axis 11 equidistant from the points of contact with the probes l ^ t and with the generators at tute 1.

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The same result is verified when the center 8 of the section considered is vertical to the line 5. In this case, the probe 25 moves vertically upwards, simultaneously driving the rack 27, while the probe 20, in moving vertically upward too, simultaneously drives the rack 22. Since the two racks are synchronized, the two pinions 24 and 30 are not rotated and the oscillating bench 13 moves vertically upwards by the same value as the racks 22 and 27. The measurement axis 11 therefore again cuts the vertical axis at the center 8 of the tube 1.

A similar consideration applies when the tube, at a given point in time, bends downwardly. In the intermediate positions traversed during the rotation of the tube 1, one can observe a combined movement of the four probes so that the vertical axis 12 and the measurement axis 11 intersect at each instant at the center 8 of the section considered of the tube 1. The pinions 24 and 30 remain deprived of rotational movement as long as the periphery of the considered section of the tube 1 remains cylindrical.

When the tube has deformations along one or more cross sections, it is necessary to redefine the center 8 of the section or sections considered. For radiographic exploration, the center of the section of the tube 1 is defined by intersection between the axis of the probes 14 and 15 and the axis of the probes 20 and 21, this intersection being carried out midway between the two contact points. of each of the couples of feelers. The probes 14 and 15, then 20 and 25, can then move towards or away from each other. When the probes 14 and 15 are moved in opposite directions, they cause the deformation of the diamond 18, but the probe 20 always remains centered between the two points of contact of the probes 14 and 15. The same remark applies * to the probe 25, coupled to the probe 20 via the slide plate 19.

When a similar deformation occurs vertically, the two racks 22 and 27 no longer move simultaneously in the same direction, as in the previous case, but on the contrary there is an upward movement of one of the racks and a downward movement of the other. In this case, the pinions 22 and 27 are rotated, and, these being integral with the oscillating bench 13, said bench is driven in a vertical movement such that the measurement axis 11 cuts at each instant, as before , center 8 of the section considered.

The mechanism becomes more understandable if we imagine replacing the two pinions 24 and 30 with a single one, interposed between the two racks 22 and 27 acting in parallel. Such a single pinion, integral with the oscillating bench 13, would undergo the same movements as the two pinions 24 and 30 coupled by the belt 31, namely a vertical rectilinear movement, when the two racks move in the same direction and by the same distance, or a rotational movement without vertical displacement, when the two racks move in opposite directions but by an equal distance.

In all other cases, a rotational movement is observed combined with a vertical displacement.

The pinion axis always travels half the sum of the two combined movements of the racks.

The mounting with two pinions 24 and 30 coupled by means of the belt 31 does not change anything in the different cases described above, but, by forcing the belt to a deflection around return pinions, allows the free space necessary for the change and the rotation of the tub e 1.

It should be noted that the invention is not limited to the gamma-graphical measurement of a tube but that it can generally be applied to the exploration or the machining of oblong objects of geometrically shaped unclear.

This type of device can be used for reading this external dimensions by returning the m · · mations · fed by the probes (.

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r I · 1 'It can also be used as a machine for reproducing oblong objects of various shapes.

Another application concerns the marking of a generating line of one! tube or several generating lines.

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Yet another application relates to the welding of two half-shells j, the joint plane of which is not straight.

j) It is also possible to envisage this same device applied to different optical, electrical or ultrasonic measuring devices always on the same type of oblong object.

In the context of the invention, certain details can be envisaged differently. For example, the thrust imparted to the probes through a pneumatic cylinder may as well be replaced by systems of spring thrust, by counterweight, and the balancing cylinders 32 and! 33 can be replaced by a motor or a counterweight.

'1. | ! "

The various pneumatic cylinders can be associated with units L for regulating pressure as well as regulating flow, so much leakage [i.

! than admission. This gives a totally balanced system, per-, putting to play on the support forces of the probes on the tube ’! to explore.

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Claims (5)

1. Self-centering device for guiding a measuring instrument or a tool relating to an oblong object (1), designed so that the measuring axis (11) is horizontal and perpendicular to the axis (8), also horizontal, of the object in question, characterized in that: - four feelers (14, 15, 20, 25) bear in pairs on either side of said object, the first two of these probes (14 and 15) ^ being aligned along the measurement axis (11), and the second two (20 and 25) being aligned along a vertical axis (12) coinciding with the measurement axis, - the first two sensors (14 and 15) are coupled to a deformable diamond (18) and to a slide plate (19) ensuring the lateral guidance of the second feelers (20 and 25) so that the vertical axis intersects the measurement axis at mid-distance between the two contact points of the two probes (14 and 15), - and that the two second probes (20 and 25) are coupled via a pinion-rack assembly re-slide (22, 23, 24) on the one hand, and a similar assembly (28, 30, 34) on the other hand, to an oscillating bench (13) supporting the first two feelers (14 and 15) as well as the measuring instrument, so that the measuring axis (11) intersects the vertical axis (12) midway between the contact points of the two probes (20 and 25). 2. Device according to claim, 1, characterized in that said assembly is composed of two vertical racks (22 and 27) each of which follows the vertical movement of the probe (20 or 25) which is coupled to it, and of two pinions (24 and 30), each of which meshes with the rack (22 or 27) which is relative to them, the axes of the pinions being integral with the oscillating bench (13) and coupled in rotation. 3. Device according to claim 2, characterized in that the coupling of the pinions (24 and 30) is effected by means of a toothed belt (31). ê - 11 - 0 4. Device according to one of claims 1 to 3, characterized in that the feelers (14, 15, 20, 25) bear in contact with the periphery of said object (1) by means of pneumatic cylinders (16 , 17, 21, 26). 5. Device according to one of claims 1 to 4, characterized in that said oscillating bench (13) is supported by pneumatic cylinders (32 and 33) balancing the total mass of said bench increased by all the elements which form it together while allowing its vertical displacement due to the oscillations of the racks (22 and 27). '”- / Λ -j ς' jjr-φ · * uxemn ourg, re j.4 a on. read Jrji r>, \ yj> Jjf u \ S'r