FR2538538A1 - OPTICAL COMPARATOR - Google Patents

Abstract

The invention relates to an optical comparison method and an optical comparator designed more particularly to facilitate the inspection of fillets 12 of cylindrical bosses 9 formed on an object, such as a rotor 3 of a gas turbine. This comparator comprises a support 18 in which a disc 21 is rotatably mounted and which is mounted on the object so that the axis 33 of the disc coincides with that of the boss. The disc carries a projector 73 which projects the image of a wire 97 onto the fillet, the image modified by the fillet configuration being projected by a second lens 112 and mirrors 88, 91 onto an observation screen 94 which intersects the axis 33 and which carries a reference image 121. By rotating the disk around its axis, it is thus possible to successively examine the entire annular fillet. Application to the measurement of welded assemblies. (CF DRAWING IN BOPI)

Description

The present invention relates to comparisons

  optical devices and, more particularly, comparators

  of the type used to measure a radius of curvature.

  When materials are joined together, like two metals when they are welded, we try to avoid the sharp angles at the junction because such angles

  tend to concentrate mechanical stresses and strains

  Instead, the sharp corners are preferably smooth, gently curved, sometimes referred to as fillet. Filleting is used to reduce the concentration of stresses otherwise present in sharp-edged joints. In many applications, dimensions and

  the particular configuration of a holiday is important.

  To determine if a leave has the dimensions and

  correct configuration, a frequently used method

  is to place a reference contour gauge in contact with the fillet, to light a light source on one side of

  the gauge and visually observe the other side for disappointment

  light gaps through gaps between leave and gauge Interstices indicate lack of compliance This review task is time consuming and may become more difficult if holidays are located in

inaccessible positions.

  The present invention aims to achieve a new improved comparator

  to compare a structural configuration to a configura-

reference;

  to create a new and improved optical comparator

  designed to be used for leave examination; and realize a new optical comparator perfec-

  allowing for contactless examination of holidays.

  An embodiment of the invention comprises a

  rotating projector for projecting an image onto

  selected rotation positions of an object to be examined and

  other means of comparing the image, as

  by the object, to a reference image.

  The following description refers to the figures

  attached which respectively represent: Figure 1, an embodiment of the optical comparator of the present invention placed on the top of a gas turbine engine rotor;

  Figure 2 is a schematic side view of cer-

  some of the optical paths of the embodiment of the pre-

  this invention shown in Figure 1;

  Figure 3 is a schematic top view of cer-

  some of the optical paths of the embodiment of the pre-

  this invention shown in Figure 1; 4, a side view of a lens 112 B placed in a different disposition from that occupied by

the objective 112 in FIG.

  FIG. 1 shows a way of realizing

  of the optical comparator of the present invention, this

  the figure also showing part of a rotor 3 of

  gas turbine engine at a stage of manufacture where it includes

  a surface 6 above which extend a number of bosses, some of which have been shown in the figure and designated by references 9A and 9D bosses 9A-9D will be drilled during steps of Subsequent Manufacture to Form Mounting Holes for Other Engine Components Each boss 9 A-9 includes, along its surface 3a, a respective annular fillet 12A-12D in the region of its connection to the engine. surface 6 As shown in Figure 1A, the bosses 9A-9D; as well as other additional bosses 9 E-9 T, are all identical to each other and are uniformly uniform.

gone around a circle.

  In FIG. 1, a set of

  base of the apparatus of the present invention disposed adjacent

  to the bosses 9 A-9 D The basic set includes a

  mobile outer annular port 18 as well as a rotating disk

  tif 21 carried by the support 18 The support 18 comprises a

  groove or annular groove 25 formed in an annular wall

  The outer edge of the disk 21 is fitted in the groove 25 so that the disk is immobilized in position in that it can not be displaced in translation relative to the support 18, although it can freely be done manually turn inside the support 18 around an axis 33 and thus slide its outer edge along

the groove 25.

  A strip 27 made of a low friction plastic material, such as that usually known under the trade name "Teflon", is fastened to at least one of the surfaces of the groove 25 to act as an anti-friction pad between the support 18 and the disc The

  the precision with which the disk 21 fits into the groove

  re 25 is as high as it is economically possible to ensure that the disk 21 rotates about the axis 33

  with as little play and relaxation as it is

  Thus, the disk 21 can rotate about an axis 33 for scanning purposes which will be described later and the

  position of the axis 33 with respect to the bosses 9 A-9 D is de-

  terminated by the position of the support 18.

  There is a series of spaces 36 formed between bosses 9A-9D and a circular wall 39 of rotor 3. This has been more clearly illustrated in FIG. 1A. These spaces -4-36, considered in combination, form a pathway. or circular path, represented by dashed lines 38 in FIGS. 1 and 1A, along which an elongated guide can move, as shown in FIGS. 1 and 1A. The guide 45 is fixed below the -support 18 and the

  The dimensions of the guide 45 are such that it adapts

  between the wall 39 and the bosses 9 A-9 D Fit without play is required to ensure that the guide 45 and

  that the support 18 to which it is attached follow the circular path

  As shown in FIG. 1A, the guide 45 has a notched region A to prevent it from interfering with the scanning of the boss 9 B.

  An indexing device 51A, or device of

  sitionnement, is fixed to the support 18 and comprises an outwardly projecting arm 51 which is rotatably mounted about a pivot 54 so as to be movable up to

  what it occupies in the position shown in broken lines

  pus denoted by the reference 57 This rotation makes it possible to release the indexing device 51 A boss 9 C to allow the displacement of the support 18 along the path

  The protruding arm 51 is preferably

  by a spring 60 so that it normally occupies the position shown in solid lines in Figure 1 The projecting arm 51 carries an indexing block 63 which comprises

  a surface 66 which preferably conforms to the shape of the sur-

  The complementarity between the surface 66 and that of the bosses serves to set up precisely the indexing block 63 when the surface 66 is placed against a boss, such as the boss 9 C. The bosses 9 A-9 D precise positioning of the index block 63, in

  combination with the fact that the distance between the surface.

  66 and the axis 33 of the disk 21 is known to advance

  this means that the axis 33 is located in a predetermined position relative to the boss 9 C which is in contact with the indexing block 63 If the boss 9 B which is the object of the inspection is cylindrical the axis 33 of the disk is then preferably located so as to be coaxial with the central axis (which has not been shown separately) of the boss 9 B If the inspected boss 9 B is not cylindrical, it is then necessary to choose an appropriate position to which the axis 33 must be placed according to the region of the leave 12 B which must be scanned in the manner that will be described

  below The criterion of choice of principle is that the distance

  this between lens or lens 101 and leave 12 B shall

  change as little as possible during the scan to re-

  at least change the focus where the linear image (described later) is projected on the fillet 12 B. Therefore, as shown in Figure 1A, the support 18 is constrained to move along the circular path 38 on a Gas turbine rotor 3 The disk 21 moves with the support 18 and its axis of rotation 33 follows a second circular path 40 which intersects each of the bosses, as described in the previous paragraph. From a certain point of view, if the the disk 21 is considered to be continuously turning while the support 18 follows the

  first circular path 38, a point 40 A of the circular disc

  The indexing means are used to position the axis 33 of the disk.

  selected predetermined positions along the circular path

  40 and these positions are determined by reference to

a surface of a neighboring boss.

  As shown in FIG.

  projection 73 which preferably comprises a light source

  76, which can be obtained under the name Model No. ILK-IV from Olympus Corp. New Hyde Park, New York, USA, is attached to disk 21. projection 73 projects a light beam 82 through an aperture 70 formed in the disk 21 on the fillet 12 B, approximately along the direction * of a radius of the boss 9 B (i.e.

  in the direction of the axis 33) The light beam 82 is

  bent in the form of a reflected beam 85 A towards a first

  first mirror 68, then in the form of a beam 85 B to a second mirror 91 and then in the form of a beam C parallel to the axis 33 (but represented as a radius coinciding with the axis 33) to a frosted glass display screen 94 which intersects the axis 33 and on which a

image 95 is formed.

  An elongate opaque object, such as a wire 97, is stretched across the path of the light beam 82 to intercept a linear portion of the light beam 82 so as to create a linear image in the form of the shadow of the light beam.

  thread 97 The image is focused on the fillet 12 B by an objective

  tif or lens 101 and shown in the form of an image

  102 The shape of the image 102 depends, in part, on the line

  wire 97 with the fillet 12 B Preferably, the wire 97

  is aligned to be coplanar with the axis 33.

  Objective 101 is preferably placed half way

  between wire 97 and leave 12 B and has, preferably,

  this, a focal length equal to half the distance between

  be the thread 97 and the fillet 12 B The shape of the image 102

  on the fillet 12 B from the linear image depends

  also of the form of the leave 12 B This image 102 is

  held in the reflected light beam 85 A and is

  by a second lens or lens 112 * so that

  the image 95 projected on the display screen 94 is in focus.

  The display screen 94 is carried by a mount 115.

  barit 118 is placed on (or near) the display screen.

  chage 94 and it carries a predetermined image 121 The image

  predetermined 121 represents the curved image that would be pro-

  thrown on the display screen 94 by a leave 12 B having a

known curvature.

  The rotation of the disc 21 about its axis 33

  sweeps the linear image along the fillet 12 so -7-

  allow examination of the entire surface of the leave.

  The mirror 91 is preferably disposed above the bos-

  9 B so that the axis of rotation 33 intersects the middle

  Thus, the rotation of the disc 21 results in the rotation of the mirror 91 about the axis 33 so that the image 95 projected on the display screen 94 does not move across the screen. screen 94 but rotates only relative to the support 18 Naturally, the display screen 94 and the template 118, because they are carried by the mount 115,

  rotate with disk 21 so that the rock positions

  relative proportions of image 95 and the template remain unchanged.

  Thus, the user can conveniently compare the image to the predetermined image 121 formed on the template 118 at any time during the rotation of the disk 21 because the image 95 does not move in translation but only in translation. In addition, the user who is likely to be placed on one side of the boss 9 B will be able to examine the parts of the leave located on the side of boss 9 B opposite to the one where it is located, parts that it can not not directly observe because they are hidden from it by the boss 9 B itself The rotation of the display screen 94 (which occurs because of its attachment to the rotary disk 21 by

  115) is not considered to be

  being strictly necessary since the screen 94 provides an imaging surface and the rotation of the imaging surface is not necessary for

  the formation of images However, it is considered that the

  tation of the template is a facility offered to the user

to compare images 95 and 121.

  Figures 2 and 3 show in more detail the geometrical arrangement of the elements described above. Figure 2 is a side view which shows the light beam 82 striking the boss 9 B The angle 130 between the light beam 82 and the surface 6 of FIG. 1 is 790. Preferably, the objective or lens 112 (represented by its outline in solid lines) directs the light reflected by the projection 9 B along a path that intersects this surface 6 (here called a horizontal surface) at an angle 136 of 45 If the distance 141 is equal to the distance 144 (these distances are not shown as equal in FIG. 2), the positioning of the mirror 88 at an angle of 22.50 (angle 145) with respect to a vertical line 147 then results that the light beam 85 B is projected in a direction parallel to the surface 6 towards the second mirror 91 If the angle that this second mirror 91 makes with the disk 21 is 45 ( angle 148), the light beam 85c then propagates parallel to the vertical line 147 towards the screen

display 94.

  FIG. 3 represents a view from above of the embodiment described above. The light beam 82 is

  projected in a normal-direction (that is, perpendicular

  to a tangent; this projection in the case of a

  wise with circular cross-section being in direct

  9 Objective 112 directs the process

  light path 85A so that the path followed by the light beam 85A to the first mirror 88 makes an angle of 450 (angle 151) with the light beam 82 The first mirror 88 returns the light beam 85 B to the

second mirror 91.

  The mirror 88 is placed so that the light beam 85 B is directed towards the axis 33 represented by a point 33 in FIG. 3 Therefore, if the sum of the dimensions 152 and 154 is equal to the dimension 156 and if the angle 157 is a right angle, the angle 161 A is 450 The line 164 is normal to the first mirror 88, which means

  that the sum of the angles 164 A and 164 B is equal to 900

  simple trigonometry in FIG. 3 makes it possible to calculate the value of the angle 164 A which is necessary for

  that the light beam 85 intersects the axis 33.

  9 - The first mirror 88 may be carried by adjusting screws 150 shown in FIGS. 2 and 3, to allow the position of the light beam 85 B to be adjusted. The second mirror 91 and the projection apparatus 73 may be worn. a similar way It is possible that a

  manual operation of mirrors 88 and 91 and the

  73 using the adjusting screws 150 to

  to obtain a correct projection of the image takes less time than the execution of geometric calculations whose conclusions are indicated in the angles represented

in Figures 2 and 3.

  As shown in FIGS. 2 and 3, the focal plane of the objective or lens 112 is represented by a broken line in strong lines 120. The focal plane 120 does not simultaneously contain the upper region 121 A and the lower region 121 B of the 102 of Figure 1 and,

  thus, these regions are focused differently

  tif 1120 One reason for this positioning of the focal plane 120

  is that, in practical practice, limitations of

  badly prevent us from being able to lower

  objective 112 in such a way that it occupies the

  presented by the contour in solid lines 112 A Such a posi-

  would improve the alignment of the upper regions

  and lower 121 A and 121 B with the focal plane 120 (which

  then moved in rotation clockwise

  of a watch) and reduce the difference in focus.

  The recommended means for reducing the difference in focus between the upper and lower regions 121A and 121B, in view of these limitations of space, is to use as a lens 112 a wide-angle lens 112B (shown in FIG. by its outline in phantom in Figures 2 and 3 and its outline in solid lines in Figure 4), such as a magnifying objective of 38 mm, f 4, and to place it as shown The wide angle lens 112 B has this characteristic that - despite the fact that its optical axis 126 (FIG. 4) does not coincide with the light beam 85 A reflected by the fillet 12 B, it can nevertheless be placed as shown in FIG.

  way that its focal plane 128 is approximately copla-

  121A and 121B, thereby reducing the focus difference between these regions. The wide field of view feature of the wide-angle lens 112B assists in capturing the image 102 even if this image is spaced from the optical axis 126 This positioning requires that we rotate

  the wide-angle lens 112 B so that it comes into use

  per position represented by its outline in

  broken in Figure 2 and that it also changes its posi-

  to place it in the position represented by its dashed outline in the vicinity of the tangent

D in Figure 3.

  However, the positioning of the lens 112 B in the vicinity of the tangent 85 D presents a new problem for the image taking due to the specular reflection (as opposed to the diffuse reflection). we consider Figure 3, it is known that an observer looking along the light beam 82 will see a view of the image 102 formed on the leave 12 B different from that seen by an observer looking along the light beam 85 A The first observer will see the image 102 in the form of a straight line and the second observer will see it in the form of a curved line It is also known that an observer looking along the tangent 85 D to the boss 9 B at the location of the image 102 would see image 102 in the exact form of the cross section of the leave 12 B However, in practice,

  if the surface of boss 9 B is specularly reflective

  it's almost impossible to see image 102 in

  looking at the tangent 85 D If the boss 9 B specula-

  reflective stretching is made more reflective of

  diffuse manner, for example by stripping, sanding or applying

  it - cation a coating of a fine powder, such as talc, the image 102 can then be seen by the mirror 88 A next

  a line close to the -tangent 85 D Sprinkling of powder

  talc on a 12 B leave allowed the inventor to posi-

  the optical axis 126 of the wide-angle lens 112 B of FIG. 3 along a line which is not

  defect of the tangent 85 D that of-eight degrees (angle 1900).

  As we know, the correspondence of the image 102 observed

  along line 126 varies, approximately, proportion-

  Thus, since the costimulus of eight degrees does not substantially differ from the cosine of zero degrees, the image viewed along line 126, using talc, does not differ substantially from the image.

  effective 102 of Figure 1 view along the tangent 85 D-

Figure 3.

  So far, the use of an operator has been

  to compare the projected image 95 on the display screen.

  However, this function can be made automatic and it is envisaged for this purpose the use of an optical configuration recognition equipment. This equipment has been schematically represented in FIG. 1 by means of FIG. a camera 155 which captures the image 95 and generates signals which represent it and

  are transmitted to a processing circuit (not shown).

  The predetermined image 121 carried by the template 118 can be generated by trigonometric calculations which

  take into account the curve of the fillet 12 B, the geometric

  this is followed by the various light beams and any magnification introduced by the optical elements, such as the lens 112. However, it is preferred that the template is generated by means of the apparatus of the invention which must be

  actually used according to this last method of general

  of a template, a reference leave is accurately machined.

  (not shown) having the configuration and dimensions

  The reference fillet is scanned in the manner described above and the image is recorded that the reference fillet generates on the display screen 94, for example.

  by photographing it We can then, from the photo-

  graphie, produce the image 121 of the template.

  It should be noted that boss 9 C is a boss

  be the boss being inspected, but that the boss

  The object of the inspection could be in contact with the index block 63 provided that the index block 63

  does not hinder the scanning process described above.

  Thus, the use of a 9 C boss for

  dexterous (ie, indexing boss) while a boss B was subjected to inspection (i.e.

  boss is the inspected boss), but these two bosses can

  can be one boss in some cases.

  The use of tape, such as Teflon tape, has been described to form a bearing surface or bearing surface for disk 21. Of course, other anti-friction devices such as ball bearings can be used.

  In addition, the projection of the im-

  ge 95 is not limited to the projection on the display screen.

  94 but the image 95 can be projected by a projection

  photograhy (not shown) on a ceiling or wall so as to produce a higher magnification if desired In this respect, it is possible that the movement of the apparatus of the invention along the circle 38 of FIG. not desirable so that the apparatus of the invention is then held stationary and that the turbine rotor 3 can then be moved instead to produce between them the relative movement represented by the circle 38, It has thus been described above an invention which provides an optical comparator which makes it possible to compare curved surfaces with a reference configuration and which allows the non-contact measurement of the configuration of connection fades. More particularly, the measurement of the leave-offs of bosses formed on the rotor has been described. a motor at 13 -

gas turbine.

  Although one embodiment has been described

  particular of the invention, it is obvious that it can be

  carry many substitutions and modifications without departing for that from the true spirit nor leave the frame

  of the invention as defined by the claims

nexées. 14 -

Claims (10)

  1 Optical comparator for configuration examination   located at selected rotational positions with respect to an axis (33), characterized in that it comprises: a) projection means (73) rotatably mounted   around an axis (33) to project a first predetermined image   terminated (102) on the rotational positions selected so that they are modified into second images   respective ones (95) according to the configurations located at the   selected rotations; b) focusing means (112, 112 B) for enabling observation of the second images; and   c) display means (94) for receiving cer-   at least second images and to compare them to a reference image (121).   Optical comparator according to claim 1, characterized in that the first predetermined image (102)   is the shadow of an elongated opaque object (97).   Optical comparator for examining an annular surface (12 B) surrounding an axis (33), characterized in that it comprises:   a) means (73) for projecting a light beam   bores (82) on the annular surface; b) means (97) for generating an image in the light beam so that it is projected onto the annular surface; c) a display screen (94) intersecting the axis (33);   d) means (15) for scanning the image along the annular surface; and e) means (112, 112 B) for focusing the image   mentioned in point d) on the display screen.   4 optical comparator according to claim 3, characterized in that the image mentioned in point b) is the shadow of an elongated opaque object (97). Optical comparator for the examination of an annular surface (12). B) surrounding an axis (33), characterized in that it comprises: a) a projector (73) rotatably mounted about the axis (33) for projecting a predetermined image (102) onto selected portions of the surface annular; b) a display screen (94) intersecting the axis; and c) optical processing means (88, 91, 112   or 112 B) rotatably mounted about said axis in a relationship   fixed relative to the rotating projector to receive   a reflection of the image of the annular surface and for   pinpoint the reflection on the display screen in the form   an image (95) that rotates about the axis.   Optical comparator according to claim 5,   characterized in that the predetermined moving image mentions   born in point a) (102) is the shadow of an elongated opaque object (97).   7 Optical comparator for examining leaves (12 A-12 T) formed at the base of bosses (9 A-9 T) formed in a turbine rotor (3), characterized in that it comprises   a) a support (18) having an annular groove   re (25); b) a disc (21) carried by the annular groove and rotatable about an axis (33); c) an anti-friction pad (27) mounted to contact the disc and to reduce frictional forces during disc rotation; d) a guide (45) attached to the support (18) to guide the support; along the bosses; e) indexing means (51 A) for positioning   the axis (33) mentioned in point (b) to a predefined position   born with respect to a first selected boss (9 C); f) projection means (73) attached to the disc (21) for projecting a light beam (82) on the fillet 16 - (12 B) of a second predetermined boss (9 B); g) interceptor means (97) attached to the projection means for intercepting an approximately linear portion of the light beam referred to in f) to generate an image (102) on the fade referred to in f), which image contains information regarding the leave configuration; h) a first lens (101) mounted on the disk   to bring the image mentioned in point (g) to a degree of calation chosen on the leave;   i) a first mirror (88) attached to the disk for re-   view the image and reflect the image as a whole in the direction of the axis (33) mentioned in point b); j) a second mirror (91) fixed to the disk (21) and intersecting the axis (33) mentioned at point b) to receive the image reflected by the first mirror and to reflect the image along the axis; k) display means (94) attached to the disk and intersecting the axis (33) mentioned at point b) to receive the image reflected by the second mirror and to display the received image; 1) a second lens (112) attached to the disk for   put the projected image on the display chosen development focus; and-   (m) reference means (118) placed in the vicinity of   display means to compare the displayed image   mentioned in point (k) to a reference image (121).   Optical comparator according to Claim 7, characterized in that the interception means mentioned   in point g) are constituted by a wire (97).   Optical comparator according to claim 7, characterized in that the second objective (112) mentioned in   point 1) is placed in such a way that -   n) a focal plane (120) of the second objective is   proximally coplanar with the image (102) projected on 17 - leave (12).   Optical comparator according to claim 9, characterized in that the second objective (112 B) mentioned in point 1) is placed in such a way that: o) the optical axis (126) of the second objective (112 B) forms an angle ( 190) less than ten degrees with the tangent (85 D) which intersects the projected image (102) on the leave (12 B).   Optical comparator according to claim 10, characterized in that the second objective mentioned in point 1) is a magnifying magnifying objective of 38 mm, 4.8. 12 A method for optically comparing an annular surface (12 B) surrounding an axis (33), characterized in that it comprises: a) scanning a predetermined image (102) about the axis along the annular surface ; b) sensing a reflection of the predetermined image during the scanning and focusing the reflection so that the reflection: i) appears as an image (95) in the region of the axis; ii) rotates about the axis (33) during the scanning mentioned in point a) 13 Method according to claim 12, characterized in that it comprises, in addition, the step of increasing the diffuse reflection characteristics of the annular surface.   Process according to claim 13, characterized   in that the predetermined image is captured along a   jet (126) at an angle (190) of less than ten degrees   with the tangent (85 D) at the location where the prede-   mine (102) is projected onto the annular surface (12 B).   A method of inspecting a cylindrical object having an axis (33) characterized in that it comprises: 18 - a) projecting a linear image in the direction of the axis and on the object; b) rotating the linear image around the axis and along a surface of the object; i) to a first mirror (88) ii) from the second mirror toward the axis to a second mirror (91), iii) from the second mirror parallel to the axis and to a display screen (94); and d) rotating the first mirror and the second mirror with the linear image to rotate the image (95)   focused on the display screen around the axis.