IL34528A - Method and apparatus for optical alignment of industrial equipment - Google Patents

Description

METHOD AND APPARATUS FOR OPTICAL ALIGNMENT OF INDUSTRIAL EQUIPMENT* This invention relates to methods and apparatus for optically aligning machinery, and more particularly, to a method and measuring devices used for identifying with precision, the distances which various points on machines connected in a kinematic train shift during the operation of such machines.

Brief Description of the Prior Art.

One of the most difficult problems in the alignment of a kinematic train of machines is knowing the final alignment after the machines are hot. The problem of aligning the shafts properly is successfully done while the machines are cold by mounting indicators between the shaft ends, with the inner couplings removed and rotating one shaft with respect to another. This method will at least determine if the shaft ends are in the same vertical and horizontal plane; however, the system presents difficulties in determining if the axis of the shafts are in the same vertical and horizontal plane. One reason for this is that the coupling diameters are fairly small in comparison to the total rest of the machine. For example, the coupling diameter could be between 4 to 6 inches while the rest of the machine may be as much as 8 to 15 feet. Therefore, an extremely small error in determining proper alignment of the couplings may still result in an extremely large error in the actual alignment of the axis of the shaft.

An article in the December 1956 issue of Power Magazine on page 117, titled "Telescope - Mirror Alignment Method", by Herman Schultz, describes a method for alignment of a train of machines such as turbine generator units using a telescope in conjunction with a plurality of mirrors. This system, however, has grave problems so far as accuracy is concerned. Any slight tilt in the position of the mirror will cause a large error in the reading. The magnitude of the error, of course, depend upon the distances involved.

In all alignment systems it is necessary to remove the alignment equipment and at some future time replace the equipment to recheck the system. It is important under these conditions to be able to compare these readings over an extended period of time. Any positioning errors that can-not be absolutely accounted for will result in erroneous alignment information. Furthermore, the system disclosed in Power is successful only for vertical alignment changes. It is virtually impossible to conceive a successful method for utilizing the principles or teachings in this article for horizontal changes in equipment alignment.

Clark Equipment Company devised a system for optically aligning a kinematic train by welding to opposite ends of each machine housing, a pair of one- inch angle irons, one of which was mounted substantially in line with the horizontal axis and the remaining angle iron was mounted in line with the vertical axis of the bearing and at each end of the machine housing. The angle iron extended beyond the machine housing sufficiently to permit visual access to the end of the angle iron. On the end of each piece of angle iron was welded or rivited a scale. A transit was then set up in position by mounting it to a platform affixed to the housing of a machine. Readings were then taken on the movement of each piece of angle iron at each horizontal and vertical location on the housings of the machine. The system was unsuccessful for several reasons. First, since the transit was mounted on the housing of the machine the vibration of the machine made the reading of the transit extremely difficult. Second, it was virtually impossible to calculate the expansion of the machine housing, the expansion of the angle iron, and the expansion of the scale, all of which were different and each unknown. Third, any slight accidental movement of the angle iron rendered the system inoperative. For example, if a worker in the area should accidentally bump the angle iron, the reading would be changed by several thousandths causing the machine, when positioned according to the erroneous readings to vibrate excessively. One extreme problem with the Clark Equipment system was that the angle iron could be very slightly moved and this slight movement was impossible to detect by the engineer. If the angle iron was moved sufficiently to be bent, of course, then the reading position could no longer be utilized. During the installation of a train, of machines using^ the Clark system several of the points became unusable due to obvious bending of the angle iron by workers around the machine. The system never proved out and was eventually discarded.

A further problem with the Clark system was that once the engineers left, the angle irons were often used for foot and hand holds by the workers in the area who needed access to the top of the machines, thus totally destroying the effectiveness of these points as a comparison at a later date.

Brief Description of the Present Invention In the method of alignment of a train of drivingly interconnected machines as practiced in accordance with the present invention, reference points are first established on the machines in the train to permit measurements to be made between these points and lines of sight established adjacent the machinery. The measurements are to be made in a horizontal direction to evaluate horizontal alignment of the machines in the train, and usually it will also be desirable to take measurements in a vertical plane to evaluate the vertical alignment of the machines. The establishment of the reference points is preferably effected by securing tooling balls at selected locations on the machinery.

An optical sighting instrument is then positioned adjacent the machinery in the train on a stable supporting platform or base. This instrument is then used to optically establish a reference line of sight extending along side of (or over) the train of machinery. Then, while the machinery is in a cold or non-operating state, the termperature of the machinery and the ambient temperature are measured. The shortest distances from the reference line of sight to the several reference points are then measured. These measurements are made along lines extending normal to the line of sight between this line and the several reference points.

The initial set of- such measurements is made while the machinery is in the cold, inoperative status. At this time the extent to which the several machinery units are aligned (or misaligned) is known, as a result of alignment measure-ments made using known millwright procedures. The initial "cold" measurements made in accordance with the present invention are thus made from units of machinery which occupy a known alignment relationship to each other at this time.

After the set of "cold" readings has been obtained in the manner described, the machinery is operated and is thus subjected to the vibrational and thermal stresses which are developed. Due to these forces, the units of machinery in the kinematic train will frequently be caused to drift or move out of alignment to a degree such that undesirable distorting forces are developed in the interconnecting shafting and transmitted to bearings, rotors and the like so that these elements are ultimately damaged and fail. Previously, the most widely used method of evaluating the extent to which such operating misalignment occurred was simply to attempt to mathematically calculate the effect of thermal expansion of the machinery units in the kinematic train, basing such calculations upon the known thermal expansion properties of the materials of construction of the machinery, and the estimated operating and environmental temperatures. This method did not take into account vibrational stresses, steam pipe expansion, and other acting forces, and was seldom more than a rough approximation of what might be expected in the way of realigning shifts in the positions of the units in the train.

Using the method of the present invention, the change in alignment occurring during operation is actually measured. Thus, while the machinery is hot and in operation, a second set of measurements are made from the same reference points on the machinery to an optically established, reference line of sight. There are also obtained at this time, measurements of the temperature of the machinery and of the ambient environment. The set of hot measurements is then corrected as may be required to compensate for thermal expansion of the measuring apparatus, and for thermal expansion of the machinery which causes the reference points to be displaced from the central longitudinal axes of the machinery units on which the reference points are located. These corrected hot measurements are then compared with the set of cold measurements in a manner to obtain a convergence factor which is used to correct the "hot" line back to the "cold" line position, and then evaluating the extent to which the units in the train have moved as a result of operation.

The accuracy with which the described measurements are made is extremely important, since the development of a few thousandths of an inch misalignment between machines interconnected by shafting can result in early failure of bearings and other elements of the apparatus. To the end of more accurately measuring the normal distances between the line of sight and the reference points, certain apparatus has been conceived and developed specifically for this purpose. This apparatus may be generally described as functioning to support, and facilitate the positioning of, a commercially available optical scale so that it may be more accurately and flexibly utilized. Broadly described, the apparatus comprises an elongated scale holder shaft which has an " v elongated, scale-receiving slot extending along a portion of its length for receiving the optical scale, means for securing the scale to the shaft, and a contact tip connected to one end of the shaft for contacting a reference point on the machinery. The apparatus may further include structure for supporting the scale holder shaft in selected positions in which the optical scale intersects the reference line of sight while extending along a line normal to the line of sight and containing the reference point. This supporting structure includes a vertical standard having a clamping device pivotally mounted thereon for clamping the scale holder shaft, or an appendage thereof, indesired position* A horizontal stabilizer rod is also provided which can be secured at one end to a point of support, and then extended, outwardly in a generally horizontal direction to permit a second clamping device to be used to connect the stabilizer rod to the scale holder shaft, or to an appendage thereof.

The invention will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is a plan view of a kinematic train of machinery units illustrating a method for checking or evaluating the alignment of the machinery units; Figure 2 is a cross section of a bearing and shaft illustrating in particular the preferred mounting of tooling balls; Figure 3 is a schematic plot of the two sets of measurements obtained in the alignment of the kinematic train in both the horizontal and vertical planes during cold and hot conditions; Figure is a partial plot of a pair of particularly misaligned shafts; Figure 4 is a cross section taken through line 4 - 4 of Figure 6; Figure 4a is a cross section of Figure 6 taken through the section labelled 4a - 4a; Figure 5 is a sectional view taken along line 5 - 5 of Figure 6; r Figure 6 is a partially sectional, partially elevational view of a preferred embodiment of a scale holder device constructed in accordance with the invention, and depicting a scale mounted in the device, and a viewing box and compound spirit level attached to the scale holder device; Figures 6a and 6b show in plan and side elevation a means for attaching the end of the device shown in Figure 6 to a tooling ball and retaining it against the tooling ballwhen the apparatus is in a horizontal position; Figure 7 is a perspective view of a base plate utilized with the vertical standard section shown in Figure 9; Figure 8 is a perspective view illustrating the manner in which the scale holder device is utilized in conjunction with apparatus for supporting the scale holder device in certain preselected positions relative to machinery to be aligned in a kinematic train; Figure 9 is a side elevation view of a section of a vertical standard utilized in the scale holder supporting apparatus depicted in Figure 8; Figure 10 is a schematic illustration of the manner in which certain laser apparatus is utilized in the practice of the method of the invention; Figure 11 is a schematic illustration of the method for using the center head; and Figure 12 is a front elevation view of the center head apparatus.

In referring to the structure shown in the drawings, lead lines having arrowheads are used to designate broad structural combinations. Lead lines not having arrowheads are used in referring to individual structural elements.

The measuring apparatus to be described is utilized in the method of the invention for checking or evaluating the optical alignment of a plurality of machinery units which are drivingly interconnected in a kinamatic train. For example, such a train of machinery may include compressors and turbines which are interconnected through a coupling between input and outut individual mac inery units in such train be maintained /ithin certain alignment tolerances, since misalignment or angulation of one unit with respect to another in the train imposes destructive stresses upon the coupling, shafting, bearings and the like.

As has been previously indicated, it is presently possible, and is the practice, to obtain alignment measurements when the machinery is in a cold inoperative state by; taking so-called dial indicator readings (usually performed by millwrights), and from these readings determining any offset of one unit which might exist with respect to another The dial indicator readings also permit determination of any angulation of the axes or rotation of the shafts of adjacent units. The same method cannot be used, however, to measure or evaluate any shifting or change of position of the units in the train at a time when these units are heated and operating. The method of the present invention allows identification of the extent of change in the relative locations of the several units which has occurred during operation, so that any misalignment which occurs as a result of operation can be recognized and corrected.

In FIGURE 1 of the drawings, the relationship of the kinematic train, transit instrument, bench marks and line is of sight is illustrated. Thus, there here shown a kinematic train of machines which includes a high speed/ Compressor 21 which has an output shaft 22 connected through suitable coupling 3 to the input shaft 2 of a gear box 25· The outpu ted through a shaft 26 to a shaft 27 of/ compressor 2- by means . 28 2¾ of, a coupling ·Θ9 The output of compressor 2-3- comprises a shaft 30 which is connected to a shaft 31 through a coupling 3 to .a., turbine 33· The compressor 21 has secured on each end on the bearing (as explained in FIGURE 2) one or more tooling balls at each bearing of the machine; for example, tooling balls a and b. The gear box 25 has mounted thereon a tooling ball c and a tooling ball d which is as nearly axially in line with shaft 2k as possible. Compressor 26- has mounted thereon tooling balls e and f while turbine 33 has mounted thereon a pair of tooling balls g and h.A tooling ball is a highly accurately machined ball which is mounted on a tool for purposes of accurately measuring the location of In the practice of the method of the invention, see t FIGURE 2, the physical environment of the kinematic train which is to be checked for alignment is first observed to determine where reference points (a - h for example) for taking certain measurements can best be established on the •several machinery units in the train, and also where a reference line of sight 16-may be optically established so as to extend alongside of, and substantially parallel to, the kinematic train with free and unobstructed access to the reference points. In other words, the reference points a - h and the line of sight ¾&· must be located in such a way relative to each other that distance measurements can be made between the reference points and the line of sight along lines which extend normal or 90° to the lihe of sight.

Referring to FIGURE 2, it is desirable in the establishment of reference points or. the machinery, units in the kinematic train to place these reference points as near to the center line of the shafting of the machinery as possible, and also to establish the reference points in locations which are accessible to the measuring apparatus which is utilized in the method, this being constituted by the scale holder TO De, devices e¾d o ic al—sa a-le-s--i¾we-iftoa¾-o-se described. It is also best to place the reference points on the lower shell of the machine, so that maintenance requiring removal of the upper housing does not disturb the* location of the said points. We have determined that the best reference points are constituted by small spherical tooling balls 10 and 11 set permanently into the lower bearing housing 12 of the machinery at locations which are substantially in horizontal alignment with the axis of rotation of the shafting 15 and which are located as near to this axis as physically possible. It is, moreover, desirable to have at least two of the reference points a or b of FIGURE 1 located adjacent opposite ends of each unit of machinery, and separated by the maximum linear distance possible and with the desirability o 'having at least two reference points located on each of the units.

In considering where the line of sight i£-should be established, it is borne ir. mind that this line of sight is ^instrument e» . theodolite for^ established with a transit /for purposes of making certain horizontal measurements, and with a tilting level instrument for obtaining certain vertical measurements where both horizontal alignment and vertical alignment along the train are to be investigated. Considering first the horizontal alignment procedure, it is necessary that a stable base platform^ l^ be located for setting up the transit 15 for ■ establishing the reference line of . sigh -ie. This base for ion the ground( the transit will, of necessity, be o fset /to one side of the train, and must be located so that a clear line of sight can be extended substantially parallel to the line along which the train extends, or more specifically, the line along which the axes of rotation of the shafts involved may extend.

It is, moreover, desirable, that the base for supporting the transit 15 be located so that the line of sight from the telescope of the transit need not be extended more than about thirty feet in each direction from the transit in order to reach to the opposite ends of the kinematic train. In some instances, this desideratum will dictate that the transit be set up about midway of the kinematic train, and in other situations where the train is relatively short, the transit may be set up at either end of the train. The instrument of the transit is then leveled and cross-leveled by adjustments provided in the conventional transit apparatus.

In the next step of the procedure, the temperature of each machinery unit is measured by any suitable means and the ambient or surrounding atmospheric temperature is also measured. These measurements of temperature are taken at a time when the machinery and the train is cold and in the nonoperating state. The measurements of temperature on the machinery units are taken as near to the several reference points as possible, and, with the ambient temperature, are noted for subsequent usage in a manner hereinafter described.

It may be pointed out that .the exact location of the platform . legs 17 of ,the transit on the 14 or supporting structure is carefully noted at this tine, since it will be desirable at a subsequent point in the procedure to return the transit as nearly as possible to the same location on the base ~. , . . platform structure. It should also oe notea that the Da e-ot ue→y¾y 14 which supports the transit should be as free from vibrational disturbance as possible.

With the transit thus positioned, and the temperature measurements taken, a clear line of sight 18 is then established as nearly parallel to the axis of rotation of the shafts along the kinematic train as is possible by visual estimation. Then, either at this time or subsequently, two aligned bench marks 19 and 20 are established on the line of sight by ait- on the ground suitable scribing structure which/is in the line of sight, or by placing suitably scribed target-type bench marks on the line of sight. The bench marks must also be located on a stable structure, and must be relatively free from vibrational disturbance. In the accuracies that are involved in aligning a train of machines, movement of a bench mak by a few thousandths of an inch will cause misalignment or apparent misalignment of the train of machines. However, it is virtually impossible to establish an accurate set of bench marks, as it is obvious that heat, cold, wind, vibration, earth movements, settling, and any of a myriad of additional natural factors will cause a bench mark, regardless of its solidity, to move by a few thousandths of an inch. These errors cannot be detected and accounted for; therefore, once the "cold" line of sight 18 has been established one piece of equipment on the train of machines is selected as the base unit and all future measurements are made relative to movement around the base unit. In practice the machine with the longest distance between tooling balls at each end of the machine is selected as the base unit and in train of machines illustrated the medium speed compressor 29 is selected. The measurements are then made by placing against the tooling ball a piece of measuring apparatus as shown is Figures 4 to 6 and which essentially comprises a rigid rod 74, a tooling ball mating socket 77 and a scale 106. e^&etttilaJLJLj-c^ rAses ■¾ rigid shaft Q, ooling..b ll described in particularity at a latter portion of this 74- application. The measuring rod /is placed against the tooling ball and horizontal measurements are taken. It is absolutely necessary that the scale face be normal to the line of sight IS. " Thus, the rod must be moved pack and forth to and away from the transit until the proper positioning is ascertained. A simplified version, of course, will be when shortest distance on the scale is measured from the tooling ball to the line of sight 18. The rod must also be horizontal and for this purpose a good bubble level will suffice. I&, the base unit, then the readings on/ tooling balls e and f will, be determined and these readings will, in the future, be used to establish "hot^_i theTine of sight. All of the remaining readings are then taken in similar manner at toolihg balls a through h.

Special equipment has been invented to assist in determining when the measuring rods are normal to the line of sight.

Such equipment is completely described in FIGURES 5 and 6 and will be subsequently described in detail.

Once the horizontal cold readings are taken the vertical readings are taken in like manner, the only exception being that a tilting level is used rather than a transit. Once all the vertical and horizontal readings have been recorded, and verified by resetting the readings untill less than a two-thousandths error is established by the succeeding readings, the machinery is the energized and heated to its normal operating temperature. This implies that the turbine v/ill be energized and the compressors will be operated at After the temperature of the equipment has been stabilized and recorded, the transit should be replaced on the base 1½ and the leg positions re-established as close as possible to the location they previously οοο ρίεΰ on base 14. The transit is then realigned With the ben h close as possible. The transit need not be absolutely realigned with the old bench marks for several reasons. First, it viould require an excessive amount of time to^ realign the transit with the old bench narks. Second, there is no assurance that the bench marks have not moved; therefore, even if the transit was perfectly realigned it may not have l or "hot'> the new/line of sight coincide with the old or priginal 'cold line of sight 18. The measuring rods are then placed successively on tooling balls e and f and the distance from new 3 these tooling balls to the pjre.&on-t line of sight/ #e¾»-examp-ld ^no -o -o-i-ght ■ 3^ , is determined. If the new distances between tooling balls e and f/is within approximately 50 thousandths of an inch of, the old reading, then the new line of sight 3½ is satisfactory for alignment purposes. Since only relative movement of the* units of the kinematic train can be determined with respect to some fixed point, it is necessary only to determine a line of sight which is parallel to the axis of the shaft of the compressor 2§- which, as previously mentioned, was determined as the base unit.

Thus, a 50 thousandths of an inch error or less will not introduce sufficient error into the system that the high degree of accuracies necessary will be lost. Once zhe dis- i and the line of sight 3 tances between the tooling balls e and f/are determined, calculations are made to connect the present line of sight to the theoretical line of sight 55* for example, which is ■τ~ ' - 16 - . . - ¾Bhe line of sight parallel to the axis of compressor 29. Even if compressor 29 moved, and such is highly likely, we are establishing only relative movement between the units thereby for all practical purposes the calculations will consider the compressor 29 did not move'. Once the calculated line of sight has been established all movement of the remaining units, regardless of their number, will be calculated not from the present line of sight but from the calculated line of sight 35. The measurements both horizontally and vertically are next made on each of the remaining tooling balls a through h in Figure 1 · The procedure for making certain the measuring rod is at right angles to the line of sight is also followed in the new measurements.

Once all the measurements are taken a readout, as shown in Fig0 3, is made for the train of machines. Figure 3 shows diagrammatically thes train of machines illustrated in Figure 1 across the centre of the figure with their various couplings and tooling balls. The readout for the measurements in the horizontal plane is shown above the train of machines while the readout for the measurements in the vertical plane is shown below the train of machines. In both cases the cold readings are shown in solid lines and the hot readings in broken lines. The various measurements are plotted accurately with reference to the calculated line of sight 35 as previously mentioned. In the horizontal readings it should be noted that the cold and the hot readings of the compressor 29 will be identical since both ends of the compressor were used as the base plane. In the vertical, however, it is only necessary to use a single tooling ball. For this purpose tooling ball e was used as the base point, thus at this point it will be noted no movement will be apparent in the hot readings. All other points in the vertical will, of course, move with relationship can accommodate a certain amount of misalignment between shafts. Some couplings, for example, can accommodate up to 20 thousandths of an inch misalignment of the axis of the shafts. An intersection of the type in FIGURE 3a will cause whipping of the coupling and result in early failure of the coupling. None of the units shown in FIGURE 3 is severally misaligned since each is within a few thousandths of an inch of a proper axial alignment. Furthermore, none of the units shows the intersection of the center line of the shafts inside the coupling. Thus, a train of kinematic machines aligned in accordance with FIGURE 3 should operate properly.

It is apparent by viewing FIGURE 3 that each of the machines in the cold alignment is deliberately misaligned in order to accommodate known shifts in the bearings and framework of the equipment as the machine heats. Thus, machines may be considerably out of alignment when cold and in perfect alignment when hot. Most machines are aligned when cold in accordance with manufacturers' specifications since each manufacturer of the individual components in the kinematic train has studied the expansion of the materials, the hearing of the bearings, movement caused by steam pipes attached to the equipment, etc. Taking these predicted movements into consideration, the manufacturer forecasts the position of the shaft once the machine is heated. The equipment described herein and the method set out will with precision determine if the manufacturers predictions and forecasts were correct.

In many instances it has been determined that through an oversight in cooling procedure for the bearings, improperly hung steam pipes and other factors, the machines do not always perform in accordance with the manufacturers· expectations thus severe damage has been alleviated knowing absolutely the precise position of the machines when the system is cold and hot. This system set out has a further advantage over the previous methods in that at any future date the alignment of the equipment can be certified while the equipment is running without the necessity for shutting down the plant. Thus, for example, a natural disturbance such as an earthquake, unexpected settling, etc. may cause questions to arise during the operation of the equipment as to whether or not the equipment is still in proper alignment. The system as previously described can accurately determine if the train of equipment is still in accordance with its previous alignment - all without shutting down the plant to make the determinations.

A preferred embodiment of the scale holder device of the invention is depicted in FIGURES 4-6 and is designated generally by reference numeral 64. As shown in FIGURES -6 the scale holder device 64 'is utilized in he practice of the method of the invention with a viewing box, designated generally by reference numeral 66, and with a compound spirit level,' designated generally by reference numeral 68.

It should be pointed out that the viewing box 66 and compound spirit level device 68 can also be utilized with the scale holder device for purposes of leveling and normalizing as will be hereinafter described when referring to the mode of use of the scale holder devices in the method of the invention. These structural elements fprrn no portion of the present invention, but are merely adjuncts to the use of the apparatus of the invention.

The scale holder device 64 includes a stainless steel \comprisin an abutment or anvil element; 72 extending to a mating bore formed in one end of a metallic rod 7 which is made of a metal having a low coefficient of thermal expansion as hereinafter explained. The contactor tip 7Q further has a head portion 76 attached to the shank 72 , and this head portion is provided with a semi-spheric l recess 77 at its free end for mating contact with a tooling ball reference point as hereinafter described. The shank 7 of the contactor 70 is provided with, a circum erential groove 78 which permits the contactor to be secured in place ih the end of the rod 74 by means of a transverse securing pin 80. The securing pin 80 can be easily removed at such time as it may be desired to renew or replace the contactor 70. It should also be here mentioned that the contactor 70 can be mounted in the rod 7 by other methods, such as by forming a screw thread around shank 72 and screwing this into a threaded bore formed in the end of the rod.

As previously stated, the rod 74 is constructed of a metal having a low coefficient of thermal expansion, and is preferably constructed of MInvarM, (Registered Trade Mark), a nickel alloy manufactured by the Carpenter Steel Company of Reading, Pennsylvania, or "Synthane" (Registered Trade lark) a material comprising a phenolformaldehyde resin having asbestos fibers embedded therein* The rod 74 includes a relatively small diameter cylindrical end portion 82, a relatively large diameter intermediate cylindrical portion 84, a relatively small diameter cylindrical intermediate portion 86, and a semi-cylindrical end extension 88. As best illustrated in Figures 6 and ?, the relatively small diame intermediate portion 86 of the rod 74 extends into a cylindrical bore 90 formed in an elongated, scale receiving shaft designated generally by reference numeral 92» The scale receiving shaft 92 is preferably constructed of aluminum, and in that portion of the shaft which extends beyondthe bored portion receiving the relatively small diameter intermediate portion 86 of the rod 74, had the cross sectional appearance depicted in Figure 4. Thus, the shaft 92, has a semicyclindrical groove 94 formed therein which receives the semi-cylindrical end portion 68 of the rod 74. The shaft 92 is further provided with a pair of substantially parallel side walls, 96 and 98, which are each provided with inwardly extending grooves 100. Adjacent the Beroicylindrical slot 94, the shaft 92 is provided with a pair of opposed scale receiving slots or grooves 102 and 104. Aa optical scale 106 is positioned in the grooves 102 and 104 and over the semicyftindrieal end portion 88 of the rod 74 in a manner hereinafter described.

For the purpose of retaining the rod 74 in its position of insertion in th© shaft 92, a securing pin lOS extends transversely through the shaft, and through a suitable diametric aperture formed in the small diameter intermediate portion 86 of the rod 74 as best illustrated in FIGURE 6.

At its end opposite the end into which the relatively small diameter intermediate portion 86 of the rod 84 is extended, the shaft 92 carries a projecting semicylindrical extension 114 which is preferably formed integrally with the remainder of the shaft. Secured by .suitable pins or screws 116 to the flat upper side of the semicylindrical extension 114 is a semicylindrical top member 118 which is complementary in configuration to the semicylindrical extension 114 nd thus forms a round sross sectional element projectin from the end of the shaft 92, (see Fig. 4a).

The o t-i-Gatr scale 106 is mounted in the scale holder device 64 by removing the top member ll8 from the semi-cylindrical extension 114 and passing the edges of the scale into the slots 102 and 104 formed in the rectangularly cross- ί!_αηά then replacing the member 118f> sectioned portion of the" shaft 2^ -The scale 106 is secured against sliding movement in the slots 102 and 104 by extending a pin (not shown) through a small hole formed in the scale 106 and into a registering hole formed in the semicylindrical extension 83 of the. rod 74. It will be noted that the inner end of the .opti&aj.. scale 106 abuts a shoulder formed on the rod at the location where the relatively; small diameter intermediate cylindrical portion 86 of the rod is joined to the semicylindrical extension 88 thereof.

The scale holder device 64 is constructed in the manner described to reduce to a minimum, the error introduced in scale readings as a result of changes in the thermal environment. In other words , the"Invar' material hereinbefore described of which the rod 74 is preferably constructed has a very low thermal expansion, and the aluminum metal of which the shaft 92 is constructed, while undergoing some elongation and contraction with changes in the thermal environment, minimally affects the locationcof the .opfcLca-l scale 106 during these movements because nof the manner in which the scale is pinned to the "Invar^ rod 74, and the manner pin 108 · in which the shaft 92 is attached by the aogo -- to 86 : the semicylindrical extension Ί·88- of the rod 74, Adjustably positioned along the length of the shaft 92 are the viewing box 66 and the dual spirit level device 68. For sufficiency" of detail in hereinafter describing the method of the present invention, it may be pointed out that the viewing box 66 includes a C-shaped (Fig. 5) channel member 130 /which can be clamped tp the shaft 92 of the scale holder device 64nby means of set screws 132 and 134, and which has secured ito the parallel legs i thereof, a pair of diverging plates 136 and 138. The plates 136 and 138 carry on the opposed or facing surfaces v_extend normal to the linear axis of the graduated indicia on the scale 106 and; thereof, a series of fine parallel lines /which are prefer- holder device 64 and the optical scale 106 which it carries *26- along a line which extends normal to a reference line of sight in the practice of the method of the invention as hereinafter described* The use of the viewing bos in the method of the invention is described in detail in our U.S.A. Patent No. 3650034. Briefly, however, an optical line of sight is established by the use of bench marks and a sighting instrument having a sighting cross-hair. The scale holder device is then placed against a reference point tooling ball on the structure to be optically aligned, and the viewing box is moved along the shaft 92 until the line of sight passes through the viewing box. The scale holder device and viewing box are then pivoted about the reference point tooling ball in a precise level plane until the parallel lines of the viewing box extend parallel to the cross-hair. In this position the scale holder device extends exactly at right angles to the reference line of sight.

The compound spirit level device 68 includes a pair of bubble or spirit levels 140 and 142 which are mounted at right angles to each other on a suitable bracket. The bracket can be clamped to the shaft 92 of the scale holder device 64 by means of a screw and flange assembly which includes a threaded bolt 148 (Fig. 6) which extends through a pair of flanges 150 and 1 2 and functions to draw these flanges toward each other so that the compound spirit level 68 may be clamped to the sides 96 and 98 of the shaft 92. It will be apparent that both the viewing box 66 and the compound spirit level 68 are adjustable in their positioning along the shaft 92» In taking the horizontal measurements, it often times becomes difficult to hold the steel contactor 70 against a tooling ball. If, for example, the end should slip the entire rod may drop striking a hard object, causing severe damage to the rod or contactor 70, thereby rendering the contactor unusable by impairing its accuracy. In order to alleviate this problem a holding mechanism was devised shown in Figures 6a and 6b. The holding mechanism essentially comprises a tubular extension 73 mounted around cylindrical end portion 82 and secured by a clamp 75 which has a thumb screw 77' mounted normally through clamp 75 has mounted normal therethrough a secure screw 8l adapted -to engage a perip eral groove 83.

Groove 83 permits j60o rotation of tubular extension 73· A portion 85 of tubular extension 73 is removed to permit cylindrical portion 32 to fit into tight' places in some machine trains, thus extension 73 does not increase the diameter of the overall rod in the portion pf the rod adjacent the machine housing. It should be noted, however, that a tubular extension 73 extends over a tooling ball 71' and supports the rod against accidental disengagement from tooling ball 71, thereby protecting the end contactor 70.

It should also be noted that cylindrical extension 73 tends to protect end 70 during periods where the rod is being handled or moved against accidental1 damage.

It should be pointed out before( departing from a discission: of the method of the invention that substantially the same general method can be utilized employing a laser apparatus. This arrangement is schematically depicted in .

FIGURE xL- In this figure, there is schematically illustrated a laser beam generator device 165 which directs a laser beam L along a line which extends substantially parallel to the axes of rotation of, the shafts 30 and 31 of the compressor 21 and turbine 33* respectively. The scale holder device 64 is used as previously described. In this 166 instance, however, a movable laser target 455 is movably positioned on the shaft 9 of the scale holder device 6 so' that, by the use of a micrometer, the laser target can be \ shifted in very small increments of distance along the scale holder device. A precise reading of the exact location of the targe.t l66 with respect to the optical scale 106 can be obtained from the micrometer device used to move the target along the shaft.9.2· T e laser target 106 is sensitive to the intensity of he electromagnetic radiation in the laser beam L, and is constructed so that the highest intensit reading is obtained when the highly coherent light beam is exactly centered in a tiny bull's eye of the target. It is ;:.¾hen-. t¾e.,„yarget has , been/moved to this position at which . its readout system indicates that it is nost nearly precisely aligned with the laser bear. L that the scale reading is taken. Due to the high coherency of the light in the laser bean and the sensitivity of the laser target, it is possible with this type of apparatus and instrumentation to obtain very accurate readings of the distance between the reference line of sight and the reference points located on the machinery units in the kinematic train. 7-9 • In FIGURES there is illustrated apparatus used for supporting the scale holder device in a selected position to facilitate the realization of greater accuracy in performing the measuring functions hereinbefore described. V7ith an accuracy of 0.001 inch within the capability of the measuring apparatus described, it is extremely difficult for a person to hold the scale holder device steady enough to avoid introducing errors which destroy this accuracy.

Also, it is occasionally difficult or inconvenient for a person to find sufficient space adjacent the scale holder device to position himself there for the purpose of holding the scale holder device in a measuring position. The supporting apparatus alleviates these di ficulties. 8 · As shown in FIGURE -9-, the supporting apparatus includes an upright or vertical standard structure designated generally by reference numeral 170. A supporting clamp 172 supporting clamp .172, and swivelly receives the upper portion of the vertical standard structure 170. In use, the sv/ivel clamp 17 is clanped to a portion of the scale holder device 64 which is extended 'through this clamp at a right angle to the vertical standard structure 170.

A stabilizer structure may also be used as a portion of the supporting apparatus, and is designated by reference numeral 176 in FIGURE' . The stabilizer structure includes a magnetic retaining element 173, rod sections l80, and a stabilizer clamp 182. The stabilizer clamp l82 is clamped about one of the rod sections 180 at a selected location, and about a portion of the scale holder device 64. Since the vertical standard structure 170, supporting clamp 172 and swivel clamp 174 can be used independently of the staoilizer structure 176, the former structures and their functions will be initially described in detail before discussing further the stabilizer structure.

The vertical standard structure 170 includes a base ■ ^ 7 plate Ιδβ (see FIGURE 6-) which- has secured to the central portion thereof, an upwardly projecting threaded bolt lS8 which carries very fine threads. The vertical standard structure 170 further includes at least one rod section 190 9 of the type illustrated in FIGURE θ. The rod section 190 has a bore 192 formed in one >end thereof which is threaded to receive the threaded bolt l38. Spaced axially from the inner end of the bore 192 is a transverse aperture 194 formed diametrically through the rod section 190. The purpose of the aperture 1 is to permit a short handle bar to be extended through this aperture for the purpose of rotating the rod section 190 about its longitudinal axis, ana thus to screw it up or down on the threaded bolt lS3.

At its end opposite the end in whieh the threaded bore 1 2 is formed, the rod section 190 carries a threaded projection 196 which is of the same diametric size as the bore 192 and as the bolt 186. The threaded projection 196 is provided with threads identical in size and pitch to the threads on the bolt 183, and formed in the bore 192. It should be pointed out that a plural:.ty of the rod sections 190 are ;. provided, and that due to the equal dimensioning of the threaded projections 196 εηά the threaded bore 192 therein, these rod sections can be screwed together to form an 8 elongated member of the type depicted in FIGURE -9* 11 12 Referring to FIGURES i2 and ~~>, method and apparatus for optically aligning a shaft when the shaft is exposed is shown. The apparatus .or performing the alignment is an optical metrology centerhead device and is designated by reference numeral 210. The centerhead device 210 is shown mounted' in an operative position on a shaft 212 with respect to the axis of which, certain optical measurements are to be taken. The centerhead device 210 includes a neck, portion 214 having a pair of diverging legs 210 and 2l8 extending downwardly therefrom and defining between them an angle The legs 2l6 and 2l8 are preferably magnetized. Mounted atop the neck 2i4 is a dial cage 220 which slidingly receives a center "punch 222. The center punc 22 has a sharpened lower end 225, and extends along a line which bisects the angle between the le^s 2l6 and 21o. At its upper end, the center punch 222 has secured thereto a spherically shaped tooling ball 224. Mounted on the front face of the dial cage 220 is a circular graduated dial plate 22o. The dial plate 226 has indicia located around the outer edge thereof with zero readings positioned at the top and bottom of the dial plate in a line which is coplanar with the axis of the center punch 222. There are also 90° readings located on each side of the dial plate 226 and intervening graduations in degrees so that the dial plate can be utilized in a manner hereinafter described. A mercury weighted pointer 228 is pivotally supported on the dial plate 226, so that tie outer end of the pointer will always be located directly below the pivot point of the pointer in a vertical line.

In using the centerhead device 210 of the invention, the device is positioned in contact with a shaft 212 or other member having a curbed outer peripheral surface so that the divergent legs 216 and 218 extend tangentially with respect to the curved surface. In the case of some very large curved peripheral surfaces, 'the legs 216 and 218 may, in actuality, extend parallel to tangents to the curved surface. The centerhead device 210 is then moved around the curbed surface in a circumferential direction with the legs in contact with the curved surface until the mercury weighted pointer 228 points to a particular indicia on the graduated dial plate 226 which is the angle which it is desired to have the axis of the center punch 222 make with respect to a vertical plane extending through the axis of rotation of the shaft, or through the center of curvature of the curbed peripheral surface with which the center punch is in contact. When the centerhead device 210 is in this position, the axis of the center punch 222 will lie along a line which extends at the angle indicated by the pointer 22δ with respect to a vertical plane passed through the axis of the shaft or the center of curvature of the curbed surface.

The manner in which the method of the invention is carried out is schematically illustrated in FIGURE 12.

In this figure, there are shown a motor 230 and a pump 23 which are drivingly interconnected by shafting. Thus, the motor has a shaft 234 which is connected through a coupling 23 to a shaft 2 8 carried by the pump 232.

There is also included in the arrangement, a shaft 240 from the motor 230, and an output shaft 242 from the pump 232.

It is desired to check the alignment of the shafting interconnecting these devices.

At the outset of the process of the invention, an optical line of sight 243 is established at a convenient location above the apparatus which is to be subjected to certain optical measurements used in the alignment procedure. The establishment of the optical line of sight may typically be effected by first establishing a permanent bench mark, and then sighting in on this bench mark with a tilting level instrument. The line of sight should be established as close, and as nearly parallel, to the center line of the shafts 234, 238, 240 and 242 as possible.

Having established the optical line of sight 243, the centerhead device 210 of the invention is next utilized to establish a number of reference points from which measurements may be made to the line of sight. Thus, the center-head device 210 may, for example, first be placed on the upper side of the shaft ∑ o where it will remain by reason of the magnetized characteristic of the divergent legs 216 and 2ΐδ. The centerhead device 210 is moved around the top of the shaft 240 until the mercury weighted pointer 228 points to the zero reading at the bottom of the dial plate 226. When the pointer 228 is thus located, assurance may then be had that the axis of the center punch 222 extends in a vertical line coplanar with the axis of rotation of tire shaft 240. Stated differently, the pointing of the mercury weighted pointer 228 to the zero reading at the bottoir. of the dial plate 226 indicates that the sharpened lower end 2 3 of the center punch 222 is precisely at the high point on the shaft 240.

With the centerhead device 210 thus located, an optical scale device 244 may then be positioned with its lower end resting on the tooling ball 224, and the remainder of the device extending upwardly so that the graduations thereon intersect the optical line of sight 24j. With the optical scale device 244 and the centerhead device 210 in the described positions, the reading of the optical scale device is next obtained by sighting along the line of sight 24j from the tilting level. Notation is made of this measurement, and the centerhead device is then removed from the shaft 240 and moved to the shaft 23 . The procedure described with respect to one shaft 240 is then repeated, so that a reading or measurement is obtained from the line of sight 2 3 to the tooling ball 224 along the optical scale 244. The procedure is then again repeated for the shaft 238 , and for the shaft 242 with the positions of the centerhead device 210 and the optical scale 244 being illustrated at these positions in dashed ..ines.

Having recorded the measurements made in this manner, any misalignment already present between the shafts 2J , 258, 2 0 and 242, or more frequently, the data may be retained and compared with a series of measurements later made when the machinery is in operation and has become heated. By comparing the hot measurements with those obtained when the machinery is not operational and is in a cold state, the amount of drift or movement which the machinery undergoes tending to cause misalignment of the shafts during operation can be ascertained.

Although certain preferred embodiments of the present invention have been herein described in order to provide an example of its construction and steps sufficient for usage by those skilled in the art, it is to be understood that various changes and innovations in the structure described, and in the method discussed, can be effected without departure from the basic principles of the invention. Changes and revisions of this sort which continue to rely on these principles are therefore deemed to be circumscribed by the spirit and scope of the invention. •¾faat io claimed io^

Claims (21)

1. 54¾-8/-ί What we claim is:- 1« Apparatus for measuring distance, said apparatus comprising a rod consisting of a material having a low thermal coefficient of expansion; an abutment or anvil element mounted in one end of said rod; a scale; scale receiving means attached to the other end of said rod in a manner so that axis of the scale receiving means lies in a plane parallel to the axis of said rod, said scale receiving means including an elongated slot, said slot extending longitudinally along a portion of the scale receiving means and slidably and freely receiving said scale therein; and securing means for connecting said scale to said rod for fixing the position of said scale with respect to said abutment or anvil element whereby expansion of said scale receiving means will not affect the position of said scale in its dimensional relationship with the abutment or anvil element mounted in said one end of said rod*

2. Measuring apparatus as claimed in claim 1 including stop means rigidly and permanently secured in said slot at one end thereof for abutting one end of a scale slidingly inserted in said slot.

3. Measuring apparatus as claimed in either one of the preceding claims in which said one end of said rod is axially bored to receive a portion of said abutment or anvil element.

4. · Measuring apparatus as claimed in claim 3» wherein said abutment or anvil element comprises a shaft portion extending into the bore in said rod; and a head on the end of said shaft portion outside said bore and having a concave depression therein for mating contact with a tooling ball.

5. Measuring apparatus as claimed in any one of the preceding claims, wherein said scale receiving means comprises an elongated shaft and said rod is connected to said elongated shaft by a sliding connection structure facilitating thermal expansion of said elongated shaft relative to said rod.

6. Measuring apparatus as claimed in claim 5, wherein said elongated shaft has a bore in one end thereof for receiving a cylindrical portion of said rod.

7. Measuring apparatus as claimed in claim 6, wherein the elongated shaft is connected to the rod by a pin or like connecting means.

8. Measuring apparatus as claimed in claim 5 or 6 having a semi-cylindrical projection projecting from the end of said elongated shaft opposite the end to which said rod' is connected.

9. Measuring apparatus as claimed in claim 8, wherein said projection terminates contiguous to said slot, the end of said slot being closed by a semi-cylindrical member which is removably attached to said semi-cylindrical projection and is complementary thereto.

10. Measuring apparatus as claimed in any one of the preceding claims 5 to 9» wherein said elongated shaft has a semi-cylindrical groove contiguous to a portion of said slot and receiving a semicylindrical portion of said rod, said semicylindrical portion of said rod being connected to said scale by said securing means.

11. · Measuring apparatus as claimed in any one of the preceding claims, wherein said rod is made of a phenolformaldehyde resin having asbestos Sirbers embedded therein.

12. · Measuring apparatus as claimed in any one of the preceding claims and further characterised to include a vertical standard structure; and means connecting said scale receiving means to said vertical standard structure for movement of said scale receiving means about a substantially verticalaxis. 13* Measuring apparatus as claimed in claim 12, wherein said connecting means comprises a supporting clamp secured to said-vertical standard structure in a fixed location therealong; and a swivel clamp resting upon said supporting clamp, clamped upon said scale receiving means and totatable upon said vertical standard structure about a vertical axis.

13. 14· Measuring apparatus as claimed in claim 12 or 13» wherein said vertical standard structure comprises a base plate; a threaded bolt extending upwardly from said base plate; and a plurality of rod sections connected in end-to-end relation and having one of said rod sections connected at one end

14. to said threaded foolt, said rod sections each having a threaded bore in one end, and a threaded projection at its end opposite the end in which said bore is located,

15. · Measuring apparatus as claimed in any one of the preceding claims further characterised to include a stabilizer structure connected to said scale receiving means and comprising elongated rod means; a stabilizer clamp secured to said rod means intermediate its length, and pivotally connected to said scale receiving means; and a retaining element secured to one end of said rod means for retaining said stabilizer structure against the side of a physical structure.;

16. Meamo-appag Measuring apparatus as claimed in any one of the preceding claims having a rigid, linear scale having graduated indicia thereon; and a rigid viewing box connected tosaid shaft, said viewing box having two diverging walls extending outwardly.from said scale, at least one of said walls having a plurality of parallel lines extending normal to the linear axis of said graduated indicia.

17. · Measuring apparatus as claimed in claim 16, wherein said viewing box comprises a C-shaped channel member slidably mounted on said scale receiving means, said channel member having said diverging walls secured thereto; and means for securing said channel member at a desired location on said scale measuring means.

18. · Measuring apparatus as claimed in any of the preceding claims including means on said scale receiving means for indicating when said means is in a vertical position, and when said means is in a horizontal position.

19. Measuring apparatus as claimed in any of the preceding claims having spirit level means having a pair of bubble levels positioned in planes extending at right angles to each other, said spirit level means being mounted on said scale receivingmeans. - -

20. A measuring apparatus substantially as described and as shown in Figures 4 to 6 of the accompanying drawings.

21. A method of optically aligning a train of machines, said method utilizing a measuring apparatus as claimed in any one of the preceding claims and being substantially as herein described with reference to the accompanying drawings. Attorivey for pp icants