WO2000023781A1

WO2000023781A1 - Methods and apparatus for measuring and adjusting for shaft misalignment in power equipment

Info

Publication number: WO2000023781A1
Application number: PCT/US1998/022319
Authority: WO
Inventors: John Zatezalo
Original assignee: Alignment Solutions, Inc.
Priority date: 1998-10-22
Filing date: 1998-10-22
Publication date: 2000-04-27
Also published as: AU1273099A

Abstract

A shaft alignment tool (10) and method includes a spacer member (16) adapted to extend from the axis of rotation and face of one shaft to the axis fo rotation on the face of another shaft; a radially extending pair of arms (26 & 28) extend from the spacer member and each arm carries a dial indicator device (38 & 40) to provide a measurement of tilt of the respective shaft's face relative to the axis of the spacer member; a method of calculating the adjustment of the support structure for one of the shafts to bring that shaft into axial alignement with the other shaft if provided.

Description

METHODS AND APPARATUS FOR MEASURING AND ADJUSTING FOR SHAFT MISALIGNMENT IN POWER EQUIPMENT

Field of the Invention

The present invention relates to an apparatus and method for determining the degree of misalignment, if any, between rotatable shafts to enable a worker to correct any misalignment detected between the shafts.

Background of the Invention

In almost every use of a power unit having a rotary output, it is essential for proper operation that the drive shaft of the power plant be properly aligned with the driven shaft to avoid damage to these implements and to any associated machinery. Frequently, however, workers who have charge of the power plant are not highly skilled and often lack the ability to carefully measure misalignment between large rotatable shafts except for large scale, usually visually apparent, misalignment. Misalignment on the order of a few thousandths of a degree corresponding to a shafts axis of rotation separation of a few thousandths of an inch are not readily detectable by even skilled workers.

To solve this problem, the prior art has proposed a number of relatively sophisticated misalignment detectors. Some of these have utilized complicated optical systems for measuring the degree and direction of any misalignment. However, in many industrial sites or power plants, the use of such sensitive optical equipment is time consuming and difficult to efficiently install and operate except by the most highly skilled optical specialist. In other attempts to simplify this process, the use of visible laser radiation devices have been employed together with somewhat simplified optical mirror systems. Frequently, these also require extensive set up time not to mention the extensive training necessary to effectively carry out reliable measurements. In addition, both of these solutions have involved considerable expense for the manufacturers and users and this is undesirable particularly where the reliability of the measurements cannot be guaranteed.

Other attempts to provide an indication of misalignment have included mechanical devices such as that disclosed in U.S. Patent Nos. 2,516,854 granted August 1, 1950, 5,479,718 granted January 2, 1996 and 4,367,594 granted January 11, 1993. The methods and devices of these patents as well as other devices have required that the user rotate at least one of the shafts of the pair that are out of alignment. For a large number of applications this requirement is either not feasible due to the weight of the shafts or is too time-consuming to be efficiently carried out. In many cases, the measurement of misalignment has not provided the necessary data to enable a user to quickly and accurately move the support for one of the shafts. As a result, machine operators have frequently had to rely on actual operation of the machinery coupled with close observation by a worker to determine whether the alignment has been achieved satisfactorily. Such methods are only useful, however, for relatively low rotational speeds. For high rotational speeds as well as those utilizing a high torque transmission, this is clearly unsatisfactory due to the danger involved both to the personnel and equipment that can be damaged by even relatively small degrees of misalignment.

Summary of the Invention

The present invention provides a greatly simplified device and method for measuring misalignment between a drive and a driven shaft and which requires no electronics and no special training for a user. In its simplest form, the present invention utilizes a spacer member in the form of a single shaft that may be extendible to reach between the end of a drive shaft to the face of the driven shaft. Adjacent each end of the spacer member, radially extending arms are provided to enable a measurement to be taken about the axis of rotation of each of the shafts with the use of a conventional dial indicator. Electronic indicators including proximity probes may also be employed. These are standard devices available from a manufacturer and which will provide a reading of a perpendicular distance which can be correlated to the tilt of the face of the shaft being measured. As explained in more detail hereinafter, the two measurements taken over each of the faces of the shafts taken at locations approximately 180° apart are used to calculate not only the degree of misalignment in the plane described by the two readings between the axis of rotation of the radial arms about each face of each of the shafts that need to be aligned but also the amount of adjustment to the machinery supports that is required to bring the shafts into alignment. With this information, and the calculations of the present invention, the degree of misalignment can be readily compensated for by shifting one or both of the shafts on their mounting machinery an amount indicated by the resulting calculation. With the method and apparatus of this invention, it is not necessary that either of drive or the driven shaft be rotated to obtain an accurate measurement of the alignment between these two shafts.

The present invention also provides apparatus for carrying out the present invention. In one embodiment, as described above, a simple shaft is provided which is extendible from the axis of rotation of one shaft to the axis of rotation of the other shaft that requires alignment. The radial arms may also be radially extendible from the first mentioned shaft and are adapted to carry a dial indicator of conventional construction. It is well understood in the power shaft field, a dial indicator is used to measure a distance indicative of the degree of tilt of the face of a shaft relative to its axis of rotation. In another form, where a gear is carried about the external surface of each shaft, a cylindrical housing is disposed about the external surfaces of the gears and extends between the gears on each shaft. The ends of the cylinder are provided with openings to enable measurement of the degree of tilt of the cylinder relative to the gears once the gears have been established on the shafts so as to extend substantially radially from the axis of rotation of each shaft. This form of the invention is particularly useful where geared couplings are involved.

The advantages of the present invention are not only an accurate measurement of the degree of misalignment but also a measurement that can be carried out quickly, by relatively low skilled workers and with equipment which is substantially less expensive than the prior art devices.

The foregoing and other advantages of consideration is given to the following description taken in conjunction with the accompanying drawings, in which:

Brief Description of the Drawings

Figure 1 is a schematic illustration of one embodiment of the present invention in side elevation and extending between two rotatable shafts;

Figure 2 is a schematic illustration in side view in elevation of another embodiment of the present invention; and

Figure 3 is schematic side view of another embodiment.

Detailed Description of the Invention Referring to the drawings, where like numerals designate similar and corresponding parts, there is shown in Figure 1 the present invention generally designated at 10 disposed between a drive shaft 12 and a driven shaft 14. As is well known in the power transmission field, for safe and efficient operation of any rotary power transmission between shafts, it is necessary that the axis of rotation of the drive shaft 12 and the driven shaft 14 be as closely aligned as possible to minimize vibration, unnecessary wear and power loss particularly where the rotary power being transmitted is done at a high speed. According to the present invention, the device 10 is provided with a ridged main shaft 16 one end of which 18 is telescopically extendible such as by including a reduced diameter shaft portion 20 which fits telescopically within the main shaft 16. Preferably, a spring is employed (not shown) to bias the shaft 20 outwardly, to the left as viewed in Figure 1 and a detent 21 is provided to prevent separation. The end of the smaller length shaft 20 may be provided with a pointed end 22 as is the opposite end 24 of the main shaft 16. In most power transmission equipment utilizing a drive and driven shaft, the shafts will include or be formed with a centrally located recess that coincides with or marks the axis of rotation of the shaft. With this recess, the points of the caps 22 and 24 will easily interfit or seat in such recesses to thereby definitely locate the axis of the shaft combination 16 and 20 on the respective axes of rotation of the shafts 12 and 14.

Extending radially from the main shaft 16 are two spaced ridged arms 26 and 28 each of which has adjacent its outer end 30, 32 an aperture (not shown) through which extends the finger 34, 36 of a dial indicator 38, 40. In some arrangements, the arms 26 and 28 may also be telescopically mounted so as to enable a worker to position the fingers 34, 36 adjacent the outer edge of the faces 42, 44 of the shafts 12 and 14. It will be understood, however, that, as will be apparent to those skilled in this art, the length of the arms 26, 28 may be adjustable in any suitable fashion so long as a ridged location of the dial indicators 38, 40 is provided.

With the dial indicators in the position shown in Figure 1, the operator will simply rotate the shaft 16 through an angle not greater than approximately 180° noting before doing so the reading of each of the dial indicators 38 and 40. At the end of the rotation of the shaft 16 about its own axis a second reading of each of the dial indicators 38 and 40 is taken and noted.

To carry out the calculations, D will equal the radial distance between the points of contact of the fingers 34 and 40 on the face of each of the shafts 12 and 14 and the axis of rotation of the shaft 16; LI is equal to the perpendicular distance between the faces of the shafts 12 and 14. Rla is the indicator dial reading for the dial 38 in a first position on face 42 of shaft 12; Rib is the reading for the dial indicator 38 in the second position for measurement on the face 42; R2a and R2b are the corresponding readings for the dial indicator 40 on the face 44 of the shaft 14. With these measurements and constants, according to the present invention, the following equations will give the amount of movement for the front foot of the support housing where L2 is a fixed distance from the shaft face 44 to the midpoint of a front foot and L3 is the distance between the front and rear foot of the support structure such as a turbine housing: FF = (Rlb-Rla)/D * LI + ( (Rlb-Rla)/D + (R2b-R2a)/D) * L2 (1)

For the rear foot: RF = FF + ( (Rlb-Rla)/D + (R2b-R2a)/D ) * L3 (2)

Referring now to Figure 2, a different alignment version of the present invention is shown at 60 and this includes a spacer tube or bar 62 which is provided at its opposite ends with apertured faces 64 and 66. Through some of the apertures, such at 68 in face 64 and 70 in face 66, a conventional flexible coupling is installed as indicated schematically at 89 and 89'. Such installation will occupy four or more of the apertures in flanges 64 and a corresponding number of apertures in flanges 74 and 80 on the respective shafts 76 and 80. Preferably, the flanges 64 and 66 are provided with two additional pairs of apertures with the apertures of each pair spaced 180° apart. Without rotating any of shafts 76, 82 or 60, an operator will be able to insert the foot of a dial indicator or equivalent tool through two pairs of unoccupied apertures in each of flanges 64 and 66 to obtain a set of distance measurements. The end of a dial indicator tool will contact the face 74 of a drive shaft 76 while the corresponding member 78 from face 66 will contact the face 80 of a driven shaft 82 with these measurements repeated in the location 180°. This will provide a different measurement as will be evident from the exaggerated illustration of the schematic view of Figure 2. The corresponding constants used above in connection with equations (1) and (2) are apparent from a consideration of Figure 2 and the distance offsets measured by the dial indicator or equivalent tools will also be easily obtained without requiring any rotation of either shaft 76 or 82. The equations given above will thus render to the user a degree adjustment of the footing of the support to cure any misalignment between the shafts 76 and 82 to bring that shaft into axial alignment with the other shaft.

With reference now to Figure 3, there is shown another embodiment of the present invention where a drive shaft 90 and a driven shaft 92 are each operated with gears such as at 94 and 96 mounted thereon for use such as to drive other equipment. In this context, as is well known in this art, it is frequently necessary to keep the gears constantly lubricated. As a consequence, it is difficult if not impossible to effect dial indicator readings in the manner described above. To obviate this difficulty, the present invention provides a cylindrical shroud 98 which may be in the form of a split tube having a hinge 100 allowing the opening of the cylindrical shroud 98 and 94 in the position shown so as to extend between the shafts 92 and 94. As installed, dial indicator measurements can be taken relative to the confronting surface of each gear through openable apertures 102 which are provided in the ends of the shroud 98 as shown. Minor changes to the calculations will be required to accommodate this change in the location of the measurements.

Claims

What is claimed is:

1. A method of determining the amount of misalignment between two rotatable shafts that are located adjacent to one another for cooperation in transmission of torque from one shaft to the other shaft and where the shaft have faces that extend substantially transverse to the axis of rotation of each of the respective shafts, comprising: a) disposing a first member having opposite ends with each said end in contact with a face of a respective said shaft with said ends of said first member contacting said respective faces at the axis of rotation of each said shaft, said first member having arms extending a distance from said first member and located adjacent one of said ends of said first member, each arm having an end remote from said first member, b) mounting a distance measuring device at said end of at least one of said arms, said device being of the type that renders a measurement of distance as the device is moved over and in contact with a surface, c) rotating said at least one of said arms through an angle no greater than approximately 180° while maintaining contact with the face of one of said shaft to determine the magnitude of any difference in angular orientation of the said face of said one shaft relative to the orientation of said first member without rotating either of said shafts, d) mounting a distance measuring device said end of the other of said arms, said device being of the type that renders a measurement of distance as the device is moved over and in contact with a surface e) rotating, said the other of said arms through an angle no greater than approximately 180° while maintaining contact with the face of the other of said shafts to determine the magnitude of any difference in angular orientation of the said face of said other of said shafts relative to the orientation of said first member without rotating either of said shafts, f) calculating the amount of adjustment of one of said shafts required to remove any misalignment using the distance between the faces of said shafts, the radial distance between said first member and the point of contact of the measuring device with the face of said respective shaft.

2. The invention as claimed in claim 1 wherein said shafts are each carried by a support structure having front and rear footings and the step of calculating the amount of adjustment includes calculating an amount of adjustment for the front and rear footings of one of the support structure using the relationships: for the front foot:

FF = (Rlb-ria)/D * LI + ((Rlb-Rla)/D+(R2b-R2a)/D) * L2

For the rear foot:

RF = FF + ((Rlb-Rla)/D + (R2b-R2a)/D)* L3, where L2 is a fixed distance from the shaft face to the midpoint of a front foot and L3 is the distance between the front and rear foot of the support structure and D is the radial distance between the points of contact of the measuring device on the face of each the shaft and the axis of rotation of the shaft, LI is the perpendicular distance between the faces of the shafts, Rla is the distance indicated by the measuring device at one position on one shaft face, R2a is the distance at the second position of the once shaft face, Rib is the distance indicated by the measuring device at one position on the other shaft face, R2b is the distance at the second position on the other shaft face.

3. The invention of claim 1 wherein the first member is resiliently extendable to accommodate the distance between said faces of said shafts.

4. The invention of claim 1 including the step of mounting a measuring device in each said end of said arms before effecting the rotation of said respective arms relative to said respective faces.

5. Apparatus for determining the amount of misalignment between the axes of rotation of two shafts, each having an end face, comprising a first member having means for fitting said first member in contact with said end faces at the axes of rotation of the shafts, said first member having opposite ends for contacting the respective end faces of the shafts, said first member including a first arm having an end located at a radial distance from said first member and including mounting means for carrying a measuring device of the type that renders a measurement of distance as the device is moved over and in contact with a surface.

6. The invention as claimed in claim 5 wherein said first member is a shaft.

7. The invention as claimed in claim 6 wherein said first member has telescoping means to facilitate spanning the distance between the end faces of the shafts.

8. The invention as claimed in claim 7 wherein a second arm is provided and said arms are located adjacent said ends of said first member.