Electronic indicating device for coaxially aligning a pair of rotary members

A machine shaft aligning apparatus includes electronic indicating devices for automatically outputting signals to a computer indicative of the magnitude and direction of radial displacement of two coupled shafts as the coupled shafts are rotated to 4 clock positions (i.e. 12, 3, 6, and 9 o'clock). The computer enables calculation and display of horizontal and vertical machine adjustments required to effect proper coaxial alignment of the coupled shafts of the machines.

BACKGROUND OF THE INVENTION 
This invention relates in general to improvements in distance measuring and 
indicating devices and deals more specifically with an improved electronic 
indicating device or instrument for monitoring radial displacement of a 
rotary member. While the instrument of the present invention may have 
other uses, it is particularly adapted for use in combination with a 
computer in an apparatus of the type for calculating the shimming 
adjustments required to effect accurate coaxial alignment between coupled 
shafts on associated machines and the like. 
Accurate alignment of rotating equipment is essential to prevent wear, 
minimize vibration, and eliminate premature breakdown. Shaft misalignment 
is a major cause of machinery component failures involving bearings, 
seals, gears, couplings and the like. Trial and error shaft aligning 
methods using feeler gauges, straight edges and the like are well-known in 
the art. However, these methods are time consuming and often do not 
produce satisfactory results. Well-known alignment methods utilizing dial 
indicators in aligning coupled shafts eliminate the need to "break" the 
coupling between shafts and generally enable a more accurate result. 
However, the various measurements and mathematical solutions necessary to 
determine the required machine adjustments to attain shaft alignment are 
time consuming and prone to human error. 
Heretofore, computers of specialized function type have been utilized in 
conjunction with dial indicators in machine alignment apparatus. A typical 
computer of the aforedescribed type has appropriate equations stored in a 
memory for calculating required machine adjustments from measurements 
taken from the machines and entered in proper sequence in the computer. 
The Machinery Alignment Analyzer MAC-5 produced by SPM Instrument Inc., 
Marlborough, Conn., assignee of the present invention, is a typical 
computer of the aforesaid type. 
While such a specialized computer substantially reduces the time required 
to obtain the necessary mathematical solutions, the accuracy of result is 
largely dependent upon the accuracy of measurements and readings taken 
from dial indicators at proper angular positions of shaft rotation and 
entered in proper sequence into the computer. 
It is the general aim of the present invention to provide an improved 
indicating device or instrument for monitoring the radial displacement of 
a rotary member, and particularly for use in a shaft aligning apparatus to 
reduce both the time required to effect shaft alignment and the risk of 
human error associated with the alignment process. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an improved electronic indicating 
device is provided for monitoring radial displacement of a rotary member. 
The device comprises a housing, mounting means for supporting the housing 
in fixed position relative to a rotary member for angular movement with 
the rotary member about the axis of rotation thereof, sensing means 
supported to move with and relative to the housing for detecting radial 
displacement of the rotary member, and transducer means disposed within 
the housing and coupled to the sensing means for generating electrical 
output signals indicative of radial displacement detected by the sensing 
means. The device further includes angular position discriminating means 
disposed within the housing and responsive to changes in angular position 
of the housing for generating enabling signals at predetermined angular 
positions of the housing, and coupling means associated with the housing 
for electrically connecting the transducer means and the angular position 
discriminating means to a receiving apparatus whereby output signals 
received from the transducer means are processed by the receiving 
apparatus in response to enabling signals received by the receiving 
apparatus from the angular position discriminating means.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Turning now to the drawings, apparatus for coaxially aligning a pair of 
coupled rotary members is illustrated in FIG. 1 and indicated generally by 
the reference numeral 10. The illustrated apparatus 10 is shown mounted on 
a pair of rotary members or cylindrical shafts which comprise part of a 
typical machine assembly which includes two machines, (not shown) each 
supported by independent base structure. The shafts of the two machines, 
indicated respectively at 12 and 14, are coupled in working relation to 
each other by a coupling assembly 16 for rotation in unison and comprise a 
shaft assembly to be coaxially aligned. Ordinarily, the adjustments 
necessary to effect coaxial alignment of such a shaft assembly will be 
made to only one of the machines, because the other of the machines may be 
more difficult to move due to its weight, size or physical attachment to 
another system or systems, as, for example, a plumbing system or the like. 
The term "Stationary Machine" (SM) is used to describe the larger machine 
which will not be moved or otherwise adjusted. Since the adjustments to be 
made usually involve shimming the machine base structure, the machine to 
be adjusted is hereinafter designated the "Machine To Be Shimmed" (MTBS). 
In the alignment process the MTBS will usually require both vertical and 
horizontal adjustment relative to the SM to achieve coaxial alignment of 
the respectively associated shafts, such as the shafts 12 and 14. 
The illustrated alignment apparatus 10 employs a pair of electronic 
indicating devices or indicators, designated generally by the numerals 
18,18. Each indicator 18 is secured to an associated one of the shafts 12 
and 14 by an associated bracket 20,20. The brackets 20,20 also support 
targets 22,22 which provide reference surfaces for the indicators 18,18. 
The illustrated apparatus 10 further includes a computer, indicated at 24 
and coupled to the indicators 18,18 to receive signals therefrom. 
Each indicator 18 is particularly adapted to provide output signals 
indicative of the magnitude and direction of radical displacement of one 
shaft relative to the other at predetermined angular positions of the 
shaft assembly. A computer 24 is electrically connected to the indicators 
18,18 to receive signals therefrom and has a keyboard used to input 
measurement data relative to the machines to be aligned. The computer 
contains algorithms which enable calculation of shimming adjustments which 
must be made to the MTBS to bring the shaft thereof into coaxial alignment 
with the shaft of the SM in a manner generally well known in the machine 
alignment art. The illustrated computer 24 comprises a Machinery Alignment 
Analyzer MAC-5 produced and marketed by SPM Instrument Inc., Marlborough, 
Conn., assignee of the present invention. 
Referring now particularly to FIGS. 2-7, a typical indicator 18 has a 
hollow generally rectangular housing indicated generally at 26, preferably 
made from dielectric plastic material, and includes a rear part of base 28 
and a removable front cover 30. Four mounting posts 31,31 project 
forwardly from the base 28, support a PC board, indicated at 32, and 
receive self-tapping fasteners 34,34 (one shown) which secure the PC board 
and cover 30 in assembly with the base 28. An outwardly open female 
electrical receptacle or modular connector 35 of the type well known in 
the telecommunication field and containing a plurality of individual 
spring contacts is mounted on the PC board 32 as shown in FIG. 6 and is 
received within a complementary laterally outwardly projecting portion of 
the housing when the cover 30 is assembled with the base 28. 
An axially elongate generally cylindrical sensing member or indicator shaft 
36 extends through the hollow housing 26, projects for some distance from 
one end of the housing, and carries a contact 38 at its free end. The 
indicator shaft 36 is supported at the one end of the housing 26 by a 
generally cylindrical split support member 40, defined by the base 28 and 
the cover 30, which contains an annular indicator shaft bushing 42. A 
tubular sleeve 44 coaxially surrounds the two halves of the split support 
member 40 in assembly to maintain its integrity as a support for the 
indicator shaft 36. The opposite end portion of the indicator shaft 36 is 
slidably received within another support member 46 secured in fixed 
position to the opposite end portion of the base 28. A threaded outer end 
portion of the support member 46 is threadably engaged within and 
maintains a generally cylindrical mounting post 48 in coaxial alignment 
with the indicator shaft 36, as best shown in FIG. 3. Thus, the indicator 
shaft 36 is supported in cantilever position on the housing 26 for 
reciprocal sliding movement along a rectilinear path defined by the 
longitudinal axis of the indicator shaft, indicated by the numeral 50 
(FIG. 3). A torsion spring 51 supported on a mounting post which projects 
from the base 28 acts between the base and a pin 53 carried by the 
indicator shaft 36 to bias the indicator shaft toward its projected 
position as it appears in FIGS. 2, 3 and 5. 
The indicator shaft 36 is coupled to a transducer or optical encoder of a 
well known type indicated generally by the numeral 52 and contained within 
the housing 26. The optical encoder 52 generates output signals indicative 
of the direction and magnitude of linear displacement of the indicator 
shaft 36 along the path 50 and includes a transmitter/receiver 54 which 
carries two LED's and two phototransistors. The transmitter/receiver 54 is 
secured to the indicator shaft 36 by fasteners 55 to travel with it. The 
optical encoder 52 further includes a leaf spring 56 which carries a 
reticle 58. The leaf spring biases the reticle 58 into engagement with a 
glass scale 60 mounted in fixed position on the housing base 28 and along 
which the reticle 58 travels in response to rectilinear displacement of 
the indicator shaft relative to the housing 28. A flexible conductor or 
ribbon cable 62 connects the two Led's and the two phototransistors 
carried by the transmitter/receiver 54 to associated amplification 
circuits on the PC board 32, as shown in FIG. 7, which are, in turn, 
connected to spring contacts in the modular connector 35 to provide output 
signals on channels A and B, FIG. 7, which signals are 90 degrees out of 
phase and which may be converted to a measurement output by an external 
phase quadrature detector for processing by the computer 24. 
The electronic indicator of the present invention also has an angular 
position discriminator responsive to changes in the angular position of 
the indicator housing for providing enabling signals at predetermined 
angular positions of the housing. The presently preferred electronic 
indicator 18 has a position discriminator, indicated generally at 68, 
capable of providing enabling signals at four clock positions of the 
housing, namely 12, 3, 6 and 9 o'clock. The enabling signals produced by 
the illustrated angular position discriminator 68 are utilized in the 
apparatus 10 to enable measurement data generated by the optical encoder 
52 to be automatically processed by the computer 24 each time that the 
shaft assembly to be aligned attains one of the aforesaid clock positions. 
The illustrated angular position discriminator 68 essentially comprises at 
least one electrical switch responsive to changes in angular position, but 
preferably, and as shown, the angular position discriminator includes two 
such identical position switches indicated at 70,70. Preferably each 
switch 70 comprises a Series 2009 Signal Systems International positioning 
switch, available from Signal Systems International, Holmdel, N.J. 07733, 
and capable of monitoring rotation. 
Each switch 70 has twelve independent electrical contacts spaced at 30 
degree increments about a switch axis and contained within a hermetically 
sealed housing which also contains a ball of mercury. The ball of mercury 
spans a distance greater than the distance between adjacent contacts. When 
such a switch is mounted with its axis oriented in a generally horizontal 
position, it is capable of monitoring rotation. Each 30 degrees of 
rotation causes the mercury to close on a new switch contact. 
The two switches 70,70 are mounted on the PC board 32 (one shown in FIG. 4) 
with the axes thereof generally normal to the frontal surface of the 
indicator housing cover 30, which surface is hereinafter designated as a 
reference surface and indicated by the numeral 72. Eight of the twelve 
contacts in each switch 70 are paired to provide four equangularly spaced 
sets of active contacts; each set of active contacts including two 
angularly adjacent contacts. The active contacts in each set are separated 
from the active contacts in the next angularly adjacent set by an unused 
or inactive contact. Thus, the resulting four sets of active contacts in 
each switch are spaced at 90 degree increments about the axis of the 
switch. 
Since the ball of mercury in each switch 70 spans a distance greater than 
the spacing between the active contacts of each set, a single such switch 
will not provide immediate response to rotation in both clockwise and 
counterclockwise directions. It will be understood that a set of active 
contacts at the six o'clock position of the switch will normally be closed 
by the ball of mercury to complete a circuit path through the switch. The 
switch may be arranged so that slight rotation in a counterclockwise 
direction, for example, will cause the leading contact at the 6 o'clock 
position to immediately or almost immediately escape from the ball of 
mercury to open or change the switch from a conducting to a non-conducting 
state. However, the same condition will not occur when the switch is 
rotated in an opposite or clockwise direction, because the other contact, 
which then becomes the leading contact in the active set, will remain 
within the ball of mercury throughout a somewhat greater degree of angular 
movement of the switch. Thus, a single switch arranged in the 
aforedescribed manner relative to the indicator 18 will have differing 
operating characteristics when rotated in clockwise and in 
counterclockwise directions. To overcome the aforesaid problem, two 
switches 70,70 are utilized in the indicator 18 and designated SW1 and SW2 
in FIG. 7. Each set of active contacts in SW1 is connected in electrical 
series to an associated set of active contacts in SW2. However, SW1 is 
angularly offset 25 degrees in a clockwise direction with respect to SW2, 
so that the mercury ball will simultaneously close the associated 
connected active contacts in both SW1 and SW2. Slight angular movement of 
the indicator in either clockwise or counterclockwise direction will cause 
one or the other of the associated sets of series connected contacts to 
open thereby interrupting the circuit path through the switches 70,70. 
Thus, the operational characteristics of the indicator will be 
substantially identical regardless of the direction of indicator rotation. 
The shaft alignment apparatus 10 illustrated in FIG. 1 is setup to align a 
pair of coupled shafts using the indicator reverse method, well known in 
the shaft alignment art. Each indicator 18 is supported on an associated 
one of the shafts 12 and 14 by associated mounting brackets 20 with the 
axis 50 thereof disposed in a radial direction relative to the related 
shaft. Each indicator is mounted with its reference surface 72 disposed 
generally within a radial plane of an associated shaft. Thus, it should 
now be apparent that the central axes of the switches 70,70 within each 
indicator 18 are disposed in generally axially parallel relation to the 
axis of an associated one of the shafts 14 and 16. 
The illustrated machinery alignment analyzer or calculator 24 contains 
algorithms related to a plurality of alignment methods and enables the 
user to select an appropriate alignment method and correctly align 
machinery in both vertical and horizontal direction in accordance with the 
method selected. The calculator 24 has a large graphic display which shows 
all of the measurements required to assure precise alignment. After the 
selected alignment method has been entered in the computer, in the present 
instance the indicator reverse method, the computer 24 "asks" the operator 
for the required measurements related to the particular setup. 
After the required measurements have been manually entered in proper 
sequence in the computer the shaft assembly is slowly rotated through four 
clock positions, (i.e. 12, 3, 6 and 9 o'clock). As each indicator 18 moves 
through a 90 degree angular increment between clock positions the 
transducers 52,52 associated with the indicators generate electrical 
output pulses, indicative of the magnitude and direction of radial 
displacement indicator shafts 36,36. The pulses are counted and the 
results are stored in the computer 24 and processed in response to 
enabling signals received by the computer from the angular position 
discriminators 68,68. 
The computer 24, using industry accepted methods, calculates and displays 
the corrections necessary for proper shaft alignment. The required machine 
movement in both horizontal and vertical directions and the amount of 
shimming necessary for the front and back feet of the MTBS is displayed by 
the computer. The computer display may also provide an indication of the 
offset and angle of the two shafts at the coupling center line.