Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
Different types Gf methods and apparatus have been
utilized for aligning machines having rotating shafts with
flexible couplings connecting the rotating shafts. These prior
art apparatus and methods have numerous disadvantages and have
been unsatisfactory for a variety of reasons. There is,
therefore, a need for a new and improved shaft alignment
apparatus and method.
According to one broad aspect of the invention there
is provided, in an apparatus of the character described, first
and second machines having first and second rotating shafts,
a flexible coupling interconnecting said first and second
rotating shafts, the flexible coupling having at least one
member connected to one of the shafts and being capable of
accommodating at least some misalignment of the first and second
shafts, one of said first and second shafts being considered as
a reference shaft and the other of said first and second shafts
being considered as a movable shaft, means carried by the shafts
having surfaces spaced apart circumferentially with respect to
the axis of rotation of the shafts which represent the orienta-
' tion of one of said shafts and serve as reference surfaces and
additional surfaces spaced apart circumferentially with respect
to the axis of rotation of the shafts which represent the
orientation of the other of said shafts and probe means for
sensing the position of said reference surfaces and said last
named surfaces during rotation of said shafts to determine
whether said shafts are placing a force on said member of the
flexible coupling which is outside of the useful operating range
of said member in the flexible coupling.
According to another broad aspect of the invention
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there is provided, in a method for aligning a pair of machines
in a machine train having first and second shafts interconnected
by a flexible coupling, the flexible coupling being of a type
having first and second spaced apart members coupled to said
first and second shafts and being capable of accommodating at
least some misalignment of the first and second shafts, one of
said first and second shafts being considered as a reference
shaft and the other of said first and second shafts being
considered as a movable shaft, the steps of sensing the orienta-
tion of at least one of said shafts by carrying out the sensing
of rotating surfaces carried by said one shaft in at least two
locations spaced apart circumferentially with respect to the
axis of rotation of said one shaft, sensing the orientation of
at least one of said members of the flexible coupling by carry-
ing out the sensing of rotating surfaces carried by said coupling
in at least two locations spaced apart circumferentially with
respect to the axis of rotation of said coupling and using the
sensed information to ascertain whether said shafts are placing
on said member a force which is outside of the useful operating
range of the member in the flexible coupling.
In general, it is an object of the present invention
to provide a shaft alignment apparatus and method which is
particularly useful for aligning any pair of machines having
rotating shafts in a machine train with a flexible coupling
interconnecting the shafts.
Another object of the invention is to provide an
apparatus and method of the above character in which measurements
can be carried with the machines at rest, during start-up and
during all running conditions and on shut-down.
Another object of the invention is to provide an
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apparatus and method of the above character in which measurements
can be made giving an indication of the axial motion of the
machines, both steady state and dynamically.
Another object of the invention is to provide an
apparatus and method of the above character in which the
measurements which can be provided include the net coupling
hub motion of each machine due to any dynamic motion of each
rotor, such as that due to fixed bows, thermal bows, unbalance
bows and other action at rotative speed in a forward direction
and also due to any other action at other than rotative speed
in a forward direction such as oil whirl, re-excitation of
balance resonances and other actions that create shaft motions.
Another object of the invention is to provide an
apparatus and method of the above character in which readings
are provided making it possible to align the machine pair or
train properly before start-up in parallel alignment, angular
alignment and axial spacing.
Another object of the invention is to provide an
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apparatus and method to provide rneasurements which yield the
condition of the alignment with respect to the above three
identified parameters plus the dynamic tiltings of the coup- -
ling hubs on start-up and initial running condition of the
machine pair at initial start-up and at subsequent start-ups.
Another object of the invention is to provide
an apparatus and method of the above character which makes
it possible to make measurements which will provide warning
of the deterioration of the alignment of the machines so that
the machines may be stopped and/or the performance parameters
changed in such a manner so as to keep the coupling parameters
within certain limits.
Another object of the invention is to provide an
apparatus and method of the above character in which the in-
formation obtained can be utilized to provide automatic
warning and shut-down of the machines.
Another object of the invention is to provide an
apparatus and method of the above character in which the
information obtained can be utilized for maintaining align-
ment between machines within allowable ranges.
Another object of the invention is to provide an
apparatus and method of the above character which can be
utilized with various types of flexible couplings such as
diaphragm-type flexible couplings and gear-type flexible
couplings.
Another object of the invention is to provide an
apparatus and method of the above character which can be
utilized in conjunction with equipment which has already
been installed.
Another object of the invention is to provide an
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ap~aratus and mcthod of the above character which will give
the actual misalignment of both ]egs of a mov~hle m<~chine with
respect to a reference machine.
Another object of the invention is to provide an
apparatus and method of the above character which will give
a visual readout of such information.
Another object of the invention is to provide an
apparatus and method of the above character in which the
misalignment information given includes parallel misalign-
ment of the shafts, angular misalignment of the shafts, and
compression and stretch of the flexible coupling.
Another object of the invention is to provide an
apparatus and method of the above character which makes it
pos~ible to ascertain whether or not a member of the flex-
ible coupling is operating within its usable range.
Additional objects and features of the invention
will appear from the following description in which the
preferred embodiments are set forth in detail in conjunction
. with the accompanying drawings.
Brief Description of the Drawings
Figure 1 is a perspective view of a pair of
machines having rotating shafts in a machine train intercon-
nected by a flexible coupling and having an alignment appar-
atus incorporating the present invention associated therewith.
Figure 2 is an enlarged isometric view of a portion
of the apparatus shown in Figure 1 and particularly shows a
flexible coupling with the alignment apparatus associated
therewith.
Figure 3 is a cross-sectional view taken along
the line 3-3 of Figure 2.
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Yigure 4 is a diagramatic ill~stration of a pure
parallel shaft misalignmemt situation, the misalignme"~
being greatly exaggerated for purposes of illustra~ion.
Figure 5 is a diagramatic illustration of a pure
angular shaft misalignment situation with the misali~nment
being greatly exaggerated for purposes of illustration.
Figure 6 is a diagramatic illustration showing the
manner in which parallel misalignment and angular misalign-
ment of the shafts are combined to provide the actual mis-
alignment of the movable shaft with respect to the reference
shaft with the actual amounts of misalignment for both the
legs of the movable shaft.
Figure 7 is a diagramatic illustration showing
stretch and compression of the flexible coupling in an axial
direction with the distortion being greatly exaggerated for
purposes of illustration.
Figures 8A and 8B are a circuit diagram, a portion
of which is in block form, of the electronics utilized in the
apparatus for providing a visual readout of the actual mea-
surements representing misalignment of both legs of the
movable shaft.
Figure 9 is a cross-sectional view of a flexible
gear-type coupling which has been modified so that it can be
utilized in conjunction with the present invention.
Figure 10 is and end elevational view of the
flexible coupling shown in Figure 9.
Figure 11 is a cross-sectional view taken along
the line ll-ll of Figure 12 showing a flexible coupling
with alternative paddle means.
Figure 12 is a cross-sectional view taken along
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th~ line 12-12 of Fi~ure 11.
Brief Description of the Preferred ~mbocliments
A machine train 11 having mounted thereon a shaft
alignment apparatus 12 incorporating the present inven~ion is
shown in Figure 1 of the drawings. The machine train 11 is
mounted upon a suitable rigid base or oundation 13. The
machine train 11 mounted therein comprises at least a pair
of machines with one of the machines being a fixed or driving
machine 14 and the other of the machines beillg a movable or
driven machine 16. By way of example, the fixed or driving
machine 14 can be in the form of an electric motor d~iving a
movable or driven machine 16 such as a generator, air com-
pressor or the like. The fixed or driving machine 14 is
proJided with a fixed or driving shaft 17, whereas the movable
or driven machine 16 is provided with a movable or driven
shaft 18. A flexible coupling 19 is provided for intercon-
necting the movable or driven shaft 18 with the fixed or
driving shaft 17.
In aligning the two shafts 17 and 18 with the flex-
ible coupling 19 therebetween, it is generally desirable to
consider one of the machines and its shaft to be fixed and a
reference and to consider the other machine as being movable
so that its shaft can be brought into alignment with the
reference shaft of the fixed machine. Thus, by way of example,
as shown in Figure 1 the fixed or driving machine 14 can be
considered as fixed to the base 13 and as shown in Figure 1 is
rigidly secured to the base 13 by supports or frame members
21 which can be welded or bol~ed to the base 13. Conversely,
the movable or driving machine ;7 is movably mounted upon the
base 13 by conventional means not shown.
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~ s can be seen from Figure 1, the movable or driven
machine 16 has a shaft 18 with a finite length which is sup- !
ported at opposite ends by bearings 22 mounted upon pedestals
23 that are secured to the base 13 by securing means in a 14
suitable manner so as to permit shifting of the pedestals IJ
axially of the shaft 18 and vertically and horizontally on
the base 13. Securing means of this type is well known to
those skilled in the art, and thus is not shown in the draw-
ings. Typically, it can consist of mounting pads having
bolts and screws extending therethrough in which screws can
be utilized for obtaining the desired positioning and bolts
are then used to secure the pedestals 23 in the desired
positions. Similarly, jack screws can be provided for shift-
ing the pedestals 23 axially of the shaft 18.
The flexible coupling 19 can be of any suitable '~
type as, for example, one of a flexible diaphragm type or of ~ I
the gear type. A flexible coupling of the flexible diaphragm I j
type is shown in Figures 1 and 2 of the drawings and as shown 1 3
therein consists of first and second hubs 26 and 27 having
radially extending flanges 28 and 29 mounted thereon. The
hubs 26 and 27 are provided with bores 31 which are adapted
to receive mating shafts. Thus, as shown in Figures 1 and 2
of the drawings, the hub 26 is mounted on the fixed or driving
or reference shaft so that the hub face is flush with the end
of the shaft. The hub 26 is secured to the shaft by suitable
means such as a key (not shown). Similarly, the hub 27 is
mounted on the driven or movable shaft 18 and is keyed thereto
in such a mannQr that the face of the hub is flush with the
end of the shaft. The faces of the flanges 28 and 29 face
each other and have a spacing therebetween for receiving the
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flexible coupling 19. This sp~cinc~, ~or ~urposes hereinafter
described, is identified as "1".
A flex unit spacer or spool 33 forms a part of the
flexible coupling and is mounted in thc space between the ~~
flanges 28 and 29. The flex unit spacer or spool 33 consists
of a center tube 34 which can be idcntified as a torque tube
which is in the form of a hollow cylinder. The outer extre~
ties or ends of the center tube 34 are mounted in openings 36
centrally disposed in circular or disc-like diaphragms 37.
The center tube 34 is secured to the diaphragms 37 by suit-
able means such as welding. The outer margins of the dia-
phragms 37 are secured to the outer margins of guards 39 by
suitable means such as rivets 41. The guards 39 with the dia-
phragms 37 secured thereto are secured to the flanges 28 and
29 by bolts 42. The guards 39 are provided with outwardly
facing planar reference surfaces 43 which are generally per-
pendicular to the axes of rotation of the shafts 17 and 18.
Each of the guards 39 has been provided with a
plurality of cut-outs 46 which extend radially from the center
tube, 34. The cut-outs 46 are of substantial width and are
placed in four ~uadrants which are spaced 90 apart for
purposes hereinafter described. A paddle 47 is disposed in
each of the cut-outs 46 of the guards 39. The paddles 47
are secured to and are mounted upon the center tube 34 so
that they have a precise relationship with respect to the
tube 34. The paddles 47 are relatively precisely formed ,~
such as by machining and are mounted upon a collar 48 which
is secured to one end of the tube 34 by suitable means such
as welding. The paddies 47 provided on,both ends of the
center tube 34 are in alignment with each other whereby two
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corresponding paddlc~ on opposite ends havc the s~me angul~r
relationship with respect to the axis of rotation of the
center tube 34.
, To accomplish the functions hereinafter described,
:, ,
'~ it-is necessary that the paddles 47 have outer planar sur- .
faces 49 which are perpendicuiar to the axis of rotation of
: the tube 34 so that the surfaces 49 provide information as to
.;~
the orientation of the ends of the center tube 34 to which
they are attached. When the fixed or driving shaft 17 ana the
' 10 movable or driven shaft 18 are in substantially perfect alicJn-
ment, that is, they have no parallel or angular misalignment
' and there is no axial stretch or compression of the f]exible
coupling, the outer surfaces 49 should be flush with the sur~
faces 43 of the guards 39. As hereinafter described, the
surfaces 43 serve as reference surfaces for ascertaining the
~ relative positions of the planar surfaces 49 carried by the f
.~ paddles 47.
Means is provided for detecting the positions of
. the surfaces 43 and 49 and consists of probe means in the form
`~ !0 of four separate probes 51 which are also positioned in four
quadrants. The probes 51 are mounted in a suitable manner
such as by placing the same in a mounting yoke 52. As shown
in Figure 2, the mo~nting yokes 52 are supported in a suit-
able manner in a fixed position by a bracket 53 which is
-~ secured to the fixed or reference machine 16. It should be
appreciated that, if deslred, the yokes 52 could be supported
upon pedestals mounted upon the base 13. Alternatively, one
; of the yokes could be secured to the fixed or reference
machine, whereas the other yoke adjacent to the driven or
O movable machine can be secured to the movable machine.
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The probes 51 are non-contact type pro~imity
detectors and are mounted so as to have suitable spacings or
gaps between the probes and the surfaces 43 and 49 as, for
example, 40 to 60 milliinches. One type of probe found to be
particularly satisfactory is the Bently non-contacting eddy
current probe manufactured by The Bently Nevada Corporation
of Minden, ~evada. Such a probe is a gap to voltage trans-
'~ ducer and measures the distance to any conductive material.
The actual transducer in the probe is a flat coil of wire
L0 locatedon the end of a ceramic tip. The probe is driven by
an RF voltage and provides a signal output which is a voltage
proportional to the gap distance between the probe and the
obserued surface. If there is no conductive material to
intercept the magnetic fiel~, there is no loss of RF signal.
When a conductive surface approaches the probe tip, eddy
currents are generated on the surface of the material ~nd
~ power is absorbed. Circuitry is provided which measures the
,~ RF voltage envelope and provides a d.c. signal output equal
,
to the negative peaks of the envelope. The output from the
0 circuitry driving the probe provides an average d.c. voltage
which gives the average gap distance.
, Timing means is provided for ascertaining when the
probes 51 are looking at the surfaces 43 and when they are
looking at the surfaces 49. As shown on the drawings, such
means consists of a pair of ti~ing probes 56 which are carried
by a mounting bracket 57 also mounted upon the bracket 53.
As will be noted from the drawings, the timing probes 56 are
positioned in such a manner so that they can view the circum-
ferential peripheral surface 58 on one end of the flexible
coupling 19. A plurality of notches 59 are formed in the
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parts forming thc end of the coupling including the flang~s
28 and 2~, the diaphragm 37 and the guard 39. The notchcs
extend in a direction which is axial of the center tube 34 and
have a f1nite width. Each of the notches is positioned so
that it is in alignment with the center of a paddle 47. Thus,
since four paddles have been provided, four notches 59 have
been provided. It will be noted that the timing probes 56
have been spaced approximately 45 apart so that when
one of the timing probes is seeing notch 59, the other f !~
the timing probes is viewins a portion of the peripheral
surface 58 which is free of a notch.
In order to understand the present method and the
method of operation of the alignment apparatus, reference i5 ,,'
now ma~e to Figures 4, 5 and 6. Figure 4 is a diagr~mmatic
illustration of a pure parallel misalignment situation in a
vertical plane in which the misalignment has been greatly
exaggerated for purposes of illustration. Figure 5 is
a similar diagrammatic illustration for pure angular mis- ~`
alignment in a vertical plane and Figure 7 is a similar
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0 illustration for stretch and compression in an axial direc-
~'~ tion. :
Returning to Figure 4, the various parts of the
machine train have been labelled such as the reference shaft
.. ,~ .
17 and the movable shaft 18. Similarly, the reference
surfaces 43 have been identified as have the paddle surfaces
49. The letter "1" denotes the length of the spool or center
tube 34 from diaphragm to diaphragm. The letter "r" repre-
sents the probe mounting radius which is the distance from
s the axis of rotation of the reference shaft 17 to the center
O of the probc 51. The letter UX" represents the amount of ~
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parallel misalignmcnt of the movable shaft 18 in mils from
its theoretical pcrfectly aligned position which is repre-
J sented by the broken line 71. The letter "d" represents the
differential measurement bctween the paddle surface ~9 and
the reference surface 43. The angle ex represents the
angle between the axis of rotation of the spool piece or
center tube 34 and the axis of rotation of the spool piece
or center tube 34 in a theoretically aligned position as !;
represented by the broken line 72.
LO The arrows shown in Figure 4 represent probes 51
which are looking at the reference surfaces 43 and the paddle 1
surfaces 49. The probes 51 which are looking at one er.d of 1'
' the flexible coupling are designated as "A" type probes,
whereas the probes looking at the other end o the f,exible
coupling are designated "B" type probes. Thus the probes
51 shown in Figure 4 have been designated as "A top" and
"A bottom", "B top" and "B bottom". It should be appreciated
that as hereinbefore described there are four probes provided
for each end of the flexible coupling. The other two probes
' O on each end can be designated as right and left probes with
the right probe corresponding to the top probe and the left _
probe corresponding to the bottom probe. In order to ascer- `
tain the right and left probes, it is assumed that one is
standing in the position of the fixed machine and looking
down on the machine train toward the movable machine.
' In examining Figure 4, it will be noted that plus . ~-
and minus signs have been placed between the surfaces 43 and
49. These designations have been arbitrarily chosen but have
been selected to make possible consistency in the mathemat-
~D ical calculations which are hereinater set forth.
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For purposes of illustration, a displacement of the paddle
surface 49 with respect to the refcrence surface 43 in a
..
direction away from the probe has been considered to be
positive and in a direction toward the probe has been con-
sidered to be negative.
For purposes of analyzing the triqonomet~y which
is involved in the present method, it has been assu~ed that
~. the angle ~xl for all practical purposes ,is very small, i.e. ' I!
ranging from zero to 5, so that the approximatior. of ~x in
radian measurement is approximately equal to x/l as sho~jn by 3
equation 1. By the theory of similar triangles, it can be
seen that the angle 6x between the paddle surface 49 and
the reference surface 43 is identical to the angle ~x
which is the angle between Lhe axis of the center tube 34 Z
and its theoretically aligned axis 72. The two triangles ~r
are similar from a corollary. Since all three sides of the
triangles are perpendicular to their corresponding sides as
in~dicated by conventional geometrical notation shown in
Figure 4, the triangles are similar. Thus as shown in
equation 2, ax is approximately equal to d/r.
Since ~x equals a , equation 3 can be written.
Solving for x as shown in equation 4, we find that x = l/r d.
An average d is ascertained by taking an average of the four
measurements which are shown in Figure 4. ~he signs of these
measurements have been taken from the assùmptions previously
made.
After d average has been ascertained, this figure
is inserted into equation 4 to solve for x and to give x mils
of parallel misalignment in a vertical dlrection. This cal-
culation is shown in equation 6 in which 1/4 represents a
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scale factor which is a constant for a particular flexible
coupling in a machine train. The l and the r can be mea~ured
in any units of length as long as they are in the same units.
It can now be seen that with the above calculations
that the figure obtained for x represents the mils in parallel
misalignment in a vertical direction. Similar calculations
are carried out to ascertain the parallel misali~nment in a
t'~ horizontal direction.
Now let it be assumed that it is desired to obtain
the angular misalignment of the two shafts 17 and 18 in a
vertical direction. For purposes of convenience, the dia-
grammatic representation shown in Figure 5 is utilized. The
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designations shown in Figure 5 are very similar to those
sh^wn in Figure 4 except that the positions of the paddle
, surfaces and the reference surfaces in the "B" machine have
been reversed. In other words, the reference surface 43 at
the top for the "B" machine is forward of the paddle surface
rather than the converse as shown in Figure 4.
The designation x represents the misalignment in
a vertical plane of the shaft 18 of the ~ovable ~achine from
a theoretically aligned position from a reference point 73
which is equidistant from the ends of the flexible coupling
~ l9 in a perfectly aligned condition.
-i Making the same assumptions as were made in conjunc-
tion with Figure 4~ ~x is approximately equal to x/l as
shown by equation 7. Now solving for ~x as shown in equation
~:: .
8, it can be seen that ~x twice the size of ~x because one
leg of the triangle for the angle 9x is twice the length
of the corresponding leg for the triangle for the angle ~x
~0 Therefore, as set forth in equation 8, ~x is approximately
equal to 2~x for small angles f ~x and ~ .
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Now using thc theory of similar triangles as set
forth above in conjunction with Figure 4~ x is approxi-
mately equal to d/r for small an~les of ~x . Then substi- r
tuting this into equation g, we find that ~x is equal to 2d/r
as shown in equation 10 to give a radian measure of ~x in
mils per inch. I!owever, it is desired to have a radian ¦,
measure in mils per foot, the numerator is multiplied by 12
as shown in equation 11.
It is now desirable to ascertain the d average b~
taking the average of all probe measuremen~s in Figu~e ;
as shown in equation 12. Substituting d average into
equation 11 gives the average measurement of ~x in mils per
foot as shown in equation 13. It has been assumed in equation
13 that (r) is measured in inches. Similar calculations are
made to ascertain the angular misalignment in a horizontal
plane.
In-Figure 6 the combined angular and parallel t
misalignment described in conjunction with Figures 4 and 5
are shown. It will be noted that in Figure 6, legs A and B
have been identified. These are the locations at which
corrections in the alignment will be made for the movable
machine or shaft. This can be accomplished by shimming the i -
two spaced apart pedestals 23 carrying the movable shaft 18 `
as hereinafter described. The dimension "a" is the distance
from the reference point 73 to the center of the first pedes-
tal 23 in a direction away from reference machine 16 and
with the letter"b" representing the distance between the
reference point 73 and the center of the second pedestal 23
in a direction away from the reference machine 16. ¦
One practicing the present method would use the
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- information gained from the equations shown in conjunction
with ~igures 4 and 5 to give respectively the parallel mis-
alignment in mils and the an~ular misalignment in mils per
~ ~,
foot in a vertical plane. In order to make the necessary
adjustment for aligning the movable shaft 18, it is desirable
,to co~bine these two measurements. This is accomplished as ¦
shown in Figure 6 in which "e" is the correction in a vertical
` correction for leg A in mils; "f" represents the vertical
correction in mils for leg B; "g" represents 'he correction
0 in mils in a horizontal direction for leg A; and "h" rep-
resents the correction in mils in a horizontal direction for
" leg B. ,
; As can be seen, the dimension "e" is obtained in
equation 14. The letter "x" represents the mils in parallél
, misalignment. The actual mils for the angular misalignment
, id obtained b~ taking the angle ~x and multiplying it by the ~ ,
length to leg A measured in feet. The sum of these two
represent the total parallel misalignment in a,vertical
direction. Simiiar calculations are made for the other
" 3 dimensions as set forth in equations 15, 16 and 17 in which
the dimensions "y" represent the same distances in a hori-
`, zontal plane as the distances "x" represents in a vertical
plane. Similarly, the angle ~y represents the same angular
--i measurement in a horizontal plane as the angular measurement
~x represents in a vertical plane.
" With the above information, it can be seen that
adjustment operations can be carried out on the pedestals 23
, by suitable shimming and the like to provide the necessary
,~ movement of the pedestals to bring the movable shaft 18
into perfect alignment ~ith the reference shaft 17.
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In addition to the parallel misalignment and
angular misalignment calculations which have horetofore been
made, it is also necessary to make calculations to ascertain
the amount of stretch or compression in an axial direction P
~,
of the flexible coupling l9. The diagram for analyzin~ I~
these calculations is set forth in ~igure 7 in which the ¦,
reference surfaces 43 and the paddle surfaces 49 are shown.
In the diagram it is assumed that the flexible couplin~ 19
is in stretch and, therefore, the paddle surfaces 49 on both
~3 0 ends of the coupling are closer to the probes 51 than are the
~:~ referonce surfaces 43. A broken line 76 represents ~he
theoretical position for the padd]e surfaces 49 when there is
~ no stretch or comprescion on the flexible coupling l9. Simi-
q ~ larly, the surfaces 43 woulJ also be on the line 76 when the
flexible coupling is in this condition. The le~ters "u" and
"w" represent the stretch on the respective di~phr~gms on
both ends of th~ flexible coupling. Normally, the stretch or
compxession would be divided equally betweer. the two dia-
phragms if the two diaphragms are of identical compliance.
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0 However, if the compliance of the two diaphragms is different,
then the dimensions "u" and "w" would be in proportion to th~
relative compliances of the two diaphragms. Equation 18
establishes that the total amount of stretch is equal to the
~ sum of w + u which is the combined stretch of the two dia-
'~, phragms.
~ ~ "w" and "u" are ascertained by obtaining an
'i~ average by taking one-fourth of the total measurements from
the four probes as shown by equations l9 and 20. Combining
equations 19 and 20 into 18 gives equation 21 to provide
the actual measuremont in mils of stretch.
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A similar analysis can be utilized for obtaining
comp~ession if that should be the case. Using this infor-
mation, the movablc machine would be moved towards the fixed
machine by suitable means such as jack screws and the like a
distance specified by the amount ~e~ to eliminate all stretch
in the flexible cou~ling 19. Conversely, if there is com- ¦
pression in the coupling 19, this could be removed b~- movln~
the movable machine in an opposite direction with respect to
the fixed machine. ~hen all this has been accomplished, the
O shafts of the two machines will be perfectly aligned.
In Figure 8, there is shown a schematic dia~ram
of the electronic circu-try which is utilized for taking
the information given by the probes 51 and deriving elec- -
.,
tronically the exact measurements in mils or meters which
are to be utilized in correcting the misalignment of the ;
movable shaft 18. ¦
As can be seen in the circuit diagram in Figure 8,
- the probes 51 have been shown in the upper left-hand corner }
with the probes Sl for one of the machines at one end of the
) flexible coupling being identified as "A" probes and the
probes associated with the other end of the flexible -
7 coupling connected to the movable machine being identified as
"B" probes. The outputs of these probes are connected to
four algebraic amplifiers 81 as shown~ As indicated in the
~; schematic diagram, four probe outputs are connected to each
of the algebraic amplifiers to provide desired algebraic
functions. For example, the first algekraic amplifier 81 ~-
is utilized for obtaining the algebraic portion of equation
6 for obtaining the parallel misalignment in a vertical
plane. The next lower algebraic amplifier is used for
i`
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obtaining a similar mc~suremcnt for angular displacement
in a vertical plane. The next algebraic amplifier is
utilized for obtaining paralleL misali~nment in the hori-
zontal plane, and the last algebraic amplifier is utilized
for obtaining angular displacement in a horizontal plane.
The algebraic amplifiers 81 are of conventional type and
each utilizes an operational amplifier 82.
Another alsebraic amplifier 84 of a t~pe different
from the algebraic amplifier 81 is utilized for providing
the algebraic function set forth by equation 21 to obtain
stretch and compression information. As will be noted,
this algebraic amplifier 8~ is connccted to the out~ut of
all eight transducers 51. The algebraic amplifier 84 also
includes an operational amplifier 86.
.~
The outputs of the algebraic amplifiers 81 are
s supplied to sample and hold circuit 87. The sample and hold
circuits 87 remember the paddle and reference voltages unti
'~ the paddles arrive at the same position, at which time the
,
information in the sample and hold circuit is updated. As
1 shown, each of the sample and hold circuits 87 includes a
;, plurality of analog gates 88 identified by gates 1-8 and
''x
~ are driven by signals Sig. 1 to Sig. 8 from the timing logic
v' circuit 91 (see Fig. 8B) in a manner as hereinafter described.
The outputs of the gates 88 are supplied to a capacitive
storage networks 92 which are connected to operational ~ 3
amplifiers 93 operated in voltage follower modes. The oper-
~- ational amplifier 93 serves to buffer the capacitive network L
to ensure that the capacitive network will store the infor-
mation contained therein for relatively long periods of time.
6 The other sample and hold circuit 87 are identical to the one
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hcrcinbcfore dcscribed. ~n additional sam~le and hold
circuit 96 is provided which is connected to thc output of
the algebraic amplifier 84 for the stretch and compre~sion
information. Only two channels are rcquired in the sample
and hold circuit 96 rather than eight channels provided in .
the sample and hold circuits 87 because all ei~ht channels
of information are supplied to the algebraic amplifier 84.
As can be seen from the circuit diagram in Figures
8A and 8B, the first four channels of the sample and hold
circuit 87 are utilized for storing information on the
positions of the paddle surfaces 49, whereas the other four
channels are utilized for storing information on the positions
of the reference surfaces 43.
The outputs of each of the sample and hold cir-
cuits 87 are supplied to a d.c. average and difference
amplifier 98. This latter amplifier averages the paddle
and reference voltages and thereby obtains the difference
of the two averages to give the average meacurement "d" as
determined by equation 5. As can be seen, the d.c. average
and difference amplifier 98 is a resistive network which
feeds into an operational amplifier 99. The other three d.c.
average and difference amplifiers are identical to the one
hereinbefore described. The output of the sample and hold
circuit 96 is supplied to a difference amplifier 101 which
simply substracts the two signals supplied to it to give an `
unscaled "z" dimension as set forth by equation 21.
Four outputs of the four d.c. average and differ-
ence amplifiers 98 are supplied to a single multiplexed
scaling circuit 103. This multiplexed scaling circuit con-
sists of a plurality of four gates 104 which have been
,~ ' .
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id~ntifi~d as gates 9~12, respectiv21y, which are of analog
~ .
~j type and are driven by signals Sig. 9-12 as indicated which
:,
are supplied from a free running clock circuit 106 herein-
after described. The outputs of the gates 104 are supplied ~,
to a buffer amplifier 107. The output of the buffer amplifier
is supplied to the input of a scaling amplifier 108 which ~,
includes an adjustable potentiometer 109 which is adjusted
so as to reflect the actual measurement "r". The output of
the scaling amplifier 108 is supplied to the inputs of
0 three different scaling amplifiers 111, 112 and 113. The
;~, scaling amplifiers 111, 112 and 113 each include adjus~able
potentiometers 114, 116 and 117 to permit insertion of the
/ information representative of the dimensions "a", "1", "b". I,
;, The output of each of the scaling amplifiers 111, 112 and '~
; 113 is supplied to a pair of gates 121 and 122 of the type _ -
hereinbefore described which are gated by the signals indi- ?
- cated from the free running clock 106. The outputs of the
gates 121 and 122 are supplied to capacitive storage networks
123 of the type hereinbefore described. The outputs of these
' 0 storage ne~works are connected to buffer amplifiers 124
which again ensure that the storage networks will retain the
information obtained therein for relatively long periods of
time. The output of each buffer amplifier 124 is supplied
to summing amplifiers 126. The outputs of the summing
amplifiers 126 are supplied to meters 127. The meters 127
are of a suitable type such as one which will take a voltage
input and convert it to visual display in the desired measure- ~
~, ment such as mils.
The difference amplifier 101 for the stretch and
D compression circuitry supplies its output to a scaling
,' ' ' .
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1048773~
circuit 131 which has a fixed gain in accordance with
the scale factor of the linear transducers 51. The out-
put of the scaling circuit 131 is supplied to a meter
132 of the type similar to meter :L27 and supplies the
stretch and compression measurement.
The timing logic circuit 91 includes a NAND gate 136
which receives on its two inputs the outputs of the two
timing transducers 56. The NAND gate will supply a "1"
whenever either of the two transducers 56 sees a notch
, .. .
in the flexible coupling. This information is supplied
to a binary counter which supplies its output to a bin-
ary to a BCD converter 138. The D gate of the converter
138 is connected to the output of the NAND gate 136 and
serves an enable function. There are eight signal out-
puts provided by the converter 138 which are ~tilized
for timing functions as hereinbefore described. In
addition, the timing logic is provided with two addition-
al outputs identified as Sig. 13 and Sig. 14 which are
also utilized in conjunction with the stretch and compres-
sion measurements.
The free running clock 106 consists of a clock 141
of a conventional type which runs at a relatively slow
rate of speed as, for example, 100 Hz. The output from
the clock is supplied to a ring counter 142 of a conven-
tional type which is provided with four outputs identi~
fied as Sig. 9-12 which are utilized in the circuitry
hereinbefore deecribed.
In order to explain more in detail the operation
of the circuitry in Figure 8, let it be assumed that it
is desired to obtain the measurement "e" as shown in
equation 14 and to display the same on the~meter 127.
~'
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~, ' ' " ~ ' '.,
10~i773 , i
. As the flexible coupling 19 makes one complet~
rotation in the machine train, the timing transducer will
emit four pulses. These four pluses are supplied through l
the N~ND gate 136 to the binary counter 137 and to the binary tto BCD converter 138 to provide signal outputs on Sig. 1-8 ¦t
in the sequence indicated within a time frame dctcrmined by
the speed of rotation of the flexible coupling 19. These I.
signals Sig. 1-8 close the gates 1-8 in the sequence 1,5,2,6,
3,7,4,8 in the sample and hold circuitry 87 and thus load the
storage networks 92 with a voltage which is proportiona~. to
the algebraic function in equation 6. This information is .stored eight different times in eight different storage
networks 92 with four of them being for the probes 51
obsc.ving the paddles 47 and the other four for the probes
51 observing the reference surfaces 43. These eight values
for this measurement are averaged in the d.c. average and
difference amplifier 98. This information is supplied to
gate 9 of the gates 104.
Similar information for the other measurements
hereinbefore described are supplied to the other sates 10,
11 and 12. This information is time shared by operation of ~ `
the gates 104 through signals Sig. 9-12 supplied from the t-
free running clock 106. This information thus is sequentially
supplied to the buffer 107 and to.the scaling amplifier 108
which inserts the scaling function l/r as hereinbefore t ,~
described. The only other gate which is closed is gate 16 ~ :
which is operated by the signal 9 from the free running clock
106 and thus this information passes through the scaling
amplifier 112 which inserts therein the scaling function "1"
and stores the same in the storage network 123. Thus, there
~,' , .
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1~4~773
is stored at this timc thç relationship l/r times the parallel
vertical albcgra represented by equation 6.
As hereinbefore described, the angular vertical
, information has alrcady stored and is available at gate 10.
When signal Sig. 10 is supplied from the free r~mning clock,
this information is sup?lied to the scaling ampli'ier l~B
to insert the scaling function of 1/4. This combined infor-
mation is then supplied through the scaling amplificrs 111
,~ and 113 and through gates 14 and 18 because these sates are
both operated by the same Sig. 10. The scaling amplifier 111
inserts the scaling function "a" whereas the scaling am~'ifier
113 inserts the caling function "b". The information from r
gate 14 is supplied to the storage network 123 associated
the~ewith to store therein the information a/r times the
, ~ angular vertical measurement as represented by equation 13.
~ This information which is supplied through gates 14 and 16
- ar.d which has becr. sto.ed n the storage networks 123 is
then supplied through the buffer amplifiers 124 to the ~!
~ , summing amplifier which combines the two voltages which ,'
.$ ~ ~0 represent equation 14 to supply a voltage which represents
the value "e" to the meter 127 identified as leg A vertical -
; and ashereinbefore described represents a measurement in ,
mils by which the leg A should be raised or lowered to bring
~, the movable shaft into aiignment with the r,eference shaft.
, At the same tim,e that ~he leg A vertical information
-,";i is being obtained, the leg B vertical information is also
obtained because the information necessary for making this ,
.,~ . ,~
calculation represented by equation 15 has been stored in
the storage network 123 associated with gate 18 triggered by
;0 signal Sig. 10 and in the storage network 123 associated with
s.3 .
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gatc 1~ tri~gcred by si~nal Si~. 9.
The horizontal information for legs ~ and ~ is
obtained in a similar manner.
From the foregoing, it can be scen that with thc
electronic circuitry s~lown in Figure 8 it is possible to
obtain misalignment measure~ents. This is ma~e possib]e
because low time constants are associated with the misalign- ¦
ment of rotating machinery hereinbefore described. Thus,
~ the apparatus and circuitry can be placed on the machine
Y~ O and left on the machine while it is in operating co~dition ~~
to observe the machine train continuously.
The circuitry also has the advantage in t~.at it is
possible to make slow motion studies with the appara~us so
.
, that it can be utilized in conjunction with the initial set-
up of a machine train when it is not known whether or not `
there is a sufficiently satisfactory alignment to permit
operation of the machine train. This is made possible
because d.c. averaging techniques are utilized with the
sample and hold circuitry.
` O In practice, it has been found that it is difficult,
if not impossible, to obtain exactly precise alignment of
all of the paddle surfaces 49 so that they all lie in the
same plane. Because of this fact, the transducers 51 may
note small variations in the positions of the surfaces 49
- which could cause jitter or noise in the readout meter 127
at low machine speeds. This has been eliminated by the use
of eight channels in the sample and hold circuitry 87. Thus
even if a paddle surface is out of alignment with the other
possible surfaces, the same information with respect to the
-, ~ paddle surface would be stored in the same storage networ~
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1~8773
Any abcrrations in the spacing of the surfaces bccause o~
their being out of alignment are averaged out with the
eight channels of sample and hold information.
If it is not necessary to eliminate this jitter or
noise with respect to paddle misalignment, the sample and
hold circuitry could be simplified to provide only two
channels of information such as in the sample and hold cir-
cuitry 96. Similarly, the timing logic circuitry co~ld be
omitted. ,
L0 It should be appreciated that in place of the ~
multiplexed scaling circuitry 103 provided, other approaches !
can be utilized. For example, the four channels of infor-
mation supplied from the four d.c. average and differential
am,lifiers instead of being supplied to the multiplexed
scaling circuitry would be supplied to four independent
scaling circuits each of which included adjustment for the
,. !J
parameters of "r", "1", "a" and "b". The outputs of the
~;~ scaling circuits would then be supplied directly to the L
; respective meters 127. p
~0 If it is not necessary or desirable to have total
misalignment information for both legs A and B, then the
alignment information could be read out in the form of
. ~ .
parallel and angular misalignment as they exit from the d.c.
average and difference amplificrs 98. This information then ~ -
can be utilized by the operator to calculate the measure-
ments which are represented by equations 14-17 to obtain the
actual mils misalignment of legs A and B.
. .
Also, if it is desired to eliminate the electronic
circuitxy as shown in Figure 8, it is possible by the use of
oscilloscope to ascertain the necessary information and
.
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1(~4~773
thereafter make the calculations required to d~termine the
alignmcnt conditions of lcgs A and B. For example, the
oscilloscope could be connected to each of the probes 51
to obtain a visual display of the information being ascer-
tained by the probe. The output would be in the form of a
~chopped squarewave. By observing the scale on the oscillo-
; scope, it is possible to calculate the differential measure-
ment between the paddle and reference surfaces. In such
a case it would be possible to utilize a single probe and '~
.0 to move it into the four different positions to obtain the
necessary four measurenents on each side of the flexible !~
coupling. ~t slow roll conditions of the shafts 17 and 18,
a d.c. voltmeter could be used to obtain this same informa-
tion. With this latter method if it is assumed that the
paddle surfaces are perfectly aligned, there is no necessity ~ ~1
for a timing probe. However, if the paddles are not per-
fectly aligned which is normally the case, a single timing
probe would be required so that it would be possible to
ascertain which time sequence of information should be
O added and which should be subtracted in the algebraic
equations.
In the electronic circuitry shown in Figure 8, ~~
s the two timing probes 56 are required in order to be able
to ascertain when the machine starts whether a paddle
surface or a reference surface is being observed. By
utilizing phase locked loop techniques, it is possible to
utilize a single probe in which the phase locked loop
would supply a pulse representing the geometrical timing for 1,
the position of the other probe. This is possible because
' ~ it is known that the notch is aligned with the paddle. The
,, . , , , ,
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1~87~3
phase loc~ed loo~ could also be utilized to provide
additional signals so that it would only be neccssary to
provide onc notch in the flexible coupling. It should be
pointed out that the notch could be any place on the rotat n~ !~
sh~fts of the machine train. Also instead of a notch a
projection could be used. All that is needed is some~hing 15
that can be observed on the rotating shaft train to provide
a timing signal. ¦`
In certain instances it may be very desirahle to
ascertain whethcr or not a diaphragm is being stressed
beyond its elastic limit or that it is operating ~ithin
usable stress levels. This can be ascertained b~ measuring
the gap distance between the probes 51 and the paddle sur- - -
faces using the reference surfaces 43 as a reference and to ~t
translate this directly into stress information utillzing
a scaling constant k which can be derived empirically or i
theoretically from the diaphragms themselves. Thus the
information supplied directly from the transducers 51 5
themselves can be utilized for making such an analysis.
It should be appreciated in conjunction wit~ ~he
foregoing that it is possible in a machine train that most
of the misalignment which is seen by a flexible coupling can
~
be bornc by one of the diaphragms and, therefore it is all
the more important to make the hereinbefore described mea-
surements to ascertain whether or not the diaphragms are ~
being stressed beyond their usable limits. 5
:;~, t
It should be pointed out that in conjunction with
the foregoing description of the invention it has been
a8sumed that the axis of the shaft is disposed in a hori-
~ I zontal direction. It should be appreciated that the same
.~ '
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104t~773
considerations would apply cven though the sha~t i5 in a
vcrtical dircction or at any othcr ancJular position. Sim-
ilarly, it should be appreciated that the yoke for mounting
the probes could be twisted or mounted as~ew with r~spect b
' to thc axis and still the same type of informatiol~ would be
c~ supplied.
s It should be appreciated that if misalignment will
only occur in one direction, that the number of linear trans-
ducers can be reduced by one-half as well as the accoMpanyin~
'"~ 0 circuitry.
~ ' As hereinbefore explained, the present invention 1'
?':' has application to other flexible couplings other than ~f
''~ the diaphragm type. Thus, there is shown in Figures 9 and 10
a gear-type flexible coupling 151. 'rhe coupling 151 consis~s
of a hollow cylindrical body lS2 which is provided with in-
wardly radially extending internal gear teeth 153 extending
axially thereof. First and second hubs 156 and lS7 are
mounted within the body 152 with hub 156 being adapted to ,~
- be secured to one shaft which can be identified as the
!0 reference shaft 158 and the other hub 157 being secured to
,.................................................................... ..
the other shaft which can be identified as the movable shaft
159. The hubs 156 and 157 have spur gears 161 and 162 formed
integral therewith and which are adapted to mesh with the
~' teeth 153 provided in the body 152 and to engage the same.
's ~
In addition, the spur gears 161 and 162 are adapted'to move
;' longitudinally of the teeth 153 provided in the body 152
' to accommodate dual movement of the shafts. A plurality ~ r
paddles 166 are providcd which extend over one end of the
hub 157 and are affixcd to the body 152 by suitable means
~0 such as bracket 167. The paddles 166 have surfaces 168 thc
. , ,
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positions of which are adaptcd to be sensed by proximity i
probes or transducers of the type hereinbefore described.
Similarly, there are provided members 169 secured to the
exterior of the hub 157 which have planar surfaces 171 which
generally lie in the same plane as the surfaces 168 a~d which
serve as refer~nce surfaces, the positions of ~hicl~ are
also sensed by the proximity probes.
In this gear type of coupling, the tor~ue forces
are transmitted by the gearing hereinbefore described. This
type of flexible coupling will acco~Modate parallel misalign-
ment as well as angular misalignment to some degree. In 1.
addition, the flexible coupling will accommodate axial mis- ';
,. j.
alignment to a greater degree than that which can be accommo-
dated by the flexible type diaphragm coupling. Since refer ~,
ence surfaces and paddle surfaces have been provided on this _
gear type flexible coupling which can be sensed in the same
manner as with the diaphragm type coupling hereinbefore
described, it is readily apparent that the present invention ~-
is also applicable to gear type ~ouplings. It also sho~lld be
appreciated that the present invention is applicable to other
types of flexible couplings such as ones which use O-ring or
other elastomer elements.
It should be appreciated that although in conjunc-
tion with the foregoing embodiments the proximity measure-
ments were measured in an axial direction, that these same
measurements can be accomplished in a radial direction by
proper construction of the paddles. Such a typical construc-
tion is shown in Figures 11 and 12. As shown in Figures 11 ¦
and 12, a portion of a flexible diaphragm type coupling is
shown and is constructed in the manner hereinbefore described.
,'~ ' .
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1~4~773
~lowever, in licu of providin~ cut-outs as hcrcirlbefore
described, the guard is provided with a plurality of four
feet 176 which extend outwardly in a direction wllich is
parallel to the axis of the ~enter tube 34 and generally
surround the tube 34. T~ey are circumferentially spaced
around the tube so that the center lines of the paddles are
spaced 90 apart. In addition, there are provided projec-
tions or tabs 177 which are mounted on the center tube 3
adjacent the paddles 176. The paddles 176 have arcuate
surfaces 178 and the tabs 177 have arcuate surfaces 179
which are in circumferential alignment when the diaphragms
of the coupling are in a natural or unstressed condition.
. .
With such an arrangement radially disposed probes Sl are
provided ~7hich are carried ~y brackets 181. With such-an
arrangement, it can be seen that with parallel misalignment
and angular misalignment, the paddle surfaces 176 will be
shifted with respect to the surfaces 179 carried by the shaft
to give indications similar to that which are obtained when
i~ - axial movement was observed. It should be appreciated that
the radial arrangement of the probes 51 is not able to ascer-
rr~ tain axial misalignment, i.e. stretch and compression of
., .
the type hereinbefore described. However, this type of an
arrangement of the probes 51 does have the ability to accommo-
date large amounts of axial movement of the hubs of the
flexible coupling such as which may occur in conjunction with
a gear type coupling.
In the event a single element flexible coupling
is utilized, it is only necessary to make the one measure-
ment, i.e. the measurements which are presently carried on
one end of the flexible coupling.
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~ It should be appreciated that in conjunction with
:,
hC foregoing apparatus and method various fail-safe features
can be provided. For example, out-of-tolerance indicators
..
can be provided for the transducers 51 to indicate when or,e
,....
or more of the same are operating out-of-tolerance. Simil~r
warning dcvices can be provided to indicate amplifiers
operating in saturation, loss of power su~ply voltages and
other malfunctions such as brea~age of cables to transducers.
Additionally, it is readily apparent to one skilled in the
art that if desired additional cirsuitry can be provid~d to
cause automatic shut-down of the machine train in the event
one or more undesirable conditions occur. Alternatively,
automatic warning to operators can be provided. In addition,
thf- information which is supplied can also be utilized for
automatically controlling the alignment.
It should be appreciated that although the probes
have generally been mounted 90 apart that the probes can b~
mounted at different angles, it merely being necessarv that
the probes be spaced apart a sufficient distance so that two
.
~s 20 degr~es of freedom of movement measurements can be made.
Vtilizing angles different than 90 merely complicates the
- mathematics which can be easily taken into account in a
computer. However, in order to obtain mutually exclusive
equations as hereinbefore set forth, it is necessary to
provide four different measurements.
c It is apparent from the foregoing that therc has
been provided a new and improved shaft alignment apparatus
, - and method whereby the alignment between any pair of machines
, ~ with rotating shafts in any machine ~rain having a flexible
couplin~ therebetween can be mcasur~d with the machines at
.~,
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1~4~773
rest and during start-up and ~uring all runing conditions
and on shut-down. The apparatu~ provides indications of the
axial motion of this machine both steady state and dynamically
and both relatively and absolutely. From the foregoing it
; can be seen that the apparatus also provides the'net couplinghub motion of each machine due to any dynamic motion of each
rotor such as that due to fixed bows, thermal bows, unbalance
bows and other action at rotative speed in a for-Jard direction
~ and also that due to any other action at other than rotative
-~ 10 speed forward direction such as caused by oil whirl, reexci-tation of balance resonances and other actions that create
; shaft motions with the above having the result of tiltin~ theplane of the coupling hub of each rotor of the machine away
from the plane normal to the axis of rotation for the mac~i~e
train. The information obtained with the apparatus makes it
;~ possible to protect the machines connected by the flexible
coupling and to protect the coupling from exposure to
various motions and stresses which are beyond its capabili-
ties. With the apparatus, readings can be provided for
first aligning the machine pair properly before start-up,
j parallel alignment, angular alignment and axial spacing.
~ This same information can be obtained during running of the
r~ machine train and also in shut-down.
The apparatus also is the tyre which can be used
in conjunction with a machine train and after alignment has
,,
been completely removed from the machine train. Alterna-
tively, if desired, the apparatus can be left on the machine
train to provide continuous monitoring to give operator
warnings which automatically shut down the machine or to
~ 30 automatically cause movement of the movabie machine with re-
- - spect to the reference machine to eliminate any misaliynment.
., .
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