U.S. patent application number 10/963209 was filed with the patent office on 2006-04-13 for method and apparatus for coupling components.
Invention is credited to Wieslaw Muskus, Jyotish Parekh, Jeffrey Post.
Application Number | 20060079335 10/963209 |
Document ID | / |
Family ID | 35708931 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060079335 |
Kind Code |
A1 |
Muskus; Wieslaw ; et
al. |
April 13, 2006 |
Method and apparatus for coupling components
Abstract
Disclosed herein is a single piece unitary metal coupling having
a first end and a second end and a convolution between the first
and second ends. Further disclosed herein is a method for making a
single piece unitary construction flexible coupling including
machining from a starting material, one or more single piece
unitary construction flexible couplings having a first coupling end
and a second coupling end and one or more convolutions at the first
and second ends.
Inventors: |
Muskus; Wieslaw;
(Wethersfield, CT) ; Parekh; Jyotish; (West
Hartford, CT) ; Post; Jeffrey; (South Windsor,
CT) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
US
|
Family ID: |
35708931 |
Appl. No.: |
10/963209 |
Filed: |
October 11, 2004 |
Current U.S.
Class: |
464/79 |
Current CPC
Class: |
F16D 3/72 20130101 |
Class at
Publication: |
464/079 |
International
Class: |
F16D 3/52 20060101
F16D003/52 |
Claims
1. A single piece unitary metal coupling having a first end and a
second end and a convolution between the first and second ends.
2. A single piece unitary metal coupling having a first end and a
second end and a convolution between the first and second ends as
claimed in claim 1 wherein the convolution is of a cross-sectional
material thickness that varies with radial distance from an axis of
the coupling.
3. A single piece unitary metal coupling having a first end and a
second end and a convolution between the first and second ends as
claimed in claim 2 wherein the cross-sectional material thickness
increases as radial distance from the rotational axis
decreases.
4. A single piece unitary metal coupling having a first end and a
second end and a convolution between the first and second ends as
claimed in claim 1 wherein the coupling is cylindrical at an inside
dimension thereof.
5. A single piece unitary metal coupling having a first end and a
second end and a convolution between the first and second ends as
claimed in claim 1 wherein the first and second ends include a
connection.
6. A single piece unitary metal coupling having a first end and a
second end and a convolution between the first and second ends as
claimed in claim 5 wherein the connection arrangement is a
flange.
7. A single piece unitary metal coupling having a first end and a
second end and a convolution between the first and second ends as
claimed in claim 5 wherein the connection arrangement is a splined
connection.
8. A single piece unitary metal coupling having a first end and a
second end and a convolution between the first and second ends as
claimed in claim 1 wherein said coupling further includes at least
one opening at a radially outward position of said coupling.
9. A flexible metal coupling comprising: a first end; a second end;
a first convolution at the first end and the second end; and
wherein the flexible metal coupling is a single piece unitary
construction.
10. The flexible coupling of claim 9, wherein the coupling is made
from a material selected from one of titanium, corrosion resistant
steels, high strength steels, nickel materials, carbon steel and
maraging steel, and combinations including at least one of the
foregoing.
11. The flexible coupling of claim 9, further including nitriding
for enhanced fatigue properties and wear resistance.
12. A method for making a single piece unitary construction
flexible coupling comprising: machining from a starting material,
one or more single piece unitary construction flexible couplings
having a first coupling end and a second coupling end and one or
more convolutions at the first and second ends.
13. The method of claim 12 wherein the machining is one of computer
controlled turning, electro-discharge machining and electrochemical
machining.
14. The method of claim 12 further comprising nitriding the single
piece unitary flexible coupling.
15. The method of claim 12 wherein the method includes pre-heat
treating the starting material.
16. The method of claim 12 wherein the method includes post heat
treating the unitary flexible coupling.
17. The method of claim 12 wherein the machining includes angling
an outside surface of each convolution relative to an axis of the
coupling and angling an inside surface of each coupling differently
relative to an axis of the coupling.
18. The method of claim 12 wherein the machining further includes
tapering of a cross-sectional thickness of the coupling
convolutions with increasing radial distance from an axis of the
coupling.
19. The method of claim 12 wherein the method includes tailoring of
axial and bending stiffness of the coupling to effect one of
frequency displacement and resonance detuning.
20. A coupling consisting of: a single unitary piece of metallic
material having a first end and a second end and a convolution
disposed at the first and second ends.
21. A coupling comprising: a first end; a second end; a convolution
disposed at the first and second ends, said convolution having a
material thickness that decreases with increasing radial distance
from the rotational axis of the coupling.
22. A coupling comprising: a first end; a second end; a convolution
disposed at the first end and second end the convolution having an
outside surface an inside surface having different angles relative
to an axis of the coupling.
Description
BACKGROUND
[0001] In order to accommodate torque transfer and potentially
misalignment between rotatable members such as shafts, flexible
couplings have been employed. Such couplings are connected by
flanges or spline connections and are specifically designed to
transmit torque from one component to the other component while
absorbing and dissipating the effects of misalignment.
[0002] While many such couplings exist, all suffer from limited
degree of flexibility. One common way of increasing misalignment
tolerance is to incorporate additional flexible elements. This
however results in a heavier and more expensive construction as
well as commonly the introduction of additional stress risers
occasioned by the manufacturing process. Some increased flexibility
can be obtained but with diminishing returns.
[0003] A common causative factor related to prior art couplings
failing is the development of fatigue fractures. These can develop
both from a lack of flexibility (rigidity) overall in the coupling
and from individual stress risers within the coupling. Some of the
structural rigidity (material and stress risers) of currently
available commercial designs comes from the means of manufacture of
the coupling. One example of a process commonly associated with
stress risers being introduced to a coupling is a welding process
to join adjacent diaphragms. Welding causes localized phase change
in the metal of the disks often resulting in a change in hardness
and heat-treating properties of the coupling in the local region.
Another weakness of prior art couplings is that they can have very
low axial stiffness due to inherent design factors and method of
construction. This low stiffness can lead to vibration problems
that can produce failures of flexing elements.
[0004] The foregoing and other drawbacks inherent in the prior art
have been tolerated for an extended period of time because there
was no viable alternative. This fact notwithstanding, the art would
be very much benefited by the availability of a more durable
flexible coupling.
SUMMARY
[0005] Disclosed herein is a single piece unitary metal coupling
having a first end and a second end and a convolution between the
first and second ends.
[0006] Further disclosed herein is a method for making a single
piece unitary construction flexible coupling including machining
from a starting material, one or more single piece unitary
construction flexible couplings having a first coupling end and a
second coupling end and one or more convolutions at the first and
second ends.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Referring to the exemplary drawings wherein like elements
are numbered alike in the several Figures:
[0008] FIG. 1 is a perspective view of one embodiment of the
coupling;
[0009] FIG. 2 is a side view of a coupling similar to that of FIG.
1;
[0010] FIG. 3 is a cut-away perspective view of coupling
illustrated in FIG. 1;
[0011] FIG. 4 is a representation of a cross-sectional view of a
coupling of the invention and a fixed thickness coupling to show
points for stress analysis;
[0012] FIG. 5 is a graphical representation of torque stress at the
points identified in FIG. 4;
[0013] FIG. 6 is a graphical representation of stress due to
angular misalignment at the points identified in FIG. 4; and
[0014] FIG. 7 is a cross-sectional view of another embodiment of
the coupling;
[0015] FIG. 8 is a perspective view of the embodiment of the
coupling illustrated in FIG. 7;
[0016] FIG. 9 is a perspective schematic representation of a
milling tool to make the coupling hereof; and
[0017] FIG. 10 is a representation cross section of a deep machined
convolution illustrating inside geometry thereof.
DETAILED DESCRIPTION
[0018] Initially in this disclosure, embodiments of the coupling
itself are discussed followed by a method of manufacturing the
couplings.
[0019] Referring to FIG. 1, a perspective view of one embodiment of
the disclosed flexible coupling 10 is illustrated. The flexible
coupling 10 may be (and as illustrated is) a disk type coupling.
The particularly illustrated embodiment includes three convolutions
14, 18, and 22. More or fewer convolutions may be used. The
coupling 10 includes a first end 26 and a second end 30 intended to
be attached to first and second shafts (not shown). Configurations
for ends 26 and 30 include flanges, splined connections, threaded
connections, geometric drive shapes, etc. In the FIG. 1 embodiment,
the first end 26 is a first flange, and the second end 30 is a
second flange. Flanges 26 and 30 are illustrated without openings
but may include openings for through passage of fasteners. Also
noted is that the convolutions are illustrated without openings
therethrough in FIG. 1. In some embodiments of the coupling
disclosed herein, openings 32 are provided (as illustrated in FIG.
2). These openings assist in nitriding processes if employed and
also function to allow escape of moisture from within the coupling
during use.
[0020] Referring to FIG. 3, a cut-away view of the flexible
coupling 10 is illustrated. This view provides visual access to
both the interior of the coupling and to the thickness of the
material of the coupling. The coupling 10 comprises an inner
surface 34 and outer surface 38. Between the surfaces, the
thickness of material is not fixed but rather is gradually reduced
with increasing radial distance from the axis of the coupling
according to particular parameters that are discussed hereinbelow.
Also important to note is that an outside surface beginning at the
root of each convolution is radiused. In the illustrated coupling
the surface is a compound radius surface. At the inside surface
near the root of the convolution in an angle is formed for stress
reduction reasons. The outside surface 40 and inside surface 42 are
labeled in FIG. 4. FIG. 4 illustrates a representative cross
section 44 of one of the convolutions of a coupling of the
invention (disk 1), and superimposed thereon in broken lines (where
visible), a representation of a cross section 46 of a fixed
thickness coupling (disk 2). The purpose of the illustration is to
show thickness variation in the coupling disclosed herein and where
stress points are measured (numerals 1-23) for a Finite Element
Analysis, the results of which are graphically depicted in FIGS. 5
and 6. FIG. 5 depicts stress associated with applied torque while
FIG. 6 depicts stress associated with misalignment of the shafts
engaging the coupling. A reader is easily able to appreciate the
reduction in stress of the coupling according to this disclosure.
The coupling herein (disk 1) uses a radiused and tapered outer
surface 40 and an inner angled surface 42 near the inner diameter
of the flexible coupling to form a tailored thickness distribution
to achieve lower stresses and an optimized stress distribution for
the coupling. Specifically, the tailored wall thickness allows for
a reduction in total stress, and it reduces the stress
concentration and localized stress magnification that is present
with uniform wall thickness designs. FIG. 5 shows that the maximum
calculated stress is reduced by approximately 33% through the use
of the tapered thickness distribution illustrated for the applied
torque load case. In addition, the peak stress due to angular
misalignment for this coupling is reduced by approximately 18% and
the stress magnification effect has also been significantly reduced
with a less pronounced stress peak and a more uniform stress
distribution (FIG. 6).
[0021] The decreasing thickness cross section (with radial distance
from the coupling axis) for the convolutions according hereto allow
for tailoring of axial and bending stiffness of the coupling for
natural frequency placement and resonance detuning. This is
beneficial over other types of couplings with a constant thickness
type configuration because such are limited in terms of stiffness
control. This limitation has resulted in couplings that have had
vibration problems in a drive train leading to wear at attachment
points such as bolted flanges and splines. Moreover, such vibration
in arrangement in which such couplings might be incorporated has
even led to failure of the flexing elements in such prior art
systems.
[0022] The flexible coupling 10 may be manufactured from a number
of materials such as titanium, corrosion resistant steels, carbon
steel, high strength steels (including Maraging steel), and nickel
materials (such as Inconel) and combinations including at least one
of the foregoing. A common nitriding process may optionally be
utilized to create a hard shell nitride thickness and enhance
durability of the coupling. Gas nitriding is preferred due to the
depth of convolutions in the coupling.
[0023] Regardless of material selection, an overriding requirement
is to achieve superior material and fatigue characteristics by
ensuring that the coupling material has about consistent material
and fatigue properties throughout. That is to say that the coupling
as disclosed herein avoids localized stress risers associated with
inconsistent material and fatigue properties in its constitution
and construction. Achieving both of these has been elusive to the
art and yields exceptional strength and durability in the coupling
described herein. The disclosed coupling does not have any welds or
bonds that might otherwise alter material and/or fatigue properties
of the coupling material. Moreover, because the coupling does not
include bonds or welds (which are for obvious reasons located at
the outermost region of each disk in couplings of the prior art),
and because material thickness in the coupling decreases with
increasing distance from the coupling axis the center of gravity of
the coupling disclosed herein is positioned more radially inward
than prior art couplings have been able to achieve thereby
rendering the coupling disclosed herein superior to the prior art
couplings. One of the benefits of a reduced radial positioned
center of gravity is that the centrifugal force acting on the
coupling is much smaller than in a similarly dimensioned coupling
having a center of gravity positioned more radially outwardly of
the coupling axis (further from the axis of rotation of the
coupling).
[0024] In another embodiment hereof, and referring to FIGS. 7 and
8, the concept of the coupling illustrated above is retained but
the coupling is essentially inverted (outside to inside). This
embodiment is configured for smaller diameter axial opening 100
applications that would not permit machining of the deeper internal
cavities due to limited size of the coupling. The coupling 110 has
ends 126 and 130 which are located near the outside of the diameter
of the coupling 110. One will appreciate that the larger reach
machining is done from the outside of the coupling rather than the
inside thereof and inside machining depth is kept to a minimum. The
depth of any inside machining to be done is limited to the cutter
blade length minus the blade support width in line with the blade.
Therefore if a small diameter opening is required in the coupling
to be produced, the depth of inside machining is limited as well.
The embodiment of FIGS. 7 and 8, address this issue while still
retaining much of the strength and durability of the previously
described embodiments. In the illustration, a two convolution
coupling is shown with the deepest machining surface at 150. It is
apparent that there are two other depth machining surfaces and
these are identified as 152 and 154, but these are much less deep
and therefore may be machined with a smaller cutter that can be fit
through the inside diameter of the coupling. Ends 126 and 130 are
illustrated without any particular drive or connection arrangement
but it will be understood that any of the arrangements set forth
hereinbefore could be utilized.
[0025] The foregoing coupling embodiments are, as noted,
constructed from a single piece of material and machined. Such a
machining process was not heretofore available to the art because
it is common knowledge that deep inside machining requires
supported cutting tools. Such a supported cutting tool could not be
employed for the couplings hereof due to end diameter versus inside
machining diameters of the proposed couplings. More specifically,
the cutting tool utilized must be able to fit through at least one
end inside diameter and be sufficiently long to machine the deep
structure of the convolution. Utilizing an unsupported tool is
known to be insufficient for such use due to chatter that
invariably exists at an end cutting surface of any long cutting
blade. Chatter would be wholly unacceptable for a coupling such as
that disclosed herein because of the inherent stress riser effect
of surface irregularity of a coupling made with a chattering
cutter.
[0026] One of ordinary skill in the art, in view of the foregoing
will immediately conclude that a coupling such as those described
herein could not be machined. The inventors hereof however, have
developed a cutting tool that enables the machining of the coupling
as described while avoiding chatter and the deleterious effects
that accompany chatter. Referring to FIG. 9, the turning milling
tool 200 is illustrated. The tool comprises a mounting shaft which
is clearanced at 202. At an end of clearanced section 202 is a
blade 204 having a cutter 206 thereon. The blade 204 has a usable
cutting length of l and is unsupported. As the blade geometry and
composition (cobalt or other having equivalent material properties)
have sufficient strength and do not produce chatter, the full cut
length of the blade is available for machining inside portions of
the coupling 10. The turning tool 200 is to be kept stationary
while the coupling 10 is rotated to remove material therefrom. In
operation the entire blade length y must be less than an inside
dimension of at least one end 26 or 30 of the coupling 10, so that
it can fit into the inside dimension of the coupling to machine the
convolution(s). In a multiple convolution configuration, blade
length y must also be less than inside dimensions at the root of
each convolution so that the blade 204 may be passed through the
coupling to reach and machine each convolution inside surface.
[0027] In the making of inside surface of each convolution, the
inside walls 60 and 62 (see FIG. 10) of each deep convolution are
kept substantially parallel to one another and in a plane
substantially perpendicular to an axis of the coupling 10 for ease
of machining. At a tip end of deep convolutions however, the walls
are radiused at 64 and 66. Also important to the method is that the
cutter is narrower than the width of the convolution to facilitate
the radiused corners 64 and 66 as shown by adjusting depth and
linear movement of the cutter simultaneously. The angled surface or
chamfer 42 illustrated in FIG. 4 is still relatively easy to
machine and together with the compound radius outer surface 40,
reduces stress and helps to optimize stress distribution.
[0028] The tool discussed above is utilized in combination with a
computer numerically controlled turning machine (not shown). The
coupling in accordance with this disclosure will be turned from a
single piece of coupling material, thus making the flexible
coupling of a single piece unitary construction. Since the coupling
10 is a single piece unitary construction, it will have consistent
material and fatigue properties throughout the material, the
coupling 10 does not have welded parts, thus the coupling 10 does
not have areas with inconsistent material and/or fatigue properties
which are subject to failure. Gas nitriding further enhances the
material properties and fatigue strength, while welding decreases
the material properties and fatigue strength relative to the
nominal heat treated properties. The operating life span of the
coupling 10 is longer and more accurately predictable than the
operating life span of those couplings that use welding, bonding or
other attaching methods which affect the material and fatigue
properties of the material. In addition, welded or bonded
assemblies of prior art have been shown to have inconsistent levels
of quality due to lack of repeatability of said joining processes.
Moreover, due to the avoidance of heat generating attachment
methods, the coupling hereof may be pre-heat treated (i.e., before
machining) without risk of the benefit of that process being
deleteriously affected by the later steps of construction of the
coupling.
[0029] Although the disclosed flexible coupling 10 has been
described with respect to computer controlled turning, other
methods of machining may be used so long as welding or other
bonding methods that create stress risers are not used in the
convolutions. These other methods of machining include, but are not
limited to electro-discharge machining (EDM) and electrochemical
machining (ECM).
[0030] The use of the terms first, second, etc. do not denote any
order or importance, but rather the terms first, second, etc. are
used to distinguish one element from another.
[0031] The couplings disclosed herein can also utilize an
anti-flail bearing known to the art. The anti-flail bearing
provides a back up centering device to preserve the centerline and
allow for continued rotation in the unlikely event of a failure of
one of the convolutions. The anti-flail bearing combines a high
speed ball bearing that is made from carbon steels, corrosion
resistant materials such as Cronidur 30, XD-15, XD-15NW, ceramics,
corrosion resistant steel, and plastics and a special self
lubricating liner system, incorporating polytetrafluoroethylene
PTFE and other special fillers in a composite matrix, on the inner
or outer diameter of the high speed bearing to allow for axial
misalignment of the coupling during anti-flail operation.
Anti-flail bearings in general are known to the art, the changes
relative to known systems that are used in this disclosure are
related to materials which have been found to perform in a superior
manner.
[0032] While the disclosed apparatus and method has been described
with reference to a preferred embodiment, it will be understood by
those skilled in the art that various changes may be made and
equivalents may be substituted for elements thereof without
departing from the scope of the disclosed apparatus and method. In
addition, many modifications may be made to adapt a particular
situation or material to the teachings of the disclosed apparatus
and method without departing from the essential scope thereof.
Therefore, it is intended that the disclosed apparatus and method
not be limited to the particular embodiment disclosed as the best
mode contemplated for carrying out this disclosed apparatus and
method, but that the disclosed apparatus and method will include
all embodiments falling within the scope of the appended
claims.
* * * * *