The driving and driven members of a magnetic drive are separated by en enlarged gap to provide clearance for a conduit or other member. Flux pins in the gap maintain the torque transmitting capability of the drive. The spacing between two of the flux pins is increased to provide space for the conduit

Carter, Edward L.

English

NASA Technical Reports Server

NASA CASE NO. fl 3 C-- ^2 ff f ~? J ~ J
PRINT FIG. /
NOTICE
/y^ f.
The invention disclosed in this document resulted from
research in aeronautical and space activities performed under
programs of the National Aeronautics and Space Administration.
The invention is owned by NASA and is, therefore, available for
licensing in accordance.with the NASA Patent Licensing
Regulation (14 Code of Federal Regulations 1245.2).
To encourage commercial utilization of NASA-owned inventions,
it is NASA policy to grant licenses to commercial concerns.
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will consider the granting of a limited exclusive license,
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license will provide the necessary incentive to the licensee to
achieve early practical application of the invention.
Address inquiries and all applications for license for this
invention to NASA Patent Counsel, Johnson Space Center, Mail
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from the above address.
(MSA-Case-BSC-,21 171-1) JSAGKEIJC DEIVE N88-23973
CCOtlING Patent Application (KSSfi) 14 p
 JSC
CSC1 131
Unclas
G3/37 0145746
https://ntrs.nasa.gov/search.jsp?R=19880014589 2020-03-20T07:01:00+00:00Z
MSC-21171-1
SERIAL NUMBER 135120
FILED 12/18/87
AWARDS ABSTRACT NSC-21171-1
MAGNETIC DRIVE COUPLING
The present invention relates to magnetic drive couplings, and more partic-
ularly to a coupling for a bioreactor which permits the passage of conduits
without an appreciable loss of torque transmission capability.
The magnetic drive coupling of the present invention includes a rotatable
driving magnetic member 30 and a rotatable driven member 32 separated by an
enlarged gap 35 to provide clearance for a conduit 23. Flux pins 40 in the gap
35 maintain the torque transmission capability of the drive while at the same
time the enlarged gap 35 and increased spacing between two of the flux pins 40
allow inclusion of the conduit 23. The driven magnetic member 32 may be
substantially exially aligned opposite the driving member 30 to form a face
drive, FIG. 1, or they may be co-planar as in FIG. 3 to form a radial drive. In
FIG. 3, the driving member is 60 and the driven member is 62 with the flux pins
70 being located in the enlarged gap 65.
The flux pins reduce the reluctance of the gap, concentrate the magnetic flux
in the interface between the driving and driven members, and enhance the torque
transmitting capability of the coupling. The enlarged gap and the increased
spacing between two of the pins provide a passageway which permits the
inclusion of a conduit or other device.
Inventor: Edward L. Carter
Employer: Lockheed Engineering & Management Services, Co., Inc.
Initial Evaluator: W. J. Huffstetler
MSC-21171-i"
SERIAL NUMBER l35120
MAGNETIC DRIVE COUPLING
Origin of the Invention
The invention described herein was made in the
performance of work under a NASA contract and is subject
5 to the provisions of Section 305 of the National Aero-
nautics and Space Act of 1958, Public Law 85-568 (72
Stat. 435; 42 U.S.C. 2457) .
Background of the Invention
The present invention relates to magnetic drive
TO couplings, and more particularly to couplings which can
accommodate and provide for passing gas lines, fluid
tubes, electrical wires, or other conduits or members
therethrough.
Critical component positioning requirements can
15 sometimes cause a conflict between those components and a
magnetic drive associated therewith. For example, in a
biological reactor vessel having an internal magnetically
driven mixer, it may be necessary to have a fluid conduit
enter the vessel on the axis of rotation of the internal
20 parts. In such a case, the external magnetic drive may
have to be spaced a considerable distance from the vessel
wall. However, the large air gap caused by spacing the
drive at this distance means there will be significant
flux leakage in the magnetic coupling. The torque trans-
5 mission capability of the magnetic drive can accordingly
be drastically reduced.
Many prior art magnetic drive mechanisms have
driving and driven members which are separated by a gap.
Some of these are provided with magnetic coupling ele-
10 ments which conduct some of the magnetic flux.
U.S. Patent No. 2,638,558 (Rankin, issued May
12, 1953) shows a stationary stainless steel sheet 19 be-
tween drive magnets 24. and driven magnets 27. Means are
provided for directing a flow of cooling fluid to the
15 steel sheet 19 to overcome eddy current induced heating
caused by the movement of the magnets.
U.S. Patent No. 2,768,316 (Neiss, issued Octo-
ber 23, 1956) shows circular arrays of magnets on driving
and driven members.
20 U.S. Patent No. 3,011,84.2 (Norris, issued
December 5, 1961) shows magnetic bearing rings separated
by steel balls. The steel balls are kept evenly spaced
by the effects of the magnets.
U.S. Patent No. 3,378,710 (Martin, Jr., issued
25 April 16, 1968) shows (Fig. 17) driven pole pieces 109
and spacers 108 between stationary magnets 97 and moving
magnets 112. The configuration of Fig. 18 shows sta-
tionary magnetizable radial bars 119 between rotating
magnets .
30 U.S. Patent No. 3,382,386 (Schlaeppi, issued
May 7, 1968) discloses stationary soft magnetic coupling
elements 3-6.
U.S. Patent No. 3,433,465 (Szpur, issued March
18, 1969) shows (Figs. 2, 4, 9, 10, and 12) flux concen-
35 trating shoes 62, 147, and 194- (See col. 3, lines
21-34.)
U.S. Patent No. 3,570,819 (Rosinger, issued
March 16, 1971) shows (Fig. 21) a dual stirring arrange-
ment in which a magnet 182, which stirs liquid in an
outer vessel, is located between a driving magnet 183 and
5 another driven magnet 186.
U.S. Patent No. 4,209,259 (Rains et al., issued
June 24, 1980) discloses (Figs. 1, 4, and 5) a high
power, high torque apparatus using circular magnet
arrays.
10 U.S. Patent No. 4,498,785 (de Bruyne, issued
February 12, 1985) shows a magnetic stirrer in a biore-
actor-type apparatus (see cols. 1 & 2).
German Offenlegungsschrift 27 09 3&5 (Wik, pub-
lished September 15, 1977) shows (Fig. 5) mu-metal discs
15 P-| , P2 for concentrating flux between drive and stirring
magnets.
Nowhere, however, do these patents teach or
suggest a magnetic drive which provides clearance for a
fluid conduit or other essential component without caus-
20 ing appreciable loss of the torque transmission capabil-
ity of the coupling.
A need therefore remains for a means for ex-
tending the usefulness of magnetic drive couplings when
relatively large gaps have to be tolerated because of
25 other constraints. Ideally, such a means will be espe-
cially effective at reducing the reluctance of such a
gap, concentrating the magnetic flux in the interface be-,
tween the driving and driven members of the magnetic
drive, reducing the torque diminishing effect of such a
30 SaP, and enhancing the torque transmitting capability of
the magnetic drive coupling.
Summary of the Invention
Briefly, the present invention meets the above
needs and purposes with a new and improved magnetic drive
35 coupling having clearance for a fluid conduit or other
essential component, but which does not suffer an appre-
ciable loss of torque transmission capability. The driv-
ing and driven magnetic members are separated by a larger
than usual gap, but without significant flux leakage.
5 Instead, flux pins of soft magnetic material are inserted
in the enlarged gap, significantly increasing the trans-
mitted torque. To provide clearance through the magnetic
drive coupling, the spacing between two of the pins is
increased as necessary, thereby forming a passageway in
10 the gap between the magnetic drive members for passing
components therethrough'.
In a preferred embodiment, the magnetic drive
coupling of the present invention includes a rotatable
driving magnetic member and a rotatable driven magnetic
15 member. The driven magnetic member may be substantially
axially aligned opposite said driving member to form a
face . drive therewith, or may be a co-planar radial drive
in which the magnetic members are positioned radially
opposite one another. In both cases the driven member is
20 rotatable on substantially the same axis as the driving
member and is located substantially adjacent the driving
member for magnetically and drivingly coupling therewith.
According to the present invention, both of the magnetic
members are also separated by a predetermined axial (face
25 drive) or radial (radial drive) gap which is substan-
tially larger than usual for magnetic drives.
A plurality of flux pins made of soft magnetic
material is located in the gap between the driving and
driven magnetic members. The flux pins reduce the reluc-
30 tance of the gap, concentrate the magnetic flux in the
interface between the members, reduce the torque dimin-
ishing effect of the gap, and enhance the torque trans-
mitting capability of the coupling.
The spacing between two of the pins, however,
35 is increased or enlarged. This provides a clearance
space between these pins, thereby creating a passageway
in the gap for passing components, such as a fluid con-
duit, therethrough.
In the preferred embodiment, a non-magnetic
solid material . separates and fixes the flux pins in sta-
5 tionary positions in the gap. The material between the
pins is non-magnetic so that the flux will hot be
shunted, which would otherwise defeat operation of the
drive coupling.
It is therefore an object of the present in-
10 vention to provide an improved magnetic drive coupling
and method; such a coupling and method in which compo-
nents, such as fluid conduits, wires, and so forth, may
be readily passed through the coupling without signifi-
cant loss of the torque transmission capabilities
15 thereof; which includes a rotatable driving magnetic mem-
ber, a driven magnetic member rotatable on substantially
the same axis as the driving member, the driven magnetic
member being located substantially adjacent the driving
member for magnetically and drivingly coupling therewith;
20 in which the magnetic members are separated by a prede-
termined gap therebetween; in which a plurality of flux
pins is located in the gap between the driving and driven
magnetic members to reduce the reluctance of the gap,
concentrate the magnetic flux in the interface between
25 the members, reduce the torque diminishing effect of the
gap, and enhance the torque transmitting capability of
the coupling; which includes at least one clearance space
between at least two of the flux pins to provide a pas-
sageway in the gap for passing components therethrough;
30 and to accomplish the above objects and purposes in an
inexpensive, uncomplicated, durable, versatile, and reli-
able method and apparatus, inexpensive to manufacture,
and readily suited to the widest possible utilization in
magnetic drive applications. .
35 These and other objects and advantages of the
invention will be apparent from the following descrip-
tion, the accompanying drawings, and the appended claims.
Brief Description of the Drawings
Fig. 1 is a somewhat figurative cross-sectional
illustration showing a face type.magnetic coupling ac-
cording to the present invention;
5 Fig- 2 is a cross-sectional view taken on line
2-2 in Fig. 1;
Fig. 3 is an illustration similar to Fig. 1
showing a radial type magnetic coupling;
Fig. 4 is a cross-sectional view taken on line
10 4-4 in Fig. 3; and
Fig. 5 is a graphical illustration showing the
increase in transmitted torque afforded by the present
invention.
Description of the Preferred Embodiments
1 Lj With reference to the drawings, the new and im-
proved magnetic drive coupling, and the method therefor
according to the present invention, will be described.
For illustrative purposes, Figs. 1 and 2 show the bottom
11 of a bioreactor vessel 12 in which, due to the need to
20 maintain a sterile system, shaft penetrations of the
reactor vessel 12 are not allowed. To drive the internal
mixer shaft 15, therefore, a face type magnetic drive 20
is used, driving the mixer shaft 15 through the non-mag-
netic end 11 of the reactor vessel 12. For this partic-
25 ular application, it is also required that the interior
of the reactor vessel 12 must minimize crevices and dead
volumes, and that a fluid conduit 23 must enter the ves-
sel on the axis of rotation of the internal mixer shaft
15-
30 As will be clear from the drawings, however, a
conduit such as a fluid conduit 23 will then have to pass
through the same space in which the magnetic drive com-
ponents are located. To avoid conflict between them, the
driving magnet 30 must then be moved far enough away from
the driven magnet 32 to allow the conduit 23 to pass
therebetween. However, the resulting gap 35 between the
driving magnet 30 and the driven magnet 32 can seriously
5 reduce the magnetic coupling between the magnets 30 and
32, resulting in a major loss of performance of the mag-
netic drive 20.
The present invention overcomes these problems
by providing a plurality of flux pins 4.0 in the gap 35-
10 Pins -40, which are arranged in a non-rotating array, are
pieces of soft magnetic material which reduce the reluc-
tance of the air gap and concentrate the flux in the
interface between the driving and driven magnets 30 and
32. This reduces the torque diminishing effect of the
15 gap 35, enhances the torque transmitting capability of
the magnetic drive coupling 20, and thereby compensates
for the unusually large gap 35 therebetween. The flux
pins. -40 are separated from one another by non-magnetic
material or air, so that they sequentially conduct the
20 magnetic flux between the poles of the magnets 30 and 32
as they rotate. If the pins were not thus separated, the
flux would be shunted.
As can also be seen in Figs. 1 and 2, the spac-
ing between' two of the flux pins 4-0 is increased. This
25 provides a clearance space 4-5 between those flux pins.
The clearance space 45 then serves as a passageway in and
through the gap 35 for passing components, such as con-
duit 23, therethrough. Preferably, space 4-5 is the
smallest width which will allow the component to pass.
30 Figs. 3 and 4- show a radial type magnetic drive
50 which is otherwise similar to the face type magnetic
drive 20 illustrated in Figs. 1 and 2. That is, in
Figs. 1 and 2 the driving and driven magnets 30 and 32
are axially aligned opposite one another, and the gap 35
35 is an axial gap therebetween. In Figs. 3 and 4-, the
driving magnet 60 and driven magnet 62 are substantially
co-planar and positioned radially opposite one another.
8The gap 65 between the driving magnet 60 and driven mag-
net 62 is accordingly a radial gap which furnishes room
for a conduit 68 to pass therebetween. Flux pins 70 are
also pieces of soft magnetic material for reducing the
5 reluctance of the air gap 65 and concentrating the flux
in the interface between the driving and driven magnets
60 and 62. This also reduces the torque diminishing
effect of the gap 65, and enhances the torque transmit-
ting capability of the magnetic drive coupling 50. The
10 flux pins 70 are similarly separated from one another by
non-magnetic material or air, so that they sequentially
conduct the magnetic flux between the poles of the mag-
nets 60 and 62 as they rotate.
As can also be seen in Figs. 3 and 4, the spac-
15 ing between two of the flux pins 70 is increased. This
provides a clearance space 75 between those flux pins,
and forms a passageway in and through the gap 65 for
passing components, such as conduit 68, therethrough.
Finally, Fig. 5 shows the results of a test
20 performed to measure the torque transmitting capability
of a magnetic drive system according to the present
invention. Commercially available samarium cobalt
(SmCon) magnets were used at various magnet gaps, with
and without flux pins. The test results showed that with
25 flux pins the maximum torque that could be transmitted
was increased by almost one half (4.7%) over that without
flux pins for the same magnet gap.
As may be seen, therefore, the present inven-
tion provides numerous advantages. It provides an impor-
30 tant new method and apparatus for extending the useful-
ness of magnetic drive couplings when relatively large
gaps have to be tolerated because of other constraints.
It is especially effective at reducing the reluctance of
such gaps and concentrating the magnetic flux in the
35 interface between the driving and driven members of the
magnetic drive. This offsets the torque diminishing
effects of such gaps and enhances the torque transmitting
capabilities of the magnetic drive couplings. The in-
vention thus furnishes an inexpensive, uncomplicated,
durable, versatile, and reliable method and apparatus,
inexpensive to manufacture, and readily suited to the
5 widest possible utilization in magnetic drive applica-
tions .
While the methods and forms of apparatus herein
described constitute preferred embodiments of this in-
vention, it is to be understood that the invention is not
10 limited to these precise methods and forms of apparatus,
and that changes may be made therein without departing
from the scope of the invention.
What is claimed is:
jwr
MAGNETIC DRIVE COUPLING
Abstract of the Disclosure
The driving (30) and driven (32) members of a
magnetic drive (20) are separated by an enlarged gap (35)
to provide clearance for a conduit (23) or other member.
Flux pins (4.0) in the gap (35) maintain the torque trans-
mitting capability of the drive (20) . The spacing be-
tween two of the flux pins is increased to provide space
for the conduit (23).
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TOTAL MAGNET GAP (IN.)


Magnetic drive coupling

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