U.S. patent application number 09/981062 was filed with the patent office on 2002-06-27 for food processing apparatus including magnetic drive.
This patent application is currently assigned to Island Oasis Frozen Cocktail Co., Inc.. Invention is credited to Karkos, John F. JR., Micheli, John.
Application Number | 20020079393 09/981062 |
Document ID | / |
Family ID | 26922314 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020079393 |
Kind Code |
A1 |
Karkos, John F. JR. ; et
al. |
June 27, 2002 |
Food processing apparatus including magnetic drive
Abstract
A magnetic induction drive for a rotatable driven member in a
sealed housing, in particular, a shaft-mounted blade in a blender
cup or a shaft-mounted blade in an ice shaver, uses a comparatively
thin circular drive plate of a magnetizable material with
circumferentially arrayed poles enclosed within a housing secured
to a drive shaft. A brushless d.c. motor in a base separate from
the housing has a rotor formed as an array of pie-shaped permanent
magnet regions that interact with an electronically controlled,
rotating electromagnetic field produced by a ring of stator coils.
A second such permanent magnet is coupled to rotate coaxially and
in unison with the rotor, with poles of opposite polarity aligned
and adjacent one another. A steel disc is sandwiched between and
bonded to the rotor and the second permanent magnet. The magnetic
field (lines of flux) of the second magnet extends axially away
from the rotor to induce magnetic poles of opposite polarity in the
drive plate. This second magnet-to-plate magnetic coupling operates
across a closely-spaced gap that includes the bottom wall of the
base, the upper wall of the housing, and air gaps between these
walls, and the plate and the second magnet. A gear train assembly
can be coupled to the drive shaft to increase or decrease the
amount of torque transmitted from the drive plate to the driven
member.
Inventors: |
Karkos, John F. JR.; (Lisbon
Falls, ME) ; Micheli, John; (Brick, NJ) |
Correspondence
Address: |
FOLEY, HOAG & ELIOT, LLP
PATENT GROUP
ONE POST OFFICE SQUARE
BOSTON
MA
02109
US
|
Assignee: |
Island Oasis Frozen Cocktail Co.,
Inc.
|
Family ID: |
26922314 |
Appl. No.: |
09/981062 |
Filed: |
October 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09981062 |
Oct 16, 2001 |
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09481482 |
Jan 11, 2000 |
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6336603 |
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09481482 |
Jan 11, 2000 |
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09473311 |
Dec 28, 1999 |
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6210033 |
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09473311 |
Dec 28, 1999 |
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09228377 |
Jan 12, 1999 |
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6095677 |
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Current U.S.
Class: |
241/92 ;
241/101.2 |
Current CPC
Class: |
A23G 9/12 20130101; Y10S
241/17 20130101; A47J 43/0465 20130101; B01F 33/453 20220101; H02K
21/24 20130101; H02K 7/11 20130101; F25C 5/12 20130101; A47J 43/085
20130101; A23G 9/224 20130101; A47J 27/004 20130101; A23G 9/045
20130101 |
Class at
Publication: |
241/92 ;
241/101.2 |
International
Class: |
B02C 019/00 |
Claims
1. A drive for a rotating a driven member, said drive comprising: a
drive plate formed of magnetizable material, a motor positioned
proximate said drive plate, said motor having a stator and a rotor,
said rotor including a rotor magnet, said stator producing an
electromagnetic field that interacts with said rotor magnet to
rotate said rotor magnet, a drive magnet coupled to said rotor
magnet to rotate therewith, said drive magnet inducing a magnetic
field in a direction toward said drive plate to transmit a drive
torque from said motor to said drive plate, and a gear assembly
including one or more gears coupled to said drive plate and to said
driven member, said gear assembly transmitting said drive torque
from said drive plate to said driven member.
2. The drive of claim 1, wherein the gear assembly increases the
drive torque transmitted from said drive plate to said driven
member.
3. The drive of claim 1, wherein the gear assembly decreases the
drive torque transmitted from said drive plate to said driven
member.
4. The drive of claim 1, wherein said motor is an electric
motor.
5. The drive of claim 1, wherein s aid electric motor is a
brushless d.c. motor.
6. The drive of claim 1, wherein said drive magnet and said rotor
magnet each include a plurality of poles.
7. The drive of claim 6, wherein said drive magnet and said rotor
magnet have a like number of poles.
8. The drive of claim 7, wherein said poles of said drive magnet
are aligned by pole polarity with said poles of said rotor
magnet.
9. The drive of claim 6, wherein said poles of said drive magnet
and said poles of said rotor magnet are
circumferentially-aligned.
10. The drive of claim 6, wherein said drive plate includes a
plurality of radial directed open slots that define a plurality of
poles on said drive plate.
11. The drive of claim 10, wherein said drive plate and said drive
magnet have a like number of poles, said poles of said drive plate
being aligned with said poles of said drive magnet.
12. The drive of claim 1, further comprising a plate of
magnetizable material secured between said drive magnet and said
rotor magnet.
13. The drive of claim 12, wherein said rotor magnet, said drive
magnet, and said plate are enclosed within a layer of plastic
material.
14. The drive of claim 1, wherein said drive plate is secured to a
drive shaft to rotate with said drive shaft.
15. The drive of claim 14, wherein said drive magnet and said rotor
magnet are centered on a common axis of rotation.
16. The drive of claim 15, wherein said common axis is coaxially
aligned with said drive shaft.
17. The drive of claim 16, wherein said driven member rotates about
an axis of rotation offset from said common axis of rotation.
18. The drive of claim 14, wherein a first gear of said gear
assembly is secured to said drive shaft to rotate therewith.
19. The drive of claim 18, wherein a second gear of said gear
assembly is coupled to said driven member to rotate therewith, said
first gear and said second gear interacting to transmit said drive
torque from said drive plate to said driven member.
20. The drive of claim 19, wherein said gear assembly further
comprises a third gear interposed between said first gear and said
second gear, said third gear interacting with said first gear and
said second gear to transmit said drive torque therebetween.
21. The drive of claim 20, further comprising a control and drive
unit electrically coupled to said motor to control operation of
said motor, said control and drive unit selectively energizing said
stator to produce an operating torque or a braking torque on said
rotor.
22. The drive of claim 21, wherein said stator includes one or more
stator coils.
23 The drive of claim 22, wherein said control and drive unit
varies current through said stator coils to produce said operating
torque or said braking torque.
24. An ice shaver comprising: an ice hopper having a blade
rotatably mounted on a shaft, a drive plate formed of magnetizable
material, a motor positioned proximate said drive plate, said motor
having a stator and a rotor, said rotor including a rotor magnet
having one or more poles, said stator producing an electromagnetic
field that interacts with said one or more poles to rotate said
rotor magnet, a drive magnet coupled to said rotor magnet to rotate
therewith, said drive magnet including one or more poles arranged
to induce a magnetic field in a direction toward said drive plate
to transmit torque from said motor to said drive plate, and a gear
assembly including one or more gears coupled to said drive plate
and to said shaft, said gear assembly transmitting said drive
torque from said drive plate to said shaft to effect shaving of
said ice with said blade.
25. A food processing apparatus comprising: a blender comprising a
blender cup having a first blade rotatably mounted on a first
shaft, a first drive plate formed of magnetizable material secured
to said first shaft to rotate therewith, a first motor positioned
proximate said first drive plate, said first motor having a first
stator and a first rotor, said first rotor including a first rotor
magnet, said first stator producing an electromagnetic field that
interacts with said first rotor magnet to rotate said first rotor
magnet, a first drive magnet coupled to said first rotor magnet to
rotate therewith, said first drive magnet inducing a magnetic field
in a direction toward said first drive plate to transmit a drive
torque from said first motor to said first drive plate thereby
rotating said first shaft and said first blade; and an ice shaver
for supplying shaved ice to said blender, said ice shaver
comprising an ice hopper having a second blade rotatably mounted on
a second shaft, said ice hopper including a chute connected to said
blender cup for supplying shaved ice to said blender cup, a second
drive plate formed of magnetizable material, a second motor
positioned proximate said second drive plate, said second motor
having a second stator and a second rotor, said second rotor
including a second rotor magnet, said second stator producing an
electromagnetic field that interacts with said second rotor magnet
to rotate said second rotor magnet, a second drive magnet coupled
to said second rotor magnet to rotate therewith, said second drive
magnet inducing a magnetic field in a direction toward said second
drive plate to transmit torque from said second motor to said
second drive plate, and a gear assembly including one or more gears
coupled to said second drive plate and to said second shaft, said
gear assembly transmitting said drive torque from said second drive
plate to said second shaft to effect shaving of said ice with said
second blade.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/473,311, filed Dec. 28, 1999, which is a
continuation of U.S. patent application Ser. No. 09/228,377, filed
Jan. 12, 1999. Both of the above-identified patent applications are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a magnetic drive to transmit
rotational motion from a motive source into an enclosed space
without a direct mechanical connection. More specifically, it
relates to blenders, mixers, and like machines, and particularly to
devices having a stirrer, impeller, blade, or other tool mounted
within a removable cup or container, and rotated by means of a
motor located in the stationary base of the machine.
[0003] Conventional home blenders and mixers incorporate a
mechanically-driven impeller rotatably mounted within a removable
blender cup. The base of the cup incorporates a generally circular
connection plate with a pattern of projections and/or depressions
formed on its lower face that is removably mateable, using a
vertical, drop-in movement, with a corresponding pattern formed on
a like plate attached to the shaft of a motor housed in a base of
the machine. This mechanical coupling between the blender cup and
the blender motor requires a rotary seal at the base of the cup
between the impeller and connecting plate. This seal is subject to
considerable wear and tear over time, as is the mechanical
coupling. Because seal failure can result in liquid leaking out of
the cup, the seal and bearings in the base of the cup are built to
ensure sealing at the expense of friction. The friction produces
wear, heat, and loss of power. Moreover, the conventional blender
produces much unwanted noise, and the mechanical interlocking
coupling between the plates can make it awkward or difficult to
remove the cup from, and return the cup to, the base.
[0004] Many drink mixers have the drive motor mounted in the base
directly under the cup. If overall height is a concern, however,
the motor may be positioned off to the side and coupled to the
driving shaft by a belt or gear arrangement.
[0005] Known home and commercial blenders use conventional a.c.
motors. While a.c. motors can be constructed and controlled to
provide speed variation, as well as the requisite output torque, a
typical such motor is generally bulky, heavy, and not well-suited
to electronic speed control, let alone electronic braking.
[0006] While d.c. brushless motors are also known per se, they have
not been used for blenders or blender/shavers. These motors use a
comparatively heavy rotor formed of a sector-like array of
permanent magnets. Blending of a mass of shaved or cubed ice and
liquid, particularly on start up or during a "freeze up" of a
frozen drink, requires a comparatively high torque. D.C. brushless
motors are characterized by a low output torque as compared to
conventional a.c. motors. They therefore have found use as a motive
power source mainly in applications such as fans where a low output
torque is acceptable.
[0007] A commercially viable blender/shaver for the production of
frozen drinks must satisfy a variety of special and important
design criteria. It should be compact, both in its footprint and
overall height, so as to utilize limited space at a bar
efficiently. It ideally has a comparatively low weight. The
straight-forward approach of placing a conventional electric motor
directly under the blender cup increases the overall height of the
machine, and therefore is not typically used. There must also be
speed control, typically provided through gearing and electronics,
to accommodate different power and speed requirements in different
phases of operation. Rapid controlled braking is also important to
limit the overall time required to blend, to avoid splashing of the
blended material after blending is complete, and for safety.
Control of vibration, prevention of overheating, or minimization of
wear, ease of maintenance, and durability are also important.
[0008] It has also known that an impeller within a blender cup may
be driven magnetically or electromagnetically rather than
mechanically. One type of magnetic drive couples a rotating
permanent magnet outside a blender cup or the like, to another
permanent magnet rotatably mounted in the blender cup. U.S. Pat.
Nos. 2,459,224 to Hendricks; U.S. Pat. No. 2,655,011 to Ihle et
al.; and U.S. Pat. No. 5,478,149 to Quigg are exemplary of this
approach. Hendricks discloses a magnetically operated stirrer for
mixing liquids, in which the stirrer has a magnet mounted at its
lower end and within the container for the liquid. Quigg discloses
a motor that drives a set of magnets, via gear box and shaft, to
couple to another set of magnets mounted on an agitator.
[0009] U.S. Pat. No. 3,140,079 Baermann uses a large rotating plate
to carry a series of circumferentially spaced magnets that pass
under one portion of a much smaller, rotatable conductive disc.
[0010] U.S. Pat. No. 1,242,493 to Stringham and U.S. Pat. No.
1,420,773 to Stainbrook disclose electrical drink mixers in which a
stator of an a.c. motor surrounds and interacts with a rotor in a
blender cup, or in its base. In Stringham, a squirrel cage rotor
lies in the plane of the stator windings. In Stainbrook an a.c.
rotor is mounted in the base of the blender cup and stator coils
are located below the cup. Such split a.c. motor arrangements are
limited by the torque, speed control, eddy current loss, and emf
interference problems of a.c. motors, as accentuated by the
physical separation of the stator windings and the rotor. They do
not provide good speed control. They do not utilize a d.c. magnetic
field coupling. And the inclusion of the rotor of the motor within
the container or cup adds unwanted weight to the cup assembly and
makes the cup difficult to handle due to gyroscopic effects if it
is picked up while the rotor is still spinning.
[0011] If the rotor of a brushless d.c. motor were to be located in
the base of a blender cup, the cup would not only become heavy and
exhibit a severe gyroscopic effect, but it would also "stick" to
metal sinks and countertops, and would attract loose metallic
implements such as silverware, barware, or coins.
[0012] It is therefore a principal object of this invention to
provide a drive system that provides reliable, speed-controlled
rotary power transmission to a rotatable driven element that is
sealed from the source of motive power.
[0013] Another aspect is to provide a drive that is automatically
clutched to disconnect the drive when the load exceeds a preset
value or the driven member is moved from its operating
position.
[0014] A further object is to provide a magnetic drive offering
these advantages, in which the driver element is located in a
removable blender cup and the blender cup is easy to insert and
remove from the blender and is easy to handle when removed from the
blender, e.g., it exhibits no significant gyroscopic effect or
magnetic attraction.
[0015] Yet another object is to provide a low wear, low
maintenance, non-mechanical coupling between motor and drive
element, and in particular, one which avoids the high maintenance
costs associated with present belt drives and mechanical clutches
and brakes.
[0016] A still further object is to provide a magnetic drive for a
blender or the like with the foregoing advantages which is compact,
low in weight, and very easy to use and clean.
[0017] Another object is to provide a drive whose operating
characteristics can be programmed and which can be braked rapidly
and reliably.
SUMMARY OF THE INVENTION
[0018] In its preferred application as a drive for a blender or
other food processing apparatus, the present invention employs an
electric motor to rotate a ring magnet, preferably an assembly of
two ring magnets with axial poles, that is closely spaced from a
disc-shaped drive plate formed of a conductive, magnetizable
material. The magnet assembly and drive plate each have matching,
circumferentially-arrayed poles. The magnet assembly preferably has
a set of an even number of generally pie-shaped, permanent magnet
poles or segments of alternating polarity. The drive plate is
preferably a thin sheet of a ferrous material such as cold-rolled
steel with open-ended radial slots that define the poles and
control eddy currents. The magnet assembly produces a sufficiently
strong field (flux lines) that despite the spacing, which typically
includes high reluctance air gaps, nevertheless induces oppositely
polarizing magnetization of the disc poles. This induced
magnetization couples the magnet assembly to the plate in order to
drive it. In a blender, the drive plate is rotatably mounted in the
base of the blender cup and supports a shaft that in turn mounts an
impeller. The magnet assembly and the motor are separately housed
from the drive plate.
[0019] The electric motor is preferably a brushless d.c. motor with
stator windings that produce a rotating electromagnetic field that
interacts with, and produce a torque on, a rotor that includes a
magnet assembly like the one magnetically coupled to the disc. The
rotor magnet ring is preferably secured to the drive magnet ring by
bonding these magnet rings to opposite faces of a circular
cold-rolled steel disc. The rotor, drive magnet ring and drive
plate are co-axially aligned when the plate and its associated
apparatus, such as a blending cup, are in an operating position.
The motor and drive housing preferably has a flat upper wall that
extends continuously through the magnet-to-plate gap, as does a
flat bottom wall on the blender cup. For a magnet assembly with a
field strength on its surface of 1400 gauss, the close spacing for
a blender application is preferably about 0.25 inch. Use of a
comparatively flat d.c. brushless motor mounted under the driven
member gives the motor part of the drive a compact configuration,
preferably with a height-to-width ratio of as little as about
1:3.
[0020] Viewed broadly as a method, the invention includes the steps
of rotating a rotor magnet with multiple circumferentially-spaced,
poles by interacting the poles with a rotating electromagnetic
field. The rotor is in turn coupled to a second drive magnet with a
like number of circumferentially-arrayed poles mechanically coupled
to rotate in unison with the rotor. The method further includes the
steps of directing the magnetic field of the drive magnet axially
away from the rotor to induce oppositely polarized magnetic poles
in a conductive drive plate that is rotatably mounted, and
closely-spacing the drive magnet from the plate so that the induced
poles in the plate follow the poles in the rotating magnet assembly
despite the spacing and despite a load that resists rotation. The
directing of the magnetic field includes bonding the magnets in a
sandwich fashion to opposite faces of a thin steel disc and
polarizing the ring magnets axially.
[0021] In accordance with another aspect of the present invention,
the drive of the present invention can include a gear assembly
having one or more gears for transmitting torque from the drive
plate to a driven member such as, for example, an output shaft. The
gear assembly can include one or more gears sized and arranged to
reduce, or to increase, the torque transmitted from the drive plate
to the driven member. In a preferred application, the drive and
gear assembly are employed to rotate the blade of an ice shaver.
The ice shaver can be a stand alone unit or can be incorporated
with a blender, such as the blender of the present invention, to
form an automatic blender/ice shaver machine for manufacturing
frozen drinks.
[0022] These and other features and objects of the invention will
be more fully understood from the following detailed description
that should be read in light of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a view in perspective of a blender/shaver machine
constructed according to the present invention;
[0024] FIG. 2 is a view in vertical section of the blender/shaver
machine of FIG. 1;
[0025] FIG. 3 is an exploded perspective view of the blender cup
shown in FIGS. 1 and 2;
[0026] FIG. 4 is a detailed view in vertical section of the
magnetic drive of the present invention as shown in FIG. 2 used to
power an impeller mounted in the base of a blender cup;
[0027] FIG. 5 is an exploded perspective view of the base of the
blender/shaver shown in FIGS. 1 and 2 showing the mounting of the
motor assembly for the magnetic drive according to the present
invention;
[0028] FIG. 6 is a view in perspective of the double magnet
assembly shown in FIG. 4;
[0029] FIG. 7 is a view in vertical section of an alternative
embodiment of the blender cup of the present invention;
[0030] FIG. 8 is a view in vertical section of the magnetic drive
and gear assembly for the ice shaver portion of the blender/shaver
of the present invention; and
[0031] FIG. 9 is a view in vertical cross-section along line F-F of
FIG. 8 of the magnetic drive and gear assembly of FIG. 8.
DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] FIGS. 1 and 2 show a principal application of the present
invention, namely, in a blender/shaver machine 10 adapted to the
automatic manufacture of frozen drinks in bars and restaurants. A
supply of ice in a hopper 12 is fed by a rotating set of blades 14
to a blade 16. The shaved ice falls through a chute 18 including a
lid 20 into a blender cup 22 to which liquid ingredients such as a
flavor concentrate and/or spirit have been added. Rotation of an
impeller (or blade set) 24 at the bottom of the cup for a preset
period of time produces a high quality frozen drink--one that peaks
when poured and has a generally uniform, non-marbled, non-watery
consistency. While the invention will be described below
principally with reference to use in the blender/shaver 20, it will
be understood that the invention can be used in a wide variety of
applications where it is desired to transmit power from a rotary
output of a motive source (e.g., a motor) to a driven member under
a load, particularly a rotating driven member held in a container
that is sealed from and removable from the motive source. The
invention can be used, for example, in a variety of food processing
equipment such as home blenders, food mixers, food processors and
juicers.
[0033] A magnetic drive 26 for the impeller 24 is the focus of the
present invention. With reference to FIGS. 3-5, the drive 26
includes a generally circular drive plate 34 rotatably mounted in
the base 22a of the blender cup 22 and a brushless d.c. motor 28
including stator coils 30 and a rotor 32. The rotor in turn
includes a double magnet assembly 35 preferably formed of a rotor
ring magnet 36, a drive ring magnet 38 and a disc 40 of a
magnetizable material, preferably cold-rolled steel, bonded between
the magnets 36 and 38.
[0034] The ring magnets 36 and 38 each have multiple
circumferentially-arrayed, axially-directed poles 42, eight as
shown in FIG. 6. Laterally adjacent segments have the opposite
polarity. While eight poles are preferred, any even number can be
used. Preferably each pole 42 is developed by a generally
pie-shaped permanent magnet region 44 formed in a continuous ring
of a strongly magnetic material such as the ceramic magnets sold by
Hitachi Corporation. The magnet regions 44 in each magnet 36 and 38
can also be separate pieces bonded or otherwise mechanically
secured to one another to form a ring assembly with flat faces and
a generally cylindrical outer wall. A plastic hub 43 with radially
directed support walls 43a fills the center of the magnets 36, 38
to facilitate mounting the assemblies on a central shaft. A north
pole magnet region 44 is adjacent a south pole magnet region 44.
Assemblies 36 and 38 are then affixed to the disc 40, preferably
with each permanent magnet region 44 in one assembly overlying a
like magnet region in the other assembly, but having the opposite
polarity to avoid the repulsive magnetic force between the magnets
36 and 38. A plastic overlayer 48 helps to secure the sandwich
assembly. This magnet assembly configuration with axially oriented
magnetic pole regions 44, and the low reluctance return path
presented by the steel disc 40 for all of the magnet regions 44,
directs the magnetic field (lines of flux) of the rotor magnet 36
axially (downwardly as shown) toward the stator coils 30 and the
magnetic field of the drive magnet 38 axially (upwardly as shown)
toward the plate 34 in the cup base 22a. The strength and this
axial directing of the field of the drive magnet 38 induce magnetic
fields of opposite polarity in a corresponding poles 24a formed in
the drive plate 34 despite the presence of a spacing 46, albeit a
close spacing, between the generally flat upper surface 38a of the
magnet assembly and the generally flat lower surface 34b of the
plate 34.
[0035] In the preferred form illustrated and shown for the
blender/shaver (used to blend up to 80 fluid ounces of a frozen
drink), the permanent magnet 36 develops a magnet field strength of
about 1400 gauss at its surface, and the spacing 46 is about 0.25
inch measured axially. This spacing includes, as shown in FIG. 4,
not only four layers 48, 50a, 52, 22b of what is typically a
plastic material, but also air gaps 54 and 56. Layers 48 and 52 are
a thin plastic over-molding for the magnet assembly 35 and the
drive plate 34, respectively. The layer 50a is the flat upper wall
portion of a base 50 of the blender/shaver 10. Layer 22b is the
flat lower wall of the cup base 22a.
[0036] The air gap 54 is a slight clearance between the rotor
over-molding 48 and the wall 50a. The gap 56 is a slight clearance
between the wall 22b and the drive plate over-molding 52. As will
be readily appreciated by those skilled in the art, this spacing is
a significant source of reluctance in the magnet circuit between
the ring drive magnet 38 and the plate 34. Permanent magnet rotors
of known d.c. brushless motors, e.g., the 5 inch disc-diameter
motor sold by Integrated Motion Controls, LLC of Torrington, Conn.
under its Model No. 50, while roughly comparable in size,
construction and field strength to the magnet 38, cannot couple to
the plate 34 across the spacing 46 with sufficient strength to
drive the disc operating a blender/shaver.
[0037] With particular reference to FIGS. 4 and 5, the motor 28 is
mounted in the base 50 by screws 60 that pass through a steel motor
cover 62 and a rear stator support 64 into threaded sockets 66
formed in a motor mount wall 50b of the base. The rear stator
support 64 has a central opening that holds a bearing assembly 68
that journals a motor shaft 70. Screws (not shown) passing through
openings 54a in the rear stator support thread into and secure a
front stator support 72 to sandwich a ring 74 of back steel in the
assembly adjacent the coils 30. The front stator support 72 has a
periphery 72a that is sloped and slotted to carry the stator
windings 30 as in the aforementioned Model 50 motor. (The portions
of the windings in the slots are not shown for clarity.) The
windings are three phase, being energized by a conventional
brushless d.c. motor drive circuit to produce a rotating
electromagnetic field. The base and stator supports are preferably
formed of a moldable, high-strength plastic, and with a wall
thickness, that rigidly supports the motor 28.
[0038] The double magnet assembly 35 with the shaft 70 secured at
its center slides axially into the bearing 68 (FIG. 4). The
assembly 35 rotates in the bearing 68 with a clearance on all sides
of the assembly 35. As noted above, the multi-pole, d.c. magnetic
field produced principally by the lower (as shown) rotor magnet 36
is directed principally downwardly to interact with the rotating
electromagnetic field produced by the stator coils 30 when they are
energized. Rotation of this electromagnetic field interacting with
the rotor magnet assembly produces a torque that rotates the rotor
at a like rotational speed. The disc 40 bonded between the magnets
36 and 38 transmits this torque to the plate drive magnet 38. As a
safety precaution against combustion should the coils 30 overheat,
a ring-like shroud 76 has a lower flange 76a that extends
substantially across the air gap between the outer edge of the
assembly 35 and the generally cylindrical inner side wall of the
rear stator support 64 (with a slight clearance to avoid frictional
contact with the magnet assembly 35). The shroud fills this gap
sufficiently to impede an air flow that would otherwise feed oxygen
to a fire.
[0039] The magnet assembly 35 in a five-inch diameter weighs
approximately three pounds. With typical operating speeds varying
from 4,000 to 10,000 rpm, it can exert significant forces on the
mounting structures, particularly rapidly varying forces that
produce vibrations. The mounting structure is made sufficiently
rigid, through choice and dimensions of materials as well as the
overall design, e.g., the use of wall reinforcements such as
exterior ribs, to resist the forces and moments produced in normal
operation, and thereby to control vibrations that would otherwise
loosen, wear and the extreme, eventually destroy the motor.
[0040] Position of the rotor is sensed by three conventional Hall
effect sensors mounted in a known manner in the motor housing, or
the base 58. Position signals provide input to a known electronic
control and drive circuit that energizes the three phase stator
windings 30 to produce (i) a start-up torque, (ii) a ramp up of the
rotor speed of rotation to a selected operating speed, (iii) a
maintained rotation at that selected speed under load, and then
(iv) a rapid and reliable braking. Operating of the motor is thus
electronically controlled and programmable. Braking is
electronic--with the braking currents induced in the windings 30
being dissipated in large resistors or FET's mounted on heat
sinks.
[0041] With reference to FIGS. 2-4, and especially FIGS. 3 and 4,
the conductive drive plate 34 is non-rotatably secured to the lower
end of a shaft 78 that is journalled in a stacked pair of needle
bearing assemblies 80. A surrounding brass collar 82 press fit into
a central, cylindrical-walled opening 22c in the plastic base 22a
holds the bearing assemblies 80. At the bottom of the cup, the
collar 82 has an enlarged diameter counter bore that receives and
secures a rotary seal 84 formed of a suitably elastomeric material
such as a wear-resistant rubber. The seal has three inwardly
facing, mutually-spaced lips 84a whose inner edges each engage, and
provide a low-friction running or sliding seal around the shaft 78.
The seal 84 retains liquid in the cup 22 despite the presence of a
rotating shaft penetrating the bottom wall of the cup. The
lower-most lip 84a engages the shaft 78 in a circumferential groove
that locates and stabilizes the seal. A deep circular groove 84b in
the lower face of the seal allows the lips to flex resiliently, yet
lightly, against the shaft. Above the seal, an acorn nut 86
threaded on the upper end of the shaft 78 secures the blades 24
sandwiched between three washers 88a, 88b, and 88c.
[0042] The drive plate 34 is part of a drive plate assembly that
includes a set of vertical, radially-arrayed, reinforcing ribs 90
angularly centered over each pole 34a (FIG. 3). The ribs 90 and a
central boss 91 that surrounds the shaft 78 are preferably molded
continuously with the bottom layer 52. The plate 34 is preferably
formed of a thin sheet of a ferrous material such as cold-rolled
steel, e.g., 0.058 inch thick, with a set of open-ended radial
slots 92 that produce the poles 34a. The slots 92 also control eddy
currents induced in the plate by the rotating field of the drive
magnet assembly 38. Because the plate 34 is thin and slotted, it
can deform when it is subjected to the significant attractive
magnetic force of the plate drive magnet assembly 38, e.g.,
typically about five pounds, and be placed in frictional contact
with the cup base 22b. The ribs 90 and the over molding generally
help the plate to retain its flat configuration.
[0043] As shown, the attractive magnetic force acting on the drive
plate 34 is preferably carried at a single, central pivot point
formed by a hemispherical ball-bearing projecting from the bottom
surface of the drive assembly and a stainless steel plate 96
mounted flush with the upper surface of the cup base wall 22b. This
arrangement resists the magnet forces pulling down on the plate 34
while at the same time facilitating a low-friction, low-wear
rotation of the shaft 78.
[0044] With reference to FIG. 7, in an alternative embodiment of
the blender cup 122, the shaft 178 is rotatably supported by two
axially spaced needle bearings 200a and 200b. A cylindrical spacer
202 is interposed between the needle bearings 200a and 200b and
surrounds the shaft 178. The drive plate 134 is attached to the
shaft 178 through a screw 206 having external threads for mating
with complementary internal threads formed in the shaft 178. A
flange 204 can be provided at the end of the shaft 178 and the
drive plate 134 is sandwiched between the flange 204 and a washer
208 adjacent the head of screw 206. This particular arrangement
allows the shaft 178 to be rotatably supported by the needle
bearings 200a and 200b and the screw 206 without the need for the
hemispherical ball-bearing projecting from the bottom surface of
the drive assembly and the stainless steel plate 96 mounted within
the cup base wall. It should be understood that the component parts
of the embodiment of FIG. 7 are similar to those previously
described herein, and accordingly the same reference numerals are
used to designate similar parts although the numerals are
incrementally increased by 100 to differentiate the embodiments
described herein.
[0045] It has been found that the coupling, or "traction", between
the magnet 38 and the drive plate 34 increases not only as a
function of the strength of the magnetic field acting on the poles
34a and the closeness of the magnet-to-disc spacing, but also as a
function of the thinness of the plate 34 and the width of the slots
92. In general, the thinner the plate and the wider the slots, the
more traction is produced for a given magnet and spacing. The
presently preferred slot width for an eight-pole, 4.425 inches
diameter plate is about 0.245 inch.
[0046] The desired level of traction depends on each application.
It is selected to reliably couple the drive plate to the drive
magnet when (i) the impellers 24 are started under the load of the
shaved ice and liquid ingredients of a frozen drink in the blender
cup, (ii) during a ramp up of the operating speed to a selected
operating speed, typically thousands of rpm, and then (iii) as the
impeller, and the slushy mass in the cup and interacting with the
impeller, is brought to a stop. However, the traction is also
selected to disconnect, and thereby automatically clutch, the drive
26 when the cup 22 is removed from its operating position on the
base wall 50a under the ice chute 18, or when the load exceeds a
preset maximum value. This latter situation can arise, for example,
when the frozen drink "freezes up" in the cup, that is, becomes
partially or totally a solid frozen mass, or when an object
inadvertently falls into the blender as it is operating, e.g., a
spoon, jewelry, or bottle cap. By de-coupling, the magnetic drive
26 automatically and immediately cuts off power to the impellers to
avoid or minimize injury to person(s) near the blender and to the
machine itself. This feature also avoids the cost of providing and
maintaining a mechanical clutch.
[0047] While brushless d.c. motors are known as having
comparatively low torque outputs, the present invention has been
found to overcome this deficiency. However, to optimize the
performance of the motor 28, the stator coils 30 are preferably
wound to optimize the torque output at a preselected operating
speed, e.g., near 8,000 rpm.
[0048] It is significant to note that the drive plate assembly,
mainly a thin metal disc and plastic molding over it, are light and
non-magnetic. There is little detectable gyroscopic effect when the
cup is removed from the blender/ shaver after use. There is a low
rotational momentum due to the impellers and drive plate assembly.
Because the cup is light-weight and nonmagnetic, it is easy to
handle.
[0049] It is also quite significant that the magnetic drive 26 of
the present invention allows the cup 22 to be placed in an
operating position on the blender/shaver 10 with a simple, lateral
sliding movement over the smooth, flat cup base 22b over the
smooth, flat base portion 50a. There is no need to drop the cup
vertically onto a mechanically interlocking drive coupling, and
then vertically lift the cup off this coupling. The lateral sliding
insertion and removal movements are not only more convenient, but
they also reduces the vertical clearance required above the cup.
This slide-in arrangement also facilitates cleaning the blender
base--one need only wipe a smooth surface. Spilled liquid and slush
can flow or be pushed over the surface to a drain 94 formed in the
base at the rear of the wall 50a. In the event of a safety hazard,
blender overload, or any unusual situation requiring a rapid
removal of the cup, it is simply and rapidly withdrawn from the
machine with a sliding motion. Further, and quite importantly, if
an operator is impatient and removes the cup before the motor has
fully stopped, a common problem in actual use in a bar, the process
of removal itself automatically disconnects the impeller drive from
the motor 28 (a misalignment and/or lifting of the cup moves the
poles 34a out of a coupled relationship with the magnetic lines of
force produced by the magnet assembly 38.) In conventional belt
driven, mechanically-clutched blender/shavers, such a premature
removal causes stress and wear on the drive train and the
clutch.
[0050] A further significant advantage of this drive is that it
places the motor directly under the blender, thus eliminating drive
belts or chains and pulleys or sprockets, but does so while still
maintaining vertical, as well as horizontal compactness, both in
terms of the height of the motor itself, the vertical height of the
coupling between the motor and the cup, and the vertical clearance
needed to maneuver the cup onto and off the coupling.
[0051] While this invention has been described with respect to its
preferred embodiment, it will be understood that various
modifications and variations will occur to those skilled in the
art. For example, while this invention has been described as
powered by a d.c. brushless motor, it is possible to achieve some
of the advantages of this invention by using an a.c. motor whose
output shaft is coupled to the plate drive magnet. While a rotating
magnet assembly has been described as the member coupling to the
plate in the cup base, it is possible to produce a rotating
electromagnetic or magnetic field using an assembly of
electromagnets or other permanent magnet arrangements such as a
single, one-piece permanent magnet magnetically configured, or
acting in combination with ferromagnetic materials, to produce the
desired array of magnetic poles. While the invention has been
described with reference to a plate rotatable in the base of a
blender cup, the driven element could assume a wide variety of
other forms, and need not even be a liquid-holding vessel. While
the magnets and plate have been described as having the same number
of poles, as is well known, this is not essential to the operating
of this invention. A variety of mounting and rotational support
arrangements are possible for both the double magnet assembly 35
and the driven conductive plate 34. Further, while a radially
slotted plate 34 has been described as forming the poles 34a and
controlling eddy currents in the plate, one skilled in the art will
readily see that a variety of other known arrangements for forming
poles and controlling eddy currents are possible. Still further,
while the magnets have been described as bonded to a metal disc, it
is not necessary to use this disc.
[0052] FIGS. 2, 8, and 9 illustrate a further application of the
present invention, namely, in an ice shaver assembly for supplying
shaved ice to the blender of the blender/shaver machine 10. The ice
shaver assembly includes a magnetic drive and gear assembly 300
that operates to rotate blades 14 to supply shaved ice to the
blender cup 22 through chute 16. The magnetic drive and gear
assembly 300 is coupled to an output shaft 302 that is connected at
its upper end to the rotating set of blades 14. The magnetic drive
and gear assembly 300 includes a magnetic drive 304 that is
analogous in structure and operation to the magnetic drive 26 of
the blender. The output of the magnetic drive is transmitted
through a gear assembly 306 to the output shaft 302 of the shaver.
The gear assembly includes three gears, namely, a motor gear 328, a
compound idler gear 332, and an output gear 334.
[0053] The magnetic drive 304 for the shaver includes a generally
circular drive plate 308 rotatably mounted in the motor housing 309
of the ice shaver assembly and a brushless d.c. motor 310 including
stator coils 312 and rotor 314. The rotor 314 in turn includes a
double magnetic assembly preferably formed of a rotor ring magnetic
316, a drive ring magnetic 318, and a disk 320 of a magnetizable
material, preferably cold-rolled steel, bonded between the magnets
316 and 318.
[0054] The ring magnets 316 and 318 each have multiple
circumferentially-arrayed, axially-directed poles, as in the case
of the ring magnets 36 and 38 of the magnetic drive of the blender
described above. The ring magnets 316 and 318, thus, have poles
constructed and arranged in a manner analogous to the ring magnets
36 and 38 of the magnetic drive of the blender. A plastic hub 321
fills the center of the ring magnets 316 and 318 to facilitate
mounting the magnets on a central shaft 322. The ring magnets are
affixed to the disk 320, preferably with each pole in one ring
magnet overlying a pole of the other ring magnet having the
opposite polarity to avoid the repulsive magnetic force between the
magnets 316 and 318. A plastic overlayer enclosing the magnets 316
and 318 and the disk 320 can help secure the magnet assembly.
[0055] The brushless d.c. motor 310 is mounted in the motor housing
309 beneath the rotor 314. The motor 310 is constructed and
operates in a manner analogous to the motor 28 of the magnetic
drive 26 of the blender described above. The stator coils 312 are
three phase coils being energized by a conventional brushless d.c.
motor drive circuit to produce a rotating electromagnetic field.
The rotor 314 with the shaft 322 secured at its center slides
axially into a bearing 324. The rotor 314 rotates in the bearing
324 with clearance on all sides of the rotor 314. The d.c. magnetic
field produced principally by the lower rotor ring magnet 316 is
directed principally downward to interact with the rotating
electromagnetic field produced by the stator coils 30 when the
coils are energized. Rotation of this electromagnetic field
interacting the rotor magnetic assembly 314 produces a torque that
rotates the rotor at a like rotational speed. The disk 320 bonded
between the magnets 316 and 318 transmits this torque to the drive
ring magnet 318.
[0056] As in the case of the rotor 32 of the magnetic drive 26 of
the blender, described above, the position of the motor 314 can be
sensed by three conventional Hall effect sensors mounted in the
motor housing 309. Position signals provide input to an electronic
control and drive circuit that energizes the three phase stator
windings 312 to produce a startup torque, a rampup of the rotor
speed of rotation to a selected operating speed, a maintained
rotation at that selected speed under load, and a rapid and
reliable braking torque. As in the case of the motor 28 described
above, operation of the motor 310 thus can be electronic and
programmable. Braking is electronic--with braking currents induced
in the windings 312 being dissipated in large resistors or FET's
mounted on heat sinks.
[0057] The drive plate 308 can be structured in a manner analogous
to the drive plate 34 of the magnetic drive 26 of the blender
described above. The drive plate 308 is non-rotatably secured to
the lower end of a drive shaft 326. The motor gear 328 is
non-rotatably attached to a motor gear shaft 329 which in turn is
attached to the upper end of the drive shaft 326. The motor gear
328 is preferably a helical gear having a plurality of helical gear
teeth 350. The drive shaft 326 axially fits within the gear shaft
329 and is non-rotably secured to the gear shaft 329 and the gear
328 to permit the drive shaft 326 and the gear 328 to rotate in
unison. Thus, rotational torque from the drive plate 308 can be
transmitted to the gear 328 through the drive shaft 326. The drive
shaft 326 and the gear shaft 329 of the motor gear 328 are
rotatably supported by a pair of journal bearings 330a and
330a.
[0058] The compound idler gear 332 is mechanically coupled to the
motor gear 328 and the output gear 334 to transmit rotational
torque from the motor gear 328 to the output gear 334. The idler
gear 332 includes an elongated, cylindrically-shaped upper gear
portion 332a having a plurality of helical gear teeth 352 and a
generally disk-shaped lower gear portion 332b. The lower gear
portion 332b is provided with a plurality of helical gear teeth 354
complementary in size and shape to the gear teeth 350 of the motor
gear 328. The gear teeth 350 of the motor gear 328 engage the gear
teeth 354 of the lower gear portion 332b to transmit rotational
motion and torque from the motor gear 328 to the idler gear 332.
The compound idler gear 332 is non-rotatably secured to a gear
shaft 356 which is rotatably supported by a pair of journal
bearings 333a and 333b.
[0059] The output gear 334 is generally cylindrical in shape and is
non-rotatably attached to the output shaft 302 to rotate with the
output shaft 302. In particular, the output gear 334 is axially
disposed over the output shaft 302 such that the output shaft is
fitted within the central opening of the output gear 334. The
output gear 334 is provided with a plurality of helical gear teeth
334a complementary in size and shape to the gear teeth 352 of the
upper gear portion 332a of the idler gear 332. The gear teeth 352
of the upper gear portion 332a engage the gear teeth 334a of the
output gear 334 to transmit rotational motion and torque from the
idler gear 332 to the output gear 334. The output shaft 302 and the
output gear 334 are rotatably supported by a pair of journal
bearings 336a and 336b.
[0060] The rotor gear 328, the idler gear 332, and the output gear
334 are preferably helical gears, having helically oriented gear
teeth, constructed of light weight, high strength plastic material,
such as acetyl or nylon. One skilled in the art will recognize,
however, that other gear types, such as spur gears, worm gears or
combinations thereof, and other materials, such as metals or
composites can be used in the gear assembly 306 of the present
invention.
[0061] The gear ratio of the gear assembly 306 of the present
invention can be adjusted to increase or to decrease the rotational
speed and torque transmitted from the drive shaft 326 of the
magnetic drive 304 to the output shaft 302 of the ice shaver. For
example, the gear ratio of the gear assembly 306 can be adjusted to
reduce the rotational speed, and thus increase the torque,
transmitted from the drive shaft 326 to the output shaft 302.
Conversely, the rotational speed transmitted by the gear assembly
306 can be increased, thereby reducing the torque transmitted, by
adjusting the gear ratio of the gear assembly 306. The gear ratio
can be adjusted by changing the number of gear teeth, the number of
gears, and/or the size of gears of the gear assembly, as known in
the art.
[0062] In the preferred embodiment of the ice shaver of the present
invention, the desired speed of the output shaft 326 of the ice
shaver is approximately 540 rpm for effective operation of the ice
shaver. The magnetic drive 300 of the present invention, employing
a brushless d.c. motor as is preferred, typically generates an
operational speed of approximately 6000 rpm. Accordingly, the gear
ratio of the gear assembly 306 is approximately 11.1:1.
[0063] One skilled in the art will readily appreciate that the
magnetic drive and gear assembly of the present invention can be
used in a wide variety of applications, in addition to the ice
shaver described above, where it is desired to transmit power from
a rotary output of a motor to a driven member under a load,
including in other food processing equipment such as blenders, food
mixers, food processors, and juicers.
[0064] Additionally, although the ice shaver of the present
invention is described as a component of a combination blender/ice
shaver machine, one skilled in the art will readily appreciate that
the ice shaver can be a stand alone unit, i.e., the ice shaver can
be independent of the blender.
[0065] Moreover, one skilled in the art will appreciate that the
type and number of gears, the size of the gears, and the number of
gear teeth of the gear assembly described herein in connection with
the ice shaver of the present invention is exemplary only. These
features, as well as other features of the gear assembly, can be
varied to achieve the same, similar or, different gear ratios, as
is desired for a specific application, without departing from the
scope of the present invention. For example, design considerations,
such as weight and size limitations, can dictate the number, type,
and size of gears, as well as the number of gear teeth, employed to
achieve the desired gear ratio.
[0066] These and other modifications and variations which will
occur to those skilled in the art having read the foregoing
specification in light of the accompanying drawings are intended to
fall within the scope of the appended claims.
* * * * *