U.S. patent application number 12/473142 was filed with the patent office on 2010-12-02 for vacuum cleaner overload clutch.
This patent application is currently assigned to Electrolux Home Care Products, Inc.. Invention is credited to Jonas Beskow, Anders Haegermarck.
Application Number | 20100299868 12/473142 |
Document ID | / |
Family ID | 43218549 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100299868 |
Kind Code |
A1 |
Beskow; Jonas ; et
al. |
December 2, 2010 |
Vacuum Cleaner Overload Clutch
Abstract
A vacuum cleaner overload clutch having an overload cog, a
spring mount, and an overload spring. The spring is engaged with
the cog to provide torque transfer, and disengaged from the cog to
terminate torque transfer. The spring may not reengage until the
parts stop rotating. A weight may be provided to bias the spring
into the disengaged position, and the spring may have an engagement
portion that is captured between the overload cog and a wall on the
spring holder when the clutch is engaged. The clutch may be part of
a system including a motor and agitator, and may have other
features, such as a graduated engagement clutch.
Inventors: |
Beskow; Jonas; (Stockholm,
SE) ; Haegermarck; Anders; (Trangsund, SE) |
Correspondence
Address: |
HUNTON & WILLIAMS LLP;INTELLECTUAL PROPERTY DEPARTMENT
1900 K STREET, N.W., SUITE 1200
WASHINGTON
DC
20006-1109
US
|
Assignee: |
Electrolux Home Care Products,
Inc.
|
Family ID: |
43218549 |
Appl. No.: |
12/473142 |
Filed: |
May 27, 2009 |
Current U.S.
Class: |
15/390 |
Current CPC
Class: |
A47L 9/0427
20130101 |
Class at
Publication: |
15/390 |
International
Class: |
A47L 5/10 20060101
A47L005/10 |
Claims
1. A vacuum cleaner overload clutch system comprising: a motor
adapted to selectively provide a drive torque; an agitator adapted
to contact a surface to be cleaned; an overload cog operatively
connected between the motor and the agitator and adapted to rotate
about a rotating axis, the overload cog having one or more first
cog portions that extend a first distance from the rotating axis; a
spring mount operatively connected between the motor and the
agitator and adapted to rotate about the rotating axis; an overload
spring mounted on the spring mount, the overload spring having: an
engaged configuration in which the overload spring wraps around at
least a portion of the overload cog and has one or more first
spring portions that contact the one or more first cog portions to
thereby transfer the drive torque between the overload cog and the
spring mount, and a disengaged configuration in which the one or
more first spring portions do not substantially contact the one or
more first cog portions to thereby not substantially transfer the
drive torque between the overload cog and the spring mount, and
wherein the overload spring is adapted to move to the disengaged
configuration when the drive torque exceeds a predetermined torque
value, and remain in the disengaged configuration until the
overload cog and spring mount substantially stop rotating.
2. The vacuum cleaner overload clutch system of claim 1, wherein:
the overload cog further comprises one or more second cog portions
that extend a second distance from the rotating axis, the second
distance being less than the first distance; and the overload
spring further comprises one or more second spring portions that
conform generally to the second cog portions when the overload
spring is in the engaged configuration.
3. The vacuum cleaner overload clutch system of claim 1, wherein
resilient tension in the overload spring biases the overload spring
towards the engaged configuration, and a centrifugal force
generated by the mass of the overload spring biases the overload
spring away from the engaged configuration when the overload spring
is in the disengaged configuration.
4. The vacuum cleaner overload clutch system of claim 1, further
comprising a weight adapted to generate a centrifugal force that
biases the overload spring away from the engaged configuration when
the overload spring is in the disengaged configuration.
5. The vacuum cleaner overload clutch system of claim 4, wherein
the weight is pivotally mounted to the spring mount and has a free
end adapted to contact the overload spring.
6. The vacuum cleaner overload clutch system of claim 1, wherein
the overload cog comprises one or more notches and the spring mount
comprises a pivoting pawl that prevents the overload cog and spring
mount from rotating relative to one another in a first
direction.
7. The vacuum cleaner overload clutch system of claim 6, wherein
the pivoting pawl comprises a weight adapted to generate a
centrifugal force that biases the overload spring away from the
engaged configuration when the overload spring is in the disengaged
configuration.
8. A vacuum cleaner overload clutch comprising: an overload cog
adapted to rotate about an axis; a spring mount adapted to rotate
about the axis; an overload spring mounted on the spring mount and
adapted to contact the overload cog in an engaged position, and not
substantially contact the overload cog in a disengaged position;
and a movable weight adapted to bias the overload spring into the
disengaged position upon rotation of the spring mount.
9. The vacuum cleaner overload clutch of claim 8, wherein the
movable weight is movably mounted to the spring mount.
10. The vacuum cleaner overload clutch of claim 8, wherein the
movable weight is pivotally mounted to the spring mount.
11. The vacuum cleaner overload clutch of claim 8, wherein: the
overload cog comprises at least one protrusion extending radially
therefrom; the spring mount comprises a wall facing the overload
cog; and the overload spring comprises a first engagement portion
that is captured between the at least one protrusion and the wall
when the overload spring is in the engaged position, and is not
captured between the at least one protrusion and the wall when the
overload spring is in the engaged position.
12. A vacuum cleaner overload clutch comprising: an overload cog
adapted to rotate about an axis and having at least one protrusion
extending radially therefrom; a spring mount at least partially
surrounding the overload cog and adapted to rotate about the axis,
the spring mount having a wall facing the overload cog; an overload
spring mounted on the spring mount and adapted to contact the
overload cog in an engaged position, and not substantially contact
the overload cog in a disengaged position; and wherein the overload
spring comprises a first engagement portion that is captured
between the at least one protrusion and the wall when the overload
spring is in the engaged position, and is not captured between the
at least one protrusion and the wall when the overload spring is in
the engaged position.
13. The vacuum cleaner overload clutch of claim 12, wherein the
first engagement portion comprises a resiliently-deformable
loop.
14. The vacuum cleaner overload clutch of claim 12, wherein the at
least one protrusion comprises a plurality of protrusions, and the
overload spring further comprises one or more second engagement
portions that resiliently contact at least a second one of the
plurality of protrusions when the overload spring is in the engaged
position.
15. The vacuum cleaner overload clutch of claim 12, further
comprises holding means for holding the overload spring
substantially out of contact with the overload cog when the
overload spring is in the disengaged position.
16. The vacuum cleaner overload clutch of claim 15, wherein the
holding means comprises a centrifugal force generated by rotation
of the overload spring about the axis.
17. The vacuum cleaner overload clutch of claim 15, wherein the
holding means comprises a weight adapted to generate a centrifugal
force upon rotation of the vacuum cleaner overload clutch.
18. A vacuum cleaner clutch assembly comprising: a motor; an
agitator; an overload clutch adapted to receive a drive torque
generated by the motor and transmit the drive torque to the
agitator when the drive torque is less than a predetermined torque
limit, and not transmit the drive torque to the agitator when the
drive torque is greater than a predetermined torque limit; and an
engagement clutch adapted to transmit the drive torque from the
motor to the agitator in a graduated manner.
19. The vacuum cleaner clutch assembly of claim 18, wherein the
engagement clutch is adapted to transmit the drive torque from the
motor to the overload clutch in one or more stages.
20. The vacuum cleaner clutch assembly of claim 18, wherein the
engagement clutch is adapted to smoothly increase the amount of
drive torque the engagement clutch transmits from the motor to the
overload clutch.
21. The vacuum cleaner clutch assembly of claim 18, wherein the
engagement clutch comprises at least two mechanical clutches.
22. The vacuum cleaner clutch assembly of claim 18, wherein the
engagement clutch is operatively positioned between the motor and
the overload clutch.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to clutch assembly features
for use with vacuum cleaners. More specifically, the present
invention relates to a clutch assembly for transferring power from
a vacuum cleaner motor unit to the brushroll. It will be understood
that the features of the clutch assembly may be used in other types
of equipment and/or appliances, and may be used in part, and in
combination with other driveline features.
BACKGROUND OF THE INVENTION
[0002] It is well known that vacuum cleaners, such as upright
vacuums, may use a rotating brushroll to help clean various
surfaces, such as carpeting. Canister type vacuum cleaners may also
use a power head having a rotating brushroll, as is known in the
art. The brushroll typically rotates about a horizontal axis and
provides surface agitation to release dirt and dust trapped in and
upon the surface being cleaned. Once agitated, the dirt and dust
are sucked into the vacuum cleaner through the dirty air inlet.
Suction force is typically generated by a fan motor unit.
[0003] The brushroll is typically driven by a motor. The vacuum may
have one motor that provides both suction and drive power for the
brushroll (a so-called "single-motor" vacuum). Alternatively, the
vacuum may have two motors--one for generating suction and one for
driving the brushroll. Such a "two-motor" vacuum configuration may
have the drawback of increased weight and cost, but may be favored
where separate control of the suction fan and brushroll are
desired, or the fan motor is for some reason not capable of driving
the brushroll. Power from a motor, in any configuration, must be
transferred from the motor to the brushroll. The brushroll may be
driven at a slower rotational speed than the motor. For example, a
motor may operate at over 10,000 revolutions per minute (rpm), and
it may be desirable to rotate the brushroll at a slower speed, such
as 3,000 rpm. As is known in the art, a drive belt is typically
used for driving the brushroll. The belt typically is a high
strength, long life belt that may be flat or ridged or toothed. A
reduction gear and clutch mechanism may be provided. A cogged belt
and/or reduction gears also may be used to provide gearing
reduction. Some vacuums may alternatively use a direct drive from
the motor to the brushroll, or incorporate the motor in the
brushroll.
[0004] While brushrolls are commonly used and typically beneficial,
they present a potential problem in that the brushroll may continue
to rotate even when it is not desirable. For example, rotation may
continue when the vacuum is stopped or placed into an upright
position with the power still on, or when cleaning smooth floors
that may not benefit from a brushroll. In fact, damage to the
surface below the rotating brushroll may result from the brushroll
rotating in one place. For example, carpet fibers may become worn
or burned from frictional heat generated from the continuous
rotation of the brushroll over a small part of the carpet. In a
typical single-motor vacuum with a direct drive brushroll, there
may be no independent control over the brushroll, such that in
order to stop the brushroll, the vacuum itself may need to be
turned off. Some single-motor vacuums may incorporate a lifting
mechanism for the brushroll, which lifts the brushroll off the
floor when the vacuum is placed in the upright position or when it
is desired to clean smooth floors, but the rotation of the
brushroll may continue. In other designs, an idler pulley
configuration may be used, in which the drive belt is placed upon
an idler pulley when the vacuum is placed in the upright position
or when it is desired to clean smooth floors, stopping the
brushroll rotation. In such devices, the driven belt must be
replaced upon the driven pulley to resume operation, which often
requires a mechanically complex and potentially unreliable
mechanism to disengage and engage the brushroll. In other cases, a
clutch mechanism may be used to disengage the brushroll.
[0005] Two-motor vacuum cleaners have potential to provide greater
control over when the brushroll is rotating, because the brushroll
motor can be operated by manually or automatically operated
switches to turn the brushroll on and off independently of the
vacuum source motor. Such devices can be heavier and more expensive
than single-motor vacuums.
[0006] Another potential problem with brushrolls is that they can
become jammed. For example, a foreign object may become lodged into
the brushroll and prevent rotation. When this happens, the drive
motor could overheat (particularly if the motor stops when the
brushroll stops) and/or the drive belt or other drive mechanisms
could be damaged. During such jams, it is desirable to disengage or
stop drive power to the brushroll to prevent damage to the vacuum
or the foreign object. Some vacuums use thermally-operated switches
to cut off power to the motor when an overheating condition is
reached. Other vacuums use a non-replaceable fuse that renders the
vacuum inoperative and irreparable if the motor locks. The vacuum
also may be designed with the belt as the weakest link, so that the
belt typically fails during a severe jam condition. Still other
vacuums use a clutch mechanism which may disengage or slip under a
high torque condition.
[0007] Different clutch mechanisms are known in the art. Clutch
mechanisms are used to provide both a power transfer function and a
torque limiting function through the use of various structural
configurations, such as friction plates, flexible couplings,
springs, detent plates, wave plates, and magnetic couplings.
Exemplary clutch mechanisms with application to vacuums
incorporating some of the aforementioned features are described in
U.S. Pat. Nos. 3,228,209; 3,797,621; 4,235,321; 4,532,667;
4,766,641; 5,601,491; 6,691,849; and 7,228,593; which references
are incorporated herein.
[0008] It has been found that many different requirements may be
desired of vacuum cleaner brushroll drive and clutch mechanisms.
For example, such requirements sometimes include: operate in the
overload condition for a long time without overheating; survive
numerous disengagement and reengagement cycles; operate
automatically to address different cleaning modes (e.g., turn off
the brushroll during accessory cleaning operations and when
vacuuming on bare floors); operate manually to allow the user to
selectively disengage the brushroll; operate in dusty environments;
and so on. Some of these requirements may oppose one another in
various respects. For example, it is desirable to provide a
brushroll overload clutch that will disengage drive torque to the
brushroll immediately upon reaching an overload torque value, to
better protect any objects that contact the brushroll, the
brushroll, and the drive components. While this could be
accomplished using an overload clutch having a relatively low
overload torque value, the clutch may be so sensitive that it will
disengage when it is not desired, such as when the brushroll is
started on thick carpets or moved rapidly from a smooth surface to
a carpeted surface.
[0009] While various prior art devices, such as those described
above, have been used, there exits a need to provide alternatives
to such devices.
SUMMARY OF THE INVENTION
[0010] In a first exemplary aspect, there is provided a vacuum
cleaner overload clutch system having a motor adapted to
selectively provide a drive torque, an agitator adapted to contact
a surface to be cleaned, an overload cog operatively connected
between the motor and the agitator, a spring mount operatively
connected between the motor and the agitator, and an overload
spring mounted on the spring mount. The overload cog is rotates
about a rotating axis, and has one or more first cog portions that
extend a first distance from the rotating axis. The spring mount is
adapted to rotate about the rotating axis. The overload spring has
an engaged configuration in which it wraps around at least a
portion of the overload cog and has one or more first spring
portions that contact the one or more first cog portions to
transfer the drive torque between the overload cog and the spring
mount, and disengaged configuration in which the one or more first
spring portions do not contact the one or more first cog portions
to not transfer the drive torque between the overload cog and the
spring mount. The overload spring is adapted to move to the
disengaged configuration when the drive torque exceeds a
predetermined torque value, and remain in the disengaged
configuration until the overload cog and spring mount substantially
stop rotating.
[0011] In a second exemplary aspect, there is provided a vacuum
cleaner overload clutch having an overload cog adapted to rotate
about an axis, a spring mount adapted to rotate about the axis, an
overload spring mounted on the spring mount and adapted to contact
the overload cog in an engaged position, and not substantially
contact the overload cog in a disengaged position, and a movable
weight adapted to bias the overload spring into the disengaged
position upon rotation of the spring mount.
[0012] In a third exemplary embodiment, there is provided a vacuum
cleaner overload clutch having an overload cog adapted to rotate
about an axis and having at least one protrusion extending radially
from it, a spring mount at least partially surrounding the overload
cog and adapted to rotate about the axis and having a wall facing
the overload cog, and an overload spring mounted on the spring
mount and adapted to contact the overload cog in an engaged
position and not substantially contact the overload cog in a
disengaged position. The overload spring has a first engagement
portion that is captured between the at least one protrusion and
the wall when the overload spring is in the engaged position, and
that is not captured between the at least one protrusion and the
wall when the overload spring is in the engaged position.
[0013] In a fourth exemplary aspect, there is provided a vacuum
cleaner clutch assembly having a motor, an agitator, and an
overload clutch adapted to receive a drive torque generated by the
motor and transmit the drive torque to the agitator when the drive
torque is less than a predetermined torque limit, and not transmit
the drive torque to the agitator when the drive torque is greater
than a predetermined torque limit. The assembly also includes an
engagement clutch that is adapted to transmit the drive torque from
the motor to the agitator in a graduated manner.
[0014] The recitation of this summary of the invention is not
intended to limit the claimed invention. Other variations are
encompassed by the appended claims and disclosed herein, and other
aspects, embodiments, modifications to and features of the claimed
invention will be apparent to persons of ordinary skill in view of
the disclosures herein. Furthermore, this recitation of the summary
of the invention, and the other disclosures provided herein, are
not intended to diminish the scope of the claims in this or any
related or unrelated application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention is described in detail with reference
to the examples of embodiments shown in the following figures in
which like parts are designated by like reference numerals.
[0016] FIG. 1A is a fragmented perspective view of a vacuum cleaner
base assembly in accordance with an exemplary first embodiment.
[0017] FIG. 1B is a schematic side view of the vacuum cleaner base
assembly of FIG. 1A.
[0018] FIG. 2 is a perspective view of a clutch assembly and
mounting and support structure in accordance with an exemplary
first embodiment.
[0019] FIG. 3 is a first perspective view of the mounting and
support structure for the clutch assembly of FIG. 2.
[0020] FIG. 4 is a second perspective view of the mounting and
support structure for the clutch assembly of FIG. 2.
[0021] FIG. 5 is a perspective view of the clutch assembly of FIG.
2.
[0022] FIG. 6 is an exploded view of the clutch assembly and
mounting and support structures of FIG. 2.
[0023] FIG. 7 is a cut-away view of the clutch assembly of FIG.
2.
[0024] FIG. 8 is a perspective view of a flywheel and drum assembly
of the clutch assembly of FIG. 2.
[0025] FIG. 9 is a perspective view of a clutch lever of the clutch
assembly of FIG. 2.
[0026] FIG. 10A is a perspective view of an expanding clutch
assembly of the clutch assembly of FIG. 2.
[0027] FIG. 10B is a schematic end view of the expanding clutch
assembly of FIG. 10A, showing the expanding clutch in a disengaged
position.
[0028] FIG. 10C is a schematic end view of the expanding clutch
assembly of FIG. 10A, showing the expanding clutch in an engaged
position.
[0029] FIG. 11 is a perspective view of an inner overload device of
the clutch assembly of FIG. 2, showing the device in a normal
operating condition.
[0030] FIG. 12 is a perspective view of an inner overload device of
FIG. 11, showing the device in the overload condition.
[0031] FIG. 13A is an end view of an alternative embodiment of a
clutch engagement mechanism, shown in the disengaged position.
[0032] FIG. 13B is an end view of the clutch lever of FIG. 13A
shown in the engaged position.
[0033] FIG. 14 is a cut-away view of a clutch assembly in
accordance with another alternative embodiment.
[0034] FIG. 15 is a side view of an overload mechanism in
accordance with an alternative embodiment.
[0035] FIG. 16A is a side view of an alternative exemplary
embodiment of a clutch assembly shown in the disengaged
position.
[0036] FIG. 16B illustrates the assembly of FIG. 16A in the engaged
position.
[0037] FIG. 16C illustrates the assembly of FIG. 16A in the
overload condition.
[0038] FIG. 17 is a side view of a clutch mechanism in accordance
with another alternative embodiment.
[0039] FIG. 18A is a side view of a clutch mechanism in accordance
with another alternative embodiment.
[0040] FIG. 18B is a side view of the clutch mechanism of FIG. 18A
in the engaged position.
[0041] FIG. 18C is a side view of the clutch mechanism of FIG. 18A
in the disengaged position.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTIONS
[0042] The present disclosure provides numerous inventive features
relating to embodiments of a clutch assembly for use in a vacuum
cleaner or in other appliances or machines. Various features and
alternative embodiments of the invention are described with
reference to their exemplary use in certain embodiments, but it
will be readily appreciated that the features could alternatively
be incorporated into other embodiments of vacuum cleaners. The
invention includes these and other variations, as will be
appreciated by persons of ordinary skill in the art in view of the
present disclosure. Furthermore, the various features described
herein may be used separately from one another or in any suitable
combination. The present disclosure illustrating various exemplary
embodiments is not intended to limit the invention in any way.
[0043] An exemplary first embodiment of the invention is
illustrated in FIGS. 1-12, which generally illustrate a clutch
assembly 100 for an upright vacuum, canister vacuum power head, or
any other type of vacuum cleaner that uses a driven brushroll. The
descriptions herein of this embodiment and other embodiments of the
clutch assembly 100 will focus on application in a vacuum cleaner,
but it will be understood that the clutch assembly 100 may be used
in other types of equipment and appliances. For example, the clutch
assembly 100 has application to any mechanism that may require a
transfer of power, in the form of rotational energy or torque, from
an input (such as a motor drive) to a driven output (such as a
brushroll), in which it is desired to provide a means to engage and
disengage the driven output on command or during overload
conditions. As will be appreciated from the disclosure herein, the
exemplary clutch assembly 100 may be configured to provide both
overload protection to the equipment (such as by decoupling the
output drive from the input drive), and a means for selectively
engaging and disengaging the motor from the driven assembly to
initiate and cease operation of the driven assembly when desired.
However, these two features and functions may be provided
separately, and are not required in all embodiments of the
invention.
[0044] As shown in FIG. 1A, the exemplary clutch assembly 100 may
be mounted in a base assembly 110 of a vacuum cleaner. The base
assembly 110 is shown with the upper cover removed to depict the
clutch assembly 100 and driven agitator, such as a brushroll 102.
In this embodiment, a fan motor 104 is provided to simultaneously
drive a vacuum fan and the clutch assembly 100. The fan motor 104
may be mounted in the base assembly 110, or mounted in an upright
housing 112 that is pivotally mounted to the base assembly 110, as
known in the art. Examples of fan motor locations are shown in U.S.
Pat. Nos. 6,122,796, 6,553,611, and 5,014,388, which are
incorporated herein. The base assembly 110 also may comprise the
frame of a self-propelled vacuum cleaner, such as shown in U.S.
Pat. No. 5,781,960, which is incorporated herein. Alternatively,
the fan motor 104 may be replaced by another motor that does not
drive a vacuum fan. As will also be appreciated, the brushroll 102
may comprise or be replaced by any suitable agitator device, as are
well-known in the art. For example, an exemplary agitator may
include a rotating spindle having helical rows of flexible
bristles, flexible flaps, rigid beater bars, or combinations of
such devices that are intended to contact and agitate the surface
being cleaned to help dislodge or remove dirt from the surface.
[0045] The location of the clutch assembly 100 may be based on
space, weight, and power transmission considerations for the
particular vacuum cleaner or specific application, as known in the
art, and it may be located in alternate positions from that
depicted in FIG. 1. The base assembly 100 may be located on or form
part of an upright vacuum cleaner or a power head of a canister or
central vacuum cleaner. Examples of upright vacuums are provided
above, and examples of power heads are provided in U.S. Pat. Nos.
4,467,495 and 4,614,003, which are incorporated herein by
reference.
[0046] In the exemplary embodiment, the fan motor 104 drives a
motor output gear 120, which is drivingly connected to a clutch
input gear 130 on the clutch assembly 100 by a motor belt 107. The
motor belt 107 may be any type of belt, such as a toothed belt with
a plurality of spaced teeth on an inner surface thereof to engage
with the spaced teeth of the first and clutch input gear wheels.
The drive belt may be a reinforced, high strength belt for
durability and lasting function. In other embodiments, a flat,
ribbed or v-type drive belt may be used, as known in the art. Of
course, the motor output gear 120 and clutch input gear 130 may be
replaced with other types of pulley, cog or gear, as necessary or
desired to accommodate power transfer from the motor 104 to the
clutch assembly 100.
[0047] As depicted in FIG. 1A, the motor output gear 120 may have a
smaller diameter than the clutch input gear 130. The diameter size
difference may provide a speed reduction, such that the clutch
input gear 130 may rotate slower than the motor output gear 120.
This speed reduction may be desirable because a typical vacuum
motor may operate at a speed greater than the desired brushroll
speed.
[0048] The exemplary clutch assembly 100 may also have a clutch
output gear 140. The clutch output gear 140 may be connected by a
brushroll belt 108 (FIG. 1B) to a brushroll input gear 106 that
drives the brushroll 102. The brushroll input gear 106 may be any
suitable gear or pulley, and may be located on, inside, or adjacent
to the brushroll. The clutch output gear 140, brushroll belt 108
and brushroll input gear 106 may comprise any suitable kind of gear
or belt. For example, the brushroll belt 108 may be a toothed belt
similar to the motor belt 107, or may be flat, ribbed, or otherwise
shaped. The difference in size between the clutch output gear 140
and the brushroll input gear 106 may provide a further gear
reduction. For example, the fan motor 104 may operate at about
30,000 RPM and the brushroll may operate at about 4,000 RPM, with a
total gear reduction ratio of about 7.4:1. While in some
embodiments, the brushroll may operate at a speed of over one
thousand RPM, speeds below this may be possible in other
embodiments. Of course, other reduction ratios may be used in other
embodiments (for example, the clutch input gear 130 may be the same
diameter as the clutch output gear 140), and in still other
embodiments there may be no reduction or even a speed-increasing
ratio.
[0049] The clutch assembly 100 may be mounted to the base assembly
110 in any suitable way. For example, the clutch assembly 100 may
be mounted in the same way a typical brushroll motor would be
mounted in a typical vacuum cleaner base or powerhead. Such a
mounting may be by one or more fasteners, such as screws, straps or
bolts. In an exemplary embodiment, a clutch assembly mount 212,
such as hereinafter described, may be used. The clutch assembly 100
also may be compression fitted into the base assembly, such as by
using a snap tight fit with plastic tabs. One or more elastic
bushings may be located between the clutch assembly 100 and the
base assembly 110 to reduce vibrations and/or accommodate
variations in manufacturing tolerances. It may also be desirable to
make the clutch assembly 100 removable from the base assembly to
facilitate repairs and maintenance. Of course, in other
embodiments, the clutch assembly 100 may not be removable from the
base assembly 110.
[0050] FIG. 2 depicts the clutch assembly 100 removed from the base
assembly 110 to help illustrate an exemplary clutch assembly mount
212. FIGS. 3 and 4 depict the clutch assembly mount 212 with the
clutch assembly 100 removed. As shown, the exemplary clutch
assembly mount 212 may include an outer base module 202, an outer
bearing holder 204, an inner base module 206, and an inner bearing
holder 208 (as used in reference to the clutch assembly mount 212,
the terms "outer" and "inner" refer to positions with respect to
the centerline of the base assembly 110). In this embodiment, the
clutch assembly 100 is secured, at one end, by the outer base
module 202, and, at the other end, by the inner base module 206.
The outer and inner base modules 202, 206 may be secured to the
base assembly 110 with one or more fasteners (not shown). The outer
and inner bearing holders 204, 208 are mounted to the upper
surfaces of the outer and inner base modules 202, 206,
respectively. The outer and inner bearing holders capture bearings
604a, 604d (see FIGS. 5 and 6) in place to thereby rotatably mount
the clutch assembly 100 in the clutch assembly mount 212. The
bearings 604a, 604d are secured in cavities 402, 404 (FIG. 4) that
are shaped to hold the bearings 604a, 604d. The cavities 402, 404
may have ridges, such as shown, to accommodate and securely hold
the bearings 604a, 604b against axial movement. While bearings may
be used on some embodiments, journals or other rotating mounting
structures may be used to rotatably hold the clutch assembly 100 in
the clutch assembly mount 212.
[0051] The clutch assembly mount 212 may include other functional
or structural elements, such as a cut-out 406 to mount and support
a solenoid 210. The purpose of the solenoid 210 is described
subsequently herein. The clutch assembly mount 212 may also
include, for example, pivot mounts 214 to pivotally hold
corresponding pivots 503 on a disengagement lever 502, as described
below. If desired, the clutch assembly mount may also include
shroud 121 that encases the clutch assembly 100, and an air passage
123 to a vacuum source, such as a suction inlet passage 122 in the
base assembly 110. In such an embodiment, the vacuum source may
draws air through the shroud and over the clutch assembly 100 to
cool the clutch assembly 100 and remove any particulate matter that
the clutch assembly 100 may generate during use.
[0052] Turning to FIGS. 5-7, the first exemplary embodiment of a
clutch assembly 100 is described in detail. The external features
of the clutch assembly 100 are best shown in FIG. 5, with the
clutch assembly mount 212 removed. As shown, the clutch assembly
100 may have a clutch input gear 130, a clutch output gear 140, a
solenoid 210 with a solenoid shaft 504, a disengagement lever 502,
a flywheel 508 with a perimeter weight 506, and a flywheel spring
holder 510.
[0053] The clutch assembly 100 may receive an input, in the form of
rotational torque, through the clutch input gear 130, as described
above. Generally speaking, the clutch assembly 100 of this
exemplary embodiment transfers the input torque to the clutch
output gear 140, as briefly described above. In the hereinafter
described first exemplary embodiment, the clutch assembly 100 may
provide several functions. First, it includes mechanisms that
selectively provide torque transfer from the clutch input gear 130
to the clutch output gear 140 in an engaged position, and prevent
such torque transfer in a disengaged position. This aspect is
referred to sometimes herein as the drive clutch feature. Second,
it includes mechanisms that automatically prevent or substantially
reduce torque transfer from the clutch input gear 130 to the clutch
output gear 140 upon detecting an overload condition. This aspect
is referred to sometimes herein as the overload clutch feature.
Thus, in this exemplary embodiment, the clutch assembly 100 may be
set in an engaged position in which torque is intended to be
transferred from the clutch input gear 130 to the clutch output
gear 140, but such torque transfer may be prevented due to an
overload condition. Further, the mechanisms the terminate torque
transfer after sensing an overload may not allow transmission of
torque until after the clutch assembly has been reset to the
disengaged position.
[0054] In the exemplary embodiment, the drive clutch feature
defaults to the engaged position. That is, power is transferred via
the clutch assembly 100 from the clutch input gear 130 to the
clutch output gear 140 unless the clutch assembly 100 is set to a
disengaged position. Any suitable mechanical or electrical device
may be used to move the clutch assembly 100 into the disengaged
position. In the exemplary embodiment the clutch assembly 100 is
disengaged by moving the flywheel 508 and its associated flywheel
weight 506 away from engagement with a drum 608 and its associated
drum lid 609. The manner in which this accomplishes clutch
disengagement is described in detail below. In this exemplary
embodiment, the flywheel 508 is biased into engagement with the
drum 608 by a spring 622 (FIG. 6) that is captured between the
flywheel spring holder 510 and the flywheel 508. The flywheel
weight 506 is formed as part of the flywheel 508 or rigidly
connected to it.
[0055] The disengagement lever 502 is provided to move the flywheel
508 against the bias of the spring 622. This is done by pivoting
the disengagement lever 502 (which rotates on its pivots 503) away
from the drum 608. Any suitable mechanism may be used to move the
disengagement lever 502. For example, a solenoid 210 having a
solenoid shaft 504 that extends when the solenoid is activated, may
be positioned adjacent the disengagement lever 502. When the
solenoid 210 is energized, the shaft 504 extends and moves the
disengagement lever 502 away from the drum 608. As the
disengagement lever 502 pivots, its side surface 507 presses
against and moves the flywheel 508 (via contact with the flywheel
weight 506) away from the drum 608, thereby disengaging the clutch
mechanism 100. The side surface 507 may frictionally engage the
flywheel 508 to decelerate it when it is disengaged, and the
disengagement lever 502 may press the opposite side of the flywheel
into frictional engagement with other surfaces, such as an inner
wall of the clutch assembly mount 212 to help decelerate the
flywheel 508 and its weight 506.
[0056] Although it is not required, the foregoing arrangement is
beneficial because it provides control over the clutch assembly 100
without requiring significant effort to engage and disengage the
working parts. In particular, the disengagement lever 502 obtains a
significant mechanical advantage to press against the biasing force
of the spring 622, which provides a simple arrangement that
facilitates easy disengagement of the clutch assembly 100, either
by hand or by a suitable mechanical or electrical device.
Furthermore, as discussed in more detail below, it may not be
necessary for the frictional forces between the flywheel 508 and
drum 608 to be particularly great in order to engage the clutch
assembly 100, and therefore the spring 622 need not have a
particularly high biasing force. This also reduces the amount of
force necessary to move the disengagement lever 502 and eases the
requirements to operate the system.
[0057] It will be readily appreciated that various modifications or
changes may be made to the clutch assembly 100 to provide for
engagement and disengagement. For example, the solenoid 210 may be
replaced by a hand-operated lever, and the disengagement lever 502
may be replaced with other structures that move the flywheel 508
out of engagement. In still other embodiments, the clutch assembly
100 may be biased in the disengaged position, and require input to
engage it, or the clutch assembly 100 may not be biased in either
the engaged or disengaged position.
[0058] FIG. 6 is an exploded view of the clutch assembly 100 and
FIG. 7 is a cut-away view of the internal components of the clutch
assembly 100. As best seen in FIG. 7, a shaft 602, such as a steel
axle, runs the length of the clutch assembly 100, and is used to
transfer torque from the clutch input gear 130 to the clutch output
gear 140. Certain parts of the clutch assembly 100 may be fixed to
rotated with the shaft 602. For example, in accordance with the
first embodiment, an overload cog 616 (described below) and the
clutch output gear 140 are fixed to the shaft 602. Parts that are
fixed to the shaft 602 may be secured using any suitable method.
For example, the overload cog 616 and clutch output gear 140 may be
secured by pins that pass through corresponding holes through the
shaft 602. Other forms of mounting may include press-fitment,
threads, keys, and eccentric mating shapes (such as a D-shaped
shaft and corresponding D-shaped holes through the fixed parts).
Other parts may be fixed to the shaft 602, as well. For example, in
this first exemplary embodiment, the end bearing 604a may be
pressed onto the end of the shaft 602 to capture parts in place
between the bearing 604a and the overload cog 616.
[0059] As noted above, the shaft 602 is rotatably mounted by two
bearings 604a, 604d. Additional bearings may be used to support the
shaft 602, and to rotatably mount other parts on the shaft 602. For
example, in an exemplary embodiment, at least six bearings, 604a,
604b, 604c, 604d, 604e, and 604f may be provided. In addition, the
bearings 604a-f may be plain roller or ball bearings, but may be
replaced by other kinds of rotating mounts, such as bushings or
journal bearings. In this first embodiment, the bearings 604a-f may
be the same type, but different types of bearings or rotating
mounts may be mixed together. The rotating mounts may allow some
axial movement of the parts they support, but they alternatively
may hold the supported part in a fixed axial location along the
shaft 602. The bearings 604 preferably are sealed, durable and last
for the life of the vacuum cleaner, but they may require periodic
maintenance.
[0060] As noted above, the clutch assembly 100 of the exemplary
first embodiment provides a selective clutch function and an
overload cutoff function. The clutch assembly 100 may be arranged
such that clutch mechanism and overload mechanism are located
together within the confines a single structural component. Such an
arrangement may provide a relatively compact structure, enabling
installation in a space-constrained environment, such as the base
assembly 110 of a vacuum cleaner, as described above. For example,
a single cylindrical module located generally within the clutch
input gear 130 may contain the clutch and overload mechanisms. As
shown in FIGS. 6-8, this module may comprise a drum 608 with a drum
lid 609. It should be appreciated that in other embodiments, the
clutch mechanism and/or the overload mechanism may be located in a
more linear arrangement, such that the components of the clutch
assembly are spaced out over the length of the shaft, and it is not
required to contain the clutch and overload mechanisms in a common
unit like the drum 608.
[0061] In the present exemplary embodiment, the drum 608 comprises
a generally cylindrical structure that is open at one end, and
closed at the other. The drum 608 is rotatably mounted to the shaft
602 by one or more bearings or bushings, such as the shown two
bearings 604b and 604c. Such rotating mounts may be spaced apart to
help distribute any loads on the drum 608 that may be caused by
belt tension or other factors. The drum lid 609 covers the end of
the drum 608 to contain the internal clutch and overload
mechanisms. The clutch input gear 130 surrounds the drum 608, and
is rigidly fixed thereto by any suitable means, such as adhesives,
press fitment, locking parts or other fasteners. The clutch input
gear 130 also may be formed integrally with the drum 608. In the
exemplary embodiment, the clutch input gear 130 or drum 608 may
include vents 611 that help dissipate the heat that may develop in
the drum 608. As explained below, the drum lid 609 may provide a
frictional contact point for the flywheel weight 506. Thus, the
drum lid 609 and flywheel weight 506 may be formed of
heat-resistant materials, such as metal or heat-resistant
plastic.
[0062] The clutch and overload mechanisms may be contained within
the drum. In one embodiment, the clutch mechanism may generally
surround the overload mechanism, although it should be appreciated
that the overload mechanism may merely be within the confines of
the clutch mechanism or alternatively located co-incidentally with
or adjacent to the clutch mechanism. For example, the overload
mechanism may be between the clutch input gear 130 and the clutch
output gear 140. The overload mechanism also may be located
remotely from the clutch mechanism in other embodiments.
[0063] Any suitable drive clutch mechanism may be used to
selectively transfer torque from the clutch input gear 130 to the
clutch output gear 140 (assuming the overload mechanism is not
preventing such transfer). For example, the drive clutch mechanism
may comprise a single stage clutch that essentially immediately
transfers all torque from the clutch input gear 130 to the clutch
output gear 140 (e.g., a simple "dog" clutch having parts that
physically interlock to transfer torque). Alternatively, the drive
clutch mechanism may comprise a graduated engagement clutch that
transfers torque from the clutch input gear 130 to the clutch
output gear 140 gradually or in blended or discrete stages. A
simple graduated engagement clutch might comprise, for example, a
disk clutch like those used in typical automotive applications,
which, depending on the speed with which it is engaged, can
smoothly increase the torque over time. Another graduated
engagement clutch may comprise one having multiple clutches. For
example, a first clutch may provide an initial rotational energy
and/or initial transfer of torque from the clutch input gear 130 to
the clutch output gear 140, and a second clutch may be engaged
after the first clutch to provide increased torque transfer.
Arrangements that provide a significantly graduated torque transfer
may be referred to as a "soft-start" drive clutch system. Examples
of such devices are described below, but other embodiments may use
other types of clutch mechanism.
[0064] As stated above, an overload mechanism may be provided to
terminate torque transfer. Such a mechanism may operate in
conjunction with or independently from a clutch mechanism. For
example, the overload mechanism may be an overload clutch that
decouples the clutch output gear from the clutch mechanism when an
excessive resistance torque is applied to the clutch output gear.
The overload clutch may be a resistance clutch, such as one that
uses friction devices and/or magnetic forces, or any other suitable
clutch device. The presently-discussed exemplary embodiment
provides clutch and overload mechanisms, which are described
together below, but may be used independently in other
embodiments.
[0065] In the first exemplary embodiment, a drive clutch mechanism
may include an expanding clutch 610, a clutch lever 612, a clutch
mount 614, and an overload spring 618. In the shown embodiment, all
of the foregoing parts are located within the drum 608, but this is
not required. The flywheel 508 operates the clutch lever 612, as
described below. The clutch mount 614 is located within the
circumference of the expanding clutch 610 and rotatably mounted on
the shaft 602 by a bearing 604e or bushing. The clutch mount 614
provides a stable mounting plane for the expanding clutch 610, the
clutch lever 612 and the overload spring 618. As shown, the
expanding clutch 610 may surround the clutch mount 614, while the
clutch lever 612 and overload spring 618 are mounted to opposite
faces of the clutch mount 614.
[0066] The clutch lever 612 is pivotally connected to the clutch
mount 614, such as by a pivot pin 624. The expanding clutch 610
comprises a generally C-shaped structure that is mounted at one end
to the clutch mount 614 by a first pin 626, and at the other end to
the clutch lever 612 by a second pin 628. Rotation of the clutch
lever 612 about its mounting pin 624 transmits a force to the
second pin 628 that tends to increase the size of the opening in
the C-shaped expanding clutch 610, which increases the diameter of
the expanding clutch 610. The first and second pins 626, 628 may be
mounted in slots on the expanding clutch 610 to allow some radial
movement as the expanding clutch 610 expands and contracts and
accommodate any wear the parts might experience. Such slots may
also provide a ramp-like structure against which the pins 626, 628
can press to generate an outward (or inward) radial component to
the opening force applied by the clutch lever 612.
[0067] In the exemplary embodiment, the clutch lever 612 is
operated by the flywheel 508. As noted above, the flywheel 508 is
biased by a spring 622 into engagement with the end of the drum
608. Contact may be directly between the flywheel 508 and drum 608,
or via one or more added parts, such as shown. The flywheel 508 is
rotatably mounted on the shaft 602 by a bearing 604f (FIG. 7), and
can rotate on the shaft 602 independently from the drum 608. When
the clutch is in the engaged position, which is the default
position in this embodiment, the flywheel 508 contacts the drum
608. In this position, rotation imparted to the drum 608 (via the
clutch input gear 130) tends to rotate the flywheel 508 by
frictional contact between these parts. If the flywheels'
resistance to rotation is great enough, the frictional contact will
be insufficient to drive the flywheel 508 at the same speed as the
drum 608, or, in some cases, to drive the flywheel 508 at all.
Conversely, where the flywheel 508 has relatively little resistance
to rotation, it may rotate at the same speed as the drum 608.
Friction and inertia can both contribute to the flywheel's
resistance to rotation at any given moment, and the weight of the
flywheel 508 (and any parts that it drives) may be modified to
provide an initial resistance to rotation (as well as a resistance
to sudden changes in the rotational speed during operation) due to
the inertia of the parts.
[0068] As best shown in FIGS. 9 and 10A, the flywheel 508 includes
a flywheel gear 902 that fits into a corresponding geared track 904
located in a cavity on the clutch lever 612. FIG. 10A shows the
clutch lever 612 and the expanding clutch 610 with the clutch mount
614 removed. The flywheel 508 and its gear 902 rotate in a
generally counter-clockwise direction in the views of FIGS. 9 and
10A. Rotation of the flywheel 508 and its gear 902 tends to pivot
the clutch lever 612 about its pin 624, as indicated by arrow D1.
This pivoting torque applies a force F1 against the expanding
clutch 610 that tends to opens the expanding clutch 610, as
indicated by arrow D2. As the clutch 610 expands, its diameter
increases, eventually causing the expanding clutch 610 to contract
and exert pressure against the interior wall of the drum 608. The
length of the geared track 904 is selected such that the expanding
clutch 610 contacts the inner wall of the drum 608 before the
flywheel gear 902 reaches the end of the track 904.
[0069] It will be appreciated that the expanding clutch 610 may,
because of the resilient nature of the material from which it is
made (plastic, for example), provide some resistance to being
expanded (this is referred to herein as the expansion resistance).
If the expansion resistance is great enough, the torque applied by
the flywheel gear 902 to the geared track 904 may not generate a
sufficient expansion force F1 to expand the expanding clutch 610
into contact with the drum 608. In other instances, the expansion
resistance may be very low, so that virtually no substantial amount
of torque is required to expand the expanding clutch 610. For
example, the flywheel gear 902 may be able to expand the expanding
clutch 610 by applying about 1/100th of the total amount of torque
that the clutch transfers.
[0070] It will also be appreciated that the magnitude of the
expansion force F1 may be limited if the clutch mount 614 begins to
rotate. This situation may occur if the inertia and frictional
resistance of the clutch mount 614 (the clutch mount's "resistance
torque") is relatively low. The clutch mount's resistance torque
will depend on its inertia and rotating friction, as well as the
inertia and rotating friction of any parts to which it is attached.
As explained below, the clutch mount 614 is normally attached to
the brushroll 102 and various other parts, all of which increase
the clutch mount's resistance torque by inertia and any friction
between these parts and their surroundings (such as contact between
the brushroll 102 and a surface to be cleaned) or between these
parts and each other (such as friction in a bearing). If the clutch
mount's resistance torque is low enough, the torque applied by the
flywheel gear 902 to the clutch lever 612 may begin to rotate the
clutch mount 614 before the expanding clutch expands to contact the
inner wall of the drum 608. In such a case, the amount of torque
that can be transmitted to the clutch mount 614 is limited by the
frictional contact between the drum 608 and the flywheel 508.
[0071] Where the expansion resistance of the expanding clutch 610
is low enough, and the resistance torque of the clutch mount 614 is
high enough, the flywheel gear 902 will rotate the clutch lever 612
and expand the expanding clutch 610 as described above. Contact and
pressure between the expanding clutch 610 and the drum 608 generate
friction, and transmits torque directly from the drum 608 to the
expanding clutch 610. In the shown embodiment, the amount of
leverage that the clutch lever 612 applies to expand the expanding
clutch 610 (and the amount of force applied to press the expanding
clutch 610 into contact with the drum 608) increases as the clutch
mount's 614 resistance to rotation increases. This is because the
clutch lever pivots on mounting pin 624, which is installed in the
clutch mount 614, and forces that resist rotation of the clutch
mount 614 are transmitted through the mounting pin 624 in a manner
that is favorable to amplify the expanding force. The use of this
feature allows the expanding clutch 610 to be engaged with
relatively force and react quickly to fluctuations in the drive
resistance. Thus, it can be said that the shown expanding clutch
610 is a self-adjusting clutch that increases the transmitted
torque as rotational resistance of the load (i.e., the clutch mount
614 and everything driven by it) increases. Since the rotational
resistance of the clutch mount 614 is a function of both friction
and inertia, the self-adjusting expanding clutch 610 will tend to
expand and transmit greater torque whenever the load encounters
greater friction (e.g., when the brushroll 102 contacts a thick
carpet), and whenever there is a high differential inertia between
the parts (e.g., when the brushroll 102 is still or rotating
relatively slowly). Conversely, if the load experiences a condition
in which it tends to overrun the expanding clutch 610--such as when
power to the motor 104 is terminated and the brushroll 102
continues to rotate by inertia--the self-adjusting expanding clutch
610 may release engagement with the drum 608 and transmit little or
no torque to the load. In addition, the rate at which the brushroll
102 can accelerate (either during startup of during speed
fluctuations, may be limited by the rate at which the flywheel 508
can accelerate via its contact with the drum 608. In one
embodiment, the expanding clutch 610 may be self-adjusting to the
point that it is self-locking, so that no amount of drive
resistance can overcome the friction generated between the
expanding clutch 610 and the drum 608.
[0072] The operation of the expanding clutch 610 in this manner is
illustrated in FIGS. 10B and 10C, which show the expanding clutch
610 in the disengaged and engaged position, respectively. These
figures are shown from the opposite side as FIG. 10A, and thus the
rotations are reversed in these views. As will be appreciated, it
may be desirable to use lubricants, such as natural or synthetic
oils or greases, lubricated coatings or layers, or
low-friction/low-wear materials, on the expanding clutch 610,
flywheel 508, as well as any other parts that engage in frictional
contact, to help prevent excessive wear.
[0073] The exemplary drive clutch mechanism may be disengaged by
operating the solenoid 201 or other disengagement mechanism. The
solenoid 201 or other disengagement mechanism may have a manual
control to allow the user to engage and disengage the drive clutch
at will. The solenoid 201 or other disengagement mechanism also may
have an automatic control that engages and disengages the drive
clutch during particular circumstances, such as when the upper
portion of an upright vacuum cleaner is pivoted to the upright
parked position, or when a bare floor cleaning mode is selected on
a vacuum cleaner. Such an automatic device might comprise, for
example, a micro-switch that activates the solenoid 201, or a
mechanical override mechanism (such as a cam or pushrod) that
presses against the lever 502, when the vacuum cleaner housing is
moved to the upright position. As noted above, the solenoid shaft
504 presses the disengagement lever 502, which rotates on its
pivots 503 and moves the flywheel 508 out of contact with the drum
608. When the flywheel 508 is disengaged from the drum 608, it no
longer applies a torque to the flywheel gear 902. When this
happens, expanding clutch's expansion resistance tends to contact
the expanding clutch 610 and pull it away from contact with the
drum 608. In addition, a weight 620 may be provided on the clutch
lever 612 to assist with disengaging the expanding clutch 610. The
weight 620 is located on the clutch lever 612 where centrifugal
force presses the weight 620 opposite the rotation imparted by the
flywheel gear 902. As a result, the weight 620 resists engagement
of the expanding clutch 610, and causes the clutch lever 612 to
retract to the disengaged position once the torque from the
flywheel gear 902 is terminated. Having terminated frictional
contact between the flywheel 508 and the drum 608 and the expanding
clutch 610 and the drum 608, torque is no longer transmitted
through the clutch assembly 100 to the clutch output gear 140.
Thus, the shaft 602 and brushroll 102 may decelerate and eventually
stop rotating. Even when the drive clutch is disengaged, however,
the clutch input gear 130 and the drum 608 may continue to rotate
for as long as the motor 104 operates. It will be appreciated that
the weight 620 may, in other embodiments, be omitted, relocated or
replaced by other mechanisms, such as a spring that tends to pivot
the clutch lever 612 against the force applied by the flywheel gear
902.
[0074] In the exemplary embodiment, the expanding clutch 610 is
able to transmit significantly more torque between the drum 608 and
the clutch mount 614 than the frictional contact between the
flywheel 508 and drum 608. This difference in torque capacity may
be attributed to the size of the contacting surfaces, as well as
the mechanical design of the parts. For example, the expanding
clutch operates as a drum-type clutch and has a relatively large
contact area, whereas the flywheel-to-drum contact surfaces operate
as a disk clutch having a relatively small contact area. Thus, the
present exemplary embodiment provides a two-clutch system. Under
normal conditions, the first clutch (the flywheel/drum system) may
have insufficient torque transferring capability to operate the
brushroll 102, and is instead used to engage the expanding clutch
610 in a controlled manner. Alternatively, if the system is
modified accordingly, the first clutch may be able to operate the
brushroll 102 under relatively low load conditions. If desired, the
shapes, sizes and kinds of these two clutch systems may be modified
to obtain different differences in their torque transferring
capabilities. For example, the frictional contact between the drum
608 and flywheel 508 may be modified by adjusting the force applied
by the spring 622 or changing the coefficient of friction between
the parts. Changing the weight of the flywheel weight 506 can also
adjust how quickly the flywheel accelerates in response to contact
with the drum 608. Similar adjustments may be made to the expanding
clutch 610. For example, the pins 626, 628 used to expand the
expanding clutch 610 may be positioned in angled slots that apply a
radial force to increase frictional contact with the drum 608, or
the shape of the clutch lever 612 may be modified to apply more or
less leverage to expand the expanding clutch 610. Other
modifications will be understood by persons of ordinary skill in
the art in view of the present disclosure.
[0075] The configuration of clutches in the foregoing embodiment
has been found to provide a relatively smooth transfer of torque
from the motor output gear 120 to the brushroll 102. This smooth
transfer of torque lessens the maximum torque differential between
the motor output gear 120 and brushroll 102. This is particularly
the case when comparing the foregoing embodiment to direct-drive
devices that drive the brushroll 102 directly by the motor output
gear 120 through a belt. Such direct-drive devices, which are in
widespread use, typically use motors that generate their maximum
torque at zero revolutions per minute. This, combined with the fact
that the brushroll is not rotating at startup and may have
frictional resistance to rotation, leads to a relatively high
torque differential between the motor and the brushroll that must
be conveyed through the driveline. While the overload mechanism
described above or elsewhere herein can be modified to accommodate
this high torque, it may take a sufficiently high differential
torque to disengage the overload mechanism. This may be suitable in
some instances, such as where the motor has relatively low power,
but may not be suitable in other instances. Thus, a clutch
engagement mechanism such as the one described above, which reduces
the maximum torque differential that can be transmitted across the
overload mechanism by providing a relatively low-torque or
graduated-torque "soft" start, may be used in conjunction with an
overload mechanism that will disengage if a relatively low torque
differential is applied to it.
[0076] As noted above, torque transmitted to the clutch mount 614
may be conveyed to the brushroll 102 via an overload mechanism. The
overload mechanism terminates the transfer of torque from the motor
output gear 120 to the brushroll 102 when an excessive amount of
torque is applied to the overload mechanism. Referring to FIGS. 11
and 12, in the present embodiment, the overload mechanism may
include an overload cog 616 and an overload spring 618.
[0077] The overload spring is connected to the clutch mount 614 on
the side opposite the clutch lever 612. Thus, in this embodiment,
the clutch mount 614 also acts as an overload spring mount. As
shown, the overload spring may be attached at a mounting bracket
1104. As shown, the overload spring 618 may be wrapped around a pin
1112 that passes through the bracket 1104, and allows the overload
spring 618 to pivot if not otherwise constrained from moving. In
other embodiments, other mounting methods may be used. For example,
an end of the overload spring 618 may be pressed into a groove or
channel on the surface of the clutch mount 614, providing a rigid
connection point, but still allowing the overload spring 618 to
flex during normal operation of the clutch and in overload
conditions, as described below. The overload spring 618 may be made
from hardened steel or any suitable alternative material. The shape
of the overload spring 618 may be modified to avoid sharp bends
that might stretch over time or create weak points in the material
structure.
[0078] The overload spring 618 wraps around the overload cog 616
and is shaped to transfer torque from the clutch mount 614 to the
overload cog 616 to thereby rotate the overload cog 616. The
overload cog 616 is rigidly mounted to the shaft 602, and directly
transfers torque and rotation to the clutch output gear 140, which
is also rigidly mounted to the shaft 602. The overload cog 616 may
be rigidly mounted to the shaft 602 by any suitable structure. For
example, as shown in a pin 1106 may pass through the shaft of 602
and engage a slot 1108 on the face of the overload cog 616. In the
shown exemplary embodiment, the overload cog 616 is not connected
only to the shaft 602 and clutch output gear 140, but in other
embodiments it may be attached to one or more other parts.
[0079] The exemplary overload cog 616 is generally circular and has
a series of teeth 617 or other protrusions that extending radially
outward. In accordance with an exemplary embodiment, the overload
cog 616 may have three teeth 617. The overload spring 618 is shaped
similarly to the overload cog 616, so that it engages the teeth 617
to transfer of torque through the overload cog 616 to the shaft
602. For example, in the shown embodiment, the overload spring 618
has a generally circular shape with rounded lobes 619 that fit over
the teeth 617 when the overload spring 618 and overload cog 616 are
in certain orientations with respect to one another. Stated
differently, the overload cog 616 has first portions that extend a
first distance from its rotating axis (e.g., the circular
portions), and second portions that extend a second distance from
the rotating axis (e.g., the teeth 617), and the overload spring
618 is configured to wrap around the overload cog 616 and have
first portions that conform generally to the first portions of the
overload cog 616, and second portions that conform generally to the
second portions of the overload cog 616. While it could be possible
to have the overload spring 618 conform more precisely to the shape
of the overload cog 616, it has been found that it is not necessary
to make these two parts match precisely, and doing so might, in
some circumstances, create undesirable stress risers in the
parts.
[0080] In normal operation the overload spring 618 is wrapped
around the overload cog 616, and the rounded lobes 619 fit over the
teeth 617. When a torque is applied to rotate the clutch mount 614
(such rotation is counterclockwise in FIGS. 11 and 12), the clutch
mount 614 pulls the overload spring 618 (via pin 1112) to rotate in
unison with the clutch mount 614. Contact between the overload
spring 618 and overload cog 616 transmits the drive torque to, and
thereby rotates, the overload cog 616. The overload spring's 618
spring tension (i.e., its resistance to deformation) maintains the
overload spring's 618 contact with the overload cog 616 in the
shown engaged, torque-transferring orientation. The parts will
remain in this orientation with respect to one another and continue
to rotate together until the drive torque transmitted through the
clutch mount 614 is terminated, or the overload cog 616 encounters
sufficient rotational resistance (resistance torque) that the
overload spring 618 disengages from the overload cog 616. Such
resistance torque can be generated, for example, if the brushroll
102 encounters high resistance to rotation or is prevented from
rotating, as may occur if a foreign object becomes entangled in the
brushroll. The amount of torque that can be transmitted from the
overload spring 618 to the overload cog 616 is referred to herein
as the overload clutch's torque rating.
[0081] The overload clutch's torque rating may be determined
primarily by the shapes of the parts and the spring's resistance to
deformation. For example, if the overload cog 616 has relatively
angular teeth 617 and the lobes 619 on the overload spring 618
conform closely to the teeth 617, the mechanical engagement between
the two may require transfer relatively more torque than if softly
rounded teeth 617 or loosely-conforming lobes 619 are used. Also,
if the overload spring 618 is made from a more resilient or thinner
material, the torque rating of the overload clutch may be reduced.
In addition, other embodiments may use other shapes to provide
releasable engagement between the overload cog 616 and the overload
spring 618. For example, the overload cog 616 may have depressions
into which inwardly-extending lobes on the overload spring 618 fit
to provide releasable, torque-transferring engagement between these
parts. In other embodiments, the overload spring 618 may be located
within a hollow overload cog 616, and in still other embodiments,
the overload spring 618 may be mounted to the shaft 602 to rotate
therewith, and the overload cog 616 may be mounted to the clutch
mount 614 to rotate therewith. These and other variations will be
apparent from the present disclosure, and a person of ordinary
skill in the art will be able to develop appropriate configurations
and dimensions for these parts in view of the present disclosure
without undue experimentation.
[0082] When the overload clutch's torque rating is exceeded, the
overload spring 618 will continue to rotate with the clutch mount
614, but the overload cog 616 will either stop or rotate at a
different, slower speed. In such circumstances, the lobes 619
disengage from the teeth 617, and the portions of the overload
spring 618 between the lobes 619 will move into contact with the
teeth 617. When this occurs, the overload spring 618 is deformed
and generally increases in diameter to pass over the teeth 617. In
this state, the overload spring 618 may still tend to wrap around
and contact the overload cog 616, in which case these two parts
will have insubstantial contact one another during overload
conditions, and such contact would not be sufficient to generate a
torque that could damage the agitator or objects that it might
contact. For example, such contact might be sufficient to rotate
the agitator when it is lifted free of the surface being cleaned
and otherwise not obstructed, but not to rotate the agitator if it
is lightly contacted by the user's fingers. This may be desirable
because contact between the parts may provide an audible sound to
signal the operator that an overload has occurred. Under this
scenario, the overload spring 618 may optionally also be able to
reengage the overload clutch 616 if the resistance torque
decreases. For example, the operator may momentarily pass the
vacuum cleaner brushroll 102 over an object (such as frayed strand
from a carpet) that generates sufficient resistance to exceed the
torque rating and disengage the overload spring 618, but then pull
the brushroll 102 free of the object to reduce the rotating
resistance, at which time the overload spring 618 may reengage the
overload cog.
[0083] While the foregoing arrangement is possible, in other
embodiments it may be desirable to prevent the overload spring 618
from reengaging the overload cog 616 until the user terminates
drive to the overload clutch. For example, preventing automatic
reengagement of the overload clutch may be desirable to limit the
likelihood that the operator will be surprised by a sudden
resumption in the brushroll's operation, and it may be desirable to
prevent the overload spring 618 from wearing on the overload cog
616 during overload. In the shown exemplary embodiment, a mechanism
may be provided to help hold the overload spring 618 away from the
overload cog 616 during overload conditions. For example,
centrifugal force may be used to hold the overload spring 618 away
from the overload cog 616 until the clutch mount 614 stops rotating
or slows significantly. To further help prevent automatic
reengagement, the expanding clutch 610 may remain pressed against
the drum 608 even after the overload clutch disengages, to provide
a high torque differential that can not be overcome until the parts
come to rest or otherwise match speeds.
[0084] As noted above, during overload conditions, the overload
spring 618 disengages from the overload cog 616. When this occurs,
overload spring 618 is free to pivot away from the overload cog
616, and centrifugal force will tend to expand the overload spring
618 radially outward and away from the overload cog 616, such as
shown in FIG. 12. The overload spring 618 may be weighted or have
sufficient weight of its own that centrifugal force holds the
overload spring 618 in the disengaged position. In addition a pawl
1102 may be pivotally mounted to the clutch mount 614, such as at
the mounting bracket 1104, to contribute its weight (and resulting
centrifugal force) to help press the overload spring 618 in the
expanded, disengaged position. The pawl 1102 may be mounted on the
same bracket 1104 as the overload spring 618, or elsewhere. In the
shown embodiment, the pawl 1104 may be pivotally mounted to the
bracket 1104 by the pin 1112, and the end of the overload spring
618 may tightly wrap around the pivoting end of the pawl 1102 to
thereby pivotally mount the overload spring 618 to the clutch mount
614.
[0085] It will be appreciated that other additional weights or
springs may be used to help hold the overload spring 618 in the
disengaged position. For example, a weight may be provided along
the length or at the free end of the overload spring 618. As
another example, a weight that slides on a sliding radial track may
be positioned inward of a portion of the overload spring 618 to
apply centrifugal force to the overload spring 618. A helper spring
may also be provided to press the overload spring 618 outward. A
helper spring may also be provided to press the overload spring 618
inward, if it is not desired to fully disengage the overload spring
618 during overload conditions.
[0086] As shown in FIG. 12, during overload conditions, the
overload spring 618 is pressed radially outward by its own weight
and the weight of the pawl 1102. One or more walls or other
blocking structures 1116 may be located on the clutch mount 614 to
control the outward movement of the overload spring 618. Such
blocking structures 1116 may also provide a fulcrum point that
cooperates with centrifugal force on the overload spring 618 to
bend the overload spring 618 so that it clears the overload cog
616.
[0087] As shown in FIG. 11, the pawl 1102 may also (or
alternatively) be provided to act as a back brake that prevents the
overload cog 616 from rotating faster than the clutch mount 614. In
this exemplary embodiment, during normal (i.e., non-overload)
operating conditions, the pawl 1102 is pivoted so that its free end
1102' engages one of the overload cog teeth 617. The free end 1102'
of the pawl 1102 and the cog teeth 617 are shaped such that the
teeth 617 can not rotate past the pawl 1102. Thus, the pawl 1102
prevents the overload cog 616 from rotating faster than the clutch
mount 614.
[0088] Such a configuration may be desirable to prevent the
brushroll 102 from continuing to rotate even after the motor 104
has been turned off, or from rotating faster than the motor 104
during normal operation when the brushroll 102 experiences a
momentary drop in rotating resistance or is accelerated by elastic
tension developed in the brushroll belt 108. For example, in the
exemplary embodiment, when the motor 104 is turned off when the
drive and overload clutches are still engaged, the brushroll 102
may tend, due to its rotating inertia, to continue rotating.
Without the pawl 1102 or other back brake, the brushroll's inertia
may be transmitted to the overload spring 618 through the overload
cog 616, possibly disengaging the overload clutch and allowing the
brushroll 102 to continue spinning. With the exemplary back brake,
however, the pawl 1102 transmits forces caused by rotating inertia
directly to the clutch mount 614 and back through the drive clutch.
If the inertial forces are great enough, the brushroll 102 may
force the drive clutch to overrun the motor, but friction between
the drive clutch elements, such as between the drum 608 and
flywheel 508 will rapidly dissipate this energy. While the pawl
1102 is shown as one exemplary embodiment, other back brake or
overrun prevention mechanisms may be used instead of the pawl 1102;
for example, the pawl 1102 may be formed by an extension of the
overload spring 618 that is folded back to face the overload cog
teeth 617.
[0089] Other features may be provided in various embodiments to
increase the torque rating of the overload clutch. For example, the
free end of the overload spring 618 (i.e., the end opposite the end
that is connected to the clutch mount 614) may include a curled end
1114, such as the shown circular knob, that fits between the
overload cog 616 and a wall portion 1110 formed on the clutch mount
614. The curled end 1114 is large enough that it can not fit
between the wall portion 1110 and the overload cog teeth 617 unless
it is deformed, but small enough that it can freely fit between the
remainder of the overload cog 616 and the wall 1110 without being
deformed. During normal operation (i.e., when the overload clutch
is engaged), the curled end 1114 fits between the wall portion 1110
and the overload cog 616. In this embodiment, the overload spring
618 will continue to transmit torque to the overload cog 616 until
there is sufficient resistance to compress the curled end 1114 so
that it can pass between the clutch mount wall 1110 and the
adjacent overload cog tooth 617. The curled end 1114 preferably is
generally circular to distribute the compression force across the
material and resist permanent deformations, but it may be V-shaped
or have other shapes. Once disengaged, the overload spring 618 is
pressed by centrifugal force away from the overload cog 616. Once
the clutch mount 614 substantially stops rotating, the overload
spring 618 returns to its contracted position against the overload
cog 616. Once this happens, the curled end 1114 will be reseated
between the wall 1110 and the overload cog 616 as the two parts
rotate relative to one another just prior to reengaging. Thus, the
shown exemplary embodiment prevents reengagement of the overload
spring 618 and overload cog 616 until the clutch mount 614 and
overload cog 616 substantially stop rotating.
[0090] When used with the drive clutch mechanism of FIGS. 6-10C,
the foregoing overload clutch may automatically disengage the
expanding clutch 610 when the overload clutch enters the overload
state shown in FIG. 12. When the overload spring 618 disengages
from the overload cog 616, clutch mount 614 can freely rotate and
may provide little resistance to the torque provided by the
flywheel gear 902. Under these conditions, the clutch lever pin 624
may no longer provide a fulcrum point through which the flywheel
gear 902 can generate force to expand the overload clutch 610. When
this happens, the expansion resistance of the expanding clutch 610
(and the clutch lever weight 620, if provided) may exert sufficient
force to return the expanding clutch 610 to the disengaged
position. Alternatively, the expansion resistance of the expanding
clutch 610 may be insufficient to disengaged the expanding clutch
610 from the drum 608, even when the overload clutch enters the
overload state, in which case the expanding clutch 610 may continue
to engage and drive the drum 608 until the flywheel is disengaged
from the drum 608.
[0091] While the foregoing overload clutch mechanism may be used
independently, it also may be used with a drive clutch, such as the
soft-start drive clutch described above. It has been found that the
combination of the features shown in FIGS. 1-12 can provide certain
benefits and simultaneously address numerous criteria desired of a
brushroll drive mechanism. For example, the drive clutch provides a
low acceleration torque that allows the use of an overload clutch
having a relatively low torque rating. This allows the overload
mechanism to disengage virtually instantaneously upon sensing a
relatively low force, but at the same time does not deactivate
during normal drive torque fluctuations. In addition, the use of a
first drive clutch that is used to engage a second drive clutch
(particularly a second drive clutch that is self-adjusting) allows
the first drive clutch to have a relatively light engagement
spring. This feature facilitates the use of a simple
engagement/disengagement mechanism, and requires relatively little
force to operate the drive clutch. Thus, the shown embodiment can
be operated with relative ease either manually or by a suitable
electro-mechanical device (e.g., a solenoid). The embodiment
described above also may provide overload protection that
terminates all or virtually all drive torque through the overload
clutch during overload conditions, and requires termination of
drive torque through the drive clutch mechanism before the
brushroll can be restarted, thus protecting against accidental
restarts. Once the overload clutch is activated, the user must
either turn off the motor or disengage the drive clutch before the
overload clutch will reset. Still another benefit that may be
realized from the above embodiment is a significant reduction in
brushroll speed as a result of the two-stages of gear reduction
provided through the clutch assembly.
[0092] While the foregoing combination of drive and overload clutch
mechanisms may be desirable in some instances, alternative
embodiments may replace the clutch and/or overload mechanisms with
alternative structures that may provide the same or different
functions. For example, the drive clutch mechanism, as described
above, may be replaced without altering the overload clutch
mechanism and vice versa. Further, the arrangement of the clutch
assembly 100 may be altered from the relatively compact structure
as described above, to an expanded arrangement having the drive and
overload clutch mechanisms spatially separated along a common
shaft. Such mechanisms also may be mounted on separate shafts or
provided as independent modules. Thus, as should be appreciated,
the embodiments presented herein may be combined in any manner and
even used independently of one another. For example, the clutch
mechanism of the first embodiment may be used without the overload
mechanism and vice versa. It will also be understood that the
various parts can be rearranged in inverted or reversed
relationships. For example, the drum and expanding clutch
configuration may be replaced by a spindle and contracting clutch,
or the initial clutch may be a drum-type clutch that is adapted to
fully engage a disk-type clutch as the main drive clutch. In other
embodiments, the overload clutch may be located "upstream" of the
drive clutch mechanism (that is, between the motor and the drive
clutch), as opposed to being "downstream" as in the above-described
embodiment. These and other variations will be understood by
persons of ordinary skill in the art.
[0093] Another embodiment of a drive clutch engagement mechanism is
illustrated in FIGS. 13A-13B. Like the foregoing embodiment, this
embodiment uses an expanding clutch to engage a drive shaft to a
drum but replaces the flywheel and clutch lever arrangement with a
pin and collar structure. This arrangement is shown in the
disengaged position in FIG. 13A, and in the engaged position in
FIG. 13B. In this embodiment, a flywheel (not shown) such as the
one described above has one or more pins 1302 that extend from the
face of the flywheel. The pins 1302 fit in corresponding notches
1304 in a collar 1306. The collar 1306 generally surrounds a shaft
1308, but includes a slot 1310 to accommodate a crossbar 1312 that
extends radially from the shaft 1308. An expanding clutch 1314
surrounds the collar 1306, and has a gap that accommodates the
crossbar 1312, as shown in FIG. 13A. On one side of the slot 1310,
the collar 1306 has a point 1316 that abuts one side of the
crossbar 1312, and an extension 1318 that fits between the crossbar
1312 and the expanding clutch 1314. A drum 1320 surrounds the
expanding clutch 1314 and collar 1306. The drum 1320 is driven by a
motor (not shown) in a counterclockwise direction as shown by the
arrow.
[0094] In the disengaged position, the collar 1306 is positioned
such that the extension 1318 is generally adjacent the crossbar
1312 and the expanding clutch 1314 is elastically contracted away
from the drum's inner surface. If necessary, a spring (not shown)
or other device may be provided to bias the parts in this position.
For example, the slot 1310 may be configured to require some amount
of elastic deformation to move from the disengaged position. When
it is desired to engage the clutch, the flywheel (not shown) is
moved into engagement with the drum 1320, such as in the embodiment
described above. Upon such engagement, friction between the drum
1320 and the flywheel rotates the pins 1302 about the shaft 1308 in
a counterclockwise direction. Movement of the pins 1302 rotates the
collar 1306 about the shaft 1308, as shown in FIG. 13B. In this
position, the point 1316 on the slot (which may comprise a
rectilinear or curved surface) contacts the side of the crossbar
1312, and acts as a fulcrum about which the collar 1306 rotates. As
the collar 1306 rotates, the extension 1318 moves away from the
crossbar 1312 and expands the expanding clutch 1314 by opening the
gap in the clutch surface. As the expanding clutch 1314 expands, it
contacts the inner surface of the drum and thereby is driven
directly by the drum 1320. As with the above embodiment, the clutch
may be disengaged by separating the flywheel from the drum.
[0095] Referring now to FIG. 14, another exemplary embodiment may
provide alternative drive clutch and overload clutch mechanisms
that are arranged axially upon a torque transmission shaft. The
embodiment of FIG. 14 comprises a clutch assembly 1400 having a
cone clutch mechanism that is used as a drive clutch, and a
magnetic coupling that is used as an overload clutch. It is known
in the art that cone shaped clutch mechanisms may provide efficient
transfer of power. It is also known that magnets may provide a way
to couple two objects, such as rotating disks, together, through an
attractive magnetic force, with no contact between the objects. The
attractive magnetic force must be strong enough to allow the
objects to couple and rotate together to transfer the required
torque loading. Such magnetic coupling may be used as an overload
mechanism for the clutch assembly.
[0096] As shown, the exemplary clutch assembly 1400 may have a
clutch engagement member 1402, a first cone 1404, a second cone
1406, a third cone 1408, a shaft 1410, and an overload drive plate
1414, and an output pulley 1416. The shaft 1410 may run the length
of the clutch assembly 1400 and be supported by bearings 1412a and
1412b. In this embodiment, the third cone 1408 and the overload
drive plate 1414 may be fixed to the shaft 1410 to rotate
therewith. A spring (not shown) may be located between the first
cone 1401 and the overload drive plate 1414 to bias the first cone
1404 into engagement with the second cone 1408, to thereby force it
into engagement with the third cone 1408. The engagement member
1402 is provided to pull the first cone 1404 against the bias of
the spring and out of disengagement. The engagement member 1402 may
be automatically or manually operated, and in other embodiments,
the first cone 1404 may be biased out of engagement with the second
cone 1406, in which case the engagement member 1402 would be
operated to engage the drive clutch, rather than disengage it.
[0097] As shown, the second cone 1406 may include a drive gear
1406' on its exterior surface. The drive gear 1406' is driven by a
motor through a belt or other suitable drive mechanism. Upon
engagement, the first cone 1404 presses the second cone 1406 into
the third cone 1408, and the conical surfaces between the parts
provide frictional engagement that locks the parts together. When
fully engaged, the motor drives the third cone 1408 to rotate the
shaft 1410. The second cone 1406 is not coupled to the shaft 1410,
such that when the clutch is not engaged, the second cone 1406 may
rotate freely around the shaft 1410 while the motor 104 is running.
Of course, other kinds of surfaces may be used to frictionally
engage these parts. For example, the conical surfaces may be
replaced by disk-like surfaces.
[0098] The shaft 1410 drives the overload drive plate 1414, which
is fixed to the shaft 1410 to rotate therewith. The overload drive
plate 1414 includes one or more magnets 1418 that face the output
pulley 1416. The output pulley 1416 includes its own magnets 1420,
which are arranged to contact the other magnets 1418 to provide a
drive coupling between these parts, as known in the art. The output
pulley 1416 is freely rotatable on the shaft 1410, and the amount
of torque that may be transmitted from the overload drive plate
1414 to the output pulley 1416 is limited by the magnetic
properties of the magnets 1418, 1420. The output pulley 1416
includes a gear surface 1416' or other surface adapted to connect
to and drive a brushroll or other downstream driven part through a
belt, gears or the like.
[0099] An arrangement of magnets may be used with the magnetic
overload mechanism described above. For example, the magnets on one
part may all have their north poles facing the other part, and the
other part may present only the south poles of its magnets.
Alternatively, the poles may be oriented to alternate or provide
other patterns. As another alternative, one or more of the magnets
may be replaced by bars of material that are not magnetized but are
attracted to the magnets that remain in the parts. Various magnetic
overload configurations are disclosed in various patents discussed
above, which are incorporated herein by reference.
[0100] It should be appreciated that the magnetic overload coupling
may have different configurations to improve torque transfer and
overload response. For example, the embedded magnets may be mounted
on angled surfaces such that the attractive force is at an angle to
the shaft 1410, and some amount of axial movement must be
accomplished before the magnets fully disengage. FIG. 15 depicts
such an alternative embodiment of the overload drive plate 1414 and
output pulley 1416. In this embodiment, the overload drive plate
1414 has angled faces in which the magnets 1418 are embedded. In
FIG. 15, the overload drive plate 1414 rotates such that the side
facing the viewer moves upwards. Thus, the magnets 1418, 1420
operate in tension, with magnets 1418 pulling magnets 1420 to
follow the rotation of the overload drive plate 1414. When the
magnets 1418, 1420 break contact, the overload drive plate 1414 and
output pulley 1416 rotate relative to one another, and ramps 1502
may be provided to facilitate relative axial movement of the parts.
In addition, one or both of the overload drive plate 1414 and
output pulley 1416 may be axially slideable on the shaft 1410 to
allow such movement. A spring or other resilient member may be used
to bias the overload drive plate 1414 and output pulley 1416
together to reestablish contact, but such movement may be provided
by the magnets 1418, 1420 instead. Of course, the opposite rotation
may be used instead, in which the magnets 1418, 1420 tend to press
together in operation.
[0101] A magnetic overload clutch also may be used with other
embodiments of drive clutches. For example, the embodiments of FIG.
14 or 15 may be used with the drive clutch described in FIGS. 6
through 10A. In another embodiment, shown in FIGS. 16A-C, a
magnetic overload mechanism is integrated into the expanding clutch
to disengage it when the torque transmitted from the drum to the
expanding clutch exceeds a threshold value.
[0102] The embodiment of FIGS. 16A-C includes a drum 1600,
expanding clutch 1602, clutch mount 1604, clutch lever 1606,
flywheel gear 1608 and flywheel (not shown) generally like those
described above with reference to FIGS. 6-10A. As before, the
expanding clutch 1602 is operated by contacting the flywheel
against the drum 1600 to thereby generate a force to pivot the
clutch lever 1606 and expand the expanding clutch 1602 into
engagement with the drum 1600. These parts are shown in the
disengaged position in FIG. 16A, and in the engaged position in
FIG. 16B. In these views, the drum 1600 rotates clockwise.
[0103] The torque applied by the drum 1600 to the expanding clutch
1602 is transmitted to the clutch mount 1604, which, in turn, is
connected to a brushroll or other load, either directly or through
any other suitable mechanisms. The trailing end of the expanding
clutch 1602 (i.e., the end an imaginary point on the drum would
pass over last as it rotates) is attached to the clutch mount 1604
by one or more magnets 1610, 1612. During normal operation, the
magnets 1610, 1612 hold the end of the expanding clutch 1602 and
allow it to be expanded into contact with the drum 1600. The
magnets 1610, 1612 transfer at least some of the torque that the
drum 1600 imparts to the expanding clutch 1602 to the clutch mount
1604, to thereby rotate the clutch mount 1604. When the clutch
mount 1604 encounters a rotational resistance torque, such as when
the brushroll becomes obstructed or stops, the magnets 1610, 1612
may disengage, allowing the expanding clutch 1602 to contract and
move out of engagement with the drum 1600. This overload condition
is shown in FIG. 16C. Thus, the magnets 1610, 1612 act as an
overload clutch mechanism. The strengths and orientations of the
magnets 1610, 1612 may, of course, be modified to regulate the
torque rating of the overload clutch. In addition, a counterweight
1616 may be attached to the clutch mount 1604 to help balance the
weight of the magnets 1610, 1612 to prevent excessive
vibrations.
[0104] In the embodiment of FIGS. 16A-C, the clutch mount 1604 does
not disengage from the brushroll during an overload condition.
Thus, the flywheel gear 1608 still continues to apply a torque to
rotate the clutch lever 1606 and rotate the clutch mount 1604. At
the same time, this torque may keep the clutch lever 1606 at least
partially rotated which may hold the expanding clutch 1602 so that
its magnets 1610 can not reengage the magnets 1612 on the clutch
mount 1604, as shown in FIG. 16C. During this time, the flywheel
may remain in contact with the drum 1600, generating friction
between the parts. As such it is preferred for the contact surfaces
between flywheel and drum 1600 to be made of a heat-resistant
material. Once the flywheel is disengaged form the drum 1600, the
clutch lever 1604 can pivot back to its resting disengaged
position, and the magnets 1610, 1612 can reengage.
[0105] Still other overload and drive clutch devices may be used
with other embodiments. For example, as FIG. 17 discloses a wave
plate clutch that may be used as an overload clutch in a vacuum
cleaner, either on its own or in conjunction with a drive clutch
such as the ones described herein. The embodiment of FIG. 17
provides a wave plate-type clutch having a first plate 1702 that is
biased by a spring 1706 to press against a second plate 1704. The
first plate 1702 is driven by a first shaft 1708, and the second
plate drives a second shaft 1710. This clutch will transmit torque
until sufficient differential loads exist to press the engaged
structures out of engagement against the bias of the spring 1706,
as will be appreciated by persons of ordinary skill in the art.
Upon clearance of the resistance torque, normal operation may
automatically resume.
[0106] Alternatively, a clutch mechanism may use a friction forces
from spring located between two toothed wheels to transmit torque.
Such an embodiment is shown in FIGS. 18A-C. In this exemplary
embodiment, a clutch mechanism may have an inner wheel 1802 with a
toothed profile around the outer diameter. The inner wheel 1802 may
be mounted to a shaft (not shown) by an inner hole 1806. An outer
wheel 1804 surrounds the inner wheel 1802, and has an
internally-facing toothed profile, similar to that of the inner
wheel 1802, around its inner diameter. One of the two wheels is
driven by a motor, either directly or through a drive clutch or
other mechanisms, and the other transmits the drive torque to an
output device, such as a brushroll. In the shown embodiment, for
example, the outer wheel 1804 may be drive by expanding clutch
mechanism, such as described above, such engaging the expanding
clutch imparts a drive torque to the outer wheel 1804 to rotate as
shown by the arrow. One or more elastic springs are located between
the inner wheel 1802 and outer wheel 1804 to transfer drive torque
from the outer wheel 1804 to the inner wheel 1802. For example, a
number of thin, flat metal strings or ribbons 1808 may be located
between the teeth of the inner wheel 1802 and the outer wheel 1804.
While three are shown, four or other numbers of ribbons 1802 may be
used.
[0107] The ribbons 1808 are shaped so that they can transfer torque
from the teeth on the outer wheel 1804 to the teeth on the inner
wheel 1802. For example, as shown, the ribbons 1808 may have a
curved profile that simultaneously fits between one or more teeth
on each wheel 1802, 1804. In normal operation, as shown in FIG.
18B, the ribbons are strong enough to generally maintain their
shape and transmit torque from the outer wheel 1804 to the inner
wheel 1802. However, when the inner wheel 1802 encounters
sufficient resistance, the ribbons 1808 may be deform and
flattened, such as shown in FIG. 18C, and thus disengage the teeth
of one or both of the wheels 1802, 1804. When this occurs, the
wheels 1802, 1804 can rotate relative to one another, and the inner
wheel 1802 may slow or stop. Upon clearing whatever caused the
resistance on the inner wheel 1802, the ribbons 1808 return to
their original shape, and normal operation may resume.
[0108] The present disclosure describes a number of new, useful and
nonobvious features and combinations of features that may be used
alone or together with vacuum cleaners and other kinds of
appliances or devices that require selective torque coupling,
overload protection or both. The various parts and devices shown
herein may be made using any suitable technology, such as
machining, casting, injection molding, sintering, and the like, and
may comprise any suitable material, such as iron, plastic (ABS, PA,
reinforced, or other kinds of plastic), aluminum, steel, and so on.
The selection of the manufacturing method and material will depend
on typical engineering factors and will be appreciated by the
person of ordinary skill in the art without further explanation
herein. In addition, the various parts provided in the embodiments
described herein can be rearranged, such as by placing an overload
clutch between a motor and an engagement clutch, and so on. The
embodiments described herein are all exemplary, and are not
intended to limit the scope of the inventions in any way. It will
be appreciated that the inventions described herein can be modified
and adapted in various ways and for different uses. For example,
embodiments of the invention may be used to drive motorized wheels
on a vacuum cleaner, or to drive other household or industrial
appliances or equipment that require selective application of drive
torque to one or more moving parts or overload protection features.
All such modifications and adaptations are included in the scope of
this disclosure and the appended claims.
* * * * *