Information
-
Patent Grant
-
6244078
-
Patent Number
6,244,078
-
Date Filed
Tuesday, December 29, 199825 years ago
-
Date Issued
Tuesday, June 12, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Goldman; David C.
- Breedlove; Jill M.
-
CPC
-
US Classifications
Field of Search
US
- 068 237
- 068 133
- 068 23 R
- 074 25
- 074 36
-
International Classifications
-
Abstract
Bearing fretting conditions are eliminated in washing machines by providing a drive system in which the bearings are not loaded during the spin mode. The drive system includes an input shaft and first and second hubs rotatively mounted about the input shaft. The second hub is movable along the input shaft between a first position adjacent to the first hub and a second position displaced from the first hub. The drive system spins the washing machine's basket when the second hub is in its first position and oscillates the agitator when the second hub is in its second position. A brake disk is mounted to the second hub for movement therewith, and a brake surface is fixedly mounted to the washing machine adjacent to the brake disk so that the brake disk contacts the brake surface when the second hub is in its second position. Separation of the two hubs is accomplished by ball bearings which are unloaded when the second hub is in its first position.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to domestic washing machines and more particularly to a drive system for agitating and spinning appropriate elements of the washing machine.
Conventional washing machines typically include a perforated basket for holding clothing or other articles to be washed, an agitator disposed within the basket which agitates the clothes in the basket, and a motor which drives the agitator and the basket. The articles to be washed are immersed in water with detergent and washed under the influence of an oscillating agitator. After agitation, the articles are rinsed with clean water and the basket is spun at high speed to centrifugally extract the rinse water from the articles. Typically, a mechanical drive system produces the oscillatory motion of the agitator upon rotation of a drive motor in one direction, and produces continuous rotation of the basket upon rotation of the drive motor in the other direction.
U.S. Pat. No. 5,605,212, issued Feb. 25, 1997 to Hans Hauser, is exemplary of such a drive system. The Hauser patent discloses a drive system including a bi-directional motor that can reverse its rotation direction to achieve different modes in the wash cycle. The motor rotates in a first direction during the agitate mode and in a second direction, opposite the first direction, during the spin mode. A transmission is provided with gears to convert the rotary motion of the motor into oscillatory motion of the agitator during agitation; during the spin mode, the transmission transfers motor rotation to the basket. The Hauser drive system further includes a spring loaded clutch/brake mechanism that holds the basket immobile during agitation mode. This mechanism uses a ball and hub assembly to engage or disengage the brake. The ball and hub assembly includes two rotatively mounted hubs having a plurality of ball bearings disposed therebetween in inclined races. The uppermost of the two hubs supports a spring loaded brake disk. When in the agitation mode, the balls remain at the bottom of the inclined races and the brake disk is biased into contact with a stationary brake drum, so that the brake is locked. When the wash cycle calls for the spin mode, the direction of motor rotation is reversed. This causes the balls to run up the inclined races, lifting the uppermost hub and the brake disk, thereby unlocking the brake. With the brake released, the transmission transfers motor rotation to the basket, resulting in the desired spinning of the basket.
Although generally operating in a satisfactory manner, this type of drive system suffers from a potential drawback in that the ball bearings are most highly loaded when the dynamic loading conditions are the worst, i.e., during spin mode. As the basket approaches its terminal speed during spin mode, the accelerating torques diminish and the brake spring force starts to force the balls back down their races. This causes the brake disk to descend until the disk tags the drum, increasing the torque, reversing the process, and re-releasing the brake. Tagging repeats over and over so that small motion of the highly loaded balls up and down the races can be stimulated, a condition that can produce fretting wear of the ball races. If the fretting becomes severe, a detent large enough to inhibit free ball rolling can develop and lead to possible brake failure. Furthermore, uneven distribution of wet clothes in the basket can aggravate the problem because large unbalanced loads during spin can concentrate the load onto one or two of the balls instead of being shared equally among the balls.
Accordingly, there is a need for an improved washing machine drive system in which the ball bearings are not loaded during the spin mode, thereby eliminating tagging and severe fretting conditions.
SUMMARY OF THE INVENTION
The above-mentioned needs are met by the present invention which provides a washing machine drive system having an input shaft and first and second hubs rotatively mounted about the input shaft. The second hub is movable along the input shaft between a first position adjacent to the first hub and a second position displaced from the first hub. The drive system spins the washing machine's basket when the second hub is in its first position and oscillates the agitator when the second hub is in its second position. A brake disk is mounted to the second hub for movement therewith, and a brake surface is fixedly mounted to the washing machine adjacent to the brake disk so that the brake disk contacts the brake surface when the second hub is in its second position. Separation of the two hubs is accomplished by ball bearings that are unloaded when the second hub is in its first position. Thus, the present invention eliminates tagging and severe fretting conditions while retaining the fail safe braking feature of conventional systems.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, however, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:
FIG. 1
is an elevational view, in cross-section, of a washing machine having the drive system of the present invention.
FIG. 2
is a sectional view of the transmission of the drive system of the present invention.
FIG. 3
is a sectional view of the transmission of FIG.
2
and taken generally along line
3
—
3
.
FIG. 4
is a sectional view of the transmission of FIG.
2
and taken generally along line
4
—
4
.
FIG. 5
is an enlarged sectional view of the clutch and brake assemblies of the drive system of the present invention.
FIG. 6
is an enlarged, partial cutaway view of the clutch assembly of FIG.
5
.
FIG. 7
is another enlarged, partial cutaway view of the clutch assembly of FIG.
5
.
FIG. 8
is a view from above of the ball ramp hub of the present invention.
FIG. 9
is a view from below of the brake disk hub of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,
FIG. 1
schematically shows a washing machine
10
including a cabinet
12
having a door (not shown) to permit access to the interior of washing machine
10
. Washing machine
10
also includes a perforated basket
14
that is rotatively mounted within an imperforate tub
16
. An agitator
18
is rotatively mounted within basket
14
. Washing machine
10
also includes a conventional control system (not shown), typically mounted to the upper surface of cabinet
12
, to allow a user to set the desired operating cycle. Typically, the operating cycle includes filling tub
16
with wash water (e.g., water and detergent), oscillating agitator
18
so that the clothes or other articles disposed in basket
14
for washing are mixed with the wash water, draining the wash water from tub
16
after agitation is completed, filling and draining tub
16
one or more times with rinse water, and spinning basket
14
to centrifugally extract water from the clothes.
Washing machine
10
has a drive system
20
for oscillating agitator
18
and spinning basket
14
. Drive system
20
includes a transmission
22
contained within a housing
24
and a reversible electric motor
26
capable of bi-directional rotation, the direction of rotation depending on the washing machine control system. In addition to being bi-directional, motor
26
can have variable speeds so as to vary the duty cycle under control of the control system. Motor
26
is supported by a frame
28
in washing machine
10
and has a drive pulley
30
fixedly mounted to its output shaft. Motor rotation is transferred through drive system
20
by a drive belt
32
connecting drive pulley
30
to an input pulley
34
. Input pulley
34
is fixedly connected to the lower end of an input shaft
36
, the other end of which is rotatively connected to transmission
22
. A basket drive shaft
38
is rotatively mounted concentrically about input shaft
36
and is fixedly connected to or integral with the lower side of transmission housing
24
. The other side of transmission housing
24
is fixedly connected to basket
14
so that rotation of housing
24
will cause rotation of basket
14
. Agitator
18
is coupled to drive system
20
by an agitator drive shaft
40
that is rotatively connected to transmission
22
and fixedly connected to agitator
18
. Drive system
20
further includes a clutch assembly
42
and a brake assembly
44
, both of which are described more fully below, that cooperate with transmission
22
to oscillate agitator
18
and spin basket
14
.
Drive system
20
has two alternate modes of operation depending on the direction of rotation of motor
24
. In a first or agitation mode, motor
26
is caused to rotate in a first direction (this first direction is counterclockwise as viewed from the bottom of
FIG. 1
for the purpose of illustration but could also be clockwise) thereby causing input shaft
36
to also rotate in this direction. The counterclockwise rotation of input shaft
36
causes clutch assembly
42
to activate or set brake assembly
44
so that basket drive shaft
38
, and hence transmission housing
24
, are locked with respect to frame
28
. Input shaft
36
thus rotates with respect to transmission housing
24
, which in turn causes transmission
22
to oscillate agitator
18
via agitator drive shaft
40
. In a second or spin mode, motor
26
is reversed to rotate in a clockwise direction such that input shaft
36
also rotates in a clockwise manner. The clockwise rotation of input shaft
36
is transmitted to basket drive shaft
38
via clutch assembly
42
and brake assembly
44
is released. Accordingly, basket drive shaft
38
and transmission housing
24
rotate along with input shaft
36
. The rotation of housing
24
causes basket
14
to rotate, thereby producing the desired spinning. And because housing
24
rotates with input shaft
36
, there is no relative rotation of shaft
36
and transmission
22
so that agitator
18
is not oscillated.
Referring to
FIGS. 2-4
, transmission
22
is shown in more detail. Input shaft
36
is rotatively mounted in the lower portion of housing
24
by a first bearing
46
, and agitator drive shaft
40
is rotatively mounted in the upper portion of housing
24
by a second bearing
48
. A ball bearing
50
is provided between the upper end of input shaft
36
and the lower end of agitator drive shaft
40
to axially locate the two shafts and permit relative rotation therebetween. An eccentric gear
52
is rotatively mounted to housing
24
by an idler shaft
54
which is mounted inside housing
24
and extends through the center of eccentric gear
52
. As best seen in
FIG. 4
, eccentric gear
52
is drivingly connected to input shaft
36
by an input pinion
56
splined to the upper end of input shaft
36
. Eccentric gear
52
includes an offset shaft
58
extending upwardly therefrom. The center of offset shaft
58
is displaced from the center of eccentric gear
52
such that when eccentric gear
52
is caused to rotate about its center by input pinion
56
, offset shaft
58
revolves in a circular fashion about the center of eccentric gear
52
.
Transmission
22
further includes an agitator rack
60
having a circular bearing
62
and a cavity
64
with teeth
66
(
FIG. 3
) and an agitator pinion
68
fixedly attached to the lower end of agitator drive shaft
40
. Agitator rack
60
is arranged so that circular bearing
62
is disposed around offset shaft
58
and agitator pinion
68
is in driving contact with rack teeth
66
. With this arrangement, the circular motion that offset shaft
58
undergoes in response to eccentric gear
52
rotating about idler shaft
54
causes agitator rack
60
to move back and forth in a reciprocating longitudinal motion. This reciprocating longitudinal motion, via the driving engagement of teeth
66
with agitator pinion
68
, causes agitator drive shaft
40
to move back and forth in a reciprocating rotary motion. A counterweight
70
is attached to housing
24
opposite eccentric gear
52
to counter balance the weight of eccentric gear
52
and the other transmission elements.
Turning now to
FIGS. 5-9
, clutch assembly
42
and brake assembly
44
are described in more detail. Clutch assembly
42
includes a unidirectional helical clutch spring
72
that surrounds a pulley hub
74
that is fixedly connected to or integrally formed on input pulley
34
for rotation therewith in either direction. A ball ramp hub
76
is rotatively mounted concentrically about input shaft
36
by a bearing
78
at a location directly above pulley hub
74
. Clutch spring
72
also surrounds ball ramp hub
76
and is helically wound so as to grasp ball ramp hub
76
and cause it to rotate with pulley hub
74
when pulley hub
74
is rotated in the counterclockwise direction, but when pulley hub
74
is rotated in the clockwise direction, clutch spring
72
mostly slips and generally does not cause ball ramp hub
76
to rotate.
A brake disk hub
80
is disposed above ball ramp hub
76
. Brake disk hub
80
, which is also mounted concentrically about input shaft
36
, is fixedly connected to basket drive shaft
38
for rotation therewith. Ball ramp hub
76
has a number of inclined races
82
formed in its upper surface, and brake disk hub
80
includes an equal number of races
84
formed in its lower surface. Although
FIGS. 8 and 9
show six such races, the present invention is not limited to this number. Inclined races
82
have a detent
86
formed at their shallowest ends. An actuation ball
88
is captured between each pair of races
82
and
84
. Actuation balls
88
separate ball ramp hub
76
from brake disk hub
80
and support relative motion therebetween. As seen in
FIG. 6
, when ball ramp hub
76
is rotated in a counterclockwise direction as viewed from the bottom of
FIG. 6
relative to brake disk hub
80
, balls
88
run up the ramps defined by inclined races
82
and into detent
86
, thereby causing brake disk hub
80
to be lifted with respect to ball ramp hub
76
. However, as shown in
FIG. 7
, when ball ramp hub
76
is rotated in a clockwise direction relative to brake disk hub
80
, balls
88
are lifted out of detent
86
and run back down inclined races
82
, so that brake disk hub
80
is not lifted with respect to ball ramp hub
76
. Thus, brake disk hub
80
is movable along input shaft
36
between a first position adjacent to ball ramp hub
76
(
FIG. 7
) and a second position displaced from ball ramp hub
76
(FIG.
6
).
As best seen in
FIGS. 8 and 9
, ball ramp hub
76
has a set of tabs
90
located about its outer surface, and brake disk hub
80
has a set of tabs
92
located about its outer surface. Tabs
90
extend beyond the upper surface of ball ramp hub
76
, and tabs
92
extend beyond the bottom surface of brake disk hub
80
. Tabs
90
and
92
are relatively positioned about the perimeter of their respective hubs so as to engage one another when ball ramp hub is rotated a sufficient amount in the clockwise direction. This corresponds to the condition where actuation balls
88
are down in inclined races
82
and brake disk hub
80
is in its first position (FIG.
7
). With tabs
90
and
92
in engagement, brake disk hub
80
is drivingly connected with ball ramp hub
76
so that continued clockwise rotation of ball ramp hub
76
is transferred to brake disk hub
80
.
Brake assembly
44
includes a brake disk
94
that is fixedly connected to brake disk hub
80
so as to move with brake disk hub
80
when it moves along input shaft
36
. A brake surface
96
is mounted directly over the outermost portion of brake disk
94
. As shown in
FIG. 5
, brake surface
96
is a friction pad in the form of a ring (either segmented or continuous) of high friction material mounted to a bearing support member
98
by an adjustable spring loaded fixture
100
which permits adjustment of the contacting force between brake disk
94
and brake surface
96
. However, it should be noted that it is within the scope of the present invention to simply affix brake surface
96
directly to bearing support member
98
. Bearing support member
98
, which also supports a bearing
102
for basket drive shaft
38
, is secured to washing machine frame
28
. Brake disk
94
and brake surface
96
are positioned relative to one another such that when brake disk hub
80
is lifted from ball ramp hub
76
by actuation balls
88
(i.e., into its second position), brake disk
94
is forced into contact with brake surface
96
, thereby locking brake disk hub
80
, and hence basket drive shaft
38
and transmission housing
24
, against rotation with respect to frame
28
.
As mentioned above, drive system
20
has two alternate modes of operation, the agitation mode and the spin mode. During agitation, motor
26
is caused to rotate in a counterclockwise direction as viewed from the bottom of the Figures, which causes pulley hub
74
and input shaft
36
to rotate in the counterclockwise direction as well. Although clutch spring
72
generally slips when pulley hub
74
rotates counterclockwise, there is a sufficient amount of drag torque present in clutch spring
72
to cause the counterclockwise rotation of pulley hub
74
to be transferred briefly to ball ramp hub
76
. The counterclockwise rotation of ball ramp hub
76
causes actuation balls
88
to be driven up inclined races
82
and into detents
86
. This causes brake disk hub
80
to be lifted into its second position so that brake disk
94
is forced into contact with brake surface
96
, thereby setting brake assembly
44
so that basket drive shaft
38
and transmission housing
24
are locked with respect to frame
28
. Clutch spring
72
now slips on ball ramp hub
76
, but pulley hub
74
and input shaft
36
continue to rotate in the counterclockwise direction. The rotation of input shaft
36
causes transmission
22
to drive agitator drive shaft
40
back and forth in a reciprocating rotary motion. This in turn results in agitation of agitator
18
.
At the proper time in the operation of washing machine
10
, the spin mode is initiated by reversing the direction of motor
26
so that it rotates in the clockwise direction. Reversal of motor
26
causes pulley hub
74
and input shaft
36
to rotate in the clockwise direction. Now, clutch spring
72
grasps ball ramp hub
76
so as to transfer clockwise rotation to it. The clockwise rotation of ball ramp hub
76
causes actuation balls
88
to be lifted out of detents
86
and driven back down inclined races
82
. This causes brake disk hub
80
to be returned to its first position adjacent to ball ramp hub
76
(
FIG. 7
) so that brake disk
94
does not contact brake surface
96
. At this point, tabs
90
and
92
are in engagement so that brake disk hub
80
is drivingly connected with ball ramp hub
76
. Accordingly, continued clockwise rotation of motor
26
is transferred to brake disk hub
80
and to basket drive shaft
38
and transmission housing
24
which are free to rotate with respect to frame
28
because brake assembly
44
is released. Rotation of transmission housing
24
is directly transferred to basket
14
, producing the desired spinning of basket
14
. Because brake disk hub
80
is in its first position during the spin mode, actuation balls
88
are unloaded and not subjected to fretting conditions during the spin mode, when the highest pounding loads are applied to drive system
20
. The present invention also provides a fail safe braking feature in that if power is interrupted or motor
26
otherwise fails during the spin mode, inertia and motor drag will cause ball ramp hub
76
to slow with respect to the clockwise spinning basket
14
. This will cause actuation balls
88
to be driven up inclined races
82
and into detents
86
, lifting brake disk hub
80
into its second position and setting brake assembly
44
, thereby stopping spinning of basket
14
.
Although the present invention has been described such that counterclockwise motor rotation produces agitation of agitator
18
and clockwise motor rotation produces spinning of basket
14
, this is for the purposes of illustration only. It should be understood that the present invention could also be configured such that counterclockwise motor rotation produces the spin mode and clockwise motor rotation produces the agitation mode.
The foregoing has described a washing machine drive system that produces agitation of the agitator and continuous direct spin of the basket. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims
- 1. A drive system for a washing machine, said drive system comprising:an input shaft; a first hub rotatively mounted about said input shaft; a second hub rotatively mounted about said input shaft, said second hub being movable along said input shaft between a first position adjacent to said first hub and a second position displaced from said first hub; a number of races formed in said first hub, an equal number of races formed in said second hub, and an actuation ball disposed between each one of said races formed in said first hub and a corresponding one of said races formed in said second hub; a brake disk mounted to said second hub for movement therewith; and a brake surface fixedly mounted to said washing machine adjacent to said brake disk so that said brake disk contacts said brake surface when said second hub is in said second position.
- 2. The drive system of claim 1 wherein said brake disk does not contact said brake surface when said second hub is in said first position.
- 3. The drive system of claim 1 wherein said races in at least one of said first and second hubs are inclined.
- 4. The drive system of claim 3, wherein each one of said inclined races has a detent formed at one end thereof.
- 5. The drive system of claim 1 further comprising a motor and means for coupling said motor to said input shaft.
- 6. The drive system of claim 5 further comprising a clutch spring, said clutch spring configured to transfer rotation of said input shaft to said first hub upon rotation of said input shaft in a first direction.
- 7. The drive system of claim 6 wherein said actuation balls cooperate with said races formed in said first hub and said races formed in said second hub to move said second hub to its first position upon rotation of said input shaft in said first direction and to move said second hub to its second position upon rotation of said input shaft in a second direction.
- 8. The drive system of claim 1 further comprising a basket drive shaft fixedly connected to said second hub.
- 9. The drive system of claim 1 further comprising a transmission connected to said input shaft and an agitator drive shaft connected to said transmission, said transmission converting continuous rotation of said input shaft in one direction into reciprocating back and forth rotation of said agitator drive shaft.
- 10. A drive system for a washing machine having a basket and an agitator, said drive system comprising:an input shaft; a first hub rotatively mounted about said input shaft; a second hub rotatively mounted about said input shaft, said second hub being movable along said input shaft between a first position adjacent to said first hub and a second position displaced from said first hub, wherein said drive system spins said basket when said second hub is in said first position and oscillates said agitator when said second hub is in said second position; and a number of races formed in said first hub, an equal number of races formed in said second hub, and an actuation ball disposed between each one of said races formed in said first hub and a corresponding one of said races formed in said second hub.
- 11. The drive system of claim 10 further comprising:a brake disk mounted to said second hub for movement therewith; and a brake surface fixedly mounted to said washing machine adjacent to said brake disk so that said brake disk contacts said brake surface when said second hub is in said second position.
- 12. The drive system of claim 11 wherein said brake disk does not contact said brake surface when said second hub is in said first position.
- 13. The drive system of claim 10 wherein said races in at least one of said first and second hubs are inclined.
- 14. The drive system of claim 13 wherein each one of said inclined races has a detent formed at one end thereof.
- 15. The drive system of claim 10 further comprising a motor and means for coupling said motor to said input shaft.
- 16. The drive system of claim 15 further comprising a clutch spring, said clutch spring configured to transfer rotation of said input shaft to said first hub upon rotation of said input shaft in a first direction.
- 17. The drive system of claim 16 wherein said actuation balls cooperate with said races formed in said first hub and said races formed in said second hub to move said second hub to its first position upon rotation of said input shaft in said first direction and to move said second hub to its second position upon rotation of said input shaft in a second direction.
- 18. The drive system of claim 10 further comprising a basket drive shaft fixedly connected to said second hub.
- 19. The drive system of claim 10 further comprising a transmission connected to said input shaft and an agitator drive shaft connected to said transmission, said transmission converting continuous rotation of said input shaft in one direction into reciprocating back and forth rotation of said agitator drive shaft.
US Referenced Citations (10)