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&#39;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&#39;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.