WO2008143528A1

WO2008143528A1 - Laundry machine with lost motion clutch

Info

Publication number: WO2008143528A1
Application number: PCT/NZ2008/000112
Authority: WO
Inventors: Brian Paul Mclean; Geoffrey Paul Batt; Sophie Elizabeth Lane; Tung Xuan Voung
Original assignee: Fisher & Paykel Appliances Limited
Priority date: 2007-05-18
Filing date: 2008-05-16
Publication date: 2008-11-27

Abstract

The present.invention relates to a laundry machine with a spin basket and an independently rotating agitator within the spin basket. A lost motion clutch is engaged between the spin basket and the agitator. The lost motion clutch absorbs greater than one revolution of relative rotation between the agitator and the spin basket. The lost motion clutch includes an interface between two members, the interface converting relative rotational movement into relative axial movement. Maximum relative travel between the two members is defined between two end conditions, the maximum relative travel permitting greater than one relative rotation.

Description

"LAUNDRY MACHINE WITH LOST MOTION CLUTCH"

FIELD OF THE INVENTION

The present invention relates to laundry machines and in particular to laundry washing machines having a spin basket and an independently rotating agitator within the spin basket.

SUMMARY OF THE PRIOR ART

In 1991 Fisher & Paykel Limited released the first model of their SMARTDRIVE washing machines. This machine included a cabinet, a tub suspended within the cabinet by a plurality of suspension rods extending between the top edge o£ the cabinet and a lower portion on the tub. A single shaft extended through the base of the tub. The stator of a salient pole electronically commutated brushless DC motor was fixed to the lower side of the tub base. An external permanent magnetic rotor was fitted to the lower end of the shaft to substantially surround the stator. Within the tub a spin basket was supported for rotation on the shaft. Within the spin basket an agitator was fixed to the upper end of the shaft. The agitator was of a central post type with three lateral vanes and a generally conical base portion. The spin basket was supported by the shaft at a lower position, was free to rise on the shaft to an upper position. The spin basket included downwardly facing hollow chambers. Vertical support of the spin basket on the shaft in the lower position included inter-engagement of a downwardly facing castellated clutch on the spin basket and an upwardly facing castellated clutch fixed to the shaft. Accordingly without sufficient wash liquid in the tub for the spin basket and any associated load to float the spin basket remained rotationally fixed to the shaft. With sufficient wash liquid in the tub the float chambers of the spin basket would provide for the basket and load to float and disengage from the ^~ shaft such that the spin basket and shaft would rotate. This arrangement is described in US Patent 5,353,613. This direct drive electronically controlled laundry machine has been very successful. A number of competing companies have sought to devise alternative arrangements for selectively transmitting power of the motor to the spin basket.

US Patent 6,212,722 proposes an improved laundry washing machine for domestic use. This machine is of the top loading type having an outer bowl, a wash basket within the outer bowl and access to the wash basket through a top opening. A motor is provided to drive rotation of the wash basket within the outer bowl. A wash plate is provided in the lower portion of the wash basket to be rotated by the motor with the wash basket or independently of the wash basket. The

• patent proposes a combination of water level control, wash plate design, wash basket design and movement pattern for the wash plate which leads to an inverse toroidal movement of the laundry load during a wash phase. The sodden wash load is dragged radially inward on the upper surface of the wash plate and progresses upward in the region of the centre. The sodden wash load then progresses radially outward to the wall of the wash basket and downward to the base of the wash basket. This has been found to provide an effective wash action with low water consumption.

When a wash system of the type disclosed in 'US 6,212,722 is applied to a machine of the type described in US Patent 5,353,613, the water volume required to operate the floating clutch can be a significant factor in overall water consumption.

US Patent 4,803,855, Kennedy, describes an agitate and spin drive for a washing machine. The mechanism includes a pair of concentric shafts extending through the lower wall of the wash tub. The upper end of the inner shaft is connected to drive the agitator. The upper end of the outer shaft is connected to drive the wash basket. A pulley at the lowest end of the inner shaft is driven by an electric motor. A lost motion mechanism or clutch in the form of a plurality of stacked disks is mounted on the agitator shaft. A lower end of the lost motion clutch is driven by the pulley. An upper end of the lost motion mechanism drives the lower end of the wash basket shaft. The lost motion clutch mechanism is located in the area between the base of the wash tub and the drive pulley. The overall arrangement requires both the wash basket shaft and agitator shaft to penetrate the wash tub.

US Patent 2,273,566 illustrates a washing machine with an agitator housed within a wash basket. The wash basket includes a central hub 41 extending up inside die post of the agitator. A lost motion clutch acts between the inner surface of the agitator and the outer surface of the hub. The clutch allows less than one revolution of relative movement between the wash basket before the agitator begins to drive the wash basket.

US Patent 2,609,697 describes a washing machine with an agitator housed within a wash basket. The wash basket is rotatably supported on the drive shaft. The agitator is fixed to the drive shaft. A downward extending lug on the agitator skirt is positioned to engage against an upward lug on the floor of the wash basket. The clutch allows less than one revolution of relative movement between the wash basket before the agitator begins to drive the wash basket. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a laundry machine which goes some way toward overcoming the above disadvantages or which will at least provide the public with a useful choice.

The present invention may broadly be said to consist in a laundry machine comprising: a tub, a spin basket in the tub, a drive assembly comprising a motor, a shaft and an agitator, the motor driving the shaft, the shaft passing through a wall of the spin basket, the agitator being located within the spinbasket, ^{■ ■ ■} a lost motion clutch interconnecting between the drive assembly and the spin basket and absorbing greater than one revolution of relative rotation; the lost motion clutch including an interface between a first member and a second member, the interface converting relative rotational movement between the first and second member to relative axial movement, at least one first pair of butting surfaces which stop relative movement between the first .member and die second member continuing beyond a first end condition under relative rotation in a first direction and at least one second pair of butting surfaces which stop relative movement between the first member and the second member continuing beyond a second end condition under relative rotation in a second direction, the end conditions defining a maximum relative travel, the maximum relative travel permitting greater than one relative rotation.

Preferably the first member is coupled to, or is, the spin basket or the shaft, and the second member is slidably and non-rotatably coupled to a third member, the third member being fixed or coupled to the other of the spin basket or the shaft.

Preferably the third member includes a first bearing surface and a bottom end of the first member has a corresponding second bearing surface, the first and second bearing surfaces supporting the first member axially and allowing relative rotation between the first member and the third member.

Preferably the first and second bearing surfaces are sloped.

Alternatively the first member is coupled to, or is, the spin basket and the second member is coupled to, or is, the shaft.

Alternatively the first member is coupled to, or is, the spin basket or the shaft, and the second member is slidably and non-rotatably coupled to the other of the spin basket or. the shaft.. Alternatively the second member rides up and down on a spline on the shaft.

Preferably the interface is a screw.

Preferably the screw comprises an internal trapezoidal thread on one of said first or second members and an external trapezoidal thread on the other said first or second member.

Preferably one of the first or second members is substantially shorter in the axial direction than the other first or second member.

Preferably the second member is substantially axially shorter than the first member.

Preferably at least one of the pairs of butting surfaces act to stop relative rotation.

Preferably at least one end of the housing includes a first set of radial teeth protruding into an inner chamber, with the second member having a corresponding second set of radial teeth, the first set and second set of teeth providing a plurality of pairs of radial butting surfaces, the pairs of radial butting surfaces arranged to stop relative rotation between the housing and the second member.

Alternatively at least one of the pairs of butting surfaces is a blind end of the screw.

Alternatively at least one end of the housing includes a lug protruding into an inner chamber and acting as a said butting surface.

Preferably at least one of the pairs of butting surfaces act to stop relative rotation by limiting axial movement.

Preferably the lost motion clutch includes an elastic buffer slowing the relative rotational or axial movement as the relative movement reaches a said end condition.

Preferably the lost motion clutch includes an elastic buffer at each said end condition slowing the relative rotational or axial movement as the relative movement reaches each said end condition.

Preferably the first member comprises a housing coupled to the spin basket, the second member is engaged over the shaft, and ends of the housing enclose and/or retain the second member.

Preferably at least one end of the housing is a separate part being rotationally fixed and axially fixed to the housing.

Preferably the first member comprises a housing and a mounting member, the housing being axially retained by and rotationally moveable with-respect-to the mounting member, the mounting .member being fixed to the spin basket, the housing interfacing with and enclosing and/or retaining the second member, the second member being engaged over the shaft, and at least one elastic buffer engaged between the mounting member and the housing to slow relative rotational movement between the mounting member and the housing once the relative movement of the housing and the second member reaches an end condition. Preferably the amount of relative rotational movement between the housing and the mounting member is a small fraction of the amount of relative rotational movement between the housing and the second member.

Preferably there is substantially no relative rotational movement between the housing and the mounting member except for elastic compression of the elastic buffer.

Preferably the screw is a multi-start thread.

Preferably the at least one first pair of butting surfaces is adjacent an upper end of the first member and the at least one second pair of butting surfaces is adjacent a lower end of the first member, the screw having a thread turn direction so that the at least one second pair of butting surfaces butt together in a worst case loading condition.

Preferably the drive assembly, but for the lost motion clutch, would be free to rotate relative to the spin basket.

Preferably the spin basket is supported for rotation at a fixed axial position on the shaft.

Preferably the shaft rotates around a vertical axis, and the tub and the spin basket are accessible through a top opening.

Preferably the shaft of the drive assembly protrudes from below a base portion of the tub, a stator of the electric motor is fixed to the spin basket, and a rotor of the electric motor is fixed to the shaft.

Preferably the motor is of the external rotor type.

Preferably the laundry machine includes a power supply circuit connected with windings of the motor, and a microcomputer having outputs connected to the power supply circuit for controlling the application of power to the windings of the motor, the microcomputer being programmed to drive the drive assembly in at least a first mode involving strokes of short duration in alternate directions, and a second mode involving continuous running for many revolutions in the same direction.

Preferably the screw has a thread turn direction that moves the second member- -downwards when the microcontroller drives the agitator/shaft in a first direction relative to the spin basket, the microcomputer being programmed to drive the motor to spin the spin basket in a direction opposite to the first direction during the second mode.

Preferably the microcomputer is programmed to limit the angular rotation of any single agitation stroke of the drive assembly to be less than about 2 revolutions.

Preferably the microcomputer is programmed to detect any occasional end condition that occurs during agitation and to terminate the drive of motor in that agitation stroke as soon as the collision is detected. Preferably the microcomputer is programmed to monitor the load on the motor and detect the end condition by an increase in the motor load.

Preferably the microcomputer is programmed to detect any directional bias in any residual rotation of the spin basket during agitation.

Preferably the microcomputer is programmed to adjust the respective agitator stroke lengths to try to reduce the bias and preferably to reverse the estimated accumulated. relative creep in one direction.

Preferably the maximum relative travel between the first member and the second member is greater than 2 revolutions.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

The term "comprising" as used in this specification means "consisting at least in part of. When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a cutaway perspective view of a laundry machine according to one embodiment of the present invention.

Figure 2 is a block diagram of a control system for a laundry washing machine.

Figure 3 is a cross-sectional side elevation of a lower part of the tub and spin basket,- the agitator and an upper part of the drive shaft according to one embodiment of the present invention.

Figure 4 is an exploded perspective view of the lost motion clutch according to one embodiment of the present invention.

Figures 5 is a perspective view of the lost motion clutch according to the preferred embodiment of the present invention Figure 6a and 6b are exploded perspective views of the lost motion clutch according to the preferred embodiment of the present invention.

Figure 7 is a cross-sectional side elevation of the shaft and lost motion clutch according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION

A laundry machine that may incorporate a clutch according to the present invention is illustrated in Figure 1. The laundry machine includes a cabinet 100 with a lid 102 and a user console 104. A controller 106 is located within the body of the user console. The controller 106 includes a power supply and a programmed microcontroller. The power supply receives power from the mains supply and supplies power to the microcontroller, to a power supply bridge for the electric motor and to ancillary devices within the machine such as a pump and valves. Delivery of power to the motor 114 and the ancillary devices is at the control of the microcontroller. The microcontroller receives inputs from a user interface on console 104.

A tub 120 is supported within the cabinet. The tub is preferably suspended from the upper edge of the cabinet, for example by suspension rods 121. The tub may alternatively be supported from below or from the sides of the cabinet. A wash or drain pump is fitted to the lower portion of the tub. The pump is preferably located at a sump portion of the tub.

A wash basket 122 is supported for rotation within the tub. Opening the lid 102 provides user access to an upper open end of the wash basket.

An agitator 124 is mounted in the lower portion of the wash basket. The agitator may be of a central post type, with or without additional moving parts, such as augers, or of a wash plate type, such as illustrated in US Patent 6,212,722, or of a pulsator type, or of any other type having independent movement from wash basket 122. The illustrated agitator is of wash plate type, intended for facilitating low water level wash exhibiting inverse toroidal rollover patterns.

The improvements and adaptations of the present invention are preferably implemented in a laundry machine of a direct drive type with motor fixed direcdy to the lower end of a single drive shaft. However other drive systems involving for example gearbox or belts driving a single drive shaft may alternatively be used.

A motor 114 below the tub direcdy drives single shaft 128. The single shaft 128 extends through the lower face of the tub, where it is supported in a pair of bearings 130. A seal 360 prevents water escaping the tub at the interface between the tub and shaft. The wash basket 122 is mounted on the shaft within the tub. The wash basket may typically comprise a base 132 and a perforated cylindrical skin 134. The perforated cylindrical skin extends up from the base to define an open ended drum. The wash basket may include a balance ring at the upper edge of the cylindrical skin.

The wash plate 124 is also fitted to the shaft, within the wash basket 122.

A clutch arrangement 142 is provided to enable the motor 114 to selectively drive either the wash plate 124 independendy of the wash basket 122, or drive die wash basket 122. In driving the wash basket the motor may also drive the wash plate. Various mechanisms have been proposed to accomplish this selective drive. The present invention relates to an improved mechanism which promotes low water consumption and is compact and effective. The mechanism may also be used inside the wash tub, where a single shaft penetrates the tub 120. Alternatively the mechanism may be used outside the tub to connect between dual shafts of a dual shaft drive system (where one shaft connects to die agitator and a concentric outer shaft connects to the spin basket). The mechanism is described in detail below.

The controller is part of a control system for coordinating the operations of the laundry machine. The control system is illustrated in the block diagram of Figure 2. The controller includes a microcontroller 800. The microcontroller may include a microcomputer and ancillary logic circuits and interfaces. The microcontroller receives user input commands on user interface 802. The user interface may include, for example, a plurality of touch controls such as switches or buttons, or may include a touch screen, or may include rotary or linear selection devices. The microcontroller may include a display device 804 to provide feedback to a user. The display device may comprise a plurality of indicators, such as lights or LEDs, or may include a screen display. The display device • 804 and the user interface 802 may be mounted to a single module incorporating the microcontroller.

The microcontroller receives power from a power supply 806. The microcontroller also controls power switches 808 applying power from supply 806 to drive motor 810. The microcontroller controls further power switches 812 applying power from supply 806 to a pump 814. The microcontroller also controls a power switch 830 applying power to a cold water inlet valve 832 and a power switch 834 applying power to hot water inlet valve 836. The microcontroller preferably receives feedback from position sensors 816 associated with the motor. These sensors may for example be a set of digital Hall sensors, sensing changes in rotor position, or may be any suitable encoder. Alternatively rotor position and movement may be sensed from motor drive current or EMF induced in unenergised motor windings.

•The microcontroller also preferably receives input from a water level sensor 818, which detects the level of water in the tub of the machine, and from a temperature sensor 820 which detects the temperature of water being supplied to the wash tub.

The preferred controller applies an initial wash plate drive profile to initiate the inverse toroidal motion. The initial drive profile is characterised by higher angular velocity and longer stroke length to start the clothes movement. This movement is subsequently maintained by a maintenance drive profile with lower angular velocity and stroke length. Many dove systems are possible for controlling wash plate drive profiles. One example is described in US, Patent 5,398,298.

The initial drive profile is varied according to load size. The profile is more vigorous for larger load sizes. Load size may be determined from a user entry or selection, or by monitoring the inlet flow and recirculation pump activity, or by one of the many methods described in the prior art.

Preferably the maintenance drive profile is also varied according to load size. Again the profile is more vigorous for larger load sizes.

Acceptable wash performance is considered a compromise between achieving regular inverse toroidal turnover of a wash load within the spin basket and wear and tear associated with wash profiles that are too vigorous (and speeds that are too high) or entanglement (angular strokes that are too long). In general agitator wash strokes are between 0.5 revolutions and 1.5 revolutions. In each wash stroke the relative rotation between agitator and wash basket is generally less than 1.5 revolutions. However longer wash strokes may be desirable for some load types. ^{• ••}

According to the invention an improved clutch mechanism can absorb relative motion between the agitator and wash tub of 2 or more rotations. The mechanism is simple yet robust and can be used inside or outside the wash tub. In the preferred embodiment illustrated in the drawings the mechanism is provided in the space between the wash plate 124 and the upper side of the base 322 of the spin basket. ^s The spin basket is rotatably supported on the shaft 128, for example by a pair of bearings 318.

The spin basket is vertically supported on the shaft 128, for example by a thrust bearing 310.

The bearings 318 are fitted within bearing tube 320 of the base portion 322. The bearings 318 are preferably of a sliding seal type. The bearings 318 provide radial support of the spin basket relative to the shaft. The bearings are vertically spaced on the shaft to provide torsional stability.

The thrust bearing 310 is fitted to the shaft 128 above the upper radial bearing 318: The thrust bearing 310 preferably engages over a spline 313. The thrust bearing 310 has an upwardly, facing thrust surface which supports the weight of the spin basket. The lower edge of the thrust bearing 310 is supported on a shoulder 317 of the shaft 128.

A support hub 308 rests on the thrust surface of thrust bearing 310 and is secured/coupled to an upper face of the spin basket base 322. A lower surface 332 of the support hub 308 bears on thrust surface 334 of thrust bearing 310.

The support hub 308 houses the lost motion mechanism. The hub has in inner axial cavity surrounding a lower spline portion 313 of the drive shaft. A drive member 303 resides in this cavity, engaged between the outer surface of the drive shaft and the inner wall surface of the cavity.

The inner wall surface of the cavity has a screw thread 302. The outer circumference of the drive member has a complementary screw thread 309. The thread is a loose enough fit that the drive member can rotate easily inside t he cavity. Rotation of the drive member in the cavity draws the drive member axially up or down the cavity.

The screw thread may be any screw type helical thread. In the preferred embodiment, the screw has a multi start thread. Preferably the screw thread has at least a two start thread form. A multi start thread provides greater cross-sectional thread strength for a given thread pitch. The preferred thread form is a trapezoidal thread, however the particular thread form is not essential.

In one embodiment, the drive member has an axial sliding engagement on the lower spline 313. In this arrangement the drive member can slide up and down the spline as the shaft rotates relative to the hub 308. Alternatively, the drive member may slide up and down on a portion of die agitator, the agitator being fixed/coupled to the shaft.

Alternatively the drive member may have a fixed engagement on the lower spline. In this arrangement the hub member (and the whole spin basket) is moved axially up and down the shaft as the shaft rotates relative to the hub 308. It is possible that this movement may prove useful for enhancing some aspect of the wash cycle.

The clutch is constructed to have sufficient relative axial travel of die drive member to allow at least two, and preferably at least four, rotations of the shaft relative to the hub between end conditions. Essentially this requires at least two, and preferably at least four, exposed turns of screw thread on die internal wall of the hub cavity. By exposed we mean threads tiiat are not engaged by die drive member. Furthermore die drive member should not encounter obstructions in travelling to the maximum end conditions.

The end conditions may be determined by limiting the relative axial movement or by limiting the relative rotational movement or a combination of both. In the preferred embodiment the end conditions are determined by limiting the relative rotational movement, and a resilient buffer is provided to absorb and reduce any impacts occurring when an end condition is reached. A resilient buffer may be provided in die axial direction to absorb any impacts occurring at each end condition, or rotational buffering may be used, or both. The resilient buffers reduce the impact at an end condition by slowing the relative rotational or axial movement before the relative movement reaches an end condition.

Relative rotational movement can be limited by providing blind ends to at least one end of the hub cavity thread. For example the preferred trapezoidal thread channel may terminate at each end in a perpendicular end face to butt against similar end faces of die thread on the drive member. At least one of these end faces would be formed on an end cap fitted to the hub. For example the end face may be provided as a face of lug 327 of end cap 325 that encloses the lower end of die hub. With the end cap seated in a recess in the bottom of the main hub member this lug 327 also engages in a notch in the inner wall of die main hub member. This secures die end cap against rotation relative to the main hub member. Alternatively butting surfaces could be provided extending axially from the annular ends of the drive member, to butt against complementary surfaces provided on the inner end faces of the hub cavity.

A similar end cap could be provided at the upper end of the hub, however the inventors prefer that that end be made integral with the hub for strength. The lower end cap is retained in part by the weight of the basket pressing the end cap down on thrust bearing 317.

Axial buffers acting in the axial direction to absorb end condition impacts may each comprise an annular cushion 300 between the drive member and the end of the hub cavity. Preferably a thrust washer 301 could be provided spaced between the annular cushion and the drive member to reduce wear on die cushion and reduce rotational friction.

The agitator 124 is fixed to the upper end of drive shaft 128. The agitator 124 rotates with drive shaft 128. Typically the drive will operate in a wash mode where the shaft is reciprocated in alternate directions, and a continuous rotation mode in which the shaft is rotated for longer periods in a single direction.

For the continuous rotation modes the drive shaft will rotate until the clutch reaches one of the end conditions, where a surface of the drive member butts a surface of die hub cavity to end relative rotation. In this condition rotation of the drive shaft drives rotation of the agitator and spin basket together.

From this drive position in a first direction the drive shaft may rotate relative to the spin basket through a number of full revolutions before meeting a second end condition where it drivingly ^■ engages the spin basket for rotation in the other direction. The number of turns between end conditions is governed by the pitch of the screw thread and die available travel of the drive member along the screw.

In one embodiment, the support hub 308 is fixed to the upper face of the spin basket base 322, for example by fasteners 312. Practically, this allows assembly of the spin basket onto the drive shaft by first fitting the radial support bearings over the drive shaft, then fixing the thrust bearing 310 over the lower spline 313, then support hub 308 (which encloses the complete lost motion clutch assembly) is fitted over the drive shaft and fastened to the spin basket base through flange 304 to support the spin basket on thrust bearing 310, then agitator 124 is fitted to the .upper spline on the drive shaft and secured in place by fastener 350.

Preferred embodiment

A preferred embodiment of the present invention is shown in Figures 5 — 7.

In the preferred embodiment, a hub 1 is engaged over drive shaft 128. Hub 1 has internal vertical splines 8 and is removeably fitted to the lower^' spline section 313 of the drive shaft. Splines 8 of hub 1 interface with splines 313 of the drive shaft so that hub 1 is rotationally fixed/coupled to the shaft 128. ■ An internal annular shoulder 23 perpendicular to the shaft axis bears against a corresponding shoulder on the drive shaft 128, to position the hub axially on the shaft 128.

The lost motion clutch assembly includes a housing 4 for housing the lost motion mechanism. The housing 4 is coupled to an upper surface of the spin basket base 322. The housing has an inner axial cavity: The inner axial cavity surrounds the hub 1.

Housing 4 is fitted with an upper end cap 7 and a lower end cap 2. Upper end cap 7 may be integrally formed- with the housing 4. Alternatively, lower end cap 2 may be integrally formed with the housing 4.

Upper end cap 7 is rotationally locked to the housing 4. The lock may be provided by a series of dogs 12 which locate into corresponding recesses 19. Screws or pins may axially fix end cap 7 to the housing 4 via the screw or pin holes 13.

The lower end cap 2 is rotational locked to the housing 4. The lock may be provided by a series of dogs 14 which locate into corresponding recesses 20. The weight of the assembly including the spin basket maintains the lower end cap in place with the housing 4.

The lost motion mechanism is a drive member 3. Dive member 3 fits over hub 1 in a sliding engagement, with internal splines 21 of drive member 3 interfacing with splines 22 in the outer surface of hub 1. Drive member 3 may be slidingly engaged over the shaft 128 by engaging with the hub 1 or could be directly engaged to the shaft as described in relation to Figures 3 and 4. The inner wall surface of the housing has a screw thread, and the outer circumference of the drive member has a complementary screw thread, as described in relation to Figures 3 and 4. Hub 1 provides a bearing surface 9. A lower surface 11 of lower end cap 2 bears against thrust surface 9 so that hub 1 and shaft 128 may rotate with respect to the lost motion clutch assembly. Hub 1 provides the benefit of having a relatively large diameter bearing surface 9 without requiring a corresponding large shaft diameter below the bearing surface 9. The machine is assembled by fitting the spin basket over the drive shaft. Hub 1 is then engaged over the shaft 128, and the drive member and other lost motion clutch components are engaged over the shaft via hub 1.

The bearing surface 9 is sloped at an angle to the axis of the drive shaft. The sloped bearing surface provides a greater thrust surface area for a given diameter and improves strength with increased cross sectional area. Additionally, the sloped surface assists with alignment of the spin basket.

The upper end cap 7 has at least one radial shoulder or tooth 17, which bears against a corresponding radial shoulder or tooth 18 on an upper surface of the drive member 2. The at least one pair of radial shoulders 17, 18 provide an end condition for rotation of the drive member, as the drive member moves axially in the upwards direction. The radial shoulders 17, 18 limit the relative rotational movement of the drive member. Similarly, the lower end cap 2 has at least one radial shoulder or tooth 15, which bears against a corresponding radial shoulder or tooth 16 on a lower surface of the drive member 2. The at least one pair of radial shoulders 15, 16 provide an end condition for the drive member, as the drive member moves axially in the downwards direction. The radial shoulders 15, 16 limit the relative rotational movement of the drive member.

Preferably each end cap and corresponding surface of the drive member has multiple radial shoulders. Preferably each end cap and corresponding surface of the drive member has at least three radial shoulders or teeth. The shoulders are positioned relative to the threads so that the end conditions are reached before the drive member 2 axially thrusts onto an end cap.

A mounting member 6 is used to couple the lost motion clutch assembly housing 4 to the upper surface of the spin basket 322. In the preferred embodiment, mounting member 6 is a separate component from the housing 4. Housing 4 has a fixed flange 25 at a lower end of the housing. A series of radial dogs 26 are attached to the fixed flange and spaced around the circumference of the housing. Mounting member 6 fits over the housing and housing fixed flange 25, the housing being axially retained by and rotationally moveable with-respect-to the mounting member.. ._. Mounting member 6 is secured to an upper surface of the spin basket base. Mounting member 6 is rotationally locked to the spin basket. The lock may be provided by radial dogs 27 fitting into corresponding recesses in the upper surface of the spin basket. Fixings such as screws secure the mounting member 6 to the spin basket base via fixing holes 28.

The mounting member 6 has an annular ring section 31, and a top section 30. The internal diameter of the top section 30 corresponds to the outside diameter of the housing 4. The internal diameter of the ring section 30 corresponds to the outside diameter of the fixed flange 25 of the housing 4. The top section 30 of mounting member 6 captures the fixed flange 25 and external radial dogs 26 of housing 4, locating the lost motion clutch assembly axially with bearing surface 11 of end cap 2 bearing against bearing surface 9 of hub 1.

Mounting member 6 has a series o£ internal radial dogs 29 on the inside surface of the top section 30 and spaced around the circumference of the internal diameter of the ring section 31.

A resilient buffer 5 comprises a series of radial buffer elements 32 spaced apart around a circumference. The outside diameter of the buffer 5 corresponds to the inside diameter of the ring section 31 of mounting member 6. An inside diameter of the buffer 5 corresponds to the outside • diameter of the housing 4. ^. .^{. ■}

The fixed flange 25 and outside diameter of housing 4 form an annular cavity with ring section 31 and top section 30 of mounting member 6. The buffer 5 is enclosed within the annular cavity. Each radial buffer element 32 is interspaced between a corresponding internal radial dog 29 of mounting member 6 and an external radial dog 26 of housing 4. The number of internal radial dogs 29 is equal to the number of external radial dogs 26. The number of radial buffer elements 32 is equal to the sum- of the internal radial dogs and external radial dogs. In the preferred embodiment there are six internal radial dogs 29 and six external radial dogs 26, and twelve radial buffer elements 32, but the particular number is not essential.

As described above, each radial buffer element 32 is sandwiched between a corresponding internal radial dog 29 and an external radial dog 26. The buffer elements 32 engage the mounting member 6 and the housing 4 via the internal radial dogs 29 and external radial dogs 26 firmly together so that there is no significant relative rotation between mounting member 6 and housing 4. However, when drive member 3 reaches an end condition, the impact of the collision between radial shoulders 15 and 16, or the impact of the collision between radial shoulders 17 and 18, is cushioned by relative rotational movement between mounting member 6 and housing 4 due to elastic compression of radial buffer elements 32.

Radial buffer elements 32 each may be separate components or may be grouped as components. However, in the preferred embodiment, each radial buffer element 32 is connected to an adjacent buffer element 32 via an upper connection element 33 and a lower connection element 34, the series of alternating buffer elements 32 and upper and lower connection elements 33, 34 forming the resilient buffer component 5.

A notch 35 is provided at the distal corner of each external radial dog 26 of housing 4, and a notch 36 is provided at the distal corner of each internal radial dog 29 of mounting member 6. Notch 35 of each external dog 26 aligns with a corresponding upper connection element 33 of resilient buffer 5. Similarly, notch 36 of each internal dog 29 aligns with a corresponding lower connection element 34 of resilient buffer 5.

The resilient elastic buffer engaged between the mounting member and the housing reduces impact at the end conditions by cushioning or slowing a change in relative rotational movement between the mounting member and the housing once the relative movement of the housing and the drive member reaches an end condition.

The arrangement includes mounting member 6 and housing 4 to allow a resilient buffer" 5 (or a plurality of resilient elements 32) to be located at one position axially within the lost motion clutch assembly, as opposed to having resilient buffers positioned at more than one location axially (for example at each end condition). The lost motion clutch assembly of the present invention is compact, an important requirement for including inside the tub of the laundry machine. Specifically, the lost motion clutch assembly of the present invention has a compact height.

End cap 7, housing 4, mounting member 6 and hub 1 may be made from acetyl, and drive member 3 and lower end cap 6 may be made from Nylon. Alternatively, these components may be made from other suitable materials such as glass reinforced plastics, metal or sintered metal parts. Resilient buffer 5 may be made from silicone, rubber or a polyurethane.

In the preferred embodiment, the thread turn direction of the screw is chosen so that a worst case impact condition occurs with the drive member 3 at the lower end condition. The lower end of the lost motion clutch assembly is more robust compared to the upper end of the lost motion clutch assembly due to the additional support provided by the spin basket 322, -the shaft 128 and the hub 1. It is therefore desirable for the worst case loading condition to occur at the end condition at the lower end cap.

An example of the worst case loading condition is the loading condition caused by relative rotation between the spin basket and the shaft/agitator at the end of a high speed dewatering spin cycle.

In the preferred embodiment, the drive assembly is rotated continuously in one direction to spin the spin basket during a high speed dewatering spin operation. In the preferred embodiment, the screw thread direction is chosen so that the drive member is at the upper end condition, at the upper end cap 7, during the high speed spin operation.

At the end of the spin operation, when braking starts, the shaft rotation slows relative to the spin basket rotation and the drive member transverses from the upper end condition to the lower end condition. As the drive member hits the lower end condition, this creates a rapid relative movement between the spin basket and the agitator/ shaft. Preferably this rapid relative movement, the worst case loading condition, occurs at the lower end condition and not the upper end condition.

For the embodiment illustrated, the drive member 3 has an external thread turn direction that moves the drive member downwards when the agitator/ shaft turns in a first direction (for example clockwise) relative to the spin basket. For the high speed spin operation, the agitator/shaft preferably should rotate in the opposite direction (anti-clockwise).

The lost motion clutch of the present invention may be implemented with any combination of the embodiments described. For example, one embodiment may include a resilient buffer between the mounting member and the housing, and a resilient buffer at each end condition.

Typical agitator motion during the agitation mode is between 0.5 and 1.5 revolutions. So the increased (typically two or more) revolutions provided by the clutch of the present invention will generally be sufficient to absorb the agitation movement of the drive shaft without engaging to drive the wash basket at the end of each stroke. . .

In the preferred electronically commutated drive system an upper limit can be applied to the agitator motion, for example an upper limit of 2 revolutions. However there may be a directional bias in the relative movement between the agitator and the wash basket. The wash basket will tend to be dragged by the action of the wash load acting as a viscous clutch between the wash plate and wash basket. This dragging action will tend to be compensated by a coast of the spin basket at the end of an agitation stroke. However a residual movement of up to about 20 degrees is observed. In any wash cycle or random part of a wash cycle the residual movement may exhibit a bias in one direction. This will result in the reciprocating agitation stroke operating further toward one end of the range of movement between end conditions. Eventually, and perhaps frequently under some conditions, the clutch will reach .an end condition at the end of an agitator stroke. Thus at the end of occasional strokes the spin basket may be driven momentarily by the clutch at the end of the stroke.

In the preferred electronically commutated drive system we propose to detect any such occasional end condition and to terminate the drive of motor in that agitation stroke as soon as the collision is detected. It is possible for the microcontroller to monitor the load on the motor with reasonable accuracy and frequency by monitoring, for example, the motor current. The end condition may be detected by an increase in the motor load.

Further, in the preferred electronically commutated drive system we propose to detect any directional bias in the residual rotation of the spin basket. For example we may detect a difference in the motor load while driving the agitator in one direction compared to the other direction, and assume that this indicates greater dragging of the spin basket in the higher load direction. Or, for example, we may detect greater load at the point of reversal of the drive direction, which may indicating that the spin basket is coasting for longer into the new stroke direction. The respective agitator stroke lengths may then be adjusted to try to reduce this bias and preferably to reverse the estimated accumulated relative creep in one direction. Alternatively we may include a rotational position sensor for the spin basket, such as a once per rotation sensor, and use this to monitor the position (in full rotations) of the spin basket relative to the position (in full rotations) of the agitator (motor).

The clutch construction described is constructed so that the impact at the end condition is already reduced.

However additional measures could be taken. For example a friction clutch engagement could be included in one of the clutch components to provide a slippable engagement to the respective support part (the spin tub or the drive assembly). This is less preferred as the absorbed energy is dissipated as heat. It is expected that with the range of movement available and the control available in the electronically controlled drive system any pick up at the end condition will be relatively light, and so an elastic shock absorber that returns energy to the system should be sufficient to absorb the impact.

The lost motion clutch of the present invention could be adapted to replace one or both of the bearings 318 supporting the spin basket on the shaft. However typically the threaded engagement of the hub and drive member may be too loose and allow an additional undesirable level of play of the basket on the shaft.

The arrangement of elements in the lost motion clutch could be reversed, so that the thread could be provided between the shaft and the drive member and the spline between the drive member and the hub. Alternatively, if the basket is intended to move axially, the drive member could be dispensed with, and the internal thread of the hub could ride direcdy on a screw thread formed on the shaft.

The drive arrangement according to the present invention allows driving of the agitator through long strokes in alternate directions with a simple, compact and self contained mechanism.

The control system also operates to avoid excessive stress on the end travel components of the clutch during the spin functions of the wash cycle. Excessive stress occurs when there is sufficient relative motion between the shaft and the spin tub combined widi motor torque and spin tub inertia.

The control system will limit the rate of change of acceleration that occurs during the velocity time profile of the spin process in order to limit the relative rotational velocity between the shaft and the spin basket. This is especially important at the transition from a relatively steady spin speed to deceleration at the end of a spin cycle.

Claims

1. A laundry machine comprising: a tub, a spin basket in the tub, a drive assembly comprising a motor, a shaft and an agitator, the motor driving the shaft, the shaft passing through a wall of the spin basket, the agitator being located within the spin basket, a lost motion clutch interconnecting between the drive assembly and die spin basket and absorbing greater dian one revolution of relative rotation; the lost motion clutch including an interface between a first member and a second member, the interface converting relative rotational movement between the first and second member to relative axial movement, at least one first pair of butting surfaces which stop relative movement between the first member and die second member continuing beyond a first end condition under relative rotation in a first direction and at least one second pair of butting surfaces which stop relative movement between the first member and the second member continuing beyond a second end condition under relative rotation in a second direction, the end conditions defining a maximum relative travel, the maximum relative travel permitting greater than one relative rotation.

2. A laundry machine as claimed in claim 1 wherein die first member is coupled to, or is, the spin basket and die second member is coupled to, or is, the shaft.

3. A laundry machine as claimed in claim 1 wherein the first member is coupled to, or is, die spin basket or the shaft, and die second member is slidably and non-rotatably coupled to die other of the spin basket or the shaft.

4. A laundry machine as claimed in claim 3 wherein the second member rides up and down on a spline on die shaft.

5. A laundry machine as claimed in claim 1 wherein the first member is coupled to, or is, die spin basket or die shaft, and the second member is slidably and non-rotatably coupled to a diird member, the third member being fixed or coupled to die other of the spin basket or die shaft.

6. A laundry machine as claimed in claim 5 wherein die third member includes a first bearing surface and a bottom end of the first member has a corresponding second bearing surface, die first and second bearing surfaces supporting the first member axially and allowing relative rotation between the first member and the third member.

7. A laundry machine as claimed in claim 6 wherein the first and second bearing surfaces are sloped.

8. A laundry machine as claimed in any one of claims 1 to 7 wherein the interface is a screw.

9. A laundry machine as claimed in claim 8 wherein the screw comprises an internal trapezoidal thread on one of said first or second members and an external trapezoidal thread on the other said first or second member.

10. A laundry machine as claimed in any one of claims 8 to 9 wherein one of the first or second members is substantially shorter in the axial direction than the other first or second member.

11. A laundry machine as claimed in claim 10 wherein the second member is substantially axially shorter than the first member.

12. A laundry machine as claimed in any one of claims 1 to 11 wherein at least one of the pairs of butting surfaces act to stop relative rotation.

13. A laundry machine as claimed in claim 12 wherein at least one of the pairs of butting surfaces is a blind end of the screw.

14. A laundry machine as claimed in 12 wherein at least one end of the housing includes a first set of radial teeth protruding into an inner chamber, with the second member having a corresponding second- set of radial teeth, the first set and second set of teem providing a plurality of pairs of radial butting surfaces, the pairs of radial butting surfaces arranged to stop relative rotation between the housing and the second member.

15. A laundry machine as claimed in claim 12 wherein at least one end of the housing includes a lug protruding into an inner chamber and acting as a said butting surface.

16. A laundry machine as claimed in any one of claims 1 to 11 wherein at least one of the pairs of butting surfaces act to stop relative rotation by limiting axial movement.

17. A laundry machine as claimed in any one of claims 1 to 16 including an elastic buffer slowing the relative rotational or axial movement as the relative movement reaches a said end condition.

18. A laundry machine as claimed in any one of claims 1 to 16 including an elastic buffer at each said end condition slowing die relative rotational or axial movement as the relative movement reaches each said end condition.

19. A laundry machine as claimed in any ^'one of claims 1 to 18 wherein the first member comprises a housing coupled to die spin basket, die second member is engaged over the shaft, and ends of die housing enclose and/or retain the second member.

20. A laundry machine as claimed in claim 19 wherein at least one end o£ the housing is a separate part being rotationally fixed and axially fixed to the housing.

21. A laundry machine as claimed in claims 1 to 20 wherein the first member comprises a housing and a mounting member, the housing being axially retained by and rotationally moveable with-respect-to the mounting member, die mounting member being fixed to the spin basket, the housing interfacing widi and enclosing and/or retaining the second member, the second member being engaged over the shaft, and at least one elastic buffer engaged between the mounting member and the housing to slow relative rotational movement between the mounting member and the housing once the relative movement of the housing and die second member reaches an end condition.

22. A laundry machine as claimed in claim 21 wherein die amount of relative rotational movement between die housing and die mounting member is a small fraction of the amount of relative rotational movement between the housing and die second member.

23. A laundry machine as claimed in claim 22 wherein there is substantially no relative rotational movement between the housing and die mounting member except for elastic compression of die elastic buffer.

24. A laundry machine as claimed in any one of claims 8 to 23 wherein the screw is a multi- start thread.

25. A laundry machine as claimed in any one of claims 8 to 24 wherein the at least one first pair of butting surfaces is adjacent an upper end of the first member and the at least one second pair of butting surfaces is adjacent a lower end of the first member, the screw having a thread turn direction so that the at least one second pair of butting surfaces butt together in a worst case loading condition.

26. A laundry machine as claimed in any one of claims 1 to 25 wherein the drive assembly, but for the lost motion clutch, would be free to rotate relative to the spin basket.

27. A laundry machine as claimed in any one of claims 1 to 26 wherein the spin basket is supported for rotation at a fixed axial position on the shaft.

28. A laundry machine as claimed in any one of claims 1 to 27 wherein the shaft rotates around a vertical axis, and the tub and the spin basket are accessible through a top opening'. "

29. A laundry machine as claimed in claim 28 wherein the shaft of the drive assembly protrudes from below a base portion of the tub, a stator of the electric motor is fixed to the spin basket, and a rotor of the electric motor is fixed to the shaft.

30. A laundry machine as claimed claim 29 wherein the motor is of the external rotor type.

31. A laundry machine as claimed in any one of claims 1 to 30 including a power supply circuit connected with windings of the motor, and a microcomputer having outputs connected to die power supply circuit for controlling the application of power to the windings of the motor, the microcomputer being programmed to drive the drive assembly in at least a first mode involving strokes of short duration in alternate directions, and a second mode involving continuous running for many revolutions in the same direction.

32. A laundry machine as claimed in claim 31, wherein the screw has a diread turn direction that moves the second member downwards when the microcontroller drives die agitator/shaft in a first direction relative to the spin basket, the microcomputer being programmed to drive the motor to spin the spin basket in a direction opposite to the first direction during the second mode.

33. A laundry machine as claimed in claim 32 wherein the microcomputer is programmed to limit the angular rotation of any single agitation stroke of the drive assembly to be less than about 2 revolutions.

34. A laundry machine as claimed in either claim 32 or claim 33 wherein the microcomputer is programmed to detect any occasional end condition that occurs during agitation and to terminate the drive of motor in that agitation stroke as soon as the collision is detected.

35. A laundry machine as claimed in claim 34 wherein the microcomputer is programmed to monitor the load on the motor and detect the end condition by an increase in the motor load.

36. A laundry machine as claimed in any one of claims 32 to 35 wherein the microcomputer is programmed to detect any directional bias in any residual rotation of the spin basket during agitation.

37. A laundry machine as claimed in claim 36 wherein the microcomputer is programmed to adjust the respective agitator stroke lengths to try to reduce the bias and preferably to reverse the estimated accumulated relative creep in one direction.

38. A laundry machine as claimed in any one of claims 1 - 37 wherein the maximum relative travel between the first member and the second member is greater than 2 revolutions.

39. A laundry machine substantially as here in described in reference to and as illustrated by the accompanying drawings.