AU630788B2

AU630788B2 - Clutch/brake drive unit

Info

Publication number: AU630788B2
Application number: AU71239/91A
Authority: AU
Inventors: Phillip Michael Brien
Original assignee: Hoover Australia Pty Ltd
Current assignee: Hoover Australia Pty Ltd
Priority date: 1990-02-23
Filing date: 1991-02-20
Publication date: 1992-11-05
Anticipated expiration: 2011-02-20
Also published as: AU7123991A

Description

To THE COMMISSIONER OF PATENTS.

SHELSTON WATERS PATENT ATTORNEYS CLARENCE STREET, SYDNEY

AUSTRALIA

Cables: 'Valid' Svdnev Tel.- .24422 qw..ln I -A- L. 'FC I I I 1

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630788 COMMONWEALTH OF AUSTRALIA FORM PATENTS ACT 1952 Cr M T, F T F. ~PECIFICATION C 0 MP L T E S P r TF T A TT 0 FOR OFFICE USE: Class Int.Class Application Number: Lodged: mplete Specification Lodged: 0..*Cbmplete Specification Lodged: 0 0 o o 09 0 o o Rriority: 0 0 Related Art: os Accepted: Published: Name of Applicant: eo4 it 9 0 .Address of Applicant: a 0 9 Actual Inventor: Actual Inventor: HOOVER (AUSTRALIA) PTY LTD BELMORE STREET MEADOWBANK NSW 2114 PHILLIP MICHAEL BRIEN .*°"Address for Service: SHELSTON WATERS, 55 Clarence Street, Sydney 4000o 'tComplete Specification for the Invention entitled: "CLUTCH/BRAKE DRIVE UNIT" The following statement is a full description of this invention, including the best method of performing it known to me/us:- (Complete of PJ8795 dated 23rd February, 1990) 1 i- I C i r .o~O0 o 0o 88 0 o 8 o8oo a a, 8 4 Oda i I Ir 0 I 0* The present invention relates to a combination electro-mechanical clutch/brake drive assembly.

The invention has been developed primarily for use in agitator type washing machines and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

Agitator type washing machines generally comprise a spin bowl rotatably mounted within an outer containment drum supported by a frame. An agitator projects upwardly within the spin bowl and is mounted for oscillatory rotation. A reversible electric motor drives the spin bowl and the agitator in response to signals from a controller according to predetermined washing and spinning cycles in a manner well known to those skilled in the art.

In known machines, a clutch (usually a wrap spring clutch) acts in association with a brake (usually a band type brake) to effect the various agitation and spinning cycles. The clutch is usually disposed intermediate an output drive shaft and the spin bowl to effect a driving connection therebetween during the spin mode. However, in the agitation mode the clutch is usually disengaged and the motor is alternately driven in the forward and reverse directions to drive the agitator in a corresponding oscillatory cycle through a reduction gearbox.

The brake acts to retard the spin bowl at the conclusion of each spinning cycle and to prevent rotation of the spin bowl during the agitation cycle.

2 However, known machines of this type require a relatively large number of moving components which are susceptible to wear and this adversely affects the overall reliability of the machine. Moreover, known devices occupy large amounts of space, are relatively complex in construction, inefficient, noisy in operation, and limited in applicability.

It is therefore an object of the present invention to provide an improved clutch/brake drive unit which will overcome or substantially ameliorate at least some of the above-mentioned shortcomings of the prior art.

Accordingl.y, in a first aspect, the invention provides a washing mrachine including a clutch/brake drive unit, said drive unit comprising a frame, a driving me.11ber and a driven member mounted coaxially for independent relativB rotation with respect to the frame, a clutch including a clutch disc and mutually opposed *00900frictional engagement surfaces respectively associated with the driving member and the driven member, said clutch being selectively engageable to permit the transmission of torque between the driving member and the :K..driven member, a brake including a brake disc and a a..mutually opposed frictional braking surfaces respectively a a associated with the driven member and the frame, said brake being selectively- engageable to retard rotation of the driven member with respect to the frame, and a solenoid disposed intermediate the clutch and the brake such that energisation of the solenoid causes either the -3brake to be released and the clutch to be engaged or the clutch to be released and the brake to be engaged, said washing machine further including a spin bowl connected with the driven member, and an agitator coupled with the driving member.

The annular solenoid preferably includes radially spaced apart concentric inner and outer poles having upper and lower outwardly depending annular pole surfaces respectively adjacent the brake and clutch discs.

Preferably, the drive unit further includes resilient bias means disposed intermediate the brake disc and the frame to urge the mutually opposed braking surfaces axially into frictional engagement when the solenoid is de-energised, to retard rotation of the driven member with respect to the frame. In the preferred configuration, energisation of the solenoid D produces a magnetic field of sufficient strength to overcome the bias force and urge the brake disc axially towards abutting engagement with the upper solenoid pole surfaces, thereby releasing the brake.

Also in the preferred embodiment, the driving member is connected to a pulley disc and the driven member is integral with the clutch disc such that energisation of the solenoid causes the driving member to CC:. be urged axially into frictional engagement with the clutch disc to drivingly conjoin the pulley and the driven member. Resilient bias means may also be provided to urge the pulley disc away from the clutch disc when the solenoid is de-energised. It will be appreciated, however, that 4 driving member could also be directly connected to the output shaft of a motor, for example, without the need for an intermediate belt and pulley assembly.

The arrangement is preferably such that upon energisation of the solenoid, the pulley disc is urged upwardly into abutment with the clutch disc, to form a U-shaped magnetic flux path of increased strength bridging the lower surfaces of the inner and outer solenoid poles.

The resultant magnetic force arising from the increase in ,l0 magnetic flux is then sufficient to overcome the resilient 0 00 bias force actuating the brake. The brake disc is o 0 .o consequently urged downwardly into abutting engagement with the upper solenoid pole surfaces, thereby releasing 0 4 .the brake and bridging the upper solenoid pole surfaces.

This then completes a substantially closed magnetic flux path around the solenoid which reinforces the magnetic **setI attraction between the clutch disc and the pulley. The oo o clutch is thereby engaged more fully to permit increased O torque to be transmitted between the driving and driven members.

The clutch disc, brake disc and solenoid poles are 0 0 preferably formed from a ferromagnetic material having a o 0 high relative permittivity such as iron.

According to a second aspect, the invention consists in a washing machine including a clutch/brake drive unit as hereinbefore described, a spin bowl connected with the driven member and an agitator connected with the driving member.

5 A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1A is a sectional side elevation of a clutch/brake drive unit according to the invention showing the unit in the solenoid energised configuration; Figure lB is a sectional side elevation of the clutch brake drive unit of figure 1A showing the unit in the solenoid de-energised configuration.

o. Referring to the drawings, the clutch/brake drive 00 0 aB unit 1 comprises a frame 2, and a driving member 3 and o 0 e driven member 4 mounted coaxially for independent relative 0 0 rotation with respect to the frame. The driving member 3 o comprises a pulley 5 adapted to be drivingly connected to the output shaft of a reversible electric drive motor (not shown) by means of an intermediate flexible V-belt.

Alternatively, however, the driving member can be o 0 o connected directly to the output shaft of the motor, in 00 D which case intermediate drive pulley 5 is not required.

The drive unit further comprises a clutch disposed between driving member 3 and driven member 4 anl a brake operable to retard rotation of the driven member with respect to the frame.

SClutch assembly 9 includes an annular clutch disc connected to driven member 4. Clutch disc 10 and driving member 3 incorporate complimentary mutually opposed frictional engagement surfaces whereby engagement of the clutch permits transmission of torque between driving member 3 and driven member 4.

6 OIL- i ;i Brake assembly 15 comprises an annular brake disc 16 mounted to frame 2 by means of keys 17 which prevent rotational movement but permit a limited range of axial sliding movement of the brake disc relative to the frame.

An annular rotary carrier plate 18 keyed to driven member 4 and having outwardly depending frictional braking surfaces 19 is disposed between brake disc 16 and bearing cup 21, both of which are fixed with respect to the frame. Braking surfaces 19 can comprise any suitable 0-10 frictional braking material and are preferably in the form of replaceable brake pads 23.

o The drive unit further includes resilient bias means in the form of compression springs 22 effectively disposed intermediate the brake disc and the frame. Upon engagement, brake disc 16 is urged upwardly by compression springs 22, thereby tending to compress rotating carrier plate 18 and urge outwardly depending braking surfaces 19 respectively into frictional engagement with the lower o surface of bearing cup 21 and the upper surface of brake disc 16 to retard rotation of driven member 4 with respect to the frame. By incorporating the carrier plate into the drive unit to provide two frictional interfaces, a greater braking torque will be achieved for a given spring pressure in comparison with a system incorporating only a single frictional interface. It will be appreciated, however, that braking surfaces 19 need not necessarily be mounted to the carrier plate, but could alternatively be mounted to the bearing cup and brake disc respectively.

A torroidal solenoid 25 comprises circumferential 7 srri -~;s'--mfl4#Vflo 0 O Q o 4 0 4 4 4 d 4 44 0 0 4.

44O 4D 444 windings 26, an inner rotating pole 27 connected to the driven member, and an outer stationary pole 28 connected to the frame. Inner and outer poles 27 and 28 are coaxially disposed intermediate clutch assembly 9 and brake assembly 15 such that energisation of solenoid simultaneously causes the brake to be released and the clutch to be engaged in a manner more fully described below.

When incorporated into a conventional agitator type washing machine, driven member 4 is connected directly to the spin bowl (not shown) and gearbox housing 20. The driving member 3 incorporating pulley 5 is selectively coupleable to the agitator (not shown) via reduction gearbox assembly 29. The input of gearbox 29 is connected to drive pulley 5 by means of central drive shaft 30 which supports sun gear 31 forming part of an epicyclic gear train incorporating ring gear 33, planet gears 34 and carrier 35. Ring gear 33 is mounted to the inner periphery of gearbox housing 20, forming part of the driven member. Planet gears 34 are supported by carrier 35 which in turn is splined to agitator shaft 36 to provide the appropriate reduction ratio which is typically of the order of 5 to 1. In one form of the invention, the central drive shaft 30 may be the output drive shaft of the electric motor.

Turning now to describe the operation of the clutch/brake drive unit in a washing machine, when the solenoid coil is de-energised, brake disc 16 is urged au a 0 0 4494 4 o 4>i Oof 8 upwardly into braking engagement with carrier plate 18 by compression springs 22 whereby driven member 4, integral with the spin bowl, is held stationary with respect to the frame. When solenoid 25 is energised, the brake disc is urged downwardly toward upper surfaces 40 of inner and outer solenoid poles 27 and 28 with sufficient force to overcome the bias force of compression springs 22 and thereby release the brake.

Similarly, when the solenoid is energised, pulley t0 disc 5 is attracted upwardly toward lower solenoid pole 0 00 00 0 surfaces 41 and into driving engagement with clutch disc a 0 o 10 with sufficient force to enable torque to be 0 o7 oo, transmitted directly from the drive motor to the spin 00 4 0° 0bowl. When the solenoid is de-energised, pulley 5 is disengaged from clutch disc 10 thereby decoupling the drive pulley from the spin bowl.

Thus, in spin mode, the solenoid is energised whereby 0 0 °o 0 the clutch couples the spin bowl, agitator and drive motor %0 directly and the brake is disengaged. In agitate mode, 0 04 the solenoid de-energised whereby the clutch is disengaged and the motor drives the agitator in an o o* oscillatory cycle indirectly through reduction gearbox 29 whilst the brake is engaged to hold the spin bowl stationary and transmit reaction torque from the gearbox to the frame.

Turning now to specifically describe the operation of the clutch, brake and solenoid in more detail, when solenoid 25 is initially energised, the magnetic flux is -9 weak because of air gaps 43 and 44 (best seen in figure IB) in the flux path respectively adjacent upper 40 and lower 41 surfaces of the solenoid poles. However, the initial magnetic force from the energised solenoid is sufficiently strong to attract drive pulley 5 upwardly

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towards lower pole surfaces 41 and into abutting engagement with clutch disc 10 This engagement then substantially closes air gaps 44 to complete a U-shaped magnetic flux path of considerably increased strength bridging the lower surfaces of the inner and outer 0 0 solenoid poles.

o 0 0 0. The resultant magnetic force arising from the oa,, increased magnetic flux is then sufficient to overcome the

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6 opposing bias force from compression springs 22 and attract brake disc 16 downwardly into abutting engagement with the upper surfaces 40 of the inner and outer solenoid poles and thereby release the brake. Engagement of brake 0o disc 16 with the inner and outer solenoid poles 0 substantially closes air gaps 43 to complete a generally closed magnetic flux path encircling the torroidal solenoid to thereby reinforce the magnetic attraction between clutch disc 10 and drive pulley 5 to permit increased torque to be transmitted between the driving and driven members and thus allow the motor to drive the spin bowl.

The solenoid preferably also incorporates a plurality of spaced apart upwardly protruding intermediate pole 10 portions 50 which correspond to slots 51 in brake disc 16. This configuration causes the magnetic flux to "zig-zag" across the air gap between the brake disc and the inner and outer poles to magnify the magnetic attractio between the brake disc and the slc-noid for a given electrical energy input and thereby increase the electrical efficiency of the unit.

The clutch/brake drive unit according to the present invention requires fewer parts and affords simpler Sa~,l0 assembly and operation than comparable prior art devices, with consequential 5' ases in reliability. Furthermore, 0 o solenoid operating noise is substantially reduced, as are the usual problems associated with conventional wrap 0°0 spring clutch and brake band assemblies. Additionally, power consumption can be reduced and operating efficiency increased. The design may also be applied to "OO'o reciprocating gearbox type washing machines.

°0 °o It will be appreciated that whereas the clutch/brake drive unit of the preferred embodiment is operative upon energisation of the solenoid to release the brake and engage the clutch, it will be appreciated that an o t arrangement in which the effect of the operation of the 0 00 solenoid is reversed, ie. in which energisation of the solenoid engages the brake and releases the clutch, will also fall within the scope of the present invention.

Although the invention has been described with reference to specific examples, it will be appreciated by 11 I F those skilled in the art that the invention may be embodied in many other forms.

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Claims

2. A washing machine according to claim 1, having a S0 spin mode wherein the clutch is engaged to couple the S-spin bowl, the agitator, and the driving member directly with the brake disengaged, and having an agitate mode wherein the clutch is disengaged and the motor drives the agitator in an oscillatory cycle with the brake engaged 13 i 1 de-energised solenoid condition. i to prevent simultaneous rotation of the spin bowlradially spaced apart relative to the frame.ly with the brake and the clutch.
3. A washing machine according to claim 2 wherein the spin mode corresponds to an energised condition of the solenoid and the agitate mode corresponds to a de-energised solenoid condition.
4. A washing machine according to any one of claims 1 energisatto 3 wherein the solenoid includes radially spaced apart substantially concnt streng tric inner and outer poles havingof the theaxially depending generally annular pole surfaces, thereby releasing associated respectively with the brake and the clutch. A washing machine according to any one of claims 16 wherein the to 4, further including first resilient bias means disposed effectively intermediate the brake disc and the frame to urge the mutually opposed braking surfaces energ axially into frictional engagement when the solenoid is de-energised and thereby retard ,ation of the driven member with respect to the frame.
6. A washing machine according to claim 5 wherein energisation of the solenoid produces a magnetic field of oa sufficient strength to overcome a biasing force of the 1o "o first bias means and urge the brake disc axially toward the associated solenoid pole surfaces, thereby releasing the brake. o*o
7. A washing machine according to claim 6 wherein the driving member is connected to a pulley and the driven member is integral with the clutch disc such that energisation of the solenoid causes the driving member to 14 L1 i 2 be urged axially into engagement with the clutch disc thereby to drivingly conjoin the pulley with the driven member.
8. A washing machine according to claim 7 further including second bias means to urge the pulley out of engagement with the clutch disc when the solenoid is de-energised and thereby release the clutch.
9. A washing machine according to claim 8 wherein energisation of the solenoid causes the pulley to be urged axially into abutment with the clutch disc to form a magnetic flux path of generally U-shaped cross section and of increased relative strength bridging the solenoid pole surfaces whereby the resultant magnetic force overcomEn the biasing force to release the brake such that the associated solenoid pole surfaces are bridged by ,I the brake disc, thereby to complete a substantially closed generally torroidal magnetic flux path around the solenoid increasing the torque transmissible through the clutch. A washing machine according to any one of claims 1 o to 9 wherein the solenoid incorporates a plurality of i spaced apart axially protruding intermediate pole portions and the brake disc incorporates a corresponding plurality of slots aligned respectively with the protruding pole portions to induce a generally sinuate magnetic flux path intermediate the solenoid poles and thereby enhance magnetic attraction between the brake disc and the solenoid for a given electric output. 15 such that energisation of the solenoid causes either the 3
11. A washing machine according to any one of claims to 10 wherein said brake includes a rotatable carrier plate incorporating a pair of mutually opposed outwardly depending frictional braking surfaces defining a corresponding pair of frictional interfaces respectively adjacent the brake disc and the frame and disposed intermediate the brake disc and the frame, and wherein said resilient bias means comprises a spring operable on the brake disc, the carrier plate being compressed between the brake disc and the frame upon de-energisation of the solenoid to retard rotation of the driven member with respect to the frame.
12. A washing machine according to any one of the preceding claims wherein the clutch disc, brake disc and solenoid poles are formed from a ferromagnetic material having a high relative permittivity.
13. A washing machine according to claim 12 wherein said ferromagnetic material is iron.
14. A washing machine according to any one of the preceding claims, wherein the driving memeber is selectively coupled to the agitator via a reduction gear box assembly. A washing machine according to claim 14 wherein the input of the gearbox is connected to the driving member by means of a central drive shaft supporting a sun gear forming part of an epicyclic gear train, said gear train fruther including a ring gear mounted to the inner periphery of a gear box housing forming part of the 4 d 4 4. 494 4 444 fr. 4 44 44 16 i. to urge the pulley disc away from the clutch d~isc when the solenoid is de-energised. It will be appreciated, <~V2'\however, that -4- driven member, and a plurality of planet gears supported by a carrier connected to the agitator.
16. A washing machine according to claim 15 wherein said gear box provides a reduction ratio of around 5 to 1.
17. A washing machine incorporating a clutch/brake drive unit, said clutch/brake drive unit substantially as hereinbefore described with reference to the accompanying drawings. DATED this 7th Day of May 1992 HOOVER (AUSTRALIA) PTY LTD Attorney: WILLIAM S. LLOYD Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS *017