GB2060795A - Automatic reversing gearing - Google Patents

Abstract

An automatic reversing mechanism, more especially for a washing machine or a tumbler dryer, has a rotary input shaft 3, a rotary output pulley 2, an epicyclic gear system interconnecting the input and output members, and first and second brake bands 15, 16 for inhibiting the movement of respective ring gears 6, 9 of the gear system for causing the output member to rotate in one or other direction. A pair of cams 56, 57 actuate the braking means alternately, the cams being rotated stepwise at a rate dependent upon but only a fraction of the speed of rotation of the input member by a lever 65 one end of which is mounted on shaft 3 by way of an eccentric and the other end of which acts on a ratchet disc 59 which rotates the cams. <IMAGE>

Description

SPECIFICATION Automatic reversing mechanism This invention relates to automatic reversing mechanisms, of the kind in which a member is required to be rotated alternately in opposite directions, and is more espeically, though not exclusively, concerned with such mechanisms for use in washing machines and tumbler dryers.

Thus one form of clothes washing machine incorporates a perforated drum mounted within an outer vessel capable of containing a quantity of washing liquid, the drum being arranged to be rotated alternately in opposite directions, usually about a generally horizontal axis, to produce a relative movement between clothes contained within the drum and the washing liquid. In another form of clothes washing machine the washing action is obtained by means of an agitator which is reversibly rotatable about an axis inclined at a substantial axis to the horizontal, usually vertical.

One object of the present invention is to provide an automatic reversing mechanism suitable for producing the reversing movement of the washing member, whether it be a perforated drum or an agitator, in a clothes washing machine, although the invention also has application to tumbler dryers and other forms of apparatus incorporating a member required to be reversibly driven, as will be apparent from the following description.

According to the invention an automatic reversing mechanism comprises a rotary input member carried by a drive shaft, a rotary output member, an epicyclic gear system interconnecting the input and output members, first and second braking means capable of inhibiting the movement of respective gears to the gear system to cause the output member to rotate in one or the other direction, a pair of cams for actuating the braking means alternately, and means for producing a stepped rotation of the cams at a rate dependent upon, but only a fraction of the speed of rotation of, the input member.

For producing the stepped rotation of the cams there is conveniently provided a ratchet disc and an associated operating lever actuated by an eccentric in a manner which produces an indexing movement of the cams, the latter, which are conveniently mounted on a common spindle, having alternate high and low dwells for producing actuation and release of the respective braking means, with the high and low dwells of the two cams angularly displaced, to cause the braking means to be actuated alternately.

Preferably the end of the lever remote from the ratchet disc is eccentrically but pivotally coupled to a rotatable member incorporating a ring gear, and within this ring gear there is located a further gear having a smaller number of teeth than the ring gear, the centre of the further gear being traversable about a circular path of diameter such that the teeth of this gear remain in mesh with those of the ring gear but without the further gear being rotated about its centre, so that with each cycle of movement of said further gear the ring gear is rotated an angular distance corresponding to the difference between the number of teeth of the ring gear and the further gear.Such an arrangement can thus be used to reduce considerably the rate of rotation of the ring gear, and consequently of the cams actuating the braking means, compared with the angular speed at which the centre of said further gear is traversed about said circular path. This is particularly advantageous where the latter is pivotally carried by an eccentric fixed to, so as to rotate with, the drive shaft. Moreover it will be seen that by altering the ratio of the number of teeth on the ring gear and the further gear the nature and period of reversal can be varied over a very wide range. The ring gear and further gear can be replaced, if desired, by a roller friction drive, operating in a similar manner.

Conveniently the epicyclic gear system includes a planetary gear system carried by a support, which constitutes the output member, the support being rotatable about the axis of a further gear which is carried by a drive shaft and which constitutes the input member, and the planetary gear system coupling the input gear to first and second ring gears, the braking means being arranged to inhibit the movement of one or other of the ring gears, and the gear system being such that the support is caused to rotate in one or other direction depending upon which of the ring gears is acted upon by the braking system.

Conveniently in such an arrangement the cams which act on the braking means are shaped so that, at least in one position, both braking means are released simulataneously and held in the release position to allow both ring gears to rotate freely, so that the output member is no longer driven reversibly through the planetary gear system, and this is preferably arranged to take place automatically if the drive shaft is rotated in the reverse direction.

In such an arrangement there is preferably provided a unidirectional clutch between the drive shaft and the support which is normally inoperative, but is brought into operation when the shaft is rotated in the reverse direction, to impart a direct unidirectional drive to the support.

This arrangement is particularly applicable to washing machines where a washing member is required to be rotated alternately in opposite directions for producing an agitation of clothes in the presence of a washing liquid, and a perforated drum is required to be rotated unidirectionally at high speed following a washing operation for the extraction of moisture from the clothes.

In order to ensure that the cams are correctly positioned to release both braking means when the drive shaft is rotated in the reverse direction, a tooth of the ratchet disc is conveniently formed so that in an appropriate position of the disc corresponding to that in which both braking means are released by the respective cams the operating lever is capable of being moved, on rotation of the drive shaft in said reverse direction, without imparting any drive to the disc.

A periodic reversal arrangement in accordance with the invention designed for use in a washing machine drive will now be described, by way of example, with reference to Figures 1 to 6 of the accompanying drawings in which, Figure 1 shows a sectional elevation of the periodic reversal arrangement, Figure 2 illustrates an exploded isometric view of the arrangment, Figures 3a to 3e and Figures 4a and 4b show a series of movements of part of the periodic reversal arrangement as it progresses through a cycle of changes, Figures 5a and 5c illustrate part of the driving mechanism assocaited with the arrangement, and Figures 6a to 6d show the alternate operation of brakes forming part of the arrangement.

Referring to Figures 1 and 2, the reversible drive for the washing member of a washing machine is supported by a housing H includes a driving motor M a planetary gear system P, a periodic reversal arrangement R, and an output pulley L capable of being reversibly driven by the gear system, but which may alternatively be driven unidirectionally through a centrifugal clutch C as will subsequently be described.

The planetary gear system P is described in detail in our'co-pending patent application No.

and consists essentially of a pair of independently rotatable ring gears 6,9 #coaxial with the shaft 3 of the driving motor M, an input gear 2 fixed to the shaft, and two planet gear trains (shown only in part at 1) carried by a support 11 rotatable about the shaft 3, and fixed to the output pulley L, the gear trains engaging the input gear 2 and a respective one of the ring gears 6, 9, and being such that alternate braking of the ring gears, as by band brakes 15, 16 as will subsequently be described, causes the support 11 and hence the output pulley L to rotate alternately in opposite directions at a relatively low speed.The motor M is a reversible induction motor having a cooling fan F, and actuation of the band brakes 1 5, 1 6 to produce periodic reversal of the support 11 and output pulley L is brought about by the reversing arrangement R when the motor operates in one direction, whereas rotation of the motor in the opposite direction causes the pulley to take up a direct drive from the motor M via a unidirectional clutch 43 and the centrifugal clutch C to give the same high speed as the motor shaft.

Thus the unidirectional clutch 43, which is provided by a spring around the shaft 3 couples the shaft to the centrifugal clutch on rotation of the motor in said opposite direction, thereby driving the pulley L when the speed of rotation is sufficient to operate the centrifugal clutch; however when the motor rotates in said one direction the spring slips relative to the shaft 3 so that the latter does not then drive the pulley L directly.

Drive from the pulley L to the washing member of the machine, which may be a perforated drum or an agitator, but which has not been illustrated as it does not form part of the present invention, is by means of a belt B. Thus the washing member is reversibly rotated at one speed in one direction of rotation of the motor, whereas rotation of the motor in the other direction causes the drum to be driven at a higher speed to effect centrifugal extraction of moisture from the clothes contained within it.In the case where the machine has an agitator, the pulley L is conveniently coupled by said belt B to a further pulley on the agitator shaft, and the drum is coupled to the shaft by means of a coupling which permits the agitator to be reversibly rotated by a required amount without producing any positive drive on the drum when the motor is driven in said one direction, but which causes both the drum and the agitator to be driven at high speed on unidirectional rotation of the shaft, when the motor is driven in the opposite direction. Such an arrangement is described in detail in our co-pending patent application No.

25241/77.

The function of the periodic reversal arrangement will now be described and additional referece will be made to Figures 3a to 3e, 4a and 4b, 5a to 5c, and 6a to 6d.

The purpose of the periodic reversal arrangement, which operates in conjunction with the plantary gear system, is to effect the regular reversal of the mechanism when driven in one direction, and to provide suspension of the reversal operation, and allow the unidirectional drive to be achieved, when driven in the-opposite direction. The former requires regular alternate application and release of the brake bands 1 5 and 16 when the mechanism is driven in said one direction, whereas the latter requires release of both bands at the same time. The rate at which reversal takes place is capable of being varied to suit the application, e.g.; the oscillation of agitator or the periodic reversal of washing drum as the case may be, and to effect the required speed rate a suitable reduction drive, for example a harmonic drive, is provided from the motor shaft 3.

In more detail two brake actuators 50 and 51 for applying or releasing each of the brake bands 15 and 16 are freely pivoted about a shaft 52 held within the housing H to one end of which the motor M is attached. One end of each of the bands 1 S, 1 5 is secured to the housing H-and the other end is attached to the respective actuator SO, 51, by adjustable spring-loaded fixing screws 58 (Fig.

6a,6b). A cross plate 54, which carries one end of the shaft 52, also serves to support a second shaft 55 to which are attached two brake actuator cams 56 and 57 arranged to engage the tops 50a and 51 a of the actuators, so as to cause them to pivot to either of two positions in which the brake bands 1 #, 1 6 are applied or released. Alternate application and release of the two bands is effected by arranging for the high and low portions of the two cams 56, 57 to be angularly displaced.

On one of the cams a single high dwell portion is omitted to permit release of both brakes at the same time, as will be described later.

Also secured to the shaft 55 is a ratchet disc 59 which has a series of upstanding teeth 61 all of similar radial length except one 62, which is shorter. The number and spacing of the teeth is related to the total number and spacing of the high and low dwells of each of the cams so that stepwise rotation of the disc effects alternate operation of the brake bands.

The ratchet disc carries on its outer edge (see Figures 3a to 3e) a series of indents 63 corresponding to the number of teeth and capable of engagement with a spring retainer 64 so as to hold the disc in any one position. Rotation of the ratchet disc 59 is effected by a connecting link 65 pivoted about a fulcrum pin 60 and rotatably connected at one end 65a to an eccentric 74 forming part of a harmonic drive 66 which is itself driven by the motor shaft 3.

The harmonic drive 66 comprises an outer circular member 71 having a series of teeth 72 regularly spaced around an inner concentric wall as shown more clearly in Figures 5a to 5c. The member carries a boss 74 eccentrically positioned and rotatable within a ring bearing 65a at the inner end of the link 65. The member 71 is freely rotatable about the shaft 3 and is driven by an inner circular member 75 which carries on its outer edge a series of teeth 76 similarly shaped to the teeth 72 so as to be capable of engagement with them but different in total number, in this example being four teeth less. The inner member 75 has a central opening fitting around an eccentric 77 which is fixed to, so as to rotate at the same speed as, the motor shaft 3.Movement of the inner member 75 resulting from the rotation of the eccentric 77 is such as to produce a periodic movement of the outer member 71 the degree of movement in one revolution corresponding to the angular distance taken up by the difference in the number of teeth i.e. four.

As illustrated more clearly in Figures 5a to 5c the inner member 75 has local engagement with the outer member 71 and is prevented from rotating by springs 78. This pulsing action provides a more resilient action than would otherwise be possible and the harmonic drive as a whole provides the considerable speed reduction which is required for the present application. Thus the member 71 is rotated in small steps at a rate consdierably lower than the speed of rotation of the motor shaft. In each revolution of the member the eccentric boss 74 causes the inner end of the link 65 to traverse a closed circular path. By virtue of the fulcrum pin 60 and slot 60a the outer end 65b of the link 65 also traverses a somewhat circular path but of smaller diameter.

This outer end 65b of the link carries a transversely arranged pawl 68, pivotably mounted and spring-loaded so as to ensure that the pawl takes up the same position after each operation.

Inter-action between the pawl and the ratchet disc, in a manner to be described in more detail, is such that the path described by the outer end 65b of the link and hence the pawl in one mode of operation is such that the lower part 68a of the pawl engages with and draws towards it a tooth 61 on the ratchet disc, causing the disc to rotate to the extent of one tooth space. The radial position of engagement between pawl and troth is such that movement of the disc is achieved even with the shorter tooth 62.However whereas on reversal of the motor and hence the locus of the paw - that is in the other mode of operation ~similar movement of the teeth 61 is achieved, no engagement with tooth 62 is possible and the ratchet disc at that point remains stationary, the pawl continuing to describe its reverse locus as long as the motor continues in the reverse direction. In this position of the ratchet disc, the cams 56, 57 have released both brake bands 15, 16.

Thus in a typical series of operations, as determined by the programme controller of the washing machine, rotation of the motor in a clockwise direction (as viewed at the motor end) effects similar movement of the inner member 75 of the harmonic drive giving intermittent rotary movement of the inner end of the connecting link 65 as it moves in a circular path in relation to the outer member 71. A somewhat similar locus is described by the outer end of the link and transmitted to the pawl 68. Engagement between the pawl 68 and the ratchet disc 59 as the pawl traverses a generally circular path is depicted in Figures 3a to 3e each of these figures representing one step forward in the rotation of the ratchet disc.Apart from showing the exact position of the pawl as it moves the ratchet disc the respective position of the spring-loaded retainer 64 can be seen; in the retained positions, i.e. Figures 3a to 3c, the pawl is free to move into its engaging position without baulking by any undue movement of the disc. In particular the drawings illustrate that the pawl engages with the outer portion of the teeth 61 and hence with the shortened tooth 62. However, referring to Figures 4a and 4b which illustrate reverse movement of the pawl, as produced by reversal of the motor direction, engagement with the inner portion of the tooth is effected and hence no rotation of the ratchet disc can take place when the shortened tooth reaches the position of normal engagement, the pawl merely riding over the tooth as it traverses its (reversed) generally circular path.

Thus, whereas clockwise rotation of the motor shaft effects a continuous reversing action of the output pulley, reversal of the motor once it has moved the ratchet disc to its 'neutral' position, as described above, ensures that no further movement of the disc and hence the cams 56 and 57 occurs. it is in this position that the cam 57 having an omitted high dwell is in such a position as to ensure that its brake band 16 is released at the same time as the low dwell of the other cam releases the other brake band. With both brake bands released actuation of the planetary gear system cannot occur and since the motor direction has been reversed the spring of the unidirectional clutch 43 tightens up around the shaft 3 and causes it to drive the clutch C, causing the pulley L to rotate and accelerate slowly until it reaches mptor speed and rotates the perforated drum at spin speed.

Although the embodiment just described could have general application to reversing drive mechanisms for both front loader and top loader washing machines it has particular application to the latter in which the low speed reversing drive provides the required oscillatory movement of the agitator, for example 72 operations per minute with an angular movement of agitator of some 2100. The perforated clothes containing drum together with the agitator can be arranged to be driven unidirectionally at about 1000 revs/min.To achieve this requirement a 2 pole induction motor having a shaft speed of 2850 revs/min is used for the driving mechanism which has a reduced speed output at the pulley L during a washing operation of 270 revs/min, with a further step down pulley ratio between the pulley and that on the agitator, Such application can make use of the single shaft coupling arrangement as described in copending patent application No. 25241/79 for providing a convenient form of drive between the driving mechanism and the agitator and drum in which the drive can act independently for the agitator or in unison for agitator and drum.

Where it is required to make sue of the reversing drive mechanism in a front loading washing machine, i.e. in which the drum is arranged to be rotated alternately in opposite directions about a generally horizontal axis then simply by providing alternative cams each having a high dwell of 1 500 and having a lower ratchet disc speed effected by changing the harmonicgear ratio an extended period of rotation in each direction (as compared with the agitator movement) can ensue. Such an arrangement would also allow a pause between reversals of rotation, this pause corresponding for example to 300 of movement of the cams. The same motor is used to achieve this 2 speed requirement and the higher drum speed, the output pulley rotating at 270 revs/min and the ratchet disc at 20 revs/min.

A similar driving arrangement may be used for a reversing tumbler dryer, such application not requiring reversal of the motor since the high speed spin facility will not be needed.

Moreover a reversing drive arrangement in accordance with the invention may be utilised in other applications where a member is required to be periodically reversed.

A reversing mechanism in accordance with the invention permits the use of a high-speed lowtorque drive which enables relatively light gears for example of an engineering plastics material, to be used in the gear mechanism, which has the advantage over reversing mechanisms requiring a low-speed high-torque drive used in existing forms of washing machines which require more expensive and heavier steel gears.

Claims (10)

1. An automatic reversing mechanism comprising a rotary input member carried by a drive shaft, a rotary output member, an epicyclic gear system interconnecting the input and output members, first and second braking means capable of inhibiting the movement of respective gears of the gear system to cause the output member to rotate in one or the other direction, a pair of cams for actuating the braking means alternately, and means for producing a stepped rotation of the cams at a rate dependent upon, but only a fraction of the speed of rotation of, the input member.

2. An automatic reversing mechanism according to Claim 1 including a ratchet disc and an associated operating lever actuated by an eccentric in a manner which produces an indexing movement of the cams, and in which the cams have alternate high and low dwells for producing actuation and release of the respective braking means.

3. An automatic reversing mechanism according to Claim 2 wherein the cams are mounted on a common spindle and the high and low dwells of the cams are angularly displaced to produce the alternate actuation of the braking means.

4. An automatic reversing mechanism according to Claim 2 or 3 wherein the end of the lever remote from the ratchet disc is eccentrically but pivotally coupled to a rotatable member incorporating a ring gear, and within this ring gear there is located a further gear having a smaller number of teeth than the ring gear, the centre of the further gear being traversable about a circular path of diameter such that the teeth of this gear remain in mesh with those of the ring gear but without the further gear being rotated about its centre, so that with each cycle of movement of said further gear the ring gear is rotated an angular distance corresponding to the difference between the number of teeth of the ring gear and the further gear.

5. An automatic reversing mechanism according to any one of Claims 2 to 4 wherein the epicyclic gear system includes a planetary gear system carried by a support, which constitutes the output member, the support being rotatable about the axis of a further gear which is carried by a drive shaft and which constitutes the input member, and the planetary gear system coupling the input gear to first and second ring gears, the braking means being arranged to inhibit the movement of one or other of the ring gears, and the gear system being such that the support is caused to rotate in one or other direction depending upon which of the ring gears is acted upon by the braking means.

6. An automatic reversing mechanism according to Claim 5 wherein the cams which act on the braking means are shaped so that, at least in one position, both braking means are released simultaneously and held in the release position to allow both ring gears to rotate freely, so that the support is no longer driven reversibly through the planetary gear system and the mechanism includes a unidirectional clutch between the drive shaft and the support which is normally inoperative, but is brought into operation when the shaft is rotated in the reverse direction, to impart a direct unidirectional drive to the support.

7. An automatic reversing mechanism according to Claim 6 wherein a tooth of the ratchet disc is formed so that in an appropirate position of the disc corresponding to that in which both braking means are released by the respective cams the operating lever is capable of being moved, on rotation of the drive shaft in said reverse direction, without imparting any drive to the disc.

8. An automatic reversing mechanism substantially as shown in and as hereinbefore described with reference to Figures 1 to 6 of the accompanying drawings.

9. A washing machine incorporating an automatic reversing mechanism according to any preceding claim.

10. A tumbler dryer incorporating an automatic reversing mechanism according to any one of Claims 1 to 5.