GB2061423A - Change-speed gear for a washing machine - Google Patents

Abstract

A drive mechanism, especially for a washing machine, has an input gear 2 carried by a drive shaft 3, a planetary gear system 1 coupling the input gear to first and second ring gears 6 and 9 and carried by a support 10, 11 rotatable about the input gear, brakes 15, 16 for inhibiting movement of one or other of the ring gears to cause the support to rotate in one or other direction at a speed lower than that of the input gear, and a clutch between the drive shaft and the support which is normally inoperative, but which can be rendered operative when both rings gears are freed to cause the support to rotate at the same speed as the drive shaft. The clutch consists of a one-way spring clutch 43 in series with a centrifugal clutch 44, 46, 47, reversal of the direction of rotation of the motor M with brakes 15, 16 disengaged producing high speed direct drive, the centrifugal clutch providing a gradual engagement. The planetary gear system comprises intermeshed planets 5, 7 and 8 with one planet 5, 7 stepped. <IMAGE>

Description

SPECIFICATION Improvements in or relating to drive mechanisms This invention relates to drive mechanisms more especially, though not exclusively, for use in clothes washing machines.

It is common for clothes washing machines to incorporate a washing member which is arranged to be rotated alternately in opposite directions at a relatively low speed to produce an agitation of the clothes being washed in the presence of a washing liquid. Thus in one form of machine the washing member is provided by an agitator reversibly rotatable about an axis inclined at a substantial angle to the horizontal, usually vertical, with the clothes contained within a perforated drum mounted for rotation within an outer container for the washing liquid, and in another form of machine the washing member is provided by the drum itself, the drum being arranged to be rotated alternately in opposite directions about a generally horizontal axis.

In both forms of machine the drum is also arranged to be rotated unidirectionally at high speed, following a washing operation, in order to extract liquid from the clothes.

An object of the invention is to provide a novel form of drive mechanism capable of producing both a slow speed reversing movement and also a high speed unidirectional rotation.

According to the invention a drive mechanism comprises an input gear carried by a drive shaft, a planetary gear system carried by a support which is rotatable about the axis of the input gear, which gear system couples the input gear to first and second ring gears coaxial with and independently rotatable about the input gear, and means for inhibiting movement of one or other of the ring gears, the planetary 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 said inhibiting means at a speed lower than that of the drive shaft, and the mechanism incorporating clutch means between the drive shaft and the support which is inoperative when either one of the ring gears is acted upon by the inhibiting means, but which can be rendered operative when both ring gears are freely rotatable, to cause the support to rotate at the same speed as the drive shaft.

As applied to a washing machine the support can be arranged to provide a relatively slow speed reversal of the washing member, and a high speed unidirectional rotation of the perforated drum.

Where the drum itself provides the washing member, the support member may be coupled to it in any suitable manner, for example through a belt and pulley system, or a further arrangement of gears.

In cases where the washing member is provided by a separate agitator within a perforated drum rotatable about a non-horizontal, for example, vertical axis the support is conveniently coupled to a shaft which imparts a drive to the agitator, and there is a further coupling between the shaft and the drum which permits the shaft to reversibly rotate at a predetermined slow speed without imparting any positive drive to the drum, but is capable of transmitting the rotation of the drive shaft to the drum, so as to cause the latter to rotate when the shaft is unidirectionally driven at high speed.

To effect reversal of the washing member during a washing operation the arrangement preferably includes means operable automatically after rotation of the support by a required amount, with movement of one of the ring gears inhibited, to reverse the operation of the inhibiting means so that it then acts on the other ring gear, thus producing an automatic reversal of the support.

Any suitable means may be provided for controlling the operation of the inhibiting means.

The inhibiting means are conveniently in the form of band brakes, and the operation of the brakes may then be effected by one or more cam devices coupled to, so as to be driven by, the shaft which drives the input gear at an appropriate speed.

The brakes are conveniently arranged to be actuated alternately when the drive shaft is rotated in one direction, but to be both released when the drive shaft is rotated in the opposite direction, the clutch means between the drive shaft and the support preferably being in the form of a unidirectional clutch operative automatically to drive the support at the same speed as the drive shaft when the shaft is rotated in said opposite direction, but being inoperative when the drive shaft is rotated in said one direction.

The unidirectional clutch is conveniently arranged to drive an intermediate member when the drive shaft is rotated in said opposite direction, and the intermediate member is arranged to be coupled to said support through a centrifugal clutch which is operative to drive the support when the intermediate member is rotated by the drive shaft at an appropriate speed.

One drive mechanism suitable for use in a washing machine will now be described with reference to Figures 1 and 2 of the accompanying drawings in which: Figure 1 shows the principle of operation of the reversing drive, and Figure 2 shows a sectional view of the drive mechanism.

In the arrangement illustrated in Figure 1 a sun gear A engages a planet gear B forming part of a gear system carried by a support (not shown) which is capable of rotating about the axis of the sun gear. The planet gear B also engages an internally toothed or ring gear C which is coaxial with and is also capable of rotation about the sun gear A.

The planet gear B carries an axial extension which engages a further gear B' on a different level, and this further gear B' meshes with another ring gear C', similarly coaxial with and rotatable about the sun gear A independently of the first ring gear C.

Now if the sun gear A is rotated in a clockwise direction as indicated by the arrow a the planet gear B will rotate in an anti-clockwise direction as will the ring gear C if the centre of B is fixed.

It is clear that the gear B' and the second ring gear C' will rotate in the opposite directions to the gears B and C i.e. clockwise in the above case.

If now the centres of the gears B and B' are allowed to rotate freely about the sun gear A, and the ring gear C is held stationary these centres will rotate in a clockwise manner, and similarly if the second ring gear C' is held, they will rotate in an anti-clockwise direction.

By arranging for brakes or clamps to be applied alternately to C and C' a reversible output is obtained from the rotatable support carrying the shafts for B and B'.

Since in the first case, with the ring gear C held, the support rotates in the same direction as the shaft driving the sun gear A and in the other case, in the opposite direction, the speeds of rotation of the support in opposite directions will be dissimilar in the simple arrangement illustrated.

Therefore in order to achieve approximatelySequal speeds in each direction it is convenient for the extension gear B' to be of appropriately smaller diameter than the gear B.

In some cases additional and/or idler gears may be provided in the gear system, for example between the planet gears and the ring gears, and additionally, in order to balance the loads and to enable smaller lighter gears to be used, the planet gears, and additional and idler gears if provided, can be multiplied symmetrically about the central axis. Now if both brakes are released, it will be seen that there will be no positive drive to the support carrying the gears B and B'.

The application of the invention to provide both a low speed reversible drive for the washing member of a washing machine and a high speed unidirectional drive for a perforated drum is illustrated in Figure 2. In this embodiment the planet gears 1 are in the form of triple compound gears in order to achieve the speed reduction required in the limited space available. A drive pinion 2, which constitutes the sun gear, is attached to shaft 3 of an induction motor M, and meshes with the larger diameter sections 4 of the compound gears 1.The central portion 5 of the compound gears 1 directly mesh with a first internally toothed ring gear 6, whilst the remaining sections 7 drive further gears 8 (which correspond to the gear B of Figure 1) and which, in turn, mesh with a second internally toothed ring gear 9, the ring gears being supported for rotation about the axis of the shaft 3 in any convenient manner.

The compound gears 1 and the further gears 8 rotate on shafts (not shown) fitted between plates 10, 1 1 which in turn rotate about motor shaft 3 on bearings 12, 13. To the upper plate 1 1 there is attached the output pulley 14 which also constitutes a clutch housing as will subsequently be described. The drive from the output pulley is conveyed by means of a belt 14' to the washing member required to be reversibly rotated at a relatively low speed, for example the agitator of a washing machine having a vertically mounted drum or the perforated drum itself where this is arranged to rotate about a horizontal or near horizontal axis, the speed of rotation of the pulley and the form of coupling between the pulley and the washing member being such that a required reversible low speed rotation is obtained.

Brakes 1 5, 1 6, which are conveniently in the form of bands, are arranged to be alternately applied to the ring gears 6, 9 by means of suitably driven cams (not shown) which can be driven through a reduction gear system from the motor shaft 3 to provide the required braking and release of the ring gears, causing the plates 10, 11, and hence the pulley 14 to rotate the desired amount in each direction.

When the motor is reversed both brake bands 1 5, 1 6 are arranged to be released, and the output pulley is arranged to be driven directly from the shaft through a clutch arrangement 44 which is normally inoperative when the motor rotates in the "wash" direction.

This clutch arrangement 44 incorporates a centrifugal clutch comprising a member 44' having a pair of clutch arms 44" supported by a bearing 45 on the motor shaft, and having pivoted thereto bob-weights 46 lined on their outer surface with friction material 47. The clutch arrangement incorporates also a spring clutch 43 coupling the motor shaft 3 to the member 44' of the centrifugal clutch. In the "wash" direction of the motor the spring clutch 43 tends to unwind, and thus slips freely, thereby allowing the pulley 14 to oscillate freely under the action of the gear system above described. However on reversal of the motor the spring tightens up and drives the member 44' and hence the clutch arms 44".The bob-weights 46 then fly outwards under centrifugal force and the linings 47 contact the inside of the pulley/clutch housing 14 which causes the pulley 14 to rotate and accelerate slowly until it reaches the same speed as the motor shaft 3, to rotate the perforated drum at spin speed. Such an arrangement has the advantage that it reduces the starting torque and facilitates a smooth acceleration up to spin speed.

In the case of a washing machine in which the perforated drum is arranged to rotate reversibly about a horizontal axis, at low speed during a wash function, and at high speed during a spin function, the drum is arranged to be driven by the belt 14' during both the wash and spin functions.

In the case of a washing machine having an agitator mounted within a perforated drum rotatable about a vertical axis, and in which the agitator alone is arranged to be driven reversibly during the wash function, and the drum together with the agitator are arranged to be driven unidrectionally at hlgh,speed during a spin function the agitator and drum may be mounted on a common drive shaft, a suitable coupling then being provided between the drive shaft and the drum which permits the shaft, and hence the agitator, to rotate to a limited extent in both directions at a relatively low speed without imparting any positive drive to the drum, but is capable of transmitting the rotation of the drive shaft to the drum when the shaft is unidrectionally rotated at high speed.Suitable forms of such couplings are described in Patent Specification No. 25241/77.

However the centrifugal clutch instead of being arranged to engage the pulley 14 could be arranged to engage and drive a further pulley to give a separate high speed unidirectional output if desired, the low speed reversible output for the wash action still being provided by the pulley 14.

Moreover the pulley 14, and the further pulley where provided, can be replaced by other rotary drive transmitting means, such as gear wheels or rollers depending upon the form of drive required.

Although the invention has particular application to drive mechanisms for use in washing machines, it will be appreciated that it can also be used to advantage in other forms of apparatus requiring a drive which is operable to give either a high speed unidirectional or an automatically reversible rotation.

In a modification, the drive shaft 3 could be arranged to be driven by a two-speed or variable speed motor giving the advantage, in the case of a washing machine, of a variety of wash and spin speeds.

Moreover for some applications instead of the ring gears being completely braked, means may be provided for partially inhibiting their rotation, for example by permitting them to rotate at a suitably controlled speed. Then by varying the speed at which the ring gears rotate it will be possible, in the reversing mode of operation, to control the speed of rotation of the output member, e.g. the pulley 14 in the embodiment described.

As applied to washing machines the drive mechanism in accordance with the invention permits the use of a high-speed low-torque drive, in place of the low-speed high-torque drive commonly used on existing forms of washing machines, thus enabling relatively light-weight gears, for example of engineering plastics material, to be employed instead of heavier and more expensive steel gears.

Claims (10)

1. A drive mechanism comprising an input gear carried by a drive shaft, a planetary gear system carried by a support which is rotatable about the axis of the input gear, which gear system couples the input gear to first and second ring gears coaxial with and independently rotatable about the input gear, and means for inhibiting movement of one or other of the ring gears, the planetary 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 said inhibiting means at a speed lower than that of the drive shaft, and the mechanism incorporating clutch means between the drive shaft and the support which is inoperative when either one of the ring gears is acted upon by the inhibiting means, but which can be rendered operative when both ring gears are freely rotatable, to cause the support to rotate at the same speed as the drive shaft.

2. A drive mechanism according to Claim 1 in a washing machine of the kind having a washing member arranged to be rotated alternately in opposite directions at a relatively low speed to produce an agitation of the clothes being washed in the presence of a washing liquid and in which liquid is arranged to be extracted from the clothes by rotation of a perforated drum unidirectionally at higher speed, wherein the support provides the drive for the relatively slow speed reversing movement of the washing member and the high speed unidrectional rotation of the perforated drum.

3. A drive mechanism according to Claim 2 wherein the perforated drum is mounted for rotation about a generally horizontal axis, and itself constitutes the washing member.

4. A drive mechanism according to Claim 2 wherein the washing member is provided by an agitator reversibly rotatable about an axis inclined at a substantial angle to the horizontal within said perforated drum, which is also mounted for rotation about said axis, wherein the support is coupled to a shaft which imparts a drive to the agitator, and there is a further coupling between the shaft and the drum which permits the shaft to reversibly rotate at a predetermined slow speed without imparting any positive drive to the drum, but is capable of transmitting the rotation of the drive shaft to the drum, so as to cause the latter to rotate when the shaft is unidirectionally driven at high speed.

5. A drive mechanism according to any preceding claim including means operable automatically after rotation of the support by a required amount, with movement of one of the ring gears inhibited, to reverse the operation of the inhibiting means so that it then acts on the other ring gear, thus producing an automatic reversal of the support.

6. A drive mechanism according to Claim 5 wherein the inhibiting means comprise band brakes operable by one or more cam devices coupled to the shaft which drives the input gear in a manner which causes the cam devices to be driven at an appropriate speed.

7. A drive mechanism according to Claim 6 wherein the brakes are arranged to be actuated alternately when the drive shaft is rotated in one direction, but to be both released when the drive shaft is rotated in the opposite direction, the clutch means between the drive shaft and the support being in the form of a unidirectional clutch operative automatically to drive the support at the same speed as the drive shaft when the shaft is rotated in said opposite direction, but being inoperative when the drive shaft is rotated in said one direction.

8. A drive mechanism according to Claim 7 wherein the unidirectional clutch is arranged to drive an intermediate member when the drive shaft is rotated in said opposite direction, and the intermediate member is arranged to be coupled to the said support through a centrifugal clutch which is operative to drive the support when the intermediate member is rotated by the drive shaft at an appropriate speed.

9. A drive mechanism substantially as shown in and hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

10. A washing machine incorporating a drive mechanism according to any preceding claim.