GB1598322A

GB1598322A - Drive mechanisms

Info

Publication number: GB1598322A
Application number: GB2744077A
Authority: GB
Original assignee: Hotpoint Ltd
Current assignee: Hotpoint Ltd
Priority date: 1977-06-30
Filing date: 1977-06-30
Publication date: 1981-09-16

Description

(54) IMPROVEMENTS IN OR RELATING TO DRIVE MECHANISMS (71) We, HOTPOINT LIMITED, of Peterborough,England, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to drive mechanisms for producing a rotary output with a periodic automatic reversal. Such mechanisms have application, for example, to clothes washing machines of the kind having a washing member which is arranged to be rotated alternately in opposite directions for producing an agitation of the clothes in the presence of a washing liquid. In one form of such a washing 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.

However, a drive mechanism in accordance with the invention can also be utilized in other forms of washing machine as well as to different types of apparatus requiring a periodically reversing drive.

According to the invention a drive mechanism has a first support carrying first and second drive wheels rotatable by an input member in opposite directions to each other, a second support carrying a further wheel and movable relative to the first support into either one of two operating positions to cause said further wheel to engage either the first or the second drive wheel, and to transmit the rotation thereof to a rotary output member, and selector means operable automatically. after rotation of the output member by a predetermined amount in either direction by engagement of said further wheel with the respective drive wheel, to produce a relative movement between the first and second supports so as to cause the further wheel to engage the other drive wheel and so reverse the direction of rotation of the output member.

The amount by which the output member is rotated in each direction before the selector means is actuated to produce a relative movement between the first and second supports, and thereby change the direction of rotation of the output member, readily be chosen to provide the degree of rotation required for the particular application to which the drive mechanism is put.

Thus the output member may be rotated through only a fraction of a revolution or through one or more revolutions as may be required.

The drive wheels may be in the form of gear wheels or rollers or a combination thereof. For example each drive wheel preferably comprises a gear wheel part and a roller part, the gear wheel part of one of the drive wheels engaging a pinion fixed to a drive shaft, which may be the shaft of an electric driving motor and, also the gear wheel part of the other drive wheel for rotating the latter in the opposite direction to the first drive wheel. The said further wheel in such a case may then also comprise a gear wheel part and a roller part, the roller part being engage able with the roller part of one or other of the drive wheels, and the gear wheel, part engaging gear teeth of the rotary output member so as to drive the latter in one or the other direction.

The use of inter-engaging rollers in the transmission system between the input output members for each direction of rotation of the output member has the advantage of ensuring a comparatively smooth take-up on the initial drive in one direction or the other, at least one of a pair of inter-engaging rollers preferably being of a resilient nature.

The rotary output member is preferably rotatable about the axis of the drive shaft, and has internal teeth meshing with the teeth of said further wheel.

The second support can then be arranged to rotate to a limited extent about the drive shaft axis to bring the roller part of the further wheel into engagement with the roller part of either the first or the second drive wheel, whilst remaining in mesh with the teeth of the rotary output means.

Movement of the second support between its two operating positions may be effected by an actuator on the rotary output means drivingly engaging a co-operating tripping member on the second support as the output means reaches the required limit of movement in each direction, the tripping member urging the support from one operating position into the other operating position which reverses the direction of rotation of the output member.

Preferably however the selector means is operable in response to a predetermined number of revolutions of the input member, for example by means of a cam and cam follower arrangement suitably coupled to the input member for example through one or more gear wheels.

Thus the selector means conveniently incorporates a cam carried by the first support and arranged to be driven, in use of the mechanism, by said input member, and operable on a cam follower carried by the second support so as to rotate the second support successively into positions in which sald further wheel engages the first or second drive wheel.

The input member conveniently comprises a shaft carrying a pinion which provides the drive for the first and second drive wheels, and also the cam of the selector means for example through a reduction gear coupling of any convenient form, which may include a Geneva type drive arrangement; the pinion may be coupled to the shaft by a clutch device which is operative to drive the pinion when the shaft is rotated in one direction but is such that when the shaft is rotated in the other direction it no longer drives the pinion.

The output member may be coupled to a rotary drive transmitting member, such as a pulley of a belt and pulley system or a gear wheel of a further gear system, through a clutch, the clutch conveniently being arranged to be engaged automatically on rotation of the input member in one direction and disengaged when the input member is rotated in the opposite direction.

The drive mechanism may then incorporate a further clutch arranged to be engaged when the input member is rotated in said opposite direction to provide an alternative coupling between the input member and the drive transmitting member, or between the input member and a further drive transmitting member, which provides a unidirectional rotary output from the drive mechanism.

Such an 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 a relatively high speed following the washing operation for the extraction of moisture from the clothes.

In such a case the further clutch means may be arranged to couple a drive transmitting member which imparts the unidirectional rotation to the perforated drum directly to the input member, which may for example be the shaft of a reversible electric motor, the drive transmitting member being coupled to the drum through a coupling having a suitable gear ratio for driving the drum at the required spin speed.

The invention is, however, also applicable to tumbler dryers having a drum which is arranged to be rotated to produce a tumbling movement of clothes contained within it whilst a current of air, usually pre-heated, is passed through it to carry away moisture from the clothes, as it has been found that a more efficient drying of the clothes is achieved by rotating the drum alternately in opposite directions instead of continuously in one direction.

One drive mechanism in accordance with the invention and a modification thereof will now be described by way of example with reference to Figures 1 to 6 of the accompanying schematic drawings in which: Figure 1 represents a part sectional elevation of the drive mechanism; Figures 2a and 2b are sectional views of a part of the drive mechanism for producing either a reversing drive or a unidirectional drive; Figures 3a and 3b are diagrammatic views showing the reversing action of the drive mechanism; Figure 4 is a partly exploded perspective view of part of the reversing gear system; and Figures 5 and 6 illustrate parts of the modified mechanism.

Referring first to Figure 1 the drive mechanism comprises a reversible electric motor 1 within a mounting frame 20 and having a rotor shaft 2 which carries a pinion 3. The pinion 3 is rotatably supported by a sleeve 3a which is keyed to the shaft 2, and is formed with a cylindrical extension 3b which is surrounded by one end of a helical spring 3c, the other end of which surrounds an end of the sleeve 3a, so that when the motor 1 is driven in one direction the spring 3c tightens round the pinion extension 3b and the sleeve 3a, thereby imparting a drive to the pinion, whereas when the motor is driven in the other direction the spring 3c is loosened so that the pinion is not driven in that direction. The shaft 2 also carries a reversing plate 4 and a gear housing 5 each rotatably supported about the shaft. Referring also to Figures 2a and 2b the shaft 2 also carries at its upper end, a driving pulley 6 which is rotatably supported by a bearing 7 about an axially movable driving bush 8 which is free to rotate to a limited extend about a sleeve 9 secured to the shaft. Also carried by the upper end of the shaft 2 are a pair of clutch arms 11, forming part of a centrifugal clutch rotatably supported about a bush 1 tea which surrounds and is free to slide axially on the sleeve 9, the clutch arms 11 being drivingly attached to the driving bush 8 by a helical spring 12 which is capable of driving in one direction only. A driving pin 13 whose ends locate in a pair of helical slots 8a in the driving bush 8 is pressed into the shaft 2. Each of the clutch arms 11 pivotably carries a shoe 14 which, in operation, drivingly contacts the inner surface of skirt 6b on the pulley 6. The pulley also carries a series of teeth 6a which can engage with a corresponding series of teeth Sa formed at the upper end of the gear housing 5. According to the position of the driving bush 8, which can ride up and down the pin 13, carrying with it the driving pulley 6, the teeth Sa and 6a are either engaged or disengaged. Thus when the motor shaft 2 rotates in the direction which causes the driving bush 8 to move up the shaft the teeth Sa, 6a are disengaged as shown in Figure 2a.

In this direction of rotation of the shaft, also, the spring 12 drives the clutch arms 11 at the same speed as the shaft, the clutch shoes 14 when engaging the pulley 6 and causing this also to be rotated at shaft speed.

However, when the motor shaft 2 rotates in the other direction the spring 12 ceases to drive theclutch arms 11, and the pulley 6 is no longer driven directly by the shaft. In addition the driving bush 8 moves downwards and with it the pulley 6 which causes the pulley teeth 6a to engage the teeth Sa of the gear housing as shown in Figure 2b.

Drive to the pulley 6 will then be effected through a gear system 15 within the gear housing 5, which will cause the pulley to be driven at a lower speed alternately in opposite directions.

Thus with reference to Figures 3a, 3b and 4 the reversing gear system comprises two series of gears and rollers driven from the motor shaft 2 by the pinion 3.

Each series of gears, only one of which is shown, comprises two intermeshing driving gears 21, 22 having integral rollers 21a and 22a, preferably of a resilient material, mounted on the motor frame 20, and a further gear 23 having a roller 23a mounted on the reversing plate 4 which is capable of a limited degree of rotational movement about the shaft axis. A further ring gear 24 is provided on the inside of the gear housing 5 which provides the output member of the gear system. Each train of gears is arranged to take up one of two positions as shown in Figures 3a and 3b. In the first of these positions (Figure 3a) the pinion 3 drives gears 21, 22, the gear 22 merely idling, and then, by engagement of the rollers 21a and 23a, it drives the gear 23 which in turn drives the gear housing 5 through the ring gear 24, and with it the pulley 6 in the same direction as the pinion 3. In the second position (Figure 3b) the combined gear 23 and roller 23a is moves so as to engage with the gear 22 and roller 22a. In this position the drive is transmitted via the gears 21 and 22 and rollers 22a and 23a to the gears 23, 24 and hence through the gear housing 5 to the pulley 6, which is thus rotated in the opposite direction to the pinion 3.

Referring now to Figure 4, automatic reversal of the gear train 15 (see Figures 3a, 3b) just described is achieved by means of a selector mechanism incorporating a rotatable cam wheel 26 having a shaped slot 27 in which ride a pair of pins 28 carried by the reversing plate 4. The cam wheel 26 is rotated intermittently by a modified Geneva drive mechanism, the lower surface 26a of the cam wheel being shaped to provide a form of star wheel engageable by a pin 19 carried by a gear wheel 30 which is driven indirectly by the pinion 3 via a further pinion 31 keyed to the shaft 21b of one of the gear wheels 21. The cam arrangement is such that the cam wheel 26 is rotated through a number of steps by the pin 29 whilst the reversing plate 4 is held in one operative position with the roller 23a engaging either the roller 21a or 22a. Consequently the gear housing 5 and hence the output pulley 6 is driven through a number of revolutions in one direction; during the next step of movement of the cam wheel 26 the reversing plate 4 is rotated to a second position in which the roller 23a engages the other of the rollers 21a or 22a, so that the gear housing 5 and the output pulley 6 are driven in the other direction. The plate 4 is held in this second position whilst the cam wheel 26 is rotated through a further number of steps, and the housing 5 continues to rotate in the second direction. The next step of the cam wheel 26 returns the plate 4 to its original position, causing the housing 5 and the output pulley to be driven again in the first direction. The process is then repeated, and regular automatic reversal of the gear train and hence the output pulley 6 is thus achieved. Any suitable means may be provided for holding the cam wheel 26 is positions set by the pin 29, during those periods in which it is not engaged by the latter.

The gear system provides a reducing gear so that when the pulley 6 is reversibly driven through the gear system it rotates at a lower speed than when driven directly from the motor shaft.

A belt 32, as shown, conveniently provides the drive from the pulley 6 to a member or members required to be rotated either reversibly at a relatively low speed or unidirectionally at a higher speed.

Thus the drive mechanism is particularly suitable for driving the agitator of a washing machine reversibly at a relatively low speed or, together with a surrounding perforated drum, unidirectionally at a much higher spin speed. The belt 32 in such a case conveniently drives a pulley fixed to the agitator shaft, a coupling between the agitator shaft and the spin drum being such as to allow the agitator to be rotated reversibly without transmitting the reversible rotation to the drum, but such that when the shaft is rotated unidirectionally at the higher speed the rotation is imparted to the drum which then rotates with the agitator.

However the clutch shoes 14 instead of being arranged to engage the pulley 6 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 still being provided by the pulley 6. Moreover the pulley 6 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.

A drive mechanism in accordance with the invention is, however, also suitable for use in tumbler dryers having a drum which is rotatable about a substantially horizontal axis, for producing a tumbling movement of clothes contained therein, whilst air is fed through the drum to carry away moisture from the clothes. It has been found that by rotating the drum alternately in opposite directions a more efficient drying operation may be achieved, and a reversing driving mechanism substantially as described above can be used for effecting the reversal of the drum. In such a case the electric driving motor 1 will only need to be driven in one direction only, and the high speed drive facility of the washing machine will not be required, the drive for the drum being taken from the output pulley 6 and the clutch mechanism for disengaging the pulley from the gear housing 5 being dispensed with. In addition thecam wheel 26, instead of being driven intermittently by a form of Geneva drive mechanism, may be rotated continuously from the pinion 31 by a system of gears as shown at 33 in Figures 5 and 6, chosen to provide the required number of revolutions of the drum in each direction of rotation.

Moreover although the invention has particular application to drive mechanisms suitable for use in washing machines and tumbler dryers, it will be appreciated that it can also be used to advantage in other forms of apparatus, especially those requiring a drive which is operable to give either a unidirectional or automatically reversible rotation.

WHAT WE CLAIM IS: 1. A drive mechanism having a first support carrying first and second drive wheels rotatable by an input member in opposite directions to each other, a second support carrying a further wheel and movable relative to the first support into either one of two operating positions to cause said further wheel to engage either the first or the second drive wheel, and to transmit the rotation thereof to a rotary output member, and selector means operable automatically, after rotation of the output member by a predetermined amount in either direction by engagement of said further wheel with the respective drive wheel, to produce a relative movement between the first and second supports so as to cause the further wheel to engage the other drive wheel and so reverse the direction of rotation of the output member.

2. A drive mechanism according to Claim 1 wherein each drive wheel comprises a gear wheel part and a roller part, the gear wheel part of one of the drive wheels engaging a pinion fixed to a drive shaft and also the gear wheel part of the other drive wheel for rotating the latter in the opposite direction to the first drive wheel.

3. A drive mechanism according to Claim 2 wherein said further wheel also comprises a gear wheel part and a roller part, the roller part being engageable with the roller part of one or other of the drive wheels, and the gear wheel part engaging gear teeth of the rotary output member so as to drive the latter in one or the other direction.

4. A drive mechanism according to Claim 2 or 3 wherein the rotary output member is rotatable about the axis of the drive shaft and has internal teeth meshing with the teeth of said further wheel.

5. A drive mechanism according to Claim 4 wherein the second support is arranged to rotate to a limited extend about the drive shaft axis to bring the roller part of the further wheel into engagement with the roller part of either the first or the second drive wheel, whilst remaining mesh with the teeth of the rotary output means.

6. A drive mechanism according to any preceding claim wherein the selector means is operable in response to a predetermined

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. periods in which it is not engaged by the latter. The gear system provides a reducing gear so that when the pulley 6 is reversibly driven through the gear system it rotates at a lower speed than when driven directly from the motor shaft. A belt 32, as shown, conveniently provides the drive from the pulley 6 to a member or members required to be rotated either reversibly at a relatively low speed or unidirectionally at a higher speed. Thus the drive mechanism is particularly suitable for driving the agitator of a washing machine reversibly at a relatively low speed or, together with a surrounding perforated drum, unidirectionally at a much higher spin speed. The belt 32 in such a case conveniently drives a pulley fixed to the agitator shaft, a coupling between the agitator shaft and the spin drum being such as to allow the agitator to be rotated reversibly without transmitting the reversible rotation to the drum, but such that when the shaft is rotated unidirectionally at the higher speed the rotation is imparted to the drum which then rotates with the agitator. However the clutch shoes 14 instead of being arranged to engage the pulley 6 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 still being provided by the pulley 6. Moreover the pulley 6 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. A drive mechanism in accordance with the invention is, however, also suitable for use in tumbler dryers having a drum which is rotatable about a substantially horizontal axis, for producing a tumbling movement of clothes contained therein, whilst air is fed through the drum to carry away moisture from the clothes. It has been found that by rotating the drum alternately in opposite directions a more efficient drying operation may be achieved, and a reversing driving mechanism substantially as described above can be used for effecting the reversal of the drum. In such a case the electric driving motor 1 will only need to be driven in one direction only, and the high speed drive facility of the washing machine will not be required, the drive for the drum being taken from the output pulley 6 and the clutch mechanism for disengaging the pulley from the gear housing 5 being dispensed with. In addition thecam wheel 26, instead of being driven intermittently by a form of Geneva drive mechanism, may be rotated continuously from the pinion 31 by a system of gears as shown at 33 in Figures 5 and 6, chosen to provide the required number of revolutions of the drum in each direction of rotation. Moreover although the invention has particular application to drive mechanisms suitable for use in washing machines and tumbler dryers, it will be appreciated that it can also be used to advantage in other forms of apparatus, especially those requiring a drive which is operable to give either a unidirectional or automatically reversible rotation. WHAT WE CLAIM IS:

1. A drive mechanism having a first support carrying first and second drive wheels rotatable by an input member in opposite directions to each other, a second support carrying a further wheel and movable relative to the first support into either one of two operating positions to cause said further wheel to engage either the first or the second drive wheel, and to transmit the rotation thereof to a rotary output member, and selector means operable automatically, after rotation of the output member by a predetermined amount in either direction by engagement of said further wheel with the respective drive wheel, to produce a relative movement between the first and second supports so as to cause the further wheel to engage the other drive wheel and so reverse the direction of rotation of the output member.

number of revolutions of the input member.

7. A drive mechanism according to Claim 6 wherein the selector means incorporates a cam carried by the first support and arranged to be driven, in use of the mechanicm, by said input member, and operable on a cam follower carried by the second support so as to rotate the second support successively into positions in which said further wheel engages the first or second drive wheel.

8. A drive mechanism according to Claim 7 wherein the input member comprises a drive shaft carrying a pinion, which pinion is coupled to the cam through a reduction coupling.

9. A drive mechanism according to Claim 8 wherein the reduction coupling includes a Geneva type drive arrangement.

10. A drive arrangement according to Claim 8 or 9 wherein the pinion is coupled to the shaft by a clutch device which is operative to drive the pinion when the shaft is rotated in one direction but is such that when the shaft is rotated in the other direction it no longer drives the pinion.

11. A drive arrangement according to any preceding claim wherein the output member is coupled to a rotary drive transmitting member through a clutch arranged to be engaged automatically on rotation of the input member in one direction and disengaged when the input member is ro tated~in the opposite direction.

12. A drive mechanism according to Claim 11 incorporating a further clutch arranged to be engaged when the input member is rotated in said opposite direction to provide an alternative coupling between the input member and the drive transmitting member, or between the input member and a further drive transmitting member, which provides a unidirectional rotary output from the drive mechanism.

13. A clothes washing machine having a washing member which is arranged to be rotated for producing an agitation of clothes in the presence of a washing liquid incorporating a drive mechanism according to any preceding claim for rotating the washing member alternately in opposite directions.

14. A tumbler dryer having a drum which is arranged to be rotated to produce a tumbling movement of clothes contained within it, incorporating a drive mechanism according to any one of Claims 1 to 10 for rotating the drum alternately in opposite directions.

15. A drive mechanism substantially as shown in and as hereinbefore described with reference to Figures 1 to 4 or Figures 5 and 6 of the accompanying drawings.