US2762483A

US2762483A - Centrifugal clutch

Info

Publication number: US2762483A
Application number: US452791A
Authority: US
Inventors: Clark Kendall
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1954-08-30
Filing date: 1954-08-30
Publication date: 1956-09-11
Anticipated expiration: 1973-09-11

Description

Sept. 11, 1956 K. CLARK ,76

CENTRIFUGAL CLUTCH Filed Aug. 50, 1954 t 32 U I .1? .5! 50 5 1534 2.9

m 6 K j i A 30 .124; J25

//V VE/V TOR KENDALL CLARK ATTORNEY- United States Patent CENTRIFUGAL CLUTCH Kendall Clark, Glen Ellyn, IlL, assignor to General Electric Company, a corporation-of New York Application August 30', 1954, Serial No. 452,791 9 Claims. or. 192-105 This invention relates to a centrifugally operated clutch, and in particular to a direction-responsive clutch in which rotation of the driving means in one direction will lock the clutch shoes in an inoperative position and rotation in the opposite direction will permit the clutch shoes to engage a clutch drum and exert a driving elfort thereon which is related to the speed of rotation of the driving means.

It is frequently required to provide means for selectively driving two mechanisms, one of which may impose a substantial and unpredictable load on the driving motor. For example, many types of automatic washing machines wash and spin-dry the clothes in a single tub or basket. The washing mechanism may comprise a dolly or agitator which operates while the tub is held against rotation; and the spin drying cycle is subsequently accomplished by rotation of the tub at a relatively hi h speed to centrifuge water from the clothes load. It has usually been the practice to provide clutches in the agitating drive and in the centrifuging drive so that either the washing or centrifuging operation may be performed to the exclusion of the other.

The maximum load on the motor during the washing operation is predictable in the sense that the tub is designed to contain a predetermined maximum amount of water and articles to be washed. However, the disposition of the articles in the tub following the washing operation is frequently unpredictably unbalanced. The

load on the motor in accelerating an eccentrically loaded tub from zero speed to the relatively high centrifuging speed'ma-y be so severeas in the circumstance when a heavy bath mat or other bulky article has been Washed-- that the motor may labor and bedamaged by overheating. Motors which are provided with protective cutout devices will, of course, be protected against damage, but if the cut-out device operates it requires the user manually to reclose the circuit to re-start the machine. The present invention provides a torque-limiting clutch mechanism which permits the motor gradually to assume the load and thus bring the tub up to centrifuging speed in gradual fashion without overloading the motor.

It is, therefore, an object of the invention to provide a novel, centrifugally operated friction clutch which will permit the motor gradually to accelerate a device from a standing start.

It is another object of the invention to provide a commondrive means for two independent driven mechanisms, said drive mechanism including a clutch effective to drive one of the driven mechanisms only upon rotation of the drive means in a predetermined direction.

It is a further object of the invention to provide a clutch mechanism in which the clutch shoes are positively locked in non-driving position immediately upon operation of the driving means in a predetermined .direction of operation.

It is a further object of the invention to provide a direction-responsive centrifugally operated clutch mechanism which is simple to construct and maintain, and

2,762,483 Patented Sept. 11, 1956 torque is transmitted to the clutch shoes by drive means including spaced drive plates fixed to the drive shaft. The clutch shoes are mounted between said plates in freely slidable relation therewith. By means including a pin and slot relationship between the clutch shoes and the drive plates, the clutch. shoes are guided for movement against the clutch drum' during one direction of rotation of the drive plates and are positively locked against such movement'during'rotation of the plates in the opposite direction. Means are provided to insure that with the clutch driving mechanism at rest the clutch shoes are retracted from the clutch drum. The clutch shoes have substantial inertia. During the first instant of rotation of the drive plates in the first-named direction, the plates can shift relative to the clutch shoes and pursuant to the pin and slot association with the shoes, establish a locking relation therewith while the shoes remain in their retracted position. Upon operation of the drive plates in the opposite direction, the pin and slot relationship of the plates to the clutch shoes permits the shoes freely to move into driving relationship with the clutch drum. The driving effort of the clutch shoes against the clutch drum is related to the speed of rotation of the drive shaft. If because of an exceptionally heavy load, the motor speed. falls ofi, the driving effort of the clutch shoes is reduced, and the shoes will slip relative to the clutch drum, reducing the load on the motor. In this. fashion the motor gradually assumes the load and brings the load. to final rotational speed without stalling or being unduly overloaded.

It will be apparent that because the clutch drum is not driven during one: direction of rotation of the driving means, it is feasible to eliminate the auxiliary clutch previously required to' disconnect a mechanism which is not'to be driven whil'e asecond mechanism is operatmg.

Other features and advantages of the invention will be understood from the following detailed description of a presently preferred embodiment read in connection with the accompanying drawing in which:

Fig; 1 is a side sectional elevation of a clutch embodying; the present invention;

Fig. 2' is a plan view thereof taken in section on lines 22 of Fig. 1, showing the clutch in driving position;

Fig; 3 is a fragmentary side sectional elevation taken on lines 33 of Fig. 2;

Fig; 4' isLa fragmentary plan view showing the clutch elements locked in non-driving position; and

Fig. 5 is a fragmentary plan view showing the clutch ina normal rest position.

Referring to Fig. 1' a presently preferred embodiment of the clutch 1 is illustrated as being mounted on drive shaft 2of an electric motor (not shown) or the like, by which said shaft may be driven in a forward or reverse direction. In' such an arrangement the sheave 3 fixed tosuch shaft is adaptable to belt-drive some external mechanisms (not shown). The exact type of driving power is of no importance in the invention although it is to'be understood that the invention is most advantageous when used with reversible drives as will later be made clear.

Sheave 3 is illustrated as being formed with a concentric extension 4 into which shaft 2 fits snugly and which in effect becomes a fixed extension of said shaft. The

0 extension 4 terminates in a non-circular end portion 5 necessarily, circular and are maintained in parallel relation normal to the shaft axis. The spacing of the plates is advantageously maintained by the spacer collar 8. Plate 7 rests upon the support collar 9 fixed about the lower portion of the extension 4. There is no motion of extension 4 or plate 7 relative'to collar 9. The plates are secured with respect to the shaft by means of the screw 10 and washer 11; it will be understood that suitable precautions are employed to secure the screw against loosening within the shaft.

The plates 6 and 7 freelythat is to say slidably confine a pair of clutch members or

shoes

12, 14. Said clutch shoes are designed to have substantial mass, in view of the fact that they move into driving position by centrifugal force engendered by the rotation of shaft 2. it is advantageous to form the

clutch shoes

12, 14 of a moldable friction material such as Raybestos-Manhattan No. R 2959 or equivalent although obviously the shoes may be of any relatively heavy material having an applied friction surface of suitable composition. In any event the

clutch shoes

12, 14 are formed with driving faces 12.1, 14.1 which are advantageously vertical relative to plates 6 and 7. These driving faces comprise the friction drive surfaces. The radially inner portions of the clutch shoes are formed to embrace the spacer collar 8 without touching it as shown best in Fig. 5 and are configurated for engagement of one clutch shoe with the other in an interlocking and self-aligning relationship.

For example, shoe 12 has a V-portion 12.2 and a notch 12.3, and shoe 14 has a V-portion 14.2 and a notch 14.3,

which interfit as indicated in Figs. 4 and 5. It will be obvious that the respective shoes are identical in shape; this facilitates manufacture and inventory control. \Ving portions 12.4 and 12.5 of shoe 12 and wing portions 14.4 and 14.5 of shoe 14 are horizontally slit as best appears from Figs. 1 and 5 to receive the looped ends of the

respective springs

15, 16. Said looped ends secure about

pins

17, 18 which respectively extend through the wing portions 12.4 and 12.5 of shoe 12 and about

pins

19, 20 which respectively extend through the wing portions 14.4 and 14.5 of shoe 14. Said pins are parallel to shaft 2, and advantageously are horizontally grooved to receive the looped ends of the springs, which thereby secure the pins against vertical displacement relative to the clutch shoes.

Drive plates 6, 7 are apertured to receive the ends of the pins. Specifically, the plates are apertured or otherwise formed to provide passages along which the end portions of the pins may slidably pass. As best shown in Fig. 2, plate 6 is formed with a pair of V-shaped apertures, each of which provides a straight line passage 21 into which may pass the

pins

18 and 19, and an arcuate passage 22 intersecting passage 21 at the radially innermost end thereof, and also accommodating the entry and passage of

pins

18 and 19 under certain other conditions of operation presently described. Plate 6 also has a second form of aperture for similar cooperation with pins 17'and 20; said apertures have a straight line passage 23 and an arcuate passage 24 communicating therewith at the radially innermost end thereof. Plate 7 has similar pairs of apertures placed directly under those of plate 6. The

springs

15 and 16 urge the clutch shoes into the interfitting relationship shown in Fig. 5. Under certain conditions of operation of the clutch, the respective

straight line passages

21 and 23 of the apertures in the plates 6 and 7 are chordal relative to the rim of the plates and are equally spaced and disposed relative to the axis of shaft extension 4. The respective

arcuate passages

22 and 24 are at all times concentric with said shaft extension and are equi-radial therefrom.

The driven portion of the clutch comprises a housing 25 rotatably supported on shaft extension 4 by an antifriction bearing 26 carried thereby. A sheave 27 typifies a power takeolf facility. The housing has a cylindrical clutch drum portion 28 parallel to the friction surfaces 12.1 and 14.1 of the respective clutch shoes. It will be understood that the clutch housing 25 is in all respects concentric with the axis of rotation of shaft 2 and extension 4. A suitable cover for the housing may comprise a cap 29 having a rim arranged to be snapped over the flanged upper rim of housing 25 and secured thereon by a garter spring 30 as indicated in Fig. 1.

It will be apparent from Figs. 2 and 5 that when in chordal alignment the

passages

21 and 23 permit the clutch shoes to travel in a radial direction between the disengaged or nondriving position of Fig. 5 and the driving position of Fig. 2; and it will be noted from Fig. 2 that the respective passages are sufliciently long to allow for wear on the shoe surfaces 12.1 and 14.1. The automatic compensation for wear thus provided very considerably extends the useful life of the clutch. It will be noted from Fig. 4 that when the

pins

17, 18, 19, and 20 occupy the associated

arcuate slots

22 and 24 the shoe surfaces 12.1, and 14.1 are positively held out of engagement with the clutch drum 28.

When used in connection with a reversible driving means, rotation of the drive shaft in one direction will positively lock the clutch shoes in non-driving position. Rotation in the other direction, however, will permit the clutch shoes to engage the clutch drum with an effective driving force which is relative to the centrifugal forces acting on the shoes, considered with respect to the bias of the

springs

15, 16 which restrain movement of the shoes outwardly of the shaft. The clutch, therefore, is particularly advantageous for driving either of two mechanisms, one of which may be subject to varying or unpredictable loads. For example, the clutch is advantageous in a clothes washing machine of the type in which the clothes are washed by means of an agitator operating in a vertical axis tub and then are damp dried by rapidly spinning the tub to centrifuge the liquid therefrom. In such an arrangement it is obvious that the tub should not be rotated during the period of operation of the agitator. Rotation of the tub from a standing start to achieve centrifugal extraction of the liquid imposes a severe starting load on the motor. The load may be unpredictably increased by the eccentric disposition of the clothes in the tub at the commencement of any particular centrifuging operation. At the start of a centrifuging operation, therefore, it is most advantageous to permit the drive motor to pick up the load gradually. By using sheave 27 for the centrifuging drive, the centrifugal friction clutch of the present invention brings the tub up to final speed without overloading the motor. The reduced speed of the motor as it attempts to pick up the load reduces the driving pressure of the clutch shoes against the clutch drum. The resultant slippage between the shoes and the drum permits the motor to accelerate, whereupon a driving impulse is transmitted to the centrifuging drive of the washing machine. If the tub is heavily eccentrically loaded, there may be a succession of such driving impulses, each being increasingly effective to overcome the inertia of the tub, until the ultimate centrifuging speed is reached.

Fig. 5 shows the clutch in an at rest position. If the drive shaft were to rotate clockwise of Fig. 5, the clutch plates 6, 7, will of course be driven in the same direction. It will be recalled that the clutch shoes are relatively loosely confined between the plates, and that the only driving connection between the clutch plates and the clutch shoes comprises the pin and slot relationship. The clutch shoes are relatively heavy, and their inertia holds them at rest relative to the plates, whereupon the plates rotate to the Fig. 4 position, in which the

pins

17, 18, 19, and 20 are at the extremeties of the associated arcuate passages of the plate apertures. It is apparent that this positional relationship of the pins to the arcuate passages will remain so long as the drive shaft is rotating clockwise, and that the confinement of the pins within the arcuate passages locks the clutch shoes against the movement toward the clutch drum. The clutch housing '5 25, therefore, remains idle and no driving force is transmitted to the sheave 27;

At the end of an operation calling for clockwise rotation of the drive shaft, the clutch elements will remain in the Fig. 4 relationship. If a succeeding operation requires power to be transmitted to sheave 27, rotation of the drive shaft in counterclockwise direction will rotate the clutch plates relative to the clutch shoes until the pins are seated at the base of the associated chordal slots at which point there is no obstruction to the radially outward movement of the clutch shoes into driving position as shown in Fig. 2. As previously noted, the driving effort of the clutch shoes against the clutch drum is related to the speed of rotation of the drive shaft.

At the termination of counterclockwise rotation of the drive shaft and associated clutch plates, the

springs

15 and 16, which had been extended when the clutch shoes moved radially outward, will draw the clutch shoes radially inward until the home position shown in Fig. 5 has beeen attained.

The notches and peaks of the respective clutch shoes accurately align the clutch shoes for proper operation at the next operating cycle of the apparatus. It is impossible for one clutch shoe to become disarranged relative to the other or relative to the passages in the drive shoes. The interfitted relationship stabilizes the clutch shoes in their non-operating position and insures that the center of mass of each shoe is at substantially the same distance from the drive shaft.

For purposes of ventilation, and escape of dust which may result from the frictional contact of the clutch shoes with the clutch drum it is expedient to provide a plurality of holes 31 about the low point of the housing 25, and a suitable grouping of holes 32 through the cap 29.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

I claim:

1. A centrifugal clutch, comprising a drive shaft rotatable in either of two directions, a drive plate fixed to said shaft normal to the axis thereof, a clutch housing rotatably mounted on said shaft and providing a clutch ing surface disposed about said drive plate in spaced concentric relation therewith, a plurality of clutch shoes slidably carried by said drive plate and having friction surfaces engageable with said clutching surface, drive means fixed to said clutch shoes, drive means carried by said drive plate slidably engaging said clutch shoe drive means to transmit power from said drive shaft to said clutch shoes, the respective drive means cooperating to guide said clutch shoes into driving position upon rotation of said drive plate in one direction, means for withdrawing said clutch shoes out of driving position when said drive plate is at rest, and means on said drive plate eifective immediately upon displacement of said drive plate from a rest position into rotation in the opposite direction to engage said clutch shoe drive means to maintain the clutch shoes withdrawn from driving position.

2. A centrifugal clutch, comprising a drive shaft rotatable in either of two directions, a drive plate fixed to said shaft normal to the axis thereof, a clutch housing rotatably mounted on said shaft, a clutch drum on said housing disposed about said drive plate in spaced concentric relation therewith, a plurality of clutch shoes slidably carried by said drive plate and having friction surfaces engageable with said clutch drum, drive means fixed to said clutch shoes, drive means carried by said drive plate slidably engaging said clutch shoe drive means to transmit power from said drive shaft to said clutch shoes, the respective drive means cooperating to guide said clutch shoes radially of said drive shaft into clutch-drum engaging position upon rotation of said drive plate in one direction, means for withdrawing said clutch shoes out of driving relation with said clutch drum when said drive plate is at rest, and locking means on said drive plate effective immediately upon displacement of said drive plate from a rest position into rotation in the opposite direction to engage said clutch shoe drive means to maintain the clutch shoes withdrawn from the clutch drum.

3. A centrifugal clutch according to claim 2, in which said first-named drive means comprises a member fixed to each of said clutch shoes and extending therefrom and said second-named drive means comprises wall means formed on said drive plate and slidably engageable with said fixed members.

4. A centrifugal clutch, comprising a drive shaft rotatable in either of two directions, a drive plate fixed to said shaft normal to the axis thereof, a clutch housing rotatably mounted on said shaft, a clutch drum on said housing disposed about said drive plate in spaced concentric relation therewith, said clutch drum being parallel to said drive shaft, a plurality of clutch shoes slidably carried by said drive plate, drive means fixed to said clutch shoes, drive means carried by said drive plate slidably engaging said clutch shoe drive means to transmit power from said drive shaft to said clutch shoes, the respective drive means cooperating to guide said clutch shoes into clutch-drum engaging position upon rotation of said drive plate in one direction, means for withdrawing said clutch shoes out of driving relation with said clutch drum when said drive plate is at rest, means including said secondnamed drive means for maintaining said clutch shoes out of direct contact with said drive shaft, and means on said drive plate effective immediately upon displacement of said drive plate from a rest position into rotation in the opposite direction to engage said clutch shoe drive means r to maintain the clutch shoes withdrawn from the clutch drum.

5. A centrifugal clutch, comprising a drive shaft, drive means including drive plates fixed in spaced parallel relation on said shaft normal to the axis thereof, a clutch housing mounted on said shaft for rotation thereon, said housing having power take-off means, a clutch drum on said housing and having a cylindrical surface surrounding said drive plates in spaced-relation concentricity therewith, a plurality of clutch shoes symmetrically disposed about said drive shaft between said. drive plates, said clutch shoes being freely slidable relative to said drive plates, means including a guide pin on each of said clutch shoes and a first wall means on said drive plates for radially guiding said clutch shoes into frictional engagement with said clutch drum when said guide plates are rotating in a predetermined direction, said guide pin and wall means forming the sole driving connection between said drive plates and said clutch shoes, means for withdrawing said clutch shoes from said clutch drum when said drive plates are at rest, and a second Wall means on said drive plates engageable with said clutch shoe guide pins immediately upon rotation of said drive plates in the opposite direction to secure said clutch shoes against movement into driving engagement with said clutch drum.

6. A centrifugal clutch, comprising a drive shaft, drive means including drive plates fixed in spaced parallel relation on said shaft normal to the axis thereof, a clutch housing mounted on said shaft for rotation thereon, said housing having power take-off means, a clutch drum on said housing and having a cylindrical surface surrounding said drive plates in spaced-relation concentricity therewith, a plurality of clutch shoes of substantialiy greater mass than said drive plates slidably disposed between said drive plates, means including a guide pin on each of said clutch shoes and a first wall means on said drive plates for radially guiding said clutch shoes into frictional engagement with said clutch drum when said guide plates are rotating in a predetermined direction; said guide pin and wall means forming a driving connection 7 .v betweenrsaid drive plates and said clutch shoes, means for withdrawing said clutch shoes from said clutch drum when said drive plates are at rest, said first wall means establishing a home position of said clutch shoes out of engagement with said drive shaft, and a second wall means on said drive plates engageable with said clutch shoe guide pins immediately upon rotation of said drive plates in the opposite direction to secure said clutch shoes against movement into driving engagement with said clutch drum.

7. A centrifugal clutch, comprising a drive shaft, drive means including drive plates fixed in spaced parallel relation on said shaft normal to the axis thereof, a clutch housing mounted on said shaft for rotation thereon, said housing having power take-off means, a clutch drum on said housing and having a cylindrical surface surrounding said drive plates in spaced-relation concentricity therewith, a plurality of substantially identical clutch shoes of substantial mass slidably disposed between said drive plates, means including a guide pin on each of said clutch shoes and a first Wall means on said drive plates for radially guiding said clutch shoes into frictional engagement with said clutch drum when said guide plates are rotating in a predetermined direction; said guide pin and wail means forming the sole driving connection between said drive plates and said clutch shoes, spring means fixed to and extending between said guide pins for withdrawing said clutch shoes from said clutch drum to a uniform home position when said drive plates are at rest, and a second wall means on said drive plates communicating with said first wall means at the radially innermost ends thereof and engageable with said clutch shoe guide pins immediately upon rotation of said drive plates in the opposite direction to secure said clutch shoes in said home position so long as said drive plates are operating in said opposite direction.

8. A centrifugal clutch according to claim 7, in which the radially innermost ends of said clutch shoes are configurated for interfitting relation one with the other to establish a uniformly symmetrical disposition of said clutch shoes relative to said drive shaft when said clutch shoes are in said home position.

9. A centrifugal clutch, comprising a drive shaft rotatable in either of two directions, a power take-off means fixed to said drive shaft, drive means including a pair of drive plates fixed in spaced parallel relation on said shaft normal to the axis thereof, a clutch housing mounted on said shaft for rotation thereon, said clutch housing having power take-01f means, a clutch drum on said housing and having a cylindrical clutch surface surrounding said drive plates in spaced-relation concentricity therewith, a pair of relatively heavy clutch shoes symmetrically disposed about said drive shaft between said drive plates, said shoes being freely movable relative to said drive plates, a guide pin fixed to each of said clutch shoes on opposite sides of said drive shaft and projecting from said shoes parallel to said shaft and in symmetrical relation thereto, wall means on said drive plates defining passages extending chordally of said clutch drum to receive the projecting guide pins for radially guiding said clutch shoes into frictional engagement with said clutch drum upon rotation of said drive plates in a predetermined direction, said guide pinsand wall means forming the sole driving connection between said drive plates and said clutch shoes, spring means for withdrawing said clutch shoes from said clutch drum when said drive plates cease to rotate, and a second Wall means on said drive plates defining arcuate passages concentric With said drive shaft and communicating with said chordally extending passages at the radially innermost ends thereof to receive said pins when said drive plates are rotated in the opposite direction from a standing start, whereby said second wall means engage said drive pins and secure said clutch shoes against movement toward said clutch drum so long as said drive shaft and thereon-alfixed drive plates are rotating in said opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,903 Royse Nov. 1, 1938 1,943,930 Rock Jan. 16, 1934 2,016,643 Lowndes Oct. 8, 1935 2,340,368 Dodge Feb. 1, 1944 2,529,919 Cunningham Nov. 14, 1950