US2733796A

US2733796A - Centrifugal force responsive clutch

Info

Publication number: US2733796A
Authority: US
Publication date: 1956-02-07
Anticipated expiration: 1973-02-07

Description

Feb. 7, 1956 s. L. M MILLAN ET AL CENTRIFUGAL FORCE RESPONSIVE CLUTCH FOR A CLOTHES WASHING MACHINE Filed April 12, 1952 Inventor's. Stephen L. McMillan,

Milton S. Williams,

Their- Attorne s.

United States Patent CENTRIFUGAL FORCE RESPONSIVE CLUTCH F OR A CLOTHES WASHING MACHINE Stephen L. McMiilan and Milton S. Williams, Louisville,

Ky., assignors to General Electric Company, a corporation of New York Application April 12, 1952, Serial No. 282,056 5 Claims. (Cl. 192-105) This invention relates to torque transmitting devices, and more particularly to a hydraulically operated centrifugal force responsive clutch.

Although our invention is not limited specifically thereto, it is particularly useful in the driving mechanism of clothes washing machines of the type in which washing is performed in a single basket which may then be rotated to centrifugally extract the water from the clothes. The basket or receptacle in which the clothes are washed is provided with a coaxial agitator which, when oscillated, flexes the clothes and imparts certain movements to the liquid which effect a turnover and redistribution of the clothes within the basket. The load imposed upon the shaft driven by the operating motor for the machine is less when it is connected to the relatively light weight agitator than when it is called upon to drive the loaded basket, which may contain from 12 to 14 gallons of water. Since the former demand is so small relative to the latter, the agitation drive presents no particular motor protection problem. It is the initial acceleration of the clothes basket during the spinning operation that imposes the greatest load on the drive motor and consequently, at this time, motor protection is most needed.

Since washers of this type must be sold on a highly competitive market, as inexpensive a drive motor as possible should be used to supply the torque requirement. An induction motor, commonly of the resistance splitphase type, is most generally used. The start Winding of such a motor can be energized only a few seconds at a time Without overheating; hence, the motor must be allowed to come up to speed quickly and to continue to operate at sufficient speed to prevent the start winding from being again energized, throughout the latter portion of the acceleration period of the basket and the remainder of its spinning operation. This requirement, for the motor to run at one speed while the loaded shaft may rotate at varying speeds, necessitates the use of a motor protective clutch between the motor and the main driven shaft. This clutch should be capable of transmitting at all times the maximum torque that the motor is then able to deliver in order to hold the acceleration time to a minimum, even with the supply voltage to the motor varying between 90 and 120 volts. The clutch must also protect the motor from being overloaded and thereby reduced in rotational speed sufficiently to reenergize the start Winding, and in addition it must be sufliciently well cooled to dissipate the heat generated during its extended period of slip.

Since it has been found most satisfactory to use a liquid coolant, it is ony natural that fluid operated clutches have been frequently used in this type of application. To protect the motor a torque sensitive arrangement is commonly employed to operate a pressure relief mechanism and provide for clutch slippage at a predetermined torque output. To fully protect the motor, however, this limit must be set below the maximum torqueof the motor at the lowest voltage at which it may be expected to operate, usually about 90 volts, and the clutch output at normal voltage is thereby limited. Other clutch arrangements have been used in which the motor is protected by making the torque output of the clutch sensitive to motor speed. This permits a fuller utilization of the torque of the motor Patented Feb. 7, 1956 at normal voltage while giving protection at reduced voltage. An example of such a construction is that shown in the application of James F. Young, S. N. 193,143, filed October 31, 1950, for Centrifugal Clutch for Washing Machines, now Patent 2,720,955, issued October 18, 1955, and assigned to the General Electric Company, assignee of the present application. The most simple and direct clutch construction, however, would be one utilizing centrifugal force both to supply the operating liquid to the clutch and to provide the clutch face engaging pressures desired.

Accordingly, it is an object of our invention to provide a hydraulic clutch which is simple in construction and direct in operation and which provides continuous motor overload protection without the use of either pressure relief valves in the clutch mechanism or pumps for supplying liquid thereto.

It is a further object of our invention to provide a hydraulic clutch in which the pressure required to effect engagement of the clutch faces is provided by the centrifugal force of a quantity of oil within the rotating clutch housing.

It is a still further object of our invention to provide a hydraulic clutch of the centrifugal force responsive type in which the liquid Within the clutch is supplied in response to rotation of a portion of the clutch housing within a reservoir of liquid.

In carrying out the objects of our invention, there is provided a hydraulic clutch which includes a housing portion connected to the rotor of the drive motor. Rotation of the housing efiects centrifugal supply of oil from a reservoir to a chamber within the housing and the resulting pressure is exerted to effect engagement of the clutch. Since the centrifugal force and the resulting pressure varies with the speed, the full clutch engagement is delayed until the motor has developed adequate torque. In one form of our invention, a spring bias is provided to prevent any engagement of the clutch until a predetermined minimum speed of the motor has been reached. In this form the motor may be completely unloaded at all times that its speed is below that at which the start winding is deenergized.

Our invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 is a vertical sectional elevation of a clothes washer drive mechanism embodying our invention; Fig. 2 is a partial sectional elevation of the lower portion of the mechanism of Fig. 1 showing our improved clutch in its disengaged position; Fig. 3 is a view similar to Fig. 2 but showing our clutch in its engaged position; and Fig. 4 is a partial sectional elevation of a drive mechanism similar to that of Fig. 1 and showing a modified form of our clutch in engaged position.

Referring now to Fig. 1, there is provided a drive mechanism enclosed by a surrounding casing 1 and including a drive motor 2, preferably of the induction type, provided with a rotor 3. The motor is suitably energized by electrical connections 4 extending through the casing 1. The mechanism further comprises a rotatable clutch housing Shaving an upstanding hub portion 6 fixed by suitable means, such as screws 7 to the bottom portion of the motor rotor 3. The lower end of the clutch housing memupwardly along the axis of the motor rotor is a main driven shaft 10.

To provide support for the driving and driven structures, we fix within the casing 1 a frame 11 supported by any suitable means, such as by screws 12, supporting lugs 13, and ring 14- attached to the casing wall. This main support frame serves as the means of supporting the drive motor 2; also it is cored to accommodate the upwardly extending shaft and is provided with a sleeve 15 in which suitable bearings 16 are fitted for supporting the ends of the shaft. The shaft itself is provided at its lower end with a thrust washer 17 supported on a snap ring to limit any upward movement within the sleeve. At.its upper end is formed an integral pinion 13, with the underside of the pinion teeth, which extend radially beyond the shaft periphery, serving to support the weight of the shaft.

The motor rotor is pressed on a tube 19 of larger diameter than the sleeve 15, and into the ends of which are pressed a pair of bearings 20. These bearings rotate, with the rotor about the sleeve 15. At the upper end of the tube 19 and integral with it is a coaxial cylindrical enlarged portion which constitutes a rotor 21 for an oil supply pump. A pump casing or housing 22 fixed to the frame 11 encloses the pump rotor 21, and a bottom cover plate 23 of the housing 22 serves as a thrust bearing beneath the pump rotor to support the motor rotor 2 and clutch housing 5. The pump housing 22 forms an eccentric generally cylindrical cavity. The pump rotor is provided with a plurality of radial slots, not shown, into which pump vanes, such as the vane 24 shown in Fig. l, are fitted. The vanes are free to slide within their slots and during rotation of the pump rotor are held against the outer housing wall by centrifugal force. Delivery of oil through a pump outlet, not shown, is accomplishcd as a result of the changing volumes of oil entrapped between adjacent vanes, the pump rotor, and the eccentric housing wall. This construction is by way of illustration only and is not a part of our invention. Any means of supplying oil under pressure for lubrication of the various parts of the mechanism as well as for actuating a spin clutch, as presently described, would be suitable for use with our improved clutch.

Also journaled within the supporting frame 11 is a second driven shaft 25. The pinion 18 formed at the upper end of the main driven shaft 10 engages a gear 26 keyed or otherwise fixed to this second shaft to provide a reduced speed drive connection between the two. The

- shaft 25 at its upper end is provided with a pinion 27 for driving an oscillation producing mechanism 28, and carries intermediate the gear 26 and pinion 27 a spin clutch drive plate 29 for rotating a clothes basket, not shown, or the like.

The oscillation producing mechanism comprises a gear rame 38 supported by but not fixed to the frame 11. t further comprises apair of gears 31 engaged with the pinion 27 and rotatably mounted on a pair of shafts 32 suitably journaled in the gear frame. Integrally formed with each gear 31. is an upwardly extending cylindrical hub portion 33 the center of which is eccentrically located with respect to its shaft. These hubs serve as eccentric stub shafts on each or" which is rotatably mounted racks 34 arranged on opposite sides of a pinion 35 carried on the lower end of a shaft 36. The shaft 36 in turn extends upwardly beyond the casing 1 for oscillatively driving a suitable load, such as a clothes washer agitator. The oscillation producing mechanism shown is by way of illustration only, and is more fully shown and described in Patent 2,222,329, Watts, granted November 19, 1940, and assigned to the General Electric Company, assignee of the present application.

As previously explained, the shaft 25 carries a spin clutch plate 29 which may be attached either to the shaft or to the upper face of the gear 26. The clutch member 29 carries on the upper side of its peripheral surface suitable clutch facing material 37 which is engageable with clutch facing material 38 carried on the underside of a portion of the gear frame 30. The gear frame 30 is gravity biased into engagement with a surface of the main frame 11 to hold the gear frame stationary during oscillation of the shaft 36. Then, as a result of fiuid pressure introduced in a manner hereinafter explained, the spin clutch member 29 may be raised, lifting the gear frame 30 out of engagement with the frame 11 and rotatably driving it. The upper ends of the shafts 32, which are carried by the frame 30, are fixed to a hub 39 by passing through an outwardly extending flange portion 40 integral therewith. The hub 39 serves to support and guide a tubular shaft 41 to which it is fixed by key 42. Consequently, upon rotation of the gear frame 30 by the spin clutch member 29, the shaft 41 is rotated at the same speed as the shaft 25. It will be understood, of course, that the shaft 41 is fixed to a suitable load such as a clothes basket of a washing machine.

While any suitable means may be used for lifting the frame 30 and drivingly connecting it for rotation with the shaft 25, I have shown a hydraulic system comprising a liquid intake pipe 43 extending into the pool of liquid in the bottom of the casing 1. The pipe 43 connects with the pump comprising the housing 22 and the eccentric vanes 24 for supplying both lubricating oil to the bearings for the shafts 10 and 25 and to the oscillation producing mechanism 28 and also for supplying, at a predetermined time, oil under pressure to the underside of the clutch member 29 to cause it to fn'ctionally engage the gear frame facing 38 and to lift the gear frame off the main support frame 11. The passageway between the pump and the space beneath the spin clutch member 29 is not shown, nor is the control system which determines the period of energization of the spin clutch. Any suitable arrangement may be used, however; for example, the control arrangement used in the copending application of Carl S. Dayton, Serial No. 226,801, filed May 17, 1951, for Drive Mechanism for Clothes Washing Machines and the Like, now Patent 2,645,110 issued July 14, 1953, assigned to the General Electric Company, assignee of the present application, could be suitably adapted. It should be understood that both the spin clutch arrangement, the oscillation producing mechanism, and the gear frame brake and release arrangement as shown and described are by way of illustration only, as any suitable means of selectively loading a driven shaft with variable loads would be suitable to illustrate the purpose and operation of our invention.

Referring now to Fig. 2, we have shown a simple and improved centrifugal force responsive motor protective clutch arrangement embodying this invention. As previously explained, this clutch comprises a substantially cylindrical housing 5 attached to and rotatable with the motor rotor. Depending from the bottom of the housing 5 is the conical oil supply device 8, the open end of which is submerged in oil. The clutch driven disk 9, slidably connected to the main driven shaft 10, is enclosed within the upper portion of the housing 5 and arranged, upon being drivingly engaged by it, to transmit torque in accordance with the speed of rotation of the rotor and housing. Also, as previously explained, clutch engagement is in response to the pressure of the oil within. the housing, which inturnis dependent on the centrifugal force exerted on the oil during rotation.

Oil is initially supplied to the clutch housing by the device 8. This device is formed in the shape of a frustum of an inverted cone and is provided with an outwardly and upwardly tapering wall portion 4.4 along which oil climbs as a result of centrifugal force during housing rotation. The bottom of the clutch housing is formedwith an aperture forming a passageway 45 spaced from the axis of the housing a distance approximately equal to the diameter of the conical device at its upper end, to admit oil into the housing. I 7

Within the clutch housing 5 we provide an intermedi- 7 ate clutch plate 46 keyed to the housing by a plurality of peripheral lugs 47 and centrally aligned within the housing on a pin 48 which extends downwardly along the axis of the housing and through the liquid supply device. This plate is suitably spaced a predetermined minimum distance above the housing bottom by 'a washer 49 aflixed to its under surface as Well as to the pin 48, thereby securing together the pin and plate. The slidable plate 46 may be provided with fins 50 depending from its lower edge to cause the accumulated oil to attain the same rotational speed as the housing more quickly than would be the case if a smooth surface were presented. The lower half of the housing 5 and the plate 46 together form a chamber 51 which may be sealed against leakage by any well known type of seal such as the resilient expandable gasket 52. This gasket may be fixed to the periphery of the under surface of the slidableplate 46 or merely compressed between it'and the bottom of the housing. Consequently, oil supplied to the housing 5 enters the'chamber 51 and rotates with the housing, exerting an upward force on the plate 46 in an amount dependent on the rotational speed.

The quantity of liquid contributing to the centrifugal force created pressure is limited by an annular series of openings 53 provided in either the housing bottom wall or the plate but shown as being in the plate 46 intermediate its center and periphery, to bleed liquid from the chamber. All liquid in the chamber between the axis of the housing and the aperture 53 will, consequently, remain at approximately the pressure of the atmosphere within the casing 1. The liquid in the chamber between the aperture 53 and the periphery of the housing, however, will build up pressure as the speed of rotation increases. It should be understood that the openings 53 could be replaced with a single large opening capable of discharging oil as rapidly as it is supplied to the chamber. Any liquid leaking past the seal 52, moreover, will be readily replaced by the constant supply through the centrifugal device 8.

If the clutch is designed for a particular application, then it-Will, of course, be unnecessary to drill the holes 53. This is because, with proper design, the clutch chamber will have just the oil capacity required to deliver at full output speed the maximum torque for which the motor is rated. When, however, only the general range of motor torque capacity, speed, and load is known at the time the clutch is designed, alternate annular rows ofopenings, not shown, may be drilled inthe housing bottom wall or in the plate, and all the rows plugged except the one which gives the optimum performance underthe conditions of its ultimate application 'When'no such openings are provided for pressure relief, then we have found it advisable to provide at leastone opening such as 53 as close to the center of the clutch driven member or disk as practicable, to allow air to escape from the clutch cavity during initial filling of the cavity with oil.

The clutch driven member 9, located immediately above the slidable plate 46, is preferably provided with clutch facings 54 and'55 respectively on bothits under and upper sides, as shown in Fig, 2. Inthe disengaged position of the clutch, the plate 9 rests lightly on the top of the plate 46, which in turn is supported by the bottom of the housing 5. In this position, there is a small space between the upper clutch facing 54 and .the top of the housing. The clutch facings should be lubricated during clutch engagement and for this purpose the oil supplied to the clutch chamber may be used. To insure an adequate amount reaching the friction surfaces, we provide near the periphery of the clutch plate 46 one or more very small openings, not shown. Such openingswill, of course, be unnecessary if the seal permits a small amount of leakage during clutch engagement.

A plurality of vent holes 56 arranged in an annular row equally spaced from its center may be provided in the member 9 so that any oil leaking into the space between member 9 and the plate '46 may readily drain without causing a pressure build-up which would oppose the upward movement of the slidable plate. Oil pressure within the housing above the member 9 is relieved by a similar aperture 56a in the housing upper wall.

At the beginning of the spin operation, as the drive motor begins to attain its rated speed, the clutch housing rotates at a sufficient speed that oil begins to creep up the face 44 of the device 8 and spill into the chamber 51. Ordinarily even the small amount of centrifugal force resulting would then cause the plate 46 to move upwardly to begin to press the respective

clutch facings

54 and 55 of the member 9 between the housing and the upper side of the plate 46, but it is desirable to give the motor a completely unloaded start until a predetermined speed has been reached. To this end, we provide spring biasing means preventing the upward movement of the slidable plate during slow speed rotation of the housing. These means include a spring 57 hearing at its upper end against the bottom of the housing and at its lower end against a thrust washer 58. This washer is supported by a pair of nuts 59 on a threaded lower end portion 60 of the pin 48. Since the pin 48 is fixed to the plate 46, the spring 57 biases the plate downwardly and, until the force of the spring is overcome, there will be no clutch engaging force exerted on the clutch driven member 9. After this predetermined speed is reached, the plate 46 will be elevated in response to the centrifugal force created pressure on its under side. This will drive the clutch driven member 9 upwardly to the position shown in Fig. 3, causing frictional engagement between the plate 46 and the facing 55 and between the upper part of the housing 5 and the facing 54. The clutch torque capacity thereafter depends upon the centrifugal force acting on the liquid contained in the chamber 51, which in turn depends upon the speed of rotation of the driving motor. When it has reached its rated output speed, the clutch will have substantially no slippage and the shaft 10 will be rotated at approximately the same speed as the motor. When a heavier load is imposed upon the shaft 10, sufiicient to overload the motor, the latters speed will be reduced, which in turn will cause a reduction of the pressure on the

clutch facings

54 and 55 and, consequently, permit increased clutch slippage to give full protection to the motor.

Referring now to Fig. 4, there is shown a modified form of our clutch which utilizes the principles of our preferred form and which, because of its simplicity and economy of manufacture, may be more suitable in certain applications. A housing 61 is provided, similar to the housing 5 of Fig. 2, and it has an upwardly extending portion 62 for attachment to a motor rotor, not shown. It will be understood, of course, that direct attachment to the rotor while highly desirable, and made possible by the motor protection afforded by our invention, is not essential; other well known means of rotating the housing can be used. A supply device 63 in the shape of an inverted truncated cone depends from the housing to dip into a pool of oil, not shown. This supply device includes apair of outwardly sloping drilled passages 64 in the cone member, beginning at the central opening 65 at the bottom and diverging as they extend upwardly to a clutch chamber or oil-receiving chamber 68. Of course, the similar conical supply device shown in Figs. 2 and 3 would also be suitable.

Within the clutch housing is a single clutch driven member 66 in the form of a circular disk free to slide from a disengaged position in the lower-portion of the housing to the engaged position of Fig. 4. The member 66 is provided with a clutch facing 67 at the periphery of its upper surface, which facing may be made of any suitable friction material. The clutch driven member is fixed to a driven shaft which may selectively drive a pair of shafts in the manner previously described, and as shown in Fig. 1.

The oil receiving chamber 68 is formed by the lower portionof the housing 61 and the bottom of .the clutch 7 driven member 66. Communication between this chamber and the oil supply device 63 is established by means ofapertures 69 formed in the bottom of the housing, and offset from its vertical axis.

The oil supplied to the chamber 68 is quickly brought up to the rotational speed of the housing by means of vanes 70 on the housing bottom wall. An oil bleed opening 71 or an annular row of such openings determines the amount of oil which will be effective in exerting pressure against the plate 66 and is located, for purposes of illustration, near the axis of the housing. In this position it permits nearly all the oil in the chamber 68 V to be pressurized in response to centrifugal force, to thereby elevate the member 66 into the clutch engaging position of Fig. 4. Torque will then be transmitted to the driven shaft in accordance with the speed of .the motor, the clutch inherently increasing its slip whenever the motor is overloaded sufiiciently to reduce its speed.

A bleed opening 72 should be provided in the housing wall above the member 66 to drain oil collecting in the upper housing portion back to the sump.

In order to permit the motor to approach its rated speed under unloadedconditions, biasing means may be added to the modified clutch of Fig. 4 in the manner of the spring 57 of Fig. 2. Upon initial starting the motor is unloaded, even without the spring, however, as there is no oil within the chamber 70. Consequently, biasing means for the clutch driven member is not necessary in all applications of our invention.

In the simple form of clutch shown in Fig. 4, the clearance between the clutch disk 66 and the side wall of the housing is made sufficiently small to permit initial pressure buildup within the chamber 68. This will cause the plate 66 to move to its engaged position, as seen in Fig. 4, and a seal will then be formed between the clutch facing 67 and the upper wall of the housing. Since this seal will become more effective as the chamber pressure increases, there is no need for any further sealing arrangement.

While we have shown a particular embodiment of our invention, it will be understood that we do not Wish to be limited thereto, since many modifications may be made. We, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of our invention.

Whatwe claim as new and desire to secure by Letters Patent of the United States is:

1. A fluid operated clutch comprising a substantially cylindrical housing rotatable on a generally vertical axis, drive means connected to said housing, a clutch driven member within said housing and freely movable along the axis of said housing, a shaft connected to said clutch driven member, a liquid reservoir, means supplying liquid a sure responsive to the centrifugal force acting thereon to move said clutch dn'ven member into engagement with the upper portion of said housing to frictionally couple said member and said housing for transmitting torque to said shaft.

2. A hydraulically operated clutch comprising a rotatable substantially cylindrical clutch housing, driving means for rotating said housing on a substantially vertical axis, an axially movable driven disk mounted Within said housing, a reservoir of oil below said housing, an oil sup ply device for supplying oil from said reservoir to said housing, said supply device comprising a member rotating with and depending coaxially from said housing with the lower end thereof dipping into said oil reservoir, said member having a passageway sloping upwardly and out wardly, a second passageway from the upper portion of said supply device into the interior of said housing whereby oil at relatively low pressure may be supplied by centrifugal force to said housing, said oil accumulated within said housing rotating therewith and exerting a pressure on said driven disk in response to centrifugal force whereby said driven disk is elevated into frictional driving engagement with the upper portion of said housing to trans mit torque to said shaft.

3. An oil operated clutch comprising a substantially cylindrical housing rotatable on a generally vertical axis, drive means connected to said housing, a clutch driven member within said housing and freely movable along the axis of said housing, a shaft connected to said clutch driven member, a liquid reservoir, means supplying oil at low pressure from said reservoir to said housing only during rotation of said housing, said oil supply means comprising an inverted frusto-conical device fixed to the lower portion of said housing and having an outwardly sloping internal passageway communicating with the interior of said housing, the lower portion of said frustoconical device being immersed in oil within said reservoir, the oil within said housing during rotation thereof exerting a pressure responsive to the centrifugal force acting thereon to move said clutch driven member into engagement with the upper portion of said housing to frictionally couple said member and said housing, and vanes carried by said clutch driving member extending downwardly into the oil within the housing.

4. A hydraulically operated clutch comprising a substantially cylindrical rotatable housing, drive means connected to said housing, an axially movable clutch actuating plate mounted within said housing for rotation therewith, a clutch driven disk within said housing above said plate, a shaft connected to said clutch driven disk, an oil reservoir below said housing, means for supplying oil at low pressure from said reservoir to said housing by centrifugal force during rotation thereof, said means including a hollow inverted truncated cone fixed to the bot tom of said housing and extending downwardly into said oil reservoir, the fluid within said housing during rotation exerting a pressure proportional to the centrifugal force exerted on it to move said plate into driving engagement with said disk for driving said shaft.

5. A fluid operated clutch comprising a housing rotatable on a substantially vertical axis, means for rotating said housing, a clutch driven plate within said housing, a driven member connected to said plate, means imparting rotarymotion to liquid within said housing as said housing is rotated whereby centrifugal force acting on the liquid exerts pressure to engage said driven plate with said housing, a liquid reservoir below said housing, a liquid supply conduit'rotating with said housing and depending substantially coaxially therefrom with the lower end thereof immersed in said liquid reservoir, the interior wall of said conduit defining an inclined surface sloping upwardly and outwardly toward said housing, and means providing communication between said conduit and the interior of said housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,118,384 Thompson Nov. 24, 1914 2,210,416 Kiep et al. Aug. 6, 1940 2,517,955 Zimmerman Aug. 8, 1950 FOREIGN PATENTS 347,511 Great Britain Apr. 30, 1931 384,836 Great Britain Dec. 15, 1932 490,131 Germany Jan. 24, 1930 684,973 France Mar. 25, 1930