US2577173A - Overload protection for drive motors of automatic washing machines and the like - Google Patents

Description

Dec. 4, 1951 J. c. WORST 2,577,173

OVERLOAD PROTECTION FOR DRIVE MOTORS OF AUTOMATIC WASHING MACHINES AND THE LIKE Filed July 1, 1949 Inventor": Joseph C. \Novst,

Hi6 Abbovrweg.

Patented Dec. 4, 1951 OVERLOAD PROTECTION FOR DRIVE MOTORS OF AUTOMATIC WASHING MACHINES AND THE LIKE Joseph 0. Worst, Bridgeport, Conn., assignor to General Electric New York Company, a corporation of Application July 1, 1949, Serial No. 102,554

2 Claims.

This invention relates to an improved control circuit and control device for the drive motor of automatic washing machines of the type in which clothes are washed and spin-dried in a single basket; and a particular objective of the invention is to provide means for automatically relieving the load on the drive motor and thus protecting its running winding against excess current resulting from an overload condition.

A popular make of automatic washing machine of the above-noted type uses a single drive motor to operate a washing device such as an agitator and to rotate the tub to extract the water from the tub and clothes by centrifugal action. By a conventional automatic program control switch the spin-dry period is initiated by the operation of an electrically operated valve which directs oil under pressure into a clutch shifting system to de-clutch the agitator mech= anism and couple the motor to means constituting a direct drive between the motor and the rotatable mounting of the basket. The inertia of the loaded basket places a severe load on the motor as the spin begins, with the result that an undesirably large current may be drawn by the running winding of the motor. If this condition is permitted to exist for even a short time the motor winding may burn out.

I accomplish my above-stated principal objective of protection against such motor overload, as well as the further objectives of simplification of the protection agency and reduction of cost thereof, by providing a unique motor starting relay having an operating coil in series with the running winding of the motor and a biased armature system for closing the customary start winding circuit on the initial inrush of current to the motor and for controlling a switching device in series with the valve circuit. The armature bias is adjusted to relay coil strength so that if the loaded basket imposes too great a burden on the motor at the commencement of spin, the additional current drawn by the motor and the relay winding will deflect the armature sufficiently to open the valve circuit for reduction of the hydraulic pressure at the clutching means. The clutch will slip, and the load on the motor drop proportionately; and as the current drawn by the motor winding and relay coil drops as the result of the lessened load, the biased armature again conditions the valve circuit to valve the hydraulic pressure to the clutch assembly. The basket drive system will experience a succession of clutch engagements and partial tie-engagements until the basket inertia has been overcome and the motor load is at a normal level.

Other features and advantages will be apparent from the following description taken in connection with the accompanying drawing in which Fig. l is a representation of the motor and bydraulic clutch system of a conventional automatic washing machine and a somewhat schematic wiring diagram for the relay incorporating the present invention; and Figs. 2 and 3 are respectively a top plan view and a side elevation of a relay embodying the invention.

Referring now to Fig. l, a washing mechanism it includes a motor in which stator 2 is suitably fixed within a housing 3 secured to a main frame structure 4. The stator is provided with a conventional start winding 5 and running windin 6. The rotor 7 has a tubular shaft 8 suitably journaled in a bearing 9. Rotatably mounted within the tubular shaft 8 is a shaft Hi, to which is suitably afiixed a clutch member it for cooperation with a complementary clutch element it mixed to the rotor. Also aflixed to the rotor is a cup 14, to the lower flange of which is secured the end of a flexible metallic bellows H5. The opposite end of said bellows is fixed to a spin clutch member it which is suitably secured to a sleeve l'l rotatable on shaft it. A spring it within cup it bears against a cap l9 suitably supported on shaft 10 and thus biases the bellows :5 toward collapse. Drive pinion meshes with a gear 2:! of a gear system carried by a frame 22. The gear frame 22 is suitably rotatably carried in a bearing 23 formed in the frame structure 4 and journaling a hub 24' extending from the frame. The main frame member 4 provides an anchorage for a brake element 25 arranged for cooperation with a combined brake and clutch element 26 having a driving connection with the hub by the ears 2'! which fit slidably but closely within slots 28 formed in the flange of a cup member 30 fixed to said hub as shown. A spring 3| confined within cup 30 and pressing against a central web of the clutch member 26 urges the said member downwardly of Fig. 1 so that it engages the brake 25.

Hub 24 is concentric with a shaft (not shown) fixed to and extending from frame 22, and by means of which the wash basket (not shown) is spun. The gearing within the frame is such that with the frame 22 held against rotation an agitator (not shown) oscillates within the basket to effect washing of the clothes.

The bearing 9 has at its base an eccentric pump chamber within which operate the blades 32 which are slidably carried within the end of the tubular rotor shaft 3. Said blades comprise the impellers of a vane pump directly driven by the motor, said pump drawing oil from a sump 33 through an intake tube 34 and discharging it through an orifice 35 provided in a plate 36 forming the base of the pump chamber and through a passage 31 for distribution of lubricating oil under pressure. Aflixed to the cover plate 36 is a dished cap 38 having an orifice 39 which forms the seat for an electrically operated valve, which most conveniently comprises a magnetic plunger valve -4|! within the solenoid coil 4|.

The foregoing structure is essentially shown and explained in greater detail in the presently pending application Serial No. 551,096, filed August 25, 1944, by Thomas T. Woodson, for Clutch Structure for Automatic Washing Machine, and assigned to the assignee of the present application. For the present it will be suflicient to note that during the washing established by the operation of a suitable program switch (not shown) the motor is energized and the solenoid coil 4| de-energized to the Fig. 1 position, whereby the greater part of the oil pressure generated by the vane pump recirculates to the sump through an aperture 35 in cover plate 36, aperture 39 in cap plate 36 and along the sides of the polygonal plunger valve 40. A lesser quantity of oil under light pressure circulates through the system for lubrication, and a portion thereof passes upwardly through the apertures 42 and 43 to flow along the side wall of the shaft I and enter the space 44 between the respective clutch elements H and i2 from which it seeps through the openings 45 in clutch member II and 46 in the cap l4 to fill the interior of the bellows |5. Venting of the bellows i is provided by the bearing clearance between shaft Hi and sleeve Under such condition of operation the spring 3| biases the element 26 against brake 25 and the shaft l0 and its thereon carried pinion is connected to the rotor by the clutch members I2. The gear frame being held against rotation by the brake, the

agitator is oscillated to effect the washing operation. When the "basket is to be spun for removal of water from the clothes, the program switch operates to energize the solenoid coil 4| to draw the plunger valve 40 upwardly to close the plate opening 39 and prevent the recirculation of oil to the sump 33. Under these conditions oil under substantial pressure flows into the chamber 44 faster than it can be bled out through the openings 45, and the clutch member II is lifted to disengage the clutch plate l2. The drive pinion 20 is then no longer powered. Oil pressure building up within the bellows |5 expands it to drive the clutch element I6 upwardly into contact with the clutch element 26. Additional bellows expansion raises the clutch element from the brake and there is then a direct drive connection between the rotor and the drive cup which, it will be recalled, is fixed to the hub 24 of the gear frame. The gear frame and thereby driven wash basket is thus arranged to be driven at motor speed.

It should be mentioned that the basket itself is purposely heavy for flywheel effect and with the water and laundry content, the total weight may be of the order of two hundred pounds. Accordingly, there is a very substantial inertia which must be overcome before the basket can be brought to motor speed and the motor is subjected to severe load conditions during the early stages of spin. Mechanical devices have been proposed and used adjustably to bleed the bellows l6, ac cording to the speed or torque of the motor and thus permit the same to collapse and withdraw the clutch member l6 partially from the combined clutch and brake member 26, so as to cause clutch slip and reduce the motor load.

The present invention utilizes the power demand of the motor, as represented by the amperage of the running winding 6, for controlling the electrically actuated valve 40 and thereby establishing direct control over the pressure of oil within the bellows l5. De-energization of the solenoid will cause the valve 40 to open the port 39 for recirculation of the oil to the sump, immediately reducing the bellows pressure.

My combined starting relay and valve control 50, see Figs. 2 and 3, utilizes a conventional coil 5| in series in the running winding circuit as appears from Fig. 1. The coil has a magnetic core 52 which advantageously comprises an end of a bracket 53 supported on the insulating base 54.

The bracket also provides a bus bar for connection of the coil, and accordingly one end of the coil is brazed to the bracket, to which also is brazed the lead conductor 55. Armature 56 is carried on a leaf spring 51 and is biased by said spring and the fiexure-adjustment screw 58 to move away from the core; in the illustrated embodiment, such movement is outward relative to the base, Fixed to the armature is a downwardly extending spring contact having a silver or equivalent contact 66 cooperating with a similar contact 6| resiliently carried by the base. A contact button 62 fixed directly to armature 56 cooperates with a contact 63 provided on an arm 64 carried by base 54 and projecting therefrom. The armature bias brings contacts 62 63 normally to circuit closing position. Contacts 62 and 63 are the overload protection contacts, as later appears, and will open and close frequently under usual conditions. Accordingly, it is preferred that they be of tungsten.

As shown in Fig. 1, contacts 60, 6| are in the start winding circuit, and initial inrush of current to the running winding energizes coil 5| sumciently to draw armature 56 to the core, as a result of which the start contact system 60. 6| will be closed and the circuit to the start winding completed. As the motor comes up to operational speed the current drawn by the running winding and the coil 5| decreases, so that the magnetism of core 52 is insuflicient to hold armature 56 against its inherent bias to open contacts 66. 6| and to close contacts 62, 63. The motor thus continues operation on its running winding. Contacts 62, 63 are in the electrical valve circuit, and are in series with a switch 65, diagrammatically shown, but representing the spin-dry switch of the program switch. Until the program switch closes switch 65, the solenoid 4| remains deenergized even though contacts 62, 63 are closed. When the program switch comes into spin operation, however, switch 65 is closed by suitable means to energize the solenoid whereupon oil under pressure is valved into the bellows IS with the aforementioned results. If because of the inertia of the basket the motor load increases undesirably the running winding will draw excessive current and the relay coil 5| will attract the armature 56. However, the

creases to a level beyond a normal or safe" operating range. Aftera number of such operations depending on the inertia factors of the basket. the motor will bring the basket up to operating speed and operation will proceed normally through the spin cycle under satisfactory motor load conditions.

As a typical example of operating ranges, the armature bias on a device which I have constructed and tested under usual operating conditions will cause the contacts 62 and 63 to close when the running winding draws twelve amperes, but will release these contacts, without closing the start winding contacts at about fourteen amperes. The load relief resulting from the operation of the electric valve is quickly effective and under normal wash loads, the clutch slippage returns the running winding current almost immediately to the twelve ampere level at which the electric valve again becomes energized.

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

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

1. In a washing machine of the single basket wash andspin-dry type having a single motor for the washing and spin-drying operations, said motor having a start winding and a running winding, a hydraulically actuated clutch system for drivingly connecting the motor to the basket, a source of hydraulic pressure, and an electrically operated valve for valving liquid under pressure to said clutch system to engage the clutch or for relieving said pressure to permit said clutch to disengage according to whether the valve circuit is closed or open, the improvement in means for relieving said pressure in the event of motor overload comprising a relay switch having an actuating coil in series with said running winding, a switch in the start winding circuit. and armature means common to said switches for closing or opening one or the other according to the condition oi energization of said coil, said armature being biased to close said valve circuit but responsive to the value of the starting current demand in said motor to open said circuit and close the start winding circuit, and under current demand conditions above normal running values but less than the starting value to open the valve circuit switch for clutch pressure relief without closing said start winding circuit switch.

2. In a washing machine of the single basket wash and spin-dry type having a single motor for the washing and spin-drying operations, said motor having a start winding and a running winding, a fluid pressure actuated clutch system for drivingly connecting the motor to the basket. a system for generating fluid pressure and conducting the same to said clutch, said system including normally open valve means and electrically responsive means eifective when energized to operate said valve to direct liquid under pressure to said clutch to engage the same and when deenergized permitting said valve to open for release of said clutch-engaging pressure, and an electric circuit for said valve operator, the improvement comprising a single pole, double throw switch having one throw position serially connected in said valve operator circuit and the other throw position in said start winding circuit, means biasing said switch'into valve circuit closing position, and electromagnetic means in series with the motor rurming winding for operating said switch in accordance with the magnitude of the current drawn by said winding, said electromagnetic means being so related to the switch biasingmeans that current drawn by the winding under normal or lightly overloaded motor demand will energize said electromagnetic means insufliciently to overcome the switch bias. moderate overload current demand will overcome said bias sufliciently to open said valve circuit without completing said start winding circuit, and the current drawn by the winding under severe motor overload will throw said switch to complete said start winding circuit after opening said valve circuit.

JOSEPH C. WORST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,007,388 Tarleton July 9, 1935 2,062,052 Horlscher Nov. 24, 1936 2,069,767 McCormack Feb. 9, 1937 2,432,272 Barim Dec. 9, 1947

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