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Publication numberUS3131566 A
Publication typeGrant
Publication dateMay 5, 1964
Filing dateOct 22, 1962
Priority dateJun 27, 1958
Publication numberUS 3131566 A, US 3131566A, US-A-3131566, US3131566 A, US3131566A
InventorsByron L Brucken, Thomas H Fogt
Original AssigneeGen Motors Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Centrifugally actuated control
US 3131566 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

y 5, 5 B. L. BRUCKEN ETAL 3,131,566

CENTRIFUGALLY ACTUATED CONTROL Original Filed June 27, 1958 s Shets-Sheet 1 INVENTORS Byron L. Bracken BY rho/770$ The/r Af/omey B. BRUCKEN ETAL 3,131,566 CENTRIFUGALLY ACTUATED CONTROL May 5, 1964 3 Sheets-Sheet 2 Original Filed June 27, 1958 INVENTORS 0 8 M. n I 5 0 mm W0 5m w The/r Attorney y 5, 1964 B. BRUCKEN ETAL 3,131,566

CENTRIFUGALLY ACTUATED CONTROL 3 Sheets-Sheet 3 Original Filed June 27, 1958 High Speed Running Condition .Srorf Winding Curouf for born High and Low Speed Current in Amperes United States Patent CENTRIFUGALLY ACTUATED CONTROL Byron L. Bracken, Dayton, and Thomas H. Fogt, West Carrollton, Ohio, assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Original application June 27, 1958, Ser. No. 745,152. Divided and this application Oct. 22, 1962, Ser. No. 231,993 3 Claims. (Cl. 73--537) This is a division of our copending application Serial No. 745,152, filed June 27, 1958, and relates to a control circuit for multi-speed motors and more particularly to a centrifugally actuated control circuit for use with multi-speed washing machines.

With the advane of man-made fabrics, the washing machine art has found it necessary to revise washing procedures to make them adaptable to the new fabrics. For this purpose, the washing machines in current vogue include a drive mechanism capable of agitating the clothes at two or more speeds. Furthermore, such mechanism is arranged to spin the clothes in a centrifuging operation at two or more speeds to remove the water from the clothes. It should be apparent that variable .loads are imposed on and variable speeds are required of any motor utilized in such drivemechanisrn. During the spin cycle, for instance, a considerable torque is required to initiate the rotation of a laundry tub up to a speed where the water is substantially spun from the tub. As the Water is removed and the tub reaches a maximum spinning speed, the torque required is much less. An-

other situation requiring a degree of motor flexibility arises in cases of blockage within the tub tending to stall the motor during either the agitating action or the spinning action. It is desirable, therefore, to select a motor which will meet these conditions automatically without requiring complicated sensing devices for the various load situations and without requiring the addition of motor control switches to the already complicated washing machine timer. A multi-speed induction motor has the desired operating characteristics to satisfy these load requirements when circuited in accordance with this invention.

A multi-speed motor in which the torque varies inversely as the speed has been found applicable. These motors are capable of being operated at a number of different speeds and adapted for greatest torque at low speed.

A specific object of this invention is to increase a start windings operational range for two-speed motor application by modifying a centrifugally actuated control device whereby said device is effective to deenergize the start winding above low speed and below high speed and to reenergize the start winding below low speed.

Another object of this invention is to provide a twospeed, single start winding motor with a manually operable speed selector switch and a centrifugally actuated switch for cutting out the start winding upon motor acceleration and establishing the circuitry necessary for the speed selected, said centrifugally actuated switch being restrained by spring biased tangs upon motor deceleration to prevent the switch from reenergizing the start winding. 7 q i It is also an object of this invention to provide a single weight centrifugal switch with means for altering the speed at which the switch is actuated.

- Further objects and advantages of the present invention will be apparent from the. following description, reference being had to the accompanying drawings where- 'in a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is an elevational view of a washing ma chine, with parts broken away, equipped with a multispeed motor for reciprocating an agitator and spinning a tub;

FIGURE 2 is a schematic wiring diagram including a 48 pole consequent pole motor, a manually operable speed selector switch had a centrifugally actuated control switch;

FIGURE 3 is a fragmentary sectional view of a deenergized two-speed electric motor provided with the centrifugal speed switching means of this invention;

FIGURE 4 is an elevational view taken along line 4-4 of FIGURE 3 showing the centrifugal weight delay spring;

FIGURE 5 is a diagrammatic view of the centrifugal switch and its actuating weight immediately after motor energization with start winding contacts engaged;

FIGURE 6 is a diagrammatic view of the centrifugal switch and its actuating weight in motor accelerating position;

FIGURE 7 is a diagrammatic View of the centrifugal switch and actuating weight during high speed motor running position;

FIGURE 8 is a diagrammatic view of the centrifugal switch and actuating weight during low speed motor running position; and

FIGURE 9 is a graph showing typical operating characteristics of a 6 HR, volts, 60-cycle, two-speed motor acceptable for use in multi-speed Washing machines and suitable for use with this invention.

In accordance with this invention, a washing machine 10 having an agitator 12 and a tub 14 is provided with a multiple speed motor 16. The motor 16, by means of an agitating and spinning mechanism 18 such as is taught in Sisson 2,758,685, issued August 14, 1956, is adapted to cause the agitator 12 to agitate at two or more speeds and the laundry tub 14 to spin at two or more speeds. A conventional belt drive 20 may be utilized in transmitting the rotative power of motor 16 to the agitating and spinning mechanism 18. Again, in accordance with conventional practice, water may be supplied to the laundry tub 14 through a thermostatic valve arrangement 22. To facilitate selective control of the washing machine operation, the machine may include a timer control 24 and a speed selector 26.

With this arrangement of washing machine components the operator may place a load of clothes to be washed within the laundry tub 14 through an access opening (not shown) in the top of the machine 10. The timer 24 may be set to initiate a washing cycle and the speed selector 26 set for either high or low operating speed. If low speed is selected, for instance, the agitator 12 will agitate for a period controlled by the timer 24. At the conclusion of this agitating or washing action, the timer 24 will condition the motor circuit to initiate a removal of the soiled washing water Within the tub 14. This is accomplished by spinning the tub in a manner to cause the water to flow through the openings 23 in the laundry tub 14 into a collecting chamber 30 disposed below. From the chamber 30 a pump 32 may be utilized to remove the water to a remote drain location by means of any suitable conduit 34. Fresh rinse Water may then be supplied to the tub 14 through the valve 22 and a second agitation or rinse cycle initiated by the timer 24. Following this, the rinse water is removed from the tub 14 with another spinning operation of the tub. Since low speed has been selected, both the agitation and the spinning action are accomplished at the low speed of motor 16. Durnig the spinning of tub 14, a variable load is placed on the motor 16, viz. with the tub 14 full of water, a greater resistance to rotation is imposed upon the motor 16 and the motor rotates more slowly at the beginning of the spincycle. It is these variations from the synchronous motor speeds that are sensed centrifugally by the concepts of this invention to control the motor to meet the changing load'conditions.

This invention particularly concerns the operation or control of a washing machine mechanism to operate in any combination of two wash speeds and two spin speeds. The drive is through a reversible motor that causes the mechanism to pulse in one direction and to spin in the opposite direction. The motor is a consequent pole (4-8 pole) motor that operates at 1,725 or 850 r.p.m. Speed selection is accomplished by connecting two sections of the motor main winding in parallel for high speed and in series for low speed. Furthermore, this motor control concept contemplates the use of only one phase or start winding in the motor, which is thus started always in high speed. The utility of this control and motor circuit lies in the fact that acceleration of the motor is accomplished in a salient pole arrangement where the motor torque is high and continuous speed is reached in the consequent pole arrangement, if selected, at lower speeds where there is much less torque available, and, in fact, little required in washing machine application. The unique and novel feature of this control circuit is based on the fact that when motor torque is needed, the motor remains or reverts to the high speed, high torque circuit arrangementa situation occurring (1) during start, (2) during excessive overload, or (3) stall conditions. 7

With reference to FIGURE 2, the motor control concepts of this invention are shown in a circuit for a motor 16 of the consequent pole type. The motor is wound with a first main winding 36 and a second main winding 38. A start winding 40 is included in an internal motor circuit with a capacitor 42. Extending from the motor casing is a first lead 44, a 'secondfio'r center tap lead 46 and a third lead 48, and from the start winding circuit leads 50 and 52. A speedselector switch, shown generally at 54, is designed for high and low speed motor settings. To centrifugally sense the washing machine load conditions imposed upon motor 16, a centrifugal switch 56 is included in the circuit. The timer 24 is utilized to energize the. motor circuit through a cam actuated. timer switch 58 at any time that motor operation is desired during a washing machine cycle. The timer 24 includes also motor reversing switches 60, 61 adapted to close agitating contacts 62 during any pulsation portion of the wash cycle, and contacte 64 during any centrifuging or tub spinning portion of the washing cycle. I

The centrifugal switching 'means 56 iscomprised of a control board 66 of nonconducting material, and a rockably mounted skillet or switch portion 68; The control board 66 has fixed thereto skillet support pins lit, 72 which act to retain the skillet in correct relationship to V the board 66. As suggested by the dashed'lines in FIG URE 2, the control circuit lines are attached to connecting pieces on the back of the control board 66 which extends through the board into selective engagement with contacts carried on the rocking skillet 68. To eliminate short circuit arc-over in a manner to be described more fully hereinafter, the control board 66 has an extended portion 1'74 at one'side thereof which is adapted to carry a" fixed 78 is attached. Further contact 76 to which a circuit line 4. engaged from the control board 66. Insulating bushings 92 circumscribe the skillet apertures 84, 86 to insulate the pins 70, 72 at the point where they pass through the skillet. Motor running contacts 94, 96 are carried on the control board and arranged to mate with skillet motor running contacts 8, 180. It will be noted that contact 94 is not connected to any line in the circuit, its only function being to balance the skillet 68 when in centrifugally actuated position. Carried also on the skillets control board 66 are start winding contacts 162, 104 arranged to mate respectiveiy with skillet start winding contacts 106, 108. Contacts 98, 100 are carried by the straight or flat skillet portion 82 but are insulated therefrom by insulating bushings 110. On the other hand, start winding skillet contacts 106, 168 are carried directly on the skillet portion 82. A bridging member 112 connects contacts 98, 100 and is insulated also from skillet 68. Connected also to skillet contact 98 and bridging member 112 is an arm 114,

details of the centrifugal switch 56 are best seen in FIG- URES 3 and 4 wherein the skillet 68 includes an annular cup-like cam surface 80. Extending'from the annular portion and integral therewith is a substantially flat electrical contact portion 82. The flat portion has apertures 84 and 86 formed therein through which the skillet support pins and 72,;respectively, project in skillet retain.-

" ing relationship; Thepinmincludes a head p'ortion 88 j which aids" in retaining a spring tl in biasing relationship between the skillet flatfpo'rtion' 82'and the support pin head 88. "Support'p1n'72 is also formed'with a head .portion 21 to prevent the skillet 68 from-becoming disto the nylon washer 132.

having a contact 116 at one end thereof, extending downwardly into engagement with the offset control panel contact 76. Although members 112 and 114 have been shown as separate parts, it is within the purview of this invention to make these members as an integral member.

To provide means for changing main winding circuitry for the motor 16, the control board 66 carries main winding switch contacts 118, 120. A flexible connection or pigtail 122 interconnects the skillet main winding contact 100 and control board contact'118. Similarly, a flexible connection or pigtail 124 interconnects skillet start winding contact 168 and control board contact 120. For mounting the control board 66 to any suitable motor frame 126, apertures 128 are'mcluded thereon.

To actuate the skillet 68, weights 130 and a guide washer 132 of nylon or other suitable material, are mounted on a pin134 which is secured to the motor shaft 136. The pin 134 is provided with a head 138 to hold the pin securely to the motor shaft 136. At the other end of the pin or rivet 134, a second head portion is formed to retain the assembly on the pin and particularly a weight return delay spring or bracket 142 'in correct relationship A continuous return bias to the skillet actuating washer 132'is provided'by'a spring 133 interposed between the spring or bracket 142 and the washer 132. The nylon washer. 132 is adapted to ride on the annular cam surface as the motor 16 accelerates. As the weight 136 and nylon guide washer 132 move out of engagement with the skillet 68, the action of skillet spring is effective to pivot the skillet into selective engagement with certain of the control board contacts, thereby to give the desired motor. control switching. a V 7 It should be apparent that, without further modification, the action of weight 136 and nylon Washer 132 on the cam surface 80 of skillet 68 during motor operation would be to energize or deenergize the motor. start winding 40 at a particular rotational speed of motor shaft 136. However, this invention oontemplates'the control of a two-speed motor having a single start winding. It is conventional on a single speed motor to drop out the start winding a-t ap-. proximately 75% of the running speed. For example; if

r a motors running speed is 1,725r'.p.n1., the start winding the motor speed decreasing, the start windings would be 7 placed back in the circuit by the action of the centnifiugally actuated switch 56 .at approximately 1150 r.p.m. The

centrifugalswitch 56, it will be noted, has an inherent speedwdiifterential of about 150 r.p.m. (1300 r.p.m. minus .1150 r.p.m.) This ;-is due to the changed center of gravity for weight and washer? 132 asthey move from a position on the motor shaft 136 at standstill to a position at the outer terminus of pin 1 34at shaft running speed. But

where this controlcircuitry is to be'utilize'd in two-speed motor operation and the low speed is below'the motor spced'at which the start winding 'is'conveniently dropped out, it is apparent that certain modifications are necessary to the centrifugally actuated switch portion of the motor control circuit if a single start winding is to be used for both motor speeds. One of the basic requirements of this invention, therefore, is a wide differential, centrifugal switch. A high differential must be used on the start winding centrifugal control so that the start winding cuts out at the cenventional point (1300 rpm.) for 1,725 high speed operation and resets at a speed (70 0 rpm. for instance) below the 850 rpm. low speed operation. The centrifugal switch 56, disclosed more particularly in the patent to Shewmon 2,623,979 issued December 30, 1952, has been modified in a novel manner to accommodate the novel motor control concepts of this invention.

, -A wide differential has been incorporated into the centrifugal switch through the application of a centrifugal weight returnfdelay spring arrangement, shown generally at 142 (FIGURE 4). The spring 142 is formed in a U shape havinga top or base portion 144 and side portions or sections-146. Each side wall 146 is provided with a drawn out tab or protuberance 148 which projects inwardly into the path of the skillet actuating washer 132. A teardrop configuration for the protuberances 148 has been. found effective in promoting a smooth, flutterless movement of the washer 132 within the spring 142. Thus, as the'fwasher 132 moves radially outwardly in response to the centrifugal force imposed thereon by [the rotation of motorshaft 136, the spring protuberances 148 are forced smoothly outwardly to permit the washer 132 to pass. In this regard, it should be apparent that the centrifugal force actingto move the'weight 160 and washer 113-2 outwardly must be suificient to overcome the radially inward bias of a spring 133 and the obstructing gripping action of delay spring protuberances 148. Conversely, on the deceleration of motor shaft 136, the actuating washer 132 will be returned to the motor shaft when the bias of spring 133 is sufficient toovercome the centrifugal force acting on the washer 132 and the resistance to return imposed by delay spring protuberances 14 8.

For purposes of clarity, schematic diagrams of the centrifugal skillet switch 56 and i-tsnovel actuating elements are shown in FIGURES 5, 6, 7 and 8 merely to illustrate the skillet positions relative to control board 66 and motor shaft 136. The wide differential producing delay spring 142 has been rotated 90 from its actual relationship in FIGURES 3 and 4 to show clearly how the skillet provides the switching concepts embodied in this invention. These relative positions will be discussed fully hereinafter in connection with the wiring circuitry for motor 16. However, briefly stated, these representations illustrate the following relationships. FIGURE 3 illustrates the motor 16 at rest or at the instant of energizration. The skillet 68 is held to the lecfit against the 'bias of spring 90 by the action of nylon washer 132 against the top ledge or surface 81 of the skillet 68. In FIGURE 5, the motor shaft 136 has started to rotate (as indicated by the arrow) and the actuating disc 1 32 started to move outwardly into sliding relationship to skillet cam surface 80. Skillet contact 116 has broken ctrcm control panel contact 76, the start winding board contacts 102, 104 and skillet contacts 106, 108 are made and main skillet contact 100 is still disengaged from control board contact 96. FIG- URE 6 shows the situation wherein board contact 76 and skillet con-tact 116 have moved apart to provide a suflicient gap at the point where contacts 96 and 100 mate to prevent shortcircuit-ing during switching. Start winding contacts 102, 6 are still in the circuit. FIGURE 7 illustrates the motor high speed running condition wherein the main win-dings are energized in parallel through contacts 96 and 100. The start winding is out of the circuit at broken contacts 102, 106 and the skillet actuating disc 132 held fully outwardly against the action of spring 133 in accordance with the centrifugal force imposed by rotating shaft 136. FIGURE 8 shows the motor situation when energized for low speed run with the main windings connected in series through contacts 96, 100. The centrifugal force imposed upon the actuating disc 132 is in sufiicient in itself at motor low speed to hold the disc 132 fully outwardly; therefore, the restraining action of teardrop protuberances =148 acts to prevent the reengagement of disc 132 and skillet cam surface during low speed run. This action effectively prevents the reenergization of the motor start winding which would cause the motor to accelerate to a higher speed.

With reference to FIGURE 3, the skillet 68 is shown. In this regard, the nylon disc 132 is shown forcing the skillet 68 to the left pivoting about contact 106 on 102 and 108 on 104. As the motor accelerates, the actuating disc 132 moves outwardly onto the skillet cam surface 80 in a manner to permit the skillet 68 to move to the right to permit contacts 76, 116 to break before contacts 96, are made. The particular design or modification of the skillet 68 over the prior teachings of Shewmon is directed to preventing short circuits or arcing during any switching operation. Therefore, the idea is to secure as great a spread or break as possible bebtween contacts 76 and 116 at the point where contacts 96 and 100 are made (FIGURE 6). Considering the axial or rocking distance along the skillet between contacts 98, 100 and 106, 108 and the parallel distance between 106, 108 and .1-16, the longer the latter distance in relation to the first distance, the greater will be the arc-preventing distance between contacts 76 and 116 when skillet contacts 98, 100 meet board contacts 94, 96. With reference to the actual skillet structure (FIGURES 3 and 4), these distances are incorporated by the addition of a depending arm 1114 which extends from skillet contact 98 to a point adjacent control board contact 76.

As evidenced in FIGURE 9, the motor accelerates to approximately 75% of high running speed for the motor 16 before the start windings are cut out. Thus, where low speed has been selected on dial 26 for switch 54, the motor 16 must coast or drift back to the low speed setting for the motor. FIGURE 7 illustrates that instant of start Winding cutout wherein the centrifugal force imposed by the rotation of shaft 136 has forced the actuating disc 132 outwardly over the teardrop protuberances 148 and against the opposing bias of spring 133. As the motor shaft 136 slows in response to the low speed selection on speed selector switch 54, the actuating disc 132 will tend to return to its position adjacent the motor shaft 136. For instance, if the start winding cutout is at approximately 75% of high speed run (1725 r.p.m.), the start winding will cut out at approximately 1300 r.p.rn. Since the low speed operation is 850 r.p.m., the motor shaft 136 must drift from 1300 r.p.rn. to 850 rpm. before the established circuitry effects a steady state low speed motor operation. Should the start winding 40 be cut in during this slow-down procedure, the motor 16 would again accelerate up to the start winding cutout point of 1300 rpm. and an unwanted cycling would occur. This invention, however, provides means for preventing the reenergization of the start Winding 40 during low speed motor operation. With reference to FIGURE 8, the actuating disc 132 is shown resting on the teardrop protuberances 148 during low speed operation. Spring 142, in this instance, has been designed to hold out the disc 132 against the bias of spring 133 as long as the motor shaft 136 is rotating at approximately 700 rpm. or above. Thus, a wide differential has been established wherein a single start Winding 40 is effective in either a low speed or a high speed situation. Of course, it should be obvious that the resilience of spring 142 and the size of the protuberances 148 may be varied to obtain any particular start winding cut-in desired.

Let us assume, now, that a high speed operation has been selected on dial 26 which places the switch 54 in position for high speed motor operation. At the instant of energization, the relationship of the centrifugally actuated switch 56 is in the position shown in FIGURE 3. As the motor accelerates in response to the high speed selection on speed selector switch 54, the skillet 68 moves through the same positions shown in FIGURES 3, 5, 6 and 7 and explained in. connection with the low speed motor operation. These positions are assumed substantially simultaneously and the start winding 40 is dropped out of the circuit when the rotational speed of motor shaft 136 reaches approximately 75% of high speed running condition, i.e., approximately l300.r.p.m. At this point, the skillet actuating disc or washer 132 is thrown outwardly into the position of FIGURE 7 and the parallel wired relationship is established for main windings 36 and 38. Since high speed has been selected on switch 54, the motor 16 will continue to accelerate from the start winding cutout to the high speed operation of 1725 rpm.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be' adopted.

What is claimed is as follows:

1. In a centrifugal device, a rotating member comprising a guide member radially fixed to a rotatable shaft, a weight member slidably mounted on said guide member for radial displacement, an actuating washer attached to said weight member, a U-shaped spring for delaying movement of said washer and a biasing spring circumscribing said guide member and interposed between said delay spring and said washer, said delay'spring having a base portion affixed to said guide member and a side portion in parallel relationship to said guide member and adjacent said washer, and said side portion having a teardrop protuberance thereon with a radially inner section and a radially outer section, said protuberance formed with a small slope on the radially inner section for passing said washer upon acceleration of said shaft and a steep slope on the radially outer ,section for restraining said washer upon deceleration of said shaft.

2. In a centrifugal device, rotating means comprising a rotatable shaft a guide member fixed to said rotatable shaft and extending therefrom and an actuating member slidably mounted on'said guide member for guided move,

ment thereon in response to the rotation of said guide member, a spring for delaying movement of said actuating member and a resilient element interposed between said delay spring and'said actuating member, said delay spring connected to said guide member and having a side portion in parallel relationship to said guide member and adjacent said actuating member, and said side portion having a protuberance thereon with an inner section and an outer section, said protuberance formed with a small slope on the inner section for passing said actuating member upon acceleration of said shaft and a greater slope on the outer section for restraining said actuating member upon deceleration of said shaft.

3. In a centrifugal device, rotatable means comprising a rotatable shaft, a guide member fixed to said rotatable shaft and extending therefrom and an actuating member relatively movably mounted on said guide member for guided movement thereon in response to the rotation of said guide member, means for rotating said shaft and said guide member, said rotating means being controlled by said actuating member, yieldable means for delaying movement of said actuating member, said yieldable means connected for rotation with said guide member and having one portion in spaced relationship to said guide member and adjacent said actuating member, and said one portion having a protuberance thereon with a radially inner section and a radially outer section, said protuberance formed with a small slope on the inner section for passing said actuating member upon acceleration of said shaft and a greater slope on the outer section for restraining said actuating member upon deceleration of said shaft.

References Cited in the file of this patent UNITED STATES PATENTS V 2,416,973 Wright Mar. 4, 1947 2,624,814 Shewmon Jan. 6, 1953 2,677,539 Winslow May 4, 1954 2,897,309 Randol July '28, 1959 2,961,229 Parks Nov. 22, 1 960 Cantonwine Apr. 24, 1 962

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2416973 *Dec 20, 1944Mar 4, 1947Gen ElectricCentrifugal switch
US2624814 *May 2, 1951Jan 6, 1953Gen Motors CorpSwitch locator
US2677539 *Jul 15, 1950May 4, 1954Winslow John CGovernor with magnetic means
US2897309 *Mar 6, 1957Jul 28, 1959Randol Glenn TSpeed-responsive switch mechanism
US2961229 *Mar 10, 1958Nov 22, 1960Caterpillar Tractor CoCentrifugal governor
US3031606 *May 27, 1957Apr 24, 1962Cantouwine Charles RElectric motor construction
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6745646Jul 14, 2000Jun 8, 2004Weatherford/Lamb, Inc.Apparatus and method for facilitating the connection of pipes
U.S. Classification73/537, 66/178.00R, 73/551, 200/80.00R
International ClassificationD06F37/30, D06F33/00, H02K11/00, H02P25/18
Cooperative ClassificationD06F37/304, H02K11/0036, D06F33/00, H02P25/182
European ClassificationD06F33/00, H02K11/00F1E, D06F37/30C, H02P25/18C