US3250927A

US3250927A - Magnetically operated motor switch

Info

Publication number: US3250927A
Application number: US295165A
Authority: US
Inventors: Kenneth R Lung
Original assignee: Tait Manufacturing Co
Current assignee: Tait Manufacturing Co
Priority date: 1963-07-15
Filing date: 1963-07-15
Publication date: 1966-05-10
Anticipated expiration: 1983-05-10

Description

y 1966 K. R. LUNG 3,250,927

MAGNETICALLY OPERATED MOTOR SWITCH Original Filed Sept. 20, 1960 FIG-1 FIG-2: 98 25 INVENTOR. KENNETH R. LUNG 8 BY 42 74 72 fl 7 ATTORNEYS 3,250 927 MAGNETICALLY OPERATED MOTOR SWITCH Kenneth R. Lung, Morehead City, N.C., assignor to The Tait Manufacturing Company, Dayton, Ohio, a corporation of Ohio Continuation of application Ser. No. 57,233, Sept. 20, 1960. This application July 15, 1963, Ser. No. 295,165 12 Claims.v (Cl. 310-68) This invention relates to submersible pump assemblies of the type including a motor as part of the entire assembly which is submerged in a well.

The invention has special relation to electric motors for use in such submersible pump assemblies and which are intended to be filled with liquid during the operation thereof, as is well known in the art, and this invention is directly concerned with the controls for such submersible motors. This application is a continuation of my application, Serial No. 57,233, filed September 20, 1960, which in turn is a continuationin-part of my application Serial No. 674,076, filed July 25, 1957, now United States Patent No. 2,997,609, both assigned to the same assignee as this application.

It is a primary object of this invention to provide a novel, simple and elfective construction for the starting switch of a liquid-filled motor whichoperates magnetically to shift the motor circuits between the starting and running positions thereof.

Another object of this invention is to provide a submersible motor as outlined above wherein a pressure differential developed within the liquid filled motor casing serves to shift a magnetically operated switch between its starting or running positions.

An additional object of this invention is to provide a magnetically operated starting switch construction for a submersible motor as outlined above wherein the motor shaft carries an impeller developing hydraulic pressure in the liquid-filled casing as the motor comes up to speed and wherein this developed hydraulic pressure is effective as a pressure differential to cause movement of an operating member for movement of a magnet thereby controlling the movement of a switch to either the starting or running position thereof.

A further object of this invention is to provide a starting switch construction for a submersible motor as outlined above wherein an operating member surrounded by the liquid in the motor casing is provided with a magnet atfixed thereto for axial and rotary movement therewith to cause axial and rotary movement of a bridging contact within the switch for control of the starting and running circuit in accordance with the speed of the motor thereby providing control for the starting and running circuits.

A still further object of this invention is to provide a starting switch assembly adapted to be submersed in a liquid and responsive to the axial and rotary movement of a magnetic member within the liquid as controlled by rotation of the motor to cause rotation of a bridging contact within the switch and axial movement thereof in a direction opposite to the axial movement of the magnetic member whereby the bridging contact is subjected to even wear as a result of the rotation thereof while controlling the starting and running condition of the motor.

Other objects and advantages of the present invention will be apparent from the following description, the accompanying drawing and the appended claims.

In the drawing:

FIG. 1 is an elevational view illustrating a submersible pump assembly incorporating a liquid-filled electric motor constructed in accordance with the invention;

FIG. 2 is an enlarged fragmentary vie-w in axial sec- I United States Patent "ice tion through the lower end of the motor portion of the assembly of FIG. 1;

FIG. 3 is a detail section on the line 33 of FIG. 2;

FIG. 4 is an enlarged view partly in section and partly in elevation of the motor control switch of FIG. 2 showing the interior working parts thereof; and

FIG. 5 is the wiring diagram for the motor of FIG. 2.

Referring to the drawing, which illustrates a preferred embodiment of the invention, the submersible motor assembly shown in FIG. 1 includes a motor casing and a pump shell 11 connected by an intake cap 12 covered by a screen 13. The motor is shown in FIG. 2 as of the oil-filled type, and the lower end of the motor casing is connected with a housing 15 which forms an extension thereof and is in turn provided at its lower end with a flexible seal between its interior and outside atmosphere, comprising a diaphragm 16 of rubber or other suitable material housed in an end cap 17 having an opening 18 therethrough for directexcess by the outside atmosphere to one side of the diaphragm 16. Details of the structure of these parts of the pump assembly are disclosed in my copending applications Serial No. 633,412, filed January 29, 1957, and Serial Nos. 646,667 and 646,693, filed March 18, 1957, all of which are assigned to the same assignee as this application.

The motor shown in part in FIG. 2 may be of the construction shown in detail in my United States Patent No. 2,919,357, issued December 29, 1959, to the assignee of this application. The motor includes a stator (not shown) which carries the main field winding 20 and the starting winding 22. A rotor (not shown) is secured to the motor shaft which is mounted on the upper end of bracket 26 as shown in one or more of the above applications. The lower end of the shaft 25 rotates in a bushing 28 held in bracket 30 secured between end ring 32 on casing 10 and the end housing 15 by bolts 34 as shown in FIG. 2. v

The motor in the casing is shown as of the split phase type requiring a single pair of leads L and L which are indicated in FIG. 1 as included in cable 35. The start-ing and running circuits for the motor are shown schematically in FIG. 5 as including a starting switch 36 and a starting capacitor 38 connected with the starting winding 22 across the lines L and L in parallel with the main winding 20. This is a well known and conventional starting circuit, and the switch 36 is intended to be opened, as shown, when the motor comes up to operating speed in order to establish a running circuit for the motor utilizing only the main winding 20. The present invention is particularly directed to the switch arrangement and the mechanism for operating this switch 36.

Referring to FIG. 2, which shows the switch 36 in the normal rest or starting position, and FIG. 4 which shows the switch in the running condition, a switch mechanism encased in an aluminum or other non-magnetic housing 40 is suspended in fixed spaced relationship from the bracket 30 and the motor shaft 25 by means of long bolts 42 and spacer sleeves 44. The starting capacitor 38 is supportedwithin the housing 15 by suitable means such as centered rib portions 46 of the housing. Located within the non-magnetic housing 40 is a steel or other magnetically permeable material washer 48 which is screw threaded to a brass or other non-magnetic and partially hollow shaft 50. A centering or guide pin 52 is embedded in the arc-resistant plastic cup-shaped member 54, the latter having side walls 55, for providing vertical move- 'ment of the shaft with respect to the housing 40. An insulating plastic Washer 56 such as polyethylene terephthlate resin, commercially available under the trade name Mylar, is held against the upper Wall of the housing 40 above the steel washer 48 by side walls 55 of the arc-resistant plastic member 54, to prevent any shorting between the metallic housing 40 and the shaft 50 as the latter moves in a vertically upward direction within the housing.

Contacts

57 and 58, are carried by

conductive support members

60 and 62, respectively, within the housing 40. The

members

60 and 62 are fitted in

slots

63 and 64, respectively provided in the side walls 55, these members being perforated as at 65 and 66 to facilitate bending, and are enclosed in the housing 40 and sealed therein by an epoxy resin potting compound 68 which fills perforations 65 and 66. The

contacts

57 and 58 act in cooperation with the bridging contact 70 to control the motor starting and running circuits, contact 57 being connected to the starting capacitor 38 by means of an insulated connector 72 secured to support member 60, and contact 58 being connected to the starting winding 22 by means of an insulated connector 74 affixed to the support member 62.

The bridging contact 70 of silver, or other conductive material, is maintained in position on the lower tapered end of contact shaft 50 by a spring 76 having one end thereof seated on the flange 79 located on the narrow end of the taper, and having the other end thereof urging the bridging contact '79 against the flange 80 located above the tapered portion of the shaft 50, the bridging contact 70 being fitted over the shaft 50 and engaging the same along the non-tapered portion 82 thereof. The shaft '50 and the bridging contact 70 are moved as a result of the movement of .a permanent ceramic magnet 85 of annular shape which is fitted over center-ing lug 88 and bonded by a suitable cement 90, such as an epoxy cement, to the base 92 of the operating member or plunger 94.

The lower end of the shaft 25 has a hollow portion 96 which extends upward from the lower end thereof. The plunger 94 is mounted for sliding telescoping movement in the guideway provided by this hollow shaft portion 96 and in the normal upright operating position is biased in the downward direction under the action of gravity, a spring 98 being provided within this guideway .to supplement the action of gravity in biasing the plunger downward against the top of the non-magnetic housing 40 as shown in FIG. 2.

The outer diameter of the hollow shaft portion 96 is of reduced diameter to provide a circumferential shoulder 99, and an annular disk 100 is secured thereon as by press fitting. The proportions of these parts are such that the lower surface of the disk 190 is in thrust bearing relation with the upper end surface of the was-her 102 mounted on the face of bracket 30. In addition, the disk 100 is provided with a plurality of passages 106, four being shown (FIG. 3), which extend radially outwardly from an internal peripheral groove 1108, and the shaft 25 is provided with radial ports 110 which connect the groove 108 with the hollow inner portion 96 of the shaft. These ports and passages thus cause disk 100 to function as a centrifugal impeller upon rotation of the shaft, and the hollow portion 96 cooperates with the ports 110 to form the inlet of the impeller.

With this construction, when the motor is at rest, the parts 1 will occupy the relative positions shown in FIG. 2 with the spring 98 biasing the plunger 94 in the direction towards the housing 40 thereby causing the steel washer 48 to be attracted to the magnet 85. Wit-h the washer 48 positioned against the upper wall of the housing, bridging contact 70 spans the gap between

contacts

57 and 58, and the switch is in the starting position, i.e. closed, and the entire open space within the hollow shaft portion 96 is filled with liquid such as oil (not shown).

When themotor is first energized, by operation of the usual remotely located switch (not shown), the impeller 100 will begin revolving with the motor shaft. As it revolves, picking up speed as a result of the increased speed of the motor, the impeller 100 which is surrounded by liquid will develop suction within the hollow shaft portion 96 by tending to discharge through its outlets 106 the liquid which was occupying the space 96. This suction will be effective as a pressure differential on opposite sides of the plunger 94 in an upward direction against the spring 98, and when the suction is sufficiently great, a pressure differential is created sufficient to overcome the force of the spring 98, which occurs when the motor has come up to switch operating speed, and the plunger 94 will move upwardly and carry with it the magnet member 85.

Due to the rotary movement of the plunger 94 with the motor shaft 25, the rotary or spinning axial movement of the magnet away from the casing 40 effectively withdraws the magnet field from around the washer 48 allowing the bridging contact assembly, including washer 48, shaft 59', bridging contact 70 and spring 76, to move in a direction opposite to movement of the magnet and on the axis of guide pin 52 which is arranged on the axis of the motor shaft 25. At the same time that thebridging contact assembly moves axially away from the plunger 94, the assembly is rotated due to the rotation of plunger 94 and magnet 85. Such rotary movement of the contact assembly prevents heating thereof and thus eliminates any jamming of the contact assembly within the housing resulting from the differential expansion of the various metallic parts thereof. With the contact assembly in the down position, as shown in FIG. 4, the shaft 50 rests on the arc-resistant plastic member 54, and the bridging contact 70 is spaced from

contacts

57 and 58, thus placing the switch in the running position and disconnecting capacitor 38 from the starting winding 22 to estabilsh a'running circuit as described.

As the motor slows down and decreases below the normal operating speed thereof, the spring 98 urges the plunger 94 in a downward axial direction towards the housing 40. At the same time that the plunger moves downward, it is rotated due to the rotation of the shaft 25, and as the magnetic lines of force move downward to the steel washer 48, the contact assembly is moved in an opposite axial direction towards the shaft 25. Since the magnet 85 is rotated, the contact assembly moves upward in axial rotary fashion to cause the bridging contact 70 to span the gap between

contacts

57 and 58 to complete the starting circuit as shown in FIG. 2. The rotary motion of the annular bridging contact 70 serves to distribute the wear evenly on this member since

contacts

57 and 58 rarely touch the surface of the contact element at the same points.

This invention accordingly provides a compact, effective and reliable mechanism for controlling the starting and running operation of a liquid-filled motor by utilizing the presence of a liquid within the motor casing to control the movement of a magnet in response to the pressure differential created by the rotation of an impeller which rotates at the same speed as-does the motor. In addition to the fact that the operation of the mechanism is simple and sure, construction of its component parts is also simple and does not require close tolerances. In particular, it is not essential that the plunger 94 fit closely within its guideway formed by the hollow shaft portion 96, and in fact it is satisfactory if there is some limited clearance around the plunger for leakage of the liquid such as oil, provided only that this leakage should not reach a point such that it will supply the suction demand of the impeller to an extent permitting spring 98 to overcome the desired suction force on the plunger.

It will be apparent that the principles of this invention may be modified to provide for mounting of the magnet on the shaft 50, and construction of the plunger 94 of magnetic material, such as steel, thereby providing movement of the bridging contact assembly as the plunger comes down to the casing 40 as a result of the magnet moving the contact assembly within the casing 40. Positioning the magnet on the plunger is a preferred embodiment which eliminates any heating of the magnet as a result of arcing which may take place in the casing 40, but it is understood that movement of the contact as;

sembly could be accomplished by reversing the position oil or other insulating liquid provided only that the cas-.

ing be normally filled with a liquid to a level capable of being pumped by the impeller on the motor shaft.

It is also apparent that the switch construction of the invention is not limited to a particular motor circuit but can be employed in combination with a wide variety of circuit arrangements requiring operation of a switch which is responsive to motor speed to shift between the starting circuit of the motor and its running circuit, and such shifting may require either opening or closing of the switch depending on the particular circuit.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that this invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined inthe appended claims.

What is claimed is:

1. In an electrical motor having a shaft and circuit means defining different starting and running circuits for said motor, the combination of operating means normally biased in a first direction and adapted to be rotated with said shaft and moved axially in a second direction, a first member movable in a rotary axial direction in response to movement of said operating means, means cooperating with said shaft for causing axial rotary movement of said operating means in said second direction, a switch in said circuit means including a second member movable in an axial rotary direction in response to movement of said first member, a contact element in said switch normally positioned in first position and movable in an axial rotary di-v rection in response to the movement of said second member to a second position for establishing respectively a starting and running circuit for said motor, and one of said members being magnetic and the other being magnetically permeable.

2. In a motor construction of the character described, the combination of a casing constructed to be filled with fluid, a motor including a shaft Within said casing, means for maintaining said casing substantially filled with fluid during the operation of said motor, circuit means defining different starting and running circuits for said motor, an

operating member normally biased in a first direction and adapted to be moved in a second direction relative to said shaft, a magnetic member movable in response to the movement of said operating member, means for circulating the fluid within said casing and for creating a pressure differential as said motor comes up to operating speed for causing movement of said operating member in said second direction, and a switch in said circuit means including a contact element normally positioned in a first position and movable in response to the movement of said magnetic member to a second position for establishing respectively a starting and running circuit for said motor.

3. In a motor construction of the character described,

' the combination of a casing constructed to be filled with fluid, a motor including a shaft Within said casing, means for maintaining said casing substantially filled with fluid during the operation of said motor, circuit means defining different starting and running circuits for said motor, an operating member normally biased in a first direction and adapted to be moved axially in a second direction relative to said shaft, a magnetic member movable in response to the movement of said operating member, means for circulating the fluid within said casing and for creating a pressure differential as said motor comes up to operating speed for causing axial movement of said operating member in said second direction, and a switch in said circuit means including a contact element normally positioned in a first position and movable axially in a di- 6 rection opposite to the movement of said magnetic member to a second position for establishing respectively a starting and running circuit for said motor.

4. In a submersible motor construction of the character described adapted to be submersed in a surrounding liquid, the combination of a casing constructed to be filled with liquid, a motor including a shaft adapted to be rotated within said casing, means for maintaining said casing substantially filled with liquid during the operation of said motor, circuit means defining different starting and running circuits for said motor, an operating member normally biased in a first direction and adapted to be rotated with said shaft and moved axially in a second direction relative theerto, a magnetic member movable in response to the axial rotary movement of said operating member, means for circulating the liquid within said casing and for creating a pressure differential as said motor comes up to operating speed for causing axial movement of said operating member in said second direction, and a switch in said circuit means including a contact element movable in the same rotary direction as said operating member and in an opposite axial direction to a first and second position in response to the movement of said magnetic member for establishing respectively a starting and running circuit for said motor.

5. In a submersible motor construction of the character described adapted to be submersed in a surrounding liquid, the combination of a casing constructed to be filled with liquid, a motor including a shaft within said casing, means for maintaining said casing substantially filled with liquid duringthe operation of said motor, circuit means defining different starting and running circuits for said motor, an operating member normally biased in a first direction adapted to be moved in a second direction relative to said shaft, a magnetic member carried by said operating member for movement therewith,'means for circulating the liquid Within said casing and for creating a pressure differential as said motor comes up to operating speed for causing movement of said operating member in said second direction, and a switch in said circuit means including a bridging contact assembly movable to a first and second position in response to the movement of said magnetic member for establishing respectively a starting and running circuit for said motor.

6. In a submersible motor construction of the character described adapted to be submersed in a surrounding liquid, the combination of a casing constructed to be filled with liquid, a motor including a shaft within said casing, means for maintainingsaid casing substantially filled with liquid during the operation of said motor, circuit means defining different starting and running circuits for said motor, an operating member normally biased in a first direction and adapted to be moved axially in a second direction relative to said shaft, a magnetic member carried by said operating member for movement therewith, means for circulating the liquid within said casing and for creating a pressure differential as said motor comes up to operating speed for causing axial movement of said operating member in said second direction and a switch in said circuitmeans including a bridging contact assembly normally positioned in a first position and movable axially in a direction opposite to the movement of said magnetic member to a second position for establishing respectively a starting and running circuit for said motor.

'7. In a submersible motor construction of the character described adapted to be submersed in a surrounding liquid, the combination of a casing constructed to be filled with liquid, a motor including a shaft adapted to be rotated within said casing, means for maintaining said casing substantially filled with liquid during the operation of said motor, circuit means defining different starting and running circuits for said motor, an operating member normally biased in a first direction and adapted to be rotated with said shaft and moved axially in a second direction relative thereto, a magnetic member carried by operating member in a second direction, and a switch in said circuit means including a bridging contact assembly movable in the same rotary direction as said operating member and-in an opposite axial direction to a first and second position in response to the movement of said magnetic member for establishing respectively a starting and running circuit for said motor.

8. In a submersible motor construction of the character described adapted to be submersed in a surrounding liquid, the combination of a casing constructed to be filled with liquid, a motor including a shaft within said casing, means for maintaining said casing substantially filled with liquid during the operation of said motor, circuit means defining diiferent starting and running circuits for said motor, an operating member normally biased in a first direction and adapted to be moved in a second direction relative to said shaft, means for circulating the liquid within said casing and for creating a pressure differential as said motor comes up to operating speed for causing movement of said operating member in said second direction, a switch in said circuit means positioned a preset distance from said shaft and including a liquid impervious non-magnetic housing, said housing containing therein a pair of stationary contacts and a bridging contact, a movable contact shaft supporting said contact element, a first actuating member secured to said contact shaft for ,eifecting movement thereof, a second actuating met ber secured to said operating member, one of said actuating elements being magnetic, the other actuating member being of magnetically permeable material for attraction by said magnetic member as said operating member moves in said first direction for maintaining said contact element engaged with said pair of stationary contacts to establish a starting circuit for said motor, and movable in a direction opposite to the movement of said operating member in said second direction for establishing a running circuit for said motor with said contact element spaced from said pair of stationary contacts.

9. In a submersible motor construction of the. character described adapted to be submersed in a surrounding liquid, the combination of a casing constructed to be filled with liquid, a motor including a shaft within said casing, means for maintaining said casing ubstantially filled with liquid during the operation of said motor, circuit means defining difierent starting and running circuits for said motor, an operating member normally biased'in a first direction and adapted to be moved in a second direction relative to said shaft, means for circulating the liquid within said casing and for creating a pressure differential as said motor comes up to operating speed for causing movement of said operating member in said second direction, a switch in said circuit means positioned a preset distance from said shaft and including a non-magnetic liquidimpervious casing, a pair of stationary spaced contacts positioned within said casing, a bridging contact assembly including bridging contact means positioned within said casing to establish a starting position with said bridging contact means in contact with said pair of spaced contacts and a running position with said bridging contact means spaced from said pair of contacts,.a first actuating member secured to said bridging contact means for movement therewith, a second actuating member secured to said operating member, one of said actuating members being magnetic, the other said actuating member being of magnetically permeable material for attraction by said magnetic member as said operating member moves in said first direction, and said preset distance being such that movement of said operating member in said first or second direction causes movement of said second actuating member in an opposite direction to establish said starting and running positions respectively.

10. A magnetically operated switch assembly for controlling operation of an electrical circuit, comprising a non-magnetic housing containing therein contact means, means for connecting said contact means to said electrical circuit, bridging contact means including a rotatable bridging contact element positioned within said housing, a first actuating member rotatably movable within said housing for effecting movement of said bridging contact, a second actuating member positioned outside of said housing for rotating movement towards and away from said housing, one of said actuating members being magnetic, the other of said actuating members being of magnetically permeable material for attraction by said magnetic member, and means for moving said actuating element in a rotary direction towards and away from said housing for causing engagement and disengagement of said bridging contact element'with said contact means.

11. A magnetically operated switch assembly for controlling the starting and running circuit of an electric motor, comprising a non-magnetic housing containing therein contact means, means for connecting said contact means to said circuit, bridging contact means including a bridging contact element positioned within .said housing for establishing said starting and running circuit, a first actuating member secured to said bridging contact element for movement therewith, a second actuating member positioned outside of said housing in axial alignment with said first actuating member for movement towards and away from said housing, one of said actuating members being magnetic, the other of said actuating members being of magnetically permeable material for attraction by said magnetic member, and means for moving said second actuating element towards and away from said housing for causing engagement and disengagement of said bridging contact with said contact means to establish respectively a starting and running circuit.

12. A magnetically operated switch assembly for controlling the starting and running circuit of an electric motor, comprising 'a non-magnetic housing containing therein a pair of stationary contacts, means to connect said contacts to a starting and running circuit, a bridging contact assembly including bridging contact means positioned within said housing to establish a starting and running circuit, a first actuating member secured to said bridging contact means for movement therewith, a second actuating member positioned outside of said housing in axial alignment with said. first actuating member for movement towards and away from said housing, one of said actuating members being magnetic, and the other said actuating member being of magnetically permeable material for attraction by said magnetic member as said second actuating member moves in a first direction, means for moving said second actuating member in an axial rotary direction towards and away from said housing, and said axial rotary movement of said second actuating member imparting axial rotary movement to said bridg ing contact element for urging said element into sliding engagement with said contacts as said second actuating member moves in said first direction and out of engagement with said contacts as said second actuating member moves in a second direction for establishing a starting and running circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,539,048 1/1951 Artutunoff 31087 2,555,571 6/1951 Chisholm ZOO-87.3 2,610,314 9/1952 Morse 31068.5 2,671,834 3/1954 Kmiecik 20087.3 3,109,908 11/1963 Clason 20087.3

MILTON 0. HIRSHFIELD, Primary Examiner.

ORIS L. RADER, Examiner.

J. W. GIBBS, Assistant Examiner.

Claims

1. IN AN ELECTRICAL MOTOR HAVING A SHAFT AND CIRCUIT MEANS DEFINING DIFFERENT STARTING AND RUNNING CIRCUITS FOR SAID MOTOR, THE COMBINATION OF OPERATING MEANS NORMALLY BIASED IN A FIRST DIRECTION AND ADAPTED TO BE ROTATED WITH SAID SHAFT AND MOVED AXIALLY IN A SECOND DIRECTION, A FIRST MEMBER MOVABLE IN A ROTARY AXIAL DIRECTION IN RESPONSE TO MOVEMENT OF SAID OPERATING MEANS, MEAN COOPERATING WITH SAID SHAFT FOR CAUSING AXIAL ROTARY MOVEMENT OF SAID OPERATING MEANS IN SAID SECOND DIRECTION, A SWITCH IN SAID CIRCUIT MEANS INCLUDING A SECOND MEMBER MOVABLE IN AN AXIAL ROTARY DIRECTION IN RESPONSE TO MOVEMENT OF SAID FIRST MEMBER, A CONTACT ELEMENT IN SAID SWITCH NORMALLY POSITIONED IN FIRST POSITION AND MOVABLE IN AN AXIAL ROTARY DIRECTION IN RESPONSE TO THE MOVEMENT OF SAID SECOND MEMBER TO A SECOND POSITION FOR ESTABLISHING RESPECTIVELY A STARTING AND RUNNING CIRCUIT FOR SAID MOTOR, AND ONE OF SAID MEMBERS BEING MAGNETIC AND THE OTHER BEING MAGNETICALLY PERMEABLE.