US3194913A - Centrifugal switch having two resilient arms with adjustable force transmitting means functioning therebetween - Google Patents

Description

July 13, 1965 N. K. LINDGREN 3,194,913

CENTRIFUGAL SWITCH HAVING TWO RESILIENT ARMS WITH ADJUSTABLE FORGE TRANSMITTING MEANS FUNCTIONING THEREBETWEEN Filed June 27, 1960 2 Sheets-Sheet 1 40 4 58 27 26 Twzzvron W16 Km '9 July 133, 1965 N. K. LINDGREN GENTRIFUGAL SWITCH HAVING TWO RESILIEN'I' ARMS WITH ADJUSTABLE FORCE TRANSMITTING MEANS FUNCTIONING THEREBETWEEN 2 Sheets-Sheet 2 Filed June 27. 1960 INVENTOR.

Arman Er United States Patent 3 194,913 CENTRIFUGAL SWlTt'lH HAVENG TWt) RESILIENT ARMS WITH ADJUSTABLE FQRCE TRANSMlT- TlNG MEANS FUNQTiONINtG THEREBETWEEN Nils Kauri Lindgren, Stockholm, Sweden, assignor to Alrtieholaget Electrolux, Stoclrhoim, Sweden, :1 corporation of Sweden Filed June 27, 1969, Ser. No. 39,082 Claims priority, application Sweden, July 3, 1959, 6 322/59 8 Claims. (Cl. 20tl-80) This invention relates to electric motors and more particularly to a regulating device for controlling the supply of electric current thereto. I

In order to avoid objectionable current surges when a motor is connected to a source of electrical supply, electric motors are often provided with a starting resistor which is connected in the motor circuit when operation of the motor is first started. After the motor has been started, such starting resistor is cut out of the motor circuit, and again connected in the motor circuit when the motor is stopped.

it is an object of the invention to provide an improvement for regulating the current supply to electric motors. More particularly, it is an object to provide such an improvement for regulating the current supply to electric motors provided with a starting resistor.

In accordance with the invention, this is accomplished by providing a centrifugally actuated control device having a switch which is mounted for rotation on the motor and includes a first fixed contact and a second movable contact which cooperates therewith and is mounted on a resilient arm whose tension is adjustable.

The above and other objects and advantages of the invention will be more fully understood upon reference to the following description and accompanying drawing forming a part of this specification, and of which:

FIG. 1 is a semi-diagrammatic side elevational view of an electrical motor equipped with a regulator constructed in accordance with this invention;

FIG. 2 is an end elevational view, larger in scale than in FIG. 1, of the regulator employed in the device of FIG. 1;

FIG. 3 is a fragmentary sectional view taken at line 3-3 of FIG. 2;

FIG. 4 is a view taken at line 44 of FIG. 2; and

FIG. 5 is a schematic diagram illustrating the electrical circuits for the motor and regulator in the device of FIG. 1.

Referring to the drawing, the universal electrical motor shown comprises a housing in which are mounted the usual armature 11 and stator 12, the stator being provided with an electromagnetic winding 13 and the armature with an electromagnetic winding 14, as seen in FIG. 5. The novel speed regulator of the invention is indicated generally at 16, being mounted on the motor shaft 15. In addition, the motor is equipped with a manual start-stop switch 17 and a suitable input connector 18. The motor is mounted on a base 19 and connected to the driven device by a coupling 20 formed of suitable insulating material.

As seen in FIG. 2, the regulator 16 includes a combined capacitor and mount 21, a centrifugal switch 22 and a resistor assembly 23. The combined capacitor and mount comprises a pair of flat circular metallic plates 24 and 25 which are disposed face to face and transversely positioned with respect to shaft 15. A thin sheet 26 of mica or other suitable dielectric material is disposed between and in direct contact with the plates 24 and 25.

The plates 24 and 25 and the dielectric sheet 26 therebetween are firmly clamped together by hollow rivets 27 extending through aligned openings in these members, one head portion of each rivet directly engaging plate 24 and the other head portion being electrically insulated from plate 25 by a flanged insulating washer 28, as seen in FIG. 3. Accordingly, device 21 is a laminated capacitor having electrically separated plates 24 and 25.

The combined capacitor and mount 21 is secured to shaft 15 by a member 29 having a bore 30 to receive the shaft, the hub having a set screw 31 for securing it to the shaft 15, as seen in FIG. 3. The member 29 includes a shoulder portion 32, an intermediate portion 33 and a threaded tip 34. Portion 33 is enveloped by a bushing 35 of electrical insulating material, such bushing having a flange 36 seated against the shoulder portion 32 of member 29. A metal sleeve 37 is disposed about the bushing 35. e

The plate 25 of capacitor and mount 21 is formed with a circular central opening snugly embracing a portion of bushing 35. One face of plate 25 is in intimate physical contact with the end of sleeve 37 opposite to flange 36, and the plate 25 is secured in place on the hub by a nut 38 threaded on tip portion 34 of the hub and separated from plate 25 by a cupped, annular washer of electrical insulating material 39. When not 38 is threaded into place, the plate 25 is clamped rigidly between washer 39 and the adjacent end of sleeve 37 and is electrically insulated from hub 29 by bushing 35 and washer 39. In this way good electrical contact is obtained between the plate 25 and the sleeve 3'7. The plate 24 is formed with a central opening which is substantially larger than that of plate 25. Hence, the plate 24 does not contact metal sleeve 3'7, as seen in FIG. 3. i

The centrifugal switch 22 includes a movable contact 40 carried by a resilient leaf spring 41, and a fixed contact 42 carried by a metal screw 43, the screw extending chordwise with respect to the circular periphery of plate 25. The screw 43 extends through a threaded opening in a flange 44 which is provided on the plate 25 and is perpendicular thereto. Contact 42 is thus mounted on and electrically connected to plate 25. The position of fixed contact 42 can be adjusted by turning screw 43 on flange 44 after which a locknut 45 can be tightened. Resilient contact-carrying spring 41 is mounted on and electrically connected to plate 24 by bracket 46, as seen in FIGS. 2 and 4.

When the shaft 15 is rotating below a predetermined speed, switch 22 is biased to its normally closed position by the action of resilient spring 41, the spring force prevailing over the centrifugal force developed due to rotation of the motor shaft. As the speed of the motor increases, the centrifugal force tending to open switch 22 increases so that, atthe proper time, the centrifugal force overcomes the spring force and contacts 40 and 42 are separated.

The resistor assembly 23 comprises a ceramic resistor element 47 having the configuration of a short cylinder, one circular face thereof being in contact with the outer face of plate 24 of capacitor and mount 21. The resistor 47 is held firmly in place and in good contact with plate 24 by a metal bow spring 48 acting on a metallic hold down and cooling plate 49 which bears against the opposite circular face of the resistor 47, the ends of the spring 48 being fixed to flanges 50 which are provided on the plate 25 and extend axially of the motor shaft 15.

The spring 48 bows toward plate 49 and has sufiicient normal curvature to cause the spring to be held under compression when the assembly is completed. Hence, considering the circular faces of resistor element 47 as being the terminals thereof, one terminal is connected to the plate 25 by the flanges 50, flat bow spring 48 and hold down and cooling plate 49, while the other terminal is in direct contact with the plate 24. Accordingly, resist Patented July 13, 1965 9 tor 47 is connected between plates 24 and 25 to provide the circuit seen diagramamtically in FIG. 5.

One terminal of winding 13 is connected by conductor 53, FIG. 5, to a carbon brush 54 so mounted as to be maintained in contact with sleeve 37, FIG. 3. It will be understood that sleeve 37 rotates with shaft 15, and that a conductive path is provided through brush 54, sleeve 37 and plate 25 to plate 24 either through switch 22 (when the switch is closed) or through resistor 47.

n its face opposite dielectric sheet 26, plate 24 has a freely exposed annular arm concentric with the axis of the shaft 15. Bearing against this area is a second carbon brush 55, mounted in any suitable fashion, the brush 55 being connected via conductor 56 to one of the usual commutator brushes for the motor. When switch 22 is in its normally closed position, and manual switch 17 is closed, a circuit is completed for windings 13 and 1 via brush 54, sleeve 37, plate 25, switch 22, plate 24 and brush 55, resistor 47 being short-circuited. When the speed of shaft increases by an amount sufficient to cause centrifugal switch 22 to open, the circuit is then completed for windings l3 and 14 via brush 54, sleeve 37, plate 25, the flanges 5% provided on plate 25, resistor 47, the plate 24 and brush 55. Hence, the resistor 4-7 is connected in series relation with the windings 13 and 14 and the motor is slowed down sufiiciently to cause centrifugal switch 22 to close so that resistor 47 will again be shortcircuited.

Since movable contact 40 of switch 22 is connected to plate 24 and fixed contact 42 is connected to plate 2 5, it will be understood that the capacitor formed by the plates 24 and 25 and the dielectric sheet 2d therebetween is connected electrically across the centrifugal switch and will be effective in the usual manner to prevent the switch from creating radio and television interference.

In accordance with this invention, the resilient contact carrying spring 41 is fixed to one face of bracket 46, which extends axially of the motor shaft 15 irom the plate 24 to which it is secured, and forms part of a cantilevered resilient arm A having a second resilient spring 57 fixed to the opposite face of the bracket 46. The resilient spring 41 is apertured to receive a threaded set screw 53 which is adapted to bear against the resilient spring 57, as shown in FIG. 2. With this arrangement the distance or separation of the resilient springs 41 and 57 by the set screw 58 can be adjusted to vary the tension of the resilient arm A upon which the movable contact an is mounted and in this way nicely controls the speed at which the contacts and 42 separate responsive to centrifugal force developed by the motor against the biasing action of the resilient arm A tending to keep the contacts 4n and 42 closed.

The arrangement provided for adjusting the tension of the resilient arms A possesses the advantage that the biasing action of the resilient arm can be varied without the need for rotating the contacts 40 and 42 with respect to one another. Accordingly, after the opposing faces of the contacts 40 and 42 have become worn during operation of the motor and good electrical contact therebetween is obtained, it is not necessary to grind the opposing faces of the contacts before the biasing action of the resilient arm A, upon which the movable contact is carried, is varied or changed.

In view of the foregoing, it will now be understood that my improved switch device includes an operating contact arm A having a contact 49 thereon normally biased toward a first position, that is, toward the axis about which the device moves in an arcuate path. Further, the contact 40 on the swingable contact arm A is movable under centrifugal force, an applied force, to a second position away from the axis. The operating contact arm A embodies two cantilevered resilient springs 41 and 57 abreast of one another, each of the resilient springs 41 and 57 being movable with respect to the other. screw 58 functions as an adjustable element for transmit- The ting force betwen the resilient springs 41 and 57 to vary the biasing of the contact arm A to the first position.

The regulator illustrated is particularly useful in connection with small, high speed electrical motors of the type employed to drive calculating machines, cash registers, and the like, where speed regulation is important because the motor is intermittently loaded.

While a particular embodiment of the invention has been shown and described, such variations and modifications are contemplated as fall within the true spirit and scope of the invention, as pointed out in the following claims.

What is claimed is:

l. A switch device including an operating contact arm having a contact thereon, said contact arm comprising at least two members normally biased toward a first position and movable under an applied force to a second position, each of said members being movable with respect to the other, and adjustable force transmitting means functioning between said members to vary the biasing of said contact arm to said first position.

2. A centrifugal switch device including an operating contact arm having contact thereon adapted to be normally biased toward an axis about which the device moves in an arcuate path, a mounting for said contact arm to permit movement thereof away from said axis under centrifugal force, said contact arm comprising at least two resilient members each of which is relatively movable with respect to the other, and force transmitting means functioning between said resilient members.

3. A centrifugal switch device including an operating cont act arm having a contact thereon adapted to be normally biased toward an axis about which the device moves in an arcuate path, a mounting for said contact arm to permit movement thereof away from said axis under centrifugal force, said contact arm comprising at least two resilient members each of which is relatively movable with respect to the other, and adjustable force transmitting means functioning between said resilient members to vary the biasing of said contact arm toward said axis.

4. A centrifugal switch device including a part adapted to be mounted on a shaft rotatable about an axis, an operating contact arm mounted on said part, said contact arm having a contact normally biased toward said axis and movable away from said axis under centrifugal force, said contact arm comprising a pair of cantilevered resilient members upon one .of which said contact is carried, each of said resilient members being relatively movable with respect to the other, and means functioning between said resilient members for transmitting force from the other of said resilient members to said contact carrying resilient member.

5. A centrifugal switch device including a part adapted to be mounted on a shaft rotatable about an axis, an operating contact arm mounted on said par-t, said contact arm having a contact normally biased toward said axis and movable away from said axis under centrifugal force, said contact arm comprising a pair of cantilevered springs abreast of one another, said contact being carried by one of said springs, and adjustable force transmitting means functioning between said springs to vary the biasing of said contact arm toward said axis.

6. A centrifugal switch device including a part adapted to be mounted on a shaft rota-table about an axis, an operating cantilevered resilient contact arm mounted on said par-t, said contact arm having a contact thereon normally biased toward said axis, said arm being swing-able away from said axis under centrifugal force and comprising at least a pair of resilient members abreast of one another, said contact being carried by one of said resilient members, and adjustable force transmit-ting means functioning between said resilient members to vary the biasing of said contact arm toward said axis, said last-mentioned means comprising an element which is carried by one of said resilient members and movable toward and from said other resilient member.

7. A centrifugal switch device including a part adapted to be mounted on a shaft rotatable about an axis, an operating contact arm mounted on said part, said contact arm having a contact thereon normally biased toward said axis, said arm being swingable away from said axis under centrifugal force and comprising at least a pair of cantilevered resilient springs abreast of one another, and force transmit-ting means functioning between said springs.

8. A centrifugal switch device including a part adapted to be mounted on a shaft rotatable about an axis, an operating contact arm having a contact thereon normally biased toward said axis,said tar-m being swingable away from said axis under centrifugal force and comprising a pair of cantilevered resilient springs abreast of one another, and adjustable force transmit-ting means functioning between said resilient springs, said last-mentioned means including an element which is carried by one of said resilient springs and engages said other resilient spring, said element being adjustable on said one resilient spring toward and from said other resilient s aring.

References Cited by the Examiner UNETED STATES PATENTS 1,855,703 4/32 Cloud 20)80 2,387,646 10/45 Crosman ZOO-89 2,715,164 8/55 Hufnagel 2003O 2,760,027 8/56 Riley 200-466 2,997,559 8/61 Caton 20()80 2,999,139 9/61 Lee 2O()-80 BERNARD A. GILHEANY, Primary Examiner.

MAX L. LEVY, Examiner.

Claims (1)

1. A SWITCH DEVICE INCLUDING AN OPERATING CONTACT ARM HAVING A CONTACT THEREON, SAID CONTACT ARM COMPRISING AT LEAST TWO MEMBERS NORMALLY BIASED TOWARD A FIRST POSITION AND MOVABLE UNDER AN APPLIED FORCE TO A SECOND POSITION, EACH OF SAID MEMBERS BEING MOVABLE WITH RE-

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