US860124A - Switch. - Google Patents

Description

No. 860,124. PATENTED JULY 16, 1907. D. M. BLISS SWITCH,

Arrmonzow FILED JULY14. 1905.

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STATES PATENT OFFICE,

DONALD ELECTRIC COMPANY, A CORPORATION or MASSACHUSETTS.

FLISS, :OF BROOKLINE, MASSACHUSETTS, ASSIGiNOR TO HOLTZER GABOT SWITCH.

No. 860,124. A

' Specification of Letters Patent.

. Patented July 16, 1907...

Application filed July 14, 1905. Serial F0; 269,649.

To all nihom it may concern:

Be known that I, DONALD M. Btrss, a subject of the King of Great Britain, residing in Brookline, in the county of Norfolk, State of Massachusetts, have inaddition to the working winding, with a starting winding in 'multiple with the working winding, the said starting windin however, being open-circuited after the rotor has rea hed a'predetermined speed.

The present invention is embodied in an automatic switch for opening the circuit through the starting coils, the purpose of the invention being to obtain a switch which will open automatically after a certain is such as to vary the leverage through which the spring acts, so that more force is required to move the switch from its closed to itsopen position, than-is required to restore the switch to its closed position after it has once been opened.

A further feature of the invention consists in an arrangement whereby the contact member of the switch is acted upon by centrifugal force in such a manner as to insure a firm sliding contact during the first opening movement of the switch and the final closing movement thereof.

Figure l isan elevation of the rotor member of an induction motorfthe switch mechanism being shown in section, the section taken on ,a line 96 of Fig. 2; Fig. 2 is a section on the line 00 of Fig. 1, looking in the direction of the arrow, and showing, in full and dotted lines, the switch mechanism in elevation; Fig. 3 isa diagram of the stator circuits and a partial view of the switch to illustrate the operation.

Referring to Fig. 3, the current is supplied to the stator from the line conductors 2 and 3, the working coils A being directly connected with the line terminals at the points 20 and 30. One terminal of the starting winding B is connected with the line 2 at 20, while the other terminal leads through a conductor 4 to a brush 5.which bears upon a collector ring a-, the circuit being completed through a brush 6 bearing upon a collector ring b and a conductor 7 which leads to the terminal 30. So long, therefore, as the collector rings a and b are electrically connected, current will flow in multiple circuit through both the windings A and B. It is desirable, however, to cutout the starting coils B after the rotor has reached a predetermined speed,'and, for this purpose, the connection between the collector rings a and b is arranged to be broken by means of a switch member c which is pivotally supportedat c upon one of thecollecting rings, the said switch mem- 7 her being arranged to be moved in one direction by centrifugal force, and in the opposite direction by a yielding mechanical force as that of a spring 0 The switch member 0 is electrically connected with the collecting ring a, the pivot member 0 affording means for electrically connecting these parts, asbest shown in Fig. 1. The rings a and b are separated from each other by a sheet of insulating material-d, so that when the switch is open, there is no electrical connec:v

tion between the brushes 5 and 6. When, however, the switch is closed, the current can pass through the .brush 5 and the ring a to the switch member 0 which,

as best shown in Fig. 2, is in electrical contact with a contact block a electrically connected through fastening screws 6 with the collector ring I). When, there fore, the rotor is at rest, the switch Will be closed, and when the current is turned on, the coils A and the coils B will both be in circuit, thus producing thephase dis placement necessary for starting the rotor. As soon, however, as the rotor has reached the speed for which the switch is'adjusted, say, for example, one thousand revolutions per minute, the centrifugal force acting on the switch member 0 will overcome the stress of the spring and cause the said switch member 0 to move to the position shown in dotted lines, Fig. 2, such movement being limited by means of a stop 0. This breaks the circuit through the coils B cutting out the said coils and leaving the working winding A alone in circuit. i In order to prevent the closing of the switch in response to a slight reduction in speed, the arrangement is such that the effective force of the spring 0 is less when the switch is open than it is when the switch is closed, this being accomplished, as herein shown, by

connecting the spring with the switch member 0 in taining device 0 to which the other end of the spring .is connected. This line, as clearly indicated in the dotted line position of the switch, is moved nearer to the axis of the pivotal support 0 when the switch is open, thereby shortening the lever-arm upon which the spring acts and reducing the efficiency of the spring as a restoring device for the switch arm. The parts may be so adjusted, therefore, that, although the switch will not open until the rotor has reached the velocity of, say, one thousand revolutions per minute, the said switch will remain open until the speed has been materially reduced, say, for example, down to five hundred or six hundred revolutions per minute. The starting coils B, therefore, will not be cut out until the motor has reached its normal maximum speed, but

the speed may afterwards be reduced through varia tions inlload, or for other causes, without causing the starting coils to be included in the circuit. In order to insure a'good sliding contact between the switch member 0 and the contact member e, the said switch member is herein shown as provided with an arm 0 which is pivotally connected at c with the member 0, while the contact member e has an extended contact portion-e having a curved guiding surface e, so that contact is insured during the preliminary movement of the member c in response to the centrifugal force.

The supplemental arm c normally stands in such a position that the centrifugal force developed by the rotation of the switch member will tend to throw it into contact with the surface 6 andmaintainit in such contact during the first part of the outward movement of the member 0. 1

In order to keep the member 0 in approximately the same position at all times, and at the same time to admit of the slight movement thereof, due .to centrifugal force, the said member is shown provided with a recess 0 the walls of which stand at opposite sides of a lug or projection e on the switch member 0, and thereby serve as stops to limit the pivotal movement of the member 0?. I

In the construction shown, the operating parts of the switch are inclosed between the main body of the rotor and the collecting rings, and the whole being within the stator member, the working parts thus-being entirely inclosed. The collecting rings a and b are shown as mounted on a sleeve f which has a flange portionf on its outer surface, the sleeve being fastened, as by a set screw P, to the shaft 0 of the rotor C. The collector ring b rests against a sheet of insulating material 9 interposed between the flange f 2 and the outer surface of said collector ring, the insulation d being between the collecting ring a and the collecting ring b. The rings a and b and the sheets of insulation d and g are clamped together by means of screws h whichextend through from the inner surface to the flange f. The parts indicated by the reference letters '5 and k, Fig. 2, are merely lugs cast on themember a for the purpose of affording weight to counterbalance. the movable switch member and the parts cooperating therewith.

While the specific construction herein shown and described for the purpose of illustrating the invention is practical and efficient, it isobvious that modifications may be made in the construction without departing from the invention.

Claims.

1. In a single phase induction motor, starting coils; collecting rings insulated from each other; brushes or collectors connecting said rings respectively with the terminals of said starting coils; a fixed switch member electrically connected with one of said collecting rings; a pivoted switch member electrically connected with the other of said collecting rings and adapted to be operated by centrifugal force; and means for exerting a mechanical force in opposition to said centrifugal force and shifting the line through which said mechanical force acts with relation to the pivotal axis of the switch member.

2. In an electric switch, a rotary support provided with a fixed contact and with a pivotally supportedswitch member adapted to be moved away from said fixed contact by centrifugal force; means for resisting said centrifugal force; and a contact member pivotally conneci'ed with said switch member and so positioned as to be retained by centrifugal force in contact witlrsaid fixed contact while the switch remains closed.

In a single phase induction motor, starting coils; collecting rings insulated from each other; brushes or collectors connecting said rings respectively with the terminals'of said starting coils; a fixed switch member electrically connected with one of said collecting rings; a centrifngally operated switch member electrically connected with the other of said collecting rings; a spring to act against the centrifugal force in the operation of said movable switch member; and means for varying the line of pull of said spring with relation to ,the axis of said movable contact member, substantially as described.

4. In an electric switch, a rotary support; a fixed contact thereon; a cooperating movable contact carried by said support and insulated from said fixed contact and normally engaging but adapted to be moved out of engagement with said fixed contact. by centrifugal force; and means for exerting a mechanical force in opposition to said centrifugal force, and shifting the line through which such mechanical force acts with relation to the pivotal axis of the switch member. I

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

DONALD M. BLISS.

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