US934920A - Centrifugal switch. - Google Patents

Description

C. L. KENNEDY.

CENTRIPUGAL SWITCH.

APPLICATION FILED JUNE 14,1909.

Patented Sept. 21, 1909.

UNITED STATES PATENT OFFICE.

CARLTON L. KENNEDY, OF SOUTH BRAINTREE, MASSACHUSETTS, ASSIGNORTO THE HOLTZER-CABOT ELECTRIC COMPANY, OF BROOKLINE, MASSACHUSETTS, A COR- FORMATION OF MASSACHUSETTS.

CENTRI'FUGAL SWITCH.

Application filed June 14, 1909. Serial No. 501,955.

certain new and usefulfImprovements in Centrifugal Switches; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same.

The invention relates to centrifugal switches adapted to open (or close) a circuit when a predetermined speed is attained and particularly adapted to open the starting circuit of a split phase induction motor.

It has heretofore been proposed to construct this type of switch with contact mem-- bers comprising twojopposed levers mounted upon a rotary support and pivoted upon opposite sides of the center of rotation. These levers are connected by parallel springs 10- cated on opposite sides of the center of rotaable in certain cases to have the switch oocupy only a portion of the space surrounding. the end of the rotary element. This rovides an unbalanced construction w ich lends itself more, readily to some conditions. The levers are provided with contact blocks or brushes which are held in engagement-- with the stationary contacts by means of cross-connected springs attached to the levers. These respective springs are attached to portions of the levers which move in the same direction and are attached at such points relative to the pivots of the levers that their leverage is very materially varied as the levers swing about;.-their pivots.

In theaccompanying;drawings Figure 1 is a plan view of the switch in closed position also showing diagrammatically asinglephase motor circuit Fig. 2 is a central ver- Spec-ification of Letters Patent.

1; and Fig. 3 is a Patented Sept. 21, 1909.

tical section of the switch as shown in Fig. plan view of the switch in open position.

The switch comprises a block or base 1, secured to a rotary support 2 by means of screws 4'. The rotary support 2 is secured to a rotating element of the motor by a. screw 5. Contact, or brush-carrying arms 8 and. 9 are pivotally mounted upon lugs 10 and 12, respectively which project from opposite ends of the block 1. These pivotal-points are on the same side of the center of rotation of the support 2. Contact blocks or brushes 14 and 16 are pivotally mounted upon the arms 8 and 9 respectively and are limited in their 7 pivotal movement by the laterally projecting stops 18 formed on said arms. The brushes 14. and 16 are adapted to engage segmental contacts 20 and 22 which are insulated from one another and maintained upon a station projection 30 formed on the arm 8, and at its other end to a projection 31 formed on the arm 9. It will be seen that these springs lie in difi'erentfplanes on opposite sides of the base or block 1, and that their points of attachment bear such relation to thepivota'l points of the arms-8 and 9 that the leverage.

of the springs is very materiallyvaried as the contact arms swing about their pivots.

The contact arms provide an unbalanced construction, by being pivoted upon the same side of the center of rotation of the rotary support 2. As the brush carrying end of the arm 8.flies outwardly the tension of the spring 24. isincreased, its leverage on said arm is reduced, and its leverage on the arm 9 is increased, thus tending to move the brush 16 away from the segmental contacts. Likewise if the brush 16 should start to move outward the spring 26 would be put under greater tension and its leverage on the arm 8 increased, thus tending to draw the brush 14 away from the segmental contacts. Thus it Wlll be noted that the crossconnected springs act to equalize the pull of the centrifugal force and cause the brushes l4- and 16 to fly out simultaneously when the motor has attained the desired speed.

The motor circuit comprises line wires 40 and 41, across which a working coil 42 is connected, and a starting coil 44 connected at one end to the wire 40 and at the other end to the segmental contact 20, the contact being connected to the wire 41. When the motor is started the switch is in the position shown in Fig. 1, and the working coil 42 is short circuited by the starting coil 44.

l Vhen the motor attains the desired speed the contact carrying arms 8 and 9 swing into the position shown in Fig. 2, the starting coil .is cut out, and the Working coil remains in circuit.

\Vhat is claimed is 1. A centrifugal switch, having, in combination, a rotary support, a pair of similar centrifugal contact arms pivoted upon the same side of the center of rotation of the support, and two springs cross-connected at their ends to the arms, substantially as described.

2. A centrifugal switch, having, in combination, a rotary support, a pair of similar centrifugal contact arms pivoted upon said support upon the same side of its center of rotation, contact brushes pivoted upon the contact arms, and two springs. cross-connected at their ends to the arms, substantially as described.

3. A centrifugal switch, having, in combination, a plurality of segmental contacts, a rotary support, a pair of similar centrifugal contact arms pivoted upon the support upon the same side of its center of rotation, two springs cross-connected at their ends to the arms to hold the latter in engagement with the segmental contacts, the springs beingso connected to said arms that the outward movement of one arm reduces the tension of the spring tending to hold in the other arm and increases its leverage on the first mentioned arm While increasing the tension of the other spring and decreasing its leverage on said first mentioned arm but increasing its leverage on said other arm, substantially as described.

In testimony whereof I afiix my signature, in presence of two witnesses. I

CARLTON L. KENNEDY.

"Witnesses:

CLARENCE B. HANIGHT, HERBERT A. BALVANE.

Images