US1910245A - Centrifugal switch - Google Patents

Description

May 23, 1933 A. M. HARRELsoN 1,910,245

CENTRIFUGAL SWITCH Filed Deo. 51, 1931 avi! awww@ aken/wu,

Patented May 23, 1933 UNITED STATES PATENT OFFICE ALLEN M. HARRELSON, F TROY, OHIO, ASSIGNOR T0 THE HOBART MANUFACTURING i COMPANY, OF TROY, OHIO, A. CORPORATION OF OHIO CENTRIIUGAL SWITCH Application tiled December 31, 1931. SerialN'o. 584,107.

It is an ob]ecti of the invention to provide l .5 a centrifugally operable device adapted to serve as a switch, which is rugged, self-contained and not subject to deterioration with long use.

It is a further object of the invention to provide a self-contained centrifugal switch that is easy to install, inexpensive to manufacture, which comprises relatively few parts and which will give uniform satisfactory -service over a long period of use.

Other objects an'd advantages of the invention will be apparent from a study of the detailed description, the accompanying drawing, and the appended claims.

In the drawing- Fig. bisV a broken view partially in-section and partially in elevation of av centrifugal switch constructed in accordance with the present invention in place on a motor;

Fi 2 is an endelevational view of the switc l Fig. 3 is an end elevational view yof the Stationary contacts of the switch.

Fig. 4 is a plan view of a detail of the switch structure; and

Fig. 5 is a perspective view of the centrifugal switch removed from the shaft.

It is well known thatsingle phase alternating current' induction motorshave no starting torque of their own. One method of starting such a motor is t0 rovide an auxiliary or starting winding w ich is dephased from themain winding by an angle sufiicient to produce an effective rotating electromagnetic field. After the motor 0 comes partly up to speed the starting winding should be disconnected to prevent its being burned out and it' is therefore common practice Ato' provide a centrifugal switch for opening the circuit to the starting winding 5 after the motor. has come partly up to running speed. The switch of the present invention is peculiarly adapted for this use, and its construction will be described with relation to an electric motor; however, this 5 is to be taken as illustrative only, and not as a limitation for the same principles are equally applicable to other installations.

Referring to the drawing in detail, where'- in there is illustrated a preferred embodiment of the invention, there is shown a motor indicated generally at 10. This motor comprises the usual field structure 11 to which is bolted 'by bolts 12 the end casting or bracket 13. ThisI bracket serves to house the outer ball race y14 of a ball bearing which serves as a support for the main shaft 15 of the motor. The inner race is held in position on the motor shaft by nuts 16. A bearing cap 20 is bolted against the ball race 14 to hold the same in place by bolts 21 and is also provided with a removable plug 22-by means of which access may be had to the bearings without v removing the end casting. Cover plate 24 v is fastened to the bearing cap by screws 25. These parts represent any conventional motor structure and have no particular bearing upon the present invention.

The centrifugal device comprises rst a carrier member 30 which is provided with an internal bore of substantially the same diameter as that'of the shaft and with an extended sleeve portion'31 at one end. A

shoulder 32 Amay be formed on the shaftl 15 if desired and the sleeve 31 preferably is drawn up tightly against the same through the action of the internal ball race and nuts 16. The force of friction will be suiiciently great to rotate thesleeve without other holding means. The sleeve is also formed with a series of depressions or pockets 33 preferably radial with respect to the shaft center, separated by walls 34. A series of balls 35 are placed one in each depression and serve as rotary weights, ada ted to move outwardly under the action o centrifugal force.

A disk 38 formed of insulating material is mounted upon the sleeve 31 with just enough clearance so thatit does not tend to bind or to produce undue friction. The rotary contact, consisting of an annular copper strip 39, is fastened to the outer side of the disk by rivets 40. A cam late 41 is fastened to the disk by means o screws 42 and is provided with a bent over portion 43 10 and guiding edge 44. A relatively lar e clearance is left between the edge 44 of tle diskand the carrier member in order that under normal conditions there will be no contact between these two metal surfaces, thus affording a guiding means for the contact plate and cam assembly which is 'sufficiently yieldablc to allow rotary contacts 5f). A yieldable com ression spring tact 39 to seat itself natura ly against con- 46 is enclosed about the sleeve between the contact disk and a groove 47 whichl is formed in the carrier member adjacent the base of its curved portion, which spring normally tends to move the disk and the carrier member apart. The sprin carrier member, and balls are complete enclosed within and protected by the ousing consisting of the disk and the cam plate.

The stationary contact members comprise two spaced copper stri s 50 which are connected in series with t e starting winding, and which are riveted to a late'51 of suitable insulating material. T is plate is fastened to the end bracket of the motor by means of bolts or screws through holes 52. The stationary contact members are so mounted with respect tothe rotational part of the switch that when the parts are sta-nding still the spring 46 will urge the rotary contact against the fixed contact.

In the operation of the motor, assuming that the current is turned on with the motor at a standstill, the annular contact 39 is bridged across the two stationary contacts I 50, and thus the circuit to the starting wind-` ing is closed.' The circuit remains closed as the motor begins to turn over, and the contact disk andthe cam plate are held stationary because the friction between the two metallic contact surfaces is greater than that between the disk and the rotating sleeve 31. Thus an even contact is maintained Without arcing or sparking which would provoke a deterioration of the switch. As the speed of the motor increases, and when it has reached a predetermined speed, the balls 35 will fly outward by centrlfugal force against the sloping face 43 of the cam plate and exert a camming action'thereon. This force overcomes that of the spring 46 and therefore the contact disk and floating cam plate Aare lquickly moved axially toward the center of' the motor and the circuit to the starting winding is opened. The limited amount of frictional engagement that occurs before the final separat-ion of the contacts assists in keeping the contacts clean. After the contacts have entirely separated, the disk and cam plate are free to rotate at the same speed as the shaft.

In slowing down after' the motor has y been deenergized, as soon as the point is reached where the force of the 'sprin exceeds the centrifugal force of the balls, the

rotating contact will be forced into contact with the stationary member and will exert a limited amount of wiping action thereon until it comes to a stop. Thereafter the motor may continue to rotate for some time but during this period there is no unnecessary wear on the contacts. The switch thus keeps its contacts clean and at the same time is designed to have' a maximum life without requiring replacement of parts'.

It will be noted that the centrifugal dcviee is enclosed, and is thus effectively protected against dirt or any foreign material which might happen to get into the interior of the switch and prevent its proper opel'ation. This feature is of importance in many motor installations where the motor must operate in an atmosphere which is filled with particles of dirt or dust. It will also be noted that this device is a unitar structure which can be slipped onto the sha t .of the motor in a single operation. It may be held in place as illustrated and previously described, or by a set screw in carrier member 30 bearing against the shaft.

While the form of ap aratus herein-described constitutes a pre erred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the i scope of the invention which is defined in the appended claims.

What' is claimed is:

1. A centrifugal starting switch for a sinn'le phase motor comprising a carrier member rotatable with the shaft of said motor and formed with a series of radialdepressions, balls in said depressions ada ted to roll outwardly under centrifugal orce, a

of rotation of said shaft, yieldable means within lsaid housin tending to cause movement of said memer in an opposite direction, and a contact carried by said disk.

3. A centrifugal switch comprising a rotating shaft, a carrier member fixed to said shaft, a plurality of radially movable weights rotated by said member, a contact disk loosely mounted on said member, a fixed contact, a cam plate attached to said disk and having a face cooperating with said cam plate and contact carrying disk assemweights, yieldable means urging said contacts toward closed position, said weights movable outwardly by centrifugal force against said plate to cause the separation of l the contacts.

4. A self-contained centrifugal device adapted to be readily attached to a rotating rier member, a floating disk mounted on said member, a cam plate carried by said disk, means tending to move said disk in one direction, centrifugally operable means cooperating with said plate for moving said disk in the opposite direction, both said inleans beng enclosed by said disk and said p ate.

6. A centrifugal starting device for a motor adapted to vbe pla-ced on the shaft of the motor as a unit comprising a carrier member formed With an extended sleeve, a disk of insulating material floating on said sleeve, a cam plate mounted on said disk-Weights rotatable With 'said carrier and cooperating with the cam plate, and'yieldable means urging the cam plate and said carrier part, said Weights at a predetermined speed of rotation adapted tomove outwardly by centrifugal said disk and plate forming a dirt proof housing enclosing said Weights and said yieldable means.

9. A centrifugal switch comprising a rotary shaft, a carrier member formed with an extended sleeve and rotatable with the shaft, centrifugally operable weights carried by said carrier member, a disk of insulating material mounted on said sleeve, a contact carried by said disk, an imperforateplate fastened to said disk and terminating closely adjacent said carrier member, said plate and said disk forming a dirt proof housing enclosing said carrier melnber and said Weights, a fixed contact, and yieldable means for urging said contacts together.

l0. A starting switch for a single phase motor having a shaft comprising spaced stationary contacts mounted on the end bracket of the motor and connected in the starting winding circuit, a carrier member slidable onto the shaft and rotatable therewith, a plurality of radially extending pockets formed .in said member, Weights in said pockets, an insulating disk floating on said member, a contact ring on said disk, a cam plate larried by said disk cooperating with said Weights, and yieldable means normally urging said ring and said contacts together to close the starting winding circuit, said Weights adapted to move outwardly by centrifugal force to cause the separation of said ring from said contacts.

In testimony whereof I hereto aflix my signature.

. ALLEN M. HARRELSON.

force to cause the disk and carrier to move relatively toward each other.

7. A centrifugal switch comprising a ro- I tary shaft, av carrier member rotatable with the shaft,a plurality of Weights carried by said carrier member, a disk of insulating material mounted on said shaft, a contact carried by said disk, lan imperforate plate fastened to said disk `and extending over said carrier member to form a dirt proof housing enclosing said member and said weights, a xed contact, and yieldable means urging said contacts together, said Weights under the action of centrifugal force adapte'd to cooperate with said plate to separate said contacts.

e. A starting Switch for a Single 'phase motor comprising a rotary shaft, a carrier member rotatable with the shaft, centrifurally operable weights carried by said carrier member, a disk of insulating material floating on said shaft, a contact carried by said'disk, a plate fastened to said disk, a fixed contact, and yieldable means for urging said contacts into circuit closing posltion,

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