US1442517A - Starting switch - Google Patents

Description

Jan. 16,1923. 1,442,517 I D. M BLISS.

STARTING SWITCH. FILED MAY 27,1921.

Patented Jan. 16, 1 923.

UNITED STATES PATENT OFFICE.

DONALD M. BLISS, OF BATTLE CREEK, MICHIGAN, ASSIGNOR TO H. B. SHERMAN MANUFACTURING MICHIGAN.

C0,, BATTLE CREEK, MICHIGAN, A CORPORATION OF STARTING SWITCH.

- Application filed May 27, 1921. Serial No. 473,185.

To all whom it may concern Be it known that I, DONALD M. BLISS, citizen of the Dominion of Canada, residing at Battle Creek, in the county of Calhoun and State .of Michigan, have invented certain new and useful Improvements in Starting Switches; and I hereby declare that the following is a full, clear, and exact description thereof, reference being had to the ac companying drawings, which form part of this specification.

This invention relates to so-called centrifugal switches which are adapted to be used in connection with rotatable members to be automaticall opened by centrifugal force after a pre etermined speed of revolution has been'reached. Such switches are commonly used in small alternating current motors ofthe single phase'type and wherein it is desirable to provide means for automatically opening the circuit through the auxiliary or starting winding when the motor has reached a predetermined speed.

The primary object of the invention is to provide a simple switch of centrifugal type in which the sparking area is reduced to a minimum.

Another object is to provide a switch in,

which the switch members will have a progressively separating action from the opposed contacts thus making successive make and break of the contact area as hereinafter explained.

F urther'objects are to provide a novel form of switch members or blade and to provide means for lubrication between the rotating and fixed contact sections of the switch.

I will explain the invention with reference to the accompanying drawings and summarize in-the claims the novel features of con struction and novel combinations of parts for which protection is desired.

In said drawings: r

Fig. lis a diagrammatical view of a centrifugal switch embodying the present invention, showing the switch closed.

Fig. 2 is a like view of the switch shown in Fig. 1, showing the position assumed by the switch blades after the motor is running but before it has attained full speed. Fig. 3 is a similar view, showing the position of the contact blades after the motor has attained the predetermined speed.

Fig. 4 is a side view of one of the contact blades partly broken away.

Fig. 5 is an end view of such blade.

Referring to Fig; 1, 1 and 2 designate the termlnal leads or posts, and 3 and4 are opposed contact segments of the motor opposed to which are relatively movable contact blades 5 and 6 which are attached to' the revolving rotor of the motor so as to be capableof movement in a radial direction away from contacts 3 and all As shown the contact blades 5 and 6 are retained on the rotor by means of pins or lugs 5*, 6 engaging slots in the blades; and the blades 5 and 6 are normally held in contact with the stationary contact segments 3' and thy means of helical contractile springs 7 and 8 connected to and between the adjacent ends of the contact blades, 5 and 6 and normally holding the blades 5 and 6 in contact with the blades 3 and 4 until the motor has attained a predetermined speed sufiicient to cause centrifugal force exerted upon the blades 5 and 6 to overcome the resistance ofthe springs 7 and 8 and cause the blades to separate from the segments 3 and 4, thus breaking the circuit. The segment 3 may be connected as usual by a conductor 11 to a starting winding 11" and the latter to the terminal lead or post 1; the contact segment 4 may be connected by a conductor 12 with the terminal post 2, a winding 12 being interposed between the terminals 1 and 2.

In switches of this design, as ordinarily constructed (Fig. 1) the edge of the contact blades tends rapidly to wear the stationary segments 3 and 4 both by reason of the extensive frictional contact between the two surfaces as well as from the sparking which takes place at various points around the circumference of the stationary segments when the contact blades 5 and 6 finally break contact with the segments during rotation.

As stated the primary object of the invention is to prevent this undue wear and sparking. For this purpose I provide means whereby the blades are caused to rock or tilt upon the segments in separating therefrom so that there is a gradual progressive lessening of the extent contact between the segments and the blades which contact is reduced to a small single point before the complete separation of the blades from the segments; this gradual separating action does away with the objectionable and injurious sparking and also does away with a great deal of the objectlonal frictlonal wear be tween the contact surfaces of the blades and segments.

For this purpose the blades are preferably hung so that their ends are unbalanced and.

anced As shown the perforated ends 13 and 14 of the blades (Figs. 1-3) are heavier than the ends 9 and 10 thereof. The springs 7 and 8 connecting the blades being of equal strength it follows that when the speed of rotation approaches the predetermlned limit, the heavier ends of the contact blades 14 and 13 will first separate from the stationary segments without any spark whatever, the lighter ends (9 and 10) of the blades are still in contact with the stationary segments at this instant (see Fig.2).

As the speed increases still further, the lighter ends 9 and 10 of the contact blades will finally leave the stationary segments thereby opening the circuit completely as shown in Fig. 3.

When the current is shutoff from the motor and the rotor gradually comes to rest, the lighter ends of the contact blades will be the first to make contact with the segments and finally the heavier ends 13 and 14 will rest on the stationary segments. By reason of this progressive action of the contact blades, the arcing or burning 'of the contact blades is confined to the light end section 9 and 10 of the contact blades, and to a very small extent of surface of the segments.

This progressive separating action of the contact blades could be secured by using balanced blades and making one of the springs 7 or 8 weaker than the other, therefore I do not limit myself to the useof unbalanced ends contact blades, but may use either or both of these methods to secure the desired progressive action.

Preferably the inner edge of each contact blade'is centrally notched, as at 5, 6 to provide a double contact surface for each blade.

As both the contact blades and the stationary segments are usually composed of similar metals of high conductivity, such as brass, cop er or bronze, and as it is not practicable to lubricate the contacting surfaces with oil heretofore there has been comparatively rapid wear between the contacting surfaces on account of mechanical friction as well as sparking.

As stated one object of the invention is to provide blades which will be practically self lubricating. For this purpose each blade is preferably made of two ormore leaves 5, 6 (see Figs. 4 and 5). The inner surfaces of these leaves are roughened or grooved as indicated at 5 and such grooves are filled with a lubricant such as graphite paste as indicated at 5, and the leaves are then riveted together with the layer of graphite between them. As the" graphite is not affected by heat it tends to distribute itself over the contact surface of the blade and so provides a practicable lubricant at the point of contact with the segments.

The general designof a centrifugal switch of this type with stationary segments and revolving contact blades cooperating therewith and connected by springs and actuated by centrifugal force to open the circuit through the starting winding at a predetermined speed is not broadly new and no claim is therefore made for such general design of switch; but having the blades unbalanced so as to have a progressive separating action as above described for the purpose of reducing the wear of the surfaces and limiting the arcing to a predetermined section is novel; also tively rotating unbalanced contact blades co-operating therewith whereby a progres- .sive making and breaking of the contact area between the blades and segments is produced by the action (if centrifugal force, substantially as described.

3. In a centrifugal starting switch, the combination of stationary contact segments, unbalanced rotating contact blades coopera'ting therewith, andspring means yieldingly holding the blades in contact with the segments, whereby a progressive making and breaking of the contact areas between the rotating blades and segments is produced by the action of centrifugal force, substantially as described.

4. In a centrifugal starting switch, the combination of stationary contact segments, with unbalanced rotating contact blades cooperating therewith to secure a progressive make and break of the contact area of'the rotating blades as described.

5; In a centrifugal starting switch, the combination of stationary contact segments with unbalanced rotating contact blades cooperating therewith and springs connecting the blades to hold them in yielding contact with the stationary segments whereby to secure a progressive make and break of the contact under the action of centrifugal force.

6. A centrifugal starting switch comprisin; stationary contact segments, rotating contact blades and springs yieldingly connecting the blades to hold them in yielding contact with the stationary segments, the contact being progressively broke-n at two predetermined contact points of each blade under the action of centrifugal force.

7. A centrifugal starting switch having one or more stationary contact segments and one or more unbalanced rotating contact blades cooperating therewith, and springs connecting the blades to hold them in yielding contact with the stationary segments, the blades rocking and partially opening the starting circuit at one speed, and fully opening the saidcircuit at a higher speed.

8. In a centrifugal starting switch, a contact member and a radially movable and slidable longitudinally unbalanced contact member cooperating therewith and rotatable relatively thereto, whereby a progressive making and breaking of the contact area between the members is produced by the rotating contactmember tilting and separating progressively from the othercont-act member under the influence of centrifugal force as a predetermined speed is attained.

9. A centrifugal starting switch having a plurality of contact members, and a plurality of radiall movable and slidable longitudinally unba anced contact members cooperating therewith and rotatable relatively thereto, whereby a progressive making and breaking of the contact area between the members is produced by the rotating contact members tilting and separating progressively from the other contact members under the influence of centrifugal force as a predetermined speed is attained.

10. In a centrifugal startingswitcha contact member and a radially movable longitudinally unbalanced contact blade cooperating therewith comprising a plurality of similar leaves and alubricant between the leaves, said blade being rotatable relatively to the contact members whereby a progressive making and breaking of the contact area between the blade and members is produced by the blade tilting and separating progressively from the contact member under the influence of centrifugal force as a. predetermined speed is attained.

11. In a centrifugal starting switch, the combination of stationary contact segments with unbalanced rotating contact blades cooperating therewith to secure a progressive make and break of the contact area of the rotating blades as described, each contact blade comprising a plurality of leaves and a heat resisting lubricant between the leaves, substantially as described.

In testimony that I claim the foregoing as my own, I affix my signature.

DONALD M. BLISS.

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