US1551598A - Short-circuiting device for alternating-current motors - Google Patents

Description

Sept. 1, 1925. 1,551,598

w. G. WINTER SHORT CIRCUITING DEVICE FOR ALTERNATING CURRENT MOTORS Filed Oct. 2'7. 1922 w/I SQW.

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Patented Sept 1, 1925.

UNITED vsiwx'rlas 4 1,551,598 PATENT OFFICE.

WILLIAM G. WINTER, OF ST. LOUIS, MISSOURI, ASSIGIN'OR TO GALVIN ELECTRIC MAN U- FACTURING COMPANY. OF ST. LOUIS. MISSOURI, A CORPORATION OF MISSOURI.

SHORT-GIRCUITING DEVICE FOR ALTEBNATI'NG-CURRENT MOTORS.

Application filed October 27, 1922. Serial No. 597,284.

To all whom it may concern:

Be it known that I, WILLIAM G. WINTER,

a citizen of the United States, and residing only and its use can be dispensed with after the motor has attained full speed. The usual way of changing from starting to running conditions on such a motor is to short circuit the commutator so as to convert the rotor winding into the equivalent of a squirrel cage connection. Many devices have been used for this purpose. Considerable difficulsuch devices on account of the fact that they must provide at all times a good, low-resistance contact with the commutator bars.

The contacting surfaces must furthermore be maintained clean and ingood condition. As the circuit is made and broken at these contact points at a time when considerable current is flowing, a great deal of trouble is experienced on account of pitting or corrosion of the contact surfaces. Such pitting tends to destroy the'effectiveness of the electrical contact and also to render the device uncertain in its mechanical operation. The device must furthermore be mechanically designed so that it will operate within fairly narrow limits at a definite speed, and such operation should be maintained reliable after repeated operation.

One of the objects of this invention, therefore, is to provide a commutator short circuiting device which will make a low resistance contact with the commutator bars.

Another object of this invention is to pro vide such a device which closes the circuit with a rubbing or scraping action so as to maintain the contacts clean and prevent corrosion.

Another object of this invention is to 5 Another object of this invention is to proure 1;

ty is experienced, however, in the design of vide centrifugal operating means which shall operate with a minimum amount of friction.

Further objects will appear from the detail description taken in connection with the accompanying drawing, in which:

Figure 1 is a fragmentary view of an armature having a commutator short-circuiting device embodying this invention;

Figure 2 is a section on line 2--2, Fig- Figure 3 is a section on line 33, Figure 1; 7

Figure 4 is a fragmentary sectional view similar to Figure 1, but showing the contacts closed: and

Figure 5 is a detail of .the contact surfaces.

Referring to the accompanying drawings, 1 designates the core of an armature of an electric motor having a shaft 2. Mounted .on the shaft 2 is a commutator hub 3 carrying a series of commutator bars 4. These parts may be of any usual construction and will, therefore, require no further descrip-- tion. I

Mounted on the shaft 2 is a sleeve 5. Slidably mounted on the sleeve 5 is a collar 6 provided with a radially extending flange 7. The flange 7 is provided with a conical cam surface 8. The outer rim of the flange 7 is provided with an annular seat adapted to receive a laminated contact ring 9. This ring 9 may be made up of a thin strip of sheet copper or bronze spirally wound in successive layers in the seat pro vided on the rim of the flange 7 The laminations may be permanently attached to the make proper contact with the beveled edges 12 of the commutator bars 4, see Figure 5. After the ring 9 is completely wound in place and properly fixed by means of the screws 10,

it may be cut by a series of slots 13. Those portions of the ring between the slots 13 will then provide a series of individual contact members, each providing a lammated contact composed of a number of resilient leaves, the ends of the leaves being beveled as shown at 11 to properly engage the comthe form of a radial disc having an outer flange 15 adapted to extend over a portion of the ring 9 and having an inner collar 16 engaging the sleeve 5. A pin 17 passing through the collar 16, the sleeve and the shaft 2 fixes said collar and said sleeve to the shaft. Pivotally mounted at 22 on the support 14 is a series of centrifugal elements or governor weights 18. These are mounted so as to lie between the support 14 and the flange 7 when the device is assembled as shown in Figure 1. Each element 18 is provided with a ball bearing 19 comprising a short tube 20 housing two steel balls 21.

With the device assembled as illustrated in Figure 1 and the motor at rest, the centrifugal elements 18 will lie between the support 14 and the flange 7 A spring 23 surrounding the collar 6 and bearing at one end against the commutator hub 3 and at the other end against the flange 7 urges said flange to the left, Figure 1, toward the centrifugal elements 18. The height of the two steel balls 21 is such that they will engage the flange 7 and take up the thrust of the spring 23 so that the elements 18 will be freell-to move in the space between the flange 7 and the support 14 under the action of centrifugal force. The ball bearing 19 is so positioned with reference to the cam surface 8 that when the motor is at rest, the pressure of the spring 23 acting through said cam surface on the ball bearings will force the elements 18 inwardly so as to rest against the sleeve 5 as shown in full lines in Figure 2. When the motor is brought up to speed, the elements 18 will be urged outwardly by centrifugal force. At a certain definite speed the centrifugal force acting through the ball bearings 19 and the cam surface 8 will be suflicient to overcome the tension of the spring 23. At this speed the elements 18 will move outwardly carrying the ball bearings along the cam surface 8 thereby forcing the flange 7 to the right, Figure 1, against the tension of the spring 23. Movement of the flange 7 to the right will carry the contact ring 9 into engagement with the commutator bars 4 so as to short circuit the Movement of the elements 18 under centrifugal force will be practically unopposed by friction since the entire pressure of the spring 23 is taken on the balls 21. Since two balls are provided, each ball will roll on the other and on the surface against which it bears, so that a true rolling bearing is provided. A minimum amount of friction is, therefore, introduced and the action of the device is rendered very reliable so that the commutator will be automatically short circuited at a definite speed. As the motor slows down, the centrifugal action of the elements 18 will be reduced and at another definite speed, these weights will be forced inwardly against the sleeve 5, thereby allowing the flange 7 to move to the left, Fig ure 1, and opening the circuit between the faces 11 and 12. As this action takes place usually after the current has been cut off from the motor, there will be no current flowing in the contacts 11 and 12 and there will, therefore, be no pitting or corrosion of these contacts.

It will be noted that a very efficient and reliable device is provided by this invention. A multiple leaf or laminated contact is provided which closes the circuit with a scraping action so as to avoid corrosion of the contacts. The laminated contact provides a very low resistance contact and the short c'ircuiting ring integral with these contacts provides a very low resistant short circuit. The centrifugal elements being provided with ball bearings having a true rolling action provide for a reliable and accurate action at a definite speed. The device is simple in construction and cheap to manufacture.

\ It is obvious that various changes may be made in details of construction without de parting from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to the specific details shown and described.

Having thus described the invention, what is claimed is: i

1. In an electric motor having a commutator the combination with a movable contacting element provided with a cam, of a rotatable support, centrifugally operated elements mounted on said support, each element having interengaging balls one of which engages said cam.

2. In an electric motor having a commutator. the combination with a movable contacting element provided with a cam, of a rotatable support, centrifugally operated elements mounted on said support. each element having interengaging balls one of which engages said cam and the other engaging said support.

3. In an electric motor having a commutator, a short circuiting device comprising, a movable element having a spirally wound leaf contact mutaton. 1

4:. In an electric motor having a commutator, a short circuiting device comprising, a movable element having a spirally wound adapted to engage the commultiple leaf contact adapted to engage the commutator.

5. In an electric motor having a commutator, a short circuiting device comprising, a movable element having a conducting membar 5 irally wound thereon to form a laminatedl leaf contact ring adapted to engage the commutator.

6; In an electric motor having a commutator, a short circuiting device comprising, a movable element having a spirally laminated contact ring adapted to engage the commutator.

tor, a short circuiting device comprising, a movable element having a s irally laminated leaf contact ring divide into circumferential sections and adapted to engage the commutator.

8. In an electric motor having a commutator provided with a bevel face, a short circuiting device comprising, a movable element having a circumferentially laminated leaf contact adapted to engage the bevel face of the commutator.

9. In a device of the character described having a rotating shaft, an axially movable member, relatively fixed supporting member, a cam on one of said members, a centrifugal element, and interengaging balls arran ed to provide rolling bearings for each ot er and engaging said members, said balls being adapted for actuation by said centrifugal element to cooperate with said cam to move I said movable element. 7. In an electric motor having a commuta- In testimony whereof I aifix my signature this 9th day of August, 1922.

WILLIAM G. WINTER.

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