US1641908A - Starting means for induction motors - Google Patents

Description

Sept. 6,1927.

B. sTEcHBART sTARmNG MEANS Fon Innucmon MoT'oRs Patented Sept. 6, 1927.

:UNITED sTATEs PATENT OFFICE.

v' BRUNO STECHBABLIOF CHICAGO, ILLINOIS, ASSIGNOR TO BOBINE ELECTRIC COH- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

STARTING MEANS FOR INDUCTION MOTORS. v

My invention relates to the class of induction motors in which an auxiliary orpstarter A winding is lprovided in the stator or lield of the motor and in which the circuit through this starter' winding is controlled in response to variations in the magnetic field induced in the armature.

Generally speaking, the objects of my invention are those of providing simple, durable and positive means responsive to stray lines of magnetism from the armature for closing the winding and for holding this circuitl closed until the said stray magnetic lield is Weak- 16 ened to a predetermined extent when the armature approaches its normal speed of rotation, -providing simple and positive means for rupturing the said starter circuit when the armature has approached this speed, providing simple and eective means Jfor cushioning the movementpof the switching member to its circuit-closing position, and providing simple and effective mountings for the switching member and for the contact lranembers which engage the switching mem- More particularly, my invention provides a mounting for the switching member which will permit the latter to rotate freely on the lo armature shaft, so as to reduce friction and so as to distribute the points of engagement of this switching member with the contact members; provides simple bumper springs for affording the said cushioning action; and $5 provides a mounting for the contact members which can readily be secured to the frame of a standard induction motor of the Y said general class.

Stil-l further and also more detailed objects will appear from the following speciiication andf from the accompanying dra-w1 ings, in which" i Fig. 1 is a side elevation of one end of an induction motor equipped with my invention, with a portion of the motor casing broken away to show the switching mechanism andwith the switching member in cen-V tral and longitudinal section.

Fig. 2 is a side elevation of the same end 5 of the armature and armature shaft,l the switching member, and the Acontact members, showing the switching member in itsv circuit-closing position.

Fig. an elevationjsimilar to F1g.2,

circuit through such a starter but showing the switching member in its circult-opening position.

Fig. 4 is a side elevation of the switching member, the contact members andthe contact carrier, taken from the 1ine-4-4 of Fig. 1 but with the switching member in its circultclosing position of Fig. 2.

Fig. 5 is a section taken along the line 5-5 of Fig. 4. i

Fig. 6 is a perspective -view of the tubular body of the slidable switching member.

lIn the drawings, Fig. 1 shows one end of the `field frame 1 of a motor, carrying an. end

housing portion 2 which supports a bearing 3 for the adjacent end ortion of the shaft 4 of the armature 5. 'lldbunted' upon, but insulated from, the housing end portion 2 are a pair of resilient contact fingers 5 and 6 which extend past the axis of the shaft 4 at opposite sides of the latter and whicli are spaced by adistance greater than the diameter of these shafts, these contact fingers being .respxectively connected to wires 7 and 8 whic form part of the circuit through the auxiliary or starter winding.

To control this circuit, I provide a switching member slidably mounted on the armature shaft and including a metal ringS which is adapted to engage the contact tips 5A and 6A of the two contact arms when the carrier is slid out of idle position of Figs. 1 and 3 to its operative or' circuit-closing position of Figs. 2 and 4.

A s here illustrated, the switching member includes an insulating disc4v 7 bored to slidably fit a part of the shaft 4 and having the metal ring 8 spun over its periphery,`and a tubular body 9 connecting this insulating discl 7 with a soft iron part which is also slidable on the s ha-t. This soft ironpart comprises a flat annular rim 10 connected by arms 11 to a hub portion 12 and the tubular 'body 9 (which may be of brass)lv has `at its opposite ends fingers 13 and 14 anchored respectively in corresponding perforations in the said hub portion and the insulating disc. To insure a-rml clinching of the fingers 14 to the insulating disc, I may extend these lingers also through a metal washer 21 bearing against the vouter vface of the said disc. Interposed between the said hub portion of the soft iron part and the armature 5 is a compression spring 19 which tends to move the slidable switching meml ao ber away from .the armature, such movement being limited by the engagementof the insulatin disc with a stop pin projecting radially rom the shaft. The soft-iron inember is centrally -dished so asto receive the spring 19.

When the motor is standing still, the spring holds the switching member in its outward position'of Figs. 1-"and 3 iny which the metal ring 8 is out of engagement with the contact arms, which form the terminals of the circuit through the starter wlndmg. As soon as current is supplied to the motor, the armature vis energized and the stray magnetic lines adjacent to its ends attract the soft iron member, thereby sliding the ,switching membertowards the armature, or

into the position of Figs. 2 and 4 in which `it closes the circuit through the starter winding. To prevent the soft iron member from sticking to the armature, I interpose non-magnetic spacer elements between thevtwo and I desirably provide these 1n the form of co r or brass s rin S16 secured P n Ppe p g of the starter winding, a slidable member v'to the iron ring 10 and formed so that they lwill be compressed between this rin'gand the armature, thereby also cushioningk the .impact'and preventing a loud slamming ac-` tion when the switching member is magnetically drawn to its circuit-.closing position. u

During the increase in speed of the armature, the stray m netism which has the above describedeifect decreases in strength until the ma etic pull becomes weaker than the thrust o the spring 19, whereupon this spring retracts the switching member `to its inoperative position of Fig. 3 so as to open lthe circuit through the starter winding, and

in practice the speed at which this opening of the circuit occurs can readily be determined by selecting a spring of suitable stiffness. l

As an elective mounting for the contact arms 6, I am showing a V-shaped support 22 having its back spaced from the housing end 2 by an insulating plate 23 and having perforated arms 22A. Thev two contact arms 5 and 6*.are respectively secured to these perforated arms22A by rivets 24:, each of which rivets is insulated' from the adjacent perforated arm by a bushing 25 as shown in Fig. 5, andeach contact arm car-r ries a binding screw 26'for securing the corresponding clrcuit'wire (such as the wire -With t ejconstruction as above described,

theannularform of the contact.. ring 8'permits this to make an effective ection to fboth of the contact arms 5 and k6@regardless of the vrotational ition of-the contact rin with respect to t e shaft, and in practice the inner soft iron portion) a.. end of the armaturer thus mounting the. contact ring, I reduce the friction between the contact arms and this ring, as even a relatively sli ht pressure of the arms on the rin against rotation whlle leaving the other parts of the switching member (including to rotate wit will. old the latter the armature. So also, this freedom of rotay tion of the contact ring causes the latter to present new points of engagement successively to the contact ti s or nubs 5A and 6A of the contact arms, t ereby insuring good electrical connections.

However, while I have illustratedH and described my invention in an embodiment including numerous highly desirable details of construction and arrangement, I do not vwish to be limited to these, since many changes might obviously be made without departing either from the spirit of my invention or from the appended claims.

I claimas my invention: l

1. In a motor of the class described, a air of contact members formingl terminals when moved inwardly of the motor througlh:

the attraction of the iron element by armature.

2. A motor construction as per claim 10,

vin whichthe cushioning means comprise ele ments secured to the lronrelement andar-i..`

symmetrically about 'the axis of theranged motor shaft.

3. In an induction motor having an aux- 111 starter winding, means for controlling the circuit through said winding including an iron bea member slidable on the motor armature s aft and disposed adjacent to urgin the member awa spac Switching me Y and enga a' with the contacts'ij-io'close' the circuit w en ve member is motied -toward the armature and combined means carried by said member and engageable withsaid om the armature,

contacts inclu ed in safid circuitt. ans connected to member means normally f end of the armature for cushioningthemember and for preventing the iron fromv ad hering to the armature composed of fiat 'ons to Krings secured atl their central,

free and s t e member and having their-en 4extending at -an angle toward` theA armatura 4. "In an induction motor having .an aux- I an end member `starter win of motor, a substa/nspaced froman end muy u of the armature shaft and secured at its base to and insulated from said end member,ucon tact amis included in the circuit and sec'il to the free ends of' the U-sha ed support andextending transversely of t c armature shaft, and vmagnetic responsive means engageable with the contact arms to close the'- V circuit upon energizing of the armature.

- from the armature.

6. In an induction motor having an aux'- iliary starter winding, means for controlling the circuit through said winding including' a magnetic responsive 'member having a rim and a hub, a coil sprin between the hub and ythe adjacent 'end of t e motor armature, a

sleevel slidable on the motor shaft and Secured at one endv to said hub, an insulating .ring secured to and about the opposite end of the sleeve,'a contact ring encircling the insulating ring, a'housing for the motor having an end spaced from the said armature end' and enclosing saidv sleeve'and the said parts connected thereto, contact arms ar.

ran ed transversely of the shaft and inclu ed in the circuit, and means to insulatingly mount the contact arms on said housing end and .at points to one Aside of the shaft. 4

7. In an induction motor having'an auxviliary starter winding, means for controlling the circuit through said windinv including a magnetic responsive memberslidable on the amature shaft, means to normally hold the member spaced from an'end of the armature,

circuit/closing means operable by the member, means included in the circuit and engageable with the circuit-closin means to close the circuit, and combined means carried by said member and eng cable with said end of thearmature for cus ioning the member and for preventing the iron from adharing to the armature.

v Signed at'A Chicago, Illinois, November 23rd, 1925. BRUNO STECHBART. -v

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