US1819228A

US1819228A - Rotor

Info

Publication number: US1819228A
Application number: US349958A
Authority: US
Inventors: Charles B Coates
Original assignee: Chicago Pneumatic Tool Co LLC
Current assignee: Chicago Pneumatic Tool Co LLC
Priority date: 1929-03-26
Filing date: 1929-03-26
Publication date: 1931-08-18
Anticipated expiration: 1948-08-18

Description

Aug. 18, 1931- c. B. coATEs 1,819,228

ROTOR Filed March 26. 1929 'J/// //v a/WW,

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or peripheries.

-15. smaller sizes of induction motors.

Patented Aug. 18, 1931 UNITED STATES.

PATENT; OFFICE.

CHARLES E. COATES, OF CLEVELAND, OHIO, ASSIGNOR '10 CHICAGO PNEUMATIC 13001: 00:01am, 01 NEW YORK, N. 'Y., A CORPORATION OF NEW JERSEY Boron Application filed. larch 26, 1929. Serial No. 349,958.

This invention relates to squirrel cage rotors of the bar type for use in induction .motors, and more es ecially to rotors of the so-called cast or in estructible type. Such j rotors, in accordance with the preferred practice,'have the windings and end rings cast inone piece upon the core.

Rotors of the described type, as heretofore used, have had absolutely smooth exteriors It has been discovered that there is a loss of efiiciency due to undue heating which results from the difiiculty in forcing air through the narrow gap between the rotor and the stator, especially in the When such rotors are used in high frequency motors, especially in the small motors used on portable tools where the gap is about .015

of an inch, the customar fan on the motor shaft cannot force air t rouigh the narrow air gap fast enough or. in su cient quantity to carry away the heat generated at the high speed of rotation.

' One object of the invention is to improve the cooling of rotors of the described type.

Another object is to produce an improved cooling efl'ect without impairing the operation ofthe motor or weakening the rotor structure. Qther objects will be a parent fromthe detailed description which ollows. I The invention comprises forming the rotor with built-in cooling features. These features consist in interrupting the smooth exterior surface of the rotor in a manner to cause movement of air axially from one end 'of the rotor to the other. In the referred arrangement, spiral grooves, exten ing from one end of the'rotor to the other, are cut in the core portion of the rotor. These grooves may be arranged to extend over and along the bars or cast windings of the rotor.

In order to illustrate the invention, one embodiment thereof is shown in the accompanying drawings, in which:

' Fig. 1 is a perspective view of the improved rotor;

Fig. 2 is a transverse sectional view substantially on the line 2-2 of Fig. 1; and 50 Fig. 3 is an end elevational view.

terior of the core coul 'In the embodiment of the invention shown in the drawings, the rotor comprises a laminated core 4, each plate of which is perforated or otherwise cut away as indicated at 5, to receive the bars or cast windings 6 which extend the full length of the core and terminate in integral end rings 7 which, in the present instance, are tapered outwardly from their bases which engage the end plates of the laminated core 4 and cover the bar openings 5. As clearly indicated in Figs. 1 and 3, the end rings are of less diameter than the plates of the core so that the latter projects somewhat therebeyond. Slots 8, extending from one end ring to the other, are provided in the portion of the rotor which extends beyond the end rings, these slots being cut substantially to the level of the end rings and on a slight curve or spiral. Slots 8 are regularly placed and dis- [0 posed in parallelism so that when the rotor 7 turns it has the effect of an. air screw in forcing air from one end of the rotor to the other.

The slots may be-variously made but it is 15 simplest to mill the slots through after the windings and end rings are secured in place, preferably by casting the same upon. the rotor core in one operation. By preference the slots are cut over the bars or cast windings as shown. In mounting the fan upon the rotor, attention must be given to the direction of rotation of the rotor so that the inclination of the spiral grooves 8 will be 4 such as to assist the fan in moving the air as through the airgap and not to oppose the action of the fan.

I am aware that in the conventional form of wire wound rotor the slots for the wind ings are cut throughthe eriphery of the rotor and that, when wedges are inserted to hold the windings in place, a groove is left in the rotor somewhat similar to the cooling means herein disclosed. But such an arrangement is the result of necessity, for only by leaving openin '5 through the exthe windings be wound and inserted. Thus the slots in the core have always been looked upon as neces sary evils and much trouble has resulted 10D from the difliculties involved in securely wedging and holding the windin s in place against the action of centrifugal orce. The grooves were not formed to effect cooling 5 of the rotor and in fact their cooling function has never been recognized, since the fan is applied to such a rotor without any attention to the direction of inclination of the grooves. That grooves in the rotor have been considered a detriment is clear from the fact that rotors heretofore constructed of the bar type, whether of the inserted bar or cast bar, have been made with smooth peripheral surfaces.

I claim as my invention:

1. A rotor for a motor having very close clearance between stator and rotor comprising a core having bars and end rings cast in one piece thereon, and means on the exterior surface of said rotor in the form of grooves extending from end to end and at a slight axial inclination for impelling movement of air from one side of said rotor to the other when said rotor is in motion.

2. A rotor comprising a core and bars and end rings cast in one piece upon said core, said core projecting slightly above said end rings, and spiral grooves in said core extending from end to end and cut to the depth of the peripheries of said rings.

3. A rotor comprising a core and bars and end rings cast in one piece upon said core said core projecting slightly above said end rings, and spiral grooves in said core extending from end to end and out to the depth of the exterior surface of said rings, said grooves being directly above said bars.

Signed by me at Cleveland, in the county of Cuyahoga, and State of Ohio this 23d day of March, 1929.

CHARLES B. COATES.