US2953826A

US2953826A - Apparatus for casting windings in electric motor rotors

Info

Publication number: US2953826A
Application number: US730918A
Authority: US
Inventors: Everett P Larsh
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-04-25
Filing date: 1958-04-25
Publication date: 1960-09-27
Anticipated expiration: 1977-09-27

Description

E. P. LARSH Sept, 27, 1960 APPARATUS FOR CASTING WINDINGS IN ELECTRIC MOTOR ROTORS Filed April 25, 1958 EVERFTT R LARBH ATTORNEYS APPARATUS FOR CASTING WINDINGS IN ELECTRIC MOTOR ROTORS Everett P. Larsh, 124 E. Monument Ave., Dayton, Ohio Filed Apr. 25, 1958, Ser. No. 730,918 2 Claims. (Cl. 22116) This invention relates to electric motor rotors and in particular to a method and apparatus for casting windings in the rotors of squirrel cage motors.

A large class of electric motors utilizes a rotor consisting of a magnetic frame and a squirrel cage or amortisseur winding thereon. Such a winding consists of a plurality of spaced bars extending axial-1y through the rotor and connected at the ends of the rotor by conductive end rings. These bars are often inserted in the slots of the rotor and the end rings applied thereto by riveting or welding, but a prefer-red manner of supplying the winding to the rotor is to cast the winding directly into the slots of the rotor while simultaneously forming the end rings on the rotor, all as a single integral casting.

Some difficulty has been experienced in obtaining sufficiently dense castings in such cases to make all of the rotors absolutely uniform as to their electrical characteristics; and there has further resulted considerable difficulty with the cast material being smeared about the A still further object of this invention is the provision' of a method and apparatus for casting windings in electric motor rotors which is adapted for being incorporated in an automatic machine thereby leading to extremely rapid production of the rotors.

A still further object of this invention is the provision of a method and apparatus for casting windings in electric motor rotors in which a minimum amount of time is required for the cast winding to commence setting up in the rotor thereby permitting the rotors to be processed extremely rapidly through the casting machine.

These and other objects and advantages will become more apparent upon reference to the accompanying drawings, in which:

Figure 1 is a perspective view showing a stack of rotor laminations preparatory to the casting operation,

Figure 2 is a vertical sectional view taken through the apparatus according to this invention in which the windings are cast into the rotor, Figure 3 is a fragmentary sectional view indicated by 'line 33 on Figure 2 but showing the rubberlike sleeve that surrounds the rotor expanded into pressure engagement with the periphery of the rotor,

Figure 4 is a fragmentary view drawn at increased scale showinghow the flexible sleeve surrounding the rotor is pressed into the mouths of the slots of the rotor thereby preventing the casting metal from obstructing the mouths of the slots thus providing for a clean pe1iphcry on the rotor, and

tates Fatent O ice Figure 5 is a sectional perspective view showing the rotor after the winding has beencast therein.

Referring to the drawings somewhat more n the stack of laminations in Figure l is generally indicated at 10 and consists of a plurality of individual laminations having slots 12 for receiving the windings to be 'cast therein and with each slot, as illustrated, having a mouth.

14 although the slots may be closedif desired. A central bore 16 is provided in the rotor for receiving the rotor supporting shaft which is placed in the rotor after the windings have been cast therein.

Turning now to the apparatus in which the-winding is cast into the rotor, this is shown in Figure 2 wherein it will be seen that there is a bottom die part 18 which may be bolted into a turret or slide 20 so that bottom die part 18 rests on a stationary base member 22. Base:

member 22 is provided with cylinder means 24 in which there is reciprocable an injection plunger 26. The space above plunger 26 at 28 is adapted for receiving molten casting metal and this metal is forced, by upward movement of plunger 26, upwardly through the openings 30- in the upper part of base member 22 and thence through openings 32 in the bottom of bottom die member 18 into cavity 34 in the said die member.

The apparatus of Figure 2 also comprises an upper die member 36 which is secured as bycap screws 38 toy-a.

vertically movable ram or support 39. The upper die member 36 is formed similarly to the lower die member and includes a cavity 40 corresponding to cavity 34 of J the lower die member and which cavity 40 communicates via passages 42 with a space 44 in ram 39.

The upper die member 36, according to the present invention, supports an annular member 46 that has therein an annular groove 48 closed toward the center of member 46 by a sleeve 50. Member 46 also carries a resilient rubberlike sleeve 52, preferably of silicon rubber or other flexible readily deformable heat resistant material. Sleeve 52 has its opposite ends turned over the end parts of member 46 and secured thereto by the draw rings 54. This provides for a fluid tight connection between sleeve 52 and member 46.

A fluid inlet pipe 58 controlled by a valve 60 extends through member 46 and sleeve 50 so as to supply fluid to the space between sleeve 50 and rubberlike sleeve 52.

A fluid exhaust conduit 62 controlled by a valve 64 connects with the recess 48. Communication between opposite sides of sleeve 50 is had by ports 66 which are preferably located in the sleeve on the side of the apparatus opposite fluid inlet pipe 58.

The upper die member 36 also has attached thereto a center post 68 slightly longer than the stack of laminations into which the winding is to be cast and with there being provided a central bore 70 in the lower die member for receiving the lower end of the post.

In utilizing the apparatus, a stack of laminations of the right height is assembled and these may be aligned with each other by bars inserted in the slots or by a keyway formed along bore 16. In any case, after the lamina tions have been stacked and aligned, they are placed on It will be noted that both the upper and lower die members engage the laminations adjacent the bore 16 in an annular region designated 72 and also at an annular region designated 74 which is at the tips of the teeth of 5 In this manner the laminations are securely and tightly clampedtogether so that when the casting the rotor.

detail,

metal is injected into the slots under pressure it will have little or no opportunity for flowing outwardly between the laminations even where considerable pressure is employed.

The length of the member 46 is such that the die members will close against the laminations under pressure and while at the same time at least lightly engaging the opposite ends of the rubberlike sleeve 52. There may even be some clearance at the ends of the sleeve 52 because a supply of pressure through conduit 58 will be suflicient to expand the sleeve 52 into pressure engagement with the entire periphery of the rotor and the upper and lower die members thereby tightly to seal the cavity into which the casting metal is to be forced.

When the stack of laminations is clamped in place as described, fluid under pressure is. introduced through con-.

duit 58 to expand rubberlike sleeve 52 in the manner also described above. This fluid may be air under pressure but I prefer to employ a liquid such as Water and which liquid is circulated continuouslyebout sleeve 52 thereby to have a cooling effect thereon. This is the reason for locating the ports 66 on the side of sleeve 50 opposite conduit 58. The pressure may be maintained about rubberlike sleeve 52 by supplying liquid under pressure through conduit 58 while restricting the discharge of the liquid through conduit 62 by adjustment of valve 64.

With the apparatus closed and the flexible sleeve 52 expanded as described, plunger 26 is then thrust upwardly and the molten casting metal is driven into the casting cavity to form the winding in the rotor. The casting of the winding in the rotor may be accompanied by the simultaneous forming on one or both of the end rings of the windings fan blades that will circulate air in the motor after it is completed. Such fan blades may be formed merely by providing one or both of cavities 40 and 34 with spaced axially extending partition members 73. Also, the fan blades may be provided with notches or recesses therein by providing the annular element 76 extending into the cavity in which the fan blades are formed. Such notches or recesses are useful for supporting switch actuators and the like on the end of the rotor. Notches or grooves of this nature could be provided in a solid end ring by the same arrangement, if desired.

It will be noted that the passages 42 at the upper end of the rotor are of small size and because of this the metal cast into the rotor will chill before it flows compeltely through the passages 42 thus preventing in most cases any metal from entering chamber 44.

Chamber 44 could have a suction drawn thereon through the member 39 for evacuating the space into which the metal is to be cast, if so desired, thereby increasing the speed with which the apparatus can be operated and preventing the formation of air pockets in the casting and permitting the metal to be introduced into the cavity with greater speed whereby it can be rammed tight while still in a fairly fluid condition thus providing for a dense high quality cast winding.

When the sleeve 52 is expanded by liquid pressure, the liquid acts as a coolant thus preventing the temperature of sleeve 52 from being raised to a point where degeneration of the material of the sleeve commences to take place. The chilling effect of the liquid on the sleeve also brings about rapid setting of the metal in the mouths of the slots and because of this a somewhat higher metal temperature can be employed than with other devices and higher pressure ramming of the metal can be ernployed, all tending to produce better quality casting than has heretofore been possible.

Furthermore, the sleeve as illustrated in the present application tightly seals about the periphery of the rotor and also against the end members of the die even in the presence of foreign particles and against irregular surfaces thereby preventing any flashing of the metal even when driven into the casting cavity in a highly lluid state and under extremely high pressures.

The manner in which the relatively thin flexible rubberlike sleeve 52 flows into the mouths of the slots is illustrated in Figures 3 and 4 and it will be seen that the rubberlike sleeve substantially confines the metal to the region of the slot proper and that the mouths of the slots are substantially free of any casting metal. The exact amount that the casting metal will be recessed below the periphery of the rotor can be controlled by controlling the pressure supplied to the outside of flexible sleeve 52.

The rotor when the winding is cast therein according to the present invention can be cleaned up readily with a light turning or grinding operation 'and there will be no casting material smeared about the rotor or dragged into the region between adjacent laminations, and the grinding wheel, if the rotor is ground, will remain clean After the metal has been cast into the cavity and has set up sufficiently to permit retraction of plunger 26, a matter of only a few seconds, the plunger is moved downwardly, the supply of pressure through conduit 58 is interrupted, and the upper die member together with member 46 carrying flexible sleeve 52 is retracted upwardly. At this time, under normal conditions, the rotor will remain on the lower die member due to the casting metal that remains in the passages 30 in base member 22. This will strip the rotor from the upper die member so that the upper die member is ready to be used with another stack of laminations.

The lower die member 18 is then moved away from casting position by actuating the turret or support member 20 and this is effective for shearing off the gates extending through the lower die member. Another lower die member at this time can be moved into casting position for receiving a new stack of laminations, and the cycle is repeated.

It will be seen that the method and apparatus of the present invention provides for highly eflicient extremely rapid casting of windings into stacks of laminations and that the method and apparatus is particularly adapted for use with automatic machines and that the casting condi tions established are such that dense void free castings are produced thus leading to uniform electrical characteristics for the rotors which are so provided with windings.

It has been mentioned that the slots of the rotor may be closed about the periphery of the rotor but even in this case it is necessary to enclose the rotor when the casting operation is carried out because the high pressure casting metal may flash out between the laminations or some of the laminations may have faults therein at the outer extremities of the slots. It will be understood, therefore, that the present invention contemplates rotors of both types.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and accordingly, it is desired to comprehend such modifications within this invention as may fall with? in the scope of the appended claims.

I claim: 1. An apparatus for casting windings into the slots of a stack of laminations that form the magnetic core of an electric motor rotor which comprises; die members adapted for engaging opposite ends of the stack of laminations, an annular member surrounding the core and having an annular cavity opening toward the core, an-

into sealing engagement with the periphery of the rotor, means interconnecting the chambers opposed from said one point and means for withdrawing liquid from the outer chamber at the said one point so that the liquid cools the sleeve upon the introduction of molten casting metal into said slots, the die members engaging the opposite ends of the stack of laminations in pressure engagement while allowing expansion of said rubberlike sleeve into sealing engagement with the surface of the rotor, and means for forcing molten casting metal into the annular cavity of one of said die members whence it flows through the said slots into the cavity of the other die member thereby forming an integral cast winding in the stack of laminations including end ring portions.

2. An apparatus for casting windings into the slots of a stack of laminations that form the magnetic core of an electric motor rotor which comprises; die members adapted for engaging opposite ends of the stack of laminations, an annular member surrounding the core and having an annular cavity opening toward the core, annular cavities in said die members communicating with the ends of said slots, an annular member surrounding the stack of laminations and comprising a thin, flexible rubberlike sleeve, a second sleeve in the cavity dividing it into inner and outer chambers, means for introducing a liquid under pressure into the inner chamber at one point of the annular cavity thereby to force the sleeve into sealing engagement with the periphery of the rotor, means interconnecting the chambers opposed from said one point and means for withdrawing liquid from the outer chamber at the said one point so that the liquid cools the sleeve upon the introduction of molten casting metal into said slots, the die members engaging the opposite ends of the stack of laminations in pressure engagement while allowing expansion of said rubberlike sleeve into sealing engagement with the surface of the rotor, said die members remaining in fixed position with respect to each other during the expansion of said rubberlike sleeve, and means for forcing molten casting metal into the annular cavity of one of said die members whence it flows through the said slots into the cavity of the other die member thereby forming an integral cast winding in the stack of laminations including end ring portions.

References Cited in the file of this patent UNITED STATES PATENTS 1,251,951 Ashdown Ian. 1, 1918 1,603,545 Johnson Oct. 19, 1926 2,192,787 Elrey Mar. 5, 1940 2,289,929 Parker July 14, 1942 2,524,737 Sawyer Oct. 3, 1950 2,781,565 Atchison Feb. 19, 1957 2,807,844 Hemphill -1 Oct. 1, 1957