US1773739A - Rotor - Google Patents

Description

73,739 Aug 26 1930. cs. w. MCCOLLUM ROTOR t 1 Filed Sept. 16, 1927 2 Sheets Shed IIlll|llllllllllllllllllllllllllllllllll'll j \lllllllllllIllIIIIIlllllllllllllllllllll Illlllllllllllllllllllllllllllllllnlu 257711 n15)? If] 6601y611/.Mc[0llum Aug. 26, 1930.

G. W. M COLLUM ROTOR Filed Sept. 16, 1927 2 Shuts-Sheet 2 Patented Aug. 26, 1930 UNITED STATES PATENT OFFICE GEORGE W. MCCOLLUM, OF DOWNERS GROVE, ILLINOIS, ASSIGNOR TO MCCOLLUM HOIST & MPG. 00., OF DOWNERS GROVE, ILLINOIS, A. CORPORATION OF ILLINOIS ROTOR Application filed September 16, 1927. Serial No. 219,949.

This invention relates to induction motors, particularl to the rotors or secondary memers there or and its objects are the provision of an improved rotor and an improved method of and means for makin same.

Heretofore the winding of tie rotor has commonly comprised suitable conducting wires, ri boned strips or bars laid in the conductor openings or radial notches of the laminated co e. The laying of windings of this sort has been relatively expensive, air spaces have been present and any joints in the winding elements have reduced the startin torque.

t has also been found that the expansion and contraction which occurs in a device of this sort will break welded joints and windings of this sort tend to work loose, shift or move, thereby producing-a defective rotor and some provision, commonly in the form of separate holding strips or pieces interlocked with the core pieces have usually been necessary to hold the winding elements in the core openings or notches.

According to more recent developments it has been proposed to pour the winding and cast same in unitary, monolithic or molecularly united form, but numerous difficulties and short-comings have been encountered. Pre-heating of the soft iron core and the mold has been necessary to get the mold to fill at all. If not pro-heated the alloy or other winding material has been found to set as the pouring of the molten winding material begins and the recesses for the conductor bars will not be completely filled. Voids and blow holes commonly occur and the poured metal is placed under stress and will crack, separate or have other imperfections.

While such cast windings, as have been proposed, have advantages over the windings previously referred to, the loss though imperfections is usually exceedingly high, it being well understood in the art that any appreciable variation in the cross sectional area of any winding bar at any place will render the entire rotor unusable.

According to the present invention, which 60 has proven exceedingly satisfactory and relatively inexpensive, in actual practice, the molten winding metal is forced, under pressure, into a mold or die cavity surrounding the magnetic core of the rotor and die-cast in the form of a unitary winding element. The forcing of the molten winding metal, or alloy, under pressure, into the conductor or winding receiving openings in the core completely and uniformly fills the openings or recesses and assures against imperfections or undesirable variations in the cross sectional areas of the winding bars. The introduction of the molten winding metal, under pressure, gets the winding metal, or allo into the core recesses and die cavity so rapi ly that all recesses or openings are completely or uniformly filled before the metal has congealed or set. Any air which might otherwise tend to be trapped is effectively and positively forced out of the core openings. There is no premature or localized setting and voids, blow holes, cracking and other imperfections are avoided.

In addition, in die-casting the winding in this manner, the core need not be preheated and the die may be maintained sufficiently warm b the repeated operations of forcing the mo ten metal or alloy into the die. Smaller conductor bars or winding elements may be cast in this matter with positive assurance that the recesses in the core and die will be uniformly and completely filled.

The conductor end rings of the winding are preferably cast integral or as a unit with the longitudinal extending winding bars and where desired suitable fan blades or cooling fins may be cast integral, or as a unit, with the winding at the opposite ends thereof, al though it is to be understood that these omitted, or otherwise formed and other variations may be made within the scope of the present invention.

Another improvement which I have made is in the construction or material of the winding element itself. I have discovered that a zinc base alloy known in trade as Zamak and containing four percent (4%) of aluminum, three percent (3%) of copper and the balance of high rade zinc, provides a highly satisfactory winding material, This material is particularly suited because it will not only not attack the steel pressure cylinders or pistons for die-casting the same under pressure, and it flows freely, under pressure and completely'and uniformly fills the winding openings in the core laminae. Aluminum has heretofore been frequently pro posed in poured cast windings, but I find that it is not desirable because it will attack the pressure cylinders and pistons and its shrinkage is great and its fluidity not as desirable as it might be in this connection. The alloy which I propose, as referred to above, flows freely, as already pointed out. Its. shrinkage is very low and it will not attack the pressure cylinders or pistons. In addition its strength is great and I find that where it is employed the possibility of cracking, separatin or other imperfections is still further avoided.

The invention is illustrated in the accompanying drawings, in which:

Fig. 1 is a more or less diagrammatic sec tional view of one form of means for compressing the rotor laminations and for diecasting the winding;

Fig. 2 is a side elevational view of a sec ondary member or rotor of an induction motor, embodying thepresent invention;

Fig. 3 is a view similar to Fig. 2 of a rotor embodying the invention without the fan or cooling blades;

Fig. 4 is an enlarged longitudinal section taken on the line 4-4 of Fig. 2;

Fig. 5 is a cross section taken on the line 55 of Fig. 8, and

Fig. 6 is a cross section taken on the line t3-6 of F i 3.

It is to e understood that the invention is not limited to the particular embodiments shown and described and that variations are contemplated within the scope of the appended claims.

In theembodiment shown in Figs. 1, 2, 4, 5 and t) the rotor or secondary member is designated, in its entirety, at 5 and is adapted to form the rotor or secondary member of an induction motor. Its outer periphery is cylindrical and the rotor 5 comprises a magnetic core member, preferably of soft iron and composed of a plurality of disc-like core laminae or pieces 6 having concentric openings 7 for receiving the rotor shaft 8 and the core pieces 6 which are alike, are stacked upon the shaft 8 and keyed thereto at 9. The laminae 6 may be punched in the usual or any suitable manner.

The core member is provided with substantially longitudinally extending conductor or winding receiving openings. These openings are preferably formed by peripheral notches 10 in the laminae 6, these notches 1O preferably opening from the periphery of the core, as shown, and being preferably radially elongated to increase the starting torque, as well understood in the art. It is to be understood that the notches 10 may be shaped to give the desired characteristics to the rotor. The notches 10 are separated by the radial core extensions 12 and the longitudinally extending winding portions 13 are die-cast in the notches 10, as will be hereafter described, as a unitarywinding and with the end rings 14 and 15 die-cast integrally or as a unit therewith and molecular-1y joined as a monolithic or unitary winding element. The end rings 14 and 15 preferably extend in radially of the periphery of the core slightly at 16 and 17, overlapping the laminae at the opposite ends of the core and binding the same axially togethcr in their axially compressed condition. The end rings 14 and 15 have concentric openings 18 and 19, exposing the laminae at the opposite ends of the core within the inward extensions 16 and 17, these exposed portions being cooperable with the die and plunger in compressing the laminations in the die.

The key 9 is preferably placed at a slight angle with respect to the axis of the shaft 8 to give the winding openings or slots 10 and thereby winding bars 13 a slight spiral effect to do away with any locking tendency the rotor might have when assembled in the stator of the motor.

If desired suitable cooling or fan blades 20. peripherally arranged and extending from the opposite ends of the rotor may be cast integral or as a unit with the end rings 14 and 15. These cooling blades or fins 20 may be formed as shown or otherwise as desired and when the motor is assembled they operate to provide a cooling effect upon rotation of the rotor. Two pairs of these fins with the two fins or blades of each pair diametrically oppositely disposed are provided on each end ring in the embodiment shown, but it is to be understood that number and arrangement of blades may be varied and that these blades may be omitted entirely, as shown in the embodiment of Fig. 3, which is otherwise substantially similar to the other embodiment.

In the lamination compressing and diecasting operation a die is employed. The die 30 comprises two halves 31 and 32 having supplementary cylindrical cavities 33 and the two halves are separated on the line 34. The two halves 81 and 32 of the die 30 are closed by means of screws 35 extending through the uprights 36 of a suitable frame 37 and provided with suitable hand wheels 38 for operating the screws to open and close the two halves of the die 30. It is to be understood, of course, that the two halves of the die may be closed by any other suitable means such as air pressure or levers.

The semi-cylindrical cavities 33, when closed form a cylindrical cavity which is adapted to receive the core or laminations 6 and to give the periphery of the winding the desired cylindrical formation.

The usual or any suitable operatin clearances may, of course, be provided. hen the two halves of the die 30 are closed they'come together in such a position as to bring the sprue 40 leading to the die cavity 33, 33 directly over the port 42", which port 42 leads from the pressure cylinder 43 to the die-cavity.

Operable reciprocably in the top of the die cavity 33, 33 is a plunger 45, which fits in the die cavity sufficiently loosely to allow any air in the die cavity to escape around the plunger in the die-casting operation. The plunger 45 is axially recessed at 46 to receive one end of the rotor shaft 8 and there may be a suitable axially aligned recess 48 for receiving the opposite end of the rotor shaft.

For depressing the plunger 45 there is a screw 50 extending through a horizontal cross piece 52 on the frame 37 and provided with a suitable hand wheel 53. It is to be understood that the screw may also raise the plunger or it may be lifted or otherwise raised independentl of the screw and any other suitable or pre erred plunger operating means may be employed. The entire frame work 37 carrying the die may be raised from the port 42.

The pressure cylinder 43 is immersed in the molten alloy 55 in a kettle or suitable receptacle 56, the level of the molten alloy in the receptacle 56 being preferably normally maintained at about the line a-a of Fig. 1. The receptacle 56 is heated to bring and maintain the alloy in the desired fluid condition by gas, oil, electricity, or in any other suitable or preferred manner.

Reciprocable in the cylinder 43 is the pressure piston 58.which may be operated by a lever 60 pivoted at 62. The lever 60 may be operated mechanically or by air or in any other suitable or preferred manner and the connection 63 between the lever 60, which is shown of bell crank formation and the piston 58 is preferably such as to permit the swinging movement of the lever relative the piston in the operation thereof. The cylinder 43 is provided with ports 65 for admitting molten alloy from the receptacle 56 into the cylinder 43 when thepiston 58 is drawn back or outwardly from the cylinder.

Relatively deep recesses 68 and 70 may be provided in the die 30 at the opposite ends of the rotor core for casting the fan blade or other projections and in the casting operation the metal or alloy will be forced into these recesses, it being understood. that the die 30 is also suitably recessed to form the end rings 14 and 15.

By the first step in the process the core laminations 6 are stacked and keyed upon the shaft 2 by engagement of the key 9 in the key-ways 75. The two halves of the die 30 are opened or separated and the compressing plunger 45 is raised upwardly. The rotor shaft 8 together with the core laminations 6 are then placed in the die 30 and the two halves of the die are closed together by the wheels 38 and screws 35. The plunger 45' is then brought down by means of the wheel 53 and screw 50 and the core laminations 6 are thereby compressed tightly together. Then with the die closed and held in this position and the core laminations compressed in this manner the piston 58 in the cylinder 43 is brought forward or moved inwardly into the cylinder 43. The forward movement of the pressure piston 58 in the pressure cylinder 43 forces the alloy into the die cavity and end ring and blade casting recesses completely filling the recesses in the laminated core and the recesses in the die for the conductor end rings and fan blades, as well as for the longitudinally extending winding portions 13.

The pressure at which the alloy is forced into the die is in-the neighborhood of 150 pounds per square inch and may vary with the amount of metal to be forced into the die and with the shape and design of the dieand sprue, also with the temperature of the die The die and the core being much below the melting point of the alloy, the alloy is immediately congealed or set. The cyllnder 43 being immersed in the molten alloy keeps the port 42 and the metal in it above the melting point of the alloy, and therefore, the alloy in the port 42 does not set. As already pointed out, the entire frame Work carrying the die may be raised from the port 42 from the cylinder. Then when the piston 58 is brought back beyond the ports 65 more molten allo is allowed to enter the cylinder and the eye e of operation may be repeated.

As already pointed out the die-casting of the conductor bars has a decided advanta e over the pouring of the molten alloy into t e die or mold. Smaller conductor ars may be cast as the metal can be forced into smaller recesses with almost positive assurance that the recess in the die will be completely filled. The die-casting under pressure gets the alloy into the die cavitand into the recesses in the core so rapidly t iat the whole recess is filled before the alloy congeals or sets. With this die-casting method the core need not be preheated at all and the die is kept sufiiclently warm by the repeated operations of forcing the molten alloy into the die. In fact, if the die is opened and closed mechanically the cycle of operation may be repeated so rapidly that it may be necessary to water cool the die and suitable water or other cooling provisions for this purpose are contemplated.

Any air which might otherwise tend to be trapped is effectively and positively forced out of the core openings in the die casting under pressure and escapes out around the plunger 45. There is no premature or localized setting and voids, blow holes, cracking and other imperfections are avoided and the lioss (tihrough imperfections is materially reuce The diameters or peripheral dimensions of the core laminations 6 are preferably slightly oversize and after the die casting of the winding element the outer generally cylindrical periphery of the rotor may be Inachined or finished to the desired diameter.

The alloy which I employ as the winding material is also of importance. The alloy preferably employed is a zinc base alloy 10 known in the trade as Zamak. A typical alloy of this sort contains four percent (4%) of aluminum, three percent (3%) of copper and the balance high grade zinc. This material is particularly suited because it furthers the complete and uniform distribution of the Winding and further reduces the rotor loss from inequalities or imperfections. This alloy will not attack the steel pressure cylinders or pistons for die casting the same under 39 pressure and it flows freely under pressure, a heat application of from 900 to 950 F. being sufficient without preheating the die or core and the shrinkage of this alloy is very low. I find that this material further reduces g premature or localized setting and Voids, blow holes, cracking, separating and other imperfections. The resulting winding has great strength and a rotor may be inexpensively constructed in this manner and has no 30 joints in the winding element. Air spaces with their poor magnetism conducting qualities are entirely avoided and I find that the above alloy conducts the magnetism much better than copper windings and the path of 35 magnetism between the stator and the rotor is increased by the magnetism conducting properties of the winding.

One tenth of one percent of 1%) or other suitable proportion of magnetism may (go be added to this alloy and further increases the resistance to oxidation strength to swelling and warping after use.

I claim 1. As an article of manufacture, a rotor ea comprising a core and a die-cast zinc base alloy containing aluminum 4%, copper 3% and the balance zinc.

2. An article of manufacture comprising a rotor having a core and a die-cast alloy Windno ing containing at least ninety percent zinc the remainder being aluminum, copper and magnesium.

3. As an article of manufacture, a rotor comprising a core and a die-cast zinc base 55 alloy Winding containing aluminum in substantially the proportion of four per cent, copper in substantially the proportion of three per cent, a trace of magnesium and substantially the balance of Zinc.

G0 111 witness whereof, I hereunto subscribe my name this 10 day of September, 1927.

GEORGE W. MCUOLLUM.

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