US2486798A

US2486798A - Method and apparatus for casting rotors

Info

Publication number: US2486798A
Application number: US661661A
Authority: US
Inventors: Clarence R Mollenhauer
Original assignee: Louis Allis Co
Current assignee: Louis Allis Co
Priority date: 1946-04-12
Filing date: 1946-04-12
Publication date: 1949-11-01
Anticipated expiration: 1966-11-01

Description

Navy L 1949 :1. R. MOLLENHAUER METHOD AND APPARATUS FOR CASTING ROTORS Filed April 12, 1946 3 Sheets-Sheet 1 New 1949 c. R. MGLLENFMUEEZZ METHOD AND APPARATUS FOR ASTING EOTOHS Filed April 12, 1946 3 Sheecs-fiheet maims mmrasam- 1949 R. MQLLENHAUER METHOD AND APPARATUS FOR CASTING ROTCJRS Filed April 12, 1946 I Klara-2m JVYUZZEYFZEZEZJ @1 2 2.2,

Patenteli Nev. 1,1949

ia'ri on AND APPARATUS FOR CASTING no'rons Clarence R. Mollcnhauer, Milwaukee, Wis assigner to The Louis Allis Company, Milwaukee;

Wis., a corporation of Wisconsin Application April 12, 1946, Serial Nb. 661,661

6 Claims.

' This invention relates to the manufacture of squirrel cage rotors for electric motors and refers particularly to rotors having cast conductor bars as shown in Patent Nos. 2,368,295, 2,368,296 and 2,370,458 all issued to S. J. Goran.

As in these patents, the present invention has as its purpose to provide an inexpensive and efficient manner of forming radial ventilating passages in the rotor during the casting of its conductor bars. These radial ventilating passages connect with longitudinally extending ventilating ducts or passages and thus provide for more eifective dissipation of the heat from the interior of the rotor.

As in the aforesaid patents, the present invention provides for the formation of radial ventilating passages opening to the periphery of the rotor betweengroups of laminations and the circumferentially cast rotor bars by which the laminations are held assembled, the groups of laminations being held in proper spaced relation by lug-like enlargements formed integrally on the I vention resides in the novel method, combination conductor bars between the groups of laminations.

In the methods employed in the aforesaid patents, the production of these lug-like enlargements on the conductor bars involves the use of destroyable spacing members assembled between the groups of laminations. In one case, these destroyable spacing members are formed of cardboard or similar material capable of being charred or burned away suiliciently by the hot molten metal to provide mold spaces which form the desired enlargements, and in the other instance the destroyable members are made of a material which will withstand the heat of the molten metal but which can be subsequently melted or dissolved.

While these past methods have been generally satisfactory, they involve additional handling of the cast rotor and thus increase the cost of manufacture. In contrast, the present invention achieves the desired result without entailing such additional handling of the cast rotor and in an exceedingly simple and inexpensive way.

Thus, stated more fully, itis an object of this invention to provide an improved method of casting squirrel cage rotors with radial ventilating passages produced during the casting operation and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrate two complete examples of the physical embodiment of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view partially in side elevation and partly in longitudinal section through a rotor embodying this invention;

Figure 2 is a plan view of a special lamination employed in the formation of the radial ventilatmg passages;

Figure 3. is a detail cross sectional view taken through Figure 2 on the plane of line 3-3;

Figure 4 is a cross sectional view taken through Figure 1 substantially on the plane of the. line 4- l, showing a segment of the entire unit;

Figure 5 is a side elevational view of the ass sembled rotor laminations preparatory to being inserted into the casting mold;

Figure 6 is a longitudinal sectional view through a casting mold withthe rotor laminations in position therein preparatory to having the conductor bars cast into the slots;

Figure 7 is a perspective view showing a portion of the cast rotor and illustrating the manner in which the mold forming devices employed in the casting operation are removed;

Figure 8 is a fragmentary perspective view illustrating one of the lug-like spacing projections which are formed integrally with the rotor bars during the casting of the rotor; and

Figure 9 is a perspective view showing a portion of the special lamination and the mold forming devices used to produce the lug-like projections but illustrating a slightly modified form of mold forming device.

Referring now more particularly to the accompanying drawings in which like numerals indicate like parts throughout the several views, the numeral 5 designates the rotor laminations which are punched from thin sheet steel or other suitable material and which are held assembled between end rings 6 by a plurality of circumferentially arranged conductor bars I cast integrally with the end rings. The laminations are punched to provide a bore 8 for the reception of an armature shaft 9 and to also provide longitudinal air passages or ducts I0. These passages or ducs communicate with radial ventilating passages between groups of laminations held spaced apart at the center by spacing collars l2 and at the outer periphery of the rotor luglike enlargements |3 formed integrally with the conductor bars.

The manner in which these lug-like enlargements are produced during the casting operation constitutes the chief feature of this invention. To this end special laminations M are provided. These special laminations (two in the rotor illustrated) are made of the same sheet material from which the regular laminations 5 are punched and have openings l5 and conductor bar slots 6 identical with those of the regular laminations.

However, in addition, each of these special laminations has a ring of tongues projecting perpendicularly from one face or side thereof. These tongues H are spaced Slightly radially inward of the inner ends or bases of the conductor bar slots |6 and are radially in line therewith so that a tongue I"! is located adjacent to the inner end of each conductor bar slot. While the tongues I? may be separately mounted on the laminations M in any suitable manner, it is obviously better to form them as integral parts of the laminations M by striking up the stock provided by openings I8 out along three (3) sides.

The upstanding tongues or projections I! on the special laminations coact with mold forming members or forms I9 to define substantially box-like molds 20 embracing the conductor bar slots so that the molten metal of which the bars are formed will flow from the slots into the molds.

The mold forming members I9 are bifurcated and have substantially resilient arms 2| spaced apart a distance greater than the width of the conductor bar slots, and in that embodiment of the invention illustrated in Figures 1 to 8 inclusive the free ends or extremities of the arms 2| have notches or transverse grooves formed in their inner faces to receive the side edges of the tongues l1. Thus as shown in Figure 2, the mold forming members H] can be easily assembled with the laminations |4 merely by engaging the notches or grooves 22 with the sides of the tongues and sliding the mold forming members down onto the laminations.

Attention is directed to the fact that the arms of the members I9 are of such length that their connected ends terminate substantially in line with the peripheral edges of the laminations so that the finished lug-like enlargement |3 (see Figure 8) will be flush with the outer surface of the rotor.

Attention is also directed to the fact that the height of the mold forming members I9 is equal to that of the tongues After the required number of special laminations (two in the rotor illustrated) have had the mold forming members applied thereto in the manner described, these preassembled spacing mandrel 24.

units are assembled with the regular laminations on a mandrel 24. A slightly spiral keyway 25 in the mandrel receives inwardly directed lugs or teats on the laminations so that the conductor slots |6 will be skewed around as required.

In the assembly of the laminations, the groups of regular laminations are spaced apart at the center by the collars l2 and at the outer periphery of the assembly by the mold forming members Ill. The complete assembly is then placed in a casting mold as shown in Figure 6.

This mold is of conventional construction and includes a cylinder or well 26 in which a plunger 21 is reciprocally received. The plunger 21 provides the base for the assembled core laminations and is formed to receive the lower end of the It is to be observed that the base formed by the plunger 21 closes the longitudinal passages I0 at the bottom. Hence molten metal cannot enter these passages.

With the assembled laminations in position as described, sheaths 28 are wrapped around the cylindrical surface of the three (3) groups of laminations to close the conductor bar slots l6; and then a cap 29 is positioned on the assembly, which like the plunger 21, is formed to accommodate the mandrel.

Tie bolts 30 with quick acting latches 3| draw the cap and base or plunger together to place the laminations in compression and hold the same in intimate contact. The cap 29 and the base or plunger 21 have annular grooves or channels 32 of a size and shape to form the cast rings 6, and the base or plunger has ports 33 leading to its channel 32 through which the molten metal enters r the same and rises up into the conductor bar slots during the casting operation.

It is, of course, understood that the assembly of the core structure in the mold takes place before molten metal is poured into the well or cylinder 2B and that after the assembly is completed the cap which is attached to the plunger 34' of a hydraulic press is raised to lift the entire assembly out of the well to permit ladling the molten metal into the well. Thereafter the plunger 34 is caused to descend forcing the molten metal up into the conductor bar slots and channel 32 of the cap. Air vents 35 in the cap preclude the entrapment of air and permit metal to rise up into the slots.

As the molten metal rises up into the conductor bar slots, it flows into and fills the molds 20 to form the lug-like enlargements l3.

After the casting is complete and the metal has hardened, the mold is opened and the assembly is stripped off the mandrel. The mold forming members l9 are then forcefully pulled from the assembly as shown in Figure 7. This is readily accomplished as the arms 2| are sufficiently resilient to allow their outer ends to spread slightly, and also the metal of which the tongues I! are formed is light and soft enough to permit the side edges of the tongues to bend and thus facilitate disengagement thereof from the notches or grooves 22, since the bent side edges will then cooperate with edges of the notches in the arms to wedge the arms apart.

When all of the mold forming members l9 have been so stripped from the assembly, the rotor is complete except for necessary machining. The radial ventilating passages defined by the spaces between the groups of laminations and the lug like enlargements on the conductor bars will be of the same size and shape and the sides of the lug-like enlargements will be neat and smooth surfaced.

In the embodiment of the invention illustrated in Figure 9, the procedure followed is identical with that described, the only difference being that the arms 2| of the mold forming members do not have notches to engage the side edges of the tongues l1. Instead, the space between the arms 2| is just sufiicient to snuggly engage the sides of the tongues l1 and the members I9 are held assembled with each special lamination by a ring 7 36 engaged in notches 31 extending across the closed ends of the bifurcated mold forming members.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention provides an exceedingly simple and inexpensive method of producing neatly formed smooth surfaced radial ventilating passages in squirrel cage rotors of the cast type.

What I claim as my invention is:

l. The hereindescribed method of making squirrel cage rotors having radial air vents between axially spaced groups of laminations and having cast conductor bars in aligned slots, said conductor bars bridging the spaces between groups of laminations and coacting with the adjacent laminations to define such vents, which comprises: forming a plurality of substantially identical laminations, each having a plurality of spaced apart radial conductor bar slots about its circumference; forming a spacing lamina having conductor bar slots adapted to align axially with the conductor bar slots in said first named laminations; forming integral lugs on said spacing lamina in radial alignment with and inwardly of said conductor bar slots; detachably mounting mold forming members on the spacing lamina in juxtaposition to the lugs to define mold cavities closed at their radially innermost ends by the lugs on the spacing lamina and into which the conductor bar slots of the spacing lamina open; stacking numbers of the laminations together in coaxial relationship and with their conductor bar slots in alignment to form two groups of laminations; inserting the spacing lamina, with the mold forming members thereon, in place between said two groups of laminations with the slots of the spacing lamina in alignment with the slots of said groups of laminations; holding said groups of laminations spaced apart by means of said mold forming members; casting the conductor bars and simultaneously filling the mold cavities to form lug-like enlargements on the conductor bars between the groups of laminations; and after the casting operation is completed, detaching the mold forming members from the spacing lamina by'forcefully pulling the mold forming members outwardly substantially radially, leaving the spacing lamina in the rotor.

2. In the art of making squirrel cage rotors having cast conductor bars embedded in aligned slots of stacked laminations, means for spacing groups of laminations in the casting of the conductor bars in a manner such that lug-like projections will be formed on the bars between the groups of laminations to hold the same spaced apart, comprising: a punched disc having conductor bar slots like those of the regular laminations and having a series of circumferentially spaced upstanding tongues on one side of said disc with one tongue opposite the inner end of each conductor bar slot; and a plurality of separate mold forming devices cooperable with said disc and the tongues thereon to form molds, each of said devices having a pair of arms spaced apart more than the width of the conductor bar slots, said arms having grooves in the inner faces of theiflfree end portions to receive the side edges of the upstanding tongues whereby said devices may be assembled with the disc and retained thereon during its assembly with the regular laminations, the side edge portions of said tongues being bendable and the arms of the mold forming devices being resilient so that said devices may be pulled oi! the tongues radially after the casting operation.

3. In the art of making squirrel cage rotors having cast conductor bars embedded in aligned slots of stacked laminations, means for spacing groups of laminations in the casting of the conductor bars in a manner such that lug-like projections will be formed on the bars between the groups of laminations to hold the same spaced apart, comprising: a punched sheet metal disc having a plurality of circumferentially spaced conductor bar slots extending around the periphery thereof and having a ring of circumferentially spaced tabs projecting from one side of the disc, said tabs being formed by striking up the metal of the disc and being located adjacent to the inner ends of the conductor bar slots; a plurality of separate mold forming devices cooperable with said tabs to define lug forming molds, said devices each having a pair of arms adapted to be bridged by one of the tabs; and means for holding said devices assembled with the disc with a tab bridging the arms of each of said devices.

4. The hereindescribed method of making a laminated squirrel cage rotor having radial air passages between axially spaced portions of the rotor and having conductor bars in axially aligned slots in the rotor laminations with enlarged portions thereof bridging the space between said axially spaced portions of the rotor to define such passages andhold said axially spaced portions of the rotor apart, which comprises: forming a plurality of substantially identical laminations, each having circumferentially spaced conductor bar slots in its peripheral portion; forming a spacing lamina having conductor bar slots adapted to align with the conductor bar slots in said laminations; forming lugs integrally on said spacing lamina in radial alignment with an inwardly of the conductor bar slots in the spacing lamina; detachably mounting mold forming members on the spacing lamina in juxtaposition to the lugs to define mold cavities closed at their radially inner ends by the lugs on the spacing lamina and into which the conductor bar slots of the spacing lamina open; stacking the laminations and the spacing lamina, with the mold forming members thereon, in coaxial relationship; adjusting the laminations circumferentially to align the conductor slots therein with one another and with the mold cavities so that the mold cavities open to the conductor bar slots of the adjacent laminations as well as with the conductor bar slots of the spacing lamina; axially clamping the assembled laminations, spacing lamina and mold defining members together; injecting molten metal into the conductor bar slots and the mold cavities to cast the conductor bars with enlarged portions thereon as defined by the mold cavities and between said axially spaced portions of the rotor; removing the axial clamping pressure; and pulling the mold forming members radially from between the axially spaced portions of the rotor and the enlargements on the conductor bars.

5. In the art of making squirrel cage rotors having cast conductor bars embedded in aligned slots in stacked laminations, spacing means adapted to be placed between laminations to hold the same spaced apart while casting the conductor bars and for forming lug-like projections on the bars to hold said laminations spaced apart, comprising: a punched sheet metal disc having a plurality of circumferentially spaced conductor bar slots opening to the periphery thereof and having a ring of circumferentialiy spaced tabs projecting from one side of the disc, said tabs being located adjacent to the inner ends of the conductor bar slots and being formed by striking up portions of the metal of the disc; a plurality of bifurcated mold forming devices cooperable with said tabs to define lug forming molds, each of said devices having its pair of arms so spaced that the free nds thereof may be bridged by one of the tabs; ,and means engageable with the outer closed ends 1 of all of the devices for releasably holding the same in cooperative engagement with the tabs.

6. In the art of making squirrel cage rotors having cast conductor bars embedded in aligned slots of stacked laminations, means for spacing groups of laminations in the casting of the conductor bars in a manner such that lug-like enlargements will be formed on the bars between the groups of laminations to hold the same spaced apart, comprising: a punched sheet metal disc having a plurality of eircumferentially spaced conductor bar slots extending around the periphery thereof and having a ring of circumferentially spaced tabs projecting from one side of the disc, said tabs being formed by striking up portions of the metal of the disc and being located in juxtaposition to the conductor bar slots; a plurality of mold forming devices cooperable with saidtabs to define lug forming molds, said de vices each having a pair of arms adapted to form the side walls of the lug forming molds, said arms being spaced apart more than the width of the conductor bar slots so that the resulting lug f orming molds are wider than the conductor bar slots, and the tabs being wide enough to bridge the space between the inner ends of the arms and thus form the radially innermost walls of the molds;

CLARENCE R. MOLLENHAUER.

REFERENCES CITED The following references are of record in the file of th' 1 is patent UNITED STATES PATENTS Number Name Date 595,081 Short Dec. 7, 1897 891,906 Card June 30, 1908 917,064 Hibbard Apr. 6, 1909 1,517,620 Ellis Dec. 2, 1924 1,880,786 Carey Oct. 4, 1932 1,913,138 Apple June 6, 1933 1,970,760 McIntire Aug. 21, 1934 1,975,889 Whiteley Oct. 9, 1934 2,176,871 Harrell et al Oct. 24, 1939 2,192,787 Elsey Mar. 5, 1940 2,348,511 Armel May 9, 1944 2,368,295 Goran Jan. 30, 1945 2,368,296 Goran Jan. 30, 1945 2,370,458 Goran Feb. 27, 1945 FOREIGN PATENTS Number Country Date 519,673 France June 14, 1921 5 Co. (1942), page 48.