US1982424A

US1982424A - Mold and method of casting metal

Info

Publication number: US1982424A
Application number: US621184A
Authority: US
Inventors: Everett G Fahlman
Original assignee: Permold Co
Current assignee: Permold Co
Priority date: 1932-07-07
Filing date: 1932-07-07
Publication date: 1934-11-27
Anticipated expiration: 1951-11-27

Description

Nov. 27, 1934.

E. G. FAHLMAN MOLD AND METHOD OF CASTING METAL Filed July 7, 1932 5 Sheets-Sheet 1 |NVENTOR Everett 6. Fahhnan BY W fi'fifc ATTORNEYS Nov. 27, 1934. E. e. FAHLMAN 1,932,424

MOLD AND METHOD OF CASTING METAL Filed July '7, 1952 5 Sheets-Sheet 2 5 2 I Z5 Z4 z & "W

INVEN I erett -Fahlman ATTORNEYS Nov. 27, 1934. E. G. FAHLMAN 1,982,424

MOLD AND METHOD OF CASTING METAL Filed July '7, 1952 3 Sheets-Sheet 5 sl 5. s

65' 6'6 e5 67 F1 1. B.

I INVENTOR Everett GFahlman ATTORNEYS Patented Nov. 27,- 1934 UNITED STATES MOLD AND METHOD OF CASTING METAL Everett G. Fahlman, Cleveland, Ohio, assignor to The Permold Company, Cleveland, Ohio, a

corporation of Ohio Application July 7, 1932, Serial No. 621,184 I 22 Claims. (01. 22-203) My invention relates to molds and to a method of casting metal having a relatively low melting point about the periphery or in slots formed in a body of metal having a higher melting point, and more particularly to a mold and method of casting conductor bars and end rings in electrical apparatus, such as rotors.

An object of my invention is to provide a method and mold for forming castings of metal having a comparatively low melting point, such as aluminum or aluminum alloys, about the periphery or in slots or apertures of a body of metal having a comparatively high melting point, wherebythe casting cavities wherein the castings are to be formed may be readily filled with casting metal,

and wherein provision is made to supply additional metal at a comparatively high temperature to the casting cavities to compensate for the shrinkage of the metal during cooling.

Another object of my invention is to provide an improved mold and method of forming castings from metal having a comparatively low melting point, whereby casting metal is uniformly supplied to the casting cavities when the mold is in 2 one position and additional casting metal is supplied under the force of gravity to the mold cavities at a comparatively high temperature to compensate for the shrinkage of the metal during cooling when the mold is in a different position.

A further object of my invention is to provide a mold and method which is particularly adapted for casting conductor bars and end rings formed of a metal having a high crystallization shrinkage, such as substantially pure aluminum or certain of its alloys, in comparatively large rotors in which the conductor bars have a correspondingly large cross section.

Metals having high crystallization shrinkage, such as pure aluminum and certain of its alloys,

40 are always difficult to cast, and this is particularly true when it is desired to form composite articles in which the metal having a high crystallization shrinkage is cast about the periphery or in passages extending througha metal having a higher melting point. Consequently, while it has previously been possible to manufacture rotors having cast conductor bars, in the case of small rotors, particularly when aluminum alloys of low crystallization shrinkage were employed, it has been difficult or commercially impracticable to manufacture large rotors by such a process. This difficulty is increased when substantially pure aluminum is utilized because of its high crystallization shrinkage. The electrical conductivity of substantially pure aluminum, however, is so much greater than that of alloys customarily used for this purpose, that it is highly desirable to utilize it in forming the end rings and conductor bars. The mold and process which I have developed is therefore especially applicable to the casting of conductor bars and end rings in comparatively large rotors having correspondingly large conductor bars, especially when such castings are formed of metal having a high crystallization shrinkage, such as substantially pure aluminum and certain of its alloys, although it may be successfully utilized in forming castings in which alloys having a lower crystallization shrinkage are employed.

In producing electrical apparatus, such as rotors, comprising a plurality of laminations of ferrous material and cast conductor bars and end rings formed of aluminum and aluminum alloys, it is highly desirable in forming-the castings to cause the metal to flow upwardly through the casting cavities at uniform pressure, so that the cast conductor bars will have uniform electrical characteristics. Since aluminum and most of its alloys have a high crystallization shrinkage during cooling, it is also essential to provide additional metal to flow into the casting cavities during the cooling to prevent the formation of sinks or depressions in the conductor bars.

By my invention I have provided a mold for and a process of casting metal having a comparatively lowmelting point, such as aluminum or aluminum alloys, about the periphery or in slots formed in a metal having a higher melting point, wherein means are provided to cause the casting metal to flow uniformly upwardly about the periphery or in the slots formed in the metal having a higher melting point. The mold is then inverted so that during the cooling of the casting metal, additional metal at a comparatively high temperature will be provided to flow into the casting cavities under the force of gravity to compensate for the crystallization shrinkage of the casting metal during cooling.

My invention is especially adapted for forming cast conductor bars and end rings in rotors and for illustrative purposes will be described in connection therewith. It will be understood, however, that I do not desire to limit my invention to a mold or process for this particular purpose, as obviously the principles of my invention may be applied to the production of various articles, such as magneto bodies, transformers, or composite articles in which a metal having a comparatively low melting temperature is cast in slots or around the periphery of a metal having a comparatively high melting point.

In the drawings,

Figure 1 is a side elevatlonal view of the mold showing the laterally moving parts in molding position and the mold both in normal and inverted positions;

Fig. 2 is a cross-sectional view on the line 2-2 of Fig. 1;

Fig. 3 isa view similar to that shown in Fig. 2, but showing the parts in inverted position;

Fig. 4 is a plan view partly broken away of a completed rotor, showing end rings and conductor bars;

Fig. 5 is a side elevational view partly broken away of the rotor shown in Fig. 4;

Fi 6 is a cross-sectional view on the line 6-6 of Fig. 2;

Fig. 7 is a view similar to Fig. 2 but showing a mold provided with a plurality of pouring sprues;

Fig. 8 is a plan view of the mold shown in Fig. 7;

Fig. 9 is a cross-sectional view on the line 9-9 of Fig. 8.

One form of rotor contemplated by my invention is illustrated in Figs. 4 and 5 of the drawings, wherein is shown a laminated core 1 comprising a plurality of thin stampings 2 formed of ferrous material, each having a centrally disposed aperture 3, a slotted aperture 4 and apertures 5, and a plurality of radially extending conductor bar receiving slots or openings 6 spaced uniformly around the plates or stampings 2 adjacent the periphery thereof. The openings 6 in the stampings 2 are shown as slightly oifset circumferentially in the rotor around the periphery thereof. Cast in association with the laminations 2 are the end rings 7 and conductor bars 8 which are formed integrally in the casting operation. The conductor bar openings 6 may, of course, be of any suitable size, shape and number, and may be open to the periphery of the rotor, as shown in Figs. 4 and 5, or may be spaced inwardly from the periphery, as will be readily understood.

The mold illustrated in the drawings is shown as comprising a horizontal mold base 10 supported by standards 11 and 11. The mold base 10 is provided on its upper surface with a. centrally disposed longitudinally extending guide rib 12 and secured to the sides of the base 10 are inwardly flanged side ribs 13. The upper surface of the base 10, together with the guides 12 and side ribs 13, form a slideway for the guide movement of mold sections into and out of molding position.

Approximately centrally of the mold base 10 is a substantially circular base plate 14 forming a mold section which is seated in a depression in the base 10. The peripheral edges of the base plate 14 extend above the surface of the base and the upper surface is recessed and faced to cooperate with other mold parts to define a mold cavity. The base plate 14 is centrally apertured at 15 and the base is centrally apertured at 16 to form a continuation of the aperture 15.

An ejector 17 provided with rack teeth 1'1 is vertically movable in the

apertures

15 and 16. A pinion 18 journaled in the base 10 cooperates with the teeth of the rack 17' to move the ejector'vertically. The pinion 18 may be actuated by means of the handle 19.

Mold sections 20 are slidable along the base 10 in the slideway defined by the side ribs 13, rib 12 5 and upper surface of the base 10.- The mold sec- 20 on the base and the side guides 13 prevent tions 20 are rabbeted at 21 to cooperate with the ribs 12 and are provided with outwardly extending flanges 22 to cooperate with the ribs 13. The rib 12 prevents transverse movement of the mold vertical movement of the mold sections. The mold sections 20 are undercut at 23 and 24 to form surfaces which cooperate with the corresponding surfaces of the base plate 14 when the mold sections are in molding position. The mold sections 20 are also provided with complementary recesses, and together define the exterior peripheral surface of the casting cavity.

The mold sections 20 may be actuated along the slideway of the mold base 10 by suitable toggle link mechanism, as illustrated. Thus, for each mold section a link 27 is pivotally carried by a pin 28 which is journaled in the rearwardly extending webs 29 of each mold section. A rod 30, oppositely threaded at its ends, is adjustably secured to one end of the link 27 and is maintained in adjusted position by the nut 31. The opposite end of the rod 30 threadably engages a link 32 which, in turn, is pivotally secured to a toggle link 33 by the pin 34, the toggle link being pivotally connected at its opposite end to a support 35 extending upwardly from the mold base 10. As the rod 30 is adjustable the distance between the links 31 and 32 may be varied. An operating handle 36 is secured in a socket in the toggle link 33. The toggle link 33 is provided with a shoulder 37 which engages the upper surface of the link 32 when the mold section is in molding position, and the toggle link isslightly past dead center position. This mechanism provides a positive 11 and rapid means of actuating and positioning each mold section 20.

Secured to the side of the mold base 10 and extending diagonally over the center of the base plate 14 is a support 38 which is apertured at 39 5 in axial alignment with the aperture 15. Journaled in the aperture 39 is a nut 40 having a lower shouldered portion bearing against the lower side of the support 38. A threaded shaft 42 is carried by the nut 40. The shaft 42 is shouldered at 43 12C and provided at its lower end with a threaded extension of smaller diameter. A vertically movable mold section 44 is carried by the shaft 42. The mold section 44 is centrally apertured at its upper end and threaded to engage the threaded lower end of the shaft 42 so as to abut the shoulder 43, the mold section 44 being secured to the shaft 42 by suitable means such as a pin 45. The mold section 44 has a shoulder 44' and a downwardly extending annular portion 46 arranged 3 to bear on the top surface of the laminated core disposed within the casting cavity, the annular portion 46 defining a hollow interior 47. The outer surface of the depending portion 46 is shaped to cooperate with the lamina: 2 adjacent the periphery thereof and the mold sections 20 to define portions of the mold cavity.

In the particular embodiment of my invention illustrated, the lamina: 2 are temporarily secured in assembled relation by a shouldered mandrel 48 having an enlarged cylindrical head 49, washer 50 and nut 51. The mandrel head 49 is arranged to fit snugly within the aperture 15, the weight of the lamina 2 resting on the upper annular surface 52 of the plate 14. The washer 50 and nut 1.45 51 are arranged to extend into the cavity 47 within the annular portion 46 of the mold section 44. When the mold sections are brought into abutting relation in molding position, the peripheral edges of the. assembled laminae 2 and the shoulder 44 15 abut the adjacent portions of the mold sections 20.

By the construction shown, suitable pressure may be exerted between the mandrel head 49, the annular surface 52 and the mold section 44 to hold the assembled laminations in desired uniformly pressed relationship during the casting operation.

When the mold sections are assembled in molding position, complementary recesses 53 in the mold sections cooperate to define the upwardly extending sprue cavity 54 which communicates with the peripheral ring sprue cavity 55 formed between complementary recesses in the mold member 14 and the mold sections 20. The ring sprue cavity 55 in turn communicates with a relatively narrow annular peripheral gate 56 formed between the plate 14 and mold sections 20. The peripheral gate 56 communicates with the lower portion 57 of the casting cavity in which the lower end ring of the rotor casting is formed, the casting cavity 57 being formed between the lamina 2, plate 14 and mold sections 20. The ring sprue cavity 55 is preferably located in a lower horizontal plane than the end ring cavity 57, although it may be located in the same horizontal plane.

It will be understood that it is not necessary to have the gate 56 completely surrounding the casting cavity, as a substantially uniform flow of metal through the gate into the casting cavity may be obtained if one or more relatively small interruptions are provided therewith. Such interruptions may be provided either for the purpose of aiding in the support of the upper portion of the mold or they may be placed opposite the sprue cavity for preventing unbalanced dynamic pressures from occurring at the bottom of the pouring sprues. It is to be understood, however, that such interruptions in the gate are not essential. I

It will also be understood that the ring sprue cavity 55 may be of peripheral extent or of less than peripheral extent, or may be composed of a plurality of smaller cavities providing such cavities have the requisite volume and are arranged to transmit the casting metal to the end ring and conductor bar cavities, and when the term substantially peripheral ring sprue cavity is utilized in the specification and claims, it will be understood that it defines a cavity having a peripheral or less than peripheral extent.

The casting cavity 57 defining the lower end ring communicates through slots or opening 6 in the laminae 2 with the cavity 59 defining the upper end ring of the casting. As shown in the drawings, the conductor bar cavities 6 are closed by adjacent portions of the mold sections 20. The upper end ring casting cavity 59 is defined by the upper surface of the assembled lamina: and by the adjacent portions of the upper mold section 44 and mold sections 20. The casting cavity 59 in turn communicates with an outwardly flaring sprue cavity defined by the cooperating surfaces of the mold section 44 and the mold sections 20. The shoulder 44' of the mold section 44 is shown as recessed at 61 to define an air vent communicating with the riser cavity 60 to the atmosphere.

If desired, the riser cavity 60 may be omitted, although it is preferably provided above the end ring cavity 59 to receive the cooler metal which is first passed through the conductor bar passages of the rotor. The size of this cavity is dependent upon the operating conditions, as will be further explained.

The base 10 is provided with axially aligned trunnions-58 which are aflixed thereto by any suitable means, such as keys 59', as shown in Fig.1 of the drawings. The trunnions 58 are journaled in the upper ends of standards 11 and 11. One of the trunnions 58v projects beyond the standard 11' in which it is Journaled and has a collar 60' attached thereto outside of the standard. The collar 60'-is provided with diametrically opposed notches 61 and 61'. A handle 62 extends through the collar 60' and provides means for rotating the base 10 to invert the molds which are supported thereby. A latch 63 is pivotally connected to the standard 11 by means of a pin 64 and serves to lock the base member with the mold in a position extending upwardly from the base or in inverted position in which the mold projects downwardly from the base.

As shown in Figs. 1 and 2 of the drawings, the sprue cavity 54 preferably extends into a recess in the base plate 14 and has an upwardly extending passage 65 leading into the ring sprue cavity 55 so that metal will flow into the ring sprue cav- The mold may be provided with only one sprue cavity, as illustrated in Figs. 1 and 2, or with a plurality of sprue cavities 54 and 54' as shown in Figs. '7 to 9, inclusive, of the drawings. When two sprue cavities are provided, means are provided to prevent the metal flowing out of the ring sprue cavity 55 during tilting of the mold; that is, when the mold base is tilted from the right to the left, as illustrated in Fig. '7 of the drawings, although if it is desired to tilt the mold base in the opposite direction the sprue cavity 54 is provided with a cover and the cavity 54 is left open. A suitable means for providing a cover for the cavity 54 is shown in Figs. 7, 8 and 9 of the drawings. As illustrated in these figures, two pins 65 are provided in one of the mold members 20 which project through a longitudinal aperture 66 in a slide 67. The slide 67 is adapted to be moved longitudinally to permit metal to be poured into the sprue cavity 54' in the normal position of the mold, and to cover the sprue cavity while the mold is being inverted. The pins 65' are provided with washers, screw threads and nuts so that the slide may be firmly maintained in either position.

In practicing my invention in accordance with the embodiments illustrated, the laminations 2 are first secured together in the desired aligned relationship under suitable pressure by means of the mandrel 48 and nut 51. Before the assembled laminations are disposed in a mold for the casting operation, they are preferably heated in a furnace to a temperature of approximately 600 to 1000 F., depending upon the volume of the laminations, the volume and surface area of the conductor bars to be cast, and the surface areaof the mold. Prior to the assembly of the laminations in the mold, the mold is also heated to a temperature of approximately 600 to 1000 F., depending upon the temperature to which the laminations are heated in order that the chilling effect of the mold will not tend to cause cold shuts and the like, but yet may be sufficient to cause the metal to solidify under advantageous permanent mold conditions. The mold is generally heated to a temperature approximating but not usually exceeding the temperature of the laminations. for the first casting in a run, the heat imparted to the mold from the poured casting metal and After the mold has been heated the heated laminations is ordinarily sufficient to maintain the mold at the proper molding temperature. As a rule, the temperature of the mold will therefore be considerably less than the temperature of the laminations, and will vary over a greater temperature cycle during the casting operation. While the optimum temperature to which the laminations of rotors of different construction should be heated varies over considerable temperature range in accordance with the factors specified, the temperature to which the laminations of a rotor of specified construction, or a series of rotors of approximately the same construction, should be heated before the casting operation, is held within a comparatively narrow range. For example, after the optimum temperature to which the laminations should be heated has been ascertained, the temperature to which laminations of the rotor, or other rotors of a similar construction are heated before the casting operation, preferably should not be permitted to vary more than approximately 50 F. from that temperature.

The preheating of the laminations to the temperature specified retards the cooling rate sufficiently to prevent the formation of voids, cold shuts or other imperfections, but allows the casting metal to cool sufficiently rapid to provide casting metal of relatively, fine grain structure and generally improved physical characteristics. If desired, the conductor bar. passages may be provided with a heat and electrical insulating coating so as to retard the solidification of the molten metal and permit the ready filling of the cavities.

Such a coating also serves as an electrical insulation between the cast conductor bars and the metal of the rotor, thereby providing a finished rotor having improved electrical characteristics.

While the core and mold are at approximately molding temperatures, as hereinbefore set forth, the assembled laminations are disposed in the mold, the large head 49 of the mandrel 48 being seated in the aperture 15 of the plate 14. The handle 41 may then be turned to lower the mold section 44 and cause the depending portion 46 to press downwardly on the laminations and hold the peripheral portions of the laminations under the desired pressure, the laminations thus being compressed between the annular surface 52 of the plate 14 and the annular section 46 of the upper mold section 44. The levers 36 may then be aluminum having a temperature of about 1200 to 1400 FL, may then be poured into the upstanding sprue cavity 54 or simultaneously through the sprue cavities 54 and 54' when a plurality are provided, as illustrated in Figs. 7 and 8. The casting metal fills the peripheral ring sprue cavity 55 and rises simultaneously through the entire periphery of the casting into the casting portion 5'7 defining the lowerend ring and rises simultaneously through all the conductor bar cavities 6 up to the casting cavity 59 defining the upper end ring, and rising simultaneously into the riser cavity 60, the rising casting metal pushing the air within the mold cavities out of the mold through the vent 61. 1

After the metal has been poured in the manner specified, the slide 67 is operated to closed position if two pouring sprues are employed, the latch 63 is released from the notch 61 and the mold base, together with the mold, is inverted by means of the handle 62to the position shown in Fig. 3 of the drawings. The key 63 is then rotated into the oppositely disposed notch 61 and the metal in the passage 65 is in a position to flow into the ring sprue cavity 55 and through the gate 56 into the ring casting 57. During the cooling of the metal in the end rings and conductor bar passages, the metal in the ring sprue cavity 55 and the passage 65 which is at a comparatively high temperature, is in a position to fiow downwardly by the force of gravity into the end rings and conductor bar passages, and will provide casting metal at the desired temperature to compensate for any shrinkage in the end ring and conductor bar passages during cooling. I

In view of the foregoing specification, the advantages of my improved mold and process will be apparent. The portion of the casting metal passing upwardly through the conductor bar passages to the riser cavity serves to heat locally the walls of the narrow conductor bar passages, whereby premaiure solidification of the casting metal in the passages is prevented and cast conductor bars of uniform solid cross section and greater electrical efficiency are obtained.

Furthermore, the area of the sprue and gate cavities shown permits the casting cavities to be filled very rapidly with molten metal, whereby the production of perfect castings is greatly facilitated. The provision of the relatively narrow gate cavity also permits the equalization of the pressure of the molten metal from the ring sprue cavity, whereby casting metal under uniform pressure may be simultaneously introduced into the conductor bar passages.

If the metal were allowed to solidify in this position, however, it would be necessary to cause a portion of the metal from the riser cavity 60 to flow back into the conductor bar passages to conipensate for the shrinkage of the metal during cooling. The metal in the riser cavity 60, however, having passed through the conductor bar passages, is comparatively cool as compared with the metal in the ring sprue cavity 55 and passage 65. For example, if the casting metal were poured at a temperature of approximately 1400 F., the metal in the riser cavity might be at a temperature of 1200 R, whereas the metal in the ring sprue cavity passages 65 would be at a substantially higher temperature, and a temperature gradient would exist from the ring sprue cavity 55 to the end rings 59 or the riser cavity 60.

By inverting the mold immediately after the metal is poured it will, therefore, be apparent that the metal in the conductor bar passages is coldest at the lowest point, the temperature being progressively higher in accordance with its distance from the lower end ring when the mold is in its new position, the hottest metal. being at the top, and that the freezing of the metal will occur in a progressive manner. It accordingly follows that the proper feeding of additional metal to compensate for the crystallization shrinkage will not be prevented.

It will also be apparent that after the mold passages during cooling. I have found that by providing metal at a comparatively high temperature to compensate for the shrinkage of the end rings and conductor bar passages during cooling, they will be substantially free from sinks, and that conductor bars and end rings having a comparativelylarge cross section may be formed which have substantially uniform physical and electrical characteristics.

When the metal has sufliciently solidified, the mold sections may be separated and the ejector pin 1'7 actuated downwardly to separate the castings from the lower mold portion 14 or, if preferred, the mold base, together with the molds, may be first rotated to normal position before the mold sections are separated. After the casting has cooled sufllciently, the mandrel 48 is removed and the riser, gate and sprue portions are severed to form a finished casting, as shown in Fig. 4, wherein the end rings and connecting conductor bars are of one integral portion of cast aluminum or aluminum alloy. The casting forming the integral end rings and conductor bars serves to hold the laminations permanently in assembled relation.

The casting metal from which the conductor bars and end rings are cast may be of any suitable alloy. Usually it is preferred, however, in the manufacture of rotors, to use commercially pure aluminum containing less than about 1% total impurities, or even electrolytic aluminum in which the impurities are still less, because substantially pure aluminum has greater electrical conductivity than aluminum alloys or aluminum containing larger amounts of impurities. Furthermore, when metal of greater conductivity is used, the cross-sectional area of the conductor bars may be reduced, which permits the use of a greater amount of magnetic material in the rotor. It is well known, however, that pure aluminum is more difficult to cast on account of its higher crystallization shrinkage. My improved method, however, is especially valuable because it makes possible the use of commercially pure aluminum in casting conductor bars in large rotors. In former practice, when commercially pure aluminum was utilized in forming the conductor bars and end rings of large rotors, the casting has been so difficult as to be commercially impracticable. It will be understood, however, that in certain cases aluminum alloys with higher electrical resistance may conveniently be employed, for example, in the manufacture of rotors where high starting torque is desired.

The conductor bar passages in the laminations may be of any suitable shape or size, depending upon the particular conditions at hand and each slot may be open to the periphery of the rotor, as shown in Fig. 5, or may be formed entirely within the laminations 2. The conductor bar passages 6, furthermore, may extend parallel to the central axis of the rotor or may be inclined at an angle thereto, as shown in Fig. 4.

Instead of holding the laminations together in assembled relation by temporary means such as the mandrel 48 and nut 51, other means such as rivets may be employed, such rivets, for example, extending through the laminations at points intermediate the aperture 3 and the periphery of the laminations. In such cases, in order to position the laminations readily and accurately in the mold, the ejector member may be provided with an extension arranged to register within the aperture 3 of the assembled laminations.

It will be seen that my invention provides a unique mold and process for controlling casting conditions, whereby castings heretofore formed with difliculty may be readily produced in commercial quantities.

My invention provides further advantages in the manufacture of articles embodying laminations held together by integral portions of cast metal, the invention providing for advantageously holding such laminated members in assembled relation until the casting metal is in condition to perform this function.

It will further be noted that by my invention I have provided a squirrel cage type of rotor for induction motors involving new and improved electrical characteristics, whereby an electrical circuit of uniform conductivity and hence uniform torque may be obtained. In addition, by my invention such rotors may be formed having advantageous features of construction whereby rotor laminations may be securely held together by cast end rings and conductor bars of a uniform character, the assembly of which may be obtained by improved and simple means.

It will also be seen that by preheating the mold sections, the laminations and the casting cavities themselves, and then by inverting the mold and providing metal of a comparatively high temperature to compensate for the shrinkage of the casting metal during cooling, conductor bars may be produced having a comparatively large cross section without sinks or imperfections.

Furthermore, I have provided by my invention a permanent mold which lends itself admirably to the formation of castings of aluminum and. alloys thereof, and more particularly to castings having long portions of comparatively large cross section which heretofore have only been cast with extreme difliculty.

While I have disclosed completely inverting the mold, that is tilting it 180, it will be apparent that many of the advantages of this invention may be accomplished by rotating the mold substantially 90 or more, and when the term inverting the mold is utilized in the specification and claims, it will be understood that it refers to completely inverting the mold or rotating it through an angle of 90 or more.

While my invention finds an extremely useful application in the casting of rotors for induction motors, it will be understood that the invention is not limited to producing such castings but may be applied to the production of other castings involving a plurality of relatively long portions of relatively small cross-section, and for casting metal having a comparatively low melting point about the periphery or in grooves or slots formed 180 in the periphery of a metal having a comparatively high melting point. In such cases, the periphery of the body of metal having a comparatively high melting point may be spaced from the mold sections 20 or have grooves in its periphery, or the metal having a higher melting point may form a core for producing annular or cylindrical castings.

Furthermore, it is to be understood that the particular forms of apparatus shown and described, and the particular procedure set forth, are presented for purposes of explanation and illustration and that various modifications of said apparatus and procedure can be made without departing from my invention as defined in the 145 appended claims.

What I claim is:

1. A permanent mold for casting metal having a comparatively low melting point about the pe- A riphery or in slots or passages in a metal having 15 a comparatively high melting point, comprising,

in combination, metal mold sections supported on a rotatable base and arranged to cooperatewith the metal having a comparatively high melting point to form a casting cavity and means for rotating said base, said mold sections being recessed to provide a sprue cavity leading downwardlyinto the base molding section and upwardly into the molding cavity, whereby molten metal may be forced upwardly through the mold cavity when the mold is in normal position and whereby molten metal may be provided at comparatively high temperatures to compensate for the shrinkage of the casting metal when the mold is in inverted position.

2. A permanent mold for casting metal having a comparatively low melting point about the periphery or in slots or passages in a metal having a comparatively high melting point, comprising, in combination metal mold sections supported on a rotatable base and arranged to cooperate with the metal having a comparatively high melting point to form a mold cavity and means for rotating said base, said mold sections being recessed to define a ring sprue cavity communicating with the mold cavity at the lower end thereof and an additional recess through which casting metal may be supplied to said ring sprue cavity to force metal upwardly into the casting cavity when the mold is in upright position, said ring sprue cavity also being adapted to supply metal at a comparatively high temperature to compensate for shrinkage of the metal when the mold is in inverted position.

3. A permanent mold for casting metal having a comparatively low melting point about the periphery or in slots or passages in a metal having a higher melting point, comprising, in combination, metal mold sections supported on a rotatable base and arranged to cooperate with the metal having a higher melting point to form a mold cavity and means for rotating said-base, said mold sections being recessed to define a substantially peripheral ring sprue cavity communicating with the molding cavity and a sprue cavity leading downwardly into the base section and upwardly into said ring sprue cavity, whereby metal may be forced upwardly through the casting cavity to form castings when the mold is in upright position and whereby molten metal at a comparatively high temperature may be provided to supply additional metal to the casting cavity when the mold is in inverted position.

4. A permanent mold for casting metal having a comparatively low melting point about the periphery or in slots or passages in a metal having a higher melting point, comprising, in combination, metal mold sections supported on a rotatable base and arranged to cooperate with the metal having a higher melting point to form a mold cavity and means for rotating said mold, said mold sections being recessed to define a riser cavity above the casting cavity and a pouring sprue cavity leading downwardly into the base cavity and upwardly to the casting cavity whereby molten metal may be supplied to preheat the casting cavity and to supply casting metal, and whereby additional molten metal at a comparatively high temperature may be supplied to said casting cavity when the mold is in an inverted position to compensate for shrinkage of the metal in the casting cavities during the cooling of the casting metal.

5. A permanent mold for casting metal having a comparatively low melting point about the periphery or in slots or es in a metal having a higher melting point, comprising, in combination, metal mold sections supported on a rotatable base and arranged to cooperate with the metal having a higher melting point to form a mold cavity, and means for rotating said mold, said mold sections being recessed to form a riser cavity extending above the molding cavity, a substantially annular sprue cavity communicating with the base of the mold cavity when the mold is in upright position, and a pouring sprue cavity leading into said ring sprue cavity whereby molten metal may be forced upwardly through the casting cavity to preheat the same and provide casting metal for the casting cavity, and whereby additional molten metal at a comparatively high temperature may be supplied to said casting cavity when the mold is in inverted position to com pensate for shrinkage of the metal in the casting cavities during the cooling of the casting metal.

6. A permanent mold for casting metal having a comparatively low melting point about the periphery or in slots or passages in a metal having a higher melting point, comprising, in' combination, metal mold sections supported on a rotatable base and arranged to cooperate with the metal having a comparatively high melting point to form a mold cavity, and means for rotating said mold, said mold sections being recessed to define a substantially annular sprue cavity having a narrow gate communicating with said mold cavity, and a pouring cavity leading into said annular sprue cavity, whereby molten metal may be forced upwardly into said casting cavity and whereby additional metal at a comparatively high temperature may be supplied to said casting cavity to compensate for the shrinkage of the casting metal during cooling while the mold is in inverted position,

,7 A permanent mold for casting metal having a comparatively low melting point about the periphery or in slots or passages in a metal having a higher melting point, comprising, in combination, metal mold sections supported on a rotatable base and arranged to cooperate with the metal having a higher melting point to form a mold cavity and means for rotating said mold, said mold sections being recessed to define a riser cavity above the mold sections, a substantially annular sprue cavity having a narrow gate communicating with said mold cavity, and a pouring sprue cavity leading into said annular sprue cavity whereby molten metal may be forced upwardly through the mold cavity to preheat the metal surrounding the molding cavity and to fill the casting cavity, and whereby additional metal may be supplied to the casting cavity from the ring sprue cavity at a comparatively high temperature to compensate for shrinkage during cooling when the mold is in inverted position.

8. A permanent mold for casting metal having a comparatively low melting point about the periphery or in slots or passages in a metal having a higher melting point, comprising, in combination, metal mold sections supported on a rotatable base and arranged to cooperate with the metal having a comparatively high melting point to form a mold cavity and means for rotating said mold. said mold sections being recessed to define a riser cavity above the casting cavity, a substantially annular sprue cavity having a narrow gate communicating with said mold cavity and a pouring sprue cavity leading downwardly into the base mold section and extending upwardly into said ring sprue section whereby metal may be forced upwardly at a uniform pressure to preheat the metal surrounding the molding cavity and to supply casting metal thereto, and whereby additional metal from the ring sprue cavity and the upwardly extending passage of the pouring sprue cavity may be supplied at a comparatively high temperature to the casting cavity when the mold is in inverted position to compensate for the shrinkage of metal during cooling.

9. A permanent mold for casting conductor bars formed of aluminum or aluminum alloys in metal rotor cores, comprising, in combination, metal mold sections arranged to cooperate with said core to form a completed mold and to support said rotor core with the conductor bar passages in upstanding position and means for inverting said mold sections, said mold sections being recessed to define a substantially peripheral sprue cavity communicating through a narrow gate with the conductor bar passages and a pouring sprue cavity leading into said peripheral sprue cavity whereby metal may be forced upwardly through said conductor bar passages when the mold is in upright position, and whereby additional metal may be supplied to said mold cavity from the peripheral sprue cavity when the mold sections are in inverted position.

10. A permanent mold for casting conductor bars formed of aluminum or aluminum alloys in metal rotor cores, comprising, in combination, metal mold sections arranged to cooperate with said core to form a complete mold and to support said rotor core with the conductor bar passages in upstanding position and means for inverting said mold sections, said mold sections being recessed to define a riser cavity located above the conductor bar passages, a substantially peripheral ring sprue cavity communicating through a narrow gate with the conductor bar passages and a pouring sprue cavity leading into the ring sprue cavity whereby molten metal may be forced upwardly through the conductor bar cavity to preheat the metal surrounding the conductor bar passages and to supply casting metal, and whereby additional metal may be provided from the ring sprue cavity at a comparatively high temperature to compensate for the shrinkage of metal in the casting cavity when the mold sections are in inverted position.

11. A permanent mold for casting conductor bars formed of aluminum or aluminum alloys in metal rotor cores, comprising, in combination, metal mold sections arranged to cooperate with said core to form a complete mold and to support said rotor core with the conductor bar passages in upstanding position and means for inverting said mold sections, said mold sections being recessed to define a riser cavity located above the conductor bar passages, a substantially peripheral ring sprue cavity communicating through a narrow gate with the conductor bar passages, and a pouring sprue cavity leading downwardly in the base molding section and forming an upwardly extending passage leading into the ring sprue cavity whereby molten metal may be forced uniformly upward through the conductor bar passages to preheat them and fill them with casting metal and whereby molten metal from the ring sprue cavity and the up- Wardly extending passage of the pouring sprue cavity may flow under the force of gravity into said conductor bar passages to provide additional metal when the mold is in inverted position to compensate for the shrinkage of metal during cooling.

ing the mold and maintaining the metal in the ring sprue cavity in such a manner that it will shrinkage of metal in the mold cavity during cooling.

13. The method of casting metal having a comparatively low melting point about the periphery or in slots or passages of a metal having a higher melting point, which comprises supporting the metal having a higher melting point within the casting cavity of a metal mold having a riser cavity located above the casting cavity, forcing molten metal into a substantially peripheral ring sprue cavity upwardly through the mold cavity to preheat the metal surrounding the mold cavity and supply casting metal thereto, and then inverting the mold and maintaining the metal in the ring sprue cavity so that it will flow into the casting cavity to compensate for shrinkage of the metal in the casting cavity during cooling.

14. The method of casting metal having a comparatively low melting point about the periphery or in slots or passages of a metal having a higher melting point, which comprises supporting the metal having a higher melting point M within the casting cavity of a metal mold having a riser cavity located above the casting cavity flow into the mold cavity to compensate for,

and a substantially peripheral ring sprue cavity communicating with the base of the casting cavity and forcing metal downwardly through a pouring sprue cavity and upwardly through a passage leading into the ring sprue cavity whereby molten metal may be uniformly forced upwardly through the casting cavity to preheat the same and supply casting metal thereto, and then inverting the mold and maintaining the metal so that it will flow downwardly by the force of gravity from the ring sprue cavity and a portion of the pouring sprue cavity to compensate for the shrinkage of the metal in the casting cavity during cooling.

15. The method of casting metal having a comparatively low melting point about the periphery or in slots or passages of a metal having a higher melting point, which comprises supporting the metal having a higher melting point within the casting cavity of a metal mold having a pouring sprue cavity comprising a downwardly extending passage and an upwardly extending passage communicating with the casting cavity, pouring metal into the downwardly extending passage, 1'.

forcing it through the upwardly extending passage and the molding cavity to supply casting metal thereto and then inverting the mold and maintaining the metal so that it will flow downwardly by the force of gravity from a portion of i.

the pouring sprue cavity into the casting cavity to compensate for shrinkage of the casting metal during cooling.

16. The method of casting metal having a comparatively low melting point about the periphery 11 3 cavity and a ring sprue cavity communicating through a narrow gate with the casting cavity, forcing molten metal upwardly through the ring sprue cavity and thence through the narrow gate and upwardly through the casting cavity to preheat the metal surrounding the casting cavity and supply casting metal thereto, and then inverting the mold and maintaining the metal so that it will flow by gravity from the ring sprue cavity to the casting cavity to compensate for the shrinkage of metal during cooling.

17. The method of producing rotors which comprises assembling laminated metal plates to form a core with longitudinal passages arranged around its periphery, supporting said core within the casting cavity of a metal mold having a substantially peripheral ring sprue cavity communicating therewith so that the conductor bar passages are in upstanding position and forcing molten metal upwardly through the ring sprue cavity into the casting cavity, and then inverting the mold and maintaining the metal in the ring sprue cavity so that it will flow into the casting cavity to compensate for the shrinkage of metal during cooling.

18. The method of producing rotors, which comprises assembling laminated metal plates to form a core with longitudinal passages arranged around its peripheral margin, supporting said core within the casting cavity of a metal mold having mold sections defining a riser cavity above the molding cavity, and a substantially peripheral ring sprue cavity communicating therewith through a narrow gate, forcing metal uniformly upward through the ring sprue cavity and thence through the narrow gateand upwardly through the mold cavity to preheat the metal surrounding the casting cavity and supply casting metal thereto, and then inverting the mold and maintaining the metal in the ring sprue cavity so that metal will flow from the ring sprue cavity into the casting cavity to compensate for the shrinkage of metal duringcooling.

19. The method of producing rotors, which comprises assembling laminated metal plates to form a core with longitudinal passages arranged around its peripheral margin, supporting said core within the casting cavity of a metal mold having sections defining a riser cavity above the molding cavity, a substantially peripheral ring sprue cavity communicating therewith through a narrow gate, and a pouring cavity having an upwardly extending passage, forcing molten metal into the upwardly extending pouring sprue passage and through the ring sprue cavity to preheat and supply molding metal to the casting cavity, and then inverting the mold and maintaining the metal in the ring sprue cavity and a portion of the pouring passage so that it will be available to supply metal at a comparatively high temperature to compensate for the shrinkage of metal in the casting cavity during cooling.

20. The method of producing rotors which comprises assembling laminated metal plates to form a core with longitudinal passages arranged around its periphery, supporting said core within the casting cavity of a metal through an upwardly extending passage mold, passing metal into a ring-shaped cavity below the core, and thence upwardly through the longitudinal passages and into a ring-shaped cavity above the core, inverting the mold, and supplying additional metal to the mold from the upwardly extending passage at a comparatively high temperature to compensate for the shrinkage of metal in the longitudinal passages and the end ring cavities during the cooling of the casting metal.

21. The method of producing rotors which comprises assembling laminated metal plates to form a core with longitudinal passages arranged around its periphery, supporting said core within the casting cavity of a mold having end ring cavities above and below the laminations, causing molten metal to flow into the lower end ring cavity for a sufficient peripheral extent so that the metal will flow simultaneously upward through the longitudinal passages at substantially the same rate and fill the upper casting cavity, inverting the mold, and supplying additional metal to the lower end ring cavity at a comparatively high temperature from metal retained in passages in the mold to compensate for the shrinkage of metal in the longitudinal passages and the end ring cavities during the cooling of the casting metal.

22. The method of producing rotors which comprises assembling laminated metal plates to form a core with longitudinal passages around its periphery, supporting said core within the casting cavity of a mold having an end ring cavity and a riser cavity above the laminations and an end ring cavity below the laminations, causing metal to flow into the lower ring cavity for a sufficient peripheral extent and in a suflicient J the mold to the casting cavities to compensate for shrinkage of metal in the longitudinal passages and the end ring cavities during the cooling of the casting metal.

EVERETT G. FAHLMAN.

CERTIFICATE OF CORRECTION. I

Patent No. 1,981,424. .November 21. 1934,

EVERETT c; EAHLMAN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 8, lines 83 and 84, claim 20; strike out the words "through an upwardly extending passage" and insert the same after "metal" in line 84, of said claim; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 12th day'of February, A. D. 1935.

Leslie Frazer (Seal) Acting Commissioner of Patenta.