US2829408A - Centrifugal casting machine - Google Patents

Description

April 8, 1958 A. B. SHUCK 2,829,408

CENTRIFUGAL CASTING MACHINE Filed July 21. 1954 3 Sheets-Sheet l JNVENTOR.

WW4 4-4M fia P 8, 58 A. B. SHUCK 2,829,408

CENTRIFUGAL CASTING MACHINE Filed July 21, 1954 3 Sheets-Sheet 2 IN VEN TOR.

April 8, 1958 A. B. SHUCK 2,829,408

CENTRIFUGAL CASTING MACHINE I Filed July 21, 1954 3 Sheets-Sheet 5 I INVENTORf Qz Zy.

United States Patent CENTRIFUGAL CASTING MACHINE-r Arthur B. Shuclr, Wheaton, 111., assignor to the United States of America as represented by the United States Atomic Energy Cornunission Application July 21, 1954, vSerial.No.-'444,93tl 8 Claims. 01. 22-45 This invention relates to a casting apparatus andmore particularly to a centrifugal casting apparatus. operat-- ing under a vacuum.

The apparatus of the present invention is. specially suited to the casting of uranium rods or slugs that are to be used in a neutronic reactor. Because ofthe small size of the rods the apparatus is designed to form a plu-- rality of them simultaneously in one operation.

In the drawings:

Fig. l is a vertical sectional view taken through the novel casting apparatus of the present invention;

Fig. 2 is a horizontal sectional view taken on the line 22 of Fig. 1 and showinga rotary. table,,molds,. and a distributor;

Fig; 3 is a plan view, with parts broken away and in. section, of the. distributor and portions of some of the molds;

Fig. 4 is a vertical sectional'view taken on the; line 44 of Fig. 3;

Fig.. 5 is a horizontal sectional view taken on the line 5-5' of Fig. l and showing the" manner in which a thermal shield is fastened to aivacuum fitting;.

Fig; 6.18 a vertical. sectional view somewhat similar to Fig. 1 but on an enlarged scale and showinga crucible and parts associated therewith;

Fig. 7 is a horizontal sectional view taken on the line 7-7 'ot'Fig. 6 and showing a viewing windowfor'lo'okinginto the crucible; and

Fig. 8' isa fragmentary view, partially in section, showing" the connection of lifting means for the crucible stopper.

As shown in Fig. l, the casting apparatusofthepresent invention comprises, in'brief,'a crucible 10, a heater 11 surrounding the crucible for melting metal in the crucible, a hollow stool 12 supporting the crucible and conducting molten metal flowing downward from the crucible, a distributor I3- rece'iving molten metal from the hollow stool 12, a plurality of molds 14 receiving molten metal from the'clistributor13', meansincluding a motor=15-for rotating the distributor and molds, and means including lines 16 and 17 for applying vacuum, respectively, to the distributor 13 and molds 14 and: to the crucible- 10.

As shown in Fig. 6,, the crucible has. a cover. 18.-

Botlr are formed of a refractory material such as. magnesia or thoria. A tantalum sheet- 18a rests-onthe top. of the. cover 18. The. crucible 10 rests on a pedestal. 19

which isformed of a refractory material: such. asmag nesia; The crucible 10 has a conical lower end which.

projects into and rests on a conical seat in. the. pedestal.

est'ali The head 21 has an annular" projection on its:

upper sidewhich centers-the pedestal 19 and. the sleeve 22 with respect to the hollow stool.12, so that the spacing of the tantalum lining 23'frorn the. crucible 10 and the pedestal is maintained.

The crucible 10 is provided with. a stopper 24 which is formed of a refractory material such. as magnesia. The stopper 24 is lifted to open the crucible 10 by means ofa tube 25 which may be of a stainless steel and is connected detachably to the stopper 24 by means of a cap 26 and a pin.27 which are associated with one another in a bayonet joint. The cap. is. of stainless steel and is bonded to the tube25. The pin is of tantalum and projects through a reducedupper end 28 onthe-stopper 24. The tube 25 is securedto a brass fitting 29 to I A tubular structure 33 which is made oi heat-resistant glass encloses the crucible 10, the pedestal 19, the sleeve 22, and portions of the tube25 and the stool 12 and lies within the heaterll, which is. aninduction-heatin'g coil formed. of hollow tubing. The endsof the tubular structure 33 engage annular seals 34' of silicone rubber which are mounted in upper and lower adapter rings.

35 and 36. These adapter rings are made of brass. and are hollow so that they may be kept. cool by cooling water supplied to them by lines 37 and removed from. them through linesv 38, the lines 37 and 38 entering. each ring at adjacent regions, and a partition. being provided across the annular cooling-water passage in the'ring between the regions where the lines. 37 and 38. are connected. The lower ring 35 restson a stainless-steel spider' ring 39' which. supportsthe stool 12 through a stainless-steel collar 40 which is bonded to the stool 12 and has threaded engagement with the spider.. An. annular neoprene seal 41 is. provided in a. groove in the spider ring, on the side thereof facing the lower. brass ring 36'.

The spider ring 39 is bond'ed to and supported onv a. stainless-steel plate 42 which forms part of'a housing. 43

enclosing'the distributor I3and the molds, 14. As shown in" Fig. 1', the housing 43 also. includes a stainless-steel drum head-which is' secured to the plate 42 by a stainless-steel bolti'ngpring 45; which is. bonded. tov the drum head 44. and'is attached to the plate by bolts 46-and nuts- 47, of which only oneof'each. is shown. There'is a-neoprene sealing ring. 43. between. the plate. 42 and the bolting ring 45'. The. drum. head. 44 is bonded to a stain-- less-steel annular plate 49- which' i's'secured to a mounting. base 50 by serewsi51. An annular neoprene seal 51a, mountedin-a groove in. the mounting. base 50, acts between: the? mounting. base: and. the: annular plate 49. The upper portiorr of a vertical drive shaft 52 is journal'ed in the mounting base 50} by" means of. a roller thrustbearing 53Lsecured in the-mounting base 56. The lower portion of the shaft- 52 is j'ournaled by'meims of a roller thrust bearing; 54 secured to the' mounting base 50 through a bracket 55 The shaft 52" is driven by the motor .15. through belts 5 6 and pulleys 57" and 58'; secured,.re-

spectively; to the lower. end" of the shaft 52 and to. a,

shaft. 59 of the motor 151. The motor 15 is secured to themounting base 50'by means of-a br-acket.60..v .A magneto tachometer 61', supported on the mounting; base;

A tantalum 50, -is driven from the lower end of the shaft 52 through a belt 62.

A rotary table 163 is keyed to the upper end of the shaft 52 soas to be supported and driven thereby. The distributor 13 and the molds 14 are secured to and sup ported on the rotary table 63. As shown in Figs. 3 and4, the distributor is formed of two complementary upper and lower parts 64 and 65 which are of graphite. The upper part 64 receives the lower end of the hollow stool in a loose fit that permits rotation of the distributor with respect to the stool. upper surface which cooperate with the lower surface of the part 64 to provide curved passages 66 which extend generally radially outwardly. However each passage 66 deviates. from a radius drawn from the center of the distributor 13 to "the inner end of, the passage 66 in increasing amounts when considered in a radially outward direction. As shown in Fig. 4, the outer portion of each passage 66 is substantially horizontal, and the remainder ofeach passage slopes somewhat downwadly and outwardly from a central conical region 66a. The distribufor parts 64 and 65 have at their radially outward regions tooth-like portions 67 each of which has a generally vertical-surface 68 in which the outer endof the associated curved passage 66 terminates while extending generally normally thereto. Each mold 14 is formed of upper and lower mating copper halves located with respect to one another by dowel projections and recesses formed thereon. The radially inner end of each "mold abuts one of the surfaces 68 of the distributor 13. The molds 14 are secured toan upper horizontal surface 69 of the rotary table. 63 by means. of screws 70, bridging finger pieces 71, and screws 72. Each screw 70 goes through the halves of the mold 14 adjacent that radially outer corner of the mold thatis shown in Fig. .2 to engage an upstanding outer rim 73 on the rotary table 63. Each screw 70 also has threaded engagement with the rotary table. Each bridging piece 71 engages two adjacent molds 14 and receives a screw 72 which is threaded into the rotary table 63. The distributor parts 64 and 65 are securely heldto the rotary table 63, because their surfaces 68 are engaged by the radially inner ends of the molds 14, and surfaces 73a, also formedon the toothlike portions 67, are engaged by regions of the mold sides adjacent the radially inner ends.

Each mold 14 has a straight horizontal cavity 74 which extends lengthwise of the m'old'and has an enlarged portion 75 at its radially inner end of the mold "in direct communication with the outer end of anassociated distributor passage 66. Each portion 75 is shaped like the frustum of a cone, the large endbeing at the end of the distributor passage 66 and larger in diameter that the same and the small end merging with the rest of the mold cavity 74. Each mold passage 74 has a closed outer end adjacent? the outer end of the mold. The vertical sides of each mold 14 adjacent the inner end of the mold converges in a direction toward the inner end of the mold so that, as shown in Fig. 2, there is room for a large number of molds 14 on the table 63 in com-.

munication with the distributor 13. In the embodiment of the. invention shown in the present applicationthere are 16 zmolds. The molds engage one another at their; inner tapering sides. As previously stated, each mold cavity 74 is straight and extends at an angle to the radial 7 direction. When considered with respect tothe radius drawn from the center. of the distributor 13 to theinner end of the associated distributor passage 66, each'moldv passage 74 makes a greater angle to the radius than any portion of the passage 66.

The bottom of the lower distributor part 65 has a recess 76 in which a coil heater77v is positioned, which may be made of stainless-steel tubing, a coil in the tubing formed of nickel-chromium-iron wire, and an insulating filler between the'cail and the tubing. Electrical leads The part 65 has grooves on its before the distributor 13 and molds 14 can be rotated.

In an alternate arrangement the heater 77 is connected to a source of electric power through slip rings so that the heater need not be cut off when the distributor and molds are rotated.

The upper portion of the vertical drive shaft 52 is provided with a seal 79 positioned in a flange 80 formed on the mounting table below'the thrust bearing 53 and a seal 81 positioned above the thrust bearing 53 in a cap 82 secured to the mounting base 50.

The adapter ring 35' onthe' upper end of the tubular structure 33 is engaged by a stainless-steel ring flange 82 whichis bonded to one end of a stainless-steel T-fittiug 83. An annular neoprene seal 84 is positioned between the adapter ring 35 and the flange 82 in a groove formed in the latter. A stainless-steel ring flange 85 is bonded to the upper end of the T-fitting 83, and a brass plate 86 is secured by bolts 87 to the flange 85. An annular neoprene seal 88 is positioned betweenthe ring 85 and the plate 86 in a groove formed in the latter. A quartz window 89 fits loosely in a recess formed in the upper or outer side of the brass plate'86, and an annular neoprene seal 90 lies between the window 89 and the plate 86in a groove formed in the latter. An opening 91 is formed in the plate 86 beneath the window 89 and is closed by the enlarged v to the upper or outer side thereof.

The T-fitting 83 is bonded to the line 17', which is also of stainless steel and has a slidable clamping fit with a stainless-steel fitting 94. The line 17 is clamped and sealed to the fitting 94 by a seal, not shown, that is mounted in the fitting 94 and squeezed against the line17 by means of a clamping ring 95 threaded on the fitting 94. The line 16 is also of stainless steel and has a sliding clamping fit with the fitting 94 similar to that of the line 17 through a seal, not shown, and a clamping ring 96 threaded on the fitting 94. The line 16 has an end flange 97 which engages the housing plate 42 at an opening 98 formed therein. An annular neoprene seal 99 lies between the-flange 97 and the housing plate 42 and the.

groove formed in the latter. The flange 97 is held against the housing plate 42 by means of clamps 100 and screws 1 01 ofwhich only one of each is shown in Fig. 1. The fitting 94 is adapted tobe connected to a source of vacuum, not shown.

The tube 25 is sealed in the plate 86 by means of a neoprene ring 102, a fitting 103 inserted in the plate 86 and bonded thereto, and a fitting 104 threaded into the fitting'103 so as to press the ring 102 against the tube 25. The fitting 94 is protected from the heat generated by the heater 11 by a transite shield 105 held between the fitting and the heater in spaced relation to both by means of a bracket 106 secured to the fitting. The bracket 106 has an arcuate slot 107 having its center coincident withthe axis of the vertical passage of the fitting 94. A threaded rod 108 goes through the slot 107 and is adjustably fixed to the bracket 106 by means of thumb screws 109 and 110,

respectively, above and below the bracket. An arm 111 secured to the'line 17 has an open-end slot receiving an upperportion of the threadedrod 108. Thumb screws 112 and 113 which are threaded to the rod 108, respectively, aboveand below the arm 111 fixed the rod to the arm. A rod 114 is adjustably secured to the housing plate 42 by means of a nut 115 which is secured to the housing plate and receives the lower end of the rod 114 in a 1 threaded connection. A bracket 116 secured to the fitting 83has an open end slot receiving the upper portion at the rod 114. Thumb screws 117 and 118 which are threaded to the upper portion of the rod, respectively, above and below the arm 116'fiir the arm to the rod;

The castingapparatus of thepresent invention-is to form rods or slugs of uranium alloyed'with 2% by weight of zirconium; Thezii'coniuin'us'ed' in the cruciblecharge is in the form of wires swaged from crystal bars of zirconium and wound on a nra'ndrel the size (if the stopper rod 24 so as to fit around" the stopper rod in the bottom of the crucible The uraniumisdn theform of 93% U enriched uranium reduction buttons which are placed in the crucible 10 above the zirconium wire. After the crucible has beenchar'ged and placed on the pedestal 19 within the sleeve 22 and the tubular structure 33, the T-fitting 83 is applied to the' open end of the tubular structure 33 as shown in" Figs. 1 and 6. Adjustment of the thumb screws 112 and117do'wnward against the.

arms 1.11 and 1 16'attache'd to the: line 17 and the fitting 83, clamps'the fittingv against the tubular structure 33,;

or more exactly, the flange ring 82 on the. fitting 83 against theupperadap'ter ring 35 on the tubular structure 33. ,The thumb screws'1'13 and 118 are now adjusted upwardly against'the arms 111 and 116. The "apparatus is evacuated by application of a vacuum tothe horizontal line of the fitting 94 which communicates through the lines 16 and 17, respectively, with the housing 43 containing the distributor 13 ahd mold 14 and the upper side of the crucible l0 which is the side away from the distributor and the mold. This application of vacuum to two regions of the apparatus has the advantage of producing equalization of vacuumin the two ends of the apparatus. Current is now applied to the heater 11 which causes the charge in the crucible 10 to melt. In the meantime current is applied tothe heater 77 to preheat the distributor 13 and the molds 14. Such preheating will under the action of the vacuum applied drive gases out of the distributor and the molds and thus prevent outgassing when the hot molten metal comes in contact with the distributor and the molds.

While the charge in the crucible 10 is being melted, the table 63, the molds 14, and the distributor 13 may be rotated by the motor 15 acting through the drive shaft 52 at some intermediate speed. As the charge in the crucible 10 is being heated, the charge may be observed through the quartz window 89 mounted in the plate 86 after the arm 92 is pivoted to uncover the opening 91 formed in the plate 86 before the window 89. Openings 119 and 120 formed, respectively, in the tantalum shield 32 and the crucible cover 18 are in line with the opening 91 in the plate 86, so that a viewer may look through the window 89 and through these openings into the crucible 10. Evaporation of metal coatings from the molten metal in the crucible 10 causes fogging of the portion of the quartz window 89 directly over the opening 91 in the plate 86. The window 89 may be rotated to bring a clean portion over the opening 91. The tantalum layer 23 lining the refractory sleeve 22 absorbs heat and reduces or prevents heat shock upon the crucible 10 such as would be produced by the heating of the charge within the crucible directly by the coil heater 11 without the tantalum lining 23. At low power the coil 11 induces heat only in the lining 23, which in turn heats the charge in the crucible 10. Thus heat is not induced directly in the crucible charge, and heat goes from the outside of the crucible to its inside, rather than in the reverse direction, with the result that the crucible is not so likely to break. The

lining 23 is sufl'iciently thin that at high power, when the 25. 4 Now moltenmetal flows" downwardly outer; the

crucible 10 and through the hollow stool' 12 into the distributor 13. In the distributor the molten metal-under centrifugal action flows outwardly through the passages 66 in the mold cavities 74. With the distributor pas sages 66 and the mold cavity 74 angularly arranged as shown inFig'. 3', the direction of rotation of'thedistributor 13 and molds 14 will be clockwise when viewed from above, asindicated by an arrow 121. Thus the mold cavities 74 and the distributor passages 66- lag behind radial lines drawn from the" center of rotation of the distributor t'o th'e' inner ends of the distributor passages 66-, with'th'eresult' that the mold cavities 74 are aligned in thefiree-flow path of the molten metal moving outwardly so that the metal fills the molds with a minimum of im= pingementupon the mold walls; The molds 14-, being 1 copper, chill the metal as it fills the mold cavity 74' and cause the metal to be fine grained. The application of vacuum to the di'stributor1'3' and the molds 14 is continued for some time after the metal has solidified in the" to machineand has-high resistance to thermal shock,-

a low thermal conductivity, and good non-wetting" and non-sticking properties.

After thecastings have cooled sufliciently, the application of vacuum isdiscontinued, and an inert gas may be supplied through the apparatus for a suitable period of time. Next the tube 25 is uncoupled from the stopper 24- and is lifted so that its coupling cap 26- is located within the fitting 83. Now the thumb screws 112, 113, 117, and 118 are backed away from the arms 111 and 116 along the rods 108 and 114, the thumb screw 110 is backed away from the bracket 106, and the clamp is loosened. Now the thumb screw 109 is screwed downwardly against the bracket 106 to raise the line 17 and the fitting 83, thus spacing the flange ring 82 on the fitting 83 from the brass ring 35 on the upper end of the tubular structure 33. Now the line 17 may be pivoted to swing the fitting 83 away from the top of the tubular structure 33. Such pivoting may take place, because the rod 108 may move along the arcuate slot 107 in the bracket 106.

The intention is to limit the invention only within the scope of the appended claims.

What is claimed is:

1. A metal-casting apparatus comprising a crucible, a distributor having arcuate passages and being positioned therebelow for receiving molten metal therefrom, a plurality of molds arranged about the distributor so as to have horizontal cavities generally aligned with tangents drawn to the passages at points where the passages meet the molds and adapted to receive molten metal from the distributor passages, the ends of the cavities at the distributor being enlarged with respect to the distributor passages and the remaining portions of the cavities to produce hot heads in the castings formed in the molds preventing shrinkage depressions in the castings, and means for rotating the distributor and the molds about a vertical axis through the distributor to enable the molten metal to move out of the distributor into the molds under the action of centrifugal force- 2. The apparatus specified in claim 1, the molds being formed of copper, and the distributor being formed of graphite.

3. The apparatus specified in claim 2 and further comprising a first vacuum line for applying a vacuum to the distributor and the molds and a second vacuum line for applying a vacuum to the crucible on the side thereof away from the distributor and the molds.

' 4. The apparatus specified in claim 3 and further comprising a heater positioned in the distributor for outgassing the distributor and the molds.

5. A metal-casting apparatus comprising rotary table having an outer rim, a'distributor positioned at the center of the table and provided with a plurality of arcuate passages, the distributor further having a plurality of non-tangential surfaceportions around the periphery of the distributor, a plurality of molds extend ing horizontally outwardly;from;theg,distributor tojthe rim of the table, the inner end of each mold abuttingoue ofsaid surface portions of ,the distributor, one corner of theouter end of each mold engaging the outer rim ,of the table, a screw passing through each mold adjacent the said corner and .into the table, a plurality oficlamps, eachclamp engaging two adjacent molds and bridging the space ;between, each mold beingengagedfby"-two.

a horizontal clamps, a screw passing through each clamp and between the molds engaged thereby and into the table, each ,mold

having a cavity extending at an angle to the radial and having an open end at the distributor and a closed end at the outer rim of the table, the molds engaging one another at their sides adjacent their inner ends. 6. Theapparatus specified in claim 5 andfurther com prising a housing enclosing the table, distributor, and molds and having an opening over the distributor, ,a tubular structure rising from the housing at the opening, a crucible positioned in the tubular structure above and in spaced relation to the distributor, means for conductingmolten metal from the crucible to the distributor, a first vacuum line connected tothe housing, radially outward of the rotary table, and a second vacuum line con-' nected to the tubular structure above the crucible;

7,= Theapparatusspecified in claim 6, the means for conducting molten metal from the crucible to the distributor comprising a tubularstoolhaving its upper end supporting the crucible and its lower end projecting into the distributor, the apparatus furtherlcomprising a support cooperating with a portion of the tubular stool intermediate its ends to carry the stool and being in turn carriedby the housing at :its connection with the tubular structure.

8, A metal-casting apparatuscomprising a distributor for receiving molten metal andiprovided with a plurality of arcuate passages leading generally radially outwardly from the center to the periphery of the distributor, a plurality of molds arranged about the distributor and having cavities generally alignedalong tangents to the arcuate passages at points where the passages join with the molds, and means for rotating thernolds and the dis-, tributor about an axis through the distributor to arrange for the molten metal to move out of the distributor into the molds along the free-flight path resulting from the action of centrifugal force on the molten metal and the movement of the distributor'with respect to the molten metal. i

References Cited in the file of this patent UNITED STATES PATENTSY 2,009,489

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