US2518055A - Apparatus for making centrifugal castings - Google Patents

Description

All@ 8; 1950 v E. R. oLsEN ErAL 2,518,055

APPARATUS FOR MAKING CENTRIFUGAL CASTINGS Filed sept. 1s, 194e Tj. i-

ATroRNEr Patented Aug. 8, 1.950

APPARATUS FOR MAKING IcEN'rRIFlUGAL onsriNcrsV Ernest R. olsen, Rudolph F. Flora., and cliff-ord J. Lonnee, Muskegon, Mich., assignors to` Hastings Manufacturing Company, Hastings, Mich.

"o Application September 13, 194,6, Serial No. 696,877

. 1 A l This invention relates to improvements in the apparatusfor making centrifugal castings. More particularly the invention relates to apparatus for centrifugally casting relatively thin Walled tubular castings which maybe slightly out-ofround and which are designed to be cut into piston rings. yThe apparatus also may be used in the forming of tubular castings for cylinder wall sleeves and the like. f. The rprincipal objects `of this invention are:

liirst,` to provide a casting for the manufacture of piston rings having improved strength and micro-structure characteristicsl due to the thickness of the casting and the cooling rate thereof obtaineclby our method.

Second, to reduce the cost of producing piston ,5 claims. (c1. .2z-113.5)

that described above were rapidly cooled as by casting the metal in a thin wall against a cooled metal mold, the carbon was largely retained in chemical combination with the iron forming an iron carbide composition, known as cementite which is extremely hard and unmachinable. yThe ring castings by reducing the amount of metal l cast and reducing the amount of machining necessary on the casting by eliminating taper or draw in the casting and reducing the irregularities and chaff on the casting which must be removed. v

Third, to reduce the cost of centrifugal tubular castings by eliminating the necessity of heat treating the casting to obtain proper machinability. I I

Fourth, to reduce the cost of producing centrifugal tubular castings by eliminating the expense of replacing and repairing the mold and by increasing the rate of production of the molding machine.

Fifth, to improve the grain structure of centrifugal tubular castings by eliminating the chilling effect of the mold -on the molten metal and thereafter accurately controlling the cooling rate of the casting.

Other objects and advantages relating to dei tails and economies of the invention will appear from the description to follow. The invention is dened and pointed out in the claims.

In the art of casting ferrous metals it has been appreciated for some time that the strength, hard-l nessl or .'machinability and lubricating properties of the nal product were interrelated -withthe carbon content of. the metal and the cooling rate of the casting. Generally speaking, a high carbon content iron slowly cooled produce a mixture of large graphite flakes intermixed with a coarse grainpearlitic matrix. This grain structure produced a relatively soft, weak metal without particularlysatisfactory wearproperties due` to the fact that the'large graphite flakes formed parting planes in the metal permitting early disintegration'or Wear thereof. y y

, if a metalof. the same chemical composition as desirable medium between these two extremes, particularly for piston rings and the like, is to cast a relatively high carbon metal so that the iron carbide or cementite is allowed to break down into free graphite in combination with a matrix of fine pearlite and to check growth of the graphite flakes and vpearlite grain structure before they have reached the objectionable size described above. In this form the evenly dispersed graphite flakes provide excellent lubricating properties to themetal without suiliciently interrupting the grain structure of the pearlite to adverselyafiect its wear and strength properties.

To accomplish this preferred form of casting and obtain tubular castings for the manufacture of piston rings having excellent wear properties and high 'tensile strength as Well as for other tubular castings we have devised apparatus and method for casting in which the molten metal of the desired chemical composition is centrifugally cast against a sheet of asbestos or other heat resistant material which is not consumed bythe heat of the molten metal and which retains its shape and form so as to be readily withdrawn from the mold with the finished casting. The asbestos surface is backed up or supported by awater-cooled metal mold having a casting cavity of the desired contour of the finished/casting. The metal mold cavity is vented as will be more particularly described hereafter, to prevent buckling and distintegration of the asbestos liner. The insulating propertiesof the asbestos serve to prevent the formation of a chilled surface on the casting while theforced cooling .character of the mold functions to cool the casting rapidly enough to prevent the formation of undesirable large flake graphite.v Thel asbestos liner lhas the additional functions of protecting the mold surface and making the casting veasily removable therefromand also formingfa smooth accurate surface Aon the: casting which may be closely, duplicated, insa series of castings produced in the same mold cavityy.

. The sum effect-of the combined use ofthe sheet asbestosliner in the ventilated water-cooled mold is to permit the economiccasting of thin tubes having a minimum of surplus stock which must bemachined @wrend having highly favorable cooling rates and consequent favorable microstructure. The structure and methods hereinafter described substantially fulll all of the objects of the invention set out above.

With this general description of our invention in mind, attention is now directed to the drawings of which there is one sheet illustrating a specific preferred embodiment of apparatus for performing our method of casting and one modified form of casting apparatus. The invention further pointed out in the claims.

Fig. 1 is a plan View partially broken away and shown in cross-section along the line i-l in Fig. 2, of a centrifugal casting device.

Fig. 2 is an end view partially broken away along the line 2 2 in Fig. l oi the mold with the end cap removed.

Fig. 3 is an end view of a modified form of a mold with the end cap removed.

Fig. 4 is a fragmentary cross-sectional view on the plane 4-4 in Fig. 3 showing the end cap in place on the modied form of mold.

Fig. 5 is a fragmentary sectional View Showing an embodiment in which the edges of the liner are: overlapped.

In the drawings reference character I indicates a hub provided with a flange section 2 arranged to be attached to a suitable spindle generally indicated at 3 which will rotate the hub at high speed about. a generally horizontal axis. At its forward end the hub is provided with a central recess 4 and annular iiange 5.

A cyl'illdral mold member ,5 is. provided with a, flange 'I arranged to mate with and be secured to the flange 5 on the hub. The interior of the mold, 6 is shaped with, the desired contour of the object to be cast and is shown in the drawings as forming a slightly out-of-round cylindrical surface 8 for the casting of tubular stock from which the piston rings may be out. The cavity formedin the mold is of uniform cross-section throughout its length and is not tapered to provide draft in the mold. The walls of the mold 5 are drilled axially in a series of inner passages 9 peripher ally sp-aced around the center cylindrical surface 8f and a series of outer passages Il) which are spaced radially outwardly from the inner passages. Radial bores II extend through the walls of the mold between the passages 9 and I from the inner cylindrical surface 8 to the outside of the mold. A cap I2 securedto the front of the mold cylinder by suitable screws, not shown, is formed with an annular groove I3 forming a header between the` ends of the inner bores 9 and the outer bores IG.

The rear or iianged end of the mold E is clamped tightly to the hub I and the passages 9 and I communicate respectively with inlet ducts I4 and outlet ducts I5 drilled axially in the hub. The inlet ducts I4 are connected to the surface of the hub by a series of radial bores I6 while` the outlet ducts I5 are connected to the surface of the hub by the radial bores I'I. A rotating seal member I8 is secured around the hub I and provided with ports I9 communicating with the radial bores I6 and Il. The annular flanges 20 formed on the rotating seal separate the inlet and outlet passages. A stationary seal member 2l is provided with internal annular grooves which receive the annular flanges 2B of the rotating seal and form a sliding gland or seal therewith. A water inlet passage 23 and a water outlet passage 24 formed in the stationary seal member communicate with suitable couplings 25 by means oi which the water supply andv outlet pipes may be attached to the mold. A retaining ring 2G having a generally U-shaped cross-section supports the couplings 25 and retains the fixed seal tightly against the rotating seal I8.

Positioned inside of the mold and against the surface 8 is a mold wall liner 21 which is of preformed bendable sheet material, desirably a sheet 0I single ply asbestos or asimilar heat. resistant material. The sheet asbestos is highly desirable because it has sufcient strength for manipulation and resists the molten metal; that is, it is not destroyed by the molten metal although the binder may be destroyed. The sheet, however, retains its sheet form so that it adheres to and may be removed with the casting. If other material than sheet asbestos is used the sheet should contain a heat resisting constituent that is not destroyed by the heat of the molten metal. The binder for the bres of the sheet should be either completely volatilized or consumed by the heat of the molten metal or be substantially unaffected by it. The sheet preferably is arranged in the mold with its longitudinal edges adjacent. but unconnected and in non-overlapping relation. The width of the sheet is thus equal to or slightly less than the circumference of the mold cavity. Overlapping of the edges of the sheet is permissible so long as the inside lap trails the direction of rotation of the mold. The unconnected character of' the edges of the liner permits it to expand firmly against the wall ofv the mold', the mold wall being ventilated or having Ventilating passages opening thereto` as at II' so that air or gas pockets are not formed behind the sheet liner either when the liner is inserted or during the molding operation- The centrifugal action of the molten metal forces the liner firmly against the wall of the mold and conforms it to the contour of the mold cavity.

An annular ring 2B of sheet asbestos is positioned at the bottom ofthe recess 4 in the hub and together with the sleeve 21 forms a casting surface which prevents the surface of the casting from becoming too rapidly chilled by contact with the walls of the mold.

Metal strips 29 secured as by welding to the sid-es of' the mold have theirouter ends twisted and folded into retaining arms 30: for engaging the handles 3i carried on the, cover plate 32. The cover can thus be secured to the mold by placing it against the mold and rotating the handles under the arms 3U, The cover defines a pouring hole 33 through which the molten metal is introduced into the mold but overhangs the edges of the mold cavity to retain the molten metal in the mold.

In operation it is contemplated that a new sleeve 2l will be installed. in the moldA prior to each casting operation. The sleeve is conveniently seated by rolling it into a small enough roll to be easily thrust into. the mold. It is then allowed to unroll and is expanded into shape by running a smooth plug into the cavity'. The cover 32 will then be installed and the hubV I and the mold carried thereby will then be rotated at high speed' and molten metal will be pou-red into the mold to form a tubular casting of desired thickness. Cooling water may be admitted through the inlet passages 2,3, I6 and 9, from where itY will flow to the header at the front end of the mold member and be returned through the outlet passages Hl, I1 and 24'. The rate of cooling. of the casting may be controlled by regulating the volume and teinperature of the cooling water passing through the mold. Gases formed in the mold by the actioni'of the fhot'metalon the binder fof the"liner 21 escape out ofthe 'boresvll and donot'tend to deform the liner. We havefound some lform of ventilation to be essential to the use ofvthe asbestos liner since otherwise thelgases bulge the liner permitting molten metal to get behind it and foul both the'mold and the casting. Itis believed that the 'close proximity ofthe asbestos to the moldvwall prevents the asbestos from being consumed `as it would otherwise be at the temperature of molten iron. j

` After the casting has reached the desiredtemperature, the cover 32 is removed and' the casting is removed from the mold, which operationis facilitated by the asbestos sleeve 21 which is drawn out of the mold with-the casting. Since the liner substantially covers all of the mold wall there is no necessity for! cleaning. the mold other than-'to blow out dust with anairV blast, and another asbestos sleeveV 21 may be immediately installed for another casting operation. f

lligs. 3 and fiillustrate a modified form ofthe mold 6A in which the inner cooling passagesy 9A are more widely spaced than the corresponding passages in Figs. 1 and' 2 and in which the outer passages IIIA are spaced around the circumferences of the mold between the inlet passages 9A and radially outwardly therefrom. Longitudinally` ,extendingI grooves IIA formed inthe Walls of the mold extend between the ends of the mold and take place of the radial bores Il in the preferred form ofl the invention to permit the escape of air and "gases from behind the liner 21 to the open end of the mold. Coacting-with the grooves Il A are holes 34 formed in the cover 32A to complete the vent passages.V 'I'he cover -32Ais retained on the mold in the same `manner' as the cover 32. In other respects the modified form of the vmold. and its operation is the same as'the preferred form. v l I Using either form of our invention, the casting with Athe liner thereon is Withdrawn from the mold as a unit. The liner serves as an insulating medium protecting the molten metal from the wall of the mold so that the casting does not have a chilled surface which requiresheat treatment to render the casting machinable. The inner surface of the liner also gives the casting a smooth, even surface andk further protects the surface from oxidation when the casting is removed hot from the mold. It willbe understood that this results in a very great saving of time and labor and cost of heat treating furnace operation. Also, the liner being removed from the casting leaves the mold cavity surface of the mold clean so that it is not necessary to clean the cavity, although in practice it is desirable to direct an air blast into the mold cavity before the liner is inserted in order to free it from dust or particles which might collect therein in foundry operation. 'I'he employment of the cooled mold increases production as it increases the number of castings which may be made in a single mold during a given time as Well as improving the microstructure of the casting. In practice, substantially as soon as one casting is removed from the mold, the mold is immediately prepared foranother casting operation by inserting a new liner sheet and repeating the molding steps.

Operation of the mold in the manner just described provides tubularcastings having a smooth and clean dense machinable outer surface quickly and inexpensively without requiring lextensive cooling periods or repair periods to change molds which have become cracked and dirty due to con.

tactfwit'hthe moiten'metai. 1 Control o'f the tem:` perature and volume of the cooling fluid accu-L rately determines the grain structure of thevcast-L ingr so that very few faulty castings 'are produced. Further,y the spinning time of the mold is reduced and the lighter impurities of the metal 4are kconcentrated at the inner surface of they casting where they are easily machined away with a min-I imum depth of cut permitting the use of less metal and obtaining better cooling characteristics as explained above. 'L

A particular advantage of the mold is that the mold cavity may be of uniform crosssection,ei ther cylindrical 'or out-of-round or other desired shape, from end to end. This produces a casting requiring less machining on the outer surface thanolder type molds which had to be tapered to permit the casting to be removed. Of course, Aif a tapered casting is `desired the mold cavityl and liner may be so formed. Sheet liners oftheftype described may beeasily obtained in uniform size, thickness and smoothness. f

While there are advantages in positioning the liner with its longitudinal edges in non-overlapping relation, the edges may be overlapped-*as shown in Fig. 5. The overlapping edge should be positionedinregard to the direction of rotation of the mold so that the metal will not tend to ilow under the liner. The invention has been herein described and'lillustrated in a highly satisfactory commercial embodiment. No attempt has 'been made toshow other adaptations, as it is believed thatthis disclosure willV enable those skilled in the art to einL body orfadapt the invention as may be desired. 'Y Having thus described our invention, what We claim `as new and desire to secure by Letters Pat-v ent is: Y f

1. Centrifugal casting apparatus comprising, a hub adapted to be rotated at high speed about -a' horizontal axis, a permanent mold member 4seicured to the end of said hub with its longitudinal axis lcoincident with said horizontal vaxis and having a generally cylindrical tubular casting cavity formed in the center thereof and having" a plurality of radial Ventilating bores formed through its Walls from said cavity to theoutside of sai'dmold,` said hub and mold having a plui' rality of aligned axially extending inlet passages formed within the walls thereof and angularl'y spaced around said cavity and having a plurality of valigned laxially extending outlet passages` formed in the walls thereof and spaced'radiall'y outwardly from said inlet'passages, said passages being located in portions of said mold wall between said bores, means forming a header connecting the outer ends of said inlet andvoutlet passages, a rotating seal member secured around said hub and having a pair of outwardly opening annular grooves, one communicating with all of said inlet passages, the other of said grooves communicating with all of said outlet passages, a stationary seal member engaging the walls of said grooves to form an' annular inlet and an annular outlet passage around said hub and having inlet and outlet ports opening to said annular inlet and outlet passages respectively, a retainer around said stationary seal member, connecting members on said retainer for attaching cooling fluid lines to communicate with said ports, and a liner of preformed sheet material having the heat resisting and insulating properties of sheet asbestos positioned within said cavity in unattached substantially covering facing relationship with the surface of said cavity and having its axially extending edges adjacent to each other but unattached.

2. Centrifugal casting apparatus for ferrous metals comprising, a rotatable mold having a casting cavity with circulatory cooling fluid passages located within the wall of said mold and positioned around said cavity, a running seal for connecting fluid circulating pipes to said passages in said mold, and a preformed liner of sheet heat resistant material covering the wall of said cavity, the wall of said mold having Ventilating passages formed therein and opening from between Said sheet and the surface of said cavity to the space around said mold, said sheet having its adjacent edges unattached and being unconnected to said mold.

3. In combination, a tubular centrifugal mold member having an approximately cylindrical mold cavity wall surface and having cooling fluid circulating passages formed in the wall of said .I

mold member land located around said cavity, such wall surface having Ventilating grooves formed therein and opening to the open end of the mold cavity, and a preformed bendable sheet asbestos liner disposed within the mold cavity in radially supported relationship to the wall thereof and constituting a mold cavity wall facing bridging said grooves, the longitudinal edges of the liner being positioned adjacent to each other but unconnected, the liner being free to expand into close supported contact with the mold cavity Wall surface of the mold member.

4. In combination, a centrifugal mold member forming an approximately cylindrical mold cavity open at one end, the surface of said cavity having Ventilating grooves formed therein and extending to the open end of said cavity, means rotatable with said mold member for directing, a circulatory flow of cooling fluid around and in Contact with the wall forming said mold cavity, and a preformed bendable sheet asbestos liner disposed within said mold cavity in rolled, radially supported, conforming relation to the wall thereof and bridging said grooves to form ventilating passages opening to the end of said mold and constituting a facing for said cavity wall surface, the liner being free to unroll and maintain close supported contact with the mold cavity Wall upon expansion of the latter but being unconnected to said cavity wall.

5. Centrifugal casting apparatus comprising a rotatable member, a mold member having an elongated casting cavity formed therein and se- 1cured to said rotatable member with the axis of the cavity coincident with the axis of rotation of said rotatable member, the surface of said cavity having grooves formed therein and extending to the open end thereof, the walls of said mold member having circulatory cooling fluid passages formed therein, a liner of preformed bendable sheet material of heat resistant composition positioned against the surface of said cavity in unattached, substantially covering non-overlapping relationship, said liner and said grooves cooperating to form Ventilating passages therebetween opening to the end of saidy mold, a cover removably secured to said mold and having a central pouring opening to said cavity formed therein, said pouring opening being .smaller than the cross sectional area of said cavity whereby said cover overlies the end of said cavity, said cover also having holes formed therethrough registering with the endsv of said Ventilating passages, and means carried on said rotatable member for attaching cooling fluid conduits to said cooling fluid passages.

ERNEST R. OLSEN.

RUDOLPH F. FLORA.

CLIFFORD J. LONNEE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 359,483 Whitleyr Mar. 15, 1887 652,756 Deming July 3, 1900 661,143 Grasser Nov. 6, 1900 665,865 Baker Jan. 15, 1901 1,320,910 Perry Nov. 4, 1919 1,550,126 Tompkins Aug. 18, 1925 1,699,848 Lower et al Jan. 22, 1929 1,785,941. Eppensteiner Dec. 23, 1930 2,023,957 Hewgill Dec. 10, 1935 2,093,286 'Millspaugh Sept. 14, 1937 2,130,726 Ardelt Sept. 20, 1938 2,266,831 Tegarty Dec. 23, 1941 FOREIGN PATENTS Number Country Date 174,258 Great Britain Jan. 26, 1922 15,435 Australia May 24, 1929 V1928 177,519 Canada June 12, 1917

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