USRE17220E - Casting process and apparatus - Google Patents

Description

FeB; 19,1929.

R. F. woon CASTING PROCESS AND APPARATUS Original Filed Aug. 7. 1919 5 Sheets-Sheet 1 Feb. 19, 1929. A

' R. F. WOQD cAs'rme PROCESS AND APPARATUS Original Filed Aug. 7. 1919 5 Sheets-Sheet INVENTOR 5050f F 5/001 A'ITDR Yd Feb. 19, 1929. Re. 17,220

R. F. WOOD CASTING PRocESs AND APPARATUS Original Filed Aug. 7. 1919 5 Sheets-Sheet 3 INVENTOR Feb. 19,1929.

R. F. WOOD (TASTING PROCESS AND APPARATUS Original Filed Au;- 7. 1919 5 Sheets-Sheet 5 1NVENTOR\\ YFaberZ A [1 006] l l \i BY v m mazs Original No. 1, 88,780, dated April 14, 1925, Seria1 No. 315,892 filed August 7,1919. Application as reissue med May 16, 1927. Serial No. 191,901. :1

Reissu d Feb. 19,1929.

UNITED STATES ROBERT E. woon, 0E NEWARK, NEW JERSEY, assrenoa cro THE rArEa arExr'rLE MACHINERY COMPANY, OFSANDUSKY, OHIO, A-coRroRA'rmN or 01110.

CASTING PROCESS AND APPARATUS My invention relates to an improved process and apparatus for making castings of metal or of other-material and is particularly applicable to the making of hollow or tubular objects having non-cylindrical bores.

The object of my invention is the provision of a new and useful casting process. ()ther objects of my invention are; the provision of apparatussuitable for carrying out my. process; the provision of a process whereby hollow or tubular castings may be produced without the use of cores of sand or of other solid material; the provision of a process for producing a casting having a paraboloidal void, from which casting there may he made, by machining in a lathe or by.

other process of manufacture, a hollowaor tubular. article whose bore or void,. though not itself paraboloidal in shape, may be more or less} approximated in shape and size by the paraboloidal void of the casting; the provision of a process for producing castings for submarine periscope tubes and cones and the provision of a centrifugal process whereby a hollow or void of predetermined p-arab oloi dal shape may.be formed'in casting an object without theuse of solid. core,

'productionof submarineperiscope tubes and cones in which it is necessary thatone end be of smaller diameter than theother, and

that the metal be of uniformly good quality free fromblow holesg internal strains and,

suchother imperfections as are common to tnhesfmade by certain other methods of casting and manufacture. My invention: may

also be used for casting hollow projectile shells. I'do not limit the uses to whichm invention be put as numerouslapplications will occur to those skilled in the various arts in which hollow or tubular parts'are used. In the accompanying drawingsI have illustrated one form" of apparatus which has proved suitable for carrying out my process- In the drawings, Fig. 1 is a side ellevation. of a" casting "machine suitable[for carrying out my process; 1 n p Fig.2 is a'vertical fragmentary cross section through the upper endof'the mold on line 11-11 of'Fig. 3; p 7

Fig. 2 is a similarview ofthe otherend of the mold showingfits stop-off plate; Fig. 3 is an endf'el'evation of" the front or axis while in: this inclined. position.

making a metal castingt'hegmolten metal is Fig. 1;

or is t hand end of. the machine shown in Fig. .1

ing the theory of my process;

Figs. 9ito ll anclusiveare sections through p'araboloids generatedxby parabolas of difierent equations and;

Figs. 18, I19 and 20. are longitudinal cross= sections of various castings suitablefor maklng submarlne perlscope tubes. I

In carrying out my process I introduce a l quantity of molten metal or of other solidifiable material into a hollow mold of metal 1 or of suitable refractory material, :the quan-.

tity of molten metal. being insuificientto-fill the mold. The Inoldis preferably first in,

clined so that, its axis makes a knownuangle with the horizontal, and is given ia rapid:

rotating motion of known .speedaboutits introducedintogt-he mold preferably whileit is rotating. .Undenthe. action of centrifugal? force and of, gravity -the'metal flows and My invention is particularly useful in' the tation or at different angles of inclinationof the axis of the mold, or both,- bores or voids of difierent shapes are formed in the molten metal. I have, discovered and demonstrated, 1

however,= that the. shape of the hollow or void formed in the liquid or molten material is independentof the shape ofthe mold and is always a paraboloidpf revolution. or some part thereof, the shape and dimensions of which are determined the size'of the mold,

its speed. ofrotation, the. angle of inclination of the axis of rotation and-,thequantity of metal in the mold. I have proved mathematicallyand have demonstrated in practice by making. numerous castings that there are a definitely. filxed relations between these factors; that the shape and dimensions ofthe hollow orloore in a;casting mayi becalculated in advance for any givensize of'mold, speed of rotation angle of 1ncl1nat1on, and

quantity of metal; and that when the size of the mold and the essential dimensionsof the required holl'ow or bore are given, the

speed of rotation of. the mold, its angle of inclination, the quantity of metal to use and the'shape of bore that will result may be predetermined by calculation. I

It is to be understood that in these specifications the term inclined or inclination comprises any position other than horizontal up to and including ninet degrees where the axis of the mold would e vertical.

In carrying out my process, the s eed of rotation of the mold and the angle 0 its inclination, or both, may remain constant throughout the entire period of pouring, casting and solidifying, but I do not consider that this is essentialin all cases. It is evident that in order to produce a simple paraboloidal void of predetermined shape, the metal must be maintained in a state of equilibrium while it passes from the molten to the solid condition, and this state of equilibrium is by that time a Is to be used would boloidal shape of the which is sti most readily obtained, by keeping the speed of rotation and the angle of inclination constant. However, it is conceivable that there might arise conditions under which the process by which the rou h casting is subsequently to be treatedor t e purpose for which it be better served if the casting process were so controlled as to modify more or less the otherwise simple parabore of the casting. It is furthermore evident that if the speed or angle be changed at a moment when the process of solidification of the metal is as yet incomplete, the ortion of the metal which has ready become solidified will retain its position in spite of such change in speed or angle, while the portion of the metal 1 molten or semi-molten will flow or tend to flow in such away as to readjust itself to the new conditions, and, under them,

i to reacha new position and a new state'of 'equillbrium. In my experience witln the practical carrying out m process I have alread encountered con itions such as I have escri'bed, and I have encountered instances in which the subsequent processes of machining the casting in a'lathe were facilitated by having the otherwise simple paraboloidal shape of the bore of the casting modified in accordance with the foregoing. It is, therefore, conceivable that other instances also may arise in which the purposes or treatment, of the casting will be .better served by the modifications described or by other modifications similar thereto, and it is one of the advantages of my process that in practice it allows of such modifications and that the modifications admit, of control because the limits of their action and effects may be predetermined by calculation by means of the equations and formulas which I have derived or by others deducible therefrom. f With the purpose in view of making castings for submarine periscoge tubes and cones I first discovered by mat ematical calculations thatthe shape of the hollow or vold formed in liquid material rotating in equilibrium about an inclined axis is, that of a paraboloid of revolution such as is formed by the rotation about its own axis of a parabola the equation of which may be expressed in terms of the speed of rotation of the li uid and the angle of inclination of the axis 0 rotation. With this fact established I deduced certain other equations which establish the relations between the speed of rotation, the angle of inclination of the axis of rotation and the shape of the paraboloid formed, from which equations the requirements for producing any desired casting which it is possible to produce b my process can be determined. I have ca culated the shapes and dimensions of many castings by the nations which are herein given and have su s'equently made castings in strict accordance with the conditions'imposed by my calculations. I have found in every instance that the actual castingsproduced conformed with. remarkable trueness to my advance calculations. V

In Figs. 1, 2,.3 and 4 there is shown amachine which I have found suitable for carrying out my process. .In these figures of the drawings, 1 representsa revoluble metal pipe or tube which is provided with suitable bear-, ing collars 3, 4, located near its front and upper end 5. A tilting housing 6 which has trunnions 7 supportedin hearings in the sides of the station ry frame 8 is provided for the sup port of the tube 1 and its driving motor. Radial-thrust rollers 9 for rotatably supporting tube -1 are provided in'the tilting housing 6.

ployed for rotating the tube 1 and that any convenient means may be used for ascertainin and controlling the speed of rotation.

ear the rear end of the tube 1 which is also the lower end when the tube is tilted, is the stationary frame or guide 14 in which there is mounted and adapted to slide vertical ly a housing 15, which is provided with radial thrust rollers 16 upon which the tube 1 lo tates. i v

The uppermost rollers 9 and 16 have bearings in spring-held, adjustable boxes 17 and 18, the springs 19 and 20 serving to maintain the rollers with yielding pressure upon the rotating tube 1. The housing 15' is provided with trunnions 21 which are adapted to slide in slots 22 in the guides 14. Attached to the. trunnions 21 by pivoted "collars 23 are the cables 24-. which extend upwardly and are connected with a device 25 for raising and lowe'ring the rear end of the tube 1 in order to tilt the-tube to the desired angle. To give added rigidity and added accuracy of setting to a known angle, holes such as 26 may be drilled through the sides of the guides 14 and the rear housing 15 and in like-manner through the sides of the stationary frame 8' and the front housing 6 in such manner as to receive throu h-bolts such as 27 with nuts which,

when drawn tight, serve to secure the several parts of the construction in perfect alinement in their inclined position.

The tube 1 is either lined with refractory material such, for instance, as a sand mold of annular cross section or, preferably, as shown 1n Fig. 2, receives a pipe or tube v.28 having a.

refractory lining 29, the opening in the refractory liningbeing of the shape which it is desired to give to the exterior of the casting to be made therein... 1 i

The back or lower end .of the mold is formed by a stop-off plate or plug A shown in Fig. 2*, set at the desired distance from the front end of the mold so as to determinethe length of the casting and secured in place by a rod B that extends between it and yoke device 30. The frontv or upper end of the mold is formed by an annular disk or plate of metal 31 which is secured to the flanged end of-the tube 1 by means of bolts 32 and which may receive a lining or facing 33 of refractory material.

In the operation of the machine to produce a. casting by my process, the tube 1 has first inserted into it thepipe 28 with its refractory lining 29 which has been preheated to drive off the moisture that it may have contained. The tube 1 is then tilted to the proper angle for producing the desired casting, for instance, the angle at which the tube is shown in dotted lines at 34. The tube 1 with the pipe and its refractory lining are next brought to thedesired speed of rotationby means of the motor 12 or by any other means that. may be providedfor the purpose, the molten metal is then introduced through the opening 35, at the upper end of the moldand is disposed by centrifugal force andlg ayity into the shape which it is made to assume by these forces.

The rotation is preferably continued until the metal has solidified.

The mold as is then reihqvdffiomthe tube 1 and the castin afterwards removed from the mold. It is t en ready for .machining or other treatment, or for use in its rough condition. Another prepared mold. is then inserted in the tube andthe operation repeated. e Fig. 18 shows in longitudinal section. a

casting suitable for making the separate cone of a submarine periscope tube. In this figure the scale of the drawing parallelto the axis of the casting is made much smaller than the transverse scale for the purpose of illustra tion.

Fig. 19 shows in longitudinal section a casting suitable for making a submarine perior stop-ofi' end 38 is of another formed in the casting shown in Fig. 20 is the resulting composite of a plurality of successively formed paraboloids.

In Flg. 18 the refractory material of the mold is indicated at 39 by the area'shaded in dotted section lines; the casting itself 40 is indicated in section; theparaboloidal bore formed inthe process of casting is indicated bythebou'ndarylines 41"anid the outline of the finished'cone'which is machined all over is indicated in dotted lines at 42. 1

In Fig. 19 the material o'f the refractory mold is shown in dotted section lines at 43; the casting itself is indicated in section at 44; the paraboloidal void in the casting is indicated by the boundary lines 45 and the finished tube is indicated in dotted lines at 46.

In Fig. 20 the material of the refractory mold is indicated in dotted section lines at 47 the casting is indicated in section at 48; the upper portion of the paraboloidal void is indicated by the boundary lines 49 extending between the up er end 36 and the point 37 of the casting; l fe portion of the paraboloidcorresponding to theboundary lines 49 which would be formed evcept for the changing of the angle of inclination or of the speed of rotationor both during the process of casting is shown by the dotted extension 50 of lines 49 the virtual vertex of the paraboloid corresponding to the boundary 49, 50 is indicated at 51; the paraboloidal void formed after changing the angle of inclination or the speed of rotation, or both, is indicated by the boundary lines 52 extending from the point 37 to the vertex 53 and the finished tube to be machined out of the castin" 48 is shown in dotted lines at 54.

in Figs. 19 and 20 the longitudinal scale of the drawings is made much smaller than clination of its axisor the proper angle of inclination of the mold for any given speed of rotation, and the quantity of metal required to form the casting.

The void formed in liquid material rotating about an inclined axis in a'mold or receptacle having. its

bottom closed and its top closed as shown in Fig. 2 to within a sufficient radial distance from the axis of rotation to prevent the egress of the liquid is as follows:

Referring to Fig. 5, let A be any particle of molten metal or. of other liquid material in the inclined mold, the angle of inclination of the axis Y of the mold with the horizontal being S. Let theweight of the particle be G pounds. Let P and Q be the components of G in directions respectively parallel to. and at right angles to the axis of the mold and in a vertical plane through the axis. Under these conditions P=G sin S. The force Q may be disregarded in the present consideration because when the mold an the particle A revolve, the action of Q toward the mold becomes in each revolution alternately and equally positive and negative so that Q, compensates itself relative to the mold and does not affect the position which the surface of the molten metal will assume within the mold. It may be noted here that Q is the force which determines the minimum speed at which the mold must be revolved in order to hold the metal against the sides of the mold. Considering the particle A, it will readily be understood thatwhen A and the mold are revolving, the force Q, must be overcome by the centrifugal force when A is at the highest point of its revolution in order that the particle may be prevented from falling away from the upper side of the mold.

t us now consider the forces which act upon the particle A after equilibrium has been established and while the mold and A are rotated at constant speed about the inclined axis of the mold. A diagram of these forces is shown in Fig. 6.

Referring to Fig. 6, as the machine and the particle A revolve, A is acted upon by two forces which together determine the shape assumed by the surface of the molten metal.

. These two forces are P and the centrifugal force C. Their resultant is the force N whose direction, if the particle A be at a point in the the proper speed of rota- I tion of the mold for any given angle of inproof of the shape of th e hollow or known and without surface of the metal, must be normal to the surface at that point. Therefore, a -line drawn through the point A at right angles to the direction of the force N, and in the plane determined'by the point A and the axis of rotation, as shown in Fig. 6, must be a tangent to the curve that is formed by the surface of the metal. This tangent will make an an le T with the direction of the axis of the mol From the construction, r

. P tan T-- I As 0 is the centrifugal force,

where M is the mass of the particle A, '0 its velocity in feet per rotation in feet. tion for the value p and 0 found above gives e Sill 's G i sin s.

Substituting in the equatan T= L M M0 r Since or the acceleration due to gravity,

' an T=-";#

g r sin S g sin'S aTa ma; (1)

(1) may be found the angle or any inclination andany speed, butonly bore when such are determining where those radii will be formed. I

In Fig. 7, let the axis of rotation be the axis Y, and X be its coordinate axis. figure the point A is taken at (m, y), angles S and T are the same as before. Fig. 6, the straight line drawn through (:v,y) is, under the conditions, the curve that forms the surface'of the metal, consequently the inclination of this line to the axis X must be the slope of the curve at (my), and that-slope is equal to the tangent of the angle H.

From the construction, 7"-?m.

From Equation T f for individual radii of the and the second and r the radius of of ten T the values of P Inthis As in Inn a, tangent to shown he represented The following relation Y The difierential equation of nowbe written and proves that the surface of the molten metal rotating about an inclined axis is a paraboloid of revolution such as would be formed by the rotation about itsaxis of the parabola of the above equation, (2)

From equation, (2), the curve for any particular case may be put into the form y=aa1 the constant, a being equal to then for any asslgned'value ofB or S a corresponding value must exist for Sor R. It is evident, therefore, that theequationof the curve maybe made independent of both R and S, provided that other determining factors aregiven. This maybe done as follows:

Referring to Fig. S'Qlet'the'parabOla there he equation y =a m two points (00 '11) this parabola 1 a i ,y. f=ee ?1e=. 1f By subtraction, s

say r, and T in the bore or void of the casting,

at two different points along its axis and ':l/ is the axial distance between them.

If L= y y, the last equation may be re- Equation (3) is the equation of theparab 01a in terms of any two radii of the bore of the casting and the, axial distancei betweenthose radii, and is theGQUEtlOIlQIIlOShCOIIl- L P v th s, the-follow ng volume formula may be monly ,used' ,to determine the" shape of the bore. Equations (2) and, (3) are the main equations for the solution of the problems of" my the curve may ld ftrue. for any g located on Now m, and 00 are identical to two radii;

depends only upon the known factors or conditions which are given, fromwhich to find the remaining conditions necessary to successfully produce the casting in practice.

Derived equations showing relations between speed and inclination for any given parabola.

Solving (2) for wehave R=- 1.2755 li (4) This may be conveniently written R==1.2755,/a Sln s (5) Remembering also the value of (a) which is used in Equation (3) we may write Equation (4) gives the revolutions per sec- 0nd in terms of the sine of the angle of inchnation, any radius of the bore expressed in feet, and the axial distance in feet of that radius from the vertex of the parabola Equation (5) gives the revolutions per second in terms of the sine of the angle of inclination and the coefficient a of m in the equation of the parabola, and is the equation most commonly used to obtain speed and-angle relations W p 1 Equation (6) gives the revolutions per second in terms of the sine of-the angle of inclination, any tworadii' of the bore expressed a in feet, and thea-xial distance in feetbetween those radii:

Transposing (4), (5) and (6), gives the angleinterms -of the revolutions per second, the other conditionscorresponding exactly to thoseenumerated above. The corresponding values for the-anglesfollow:

. R x .=s1n- (O.61463 y (-7) the mold. The volume-of the mold may be found by addingtogether the volumes of its "arts; If the'frustum'ofa cone enters into used '2' h sew bases, his the altitude'ofthe frustum and 4 d, and

- these equations to 1 the required tube d, are the diameters of the two bases respectively. n

The volume of the voidwill be the volume of so much of the paraboloid as is contained between the front and back ends of the mold. The position of the vertex of the paraboloid relative to the back end of the mold is preferably to be first known and may be found by makingsthe proper substitutions in Equation (2) or quation 3) or, better, directly in the equation y=aw after (a) is known.

If V represents the volume of the paraboloid between the front and back ends of the mold when the vertex lies behind the back end of the mold, then 1 .5 O Y Z 6 12 -101 If the vertex lies within the mold, y, becomes zero and To illustrate the practical application of the determination of the conditions that should be observed in maki a casting by'my process, I herein show the 'solution of a concrete case such as might occur in ractice. I

eferring to Fig. 19 of the drawings, let it be reglnired to provide acasting from which to m e a submarine Periscope tube such as is shown in dotted outline and longitudinal section at 46. Let the finished dimensions of inches at m, and 6% inches at n and over all length 14 feet, for 10 feet of which, from o to n, the tube is the remaining 4 feet, from n to m, uniformly tapered; wall thickness, inch. In order to produce a finished tube conforming to these measurements, let there be required a rough casting such as is indicated at 44 in Fi 19, of the following dimensions: outside iameter 4 4 inches at p and m, and 6% inches at n, o and 9; inside diameter 2% -inches at p,

and 5 inches at g; over-all length 14 feet this 6 inches, of which 14 feet is the length of the finished casting, 2 inches an extra allowance in length at the small end p, and 4 inches an extra allowance in, length at the large end 9.

Examination of the data discloses that for casting the measurements given are reucible to the requirements of Equation (3), viz, two radii of the bore and the axial distance between them. Expressed in feet the radii of the desired inside diameters, 2% and 5 4 inches res ectively, will be w,=0.1146 ft and w '=0.218 ft., and the length L of the casting equals 14.5 ft. Introducing these values into equation (3) be: outside diameter 4 to be cylindrical, and for.

which, if revolved about its axis would enerate a paraboloid, part of which would be of the shape and size of the bore which would be obtained in the rou h casting.

It now remains to fl x the sped and angle relations, which may be done through either Equation ('5) or (8). If the angle of inclination be assigned, Equation (5) will determine the speed of rotation while if the speed of rotation be assigned, Equation (8) will determine the angle of inclination. In either case the value of a 418, as found above, will also be used. Accordingly if the assigned angle of inclination be 10 degrees, its sine, 0.1736, and the value 418, found for a, may be substituted in Equation (5), yielding R=,1.275 51/418X0.1736, whence R, the revolutions per second equals 10.87 and the revolutions per minute equals Whence S=827, which would be the mold inclination corresponding to a speed of rotation of 600 revolutions per minute.

To determine the volume of the mold, the

volume of the parts may be determined sepor S sin"0.14704 arately and then added together:

- I Cubic inches. 11 to m (cylinder) 28 m to n (frustum of cone) .1160 nto g (cylinder) 4437 Total volume of'mold 5625 To'determine the volume of the bore of the casting, Equation (11) may be used. The values of y, and y, may be found by substituting back into y=418 as the values bf w, and :27, already used, 0.1146 and 0.2187 respectively. Accordingly,

the speed of rotation cor- It may be noted here that y,, or 5.5 feet is, v I

the distance from the back or smaller end of the casting to the virtual vertex of the paraboloid, as from p to'55 in Fig. 19, and that having found it, the value of 3 may be determined by addin to it L, or 14.5 feet, giving 20.0 feet, whic is identical, as it should be, to the value obtained by substitution,

From these values, and" the value of a, by Equation (11).,

ent:

mold revolubly tained by point, obviously,

' and said housing.

4. In apparatus of the class described, a

This is in cubic feet, and is cubic inches. I

To determine the quantity of metal in the rough casting,its volume may first be found, and then its weight. Its volume may be obfinding the diiference between the volumes of themold and of the bore, 5625 and 2401-cubic inches respectively, or 3224 cubic inches. If the weight per cubic inch of equal to 2401 the metal employed be 0.30pound, theweight of the casting would then be 3224 times 0.30 pound, or 967 pounds. f

the specific gravity of In using my process the material cerns the relations of the bore of the casting. num, lead, or any other substance be used, 1s, therefore, a matter of indifference everywhere in the computations, except only in theoperation of deducing the weightof-the casting from the value found for its volume, at which a} correct value for the weight per unit of substance should be used.

The proof that these relations and the; equations representing them are thus independent of the specific gravityof the material is seen in the derivation of Equation (1) where the mass, M, of the particle, has been shown to disappear.

Having thus described my invention, I claim and desire 1. In apparatus and: the like having parabolo'idal hollow bores, a mold the interior of which has the desired form of the exterior of the casting, means for rotating said mold at the requisite speed and means for giving to the axis of: said mold the requisiteinclination to produce within the casting a cavity of the desired paraboloidal form. f r

,3. In apparatus for casting metal tubes and the like having paraboloidal hollow bores formed under the joint action of centrifugal force and gravity, a revoluble mold, a support therefor, bearingsdgr said revoluble mold carried by said'support, and means for revolvin said mold, the axis of rotation of said mol being inclined to thehorizontal.

3. In apparatus of the class described, a mounted in a tilting housing, a motor mounted on said tilting housing, driving connections between said motor and said mold, and means for tilting said mold mold revolubly mounted in a housing, a support for said housing, a. motor mounted on said housing in driving connection with said mold, and means for tilting said mold and said housing.

5. In apparatus of theclass described two stationary supports, a tilting housing mountfromw'hich acasting is to be made is'a matter of i" difference so far as conbetween the speed of rotation, the angle of inclination, andthe shapef Whether alumi i to secure by Letters Pat-' for casting metal tubes ed on one of said supports, a vertically adjustable tilting housing mounted upon the other ofsaid supports, and a revoluble mold carried in bearings in said housings.

6. In apparatus of the class described, a stationary support, a tilting housing mounted on said supportfa vertically adjustable tilting housing, a ,revoluble mold carried in bearings in said housings, and means for rotating said mold. i

7. In apparatus of the class described, a stationary'support, a tilting housing mounted on said support, a vertically adjustable tilting housing, a revoluble mold carried in hearings in said housing, means for rotating said mold about its axis and means for inclining said'axis of said mold. stationary support, a tilting housing mounted upon said support, a vertically adjustable tiltinghousing, arevoluble mold car- 8. In apparatus of the class descrbed, a

ricd in bearlngs in said housings, means for rotating said mold about its axis, means for inclining said axis of said mold, and means for securing said vertically adjustable housing in its adjusted position.

9. In apparatus f the class described, a

revoluble mold, two bearings for said mold,

one of said bearings being mounted for tilt:

ing'about an axistransverse to the axis of rotation of said mold and the othenof said bearings being mounted for tilting about an axis transverse to the axis of rotation of said mold, and means for vertically adjusting one of said bearings. a

10. In apparatus of the class described, a revoluble mold, two bearings for said mold, both. ofsaid bearings beingprovided with trunnions having their axes transverse to the axis of rotation of said mold, one of said terial which consists of placing a quantity 3 of said fluid material in a hollow mold, the volume of said fluid material being insufi'icient to fill said mold, imparting a rotating movement to the fluid material in said mold whereby a paraboloidal void is formed in said material about the axis of rotation thereof, continuing the rotation of the material in this position until a portion-of the material is solidified, then inclining the axis of rotation from the position it tained and continuing the rotation of the material until another portion of it has solidified; i

as thus far mainternal cavity of said shell mold coinciding, said 13. The processof forming hollow tubular objects which consists of imparting to a quantity of solidifiable fluid material a rapid so that it forms within such limits a hollow shell of non-uniform inside diameter, the inbeing a parabolold symmetrical with the axis of rotation,- continuing the rotation of the material about said inclined tation'of. the material until another portion of it is solidified. V I The process of'forming hollow tubular objects which consists of imparting to a quantity of solidifiable fluid material a rapid rotatin movement about an axis,c onfining the s ai material within radi al limits but uniform diameter, the" internal cavity of said shell being a paraboloid symmetrical with the axis of rotation, continuing said rotation at a constant speed until a portion of said material is solidified, then changing the speed of rotation andcontinuing it at said changed speed until another portion of the material has solidified, 15. The method of making periscope tubes or the like of cast metal which consists of centrifugally casting a long paraboloidal void in a metal cylinder the contour of the longitudinal cross section of said void approximatingthe desired contour of the finished tube with allowance for internal finish, and subsequently finishing the inner surace to the desired dimensions and contour. 16. I casting machine, a shaft, bearings supporting said shaft, saidbearings being adjustable to incline the axis'of said in said shaft," the axis of said shaft and said shaft and said mold means for said shaft.

' ta'table hollow shaft pivoted shaft, a hollow mold being open'at their upper ends, and driving a centrifugal casting machine, a revoluble hollow shaft, bearings supporting said shaft, said bearings being adjustable to incline the axis of said shaft, a hollow mold in said shaft, the axis of said shaft and said mold coincidin said shaft and said mold being open'at t eir upper ends, and driving means for said shaft operable to drive the same in any of its adjusted positions.

' 18. In a centrifugal castin or tilting movement on an axis transverse thereto and adjacent one end thereof, a housing arranged to tilt with said shaft, a motor on said housing operatively connected and a hollow mold in said shaft adapted to receive molten metal and to form a casting therein.

19. In a centrifugal-casting machine, a ro tatable hollow shaft pivoted for jacent the other end of the pivoted shaft for raisin and lowering the shaft on its pivot.

20. n a centrifugal castin machine, a rotatable hollow shaft pivoted or tilting movement on an axis transverse thereto andad:

and. means adjacent the a casting therein, other end of the and lowering the shaft on its'pivot.

witness whereof, I have hereunto set day of April, 1927.

my hand this 29th J ROBERT F. 'WOOD.

to rotate the shaft,-

plvoted shaft for. raising machine, a ro-

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