US1549124A - Method of and apparatus for centrifugal casting - Google Patents

Description

Aug. 11, 1925.

1,549,124 F. ARENS METHOD OF AND APPARATUsFoR CENTRIFUGAL CASTING Filed Dec, 5. 1923 2 Sheets-Sheet l I INVENTOR Aug. 11, 1925;

.F. ARENS METHOD OF AND APPARATUS FOR CENTRIFUGAL CASTING Filed Dec. 5. 1923 2 Sheets-Sheet 2 Q mu -m mh.

QR ww Patented Aug. 11, 1925. v

FERNANDO ARENS', or sac rau'no, BRAZIL.

METHOD OF AND APPARATUSI'OR CENTRIFUGAL CASTING.

Application filed December 5, 1923. Serial No. 678,770.

To all whom it may concern:

Be it known that I, FERNANDO ARENs, a citizen of Brazil, residing at Sao Paulo, Brazil, have invented certain new and useful Improvements in Methods of and Apparatus for Centrifugal Casting, of which the following is a specification.

This invention relates to improvements in molds for casting pipe and the like, and has special reference to a rotary castin mold, particularly for elongated or sleeveike articles, and the method of making and operating the same. I

It has been proposed to form pipe by what is known as the rotary casting process wherein the molten, ferrous metal used is spirally fed or spilled into a metallic mold, the body of which has heretofore been actually or substantially of solid or unitary construction. In thus casting the pipe it has been found desirable, for certain kinds of best ferrous metal pipe, to chill the casting and thereafter subject the same to a super-heating treatment for about one minute during which the pipe is brought to a temperature of approximately 1800 F. This super-heating has been found actually to result in immediate conversion of all the combined carbon into graphitic carbon, thus producing an iron of the soft gray type embodying great strength and toughness and resistance to corrosion. For the purpose of chilling the pipe it has been customary to cool the mold by circulation of water about the same, sometimes under high pressure, to additionally increase the refrigerating effect.

The molds heretofore used in theabove process have been made of the most expensive steel alloys, but notwithstanding this fact have repeatedly proven to be inefiicient, due to the fact that they have sooner or later cracked. This difliculty in the process has, up to the present time, been rather ,serious from the economical and commercial The reason for this breakage standpoints. or crackage of .the molds becomes readily apparent when it is realized that during the casting process the interior walls or peripheries of the solid molds are heated to a temperature, from the molten metal of which the molds are formed, of approximately 3000 F., while the exterior walls thereof are being cooled or refrigerated, thus creating a simultaneous expansion and contraction which produces an undue stress upon the body of the mold. In addition to this detrimental effect upon the mold, it will be realized that a transverse or spiral stress is 1mparted thereto, due to the spiral method of feeding the molten metal throughout the length, sometimes 16 feet, of the mold, requiring a period of from fifteen to twentyone seconds for the iron to be applied to the full length of the mold. i

The present invention is designed primarily to overcome the objections above pointed out and accordingly has for one of its objects the provision of an improved mold in which the possibility of breakage or fracture, due to heat expansion and contraction, is greatly minimized, if not absolutely prevented.

According to the invention, there is provided a mold the body of which is made of spaced component sections havin interposed therebetween a heat conducting me dium, which not only facilitates or minimizes, as desired, the chilling of the casting, but also permits of independent movements between said sections occasioned by the expansion and contraction thereof without imparting to said sections the stress or strain which inevitably results when using a solid mold body.

Another object is to interpose between the sections of the mold a layer of material the nature of which is such that its character is changed by the application of heat thereto to permit of relatively free movements of said sections with respect to said layer and to each other.

A further object is to control the expansion of one of the sections of the mold relative to the other by means which offers a yielding resistance to such expansion.

The invention further contemplates the provision of a method of making and operating a casting mold wherein the sections thereof are maintained in'spaced relation and a filler is introduced in the space between said sections which will form a highly conductive medium for heat and which will not only uniformly control the distribution and conduction of heat in and through said space, but will also facilitate the disslpation of heat.

A still further object is to prevent the formation of air pockets or spaces in the filler medium between the sections of the mold by exerting a pressure on said medium during the casting operation.

Again, the invention provides a mold the initial cost of which is reduced to a minimum by reason of the fact that, due to the absence of stresson the outer. section thereof, an inferior grade of material may be utilized in making said section.

And still again, the invention provides a method of making one or both of the said sections at considerably smaller cost and very quickly although a superior grade of material may be utilized for their making.

The above and other objects will appear more clearly from the following detail description when taken in connection with the accompanying drawings, which illustrate preferred embodiments of the inventive idea.

In the drawings- Fig. '1 is, rather diagrammatically, a longitudinal section through a rotary casting mold constructed in accordance with the invention;

Fig. 2 is a transverse section therethrough;

Fig. 3 is a longitudinal section of the mold body;

Fig. 4 is an end elevation thereof;

Fig. 5 is an enlarged fragmentary transverse section through the mold body showing the mechanism for controlling the pressure on the filler medium which is introduced between the sections ofthe mold;

Fig. 6 is a fragmentary plan view of the mechanism shown in Fig. 5;

Fig. 7 is an enlarged elevation of the means for controlling the. expansion of one of the sections of the mold; and

Fig. 8 is a fragmentary enlarged detail view.

In its preferred form the mold of the present inventioncomprises a receptacle 10,

which may be of a well known construction and in which the mold body, including the essential features of this invention, is rotatably supported below its horizontal axis by the rollers 11 mounted upon shafts 12, one of which may be driven in any preferred manner (not shown) well known in the art to impart rotation to the mold body. The receptacle 10 is designed to contain a cooling liquid, such as water, which may be constantly circulated through the receptacle, as is commonly done in the art of rotary casting and in which the mold body is partially immersed so that the outer surface of said body will receive the desired refrigerating effect of the water.

In accordance with the present invention the mold body comprises the outer and inner cylindrical sections 13 and 14 made of any suitable material and arranged one within the other in spaced relation, corresponding ends of said sections'being outwardly flared, as indicated at 15, to form what is commonlyknown as the bell end of the mold. The sections 13 and 14 are positioned in spaced relation with respect to each other by means of a plurality of set screws 16 arranged about the body of the mold and extending through the outer section 13 and into engagement with the outer periphery of the inner section 14.

In assembling the mold body the space between the sections 13 and 14 is closed at one end by a plate 17 secured to the sections by suitable fastening means, such as bolts 18. The body is then heated and placed in a vertical position, with the plate 17 removed and the plate 20 lowermost, and a metal filler 19, such as lead, in a molten state, is poured into said space to completely fill the same. Following this operation the opposite end of the mold body into which the filler 19 is introduced is closed by means of plate 17. Plate 20 is yieldably held in position by a plurality of bolts 21 having interposed between the heads thereof and the adjacent face of the plate 20 a plurality of solid and split resilient washers 22 and 23 respectively, arranged in alternating relation, as shown in Fig. 7. The inner face of the plate 20'is preferably provided with an annular shoulder 24 within which fits the adjacent end of the inner section 14 of the'mold body. By providing the resilient washers, it will be apparent that a yielding resistance is offered to the plate 20 which has a tendency to move outwardlyin an endwise direction with respect to the mold body when the inner section 14 thereof is expanded by the heat of the molten metal poured into said section when a casting is being formed, and then the required additions to the element 19 as a layer-structure are automatically made by devices 28, 29, 30 hereinafter described.

It is highly desirable that the filling ele- U .quick and uniform transmission of the chilling or refrigerating effect of the outer section which is rotating in the water in the receptacle 10, thereby properly chilling the casting as it is being formed. Due to the 'fact thataspace is provided between the sections of the mold and a material introduced into said space which is capable of being fused, it will be obvious that the expansion of the inner section 14 and contrac tion of the outer section 13 will be balanced and the filler medium will not only act thermally, as a heat conductor, and resiliently, as an annular cushion, but will permit said sections to expand and contract independently of each other so that no undue stress on said sections will'be occasioned during the casting operation. It has been found in actual tests that, by reason of this independent contraction and expansion of the molds, a number of castings can be produced greatly in excess of the highest number of castings made with any one of several mold bodies of a unitary construction. Furthermore, the mold constructed in accordance with the invention and used in these experimental tests has withstood all of the casting operations made without giving any indication of a fracture or cracking. Additionally, it is pointed out that the outer, larger section of this mold body used in said tests has been made of a material inferior in grade, or at least in cost, as compared with the solid mold bodies which have been previously used.

It has been found in practice to be desirable in order that the filler medium 19 maintain a uniform degree of conductivity, to exert a constant pressure upon said medium while the mold body is. being rotated and a casting being formed. This pressure, in accordance with the invention, is controlled by the centrifugal force generated by the rotation of the mold body. To this end, the outer section 13 of the mold is provided, in addition to the provision at suitable intervals of a plurality of reservoir domes or recesses 25 for the filler medium 19, with a plurality of recesses 25 in its outer periphery (see Figs. 5 and 6) extending partially through the section and communicating with the space between the sec-- tions 13 and 14 through lateral passages 26,

preferably having constricted inner ends and into which the filler medium is poured in a molten state into said space between the sections. Mounted in suitable hearings in each of the recesses 25 is atransverse shaft 2'] carrying a pair of-rocker arms 28 thereon, opposite ends of which support the weights 29. At the end of each arm 28 opposite that carrying the Weight 29, is pivoted one end of a plunger 30, the opposite end of which extends into the outer end of an adjacent passage 26. By this arrange ment it will be apparent that as the mold body is rotated the centrifugal force created by such rotation will throw theweights 29 outwardly and thereby rock the arms 28 about the shaft causing the plungers 30 to move inwardly into the passages 26 and thus exert a pressure upon the filler 19 which has been fused by the introduction into the mold of the molten metal to be cast. In this manner all possibility of air spaces vor pockets being formed by the fusing ofv the filler 19 will be precluded and a uniform distribution of heat created in the casting operation will be effected.

As shown most clearly in Fig. 8, the outer the space between the sections and beyond the annular flange 31, said flange is provided with packing rings 32, as ordinary metal piston rings, forming a tight joint between the sections. With this construction the filler 19 may be introduced into the space between the sections from the opposite end of the mold body as will readily be un-' derstood, that is, with the plate 17 removed and the plate 20 attached and with the mold body standing vertical and the latter plate lowermost.

I have found that a mold embodying my invention as above described may expeditiously and cheaply be made in the following manner: I

I The outer section 13 may be made of cast iron or practically any kind of metal and by anykind of process including casting.

The inner section, however, is preferably made by centrifugal casting, according to the principle of operation involved in this invention, on a mold the inner surface of which corresponds to the outer surface of the inner section 14 to be produced.

By this method the cost of a mold body embodying the invention is only a fraction of the cost of a unitary mold of nickelsteel material heretofore extensively used in the art.

I claim:

1. In a rotary casting mold, a body including an outer and an inner section defining an interspace permitting of independent expansion and contraction of the sections and means confined in the intersaid sections.

2. In a rotary casting mold, a body including inner and outer sections arranged in spaced relation, and heat conducting normally elastic means confined in the space between said sections permitting independent expansion and contraction of said sections.

3. In a rotary casting mold, a body including an inner and an outer section defining an int-erspace, metallic material till-- ing the interspace, the said material being liquid under heat conditions incident to casting operations and being confined under pressure. v v

4. In a rotary casting mold, a body including inner and outer sections arranged in spaced relation, a fusible material forming a layer in the space between said sections, and means for exerting a pressure on said material when the same is in fused condition.

' 5. In a rotary casting mold, a body including inner. and outersections arranged in spaced relation, a fusible material in the space between said sections, and means controlled by the rotation of said mold for exerting a pressure on said material when the same is in fused condition.

6. In a rotary casting mold, a body including inner and outer sections in spaced relation, a heat conducting fluid in the space between said sections, and means controlled by the rotation of the mold for exerting a. constant pressure on said fluid.

7. In a rotary casting mold, a body including inner and outer sections in spaced relation, a heat conducting fluid in the space between said sections, and means controlled by the rotation of said mold for exerting a. pressure on said fluid directly proportional to the speed of rotation of the mold.

8. In a rotary casting mold, a bodyincluding inner and outer sections-arranged in spaced relation, a fusible material in the space between said sections, and means controlled by the centrifugal force created during the rotation of said mold for exerting a pressure upon said material when the same is in fused condition.

9. In a rotary casting mold, a bodyincluding inner and outer .sections arranged in spaced relation, one of said sections having a passage therein communicating with the space, betweensaid sections, a heat conduct-- ing fluid in said space and passage, and means'movable in said passage and controlled by rotation of said mold to exert a pressure on said fluid.

10. In a rotary casting mold, a body including inner and outer sections arranged in spaced relation, one of said sections having a passage therein communicating with the space between said sections, a heat conducting fluid in said space and passage, a plunger movable in said passage, and means connected to said plunger and actuated by the rotation of said mold for forcing said plunger inwardly into said passage to exert a pressure on said fluid. V

11. In a rotary casting mold, a body including inner and outer sections having a space therebetween permitting of independent expansion and contraction of*said sections, and resilient means tending to maintain the sections in a predetermined normal relationship, said means comprising essentially a heat conductive medium fluid under normal conditions of operation and means for controlling the density of the fluid.

12: In a rotary casting mold, a body including an inner and an outer section defining an interspace, a heat conducting medium in the interspace, fluid under normal operating conditions, and pressure means operative to vary the pressure upon the fluid as a function of the speed of the mold.

13. In a rotary casting mold, a body including an inner and an outer section defining an interspace, a heat conductive medium in the interspace, fluid under normal operating conditions, pressure means acting upon the said medium and centrifugal means controlling. the said pressure means.

14. In a rotary casting mold, a body including an inner and an outer section defining an interspace, a fluid confined in the interspace and means for yieldingly exerting pressure upon the fluid.

15. In a rotary casting mold, a-body including inner and outer sections having a space therebetween permitting of independent expansion and contraction of said sections, an end plate carried by said body and engageable by a section of said mold when the same expands, and means offering a yielding resistance to said plate when the same is moved by the expansion of said section.

16. In a rotary casting mold, a body in cluding inner and outer sections having a space therebetween permitting of independent expansion and contraction of said sections, a heat conducting element in said space, and yieldable means offering a resistance to relative movement due to the expansion of one of said sections.

17. In the art of rotary casting, the method of distributing the heat transferred from the molten metal to the casting mold, which method consists in maintaining a body of molten metal in contact with .the outer. walls of a casting mold.

18. In the art of rotary casting, the method of distributing the heat transferred from the molten metal to the casting mold, which method consists in maintaining a fluid medium of good heat-conducting quality under pressure in contact with the outer walls of a casting mold.

19. In the art of rotary casting, the method of distributing the heat transferred from the molten metal to the casting mold, which consists in maintaining a body of molten metal under pressure in contact with the outer walls of the casting mold.

20. In the art of rotary casting, the method of dissipating-heat transferred from the molten metal to the casting mold, which method consists in maintaining a fluid medium of good heat-conducting quality in contact with the outer walls of a casting mold and maintaining a coolin' medium in heat-transfer relation with the uid medium.

21. In the art of rotary casting, the method of dissipating heat transferred from the molten metal to the casting mold, which method. consists in maintaining a fluid medium of good.heat-conducting quality under pressure in contact With the outer Walls of a casting mold and maintaining a cooling medium in heat-transfer relation with the fluid medium.

22. In the, art of rotary casting,-the method of distributing heat transferred from the molten metal to the casting mold, which method consists in maintaining a metal having a low point of fusion in fluid contact with the outer walls of a casting mold and maintaining a cooling medium in ing a low point of fusion under pressure in fluid contact with the outer walls of a cast ing mold and maintaining a cooling medium in heat-transfer relation with the metal surrounding the casting mold.

Iii-testimony whereof, I affix my signature.

FERNANDO AREN S.

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