US1963149A - Centrifugal pipe casting apparatus - Google Patents

Description

June 19, 19-34. N, F. s. RUSSELL ET AL 1,963,149

CENTRIFUGAL PIPE CASTING APPARATUS Filed June 6, 1933 Jwuewtou [1 6: fiwssell ?Mrman Eek/2M dimge 3 w .l M I My Patented June 19, 1934 963,149 CENTRIFUGAL PIPE CASTING APPARATUS Norman F. 8. Russell and Frederick G; Langenhm Edlewater Park,

N. 1., asslgnors to United States Pipe and Foundry Company, Burlington, N. 1., a corporation of New Jersey Application June 6, 1933, Serial No. 674,505

2 Claims.

Our invention relates to pipe casting apparatus of the type in which a rotatable pipe mold having a cylindrical section is operatively combined with a retractable dumping trough for 5 molten metal which can be inserted in and withdrawn from the mold and which, when in operative position in the mold, is adapted to deliver its charge of molten metal along the entire length of the cylindrical portion of'the mold and the object of our, invention is to provide suitable means whereby the cylindrical surface of the pipe mold may be progressively coated with finely divided dry coating material in advance of the pouring of molten metal from the dump trough in contact with said coated surface. a

In our application filed October 19, 1932, Serial Number 638,480, we have described the method of coating the cylindrical surface of a pipe mold with finely divided dry coating material by means of a charged jet of a carrier-gas charged with such coating material and directed against the cylindrical surface of the mold so as to build up thereupon a coating which as applied consists not only in the particles of finely divided dry coating material but also of adsorbed films of gas surrounding the particles of coating material and particularly we have described in our said prior application a method in which the cylindrical portion of the pipe mold is progressively charged with molten metal through a relatively retractable runner delivering the molten metal to the rotating mold in the form of a helix and in which a jet of carrier gas is progressively directed against successive areas of the mold shortly before the so coated portions of the mold are contacted by the molten metal issuing from the run- I ner, the jet of carrier gas being progressively retracted through the cylindrical portion of the mold at substantially the same rate of retraction as that of the runner through which the molten metal is delivered and we have pointed out in our said application the importance of contacting the coated surface of the mold with molten metal as promptly as possible after the deposit of the coating upon the mold and the importance of so regulating .the supply of finely divided dry coating material delivered by the jet as to form a coating not substantially thicker than that the desired retardation in heat transfer from the molten metal to the mold; such a retardation, for example, as would prevent the formation of areas of chili upon the outer surfaceof. the casting. The avoidance of an excessive use of coating material and consequent excessive thickthicizncss which is found effective to bring about.

ness of the coating is important not only as affooting. the structure of the casting but also because we have found it to be true thatwith'increasing thickness of the coating there is increased liability for portions of the coatin'g'to'be- 00 come displaced, that is, to flake off or slip'in advance of the contact of molten metal overthe coated surface and to be displaced by contact with the stream of molten metal fed to, the, mold.

While, for reasons that we havestated'it 'is 66 advisable that the thickness of the coating deposited upon the mold should be kept as thin as will make it effective to prevent the formation of a chill, particularly with regard tothe quality of the casting produced and'while it is true that 10 thicker coatings are more liable to fracture than 1 thinner coatings, we have found that in using the dump trough method of charging a coated mold with molten metal there is less tendency for the occurrence of fractures and displacement of 15 the coating from the impact of the molten metal than is the casewhere the molten metal is supplied through a retracting runner and that in such a method of casting it is practical to use a considerably thicker coating than where the metal is supplied through a retracting runner. The special object which we have in view in our present invention isto provide an effective means for coating the cylindrical portion ofa pipe mold with finely divided dry coating material in .advance of the charging of molten metal into the pipe mold from a dump trough delivering its charge of molten metal substantially simultaneously along the entire length of the cylindrical portion of the mold and our invention consists, 00 generally speakingiin combining with a centrifugal pipe mold and a relatively retractable dump trough which is moved outward from the mold to be charged with molten metal and moved into the mold when chargedsc as to extend over the entire cylindrical portionv thereof and, when tilted, discharge its contents along the length of the cylindrical portion of the mold, a comparatively short jet noz'ale of a length in the direction of the axis of the mold which is only a fraction of. the length of the cylindrical portion of themold such jet nozzle being secured at the end oi-the dump trough and provided with means for'feeding to it a supply of carrier gas charged with finely divided dry coating material. It will be obvious that in an apparatus so constructed the jet nozzle moving in and out of the mold as the dump trough is inserted or retracted will be progressively directed against all portions of the rotating pipe mold and that a Jet of charged carrier 11o gas issuing from the nozzle during the in or out movement of the dump trough will deposit upon the rotating surface of the mold a helical band of the coating material and that with a proper regulation of the speed of travel of the dump trough this band will be so laid down as to have over-lapping edges in adjacent coils so as to build up uponthe surface of the mold a substantially uniform coating of the dry finely divided materialv with more or less permeation by the adsorbed films of carrier gas surrounding the particles of coating material.

As noted in our prior application, the volume and velocity of the jet of carrier gas issuing from the nozzle should be so regulated as to avoid the impingement of the carrier gas against the surface of the mold with sufiicient energy to rement, the mold, housing and mixing chamber being shown in longitudinal section, and

Figure 2 is a fragmentary isometric view of a portion of the apparatus shown in Fig. 1, on a larger scale.

A is the mold housing which may serve as a water box, B a centrifugal mold extending through the housing and rotatably supported on the end walls of the housing, the mold having, as shown, a bell end B and a cylindrical section indicated at B. C indicates a motor supported on the housing and coupled to rotate the mold by gearing indicated at C D indicates a core secured in place in the bell mouth of the mold. E indicates a carriage movable longitudinally on tracks indicated at E in alignment with the mold. F indicates a dump trough for a molten metal adapted, when in operative position, as shown in Fig. 1', to extend over the cylindrical portion of the mold and over an adjacent portion of the bell end. F indicates the pouring lip of the dump trough and 1 a cylindrical ex tension from the end of the dump trough proper. This is rotatably supported in bearings E E secured to the carriage E. F indicates a lever handle for tipping the dump trough. G is a counter-weight extending rearwardly from the mold and adapted to balance the weightof the charged dump trough. H indicates a conduit pipe fora carrier gas which is secured to the dump trough on the opposite side from its pouring lip and which is connected, as shown, by a hose H with suitable mechanism for supplying carrier gas and charging the carrier gas with finely divided dry particles of the mold coating material. As shown, we have indicated a mixing chamber or gun I, supplied with carrier gas by means of a nozzle J, provided, as shown, with a regulating valve J and a gauge J and receiving gas under pressure from a source, not shown. K indicates the presenceof mechanism for feeding finely divided dry coating material into the mixing chamber. As any satisfactory feeding device can be used, we have not thought it necessary to illustrate the particular construction of this part of the mechanism which, so far as it is shown, is that forming the subject matter of the patent application filed by Hunt and Arnold, October 29, 1932, Serial Number 640,258, new Patent No. 1,939,703., dated Dec. 19, 1933. L innold, October 29, 1932, Serial Number 640,257.

In operation, the mold, after the securing of the core D in its place in the bell end, is set in rotation and the carriage E having been retmted so as to withdraw thedumping trough F from the mold, the dumping trough is charged with molten metal. The carrier gas is conducted to the mixing chamber I through the nozzle J and finely divided dry coating material fed to the mixing chamber as by the feeding device indicated at K and the charged carrier gas passes 'through the hose H and pipe H into and through the nozzle L. The carriage E is then moved toward the mold in such manner that the dumping trough F will be projected into and through the cylindrical portion of the mold at a regulated rate of speed and so that the jet of charged carrier gas will be projected against the rotating cylindrical wall of the mold in such manner as to progressively deposit upon said wall a helical band of finely divided dry coating material with the edges of such helical band over-lapping adjacent coils of the helix, thus building up upon the entire cylindrical surface of the mold a continuous coating made up of the particles of coating material and adsorbed films of the carrier gas surrounding said particles. The coating of the cylindrical portion of the mold will be completed when the dump trough and supported nozzle reach the position shown in Fig. 1 and as soon as this is effected the supply of carrier gas is cut off as by means of the valve J so that no further charge offcarrier gas is fed to the nozzle L and the dump trough F is then tilted as by the lever l to feed its contents of molten metal substantially simultaneously along the entire length of the cylindrical portion of the coated rotating mold after which the dump trough is retracted from the mold, the core D removed from the bell end of the mold and the cast pipe extracted and the apparatus operated, as described, for the renewed coating of the mold and casting of a new pipe.

It is, of course, practicable to apply the coating to the mold in advance of the pouring of molten metal by first inserting the dump trough in the mold, as shown in Fig. 1, then turning on the supply of charged carrier gas and, as the jet of charged gas issues from the nozzle L, withdrawing the dump trough at a substantially uniform rate of speed so that the coating is applied to the mold progressively, beginning with the portion of the cylindrical section adjacent to the bell and ending with the spigot end of the mold, then turning off the supply of charged carrier gas and re-inserting the dump trough, charged with molten metal, into the mold, as shown in Fig. 1, and then tilting the dump trough to feed its charge of molten metal to the coated surface of the mold, although such a method of procedure would involve an undesirable delay in the pouring of the metal after the coating is applied.

The quantity of finely divided dry coating material delivered through the jet nozzle L during the coating of the mold should, for the best results, be so regulated as to build up a coating on the cylindrical portion of the mold not materially exceeding that thickness which will effect such a retardation in the heat transfer from the molten metal to the mold as is found desirable in practice; such a retardation, for example, as will prevent the formation of what is known as a chill on the outer surface of the casting and, as the eiiiciency of the coating as a retarder of heat transfer diminishes to acertain extent if the coated surface is not promptly covered by molten metal, due, no doubt, to the escape of some of the entrained carrier gas, the amount of finely divided dry coating material to be delivered through the jet nozzle and the consequent thickness of the coating as initially applied to the mold will vary to a certain extent for the time interval lapsing between the coating of the mold and the pouring of the metal upon the coated surface and it will be obvious that the metal should be poured as soon as possible after the coating is applied to the mold but in all cases the application of the coating of materially greater thickness than that found to eiiect a desirable retardation of heat transfer should be avoided as with increased thickness in the coating there is greater liability for portions of the coating to flake of! or become displaced and greater liability for portions of the coating to be displaced by the impact the molten metal upon the coated surface.

- Having now described our invention, what we claim as new and desire to secure by Letters Patent, is:

entire length of the cylindrical portion of the mold, a jet nozzle of a length in a direction .the axis of the mold which is a comparatively small fraction of thelength of the cylindrical portion of the mold adapted for the delivery of a jet of carrier gas charged with finely divided dry -"coating material, said jet nozzle being supported by'the dump trough and located adjacent to the free end thereof, means for supplying the Jet nozzle with a carrier gas charged with finely divided dry coating material and means for outting off the supply of charged carrier gas to the nozzle.

2. Apparatus as called for in claim 1,in which the nozzle is secured at the end of a pipe attached to the side of the dump trough opposite to its pouring lip and forming a part 01' the means for supplying the nozzle with charged carrier gas.

NORMAN F, S. RUSSELL. FREDERICK C. LANGENBERG.

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