US2207150A - Centrifugally cast plunger and tube - Google Patents

Description

y 9 1940 w. F. HIRSCH ETAL 2 207,150

CENTRIFUGALLY CAST PLUNGER AND TUBE Filed Feb. 14, 1938 3 Sheets-Sheet 1 2 8 /0 A gk I Wfim INVENTORS WALTER E HIRSCH FRANK B. BAYLEss y 9, 1940- w. F. HHRSCH ET AL 2,207,150

CENTRIFUGALLY CAST PLUNGER AND TUBE Filed Feb. 14, 1933 5 Sheets-Sheet 2 M \jx/x x 7 INVENTORS WALTER E H/RSCH FRANK 5. B YLEss t g iATTORNEY.

y 9, 1940- w. F. HIRSCH ET AL 2,207,150

CENTRIFUGALLY CAST PLUNGER AND TUBE Filed Feb. 14, 1938 3 Sheets-Sheet 5 m YA INVENTORS WALTER F Hl/ZSH FRANK B. BAYLESS Patented July 9, 1940 UNITED STATES CENTRIFUGALLY CAST PLUNGER AND TUBE Walter F. Hirsch, Huntington Park, Calif., and Frank B. Bayless, Oil City,'Pa., assignors to Industrial Research Laboratories, Ltd., San

Francisco, Calif., a corporation of Nevada Application February 14, 1938, Serial No. 190,454

16 Claims.

This invention relates to cylindrical plungers as particularly used for oil well and other pumps, and to tubular and cylindrical objects generally, and the invention has for its principal purpose the production of such objects of wear-resisting alloys or metals by centrifugal casting, and particularly the production of such objects with the main or body portion formed wholly of such wear-resisting metal. A specific object of the invention is the production of dense, accurate centrifugally cast objects of the character mentioned from extremely hard substantially unmachinable alloys which can only be practically finished by grinding, and the maintaining of said grinding requirement at the very minimum.

Other objects and advantages of the invention will appear in the following description and accompanying drawings.

In the drawings: 1

Figure 1 is a longitudinal sectional view of a tubular casting assembly complete with its charge of alloy, for the centrifugal casting of a plain pump plunger section, or hard metal tube in accordance with our invention.

Figure 2 is a view similar to that of Figure 1, but showing the alloy after melting and spinning in place within the outer shell.

Figure 3 is a longitudinal sectional view of the finished hard metal tubular section after ma chining off the outer shell and end closures and grinding the surface.

Figure 4 is a longitudinal sectional view showing several of the hard metal sections of Figure 3 assembled on an inner supporting tube to form a pump plunger.

Figure 5 is a longitudinal sectional view of an assembly similar to that of Figure 1, but providing end hubs or connecting ferrules for the cylinder to be cast.

Figure 6 shows the assembly of Figure 5 after centrifugal casting.

Figure '7 shows the finished and threaded product from Figure 6.

Figure 8 is a longitudinal sectional view of an r assembly similar to that of Figure 5 showing a modified form of the end hubs or ferrules.

Figure 9 shows the assembly of Figure 8 after centrifugal casting.

Figure 10 shows the finished product from Figure 9.

Figure 11 is a longitudinal sectional view similar to that of Figure 9, but showing a central hub or ferrule in the assemblage.

Figure 12 is a longitudinal sectional view of an assembly similar to that of Figure 5, but showing a modified form of tapered end hubs or ferrules.

Figure 13 shows the finished product made from the assembly of Figure 12.

Before describing the invention and drawings in detail it may be stated that heretofore it has been known to line a steel or iron tube or cylinder with hard or wear-resisting metals or metal alloys melting at more than 1000 F., by centrifugally forcing the molten layer against the wall of the tube or cylinder by rapidly spinning the same until the metal chilled to a dense smooth internal layer firmly bonded to the tube. Brown patents, No. 1,923,075 and No. 2,033,814, and also Kormann et al. Patent No. 2,046,914 clearly illustrate the prior art of the internal centrifugal lining of tubes and other circular hollow articles with various metals and alloys, such as hearing metals, bronze, stellite, hard boron-iron alloy, etc., and more recently a variation of such processes of centrifugal casting has come into usage for the centrifugal lining or casting of a thin layer of wear-resisting hard alloy on the exterior of shafts and tubes for use as pump plungers and pistons in the handling of gritty liquids, such as oil and other pump service, etc.

Such centrifugally exteriorly hard lined shafts and tubes have only found limited use in industry, and it is one of the objects of the present invention to overcome the difficulties and uncertainties attendant upon the production of such exteriorly hard-lined plungers, as it produces a better wear-proof plunger of dense centrifugally cast hard alloy, yet avoids entirely the former necessity of forcing the molten alloy into a very narrow space formed in the casting assembly between the outer surface of the shaft or tube to be covered and the inner surface of an outer surrounding shell or temporary mold which later was machined away from the thin hard layer.

In the exterior coating or lining of tubes and shafts with extremely hard alloys, particularly of the stellite or boronized iron type, which are substantially unmachinably hard, so that they can only be exteriorly finished by grinding, it is manifest that the layer as cast should be so accurate as to require only the minimum of grinding to reduce it to the actual finished dimension desired, otherwise the cost would make the use of the article prohibitive in industry; also that if a steel tube were to be lined exteriorly without increasing its diameter objectionably, the coating applied would have to be very thin, and hence the casting space between the exterior of the tube or shaft to be coated and the outer or casting shell would be but a mere annular crack into which the molten metal would have to be forced, and with a result that the layers are sometimes imperfect, lacking in density, continuity, or contain gas bubbles, as such annular casting spaces or cracks are not easily vented to permit escape of gas.

The present invention in overcoming the difficulties pointed out provides a centrifugally cast tube or hollow plunger of exterlorly unmachinably hard or other wear-resisting metal or alloy by centrifugally forming the tube or plunger entirely of the metal or alloy and hence dispenses with the centrifugal forcing of such high melting point metals into narrow annular spaces as formerly required in order to form dense hard exterior facings, and makes it much simpler and quicker to produce the required articles, while insuring perfect results at all times.

Briefly described, the invention in its simplest form comprises providing a cylindrical outer, preformed metal tube or temporary casting shell of readily machinable metal such as of steel or iron, and of a weight or thickness just suflicient to insure rigidity during the casting and spinning operations, and applying an inner, very thick layer of r the desired wear-resisting alloy or metal within the tube by spinning the tube, while hot, horizontally on its axis to force the alloy in molten state in the tube against the inner wall of the tube to form the desired concentric layer thereon, and continuing the spinning until the layer has set, then removing the outer shell from the layer as by destructively machining or stripping it therefrom, and thereafter finishing the surface of the hard layer by grinding, as the alloy is generally firmly bonded to the temporary outer shell by the casting operation. The actual thickness of the layer applied by centrifugal casting is suflicient to produce (when the outer shell has been stripped from it) a rigid self-sustaining tube of solid hard alloy which is usable as such for the purpose of a pump plunger or working piston, thus dispensing with the heretofore required further bonding of the layer either externally (or internally) to another tube for permanent support.

Another important advantage of forming such articles of the solid hard metal instead of by applying thin layers to either inner or outer steel supporting tubes, is that in the latter method there is a dilution of the alloy and its properties become impaired through its molten contact with the. supporting tube, tubes, or shaft, on account of the relatively thin layer of lining or facing metal used as against the heavy mass of the supporting body, and which is substantially eliminated by the improved method.

The hard, centrifugally formed tube thus produced may be ground externally, or internally, or both, depending on the use intended. As a final form of the invention the centrifugally cast tube may have end hubs or ferrules cast in place or inserted afterward and secured as by soldering or welding, to serve as connections, aligning of several sections, threading, etc.

In the variations shown in the drawings the outer or temporary shell, preferably a preformed wrought steel tube, is for uniformity designated I in all of the figures, and the centrifugally cast layer of wear-resisting or hard metal alloy is designated 2, and the finished article from each respective assembly is designated 2 2 2 2 The arrangement shown in Figure 1 is a casting assembly for the production of the article shown in Figure 3, and the assembly comprises a preformed wrought steel or iron outer tube or shell I, closed at both ends by tightly fitting flanges 3 preferably welded in place clear around as at 4 to prevent possible leakage of molten metal while spinning, or the flanges may otherwise be tightly sealed in place as by threading or beading over, if desired, and at least one of the flanges is provided with a very small central vent hole 5 to permit escape of air or gases formed during the heating of the assembly, to

melt the alloy or hard metal 6 which is preferably as it melts at about 2000 F. The charging metal may of course include a fluxing agent to make It flow better, if desired,

The assembly is best heated by slowly revolving it in a suitable furnace until the alloy inside has completely melted, and it is then removed from the heat zone and spun horizontally on its axis in any suitable machine, at a high rate of speed suflicient to throw the molten metal against the inner wall of tube I in an even layer and kept spinning till the layer has chilled, as indicated at 2 in Figure 2. when further cooled, the outershell I, which generally becomes firmly bonded to the casting, is destructively removed from the inner cast hard metal tube 2, as by machining it off in a lathe or otherwise, and after which the outer and/or inner surface of the hard metal tube is ground to perfect cylindrical form as may be desired for use. The end flanges are similarly cut away either before or after the exterior grinding operation, as may best facilitate the operation, and the ends of the hard cylinder may be squared oil! or ground slightly convex and concave as indicated respectively at G and I in Figure 3 so as to provide means for more readily centering a series of such tubes or 7 sections 2' on a mandrel 8 in Figure 4.

In Figure 4 the mandrel is shown itself as a hollow tube threaded at both ends and provided with clamping nuts 9 and III each having one end either concave or convex to center with the adjacent end of the hard metal section as indicated. For some purposes the supporting mandrel may be solid, and in other cases the mandrel may be entirely dispensed with as will hereinafter appear.

Insofar as the present invention is concerned the hard metal alloy, instead of being melted within the closed outer shell, may be poured into it during the spinning operation through an enlarged central opening taking the place of vent 5 or provided at the opposite end, it being understood that the shell be first preheated to prevent premature chilling of the melted casting metal. Any desired metal melting at a substantially lower temperature than the outer shell may be used when melting the metal within the shell, but when pre-melting and pouring it in while spinning, a metal melting at even a higher temperature than the shell may be used, as it will cool before material injury to the shell, especially it outside air circulation be used.

The metal when introduced in the solid state may be in broken pieces, or in bar form, in fact it may substantially fill the interior of the shell where a very thick tube of the alloy is required as a final product.

If the assembly is held vertically while spinning and sumcient alloy is placed inside or introduced while spinning it is manifest that solid bars or shafts of the hard alloy may be centrifugally produced instead of the more useful tubular form of product. A bar thus centrifugally produced will have an extremely dense outer surface free from imperfections usually resulting from other methods of casting.

In view of the complete description set out in connection with Figures 1 to 4, only the points of variation therefrom will be taken up in regard to the remaining figures as the handling is the same for all forms.

Figure 7 shows the solid hard alloy tube 2 provided with soft or machine steel ends or ferrules ll threaded exteriorly as at l2, or internally if desired, to provide for connection to other members. These machinable ends are produced by providing special machine steel end closures for the shell I as indicated at l3 in Figure 5, and which closures are preferably hollow or pre-bored for most of theirlengthas at It to overcome the necessity of doing this later on, and they are reduced in diameter at their inner ends as at l5,

and also preferably tapered so as to become encased in the hard metal alloy tube 2 when cast as shown in Figure 6, and after which the outer tube or shell I is removed as described for Figure 2 and the inner ends l6 of the closures bored through and the tube ground exteriorly, and/or interiorly. It is manifest that if less alloy is used, or if bore I4 is not finally enlarged to the full diameter of the hard metal tube, that the end ferrules will project inward within the tube 2 as dotted at H in Figure 7, and which is advantageous for some purposes. With a casting assembly as shown in Figure 5, one or more additional small vent holes are required as at 5 where the hard metal overlaps the ferrule ends.

Figure 10 shows the solid alloy tube 2 provided with inwardly projecting ferrules i1 formed from annular members l1 projecting inwardly from the closure fianges 3' of the casting assembly of Figure 8. Figure 9 shows the assembly after spinning and with an inner shoulder ll" formed at both ends of a size depending on the amount of alloy used, but which shoulder generally need be only suflicient to provide for boring the ferrules without striking the hard tube 2 with the tool. This facilitates aligning a plurality of the finished tubes on an inner mandrel in the general man ner shown in Figure 4, or provides for internal threading of the ends.

The casting assembly of Figure 11 is similar to that of Figure 8, but shows the provision of two outer shells l abutted endwise and welded at l8 and a central ferrule or hub IS. The final product of this assembly after the end closures 3" were cut off would be like that shown in Figure 10 with an additional centrally located ferrule. or it would produce two articles as shown in Figure 10 if transversely cut through the weld 18.

Figure 13 shows a hollow hard alloy pump plunger 2 with inwardly projecting tapered end ferrules l9 completely embedded in the hard alloy and with outer ends counterbored and internally threaded as at 20 for attaching to pump fittings, valve cages, etc.

The assembly for producing this is shown in Figure 12, and is similar to that of Figure 5, except that the end closure plugs 2| are initially bored part way from their inner ends as indicated at 22 instead of from the outer ends as indicated at H in Figure 5.

The final product shown in Figure 13 comprises a relatively thick tubular plunger 2 of solid hard alloy or wear-resisting metal such as the boron-nickel-iron alloy mentioned, or of the stellite type, hard white iron, or any other type or variation of these metals desired, and provided with machine steel connecting ferrules welded or bonded into the plunger at one or both ends either of slightly smaller diameter than the hard working surface of the plunger as indicated in Figure 13, or of the same diameter. The ferrule may have a rough cut on its outer surface as indicated, to facilitate bonding to the molten hard metal layer when spun, and the tapering of the inner ends of the ferrules avoids any line of weakness in the plunger which might cause a transverse fracture in the hard tube.

In considering the present invention and prod not of a hollow or solid pump plunger or piston of solid, unmachinably hard alloy, as against the exteriorly hard-faced wrought steel tubular or solid plungers of the kind heretofore made, as explained on page one, its chief points of advantages are that being of solid alloy instead of a facing, it is free from any cracking or chipping tendencies, also free from entrapped air or other gases, or scale particles so liable to be developed in the narrow annular crack in which the facing type of hard coating had to be forced, and since the spinning operation is conducted in a plain hollow tube or shell it may be much more easily and quickly produced, and the centrifugal castings are always of dependable density and soundness. Besides this, the casting assembly is simpler and cheaper than required for the exteriorly faced article. of production of this improved product is such that is has practically supplanted the exteriorly faced article in oil well and other pump plungers for which the invention was principally developed.

We have tried producing such plungers wholly of hard alloys by the common sand and permanent mold method of casting, but found that the difficulty of obtaining defect-free outer surfaces, and also the excessive amount of grinding required to bring the articles to the required condition was prohibitive. Besides this the centrifugal casting method of the invention not only insures freedom from surface defects and reduces the finish grinding to the very minimum, but also produces an increasing density to the metal which reaches its maximum at the outer or working surface of the article, and adds considerably to the strength of the casting.

While it is one of the objects of the invention to provide a method of making such plungers of extremely hard alloys which could not be otherwise produced, the word alloy as used in the claims, is intended to cover any desirable metal useful for the purpose intended whether strictly considered as an alloy or not.

Having thus described our invention, what we claim is:

1. The method of producing hard alloy cylindrical objects which comprises providing a preformed cylindrical shell of readily machinable metal of an internal diameter slightly larger than the finished diameter of the desired object, spinning the shell and a mass of the molten alloy within the shell under conditions to produce a dense concentric mass of the alloy in said shell and until the mass solidifies, and thereafter destructively stripping or machining the shell from the solid object produced and finishing the surface of the object.

2. The method of producing hard alloy metal tubes or rods which comprises providing a preformed shell of readily machinable metal of an internal diameter slightly larger than the finished diameter of the desired metal tube or rod, substantially sealing the ends of the shell, and spin- In fact the superiority and ease P ning the shell on its axis together with an internal charge of molten metal alloy sufficient to yield a tube of the thickness desired under the action of.centrifugal force and until the tube or rod has chilled, and thereafter destructively stripping or machining the shell from the centrifugally cast tube or rod and finishing the surface of the latter.

3. The method of producing hard alloy tubes which comprises providing a preformed tubular shell of readily machinable steel, placing a charge of the desired alloy within the shell, providing end closures for the shell having annular portions extending inwardly into the shell in spaced relation to its inner surface and one of said closures being vented, thereafter heating the assembly to melt the alloy, spinning the assembly to distribute the molten alloy evenly within the shell and embracing said annular portions and maintaining the spinning until the alloy has chilled, and thereafter stripping or machining the shell from the alloy tube thus formed and removing the end closures while leaving the annular portions attached to the tube, and finishing the surface of the tube.

4. The method of producing hard alloy tubes which comprises providing a relatively thin preformed tubular shell of readily machinable steel, placing a charge of the desired alloy within the shell, providing end closures for the shell, an annular portion extending from one of said closures inwardly into the shell in spaced relation to its inner surface, and one of said closures being vented. thereafter heating the assembly to melt the alloy, spinning the assembly to distribute the molten alloy evenly within the shell and embracing said annular portion and maintaining the spinning until the alloy has chilled, and thereafter stripping or machining the shell from the alloy tube thus formed and removing the end closures, and finishing the surface of the tube.

5. A centrifugal casting assembly comprising a preformed steel tube, closures at both ends of the tube, and at least one of said closures provided with a cylindrical extension projecting a relatively short way into the tube in spaced relation to its inner surface, and a charge of metal alloy within the tube adapted to be melted therein without substantial injury to the tube.

6. A centrifugal casting assembly comprising a preformed steel tube, closures at both ends of the tube, and at least one of said closures provided with a cylindrical extension projecting a relatively short way into the tube in spaced relation to its inner surface, and a charge of metal alloy within the tube adapted to be melted therein without substantial injury to the tube, said extension ta'pering to smaller diameter toward its inner end.

7. A pump plunger or the like comprising a relatively thick uniform cylindrical tube of solid dense cast hard metal alloy having the characteristics of centrifugally cast metal, and provided with means at its ends for aligning in abutting relation with similar tubes.

8. A pump plunger or the like comprising a relatively thick cylindrical tube of solid dense cast substantially unmachinably hard metal alloy having the characteristics of centrifugally cast metal, and provided with an integrally attached machinable steel'ferruie at the end.

9. A pump plunger or the like comprising a relatively thick cylindrical tube of solid dense cast substantially unmachinably hard boron-nickeliron alloy having the characteristics of centrifugally cast metal, and a ground exterior surface.

10. A pump plunger or the like mprising a relatively thick cylindrical tube of solid dense cast substantially unmachinably hard metal alloy having the characteristics of centrifugally cast metal, and provided with machinable steel ferrules at its ends embedded and bonded into the metal of the tube.

11. A pump plunger or the like comprising a relatively thick cylindrical tube of solid dense cast substantially unmachinably hard metal alloy having the characteristics of centrifugally cast metal, and provided with machinable steel ferrules at its ends embedded and bonded into the metal of the tube, said ferrules being of tapered reduced thickness as they extend into the metal of the tube and being embraced both inside and outside by the tube metal.

12. A pump plunger or the like comprising a relatively thick cylindrical tube of solid dense cast substantially unmachinably hard metal alloy having the characteristics of centrifugally cast metal, and provided with ferrules of machinable steel at its ends bonded thereto, and a similar ferrule intermediate its length bonded thereto.

13. In a method as set out in claim 4, the additional step of securing a ferrule in said shell intermediate said closures, and with the ends of the ferrule spaced inwardly from the inner surface of said shell.

14. A pump plunger or the like comprising a plurality of relatively thick cylindrical tubes of solid dense cast hard metal alloy having the characteristics of centrifugally cast metal, assembled in abutting end to end alignment, and provided with means holding them together.

15. The method of producing cylindrical metal objects which comprises providing a preformed cylindrical shell of readily machinable metal, spinning the shell about its longitudinal axis with a mass of the molten metal desired within the shell under conditions to produce a dense concentric mass of the metal in said shell and until the mass solidifies, and thereafter destructively stripping or machining the shell from the metal object thus produced, the thickness of said metal object being sufllcient to make it self-sustaining for further mechanical operations.

16. The method of producing metal tubes which comprises providing a preformed tubular shell of readily machinable metal, substantially sealing the ends of the shell, and spinning the shell about its longitudinal axis together with an internal charge of the molten metal desired sufficient in quantity to yield a tube of the desired thickness under the action of centrifugal force and until the tube has chilled, and thereafter destructively stripping or machining the shell from the thus centrifugally cast tube, the thickness of the wall of said tube being suflicient to make it self-sustaining for further mechanical operations.

WALTER F. HIRSCH. FRANK B. BAYLESS.

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