Method of making composite valves

Aug. 13, 1935. e: _{M MAY} 2,011,007

METHOD OF MAKING COMPOSITE VALVES Original Filed Oct. 23, 1931 2 Sheets-Sheet 1

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Aug. 13, 1935. e. m. may 2,011,007

METHOD OF MAKING COMPOSITE VALVES Original Filed Oct. 23, 1931 2 Sheets-Sheet 2

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Patented Aug. 13, 1935

2,011,007

UNITED STATES PATENT OFFICE

2,011,007 METHOD OF MAKING COMPOSITE VALVES Edward M. May, Detroit, Mich.

Original application October 23, 1931, Serial No.

570,647. Divided and this application October

13, 1933, Serial No. 693,481

Claims. (Cl. 29—157.1)

The invention relates to the production of composite valves and especially valves having seat-engaging parts formed of very hard wearresisting metal, the present application being a β division of my copending application Serial No. 570,647, filed October 23, 1931.

For various uses valves are required which are capable of prolonged use without sufficient deterioration from mechanical wear or corrosion to 10' impair their effectiveness. This is especially true of uses in which the working conditions are such as to make renewal of a valve difficult and a thing to be avoided if possible. The known metals which have the requisite durability to meet these ¹⁵ requirements are exceedingly hard and, in some cases at least, cannot be forged or finished by machining but must be formed by casting and finished by grinding. Furthermore, such metals, or at least some of them, tend when cast, espe²⁰ daily when cast in metal molds and rapidly chilled, to have a porous interior structure ₍and this makes it difficult to secure smoothly finished ' seat-engaging surfaces when it is necessary to grind away the outer metal of the casting. The ® alloy stellite is an example of such metals, it being particularly suitable, because of its great hardness and ability to resist wear and corrosion, to form the seat-engaging part of a valve of the character in question.

30’ The nature of the method and the maimer in which it is carried out will most readily be understood from a consideration of specific valve constructions and of apparatus suitable for the carrying out of the method. In the accompanying 35' drawings I have illustrated two forms of valve construction by way of example and mold apparatus such as I prefer to employ.

While my improved method, at least in some of its aspects, is adapted to the production of vari40 _ous forms of valves, it is, in certain respects, particularly applicable to needle valves which may have an elongated shank part of steel or other suitable metal and a tip or head part formed of metal having great hardness and the ability to 45 strongly resist wear and corrosion. Accordingly I shall explain and describe my improved method in connection with the production of needle valves of this character.

One of the chief objects of the present inven50 tion is the provision of a method of producing composite valves of the character referred to In which difficulties incident to the porosity of the cast part of the valve structure are effectively overcome.

⁵⁵ Another object of the invention is the-provision of a method of producing a composite valve in which the different parts of the valve are effectively united to form a rigid unit.

A further object of the invention is the ptovl⁶⁰ sion of a method of producing composite valves of the character in question in which the labor required and the loss of materials resulting from defectives or otherwise are minimized, with resultant lowering of the cost of production.

Other objects more or less Incidental or ancil- ® lary to those above stated, as well as preferred ways of attaining the objects, will be apparent from the following description.

In the drawings, Fig. 1 is a plan view of one form of mold with parts thereof broken away to 1° show interior construction.

Fig. 2 is a view, partly in side elevation and partly in vertical axial section, of the mold shown in Fig. 1.

Fig. 3 is a view of the same character as Fig. 2 ¹⁵showing a modified form of mold.

Fig. 4 is a side view, partly in axial section, of a valve produced by my improved process.

Fig. 5 is a similar view of a modified form of valve construction produced by a somewhat modi- ²® fled form of the method employed in producing the valve in Fig. 4.

Referring first to the valve construction shown in finished form in Fig. 4, and disregarding the dot-and-dash lines of said figure which have to »» do with the method of manufacture, said valve comprises a shank I formed of steel or other suitable metal having physical characteristics adapting it to be readily machined and to perform suitably the usual functions of a valve shank. If 3® the contemplated use of the valve is such as to call for high resistance to corrosion, I prefer to make the shank of a metal such as stainless steel. The shank I is machined at one end to₀form an axially extending cavity, the walls of which are 35 undercut at the inner end of the cavity to form a taper shoulder 2 and are beveled at the outer end of the cavity to form an oppositely inclined taper shoulder 3. The outer surface of the shank at the same end is formed with an outer taper 40 or bevel 4.

To the end of the shank I is secured a seatengaging tip 5 of suitable hard, wear-resisting metal such, for example, as stellite. As is well known, stellite is both exceedingly hard and 45 highly resistant to corrosion. Because of its hardness it cannot be rolled or forged but must be formed by casting and, for the same reason, it cannot be machined but must be finished by grinding. Accordingly I secure the tip to the 50 shank by casting it on the end thereof, the molten metal of the casting entering the cavity in the end of the shank and forming, when the metal sets, an interlocking connection between the two parts. That is, the enlarged inner end or 55 knob 5» of the tip 5 is formed with an annular taper 6 which engages the opposing taper 2 of the shank and the outer part of the tip is formed with an annular taper 7 which similarly engages the opposing taper 3 of the shank. The crys- 60

2,011,007 tallization and temperature shrinkage of the metal of the stem 5^b of the tip on setting and cooling causes the tapered shoulders 6 and 7 thereof to be drawn very strongly against the 5 opposing shoulders 2 and 3 of the shank so as to secure the tip and shank rigidly together. The contraction of the metal of the tip leaves . small voids or clearances at the inner end of the tip and around the periphery thereof as shown 10 in Fig. 4, but the firm engagement of the taper shoulders of the tip and shank very effectively holds the two parts rigidly together. In the drawings the size of the voids Is exaggerated for the sake of clearness.

The shank I of the valve may, if desired, be formed with a hole as at l^a to receive a securing screw or pin.

I shall now describe the mold apparatus shown in Figs. 1 and 2 and the manner of using it in 20 carrying out my improved method of producing composite, valves. The specific mold construction illustrated is designed for the simultaneous casting of a considerable number of valve tips or heads of valves of the character shown in Fig. 4 ²⁵ and the mold is adapted to employ centrifugal force for feeding the molten metal into the mold cavity. The mold body comprises a circular bottom part 8 and a similarly shaped top part 9 which is secured to the bottom part by a plurality ³⁰ of stud bolts 10 and nuts Η. I have found meehanite a suitable, material for the main mold parts 8 and 9, the same being a cast metal with properties between those of cast iron and cast steel. The stud bolts are secured ridily in ³⁵ threaded holes in the bottom part and extend through plain holes in the top part so that the top part of the mold can readily be lifted off when the nuts 11 are removed. To provide for the rotation of the mold, the bottom part 8 is 40 formed with a depending hub 8^a which is drilled out to fit the upper end of an upright drive shaft 12 to which the hub is detachably secured by a set screw 8^b. In the construction shown, this shaft is the upwardly projecting end of the arma45 ture shaft of an electric motor 13.

The upper part 9 of the mold is formed vdth a relatively large central opening 14 which, in conjunction with the upper face of the lower part 8, forms the pouring cavity of the mold. 50 The opening 14 preferably has its side wall undercut as shown in Fig. 2. Surrounding the opening 14 are a circumferential series of cavities 15, 15 to receive valve shanks and, in conjunction with the shanks, form a corresponding number 55 of casting cavities for the valve tips. These mold cavities extend radially and are formed by mating depressions in the opposing faces of the lower and upper parts of the mold. Each cavity at its inner end is tapered at 15^a to form 60 the conical or taper part of the . valve tip, and this part of the cavity is connected with the pouring cavity by means of a small cylindrical ingate 16. Each of the mold cavities is formed at its outer end with an enlarged threaded sec65 tion 15^b designed to receive a screw plug 17 which serves as an abutment for the outer end of the valve shank and prevents its outward displacement by the centrifugal force of the molten metal. The threaded plugs 17 can easily be turned to ad7° just their position according to the length of the valve shank. To avoid the necessity of screwing the plugs in each time the mold is assembled, said plugs can be carried in one or the other of the two main parts of the mold so that its adjusted position is not disturbed when the mold sections are separated. Thus, in the construction illustrated, the bottom part 8 of the mold has its upper face formed with a, depression or annular rabbet I7^a and the top part 9 of the mold is formed with a corresponding annular downward 5 extension so that the screw plugs have more than half of their peripheral surfaces embraced by the top part 9 of the mold and are therefore not separated from said mold part when it is removed from the bottom part of the mold. io

A guard casing 18 having its bottom side open and its top side formed with a central aperture f 8^ais adapted to be detachably mounted on the top of the casing or frame of the motor 13 so as to substantially enclose the mold and stop flying IS molten metal that might esca'pe from the pouring cavity 14 when the mold is rotated.

In operating the mold, with the top part thereof removed, the prepared valve shanks I are placed in position on the bottom part 8 of the 20 mold. The top part 9 is then placed in position on said bottom part and secured by nuts 11. in the initial operation of the mold, the screw plugs 17 are then inserted until their inner ends press the valve shanks as far inward as the mold cavity 25 will permit whereupon the screws 17 are backed off slightly to provide a slight clearance between them and the valve shanks.

The form of the valve shank when it is placed in the mold is shown by the full lines in Fig. 4 ex- 30 cept at the bevel or taper 4 where the form of the shank taper is represented by the dot-and-dash lines. Furthermore the taper part i5^a of the mold cavities also correspond to the dot-and-dash lines in Fig. 4 of the drawings, thus providing for metal to be removed in finishing the tip end of the valve.

The mold is preferably heated to some extent before pouring the molten metal into it. Accordingly when the mold parts have been assembled 4· with the valve shanks therein the entire structure including the shanks is heated to a temperature of about 750° F. This can be done with a suitable torch, but I prefer to do it by detaching the mold from the drive shaft 12 and placing it in 45 an oven which is maintained at the desired temperature. When the mold has been heated the guard or cover 18 is placed in position, the motor started and the molten stellite or other metal is poured through the aperture 18^a into the pouring 50 cavity 14. In the use of stellite I pour the molten metal at a temperature of about 3200° F.

When the molten metal enters the pouring cavity 14 the rotation of the mold, for which I have found a speed of about 2200 R. P. M. suit- 55 able, sets up a rotary movement of the molten metal and the resultant centrifugal force feeds the molten metal under corresponding pressure through the small ingate 16 into the casting cavity formed by the mold proper and the inner ends of 00 the valve shanks 15. Although the entering molten metal is strongly chilled by the walls of the ingate and casting cavities, the latter are always effectively filled because of the strong centrifugal force to which the molten metal is sub- 05 jected. However, when the molten metal sets and cools, the combined effect of the crystallization, shrinkage and the contraction due to cooling is to cause a substantial contraction of the cast metal. While this has the effect of forming the 70 voids illustrated in Fig. 4 and above referred to, it also results in the drawing of the tapered shoulders of the cast tip strongly against the opposing shoulders of the valve shank so that the tip and shank are powerfully clamped together. The 75

3,011,007 contraction also Usually has the effect of rupturing “the cast metal in the ingate where it joins the larger body of the cast metal remaining in the pouring cavity 14. Thus, when the mold is dis5 assembled by removing the top part 9, the valves are ordinarily already separated from the sprue in the pouring cavity 14 and can be individually lifted or shaken out.

The valves, on removal from the mold, have the 10 form shown by the dot-and-dash lines in Fig. 4 and the next step in the manufacture of the valve is the grinding away of the excess metal of the tip to reduce it to the form shown by full lines in Fig. 4. In grinding the tip 5 to the finished 1« conical or taper form shown in full lines, a corresponding amount of metal at the taper 4 of the shank I is simultaneously removed.

On referring to Fig. 4, it will be observed that it is necessary to remove but a small amount of the 20 cast stellite in the grinding operation. This is an important consideration because the .strong chilling effect on the outer layer of the casting produces a dense, fine-grained structure free from porosity and, by so forming the cast tip that it is 25 not necessary in the finishing operation to cut through this outer fine-grained layer of the casting, I avoid exposing the porous structure which tends to exist in the deeper, less chilled layers of the casting. In other words, I thus secure valve 30 tips with smooth surface and avoid losses which would occur due to the exposure of porous metal if the above mentioned conditions were not secured. As shown by Fig. 4, the grinding operation penetrates to the axis of the Ingate metal at 30 the valve point. Consequently the provision of a relatively small ingate for the molten metal is essential to insure chilling and the resulting dense, fine-grained structure of the metal throughout the ingate part of the casting. Hence, 40 with the small ingate and the heavy chilling action, the strong centrifugal force to which the molten metal is subjected plays an important part in insuring the complete filling of the mold cavity and the avoidance of imperfect castings.

The contraction of the stem 5» of the tip 3, which is relied upon to rigidly secure the tip to the shank of the valve, sets up a relatively high Stress in the stem part of the cast tip and it is therefore important to avoid porosity in this 50 stem part in order to avoid fracture thereof. I prevent such porosity in the stem 5^b of the tip as well as in the ingate to the cavity by suitable design of the casting cavity. It will be observed that the shape of the cavity is made such 55 that the cast valve tip has the largest mass of its constituent, metal in the region between the ingate and the stem 5^b. Consequently, in casting the valve tip the interior part of this larger mass of metal in the intermediate zone remains molten 50 longer than the metal in the stem 5» and the metal which is to form the conical seat-engaging surface of the tip (including the metal in the innermost part of the ingate), with the result that crystallization shrinkage of the earlier setting 65 metal in these two regions is compensated for with metal drawn from the interior mass of metal still remaining in the molten state in the enlarged intermediate section of the casting. This Usually - results in some porosity in the Interior region of 70 the tip between the stem 5^b and the conical seatengaging walls of the tip, but such interior porosity is not exposed by the relatively shallow finishing operation on the valve and does not reach the stem 5^b and so does no harm.

It is to be observed, in connection with, valves of the type shown in Figs. 1,2, 3 and 4, that since the shrinkage of a metal such as stellite on casting is quite considerable, the internal stresses set up are correspondingly large and this must be borne in mind in designing the valve and 5 stresses great enough to rupture the metal avoided. In Fig. 4, for example, the length of the neck section 5^b of the tip 5 between the latter’s taper shoulders 6 and 7 is so proportioned that the contraction of the tip on casting shall be just io sufficient to effect the desired clamping action between the tip and the shank without setting up unduly large stresses in the metal of the tip. The valve shown in Fig. 3 and presently to be referred to is to be designed with similar precau- 15 tion.

While the type of valve construction shown in Fig. 4 is one that I have found especially satisfactory in the production of needle valves, other forms of construction can be used in carrying out 20 my invention. In Fig. 5 I have shown a form of valve having the same general structural and functional characteristics as the valve shown in Fig. 4. Here, as in Fig. 4, the full lines show the finished construction and the dot-and-dash lines 25 show the valve as it is taken from the mold after casting on the valve tip. In this last construction the shank 19 is machined out at one end to form a cavity with walls that are undercut with relation to the end opening of the cavity, said 30 walls comprising a short taper at 19· and a long taper at I9^b. The outer surface at this same end of the shank is formed with a bevel or taper I9^C. Into this cavity 6f the shank is cast a tip 20 of stellite or other suitable metal. Obviously this 35 can be done in a mold of the character above described. When the tip 20 shrinks, on casting, it tends to draw away from the walls of the shank cavity and become loose. To secure the tip tightly in the cavity, I place the valve shank in swag- 40 ing dies and subject It to pressure to form the circular groove I9^d. This forces the metal of the shank inward against the inner tapered end of the tip 20 and forces the tip outward against the inwardly tapered surfaces 19» of the shank 45 thus detaining and rigidly securing the tip. After this swaging operation the valve is ready for the finishing grinding operation which effects the removal of excess metal on the outer conical surfaces of the valve represented by the dot-and- 50 dash lines in Fig. 5.

It will be seen that the principles involved in the constructions and the methods of production of the two forms of valve above described have much in common. In each case the con- 55 struction of the valve is such that the cast tip is very rigidly and firmly secured to the shank by internal stresses that are set up in one or the other of the two valve parts. In the first form of valve the construction of the cast tip on cast- 60 ing sets up a strong internal tension in the tip so that the latter has its taper surfaces drawn against corresponding opposing surfaces of tha¹shank, thereby producing a very strong clamping force. In the second valve the swaging of 65 the shank 19 sets up a reaction between the taper surfaces of the cast tip and of the shank respectively, with corresponding tension in the metal of the shank which surrounds the tip. In making the valves, in each case, porosity of the 70 cast metal forming the seat-engaging portions of the valve is avoided by the use of a suitably constructed ingate and by providing a relatively large mass of cast metal adjacent to the seat-engaging surfaces so that the crystallization shrinkage of 75

2,011,007 the metal forming such surfaces is compensated for with molten metal drawn from the interior of the tip where resultant porosity does no harm.

The mold shown in Fig. 3 of the drawings is 5. of the same general construction as that shown in Figs. 1 and 2 but presents some detail differences which in practice I have found advantageous. The mold consists of bottom and top parts 21, 22, respectively, formed with opposite 10 radial recesses 2l^a, 22^a, to receive the valve shanks, the top part being detachably secured to the bottom part by machine screws 23. The top part is provided with the undercut pouring opening 22^b and the central top surface of the 15 bottom part 21 is raised in convex form at 2l^b. Each of the radial grooves of the bottom part is supplied with a malleable metal stop pin 24 to position the outer end of the valve shanks when they are assembled in the mold. These 20 stop pins can be slightly adjusted by bending them with a hammer or the like to secure the correct positioning of .the valve shanks. The shank and cast tip parts of a valve are shown in section, the valve shank being designated by 25 the numeral 25 arid the tip part by 26. Here the stem part 26^a of the tip has its diameter and length approximately the same as the diameter and length, respectively, of the ingate part 26^b.

The mold shown in Fig. 3 is operated in sub30 stantially the same manner as the mold shown in Figs. 1 and 2 so that its operation need not be described. I have found in practice that the convex surface 2l^b of the mold tends to prevent the sprue metal from sticking to the mold. I 35 have also found that by making the stem 26* of the valve tip of approximately the same diameter and length as the ingate metal 26^b the porosity of the cast tip is limited more completely or perfectly to the central interior region 40 of the main mass of the tip metal so that there is a more perfect avoidance of defective valves due either to outcropping of porosity on the seat-engaging surfaces of the finished valve or to encroachment of porosity upon the stem sec45 tion of the tip with resultant weakening and breakage of the stem incident to the tension set up in it on the freezing of the metal.

Where large numbers of valves are to be produced of given length it is obvious that the use 5Q of stop pins 24 in lieu of adjustable screws considerably reduces the cost of the mold and provides a construction that is equally satisfactory in operation.

By the use of my improved method of produc55 ing composite valves, economies are realized in production which are quite notable in comparison with other methods known to me. Perhaps the most important economy is due to the minimizing of defectives resulting either from poros₆0 ity or from fracture of the cast tip part of the valve. Another economy which results from the casting of the hard metal tip on the shank with interlocking relation, is due to the fact that metals suitable for such casting purposes are _6g available at a much lower price than similar metal purchased in definite forms or shapes. This is notably true in the case of the alloy stellite. By the use of mold apparatus of the character herein disclosed and'by following pro»0 cedures such as have been described, my method can be carried out rapidly and precisely with a minimum amount of labor and with the production of a highly uniform product, all of which factors contribute to economy of production.

While I have described specific forms of valve ⁷⁵ construction and of mold apparatus and pre ferred procedure, it will be understood that the carrying out of the method is subject to variation in all these respects within the bounds of the appended claims.