US2011007A

US2011007A - Method of making composite valves

Info

Publication number: US2011007A
Application number: US693481A
Authority: US
Inventors: Edward M May
Original assignee: Individual
Current assignee: Individual
Priority date: 1931-10-23
Filing date: 1933-10-13
Publication date: 1935-08-13
Anticipated expiration: 1952-08-13

Description

Aug. 13, 1935. V E; M. MAY 2,011,007

METHOD OF MAKING COMPOSITE VALVES Origina l Filed Oct. 23, 1931 2 Sheets-Sheet 1 "mi HM.

l :{MMWI Aug. 13, 1935. A 2,011,007

METHOD OF MAKING COMPOSITE VALVES Original Filed Oct. 23, 1951 2 Sheets-Sheet 2 I a 0/ 5 2 52% win! j '5 f g z 26 f 2 i E I 7 /1 r rap/v5 Y Patented Aug. 13,1935

- UNITED STATES PATENT OFFICE salmon or mama c'omrosrrs VALVES Edward M. May, Detroit, Mich.

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ginal application October 23, 1931, Serial No. 570,647. Divided and this application October 13, 1933, Serial No. 003,401

12 Claims. (01. zit-15ml impair their effectiveness. This is especially true of uses in which the working conditions are such as to make renewalof a valve diflicult and a thing 4 to be avoided if possible. The known metals which have therequisite durabilityto meet these requirements are exceedingly hard and, in some cases at least, cannot be forged or finished by machining but must be formed by casting and Y finished by grinding. Furthermore, such metals, or at least some of them, tend when cast, especially when cast in metal molds and rapidly chilled, to have a porous interior structure and this akes it difficult to secure smoothly finished seat ngaging 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.

The nature of the method and the manner in which it is carried out will most readily be understood from a consideration of specific valve constructions andv of apparatus suitable for the carrying out of the method. In the accompanyin drawings I have illustrated two forms of valve metal having great hardness and the ability to strongly resist wear and corrosion. vAccordingly 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 invention 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. a

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

Other objects more or less incidental or ancillary 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 show interior construction.

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

.Fig. 3 is a view of the same character as Fig. 2

showing a modified form of mold.

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

Fig. 5 is a similar view oi. a modified form of valve construction produced by a somewhat modifled iorm 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 suitablemetal having physical characteristics adapting it to be readily machined and to perform suitably theusual functions of a valve shank. If the contemplated use of the valve is such as to call for high resistance to'corrosion, I prefer to engaging tip 5 of suitable hard, wear-resisting metal such, for example, as stellite. As is well known, stellite is both exceedingly hard and 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 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 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 I which similarly engages the opposing taper 3 of the shank. The crystallization and temperature shrinkage of the metal of the stem of the tip on setting and cooling causes the tapered shoulders 6 and 1 thereof to be drawn very strongly against the 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 in Fig. 4, but the firm engagement of the taper shoulders of the tip and shank very efiectively holds the two parts rigidly together. In the drawings the size of the voids is exaggerated for the sake of clearnes s.

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

I shall now describe the mold apparatus shown in Figs. 1 and 2 and themanner of using it in carrying out my improved method of producing compositevalves. 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

I 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 whichis secured to the bottom part by a plurality of stud bolts l0 and nuts I I. 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 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 oif when the nuts. II are removed. To provide for the rotation of the mold, the bottom part 8 is formed with a depending hub 8 which is drilled out to fit the upper end of an upright drive shaft I! to which the hub is detachably secured by a set screw 8*. In the construction shown, this shaft is the upwardly projecting end of the arma- I tur'e shaft of an electric motor I3.

, The upper part 9 of the mold is formed ith a relatively large central opening M which, in conjunction with the upper face of the lower part 8, forms the pouring cavity of the mold. The opening l4 preferably has its side wall undercut as shown in Fig. 2. Surrounding the opening [4 are a circumferential series of cavities l5, l5 to receive valve shanks and, in conjunction with the shanks, form a corresponding number 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 to form 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 l6. Each of the mold cavities is formed at its outer end with an enlarged threaded section I 5 designed to receive a screw plug I1 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 I! can easily be turned to adjust 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 adepression or annular rabbet Fl and the top part 9 of the mold is formed with a corresponding annular downward 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.

A guard casing l8 having its bottom side open and its top side formed with a central aperture [8 is adapted to be detachably mounted on the top of the casing or frame of the motor I3 so as to substantially enclose the mold and stop flying molten metal that might escape from the pouring cavity l4 when the mold is rotated.

In operating the mold, with the top part thereof removed, the prepared valve shanks l are placed in position on the bottom part 8 of the mold. The top part 9 is then placed in position on said bottom part and secured by nuts II. In the initial operation of the mold, the screw plugs I! are then inserted until their inner ends press 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 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 l2 and placing it in an oven which is maintained at the desired temperature. When the mold has been heated the guard or cover I8 is placed in position, the motor started and the molten stellite or other metal is poured through the aperture l8 into the pouring cavity M. 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 M the rotation of the mold, for which I have found a speed of about 2200 R. P. M. suitable, sets up a rotary movement of the molten metal and the resultant centrifugal force feeds 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 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

contraction also usually has the effect of rupturing .the cast metal in the ingate where it Joins the 1 are ordinarily already separated from the sprue in the pouring cavity I4 and can be individually lifted 'or shaken out. 1

The valves, on removal from the mold, have the 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 conical or taper form shown in full lines, a corresponding amount of metal at the taper 4 of. the shank is simultaneously removed.

On referring to Fig. 4, it will be observed that it is necessary to remove but a small amount of the 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 not necessary in the finishing operation to cut through this outer fine-grained layer of the cast-.

ing, 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 tips withsmooth surface and avoid losses which would occur due to the exposure of porous metal if the above mentioned conditions were not secured. I As shown by Fig. 4, the grinding operation penetrates to the axis of the ingate metal at 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. 4 Hence, with thesmall ingate and the heavy chilling action, the strong centrifugal force to which the molten metal issubjected 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 I, 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 stem part in order to avoidfracturethereof. I prevent such porosity in the stem l of the tip as well as in the ingate to the cavity by suitable It will be obdesign of the casting cavity. served that the shape of the cavity is made such that the cast valve tip has the largest mass of its constltuentmetal in the region between theingate and the stem 5". Consequently, in casting the valve tip the interior part of this larger mass of metal in the intermediate zone remains molten.

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- 1 innermost part of the ingate) with the result that finishing operation on the valve and does not reach the stem 5 ,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 stresses great enough to rupture the metal avoided. In Fig. 4, for example, the length of the neck section 6'' of the tip 5 between the latters taper shoulders 6 and I is so proportioned that the contraction 'of the tip on casting shall be just sufilcient to effect the desired clamping action between the tip and the shank without setting up undulylarge stresses in the metal of the tip. The valve shown in Fig. 3 and presently to be referred is to be designed with similar precaution.

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 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 show the valve as it is taken from the mold after casting on the valve tip. In this last construc tion the shank I9 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 walls comprising a short taper at l!!- and a long taper at It". The outer surface at this same end of the shank is formed with a bevel or taper l9. Into this cavity of the shank is cast a tip of stellite orother suitable metal. Obviously this 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 swagingdies and subject it to pressure to form the circular groove I9 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 l9 of the shank 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 surfacesof the valve represented by ,the dot-anddash 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 construction 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 castingsets up a strong internal tension in the tip so 'that the latter has its taper surfaces drawn against corresponding opposing surfaces of theshank, thereby producing a very strong clamping force. In the second valve the swaging of the shank It 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, porosityof the cast metal forming the seat-engaging portions of the valve is 'avoided by the use of a suitably structed ingate and by providing a relatively large mass of cast metal adjacent to the seat-engaging surfaces so that the crystallization shrinkage of 4 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 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- 2|, 22, respectively, formed with opposite radial recesses 2I 22 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 and the central top surfaceof the bottom part 2| is raised in convex form at 2l 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 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 the numeral 25 and the tippart by 26. Here the stem part 26 of the tip has its diameter and length approximately the same as the diameter and length, respectively, of the ingate part 26*.

The mold shown in Fig. 3 is operated in substantially 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 2| of the-mold tends to prevent the sprue metal from sticking to the mold. I have also found that by making the stem 2t of the valve tip of approximately the same diameter and length as'the ingate metal 25 the porosity of the cast tip is limited more completely or perfectly to the central interior region 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 1 I valve.

seat-engaging surfaces of the finished valve or to encroachment of porosity upon the stemsection of the tip with resultant weakening and breakage of the stem.incident to the tension By the use of my improved method of producing composite valves, economies are realized in production which are quite notable in comparison with other methods known to me.

mizing of defectives resulting either from porbsity or fromfracture of the cast tip part of the 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 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 stcllite. By the use of mold apparatus of the character herein disclosed and Kby following procedures 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 construction and of mold apparatus and me- Perhaps. the most important economy is due to the miniferred 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.

What I claim is:

1. A method of making a composite valve comprising a metal shank and a seat-engaging head of hard, wear-resisting cast metal subject to porosity when cast, the said method consisting in placing the shank in a metal mold with a portion of the shank forming part of the wall of a casting cavity which approximates the form of the cast metal head part of the finished valve; pouring the molten casting metal into the mold cavity to form the valve head; compensating for crystallization shrinkage of the metal forming the seat-engaging portion of the head with molten metal from the interior of'the head; and thereafter. reducing the cast part of the valve to finished form.

2. A method of making a composite needle valve'comprising a metal shank and a conical seat-engaging tip of hard, wear-resisting cast metal subject to porosity when cast, the said method consisting in placing the shankin a metal mold with one end of the shank forming part of the wall of a casting cavity which approximates the form of the cast metal tip.

part of the finished valve and which has a restricted ingate passage leading axially into the conical end of the cavityj forcing molten casting metal into the casting cavity through said ingate passage to form the valve tip; compensating for crystallization shrinkage of the metal forming the conical sides of the finished valve tip with molten metal from the interior of the p; and thereafter reducing the cast part of the valve to finished form.

3. A method of making a composite needle valve comprising a metal shank and a conical seat-engaging tip of hard, wear-resisting cast metal subject to porosity when cast, the said method consisting in placing the shank in a metal mold with one end of the shank'forming part of the wall of a casting cavity which approximates the form of the cast metal tip part of the finished valve andwhich has a restricted ingate passage leading axially into the conical end of the cavity;

centrifugal force to form the valve tip; crfinpensating for crystallization shrinkage of the metal forming the conical sides of. the finished valve tip with molten metal from the interior ofthe tip; and thereafter reducing the cast part of the valve to finished form.

4. A method of making a composite needle valve comprising a metal shank and a conical seatengaging tip of cast metal, the said method consisting in placing the shank in a metal mold with one end of the shank forming part of the wall of a casting cavity which approximates the form of the cast metal tip part of the "finished valve and which has a restricted ingate passage leading axially into the conical end of the cavity;

pouring molten castingmetal into the mold and simultaneously rotating the mold to introduce the molten metal through the ingate passage by centrifugal force to fill the cavity and form the valve tip; and thereafter reducing the cast part of the valve to finished form.

5. A method of making a composite needle valve comprising a metal shank and a conical seatengaging tip of cast metal, the said method con-.

, ingate passage leading axially into theconical end of the cavity; pouring molten casting metal into the mold and simultaneously rotating the mold to introduce the molten metal through the ingate passage by centrifugal force to fill the cavity and form the cast tip of the valve with an interlocking connection with the shank; and thereafter reducing the cast part of the valve to finished form.

6. A method of making a composite needle valve comprising a metal shank and a conical seatengaging tip of cast metal, the said method consisting in forming the shank with an undercut axial bore in one end; placing the shank in a metal mold with its said end forming part of the wall of a casting cavity which approximates the form of the cast metal tip part of the finished valve and which has a restricted ingate passage leading axially into the conical end of the cavity; pouring molten casting metal into the mold and simultaneously rotating the mold to introduce the molten'metal through the ingate passage by centrifugal force to fill the cavity and form the cast tip of the valve with an interlocking connection with the shank; and thereafter reducing the cast part of the valve to finished form.

7. A method of making a composite needle valve comprising a metal shank and a conical seatengaging tip of cast metal, the said method consisting in formingthe shank with an undercut portion at one end; placing the shank in a metal mold with the undercut end ofthe shank forming part of the wall of a casting cavity which approximates the form of the cast metal tip part of the finished valve and has a restricted ingate passage leading axially into its conical end and the ingate passage by centrifugal force to fill the cavity and form the cast tip of the valve with an interlocking connection with the shank; and

thereafter reducing the cast part of the valve to fiinished form.

8. A method of making a composite valve comprising a metal shank and a seat-engaging head of hard, wear-resisting cast metal subject to porosity when cast, the said method consisting in placing the shank in a metal mold with a portion of the shank forming part of the wall of a casting cavity which approximates the form of the cast metal head part of the finished valve; pouring the molten casting metal into the mold cavity ,to form the valve head; compensating for crystallization shrinkage of the metal forming the seat-engaging portion of the head with molten metal from the interior of the head; subjecting the shank to a swaging operation to effect a rigid interlocking connection between the shank and wall of acasting cavity which approximates the form of thecast metal tip part of the finished valve and which has a restricted ingate passage leading axially into the conical end of the cavity; pouring molten casting metal into the mold and simultaneously' rotating the mold to introduce the molten metal through the ingate passage by valve tip; subjecting the shank to a swaging operation to effect a rigid interlocking connection between the shank and tip; and thereafter recentrifugal force to fill the cavity and form the ducing the cast part of the valve to finished form. r

10. A method of making a composite needle valve comprising a metal shank and a conical seat-engaging tip of cast metal, the said method consisting in forming the shank at one end with an axially extending cavity having its side wall undercut in relation to its mouth; placing the shank in a metal mold with its cavityend forming part of the wall of a casting cavity which approximates the form of the cast metal tip part of the finished valve and which has a restricted ingate passage leading axially into the conical end of the cavity; pouring molten casting metal into "11. 'A method of making a composite needle valve comprising a metal shank and a conical seatengaging tip of cast metal, the said method con sisting in forming the shank at one end with an axially extending cavity having its side wall undercut in relation to its mouth and with an annular shoulder surrounding the mouth of the cavity; placing the shank in a metal mold with the wall of the cavity and the said shoulder for ing part of the wall of a casting cavity which approximates the form of the cast metal tip part of the finished valve and which has a restricted ingate passage leading axially into its conical end; pouring molten casting metal into the mold and simultaneously rotating the mold to introduce the molten metal through the ingate passage by centrifugal force to fill the cavity and form the cast tip of the valve with an interlocking connection with the shank; and thereafter reducing the cast part of the valve to finished form;

12. A method ofmaking a composite needle valve comprising a metal shank and a conical seat-engaging tip of cast metal, the said method consisting informing the shank at one end with an axially extending bore and with two annular shoulders surrounding theside wall'of the bore and facing away from each other; placing the shank in a metal mold with the wall of its bore and the said shoulders forming part of the wall i thereafter reducing the cast part of the valve to finished form.

of a casting cavity which approximates the form of the cast metal tip part of the finished valve and which has a restricted ingate passage lead ing axially into the conical end of the cavity: pouring molten casting metal into the mold and simultaneously rotating the mold to introduce WARD n. MAY.