US2239381A - Mold for making hollow cast metal valves - Google Patents

Description

April 22, 1941. A. T. coLwELl. 'I 2,239,381

HOLD FOR MAKING HOLLOW CAST METAL VALVES Filed March 16, 1939 I5 Sheets-Sheet 1 [v lm /0 @www w\\\\ ,2

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April 22, 1941. A. T. COLWELL y HOLD FOR MAKING HOLLQW CAST METAL VALVES Filed March 16, 1939 I April 22, 1941- A. T. COLWELL v 2,239,381

MOLD FOR M AKING HOLLOW CAST METAL VALVES Filed March 16, '1939 3 Sheets-Sheet 3 Taz/EFT :1 1

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Patented Apr. 22, 1941' UNITED lSTATES PATENT OFFICE VALVE Archie T. Calwell, cleveland, ohio, assignmal Thompson Products Incorporated, Cleveland, Ohio, a corporation of Ohio Y Application March 16, 1939, Serial No. 262,091 I resilient and readily withdrawn through the valve 2 Claims.

This invention relates to hollow head poppet valves for internal combustion engines and to a method of making the same.

More specifically the invention relates tothe casting of poppet valves having hollow head and stem portions in a manner avoiding the necessity for appreciable machining or grinding of the casting.

Hollow poppet valves are usuallyprepared by metal working operations such as' forging. Thev forging operations are expensive and many. desirable metals for poppet valves do not lend themselves to the forging processes because they are very diiilcult to forge and, in many cases, cannot be forged at all. K

4According to this invention. however, hollow poppet valves are formed by casting molten metals to the desired vexternal shape and by forming the cavity in the head and/or stem at the same time with suitable cores. The castings of this l invention so closely approximate the desired iinal valve shape that very little machining or grinding is necessary.

Since hollow poppet valves must haveuniform t walls, it is necessary that the core member for I .the valve castings be suspended in the valve cavity of a mold so as to be equally spaced from the cavity walls at each portion of the cavity. Thus while the valve head may have walls of different thickness than the valve stem, one side of the valve head should not be thicker than the other side, nor should one side of vthe valve stem be thicker than the other side.

According to this invention, the core member r Sand or metal molds can be used. 'Ihe molds can be stationary or mounted for centrifugal rol vThe core is made of the usual core material such as core sand and binder molded to shape and baked. A feature of the invention includes reinforcing the core with a metal rod having a .pronged end. The rod extends axially through the core and the pronged end thereof spreads out into the core head for holding the core ma terial together.' The pronged end of the rod is Cil It is. then, an object of the invention to make Acore ends to suspend the main body. of the core in uniform spaced relation from thewalls deiining the mold cavity.

Otherand further objects of the invention will become apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings, which disclose preferred embodiments o1' the invention.

'I'he invention Will hereinafter be described as involving the use of permanent metal molds. but it should be understood that sand molds are operative.

On the drawings:

Figure 1 is a top plan view of a pair of permanent molds mounted in axial alignment for centrifugal rotation.

Figure 2 is a vertical cross-sectional view, with parts in elevation, taken along the line II-II of Figure l.

Figure 3 is an enlarged broken side elevational view of a core rod shown in Figure 2.

Figure 4 is an end elevational view of the rod shown in Figure 3.

Figure 5 is a top plan view of another form' of mold suitable for preparation of cast hollow valves Figure 9 is a longitudinal cross-sectional view 'of a core used in the mold shown in Figures 5 to 7 inclusive.

Figure 10 is a longitudinal cross section of a ilnished valve made from the casting shown in Figure 8. f i

Figure 11 isa longitudinal cross-sectional view for reinforcing the cores.

of a valve casting formed in the mold shown in Figures 1 and 2.'

Figure 12 is a longitudinal cross-sectional view of a finish valve formed from the casting shown in Figure 11.'

As shown on the drawings:

In Figures 1 and 2 the reference numerals I8 and II designate generally complementary molds each composed of cope and drag sections I2 and I3 respectively. The copes and drags of each mold I8 and II are held together by means of bolts such as I4. The molds Il) and II are of the permanent or metal type.

Each mold I9 and II defines a valve shaped cavity I therein and axially aligned core-receiving cavities I6.

Each cope I2 of the molds i 0 and I I has a complementary semi-cylindrical pour hole I1 extending downwardly from the top thereof at the inner ends of the molds. The pour hole sections communicate at their 'bottoms with gate holes I8 joining the pour hole with the mold cavities I5.

As best shown in Figure 2, the molds I8 andv I I are bolted in axial alignment on the platform I9 of a centrifugal device 28 by means of bolts shaped head portions 23a and elongated stem portions extending from the head 23a axially through the mold cavities I5. The ends 23h of the stems are snugly seated in the cavities I6 of the molds. In this manner the cores 23 are suspended in the mold cavities.

Reinforcing rods 24 can be inserted into the centers of the cores when the Icores are prepared The rods 24 are preferably cross-split at one end thereof and four prongs 24a, 24b, 24e, and 24d are bent outwardly as best shown in Figures 3 and 4. The pronged ends of the rods project into the heads 23a of the cores to hold the core 'material together even under the centrifugal force of the whirling operation.

In assembling the mold for the casting operation the copes I2 -are removedA and the mold cavities of both the copes and drags are coated with graphite. The cores 23 have their' ends 23h seated in the cavities I6 of the drags I3. The copes I2 are then bolted in position on the drags I3 and the complementary cavities I6 of the copes clampthe cores in position to hold the same in spaced relation-from the valveshaped mold cavities I5. The pair of molds I9 and II are then mounted on the platform I9 of the whirling device 20 and Amolten metal. 25 is poured into the pour hole I1 from which it flows through the gate holes I8 into the mold cavities. The platform I9 is rotated by the motor 22 thus forcing the metal 25- outwardly to ll up the entire mold cavities I5. The centrifugal action drives out all-of the 'air and gas in the cavities and the molds are -rotated until the metal solidifies. The motor 22 is then stopped and the molds are openedl The gates are cut or broken off and two valve castings 26 are removed. 'I'he valve castings 26 have the cores 23 therein. These cores are readily removed since the cores are frangible and the pronged ends of the re lnforcing rods will collapse as the rods are retracted through thestems of the castings 26.

As best shown in Figure 11, the casting 26 has a head portion 21 provided with .a mushroom-shaped cavity 21a and a stem portion 28 extending from the head portion 21 and provided with a cylindrical cavity 28a merging with the cavity 21m.

A centering boss 29 is integrally cast on the center of the head 21. as a center point for a lathe pivot. l

The end of the stem 28 has a thickened portion 30 thereon. f

The casting 26 is made into the nished valve 3| shown in Figure 12. The valve 3l has a sealed cavity 32 in the head and stem thereof. 'I'he cavity 32 is partially iilled with a cooling material such as metallic sodium 33. The thickened portion 30 of the casting 26 is worked down to form the solid end 34 ofthe stem of thevalve 3|. This solid portion 34 seals the cavity 32 and preferably has an annular recess 35 cut in the side thereof for receiving a retainer collar (not shown) The centering lug 29 is ground or cut oif of the casting to produce a smooth head for the valve 3|.

The cavities 21a and 28a of the casting 2'6 need not be ground to form the cavity 32 of the finished valve but it is advisable to polish the cavity 28a in the stem 28 of the casting 26 with emery cloth and to sandblast the cavity 21a inl the head 21 of thev casting 26.

As shown in Figures 5 to 7, a stationary vertical mold 48 can be used to form cast valves according to this invention in place of the rotary horizontal molds shown in Figures 1 and 2.

The mold 48 is composedV of two complementary metal halves 4I and 42 secured together..

' by means of dowel pins or bolts 43. Each mold section 4I and 42 has complementary cavities in their inner faces dening together a conical pour A core ,member 48 having a. mushroom-shaped Y head portion 49 and an elongated stem portion 59 extending from the head portion 49 is provided for forming the cavity in the cast valve.

As shown in Figure 6 the stem 5I)v of the core 48 is longer than the valve-forming cavity 46 and is of the same diameteras the hole 41. The end of the stem is thus snugly received in the hole 41 so that the cavity-'forming portion of the core is suspended in spaced relation from the Walls of the mold-forming cavity 46.

As shown in Figures 6 and 9, the core 48 is premolded in the shape of the desired cavity in the cast valve and need not be provided with a reinforcing rod. The core can be composed of the usual core sand land binder and is baked to form a hard, cohesive mass.

When the mold sections il and 42 are clamped together by means of the bolts' or dowel pins 43,

the end of the stem 50 of the core'will be securely I clamped in position in the hole 41 provided in the mold. This will automatically suspend the main body of the core in the proper spaced re- The boss 29 can serve Y assassi left in a rough condition so that airl can escape along the joint between the mold sections as the molten metal is poured into the mold cavity. The molten metal lls the entire cavity around the core Il to provide a valve casting 60 (Figure 8). 'Ihe casing 80 has a mushroom-shaped head portion Il with a cavity 6ta therein and an elon- 4 gated cylindrical stem portion i2 extending axially from the head portion and provided with a cylindrical cavity emerging with thehead cavity Gia. The head has a centering lug 63 on the center thereof.

The mold lll is preferably coated with graphite before the core and molten metal are introduced therein. 'I'he core is readily removed from the resulting casting 60 since it is composed of sand or other franglble material.

The casting SII then can be ground to remove the centeringlug 6I and other casting irregularities to produce a finished poppet valve 64 as shown in Figure 10. 'Ihe valve B4 has a cavity 65 in the head and stem portion thereof. 'I'he cavity 85 is partially iilled with a cooling material such as metallic sodium 66 and the open end of the stem is closed by a cap 61 welded, brazed, or force-fitted into the stem end. 4

The stem can be provided with an annular groove or recess $8 in the end portion thereof for receiving a retainer collar (not shown).

The valve 84 can be completely formed from the casting 60 without metalworking operations, since all of the nishing can be done by grinding.

Thislmakespossible the use of non-machinable alloys for producing valves according to this invention. 4

Suitable metals for forming the valve castings of this invention are: nickel, chromium, and iron alloys such as Nichi-ome steels; nickel, `molyb denum and iron alloys such as Hastelloy steels;

non-ferrous nickel-chromium alloys such as Brightray and cobalt, chromium and tungsten alloys such as Stellite. It should be understood, of course, that the invention is not limited to vthe use of such alloys but a number of these very hard alloys do not lend themselves to forsing and at the same time'are highly desirable metals for poppet valves. This invention now makes possible the use of these non-forgeable and even non-machinable alloys.

From the above descriptions it should be understood that permanent molds or sand molds are provided with poppet valve-shaped molding cavities and core stem receiving cavities spaced from the molding cavities to suspend the main body of the core in proper spaced relation from the walls of the mold cavities. 'I'he core stem receiving cavities, provided for suspending the cores, are axially aligned with the mold cavities and are of suilicient length to receive an appreciable portion of the core stem so that a mere seating of they core stem in the cavity will automatically align the body of the core with the mold forming cavity.

It will, of course, be understood that various details may be varied through a wide range without departing ,from the principles of this invention and itis, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by thel scope of the appended claims.

I claim' as my invention:

l. A .mold for forming cast hollow poppet valves which comprises complementary mold sections dening together a molding cavity having an enlarged head portion and a reduced stem portion, a core suspension cavity spaced longitudinally from the mold cavity adapted to receive the end of a core member therein for suspending the main body of the core in fully spaced relation from the walls of the mold cavity, and a gate cavity between the mold cavity and suspension cavity whereby the gate and core are readily removable from the casting formed in the mold.

2. Al mold for the simultaneous casting of aV plurality of hollow poppet valves which comprises complementary mold sections dening an openi ended'core suspension cavity adapted to snugly receive the stem ends of poppet valve shaped cores to rmly hold the same in cantilever fashion, said mold sections also defining a pair of poppet valve shaped molding cavities extending radially outward from the suspension cavity,

gate cavities between the suspension cavity vand molding cavities, and a common pour hole-for the gate cavities.

. ARCHIE T. COLWELL.

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