US1619901A - Method of making two-piece valves - Google Patents

Description

March 8', 1927. 1,619,901

\ w. H. WASHBURNE METHOD OF,MAKING TWOPIBCE VALVES Filed Feb. 23. 1922 my 4 /l M a g am ill Patented Mar. 8, 1927.

UNITED STATES WILLIAM H. WASI-IBURNE, OF CHICAGO, ILLINOIS, AS$IGNOPJ TO THE OLIVER TYPE- WRITER COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

METHOD OF MAKING TWO-PIECE VALVES.

Application filed February 23, 1922.

My invention relates to poppet valves in which it is desired to have the head and stem made of different materials. Thus poppet valves employed in internal combustion engine should have heads composed of a heatresistmg alloy while the stems should be made out of wear-resisting or friction-resisting alloy. I-Ieretofore, so far as I know, whether heads have been cast, welded or riveted on the stems, it has always been necessary to machine the valves, including both the head and the stem, in order to make them fit for use. Therefore, the expense of finishing the valves after the heads and the stems have been united has heretofore added con-- siderably to the cost of the valves. Furthermore, many of the processes by which heads and stems have heretofore been fastened together have been expensive and have not produced uniform results.

The object of the present invention is to produce a simple and novel valve and method of making the same, which will insure perfect union between the valve head and the stem in a simple manner and at low cost, regardless of the kinds of alloys employed, and will permit each valve to be placed in service without any subsequent finishing operation except the grinding of the valve face.

The various features of novelty whereby my invention is characterized will hereinafter be pointed out with particularity in the claims; but, for a full understanding of my invention and of its object and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawing, wherein:

Figure 1 is a vertical section through a pair of forming dies ready to close upon a valve-head blank to secure it to the stem and forge it into theshape of a valve head;

Figs. 2, 3 and 4 are views similar to Fig. 1, the lower portion of the lowerforming die being omitted, showing successive stages in the forging operation; and

Fig. 5 is a side elevation of the completed valve head and aportion of the stem.

In accordance with my invention I employ two forming dies, a lower die 1, and an upper die 2; the lower die having a die cavity 3 so shaped that when the upper die member has moved down into the cavity to the lowermost limit of its movement, that portion of r the die cavity lying below the upper die member will have the size and shape of the Serial No. 538,548.

may be completely finished before it is placed 7 in the die.

The head, which is to be forged upon the screw threaded end of the stem, may initially take any desired form as long as it has a central opening larger in diameter than the screw threaded end of the stem. The cheapest and simplest form of blank is a thick disc having a hole punched in the center and in Fig. 1 of the drawings 1 have indicated such a disc at 7 the hole in the disc being indicated at 8.

The valve stem, when placed in the die is cold, being conveniently at room temperature. The blank for the head is highly heated, preferably almost to a welding temperature. After the stem has been placed in posltion the blank is dropped into the mold cavity, as illustrated in Fig. 1, the screw threaded upper end of the stem lying within the hole in the blank. The upper die memher is then forced down. ,The first action of the dies closing on the blank is illustrated in Fig. 2, the central portion being caused to flow inwardly toward the axis of the stem and also downwardly, the top of the blank taking the shape of the bottom of the upper die which, in the arrangement shown, is flat. It will be seen that in this first stage of the forging operation the metal midway between the upper and lower faces of the blank flows radially toward the axis more rapidly than at the top and at the bottom so as to form a waist between the top and the bottom. During the next stage of the process the die descends into the position shown in Fig. 3 in which the mold cavity is completely filled with the metal of the blank and this metal has also been brought into intimate contact with the threads on the stem. The process may be stopped at this point or it may be carried farther to bring about the condition illustrated in Fig. 4. There is a tendency for the metal of the blank to continue the condition illustrated in Fig. 2, that is to flow closer to the axis of the stem between the top and bottom faces of the head than in the vicinity of those faces. Consequently when the upper die is lowered below the level which causes the metal of the blank completely to fill the mold cavity and come into intimate contact with the stem, pressures will be set up which will cause that portion of the stem surrounded by the head to be reduced in diameter at the middle; in other words, a neck or waist will be formed in the screw threaded portion of the stem so that the stem will be larger in diameter near the top and bottom faces of the valve than midway between these faces. The whole operation is performed so quickly that the stem does not have time to become heated and therefore the formation of the waist or neck is the result of a cold drawing process imposed on the stem. The result is that the head and stem are so firmly interlocked that there is no way of disconnecting them except by cutting the head in two. It will be seen that the process of forming the neck or waist in the screw threaded portion of the stem distorts the threads, the pitch diameters of the threads midway between the ends of the screw threaded portion being less than at the ends of such portion. Further distortion of the threads, aside from that which affects the pitch diameters will of course also occur.

WVhile drawing the metal of the stem to form a neck or waist is believed to be desirable, this process should not be carried too far as it may set up undesirable stresses.

In view of the fact that the metal in the stem must flow in the direction of the length of the stem during the formation of the neck or waist, I prefer to have the stem resting at its lower end upon a yielding support so that the stern may yield in the downward direction during the drawing operation. In the arrangement shown, the lower end of the stem rests on a block 9 which in turn rests on a coiled spring 10 supported by an adjustable plug 11 screw threaded into the bottom of the lower die member. The members 9 and 11 are preferably provided with axial openings 12 and 13 through which a knock out rod may be inserted to eject the valve at the end of the forging process.

The upper die member is preferably provided in its bottom face with a. central recess 14 somewhat larger in diameter than the diameter of the stem, so that the stem may rise above the top of the head without engaging with the upper die.

An important factor in securing perfect results is the cooling of the valve as soon as it is completed. It is a well known fact that the expansion and contraction of a metal upon heating and cooling is not at a constant ratio per degreeof temperature rise or fall, but is greatest between the approximate limits of 60 degrees F. and 700 degrees F. If the valve head is hot, say about 1450 degrees F. and the stem is cold, say about 60 degrees F., at the instant the swaging blow has been delivered, it is evident that if the valve is removed from the die and permitted to cool to normal temperature slowly, there will be a transference of heat from the head to the stem until both are at an approximately uniform temperature of say about 600 degrees F. In thus becoming heated, the stem will have expanded considerably so that after the temperature between the stem and the head has been equalized, the head and the stem will cool and shrink at the same rate. in other words, the full effect of the shrinkage'of the head will not be utilized in the grip which the head has on the stem. However, if the head can be cooled before the stem becomes hot, the shrinking of the head will take place without a corresponding vshrinking of thestem. I therefore take the valve directly from the die, while the head. is still at a red heat, and the stem is still cool enough to permit it to be taken up in the bare hands, and immerse the valve in a con iparatively cool quenching oil; a quenching oil having a temperature of about degrees F. having been used for this purpose. In this way expansion of the stem which otherwise would largely counteract the shink'ing of the head, is almost entirel avoided.

I claim: 7

1. The method of making a two-part valve which consists in inserting a stem into a hole of larger diameter in a heated valve-head blank, then forging the blank to cause the metal 'to flow into intimate contact with the stem and simultaneously give to the blank the shape of a valve head, and then quickly cooling the head by quenching.

2. The method of making a two-part valve which consists in inserting a comparatively cool stem into a hole of larger diameter in a highly heated rive-head blank. then forging the blank to cause the metal to flow into intimate contact with the stem and simultaneously give to the blank the shape of a valve head, and then quickly cooling the head by quenching.

3. The method of making a tw'o-pa-rt valve which consists ininserting 'a comparatively cool yieldingly-supported stem into a hole of larger diameter extending through a highly heated valve-head blank, then forging the blank to cause the metal to flow into intimate contact with the stem and simultaneously give to the blank the shape of a valve head while the stem is supported so as to be free from forging stresses tending to move it lengthwise, and then quickly cooling the head by quenching before that part of the stem surrounded by the head has become hot.

i. The method of making a two-part valve which consists in inserting a yieldingly-supported stem into a hole of larger diameter extending through a heated valve-head blank, then forging the blank by compressing it in dies to cause the metal to flow into intimatecontact with the stem and simultaneously give to the blank the shape of a valve head without subjecting the stem to forging stresses tending to move it length- Wise, and then quickly cooling the head by quenching it in oil.

5. The method of making a two-part valve which consists in inserting a compa 'atively cool stem into a hole of larger diameter extending entirely through a heated flat washer-like blank; and then forging the blank by applying a forging pressure only to the blank while the stem is supported in such a manner that it may move lengthwise in either direction without being required to overcome any component of the forging pressure in the direction of the length of the stem to cause the metal to flow into intimate contact with the stem and sin'iultaneously give to the blank the shape of a valve head.

6. The method of making a two-part valve which consists in inserting a comparatively cool stem into a hole of larger diameter in heated valve-head blank, and then forging the blank to cause the metal to flow into intimate contact with the stem and simultaneously give to the blank the shape of a valve head and form a reduced neck in that portion of the stem surrounded by the head.

7. The method of making a two-part valve which consists in inserting into a hole of larger diameter in a heated valve-head blank the comparatively cool end of a stem provided with surrounding V-shaped grooves spaced apart by V-shaped ridges, then forging the blank to cause the metal to flow into intimate cont-act with the grooves on the stem and simultaneously give to the blank the shape of a valve head, and then cooling the head by quenching before that part of the stem surrounded by the head has become hot.

8. The method of making a two-part valve which consists in inserting a comparatively cool screw-threaded stem into a hole of larger diameter in a heated flat washer-like valve-head blank, then forging the blank to cause the metal to flow into intimate contact with the screw threads on the stem and simultaneously give to the blank the shape of a valve head, and then cooling the head by quenching before that part of the stem surrounded by the head has become hot.

9. The method of making a two-part valve which consists in inserting a comparatively cool screw-threaded stem intoa hole of larger diameter in a heated valve-head blank, then for ing the blank to cause the metal to flow into intimate contact with the screw threads on the stem and simultaneously give to the blank the shape of a valve head and reduce the diameter of the middle portion of that part of the stem surrounded by the head.

10. The method of making a two-piece valve which consists in yieldingly supporting a cool valve stem in a die with one end projecting into a die cavity so as to permit the stem to move lengthwise but be held against movements in other directions, placing in the die cavity so as to surround the stem a hot blank having a hole larger in diameter than the stem extending entirely through the same, and then applying a forging pressure only to the outer exposed surfaces of the blank to cause the blank to conform to the cavity and intimately engage with the stem.

11. The method of making a two-piece valve which consists in heating a Washerlike blank, inserting in the hole in the blank a part near one end of a stem smaller in diameter than in said hole and yieldably supported against endwise movement, then forging the blank into the shape of a head intimately engaged with the stem in dies Without exerting any forging pressures on the stem in the direction of its length, and then cooling the head without permitting the stem to become objec-tionably heated.

In testimony whereof, I sign this specification.

WILLIAM H. VVASHBURNE.

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