US2004259A - Valve seat - Google Patents

Description

J. A. WEIGER Jung 11, 1935.

VALVE SEAT Filed Oct. 22, 1931 INVENTOR BY s Patented June 11, 1935 UNITED STATES PATENT OFFICE VALVE SEAT Joseph A. Weiger, Indianapolis, Ind., assignor to P. R. Mallory & 00., Incorporated, Indianapolis, Ind., a corporation of Indiana Application October 22, 1931, Serial No. 570.339

6 Claims.-

This invention relates to valve seats, and more particularly to valve seats for use in internal combustion engines.

A general object of the invention is the provision of an improved valve seat which is admirably suited to withstand the deteriorating conditions encountered at the ports of an intemal combustion engine, and'particularly at the exhaust ports thereof.

More specifically, the invention has for objects the provision of a valve seat having enhanced heat resisting properties which will not anneal in the product hereinafter described .and the,

scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawing, in which: c

Fig. 1' is a plan view showing one form of valve seat embodying features of the present invention;

Fig. 2 is a transverse sectional view taken on a diameter of the seat shown in Fig. 1;

Fig. 3 is a plan view showing a modified form of valve seat; a

Fig. 4 isa transverse sectional view taken on a diameter of the seat shown in Fig. 3; and

Fig. 5 is a fragmentary sectional ,view taken through a portion of an engine cylinder block showing, on a reduced scale, the valve seat of f Fig. 1 inserted in place therein.

In accordance withthe present invention, it

has been found that generally enhanced characteristics can be imparted to valve seats which are designed for use in internal combustion engines by using in their formation a metallic body comprising, in its preferred form, tungsten which has been treated with a hardening agent, such as carbon, and cemented or impregnated with a relatively low melting point material such as copper. Such material is particularly well suited successfully to withstand the deteriorating conditions encountered at the exhaust ports of such an'egnine. A material of this kind is disclosed in a co-pending application of George N. Sieger and Joseph A. Weiger, Serial No. 52,690, which has matured into Patent No. 1,848,437, and does not, per se, form any part of the present invention, except insofar as it is utilized in connection with valve seats which are subjected to deteriorating influences such as those encountered 10 in internal combustion engines. A composite valve seat formed by inserting the herein contemplated improved metallic material in a metallic seat member is described and claimed in my co-pending application, Serial No. 570,338. The 15 seats there shown are more particularly suited for use with valves of large size, and may be manufactured more economically than rings formed entirely of the herein described hard metallic material. The invention claimed in this 20 application refers to valve seats formed in toto of this material. Such a ring is well'adapted for use with smaller sizes of valves, where the amount of material required to form a complete seat is relatively limited. It is, of course, also 2 applicable to valves of larger size, and no limitation as to size is intended in the present description and claims.

The material from which it is here proposed to make valve seats may be formed in ways. The preferred method of forming a hard metallic valve seat material comprises forming a porous slug of refractory metal, treating with a hardening agent, sintering and impregnating it with a fused low'melting point metal. Such a 35 slug may be obtained by mixing powdered tungsten and carbon, pressing the mixture to shape, and sintering it; or powdered tungsten maybe pressed into form and sintered in a carbonaceous atmosphere. mersed in or subjected to fused copper, which will run throughout the porous structure, the impregnation being abetted by capillary action.

For the-purposes of the present invention, tungsten is a preferred refractory metal, al- 45 through othersimilar metals in the same group and subgroup of Mendelejeifs periodic table, a

, such as molybdenum, which may in some cases prove satisfactory, are contemplated. The hardening agent preferably is carbon, in the form 0 of lamp black, although other hardening materials for the refractory metal may be used, wherefore no specific limitation is intended. The hardening agent may be present in any desired amount, but preferably is present in an amount 55 several 30 The slug thereafter may be im- 40 less than the combining weight thereof with the amount of refractory metal used. When carbon and tungsten are used, for example, the preferred amount of the carbon is less than that needed to convert all the tungsten into a carbide, whereby the tungsten becomes partially carburized upon heating, but does not lose its identity. Carbides of tungsten are, among other things, more difficult to machine than the preferred product. Copper is a preferred low melting point metal, although any metals having proper characteristics as to fusion point, corrosion resistance, mechanical strength, and the like, are contemplated. Silver, for example, is a suitable cementing material where the operating temperatures to which the valve seat is subjected do not run toohigh. The heating is preferably carried out in a. reducing, neutral or carburizing atmosphere, such as, for example, hydrogen, nitrogen, or hydrocarbon atmosphere.

While the ingredients and proportions used in the present valve seat are subject to variations within reasonable limits, a preferred form of material embodying the invention is given by way of example as follows:

Percent Tungst n 80 Car 0.3 Copper -l 19.7

A cemented, sintered body made from these ingredients, in accordance with the above outline, or any other suitable methods, is remarkably suited for its intended function as a valve seat.

Referring more particularly to the drawing, and especially to Figs. 1 and 2 thereof, there is showna centrally perforate seat member I I, having its upper internal margin bevelled to an angle of approximately 45, as illustrated at II, to provide a seating surface for cooperation with the valve head. This valve seat is formed of the herein described hard cemented or impregnated tungstic material. The finely divided ingredients used in the manufacture of this material may be pressed in a ring shaped mold, in order to give the ultimately formed product substantially its proper shape. After a ring of such cemented or impregnated tungsten-carbon-copper has been formed, it is suitably machined.

In Figs. 3 and 4, there is shown a somewhat different form of valve seat which also is formed of the herein contemplated hard tungstic composition. This seat comprises a ring 2|, having a generally rectangular cross section, as shown in Fig. 4, the net upper face 22' of which is adapted to provide the wearing surface. The powdered materials used in the formation of this type of ring may be pressed into form in a ring shaped mold, as in the case of the preceding embodiment, after which they likewise are heat treated in a hydrogen atmosphere, in order to sinter and harden the tungstic base and fuse the low melting point metal, which is adapted to cement or impregnate such base.

In each of the modifications shown, after the ring is removed from the heat treating furnace, it is necessary to machine at least the inside diameter and one face of the valve seat. The

material used in the present ring, while possessing the proper hardness, strength, and non-corrosive qualities to assure an extremely long and satisfactory service life, has good machining properties and may be readily ground and lapped. These rinding and lapping operations ordinarily cooperating fit between the valve head and seat.

The described forms of seats made from this material are admirably suited for shrink-fitting to the cylinder block of an engine. The block, which usually is made of cast iron, may be locally heated and the valve seat dropped into place. If preferred, the seat may be cooled, for example, by immersion in liquid air, and "dropped into place in the cylinder block. Upon return to room temperature, a tight fit is secured, it being possible even to obtain a slight dovetail fit between the parts. The valve seat of the herein contemplated improved material is shown thus fitted to a cast iron cylinder block in Fig. 5. The coefiicient of thermal expansion of the improved hard metal composition is such as admirably to suit it to these shrink-fitting operations, and also to preserve a tight fit between the valve seat and cylinder block under operating conditions. In addition, this composition has proper heat resisting qualities and will not anneal during engine operation, nor will it pit or transfer metal to the cooperating valve part. Coupled with these desirable qualities, it has extremely long service life as compared with other materials. No previously used valve seat material of which applicant is aware has the long life, coupled with good machining qualities, propfor example molybdenum, may be used in lieu.

thereof, or in combination therewith. Accordingly, it is intended that the recital of tungsten as an element in these claims shall be construed to refer not only specifically to that element, but also to other equivalent elements and particularly to those which are herein mentioned.

It will be seen that there has been disclosed a valve seat which is admirably suited to fulfill its intended functions.

Since certain changes may be made in the above product and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of thegeneric and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Particu1arly, it is to be understood that in said claims, ingredients or compounds recited in the singular are intended to include compatible mixtures of such ingredients wherever the sense permits.

Having described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. A valve seat for internal combustion engines, formed of a cemented metallic body comprising approximately four-fifths of a refractory metallic element chosen from the group and subgroupof Mendelejeffs periodic table of elements which includes tungsten, a metal of a lower melting point incorporated therewith, and a hordening agent present in an amount less than the combining weight thereof with the quantity of tungsten present.

2. A valve seat for internal combustion engines, formed of a cemented metallic body comprising a porous base of tungsten in preponderating amount, and carbon in an amount sufficient to harden said base, and copper impregnating said porous base.

3. A valve seat for internal combustion engines, formed of a cemented metallic body com--. prising approximately four-fifths tungsten forming aporous base, copper incorporated in the pores of said base, and carbon in an amount less than the combining weight thereof with the amount of tungsten used to form a carbide of tungsten.

4. A valve seat for internal combustion engines, formed of a porous partially carburized tungsten base and copper impregnating said porous base.

5, A valve seat for internal combustion engines,

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