US2963011A - Valve lifter - Google Patents

Description

Dec. 6, 1960 A. F. DAVIS ETAL VALVE LIFTER Filed June 29, 1959 IN VEN T 0R5 United States Patent VALVE LIFTER Albert F. Davis, Grand Rapids, and Charles H. Palmer,

Holland, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 29, 1959, Ser. No. 823,572

20 Claims. (Cl. 123-90) This invention relates to a composite valve lifter and similar articles and to an improved method of making same.

A specific object of this invention is to provide a new and improved valve lifter of the mechanical type formed of a tubular steel body member having an imperforate push rod seat and an end closing wear-resistant metal foot piece secured to the tubular member by a brazed joint having a bonding interface formed from areas having an accurately controlled surface finish.

Among other objects of this invention are: to provide a method of forming an improved composite article, such as a valve lifter body or similar article; to provide a more economical improved valve lifter having an imperforate push rod seat integral with the tubular body thereof and to provide an improved method of forming composite valve lifter bodies and similar articles which lends itself to high production operation under conditions resulting in excellent metallurgical control and maximum uniformity of the product. 7

In accordance with the invention there is provided a composite mechanical valve lifter or similar article having an imperforate push rod seat member adjacent one end of a tubular body member, preferably integral therewith. A foot piece of cast iron or the like having an accurately controlled surface finish is brazed to the other end of the tubular body member. The end cap or foot of the valve lifter engages the cam or other operating member and must be formed of a hard, wear-resistant material, such as cast iron while the body member can be of a low carbon steel. Excellent results have been obtained by brazing the foot piece to the body member with a copper-tin alloy. The foot piece is first coated with the alloy and then assembled with the tubular body member. The assembled parts are thereafter heated to a sufficient temperature to melt the copper coating and suitably bond the parts securely together.

Reference is made herewith to the accompanying drawing, in which:

Figure 1 is a fragmentary elevational view, in partial section, showing a tubular body member for a valve lifter or similar article and an alloy coated foot piece; and

Figure 2 shows. a sectional view taken longitudinally through a mechanical valve lifter, such as can be formed in accordance with the present invention.

Referring now to Figure l, a valve lifter generally comprises a tubular body member 10 to one end of which a cast metal foot or end cap 12 is secured. The end of the tubular body member has a bore 14 of suitable dimension to snugly receive the end cap 12. The end cap is a generally cylindrical member, a portion 16 of which is of a reduced diameter and slightly tapered for insertion in close-fitting relationship within the bore 14 of the tubular body member. The reduced diameter portion 16 gives rise to a shoulder 18 on the end cap 12 which abuts the end surface 20 of the tube when the end cap and tubular body member are assembled.

The tubular body member of a mechanical valve lifter; or the like, can be cold formed from SAE 1010, SAE 1016 or equivalent low carbon steel. As shown in connection with Figure 2, the steel is extruded to form a tubular body 10 having, adjacent one end, an imperforate integral transverse wall 22 in which is formed a push rod seat 24. Upon assembly of the parts 10 and 12, a closed chamber 26 is formed in the lifter.

The foot piece or end cap for a valve lifter is preferably made of a hard, wear-resistant material, such as cast iron or the like. One such material which can be used is as follows:

Generally the composite valve lifter is made by brazing the cast iron foot piece 12 to the tubular body member 10. In order to obtain a satisfactory high strength joint between the foot piece and the tubular body member, it has heretofore been believed necessary to resort to the use of atmosphere for protection against oxidation of alloy or joint surfaces for good bonding. Heretofore in the presence of at least one aperture in the push rod seat member or wall 22, flushing or purging air from the interior 24 of the valve lifter was necessary. It has now been found that an improved valve lifter can be obtained if it is formed with an imperforate transverse wall. Moreover, a highly satisfactory brazed joint is obtained without purging the exterior of the lifter if the surface finish of the mating interfacial bonding areas is accurately controlled. By making a valve lifter in accordance with our invention not only is the requirement for atmospheric protection of the joint during brazing materially minimized but, in certain instances, it is possible to bond the two parts entirely without the use of any protective atmosphere. Thus not only is the resultant product improved but also its method of manufacture.

It is also desirable to form a sealed chamber 26 in the valve litter in order to maintain a constant light weight of the valve lifter and to insure unIform weight distribution of the plurality of valve lifters used in an engine. Although it is extremely advantageous to form a valve lifter having the sealed inner chamber, heretofore it was not possible to make such a satisfactory valve lifter with an integral imperforate transverse wall in a tubular body member.

We have now found, however, that if the relative surface finishes of the mating surfaces of the tubular body member and the foot piece are accurately controlled, an excellent brazed joint can be formed. When using a tubular body member having a surface finish of approximately 10 micro inches R.M.S. to micro inches R.M.S., excellent brazed joints can be obtained if the surface of the cast iron foot piece is maintained between approximately 70 micro inches R.M.S. and micro inches R.M.S. and the amount of brazing alloy accurately controlled. When using a tubular body member having the described surface finish a satisfactory brazed joint, in certain instances, may be obtained using a surface finish as low as approximately 60 micro inches R.M.S. More: over, in some instances, it may be possible to obtain satisfactory results with surface finishes as high as 200 micro inches R.M.S. on the cast iron foot piece.

It is also contemplated that the steel body member can be made with a surface finish exceeding 80 micro inches R.M.S. In such instance the surface finish of the cast iron foot piece can be. correspondingly reduced. If the-bonding area of the tubular body member had a surface finish in excess of 100 micro inches'R.M.S., the surface finish of the mating portion of the end cap could be as low as 50 micro inches R.M.S. In general, however, we prefer to employ a tubular body member having a surface finish below approximately 100 micro inches R.M.S.

The brazing material may be applied to the parts in a variety of ways, such as in powdered form or a solid ring to obtain a suitable brazed joint. However, an especially durable bond can be obtained in forming our valve lifter if the brazing alloy is applied as a coating on the foot piece 12 in accordance with the method set forth in the previously filedpatent-application Serial No. 754,822, filedAugust 13, 1958, in the names of John Dornbos, Ell-en-L'. Karchnerand Charles H. Palmer and assigned to the assignee of the present invention.

The previously filed application describes using an electrodeposited copper-tin alloy coating on the cast iron foot piece as the source ofbrazing material to the bonding interface. When brazing the alloy coated cast iron foot piece to the body-member by induction heating, the use of a protective atmosphere is not only minimized but may also even be eliminated.

By using the copper-tin alloy coating on a cast iron end cap for the desired surface finish, the foot piece can be brazed to a tubular body member having an imperforate transverse wall simply and economically with a joint as strong as a joint made with the use of a protective atmosphere. Exceedingly satisfactory joint strength was achieved with this type of alloy which has an especially uniform melting point. Moreover, maximum uniformity of the product and excellent metallurgical control of the bonding can be achieved when the thickness of the coating and composition of the brazing alloy is accurately controlled.

More particularly by using an electroplating bath, such as hereinafter set forth, the composition of a copper-tin brazing alloy having an unusually high tin content can easily be accurately controlled under commercial high production conditions. A copper-tin brazing alloy containing about to 60%, by weight, tin and about 40% to 80%, by weight, copper has been satisfactory in producing a strongly bonded composite assembly. However, in general, it is preferable to use an alloy having a composition of about to by weight, tin and about 60% to 75%, by weight,-copper. This latter brazing alloy is especially preferred due to its uniform melting point temperature in the range'from about 1360 F. to 1550 F. while in the former alloy the melting point temperature varies from about 1360" F. to l650 F. It is especially desirable to employ a brazing alloy which uniformly melts to form a bond of superior strength and which provides a uniform impervious joint.

As hereinbefore mentioned, maximum uniformity of the product and excellent metallurgical control of the bonding can be achieved when the thickness of the coating and the composition of the brazing alloy is accurately controlled. The thickness of the coating is easily controlled very precisely when the coating is formed by electrodeposition. The nature of a copper-tin alloy coating of the composition, such as hereinbefore described, can be easily and precisely controlled by electrodepositing the alloy from an aqueous alkaline copper cyanidepotassium stannate bath solution. We have found such an electroplating solution canbe effectively used to deposit an alloy of our preferred composition if the relative proportion by weight of free potassium cyanide to the potassium cupro cyanide in the bath is maintained at about 0.8 to 1 respectively. A cast iron foot piece of a valve lifter, 'forexample, can be coated with a copper-tin alloy of suitable composition using a bath solution which in operation is as follows:

Ounces per gallon A wear-resistant metal foot piece is placed in the abovedescribed plating solution and the copper-tin alloy is electrodeposited at a bath temperature of about F. to l70 F. using a current density from approximately 10 amperes per square foot to 70 amperes per square foot.

The electrodeposition is continued until a sufficient plate thickness is achieved, preferably at least about 0.0008 inch. The specific depth or thickness of the electrodeposited layer of brazing alloy is dependent upon the roughness of the casting surface, the fit or clearance desired between the tubular body member and the end cap, objections to an excess of brazing alloy, etc. In general, plating thicknesses of at least about 0.0008 inch are used to form a satisfactory bonding while thicknesses in excess of about 0.00 15 inch are undesirable. Coating thicknesses substantially greater than about 0.0015 inch tend to contribute to a displacement of the end cap during brazing. Moreover, excessive thicknesses may produce a poor bond which may be deleteriously affected in subsequent hardening operations. Moreover, if an excess of brazing alloy is present, it may flow during the brazing operation into undesired areas.

We have found that the composition of the brazing alloy can more precisely be contained within the preferred limits when using a plating bath which, as formed, is as follows:

Ounces per gallon Free KCN n 2.5-3.5 KCu(CN) 3.0-3.5 KOH 0.5l.0 K2SI'1(OH)6 A satisfactory coating is obtained when electrodepositing the bronze alloy from the above bath at a temperature of from about F. to F. using a cathode current density of about 10 amperes per square foot to 15 amperes per square foot.

The alloy coated end piece is assembled with the tubular body member to which it is to be secured to form a composite assembly. The assembled parts are then heated in a furnace to about 1550 F. to about 1700" F. for a duration of about 30 minutes to about 60 minutes. However, if induction heating is used, the assembly is preferably heated to a brazing temperature of approximately 1800" F. to 1900 F. for approximately 30 seconds.

Iigher temperatures used in the induction heating require a shorter duration of heating in order to approximate essentially the same flow and diffusion of the alloy into the parts as produced by furnace heating. An insufficient brazing temperature or duration of the treatment is characterized by a low strength bond in which there hasbeen a non-uniform flow of the brazing alloy.

As previously pointed out, the requirement of using a protective atmosphere to obtain-a satisfactory brazed joint is not only materially reduced but may even be eliminated. When brazing the parts by induction heating, the protective atmosphere need not be used. If furnace brazing the parts, it is desirable to use a protective atmosphere to some extent to avoid excessive scaling, spalling, etc. of the outer surfaces of the parts. No purging of the body member is necessary, however. One protective atmosphere which can be used has the following analysis: 20% carbon monoxide, 40% hydrogen and 40% nitrogen, all proportions by volume. However, substantially pure mixtures of hydrogen, carbon monoxide, nitrogen, helium, argon, etc., can also be used.

We have additionally found that the strength of the bond between the end cap 12 and the tubular body member is particularly is in an extremely close fitting relationship with the tubular body member. Accordingly, it is especially desirable to have the diametrically smaller portion 16 of the coated end cap be of at least about the same dimension as the configuration of the bore 14 of the tubular body member. We have found that by press fitting the alloy coated end cap 12 within the end of the tubular member, an intimate contact of the bonding surface is obtained which facilitates uniform distribution and flow of the brazing alloy during brazing. The intimate contact and resultant uniform flow are particularly effective in producing an imperforate joint or bond between the members. Highly satisfactory results are obtainable when the diametrically smaller portion 16 of the end cap 12 for a valve lifter having an outer diameter of about 0.875 inch is at least about 0.004 inch greater than the inner diameter ofthe tubular member. With this relative construction the end cap must be press fitted on the end of the tubular member in the assembly of the composite article prior to brazing. In general, the limiting dimension for the maximum diameter of the smaller portion of the end cap is determined by the strength of the tubular member. In most instances, this maximum limit is approximately 0.028 inch.

The tubular member of a typical valve lifter, such as shown in Figure 2, has an outer diameter of approximately 0.90 inch and an enlarged tapered bore adjacent one end of approximately 0.78 inch in maximum diameter for receiving the end cap. The tapered part of the coated end cap has a transverse dimension of between approximately 0.0008 inch and 0.0015 inch greater than that of the bore of the tubular member. The smaller portion of the end cap is compressed into the enlarged bore of the tubular member so that the shoulder of the end cap abuts the end surface of the tubular member.

In making a valve lifter, such as just described, the foot piece was cleaned prior to applying the alloy coating to remove rust, dirt, grease, etc. An initial cleaning to remove foundry sands and rust can be effected by a wheel-abrate cycle of about 10 minutes using about a 500 pound load. The part can then be degreased, if necessary, in the usual way as by means of solvents such as trichloroethylene or the like. After degreasing the part, it can then be pickled in a suitable acid solution in the known and accepted manner for such cleaning, such as by immersion for about two minutes in an aque ous solution containing 9% to 10% muriatic acid.

After suitable cleaning the part was rinsed to remove the acid adhering thereto and preferably placed in an aqueous solution containing about 2.5 ounces to 3 ounces of potassium cyanide per gallon of water. After immersion in the potassium cyanide solution for approximately 2 minutes the part was removed therefrom and directly placed in the plating bath.

The end cap was placed in a bronze plating solution which, as formed, was compounded to deposit a bronze alloy containing about 30%, by weight, tin and about 70%, by weight, copper. This plating solution was formed with de-ionized Water, as follows:

Ounces per gallon Free KCN 3.0 KCu(CN) 3.0 KOH 0.4 K Sn(OH) 13.5

increased when the end cap The assembly was then placed in a brazing furnace under a temperature of approximately 1600 for approximately 40 minutes under a protective atmosphere, such as hereinbefore described. It was removed from the brazing furnace and subsequently cooled under the protective atmosphere.

Due to the continuous succession of shocks and various dynamic stresses to which a valve lifter is subjected, it is readily apparent that an exceptionally strong bond ing of the end cap to the body member must be obtained. Moreover, in commercial applications, it is of extreme importance that this bond be consistently uniformly but economically formed under production conditions. By uniformly coating the bonding surface of the end cap with the brazing alloy, it is inherently uniformly distributed throughout the bonding interface when the parts to be joined are assembled. Moreover, a separate step in the assembly operation of each composite unit is omitted, thus expediting manufacturing operations. By coating the end caps as large groups, only one coating step is necessary for a great many parts.

Although this invention has been described in connection with certain specific embodiments thereof, no limitation is intended thereby except as defined in the appended claims.

We claim:

1. A valve lifter comprising a tubular member, an imperforate integral transverse wall within said tubular member and an end cap, said end cap being brazed to one end of said tubular member.

2. A valve lifter comprising a tubular member, an imperforate integral transverse wall within said tubular member and an end cap, a portion of said end cap extending within one end of said tubular member and suitably brazed to said tubular member.

3. A valve lifter comprising a tubular member, an imperforate transverse wall within said tubular member and an end cap, a portion of said end cap extending within one end of said tubular member and suitably brazed to said tubular member with a copper-tin alloy, said alloy supplied as an electrodeposited coating on said end cap.

4. A composite article comprising a tubular member, an imperforate transverse wall in said tubular member and an end cap on said tubular member having a portion thereof extending into said member, said end cap bonded to said member by a suitable brazed joint having a bonding interface, said interface formed from mutually contacting areas, one of which has a surface finish below about micro inches R.M.S. and the other of which has a surface finish of about 60 micro inches R.M.S. to 200 micro inches R.M.S.

5. A composite article comprising a tubular member, an imperforate transverse wall in said tubular member and an end cap on said tubular member having a portion thereof extending into said member, said end cap bonded to said member by a suit-able brazed joint having a bonding interface, said interface formed from mutually contacting areas, one of which has a surface finish below about 100 micro inches R.M.S. and the other of which has a surface finish of about 70 micro inches R.M.S. to micro inches R.M.S.

6. A composite article com-prising a tubular member, an imperforate transverse wall in said tubular member and an end cap on said tubular member having a portion thereof extending into said member, said end cap bonded to said member by a suitable brazed joint having a bonding interface, said interface formed from mutually contacting areas, one of which has a surface finish of about 10 micro inches R.M.S. to 80 micro inches R.M.S. and the other. of which has a surface finish of about 70 micro inches,R.M.S.,to 160 micro inches R.M.S.

7'. A composite article, comprising-a tubular-,member,

an imperforate transverse wallin saidtubular member and an end cap on said tubular member having a por-,

of extending into said member, said end cap bondedv to said member by a suitable brazed joint having a bonding interface, said interface formed frommutually contacting areas, one of which has a surface finish below about 100 micro inches R.M.S. and the other of. which has a surface finishof about 60 micro inches R.M.S. to 200 micro inches R.M.S.

9. A valve lifter comprising a tubular member, animperforate transverse wall, a push rod seat in said Wall and an end cap on said member having a portion thereof extending into said member, said end cap bonded to said member by a suitable brazed joint having a bonding interface, said interface formed from end cap and member mutually contacting areas which respectively have surface finishes of about 70 micro inches R.M.Sfto 200 micro inches R.M.S. and 10 micro inches R.M.S to 100 micro inches RM.S.

' 10. A valve lifter comprising a tubular member, an imperfor-ate transverse wall, a push rod seat in said wall and an end cap on said member having a portion thereof extending into said member, said end cap bonded to said member by a suitable brazed joint having a bonding interface, said interface formed from mutually contacting areas, one of which has a surface finish below about 100 micro inches R.M.S. and the other of which has a surface finish of about 60 micro inches R.M.S. to 200 micro inches R.M.S., said areas being bonded by an alloy containing, by weight, about 20% to 60% tin and 40% to 80% copper, supplied as an electrodcposited coating on said end cap.

11. The method of making a composite article which comprises forming a tubular member having at one end a surface adapted to receive an end cap, forming an imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, applying a brazing alloy to one of said surfaces, assembling said end cap with said tubular member to form a composite article, heating said composite article to a brazingtemperature for a sufiicient duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said composite article.

- 12. The method of making a composite article which comprises forming a tubular member having at one end a surface adapted to receive an end cap, forming an integ-ral imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, applying a brazing alloy to one of said surfaces, assembling said end cap with said tubular member to form a composite article, heating said composite article to a brazing temperature for a suificz'ent duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said composite article.

13. The method of making a composite article which comprises forming a tubular member having at one end a surface adapted to receive an end cap, forming an imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, electrodepositing a coating of a copper-tin alloy on said end cap surface, assembling said end cap with said tubular member.- to; orm,a compositearticle, heating said composite article to a brazing temperature for a sufficient duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said 1 composite article.

14. The method of making a composite article which comprises forming a tubular member having at one end a surface adapted to receive an end cap, forming an imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, one of said surfaces having a surface finish below about 100 micro inches R.M.S., the other of said surfaces having a surface finish.

of about 60 micro inches R.M.S. to 200,micro inches R.M.S., applying a brazing alloy to one of said surfaces, assembling said end .cap with said tubular member to form a composite article, heating said composite article to a brazing temperature for a suflicient duration to suitably bond said end cap to said tubular. body member by means of said brazing alloy and cooling said composite article.

15. The method of making a composite article which comprises forming a tubular member having at one end a surface adapted to receive an end cap, forming an imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, one of said surfaces having a surface finish below about 100 micro inches R.M.S., the other of said surfaces having a surface finish of about 70 micro inches R.M.S. to 160 micro inches R.M.S., applying a brazing alloy to one of said surfaces, assembling said end cap with said tubular member to form a composite article, heating said composite article to a brazing temperature for a sufficient duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said composite article.

16. The method of making a composite article which comprises forming a tubular member having at one end a surface adapted to receive an end cap, forming an imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, one of said surfaces having a surface finish of about 10 micro inches R.M.S. to micro inches R.M.S.. the other of said surfaces having a surface finish of about 70 micro inches R.M.S. to 160 micro inches.R.M.S., applying a brazing alloy to one of said surfaces, assembling said end cap with said tubular member to form a composite article, heating said composite article to a brazing temperature fora sufficient duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said composite article.

17. The method of making a composite article which comprises forming a tubular member having at one end a surface adapted to receive anvend cap, said surface having a surface finish below about micro inches R.M.S., forming an imperforate .transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, said end cap surface having a surface finish of about 60 micro inches R.M.S. to 200 micro inches R.M.S., applyinga brazing alloy to one of said surfaces, assembling said end cap with said tubular member to form a composite article, heating said composite article to a brazing temperature for a sufficient duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said composite article.

18. The method of making a valve lifter which comprises forming a tubular member having at one end a surface adapted to receive an end cap, said surface having a surface finish below about 100 micro inches R.M.S., forming an imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement'with the surface of said tubular member, said end cap surface having a surface finish of about 70 micro inches R.M.S. to 160 micro inches R.M.S., applying a brazing alloy to one of said surfaces, assembling said end cap with said tubular member to form a composite article, heating said composite article to a brazing temperature for a sufficient duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said composite article.

19. The method of making a valve lifter which comprises forming a tubular steel member having at one end a surface adapted to receive an end cap, said surface having a surface finish below about 100 micro inches R.M.S., forming an imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, said end cap surface having a surface finish of about 70 micro inches R.M.S. to 160 micro inches R.M.S., coating said end cap with a brazing alloy containing, by weight, about 20% to 60% tin and 40% to 80% copper, assembling said coated end cap with said tubular member to form a composite article, heating said composite article to a brazing temperature for a sufficient duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said composite article.

20. The method of making a valve lifter which comprises forming a tubular steel member having at one end a surface adapted to receive an end cap, said surface having a surface finish of about 10 micro inches R.M.S. to 80 micro inches R.M.S., forming an imperforate transverse wall in said tubular member, forming an end cap having a surface for mating engagement with the surface of said tubular member, said end cap surface having a surface finish of about 70 micro inches R.M.S. to 160 micro inches R.M.S., coating said end cap with a brazing alloy containing, by weight, about 20% to 60% tin and 40% to 80% copper, assembling said coated end cap with said tubular member to form a. composite article, heating said composite article to a brazing temperature for a sufficient duration to suitably bond said end cap to said tubular body member by means of said brazing alloy and cooling said composite article.

References Cited in the file of this patent UNITED STATES PATENTS 2,178,724 Hoern Nov. 7, 1939

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