US2726165A

US2726165A - Method of applying metal coating to valves

Info

Publication number: US2726165A
Application number: US425995A
Authority: US
Inventors: Isler William
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-04-17
Filing date: 1954-04-17
Publication date: 1955-12-06
Anticipated expiration: 1972-12-06

Description

Filed April 27, 1954 FIG? A TTOR/VE Y5 Patented Dec. 6, 1955 [ice METHOD OF APPLYING METAL COATING TO VALVES This invention relates generally to methods of and apparatus for applying metal coatings, but has reference more particularly to the application oflayers or facings of protective heat and wear-resistant metal tothe surfaces of: valves, which, in use, are subjecte'dto high temperatures and abrasive wear.

It 'has heretofore been common practice, in the application of such metal to the seat portions of poppet valves; for example, to rotate the valve at a uniform rate about a vertically-disposed axis, to preheat the area to be coatedto a'welding temperature by means of gas flames, and to then progressively deposit the molten protective metal at a uniform rate upon successive portions} of said area while continuing the rotation of the valve, said protective metal being derived from the melting of welding rods. Such practice is disclosed, by way of example, in Wagner Patent No. 2,301,763.

The aforesaid method is disadvantageous in the following respects: (1) the necessity of rotating each valve as the molten protective metal is applied requires the use of a great deal of mechanism, including, gears, chains, etc., which are likely to get out of order and require considerable maintenance, (2) the application of protective metal by the gradual melting anddepositin'g, of molten drops upon successive portions of the annular preheated zone (see lines 55-68, first column, page 3 of the Wagner patent) is rather slow and difiicult, particularly from the standpoint of depositing the metal in uniform, predetermined amounts, it being stated in. the Wagner patent that they total time required for preheating andcoating a valve head about two inches in diameter is approximately ninety seconds, (3) .the thickness and uniformity of the coating is extremely difficult. to control, so that a large portion of the aforesaid time is taken up .by the necessity of spreading of the molten deposited metal by means of the gas torches subsequent to depositionof the metal (see lines 69-75, first column, page 3, and lines 7-12, second column,.page 3 of the Wagner patent), and (4) the fact that preheating ofthe area tobe coated to a mere .Welding temperature? is not sufficient to enable production to be speededflupto. anyextent.

The present invention has as its primary object a method of and apparatus for applying protective metal coatings of the aforesaid character, whereby the articles can'be coated at much greater speed than has heretofore been possible, and in a much more efficient manner, andwhereb'y the thickness and uniformity of the coating are better 'controlled.

Other objects and advantages of the. invention 'will'be apparent during the course of the following description.

In the accompanying drawings, forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Fig. l is a plan view illustrating more or less diagrammatically one type of apparatus which may be used for practising the invention; I

Fig. 2 is'a cross-sectional view, at approximately. full size scale, taken on theline 22 of Fig. 1;

Fig. 3 is a transverse crossasectional' view, taken on the line 3-3 of Fig. 2, and

Fig. 4 is a transverse crosssectioual view, taken on' the line 4-4 of Fig. 2.

Referring more particularly to the drawings, reference numeral 1 designates a circular rotatable platform, which may be rotated by any suitable mechanism, such, for example, as that disclosed inthe aforesaid Wagner patent. The platform 1 is provided at circumferentially spaced points with circular recesses 2, in each of which is mounted an annular work supporting member 3 of heat-refractory material such as Alundum.

Each of the members 3'l1as. an. inwardly and downwardly tapered upper surface 4 provided. with an. annular step or groove5 therein adjacent the inner margin adapted to contact a narrow annular portion of the head of a valve 6 of the poppet-type and support said: valve during application of the protective metal onto the annular zone 7 of the valve head.

As each valve is brought to a position, indicated by reference letter S, and which I shall hereinafter desig mate as the coating station, rotation of' the platform l'is stopped until the coating of the valve has been completed. Q

When the valve has reached the station S and rotation of the platform 1 has been stopped, an applicator head, generally designated by reference numeral 8, is placed over the valve, as shown in the drawings, and is supported in the position shown until completion of the coating of the 'valve; 1' have. not attempted to show means for positioning and supporting the head 8 during the coating operation, but it will be readily understood that any suitable mechanism may be provided for this purpose, and that the positioning, supporting and removal of the head may be effected automatically, and in syn,- chronism with the movements, of the platform 1.

The applicator head 8 comprises a tubular torch or nozzle 9 provided with a multiplicity of circumferentiallyspaced passageways 10 extending through the wall thereof parallel with the axis of the nozzle.

Threadedly secured to'the upper end of the nozzle 9 is a hopper'member'll having in its lower end an annular recess or groove 12, which is, in registration withthe upper ends of the passageways 10, and is supplied with a combustible gas mixture through a passageway 13 extending radially through the member 11. The passageway 13 is supplied with gas by means or" a conduit 14 secured to the member 11;

The inner cylindrical surface 15' of the nozzle 9 is fiush with the inner cylindrical surface 16 of the hopper member 11, and above the surface 16', the hopper member 11 is provided with an outwardly and upwardly sloping conical surface 17. w Y

The hopper member 11 is provided with a cover or cap 18 having an air vent19, and the cap is provided with an annular flange 20 which is 'interiorly threaded for threaded 'securement to the upper end of the hopper member 11.

Secured, as by welding, to the central portion of the lower surface of the cap 18 is a tubular member 21 which extends substantially to the "lower end 'of the nozzle 9. The member 21 has a portion 22 of reduced external diameter the outer surface of which forms with the

surfaces

15 and 16 an annular passageway 23, through which powdered metal contained in the hopper 11 may be dropped onto the zone 7' of the valve head.

It may be noted that anannular shoulder 24 is'provided at the upper end of the portion-22- of the'member 21, and that the outer peripheral edge of this shoulder bears against the surface 17 of the hopper 11 when the cap 18 bears against the upper end 25 of the hopper, so as to stop off flow of the powder into the passageway 22.

When it is desired to feed powder, the cap 18 is unscrewed and the amount of powder fed is controlled by the extent to which the cap is unscrewed. The member 21 thus constitutes a means for controlling or regulating the quantity of powder fed, as well as a passageway for the powder. a

The protective metals employed for coating the surface 7 of the valve are preferably selected from hard facing high temperature metals, of which those described in Cape Patents 2,396,552; 2,458,502 and 2,481,976, are representative. These have melting points in the range 2400 F.-2500 F. Another metal which may be used for this purpose is a Stellite composition containing 6% cobalt, 30% chromium, and 4 /2% tungsten, with the remainder iron, silicon and manganese, and having a melting point of about 2400 F. These metals are preferably in powder form, and of a mesh or size such that they can flow freely into the passageway 22.

Before the powder is fed through the passageway 22, and onto the seat portion 7 of the valve, 'the portion 7 is preheated to a temperature at which actual melting of said surface occurs. This preheating is accomplished by igniting the gases issuing from the lower end of the passageways 10 and causing the flame thus produced to heat the surface 7 to the desired temperature. This actual melting of said surface occurs at a temperature very close to or approximating the melting temperature of the valve material.

Since the passageways 10 are uniformly spaced about the valve seat, the surface 7 is uniformly preheated, without the necessity of rotating the valve. This eliminates the need for complicated mechanism usually provided for this purpose.

After the surface 7 has been thus preheated, the flame is reduced in intensity, after which powdered metal, in an amount sufficient to provide the entire hard facing for the valve seat, is dropped through the annular passageway 22 onto the surface 7. Since the surface 7 has been heated to a high temperature, the particles of powdered metal will become sintered to the surface 7 and to each other, and in order to remelt the particles and cause them to become bonded to the surface 7, the flame is again increased in intensity and continued in operation until a coating of uniform character is formed. Since the powdered metal is uniformly distributed about the valve seat, and is uniformly heated throughout the circumference of the valve seat, it is unnecessary to rotate the valve in order to obtain such uniform distribution.

The method, as described, is also advantageous in that it takes considerably less time to coat the valves than is required in the Wagner method, and the thickness and uniformity of the coating is controlled in a more desirable manner. Moreover, no excess coating metal is formed, which requires removal by costly grinding operations.

Instead of rotating the platform 1 to the station S, the platform may be stationary, and the applicator head moved into position over the valves successively. Moreover, a plurality of applicator heads may be provided, so that coating of all of the valves on the platform may be accomplished simultaneously. In this latter case, a single hopper for all of the applicator heads may be provided, as Well as a single source of gas for all of the heads, thereby enabling production to be greatly speeded.

It may be noted that if desired, the valves may be individually rotated about their own axes during coating, since the apparatus and method described do not preclude such a possibility.

It is to be understood that various changes may be made in the method and apparatus herein specifically described without departing from the spirit of the invention or the scope of the appended claims.

Having thus described my invention, I claim:

1. The method of providing the wearing surface of valves and similar articles with welded-on facings of a protective metal, which comprises supporting a poppettype valve along an annular zone at the margin of the valve head, said valve head having an annular seating surface facing in an upward direction and supported at an acute angle to the horizontal, uniformly preheating said valve to raise said seating surface to an elevated temperature at which actual melting of said surface occurs, thereafter depositing powdered facing metal selected from hard-facing, high temperature metals which have melting points in excess of about 2400 F. substantially uniformly about said seating surface, and then heating said powdered metal to cause it to become fused and bonded to said seating surface and be uniformly distributed thereover.

2. The method, as defined in claim 1, in which said powdered metal is fed directly onto said surface in a substantially annular stream of a diameter corresponding substantially to the diameter of said seating surface.

3. The method, as defined in claim 1, in which said preheating is accomplished by means of gas flames playing simultaneously on the entire seating surface.

4. The method of providing the wearing surface of valves and similar articles with welded-on facings of a protective metal, which comprises supporting a poppettype valve along an annular zone at the margin of the valve head, said valve head having an annular seating surface facing in an upward direction and supported at an acute angle to the horizontal, uniformly preheating the valve, while stationary, to raise the entire seating surface simultaneously to a temperature approximating the melting point of the valve material, thereafter depositing upon said surface, in a single operation, and in an annular stream, only a sufficient amount of powdered facing metal selected from hard-facing, high temperature metals which have melting points in excess of about 2400 F. to provide said welded-on facing, and then heating said powdered metal to cause it to become fused and bonded to said seating surface and to be uniformly distributed thereover.

5. The method, as defined in claim 4, in which said annular stream is of a diameter corresponding substantially to the diameter of said seating surface.

6. The method, as defined in claim 4, in which said preheating is accomplished by means of gas flames play ing simultaneously on the entire seating surface, and said fusion of the facing metal is likewise accomplished by means of gas flames playing simultaneously on all parts of the facing metal.

7. The method, as defined in claim 4, in which the powdered facing metal is selected from metals having melting points in the range of from about 2400 F. to about 2500 F.

References Cited in the file of this patent UNITED STATES PATENTS 701,298 Cowper-Coles June 3, 1902 806,900 Leonard Dec. 12, 1905 933,725 Schroeder Sept. 7, 1909 1,244,414 Bernheim Oct. 23, 1917 2,277,571 Wagner Mar. 24, 1942 2,301,763 Wagner Nov. 10, 1942 2,326,403 Snyder Aug. 10, 1943 2,354,113 Gould July 18, 1944 2,358,090 Longoria Sept. 12, 1944

Claims

1. THE METHOD OF PROVIDING THE WEARING SURFACE OF VALVES AND SIMILAR ARTICLES WITH WELDED-ON FACINGS OF A PROTECTIVE METAL, WHICH COMPRISES SUPPORTING A POPPETTYPE VALVE ALONG AN ANNULAR ZONE AT THE MARGIN OF THE VALVE HEAD, SAID VALVE HEAD HAVING AN ANNULAR SEATING SURFACE FACING IN AN UPWARD DIRECTION AND SUPPORTED AT AN ACUTE ANGLE TO THE HORIZONTAL, UNIFORMLY PREHEATING SAID VALVE TO RAISE SAID SEATING SURFACE TO AN ELEVATED TEMPERATURE AT WHICH ACTUAL MELTING OF SAOD SURFACE OCCURS, THEREAFTER DEPOSITING POWDERED FACING METAL SELECTED FROM HARD-FACING, HIGH TEMPERATURE METALS WHICH HAVE MELTING POINTS IN EXCESS OF ABOUT 2400*F. SUBSTANTIALLY