US2948052A - Method of manufacturing hollow poppet valves for internal combustion engines - Google Patents

Description

Aug. 9, 1960 G. KUBERA METHOD OF MANUFACTURING HOLLOW POFPET VALVES FOR INTERNAL COMBUSTION ENGINES Flled May 27 957 INVENTOR. GER/ 19190 4 1/85 9 BY #esfiued 2,

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United States Patent METHOD OF MANUFACTURING HOLLOW POP- FOR INTERNAL COMBUSTION Gerhard Kubera, Blumberg, Baden, Germany, assignor to Alfred Teves Maschinenund Armaturenfabrik KG., Frankfurt am Main, Germany Filed May 27, 1957, Ser. No. 661,647

Claims priority, application Germany June 30, 1956 i 3 Claims. (Cl. 29156.7)

The present invention relates to a method of manu' facturing hollow poppet valves, and is an improvement on the method described in my previous U.S. Patent No. 2,731,708. In that patent there is described a method of manufacturing hollow disc valves wherein the unfinished blank, formed with a blind end bore into which is inserted a core portion of steel, is subjected to a drawing operation so as to produce a forging. The drawing operation results in the formation of a stem having a predetermined outer diameter and an integrally formed therewith valve head portion. Following the drawing step, the core is Withdrawn from the blind end bore, or may remain therein when properly shaped, whereupon a forging operation takes place.

Forging dies of high strength alloy substances have been employed in the process heretofore. However, these dies have been unable to meet the exacting demands of the process. Their span of usefulness has been very short, especially when employed with bores of smaller diameters e.g. under 15 mm. The wear on the outer surfaces of such dies has been so extensive, that the blind end bores have been subject to undesirable variations.

In addition, since the core portion could not be specially fitted in each bore, it has been necessary to change the forging dies frequently to maintain a better tolerance.

The present invention seeks to overcome the above disadvantages.

According tothe invention, a set of blanks is heated to forging temperature and inserted into a die. Next, the cold core pieces which have been previously tempered to a predetermined hardness are inserted centrally in the heated and consequently glowing set of blanks to a given depth.

The blanks, together with the core pieces therein are subsequently processed substantially according to the method described in my previous U.S. Patent referred to above.

The process will be further illustrated and described in terms of the accompanying drawing which is given by way of illustration and not of limitation, and wherein Fig. 1 indicates an unfinished blank 7 formed with a blind end bore in which the cold core piece 2, previously tempered to a predetermined hardness has been inserted.

2,948,052 Patented Aug. 9, 1960 Blank 7 has been pre-heated to a forging temperature and is in a glowing state.

Fig. 2 shows the same blank 7 and a core piece 6 therein, resulting from a drop-forging operation. Numeral 8 in that figure indicates a head of the core blank in a correspondoing recess of the blank.

Fig. 3 illustrates another form of a blank 9 and a core portion 10.

Fig. 4 illustrates the finished valve with the core piece removed and the resulting opening closed OE With a cover 11.

The steps of the method according to the invention are as follows:

Into a billet wherein a blind bore has been formed, and which has been heated to forging temperature, is inserted a cold core piece which has been previously tempered to a predetermined hardness. Next, the blank is drop-forged so that the top of the blank is expanded to form a cavity in the valve bonnet for purposes of more effective cooling. The core remains in the blank while being forged. When the operation is completed, the core piece is removed from the blank now formed into a valve body and the valve head is formed in a. known manner.

Finally, the valve is closed with a cover before or after introducing a coolant medium into the cavity in a known manner. Butt or lap welding may be advantageously used to attach the cover. Alternatively, the stock of the valve itself may be used to close the cavity.

Having thus described the method of my invention, what I claim as new and desire to secure by U.S. Letters Patent is:

1. The method of manufacturing hollow poppet valves for internal combustion engines which comprises the steps of piercing a blind hole in a billet, next heating the billet to forging temperature and glowing state, inserting into the blind hole of the billet a steel core portion which has been previously tempered to a given hardness, subjecting said billet with the steel core portion therein to a forging operation for forming a valve body, removing the steel core piece from the valve body thus formed, and finally closing the open end of the valve body.

2. The method according to claim 1, wherein a coolant is introduced into the valve blank after the removal of the core portion and prior to closing the opening'in said valve.

3. The method as claimed in claim 1, wherein the valve is additionally finished by forging the material at the head thereof.

References Cited in the file of this patent UNITED STATES PATENTS 774,242 Gates Nov. 8, 1904 2,170,811 Cornell Aug. 29,1939 2,177,192 Scrimgeour Oct. 24, 1939 2,452,628 Bartlett et al. Nov. 2, 1948 2,452,636 Cunningham et a1 Nov. 2, 1956 2,731,708 Kubera Ian. 24, 1956

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