US2029508A - Method of making hollow articles - Google Patents

Description

Feb. 4, 1936. w. SCRIMGEOUR 0 Filed March 27. 1935 s Sheets-Sheet 1 Feb. 4, 1936. w. SCRIMGE'OUR 2,029,503

METHOD OF MAKINQ HOLLOW ARTICLES Filed March 27, 19:55 :5 Sheets-Sheet 2 Feb, 4, 1936 W. SCRIMGE OUR METHOD OF MAKING HOLLOW ARTICLES Filed March 27, 1935 3 SheetsSheet 5 gig Patented Feb. 4, 1936 UNITED STATES PATENT OFFICE 10 Claims.

This invention relates to methods of making hollow articles, particularly poppet valves for internal combustion engines, by forging operations.

The method which is described in my prior patent, No. 1,992,245, includes the punching of the closed end of a counterbored blank to form a rounded end wall, swaging the tubular part 01' the blank to form an elongated stem, and stamping the closed or ball end to form the! hollow head. While this method is entirely practical, the machining of the cylindrical blank and the swaging down of the stem are'relatively slow and expensive operations.

An object of theinvention. is to provide improved and economical methods for forging onepiece hollow articles. An object is to provide a method of forming metal blanks or shells which can be forged to produce hollow articles having ends of substantially different diameters. Further objects are to provide methods of forging hollow valves by punching and rolling. I

These and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawings, in which: i

Fig. 1 is a horizontal section, as taken on line l-l ofFig. ,2, of an economical form of'die in which the first operation is performed;

Fig.2 is avertical central section of the die;

Fig. 3 is a vertical section, taken at right angles to Fig. 2, through the die and punch;

Fig. 3a is a fragmentary section showing an alternative construction for the base of the die;

Fig. 4 is a side elevation of the metal blank;

Fig. 5 is a fragmentary section, similar to Fig. 3, illustrating the removal of the punched blank from the die;'

Figs. 6a to 6e, inclusive, are fragmentary sections showing alternative shapes for the die;

' Fig. 7 is a fragmentary plan view of apparatus for rolling down the stem portion of the valve blank;

Fig. 8 is a vertical section on line 8-8 of Fig. 'I;

Fig. 9 is a vertical section on line 9-9 of Fig. 8;

Figs. 10' and 11 are schematic views illustrating successive rolling operations upon the blank;

Fig. 12 is a sectional view through dies for forming the valve head; and

Fig. 13 is a side elevation of a valve blank as it leaves the head-forming dies.

The metal commonly employed for the manufacture of hollow valves is steel which contains nickel, tungsten and chromium or the like in suchquantity as to provide high resistance to corrosion and damage by heat. Steels of this type are somewhat plastic at high temperature but excessive wear on the dies has characterized prior attempts to forge hollow shells having a diameter approximating that of the finished 5 valve head. The flow of the hot steel under heavy pressure alongthe curved and/or junction surfaces of the dies results in a pitting or wear of the die surfaces which renders them useless after a comparatively few operations. Shaping l0 methods and dies which have been employed with relatively plastic metals and alloys have proved to be unsatisfactory in the working of corrosion-resistant steel and similar hard metals.

According to this invention, a cylindrical blank 15 of hot steel is punched in dies which are so shaped as to avoid destructive wear. As shown in Figs.

1 to 3, a heavy die'block l is counterbored from the top to provide a seat for the die 2 which has an unbroken or continuous inner wall meeting 20 the edge of the shape-imparting surface 3 of an end die member 4 which is held securely against the die 2 by a wedge 5. The die 2 is locked in place by pins 6 which extend through the block I. The block I is provided with integral ears I for 25 attaching the block to the table of .a press or, as shown in Fig. 3a, the base of the block may be formed as a dovetail 'l' for this purpose.

The movable head 8 of the press carries a punch 8 which has a rounded lower end for en- 30 tering the die. The punch is tapered to provide clearance and the inner wall of the die also tapers slightly towards the top. The starting material for forming the valve is a short cylindrical blank III which is of such diameter as to 35 drop freely into the die 2 when hot, and of such length as to provide sumcient material for a valve of the desired size and length. The blank is solid and has a diameter substantially less than that of the finished valve head but is much great- 4 er than the desired stem diameter.

It will be noted that the surfaces of die members 2 and 4 meet at the maximum diameter section of the shape which is to be imparted to the blank and that there will be a flow of metal tov wards, but not along, this junction of the dies. The cylindrical blank i0 is punched by rapidly forcingthe punch 9 into and withdrawing the same from the hot blank. This may be accom A plished in one or a pluralityof strokes of the 5 upper head 8 but, in any event, the punch 9 is quickly withdrawn from the blank before it can expand and lock to the hot steel. The tapering of the die 2 facilitates this withdrawal of the punch as the slightly conical form of the die locks 55 the punched blank I 0 against upward movement. Separate members may be used to hold the blank I0 as the punch 9 is lifted but, in general, separate holding members are not required when the die 2 is appropriately shaped. Upon removal of the punch 9, the wedge 5 is shifted to the right, Fig. 2, to permit removal of die member 4, and the blank [0' is then forced downwardly out of die 2 by a stripper II.

The dies shown in Figs. 1 to 3 will transform the cylindrical blank l0, Fig. 4, into a tubular shell l0, Fig. 3, of slightly larger diameter and having a rounded end wall of about the thickness Dies 2a and 4a of Fig. 6a are of the side walls. cut back at their meeting edges to form a groove l2 which will result in a thickened rib or bead at the base of the rounded end of the tubular shell. As shown in Fig. 6b, the lower end of die 2b may be flared outwardly to form a conical surface l3 that meets the rib-forming surface of die 4a. In the form shown in Fig. 6c, the die members 2c, 40 may have meeting surfaces It that form an enlarged globular head on the blank. This form is desirable when relatively large diameter valves are to be formed from small diameter stock. Another die formation appropriate for large valves is shown in Fig. 6d. The lower end of the slightly conical bore of die 2d is Small diameter valve heads and other hollow articles which are to have portions rolled down to smaller sizes may be made from punchings in the simple dies 2e, 4c of Fig. 6e. The lower die 4e has a central cylindrical recess H but has a flat surface l8 meeting the slightly conical surface IQ of die 2e.

The tubular shell III" that is stripped from the die 2 is transferred, either directly or after reheating, to the pressure rolling apparatus shown in Figs. 7 to 9. A pair of rolls 20 are mounted in brackets 2| on a supporting base 22 and are rotated in the same direction by a shaft 23 and gearing 24. An idler roller 25 is carried by the moving head 26 of the pressure piston 21, the head having a dovetail extension 28 that is slidable on the base 22. The movement of the head 26 and idler roll 25 is controlled by the admission of pressure fluid to the cylinder 23. The shaping rolls 2!), 25 have the same profile and each is reinforced by a set of idler or backing rolls 30. A pin or mandrel 3| is arranged parallel to the axes of the rolls to receive the blank l0 and support the same during the initial stage of the rolling operation.

The blank I0 is dropped over the mandrel 3| and pressure fluid is supplied to chamber 29 to force the idler roll 25 towards the driven rolls 20. The blank l0 rotates on mandrel 3! during the initial working of the tubular section of the blank and the mandrel is then lowered by means, not shown, into the position shown in Fig. 10. The upper ends of the shaping rolls are concave and shape the end portion Illa of the blank to approximately globular form and lower sections of the rolls reduce the adjacent portion lllb of the blank to a cylinder of small diameter. The lower ends of the rolls taper down to form the flaring end section we of the blank. By thus working down the intermediate portion of the blank, it is not necessary to provide a separate support to take up end thrust as the axial pressures exerted upon the blank by the rolls are substantially balanced and there is no tendency for the blank to move axially out of the rolls. The flaring section lllc of the blank is then rolled to form an extension of the stem section lflb in another set of rolls 20 which have upper ends shaped to engage the globular ends Illa. The lower ends of the blanks are preferably reheated before this operation, and the heads Illa are relatively cool.

The bore of the stem may be completely closed during the rolling operation, as shown in Fig. 11, or a mandrel of softer metal could be left within the blank to form a soft core that could be readily drilled out in the subsequent finishing of the valve. The head Id of the valve is formed, in known manner, by die forging the globular end section. The blank such as shown in Fig. 11 is placed in the split die members 32 and is pressed axially by die 33 to flatten the rounded end and shape the metal to the form of the recessed ends of the dies.

As compared with the process described in my prior patent, the present invention has the advantages of speed and economy in manufacture. The punching of the cylindrical blank to form a tubular shell avoids loss of metal by machining and is more rapid and less expensive than the prior counterboring operation. It is also economical to roll down the stem section of the blank as this operation does not require the high skill that must be employed in swaging down. the blank. Automatic control devices of known design may be used with the pressure cylinder to regulate the rate and extent of movement of the idler roll, and the factor which the operator is required to judge is that of the temperature of the blanks which are placed between the rolls. Forged valves ready for machining can be produced rapidly and with practically no defects so long as the temperature ranges for the different operations are properly selected and maintained. Wear on the dies of the punching machine is comparatively low as the metal does not flow across but towards the junctions of the die members.

It is to be understood that there is some latitude in the particular design of the dies and rolls, and that the form of the blank at different intermediate stages of the forging operations may therefore vary somewhat from the blanks illustrated herein. 7

I claim:

1. The method of forming a hollow valve which comprises punching a solid cylindrical blank to form a hollow tube having an end wall of substantially the thickness of the side wall thereof, working down the tubular portion of the blank from a portion adjacent said end wall to form an elongated stem, and pressing the end wall axially to form a valve head.

2. The method of forming a hollow valve which comprises punching a cylindrical metal blank against an end block and restricting lateral flow of the metal by a die having a continuous circumferential wall, whereby metal displaced by the punch flows rearwardly along the same to form a tubular portion extending from the end wall formed between the punch and the end block, working down the tubular portion into an elongated stem, and shaping the end wall portion into a hollow valve head of larger diameter than the stem.

3. In the manufacture of hollow valves, the steps which comprise forcing a punch into a solid blank positioned in a stationary die to form a shell having a rounded end, rolling down the tubular part of the shell to form a stem, and diestamping the rounded end portion to form a hollow head.

4. In the manufacture of hollow steel articles, the method of forming a tubular shell which comprises forcing a punch into a solid cylindrical steel blank resting-upon an end die having an approximately hemisphericalrecess, and restricting lateral flow of the steel by a die having a continuous inner circumferential wall, thereby to form a tubular shell having a closed hemispherical head.

5. The process of forming a tubular shell from which a hollow-head valve may be forged, which comprises placing a heated metal blank in a die havingan unbroken end surface meeting an unbroken circumferential surface tapering inwardly in a direction away from the end surface, forcing a punch into said blank to effect a flow of metal into close contact with said surfaces, withdrawing the punch, separating the end surface portion of the die from the punched blank, and forcing the punched blank from the other of said surfaces by pressure applied in the direction of the punching pressure.

6. The method of forming a valve which comprises placing a billet in a die having a continuous inner circumferential wall meeting the shape-defining surface of an end block, forcing a punch towards the end block and into the blank to form a tubular blank having a closed end wall, working down the tubular portion of the blank to form a stem section, and pressing said end gall axially of the stem to form a hollow valve ead.

7. The method of forming a valve which comprises placing a billet in a die having a continuous inner circumferential wall meeting the shape defining surface of an end block, forcing a punch towards the end block and into the blank to form a tubular blank having a closed end wall, rotating the blank about its axis and pressing radially upon the tubular portion thereof to form a. stem section, and pressing said end wall axially of the stem to form a hollow valve head.

8. In the manufacture of hollow head valves, the steps which comprise punching a solid blank to form a tube having one end wall, forming the tube from a point adjacent the end wall into a smaller diameter stern portion by rotating the tube about its axis while subjected to radial pressure from a plurality of circumferentially spaced rolls, and die-forging the end wall and adjacent portion to form a hollow valve head.

9. In the process of forming hollow one-piece articles, the steps which'comprise'punching a cylindrical billet to form a tube having one end wall, and rotating the tube about its axis while subjected to radial pressure from a plurality of circumferentially spaced and rotatable rolls, thereby to reduce the diameter of and to elongate the tube at the region where such radial pressure is applied.

10. In the process of forming hollow one-piece articles, the steps which comprise punching a solid cylindrical metal blank to form a tubular shell having a. rounded end wall, working down the tubular portion of the shell without reducing the diameter of the rounded end, and pressing the rounded end to form a hollow valve head.

WILLIAM SCRIMGEOUR.

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