US2349570A - Apparatus for making shell bodies - Google Patents

Description

23, 1944. c. A. WITTER I zvmgfim I G SHEL L BODIES Filed July 16, 1940 Patented May 23, 1944 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates toapparatus for forming blanks for high explosive shells. It is an improvement upon my application, Serial No. 312,499, filed January 5, 1940, now Patent Number 2,251,094, granted July 29, 1941.

According to the method of the aforesaid application, such shell bodies can be manufactured without eccentricity or substantial eccentricity as between inner and outer diameters, whereby it is possible to produce a forging so closely to finish outside diameter requirements that only a light finish machining or grinding operation is required, thus effecting a great saving in a number of respects.

As therein described, a relatively thick or squat slug, containing the needed amount of metal, is placed in a die and is caused to fill the die by means of a punch, which at the same time forms a small centering cavity inthe top surface of the slug. Then, either in the same die or another, a blank is formed by a piercing punch, which is centered in the aforesaid cavity. The blank produced by the piercing punch is relatively short as compared with the length of the finished forging, is larger in outside diameter, and the internal bore may likewise be somewhat larger and differ in contour from the bore of the finished forging. It is, of course, to be understood that the blank which is produced has a closed end.

In proceeding in this fashion for reasons set forth in said copending application, eccentricity of the inner and outer rounded surfaces is very small, if not entirely eliminated.

The blank is then cross-rolled on a mandrel, as, for example, in a cross-rolling mill such as shown in the patent to Assel, No. 2,060,768, of November 10, 1936. The mandrel is of the dimensions and contour required for the bore of the finished forging, In this cross-rolling operation a substant al reduction in outside diameter is effected in consequence of which there is a great gain in length. The outside diameter of the fork. ing is reduced to the approximate outside finish diameter of the finished shell body, so that only the light machining or commercial grinding operation hereinbefore referred to is required. Moreover, the metal i ironed in on the mandrel so that the bore of the shell body conforms in dimension and contour to finish requirements.

There is one difficulty incident to the aforementioned method. The Assel mill has three tapered rolls providing a pass, the axes of the rolls being inclined with respect to the axis of the pass both vertically and horizontally, Each roll has a rather sharply inclined shoulder for effecting the aforesaid reduction. The blank on its mandrel enters the pass at the large end of the rolls, in consequence of which there is a tendency toward ballooning. What is meant by ballooning will be clear from the following. If a straight edge be applied to the inner surface of the wall of the bore, a slight arcuity may be noticed. To overcome this, the reduci shoulder of the rolls in the Assel mill is followed by a tapering relieving section. However, "ballooning is not always avoided.

- The object of the present invention is to overcome this ballooning so as to reduce the number of rejects. I accomplish this by making some changes in the Assel mill and by the procedure now to be described, all taken in connection with the accompanying drawing, wherein- Figure 1 is an enlarged view showing my im proved roll in side elevation, and certain other portions in section;

Figure 2 is a diagrammatic cross-sectional view showing the arrangement of the three rolls and the blank in process of being cross-rolled; and

Figure 3 is a more or less diagrammatic side elevation of the rolls of Figure 2.

Referring now to Figure 1, it will be seen that the mandrel l carrying the blank 8 enters the pass at the small ends of'the roll instead of the large ends as shown in the Assel patent. The rolls A are counterparts and, therefore, a description of one will apply for all. It will be seen that approximately midway of the length of the roll there is, the reducing'shoulder 9 hereinbefore referred to. The shoulder 9 rises from the tapered or conical portion 10 of the roll. This portion or zone of the roll has the primary function of gripping and frictionally engaging the blank, causing it to rotate on its own axis and to feed it longitudinally. A slight reduction may also be effected by this portion. The shoulder 9 effects the main reduction hereinbefore referred to. The portion or zone H of the roll is likewise tapered, and its primary purpose is to feed and to size and remove or prevent the "ballooning' hereinbefore described. It will be observed that there is no need for a relieving section or zone following the shoulder 9 as is the case in the Assel mill.

It will be seen from what has been said that the roll may be much simpler, and the feeding of the blank to the pass at the small end of the rolls instead of at the large end of the rolls accomplishes the desired result of eliminating or preventing ballooning." I attribute this result to the fact that the zone H is of larger diameter than the zone [0 end, therefore, operates at higher peripheral speed and tends to feed more rapidly. It is, of course, to be understood that the axes of the rolls are so inclined that the slopes of the zones I0 and l l at the point of contact with the piece will be parallel to the axis of the line of feed.

In Figure 1 a blank is shown in process of being cross-rolled, and it will be understood that the metal is ironed in on the mandrel as the blank travels through the pass. It is likewise to be understood that the mandrel is guided and supported and that sufficient pressure is applied thereto to cause entry into the pass and to bottom the mandrel in the blank.

As in the process of my aforesaid application, the finished rolled body has an outside diameter so close to the finish requirements that only a light finish machining or commercial grinding is required. Likewise, the internal bore is to finish dimensions and contour, but is free of any ballooning.

I claim:

Cross-rolling equipment for lengthening a short, closed end thick wall blank including at least three tapered rolls, the rolls being annularly arranged to provide a pass with a smaller end of the roll adjacent the entrance end of the pass, each roll having a feeding section or zone at the small end and a feeding-sizing section or zone at the large end with an annular reduction shoulder rising from the first zone and terminating in the feeding-sizing zone, and the roll being positioned with its axis diverging from the line of feed through said pass in the direction of feed therethrough and further with its axis laterally obliquely inclined to the feed line of said pass to effect feeding of the blank therethrough, the configuration and positioning of the rolls being such that the working surface of the feeding section and the feeding-sizing section are parallel to the axis of the pass, and a mandrel cooperating with the inside surface of the blank during rolling 'whereby lengthening of said short blank is effected substantially without ballooning.

CLAUDE A. WI'I'IER.

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