US2608140A - Shot shell manufacture - Google Patents

Description

Aug. 26, 19152 w. 1.. FIN L.AY ET L ,6 3, 40

SHOT SHELL MANUFACTURE 7 Filed Feb. 15, 1947 U VILL %MMMMWM m MIMMMM... s ME F INVENTORS 14/4 L75? .4. Fm/LA Y WW (I n "I J mmmm in ii... 1 III! a wmmmw u Mm a? 2 m r R 0 0 m M W N H m 0% m Patented Aug. 26, 1952 SHOT SHELL MANUFACTURE Walter L. Finlay, Fairfield, and Dorothy a.

Adessa, Bridgeport, Conn, assignors to Remington Arms Company, Inc., Bridgeport, Conn., a

corporation of Delaware Application February 15, 1947, Serial No. 728,790

2 Claims.

This invention relates to ammunition, particularly to shot shells, and contemplates a novel method of manufacture which enables the use of lower cost materials.

The conventional shot shell as used extensively for small game hunting and skeet and trap shooting comprises a primer, basewall, powder charge, filler walls, and shot charge; all housed 2 removed from the cylinder by contact with a moving'felt blanket. Special devices to provide a uni-directional flow of pulp stock toward the cylinder are provided, the whole combination resulting in a web in which a substantial portion of the fibers are laid lengthwise. By building a sheet of four such webs, a transverse stretch or elongation up to 12% or 15% is sein a container which ordinarily consists of a metallic cup-shaped head and a tubular body. While the body may be of metal and may be integral with the head, in common practice the body is of a non-metallic material, and while the use of various plastics has been attempted the body is almost universally formed of a rolled sheet of paper. In the firing of such a shot shell in the gun chamber, the shell is subjected to an interior pressure of the order of 10,000 pounds per square inch and inevitably expands until it is supported by the chamber wall. By reason of the fact that commercial shot shells are used under an extremely wide variety of conditions of temperature and atmospheric humidity, an allowance must be made for the swelling of the non-metallic body by the absorption of moisture. Accordingly, shot shells are finished to an outside diameter which is somewhat less than the minimum average chamber diam-eter of a new gun and substantially less than the chamber diameter of an old and worn gun. When the shell is fired, the body material must stretch without longitudinal rupture until it is engaged by the chamber wall. It is essential that such body splits be avoided, since a body split may expose the breech mechanism to a flow of burning gas under high pressure, with damage to the gun action and possible injury to the shooter.

Throughout the history of the manufacture of paper bodied shot shells, it has been deemed necessary to use a paper especially manufactured to provide a very high transverse stretch or elon-.

gation to permit the necessary transverse enlargement of the shell body on firing. Ordinary paper does not possess this property. Shot shell paper is quite universally made by superposing four plies of a thin web produced on a cylinder machine. A specially prepared and extensively beaten pulp stock is introduced into a tank containing a horizontally disposed revolving screen cylinder. The water level within the cylinder is maintained several inches below the stock level outside the cylinder. As the screen cylinder revolves, the water of the pulp stock passes through the screen and pulp fibers adhere to its surface. The web thus formed is cured. The absolute minimum requirement for paper to be processed into shot shells by heretofore known methods is a transverse elongation of 9%. It is quite obvious that this cylinder process is much more expensive than the Fourdrinier process, in which the stock is simply flowed from the tank in a flat stream onto a longitudinally moving and vibrating screen, from whicha full sheet thickness web is continuously removed. While in this process there is still considerable lengthwise laying of fiber, there is a substantially greater random orientation, and while transverse elongation is somewhat greater than longitudinal elongation, the former rarely exceeds 6%. Such paper has heretofore been deemed wholly unsuitable for the manufacture of shot shells.

The present invention contemplates a process which enables the utilization of relatively low cost Fourdrinier paper, instead of high cost specially made composite sheet cylinder paper. The utility of the process, however, is not limited to Fourdrinier paper; its application to the specialty papers customarily used, and variations of such papers, results in a marked improvement in quality.

In the drawings: Fig. 1 is a diagrammatic representation of end views of shot shell tubes made in accordance with the present invention, illustrating the relative diameters of the tube as wound, the tube as sized, and the shot shell body after firing.

Fig. 2 isa fragmentary diagrammatic sectional viewof the tube sizing devices.

There are several factors which eifec't the fit and behavior of a shot shell in different guns. Gun chambers are contracted forwardly from the breech end or mouth toward the forcing cone, the taper of a new chamber being about .005" per inch. A certain variation or tolerance necessarily exists in the dimensions of new gun chambers, and with extensive use an indefinite amount of chamber enlargement takes place. A certain tolerance is likewise necessary in shell diameter. Again, the shell Wall may be thicker in some parts than in others. The usual convolute 12 gauge tube, for example, comprises paper is laid.

about four-and-one-half turns of paper, and is thus 20% thicker on one side than on the other; this produces an asymmetric stress pattern. The load applied upon firing is an impact load, and the effect differs from that of a static load.

1; Average chamber diameter as used herein indicates mean diameter of anew chamber midway of its length Asmentioned above, shot shell bodies must be finished to an outside diameter somewhat less than the average minimum chamber diameter. Prior to the present invention', it has been the universal practice to make shotshell tubes by winding paper sheets upon an arbor of, such dimensions thatpthe outside diameter of the tube as Wound doesnot exceed average chamber diameter. Such tubes, after drying, were then sized to the-required exterior diameter by being impaled upon a mandrel and pushed through a sizing die. Upon firing in an average.

chamber, the sized tube should theoretically be symmetrically stressed and expand to its wound diametenbut, due to the asymmetry oftheltube itself, the impact load, and probablyother factors," the stressing of the tube, even in new chamber, is irregular andlocalized. When fired in-a loose or worn chamber, any or all of these stress effects tend to be'intensified, with the result that the use of paper having a high transverse elongation has heretofore' been deemed a necessity; The presentinvention comprises the discovery'of a process which enables the use of ordinary Fourdrinier paper havinga transverse elongation far less than that heretofore 'considered necessary.

Fourdrinier paper of a thickness substantially equal to that of standard specialty shot shell paper is Wound on an oversize mandrel, the out-'- side diameter of 'the'wound tube being substantiallygreater than average chamber diameter as above defined." The cross-section of such a tube is shown at the left in Fig. 1. At the right in Fig. 1 is a diagrammatic showing of a section of a gun chamber of an 4 average diameter d, and the measure of this diameter is extended across the figure for thepurpose of comparison. It will be noted that the tube as-wound (shown at left in Fig. 1) is of considerably greater diameter thanthe :gun chamber. 1

The-oversize wound-tube is next humidified to such a moisture content as will enable'severe sizing, that is, sizing down to the 'usual outside diam eterpshown in the center of Fig. 1. If the tube contains inadequate moisture, it may be sized down to the requiredexterior diameter but may not retain this diameter in storage. For ordinary Fourdrinier kraft paper, minimum practiits diameter is substantially less than the diameter of the unsized tube shown at the left and is less than the average chamber diameter d by the usual amount. Fig. 2 shows, somewhat schematically. the sizing equipment. The. oversize tube T is impaled on a mandrel I of conventional design. A part or allof the mandrel surface may be roughened.orcorrugated as shown at The i l, in accordance with common, practice. end of the tube abuts a thrust collar I2 secured to the mandrel. The mandrel reciprocates with respect to a stationary sizing die' l3 of conven tional construction. Due to the fact that the tube is oversize, it fits loosely upon the standard size mandrel but, as the leading end of the tube and mandrel enter the throat of the die,

the end portion of the tube is compressed into gripping engagement with the mandrel and the remainder of the tube is virtually pulled through the die by frictional engagement of the sized portion of the tube with the mandrel. V n 'The sized tubes are thereafter processedirr the usual manner and assembled with the other components of a shot shell. Many thousands of shot shells have been madein this manner from different lots of Fourdrinier kra'ft paper having a cable moisture content at sizing is of the order of 10%. The maximum permissible moisture content depends upon the character of the sizing equipment. Over-humidified tubes are soft and require special handling. With conventional siz ing' equipment, the maximum permissible moisture content is of the-order of 18%. Standard specialty shot shell paper may be'sized according transverse elongation not over 6%. These shells weresubjected to the usual severe acceptance tests and found to be in all respects eq'uaL'if notsu;

perior, to shot shells made by conventionaltmeth-LI ods from expensive specialty paper.

The inven'tion may be. illustrated by wi erto outside diameters as follows: Maximum .835 Minimum .825 Average .830

After appropriate humidiflcation, these tubes were sized to outside diameters: n I

Maximum J78? Minimum .781 Average .734

The maximum diameter reduction is approximately 6.5%; the minimum reduction isv approximately 4.6%; and the average reduction is 5.5%; The maximum diameter reduction in con-1,

ventional processing, under themore liberal tolerances provided for commercial manufacture,

does not "exceed about 2.6%, and probablyonly rarely approaches this figure.

' The severe sizing enables the use of many lower grade papers. Notransverse elongation minimum has been found. Satisfactory shooting results' have been secured with Fourdrinier krait having a transverse elongation as low as 1.6%.

The invention is not limited to tubes of any particular size or style of winding. It is applicable to tubes of any size, and to spiral or parallel wound tubes as well as to the more common convolute tubes.

What is claimed is:

1. In the manufacture of tubes for shot shell bodies from Fourdrinier kraft paper, the method which comprises Winding and adhesively securing paper into tubes of a diameter not less than.

5% greater than the desired finished diameter, humidifying such wound tubes to a moisture content determined by the transverse elongation of the paper but not less than '7 or more than 18%. and compressing the humidified tubes to reduce the diameter by not less than 4.5%.

2. In the manufacture of bodies for shot shells for use in gun chambers of varying average diam eter, themethod which comprises winding and, adhesively securing paper having a transverse elongation not substantially exceeding 6% into tubes having an outside diameter notmaterially ample: Tubes for l2 gauge shot shells were Wound less than 5% greater than maximum average chamber diameter, humidifying such wound tubes to a moisture content between 10% and 18%, the moisture content being determined by the transverse elongation of the paper, and thereafter reducing the outside diameter of the wound tubes to less than minimum average chamber diameter.

WALTER L. FINLAY. DOROTHY R. ADESSA.

REFERENCES CITED The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Number Name Date 887,809 Hurd. May 19, 1908 1,412,018 Keller Apr. 4, 1922 1,623,965 Marshall Apr, 12, 1927 1,959,109 Rosien May 15, 1934 2,034,731 Saalbach Mar. 24, 1936 Gardner Dec.. 16, 1941 OTHER REFERENCES Chemical Engineering Handbook-page 1088, 2nd Ed., McGraw-Hill Pub. (20., 2nd Ed., 1941.

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