US2232634A - Shotgun cartridge - Google Patents

Description

Feb. 18, 1941;

H. A. ROBERTS ETAL SHOTGUN CARTRIDGE Filed July 22, 1936 2 Sheets-Sheet 2 v v w 3 J u y, 1 fimw I 1.24; v l

PatentedFeb. 18, 1941 PATENT OFFICE SHOTGUN CARTRIDGE llorace Ainley Roberts, Huddersfield, and William Dickson, Streetly, England Application July 22, 1936, Serial No. 91,980 In Great Britain August 12, 1935 9 Claims.

This invention relates to shotgun cartridges, and the manufacture thereof, and, more particularly to the closing and sealing of the mouth of the cartridge case.

Hitherto the mouth of the cartridge case has been closed and the shot retained in position with the aid of a cardboard disc (hereinafter referred to as the over-shot card) which is held in position by turning or folding over the edge of the mouth of the case in such a manner that a retaining rim is pressed on to the disc. Cartridges made in this manner, however, have been found subject to deterioration owing to the fact that under certain conditions moisture permeates into the interior of the cartridge which not only causes swelling of the wads but also affects the moisture content of the powder charge with deleterious efiects upon the ballistics of the cartridge.

Cartridges made from rolled paper tubes which are closed in the manner described, have been waterproofed in various ways, usually by dipping the loaded cartridge in a waterproofiing lacquer. Unless special precautions are taken, however, the film of lacquer is liable to crack and its waterproofing properties are destroyed. It has been proposed to waterproof the end closure by covering the overshot card and the crevice between the card and the turned-over edge of the case with a coating of waterproof material, e. g. shellac or cellulose varnish. It has been found that cartridges treated in this manner are not entirely satisfactory, since the lacquer does not always form an efficient bond between the paper tubular portion and the overshot card, with the result that small cracks are formed which permit a certain amount of moisture to enter the cartridge case with consequent deleterious'results. It has also been proposed to make the tubular portion of the cartridge case from an entirely waterproof material such as Celluloid, but the use of highly inflammable material such as Celluloid in this art is to be dep-.

recated. Proposals have also been made to mould the tubular portion and the head of the cartridge case from plastic materials having waterproof properties, but these proposals have not described any solution of the problem of providing a completely waterproof end closure for the cartridge.

The present invention has for an object to provide cartridges of high ballistic efliciency in which the cartridge case and closure thereof are .formed in a simple and effective manner to provide a completely waterproof assembly.

The present invention involves the production of a shotgun cartridge including a moulded tubular casing portion consisting of a substantially non-inflammable waterproof plastic material, the mouth of which is sealed by a waterproof plastic closure, either integrally .moulded or bonded by fusion to the said tubular portion, or firmly united thereto with the aid of an auxiliary waterproof adhesive joining the plastic material of the closure and the plastic material of the tubular portion. The plastic material, in addition to being highly waterproof, should be nonbrittle and capable of being shaped by a moulding operation. Thus, for example, thermoplastic materials, such as those containing cellulose ethers, or cellulose esters such as cellulose acetate, together with suitable plasticisers and fillers, may be used. In particular we prefer to employ the compositions described and claimed in U. S. Patent 2,137,350. The arrangement is preferably such that the plastic material extends in an unbroken manner throughout the whole of the tubular portion and end closure, which thus constitute an integral unit. This may be carried out by softening the plastic material of the side Walls of the tubular portion and the end closure by the application of heat and/or a solvent, pressure being preferably applied to complete the bonding action.

Alternatively, the tubular portion and the end closure may be moulded in the form of a single cup-shaped unit, and in this case the flanged base portion which is made separate from the tubular portion is joined to the latter in a.waterproof manner, after the cartridge case has been loaded, by means of a suitable cement or by softening the contacting portions by the application of heat or a solvent. In a further alternative method of carrying out our invention, the end closure is united with the tubular portion of the case by turningover the side walls of the case on to a plastic disc and sealing the joint so formed with a waterproof cement or adhesive between the contacting surfaces.

It will be understood that our invention is not limited to cartridge cases in which the end closure is formed wholly of plastic material as the end closure may comprise a disc formed partly of a. plastic composition and partly of cardboard or like material. Where a composite disc is used, however, it is essential that the plastic side wall of the case shall be bonded with or made to adhere to the plastic portion of the said disc. The moulded side walls of the case, moreover, may be reinforced with paper, fabric or other suitable material. Furthermore, the invention is not limited to the use of the same plastic material for the tubular portion and the end closure, as difi'erent plastic materials may, if desired, be used for these two parts of the case provided that the bond between the components is waterproof and suificiently strong to ,provide the necessary ballistic properties of the cartridge.

Various methods of carrying out our invention are illustrated in the accompanying drawings in which:

Figure 1 is a sectional elevation of a cartridge constructed in accordance with our invention.

Figure 2 is a perspective view of the cartridge showing one stage in the mouth closing opera tion.

Figure 3 is a diagrammatic part sectional elevation of an apparatus for carrying out the final closing operation.

Figure 4 is a sectional elevation of the mouth of a cartridge showing a groove formed in the tubular portion of the case.

Figure 5 is a sectional elevation of the mouth of a cartridge showing an annular groove formed in the end closure.

Figure 6 is a sectional elevation of the mouth of a cartridge showing an alternative form of end closure.

Figure 7 is a sectional elevation of the mouth of a cartridge showing yet a further form of end closure.

Figure 8 is a sectional elevation of a cartridge showing an alternative construction.

Figure 9 is a perspective view of a charged cartridge showing the end of the case turned over onto an overshot card preparatory to the application of heat and pressure.

Referring to Figures 1 to 3 of the drawings, the numeral I denotes a cartridge case which is moulded in a suitable pressure moulding or injection moulding press, not shown in the drawings, from a non-inflammable plastic material of the kind described containing cellulose ethers, or esters such as cellulose acetate, together with one or more plasticisers, e. g. tri-phenyl phosphate,

tricresyl phosphate, diamyl tartrate or di-ethylphthalate and a suitable filler. e. g. French chalk. The cartridge is provided with a priming cap 2 and is loaded with a powder charge 3, a wad 4 and a shot charge 5. In the process of manufacture an overshot card 5 is inserted in the cartridge and the end of the case is crimped into the form of a short truncated cone 1, as shown in Figure 2, by means of a suitable crimping tool, not shown in the drawings.

In order finally to close and seal the mouth of the cartridge, the latter is placed in a suitably supported metal die 8, as shown in Figure 3, the base of the cartridge being supported by a removable block 9 which allows the cartridge to be inserted into and removed from the die. The die is maintained at normal room temperature by means of cooling water which is circulated through channels l0. A concentric punch II, which is suitably guided by means of guides I 2, is lowered in the direction of arrow A and is pressed into firm contact with the crimped edge of the case by means of either a dead weight, a suitable weighted lever mechanism or a hydraulic ram, not shown on the drawings. The punch II is heated by passing steam through channels I3 and the heated punch causes the thermoplastic material to soften and flow over the overshot card 6, thus sealing the mouth of the case wi ha end closure l4 (Figure 1) consisting of a layer of homogeneous material of substantial thickness.

When the heated punch II has been in contact with the end of the case for a suilicient length of time to cause softening and flow of the material, the steam supply to the punch is cut ofi" and a quantity of cold water is circulated through the channels l3, thus chilling and setting the thermoplastic material and enabling the-cartridge to be removed from the die. The punch II is reduced in diameter at its extremity I5 to provide a step, the purpose of which is to form an upstanding flange "5 at the end of the cartridge case, as shown in Figure- 1. The flatannular surface of the punch l I, indicated by the numeral I! of Figure 3. is arranged to contact with the edge of the flange I 6 so that a smooth square edge free from any moulding flash is provided.

. The bursting pressure of the cartridge may be adjusted by varying the thickness of the material above the overshot card. This may conveniently be. carried out by regulating the length of the cartridge case allotted for turn-over. It will be understood that as the turned-over portion is spread over the whole area of the end of the case a comparatively large variation in the length of the turned-over portion results in quite a small variation in thickness of the plastic material covering the overshot card. Thus, any small variation in the length of the turned-over portion such as may occur in practice due to inequalities in the depth of the wad, or in the quantity of powder or shot charge, afl'ects the thickness of the plastic covering to such a small extent that the bursting pressure is unaffected and remains constant for any given setting of the turn-over and the loading pressure.

In order to locate definitely the position at which bursting of the cartridge takes place, a peripheral groove l8 may be provided in the side wall of the case, as shown in Figure 4. This may be conveniently carried out after the sealing operation by means of a revolving cutter or like tool. The depth of the groove may be regulated to give any desired bursting pressure, and the provision of such a groove ensures that a particularly clean cut edge is formed at the end of the case after firing. Instead of making the groove in the side .wall of the case, an annular groove may be provided in the end closure, adjacent the surrounding tubular portion of the case as shown at 19, in Figure 5. This groove may conveniently be formed or pressed into the external face of the closure wall during the sealing operation, by providing a projecting annular ring (not shown) on the end of the punch II. If desired, the end of the punch which comes into contact with the mouth of the case may be suitably embossed with letters or figures denoting the trade-mark, shot size or the like.

It will be understood that the apparatus illustrated diagrammatically in Figure 3 may be adapted to seal the ends of a number of cartridges by arranging a plurality of punches which are operated simultaneously in conjunction with a corresponding number of dies. Our improved method of closing the mouth of the cartridge may be further adapted to mass production methods by feeding the cartridges automatically and in succession into the dies by means of asuitable conveyor system.

Instead of crimping the end of the case to provide the necessary turn-over-this may be accomplished by turning over'the edge in the normal manner with the aid of a rotary turnover tool,

as will be understood from Figure 9, after which the turned-over edge is subjected to pressure and heat in the manner previously described, so that the plastic material is made to flow over the whole surface of the overshot card to form a homogeneous layer.

In Figure 9, the case is indicated at l and the overshot card at 6.

In an alternative method of closing the mouth of the cartridge case in accordance with the present invention the ends 20 of the case are shaped as shown in Figure 6, and a plastic disc 2| is inserted above the overshot card 6. A solvent is applied to the periphery of the disc and the edge, as indicated at 22 on the drawings, the purpose of the solvent being to bond the side walls and the disc together. Where plastic materials containing cellulose esters or ethers are used a solvent such as acetone or methylene chloride may be employed. Instead of employing a plastic disc, a quantity of moulding powder may be used which is treated with a solvent and applied to the top of the overshot card to form a homogeneous layer which is bonded to the side walls of the case. Alternatively, the side walls of the case may be turned over and a solvent employed to soften the material and enable same to flow over the whole surface of the end of the case, pressure being preferably applied to complete the bonding action. In an alternative method heat and pressure may be used to effect the bonding action of either a separate plastic disc or a moulding powder and, if desired, the end closure may be moulded or bonded with the side walls of the case without the latter being crimped or turned over. Where a separate plastic disc is used this may be bonded to the side walls of thecase by the application of a heated punch before turning over the free end of the case, the said end being subsequently turned over to provide a rounded off finish. Where a moulding powder is used this may be united with the side walls of the case by means of an injection moulding operation which is carried out by placing the end of the case in a suitably shaped mould and injecting heated plastic material therein under pressure.

In all of the forms thus far described,-fusion of the plastic end closure material occurs, heat being employed in some instances, and a solvent in others, as the agency for causing fusion to occur.

In a further modification, as shown in Figure '7, an auxiliary waterproof adhesive, as indicated at 23, is used to secure the turned over portion 20 to the plastic surface of the, disc 24. It is essential for the formation of a satisfactory waterproof seal that the two surfaces in contact with the adhesive shall consist of plastic material.

Although a cardboard overshot card is shown in the foregoing drawings, this may be omitted provided that a suitable plastic material is chosen for the end closure which does not adhere to the shot charge.

In a still further modification, as shown in Figure 8, the tubular portion denoted by the numeral 25 is moulded in the form of a single cup shaped unit with the end closure 26. In a case portion 21 containing the percussion cap 2. The

base portion is preferably made of moulded plastic material which is firmly bonded to the side walls of the tubular portion 25 by softening the contacting surfaces 28 with ,a suitable solvent. Where the plastic material of the tubular and base portions is of the thermo hardening type which is not readily soluble, an auxiliary adhesive may be used to unite the parts together.

We have found that the ballistics of shotgun cartridges made in accordance with our invention are constant and unvarying over long periods of service when in hot moist climates, this being due largely to the fact that a completely waterproof case is obtained. By way of comparison it may be mentioned that such cartridges, after having been immersed in water for twenty-four hours, showed no appreciable signs of swelling and the powder moisture remained within the specified limits, whereas the known type of cart ridge having a paper tubular portion with standard turned-over end and waterproofed by dipping in a solution of waterproof material, showed distinct signs of swelling and the powder moisture exceeded the specified amount. Moreover, our method of manufacture enables the loading pressure applied tothe shot and powder charges and also the bursting pressure of the cartridge to be readily and accurately controlled, which factors contribute to the increased ballistic efficiency of the cartridge.

As many apparently widely different embodiments of our invention may be made without departing from the spirit and scope thereof, we do not limit ourselves to the specific embodiments thereof, except as defined in the appended claims We claim:

1. A method of manufacturing waterproof shotgun cartridges, having a base, a tubular case portion united with said base, and an end closure for the tubular case, which includes the steps of molding a tubular case portion and base from substantially non-inflammable, waterproof, nonmetallic, plastic material, placing the powder, wad and shot charge therein, bringing into position across the discharge end of the tubular case portion a body of non-inflammable, non-metallic, waterproof, plastic material, and sealing the discharge end by fusion of said end material and by applying external pressure to said end material forcing such material against the charge and the case portion to form a waterproof end closure integral with the tubular case portion extending over the entire area of the end.

2. The method of manufacturing waterproof shotgun cartridges, having a tubular case portion provided with a base, and an end-closure for the tubular case portion, which includes the steps of molding the tubular case portion and base from substantially non-inflammable, waterproof, non-metallic, thermo-plastic material, said tubular body being made long enough to provide both the charge-enclosing wall portion and also an additional length containing, a surplus of material sufficient to form an end closure, placing the powder, wad, and shot charge in the tubular case portion, bringing into position, across the discharge end of the tubular case portion, the said surplus material by a bending operation, and sealing the discharge end by fusion of said surplus material and byapplying external pressure to it forcing such material against the charge and the case portion to mold it into a complete waterproof end-closure integral with the tubular case portion.

3. A loaded shotgun cartridge comprising a powder-clfarge', a wad, and a shot-charge, an integral waterproof casing including a base portion,

a tubular case portion, and an end-closure portion closing the discharge end of said tubular case portion, said casing entirely enclosing and sealing said powder, shot charge, and wad therein, said casing consisting of substantially homogeneous, non-metallic, non-inflammable waterproof plastic material, said base portion being arranged to receive a primer, said charges being held'under compression by the end-closure portion.

4. A loaded shotgun cartridge comprising a powder-charge, a wad, and a shot-charge, an integral waterproof casing including a base portion, said casing entirely enclosing and sealing said powder, shot charge, and wad therein, a tubular case portion, and an end-closure portion closing the discharge end of said tubular case portion, said casing consisting of substantially homogeneous, non-metallic, non-inflammable, waterproof, plastic material, said base portion being arranged to receive a primer, said casin having near its discharge end a definite line of weakness arranged to determine the bursting pressure developed by the cartridge when exploded.

5. A loaded shotgun cartridge comprising a powder-charge, a wad, a shot-charge, and an over-shot disc, an integral waterproof casing including a base portion, a tubular case portion, and an end-closure portion closing the discharge end of said tubular case portion, said casing entirely enclosing and sealing said powder, shot charge, and wad therein, said casing consisting of substantially homogeneous, non-metallic, noninflammable, waterproof, plastic material, said base portion-being arranged to receive a 'primer, said over-shot disc being located between the shot-charge and the end-closure whereby adhesion between the shot-charge and the end-closure is avoided.

6. The method of manufacturing waterproof shotgun cartridges having a tubular case portion provided with a base, and an end-closure for the tubular case portion, whichincludes the steps of molding a tubular body from substantially non-inflammable, waterproof,- non-metallic thermoplastic material, said tubular body portion being made long enough to project beyond the charge to provide a surplus of material sufficient to form an end-closure, placing the powder, wad, and shot charge in the tubular case portion, bringing into position across the discharge end of the tubular case portion a body of substantially non-inflammable, non-metallic,

thermoplastic material, which comprises placing the charged cartridge in a die, providing at the end to be closed a quantity of the material from which the case is formed sufiicient to form the closure and. pressing on .this material a punch heated to a temperature sufficient to fuse the said material, meanwhile maintaining thetemperature of the sides of the cartridge case below the softening points.

8. A method of manufacturing a waterproof end-closure to a cartridge, the case of which is of substantially non-inflammable, non-metallic, thermoplastic material which comprises charging a cartridge which has an elongated case of such length that the material in that part of the cartridge case which projects beyond the charge is suflicient to form the end-closure, turning over the said projecting portion of the cartridge case inwardly, placing the charged and turned over cartridge in a die and pressing on the turned over end a punch heated to a temperature sufficient to fuse the turned over portion, meanwhile maintaining the temperature of the sides of the cartridge case below the softening point.

9. A method of manufacturing a waterproof end-closure to a cartridge, the case of which is of substantially non-inflammable, non-metallic, thermoplastic material which comprises placing thecharged cartridge having an overshot card in a die, placing on the overshot card a quantity of molding powder suflicient .to form the closure and pressing on this molding powder a punch heated to a, temperature suflicient to fuse the molding powder, meanwhile maintaining the temperature of the sides of the cartridge case below the softening point.

HORACE AINLEY ROBERTS. WILLIAM DICKSON.

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