US3439620A - Projectile driving bands - Google Patents

Description

April 22, 1969 H. M. CROSSLEY ET AL 3,439,620

PROJECTILE DRIVING BANDS Sheet Filed Oct. 15, 1967 INVENTORS HENRY NORTON CROSSLEY PERCIVAL WILLIAM BAILEY April 22, 1969 Filed Oct. 13, 1967 ASBESTOS CLOTH H. M. CROSSLEY ET PROJECTILE DRIVING BANDS INPREGNATE WITH RESIN IMPREGNATE WITH EBONITE LANINATING PROCESS HA NU FACTU RE 0F WEDGES LOAD HOULDING DIE CURE UNDER HEAT AND PRESSURE Sheet 3 012 EBONITE SOLUTION INVENTORS HENRY ILRTON CROSSLEY PERCIVAI. WILLIAM BAILEY ATTORNEYS" United States Patent US. Cl. 10293 9 Claims ABSTRACT OF THE DISCLOSURE A projectile driving band comprising a radially laminated fibrous material such as woven asbestos cloth, woven cotton cloth, jute, hessian or glass cloth, and a thermosetting resinous material selected from the phenol group of resins with which the fibrous material is impregnated to bond the laminations together, whereby on firing of the projectile, the driving band is discarded. The laminated structure may have an inert filler incorporated therein such as, for example, an ebonite solution of P.T.F.E. The laminated structure is formed from a number of wedge shaped members giving to the band an inward taper externally and an outerward taper internally.

This invention relates to projectile driving bands and to a method of production thereof.

In artillery weapons, such as guns, rifles, mortars and the like, accuracy, which is very necessary over a variety of ranges, is assisted by spinning the projectile. Imparting spin to the projectile is carried out, as is well known, by providing the barrel of the weapon with splines or helical grooves, the helix angle being a predetermined factor which is related to the ballistic requirement. To co-operate with the barrel splines or grooves, the projectile has firmly secured thereto, eg by circumferential swaging, a narrow metallic stay-on driving band, most usually of copper.

Under the impact of firing of the propellant charge, the projectile is propelled forwardly in the barrel of the weapon, the copper band engaging with the barrel splines or grooves, whereby a mirror image thereof is engraved in the copper band. The engagement of the said band in the splines or grooves ensures that the projectile is subjected to a turning or twisting movement during its passage through the bore, so that, when the projectile emerges from the muzzle of the weapon, it is spinning about its longitudinal axis.

Stay-on copper driving bands suffer from a number of adverse properties, amongst which are that copper is a material which could be in short supply; it is difiicult mechanically to attach copper to a projectile in such a manner that 100% torque will be transmitted; elaborate inspectional techniques have to be resorted to and generally machining operations are necessary after attachment of the copper driving band to the projectile; furthermore, due to centrifugal effect, there is a limitation on the spin obtainable with such a metallic one-piece driving band.

The object of this invention is to provide a non-metallic 3,439,620 Patented Apr. 22, 1969 or substantially non-metallic driving band which will discard at the muzzle and hence is wholly different from the stay-on type. This new kind of driving band, which will hereinafter be described as a driving band of the discarding-type, will include none of the above disadvantages and will still impart the ballistically desired spin requirement of the projectile.

According to the present invention, a projectile driving band of the discarding-type, comprises a radially laminated fibrous material, the laminations being bonded together by impregnation with a thermosetting resinous material.

It is preferred to use, as the fibrous material, woven asbestos cloth, although woven cotton cloth can also be used. The cloth must be so selected that it has a low water absorption property and it is even possible, bearing this in mind, although not preferable, to use jute or hessian or even glass cloth as the fibrous material.

To provide such a driving band for relatively large weapon bores, it may be advantageous to include in the formation of the fibrous material a comparatively small amount of metallic strands such, for example, as copper.

The thermosetting resinous material is preferably selected from the phenol group of resins and the preferred material is cresol formaldehyde; phenol formaldehyde itself is another example of a thermosetting resin which may be used.

Preferably, the driving band includes an inert filler incorporated in the laminated structure, and as one example, an ebonite solution may be utilised which both imparts strength to the driving band while it is moving up the barrel and assists fragmentation thereof after firing, when the projectile emerges from the muzzle, which fragmentation is of importance with this new discardingtype of driving band, since the ebonite assists in reducing the strength of the bond imparted to the laminates by the resinous material. As another example of filler, P.T.F.E. powder may be provided between the laminates to increase fragmentation of the driving band, and to assist in reducing barrel wear.

The method of producing such a discarding-type driving band, according to this invention, consists in impregnating strips of fibrous material with a thermosetting resinous material, dipping the impregnated strips in an inert filler, if required, superimposing a number of so treated strips, one on top of the other, to provide a laminated product, unifying the said laminates under heat and pressure, forming, for example, by cutting or punching, a plurality of wedge shaped multi-ply members from said laminated product, assembling said members in a circular die in such a manner that the laminates are radially arranged, and finally bonding said members together under heat and pressure to form a rigid moulding.

One form of non metallic driving band, of the discarding-type, is illustrated in the accompanying drawings, in which:

FIGURE 1 is an axial section of a band according to the invention;

FIGURE 2 is a bottom plan view thereof; and

FIGURE 3 is a flow sheet illustrating a method of forming the band shown in FIGURES '1 and 2.

Referring to FIGURES 1 and 2, the driving band comprises a unitary structure of woven asbestos cloth impregnated with cresol formaldehyde and including an inert filler, in the form of an ebonite solution, and the structure is formed of a number of wedge shaped members having a plurality of laminations 6, as described above, so that, in the finished product, the band 1 is formed with a portion 2, which externally is inwardly tapered, and internally, outwardly tapered, the tapering being provided due to the moulding of the various wedge shaped members 5 to form a unified structure. The lower end of the band is provided internally with a screw thread 3 to mate with an external thread, provided on the boat-tail end of the projectile. The wedge formation of the upper end of the driving band is such as to provide a friction fit with the interior of the lower end of the projectile. Apertures 4 are provided in the annular base of the driving band, which apertures provide for the use of a tool for securing the driving band to the projectile.

The method of forming such a discarding-type driving band as illustrated by the flow sheet, FIGURE 3, comprises impregnating a length of asbestos cloth with cresol formaldehyde, and then dipping the length in an ebonite solution. A suitable increase in weight of the cloth, after impregnation, would be 30% plus or minus 5% and, after the dipping treatment, a desired weight increase would be 25% plus or minus to provide an overall weight increase from the initial cloth to the finished impregnated and dipped cloth of 60% plus or minus 10%. The length of cloth is then cut into suitable strips, for example, 13 inches long by 2 /2 inches wide. It will, of course, be appreciated that, instead of starting with a length of cloth, the cloth could be processed as above but in strip form. A number of such strips are then placed on top of each other in a suitable mould so as to )rovide a multi-ply cloth, and preferably six plies are 186d. In order to bond the plies together, pressure is applied to the mould, for example, at a pressure of 1 ton aer square inch, so that the product at this stage has ;he appearance of a board, but without complete cure of he thermosetting resin.

The thus-formed laminated board is then formed into iarrow wedges, for example, by a cutting or punching peration, and the said wedges are loaded into a circular lie so that the natural lie of the laminates is radially r- "anged in the die. Pressure and heat are then applied to he mould, the temperature preferably being 320 F., and treasure approximately 3 tons per square inch, so as 0 bond the wedges together to form a rigid moulding.

As one example of cresol formaldehyde resin, it is ureferred to use that having the following composition:

Cellobond 15940/85 supplied as an 80% solution in ndustrial methylated spirits, and this is preferably furher diluted to reduce to 50% solution, by weight, to imrove the impregnation effect.

As an example of ebonite solution, the following is referred:

"Percent [year 1041 50.0 'ulcafor BA (butyraldehyde/aniline complex) 1.0 110 2.5 .ight calcined magnesia 2.0 .ed iron oxide 17.5 )ibutyl phthalate 7.0 .33 carbon black 2.5 [C sulphur 17.5

This is then made up into a 20% solution by adding pounds thereof to toluol 3 /2 gallons and ethylene chloride %1 gallon to provide a dipping solution.

Up to 15% of a fine P.T.F.E. powder such as I.C.I. luon grade L169 may be added to the ebonite mix ior to the solution stage. The lubricating properties of is P.T.F.E. powder would also assist in reducing barrel ear.

As has been stated above, P.T.F.E. may also be employed to provide increased fragmentation of the driving band when the projectile is fired. The wedge members in these circumstances are preferably slightly warmed and dipped into a P.T.F.E. powder; alternatively, the impregnated strips can be coated with P.T.F.E. before unifying the strips into a laminated product.

It will be appreciated that, with such a discardingtype driving band, if in mounting the wedge shaped laminates in the circular die, they are placed tightly together, torque transmission during the moulding is transmitted from one laminate to the next and, due to the close proximity of the laminates, n0 relative movement takes place. The torque transmission, of course, carries on right round the band in the weapon barrel, with the result that one laminate behind is always pushing the one in front thus preventing the structure from collapsing, so that there is no slip between the outside diameter of the driving band and the rifling of the bore of the weapon barrel or the inside diameter of the band and the splining on the projectile.

The use of non-metallic discarding-type driving bands, according to the present invention, have, amongst many advantages, the following:

(a) Very good moisture proof properties;

(b) A capability of withstanding high gun temperatures at relatively high elevations when the projectile is in the barrel;

(0) Good fragmentation properties since the driving band, after firing of the weapon, is found to disintegrate into relatively small fragments which are, for example, such as will only impart slight superficial wounding effect; furthermore, the provision of the apertures in the base of the driving band is found to assist in fragmentation due to the consequent reduced strength areas of the band at the apertures;

(d) The provision of better aerodynamic form for the projectile after fragmentation of the driving band as compared with such form of projectile utilising stay'on driving bands, and consequent better range accuracy;

(e) Simple inspection techniques involving less costly production.

What we claim is:

l. A projectile driving band of the discarding-type comprising a radially laminated fibrous material, the laminations being bonded together by impregnation with a thermosetting resinous material.

2. A projectile driving band as claimed in claim 1 in which the fibrous material is one of the following: woven als'belstos cloth, woven cotton cloth, jute, hessian or glass 0 0t 3. A projectile driving band as claimed in claim 2 in which the thermosetting resinous material is selected from the phenol group of resins.

4. A projectile driving band as claimed in claim 3 in which the thermosetting material is either cresol formaldehyde or phenol formaldehyde.

5. A projectile driving band as claimed in claim 2 in which an inert filler is incorporated in the laminated structure.

6. A projectile driving band as claimed in claim 5 in which the filler is either an ebonite solution or P.T.F.E.

7. A projectile driving band as claimed in claim 2 in which a comparatively small amount of metallic strands is incorporated in the fibrous material.

8. A projectile driving band as claimed in claim 2 in which the laminated structure is formed from a number of wedge shaped members giving to the band an inward taper externally and an outerward taper internally.

9. A method of making a projectile driving band of the discarding-type which consists in impregnating the length of fibrous material with the thermosetting resin and then dipping the length in an inert filler, thereby increasing the weight of the cloth, after impregnation, to

between 30% plus or minus 5% and, after the clipping treatment, a weight increase of 25% plus or minus 10% to provide an overall weight increase from initial cloth to the finished impregnated and dipped cloth of 60% plus or minus 10%, cutting the so impregnated and dipped cloth into strips, assembling a number of said strips in superposition in a mould, bonding said superimposed laminates by pressure, without complete curing of the thermosetting resin, forming the laminations into narrow wedges by a punching or cutting operation, loading said wedges into a circular die so that the natural lie of the laminates is radially arranged in the die, and applying heat and pressure to the mould so as to bond the wedges together to form a rigid moulding.

References Cited UNITED STATES PATENTS 8/1951 Johnson et al 102-43 1/ 1956 Richards. 5/1957 Daley et al. 156181 3/1960 Zisman et al. 102-93 8/ 1961 Critchfield et al. 102-93 10/1961 Prosen et al. 102-93 FOREIGN PATENTS 6/ 1963 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner.

JAMES FOX, Assistant Examiner.

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