US3447466A - Sabot projectile with core guiding means - Google Patents

Description

June 3, 1969 w. ENGEL 1 SABQT PROJECTILE WITH CORE GUIDING MEANS Filed Sept. 5, 1967 2 i 1 2 .5 m 5 w. i5 I M W \w t 3 l 7 Ina/ll .9 W W 8 7 H l\\\ 2 R. 2 H 1 M 0 I I h w w Il 2 I 3 m T U .6 a 6 a o u 8 w H B w 9 7 2 1 5 2 United States Patent US. Cl. l02-93 2 Claims ABSTRACT OF THE DISCLOSURE In a sabot projectile the sabot is provided with a drilling in which the subcalibre core is guided during emergence from the sabot. This subcalibre core has a tail portion which is seperated from the centre section of the core by an annular groove, the tail portion being located within a spherical zone the radius of which is equal to the radius of the sabot drilling. The tail portion has at least approximately the same diameter as the centre section of the subcalibre core, as a result of which canting and jamming of the subcalibre core on emerging from the sabot are obviated.

The present invention relates to a sabot projectile and in particular to a sabot projectile embodying a sabot with a drilling in which a subcalibre core is guided during emergence from the sabot.

The object of the invention is to produce a sabot projectile in which canting and jamming of the subcalibre core on exit from the sabot are obviated.

The invention has as a further object the production of a sabot projectile in which the emergence of the subcalibre core from the sabot is facilitated.

An additional object of the invention is the production of a sabot projectile in which the tail portion of the subcalibre core is so formed that complete exit of the subcalibre core from the sabot is assured.

The drawing illustrates two examples of execution of the subject of the present invention:

FIG. 1 shows a longitudinal section through a first example of execution of the sabot projectile,

'FIG. 2 shows a view of the rearward portion of the subcalibre core in accordance with a second version of the execution of the sabot projectile, and

FIG. 3 shows a view of the rearward portion of the subcalibre core as it emerges from the sabot.

In accordance with FIG. 1 a sabot 1 encloses a subcalibre core 2. Until firing the sabot 1, manufactured in the form of a sleeve of an aluminium alloy or some other light metal, has its rearward portion located in the conventional manner in the mouth of a cartridge case not illustrated. On the sabot 1 is mounted a rotating band (driving band) 3 which transfers the torsional momentum from the grooves in the bore of the weapon, not illustrated, to the sabot 1 and which is made of steel. A further similar rotating band (driving band) 4 is located at the forepart of the sabot 1. In order to save weight that portion of the sabot 1 situated between the two rotating bands (driving bands) 3 and 4 has been given a smaller external diameter than the tail portion.

A cylindrical drilling 5 at the front of the sabot 1 serves to centre and guide the subcalibre core 2. This drilling 5, which is anodised by the Ematal process and then barrel burnished, opens into a coaxial drilling 7 of larger diameter machined into the tail of the sabot 1 and threaded as to its rearward portion. The transition from drilling 5 to drilling 7 takes the form of a shoulder 6. In the aforementioned thread of the sabot a solid piece 8 with a depression 9 in its forward face is located by screwing. This depression '9 is surrounded by an annular surface 3,447,466 Patented June 3, 1969 10 against which the tail surface of the subcalibre core 2 is braced. In the annular cavity 11 delimited by the shoulder 6 and the forward face of the screwed piece 8 are the orifices of two drillings 12 which penetrate the wall of the sabot 1.

It is advisable for the subcalibre core 2 to be made partly or wholly of tungsten carbide and to be provided with a cylindrical centre section which culminates in an ogive 13 in front and has a tail portion 14. Borne between the centre section and the tail portion 14 in an annular groove 15 machined into the subcalibre core is an annular safety element 16 in the form of a holding device with a rectangular cross-section which is provided with a slit 18 the outer surface of which is numbered 17. This safety element 16, which projects beyond the tail portion 14 and is capable of being expanded under the influence of centrifugal force, is located between the shoulder 6 of the sabot 1 and the grooved wall arranged perpendicular to the axis of the projectile as the rear supporting surface of the subcalibre core 2.

As shown in FIG. 1, a forward zone 19 of the tail portion 14 of the subcalibre core limited by the rear grooved wall 26 is formed by a truncated cone expanding towards the rear. A further cylindrical piece 21 adjoining the aforementioned truncated cone 19 at the rear and hereinafter referred to as the guide zone has an equal diameter to the centre section but in relation to the drilling 5 in the sabot 1 has a small amount of play which may for example amount to 0.03 mm. Taking account of the aforesaid small amount of play, the height of this guide zone 21 is determined by the requirement that the tail portion 14 of the subcalibre core 2 be able to rotate in the drilling 5 about the forward edge 24 of the zone 21, i.e. by an angle corresponding to the maximum angle of pitch occurring in the subcalibre core 2. Thus the tail portion must be located within a spherical zone the radius R of which is equal to the radius of the drilling 5 of the sabot 1 and with approximately the same diameter as the centre section of the subcalibre core. The third zone forming the rear end of the tail portion 14 is a truncated cone 22 which tapers towards the rear from the diameter of the guide zone 21. The generatrices of the said truncated cone form an angle with the base surface 27 which is greater than for example in order to obviate material crumbling away along the periphery of the base surface 27 under the heavy pressure loadings of firing.

The generatrices of the truncated cone 19 coincide with straight lines which connect the leading edge 24 'of the cylindrical guide zone 21 with the interior edge of the grooved wall 25 laid out transverse to the axis of the projectile and limiting the annular groove at the front. These sraight lines form with the axis of the projectile an angle which is at least as large as the maximum angle of pitch the subcalibre core 2 can take up on emerging from the sabot 1.

The second execution version of a subcalibre core 2 as illustrated in FIG. 2 is distinguished from the example illustrated in FIG. 1 by the fact that the guide zone 20 reaches as far as the annular groove 15 and is formed by a zone of a sphere. The largest cross-section of the spherical zone 20 aligned perpendicular to the axis of the projectile and parallel to a terminal surface displays a diameter which corresponds to the diameter of the sphere and therefore to the diameter of the centre section of the subcalibre core 2. A tangential surface laid out at the leading edge 28 of the spherical zone 20, which forms with the axis of the projectile an angle at least equal to the angle of pitch of the subcalibre core, touches the interior edge of the transverse surface 25 limiting the annular groove 15 at the front.

Before the subcalibre core 2 is mounted in the sabot 1 it is processed as follows:

After microfinish grinding and degreasing of the cylindrical outer surface it is coated by spraying with a layer consisting of a mixture of 9.1% (parts by weight) of molybdenum disulphide M08 7.6% phenol resin (binding agent) and 83.3% ethyl acetate (solvent and thinner).

This layer, which adheres to the outer surface to a thickness of 1.5 to 2, 0.10- mm., is then lightly polished after which the subcalibre core is heated and held at a temperature of 80 to 100 degrees centigrade for at least 2 minutes. During this period the solvent and thinner agent evaporates so that finally a dry lubrication film consisting of M05 is left adhering to the subcalibre core. The composition of this film will not alter even during years of shelf life.

The method of operation of the sabot projectile described follows from the construction:

After ignition of the propellant charge the sabot projectile accelerates rapidly in the bore and the subcalibre core 2 is pressed against the bearing surface and compresses, i.e. plastically deforms it. In relation to the sabot 1 the subcalibre core 2 thus moves to the rear and this releases the grip of the safety element 16.

On axial acceleration by the subcalibre core 2 the safety element 16 is pressed against the rear grooved wall and is itself set in rotation by the frictional force that is thus generated, so that even before the sabot projectile leaves the bore of the weapon the safety element expands under the influence of the centrifugal force acting upon it, moves completely free of the annular groove and positions itself in the buffer chamber 11 with its outer surface 17 against the inner surface of the drilling 7.

After emergence of the sabot projectile from the bore of the weapon, the sabot 1 is by reason of its large leading surface more heavily decelerated than the subcalibre core 2 so that the latter moves forward in relation to the sabot 1, i.e. overruns it, and by reason of the low level of friction to be overcome by the subcalibre core 2 with its coating of lubricating film when moving within the drilling 5 of the sabot 1 this overrunning effect is almost Without impediment.

When the centre section of the subcalibre core 2, which is located forward of the annular groove 15, emerges from the drilling 5 of the sabot 1 and is no longer guided therein, it is impossible for canting or jamming symptomised by heavy resistance to movement to occur should the subcalibre core 2 be subjected to forces operating transversally to its axis. On the contrary, the subcalibre core 2 is able under the influence of these transversally acting forces to take up an attitude in which it forms with the axis of the sabot drilling an angle corresponding to its maximum pitch angle (see FIG. 3). At the time, in the version illustrated in FIG. 1 the truncated cone forming the leading zone 19 of the tail portion of the subcalibre core 2 is able to position itself against the wall of the sabot drilling 5 and slip along it in a forward direction without any diametrically adjacent portion of the tail portion 14 touching the wall of the drilling 5. With the version of the subcalibre core 2 illustrated in FIG. 2 the spherical guide zone 20 acts as an articulation preventing jamming.

The size of the distance between the rearward end of the centre section of the subcalibre core 2 and the guide zones 21 and 20, or between the edges 23 and 24 (FIG. 1), or between the edge 23 and the greatest diameter of the spherical zone 20, designated 29 (FIG. 2), conditions the size of the bearing forces transmitted to the subcalibre core 2 by the wall of the drilling 5, forces which are generated when forces acting transversely to the subcalibre core 2 affect it. By properly selecting this distance the facility is obtained to influence favourably the frictional resistance forces generated by these bearing forces.

I claim:

1. Sabot projectile with a subcalibre core embodying a cylindrical centre section, a tail portion and an annular groove between these two parts, and a sabot having a cylindrical drilling in which the subcalibre core is guided during emergence from the sabot, the tail portion of said subcalibre core has a section tapering towards the front in the form of a spherical zone, this zone having a diameter which is at least approximately equal to the diameter of the cylindrical centre section of the subcalibre core.

2. Sabot projectile in accordance with claim 1 with a film of dry lubricating agent covering the subcalibre core and with an anodized and burnished bore in the aluminium alloy sabot.

References Cited UNITED STATES PATENTS 405,690 6/1889 Ball .102-93 3,359,905 12/1967 Engel 10293 FOREIGN PATENTS 8/1919 Great Britain.

OTHER REFERENCES BENJAMIN A. BORCHELT, Primary Examiner.

JAMES FOX, Assistant Examiner.

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