SABOT FOR A PROJECTILE

Abstract: The disclosure relates to an apparatus which makes possible the loading and automatic firing in a weapon of an ammunition unit provided with a sabot (2a), without consequential deterioration of the ballistics of the ammunition unit. The apparatus comprises a unit consisting of a number of prismatic or cuneiform elements which together form a rotationally symmetrical body (3a) with an external surface (3a′). This surface is truncated or curved and flares rearwardly from its leading portion. The apparatus also comprises a device (3b) enclosing these elements at the trailing portions of the body (3a), and unifying the elements on loading of the ammunition unit into the barrel of the weapon. The device also encloses the leading portions of the sabot. This device (3b) is arranged to burst on movement of the ammunition unit in the barrel. The elements will namely execute flip movements about their trailing portions which are defined by the inner wall of the barrel and entail that the rotationally symmetrical body is splayed forwardly, which facilitates parting of the elements with the aid of aerodynamic forces on departure of the unit from the barrel.

Description: The present invention relates to a guiding cap for facilitating the loading into and automatic firing from a weapon of an ammunition round provided with a sabot, without consequential deterioration in the ballistic properties thereof. Said guiding cap surrounds the ammunition round and is placed between the tip of the ammunition round and the sabot in abutting engagement with the front portion of said sabot and comprises a unit consisting of a number of prismatic or cuneiform elements which, together, form a rotationally symmetrical body with an external surface which is conical or curved and, from its leading portion, flares rearwardly towards its trailing portion. It is previously known in this art to employ sabots on so-called rod or needle rounds. There are different types of sabots in existence and so-called reel sabots may be mentioned by way of example. In the type of ammunition round under consideration here, problems may arise in feeding the ammunition round into the weapon without some leading edge, for instance on the sabot, becoming jammed. Guiding caps according to the above are known from,for example, US-A-4 719 860 and FR-A-2 401 399. In these cases the elements are connected by fragile zones and the elements are separated into separate elements in an actuation state to follow after the initial state. When using guiding caps with fragile zones according to said cited prior art, a non-uniform separation of the elements may occur affecting the ammunition rounds leaving the barrel due to the element separation based upon a breaking procedure. The object of the present invention is to propose another solution to the problems which may arise in feeding the ammunition round into the weapon, which is reliable and does not deteriorate the ballistic properties. According to the invention the guiding cap is characterized in that the rotational symmetrical body is formed by said elements individually arranged side by side and in that the guiding cap further comprises a device enclosing said elements at the trailing portion of said body and unifying the elements during loading of the ammunition round into the barrel of the weapon. The combination of a symmetrical body with individually arranged elements and a device enclosing the elements results in a feeding of the ammunition rounds essentially free of problems and a reliable separation of the guiding cap parts from the ammunition round without adversely affecting the ballistic properties of the ammunition round. The enclosing device is arranged to burst preferably during its movement in the barrel, in which immense stress forces arise during discharge or launching of the ammunition round. When this device bursts, the above-mentioned elements execute flip movements about their trailing portions and, by such means, the rotationally symmetrical body is splayed at its leading area and meets the aerodynamic forces in the splayed condition on exit of the unit form the barrel. In one embodiment, the enclosing device consists of an annular device provided with slots extending in the main longitudinal direction of the ammunition round and being of a length which is slightly less than the length of the annular device itself. The annular device displays an externally coned surface which forms a common coned or curved surface with the outer surface of the body proper. At each respective slot, there is disposed a small portion of residual material which bursts during the above-mentioned movement in the barrel of the weapon. In one embodiment, the annular device is designed with a portion which is coned in the longitudinal section of the device and merges into a straight portion, each respective slot extending, in such instance, along the entire coned portion and into the straight portion. In a further embodiment, each respective slot extends into the straight portion for more than half of its length (extending in the longitudinal direction of the ammunition round). The termination of the slot in the straight portion is, in this instance, registered with a recess which extends in from the trailing edge of the straight portion. Furhtermore, each respective slot and recess may be designed with an acute-angled bottom and display a bottom angle of, for instance, 90°. The coned or curved surface of the body may rearwardly merge into a surface which is straight in the longitudinal section of the body and is registrable with a straight internal surface on the enclosing device. In its turn, the straight surface of the body merges rearwardly in a further coned surface which is registered with an internally coned surface on the enclosing device. This further coned surface of the body subsequently merges in an arcuate surface of decreasing diametric size, from which surface a boss-like portion extends. By means of the boss-like portion, the body may be abutted against and journalled in leading portions of the above-mentioned sabot. In this embodiment, the enclosing device may display a rear, straight inner surface by means of which the enclosing device is journalled on the sabot, at the forward portion thereof. By such means, a space will be formed between the trailing portion of the enclosing device and the above-mentioned boss-like portion on the body. The enclosing device and the boss-like portion house, in this space, a forwardly projecting portion or portions of the sabot. The body is designed with a longitudinal central recess, by means of which the body surrounds a neck-shaped portion on the ammunition round. In such instance, the diameter of the leading portion of the body is dimensioned to be such that it corresponds to that of the neck-shaped portion at its forward regions and such that there is a transitional region from the nose of the ammunition round which flares rearwardly to the full calibre of the sabot/ ammunition round. The slots on the enclosing device are preferably 2-4 in number, and most appropriately 3 in number. The arrangement proposed in the foregoing makes possible a guiding cap which substantially facilitates loading of the pertinent ammunition round (rod or needle round) into the weapon. The guiding arrangement is designed so as to retain its cohesion on ramming, but to splay forwardly when the projectile moves in the barrel. The problem inherent herein is solved in that the enclosing or annular device is provided, for instance, with three nicks specifically adapted for this function. By such means, the ramming operation may be catered for, as well as a satisfactory separation function for the elements and the parts of the sabot. The nature of the present invention and its aspects will be more readily understood from the following brief description of the accompanying Drawings, and discussion relating thereto of one currently proposed embodiment of an guiding cap displaying the characterizing features significative of the present invention. In the accompanying Drawings: Fig 1 is a longitudinal section showing an ammunition round or unit of the type generally known as a rod or needle round, with sabot and guiding cap, cuneiform elements included in the latter being shown in two different operational positions; Fig 2 is a perspective view of a rotationally symmetric body composed of prismatic or cuneiform elements and included in the ammunition unit according to Fig 1; Fig 3 is a perspective view of a unifying device for the body according to Fig 2; Fig 4 is a side elevation of the unifying device according to Fig 3; Fig 5 shows, in longitudinal section, parts of a sabot included in Fig 1; Fig 6 is a perspective view of a prismatic or cuneiform element in the body according to Fig 2; and Fig 7 is a cross section showing parts of the body, the enclosing device and the sabot in the composed state. Referring to the Drawings, an ammunition unit of the rod or needle type is indicated by reference numeral 1 in Fig 1.The ammunition unit is previously known per se and will not, therefore, be described in greater detail here. The ammunition unit is of the type which carries a sabot 2 consisting of a number of parts which are parted on the exit of the ammunition unit from the weapon, this being represented by a barrel portion E. The construction and design of the sabot are also previously known per se and will not, therefore, be described in greater detail here. At the leading portion of the sabot, there is disposed a guiding cap 3 according to the present invention. The guiding cap fundamentally consists of two parts, of which the first comprises a body 3a, 3aa composed of a number of prismatic or cuneiform elements, and an annular device 3b unifying these elements. The elements may assume two different functional states, of which an initial state is represented by reference numeral 3a and an actuation state is represented by reference numeral 3aa. In the initial state, the body 3a, 3aa and the annular device display an externally composed, rotationally symmetric surface 3a', 3b' which flares, from the leading portion of the body rearwardly and which may be straight or curved. In the actuation state, each respective element has turned about its trailing portion so that the body 3 is splayed forwardly. The turning movement for each respective element is defined and limited by the inner surface E' of the barrel, by cooperation with the surface and an outer surface on each respective element. The tip of the ammunition unit is indicated by reference numeral 1a and thence the outside of the tip merges, through the intermediary of the outer surface 3a', 3b' of the guiding unit, to the full calibre of the ammunition unit/sabot at the above-mentioned initial state. The construction (initial state) of the body 3a is apparent from Fig. 2. In the present case, the number of elements has been set at 9. However, this number may be optionally selected and may, for instance, lie within the order of between 6 and 12 elements. The enclosing device or annular device 3b in accordance with Fig. 1 is shown in Figs. 3 and 4. The annular device is rotationally symmetric and displays a truncated portion 4 and a straight portion 5. The device is provided with longitudinal slots 6 uniformly distributed about its periphery. In the present case, the number of slots has optionally been set at 3, but may, for example, be selected from within the order of between 2 and 4 slots. Each respective slot extends throughout the entire length of the conical portion and into the straight portion 5. In one embodiment, the slot extends in more than half of the length of the straight portion. A recess 5b is disposed in register with the termination of each respective slot from the trailing edge 5a of the straight portion. Each respective slot and recess is provided with an acute angled bottom, with a bottom angle α of, for instance, 90°. Each respective slot and recess leaves a residual portion 7 with material which is arranged to burst upon departure of the ammunition unit from the barrel, or preferably already inside the barrel. This residual material is of a length a which lies within the order of between 2 and 6 mm and is preferably approx. 4 mm. At the straight portion, the wall thickness of the annular device is 1-2 mm, and at the truncated portion 2-4 mm. The straight portion is provided with an inner recess 8 with which the device 3b surrounds and encloses leading portions of the sabot 2 according to Fig. 1. The device 3b is further designed with a straight inner surface 9 at the leading portion of the device. Moreover, the device 3b displays a truncated inner surface 10. Fig. 5 illustrates the leading portions of the sabot, it being apparent from this Figure that the sabot includes forwardly projecting portions 2a, a straight journalling surface 2b for the enclosing device 3b and a curved trailing surface 2c which is provided to journal the boss-like or sphere-shaped trailing surface of the body 3a. Fig. 6 shows one element 3a'' in greater detail. The truncated surface 3a' merges in a surface 11 which is straight in the side elevation. In its turn, this surface merges in a further surface 12 which is truncated in side elevation and which flares rearwardly. Finally, the truncated surface 12 merges in a surface 13 which is arcuate or straight in side elevation and which displays a rearwardly tapering diameter dimension. A portion 14 departs from this latter surface 13 and, together with the portions of the other elements, forms a boss-shaped trailing journalling portion for the rotationally symmetrical body. In Fig. 7, the device 3b has been fitted on the body elements 3a. In the composite position, the inner surface 9 (see Fig. 4) of the device 3b is in register with the surface 11 (see Fig. 6) on 3a and the inner surface 10 on the device 3b is in register with the truncated outer surface 12 on the body 3a. At the trailing portions where the surface 13 on the body merges in the boss-shaped portion 14', a space is formed between the body 3a and the device 3b. The afore-mentioned forwardly projecting portions 2a (see Fig. 5) project into this space. Furthermore, the inner lfl surface 8 of the device 3b is in register with the journalling surface 2b on the leading edge of the sabot. The device 3b thus surrounds both the elements in the body 3a and the various parts of the sabot. A guiding cap formed in this manner will, in accordance with the foregoing disclosure, be resistant to ramming forces in the weapon. Through the intermediary of its outer surfaces 3a' and 3b', the guiding cap is capable of assisting in an efficient and purposeful guiding of the warhead into the weapon. On propulsion in the barrel, the prismatic or cuneiform elements are enabled to execute turning movements in their journals in the enclosing device 3b and the leading end of the sabot. However, this movement does not affect the internal ballistic properties. When the unit departs from the muzzle of the weapon, the elements 3a' splayed in the leading ends are exposed to aerodynamic forces which strive to splay the elements further in a radial direction. Thereafter, the parts of the sabot are radially parted in a per se known manner. A combination of the forces thus acting on the body 3a and the device 3b entails an efficient release function which ensures purposeful spreading of both the prismatic and cuneiform elements and the parts of the sabot. These elements and parts are radially discarded on exit from the muzzle of the weapon. The present invention should not be considered as restricted to that described above and shown on the Drawings, many modifications being conceivable without departing from the spirit and scope of the appended Claims and inventive concept as herein disclosed.

Claims: A guiding cap for facilitating the loading into and automatic firing from a weapon, of an ammunition round (1) provided with a sabot (2), without consequential deterioration of the ballistic properties thereof, the guiding cap surrounding the ammunition round and being placed between the tip of the ammunition round (1) and the sabot in abutting engagement with the front portion of said sabot and comprising a unit consisting of a number of prismatic or cuneiform elements (3a'') which, together, form a rotationally symmetrical body (3a) with an external surface (3a') which is conical or curved and, from its leading portion, flares rearwardly towards its trailing portion, characterized in that said body (3a) is formed by said elements (3a'') individually arranged side by side and in that the guiding cap further comprises a device (3b) enclosing said elements (3a'') at the trailing portion of said body (3a) and unifying the elements during loading of the ammunition round (1) into the barrel of the weapon. A guiding cap as claimed in Claim 1, characterized in that the enclosing device (3b) bursts because of the barrel pressure during the movement of the ammunition round in the barrel; and that the elements, in such instance, execute flip movements about their trailing portions, which movements are defined by the inner wall of the barrel and which entail that the rotationally symmetrical body is forwardly splayed so that, on departure of the ammunition round from the muzzle of the barrel the rotationally symmetrical body meets the aerodynamic forces in the splayed condition. A guiding cap as claimed in Claim 1 or 2, characterized in that the enclosing device displays an external surface (3b') which forms a common external and rearwardly flaring surface with the external surface (3a'') of the body; and that the enclosing device also encloses leading portions of the sabot (2). A guiding cap as claimed in Claim 1, 2 or 3, characterized in that the enclosing device (3b) consists of an annular device provided with slots (6) extending substantially in the longitudinal direction of the ammunition round and each respectively extending along the major longitudinal direction of the annular device; and that there is disposed, at each respective slot (6) a small section (7) with residual material which bursts on said movement in the barrel. A guiding cap as claimed in Claim 4, characterized in that the annular device is designed with a truncated portion which merges in a straight portion; that each respective slot(6) extends along the whole of the truncated portion and into the straight portion that each respective slot (6) extends into the straight portion for more than half of the length thereof; and that the termination of the slot in the straight portion is in register with a recess (5b) which extends in from the trailing edge (5a) of the straight portion. A guiding cap as claimed in Claim 5, characterized in that each respective slot and recess (5a) is designed with an acute-angled bottom; and that the angle (oe) of the bottom is, for example, 90°. A guiding cap as claimed in any one of the preceding Claims, characterized in that the truncated or curved surface (3a') of the body rearwardly merges in a straight surface (11) which is registrable with a straight interior edge surface (9) on the enclosing device; that the straight surface (11) of the body rearwardly merges in a further truncated surface (12) which is in register with an interior surface (10) on the enclosing device (3b); and that the further truncated surface (12) of the body merges in a surface (13) of tapering diameter dimensions, whence departs a boss-shaped portion for enabling flip movements of the elements. A guiding cap as claimed in Claim 7, characterized in that the enclosing device displays a trailing straight inner surface (8), by means of which the enclosing device encloses a journalling surface (2b) on the leading portion of the sabot. A guiding cap as claimed in Claim 7 or 8, characterized in that a space is formed between the trailing portions of the enclosing device and said boss-lithe portion on the body; and that the enclosing device and the body surround forwardly projecting portion or portions (2a) on the sabot. A guiding cap as claimed in any one of the preceding Claims, characterized in that the body is designed with a longitudinal central recess, by means of which the body surrounds a neck-shaped portion on the ammunition round; and that the diameter of the leading portion of the body closely coincides with the diameter of the neck-shaped portion such that there is formed a transitional portion (3a', 3b') from the nose portion (1a) of the ammunition round which flares rearwardly to the full calibre of the sabot ammunition round.

Inventors: GUSTAVSSON, LENNART, KARLSSON, EWA, REINHOLDSSON, JAN
Applicants: AKTIEBOLAGET BOFORS
Application year: 1989
Main classification: F42B14
IPC codes: F42B14