STUB CASE FOR A MORTAR SHELL TECHNOLOGICAL FIELDThe invention generally contemplates a stub case or a support element for mortar shells. BACKGROUND OF THE INVENTIONMortars are smooth-bored weapons. Their structure typically includes a tail shaft extending from the shell body, an explosive and fuze. The tail shaft is provided with four or more guiding fins which provide stability during the flight of the weapon. The mortar tail shaft usually includes an ignition cartridge, which ignites upon firing and provides the weapon with a muzzle velocity of a certain magnitude, causing it to fly in a predetermined manner. A mortar can be either breech-loaded or muzzle-loaded and can be used in either an indirect or a direct firing mode. While breech-loading provides the advantage of crew protection, it requires sealing of the pressure chamber after each round is loaded to ensure that hot gases will remain contained within the barrel to provide the required velocity to the round and prevent them from risking the operating crew. To secure sealing and containment of the gas-generated pressure during and after ignition, and further to provide secure placement of the round within the barrel, a stub case has been proposed as physical means to achieving both sealing and positioning. Kuru et al [ 1 ] disclose a support member for supporting a mortar shell into a barrel of a breech-loading weapon and sealing of pressure chamber back area, the support member comprising a support element including a rim flange and a firing mechanism for firing the actual primer of the mortar shell, at least one attachment piece for attaching the support element to at least one guiding fin disposed at the tail of the mortar shell, the attachment piece including at least one longitudinal shaft, the shaft being adaptable substantially longitudinally relative to the mortar shell, and a first end of the shaft being supportable to the support element; and a second end of the shaft of the attachment piece including a support portion transversal to the longitudinal axis of the mortar shell for supporting the attachment piece to the front surface of the guiding fin; and the attachment 30
piece including at least one predetermined deformable point allowing a fired mortar shell to be detached from the support member. Reunamaki et al [ 2 ] disclose a support member for supporting a mortar shell into a breech-loading weapon barrel, the support member comprising a support element with an edge flange and a firing mechanism for firing the actual primer of the mortar shell and further comprising connecting means for attaching the support element to a tail of the mortar shell. The connecting means for attaching the support element to the tail comprises at least one flexible part arranged to be attached to the tail of the mortar shell by means of spring force. Nurminen et al [ 3 ] discloses an arrangement for supporting a shell into the barrel of a breech-loading weapon, the arrangement comprising a support member to be fastened to a shell tail, and comprising a support element provided with a rim flange and means for fastening the support element to the shell tail, and a firing member in the support element for firing the actual primer of the shell for firing the shell. The means for fastening the support element to the shell tail comprises a sleeve-like fastening element having grooves for the tail fins of the shell and, between the grooves, jaws settling onto the shell tail tube. The outer surfaces of the jaws are outwardly bevelled at least up to the ends of the jaws. Reunamaki [ 4 ] discloses an arrangement for supporting a shell into the barrel of a breech- loading weapon, the arrangement comprising a shell and a support element to be fastened to a shell tail, the element comprising firing means for firing the actual primer of the shell, characterized in that the firing means of the support element comprise a power source, which is arranged to produce electric current for the electric primer of the shell as a result of a stimulus applied to its structure. Niemi et al [ 5 ] disclose an arrangement for supporting a shell into a barrel of a breech-loading weapon, the arrangement comprising a rim-flanged support element to be fastened to a shell tail. The arrangement comprises a propelling charge element comprising a propelling charge and a primer and having a threading suited for the shell tail in such a manner that by rotating the propelling charge element placed through the support element and the shell relative to one another, the axial position therebetween changes, whereby the support element is displaceable towards the tail of the shell.
REFERENCES[ 1 ] US Patent No. 6,772,693; [ 2 ] US Patent Application No. 2010/288112; [ 3 ] US Patent Application No. 2010/326309; [ 4 ] International Patent Publication No. WO2009/106693; [ 5 ] US Patent Application No. 2010/294159. GENERAL DESCRIPTION The invention disclosed herein provides an improved stub case or a support element for supporting a mortar shell into a barrel of a weapon, wherein the stub case provides not only a secure placement of the shell within the barrel but also an efficient sealing of gases. The stub case may be mounted in the field by military personnel on shells of varying configurations and number of fins. The stub case is provided with a physical locking pattern or a fin-engaging means that is of a material and structure that acts as a weakened point or a break point. The locking pattern is arranged to detach or break or deform from the case or from the mortar shell when the shell is fired. The pattern position and structure ensure that the detachment or breaking does not occur accidently or at a time prior to the firing of the shell, but rather occurs at a time when a force associated with the firing of the shell is greater than the association of the pattern with the stub case or the shell due to its material and structure. The detachment of the stub case from the shell upon initial firing does not, in any way, impede the shell ejection from the barrel and the projectile flight capabilities. In a first of its objects, the invention concerns a stub case for securely fitting around a shell tail of a mortar shell, the stub case having a cup shape with a plurality of inwardly projecting fin-engaging elements, a distance between any two fin-engaging elements defines a guiding slot for a tail fin of the shell tail, wherein each of the plurality of fin-engaging elements is arranged to irreversibly receive a tail fin of the mortar shell (i.e., to be fitted into the stub case). In a further of its objects, the invention concerns a stub case for securely fitting around a shell tail of a mortar shell at a breech end of a breech-loading weapon, the stub case having a cup shape with a plurality of inwardly projecting fin-engaging elements, a distance between any two fin-engaging elements defines a guiding slot for a tail fin of the
shell tail, wherein each of the plurality of fin-engaging elements is arranged to irreversibly receive a tail fin of the mortar shell (i.e., to be fitted into the stub case). The invention further provides a stub case for securely fitting around a shell tail of a mortar shell (at a breech end of a breech-loading weapon) for sealingly containing gases generated by the mortar shell upon firing, the stub case having a cup shape with a plurality of inwardly projecting fin-engaging elements, a distance between any two fin-engaging elements defines a guiding slot for a tail fin of the shell tail, wherein each of the plurality of fin-engaging elements is arranged to irreversibly receive a tail fin of the mortar shell (i.e., to be fitted into the stub case). In some embodiments, each of the fin-engaging elements is arc-shaped. In some embodiments, each of the fin-engaging elements is provided or associated with a serrated fin-arresting surface (or element). In some embodiments, the arc-shaped fin-engaging elements are oriented such that rotation of a mortar shell placed in the stub case transitions each of a fins roof regions (top end region of a fin) to a region below each of the arc-shaped fin-engaging elements and over at least one of the fin-arresting elements and locks the fins in position. The invention further provides a stub case for supporting a shell tail (at a breech end of a breech-loading weapon), the stub case having a tail-fin engaging ring extending inwardly from an inside wall face of the stub case, the tail-fin engaging ring comprising a plurality of arc-shaped segments (arc-shaped fin-engaging elements), spaced from one another, wherein a distance between any two neighboring arc-shaped segments defined a guiding slot for guiding through a fin of the mortar shell. The invention further concerns a stub case for supporting a shell tail at a breech end of a breech-loading weapon, the stub case having a tail-fin engaging ring extending inwardly from an inside wall face of the stub case, the tail-fin engaging ring comprising a plurality of spaced-apart arc-shaped segments (arc-shaped fin-engaging elements), each configured or provided with a serrated fin-arresting surface or element. The invention further concerns a stub case for supporting a shell tail at a breech end of a breech-loading weapon, the stub case having a cup shape extending along a longitudinal axis, with a side wall configurable for snug receiving at the breech end of a barrel of the weapon (thereby forming a pressure chamber); said stub case having a tail-fin engaging ring extending inwardly from an inside wall face of the stub case, the tail-fin engaging ring comprising a plurality of arc-shaped segments (arc-shaped fin-engaging
elements), spaced from one another and each configured (or provided) with a serrated fin-arresting surface. The stub case of the invention is a cup-shaped unit of an inner diameter selected to accommodate shells of varying configurations and number of fins. The contour of an inside bottom face of the stub case may be concave and may correspond with the shape of a bottom portion of the tail fins of the shell tail. The case’s height extends along a longitudinal axis such that the height of the case is substantially greater than the length or height of the tail fins. A laterally projecting rim flange is provided at a rear end portion of the stub case. Typically, to sustain high temperatures and pressures associated with the firing of the mortar shell within the case, acting as a pressure chamber, and to further provide robust sealing and support, the stub case may be formed of a metal or another non-metallic material. The rim end of the stub case may be formed of a non-metallic material (such as a polymeric material, e.g., hard silicones, composite materials, etc) that may, upon firing of the shell, expend outwards to seal a distance between the stub case and the inner surface of the barrel. The stub case may further comprise a centrally positioned firing mechanism, which comprises a firing pin, e.g., an electrical firing pin or a mechanically operable firing pin. A region of the case’s inner wall surface or face is provided with a plurality of fin-engaging elements and guiding slots defined by a distance or gap between any two neighboring fin-engaging elements. The distance between any two neighboring elements is typically identical or slightly larger than a thickness of a mortar shell fin. The fin-engaging elements are arranged around the inner surface in a loop-like pattern. Each element is projected from the inner wall surface or may be optionally mounted on a ring extending inwardly from the wall surface. Each of the fin-engaging elements is arc-shaped and is provided or associated with a serrated fin-arresting surface. The arc shape of each of the fin-engaging elements may be circular or elliptical arc shape. Each fin-engaging element is positioned such that the two ends thereof are not positioned at the same distance from a bottom surface of the stub case. One end is provided at a distance from the bottom surface of the stub case that is higher to a roof region of each of the tail fins of the mortar shell. In other words, the distance of one end of the arc-shaped elements from an inside bottom face of the stub case may be greater than the height of the tail fins
of the shell tail. The other end of the arc-shaped element is provided at a distance that may be shorter than the height of the tail fins. The fin-engaging elements are positioned such that a space or a distance between any two neighboring elements corresponds with an angular distance of any two neighboring tail fins. This space defines a guiding slot through which a fin of the mortar shell may be guided. Thus, the number of guiding slots is determined by the number of fin-engaging elements and is typically the same as the number of fins on the mortar shell to be fitted into the stub case. Each of the arc-shaped fin-engaging elements is provided or associated with a serrated fin-arresting surface or elements. The serrated fin-arresting surface may be a continuous serrated surface that is provided below the fin-engaging elements and which comprises a plurality of surface extending teeth; or the fin-arresting surface may comprise a plurality of rachet elements that are provided or grouped below each arc-shaped fin-engaging element. The arc-shaped elements are oriented such that arresting the tail fins of the shell tail within the cup-shaped stub case is facilitated by a screw-like fastening of the stub case against the tail fins of the shell tail. Putting it differently, the arc-shaped elements are oriented such that rotation of a mortar shell placed in the stub case transitions each of the fins roof regions (top end of a fin) to a region below each of the arc-shaped fin-engaging elements and over at least one of the fin-arresting elements and locks the fins in position. The fins are thus locked between a ratchet end of the fin-arresting element and an end of the arc-shaped fin-engaging element that is closer to the inner surface of the stub case. Rotation of the mortar shell in the opposite direction is thus prevented or not possible and movement of the mortar shell in any direction is prevented. The position of both the fin-engaging elements and the serrated fin-arresting surface, i.e., plurality of ratchet elements, ensures that the release from the stub case does not occur accidently or at a time point prior to the firing of the shell, but rather requires a force that is greater than the force associated with the mechanical properties of the pattern due to its material and structure. The invention further provides a method for securely mounting a stub case on a shell tail of a mortar shell (at a breech end of a breech-loading weapon), the method comprising inserting the shell tail into a stub case having an inner cup shaped surface with a plurality of inwardly projecting fin-engaging elements, such that each of the shell tail fins is inserted between two fin-engaging elements (defining a guiding slot for the tail
fins), and rotating the mortar shell to engage the tail fins in the plurality of fin-engaging elements arranged to irreversibly receive each of the tail fins, as further disclosed herein. Each of the embodiments relating to the stub case unit, as disclosed herein, is similarly relevant and applicable to the method of the invention. The invention thus provides: A stub case for securely fitting around a shell tail of a mortar shell at a breech end of a breech-loading weapon, the stub case having an inner cup shaped surface with a plurality of inwardly projecting fin-engaging elements, a distance between any two fin-engaging elements defines a guiding slot for a tail fin of the shell tail, wherein each of the plurality of fin-engaging elements is arranged to irreversibly receive a tail fin of the mortar shell. In some configurations of a stub case of the invention, each of the fin-engaging elements is arc-shaped. In some configurations of a stub case of the invention, each of the fin-engaging elements is provided or associated with a serrated fin-arresting surface (or fin-arresting element). In some configurations of a stub case of the invention, the stub case having a tail-fin engaging ring or region extending inwardly from an inside wall face of the stub case, the tail-fin engaging ring or region comprising a plurality of arc-shaped segments, spaced from one another, wherein a distance between any two neighboring arc-shaped elements defines a guiding slot for guiding through a fin of the mortar shell. In some configurations of a stub case of the invention, the fin-engaging elements are arranged around the inner wall surface in a loop-like pattern. In some configurations of a stub case of the invention, the serrated fin-arresting surface is a continuous serrated surface provided below the fin-engaging elements. In some configurations of a stub case of the invention, the serrated fin-arresting surface comprising a plurality of surface extending fin- arresting elements in a form of teeth or a plurality of rachet elements grouped below each of the arc-shaped fin-engaging elements. In some configurations of a stub case of the invention, the arc-shaped elements are oriented such that arresting the tail fins of the shell tail within the cup-shaped stub case is facilitated by a screw-like fastening of the stub case against the tail fins of the shell tail.
In some configurations of a stub case of the invention, the arc-shaped elements are oriented such that rotation of a mortar shell placed in the stub case transitions each of the fins roof regions (top end of a fin) to a region below each of the fin-engaging elements and over at least one of the fin-arresting elements and irreversibly locks the fins in position. In some configurations of a stub case of the invention, each of the arc shaped elements having a circular or an elliptical arc shape. In some configurations of a stub case of the invention, each fin-engaging element is positioned such that the two ends thereof are positioned at a different distance from a bottom surface of the stub case. In some configurations of a stub case of the invention, one end of each of the fin-engaging elements is provided at a distance from the bottom surface of the stub case that is higher to a roof region of each of the tail fins of the mortar shell. In some configurations of a stub case of the invention, the stub case comprising a centrally positioned firing mechanism. BRIEF DESCRIPTION OF THE DRAWINGSIn order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Figs. 1A-B show a depiction of an exemplary mortar shell positioned in a stub case according to some embodiments of the invention. Figs. 2A-C show different views of a stub case according to the invention. Fig. 3provides a top view of a mortar shell positioned in a stub case according to the invention. Fig. 4 shows locking of a mortar shell’s fins in a stub case. Fig. 5 is a bottom view of a stub case. DETAILED DESCRIPTION OF EMBODIMENTS Reverting to the figures provided herein, the figures generally depict an exemplary stub case according to some embodiments of the invention.
As depicted in Figs. 1Aand 1B , provided is a stub case 10 for supporting a tail end of a shell 100 at a breech end of a breech-loading weapon (the end of the barrel, the breech block side). The stub case 10 has a cup shape 16 extending along a longitudinal axis 18 . The case has a side wall 20 configurable for snug receiving at the breech end of a barrel of the weapon. Figs. 2A , 2B and 2C provide different side views of a stub case 10 . The stub case 10 having has a tail-fin engaging ring 26 extending inwardly from an inside wall face 28 of the stub case 10 . In some cases, the ring 26 defines a ring-like region of the inner wall and in other configurations may be provided in a form of a material ring element that runs along the inner wall of the stub case. The tail-fin engaging ring or ring like region 26 comprises a plurality of arc-shaped fin-engaging elements 30(e.g., 30A , 30B , 30C , etc), spaced from one another by a distance 36 , and configured with a serrated fin arresting surface 32 . In cases where the ring element 26 is absent, the arc-shaped segments 30 and the serrated surface may be mounted or provided directly on the inner wall face 28 of the stub case 10 . The cup-shaped stub case 10has an inner diameter selected to accommodate shells of varying configurations and number of fins. The contour of an inside bottom face (not shown) of the stub case may be concave. The case’s height H extends along the longitudinal axis 18 (shown in Fig. 1 ) such that the height H of the case may be, in some cases, substantially greater than the height of the tail fins ( Fig. 1 ). A laterally projecting rim flange 22 is provided at a rear end portion 29 of the stub case 10 (as further shown in Fig. 5 ). As explained, a region of the member’s inner wall surface 28 or face is provided with a plurality of fin-engaging elements 30 and guiding slots 34 (e.g., 34A , 34B , 34C , etc) defined by a distance or gap 36 between any two neighboring fin-engaging elements 30 , as shown in Fig. 2C . The arc shape of each of the fin-engaging elements 30 may be a circular or an elliptical arc shape. Each fin-engaging member 30 is positioned such that the two ends thereof X1 and X2 , are not positioned at a same distance from the bottom inner surface of the stub case 10 . One end X1 is provided at a distance from the bottom surface of the stub case that is higher to a roof region ( 40 , Fig. 3 ) of each of the tail fins of the mortar shell, while the other end X2 is provided at a distance that is shorter than the height of the tail fins.
The fin-engaging elements 30A , 30B , 30C , etc are positioned such that a space or distance 36 between any two neighboring elements 30 corresponds with the angular distance of any two neighboring tail fins of the mortar shell 100 . This space 36defines the guiding slot 34 through which a fin of the mortar shell may be guided. Thus, the number of guiding slots 34 is determined by the number of fin-engaging elements and is typically the same as the number of fins on the mortar shell to be fitted into the stub case. The serrated fin-arresting surface 32 ( Fig. 2 ) typically comprises a plurality of surface extending teeth 38 ( 38A , 38B , 38C , etc) or a plurality of rachet elements that are provided or grouped below each arc-shaped fin-engaging element 30 . As depicted in Fig. 3 , the arc-shaped elements 30 are oriented such that rotation of a mortar shell placed in the stub case in an unlocked position along an imaginary rotation line R transitions each of the fins roof regions 40 (top end of a fin) from the guiding slots 34 to a region M below each of the fin-engaging elements 30 and over at least one of the fin-arresting elements 32 (or teeth 38 ), Fig. 2C , and locks the fins in position. This is further depicted in Fig. 4 . The fins are thus locked between a ratchet end of the fin-arresting element 32 (elements 38 ) and an end X2 of the arc 30 that is closer to the inner surface of the stub case. Fig. 5 shows a back side 29 of a stub case 10.