Patent Publication Number: US-7581499-B2

Title: Insulated cartridge case and ammunition, method for manufacturing such cases and ammunition, and use of such cases and ammunition in various different weapon systems

Description:
TECHNICAL FIELD 
   The present invention relates to a cartridge case and ammunition round primarily for electrothermal and/or electrothermochemical weapon systems, which round comprises the said cartridge case. 
   The invention also relates to a method for manufacturing such a cartridge case and an ammunition round primarily for electrothermal and/or electrothermochemical weapon systems, which round comprises the said cartridge case. 
   The invention also relates to use of the cartridge case and the ammunition round in other more conventional weapon systems than the said electrothermal and/or electrothermochemical weapon systems, but preferably in electrothermal and electrothermochemical weapon systems. 
   PROBLEMS AND BACKGROUND OF THE INVENTION 
   Various different propulsion principles exist today for accelerating projectiles through the barrel of a weapon system. The main division between these principles is based on whether projectile propulsion takes place by means of gas operation, electric operation or via a combination of these, at the same time as the propulsion principle(s) used in turn essentially determine which problems may arise in the different weapon systems. 
   Gas-operated weapon systems normally mean those systems which utilize the combustion gases which are formed after ignition of the propellant concerned for the shell, which propellant may now be liquid, solid or gaseous, although powder is still usually used. For example, in a conventional weapon, an ammunition round is fired by means of a firing device, normally a fuse, which ignites a propellent charge which, on combustion, develops a propellent gas quantity which is sufficiently powerful and expansive to accelerate the projectile rapidly out through the barrel of the weapon. 
   Electrically driven weapon systems instead utilize short electric pulses with high voltage and/or high current intensity in order to fire and propel the shell in ammunition adapted especially for electric operation. 
   In recent years, weapon systems based on combinations of both gas operation and electric operation, such as, for example, cannons which comprise either electrothermal propulsion or electrothermochemical propulsion, what are known as ETC cannons, have become increasingly important. In ETC cannons, use is made of, for example, electrical energy from a high-voltage source in order to bring about the actual ignition of the propellent charge, and then of on the one hand chemical energy from the combustion of this propellent charge and on the other hand electrical energy in the form of one or more pulses in order to supply more energy to the propellent gas in the form of plasma formation from the latter or via the creation of an electric potential difference along the barrel in order to increase the speed of the projectile. 
   In many hitherto known electrothermochemical weapon systems, the conventional fuse is replaced by a plasma generator. The plasma generator is filled with a preferably metal material which, via the electric pulses, is heated, vaporized and finally partly ionized, a plasma being produced, which, depending on the type of plasma generator, flows out through the front opening of the plasma generator or through a number of openings along its sides, what is known as a “piccolo”. The very high temperature (roughly 10,000° K) of the plasma influences the combustion of the propellant in several positive ways, which together result in a desired higher muzzle velocity of the projectile. 
   Rather briefly, it can be said that a typical modern ETC cannon consists of a cannon, the shell projectiles of which are essentially powder-gas-propelled, but where the shell is fired by means of electric ignition and its projectile is given an extra “push” via the plasma formation in connection with combustion of the propellent charge. However, there are also ETC cannons in which, after firing by means of a conventional fuse add “normal” combustion of the powder charge carried out subsequently, extra electrical energy is supplied to the projectile via the propellent gas further forward in the barrel by devices specially arranged there (see, for example, U.S. Pat. No. 5,546,844). 
   The technical problems which form the basis of the present invention are on the one hand the handling and storage problems which exist or can arise in the different weapon systems due to the weight, the moisture-sensitivity, the risk of electric short-circuiting etc. of the shell, and on the other hand the specific risk for ETC cannons that the cartridge case burns on in the barrel owing to electric short-circuiting between the cartridge case and the barrel. This is because the modern conventional cartridge case is manufactured from electrically conductive metal, usually brass. The burning-on is caused by the current and/or the voltage used during firing being intentionally or unintentionally conducted across to the cannon/artillery piece via the barrel. Moreover, the fact that the cannon/artillery piece becomes live constitutes an extra disadvantage for the gun crew. 
   It is therefore highly desirable to produce a new type of ammunition which is different from the abovementioned electrically conductive metal ammunition, has a considerably lower projectile weight than all comparable ammunition for conventional weapon systems and moreover is electrically insulated in order to prevent short-circuits and to minimize the risk of all or parts of the cartridge case burning on in the chamber or in the barrel. 
   PRIOR ART 
   Patent specification U.S. Pat. No. 6,186,040 describes a known plasma torch arrangement for electrothermal and electrothermochemical cannon systems where the necessary current and voltage are transferred to the plasma fuse via the rear part of the latter and then on to earth via the case jacket of the round and the barrel of the cannon system. A major problem in plasma cannons of this type is therefore that they use the cannon barrel as a counterelectrode, and so these constructions also apply current and voltage to the cannon barrel itself and thus other important parts of the weapon system concerned. Apart from the obvious disadvantages of this, such as the risk of personal injury as a result of electrical hazard and short-circuiting of the weapon system, it is clear that there is a considerable risk of the cartridge case burning on in the barrel when current and voltage are conducted across to the cannon. 
   An electrothermal firing arrangement with associated ammunition is also known from U.S. Pat. No. 5,331,879, where the arrangement comprises a barrel which comprises an inner “combustion chamber part”, in which the propellent charge burns, and an outer “projectile guide part” for accelerating the projectile. The ammunition comprises an only partly electrically insulated cartridge case, as the front part adjacent to the projectile consists of a front electrode which is electrically connected to the said projectile guide part of the barrel. The current transfer path for the arrangement via the ammunition therefore consists of an earthed metal breech block for current supply, a first and second electrode of the round between which a metal wire runs, and the barrel itself. It is easy to see that such a design of a cannon barrel constitutes neither a conventional construction nor a valid solution for conventional use in the field in a real weapon system, as opposed to here in a theoretical laboratory construction. For example, the ammunition round does not have a cartridge case proper, as the cartridge case and the firing device are the same component here. The projectile can therefore be considered to be mounted directly at the end of a fuse, as a result of which the round is always armed and cannot be disarmed without being destroyed at the same time. 
   It is true that the combustion chamber part and the projectile guide part have been insulated from one another via a high-voltage seal made of rubber or silicone rubber arranged between them, but the rubber will age very rapidly and be destroyed by use, after which the problems of short-circuiting etc. described above will occur. Moreover, it has been necessary to insulate, in addition to a small area intended for a cable terminal for the front electric connection, the entire front part of the barrel with a surface coating on its outside. 
   In addition to the constructions with metal barrels exemplified above, alternative barrels made in their entirety of non-conductive material have also been manufactured. An example of these is inter alia the grenade sleeve of the Carl-Gustaf anti-tank rifle, which is today manufactured from wound, glass-fibre-reinforced epoxy. In this case, however, the selection of material would be due to the resulting weight reduction. 
   One problem in the use of such non-metal barrels for conventional barrels as well is that the pressure from the combustion of the propellent charge will burst the barrel when the latter is closed at the rear end, which is of course the case in, for example, conventional artillery pieces, anti-tank weapons, cannons for tanks etc. 
   OBJECTS AND FEATURES OF THE INVENTION 
   An important object of the present invention is therefore to produce a new type of insulated or insulating cartridge case and ammunition round primarily for electrothermochemical weapon systems, which cartridge case and which ammunition round are insulated in such a way that they considerably reduce or completely eliminate all the abovementioned problems and in particular the problems of the application of current and voltage to the barrel and other sensitive parts of the weapon system and also the risk of the cartridge case burning on in the said barrel and chamber. 
   Another object of the present invention is to produce cartridge cases and ammunition for use in weapon systems other than the said electrothermochemical weapon systems, which cartridge cases and which ammunition moreover have a considerably lower total weight compared with conventional ammunition. 
   It is also an object of the present invention to produce a new method for manufacturing cartridge cases and ammunition which are insulated in relation to their surrounding environment, that is to say which are not only electrically insulated but which can also be insulated with regard to water, moisture, temperature etc. 
   The said objects, and other aims not listed here, are achieved within the scope of what is stated in the present independent patent claims. Embodiments of the invention are indicated in the dependent patent claims. 
   The solution according to tie present invention is, in a way described in greater detail below, to replace the normally heavier, metal cartridge case with a lighter case which is electrically insulated or which is made of a material which does not conduct current, for example a plastic, ceramic or glass-fibre material etc. The result of the said insulation or replacement is that electric flashover, that is to say a short-circuit, normally cannot happen, and in most cases a considerable weight reduction as well and also thermal insulation etc. are obtained when a metal case is replaced with a non-metal case. 
   Examples of suitable replacement materials are polyethylene, glass-fibre-reinforced epoxy etc. 
   According to the present invention, an improved cartridge case and ammunition round comprising the said cartridge case have therefore been produced, which are characterized in that:
     the casing of the cartridge case comprises or consists of one or more insulated or insulating shells, layers or surfaces for, at least electrically, insulating the casing of the cartridge case from the barrel of the weapon system and also preferably from at least the bottom and/or firing device of the ammunition round as well, but preferably also from the rest of the ammunition round, when the round is used, and also preferably from at least the bottom and/or firing device of the ammunition round as well, but preferably also from the rest of the ammunition round, when the round is stored and handled.   

   According to other aspects of the cartridge case and the ammunition round according to the invention:
     the casing of the cartridge case comprises a load-bearing case shell, for example in the form of a conventional cartridge case manufactured from an electrically conductive metal, for example brass, and also at least one inner and/or outer coating, surface or layer, of which at least the shell or one inner and/or outer coating, surface or layer is dielectric for electric insulation of the case in relation to at least the barrel and preferably also to the bottom and/or firing device of the ammunition round, but preferably also to the rest of the ammunition round;   the cartridge case has a casing which comprises at least one inner and/or outer coating, surface or layer which is a mechanically applied layer or a chemically or electrochemically applied surface;   at least one inner and/or outer coating, surface or layer consists of a material applied by phase transformation, such as vaporization and condensation to form an insulating film, preferably a dimeric or polymeric raw material comprising hydrocarbons, such as poly-para-xylylene or another suitable plastic;   at least one inner and/or outer shell or layer consists of shape-imitating shrink film or flexible tube made of preferably non-conductive material, such as rubber or plastic;   the casing of the cartridge case comprises or consists of a non-conductive or electrically insulating load-bearing material, shell, layer or surfaces, such as hard plastic, ceramic, rigid rubber, fibre composite etc.;   the casing of the cartridge case comprises or consists of a relatively flexible non-conductive or electrically insulating shell or layer which is constructed from a glass-fibre laminate comprising woven glass-fibre fabric and glass-fibre thread, for example glass-fibro-reinforced epoxy in the form of a case jacket wound in a number of plies;   the casing of the cartridge case has a thread winding which is arranged along the case jacket at a winding angle α defined for each ply to the longitudinal axis Y of the case, and which casing includes several different thread-winding angles α for bringing about locking of the glass fibre, preferably at least 4 different angles α in relation to the longitudinal axis Y of the case;   the firing device is arranged detachably on a bottom integrated with the casing of the cartridge case or on a separate bottom piece arranged preferably demountably with the casing;   the separate bottom piece is manufactured with an interference fit to the cartridge case jacket which is greater than the expansion possibility of the round in the cartridge chamber plus the maximum compression which can be brought about by the inner overpressure when firing takes place;   the round also comprises at least one projectile, and, enclosed in the cartridge case, a propellent charge which essentially follows the inner dimensions of the case;   the shrink film or the tube is arranged directly on the outside of the propellent charge;   the propellent charge consists of a cartridge-shaped charge which is surrounded by an outer shrink film or flexible tube for forming a cartridge-shaped, and if appropriate vacuum-packed, round which stands up to normal handling of the round;   the bottom piece is electrically non-conductive, suitably made of glass-fibre epoxy, and arranged on the rear end of the casing in a tight-fitting manner by means of screw-thread cutting, adhesive bonding or by means of another connection suitable for the function;   the bottom and/or the rear end of the firing device comprise(s) an electric connection, by means of which the ammunition round, once introduced into the chamber of the weapon concerned, is in electric contact with the high-voltage source of the weapon concerned via the firing device;   the firing device comprises an outer, electrically conductive metal combustion chamber which is arranged projecting from and detachably fastened to the rear end of the cartridge case, and a central electrode arranged inside the chamber, the central electrode comprises a first, “input” electric connection, the rear end of the combustion chamber comprises a second, “output” electric connection, an electrically insulating device is arranged between the said two, “input” and respectively “output”, electric connections and along the entire length of the combustion chamber between the said “input” electric connection and a front opening arranged on the plasma torch, at least one but preferably more electric conductors extend inside the combustion chamber and the electrically insulating device, between the first, “input” electric connection and the front opening of the combustion chamber, the combustion chamber, the electric conductors and the central electrode all being electrically conductive, as a result of which the current transfer path, the polarity of which can be changed, for the necessary current and voltage is therefore arranged so as to run from the first, “input” electric connection and on to the front opening of the combustion chamber via the electric conductors for ionization of these to form a very hot, expansive plasma, which squirts out through the said front opening, for igniting the propellent charge, and finally from the plasma and the front opening of the combustion chamber back to the “output” electric connection via the casing of the combustion chamber;   the firing device of the ammunition round can consist of a fuse for use of the cartridge case and the ammunition round in other more conventional weapon systems than the said electrothermal and/or electrothermochemical weapon systems.   

   According to the invention, furthermore, the method for manufacturing the said cartridge case and ammunition is characterized in that:
     at least one of the shells or layers which form part of the casing of the cartridge case is manufactured by glass-fibre thread being wound with resin in thin layers with varying winding angles α sandwiched with woven glass-fibre fabric so that a plurality of winding plies/laminate layers are obtained after hardening.   

   According to other aspects of the method for manufacturing the cartridge case and the ammunition round according to the invention:
     for every such winding ply/laminate layer, a fibre winding with fibre angles of essentially roughly 90° to the longitudinal axis of the tube on the inside and +/− roughly 15-25°, preferably +/−20°, on the outside is selected, and a number of such winding plies are laid on top of one another and sandwiched with woven glass-fibre fabric between a number of the thread-winding plies so that an essentially flexible case jacket is obtained, as a result of which the casing of a round introduced into the cartridge chamber tolerates being expanded towards the walls of the cartridge chamber by the inner overpressure inside the cartridge case brought about when firing takes place without for that reason cracking, delaminating or disintegrating;   at least one of the shells or layers which form part of the casing of the cartridge case is manufactured by an innermost, tightly woven glass-fibre fabric first being applied to a winding and shaping tool which is rotated while the fabric is draped over it, the last piece of the woven glass-fibre fabric being laid so that a small overlap is formed, after which a first winding ply of glass-fibre thread in resin is wound with a fibre angle to the longitudinal axis of the tube of essentially 90°, followed by two or more winding plies of thread with a fibre angle, which is varied for the component plies, of on the one hand roughly +15-25°, preferably +20°, and on the other hand roughly −15-25°, preferably −20°, after which the subsequent, thin winding plies/laminate layers are also given a fibre winding with a fibre angle to the longitudinal axis of the tube which varies between essentially roughly 90° and +/±roughly 15-25°, preferably +/±20°, as the thickness of the casing is built up to roughly half-thickness, after which woven glass-fibre fabric is sandwiched with fibre windings with a fibre angle of essentially 90° until full shell or layer thickness has been achieved;   a relatively low winding speed is used, preferably roughly 4-6 m/min, while a relatively high thread tension, roughly 21-23N/roving, and a hardening cycle which comprises a plurality of hardenings at increasing temperatures are selected;   use is made of a hardening cycle of roughly 5 hours at roughly 80°, followed by roughly 5 hours at roughly 120°, after which after-hardening takes place for roughly 4 hours at roughly 140°;   after shaping of a blank for the casing, this is cut and/or turned/ground to essentially the desired length, thickness and predetermined shape, after which a bottom piece is mounted on the rear end of the casing in a tight-fitting manner, preferably by adhesive bonding or screw-thread cutting;   the bottom piece is manufactured from glass-fibre epoxy, either by glass-fibre thread and/or woven glass-fibre fabric being given during shaping the form of a hammock where only tensile loads in the fibres can occur or by glass-fibre thread and/or woven glass-fibre fabric being given during shaping the form of a plane bottom so that pressure loads can also occur, after which the bottom piece, after shaping and hardening have been completed, is then turned out, attention being paid to obtaining the correct interference fit for the casing concerned;   the bottom piece is manufactured from an electrically conductive material, suitably from metal;   an insulation coating is applied over all the shell or layer surfaces of the cartridge case concerned which are accessible to gas by phase transformation via a number of phases, a dimeric or polymeric raw material being vaporized so that the polymer or the dimer is first transformed from solid phase to gas phase and then, at a further increased temperature, is transformed to a reactive monomer gas which is made to condense and polymerize, a thin insulating plastic film layer being deposited on all the free surfaces of the cartridge case;   the condensation of the reactive monomer gas to form an insulating film takes place under low pressure, preferably in a vacuum.   

   The use of such cartridge cases and ammunition according to the invention is characterized in that the firing device of the ammunition round can consist of a fuse for use of the cartridge case and the ammunition round in other more conventional weapon systems than the said electrothermal and/or electrothermochemical weapon systems. 
   ADVANTAGES OF THE INVENTION 
   The advantages include the fact that, compared with the conventional metal cases, a considerable weight saving (roughly 70%) is obtained while the ammunition quantity remains the same. Alternatively, if the storage space allows, a greater quantity of ammunition can be carried in spite of an unchanged total weight. 
   From a technical point of view, manufacturing is simple, as a result of which the cases can be manufactured with uniform and high quality for a low manufacturing cost. The form and execution selected for the winding plies result in tight laminate shells, which prevent overpressure being built into the casing of the case, a high expansion capacity without the case cracking, and also the laminate sealing itself the more the overpressure in the round increases. Moreover, the cases have great impact-resistance at the same time as they tolerate a certain delamination in the event of careless handling. 
   By using a cartridge case made of electrically insulating material, that is to say non-conductive plastic, glass fibre, ceramic etc., or by using a metal case which has been provided with a coating, surface or layer which insulates the case electrically, for example by vaporization of a plastic to form an insulating plastic film of suitable thickness, the risk of flashover, that is to say electric short-circuiting, has on the whole been eliminated. 
   Even if the current should happen to be conducted across to the cannon/artillery piece when firing of a round takes place, the cartridge case will not burn on in the barrel, which is often the result when the cartridge case is made of metal. 

   
     LIST OF FIGURES 
     The invention will be described in greater detail below with reference to the accompanying figures, in which 
       FIG. 1  is a diagrammatic perspective view of a round comprising an insulated or insulating cartridge case according to the present invention, which round is here intended in particular for an electrothermochemical weapon system; 
       FIG. 2  is a diagrammatic longitudinal section through parts of the round according to  FIG. 1 , which longitudinal section shows inter alia a plasma torch arranged inside the insulated or insulating cartridge case; 
       FIG. 3  is a longitudinal section through parts of a diagrammatic weapon for firing the round according to  FIG. 1 ; 
       FIG. 4  is a diagrammatic longitudinal section through parts of the cartridge case for the round according to  FIG. 1 ; 
       FIG. 5  shows diagrammatically a perspective view of an alternative cartridge case made of, for example, glass-fibre-reinforced epoxy for use in a round according to the invention, and 
       FIG. 6  is a diagrammatic longitudinal section through the cartridge case according to  FIG. 5 . 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   With reference to  FIG. 1 , a perspective view is shown of an ammunition round  1  comprising an, at least electrically, insulated or insulating cartridge case  2  according to the present invention. Here, the round  1  is intended in particular for an electrothermochemical (ETC) weapon system comprising armour-piercing dart ammunition for use in tanks, combat vehicles and various anti-tank weapons but also in, for example, combat aircraft, anti-aircraft weapons and other artillery. 
   It will be understood, however, that the round  1  shown is not only intended for such ETC ammunition and that it can also include several different sizes and projectile types depending on the area of use and calibre. Here, however, it is at least the commonest ammunition types today, between roughly 25 mm and 160 mm, which are concerned. 
   The expressions “at least electrically insulating” or “at least electrically insulated” mean that the material, the case etc. so designated can also function as insulating or be insulated in relation to the surrounding environment with regard to water, moisture, temperature etc. 
     FIG. 2  shows a diagrammatic longitudinal section through parts of a first embodiment of the round  1  according to  FIG. 1 , which round  1  also comprises, in addition to the said insulated or insulating cartridge case  2 , a projectile  4  mounted at the front end  3  of the cartridge case  2 , a firing device in the form of a plasma torch  5  arranged at the rear, flanged end  6  of the round  1 , and a propellent charge  7  which is enclosed in the cartridge case  2  and is indicated diagrammatically only in the centre of the case  2 . Preferably, however, the entire cavity  8  of the case  2  is filled with a propellent charge  7  which can consist of a solid powder or a suitable liquid propellant. The solid propellent charge  7  suitably consists of what is known as a progressive perforated powder provided with a large number of holes in the form of one or more, for example cylindrical, bars, plates, blocks etc., which powder essentially follows the inner dimensions of the case  2 , or of a charge comprising grain powder, also known as powder pellets  9 , for example a compacted NC powder grain charge. In this connection, the said powder grains  9  have first been treated with a suitable chemical in order to bring about adhesion between the individual grains  9 , after which the grains  9  are pressed together to form a charge  7  with a desired shape determined by the cavity  8 . Alternative embodiments of the powder charge  7  also include multi-perforated double-base (DB) powder with inhibition, Fox  7 , AND, nitramine, GAP and other known powder types. 
   It applies generally that the cartridge case  2  comprises an, at least electrically, insulating and/or electrically insulated casing  10 . This casing  10  can then consist of only one or the same essentially homogeneous material layer, shell or laminate  11  which is then dielectric (that is to say non-conductive), for example a fibre composite, or of a combination of several different shells, layers or surfaces  11 ,  12 ,  13 , where at least one of these acts in an electrically insulating manner for the others and for the cartridge case  2  as a whole. 
   A combined casing  10  (compare  FIG. 4 ) can, for example, consist of an essentially supporting or load-bearing shell  11  and also at least one inner  12  and/or outer  13  mechanically applied layer or chemically applied surface, that is to say coating. The essentially supporting or load-bearing shell  11  is preferably non-conductive and then suitably made of glass-fibre epoxy, rubber etc., but the said shell  11  can be conductive, in which case at least one of the inner and/or outer layers or surfaces  12 ,  13  of the casing  10  is then dielectric in order to bring about the said electric insulation of the inside and/or outside of the casing  10  in relation to at least the barrel  14  and preferably also to the plasma torch  5 . 
   Preferably, the casing  10  (see  FIGS. 5 and 6 ) is constructed from a glass-fibre laminate comprising a thin tight woven E-glass fibre fabric on the inside, suitably what is known as a Fothergill fabric, on the outside of which E-glass fibre thread (for example R25 glass) is wound with resin in thin layers with varying winding angles α sandwiched with further woven E-glass fibre fabric (see below). 
   In an example of the said embodiment of a cartridge case  2  with a conductive shell  11 , the case comprises a load-bearing, metal shell  11 , on which a plastic film coating  12 ,  13  (see below) has been applied. See in particular  FIG. 4  which shows a load-bearing shell  11  made of brass which has been insulated with, for example, shrink film or a plastic film coating  12 ,  13  in order to bring about electric insulation in relation to the barrel  14 . Here, load-bearing  11  or supporting shell means that a load-bearing shell  11  in itself stands up to normal stresses without being deformed appreciably during handling of the case  2  and the round  1 , while supporting means an essentially flexible shell which is, for example, arranged directly on the outside of the propellent charge  7  without an inner, rigid case casing being present, the shell together with the propellent charge  7  then standing up to the said normal handling of the round  1 . An example (not shown) of a round comprising a supporting shell will consist of an inner cartridge-shaped charge which is enclosed in an outer shrink-film or flexible tube which surrounds the charge and is shaped according to the said cartridge-shaped charge. If appropriate, extra rigidity can be obtained by vacuum-packing. 
   In this connection, the supporting shell is arranged so that it extends between the projectile and the bottom piece with a rigidity as is required for the function. In this embodiment, after firing the finished round, only the metal bottom of the cartridge case remains, and the rest is combusted in the barrel. 
   In the embodiments of the cartridge case  2  according to the invention shown in particular in  FIGS. 4 and 6 , these comprise an at least electrically insulating and/or electrically insulated casing  10  which consists of a load-bearing shell  11 , on the outside of which an outer layer or surface  13  is (see  FIG. 4 ) or can be arranged ( FIG. 6 ). Either of or both the shell  11  and the outer layer or surface  13  is then dielectric, the layer suitably consisting of the abovementioned shape-imitating shrink film or elastic tube, while the surface consists of a suitable insulating coating. If the shell  11  consists of a glass-fibre composite, for example, the said layers or surfaces  12 ,  13  can instead consist of, for example, a coating which increases wear protection or moisture protection in order to bring about a reduction of the stresses on the shell  11  or respectively an improvement of the moisture protection for the round  1 . An example of a suitable electric insulation coating is a dimeric or polymeric raw material comprising hydrocarbons, such as poly-para-xylylene. 
   In the other embodiment of the cartridge case  2  according to the invention shown in  FIG. 6 , the case has an electrically insulating casing  10  which comprises a relatively flexible laminate shell  11  in the form of a case jacket  15 , wound in several plies, suitably made of glass-fibre-reinforced epoxy, for example of polyethylene like the abovementioned barrel for the Carl-Gustaf anti-tank rifle. The glass-fibre reinforcement comprises a number of wound plies of thread and/or fabric, preferably both. In a special embodiment of the cartridge case  2 , the casing  10  is constructed from a glass-fibre laminate comprising a thin tight woven E-glass-fibre fabric on the inside, suitably what is known as a Fothergill fabric, on the outside of which E-glass fibre is wound with thin layers sandwiched with further woven E-glass-fibre fabric. Suitably, the thread-winding is arranged along the case jacket  15  at a winding angle α defined for each ply, which varies in relation to the longitudinal axis Y of the case  2 . In order to bring about locking of the glass fibre, it is essential that the casing  10  contains a number of different fibre directions which lock one another, preferably at least 4 different directions in relation to the longitudinal axis Y of the case  2 , for example essentially roughly 0°, 90° and +/− roughly 15-25°, preferably +/−20°. 
   In the embodiment according to  FIGS. 5 and 6 , a separate bottom piece  16  (not shown), which can be either electrically conductive or non-conductive, suitably made of metal material or of glass-fibre epoxy, is also arranged on the rear end  6  of the case jacket  15  in a tight-fitting manner by means of screw-thread cutting, adhesive bonding or by means of another connection suitable for the function (compare  FIG. 1  where the round  1  instead comprises a bottom  16  which is integrated with the rest of the casing  10  of the cartridge case  2 ). In the embodiment according to  FIGS. 5 and 6 , the bottom piece  16 , including the plasma torch  5 , can therefore be arranged unscrewably from the rest of the cartridge case  2  or be more or less permanently fastened thereto. The detachably arranged plasma torch  5  also affords the possibility of replacing the plasma torch  5  with a conventional fuse, as a result of which the round can thus be used in a conventional weapon system, that is to say in the abovementioned only gas-operated systems as well. 
   However, when the round  1  according to the embodiment with the separate bottom piece  16  is fired, there is an obvious risk that undesirable pressure forces can penetrate between the cartridge case jacket  15  and the bottom piece  16 . These pressure forces can then split apart the laminate in the case jacket  15  and in the bottom piece  16 . In order to minimize the risk of this happening, the separate bottom  16  is manufactured with an interference fit to the cartridge case jacket  15  which is greater than the expansion possibility of the round  1  in the cartridge chamber plus the maximum compression which can be brought about by the inner overpressure when firing takes place. Moreover, a rubber ring seal (not shown) can be mounted between the cartridge case jacket  15  and the bottom piece  16  to bring about extra sealing. 
   The abovementioned metal bottom  16  and/or the rear end  30  of the plasma torch  5  (see below) lie(s) against the chamber  17  of the weapon concerned (see  FIG. 3 ), as a result of which the plasma torch  5  is in electric contact with a high-voltage source  18 , the polarity of which can be changed, via an electric connection  19 . After the current/voltage has been transferred to the fuse/plasma torch  5 , it is returned via the outer casing  15  of the latter  5  to its rear part  30  and the electric connection  19 . By virtue of the fact that the current follows the easiest path through the plasma torch  5 , which path is via the plasma formed, and because the cartridge case  2  according to the embodiments described above consists of one or more materials which do not conduct current or voltage across to the barrel  14 , there is therefore no risk of flashover/short-circuiting or of the cartridge case  2  burning on in the weapon/cannon concerned. 
   In the embodiments of the round  1  shown in the figures (see in particular  FIG. 2 ), the projectile  4  comprises an armour-piercing dart  20  with a guide cone or guide fins  21 , which armour dart  20  is at least partly enclosed in and supported inside the case casing  10  by a multi-part dart support body  22 . Arranged around the body  22  is a belt  23  made of plastic for sealing the round  1  in relations to the inside of the barrel  14 . A connection  24  in the form of, for example, grooving, adhesive bonding etc. connects the projectile  4  to the casing  10  of the cartridge case  2  (see  FIG. 2 ). Amour-piercing dart ammunition  1  achieves its great effect because the dart  20  has a considerable weight (density roughly 17-20 g/cm 3 , for example tungsten). 
   The plasma torch  5  (see  FIG. 2 ), which constitutes the equivalent of the ETC round  1  to a conventional fuse with suitably the same or similar external shape as the latter, comprises an outer, electrically conductive combustion chamber  25  and, arranged inside the latter, a central electrode  26 . Here, the combustion chamber  25  is in the form of a metal cylindrical tube which projects from and is detachably fastened to the rear end  6  of the cartridge case  2  by means of a suitable external screw thread  27 . In the embodiment shown in  FIG. 2 , the plasma torch  5  is screwed firmly to the bottom  16  integrated with the casing  10  of the cartridge case  2  or to the bottom piece  16  arranged demountably with the casing  10 . 
   The plasma torch  5  also comprises a front opening  28 . The central electrode  26  comprises a metal, cylindrical contact device  29  for bringing about a first “input” electric connection  19   a . The rear end  30  of the combustion chamber  25  has a metal flange  31  as the “output” electric connection  19   b . An electrically insulating tube  32  (see  FIG. 1 ) is arranged between the said two, “input” and respectively “output”, electric connections. Extending inside the combustion chamber  25  and along its entire length between the said front opening  28  and the metal contact device  29  is at least one but preferably more electric conductors (not shown), such as thin metal wires, wool, rolled metal foil, net structures, porous thin films etc. made of, for example, aluminium, copper or steel etc. The combustion chamber  25 , the contact device  29 , the electric conductors and the central electrode  26  are all electrically conductive, and so the current path, the polarity of which can be changed, runs from the metal contact device  29 , on to the front opening  28  of the combustion chamber  25  via the electric conductors, which are then ionized to form a very hot and expansive plasma which squirts out and ignites the propellent charge  7  through the said front opening  28 . From the plasma and the front opening  28  of the combustion chamber  25 , the current is conducted back to the “output” electric connection  19   b  via the casing of the combustion chamber  25 . For a more detailed description of the design of the plasma torch, reference is made to our Swedish application entitled “Plasma torch for electrothermochemical weapon system, ETC round for use in such a weapon system and method for firing the said round”. 
   METHOD AND DESCRIPTION OF FUNCTION 
   The method for manufacturing the cartridge case  2  and the ammunition  1  according to the embodiment comprising a casing  10  and a separate bottom piece  16  made of glass-fibre epoxy is as follows. 
   A first design philosophy was based on manufacturing a cartridge case  2  which was as strong as possible, that is to say that the shell  11  of the case jacket  15  would be rigid. For each winding ply/laminate layer  11 ,  12 ,  13 , a fibre winding with fibre angles of essentially roughly 90° to the longitudinal axis of the tube on the inside (like on a conventional spool) and +/− roughly 20° on the outside was selected. In order to obtain an extra strong case jacket  15 , many such winding plies  11 ,  12 ,  13  were laid one on top of another. It was found that such casings  10  burst during test firing due to the great risk of crack formation and the build-up of overpressure in the glass-fibre laminate. As mentioned above, it is an absolute requirement that the cartridge case  2  can be removed from the cartridge chamber after the shell has been fired. This requirement is complicated or rendered impossible if the casing  10  is not in one piece. 
   The current design philosophy, which forms the basis for the case  2  and the ammunition  1  according to the present embodiment of the invention, is that the casing  10  is instead essentially flexible, that is to say that the casing  10  of a round  1  introduced into the cartridge chamber tolerates being expanded towards the walls of the cartridge chamber by the inner overpressure inside the cartridge case  2  brought about when firing takes place without for that reason cracking, delaminating or disintegrating. This is achieved by sandwiching woven glass-fibre fabric between several of the thread-winding plies. In this connection, the said inner overpressure which is handled can be assumed to vary from roughly 450 MPa to at least 750 MPa depending on the calibre, type etc. of the round. 
   Manufacture is started by an innermost, tightly woven glass-fibre fabric first being applied to the winding and shaping tool, while it is ensured that any air bubbles are carefully pressed out of the laminate so that there is no risk of air pockets being built into the laminate. The simplest way of doing this is to rotate the tool while the fabric is draped over it. The last piece of the glass-fibre fabric is laid so that a small overlap is formed. Then, a first winding ply of glass-fibre thread in resin is laid with a fibre angle to the longitudinal axis of the tube of essentially 90°, followed by two winding plies of thread with a fibre angle of on the one hand roughly +20° and on the other hand −20°. The subsequent, thin winding plies/laminate layers  11 ,  12 ,  13  are then given a fibre winding with a fibre angle to the longitudinal axis of the tube which varies between essentially roughly 90° and +/− roughly 20° as the thickness of the casing  10  is built up to roughly half-thickness. After that, woven glass-fibre fabric and fibre windings with a fibre angle of essentially 90° are sandwiched until full case thickness has been achieved. Suitably, two cartridge cases  2  are wound simultaneously by virtue of the blank of the case  2  being manufactured in such a way that, after winding has been completed, the blank can be divided into two equal parts, the cut taking place between the rear and therefore rougher ends  6  of the two cases. 
   The winding speed, thread tension and hardening cycle are selected carefully so as to obtain optimum and economical manufacture. The winding speed should be relatively low, 4-6 m/min and preferably roughly 5 m/min, while the thread tension should be quite high, roughly 21-23 N/roving and preferably 22 N/roving, in order to avoid any risk of delamination. In order further to minimize the risk of delamination, use is suitably made of a hardening cycle comprising a plurality of hardenings at increasing temperatures, for example a hardening cycle of roughly 5 hours at roughly 80°, followed by roughly 5 hours at roughly 120°, after which after-hardening takes place for roughly 4 hours at roughly 140°. 
   After shaping of the blank for the case jacket  15 , this is cut and turned/ground to the desired length, thickness and predetermined shape, for example comprising the flange  6 , after which a bottom piece  16  is mounted on the rear end  6  of the case jacket  15  in a tight-fitting manner, preferably by adhesive bonding by means of epoxy adhesive, but use can also be made of screw-thread cutting or another connection (not shown) suitable for the function. Any steel components, such as the plasma torch  5  and the steel bottom  16  if one is used, are surface-treated before adhesive bonding. 
   When a bottom  16  made of glass-fibre epoxy is used, this can be manufactured according to two methods, either via a hammock method where only tensile loads in the fibres can occur or via a plane bottom method so that pressure loads can also occur. After shaping and hardening have been completed, the bottom piece is then turned out, attention being paid to obtaining the correct interference fit as above. 
   Mounting of the fuse or alternatively the plasma torch is effected via screw-thread cutting so that they can be interchanged. Mounting of the projectile, propellent charge and other components included in the finished round is carried out in a conventional way. 
   The method for manufacturing the cartridge case  2  and the ammunition  1  according to the embodiment comprising a metal casing  10  with electric insulation coating  12 ,  13  is as follows. An example of such a coating  12 ,  13  is what is referred to as polymer vaporization. 
   This coating  12 ,  13  is applied over a conventional cartridge case  2  via three phases comprising vaporization of a dimeric or polymeric raw material comprising hydrocarbons (plastic), such as poly-para-xylylene, the polymer or the dimer first, at roughly 150° C., being transformed from solid phase to gas phase and then, at a further increased temperature of roughly 650° C., being transformed to a reactive monomer gas which is finally made to condense (that is to say polymerize) on the cartridge case  2  which is at room temperature and under vacuum, a thin inner and outer insulating plastic film layer  12 ,  13  being deposited on all the free surfaces of the case  2  with a thickness of roughly 20-70μ. 
   The resulting highly pure, hole-free, tough and elastic polymer film  12 ,  13  is completely smooth and has a low friction coefficient (as a result of which the cartridge case is provided with spontaneous lubrication), high abrasion-resistance, low water absorption, and also a high dielectric constant of roughly 200 V/μm. Moreover, the polymer film is non-sensitive to gases, solvents, chemicals, water and moisture. 
   ALTERNATIVE EMBODIMENTS 
   The invention is not limited to the embodiment shown but can be varied in different ways within the scope of the patent claims. It is clear, for example, that an insulating coating and protective layer can also be obtained by means of conventional varnishing of the round and the case. Compared with the polymer vaporization described above, however, varnishing has the disadvantages of higher permeability and worse adhesion, and the varnish can also crack. 
   Materials other than polyethylene, glass-fibre-reinforced epoxy etc. and different thread tension, fibre angles, hardening cycles etc. and winding plies may be possible in future. It is clear that the number, size, material and shape of the elements and components included in the round  1  and the cartridge case  2 , for example the bottom piece  16 , the fabric, resin and thread type etc., are adapted according to the weapon system(s), calibres, active part etc. and also the surrounding environment concerned. It is therefore clear that the invention is in no way limited to the embodiments shown in particular, but that every other configuration according to the above falls within the inventive idea.