Projectile, seal ring for a projectile, and method for sealing a projectile

Abstract

The object of the invention is a seal ring (3) of a projectile (1), the seal ring sealing the gap between the projectile (1) and the barrel of a weapon during firing of the weapon, whereby the seal ring (3) comprises a part of the seal ring (3) located inside the groove (2) of the projectile and a part of the seal ring (3) extending to outside the groove (2). The seal ring (3) also comprises a space / cavity (6) extending around the entire projectile (1), whereby a number of channels (8) open into the space / cavity (6), through which channels the powder pressure generated during firing enters the space / cavity (6), and in that the mouths of the channels (8) are positioned in the part outside the groove (2) of the seal ring (3) in such a way that said mouths are located in the part of the seal ring (3) facing the rear part of the projectile ( 1 ), or the mouths of the channels (8) are positioned against the surface of the groove (2) and are connected to the pressurized inner part of the projectile (1) by channels (11). The object of the invention is also a projectile (1) comprising a seal ring (3) and also a method for sealing a projectile (1).

Description

[0001] PROJECTILE, SEAL RING FOR A PROJECTILE, AND METHOD FOR SEALING A

[0002] PROJECTILE

[0003] The object of the invention is a projectile, a seal ring for a projectile, and a method for sealing a projectile according to the independent claims. The solutions according to the invention are suited for use particularly, but not exclusively, in heavy weapons, in which case they offer improved targeting accuracy and impact velocity compared to conventional projectiles.

[0004] Cartridges suitable for weapons typically comprise projectiles, which is a general term comprising all objects that are propelled by an external force and that then move freely under the influence of gravity and air resistance. The main types of projectiles are bullets, grenades and special projectiles. Projectiles can include inter alia sharp arrows, blunt-headed bolts, sling shots, cannonballs, shrapnel shells, and stones released from catapults. A cartridge, on the other hand, is an ammunition combination, in which the projectile plus primer, case, powder charge and detonator are combined into a single assembly. A cartridge comprises in a single unit all the elements needed for propelling the projectile. Almost all small-caliber firearms are weapons firing cartridge rounds.

[0005] In a canister round, the projectile and propelling charge are loaded into the weapon separately. This type of round is used especially in large-caliber (over 100 mm) guns, in which the use of cartridge rounds is not reasonable for technical reasons: the physical size and weight of a cartridge would become excessive. In this case the projectile is first loaded into the powder chamber and then the canister containing the propelling charge, which charge can be in a brass case containing the primer, or in a textile or cardboard package, in which case a separate primer is placed in last before closing the lock. Powder bags packed in textile are especially popular in naval guns of very large caliber, whereby the amount of propelling charge can easily be adjusted in relation to the range.

[0006] A bullet generally refers to a non-explosive projectile of a small-caliber, generally less than 20 mm, weapon, i.e. the part of a cartridge that is propelled to the target. The bullets of hunting weapons generally comprise a brass-alloy jacket and a lead core. The jacket can also be soft steel and the core can be some other metal than lead. Bullets can also be made completely of lead or of some other metal. Nowadays all-copper bullets are also used in big game hunting owing to the suitable softness (no damage to the barrel of the weapon) and toughness (changes its shape on impact but does not fragment) of the material.

[0007] Rifling (grooving, fluting) in everyday language nowadays most commonly means a gently rotating groove running on the inside surface of the barrel of a firearm, the purpose of which groove is to improve accuracy by getting the bullet or other object being shot to spin around its longitudinal axis during its flight. Rifled barrels are nowadays used in almost all rifles, pistols and guns. Unrifled, i.e. smooth-bore, barrels are nowadays used in shotguns, mortars, rocket launchers, tank canons and also in some guns. In most cases there are from four to eight rifling grooves in the barrel of handguns, but also other solutions are applied. The number of rifling grooves in rifle-caliber weapons is generally from four to six, and they are made for the whole length of the barrel. One exception is a separate rifled choke tube manufactured for a shotgun. The distance over which one rifling groove makes a complete revolution in the barrel is called the rifling twist rate. The depth of rifling grooves in a handgun is generally between 0.1-0.3 mm and the twist rate is approx, one revolution per 20-30 cm. A long bullet generally needs a short rifling twist rate to stabilize it. A rifling twist rate that is too dense might cause a phenomenon called overstabilization, whereby the axial angle of the bullet does not follow exactly the angle of the trajectory. In such a case, it travels on its trajectory at an inclined attitude with respect to its direction of travel, which is detrimental in terms of both accuracy and power. Also the pressure level and the susceptibility of the weapon to wear might increase, the barrel copperize more rapidly than normal, and accuracy therefore decline.

[0008] Although rifle-caliber weapons significantly improved in accuracy after adopting rifling, contrary developments have also taken place. For instance, guns with smooth-bore barrels are used in tanks, from which fin- stabilized projectiles are fired. Accuracy and penetration are good and the first shot towards e.g. an enemy tank can be fired at a distance of approx. 3,000 meters or from even farther away. Higher muzzle velocities can be achieved with smooth-bore barrels than with a rifled barrel, which in this context means a longer sweep and better armor penetration, especially with sub-caliber projectiles, flechettes and armor- piercing ammunition. There can also be grooving, called rifling, on bullets. This is the case with some shotgun slugs. This rifling on the outside of the slug is referred to as ribs and has the same purpose as rifling in the barrel: to bring about rotational movement of the bullet, in this case by means of air resistance.

[0009] A flechette projectile or flechette cartridge is based on arrow-shaped “bullets”. They resemble nails, at the end of which are arrow-type fletchings stabilizing their flight. They do not fragment at the target. Flechettes are used in military action against human targets. They are designed for different weapons: guns, rifles, pistols and shotguns. Flechettes are particularly effective against a variety of protection equipment, such as body armor, flak jackets and helmets. For this reason, the use of flechettes is often restricted to use by official authorities.

[0010] As a rule, sub-caliber flechettes are mainly used against other tanks. A flechette to be used in a smooth-bore tank canon (100-125 mm) reaches a muzzle velocity of over 1,500 m / s. The arrow itself is a sharp-nosed “dart” 2-3 cm in diameter and over half a meter in length (the dimensions depend on the caliber of the weapon), on the rear of which are small flightstabilizing fins. The manufacturing material of the arrow is hard and very heavy metal: ’’tungsten”, i.e. wolfram carbide or ”DU” (depleted uranium). The penetration of a flechette is based on an extremely high impact speed, high kinetic energy and a small impact area. The tip of the flechette is already inside the tank while the tail is still outside. The great weight of the flechette in relation to its cross-sectional area upholds the flight velocity and allows other weaponry to open fire earlier, and the short flight time is forgiving to errors in range-finding and other preliminary estimates. The high penetration velocity detaches hot fragments from the tank that cause fires and explosions inside the tank, destroying the structures and crew of the tank. The oxidization of depleted uranium (DU) in the penetration reduces penetration friction and causes an explosion inside the tank.

[0011] The caliber (100-125 mm) of the main gun of main battlejanks (MBTs) is larger than a flechette, for shooting fragmentation grenades, shaped charges and missiles. For this reason, the flechette is bound to its case with a sabot that seals and centers the flechette, the sabot being e.g. a sleeve seal comprised of aluminum sectors. The sabot accompanies the flechette through the barrel and opens due to air resistance, falling away from the flechette and scattering in the forefield. The arrow might penetrate several meters of armor steel. Nowadays a sub-caliber flechette is the most common anti-tank projectile used against heavily armored targets, such as main battle tanks.

[0012] The solution according to the invention enables better sealing of projectiles fired with unrifled, smooth-bore, barrels against the inside wall of the barrel, thereby making better use of the powder pressure generated by the charge to increase the kinetic energy of the projectile. With the solution according to the invention, a higher muzzle velocity of the projectile is achieved with a smaller charge, which enables an improvement in shooting accuracy as well as an increase in impact velocity. The solution also enables the use of larger charges without allowing a larger proportion of powder pressure to escape through the gap between the projectile and the inside wall of the barrel. For example, it eliminates or reduces the problems of conventional flechettes that are in use, such as by rendering sleeve seals unnecessary. The structure of the projectile is particularly suited to weapons having a smooth-bore barrel, which enables firing with hard charges. The projectiles can therefore be both conventional projectiles and flechettes. The velocity of projectiles fired with larger charges is higher, in which case a stable trajectory and a high impact velocity at target impact are achieved. The effect on targeting accuracy caused by the rifling grooves is likewise eliminated, which becomes significant when firing over long distances. A rifled barrel also wears with every shot fired. This wear becomes especially significant when firing with large- caliber weapons. Wear is affected both by the discharge of pressure via the rifling and by the friction of the projectile surface against the inside surface of the barrel. The solution according to the invention causes minimal wear on the barrel because the seal ring can be designed so that it expands radially in just the right way for the pressure to remain behind the seal ring, but the pressure does not however press the inflated seal ring unnecessarily hard against the inside surface of the barrel of the weapon. The material and dimensions of the seal ring are designed for each projectile and charge on a case-by-case basis to ensure optimal functioning of the seal ring.

[0013] The solution according to the invention comprises a projectile that is fired into motion with a smooth-bore barrel. When the projectile is in the barrel of the weapon, the powder gas generated during firing swells / expands and presses the seal of the projectile against the inside wall of the barrel. There may be one or more seal rings on a projectile. The use of a smooth- bore barrel enables the use of higher muzzle velocities than earlier, and thus enable lengthening of the range and increased accuracy, especially over long ranges. A rotating motion like the motion brought about by rifling grooves can be induced in the projectile by the shaping of the tail fins. The projectile in this case is to be a so-called flechette, but the use of the solution according to the invention does not require a flechette, but instead is suitable for use in all smooth-bore barrels. When rifling is not needed in the barrel of a weapon, the manufacturing process of the barrel is simplified. Typically the solution according to the invention is advantageous for projectiles possessing a diameter of * inch or larger.

[0014] In the following the invention will be described in more detail with the aid of some examples of its embodiment with reference to the attached simplified drawings, wherein

[0015] Fig. 1 presents a simplified conceptual drawing of a preferred projectile according to the invention, without any seal rings,

[0016] Fig. 2 presents a simplified conceptual drawing of a preferred projectile and seal ring according to the invention, as a partial figure,

[0017] Fig. 3 presents a simplified conceptual drawing of a second preferred projectile and seal ring according to the invention, as a partial figure

[0018] Fig. 4 presents a preferred embodiment of a seal ring, as a partial figure

[0019] Fig. 5 presents a preferred embodiment of a second seal ring, as a partial figure, and

[0020] Fig. 6 presents a simplified conceptual drawing of yet another preferred embodiment of a seal ring and projectile, as a partial figure.

[0021] The terms frontmost, front and the like hereinafter refer to the direction or surface corresponding to the direction of flight of the projectile and, correspondingly, the terms rearmost, rear and the like refer to the opposite direction or surface with respect to the direction of flight of the projectile. The longitudinal direction refers to the direction of the barrel of the weapon.

[0022] Fig. 1 presents a simplified conceptual drawing of a preferred projectile 1 according to the invention, without any seal rings. There are one or more seal rings on a projectile. In this embodiment, the projectile will have two seal rings, and two grooves 2 are prepared for them in the projectile. The grooves 2 circle the entire projectile 1 on its outer rim and the depth of the grooves has been selected according to the seal ring to be placed in the groove in such a way that the best possible sealing is achieved between the projectile and the inside surface of the barrel of the weapon.

[0023] Fig. 2 presents a preferred embodiment of the seal ring 3 of the projectile 1 according to the invention. The seal ring 3 is installed in the groove 2, the groove being preferably rectangular in cross-sectional shape. Grooves 2 of other shapes are also possible, but in its simplest form, from the viewpoint of making a groove and seal 3, the groove is rectangular in shape.

[0024] These seal rings 3 prevent powder gas from escaping to the front of projectile 1 in the barrel of the weapon, through the gap between the projectile and the inside surface of the barrel after firing of the projectile, and allow maximum acceleration and muzzle velocity for the projectile. Such seal rings 3 are used especially when firing with smooth-bore barrels. Seal rings known in the art are rectangular in cross-sectional shape or, possibly, slightly rounded on the side towards the inside surface of the barrel of the weapon.

[0025] The seal ring 3 according to the embodiment shown in Figure 2 comprises a section remaining inside the groove 2, the function of the section being to hold the seal ring in place in the groove, and also a section extending out from the groove, i.e. to above the cylinder surface defined by the outer surface of the projectile. The seal ring 3 has a lip-like protrusion 4 that protrudes obliquely out of groove 2 in such a way that the end 5 of the protrusion faces the rear part of projectile 1 and the pressure brought about by the powder gas. A space / cavity 6 remains under the protrusion 4, into which space / cavity the pressure of the powder gas can penetrate, according to arrow 10, through the gap 7 between the cylindrical outer surface of the projectile 1 and the end 5 of the lip-shaped protrusion 4 of the seal ring after the firing 7 of a projectile 1. The space / cavity 6 may be located in the section of the seal ring 3 that remains inside groove 2, in the part of the seal ring outside the groove of the projectile, or in such a way that a part of it is inside the groove and a part outside the groove. The pressure of the powder gas causes the protrusion 4 to press against the inside surface of the barrel of the weapon, providing good sealing between the projectile 1 and the inside surface of the barrel of the weapon. This sealing maintains the pressure of the powder gas on the rear side of the projectile 1 and allows efficient use of the pressure of the powder gas for accelerating the velocity of the projectile without a significant amount of the pressure of the powder gas being discharged from the gap between the projectile and the inside surface of the barrel of the weapon. Thus, the pressure of the powder gas causes the seal ring 3 to expand radially in the direction of the radius of the cross-section of the projectile 1 against the inside surface of the barrel of the weapon. The end 5 of the protrusion 4 of the seal ring 3 forms a uniform gap in the seal ring for 7 for the powder pressure along the entire circumference of the seal ring, from which gap the powder pressure enters the space / cavity 6 to radially expand the seal ring. When the powder pressure can be better used to increase the velocity of the projectile 1, smaller charges can be used to achieve the same velocity or, correspondingly, a faster moving projectile can be obtained with the same charge. Good sealing also allows the use of larger charges, which significantly increases the velocity of the projectile 1. This enables higher impact velocities on the target and improved shooting accuracy, especially for long-range shooting.

[0026] The seal rings 3 are typically manufactured from copper, a copper-bronze alloy, brass, or a corresponding metal alloy suited to sealing a projectile. The mixture ratios and materials used are selected according to the size of the projectile and the powder pressure. What is essential is that the sliding properties and toughness of the material used are sufficient for the functioning of the seal ring.

[0027] Fig. 3 presents a second embodiment of the seal ring 3 according to the invention. In this embodiment also, the seal ring is divided into two parts, i.e. the part inside the groove 2, which part holds the seal ring in place, and the part extending out of / over the groove, i.e. the cylinder surface defined by the outer surface of the projectile. In this embodiment a space / cavity 6 is formed inside the seal ring 3, into which space / cavity the pressure of the powder gas enters through the channels 8 formed in the seal ring. The space / cavity 6 may be located in the section of the seal ring 3 that remains inside groove 2, in the part of the seal ring outside the groove of the projectile, or in such a way that a part of it is inside the groove and a part outside the groove. In contrast to the embodiment shown in Figure 2 above, the seal ring 3 does not have a uniform gap circling the entire seal ring, but instead separate channels 8 are formed in the seal ring, through which channels the powder pressure enters the space / cavity 6 and radially expands the seal ring. Of course, the channels 8 are placed on the pressurized side of seal ring 3, i.e. on the side facing the rear part of the projectile 1 and the resulting powder pressure.

[0028] Fig. 4 presents a preferred embodiment of the seal ring 3 according to Fig. 3, the seal ring having channels 8 for displacing the powder pressure into the space / cavity 6 inside the seal ring. The seal ring 3 is depicted from the direction of the rear part of the projectile, with a dashed line 9 depicting the plane of the cylindrical outer surface of the projectile relative to the seal ring. Part of the seal ring 3 remains in the groove 2 and holds the seal ring in place, while part extends to above the cylinder surface of the projectile. The channels 8 of the seal ring 3 are elongated ring-shaped openings located along the entire circumference of the seal ring above the cylindrical surface formed by the outer surface of the projectile in the area affected by the powder pressure.

[0029] Fig. 5 presents a second preferred embodiment of the seal ring 3 according to Fig. 3, the seal ring having channels 8 for displacing the powder pressure into the space / cavity 6 inside the seal ring. The seal ring 3 is depicted from the direction of the rear part of the projectile, in which case the dashed line 9 depicts the plane of the outer surface of the projectile relative to the seal ring. As in the embodiment of Figure 4, part of the seal ring 3 remains in the groove 2 and holds the seal ring in place, while part extends to above the cylinder surface of the projectile. The channels 8 of the seal ring 3 in this embodiment are circular openings in shape located along the entire circumference of the seal ring above the cylindrical surface formed by the outer surface of the projectile in the area affected by the powder pressure.

[0030] Fig. 6 presents yet another preferred embodiment of the seal ring 3 and the projectile 1. In this embodiment also, the seal ring 3 is divided into two parts, i.e. the part inside groove 2, which part holds the seal ring in place, and the part extending out of / over the groove, i.e. the cylinder surface defined by the outer surface of the projectile 1. In this embodiment a space / cavity 6 is formed inside the seal ring 3, into which space / cavity the pressure of powder gas enters through channels 8 formed in the seal ring. The space / cavity 6 may be located in the section of the seal ring 3 that remains inside the groove 2, in the part of the seal ring outside the groove of the projectile, or in such a way that a part of it is inside the groove and a part outside the groove. In contrast to the embodiment shown in Figure 2 above, the seal ring 3 does not have a uniform gap circling the entire seal ring, but instead separate channels 8 are formed in the seal ring, through which channels the powder pressure enters the space / cavity 6 and radially expands the seal ring, as also shown in Fig. 3. In contrast to the embodiment in Figure 3, the channels 8 are positioned against the surface of the groove 2 of the projectile. Channels 11 are prepared in the projectile 1 from the pressurized inner part of the projectile, which channels 11 connect to the channels 8 of the seal ring. The internal pressure of the projectile 1, created by the powder pressure, seals the seal ring 3 against the inside surface of the barrel of the weapon. The shape of the sealing groove 2 is depicted in its simplest form in the examples above, but its shape may be different from that shown in the figures. What is essential is to bring the powder pressure to inside the seal ring 3, whereby the sealing of the seal ring against the inside surface of the barrel of the weapon is achieved.

[0031] The method according to the invention for sealing a projectile 1 against the inside surface of the barrel of a weapon comprises the following phases:

[0032] - one or more grooves 2 extending around the rim of the projectile are formed on the cylindrical outer surface of the projectile 1,

[0033] - one or more seal rings 3 are produced in one or more grooves 2,

[0034] - a space / cavity 6 is formed in the seal ring 3, the space / cavity circling together with the seal ring around the entire rim of the projectile,

[0035] - the pressure of the powder gas is guided into the space / cavity 6 of the seal ring 3 through the gap 7 or the channels 8, thereby expanding the seal ring 3 in the direction of its radius by means of the powder pressure entering the space / cavity 6.

[0036] The pressure inside the seal ring 3 can be introduced by the powder pressure of the projectile 1 via the pressurized inner part through the channels 11 or through the gap between the inside surface of the barrel of the weapon and the outer surface of the projectile. The charge used in conjunction with the projectile according to the invention need not be as large as that of projectiles known in the art in order to achieve the same muzzle velocity, since the projectile according to the invention is able to make better use of the powder pressure created by the charge used to increase the velocity of the projectile. This is due to the fact that the seal according to the invention better holds the powder pressure behind the projectile during firing. When using a larger charge, a greater amount of powder pressure will be released during firing when using projectiles known in the art through the gap between the projectile and the inside surface of the barrel of the weapon. When using the solution according to the invention, the sealing is improved because the higher powder pressure presses the seal even harder against the inside surface of the barrel of the weapon. The invention enables the use of larger charges, giving the projectile a higher muzzle velocity and impact velocity. A higher muzzle velocity results in a more stable trajectory and a higher impact velocity when striking the target. At the same time the targeting accuracy of the projectile improves compared to a conventional projectile. This is considerable, especially at long ranges of fire. At the same time the effects caused by rifling on the trajectory and targeting accuracy of the projectile are eliminated. Rifling grooves affect the stability of a weapon and try to turn the barrel / tube of the weapon when the projectile is in the barrel / tube of the weapon. The effects of rifling on targeting accuracy are highlighted in particular when shooting rounds requiring accuracy at targets a long way away. Furthermore, some of the pressure of the powder gas is able to discharge via the rifling, in which case the type of smooth-bore solution of the invention utilizes the pressure generated more efficiently.

[0037] It is obvious to the person skilled in the art that the invention is not limited solely to the examples described above, but that it may be varied within the scope of the claims presented below.

Claims

CLAIMS1. A seal ring (3) of a projectile (1), the seal ring sealing the gap between the projectile (1) and the barrel of a weapon during firing of the weapon, whereby the seal ring (3) comprises a part of the seal ring (3) located inside the groove (2) of the projectile and a part of the seal ring (3) extending to outside the groove (2), characterized in that the seal ring (3) comprises a space / cavity (6) extending around the entire projectile (1), whereby a number of channels (8) open into the space / cavity (6), through which channels the powder pressure generated during firing enters the space / cavity (6), and in that the mouths of the channels (8) are positioned in the part outside the groove (2) of the seal ring (3) in such a way that said mouths are located in the part of the seal ring (3) facing the rear part of the projectile (1), or the mouths of the channels (8) are positioned against the surface of the groove (2) and are connected to the pressurized inner part of the projectile (1) by channels (11).

2. A seal ring (3) of a projectile (1) according to claim 1, characterized in that the seal ring (3) is manufactured from copper, a copper-bronze alloy, brass, or a similar metal alloy suitable for sealing a projectile.

3. Projectile (1), characterized in that the projectile comprises one or more seal rings (3) according to claim 1.

4. Projectile (1) according to claim 3, characterized in that the projectile (1) is a bullet, grenade, or some special projectile, such as a fin- stabilized projectile.

5. Method for sealing a projectile (1), the method comprising the following phases:- one or more grooves (2) extending around the rim of the projectile (1) are formed on the cylindrical outer surface of the projectile (1),- one or more seal rings (3) are produced in one or more grooves (2), characterized in that- a space / cavity (6) is formed in the seal ring (3), the space / cavity circling together with the seal ring (3) around the entire rim of the projectile (1),- the pressure of the powder gas is guided into the space / cavity (6) of the seal ring (3) through channels (8), thereby expanding the seal ring (3) in the direction of its radius by means of the powder pressure entering the space / cavity (6).

6. Method according to claim 5, characterized in that the pressure of the powder gas is brought inside the seal ring (3) through the gap between the outer surface of the projectile (1) and the barrel of the weapon.

7. Method according to claim 5, characterized in that the pressure of the powder gas is brought inside the seal ring (3) through the pressurized inner part of the projectile (1) via the channels (11), which channels (11) are connected to the channels (8) of the seal ring (3) on the surface of the groove (2).

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