GB2251291A - Firing pin arrangement for a weapon - Google Patents

Description

FIRING PIN ARRANGEMENT FOR A WEAPON This invention relates to a weapon, preferably an automatic hand weapon, with a firing pin displaceably mounted in a part of the weapon behind the cartridge chamber, the firing pin, over a portion of its length, being surrounded by a compartment which is disposed in the aforementioned weapon part.

In an arrangement for a weapon with case ammunition known from US Patent 2 842 885 a compartment surrounding a portion of the firing pin is provided with a sleeve of elastic plastics material which is intended to serve as a buffer for when the weapon is firing empty, i.e.

without ammunition, to prevent the firing pin impacting hard with a shoulder against a stop of a part of the weapon, as a result of which the firing pin may be damaged. The known weapon is not suitable for caseless ammunition because, as a result of the very high gas pressure occurring in such a weapon, it is not possible to prevent the escape of the hot combustion gases along the firing pin, and in such a case it is not possible for the elastic sleeve to form a seal because the firing pin is thrown backward by the combustion gases with the result tnat it lifts off the sleeve.

In addition, DE-A 28 13 633 ad correspordir.e .S-A 4 348 941 disclose an automatic weapon for caseless Ir. J P. 1 which has a firing pin displaceably @@@@@@@ 1 P. a part t the weapon behind the cartridge chamber.

In this known weapon, on its side facing away from the cartridge chamber the firing pin has a truncated conical contact shoulder which is thrown back by the combustion gases when the cartridge ignites and comes up against a contact face which is tailored to the contact shoulder.

Not until the two faces are in contact is there a seal for the combustion gases. Since in the short period of time prior to contacting of the two faces it is possible for combustion gases or propellant gases to escape to the rear, wear on the firing pin and other parts of the weapon as well as fouling of the weapon is possible.

According to this invention, a weapon for firing caseless ammunition has a cartridge chamber, and a firing pin displaceably mounted in a part of the weapon behind the cartridge chamber, wherein:- the firing pin, over a portion of its length, is surrounded by a compartment disposed in the said weapon part; the compartment contains an elastically deformable sealing compound supported in the said weapon part on its side facing away from the cartridge chamber; and the compartment is closed off from the cartridge chamber by a movably mounted plate.

In this way, it is possible to provide a good seal against the escape of propellant gases along the firing pin to the rear. The seal is particularly effective if the sealing compoun I ~ills afc.rer.tion- compartment and is also in close contact with a preferably cylindrical outer surface of the firing pin.

In the preferred embodiment of the invention, the elastically deformable nature of the sealing compound is taken advantage of by allowing the compound to be pressed by the pressure of the propellant gases firmly against the wall of the firing pin and also against the limiting walls of the compartment, further intensifying the sealing effect. The movably mounted plate is provided to prevent the propellent gases from coming into contact over a large area with the sealing compound, and preferably moves under the pressure of the propellant gases in a similar manner to e pneumatically driven piston, transmitting the pressure of the propellant gases to the sealing compound.Since the sealing compound is elastically deformable, it tends to re-assume its original shape when the pressure of the propellant gases disappears, with the result that the contact force between the firing pin and the sealing compound as well as the resultant friction force when the pressure of the combustion gases ceases is reduced.

Thus, when a round is triggered the firing pin can easily be moved by the firing hammer in the direction of the cartridge chamber without great frictional forces having to be overcome.

With the sealing compound supported on its side facing away from the cartridge chamber, it is possible for tne high pressure exerted by the @@@@ellart gases @@ b roed without the sealing compound undergoing an undesired change of position.

In the preferred embodiment of the invention, the sealing compound has approximately hydrostatic properties. This means that the pressure exerted on the sealing compound by the combustion gases is largely free to spread in all directions in the sealing compound and ensures in particular that the sealing compound is pressed firmly against the firing pin. While, strictly speaking, hydrostatic pressure is a phenomenon occurring only in liquids it is possible in the event of sufficiently high pressures to say also, for example, that rubber - which, however, is unlikely to be used as sealing compound for the purposes of the invention does to a certain extent have hydrostatic properties.

Such hydrostatic properties may also be present if the sealing compound itself is elastically compressible, i.e. if it undergoes a noticeable change in volume as a function of pressure, as is the case with the sealing material described in the specimen embodiment.

If the aforementioned plate consists of a heatconducting material, preferably metal, and is in contact with the wall of the compartment so as to adequately conduct heat, it is possible for the plate to dissipate heat received from the combustion gases. In this way, the plate protects the sealing compound from the hie temperature of the combustion gases.For example, I must be expected that the combustion gases will have a temperature of about 35 .jJ C, wre C as ne p re Cr r a sealing compound used, namely the later described graphite, merely withstands temperatures of up to about 25000 C. Hence in addition to its function of uniform pressure transfer, the plate has the functions of temperature absorption and temperature distribution.

In an embodiment of the invention the end of the firing pin facing the cartridge chamber is led through a recess in the aforementioned plate. This embodiment is well suited for simple manufacture. To form the compartment, it is merely necessary to provide a bore which is centralized with respect to the firing pin axis and which leads from the cartridge chamber into the aforementioned weapon part and into which the sealing compound is applied and which is then closed by the movable plate whereby the firing pin can fire the cartridge through a centralized recess in the plate.

Preferably, when in its ready-to-fire position, i.e. when in its retracted position, the firing pin does not project beyond the aforementioned plate. In a further preferred embodiment of the invention the end region of the firing pin facing the cartridge chamber is substantially circular in cross section. The circular cross section is adapted to the recess in the plate through which it passes. The advantage of this embodiment is that when, after the firing of a roc, the firing pin has Deer thrown back by the propellant e I t d o e S P. t project beyond the plate with the result that the firing pin is not exposed to excessive heat which night lead to the firing pin weary @@@ quickly. A further advantage is that the plate which consists preferably of metal, preferably steel, is able effectively to cool the end region of the firing pin due to the fact that it conducts the heat from the end of the firing pin into the adjacent parts of the weapon.

Should the sealing compound likewise exhibit a sufficiently high thermal conductivity, the sealing compound also promotes the cooling of the firing pin and thus contributes toward a long service life. A long service life of the firing pin is also promoted if the firing pin is flat, i.e. it does not exhibit any projecting tip. The diameter of the firing pin in the region of its end facing the cartridge chamber is as large as possible in view of the maximum mass which the firing pin may exhibit and in view of the maximum allowable diameter with which a cartridge can still be fired.

The preferred sealing arrangement also has the advantage that, after the firing of a caseless cartridge, the firing pin is subjected, compared to the prior art, to a considerably smaller force trying to throw back the firing pin. This force is equal to te pressure of the combustion gases multiplied by the effective cross-sectional area of the firing pin facing the cartridge chamber. As will become apparent fro- the description hereina5ter , this crtss-sectiore art : > preferably relatively small, considerably smaller that the maximum cross section o tne firing pin which is in a central region along the length of the firing pin.

Conversely, in the initially described, known weapon, the pressure of the combustion gases acts on the maximum cross section of the firing pin and consequently throws the latter back with a correspondingly greater force and at a correspondingly higher velocity, as a result of which there is increased wear compared with the weapon decribed hereinafter when impact is made on a stop (the above described sealing face). It should be noted in this respect that because the pressure front of the combustion gases advances very rapidly it is in fact the maximum cross-sectional area of the firing pin which should be taken as the effective area determining the force which throws back the firing pin, because the combustion gases find no time to build up any appreciable back-pressure in the area between the contact shoulder and the contact face.Only if this back-pressure were precisely the same as the pressure of the propellant gases acting on the fact of the firing pin facing the cartridge chamber would there result a force throwing back the firing pin which would be comparable with the force occurring in the present weapon.

A further advantageous feature which ; be included is the provision of a truncated conical face on the firing pin which points away from the seal and interacts with a @ounterface forming a stop in another weapoIr part. The aforementioned faces are similar to the contact shoulder and the contact face of the known weapon. In the preferred embodiments of the invention, however, the aforementioned faces serve in general merely as a stop which is contacted by the firing pin in the course of its backward motion.Should, for any reason. (for example if the weapon has not been adequately maintained) the sealing compound no longer seal sufficiently well, then the aforementioned faces have the function of a safety seal which, although exhibiting the same disadvantages as in the prior art, is still capable of preventing the escape of excessive quantities of propellant gas into tne region behind the firing pin.

In that part of the weapon housing the compartment, it is possible to provide a stop which limits the travel of the firing pin in the direction of the cartridge chamber. The advantage of this is that the stop face of the firing pin interacting with the stop is relatively far to the front on the firing pin so that the tensile forces or tensile stresses in the firing pin occurring when the firing pin impacts on the stop are relatively small and consequently easy to control due to the relatively low masses forward of the stop face.

Conversely, a firing pin would be subjected to considerable risk of damage if 2 S, ? terwirating the forward motion of the firing pin were t@ be situated in the rear era region of tne firing @@@ because there would then be a relatively large proportion of the mass of the firing pin forward of this stop.

Such a stop is also advantageous to prevent malfunctions of the weapon if the firing hammer is allowed to strike an empty cartridge chamber, i.e.

without there being a cartridge in the cartridge chamber. Depending on the design. of the weapon and perhaps also of the ammunition, the above-depicted stop may possibly only come into action in the last-mentioned case, because if a cartridge is fired the combustion gases are able to develop so quickly and build up a corresponding pressure that in its forward motion the firing pin does not reach the stop, but is braked beforehand by the combustion gases and is moved back by them.

The counter-face limiting the backward motion of the firing pin may be provided in a further part which is releasably connected to the aforementioned weapon part. If, as provided for in the specimem embodiment, this further part is easily releasable, when the firing pin can very easily be removed from the weapon to the rear, which is of advantage for carrying out repairs.

The most varied materials are conceivable for the sealing compound, for example a material containing carbon fibres or other suitable fibres capable of with standing sufficiently high temperatures, or excluslely such fibres which are stuffet with sufficient firmmess into the aforementioned compartment. It also appears possible to use elastic plastics for the sealing compound into which are embedded particles or fibres of material of high thermal conductivity for improved heat dissipation. However, the preferred sealing compound is graphite.Preferably, a form part of this sealing compound is made from graphite which is available in the form of a ribbon-like starting material, this being crystalline graphite, i.e. having basically a flaky structure. This premoulded material exhibities a relatively high elasticity, sufficiently good thermal conductivity, very low friction and, despite its great softness, has proved capable of withstanding the heavy loading in the weapon. Conversely, it has previously always been felt in the field of weapon technology that the parts required for the design of the weapon should be as hard as possible.

The invention will now be described by way of example with reference to the drawings in which: Figure 1 is a longitudinal section through an automatic rifle in the region of the firing pin witn the firing pin in the ready-to-fire position; Figure 2 is a view similar to that of Figure 1, truncated in comparison with Figure 1, with the firing pin in its fired position; Figure 3 is a view in the direction of arrow III in Figure 2; Figure 4 is a section on line IV - in Figure 1; Figure 5 is a view similar to that of Figure - in which the firing hammer, naving struck, is visible.

The drawings show parts of an automatic rifle in accordance with the invention for firing caseless cartridges. Only those parts which are essential for understanding the invention are shown. Referring to the drawings, a weapon part 2 which is rigidly connected to the barrel of the weapon (not shown) contains a cylindrical bore 3 whose axis is perpendicular to tne barrel axis and intersects the barrel axis. Mounted in this hole 3 is a cylindrical breechblock 4 which is rotatable about the axis of the hole 3. The drive mechanism of the weapon is described in the two initially mentioned publications. Figure 1 shows the breechblock 4 in the firing position. In this firing position a cartridge chamber 9 in the breechblock 4 aligns with a bore 5 which becomes the bore of the barrel.A caseless cartridge in the cartridge chamber 9 exhibits a propellant body 8 with projectile 7 projecting at the front. The cartridge chamber 9 exhibits projections 6 which project into its inside and which form contact faces for positioning the caseless cartridge. In its end region facing away from the projectile 7 the propellant body 8 contains as ignition charge 10. The caseless cartridge was loaded with the breechblock 4 in a position which is turned through 90" in a counterclockwise direction in relation to the position shown, and the caseless cartridge was inserted into the cartridge chamber 9 from a magazine (not shown) through a bore 12 disposed in the part 2 which is rigid with the barrel.

A firing pin 20 is displaceably mounted in the barrel-rigid part 2 in the region behind the cartridge chamber 9 and is in the ready-to-fire position. In its middle region the firing pin 20 exhibits a thicker section 22 which, as shown in Fig. 1, has a left-hand truncated conical face 24 which becomes a circularly cylindrical section 26 ending just outside the hole 3 when the firing pin is in the readyto-fire position. The thicker section 22 is adjoined on its side facing away from the truncated conical face 24 by another truncated conical face 28 which becomes a section 30 of the firing pin exhibiting a spherical end face 32 which is impacted by a firing hammer (not shown).In the course of the manufacture of the firing pin the section 30 is manufactured first of all with a circularly cylindrical cross section throughout, and then two faces 34 extending parallel to the plane of projection in Fig. 1 are machined on two opposite sides of the section 30. In their rear region, i.e. on the right in Fig. 1, these faces 34 change into the circularly cylindrical part by means of a step 36.

The step 36 serves to move the firing pin into the position shown in Fig. 1 through the engagement of a displacement mechanism 38 if this is required. This may, for example, be necessary if the firing hammer has been released without there being a cartridge in the cartridge chamber 9. In this case, it is necessary by special measures to move the firing pin 20 out of its position shown in Fig. 2 back into the position shown in Fig. 1.

The barrel-rigid part 2 exhibits a bore 40 which is adapted to the cross section of the cylindrical section 26 and through which the cylindrical section 26 extends. On the side toward the hole 3 the bore 40 is adjoined by an enlarged bore 42 which is very slightly wider in its middle region at the point identified by reference character 44; the drawing shows this widened point as being much wider than it actually is, for reasons of clarity. The bore 42 contains a graphite form part 50. This form part 50 is supported by its end face pointing to the right in Fig. 1 on a face 52 of the barrel-rigid part 2 limiting the bore 42.

The form part 50 exhibits a centric recess 53 which is adapted to the diameter of the cylindrical part 26 of the firing pin. The length of the form part 50 in the longitudinal direction of the firing pin 20 is smaller than the length of the bore 42, and the limiting face of the form partS0 pointing to the left in Fig. 1 is adjoined by a metal plate 54 which is inserted into the bore 42 and which likewise exhibits a bore 55 adapted to the diameter of the cylindrical section 2. In the region of the widened point 44 the metal plate 54 is likewise slightly wider in cross section (a few hundredths of a mm), just enough so that the metal plate 54 in Fig. 1 cannot drop out of the bore 42 to the left, but can be pressed into the bore 42 in a direction from left to right whereby the slightly wider crosssectional region of the metal plate 54 undergoes corresponding elastic compression. The metal plate 54 is relatively easily displaceable toward the right parallel to the direction of displacement of the firing pin 20. In the position shown in Fig. 1, on the other hand, the metal plate 54 cannot be pushed in the opposite direction, as has already been mentioned above. Theform part 50 completely fills the space which is limited by the bore 42, the metal plate 54 and the cylindrical section 26 of the firing pin 20.

In the barrel-rigid part 2 the bore 40 is adjoined at the rear (on the right in Fig. 1) by a conical bore 60 which forms a stop for the truncated conical section 24 of the firing pin, thus limiting the furthest forward position of the firing pin.

The thicker section 22 of the firing pin 20 is not directly guided in the barrel-rigid part 2, but in a part 65 releasably connected to the barrel-rigid part 2 and containing a bore 68 adapted to the outer diameter of the thicker part 22. At the front end face 70 of the part 65 this cylindrical bore 68 changes directly into the conical bore 60. The truncated conical face 28 of the firing pin interacts with a truncated conical face 72 in the part 65 adjoining the rear end of the cylindrical bore 68. This truncated conical face 72 forms a stop which limits the movement of the firing pin 20 to the rear. The truncated conical face 72 is adjoined in the part 65 by another cylindrical bore 74 through which the section 30 of the firing pin is guided.

The part 38 is swivel-mounted by means of a hinge pin 76 on a tab 78 which is attached to the part 65. The part 65 is connected to the barrel-rigid part 2 in the manner of a bayonet catch. A spring-loaded pin 79 engages a groove-type indentation at the edge 80 of the part 65 and secures the latter in its locked position. After turning through 90" in a counterclockwise direction as viewed in Fig. 3 the part 65 can be removed out of the recess 82, 84 accommodating the part 65 whereby the firing pin 20 is also removed. After releasing the hinge pin 76 it is possible to release the connection between the firing pin 20 and the part 38, it thus being possible to exchange the entire firing pin, if necessary, easily and quickly.

The broken lines in Fig. 2 indicate the left-hand end position of the end face 27 of the firing pin 20. This furthest left position is not necessarily assumed by the firing pin 20 when a cartridge is present because although the end face 27 of the firing pin penetrates into the detonating compound 10, the throwing back of the firing pin begins immediately with the development of the propellant gases and, consequently, the firing pin may already have been thrown back before it reaches the furthest leftward end position shown in Fig. 2.

Fig. 5 shows that, once it has struck, the firing hammer 100 (which is not shown in the other Figures for the sake of simplicity) remains with its striking face 101 on the face 32 of the firing pin 20; the firing hammer is thus of the follow-through type.

The form part50 is made in the following manner: A graphite ribbon marketed by UNION CARBIDE EUROPE S.A., Geneva, Switzerland, under the name GRAFOIL RIBBON-PACK is placed into a mould which is adapted to the bore 42, but whose diameter is slightly smaller and in which there is a releasable, centralized rod whose diameter is slightly larger than that of the cylindrical section 26 of the firing pin. This graphite ribbon is manufactured in the form of thin sheets of pure natural graphite. The crystal structure is flaky and flexible in contrast to synthetic industrial graphite. The graphite ribbon is cut to appropriate length and wound around the rod or mandrel which can be removed from the mould.Subsequently, the rod with the graphite ribbon wound onto it is placed in the mould and then the graphite ribbon is pressed by means of a sleeve which is inserted into the annular space between the cylindrical wall of the mould and the rod. A pressure of about 6000 N/cm2 is applied. The cross-8ection of thus produced form part will correspond to the cross-section of the mould having the rod inserted. The height of the form part is greatly reduced compared with the original height as a result of the pressing process. If, depending on the width of the graphite ribbon used as the starting material, this height is not sufficient, a further layer of the graphite ribbon is wound onto the rod and is pressed anew.The slight dimensional differences between the mould and the bore 42 are intended to facilitate the insertion of the finished form part into the bore 42.

When using this graphite material it should be noted that gaps of a thickness greater than approximately 0.25 mm should be avoided so that when subjected to high pressure the graphite material cannot extrude through gaps which are too thick.

The graphite formpart 50 exhibits a certain elasticity of volume, i.e. it temporarily reduces its volume when subjected to the pressure of the combustion gases. The pressure of the combustion gases may be approximately 4000 bar. The pressure of the combustion gases which is transferred to theform part 50 by the plate 54 propagates basically uniformly in all directions in the form part 5o,in a manner similar to what would happen with a liquid (hydrostatic pressure). As a result, theform part50 is pressed particularly effectively against the firing pin and reliably seals the latter. Since the outer surface of the form part is also simultaneously pressed against the wall of the bore in which it is disposed this also reliably prevents the escape of combustion gases along the wall of the bore.Another particular advantage of the sealing material used is its low friction coefficient with the result that the firing pin which is already in close contact with the sealing compound before a round is fired can easily be moved by the firing hammer of the weapon.

The fact that the end of the firing pin causing detonation is well cooled so that the firing pin cannot assume high temperatures also has the advantage that when in the readyto-fire position as in Fig. 1 the end of the firing pin can be in the immediate vicinity of the detonating compound 10 of the cartridge without this resulting in the risk of undesired spontaneous firing (cook-off). There is little heating of the firing pin, firstly due to the relatively good cooling, and secondly because the end of the firing pin is not so heavily exposed to the combustion gases as is the case in the prior art. In the prior art there is additional heating of the firing pin through the supersonic flow of combustion gases along the firing pin, resulting in additional heating through friction.

Since the aforementioned end of the firing pin is quite solid it is also less affected by the (however much reduced) heat, and any unavoidable wear does not so quickly necessitate the replacement of the firing pin as would be the case if the end of the firing pin were relatively thin.

The fact that the firing pin 20, as described above, is thrown back with relatively low force and at relatively low velocity after the detonation of the cartridge has the further advantage that there is no danger of the firing hammer of the weapon being damaged by the firing pin as it is thrown back. It is not therefore necessary to take special steps to protect the firing hammer of the weapon. On the contrary, after striking the rear end of the firing pin, the firing hammer can remain in contact.

This makes it possible to transfer to the firing pin the entire energy contained in the kinetic energy of the firing hammer and in the firing spring driving the firing hammer and to use this entire energy for firing the cartridge. Therefore, the firing hammer can be relatively light and the firing spring can be relatively weak so that after a round has been fired, which takes place automatically in the depicted weapon, the cocking of the firing hammer does not require excessive energy.

If, conversely, it were necessary to take special steps to protect the firing hammer against the recoil of the firing pin, this could be done by employing a floating firing pin, i.e. after the firing hammer strikes the firing pin the firing pin moves in the direction of the cartridge without having a driving connection to the firing hammer. In this case, the firing pin is driven merely by an elastic impact. In this case the kinetic energy contained in the firing hammer at the moment of impact on the firing pin must be very much greater.Furthermore, to protect the firing hammer, it might be practical in addition to the floating firing pin to take steps to ensure that after striking the firing pin the firing nammer is moved back quickly so far that the firing pin which is thrown back by the propellant gases cannot strike the firing hammer or cannot strike it with its full force. The possibility of using a firing hammer of the followthrough type in the described manner also exists since the front end of the firing pin does not assume excessive temperatures, as was previously explained, and it is not therefore necessary to have a safety gap between the front end of the firing pin and the detonating compound of the caseless cartridge.

If the energy of the firing hammer required for firing can be kept low this also makes it possible for the trigger force ("trigger weight") of the weapon to be kept low.

The described sealing body 50 also has the advantage that the seal formed by it is self-adjusting, i.e. for example, minimal losses of mass of the form part 50 which may arise through the friction of the firing pin can be compensated for by the deformability of the form part 50 and by the mobility of the metal plate 42.

The particular weapon described above is intended for 4.7mm calibre. The total length of the firing pin 20 is 29mum. The bore 42 has a diameter of 6mm; the form part 50 jas a length of 4mm and the diameter of the cylindrical part 26 of the firing pin is 2.5mum. The other dimensions can be taken from tne scale drawing.

Claims (13)

1. A weapon for firing caseless ammunition, having a cartridge chamber, and a firing pin displaceably mounted in a part of the weapon behind the cartridge chamber, wherein: - the firing pin, over a portion of its length, is surrounded by a compartment disposed in the said weapon part; the compartment contains an elastically deformable sealing compound supported in the said weapon part on its side facing away from the cartridge chamber; and the compartment is closed off from the cartridge chamber by a movably mounted plate.

2. A weapon according to claim 1, wherein the plate is metallic and is in contact with the wall of the compartment for the purpose of heat conduction.

3. A weapon according to claim 1 or 2, wherein the end portion of the firing pin nearest the cartridge chamber is housed in an aperture in the plate.

4. A weapon according to any preceding claim, wherein the sealing compound has approximately hydrostatic properties

5. A weapon according to any preceding claim, wherein the sealing material comprises graphite.

6. A weapon according to claim 5, wherein prepressed natural graphite is used.

7. A weapon according to any preceding claim, wherein the firing pin in a retractable position thereof, basically does not project beyond the plate.

8. A weapon according to any preceding claim, wherein the end portion of the firing pin nearest the cartridge chamber is substantially cylindrical.

9. A weapon according to any preceding claim, operable such that, when a firing hammer of the arrangement is released, the rear end of the firing pin is substantially constantly in contact with the firing hammer from the time of impact of the firing hammer on the firing pin up to the time of firing of the cartridge.

iO A weapon according to any preceding claim, wherein the firin pin, in a region behind the seal, has a truncated conical face which faces away from the seal and interacts with a counterface forming a stop in a c. t e. weapon r. p a r t

11. A weapon according to any preceding claim including a stop formed in the said weapon part behind the cartridge chamber to limit the movement of the firing pin towards the cartridge chamber.

1 2. A weapon according to claim 10, wherein the said another weapon part is releasably connected to the said weapon part which is behind the cartridge chamber.

13. A weapon substantially as herein described with reference to and as illustrated in the accompanying drawings.