EP0437675A2 - Grooves for a gun barrel - Google Patents

Abstract

To improve the lifetime of known gun barrels and to improve the ballistics of a projectile fired by them, according to the invention a gun barrel having optimised rifling is proposed. …<??>An edge-force trend (R(x)) according to the invention, obtained from this rifling and taken along the gun barrel (x), exhibits an essentially trapezoidal trend, with a markedly reduced edge-force maximum in comparison with such edge-force trends of conventional riflings (constant rifling: dot-and-dash line; parabolic rifling: dashed line). …<IMAGE>…

Description

The invention relates to a weapon barrel with the features of the preamble of claim 1.

mit den Bedingungen:

Dabei sind:

As is known, the lifespan of such drawn gun barrels depends essentially on the last force. This relationship, also with regard to the design of a train-field profile and a corresponding swirl course in the weapon barrel, is explained and described in detail in the "Weapon Technical Pocket Book" from Rheinmetall GmbH, 5th edition 1980, pages 523 to 529. Then the last force R (x) can be described in good approximation over the projectile path x in the longitudinal direction in the weapon barrel by:

with the conditions:

Here are:

It is therefore clear that with a given projectile mass m _G , projectile velocity V _G (x) and gas pressure curve p (X), the swirl curve of the weapon barrel under consideration has a decisive influence on the groin force curve R (x).

In the case of the constant twist most commonly used up to now - especially in the case of large-caliber gun barrels - for manufacturing reasons, in which the twist angle a (x) is independent of the projectile path x, the rail force curve R (x) disadvantageously follows proportional to the gas pressure curve p (x) . There is a pronounced, local maximum of the groin force, which coincides locally with the gas pressure maximum in the weapon barrel and leads to an undesirably high, local stress.

Considerations were therefore made at an early stage to reduce the groin force by using a parabolic, sinusoidal or cubic-parabolic swirl course, as stated in the "Weapon Technical Pocket Book" by Rheinmetall GmbH, 5th edition, 1980, pages 523 to 529.

These, in particular in Figure 1137 on page 525 of the "Weapon Technical Handbook", referred to as progressive swirl courses, show that with parabolic and cubic-parabolic swirl a large groin force R (x) occurs at the muzzle of the gun barrel, which adversely affects the trajectory of the projectile can impact. In addition, it has a so-called torsional impulse effect on the gun barrel and thus causes undesirable gun barrel vibrations around the barrel core axis, with an additional load on the projectile.

As can be seen from Figure 1137 on page 525 of the "Weapon Technical Handbook", the sinusoidal swirl curve shows a pronounced maximum of the groin force but also a significantly reduced groin force at the muzzle. However, since in previously manufactured weapon barrels with a sinusoidal swirl course for machine guns, the helix angle a (x) increases from an initial helix angle α _A = 0 ° to a final helix angle α _E = 6.5 ° at the muzzle of the weapon barrel, which is due to the reduced last force at the muzzle achieved advantage partially consumed by a pronounced forming process of a guide band of the projectile. The wider the guide band, the more unfavorable these conditions become.

In artillery tubes, the projectiles of which usually have particularly wide guide bands, a progressive swirl angle profile starting at the initial swirl α _A = 0 increases the load on the guide bands, especially if a normal final twist angle of αE ≈ 9 ° is to be achieved. In this case, almost the entire width of the guide band is reshaped by changing the helix angle, so that there is a risk that the guide band will fail in the barrel.

The invention is therefore based on the object of avoiding the above-described disadvantages of the known types of swirl used in weapon barrels and to improve the lifespan and the inside and outside ballistics of missiles fired therefrom by means of an improved barrel in a twisted barrel with a reduced groin force maximum.

This object is achieved by a generic weapon barrel with the features according to the invention of the characterizing part of patent claim 1.

The particular advantage of a weapon barrel designed according to the invention is that a locally pronounced maximum of the last force is avoided and the maximum occurring last force is significantly reduced, so that the entire train field profile is less stressed and thus the life of the weapon barrel in terms of fatigue and wear is improved.

Another advantage of the weapon barrel according to the invention can be seen in the fact that, as provided in a preferred embodiment of the invention, a swirl angle described by a higher-order Fourier series approach correspondingly adjusts the desired last force curve to a predetermined gas pressure curve with a sufficient number of coefficients. Through known numerical optimization of the coefficients of the Fourier series, an exact definition of the last force at the weapon barrel muzzle, a clear reduction of the last force maximum, an adjustment of a small change in the twist angle via the projectile path can be carried out to protect a guide band of the projectile.

Further advantageous embodiments of the invention emerge from the subclaims.

The invention is explained and described in detail below with reference to a preferred embodiment of an artillery barrel of 155 mm caliber and a weapon barrel length of 52 calibers.

• Figur 1: ein Diagramm eines Drallwinkels a(x) aufgetragen gegen eine Waffenrohrlänge x des erfindungsgemäßen Waffenrohres im Intervall zwischen den auf der Abszisse markierten Positionen x_A und _XE;
• Figur 2: ein Diagramm einer sich aus dem Drallwinkelverlauf a(x) gemäß Figur 1 ergebenden Leistenkraft R(x) aufgetragen gegen die Waffenrohrlänge x;
• Figur 3: ein Diagramm (gegenüber Fig. 1 in verkleinertem Maßstab) Drallwinkelverlauf a(x) mit dem erfindungsgemäßen Drallwinkelverlauf gemäß Figur 1 im Vergleich zum Konstantdrall und zum parabolischen Drall in einem entsprechenden Waffenrohr und
• Figur 4: ein Diagramm der sich aus den Drallwinkelverläufen a(x) gemäß Figur 3 ergebenden Leistenkräfte R(x) für die in Figur 3 dargestellten Drallarten.

Two diagrams are used for a better understanding and to clarify the invention. The following show in detail:

• FIG. 1: a diagram of a swirl angle a (x) plotted against a weapon barrel length x of the weapon barrel according to the invention in the interval between the positions x _A and _XE marked on the abscissa;
• FIG. 2: a diagram of a last force R (x) resulting from the swirl angle curve a (x) according to FIG. 1 plotted against the barrel length x;
• FIG. 3: a diagram (compared to FIG. 1 on a reduced scale) swirl angle curve a (x) with the swirl angle curve according to the invention according to FIG. 1 in comparison to the constant swirl and to the parabolic swirl in a corresponding weapon barrel and
• 4 shows a diagram of the strip forces R (x) resulting from the swirl angle profiles a (x) according to FIG. 3 for the types of swirl shown in FIG.

eine gerade Fourier-Reihe angesetzt. Der Enddrallwinkel α_E ist aus ballistischen Gründen mit α_E = 8,969°. Um am Drallbeginn x = x_A und am Drallende x = x_E ähnlich günstige Verhältnisse wie beim bekannten Konstantdrall zu erzielen, muß der Drallverlauf a(x) an diesen Stellen _XA, _XE eine nahezu horizontale Tangente besitzen, so daß

der Faktor f im Argument der trigonometrischen Glieder der obigen Fourier-Reihe dient zur Verkürzung der Periode und beeinflußt daher die Leistenkraft R(x) an der Waffenrohrmündung x = x_E. Vorzugsweise gilt für den Faktor f

Starting from a given gas pressure curve p (x) and a given projectile velocity v _G (x), an artillery gun barrel of caliber D = 155 mm and a gun barrel length x with 0 ≦ x ≦ 52 D for the desired swirl angle course a was used in the preferred exemplary embodiment of the invention (x) according to

set up a straight Fourier series. For ballistic reasons, the final twist angle α _E is α _E = 8.969 °. In order to achieve similar favorable conditions at the start of the swirl x = x _A and at the end of the swirl x = x _E as in the known constant swirl, the swirl course a (x) at these points _XA , _{XE must have} an almost horizontal tangent, so that

the factor f in the argument of the trigonometric terms of the Fourier series above serves to shorten the period and therefore influences the last force R (x) at the muzzle x = x _E. The following preferably applies to the factor f

Another important parameter for influencing the strip force R (x) is the initial helix angle a (x) = X _A.

The diagram of the groin force curve a (x) of a weapon barrel according to the invention shown in FIG. 1 is based not only on the values already mentioned, but also on the following coefficients, which were determined with the aid of a numerical optimization method known per se:

und den Beziehungen

ist bei vorgegebenem Gasdruck-Verlauf p(x) und Geschoßgeschwindigkeitsverlauf v_G(x) die Leistenkraft R(x) entlang des Rohres gemäß

festgelegt. Die derart bestimmte Leistenkraft R(x) ist im Diagramm in Figur 2 dargestellt.With the derivation mentioned above

and relationships

For a given gas pressure curve p (x) and floor velocity curve v _G (x), the strip force R (x) along the pipe is in accordance with

fixed. The strip force R (x) determined in this way is shown in the diagram in FIG.

Due to the selected final twist angle of α _E = 8.969 °, there is a large initial twist angle of α (x _A ) = 5.298 °. The twist angle change thus achieved along the tube of Δα = α _E - α _A = 3.6289 ° is advantageously very small, so that a conventional guide band is only slightly deformed on its way through the weapon barrel. In addition, Figure 2 shows that the maximum of the strip force R (x) remains essentially constant over the projectile path x.

The small initial helix angle of α _A = 5.298 ° determined according to the invention is also advantageous, since it has a favorable effect on the so-called torsional impulse effect and therefore reduces the tendency of the gun barrel to vibrate.

For clarification, FIG. 3 shows the swirl angle curve a (x) according to the invention, which is shown here as a solid line as in FIG. 1, in comparison with the types of swirl previously used for a corresponding weapon barrel. In Figure 3, the constant swirl is shown as a dash-dotted curve and the parabolic swirl as a dashed curve.

Starting from the swirl angle curves a (x) shown in FIG. 3, the strip force curves R (x) shown in FIG. 4 result for the respective types of swirl. In FIG. 4, the way in which the curves are represented according to FIG. 3 was used.

From Figure 4 it is clear that in a weapon barrel according to the invention compared to the constant twist still common today in artillery tubes, the last force is reduced by approximately 42%.

• Demgegenüber beträgt die mündungsseitige Leistenkraft R(x_E) des erfindungsgemäßen Waffenrohres - wie Figur 4 zeigt - lediglich noch 10% des Maximalwertes.

In the parabolic swirl common today in machine guns, which here is based on the invention According to the example, the artillery tube was transferred for comparison purposes, although with a weapon barrel constructed according to the invention only a reduction of the groin force maximum by approx. 11% would be possible, but the parabolic twist would cause the guide band of a projectile to pass through the projectile from x _A to x _E because of Δα ≈ 9 deform strongly and possibly fail. In addition, with the parabolic swirl, the groin force R ( _XE ) at the muzzle takes on its maximum value, so that there is a torque surge on the exiting floor and u. U. to a fault in the floor outlet.

• In contrast, the muzzle-side force R (x _E ) of the weapon barrel according to the invention - as shown in FIG. 4 - is only 10% of the maximum value.

• o geringere Belastung des Zug-Feldprofiles, d. h. geringerer Rohrverschleiß und bessere Ermüdungslebensdauer
• o geringere Führungsbandbeanspruchung
• o geringere Belastung der Drallaufnahme
• o geringere Anregung von Rohrschwingungen
• o günstige Abgangsballistik des Geschosses durch verringerte Leistenkraft an der Waffenrohrmündung o geringfügige Umformung des Führungsbandes des Geschosses durch verringerte Drallwinkeländerung während des Geschoßdurchlaufes durch das Waffenrohr.

All in all, the following advantages result from known weapon barrels with the usual swirl courses in the weapon barrel according to the invention:

• o Less strain on the train field profile, ie less tube wear and better fatigue life
• o lower guide belt stress
• o less strain on the swirl mount
• o less excitation of pipe vibrations
• o Favorable ballistic exit of the projectile due to reduced groin force at the muzzle of the weapon barrel. o Slight deformation of the projectile's guide band due to reduced change in swirl angle during the passage of the projectile through the weapon barrel.

The manufacture of gun barrels according to the invention, even of large caliber, with the twist regularities according to the invention discussed above, is possible with the CNC-controlled groove-drawing machines known today without great difficulty.

Claims (5)

1. weapon barrel with a swirl course with a variable swirl angle and a last force acting when firing a projectile,
characterized in that the weapon barrel is constructed in such a way that the last force (R (x)) over the projectile path (x) in the weapon barrel at a given projectile mass (m _G ), projectile velocity (V _G (X)) and gas pressure curve (p ( x)) rises steeply at the beginning of the moves (x = x _A ), remains essentially constant over a subsequent wide area of the weapon barrel and drops steeply towards the muzzle (x = x _E ), i.e. essentially in a diagram R (x) has a trapezoidal shape, the maximum of the last force (R (x)) being reduced by at least a quarter compared to a corresponding weapon barrel with a conventional constant twist. 2. weapon barrel according to claim 1,
characterized in that the swirl angle (α (x)) determining the inguinal force (R (x)) is determined by a Fourier series according to α (x) = E (S _n 'sin n ° F ° x + C _n ° cos n ° F ° x); 0 ≦ n ≦ z is described, where z is a positive, integer value and F is a constant factor. 3. weapon barrel according to claim 2,
characterized in that the Fourier series determining the helix angle (α (x)) is a straight Fourier series. 4. weapon barrel according to claim 3,
characterized in that the constant factor (F) determining the twist angle (α (x)) of the weapon barrel is described in the argument of the trigonometric terms of the Fourier series by F = πf / x _E , where f is a factor for influencing the last force (R (x)) at the mouth (x = x _E ) and 1.0 <f <1.2 applies. 5. weapon barrel according to claim 4,
characterized in that, in order to protect a guide band of the projectile, a change (Aa) in the twist angle (a (x)) from an initial twist angle (a _A = a (x _A )) at the start of the trains up to a final twist angle (α _E = a ( x _E )) at the mouth is less than 5.5 °, so that the following applies: Δα = αE - αA <5.5 °

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