Breechblock return mechanism

June 19, 1951 p. mOdespacher 2,557,134

BREECH BLOCK RETURN MECHANISM

Filed Jan. 7, 1942

Fig-1 Fig. 2

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Patented June 19, 1951

2,557,134

UNITED STATES PATENT OFFICE

2,557,134

BREECHBLOCK RETURN MECHANISM

Patil MiideSpacher, Zurich-Oerlikoii, Switzerland, assignor to VerwaltungsgeseUschaft der Werkzeugmaschinenfabrik Oerlikon, -ZurichOerlikon, Switzerland

Application January 7,1942, Serial No. 425,892 In Switzerland October 23, 1940

Section 3, Public Law 690, August 8,1946 Patent expires October 23, I960

Claims.

It is known that mass or inertia locked automatic firearms in which the stationary breech block absorbs the gas pressure forces by backward and forward motion under the action of a recoil spring have various advantages over rigidly locked weapons. As a result of their relatively simple construction, the mass locked weapons are in particular extremely robust and sure in action.

On the other hand, a disadvantage of the mass locked system is that there are limits to any increase in the rate of firing. This is due to the fact that the breech block requires a certain time for its backward and forward movement which, even with strong recoil springs in combination with a far-reaching reduction of the weight of the breech block mass, cannot be reduced to such an extent that very high rates of firing can be obtained. Particularly in cases where a breech block mass which is heavy in relation to the total weight of the weapon is provided, a rate of firing of over 300 shots per minute is scarcely attainable. But even in the case of weapons with a relatively light breech block, the maximum rate of firing is about 600 shots per minute.

This firing rate could not be reached by alterations in the construction of the prior, mass-locked weapons on account of the fact mentioned, viz., that the principle of mass locking sets limits to any increase in the rate of firing. Hence fundamentally new methods had to be sought to obtain rates of firing in keeping with modern requirements whilst retaining the proved system of mass or inertia locking.

The present invention solves the above mentioned problem by the fundamentally new idea in mass locked weapons of reducing the travel of the breech block, and hence the time between the individual shots, by movably mounting the barrel and the parts rigidly connected therewith. Hence, a counter movement is produced between the breech block on the one hand and the barrel on the other hand which considerably reduces the movement of the breech block.

Fundamentally, when two masses move against one another like the barrel and the breech block in accordance with the present invention, the breech block movement will be shortened in every case, irrespective of the weights of the two masses. On the other hand, by suitably dimensioning the barrel and the breech block, an optimum can be attained, possibly if the path travelled by both masses moving to and from one another is equally great. This is the case if the combined weight of the barrel and the parts rigidly fixed thereto corresponds approximately to that of the breech (Cl. 89—198) _: 2 block. The path to be traversed by the breech block is then reduced to a half, which corresponds to an increase in the rate of firing of about 50%.

In the accompanying drawings are shown, by 5 way of example, two constructional forms of the invention.

In said drawing, Figs. 1 and 2 are, respectively, horizontal and vertical sections through a firearm constructed in accordance with the inven10 tion, while Fig. 3 is a vi6w similar to Fig. 2 but showing the parts at the instant Of firing. The barrel I is fixed in the breech casing 2 by means of a bayonet joint 3. In the housing 4, which is rigidly fixed to the mounting are buffer springs 15 5 and 6, of which the rear spring 6 acts as a buffer for the barrel if, in tire extreme case, its recoil movement oversteps the normal value, while the front spring 5 acts as a buffer for the barrel when after the last shot and in company with 20 the breech block, it returns to its forward rest postition under the action of the return spring 10. The breech block recoil spring 9 is arranged directly in the breech block casing 2 and bears at its rear end against a band 16. The rear part 25 of the breech block casing 2 slides in an enlargement of the housing 4 in which the trigger mechanism I i is also arranged. The trigger levers for continuous and single-shot firing are shown at 14 and 15. The trigger setting takes place by ro30 tation of a frame on which the roller of the lever 12 slides along with the movement of the barrel. The return spring 10 is arranged round the front part of the barrel, and bears on a sleeve 13 screwed on to the housing 4.

The manner of operation of the firearm shown in Figs. 1 to 3 is briefly as follows: In the stationary position shown in Figs. 1 and 2, the breech block recoil spring 9 is relieved from tension down to the pre-tension. If the firearm is 40 cocked by drawing back the breech block 7, the breech block recoil spring is compressed. If now the trigger is set, the barrel and the breech block casing are driven rearwardly in opposition to the advancing breech block. The firing position is 45 shown in Fig. 3, and, as can be seen, the barrel is situated in its rearmost position. At the instant of firing, the breech block 7 will be driven backwards, the recoil spring 9 will be compressed, and the barrel and breech block casing will be ⁵⁰ driven forward under the action of the previously fully tensioned return spring (0, aided by the expanding explosion gases.

During continuous firing the barrel will never completely reach its most forward position since, 55 before it can take up this position under the ac2,557,134 tion of the spring i 0, the breech block will already have begun to run forward again after reaching its rearmost position under the tension of the recoil spring 9, and, therefore, the barrel will already have been driven back again by the 5 tensioned recoil spring.