Method for coupling the barrels of rifles in the breech

Abstract: A method, as well as a firearm formed by the method, for coupling the barrels of rifles in the breech starting from at least one barrel and from a monoblock casing. The breech of each barrel has an end portion of predetermined shape and diameter; the casing has a through hole for each barrel and a striking surface of axial stop of the barrel. The barrel and the casing are coupled mechanically, fitting the end portion of the barrel in the respective hole of the casing; the barrel and the casing are joined by means of laser fusion in at least two zones at the opposite ends of the casing and of the end portion of each barrel.

Description: The present invention pertains to a method for coupling the barrels of rifles in the breech and pertains to the resulting set of barrels as well. According to the state of the art on the subject of rifles with one, two or more barrels, the barrels are essentially coupled according to two different methods, commonly defined as semiblock (demiblock) and monoblock, respectively. In the first method, each pipe forming a barrel is made in one piece with a semiblock or block full of semitenons or hooks in the breech. The semiblocks of the barrels to be joined are then joined lengthwise by means of complementary guides on their adjoining faces. The barrels and the semiblocks are therefore made of the same material, and the stability of the mechanical coupling obtained depends on the precision of the coupling guides and is often questionable, but not reliable, as required. In the second method, the barrels are separated and joined together in the breech by means of a monolithic casing. This monolithic casing may be in a single piece with the tenons or hooks and is provided with holes, in which the breech ends of the barrels are threaded and welded by means of welding with a filler metal such as tin or brass. In this case, the barrels and the monolithic casing may be made of different materials, and a specific procedural technique that the persons skilled in the art know well, is necessary for the coupling and welding. However, the assembly of the barrels either using one method or the other leaves visible signs of joining even though this joining is concealed as well as possible. In the second coupling method, the chemical-physical structure of the materials forming the barrels and the casing becomes nonuniform at least in the joining zones. Moreover, the use of filler metals for the welding involves a reheating in the oven of the components up to a high temperature and with the risk of tempering and thermal stress of the barrels, especially when using brass as the filler metal for a strong welding. On the other hand, if the welding is not strong, there is less resistance to uncoupling and to tearing. The primary object of the present invention is to propose a novel method for coupling the barrels of rifles in the breech, which is suitable for preventing the disadvantages and drawbacks of the prior art. The method is applicable to all rifles with one or more barrels, either smooth barrels or rifled barrels, and is carried out starting from the single barrels and from a monoblock casing and by means of a laser fusion of the parts in contact for their intimate joining, without support material. The method proposed here makes it possible to achieve advantages, such as: chemical-physical uniformity of the materials of the barrels and the casing, particularly in the joining zones; high increase in the resistance to tearing between the barrels and casing; indissolubility of the coupled parts; invisibility of the coupling lines even after the surface finishing of the parts; possibility of reducing the thicknesses and resistant sections in the coupled parts for the greater resistance obtained; decrease in the overall weight thanks to the reduction in the thicknesses of the parts to be coupled; possibility of automating the joining process without running into unusual thermal stresses of the barrels; complete control of the effectiveness of the joining of the parts. Greater details of the present invention become evident from the following description with reference to the attached drawings and, for greater simplicity, with reference to the coupling of two barrels. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention are illustrated. In the drawings: Figure 1 is a top partially cutaway view of the starting barrels and casing separated; Figure 2 is a rear view of the barely coupled barrels and casing; Figure 2a is a section according to the line II-II of Figure 2; Figures 3 and 3a show two views similar to those of Figures 2 and 2a, but with the barrels and casing barely tightly joined; Figures 4 and 5 are cross-sectional views of two enlarged coupling zones corresponding to the encircled parts IV and V in Figure 3a, respectively; Figures 4a and 5a are two views similar to those of Figures 4 and 5, but of the finished coupling; Figure 6 is a graph illustrating the course of the relationship between the laser power applied and the volume of fused material; Figure 7 is a graph illustrating the welding efficiency based on the laser power; and Figure 8 is a graph illustrating the welding efficiency based on the penetration. Referring to the drawings in particular, the starting barrels 11 and the monoblock casing 12, still separated, are illustrated in Figure 1. The barrels 11 and the casing 12 are made of materials that are identical in terms of chemical composition and structural state. Each barrel is machined on the outside in the breech to have an end portion 11' that is preferably but not necessarily cylindrical, starting from a shoulder 11" that is turned towards the rear end and completely at right angles to the axis of the barrel itself. On the other hand, the casing is provided with a through hole 12' for each barrel 11 and is machined at the top so as to have a surface that is completely at right angles to the axis the hole 12' and is intended for coinciding with the shoulder 11" of each barrel 11. The end portion of each barrel and each hole in the casing shall have equal diameters with a suitable machining allowance in the coupling zones. The barrels 11 and the casing 12 prepared in this manner are then machined and prepared for a preliminary mechanical coupling. This coupling is performed by force-fitting the end portions of the barrels in the respective holes in the casing in order to bring the shoulder 11" of the barrels into close contact with the top surface 12" of the casing as shown in Figures 2 and 2a. The striking contact between the barrels and the casing may be maintained with appropriate mechanical devices and ensures the correct arrangement of the barrels. Other devices may be provided for keeping the parts dry and cleaning them. After the preliminary coupling, the barrels and the casing are joined by means of laser fusion in their circumferential zones A and B, respectively, on the striking surface (11" and 12") between the barrels and the casing and at the rear ends of the barrels and of the casing as shown in Figures 3 and 3a. The joining is thus done without material support, and with a homogenizing in the fusion zones A and B of the material that forms the barrels and the casing. In the field, this is a joining of two metal components with fusion of same in the absence of plasma and under an inert atmosphere. The fusion not obtained in the absence of material support would cause a detrimental thermal-structural change for the mechanical features of the fused zone. The inert atmosphere, in the form of gas injected directly close to the point of joining, eliminates the possibility of oxidation and of decarbonization of the fused zone. An excellent result is obtained, e.g., with a ratio of the fused material volume to the time used ranging from 5 mm 3 /sec. to 10 mm 3 /sec. The joining zone of the parts adapts to the level of structural stresses immediately after the fusion. This makes it possible to regulate the internal structure of the fused zone to the same extent as the surrounding, not thermally changed zone. The optimization of the process, set up by the inventor, for the assumed purpose is confirmed by tests, whose results appear from the attached graphs. In particular, the graph of Figure 6 represents the course of the relationship between the power applied and the volume of fused material; the graph of Figure 7 represents the efficiency of the welding and the power/penetration ratio; the graph of Figure 8 shows how, though being less than 3, the depth/width ratio (essential requirement given the thickness and the geometry of the joined components), the efficiency of the joining, as well as the final aesthetic result is very good The optimization sought was thus achieved. Figures 4 and 5 show, on an enlarged scale, the joining zones A and B, which may appear with protuberances which are then removed. The protuberances, and where provided, the starting machining allowance on the outline of the zones A and B are then removed in order to achieve predetermined finishing heights as shown in Figures 4a and 5a. The result is a set of barrels and monoblock joined together by means of laser fusion in at least the zones A and B, which makes the joined components indissoluble, as in a single piece (integral), and which does not leave apparent signs of joining which show their initial contact discontinuity. While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims: A method for coupling the barrels of firearms in the breech starting from at least one barrel and from a monoblock casing, the method comprising the steps of: providing the breech of each barrel with an end portion (11') of predetermined shape and diameter, starting from a striking shoulder (11") turned towards the rear end of the said barrel and at right angles to the axis of said barrel; providing the monoblock casing with a through hole (12') for each barrel and with a striking surface (12") turned towards the striking shoulder (11") of the barrel, the hole having a shape and a diameter corresponding to that of the end portion of the barrel and the striking surface (12") being at a right angle to an axis of the hole; mechanically coupling the barrels and the casing by fitting the end portion of the barrel in the respective hole of the casing in order to bring the striking shoulder into close contact with the striking surface; permanently joining the barrels and the casing by means of laser fusion in at least two zones (A,B) at the level of the said shoulder and of the striking surface in close contact and of a rear end of the barrel and of the casing; and removing any excess material in the joining zones (A,B). A method in accordance with claim 1, wherein each barrel and the casing are prepared with a possible machining allowance in the zones intended for being joined by means of laser fusion. A method in accordance with claim 1, wherein the end portion (11') of the barrel and the hole in the casing are cylindrical and have the same diameter. A method in accordance with claim 1, wherein the barrel and the casing are machined and prepared before the mechanical coupling, and in which this mechanical coupling is maintained with locking means during the joining by means of laser fusion in the zones. A set of barrels for firearms comprising at least one barrel and a casing, into which is inserted a breech part of the barrel, characterized in that the barrel and the casing are joined together by means of laser fusion in at least two zones (A,B). A set of barrels for firearms in accordance with claim 5, wherein said joining zones are in proportion to the said opposite ends of the said casing and extend around the said barrels without apparent joining lines. A firearm comprising: at least one barrel and a casing, into which is inserted the said breech part of the barrel, characterized in that the barrel and the casing are joined together by the steps comprising: providing the breech of each barrel with an end portion (11') of predetermined shape and diameter, starting from a striking shoulder (11") turned towards the rear end of the said barrel and at right angles to the axis of said barrel; providing the monoblock casing with a through hole (12') for each barrel and with a striking surface (12") turned towards the striking shoulder of the barrel, the hole having a shape and a diameter corresponding to that of the end portion of the barrel and the striking surface being at a right angle to an axis of the hole; mechanically coupling the barrels and the casing by fitting the end portion of the barrel in the respective hole of the casing in order to bring the striking shoulder into close contact with the striking surface; permanently joining the barrels and the casing by means of laser fusion in at least two zones (A,B) at the level of the said shoulder and of the striking surface in close contact and of a rear end of the barrel and of the casing; and removing any excess material in the joining zones. A firearm according to claim 7, wherein each barrel and the casing are prepared with a possible machining allowance in the zones (A,B) intended for being joined by means of laser fusion. A firearm according to claim 7, wherein the end portion (11') of the barrel and the hole (12') in the casing are cylindrical and have the same diameter. A firearm according to claim 7, wherein the barrel and the casing are machined and prepared before the mechanical coupling, and in which this mechanical coupling is maintained with locking means during the joining by means of laser fusion in the zones (A,B).

Inventors: GUSSALLI BERETTA UGO, GUSSALLI BERETTA, UGO
Applicants: BERETTA ARMI SPA, FABBRICA D'ARMI P.BERETTA S.P.A.
Application year: 1996
Main classification: F41A21
IPC codes: F41A21, B23K26