IMPROVEMENT IN LOCK BOLT FOR FIRE ARMS

Abstract: Improvement in fire arms of the type comprising a receiver (1) in which a lock bolt (2) is moveable and can be locked in fire position while introducing a cartridge (14) into fire position and in which the lock bolt is formed with two or more closing shoulders (7, 8) adapted to lock the bolt (1) in the fire position with the rear edges thereof and over corresponding contact surfaces of the receiver. According to the invention the rear edges (15) of the lock bolt and the corresponding contact surfaces of the receiver are conically widened, as seen in the fire direction of the fire arm, and form an angle to a radial plane of the lock bolt and the receiver respectively of between 5<o> and 20<o> or preferably of about 15<o>.

Description: Improvement in lock bolt for fire arms. 0 The present invention generally relates to an improvement in lock bolts for fire arms, and the invention is more specifically concerned with a new and improved design of the closing shoulders 5 of the lock bolt of a fire arm and the corresponding end surfaces of the receiver of the weapon, whereby the lock bolt is self centering in the receiver. In priorily known lock bolts the radially projecting closing shoulders of the lock bolt and the corresponding receiving 0 surfaces of the receiver of the weapon generally are formed with plane radial surfaces extending substantially at 90° to the axial direction. In order to allow the lock bolt to be smoothly displaced in the receiver the lock bolt has to be formed with a slight play in relation to the circular cylindric guide of the 2.5 receiver, and this has as a result that the front end of the lock bolt in its fire position may be located slightly out of centering or side displaced in the receiver in relation to the axis of the receiver. This side displacement of the front end of the lock bolt irrevocably makes the bullet get another direction 30 than the direction set by the sight of the weapon, and as a consequence a false hit area is obtained. Tests with rifles have shown that the shot, at an extreme side displaced position of the front end of the lock bolt in relation to the receiver, can hit the target as much as 2-3 centimetres wrong at such short 35 distance as 100 metres. Such side displacements of the the lock bolt sometimes appear in one direction, sometimes in the another direction, and there is no possibility to set the sight so as to correct or compensate for said side displacement. The invention is intended to solve the above mentioned problem by forming the rear edges of the closing shoulders of the lock bol and the corresponding guide surfaces of the receiver conically widened forwards, as seen in the fire direction, whereby the lock bolt in case of a possible tendency to side displacement in relation to the axis of the receiver automatically adjusts itself into the exact axial position in that the conical contact surfaces of the lock bolt shoulders slide along the corresponding surfaces of the receiver until all lock bolt shoulders are in contact with the conical support surfaces of the receiver. Tests have proved that the opening angle for the said forwarly conically widened contact surfaces should be between 140° and 170° or preferably about 150°, that is an angle to the radial plane of between 5° and 20° or preferably about 15°. Tests also have shown that the part of the weapon having the above mentioned plane parallel lock bolt shoulders which is most sensitive to rupture is the very lock bolt shoulders which when subjected to breaking strength tests break. If the lock bolt shoulders and the corresponding contact surfaces of the receiver are formed conically widened the tendency of breaking of the lock bolt shoulders is reduced. On the other hand the tendency that the receiver breaks is increased, but such breaking follows at substantially higher forces that those necessary to break the lock bolt shoulders at the discussed conventional embodiment. It is also well possible to increase the radial thickness of the receiver at the recoil contact place thereby eliminating the tendency of rupture. So, there is a possibility of getting a substantially stronger weapon system than so far appearing on the market, and still the weight of the weapon does not increase to any noticable degree. As mentioned the invention solves two different problems at the same time, namely both to provide a self centering of the front end of the lock bolt, thereby eliminating the risk that said end of the lock bolt is side displaced 1n relation to the receiver, and to reduce or eliminate the risk that the lock bolt shoulders break. In addition thereto the weapon system as a whole presents the advantage of being stronger than the present weapons of the corresponding type. Now the invention is to be .described more in detail with reference to the accompanying drawings. In the drawings figure 1 shows a fragmentary cross section through a part of a weapon having a receiver and a lock bolt designed according to the invention. Figure 2 diagrammatically shows a lock bolt designed as in conventional weapons and in which the front end is shown in two opposite side displaced extreme positions. Figure 3 shows, likewise diagrammatically-, an apparatus according to the invention. Figure 4 shows a cross section along line IY-IV in figure 1. Thus, figure 1 shows a part of a fire arm, especially a repeating fire arm, and for the sake of clearness the main part of the weapon has beed excluded in the figure. The illustrated parts are the receiver 1, in which a lock bolt 2 is introduced and is locked in the firing position. In the illustrated case the receiver 1 is formed with a circular cylindric guide groove 3 for the lock bolt and with three guide grooves 4, 5 and 6 for the closing shoulders 7, 8 and 9 of the lock bolt. At a projecting end 10 of the receiver the barrel 11 is thread connected and between the receiver and the barrel a recoil shoulder 12 is cla pled. The figure syows, somewhat exaggeratedly, that the lock bolt 2 is engaging the cylindrical guide groove 3 of the receiver with some play 13. For eliminating the risk that the lock bol with the front end thereof is placed acentrally in relation to the axis of the receiver the rear edges 15 of the lock bolt shoulders and the corresponding contact surfaces of the receiver are, according the invention, formed conically widened in the fire direction. In the drawing the angle is Illustrated as the angle V between the radial plane of the receiver and the rear edge of the lock bolt sholder 8 and the contact surface of the receiver therefore. The magnitude of the angle is of importance. A too little angle both gives a too slight shearing force to allow the lock bolt, on all occasions, to slide into the correct position In relation to the contact surfaces of the receiver when the bolt is locked by being rotated in the receiver, and apart therefrom the reduction of the axial force to which the lock bolt shoul ers are subjected does not become so strong that the risk that the lock bolt shoulders break can be considered eliminated. At a too large angle, on the other hand, a too strong radial force is transmitted to the receiver at the recoil moment, so that there is a risk that the receiver is damaged. In addition thereto there is a risk that the lock bolt, by wedge action, is pressed to a too strong engagement with The receiver. Tests have shown that the angle should be between 5° and 20°, equivalent to an opening angle for the cone surfaces of between 140° and 170°. By trials is has been established that the angle v should be about 15°, equivalent to an opening angle for the cone surfaces of 150°. At said angle the shearing force is sufficiently great for pressing a side displaced lock bolt into the correct position in the receiver, and at the same time the relationship between the risk of rupture of the lock bolt shoulders and of the receiver is equalized whereby the best possible strength is obtained. In the case illustrated in the drawings there are three lock bolt shoulders 7-9 provided evenly distributed round the lock bolt and three corresponding guide grooves 3-5 in the receiver. This is only an example, and it is obvious to the expert that more or fewer lock bolt shoulders and corresponding guide grooves can be provided as desired, for instance two diametrically opposed lock bolt shoulders, the size of which is calculated as conventional so that the two lock bolt shoulders get the desired total area.

Claims: C L A I M S 1. Improvement in lock bolt for fire arms of the type which is formed with a receiver (1) in which a lock bolt (2) is movable and can be locked in fire position while introducing a cartridge (14) into fire position, and in which the lock bolt (2) is formed with two or more closing shoulders (7-9) adapted to lock the bolt (2) in fire position with their rear edges (15) over corresponding contact surfaces of the receiver (1), c h a rac te r i ze d in that rear edges (15) of the lock bolt shoulders (7-9) and the corresponding contact surfaces of the receiver (1) are conically widened in the fire direction of the fire arm, whereby the lock bolt, if eventually side displaced in relation to the axis of the receiver (1), is automatically centred in a correct position when the bolt (2) is being locked. 2. Apparatus according to claim 1, c h a ra c te ¬ ri zed in that the rear edges (15) of the lock bolt shoulders (7-9) and the corresponding contact surfaces of the receiver (1) form an angle against a radial plane of the lock bolt and the receiver (1) respectively of between 5° and 20°. 3. Apparatus according to claim 1 or 2, c h aracte¬ ri zed in that the rear edges (15) of the lock bolt shoulders (7-9) and the corresponding contact surfaces of the receiver (1) respectively form an angle to a radial plane of the lock bolt (2) and the receiver (1) respectively of about 15°. 4. Apparatus according to any of claims 1-3, c ha rac¬ t e r i z e d in that the lock bolt (1) is formed with three closing shoulders (7-9) provided substantially at 120° angle to each other.

Inventors: KARLSTROEM ROLF, KARLSTROEM, ROLF
Applicants: AFFARSVERKET FFV, AFFAERSVERKET FFV
Application year: 1986
Main classification: F41C11
IPC codes: F41A3