Patent ID: 12203717

DETAILED DESCRIPTION

According to the present disclosure, the problems that characterized prior art bolt heads are solved by a bolt head according to the present disclosure, in particular a bolt head having at least two centering ramps projecting obliquely toward the rear for self-centering the bolt head when it is moved in and out of the locking space of a barrel/cartridge chamber. Self-centering can help to obviate premature wear and material fatigue. Furthermore, the reloading process is smoother and freer of disturbances with such a bolt head.

In one embodiment, at least one alignment surface can be located on the bolt head directly in the region axially adjoining the locking lugs, which alignment surface functionally interacts with a counter-surface in the locking space, as a result of which the movement of the bolt head is further smoothed because it is provided with better guidance.

In another embodiment, the bolt head can have locking lugs provided with rounded portions and chamfers, as a result of which the stress applied to the bolt head is further reduced.

In yet another embodiment, the cam pin of the bolt head can have a stepped taper at its end, and the bolt head can have a corresponding shape-complementary, stepped bore for receiving the end of the cam pin, resulting in improved torque absorption. In the context of the present disclosure, the meaning of “shape-complementary” indicates that a geometrical shape of a second object (“shape-negative”) is chosen in order to fit roughly to the geometrical shape of a first object (“shape-positive”), which interact with each other. An example for “shape-complementary” could be the “key-lock” principle.

In another embodiment, the bolt carrier associated with the bolt head can have additional front and rear alignment surfaces to secure it against any tilting movement.

A comparison of different, preferred embodiments with the prior art results in the following advantages:self-centeringlow-friction sliding in and out of the bolt headminimally malfunction-prone reloading processsmoother behavior of the weaponhigher mechanical stability of the cam pinimproved service life

Above all, the solution according to the present disclosure allows a prolonged service life of the bolt head. It has been recognized that the self-centering design helps to reduce premature wear of material and fatigue because the bolt head is smoothly guided into and out of the locking space without disturbing impacting or striking caused by acentric movement. It has been found to be particularly advantageous if the locking sleeve is provided with counter-surfaces to the centering ramps on the bolt head. Such counter-surfaces are described in EP19201453.8. In the following context, these counter-surfaces are also referred to as counter-ramps.

The specially-shaped front and rear alignment surfaces on the bolt carrier achieve additional stabilization of the bolt carrier as it moves in the receiver during the loading process and reduces premature wear and material fatigue, and in particular the bolt head is also stabilized using the bolt carrier.

Preferably, chamfers are formed on the cartridge guides to prevent the cartridge guides from slipping off the cartridge bottom during the loading process, as is possible on curves. This can avoid feed jams and reduces the corresponding shocks and impacts on the bolt head. Likewise, a misaligned movement of the bolt head occurring during a jam can be significantly reduced, which in turn has a positive effect on premature wear and material fatigue.

A further aspect of the present disclosure relates to the special and novel stepped design of the cam pin and the shape-complementary bore in the bolt head. The taper at the end of the cam pin is accompanied by an increased wall thickness of the bolt head in the region of the cam pin, which, drastically reduces the susceptibility to material fatigue and fractures in this region. In addition, any occurring transverse forces are additionally absorbed by the bolt head via the additionally created side surface in cooperation with the additionally created support surface, and sufficient torque absorption is ensured.

In the context of the present disclosure, the locking lugs on the barrel/cartridge chamber or the locking sleeve are fixed in position, whereas the locking lugs on the bolt head can be moved relative to the locking lugs of the locking sleeve.

FIG.1andFIG.7show a bolt system having a bolt carrier1, a bolt head2and a firing pin3in an exploded view. In the illustrated embodiment, a bolt for direct gas operation, as can be used for example in firearms of the M4/M16/AR-15 series, the gas deflecting piece, hereinafter referred to as gas key5, is arranged on the bolt carrier1. The bolt head2having gas rings19, a cam pin bore20, locking lugs7and a firing pin bore23is, in the installed state, located in the bolt head bore24of the bolt carrier1, and the firing pin3is located in the firing pin bore23and is prevented from falling out by the retaining pin4. The cam pin6having a head21, which runs in a corresponding groove in the receiver to obviate a premature locking movement or any rotation that could hinder the firing pin, having a step14and an end15extends through a cam10that is provided in the bolt carrier1and is located in the bore20of the bolt head2. Said cam pin6is held in position by the firing pin3, which passes through the firing pin through hole36, and the head21protrudes beyond the bolt carrier1.

In the case of axial movement of the bolt head2relative to the bolt carrier1, a rotating movement of the bolt head2is effected and limited by the interaction of the cam pin6and the cam10. Furthermore, this limits the axial movement of the bolt head2relative to the bolt carrier1.

The firearm is loaded by means of an axial movement of the bolt carrier1in the receiver in the firing direction (to the left inFIG.1). The bolt head2movably mounted in the bolt carrier1takes along an uppermost cartridge (not shown) from a magazine (not shown) in that the bolt locking lugs7facing the magazine and located at the bottom in the installation situation having cartridge guides13formed on them push the cartridge on the cartridge bottom across the loading ramps (not shown) and into the cartridge chamber46(shown inFIG.8) substantially parallel to barrel bore axis and in the direction of the muzzle.

After the bolt head2has completed the forward movement and has reached its final position with the bolt locking lugs7in the locking space44(FIG.8) of the locking sleeve45(FIG.8), the bolt carrier1continues to push forward, causing a relative movement with respect to the already stationary bolt head2. Due to the interaction of cam10and the cam pin6, the bolt head2performs a forced rotational movement. As a result, the bolt locking lugs7engage behind the sleeve locking lugs43(shown inFIG.8) of the locking sleeve45of a barrel48having a cartridge chamber46, and the bolt is thus locked. The firearm is in the loaded state.

The bolt carrier1movably mounted in the upper receiver has at least one front alignment surface12and at least one rear alignment surface11, which alignment surfaces rest against the upper receiver and allow and stabilize the axial alignment and movement of the bolt carrier1within the upper receiver. Said alignment surfaces counteract the so-called “carrier tilt” or “catching” of the bolt carrier in the rear region, which is caused by the bolt carrier's own weight and by acentric movements such as oscillations, shaking, vibrations and/or other influences. This stabilization of the bolt carrier1in the receiver also stabilizes the bolt head2with respect to acentric (transverse) movements, which bolt head is freely movable in the axial and tangential (circumferential) direction in the bolt carrier1.

More preferably, a plurality of front and/or rear alignment surfaces11,12are provided, which alignment surfaces are distributed in the circumferential direction like a “balancing weight” such that the barrel properties are stabilized. Compared with the prior art, this stabilization can reduce malfunctions and fosters low-friction movement during the loading process and during the corresponding insertion and removal of the bolt head2from the locking chamber44of the locking sleeve45(also often referred to as barrel extension) and thus increases the service life of the bolt head2. Both premature wear of the locking lugs7due to acentric insertion into the locking space44(seeFIG.8) and impacts on the locking lugs7caused by this can be significantly reduced, and the relatively thin wall region of the bolt head2around the cam pin6can be more effectively saved from damage (because fewer unintentional transverse forces are exerted and, as a result, only a small torque from the cam pin6acts on the bolt head2).

In a particular embodiment, the longitudinal extensions of the front and/or rear alignment surfaces11,12can be formed differently from each other, wherein such a distribution of the bearing surfaces also results in an optimization of the center of mass of the bolt carrier. This can be easily seen when viewingFIGS.1and7together. It should be explicitly mentioned at this point that, according to the present disclosure, a different length of the rear alignment surfaces11in the circumferential direction can be formed. This measure allows the barrel properties to be adjusted in a targeted manner, which is easy for those skilled in the art to determine with a small number of attempts.

FIG.2is a perspective view showing a possible embodiment according to the present disclosure of a bolt head2obliquely from below/in front. As in the prior art, the bolt head comprises an extractor8and an ejector9. The lower side of the bore20for receiving the cam pin6is also shown. A recess50is formed between two (adjacent) locking lugs7. The bolt locking lugs7are provided with rounded portions17for the smoothest possible sliding in and out of the locking space44. The rounded portions17(in the illustration they appear as large chamfers, but they are actually rounded portions) reduce unwanted catching of the bolt head2when it is inserted into the locking space44at the lugs thereof because the rounded portions17facilitate sliding on edges, etc.

In the region of the cartridge guides13facing the magazine that is not shown, the rounded portions facing the cartridge to be introduced are replaced by chamfers16, which prevents possible slippage of the cartridge guides13from the cartridge during the loading process and thus achieves easier and more trouble-free loading than in the prior art.

The alignment surface25, which is located behind and directly after the locking lugs7and/or recesses50as viewed in the axial direction and has the radius r234(FIG.4), forms a counter-surface to the transverse surface portions, in short transverse surfaces49, of the locking lugs43of the locking sleeve45of the barrel48(FIG.8). The alignment surfaces25thus act as additional alignment surfaces for the bolt head2in the locking space44. The alignment surface25can, as shown inFIG.5F, be designed to be annular and continuous or to have interruptions, as shown, for example, inFIGS.5A-5E.

The centering ramp18provided according to the present disclosure is formed as an oblique transition between the recesses50, between two locking lugs7, and the adjacent alignment surface25, as can be seen in particular inFIGS.5A-5F. The centering ramps18automatically center the bolt head2during insertion into the locking space44of a barrel48, as a result of which premature wear and material-stressing knocks and impacts are avoided, thus increasing the service life.

Influences occurring in the field or during automatic firing, such as contaminations, oscillations, shaking, vibrations, and the like, can lead to an acentric movement of the bolt head2. By means of the centering ramps18, these acentric movements are avoided and the bolt head2is automatically centered, as a result of which possible jams and premature wear are avoided and a corresponding increase in the service life is achieved. This automatic centering is done particularly well by the centering ramps18according to the present disclosure in a combination of the bolt head2and a firearm that has corresponding counter-surfaces in the locking sleeve44that are complementary to the centering ramps18in terms of shape and function. Such counter-surfaces in a locking sleeve of a firearm are described in EP19201453.8, which was mentioned above, and are shown as counter-ramp47inFIG.8.

A longitudinal section of an embodiment of the bolt head2is shown inFIG.3. The angle α designated by22is defined by the surface normal29of the centering ramp18and by the bolt head axis28. The following applies in this case: 5°<α<85°, preferably 15°≤α≤65°, and particularly preferably 25°≤α≤50°.

FIG.4shows the bolt head2according to the present disclosure in a view in the direction of the bolt head axis28or of the arrow IV ofFIG.3. The chamfer16on the cartridge guides13has an angle of 30° to 60°, preferably an angle of 40° to 50° with respect to the normal plane to the bolt head axis28. The width of the chamfer16is within the range of 0.05 mm to 0.2 mm, preferably 0.08 mm to 0.12 mm. The radius of the rounding portion17on the locking lugs7is within the range of 0.2 mm to 2 mm, preferably within the range of 0.3 mm to 1 mm.

FIGS.5A-5Eare partial detailed views analogous toFIG.4, wherein, by means of dashed lines, different embodiments of interruptions of the alignment surface25extending parallel to the bolt head axis28are shown. Such interruptions can be formed, for example, as one or a plurality of flattened portions37or as one or a plurality of trench-forming alignment surface recesses38. “Trench-forming” is used for illustrative and visualization purposes and refers to the embodiment ofFIG.5B.FIG.5Ashows an embodiment having, in each case, one flattened portion37between the alignment surfaces25located directly after the respective centering ramps18. The normal distance N1, designated by39, is the shortest distance between the bolt head axis28and the flattened portion37, which distance is formed by a normal. The normal distance N139is smaller than the radius r2 designated by35.

FIG.5Bshows an embodiment having, in each case, one recess or trench-forming recess38as an interruption between the alignment surfaces25located adjacent to the respective centering ramps18. The normal distance N2, designated by40, is the shortest distance between the bolt head axis28and recess38, which distance is formed by a normal. The normal distance N240is smaller than the radius r235.

FIGS.5C,5Dshow variants having two or three directly adjacent flattened portions37between the alignment surfaces25located after the respective centering ramps18.FIG.5E, in turn, shows a preferred variant with a flattened portion37between two alignment surfaces25, wherein one of these two alignment surfaces25is located after the respective centering ramps18, and the other alignment surface25is located behind a respective locking lug7as viewed in the axial direction.

FIG.5Fis a detailed view of a continuous alignment surface that is annularly formed around the bolt head2without interruption.

The present disclosure is not limited to the interruptions shown inFIGS.5A-5F, but also extends to other embodiments such as semi-cylindrical or concave recesses or bionic surfaces and other types of surfaces conventionally used in additive design and manufacturing.

The interruptions of the alignment surface25act advantageously to reduce the friction between the parts that are moved during the locking process and thus allow easier and smoother locking and unlocking of the bolt, thus premature material wear and correspondingly can be reduced extending the service life, even in unfavorable conditions such as under-lubrication or dust and dirt contamination that occurs during field use.

FIG.6is a schematic view of the substantially rotationally symmetric cam pin6according to the present disclosure having a stepped design, a head21, a firing pin through hole36, an end15, a step14, an outer surface30, and an additional side surface31formed by the stepped shape. The length L2, designated by42, of the tapered and stepped end15of the cam pin6corresponds to a minimum of 0.05 to a maximum of 0.5 times the total length L1 of the cam pin6, designated by41. Preferably, the length L2 is within the range of 0.1 to 0.3 times the total length L1 of the cam pin6. The diameter D2, designated by33, of the tapered and stepped end15of the cam pin corresponds to a minimum of ⅕ and a maximum of ⅘ of the diameter D1, designated by32, of the cam pin. Preferably, the diameter D2 is within the range of ⅓ to ⅔ of the diameter D1. The ideal ratio L2/L1 and D2/D1 can easily be determined by those skilled in the art as a function of the bolt head dimensions. In addition to the single-step shape shown, multi-step embodiments of the end15are also possible.

FIG.7shows a longitudinal section of a bolt carrier1having a bolt head2and a cam pin6. The cam pin6comprises a head21and one or a plurality of steps14at its end15. The bore20of the bolt head2is accordingly complementary in shape and design to the lower part of the cam pin6and receives most of the cam pin6. The stepped and tapered configuration of the end15of the cam pin6creates the additional (cylindrical) side surface31parallel to the axis of the cam pin6. At the same time, the shape-complementary design of the bore20creates a taper toward its end and entails corresponding greater wall thicknesses of the bolt head2at precisely this end. Thus, the bolt head2according to the present disclosure has more material in the region of the end of the bore20than in the prior art, and fatigue fractures of the bolt head2in the region of the cam pin can be prevented. Furthermore, the bolt head2having bore20that is shape-complementary to the step-shaped cam pin6absorbs the additional transverse forces acting on the cam pin6. These transverse forces, caused for example by the movement along the sliding guide and/or by vibration, shaking, oscillations, etc., are transmitted onto the support surface27and the additional support surface26of the bolt head2through the side surface30and the additional side surface31of the cam pin6(FIG.6) (parallel to the longitudinal axis of the bore20, also seen inFIG.3) and absorbed by the bolt head2.

In the illustrated embodiment, the gas key5is fastened on the bolt carrier1using two screws. During the gas-pressure-induced reloading process, gas is passed into the bolt carrier1via the gas key5. Due to the high gas pressure suddenly arising upon firing, corresponding forces occur at the gas key, which forces are relayed to the bolt carrier via the screw connection.

For better transmission of the force from the gas key5to the bolt carrier1, a nose51is formed on the gas key5, which nose engages in a shape-complementary catch52of the bolt carrier1. Surprisingly, it has been found that this additional possibility of force transmission and force dissipation causes the screw connection of the gas key5to the bolt carrier1to be subjected to less stress, thereby preventing loosening of the screw connection during use. A gas key that is permanently loose during use promotes, in addition to potential, unwanted gas leakage at the wrong place, namely between the gas key5and the bolt carrier1, an acentric movement of the bolt carrier1and thus of the bolt head2by shifting the center of gravity. Because of the described additional possibility of force transmission from nose51to detent52, preventing acentric movement of the bolt carrier1and the bolt head2can ultimately extend the service life of the bolt head2.

FIG.8is perspective view of a barrel48having a cartridge chamber46, a locking sleeve45and a locking space44and of a bolt head2, and the barrel is also shown in axial section. The locking lugs43of the locking sleeve45have transverse surfaces49that guide the bolt head2during insertion into the locking space44and act as counter-surfaces to the alignment surfaces25in the inserted state. The counter-ramps47are complementary to the centering ramps18in terms of shape and function and support the self-centering of the bolt head2during insertion into the locking space44. If the bolt is in the closed state, the locking lugs7of the bolt head2are in the locking space44of the barrel48, and the transverse surfaces49of the locking lugs43of the locking sleeve44rest on the alignment surfaces25.

The present disclosure is not limited to the embodiments shown, but also includes other bolt system variants such as gas piston systems and others. For the purposes of the present disclosure, the cam pin6is to be understood as a part of the bolt head2.

The bolt head2according to the present disclosure can be produced, for example, by means of machining processes such as milling, turning or grinding. The bolt head2according to the present disclosure can also be produced using forming processes such as forging or hammering, powder metallurgy or metal injection molding (MIM), or else by means of additive manufacturing processes such as 3D printing or a combination of these methods.

All the materials used for the mentioned components in the prior art can also be used for the components designed according to the present disclosure.

The various embodiments described can be combined with each other arbitrarily, thereby also making the explained embodiment of the cam pin6advantageously possible in bolt heads without centering ramps18, as well as the use of the front and rear alignment surfaces, which also do not depend on the embodiment of the bolt head. This also applies to the alignment surfaces25and the other characteristics and features described.

List of reference numerals:1Bolt carrier2Bolt head3Firing pin4Retaining pin5Gas key6Cam pin7Bolt locking lugs8Extractor9Ejector10Cam11Rear alignment surface12Front alignment surface13Cartridge guide14Step15End16Chamfer17Rounded portion18Centering ramp19Gas ring20Bore21Head22Angle23Firing pin bore24Bolt head bore25Alignment surface26Additional support surface27Support surface28Bolt head axis29Surface normal30Outer surface31Additional side surface32Diameter D133Diameter D234Radius r135Radius r236Firing pin through hole37Flattened portion38Alignment surface recess39Normal distance N140Normal distance N241Length L142Length L243Sleeve locking lugs44Locking space45Locking sleeve46Cartridge chamber47Counter-ramps48Barrel49Transverse surface50Recess (between locking lugs)51Nose52Detent