EP2159530B1 - Interchangeable choke for a smooth bore firearm - Google Patents

Description

The present invention relates to an interchangeable choke for a smooth-bore firearm.

More specifically, the invention relates to firearms that are intended for lead cartridges whose charge, as is well known, is a certain amount of small balls or small balls of lead or other material.

It is known that when firing a cartridge, the impact of the lead has a certain dispersion which increases proportionally to the distance at which the impact takes place.

This dispersion can be influenced by the use of what is called a choke.

The object of a choke of this type is to obtain a higher or lower dispersion of the lead, the choke forming a passage for the lead, which extends in the barrel extension and whose inner diameter is reduced towards the mouth of the barrel.

The pace of the diminishing passage determines the measure of the greater or lesser concentration of the impact of lead.

As the passage narrows, the higher the concentration of the impact.

The difference between the inner diameter of the barrel and the internal diameter at the mouth is designated by the word chokage.

Depending on the type of target and the distance to the target, higher or lower chokage will be more appropriate or desired.

Traditionally, firearms chokes have been divided into two families, so-called "fixed chokes" and "interchangeable chokes".

As for the fixed chokes, the chokage is made in the mass of the barrel; for this purpose, the diameter of the barrel is varied to the mouth according to the desired chockage.

These fixed chokes offer the advantage of not requiring additional maintenance.

However, their disadvantage lies in the fact that the chokage can not be changed reversibly depending on the needs of the shooter.

The family of interchangeable chokes is also known.

An interchangeable choke includes a bushing made of treated steel, which is attached to the inside of the muzzle of the barrel.

Here again, the principle of chokage is based on a reduction of the internal diameter towards the mouth of the barrel.

The advantage of this family is that the chokage can be easily adapted to the needs of the shooter by mounting a choke having another configuration of the output diameter or by using a variable choke choke.

One of the drawbacks of these interchangeable chokes lies in the fact that they tend to unscrew during firing.

Another disadvantage of these interchangeable chokes lies in the fact that they can hang in the barrel.

Indeed, between the outer diameter of the choke and its housing in the barrel, is provided an essential functional game.

Nevertheless, because of this, residues of powder, wad, lead, etcetera can penetrate in the space between the choke and the barrel, so that, over time, this deposition of dirt can make that the choke hangs in the barrel of the gun.

In this case, we sometimes have to resort to using a gunsmith to disassemble parts or it becomes quite impossible to separate them without damaging them.

The problem is manifested especially in chokes embodiments which have an external screw thread through which the choke can be screwed into the housing of the barrel, this housing being provided for this purpose with a corresponding screw thread. Since most of the time a fine screw thread is favored, this mechanism represents a delicate point of the screwed choke.

A firearm according to the preamble of claim 1 is disclosed in the document US4386477 .

The present invention aims to provide a solution to one or more of the aforementioned drawbacks as well as others.

For this purpose, the invention relates to a smooth-bore firearm, the barrel being provided with an interchangeable choke in the form of a bush which is housed in a housing of the barrel, the choke being provided at one end oriented towards the mouth of the barrel, mechanical coupling means for mounting and dismounting the choke, the choke being provided with sealing means at its other end facing towards the inside of the barrel, characterized in that the sealing means are made using a sealing ring of a flexible material such as rubber, elastomer or heat-shrinkable material, or a piston ring according to the principle used for sealing the cylinders in an engine with combustion, the sealing ring or the piston ring is housed in a necking in the outer surface of the choke; and the necking is located in a beveled portion of the choke which narrows toward the other end facing the barrel.

To this end, the invention also relates to an interchangeable choke for a smooth-bore firearm, said choke being provided with mechanical coupling means for mounting and dismounting the choke, characterized in that the choke is provided with means additional sealing to give the choke, at least in one place, a seal relative to the barrel.

An advantage associated with the use of the sealing means lies in the fact that the choke has practically no possibility of locking in its mounting position since these means make the dirt, mainly residues of Powder, wad or lead will not have the possibility of being deposited between the choke and the housing of the choke in the barrel, so that the choke, even after long shooting sessions, can be dismounted without problem.

An additional advantage to the deposition of dirt is that it facilitates the maintenance of the choke and the barrel, so that we can do without the intervention of a specialist armament.

An advantage of this embodiment lies in the fact that the choke has practically no opportunity to unscrew during the shot. The frictional forces that result from contacting the compressed sealing ring ultimately result in a torque that opposes the force torque required to disassemble the choke.

By applying the sealing ring in a necking of the outer surface, it prevents a displacement of the sealing ring during the insertion of the choke into the barrel.

Alternatively, the sealing means can be fixed permanently on the choke, for example by molding the sealing means on the choke or using special glues.

Instead of seals made of flexible materials, rigid materials such as metals or hard plastics can also be used.

When this type of material is used, it is possible, for example, to produce the seals in the form of a piston ring in accordance with the principle used for sealing the cylinders in a combustion engine.

• la figure 1 représente, de manière schématique et dans une vue en coupe, un choke interchangeable selon l'invention, monté dans le canon d'une arme à feu à canon lisse ;
• la figure 2 représente, à une plus grande échelle, la partie représentée par F2 en figure 1 ;
• la figure 3 représente une vue analogue à celle de la figure 1, mais par laquelle on représente le choke à l'état partiellement démonté.
• la figure 4 représente une vue analogue à celle de la figure 1, mais pour une configuration comprennant deux anneaux d'étanchéité

In order to better indicate the characteristics of the invention, an embodiment of the invention is described below, by way of example and without any limiting character, preferred embodiment of an interchangeable choke according to the invention for a smooth-bore firearm, with reference to the accompanying drawings in which:

• the figure 1 schematically shows in sectional view an interchangeable choke according to the invention mounted in the barrel of a smooth-bore firearm;
• the figure 2 represents, on a larger scale, the part represented by F2 in figure 1 ;
• the figure 3 represents a view similar to that of the figure 1 , but by which we represent the choke in the partially disassembled state.
• the figure 4 represents a view similar to that of the figure 1 , but for a configuration comprising two sealing rings

The operation of the device is very simple and as indicated below.

In figure 1 , schematically represents the end of the side of the mouth 1 of a barrel 2 in which is mounted a choke 3.

The choke 3 consists mainly of a bush 4 having a predominantly cylindrical outer surface 5 and an inner surface 6 which forms a passage for the lead, which extends narrowing in the direction of an end 7 of the bushing 4 , more precisely the end 7 facing the muzzle of the barrel 1.

This end 7 is provided with mechanical coupling means which, in this case, are in the form of an external screw thread 8 over a certain length of the nozzle 4 and which can cooperate with an internal screw thread. 9 which is provided in the barrel 2, more precisely at the mouth of the barrel 1, the barrel being provided with a housing 10 in the form of a portion of the barrel 2 having an internal diameter D which is greater than internal diameter d of the core 11 of the barrel 2.

At the other end 12 of the choke 3, more precisely the end 12 facing inwards, there is provided a tapered beveled portion 13 which extends conically tapering towards the corresponding end 12.

The housing 10 of the barrel 2 has a corresponding bevel 14 which extends narrowing in a direction which deviates from the mouth of the barrel 1.

The tapered portion 13 of the choke 3 is provided with a constriction 15 in which there are provided sealing means which are in the form of a sealing ring 16 made of elastomer or heat-shrinkable material.

The dimensions of the choke 3 and the housing 10 of the barrel 2 are such that one always obtains the presence of a functional clearance 17 between the two.

The diameters indicated in figure 1 , respectively d1 at the end 7 of the choke 3 and d of the core 11, determine the chokage of the choke 3.

The use of a choke 3 according to the invention is very simple and as indicated below.

The choke 3 is disposed with its conical end 12 in the housing 10 of the barrel 2 and then, as shown in FIG. figure 3 it is screwed in using screw threads 8 and 9, so that the sealing ring 16 is compressed between the beveled portion 13 of the choke 3 and the bevelled portion of the barrel 2, in order to obtain a decisive seal which makes impossible the incrustation of residues of powders when firing a cartridge, in the space provided by the functional clearance 17 between the two parts.

Thanks to the corresponding beveled portions 13 and 14, the centering of the choke 3 is facilitated during its assembly, and the initiation of the screw connection formed by the screw threads 8 and 9 is simplified.

The length of the choke is preferably such that, during the priming of the screwing, the sealing ring 16 does not come into contact with the barrel 2.

Therefore, in this priming phase, one does not face forces emanating from a contact between the sealing ring 16 and the barrel 2, so that the first part of the assembly takes place with ease.

In the second phase, it is after having already sufficiently screwed the choke 3 and the barrel 2 into each other to ensure a good connection that is placed the sealing ring 16 in contact with the barrel 2 .

When continuing the screwing, the sealing ring 16 is compressed to be able to play its role of sealing means.

During a firing session, the seal thus produced will prevent the penetration of powder residues through this sealing ring 16. Therefore, the sensitive connection by screw thread 8-9 and the space provided for the functional play 17 remain safe from a dirt deposit.

Thus, we obtain a possibility of disassembly without problems and we limit the necessary maintenance.

Another embodiment of the invention is represented in the figure 4 and consists in providing choke 3, in addition to a first sealing ring 16 on the soul side, of a second sealing ring 18 on the mouth side. This sealing ring 18 can be made using the same means as those available for producing the first sealing ring 16. This variant has the advantage that after the complete introduction of the choke 3, the water penetration between the outside of the choke 3 and its housing 10 in the barrel 2 will be impossible, as well as contamination by any parasitic particles that could generate oxidation and adhesion between the barrel 2 and the choke 3 Instead of the sealing ring 16, it is also possible to use the variants described above without departing from the scope of the invention.

The present invention is in no way limited to the embodiment described by way of example and shown in the figures.

Claims (10)

1. Firearm with a smooth gun barrel, with an exchangeable choke (3) formed by a bushing that is lodged in a housing (10) of the gun barrel (2), whereby the choke (3) is provided with mechanical coupling means (8-9) for mounting and dismounting the choke (3) at the end towards the mouth (1) of the gun barrel (2), and whereby the choke (3) is provided with sealing means (16) at the other end (12) towards the inside of the gun barrel (2), characterized in that :

   - the sealing means (16) comprises a sealing ring made of a flexible material such as rubber, elastomer or thermoretractable material, or from a piston segment as used for the sealing of cylinders in a combustion engine;

   - the sealing ring or the piston segment is located in a contraction (15) in the external surface of the choke (3), and ;

   - the contraction (15) is located in a bevelled part (13) of the choke that retracts towards the other end (12) to the inside of the gun barrel (2).
2. Firearm according to claim 1, characterised in that the aforesaid mechanical coupling means (8-9) are made in the form of a screw thread.
3. Firearm according to claim 1 or 2, characterised in that the aforesaid sealing means (16) are realised by means of a sealing ring made of a piston segment made of a rigid material such as for example metal or a hard plastic.
4. Firearm according to any one of the preceding claims, characterised in that the sealing means (16) are permanently applied on the busher (4) of the choke, for example by means of moulding.
5. Firearm according to any one of the preceding claims, characterised in that the sealing means (16) are applied by creating a contraction in the external surface (15) of the choke (3).
6. Firearm according to claim 5, characterised in that the contraction (15) is provided at a bevelled part (13) of the busher (4).
7. Firearm according to claim 6, characterised in that the bevelled part (13) narrows conically.
8. Firearm according to claim 1, characterised in that the sealing means (16 and 18) are provided at the two far ends (7 and 12) of the busher (4).
9. Firearm according to claim 1, characterised in that the aforesaid mechanical coupling means (8-9) are realised as a threaded connection, such that, as soon as the choke (3) is screwed down catches in the gun barrel (2), the sealing means (16) will not make contact with the gun barrel (2).
10. Fire arm according to any one of the preceding claims, characterised in that the choke (3), on its external surface (5), and the housing (10) for the choke (3) in the gun barrel (2), have a cylindrical configuration over their entire length.

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