RU2807771C1 - Silencer for firearms, housing for this silencer and expansion chamber block for this muffler (options) - Google Patents

Abstract

FIELD: weaponry.

SUBSTANCE: silencers for weapons. The silencer contains a tubular body in which a flange plug is fixed, connected to a bushing for inserting the weapon barrel from the muzzle end of the latter and dividing the pipe cavity into two chambers communicating through channels in the bushing. In the second chamber, in the direction from the muzzle of the weapon, separators are fixed, arranged in series and forming a block of expansion chambers. The body on the bullet exit side is made with a screw thread for screwing in the end cap with a hole for the bullet and a central annular protrusion with an external screw thread for installing a muzzle brake. Behind the section with this screw thread, on the same wall of the housing, a screw thread is formed for screwing the block of expansion chambers all the way into the shell with holes in the cylindrical wall, which is pressed against the plug with holes in the flange. In the section of the screw thread of the housing for screwing in the block of expansion chambers, an additional screw thread is made with an angle of inclination of the turns and a width of the turns greater than the angle of inclination and width of the turns of the screw thread for the block of expansion chambers. The recesses of the additional screw thread on the bullet exit side are connected through holes in the end plug with the external environment, and on the bushing side - with the cavity formed between the inner wall of the body and the outer wall of the shell, located between the block of expansion chambers and the bushing.

EFFECT: improving the durability and reliability of the muffler.

5 cl, 9 dwg

Description

The invention relates to multi-chamber expansion-type silencers designed for mechanical suppression of sound when fired from small arms with a low unmasking effect.

Expansion-type multi-chamber muzzle devices are muzzle attachments for standard weapons, in which transverse diaphragms divide the internal volume of the device body into separate compartments - expansion chambers. The action of most of them is based on considering the flow of powder gases as an ideal gas, subject to the Boyle-Mariotte and Gay-Lussac laws. According to the Boyle-Mariotte law, the product of pressure and volume of a given mass of gas is directly proportional to its temperature. Thus, a decrease in the pressure of the flow of powder gases - and hence a decrease in the sound level of the shot - can be achieved by increasing their volume and decreasing the temperature before release into the external environment. Powder gases, moving after the bullet, consistently expanding and cooling in the silencer chambers, gradually lose their energy, significantly reducing the sound pressure at the output of the device and reducing the flash of the shot.

Thus, an expansion-type muffler for firearms is known, containing a body in the form of a seamless pipe carrying bushings welded into this pipe at the ends, one of which is made with a hole for a bullet, and the other with a hole for inserting a firearm barrel into the cavity of the pipe, in in the middle part of the pipe there is a bushing for screwing in the barrel of the weapon from the muzzle end of the latter, dividing the cavity of the pipe into two chambers, the first of which, located before the muzzle of the weapon, communicates with the second, located after the muzzle of the weapon, through channels in the bushing used for screwing the barrel of the weapon, and in the second chamber in the direction from the muzzle of the weapon there is fixed, forming the first expansion chamber, a cone-shaped partition welded to the pipe wall with a central hole for the bullet, and a number of partitions attached to the pipe wall with a central hole for the bullet, which are located one behind the other and in direction towards the bullet hole at the end of the body and are each made in a toroidal shape to form a number of sequentially located additional expansion chambers, the wall of the cone-shaped partition is made thicker than the thickness of the walls of the other partitions and inclined with the imaginary top of the cone towards the first chamber, to direct the flow of gases into the side of the holes made in the wall of the cone-shaped partition, and towards the channels in the sleeve used for screwing in the barrel of the weapon, while in the walls of the partitions of the toroidal shape there are holes made in the areas of their attachment to the pipe to form channels connecting additional expansion chambers and these chambers with the first expansion chamber, and in the walls of the partitions there are holes that are not coaxial with each other, located non-concentrically to each other (RU 190816, F41A 21/30, publ. July 12, 2019).

This solution was adopted as a prototype.

The disadvantages of the known muffler are the difficult removal of heated powder gases from the preliminary expansion chamber due to the rapid increase in pressure and the insufficient cross-section of the passage holes. The pressure of the powder gases in the barrel reaches 200 atmospheres, and the temperature - 1000 degrees. As a result, this leads to an excessive increase in pressure in the return mechanism on automatic and semi-automatic weapons. In addition, the muffler has a low service life due to the fact that it is welded, which leads to its deformation and failure of the entire structure. In fact, such a muffler is a non-repairable product, the lifespan of which is determined by the breakdown of the part that has low survivability. On the one hand, welding allows you to quickly and firmly connect parts in a product, and on the other hand, welding points or lines are stress concentrators since it is at these points and lines that the structure of the metal is changed by thermal heating. When heated powder gases pass through, the metal elements of the muffler are heated, and the elastic characteristic of the metal at the welding points is significantly lower than the elastic characteristic of the metal in the unwelded zones. This leads to deformation of the body and, as a consequence, to deformation and loss of shape of the muffler elements associated with the body.

If we evaluate the effectiveness of a known silencer in general, we can say that its properties in reducing the sound wave of a shot decrease when firing in bursts due to the fact that the expansion chambers switch to the mode of pressure-locked cavities in them. At the same time, high pressure of powder gases is also created in the bullet channel of the barrel (according to Pascal’s law), which creates increased pressure in the return mechanism on automatic and semi-automatic weapons. The only way to reduce the pressure in the chambers is for gases to escape through the bullet holes. But it is precisely this hole that causes the formation of a supersonic wave. In addition, the reduction in sound waves directly depends on the temperature of the gases, which must decrease from the muzzle of the weapon to the outlet from the muffler. And this is only possible if gas heat exchange is ensured. But in locked mini-chambers there is a process of constant heating of gases from the gas flow of the next shot. Therefore, the known silencer can function normally only for weapons in single-shot mode (that is, with breaks between shots). And for automatic and semi-automatic weapons, such a silencer quickly loses its resource and does not adequately demonstrate those qualities of reducing the pressure of the flow of powder gases (to reduce the sound level of a shot), which the user expects to receive from the use of a silencer in accordance with its functional purpose.

The objective of the invention is to eliminate these disadvantages and increase the service life of the muffler.

The invention is aimed at achieving a technical result consisting in increasing durability and reliability by eliminating welding connections and making a muffler structure assembled from separate replaceable modules.

The specified technical result is achieved by the fact that in a silencer for firearms, containing a body in the form of a seamless pipe, in which a plug with a flange is fixed, connected to a sleeve for inserting the barrel of a weapon from the muzzle side of the latter and dividing the pipe cavity into two chambers, the first of which , located before the muzzle of the weapon, communicates with the second, located after the muzzle of the weapon, through channels in this sleeve, and in the second chamber in the direction from the muzzle of the weapon, separators with a central hole each for a bullet are fixed, located sequentially and at a distance from each other along the longitudinal axis of the body to form a block of expansion chambers, the body in the form of a seamless pipe on the bullet exit side is made on the inner wall with a screw thread for screwing in an end cap with a hole for the bullet and a central annular protrusion with an external screw thread for installing a muzzle brake, behind the area with with a screw thread for screwing the end plug on the same wall of the housing, a screw thread is formed for screwing the block of expansion chambers all the way into the shell with holes in the cylindrical wall and pressing this shell against the plug with a flange. an additional screw thread is made with an angle of inclination of the turns and a width of the turns greater than the angle of inclination and width of the turns of the screw thread used to screw in the block of expansion chambers, and the recesses of the additional screw thread on the side of the bullet exit are communicated through holes in the end plug used to install the muzzle brake, with the external environment, and on the side of the bushing dividing the pipe cavity into two chambers, with a cavity formed between the inner wall of the housing and the outer wall of the shell, located between the block of expansion chambers and the bushing dividing the pipe cavity into two chambers.

The specified technical result is also achieved by the fact that the silencer body for a firearm is a seamless pipe, on the bullet exit side, made on the inner wall with a screw thread for screwing in an end cap with a hole for the bullet and with holes around the hole for the bullet, behind the area with the screw threading for screwing the end plug on the same wall of the body forms a screw thread used for screwing in the block of expansion chambers; in the section of the screw thread of the body used for screwing in the block of expansion chambers, an additional screw thread is made with an angle of inclination of the turns and a width of the turns greater than the angle of inclination and the width of the turns of the screw thread used to screw in the block of expansion chambers, the recesses of the additional screw thread on the bullet exit side are connected through holes in the end plug with the external environment, and on the muzzle side with an annular cavity formed in the inner wall in the area behind the area with the screw thread , used for screwing in a block of expansion chambers and the depth of which is not less than the depth of the recesses of the additional screw thread.

The specified technical result is also achieved by the fact that the block of expansion chambers for a silencer for firearms is a cylindrical body with a screw thread on the outer wall for fastening in the silencer body, in which separators in the form of disc-shaped plates are placed sequentially and at a distance from each other with a central hole for a bullet in each, connected along the outer contour to the inner wall of the body, with each plate in the area of the bullet hole made with a conical bend of the wall, the smaller base directed towards the muzzle, and the larger base turning into a flat one transversely oriented to the axis holes for a bullet, a wall that is arcuately bent towards the muzzle and is made with a height exceeding the height of the conical bend of the wall.

The specified technical result is also achieved by the fact that the block of expansion chambers for a muffler for firearms, characterized in that it is made in the form of a set of cylindrical modules, each of which is made with an external screw thread for fastening in the muffler body, with each module being glass-shaped forms with a central hole for a bullet, in the wall on the inner surface of the bottom part of the module there are cylindrical recesses made around the bullet hole, the axes of which are directed along the axis of the bullet hole and communicated with the cavity of the bullet hole, and on the outer surface the bottom part is made in the form of a cylindrical the form of a protrusion, on the outer wall of which there are open recesses, the axes of which are directed along the axis of the hole for the bullet, wherein one part of this cylindrical protrusion is made in height less than the other part of this protrusion, and when forming a block of expansion chambers, one module with the said protrusion is placed in the cavity of another module opposite the inner wall of the bottom part with contact support of the screw thread-bearing side walls of adjacent modules.

These features are essential and are interrelated to form a stable set of essential features sufficient to obtain the required technical result.

The present invention is illustrated by specific examples of implementation, which, however, are not the only possible ones, but clearly demonstrate the possibility of achieving the required technical result.

In fig. 1 shows a longitudinal section of the muffler housing;

fig. 2 - the same as in Fig. 1, with pre-expansion chamber elements;

fig. 3 - fragment of a section of the body with combined screw threads;

fig. 4 - block of expansion chambers with separators;

fig. 5 - muffler assembled with the side of the expansion chambers according to FIG. 4;

fig. 6 - longitudinal section of the expansion chamber block module;

fig. 7 - view A according to FIG. 6;

fig. 8 - view B according to FIG. 6;

fig. 9 - muffler assembled with a side of expansion chambers, consisting of modules according to FIG. 6.

According to the claimed invention, an expansion-type muffler device for firearms is considered.

A feature of the claimed muffler is that the body and all parts placed in the body are made in the form of separate structural modules, which are connected to the body via screw connections. In this case, the muffler acquires high maintainability and a high degree of various modifications due to the addition of individual units, the exclusion of individual units, or the replacement of one unit with a similar one with higher characteristics.

An expansion-type silencer for firearms, including automatic and semi-automatic ones, contains as a basic element a housing 1 in the form of a seamless pipe. Making the tubular body seamless ensures equal strength of the structure according to the structure of the wall material, preservation of the elastic characteristics of the material at any point of the body and the same degree of expansion of the material when the body is heated. This indicates that when heated, the body will not deform relative to its longitudinal axis - the vector of the bullet’s departure (Fig. 1).

In the middle part of the body there is a flange plug 2 connected to a sleeve 3 for inserting the weapon barrel from the muzzle end of the latter (Fig. 2). This sleeve 2 divides the cavity of the pipe into two chambers, the first of which, located before the muzzle of the weapon, communicates with the second, located after the muzzle of the weapon, through channels 3 in this sleeve (the channels are made in the form of holes 4 in the flange of the plug 2).

The plug 2 is made in the form of a part located transversely in the body with a conical flange and with a central hole for the bullet and with holes in the flange for passing powder gases into the cavity, which is formed between the wall of the body 1 and the sleeve 3 for the barrel. This cavity forms a pre-expansion chamber to relieve the initial peak gas pressure during firing.

On the section of the inner wall of the housing where the flange plug 2 is located, a screw thread 5 is made, and on the side wall of the plug there is a counter screw thread. During assembly, the plug is screwed into the housing.

Around the bullet hole on the flange plug there is an annular protrusion 6, which also carries a screw thread for screwing bushing 3 onto it for inserting the weapon barrel.

When screwing the bushing 3 onto the protrusion 6, the flange 7 of the bushing rests against the end 8 of the housing 1 (Fig. 2)

The second chamber in the direction from the muzzle of the weapon (from plug 2) is used to install a block of expansion chambers from separators with a central hole each for a bullet, sequentially and at a distance from each other located along the longitudinal axis of the body.

The housing 1 on the bullet exit side is made on the inner wall with a screw thread 9 (Fig. 1) for screwing in the end cap 10 (Fig. 6) with a hole for the bullet and with a central annular protrusion 11 with an external screw thread 12 for installing a muzzle brake 13 ( Fig. 5). The end plug on the side wall is made with a screw thread, corresponding to the screw thread 9 on the body 1. When screwed in, this plug 10 rests with a shoulder against the end of the body 1. In the flange part of the plug 1, through holes 14 are made to communicate the body cavity with the external environment (atmosphere) . Alternatively, the muffler may only carry an end cap, as shown in FIG. 9, or a muzzle brake is screwed onto this plug, as shown in FIG. 5.

Behind the section with a screw thread 9 (for screwing on the end cap 10), a screw thread 15 is formed on the same wall of the housing (Fig. 1 and 3) for screwing in a block 16 of expansion chambers (for example, in Fig. 4). In this case, in the section of the screw thread 15 used for screwing in the block 16 of the expansion chambers, an additional screw thread 17 is made with an angle of inclination of the turns and a width of the turns greater than the angle of inclination and width of the turns of the screw thread 15. The recesses of the additional screw thread 17 on the side of the bullet exit are communicated through the holes 14 in the end plug 10 with the external environment, and on the side of the flange plug 2, dividing the pipe cavity into two chambers, with cavity 18 (Fig. 1). This cavity is formed between the inner wall of the housing 1 and the outer wall of the shell 19, located between the block 16 of expansion chambers and the flange plug 2. The shell 19 in the form of a thin-walled sleeve is made with holes 20 in the side wall. The inner cavity of the shell communicates with the area in front of the flange plug 2, into which powder gases enter when fired. This cavity separates the gases into the first flow, which goes behind the bullet into the block 16 of expansion chambers, and into the second flow, redirected through the holes 20 into the cavity 18 (Fig. 2). During separation, the total volume of gases is divided and in each flow decreases due to a change in the movement vector. From the cavity 18, gases under pressure are directed along the recesses of the screw thread 17 along the outer surface of the block 16 of expansion chambers in the direction of the holes 14 of the flange plug 10. With this design, the degree of noise reduction significantly increases, since the decrease in pressure in the block 16 occurs with a reduced volume of powder gases . When moving along the recesses of the screw thread 17, the movement vector constantly changes, which leads to the damping of the movement energy and a decrease in pressure.

It is important that after screwing in, the two nodes must be pressed against each other in order to prevent displacement and shifting of the nodes. When screwing in the expansion chamber block 16, this block 16 rests against the shell 19 and presses it against the flange plug 2. After this, the end plug 10 is screwed in and presses the end of the expansion chamber block 16 with it. If necessary, use a washer 21 (Fig. 9) with a central hole through which the end plug 10 will press the block 16. It all depends on the design of the block 16 itself and its size along the length.

Since welding, as a method of connecting assemblies and parts together, is not used in the claimed design, but a threaded connection is used, then pressing all the way is necessary. The need is due to the fact that on the screw thread line the pressure force of the powder gases is decomposed into a transverse component relative to the longitudinal axis of the body 1 and a longitudinal component. The transverse component does not participate in the organization of displacements, but the longitudinal component causes a shift along the longitudinal axis of the housing 1. In the claimed solution, a block 16 of expansion chambers and an end plug 10 are screwed along the longitudinal axis of the housing, which supports this block. Even when using screw threads with the same parameters, the block 16 is secured in the housing like a lock nut, where the end plug 10 serves as a lock nut.

Thus, the muffler is designed in such a way that all parts and blocks in it are secured by means of a threaded connection, which makes it possible to replace one part with another during repairs or with more advanced parameters. At the same time, the silencer becomes repairable and has the possibility of modernization and improvement depending on the type of weapon used.

For example, the block 16 of expansion chambers (Fig. 4) for the claimed muffler may be a cylindrical body 22 with a screw thread on the outer wall for fastening in the muffler body 1. In the housing 22, separators are placed sequentially and at a distance from each other in the form of disc-shaped plates 23 with a central hole for a bullet in each. These plates are connected along the outer contour to the inner wall of the body 22. Each plate in the area of the bullet hole is made with a conical bend 24 of the wall, directed by the conditionally smaller base towards the muzzle, and by the conditionally larger base turning into a flat wall transversely oriented to the axis of the bullet hole 25, which is arcuately bent towards the muzzle and is made with a height exceeding the height of the conical bend 24 of the wall.

When fired, the flow of gases under pressure in the first expansion chamber is divided into a part of the flow that leaves along with the bullet through the through holes in the plates. The second part of the gas flow unfolds on the conical surface of the plate and is directed tangentially to the periphery of the plate. The first part of the flow, passing the minichambers between the plates, expands and fills the cavity of each minichamber, while the pressure (due to the expansion of the flow) drops and its temperature drops. The minimum gas pressure is formed in the last mini-chamber during the flight of the bullet at the end cap 10. When firing in bursts, when the process of formation of gas pressure at the exit from the muzzle of the weapon takes on a temporarily almost constant character, in which pressure peaks follow at the rate of shots. In this mode, the pressure in the pre-expansion chamber quickly increases and practically becomes equal to the pressure before entering block 16. The flow of gases into the expansion chambers of block 16 is slowed down. Excess gas under pressure in front of the first expansion chamber of the block leaves through the separator holes into the channels formed by the recesses of the screw thread 17, thereby creating an ejector effect, leading to the removal of gases from the pre-expansion chamber. The presence of heat exchange due to the constant flow of gases in ejector mode is essential. In this regard, the declared silencer has a longer service life when working with automatic and semi-automatic weapons.

This example shows a non-separable design of a block of separators, between which mini-chambers for extinguishing the energy of powder gases are formed. When it fails (the appearance of increasing gunshot noise means the destruction of at least one separator), this block is unscrewed and replaced with the same block or with a modular version of the block 16 expansion chambers, shown in Fig. 9 and fig. 6-8.

The modular design of the expansion chamber block shown assembled in FIG. 9, for the claimed muffler, is made in the form of a set of cylindrical modules 26, each of which is made with an external screw thread 27 for fastening in the muffler body. This thread is in response to the screw thread 15 on the inner surface of the wall of the housing 1. Each module is made in a glass shape with a central hole for a bullet; in the wall 28 on the inner surface of the bottom part of the module, cylindrical recesses 30 are made around the hole 29 for the bullet, the axes of which are directed along the axis bullet holes (Fig. 6 and 7). The cavities of these recesses communicate with the cavity of the hole 30 for the bullet.

On the outer surface, the bottom part 31 (Figs. 6 and 8) is made in the form of a cylindrical protrusion, on the outer wall of which there are open recesses 32, the axes of which are directed along the axis of the hole 30 for the bullet. In this case, one part of this cylindrical protrusion is made in height less than the other part of this protrusion. When forming a block 16 of expansion chambers, one module with the indicated protrusion is placed in the cavity of another module opposite the inner wall of the bottom part with contact support of the side walls of adjacent modules bearing screw threads (Fig. 9). This version of the modular design of block 16 allows you to change the vector of movement of the powder flow, redirecting it to the labyrinth area between the protrusion of one module embedded in an adjacent module. In this case, when the direction of movement changes, gas enters the cavities of the recesses, which extinguish the energy of the flow and introduce turbulence into the flow itself. In fact, the cavities of these recesses are local resistances.

The muffler expansion chamber unit 16 is based on the application of the condition that the flow of pressurized gases always moves towards the low pressure region. In the claimed muffler, due to the ejection phenomenon in the chambers located at the exit of the bullet from the body, the pressure is always less than the pressure in other chambers. This ensures a constant flow of gases. When firing stops, gases escape into the atmosphere through the channels and the central bullet span and release all chambers, equalizing the pressure in them to atmospheric levels. At this moment, all metal elements of the muffler are cooled, as in all known mufflers. Since during operation of the silencer there is an escape of gas under pressure towards the low pressure area at the exit of the bullet from the pipe, there are no conditions for the flow of gas into the muzzle opening to influence the operation of the mechanisms of the weapon itself.

The present invention is industrially applicable and can be manufactured using technologies used in the production of small arms weapons equipment. A feature of the claimed muffler is its modularity, which makes it possible to transform the muffler from a disposable product into a repairable and modifiable one without changing the layout as a whole. At the same time, the reliability and durability of the product significantly increases due to the elimination of welding joints, since when heated and overheated, the material of each steel part connected by a threaded connection to another part expands and selects gaps in the threaded connection, which eliminates the transfer of deformation loads from one part to another and does not lead to a change in the geometric shape of the silencer as a whole, which could affect the accuracy of the spatial position of the bullet departure line.

Claims (4)

1. A silencer for a firearm, containing a body in the form of a seamless pipe, in which a plug is fixed with holes in the flange, connected to a sleeve for inserting the weapon barrel from the muzzle end of the latter and dividing the pipe cavity into two chambers, the first of which is located before the muzzle cut of the weapon, communicates with the second, located after the muzzle of the weapon, through channels in this sleeve, and in the second chamber, in the direction from the muzzle of the weapon, separators with a central hole each for a bullet are fixed, sequentially and at a distance from each other located along the longitudinal axis of the body to form a block of expansion chambers, characterized in that the body in the form of a seamless pipe on the bullet exit side is made on the inner wall with a screw thread for screwing in an end plug with a hole for the bullet and a central annular protrusion with an external screw thread for installing a muzzle brake, behind the section with with a screw thread for screwing the end plug on the same wall of the housing, a screw thread is formed for screwing the block of expansion chambers all the way into the shell with holes in the cylindrical wall and pressing this shell against the plug with holes, while in the area of the screw thread of the housing for screwing in the block of expansion chambers additional screw thread with an angle of inclination of turns and a width of turns greater than the angle of inclination and width of the turns of the screw thread used to screw in the block of expansion chambers, and the recesses of the additional screw thread on the side of the bullet exit are communicated through holes in the end plug used to install the muzzle brake, with external environment, and from the side of the sleeve dividing the pipe cavity into two chambers - with a cavity formed between the inner wall of the housing and the outer wall of the shell located between the block of expansion chambers and the sleeve dividing the pipe cavity into two chambers. 2. A silencer body for a firearm, characterized in that it is a seamless pipe, on the bullet exit side, made on the inner wall with a screw thread for screwing in an end cap with a hole for the bullet and with holes around the hole for the bullet, behind the area with a screw thread for screwing the end plug on the same wall of the housing, a screw thread is formed, used for screwing in the block of expansion chambers; in the section of the screw thread of the housing, used for screwing in the block of expansion chambers, an additional screw thread is made with an angle of inclination of the turns and a width of turns greater than the angle of inclination and width of the turns a screw thread used to screw in a block of expansion chambers, the recesses of the additional screw thread on the bullet exit side are connected through holes in the end plug with the external environment, and on the muzzle side - with an annular cavity formed in the inner wall in the area behind the area with the screw thread, used for screwing in the block of expansion chambers and the depth of which is not less than the depth of the recesses of the additional screw thread. 3. A block of expansion chambers for a silencer for firearms, characterized in that it is a cylindrical body with a screw thread on the outer wall for fastening in the silencer body, in which separators in the form of disc-shaped plates with a central a hole for a bullet in each, connected along the outer contour to the inner wall of the body, while each plate in the area of the bullet hole is made with a conical bend of the wall, the smaller base directed towards the muzzle, and the larger base turning into a flat one transversely oriented to the axis of the hole for bullet wall, which is arcuately bent towards the muzzle and is made with a height exceeding the height of the conical bend of the wall. 4. A block of expansion chambers for a silencer for firearms, characterized in that it is made in the form of a set of cylindrical modules, each of which is made with an external screw thread for fastening in the silencer body, while each module is made of a glass-shaped shape with a central hole for a bullet, in the wall on the inner surface of the bottom part of the module, cylindrical recesses are made around the bullet hole, the axes of which are directed along the axis of the bullet hole and communicate with the cavity of the bullet hole, and on the outer surface the bottom part is made in the form of a cylindrical protrusion, on the outer wall of which there are open recesses, the axes of which are directed along the axis of the bullet hole, wherein one part of this cylindrical protrusion is made in height less than the other part of this protrusion, and when forming a block of expansion chambers, one module with the said protrusion is placed in the cavity of another module opposite the inner wall of the bottom part with a contact by supporting the screw-threaded side walls of adjacent modules.

Images