RU2777507C1 - Electrical cartridge for remote shock device - Google Patents

Abstract

FIELD: electroshock devices.

SUBSTANCE: cartridge for a remote-action electroshock device contains a body with a guide channel made, containing a working channel, in which a propellant charge and a wad or a pusher are placed, and an accelerating channel coaxial with the working channel. In the accelerating channel there is a projectile electrode-probe, mechanically interacting with its rear end with a wad or a pusher, equipped with a needle in its front part. The needle is made with a beard and electrically interacts with a flexible electrical conductor. In the accelerating channel, a rifling or a leading belt is made. The body of the electrode-probe is made in the form of a core and a shell made with the possibility of rotation around its longitudinal axis. On the outer surface of the electrode-probe, a leading belt is made corresponding to the grooves of the accelerating channel or a groove corresponding to the leading belt or leading belts of the accelerating channel.

EFFECT: increasing the range and stability of the flight of probe electrodes, improving the accuracy of fire of a remote-action electroshock device.

9 cl, 4 dwg

Description

Application area

The device relates to electric shock devices of remote action, in particular, to the means of delivering electric current from an electroshock device to a target using flexible electrical conductors.

State of the art

Electroshock devices of remote action or ESHU DD are a modern type of non-lethal weapon successfully used by law enforcement officers for law enforcement, as well as citizens for self-defense.

The action of the EShU DD is ensured by organizing an electrical contact between the output electrodes of the device and the target, mainly with the help of a shot from a cartridge - a replaceable device attached to the EShU DD to provide remote impact on the target and containing at least two electrodes thrown towards the target as a result of the shot - probe, electrically interacting with the output electrodes of the EShU using flexible electrical conductors (FEC). The stack with the GEF, as a rule, made in the form of a single-layer spiral or a multilayer coil of insulated, bare or partially insulated wire, can be placed in a cavity made in the cartridge body, or in a cavity made in the probe electrode itself, or in both of the mentioned cavities . During the flight of the electrode-probe, the GEP is pulled out of the cavity or cavities, maintaining the electrical connection between the electrode-probe and the corresponding output electrode of the EShU DD, thereby providing an electrical effect on the offender.

The important ballistic parameters of the thrown electrodes-probes, which determine the operational and tactical properties of the EShU DD, are:

- stability of the flight trajectory of the thrown electrodes-probes;

- flight range of the thrown electrodes-probes;

- Accuracy of shooting.

An electric cartridge for EShU DD is known, containing a housing with a removable installation mechanism on an electroshock device, equipped with electrical contacts located with the possibility of electrical communication with an electroshock device, a propellant charge placed in a working channel made in the housing, placed in accelerating channels made in the housing, mainly coaxial with corresponding working channels, which in pairs make up guide channels, two probe electrodes, as well as two ejected flexible electrical conductors placed in cavities made in the housing [1, 2]. The disadvantage of the devices is the low stability of the electrode-probes on the trajectory due to their relatively small mass, the limited flight range determined by the relatively low initial velocity of the probes from the cartridge (due to a significant decrease in the probe flight trajectory at distances exceeding 5 m) and, as consequently, low accuracy of fire, in which the spread of points of contact of electrode-probes on the target from shot to shot is ± 5 ... 10 cm.

Of the known devices, the closest to the proposed one is an electric cartridge for a remote-action electroshock device, containing a housing with a removable installation mechanism on the electroshock device, equipped with electrical contacts located with the possibility of electrical communication with the electroshock device, propellant charges placed in the working channels made in the housing, placed in electrodes-probes (projectiles) made in the body of accelerating channels, as well as projectile flexible electrical conductors placed in cavities made in the body, the front ends of which electrically interact with the probe electrodes, and the rear ends - with the mentioned electrical contacts [3]. The cartridge is implemented as a BTER product manufactured by the Russian company MART GROUP.

The disadvantage of the device is the low stability of the electrode-probes on the trajectory due to their relatively small mass, the limited flight range determined by the relatively low initial velocity of the probes from the cartridge (due to a significant decrease in the probe flight trajectory at distances exceeding 5 m) and, as as a result, low accuracy of fire, in which the spread of points of contact of electrode-probes on the target from shot to shot is ± 5 ... 10 cm.

Disclosure of invention

The problem solved by the proposed device is to create a cartridge devoid of the shortcomings of the prototype. The technical result provided by the proposed device is to increase the stability of the probe electrodes on the trajectory of their flight, the flight range and the accuracy of fire of the EShU DD.

The problem is solved by the fact that the electric cartridge for a remote-action electroshock device contains a housing with at least one guide channel made in the housing, containing a working channel in which a propellant charge and a wad or a pusher are placed, and an accelerating channel, mainly coaxial with the said working channel , in the accelerating channel there is a projectile electrode-probe, mechanically interacting with its rear end with a wad or a pusher, equipped in its front part with at least one needle electrically interacting with a flexible electrical conductor, made mainly with at least one barb, in the accelerating channel at least one groove or at least one leading belt is made, the body of the probe electrode is made in the form of a core and a shell made with the possibility of rotation around its longitudinal axis, at least one leading belt is made on the outer surface of the probe electrode, corresponding to and grooves of the accelerating channel or at least one groove corresponding to the leading band or leading bands of the accelerating channel.

An additional feature of the device is that the mass of the shell exceeds the mass of the core.

An additional feature of the device is that at least one cavity is made in the cartridge body, in which a flexible electrical conductor is placed, electrically connected to the needle of the corresponding probe electrode with its front end, and with its rear end electrically interacting with the corresponding contact installed on the cartridge body. , made with the possibility of electrical interaction with the corresponding output electrode of the electroshock device.

An additional feature of the device is that in the body of the probe electrode in the cavity between the core and the shell there is a flexible electrical conductor, electrically interacting with its front end with the said probe electrode needle, and with its rear end electrically interacting with a flexible electrical conductor placed in the cavity, made in the cartridge body, or with a contact mounted on the cartridge body, made with the possibility of electrical interaction with the corresponding output electrode of the electroshock device.

An additional feature of the device is that a lubricant based on oil, or graphite, or silicone, or other friction-reducing materials, such as anti-friction coatings, is introduced between the core and the shell of the probe electrode.

An additional feature of the device is that the electrode-probe is provided with front and rear bushings mounted on the core, between which a shell is placed, while the diameters of said bushings do not exceed the diameter of the shell.

An additional feature of the device is that at least one rotation bearing is installed between the core and the shell, the inner ring of which mechanically interacts with the said core, and the outer ring mechanically interacts with the shell.

An additional feature of the device is that the direction of rotation of the probe electrode shell due to its movement along the mentioned grooves is chosen opposite to the direction of rotation of the coils of the flexible electrical conductor when it is pulled out of the probe electrode or the cartridge body, while the pitch of the mentioned grooves can be chosen in such a way that the angular velocity of rotation of the electrode-probe corresponded to the angular velocity of the turn of the coils of the flexible electrical conductor when they were pulled out.

An additional feature of the device is that the depth of the groove is selected in the range from 1.5...5% of the diameter of the said accelerating channel, and the width of the groove field corresponds to half of the groove width.

An additional feature of the device is that in the front part of the device, shutters can be placed, made mainly of non-conductive material, which keep projectiles or coils (stacks) of the mentioned flexible electrical conductors, or a combination of them, from falling out of the housing under external mechanical influences, for example, shock, fall or vibration prior to firing, wherein said shutters break or open or separate from the body when the shot is fired.

An additional feature of the device is that the housing can be made in the form of a monoblock.

An additional feature of the device is that the housing can be made as a composite of an external and an internal block located in it, while the mentioned contacts are placed on the external block, and the said working and accelerating channels with the elements of the device located in them are located in the internal block.

Brief description of the drawings

The design of the device is illustrated by drawings, which show:

Fig. 1. An example of a general view of a single-wire and two-wire version of the device.

Fig. 2. One guide channel design.

Fig. 3. Internal design of the two-wire version of the device.

Fig. 4. Variants of the internal design of the probe electrode.

Detailed description of the invention

On FIG. 1a shows an example of a general view of a single-wire cartridge. In the cartridge body 1 there is one guide channel with an outlet 2 in its front part for throwing a probe electrode, containing coaxial working and accelerating channels (not shown in Fig. 1a). Electrical contacts are installed on the cartridge body to supply high voltage for subsequent impact on the target, as well as contacts to initiate the process of throwing the probe electrode (not shown in Fig. 1a).

To fire a shot from the EShU DD at the target and impact the target with a high voltage current, two such cartridges are required to ensure complete closure of the electrical circuit of the EShU DD - target - EShU DD.

On FIG. 1b shows an example of a general view of a two-wire cartridge of a typical design corresponding to the prototype. The case can be made composite of the outer 4 and the inner 5 blocks (cases) placed in it, while the mentioned contacts are placed on the outer block, and the mentioned working and accelerating channels with the device elements located in them are placed in the inner block. The cartridge 3 includes an outer case 4 and an inner case 5 placed in the outer case 4. In the inner case there are two guiding channels having outlet holes 6 for throwing probe electrodes. Cavities 7 are also made in the inner body 4, intended for laying flexible electrical conductors in them. Electrical contacts are installed on the cartridge body to supply high voltage for subsequent impact on the target, as well as contacts to initiate the process of throwing probe electrodes (not shown in Fig. 1b).

In the front part of the device, shutters can be placed, made mainly of non-conductive material, which keep the thrown electrodes-probes or the stacks of the mentioned flexible electrical conductors, or a combination of them, from falling out of the case due to external mechanical influences, for example, shock, fall or vibration before the shot, at the same time, said curtains are destroyed, or open, or separated from the body when a shot is fired (not shown in Fig. 1b).

On FIG. 2 shows the construction of one guide channel corresponding to section A-A of FIG. 1a.

The guide channel contains a working 7 and accelerating 8 channels. In the general case, the working and accelerating channels are not necessarily coaxial, for example, in some ESD DD Taser cartridges manufactured by the American company AXON they are made at an angle to each other, but in Russian-made cartridges they are predominantly coaxial. First of all, such a constructive solution (alignment of the working and accelerating channels) is associated with the use of pyrotechnics as a propellant charge (in American cartridges, compressed gas, mainly air or CO ₂ , is used as a propellant charge), as well as the use in some cases of a gas cut-off system , formed during the combustion of the propellant charge, to reduce the impact of combustion products on the environment, while the electrode-probe is not thrown, but is pushed out of the cartridge by a special pusher coaxial to the electrode-probe (see below).

In the working channel, a baric discharger 9 is placed, containing a body, the actual propellant charge, protected from the back by a cover 10, which forms high-pressure gas 11 upon ignition, as well as a means of its initiation (ignition). Ignition of the propellant charge of the baric discharger 9 in EShU DD cartridges is usually provided by low voltage current pulses using an electric heating bridge located in the housing of the baric discharger 9, or by a high-voltage spark if the propellant charge of the baric discharger 9 is initiated by high voltage current pulses.

A wad or a pusher 12 is also placed in the working channel 7, which ensures the movement of the electrode-probe along the accelerating channel 8 in the direction of the target after the initiation of the cartridge. If element 12 is made in the form of a wad, then its function is similar to the role of a wad in a firearm, it consists in ensuring the transfer of energy from high-pressure gases generated during the initiation of a baric discharge to the probe electrode for throwing it at a target (similar to a bullet) and obturating these gases. When fired (after the probe electrode leaves the cartridge), the wad can also fly out of the accelerating channel. If the element 12 is made in the form of a pusher, then its rear face mechanically interacts with the baric discharger 9, and the front face mechanically interacts with the probe electrode 13, placed partly in the working channel (its rear part), and partly in the accelerating channel 8 (its middle and front). When fired, the pusher moves forward under the influence of the formed gases, pushing the probe electrode in the direction of the target, and then locks the working channel, preventing the gases from escaping to the outside. To do this, its front part can be made in the form of a tapering truncated cone entering the accelerating channel, and its diameter, respectively, the diameter of the working channel, must exceed the diameter of the accelerating channel. For better locking of the accelerating channel, the pusher is usually equipped with a sleeve made in the form of a cylinder with a variable diameter with a through hole made along the longitudinal axis of the cylinder, and is mounted on the pusher in that part of it that is located in the working channel (not shown in Fig. 2).

The front part 14 of the electrode-probe 13 can be made rounded to reduce aerodynamic resistance, it has a needle 15 made with a beard made near the tip of the needle 15 or in another place of the needle. In some designs, the needle 15 may be provided with several barbs located in the same or different planes to more securely fix the probe electrode on the body or clothing of the target. In some design versions of the device (for example, if the working fluid of the propellant charge is compressed gas or a pre-compressed spring), element 12 (wad or pusher) may be absent.

For accurate shooting, you need to stabilize the flight of the probe electrode. In the proposed device, this method is gyroscopic stabilization by imparting rotation to the electrode-probe due to screw cuts in the accelerating channel, since any rotating body tends to maintain the direction of the axis of rotation. The rifling provides gyroscopic stability of the electrode-probe on the trajectory and accuracy of fire by imparting rotational motion to the electrode-probe. In addition, the rifling increases the pressure in the accelerating channel, hindering the movement of the electrode-probe and increasing the speed and range of its flight.

In the accelerating channel 8, a groove or grooves 16 are made, similar in purpose to the grooves made in the barrels of rifled firearms (the dimensions, pitch and design of the grooves are shown in Fig. 2 conditionally), and at least one leading belt is made on the surface of the probe electrode 17, corresponding to the mentioned grooves and entering into interaction (engagement) with them, forcing the probe electrode to rotate around its axis.

The groove depth is usually selected in the range of 1.5...2% of the diameter of the said accelerating channel, and the groove field width usually corresponds to half the groove width; for the proposed device, the groove depth is chosen in the range of 1.5... generatrix of the accelerating channel) is made of plastic, and the material of the shell is usually made of metal.

In another constructive embodiment of the device, the groove or grooves are made on the outer surface of the probe electrode, and the leading band or bands are made in the accelerating channel. However, the implementation of the leading belts on the inner surface of the accelerating channel is a more complex technological problem, especially when manufacturing the guide channel by injection molding, so the first constructive embodiment seems to be preferable.

Electrical contacts are installed on the cartridge body to supply high voltage for subsequent impact on the target, as well as contacts to initiate the process of throwing the electrode-probe (not shown in Fig. 2). If the same high-voltage current pulses are used to influence the target and initiate the baric discharger, then the electrical contacts providing the supply of the above-mentioned electric pulse of the baric discharger initiation and the high-voltage current supply to the said needle can be structurally combined in pairs.

On FIG. 3a shows the internal structure of a two-wire cartridge, including two guide channels, corresponding to the section B-B of FIG. 1b.

The design of each of the two guide channels is identical to that of the guide channel shown in FIG. 2, the difference lies in the design of the cartridge body 4, which combines both channels.

On FIG. 3b shows the internal structure of a two-wire cartridge with flexible electrical conductors placed in cavities made in the cartridge body, which includes two guide channels, corresponding to the section B-B of Fig. 1b.

The cartridge body contains two cavities 7, in which two flexible electrical conductors 18 are placed, the front end of each of which electrically interacts with the needle of the corresponding probe electrode, and the rear end - with the corresponding high-voltage contact located on the cartridge body, which is responsible for connecting the cartridge with the output electrodes ESHU DD.

Thus, shown in FIG. 3 cartridge is essentially a combination of the two proposed single-wire cartridges shown in FIG. 1a and Fig. 2 combined into a common body. For the production of a shot from the EShU DD at the target and the impact on the target with a high voltage current, one such cartridge is required, which provides a complete circuit of the electrical circuit of the EShU DD - target - EShU DD.

A certain technical difficulty is the design of the probe electrode itself, which ensures its rotation in the accelerating channel and during the flight to the target. The fact is that the flexible electrical conductor attached to the probe electrode with its front end should not rotate during the flight, since this rotation twists the said conductor, increasing its pulling force, thereby reducing the flight speed of the probe electrode, and also reduces the maximum distance of defeat (obviously, the length of the twisted wire is always less than the length of the stretched wire).

Possible variants of the probe electrode design that solve this problem are shown in Fig. four.

Fig. 4a. The probe electrode contains a core 19, equipped in its front part with a needle 15, and a shell 20 coaxial to the core, made with the possibility of rotation around its longitudinal axis, respectively, around the core. The position of the shell relative to the core is ensured by bushings 21 and 22 fixed on the core, while the diameters of said bushings do not exceed the diameter of the shell. A flexible electrical conductor 18 is attached to the back of the core. At least one leading belt 17 is made on the outer surface of the shell 20.

Since in this design the shell 20 can freely rotate around the core 19 when the leading belt enters the groove or grooves of the accelerating channel and the electrode-probe moves forward along the accelerating channel and further during the flight to the target, the core remains non-rotating, respectively, the flexible the electrical conductor also does not rotate. In some cases, a small movement (parasitic rotation) of the core around its longitudinal axis is possible due to the occurrence of a friction force between the core and the shell in the event of an accidental tangential displacement of the shell, i.e. residual mechanical interaction between the core and the shell.

To reduce this mechanical interaction of an almost stationary core and a rotating shell, a lubricant 23 can be introduced between the outer surface of the core and the inner surface of the shell, made on the basis of oil, or graphite, or silicone, or other friction-reducing materials, for example, anti-friction coatings.

Fig. 4b. In the body of the probe electrode, in the cavity between the core and the shell, a flexible electrical conductor 18 can be placed, electrically interacting with its front end with the said probe electrode needle, and with its rear end electrically interacting with a flexible electrical conductor placed in the cavity made in the cartridge body , or with a contact mounted on the cartridge body, made with the possibility of electrical interaction with the corresponding output electrode of the electroshock device (not shown in Fig. 4b). During the flight of the probe electrode towards the target, the flexible electrical conductor 18 is pulled out of the cavity towards the EShU DD through the hole made in the rear sleeve 22.

The flexible electrical conductor 18, as already mentioned, can be the main element connecting the probe electrode to the output electrodes of the EShU DD, or be part of a combined design when it is connected to a similar flexible electrical conductor placed in a cavity made in the cartridge body, which, in turn, electrically interacts with the output electrodes of the EShU DD. This design provides a significant increase in the maximum target engagement distance.

Fig. 4c. Between the core and the shell, at least one rotation bearing 24 can be installed, the inner ring of which mechanically interacts with the said core 19, and the outer ring mechanically interacts with the shell 20. Firstly, this technical solution fixes the position of the shell 20 with respect to the core 19 , secondly, it allows you to significantly increase the mass of the shell (it is known that the greater the mass of a rotating projectile, for example, a rifled bullet, the higher its trajectory stabilization, all other things being equal), which gives a noticeable positive effect. In this version of the technical implementation of the device, the mass of the shell can significantly exceed the mass of the core.

The bearing can also be lubricated with oil, or graphite, or silicone, or other friction-reducing materials, such as anti-friction coatings.

It should be noted that at least one of the bushings 21 and 22 shown in FIG. 4a, it is also possible to perform in the form of a rotation bearing, in this case it is installed in such a way that its inner ring interacts mechanically with the said core 19, and the outer ring mechanically interacts with the shell 20.

The electrical interaction of the flexible electrical conductor 18 and the needle 15 can be ensured, for example, by making the bearing 24 and the shell 20, to the front of which the needle 15 is attached in this technical solution, from electrically conductive materials, mainly metal, for example, brass or steel, or their combinations, while some possible gaps between the mentioned structural elements, totaling fractions of a millimeter, do not interfere with high-voltage electrical communication.

When pulling the turns of a flexible electrical conductor from the cavity of the cartridge body, with some designs of laying the conductor into a coil for packing it into the said cavity, for example, when using multilayer winding of the conductor, in which adjacent layers of turns are laid at an angle to each other, they can be rotated around the longitudinal axis cartridge.

This effect can be used to further reduce the parasitic rotation of the core as follows: the direction of rotation of the probe electrode shell due to its movement along the mentioned grooves can be chosen opposite to the direction of rotation of the flexible electrical conductor when it is pulled out of the probe electrode or the cartridge body, while the pitch of the mentioned grooves can be chosen in such a way that the angular velocity of rotation of the electrode-probe corresponds to the angular velocity of the turn of the turns of the flexible electrical conductor when they are pulled out. In this case, the turning force of the turns will partially or completely compensate for the frictional force leading to parasitic rotation of the core.

The device works as follows.

At the time of the shot, that is, the initiation of the cartridge, propellant charges, if they are made with the use of pyrotechnic substances, ignite, forming a high-pressure gas, which, acting on the probe electrodes with or without wads or pushers, pushes them in the direction of the target . The rotation of the probe electrodes, due to the interaction of the rifling and the leading belt, ensures the stabilization of the flight path of the probe electrodes, a corresponding increase in their flight range and accuracy of fire.

At the time of the shot, the shutters, if they are placed in the front part of the cartridge body, are destroyed, or open, or are separated from the body due to the mechanical action of the probe electrodes on them, opening the mentioned cavities for pulling flexible electrical conductors and accelerating channels for probe electrodes that draw flexible electrical conductors during their flight.

Another option for ejection of probe electrodes can be the use of compressed gas (for example, air or CO ₂ ) as a propellant charge, as in pneumatic weapons. There are other options for the means of propelling projectiles, for example, the use of a pre-compressed spring.

When hitting the target, the electrical circuit of the EShU DD - target - EShU DD is closed, providing a non-lethal electrical effect on the target.

Technical implementation

The device was implemented in pilot production and has the following characteristics in comparison with the corresponding characteristics of the prototype:

These features of the proposed design make it possible to significantly stabilize the flight path of the probe electrodes, increase the range of target destruction and the accuracy of hitting the probe electrodes on the target.

Thus, the use of rifling in the accelerating channel and a leading belt made on the outer surface of the probe electrode, which ensure the rotation of the probe electrode during the flight to the target, as well as the design of the probe electrode, ensuring the absence of rotation of the flexible electrical conductor, allows us to solve the problem increasing the stability of probe electrodes on their flight path, the maximum flight range and accuracy of fire of the EShU DD.

List of sources cited

1. US patent No. 6636412. Hand-held stun gun for incapacitating a human target.

2. US patent application US 20050262994 A1. Method and apparatus for improving the effectiveness of electrical discharge weapons.

3. RF patent No. 2351871. Cartridge for electroshock device with remote defeat.

Claims (9)

1. An electric cartridge for a remote-action electroshock device, containing a housing with at least one guide channel made in the housing, containing a working channel in which a propellant charge and a wad or a pusher are placed, and an accelerating channel, mainly coaxial with the said working channel, in the accelerating the channel contains a projectile electrode-probe, mechanically interacting with its rear end with a wad or pusher, equipped in its front part with at least one needle electrically interacting with a flexible electrical conductor, made mainly with at least one beard, characterized in that in the accelerating channel is made at least one groove or at least one leading belt, the body of the electrode-probe is made in the form of a core and a shell, made with the possibility of rotation around its longitudinal axis, on the outer surface of the electrode-probe is made at least one leading belt corresponding to rifling ra of an accelerating channel or at least one groove corresponding to the leading band or leading bands of the accelerating channel. 2. The cartridge according to claim 1, characterized in that the mass of the shell exceeds the mass of the core. 3. The cartridge according to claim 1, characterized in that the cartridge body has at least one cavity in which a flexible electrical conductor is placed, electrically connected to the needle of the corresponding probe electrode with its front end, and with its rear end electrically interacting with the corresponding contact mounted on the cartridge body, made with the possibility of electrical interaction with the corresponding output electrode of the electroshock device. 4. The cartridge according to claim 1, characterized in that in the body of the probe electrode in the cavity between the core and the shell there is a flexible electrical conductor, electrically interacting with its front end with the said probe electrode needle, and with its rear end electrically interacting with a flexible electrical conductor placed in a cavity made in the cartridge body, or with a contact mounted on the cartridge body, made with the possibility of electrical interaction with the corresponding output electrode of the electroshock device. 5. The cartridge according to claim 1, characterized in that a lubricant based on oil, or graphite, or silicone, or other friction-reducing materials, such as anti-friction coatings, is introduced between the core and the shell of the probe electrode. 6. The cartridge according to claim 1, characterized in that the probe electrode is equipped with front and rear bushings mounted on the core, between which a shell is placed, while the diameter of said bushings does not exceed the diameter of the shell. 7. The cartridge according to claim 1, characterized in that at least one rotation bearing is installed between the core and the shell, the inner ring of which mechanically interacts with the said core, and the outer ring mechanically interacts with the shell. 8. The cartridge according to claim 1, characterized in that the direction of rotation of the shell of the electrode-probe due to its movement along the said grooves is chosen opposite to the direction of rotation of the flexible electrical conductor when it is pulled out of the electrode-probe or the cartridge body, while the pitch of the said grooves can be selected so that the angular velocity of rotation of the electrode-probe corresponds to the angular velocity of the turn of the turns of the flexible electrical conductor when they are pulled out. 9. The cartridge according to claim 1, characterized in that the depth of the groove is selected in the range from 1.5 ... 5% of the diameter of the said accelerating channel, and the width of the groove field corresponds to half the groove width.

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