RU2442508C2 - Tobacco smoke filter and methods of its production - Google Patents

Abstract

FIELD: tobacco industry. ^ SUBSTANCE: tobacco smoke filter has a cylindric cover containing a spiral element with diameter approximately equal to the inner diameter of the cover as well as filtering means placed between the spiral element and the cover. The spiral element contacts the cover to the its inner diameter and is made by means of sideward compressing with the ability to maintain the contact after the compression. Filter production requires the preparation of the cylindric spiral having the inner space inside the spiral volute and outer edge making a cylindrical form. In the specified inner space filter means are located along with wrapped outer edge of the filled spiral cover. Spiral element is used sidewards thus providing its contact with the cover which is preserved after the spiral element copression. ^ EFFECT: this filter provides the increased contact time with the filtering material and expanded space of the filtering material contact surface. ^ 15 cl, 13 dwg

Description

Technical field

The present invention generally relates to devices for filtering tobacco smoke, their manufacture and use. More specifically, the present invention relates to filters suitable for use in smoking articles.

BACKGROUND OF THE INVENTION

Disposable filters have been used in smoking products for many decades. Filters are typically made from cellulose acetate based on a process by which cellulose acetate is dissolved in a solvent, such as acetone, and a polymer fiber is formed from the solution. The fiber is oiled and connected into bundles, and then crimped and dried. Alternative filter materials include polypropylene and cellulose. Filters can be segmented, possibly with different materials in different segments; they may contain granular additives such as carbon.

The filter is located at one end of the tobacco rod, so that smoke from the lit tobacco rod, which contains the solid phase and the vapor phase, passes through the filter before the smoker inhales it. The filter fibers form a mechanical barrier that traps solid particles in the smoke stream. Previously, the action of filters was based only on this mechanical filtration; see, for example, patent US 4502495.

Subsequently, ventilation holes were provided along the paper wrapper outside the filter to dilute the inhaled smoke. They are also designed for the volatile constituents of smoke, which are not normally affected by the physical filter barrier. For example, absorbent or absorbent materials are often added to selectively remove volatile components from the smoke stream.

Activated carbon, porous minerals such as sepiolite, silica gel and cationic or anion exchange resins are often used as filter additives. Carbon or coal can be used to remove acid gases. Sepiolite has a strong ability to absorb charged particles. Silica gels readily absorb aldehydes and hydrogen cyanide. Cation exchange resins are proposed to remove nicotine, while anion exchange resins are proposed to remove acids from smoke. Researchers continue to develop new additives that are designed for entire classes or specific constituents of smoke.

One of the problems associated with adding granular or solid particulate material to the filter fibers is how to adhere the individual particles so that they remain active. For example, adhesives that hold solid particles in position on fibers can block the reaction sites on solid particles. One solution is to create cavities in the filter and load batches of solid particles into them, although there is another problem, namely how to direct the flow of smoke through such a loosened layer of solid particles during use.

An additional solution for retaining particulate matter is to enclose them in tubes that run parallel to the direction of the smoke stream, whereby smoke passes through the tubes and contacts the solid particles in them. If the tubes are made non-linear, the filtration path becomes longer, see US patent 4373539.

Other examples of known filters are described in publications WO 86/03381, US 2003/0200973 and EP-A 0033772, which offer various filters with a spiral channel for smoke.

Since the reduction of solid and steam constituents of smoke remains an urgent need in this area, new materials and methods for improving existing filters are needed. In particular, solutions that can be used in combination with various conventional or new filter and additive materials are especially needed.

SUMMARY OF THE INVENTION

The present invention provides a tobacco smoke filter used in a tobacco product, comprising an axially extending filter section forming a path along which smoke passes through the filter material during use, and this path extends spirally around the filter axis. By providing a path of smoke, which thus twists around the axis of the filter, it is possible to increase the contact time of the smoke with the filter material and the area of the contact surface of the filter material.

In one embodiment, a tobacco smoke filter is provided that comprises a generally cylindrical shell with an inner diameter and a spiral element with a diameter located inside the shell, the diameter of the spiral element being approximately equal to the inner diameter of the shell. The filter also contains filtering means located between the spiral element and the sheath.

The shell may include a filter swab wrapper, which may have multiple ventilation openings. If ventilation openings are provided, they can be arranged to correspond to areas of the casing that do not overlap the scroll element. The shell may comprise at least two layers, for example, an outer layer of a filter swab wrapper and an inner layer of cellulose acetate connecting a spiral element.

The spiral element may contain polypropylene, polyethylene, paper, carbon paper, impregnated paper or any other materials suitable in accordance with the present disclosure of the invention, and may contain a coating layer on its outer surface. The coating layer may contain activated carbon, activated coconut carbon, activated carbon based on coal, zeolite, silica gel, sepiolite, alumina, carbon-containing resin, and combinations thereof. The spiral element may have compressible edges at the point where this element can be in contact with the inner diameter of the shell. Alternatively or additionally, the central portion of the spiral core may be compressible.

The filtering agent may contain at least one material selected from the group consisting of cellulose acetate, polypropylene, polyethylene, corrugated paper and combinations thereof, for example, randomly oriented cellulose acetate. The filtering agent may further comprise activated carbon, flavoring, adsorbent or absorbent.

In one embodiment, the filtering means occupies substantially the entire space between the spiral element and the inner diameter of the sheath. This ensures that smoke flowing along the spiral element passes through the filtering means, thereby guaranteeing good filtration performance. In addition, the dense packing of the filter medium inside the filter gives the impression of a solid and reliable filter. This dense packing can be achieved by using small fibers or the like of filter media.

The present invention also provides a smoking article that comprises a tobacco smoke filter of the present invention.

The present invention also provides a method for manufacturing a tobacco smoke filter, in which a substantially cylindrical spiral is prepared with an inner space of the spiral coil and an outer edge, filtering means are placed in the inner space of the spiral coil and the outer edge of the filled spiral is enclosed in a shell.

As used herein, the term “tobacco” refers to any portion, for example, leaves, flowers, stem, any member of the genus Nicotiana and materials recovered from them. It includes derivatives, such as specific compounds found in natural tobacco, for example nicotine, extracted or synthesized, as well as structural derivatives, such as the fibrous portion of a tobacco sheet. It further includes tobacco substitutes that contain individual chemicals and / or complex chemical structural elements that resemble natural tobacco in physical properties when they are prepared accordingly.

As used herein, the term “tobacco smoke filter” means any element that is intended to be used as a unit through which tobacco smoke passes (i.e. used when smoking tobacco), and in which some components of the tobacco smoke are slowed down, cooled, and / or are held. Tobacco smoke also contains by-products of tobacco combustion and heating of tobacco in the absence of actual combustion.

Brief Description of the Drawings

The present invention can be easily understood and implemented with reference, as an example, to the accompanying schematic drawings, in which:

1 is a perspective view of a partially disclosed filter of the present invention;

figure 2 shows a side view partially in cross section and partially opened filter of the present invention;

figure 3 shows a view of the filter of the present invention in section along the line aa in figure 2;

4 is a perspective view of a partially disclosed filter of the present invention;

figure 5 shows a view in axial section of the filter of the present invention;

6A and 6B show two views of the element B of FIG. 5, one when the filter of the present invention is not compressed, and one when the filter is compressed;

6B and 6G show alternative configurations of element B of FIG. 5;

7 shows a schematic process for manufacturing the filter of the present invention;

Fig. 8 shows a portion of an embodiment of a filter manufacturing machine of the present invention;

figure 9 shows a side view of a variant of implementation of the machine for stuffing the inner spiral space of the filters of the present invention and

figure 10 shows a view in section along the line aa in figure 9.

Detailed description

The present invention relates to tobacco smoke filters that contain a spiral element located inside centrally relative to the axis. This element can take various configurations in cross section, although it is mainly described herein as a single spiral line. With reference to FIG. 1, tobacco smoke filter 10 is shown with a spiral core 11. A spiral core is provided, as shown in the embodiment of FIG. 1, with filter means 12. The spiral core 11 and filter means 12 are visible due to the partial opening of the casing 13 referred to as well as a filter swab wrapper.

The spiral core 11 has a diameter approximately equal to the inner diameter of the sheath 13. That is, the outer edges of the spiral are generally adjacent to the shell. The filtering means 12 is located in the grooves formed by the edges of the spiral between the spiral core 11 and the shell 13.

As is well known to specialists, the spiral curve can either pass from the lower left side to the upper right side, which makes it a spiral with a right winding, or from the lower right side to the upper left side, i.e. it is a left-hand spiral. Spirals with both right and left windings can be used as a spiral core in the practice of the present invention.

Spiral pitch i.e. the length of one full turn of the spiral is selected on the basis of a balance between the desire to increase the filtration path and the need to ensure ease of inhalation. This step, which applies to any filter of the present invention, can be optimized by one skilled in the art based on variables such as material for the spiral element, especially whether it is porous or not; the material surrounding the spiral and how tightly packed it is, and, among other things, ventilation. The pitch of the spiral can be 1-4 mm, for example, 2-3 mm.

The permeability of the material used in the spiral core may preferably be low in some applications, so that it is effectively non-porous. This, combined with the placement of a less porous shell tightly relative to the spiral, ensures that when inhaled smoke it is forced to spiral in through the filter. This increases the physical filtration and provides the possibility of additional removal of volatile components from tobacco smoke. Extruded plastic, foil, or coated paper are some examples of materials that can be used to create a spiral core.

In another embodiment, the material used in the spiral core is porous. The pores in this material can be created to specifically capture selected smoke constituents. For example, the material may be a polymer with molecularly imprinted target components. Pores in the material can be impregnated with additives such as flavoring or diluent, the additive of which can be fully retracted by inhalation during the first few puffs during use, leaving behind empty pores that can interact with subsequent streams of smoke passing through them. The spiral core can be formed from activated carbon, the density of which is such that most of the smoke is forced to spiral, and a smaller part of the smoke passes through the carbon structure of the spiral core. A binder can be used to ensure the formation of granules of activated carbon and the preservation of a spiral shape.

In another embodiment, the spiral core is non-porous, but a porous surface is provided for interacting with smoke components. Alternatively or additionally, the spiral core may be coated, for example, with a flavor or with a reagent designed to trap, neutralize, or otherwise counteract smoke constituents.

The width and length of the spiral core is preferably approximately equal to the width and length of a standard tobacco smoke filter. For example, a standard cigarette filter is typically in the range of 10-30 mm in length and 25-30 mm in circumference. The width of the spiral core can be smaller than the standard, thus providing a coaxial or multicomponent sheath.

When the spiral core is made of a solid and inflexible material, it is preferable to provide a region of densely packed cellulose acetate coaxially around the outside of the spiral so that, in use, the filter more closely matches the feel of a standard filter. The length can also be adjusted, for example, it can be part of the length of a standard filter to accommodate one or more filter elements at one or both ends.

In order to obtain a filter that looks standard, it may be preferable to have a cellulose acetate filter segment at the end of the mouthpiece of the smoking article that the smoker sees, so that the multi-segment filter of the present invention can be half of the cellulose acetate on the side of the smoker and a half new tobacco filter smoke - from the side of the tobacco rod. When the spiral element forms only one part of a multi-element filter, it is preferable to refrain from adding filter media into the spiral.

The thickness of the material forming the spiral core is also different for different products. When the spiral line is impervious to smoke, it can be on the order of 0.5-2 mm. When the spiral line is assumed to be selectively permeable to constituents of smoke and / or ambient air, the thickness may be 0.5-3 mm. It may be uneven in cross section in order to simplify the manufacture or provide a pleasant sensation of the product in the hands of a smoker; it may be larger in the center of the spiral than at remote edges. Alternatively or additionally, the central axis of the spiral core may be solid, with the formation in cross section of a circle with radial flanges extending outward. In combination with the selection of the thickness of the material forming the spiral, you can adjust the pitch of the spiral, which helps to provide the necessary resistance to traction during inhalation or pressure drop.

Ventilation holes, widely known to specialists in this field, can be performed in the filter of the present invention. Such openings should increase the dilution of tobacco smoke and facilitate inhalation through a bypass filtration path. It may be most effective for the ventilation openings to be arranged in the form of a spiral corresponding to the spiral core, in places where the shell does not abut the edge of the spiral core. The pressure difference can be taken into account when determining whether to use ventilation openings, the number and location of which depends on the shape and material of the spiral, and also taking into account whether any filtering means are used.

The spiral core of the present invention can be made by any suitable method. Specific manufacturing requirements vary depending on the material and size selected and whether there is a coating on the spiral core. For example, the extruded core is loaded into cellulose acetate in a conventional filter manufacturing process.

The spiral core and its location relative to the shell leads to the fact that the inhaled stream of smoke passes a longer than usual bypass path through the filter before it reaches the smoker. This allows a larger surface area and longer filtering time. Accordingly, the spiral core itself includes one of various types of filter media.

If the sheathed spiral core is surrounded only by ambient air, the inhaled smoke will not be filtered to the maximum extent, as it should simply go a longer way before getting into the smoker's mouth. A longer path serves to cool the air, and part of the solid particles precipitate and adhere to the core or surrounding paper. Even when the spiral core itself contains filter material and even when such a spiral core is used as one segment of a multi-segment filter, such a design does not maximize the use of available smoke filtering capabilities, and thus can only be used in particular embodiments for special applications.

Based on the foregoing, additional materials are provided in the space around the spiral to the sheath in order to realize maximum filtration capabilities for standard applications. For example, randomly oriented acetate fibers, i.e. pieces of standard filter material can be packed more or less tightly around the spiral to provide filtering means, while at the same time not preventing the inhalation of smoke. Acetate fibers can be used in any size range allowing insertion into the filter, for example, 2 mm.

Other material options around the spiral core include any filter materials that are suitable for use and filtering inhaled smoke, and may be particles, twisted threads, and the like. The material located around the spiral core may contain any number of additives, such as absorbents, absorbents, diluents, flavors, and the like. Materials and methods for their incorporation into various filter components are known to those skilled in the art. For example, activated carbon and resins are commonly used and may be provided.

Conventional means for making smoking articles may be used in the present invention. The equipment can be supplied with the tobacco smoke filter material of the present invention with the same dimensions and handling properties as standard filters. Such equipment combines a new filter with tobacco rods, wrapping paper, and curl paper to form a product resembling conventional products in size and appearance, but equipped with the new filter of the present invention.

The shell containing the spiral core may be a conventional filter swab wrapper. It can be coated on one or both sides with the desired additive, such as a colorant and an aromatic substance, along the outer surface, which gives a cork-like structure and an attractive aroma, and can have an inner coating of diluent, flavor, materials that improve filtration, such like activated carbon particles, etc. To improve the tactile qualities of the filter along the inner surface, a layer of material may be provided, for example a layer of cellulose acetate, forming the inner diameter of the shell and giving a sensation similar to conventional filters, which may be more attractive to the user.

Under the existing manufacturing conditions, the filter section is compressed about 1 mm around the circumference when curling paper is added to attach the filter element to the tobacco rod. In one embodiment of the present invention, which is provided with a cellulose acetate layer between a filter swab wrapper and a spiral core, the cellulose acetate layer may be arranged to provide compression. However, and in particular in the case of a spiral core that is directly compressed by the addition of a single-layer shell, some flexibility or compressibility of the spiral core is preferably provided.

FIG. 5 shows one example of a cross section of a spiral core 11 surrounded by a sheath 12. The region B in the circle is shown in more detail in FIGS. 6A and 6B. On figa shows how the edge of the spiral core 11 can be configured in the area where it is expected to contact with the shell 12. The edge has a feature in the form of a deformable flange, which bends when compressed, providing inward pressure from the side of the shell 12. In figb shows how this area provides compression. After the compression is stopped, the edge of the spiral core 11 restores its configuration according to figa.

An additional advantage of the type of configuration shown in FIGS. 6A and 6B is that it creates a sealing effect between the core and the casing, further guaranteeing that the smoke inhaled through the filter is forced to pass along the spiral path. Depending on the configuration and materials used for the spiral core, the compressibility can also provide an improved tactile sensation for the user. For example, the material used for the spiral core can be elastic and provide tension during deformation, so that it re-expands to its original configuration after the application of the folding paper for folding. The steps of alternatively applying border paper are needed, for example, when it is economically preferable or when a spiral core is provided that is not intended to be compressible.

Alternatively, the spiral core may be compressible. Preferably, it also re-expands to return to its original size after compression. Such an embodiment may be provided with rounded edges along a portion of the spiral core that is in contact with the shell to prevent puncture or rupture during compression or handling, see FIG. 6B. In another alternative, a smoothed edge is provided, the smoothed portion of which is adjacent to the shell, which also reduces the risk of tearing and possibly also increases the sealing effect and improves tactile sensation, see FIG.

One embodiment of the filter manufacturing method of the present invention is shown schematically in FIG. 7. The device 70 contains a block 71 of the supply of spiral material, which may be a bale (skein) of spiral made of extruded plastic. The filter medium supply unit 72 may comprise a stack of cellulose acetate fibers. The casing supply unit 73 provides a means for covering the filter components and may be a roll of a filter swab wrapper.

While standard methods typically produce filter materials in the form of a long cylinder that is cut into small blocks for individual use, in some cases it may be preferable that the spiral core be made individually and then inserted into the filter and attached to the tobacco rod . It can occupy the entire filter area in length, and in the alternative, part of a multi-segment filter.

In use, the device 70 feeds the spiral material from the supply unit 71 to the filter medium additive area 74. Here, materials from the filter medium supply unit 74 are fed into a spiral. An additive application means 75 is provided, which may be a single agent, as shown in the figure or a series of agents, in principle, supply different additives. Means 76 are also provided which can dry the internal components of the filter before or after adding the casing from the casing supply unit 73. In addition, there is a block 77 for cutting the prepared filter material to the desired length.

Any suitable known or developed alternative methods can be used to make the tobacco smoke filter of the present invention. For example, FIG. 8 shows the manufacture of a multi-segment filter. A continuous rod 81 is shown which is intended to be finally divided into a plurality of individual filter units 82. Each filter unit 82 comprises a first filter segment (segment) 83, a second filter segment 84, and a third filter segment 85. In the shown embodiment, a portion of the spiral core is provided in the second filter segment 84.

The solids 86 are added to the spiral core of the second filter portion 84 by means of a metering means 87. The solids 86 can be a filter medium, additives or a mixture thereof. In one embodiment, such as that shown in FIG. 8, there is a first segment of a cellulose acetate filter, a second segment of a non-porous spiral filter provided with flavors in the space inside the spiral, and a third filter segment containing carbon, such as a filter with a cavity, filled with carbon particles or carbon paper converted into a filter segment. As is apparent to those skilled in the art, many existing methods can be used, similar to the dispensing agent of FIG.

It is contemplated that a plurality of dispensing agents may be provided for the same rod, each means supplying different material to the spiral core. For example, the first agent delivers the first flavor, the second agent delivers the absorbent, and the third agent delivers the second flavor. These three means can be provided side by side to fill separate areas of the same spiral core with appropriate additives; alternatively, they can add appropriate materials throughout each spiral core one after the other.

When the spiral core is configured to provide various smoke paths, one or the other of these configurations may be preferred. For example, so that the initial portion of the inhaled puff of smoke extends mainly along the central region of the core, and the last portion of the same puff extends along the outer regions of the core to the shell, there may be preferably a multi-stage or multi-layer filling to provide first materials that act on the initial portion of the puff and second materials that act on the last tightening section.

An additional example is shown in FIG. 9, where the spiral core 11 passes through a rotating feed mechanism 91, which simultaneously provides material 92 around the core and holds the filled core in the casing 13. FIG. 10 shows a section along line AA, which is obviously that the material 92 passes into the feed mechanism 91 and fills the entire space around the core 11.

Meanwhile, the addition of filter material or additive material to the spiral core after its formation may be the preferred method for some applications where the materials and construction provide a one-step process by which all functions are performed. For example, a rotating head allows extrusion of the spiral core while filling the space inside the spiral with filter material and / or additive material. A plurality of materials may be mixed first and then added as a mixture; alternatively, one or more streams of each additive may be present individually. This order may be preferred when the handling of the added materials is different, or when precipitation or other problems occur in the mixture.

Although FIGS. 7-10 relate to one production line for manufacturing a spiral core of the present invention, it will be apparent to those skilled in the art that efficient manufacturing can be best achieved by providing multiple blocks or a series of parallel steps. For example, two or three of the means shown in FIGS. 9 and 10 may be provided, thus creating twice or three times more filter material.

Example 1. The manufacture of the filter

Activated carbon forms a spiral shape of approximately 6 mm in diameter. The average helix pitch and low porosity are used, i.e. low permeability. Carbon is cut into pieces of a length of approximately 20 mm. Provided are blocks of a standard cellulose acetate tow of approximately 6 mm in diameter and approximately 10 mm in length, which are arranged alternately with a length corresponding to a carbon helix.

The space inside the carbon spiral is provided with a mixture of flavor and absorbent material before the indicated length of the spiral / tow of cellulose acetate is wrapped with a layer of cellulose acetate about 0.5 mm thick around the circumference. As is known to those skilled in the art, a wrapper of a filter plug may optionally be provided around a layer of cellulose acetate.

This ensures a length of filter material, which can be cut along the middle of about 10 mm of the length of the cellulose acetate tow, to obtain a plurality of filter blocks, each about 30 mm long and with a cellulose acetate tow of about 5 mm at each end, the filter material surrounding carbon spiral with additives in the inner space of the spiral.

The filters thus obtained can be introduced into smoking articles, such as a mouthpiece or a hookah mouthpiece, to provide an effective, but disposable filter material for inhaled smoke passing through it. Different lengths and thicknesses may be provided depending on the intended use. When used with slightly flattened mouthpieces, a spiral core can be formed with an oval cross-section. This should be considered as a generally cylindrical product, as proposed by the present invention.

Example 2. The manufacture of cigarettes

The resin, commonly used in tobacco smoke filters, is extruded through a die with a knife to obtain a strong spiral shape of approximately 7 mm in diameter and 10 m in length. The resulting mold is fed to a machine that uses suction or vacuum, such as vacuum fittings, to pack cellulose acetate fibers around a spiral. The spiral line with the packing is wrapped in a filter swab wrapper and dried on a drying fixture. The dried filter is cut into pieces 60 mm long, which are fed to a cigarette making machine.

In a cigarette making machine, a filter is used to make cigarettes by known methods. In short, two tobacco rods are located at one end of the filter and, when attached, the filter is cut in the middle. An optional end segment, such as a cellulose acetate pad, is added at the end of the cigarette mouthpiece to close the spiral core block. The resulting article is a cigarette including the new tobacco smoke filter of the present invention.

The foregoing description and examples are provided merely to illustrate the present invention and are not intended to be limiting. Since modifications to the described embodiments encompassed by the present invention may appear to those skilled in the art, the present invention should be interpreted broadly as including all possible variations within the scope of the claimed claims and their equivalents.

Claims (15)

1. A tobacco smoke filter containing
basically a cylindrical shell with an inner diameter,
a spiral element housed in the shell and having a diameter approximately equal to the inner diameter of the shell, and
filtering means located between the spiral element and the sheath,
moreover, the spiral element is in contact with the inner diameter of the shell and made compressible in the lateral direction with the possibility of maintaining contact with the inner diameter of the shell after compression. 2. The filter according to claim 1, in which the shell includes a wrapper of a filter swab. 3. The filter according to claim 2, in which the wrapper of the filter tampon has many ventilation holes. 4. The filter according to claim 3, in which the ventilation holes are located so that they correspond to areas of the shell that do not lie on top of the spiral element. 5. The filter according to claim 1, in which the shell consists of at least two layers. 6. The filter according to claim 5, in which the shell forms the outer layer of the wrapper of the filter plug and the inner layer of cellulose acetate. 7. The filter according to claim 1, in which the spiral element contains polypropylene, polyethylene, paper, carbon paper or impregnated paper. 8. The filter according to any one of the preceding paragraphs, in which the spiral element has a covering layer on its outer surface. 9. The filter of claim 8, in which the coating layer contains activated carbon, activated coconut carbon, activated carbon based on coal, zeolite, silica gel, sepiolite, alumina, carbon-containing resin, and combinations thereof. 10. The filter according to claim 1, in which the filter medium contains at least one material selected from the group consisting of cellulose acetate, polypropylene, polyethylene, corrugated paper, carbon, and combinations thereof. 11. The filter of claim 10, in which the filter medium contains a randomly oriented cellulose acetate. 12. The filter according to claim 1, in which the filter medium further comprises a flavoring, adsorbent or absorbent. 13. The filter according to claim 1, in which the filtering means occupies essentially the entire space between the spiral element and the inner diameter of the shell. 14. A smoking article comprising a tobacco smoke filter according to any one of claims 1 to 13. 15. A method of manufacturing a tobacco smoke filter, the implementation of which:
a generally cylindrical spiral is prepared with a space inside the spiral coil and an outer edge forming a generally cylindrical shape,
place filtering means in said inner space of the spiral loop; and
cover the outer edge of the spiral-filled shell having an inner diameter,
moreover, they use a laterally compressible spiral element and ensure its contact with the inner diameter of the shell, so that it remains after compression of the spiral element.

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