WO2021136770A1

WO2021136770A1 - Drafting device of a textile machine, the textile machine and a movable sliding element of the textile machine and a method for reducing friction between a drafting apron of a fibre strand and at least one stationary component of the drafting device of the fibre strand on the textile machine

Info

Publication number: WO2021136770A1
Application number: PCT/EP2020/087963
Authority: WO
Inventors: Petr Haska; Gernot SCHÄFFLER; Peter Blankenhorn; Jakub MAREK
Original assignee: Maschinenfabrik Rieter AG
Current assignee: Maschinenfabrik Rieter AG
Priority date: 2019-12-31
Filing date: 2020-12-29
Publication date: 2021-07-08
Anticipated expiration: 2022-06-30
Also published as: CZ2019810A3

Abstract

The invention relates to a drafting device of a fibre strand on a textile machine for preparing fibres for spinning and/or for the spinning of staple yarns on a textile machine, the device comprising at least one drafting apron (2) wrapped around a drive roller (4) and around at least one stationary component (7) of the drafting device (1). Between at least one drafting apron (2) and at least one stationary component (7) of the drafting device (1), a movable sliding element (6) is inserted. The invention also relates to a textile machine for producing roving, comprising at least one drafting device (1) of roving according to the invention. In addition, the invention relates to a movable sliding element for a drafting device of a fibre strand on a textile machine. The invention also relates to a method for reducing friction between a drafting apron (2) and at least one stationary component (7) of a drafting device (1) of a textile machine.

Description

Drafting device of a textile machine, the textile machine and a movable sliding element of the textile machine and a method for reducing friction between a drafting apron of a fibre strand and at least one stationary component of the drafting device of the fibre strand on the textile machine

Technical field

The present invention relates to a drafting device of a fibre strand on a textile machine for preparing fibres for spinning and/or for spinning staple yarns on a textile machine, the device comprising at least one drafting apron wrapped around a drive roller and around at least one stationary component of the drafting device.

The invention also relates to a textile machine with a drafting device of a fibre strand.

In addition, the invention relates to a movable sliding element for a drafting device of a fibre strand on a textile machine.

Furthermore, the invention relates to a method for reducing friction between a drafting apron and at least one stationary component of a drafting device of a textile machine for preparing fibres for spinning and/or for spinning staple yarns, in which the drafting apron is driven by a drive roller and further the drafting apron wraps the stationary component of the drafting device.

Background art

One of the basic textile technological processes in the production of staple yarns is refining fibre ribbons or fibre strands by drafting in a drafting device. For this purpose, a drafting device provided with one or two drafting aprons is commonly used, whereby the drafting aprons are driven by rollers and at the fibre outlet the aprons pass over a stationary element, the so-called bridge, or over a tensioning element which can be installed both inside and outside the drafting apron of the drafting device. The demands put on the properties of such drafting aprons are considerable and often even contradictory. The drafting apron must guide the drafted textile fibres well, which is ensured by the optimal coefficient of friction of the outer layer of the drafting apron, and it must have a suitable coefficient of friction of the inner layer against the drive roller, so as to prevent slipping on this roller. However, in contrast to this requirement, it is desirable for the coefficient of friction of the drafting apron against the stationary components through which the apron passes to be low enough to ensure low abrasion and thus sufficient lifespan of both the drafting apron and the above-mentioned stationary components of the drafting device.

This problem is solved in numerous documents, e.g., in EP1350871 or CN103469388, which solve this discrepancy by providing a multi-component drafting apron, the outer surface of which is coarser and the inner surface together with the surface of the stationary elements is realized with a mutual friction coefficient as low as possible. The utility model DE102005056534 describes a drafting apron with different outer and inner surfaces, wherein the outer surface is structured to guide the fibres well and the inner surface has a reduced coefficient of friction, so as to be well guided over the stationary components of the drafting device.

Furthermore, EP0407715 (DE3922507) also solves this problem by a drafting apron consisting of several layers with different properties, whereby the reinforcing layer also forms a smooth inner layer for movement on the stationary elements of the drafting device.

Document DE102006030155 (published also as W02008000451) seeks a compromise solution in which the surface of the drafting apron would be suitable for guiding the fibres slidingly on the stationary metallic components of the drafting device. An advantage is the possibility of rotating the drafting apron depending on the type of fibrous material being spun.

Document DE2407118 discloses a solution of a drafting apron for a roving frame, where there is a fabric inside the apron and both surfaces of the fabric are covered with a layer of microporous polyurethane film. The document does not solve friction between the drafting apron and the stationary components of the drafting device. DE19730098 describes a longitudinally oriented structure of protrusions and grooves on the surface of a drafting apron for guiding a fibre strand, having a depth of less than 0.5 mm.

Document DE10029301 discloses different structures of the inner surfaces of a drafting apron for sliding over the stationary components of the drafting device and for a drive roller, whereby the surface for sliding has a lower coefficient of friction and is placed in the middle between surfaces with a higher coefficient of friction for the drive roller. It is obvious that the production costs of such a complicated construction of the drafting apron are considerably high The operational disadvantage of this solution is that the compromise width of both types of surfaces may be insufficient for the desired function.

New features of the solution according to DE102005056534, ES2303429, consist in that an upper drafting apron has a structured surface at least on the outer side and the inner side of the upper drafting apron is made of a material freely slidable over the stationary components of the drafting device.

Document CN104975387 describes placing rubber balls in the holes of the drafting apron to reduce friction on the inner side of the drafting apron.

Despite a certain reduction in friction between the apron and the stationary components of the drafting device, which is achieved in the above- mentioned background art, a common disadvantage of the background art described above is the complex and expensive production of multicomponent aprons consisting of different layers, not only in the direction of the apron thickness but also in the apron width direction, but also the use of small rubber balls placed in the holes of the drafting apron. DE 102005039108 A1 discloses an arrangement of a drafting device in which in the "tip" of the stationary component (bridge), i.e., at the point of the smallest radius of the bend of the drafting apron, a rotating element in the form of a roller is arranged. This roller is mounted in the tip of the stationary component rotatably about its longitudinal axis, wherein this longitudinal axis of the rotatable element is parallel to the width of the apron. To prevent this rotating element from falling out and to make it rotate easily about its longitudinal axis, a radial (rolling) bearing is provided in the tip of the stationary component, the radial bearing being complemented by a pair of axial bearings. The disadvantage of this arrangement is mechanical complexity, an increase in the radius of the tip of the stationary component and also a risk of clogging the rotatable element with dirt and a significant reduction in the rotation of the rotatable element, or a rapid and significant increase in friction between the small-diameter rotatable roller and the radial bearing in the stationary component and thus a substantial increase in the friction between the rotatable roller and the drafting apron. Another disadvantage is that the small-diameter rotatable roller does not prevent the contact of the inner surface of the apron and the outer surface of the stationary component, especially not in the zone of the contact of the two aprons, i.e., in an important zone where the aprons act on the fibres compressed between them.

The object of the invention is therefore to remove or at least minimize the disadvantages of the background art, especially to eliminate the need for multi- component aprons to reduce friction between the drafting apron of the drafting device and the stationary components of the drafting device.

Principle of the invention

The object of the invention is achieved by a drafting device of a fibre strand on a textile machine for preparing fibres for spinning and/or for spinning staple yarns on a textile machine, the device comprising at least one drafting apron wrapped around a drive roller and around at least one stationary component of the drafting device, the principle of which consists in that between at least one drafting apron and at least one stationary component of the drafting device, a movable sliding element is inserted.

The invention is thus characterized by the insertion of an independent separate movable sliding element between the inner surface of the drafting apron and the stationary component of the drafting device. The sliding element moves together with the drafting apron, being driven only by the compression between the inner surface of the drafting apron and the surface of the respective stationary component of the drafting device, without the sliding element wrapping around the drive roller of the drafting apron. It is fully sufficient if the sliding element is only arranged around the respective stationary component, without having to wrap it tightly all along its entire circumference. The advantage of this solution is transferring friction between the inner surface of the drafting apron and the stationary component of the drafting device to the point of contact of the sliding element and the respective stationary component of the drafting device, which allows to set or adapt the coefficient of friction between the inner surface of the sliding element and the respective stationary component of the drafting device, independently of the material of the drafting apron and of the required coefficient of friction of the outer surface of the drafting apron by which the drafting apron is in contact with the textile fibres, but also independently of the required coefficient of friction of the inner surface of the drafting apron and the outer surface of the drafting roller by which the drafting apron is driven. This solution therefore makes it possible to make the drafting apron as is customary and has long been proven for textile technology, and, at the same time, to optimize the friction between the individual parts of the drafting device at a very low cost. The advantage of this solution is also a longer service life of the drafting apron due to its lower wear by abrasion of the stationary elements, components of the drafting device, since the drafting apron, on its inner side, only rolls on the drive roller, as well as on the sliding element, without friction between the inner surface of the drafting apron and the outer surface of the stationary component, being part of the drafting device. This reduction in the cost of the drafting apron, together with the extension of its service life, compensates for the additional costs for the production and assembly of the inserted sliding element, the dimensions of which, e. g. length, are significantly smaller than the dimensions, e.g. length, of the drafting apron and also such a sliding element can be made by a simple technology as an apron from a single material, e.g. PTFE, low friction fibre fabric, fibre-reinforced composite material, etc. From the point of view of force transmission, it is advantageous if the movable sliding element is frictionally driven by pressing the movable sliding element between the drafting apron and the stationary component of the drafting device. In terms of function and limitation of the warming of the drafting apron by friction, it is advantageous if the movable sliding element, when carried by the drafting apron, moves at a speed which is close to or equal to the speed of the inner surface of the drafting apron. Therefore, it is advantageous if there is greater friction between the movable sliding element and the drafting apron than between the movable sliding element and the stationary component of the drafting device. In terms of production and function, it is advantageous if the movable sliding element is formed by a movable closed apron.

The movable sliding element has a low coefficient of friction against the surface of the stationary component, which is advantageous for minimizing mutual friction. From a material point of view, it is advantageous if the movable sliding element is made of PTFE, or it is made of low friction fibre fabric, or it is made of a fibre-reinforced composite material or the movable sliding element consists of a fabric made of polyamide filaments or the movable sliding element consists of a lattice fabric made of filaments of polyamide 6.6 (PA 66). To prevent or reduce occurrence of static charge due to the sliding of the movable sliding element on the stationary component, which would lead to accumulation of fluff from the environment at the movable sliding element, whereby the fluff accumulation often comes into the yarn, at least part of the fibres or filaments or the movable sliding element as a whole is coated with a thin layer of metal, in particular a thin layer of silver or at least part of the fibres or filaments or the movable sliding element as a whole is coated with antistatic or conductive polymers ranging from conductive carbon black through metal powders and fibres to intrinsically conductive polymers. Therefore, it is advantageous when the fibres or filaments or the movable sliding element as a whole have a surface electrical resistance of 100 Ohm to 10¹² Ohm.

From the point of view of the function and preservation of the geometry of the drafting device, it is advantageous if the movable sliding element has a thickness in the range from 0.1 mm to 2 mm.

To reduce cases of failure in the guidance of the movable sliding element, it is advantageous if the movable sliding element passes in the area out of contact with the inner surface of the drafting apron by at least one auxiliary guiding element. To effectively reduce friction, it is advantageous if the movable sliding element has a width ranging from 0.8 to 1.2 times the width of the drafting apron.

For use in textile engineering, it is advantageous if at least one drafting device of roving according to the invention is used in a textile machine for producing roving or on a ring spinning machine or an air-jet spinning machine.

The principle of the movable sliding element for the drafting device of the fibre strand on the textile machine consists in that it is formed by a closed apron adapted to be placed between the drafting apron and the outer surface of at least one stationary component of the drafting device.

The principle of the method for reducing friction between the drafting apron and at least one stationary component of the drafting device of the textile machine for preparing fibres for spinning and/or for spinning staple yarns, in which the drafting apron is driven by a drive roller and further the drafting apron wraps a stationary component of the drafting device, consists in that the drafting apron rubs on the outer surface of a movable sliding element and drives the movable sliding element, while the movable sliding element rubs on the stationary component of the drafting device by its inner surface.

By applying the invention, the friction of the drafting apron around the stationary components of the drafting device is dramatically reduced. The invention also increases the uniformity and quality of the spun yarn, reduces the electricity consumption and heat loss. It is thus possible to use a smaller motor to drive the drafting device, which has a favourable effect on the manufacturing cost of a textile machine, etc.

Description of the drawings

The drawings serve to illustrate the invention, in which Fig. 1 shows a drafting device according to the invention with a movable sliding element, Fig. 2 shows the drafting device according to the invention with the movable sliding element and an apron tensioner, Fig. 3 shows a separate movable sliding element outside the drafting device and Fig. 4 shows an arrangement of the drafting apron, the movable sliding element and the stationary component of the drafting device.

Examples of embodiment The invention will be described with reference to exemplary embodiments of a drafting device 1 of a fibre strand 8 for preparing fibres for spinning and/or for spinning staple yarns on a textile machine. The textile machine comprises at least one workstation, but usually comprises a plurality of workstations arranged next to each other. The drafting device 1 of the fibre strand 8 is arranged at a workstation.

The drafting device 1. of the fibre strand 8 comprises an inlet A of the fibre strand 8 and an outlet B of the fibre strand 8. In the drafting device 1 of the fibre strand 8, the fibre strand 8 is drafted between the inlet A of the fibre strand 8 and the outlet B of the fibre strand 8 and the thus prepared fibre strand 8 is further used in the yarn production process, e.g., in the case of a drawing frame, the drafted fibre strand 8 is placed in sliver cans (not shown), in the case of a roving frame, the drafted fibre strand 8 is wound on a bobbin, the so-called cop, or in the case of a machine for producing staple yarns, the drafted fibre strand 8 is twisted into a staple yarn, mechanically in a ring spinning machine, by an air nozzle in the case of an air-jet spinning machine, etc.

Between the inlet A of the fibre strand 8 and the outlet B of the fibre strand 8_j the drafting device 1 comprises at least one movable drafting apron 2, which is wrapped around a driven drive roller 4 and further guided by wrapping around part of the circumference of the stationary component 7 of the drafting device 1 over the stationary component 7 of the drafting device 1, the so-called bridge. Between the inner surface of the drafting apron 2 and the outer surface of the stationary component 7 of the drafting device 1 is arranged (inserted) a movable sliding element 6, which encircles at least part of the circumference of the stationary component 7, extending outside the drive roller 4, i.e., it is not wrapped around the drive roller 4. The movable sliding element 6 separates the drafting apron 2, or, more specifically, its inner surface, from the stationary component 7, or, more specifically, its outer surface, which means that the movable sliding element 6 is a barrier preventing the mutual contact of the inner surface of the drafting apron 2 and the outer surface of the stationary component 7 of the drafting device 1. Due to the movement of the drive roller 4^ the drafting apron 2 moves in the direction of its endless length, thus causing the movement of the movable sliding element 6 in the same direction in which the drafting apron 2 moves.

The source of the movement of the movable sliding element 6 is therefore solely the friction between the inner surface of the drafting apron 2 and the outer surface of the sliding element 6 at the point at which the apron 2 and the element 6 pass over the stationary component 7 of the drafting device 1, i.e., the bridge, i.e., at the point of the contact of the sliding element 6 a of the drafting apron 2. In an exemplary embodiment shown in Fig. 1 , this is in the area where the inner surface of the sliding element 6 abuts the outer surface of the stationary component 7 of the drafting device 1 and where at the same time the inner surface of the drafting apron 2 abuts the outer surface of the sliding element 6. Consequently, the inner surface of the sliding element 6 abutting the outer surface of the stationary component 7 of the drafting device 1 frictionally moves, i.e., moves on the outer surface of the stationary component 7. In an exemplary embodiment shown in Fig. 2, this is in the area where the inner surface of the sliding element 6 abuts the outer surface of the stationary component 7 of the drafting device L_, i.e., the bridge, and the outer surface of the tensioning element 9 and, at the same time, where the inner surface of the drafting apron 2_abuts the outer surface of the sliding element 6. Consequently, the inner surface of the sliding element 6 abutting the outer surface of the stationary component 7 of the drafting device 1 and the outer surface of the tensioning element 9 frictionally moves, i.e., moves on the outer surface of the stationary component 7 and of the tensioning element 9. On the rest of its length, the movable sliding element 6 passes freely through the space X defined by the inner surface of the drafting apron 2 and the outer surface of the drive roller 4, whereby in this area the sliding element 6 is either not exposed to any stress and is therefore not subject to wear, or wraps around part of the outer surface of at least one unillustrated auxiliary guiding element to limit possible uncontrolled behaviour of the movable sliding element 6 in the area out of contact with the inner surface of the drafting apron 2.

The movable sliding element 6 is, for example, formed by a closed, i.e., endless, apron of a shorter length, or, more precisely, of a shorter length of the circumference than is the length, i.e., the length of the circumference, of the drafting apron 2. The movable sliding element 6 is, for example, formed as a single layer of a single material, e. g. PTFE, or is made of a fabric made of fibres with a low coefficient of friction, or is made of a composite, or is made of a composite with fibrous reinforcement, etc., e. g. PTFE apron with a textile net incorporated inside, etc.

In another exemplary embodiment, the movable sliding element 6 is formed as a fabric, or woven fabric, formed of polyamide filaments, in particular it is formed by a lattice fabric of polyamide filaments. A particularly suitable type of polyamide for forming the movable sliding element 6 as the fabric formed of polyamide filaments or as the lattice fabric formed of polyamide filaments is a polyamide 6.6, PA 66, which has very high wear resistance, whereas the thickness of a fabric made of filaments is reduced compared to the thickness of a fabric made of fibres or yarns.

To prevent or reduce occurrence of static charge due to the sliding of the movable sliding element 6 on the stationary component , which would lead to accumulation of fluff from the environment at the movable sliding element 6 while the fluff accumulation often comes into the yarn, which has to be avoided, the movable sliding element 6, or at least some of its parts, is made as electrically conductive. Therefore at least part of the fibres or filaments creating the movable sliding element 6, or the movable sliding element 6 as a whole, is treated in a special manner to make the movable sliding element 6 electrically conductive. Therefore at least part of the fibres or filaments creating the movable sliding element 6, or the movable sliding element 6 as a whole, is in one embodiment coated with a thin layer of metal, in particular, of silver. In the second embodiment regarding the electrical conductivity of at least part of the fibres or filaments creating the movable sliding element 6, or the movable sliding element 6, as a whole, they are coated with antistatic or conductive polymer or polymers ranging from conductive carbon black through metal powders and fibres to intrinsically conductive polymers. In another embodiment, part of fibres or filaments creating the movable sliding element 6 or part of the movable sliding element 6 as a whole are coated with a thin layer of metal, in particular a thin layer of silver, and part of them are coated with antistatic or conductive polymers ranging from conductive carbon black through metal powders and fibres to intrinsically conductive polymers. For good or optimal functioning, the fibres or filaments creating the movable sliding element 6, or the movable sliding element ^ as a whole, which are treated to achieve their electrical conductivity, have a surface electrical resistance of 100 Ohm to 10¹² Ohm (10 to the power of 12 Ohm).

The width h of the movable sliding element 6 substantially corresponds to the width of the drafting apron 2 or ranges ideally from 0.8 to 1.2 times width of the drafting apron 2. To preserve the geometry and functionality of the drafting device

the thickness t of the movable sliding element 6 is in the range from 0,02 mm to 2 mm.

In the embodiment of the drafting device 1. shown in Figs. 1 and 2, a counter-assembly of an auxiliary apron 20, an auxiliary roller 40 and an auxiliary stationary component 70 is assigned to the assembly consisting of the drafting apron 2, the drive roller 4, the stationary component 7 of the drafting device L_ and the movable sliding element 6. In the direction of the draft, downstream of the assembly of the drafting apron 2, the drive roller 4, the stationary component 7 of the drafting device 1, the movable sliding element 6 and the assembly of the auxiliary apron 20, the auxiliary roller 40 and the auxiliary stationary component 70, a pair of secondary rollers 5 is arranged. In an unillustrated embodiment, the movable sliding element 6 is also inserted between the auxiliary apron 20 and the auxiliary stationary component

70.

Ideally, the invention is used in a textile machine for producing roving or in a ring or air-jet spinning machine. Industrial applicability

The invention can be used in all textile machines for refining a continuous structure of staple fibres, such as a fibre ribbon, a fibre strand, etc., in which at least one drafting apron is used in the drafting device. These textile machines include mainly, but not exclusively, a drawing frame, a roving frame, a ring spinning machine and an air-jet spinning machine.

List of references

1 drafting device of a fibre strand

2 drafting apron

20 auxiliary apron 4 drive roller

40 auxiliary roller

5 secondary roller

6 movable sliding element

7 stationary component of the drafting device 70 auxiliary stationary component

8 fibre strand

9 tensioning element

A inlet of the fibre strand

B outlet of the fibre strand

Claims

Patent claims

1. A drafting device of a fibre strand on a textile machine for preparing fibres for spinning and/or for the spinning of staple yarns on a textile machine, the device comprising at least one drafting apron (2) wrapped around a drive roller (4) and around at least one stationary component (7) of the drafting device (1), characterized in that between at least one drafting apron (2) and at least one stationary component (7) of the drafting device (1), a movable sliding element (6) is inserted.

2. The drafting device according to claim 1, characterized in that the movable sliding element (6) is formed by a movable closed apron.

3. The drafting device according to claim 1 or 2, characterized in that the movable sliding element (6) has a low coefficient of friction against the surface of the stationary component (7).

4. The drafting device according to claim 3, characterized in that the movable sliding element (6) is made of polytetrafluoroethylene (PTFE).

5. The drafting device according to claim 3, characterized in that the movable sliding element (6) consists of a fabric made of fibres with a low coefficient of friction or is made of a composite.

6. The drafting device according to claim 3, characterized in that the movable sliding element (6) is made of a fabric consisting of polyamide filaments.

7. The drafting device according to claim 3, characterized in that the movable sliding element (6) is made of a lattice fabric consisting of filaments of polyamide 6.6 (PA 66).

8. The drafting device according to any of claims 4 to 7, characterized in that at least part of the fibres or filaments or the movable sliding element (6) as a whole are coated with a thin layer of metal, in particular a thin layer of silver.

9. The drafting device according to any of claims 4 to 7, characterized in that at least part of the fibres or filaments or the movable sliding element (6) as a whole are coated with antistatic or conductive polymers ranging from conductive carbon black through metal powders and fibres to intrinsically conductive polymers.

10. The drafting device according to any of claims 4 to 7, characterized in that the fibres or filaments or the movable sliding element (6) as a whole have a surface electrical resistance of 100 Ohm to 10¹² Ohm.

11. The drafting device according to any of claims 1 to 10, characterized in that the movable sliding element (6) has a thickness ranging from 0.02 mm to 2 mm.

12. The drafting device according to any of claims 1 to 11 , characterized in that the movable sliding element (6) passes in the area outside the contact with the inner surface of the drafting apron (2) through at least one auxiliary guiding element (9).

13. The drafting device according to any of claims 1 to 12, characterized in that the movable sliding element (6) has a width ranging from 0.8 to 1.2 times the width of the drafting apron (2).

14. A textile machine for producing yarn, which comprises at least one drafting device (1) of a fibre strand, characterized in that the drafting device (1) is made according to any of claims 1 to 13.

15. A ring spinning machine or an air-air-jet spinning machine comprising at least one drafting device (1) of a fibre strand, characterized in that the drafting device (1) is made according to any of claims 1 to 13.

16. A movable sliding element for a drafting device of a fibre strand on a textile machine, characterized in that it is formed by a closed apron adapted to be placed between the drafting apron (2) and the outer surface of at least one stationary component (7) of the drafting device (1).

17. A movable sliding element according to claim 16, characterized in that the closed apron is made as a movable sliding element (6) made of PTFE or made of a low-friction fibre fabric or made of a composite or made of a polyamide filament fabric or made of a polyamide 6.6 (PA 66) filament lattice fabric.

18. The movable sliding element according to claim 17, characterized in that at least part of the fibres or filaments or the movable sliding element (6) as a whole are coated with a thin layer of metal, in particular a thin layer of silver, and/or are coated with antistatic or conductive polymers ranging from conductive carbon black through metal powders and fibres to intrinsically conductive polymers.

19. The drafting device according to any of claims 17 to 18, characterized in that the fibres or filaments or the movable sliding element (6) as a whole have a surface resistance of 100 Ohm to 10¹² Ohm.

20. A method for reducing friction between a drafting apron (2) and at least one stationary component (7) of a drafting device (1) of a textile machine for preparing fibres for spinning and/or for spinning staple yarns, in which the drafting apron (2) is driven by a drive roller (4) and further the drafting apron (2) wraps a stationary component (7) of the drafting device (1), characterized in that the drafting apron (2) rubs on the outer surface of a movable sliding element (6) and drives the movable sliding element (6) while the movable sliding element (6) rubs on the stationary component (7) of the drafting device (1) with its inner surface.