DE20114667U1 - Expandable network - Google Patents

Description

PATENT ATTORNEYS

Dipl.-lng. A. Wasmeier

Dipl.-lng. H. Graf

Authorized before the European Patent Office + Trade Mark Office · Professional Representatives before the European Patent Office + Trade Mark Office

Patent Attorneys PO Box 10 08 26 93008 Regensburg D-93008 REGENSBURG PO BOX 10 08 26 German Patent D-93055 REGENSBURG
GREFLINGERSTRASSE 7 and Trademark Office Telephone (0941)79 20 85 Zweibrückenstr. 12 (0941)79 20 86 Fax (0941)79 5106 E-mail: 80297 Munich wasmeier-graf@t-online.de

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C/g 20.338

Date

Date

04 September 2001 W/He

Applicant:

CathNet-Science Holding A/S Langebjergvaenget 8 B DK-4000Roskilde Denmark

Title:

Expandable network

Priority:

Great Britain - No. 0022097 of 08 September 2000

Accounts: HypoVereiiisbint*(BLZ 750^00 73) 5*939 300; ·.:. ···.···. .·* * ·

Postgiroani-Munbhan (BUlAOOAfJD 8φ^93 ®r80t ·*·* :

Place of jurisdiction Regensburg

. A20338.DOC
05.09.01 15:44

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Expandable network

The innovation concerns an expandable tubular mesh for implantation into the lumen of a body passage in order to form a flow channel therein.

Such meshes are mainly used for the treatment of blood vessels showing stenosis and in particular for the treatment of diseases of various anatomical passages of the human or animal body, e.g. for urinary passages, in particular the urethra, or digestive passages, in particular the esophagus.

Percutaneous implantation of an expandable tubular mesh in a stenotic blood vessel is generally recommended, e.g. after conventional angioplasty, to prevent the dilated vessel from spontaneously re-closing or to prevent clogging by the formation of a new atheromatous plaque and the possible recurrence of stenosis.

International patent application WO 98/58600 describes an expandable tubular mesh consisting of an array of radially expandable tubular elements aligned along a common longitudinal axis and connected in succession in pairs by corresponding sets of linking links. Each of the tubular elements consists of a strip forming a zigzag-shaped corrugation, defining curved extreme parts connected in succession and together in pairs in opposite directions by rectilinear intermediate parts. Due to the zigzag-shaped corrugation, the mesh is expandable between a first, non-expanded state, which allows it to be introduced percutaneously, i.e. through the skin, by means of an introducer of reduced diameter, and a second, expanded state, in which the mesh allows a passage channel to be achieved into the lumen of the body passage. To install the mesh, it is placed in the non-expanded state on an angioplasty balloon catheter. If it is his

Once the patient has taken up the correct position, the balloon is inflated, expanding the mesh. Alternatively, the mesh can be made of a material that is regenerative, so that the mesh can expand automatically once it is in place.

International patent applications WO 96/26689 and WO 98/20810 describe networks of a similar type to that of the aforementioned WO 98/58600, but in which the linking links are aligned at an angle to the longitudinal axis of the network. In addition, EP 0928606 teaches a network in which the linking links are not only arranged at an angle to the longitudinal axis, but in which these angles change in polarity in the longitudinal direction of the network.

The essential purpose of the mesh is to support the interior of the body passage to maintain a flow channel through the passage. As the mesh expands, the corrugations forming the tubular elements open from their unexpanded position so that, in the fully expanded mesh, fairly large gaps exist between individual parts of the strip forming the corrugations. The presence of particularly large gaps may result in a deterioration of the support properties of the mesh in that area. The opening of the corrugations is of course an unavoidable consequence of the expansion of the mesh, but one of the objects of the present innovation is to provide a mesh in which particularly large gaps are avoided so that, in the expanded state, the mesh provides as uniform a support surface as possible.

It has further been found that different and possibly useful characteristics can be achieved by making the sign of at least some of the angles of the linking links different. It will be appreciated that the sign of the angle of each linking link with respect to the longitudinal axis can be either positive or negative or neither positive nor negative, in the latter case the linking link is at a zero angle to the longitudinal axis, i.e. parallel to the axis.

This is shown in Fig. 1 of the drawing. In Fig. 1 only a single link 4 is shown in isolation and the three possible angular positions with respect to the longitudinal axis 10 of the network are shown schematically. With numeral 4A is shown the link at a positive angle φ to the axis 10, with numeral 4B the link with a negative angle φ, and with numeral AC the link with an angle which is neither positive nor negative to the axis, in other words parallel to the axis. The terms "positive" and "negative" are used here in a relative sense and may just as well be interchanged - in other words, no importance is to be attached to the fact that the link with a positive angle to the axis is shown on the left hand side of the axis 10 in Fig. 1; this could just as well be the right hand side. What is crucial, however, is the fact that the sign of the angles that the corresponding linking elements 4A, 4B, 4C enclose with the axis 10 is different and that, in particular, the linking elements 4A and 4B enclose equal but opposite angles with the axis.

According to the innovation, a mesh is proposed for implantation in the lumen of a body passage to form a channel therein, the mesh consisting of an arrangement of tubular elements aligned along a common longitudinal axis and successively connected to one another by respective sets of linking members, each of which extends at an angle to the longitudinal axis, each tubular element consisting of a continuous strip forming an approximately zigzag-shaped corrugation defined by a first set of curved parts facing in one direction and a second set of curved parts axially spaced from the first and facing in the opposite direction, and the curved parts being successively connected to one another in pairs in opposite directions by rectilinear intermediate parts, characterized in that

(a) in the non-expanded state of the net, the facing, bent parts belonging to adjacent tubular elements in circumferential

direction from each other by a distance approximately equal to half the distance between the curved parts of each set,

(b) each of the linking links extends from a curved portion associated with one tubular element to a facing curved portion associated with the next adjacent tubular element, the curved portions being connected to one another so as to be circumferentially offset from one another by a distance approximately equal to half the distance between the curved portions of each set, and

c) at least some of the angled linking links are arranged at an opposite angle to the other angled linking links when viewed in the direction of the longitudinal axis.

The structure of the net is substantially cylindrical, with each adjacent pair of tubular elements being connected to the next by a corresponding set of linking links. Each set of linking links may consist of one or more linking links, but preferably all sets contain the same number of linking links.

In the present invention, the angled links of at least some of the sets are arranged at an opposite angle with respect to the longitudinal axis of the net to the angled links of the remaining set. In addition, the net may comprise non-angled links, which are to be regarded as links whose angle to the longitudinal axis is zero. The size of the angles is preferably the same - typically about 50° to the longitudinal axis - but the invention includes the possibility of the size of the angles between different links being different in order to achieve different mechanical properties in different parts of the net.

Preferably, the relative number of linking links which enclose a positive angle to the longitudinal axis compared to those which enclose a negative

Angles to the longitudinal axis are approximately balanced so that the network provides overall structural stability; however, small sections of the network may be specially designed to have a non-stable distribution in order to achieve special properties. In a preferred specific embodiment of the invention, each set of one or more linking links at a specific angle to the longitudinal axis is balanced by a corresponding set of one or more linking links having an equal angle but opposite to the axis. In particular, such equal and opposite sets of linking links are arranged spatially quite close to each other so that a reasonably regular distribution of the two types of linking links (negative and positive) is achieved over the structure of the network. For example, the structure may be designed so that the sign of the angle of the linking links alternates in the longitudinal direction of the network, namely positive, negative, positive, negative, etc.

The linking links may be arranged in any angular position around the circumference of the net; however, it is desirable not to impart a prestress to the structure which would result in unequal bending. To this end, it is preferred to position the linking links of individual sets in differently spaced radial positions around the circumference so that the linking links are approximately uniformly distributed around 360° of the circumference of the net. This does not mean that no two linking links can occupy the same angular position, but merely that it is preferable to choose a balanced distribution of the linking links around the 360°.

It is further preferred that, when the net is considered as a whole, the various linking links are arranged approximately evenly around the circumference so that, for example, there is no concentration of linking links in a particular angular position which could lead to a mechanical prestress for the net. In the preferred embodiment of the invention, the sets of linking links are arranged in a regular pattern along the net and are provided spaced apart in the circumferential direction, such as between each

Pair of tubular elements in an approximately helical shape. The circumferential spacing between adjacent sets of linking links may be chosen according to circumstances, but is conveniently equal along the network. In practice, adjacent sets of linking links are arranged circumferentially offset from one another at a distance approximately equal to the distance between the curved parts of each set or a multiple thereof, for example twice or three times that distance.

Preferably, the linking links are designed to be straight, which means that between their attachment point with the curved part of a tubular element and their attachment point with the curved part of the immediately adjacent tubular element, the linking links run essentially straight. They also expediently have a rectangular cross-section and a depth in the radial direction of the network that is greater than their width. However, they can also have other cross-sections, e.g. be square.

Although it has been pointed out above that the linking links are straight, it should be noted that in practice, since they extend at an angle to the longitudinal axis of the net, unless they are very rigid, they bend slightly outwards with a radius of curvature approximately equal to that of the net. Strictly speaking, such linking links can thus be more accurately described as having a partially helical shape. The use of the word "straight" in the present description should therefore be understood in this sense.

As already stated above, each set of linking elements may comprise one or more linking elements. If a plurality of linking elements are provided in each set, they may be designed to form a balanced set - i.e. having the same number of positive linking elements as negative linking elements - or an unbalanced set in which a smaller number are provided with one sign than with the other.

However, it is also possible that all angularly arranged linking links of each set have a sign. In the case of such an unbalanced set of linking links, this is preferably compensated by the fact that other sets in the longitudinal direction of the network are also unbalanced, but in the opposite sense. Thus, for example, alternating sets of linking links in opposite directions may be unbalanced.

In the preferred embodiment of the invention, each set of linkages comprises only a single linkage, and this will be assumed throughout the remainder of the description. The result of using only a single linkage is that each linkage can act independently and is not subject to the influences of the other linkages connecting the same pair of tubular elements. In particular, the use of a single linkage between adjacent tubular elements allows maximum freedom of movement between adjacent elements, provided that the network as a whole is exceptionally flexible. Thus, adjacent tubular elements can move freely with respect to one another about an axis which is approximately radial with respect to the network, and about an axis through the circumference which is approximately at right angles to the radial direction and about all axes therebetween. It also results in adjacent tubular elements being able to move freely around an axis through the circumference that is approximately parallel to the longitudinal axis of the network, resulting in twisting or distortion in the individual link.

The linking links can be attached at their ends by means of adhesive or by welding. Preferably, however, the linking links are formed integrally with the tubular components.

The innovation is applicable to any type of network having the general structure described above, for example that described in application WO

98/58600. In the net described in the present application, the thickness of the strip forming each of the tubular elements, measured radially with respect to the tubular element, is greater than the width of the strip in the bent parts. In this way, the distribution of the deformation forces during expansion of the net is optimized by adjusting, at least in certain parts constituting each tubular element of the net, the thickness to width ratio as a function of the forces exerted thereon.

Advantageously, the geometry of the rectangular parts should promote bending in the radial direction of the net over the circumferential direction.

For a better understanding, the innovation is described below in conjunction with further objectives, characteristic properties and advantages in conjunction with the schematic representations which merely represent a non-limiting example or a preferred embodiment of the invention. In the drawings:

Fig. 1 is a schematic representation to explain the three possible orientations of the linking link with respect to the longitudinal axis of the network,

Fig. 2 a two-dimensional view of the evolute of the surface of a net after the innovation in the non-expanded state,

Fig. 3 is an enlarged view of a portion of the illustration in Fig. 2, and Fig. 4 is a plan view of a net according to the innovation in the expanded state.

The net of Fig. 2 consists of an elongate, generally tubular body or frame defined by a plurality of tubular elements 1 aligned along a common longitudinal axis and successively connected to one another by a plurality of linking links 4, which are described in more detail below. In the drawing a net of six elements is shown, but typical nets may have as few as three elements or as many as twenty elements or more, depending on the circumstances.

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Each tubular element 1 consists of a strip forming a zigzag waveform defined by curved parts 2 successively connected to each other in pairs in opposite directions by intermediate straight parts 3. For each tubular element, two sets of curved parts can thus be defined, namely the curved parts 2A connecting the straight parts 3 at one end of the tubular element and the curved parts 2B connecting the straight parts 3 at the opposite end of the tubular element. In Fig. 2, the curved parts 2A and 2B are arbitrarily shown at the left and right ends of each tubular element. Fig. 2 shows a two-dimensional evolute of the mesh, showing the mesh as it looks when cut lengthwise and laid flat. The waveform formed by each tubular element 1 is in the form of a closed loop - in other words, the cut ends 12, 13 are actually connected to each other.

Advantageously, for a given tubular element, the straight portions 3 are all of the same length and the curved portions are all identical and approximately semicircular. Thus, the undulation in particular has a uniform shape. The tubular elements 1 are connected in such a way that each curved portion 2A is formed in approximately axial alignment with a corresponding curved portion 2A on each of the remaining tubular elements 1. Accordingly, each curved portion 2B is approximately axially aligned with a corresponding curved portion 2B on each of the remaining tubular elements 1. In addition, each of the curved portions 2A is arranged approximately midway between two adjacent curved portions 2B when viewed in the circumferential direction of the network. In other words, each undulation of each tubular element 1 is arranged in approximately the same angular position around the circumference of the network as a corresponding undulation of the immediately adjacent network. The wave formations of adjacent tubular elements and of all tubular elements can thus be described as spatially in phase with each other, with the result that

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the expanded mesh provides uniform support for the body passage to be treated. This is explained in more detail below.

As best seen in Fig. 2, the thickness of the strip forming each tubular element 1 in the bent parts 2 is greater than the width I of that strip in the bent parts 2. The thickness of the strip in the straight parts 3 is approximately equal to the thickness of the strip in the bent parts 2. The thickness in this context is measured radially relative to the corresponding tubular element.

The profile described above (thickness greater than width) ensures that the bent parts behave properly when subjected to the radial forces that occur during the expansion of the tubular elements.

Preferably, the width 1 ₀ of the strip in the straight parts 3 is greater than the width I of the strip in the curved parts.

For example, the thickness in the bent parts is of the order of 0.135 mm, the width I in the bent parts is approximately of the order of 0.116 mm and the width I ₀ in the straight parts is of the order of 0.165 mm. The length of each tubular element 1, measured in the direction of the longitudinal axis, is approximately 2 mm.

Preferably, the thickness and width transitions between the straight parts 3 and the curved parts 2 are gradual in order to avoid the formation of an incipient fracture.

Between each tubular element 1 and the immediately adjacent tubular element 1, a single linking link 4 is provided, which is the only mechanical connection between the successive tubular elements. As already mentioned, the present innovation includes the possibility of connecting adjacent tubular elements to one another by means of multiple linking links.

• *· • • • ·· · · • ·· ·· ···· • • • * · • · · · • ··· ··· • • • · • · · • ■ · · •

are connected, and that these links are preferably evenly spaced circumferentially of the network. However, the present description only explains a network in which a single link is used to connect each adjacent pair of tubular elements, since this feature itself has certain advantages. Each link 4 is rectilinear and extends from the curved part 2A of one tubular element 1 to the immediately adjacent curved part 2B of the immediately adjacent tubular element 1. Since the curved parts 2A and 2B are angularly spaced around the circumference of the network, the linking links are necessarily arranged at an angle to the longitudinal axis of the network, the circumferential distance between the connection points at opposite ends of the linking link 4 being approximately equal to half the distance between adjacent curved parts 2A, which is of course equal to the corresponding distance between adjacent curved parts 2B. This distance is designated in Fig. 2 by the letter L.

From Fig. 2 it can be seen that the angles of the linking links 4 are not all equal. In particular it can be seen that the leftmost linking link 4 extends from a curved part 2A of a tubular element 1 to the immediately adjacent higher curved part 2B of the immediately adjacent tubular element 1. The next linking link 4 in the direction to the right, however, extends from a curved part 2A of a tubular element to the immediately adjacent lower curved part 2B of the next adjacent tubular element 1. The terms "bottom" and "top" are used herein with reference to the orientation of Fig. 2, but not to denote physical differences in height, as is the case between the curved parts.

As can be seen from Fig. 2, the pattern continues along the length of the net and means that the angle of the link 4 alternates positive and negative along the longitudinal axis of the net. This means that the links fall into two groups: one group whose angle is positive with respect to the longitudinal axis and another group whose angle is negative with respect to the longitudinal axis.

Preferably, the size of the angles for each group is approximately the same, only the sign of the angle is different. The two groups can be arranged in various ways along the length of the network; the preferred way is that one or more links from one group alternate with one or more links from the other group along the length of the network. In this way, the number of linking links from one group is the same or almost the same as the number of linking links from the other groups.

The configuration of the links 4 is chosen such that during bending of the entire net into the expanded state, the primary force exerted on each of the links 4 is a torsional force which causes the link to tend to twist in a corkscrew manner.

The cross-sectional shape of the connecting links 4 is rectangular with a thickness in the radial direction that is greater than the width I ₁ . For example, the thickness of the connecting links 4 is on the order of 0.135 mm, while the width I ₁ is about 0.086 mm. The width of the connecting links 4 is smaller than that of the bent parts 2A, 2B.

The geometry of a single connecting link 4 is shown in enlarged view in Fig. 3. The connecting link 4 extends in a tangent to the circular curved part 2A and in a tangent to the circular curved part 2B. In particular, the connecting link 4 is arranged so that its center line is tangent to the center lines of the two curved parts 2A, 2B to which it is connected at each end.

As already explained, the various linking links 4 should be evenly angularly spaced around the circumference of the net to allow uniform bending in all directions. The circumferential distance between adjacent linking links in the embodiment of Fig. 2 is 4L; other multiples of the distance 2L are possible, including the value of 2L itself. 2L

corresponds to the circumferential distance between adjacent curved parts 2A (or 2B) in each tubular element 1. Preferably, this connection distance continues for all linking links and in the same direction: thus, link 4.2 is spaced from link 4.1 by a circumferential distance 4L in a certain direction, similarly link 4.3 is spaced from link 4.2 by the same distance 4L, in the same direction. This pattern continues in the longitudinal direction of the network and results in an approximately helical distribution of linking links. This ensures that the linking links are regularly offset around the circumference of 360° for the reasons given above.

Reference is now made to Fig. 4 which shows the expanded state of the mesh. Although the mesh shown is the same as that of Fig. 2, only four elements 1 are shown so that more detail can be shown. This drawing is also different from that of Fig. 2 in that it attempts to show the three-dimensional structure of the mesh rather than the artificially flattened shape of Fig. 2.

When the web is expanded, the corrugations forming the tubular members 1 open outwardly from the position shown in Fig. 2 such that in the fully expanded web there are fairly large gaps between individual elements of the strip forming the corrugations. The opening of the corrugations during expansion cannot of course be prevented, but excessively large gaps have been avoided by designing the web described so that in the expanded state the corrugations as between the individual tubular members 1 remain in phase with each other as far as physically possible. This gives a support surface which is as uniform as possible. It will be seen from Fig. 4 that this aim has not been perfectly achieved, but that the corrugations are in phase to a reasonable approximation. The fact that there is only a single link between the tubular members is largely responsible for this advantageous arrangement in the expanded web; the presence of

The absence of a link from one tubular element to another has the effect of preventing the tubular element from expanding naturally, so that the fewer the number of links between the tubular elements, the better the arrangement.

The circumferential distance between adjacent links 4.1, 4.2 etc. also has an influence on the way in which the network expands: as mentioned above, the distance in the network shown is equal to twice the distance between adjacent curved parts 2A (or 2B). This gives the same number (2) of phase relationships between the corrugations of the various tubular elements forming the network. If we look more closely at Fig. 4, it can be seen that the corrugations of any two tubular elements are almost exactly in phase with each other, with the only exception being in the region of the link itself, which disturbs the local image. If the circumferential distance between adjacent links 4.1, 4.2 etc. were only the single distance between adjacent curved parts 2A (or 2B), the corrugations of each tubular element would be approximately in phase with each other, as before, subject to a disturbance in the region of the link.

The described mesh is therefore expandable between an unexpanded state which allows it to be guided within the lumen through a body passage, e.g. a blood vessel, and an expanded state in which the mesh, after a uniform expansion, comes into contact with the inner wall of the body passage, forming a passage channel of approximately constant diameter within the passage.

The mesh is generally expanded mechanically under the action of a radially outward force, e.g. due to the inflation of a balloon.

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A2033a.DOC

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Alternatively, the mesh may be designed to be self-expanding, i.e. capable of changing itself from a first, unexpanded state that allows it to be passed through the body passageway to a second, expanded operating state.

The mesh may be made of any material that is compatible with the body passage and the body fluids with which it comes into contact.

In the case of a self-expanding mesh, materials with a recovery property, e.g. corrosion-resistant steel, Phynox® or Nitinol, are preferably used.

In the case of a mesh that uses forced expansion, a material with a low elastic recovery property can be advantageously used. Examples of this are metallic materials, e.g. tungsten, platinum, tantalum, gold or corrosion-resistant steel.

The mesh can be made from a hollow tube of approximately constant thickness corresponding to the desired thickness. The pattern of tubular components and linking links can be produced either by laser cutting followed by electrochemical polishing, or by chemical or electrochemical treatment.

The mesh can alternatively be made from a thin plate of approximately constant thickness corresponding to the desired thickness of the mesh. The geometric configuration of the mesh can be achieved either by laser cutting and subsequent electrochemical polishing, or by chemical or electrochemical treatment. The thin plate cut in this way is then rolled into the shape of a cylinder and welded so that the desired final structure is achieved. The mesh described can be inserted in a manner known per se. In the case of a mesh using mechanically forced expansion, the insertion system has

stem preferably comprises a balloon-tipped catheter on which the device is positioned in the unexpanded state before being inserted into an insertion tube to deliver it to the site to be treated.

Claims (13)

1. A mesh for implantation into the lumen of a body passage to form a channel therein, the mesh consisting of an array of tubular elements aligned along a common longitudinal axis and sequentially connected to one another by respective sets of linking members each extending at an angle to the longitudinal axis, each tubular element consisting of a continuous strip forming a substantially zig-zag-shaped corrugation defined by a first set of curved parts facing in one direction and a second set of curved parts axially spaced from the first and facing in the opposite direction, the curved parts being sequentially connected to one another in pairs in opposite directions by rectilinear intermediate parts, characterized in that (a) in the unexpanded state of the net, the facing curved parts belonging to adjacent tubular elements are circumferentially offset from one another by a distance approximately equal to half the distance between the curved parts of each set, (b) each of the linking links extends from a curved portion associated with one tubular element to a facing curved portion associated with the next adjacent tubular element, the curved portions being connected to one another so as to be circumferentially offset from one another by a distance approximately equal to half the distance between the curved portions of each set, and c) at least some of the angled linking links are arranged at an opposite angle to the other angled linking links, viewed in the direction of the longitudinal axis. 2. A network according to claim 1, wherein each set of links consists of only a single link. 3. A net according to claim 1 or 2, wherein the angle of a first group of angled linking links is positive with respect to the longitudinal axis, while the angle of a second group of angled linking links is negative with respect to the longitudinal axis. 4. A network according to claim 3, wherein the relative number of linking members in the first and second groups is substantially balanced to provide overall structural stability to the network. 5. A net according to claim 3 or 4, wherein one or more links from the first and second groups of linking links alternate when viewed in the direction of the longitudinal axis. 6. A net according to any preceding claim, wherein all angled linking links enclose the same angle with the longitudinal axis. 7. A network according to any preceding claim, wherein each link at a given angle to the longitudinal axis is matched by a corresponding link at an approximately equal but opposite angle to the longitudinal axis. 8. A net according to any preceding claim, wherein each link has a rectangular cross-section with a thickness which is greater in the radial direction than the width. 9. A net according to any one of the preceding claims, wherein the linking links are formed as a group and are distributed approximately uniformly over the circumference of the net. 10. A net according to any preceding claim, wherein each set of linking links is circumferentially offset from the adjacent set or sets of linking links by an amount equal to a multiple of the circumferential distance 2L between adjacent curved members belonging to one of the sets of curved members. 11. A net according to claim 10, wherein the circumferential spacing between all sets of linking links in the longitudinal direction of the net is equal, so that a generally helical pattern of linking links is formed along the net. 12. A net according to any preceding claim, wherein each link terminates in a tangent to the corresponding curved portions. 13. A net according to claim 12, wherein the curved parts are approximately semicircular in shape and wherein the center line of the linking link runs tangentially to the center lines of the corresponding curved, adjoining parts.