Cable routing device for cleanroom applications and holding element therefor

Abstract

Cable guide device, in particular for clean room applications, for the protected routing of supply lines such as cables, hoses or the like between two connection points, at least one of which is movable relative to the other, wherein the cable guide device has a longitudinal direction (L) and is movable back and forth to form a lower run, an upper run and a deflection bend located between the two, wherein the cable guide arrangement is in a substantially extended position with respect to its longitudinal direction (L) within the upper run and in a curved deflection position within the deflection bend, comprising: - at least two flexible sheaths in the form of bands lying one above the other to form a stack, each of which is formed from receiving channels extending in the longitudinal direction at least between the connection points for at least one supply line and / or for a support element, each sheath having lateral and central receiving channels and an inner and outer side defined by the deflection curve, characterized in that - the cable guide device has at least one holding element which is removably attached to at least one lateral receiving channel and which projects in a direction perpendicular to the band beyond the height of this lateral receiving channel in one or both directions.

Description

Technical field of the invention

[0001] The invention generally relates to a cable guide device with a holding element, in particular for clean room applications, for the protected dynamic guidance of supply lines such as cables, hoses or the like between two connection points, at least one of which is movable relative to the other. Technical background of the invention

[0002] Such dynamic or active cable guide devices protect the cables against unwanted stress during movement, usually between a stationary connection and a moving load, e.g., on a machine. They are typically linearly movable or can be moved back and forth along a longitudinal direction and typically form two strands—a lower strand and an upper strand—and a roughly U-shaped deflection bend between them.

[0003] Furthermore, the invention relates to a holding element suitable for use in this cable guide device.

[0004] The invention specifically relates to a cable routing device intended for cleanroom applications, comprising at least one dust-tight, flexible sheathing, which, for dust-protective sheathing of supply lines, has a number of adjacently arranged and longitudinally extending receiving channels, each of which typically accommodates at least one supply line. The sheathing is intended, in particular, to prevent abrasion of the lines, which inevitably occurs during travel, from being released into the environment. Furthermore, a sheath made of a suitable material can improve the overall abrasion behavior. Furthermore, it is necessary to prevent the upper run from sliding on the lower run when the cable routing device is moved, which is why at least the upper run must assume a substantially elongated shape so that it does not touch the lower run.

[0005] Cable routing devices of this type are offered, for example, by the applicant under the name e-skin® ribbon cable (https: / / www.igus.de / info / e-skin-flat, accessed on April 15, 2024). They essentially comprise two connection points, one of which is assigned to the power sources and is generally fixed, while the other, generally connected to the moving machine part to be supplied, is moved back and forth against the first during operation. The supply cables are generally routed through the connection points so that their protruding ends can be further connected, while the flexible sheath is attached to the connection points by its ends.

[0006] The sheath has a series of receiving channels that run longitudinally side by side from one connection point to the other. For example, multi-core cables or so-called stranded structures for electrical signals, or even fluid lines, can be inserted into these receiving channels. The arrangement of the receiving channels results in the shape of a strip, whereby the individual receiving channels can be connected to one another. The receiving channels located on the outer sides of the strip are referred to below as lateral receiving channels, and those arranged in between are referred to as central receiving channels. Examples of such strips are described, for example, in the published applications WO 2020 / 148300 A1, WO 2020 / 249642 A1 and WO 2021 / 116467 A1 of the applicant of the present invention. The receiving channels can be provided individually, placed side by side and, if necessary, connected to one another with connecting means.It is also possible to create adjacent receiving channels with a lens-shaped cross-section. Each receiving channel can be closed circumferentially, so that the cables must be threaded in from one end. It is also possible to provide the receiving channels with a closable opening running longitudinally, which facilitates inspections and repairs in particular.

[0007] For complex supply applications, it is possible not only to stack the receiving channels next to each other in a single strip, but also to arrange multiple strips or layers on top of each other. This is shown, for example, in the above-cited WO 2021 / 116467 A1 and also described on the applicant's aforementioned website "Flat Ribbon Cable e-skin®." According to this document, up to six layers of receiving channels are possible. Typically, connection points with several "levels" of feedthroughs and attachment points for the sheathing are provided.

[0008] It is also known to design the cable guide device so that it is asymmetrical in terms of bending behavior, i.e., it is bent from the extended configuration in the deflection bend, while it remains largely extended in the cantilevered upper run and essentially does not sag under the influence of gravity. This can be achieved both by designing the sheath (for example, WO 2016 / 042134 A1) and by inserting support elements connected to the connection points, preferably in the form of support chains, into at least one of the receiving channels.

[0009] Due to the shape of the individual receiving channels, when folded together to form a belt, a structure of grooves running in the longitudinal direction is created, which varies in depth. This means that there is a general tendency for the receiving channels of an inner belt lying on top to sink into these grooves when shifted laterally. This can provide a certain degree of stabilisation for the layer package. In practice, however, it has been shown that this is not sufficient to reliably prevent the layers from shifting against each other, particularly in the area of ​​the deflection bend, as well as during lateral acceleration and over longer travel distances. It can also happen that layers separate from each other instead of remaining in contact with one another. This leads to parts of the casing sliding against one another, which must be avoided at all costs due to the risk of particle formation due to abrasion.

[0010] In addition, individual parts of the cable guide device may not move parallel to each other as required. Increased friction between the cables inside the receiving channels may create additional moments of resistance and increase wear.

[0011] Attempts were made to avoid these problems by using a closed, elastic, tensioned belt that runs transversely around the entire layer stack. However, this approach is not secure and also has the disadvantage that the belt must be applied before the connection points are connected to the wrapping and therefore cannot be retrofitted. This measure also carries the risk that the movement of the receiving channels against each other under the pressure of the tensioned elastic belt will result in increased wear and corresponding abrasion. Furthermore, significant wear of the belt was observed on the outer sides of the multi-layer stack. Object of the invention

[0012] Therefore, it is an object of the invention to provide a cable routing device suitable for clean rooms, in which a safe routing of the individual receiving channels and cables is ensured at all times during operation.

[0013] A further object of the invention is that the measures proposed to achieve the above object can be implemented at any time in the form of a retrofit, even in existing cable routing devices.

[0014] These objects are achieved by a cable guiding device according to the main claim and a holding element according to the independent subsidiary claim 12.

[0015] The dependent subclaims relate only to preferred embodiments of the cable guide device according to the invention and the holding element according to the invention and are not intended to limit their scope of protection. General description of the invention

[0016] It was surprisingly discovered that, through the relatively simple measure of attaching at least one retaining element to at least one of the lateral receiving channels, the part of the retaining element that projects inward and / or outward beyond the height of this receiving channel can stabilize the receiving channels located inside or outside this receiving channel in an adjacent layer, particularly if it touches this layer. This effect is not limited to the adjacent layers but, depending on the size of the retaining element, also extends to more distant layers if these can come into contact with the retaining element.

[0017] Since the orientation of the layers in the stack changes according to height at the transition from the lower run to the upper run, the layer located outside the deflection bend, i.e., on the side facing away from the cable guide device, is referred to as the outer layer, the layer located inside the deflection bend, i.e., on the side facing the cable guide, is referred to as the inner layer, and any additional layers present in between are referred to as the middle layers. The at least one retaining element is preferably attached to the outer layer.

[0018] In a preferred embodiment, the holding element has a clamping section that partially encloses the lateral receiving channel onto which it is attached, as well as at least one flat tab section, the plane of which is oriented both substantially perpendicular to the plane of the casing and in its longitudinal direction. In the installed position, the at least one tab section can then be applied to the outer side of the stack of multiple layers of the casing and stabilize it.

[0019] The cable routing device according to the invention preferably comprises a plurality of such holding elements. These can more preferably be attached in pairs to both lateral receiving channels of the same or different layers and can be arranged opposite each other in pairs. Other arrangements are also possible.

[0020] The cable guiding device according to the invention preferably has two to six superimposed layers of band-shaped sheaths.

[0021] To fully utilize the advantages of the invention, the tab sections of the holding elements are dimensioned so long that they reach at least to the height of the outer or inner layers in the stack. Therefore, if the holding element is plugged onto a lateral receiving channel of the outer layer, the tab section extends at least to the inner layer. If the holding element is plugged onto a lateral receiving channel of the inner layer, the tab section extends at least to the outer layer. If, in the case of multiple layers, the holding element is plugged onto a receiving channel of a middle layer, two tab sections are preferably present, which extend at least to the inner or outer layer.

[0022] It happens that the individual layers or band-shaped wrappings have different widths, for example, because they comprise a different number of receiving channels or channels with different diameters. In this case, it is particularly advantageous if the tab section adjacent to the outside of the multi-layer stack is adapted to the profile of this outer surface. This means, for example, that the tab section has a bulge that engages with a recess in the outer surface of the stack.

[0023] In a further preferred embodiment, at least one support element is provided, which runs in at least one of the receiving channels and is attached by its ends to the two connection points. Such support elements are intended to prevent the freely suspended upper strand from sagging under the influence of gravity and coming into contact with the lower strand during movement. Suitable support elements include, for example, structures made of wires, spring steel, or a suitable plastic. Support chains, such as those described in the published applications WO 2020 / 249642 A1 and WO 2021 / 116462 A1, are particularly preferred.

[0024] If the holding elements are attached to both sides of the multi-layer stack and lie opposite one another in pairs, both holding elements of such a pair can preferably be connected to one another by a flexible band, which can particularly preferably also be under tension. The band preferably encloses the layer of the layer stack to which the clamp sections of the holding sections are held, particularly preferably the outer layer. This band is preferably not particularly elastic. This ensures that the holding elements do not slip and the stack is further stabilized. The band preferably has a closure part that can be closed after attachment by connecting both ends. So-called cable ties, for example, are suitable.

[0025] Preferably, this flexible band runs from the outside of the clamp section of the holding element through an opening in the tab section.

[0026] The invention also includes a holding element for use in the cable routing device described above. It has a clamp section that can be placed on and removed from a lateral receiving channel of the multi-layer stack. The clamp section has a longitudinal axis that, in the installed position, runs parallel to the longitudinal direction of the casing or to the longitudinal axis of the receiving channel. The holding element also has at least one flat tab section that, in the installed position, extends essentially perpendicular to the plane of the casing. Two tab sections can also be provided, which then run in opposite directions from the clamp section.

[0027] The clamp section preferably has two legs that complement each other to form an open ring. To attach or remove the retaining element from the receiving channel, the open ring can be elastically opened further and closes elastically around the receiving channel after attachment. The removal procedure can be similar. At least one of the at least one tab section is connected to at least one of the legs substantially opposite the opening of the open ring, for example, by being integrally formed.

[0028] The shape of the legs or the open ring is preferably adapted to the circumference of the lateral receiving channel to which the holding element is to be attached.

[0029] The length of at least one tab section can advantageously be adapted to the height of the multi-layer stack of wrappers. This allows a specific shape of the holding element to be used for stacks of different heights.

[0030] In order to adjust the length of a tab section, one or more predetermined breaking points, for example notches, created by weakening the material are particularly preferably provided, which run transversely to the tab section.

[0031] To reduce the required number of retaining elements to be kept in stock, the retaining element can advantageously consist of two parts that can be connected together for use. One part comprises a first leg of the clamp portion and the tab portion connected to it, while the other part comprises the second leg and, optionally, a second tab portion.

[0032] The material of the retaining element is generally elastic, with the dimensions and thicknesses being selected according to the task at hand: to be able to be placed on and removed from the receiving channel while simultaneously exhibiting sufficient holding force. The retaining element is preferably made of a thermoplastic elastomer. Short description of the drawings

[0033] The invention will now be explained in more detail by way of example and without limitation with reference to the accompanying drawings. They show: Fig. 1A and Fig. 1B: a cable guide device according to the invention in a schematic side view, Fig. 2: the upper run of a cable guide device according to the invention in an oblique view from above, Fig. 3A: a section AA' through the upper run to Fig. 2, Fig. 3B: a side view B after Fig. 2, Fig. 4: an oblique view of a cable guide device according to the invention, Fig. 5: a section through the upper run according to an alternative embodiment of the invention, Fig. 6A to 6E: a holding element according to the invention in front, side, rear, top and oblique views, Fig. 7A and Fig. 7B: a second embodiment of the holding element according to the invention in side view. Detailed description of preferred embodiments

[0034] In the Fig. 1A and Fig. 1B, a cable guide device according to the invention is shown schematically in side view, the cables 45 (see Fig. 4) from a fixed connection point 10 on a base to a mobile connection point 9 on a moving component (not shown in detail), for example an automatically operated tool. The cable guide device is divided into a lower run 3, a deflection bend 4 and an upper run 2. During operation, the mobile connection point is moved back and forth in the longitudinal direction L, whereby the runs become shorter or longer in opposite directions. In general, the lower run rests on a support surface and rolls there during movement, while the upper run floats freely or rests on the lower run and slides in the longitudinal direction L. In cleanroom applications, however, the latter is not possible because the sliding poses the risk of contamination through abrasion. In order to further limit contamination of the cleanroom even with a freely suspended upper run, the cables are guided in flexible sheaths, for example made of soft plastic.For this purpose, the cable guide device 1 has several receiving channels 25 (. Fig. 2) that are arranged parallel to one another and can be interconnected to form a ribbon-like structure. The receiving channels can each accommodate one or more lines. Typically, several of the ribbon-like structures are stacked on top of one another, with each structure forming a layer of the stack. In the example shown, there are three layers. Depending on their position in the stack, the layers are referred to as the outer 7, middle 6, and inner 5 layers.

[0035] The cable guide device according to the invention also has holding elements 8 which are fixed to the outer layer 7 with their clamp section 62 ( Fig. 6B). The tab section 61 ( Fig. 6B) of the holding elements rests laterally on the side edges of the middle and inner layers 5, 6 and thus stabilizes the layer stack, particularly during the process.

[0036] In Fig. 1A, the retaining elements 8 are dimensioned such that their tab sections extend inward (relative to the entire cable routing device) beyond the layer stack. This has the advantage that additional layers of support channels can be added as needed during retrofitting, provided the connection points can be retrofitted accordingly. Fig. 1B Retaining elements in which the tab sections are substantially aligned with the inner layer.

[0037] Fig. Figure 2 shows the upper run of a cable guide device according to the invention in an oblique view of the outer layer of the layer stack. In this layer, five receiving channels 25 are arranged side by side, which are held in the outer clamping block 23 of the connection point 22. The connection point 22 also includes an inner clamping block 24 for the inner layer of receiving channels (hidden here). To stabilize the stack, four holding elements 21 are provided, which are arranged in pairs opposite each other on the two lateral receiving channels. They are held to the lateral receiving channels by their clamp sections.

[0038] Fig. 3A shows a section AA' through the Fig. 2 shows the upper run 30 of a cable guide device according to the invention. It has two layers 32, 33 of receiving channels. The inner layer 33 here consists of four receiving channels 31, on which the outer layer 32 rests. Holding elements with their clamp sections 34 are held on the lateral receiving channels of the outer layer 32, and their tab sections 35 protrude beyond the height of the layer stack.

[0039] Cables can be inserted into the still empty receiving channels 31 shown here, for example, individually or in the form of stranded structures. This can be done from the end, but also after opening laterally, if the receiving channels are designed accordingly (for example, according to WO 2020 / 148596 A1). If stiffening of the upper run is necessary, for example due to a long travel path and / or higher weight of the guided cables, support elements, such as support chains, can also be inserted into individual or all receiving channels 31 of the inner layer 33. The ends of the support elements as well as the receiving channels must be attached to the connection points.

[0040] The tab sections 35 of the retaining elements extend inward beyond the layer stack. This opens up the possibility of incorporating additional layers into the cable guide device even within layer 33. The curved design of the tab sections 35 allows a certain holding force to act on these additional layers, preventing them from possibly detaching from layer 33, which is stiffened by support elements.

[0041] Fig. 3B shows a view from direction B ( Fig. 2) to the front side of the connection point 9 for the upper run. This connection point comprises two clamping blocks 37, 38 for the receiving channels of the two layers 32, 33. The fastening of the receiving channels and, if applicable, the support elements in the clamping blocks can be effected in a known manner using force-locking and / or form-locking methods and is not shown in detail here.

[0042] Fig. Figure 4 shows a further embodiment of a cable guide device 40 according to the invention, with an outer layer 42 consisting of five receiving channels 47 and a corresponding inner layer 41. Cables 45 are already inserted into the receiving channels. Due to the relatively short design, no support elements are present between the connection points 44 and 43. They can be installed in free receiving channels if necessary by rearranging the cables. The retaining elements 46 are sufficient for stabilization here.

[0043] A second embodiment of the cable guide device according to the invention is shown in Fig. 5, specifically a cross-section through the upper run. Two holding elements can be seen with the clamp sections 52 and the tab sections 51, which are held on the lateral receiving channels 59 of the outer layer 56 and lie opposite each other as a mirror-image pair. Furthermore, a middle layer 57 and an inner layer 58 are arranged between the tab sections 51, which are only indicated schematically here and can be designed variably with regard to the number and shape of the receiving channels. A flexible band 53 runs around the receiving channels of the outer layer 56, specifically in the area of ​​the clamp sections 52 outside the holding elements and in the area of ​​the tab sections 51 inside on the inward-facing side of the outer layer. It is guided through openings 55 in the holding element. This band is typically narrower than the width of the holding element. The band can be an endless elastic band.According to the invention, it is particularly provided that the band can be closed into an endless ring by means of a closure part 54. This closure part can be, for example, a hook-and-loop fastener. So-called cable ties are also usable. The closure part can also be formed by a material connection such as gluing or welding the band ends. This band further stabilizes the layer stack. Furthermore, this embodiment offers the possibility of replacing the band or adding, replacing, or even removing additional layers of receiving channels in a retrofitting process.

[0044] The holding element according to the invention is in Fig. 6A to 6E are shown in detail. Fig. Figure 6A is a front view of the retaining element 60 with the tab portion 61 and the clamp portion 62. The clamp portion 62 comprises, as better shown in Fig. 6B shows the two legs 63 and 64, which are connected to one another at one end to form the clamp section 62 and separated at the other end by a gap 65. If the holding element is made of an elastic material, the legs 63, 64 can be moved apart, widening the gap 65, so that the holding element can be pushed from the side onto a lateral receiving channel of the band-like structure, forming the cable guide device according to the invention. The tab section 61 is attached to the clamp section at one end near the connection point of the legs 63, 64.

[0045] The retaining element according to Fig. 6A, notches 67 are provided in the tab section 61 as predetermined breaking points in order to shorten the length of the tab section if necessary.

[0046] Fig. Figure 6C is a rear view of a retaining element according to the invention. Here, an opening 66 for the passage of the flexible band can be seen in the second embodiment of the cable guide device according to the invention. This is also shown in the plan view according to Fig. 6D to recognize.

[0047] The oblique view Fig. 6E also shows the features of the holding element according to the invention.

[0048] A second embodiment of the holding element according to the invention is shown in the Fig. 7A and Fig.7B. The tab section 71 is connected only to a first leg 73 of the clamp section, while the other, second leg 74 is initially a separate component that is also provided with a pin 75. This pin can be inserted into a blind hole (not shown here) on the underside of the first leg 73. The pin 75 is provided with a toothed profile on its surface so that it is held in the blind hole by friction. This means that the force required for insertion is significantly less than that required for removal.

[0049] When attaching a retaining element of this embodiment to the layer stack of a cable routing device, the gap between the legs 73, 74 no longer needs to be opened by elastically deforming the material. Instead, each leg can be individually placed against the lateral receiving channel and then the pin 75 can be secured in the blind hole. This makes it possible to use materials with low elasticity but higher strength values. If necessary, opening the clamp section can also be achieved by destroying the retaining element, as this generally does not entail high costs.

[0050] In this embodiment, it is also possible to keep the gap between the two legs very small, so that the receiving channel is almost completely enclosed by the clamp section. List of reference symbols 1 cable routing device 2 upper strand 3 lower strand 4 deflection bends 5 inner layer 6 middle position 7 outer layer 8 holding elements 9 Mobile connection point 10 fixed connection points 20 upper run 21 holding elements 22 Mobile connection point 23 outer terminal block 24 inner terminal block 25 recording channels 26 outer layer 30 upper run 31 recording channels 32 outer layer 33 inner layer 34 Holding element, clamp section 35 Holding element, tab section 36 Mobile connection point 37 outer terminal block 38 inner terminal block 39 bridges 40 Cable routing device 41 Lower strand 42 Upper Drum 43 Mobile connection point 44 fixed connection point 45 lines 46 holding elements 47 recording channels 48 deflection bends 50 upper run 51 Holding element, tab section 52 Holding element, clamp section 53 flexible band 54 closure part 55 Opening 56 outer layer 57 middle position, schematic 58 inner layer, schematic 59 recording channels 60 holding element 61 tab section 62 bracket section 63 legs 64 legs 65 gap 66 Opening 67 notch 70 holding elements 71 Tab section 73 first leg 74 second leg 75 cones QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2020 / 148300 A1

[0006] WO 2020 / 249642 A1 [0006, 0023] WO 2021 / 116467 A1 [0006, 0007] WO 2016 / 042134 A1

[0008] WO 2021 / 116462 A1

[0023] WO 2020 / 148596 A1

[0039] Cited non-patent literature

[0000] https: / / www.igus.de / info / e-skin-flat, accessed on April 15, 2024

[0005]

Claims

[1] Cable guide device, in particular for clean room applications, for the protected guidance of supply lines such as cables, hoses or the like between two connection points, at least one of which is movable relative to the other, wherein the cable guide device has a longitudinal direction (L) and is movable back and forth to form a lower run, an upper run and a deflection bend located between the two, wherein the cable guide arrangement is in a substantially extended position with respect to its longitudinal direction (L) within the upper run and in a curved deflection position within the deflection bend, comprising: - at least two flexible sheaths in the form of strips lying one above the other to form a stack, each of which is formed from receiving channels extending in the longitudinal direction at least between the connection points for at least one supply line and / or for a support element, each sheath having lateral and central receiving channels and an inner and outer side defined by the deflection curve, characterized by , that - the cable guide device has at least one holding element which is removably attached to at least one lateral receiving channel and which projects in a direction perpendicular to the band beyond the height of this lateral receiving channel in one or both directions. [2] Cable guiding device according to claim 1, characterized bythat the holding element has a clamp section which at least partially encompasses the lateral receiving channel, and at least one flat tab section which is oriented with its plane both substantially perpendicular to the plane of the casing and in its longitudinal direction. [3] Cable guiding device according to claim 1 or 2, characterized by that it has several holding elements. [4] Cable guiding device according to claim 3, characterized by that the holding elements are arranged in pairs opposite each other on both lateral receiving channels. [5] Cable guiding device according to one of the preceding claims, characterized by that it has two to six superimposed layers of band-shaped coverings. [6] Cable guiding device according to claim 5, characterized by that the tab sections of the holding elements extend at least to the outer and / or inner layer. [7] Cable guiding device according to claim 5 or 6, characterized by that the tab sections of the holding elements are adapted to the profile of the outer surface of the stack of superimposed wrappers. [8] Cable guiding device according to one of the preceding claims, characterized by that a support element runs in at least one of the receiving channels. [9] Cable guiding device according to claim 8, characterized by that the support element is a support chain. [10] Cable guiding device according to one of the preceding claims 4 to 9, characterized by that opposing holding elements are connected in pairs by a flexible band which runs transversely around the layer of the multi-layer stack by which the holding elements are held. [11] Cable guiding device according to claim 10, characterized bythat the tab section of the holding elements has an opening for the passage of the flexible band. [12] Holding element for use in the cable guide device according to one of the preceding claims, characterized by in that it has a clamp section which can be placed on and removed from a lateral receiving channel, wherein the clamp section has a longitudinal axis which, in the installed position, runs parallel to the longitudinal direction of the casing, and at least one tab section which, in the installed position, extends from the clamp section substantially perpendicular to the plane of the casing. [13] Holding element according to claim 12, characterized by that the clamp section has two legs which can be elastically opened and can engage around the lateral receiving channel, wherein at least one of the at least one tab section is connected to one of the legs. [14] Holding element according to claim 13, characterized bythat the shape of the legs is adapted to the circumference of the lateral receiving channel. [15] Holding element according to one of claims 12-14, characterized by that the length of at least one tab section can be adapted to the height of the multi-layer stack of wrappers. [16] Holding element according to claim 15, characterized by that the tab section is provided with at least one predetermined breaking point. [17] Holding element according to one of claims 13-16, characterized by that it consists of two parts which can be connected to one another, one of which comprises a leg of the clamp section and the tab section connected thereto and the other of which comprises the second leg of the clamp section and optionally a second tab section. [18] Holding element according to one of claims 12-17, characterized by that it is made of an elastic, preferably thermoplastic, plastic.

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