CN107531000B

CN107531000B - Multilayer corrugated pipe

Info

Publication number: CN107531000B
Application number: CN201680025597.2A
Authority: CN
Inventors: R·维林格
Original assignee: Fraenkische Industrial Pipes GmbH and Co KG
Current assignee: Fraenkische Industrial Pipes GmbH and Co KG
Priority date: 2015-03-20
Filing date: 2016-03-17
Publication date: 2020-03-03
Anticipated expiration: 2036-03-17
Also published as: CN107531000A; WO2016150804A1; DE102015205081A1

Abstract

A multilayer corrugated pipe (10) having an outer layer (14) and an inner layer (16), characterized in that an intermediate layer (18) is arranged between the outer layer (14) and the inner layer (16), the material of the intermediate layer being selected such that no connection is formed between the material and the material of at least one layer adjoining it.

Description

Multilayer corrugated pipe

Technical Field

The invention relates to a multilayer corrugated tube having an outer layer and an inner layer, in particular to a cable protection tube designed as a corrugated tube.

Background

Such bellows are used, for example, in industrial robots for protecting the power supply lines leading to the drive motor, so that they are prevented from being worn out by frequent contact with the robot arm and/or with other parts of the fixed arrangement located around the robot when the robot arm is moved.

Furthermore, in this case it is necessary to be able to detect whether the protective tube is still able to fulfill its protective function or has already suffered a certain degree of wear, so that there is a risk that it can no longer fulfill its protective function reliably.

It is known from the prior art to use multilayer protective tubes, the layers of which are made of the same material, in particular the same plastic, wherein the layers have different colors. If a layer of one color is worn so that layers of other colors are visible, the user recognizes that the wear limit has been reached and the bellows must be replaced.

The disadvantage of the multilayer bellows is that the wear, which often occurs in spots, is often found to be late.

Disclosure of Invention

It is therefore an object of the present invention to provide a bellows of this type with an improved wear indication.

According to the invention, this object is achieved by a multilayer corrugated tube having an outer layer and an inner layer, wherein an intermediate layer is arranged between the outer layer and the inner layer, the material of the intermediate layer being selected such that it is not connected to the material of at least one layer adjoining it.

If the outer layer is worn down to a predetermined minimum layer thickness, even if only subjected to a point-like load, the outer layer cracks over a large area when the bellows is bent as a function of the operation due to the lack of connection to the layer arranged further inside, which can be recognized very well even if the inner and outer layers are not of different colors, since the fraying edges project from the tube. The effect is also enhanced by the inherent stiffness of the outer layer material. In the case of different color constructions of the inner and outer layers, the frayed outer layer has the further advantage that the intermediate layer or the inner layer can be seen over a large area. The inner layer will then act as a protective layer until the tube is replaced.

The protective tube according to the invention is also particularly flexible (bending of the tube axis) because the layers are not connected. This is because the layers can move relative to each other, similar to the relative displacement of the individual layers of the leaf spring, as is known, for example, from older trucks.

As the material of the inner layer and/or the outer layer, for example, polyamide is used, which is known to be suitable for producing protective tubes. If both the outer and inner layers are composed of polyamide, the inner layer also provides sufficient wear protection after the outer layer has worn through. The polyamide may be, for example, PA 12.

The intermediate layer is made of, for example, polyethylene or ethylene-vinyl acetate copolymer. In this connection, polyethylene, for example LDPE(s) ((s))lowdensitypolyeEthylene-low density polyethylene) offers the advantage that polyethylene is hardly bonded to other materials due to its inherent properties. Thus, according to the inventionThe bellows is free of a bonding layer connecting the intermediate layer and the layer adjacent thereto. Furthermore, no special precautions are required to prevent layer connections when producing the bellows according to the invention.

In principle, however, it is sufficient if there is no adhesive layer between the intermediate layer and only one of the layers adjoining it, for example the inner or outer layer. In which case the inner and outer layers are not connected to each other and are thus relatively movable. Preferably, however, the intermediate layer does not form a connection with any adjoining layer.

It has been surprisingly found that the multilayer corrugated pipe according to the invention can be manufactured by co-extruding all layers. This is not obvious to the skilled person, since different materials have different processing characteristics, in particular different processing temperatures, different shrinkage rates, etc. Surprisingly, however, the "closure" of the intermediate layer between the outer layer and the inner layer, i.e. the processing of polyethylene, for example under the conditions required for processing polyamides, in particular at the temperatures required for processing polyamides, is achieved by the inner and outer layers limiting the intermediate layer inwards and outwards.

Since the intermediate layer has the task only of separating the outer layer and the inner layer from one another, so that the outer layer and the inner layer can be displaced relative to one another when the bellows is bent, it is proposed that the intermediate layer is constructed thinner than the outer layer and/or the inner layer. For example, the layer thickness of the intermediate layer is between about 5% and about 20% of the total layer thickness of the wall of the bellows.

Since the outer layer serves the main protective function, while the inner layer only has to ensure that sufficient additional protection is provided up to the time of replacement of the bellows, it is advantageous if the outer layer is constructed at least as thick as the inner layer. For example, the layer thickness of the outer layer is between about 40% and about 70% of the total layer thickness of the wall of the bellows.

According to one embodiment, the thicknesses of the outer layer, the intermediate layer and the inner layer are in a proportion of 45% to 10% to 45% to one another with respect to the total layer thickness of the wall of the bellows. In this regard, the total thickness of the layers is between about 0.3mm and about 1.3mm, preferably between about 0.6mm and about 1.0mm, and more preferably between about 0.7mm and about 0.9 mm.

In a further development of the invention, it is proposed that the intermediate layer is transparent. In this case, the inner layer is directly visible in the event that the worn-out outer layer bursts. Suitable as transparent material for the intermediate layer is, for example, LDPE, since it has a higher molecular weight than HDPE: (highdensitypolyeVinylene-high density polyethylene) lower crystallinity. It is also possible to make the material of the outer layer and the material of the intermediate layer have different colors from each other. Further, the color of the middle layer may be the same as or different from the color of the inner layer.

Although the invention has been described so far in the example of a bellows with only three layers, the bellows according to the invention may also have more than three layers.

Thus, for example, a further inner layer can be arranged within the inner layer. The further inner layer can be designed, for example, as a sliding layer for the cables guided in the protective tube and thus reduce wear between the power supply lines guided in the protective tube and the inner layer. As material for the sliding layer use can be made of a dynamically vulcanised thermoplastic material (TPV), for example TPV, a special form of thermoplastic elastomer. Although the material is directly attached to the polyamide, an additional adhesive material is provided in order to increase the connection between the two materials.

Another outer layer may be provided in addition to the outer layer. The further outer layer may be, for example, a protective layer which protects the outer layer against moisture, or/and may be an electrically conductive layer and/or a layer which is particularly abrasion-resistant. As conductive layer use can be made of polyamides with the addition of conductive additives, for example carbon black or carbon nanotubes. As particularly abrasion-resistant material, particularly abrasion-resistant polyamides can be used. For cost reasons, it is preferred that the thickness of the further outer layer is at most 0.2mm, preferably at most 0.1 mm.

Drawings

The invention is described below with reference to the drawings of two embodiments. Wherein:

figure 1 shows a schematic cross-sectional view of a corrugated tube according to the invention;

FIG. 2 shows an enlarged schematic view of detail II/III in FIG. 1 for the case of a three-layer bellows; and

fig. 3 shows an enlarged schematic illustration of detail II/III in fig. 1 for the case of a five-layer bellows.

Detailed Description

Fig. 1 shows a schematic cross-sectional view of a corrugated tube 10 according to the invention. The bellows 10 has, in its axial direction, peaks 11 and valleys 12 typical for bellows, two of which are shown by way of example in fig. 1 with reference numerals.

Fig. 1 also shows regions II/III, which are shown in fig. 2 and 3 in an enlarged schematic view in two embodiments.

Fig. 2 shows an enlarged schematic view of the region II/III for the case of a three-layer bellows. In this embodiment, the wall of the corrugated tubing 10 includes an outer layer 14, an inner layer 16, and an intermediate layer 18 disposed between the outer layer 14 and the inner layer 16.

The outer layer 14, the inner layer 16 and the intermediate layer 18 have the same orientation but are never connected to one another. I.e. the three layers can be displaced with respect to each other. By allowing the three layers to be displaced from each other, each of the layers may be independently deformed accordingly when the bellows 10 is bent about the axis a (see fig. 1), thereby allowing the flexibility of the bellows 10 to be increased.

Of course, this effect may also be achieved when the intermediate layer 18 is joined to the outer layer 14 or the inner layer 16. Preferably, however, intermediate layer 18 forms a connection with neither outer layer 14 nor inner layer 16. This can be achieved, for example, by the outer layer 14 and the inner layer 16 being made of polyamide, while the intermediate layer 18 is made of polyethylene.

As can also be seen in fig. 2, in this embodiment the outer layer 14 and the inner layer 16 may have substantially the same layer thickness. While intermediate layer 18 has a significantly thinner layer thickness than outer layer 14 or/and inner layer 16. The percentage distribution of the layer thicknesses of the outer layer 14, the intermediate layer 18 and the inner layer 16 can be, for example, 45% to 10% to 45%, wherein the total layer thickness d (see fig. 1) can be approximately 0.7 mm.

As already mentioned above, the lack of connection of the intermediate layer 18 to the outer layer 14 and to the inner layer 16 contributes to extensive cracking of the outer layer 14 in the event of damage. The extensive splitting of the outer layer 14 makes it possible to see from the outside large-area sections of the intermediate layer 18 and/or of the inner layer 16, wherein preferably at least the inner layer has a different color than the outer layer 14, so that damage to the outer layer 14 can be clearly detected.

Preferably, the intermediate layer 18 is transparent so that the differently colored inner layer 16 of the bellows 10 can be seen even without damaging the intermediate layer 18 due to damage to the outer layer 14.

Fig. 3 shows an enlarged schematic view of detail II/III from fig. 1 for the case of a five-layer bellows, which substantially corresponds to the bellows according to fig. 1 and 2. Similar parts in fig. 3 have therefore the same reference numerals as in fig. 1 and 2, but the numerals are increased by 100. The bellows 110 according to fig. 3 is therefore described below only in terms of the differences from the exemplary embodiment according to fig. 1 and 2, with reference being made to the description of the exemplary embodiment according to fig. 1 and 2 with regard to the further description.

The bellows 110 shown in fig. 3 has an additional outer layer 120 outside the outer layer 114, which may have, for example, an electrically conductive and/or moisture-proof function. The additional outer layer 120 is made of, for example, polyamide with embedded conductive fibers, such as carbon fibers. Additional outer layers 120 may form a connection with layer 114, but this is not required.

Furthermore, the bellows 110 has an additional inner layer 122 within the inner layer 116, which may for example have a high degree of sliding properties, so that elements guided in the bellows 110, such as cables, can slide easily in the bellows 110. For this purpose, the additional inner layer 122 can be composed, for example, of a dynamically vulcanized thermoplastic. An additional inner layer 122 may form a connection with layer 116, but this is not required.

In the embodiment shown in fig. 3, the outer layer 120, the inner layer 116, the protective layer 120 and the sliding layer 122 have the same layer thickness, so that the layer thickness of the intermediate layer 118 is preferably less than 10% of the total wall thickness of the corrugated tube 110.

The material of the

outer layers

14, 114 is preferably polyamide, for example PA12, the material of the

inner layers

16, 116 is likewise preferably polyamide, for example PA12, and the material of the

intermediate layers

18, 118 is preferably polyethylene or ethylene-vinyl acetate copolymer.

Claims

1. A multi-layer corrugated pipe having an outer layer and an inner layer,

characterized in that an intermediate layer is arranged between the outer layer and the inner layer, the material of the intermediate layer being selected such that the material and the material of at least one layer adjoining it do not form a connection, the material of the outer layer and the material of the inner layer having mutually different colors, a further inner layer being arranged within the inner layer, the further inner layer being configured as a sliding layer for the cable guided in the multilayer bellows and thus reducing wear between the supply line guided in the multilayer bellows and the inner layer.

2. The bellows of claim 1 wherein the bellows is,

characterized in that the inner layer or/and the outer layer consists of polyamide.

3. The bellows of claim 2 wherein the bellows is,

characterized in that the inner layer and/or the outer layer consist of PA 12.

4. The bellows according to any one of claims 1 to 3,

characterized in that the intermediate layer is composed of polyethylene or ethylene-vinyl acetate copolymer.

5. The bellows according to any one of claims 1 to 3,

characterized in that the corrugated tube is made by co-extruding all layers.

6. The bellows according to any one of claims 1 to 3,

characterized in that the intermediate layer is configured to be thinner than the outer layer and/or the inner layer.

7. The bellows according to any one of claims 1 to 3,

characterized in that the layer thickness of the intermediate layer is between 5% and 20% of the total layer thickness of the wall of the corrugated tube.

8. The bellows according to any one of claims 1 to 3,

wherein the outer layer is configured to be at least as thick as the inner layer.

9. The bellows according to any one of claims 1 to 3,

characterized in that the layer thickness of the outer layer is between 40% and 70% of the total layer thickness of the wall of the corrugated tube.

10. The bellows according to any one of claims 1 to 3,

characterized in that the intermediate layer is transparent.

11. The bellows according to any one of claims 1 to 3,

characterized in that the material of the outer layer and the material of the intermediate layer have different colors from each other.

12. The bellows according to any one of claims 1 to 3,

it is characterized in that another outer layer is arranged outside the outer layer.