Multilayer tube for a vehicle tire

Abstract

The invention relates to a multilayer tube for vehicle tires, in particular for tires for bikes, at least comprising a first and a second closed layer (1, 3) made of polymer material, characterized by at least one layer of foamed polymer material (2) which is situated between the first and the second closed layer (1, 3).

Description

[0001] Multi-layer air hose for vehicle tires

[0002] The present invention relates to a multi-layer air tube for vehicle tires.

[0003] Background of the invention

[0004] Tires for vehicles usually consist of a casing, a rim and an air-filled tube which is positioned between the rim and the casing.

[0005] The casing, as the outer part of the vehicle tire, keeps the tire dimensionally stable and transfers acceleration, braking and lateral guidance forces to the ground.

[0006] The hose is equipped with a valve for filling with air and maintains the internal pressure.

[0007] Air tubes for vehicle tires are preferably lightweight and, in conjunction with the casing, low rolling resistance to reduce friction loss during driving. To ensure the puncture resistance of the air-carrying tube, tubes must also be airtight and resistant to damage.

[0008] To reduce the weight of air hoses and avoid friction losses, the wall thickness of the hose can be reduced. However, a reduced wall thickness impairs other properties, such as the air retention or durability of the hose, and thus its puncture resistance.

[0009] As a result, damage to the hose, such as punctures, pinching, aging or incorrect air pressure, can lead to unwanted air leakage from the hose.

[0010] For this purpose, certain materials can be used to improve the properties of air hoses.

[0011] Butyl rubber, for example, is a common material for vehicle hoses. Butyl hoses are inexpensive, durable, and lose air slowly. However, due to their comparatively high weight, hoses made of this material result in higher rolling resistance than other materials.

[0012] To save weight and reduce the rolling resistance of the tire, latex or thermoplastic elastomers, including thermoplastic polyurethane (TPU), can be used instead of butyl rubber for air tubes.

[0013] TPU hoses weigh about a quarter of rubber-based alternatives and have a significantly smaller pack size while still offering good stability and air retention.

[0014] Latex is more flexible than butyl rubber or TPU and has low rolling resistance. However, air can escape through the material relatively quickly, so latex tubes require frequent inflation. Latex tubes are generally lighter than butyl tubes, but are comparatively expensive and require more maintenance.

[0015] Multi-layer hoses with an inner and outer layer are also known. Such multi-layer hoses are said to offer improved properties, such as increased air retention and puncture resistance, compared to single-layer hoses.

[0016] Nevertheless, even multi-layer hoses can be severely damaged by punctures, pinching, etc. This is due to the fact that sharp or sharp objects can penetrate the inner and outer layers despite the multi-layered design, causing the entire hose to be damaged by crack propagation, and in turn, air can escape.

[0017] To increase the puncture resistance of multi-layer hoses, hoses can be equipped with one or more intermediate layers.

[0018] DE 102017118314 A1 discloses a multi-layer tube for a vehicle wheel, which comprises an inner layer and / or outer layer made of TPU to reduce weight and increase air retention compared to known butyl tubes. Furthermore, the tube can have an intermediate layer made of an ethylene-vinyl alcohol copolymer, a gel, or thermoplastic polyurethane to increase the tube's puncture resistance. Summary of the Invention

[0019] The present invention is based on the object of providing an air tube for vehicle tires with high puncture resistance and low weight.

[0020] The object is achieved by a multi-layer air hose for vehicle tires, in particular for tires for bicycles, with at least a first and a second closed layer of polymer material, characterized by at least one layer of foamed polymer material which is arranged between the first and the second closed layer.

[0021] Short description of the characters

[0022] Figure 1 shows the schematic structure of the multi-layer air hose according to the invention, wherein the foamed polymer material 2 is arranged between a closed outer layer 1 and a closed inner layer 3.

[0023] Figure 2 shows the schematic cross-section of the air-conducting hose according to the present invention comprising a layer of foamed polymer material 2, a closed outer layer 1 and a closed inner layer 3.

[0024] Figure 3 shows the schematic structure of the multi-layer air hose according to the invention with an outer layer 1, inner layer 3 and several layers of the foamed polymer material 2, which are separated from each other by a closed intermediate layer 5.

[0025] Figure 4 shows the schematic structure of the multi-layer air hose according to the invention, wherein the foamed polymer material 2 is arranged between a closed outer layer 1, a closed inner layer 3 and two closed intermediate layers 5.

[0026] Figure 5 shows the schematic structure of the multilayer air hose according to the invention, comprising an inner layer 3 and several layers of foamed polymer material 2, separated from each other by a closed intermediate layer 5. In this arrangement, one of the foamed layers 2 forms the outer layer. Description of the embodiments

[0027] The term "foamed polymer material" refers to a polymer material whose density is reduced by the presence of numerous small, open or closed cavities (pores) distributed throughout its mass and created by foaming. The foaming of polymer material is known to those skilled in the art and can be carried out physically or chemically.

[0028] Surprisingly, it has been shown that by arranging the foamed polymer material between a first and a second closed layer, high wall thicknesses of an air tube can be achieved with minimal weight increase. The multi-layer air tube has proven particularly advantageous for vehicle tires, especially bicycle tires.

[0029] The term "closed layer" means a continuous layer of polymer material without gaps or voids. The closed layers of the present invention preferably have a higher density than the layer of foamed polymer material.

[0030] By separating the two closed layers with the foamed polymer material, the resistance of the hose according to the invention is increased compared to hoses without a foamed inner layer. The inventive arrangement of the individual layers limits any damage that occurs, such as cracks or punctures, to a closed layer, since the closed layers of the air hose are largely decoupled from each other by the foamed polymer material.

[0031] The foamed polymer material thus prevents further damage to at least a second closed layer. In the event of an object penetrating or crushing the air hose, the multi-layer structure of the hose according to the invention makes it significantly more difficult to penetrate or damage all layers. The structure of the air hose according to the invention further has the advantage that the air hose is additionally cushioned by the foamed polymer material, which consequently leads to less damage and increases the puncture resistance of the hose. Surprisingly, it has been shown that the roughness of the hose can be increased by the layer of foamed polymer material. In particular, the size of the pores in the foamed polymer material can influence the roughness of the hose. It has been found that the roughness of the hose increases with the size of the pores in the material.

[0032] The pore size can typically be influenced by the conditions of the foaming process. Such processes and their influence on pore size are known to those skilled in the art. For example, it is known that the addition of foaming agent can influence pore size.

[0033] A higher roughness of the tube has the advantage that the tube can be better inserted between the rim and the casing during assembly due to optimized sliding properties and the abrasion resistance of the tube is increased.

[0034] The thickness of the closed layers can also influence the roughness of the hose. The thicker at least one closed layer is, the more the roughness of the hose is reduced. Preferably, the closed layers are designed in such a way that the roughness of the hose is not reduced.

[0035] The hose according to the invention has, regardless of the thickness of the closed layers, the advantage that the multi-layer arrangement of the individual layers significantly reduces the risk of damage to all layers.

[0036] The term "roughness" refers to the vertical deviation of the actual surface from its ideal shape. The roughness of the present invention is determined by measuring the Ra value according to ISO 25178. The "Ra value" corresponds to the arithmetic mean of all deviations of the roughness profile along the reference line. In ISO standards, the term "CLA" (center line average) is used for this purpose. Both terms, "Ra value" and "CLA," are synonymous. According to the present invention, the Ra value is preferably determined using a conventional roughness measuring device according to the method specified in ISO 25178, for example, using a "MarSurf PS 10" device (manufacturer: Mahr).

[0037] In an advantageous embodiment of the present invention, one of the two closed layers forms an outer layer of the hose. The outer layer is in contact with the external environment of the hose, preferably with the casing. Preferably, one of the two closed layers forms an inner layer of the hose. The inner layer of the hose is arranged such that it is in contact with the air-filled cavity of the hose.

[0038] Figures 1 and 2 show an embodiment in which a closed layer forms an outer layer 1 and a second closed layer forms an inner layer 3 between a foamed polymer material 2 of the hose.

[0039] The outer and inner polymer layers 1,3 take on the task of keeping the hose airtight.

[0040] It has been found to be particularly advantageous if the layer of foamed polymer material is as thick as possible and the outer layer is as thick as necessary.

[0041] A particularly preferred embodiment of the method is characterized in that the inner layer of the hose has a layer thickness of 0.1 mm and more, in particular up to 2 mm.

[0042] Preferably, the outer layer of the hose according to the invention has a layer thickness of 0.05 to 1 mm.

[0043] In a further preferred embodiment, the layer thickness of the foamed polymer material is between 0.1 and 1.5 mm.

[0044] In a further embodiment of the present invention, the air hose is characterized by the presence of one or more further closed layers and / or one or more further layers of foamed polymer material.

[0045] Multi-layer structures of the hose according to the invention can be designed both symmetrically and asymmetrically if additional functional layers are required for improved layer adhesion, optimized air retention or increased robustness.

[0046] A variant of the design of the hose according to the invention is shown in Figure 3. The

[0047] The air hose comprises two layers of a polymer material 2, which are separated from each other by a closed intermediate layer 5. The air hose is defined by a closed outer layer 1 and a closed inner layer 3.

[0048] Another embodiment is shown in Figure 4, which relates to a multi-layer air hose comprising a closed outer and inner layer 1, 3 and two closed intermediate layers 5. The layer of foamed polymer material 2 is arranged between the first and second closed intermediate layers 5.

[0049] Preferably, a further layer of foamed polymer material can form an outer layer of the hose. The foamed outer layer can be in contact with the casing.

[0050] Furthermore, a further layer of foamed polymer material can form an inner layer of the hose.

[0051] Figure 5 shows a further preferred embodiment of the hose according to the invention comprising two layers of foamed polymer material 2, which are separated from each other by a non-foamed, closed intermediate layer 5. The air hose according to this embodiment is delimited by a closed inner layer 3 and by a foamed layer 2 as the outer layer.

[0052] Preferably, the material of the closed layers contains thermoplastic polyurethane or consists of thermoplastic polyurethane.

[0053] The material of at least one closed layer may differ from the material of another closed layer.

[0054] In a particularly advantageous embodiment, the polymer material is a thermoplastic polymer material.

[0055] The thermoplastic polymer material is preferably selected from the group consisting of thermoplastic polyurethane, thermoplastic vulcanizate, thermoplastic styrene block copolymer and thermoplastic polyamide elastomer.

[0056] In a further embodiment of the present invention, the air hose is characterized by a roughness Ra of the outer layer or the inner layer of 0.5 pm and more, in particular from 0.8 pm to 25 pm, measured according to ISO 25178. It is known from the prior art that vehicle hoses made of thermoplastic polymer material have Ra values ​​in the range of a few tenths of a micrometer. At least one outer layer or inner layer of the air hose according to the invention has, due to the presence of the foamed polymer material R a-values ​​of several micrometers. A higher Ra value allows for the advantageous application of a higher surface roughness of the hose, which offers additional advantages during installation and the unwinding behavior of the hose.

Claims

Claims:

1. Multi-layer air tube for vehicle tires, in particular for bicycle tires, with at least a first and a second closed layer (1, 3) made of polymer material, characterized by at least one layer of foamed polymer material (2) which is arranged between the first and the second closed layer (1, 3).

2. Air hose according to claim 1, characterized in that one of the two closed layers forms an outer layer (1) of the hose.

3. Air hose according to claim 1 or 2, characterized in that one of the two closed layers forms an inner layer (3) of the hose.

4. Air hose according to one of the preceding claims, characterized by the presence of one or more further closed layers (5) and / or one or more further layers of foamed polymer material (2).

5. Air hose according to one of claims 1, 3 and 4, characterized in that a further layer of foamed polymer material (2) forms an outer layer of the hose.

6. Air hose according to one of claims 1, 2 and 4, characterized in that a further layer of foamed polymer material (2) forms an inner layer of the hose.

7. Air hose according to one of the preceding claims, characterized in that the material of the closed layers (1, 3, 5) contains thermoplastic polyurethane or consists of thermoplastic polyurethane.

8. Air hose according to one of the preceding claims, characterized in that the foamed polymer material (2) is a thermoplastic polymer material.

9. Air hose according to claim 8, characterized in that the thermoplastic polymer material is selected from the group consisting of thermoplastic polyurethane, thermoplastic vulcanizate, thermoplastic styrene block copolymer, thermoplastic polyamide elastomer and mixtures thereof.

10. Air hose according to one of the preceding claims, characterized by a roughness Ra of the outer layer (1) or the inner layer (3) of 0.5 pm and more, in particular from 0.8 pm to 25 pm, measured according to ISO 25178.

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