Multi-layer air hose for vehicle tires

Description

[0001] The present invention relates to a multi-layered air hose for vehicle tires. Background of the invention

[0002] Vehicle tires typically consist of a casing, a rim, and an air-filled tube positioned between the rim and the casing.

[0003] The casing, as the outer part of the vehicle tire, keeps the tire dimensionally stable and transmits acceleration, braking and lateral forces to the ground.

[0004] The hose is equipped with a valve for filling with air and maintains the internal pressure.

[0005] Inner tubes for vehicle tires are preferably lightweight and, in combination with the tire casing, offer low rolling resistance to minimize frictional losses during driving. To ensure the puncture resistance of the inner tube, it must also be airtight and resistant to damage.

[0006] To reduce the weight of inner tubes and avoid friction loss, the wall thickness of the tube can be reduced. However, reduced wall thickness negatively impacts other properties such as air retention and durability, thus reducing puncture resistance.

[0007] This means that damage to the hose, such as punctures, pinching, aging or incorrect air pressure, can lead to the unwanted escape of air from the hose.

[0008] For this purpose, certain materials can be used to improve the properties of air hoses.

[0009] Butyl rubber, for example, is a common material for vehicle hoses. Butyl hoses are inexpensive, durable, and have a slow air loss rate.

[0010] Due to the comparatively high weight of butyl hoses, hoses made from this material result in higher rolling resistance than other materials.

[0011] 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.

[0012] 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.

[0013] Latex is more flexible than butyl rubber or TPU and has low rolling resistance. However, air can escape relatively quickly through the material, so latex tubes often need to be inflated. Latex tubes are generally lighter than butyl tubes, but are characterized by a comparatively high price and maintenance requirements.

[0014] Furthermore, multi-layered inner tubes with an inner and an outer layer are known. Such multi-layered inner tubes are said to have improved properties such as increased air retention and puncture resistance compared to single-layer inner tubes.

[0015] Nevertheless, even multi-layered hoses can be severely damaged by punctures, pinching, etc. This is because sharp or angular objects can penetrate the inner and outer layers despite the multi-layered construction, causing the entire hose to be damaged by crack propagation and resulting in air leakage.

[0016] To increase the puncture resistance of multi-layered hoses, hoses can, for example, be equipped with one or more intermediate layers.

[0017] German patent DE 102017118314 discloses a multi-layered inner tube for a vehicle wheel, comprising an inner layer and / or an outer layer made of TPU to reduce weight and increase air retention compared to known butyl inner tubes. Furthermore, the inner tube may have an intermediate layer made of an ethylene-vinyl alcohol copolymer, a gel, or thermoplastic polyurethane to increase the tube's puncture resistance.

[0018] Other multilayer hoses are known from documents JP S62249737A, JP S63 195003A and GB 216045A. Summary of the invention

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

[0020] The problem is solved by a multi-layered air hose for vehicle tires, in particular for bicycle tires, 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. Brief description of the characters

[0021] Figure 1 Figure 1 shows the schematic structure of the multilayer 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. Figure 2 Figure 1 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. Figure 3Figure 1 shows the schematic structure of the multilayer air hose according to the invention, comprising an outer layer 1, an inner layer 3 and several layers of the foamed polymer material 2, which are separated from each other by a closed intermediate layer 5. Figure 4 Figure 1 shows the schematic structure of the multilayer 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. Figure 5 Figure 1 shows the schematic structure of the multilayer air hose according to the invention, comprising an inner layer 3 and several layers of the foamed polymer material 2, which are 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

[0022] 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.

[0023] 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. This multi-layered air tube has proven particularly advantageous for vehicle tires, especially bicycle tires.

[0024] 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.

[0025] The separation of the two closed layers by the foamed polymer material increases the resistance of the hose according to the invention compared to hoses without a foamed inner layer. The arrangement of the individual layers according to the invention limits any damage, such as cracks or punctures, to a single closed layer, since the closed layers of the air hose are largely decoupled from each other by the foamed polymer material.

[0026] The foamed polymer material thus prevents further damage to at least a second closed layer. In the event of an object penetrating the hose or if it is pinched, the multi-layered structure of the hose according to the invention makes it significantly more difficult to penetrate or damage all layers. Furthermore, the structure of the hose according to the invention has the advantage that the foamed polymer material provides additional cushioning, resulting in less damage and increasing the hose's puncture resistance.

[0027] 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 hose's roughness. It has been found that the hose's roughness increases with the size of the material's pores.

[0028] The size of the pores 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 agents can affect the pore size.

[0029] A higher roughness of the tube has the advantage that the tube can be inserted better between the rim and tire during assembly due to optimized sliding properties, and the abrasion resistance of the tube is increased.

[0030] 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 such that the roughness of the hose is not reduced.

[0031] The hose according to the invention has, regardless of the thickness of the closed layers, the advantage that the risk of damage to all layers is significantly reduced by the multi-layered arrangement of the individual layers.

[0032] 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. Both terms, Ra value and CLA, are synonymous. According to the present invention, the Ra value is preferably determined by a conventional roughness measuring instrument using the method according to ISO 25178, for example, with a device of the type "MarSurf PS10" (manufacturer: Mahr).

[0033] 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 jacket.

[0034] 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.

[0035] The 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.

[0036] The outer and inner polymer layers 1,3 take on the task of keeping the hose airtight.

[0037] It has proven particularly advantageous if the layer of foamed polymer material is as thick as possible and the outer layer is as thick as necessary.

[0038] 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.

[0039] Preferably, the outer layer of the hose according to the invention has a layer thickness of 0.05 to 1 mm.

[0040] In another preferred embodiment, the layer thickness of the foamed polymer material is between 0.1 and 1.5 mm.

[0041] 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.

[0042] Multi-layered 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.

[0043] One variant of the design of the hose according to the invention shows Figure 3 The air hose comprises two layers of a polymer material 2, separated from each other by a closed intermediate layer 5. The air hose is bounded by a closed outer layer 1 and a closed inner layer 3.

[0044] Another embodiment is in Figure 4 Figure 1 shows a multi-layered 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.

[0045] Preferably, a further layer of foamed polymer material can form an outer layer of the hose. This foamed outer layer can be in contact with the outer casing.

[0046] Furthermore, another layer of foamed polymer material can form an inner layer of the hose.

[0047] Figure 5 Figure 1 shows a further preferred embodiment of the hose according to the invention comprising two layers of the 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 bounded by a closed inner layer 3 and by a foamed layer 2 as an outer layer.

[0048] Preferably, the material of the closed layers contains or consists of thermoplastic polyurethane.

[0049] The material of at least one closed layer can differ from the material of another closed layer.

[0050] In a particularly advantageous embodiment, the polymer material is a thermoplastic polymer material.

[0051] The thermoplastic polymer material is preferably selected from the group consisting of thermoplastic polyurethane, thermoplastic vulcanizate, thermoplastic styrene block copolymer and thermoplastic polyamide elastomer.

[0052] 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 µm and more, in particular of 0.8 µm to 25 µm, measured according to ISO 25178.

[0053] 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 micrometers. At least one outer or inner layer of the air hose according to the invention exhibits Ra values ​​of several micrometers due to the presence of the foamed polymer material. A higher Ra value allows for the advantageous application of achieving a higher surface roughness of the hose, which brings additional benefits during installation and in the hose's unwinding behavior.

Claims

1. A multi-layer air hose for vehicle tyres, in particular for tyres for bicycles, with at least a first and a second closed layer (1, 3) made of polymer material, characterized by at least one layer made of a foamed polymer material (2), which is arranged between the first and the second closed layer (1, 3).

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

3. The 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. The air hose according to any 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. The air hose according to any 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. The air hose according to any 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. The air hose according to any 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. The air hose according to any of the preceding claims, characterized in that the foamed polymer material (2) is a thermoplastic polymer material.

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

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