US20200032428A1

US20200032428A1 - Spacer fabric and use thereof

Info

Publication number: US20200032428A1
Application number: US16/519,666
Authority: US
Inventors: Stefan Mueller; Joachim Weis
Original assignee: Individual
Current assignee: Mueller Textil GmbH
Priority date: 2018-07-27
Filing date: 2019-07-23
Publication date: 2020-01-30
Also published as: DE102018118254A1; CN110777476A

Abstract

A spacer fabric has two transversely spaced cloth layers. First spacer yarns bridge and transversely connect the cloth layers and are each formed by a core yarn and a helical wrapping made of metal or having a metallic layer. Second spacer yarns also bridge and transversely connect the cloth layers but are of different construction from the first yarns.

Description

FIELD OF THE INVENTION

The present invention relates to a spacer fabric. More particularly this invention concerns a knitted spacer fabric and a use thereof.

BACKGROUND OF THE INVENTION

A typical spacer fabric comprises two usually substantially flat or planar cloth layers and spacer yarns that transversely bridge and interconnect the cloth layers. Some of the spacer yarns and optionally even all of the spacer yarns having a core made of a yarn and a spiral wrapping.
Spacer fabrics and, in particular, knitted spacer fabrics are characterized by a light, air-permeable structure, with spacer fabrics generally having an elasticity in the transverse direction of their thickness as a result of spacer yarns that run between the two cloth layers. By virtue of these properties, knitted spacer fabrics are often provided as a soft, elastic layer that enables air circulation in mattresses, upholstered furniture, garments, or shoes. A conventional knitted spacer fabric is known from DE 90 16 062.
In addition to such conventional applications in the consumer sector, spacer fabrics and, in particular, knitted spacer fabrics are frequently also used as technical fabrics for highly specialized applications. For instance, knitted spacer fabrics are also used in the automotive industry, for example for climate-controlled seats under the seat covers, with knitted spacer fabrics allowing for good contour adjustment due to their cushioning properties and very good restorative behavior despite the overall low weight per unit area. Knitted spacer fabrics are also used for the interior lining of vehicles, and it is even possible to use them over air bags through the introduction of local tear lines. The possible applications of knitted spacer fabrics are not limited to the areas of ventilation and/or elastic support. For instance, it is known from WO 2012/139142 to use knitted spacer fabrics for railway sleepers for connecting a concrete body to a sleeper pad, the knitted spacer fabric being embedded partially in the concrete body and in the sleeper pad during the manufacture of the sleeper body, thus enabling the especially reliable, permanent connection of these two elements.
Another known application is the provision of a heating or sensor function, for which purpose wires and, in particular, stranded wires are incorporated into the fabric structure. Corresponding configurations are known from DE 19 903 070, DE 10 2008 034 937, and DE 10 2009 013 250.
According to DE 10 2015 114 778, a knitted spacer fabric is proposed for heating purposes in which conductive yarns of a flat knitted cloth layer are formed from a plastic multifilament yarn provided with a conductive coating. The multifilament yarn has the advantage that, despite the conductive and, in particular, metallic coating of the individual filaments, it still has relatively good flexibility, thus enabling processing in a knitting process. The conductive yarns are exposed in at least the flat knitted layer that is usually facing a user.
Another highly specialized application of a spacer knitted fabric is known from US 2008/20299854 that also discloses a spacer fabric with the above-described features. A spacer fabric with two cloth layers and spacer yarns connecting the cloth layers is described, the spacer yarns having a core that is made of a yarn and a helical wrapping around the core. The knitted spacer fabric is fire resistant to a certain extent. This property is achieved particularly by the fact that the core is enclosed and protected by the wrapping, for which purpose the wrapping is made of a sufficiently insulating material wound up tightly around its core yarn.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide an improved spacer fabric.
Another object is the provision of such an improved spacer fabric that overcomes the above-given disadvantages, in particular that has a new functionality.
Another object is a preferred use of such a spacer fabric.

SUMMARY OF THE INVENTION

A spacer fabric has according to the invention two transversely spaced cloth layers. First spacer yarns bridge and transversely connect the cloth layers and are each formed by a core yarn and a helical wrapping made of metal or having a metallic layer. Second spacer yarns also bridge and transversely connect the cloth layers but are of different construction from the first yarns.
In the context of the invention, a wrapping is thus provided in at least the first spacer yarns that is made of metal or at least has a metallic layer. A spacer fabric is thus provided that is electrically and thermally conductive between the two cloth layers transversely, i.e. in the direction of thickness. However, the spacer yarns are not provided with a continuous sheath, which would lead to substantial stiffening. In particular, the wrapping can also be selected such that the spacer yarns can still be processed easily during manufacturing of the spacer fabric, which is not the case with solid or stranded metallic wires. The core of the spacer yarns is formed by a yarn. In keeping with its general meaning, the term “yarn” refers in this context to monofilaments, multifilaments, or threads.
However, the core is especially preferably formed by a multifilament yarn that is substantially softer and more flexible than a monofilament yarn with the same fineness. Although the metallic or metal wrapping does not form a closed surface and is flexible, the metallic material stiffens the composite first yarns. Particularly in this context, it can be advantageous if the core is made of a multifilament yarn, even if poorer restorative properties are produced in terms of a compression hardness as compared to a monofilament yarns.
According to a preferred embodiment of the invention, in order not to adversely affect the flexibility of the spacer yarns that are provided with the wrapping and, beyond that, in order to achieve good functional properties, the wrapping is strip-shaped and has a width and a thickness with the ratio of the width to the thickness being at least 5:1.
Several embodiments of such a strip-shaped material are conceivable in principle. For example, the wrapping can be separated in the form of a strip from a thin foil or another strip stock. According to an especially preferred embodiment of the invention, however, a wire is provided that is flattened and thus formed into the flat strip. Such a reshaping of a round wire that is usually flat at first is also referred to as flattening.
According to a preferred development of the invention, the wrapping can be made of copper or have a layer of copper in the interest of good thermal and/or electrical conductivity. Particularly in consideration of material costs, copper is preferable to more noble metals such as gold or silver, but these materials and other metals can also be used in principle within the scope of the invention.
In order to achieve long-term protection in the case of a wrapping that consists substantially of copper, a covering layer of tin can be provided provides protection from corrosion while not impairing the thermal and/or electrical conductivity. In particular, it is also possible to flatten tin-plated copper wire as described above and thus to transform it into a strip-shaped material without removing or damaging the tin coating.
As already explained above, the spacer yarns provided with the wrapping retain a high degree of flexibility, because the successive helical turns can still be moved and, in particular, angled relative to one another.
According to a preferred embodiment of the invention, the wrapping covers between 30% and 95% of the core yarn on its lateral surface, particularly between 40% and 80%. This degree of coverage provides good flexibility on the one hand while also providing sufficient conductivity in terms of heat and/or electricity on the other hand.
It is assumed that, in the usual embodiment of a core made of a basically nonconductive polymeric yarn, not only the electrical conduction but also the heat conduction takes place substantially via the wrapping, which is metallic or has at least one metallic layer.
It should also be noted in this regard that, due to the helical shape of the winding, the effective length to be considered for electrical conduction and heat conduction is substantially greater than the length of the spacer yarn itself. With a typical width and coverage of the wrapping, the length of wrapping in the unwound or rectified state is between 1.5 and 4, preferably between 2 and 2.5 times greater than the length of the wrapped core yarn itself. The spacer fabric, which is preferably embodied as a knitted spacer fabric, is surprisingly characterized by very good conductivity in terms of electricity and heat.
For example, the total thickness of the spacer fabric can be between 1 mm and 20 mm, preferably between 2 mm and 10 mm. The core, which is preferably made of multifilament yarn, preferably has a fineness of between 50 dtex and 150 dtex.
As already explained above, the wrapping preferably is a strip in order to be wound around the core in a helical manner with the smallest possible thickness. In order to ensure sufficient stability on the one hand and good processability on the other hand, and in order to provide the desired conductive properties, the wrapping preferably has a cross-sectional area of between 200 μm²and 10,000 μm², especially preferably between 600 μm²and 40 μm².
The two flat cloth layers are not limited in their specific design. Preferably, the flat cloth layers are made of polymeric yarns and are also preferably free of metal and thus electrically non-conductive and thermally insulating.
In an embodiment as a knitted spacer fabric, different laying patterns are possible, and openings can also be provided in the cloth layers, each of which is formed by a plurality of stitches.
Particularly if the cloth layers are made of nonconductive yarns according to a preferred embodiment of the invention, it can be advantageous if the spacer yarns are integrated into the cloth layers so that they are exposed to or even protrude beyond the outer faces of the spacer fabric. At the same time, the fact that the wrapping of the spacer yarns results in a certain stiffening can also be advantageously exploited, so that they are less strongly angled in the stitch formation. In particular, the first spacer yarns provided with the wrapping can be adjusted in the same way through suitable selection of the core on the one hand and of the wrapping on the other hand, that the first spacer yarns still have good processability but also have a certain strength and rigidity at the same time.
In the context of the invention, both the first and the second spacer yarns can be provided with the wrapping in the manner described.
According to an alternative, preferred embodiment of the invention, the first spacer yarns have core yarns with helically wound wrapping, while a second portion of the spacer yarns is provided without wrapping.
The proportion of the number of one of the spacer yarns to the total number of the first plus the second spacer yarns in a given area is typically between 10% and 90%, preferably between 30% and 70%. The second spacer yarns are especially preferably made of monofilament yarn in order to impart good elastic properties and good compression hardness to the spacer fabric. In the context of such an embodiment, a functional division then takes place between the first spacer yarns and the second spacer yarns.
According to an embodiment of the invention, the spacer yarns can be deformed after they are wrapped in order to stabilize the spacer yarns provided with the winding to some extent. As with the flattening of a wire to form the wrapping, the yarns provided with the wrapping can be flattened between rolls prior to processing, i.e. particularly knitting, in which case the spacer yarns are given an approximately oval cross-sectional shape. By virtue of such an oval, flatly pressed cross section, the structure of the first spacer yarns is stabilized on the one hand and, on the other hand, the flexibility in the spacer fabric formed is reduced. In particular, this can prevent the spacer yarns from twisting or the wrapping from twisting relative to the core.
The spacer fabric according to the invention can be provided in an especially advantageous manner as a heat-conduction layer, for best service as the preferred use with an electrical or electronic component.
The knitted spacer fabric is characterized by a particularly light structure, but good heat transfer is possible in the transverse direction of thickness. It is also of particular advantage that the spacer fabric is elastic in the direction of thickness. For example, the spacer fabric can also be used in gaps and cracks in order to allow heat transfer there.
Such an arrangement is advantageous particularly if electrical components are to be cooled in a housing. For example, if rechargeable batteries, motors, and other electrical components are placed in a housing with an ohmic resistance, the spacer fabric can be used for heat transfer in such installation situations. Optionally, an adhesive, a paste, or the like can be used on the cloth layers for better fixation and/or contacting, it being possible even then for thickness compensation or thickness adjustment to be performed by the spacer yarns. Different gap dimensions due to production-related fluctuations can be compensated for by the knitted spacer fabric in a particularly advantageous manner, and because of the low weight per unit area compared to known designs, weight savings can often also be achieved. Especially for the described applications, the heat conduction is sufficient despite the overall airy structure.
Finally, applications are also conceivable in which the cooling is improved even further through ventilation of the spacer fabric, so that a cooling by convection or a cooling air flow then also occurs in addition to the heat conduction via the thickness.
One specific application in which the advantages described above are especially evident is for an electrical component fitted in a housing, in which case small gaps may remain due to assembly. The electrical component can be a motor, a rechargeable battery module, an inverter, or the like. In this context, it should also be noted that, particularly with regard to the storage of electric current for mobile applications such as electric vehicles or in connection with photovoltaic systems, increasing demand exists for corresponding electrical components, with weight minimization being desired particularly for mobile use.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a perspective view of a piece of a knitted spacer fabric or fabric according to the invention;

FIG. 2 is a larger-scale view of a detail of the fabric of FIG. 1;

FIG. 3 is a view of a short piece of a spacer yarn of the knitted spacer fabric according to FIG. 1 that is made of a yarn and a wrapping;

FIGS. 4a to 4c shows method steps for forming the spacer yarn of this invention; and

FIG. 5 is a schematic view of a rechargeable battery module in a housing.

SPECIFIC DESCRIPTION OF THE INVENTION

FIG. 1 shows a spacer fabric in the form of a knitted spacer fabric with two cloth layers 1 and first and second spacer yarns 2 a and 2 b that extend transversely between the planes of and connect the layers 1. FIG. 1 and the detail view of FIG. 2 show that the spacer yarns 2 a and 2 b are configured differently. The first spacer yarns 2 a each have a core 3 formed by a multifilament yarn and a helical wrapping 4 around the core 3. The wrapping 4 is made of metal or has at least one metallic layer.
It can already be seen from the detailed view of FIG. 2 that, if desired, good electrical conduction can also be achieved by the metallic wrapping 4 transversely, in the direction of thickness, the other spacer yarns 2 b are formed of polymeric monofilaments.
The different spacer yarns 2 a and 2 b extend similarly between the two cloth layers 1 and also are of a similar thickness. While the metal-wrapped first spacer yarns 2 a ensure good conduction of heat and electricity, the second spacer yarns 2 b can provide the compression hardness and elastic recovery that are typical of a spacer fabric and particularly a knitted spacer fabric.
The exact configuration of the first spacer yarns 2 a provided with the sheath 4 can be seen from the sectional view of FIG. 3. In the illustrated embodiment, the core 3 is a multifilament yarn with for example a fineness of 76 dtex. Polyethylene terephthalate is particularly suitable as the material, but other typical materials such as various polyolefins, polyamide, and the like can also be employed.
It can be seen from FIG. 3 that the wrapping 4 has a strip-shaped configuration with a width b and a thickness d, the ratio of the width b to the thickness d being at least 5:1. In the illustrated embodiment, the wrapping 4 is made of tinned copper, it being possible for an initially circular-section tinned copper wire to be flattened in order to form the strip-shaped configuration. Such a method step is shown by way of example in FIG. 4 a.
It is also apparent from FIGS. 2 and 3 that there is a gap between the successive turns of the wrapping 4, 30% and 95% of the core being covered.
The helical wrapping 4 also has the effect that the effective length for heat conduction or electrical conduction of the wrapping 4 is greater than the length of the core. In the unwound state, the wrappings 4 typically have a length that is 2 to 2.5 times greater than that of the respective core yarns 3. Despite this increased path length, very good conduction of heat is observed overall.
For example, the wrapping can have a cross-sectional area of between 200 μm²and 10,000 μm², particularly between 600 μm²and 4000 μm². The multifilament yarn that is here provided as the core 3 can have 24 or 36 filaments, for example.
FIG. 4b indicates how the core 3 of multifilament yarn can be provided with the wrapping 4. Finally, FIG. 4c shows that the first spacer yarns 2 a can also be flattened to some extent before the knitting process to stabilize their cross-sectional shape and wrapping.
The spacer fabric according to the invention is provided in an especially advantageous manner as a heat conduction layer, it being also optionally possible for ventilation to take place through it. In this context, the highly schematic representation of FIG. 5 shows the arrangement of a rechargeable battery module 5 in a housing 6, with the spacer fabric forming an intermediate layer 7 between the outer surface of the module Sand the inner surface of the housing 6. In particular, this spacer fabric as an intermediate layer 7 can be used to compensate for a remaining gap between the rechargeable battery module 5 and the housing 6. It should also be noted that the actual gap to be bridged can vary greatly due to manufacturing-related variations. Particularly in this context, the invention offers the advantage that the spacer fabric can be compressed when used as a heat conduction layer and also resets elastically to a certain extent. Such compensation is not possible with a thermally conductive paste or other compact media.

Claims

We claim:

1. A spacer fabric comprising:

two transversely spaced cloth layers; and

first spacer yarns that bridge and transversely connect the cloth layers and that are each formed by a core yarn and a helical wrapping made of metal or having a metallic layer.

2. The spacer fabric defined in claim 1, wherein the wrapping is formed of metallic strip having a width and a thickness, a ratio of the width to the thickness bing at least 5:1.

3. The spacer fabric defined in claim 2, wherein the strip is flattened wire.

4. The spacer fabric defined in claim 3, wherein the wire is of copper or has a coating of copper.

5. The spacer fabric defined in claim 2, wherein the strip is wound helically around the core yarn and forms a plurality of spaced turns between which the yarn is exposed.

6. The spacer fabric defined in claim 5, wherein the strip covers 30% to 95% of the core yarn.

7. The spacer fabric defined in claim 1, further comprising:

second monofilament spacer yarns that also bridge and transversely connect the cloth layers but that are of different construction from the first yarns.

wherein the second spacer yarns are monofilaments.

8. The spacer fabric defined in claim 1, wherein the core yarn is a multifilament yarn.

9. The spacer fabric defined in claim 1, wherein the cloth layers and first and second spacer yarns are knitted.

10. The spacer fabric defined in claim 1, wherein a total thickness of the spacer fabric is between 1 mm and 20 mm.

11. The spacer fabric defined in claim 1, wherein the core yarn has a fineness between 50 dtex and 150 dtex.

12. The spacer fabric defined in claim 1, wherein the wrapping has a cross-sectional area of between 200 μm²and 10,000 μm².

13. The spacer fabric defined in claim 1, wherein the first spacer yarns have a cross-sectional shape that is not circular.

14. Use of the spacer fabric of claim 1 as a heat conduction layer.

15. The use defined in claim 14, wherein the spacer fabric is connected to an electrical component.

16. The use defined in claim 14, wherein the spacer fabric is in a gap between a housing wall and the electrical component.

17. A method comprising the steps of:

forming first yarns of a multifilament nonconductive core yarn wrapped helically by a conductive and flexible metal strip;

providing second monofilamentary yarns; and

knitting together the first and second yarns into a spacer fabric formed of two transversely spaced cloth layers largely formed of the second yarns and bridged by first spacer yarns formed by the first yarns and by second spacer yarns formed by the second yarns.