KR20030032932A - Conductive pressure sensitive textile - Google Patents

Abstract

A fabric comprising a first stretched electrical conductor in a structure that intersects a second stretched electrical conductor, wherein the conductors are typically separated at the intersection of the fibers by an air gap therebetween, thereby Pressure applied in a direction substantially perpendicular to the face discloses the fabric contacting the conductors. The fabric can be woven, knitted, nonwoven or woven. The fabric can be used as a pressure sensor, switch or other sensor.

Description

Conductive Pressure Sensitive Fabrics {CONDUCTIVE PRESSURE SENSITIVE TEXTILE}

Electrically conductive fabric sheets are known in the art and are described, for example, in the applicant's early British patent application 2,339,495. Known conductive fabric sheets typically comprise two conductive layers separated by an insulating layer that can be transferred upon pressure application to the conductive layer. While such fabric assemblies can work well, there are inevitable drawbacks to having three or more fabric layers, including additional cost, fabric thickness, the need to maintain alignment between the various layers, the movement of the layers during use, and the like.

Summary of the Invention

The present invention seeks to provide an improved conductive fabric.

According to an aspect of the invention, there is provided a fabric as defined in claim 1.

Preferred embodiments provide the woven, knitted, nonwoven or interwoven fabric comprising a first elongated electrical conductor intersected with a second elongated electrical conductor in a woven, knitted, nonwoven or interwoven structure, wherein the The conductors are typically staggered at the intersection by air gaps between them, whereby the conductors are contacted by the application of pressure perpendicular to the face of the fabric.

Preferably, the fabric comprises a plurality of spaced first conductors and / or a plurality of spaced second conductors to form a plurality of intersections. The conductors may comprise electrically conductive filaments or fibers.

Advantageously, the fabric is a woven fabric; The warp may comprise one or more of the first electrical conductors and the weft may comprise one or more of the second electrical conductors.

Multiple means may be used separately or together to stagger the conductors at the intersections; In one preferred embodiment, this is done by including insulating fibers or filaments in the fabric. For example, staggered separation can be achieved by using one or more of the electrical conductors, the electrical conductor having the insulation filaments or fibers wound around such that the surface of the conductor is exposed at the intersection. In another example, the staggered separation is performed by twisting one or more of the electrical conductors together with insulating filaments or fibers. On the one hand, the staggered separation can be performed by using, as one or more of the electrical conductors, an electrical conductor supported between and on the deformable projections of the insulating filament or fiber. In yet another embodiment, the staggered separation can be accomplished by including warp and / or weft adverbs over one or more of the yarns.

The electrical conductors preferably have an electrical property that is proportional to or reproducible from the length of the conductor. The length of the conductor or the plurality of connecting conductors can then be determined from the measurement of this property. Advantageously, the electrical property is resistance.

For some uses it will be advantageous for the fabric to have one or more sets of spaced electrical conductors, where at least some of the sets are electrically connected together to form one or more busbars. If the set of spaced electrically conductors comprises electrically conductive filaments or fibers in the warp or weft of the woven structure, the electrical connection between the conductors of the set is respectively by one or more electrically conductive filaments or fibers of the weft or warp. Can be provided. On the one hand, the electrical connection can be made after the weaving process.

In a preferred embodiment, there is provided a fabric comprising a plurality of weft fibers and a plurality of warp fibers, first and second conductive fibers in the weft and warp fibers, and one or more insulating fibers in the weft and / or warp fibers, In this case, the insulating fiber alternately separates the fibers to provide a space between the first and second conductive fibers.

The fabric may comprise a plurality of insulating fibers in one of the weft and warp fibers, wherein the insulating fiber provides a transfer to the conductive fiber and the other of the weft and warp fibers, thereby transferring the conductive fiber to the weft and Suspended over one or more conductive fibers in one of the warp fibers.

In another embodiment, one or more insulating fibers are provided around one or more of the conductive fibers, for example spirally disposed around the periphery. On the one hand, one or more conductive fibers can be provided around the one or more insulating fibers, wherein the insulating fibers comprise portions, for example protrusions, extending beyond the periphery of the conductive fibers or fibers. The insulating fiber may thus provide a separation means for separating the conductor from other conductors in the fabric layer.

It will be apparent that the present invention can provide a conductive fabric for a pressure sensor or switch or other conductive device within a single layer of the fabric. This can avoid the problems discussed above.

It is also possible to reduce the edge effect (nonlinearity of resistance to position) that must be corrected to provide an intrinsic and accurate measurement for the three layer structure. Moreover, it is possible to have a significantly higher resolution, estimated 10 times more than the three-layer device; The resolution varies depending on the weaving technique and the fiber dimensions.

In a preferred embodiment, it is possible to provide contact of the conductive fiber when applying certain pressures or pressures to the fabric, which can be determined by the size of the air gap, the weave tension, the deformability of the conductor and the compressibility of the insulator. Moreover, a range of pressure sensitive properties can be provided within a single fabric structure. For example, in embodiments of floating conductors (disclosed in connection with FIG. 3 below), a plurality of conductors having different pressure levels have different numbers of conductors under different inductances and / or different, eg different thicknesses or compressive insulating fibers. Can be provided by the dog's whole school. Similar effects can be considered in connection with other embodiments for the fibers disclosed herein.

On the one hand, two or more layers of the disclosed fabric may be provided having the same or different structure.

According to another aspect of the invention, a fiber having a conductive yarn surrounded by one or more insulating yarns is provided. Preferably, at least two insulating yarns are provided spirally wound around the conductive yarns.

According to another aspect of the invention, there is provided a fiber comprising an insulating yarn surrounding at least one conductive yarn, wherein the insulating yarn comprises a portion extending beyond the conductive yarn or yarns. Preferably, at least two conductive yarns are provided spirally wound around the insulating yarn. The protruding portion may be strands, protrusions, or the like of the fiber.

With the present invention, it is possible to provide an electrically conductive fabric having the features disclosed in British Patent Application No. 2,339,495 by using only one fabric layer.

Preferred embodiments of the fabric can be produced much cheaper than the structure disclosed in British Patent Application No. 2,339,495.

Various embodiments of the invention are described below by way of example only with reference to the accompanying drawings.

The present invention relates to a method of manufacturing one or more pressure activated electrical switches or sensors in a fabric, in a particularly preferred embodiment as an integral element of a single fabric sheet.

1 is a perspective view of a grid arrangement of elongated conductors;

2 shows the effect of the applied pressure on the intersection between two conductors;

3 is a perspective view of an embodiment of a fabric with floating conductors;

4 illustrates the operation of the fabric of FIG. 3;

5 shows various views of an embodiment of a yam;

6 shows various views of another embodiment of a yaan;

7A-7C illustrate various embodiments for conductive and insulating yarns;

8 illustrates another embodiment of a composite yarn;

9 shows a variation on an embodiment of a yaw with floating conductors;

10 is a schematic diagram of an embodiment of a woven busbar;

11 shows an example of technical specification of a weave structure;

12 illustrates an example of an individually addressable composite switch in a woven fabric structure.

In connection with the figures, in the embodiment of FIG. 1, the fabric piece preferably comprises two or more sets of elongated electrical conductors. Typically, each set of conductors is arranged parallel to each other, as shown in FIG. 1 and one set of conductors is arranged perpendicular to the other set to form an arbitrarily spaced grid. The elongated electrical conductors are typically single-filament or multifilament conductive fibers, while the remainder of the fabric piece consists of insulating fibers.

When any two conductors cross each other, the structure of the fabric and / or conductive fiber maintains its physical separation as shown in the cross-sectional view of the two conductors in FIG. When pressure is applied perpendicular to the face of the fabric as in FIG. 2 (b), the conductive fibers are bent and in electrical contact. Thus, each of the intersections constitutes a momentary contact electrical switch and the contact will be maintained while the applied pressure exceeds the limit. The limit pressure can be predetermined and adjusted at the time of manufacture.

The switch also exhibits an analogue open / close area, as shown in Fig. 2 (c), since the contact area shared by the two conductors changes with applied pressure until the maximum contact area is reached. The fabrication parameters of the fabric piece can be adjusted so that, in use, the switch operates periodically within the analog region defined by the dashed line in FIG. When the contact area is measured through some electrical property, for example resistance, the intersection may constitute a pressure sensor.

The piece of fabric may be knitted or made of felt, but the primary application of the present technology would be a woven fabric structure. In the case of the woven fabric structure, two sets of conductive fibers may each constitute warp and weft yarns, wherein the insulating ayans serve to form the rest of the fabric and to separate the individual conductive yarns of each set. A typical example of a piece of woven fabric comprising two intersections is shown in FIG. 3.

Separation techniques

Multiple techniques can be used to maintain some degree of physical separation between two conductive fibers at the intersection. Such techniques include the use of woven structures with adverbs and complex conductive / insulating yarns. Different techniques can be used together, which allows, for example, fabric pieces that include both composite yarns with conductive cores and woven structures with adverbs.

Separation Techniques-Weaving with Adverbs Over One or More Yarns

The first disclosed separation technique is the use of a woven structure with an adverb (the term applies to a portion of the weft thread passing over or below one or more slopes). To separate the two conductive yarns at the intersection, a conductive weft is typically suspended on a conductive slope and one or more insulating slopes on either side, as shown in FIG. As a result, the two conductive yarns share little or no physical contact area, as shown in the longitudinal cross section with respect to the weft in FIG. 4 (a).

If the conductive warp has a diameter smaller than the surrounding weft, the physical separation thereof can be made as shown in Fig. 4 (b). When pressure is applied perpendicular to the face of the fabric, as shown in Fig. 4 (c), the yarn and the surrounding fabric are bent and the two conductors are in electrical contact. Increasing the applied pressure increases the contact area as shown in Fig. 2 (c). The yarns must exhibit sufficient elasticity to recover from the bending upon removal of the applied pressure, thus returning to their separate position and stopping electrical contact.

Separation Technique—Yarn with Conductive Core Surrounded by Replaceable Insulators

Another separation technique involves the use of specific composite structures for conductive yarns. In such composite yarns, the conductive mono-filament or multi-filament core yarns may be twisted, woven, twisted, woven, molded together, coated, sleeved by an insulating material as shown in FIG. 5 (a). Or otherwise partially enclosed.

If no pressure is applied at the intersection between two conductive yarns, at least one of which has the above properties, an insulating material is inserted between the conductors as shown in FIG. 5 (b) to ensure physical separation. However, when pressure is applied perpendicularly to the face of the fabric, the surrounding insulating material is twisted, compressed, laterally moved or otherwise bent between the core conductor yarns as shown in Fig. 5 (c). Electrical contact can be allowed. Upon removal of the applied pressure, the insulating material springs back to the position and / or shape between the conductors and the electrical contact is broken (opened).

The geometry and compressibility of the composite yarn, the hardness and surface texture of its constituent yarns contribute to measuring the pressure limits of the intersection and can easily be measured experimentally. Composite yarns of this type can also be used to make plain weave intersections without the floating structures described above.

Separation Technique-Yard with Compressible Insulating Core Surrounded by Conductor

Another separation technique involves another type of complex configuration for conductive yarns. In this composite yarn, which is the opposite of the yarn described in detail above, the insulating single-filament or multi-filament core yarns are twisted, woven, twisted, woven, molded together, coated, sleeved by a conductive yarn or material Or otherwise partially enclosed.

Additionally or on the other hand, the conductive core may be coextruded with an insulating coating and then post-processed to selectively expose regions of the conductive core. The conductive yarns are partially buried in the insulated core yarn guide as shown in FIG. 6 (a), so that the compressible flexible surface of the core yarns remains the conductive yarns exposed. On the other hand, although not the same purpose, it is possible to twist or twist a thin conductive yarn with a larger insulating yarn so that the insulating yarn remains the conductive yarn.

If no pressure is applied at the intersection between two conductive yarns (one or more of which have the above properties), the insulating material remaining exposed to the conductive yarns will physically separate the conductors as shown in Figure 6 (b). Let's do it. However, when pressure is applied perpendicular to the face of the fabric, the insulating material may be compressed to allow electrical contact between the buried conductor yams as shown in FIG. 6 (c). Upon removal of the applied pressure, the insulating material bounces back into place to separate the conductors and break electrical contact.

The geometry and compressibility of the composite yarn, the hardness and surface texture of its constituent yarns contribute to measuring the pressure limits of the intersection and can easily be measured experimentally. Composite yarns of this type can also be used to make plain weave intersections without the floating structures described above.

Separation Technique-Yaw with a Conductive Core Surrounded by Replaceable Insulators

With reference to FIGS. 7A-7C, various embodiments for an eye with both an insulator and a conductor are shown. In Figure 7 (a), the cross-section shows the causal core yaw substantially, which can be insulated or conductive as desired. Larger diameter insulating yarns and smaller diameter conductive yarns are twisted, woven or twisted around the core. As can be seen in the figure, the conductive fiber remains spaced apart from other conductor (s) unless pressure is applied to the eye. However, if compressive force is applied above the limit, the insulating yarns may be compressed and / or moved to allow contact of the conductive yarns to the conductive base (which may be another composite yarn of this type).

In Figure 7 (b), there is a simple conductive core that is coated on the surface or extruded together, preferably with one or more insulating lips, preferably in a spiral arrangement. As can be seen, if no pressure is applied, the conductive core remains spaced apart from any conductive base on which the composite is placed (which may be another composite structure as described above). However, when a compressive force is applied, the insulating lip (s) is compressed to make electrical contact.

In FIG. 7C, a deformable conductive core is formed with an insulating sleeve that is removed to create a groove with conductive valleys. Compression of the structure deforms the grooves so that a conductive substrate (which may be a plate or fibrous conductor, for example) is in electrical contact with the conductive core. It is not necessary to remove any part of the conductive core in order to create a groove, it just needs to be enough to remove the insulator to allow access to the core.

Separation Techniques-Self-Separation Perceptual Compound Yarns

In FIG. 8, an embodiment of a composite yarn with a core woven around a conductive / insulating yarn with floating conductors capable of detecting the applied pressure at a given point along the length of the structure is shown.

Variable regulating working pressure

A number of adjustable fabrication parameters determine the operating pressure of the intersection between two conductors in a piece of woven fabric.

a) relative diameters of conductive and insulating yarns

As discussed above, where the woven conductive yarns have a smaller diameter or cross-sectional area than the insulating yarns, the conductive yarns are separated by a greater distance at the intersection. The contact requires further bending of the conductive yarns, thus requiring a higher working pressure.

b) the propensity of conductive yarns to make electrical contact

Many variables contribute to the mechanical electrical contact tendency of the conductive yarns. Conductive yarns with very smooth and / or hard surfaces tend to produce smaller contact areas than fibrous and / or compressible yarns when contacted together under similar pressure. Single-filament conductors having an annular cross section similarly provide less contact area than prismatic or multi-filament yarns. The properties of the composite yarn are disclosed above.

c) fabric hardness

The operating pressure necessary to bend the conductors at the intersections and bring them into electrical contact is directly governed by the hardness of the conductive and surrounding insulating yarns and the general hardness of the fabric, which in turn is dependent upon the weave structure used, the yarn spacing and the weft fill level or tapping. Is dominated by More rigid fabrics require greater force for a certain bend, so a greater working pressure will be created at the intersection.

d) number of adjacent conductive yarns

As shown in Fig. 9A, when a plurality of adjacent conductive yarns are used instead of a single conductive warp yarn or weft yarn, the working pressure decreases. As shown in Figure 9 (b), wider conductors with a larger number of adjacent yarns provide greater contact area at the intersection and require less angular deflection of the yarns, thus requiring less pressure for contact. Do.

e) number of rich eyes

When floating above a minimum number of inclinations to be reliably separated at the intersection point as shown in Fig. 9 (a) between the conductive phases, the operating pressure is above a larger number of adjacent slopes as shown in Fig. 9 (c) between the conductive phases. Correspondingly less than in the case of floating.

Things to keep in mind about working pressure

The aforementioned manufacturing parameters are adjusted to weave intersections with the desired operating pressure into the fabric pieces. The limit pressures for both performing electrical contact and achieving maximum contact can be measured independently. Intersections with different pressure limits can be incorporated into a single piece of fabric. This makes it possible, for example, to construct a group of neighboring intersections that make continuous contact with increasing pressure and constitute a quantified pressure sensor.

Another implication of variable control at the intersection is that the two conductive yarns may be woven into permanent electrical contact regardless of the applied pressure. In general, this can be achieved through the use of a plain weave structure at the intersection, where the conductive weft does not float over any additional slope, but instead shares a large permanent contact area with a conductive slope. This allows for example the woven fabrication of the busbars discussed in the present invention.

Conversely, if the operating pressure limits of the intersections become very large, the two conductive yarns may be woven so as to never be in electrical contact under typical operating conditions. This allows the two conductors to remain electrically independent of each other. The easy intersection design, with or without contact within the conductor grid, permits the journey of current through the entire piece of fabric, similar to the trajectory of a printed circuit board.

Intersection Matrix Processing

Each intersection between the two conductors can be treated as an independent switch with an array of intersections making up a heat-column matrix, similar to most existing keyboards. To achieve this, each conductive yarn must be individually connected to a circuit suitable for scanning the matrix. Creating this number of connections in the piece of fabric can prove inconvenient.

On the one hand, an approach that requires much less connection to the fabric pieces deals with a matrix of intersections through electrical busbars as shown in FIG. These busbars each interconnect a set of conductors. The number of connections to the fabric piece is not judged by the number of intersections.

The busbars may be sewn, embroidered, printed, attached, mechanically clamped or crimped to the piece of fabric in electrical contact with the matrix of the conductor. Most attractively, it may also have a woven structure integrated into the fabric piece in a manner similar to the matrix. A typical arrangement is also shown in FIG.

Some reproducible electrical properties, for example resistance, can be measured to determine the length of the conductor and / or busbar. The position of the "closed switch" at the intersection of the matrix can be deduced from these measurements.

For example, first assume that the conductive yarns of the matrix exhibit primary resistance and connect to three fully conductive bus bars as shown in FIG. 10. When the switch is closed at intersection D, the resistance R AB measured from bus A to bus B is given by:

RAB = K (X + Y)

In the above,

K is a constant measured by the absolute length, cross-sectional area and resistance of the conductive yarns,

Distances X and Y are orthogonal vector components of point D.

At this time, 0 ≦ (X, Y) ≦ 1.

Similarly, the resistance measured from bus B to bus C is given by:

RBC = K (Y + 1-X)

By replacing the above

X = [((RAB) / K)-((RBC) / K) + 1] / 2 and

Y = [((RAB) / K)-((RBC) / K)-1] / 2

To provide.

This section details examples of weaving instructions for making a typical piece of fabric. Pieces of fabric of any size, including repeats of width 250 mm, can be reproduced from these specifications. The intersection is evenly spaced about 8.5 mm away from the grid. Using the specified eye and weave structure, the pressure limit at the junction is roughly 80 kilopascals, which is equivalent to 4 Newton forces for a typical fingertip area of 50 mm 2.

As shown schematically in Fig. 10 (a), a slope with two standing edges consisting of eight warp yarns, twisted multi-filament yarns, and BASF F901 G004 was designed on either edge of the warp on the shafts 1-4.

The warp continues to use a 100% cotton 2/18 yard set at 24 ends per inch. Conductive single-filament type BASF F901 A013 is interspersed for every eight warp yarns on shafts 8, 16 and 24.

The lifting order / fixing scheme determines the order in which the shaft moves to lift or leave the warp yarn.

The same side weft yarn is passed through the shed of raised warp yarn as in the fixed manner of FIG. 10 (b) and replaced with conductive mono-filament F901 A013 every sixth pick.

Complex switches can be handled individually within the woven fabric structure

12 illustrates an embodiment of an individually processable composite switch that can be fabricated from any of the embodiments described above. As can be seen, the grid of conductor intersections is created in any of the above-described ways and provides two busbars which are permanently electrically connected as shown in the figure. The switch provides a closed circuit as shown in the embodiment matrix form upon closure. More specifically, when each input line D ^* is in contact with a positive potential in turn, three 3-bit patterns generated at the outputs Q1, Q2, Q3 identify the closed switch in the matrix of the intersection. Connecting the matrix to the inputs D1, D2, D3 and the outputs Q1, Q2 and Q3 according to the binary code allows a more straightforward response to the multiple closed switches.

Claims (18)

A fabric comprising a first stretched electrical conductor in a structure that intersects a second stretched electrical conductor, wherein the conductors are typically separated at the intersection of the fibers by an air gap therebetween, thereby A fabric applied in a direction substantially perpendicular to a surface contacting said conductors. The method of claim 1, A fabric forming a plurality of intersections comprising a plurality of spaced first conductors and / or a plurality of spaced second conductors. The method according to claim 1 or 2, A fabric wherein the conductor comprises an electrically conductive filament or fiber. The method according to any one of claims 1 to 3, Woven, knitted, nonwoven or woven fabric. The method of claim 4, wherein Fabric comprising a warp and weft filament, wherein the warp filament comprises a first electrical conductor or conductors, and the weft filament comprises a second electrical conductor or conductors. The method according to any one of claims 1 to 5, A fabric comprising insulating fibers or filaments that stagger the first and second electrical conductors alternately at intersections. The method of claim 6, Staggered separation is performed by placing electrical conductors having a relatively smaller cross section between insulating filaments or fibers having a relatively larger cross section. The method of claim 6, A fabric in which weaving staggers the first and second electrical conductors at an intersection, including warp and / or weft floats over one or more yarns. The method of claim 6, Staggered separation is performed by using an electrical filament wrapped around an insulating filament or fiber around one or more of the electrical conductors such that the conductor surface remains exposed at the intersection. The method of claim 6, Staggered separation is performed by twisting one or more of the electrical conductors together with insulating filaments or fibers. The method of claim 6, Staggered separation is performed by using, as one or more of the electrical conductors, an electrical conductor supported over and between the deformable protrusions of the insulating filament or fiber. The method according to any one of claims 1 to 11, An electrical conductor having an electrical property that is proportional to the length of the conductor, whereby the length of the conductor or the plurality of connecting conductors can be measured from the measurement of the property. The method of claim 12, Fabrics whose electrical properties are electrical resistance. The method according to any one of claims 1 to 13, One or more spaced sets of electrical conductors, wherein at least a portion of the set is electrically connected together to form one or more busbars. The method of claim 14, Wherein the set of spaced electrical conductors comprises filaments or fibers that are electrically conductive to the warp or weft of the woven structure, wherein electrical connection between the conductors of the set is provided by one or more electrically conductive filaments or fibers of the weft or warp, respectively. fabric. The method of claim 14, Wherein the set of spaced electrical conductors comprises filaments or fibers that are electrically conductive to the warp or weft of the woven structure, wherein the electrical connection is performed after the weaving process. A fiber comprising an insulated yarn and a conductive yarn, wherein the fiber comprises a portion extending beyond the conductive yarn. The method of claim 17, Fibers in which two or more conductive yarns are spirally wound around an insulated yarn.