Patent Application
20060076103
This invention relates to the manufacture of products that include a sinuous (i.e. wavy or serpentine) arrangement of one or more elongated elements the elongated elements may comprise conductors, such as optical fibres, wires or the like. Particular embodiments of this invention relate to the manufacture of sensors in which one or more optical fibres are arranged in a sinuous manner. For example, this invention may be applied in the manufacture of fibre-optic pressure sensors of the general type disclosed in Lokhorst et al (PCT Publication WO 2004/006768).
Some sensors have optical fibres or other flexible conductors, disposed in sinuous arrangements. Examples of such sensors are described in U.S. Pat. No. 4,947,693 (Szuchy et al.), U.S. Pat. No. 4,408,495 (Couch et al.), and U.S. Pat. No. 6,854,327 (Rambox et al.). A sinuous arrangement can be desirable both for its effects on the transmission properties of conductors and also because such an arrangement can contribute to the overall flexibility, resiliency and reliability of a sensor or other device.
One difficulty in the mass production of sensors of the general type described by Lokhorst et al. involves finding an efficient way to arrange optical fibres or other conductors in a neat, sinuous, arrangement. Fabricating sensors that include such arrangements by hand is unduly expensive and time consuming for many applications. A cost-effective method for manufacturing such sensors is therefore desirable. Such methods could also be applied to advantage in fabricating products of other types that include arrangements of sinuous elements on a substrate.
There is a need for methods for making sensors or other devices having sinuous arrangements of flexible elongated elements, such as optical fibres, wires or other conductors.
In general, the invention relates to methods and associated apparatus for the manufacture of sensors or other devices that include sinuous arrangements of flexible elongated elements such as optical fibres, wires or other conductors.
One aspect of the invention provides a method for manufacturing a composite structure comprising an elastically-extendable layer and one or more elongated flexible elements. The method involves stretching the elastically-extendable layer and attaching the elongated flexible elements to the stretched elastically-extendable layer at a plurality of locations that are spaced apart along the elastically-extendable layer in a direction of the stretch. Attaching the elongated flexible elements to the elastically-extendable layer may comprise applying adhesive to the elastically-extendable layer, the elongated flexible elements, or both and adhering the elongated flexible elements to the stretched elastically-extendible layer. The elongated flexible elements may be held to be straight, for example by applying some tension to them, while they are being attached to the elastically-extendible layer. The method relaxes the elastically-extendable layer and allows the elongated elements to assume sinuous configurations as the points of attachment between the elongated elements and the elastically-extendible layer become closer together.
A further aspect of the invention provides an apparatus that has application for manufacturing composite structures comprising an elastically-extendable layer and one or more elongated flexible elements. The apparatus includes a support surface and clamps disposed on opposite sides of the support surface. The clamps are mounted adjacent to the support surface. At least one clamp is movable toward or away from at least one other one of the clamps.
Yet another aspect of the invention relates to the use of such an apparatus for manufacturing a composite structure comprising an elastically-extendable layer and one or more elongated flexible elements.
Further aspects of the invention and features of embodiments of the invention are described below.
In drawings which illustrate non-limiting embodiments of the invention:
Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.
In the illustrated embodiment, several bundles 7 of optical fibre pairs 14, 15 carry light energy to and from the pressure sensors 5. It is generally desirable that pad 1 be flexible. Optical fibres 8 are secured to the layers of compressible material 9,10 above and below each sensor 5 by areas of adhesive 11. Other portions of optical fibres 8 are left free so as to provide some flexibility and resilience to the entire assembly.
In the assembled device, optical fibres 8 are not stretched tightly and do not extend in straight lines to sensors 5 but follow sinuous paths. It can be difficult to repeatably form fibres 8 into the desired sinuous configurations and then attach the fibres 8 to compressible material layers 9, 10.
A method for manufacturing a sensor or other device having a structure like that of pad 1, involves stretching an elastic substrate layer that will be adjacent to the fibres, or other flexible elongated elements, of the device. For example, if a sensor pad of the type shown in
The method involves placing fibres 8 (or other flexible elongated members) on the stretched substrate layer in a substantially straight manner. Fibres 8 are then attached to the substrate layer at spaced-apart locations. The substrate layer is then allowed to relax. Relaxation of the substrate layer constricts the entire assembly and, in particular, brings together the locations at which the fibres are attached to the substrate layer, thereby forcing the fibres to assume a sinuous arrangement.
The size of the meanders in fibres 8 may be adjusted by selecting an amount by which the substrate layer is stretched and a distance between the locations where fibres 8 are attached to the substrate layer. In some embodiments, the locations where the fibres, or other elongated elements, are attached to the substrate layer are, at least approximately, equally spaced apart.
A mechanical jig may be used in the practice of the invention.
Clamps 34, 35 can each be opened to receive an edge of a sheet of material 10 and then closed to grip the material 10. In the illustrated embodiment, each clamp comprises a jaw (32 and 33 respectively) that extends substantially the full width of a sheet of material 10.
In block 21 a substrate layer (e.g. bottom layer 10) is placed on support surface 31 of jig 30. The substrate layer is arranged such that its ends can be engaged by the jaws 32, 33 of clamps 34, 35. Jaws 32, 33 of clamps 34, 35 are then closed to secure the ends of the substrate layer to the clamps.
In block 22 an area of adhesive 11 is applied to the substrate layer at each location where it is desired to secure a fibre 8 (or other elongated flexible element). For example, areas of adhesive 11 may be applied in a grid pattern or in stripes extending across the substrate layer. The areas of adhesive are deposited in a pattern which provides spaced-apart locations for affixing fibres 8 to the substrate layer.
In block 23 the substrate layer is stretched by sliding clamps 34, 35 apart by a set amount. The amount of stretch 50 applied is preferably between 5% and 25% of the length of the substrate layer. Clamps 34, 35 are locked in place when the desired degree of stretch has been achieved. A stop may be provided to stop the travel of one or both of clamps 34, 35 when a desired degree of stretch has been achieved. An actuator may be provided to move clamps 34, 35 apart by an amount sufficient to achieve a desired degree of stretch.
In block 24, fibres 8 of fibre pairs 14, 15 are applied (in a straight manner) to the areas of adhesive 11 on the stretched substrate layer. Each fibre pair 14, 15 may extend across several areas of adhesive 11. Each fibre 8 is caused to adhere to adhesive 11 at a number of spaced-apart locations along its length. Fibres 8 are preferably applied substantially parallel to direction 37. Fibres 8 may be applied at an angle to direction 37 if reduced sinuosity is desired.
In block 25 the substrate layer is allowed to relax by sliding clamps 34, 35 back to their original positions. This is illustrated in
Where fibres 8 are parallel to one another, when attached to the substrate layer and the locations at which fibres 8 are attached to the substrate layer are aligned with one another in stetch direction 37, it can be seen that the sinuous arrangements of fibres 8 can be made neat and complementary to one another.
In block 26 the sinuous curves of the fibre pairs are arranged as desired. The inventor has found that curves in fibres 8 may occur to either side of a line joining the points at which the fibres are attached to the substrate. If a particular arrangement is desired, the curves in fibres 8 may easily be moved left or right.
In block 27 a top layer 9 is applied to sandwich the sinuous fibres between the substrate layer 10 and top layer 9. The assembly may then be removed from jig 30 by opening jaws 32, 33 of clamps 34, 35.
The inventor has found that the operation of pressure sensors of the type described by Lokhorst et al. that are made as described herein may be improved by altering some details of the design of sensing pad 1. In particular, in some embodiments:
Bottom layer 10 (see
Some or all of the areas of adhesive 11 may further comprise a layer of non-elastic material. The non-elastic material prevents bottom layer 10 from stretching in the immediate area of a location at which a fibre (or other elongated flexible element) is adhered to bottom layer 10. This may improve the adhesion of fibres 8 to layer 10.
Some or all areas of adhesive 11 may further comprise a layer of reflective material. A suitable such material is aluminized mylar. Providing a reflective material may improve the function of pressure sensors 5, especially in cases where bottom layer 10 is chosen for good mechanical properties even through it may have sub-optimal optical properties.
As will be apparent to those skilled in the art, in light of the foregoing disclosure there are many possible alterations and modifications in the practice of this invention without departing from the scope thereof. For example:
The invention may be applied to make sensors or products of types other than the particular sensors that are described herein as example applications of the invention.
Fibre bundles 14, 15 may each comprise a single or multiple fibres wires or other conductors.
Adhesive areas 11 may be located in any suitable pattern on the substrate layer that permits attachment of fibres or other elongated flexible elements at spaced-apart locations.
The areas of adhesive 11 may comprise adhesive strips extending in a direction substantially transverse to the direction in which the bottom layer is stretched.
The adhesive may be applied before or after arranging the elongated members on the bottom layer and before or after stretching the substrate layer.
The adhesive may be applied under the elongated elements or over top of the elongated elements.
The adhesive may comprise any suitable adhesive. Some examples of different forms that the adhesive may take are double-sided sticky tape, adhesive decals, suitable spray-on adhesive, suitable liquid adhesive; suitable hot-melt adhesive, or the like.
The elongated flexible members may be affixed to the substrate layer by means of non-adhesive fastenings such as suitable staples, clamps, barbs, or the like.
Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
This application claims the benefit of U.S. application No. 60/616,634 filed on 10 Oct. 2004 and entitled METHOD FOR MANUFACTURING A SENSOR HAVING WAVY CONDUCTORS, which is hereby incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 60616634 | Oct 2004 | US |
