Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1994-11-30
1997-10-14
Hofsass, Jeffery
Communications: electrical
Condition responsive indicating system
Specific condition
340550, 340564, 340565, 340566, G08B 1300
Patent
active
056776748
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of making a flexible closure and to a flexible closure for incorporation in an alarm system.
In my earlier publication, WO 87/06749, I have disclosed an alarm system for flexible closures consisting of a network of conductive sensing elements which are attached to or incorporated into the closure. If the closure is cut to any significant extent, the elements will be disturbed or broken causing a change in the current flowing therein or a change in the resistance. This exchange is used to trigger an alarm, alerting the owner to any attempted unauthorized access to the area enclosed by the flexible closure.
In that prior arrangement, the network of conductive sensing elements is stitched, bonded or webbed to a layer of material which forms the flexible closure. It is necessary to use such a layer on which to lay down the network. In an attempt to make it more difficult to detect one of the elements of the network and subsequently attempt to by-pass the alarm system, I disclosed in my European Publication No. 0359762 an alarm system in which the conductive sensing elements comprise conductors in a common outer sheath together with at least one other dummy conductor.
Other prior arrangements for deterring unauthorized access include U.S. Pat. Nos. 3,051,935 and 4,293,778. U.S. Pat. No. 3,051,935 discloses a screen structure comprising a sheet of non-conductive screen material secured in a frame with strands of conductive wire then being woven through the screen material. The wire and the screen material are preferably coated with a vinyl material so as to be visibly indistinguishable. U.S. Pat. No. 4,293,778 discloses an anti-theft screen construction in which lengths of conductive wire are laid on a mesh screen and then mechanical bonded to the screen at the points of intersection. However, these prior arrangements suffer from the disadvantage that the screens are rigid, moreover all the prior arrangements suffer from the disadvantage that the conductive elements are applied to a preformed substrate.
It is an object of the present invention to provide an improved method of making a flexible closure incorporating a conductive sensing element for an alarm system and to a flexible closure incorporating a conductive sensing element.
According to the invention, there is provided a method of making a flexible closure for incorporation in an alarm system the method comprising interlacing a conductive sensing element with fibre material forming the matrix of the closure so that the interlaced conductive sensing element provides a network over at least part of the closure. Preferably the network is formed integrally with the formation of the matrix of the closure thereby simplifying its manufacture. The interlacing may be by means of knitting, weaving, crocheting or other entwining of materials or non-woven matrix material may be stitched through the matrix.
In a preferred embodiment, the closure is knitted. The closure may be knitted from a mixture of the conductive sensing element or elements and other material forming the matrix of the closure such as cotton, nylon, polyester, wool, fibres, etc. The interlacing of the conducting sensing elements renders the conductive sensing elements more difficult to detect. The term `fibre` includes any elongate strand, filament, yarn or the like.
The conductive sensing elements may be of any type of conductive fibre or filament, e.g. carbon fibre, glass fibre. Preferably, the conductive sensing elements are of copper tinsel. The copper core may be sheathed in conventional PVC material or in ELVALOY resin material or any other suitable insulating material.
The closure may be interlaced into any shape and may include open areas or holes. The method also may include applying one or more protective layers to the or each face of the closure.
The invention also includes a flexible closure, for use in an alarm system, comprising a conductive sensing element interlaced with fibre matrix material providing a network over at least part of the closure for
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Cover Protection Limited
Hofsass Jeffery
Lee Benjamin C.
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