GB2139790A - Access alarm - Google Patents

Abstract

An access indication arrangement for use at a window or doorway includes a curtain (4) hanging down from a rod or bar (1) such that when an intruder passes through, the movement of the curtain rocks the rod or bar. The rod or bar (1) carries a flag (5) whose movement due to the rocking action influences an optic switch (6) to give an indication in response to the curtain movement. The curtain as shown is an array of semi-rigid coloured wires. <IMAGE>

Description

SPECIFICATION Access alarm This invention relates to an access indication arrangement for giving an alarm when an intruder passes through a window or a doorway. In the present context the term intruder is interpreted broadly, so as to include a customer entering a shop whose door is open.

According to the invention there is provided an access indication arrangement, for giving an alarm when an intruder passes through a window or a doorway, which includes a rockable rod or bar from which a curtain or the like is suspended, such that when an intruder passes through the window or doorway the rod or bar is rocked, a movable member on the rod or bar, and an optical detector mounted in operative relationship with movable member in such a way that when an intruder passes through the window or doorway the movement of the curtain or the like rocks the rod or bar, to move to the movable member, so that the optical detector responds to the movement of the rod or bar to give an alarm to indicate that an intruder has passed through the window or doorway.

An embodiment of the invention will now be described with reference to the accompanying highly schematic drawing.

The arrangement shown includes a curtain bar 1 or rod so mounted, e.g. using brackets such as indicated at 2,3 as to be rockable. This bar carries an array of downwardly-extending semi-rigid coloured wires 4 or a curtain, the arrangement being such that when an intruder passes through the window or doorway he has to disturb the wire array or curtain in such a way as to rock the bar 1.

The bar 1 has a flag 5 with a small hole in it, which fits between the legs of a slotted opto switch 6 in such a way that when at rest light passes through the hole between the legs. When the bar is rocked the light passing between the legs of the switch is interrupted, and associated circuitry gives the alarm.

It will be appreciated that the intruder may be a welcome one, e.g. when he or she is a customer in a shop with its door open.

The bar can be a plain rod, and the curtain can be extendable, in which case a separate alarm arrangement may be needed to detect sideways movement of the curtain. The wires 4 would be weighted if necessary, the extent of the weighting being adjustable to vary sensitivity and could be replaced by a conventional curtain as long as the passage of the intruder rocks the curtain bar or rod.

The opto switch can take various forms, e.g. a light source-detector arrangement or two aligned optical fibre ends with light from one received at the other in one condition. The use of optical fibres allows the system to be used in high fire risk areas, such as munitions manufacturing area.

The associated circuitry (not shown) can be designed to respond to movements of the bar or rod due to sharp movements or tension effects, while not responding to gentler movements due to, for example, a summer breeze.

1. An access indication arrangement, for giving an alarm when an intruder passes through a window or a doorway, which includes a rockable rod or bar from which a curtain or the like is suspended, such that when an intruder passes through the window or doorway the rod or bar is rocked, a movable member on the rod or bar, and an optical detector mounted in operative relationship with the movable member in such a way that when an intruder passes through the window or doorway the movement of the curtain or the like rocks the rod or bar, to move the movable member, so that the optical detector responds to the movement of the rod or bar to give an alarm to indicate that an intruder has passed through the window or doorway.

2. An arrangement as claimed in claim 1, and in which the curtain or the like is formed by an array of semi-rigid downwardly-extending wires.

3. An arrangement as claimed in claim 1 or 2, and in which the optical detector is a switch with a light source separated from a detector by the movable member.

4. An access indication arrangement, substan tial ly as described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Access alarm This invention relates to an access indication arrangement for giving an alarm when an intruder passes through a window or a doorway. In the present context the term intruder is interpreted broadly, so as to include a customer entering a shop whose door is open. According to the invention there is provided an access indication arrangement, for giving an alarm when an intruder passes through a window or a doorway, which includes a rockable rod or bar from which a curtain or the like is suspended, such that when an intruder passes through the window or doorway the rod or bar is rocked, a movable member on the rod or bar, and an optical detector mounted in operative relationship with movable member in such a way that when an intruder passes through the window or doorway the movement of the curtain or the like rocks the rod or bar, to move to the movable member, so that the optical detector responds to the movement of the rod or bar to give an alarm to indicate that an intruder has passed through the window or doorway. An embodiment of the invention will now be described with reference to the accompanying highly schematic drawing. The arrangement shown includes a curtain bar 1 or rod so mounted, e.g. using brackets such as indicated at 2,3 as to be rockable. This bar carries an array of downwardly-extending semi-rigid coloured wires 4 or a curtain, the arrangement being such that when an intruder passes through the window or doorway he has to disturb the wire array or curtain in such a way as to rock the bar 1. The bar 1 has a flag 5 with a small hole in it, which fits between the legs of a slotted opto switch 6 in such a way that when at rest light passes through the hole between the legs. When the bar is rocked the light passing between the legs of the switch is interrupted, and associated circuitry gives the alarm. It will be appreciated that the intruder may be a welcome one, e.g. when he or she is a customer in a shop with its door open. The bar can be a plain rod, and the curtain can be extendable, in which case a separate alarm arrangement may be needed to detect sideways movement of the curtain. The wires 4 would be weighted if necessary, the extent of the weighting being adjustable to vary sensitivity and could be replaced by a conventional curtain as long as the passage of the intruder rocks the curtain bar or rod. The opto switch can take various forms, e.g. a light source-detector arrangement or two aligned optical fibre ends with light from one received at the other in one condition. The use of optical fibres allows the system to be used in high fire risk areas, such as munitions manufacturing area. The associated circuitry (not shown) can be designed to respond to movements of the bar or rod due to sharp movements or tension effects, while not responding to gentler movements due to, for example, a summer breeze. CLAIMS

1. An access indication arrangement, for giving an alarm when an intruder passes through a window or a doorway, which includes a rockable rod or bar from which a curtain or the like is suspended, such that when an intruder passes through the window or doorway the rod or bar is rocked, a movable member on the rod or bar, and an optical detector mounted in operative relationship with the movable member in such a way that when an intruder passes through the window or doorway the movement of the curtain or the like rocks the rod or bar, to move the movable member, so that the optical detector responds to the movement of the rod or bar to give an alarm to indicate that an intruder has passed through the window or doorway.

2. An arrangement as claimed in claim 1, and in which the curtain or the like is formed by an array of semi-rigid downwardly-extending wires.

3. An arrangement as claimed in claim 1 or 2, and in which the optical detector is a switch with a light source separated from a detector by the movable member.

4. An access indication arrangement, substan tial ly as described with reference to the accompanying drawing.