GB2451115A - Letterbox alarm with time delay - Google Patents

Abstract

An alarmed letterbox permits normal usage, but activates an audio or visual alarm if the letterbox flap is held open for longer that a pre-set period of time. The inside face of an external door 1 has a letterbox flap 2 movable to an open position by a hinge 4 by insertion of an article through slot 7 in the door. A shield 3 is hinged to the flap so that contacts under the shield make or break a circuit via wires 6 leading to alarm means. The pre-set time period defined the time period the flap is allowed to be open. This period may be altered by the user. The period may be made relatively shorter for times of day when mail deliveries are not expected, such as night-time or for specific days such as Sundays.

Description

1 2451115 NAME OF INVENTION: Anti-intrusion Letterbox concept

THE CONCEPT

This invention relates to an alarmed letterbox designed to.Rermit normal usage without the alarm sounding, but which would activate an aural or visual alarm if the letterbox flap was held open for a pre-prescribed period of time. This permits postal workers or deliveries of newspapers to insert legitimate items through the letterbox without disturbing the occupants or neighbours, but would raise the alarm if potential burglars or thieves inserted devices with the intention of surveying the interior of the house or removing items such as keys.

JUSTIFICATION OF NEED

It is recorded that there are increasing numbers of burglaries where thieves are obtaining household/car keys via the letterbox. This is a security risk to the householder as thieves are not only able to gain access to the property at any given time but even if a security alarm is present they are able to steal the owner's car.

Householders often forget to secure keys in a safe place away from doors as when they get home they are often tired and drop them in the nearest place, most likely on a table or shelf near to the front door. This gives a burglar an ideal opportunity to insert an instrument through the letterbox, hooking keys and removing them without disturbing the occupants. A potential burglar could also insert a device such as a fibre optic viewer to survey the immediate interior of a property and thereby judge whether or not it may be worth breaking into.

STATEMENT OF INVENTION

To overcome this, this invention proposes an alarmed letterbox flap. The alarm would activate after a short delay long enough to allow normal letter and paper delivery but short enough to deter a burglar looking through the letterbox and inserting an instrument.

ADVANTAGES

The advantages of this system would be: * The alarm would not be visible to the potential thief from outside * The internal fit would be unobtrusive * Installation would be feasible for the average person with minimal DIY skills or could be incorporated within supplied doors.

* Battery and/or mains power versions would be available * The occupier could set the period of delay of activation depending on personal requirement * The alarm would be set at a pitch high enough to wake sleeping occupants and deter the burglar, or could be of a visual nature -e.g. flashing lights.

* The delay period in activation can be set at the discretion of the consumer.

* This allows the consumer to set a shorter delay between the opening of the flap (i.e. the moment of detection, and the activation of the alarm.

* This flexibility would allow the consumer to shorten the period of delay for times when legitimate opening, such as postal deliveries, are unlikely, such as night time or Sundays.

INTRODUCTION TO DRAWINGS

An example of this invention will now be described by referring to the accompanying drawings Figure 1 Front elevation of door section -internal Figure 2 Elevation Figure 3 Side view

Description

In this configuration, the alarm is triggered by a movable contact completing a circuit.

In figures 1, 2 and 3 and interior letterbox flap 2 is hinged 4 to the inside of the door 1. As letters are pushed through the letterbox slot 7 the flap is raised and contacts under shield 3 which is hinged 5 to the flap 2 make a complete circuit which is passed down wires 6 to the alarm.

A similar design could be employed using the reverse concept of breaking a continuous circuit.

The advantages of the above conceptual designs are simplicity and therefore cheap cost Alternatively, the basic concept could be incorporated into a more sophisticated application using more hi-tech non-mechanical means, such as infra-red detection.

An important feature of any alternative method of activation will be that the actual mechanics of the activation would have to be both out of sight and out of reach of a potential intruder. In the basic conceptual design illustrated, the trigger device is behind and above the interior flap completely complying with these criteria.

Claims (7)

1. I) This invention proposes an alarmed anti-intrusion letterbox flap or similar opening in a door to allow the insertion of everyday items but which would activate after a delay long enough to allow normal letter and paper delivery but short enough to deter a potential burglar looking through the letterbox and inserting an instrument.
2. 2) The length of the delay between detection and activation of the alarm will be variable at the consumers discretion.
3. 3) This allows for a shorter delay to be set for periods when legitimate opening of the flap is unlikely such as night time.
4. 4) The method of activating the alarm would be either electro-mechanical by means of either making or breaking a circuit or by any appropriate non-mechanical method such as infra-red or motion detection.
5. 5) The alarm mechanism or activation system would be either battery or mains powered at the choice of the consumer.
6. 6) The alarm would be either audio or visual or both at the choice of the consumer.
7. 7) The concept allows simplicity for DIY fitting or incorporation in manufactured doors sold complete with fittings.