GB2405511A

GB2405511A - Door alarm enabled by removal of magnetic key

Info

Publication number: GB2405511A
Application number: GB0319779A
Authority: GB
Inventors: Michael Gilber Chetwynd-Talbot
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-08-22
Filing date: 2003-08-22
Publication date: 2005-03-02
Anticipated expiration: 2023-08-22
Also published as: GB0319779D0; GB2405511B

Abstract

An alarm 20 to detect the opening of a door 10 which is enabled by the removal of a key. The key may be magnetic and may be detected using a reed switch. The opening of the door may be detected by placing a magnet 22 on the door frame 12 and a reed switch SW2 in the alarm apparatus on the door. A buzzer may be used to signal that the door has been opened. The alarm may be attached to the door and frame using screws, nails, adhesive tape or hook and loop fasteners.

Description

240551 1 DOOR ALARM, DOORWAY AND USE OF THE ALARM

FIELD OF THE INVENTION

The present invention relates to door alarm for fitting to a doorway, to a doorway fitted with an alarm, and to the use of the alarm for providing a signal when a person in or liable to be in a confused mental state has opened the door of a room where the person is expected to remain and is in imminent danger of wandering.

BACKGROUND TO THE INVENTION

There are many patent specifications that describe supervision of confused, or potentially confused patients e.g. patients suffering from Alzheimer's disease or other forms of age-related mental deterioration in hospitals or other medical care facilities. Such specifications recommend the use of electronic tagging systems and secure zones within the facility, e.g. US-A-6048513. However, such tagging systems are costly and depend on persuasion of a patient, possibly in the early stages of the disease, to wear such a tag, which may cause alarm and distress to the patient as well as objections to loss of personal dignity.

US-A-4638307 (Swartout) discloses apparatus for sounding an alarm when an invalid patient attempts to get up from a chair or bed. Such patients are usually held in place with a positioning belt that may be uncomfortable and distasteful to the patient, who is usually capable of working his way out of such belts. The need to use such a belt can be avoided by apparatus for issuing an alarm when a weight is lifted from a pad, the apparatus comprising: a compressible pad; a thin, sealed reed switch affixed near the bottom of the pad; and a magnet affixed near the top of the pad in approximate vertical and parallel registry with the switch, d.

ë ë Be d e Me, the reed switch being connected in an electrical circuit containing a power source and an alarm issuing means such that when the pad is compressed by a weight, causing the magnet to be in close proximity to the reed switch, no alarm issues, but when the weight is lifted and the pad decompresses, causing the magnet to move away from close proximity to the reed switch, the alarm issues.

In the above mentioned apparatus, the pad will typically comprise a compressible foam stuffing having a resilient, flexible, waterproof covering thereover, the covering encapsulating the foam, the reed switch and the magnet.

The alarm may be sound emitting or light emitting or both sound emitting and light emitting. In an alternate embodiment, when the pad decompresses and the magnet moves away from the reed switch, a signal may be sent to the alarm means via radio transmission to issue the alarm at a remote location.

SUMMARY OF THE INVENTION

This invention is based on the realization that one of the major subjects on which a person having responsibility for the care of a confused patient requires reassurance, especially in a home care situation, is that the patient remains within the room allocated and is not liable to wander about. In particular, there is a need for such a system that is inexpensive, rapid and simple to set up, and unlikely to be defeated by the actions of the confused person erg. in brief periods of increased lucidity.

In one aspect the invention provides a door alarm for fitting to a doorway comprising electrical alarm means adapted to provide a signal when the door is open on activation by removal of a key.

The invention further provides a doorway for a room in a building having alarm means for signalling when a door forming part of said doorway is open and . A . . ... . . . . . . . control means for selectively activating the alarm means on removal of a control member.

The invention yet further provides a doorway for a room in a building, said doorway comprising, a door frame, a door movably attached to the frame, and electrical alarm circuit means for providing an alarm when the door is open, said circuit means comprising first proximity switch means having portions attached to the door and to the frame and operable when the door is open to switch to an alarm state; output means responsive to the alarm state of the fist proximity switch means to provide a perceptible output; and second proximity switch means arranged to deactivate and activate the alarm circuit means depending on the presence or absence of a removable control member.

Other preferred aspects of the invention are apparent from the accompanying claims to which attention is directed.

BRIEF DESCRIPTION OF THE DRAWINGS

How the invention may be put into effect will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of apart of a doorway with the door in a slightly open position, the door and frame carrying portions of an alarm system according to the invention; Fig. 2 is a diagrammatic circuit diagram for an embodiment of the alarm.; and Fig 3 is a diagram of a reed switch. . .

:. e. ...

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

In Fig 1, a doorway e.g. of a room in a dwelling-house comprises a door 10 and a frame 12 made up of a door lining 14, a door stop 16 and an architrave 18.

An alarm unit 20 is attached to the door l0 adjacent its free edge and includes a reed switch SW2 that is in vertical register with a magnet 22 secured in a recess defined between the door lining 14 and the architrave 18. The switch SW2 is normally closed but opens when adjacent to the magnet 22. The switch is SW2 is in series with another reed switch SW1 controlled by a magnetic key 24 which is insertable into a top aperture in the housing of the alarm unit 20 into register with switch SW1. Again SW1 is normally closed but opens when the magnet of key 24 is present. A top cap 26 on the key 24 serves to limit the ingress of the key into the housing and ensure correct registration of the magnet of key 24 with SW1.

Advantageously the top cap has a colour that contrasts with the housing so that it can be seen whether or not the key is in place. The switches SW1 and SW2 are in series with battery 28 and buzzer 30 and are contained within the housing that is carried by the door 10.

In use, the alarm is inactive when the key 24 is in place because SWl is open, so that the buzzer 30 does not sound irrespective of door position. However, if the key 24 is removed, SW l is closed and SW2 opens and closes depending on the proximity of SW2 to the magnet 22, thus giving an audible alarm when the door is opened and there is a risk of the room occupant wandering.

Reed switches are preferred for SWI and SW2 because they are compact and inexpensive. In the preferred form they comprise a glass envelope 32 with an inert gaseous atmosphere and hermetically sealed contacts, an input contact 34 of resilient ferromagnetic material, a normally open first output contact 36 also of ferromagnetic material and a normally closed second output contact 38 of non magnetic material. The contact 34 is arranged within the envelope so as to normally make contact with the nonmagnetic contact 34 as shown by the solid a. .-. A. . a. : lines. When the switch is subjected to a magnetic field, however, the induced magnetism causes contacts 34 and 36 to attract one another moving the contact 34 into electrical contact with the output 36. In the present circuit the input contact 24 and the normally closed contact 38 is used for both SWI and SW2 and the contact 36 is not used. An alternative normally closed two-contact reed switch (in the rest or no-magnet position the circuit is closed) is available inexpensively in the UK from Maplin Electronics.

In a variant SWI and SW2 can be combined so that the same reed switch acts as the alarm means and the control means. In order to achieve this, the magnet of key 24 and the magnet 22 have to be correctly positioned so as to be mutually reinforcing at the closed position of the door, so that the presence of either of them adjacent the reed switch will cause it to open, and it will remain open if neither one of them is present. It has been found, however, that this arrangement tends to be intermittent and requires careful selection of the position of the magnet 22, so that this arrangement is less preferred.

The alarm unit 20 and the magnet 22 may be attached to the door and frame by any suitable means e.g. screws, nails, adhesive tape, double-sided adhesive tape or Velcro_.

The output from the alarm is provided by the buzzer 22, but if preferred the signal may be a light from a flashing or continuously illuminated lamp forming part of the alarm unit. In a further variant, the output may be to a control of a low power radio unit that can transmit a signal to a remote receiving station to set off an alarm at that station. Radio units of this type are well known e.g. for use with vehicle locking systems and are typically worked by surface acoustic wave resonators in the hundreds of MHz or low GHz range and include address encoders so that the receiving station, if so equipped, can monitor a number of the transmitter units so as to show not only that an alarm has been activated but also the identity of the alarm that has become activated. Such a system may be e e eee e e e e e ee e e e ee e e ee- e e e e e e e e e e e e e e appropriate for use in nursing homes where the presence of a number of residents in their rooms may need to be monitored. In a further variant the amplitude of the signal from the buzzer 22 can be adjusted by a series-connected variable resistor.

Claims

e.. a. .. . . . . . : a. ..e I. . CLAMS

1. A door alarm for fitting to a doorway comprising electrical alarm means adapted to provide a signal when the door is open on activation by removal of a key.

2. The alarm of claim l, wherein the electrical alarm means comprises a first magnetic proximity switch adapted to provide a signal when the door is open.

3. The alarm of claim 2, wherein the electrical alarm means further comprises control means which is a second magnetic proximity switch responsive to a magnetic key.

4. The alarm of claim 2 or 3, wherein said switches are reed switches.

5. The alarm of any preceding claim, further comprising a buzzer adapted to be sounded to provide said signal.

6. The alarm of any preceding claim, further comprising a battery for providing power to the alarm means.

7. The alarm of any preceding claim, further comprising: a housing for door attachment, said housing containing a first portion of said electrical alarm means, and being formed at a top surface with an aperture for insertion of a key.

8. The alarm of claim 7, wherein the key is formed with a distal portion for entering the aperture to disable the alarm means and a proximal portion for protrusion from the housing to provide a visible indication when the key is present.

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9. A door alarm substantially as described with reference to the accompanying drawings.

10. A doorway for a room in a building having alarm means for signalling when a door forming part of said doorway is open and control means for selectively activating the alarm means on removal of a control member.

11. The doorway of claim 10, comprising a housing attached to the door for active components of said alarm means and for said control means, and a passive component for said alarm means attached to the fame.

12. The doorway of claim 11, wherein the passive component is attached within a recess defined between a door lining and an architrave forming part of said frame.

13. The doorway of claim I I or 12, wherein said housing has a top face and an aperture formed in the top face for receiving the control member.

14. The doorway of any of claims 11-13, wherein the passive component is: adhesively secured to the frame.

15. The doorway for a room or building having an alarm system substantially as hereinbefore described with reference to the accompanying drawings.

16. A doorway for a room in a building, said doorway comprising, a door frame, a door movably attached to the frame, and electrical alarm circuit means for providing an alarm when the door is open, said circuit means comprising first proximity switch means having portions attached to the door and to the frame and operable when the door is open to switch to an alarm state; - output means responsive to the alarm state of the fist proximity switch means to provide a perceptible output; and . . . . . ... . . . . . .e.

second proximity switch means arranged to deactivate and activate the alarm circuit means depending on the presence or absence of a removable control member.

17. Use of an alarm according to any of claims 1-9 for providing a signal when a person in or liable to be in a confused mental state has opened the door of a room and is liable to wander.