GB2289330A - Sensor for electronic lock - Google Patents

Abstract

Sensor apparatus 2 comprises infrared transmitter/receiver 4 in a door 6, reflector 8 for reflecting infrared back to the transmitter/receiver from the door frame 10, an ND converter 12, and computer 14, the A/D converter being for generating a number representative of the reflected light intensity, the computer being for storing the number generated, and the reflector being a linear reflector whereby the amount of infrared reflected is proportional to the distance between the transmitter/receiver and the reflector thus enabling correct closure of a door to be verified before an electronic lock is activated. <IMAGE>

Description

SENSOR APPARATUS FOR USE WITH AN ELECTRONIC LOCK This invention relates to sensor apparatus for use with an electronic lock.

Electronic locks are well known and they are widely used on doors to premises, to safes or to strongrooms.

Irrespective of where the electronic lock is fitted, it is necessary for the door to be shut before the electronic lock locks the door. In order to ensure that the door is shut, .it is known to use proximity switches such for example as a reed switch. The proximity switches can often be falsely caused to operate by thieves, with the result that an electronic lock can be caused to operate when a door is not shut. Loss of security results.

It is an aim of the present invention to obviate or reduce the above mentioned problem.

Accordingly, in one non-limiting embodiment of the present invention there is provided sensor apparatus for use with an electronic lock, which sensor apparatus comprises infrared transmitter/receiver means, reflector means for reflecting infrared from the transmitter/receiver means back to the transmitter/receiver means, an analogue to digital converter, and computer means, the analogue to digital converter being for generating a number in dependence upon the amount of infrared reflected by the reflector means, the computer means being for storing the number generated by the analogue to digital converter, and the reflector means being a linear reflector means whereby the amount of infrared reflected by the reflector means is proportional to the distance between the transmitter/receiver means and the reflector means, whereby a change in the distance between the transmitter/receiver means and the reflector means causes a change in the amount of infrared reflected by the reflector means, whereby a change in the amount of infrared reflected by the reflector means causes a change in the number generated by the analogue to digital converter, and whereby a change in the number generated by the analogue to digital converter is able to be used by the sensor apparatus to control operation of the electronic lock.

The electronic lock is preferably an electronic door lock. In this case, the reflector means will usually be mounted on a door frame, and the transmitter/receiver means will usually be mounted on the door. The distance between the transmitter/receiver means and the reflector means will vary if the door is not properly shut. This distance will also vary if something is interposed between transmitter/receiver means and the reflector means in order to try and produce a false infrared reflection.

The electronic door lock and the associated sensor apparatus can be used substantially anywhere where there is a door, for example on entrance doors to flats and hotels, on doors to secure rooms, and on safes, chests and strongrooms.

The electronic lock need not only be an electronic door lock and the electronic lock can be used on other things such for example as windows and machine guards.

In this case, the sensor apparatus of the present invention can equally well be used with the electronic lock.

The number generated by the analogue to digital converter can be the same or different on each operation. The number generated by the analogue to digital converter depends upon the precise distance between the transmitter/receiver means and the reflector means. This generated number has to be the number stored in the computer means and subsequently sensed by the computer means in order for a permitted operation of the electronic lock to be allowed. If the distance between the trannsmitter/receiver means and the reflector means is likely to vary slightly, for example as in the case of a hinged door on worn hinges or a sliding door, then the sensor apparatus can be such that it operates with a new number being generated by the analogue to digital converter means on each request for opening of a door.Where the distance between the transmitter/receiver means and the reflector means is not likely to vary, for example in the case of a safe, then the first generated number can be the only one that is used.

The distance between the transmitter/receiver means and the reflector means is the same as the length of the reflected infrared path, and is thus approximately twice the distance between the transmitter/receiver means and the reflector means. A very small variation in the distance between the transmitter/receiver means and the reflector means produces a large variation in the number generated by the analogue to digital converter means.

Thus the chances of a would-be thief generating the same number as that generated by the analogue to digital converter means is so small as to be negligible.

As indicated above, one application of the sensor apparatus of the present invention is on general door access. The doors may be hinged doors or sliding doors.

With such general door access, it is desired that, where an electronic door lock is employed, then the electronic door lock should operate to lock the door closed only when the door is in its correct closed position. In this case, the sensor apparatus of the present invention is such that it is able to control the electronic door lock such that the electronic door lock will only go through its locking sequence when the correct distance is between the transmitter/receiver means and the reflector means and thus the correct number has been generated by the analogue to digital converter. This can only happen when the door is correctly shut.

For use of the sensor apparatus for general door access, the sensor apparatus will usually be such that it will go into an energy-conserving mode when the door is shut and the electronic door lock has operated. In this energy-saving mode, the sensor apparatus may only sense an attempt to open the door in a normal manner.

The computer means is able to act to compare the number generated by the analogue to digital converter at the instant when the door is opened with the number generated by the analogue to digital converter at the instant when the door is closed. If the two numbers do not agree, then the electronic door lock will not operate to lock the door.

The sensor apparatus of the present invention may thus act as a self-seeking device for general door access. The number generated at the opening of the door is lost when the door is correctly shut. A new number is generated each time the door is requested to open and this new number is lost each time the door is correctly shut and the electronic door lock has been allowed to operate. Thus the sensor apparatus of the present invention is automatically able to allow for small variations in distance between the transmitter/receiver means and the reflector means, for example as may occur with poorly fitting doors which are loose on their hinges, or as may occur with variations in temperature and/or light.

In a second mode of use of the sensor apparatus of the present invention, the sensor apparatus may be used on safes, chests, security rooms, deed boxes and similar objects and installations. In such a second mode of use, the distance between the transmitter/receiver means and the reflector means, that is the distance between a door and its frame, will normally be fixed and will not alter. In this case, the number first generated on the opening of the door can be a fixed number which is retained for all future openings and shuttings of the door. If the number stored in the computer means is not regeneratedon the closing of the door on any occasion, then the sensor apparatus can be arranged to cause an alarm to be activated. The alarm may also be activated when the door has been correctly shut but the distance between the transmitter/receiver means and the reflector means varies, for example as might occur if a door to a safe or a strongroom were tried to be opened using explosives or a drill which would cause vibration, or using heat which would cause expansion.

The transmitter/receiver means may be a separate transmitter and a separate receiver. Alternatively, the transmitter/receiver means may be a transceiver.

The analogue to digital converter may be a 4, 8, 12, 16, 24 or 32 bit analogue to digital converter.

The analogue to digital converter may be a separate analogue to digital converter. Alternatively, the analogue to digital converter may be in a computer or micro controller. In this latter case, with the analogue to digital converter in a computer or a micro controller, the possibility is afforded of security personnel being able to see a precise door opened or tampered with in an entire building.

Usually, the reflector means will be such that it gives a consistent ratio of infrared reflectance to the distance between the transmitter/receiver means and the reflector means.

The reflector means is preferably made of a semiopaque material which may be coloured.

The present invention also includes an electronic lock when provided with the sensor apparatus.

The electronic lock may be an electronic door lock or any other suitable and appropriate electronic lock.

The electronic lock may be an electronic time lock. The electronic time lock may provide one or more timed periods, for example timed delay periods prior to opening of a door.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawing which shows the sensor apparatus fitted to a door on a door frame.

Referring to the drawing, there is shown sensor apparatus 2 for use with an electronic door (not shown).

The sensor apparatus 2 comprises infrared transmitter/receiver means 4 mounted on a door 6. The sensor apparatus 2 also comprises reflector means 8 which is mounted on a door frame 10 and which is for reflecting infrared from the transmitter/receiver means 4 back to the transmitter/receiver means 4. The transmitter/receiver means 4 and the reflector means 8 are separated.

The transmitter/receiver means 4 is connected to an analogue to digital converter 12. The analogue to digital converter 12 is for generating a number in dependence upon the amount of infrared reflected by the reflector means 8. The analogue to digital converter 12 is itself connected to computer means 14. The computer means 14 is for storing the number generated by the analogue to digital converter 12.

The reflector means 8 is a linear reflector means whereby the amount of infrared reflected by the reflector means 8 is proportional to the distance "d" between the transmitter/receiver means 4 and the reflector means 8. This means that a change in the distance "d" between the transmitter/receiver means 4 and the reflector means 8 causes a change in the amount of infrared received by the receiver of the transmittertreceiver means 4. This in turn means that a change in the amount of infrared reflected by the reflector means 8 causes a change in the number generated by the analogue to digital converter 12. This further means that a change in the number generated by the analogue to digital converter is able to be used by the sensor apparatus 2 to control operation of the electronic door lock, for example to prevent the electronic door lock going through its locking mode of operation when the door 6 is in fact not correctly shut in the door frame 10.

It is to be appreciated that the embodiment of the invention described above with reference to the accompanying drawing has been given by way of example only and that modifications may be effected. Thus, for example, the sensor apparatus 2 may be used on security equipment such for example as a safe where the door frame 10 would normally form part of the body of the security equipment.

Claims (14)

1. Sensor apparatus for use with an electronic lock, which sensor apparatus comprises infrared transmitter/receiver means, reflector means for reflecting infrared from the transmitter/receiver means back to the transmitter/receiver means, an analogue to digital converter, and computer means, the analogue to digital converter being for generating a number in dependence upon the amount of infrared reflected by the reflector means, the computer means being for storing the number generated by the analogue to digital converter, and the reflector means being a linear reflector means whereby the amount of infrared reflected by the reflector means is proportional to the distance between the transmitter/receiver means and the reflector means, whereby a change in the distance between the transmitter/receiver means and the reflector means causes a change in the amount of infrared reflected by the reflector means, whereby a change in the amount of infrared reflected by the reflector means causes a change in the number generated by the analogue to digital converter, and whereby a change in the number generated by the analogue to digital converter is able to be used by the sensor apparatus to control operation of the electronic lock.

2. Sensor apparatus according to claim 1 and for use with an electronic door lock, and in which the number generated by the analogue to digital converter is different on each operation.

3. Sensor apparatus according to claim 1 or claim 2 and for use with an electronic door lock, in which the door lock operates to lock the door closed only when the door is in its correct closed position, and in which the sensor apparatus is such that it is able to control the electronic door lock such that the electronic door lock will only go through its locking sequence when the correct distance is between the transmitter/receiver means and the reflector means and thus the correct number has been generated by the analogue to digital converter.

4. Sensor apparatus according to any one of the preceding claims and which is for use with an electronic door lock, and in which the sensor apparatus is such that it goes into an energy-conserving mode when the door is shut and the electronic door lock has been operated.

5. Sensor apparatus according to claim 1 and for use with an electronic lock for a secure installation, and in which the number generated by the analogue to digital converter is the same on each operation.

6. Sensor apparatus according to any one of the preceding claims in which the transmitter/receiver means is a separate transmitter and a separate receiver.

7. Apparatus according to any one of claims 1 to 5 in which the transmitter/receiver means is a transceiver.

8. Sensor apparatus according to any one of the preceding claims in which the reflector means is such that it gives a consistent ratio of infrared reflectance to the distance between the transmitter/receiver means and the reflector means.

9. Sensor apparatus according to any one of the preceding claims in which the reflector means is made of a semi-opaque material.

10. Sensor apparatus according to claim 9 in which the semi-opaque material is coloured.

11. Sensor apparatus for use with an electronic lock, substantially as herein described with reference to the accompanying drawing.

12. An electronic lock when provided with sensor apparatus according to any one of the preceding claims.

13. An electronic lock according to claim 12 and which is an electronic time lock.

14. An electronic lock according to claim 13 in which the electronic time lock is provided with one or more time delay periods.