GB2298233A

GB2298233A - Lock alarm warning of un-removed key.

Info

Publication number: GB2298233A
Application number: GB9503780A
Authority: GB
Inventors: William George Hill
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-02-24
Filing date: 1995-02-24
Publication date: 1996-08-28
Anticipated expiration: 2015-02-24
Also published as: GB2298233B; GB9503780D0

Abstract

A warning (e.g. sound or light signals) is generated by a door lock if the key is not removed. As described a switch is incorporated between the inside door furniture and the cylinder of a conventional door lock, which switch is operated either by the end of an extra long key projecting beyond the end of the cylinder, or by a normal length key in conjunction with a plunger mediating between the cylinder bore and the switch. A delay timer may prevent the annunciator from being activated until a reasonable time for key-removal has elapsed.

Description

Title: IMPROVEMENTS IN OR RELATING TO LOCKS This invention relates to locks and is particularly concerned with a lock having means for ensuring that a key is not inadvertently left in the lock.

When a door is opened by means of turning a key in a lock fitted to a door, it not infrequently happens that the key is left in the lock. This can occur, for example, with old people who tend to be forgetful or when a housewife returns from shopping with two full shopping bags and who, having opened the door with the key, is then distracted by a child or perhaps by a telephone call. She passes through the doorway with the shopping bags, closes the door behind her and, because of the distraction, forgets that the key has been left in the door lock. It is then possible for unauthorised persons to gain entrance to the premises.

The present invention aims to solve this problem by providing a lock with alarm means which are activated when a key is placed in the lock.

According to the invention, there is provided a lock having alarm means which are activated when a key or other implement is inserted into the lock.

The alarm means may be audible and/or visual.

Preferably, there is time delay between insertion of a key or other implement in the lock and activation of the alarm means.

The invention will now be described in detail, by way of example, with reference to the drawings, in which: Fig. 1 is a side elevation of one embodiment of a lock according to the invention installed in a door, only part of the door surrounding the lock being shown; Fig. 2 is a rear view of the lock shown in Fig. 1; Fig. 3 is a side elevation of a nylon block and side plates forming part of the lock shown in Figs. 1 and 2; Fig. 4 is a front elevation of the block shown in Fig. 3; Fig. 5 is a side elevation of a barrel adapted to be rotatably mounted in the block shown in Figs. 3 and 4; Fig. 6 is a front elevation of the barrel shown in Fig. 5; and Fig. 7 shows a detail of a modified form of the lock shown in Fig. 1.

In the drawings, like parts are denoted by like reference numerals.

Referring to the drawings, the lock according to the invention comprises a barrel 1 with a face plate 2 and a ring surround 3. The barrel body is provided with a pair of lugs 4 each having a screw-threaded bore in which are engaged respective screws 6. A block 11 of nylon material is mounted on the screws 6 and is secured in position on the screws by means of nuts 7. The block 11 is formed with a cylindrical bore 12 in which a barrel 15 of nylon material is located. The barrel 15 is free to rotate with respect to the block 11 and is held in place in the bore 12 in the block 11 by means of side plates 14 which are located at each end of the block 11 and are provided with bores through which pass the screws 6.

The barrel 15 is provided with a slot 16 through which extends the blade 5 of the lock which blade is of such a length that it can extend from the lock barrel 1 into the lock casing 8 on the other side of the door 9 from which the face plate 2 and ring surround 3 are located. A micro-switch 17 is set into the barrel 15 and is arranged to be closed by a key 19 when the key is inserted into the lock barrel 1.

A pair of slip rings 18 are provided on the barrel 15 as shown in Figs. 5 and 6, the rings being made of copper or other material having good electrical conductivity.

The block 11 has a pair of slots 13 in which are located carbon brushes 20, each brush making contact with a respective one of the slip rings 18. Respective wires 21 extend from each of the carbon brushes 20, are wound around respective pegs 22 located on the block 11 and are then connected to a buzzer or other audible alarm means and/or to a lamp.

The arrangement is such that when the key 19 is inserted into the lock barrel 1, the end of the key engages the blade of the micro-switch 17 to close said switch.

This has the effect of activating the buzz or other audible alarm means and/or the lamp which will remain activated until the key is removed from the lock. The lamp may take the form of a flashing lamp and the electrical circuit may include a time delay relay or other delay means arranged to delay activation of the buzzer or lamp for a time, for example fifteen seconds. Power for the buzzer or other audible alarm means and/or the lamp may be obtained by wiring the circuit into the ring main circuit of a building in which the alarm is to be installed or from a separate power source such as a battery.

A slight disadvantage with the embodiment shown in Fig. 1 is that the key 19 must be longer than a standard length key in order to engage the blade of the micro-switch 17. This disadvantage can be avoided if the lock is modified as shown in Fig. 7 in which a pin 31 having a flat head 32 is inserted into the end of the lock barrel 1. A standard length key 33 can then be used and when it is inserted into the barrel 1, its end will engage the pin 31 which will be moved by the key to engage the blade of and hence close the micro-switch 17. The flat head 32 of the pin 31 prevents the pin from falling into the lock barrel.

It will be seen that by means of the invention it is possible to ensure that a key is not inadvertently left in a lock or, if it is, attention will soon be brought to this fact by the alarm means.

The invention is not restricted to the aboveaescribed embodiments but variations and modifications may be made without departing from the scope of the invention.

Further, although described with reference to doors, the lock according to the invention is equally applicable to other closable openings such as hatches or windows.

Claims

1. A lock having alarm means which are arranged to be activated when a key or other implement is inserted into the lock.

2. A lock according to claim 1, wherein the alarm means comprise an audible alarm.

3. A lock according to claim 1, wherein the alarm means comprise a visual alarm.

4. A lock according to claim 1, wherein the alarm means comprise both an audible and a visual alarm.

5. A lock according to any one of the preceding claims, wherein time delay means are provided whereby there is a time delay between insertion of a key or other implement into the lock and activation of the alarm means.

6. A lock according to any one of the preceding claims, wherein said alarm means comprise an electric circuit connected to an audible and/or a visual alarm device and a switch which is normally open and which is arranged to be closed when a key or other implement is inserted into the lock.

7. A lock according to claim 6, wherein the switch comprises a micro-switch having a blade which is arranged to be acted on directly by said key or other implement in order to close the switch.

8. A lock according to claim 6 and having a barrel and wherein a pin is inserted into said lock barrel and the switch comprises a micro-switch having a blade, the arrangement being such that the pin is arranged to be acted on by the end of a key or other implement inserted into the lock and is arranged, in turn, to act on the blade to close the switch.

9. A lock according to claim 8, wherein the pin is provided with a head which is arranged to engage with the blade of the micro-switch.

10. A lock according to any one of claims 6 to 9, wherein the alarm means comprise a block made of electrically insulating material which is secured to but spaced from the lock, said block having a bore in which a barrel of electrically insulating material is rotatably located and said barrel having a slot through which a blade of the lock is designed to pass.

11. A lock according to claim 10, wherein the block is connected to the lock by means of screws.

12. A lock according to claim 11, wherein the barrel of electrically insulating material is held in the block by means of side plates which are mounted on the screws.

13. A lock according to any one of claims 10 to 12, wherein the barrel is provided with a pair of slip rings of electrically conductive material and wherein the block is provided with a pair of slots each of which is adapted to receive a respective carbon brush, each brush making contact with a respective slip ring and being connected to a respective contact of the switch.

14. A lock according to claim 13, wherein the slip rings are made of copper.

15. A lock according to claim 13 or claim 14, wherein the carbon brushes are connected by electrical wires to a power source and to the alarm device.

16. A lock according to claim 15, wherein wires from the carbon brushes are wound around respective pegs on the block of insulating material.

17. A lock according to claim 15 or claim 16, wherein the power source comprises a battery.

18. A lock according to any one of the claims 10 to 17, wherein the insulating material of the block and barrel is nylon.

19. A lock having alarm means substantially as described herein with reference to the drawings.