GB2208305A

GB2208305A - Intruder alarm

Info

Publication number: GB2208305A
Application number: GB8717686A
Authority: GB
Inventors: John Bramall
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-07-25
Filing date: 1987-07-25
Publication date: 1989-03-22
Anticipated expiration: 2007-07-25
Also published as: GB2208305B; GB8717686D0

Abstract

Micro switches 1 and 2 are connected in series (wiring not shown) and positioned adjustably within recess 17 behind the striker plate 12 of a door jamb. Switch 1 has normally closed contacts which are opened by latch 3 snapping into recess 17 and acting on switch plunger 7 when door 16 shuts, and which remain open until latch 3 is retracted. Switch 2 has normally open contacts and is switched on by locking door 16, when door bolt 14 is ejected against switch plunger 8 to close its contacts and thereby pass electrical potential to switch 1 and prime it. In this mode operating door handle 4 retracts latch 3 thereby allowing the contacts on switch 1 to reclose and make a circuit to initiate a warning device. <IMAGE>

Description

Intruder Alarm This invention relates to security devices for doors and is particularly concerned with the provision of means which, when primed, will serve to actuate warning means such as an audio or visual alarm when an intruder seeks to gain access to premises through a door.

According to the invention there is provided an intruder alarm device for a door having a latch mechanism including means whereby the latch may be withdrawn from outside for the opening of the door, the device comprising switch means connected or for connection to alarm means and so located so as to be changed on operation of the latch withdrawal means, from a first position to a second position at which, when primed, the switch operates to initiate the alarm, and priming means to make said switch so effective.

The priming means preferably comprises a further switch, and the further switch, in a door having a bolt, is preferably arranged to prime the first mentioned switch when the said bolt is in the closed position.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings of which: Figure 1 is a front view of a door jamb fitted with an alarm device; Figure 2 is a sectional view on line Il-Il of Figure 1; Figure 3 is a section along lines III- III of Figure 2 showing an associated door latch mechanism with the alarm unprimed; Figure 4 is similar to Figure 3 but with the alarm primed but not initiated; and Figure 5 is similar to Figure 3 but with the alarm initiated.

Referring first to Figures 1 to 3, the door jamb 15 in the conventional manner is provided with a recess 17 for the reception of a latch and a bolt of a conventional door latch mechanism shown schematically in Figure 3. The recess is covered, again as is common practice, by a striker plate 12 which has openings 18, 19 respectively for the passage of the latch and the bolt into the recess 17.

Whilst a recess is conventional, the recess as shown particularly in Figures 2 and 3 is formed deeper than normal in order that it may accommodate microswitches 1, 2, the first being located in line with the latch 3 and the microswitch 2 being located in line with bolt 14.

For convenience, the microswitches are themselves mounted on a plate 9 which is fitted in the recess 17 by means of screws 10 acting against springs 11 in order that the microswitches may be positioned at the precise depth whereat the latch 3 in its outermost position as shown in Figure 3 depresses the button 7 so as to activate the switch in one direction, whilst a withdrawal of the latch, as shown in Figure 5, allows the button 7 to return to its projecting position with the switch in the opposite mode. Likewise the microswitch 2 is positioned so that the spring loaded button 8 which projects as shown in Figure 3 when the lock is retracted, is depressed when the bolt is shot outwardly as shown in Figures 4 and 5.

In use of the apparatus electrical potential is arranged to be connected to alarm means, not shown, which may comprise an audio alarm such as a klaxon or a visual alarm such as a bright external light, or a combination of the two, via switches 1 and 2 which are in series. Microswitch 2 is arranged to be in the off position when its button 8 projects as shown in Figure 3, whilst microswitch 1 is arranged to be in the on position when its button 7 projects as is shown in Figure 5. Thus, when a householder locks the door, for example when leaving the premises or retiring to bed, by turning a key in the keyhole 6 and shooting the bolt 14 into the position shown in Figure 4, button 8 is depressed so that switch 2 is closed so that electrical potential is exerted across microswitch 1.

It is the basis for the effectiveness of the invention that a would-be intruder will first turn the latch of the door in the hope of finding the door unlocked.

Whilst the latch 3 remains projecting into the recess 17 far enough to depress the button 7 of the microswitch 1, the alarm will not operate because switch 1 will remain in the off position, but if an intruder were to "tryn the latch by turning the knob 4 or, as it may be, the corresponding handle, a withdrawal of the latch 3 will allow the button 7 to spring out so that switch 1 is closed and the electric circuit made to the alarm means which then operate.

It is expected that the alarm will deter at least some potential intruders and at least for a period. It is, in any case, within the scope of the invention that the alarm shall operate for a predetermined time sufficient to act as a deterrent if not also to summon assistance from the householder's neighbours, even if the intruder were to release the knob 4 and allow the latch to return to its Figure 4 position where, of course, it is ready to initiate a further alarm signal on being again displaced.

The invention is capable of modification, and thus for example the latch mechanism may be spaced from the lock mechanism provided that the electrical connections are made as indicated above. The priming function of the microswitch 2 may be provided by a conventional switch, such as a toggle switch mounted interiorally of the door. On retirement to bed the householder may then turn the toggle switch which is arranged to prime or set an electrical potential across the microswitch 1.

If this arrangement is to be used by a householder when he leaves the premises, it is envisaged that the toggle switch will be associated with a time delay so that the householder has time to leave the house and close the door behind him, ensuring that the button 7 will be depressed by the latch 3 before electrical potential is passed to the alarm means. It is also within the scope of the invention that the latch 3 shall take the form of a latch-lock of the "Yale" type, provided that it is associated with a priming switch such as a toggle switch referred to above. Thus the latch lock would be primed by means of the toggle switch and the alarm would be triggered by the withdrawal of the latch lock either by the use of a key or by the use of house breaking tools.

Claims

1 AN INTRUDER ALARM DEVICE FOR A DOOR HAVING A LATCH MECHANISM INCLUDING MEANS WHEREBY THE LATCH MAY BE WITHDRAWN FROM OUTSIDE FOR THE OPENING OF THE DOOR, THE DEVICE COMPRISING SWITCH MEANS CONNECTED OR FOR CONNECTION TO ALARM MEANS AND SO LOCATED SO AS TO BE CHANGED ON OPERATION OF THE LATCH WITHDRAWAL MEANS, FROM A FIRST POSITION TO A SECOND POSITION AT WHICH, WHEN PRIMED, THE SWITCH OPERATES TO INITIATE THE ALARM, AND PRIMING MEANS TO MAKE SAID SWITCH SO EFFECTIVE.

2 AN INTRUDER ALARM AS CLAIMED IN CLAIM 1 WHEREIN THE PRIMING MEANS COMPRISES A SWITCH IN A DOOR HAVING A BOLT ARRANGED TO PRIME THE FIRST SWITCH WHEN SAID BOLT IS IN THE CLOSED POSITION.

3 AN INTRUDER ALARM AS CLAIMED IN CLAIM 1 AND CLAIM 2 WHEREIN THE PRIMING AND ALARM INITIATION MEANS FORM A COMBINED UNIT.

4 AN INTRUDER ALARM AS CLAIMED IN CLAIM 1 AND CLAIM 2 WHEREIN THE PRIMING AND ALARM INITIATION MEANS ARE SEPARATE AND SPACED APART.

5 AN INTRUDER ALARM AS CLAIMED IN CLAIM 1 OR CLAIM 2 OR CLAIM 3 OR CLAIM 4 WHEREIN MEANS ARE PROVIDED FOR THE SWITCH MEANS TO BE MOUNTED IN THE RECESS IN THE JAMB OF A DOOR ADJUSTABLY AND FLEXIBLY TO COOPERATE WITH ASSOCIATED LATCH OR LOCKING MEANS OR BOTH.

6 AN INTRUDER ALARM AS CLAIMED IN CLAIM 1 OR CLAIM 5 WHEREIN THE PRIMING MEANS MAY BE POSITIONED INTERIORALLY OF THE DOOR.

7 AN INTRUDER ALARM AS CLAIMED IN ANY PRECEDING CLAIMS WHEREIN WHEN PRIMED, 'TRYING' THE LATCH MEANS CLOSES AN ALARM CIRCUIT.

8 AN INTRUDER ALARM SUBSTANTIALLY AS DESCRIBED HEREIN WITH REFERENCE TO FIGURES 1-5 OF THE ACCOMPANYING DRAWINGS.