AU663989B2

AU663989B2 - Intruder alarm

Info

Publication number: AU663989B2
Application number: AU55148/94A
Authority: AU
Inventors: Rene Lange
Original assignee: Cerberus AG
Current assignee: Cerberus AG
Priority date: 1993-03-19
Filing date: 1994-02-16
Publication date: 1995-10-26
Anticipated expiration: 2014-02-16
Also published as: EP0616307B1; AU5514894A; CH685408A5; EP0616307A1; DE59405743D1

Description

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AUSTRALIA

Patents Act 1990 COM~PLETE SPECIFICATION STANDARD PATENT 4t* 4 Applicant: CERBERUS AG Invention Title: INTRUDER ALARM The following statement is a full description of this invention, including the best metho d of performing it known to me/us: pr Description The invention relates to an intruder alarm according to the preamble of Patent Claim i.

Such intruder alarms are already commercially available in various embodiments. They are employed for the detection of movements of objects or persons who have penetrated within a specified room. Such alarms mainly comprise two types of alarms, the so-called passive infrared alarms and ultrasonic alarms. Combinations of these two detection principles are also used. The alarms are part of a system which, in addition to the alarms, further comprises a signal reception control station and acoustic warning devices. The alarms are connected via a line network to a control station. These intruder alarms 15 generally comprise a two-part housing, which encloses a it, movement sensor such as, for example, an infrared sensor or an ultrasonic sensor, and an evaluating circuit. The housing further exhibits an entrance window through which the infrared rays or the ultrasonic waves can pass to the sensor in the interior of the housing. The two-part .0 housing comprises a base part and a cap part, which are Gttl usually connected to one another by a screw at the side of the housing or by a snap fastening.

One of the main problems in the use of such alarms resides in preventing sabotage. This term is understood as referring to any attempt to place an alarm or its connection to the control station out of operation by direct or indirect interventions or manipulations. In order to prevent such sabotage, some alarms additionally exhibit a switch which triggers a signal if the cap part is separated from the base part. This signal is reproduced by the evaluating circuit as, for example, a disturbance to the control station or an acoustic warning signal. Other alarms, as described in US Patent 4,451,733, are equipped with a cap switch. These switches are disposed in relation to the two housing parts so that, upon lifting the cap part off from the base part up to a specified height the switch is actuated and a signal is emitted to the evaluating circuit. These switches

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r -7 2 accordingly serve to make it more difficult to open the housing without authorization and at all events to sabotage the alarm.

A disadvantage of such security switches rrsides in that it is nevertheless possible to sabotage the alarm without the switch being actuated. This can take place by partial releasing of the screws or lifting off the cap so that a narrow air gap is created between the two housing parts, without the switch responding. It is possible for substances, such as, for example, foam or dye to be introduced into the interior of the alarm through the narrow gap, so that the sensor or the entrance window of the alarm is masked and in this manner the alarm is made insensitive.

15 A method of preventing sabotage of a passive infrared alarm by masking the sensor or the entrance ,eeo,: window is described in EP 0,189,536. In this case, a 1 e radiation source is secured to the housing cap, by which source the transmissivity of the entrance window and of the radiation path up to the sensor is monitored.

A significant component part of the measures which can prevent sabotage is the correct.installation of the alarms. It repeatedly occurs that an alarm is not correctly closed and therefore the sabotage protection device does no- operate perfectly. However, a correct closure of the alarm housing is dependent upon the care exercised by the installation personnel. This can be checked by the currently commercially available alarms only by a test from the control station or visually from the vicinity. Such a visual test from the vicinity can Showever be difficult or even impossible if the alarm has been mounted at a location which is difficult to reach or in an elevated position. The object of the invention is to reduce the aforementioned disadvantages of the known intruder alarms for the prevention of sabotage, and especially to facilitate the checking of the correct closure of the alarms and to make sabotage attempts more difficult.

According to the invention, this object is L. 3 achieved in that the housing cap includes a locking device which firmly connects the cap part' to the base part, a firm locking being clearly visible by an optical display at an opening in the locking, device.

In the locking device an opening is formed, which moves upon actuation of the locking. A light source is situated below.the housing cap. When the housing cap and the housing base are firmly connected to one another by actuation of the locking device, at the same time the opening is brought over the light source. The light emerging from it passes through the opening to the outside and is also visible to the eye from a distance.

If the two housing parts are not firmly connected to one another, then the opening is not situated over the light source. In this case, no light is visible from outside.

Preferably, the locking device comprises a rotatable screw closure. As a result of this, the housing can, for example, be closed by a 900 rotation of the screw closure and the opening can be moved to above the light source. Instead of a rotary closure, it is also possible to use a slide closure, which likewise brings Lthe opening to above the light source, as soon as the two housing parts have been firmly connected to one another.

If the intention is further to prevent a situation in which after correct locking of the housing by the expert the housing is opened by lay persons, then the screw closure can be provided with a safety screw, the release of which is possible only by an appropriate special tool. The light source can be disposed directly below the housing cap. However, in a further embodiment it can also be sunk vertically to the housing cap or be disposed laterally. In order to guide the light to the opening, a light guide or optical components, such as mirrors, prisms or lenses can be employed.

In order to make it even more difficult to sabotage the alarm by opening the alarm and altering the interior of the alarm, the locking device can be connected to a switching element which, in the event of an unlawful opening of the locking, is actuated and conducts r 7- -4a disturbance signal to the control station. At this instant, the housing parts have not yet been separated from one another, so that no gap exists between them, through which the interior of the alarm could be altered.

Thus, the disturbance is communicated both to the control station and also by the light source already during the attempt to open the alarm, before sabotage could take place.

The invention is explained in greater detail with reference to the illustrative embodiments reproduced in Figures 1 to 4: Figure 1 shows a longitudinal section through a passive infrared alarm according to the present invention, in which alarm the locking device is rotatable.

Figure 2 shows the front elevation of a passive infrared alarm according to Figure 1.

SFigure 3 shows a longitudinal section through another embodiment of a passive infrared alarm, in which the locking device is slideable.

Figure 4 shows a longitudinal section through a further embodiment of a passive infrared alarm, in which the locking device includes a light guide.

ct i The housing 1 of the intruder alarm comprises a cap 2 and a base 3. On the front surface of the cap 2 there is situated a screw closure 4, which locks the cap 2 to the base 3. An opening 5 is disposed in the screw closure 4, which opening moves with the screw closure ti. when the latter is actuated.

SC The screw closure 4 is brought, using a Philips screwdriver, through a 90* rotation into the "open" or "closed" position; in this case, in the "open" position y the cap is not locked to the base and, respectively, in the "clos~ed" position the cap is locked to tthe. base. A light source 6 is disposed below the cap 2 on a printed circuit board 7, so that it lies under the opening 5 in the screw closure 4 when the latter is in the "closed" position. In this "closed" position, the light passes from the light source 6 through the opening 5 to the outside. When the screw closure 4 is in the "open" position, the opening 5 is not situated above the light source 6, so that no light passes to the outside, In another embodiment, shown in Figure 3, a slide closure 8 is provided. The slide closure 8 is, for example, brought by a pin, by sliding, into the "open" or "closed" position. The slide closure 8 likewise includes an opening 5 which moves with the slide closure 8 when the latter is actuated. A light source 6 is disposed below the cap 2 on a printed circuit board 7 so that it lies under the opening 5 in the slide closure 8 when the latter is situated in the "closed" position.

In the event that it should be unfavourable, for reasons associated with design or space, to fit the light source 6 directly below the cap 2, said source may also be disposed deeper vertically or also laterally below the cap, as shown in Figure 4. In order to conduct the light from the light source 6 to the opening 5, a light guide 9 is disposed in the screw closure 4 so that this guide C ends in the opening 5. For the purpose of concentrating the light, which emerges from the light guide 9 through the opening 5, the end of the light guide 9 is designed in the manner of a lens or in the manner of a cone. The effect of the concentration is that the light is still visible to the eye from an even greater distance.

Furthermore, a switching element 10 is fitted in such a manner that it sends a signal to the control station as soon as the screw closure 4 has been brought into the "open" position. At the control station, the signal is communicated as a disturbance or alarm. hus, an attempt to open the housing 1 will trigger a disturbance communication or an alarm already upon the actuation of the screw closure 4, before the cap 2 can be removed or lifted off from the base 3 by a gap width.

With this invention, as a security measure the individual intruder alarms can be checked for the correct locking of their housings by a simple visual monitoring of the illuminated opening on the locking device, from a distance. The monitoring can likewise be carried out from the control station by checking the condition of the 1 I i -I li~i 6 switching elem.ent In the event that while the system is disarmed, for example during the day, sabotage of an intruder alarm should have taken place by opening, sabotaging and reclosing the housing, this can be discovered in that the control station is equipped with a memory function. This stores the disturbance signal which was triggered by actuation of the switching element 10 and triggers a disturbance communication when the system is armed.

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Claims

2. Intruder alarm according to Patent Claim 1, f 15 characterized in that the locking device is rota- all. table.
3. Intruder alarm according to Patent Claim i, characterized in that the locking device comprises a slider
4. Intruder alarm according to one of Patent Claims 1 to 3, characterized in that the locking device (4) exhibits a safety screw which can be released only by means of an appropriate special tool. Intruder alarm according to one of Patent Claims 25 1 to 4, characterized in that the light source is disposed to be sunk below the cap of-the housing (1) S, or displaced laterally with respect to the locking device 6 and a light guide conducts the light emerging from the light source to the opening in the locking device
6. Intruder alarm according to one of Patent Claims 1 to 4, characterized in that the light source is disposed to be su'ik or displaced laterally from the locking device and the light emerging from the light source is conducted mirrors, lenses or prisms to the opening in the locking device
7. Intruder. alarm according to one of Patent Claims 1 to 6, characterized in that a switching element (10) is provided, which triggers an alarm signal upon opening of
8- the locking device. 'tit DATED THIS 16TH DAY OF FEBRUARY 1994 CERBERUS AG By its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia 4 1 t Abstract An intruder alarm comprising a housing a movement sensor and an evaluating circuit, the housing cap of which includes a locking device with an opening. Upon actuation of the locking device the housing cap is firmly connected to the housing base or released from it. Upon closing of the locking device the opening is moved so that it comes to lie over a light source which is situated below the housing cap The light of the light source passes through the opening and indicates the correct locking of the housing cap to the base An expanded embodiment serves for anti-sabotage, in that it includes a switching element (10) which emits a disturbance signal as soon as the firm connection of the housing cap to the base has been released. i 1