EP0349565B1

EP0349565B1 - Alarm apparatus, preferably in a window structure

Info

Publication number: EP0349565B1
Application number: EP19880902594
Authority: EP
Inventors: Lars Eriksson
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-03-06
Filing date: 1988-03-07
Publication date: 1993-10-13
Anticipated expiration: 2008-03-07
Also published as: AU1397888A; FI894188A0; FI98964C; DE3884943T2; FI98964B; SE8700952L; EP0349565A1; DE3884943D1; SE8700952D0; SE456951B; WO1988006774A1

Abstract

The invention relates to an alarm apparatus, preferably in a window structure, and including at least one glass pane (1) or similar sheet-like element. The alarm apparatus comprises at least one transmitter (6) of impulses, e.g. ultrasound, mounted at a first place on a glass pane (1) so that it can be subjected to said impulses, and at least one receiver (7) of the impulses transmitted in the pane (1), and mounted at an other place on the pane for registering impulses received from it, an alarm connected to the receiver (7) being triggerable when the impulses received from the pane (1) change, e.g. when the pane (1) is broken.

Description

The present invention relates to an alarm apparatus, preferably in a window structure including at least one glass pane.
On the market today there is a number of different methods for providing an alarm function in a glass pane included in a window structure. All these methods have the disadvantage that either a false alarm can be triggered, or it is possible to get through the structure provided with the alarm in one way or another without triggering the alarm. Vibrational sensors often give false alarms and do not sense all kinds of vibrations, thus enabling a breakthrough. Electrical wires molded into glass layers can be disconnected or bypassed, or there is the possibility or making small holes between the wires and using them in co-action with small flexible tools to tram a desirable object, e.g. in a shop Window.
Electronic sensors also often give false alarms and can be got past. These can often only be used on single panes of glass of the float glass type, or on hardened glass. Silk screen printed circuits made at the edge of a hardened glass pane and hidden in the rebate can also be used as means for giving an alarm. In this case there are methods of getting past the alarm means without the hardened glass granulating, thus not setting off the alarm since the silk screen circuit is not broken. In addition, this method does not always work on laminated glass. Active systems, based on propagating a known ultrasonic wave in the glass, such as described in DE-A-2541764, may be inadventently triggered by a change in the surface impedance of the glass, for instance by touching or washing the glass surface. Signal processing techniques may be used to overcome this problem, but the system becomes less sensitive.
One object of the present invention is to achieve an alarm function which is not triggered without proper cause and which cannot be forced by some penetration method without the alarm being triggered, while at the same time the alarm also functions on laminated multilayer structures. It is important that the alarm function is combined with a glass structure which tales a long time to force. When the alarm is triggered at the beginning of the break-in on the first attack attempt, much time and work must pass before the object comes accessible. This can usually only be achieved with multilaminated structures, and so far there has not been any satisfactory alarm apparatus for such structures. In accordance with the invention it is possible to create a solution to the above mentioned problems with the aid of ultrasonics. The distinguishing features of the present invention are apparent from the accompanying claims. In accordance with the invention the risk of false alarm is minimum in the cases where the ultrasound is transmitted and registered in the glass pane in a multipane structure where the pane is inwards in the room or premises which is to be protected. If a laminated multipane structure is used, the risk of false alarm is even less, since the laminations can isolate the ultrasound solely to the inmost glass pane, simultaneously as each crack, hole or the like in the area of glass directly triggers the alarm. Naturally, the ultrasound can be used on other glass but a deteriorated function is then obtained.
The invention will now be described in more detail below with reference to the accompanying drawing, which schematically illustrates the alarm configuration in accordance with the invention in a cross section and mounted in a multiglass pane structure.
A window structure is illustrated on the drawing, and includes three glass panes 1-3, which are kept together by two laminate layers 4,5. A transmitter 6 of the ultrasonics type is mounted at a first place, preferably at the inner glass pane 1, i.e. on the inside 10 of the window structure, and so that it is bedded into the laminate 4 contiguous with the inner glass pane 1, the transmitter 6 preferably engaging directly against the actual surface of the glass pane 1 with one of its surfaces. A receiver 7 of the ultrasound sent in the glass pane 1 is mounted in an other place against the glass pane 1 for registering impulses received from this pane. An alarm unillustrated on the drawing is connected to the receiver 7 via connection cables 9, and the transmitter 6 is in turn connected via connection cables 8 to an unillustrated, suitable source of energy. The window structure is conventionally mounted in a rebate 11. The receiver 7 can also be placed in the laminate 4 contiguous to the inner glass pane 1 at a distance from the transmitter 6, and then suitably in an area of the glass pane 1 which is in the rebate 11.
The transmitter 6 can send an ultrasonic wave with a secret pulsation so that it cannot be got past and the transmitter can be of the Pico crystal type. The transmitter 6 is suitably placed such that only one pane is subjected to the ultrasonic wave, if a multipane laminated window structure is used. If a single pane is used the risk of false alarm increases. The placing of the receiver 7 on the pane 1 should be made so that the best possible registration of the ultrasonic wave sent in the glass pane 1 is achieved, and thus the receiver should be at a suitable distance from the transmitter 6. The nature, size, thickness, resistance and impedance etc of the glass enables the ultrasonic wave, which is sent from the transmitter 6, to be received in the receiver 17 in a certain way. It is of course also possible to use two or more transmitters 6, as well as two or more receivers 7 on optional glass panes, in the cases where this is necessary.
If the glass pane is damaged in any way as a result of making holes in it, breaking it etc, there is a registration in the receiver 7 that an alteration has taken place in the received impulses, e.g. in the form of frequency increase or frequency decrease. It is possible that the electronics controlling processes in the transmitter 6 and the receiver 7 can include a time factor, so that changes which take place in the impedance of the pane due to exterior action have a longer time than what intentional damage takes in times, thus reducing the risk of false alarm. The described system functions best together with other panes and plastics layers in a laminated packet. In such a case the transmitter 6 is preferably fixed tightly against the inner pane 1 for sending the ultrasonic wave in the best way through the pane. The laminate layer 4 also beds in the transmitter crystal so that the ultrasonic wave can penetrate into the outer panes 2 and 3 to the minimum extent. In this way the risk of false alarm is limited to a minimum, since exterior damaging action is not capable of affecting the impedance it, the innermost pane 1. Analogously the system can be compared with a swimming pool where a transmitter makes waves in the water. The waves are deflected against walls, the bottom, corners etc and create a certain wave state depending on the resistance in the water, walls etc, which can be regarded as the impedance of the pool. If an object is placed in the water, the entire wave movement pattern is changed, which is registered by the receiver or receivers. The change triggers the alarm. If the pool leaks over to an other pool, via a channel, the change can act on the inner basin so that an alarm is triggered.
With a glass pane, it can be sufficient to lay a hand against it for giving a false alarm. Of course, the electronics can remedy this phenomenon by adjusting the time factor upwards or downwards. In a laminated structure, the outmost pane 3 does not actuate the alarm if a hand is laid on it, as is the case when a single glass pane is used, and thus a false alarm is practically completely excluded. Each crack, hole or the like in the glass packet does trigger the alarm, however.
The electronics can also be combined with other sensing patterns than ultrasonics for further improving the function of the alarm.
A transmitter 6 or a receiver 7 can also be placed on the edge or short side of the pane 1 or the panes 2, 3.
The ultrasonics used can of course be replaced by impulses of some other kind, which can be transmitted and received by the intermediary of at least one glass pane included in a window structure, or by a similar sheet-like element.
An other conceivable placing of the transmitter 6 and receiver 7 can be in the corner portions of the window structure, inside the rebate 11, the impulses being sent diagonally across the glass pane in question. Depending on what "thickness" the transmitter 6 and receiver 7 indicate, and if three panes are used, for example, the corners of the outmost pane can be cut off so that the transmitter and receiver can be thicker than the laminate layer used, simultaneously as this cut lies within the rebate width, so that transmitter and receiver are protected in the rebate 11 and also hidden by it.

Claims

Alarm apparatus, preferably in a window structure, and including at least one transmitter 6, which sends impulses of such as ultrasound and is mounted at a first place on at least one glass pane or similar sheet-like element (1-3) in a window structure, so that the pane can be subjected to the impulses, and at least one receiver (7) of the impulses transmitted in the glass pane from the transmitter (6), this receiver being mounted in an other place at a distance from the transmitter (6) on the pane for registering impulses received from the pane, an alarm connected to the receiver (7) being triggerable when the impulses have such values as occur when the pane is broken, for example, characterized in that the pane comprises a glass (1-3) included in a laminated packet (1-5), and in that the transmitter (6) and receiver (7) are fastened to the edge of an intermediate glass pane (2), or on a side of the panes (1-3) facing towards a pane (1-3) included in the packet (1-5).
Alarm apparatus as claimed in claim 1, characterized in that the glass pane is the inmost pane (1) in the laminated packet (1-5).
Alarm apparatus as claimed in claim 1 or 2, characterized in that both transmitter (6) and receiver (7) of the impulses are mounted in an area of a pane included in the packet (1-5) which is in a rebate (11) carrying a window structure.