EP0582733A1

EP0582733A1 - A device for monitoring whether a door or window, for example of a building or vehicle, is open or closed

Info

Publication number: EP0582733A1
Application number: EP92113696A
Authority: EP
Inventors: Domenico Lazzaroni
Original assignee: LEDA Logarithmic Electrical Devices for Automation Srl
Current assignee: LEDA Logarithmic Electrical Devices for Automation Srl
Priority date: 1992-08-11
Filing date: 1992-08-11
Publication date: 1994-02-16

Abstract

A device for detecting the opening or closure of a door or window of a building or vehicle is described, for example for the purpose of activating or disactivating an illumination device or an alarm; this detector device includes a continuous perimitral seal against which the said door or window can cooperate by contact under predetermined pressure in a closure position, and means for detecting the compression state of the seal comprising means for detecting the electrical resistance of at least a predetermined section of the said seal, at least the said predetermined section being made of an electrically conductive elastomeric material the electrical resistance of which varies as a function of the compression state to which it is subjected.

Description

The present invention relates to a device for detecting the state of a door or window, namely whether it is open or closed, for use for example in a building or a vehicle, adapted to be utilised in conjunction with an electrical illumination device or alarm to cause activation thereof.
It is known that in very many technical applications it is necessary to detect whether a door or window is open or closed. For example, in the field of motor vehicle construction it is necessary to detect whether the access door to the passenger compartment of the vehicle is open in order consequently to illuminate the courtesy light within the vehicle and, possibly, to activate a door open indicator on the vehicle dashboard. Equally, both in the motor vehicle field and in the civil field it is necessary to detect unwanted opening of a door or window to activate an alarm device performed either by mechanical switches disposed upon a post of a door jamb or door or window opening, which cooperates with a corresponding strut of this latter only when it is in the closure position, being maintained with its push button in the retracted position, or else by sensor switches made of two elements one of which is placed on the door or window and the other on the door jamb or on the opening thereof and which is activated when the two elements are separated from one another following opening of the door or window.
The known detector devices described above have numerous disadvantages: they are expensive, must be suitably installed, can create problems of size or, if mounted in view, aesthetic problems, and are of relatively low reliability in that they are sensitive to water and moisture which can cause damage in them.
The object of the invention is that of providing a device for detecting the opening or closure of a door or window which will be free from the described disadvantages and, in particular, which will be reliable, small and inexpensive.
The said object is achieved by the invention, which relates to a monitoring device for detecting whether a door or window of a building or vehicle is open or closed, for example for the purpose of activating or disactivating an illumination or alarm device of the vehicle or building, characterised by the fact that it includes a continuous perimetral seal against which the said door or window is able to cooperate by contact with predetermined pressure in a closure position, and means for detecting the state of compression of the seal comprising means for detecting the electrical resistance of at least one predetermined section of the said seal, at least the said predetermined section being made of an electrically conductive elastomeric material the electrical resistance of which is variable as a function of the state of compression thereof.
For a better understanding of the invention there will now be given a non-limitative description of an embodiment, with reference to the attached drawings, in which:

Figure 1 illustrates the device of the invention fitted to a door of a building;
Figure 2 illustrates the same system fitted to a window of a building and, on an enlarged scale, a detail of the device itself;
Figure 3 illustrates a variant of the device of Figure 1 fitted to the doors and the bonnet of a vehicle; and
Figures 4 and 5 illustrate a detail of the device of Figure 3 on an enlarged scale.

With reference to Figures 1 and 2, there is shown a monitoring device generally indicated 1, usable for detecting whether a door 2 or window 3 of a building 4 is open or closed, for example for the purpose of activating or, respectively, maintaining inactivated, a known alarm device 5 provided, for example, with a siren 6. The device 1 essentially comprises a continuous perimetral seal 8 of known form, against which the door 2 or window 3 is able to cooperate by contact under predetermined pressure in its closure position, and means for detecting the state of compression of the seal 8 comprising, according to the invention, any known electrical resistance detecting device, indicated in broken outline 9, and for example integrated in the device 5, electrically connected to the seal 8 in such a way as to be able to detect its overall electrical resistance: the seal 8 is in fact made, according to the invention, of an electrically conductive elastomeric material the electrical resistance of which varies as a function of its compression state.
Such a material, and its process for manufacture, are described in Italian Patents Nos 1206890, 1210777 and 1211401 in the name of the same applicant, the contents of which are incorporated herein by reference as far as necessary. As is shown in detail on an enlarged scale in Figure 2, such a material has the characteristic of comprising a non-conductive elastomeric matrix 10 which is resiliently deformable and subject to a triaxial precompression state and provided with a plurality of open cells, which are not visible in the drawing in that they are occupied by particles of electrically conductive material 11 which are uniformly distributed throughout the matrix 10 in such a way as to form chains of particles, closely in contact with one another throughout the matrix itself. In this way, when the material which forms the seal 8 is subjected to a compression stress the particles 11, which in any case are already in contact with one another even when the seal 8 is not compressed, thereby ensuring that it in any case always has a certain electrical conductivity, are pressed more closely against one another and thereby consequently increase the electrical conductivity of the seal 8 according to a predetermined relationship which is characteristic of the material from which it is formed.
In use the seal 8 is mounted in an abutment zone 12 of the door 2 or window 3, for example formed on a known support and abutment frame 13 in such a way as to be compressed under pressure when the door 2 or window 3 is in a closure position not illustrated (in Figures 1 and 2 the door 2 or window 3 is shown open in such a way as to make the seal 8 visible) by a perimetral edge 14 of the door 2 or window 3 which faces towards the zone 12 in abutment therewith: in this way when the door 2 or window 3 is closed there is obtained on the one hand a substantially fluid tight sealing closure of a respective door opening 15 or, respectively, window opening 16 and, on the other hand, a reduction in the electrical resistance of the seal 8 following its compression caused by cooperation with the edge 14. On the other hand, upon opening the door 2 or window 3 this terminates the compression state of the seal 8 with consequent increase in its electrical resistance by an amount equal a predetermined quantity, which is a function of the characteristic curve of the material used for the manufacture of the seal 8: this variation in the electrical resistance can be measured and detected by the device 9, which is adapted to emit a consequent signal to the device 5 to which it is connected. If this is armed, this signal can be used to initiate the actuation of the siren 6 in that the increase in electrical resistance of the seal 8 when the device 5 is connected can only indicate that the door 2 or window 3 has been opened by a forced entry into the building 4.
The electrical connection between the resistance measurement device 9 and the seal 8 is obtained by a pair of wires 20, 21 of opposite polarity which are connected to respective flexible contact elements, for example constituted by metal meshes 22, which are embedded in the matrix 10 (Figure 2) at respective opposite faces 23 of the seal 8 intended to be disposed, in use, facing the edge 14 and the abutment 12. Preferably, moreover, the electrically conductive elastomeric material forming the seal 8, and the meshes 22 embedded in the matrix 10, are enclosed in an electrically insulating skin 24 which delimits the outer surface of the seal 8. In this way it can be mounted on fixings made of any material where the door 2 or window 3 and/or the frame 13 are made of conductive metal material. In any event the seal 8 described above can be easily obtained by extrusion of a continuous element, which can then be cut to size and mounted; its fixing to the abutment 12 can be achieved in any known way, utilised for normal seals for openings in buildings, for example by adhering a face 23 against the frame 3 or by supporting the seal 8 by means of a suitable small frame of a type known and not illustrated for simplicity, fixed to the abutment 12 by screws.
In a possible variant, not illustrated for simplicity, the same function of the seal 8 can also be obtained by fitting between one of the electrically conductive elements 22 and the associated matrix 10 a screen made of an electrically non-conductive sheet provided uniformly with holes through which the matrix 10 and its particles 11, upon resiliently deforming under the effect of a compression stress applied to the seal 8, can contact the conductive element 23 as described in Italian Patent No 1210778 by the same applicant, the contents of which are incorporated herein by reference as far as necessary. In this case, whilst the seal 8 is clamped between the abutment 12 and the edge 14 of the door 2 or window 3, the electrical resistance measured by the device 9 will be equal to a finite and relatively small value (the material upon which the seal 8 is formed being conductive) with consequent achievement of a condition equivalent to closed contacts, whilst, when the door 2 or window 3 is opened, with consequent separation of the edge 14 from the abutment 12 and release of the compression state of the seal 8, the device 9 will detect an electrical resistance approximating to infinity (a situation equivalent to open contacts) which condition can be easily used to obtain opening of an electrical circuit which consequently determines activation of the alarm device 5.
As is illustrated in Figures from 3 to 5, in which the same or equivalent details to those already described are indicated for simplicity by the same reference numerals, the device 1 can also be utilised on a vehicle 40 of any known type by using the said elastomeric electrically conductive material the electrical resistance of which varies as a function of its compression to form the normal perimetral seals or draft proofing, indicated 80, which are mounted around respective door openings 81, an access opening 82 to a boot of the vehicle 14 and around an engine compartment opening 83 thereof, and respectively intended to cooperate under compression in use with, respectively, a side door 84, a tail gate 85 and a bonnet 86 of the vehicle 14. In the non-limitative specific example illustrated (Figures 4 and 5) only a section 90 of predetermined length of each seal 80 is made of the conductive elastomeric material described above, which is illustrated in detail by utilising the same reference numerals previously used in Figure 5, whilst the remainder of the seal 80 can be made of a normal non-conductive elastomer; in this case the wires 20, 21 are connected in such a way as to connect only the section 90 to an electrical resistance measuring device indicated 92.
Each section 90 is made in a similar manner to the seal 80, enclosed in a non-conductive skin 24 and connection to the wires 20, 21 is effected by metal meshes 22. In this case, too, a perforated non-conductive screen can be fitted between a metal mesh 22 and the matrix 10 in such a way that between the compressed and uncompressed state of the seal 80 there is not only a finite and measurable variation in the electrical resistance but a complete passage from conductive conditions to non-conductive conditions. The device 92, for its part, is in this variant more complex than a simple electrical resistance measuring device; for example it is constituted by an electronic central control unit, such as a microprocessor, having the dual function of controlling the illumination of respective internal courtesy lamps 100 of the vehicle 40 as well as an alarm device 101 of the same type as the device 5 provided with its own central control unit 102 and a siren 103.
In use, when the doors 84 or the tail gate 85 are opened, the associated seal 80 adopts a non-compressed state and experiences an increase in electrical resistance (possibly limited to the section 90 if only this section is made according to the invention); this increase is detected by the central control unit 92 which consequently illuminates the lights 100; for example, this central control unit 92 can be programmed in such a way as to illuminate the lights 100 selectively, for example to illuminate only one light 100 positioned adjacent the door 84 which is open, or an illumination light for the baggage space or the engine compartment 83 upon opening of the tail gate 85 or the bonnet 86; the central control unit 92 can moreover control the illumination of appropriate door-open warning lamps positioned on the vehicle dash board, which are known and not illustrated for simplicity. When the central control unit 102 is fitted the central control unit 92 can, finally, by used to send to the central control unit 102 a signal indicating that a forced entry has taken place (opening of any of the bonnet 86, the doors 84 or the tail gate 85) which activates the siren 103.
From what has been described the advantages connected with the invention are evident; with the simple arrangement of replacing normal seals (or sections of these) with a conductive elastomeric material the electrical resistance of which varies with its compression shute in a known and reproducible manner, a system for detecting the opening of a door or window can be obtained which is free from the disadvantages of known systems utilized to date: this system is in fact of no dimensions or size in that it utilises as sensor an element (the seal) which is in any case already present, and this without in any way reducing the primary function of the seal, that is that of sealing against dust and moisture (the electrical resistance detector device can in fact be arranged remote from the door/window; the system is furthermore of low cost and complete reliability: in fact, the production cost of the seals 8, 80 is practically equal to that of normal non-conductive seals; furthermore since the seals 8, 80 are made of elastomer, in one piece and without movable parts they provide sensor/switching elements which are almost impossible to break and which are not sensitive to moisture or dirt.

Claims

A device for detecting whether a door or window of a building or vehicle is open or closed, for example for the purpose of activating or disactivating an illumination device or a vehicle or building alarm, characterised by the fact that it includes a continuous perimetral seal against which the said door or window is able to cooperate by contact under predetermined pressure in a closure position, and means for detecting the state of compression of the seal comprising means for detecting the electrical resistance of at least a predetermined section of the said seal, at least the said predetermined section being made of an electrically conductive elastomeric material the electrical resistance of which varies as a function of the compression state to which it is subjected.
A device according to Claim 1, characterised by the fact that the said seal is entirely made of the said electrically conductive elastomeric material the electrical resistance of which varies as a function of the state of compression to which it is subjected; the said electrical resistance detection means comprising a device for detecting the electrical resistance of the whole seal.
A device according to Claim 1 or Claim 2, characterised by the fact that the said electrical resistance detection means are connected to a central control unit operable, if arranged to activate an alarm indicator when an increase in the electrical resistance of at least the said predetermined section of the seal by an amount greater than a predetermined amount is detected.
A device according to Claim 1 or Claim 2, characterised by the fact that the said electrical resistance detection means are connected to a central control unit operable selectively to activate the courtesy lights or alarm indicator of a vehicle in dependence on the detection of a predetermined variation in the electrical resistance of at least the predetermined section of the seal and the selection of a predetermined program by a user.
A device according to any preceding Claim, characterised by the fact that at least the said predetermined section of the said seal made of the said electrically conductive elastomeric material the electrical resistance of which is variable with a variation in its compression state is enclosed in an electrically insulating skin which delimits the outer surface thereof; opposite faces of at least the said predetermined section of the said seal disposed in use facing the said door or window and an abutment therefor being provided, immediately beneath the said skin, with respective flexible contact elements, for example metal meshes, which are each electrically connected to a respective conductive wire.