A security system and detector means therefor

Abstract: A security system for detecting the fracture of a pane of glass is disclosed in which a fracture detector means 14 is provided in the form of a resilient sealing member 16, 216, 316 with which the glass 20, 220, 320 is normally in contact. The resilient sealing member 16, 216, 316 has at least one sensor 18, 19; 118, 119; 218, 219; 318, 319 formed as part of it, the state of which is changed when the glass 20, 220, 320 is fractured. A control means 11 upon sensing the change of state of the or each sensor 18, 19; 118, 119; 218, 219; 318, 319 is arranged to energise a warning device 12.

Description: This invention relates to a security system and in particular to a system for detecting the fracture of a pane of glass. It is a problem when using glass as part of the structure of a building or motor vehicle that the building or vehicle can be illegally entered by breaking the glass. It is known from DE-3923608-A to provide a security system for detecting the fracture of a pane of glass, the system comprising at least one glass fracture detector means the electrical state of which is altered when the pane of glass is fractured, a control means connected to the or each detector means to sense said change in electrical state and a warning means connected to said control means to provide a warning of the fracture of said pane of glass in response to a signal received from said control means. It is an object of this invention to provide a simple and inexpensive security system of the glass fracture detection type. US-A-3 830 018 discloses to form a sensor for detecting the presence of a foreign object between the upper edge of a car window and the sealing member as an integral part of the sealing member. According to a first aspect of the invention there is provided a security system for detecting the fracture of a pane of glass, the system comprising at least one glass fracture detector means the electrically conductive state of which is altered when the pane of glass is fractured, a control means connected to the or each detector means to sense said change in electrically conductive state and a warning means connected to said control means to provide a warning of the fracture of said pane of glass in response to a signal received from said control means characterised in that the fracture detector means comprises of at least one sensor formed as an integral part of a resilient sealing member used to form a seal between the pane of glass and a frame of the pane of glass. This has the advantage that no separate mounting or adjustment of the detector means is required. The or each sensor may be a switch held in a closed conductive state by contact between the pane of glass and the resilient sealing member and changed to an open non-conductive state when the pane of glass is fractured in the vicinity of a switch. The or each sensor may be a switch held in an open non-conductive state by contact between the pane of glass and the resilient sealing member and changed to a closed conductive state when the pane of glass is fractured in the vicinity of a switch. The or each sensor may be a pressure sensitive device the resistance of which is dependant upon the amount it is compressed by contact with the pane of glass. The pane of glass may be a moveable side window of a motor vehicle. The or each sensor may be formed in a passageway within said resilient sealing member. The or each sensor includes two electrical conductors at least one of which is a metal conductor. Alternatively, the or each sensor includes two electrical conductors at least one of which is made from a conductive rubber or elastomer in which case the or each conductor is formed as an integral part of the resilient sealing member by co-extrusion. Alternatively, the or each conductor that is made from a conductive rubber or elastomer is formed as an integral part of the resilient sealing member by co-moulding. The or each metal conductor may be formed as an integral part of the resilient sealing member by being moulded into the resilient sealing member. There is also provided a security system as set forth above in which the resilient sealing member is of a U-shaped cross-section having two limbs defining a groove. Advantageously, the or each sensor of the detector means may be located in a passageway formed in one of the limbs of said resilient sealing member. The or each sensor of the detector means may be formed by a first conductor formed at or near the end of a lip extending from one of said limbs into said groove and a second conductor formed on an adjacent surface of said limb, the two conductors being pressed into engagement by the pane of glass when it is present in the groove. Alternatively, the or each sensor of the detector means may be formed by a first conductive lip extending from one of said limbs into said groove and a second conductive lip extending from the other of said limbs, the two conductive lips being held apart by the pane of glass when it is present in the groove. The resilient sealing member may be a window seal for a moveable side window of a motor vehicle, in which case the resilient sealing member may advantageously include a second sensor means used to detect the presence of a foreign object between the upper edge of said moveable side window and the resilient sealing member. According to a further aspect of the invention there is provided a resilient sealing member for a window of a motor vehicle having a first sensor means formed as an integral part of said sealing member to detect, in use, contact between the sealing member and a side face of the window for use as a glass fracture detector means in a security system and a second sensor means formed as an integral part of said sealing member to detect, in use, the presence of a foreign object trapped between one edge of the sealing member and an upper edge of the window for use as a trap detector in an anti-trap system of a power operated moveable window system in a motor vehicle. This has the advantage that detection for glass fracture and entrapment are formed economically in a simple manner as part of the resilient seal. The invention will now be described by way of example with reference to the accompanying drawing of which:- Fig 1: is a schematic circuit diagram of a security system in accordance with a first aspect of the invention; Fig 2: is a cross-section through a detector means according to a second aspect of the invention showing two alternative switch means in which the resilient sealing member is in accordance with a third aspect of the invention; Fig 3: is a cross-section through a detector means according to the second aspect of the invention showing a first modification in which the resilient sealing member is in accordance with a third aspect of the invention; Fig 4: is a cross-section through a detector means according to the second aspect of the invention showing a second modification in which the resilient sealing member is in accordance with a third aspect of the invention. With reference to Figure 1 there is shown a security control means 11 to which is connected a warning means in the form of a siren 12. The security control means is supplied with a source of electric power from a battery 13 connected thereto which is used to activate the siren 12 and also for detecting the fracture of a pane of glass in the form of a window 20 by means of the fracture detector means 14. The detector means 14 comprises of a sensor in the form of a normally open switch formed as part of a resilient sealing member in the form of a U-shaped window seal 16. The window seal 16 is located in a rigid U-shaped frame member in the form of a door window frame 15 for a motor vehicle and comprises of two limbs defining therebetween a U-shaped groove into which the window 20 can be engaged. The switch of the detector means 14 is formed by two spaced apart electrical conductors in the form of two metal strips 18, 19 moulded into the seal 16 within a passageway 17 near to the surface of one of the limbs of the window seal 16. When the window 20 is slid into the groove in the window seal 16 corresponding to a window closed position, the two switch conductors 18, 19 are pressed together forming an electric circuit through which current from the control means 11 will pass. If the window 20 is fractured by any means then pieces of broken glass will become disengaged from the groove in the window seal 16 thereby allowing the conductors 18, 19 to separate and return the switch to its normally open position. This change in state of the electrical circuit through the two conductors 18, 19 is sensed by the control means 11 and used as an indication that the window 20 has been fractured. Upon sensing fracture of the window 20 the control means 11 sends a signal to the siren 12 causing the siren 12 to be sounded. To prevent the siren 12 being activated erroneously, such as when the window 20 is slid down into an open position, a switch 10 is provided to activate the control means 11. The switch 10 is formed by a set of contacts formed as part of the ignition switch of the motor vehicle and arranged to be switched on only when the ignition switch is in an off position. In accordance with a first modification of the invention the electrical conductors of the fracture detector means are formed from electrically conductive rubber or elastomer and are co-moulded or co-extruded as an integral part of the window seal 16. Such a modification is shown in Figure 2 where a first conductor 118 is formed of an electrically conductive elastomer co-moulded as part of one of the limbs of the window seal 16 and a second electrically conductive member 119 co-moulded as part of a lip 117 extending into the groove in the window seal 16. The first and second conductors 118, 119 form a switch and act in the same manner as the metal conductor switch 18, 19 described above. In addition to the glass fracture detection means 18, 19 the resilient seal means 16 is also provided with an anti-trap sensor to detect the presence of a foreign object trapped between the lower edge 30 of the window seal 16 and the upper edge of the window 20. The anti-trap sensor is formed by a pair of spaced apart electrical conductors 21, 22 located within a cavity near to the free end of one of the limbs of the window seal 16. Each of the conductors 21, 22 extends along substantially the entire length of the portion of the window seal 16 that in use co-operates with the upper edge of the window 20. Any object placed between the upper edge of the window 20 and the limb will, upon closing of the window 20, cause the two conductors 21, 22 to be brought into contact thereby providing an indication of entrapment which could be utilised in an anti-trap system of the type described in US-A-3,815,005. The provision of an anti-trap sensor as part of the detector means 14 is useful when the window seal 16 is used for sealing a power actuated sliding window on a motor vehicle as the detector then provides in a simple and cost effective manner sensors for both window fracture and entrapment. With particular reference to Fig 3 there is shown a detector means in the form of a U-shaped window seal 216 located within a window frame 215 in which the sensor is formed by two conductive limbs 218, 219 which form a normally closed switch and are co-extruded with the rest of the window seal 216. When a window 220 is inserted into a groove in the window seal 216 the limbs 218, 219 are forced apart and the electrical state of the switch is changed from closed to open. In addition to the glass fracture detection means 218, 219 the resilient seal 216 is also provided with an anti-trap sensor to detect the presence of a foreign object trapped between the lower edge 230 of the window seal 216 and the upper edge of the window 220. The anti-trap sensor is formed by a pair of spaced apart electrical conductors 221, 222 located within a cavity near to the free end of one of the limbs of the window seal 216. Each of the conductors 221, 222 extends along substantially the entire length of the portion of the window seal 216 that in use co-operates with the upper edge of the window 220. Any object placed between the upper edge of the window 220 and the limb will upon closing of the window 220 cause the two conductors 221, 222 to be brought into contact thereby providing an indication of entrapment which could be utilised in an anti-trap system. As shown in Fig 4 the detector means and resilient sealing means is similar to that shown in Fig 2 but in this case is intended for use with a frameless window structure. The resilient seal 316 is attached to a lip 340 formed as part of the structure surrounding the window 320 and not within a U-shaped groove. Such a frameless window structure is often used on a motor vehicle in which a window is slidingly supported by a door structure and the seal is attached to part of the vehicle body structure surrounding the door. In such an application when the door is closed the window 320 is pressed against the resilient seal 316 but when the door is opened there is no contact between the seal 316 and the window 320. In addition to the glass fracture detection means 318, 319 the resilient seal 316 is also provided with an anti-trap sensor to detect the presence of a foreign object trapped between the lower edge 330 of the window seal 316 and the upper edge of the window 320. The anti-trap sensor is formed by a pair of spaced apart electrical conductors 321, 322 located within a cavity near to the free end of a limb forming part of the window seal 316. Each of the conductors 321, 322 extends along substantially the entire length of the portion of the window seal 316 that in use co-operates with the upper edge of the window 320. Any object placed between the upper edge of the window 320 and the limb will upon closing of the window 320 cause the two conductors 321, 322 to be brought into contact thereby providing an indication of entrapment which could be utilised in an anti-trap system. It will be appreciated by the man skilled in the art that the control means could be a relay or an electronic control unit. Although the invention has been described by way of example with reference to the use of a single fracture detection switch means there could be provided a number of switch means connected to the control means the switch means being positioned at various places along the window seal. With such an arrangement it is desirable to connect the separate switch means in parallel when the switch means are of the normally open type and in series if of the normally closed type. It will be further appreciated that if a normally open arrangement is used a single switch means could be made to extend around a large part of the periphery of the pane of glass so that fracture at any position would be detected. It will also be appreciated that the or each sensor used to sense fracture of the window could be a pressure sensitive device in which the resistance varies depending upon the applied pressure. In which case the change of state of the device that occurs upon fracture of the glass is a change in resistance. A pressure sensitive device suitable for such use is disclosed in US-A-3,710,050. Although the invention has been described with reference to a warning device in the form of a siren other -forms of warning device could be used such as a visual warning device in the form of a light emitting diode. If such a low power device is used it would be possible to directly couple the fracture detector means to the diode.

Claims: A security system for detecting the fracture of a pane of glass (20, 220, 320), the system comprising at least one glass fracture detector means (14) the electrically conductive state of which is altered when the pane of glass (20, 220, 320) is fractured, a control means (11) connected to the or each detector means (14) to sense said change in electrically conductive state and a warning means (12) connected to said control means (11) to provide a warning of the fracture of said pane of glass (20, 220, 320) in response to a signal received from said control means (11) characterised in that the fracture detector means comprises of at least one sensor (18, 19; 118, 119; 218, 219; 318, 319) formed as an integral part of a resilient sealing member (16, 216, 316) used to form a seal between the pane of glass (20, 220, 320) and a frame (15, 215, 340) of the pane of glass. A security system as claimed in Claim 1 in which the or each sensor is a switch (18, 19; 118, 119; 318, 319) held in a closed conductive state by contact between the pane of glass (20,320) and the resilient sealing member (16, 316) and changed to an open non-conductive state when the pane of glass (20, 320) is fractured in the vicinity of a switch (18, 19; 118, 119; 318, 319). A security system as claimed in Claim 1 in which the or each sensor is a switch (218, 219) held in an open non-conductive state by contact between the pane of glass (220) and the resilient sealing member (216) and changed to a closed conductive state when the pane of glass (220) is fractured in the vicinity of a switch (218, 219). A security system as claimed in Claim 1 in which the or each sensor is a pressure sensitive device the resistance of which is dependant upon the amount it is compressed by contact with the pane of glass. A security system as claimed in any of Claims 1 to 4 in which the pane of glass is a moveable side window (20, 220, 320) of a motor vehicle. A security system as claimed in any preceding Claim in which the or each sensor (18, 19; 318, 319) is formed in a passageway of said resilient sealing member (16, 316). A security system as claimed in any of Claims 1 to 6 in which the or each sensor includes two electrical conductors (18, 19; 318, 319) at least one of which is a metal conductor. A security system as claimed in any of Claims 1 to 6 in which the or each sensor includes two electrical conductors (118, 119; 218, 219) at least one of which is made from a conductive rubber or elastomer. A security system as claimed in Claim 8 in which the or each conductor (218, 219) is formed as an integral part of the resilient sealing member (216) by co-extrusion therewith. A security system as claimed in Claim 8 in which the or each conductor (118, 119) is formed as an integral part of the resilient sealing member (16) by co-moulding therewith. A security system as claimed in Claim 7 in which the or each metal conductor (18, 19; 318, 319) is formed as an integral part of the resilient sealing member (16, 316) by being moulded into the resilient sealing member (16, 316). A security system as claimed in any of Claims 1 to 4 in which the resilient sealing member (16, 216) is of a U-shaped cross-section having two limbs defining a groove. A security system as claimed in Claim 12 in which the or each sensor (18, 19) is located in a passageway formed in one of the limbs of said sealing member (16). A security system as claimed in Claim 12 in which the or each sensor is formed by a first conductor (119) formed at or near the end of a lip (117) extending from one of said limbs into said groove and a second conductor (118) formed on an adjacent surface of said limb, the two conductors (118, 119) being pressed into engagement by the pane of glass (20) when it is present in the groove. A security system as claimed in Claim 12 in which the or each sensor is formed by a first conductive lip (218) extending from one of said limbs into said groove and a second conductive lip (219) extending from the other of said limbs, the two conductive lips (218, 219) being held apart by the pane of glass (220) when it is present in the groove. A security system as claimed in any of Claims 12 to 15 in which the resilient sealing member (16, 216, 316) is a window seal for a moveable side window of a motor vehicle. A security system as claimed in Claim 16 in which the resilient sealing member (16, 216, 316) includes a second sensor means (21, 22; 221, 222; 321, 322) used to detect the presence of a foreign object between the upper edge of said moveable side window and the resilient sealing member (16, 216, 316). A resilient sealing member for a power operated window system in a motor vehicle having a first sensor means (18, 19; 118, 119; 218, 219; 318, 319) formed as an integral part of said sealing member (16, 216, 316) to detect, in use, contact between the sealing member (16, 216, 316) and a side face of the window (20, 220, 320) for use as a glass fracture detector means in a security system and a second sensor means (21, 22; 221,222; 321, 322) formed as an integral part of said sealing member (16, 216, 316) to detect, in use, the presence of a foreign object trapped between one edge (30, 230, 330) of the sealing member (16, 216, 316) and an upper edge of the window (20, 220, 320) for use as a trap detector in an anti-trap system.

Inventors: GREENWOOD JEREMY JOHN, GREENWOOD, JEREMY JOHN
Applicants: ROVER GROUP, ROVER GROUP LIMITED
Application year: 1995
Main classification: G08B13
IPC codes: G08B13, H01H1, B60R25, H01H3