GB2215896A - Intruder alarm system - Google Patents

Abstract

An intruder alarm system comprising an intruder alarm device (16) comprises a housing (1) which is secured to a surface of the transom member (14A), a canister (24) containing an inertia mass and a pair of electrical switch contacts, the canister being firmly but releasably held by clamp tongues (26) and fingers (27) which are fixed to a removable section of the housing (1a) facilitating replacement of canister (24), electrical cable (17) being recessed within the interior of transoms (14A, 14B) until it emerges from framing members at aperture (18). <IMAGE>

Description

INTRUDER ALARM SYSTEMS This invention relates to intruder alarm system.

Known forms of intruder alarm systems include vibration detectors which are retro-fitted to existing doors and windows of a building or the like to be protected by the alarm system, these detectors being surface mounted on a suitable support structure the vibration of which is to be detected as an indicator of intrusive activity, the vibration detectors comprising switch contacts operable by an inertia mass, the contacts being connected by way of an electric cable to a centralised control unit of the alarm system. Accordingly in the known systems the cabling leading to the control unit is particularly visible due to retro-fitting to existing structures.

In accordance with the present invention an intruder alarm system comprises an intruder alarm device fitted to framing for a glazed unit, the framing being of hollow section and the device including electrical switching contacts operable by an inertia mass mounted on or in the framing and a length of electrical cable leading from the switch contacts and extending along the hollow framing to an aperture in the frame.

Preferably the device comprises a canister containing the inertia mass and electrical switch contacts. Preferably said canister and electrical switch contacts are releasably held within a housing mounted on the surface of the frame.

Said canister may alternatively be releasably held in a recessed position within the hollow framing by a face plate incorporating resilient fingers adapted to engage an internal surface of the hollow framing. The face plate may-be essentially planar or may be bulbous.

The hollow framing may take the form of a window frame or a door frame and may be constructed in extruded form from either metal or plastics material, for example, aluminium or uPVC. The framing preferably is adapted to receive hermetically sealed double glazing units.

By virtue of the present invention the vibration detectors of the intruder alarm system may be located in a desired location in or on the framing in an unobtrusive manner and the associated electric cable is hidden from view by virtue of its passage through the hollow section framing. The aperture for the cable may be located at a corner of the framing to enable the cable to traverse upwardly or downwardly from the framing through the structure of the building to which the framing is subsequently fitted. In this connection it will be appreciated that the present invention contemplates provision of replacement windows and doors with vibration detection devices fitted thereto and with the associated electric cabling threaded through the existing structure either to an attic space or to an under-floor space for subsequent connection to an alarm system control unit.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 schematically illustrates the present invention; Fig. 2 illustrates a sectioned vertical view of a preferred first embodiment of the present invention; Fig. 3 is a vertical sectional view of a detail of a second embodiment of the present invention; Fig. 4 is a horizontal sectional view of the Fig. 3 detail.

As is illustrated in Fig. 1 an existing structure 10 comprises window aperture 11 to which is fitted a window formed by upper and lower glazed units 12, 13, mounted in a uPVC frame 14 the framing members of which are of hollow section and in turn mounted in a wooden surround 15 which is secured to the structure 10. An intruder alarm device 16 is indicated as being carried by the transom framing member 14A which separates glazed units 12, 13, so that the device 16 is essentially centrally located with respect to aperture 11 thereby to be maximally sensitive to intrusive vibrations imposed on any part of the window.The device 16 is electrically connected by way of cable 17 to the control unit (not shown) of the alarm system, cable 17 being recessed in the hollow interior of transom member 14A, the hollow interior of side frame member 14B and emerging therefrom at an aperture 18 to traverse a passageway formed through the wooden surround 15 and thereafter to be threaded upwardly through the structure 10 to an attic space. As is known threading of cabling 17 through the structure 10 is conveniently undertaken via the inter leaf cavity when structure 10 is in the form of a cavity wall.

By way of example Fig. 1 also illustrates a second intruder alarm device 19 located in side frame member 14C for--the purpose of illustrating an alternative position for the vibration detector within window opening 11.

With reference to Fig. 2 a preferred first embodiment of the present invention is shown in vertical section.

Transom member 14A comprises an inner hollow section component 20 made of uPVC, the hollow sections 20A, 20B being arranged to receive the glazed units 12, 13, both of which are hermetically sealed double glazed structures.

Device 16 comprises a housing 1 which is secured to a surface of the transom member 14A by screws 2. A canister 24 contains an inertia mass and a pair of electrical switch contacts are disposed on either side of the canister 24.

The canister is firmly but releasably held in its position by clamp tongues 26 and resilient fingers 27 which are fixed to a removeable section of the housing 1A facilitating replacement of the canister 24. Electrical cable 17 passes through a hole in the housing 1 and wall 23 of the component 20 and is recessed within the interior of the transoms 14A, 14B until it emerges from the framing members at aperture 18.

With particular reference to Fig. 3 a second embodiment of the present invention is shown. Transom member 14A is illustrated in cross section as comprising an inner hollow section component 20 made of uPVC as before and an outer component 21 made of aluminium, these components being interengaged and arranged to carry the glazed units 12, 13.

Component 20 is extruded and comprises spaced walls 22, 23, which are locally cut away to receive the alarm device 16.

Device 16 comprises a canister 24 containing an inertia mass and a pair of electrical switch contacts as previously.

The canister 24 is firmly but releasably held in its position by a face plate 25 carrying canister clamp tongues 26 and resilient fingers 27 the latter being adapted to fit into the cut out in the transom component 20 and engage the rear surface of wall 23 in the manner of a hollow fixing.

Dependent upon the relative dimensions of the canister diameter and the spacing between walls 22, 23, the cut out may penetrate both walls 22 and 23 to enable the face plate 25 to present a planar outer surface or, alternatively, only wall 23 may be apertured and the face plate 25 formed in a bulbous fashion to accommodate a protrusive portion of canister 24. In either event canister 24 incorporates a serrated ring 28 which facilitates rotation of the canister 24about its longitudinal axis so as to set the operating sensitivity of the detector, the setting being maintained by engagement of the serrations of ring 28 with the edges 29 of an actuating window 30 formed in the face plate 25.

The enclosure 1 of the embodiment may also facilitate rotation of the canister 24 by cutting a slot in section la through which said serrated ring may be accessed. The electric cable 17 extends through the hollow space formed between walls 22, 23 of component 20 and is recessed within the interior of the transoms 14A, 14B as in the first embodiment.

- It will be understood that in accordance with the present invention a vibration detector suitable for use with an intruder alarm system is provided in a glazed unit framing member essentially as an integral component thereof and concealed cabling to the detector is provided within the hollow section of the framing which may be fitted to a building structure either as a replacement unit or as an initially installed unit. As a result the cost of fitting the detector to the framing is low due to the fitting being effected during construction of the framing in a factory envi#ronment and the cost of threading the cable through the existing building structure is also low due to the accessibility provided to cavity air spaces and the like prior to securing the framing unit in place.

Claims (6)

1. An intruder alarm system comprising an intruder alarm device fitted to framing for a glazed unit, the framing being of hollow section and the device including electrical switching contacts operable by an inertia mass mounted on or in the framing, and a length of electrical cable leading from the switch contacts and extending along the hollow framing to an aperture in the frame.

2. An intruder alarm system as claimed in claim 1, wherein said alarm device includes a canister containing the inertia mass and electrical switch contacts.

3. An intruder alarm system as claimed in claim 2, wherein said canister and electrical switch contacts are releasably held within a housing mounted on the surface of the frame.

4. An intruder alarm system as claimed in claim 2, wherein said canister is releasably held in a recessed position within the hollow framing by a face plate incorporating resilient fingers adapted to engage an internal surface of the hollow framing.

5. An intruder alarm system as claimed in claim 1, wherein said aperture in the framing is located at a corner of the framing.

6. An intruder alarm system as claimed in claim 1, wherein said framing is adapted to receive hermetically sealed double glazing units.