GB2114206A - Improvements in door security devices - Google Patents

Abstract

A device for preventing a door being opened to more than a limited degree comprises two parts 10, 12, one to be attached to the door and one to be attached to the frame, with one of them having a resilient member to absorb the shock of an attempt to force the door. The parts have means for fastening to each other such as the spring clip 26 and aperture 28, or a key and latch receptacle as in Fig. 3 (not shown). Spring 22 tends to restore the door to its closed position. Alternatively two springs may be used, one relatively weak one allowing easy opening to the set limit and a stronger one resisting further opening force. <IMAGE>

Description

SPECIFICATION Improvements in door security devices This invention relates to a door security device, which as used herein means a door restraint device which can be operably connected between a hinged door and its frame or surround to restrict the amount by which the door can be opened on its hinges.

The commonly used door restraint device comprises two parts, a first part for fixing to the door frame and which includes a chain carrying a headed stud, and a second part for fixing to the door and which includes an extended keyway slot in which the headed stud can be releasably engaged. Given that the chain and the screw fixings are adequately manufactured for the purpose, this type of restraint can withstand substantial controlled pressure applied to a partially opened door.

However, the conventional door restraint as above described has a major disadvantage in that it is much- less able to withstand shock pressure applied to the door. Thus, if, for example, a potential intruder pulls the door towards its closed state and then slams it back against the restraint, the chain and/or screw fixings, especially the latter, are liable to break under the sudden impact.

Additionally, the conventional restraint device is aesthetically unattractive and, unless carefully and precisely fitted, may be quickly releasable, especially with the aid of a suitable implement, when the door is marginally open to an extent less than the limit afforded by the restraint.

It is an object of this invention to provide an improved door security device which can avoid or minimise the above-described disadvantages.

According to the present invention, a door restraint device comprises two parts, one for securing to the door and one for securing to the door frame, one part including a fitting which can be releasably engaged with a cooperating fitting incorporated in the other part, at least one such fitting being resiliently mounted to yield and absorb a possible impact applied to a partially opened door without permitting the door opening to increase beyond a predetermined limit.

The resilient mounting means, normally a spring, may be operative with a light restoring force even during the initial stage of opening of the door towards the predetermined limit, but preferably will not be operative during such initial stage of opening movement, and in both cases will thereafter be operative with a strong restoring force effective for impact absorption. In stating the above, it will be understood that the initial stage of opening movement may generally correspond to the opening movement normally permitted by a conventional door restraint, in which case the resilient mounting means will apply the strong restoring force throughout a short extension of the opening movement up to the predetermined limit. At this limit, the door will, of course, still be insufficiently open to afford access.In addition, the maximum restoring force operative to close the door will be effective, so that an impact on the door will invariably produce a spring reaction which slams the door shut.

In one simple arrangement, a chain may be attachable to the door frame or adjacent wall surrounding the door, this chain carrying at its end a spring clasp for detachable engagement with an apertured head formed on a rod which projects out of the end of an elongated housing attachable to the door, a spring within the housing acting on the rod in a manner to urge its withdrawal into the housing. Preferably, a strong spring will be employed, housed in a manner which permits the two parts of the restraint to be connected ready for operation without causing compression of the spring, and furthermore permits an initial stage of opening movement of the door without causing spring compression.Moreover, the strength of the spring will be so high as normally to arrest the door at the end of this initial opening stage whilst remaining compressible under an impact substantially to eliminate (or at least materially to reduce if the impact is great enough fully to compress the spring) the breakage strain on the chain or fixings, especially the latter. It is to be noted that the strain is eliminated or substantially reduced both at the fixings of the one part of the restraint to the door and at the fixings of the other part to the door surround.

In an alternative embodiment, the fixing chain is replaced by a coiled wire of sufficient strength to resist normal cutting tools and withstand impact. A return spring can then be incorporated in a housing fixed on or embedded in the door surround to withdraw the coiled wire therein when the restraint is not in use. It is to be noted, however, that the impact absorbing spring will still be retained in the part of the restraint on the door. However, it is conceivable that a weak return spring and a strong impact absorbing spring could be incorporated in the housing associated with the door surround; the part of the restraint on the door can then become an eyelet having a stem firmly embedded in the door, the free end of the coiled wire carrying a clasp for attachment to such eyelet.This clasp can also serve as a stop preventing total withdrawal of the coiled wire into the door surround housing when the restraint is not in use.

Arrangements as above described, especially when using a coiled wire, can be made and arranged to be aesthetically much less obtrusive than a conventional door restraint.

In accordance with a further feature of the invention, as a further safety feature, the two fittings on the respective parts of the device may comprise a key on the end of the chain or coiled wire and a slotted key receiving housing having a resiliently loaded key engaging element therein.

Preferably, a spring latch is employed in such arrangement to hold the key and key engaging element in a locked condition, which latch is releasable only from that side of the housing which is most remote from the edge of the door.

Practical embodiments of the door restraint of the invention will now be briefly described by way of example with reference to the accompanying drawings, in which: Figure 1 shows one possible arrangement diagrammatically; Figure 2 shows a second possible arrangement diagrammatically; and Figure 3 is a diagrammatic view of a third possible arrangement.

The door restraint of Figure 1 comprises two parts, namely a chain 10 having at one end a fixing element (not shown) by which the chain can be firmly and fixedly attached at said end to a door post or possibly to the wall adjacent the door, and a part 12 which can be firmly and fixedly mounted to a door.

The part 12 comprises an elongated housing 14 from one end of which projects the apertured head 18 of a rod 16. Within the housing 14, a rod back plate 20 is slidable within the housing and serves as an abutment for a strong flat coil spring 22 located around the stem of the rod between said plate 20 and the end wall 24 of the housing through which the rod 1 6 projects.

The free end of the other part of the restraint, i.e. the chain 10, carries a hook or spring clasp 26 which can be engaged with the apertured head 1 8 of the rod 1 6 to render the restraint operative.

The arrangement is such that the chain can be tautened and the rod 1 6 can be withdrawn out of the housing sufficiently to permit the door to be opened to a first limited extent without compressing the spring. If at this time a strong impact is applied to the door in an endeavour to break it open, the door is able to open a small further amount by compression of the spring 22, which thus absorbs the impact and prevents the impact force being transmitted to the fixings by which the two parts of the restraint are attached to the door and to the door surround. Even if the spring 22 is fully compressed under the impact, the door will only be opened to a second limited extent insufficient to afford access. Furthermore, following the impact, the high restoring force of the compressed spring will tend to slam the door shut.

In a modification, a weak return spring and a strong impact absorbing spring are incorporated in the housing, the first being operative up to the first predetermined limit of door opening and the second being operative thereafter up to the second predetermined limit of door opening.

Alternatively, a differential spring may be incorporated in the housing, developing its impact absorbing force only during the latter part of its compression (or tensioning).

In the arrangement shown in Figure 2, the chain is replaced by a coiled wire. Thus, the part of the restraint which fixes to the door surround comprises an elongated housing 28, conveniently vertically mounted and possibly embedded within the door post, within which a strong coiled wire 30, resistant to normal cutting tools, is accommodated. The end of the coiled wire projects from the housing 28 and carries the clasp 26 which can be engaged with the apertured head 18 of the rod 16 incorporated in the part of the restraint fixed to the door. A return spring 32 may be provided to withdraw the coiled wire 30 into the housing 28 when the restraint is not in use, as far as permitted by the clasp 26, which thus acts as a stop.

In the embodiment shown in Figure 3, the chain 10 (or coiled wire 30) carries a key 34 instead of the hook or clasp 26. The part of the restraint which fixedly attaches to the door, and again may be at least partly embedded therein, comprises a slotted key receiving housing 36 accommodating a key engaging element 38 therein, mounted to a back plate 40 slidable within the housing. A strong impact absorbing coil spring 42 acts between said back plate 40 and the end wall 44 of the housing 36 having the key receiving slot therein. The housing 36 also incorporates a spring latch 46 which projects from the rear of the housing remote from the key slot.

When the key 34 is inserted, the latch 46 is lifted and then springs back to lock the key to the key engaging element 38. The key can then only be withdrawn after releasing the latch 46 at the rear of the housing, which is remote and hidden from the edge of the door and therefore is virtually inaccessible when the door is only partially opened.

In the arrangement shown in Figure 4 coil spring 48 is located in a tubular metal housing 50 with a bolt 52 passing through the spring, inside the housing. A washer 54 is located between the bolt head and spring, serving as an abutment for the spring, with the free end of the bolt passing through an aperture 56 in the end of housing 50 and being pivotally attached to a mounting plate 58 secured to door frame 60. The aperture 56 is dimensioned to act to retain the spring 48 within the housing.

A chain or cable 62 is secured to the other end of tubular housing 50 in an appropriate manner, with a fitting 64 provided at the free end of the chain or cable 62 adapted to be releasably secured to an attachment member (not shown) secured to door 66. The connection of fitting 64 and attachment member may be of any convenient form.

In use, when the fitting 64 is secured to the attachment member and the door 66 is opened, the device assumes the position shown in Figure 4, with the housing 50 extending across the gap between the frame and door. The housing thus protects and conceals the spring and further more forms a more substantial and robust barrier than a simple chain. The device otherwise operates in generally the same manner as the previously described embodiments.

In order to function effectively, the housing should be of robust and substantial construction, e.g. of suitably high gauge steel, to withstand impact shock and/or interference e.g. by sawing.

When the device is not in use the housing hangs down vertically from the pivotal connection, and a fixing may possibly be provided to retain the housing temporarily in this position.

Claims (12)

Claims

1. A door restraint device comprising two parts, one for securing to the door and one for securing to the door frame, one part including a fitting which can be releasably engaged with a cooperating fitting incorporated in the other part, at least one such fitting being resiliently mounted to yield and absorb a possible impact applied to a partially opened door without permitting the door opening to increase beyond a predetermined limit.

2. A device according to claim 1, wherein the resilient mounting means comprises a spring.

3. A device according to claim 1 or 2, wherein the resilient mounting means is not operative during the initial stage of opening of the door towards the predetermined limit, and is thereafter operative with a strong restoring force effective for impact absorption.

4. A device according to any one of the preceding claims, comprising a chain attachable to the door frame or adjacent wall surrounding the door, this chain carrying at its end a spring clasp for detachable engagement with an apertured head formed on a rod which projects out of the end of an elongated housing attachable to the door a spring within the housing acting on the rod in a manner to urge its withdrawl into the housing.

5. A device according to claim 4, wherein a strong spring is employed, housed in a manner which permits the two parts of the restraint to be connected ready for operation without causing compression of the spring, and furthermore permits an initial stage of opening movement of the door without causing spring compression.

6. A device according to claim 5, wherein the strength of the spring is so high as normally to arrest the door at the end of this initial opening stage whilst remaining compressible under an impact substantially to eliminate the breakage strain on the chain or fixings, especially the latter.

7. A device according to claim 1,2 or 3, comprising a coiled wire of sufficient strength to resist normal cutting tools and withstand impact.

8. A device according to claim 7, wherein a return spring is incorporated in a housing fixed on or embedded in the door surround to withdraw the coiled wire therein when the restraint is not in use. Be noted, however, that the impact absorbing spring will still be retained in the part of the restraint on the door.

9. A device according to claim 7 or 8, wherein a weak return spring and a strong impact absorbing spring are incorporated in the housing associated with the door surround.

10. A device according to anyone of claims 1 to 3, comprising a tubular housing adapted to be pivotally mounted with respect to a door frame via a rod protruding from the housing, a spring within the housing acting on the rod in a manner to urge its withdrawal into the housing, elongate connecting means extending from the free end of the housing and terminating in a fitting adapted to be releasably secured to a cooperating fitting mounted to the door.

11. A device according to anyone of the preceding claims, wherein the two fittings on the resepotive parts of the device comprise a key on the end of the chain or coiled wire and a slotted key receiving housing having a resiliently loaded key engaging element therein.

12. A door restraint device substantially as herein described with reference to, and as shown in, the accompanying drawings.