GB2260569A

GB2260569A - Door bolt

Info

Publication number: GB2260569A
Application number: GB9221721A
Authority: GB
Inventors: Peter Douglas Mayhew
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-10-18
Filing date: 1992-10-15
Publication date: 1993-04-21
Anticipated expiration: 2012-10-15
Also published as: GB9221721D0; GB2260569B; GB9122135D0

Abstract

A fastening for a door consists of a slidable bolt 10 carried in a mounting plate 17, for attachment to the door, and a keeper 25 for attachment to the door frame, the bolt including a frangible zone 16 which will give way under pressure to permit access to the room through the locked door in the event of an emergency. <IMAGE>

Description

DOOR LOCK This invention relates to a door lock of the type including a slidable bolt and a keeper therefor.

Door locks of the above type are manufactured in various sizes and strengths according to the intended purpose thereof. For example, a lock for an external door or gate would generally be of heavier duty than for an internal door where, for domestic purposes, such locks are generally provided for ensuring personal privacy in rooms such as bathrooms and lavatories.

Occasions have arisen in which it is necessary to gain access to a room despite the fact that the occupant has closed and locked the door from within the room. Such occasions arise when, for example, a person has fallen in the bathroom or slipped in the bath itself, resulting injury preventing the person from unlocking the door. Under such circumstances, access can be gain only by forcing open the door with damage being caused as a result to the frame and/or to the door itself as the lock securing screws are forced away. Occasions may also arise when children engage the sliding bolt from the inside of a room in which they are playing and an emergency arises within the room. Yet again, a person under the influence of alcohol or drugs may become trapped in a locked room.

It is an object of the present invention to provide a lock for a door and which allows the door to be opened from the remote side without causing damage to the fabric of the door or frame.

According to the invention, a lock for a door includes a bolt and a keeper therefor, in which either the bolt and/or the keeper includes a frangible zone whereby the lock gives way under a substantial applied pressure.

By "substantial applied pressure" is meant either a sustained and increasing pressure or the force exerted by a shoulder-barge, for example; such a pressure is to be distinguished from that exerted by a person merely attempting to open the door in the normal course of events.

In a preferred embodiment, the frangible zone is provided in the bolt, whereby the bolt will fracture or shear under the applied pressure to leave a portion thereof engaged by the keeper, the door being then free to open.

The bolt may have any cross-sectional shape but will generally be circular or rectangular in cross-section, thus causing the bolt to be either in the form of a cylinder or a bar. The frangible zone may be provided by a zone of weakness in the bolt, for example by forming the bolt with a waist, a groove or other dimensional modification from its regular form.

Alternatively, the frangible zone may comprise an interface between two parts of the bolt which are joined together across the interface in a fracturable manner, or by locally modifying the material of the bolt, for example by modifying the crystal structure of the bolt material, which may be a metal, for example aluminium or an alloy thereof, or a plastics material.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which Figure 1 is a side elevation of a door bolt and Figure 2 is a side elevation of the components of a door lock including the bolt of Figure 1.

With reference to Figure 1, the bolt is shown generally at 10 and consists essentially of a cylindrical pin at the tail end of the body portion 13 thereof, an arm 11 carrying a finger knob 12.

An annular groove 14 is formed towards the head end 15 of the pin and defines a frangible zone 16. The bolt may be formed from metal or a plastics material and the dimensions of the groove are such that the head end of the pin will shear or break away from the body portion under the influence of a substantial applied pressure as between the head end and body portion.

With reference to Figure 2, the lock includes a mounting plate 17 which carries a cylindrical open-ended housing 18 in which the bolt is slidably journalled. The plate 17 is provided with holes 19 for receipt of screws and also with two pairs 20, 21 of upstanding lugs with inwardly turned upper ends defining respective slots 22, 23 through which the arm 11 can pass. A pair of inwardly-directed protrusions 24 are carried by the lugs 21 to form a constriction to the slot 23 to prevent inadvertent removal of the bolt from the mounting plate.

The lock also includes a keeper 25, shown remote from the bolt for the sake of clarity, which consists of a base plate 26 having screw holes 27 and a cylindrical housing 28 which is open at one end (which in use faces towards the bolt) and closed at the other end by wall 29.

In use, the mounting plate 17 is attached, oriented either horizontally or vertically or indeed at any other desired angle, to a door and the keeper base plate is secured to the door frame with the respective cylinder axes in alignment. In order to lock the door, the bolt pin 10, which is initially retracted within housing 18 with the arm 11 between the pairs of lugs 20, 21, is slid forwardly so that the arm 11 passes through slot 22 until it assumes the position as shown in Figure 2 with the head end 15 of the pin extending from housing 18 and received within keeper housing 28, the end of the pin abutting wall 29 to prevent further forwards movement of the pin and with the groove 14 between the housings. In this position, the lock will resist gentle pressure against the door from outside, thus indicating that the room is occupied, but will give way at the frangible zone under substantial stronger pressure or a shoulder-barge, to afford access to the room in an emergency.

Once the head end 15 of the pin has been sheared off, the body portion can be removed from the mounting plate cylinder by forcing the arm 11 through the constriction in slot 23; a new pin can then be inserted by the reverse procedure.

In an alternative embodiment, the lugs 21 are replaced by a cylindrical housing and the arm 11 is detachable from the pin 10, for example by being screw-threadedly engageable therein, whereby the arm is detached from a pin, the head end of which has been sheared off, before removal of the pin from housing 18 and the insertion of a new pin.

Claims

1. A lock for a door, the lock comprising a slidable bolt and a keeper therefor, in which either the bolt and/or the keeper includes a frangible zone whereby the lock in use will give way under a substantial applied pressure.

2. A lock according to claim 1, in which the frangible zone is provided in the bolt.

3. A lock according to claim 2, in which the frangible zone is provided by a dimensional modification from the regular form of the bolt.

4. A lock according to claim 3, in which the bolt is provided with an annular groove defining the frangible zone.

5. A lock according to any preceding claim, in which the keeper includes an end wall to limit sliding movement of the bolt.

6. A lock according to any preceding claim and including a mounting plate which comprises constriction means to prevent inadvertent removal of the bolt.

7. A lock substantially as herein described with reference to and as illustrated in the accompanying drawings.