GB2140492A - Safety mechanism for a fastening - Google Patents

Abstract

A fastening for a sliding door is provided with means for preventing the bolt being moved to its fastening position unless the door is substantially closed. As shown the bolt 21 has a stud shape with enlarged head 23 and is intended to slide vertically to hold the door by engaging behind a keeper plate with a key-hole shaped aperture. To prevent this sliding prematurely a plate 13 is biased to the Fig. 3 position where the wider part 31 of the bolt stem lies in wider part 11 of a keyhole aperture in plate 13. When the door is shut the narrower part 53 of the bolt stem lies in this keyhole aperture and, since this is small enough to pass into the narrower portion 9 of the aperture, the bolt may be raised to its fastening position. <IMAGE>

Description

SPECIFICATION Safety mechanism for a lock This invention relates to a safety mechanism for a lock for a sliding door, sliding window or the like and is particularly suited for use on sliding patio doors which incorporate one or more locking bolts in the leading edge of the door. The invention will hereinafter be described with reference to sliding doors but is not so limited.

With the increasing popularity of sliding doors especially patio doors, there is a need to produce an inexpensive and reliable locking mechanism for the door which can withstand mis-use without any damage to the mechanism.

In its simplest form a locking mechanism for a sliding door includes one or more locking bolts projecting from the leading edge of the door in the direction of a door jamb adjacent which the door will be located when in a closed position,there being a keeper plate associated with the locking bolt mounted on the doorjamb, the keeper plate having a retaining portion behind which the head of the locking bolt is engaged when the bolt is moved to a locking position.While it is envisaged that the locking bolt could be of the hooked type mounted for swinging movement between its locked and unlocked positions, it is more usual to provide a locking bolt with an enlarged head portion somewhatsimi- lar to the head of a mushroom which, when the door is moved to a closed position, moves through an aperture in the keeper plate, whereupon, on locking the door, the bolt is moved bodily at right angles to its longitudinal axis so that the head slides behind a retainer portion on the keeper plate, thus preventing the door from being slid open again.The retainer portion is best formed by providing a generally keyhole shaped aperture in the keeper plate, the enlarged portion of the keyhole aperture being sufficient to allow the head of the locking bolt to pass therethrough and the narrower portion of the keyhole aperture being such as to allow the stem of the bolt immediately adjacent the head to slide therealong so that the head engages behind the walls defining the narrower portion.

It will of course be appreciated that many different constructions of bolt and keeper plate operating on this principle could be provided and it is possible to fix the locking bolt on the jamb and the keeper plate on the door although more normally the two members would be fixed the other way around.

With locking mechanisms of the types described above there is always the possibility of the locking bolt being moved to a locking position prior to the door being closed. This is especially so when the handle of the door to which the bolt is fitted is used to activate a locking mechanism, since it is not unusual for the user to use the handle actually to shut the door. Obviously, inadvertent locking movement of the handle could cause the bolt to be moved to its locking position. Should this happen, there is a real risk that as the door moves towards the door jamb so the bolt now in its locking position will strike against the outer face of the retaining portion of the keeper plate thus damaging the latter or the former or indeed some other part of the locking mechanism.

The present invention has been devised to prevent damage of the type described above occurring to the locking mechanism of a sliding door or the like.

According to the present invention, we provide a safety mechanism for a lock for a sliding door, movable towards and away from a jamb, in which a locking bolt is arranged to be movable from a first unlocked position to a second locked position wherein part of the bolt is located behind a retaining part of a keeper plate, said mechanism including means to prevent the bolt from being moved to its locked position except when the leading edge of the door is adjacent the jamb, said means comprising a Icoking bolt having a head portion for engagement with the retaining part of the keeper plate and a stem portion, and a latch device which, when the door is open, by virtue of its association with the locking bolt, prevents the locking bolt being moved from its unlocked position, but upon movement of the door to its closed position, permits the locking bolt to be moved to its locking position.

Preferably, the bolt has a generally mushroom shaped head portion and a stem portion, a first part of which, adjacent to the head portion, is of a first profile, and a second part of which is spaced from the head portion by the first part and is of a second profile smaller than that of the first part, and the latch device comprises an apertured plate arranged in use with the aperture surrounding the stem of the bolt, the aperture having a first portion, the dimensions of which are sufficient to accommodate the first part of the bolt stem, and a second portion, the dimensions of which are only sufficient to accommodate the profile of the second bolt part, the bolt, when it is moved from its unlocked position to its locked position, moving bodily at right angles to its longitudinal axis and there being biasing means associated with the plate holding the plate such that the enlarged portion of the aperture therein surrounds the first part of the bolt stem when the door is open and the arrangement being such that when the door is closed the plate will be moved against its biasing means so that the bolt aperture is located around the second part of the bolt of reduced profile thus allowing the bolt to slide bodily into its locking position.

Preferably, both parts of the stem portion of the bolt are of round cross-section and the aperture in the plate is of generally keyhole shape.

Preferably, the plate is formed of spring steel and comprises a first portion provided with means for connecting the plate to the door or jamb from which the bolt projects and with a second portion inclined at an obtuse angle to the first portion, the aperture in the plate being located in said second portion and the spring bias to the plate being provided by the natural resiliency of the material of the plate.It will of course be appreciated that when the door is in an open position the second portion of the plate will be inclined relative to the face of the member two which it is secured, e.g. the leading edge of the door, but when the door is moved to a closed position, the end of the second plate portion remote from the first plate portion will abut the doorjamb and be deformed against its natural resiliency so as to lie generally in line with the first plate portion, thus permitting the reduced profile second bolt part to slide along the second portion of the aperture in the plate.

A safety mechanism in accordance with the present invention is now described by way for example with reference to the accompanying drawings, in which Figure 7 is a plan view of a plate part of the mechanism; Figure 2 is a side elevation of the plate fitted to the leading edge of a door, and Figure 3 is a side elevation of a locking bolt fitted into the leading edge of a door (sectioned).

Referring to the drawings, part of the leading edge of a door D is shown having a plate 1 secured thereto by means of a screw or other means (not shown) passing through a countersunk aperture 3. The plate has a first portion 5 which lies flush on the face of the door and a second portion 7 which is inclined relative to the first portion 5 at an obtuse angle a.

The second portion has a generally keyhole shaped aperture 9 therein, the aperture having at one end an enlarged portion 13 narrower than the diameter of the portion 11.

As can readily be seen from Figures 2 and 3, a locking bolt 21 is mounted in the leading edge of the door so as to project from its leading face, the locking bolt having an enlarged generally mushroom shaped head portion 23 and a tail portion 25 which may be screw-threaded for engagement in part of a lock actuating mechanism indicated generally at 27. Between the head portion 21 and tail portion 25, the locking bolt has a stem portion 29, a first part 31 which has a profile (diameter) slightly smaller than the diameter of the portion 11 of the aperture 9 in the plate 1 and the second part of which, 33, has a profile (diameter) slightly less than the width of the narrower second portion 13 of the aperture 9.

In Figure 3 the locking bolt is shown in an unlocked position and in order to move it to its locking position it is moved bodily in the direction of the arrow Bso that the part 27 of the actuating mechanism takes up the position represented by the dotted lines 35 in Figure 3. However, as can clearly be seen from Figures 2 and 3, in which the locking bolt is shown in its unlocked position, the first part 31 of the bolt stem 29 is located in the enlarged portion 11 of the aperture 9 in the plate 1 and in this position of the plate 1 it is impossible for the locking bolt 21 to be moved to its locking position because the enlarged diameter part 31 of the bolt stem 29 cannot move into the narrower portion 13 of the aperture 9.This means, therefore, that it is impossible for anyone inadvertently, for example by using the handle of the door to close the door, to move the locking bolt to its locking position.

The locking bolt can only be moved to its locking position when the second portion 7 of the plate 1 is moved to its broken line position illustrated by the dotted lines 37 in Figures 2 and 3. The plate 1 is fomed of a resilient or springy material such as stainless spring steel and is therefore resiliently deformable and can be moved from its full line position to its broken line position 37 simply by sliding the door to its closed position and as the door approaches the doorjamb, so the free edge portion of the plate portion 7 will abut the door jamb and continued closing movement of the door will deform the plate portion 7 as necessary.This moves the apertue 9 in the plate into a position in which it is surrounding the reduced diameter portion 33 of the bolt stem 29, whereupon the bolt can then be slid to its locking position 35 by virtue of the stem portion 33 sliding along the narrow portion 13 of the aperture 9.

Of course, when the door is moved to its closed position the enlarged head 23 on the bolt 21 can move through an enlarged portion at one end of a keyhole aperture in a keeper plate on the door jamb (similar to aperture 9) and when the bolt is then moved to its locking position, the enlarged head 23 will slide up behind a retaining portion on the keeper plate formed by the cheeks defining the narrower portion of the aperture in the keeper plate.

it will of course be appreciated that a spring bias to the plate portion 7 may be provided by an alternative biasing means such as a leaf spring or a coil spring and it is even envisaged that the whole plate 1 could be mounted for bodily sliding movement against a spring bias towards the end face of the door D.

It is also envisaged that different shaped locking bolts and plates 1 could be provided and it is even envisaged that the locking bolt could be of the hook variety, or pivotally movable between locking and unlocked positions, in which case the construction of the means to prevent the bolt moving to its locking position would have to be different.

It is also envisaged that instead of mounting the locking bolt 21 and plate 1 on the leading edge face of the door, they could be mounted on the door jamb.

Claims (5)

1. A lockfora sliding door which is movable towards and away from a jamb, the lock comprising a locking bolt movable when the door is closed from a first unlocked position to a second locked position wherein part of the bolt is located behind a retaining part of a keeper plate, and a safety mechanism including means to prevent the bolt from being moved to its locked position except when the leading edge of the door is adjacent the jamb, said means comprising head portion of the locking bolt for engagement with the retaining part of the keeper plate and a stem portion of the locking bolt, and a latch device which, when the door is open, by virtue of its association with the locking bolt, prevents the locking bolt being moved from its unlocked position, but upon movement of the door to its closed position, permits the locking bolt to be moved to its locking position.

2. A lock according to claim 1 wherein the bolt has a generally mushroom shaped head portion at an end of the stem portion, a first part of which, adjacent to the head portion, is of a first profile, and a second part of which is spaced from the head partion by the first part and is of a second profile smaller than that of the first part, and wherein the latch device comprises an apertured plate arranged in use with the aperture receiving the stem of the bolt, the aperture having a first portion, the dimensions of which are sufficient to accommodate the first part of the stem portion, and a second portion, the dimensions of which are only sufficient to accommodate the profile of the second part of the stem portion, the bolt, when it is moved from its unlocked position to its locked position, moving bodily at right angles to its longitudinal axis and there being biasing means associated with the plate holding the plate such that the enlarged first portion of the aperture therein surrounds the first part of the bolt stem portion wherrthe door is open and the arrangement being such that when the door is closed, the plate will be moved against its biasing means so that the bolt aperture accommodates the second part of the bolt stem portion of smaller profile, thus allowing the bolt to slide bodily into its locking position.

3. A lock according to claim 2 wherein both parts of the stem portion of the bolt are of round cross-section and the aperture in the plate is of generally keyhole shape.

4. A lock according to claim 2 or 3 wherein the plate is formed of spring steel and comprises a first portion provided with means for connecting the plate to the door or jamb from which the bolt projects and a second portion inclined at an obtuse angle to the first portion, the aperture in the plate being located in said second portion and the spring bias to the plate being provided by the natural resiliency of the material of the plate.

5. A lock for a sliding door and incorporating a safety mechanism said lock being substantially as hereinbefore described with reference to the accompanying drawings.