GB2269418A - Latch mechanism with reversable handedness - Google Patents

Abstract

A latch mechanism comprises a housing 10, a latch member mounted in the housing and consisting of a latch head 3 and a latch tail 2. The tail is axially fixed to the head so that the latch member is reliably pulled back by a follower 31 when this follower is actuated by a lock or a handle for the latch mechanism. In normal operation the latch head 3 emerges to the usual extent from the housing 10 under the action of the spring 17 acting on the latch via an intermediate abutment block 5 which stops against the housing 10. For reversal of the handedness of the latch member this and the follower 31 are so arranged that the latch head 3 can be drawn out clear of the housing 10 and the latch head 3 can then be rotated to the reversed operating configuration, after which it is retracted into the housing 10 by a spring 9. <IMAGE>

Description

LATCH MECHANISM The invention relates to a reversible latch mechanism for doors, in particular to such a mechanism of the deadlocking type.

Latch mechanisms can be either left- or righthanded, in accordance with the opening of the door to which the latch is to be fitted. Although it is possible to keep a stock of both hands of latch, efforts have been made to provide dual-handed mechanisms which can be adjusted on site to the required handedness. This avoids the necessity for ordering the correct number of each type of latch, and any inconvenience resulting from an incorrect order, and also means that the supplier's stock can be kept smaller.

Reversing the handedness of the latch mechanism involves turning the latch head by 1800 about its own axis. This is possible if the cover plate of the latch mechanism is removed and the latch is taken out, turned round and re-inserted, assuming that the construction of the mechanism allows this. However, this is a tricky operation to perform on site and frequently leads to the return springs of the latch mechanism escaping.

A prior proposal for a latch mechanism which is reversible without removing the cover plate involves the use of a two-part latch member, as shown schematically in Fig.2 of the accompanying drawings.

In this proposal the head of the latch member is spring-loaded on the latch body or tail. In order to reverse the latch the face plate is removed and the head is pulled out against the force of the spring until it is just clear of the latch casing. The head can then be rotated and allowed to spring back into the casing, whereupon the face plate is replaced.

The latch has to be so arranged that the face plate prevents rotation of the latch head even when the latter is pulled out to its fullest extent, as otherwise it is too easy for an unauthorised person to reverse the latch, for instance as a practical joke, causing some inconvenience for the next user of the door.

A further problem arising with this arrangement is that, if the fitting of the latch head in the striker plate is tight, for instance if the clearance between door and frame is very small, then turning the handle may fail to pull back the latch head since the spring loading is not strong enough to overcome the friction between the latch head and the striker plate. This is dangerous as well as inconvenient. It is an aim of the present invention to improve this situation.

According to the invention there is provided a latch mechanism comprising a housing, a latch member mounted in the housing and consisting of a latch head and a latch tail axially fixed to the head, the latch member being adapted to be pulled back by a follower when this follower is actuated by a lock or a handle for the latch mechanism, the latch member and follower being so arranged that the latch head can be drawn out clear of the housing, and the latch member being mounted in the housing in such a way that, following this withdrawal, the head can be rotated to the reversed operating configuration; the mechanism further including an abutment member arranged to bear against the latch head up to a point where the abutment member stops against the housing, while the latch head can be drawn from this point clear of the housing as aforesaid.

Normally such a latch mechanism will have a restoring means such as a spring urging the latch head into its usual rest position, i.e. with the head protruding from the housing so as to engage a striker plate. This rest position corresponds to the position where the abutment member comes to a stop directly or indirectly against the housing. With the invention it can be arranged that this restoring means acts on the abutment member instead of directly on the head or tail of the latch, so that no separate stop is required to prevent the restoring means pushing the latch head fully out of the housing into its rotatable position.

There is preferably a further restoring means, such as a spring, arranged between the latch member and the abutment member; the head is then pulled out of the housing against the action of this spring, rotated, and allowed to re-enter the housing.

Meanwhile the non-displaceable attachment of the head to the tail ensures that the latch head is reliably retracted into the casing upon operation by the handle. At the same time reversal of the head by withdrawing it from the housing is still possible, for instance by virtue of a gap between the follower and the bolt tail, or because of a capacity of the follower to follow the consequent movement of the tail upon which it acts.

For simplicity the latch head and tail are securely fixed to or integral with each other, although it would be possible to have the two rotatably attached to each other as long as no significant mutual axial displacement is possible. The rotatable mounting of the latch member can be achieved by giving at least part of the tail a circular cross-section and slidably arranging it in a block having a corresponding circular hole and fixed in the housing.

The abutment member is preferably in the form of a block having an aperture through which the tail of the latch passes in a rotatable fashion. This ensures axial guidance of the block; the block may be free to rotate within the housing but is preferably constrained, for instance by the housing itself, so as not to rotate. The spring restoring the latch member to its normal rest position may then be arranged around the latch tail acting between the abutment member and a shoulder on the latch tail. Clearly the intermediate member need not be a solid block but could be of pressed sheet material and/or in more than one piece.

For a better understanding of the invention, an example will now be described with reference to the accompanying drawings, in which: Fig. 1 is a diagram of a prior latch arrangement, already referred to; and Fig. 2 shows a view on a latch mechanism representing an embodiment of the invention, with the cover removed.

Fig.l shows an embodiment of the invention and represents the rest position of the latch in use. The latch in question is the usual planar-format latch mechanism for a door, with a latch head 3 emerging from the housing generally designated 10 to engage a striker plate in a door frame to the right in Fig.l. The latch member 1 consists of the asymmetrical head 3 and a rodshaped tail 2 and is arranged for sliding movement in its axial direction in corresponding holes in a block 12 and in the front plate of the casing 10. The tail 2 has a stop 4 to be acted on by either a follower 31 of the handle mechanism 30 described below or the lug of a cylinder lock which in use would be mounted in the aperture 20. A return spring 17 is provided for restoring the latch member 1 to its rest position when pressure on the door handle or key is released.

As is apparent, the latch mechanism in this example is of the type known as a deadlocking nightlatch, which is openable from the outside only by a key and from the inside also, or alternatively, by a handle; the latch cannot be opened merely by pushing back the latch member. The mechanism generally denoted 30 for opening the door using a handle consists of the follower 31 which pivots in the casing 10 on a journal 32 and engages a bushing 34 likewise mounted in the casing by means of interengaging cogs 33. The bushing 34 has the usual square hole for insertion of a square rod to which the handle is attached.

The latch also includes a deadlocking mechanism given the reference 40. This deadlock includes a first lever 41 pivoted on a journal 42 fixed in the housing and having a shoulder 41a which in the rest position (pivoted fully clockwise) prevents the stop 4 of the latch member from retreating into the casing. The lever 41 has a lug 43 co-operating with a cam surface of the follower 31 in such a way that the lever 41 is rotated and its shoulder 41a is out of the path of the stop 4 before the follower 31 pushes the stop 4 against the shoulder 41a. A restoring spring 45 urges the lever 41 into the stop position.

The lock region likewise has a lever arrangement 50 constituted so that the first lever 41 is swung out of the way of the stop 4 before the lug of the cylinder lock, mentioned above, starts to urge the stop 4 against the shoulder 41a.

In accordance with the invention, although the tail 2 of the latch member 1 is fixed to the head 3, the spring 17 does not bear directly against the head but only via an intermediate block 5. This block has a central recess 6 penetrated by the tail 2, the floor of the recess, adjacent to the head 3, having an aperture 7 of smaller diameter than the recess itself and penetrated by a section 8 of the tail. This section 8 is of correspondingly smaller diameter than the main body of the tail 2 and is fixed, for instance by a pin (not shown) to the head 3. In the rest position of the latch, as shown, the shoulder 2a of the tail 2, formed where the main section passes into the narrower section 8, lies axially just inside the recess of the block 5; this assists in maintaining the alignment of the parts but is not strictly necessary for the function of the device.

A spring 9 is located between the shoulder 2a and the floor of the recess 6, in the clearance between the narrower portion 8 and the side wall of the recess.

In normal use the block 5 remains in abutment against the rear of the head 3 and functions as the rear section of the head; since it is somewhat larger than the head 3 proper, in the radial direction, it comes to rest in the forwards direction against the surround of the usually rectangular aperture in the face of the casing 10 through which the head 3 passes.

On withdrawal of the latch into the casing by the lock or the handle, however, the block 5 is carried with the head 3.

If the head 3 is to be reversed the face plate 11 is removed and the head 3 is manually withdrawn.

Since, in contrast to known designs, the tail is fixed to or integral with the head, it follows the head to the right in the drawing; this motion is allowed by the construction of the follower 31 and its connection to the handle mechanism 30 and lock 20, at least to the extent that the latch head 3 is clear of the housing 10. During this withdrawal the main body of the tail 2 travels into the recess 6, compressing the spring 9.

The latch head and tail can then be rotated a half revolution, by virtue of the circular mounting 12 and the circular sections in the recess 6 and aperture 7, so as to reverse the handedness of the mechanism. The latch head 3 is then released and springs back into the latch aperture, whereupon the mechanism is ready for use. For this operation no removal of the cover or of any auxiliary parts is necessary.

The lock shown also includes a ram generally denoted 50, which like the latch is reversible. The ram head 53 is urged out of the casing by a spring 67, to rotate the first lever 41 so that the shoulder 41a is clear of the stop 4. However, when the door is closed the striker plate pushes the ram 53 into the casing, whereupon the spring 45 pushes the lever 41 back into the dead-locking position. In the diagram the ram is shown partly retracted, whereas with the door open the right-hand flange of the abutment 55 would rest against the casing.

The ram head 53 can be reversed by pulling it out against the force of a spring 51 in a mechanism similar to that shown in Fig.l. This is an acceptable mechanism for the ram since there is no possibility of the ram head sticking in the striker plate.

Claims (8)

Claims:

1. A latch mechanism comprising a housing, a latch member mounted in the housing and consisting of a latch head and a latch tail axially fixed to the head, the latch member being adapted to be pulled back by a follower when this follower is actuated by a lock or a handle for the latch mechanism, the latch member and follower being so arranged that the latch head can be drawn out clear of the housing, and the latch member being mounted in the housing in such a way that, following this withdrawal, the head can be rotated to the reversed operating configuration; the mechanism further including an abutment member arranged to bear against the latch head in the direction of exit of the head from the housing up to a point where the abutment member stops against the housing, while the latch head can be drawn from this point clear of the housing as aforesaid.

2. A latch mechanism according to claim 1, in which the abutment member is in the form of a block of larger radial extent than the latch head, the block having an aperture slidingly penetrated by the tail of the latch.

3. A latch mechanism according to claim 2, in which the latch tail has a thinner front section and a thicker rear section, the thinner section passing through the aperture in the abutment block.

4. A latch mechanism according to any preceding claim and further including a restoring means for latch operation urging the latch head into its usual rest position, i.e. with the head protruding from the housing so as to engage a striker plate, this restoring means acting via the abutment member on the latch member.

5. A latch mechanism according to any preceding claim and including a restoring means associated with the reversal of the latch head, arranged operatively between the latch member and the abutment member so that the head can be pulled out of the housing against the action of this restoring means, rotated, and retracted into the housing.

6. A latch mechanism according to any preceding claim, in which the latch head and tail are securely fixed to or integral with each other, the latch member as a whole being rotatable about its axis in the housing.

7. A latch mechanism according to any of claims 1 to 5, in which the latch head and tail are rotatably attached to each other.

8. A latch mechanism substantially as described herein with reference to the attached Figure 2.