GB2185059A

GB2185059A - Multiple latch mechanism

Info

Publication number: GB2185059A
Application number: GB8528914A
Authority: GB
Inventors: John Rogers; Stephen John Weaver
Original assignee: ABT HARDWARE Ltd
Current assignee: ABT HARDWARE Ltd
Priority date: 1985-11-23
Filing date: 1985-11-23
Publication date: 1987-07-08
Also published as: GB2185059B; GB8528914D0

Abstract

A latch mechanism for a wing, such as a door (20) or window, comprises a primary unit (10) and at least one secondary unit (11, 12), the primary unit (10) and the or each secondary unit (11, 12) each having a latch (12, 14, 15) which is retractable by the operation of a latch operating means (17, 41) of the primary unit (10), an actuating mechanism (50, 51) operable when in a locking condition to prevent the latches (13, 14, 15) being retracted by the latch operating means (17, 41). As shown the actuating mechanism is key operated and functions to extend a dead bolt (26). Action to retract the deadbolt freeing an abutment from the latch operating member (41). <IMAGE>

Description

SPECIFICATION Latch mechanism This invention relates to a latch mechanism for a wing, such as a door or window, and more particularly to a latch mechanism comprising a primary unit and at least one secondary unit, the primary unit and the or each secondary unit having a latch which is retractable to permit the wing to be pivoted relative to a frame in which the wing is in use, mounted.

It is an object of the present invention to provide a new or improved latch mechanism.

According to one aspect of the invention we provide a latch mechanism comprising a primary unit and at least one secondary unit, the primary unit and the or each secondary unit having a latch which is retractable by operation of a latch operating means of the primary unit, an actuating mechanism operable when in a locking condition to prevent the latches being retracted by the latch operating means.

Thus unauthorised opening of the wing can be prevented by operation of the actuating mechanism to place the actuating mechanism in the locking condition.

The latch operating means may comprise a handle assembly including a handle and a spindle, the handle being operable by a user of the wing to rotate the spindle, rotational movement of the spindle being transmitted via a linkage to the or each secondary unit.

In one example, the spindle carries an engaging formation which, as the spindle is rotated is brought into engagement with a sliding member of the linkage whereby the rotational movement of the spindle is converted to a linear movement of the sliding member, which linear movement of the sliding member is received by the mechanism of the or each secondary unit, to cause retraction of the latch of the secondary unit or units.

When the actuating mechanism is in a locked condition, the, or another engaging formation carried by the spindle, may be engaged with a preventer of the actuating mechanism which prevents rotation of the spindle and hence retraction of the latches.

The latches of the primary and secondary unit or units may be resiliently biased to an extended position, the latch operating means being operable to move the latches against the resilient means to retract the latches.

The latches may each have a cam surface which is adapted to engage with a striker of the frame in which the wing is mounted as the wing closes so that the latches can be moved to a retracted position as the wing is closed in the frame without having to operate the latch operating means.

Where the latches are resiliently biased, when the wing is in its closed position in the frame, the latches may spring back under the force of their resilient means into an extended position in which the latches are each in engagement with a recess if an associated keeper of the frame to retain the wing in the closed position until the latches are retracted by the latch operating means.

The actuating mechanism which, when in a locked condition, prevents retraction of the latches, may also operate a locking member of a deadlock assembly which locking member is moved from a retracted position to an extended position in which the locking member may engage with a keeper of the frame.

The locking member may carry an abutment which is itself movable from a first position when the locking member is in its retracted position, to a second position as the locking member is moved to its extended position, the abutment being adapted to engage with a keeper in its second position.

The primary unit may include an auxiliary operating means which may be operated to retract the latch of the or each secondary unit only, the latch of the primary unit being retractable by an auxiliary actuating mechanism.

The auxiliary operating means may include a handle assembly having a handle and a further spindle.

The actuating mechanism which prevents retraction of the latches and the auxiliary actuating mechanism which retracts the latch of the primary unit only, may both be actuated by a common key. Where the actuating mechanism is entirely mechanical, the key may be rotated within a first arc of rotation to retract or extend the locking member, and rotated in a second arc of rotation, when the locking member is retracted, to retract the latch of the primary unit only.

The latch operating means may be operated from one side of the wing along with the actuating mechanism and the auxiliary operating means and actuating mechanism and auxiliary actuating mechanism may be operated from the other side of the wing.

Thus where the wing is for example an outside door, the one side of the door may be inside, to enable a user of the latch mechanism to retract all of the latches with the operating means, provided that the actuating mechanism is not in its locked condition to open the door, and the other side of the door may be outside to enable the user to open the door only by retracting the latch of the primary unit with the auxiliary actuating mechanism, and retracting the latch of the or each secondary unit with the auxiliary operat ing means, and only when the actuating mechanism is not in its locked condition. The actuating mechanism may be operated from inside and outside the door.

Where the latch mechanism is for a back door application, the operating mechanism may be operated from both sides of the door and the actuating mechanism may also be actuated from the inside or the inside and outside of the door. This may be achieved as the spindle of the operating means may extend from both sides of the door and a handle may be provided on each side of the door.

Where the latch mechanism is for a front door application, the spindle of the operating means may only extend from the inside of the door and the spindle of the auxiliary operating means may extend from the other side of the door. Thus for a front door application the axes of rotation of the spindles of the operating means and the auxiliary operating means may be spaced from one another.

The primary unit and the or each secondary may comprise a housing, the latch, and any locking member, extending from one side of the housing in a first direction, and the linkage or linkages for the or each secondary unit may extend from the housing of the primary unit in a second direction transverse to the first direction.

The housings may be mounted in a door so that the latches extends from the edge of the door.

The secondary unit or at least one of the secondary units may comprise a snib device which is operated as the latch of the secondary unit springs back to its extended position when the wing is closed, to prevent the latch being retracted against the resilient means until the operating means, or the auxiliary operating means, is operated.

The snib device may include a probe which is resiliently biased outwardly of the wing along with the latch, but is prevented from moving to an extended position for example by means of a keeper of the frame in which the wing is mounted, when the wing is closed, but causes a locking arm to move to a position in which retraction of the latch is prevented.

Preferably where two or more secondary units are provided, each secondary units are provided, each secondary unift has such a snib device.

The or each secondary unit may comprise means to convert the linear movement of the linkage from the primary unit, to a movement to retract the latch against the auxiliary means. In one example, the linear movement of the linkage is converted into a rotary movement of a cam follower which is engageable with the latch so that the rotary movement of the follower causes retraction of the latch, regardless of the condition of the snib device.

The invention will now be described with the aid of the accompanying drawings in which: Figure 1 is an exploded perspective view of a primary unit of a latch mechanism in accordance with the invention.

Figure 2 is a side view of the unit of Fig. 1 shown assembled, with part of the housing omitted for clarity.

Figure 3 is an exploded perspective enlarged detail of the deadlock assembly of the latch mechanism of Figs. 1 and 2.

Figure 4 is a view similar to Fig. 2 but showing a secondary unit.

Figure 5 is a side view through a wing of a latch mechanism in accordance with the invention having a primary unit and two secondary units.

Referring first to Fig. 5 of the drawings, a latch mechanism comprises a primary unit 10 and two secondary units 11,12, the primary unit 10 and each of the secondary units having a latch 13,14,15, respectively. The latches 13,14,15, are retractable by a latch operating means which will be described hereinafter in detail, the latch operating means including a handle assembly comprising a handle 16 which when operated rotates a spindle 17 on which the handle 16 is mounted.

The secondary units 11,12, are connected to the primary unit 10 by a linkage 18 which in the present example, comprises a pair of wire rods 19a,19b. Rotational movement of the spindle 17 is converted within the primary unit 10, to a linear movement of the wire rods 19a.19b, which linear movement is transmitted to the secondary units 11,12, to retract the latches 14,15.

The latch mechanism is mounted inside a wing such as a door 20 so that the latches 13,14,15, each extend from an edge 21 of the door, the latches 13,14,15, when the door 20 is closed in a frame in which the door is mounted, engaging with keepers mounted on the frame to prevent opening of the door 20 until the latches 13,14,15, are retracted.

The door 20 or other wing is pivoted to the frame e.g. on hinges, at an opposite side to that on which the latch mechanism is provided.

The latches 13,14,15, each have a cam surface 22 provided by a striker plate which engages with the associated keeper to retract the latches 13,14,15, automatically as the door is closed without having to operate the latch operating means.

The latches 13,14,15, are each spring biased to their extended positions, and spring back as the door reaches its closed position in the frame, to engage within recesses of the associated keepers.

The primary unit 10 of the latch mechanism includes a deadlock assembly 25 having a locking member 26 which is extended or retracted by a key operated actuating mechanism, a keyhole in each side of the housing in the door 20, and in the handle assemblies, being indicated at 27 in Fig. 5.

Referring now to Figs. 1 and 2, the construction and operation of the primary unit 10 will now be described.

The primary unit 10 comprises a housing 28 fabricated in two parts 29,30, only part of housing part 30 being shown in Fig. 1, and housing part 30 being omitted altogether in Fig. 2, for clarity. The housing parts 29,30 are secured together by virtue of fixing posts 37 and 56b described hereinafter, which extend between the housing parts 29,30.

The housing 28 provides, in a side thereof, two openings 31,32, opening 31 receiving the latch 13, and opening 32 receiving the locking member 26. The latch 13 has a tail 33 with a stop 34, the tail 33 also providing an outwardly extending lug (not seen) which is received in a slot 35 of the housing part 29, to guide the latch 13 as the latch 13 slides between extended and retracted positions.

The latch 13 is spring biased to its extended position by a coil spring 36 received around a post 37 within the housing 28, one end 38 of the spring 36 engaging the latch 13, and the other end 39 of the spring 36 engaging a top wall 40 of the housing part 29.

The spindle 1 7 of the handle assembly is received by a first cam follower 41 of the primary unit, the cam follower 41 comprising part of the latch operating means mentioned above, and the cam follower 41 being mounted for rotation in openings 42 in each of the housing parts 29,30.

As the first cam follower 41 is rotated clockwise as seen in the drawings by the handle 16 through the spindle 17, a first engagement portion 43 will engage stop 34 of the latch tail 33 to retract the latch 13 against the force of the spring 36. When the handle 16 is released, the first cam follower 41 will be rotated anticlockwise as seen in the drawings by the spring 36.

The first cam follower has a second engagement portion 44 which is received in a slot 45 of a sliding member 46, the sliding member 46 being part of the linkage 18 and being attached to each of the wire rods 19a,19b.

The housing 28 mouths guides G (only seen in fig. 2) to guide the rods 19a,19b whilst the slider 46 has a pair of lugs 47a to 47b on each side, which lugs are received in slots 48 of the housing parts 29,30 so that the sliding member 46 and the rods 19a,19b will slide linearly.

Thus the rotational movement of the first cam follower 41 is converted to a linear sliding movement of the rods 19a,19b, which linear movement is transmitted to the secondary units 11,12, described below.

As mentioned above, the primary unit 10 includes a deadlock assembly 25 which is key actuated. A key receiving barrel is shown schematically at 50, the barrel 50 being accessible through the key holes 27 in each of the housing parts 29,30 and in the door 20.

When an actuating part 51 of the barrel 50 is rotated in a first arc of rotation, the actuating part 51 engages the locking member 26, in a guide ,f, to move the locking member 26 to and from an extended position. The locking member 26 has a pair of lugs 55, one lug 55 projecting from each side of the locking member 26, which lugs 55 are received in guide slots 57 of the housing parts 29,30. Upon rotation of the actuating part 51,clockwise as seen in the drawings, when the body member 26 is retracted, an actuating arm 52 is engaged by the part 51 and is pushed upwardly by the part 51 engaging a stop 53 of the arm. Movement of the stop 53 is guided by a cam surface 54 of the locking member 26.

The actuating arm 52 is pivotable with respect to an actuating element 58 which is received on the first cam follower 41 and is rotatable about the same rotational axis as the first cam follower 41. As the actuating arm 52 moves upwardly, a lug 79 of the element 58 engages the stop 34 of latch tail 33 to retract the latch 13.

The arm 52 and element 58 together with barrel 50, provide an auxiliary actuating mechanism which in the present example is operable with the same key as the actuating mechanism which operates the deadlock assembly.

Operation of the deadlock assembly 25 is described in more detail hereinafter with reference to Fig. 3. However, when the locking member 26 is in its extended position, an actuating member 56 will be moved against the force of a spring 56a (not shown in fig. 2) received around post 56b, by a second cam surface 54a of the body member 26 into engagement with a third engagement portion 60 of the first cam follower 41 to prevent rotation of the cam follower 41 by the handle 16, to retract the latches 13,14,15. When the body member 26 is retracted, the actuating member 56 will disengage the portion 60 of the cam follower 41, as the spring 56a will urge the member 56 downwardly into engagement with cam surface 54a.

When the sliding member 46 moves linearly, the latches 14,15, of the secondary units 11,12, may be retracted. The slider 46 may be thus moved by an auxiliary operating means which will now be described.

The auxiliary operating means includes a second cam follower 61 which is pivotable in openings 62 in the housings parts 29,30, the second cam follower being engageable by a second spindle 63 (see Fig. 5) and is thus rotatable by a handle 64 of a further handle mechanism mounted on the door 20.

When the second cam follower 61 is rotated, a first engagement portion 65 thereof which engages an abutment surface 66 of sliding member 46, moves the sliding member 46 to retract the latches 14,15. However, the cam follower 61 cannot retract latch 13 of the primary unit 10. The actuating arm 52 and actuating element 58 of the auxiliary actuating mechanism does however enable the latch 13 to be retracted with a key, as described above.

However the latches 14,15, cannot be retracted until latch 13 is retracted by virtue of a preventer of the actuating mechanism.

The preventer includes a locking arm 69 which is rotatable in the housing by lugs 70 which are received in openings 71 in the housing parts 29,30. The locking arm 69 is spring biased in a clockwise sense as seen in the drawings by a coil spring 72 which is received around post 37. The spring 72 has a first end 73 which engages the locking arm 69, and the other end 74 of the spring 72, like spring 36, engages the top wall 40 of the housing part 29.

The locking arm 69 has an abutment part 76 which is biased by spring 72 into engagement with a second engagement portion 77 of the second cam follower 61, to prevent the cam follower 61 being rotated clockwise as seen in the drawings, to retract latches 14,15.

However a second abutment 78 of the locking arm 69 is engageable by the first engagement portion 43 of the first cam follower 41 when the first cam follower 41 is rotated, again in a clockwise sense as seen in the drawings. Thus when the operating means is operated to retract latch 13 as described above, the abutment 76 is moved against the force of spring 72 by portion 43 to permit the second cam follower 61 to rotate, to permit the sliding member 46 to slide.

When the auxiliary operating means is operated i.e. the second cam follower 61 is rotated by handle 64, the abutment 76 will prevent the second cam follower 61 rotating. If however the latch 13 is first retracted by using the key to rotate actuating member 58, the lug 79 of the actuating member 58 will engage the second abutment 78 of the locking arm 69 to disengage the abutment 76 from the second engaging formation 77, thus permitting the cam follower 61 to rotate.

Thus in order to retract all of the latches 13,14,15, using the auxiliary operating mechanism, the latch 13 has first to be retracted with a key and then the latches 14,15, can be retracted by operating handle 64.

A further coil spring 80 is received around the second cam follower 61, one end 81 of the coil spring being hooked around an adjacent lug 47a of sliding member 46, and the other end 82 of the spring 80 engaging part of housing part 29, such as the adjacent guide G hereinbefore mentioned for the wire rod 19a so that the slider 46 is normally biased upwardly.

Referring now to Fig. 3, the construction and operation of the deadlock assembly 25 will be described.

The locking member 26 is made of a plurality of laminae 90-94 for convenience of manufacture, but could be made as a casting or solid fabrication if required.

The laminae 90-94 are identical but different from the laminae 90-93 which are all identical to each other. The laminae 90-94 are connected together by rivets 95 in holes 96, some rivets 95 not being shown.

Between the laminae 90 and 94 the laminae 91-93 define a recess R in which a locking element 97 is mounted, the locking element 97 being pivotable with respect to the locking member 26 about pivot axis 98 by virtue of a roll pin 99 received in openings 100 in the laminae 90,94.

The locking element 97 is itself laminated and provides at the end remote from the pivot axis 98, an abutment 101 which is hookshaped. When the locking member 26 is in its retracted position in which substantially all the locking member 26 is contained within the housing 28 of the primary unit, the locking element 97 will fall under gravity so that the abutment 101 is contained wholly within the recess R so as not to interfere with movement of the locking member 26 to the extended position.

However, as the locking member 26 moves to its extended position, a first co-operating formation 102 of the locking element 97 will engage a second co-operating formation 103 of the housing provided by the periphery of opening 32 in housing 28. This will cause the locking element 97 to pivot about axis 98 so that the abutment 101 will move upwardly as seen in the drawings to engage behind a keeper of the frame.

When the locking member 26 is retracted again, the first and second co-operating formations 101,102 will disengage and the locking element 97 will move under gravity about pivot 98 so that the abutment 101 will be contained wholly within the recess R again and will prevent retraction of the locking member 26.

It can be seen from Fig. 3 that the lugs 55 which guide the locking member 26 as the locking member 26 slides, are provided by the ends of a pin 106 which extend through the laminae 90-94.

A locating member 108 is provided as is well known in the art, which is biased downwardly by a spring (not shown) although constrained to move in the guide f provided by the locking member 26. Locating member 108 has lugs 109 which co-operate with slots 110 of the housing parts 29,30 to prevent the locking member 26 being forcibly retracted without the use of a key The actuating part 51 of the barrel 50 moves the locating member 108 against a spring (not shown) to enable the lugs 109 of the locating member 108 to move along the slots 110.

Referring now to Fig. 4, the construction and operation of one of the secondary units will be described, although it will be appreci ated that the construction and operation of unit 12 is similar but oppositely handed.

The wire rod 19a is received in guides 112 mounted in a housing 113. The wire rod 19a has a kink 114 which is received in a bifurcated part 115 of a cam follower 116, and is retained by a pin 117. The follower 116 is rotatable by means of lugs 118 received in corresponding openings in the housing 118 and has a first engagement portion 119.

The latch 14 has a latch tail 120 with a stop 121 and is biased by a spring 122 received around a post 123 to an extended position. As the cam follower 116 rotates, in a clockwise sense as seen in the drawings, the first engagement portion 119 will engage stop 121 to retract the latch 14 against the force of spring 122.

However a snib device is provided to prevent the latch 14 being retracted when a probe 130 is not in an extended position.

The probe 30 is mounted to slide with latch 14 as the latch 14 is retracted, by virtue of a retainer plate 131 which is part of the latch tail 120. The probe 130 carries a lug 135 which is received in an opening 136 of a locking arm, the arm 137 being pivoted by virtue of lugs 138 received in corresponding openings in the housing 113.

The opening 136 is joggled as seen at 139, and the lug 135 is generally square, and as shown is received in a square part of the opening 136.

As the door 10 in which the latch mechanism is mounted is closed, the cam surface of latch 14 will engage the keeper to retract latch 14 and hence probe 130. The abutment 135 of probe 130 will move along the opening 136 in Ithe locking arm 137. As the door 20 reaches its closed position, the latch 14 will spring outwardly due to spring 121, to engage in a recess in the keeper. No recess is however provided for probe 130 which will thus stay retracted. The locking arm 137 can thus pivot anti-clockwise as seen in the drawings under gravity about lugs 138, so that an abutment 140 will engage the stop 121 to prevent the latch 14 being retracted. An undercut not seen in the drawings is provided in the locking arm 137 to accommodate the tip of the first engagement portion 119 of the cam follower 116 as the locking arm 137 moves anti-clockwise.

Thus the latch 14 cannot be retracted until the operating mechanism or auxiliary operating mechanism of the primary unit 10 is operated to move rod 19a. In this event, the tip of the first engagement portion 119 of the cam follower 116 will dislodge the locking arm 137 upwardly as follower 116 initially rotates to permit the latch 14 to be retracted. When the handle 16, 64, of the operating means or aux iliary operating means is released, to permit the latch 14 to move outwardly when the door is opened, the probe 130 can again move to its extended position as shown in Fig. 4, and due to the joggled configuration of the opening 136, the locking arm 137 will be moved upwardly to permit the lug 135 of the probe 130 to be again received in the corresponding square part of the opening 136.

Operation of the latch mechanism will now be described.

Referring again to Fig. 5, the latch mechanism is specificaily intended for a front door application. In this event, the handle 16 of the operating means will be located on the inside of the door 20, whilst the handle 64 of the auxiliary operating means will be located on the outside of the door 20.

It can be seen that the axes of rotation of the spindle 17,63, are thus spaced from one another.

From the inside, a user of the door may operate handle 16 to retract each of the latches 13,14, and 15 to open the door, and, using a suitable key, can operate the deadlock assembly 25 to move the locking member 26 to its extended position as shown in order to deadlock the door 20.

When the locking member 26 is extended, the handle 16 cannot then be operated to retract any of the latches 13,14,15, thus providing protection against forced entry.

From the outside, the door 20 can only be opened if a user has a key, because the handle 64 can only be used to retract the latches 14 and 15.

However a user needs to retract the latch 13 using the key, from the outside, before he can operate handle 64 in order to retract the latches 14 and 15. This is of course assuming that the key has already been used to retract the locking member 26 if extended. Again, if the locking member 26 is extended, the handle 64 cannot be rotated to retract the latches 14 and 15, because the sliding member 46 within the primary unit 10 cannot slide because the first cam follower 41 is prevented from being rotated by the actuating mechanism.

The latches 14 and 15 cannot be forcibly retracted independently of the handle 67 because of the snib devices described and added protection is provided to forced entry by virtue of the abutment 101 provided on the locking element 97 mounted within the locking member 26 of the deadlock assembly 25.

If desired, the auxiliary operating means can be dispensed with, for example where the latch assembly is to be used for a back door operation. In this event the spindle 17 may extend entirely through the primary unit 10 and have a handle secured thereto at each side of the door 20.

In this event, each of the latches 13,14, and 15 can be retracted from both inside and outside the door, provided of course that the actuating mechanism is not in a locked condi tion i.e.the deadlock assembly 25 has not been actuated to extend the locking member 26, in which event none of the latches 13,14,15, can be retracted by operating the operating means.

Although as described, the invention has been applied to a wing comprising a door, the invention may be applied to a latch mechanism for any other wing, for example a window.

Various modifications made by made without departing from the scope of the invention.

For example, although as described, the actuating mechanism comprises a barrel 50 in which a conventional mechanical key is received, if desired an electronic type of lock could be substituted for the mechanical barrel 50 in which case an electronic key, suitably coded, may be used to operate the actuating mechanism.

Although as described, the latch mechanism has comprised two secondary units 11 and 12, if desired, only one, or more than two secondary units can be provided.

The detailed mechanical features of the primary 10 and secondary units 11, 12, described, can of course be modified significantly as will be apparent to those skilled in the art. For example, the latch tails 33 and 120 could be of alternative configurations.

The cam followers 41,61 and 116, and springs 36,71, 80 and 121 could be mounted in alternative positions and be of alternative configurations, and the housing 78,113, could be of entirely different configurations. The actuating mechanism may comprise additional or alternative parts to those described and an alternative deadlock assembly could be provided. Preferably however, the deadlock assembly is provided with an abutment 101 which can be moved between a first position in which the abutment 101 is contained wholly within the locking member 26 and an extended position in which the abutment can engage behind a keeper mounted on the wing frame, when the locking member 26 is in an extended position.

The invention disclosed in the foregoing description, in the following claims,or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or on any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A latch mechanism for a wing, the mechanism comprising a primary unit and at least one secondary unit, the primary unit and the or each secondary unit having a latch which is retractable by operation of a latch operating means of the primary unit, an actuating mechanism operable when in a locking condition to prevent the latches being retracted by the latch operating means.

2. A mechanism according to Claim 1 wherein the latch operating means comprises a handle assembly including a handle and a spindle, the handle being operable by a user of the wing to rotate the spindle, rotational movement of the spindle being transmitted via a linkage to the or each secondary unit.

3. A mechanism according to Claim 2 wherein the spindle carries an engaging formation which, as the spindle is rotated is brought into engagement with a sliding member of the linkage whereby the rotational movement of the spindle is converted to a linear movement of the sliding member, which linear movement of the sliding member is received by the mechanism of the or each secondary unit, to cause retraction of the latch of the secondary unit or units.

4. A mechanism according to Claim 3 wherein when the actuating mechanism is in a locked condition, the engaging formation carried by the spindle, is engaged with a preventer of the actuating mechanism which prevents rotation of the spindle and hence retraction of the latches.

5. A mechanism according to anyone of the preceding claims wherein the latches of the primary and secondary unit or units are resiliently biased to an extended position, the latch operating means being operable to move the latches against the resilient means to retract the latches.

6. A mechanism according to anyone of the preceding claims wherein the latches each have a cam surface which is adapted to engage with a striker of a frame in which the wing is mounted as the wing closes so that the latches can be moved to a retracted position as the wing is closed in the frame without having to operate the latch operating means.

7. A mechanism according to Claim 6 where appendent to Claim 5 wherein when the wing is in its closed position in the frame, the latches spring back under the force of their resilient means into an extended position in which the latches are each in engagement with a recess if an associated keeper of the frame to retain the wing in the closed position until the latches are retracted by the latch operating means.

8. A mechanism according to anyone of the preceding claims wherein the actuating mechanism which, when in a locked condition, prevents retraction of the latches, also operates a locking member of a deadlock assembly which locking member is moved from a retracted position to an extended position in which the locking member may engage with a keeper of a frame in which the wing is mounted.

9. A mechanism according to Claim 8 wherein the locking member carries an abutment which is itself movable from a first position when the locking member is in its retracted position, to a second position as the locking member is moved to its extended position, the abutment being adapted to engage with the keeper in its second position.

10. A mechanism according to anyone of the preceding claims wherein the primary unit includes an auxiliary operating means which is operable to retract the latch of the or each secondary unit only the latch of the primary unit being retractable by an auxiliary actuating mechanism.

11. A mechanism according to Claim 10 wherein the auxiliary operating means includes an auxiliary handle assembly having a handle and a further spindle.

12. A mechanism according to Claim 10 or Claim 11 wherein the actuating mechanism which prevents retraction of the latches and the auxiliary actuating mechanism which retracts the latch of the primary unit only, are both actuated by a common key.

13. A mechanism according to Claim 12 wherein the actuating mechanism is entirely mechanical, and the key is rotatable within a first arc of rotation to retract or extend the locking member, and is rotatable in a second arc of rotation, when the locking member is retracted, to retract the latch of the primary unit only.

14. A mechanism according to anyone of Claims 10 to 13 wherein the latch operating means is operable from one side of the wing along with the actuating mechanism, and the auxiliary operating means and the auxiliary actuating mechanism being operatable from the other side of the wing.

15. A mechanism according to Claim 14 wherein the wing is a door, the one side of the door being the inside, a user of the latch mechanism being able to retract all of the latches with the operating means from the inside provided that the actuating mechanism is not in its locked condition, to open the door, and the other side of the door is the outside the user being able to open the door only by retracting the latch of the primary unit with the auxiliary actuating mechanism, and retracting the latch of the or each secondary unit with the auxiliary operating means, and only when the actuating mechanism is not in its locked condition.

16. A mechanism according to Claim 15 wherein the actuating mechanism is operable from inside and outside the door.

17. A mechanism according to anyone of Claims 1 to 14 wherein the operating means is operable from both sides of the door and the actuating mechanism is also operable from both sides of the door.

18. A mechanism according to anyone of Claims 10 to 1 7 wherein appendent to Claim 10 wherein the axes of rotation of the operating means and the auxiliary operating means are spaced from one another.

19. A mechanism according to anyone of Claims 2 to 18 where appendent to Claim 2 wherein the primary unit and the or each secondary comprise a housing, the latch, and any locking member, extending from one side of the housing in a first direction, and the linkage or linkages for the or each secondary unit extending from the housing of the primary unit in a second direction transverse to the first direction.

20. A mechanism according to Claim 19 wherein the housings are mounted in a door so that the latches extend from an edge of the door.

21. A mechanism according to anyone of Claims 5 to 20 where appendent to Claim 5 wherein the secondary unit or at least one of the secondary units comprises a snib device which is operated as the latch of the secondary unit springs back to its extended position when the wing is closed, to prevent the latch being retracted against the resilient means until the operating means, or the auxiliary operating means, where provided, is operated.

22. A mechanism according to Claim 21 wherein the snib device includes a probe which is resiliently biased outwardly of the wing along with the latch, but is prevented from moving to an extended position when the wing is closed, but causes a locking arm to move to a position in which retraction of the latch is prevented.

23. A mechanism according to anyone of Claims 2 to 22 where appendent to Claim 2 wherein the or each secondary unit comprises means to convert the linear movement of the linkage from the primary unit, to a movement to retract the latch.

24. A mechanism according to Claim 23 wherein the linear movement of the linkage is converted into a rotary movement of a cam follower which is engageable with the latch so that the rotary movement of the follower causes retraction of the latch.

25. A latch mechanism substantially as hereinafter described with reference to and as shown in the accompanying drawings.