AU2022204017A1

AU2022204017A1 - A Lock

Info

Publication number: AU2022204017A1
Application number: AU2022204017A
Authority: AU
Inventors: Simon Butt; Frankie Ngan
Original assignee: TNBT Holdings Pty Ltd
Current assignee: TNBT Holdings Pty Ltd
Priority date: 2019-07-25
Filing date: 2022-06-09
Publication date: 2022-06-30
Also published as: AU2024205852A1; AU2020207888A1

Abstract

Disclosed herein is a lock.

Description

A LOCK

Technical field

The present disclosure generally relates to locks, and particularly but not exclusively to locks with hold back.

Background

Some locks, including night latches and some rim locks, have an outwardly biased ("sprung") latch bolt. An example of such a lock has a latch bolt operationally coupled to a rotatable handle for a user to retract the latch bolt. Examples of rotatable handles include but are not limited to a ) knob and a lever. The example lock has a self-latching function. When a door having the example lock attached closes, the outwardly biased latch can automatically enter a corresponding latch receiver on an adjacent structure to lock or latch the door, without the user having to operate the lock. This can result in lock out. Examples of adjacent structures include but are not limited to door jambs, walls, or posts. Examples of latch receivers include but are not limited to a latch keeper and a strike plate.

The self-latching function of the example lock is not always desired. The user may wish to temporarily disable the self-latching function, for example during a short period in which the user expects to pass many times through a doorway of the door, or during the day time for doors that are heavily used during the day. Some rim locks and night latches have a mode in which a ) latch bolt is held within a lock housing, which is known in the art as hold back. The user can activate hold back in the example lock by rotating the rotatable handle past a retracted latch bolt position to a latch bolt hold back position, at which the latch bolt is held within the housing. The user can cancel hold back by counter-rotating the rotatable handle.

Summary

Disclosed herein is a lock. The lock comprises a latch bolt biased in an outwardly direction and a latch bolt carriage operationally coupled thereto. The latch bolt carriage is movably mounted for movement thereof between a first position wherein the latch bolt is extended and a second position wherein the latch bolt is withdrawn. The lock comprises a latch bolt carriage actuation mechanism operationally coupled to the latch bolt carriage and operable to move the latch bolt carriage counter to the outwardly direction to the second position. The latch bolt carriage actuation mechanism and the latch bolt carriage cooperate to realisably retain the latch bolt carriage when in the second position. The lock comprises a carriage stop receiver configured to receive a carriage stop such that the carriage stop when so received blocks a movement of the latch bolt carriage into the second position.

In an embodiment, the carriage stop receiver is configured to releasably receive the carriage stop.

i In an embodiment, the carriage stop receiver is configured to receive a carriage stop in the form of an insert.

In an embodiment, the carriage stop receiver comprises a thread for engaging the carriage stop.

An embodiment comprises the carriage stop. The carriage stop may comprise a threaded shank.

An embodiment comprises a carriage stop comprising at least one of a clip and a push fit.

) An embodiment comprises a closure to which the carriage stop receiver is attached.

In an embodiment, the carriage stop receiver is integral with the closure.

In an embodiment, the latch bolt carriage actuation mechanism comprises a cam and the carriage comprises a cam follower. The cam may define a notch in which the cam follower is releasably retained when the latch bolt carriage is in the second position.

In an embodiment, the latch bolt carriage is movable between a first position and a third position, intermediate the first position and the second position, in which the latch bolt is withdrawn.

An embodiment comprises a handle and a lock cylinder at opposite lock sides.

An embodiment comprises a spindle.

In an embodiment, the handle is rotatably mounted.

In an embodiment, the latch bolt carriage is attached to the latch bolt.

Disclosed herein is a lock. The lock comprises a latch bolt biased in an outwardly direction and a latch bolt carriage operationally coupled thereto, wherein the latch bolt carriage is movably mounted for movement thereof between a first position wherein the latch bolt is extended and a second position wherein the latch bolt is withdrawn. The lock comprises a latch bolt carriage actuation mechanism operationally coupled to the latch bolt carriage and operable to move the latch bolt carriage counter to the outwardly direction to the second position, wherein the latch bolt carriage actuation mechanism and the latch bolt carriage cooperate to releasably retain the latch bolt carriage when in the second position. The lock comprises a carriage stop movable to a carriage stop position and when so at the carriage stop position is arranged to block a movement of the latch bolt carriage into the second position.

In an embodiment, the carriage stop is movable between the carriage stop position and another ; carriage stop position whereat the carriage stop is not arranged to block the movement of the latch bolt carriage into the second position.

In an embodiment, the carriage stop is slidable to the carriage stop position.

In an embodiment, the carriage stop can be rotated into the carriage stop position.

In an embodiment, the latch bolt carriage actuation mechanism comprises a cam and the carriage ) comprises a cam follower.

In an embodiment, the cam defines a notch in which the cam follower is releasably retained when the latch bolt carriage is in the second position.

In an embodiment, the latch bolt carriage is movable between the first position and a third position, intermediate the first position and second position, in which the latch bolt is withdrawn.

An embodiment comprises a handle and a lock cylinder at opposite lock sides .

An embodiment comprises a spindle.

In an embodiment, the handle is rotatably mounted.

Any of the various features of each of the above disclosures, and of the various features of the embodiments described below, can be combined as suitable and desired.

Brief description of the figures

Embodiments will now be described by way of example only with reference to the accompanying figures in which:

Figure 1 shows a plan view of an embodiment of a lock.

Figure 2 shows an isometric view of the lock of figure 1.

Figure 3 shows a right hand side elevational view of the lock of figure 1.

Figure 4 shows a front elevational view of the lock of figure 1.

Figure 5 shows a left hand side elevational view of the lock of figure 1.

Figure 6 shows a back elevational view of the lock of figure 1, with an example mounting plate at the back face.

Figure 7 shows an exploded view of the lock of figure 1, and the example mounting plate, and an example of a lock cylinder.

Figure 8 shows a back isometric view of the lock of figure 1 with the back plate hidden, with a hold back disabling screw received by the lock of figure 1.

Figure 9 shows a back isometric view of the lock of figure 1 with the back plate removed, with the hold back disabling screw removed.

) Figure 10 shows a back elevational view of the lock of figure 1, with the hold back disabling screw received thereby.

Figure 11 shows a back elevational view of the lock of figure 1, with the hold back disabling screw shown in figure 10 removed.

Figure 12 show a back elevational view of the lock of figure 1, with the back plate 3 hidden, the hold back disabling screw received, and a further movement of a latch bolt carriage blocked by the hold back disabling screw.

Figure 13 shows a back elevational view of the lock of figure 1, with the back plate removed, the hold back disabling screw removed to enable the further movement of the latch bolt carriage into a hold back position.

Figure 14 shows a simplified back elevational view of the lock of figure 1, with a back plate and other parts removed to reveal a cam mounted within a lock housing.

Figure 15 shows a front elevational view of the cam of figure 14.

Figure 16 shows an rear exploded isometric view of another embodiment of a lock.

Figure 17 shows a front isometric exploded view of the lock of figure 16.

Figure 18 shows a back elevational view of the lock of figure 16 with the back plate hidden and with a lock bolt extended.

Figures 19 and 20 show respective rear isometric and rear elevational views of the lock of figure 16 with the back plate hidden and the lock bolt held back.

Figures 21 and 22 show respective rear isometric and back elevational views of the lock of figure 16 with the back plate hidden and the lock bolt prevented from moving into a ) hold back position.

Figure 23 shows a rear exploded isometric view of yet another embodiment of a lock.

Figure 24 shows a front isometric exploded view of the lock of figure 23.

Figure 25 shows a rear elevational view of the lock of figure 23 with the back plate hidden and with a lock bolt extended.

) Figures 26 and 27 show respective rear isometric and rear elevational views of the lock of figure 23 with the back plate hidden and the lock bolt held back.

Figures 28 and 29 show respective rear isometric and rear elevational views of the lock of figure 23 with the back plate hidden and the lock bolt prevented from moving into a hold back position.

3 Description of embodiments

Figures 1 to 6 show various external views of an embodiment of a lock in the form of a rim lock, specifically a night latch, the lock being generally indicated by the numeral 10. Figure 6 shows a rear view of the lock with amounting plate 12 attached to a lock housing 14. In use, the mounting plate is fastened to a face of a door and adjacent to the swingable edge thereof, and the lock 10 is fastened to the mounting plate 12. An alternative embodiment does not use a mounting plate, but does have lugs with through holes attached to the external corners of the housing 14 for door fasteners, for fastening the lock 10 to the door. The doors fasteners may be in the form of security screws, security bolts and nuts, or generally any suitable form of fastener.

Figure 7 shows an exploded view of the lock 10, with the mounting plate 12, and a lock cylinder 17 for enabling ingress. The lock 10 may or may not have lock cylinder 17. The lock 10 comprises a latch bolt 16 biased in an outwardly direction 28 by a biasing member 50 in the form of a compression spring. The outwardly direction is parallel to a rear face 30 of the lock 10 and towards one of two opposite sides 32, 35 of the lock 10. The compression spring is disposed in spring casing 58. The lock 10 comprises a latch bolt carriage 18 comprising a turned out end tag 62 to which is operationally coupled to the latch bolt 16. In the present embodiment, the latch bolt 16 is operationally coupled to the latch bolt carriage 18. Disposed within and attached to the housing 14 is at least one latch bolt carriage guide 80 in the form of rails that the latch bolt carriage 18 is disposed between, along which the latch bolt carriage 18 can travel. The spring extends between a wall 60 of the spring housing 58 and the end tag 62 of the latch bolt carriage 18. Figures 8 and 9 shows rear view of the lock 10 with a closure 40 in the form of a back plate unfastened and removed from the rear of the housing 14. Figure 10 and 11 show rear views of the lock 10 with the closure 40 fastened to the housing 14 with fasteners in the form of screws 42, 44. The latch bolt 16 is attached to the latch bolt carriage 18 with a fastener 19 in the form of a screw, however generally any suitable fastener such as a bolt or rivet may be used. A pin 46 3 penetrates the turned out tag end 62 and the latch bolt 16 adjacent the fastener 20 to prevent relative rotation. An embodiment may not comprise pin 26. The latch bolt carriage 18 is movably mounted for movement thereof between a first position wherein the latch bolt 16 is extended, shown in figures 10 and 11, and a second position, shown in figures 8 and 9, wherein the latch bolt 16 is withdrawn.

Operationally coupled to the latch bolt carriage 18 is a latch bolt carriage actuation mechanism 20, which comprises a cam 24 in the form of a cam plate that acts on a cam follower 56 of the carriage 18. The cam 24 is attached to the handle 64 and disposed within the lock housing 14. In this embodiment there are two cam followers 56 in the form of turned-out tags and the cam 24 can act on either of the two cam followers, allowing actuation of the latch bolt carriage 18 by 3 rotation of the cam 24 in either clockwise or counter clockwise directions. The latch bolt carriage actuation mechanism 20 is operable to move the latch bolt carriage 18 in a direction counter to the outwardly direction 28 to the second position, wherein the latch bolt carriage actuation mechanism 20 and the latch bolt carriage 18 cooperate to retain the latch bolt carriage 18 when in the second position. The spring 50 cannot move the carriage 18 outwardly when the carriage 18 is in the second position. When the latch bolt carriage 18 is so retained, the lock 10 is in a hold back mode.

The lock 10 comprises a carriage stop receiver 34 in the form of an internal threaded surface attached to the back plate 40 (in this but not all embodiments integral thereto) and configured to receive a carriage stop 36 in the form of an insert such that the shank of the carriage stop 36 when so received is arranged to block a movement of the latch bolt carriage 18 into the second position. The carriage stop 36 comprises a threaded shank for engaging the carriage stop receiver 34. The carriage stop 36 may take the form of a screw, or alternative a bolt, however in an alternative embodiment the carriage stop receiver defines a cavity for receiving a carriage stop in the form of a pin, the cavity being configured for a slip fit for facilitating insertion and removal of the pin. In these embodiments, the carriage stop receiver 34 is generally configured to releasably receive the carriage stop 36. Alternative carriage stops include a clip and a push fit, and alternative embodiments may be configured to receive such carriage stops. The lock carriage stop receiver 34 may generally be configured for any suitable carriage stop receiver. That is, a user may insert or remove the carriage stop 36 depending on whether the lock 10 is to be configured for allowing a user to place the lock 10 in a hold back mode. In an alternative embodiment, the carriage stop receiver 34 may be configured to permanently capture the carriage stop 36, for example it may be configured to receive a pin that is press fitted therein (an interference fit), or comprise a clip that permanently captures a carriage stop.

3 Figure 12 shows a rear elevational view of lock 10 with the closure 40 removed, revealing the lock's internals disposed within the housing 18. The carriage stop 36 is received by the carriage stop receiver 34 and so is positioned to interfere with the latch bolt carriage 18, in this embodiment the cam follower 56, when moved towards the second position. This prevents the latch bolt carriage 18 from being moved into the second position in which hold back mode is active. Figure 13 corresponds to figure 12, however the carriage stop 36 has been removed, and the latch bolt carriage 18 is at the second position, and so hold back mode is active.

The head of the carriage stop 36 is external of the lock, at the rear face 30 of the back plate 40 and so is user insertable or removable without opening the lock 10. Figure 10 shows the rear of the lock 10, with the carriage stop 36 penetrating the back plate 40 and the head of the carriage ) stop 36 at the rear face 30. The head of the carriage stop 36 is configured to receive a carriage stop attachment tool in the form of a screwdriver. Figure 11 shows the carriage stop 36 having been removed by a user using the carriage stop attachment tool.

A user can operate turn handle 64. By turning the handle 64, the latch bolt carriage 18 is moved inwardly away from the first position and so the latch bolt 16 is withdrawn. A user may wish to open a door without placing the lock 10 in hold back mode. When the latch bolt is withdrawn, but not inwardly moved to such an extent that the latch bolt carriage 18 has yet reached the second position, the latch bolt carriage 18 is at a position intermediate the first position and the second position. The intermediate position is designated as a third position. The user can turn the handle to move the latch bolt carriage 18 to the third position to open the door without engaging hold back. When the user releases the handle, the latch bolt carriage 18 and so the latch bolt 16 is moved outwardly by the biasing element 50, without further intervention by the user. Handle spindle 65, having a cylindrical form, is received by bearing surface 67 that defines a spindle receiving aperture 69 in the housing 14. Handle 64 passes through an aperture in the lock housing 14 and is attached to cam 24 by spin riveting, however attachment may be by a bracket and fasteners, rivets, screws or generally any suitable means. When the user releases handle 64, the latch bolt 16 is extended by the biasing force exerted by the spring 50 without the user being requires to turn the handle.

Retention (that is, holding back) of the latch bolt carriage 18 by the latch bolt carriage actuation mechanism 20 is now described in further detail. As best seen in figure figures 14 and 15, the cam 24 defines a notch 68 in an arcuate portion 70 thereof. The cam follower 56 is releasably retained in the notch 68 when the latch bolt carriage 18 is in the second position. This works as follows. When the latch bolt carriage 18 is moved in the outwardly direction 28, the cam 24 and ) the latch bolt carriage 18 jamb, preventing further clockwise rotation of the cam 24, and so outward movement of the cam follower 56 is stopped. The cam 24, however, can be rotated counterclockwise, moving the arcuate portion and the projecting end out of engagement with the cam follower 56. The notch 68 is only at one end of the arcuate portion 70 and so hold off can only be activated when the knob is rotated in one direction but not the other, but in an alternative embodiment there may be a second notch at the other side of the arcuate portion 70 so that hold off can be activated by rotation of the handle in either direction. In an alternative embodiment, a latch may be used instead of the notched cam 24, the latch being disengaged by another cam or linkage. Alternatively, separate cams may be used for actuating the latch bolt carriage 18 and the retention function. Gears, belts or linkages may alternatively comprise the latch bolt carriage ) actuation mechanism. Generally, any suitable latch bolt carriage actuation mechanism may be used.

The lock comprises handle 64 in the form of a knob and a lock cylinder 17 at opposite lock sides. A spindle 22 in the form of a flat bar is operationally coupled the handle, the lock cylinder 17 and another latch bolt carriage actuation mechanism comprising another cam for engaging the carriage 18, hidden from view. The cam 24 is spin riveted to the handle 64, however in other embodiments it may be threaded and engaged with a spindle engaged with the handle 64, or may be generally operationally coupled in generally any suitable way.. The latch bolt actuator mechanism 20 is user operated via handle 64. The action of the biasing member 50 on the latch bolt carriage 18 is transmitted by the latch bolt carriage actuation mechanism to the handle. In the locks neutral state, the latch bolt is extended.

The latch bolt carriage 18 comprises an elongated plate of metal comprising the cam follower 56 at one end of the plate of metal and the end tag 62 at the other end of the plate of metal. The cam follower 56 and the end tag 62 are out of the plane of the body 76 of the latch bolt carriage

18. The latch bolt carriage is die cast, however it alternatively may be formed by punching and bending a sheet of metal.

In use, the mounting plate 12 is fastened to a face of a door - generally the inside face - using a fastener in the form of a screw or bolt, or generally any suitable form of fastening, for example a 3 rivet or adhesive. The lock 10, in this embodiment specifically the housing 14, and the mounting plate 12 are cooperatively configured for fastening the housing 38 to the mounting plate 12. The housing 14 is configured to slidingly receive longitudinal tags 48 and receive therein end flange 50. Mounting plate fasteners 52 penetrate the end 34 of the housing 14 and engage threads 54 at the end flange 50. The lock's internal assembly can be accessed by removing the mounting plate ) fasteners 52, slidingly disengage the tags 48, and separating the lock 10 from the mounting plate 12.

Figures 16 to 22 show various views of another embodiment of a lock 100 in the form of a rim lock, where parts similar or identical in form and/or function to those illustrated in figures 1 to 16 are similarly numbered. A mounting plate is omitted for clarity. Embodiments may or may 3 not have a mounting plate. The lock 100 comprises a latch bolt 16 biased in an outwardly direction and a latch bolt carriage 18 operationally coupled thereto. The latch bolt carriage 18 is movably mounted for movement thereof between a first position wherein the latch bolt is extended (figure 18) and a second position wherein the latch bolt is withdrawn (figures 19 and 20). The lock 100 comprises a latch bolt carriage actuation mechanism 20 operationally coupled ) to the latch bolt carriage 18 and operable to move the latch bolt carriage 18 counter to the outwardly direction to the second position shown in figures 21 and 22, wherein the latch bolt carriage actuation mechanism 20 and the latch bolt carriage 18 cooperate to releasably retain the latch bolt carriage 18 when in the second position. The spring cannot initiate outward return of the latch bolt carriage 18 when releasibly retained, in which case the lock 100 is in a hold back mode. The lock 100 comprises a carriage stop 136 movable to a carriage stop position (figure 21 and 22) and when so at the carriage stop position is arranged to block a movement of the latch bolt carriage 18 into the second position (figures 19 and 20). The carriage stop 136 contacts the carriage 18.

The latch bolt carriage actuation mechanism 20 comprises a cam 24 and the carriage 18 comprises a cam follower 56. The cam 24 defines a notch 68 in which the cam follower 56 is releasably retained when the latch bolt carriage is in the second position.

The carriage stop 136 is movable between the carriage stop position (figures 21 and 22) and another carriage stop position (figures 19,20) whereat the carriage stop 136 is not arranged to block the movement of the latch bolt carriage 18 into the second position (figures 19 and 20). The carriage stop is slidably mounted within the lock housing 14. The carriage stop is slidable to the carriage stop position from the other position, and from the other position to the carriage stop position as desired and suitable. The back plate requires removal before carriage stop 136 can be moved into and out of the carriage stop position, however in other embodiments the back plate may be configured to provide through access to the carriage stop 136.

The latch bolt carriage 18 is also movable to a third position shown in figures 21, 22 wherein the latch bolt 16 is withdrawn but hold back mode is not enabled.

Lock 100 also comprises another cam 102 for operational coupling to a lock cylinder. Generally, ) but not necessarily, the lock cylinder may be mounted within the door and present a keyhole outwardly. Rotation of the other cam 102 by operating the lock cylinder with a key can withdraw the lock to gain access from the exterior. A spindle in the form of a bar may couple the lock cylinder and the other cam 102, the other cam 102 may engage the lock cylinder, or the other cam 102 and the lock cylinder may be operationally couple in generally any suitable way.

S Figures 23 to 29 show various views of another embodiment of a lock 200 in the form of a rim lock, where parts similar or identical in form and/or function to those illustrated in figures 1 to 16 are similarly numbered. A mounting plate is omitted for clarity. Embodiments may or may not have a mounting plate. The lock 200 comprises a latch bolt 16 biased by a biasing member 50 in an outwardly direction and a latch bolt carriage 18 operationally coupled thereto. The latch ) bolt carriage 18 is movably mounted for movement thereof between a first position wherein the latch bolt is extended (figure 25 and a second position wherein the latch bolt is withdrawn (figures 26 and 27). The lock 200 comprises a latch bolt carriage actuation mechanism 20 operationally coupled to the latch bolt carriage 18 and operable to move the latch bolt carriage 18 counter to the outwardly direction to the second position shown in figures 26 and 27, wherein the latch bolt carriage actuation mechanism 20 and the latch bolt carriage 18 cooperate to releasably retain the latch bolt carriage 18 when in the second position. The spring cannot initiate outward return of the latch bolt carriage 18 when releasibly retained, in which case the lock 100 is in a hold back mode. The lock 200 comprises a carriage stop 236 movable to a carriage stop position (figure 28 and 29) and when so at the carriage stop position is arranged to block a movement of the latch bolt carriage 18 into the second position. The carriage stop 236 contacts the carriage 18.

The carriage stop 236 is movable between the carriage stop position (figures 28 and 29) and i another carriage stop position (figures 26,27) whereat the carriage stop 136 is not arranged to block the movement of the latch bolt carriage 18 into the second position. The carriage stop 236 is rotationally mounted within the lock housing 14. The carriage stop 236 is rotatable to the carriage stop position from the other position, and from the other position to the carriage stop position as desired and suitable.

) Lock 200 also comprises another cam 202 for operational coupling to a lock cylinder. Embodiments may or may not comprise a lock cylinder. Generally, but not necessarily, the lock cylinder may be mounted within the door and present a keyhole outwardly. Rotation of the other cam 202 by operating the lock cylinder with a key can withdraw the lock bolt 16 to gain access from the exterior. A spindle in the form of a bar may couple the lock cylinder and the other cam 202, the other cam 202 may engage the lock cylinder, or the other cam 202 and the lock cylinder may be operationally coupled in generally any suitable way.

Now that embodiments have been described, it will be appreciated that embodiments have the advantage of having a hold off mode that can be selectively blocked by a user. A locksmith can replace two sets of stock, one with hold off permanently activatible and another with hold off ) permanently blocked, with one set of stock. A user may block or unblock hold off after a lock is installed as the need arises.

Variations and/or modifications may be made to the embodiments described without departing from the spirit or ambit of the invention. For example, the latch bolt may be fastened to the carriage 18 with adhesive, and in yet another alternative embodiment the latch bolt 16 is integral with the carriage 18. The latch bolt carriage may comprise a single cam follower. The handle may take the form of a knob, lever or generally any suitable form. There may be a second lock cylinder on the other side of the lock, which may allow deadlocking. The lock may take the form of a mortice lock or generally any suitable form of lock. The handle may be rotationally mounted to the case using a ball bearing race assembly. The latch bolt may not be attached to the latch bolt carriage. The latch bolt may alternatively be operationally coupled to the latch bolt carriage by a lost-motion mechanism for an anti-carding function, for example. The latch bolt and latch bolt carriage may be operationally coupled by being integral with each other (e.g. a single piece of metal). The latch bolt may be operationally coupled to the latch bolt carriage 18 in generally any suitable way. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. Reference to a feature disclosed herein does not mean that all embodiments must include the feature.

Prior art, if any, described herein is not to be taken as an admission that the prior art forms part of the common general knowledge in any jurisdiction.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, that is to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

1. A lock with a hold back function, the lock comprising: a latch bolt biased in an outwardly direction and a latch bolt carriage operationally coupled thereto, wherein the latch bolt carriage is movably mounted for movement thereof between a first position wherein the latch bolt is extended, a second position wherein the latch bolt is withdrawn and held back, and a third position where the latch bolt is withdrawn but not held back; a latch bolt carriage actuation mechanism operationally coupled to the latch bolt carriage and operable to slidably move the latch bolt carriage counter to the outwardly direction to the second position in a linear manner, wherein the latch bolt carriage actuation mechanism and the latch bolt carriage cooperate to releasably retain the latch bolt carriage when in the second position; and a carriage stop receiver configured to receive a removable carriage stop such that the removable carriage stop when so received blocks a movement of the latch bolt carriage into the second position thereby disabling the hold back function.

2. A lock defined by claim 1 wherein the carriage stop receiver is configured to receive the carriage stop which is in the form of an insert.

3. A lock defined by any one of the preceding claims wherein the carriage stop receiver comprises a thread for engaging the carriage stop.

4. A lock defined by any one of the preceding claims comprising the carriage stop.

5. A lock defined by claim 4 wherein the carriage stop comprises a threaded shank.

6. A lock defined by any one of the claims 1 to 3 comprising the carriage stop which comprises at least one of a clip and a push fit.

7. A lock defined by any one of the preceding claims comprising a closure to which the carriage stop receiver is attached.

8. A lock defined by claim 7 wherein the carriage stop receivers integral with the closure.

9. A lock defined by any one of the preceding claims wherein the latch bolt carriage actuation mechanism comprises a cam and the carriage comprises a cam follower.

10. A lock defined by claim 9 wherein the cam defines a notch in which the cam follower is releasably retained when the latch bolt carriage is in the second position.

11. A lock defined by any one of the preceding claims wherein the third position intermediates the first position and the second position.

12. A lock defined by any one of the preceding claims comprising a handle and a lock cylinder at opposite lock sides.

13. A lock defined by claim 12 comprising a spindle.

14. A lock defined by either of claim 12 or 13 wherein the handle is rotatably mounted.

15. A lock defined by any one of the preceding claims wherein the latch bolt carriage is attached to the latch bolt.

16. A lock with a hold back function, the lock comprising: a latch bolt biased in an outwardly direction and a latch bolt carriage operationally coupled thereto, wherein the latch bolt carriage is movably mounted for movement thereof between a first position wherein the latch bolt is extended, a second position wherein the latch bolt is withdrawn and held back, and a third position where the latch bolt is withdrawn but not held back; a latch bolt carriage actuation mechanism operationally coupled to the latch bolt carriage and operable to slidably move the latch bolt carriage counter to the outwardly direction to the second position in a linear manner, wherein the latch bolt carriage o actuation mechanism and the latch bolt carriage cooperate to releasably retain the latch bolt carriage when in the second position; and a carriage stop adapted in use to disable the hold back function; wherein the carriage stop is movable to a carriage stop position and when so at the carriage stop position is arranged to block a movement of the latch bolt carriage into the second position.

17. A lock defined by claim 16 wherein the carriage stop is movable between the carriage stop position and another carriage stop position whereat the carriage stop is not arranged to block the movement of the latch bolt carriage into the second position.

18. A lock defined by either one of claim 16 and 17 wherein the carriage stop is slidable to o the carriage stop position.

19. A lock defined by either one of claim 16 and claim 17 wherein the carriage stop can be rotated into the carriage stop position.

20. A lock defined by any one of the claims 16 to 19 wherein the latch bolt carriage actuation mechanism comprises a cam and the carriage comprises a cam follower.

21. A lock defined by claim 20 wherein the cam defines a notch in which the cam follower is releasably retained when the latch bolt carriage is in the second position.

22. A lock defined by any one of the claims 16 to 21 wherein the third position intermediates the first position and second position.

23. A lock defined by any one of the claims 16 to 22 comprising a handle and a lock cylinder at opposite lock sides .

24. A lock defined by claim 23 comprising a spindle.

25. A lock defined by either one of claim 23 and claim 24 wherein the handle is rotatably mounted.