AU2014274550B1

AU2014274550B1 - Self-latching micro-switch box for use with fire doors

Info

Publication number: AU2014274550B1
Application number: AU2014274550A
Authority: AU
Inventors: Trevor David Leisk
Original assignee: Ams Australia Pty Ltd
Current assignee: Ams Australia Pty Ltd
Priority date: 2005-07-21
Filing date: 2014-12-04
Publication date: 2015-11-12
Anticipated expiration: 2025-07-21
Also published as: AU2017202920A1; AU2013216589A1; AU2013216589B2; AU2011201414B2; AU2017202920A8; AU2011201414A1; AU2017202920B2; AU2015252030A1

Abstract

Abstract. A micro-switch box that enables an open door, having the square bolt of its lock extended, to be closed, has the open front of the box structure (101, 102, 104, 124, and 107) in which a micro-switch is mounted closed by a front plate (200). A tongue member (202) extends from one side edge (212) of the front plate. The box structure and its front plate can slide in a channel formed by a channel plate (220) and the cover plate component (151) of a cover member (150). The cover member has a face plate component (110) for mounting the micro-switch box in a door frame. An aperture (152) in the cover member permits the end of the lock bolt and the tongue member (202) to move freely rearwardly. Biasing springs (206, 218) hold the front plate (200) adjacent to the face plate component (110) under normal use conditions. When an open door with an extended lock bolt is closed, the end of the lock bolt contacts an arcuate surface (213) of the tongue member (202), thus applying a force to the tongue member which moves the tongue member, and all the components attached to it, rearwardly. The biasing springs (206, 218) return the front plate (200) to its normal use position, adjacent to the face plate component (110), when the end of the lock bolt has passed over the front face of the displaced front plate (200) and has become aligned with the aperture (201) in the front plate. Dead latching of the lock bolt is among the additional features that may be included with the micro switch box.

Description

Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION (Patent of Addition) Name of applicant/Nominated Person: Trevor David Leisk Address for Service: Davies Collison Cave, Patent Attorneys 1 Nicholson Street, MELBOURNE, Victoria, 3000. Invention title: "Self-latching micro-switch box for fire doors" Details of the Patent of the Main Invention: Australian Patent No. 2005270713. The following statement is a full description of this invention, including the best method of performing it known to me: 2 Technical field. This invention concerns micro-switch boxes. More particularly, it concerns a modified micro-switch box of a type that is described and claimed in the specification of my Australian patent No. 2005270713. The 5 modified micro-switch box of the present invention was developed for use with, inter alia, an electronic unit for monitoring the lock status of a door that has a square bolt lock, and that is also a fire door. However, the modified micro-switch box of the present invention will be useful in other door locking arrangements. The present invention also encompasses a io door lock monitoring and entry control unit that is constructed using the modified micro-switch box. Preliminary note. In this specification, including the claims, terms implying a direction or a is relative position, such as "top", "bottom", "front", "back", "side", "horizontally", "vertically", "rearwardly", "upwardly", and the like, will be used in the sense that these terms have when the unit or component being referred to is positioned as shown in Figures 1, 2 and 3 of the accompanying drawings. Also, in this specification, including the claims, the term "square bolt" of 20 a lock is the normal locksmith term meaning a bolt with at least the end thereof that extends from the lock having a cross-section that is rectangular, even if the rectangular cross-section is not a square cross section. 25 Background to the invention. As noted in the specification of my Australian patent No. 2005270713, in recent years, organisations that have rooms in which sensitive, classified, secret (including trade secret and top secret) information and/or equipment is stored or used, have become aware that (a) special locking 30 arrangements are required to ensure that a door into such a room can be securely locked, and (b) there needs to be some way of monitoring when 3 the door into such a room is no longer locked and when the door has been opened. Accordingly, electrical and electronic circuits have been developed to detect when the extended bolt of a lock has been withdrawn into the body of the lock (that is, the lock bolt no longer locks its associated 5 door) and/or a door has been opened. Such monitoring circuits usually include a mechanism for generating an alarm signal when the door to a secure room has been unlocked, and/or opened, by an unauthorised person. io Most companies that provide secure locking arrangements have developed their own special "end of line" for use with such electrical circuits. The "end of line" is understood to be an assembly of electronic components so connected together that they provide a signal to a monitoring location when specified events occur, or specified situations exist. (The specified is situation will normally include "door locked' and "door unlocked" signals.) Each company that has developed an "end of line" regards it as a trade secret, the details of which are not to be made public. The specification of my Australian patent No. 2005270713 describes a 20 micro-switch box in which a micro-switch and an "end-of-line" of a door lock monitoring arrangement for a high security room (a "Type 1 secure room") can be mounted. That micro-switch box is constructed to be strong, and to be mounted within a door frame, where access to the micro-switch box can occur only when the door that is being monitored is open. 25 That micro-switch box has been used, successfully, since shortly after its introduction to the security market. However, recent assessments of the doors to Australian Government T1 secure rooms that are required to be both security doors and fire doors has shown that there could be a 30 problem when the micro-switch box is used with such a door, because doors to T1 secure rooms usually have locks that have a square bolt.

4 Fire regulations do not permit fire doors to have locks with a square bolt. The concern that the fire door approval authorities have is that, in an emergency, when a fire door has been opened to allow persons inside a 5 room to leave that room, and when the last person has left the room, it is possible that the bolt of the lock of that door will have been extended again before the door is closed, or that the bolt (accidentally) will have been at least partially extended again and will not retain its full retraction into the lock. Therefore, when the last person to leave the room swings the door io to close it, the projecting end of the square bolt will contact the edge of the face plate on the door frame. The square bolt will not automatically retract. So the door will not be properly closed and air (with its combustion assisting oxygen component) and flames can pass through the gap between the door frame and the edge of the "almost closed" door. In this situation, 15 the fire resistance of the door is lost. If the door is at the entrance to a secure room or location and is fitted with a micro-switch box, the inability to fully close the door also means that the security of the entrance has been compromised. 20 It is now common practice for the door to a secure room to be equipped with two locks that can be unlocked simultaneously by the movement of a single handle (for example, using the arrangement described in the specification of my Australian patent No. 2010202397. That arrangement 25 has become widely adopted because it is convenient for one of the locks to be a conventional latch lock, for access to the room during normal daytime working hours, and for the other lock - possibly a night security lock - to have a square bolt, the position of which is monitored by circuitry connected to a micro-switch in a micro-switch box of the type 30 described in the specification of my Australian patent No. 2005270713. For the reason given above, such doors to secure rooms cannot be given 5 an approved fire rating. Until recently, most certifying fire authorities have allowed a security door that is also constructed to be a fire door, with a lock that has a square bolt, 5 to be certified as a "non-tagged fire door". However, a number of fire authorities will no longer issue this form of certification, and it is expected that, very soon, such certification will no longer be available anywhere in Australia. io Disclosure of the invention. The present invention is a modified micro-switch box for use with circuitry for monitoring the state of the lock of a door, which circuitry includes a micro-switch, mounted in the micro-switch box, that is activated by the bolt of the lock. It is an objective of this modified micro-switch box to permit is an open door, having a lock with a square bolt, to be closed, and the micro-switch to be activated, notwithstanding that the bolt has not been fully retracted and its end projects from the lock. This objective is achieved by modifying the basic micro-switch box 20 configuration that is described and claimed in the specification of my Australian patent No. 2005270713. That basic micro-switch box has a top wall, a bottom wall, a back wall and two substantially planar side walls. It has a substantially rectangular open front, from the top and bottom walls of which respective flanges extend vertically. The basic micro-switch box 25 also has a micro-switch support plate extending from one of the side walls to the other side wall, on which either a plunger type micro-switch or a lever type micro-switch may be mounted. The modification is the provision of an arrangement that, when the micro 30 switch box has been installed in a door frame, causes the micro-switch support plate (and therefore the walls to which the support plate is 6 attached) to be moved rearwards, further into the door frame in which it is located, as the outer edge of the associated door (that is, the edge of the door that is remote from the door's hinges) reaches the door frame, if the square bolt of the lock of the door has been extended. To enable such 5 movement of the support plate, the flanges of the basic micro-switch box (that extend vertically from the top and bottom walls) are removed and a "front plate" (my term for this integer) that extends across (and thus closes) the open front of the basic micro-switch box is added. This front plate has a tongue member that extends beyond one of the side walls. Asthedooris 10 closed, the (at least partially) extended square bolt contacts the tongue member and forces it (and thus the front plate) rearwards, to permit the end of the extended bolt to pass over the front plate until, when the door is fully closed, the front plate (and thus the micro-switch support plate) can return to its normal position, in which the plunger or lever of the micro-switch 15 that is mounted on the micro-switch support plate is again contacted and depressed by the extended bolt of the lock. In more detail, the modification of the basic micro-switch box comprises the replacement of the vertical flanges at the front of the basic micro 20 switch box by a vertical, elongate plate that, as noted above, I have called a "front plate" (which is the term for this component that will now continue to be used in this specification, including the claims). This front plate has a width that is substantially equal to the distance between the side walls of the basic micro-switch box. It has a length such that, in preferred 25 embodiments of the present invention, it extends over the entire space bounded by the top wall, the bottom wall and the two side walls, and projects above and below the top and bottom walls of the basic micro switch box. 30 This front plate has an aperture that is so positioned and dimensioned that, when the micro-switch box of the present invention is installed in a 7 door frame and is in use, when the associated secure door is closed normally (that is, with the bolt of its lock fully retracted) and is then locked, the bolt of the lock of the door passes freely through its aperture to activate (that is, to depress the plunger or lever of) the micro-switch 5 mounted on the micro-switch support plate. This front plate, as indicated above, also has a vertically elongate tongue member. This tongue member projects horizontally from one edge of the front plate, and has a substantially arcuate front surface; the centre of curvature the arcuate surface being a remote vertical line. 10 The structure comprising the front plate, the top wall, the bottom wall and the side walls is not rigidly attached to the door frame, but is supported for rearward and forward movement, within a channel formed by a cover member and a vertical plate (which I have called a "channel plate"). The is cover member comprises a conventional, planar, vertical face plate, from one edge of which a vertical planar cover plate extends rearwardly. The planes of the face plate component of the cover member and the cover plate component of the cover member are at right angles to each other. A single aperture that extends across the junction of the face plate 20 component of the cover member and the cover plate component of the cover member permits both the square bolt of the door lock and the tongue member of the front plate to be moved relative to the cover member without making contact with it. Respective optional (but preferred) horizontal plates will normally extend towards the channel 25 plate from the upper and lower edges of the cover plate component. A spring biasing arrangement, operatively associated with the channel plate, ensures that, during normal operation of the secure door, the front plate is biased to its normal position, in which the front plate is adjacent 30 to the face plate component of the cover member. Then, assuming the situation that 8 (1) there has been a need to rapidly evacuate the room to which access is through the secure door; (2) the door has been unlocked and opened to permit such evacuation; then 5 (3) the door is swung closed with the square bolt of its lock at least partially extended; when the end of the square bolt contacts the substantially arcuate surface of the tongue member, it applies a force to the tongue member that causes the tongue member (and thus the front plate and the components 10 of the micro-switch box that are attached to it) to move rearwardly in the channel formed by the channel plate and the cover plate, against the spring bias. Once the front plate has been moved rearwardly a distance such that the end of the square bolt can move over the front surface of the front plate, the closure of the door can continue until the end of the square is bolt has moved over the surface of the front plate and into the region of the aperture in the front plate. When this happens, (a) the end of the square bolt becomes aligned with the aperture in the front plate, and (b) the front plate is no longer held in its rearward position into which it has been forced. So the spring bias moves the front plate forwards to its normal position (and 20 the end of the square bolt essentially passes through the aperture in the front plate to depress the plunger or lever of the micro-switch to activate the micro-switch and generate the "door closed and locked" signal in the monitoring equipment). 25 Various forms of the spring biasing arrangement may be used. Thus, according to the present invention, there is provided a micro-switch box for installation in a door frame; said micro-switch box being for use with circuitry, including a micro-switch, that monitors the position of a square bolt 30 of a lock of an associated door that is mounted on said door frame; said micro-switch box comprising a chamber defined by a top wall, a bottom wall, 9 a substantially planar first side wall, a substantially planar second side wall, and a micro-switch support plate on which said micro-switch is to be mounted, said micro-switch support plate extending from said first side wall to said second side wall; the front of said chamber being closed by a vertical, 5 elongate front plate having a width substantially equal to the distance between said side walls and a length such that it extends over the entire front of said chamber; said micro-switch box being further characterised in that: (1) said front plate has an aperture; said aperture having dimensions 10 that permit the end portion of the bolt of said lock that projects from said lock, when said door is closed and said bolt is extended into the position it has when said door is locked, to pass through said aperture; (2) a vertically elongate tongue member projects horizontally from one 15 edge of said front plate; said tongue member having a substantially arcuate front surface; the centre of curvature said substantially arcuate surface being a remote vertical line; (3) said micro-switch box has an associated cover member comprising an elongate face plate component for attachment to said door 20 frame and a vertical cover plate component extending rearwardly at right angles from one edge of said face plate component; said cover member having a single cover member aperture that extends across the junction of said face plate component and said cover plate component; said cover member aperture being so dimensioned that 25 it permits both said end portion of said square bolt of said door lock and said tongue member to be moved rearwardly relative to said cover member without making contact with said cover member; (4) said cover plate component forms a channel with a vertical channel plate; said top wall, said bottom wall, said first and second side 30 walls, said front plate, but not said tongue member, being positioned within said channel, with the planes of said side walls, said channel 10 plate and said cover plate component being parallel, and with said first side wall being adjacent to said channel plate and said second side wall being adjacent to said cover plate component; and (5) spring biasing means associated with said channel plate; said 5 spring biasing means being operative to ensure that, during normal operation of said door, said front plate is biased to its normal position in which said front plate is adjacent to said face plate component of said cover member; whereby, if said door has been unlocked and opened, and is being closed io with said square bolt at least partially extended from said lock, when the end of said bolt contacts said substantially arcuate surface of said tongue member, said bolt applies a force to said tongue member that causes said tongue member to move rearwardly in said channel against the bias applied by said spring biasing means, but when the end of said bolt has moved into 15 the region of said aperture in said front plate, said front plate is no longer held in its rearward position and the spring bias applied by said spring biasing means moves said front plate back to its normal position. As noted above, various forms of the spring biasing arrangement may be 20 used. In one form of the present invention, a dead-latching feature may also be included. 25 By way of example, embodiments of the present invention will now be described, with reference to the accompanying drawings. Brief description of the drawings. Figure 1 is a partly schematic perspective sketch of one realisation of the 30 micro-switch box of the present invention.

11 Figure 2 is a partly schematic, perspective sketch showing, in exploded form, the components of the micro-switch box illustrated in Figure 1. Figure 3 is a front view of the micro-switch box of Figure 1, with the cover 5 member of the micro-switch box removed. Figure 4 depicts an alternative form of the front plate of the micro-switch box of Figures 1, 2 and 3. io Figure 5 illustrates one alternative way in which the spring bias applied to the front plate of the micro-switch box may be implemented. Detailed description of the illustrated embodiments. Figures 1, 2 and 3 depict a preferred form of the basic micro-switch box of 15 the present invention. The micro-switch box of Figures 1, 2 and 3 has a top wall 101, a bottom wall 102, a first side wall 104 and a second side wall 124. A substantially vertical, planar, micro-switch support shelf or support plate 107 (it need not 20 be planar) extends from the first side wall 104 to the second side wall 124. An aperture 108 in the support plate 107 is provided to enable either a plunger type micro-switch or a lever type micro-switch to be mounted on the support plate 107. A vertically elongate front plate 200, having vertical side edges 211 and 212 that are parallel, is attached to (for example, by 25 welding since the micro-switch box will normally be constructed of steel) the open front of the structure formed by the top, bottom and side walls (101, 102, 104 and 124, respectively) of the micro-switch box. The front plate 200 has a generally rectangular aperture 201 (shown more clearly in Figure 4) through which the end of the square bolt of a lock will pass when 30 the micro-switch box is mounted in the door frame that supports a door having a lock with a square bolt. (Although, in the embodiment depicted 12 by Figures 1, 2 and 3, the aperture 201 is generally rectangular, it may have any suitable shape that permits the end of a square bolt to pass through it freely.) The aperture 201 shown in Figures 1, 2 and 3 has a cut-away region 205 (shown in dashed outline) that extends from the 5 aperture 201 to the side edge 211 of the front plate 200. This cut-away region permits an optional dead-latch feature to be included in the micro switch box, as will be explained later in this specification. A vertically elongate tongue member 202 (that, preferably, as shown in 10 the drawings, is formed integrally with the front plate 200) extends from the side edge 212 of the front plate 200. The horizontal cross-section of the tongue member 202 is uniform over at least the operative length of the tongue member. (The operative length of the tongue member is that length of the tongue member that is horizontally aligned with the aperture 201 in 15 the front plate 200.) The tongue member has a generally arcuate front surface 213, the centre of curvature of the horizontal arc (or approximate arc) of this surface being a remote vertical line. In the extreme case, the vertical line of this centre of curvature is at infinity, so that the arcuate surface 213 becomes planar and the horizontal cross-section of the 20 tongue member 202 is then triangular. Figure 4 shows an alternative construction of the front plate 200, pressed or cut from a flat sheet of stainless steel, with the tongue member 202 being bent to form the arcuate surface 213. This form of front plate 200 25 is suitable when the micro-switch box is to be used with relatively lightweight doors, but when the micro-switch box is to be used with heavier doors, the front plate should be made from the thicker (preferably 2.5 to 3 mm thick) steel plate - as depicted in Figures 1 and 2. 30 The front plate 200 of the micro-switch box illustrated in Figures 1, 2 and 3 has an upper extension above the top wall 101 and a lower extension 13 below the bottom wall 102. A respective threaded aperture 204 of circular cross-section in each of these extensions is used in the spring-biased control of the position of the front plate 200 (and thus the position of the attached structure comprising the top wall 101, the bottom wall 102, the side 5 walls 104 and 124, and the micro-switch support plate 107). The spring biased control feature is explained in more detail below. The front plate 200 and its attached structure comprising the top wall 101, the bottom wall 102, the side walls 104 and 124, and the micro-switch io support plate 107 are located within a channel formed by a channel plate 220 and a cover plate component 151 (a cover plate) of a cover member 150. The cover member 150 is an essential component of the micro-switch box is of the present invention. It comprises an elongate, vertical face plate component 110 (a face plate), by which the micro-switch box is mounted in the door frame (typically by screws that pass through countersunk holes 114 in the end regions of the face plate) and a planar cover plate component 151. The cover plate component 151 extends rearwardly from 20 the face plate component 110, with its plane at right angles to the plane of the face plate component 110. The cover member 150 of the embodiment illustrated by Figures 1, 2 and 3 has the optional (but preferred) planar channel edge plates 153, that extend horizontally from the top and bottom edges of the cover plate component 151. (Only the top channel side plate 25 153 is shown in Figures 1 and 2.) The cover member 150 has an aperture 152 in it. The aperture 152 is essentially the combination of two contiguous rectangular apertures; one in the face plate component 110 and the other in the cover plate component 30 151. These apertures meet each other along the vertical line of contact of the face plate component 110 and the cover plate component 151. The 14 dimensions of the aperture 152 are such that, when the micro-switch box is mounted in a door frame, the end of the square bolt of the lock of the associated door can pass through that part of the aperture 152 that is in the face plate component 110, and the tongue member 202 of the front 5 plate 200 can move freely within that part of the aperture 152 that is in the cover plate component 151. The normal way of fabricating the cover member is by bending a steel sheet blank after the apertures 152, 114 and 154 have been made in it. 10 Thus, in principle, the aperture 152 could be formed as two separate (preferably rectangular) apertures, separated by a thin rod or bar of steel. This "double aperture" form of the aperture 152 is not preferred. The channel plate 220 of the micro-switch box has its plane vertical. Two 15 posts 207 extend from the channel plate 220. One post 207 is adjacent to the upper edge of the channel plate 220; the other post 207 is adjacent to the bottom edge of the channel plate 220. Each post 207 is located adjacent to, or near, the back edge 215 of the channel plate 220. A respective pin 208 extends horizontally forward from each post 207, and 20 a respective threaded cavity 209 extends horizontally into each post 207 from the surface of the post that is remote from the channel plate 220. When a respective screw or bolt is passed through each hole 154 in the cover plate component 151, and is screwed into a cavity 209 of a post 25 207, the cover plate component 151 and the channel plate 220 form a channel or duct within which the structure comprising the top wall 101, the bottom wall 102, the side walls 104 and 124, and the micro-switch support plate 107, with the front plate 200 (but excluding the tongue member 202, which extends through that part of the aperture 152 that is in the cover 30 plate component 151) is a sliding fit. Conventional bushing, using neoprene or brass, material may be included to facilitate the sliding nature of this fit.

15 In normal use of the micro-switch box, the front plate 200 is biased towards the face plate 110 by upper and lower helical compression springs 206. Each compression spring 206 is supported at one end (its rear end) by a respective one of the pins 208, and at the other end (its front end) 5 by a respective pin-like rearward projection from the back face of the front plate 200. In the embodiment illustrated in Figures 1, 2 and 3, these pin like projections are provided by the parts of respective bolts or screws 210 that extend beyond the rear face of the front plate 200 when the bolts or screws 210 are screwed into respective apertures 204 in the front io plate 200. The micro-switch box of Figures 1, 2 and 3 functions in the following manner. Assume that the door supported by the door frame within which the micro-switch box is mounted is open, and the square bolt of the lock is of that door is extended. When an attempt is made to close the door, the end of the square bolt will contact the substantially arcuate surface 213 of the tongue member 202. As noted earlier in this specification, when the end of the square bolt presses against the substantially arcuate surface 213 of the tongue member 202, it applies a force to the tongue member 20 that causes the tongue member 202 (and thus the front plate 200 and the components of the micro-switch box that are attached, directly or indirectly, to the front plate 200) to move rearwardly in the channel formed by the channel plate 220 and the cover plate 151, against the bias applied by the springs 206. When the front plate 200 has been moved rearwardly 25 a distance such that the end of the square bolt can move over the front surface of the front plate 200, the closure of the door can continue until the end of the square bolt is aligned with the aperture 201 in the front plate 200. In this position, the door is fully closed and since the front plate 200 is no longer held by the end of the square bolt in the rearward position 30 into which it has been forced, the spring bias moves the front plate 200 back to its normal position adjacent to the face plate component 110 of 16 the cover member 150. The micro-switch support plate 107 had been moved rearwards with the front plate, and as it returns to its normal position, the plunger or lever of the micro-switch mounted on the support plate 107 contacts the end of the square bolt, which then activates the 5 micro-switch to generate the "door closed and locked" signal in the monitoring equipment. Figure 5 depicts an alternative form of spring biasing that, under normal operating conditions, keeps the front plate 200 adjacent to the face plate io component 110. In the Figure 5 arrangement, respective posts 207 are mounted adjacent to the top and bottom edges of the channel plate 220, at or near the back edge 215 of the channel plate. Each post 207 has a threaded aperture 15 209 so that the cover plate component 151 of the cover member 150 can be secured in contact with the post using screws or bolts. Each post 207 also has a planar, substantially vertical, forward facing surface on which a respective leaf spring 218 is mounted. Each leaf spring 218 has a free end 219 which bears against a back wall (not shown in Figures 1, 2 and 20 3), or against a respective back wall component (not shown in the drawings) that is affixed to the rearmost parts of the structure comprising the top wall 101, the bottom wall 102 and the side walls 104 and 124. Under normal operating conditions, the springs 218 apply a force to this structure that holds the front plate 200 adjacent to the rear surface of the face plate 25 component 110. If a rearward force is applied to the tongue member 202 (for example, by the extended bolt of a lock of a door that is being closed), that force will move the front plate (and therefore the structure comprising the top wall 101, the bottom wall 102, the side walls 104 and 124, and the micro-switch support plate 107) rearwardly, against the force applied by 30 the springs 218.

17 An advantage of the spring biasing arrangement shown in Figure 5 is that the front plate 200 need not have respective extensions above the top wall 101 and below the bottom wall 102. Thus a smaller micro-switch box construction is possible. 5 Reverting to the micro-switch box construction of Figures 1, 2 and 3, it should be noted that some variations of the illustrated form of the components of the micro-switch box are possible. For example, the screws or bolts 210 in the threaded apertures 204 may be replaced by studs io mounted in the apertures 204, with each stud having a pin-like component that extends horizontally rearward from the front plate, to form a support for the front end of a respective compression spring 206. And the posts 207 need not have six planar surfaces (though this is a convenient way to form the posts 207). The posts may be made, for example, by being cut is from a steel bar having a cross-section that is hexagonal or circular. Additional features may be included in the micro-switch box. For example (as foreshadowed earlier in this specification), it may include a conventional dead-latch feature. To do this, a pivoted latching bar is positioned with one 20 end (its front end) in the cut-away portion 205 of the front plate 200 (see Figure 2). This latching bar extends rearwardly. The front end of the latching bar is depressed when the square bolt of the lock of the associated door is extended under normal operation of the lock when the associated door is closed, thus pivoting the latching bar to "dead-latch" 25 the bolt of the lock. It is also advantageous, in some situations, to include a magnetically activated, balanced reed switch, mounted on the support plate 107. If such a balanced reed switch is present, a magnet (or a ferro-magnetic 30 rod, plate or bar) will be mounted on the edge of the associated door, so that it is closely adjacent to the reed switch when the door is fully closed, and will 18 activate the reed switch. An electrical connection between the reed switch and a remote monitoring station will be through an aperture in a back wall of the micro-switch box, then via a conduit to the remote monitoring station. If a siren or "screamer" is associated with the balanced reed switch, an audible 5 signal can be generated when the door has been open for more than a pre-determined time. Thus the balanced reed switch may form part of a DOTL ("door open too long") unit. Other features that may be included in the micro-switch box of the io present invention, to enhance the security of the room into which the door opens, are a separate DOTL unit, a Magnasphere switch ("Magnasphere" is a trade mark) and an RFID ("radio frequency indication device"). Details of these additional features (and of the balanced reed switch) are given in the specification of my Australian patent No. 2011201414, the contents is of which are incorporated into the present specification by this reference thereto. This listing of additional features that may be included in the micro-switch box is not exhaustive. 20 Locksmiths and security experts will appreciate that examples only of micro-switch boxes constructed in accordance with the present invention have been described in this specification, and that variations in or modifications to the construction of the micro-switch boxes may be made without departing from the present inventive concept, as set out in the following claims.

Claims

1. A micro-switch box for installation in a door frame; said micro-switch box being for use with circuitry, including a micro-switch, that monitors the position of a square bolt of a lock of an associated door that is mounted on said door frame; said micro-switch box comprising a chamber defined by a top wall, a bottom wall, a substantially planar first side wall, a substantially planar second side wall, and a micro-switch support plate on which said micro-switch is to be mounted, said micro-switch support plate extending from said first side wall to said second side wall; the front of said chamber being closed by a vertical, elongate front plate having a width substantially equal to the distance between said side walls and a length such that it extends over the entire front of said chamber; said micro-switch box being further characterised in that: (1) said front plate has an aperture; said aperture having dimensions that permit the end portion of the bolt of said lock that projects from said lock, when said door is closed and said bolt is extended into the position it has when said door is locked, to pass through said aperture; (2) a vertically elongate tongue member projects horizontally from one edge of said front plate; said tongue member having a substantially arcuate front surface; the centre of curvature said substantially arcuate surface being a remote vertical line; (3) said micro-switch box has an associated cover member comprising an elongate face plate component for attachment to said door frame and a vertical cover plate component extending rearwardly at right angles from one edge of said face plate component; said cover member having a single cover member aperture that extends across the junction of said face plate 20 component and said cover plate component; said cover member aperture being so dimensioned that it permits both said send of said square bolt of said door lock and said tongue member to be moved rearwardly relative to said cover member without making contact with said cover member; (4) said cover plate component forms a channel with a vertical channel plate; said top wall, said bottom wall, said first and second side walls, and said front plate, but not said tongue member, being positioned within said channel, with the planes of said side walls, said channel plate and said cover plate component being parallel, and with said first side wall being adjacent to said channel plate and said second side wall being adjacent to said cover plate component; and (5) spring biasing means associated with said channel plate; said spring biasing means being operative to ensure that, during normal operation of said door, said front plate is biased to its normal position in which said front plate is adjacent to said face plate component of said cover member; whereby, if said door has been unlocked and opened, and is being closed with said square bolt at least partially extended from said lock, when the end of said bolt contacts said substantially arcuate surface of said tongue member, said bolt applies a force to said tongue member that causes said tongue member to move rearwardly in said channel against the bias applied by said spring biasing means, but when the end of said bolt has moved into the region of said aperture in said front plate, said front plate is no longer held in its rearward position and the spring bias applied by said spring biasing means moves said front plate back to its normal position. 21

2. A micro-switch box as defined in claim 1, in which said channel plate has a top edge, a bottom edge and a back edge, and (a) a first post extends from said channel plate towards said cover plate component from a position adjacent to said top edge of said channel plate and adjacent to or near said back edge of said channel plate, for a distance such that the surface of said first post that is remote from said channel plate contacts said cover plate component; and (b) a second post extends from said channel plate towards said cover plate component from a position adjacent to said bottom edge of said channel plate and adjacent to or near said back edge of said channel plate, for a distance such that the surface of said second post that is remote from said channel plate contacts said cover plate component; and (c) said cover plate component is held firmly in contact with said first and second posts.

3. A micro-switch box as defined in claim 2, in which each of said posts has a planar front surface and said spring biasing means comprises a pair of leaf springs, each of said leaf springs having one end rigidly attached to the planar front surface of a respective one of said posts and its other end bearing against a back wall, or a respective back wall component, that is affixed to the back edges of first and second side walls; said leaf springs being shaped so that each of said leaf springs applies a force to said back wall, or to its respective back wall component, to bias said front plate to a position adjacent to said face plate component.

4. A micro-switch box as defined in claim 2, in which said front plate has an upper extension above said top wall and a lower extension below said bottom wall; a first pin extends horizontally from said first post towards said upper extension of said front plate; a second pin extends horizontally from said second post towards said lower extension of said front plate; a first pin like rearwards projection from said upper extension of said front plate is aligned with said first pin; a second pin-like rearwards projection from said 22 lower extension of said front plate is aligned with said second pin; a first helical compression spring extends between and is supported by said first pin-like projection and said first pin; and a second helical compression spring extends between and is supported by said second pin-like projection and said second pin; said first and second compression springs having dimensions such that they each apply a force to bias said front plate to a position adjacent to said face plate component.

5. A micro-switch box as defined in any preceding claim, including top and bottom channel edge plates extending horizontally towards said channel plate from, respectively, the top and bottom edges of said cover plate component.

6. A micro-switch box as defined in any preceding claim, including a cut away region of said front plate, said cut-away region extending from said aperture in said front plate to the edge of said front plate that is remote from said tongue member, and a latching bar having one end located in said cut away region, said latching bar extending rearwardly from said cut-away region.

7. A micro-switch box as defined in any preceding claim, including a magnetically activated, balanced reed switch, mounted on said support plate, and a magnet or a ferromagnetic rod, plate or bar mounted on the edge of said door, so positioned that said magnet or ferromagnetic rod, plate or bar is closely adjacent to said reed switch when said door is fully closed.

8. A micro-switch box as defined in any preceding claim, including at least one additional component selected from the group consisting of: a Magnasphere (trade mark) switch, a DOTL unit, and an RFID unit. 23

9. A micro-switch box as defined in any preceding claim, including bushing to facilitate movement within said channel.

10. A door lock monitoring unit for a door having a lock, said unit including a micro-switch box as defined in any preceding claim. Dated this fourth day of December, 2014 TREVOR DAVID LEISK Patent Attorneys for the Applicant DAVIES COLLISON CAVE.