Primarily the present invention relates to security systems which form physical barriers across an opening to a building. For example security grilles may be placed across a window in order to prevent unauthorised access to the building. The security grille may be in the form of bars, shutters or screen mesh.

Background of the Invention A major problem with each of the above exemplified security systems is the safety of the occupants of the building if an emergency evacuation of the building is required.

For example if a fire occurs in the building the occupants of the building are unable to escape through windows or doors which have security barriers placed across them.

Accordingly it is important that security systems have a releasable locking feature so that building occupants may escape through the openings in the event of an emergency.

One example of releasable locking assemblies is described in Australian patent no. 702496.

The above referenced patent discloses a releasable locking assembly with a movable frame with a latch assembly which is able to engage a strike located in a fixed outer frame of the assembly.

The present invention is aimed at providing an alternative method of releasably retaining a security grille which may be located in an opening to a building in order to prevent or hinder access to the building.

Summary of the Invention According to one aspect of the present invention there is provided an assembly for releasably retaining a security grille, the assembly including a base frame which

is adapted to be located in an opening, a latch assembly attachable to the base frame and including a coupling portion and a movable frame having a security grille portion for retaining a security grille and an engagement portion for engaging with the coupling portion of the latching assembly wherein the coupling portion is able to either engage with the engagement portion to retain the movable frame in a closed position or disengage with the engagement portion to permit the movable frame to move to an open position.

It is preferred that the assembly is able to releasably retain any type of security barrier across or within an opening.

The grille may be in the form of a screen or bars of other form of barrier.

Preferably the base frame is adapted to be fixed to a peripheral structure of the opening.

The base frame preferably acts as an outer frame and the movable frame as an inner frame.

The latch assembly may include a lever member.

Preferably the latch assembly includes an urging means for urging the lever member to engage the engagement portion.

The lever member may have a ball portion at one end which ball portion is adapted to be received within a socket of the base frame.

The lever member coupling portion may be in the form of a catch, although it could be any alternative part of a device which is able to perform an engagement or locking function.

The lever member preferably includes a finger operable lever.

Preferably the lever member has the finger operable lever oriented at substantially 90° with respect to a ball section of the lever member.

The latch assembly may include a pivot means which permits the lever member to pivot with respect to

the base frame.

The urging member preferably comprises a spring.

Preferably the base member comprises an outer frame having a latch lever retaining portion.

The latch lever retaining portion preferably comprises a socket adapted to receive the ball portion of the latch lever.

The latch lever retaining portion preferably comprises an inwardly directed portion extending from a front wall of the base frame.

The base frame may include a front wall with an innermost edge extending into an inwardly directed inner wall portion.

The base frame preferably defines a cavity between the latch lever retaining portion and the inwardly directed inner wall portion, which cavity is adapted to receive a channel portion of the movable frame.

The latch lever retainer portion may comprise a leg portion having a foot portion which is directed outwardly towards an outer channel section of the base frame.

The foot portion is preferably oriented at 90° with respect to the base frame channel section.

The base frame preferably includes a spring retaining portion for retaining a spring of the latch assembly.

The base frame is preferably symmetrical.

The assembly preferably includes a hinge means for coupling the moving frame to the base frame, whereby the moving frame is able to pivot with respect to the base frame.

The hinge means preferably comprises a hinge mechanism or pivot.

The hinge means may comprise a hinge member having a ball portion at one end.

The ball portion preferably has a generally arcuate outer surface at the end of a straight wall

section.

It should be noted that the hinge member and latch lever may be elongate strips or extrusions so that the ball portion may be a rounded lip or ridge at the end of a flat wall or strip. In addition instead of a continuous hinge along the length of the base frame a hinge may be located at upper and lower end portions of the movable frame and consequently the adjacent parts of the base frame.

In an alternative embodiment the hinge means is located at a generally central region of the movable frame and adjacent base frame.

The hinge means preferably includes a resilient/bendable section.

The other end of the hinge member preferably includes a curved tongue section adapted to couple with a hinge portion of the movable frame.

It is preferred that the curved tongue is adapted to engage the curved surface of the hinge portion of the movable frame.

Preferably the resilient section comprises the curved portion.

The hinge member may include a knee section which is adapted to engage with an end portion of the foot portion of the base frame.

It is preferred that the knee forms a recess for the end of the latch lever receiving portion.

Preferably the movable frame is only able to pivot inwardly to an open position.

The movable frame preferably includes a security grille receiving portion.

The movable frame engagement portion is preferably located at an outer end of the movable frame.

The hinge portion of the movable frame is preferably located closer to the centre of the movable frame compared to the engagement portion.

The hinge portion arcuate cavity preferably

includes a curved head portion.

The movable frame preferably includes front frame channels which extend in front of the movable frame on either side of the security screen receiving portion.

The base frame preferably includes front shield portions which are adapted to cover the front frame channels of the movable frame.

The assembly preferably includes a guard which is adapted to be located on the inside of the assembly and is provided with an access panel whereby access can be provided to the latch lever.

According to another aspect of the present invention there is provided a releasable closure assembly for security systems, the assembly comprising a base frame which is adapted to be located in an opening, a latch assembly attachable to the base frame and including a coupling portion and a movable frame having a security grille portion for retaining a security grille and an engagement portion for engaging with the coupling portion of the latching assembly, wherein the releasable closure includes a hinge means for coupling the movable frame to the base frame, whereby the coupling portion is able to either engage with the engagement portion to retain the movable frame in a closed position or disengage with the engagement portion to permit the movable frame to pivot to an open position.

According to one embodiment the hinge means includes a hinge assembly which is adapted to interconnect the movable frame and the base frame.

According to an alternative embodiment the hinge means comprises hinge portions of the base and movable frame members respectively which are able to be coupled together to enable the movable member to pivot with respect to the base member.

The hinge means preferably permits the movable member to pivot outwardly with respect to the base member.

The hinge portion of the base frame preferably

comprises a forwardly extending member with a coupling section at an outer end thereof.

The coupling section preferably comprises a curved lip.

The curved lip may be resiliently deformable.

The coupling section alternatively may be in the form of a hooked finger extension.

The coupling section preferably extends outwardly.

Preferably the latch assembly comprises a lever member with a pivot ball which is adapted to engage in a socket exclusive of the moveable frame.

The pivot ball is preferably adapted to fit into a socket located in the base frame.

The lever member may comprise a lever handle, the coupling portion and a pivot ball arm.

Preferably the coupling portion comprises a catch arm which branches from the lever handle.

The lever handle may be substantially parallel to the pivot ball arm.

Preferably the catch arm extends in an arcuate path outwardly for engagement with a catch of the moveable frame.

Preferably the latch assembly includes an urging means which is adapted to urge the coupling portion to engage with the engagement portion.

The urging means may be a compression spring which abuts the pivot ball arm.

Preferably the lever arm is connected to a controlling mechanism which is adapted to move the lever arm to engage or disengage the catch from the engagement portion of the moveable frame.

The base frame preferably includes one side frame section with the hinge portion and an opposite side frame portion with a latch lever retaining portion.

The hinge portion of the base frame may include an attachable lip portion.

The base frame preferably includes a side shield portion to prevent access to the side of the movable frame opposite to where the hinge means is located.

The side shield portion preferably extends forwardly into the cavity of the hinge portion of the movable frame.

The movable frame engagement portion may comprise an inwardly directed wall.

The inwardly directed wall is preferably located on both sides of the movable frame.

The inwardly directed wall preferably includes a catch which faces a central area of the opening.

It is preferred that the inwardly directed wall is protected by the side shield portion.

The base frame preferably includes a latch lever wall oriented at 90° with respect to the side shield portion.

According to another embodiment of the present invention the base frame includes a latch lever frame which is removably attachable from an outer frame of the base frame.

It is preferred that the side shield portion extends far enough into the cavity of the hinge portion in order to make it as difficult as possible to tamper with the side shield portion.

It is preferred that the latch lever base frame includes a spigot portion which is adapted to fit into a recess portion of the base frame outer frame.

Preferably the latch lever base frame includes an access panel to the latch lever.

It is preferred that the side shield portion includes an elbow portion which rests on an opposing wall of the latch lever base frame.

It is preferred that the latch lever base frame includes a shoulder region from which the spigot portion extends, which shoulder portion limits or prevents sideways movement of side walls of the cavity of the outer

base frame within which it is located.

According to another aspect of the present invention there is provided a releasable closure assembly for security systems, the assembly having a base frame which is adapted to be located in an opening, a latch assembly attachable to the base frame and including a coupling portion and a movable frame having a security grille portion for retaining a security grille and an engagement portion for engaging with the coupling portion of the latching assembly, wherein the coupling portion is able to either engage with the engagement portion to retain the movable frame in a closed position or disengage with the engagement portion to permit the movable frame to slide with respect to the base frame.

Preferably one of the base frame and the movable frame includes one or more guides for guiding one or more slidable portions of the other of the base frame and movable frame.

Preferably the guide (s) include interior and exterior guide (s).

In the embodiment of the invention where there are two guides each guide comprises a channel.

Alternatively each guide comprises a rail.

The slidable portion preferably includes an extension portion.

The slidable portion may include a roller.

The base frame preferably includes one or more guides.

The base frame may include channels which limit sideways movement of an extension of the movable frame which is located therebetween.

Each channel may include parallel side wall portions which are adapted to receive an extension portion of the movable frame.

Preferably the extension portion includes one or more rollers.

The base frame may include a pair of generally

parallel channels.

One of the parallel walls preferably is shorter than the other and has a rail or track on its distal surface.

Preferably the extension portion is planar.

The base frame may have one or more extension portions.

One or more of the extensions portions preferably include a track or rail on a distal surface thereof.

Each extension portion preferably is directed inwardly.

The channels preferably comprise parallel walls directed inwardly.

The extension portions of the base frame preferably extend between the parallel walls of the movable frame.

It should be noted that reverse configurations of the base frame and movable frame are encompassed by the present invention.

Extension portions of the base frame and movable frame have a distal wall which extends perpendicular to parallel walls of channels within which it is located.

Desirably this prevents sideways movement of the movable frame.

Preferably the outermost portion of the movable frame comprises a channel or extension portion.

The engagement portion is preferably located inwardly with respect to the extension portion or channel of the movable frame depending upon which embodiment is utilised.

The movable frame preferably comprises exterior and interior portions, with the exterior portion adapted to slide with respect to an exterior guide of the base frame and the interior portion adapted to slide with respect to an interior guide of the base frame.

The movable frame preferably has a central coupling portion for coupling exterior and interior

portions.

It is preferred that the engagement portion of the movable frame is in the form of a catch or strike located behind each channel on either side of the movable frame.

The central coupling portion preferably includes interengaging portions which permit sliding of exterior and interior portions therebetween.

It is preferred that the assembly includes a guard to cover edges of the movable frame adjacent the base frame.

It is preferred that the assembly includes an interior guard in the form of a right angled cover which is located over an outer end of the movable frame and includes an inwardly directed wall which extends towards an extension portion of the base frame.

Preferably the guard is adapted to restrict sideways movement of the innermost channel wall.

Brief Description of the Drawings Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure la shows an end view of an assembly for locking a security grille according to a first embodiment of the present invention; Figure 1b shows an end view of a variation to the assembly shown in Figure 1A ; Figure 2a shows an end view of an assembly for locking a security grille according to a second embodiment of the present invention; Figure 2b shows an end view of a second version of the second embodiment of the present invention; Figure 3 shows an end view of an assembly for locking a security grille according to a third embodiment of the present invention ; Figure 4 shows an end view of a variant to the third embodiment of the present invention ;

Figure 5 shows an end view of the fourth embodiment of the present invention; Figure 6 shows an additional feature of the fourth embodiment of the present invention; Figure 7 shows an end view of a central interlocking assembly for the third and fourth embodiments of the present invention; Figure 8 shows a variation to the first embodiment of the invention shown in Figure 1A ; Figure 9 shows a variation to the embodiment of the invention shown in Figure 2A; Figure 10 shows a variation to the embodiment of the invention shown in Figure 3; and Figure 11 shows a further variation to the embodiment of the invention shown in Figure 3.

Detailed Description of the Drawings Referring to the first embodiment of the invention shown in Figure 1 the assembly 10 consists of a base frame 11 which is adapted to be fixed to a window frame or door frame or anything similar.

This base frame 11 is connected through a hinge member 12 to a movable frame or sash 13.

One end of the sash 13 is connected to the fixed frame 11 through a hinge member 12 while the other end is able to connect or disconnect from a latch assembly 14 of a latch lever assembly to allow the sash to open or close.

The base frame 11 consists of a generally right angled structure consisting of an outer channel side wall 15 and an outer planar wall 16 which at its innermost extent extends inwardly at 90° to act as a guard section 17 for the sash 13.

Behind the front wall section 16 the base frame 11 is configured with a hinge receiving wall 18 in the form of an angled leg portion 19 which extends into an outwardly directed foot 20 with an acute angled socket region 21 defined therebetween.

Between the beginning of the leg portion 19 and a

short inwardly directed spigot portion 22, a spring 23 of the hinge 12 is arranged to be located.

A gap exists between the guard section 17 and the opposing wall of the socket region 21.

This gap is adapted to receive a forwardly projecting channel 24 of the sash 13.

The sash 13 is a generally planar structure which is symmetrical about the centre.

Each end of the sash 13 consists of an angled protrusion or catch 25. As the latch assembly 14 is only located on one side of the assembly 10 only one of the catches 25 is used.

The inward facing side of the sash 13 is provided with a curved cavity 26 and an adjacent rectangular recess 27 separated by a thin wall 28.

The curved cavity 26 curls around an inwardly extending wall 29 having a bulbous lip or ridge 30 located on its innermost end. The curved exterior surface of this lip 30 abuts with a curved tongue 31 of the hinge member 12.

The innermost major surface of the sash 13 holds a wire screen mesh or equivalent 32. For convenience the mesh 32 is shown as being held between parallel walls 33 and 33A, although any conventional manner of fastening a mesh within the sash frame is envisaged.

The hinge member 12 has a ball or rounded ridge 35 located at one end and this ball 34 is housed within socket 21 of the base frame 11.

The hinge member 12 extends from the ball end 34 along the outer face of the foot 20 around its outermost end to form a knee section 36 which then extends into a long curved section which terminates in the tongue 31.

The hinge member 12 permits the sash to pivot inwardly with respect to the base frame 11.

The latch assembly 14 consists of a latch lever 37 having a catch 38 for engagement with the catch 25 of the sash 13 and a rounded ball shaped end or pivot ball 39

which fits into the complimentary shaped socket 21 of the base frame 11.

Accordingly it will be noted that the socket 21 is sized and shaped so that it is able to receive both of the ends of the hinge member 12 and the latch lever 37.

The latch lever assembly 14 also includes a spring 40 which fits into the recess 23.

An outwardly curved section of the latch lever 41 compresses the spring 40 whenever the latch lever 14 is moved out of engagement with the catch 25. Thus forcing the catch 38 of the latch lever 14 back into engagement with the catch 25.

Access to the latching assembly 14 is blocked by an access panel 42 provided in a lock shield 43 on the inward side of the sash 13. Removal of the access panel allows access to the handle 44 of the latch lever 14.

It is noted that both the base frame and the sash are manufactured so as to be symmetric about their centres. Accordingly it does not make any difference which way the sash 13 is oriented with respect to the base frame 11, as the hinge member 12 and latch assembly 14 can be connected to either side of the sash and base frame 11.

Figure 1b shows a variation to the embodiment shown in Figure la. In Figure 1b the base frame 51 corresponds to base frame 11.

It will be noted that the base frame 51 has a front wall 52 which has a small step 53 half way along its length and an innermost wall 54 which curves inwardly through 90° rather than at 90° like guard 17 of Figure 1A.

The hinge member 12 shown in Figure 1A is replaced by a different shaped hinge member 55. This hinge member 55 has one end 56 in the form of a T-shaped wall which fits within a rectangular recess 57 on the inner face of wall 52. Thus in contrast to the embodiment shown in Figure 1A the hinge member 55 is able to slide into the recess 57 rather than snap into a recessed socket.

The opposite end of the hinge member 55 has a tongue 58 similar to that shown in the previous embodiment.

The shape of the sash 59 is slightly different to that shown in Figure 1A. For example the outermost catch 60 has an outwardly directed wall 61 at an outermost end thereof.

Also the wall 62 separating the curved cavity 63 from the adjacent rectangular cavity 64 begins with a slightly curved section and then terminates in a straight section. This results in the rectangular cavity 64 having an enlarged width on the side of the wall 62.

The latch assembly 65 in Figure 1b is also slightly modified to incorporate an additional removable insert 66. This insert 66 has a generally T-shaped wall 67 at one end which is housed within the recess 57. The wall 67 includes a small channel 68 which is adapted to house spring 69 of the latch assembly 65.

The insert 66 also includes a centrally located socket portion 70 which is shaped to house the ball pivot 71 of latch lever 72.

The insert 66 functions in the same way as the walls 19,20 of the base frame 11 in Figure la, but has the advantage of being removable.

In addition the insert 66 has an inwardly directed wall 73 which is designed to abut the outer face of the curved wall of the cavity 63. In addition the back wall adjacent socket 70 is designed to abut an inwardly directed wall 74 of the base frame 51.

It is also noted that the forwardly projecting channels 75 of the sash 59 are located between an inwardly directed wall 75 and wall 54 of the base frame 51.

It should be noted that the embodiment of the assembly shown in Figure 1B has additional manufacturing advantages.

According to the second embodiment shown in Figure 2A sash 80 is pivotally connected to base frame 81

so as to permit outward pivotal movement of the sash.

The general shape of the sash 80 is similar to that shown in Figure la, except that the front face is generally planar and the inner face includes an inwardly directed wall 82 with a catch 83 on an inside face thereof directed towards the centre of the overall assembly 80, 81. In addition instead of a recess being formed next to the cavity 84 which houses tongue 85 of a hinge wall 86, an enclosed channel 87 is provided.

Adjacent the channel 87 moving towards the centre of the sash 80, a gripping cavity 88 is provided. This gripping cavity 88 is shown having a generally rectangular shape but the embodiment covers any shaped cavity which is able to secure edges of the screen mesh therein in a conventional manner.

Base frame 81 consists of an outer rectangular channel section separated by a small wall from an inner open channel section 90. The inner open channel section 90 houses a latch assembly 93 on one side thereof extending outwardly from an outermost wall 91 of the open channel section, which wall 91 is directed towards the opposite side of the inner open channel section 90.

The inner open channel section 90 in effect has two parallel walls 91 which run parallel with the sash 80.

Because latch assembly 93 is accommodated by the base frame 81 the configuration of the inner open channel section 90 is altered for this purpose.

For ease of manufacture the base frame 81 is made so that minimum alterations are required in order to accommodate the latch assembly 93. Accordingly hinge wall extension 86 is mirrored by outwardly extending wall 99 which extends from outermost wall 100 of the channel 90.

The outermost wall 100 corresponds to the outermost wall 91 on the opposite side of the base frame 81.

The base frame 81 in order to accommodate the latch assembly 93 comprises outermost wall 100 and

innermost wall 94 which are parallel to each other and axially aligned with outermost wall 91 and its corresponding innermost wall 91 on the hinge side of the base frame 81.

The space between walls 100 and 94 accommodate one leg of latch lever 98 of the latch assembly 93 as well as a compression spring 92.

A socket 96 is formed in the outermost corner at the juncture between the outermost wall 100 and the innermost wall 94. The socket 96 consists of an inner part circular wall 95 which is configured to receive the pivot ball 97 and retain it snugly therein. It is preferred that this pivot ball 97 may be pushed into the socket 96 and retained therein by a snug interference type fit.

The latch assembly 93 consists of the latch lever 98 and the spring 92.

The latch lever 98 consists of a lever handle 130 which extends towards the opposite side of the base frame 81 and generally in parallel with outermost walls 91 and 100.

In the opposite direction the lever handle 103 branches into outer arm 131 with catch 101 and an inwardly directed arm 132 which extends away from the handle lever 130 generally in parallel with wall 100. The outer end of this arm 132 is provided with the pivot ball 97.

Furthermore this arm 132 has an inwardly directed bulge 133 which is designed to abut the outer surface of spring 92.

The spring 92 is located between two outwardly directed stops on the innermost wall 94.

It should be noted that the outer surface refers to the surface which is directed outwardly towards the external environment.

An outwardly extending wall 99 extends from the outermost wall 100 of the channel 90. Because this wall 99 does not need to act as a hinge it does not have an

outermost tongue to engage in the cavity 84 of the sash 80. Accordingly this wall 99 acts as a guard to prevent tampering of the assembly 80,81. The wall 99 extends part way into the cavity 84 to make it more difficult to attack the wall 82 of the sash located on the other side thereof.

The latch lever catch 101 engages with the catch 83. The handle of this latch lever 98 is accessible through an access panel 102 which is generally rectangular and extends around the latch assembly 93 and includes an inner wall 103 which has a small catch which engages a correspondingly shaped catch extending outwardly from an opposing wall of the channel 90 next to the channel sections 89.

The innermost straight wall 104 of guard 105 has an inside surface (corresponding to the outer wall) which includes a centrally located T-shaped wall 106 which serves to house channel wall 90 on one side between it and the wall 103 and on the other side in conjunction with an opposite facing wall 107 serves to house the access panel 102.

Thus the second embodiment of the invention works in reverse to the first embodiment in that the sash 80 opens outwardly rather than inwardly.

Figure 2B shows a variation to the second embodiment of the invention in which the base frame 81 is modified so that it is not directly connected to the latch assembly 98.

The shape of the base frame 81 is generally the same as the shape shown in Figure 2a on the left hand side of the drawing, although the channel 90 shown is much smaller and has an inside cylindrical recess 110 which acts as a socket.

In addition the exterior shape of the base frame is generally rectangular with a generally rectangular outermost cavity 111 substituting for the channel 89 shown in Figure 2A.

The major change to this embodiment is the provision of a disengageable interconnecting component 112 located on the opposite side of the base frame 81. This interconnecting component 112 has an outermost T-shaped wall 113 with a leg of the T being provided with a pivot ball 114 which fits into the socket 110 of the base frame 81.

The width of the head of the T 113 extends across the width of the channel 115 of the base frame 81.

The outermost part of the T-shaped wall 113 extends towards the centre of the assembly through an interconnecting wall 116 which opens into a clasping wall configuration 116 facing towards the centre of the assembly and forming a socket 117 on its inner face.

The socket 117 is adapted to engage with a pivot ball 118 of the latch lever 98 in a similar fashion to that described in relation to Figure 2A.

A spring 119 of the latch lever 98 is housed in a recessed area on the outer face of inner wall 119 of the interconnecting component 112.

The interconnecting component 112 effectively combines the guard 105 and the wall configuration forming the socket 95 of the base frame 81 shown in Figure 2A.

Thus it is possible to make the base frame as simple as possible by adding the interconnecting components 112 as a snap in component which fits into socket 110 of the channel formed in the base frame 81.

Figure 3 shows a third embodiment of the present invention in which a sash 200 is no longer hinged to a base frame 201 but instead is slidably engaged therewith.

The base frame 201 includes a pair of channels 202,203 and a pair of latch lever receiving walls 204, 205.

The channels 202 consist of a pair of parallel walls which are directed towards the centre of the overall assembly. Each outermost wall 206,207 is slightly longer than the parallel innermost wall.

The innermost walls 208,209 each have a distal end provided with a rail thereon.

Each channel 202,203 is adapted to receive therebetween a planar wall section at the end of each sash 200.

Each of the channels 202,203 are aligned in parallel and are separated by a recessed area 500 which is adapted to house part of the latch assembly 210.

The inner surface of the wall defining this recessed area defines a socket 211 which is adapted to house the pivot ball 212 of the latch assembly 210.

The inner surface of the recess 212 also includes a small channel 212 for receipt of the spring 213 of the latch assembly 210.

Each socket 211 is located behind each channel 202,203 in an outermost corner region 214,215.

The latch lever 20 extends out of the recessed area 500 between the two channels 202,203 so that its catch 215 can engage catch 216 of the sash.

An inner cover guard 217 covers the latch assembly from an inner wall of the sash 200 around to an outermost edge of the base frame 201.

This guard 217 also includes an access panel 218 to enable a person to operate the handle of the lever 210.

Because the latch assembly in this embodiment is only located at the extremities of the base frame and sash, Figure 3 does not show the roller assembly which rolls on the rails of the innermost walls 208,209. This is shown more clearly in Figure 4. Thus it can be seen how the sash 200 is provided with parallel channel walls 220,221 at its extremities, with a roller 222 fixed inside the channel defined by both walls 220,221.

As shown in Figure 7 because the third embodiment of the invention involves a dual sliding assembly, the sash 200 consists of an inner sash 223 and an outer sash 224. Both sashes 223 and 224 are connected together through a sash coupling 225 located in the centre of the

assembly. This coupling 225 consists of a coupling arm 226 and 227 which are connected to the distal ends of sashes 223 and 224 which are most remote from the base frame 201. Both arms 226 and 227 are connected to adjacent faces of sashes 223 and 224 and include overlapping extensions 228,229 which allow a sliding engagement therebetween.

Both arms 226,227 are fastened using any other suitable fastening device to their respective adjacent sash walls.

Referring back to Figure 3 it can be seen how outermost sash 223 couples with the outermost channel 202 and innermost sash 224 couples with channel 203.

In operation the latch lever 210 of either sash 223 or 224 can be disengaged with its engaging catch 216 to allow the sash to slide on its roller 222 on the rail of the associated channel 202,203.

Figure 5 shows a variation to the embodiment shown in Figures 4 and 3.

In this embodiment the base frame is modified so that walls 208 and 209 have right angled distal ends 230, 231 with the rails provided on the inner centrally directed wall thereof.

The opposing parallel wall for each wall 208,209 is reduced in length for wall 208 and is removed completely for wall 209.

The sash 200 is effectively the same in shape but because of the right angled outer ends 230,231 sideways movement of the sash is restricted because the length of the outer ends 231,231 is almost the same as the inner width of the sash channel between walls 221 and 222.

To accommodate the changes referred to in relation to Figure 5, the base frame 201 has also been modified in order to incorporate a single inner wall surface 232 which is adapted to receive the latch lever assembly.

Thus as shown in Figure 5 latch lever assembly

233 remains housed in the same location in the base frame 233 for both the outermost sash 223 and the innermost sash 224.

Thus the latch lever 234 is provided with an extra long leg which extends to the catch 235. The handle 236 of the lever 234 is also located in a different position and extends from the junction of the leg and foot 237 which has the ball pivot.

For the outermost sash 223 the latch lever has a slightly different shape to that for the innermost sash 224. In this respect it is noted that the latch lever 234 has a leg with a knee section whereas sash 224 has a latch assembly with a straight leg section.

It is also noted in relation to Figure 3 that the handle of the lever for the outermost sash extends from close to the catch whereas for the innermost sash the handle extends from a junction of a leg and pivot ball section of the latch lever.

As with previous embodiments a guard covers the latch assembly and access to the latch is provided through an access hatch 238.

Figure 6 shows a variation to the embodiment shown in Figure 5. In this variation an anti-lift mechanism 239 is provided at the corner of the innermost sash. Thus if a person tries to bend back the outermost wall 240 of the innermost sash 224 the anti-lift mechanism 239 prevents movement of the parallel wall 241. Thus as wall 241 will not bend as easily wall 241 is much more difficult to get behind because this can only be achieved with some play of the parallel wall 241.

The anti-lift mechanism may be screwed, welded, taped, glued, pressed or crimped onto the end of the wall 241 or be part of the extruded wall 241.

The anti-lift mechanism may be attached by any known fastening or securing means or be part of the extruded wall 241.

As shown in Figure 8 the latch assembly 14 may be

provided with an automated control mechanism 300. This control mechanism consists of a Bowden wire type mechanism consisting of an outer cable 301 which is connected by a wall bracket 302 to a controlling solenoid 303. The outer cable 301 is mounted by lock nuts 304 to the outer channel side wall 15. This outer cable 301 extends through side wall 15 so that inner cable 305 protrudes beyond the end thereof through an outer end of lever 14 and is secured thereto by suitable lock nuts 306. The level 14 can then be easily controlled by operating the electric solenoid 303 to extend or withdraw the inner cable 305. This results in clockwise or anti-clockwise movement of lever 14 which results in engagement or disengagement of catch 38 of the lever 14 from catch 25 of the sash 13.

Figure 9 shows a similar control mechanism 300 with inner cable 305 connected to lever 98.

In Figure 10 the control mechanism 300 is connected to the lever handle of lever 210 in a similar fashion and is operated in the same way.

Figure 11 shows an alternative configuration for latching the sash to a base frame when the sash is slidably engaged therewith.

In contrast to the embodiment shown in Figure 3, latch assembly 410 (corresponding to latch assembly 210) has a straight leg 411 with a short slightly angled outwardly directed foot 412 configured with a pivot ball 413 on its outer end. To accommodate this pivot ball 413 the configuration of the latch lever receiving walls 404 and 405 is different. Instead a generally straight wall 450 is formed extending between the outermost wall 406 of the base frame 401 and innermost wall 430 which is parallel to outermost wall 406.

Socket walls 411 extend radially inwardly from this wall 431 and are adapted to receive the pivot balls of the latch assembly 410.

Compression spring 413 is seated in a recess facing outwardly from a radially inwardly directed wall

432,430.

The latch assembly 410 operates in basically the same way as described in relation to Figure 3 except the pivot point is slightly changed and the position of the spring 413 now abuts the leg 411 rather than the foot at the end thereof.