GB2515455A

GB2515455A - Anti-barricade lock

Info

Publication number: GB2515455A
Application number: GB1306106.4A
Authority: GB
Inventors: Clive Stone; David Falkingham
Original assignee: PRIMERA LIFE Ltd
Current assignee: PRIMERA LIFE Ltd
Priority date: 2013-04-04
Filing date: 2013-04-04
Publication date: 2014-12-31
Anticipated expiration: 2033-04-04
Also published as: GB201306106D0; GB2515455B

Abstract

An anti-barricade lock 1 comprising a handle 4 locatable on a first side 6 of a door 2 in use, a plate 8 having an occupation indicator locatable on a second side 10 of the door, the occupation indicator comprising a disc 16 rotatable by a spindle 12, and a cover 22 securable over the indicator disc and the spindle. Also claimed is a kit of parts. Also claimed is an override mechanism in which the cover is arranged to slide relative to the plate from a normal operating position to an emergency position. An end of the spindle could be engaged by a suitable tool to be operated from the second side of the door. The cover and plate are arranged to resist insertion of a ligature, such as a wire, between the plate and the cover. The lock may be used in hospitals or bathrooms occupied by vulnerable people, such as mental health patients or elderly people.

Description

I

ANTI BARRICADE LOCK

This invention relates to an anti barricade lock having an occupation indicator suitable lbr fitting to a door in order to prevent the door being barricaded and also to an anti-barricade lock having an override mechanism provided with a sliding cover.

It has been known thr some time that in some situations it is desirable to prevent a door to a room from being barricaded such that the door cannot be opened from outside the room. One situation in whcrc this is a particular issue is within mental health institutions. A patient may occupy a private room and it is desirable that the patient is provided with a degree of privacy within the room and that the patient is able to close and lock the door. It is helpful fur staff to be aware that a room is occupied and so an occupation indicator can be provided on an outside of the door that is operated by a handle provided on an inside of the door. It is also desirable lbr staff to be immediately aware from outside a room whether the room has been locked from the outside of the room by a staff member fur isolation purposes or whether the room has been locked fitm inside the room by a patient. Therefore it is desirable that the occupation indicator is operated only by a handle provided on the inside of the door and in addition a lock may be provided on the outside of the door that is operated by a key kept by the staff.

In addition it is desirable to provide an occupation indicator on the outside of a door to a bathroom or toilet such that the staff can see fit,m outside the room that it is occupied.

Anti barricade locks have been known, and available fur some time, that allow a door to be opened fivm an outside of the door. Typically such locks are provided with a means for accessing a spindle of the lock located in an aperture within the door and a tool may be used to turn the spindle from outside so opening the door. Typically fixings are also provided such that the door can be opened in the opposite direction to normal operation in the case of an emergency Typically such a door will open into the room in normal operation but can be opened out of a room in the case of an emergency so that any barricade located on the inside of the room does not prevent the door from opening.

An object of the invention is to provide an improved anti-barricade lock with an occupation indicator. Another object of the invention is to provide an anti-barricade lock with an improved cover for an over-ride mechanism.

According to a first aspcct of thc invention thcrc is provided anti-barricade lock having an occupation indicator and comprising a first handle locatable on a first side of a door to which the lock is fixed in use, a plate having an occupation indicator locatable on a second side of the door, and spindle arranged to connect the handle to the occupation indicator wherein the occupation indicator comprises a disc rotatable by the spindle, the anti-barricade lock having a cover securable over the indicator disc and the spindle and whcrcin thc occupation indicator is sccurcd in use between thc door and the plate.

Prcfcrably thc anti-barricadc lock also compriscs a lock case providcd within thc door and arranged to have a lock operable from the second side of the door to lock the door.

Thc lock casc may bc conventionaL Prcfcrably the spindlc passcs through thc lock case.

Preferably the anti barricade lock has an override mechanism that enables the spindle to be rotated from the second side of the door. In a preferred embodiment the override mechanism can comprise an end of the spindle that can be engaged by a suitable tool and rotated. Preferably the override mechanism also comprises a means of exerting a force on the door to open the door. In many situations this entails pulling the door open.

In a preferred embodiment the override mechanism also comprises a keyed entryway arranged such that the tool can be inserted through the keyed entryway and rotated.

Preferably the tool is provided with lugs that can pass through the keyed entryway in a first position and which on rotation are retained by the entryway and can act on a rear face of the entryway to allow the door to be pulled open.

In the case of an emergency, the cover can be moved such that the override mechanism can be engaged. The cover may be rotated or may be provided with a sliding mechanism allowing the cover to be moved from a normal operating position in which the occupation indicator and spindle are covered and secured from tampering to an emergency position in which the override mechanism can be accessed and engaged. In a preferred embodiment the cover may be slideable from the normal operating position.

Preferably the cover is sccurable in the normal operating position by means such as a screw or in particular an anti-tamper security screw.

Preferably the cover is provided with an aperture overlying the indicator disc when the cover is in the normal operating position such that the indicator disc is visible through the aperture.

In a preferred embodiment the plate is provided with an opening through which the indicator disc is visible. Preferably the opening is circular. In a particularly preferred embodiment the indicator disc may project at least partially through the opening.

Preferably the opening extends from a front side of the plate to a rear side of the plate.

Preferably the indicator disc is moveable between a first position located adjacent or in contact with a rear surface of the plate and a second position in which the override mechanism is accessible. In a preferred form the indicator disc comprises a body having an extension a first side of which may be provided with indicator markings on a front face. Preferably the extension of the indicator disc is arranged to project through the opening in the cover. The first side of the extension may be substantially planar.

The indicator disc may have a rear portion having a rear face. A centrally located aperture may be provided in the indicator disc extending from the first side of the extension to the rear face. The rear face of the indicator disc may have location means arranged to locate a spring acting between the rear face of the indicator disc and the lock case located within the door.

In a preferred embodiment the indicator disc comprises a follower located on and moveable by the spindle. Preferably the spindle is square. Rotation of the spindle causes the indicator disc to rotate and a marking on the first side of the extension located in alignment with the aperture in the cover is changed. Commonly the front face of the indicator may be provided with markings comprising a red section for occupied and a white section for unoccupied. The indicator disc may be fitted appropriately on the spindle when the lock is installed on the door Preferably the location means on the disc comprises a lip extending from the central aperture and a rearwardly extending shoulder of the body defining a recess within which the spring can be located. Preferably the shoulder comprises a rearwardly extending rim around a periphery of the body of the indicator disc.

Preferably the spring comprises a tapered coil. Preferably the taper of the coiled spring is such that when completely compressed each coil of the spring fits within a preceding adjacent coil and a total thickness of the spring is a thickness of one coil. Preferably a smallest coil of the spring is dimensioned to be larger than the lip extending from the central aperture. Preferably a largest coil of the spring is dimensioned to be smaller in diameter than the rim of the disc. In a preferred embodiment the rim and the lip define a recess therebetween having a size such that the compressed spring can be located between the rim and the lip.

In a preferred embodiment the spring acts on the indicator disc in the normal operating position such that the indicator disc sits fully forward against the rear surface of the cover so that the front face of the indicator disc is fully visible though the aperture in the cover. In such a position the body of the indicator disc may be in contact with the rear side of the plate and the extension may project forward through the opening and into contact with the cover such that the markings on the first side of the indicator disc are visible through the aperture in the cover. In a barricade scenario the indicator disc can be moved back against the action of the spring by the action of the tool moving through the keyed entryway.

In a preferred embodiment the cover comprises a slider arranged to extend from a first edge of the plate to a second edge of the plate. Preferably the slider is shaped to conform to a shapc of the first edge and the second edge of the plate.

In a preferred embodiment the plate has a channel within which the cover can slide.

The channel may extend from the fir st edge of the plate to the second edge. The channel is preferably provided with at least one recess arranged to receive and retain a complimentary ridge provided on the slider. The or each recess preferably extends along each edge of the channel. The or each recess may be open to the periphery of the plate.

Preferably the slider has a substantially planar outer surface. The outer surface is visible when the slider is in a normal operating position on the plate. The outer surface of the slider may be provided with a surface finish that complements a surface finish of the front of the plate. The outer surface may have one or more curved portions that are shaped to complement the surface of the front of the plate. Alternatively or in addition one or more raised portion may be provided allow easier movement of the slider. The or each raised portion may be arranged such that it can be engaged by a thumb to move the slider from the normal operating position towards an edge of the plate.

In a preferred embodiment the slider has a rear surface that has at least one ramped portion. Preferably the slider has at least two ramped portions on the rear surface. In a most preferred embodiment the rear face has a central depression. A middle section of the slider may be thinner than outer portions of the slider.

Preferably the depression is sized such that the extension on the indicator disc can sit within the depression in the normal operating position. Tn a preferred embodiment in which the disc can be located in the depression the disc is arranged to sit forward with the front face against the rear surface of the cover and the markings visible through the aperture. In the case of an emergency in which it is suspected that the door has been barricaded by a patient within the room the cover can be moved and the override mechanism accessed so that the door can be unlocked and opened.

Typically the override mechanism comprises a uniquely shaped aperture forming an entryway such that a bayonet tipped override tool can be inserted through the entryway and engage the spindle allowing the lock to be turned and the door opened. The tip of the tool can pass through the entl3way and rotate behind the entryway. It will be appreciated that the shaping of the aperture chosen for the entryway may be varied. The cover may be provided with a fixing mechanism such as a screw that has to be released before the cover can be moved. As the cover is moved the ramped portions around the depression engage the extension of the disc and move the disc rearwardly against the action of the spring such that the cover can be slid to a position in which the override mechanism can be accessed by the override tool. Once the override tool has been inserted into the keyed entryway the indicator disc is pushed back fully against the action of the spring allowing the override tool to engage the spindle.

According to a second aspect of the invention there is provided a kit of parts which whcn assembled form an anti-barricade lock in accordance with the first aspect of the invention wherein kit of parts the comprises at least one of the following: a handle adapted to be fitted to a first side of the door; a plate arranged adapted to be fitted on a second side of a door; a spindle adapted to connect to the handle; an occupation indicator comprising a disc rotatable by the spindle; an override mechanism, and a cover arranged to fit to the plate over the override mechanism.

According to a third aspect of the invention there is provided a method of fixing an anti barricade lock to a door wherein the method comprises fitting a first handle to a first side of the door over a passageway through the door, connecting a spindle to the first handle and arranging the spindle to extend through the passageway to a second side of the door, locating a spring over the spindle, locating an indicator disc comprising a follower having a fir st surface with indicator markings, over the spindle, placing a plate on the second side of the door with the indicator disc extending through an opening in the plate and fixing the plate to the second side of the door, placing a cover over the indicator disc and securing the cover in place, wherein the lock has an override means concealed by the cover.

According to a fourth aspect of the invention there is provided an anti barricade lock comprising a handle fixable to a first side of a door in usc and a plate arranged to be fixable to a second side of the door and a spindle arranged to extend from the handle through the door wherein the anti-barricade lock has an override mechanism allowing the spindle to be operated from the second side of the door and further comprising a cover arranged to be moveable from a normal operating position in which the cover is secured over the override mechanism and an emergency position in which the cover exposes the override mechanism wherein the cover is arranged to slide relative to the plate.

Preferably the cover and plate are arranged to resist insertion of a ligature between the plate and the cover.

Preferably the cover and the plate each have a profile that is arranged to correspond.

Preferably the cover is arranged to slide in a channel in the plate. Preferably first and second ends of the cover are arrange to have a shape complementary to first and second edges of the plate at first and second ends of the channel. In a preferred embodiment the plate is provided with at least one recess along an edge of a side of the channel.

Preferably recesses are provided on both sides of the channel. It is desirable that the cover has a corresponding profile. Preferably the cover is provided with a longitudinally extending ridge along first and second sides of the cover.

Preferably the cover has a chamfered surface along the first and/or second side of the cover that slides along a corresponding chamfered surface on the plate. The chamfered surface on the plate may be provided in the channel. Preferably the chamfered edges are arranged to be angled relative to a base of the channel. Preferably an angle of incline of the chamfered surface measured from a centre of the channel is between 900 and 170°. More preferably the angle of incline is from 95° to 135° and more preferably still the angle of incline is from 1000 to 120° and in a particularly preferred embodiment the angle of incline is from 1100 to 115°.

The cover may be secured in position in the normal operating position by means of the locking screw Preferably the locking screw is an anti tamper locking screw such as a pin-torx screw The locking screw may be adapted to be received in an aperture located on a first side of the cover. Preferably the aperture is substantially centrally located along the first side of the cover. In a preferred embodiment the profile as arranged such that tightening of the locking screw acts on the cover so as to pull the chamfered surface of the cover against the corresponding chamfered surface on the plate and creates a pressure between the two surfaces. This seals a gap resulting from the sliding tolerances between the cover and the plate.

Preferably the cover and the plate arc clamped together so as to prevent any gap resulting in a potential ligature risk. Preferably a wire having a diameter of 4mm or greater is prevented from entering the gap. More preferably a wire of diameter 2mm or greater is prevented form entering the gap. More preferably still a wire of diameter 1mm or more is prevented from entering the gap and most preferably a wire of 0.5mm or more is prevented from entering the gap. Such a lock is considered to meet the standards set out in the technical specification written by the Door and Hardware Federation (DHF TS000I).

In a preferred embodiment a stop means is provided such that the cover can be slid from the normal operating position to allow access to the override mechanism but is prevented from disengaging with the plate. Preferably a stop means is provided to limit movement of the cover. In a preferred embodiment the stop means comprises a stop pin. In a more preferred embodiment the stop means is concealed when the cover is in place.

Preferably the aperture on the first side of the cover is sized such that the stop means can be fitted to the plate through the aperture. Preferably the stop means comprises a grub screw that can be fitted into a receiving hole in the plate in a fitting position. In a preferred embodiment the grub screw can be fitted to the plate through the central aperture. Once the grub screw has been fitted the cover can slide from the fining position to the normal operating position.

Preferably each cover is universal and is slideable in both directions from the normal operating position. Preferably in fitting the cover to the plate the stop means is fitted to the plate such that the cover is arranged to slide in only one direction from the normal operating position. The direction of sliding may be selected to correspond to the direction in which the door opens.

The invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic view of an anti-barricade lock in accordance with the invention; Figure 2 is a perspective view of a front of the plate; Figure 3 is a perspective view of a rear of the plate; Figure 4 is a side view of the plate; indicator disc and spring; Figure 5 a front view of a front of a plate of the lock together with a cover; Figure 6 is a rear perspective view of the plate and the cover; Figure 7 is an exploded cross section of a plate, cover and indicator disc; Figure 8 is a series of sketches showing a tool being used to operate the override mechanism.

Figure 1 shows a schematic view of a lock I in accordance with a first aspect of the invention in combination with a door 2 to which the lock 1 is fitted. The lock 1 comprises a first handle 4 located on a first side 6 of the door. A plate 8 is located on a second side 10 of the door together with a separate handle 11. A spindle 12 is arranged to extend from the handle 4 through a hole 14 in the door and a through a lock case 15 located within the door. An occupation indicator in the form of a disc 16 is positioned on the spindle and is arranged to rotate with the spindle. The disc is arranged to be retained between the second side 10 of the door and a rear face 18, best seen in Figure 3 of the plate 8. The disc 16 is also arranged to extend through an opening 20 in the plate.

A cover 22 is provided on a front 24 the plate and is secured to the plate 8 in normal use. An override mechanism is provided behind the cover 22 and this together with the cover will be described in more detail below. An aperture 26 in the cover allows the disctobevisible.

The plate will now be described in more detail in relation to Figures 2 and 3 and comprises a lock portion 28 arranged to locate and secure a cylinder lock 29. The cylinder lock 29 is located and secured within a lock aperture 30. Screw holes 32 are provided on either side of the lock aperture 30 to ensure that the plate 8 is secured to the door and that the lock cannot be tampered with. The cylinder lock allows the door to be locked from the outside of the door. The cylinder lock is conventional in the field and is operated by means of a key. Typically only staff would have access to the key A central portion 34 of the plate extends from the lock portion 28 towards an occupation indicator portion 36. The central portion is aesthetically pleasing. The central portion of plate often provides a useftil function of covering a surface of the door that has been degraded in opening a door in an earlier barricade scenario.

The occupation indicator portion 36 is arranged to extend around the occupation indicator disc 16 and the hole 14 in the door. The occupation indicator portion has a pcripheiy 38 that is substantially circular. The opening 20 is centrally located within the occupation indicator portion 36. Apertures 40 on either side of the central opening 20 arc arranged to receive securing screws which secure the plate to the door.

An override means is provided in the form of a uniquely shaped aperture forming an entryway 42 in the plate 8 around the opening 20. In this embodiment the uniquely shaped entryway 42 comprises a rim 44 having opposing recesses 46 arranged to receive the ends of a complimentary opening tool. Such override mechanisms are well known and conventional in the field. Complimentary tools have been provided in the past and are typically kept in a secure place by staff in a mental health institution. A suitable tool is shown in Figure 8 for completeness but it will be appreciated that alternative override mechanisms and tools can be used. In this embodiment the tool comprises a handle 48 and a shaft 50 having an engagement portion 52 comprising a spindle key 54 arranged to slide over an end of the spindle and to be able to rotate the spindle. The handle 48 enables the spindle to be rotated against any force exerted on the first handle 4 on the first side of the door by a patient. The engagement portion also comprises a pair of opposed lugs 56 sized and arranged to cooperate with the entryway 42. The tool is provided with two lugs and corresponding recesses are provided in the rim 44. A thickness of the lugs 56 is chosen such that the lugs can pass through the recesses 46 and rotate between a rear face 58 of the plate and a surface of the door. Once the lugs 56 have rotated the are retained behind the rim 44 and can act on a rear surface of the rim and pull the door open.

As seen in Figure 5 the cover 22 is arranged to be in place over the indicator disc 16 and the entryway 42 in normal use. The cover 22 is secured in place with a tamper resistant screw located in a central screw hole 60 in the cover. The cover 22 also has a centrally located aperture 26 located over the indicator disc 16 in normal use and through which the indicator disc can be used. In the event of an emergency the tamper resistant screw can be removed and the cover 22 slid from the normal position one which in the override mechanism can be accessed.

A front surface 62 of the cover is shaped to be aesthetically pleasing and complement the plate. Ends 64 of the cover arc curved to match the periphery of the indicator portion of the plate. The front surface 62 is also shaped such that the cover 22 can be slid from the normal position. In this embodiment the cover is provided with shaping 66 such that the cover is cuwed towards the ends, allowing a force to be applied to the cover.

As best seen in Figure 6 a rear surface 68 of the cover is ramped from a central depression 70 towards the ends of the cover. A central portion 70 of the cover is thinner than the ramped sections 72 and ends 64 of the cover. In this embodiment the depression 70 is centrally located.

Turning to Figure 7 the indicator disc 16 comprises a body 74 having an extension 76 on a first side of the of the body. The extension 76 is arranged to project through the opening 20 in the plate and has a front face 78 of the first side adjacent the rear face of the cover. The front face 78 is substantially planar and is provided with markings arranged in quadrants. The extension 76 of the indicator disc is arranged such that it locates within the depression on the rear face 68 of the cover. If the cover is slid to one side the ramped portions 72 of the cover act on the extension 76 to move the indicator disc 16 against the action ofa spring 80 acting on a rear face 82 of the indicator disc 16 as can be seen in Figure 5.

The rear face 82 of the indicator disc is provided with a location means arranged to locate the spring. In this embodiment the location means comprises recess 84 defined by a lip 86 arranged around a central aperture 88 of indicator disc, through which the spindle passes, and a rearwardly extending rim 90 around a periphery of the body.

Referring to Figure 4 the spring 80 has a first end 92 located within the recess and a second end 94 that acts on a lock case in the door. The spring 80 is tapered and each coil reduces in diameter such that when the spring is fully compressed each coil is able to fit within the adjacent outer coil. The spring 80 can therefore reduce to a thickness that is a thickness of one coil of the spring.

When the override tool is inserted through the key way 42 an end of the engagement portion 52 acts on the first side of the extension 78 and moves the indicator disc against the action of the spring such that the engagement portion can fit over the end of the spindle. The spring may be fully compressed or may only be partially compressed. The indicator disc is moved a sufficient distance to allow the lugs of the tool to fit under the ledge and rotate the spindle.

Since the indicator disc is movable behind the rear face of the plate the disc 16 is able to move against the action of the spring 80 but is held captive between the plate 8 and door. A significant advantage over the prior art is thus achieved in that the cover can be removed and the override mechanism engaged without risk of the indicator disc coming out of the lock and being lost.

An alternative aspect of the invention will now be described.

An anti barricade lock is provided comprising a handle fixed to the first side of a door in usc and the plate fixed to a second side of the door. A spindle is provided extending flt,m the handle through the door and through an opening in the plate. An override mechanism is provided in the opening allowing the spindle to be operated from the second side of the door and a cover arranged to be slideable from a normal operating position in which the cover is secured over the override mechanism and an emergency position in which the cover exposes the override mechanism.

The cover 22 and plate 8 are arranged to resist insertion of a ligature between the plate and the cover. The cover has a channel 96 extending from a first side 98 to a second side 100 of the indicator portion. The channel extends to the periphery of the indicator portion. The cover has first and second ends 64 that correspond in shape to the periphery of the indicator portion.

In this embodiment each side 102 of the channel is provided with a recess 104 shaped to receive a complementary longitudinally ridge 106 extending along first and second side of the cover. Each of the sides 102 has a chamfered surface 108 that slides along a corresponding chamfered surface 110 on each side of the cover. The chamfered surftces 108 and 110 are angled and the angle ofthe chamfered surfaces 108, 110 is selected to ensure that the cover and the channel can be closed when the cover is in the normal operating position in order to prevent a ligature being inserted between the surftces. In the disclosed preferred embodiment an angle of incline of the chamfered edge is measured from a centre of the channel and is between 1000 and 1200. In this embodiment the angle of incline is 1100. In the normal operating position a locking screw secures the cover in position and the screw is typically an anti-tamper locking screw such as a pin-ton screw. A central aperture 112 on a front side of the cover is arranged to receive the locking screw and the screw acts on the plate and pulls the chamfered surface 110 of the cover against the corresponding chamfered surface 108 on the plate and creates a pressure between the two surfaces. The pressure is such that a gap resulting from sliding tolerances between the cover and the plate is closed by the action of the screw. In a preferred embodiment the gap is sufficiently small that a ligature of 0.5mm cannot be inserted in the gap.

The cover and plate arc provided with stop means such that the cover can slide in only one direction, dependent on the handedness of the door, and such that the cover cannot be removed from the plate. The stop means comprises a grub screw located to one side of the central aperture. A slot 114 is provided in a rear face of the cover. The slot is provided extending along one side of the cover and in line with the aperture 112 through which the locking screw is located. The grub screw can be inserted in position during installation of the lock by sliding the cover 22 to one side and locating the grub screw into a receiving hole 114 in the plate. Once the grub screw has been inserted the cover can be slid towards the normal operating position. An end 116 of the channel acts on the grub screw to prevent the cover being slid past the grub screw. The grub screw is concealed and prevents the cover from being slid off the plate.

Once the plate has been installed with the cover in place on the plate, the override mechanism, which has already been described, caimot be accessed. In the case of an emergency the anti tamper screw can be removed and the cover slid to one side until it is stopped from moving further by the concealed grub screw. The override tool can then be inserted and the spindle rotated so that the door can be opened.

It will be appreciated that the sliding cover can be used in conjunction with the indicator disc afready described. In such an embodiment the cover has a viewing aperture allowing the indicator disc to be visible. Alternatively the cover can be used in combination with a lock that does not incorporate an indicator disc in which case the cover does not need to have a viewing aperture.

The lock can be fitted to a door by fixing the first handle to an inside of the door and securing the spindle to the first handle. The spindle is arranged to pass through a passageway in the door and is sized such that a distal end of the spindle is substantially flush with a second side of the door. The spring is located over the spindle and an indicator disc is placed over the spring and onto the spindle such that the indicator disc is rotatable with the spindle. The plate is secured to the second side of the door with the indicator disc extending through the opening in the plate. A uniquely shaped aperture forms an entryway in the plate around the opening so that an override tool can access the spindle by moving the indicator disc back against the action of the spring. A cover can be secured over the opening and the override means. The indicator disc is secured in place between the plate and door and will not fall out when the cover is removed.

The cover can be lid into a fitting position and a stop pin fitted through a central lock aperture. Once the stop pin has been fitted the cover can be slid to a normal operating position and a locking scrcw fitted. The cover has a viewing aperture located over the indicator disc in the normal operating position.

Claims

CLAIMS1. An anti-barricade lock having an occupation indicator and comprising a first handle locatable on a first side of a door to which the lock is fixed in use, a plate having an occupation indicator locatable on a second side of the door, and spindle arranged to connect the handle to the occupation indicator wherein the occupation indicator comprises a disc rotatable by the spindle, the anti-barricade lock having a cover securable over the indicator disc and the spindle and wherein the occupation indicator is secured in use between the door and the plate.
2. An anti-barricade lock according to claim 1 wherein the lock has an override mechanism that enables the spindle to be rotated from the second side of the door.
3. An anti-barricade lock according to claim 2 wherein the override mechanism can comprise an end of the spindle that can be engaged by a suitable tool and rotated.
4. An anti-barricade lock according to claim 2 or claim 3 the override mechanism comprises a uniqucly shaped cntryway arranged such that the tool can be inserted through the shaped entryway and rotated.
5. An anti-barricade lock according to any preceding claim the cover is moveable such that the override mechanism can be engaged.
6. An anti-barricade lock according to claim 5 wherein the cover may be rotated or may be provided with a sliding mechanism allowing the cover to be moved flvm a normal operating position in which the occupation indicator and spindle to an emergency position in which the override mechanism can be accessed and engaged.
7. An anti-barricade lock according to claim 6 wherein the cover is slideable from the normal operating position.
8. An anti-barricade lock according to any preceding claim wherein the cover is provided with an aperture overlying the indicator disc when the cover is in the normal operating position such that the indicator disc is visible through the aperture.
9. An anti-barricade lock according to any preceding claim wherein the plate is provided with an opening through which the indicator disc is visible.
10. An anti-barricade lock according to claim 9 wherein the indicator disc projects at least partially through the opening.
11. An anti-barricade lock according to any preceding claim wherein the indicator disc is movcablc between a first position located adjacent or in contact ith a rear portion of the plate and a second position in which the override mechanism is accessible.
12. An anti-barricade lock according to claim 11 wherein the indicator disc comprises a body having an extension a first side of which may be provided with indicator markings.
13. An anti-barricade lock according to claim 12 wherein a rear face of the indicator disc has location means arranged to locate a spring acting on the rear face of the indicator disc.
14. An anti-barricade lock according to claim 13 wherein the spring comprises a tapered coil.
15. An anti-barricade lock according to claim 14 wherein the taper of the coiled spring is such that when completely compressed each coil of the spring fits within a preceding adjacent coil and a total thickness of the spring is a thickness of one coil.
16. An anti-barricade lock according to claim 1 wherein the cover comprises a slider arranged to extend fmm a first edge of the plate to a second edge of the plate.
17. An anti-barricade lock according to claim 16 wherein the slider has a rear face that has at least one ramped portion.
18. An anti-barricade lock according to claim 17 wherein the slider has a depression sized such that a part of the indicator disc can sit within the depression in the normal operating position.
19. Akit of parts which when assembled fbrms an anti-barricade lock in accordance with claim 1 wherein the kit of parts the comprises at least one of the fbllowing: a handle adapted to be fitted to a first side of the door; a plate arranged adapted to be fitted on a second side of a door; a spindle adapted to connect to the handle; an occupation indicator comprising a disc rotataNe by the spindle; an override mechanism, and a cover arranged to fit to the plate over the override mechanism.
20. An anti barricade lock comprising a handle fixable to a first side of a door in use and a plate arranged to be fixable to a second side of the door and a spindle arranged to extend from the handle through the door wherein the anti-barricade lock has an override mechanism allowing the spindle to be operated from the second side of the door and further comprising a cover arranged to be moveable from a normal operating position in which the cover is secured over the override mechanism and an emergency position in which the cover exposes the override mechanism wherein the cover is arranged to slide relative to the plate.
21. An anti-barricade lock according to claim 20 wherein the cover and plate are arranged to resist insertion of a ligature between thc plate and the cover.
22. An anti-barricade lock according to claim 20 or 21 wherein the cover is arranged to slide in a channel in the plate.
23. An anti-barricade lock according to claim 22 wherein plate is provided with at least one recess along an edge of a side of the channel.
24. An anti-barricade lock according to claim 23 wherein the cover has corresponding longitudinally extending ridge along at least one sides of the cover.
25. An anti-barricade lock according to claim 24 wherein the cover has a chamfered surface along the first andior second side of the cover that slides along a corresponding chamfered surface on the plate.
26 An anti-barricade lock according to any one of claims 20 to 25 wherein the cover is securable in the normal operating position by means of a locking screw.
27. An anti-barricade lock according to claim 26 wherein the profile is arranged such that tightening of the locking screw acts to pull the chamfered surface of the cover against the corresponding chamfered surface on the plate.
28. An anti-barricade lock according to any one of claims 20 50 27 wherein a wire having a diameter of 4 mm or greater is prevented from entering between the cover and the plate and more preferably a wire of diameter 2 mm or greater is prevented from entering between the cover and the plate and more preferably still a wire of diameter 1 mm or more is prevented from entering between the cover and the plate and most preferably a wire of 0.5 mm or more is prevented from entering between the cover and the plate.
29. An anti-barricade lock according to any one of claims 20 to 28 wherein a stop means is provided such that the cover is prevented from disengaging with the plate.
30. An anti-barricade lock according to claim 29 wherein the stop means is concealed stop means is provided to limit movement of the cover.
31. An anti-barricade lock according to any one of claims 20 to 30 wherein each cover is "handed" in that it is arranged to slide in one direction from the normal operating position.
32. An anti-barricade lock substantially as described hereinbefore with reference to the accompanying drawings.