AU735656B2 - A lock - Google Patents

Description

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AUSTRALIA

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-John Russali WAttc YCrr4 Ri A P R LU ADDRESS FOR SERVICE: Patent Attorneys, ?O 13ox ILittle ins Street LC030V~tie vic ARJTHUR~ IZR1HSoN aHDD~~~k 3001 INVENTION TITLE: A Lock The following statement is a full description of this invention, including the best method of performing it known to me: Q.\OPER\RSH\696343.D1V Y12/98 L. may. uI 1 :4 R~ X hi MPLblUUINPlJ. Oi J0144001 110. JDJ r. J/O0 A lock Field of the invention This invention relates to door locks and in particular relates to locks for security doors.

Summary of the invention According to the invention there is a lock including a strike plate mountable to an element defining part of a door opening and a lock body mountable to the door, said lock body including a casing, an auxiliary bolt supported by the casing and having a leading portion said auxiliary bolt being displaceable from an extended position where the leading portion protrudes from the casing, a first displaceable member both distinguishable from and operably associated with the auxiliary bolt, an outwardly biassed latch bolt supported by the casing and having a leading portion, said latch bolt being rectilinearly displaceable between a retracted position where the leading portion is substantially within the casing and a fully extended position where the leading portion protrudes from a casing aperture in the casing, the lock being characterized by the bolt and auxiliary bolt each being engageable on either same side by the strike plate to be displaced away from the strike plate during latching, and a pre-latching configuration in which the auxiliary bolt is in the extended position 2o and the first displaceable member is restraining the latch bolt from displacing towards the fully extended position.

Preferably, the casing adjacent the casing aperture is strengthened by the construction wherein opposed side portions of the casing are comprised of the same casting.

Preferably, the casing adjacent the casing aperture is strengthened by the construction wherein at least one web connects the front wall to at least one side portion, RA4c,, R clrrn MOI 109324I10W 151503 22/05 '01 TUE 15:00 [TX/RX NO 9750] lb said case strengthening providing improved support for the bolt to enable the extended bolt to better resist side loadings applied during attempted forced entry of the door.

Preferably, the strike plate has an engageable strike plate aperture with which the latch bolt engages by extending from the casing to pass through the strike plate aperture, said strike plate aperture and latch bolt cooperating to provide longitudinal engagement when the latch bolt is urged towards a side edge of the strike plate aperture, said longitudinal engagement being provided by a channel in the side of the latch bolt and the strike plate aperture side edge.

oo Preferably, in the pre-latching configuration the latch bolt is restrained in a partly i extended position free to be displaced towards the retracted position.

Preferably, the auxiliary bolt is displaceable from the extended position whereby S 15s to enable the latch bolt to be displaced to the fully extended position.

i .Preferably,.the first displaceable member is engageable by the auxiliary boltto.

retain the latch bolt in the restrained position 20 Preferably, the first displaceable member has an engaging shoulder engageable i with an engageable shoulder of the auxiliary bolt when the auxiliary bolt is in the extended position.

Preferably, the engageable shoulder is displaceable from the locus of movement of the engaging shoulder by auxiliary bolt displacement.

Preferably, the auxiliary bolt includes a rearwardly disposed portion engageable with a ramped shoulder of the casing by auxiliary bolt displacement to be displaced away from the first moveable member whereby to move the engageable shoulder of the auxiliary bolt from the locus of movement of the engaging shoulder of the first displaceable member.

Preferably, the lock includes operating means by which to cause the latch bolt to be displaced towards the retracted position, said operating means including a hand operable member operably operably connected to the latch bolt by the first displaceable member.

Preferably the lock includes a handle assembly comprising the hand operable member and a spring biased slide supported for rectilinear displacementbb and acting to urge the hand operable member towards an undisplaced position.

Preferably, the lock includes deadlocking means to restrain the bolt from being displaced towards the retracted position, said deadlocking means including a key operable cylinder and a hand operable snib lever.

15 Preferably, the deadlocking means includes a deadlocking slide operatively connected to the cylinder and snib lever and displaceable by cylinder operation and snib i ~lever rotation, said deadlocking slide being displaceable between a deadlocking position in which it restrains the bolt from being displaced towards the retracted position and a free position where it does not so restrain the bolt.

'Preferably, the leading portion of the latch bolt comprises similarly curved or bevelled sides.

Preferably, the leading portion of the auxiliary bolt comprises similarly curved or bevelled sides Description of the Drawings Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is an isometric view of a lock in a door with a fully extended latch bolt, where the front edge of the lock body and the interior lever assembly is shown with the "snib" locking lever Figure 2 is schematic side view of a deadlocked lock body showing the latch bolt supported between casing ribs extending from the front edge of the casing, Figure 3 is a schematic side view of the lock body with the latch bolt held partly retracted, Figure 4 is a schematic plan view of the lock body, •Figure 5 is a partial front edge view of the lock body showing the latch bolt aperture wholly within a single casting and having radiussed corners; this single casting :i including the front edge of the casing, s5 Figure 6 is a side edge schematic view of a lever assembly having a slide, Figure 7 is a partial sectional schematic view of the lever assembly of Figure 6 i from the back sectioned through the slide, Figure 8 is a partial sectional schematic view of the lever assembly of Figure 6 from the back sectioned through the driven cam, 20 Figure 9 is a is a side edge schematic view of an interior lever assembly, Figure 10 is a partial view of the back of the lever plate of Fig. 9 showing the barrel and surrounding cylinder housing, Figure 11 is the sectional view BB Figure 9, Figure 12 is the sectional view AA Fig 9, Figure 13 is a schematic plan sectional view of a lock body with a protruding bolt located within a strike plate, Figure 14 is a schematic plan sectional view of a lock body with a protruding latch bolt located within a strike plate where the bolt has been forced against the edge of the strike plate aperture and the lock has been forced away from the door jamb.

Figure 15 is a partial sectional schematic side view of a lock body with a pivotally displaceable latch bolt, Figure 16 is a is a schematic plan view of the lock body of Figure Description of the Preferred Embodiments The accompanying drawings illustrate a number of embodiments of the invention which provides a number of locks and portions of locks which are applicable to other types of locks without being limited to locks for security doors. Generally, the same reference numerals are used for like components in all embodiments as shown. The positional prepositions such as rear forward used with reference to the accompanying figures and are used to assist in description of the preferred embodiments and have in general no absolute meaning One embodiment of the invention as shown in Figures 1 and 2 comprises in summary, a lock comprising a lock body assembly, a pair of handle assemblies and a strike plate. The lock body includes a casing 10 supporting other component parts, including a latch bolt 20 supported within the casing and displaceable under biasing'of spring 30 to extend from the casing where it can engage in a recess 2 within the strike plate 1, as shown in Figure 13, which has a fin 1A engageable by the latch bolt to facilitate latching during which process the latch bolt is driven inwardly as the leading i ~portion slides up the ramped portion of the fin. The latch. bolt is retractable by operation of a lever 61 in a lever assembly 60 connected to the lock body by a shaft 55 as shown in Figure 9. In a preferred embodiment there is wilh;in the casing a deadlocking slide 20 Figure 2, which can be moved into engagement with a shoulder on the latch bolt to restrict inward displacement of the latch bolt. This is caused by actuation of a key operable barrel 112, Figure 1, or actuation of other actuating means.

In preferred embodiments the lock has a pre-latching configuration to enable latching with the strike plate. In this pre-latching configuration the latch bolt is retained in a partly extended position, outwardly biased but restrained from outwardly displacing by means including the auxiliary bolt 70; in normal operation inward displacement of the auxiliary bolt and latch bolt during latching causes the auxiliary bolt to displace to a configuration where it cannot act to cause restraint of the latch bolt thereby enabling the latch bolt to displace to the fully extended position when it becomes aligned with an aperture in the strike plate.

The locks provided by the invention are different from those described in the prior art both in construction and in function. The invention provides locks which include some or all of the following features: unlatching when inverted by having levers that function in either angular direction, reduced manufacturing cost by combining the cylinder with the lever assembly, levers that can be quickly dismantled for packaging reasons, a casing of increased strength, resistance to forced entry, improved means of restraining the latch bolt partly retracted to facilitate latching.

In an embodiment and as shown in Figures 2 and 5, the lock casing 10 is box like having a front wall 16, a rear wall 19 and upper and lower walls 18 and an upper tab 0 and a lower tab by which the casing is attachable to a door. Within the front wall 16 .there is an aperture 11 through, which a -latch bolt20 has, passagett- be displaceable to an extended position where it protrudes from the casing.

S" In a preferred embodiment there is also an aperture 14 through which the auxiliary bolt 70 has passage to be displaceable to an extended position where it protrudes from the casing.

20 Within the side walls of the casing there are apertures which support lock body internal component parts. The casing comprises a front portion and a rear portion abutting at a plane orthogonal to the direction of displacement of the latch bolt and intersecting the casing; the front portion comprising the front wall 16 with the aperture 11, the fixing tabs, side wall portions on each side and upper and lower end wall portions which together comprise a single casting to provide greater strength.

The front portion preferably has blades 13 extending rearwardly which pass through mating apertures in the rear casing portion and which are preferably peened over to secure the two portions together as shown in Figure 2. Within the front portion there are preferably internal webs 12 joining the front wall 16 to a side wall to strengthen the casing adjacent the aperture 11 while the aperture 11 has radiussed corners, Figure to resist cracking the additional casing strength providing greater support for the bolt so that the extended bolt and casing are better able to resist the side loadings that occur during attempted forced entry.

In preferred embodiments the latch bolt 20 is of a solid box like construction with radiussed top and bottom edges to mate with the radii in aperture 11 and it is supported between the webs 12 which are elongated rearwardly to provide therebetween a substantially parallel walled recess in which to support the latch bolt while enabling it to be freely, substantially rectilinearly, slideable. This latch bolt has a leading portion 22 which is displaceable between a retracted position where it is within the casing and a fully extended position where it protrudes from the casing. The latch bolt is outwardly biassed and moveable by spring 30 and inwardly moveable by a first moveable member said first moveable member including an operating arm 40, which is operably connected to the lever 61. The latch bolt rearwardly has a recessed portion 24 within which the operating arm 40 locates in front of a protruding drive shoulder 23 of the latch bolt.

Rearward movement of.the..operatingarm 40 causes the arm to engage the drive shoulder 23 and move it rearwardly to retract the latch bolt.

In preferred embodiments, Figures 3 and 4, where the lock has a "pre-latching" configuration in which the latch bolt is retained partly extended prior to latching, 'the latch bolt leading portion has both sides similarly curved as shown in Figure 4, progressively reducing in width by being curved, radiussed and/or bevelled on the sides), to facilitate inward displacement by the strike plate when engaging the leading portion on either side. This is to accommodate both left and right hand opening doors. In this embodiment, the operating arm 40 passes across the latch bolt so that a shoulder 41 on its free end is engageable by a shoulder 71 of the auxiliary bolt 70 to restrain the portion of the operating arm 40 which engages shoulder 23 from displacing in a forward direction Depression of the auxiliary bolt causes the shoulder 71 to move out of the path of movement of shoulder 41 to preclude engagement between the said shoulders and so enable the latch bolt to displace, under the action of spring bias, to the fully extended position.

In another preferred embodiment, Figure 15, the latch bolt comprises a pivotal bolt 29 angularly displaceable and supported on a pin 29A within the casing which passes from one side to the other to be supported in both sides of the casing. It is similarly spring biased to displace towards an engageable position and moveable away from this position by the operating arm acting similarly as described above.

In an embodiment configured for sliding doors, the pivotal latch bolt operates entirely or substantially within the confines of the casing and the strike plate comprises a catch plate with a protruding portion with an engageable recess which has passage through the aperture 11 to be engaged by the latch bolt.

In an embodiment configured for a hinged door the pivotal latch bolt has a leading portion 22 which is displaceable between a retracted position where it is within the casing and a fully extended position where it protrudes from the casing; the leading portion preferably having a hooked end which engages in and behind the strike plate aperture. This latch bolt leading portion preferably has both sides similarly contoured -as' shown in Figure 16, and as described above in relation to the rectilinearly displaceable 15 latch bolt, to facilitate inward displacement by the strike plate when engaging the leading portion on either side. This is to accommodate both left and right hand opening doors.

:In preferred embodiments where the lock has a "pre-latching" configuration in which the pivotal latch bolt is retained partly extended prior to !atchirlg to facilitate 20 latching, the operating arm 40 passes across the latch bolt so that a shoulder 41 on its free end is engageable by shoulder 71 of the auxiliary bolt 70 as described above in :relation to the rectilinearly moveable latch bolt. Depression of the auxiliary bolt causes the shoulder 71 to move out of the path of movement of shoulder 41 to preclude engagement between the said shoulders The auxiliary bolt, Figure 3, preferably comprises a leading portion 75 which is displaceable to extend from the casing under the action of biasing spring 73 and a rear portion comprising an angled face 72 adjacent the shoulder 71 extending towards the latch bolt. The casing has a ramped rib portion 17 which when the auxiliary bolt is fully extended is adjacent the angled face 72 whereby inward displacement of the auxiliary bolt by strike plate fin engagement during latching causes face 72 .to slide up the ramp 17 to displace the shoulder 71 away from the latch bolt operating arm shoulder 41 and out of the path of movement of the shoulder. The rear portion of the auxiliary bolt is free to- move vertically to a limited extent against biasing means derived from the biassing spring 73. The auxiliary bolt leading portion preferably has both sides similarly contoured as shown in Figure 4, progressively reducing in width by being curved, radiussed and/or bevelled on the sides), to facilitate inward displacement by the strike plate when engaging the leading portion on either side.

In an embodiment, the latch bolt, Figure 3, is driven inwards against biasing by spring 30 by the operating arm 40 which is supported on a cylindrical portion of operating cam 50 which is supported in circular apertures in the side walls of the casing. The 0io operating arm has an engageable, preferably substantially opposite, shoulder 42 radially o: displaced from, and preferably on the opposte side of its axis of rotation, whereby i forward displacement of the shoulder 42 causes the operating arm to rotate to engage S the-drive shoulder 23 of the latch bolt to drive the latch, bolt rearwardly and inwardly. The..

operating cam 50 being coupled to the lever 61 in the external lever assembly 60 bythe S 15 substantially rectangular shaft 55, is caused to rotate when the lever is rotated by lever operation. The shaft 55 engages in a mating coaxial recess in the operating cam.

o°• In an embodiment, there is an operating slide 90 operably interspaced between the lever 61 and operating arm 40 to enable the latch bolt to be displaced rearwardly by 20 lever rotation in either direction. The operating slide 90 may be within the lever 0O00 assembly, Figures 6 to 8, but it is preferably within the casing 10, Figures 3. In the latter case, the operating cam 50 has two, (preferably substantially opposite) shoulders 53 one on each side of its axis of rotation and the operating slide has a corresponding shoulder 91 one on each side of the axis of rotation of the operating cam adjacent the said operating cam shoulders 53 and engageable by the corresponding shoulder.

The operating slide is supported between webs 12 and web 13 in the casing and is free to slide. It is biassed by springs 92, which locate within elongated recesses within the operating slide, towards the operating cam. In the undisplaced position the shoulders 91 are held pressed against the shoulders 53 to cause the operating cam to adopt an undisplaced position. Preferably the shoulders 53 are winged extensions of the operating cam and the shoulders 91 mate with shoulders 53 in the undisplaced positions of the operating cam and operating slide. On the operating slide is a pinned protrusion 93, preferably being an extension to the lower shoulder 91, which is engageable with the operating arm shoulder 42. Rotation of the lever 61 in either direction causes one of the shoulders 53 to displace the operating slide away from the cam 50 to cause the portion of the operating arm which engages the drive shoulder 23 to displace rearwardly.

Although shown sliding in a direction parallel to the direction of latch bolt displacement, and this is the preferred direction of movement), the operating slide can move in any direction within the plane of the latch bolt; provided the pinned protrusion 93 and shoulder 42 are radially displaced from the axis of rotation of the operating arm and provided the pinned protrusion 93 displaces in a direction having a component tangential to the axis of rotation of the operating arm.

i In another embodiment Figures 6, 7, 8, operating slide 90 is within the lever assembly 60 and the operating cam 50 islcoupled directlyto theflever 61' by splined engagement as shown in Figure 7. In this embodiment the operating arm 40 is attached 15 directly to a cylindrical boss which has a recess to receive to operably couple to the shaft said boss being supported within apertures in the side walls of the lock body casing.

i ~In this embodiment the operating arm is caused to angularly displace by boss angular displacement itself angularly displaced by angular displacement of the drive shaft.

The operating slide 90 on one layer, Figure 7, has the shoulders 91 and the cam has wings 53 on the same vertical layer, so rotation of the lever and cam in either direction causes one of the wings 53 to drive the operating slide away from the axis of rotation of the cam 50 against urging by the biassing means comprising spring 92A. (A layer being a vertical plane parallel with a side of the casing). On another layer, Figure 8, the slide has has a protrusion 93 which locates in a recess 56 in a disc-like cam 100 member. This cam 100 has an integrally attached shaft portion 55, which in useage connects to the boss connected to the operating arm within the lock body. The disc-like cam 100 peripheral recess 56 has clearance below the protrusion 93 and a radial shoulder 101 adjacent the top of the protrusion 93 so that operating slide movement in response to lever rotation in either direction causes the operating slide to displace away from the axis of rotation of the cam 50 against urging by the spring 92A to rotate the cam 100 in the same direction, a direction corresponding with actuation of the operating arm to retract the latch bolt. As described above in relation to a previously described embodiment, in the undisplaced positions of the operating slide and operating cam, the shoulders 91 are held pressed against the shoulders 53.

In an embodiment, the latch bolt is securable in the fully extended position by a deadlocking slide supported adjacent the latch bolt within the casing and having a leading portion 81 which can be actuated by one or other actuating means to displace towards the latch bolt to engage it wherein the leading portion 81 engages behind the shoulder 28 of the latch bolt, Figure 2, to restrain the latch bolt from being moved inwardly.

**The actuating means includes a key operable barrel 112, Figure 1 and Figure 9, V comprising a portion of a locking cylinder operably coupled to an angularly displaceable cam 110, Figure 3. This cam has-an-armed extension 111 which locates within a .0 concave recess 82 in the deadlocking slide which is bounded by a lower shoulder 83 15 and an upper shoulder 84. The deadlocking slide can be moved towards and away from the latch bolt by cam rotation by the armed extension 111 engaging one of the shoulders 0i 84 or 83 respectively and the cam can be rotationally displaced, within limits, by deadlocking slide movement. While the armed extension remains within the bounds of the shoulders 84 and 83 it remains optrab!y coupled to the deadlocking slide, for S. 20 convenience called a first range of coupled movement but when the deadlocking slide is substantially fully travelled towards the latch bolt and is in the deadlocking position, for convenience called a second locking configuration, the cam can be partially further rotated to effect a surface of contact between the extension 111 and an angled shoulder 84A of the deadlocking slide extending from shoulder 84 which is substantially orthogonal to the cam centre of rotation thereby preventing the deadlocking slide from driving the cam, for convenience called a first locking configuration, at which position the the deadlocking slide cannot be actuated by the other actuating means and the lock can only be released from this configuration by cam rotation. In a preferred embodiment, the cylinder comprises a double cylinder having two barrels, one on each side of the cam, and connected to the cam, said cam being operable by either barrel.

In a preferred embodiment the key operable cylinder comprises the angularly displaceable cam 110 supported in apertures within the side walls of the casing and a key operable angularly displaceable barrel 112 supported in acylinder housing 152 comprising a portion of the lever assembly 60, Figure 9. The barrel preferably has a peripheral end side protrusion 151 in line with the wafers 153 and similar in form to an extended wafer. The housing has the normal longitudinal elongated slotted 155 recesses to facilitate wafer movement as is well known; however in this case one recess has an end wall 156 while the other has an aperture 157 to permit passage of the end side protrusion so that when the barrel is inserted through the aperture and rotated it cannot be removed. Preferably the barrels and cam are coaxially supported and the barrel extension engages in a recess 158 in the cam, Figure 3, to operate the cam.

Once assembled the barrel movement is restricted by its engagement with the cam to 0% 0 positions where the protrusion 151 does not become aligned with the aperture 157 thereby ensuring the barrel cannot be removed in normal usage. In some embodiments the lock body is mounted'within-a frame having thin wallsand the lever assemblies are mounted on the external surface of the frame and the barrels extends through the frame 15 to communicate with the lock body. To accommodate variation in the distance between the lever assemblyies and the lock body the engagement between the barrels and cam recess is splined in form The "snib" actuatirg means, comprises a cylindrical cam 121, Figure. 3, having a coaxial recess engageable by the shaft 163 of a snib lever 164, Figure 1, 9 in the interior lever assembly. The cam 121 has an armed extenstion 122 with a protruding pin which protrudes sideways to locate within a substantially horizontal recess 85 in the deadlocking slide so that the slide is moveable between extreme positions by snib lever rotation subject to the deadlocking slide not being restrained in the first locked configuration.

The lever 61, Figure 9, is removeably retained within the lever assembly 60. It comprises a hand operable ball or lever 62 integrally connected to a cylindrical shaft 63 which is retained free to rotate within a substantially cylindrical aperture 64 in a boss of the lever assembly backplate 66. The shaft has peripheral end protrusions 67 and the boss has elongated slotted apertures 68 to permit pasage of the protrusions 67. When the lever is assembled onto the back plate and is rotated the lever is retained by the protrusions. Preferably there are two opposite protrusion and the coupled operating cam 11 requires less than 90 degree movement so that once the lever is connected by the shaft to the operating cam its movement is restricted so that the apertures 68 and protrusions 67 do not align in normal usage. It will be appreciated that prior to assembly of the lever assembly to the casing both barrels and levers can be inserted and/or changed as is required.

In a preferred embodiment a snib locking lever, Figure 1, 9 comprises a cylindrical boss portion 161 integrally connected to its associated shaft 163 which extends from the underside of the back plate and has a hand operable portion 164 within a concave recess 165 in an end of the back plate as distinct from "snib" levers in •common use which sit on the face of the back plate and protrude from the form of the back plate the recess providing protection from exterior operation of the member.

Preferably the hand operablemember164 comprisestwo arms which are angularly displaced in relation to each other and project substantially radially from the cylindrical boss portion. They are relatively disposed at approximately the same angle as the cam 121 moves between its limits of rotation and angularly disposed so that when the deadlocking slide is in the deadlocked position a side of the operable portion 164 is adjacent a side of the recess while when the deadlocking slide is at the other extent of its travel, the unlocked, position, another side of the operable portion 164 is adjacent a side o 20 of the recess these obviously recognizable configurations providing a visual indication the configuration of the lock; i.e. locked or unlocked. This member is substantially oo supported by the shaft 163.

In a preferred embodiment the lock includes a latch bolt supported within a casing and having a leading portion displaceable between a retracted position and a fully extended position, the latch bolt being engageable within an aperture in the strike plate in catching engagement and also being in longitudinal engagement to restrain the latch bolt from being longitudinally removed from the strike plate. This is achieved by having a channel 400 in the side of the latch bolt which, in relation to an extended latch bolt, comprises an exposed orthogonal elongated concave recess extending from top to bottom of the side of the latch bolt. This channel, preferably has an inclined wall 401 on the leading side of the latch bolt engageable by the edge 402 of the strike plate recess when the latch bolt is forced against the edge 402 of the recess. The inclined wall lla enables the latch bolt to be retracted during normal unlatching, without catching on the edge of the aperture whereas a recess having "straight" side walls may catch and impede the latch bolt from retracting. It will be appreciated that the steeper the angle the better the longitudinal engagement but the greater the risk of fouling a satisfactory trade off has been achieved with the design shown in the figures. In the case of the pivotal latch bolt 29 the hooked portion 213 engages behind the aperture in the strike plate.

In a preferred embodiment the strike plate, Figure 13 and Figure 14, comprises a fixable first portion 460 connected to a second portion 461 by a deformable interconnecting portion 462 said second portion including the engageable aperture within and behind which the latch bolt is engageable; the second portion being displaceable relative to the'firstportion to restrain relative displacement between the bolt and plate aperture. Such a strike plate enables the latch bolt and strike plate aperture to remain 15 engaged while they are displaced together relative to the fixed portion attached in usage, to a door jamb. This mutual displacement can occur during attempted forced entry when a door is subjected to side loadings.

The positional prepositions such as rear forward are used in reference to the 20 accompanying drawings to assist in description of the preferred embodiments and have in general no absolute other significance.

ooo* Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

Claims (4)

1. A lock including a strike place mountable to an clement defining part of a door opening and a lock body mountable to the door, said lock body including a casing, an auxiliary bolt supported by the casing and having a leading portion said auxiliary bolt being displaceable from an extended position where the leading portion protrudes from the casing, a first displaceable member both distinguishable from and operably associated with the auxiliary bolt, an outwardly biassed latch bolt supported by the casing and having a leading portion, said latch bolt being rectilinearly displaceable between a retracted position where the leading portion is substantially within the casing and a fully extended positon where the leading to portion protrudes fron a casing aperture in the casing. the lock being characterized by the bolt and auxiliary bolt each being engageable on S either same side by the strike plate to be displaced away from the strike place during latching, and a pre-latching configuration in which the auxiliary bolt is in the extended position and 15 the first displaceable member is restraining the latch bolt from displacing towards the fully extended position.

2. A lock according to Claim 1, wherein the casing adjacent the casing aperture is strengthened by the construction wherein opposed side portions of the casing ate comprised S. of the same casting. o 20

3. A lock according to Claim 1 or Claim 2, wherein the casing adjacent the casing aperture is strengthened by the construction wherein at least one web connects the front wall to at least one side portion, said case strengthening providing improved support for the bolt to enable the extended bolt to better resist side loadings applied during attempted forced entry of the door.

4. A lock according to any one of the above claims, wherein said strike plate has an engageable strike plate aperture with which the latch bolt engages by extending from the casing to pass through the strike plate aperture, said strike plate aperture and latch bolt cooperating to provide longitudinal engagement when the latch bolt is urged towards a side edge of the strike plate aperture, said longitudinal engagement being provided by a channel in Sthe side of the latch bolt and the strike plate aperture side edge. clrn MO110932410vI 151503 22/05 '01 TUE 15:00 [TX/RX NO 9750] A lock according to any one of the above claims, wherein in the pre-latching configuration the latch bolt is restrained in a partly extended position free to be displaced towards the retracted position. 6 A lock according to any one of the above claims, wherein the auxiliary bolt is displaceable from the extended position whereby to enable the latch bolt to be displaced to the fully extended position. 7 A lock according to any one of the above claims, wherein the first displaceable member is engageable by the auxiliary bolt to retain the latch bolt in the restrained S° position 8 A lock according to Claim 7 or any claim dependent on Claim 7, wherein the first 15 displaceable member has an engaging shoulder engageable with an engageable shoulder of the auxiliary bolt when the auxiliary bolt is in the extended position. 9 A lock according to Claim 8, wherein the engageable shoulder is displaceable from the locus of movement of the engaging shoulder by auxiliary bolt aospacement. 0o0.. 10 A lock according to Claim 7 or any Claim dependent on Claim 7, wherein the auxiliary bolt includes a rearwardly disposed portion engageable with a ramped shoulder of the casing by auxiliary bolt displacement to be displaced away from the first moveable memberwhereby to move the engageable shoulder of the auxiliary bolt from the locus of movement of the engaging shoulder of the first displaceable member. 11 A lock according to any one of the above claims, including operating means by which to cause the latch bolt to be displaced towards the retracted position, said operating means including a hand operable member operably operably connected to the latch bolt by the first displaceable member. 14 12 A lock according to Claim 11, including a handle assembly comprising the hand operable member and a spring biased slide supported for rectilinear displacement and acting to urge the hand operable member towards an undisplaced position. 13 A lock according to any one of the above claims, including deadlocking means to restrain the bolt from being displaced towards the retracted position, said deadlocking means including a key operable cylinder and a hand operable snib lever, 14 A lock according to Claim 13, wherein deadlocking means includes a deadlocking slide operatively connected to the cylinder and snib lever and displaceable by cylinder operation and snib lever rotation, said deadlocking slide being displaceable between a deadlocking position in which it restrains the bolt from being displaced towards the retracted position and a free position where it does not so restrain the bolt. C 5 15 A lock according to any one of the above claims, wherein the leading portion of S.o the latch bolt comprises similarly curved or bevelled sides 16 A lock according to any one of the above claims, wherein the leading portion of the auxiliary bolt comprises similarly curved or bevelled sides Yarra Ridge Pty Ltd 7 May 2001 a' ee..