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TECHNICAL FIELD  
       [0001]     This invention relates to a deadbolt.  
         [0002]     BACKGROUND OF THE INVENTION  
         [0003]     There are known deadbolts of the type where a bolt is secured in a housing which is adapted to be mounted on the face of a door or window or the like. The bolt can be moved into an extended position to engage with a keeper or the like. Such arrangements have been used in window or door security locks.  
         [0004]     There is a need for an arrangement which would ameliorate at least one of the above problems.  
         [0005]     Limitations exist in commonly known deadbolt arrangements and the present applicants envisage that new and useful alternatives with enhanced functionality would be desirable.  
       SUMMARY OF THE INVENTION  
       [0006]     In a first aspect, the present invention provides a deadbolt having a housing, a bolt mounted in the housing and movable in the direction of the length of the bolt between a retracted position and an extended position, locking means which can lock the bolt in the extended position and retaining means to prevent removal of the bolt from the housing without disassembly of the deadbolt. In this way, the bolt cannot be removed from the housing and thus cannot be accidentally separated or lost.  
         [0007]     Accordingly, a new and useful alternative over the known deadbolts is provided for with the more sophisticated construction which will be exemplified in more detail below and for the purpose of retaining the bolt in the housing to prevent its accidental separation or loss.  
         [0008]     The retaining means may include a projection extending laterally from the bolt for retaining the bolt in the housing. Use of such a projection avoids machining a narrowed portion of the bolt for locking purposes, thereby avoiding weakening the bolt.  
         [0009]     A further advantageous feature now proposed by the present applicants is to provide an arrangement whereby the bolt can be secured and preferably locked in a retracted position so that it is not inadvertently moved to the extended or normal locking position with possible damage to surrounding structure. This may be achieved by providing for the locking means to lock the bolt in the retracted position and then the key can be removed to prevent unintentional locking or movement of the bolt.  
         [0010]     The retaining means can include first and second abutment regions against which the projection will abut to restrain further axial motion of the bolt and to prevent removal of the bolt from the housing. This provides a simple mechanism for preventing removal of the bolt from the housing.  
         [0011]     The deadbolt with advantage may include a detent such as a spring loaded finger which engages in a recess in the bolt so that it is positively located at each limit position, ie extended and retracted, and the user can feel and/or hear that this position has been reached. The spring loading will retain the bolt in that position to permit the user then to use a key to achieve any desired locking.  
         [0012]     The locking means can further include a locking tongue which is movable between a locked and an unlocked position, for example by actuation of a key through a lock. In the locked position the projection is trapped between the locking tongue and either one of the abutment regions to restrain axial movement of the bolt.  
         [0013]     With advantage, a lock of cylindrical form is provided for engagement with a key and, upon rotation of the key, there is motion transmitted through a cam and cam follower arrangement to displace the locking tongue.  
         [0014]     The present invention lends itself to embodiments in which the orientation of the bolt within the housing may be reversed so that the lock may be selectively configured for right hand or left hand operation. This enables one model of lock to be manufactured.  
         [0015]     For the purpose of providing improved durability, embodiments of the invention may utilise two laterally extending projections which, when locking is achieved, restrain axial movement of the bolt. This may be achieved by providing a pin extending through a transverse bore in the bolt, the respective projecting tip portions of the pin providing the engagement projections.  
         [0016]     Advantageously, the pin may be a spring pin which is radially compressible for fitting into the bore so that easy installation during manufacture is possible.  
         [0017]     Preferably, the deadbolt further includes another projection extending in an opposite direction to the projection. This improves the durability of the deadbolt over a single projection arrangement.  
         [0018]     A further embodiment provides an alternative and advantageous structure wherein the bolt has an axial groove of relatively shallow depth extending into the side wall of the bolt, a recess deeper than the groove intersecting the groove at at least one end of the groove, and a displaceable projecting element is mounted to be operable when the bolt is in an extended position, responsive to operation of the locking means to engage in the recess thereby locking the bolt, unlocking of the bolt causing partial retraction of the projecting element whereby a tip of the projection is engaged within the groove and the bolt may be slideably moved from the locked position to a retracted position. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which:  
         [0020]      FIG. 1  is a front elevation of a deadbolt embodying the present invention;  
         [0021]      FIG. 2  is a side elevation of the deadbolt of  FIG. 1 ;  
         [0022]      FIG. 3  is an underside view of the deadbolt of  FIG. 1 ;  
         [0023]      FIG. 4  is a side cross-sectional view of the deadbolt of  FIG. 1  taken along the line A-A;  
         [0024]      FIG. 5  is an inverted plan cross-sectional view of the deadbolt of  FIG. 1  along the line B-B;  
         [0025]      FIG. 6  is a plan cross-sectional view of the deadbolt of  FIG. 1  along the line C-C;  
         [0026]      FIG. 7  is an exploded view of the deadbolt of  FIG. 1 ;  
         [0027]      FIG. 8  is an isometric view of the deadbolt of  FIG. 1  along with a keeper with the bolt in the extended position;  
         [0028]      FIG. 9  is an isometric view of the deadbolt of  FIG. 1  along with a keeper with the bolt in the retracted position;  
         [0029]      FIG. 10  is an isometric view of the deadbolt of  FIG. 1  shown with an alternative keeper;  
         [0030]      FIG. 11  is a part-assembled side view taken along the lines XI-XI of  FIG. 7 ;  
         [0031]      FIG. 12  is an inverted plan, central cross-sectional view of a second embodiment and taken along the line E-E of  FIG. 14 ;  
         [0032]      FIG. 13  is a plan cross-sectional view through the axis of the cylinder lock of the embodiment of  FIG. 14  and taken along the line F-F;  
         [0033]      FIG. 14  is a front view of the second embodiment in the extended, locked position of the bolt;  
         [0034]      FIG. 15  is a right hand end elevation of the embodiment of  FIG. 14 ;  
         [0035]      FIG. 16  is an inverted plan view of the embodiment of  FIG. 14 ;  
         [0036]      FIG. 17  is a cross-sectional side elevation taken along the line D-D of  FIG. 14 ;  
         [0037]      FIG. 18  is an exploded view of components of the deadbolt of FIGS.  12  to  17 ;  
         [0038]      FIG. 19  is a partial view on an enlarged scale showing detail of the configuration in the locked position; and  
         [0039]      FIG. 20  is a view corresponding to  FIG. 19  but showing the components in the unlocked position. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0040]     Referring to FIGS.  1  to  7 , a deadbolt  10  is shown including a housing  12  and a bolt  14  mounted in housing  12 . The housing  12  has a front cover  13  and backing plate  28 . The bolt may be moved between a retracted position (see  FIG. 9 ) and an extended position (see  FIGS. 1-6  and  8 ).  
         [0041]     The bolt  14  includes a cylindrical insert  15  (see  FIG. 5 ) made from hardened metal located in an axial bore in the bolt to provide added security by resisting cutting of the bolt.  
         [0042]     Bolt  14  includes a plastic handle  17 . This allows a user to easily grasp bolt  14  for the purpose of moving it between the extended position and the retracted position.  
         [0043]     The bolt mounts a transverse spring pin  20 , having respective end projections  16  and  18 , mounted in a cross-bore drilled in the bolt  14 . Projection  16  extends into channel piece  30  which defines a channel  29 , extending from an opening  31  which allows a locking tongue  32  to move into channel  29 . When the locking tongue  32  is outside channel  29 , projection  16  is free to move along the length of channel  29 . When projection  16  is at either end of channel  29 , locking tongue  32  may be introduced into channel  29  through opening  31  so that the locking tongue  32  then obstructs channel  29  and restricts the movement of projection  16  and hence restricts axial movement of bolt  14 . The end of channel  29 , at which projection  16  is located when locking tongue  32  enters channel  29 , dictates whether bolt  14  is locked in the extended position or the retracted position.  
         [0044]     The deadbolt  10  includes transverse abutment shoulders  22 ,  24  extending respectively in the cover  13  and baseplate  28  at right angles to the axis of the bolt  14 , the shoulders  24  defining the ends of the channel  29 . The projections  16 ,  18  of the spring pin  20  abut against these shoulders at the end of axial travel of the bolt to prevent removal of the bolt from the housing.  
         [0045]     The deadbolt  10  includes a detent  34  which, as most clearly seen in  FIG. 7 , comprising spaced interconnected arms  35 ,  36  extending parallel to the bolt and biased onto bolt  14  by way of a spring (not shown) positioned between detent  34  and front cover  13 . When bolt  14  is in the extended position, tip projections  37  (at the right hand end of the arm when viewed as in  FIG. 7  but at the left hand end when viewed as in  FIG. 5  but hidden from view in that Figure) engage with an annular recess  40  in the periphery of the bolt. The tip projections  37  and the recess  40  are obscured in  FIG. 5  but shown in  FIG. 7 . When bolt  14  is in the retracted position, a second set of tip projections  38  engage with the annular recess  40 . The bolt  14  may be pushed or pulled by hand to release engagement of the detent projections from the recess  40 .  
         [0046]     The bolt is mounted in the housing by being held between the detent  34  and channel piece  30 . Detent  34  biases bolt  14  against channel piece  30  by way of the spring (not shown) to reduce rattle. Detent  34  and channel piece  30  are formed from a material which exhibits low friction when in contact with the material of the bolt to provide for smooth movement of the bolt. Typically detent  34  and channel piece  30  are moulded from an engineering grade polymer such as nylon and the bolt  14  is formed from metal such as stainless steel.  
         [0047]     As most clearly shown in  FIG. 7 , a lock cylinder  48  is provided for key actuation and mounted in the housing. Lock cylinder  48  is retained in the front cover  13  by retaining element  49  which is secured by a screw (not shown) onto the interior of the cover  13 . The lock has a rearwardly projecting tab  43  which engages in a corresponding slot  45  in a rotor  46  which has a cam groove  42  in which a lug  44  (functioning as a cam follower) is engaged, the lug  44  projecting from a base portion of the locking tongue  32 . The locking tongue  32  has a rear spline  47  for engaging in a corresponding vertical groovelike guide  27  formed in the baseplate  28 . Thus, rotation of a key in the lock cylinder  48  rotates the rotor  46  and the cam function then raises or lowers the tongue  32  into the channel  29  to establish a locked position and retracts the tongue out of the channel for an unlocked position.  
         [0048]     A U-shaped spring clip  41  has legs which are biased against either sides of a dog  50  mounted on rotor  46 . Clip  41  serves to positively locate rotor  46  at a selected rotary position. The angle of rotation required of rotor  46  to move locking tongue  32  between the locked position and the unlocked position is 90° and this corresponds to the profile of the dog  50 . This feature gives the user tactile feedback that the correct amount of rotation has been performed by the key. Assembly is achieved by locating the upper portion of the spring  41  over a lug  58  (shown in  FIG. 5 ) of the baseplate. The channel piece  30  is located in a cradle  27  of the baseplate with lugs  56  projecting rearwardly from the channel piece engaging in holes  57  in the baseplate and thereby aligning tapped bores  59  in the channel piece with screw-receiving holes  60  in the baseplate. The locking tongue  32  is inserted from below into the channel piece  30  and fixing screws used to retain the components on the baseplate.  
         [0049]     The tip  55  of rotor  46  is inserted into a central aperture  52  of the baseplate with the dog  50  snap-fitting between the legs of the spring dip.  
         [0050]     The deadbolt  10  is arranged such that it may be disassembled for the purpose of reversing the orientation of bolt  14 . This allows the deadbolt  10  to operate in either a left handed or right handed configuration.  
         [0051]     Installation, e.g. on a door, is achieved by assembly of the lock with screws (not shown) which pass through corner holes  61  in the backplate (see  FIG. 7 ), the screws extending into an engaging tapped bores  62  formed in an internal body structure of the housing  12 . The assembled unit is fixed to a structure such as a door by mounting screws  63  which pass through larger apertures to  64  in the baseplate to engage in respective major tapped bores  65  in the interior of the body of the housing  13 .  
         [0052]     Thus, no screws or bolts remain accessible from the front side of deadbolt  10  when it is mounted for use.  
         [0053]     Referring to  FIGS. 8 and 9 , the deadbolt  10  is shown in use mounted to adjacent door frame member  70 ,  FIG. 8  showing the deadbolt  10  in the extended or locked position in which the bolt  14  engages with keeper  72  mounted on a frame element  73 . Keeper  72  is exposed and thus is fabricated to be strong for the purpose of resisting forcing of the lock.  
         [0054]     Referring to  FIG. 10 , the deadbolt  10  is shown with alternative keeper  74 . This form of keeper may be used when bolt engages with a hole drilled into a wall or into the floor, ground or ceiling or the like. The keeper  74  reinforces the hole and protects the hole from damage. If the material into which the hole is drilled is tough, keeper  74  may be dispensed with.  
         [0055]      FIGS. 8, 9  and  10  show the deadbolt mounted vertically. It can also be mounted horizontally at the bottom of a frame to engage with the ground or at the top of a frame to engage with the top of the frame mounting member. The frame can be a hinged or sliding door.  
         [0056]     The pin  20  is designed with a resilient form so that by its resilience it has retained the desired illustrated position in the cross-bore in the bolt. However, that form of pin may be replaced by a solid pin retained in a bore through bolt  14  by an interference fit.  
         [0057]     Reference will now be made to the second embodiment of FIGS.  12  to  20  where like parts have been given like reference numerals and only the variations will now be described in detail.  
         [0058]     The principal differences in the second embodiment are a modification to the bolt  14  and the locking tongue arrangement to provide a different form of retention and locking of the bolt.  
         [0059]     As most clearly shown in  FIG. 18 , the bolt  14  has an axially extending groove  100  having a central shallower profile  101  and deeper profiles  102  (best shown in  FIG. 12 ) in the form of cylindrical partial cross-bores at each end region. The locking tongue is modified to form a two-part unit comprising a locking element  104 , a vertically displaceable main body  103  which inter-engages with the backplate  28  on one side and the rotor  46  on the other side in the same manner as the first embodiment. However, the locking element  104  is displaceably mounted on the main body  103  with a cam action to cause it to have its axially projecting locking pin  105  move transversely to the axis of the bolt  14  and into its groove  100 . Reference to  FIGS. 19 and 20  shows the detail wherein the main body  103  has spaced, upwardly extending walls  106  across which a spring pin  107  is inserted after positioning the locking element  104  so that a slot  108  through the locking element receives the spring pin therethrough for retention purposes. An angled face  109  of the locking element extends parallel to the groove and provides a cam follower surface while the main body provides a corresponding cam surface  110  below the region of the spring pin. As shown in  FIG. 20 , in the unlocked position, the locking projection  105  of the locking element extends into the groove, but not into a deeper cross-bore  102 , one of which is at each end of the groove. Therefore, the bolt can slide freely within the limits of the groove and is constrained against removal by axial end walls of the groove.  
         [0060]     When the cylinder lock is rotated, the main body  103  is displaced vertically upwardly while constrained in a corresponding guideway  27  extending from the base plate  28  by engagement of the spline  47  and the cam surfaces engage to displace the locking pin  105  into the bolt  14 . This can only occur when the bolt is at one of its end positions and the locking pin can extend into one of the deeper cross-bores  102 .  
         [0061]     Assembly of the unit is achieved by firstly positioning the spring clip  41  over the locating lug  58  on the baseplate and with the legs extending downwardly outside the location guide  27 . The main body and locking element are assembled as shown most clearly in  FIG. 20  and inserted upwardly into the channel piece  130  with the spline  47  engaging in the guide  27  and the channel piece then inter-engages with a cradle  131  of the baseplate, the cradle being integrally formed with the baseplate. The locating lugs  56  are engaged within the locating bores  57  in the baseplate in a similar manner to the mounting arrangement for the first embodiment.  
         [0062]     A further minor alteration is that mounting of the cylinder lock is by a saddle  112  and two mounting screws  113  as shown in  FIG. 18 .

Summary:
A lockable deadlock for face mounting has a housing and an axially displaceable securing bolt mounted in the housing and moveable between a retracted position and an extended position, the deadbolt further comprising locking means to lock the bolt in at least the extended position and retaining means to retain the bolt in the housing.