Abstract:
An assembly comprising a pair of latch drive mechanisms each being mountable on opposite sides of a door and including drive members to actuate a door latch mechanism mounted within the door. The assembly further includes a pair of handles, each of which is rigidly fixed to the surface of an escutcheon component which attaches to the latch actuating member of the latch drive mechanism and, when so attached, conceals the latch drive mechanism. Also included is a privacy locking set adapted for use with the latch drive assembly which provides a control function at the inside of the door which locks the handle at the outside of the door. The control side also includes an automatic release function actuated by the operation of the handle at the control side. The release function incurs no lost motion due to an independent handle operation feature of the latch drive mechanism.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to door handles and the associated latch operating mechanisms and is concerned in particular with providing a mechanism which facilitates greater scope for the aesthetic design of door handles. Also included as part of this invention is a “privacy” handle locking mechanism which can be installed with the latch drive assembly where a privacy locking function is required. The doors referred to herein being access doors to buildings and rooms within buildings. 
     BACKGROUND ART 
     Most hinged doors in any building are equipped with door handles. The handles facilitate the manual operation of the latching mechanism and the manual opening and closing of the door. A door handle requires some componentry to facilitate these two functions and typically comprise the following; The handle itself, being a knob or lever with a projecting stem rotatably attached to a mounting plate, generally defined as an escutcheon. The escutcheon provides a bearing for the stem and for attachment to the door, and means provided within the handle stem for rotational actuation of the latch mechanism, usually via mutual engagement with a square section shaft. 
     The handle and the escutcheon, being visible components, are generally required to have a good appearance and traditionally have been designed, ornamented and finished to maximise their esthetic appeal. Various methods have been devised to improve their appearance by concealing the fixing screws, commonly used to attach the escutcheon to the door. This is generally achieved by providing a mounting plate, which employs the normal screw attachment to the door, and some concealed coupling arrangement which provides for the attachment of the escutcheon to the mounting plate. Examples of this are disclosed in Australian patent 653083 in which a threaded central boss within the escutcheon engages within a central thread of the mounting plate, and the lug and groove twist action of Australian patent 14803/95. 
     Lever handles are preferable to knobs from a functional point of view, and are the normal form of door handle in most commercial or public premises. Knobs cannot be operated by any means other than hand rotation, and are thus more difficult to operate for persons with some types of disability of the hand. Lever handles are less reliant on the strength of grip and can be easily operated by downward pressure of a hand or even an elbow. However, lever handles are not without disadvantages. A spring is generally required within the mechanism to return the lever after operation to its “at rest” position and to prevent lever droop. Also, the requirement for the lever to be fixed at one end to a stem has meant that the range of lever handle shapes, though often embodying good design, has been quite limited. 
     Prior art also acknowledges the requirement to include a “privacy” locking function as an option within a door handle product range. This facility is generally required in toilets and bathrooms where the occupant is able to engage the locking function to prevent the accidental intrusion of other persons. Typical examples of this facility are disclosed in U.S. Pat. No. 5,505,508 and Australian patent 653083 wherein the locking function is provided as a separate accessory which is adapted to be installed together with the handle assembly. These patents also, coincidentally, include an example of a concealed handle mounting arrangement mentioned above. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to at least in part overcome the above-mentioned limitation on the range of possible designs of lever handles and also to incorporate a concealed mounting arrangement. 
     To achieve this objective, the invention provides an arrangement which allows different methods and locations for the attachment of lever handles, thus avoiding the prior insistence on the attachment of lever handles to a stem at the axis of rotation. 
     The invention provides, in a first aspect, a latch drive assembly comprising: 
     a pair of latch drive mechanisms each being mountable on opposite sides of a door and including means to engage with and rotationally actuate a conventional door latch mechanism mounted within the door via engagement with a drive shaft; 
     each latch drive mechanism comprising a mounting plate member with means for mounting to an outer surface of a door and including concentric bearing means for rotationally locating a drive member; 
     the drive member comprising a substantially circular plate and includes a cylindrical boss component projecting from the center of one face, the boss being rotatably engaged within the central bore of the mounting plate member and the face of the circular plate overlying and in parallel contact with the outer face of the mounting plate, 
     the boss component further includes a concentric passage shaped to engage with and transmit rotational action to the drive shaft, 
     the latch drive mechanism preferably includes a spring means acting between the mounting plate member and the drive member for returning the drive member to the rotational stop position after actuation; 
     the latch drive assembly further includes a pair of handle units, each comprising a manually graspable lever element joined to a preferably circular escutcheon; and 
     means within the escutcheon to attach the handle unit to the drive member by engagement with complementary means provided at the periphery of the drive member such that rotation of the handle is transmitted to the drive mechanism via its attachment to the escutcheon, the escutcheon, when so attached, substantially enveloping and concealing the latch drive mechanism; 
     the drive member further includes disengagable latch means for irrotationally retaining the escutcheon; 
     The shaped passage within the boss section of the drive member can be of a partially circular cross section which permits a limited degree of free rotation within the drive shaft engagement, the orientation of these passages in the two opposing latch drive units arranged to provide the transmission of rotational drive to the latch unit by the actuation of either handle whilst allowing the opposite latch drive unit to remain stationary. 
     It has been recognised that the market requires that any product range of door handle fittings must include a privacy locking function for bathroom, toilet, and bedroom applications. To this end the invention preferably includes a novel privacy locking arrangement and, in a second aspect, provides a latch drive set including this feature. More specifically, the invention according to the first aspect preferably includes privacy locking means, which includes; 
     a control unit for mounting at one side of a door and having finger operable setting means; 
     a lock unit for mounting at the other side of the door selectively settable at a lock condition in which the handle unit at that side of the door is locked against rotation; 
     means for linking the control unit to the lock unit whereby finger operation of the setting means is effective to set the lock unit in its lock condition; and 
     means in the control unit whereby rotation of the handle at the one side of the door actuates the setting means and in turn, by virtue of the linking means, disengages the lock condition, during the independent operative rotation of the handle at one side of the door relative to the handle at the other side of the door, 
     In its second aspect, the invention provides for use in conjunction with a door latch set including a latch unit, drive shaft means, a pair of handle units adapted to be mounted at opposite sides of a door panel, and means for drivingly coupling the handle units to the shaft means so that the respective handle means independently rotate the shaft means without rotation of the other handle unit, a privacy locking set including; 
     a control unit for mounting at one side of the door and having finger operable setting means; 
     a lock unit for mounting at the other side of the door selectively settable at a lock condition in which the handle unit at that side of the door is locked against rotation; 
     means for linking the control unit to the lock unit whereby finger operation of the setting means is effective to set the lock unit in its lock condition; and 
     means in the control unit whereby rotation of the handle at the one side of the door releases the setting means and in turn, by virtue of the linking means, the lock condition, during the independent operative rotation of the handle at the one side of the door relative to the handle at the other side of the door. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is an exploded three dimensional view of the principal components of a basic door latch set incorporating a pair of latch drive assemblies formed from latch drive sets according to a first embodiment of the first aspect of the invention; 
     FIG. 2 is an exploded view showing the components of one of the latch drive assemblies; 
     FIG. 3 depicts the door latch set installed in a door; 
     FIG. 4 shows the installation of the fixing screws into one of the latch drive assemblies; 
     FIG. 5, depicts the details of a coupling system for mounting a handle unit to the drive plate of the latch drive assembly; 
     FIGS. 6 and 7 depict the engagement of the components of the handle unit coupling; 
     FIG. 8 depicts the latch set of FIGS. 1 to  7  installed in a door, and shows three successive steps (a, b, c) in mounting a handle unit to one of the latch drive assemblies; 
     FIG. 9 depicts a full installation of a latch set and handle units with a privacy locking set in the locked position; 
     FIG. 10 is an exploded view of the components of the door latch set of FIG. 9 including the privacy locking set; 
     FIGS. 11 and 12 are schematic illustrations showing the function of the privacy locking set; 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Basic Set 
     In FIG. 1, the illustrated door latch set  1  includes a latch unit  10  of conventional construction, a pair of similar latch drive assemblies  2   a  and  2   b  which are each formed from an individual latch drive set, and a latch drive shaft  18  of uniform rectangular cross section. 
     The two latch drive assemblies  2   a  and  2   b  are basically identical save for being a mirror image of each other and being of opposite rotation. Their main difference lies in their provision for the screws  19 , one assembly having countersunk clearance holes  23  provided in the mounting plate  20 , the other equipped with corresponding threaded holes  24  in bosses  25  of the opposing mounting plate. It is therefore proposed to described only one of the assemblies and to identify the differences where appropriate. 
     Each latch drive assembly  2   a,   2   b  includes a mounting plate  20 , a drive member  40  comprising an annular drive plate  30  about a boss  50 , and a handle unit  70 . 
     The mounting plate  20  (FIG. 2) is essentially a disc for covering the cross passage in the door panel and rotatably mounting the drive member  40 . It may be produced as a metal die casting, a metal pressing or as a plastic molding. Plate  20  comprises a flanged surface  21  which provides a clamping interface with the door panel, and has a circular central aperture  22  at its center which serves as a bearing to accommodate a cylindrical body section  51  of drive boss  50 . An integral central boss  29  projects on the reverse side (i.e. inside) of mounting plate  20  (FIG.  1 ), its purpose being to laterally position a cam washer  69  (discussed further later) for its required function relating to the optional privacy locking assembly  100  (FIGS. 8 to  10 ) when this is provided. The raised arcuate land or annulus  27  provides a bearing surface at its interface with the drive plate  30 . It also defines and bounds a space to accommodate a spiral leaf return spring  60 . 
     Two arcuately spaced facing shoulders  28   a,    28   b  project from the inner side of the raised land or annulus  27 . Shoulders  28   a,    28   b  interact with a projecting tag  36  of the drive plate  30  to define limits to the relative rotation of drive member  40  with respect to mounting plate  20  about axis  9 . Shoulder  28   a  determines the return stop or ‘at rest’ position of the spring return rotational travel of the drive plate  30 . 
     The drive plate  30  is ideally produced from spring steel and forms a sub-assembly with the drive boss  50  and the return spring  60 . The cylindrical body section  51  of drive boss  50  forms a close fit with a central aperture  32  of the drive plate and rotational drive is transmitted via the engagement between integral key tags  33  of the drive plate adjacent aperture  32 , and respective slots  54  in a flanged head  52  of the drive boss. The return spring  60  is assembled on the reverse side of the drive plate  30 , between the drive plate and mounting plate and within land  27 . The spring is concentric with the drive boss  50 , with an end inner tag  61  of the spring engaging in a slot or hole (not shown) provided in the cylindrical section  51  of the drive boss. The outer hooked end  62  of spring  60  locates about an anchor spigot  26  projecting from the mounting plate  20  adjacent one end of land  27 . 
     This sub assembly locates with the mounting plate  20 . The cylindrical section  51  of the drive boss  50  rotatably engages within the central aperture  22  of the mounting plate. With the end hook  62  of the return spring  60  engaged about spigot  26  of the mounting plate, the sub-assembly is rotated in the appropriate direction to pre-tension the return spring to ensure the engagement of the stop tag  36  of the drive plate with the rotational stop  28   a  of the mounting plate. 
     As already noted, the back or inside face of the drive plate locates against the raised land or annulus  27  of the mounting plate. The cylindrical body  51  of the drive boss projects beyond the end face of the rear boss  29  of the mounting plate. Thus, the drive member  40  overlies the mounting plate  20 . A central aperture  66  of the cam washer  69  engages with the projecting section of the drive boss, the two being rotationally keyed by engagement of an inner key tab  67  on the cam washer with a longitudinal keyway  55  of the drive boss. The inner face of the cam washer  69  locates against the end face of the rear boss  29 , and a circlip  64  engages in a circular groove  56  of the drive boss to maintain the assembly of the drive member  40  with the mounting plate  20 . The axial location of the circular groove  56  relative to the flanged drive boss head  52  is set to provide close contact between the assembled components when the circlip is engaged within the groove. The closeness of the contact between these components must allow freedom for rotational movement about axis  9  (within the limits set by the stops  28   a,    28   b ) while allowing only minimal lateral movement in the axial direction. 
     In FIG. 3 the latch set is shown mounted on a door panel  5  overlying and concentric with a transverse hole  6  which represents the trade standard 54 mm diameter hole. A standard 22 mm bore (not shown) accommodates latch unit  10 . 
     Latch unit  10  includes a faceplate  11  with apertures  12  by which screws  13  are employed to fasten the faceplate in a rebate at the edge of the door panel, thereby securing the latch unit in the door. The latch drive assemblies  2   a  and  2   b  are fitted, one on either side of the door at opposite ends of the transverse passage  6 . They are coupled by the rectangular shaft  18  which passes through the passage  15  (FIG. 1) of the latch unit  10  and engages at either end within shaped passages  53  of drive bosses  50  located within the keyed apertures  32  of the rotatable drive plates  30   a  and  30   b.    
     The latch drive assemblies  2   a,    2   b  are fastened together by a pair of fixing screws  19  which pass through the countersunk holes  23  (FIG. 2) in one assembly, and through holes  16  in the latch unit  10 , and engage in threaded holes  24  (FIG. 1) of the other drive assembly. The screws draw the respective drive assembly mounting plates  20  together, clamping them firmly against the surfaces of the door panel about the open ends of the transverse passage  6 . Either drive plate  30  transmits rotational movement to its respective drive boss  50  by means of the key tags  33 , engaged in the slots  54  of the drive boss  50 . Rotational movement is further transmitted to the rotatable sleeve  14  of the latch unit  10  via the rectangular shaft  18 . Shaft  18  engages both the shaped passage  53  of each drive boss  50  and the rectangular passage  15  in the latch unit and, by virtue of a retractor mechanism (not shown) within the latch unit  10 , rotation of shaft  18  is effective to retract latch bolt  17  behind facing plate  11  against an internal spring (not shown) biased to return the latch bolt outwardly. (the rectangular shaft requiring a 3.7 mm square section at its center to engage with most standard latches) 
     By virtue of the shaped passages  53  of the two opposing drive bosses  50 , the rotation of either latch drive assembly will transmit sufficient rotation to shaft  18  and to the latch unit to retract the latch bolt  17 , without causing the other latch drive assembly to rotate. This feature of independent rotation of the latch drive assemblies is required for the functioning of the privacy locking assembly, discussed further below. 
     FIG. 4 shows the proposed method of installing the two screws  19  into the latch drive assembly. The reasons for this slightly complex procedure are as follows. It is necessary, when installing the latch drive assemblies, to gain access to the heads of the fixing screws by means of a screwdriver in order to engage them with the corresponding threaded bosses of the other assembly. This access may be facilitated by means of appropriately located holes through the drive plate  30 . However, if these holes are large enough to facilitate the installation of the screws through the drive plate there would then exist a possible safety hazard for this product in service. In the event of either of these screws  19  becoming loose, it would be possible for the screw head to engage within the hole provided in the drive plate and thus render the door locked. By the alternative provision of the smaller holes, large enough to provide access for a suitable screwdriver but too small to accommodate the screw head, this problem is prevented. 
     The solution to the above problem however generates another in the installing of the screws into the latch drive assembly. The screws could be pre-assembled into the appropriate latch drive assembly but the length of the screws installed could not accommodate any variation of door thickness greater than 8 mm. For this reason the person installing the product must be able to select and install the appropriate length of screw for the particular door being fitted. 
     To facilitate the above requirements, the following principals have been devised. In the left diagram a of FIG. 4, the drive plate  30  is shown rotated against the return spring force to the second stop position defined by shoulder  28   b.  At this point two larger holes  35  in the drive plate align with the countersunk screw holes  23  of the mounting plate. These holes  35  are large enough to allow passage of the heads of the screws  19 . The screws are therefore inserted through holes  35  into the screw clearance holes  23  of the mounting plate, the heads passing through the clearance holes  35  of the drive plate to engage with the countersinks of holes  23  provided in the mounting plate. The drive plate  30  is then released, allowing it to rotate under spring pressure to return to the stop position defined by shoulder  28   a  (right diagram b of FIG.  4 ). At this position two smaller holes  34  in the drive plate align with the screw heads allowing screwdriver access. 
     FIG. 5 shows handle unit  70  with lever handle  79  fixed at one end to escutcheon  71  by a joining member  78 . The escutcheon is designed to be detachably mounted to drive plate  30  by the engagement of coupling arrangements within the escutcheon and at the perimeter of the drive plate. The normally circular escutcheon is recessed, defining a cylindrical wall  72  and an adjacent annular mounting surface  73 . Four integral undercut lugs  74  are positioned around the inner wall  72 . There is an opening  75  in the inner wall located non-symmetrically about the vertical centerline of the circular and a recess  76  in the mounting surface  73  is located symmetrically about the vertical centerline. A projecting lug  77  located in the upper half of the escutcheon recess provides an abutment to transmit the rotational drive force from the handle to an opposed projection  41  of the drive member  30 . 
     Four crescent shaped or arcuate resiliently deflectable tag members  37 , equispaced around and concentric with the rim of the drive plate  30 , are inclined slightly away from the surface plane of the drive plate. A short section  38  at the free end of each crescent member is angled back towards the surface plane of the drive plate. Four notches  31  are provided beyond the end of each crescent member. A resiliently deflectable pawl is formed by a strip  39  extending radially downwards from near the central aperture of the drive plate. This strip is similarly inclined from the surface plane of the drive plate but opposite to that of the four crescent shaped arcuate tag members  37 . 
     FIG. 6 shows the method of engagement of the coupling between the escutcheon  71  of handle unit  70  and the drive plate  30  of the latch drive assembly. The four notches  31  of the drive plate freely accommodate the four inwardly protruding undercut lugs  74  within the escutcheon. Rotation of the handle in the direction indicated by the arrow X engages the angled faces  38  of the crescent or tag members  37  with the underside faces of the undercut lugs  74 . The ramp effect of the angled faces and the resilient nature of the material of the drive plate allows the crescent or tag members and the pawl  39  to deflect to conform with the fixed constraints of the undercut lugs and the reaction against the annular mounting face  73  of the escutcheon. It will be appreciated that the tag members  37  with notches  31  and undercut lugs  74 , together form means for rotatably coupling the handle unit  70  to drive plate  30 . Drive plate  30  may be considered to provide a platform to which the handle unit may be detachably fixed. Likewise, the escutcheon provides a platform for handle mounting thus liberating the designer from the normal constraint of the handle attachment at the axis of rotation. 
     FIG. 7 shows the handle unit  70  fully engaged with the drive plate  30 . In this relationship the pawl  39  engages the recess  76  simultaneously with the abutment of the complementary lug  77  of the escutcheon and projection  41  of the drive plate. The engagement the pawl  39  within the recess  76  prevents reverse rotation and consequent disengagement of the handle unit mounting. To remove the handle unit, the pawl  39  is deflected with a suitable tool to disengage it from the recess  76  to allow reverse rotation to disengage the coupling between the drive plate and the escutcheon. 
     It will be appreciated that, once the handle unit  70  is engaged and locked into the drive plate  30 , and with the lever handle  79  in its normal return stop or “at rest” position, rotation of the handle  79  will be effective to rotate drive shaft  18  via drive member  40 , and thereby to withdraw the latch bolt  17 . Return of the handle unit  70  to the return stop position is assured by the coil spring  60  retained within the latch drive assemblies  2   a  and  2   b.    
     FIG. 8 sequentially illustrates the mounting of a handle unit to a latch set installed within a door. FIG. 8 a  shows the latch set mounted in a door with the appropriately handed handle unit  70  at a particular rotational position to be presented for engagement with the drive plate  30 . In FIG. 8 b  the handle unit is shown engaged with the drive plate, the pawl  39  being accommodated within the recess  76  of the escutcheon. The handle unit  70  is pressed firmly against the drive plate  30  and rotated in the direction of arrow X to engage the coupling. The rotation of the handle induces the drive plate to rotate and withdraw the bolt (this movement has been omitted from the illustration to simplify the description) but further rotation of the handle is required to fully engage the coupling. FIG. 8 c  shows the handle unit fully engaged with the latch drive assembly, The pawl  39  being engaged within the recess  76  to prevent removal of the handle unit by opposite rotation. Removal of the handle unit is effected by deflecting the pawl  39  with a suitable tool to disengage it from the recess  76 , thus allowing contra-rotation and disengagement of the coupling. 
     FIG. 8 c  also well illustrates how, in the assembled condition of the latch drive set, the escutcheon  71  substantially envelopes and conceals the latch drive assembly  2   a.    
     It will be apparent to those skilled in the door handle arts that the handle unit  70   b  (FIG. 5) is significantly different from conventional door handle levers. With conventional handle levers, the lever is supported at one end by a perpendicular stem which is rotationally engaged within an escutcheon, the lever being a cantilever which rotates about an axis concentric with the stem. Thus the manually graspable portion of the handle lever is extending sideways from the axis of rotation. 
     In the handle arrangement proposed in this invention, the design of the handle is not subordinated to the central axis. The handle can be fixed at any position on the face of the escutcheon and the escutcheon can be of any shape or size which will accommodate the internal mounting arrangements. Furthermore, the joining portion  78  which connects the lever handle lever  79  to the escutcheon  71  can be of any shape, style or dimension, even merging with the escutcheon. Likewise the handle lever can be of any shape and any angular disposition, these features providing greater scope for both handle and escutcheon design. 
     Privacy Locking Set 
     An optional privacy locking set for the door latch set of FIGS. 1 to  8  will now be described with reference to FIGS. 9 to  12 . This privacy locking set may be readily applied to a variety of other latch sets. Accessories of this kind are considered to be an important option within any range of door handle sets, in order to provide a privacy locking function for a latch drive set installed in a bathroom, toilet or bedroom doors. 
     Ideally, a privacy locking set provides the facility for a door to be “snibbed” or locked from inside a room e.g. a bathroom, toilet or bedroom to prevent the entrance of other persons. It is also desirable to include an emergency release function, i.e. a safety override which allows release from the locked condition to be effected from the outside of the door by the use of a simple tool such as the tip of a pencil or similar pointed object. A third desirable feature is to include an automatic release function whereby the normal operation of the door handle on the inside of the room will disengage the lock mechanism without the need to first disengage the snib. 
     FIG. 9 shows a privacy locking set  100  as it would be installed with the latch drive set  1  complete with handles. The set includes a control unit  110  and a lock unit  120  on opposite sides of the door, operatively coupled by a link rod  116  which transmits rotation from a trigger  102  of the control unit to a locking arm  122  of the lock unit. Appropriate areas are illustrated cut away to show the inner mechanism of the privacy function. An exploded view which illustrates the relationship of the separate units as required for installation is depicted in FIG.  10 . Control unit  110  is on the near side in these views, but the privacy set is ambidextrous and can equally well be installed with the units  110  and  120  on the opposite sides to that shown. This provides the option of installing the privacy set with the control unit  110  mounted on the appropriate side of the door. 
     Privacy control unit  110  is normally installed on the inside face of the door. This unit comprises four components, a circular peripherally flanged housing  111  and the trigger  102  (which would ideally be produced as metal die castings or plastic moldings), an omega shaped indexing spring  109  and a cover plate  118  (FIG.  10 ). Lock unit  120  is normally installed on the outside face of the door and comprises three components, a circular peripherally flanged housing  121 , the locking arm  122  and a cover plate  128 . Both housings  111 ,  121 , of units  110 ,  120  respectively, and cover plates  118 ,  128  are provided with two holes  114  which engage on installation with the protruding fixing screw bosses  25  of the respective latch drive assemblies. The close fit of these items controls the concentric relationship between the individual units. Each unit  110 ,  120  of the privacy set is installed with the cover plate  118 ,  128  facing the back face of the respective latch drive assembly, a shaped central aperture  117  allowing entry into the housing of cam washer  69 . 
     With reference in particular to FIG. 11, The trigger  102  pivots about a boss  103  which locates in a complementary hole provided in the back wall of housing  111 . The boss  103  has a square or appropriately non circular passage  104  concentric with the boss axis for receiving link rod  116 . The main profile of the trigger is designed to provide a head  108  which protrudes outside the housing via aperture  119  to provide access for actuation by depression with a finger tip. In the locked position the angled or V-shaped projection  105  intrudes within the rectangular notch  68   a  of the cam washer  69   a  at that side of the door. A “V” notch  107  accommodates one end of indexing spring  109 , the other end being engaged within a similar “V” notch  115  in the inner rim  113  of the housing  111 . The indexing spring is ideally made from spring steel of a rectangular cross section formed to the shape of the “omega” symbol. It is compressed lengthwise to engage with the two notches  107  and  115  and causes the trigger  102  to snap either side of a center line between the pivot point  103  and the V notch  115 . 
     The locking arm  122  is similarly pivoted about boss  123  with a square passage  124  for link  116 . The arm provides a rectangular dog  125  which, when the arm is set to the locking condition, engages notch  68   b  of cam washer  69   b  at the outside of the door, to lock the latch drive assembly at this side against rotation. 
     A safety override function is provided to unlock a door from the outside by the provision of an access aperture  127  in the outer rim of the housing  121 . The locking arm  122 , when in the locked position, can be engaged through the aperture  127  with a suitable tool and so pressed downwards to cause the arm to rotate and disengage dog  125  from the cam washer. 
     Square-section apertures  104 ,  124  are coupled by link rod  116  of matching cross-section. The engagement of these two elements with the common link rod ensures that the movement of the trigger  102  controls the positioning of the locking arm  122 . 
     The two matching positions of the units are shown in FIGS. 11 a,    11   b  and  12   a  and  12   b.  When the trigger  102  is set down (FIG. 11 a ), the locking dog  125  is engaged, rendering the door locked to entry from that side. Actuation of the handle on the inside latch drive assembly causes the cam washer  69   a  to rotate, bringing one corner of the rectangular notch  68   a  of the cam washer into contact with one edge of the V-shaped projection  105 . Further rotation lifts this projection, causing the trigger  102  to rotate about its pivot boss  103  to a position where the indexing spring  109  passes beyond the centerline of its operation. At this point the spring drives the trigger to fully disengage from the cam washer and comes to rest with the stop face engaging the inner rim  113  of the housing  111 . This movement of the trigger is transmitted via the link rod  116  to the locking arm  122  of the opposing side to disengage the dog  125  of the locking arm from the rectangular space  68   b  of the cam washer  69   b,  thus freeing the outside latch drive assembly for normal functioning. 
     The privacy locking set thereby has the desired automatic release function. It will be appreciated that the rotation of the inside handle to affect automatic release is possible because of the aforementioned independent rotational drives of the two handle units, the shape of shaft socket openings  53  permit the shaft to rotate in the normal direction at either boss  50  without rotating the respective handle unit. 
     It will be appreciated that, in its broadest aspects, the invention extends to handles and knobs other than lever handles. The illustrated embodiment eliminates the major constraints on door handle designs in that with these principals there is no need to design handles around a requirement to provide a socket to directly receive the shaft. All manner of molded, cast or fabricated shapes of handle can be applied to the more generous mounting facility proposed. 
     It will also be understood that the term “comprises” or its grammatical variants as used herein is equivalent to the term “includes” and not to be taken as excluding the presence of other elements or features.