Abstract:
A latch device for sliding and hung window systems. The latch device has a mounting base ( 15 ) with which a pair of counter-rotatable cam elements ( 11 ) are mounted. A lever cover ( 12 ) is slidingly mounted on the base ( 15 ). The lever cover ( 12 ) is coupled to the cam element ( 11 ) so that sliding movement of the lever cover ( 12 ) causes the cam elements to counter-rotate. Each cam element ( 11 ) has a cam portion ( 22 ) which is engageable through an opening ( 41 ) in a keeper ( 14 ) to latchingly engage behind a cam engagement surface ( 42 ) associated with the opening ( 41 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a latch device.  
           [0002]    With sliding and hung window systems it is necessary to include a latch device (sometimes referred to as a “sash lock”) to latch the window in a closed position. Over the years there have been many proposed types of window latches which aim to provide not only secure latching but also ease of operation. Despite the wide range of proposals which have been developed over the years there still exists the possibility of an improved latch device for sliding and hung window systems.  
           [0003]    For example, with known latches for sliding and hung window systems forces can arise when the latching operation is carried out which causes the window to move off centre. This can result in sealing problems, distortion of window sash/rails, undesirable loadings applied to mounting hardware etc. These undesirable forces generated in the window generally arise from the use of a cam and keeper arrangement which is a typical latching mechanism for sliding and hung window systems.  
           [0004]    Also there exists the need to ensure that that latching device prevents or renders difficult unauthorised access to be gained by external manipulation of the latch in order to release the latch tongue. To achieve this objective it is known to include a shroud or shield arrangement which prevents someone outside the window from engaging between, e.g. the window sashes, a thin tool to apply force to the latching tongue or cam to release it from the keeper. Such arrangements have not always been successful.  
           [0005]    There also exists the possibility of improving the operative mechanism of such latches to not only improve the application of physical effort to operate the latch device but to additionally try and improve the aesthetic appeal of the latch. There is a move these days to have window hardware which, when visible, has a more pleasing appearance than has hitherto been thought to be necessary.  
         SUMMARY OF THE INVENTION  
         [0006]    It is thus an object of the present invention to provide a latch device for sliding and hung window systems the latch device being of a construction which goes some way to achieving one or more of the above identified desired features.  
           [0007]    Broadly, according to one aspect of the invention there is provided a latch device for sliding and hung window systems the latch device including a mounting base, a pair of counter-rotable cam elements coupled to the base, a lever cover slidingly engaged with the mounting base and a coupling mechanism which couples the lever cover to the cam elements whereupon in use a sliding movement of the lever cover is translated into pivotal movement of the cam elements.  
           [0008]    The latch device further includes a keeper having a pair of cam engagement surfaces with which the cam elements are engagable to latch the mounting base to the keeper. Preferably the keeper includes a body having a pair of openings within each of which is located a said cam engagement surface.  
           [0009]    Preferably the latch further includes a deadlocking means for whereby in use the cam elements can be deadlocked when in the latching position.  
           [0010]    According to one preferred embodiment to the invention each cam element includes a follower which engages within a groove associated with the lever cover.  
           [0011]    In a preferred form of the invention the latch device further includes detent means whereby the lever cover is releasably held in positions corresponding to the latch device being in the latching and unlatching positions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    In the following more detailed description of the invention according to one preferred embodiment reference will be made to the accompanying drawings in which:  
         [0013]    [0013]FIG. 1 is an exploded view of the components of the latch device,  
         [0014]    [0014]FIG. 2 is a perspective view of the latch device in the latched position,  
         [0015]    [0015]FIG. 3 is an underside view of FIG. 1,  
         [0016]    [0016]FIG. 4 is a perspective view from essentially the opposite direction of that of FIGS. 1 and 2 but showing the latch device in an unlatched position,  
         [0017]    [0017]FIG. 5 is a view similar to FIG. 3 but showing the underside of the latch device,  
         [0018]    [0018]FIG. 6 is an underneath perspective view of the lever cover,  
         [0019]    [0019]FIG. 7 is a detailed drawing of the latch in the latched position showing hidden detail,  
         [0020]    [0020]FIG. 8 is a section view on line A A of FIG. 7, and  
         [0021]    [0021]FIG. 9 is a view similar to FIG. 7 but showing the latch device in the unlatched position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    Referring firstly to FIG. 1 of the drawings the various components of the latch device are shown in exploded view. The components comprise a base  10 , a pair of cam arms  11 , a lever cover  12 , a support finger  13 , and a keeper  14 . Conveniently the cam arms  11  are identical.  
         [0023]    The base  10  (which can be formed for engineering plastic) includes a floor  15  with a pair of opposing end walls  16 .  
         [0024]    Adjacent each end wall is a spigot  17  each of which engages within bore  18  of boss  19  of a cam arm  11 . The cam arm  11  is thus able to pivot about a pivot axis defined by the spigot  17 .  
         [0025]    Each cam arm  11  includes an arm  20  which radiates from boss  19 . Upwardly projecting from arm  20  is a pair of pins  21 . The distal end of the arm  20  includes an upstanding cam portion  22 .  
         [0026]    The lever cover  12  (which can be of die cast Zinc construction) includes a cover portion  23  from one side of which projects an upstand  24 . A wall  25  extends downwardly from the upstand  24  and merges into a pair of opposed end walls  26 . The upstand  24  forms a gripping portion to be gripped in or engaged by the fingers of a user.  
         [0027]    Projecting downwardly from the underside of cover portion  23  is a pair of shaped continuous walls  27  each of which define an actuation slot  28  (see more particularly FIGS. 6, 7 and  9 ). Into each of these actuation slots  28  engages a pin  21  of a cam arm  11  as can be seen for example in FIGS. 7 and 9.  
         [0028]    Referring to FIG. 6 there is shown a pair of spaced apart opposing L shaped walls  29  which extend from the inner surface of the wall  25  and define therebetween a slot  30 . Into this slot engages a tongue  31  which projects from a base portion  32  of support finger  13 . A pair of pins  33  which project from an edge of each of walls  29  engage in openings  34  in the base  32 .  
         [0029]    As can be seen, for example, in FIGS. 3 and 5 the support finger  13  when installed in the lever cover  12  is arranged so that the finger  35  projects laterally relative to wall  25  of the lever cover  12 . These Figures also show how the finger  35  engages in an elongate recess  36  in the underside of floor  15  of base  10 . The elongate recess  36  is one at one end to receive the finger  35 .  
         [0030]    The keeper  14  is formed of a body  37  which has a centrally located mounting bore  38 . This bore  38  is formed in a spigot  39  and is accessible through a counterbore  40  in the front surface of the body  37 .  
         [0031]    Flanking the counterbore  40  is a pair of elongate openings  41 . As can be more clearly seen in FIGS. 1 and 9 a cam engagement surface  42  is associated with each opening  41 . The cam engagement surface  42  is of curved configuration such that it is inter-engagable with the curved cam portion  22  of the cam arm  11 . A clearance  43  is provided between cam engagement surface  42  and one long side of opening  41 .  
         [0032]    Referring to FIG. 6 of the drawings it will be observed that running parallel to the inside surface of end walls  26  and extending from wall  25  is a partition wall  44 . The spaced apart walls  26  and  44  thus form a track  45  into which the sidewall  16  of base  10  slidingly engages.  
         [0033]    A tab  46  at the distal corner of wall  26  engages (see FIGS. 3 and 5) in a recess  47  in the underside of floor  15  of base  10 . A shoulder  48  at the end of recess  47  inter-engages with the tab  46  to form a stop which defines the end point of the movement of the lever cover  12  relative to base  10  when the latch device is in the open or unlatched position (see for example FIGS. 5 and 9).  
         [0034]    As can be seen in e.g. FIG. 9 a small projection  50  is formed in the floor of the track  45 . This projection  50  can engage in respective detents  51  and  52  in the upper edge of end wall  16  of base  10 . The projection  50  engages in detent  51  when the lever cover  12  is in the open or unlatched position and in detent  52  when the lever cover  12  is in the closed or latched position.  
         [0035]    In use of the latch device the keeper  14  is mounted by a single mechanical fastener such as a self-tapping screw engaged through bore  38  to the moving rail or fixed rail of one window sash or to a mullion or other fixture such as a portion of a fixed window frame or surround. Similarly by using suitable mechanical fasteners engaged through openings  53  in the floor  15  of base  10  the base is fitted to a rail of the movable window sash.  
         [0036]    When the moving window sash is in the “closed” position the components of the latch device will have the relationship shown in FIGS. 2, 3,  7  and  8 . To latch the window in the closed position the lever cover  12  is pushed, via pressure applied to upstand  24 , toward the keeper  14 . The resultant relative movement of lever cover to base causes the pins  21  of cam arms  11  to track along respective of the slots  28  which cause a counter-rotation of the two cam arms  11  about spigot  17 . As a result the leading edges  54  of the cam arms  11  enter into openings  41  and moves behind the cam engagement surfaces  42 . The clearances  43  adjacent curved cam receiving surfaces  42  provide a clearance for the arm  20  during such movement.  
         [0037]    The cam portions  22  are thus moved so that the cam portions  22  fully engage behind the respective engagement surfaces  42  when the lever cover  12  has been moved to its fully closed position i.e. projections  50  engage in respective of detents  52 . This engagement can be seen in FIGS. 2, 3 and  7 .  
         [0038]    Toward the end of the movement of lever cover  12  there is a degree of free motion which results in the pins  21  moving into portions  28   a  of slots  28 . Consequently, a deadlocking action occurs in respect of the cam arms  11 . This occurs because if someone wishes to gain unauthorised access through the window engages a thin object between the base  10  and keeper  14  to engage cam arm  11  a force cannot be applied to the cam arm  11  to cause it to rotate because of the location of pin  21  in portion  28   a.  The only way that the cam arm can rotate is by firstly moving the lever cover  24  so that the pins  21  become aligned with the main slotted portion  28 . At this point rotation of the cam arms  11  can commence to release the cam arms from the keeper  14 .  
         [0039]    Because of the counter rotating cam arms  11  the action of the cam arms  11  engaging with the keeper  14  actually produces a centralising action on the window sash. Also the latch device exhibits good pull-in characteristics so that the window sash can pull onto seals at the final closed position.  
         [0040]    Because the latch device relies on a push-pull type action applied to the lever cover  12  it is consequently easy to operate. The large gripping area formed by wall  24  allows for easy gripping in the fingers of the user so as to provide the necessary pulling action to release the latch device. Furthermore, it enables the user to pull the window to an open position. Similarly the combination of walls  24  and  25  provide a good contact area for a user to apply a pushing action to the lever cover  24  when closing and latching the window.  
         [0041]    Because of the lost motion at the final closing of the latching device which moves the pins  21  into end portions  28   a  of slots  28  a deadlocking action on the cam arms  11  is achieved. This ensures that the latching device is secure when in the latched position and thereby resists any attempt by someone wishing to gain unauthorised access to manipulate the cam arms  11  from outside the window. The fact that the latch device employs two counter rotating latch arms  11  further ensures that unauthorised access is prevented because someone gaining access would need to simultaneously manipulate both cam arms.