Patent Publication Number: US-6698803-B2

Title: Door latching mechanism

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to a latching mechanism for securing a door and particularly to a door latching mechanism which includes a lock chassis designed to move a latchbolt between an extended and a retracted position. 
     Conventional door latching mechanisms include a lock chassis which moves a latchbolt between an extended position and a retracted position. In the extended position, the latchbolt engages a hole in the door frame and the door cannot freely open. With the latchbolt retracted, the door can be freely opened. 
     A typical lock chassis includes a spindle that interacts with a slide. The slide is typically slidably positioned between a chassis frame and a chassis flange coupled to the chassis frame. Rotation of the spindle translates into linear motion of the slide through a camming action. The slide engages the latchbolt and “pulls” the latchbolt out of its extended position and into its retracted position. The spindle of a typical lock chassis is coupled to a door handle or lever and is rotated when a user turns the door handle. Thus, turning the door handle draws the latchbolt out of its extended position and into its retracted position, allowing the door to be opened. Further, a typical lock chassis includes a cover, which surrounds and contains the chassis frame, the slide, and the flange. 
     Given the structure described above, a lateral blow to the door handle is translated through the lock chassis via the spindle. Because of this, such a blow to the door handle can cause the chassis frame to separate from both the chassis flange and the cover inside the door. In this way, access to the lock chassis can be gained from the outside of the door and the latchbolt can be retracted, thus allowing the door to be opened by an unauthorized user. 
     For a door latching mechanism to achieve a particular rating, industry regulations dictate that the lock chassis withstand certain lateral forces applied to the door handle. Therefore, a device that is readily installable on a lock chassis and which enables a lock chassis to withstand certain lateral forces would be welcomed by users of such a lock chassis. 
     According to the present invention, a lock chassis includes an insert having two wings positioned on opposite sides of a slide of the lock chassis from each other and at least a portion of each wing is positioned to lie between the slide and an interior surface of a cover, which houses the slide. 
     In preferred embodiments, the insert is positioned around a spindle and a hub of the lock chassis and the two wings flank a chassis frame housed within the cover. The frame is coupled to a flange and houses the slide, which is adapted to move linearly with respect to the frame. In preferred embodiments, the insert is made of zinc and its wings consume a substantial portion of a void which exists between an exterior surface of the frame and the interior surface of the cover. 
     Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The detailed description particularly prefers to the accompanying figures in which: 
     FIG. 1 is an exploded view of a door latching mechanism in accordance with the present invention, including a lock chassis, two door handles, and various other components of the latching mechanism; 
     FIG. 2 is an exploded view of the lock chassis of FIG. 1, including an insert, a cover, spindles, hubs, a frame, a flange, and a slide; 
     FIG. 3 illustrates a core of the lock chassis assembled, including the hubs, frame and flange, and the insert and cover being secured around the assembled chassis core; and 
     FIG. 4 illustrates the chassis core of FIG. 3 with the insert and cover coupled to the chassis core. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring to FIG. 1, a door latching mechanism  10 , according to the present invention, includes inside and outside levers  12 ,  14 , spring cages  16 ,  18 , roses  20 ,  22 , drivers  24 ,  26 , caps  28 ,  30 , bushings  32 ,  34 , and a spacer  36 , as is typical in conventional door latching mechanisms. According to the present invention, door latching mechanism  10  further includes a lock chassis  38 , which includes an insert  80  (not visible in FIG.  1 ), the structure and position of which will become apparent below with reference to FIGS. 2,  3 , and  4 . Additionally, the door latching mechanism  10  includes a draw bar and latch bolt (both not shown), which will be readily apparent to one of ordinary skill in the art viewing FIG.  1 . 
     FIG. 2 illustrates an exploded view of the lock chassis  38  of the door latching mechanism  10 . The lock chassis  38  includes inside and outside spindles  40 ,  42  and hubs  44 ,  46  aligned along a chassis axis  25 , and a frame  48  and a flange  50 , which house slide  52 . Referring to FIGS. 1 and 2, as will be readily apparent to one of ordinary skill in the art, rotation of levers  12 ,  14  rotates spindles  40 ,  42 , respectively, thereby causing the slide  52  to slide within a chamber  49  defined between sidewalls  47  of the frame  48 . As will also be readily understood by one of ordinary skill in the art, sliding motion of the slide  52  within the chamber  49  is accomplished by inside and outside cams  54 ,  56 , formed as part of inside and outside spindles  40 ,  42 . Inside and outside cams  54 ,  56  engage inside and outside cam surfaces  58 ,  60  of the slide  52  when spindles  40 ,  42  are rotated. Rotation of spindles  40 ,  42  thus causes the slide  52  to linearly translate within the frame  48 . Linear translation of the slide  52  causes the draw bar and corresponding latchbolt (both not shown) to move between an extended and retracted position. It will also be readily apparent to one of ordinary skill in the art that cams  54 ,  56  may be formed as separate structures instead of being formed as part of inside and outside spindles  40 ,  42  as they are shown in FIG.  2 . 
     Inside and outside hubs  44 ,  46  provide bearing surfaces for spindles  40  and  42 , respectively. Sliding movement of the slide  52  within the chamber  49  of the frame  48  is facilitated by rollers  62  mounted on axles  64  and springs  66  positioned between a seat  68  and the slide  52 . A user rotates either lever  12  or  14  to rotate spindle  40  or  42  to retract the slide  52  and thereby retract the latchbolt. The slide  52 , and thus the latchbolt, are returned to an extended position by the springs  66 . Spring-loaded knob catches  70  are placed within inside and outside spindles  40  and  42  and engage levers  12 ,  14  to secure levers  12 ,  14  to spindles  40  and  42 , respectively. 
     Referring to FIG. 3, a chassis core  72 , which comprises the frame  48 , flange  50  and hubs  44 ,  46 , is held together by four hook-shaped legs  74  formed as part of the frame  48  and extending from sidewalls  47 . The legs  74  extend through and engage slots  76  in the flange  50 . Additionally, the chassis core  72  is secured by a cover  78  which houses the frame  48  and the flange  50 , and the insert  80 , which is positioned to lie around the outside hub  46  and includes two wings  102  positioned between outward faces  43  of sidewalls  47  and an interior surface  84  of the cover  78 . The interior surface  84  of the cover  78  defines an interior space  85  which houses the frame  48 , the flange  50 , and the slide  52 . And, the outside spindle  42 , along with the outside hub  46 , extends through an aperture  45  formed in the insert  80 . Two screws  86  fit through openings  88  in the cover  78  and openings  90  in the flange  50  and into threaded holes  92  in the wings  102  of the insert  80  to further secure the chassis core  72 . However, it will be understood by one of ordinary skill in the art that other methods (e.g., self-tapping screws, bolts and nuts, rivets, pins, stakes, etc.) may be used to secure the cover  78  to the insert  80 . 
     Referring again to FIGS. 1 and 2, the door latch and draw bar, mentioned above, fit through window  94  in the cover  78 . The draw bar engages jaws  96  of slide  52 , thereby moving between an extended and retracted position as lever  12  or  14  is rotated. 
     According to a presently preferred embodiment of the present invention, as shown in FIGS. 3 and 4, the insert  80  comprises zinc and includes two wings  102 , which fit snuggly in a void  75  between an exterior surface  82  of the frame  48  and portions of the interior surface  84  of the cover  78 . In this way, exterior surfaces  98  of wings  102  lie in close proximity to portions of the interior surface  84  of cover  78 , and interior surfaces  100  of wings  102  lie in close proximity to the exterior surface  82  of the frame  48 . In the event a lateral force is applied to either lever body  13  or  15  of lever  12  or  14  (see FIG.  1 ), the force will be translated to the chassis core  72  via spindles  40 ,  42 . The force will be dissipated by the insert  80  which distributes the force over a portion of the surface area of the interior surface  84  of the cover  78 . The cover  78  in turn distributes the force over an interior surface of a bore (not shown), which is cut into the door to house the latching mechanism  10 . The force is then further dissipated through the door itself (also not shown). 
     Moreover, the screws  86  tighten the cover  78  and the insert  80  around the flange  50 , with a back wall  104  of the insert  80  firmly holding the frame  48  to the flange  50  when assembled, as illustrated in FIGS. 3 and 4. In this way, the chassis core  72  is held rigid and can withstand both lateral forces applied to the lock chassis  38  perpendicular to the chassis axis  25  and axial forces applied to the lock chassis  38  parallel to the chassis axis  25 . It will be readily understood by one of ordinary skill in the art that the insert  80  may be constructed of materials other than zinc (e.g., other metals, such as aluminum, steel, etc. and plastics, etc.). 
     Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.