Patent Publication Number: US-7222890-B2

Title: Multiple backset latch

Description:
RELATED APPLICATIONS 
   This application claims priority under 35 USC § 120 to prior U.S. Provisional Application No. 60/580,550 to the same Applicant, filed Jun. 17, 2004, titled Multiple Backset Latch. 

   GOVERNMENT GRANTS/SUPPORT 
   None 
   FIELD OF THE INVENTION 
   The present invention relates to a latch adjustable to multiple backsets to permit one latch device to meet either 60 mm (2⅜ inches) and 70 mm (2¾ inches) backsets. The invention relates particularly to a latch mechanism design utilizing one cam instead of multiple cams. 
   BACKGROUND OF THE INVENTION 
   Industry standards in door geometry dictate lock placement and generally offer contractors two latch and knob axis-to-door-edge distances. Latch and knob axis-to-door-edge distance is described and understood within the trade as “backset”. Backset is the distance from the edge of the door (wood or metal), from which the latch bolt extends, to the center of rotation of the knob. The two common backsets are 60 mm (2⅜ inches) often found in older doors and 70 mm (2¾ inches) found in more modern doors. 
   In the past, it was common for producers to produce separate lock and latch assemblies for each backset, and retailers would stock both types. However, both retailers who have limited shelf space, and contractors who must purchase and install latch and lock sets have demanded single latch and lock sets that can easily be adjusted to fit either backset. 
   A modern latch mechanism generally has a tubular latch housing mounted in a lateral bore at the edge of the door. The latching bolt has a canted forward face that provides retraction of the bolt when the face abuts against a striker plate in the doorjamb upon closing the door. The bolt springs back into the hole of the striker plate to latch the door shut. In wood doors the faceplate is conventionally rectangular in shape and fits within a mortised or chiseled recess in the door edge. The rectangular shape may have rounded corners for aesthetic purposes. In metal doors, a circular faceplate is conventionally used which has a plurality of serrations or ribs in its periphery and which is driven into and secured to the lateral bore in the door. 
   To date, several types of adjustable backset latches have been developed. Attempts to solve the problems associated with two common backsets have included various mechanisms to vary the backset, including latches of various lengths, multiple movable cams, linkages incorporated within the latch, fixed cam/axis devices offering two backset dimensions, moveable cams and linkages incorporated within the knob, and latch housings with multiple settings. However, many are very complex, with many parts. In addition, there is limited space available within a door, and many of the adjustable backset latch devices must have portions removed and replaced in order to change backsets, which requires disassembly of the latch mechanism in order to change backsets. Thus, there is a need for a simple, compact and efficient adjustable backset latch mechanism that can be cost-effectively manufactured, stocked, purchased, and installed with ease without disassembly of the latch mechanism in order to change backset. 
   SUMMARY OF THE INVENTION 
   The invention provides an improved door latch assembly and its installation by offering multiple backset adjustments. The present invention maintains integrity to meet American National Standards Institute (ASNI) tests and accomplish the multiple backset function by moving a single cam to either of two backset positions with the least number of components. The single rotatable lever comprised in this invention is manually moveable and easily pressed into a fixed and secured position during installation to suit the chosen backset without the need of many tools. The latch assembly of the present invention, with a singular cam lever, is radially acted upon by means of an axis and knob, of which the same mechanical means affects its incorporated pinion members and bolt retractor linkage to result in retracting a coupled latch bolt. 
   Most basically the invention is a multiple backset latch having as primary components a housing body assembly and a latch bolt housing assembly. The latch bolt housing assembly includes a housing body channel member, a cam support plate member, a bolt retractor member, a cam lever member, a positioning spring member, and a housing body plate. The latch bolt housing assembly further includes a latch bolt head. The housing body channel has an oval aperture corresponding to accept the cam lever member. The oval aperture has multiple radii sufficient to accommodate lateral movement to accommodate a range of 60 mm (2⅜ inches) to 70 mm (2¾ inches) backset positions. 
   It is a unique objective of the present invention to provide a door latch assembly having an integrated means to accommodate multiple backset dimension requirements while facilitating the backset adjustment selection to be done in an easy and convenient manner. In addition, other objectives are accomplished in a latch assembly generally installed inside a door core consisting of a latch bolt, operable and traversing longitudinally from a normal projected state beyond the door edge, and upon actuation being retracted fully into the door core. Latch retracting action is accomplished with assembly components activated by a rotatable axis displacement about a cam lever and by reversing accomplishing reciprocation of the adjacent connected latch bolt. Other objectives and aspects of the invention will become apparent by reference to the following description, drawings, and appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following invention can be best understood by reference to the drawings described below, and the following detailed description of the preferred embodiment. 
       FIG. 1  is a partial top view of the door latch assembly of the present invention with integrated components to accomplish multiple backset dimension requirements and viewed as the latch bolt would be normally extended. This detailed view simply illustrates the cam lever, bolt retractor link and the embodied pinion elements. 
       FIG. 2  is a side elevation of the latch assembly which illustrates the assembly housing geometry further revealing all member features as they effect the necessary multiple backset options. 
       FIG. 3  is an end view of the latch bolt and latch assembly escutcheon shown as it would be installed for a right hand hinged door. 
       FIG. 4  is a side elevation of the latch assembly revealing the scheme of the device with the bolt retractor link in a compressed position and embodied cam lever member being typical for a latch assembly installed for a 60 mm backset requirement. 
       FIG. 5  is a side elevation of the latch assembly revealing the scheme of the device with the bolt retractor link in a compressed position and embodied cam lever member being typical for a latch installed for a 70 mm backset requirement. 
       FIG. 6  is an exploded isometric view illustrating the assembly components of the preferred door latch embodiment. 
       FIG. 7  is a top view showing features of the hosing body channel. 
       FIG. 8  is a side view showing features of the housing body channel. 
       FIG. 9  is a top view showing features of the positioning spring. 
       FIG. 10  is a side view showing features of the positioning spring. 
       FIG. 11  is a top view showing features of the housing body plate. 
       FIG. 12  is a side view showing features of the housing body plate. 
       FIG. 13  is a top view showing features of the cam lever. 
       FIG. 14  is a side view showing features of the cam lever. 
       FIG. 15  is a top view showing features of the cam support plate. 
       FIG. 16  is a side view showing features of the cam support plate. 
       FIG. 17  is a top view showing features of the bolt retractor. 
       FIG. 18  is a side view showing features of the bolt retractor. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following is a description of the preferred embodiment of the invention. It is clear that there may be variations in the size and the shape of the mechanism, in the materials used in the construction and in the orientation of the various parts and devices of the system. However, the main features are consistent and the particular objectives, features and advantages are as disclosed herein. 
   Referring now to the Figures, in  FIG. 2 , a preferred embodiment of the multiple backset mechanism of the invention is illustrated. The preferred embodiment comprises integrated components of a housing body assembly  10  and a latch bolt housing assembly  20  consisting of a latch bolt head  21  of a type typically known in the Art. For simplicity, further description of latch bolt heads is not included nor required for one of ordinary skill in the art to understand the invention. 
   The housing body assembly device  10  in this preferred invention is comprised of a housing body channel member  30 , a cam support plate member  40  as viewed in  FIG. 4 , a bolt retractor member  50 , a cam lever member  60 , a positioning spring member  70 , and a housing body plate  80 . 
   As shown in  FIG. 2 , the housing body channel member  30 , and also in greater deal in  FIG. 8 , includes an oval aperture feature  31  sized and shaped appropriately to rotatably accept the bossed end  61  of the cam lever member  60 , shown in detail in  FIG. 13 . Oval aperture feature  31  has, embodied in its elongation, multiple radii permitting the cam lever member  60  to move laterally as it is required for assembly offering cam lever  60  axis differences to accommodate 60 mm (2⅜ inches) or 70 mm (2¾ inches) door backset. As shown in  FIG. 8 , the housing channel body  30  has necessary multiple apertures  32  and  33  which are paired to clear fastening devices embodied in a latch-knob assembly for a 60 mm door backset dimension. Additionally, as shown in  FIG. 8 , the housing body channel member  30  has an additional necessary aperture  34  located between apertures  32  and  33  which is intended to clear fastening devices embodied in a latch-knob assembly for a 70 mm door backset dimension. 
   As shown in  FIG. 4 , the cam support plate member  40 , and also in greater detail in  FIG. 16 , includes an aperture feature  41  appropriate to rotatably accept the bossed end  61  of the cam lever member  60 . Additionally, the height and thickness of the cam support plate member  40  is particularly designed to traverse laterally inside the housing body channel member  30  while also supporting the inserted cam lever member  60 , therefore providing the requirement for that assembly to offer cam support plate member  40  axis differences to accommodate 60 mm or 70 mm door backsets. 
   As shown in  FIG. 4 , and also in greater detail in  FIG. 18 , the bolt retractor member  50  has incorporated therein an elongated aperture  51  appropriate for its central aperture to rotatably accept the bossed end  61  of cam lever member  60 . But, the same central aperture feature  51  diameter, shown in detail in  FIG. 18 , is limited to accommodate the diameter breadth of the cam lever tangs  62  shown in detail in  FIG. 13 , therefore causing the cam lever shoulder face  63  of the cam lever member  60  shown in detail in  FIG. 13  to bear against the bolt retractor face  52  of bolt retractor member  50 . Additionally, the bolt retractor member  50  shown in detail in  FIG. 18  has pairs of integrated pinions  53  situated symmetrically on the top and bottom and protruding outwardly from the bolt retractor face  52  and providing an assembly mechanical function with the cam lever member  60  by means of the cam lever tangs  62  shown in detail in  FIG. 14 . Moreover, the paired pinions  53  centers are also located laterally as it is required for the assembly to offer cam lever  60  axis differences to accommodate 60 mm or 70 mm door backset requirements. In whichever backset positions the latch bolt assembly is situated, the cam lever member  60  will allow interaction by means of the cam lever tangs  62  and ultimate bearing on the correspondent pinion member  53  of the bolt retractor  50  while accomplishing the same effect on the bolt retractor  50  reciprocation regardless of the rotational direction on the door latch-knob axis. 
   Additionally, the bolt retractor member  50  functions during the door latch-knob mechanical axis operation to retract the necessary latch bolt head  21  contained in the latch bolt housing  20  as shown in  FIG. 4  by means of a pawl  54  being contained in the housing body assembly  10  adjacent to the latch bolt housing  20  and being part of the bolt retractor member  50 . 
   As shown in  FIG. 6 , with reference to  FIG. 10 , a positioning spring member  70 , being a traversing device particularly intended to secure the assembly, consisting of the cam support plate member  40  with the cam lever member  60 . The positioning spring member  70 , shown in greater detail in  FIG. 10 , includes an aperture feature  71  appropriate to rotatably accept the bossed end  65  of the cam lever member  60  as it is required for the assembly to offer cam lever  60  axis differences to accommodate 60 mm or 70 mm door backset. 
   Furthermore, as shown in  FIG. 6 , with reference to  FIG. 10 , the positioning spring member  70  has two protruding formed dimples  72  and opposing dimple  73  on the perimeter of the aperture  71  which interact with the housing body plate member  80  recessed openings  83  and  84  as shown in detail in  FIG. 12 . The detent effect of the protruding feature  72  of the positioning spring member  70  with the recess  84  in the housing body plate member  80  serves to secure the housing body assembly device  10  axis difference to accommodate the 60 mm door backset. Likewise, the detent effect of the protruding feature  73  of the positioning spring member  70  with the recess  83  in the housing body plate member  80  serves to secure the housing body assembly device  10  axis difference to accommodate the 70 mm door backset. 
   As described above, a single latch mechanism can be made easily adjustable to either a 60 mm or a 70 mm backset. No special or complex tools are required to adjust the backset of the present invention and only a single rotatable cam device is required. In addition, no parts must be removed or installed in order to adjust the backset. The cam lever member  60 , cam support plate member  40  and positioning spring member  70  are all simply laterally slidable with respect to the housing body channel member  30 , the bolt retractor member  50 , and the housing body plate member  80 . 
   The multiple backset latch device of the present invention and many of the attendant advantages are understood from the foregoing description. As noted, various and several changes may be made in the form, construction and arrangement of the parts thereof without departing from the spirit and scope of the invention or sacrificing its material advantages, the forms hereinbefore described being merely exemplary embodiments.