Patent Publication Number: US-6991271-B2

Title: Latch assembly with adjustable backset

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a latch assembly with adjustable backset. In particular, the present invention relates to a backset-adjustable latch assembly that prevents undesired displacement of a spindle. 
   2. Description of Related Art 
   A typical latch Assembly with adjustable backset has been disclosed in, e.g., U.S. Pat. No. 4,615,549. As illustrated in  FIGS. 8 through 10  of the drawings which correspond to FIGS. 1 through 3 of U.S. Pat. No. 4,615,549, the dual backset latch includes a lock case (bolt housing)  10 , two pulling plates (housing shell halves)  20 , a latch bolt  30 , a connecting plate (latch operating plate)  40 , and front and rear cams  50 ,  50 ′. The lock case  10  and the assembling plates  20  together form the main body of the latch assembly. A base portion of the latch bolt  30  extends into the lock case  10 . The connecting plate  40  extends through the lock case  10  and between the assembling plates  20 , with a front end of the connecting plate  40  being connected to the latch bolt  30  to move therewith. The connecting plate  40  is provided with a pair of rear latch bosses  41  and  42 . The assembling plates  20  include two aligned holes  21  and  22 . Each cam  50 ,  50 ′ has a hub portion  51 ,  51 ′, a rectangular spindle slot  52 ,  52 ′, and a pair of ears  53 ,  53 ′. The cams  50  and  50 ′ are spaced by the connecting plate  40  and rotatably received in the holes  21  and  22 , respectively. When either cam  50 ,  50 ′ is turned, the respective ear  53 ,  53 ′ presses against the respective latch boss  41 ,  42 , thereby retracting the latch bolt  30  into the lock case  10 . 
   The backset of the front cam  50  is under industry standard 2 and ⅛ inches (or approximately 60 mm) and for the rear cam  50 ′ 2 and ¾ inches (or approximately 70 mm). When the latch assembly is mounted together with other parts of a door lock to a mounting hole in a door, the installer may selectively extend a spindle (not shown) through either one of the spindle slots  52  and  52 ′ respectively of the cams  50  and  50 ′ without adjusting the latch assembly, thereby accomplishing installation. 
   Although this latch assembly can be used with doors having two standard backset sizes, there are still several drawbacks. Firstly, the spindle holes  52  and  52 ′ respectively of the cams  50  and  50 ′ are substantially slanted U-shaped and communicated with each other such that the spindle extending through, e.g., the spindle hole  52  of the cam  50  is apt to slide into the spindle hole  52 ′ of the cam  50 ′. The spindle is thus stuck and rotation of either handle (not shown) of the door lock is impossible. Second, the joint area between the two holes  21  and  22  of the respective assembling plate  20  is relatively large such that either cam  50  or  50 ′ may undesirably enter the incorrect hole  22  or  21 . As a result, the cams  50  and  50 ′ are stuck in the same hole  21  or  22 . 
   OBJECT OF THE INVENTION 
   The object of the present invention is to provide a backset-adjustable latch assembly that prevents undesired displacement of a spindle. 
   SUMMARY OF THE INVENTION 
   To achieve the aforementioned object, the present invention provides a latch assembly including a lock case, two assembling plates securely mounted to the lock case, a latch bolt received in the lock case and movable between a retracted position and an extended position, a connecting plate extending through the lock case and between the assembling plates, a first cam, and a second cam. 
   Each assembling plate includes a first hole and a second hole, with the first holes of the assembling plates being aligned with each other and with the second holes of the assembling holes being aligned with each other. The connecting plate is connected to the latch bolt to move therewith. The first cam is received in the first holes of the assembling plates. The first cam has a first spindle hole. The first cam further has a stop wall that closes the first spindle hole to form a closed non-circular hole. The second cam is received in the second holes of the assembling plates. The second cam has a second spindle hole. 
   The first cam and the second cam are connected to the connecting plate to move therewith such that pivotal movement of either one of the first cam and the second cam causes retraction of the latch bolt. The first spindle hole of the first cam and the second spindle hole of the second cam are separated by the stop wall, thereby preventing a spindle extending through one of the first spindle hole and the second spindle hole from entering the other of the first spindle hole and the second spindle hole. 
   Other objects, advantages and novel features of this invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of a latch assembly in accordance with the present invention; 
       FIG. 2  is a side view, partly sectioned, of the latch assembly in accordance with the present invention; 
       FIG. 3  is a sectional view taken along line A—A in  FIG. 2 ; 
       FIG. 4  is a view similar to  FIG. 2 , wherein a spindle is extended through one of two spindle holes; 
       FIG. 5  is a view similar to  FIG. 3 , wherein a spindle is extended through one of two spindle holes as shown in FIG.  4  and wherein the latch bolt is retracted; 
       FIG. 6  is a view similar to  FIG. 4 , wherein the spindle is extended through the other spindle hole; 
       FIG. 7  is a view similar to  FIG. 5 , wherein the spindle is extended through the other spindle hole and wherein the latch bolt is retracted; 
       FIG. 8  is a side view of a conventional latch assembly; 
       FIG. 9  is a top view of the latch assembly in  FIG. 8 ; and 
       FIG. 10  is a view similar to  FIG. 8 , illustrating retraction of the latch bolt. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 through 3 , a latch assembly in accordance with the present invention includes a lock case  10 , two assembling plates  20 , a latch bolt  30 , a connecting plate  40 , a first cam  50 , and a second cam  50 ′. The lock case  10  and the assembling plates  20  are assembled together by, e.g., fasteners, engaging grooves, engaging slots, etc. to form the main body of the latch assembly. Each assembling plate  20  includes a first hole  21  and a second hole  22 , with the first holes  21  being aligned with each other and with the second holes  22  being aligned with each other. The position of a center of the respective first hole  21  corresponds to the backset under industry standard 2 and ⅛ inches (or approximately 60 mm), and the position of a center of the respective second hole  22  corresponds to the backset under industry standard 2 and ¾ inches (or approximately 70 mm). Of more importance, a necked portion  23  is formed between a joint area between the respective first hole  21  and the respective second hole  22 . In this embodiment, the necked portion  23  is in the form of two tooth-like structures facing each other. 
   The latch bolt  30  and an elastic element  11  ( FIG. 2 ) are mounted in the lock case  10 . The latch bolt  30  has an end connected to a base plate  31  having a slot  32 . The connecting plate  40  extends through the lock case  10  and between the assembling plates  20 . The connecting plate  40  has an elongated longitudinal slot  401  for receiving the cams  50  and  50 ′, with a rear end of the connecting plate  40  being bent to form two pairs of protrusions  41  and  42 , and with a front end of the connecting plate  40  having a hook  43  that is connected to the latch bolt  30  to move therewith. Thus, reciprocal movement of the latch bolt  30  is allowed when the connecting plate  40  moves. 
   Still referring to  FIGS. 1 through 3 , the first cam  50  has a hub portion  51 , a first spindle hole  52 , at least one ear  53 , and a stop wall  54 . The second cam  50 ′ has a hub portion  51 ′, a second spindle hole  52 ′, and at least one ear  53 ′. A reinforcing ring  55  extends between and connects the ears  53 ′ and defines an additional first spindle hole  56  aligned with the first holes  21  of the assembling plates  20 . The cams  50  and  50 ′ are spaced by the connecting plate  40 . Further, the hub portions  51  and  51 ′ respectively of the first cam  50  and the second cam  50 ′ are rotatably received in the holes  21  and  22 . The ear  53 ,  53 ′ of the respective cam  50 ,  50 ′ abuts against the respective protrusion  41 ,  42 . When either cam  50 ,  50 ′ is turned, the respective ear  53 ,  53 ′ presses against the respective protrusion  41 ,  42 , thereby retracting the latch bolt  30  into the lock case  10 . The spindle hole  52  of the first cam  50  can be closed by the stop wall  54  to form a non-circular hole. The spindle hole  52 ′ of the second cam  50 ′ includes a non-circular hole, which is a substantially slanted U-shaped hole with an opening. 
   Referring to  FIGS. 4 and 5 , in a case that a spindle “a” is extended through the spindle hole  52  of the first cam  50 , since the spindle hole  52  of the first cam  50  is a non-circular hole closed by the stop wall  54 , the stop wall  54  serves to prevent the spindle “a” from entering the spindle hole  52 ′ of the second cam  50 ′ and to prevent the spindle “a” from displacing and getting stuck. Further, since a necked portion  23  (see the width “w” in  FIG. 1  that is smaller than the smallest portion of the hub  50  of the cam  50 ) is provided in the joint area between the respective first hole  21  and the respective second hole  22 , the first cam  50  is prevented from entering the respective second hole  22  during rotational movement of the first cam  50 . Thus, the first cam  50  is avoided from moving to an improper location and thus getting stuck. 
   Further, as illustrated in  FIG. 5 , the stop wall  54  of the first cam  50  is preferably concave to avoid interference with or hindrance to pivotal movement of the second cam  50 ′. The spindle hole  52  of the first cam  50  is preferably a square hole. 
   Referring to  FIGS. 6 and 7 , in a case that the spindle “a” is extended through the spindle hole  52 ′ of the second cam  50 ′, although the spindle hole  52 ′ of the second cam  50 ′ is a substantially slanted U-shaped hole without being delimited by a stop wall, the spindle “a” is retained in the spindle hole  52 ′ by the stop wall  54  of the first cam  50 . Thus, the spindle “a” is prevented from entering the spindle hole  52  of the first cam  50  and from getting stuck. Further, since a necked portion  23  (see the width “w” in  FIG. 1  that is smaller than the smallest portion of the hub  50 ′ of the cam  50 ′) is provided in the joint area between the respective first hole  21  and the respective second hole  22 , the second cam  50 ′ is prevented from entering the respective first hole  21  during rotational movement of the second cam  50 ′. Thus, the second cam  50 ′ is avoided from moving to an improper location and thus getting stuck. 
   Further, as illustrated in  FIG. 7 , the stop wall  54  of the first cam  50  is preferably concave to avoid interference with or hindrance to pivotal movement of the second cam  50 ′. Alternatively, the second cam  50 ′ may also include a stop wall to close the spindle hole  52 ′. In another embodiment, each cam  50 ,  50 ′ has a stop wall  54  that closes the respective spindle hole  52 ,  52 ′. 
   By contrast, the spindle holes  52  and  52 ′ respectively of the cams  50  and  52 ′ are substantially slanted U-shaped holes having openings, and the width “w” in the joint area between the holes  21  and  22  is too large. As a result, the spindle “a” is apt to displace and/or get stuck. The drawbacks of the conventional latch assembly shown in  FIGS. 8 through 10  are avoided by the latch assembly shown in FIG.  1 . The latch assembly in accordance with the present invention can be used with doors having different backset sizes. Further, the latch assembly provides improved stability in use through the provision of the stop wall  54  and the necked portion  23 . 
   While the principles of this invention have been disclosed in connection with its specific embodiment, it should be understood by those skilled in the art that these descriptions are not intended to limit the scope of the invention, and that any modification and variation without departing the spirit of the invention is intended to be covered by the scope of this invention defined only by the appended claims.