Patent Publication Number: US-7717480-B2

Title: Latch assembly

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a latch assembly, and in particular to a latch with an adjustable backset. 
   2. The Prior Arts 
   “Backset” refers to the distance from the edge of the door to the center of the pre-drilled hole for the lock. Most tubular locks come in a single size: 60 mm or 70 mm backset. The user needs to know the backset dimension to purchase the lock. If the lock purchased by the user has a backset different from the hole drilled on the door, the lock is unusable. Thus, the lock has only a single backset dimension is restricted to be used on the door having the pre-drilled hole with the same backset dimension. Accordingly, a latch assembly with an adjustable backset has been developed. The latch assembly can change the assembly method of transmission members of the lock and the backset distance can be set to one of two predetermined distances. The latch assembly according to the present invention is more applicable than the conventional latch assembly. 
   China Patent No. 99248490.1 discloses a “Latch bolt mechanism of a tubular lock with adjustable backset by an extension casing”, which can be adjusted to provide two predetermined backset positions. The latch bolt mechanism includes a latch bolt housing, a plate assembly including a first plate and a second plate, an actuating plate, a follower plate located between the first plate and the second plate, and an extension casing mounted around an inner end of the plate assembly and movable longitudinally to the plate assembly. One end of the actuating plate includes a hook-shaped connecting member for retracting the latch bolt and the other end of the actuating plate includes an upper tooth and a lower tooth. The follower plate includes an upper tooth and a lower tooth, each of which includes a block formed thereon. When the spindle of the lockset is turned, one of the upper tooth and the lower tooth of the follower plate is pressed by a lateral side of the spindle. The follower plate presses the blocks of the actuating plate, and therefore the follower plate retracts the latch bolt. Moreover, the extension casing includes upper and lower slots in top and bottom sides thereof, respectively. The slots receive the blocks of the follower plate, respectively. Because the slots have a length longer than that of the blocks of the follower plate, the extension casing can drive the follower plate to move relative to the actuating plate and the extension casing can move relative to the follower plate, i.e. the extension casing and the follower plate can have different moving distance relative to the actuating plate. Thus, a latch of a tubular lock is adjusted to form two different backset dimensions by moving the extension casing. However, a disadvantage of this configuration is that this positioning mechanism of the latch bolt can not be adjusted accurately, because when the extension casing moves together with the follower plate between two backset dimensions, the relative moving space between the extension casing and the follower plate is realized by the slots of the extension casing that have a length longer than that of the blocks of the follower plate, and there is no position fixing member for the two different backset dimensions. 
   SUMMARY OF THE INVENTION 
   The objective of the present invention is to provide a latch assembly with an adjustable backset, by which the latch can be accurately set to one of two predetermined backset positions. The latch assembly can change from one backset dimension to the other back dimension quickly, conveniently and accurately. 
   A latch assembly according to the present invention includes a latch bolt, a housing, an actuating plate passing through the housing and connected with the latch bolt, a lower connecting plate connected with the housing and positioned under the actuating plate, an upper connecting plate positioned above the actuating plate, a driving plate mounted between the actuating plate and the lower connecting plate, and a positioning casing, in which the upper connecting plate combined with the lower connecting plate is placed. 
   The positioning casing is formed with a middle hole on the middle portion for a spindle to pass through, a front hole and a back hole on the front portion and back portion for fixing bolts to pass through respectively, and two protrusions symmetrically located on the left and right side of the middle hole. 
   The middle portion of the upper connecting plate is formed with a long hole for the spindle to pass through; a first pair of symmetrical recesses corresponding to the protrusions of the positioning casing is formed on both sides of the front portion of the long hole, and a second pair of symmetrical recesses corresponding to the protrusions of the positioning casing is formed on both sides of the back portion of the long hole. 
   The actuating plate is provided with a long slot along the length direction, and two symmetrical protrusions projecting from the left and right side of the middle portion of the bottom surface of the long slot. 
   The driving plate is formed with a square hole to allow the spindle to pass through, and the front side wall of the square hole is in contact with the protrusions of the actuating plate. 
   The upper connecting plate is provided with a first hole and a second hole at the front and back ends of the long hole respectively for the fixing bolt to pass through, and a third hole in the front portion of the upper connecting plate. 
   The lower connecting plate is provided with a long hole on the middle portion for the spindle to pass through, a first hole and a second hole on the front and back ends of the long hole for the fixing bolts to pass through, and a third hole in the front portion of the lower connecting plate. 
   When the protrusions of the positioning casing are engaged with the second pair of recesses of the upper connecting plate, the middle hole of the positioning casing is aligned with the long hole of the upper connecting plate, the long slot of the actuating plate and the long hole of the lower connecting plate; the front hole of the positioning casing is aligned with the first holes of the upper and lower connecting plates; the back hole of the positioning casing is aligned with the second holes of the upper and lower connecting plates. 
   When the protrusions of the positioning casing are engaged with the first pair of recesses of the upper connecting plate, the middle hole of the positioning casing is aligned with the long hole of the upper connecting plate, the long slot of the actuating plate, the square hole of the driving plate and the long hole of the lower connecting plate; the front hole of the positioning casing is aligned with the third holes of the upper and lower connecting plates; the back hole of the positioning casing is aligned with the long holes of the upper and lower connecting plates. 
   The latch assembly of the present invention can be set to two different backset dimensions by configuring the positioning casing, the driving plate and the upper and lower connecting plates without other tool. A larger backset dimension can be obtained by connecting the protrusions of the positioning casing with the second pair of recesses of the upper connecting plate, and a smaller backset dimension can be obtained by connecting the protrusions of the positioning casing with the first pair of recesses of the upper connecting plate. When the larger backset dimension is employed, the spindle is engaged with the actuating plate to retract the latch bolt. When the smaller backset dimension is employed, the spindle is engaged with the driving plate to retract the latch bolt. The latch assembly according to the present invention is configured simply and can be adjusted from a backset dimension to the other backset dimension easily and accurately. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be apparent to those skilled in the art by reading the following detailed description of a preferred embodiment thereof, with reference to the attached drawings, in which: 
       FIG. 1  is an exploded perspective view showing a latch assembly according to an embodiment of the present invention; 
       FIG. 2  is a schematic view showing an actuating plate of the latch assembly according to the embodiment of the present invention; 
       FIG. 3  is a schematic view showing a driving plate of the latch assembly according to the embodiment of the present invention; 
       FIG. 4  is a schematic view showing the latch assembly assembled with a spindle in a first backset dimension; 
       FIG. 5  is a schematic view showing an initial state of the latch assembly employing the first backset dimension; 
       FIG. 6  is a schematic view showing the latch assembly assembled with the spindle in a second backset dimension; and 
       FIG. 7  is a schematic view showing the initial state of the latch assembly employing the second backset dimension. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A preferred embodiment in accordance with the present invention will now be described with reference to the accompanying drawings. 
   With reference to  FIG. 1 , a latch assembly according to the present invention includes a housing assembly, an upper connecting plate  11 , a lower connecting plate  14 , an actuating plate  12 , a driving plate  13  and a positioning casing  15 . 
   The housing assembly includes a housing  10 , a latch bolt  101 , a linking member  102 , a clip plate  103 , a face plate  104 , an anti-theft pin  105 , an elastic element  106  and a guarding plate  107 . The latch bolt  101  is connected with the linking member  102 . The linking member  102  is connected with the clip plate  103  and can be driven by the actuating plate  12 . 
   Referring to  FIGS. 1 and 2 , the actuating plate  12  includes a hook at one end, which is connected with the linking member  102  in the housing  10  by means of the clip plate  103  for driving the latch bolt  101  to move. The actuating plate  12  is disposed between the upper connecting plate  11  and the lower connecting plate  14 . A long slot  123  formed on the actuating plate  12  along the length direction includes an assembly plane  124  on the side surface thereof, which can be engaged with a rotating plane  164  of a spindle  163  (referring to  FIG. 4 ). The back end of the long slot  123  has a notch for receiving the spindle  163 . On the left and right sides of the middle portion of the long slot  123 , two first protrusions  121  are formed symmetrically, which are projected from the bottom surface of the actuating plate  12 . The other end of the actuating plate  12  opposing to the hook is provided with two second protrusions  122  symmetrically formed on the edges of the actuating plate  12 , which can be tightly contacted with the upper connecting plate  11  disposed above the actuating plate  12  for preventing the actuating plate  12  from shaking. 
   One end of the lower connecting plate  14  is connected with the housing  10 . A long hole  143  is formed in the middle portion of the lower connecting plate  14  to allow the spindle  163  to pass through (Referring to  FIGS. 4 and 6 ). The lower connecting plate  14  also includes a first hole  145  and a second hole  146  located at the front and back ends of the long hole  143  respectively for the fixing bolts to pass through, and a third hole  144  located at the front portion of the lower connecting plate  14 . Furthermore, the lower connecting plate  14  is provided with two symmetrical clamping blocks  141  on the two long edges respectively for engaging the lower connecting plate  14  with the upper connecting plate  11 . 
   Referring to  FIGS. 1 and 3 , the driving plate  13  is a thin flat piece and is disposed between the actuating plate  12  and the lower connecting plate  14 . The driving plate  13  is formed with a square hole  133  for the spindle  13  to pass through. Also, the square hole  133  includes a semicircular hole  134  corresponding to the spindle  163  on the back end thereof. The front side wall of the square hole  133  includes a first assembly plane  131  and the back side wall of the square hole  133  includes a second assembly plane  132 . The first assembly plane  131  can be engaged with the first protrusions  121  of the actuating plate  12  for driving the actuating plate  12  to move. 
   The upper connecting plate  11  having the configuration corresponding to the lower connecting plate  14  is provided with a long hole  113  formed in the middle portion thereof. The spindle  163  passes through the long hole  113 . The upper connecting plate  11  is also provided with a first hole  115  and a second hole  116  located at front and back ends of the long hole  113  respectively for the fixing bolts to pass through. Also, the upper connecting plate  11  is formed with a third hole  114  at the front portion thereof. A first pair of symmetrical recesses  111  and a second pair of symmetrical recesses  112  are formed at the two sides of the long hole  113 . The second pair of symmetrical recesses  112  is positioned at the back portion of the upper connecting plate  11  and the first pair of symmetrical recesses  111  is positioned at the back portion of the upper connecting plate  11 . Furthermore, the upper connecting plate  11  is formed with two symmetrical notches  117  corresponding to the clamping blocks  141  of the lower connecting plate  14  on the two edges thereof. The upper connecting plate  11  is assembled with the lower connecting plate  14  by engaging the clamping blocks  141  with the notches  117 . 
   The upper and lower connecting plates  11 ,  14 , the actuating plate  12  and the driving plate  13  are connected together and are disposed in the positioning casing  15 . The positioning casing  15  is formed with a middle hole  153  for the spindle  163  to pass through, and is also formed with a front hole  154  and a back hole  155  for the fixing bolts to pass through. Also, two protrusions  151  are formed on the left and right sides of the middle hole  153 , respectively. The protrusions  151  can be engaged with the first pair of recesses  111  or the second pair of recesses  112 . One end of the positioning casing  15  is provided with two assembly blocks  156  symmetrically placed on the edges for fixing the positioning casing  15 . 
   For assembling the latch assembly, the lower connecting plate  14  is installed in the housing  10  first, and then the actuating plate  12  is installed. In the housing  10 , the actuating plate  12  is connected with the linking member  102  and the clip plate  103  to drive the latch bolt  101  to move. Afterward, the driving plate  13  is installed between the actuating plate  12  and the lower connecting plate  14 . The first assembly plane  131  of the driving plate  13  is engaged with the first protrusions  121  of the actuating plate  12 , whereby the driving plate  13  can drive the actuating plate  12  to unlock the lock. Then the upper connecting plate  11  is installed by engaging the clamping blocks  141  of the lower connecting plate  14  with the notches  117  of the upper connecting plate  11 . Meanwhile, the second protrusions  122  of the actuating plate  12  are in contact with the upper connecting plate  11  tightly for preventing the actuating plate  12  from shaking. Finally, the outside of the upper connecting plate  11  and the lower connecting plate  14  is covered with the positioning casing  15 , and then the assembly blocks  156  are riveted. Thus the assembly process of the latch is completed. 
     FIG. 4  is a schematic view showing the latch assembly assembled with the spindle  163  in a first backset dimension. When the latch assembly according to the present invention is adjusted to a larger backset dimension, the positioning casing  15  is moved to engage the protrusions  151  of the positioning casing  15  with the second pair of recesses  112  of the upper connecting plate  11 . In assembling the lock body  16 , the spindle  163  passes through the middle hole  153  of the positioning casing  15 , the long hole  143  of the lower connecting plate  14 , the long slot  123  of the actuating plate  12  and the long hole  113  of the upper connecting plate  11  so that the rotating plane  164  of the spindle  163  can engage with the assembly plane  124  of the actuating plate  12 . It is important to note that as shown in  FIG. 4 , the spindle  163  is positioned behind the driving plate  13  without passing through the semicircular hole  134 . When the spindle  163  is turned, the rotating plane  164  presses the assembly plane  124  and then drives the actuating plate  12  to move. Thus, the latch bolt  101  is driven by the hook of the actuating plate  12  to retract to the housing  10 . Moreover, referring to  FIG. 5 , a first fixing bolt  161  passes through the back hole  155  of the positioning casing  15 , the second hole  146  of the lower connecting plate  14  and the second hole  116  of the upper connecting plate  11 . Also, a second fixing bolt  162  passes through the front hole  154  of the positioning casing  15 , the first hole  145  of the lower connecting plate  14  and the first hole  115  of the upper connecting plate  11 . Accordingly, the lock body  16  can be fixed. 
     FIG. 6  is a schematic view showing the latch assembly assembled with the spindle  163  in a second backset dimension. When the latch assembly according to the present invention is adjusted to a smaller backset dimension, the positioning casing  15  is moved to engage the protrusions  151  of the positioning casing  15  with the first pair of recesses  111  of the upper connecting plate  11 . In assembling the lock body  16 , the spindle  163  passes through the middle hole  153  of the positioning casing  15 , the long hole  143  of the lower connecting plate  14 , the semicircular hole  134  in back of the square hole  133  of the driving plate  13 , the long slot  123  of the actuating plate  12  and the long hole  113  of the upper connecting plate  11  so that the rotating plane  164  of the spindle  163  can engage with the second assembly plane  132  of the driving plate  13 . Meanwhile, the first assembly plane  131  of the driving plate  13  is engaged with the first protrusions  121  of the actuating plate  12 . When the spindle  163  is turned, the rotating plane  164  presses the second assembly plane  132  and then drives the driving plate  13  to move. Thus, the driving plate  13  drives the actuating plate  12  and the hook of the actuating plate  12  retracts the latch bolt  101  back into the casing. Moreover, referring to  FIG. 7 , the first fixing bolt  161  passes through the back hole  155  of the positioning casing  15 , the long hole  143  of the lower connecting plate  14  and the long hole  113  of the upper connecting plate  11 . Also, the second fixing bolt  162  passes through the front hole  154  of the positioning casing  15 , the third hole  144  of the lower connecting plate  14  and the third hole  114  of the upper connecting plate  11 . Accordingly, the lock body  16  is fixed. 
   From above all, the latch according to the present invention can be set to two backset dimensions without any tools. The latch assembly can be accurately kept at the predetermined backset dimension and can prevent the backset dimension from being unintentionally changed to other dimensions. Therefore, the latch assembly according to the present invention has a simple structure and can adjust the backset dimension conveniently. 
   Although the present invention has been described with reference to the preferred embodiment thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.