Patent Publication Number: US-6334635-B1

Title: Latch bolt mechanism of a tubular lock with adjustable backset by an extension casing

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a latch bolt mechanism of a tubular lock that is adjustable in backset by using an extension casing. 
     2. Description of the Related Art 
     Many devices have been proposed to allow adjustment in backset of a lockset such that the lockset can be used with either one of two kinds of backset configuration in the structure of traditional latch bolt mechanism—namely, a 2⅜ inch type and a 2¾ inch type. An example of backset-adjustable latch bolt mechanisms is disclosed in U.S. Pat. No. 4,711,477 issued to Fann et al. on Dec. 8, 1987. The present invention is intended to provide a different design in this regard. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a latch bolt mechanism of a tubular lock that is adjustable in backset in response to the user&#39;s need by using an extension casing. 
     A latch bolt mechanism of a tubular lock in accordance with the present invention allows adjustment in backset by using an extension casing. The latch bolt mechanism has a latch bolt housing having a latch bolt mounted therein, the latch bolt being movable beyond a face plate or retracted into the face plate. Two plates are connected together and mounted to an inner end of the latch bolt. The plates includes aligned two first positioning holes, aligned second positioning hole, and aligned openings. An actuating plate is mounted between the plates and includes an end operably connected to the latch bolt. The other end of the actuating plate includes two teeth each having a block formed thereon. The blocks are pressed against by a follower plate that also includes two teeth. When either tooth of the actuating plate or the follower plate is pressed against by a spindle of the lockset, the latch bolt is retracted. An extension casing is mounted around the plates and movable toward or away from the latch bolt housing. The extension casing includes a first hole and a second hole through which the spindle of the lockset is selectively extended. 
     Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a first embodiment of a latch bolt mechanism of a tubular lock in accordance with the present invention. 
     FIG. 2 is a sectional view of the latch bolt mechanism in a shorter backset state. 
     FIG. 3 is a top view of the latch bolt mechanism in FIG.  2 . 
     FIG. 4 is a sectional view taken along line  4 — 4  in FIG.  3 . 
     FIG. 5 is a view similar to FIG. 4, illustrating unlatching operation of the latch bolt. 
     FIG. 6 is a view similar to FIG. 3, wherein the latch bolt mechanism is in a longer backset state. 
     FIG.  7 . is an exploded perspective view of a second embodiment of a latch bolt mechanism of a tubular lock in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments in accordance with the present invention will now be described with reference to the accompanying drawings. 
     Referring to FIGS. 1 and 2, a latch bolt mechanism in accordance with the present invention generally includes a latch bolt housing  1 , a plate assembly  2 , an actuating plate  3 , a follower plate  4 , and an extension casing  5 . 
     The latch bolt housing  1  is conventional and includes a latch bolt and an anti-theft pin  12 . The latch bolt is driven by the actuating plate  3  so as to be retracted into a face place  13  (FIG. 5) to thereby allow opening of the door to which the latch bolt mechanism is mounted. When the actuating plate  3  is not actuated, the latch bolt  11  is biased by an elastic element (not shown) so as to be extended beyond the face plate  13  (FIG. 3) to thereby provide required latching function. 
     The plate assembly  2  includes a first plate  2   a  and a second plate  2   b  that are connected together to form a housing or the like so as to protect the actuating plate  3  and the follower plate  4  mounted therein. The first plate  2   a  and the second plate  2   b  are connected to an inner end face of the latch bolt housing  1 . The first plate  2   a  and the second plate  2   b  include aligned first positioning holes  21   a  and  21   b,  aligned second positioning holes  22 , and openings  23  through which a spindle  62  of a lockset  6  extends. A doorknob  61  is movably connected to the spindle  62 . 
     The actuating plate  3  includes an end having a connecting member  31  (such as a hook) for retracting the latch bolt  11 . The other end of the actuating plate  3  includes an upper tooth  32   a  and a lower tooth  32   b.  When the latch bolt mechanism is adjusted to have a longer backset and when the spindle  62  of the lockset  6  turns, one of the teeth  32   a,    32   b  is pressed by a lateral side of the spindle  62  (depending upon the turning direction of the spindle  62 ) for retracting the latch bolt  11 . Each tooth  32   a,    32   b  of the actuating plate  3  further includes a block  33  formed thereon. 
     The follower plate  4  is in intimate contact with the actuating plate  3  and bears against the blocks  33 . The follower plate  4  includes two teeth  41   a  and  41   b.  When the latch bolt mechanism is adjusted to have a shorter backset and when the spindle  62  of the lockset  6  turns, one of the teeth  41   a,    41   b  is pressed by the spindle  62  (depending upon the turning direction of the spindle  62 ), which, in turn, presses against one of the teeth  32   a,    32   b  for retracting the latch bolt  11 . The follower plate  4  further includes a notch  42  through which one of two mounting posts  63  of the lockset  6  extends. The follower plate  4  further includes upper and lower blocks  43 . 
     The extension casing  5  is mounted around an inner end of the plate assembly  2  and movable longitudinally relative to the plate assembly  2 . The extension casing  5  includes upper and lower slots  51  in top and bottom sides thereof, respectively. The slots  51  receive the blocks  43  of the follower plate  4 , respectively. The slots  51  have a length longer than that of the blocks  43  to thereby allow relatively movement between the extension casing  5  and the follower plate  4 . The extension casing  5  includes a first hole  52  and a second hole  53  through which the spindle  62  of the lockset  6  is selectively extended. Further, the second hole  53  allows extension of one of the mounting post  63 . 
     Referring to FIGS. 2 through 4, when used with a shorter backset L 1 , the extension casing  5  is mounted to the inner end of the plate assembly  2  far away from the latch bolt housing  1 . One of the two mounting posts  63  of the lockset  6  is extended through the first positioning holes  21   a  of the plate assembly  2  and the other mounting post  63  is extended through the positioning holes  21   b  of the plate assembly  2  and the second hole  53  of the extension casing  5 . The spindle  62  of the lockset  6  is extended through the openings  23  of the plate assembly  2  and the first hole  52  of the extension casing  5 . Two lateral sides of the spindle  62  press against the teeth  41   a  and  41   b  of the follower plate  4 , respectively, and the follower plate  4  presses against the blocks  33  of the actuating plate  3 . 
     Referring to FIG. 5, when the spindle  62  of the lockset  6  turns, one of the teeth  41   a,    41   b  is pressed by the spindle  62 , which, in turn, presses against one of the teeth  32   a,    32   b  of the actuating plate  3  for retracting the latch bolt  11 . 
     Referring to FIG. 6, when used with a longer backset L 2 , the extension casing  5  is moved toward the latch bolt housing  1 . The follower plate  4  leaves the blocks  33  of the actuating plate  3  to a position in which the notch  42  of the follower plate  2  is aligned with the second positioning holes  22  of the plate assembly  2 , thereby allowing one of two mounting posts  63  of the lockset  6  to pass therethrough. The other mounting post  63  is located outside the plate assembly  2 . The spindle  62  of the lockset  6  is extended through the openings  23  of the plate assembly  2  and the second hole  53  of the extension casing  5 . Two lateral sides of the spindle  62  directly press against the teeth  32   a  and  32   b  of the actuating plate  3 , respectively, and the follower plate  4  is more adjacent to the latch bolt housing  1  with the notch  42  thereof extended through by one of the mounting posts  63 , as mentioned above. Thus, when the spindle  62  of the lockset  6  turns, one of the teeth  32   a,    32   b  is directly pressed by the spindle  62  for retracting the latch bolt  11 . 
     FIG. 7 illustrates a modified embodiment of the invention, the only difference between this modified embodiment and the above-mentioned embodiment is that each assembly plate  2   a,    2   b  is longer and includes a second positioning hole  22 ′ in the inner end thereof to allow passage of the other mounting post  63  of the lockset  6  when in the longer backset state. 
     According to the above description, it is appreciated that the backset of the latch bolt mechanism is adjusted easily by means of moving the extension casing  5  longitudinally relative to the plate assembly  2  toward or away from the latch bolt housing  1 . 
     Although the invention has been explained in relation to its preferred embodiment as mentioned above, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention. It is, therefore, contemplated that the appended claims will cover such modifications and variations that fall within the true scope of the invention.