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FIELD OF THE INVENTION  
       [0001]     The present invention relates to tubular locks and more particularly to a tubular lock having a two-stage latch bolt mechanism adapted to enter into one of two positions in which in one position a handle is an inoperable state for inhibiting a thief from opening the lock. The lock is further advanced for preventing a break or damage from occurring.  
       DESCRIPTION OF RELATED ART  
       [0002]     Conventionally, a lock (e.g., tubular lock) is designed to allow a user to lock a door only. However, means for inhibiting a thief from directly opening the lock or using a tool to open the lock is not provided by such lock. Unfortunately, our living environment is not improved much or even deteriorated for making the elimination of lock in our daily impossible. Thus, it is desirable to provide a novel tubular lock capable of inhibiting a thief from directly opening the lock or using a tool to open the lock.  
       SUMMARY OF THE INVENTION  
       [0003]     It is an object of the present invention to provide a tubular lock having a two-stage latch bolt mechanism in which a handle is adapted to rotate to activate the two-stage latch bolt mechanism when the lock has been opened by using a key. Also, the key may be adapted to push the two-stage latch bolt mechanism to entere into one of two positions for inhibiting the operation of the handle. As a result, an opening of the lock is prohibited. Further, a possible break or damage of the lock by force exerted by a thief is substantially prevented.  
         [0004]     It will be evident that the present invention has the following advantages: (1) Two space bars of the outside knob are driven through the two-stage latch bolt mechanism and the inside knob for fastening them together. Hence, the inside knob turns as the outside knob turns. An elongate, flat spindle is extended from one end of the spindle unit. Hence, insert the spindle into a cam of the two-stage latch bolt mechanism and turn the spindle to dispose vertically with the left clamping member and the right clamping member fitted in the recessed portion of the fastening sleeve from both sides. Also, indentations of the left clamping member and the right clamping member are aligned each other. Thus, a handle is adapted to rotate downwardly to open the two-stage latch bolt mechanism. (2) In a locked position of the door a turning of a key may cause the two-stage latch bolt mechanism to enter into one of two positions in which in one position the spindle is disposed horizontally, the left clamping member and the right clamping member are spaced in the recessed portion of the fastening sleeve, and the indentations of the left clamping member and the right clamping member are not aligned each other. Thus, the handle enters into an inoperable state. As a result, an opening of the lock is prohibited. Further, a possible break or damage of the lock by force exerted by a thief is substantially prevented.  
         [0005]     The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is an exploded view of the inside knob of a tubular lock according to the invention;  
         [0007]      FIG. 2  is an exploded view of the outside knob of the tubular lock;  
         [0008]      FIG. 3  is an exploded view of the two-stage latch bolt mechanism of the tubular lock;  
         [0009]      FIG. 4  is an exploded perspective view showing the tubular lock to be assembled;  
         [0010]      FIG. 5  is a cross-sectional view of the assembled inside knob;  
         [0011]      FIG. 6  is a cross-sectional view of the assembled outside knob;  
         [0012]      FIG. 7  is a front plan view of the outside knob of the opened lock, where the left clamping member and the right clamping member are aligned in the indentations by turning the spindle unit;  
         [0013]      FIG. 8  is a rear plan view of the inside knob of the opened lock, where the follower is rotating;  
         [0014]      FIG. 9  is a view similar to  FIG. 7 , where the left clamping member and the right clamping member are not aligned in the indentations by turning the spindle unit, and the handle is in an inoperable state;  
         [0015]      FIG. 10  is a view similar to  FIG. 8 , where the follower is held in place without rotation;  
         [0016]      FIG. 11  is a front plan view in part section of the outside knob of the opened lock, where a change of the handle is allowed; and  
         [0017]      FIG. 12  is a view similar to  FIG. 11 , where a change of the handle is prohibited. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     Referring to FIGS.  1  to  3 , there is shown a tubular lock constructed in accordance with the invention. The lock comprises an inside knob  1 , an outside knob  2 , and a two-stage latch bolt mechanism  3  interconnecting the inside knob  1  and the outside knob  2 .  
         [0019]     The inside knob  1  comprises a knob member  10 , a shroud  11 , a fastening sleeve  12 , a rotation cylinder  13 , an abutment member  14 , a cap  17 , a spring  18 , and a follower  19 . Each component will be described in detail below.  
         [0020]     The knob member  10  comprises a central aperture  101  at a front side, two opposite protuberances  100  in an interior wall of the central aperture  101 , a hollow shell  102  at the rear, a dent  103  on the shell  102 , and an arcuate slit  104  in the shell  102 . The shroud  11  comprises a front bell  110  fitted on the shell  102  of the knob member  10 , a recessed portion  111  at the rear with the cap  17  fitted thereon, and a central cavity  112 . The fastening sleeve  12  is put on the shell  102  of the knob member  10  and comprises an axial gap  120 , a well  122  adjacent the gap  120 , an arcuate groove  121 , a C-shaped clip  123  having two bent ends  1230  received in the arcuate groove  121 , an arcuate member  125  put on the clip  123  for anchoring in the arcuate slit  104  in the shell  102 , a central bore  126 , an arcuate trough  124  in an interior wall, and a rear ring  127  having an interior, peripheral recess  1270 . The rotation cylinder  13  comprises a front pivot  130  having an annular flange  1300 , a rear slit  131 , and a triangular well  132  on a surface. The rotation cylinder  13  is received in the central aperture  101  of the knob member  10  and is urged against the flange  130 .  
         [0021]     The abutment member  14  is a hollow, cylindrical member and comprises a rear projection  141 , four gaps  140  equally spaced around the projection  141 , two opposite protrusions  142  adjacent the projection  141 , the protrusions  142  being fitted in the ring  127  and being stopped by the peripheral recess  1270 , an arcuate groove  143 , a snapping member  145  having a central opening  1450 , a C-shaped clip  144  fastened on the snapping member  145  prior to fitting in the arcuate groove  143 , a peripheral, elongate opening  146  extended from the front end for matingly engaging with the protuberance  100  of the knob member  10 , and a slit  148  adjacent the peripheral opening  146 , the slit  148  being aligned with the triangular well  132  of the rotation cylinder  13 . The cap  17  comprises a recessed portion  170  around a central opening, two spaced bosses  172  having a hole  171 , two studs  173  each below the boss  172 , an arcuate shoulder  175  interconnecting the bosses  172 , and a space  174  further recessed within the recessed portion  170 . The spring  18  comprises two ends  180 ,  181  fastened in the space  174 . The follower  19  comprises two top legs  190  pressed on the spring  18 , a bottom protruding sector  191 , a central opening  192 , and a plurality of equally spaced arcuate channels  193  around the opening  192  for permitting the projection  141  of the abutment member  14  to insert as detailed later. Referring to  FIGS. 4, 5 , and  8  in conjunction with  FIG. 1 , an assembly of the inside knob  1  will now be described in detail below. Put the shroud  11  on the shell  102  of the knob member  10 . Next, insert the fastening sleeve  12  into the central cavity  112  of the shroud  11  with the rotation cylinder  13  fastened in the fastening sleeve  12 . Next, put the ring  127  on the abutment member  14  with the protrusions  142  being stopped by the peripheral recess  1270  of the ring  127 . Next, insert the ring  127  and the abutment member  14  into the bore  126  of the fastening sleeve  12 . Next, snap the cap  17  in the recessed portion  111  of the shroud  11 . Next, put the spring  18  on the abutment member  14  and insert the projection  141  through the channels  193  of the follower  19 . Finally, slightly bend the projected portions of the projection  141  for fastening the follower  19 .  
         [0022]     Referring to  FIG. 2  specifically, the outside knob  2  comprises a knob member  20 , a fastening sleeve  21 , a ring  22 , a spindle unit  23 , a bushing  24 , an abutment member  25 , a shroud  26 , a cap  27 , a spring  28 , and a follower  29 . Each component will be described in detail below.  
         [0023]     The knob member  20  comprises a front, hollow shell  201 , a peripheral, elongate opening  202 , a dent  203  on the shell  201 , and an arcuate slit  204  in the shell  201 . The fastening sleeve  21  is put on the shell  201  of the knob member  20  and comprises an axial gap  210 , a well  212  adjacent the gap  210 , an arcuate groove  211 , a C-shaped clip  214  having two bent ends  2140  received in the arcuate groove  211 , an arcuate member  215  put on the clip  214  for anchoring in the arcuate slit  204  on the shell  201 , a central bore  216 , a recessed portion  217  on the edge of the bore  216 , and an arcuate trough  213  in an interior wall. The spindle unit  23  comprises an elongate, flat spindle  230  inserted through the two-stage latch bolt mechanism  3  into the rear slit  131  of the rotation cylinder  13 , and a top ridge  231  for matingly engaged with a peripheral, elongate opening  259  of the abutment member  25  as detailed later. The bushing  24  comprises an annular flange  240  in the front, a ring  241 , and a central opening  242  put on the shell  201  of the knob member  20 . The ring  22  has an interior, peripheral recess  220 .  
         [0024]     The abutment member  25  is a hollow, cylindrical member and comprises a front projection  251 , four gaps  250  equally spaced around the projection  251 , two opposite protrusions  252  adjacent the projection  251 , the protrusions  252  being stopped by the peripheral recess  220  of the ring  22 , an arcuate first groove  253 , an arcuate second groove  254 , a left clamping member  255  including an indentation  2550  and a lower hole  2551 , a right clamping member  256  including an indentation  2560  and a lower hole  2561 , the left clamping member  255  and the right clamping member  256  being fitted in the second groove  254 , a C-shaped clip  257  having two ends  2570 ,  2571  fastened in the holes  2251 ,  2261  respectively, a snapping member  258  having a central opening  2581  and a C-shaped clip  2580  fastened in the first groove  253 , and a peripheral opening  259  extended from the rear end for matingly engaging with the ridge  231  of the spindle unit  23 . The shroud  26  comprises a rear bell  260  fitted on the shell  201  of the knob member  20 , a recessed portion  261  at the front with the cap  27  fitted thereon, and a central cavity  262 . The cap  27  comprises a recessed portion  270  around a central opening, two spaced bars  271  having a threaded hole  2710  for threadedly coupling to the bosses  172  of the cap  17 , a space  273  further recessed within the recessed portion  270 , and an arcuate shoulder  272  on the edge of the space  273 . The spring  28  comprises two ends  280 ,  281  fastened in the space  273  of the cap  27 . The follower  29  comprises two top legs  290  pressed on the spring  28 , a bottom protruding sector  291 , a central opening  292 , and a plurality of equally spaced arcuate channels  293  around the opening  292  for permitting the projection  251  of the abutment member  25  to insert prior to bending for fastening.  
         [0025]     Referring to  FIGS. 4 and 6  in conjunction with  FIG. 2 , an assembly of the outside knob  2  will now be described in detail below. Put the shell  201  of the knob member  20  on the fastening sleeve  21 . Next, insert the spindle unit  23  into the fastening sleeve  21 . Next, put the bushing  24  on the spindle unit  23 . Next, put the ring  22  on the abutment member  25  with the protrusions  252  being stopped by the peripheral recess  220  of the ring  22 . Next, insert the ring  22  and the abutment member  25  into the cavity  262  of the shroud  26 . Next, insert the projection  251  of the abutment member  25  into the cap  27  prior to fitting the cap  27  in the recessed portion  261  of the shroud  26 . Next, put the spring  28  on the abutment member  25  and insert the projection  251  through the channels  293  of the follower  29 . Finally, slightly bend the projected portions of the projection  251  for fastening the follower  29 .  
         [0026]     Referring to  FIG. 3  specifically, the two-stage latch bolt mechanism  3  comprises a lock housing  30 , a latch bolt  31 , a second faceplate  32 , an abutment member  33 , a left board  34 , a right board  35 , and a cam  36 . Each component will be described in detail below.  
         [0027]     The lock housing  30  comprises a first faceplate  300  having upper and lower holes  301 , and a rear opening  302 . The latch bolt  31  is partially received in the lock housing  30 . The latch bolt  31  comprises an axial, central hole  310 , a cylinder  311  received in the hole  310 , a slit  312  passed the hole  310  and being perpendicular thereto, and a lateral aperture  314  through the hole  310 . The second faceplate  32  comprises upper and lower bosses  321  having a hole  320 , the bosses  321  being adapted to matingly engage with the holes  301  for fastening the second faceplate  32  and the lock housing  30  together. The abutment member  33  has its front end fitted in the slit  312  of the lock housing  30  and comprises a front aperture  330  for permitting a pin  315  passing the lateral aperture  314  to insert through for fastening the abutment member  33 , a rearwardly projecting stud  331  adjacent the front aperture  330 , a spring  332  put on the stud  331 , a peg  333  at the right side being adapted to slide in a slit  335  of the right board  35  as detailed later, and a rear, longitudinal tunnel  334  having a half-circular recess  3340 , the tunnel  334  being adapted to permit a pin  362  of the cam  36  to fit therein for locking or unlocking the latch bolt  31  and fastening the locked latch bolt  31 .  
         [0028]     The rectangular left board  34  comprises two side hooks  340  fastened at one side of the rear opening  302  of the lock housing  30 , a rear slit  341 , two first holes  343 , a second hole  344  between the first holes  343  for permitting a peripheral member  361  of the cam  36  to fit therein, and a receptacle (not numbered) adjacent the hooks  340  for anchoring the other end of the spring  332 . The rectangular right board  35  comprises two side hooks  350  fastened at the other side of the rear opening  302  of the lock housing  30 , a stud  351  at a rear side fitted in the rear slit  341 , an opening  352  below the stud  351 , a pin  356  having a hooked head  3561 , the pin  356  being adapted to fasten in the opening  352 , two first holes  353 , a second hole  354  between the first holes  353  for permitting the peripheral member  361  of the cam  36  to fit therein, a slit  335  near a top side for permitting the peg  333  to slide therein, and a tab  357  having an indentation  3570  below the right one of the first holes  353 , the indentation  3570  being adapted to permit the hooked head  3561  to fasten therein. The cam  36  comprises a crossmember  360 , a peripheral member  361  fitted in the second holes  344 ,  354  of the left board  34 , the right board  35  so that a fastener (e.g., bolt) can be driven through the first holes  343 ,  353  for fastening the left board  34 , the right board  35  together, and a protruding actuator  363  having a pin  362  fitted in the longitudinal tunnel  334 .  
         [0029]     Referring to  FIG. 4  specifically, an assembly of the tubular lock of the invention will now be described in detail below. Insert the bars  271  of the cap  27  of the outside knob  2  through the first holes  343 ,  353  of the left board  34 , the right board  35  of the two-stage latch bolt mechanism  3 . Next, further insert the bars  271  of the cap  27  for engaging with the bosses  172  prior to fastening by bolts.  
         [0030]     Referring to  FIGS. 5, 6 ,  7 , and  8 , an operation of the tubular lock of the invention will now be described in detail below. Insert a key into a keyhole. Next, turn the key to cause the spindle  230  of the spindle unit  23  to insert into the crossmember  360  of the cam  36  of the two-stage latch bolt mechanism  3  until the spindle  230  inserts into the rear slit  131  of the rotation cylinder  13 . For opening the lock, turn the spindle  230  to dispose vertically with the left clamping member  255  and the right clamping member  256  fitted in the recessed portion  217  of the fastening sleeve  21  from both sides. Also, the indentations  2550 ,  2560  of the left clamping member  255  and the right clamping member  256  are aligned each other. At the moment, a handle  4  is adapted to rotate downwardly to open the two-stage latch bolt mechanism  3 . Also, the inside knob  1  is rotated to dispose in the space  174  of the cap  17 . The sector  191  of the follower  19  is biased to the left by the spring  18  for urging the studs  173 . As a result, the door is opened.  
         [0031]     Referring to  FIGS. 9 and 10 , in a locked position of the door a turning of the key may cause the two-stage latch bolt mechanism  3  to enter into one of two positions in which in one position the spindle  230  is disposed horizontally, the left clamping member  255  and the right clamping member  256  are spaced in the recessed portion  217  of the fastening sleeve  21 , and the indentations  2550 ,  2560  of the left clamping member  255  and the right clamping member  256  are not aligned each other. At the moment, the handle  4  enters into an inoperable state. As a result, an opening of the lock is prohibited. Further, a possible break or damage of the lock by force exerted by a thief is substantially prevented.  
         [0032]     Referring to  FIG. 11 , there is shown a front plan view in part section of the outside knob  2  of the opened lock. The snapping member  258  of the abutment member  25  in the arcuate first groove  253  contacts both the clip  214  of the fastening sleeve  21  in the arcuate trough  213  and the arcuate member  215 . At the same time, the snapping member  258  moves to the right for locking the spindle  230  at the side of the central opening  2581 . At this moment, a change of the handle  4  is allowed.  
         [0033]     Referring to  FIG. 12 , there is shown a rear plan view of the inside knob  1  of the opened lock. The snapping member  258  of the abutment member  25  in the arcuate first groove  253  contacts the clip  214  of the fastening sleeve  21  in the arcuate trough  213 . The arcuate member  215  projected into the arcuate trough  213  and the snapping member  258  do not move to the right. As such, the horizontally disposed spindle  230  is still positioned in the central opening  2581  of the snapping member  258 . At this moment, a change of the handle  4  is prohibited.  
         [0034]     While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.

Summary:
Disclosed is a tubular lock. The lock comprises an inside knob, an outside knob, and a two-stage latch bolt mechanism interconnecting the inside and outside knobs. Using a key to insert a spindle into a cam, and turning the spindle to dispose vertically with left and right clamping members fitted in a recessed portion of a fastening sleeve from both sides will align indentations of the left and right clamping members, thereby opening the lock. In the locked stated, a turning of the key causes the latch bolt mechanism to enter into one of two positions. In one position the spindle is disposed horizontally, the left and right clamping members are spaced in the recessed portion of the fastening sleeve, and the indentations of the left and right clamping members are not aligned, thereby deactivating a handle for preventing an unauthorized opening of the lock from occurring.