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FIELD OF THE INVENTION  
       [0001]     The invention relates to a double locking device that uses a key or numeric combination mechanical device to lock or unlock two members such as a pair of zipper sliders so that they may be latched together or separated to close or open the zipper.  
       BACKGROUND OF THE INVENTION  
       [0002]     Zipper locks are well known in the art. Reference can be found in U.S. Pat. Nos. 4,221,027, 4,262,502, 4,271,689, 4,578,966, 4,930,323, 4,951,485, 5,063,760, 5,103,657, 6,062,051, etc. These zipper locks are widely used in products of trunks and bags such as hang bags, luggage, or carrying cases. When two sliders are moved close to each other, they may be locked by the zipper lock to prevent from separating so that the luggage or cases cannot be opened without proper authorization.  
         [0003]     There are many types of zipper locks available on the market. Some are individual zipper locks in which two sliders are moved close to each other and the pull tabs are coupled on the zipper lock for fastening. Such a zipper lock is an independent item. When it is removed from the sliders, it is often disposed separately and prone to being lost. Hence it is not a desirable design.  
         [0004]     There is another type of zipper lock in which the lock structure is directly built in a slider. When two sliders are moved close to each other, the slider equipped with the lock structure can latch on the other slider to create coupling without separation. While it is easier to use, the slider has size limitations, and thus cannot accommodate a more complicated lock structure. It usually adopts a simpler key lock or combination lock. For instance, U.S. Pat. No. 4,578,966 discloses such a slide fastener that employs a key lock, and U.S. Pat. No. 4,951,485 discloses a dial lock for slide fasteners. Consumers can select different types of zipper locks according to their requirements. For the slider equipped with a key lock, users still have to carry a key, which is not convenient. Hence in the market, the slider with a built-in combination lock is more popular.  
         [0005]     Take U.S. Pat. No. 4,951,485 as an example. It has a dial ring on the slider. One of the marked numbers on the dial ring is set as the unlocking number. The number of attempt to unlock is X 1  (where X is the number set on the dial ring). For instance, with ten marks 0-9 on the dial ring, 10 1  is 10 times. That is, the dial lock may be unlocked by turning a maximum of ten times. This is not effective to meet the design purpose. Moreover, there are often two movable sliders on the luggage zipper, with only one slider equipped with the lock structure, and only one latch hook is provided to latch another slider. Hence the two sliders form only one kind of latching relationship. They are easily unfastened by incidental impact during transportation of the luggage. They are easily broken and separated by malicious hitting.  
         [0006]     In addition, from the prospective of zipper producers, the slider equipped with a lock structure is different from those that are not. Different specifications of elements have to be prepared for fabrication, and different production processes have to be set up. All this complicates the design and production.  
       SUMMARY OF THE INVENTION  
       [0007]     In view of the aforesaid disadvantages of the conventional zipper designs that have a dial lock built into one slider, the invention provides a modular slider design that has two corresponding sliders forming a double locking device that makes unauthorized unlocking more difficult and enhances the latching relationship of the two sliders.  
         [0008]     The double locking device according to the invention includes two identical sliders that are movable relative to one another on two sides of a zipper, and may be close to each other or separated to open or close the zipper. One of the sliders may be stationary, and the other slider movable to close or open the zipper. The slider includes a sliding dock and a latch lock. The sliding dock is movable on the zipper. The latch lock is located in the sliding dock. The latch lock has a movable hook and a lock assembly. The lock assembly may be controlled and switched to an unlocking condition or a locking condition. When the two sliders are close to each other, the movable hook of one slider can latch the latch lock of the other slider. When the lock assembly is in the unlocking condition, the movable hook may be moved to a separation position to release the latching relationship of the two movable hooks and the two sliders may be separated. When the lock assembly is in locking condition, the two movable hooks cannot be moved and maintain the latching relationship, and the two sliders cannot be separated.  
         [0009]     The double locking device according to the invention has two corresponding sliders of the same structure and two lock assemblies. Taking the dial lock as an example, the two lock assemblies provide an unlocking probability that is twice the involution of the number being set. Thus it significantly increases the difficulty of unauthorized unlocking. Moreover, the two sliders can latch with each other and improve the coupling relationship to withstand greater impact force, and are therefore more suitable for travelling luggage.  
         [0010]     The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIGS. 1A and 1B  are perspective views of a first embodiment of the invention.  
         [0012]      FIGS. 2A and 2B  are exploded views of the first embodiment of the invention, including details of the sliders.  
         [0013]      FIGS. 3A, 3B  and  3 C are schematic views of the first embodiment of the invention in operating conditions, with two sliders coupled and separated.  
         [0014]      FIGS. 4A, 4B  and  4 C are schematic views of a second embodiment of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     The double locking device according to the invention is adopted for products that have zippers such as trunks and bags that include hang bags, luggage, or carrying cases, and particularly to luggage or travelling cases that require zippers equipped with latch locks to prevent unauthorized opening.  
       First Embodiment  
       [0016]     Referring to  FIGS. 1A and 1B , the double locking device according to the invention includes two sliders  10   a  and  10   b  that have the same structure. The two sliders  10   a  and  10   b  are movable on two sides of a zipper (shown by broken lines in the drawings) and correspond to each other. The two sliders  10   a  and  10   b  may be moved close to each other or separated to close or open the zipper. As the two sliders  10   a  and  10   b  are identically constructed, only the details of the slide  10   a  will be discussed as follows, and will be marked by “ 10 ” for identification.  
         [0017]     Referring to  FIGS. 2A and 2B , the slider  10  includes a sliding dock  11  and a latch lock  12 . The sliding dock  11  has a cross section in an I-shape to form two sliding channels  111  and  112  to couple with two sides of the zipper so that when the sliding dock  11  is moved on the two sides of the zipper, the zipper may be closed or opened.  
         [0018]     The latch lock  12  is located on the sliding dock  11  and is movable with the sliding dock  11  on the two sides of the zipper. The latch lock  12  includes a shell  13 , a lock assembly  14  and a movable hook  15 . The shell  13  includes a base plate  16  and a cap  17 . The base plate  16  has one rectangular end and one semi-circular end. The semi-circular end of the base plate  16  has an anchor hole  161 , while the other end has two anchor holes  162  and  163 . The cap  17  is formed to mate with the base plate  16 . The rectangular end of the cap  17  has two walls  171  and  172  extending vertically from two sides to connect to the base plate  16  and form a housing space between the cap  17  and the base plate  16 . The semi-circular end is not sealed. The semi-circular end of the cap  17  has an axle  173  on the same side of the walls  171  and  172 . The axle  173  is surrounded by a plurality of sensing stubs  174 . The top end of the axle  173  has a pin  1731  corresponding to the anchor hole  161 . The rectangular end abutting the wall  171  has a vertical wall  175  with a width one half of the rectangular end so that when the cap  17  and the base plate  16  are coupled, the edge of the rectangular end forms an opening  131 . The wall  175  is extended to form a hook  132 . The wall  175  has another side corresponding to the hook  132  and forming a bucking surface  1751 .  
         [0019]     The center of the rectangular end of the cap  17  has a coupling strut  176 . The walls  171  and  172  have pins  1711  and  1721  corresponding to the anchor holes  162  and  163 . Moreover, the wall  172  has a round hole  1722 . The semi-circular end of the cap  17  has an indented viewing window  177  adjacent to the peripheral end. The cap  17  further has a coupling ring  178  located on another side corresponding to the walls  171  and  172 . The coupling ring  178  is coupled with a pull tab (not shown in the drawing) to be grasped by users for moving the slider  10 .  
         [0020]     The lock assembly  14  includes a dial ring  141 , a locking wheel  142 , a latch  143  and an alteration pin  144 . The dial ring  141  has a diameter substantially the same as the semi-circular end of the cap  17 , has teeth formed on the perimeter to facilitate turning for users, and has an aperture  1411  in the center to couple with the axle  173  to facilitate turning by users. One side of the dial ring  141  has ten numeric marks  1412  formed in an annular manner ranging from 0 to 9. The dial ring  141  further has sensing cavities  1413  abutting the center corresponding to the numeric marks  1412 . The dial ring  141  is coupled to the axle  173  on the side where the numeric marks  1412  located, with the sensing cavities  1413  coupling with the sensing stubs  174  on the periphery of the axle  173 . When the dial ring  141  is turned, the sensing cavities  1413  can detect the sensing stubs  174  to confirm the location of the corresponding numeric marks  1412  of the dial ring  141 . The dial ring  141  has another side which is opposite the numeric marks  1413  and that has a plurality of anchor bosses  1414 .  
         [0021]     The locking wheel  142  has a diameter smaller than the dial ring  141 , and has a hole  1421  in the center to couple on the axle  173  so that the locking wheel  142  is in contact with the dial ring  141 . The hole  1421  has an inner rim  1424 . The locking wheel  142  has anchor cavities  1422  on one side corresponding to the anchor bosses  1414  of the dial ring  141  that oppose the numeric marks  1412 . The locking wheel  142  further has a recess  1423  on another side opposing the anchor cavities  1422 .  
         [0022]     The latch  143  is movable in the cap  17  corresponding to where the locking wheel  142  is located. The latch  143  has a head end  1431 , which is formed substantially mating with the recess  1423 . When the locking wheel  142  is turned with the dial ring  141  and the recess  1423  corresponds to the head end  1431  of the latch  143 , the latch  143  moves towards the recess  1423  with the head end  1431  entering the recess  1423 . The latch  143  has a coupling hole  1432 , a first retaining member  1433  and a second retaining member  1434 . The first retaining member  1433  is located on another side of the latch  143  at one end opposing the head end  1431  and corresponding to the wall  175  of the cap  17 . The second retaining member  1434  is located on another side of the coupling hole  1432 .  
         [0023]     The alteration pin  144  consists of a shaft  1441  and a retaining strut  1442 . The shaft  1441  is housed in the round hole  1722  of the wall  172  and is turnable therein. The shaft  1441  has one end forming a latch notch  1443  to enable users to turn the alteration pin  144  with a hand tool. The alteration pin  144  has at least a first position where the retaining strut  1442  is in contact with the second retaining member  1434  of the latch  143 , and a second position where the retaining strut  1442  is not in contact with the second retaining member  1434  of the latch  143 .  
         [0024]     To assemble the lock assembly  14 , couple the dial ring  141  on the axle  173 , with the numeric marks  1412  corresponding to the cap  17 , and the sensing cavities  1413  of the dial ring  141  coupling with the sensing stubs  174  of the axle  173 . Then couple the locking wheel  142  on the axle  173 , with the anchor cavities  1422  coupling on the anchor bosses  1414  of the dial ring  141 . Dispose a spring  20  to press the inner rim  1424  of the locking wheel  142  so that the dial ring  141  and the locking wheel  142  are in contact with each other and are in contact with the cap  17 . Turn the dial ring  141  to drive the locking wheel  142  to rotate. There is a spring  30  between the first retaining member  1433  of the latch  143  and the bucking surface  1751  on the wall  175 . The elastic force of the spring  30  enables the latch  143  to press the locking wheel  142 . When the recess  1423  of the locking wheel  142  faces the latch  143 , the head end  1431  of the latch  143  enters the recess  1423  to form an “unlocking condition” of the lock assembly  14  (as shown in  FIG. 3C ). As the numeric marks  1412  of the dial ring  141  are masked by the cap  17 , only one of the numeric marks  1412  is shown in the viewing window  177  of the cap  17 . The exposed numeric mark is the unlocking number. When the head end  1431  of the latch  143  leaves the recess  1423  and presses the perimeter of the locking wheel  142 , the lock assembly  14  is in a “locking condition” (as shown in  FIG. 3B ).  
         [0025]     After the lock assembly  14  has been assembled, the alteration pin  144  is located on the second position. The number corresponding to the unlocking condition for the lock assembly  14  is set. However, users still can change the unlocking number through the alteration pin  144 . If the user wants to change the unlocking number, first, the lock assembly  14  has to be in the unlocking condition, i.e. the head end  1431  of the latch  143  enters the recess  1423  of the locking wheel  142 , then the alteration pin  144  is turned to the first position to press the retaining strut  1442  of the alteration pin  144  on the second retaining member  1434  of the latch  143  so that the head end  1431  of the latch  143  cannot escape the recess  1423 . The dial ring  141  may be turned to extend the head end  1431  of the latch  143  into the recess  1423  of the locking wheel  142 , the locking wheel  142  cannot be turned with the dial ring  141 , and the anchor bosses  1414  of the dial ring  141  passes over the anchor cavities  1422  of the locking wheel  142 . When the dial ring  141  is turned and another one of the numeric marks  1412  is shown in the viewing window  177  of the cap  17 , the anchor bosses  1414  of the dial ring  141  are coupled with the anchor cavities  1422  of the locking wheel  142  again, and the alteration pin  144  may be moved to the second position. The number exposed in the viewing window  177  is the new unlocking number. Hence changing the number is accomplished by forced separation of the dial ring  141  and the locking wheel  142  to alter the relative anchor position of the two.  
         [0026]     The movable hook  15  includes a sleeve  151 , latch hooks  152  on two sides of the sleeve  151  and a connection strut  153 . The sleeve  151  may be coupled on the coupling strut  176  of the cap  17  to enable the movable hook  15  to be coupled on the cap  17  in a turnable manner. The connection strut  153  of the movable hook  15  is inserted into the coupling hole  1432  of the latch  143 . The coupling hole  1432  is substantially a rectangular slot. When the latch  143  is moved, the coupling hole  1432  pushes the connection strut  153  so that the movable hook  15  may be turned about the sleeve  151  and the latch  143  can drive the movable hook  15  to turn, so that the latch hooks  152  of the movable hook  15  have a “separation position” corresponding to the unlocking condition of the lock assembly  14 , and a “latch position” corresponding to the locking condition of the lock assembly  14 .  
         [0027]     After the lock assembly  14  and the movable hook  15  have been assembled on the cap  17 , couple the base plate  16  and the cap  17 . The anchor holes  161 ,  162  and  163  are coupled with the pins  1711 ,  1721  and  1731  to complete the assembly of the latch lock  12 .  
         [0028]     Referring to  FIGS. 3A, 3B  and  3 C, the two sliders  10  are located on two opposite sides of the zipper (not shown in the drawings), and are identical. When the lock assemblies  14  of the two sliders  10  are in the unlocking condition, the movable hooks  15  are at the separated positions. When the two sliders  10  are moved close to each other, the hook  132  of the sliders  10  goes into the latch lock  12  through the opening  131 . When turning the dial ring  141 , the lock assembly  14  is changed to the locking condition, and the movable hooks  15  are moved to the latch position. Thus the movable hooks  15  and the hooks  132  of the two sliders  10  are latched to each other to couple the two sliders  10  securely. By means of the double locking device of the invention, the two sliders  10  each have a lock assembly  14 , the number of attempts to unlock is X 2  (where X is the number set on the dial ring). For instance, if the numeric marks  1412  on the dial ring  141  are set 0-9, then 10 2  is 100. That is, the probability of unauthorized attempt for unlocking decreases (with different unlocking numbers set for the two lock assemblies  14 ). Moreover, the movable hook  15  and the hook  132  may be latched with each other to enable the two sliders  10  to form a firmer coupling to withstand greater external impact.  
         [0029]     In the locking condition, the two sliders  10  cannot be separated. When separating the two sliders  10 , the dial rings  141  of the two lock assemblies  14  must be turned to the unlocking numbers first to move the movable hooks  15  to the separation position. Then the two sliders  10  may be separated.  
         [0030]     In addition, in this embodiment one of the sliders  10  may be stationary. Closing or separating movement is accomplished by another slider  10 .  
       Second Embodiment  
       [0031]     In the first embodiment set forth above, the lock assembly  14  has one dial ring  141 , and two lock assemblies  14  provide X 2  times of unlocking combinations (where X is the number set on the dial ring). According to the double locking device of the invention, the number of the dial ring  141  in the lock assembly  14  may be increased to increase unlocking combinations and reduce the probability of unauthorized unlocking.  
         [0032]     Referring to  FIGS. 4A, 4B  and  4 C, the latch lock  12  in the cap  17  has two juxtaposed dial rings  141  and locking wheels  142  (the operation principle is the same as the first embodiment, thus details are omitted; only the differences are elaborated herein). The latch  143  has two head ends  1431   a  and  1431   b  corresponding to the two locking wheels  142 . A torsional spring  40  is disposed between the latch  143  and the cap  17  to provide a force to move the latch  143  towards the locking wheels  142 . The movable hook  15  is located in the cap  17  and may be moved transversely. There is a bucking member  1435  located between the latch  143  and the movable hook  15 . Another spring  50  is provided to push the movable hook  15  to the latch position (in normal conditions). In the unlocking condition, the bucking member  1435  is separated from the movable hook  15 , so that the movable hook  15  may be moved by force to resist the spring  50  to the separation position. In the locking condition, the bucking member  1435  presses the movable hook  15  so that the movable hook  15  cannot be moved from the latch position to the separation position.  
         [0033]     By providing two sets of unlocking number in one slider  10 , the two sliders  10  provide four sets of unlocking numbers. The unlocking combination is X 4  times. Thus it can reduce the probability of unauthorized unlocking.  
         [0034]     According to the double locking device of the invention, the unlocking or locking number of the slider  10  may be set freely as desired. For instance, in the embodiments set forth above, there are one to one and two to two unlocking combinations. It can also be arranged to have one dial ring  141  on one slider  10 , and two dial rings  141  on another slider  10  to provide a one to two unlocking combination. Of course, it is also allowable to provide a one to three or two to three combination, or the like. In addition, the numeric marks  1412  on the dial ring  141  may have two or more unlocking numbers so that the unlocking combination and unlocking number combination may be altered as desired to form multiple types of double locking devices.  
         [0035]     While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are tended to cover all embodiments which do not depart from the spirit and scope of the invention.

Summary:
A double locking device includes two identical sliders movable close to or separate from one another. The slider has a sliding dock and a latch lock located on the sliding dock. The sliding docks of the two sliders may be moved close to each other and the latch locks may be latched securely through movable hooks. The latch lock is controllable for switching to an unlocking condition or a locking condition. In the unlocking condition, the movable hooks may be moved to a separation position so that the movable hooks release the latching relationship. In the locking condition the two movable hooks cannot be moved in order to maintain the latching relationship and prevent the two sliders from being separated.