You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION  
       [0001]     The invention relates to a status indicator for a lock adopted for use on padlocks, locking devices or structural objects and particularly to a lock that has two locking units that function independently to execute locking and unlocking operations.  
       BACKGROUND OF THE INVENTION  
       [0002]     A lock is a widely used to guard articles that have obvious or potential security concern and to protect the articles. For instance, a padlock may be used to lock the zipper of luggage to prevent unauthorized opening.  
         [0003]     Due to security concerns, nowadays airports have very strict standards for luggage inspection. To luggage having security concern, mandatory inspection of unfolding luggage could take place. For luggage that has been locked, the lock has to be broken. After inspection, the lock is damaged and not usable again. As a result, the damaged lock can no longer provide protection after the inspection has finished.  
         [0004]     To remedy the problem of lock damage during security inspection, a lock equipped with two locking units has been developed. For instance, Travel Sentry™ Co. of U.S.A. introduces a number of locks for this purpose. They mainly have one set of locks to allow users to lock and unlock during use, and another set of locks for use during inspection. Hence the inspection people can perform routine security inspection through a normal unlocking procedure to open the lock, and close the lock after the inspection is finished. Therefore the lock may be prevented from damaging, and the luggage can have proper protection after inspection.  
         [0005]     However, the locks mentioned above still have a drawback, namely after the security inspection of the luggage has finished and the lock is closed again, there is no indication to show that lock has been unlocked.  
       SUMMARY OF THE INVENTION  
       [0006]     In view of the aforesaid problem, the primary object of the present invention is to provide a lock that has two locking units functioning independently so that users can recognize which locking unit has been unlocked.  
         [0007]     In order to achieve the foregoing object, the invention provides a status indicator for a lock with two locking units that has a window on the surface of a lock body and an indicator in the lock that has different indication positions switchable to the window once a locking unit has been unlocked, so that users can see the indicator through the window to identify the locking unit that has been unlocked.  
         [0008]     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  
       [0009]      FIG. 1  is a perspective view of the invention;  
         [0010]      FIG. 2  is a plane view of the invention;  
         [0011]      FIG. 3  is a fragmentary schematic view of an embodiment of the invention;  
         [0012]      FIGS. 4 and 5  are schematic views of the invention in operating conditions;  
         [0013]      FIG. 6  is a fragmentary perspective view of the invention;  
         [0014]      FIGS. 7A and 7B  are schematic views of the invention in operating conditions;  
         [0015]      FIGS. 8A and 8B  are fragmentary schematic views of embodiment variations and operating conditions of the invention;  
         [0016]      FIG. 9  is an exploded view of another embodiment of the invention;  
         [0017]      FIGS. 10A and 10B  are schematic views of another embodiment of the invention in operating conditions;  
         [0018]      FIGS. 11A and 11B  are schematic views of another embodiment of the invention in operating conditions; and  
         [0019]      FIG. 12  is a fragmentary schematic view of an embodiment variation of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     Referring to  FIG. 1 , the lock  1  according to the invention includes a body  10  and a shackle  20  for coupling a targeted object. The body  10  has a window  100  on the surface to indicate conditions.  
         [0021]     Referring to  FIG. 2 , the body  10  contains two locking units  13  and  14 , an indicator  11  and a brake bolt  12 . The two locking units are named a first locking unit  13  and a second locking unit  14  hereinafter to facilitate discussion.  
         [0022]     The indicator  11  has one or more identified notations  111  and  112  that may be, but is not limited to, graphics, characters, color patches and combinations thereof that are distinguishable and may be differentiated visually. The identified notations may be formed on the indicator  11  by, but is not limited to, printing, carving, painting, sticking paper, and the like. In addition, the indicator  11  is coupled with a returning elastic element  113  (such as a compression spring) which has one end pressing the body  10 , to allow the indicator  11  at a first indication position as shown in the drawing in normal condition.  
         [0023]     The brake bolt  12  aims to generate a latch function. It is coupled with a ramming elastic element  121  which has one end pressing the body  10  to push the brake bolt  12  in contact with the indicator  11  in normal condition and latche the indicator  11 .  
         [0024]     As shown in the drawings, the brake bolt  12  has a one-way retaining section  122 . The indicator  11  has a means mating the one-way retaining section  122 , such as an extending sloped member  114 , or a notch  115  shown in  FIG. 3 . Therefore, the one-way retaining section  122  can latch the sloped member  114  or notch  115  to anchor the indicator  11  on the first indication position.  
         [0025]     The first locking unit  13  is movable under operation. It has a locking position (referring to  FIG. 2 ) relative to the body  10  and an unlocking position (referring to  FIG. 4 ). The first locking unit  13  includes a cylinder  131 , which has a concave head  133  extended from a shaft  132 . Referring to  FIG. 4 , the locking state between the body  10  and the cylinder  131  may be released by inserting a key K into a key way of the cylinder  131 , so that the cylinder  131  may be sunk axially, to disengage the turning restriction formed between the concave head  133  and the shackle  20 . The shackle  20  may be turned outwards relative to the body  10  about another leg. In addition, while the cylinder  131  is moved, the concave head  133  is driven simultaneously to move the indicator  11  from the first indication position to a second indication position shown in the drawings. The brake bolt  12  retracts and returns again to form a latch condition with the indicator  11  to keep the indicator  11  at the anchor position. When the cylinder  131  is returned to the locking state through operation of the key K, the indicator  11  remains at the second indication position. Therefore, with the indicator  11  driven one-way by the first locking unit  13 . Changing of the second identified notation  112  from the first identified notation  111  corresponding to the window  100  may recognize its position.  
         [0026]     The second locking unit  14  may also be switched between an unlocking state and a locking state through operation. In this embodiment, the second locking unit  14  includes, but is not limited to, a combination lock, which has a dial wheel  141 . The second locking unit  14  also can lock one leg of the shackle  20 . The shackle  20  is inhibited from axial movement when the second locking unit  14  is in the locking state, and the shackle  20  has another leg extended in the concave head  133 .  
         [0027]     When the second locking unit  14  is switched to the unlocking state through operation, the shackle  20  is in the condition shown in  FIG. 5 , and moved axially relative to body  10  for a selected distance. During the axial movement, or by adding an extra operation, the brake bolt  12  is driven to release the latch condition on the indicator  11  so that the indicator  11  returns from the second indication position to the first indication position, and the notation corresponding to the window  100  is changed from the second identified notation  112  to the first identified notation  111 .  
         [0028]     Refer to  FIG. 6  for the brake bolt  12  releasing the latch condition on the indicator  11  after the shackle  20  has driven the brake bolt  12 . The shackle  20  has a lug  21 . When the second locking unit  14  has released the locking state on the shackle  20 , the shackle  20  may be moved axially to release the turning restriction on the concave head  133 . Referring to  FIGS. 7 and 8 , then the shackle  20  may be turned and the lug  21  pushes a bucking portion  123  on the brake bolt  12  to move the brake bolt  12  in a direction, to release the latch condition on the indicator  11 .  
         [0029]     Referring to  FIGS. 8A and 8B , the lug  21  mates the bucking portion  123  in shape and position. While the shackle  20  is moved axially, the lug  21  pushes the bucking portion  123  on a sloped surface to release the latching of the brake bolt  12 .  
         [0030]     As previously discussed, while the indicator  11  has been moved to the second indication position through the latching of the brake bolt  12 , the indicator  11  can return to the first indication position again only through the unlocking operation of the second locking unit  14 . Hence by seeing different identified notations  111  and  112  through the window  100 , a use condition of the lock may be recognized.  
         [0031]     Refer to  FIGS. 9, 10A  and  10 B for another embodiment of the invention. It differs from the previous embodiment, in which the indicator  11   a  is moved by turning to switch the first indication position and the second indication position.  
         [0032]     The concave head  133   a  of the first locking unit  13   a  has a notch  134   a , which enables the key K to drive the concave head  133   a  by turning the cylinder  131   a  so that the notch  134   a  may be switched to turn the shackle  20   a  at an unlocked position. Namely, the first locking unit  13   a  is moved to an unlocked position (referring to  FIG. 1A ) and locked position (referring to  FIG. 19B ) by turning.  
         [0033]     As shown in the drawings, the indicator  11   a  has identified notations  111   a  and  112   a , and a dial hole  113   a  in the axial direction, to enable the indicator  11   a  to run through the dial hole  113   a  and couple on the shaft  132   a . Moreover, the indicator  11   a  is coupled with a returning elastic element  114   a , which may be, but is not limited to, a torsion spring. In addition, the indicator  11   a  has a first latch notch  115   a  and a second latch notch  116   a  on the periphery, to engage with the brake bolt  12   a  when the indicator  11   a  is moved to the first indication position and the second indication position, to maintain the indicator  11   a  in a stationary condition.  
         [0034]     By means of the construction set forth above, when the first locking unit  13   a  is turned from a locked position shown in  FIG. 11A  to an unlocked position shown in  FIG. 11B , the indicator  11   a  also is pushed by a picking bar  1321   a , extended radially from the shaft  132   a  and moved from the first indication position to the second indication position. When the first locking unit  13   a  returns to the first indication position through operation, the indicator  11   a  still remains at the second indication position. The brake bolt  12   a  can only release the latch condition on the indicator  11   a  through the unlocking operation of the second locking unit  14 . Likewise, the indicator  11   a  returns to the first indication position.  
         [0035]     Refer to  FIG. 12  for another latch operation of the brake bolt  12 . Instead of driving the indicator  11  by the shackle  20  to release the latch condition, the brake bolt  12  is coupled with a brake knob  30  which may receive a force to drive the brake bolt  12  and release the latch condition on the indicator  11  and allow the indicator  11  to return to the first indication position.  
         [0036]     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 intended to cover all embodiments, which do not depart from the spirit and scope of the invention.

Summary:
A status indicator for a lock includes two locking units that operate independently, to execute locking and unlocking operations. The lock has a body, which contains an indicator and a brake bolt. The indicator is latched by the brake bolt to remain at a selected indication position. When one locking unit executes the unlocking operation, the indicator is driven concurrently to switch to another indication position corresponding to a window, and is latched by the brake bolt without returning. The brake bolt can only release the latch condition on the indicator through the unlocking operation of another locking unit. Likewise, the indicator returns to the original indication position. Thus through the window formed on the body surface, the indication position of the indicator may be recognized.