Patent Publication Number: US-6338586-B1

Title: Locking structure of retractable draw bar

Description:
FIELD OF THE INVENTION 
     The present invention relates to an improved locking structure and, more particularly, to an improved locking structure installed in a retractable draw bar of a travelling case to facilitate the protraction/retraction and the positioning of the retractable draw bar. The retractable draw bar can be pulled upwards or pushed downwards to achieve smoother operation. Moreover, more convenient assembly of the retractable draw bar can be achieved. 
     BACKGROUND OF THE INVENTION 
     For a travelling case with rollers installed at the bottom thereof, there is a retractable draw bar allocated to facilitate the protraction/retraction of a draw handle so that the draw handle can be gripped conveniently when used and occupies no space when not used. Moreover, to let the retractable draw bar be positioned at a proper position when protracted, there is a locking structure installed between a first joint tube and a second joint tube to control the retractile state of each joint tube. 
     With the retractable draw bar of a commercial travelling case as an example, the locking structure has a shell body, which has a top hole and two side holes disposed at two opposite sides. A longitudinally movable control element pushed by a main resilient element is inserted in the top hole. The control element has a first bevel and a second bevel spaced vertically. A first click element and a second click element respectively pushed by the first resilient element and the second resilient element and respectively protruding transversely to the first side hole and the second side hole are installed in the shell body. The two click elements are vertically spaced and have slanting parts corresponding to the first bevel and the second bevel, respectively. When the retractable draw bar is pulled upwards or pushed downwards, the first bevel of the control element can push sideward the slanting part of the first click element or the second bevel of the control element can push sideward the slanting part of the second click element so that the first click element or the second click element will be retracted from the side hole. The retractable draw bar can thus be protracted or retracted freely. 
     However, the design of this kind of locking structure may generate the following problems in assembly and use. 
     (1). The components of the locking structure comprises at least a shell body, a control element, a main resilient element, a first click element, a first resilient element, a second click element, and a second resilient element. There are a large number of components having small volumes. The shell body is formed by joining a front shell and a back shell. Moreover, there are many separate resilient elements. Therefore, assembly of the locking structure is time-consuming and laborsome. 
     (2). Although the first click element and the second click element of the locking structure work in reverse directions to be secured and positioned timely in the upper side hole and the lower side hole when the draw bar is pulled upwards or pushed downwards, they are spaced vertically and work independently. That is, there is no interaction between them. On one hand, this results in increase and dispersion of components. On the other hand, discord may arise between them to deteriorate smooth protraction/retraction and steady positioning of the retractable draw bar. 
     (3). This kind of locking structure having two click elements is mainly used in each draw bar except the first draw bar and is pushed downwards to work. Another simplified locking structure having only a click element must be used in the first draw bar. This simplified locking structure is also pushed downwards to work. Another working way of pulling upwards via a steel cord can not be used, resulting in limited use. 
     SUMMARY AND OBJECTS OF THE PRESENT INVENTION 
     One object of the present invention is to provide an improved locking structure of a retractable draw bar, wherein the number of components thereof is reduced and there are higher compatibility and interaction between them. Easy assembly and smooth protraction/retraction and steady positioning of the retractable draw bar can thus be achieved. 
     Another object of the present invention is to provide an improved locking structure of a retractable draw bar, which not only can be widely used between any two draw bars of a retractable draw bar, but also applies to both the upward-pull type and the downward-push type retractable draw bars. 
     To achieve the above objects, a locking mechanism of the present invention comprises a fixed assembly, a movable assembly, an upper click button, a lower click button, and two resilient elements. The movable assembly is inserted in the fixed assembly and can steadily move upwards or downwards with respect to the fixed assembly. The upper click button, the first resilient element, the lower click button, and the second resilient element are axially adjacent and are installed in a transverse allocation hole of the fixed assembly so that the upper click button penetrates in the movable assembly. The upper and lower click buttons can thus work in opposite directions. A wedged guide groove and a wedged guide block both having an upper bevel and a lower bevel are installed at corresponding positions on the movable assembly and the upper click button, respectively. No matter the movable assembly is pulled upwards or pushed downwards, the upper click button can be pushed sideward and retracted transversely from the click hole. 
     The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings, in which: 
    
    
     BRIEF DESCRIPTION OF DRAWING 
     FIG. 1 is an exploded perspective view according to a first embodiment of the present invention; 
     FIG. 2 is a perspective view according to a first embodiment of the present invention; 
     FIG. 3 is an axially cross-sectional view when the first joint tube is pulled upwards with respect to the second joint tube and positioned through the fastening of the upper click button in the upper click hole according to a first embodiment of the present invention; 
     FIG. 4 is an axially cross-sectional view when the upper click button is retracted from the upper click hole so that the first joint tube can be pushed downwards with respect to the second joint tube according to a first embodiment of the present invention; 
     FIG. 5 is an axially cross-sectional view when the first joint tube is pushed downwards to the bottom with respect to the second joint tube and positioned through the fastening of the lower click button in the lower click hole according to a first embodiment of the present invention; 
     FIG. 6 is an exploded perspective view according to a second embodiment of the present invention; 
     FIG. 7 is an axially cross-sectional view when the first joint tube is pulled upwards with respect to the second joint tube and positioned through the fastening of the upper click button in the upper click hole according to a second embodiment of the present invention; 
     FIG. 8 is an axially cross-sectional view when the upper click button is retracted from the upper click hole so that the first joint tube can be pushed downwards with respect to the second joint tube according to a second embodiment of the present invention; 
     FIG. 9 is an exploded perspective view according to a third embodiment of the present invention; 
     FIG. 10 is an axially cross-sectional view when the first joint tube is pulled upwards with respect to the second joint tube and positioned through the fastening of the upper click button in the upper click hole according to a third embodiment of the present invention; 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     As shown in FIG. 1, an improved locking structure of a retractable draw bar according to a first embodiment of the present invention comprises a first joint tube  1 , a second joint tube  2 , a fixed assembly  3 , a movable assembly  4 , an upper click button  5 , and a lower click button  6 . 
     Through holes  100  and positioning holes  101  are disposed on two opposite tube walls near the bottom opening  10  of the first joint tube  1 , respectively. 
     The diameter of the second joint tube  2  is slightly larger than that of the first joint tube  1  so that the first joint tube  1  can be retractably inserted in the second joint tube  2 . Buckling holes  201  are disposed on two opposite tube walls near the top opening  20  of the second joint tube  2 . An upper click hole  200  is disposed on one tube wall near the top opening  20 . A lower click hole  220  is disposed on the opposite tube wall near the bottom opening  22 . A tube bushing  21  is sheathed in the top opening  20 . Resilient buckling button  210  are formed on two opposite sides of the tube bushing  21  to be secured in the buckling holes  201  so that the tube bushing  21  can be joined at the top opening  20 . 
     An annular groove  30  of a comparable diameter with that of the first joint tube  1  is formed at the top of the fixed assembly  3 . Projecting fasteners  300  are formed on two opposite groove walls so that the first joint tube  1  can be inserted in the annular groove  30 . The fixed assembly  3  can be joined at the bottom opening  10  of the first joint tube  1  through the fastening of the projecting fasteners  300  in the positioning holes  101 . The width of the fixed assembly  3  is comparable with the diameter of the second joint tube  2 . When the first joint tube  1  is inserted in the second joint tube  2 , the fixed assembly  3  will be situated below the tube bushing  21  so that the first joint tube  1  will be blocked by the tube bushing  21  even when pulled upwards to the highest position. Additionally, a transversely extending penetrated hole  31 , an allocation hole  33  corresponding to the upper click hole  200 , and a mobile tank  32  vertically crossing and connected to the allocation hole  33  are installed on the fixed assembly  3 . 
     A long guide hole  40  extending a proper length longitudinally is disposed in the movable assembly  4 . A wedged guide groove  41  having an upper bevel  410  and a lower bevel  411  is formed on each of the two side walls of the long guide hole  4  adjacent to the fixed assembly  3 . The movable assembly  4  is inserted in the mobile tank  32  of the fixed assembly  3 . A pin bar  102  is used to penetrate through the long guide hole  40 , the penetrated hole  31  of the fixed assembly  3 , and the through hole  100  of the first joint tube  1 . Therefore, the movable assembly  4  can be joined with the fixed assembly  3  and can steadily move upwards or downwards with respect to the fixed assembly. Moreover, the fixed assembly  3  and the movable assembly  4  are joined at the bottom opening  10  of the first joint tube  1 . 
     The upper click button  5  having a groove  52  to allocate a first resilient element  50  is allocated at one end of the allocation hole  33  of the fixed assembly  3 . The upper click button  5  can thus be pressed to protrude in the long guide hole  40  of the movable assembly  4  so as to be secured in the upper click hole  200  of the second joint tube  2  timely. A wedged guide block  51  having an upper bevel  510  and a lower bevel  511  is formed on each of the two sides of the upper click button  5  and is secured in the wedged guide groove  41  of the movable assembly  4 . 
     The lower click button  6  matched to a second resilient element  60  is allocated at the other end of the allocation hole  33  of the fixed assembly  3 . The lower click button  6  is disposed axially adjacent to the upper click button  5 . The lower click button  6  is sandwiched between the first resilient element  50  and the second resilient element  60  and works in reverse direction with respect to the upper click button  5 . The lower click button  6  can thus be secured in the lower click hole  220  of the second joint tube  2  timely. 
     When the locking structure is to be assembled, the fixed assembly  3 , the movable assembly  4 , the upper click button  5 , the first resilient element  50 , the lower click button  6 , and the second resilient element  60  can be assembled in advance to form a single entity. After the first joint tube  1  is inserted in the fixed assembly  3  and the pin bar  102  penetrates through the long guide hole  40 , the penetrated hole  31 , and the through hole  100 , the assembled single entity is installed on the first joint tube  1 , as shown in FIG.  2 . Next, the tube bushing  21  is sheathed on the first joint tube  1 . The first joint tube  1  is then inserted in the second joint tube  2 . Through the fastening of the tube bushing  21  on the top opening  20 , the first joint tube  1  and the second joint tube  2  can be easily joined. 
     Therefore, the number of components used in the improved locking structure of the present invention is less, and higher compatibility and interaction between them can be achieved. Progressive and systematic production process can thus be achieved so that manpower and time will not be wasted. Moreover, because the fixed assembly  3 , the movable assembly  4 , the upper click button  5 , the first resilient element  50 , the lower click button  6 , and the second resilient element  60  can be assembled in advance to form a single entity and then preinstalled on the first joint tube  1 , the assembled single entity, the first joint tube  1 , and the second joint tube  2  can be produced, assembled, stored, and transported separately. Easy and fast assembly of the draw bar can thus be achieved so that production efficiency can be greatly enhanced. 
     The retractable draw bar in the above embodiment comprises at least three draw bars. The first joint tube  1  and the second joint tube  2  can be any two joined draw bars except the first draw bar. For instance, the first joint tube  1  and the second joint tube  2  are the second and the third draw bars in this embodiment, respectively. 
     When a user pulls the retractable draw bar upwards, the first joint tube  1  will be pulled upwards with respect to the second joint tube  2  till the fixed assembly  3  sticks to the tube bushing  21 , as shown in FIG.  3 . At this time, the wedged guide block  51  of the upper click button  5  is locked with the wedged guide groove  41  of the movable assembly  4 . The first resilient element  50  and the second resilient element  60  will push the upper click button  5  to be secured in the upper click hole  200 . The first joint tube  1  can thus be steadily positioned with respect to the second joint tube  2 . When the retractable draw bar is pushed downwards to press the movable assembly  4 , as shown in FIG. 4, the upper bevel  410  will smoothly push sideward the upper bevel  511  of the upper click button  5 . The click button  5  will be retracted transversely, leave from the click hole  200 , and press the first resilient element  50  and the second resilient element  60  to generate higher resilient forces. The first joint tube  1  can thus be retracted freely in the second joint tube  2  till the lower click button  6  moves downwards to the lower click hole  220  and is pressed by the second resilient element  60  to be secured and positioned in the lower click hole  220 , as shown in FIG.  5 . Therefore, the protraction/retraction of the retractable draw bar is very steady and smooth. 
     As shown in FIGS. 6 to  8 , the retractable draw bar comprises at least four draw bars according to a second embodiment of the present invention. Similarly, the third draw bar is the first joint tube  1 , and the fourth draw bar is the second joint tube  2 . The locking mechanism and operation principles are the same as those in the first embodiment. 
     It is noted that the present invention also applies to the first draw bar and the second draw bar of a retractable draw bar, as shown in FIGS. 9 and 10. It is only necessary to connect a connection hole disposed on the movable assembly  4  and a working element  700  controlled by a push mechanism  70  of a draw handle  7  where the working element  700  may be formed by a soft steel cord or a hard steel rod. A soft steel cord may be used as the working element  700  to pull the movable assembly  4  upwards by a pulling force. Because there are the lower bevel  511  and the lower bevel  411  respectively installed on the wedged guide block  51  of the upper click button  5  and the wedged guide groove  41  of the movable assembly  4 , the lower bevel  411  can push sideward the lower bevel  511  to let the upper click button  5  be retracted. Alternatively, a hard steel rod can also be used as the working element  700  to pull the movable assembly  4  upwards by a pulling force. Moreover, using the upper bevel  410  to push sideward the upper bevel  510  to let the upper click button  5  be retracted, the hard steel rod can also push the movable assembly  4  downwards by a pushing force. 
     In other words, the locking structure comprising the fixed assembly  3 , the movable assembly  4 , the upper click button  5 , the first resilient element  50 , the lower click button  6 , and the second resilient element  60  not only can apply to draw bars except the first draw bar for passive operation, but also can apply to the first draw bar for active operation. Moreover, the locking structure of the present invention can apply to the upward-pull type or the downward-push type retractable draw bars. More versatile use and wider range of use can thus be achieved. 
     Although the present invention has been described with reference to the preferred embodiments thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.