Abstract:
The invention is related to a shell opening and closing mechanism for utility knife. The utility knife comprises an upper shell, a lower shell and a lock button in the terminal end of the upper shell. Mainly, the upper shell and the lower shell are assembled into one unit in the middle through an axle. Thus, the two shells can open or close to each other by rotation. Further, the lock button in the terminal end of the upper shell provides closing lock. Thus, the utility knife is provided with operational safety and convenience. Moreover, the front of the shells of the utility knife bears maximum deviated cutting force and therefore safety is enhanced when the blade in cutting.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention is related to opening and closing mechanism for utility knife to replace blade, especially an easy-operation and safe opening and closing mechanism for utility knife. 
         [0003]    2. Description of the Prior Art 
         [0004]    A common utility knife comprises shells for user to grasp and exert force, a blade holder inside the shell front to hold a protruding blade that usually is trapezoidal and the cutting edge forms two sharp points to complement each other in cutting, and a storage compartment inside the shells for storing several spare blades. Therefore, the shells of a utility knife provide the basic functions in opening for replacing blade and closing for hand-grasping. Please refer to U.S. Pat. Nos. 5,121,544 and 5,864,952 and 6,317,985 for the known technologies for utility knife shells with the basic functions in opening for replacing blade and closing for hand-grasping. In the known technologies, there are an upper shell and a lower shell that can open and close to each other. Along the peripherals of the upper shell and the lower shell, there are alternating concave edge and convex edge to match to each other and provide locking in closing. In the middle of the shells, there is a lock-button to secure the locking of the upper shell and lower shell and prevent separation of the upper shell from the lower shell when the utility knife opens to replace blade. To improve the accuracy of closing, the known technologies combine the terminal ends of the upper shell and the lower shell. Nevertheless, a thorough understanding of the disclosed shells for utility knife with known technologies finds the following drawbacks: 
         [0005]    Firstly, opening the shells requires one hand to press the lock button and the other to hold the shells. Obviously, there is instability and difficulty associated with opening the shells. 
         [0006]    Secondly, the shell opening process involves the upper shell lifting up by 90 degrees or to complete separation from the lower shell, and then the closing process has the risk potential of severe falling. 
         [0007]    Thirdly, because the lock button is located in the middle of shells, it limits the quantity of stored spare blades. 
         [0008]    Fourthly, because the lock button is located in the middle of shells to provide tightening in closing and its front only provides snap-in lock through concave and convex edges, during cutting, the deviated cutting force has the risk potential of opening up the shell front. 
         [0009]    The above drawbacks with the utility knife of known technologies have been long criticized by the manufacturers and the consumers. Thus, it is necessary to have an easy-operation and safe shell opening and closing mechanism. This is the driving force for the invention. 
       SUMMARY OF THE INVENTION 
       [0010]    The main objective for the invention is to provide a shell opening and closing mechanism for utility knife. The utility knife shall have an upper shell and a lower shell, which combine in the middle to be able to open or close by rotating to each other. As a result, the lock button can be located in the end of the upper shell and provides the utility knife shells with safety and convenience in opening and closing. 
         [0011]    Another objective for the invention is to provide a shell opening and closing mechanism for utility knife, which enables shell opening and closing by rotating shells and allows the shell front to support maximum deviated cutting force by improving the adhering of the fronts of upper shell and lower shell. Therefore, the cutting safety is assured. 
         [0012]    Another objective for the invention is to provide a shell opening and closing mechanism for utility knife, which in addition to improving the adhering of the fronts of upper shell and lower shell further prevents thumb cutting injury due to slippage by a snap-in edge design on the upper shell with a force-exerting portion for the thumb to press and push. 
         [0013]    Another objective for the invention is to provide a shell opening and closing mechanism for utility knife, which allows a single hand to complete opening and closing by rotating shells. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    To further understand the features and the functions for the shell opening and closing mechanism for the utility knife in the invention, a preferred embodiment is provided with illustrative figures in the following: 
         [0015]    Please refer to  FIG. 1 . The utility knife in the invention comprises an upper shell  10 , a lower shell  20  and a lock button  30  in the end of the upper shell  10 . On the upper shell  10  the exterior forms a handle  11  and the interior forms a blade restrictive surface  12 . The outer side of the restrictive surface  12  forms a snap-in edge  13  with a groove  131 . In the middle of the shell interior there is a shaft block   14  with a through-hole  141 . In the end of the shell interior there is a snap-in hole  15  and two buckles  16  on the side. Between the two buckles  16  there is a gap  17  of suitable depth and width and shaft troughs  18  on the sidewall of the gap  17 . There forms a plate  19  in the bottom of the snap-in hole  15 . On the snap-in edge  13  there forms a force-exerting portion  132  for thumb to press and push. On the lower shell   20  there forms a handle  21  in the exterior, a blade compartment  60  in the interior and a blade holder  22  in the front. Please refer to  FIG. 8  and  FIG. 9 . On the blade holder  22  there is a lock-block  23  to secure the accommodation of trapezoidal blades  40  and a lock-strip  24  to secure the accommodation of long blades  50 . On the lock-strip  24  there is a magnet  241 , which magnetic attraction further prevents trapezoidal blades  40  from leaving the blade holder  22 . On the inner side of the blade holder  22  there forms a snap-in edge  26  with a groove  25 . On the outer side of the middle of the interior there is an axle  27  with a through-hole  28 . In the end of the interior there is a stop-block  29 . As shown in  FIG. 10 , one end of the lock button  30  forms a press-block  31 , while the other end forms a lock-block  32 . One side of the lock-block  32  appears in bevel face  33 , while on each side of the middle there is a protruding axle  34 . Under the press-block  31  there is a block  35  and an elastic piece  36  with one end curving up to form a push section  37 . Please refer to  FIG. 11  and  FIG. 12 . When the lock button  30  is placed in the gap  17  between the two buckles  16  on the inner side of the upper shell  10 , the axle  34  on each side can enter the shaft trough  18  of the buckle  16 . And the press-block  31  is in the snap-in hole  15  of the upper shell  10 . When the elastic piece  36  is locked onto the buckle  16  surface by a fixture  38 , it can restrict the axle  34  of the lock button  30  without leaving the shaft trough  18 , and the push section  37  of the elastic piece  36  can push against the block  35  under the press-block  31  to provide the press-block   31  with upward tension and allow the lock-block  32  in the end of the lock button  30  to horizontally protrude in the end of the upper shell  10 . 
         [0016]    Please refer to  FIG. 1 . When the lower shell  20  is placed into the shaft block   14  of the upper shell  10  by the axle  27  and passes through the through-hole  141 ,  28  of the upper shell  19  and the lower shell  2  by the fixture  70 , it allows combination of the upper shell  10  and the lower shell  20  into one body, i.e. the upper shell  10  and the lower shell  20  can use the axle  27  as axle to rotate for opening or closing. Please refer to  FIG. 12 . Pressing down the press-block  31  of the lock button  30  makes the lock-block  32  in the terminal end to move up into the interior of the upper shell   10 , allowing the release of the upper shell  10  and the lower shell  20 , which is to rotate and open the upper shell  10  and the lower shell  20  to replace the blades  40 ,  50  in the blade holder  22  of the lower shell  20 . Please refer to  FIG. 13  and  FIG. 14 . When the upper shell  10  and the lower shell  20  rotate to close, the lock-block  32  of the lock button  30  protruding in the terminal end of the upper shell  10  uses the bevel face  33  to push against the side of the lower shell  20  and make the lock-block  32  push upward stepwise until passing the stop-block  29  of the lower shell  20 . As soon as the upward force disappears, the elastic piece  36  uses tension to push the lock-block  32  downward to protrude in the inner side of the stop-block  29 . In this way, the upper shell  10  and the lower shell  20  close tightly. Please refer to  FIG. 15 . When the upper shell  10  and the lower shell  20  complete the closing process, the snap-in edge  13  in the front of the upper shell  10  allows one side of the lower shell  20  to enter the groove  131  and adhere to the back. At the same time, the snap-in edge  26  in the front of the lower shell  20  also allows one side of the upper shell  10  to enter the groove  25  and adhere to the back. This is actually to allow the blade holder  22  in the front of the lower shell  20  to work with the restrictive surface   12  in the front of the upper shell  10  to tightly adhere to the blades  40 ,  50  and bear maximum deviated cutting force of the blades  40 ,  50  and assure the cutting safety. 
         [0017]    From the above embodiment, it can be found that the shell opening and closing mechanism for utility knife at least possesses the following functions: 
         [0018]    Firstly, the opening and closing between the upper shell and the lower shell can be completed by a single hand and can facilitate fast blade replacement. 
         [0019]    Secondly, the upper shell and the lower shell combine in the middle through an axle and rotate to open or close, providing operational ease and safety for shell opening and closing for utility knife. 
         [0020]    Thirdly, when the upper shell and the lower shell close to each other, in the front each has the snap-in edge to adhere to each other on the back and bear the maximum deviated cutting force, providing utility knife with safety. 
         [0021]    Fourthly, because the lock button is located in the terminal end of the shells, the lower shell has more space to accommodate spare blades. 
         [0022]    Fifthly, when the upper shell and the lower shell close to each other, the snap-in edge of the upper shell provides the thumb with stable pressing and pushing through the force-exerting portion and further prevents unexpected cutting injury due to slippage. 
         [0023]    Specific Drawing: 
         [0024]    (1) The designated diagram for the present invention is  FIG. 1 . 
         [0025]    (2) The legends for the components 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
             
             
               
                 10 
                 upper shell 
                 11 
                 handle 
               
               
                 13 
                 snap-in edge 
                 132 
                 force-exerting portion 
               
               
                 15 
                 snap-in hole 
                 20 
                 lower shell 
               
               
                 22 
                 blade holder 
                 23 
                 lock-block 
               
               
                 24 
                 lock-strip 
                 241 
                 magnet 
               
               
                 26 
                 snap-in edge 
                 29 
                 stop-block 
               
               
                 31 
                 press-block 
                 40 
                 trapezoidal blade 
               
               
                 50 
                 long blade 
                 60 
                 blade compartment 
               
               
                 70 
                 fixture 
               
               
                   
               
             
          
         
       
     
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
       [0026]      FIG. 1  is an embodiment to illustrate the shell opening and closing for the utility knife in the invention. 
         [0027]      FIG. 2  is the side view for the upper shell for the utility knife in the invention. 
         [0028]      FIG. 3  is the top view for the upper shell for the utility knife in the invention. 
         [0029]      FIG. 4  is the cutaway view in A direction for  FIG. 2 . 
         [0030]      FIG. 5  is the side view for the lower shell for the utility knife in the invention. 
         [0031]      FIG. 6  is the top view for the lower shell for the utility knife in the invention. 
         [0032]      FIG. 7  is the cutaway view in A direction for  FIG. 6 . 
         [0033]      FIG. 8  is an illustration of the placement of trapezoidal blades in the front of the lower shell of the utility knife in the invention. 
         [0034]      FIG. 9  is an illustration of the placement of long blades in the front of the lower shell of the utility knife in the invention. 
         [0035]      FIG. 10  is the exterior view for the lock button in the invention. 
         [0036]      FIG. 11  is an illustration of the lock button assembled in the upper shell in the invention. 
         [0037]      FIG. 12  is an illustration of the lock button releasing and locking in the invention. 
         [0038]      FIG. 13  is an illustration of the lock button ready to be locked in the invention. 
         [0039]      FIG. 14  is an illustration of the lock button to complete locking in the invention. 
         [0040]      FIG. 15  is an illustration of the front assembly when the shells close for the utility knife in the invention.