BACKGROUND OF THE INVENTION 
     The present invention relates to toy guns and more particularly to a toy gun for firing the paint bullets which toy gun is characterized in the rapid changing of its air pressure container and provides suitable air pressure to the gun for firing a paint bullet. 
     In a battle game, the teenagers use the toy guns to shoot each other with the paint bullets in order to obtain a great fun among them. These toy guns include pistol, rifle and/or machinegun for a single firing or continuous firing of the paint bullets by using the air pressure from a gas or pneumatic container. However, they have the common disadvantage that the air pressure is supplied by an external pneumatic source so that the teenagers have to carry a heavy gas container on their shoulders, causing a great burden and inconvenience to them. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention has a main object to provide a structurally improved toy gun for firing a paint bullet which includes a chamber in a rear side to enable the gun to carry a mini-gas can itself for providing suitable air pressure to fire a paint bullet. The mini-gas can is readily replaceable so as to provide great convenience to the user. 
     Another object of the present invention is to provide a structurally improved toy gun for firing a paint bullet which is readily to assemble or disassemble. 
     Further object of the present invention is to provide a structurally improved toy gun for firing a paint bullet in which a safety device is provided to prevent the gun from being inadvertently triggered. 
     The present invention will become more fully understood by reference to the following detailed description thereof when read in conjunction with the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view to show a preferred embodiment of a toy gun according to the present invention, 
     FIG. 2 is a side view to show an assembly of FIG. 1, 
     FIG. 3 is a transverse cross section of FIG. 2, 
     FIG. 4 is a sectional view of FIG. 2 showing that the catch plate is moving forward, 
     FIG. 5 is a sectional view of FIG. 2 showing that the catch plate is moving backward, 
     FIG. 6 is a sectional view of FIG. 2 showing that the gun is triggered, and 
     FIG. 7 is a perspective view to show an outlook of the toy gun according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 1,  2  and  3  of the drawings, the toy gun of the preferred embodiment according to the present invention comprises a casing  10  symmetrically combined with first and a second halves  20  and  30  each having a plurality of semi-circular ribs  201  formed spaced apart in a rear portion to define a tubular chamber therebetween and a narrowed, threaded outer periphery  21  and  31  on the rear end. 
     The first half  20  further has a plurality of protrudent screw holes  202 , a grooved plate  203 , an upper positioning plate  204 , a lower positioning plate  205 , a check plate  206 , an upper pivot  207 , a lower pivot  208 , a protrudent rod  209  and an access  210 . 
     The second half  30  further has a plurality of screw holes  301  made in registry with the protrudent screw holes  202  of the first half  20  for coupling the two halves  20  and  30  together with screws  302 . A safety catch  304  slidably engaged into the gap between the upper and lower positioning plates  204  and  205  of the first half  20  through a rectangular recess  303  includes a thumbplate  305  on outside of the casing  10 . 
     A cap  32  covers the rear end of the casing  10  and has a threaded inner periphery  321  engageable with the threaded outer periphery  21  and  31  of the casing  10  and a plurality of pinch plates  322  centrally projected forward from the inner wall of the end (as shown in FIG.  2 ). 
     A mini-gas can  40  is inserted into the chamber in the rear portion of the casing  10  and is stopped on rear end against the pinch plate  322  of the cap  32  and has a sealed air outlet  41  in a reduced front end. The mini-gas can  40  which is replaceable from the casing  10  and contained with the carbon dioxide gas, now is available on the market. 
     A sleeve  51  sleeves on the front end of the mini-gas can  40  and has a threaded inner periphery  511  abutting the front thereof and a reduced opening in rear end tightly engaged with the front end of the mini-gas can  40 . 
     A bushing  52  which is made of flexible plastic disposes in the rear portion of the sleeve  51  and tightly wraps on the front end of the mini-gas can  40  and has a small central bore  522  in front end communicating with the sealed air outlet  41  of the can  40 . 
     A circular stinger seat  53  disposes on the outer end of the bushing  52  and a stinger  531  pierces into the sealed air outlet  41  of the mini-gas can through the small control bore  522  of the bushing  52 . 
     A tubular shaft seat  50  is fastened to the sleeve  51  and has a threaded outer periphery  501  on rear end engageable with the threaded inner periphery  511  of the sleeve  51 , a large central bore  502  communicating with small central bore  503  so as to define a shoulder  505  therebetween and a pair of concave portions  504  symmetrically formed on opposing outer peripheries engageable with the semi-circular ribs  201  of the first half  20 . 
     A hollow shaft  56  inserts into the shaft seat  50  and is biased by a spring  54  on rear end thereof and has a shoulder  561  stopped against a front end of the spring  54 , a narrow central bore  562  to define an air inlet  5621  and an air outlet  5622  respectively at two ends, a flange  563  on front portion and pair of annular-rings spacedly formed on an outer periphery between the air outlet  5622  and the flange  563  for flexibly engaged with a bushing  57  which is also made of flexible plastic has a central bore in a front end, and a pair of sealing rings  55  spacedly secure on an outer periphery abutting the rear end thereof. 
     A barrel  60  disposes into the front portion of the casing  10  with its rear end engaged with the front end of the shaft seat  50  has a tubular loader  61  perpendicularly with the body and inserted outward through the access  210  of the first half  20  and a rectangular hole  62  in an underside. 
     A trigger  70  rotatably pivots to a pivot  208  of the first half  20  and has a retaining ring  73  on a top engageable with the pivot  208  and secured with a pin  77 , a projection  74  on the top of the retaining ring  73 , an angled portion under the retaining ring  73  stopped against a bottom of the check plate  206 , a small post  75  projected upward from a flat surface  78  on a top of the trigger  70  and a spring  76  having a lower end sleeved on the small post  75  and an upper end engaged into the grooved plat  203  of the first half  20 . 
     A rotor includes an upper portion  71  and a lower portion  72  each having a retaining ring  711  and  721  respectively and rotatably secured to the pivot  207  with a pin  701  and a roughly triangular plate  712  and  722  engageable with each other. The triangular plate  712  has retaining hole  7121  for retaining one end of a spring  702  which has on the other end retained to the protrudent rod  209  of the first half  20  and a top stopped against the flange  563  of the shaft  50  through the rectangular hole  62  of the barrel  60 . The triangular plate  722  has a lower end stops against the projection  74  of the trigger  70 . 
     When assembling, it is known to first assemble all components as described above into the first half  20  of the casing  10  except the mini-gas can  40  and the cap  32 , then combine the second half  30  with the first half  20  with screws  302  and then slidably engage the safety catch  304  into the gap between the positioning plates  204  and  205  through the rectangular recess  303 . When the safety catch  304  is slid forward (as shown in FIG.  4 ), its bottom stops against the flat surface  78  of the trigger  70  so that the trigger is locked from any movement and when it moves backward and leaves the flat surface  78 , the trigger  70  becomes operable (as shown in FIG.  5 ). FIG. 7 shows an outlook of an assembled toy gun of the preferred embodiment according to the present invention. 
     Referring to FIG. 6, when the safety catch  305  is positioned at a forward position (as shown in FIG.  4 ), insert a mini-gas can  40  into the chamber in rear end of the casing  10  and fasten the cap  32  on the rear end so that the rear end of can  40  is secured by the pinch plates  322  of the cap  32 , then load a certain number of the paint bullets  80  into the loader  61 , the bullets will enter into the barrel on one by one basis, and then slide the safety catch backward (as shown FIG.  5 ); the gun is therefore ready to fire. 
     When shooting, press the trigger  70  backward, the triangular plate  722  of the lower portion  72  of rotor is actuated by the projection  74  of the trigger  70  to operate the triangular plate  712  of the upper portion  71  of the rotor to rotate clockwise so as to push the flange  563  of the tubular shaft  56  to move rearward so that the read end of the shaft  56  pushes the stinger seat  53  via the spring  54  to move rearward, too. The stinger  531  pierces into the sealed air outlet of the mini-gas can  40  from which a suitable amount of the air pressure puffs out through the stinger seat  53  and the narrow central bore  562  of the shaft  56  to shoot a paint bullet  80  out of the barrel  60 . When the trigger  70  is released, it will be immediately returned to the original position because of the resilience of the spring  76 , and the triangular plate  712  of the rotor is also returned to its original position because of the spring  702 . If one presses the trigger  70  repeatedly, the toy gun will be operated repeatedly as described above to fire a certain number of the paint bullets  80 . Since the bullets  80  are reloaded and the mini-gas can  40  is replaceable, the toy gun of the present invention is rather more convenient than the prior art toy guns. 
     Note that the specification relating to the above embodiment should be construed as exemplary rather than as limitative of the present invention, with many variations and modifications being readily attainable by a person of average skill in the art without departing from the sprit or scope thereof as defined by the appended claims and their legal equivalents.
A toy gun for firing paint bullet includes a casing symmetrically combined with first and second halves, a chamber in a rear portion for placing a mini-gas can, a barrel having a tubular loader in a front portion, a tubular shaft seat including a hollow shaft and a stinger disposed between the mini-gas can and the barrel, a trigger operating a rotor to actuate the shaft and the stinger to pierce the front end of the mini-gas can to provide suitable air pressure to fire the paint bullet inside the barrel and a safety catch controlling the trigger from accidental operation. The mini-gas can is readily replaceable in order to provide great convenience to the user.