Door operator of fireproof door

A door operator of a fireproof door for releasing a reel of a door curtain in an event of a fire accident, said door operator comprising:

• a housing for supporting said door operator:
• an input shaft pivoted in said housing, said input shaft having one end connected to a brake mechanism, and having one other end connected to a second gear disc;
• a driving mechanism further comprising a driving force, said driving force actuating said brake mechanism to transfer the said driving force to said input shaft, wherein said driving force rotates said input shaft;
• an output shaft pivoted in said housing, said output shaft having a first end connected to an output wheel for rolling up the door curtain to an open position, and a second end;
• a central shaft pivoted in said housing, said central shaft having one end coupled to said second end of said output shaft, and having one other end connected to an end disc;
• and
• a clutch mechanism having a sliding sleeve disposed on said central shaft, said sliding sleeve being configured to move between a first position and a second position on said central shaft, one end of said sliding sleeve being provided with a first gear disc arranged to engage with said second gear disc;
• wherein said brake mechanism comprises a first bushing fitted on said input shaft and fixed to said housing at one end portion thereof, and a torsion spring fitted on the other end portion of said first bushing;
• whereby when said sliding sleeve of said clutch mechanism reaches the first position, said first gear disc attached to said sliding sleeve is moved to engage said end disc of said central shaft, said driving force actuates said brake mechanism to extend said torsion spring, said driving force transfers through said input shaft, central shaft, and output shaft to roll up the door curtain to said open position;
• when said driving force is not applied, the potential energy exists in the door curtain transfers through said output shaft, central shaft, and input shaft to contract said torsion spring to thereby locking said input shaft, and wherein when said sliding sleeve reaches the second position, the first gear disc disengages from said end disc, to thereby disconnecting said central shaft from said input shaft and releasing the reel such that the door curtain drops by gravity to close the fireproof door.