Automatic overload release and power stoppage device

An automatic overload release and power stoppage device installed in a power tool having a power switch, a rectifier circuit, a motor, a fan, and a speed reducing gear, comprising;

• a central control mechanism consisting of a central control rod, a first stop ring, a first metal ring, a first spring, a sliding bushing, a spring pin, a switch control lever, a second spring, and a second stop ring, wherein said central control rod has a through hole into which said spring pin is inserted to link said switch control lever for controlling said power switch;
• a power switching mechanism consisting of said sliding bushing, a ring-shaped upper driven member, a roller set, a first steel ball set, and a main shaft, wherein said sliding bushing is controlled by said central control rod to move said first steel ball set radially, causing said first steel ball set to control the engagement between said main shaft and said roller set for power transmission;
• a power output mechanism consisting of a third stop ring, a second metal ring, a second steel ball set, a fourth stop ring, a lower driven member, a lower thrust bearing, a third steel ball set, a fourth steel ball set, a third metal ring, an output shaft, and a steel ball, wherein said upper driven member, said lower driven member, and said output shaft are linked and turned by said main shaft as said central control mechanism and said power switching mechanism are started upon depression of said output shaft;
• a torque control mechanism consisting of a fifth stop ring, a sixth stop ring, a torque regulating ring, a round rod, a seventh stop ring, a torque member holder, a spring washer, a torque control spring said third stop ring, said second metal ring, said second steel ball set, said fourth stop ring said lower thrust bearing, said third steel ball set, said fourth steel ball set, and said upper and lower driven members, wherein said torque regulating ring is moved to change its position relative to said torque member holder so as to set a predetermined critical torque for permitting said upper and lower driven members to disconnect from each other as the torque from said power output mechanism surpasses said critical torque;
• and a release control mechanism consisting of a third spring, a release control ring, a fifth steel ball set, said central control rod, said first stop ring, said first metal ring, said first spring, and said sliding bushing, wherein said release control ring is pushed by said lower driven member to carry said central control rod downwards as the torque of said power output mechanism surpasses said critical torque.