Door machine having chain disk locking mechanism

An electric door machine comprising a chain disk locking mechanism and an electric motor having a drive shaft, said chain disk locking mechanism comprising:

• a chain disk having a chain wheel, a wall disk, a holder, and a plurality of fixed pins, said wall disk having an axial hole at the center portion and being fastened on one side surface of said chain wheel, said chain wheel having a central opening for receiving said holder, said holder being fixedly connected to an outer casing to define with said wall disk a central circular bore, said plurality of fixed pins being axially positioned within said central circular bore and being fixed on said wall disk;
• an engaging rotary block, said engaging rotary block being received within said central circular bore, and having a plurality of axial slots corresponding to said plurality of fixed pins in number;
• each axial slot including a first end face and two second end faces with said two second end faces respectively disposed at both sides of said first end face, said first end face and an inner wall of said central circular bore being spaced apart by a first gap;
• said second end faces and the inner wall of said central circular bore being spaced apart by a second gap, and said first gap being narrower than said second gap;
• a stationary shaft, one end of which being coupled to said drive shaft of said electric motor, and the other end of which passing through said axial hole of said chain disk and being fixedly connected to said engaging rotary block;
• and
• a plurality of moving pins, each being received within each of said plurality of axial slots, and is positioned between one of said second end face and said inner wall of said central circular bore;
• wherein:
• a diameter of each said moving pin is bigger than said first gap but smaller than said second gap;
• the diameter of each said fixed pin being smaller than said first gap;
• when said chain disk is rotated, said fixed pins bias against said moving pins to push said engaging rotary block to rotate and to cause said stationary shaft to rotate;
• when said stationary shaft is about to rotate, said moving pins is engaged between said first end face of said engaging rotary block and said inner walls of said central circular bore, whereby said stationary shaft is prevented from rotating.