Patent ID: 7564202

Claim:
An error start prevention device for door opener, in which the door opener ( 1 ) has a housing ( 10 ) with one end having a fixing base ( 20 ) and the other end receiving a power unit, a gear box ( 30 ) being located between the two ends, and the gear box ( 30 )including a gear set and a last gear ( 31 ) that the driving force of the power unit is transmitted to; wherein said error start prevention device comprises: an output shaft ( 40 ) journaled on the housing ( 10 ), on one end being extended into the gear box ( 30 ) and fixed at the center of the last gear ( 31 ), the other end being extended and mounted outside the base ( 20 ), the center of the output shaft ( 40 ) being formed as hollow to serve as an accommodation portion ( 41 ) and having as a pair of axial sliding slots ( 42 ) on the periphery along the radial direction through the accommodation portion ( 41 ); a sprocket assembly ( 50 ) rotationally invaginated outside the output shaft ( 40 ), one end having a sprocket ( 52 ) for driving the reel of the door, and the other end being integrally formed with a sleeve ( 54 ), the periphery of the sleeve ( 54 ) being formed with a pair of V-shaped slots ( 56 ) which corresponds to the sliding slot ( 42 ) on the output shaft ( 40 ), said v-shaped slots ( 56 ) each including a narrow portion ( 56 a ) and a wide portion ( 56 b ); a sliding pin ( 60 ) radially inserted, in the sliding slot ( 42 ) with both ends protruded and latched in the V-shaped slots ( 56 ) respectively; a pair of elastic elements ( 70 , 70 ′) received in the accommodation portions ( 41 ) at both ends of the output shaft ( 40 ), and the outer end of each elastic element being fixed by a bolt ( 72 , 72 ′), and the inner end of each elastic element abuts against the sliding pin ( 60 ) so as to urge the pin into the narrow portions ( 56 a ) of the V-shaped slots ( 56 ); a swaying plate ( 80 )located at the position that the sliding pin ( 60 ) can abut against it, one end ( 80 a ) being fixed on the base ( 20 ), and the other end ( 80 b ) being a free end; an obstacle sensing device ( 82 )located at the position that the free end ( 80 a ) of the swaying plate ( 80 ) can abut against it, when the rotation of the door opener ( 1 ) is stopped due to error start and the torque of the sliding pin ( 60 ) is limited, the sliding pin ( 60 ) slides back toward the direction of the gradually larger opening of wide portion ( 56 b ) of the V-shaped slot ( 56 ) to press the swaying plate ( 80 ) and to trigger the obstacle sensing device ( 82 ) to cut off the circuit, and simultaneously supply reverse current to the door opener ( 1 ) so that the door opener ( 1 ) rotates in opposite direction to cause the door plate slideing down and returning to the original position.