Apparatus for driving an automatic door to reciprocate

An apparatus for driving an automatic door to reciprocate, the door having a left side and a right side, said apparatus comprising:

• an elongated stationary horizontal first mounting member adapted to be disposed over the door and having a left end with a first left cable-guiding unit, and a right end with a first right cable-guiding unit;
• a first driving unit;
• a first sliding block driven by said first driving unit to reciprocate horizontally on said first mounting member and having a left side with a first left cable-guiding unit, and a right side with a first right cable-guiding unit;
• a pair of first left and right lower guiding members disposed respectively under said left and right ends of said first mounting member and located at the same level;
• a first left cable extending around said left lower guiding member and having a first end that is fastened to one of said left end of said first mounting member and said first sliding block, a second end that is adapted to be fastened to the left side of the door, a left lower horizontal cable portion located between said second end of said first left cable and said left lower guiding member, and a first predetermined number of left upper horizontal cable portions formed between said first left cable-guiding units of said first sliding block and said first mounting member under tension one above another;
• and
• a first right cable extending around said right lower guiding member and having a first end that is fastened to one of said right end of said first mounting member and said first sliding block, a second end that is adapted to be fastened to the right side of the door, a right lower horizontal cable portion located between said second end of said first right cable and said right lower guiding member, and the first predetermined number of right upper horizontal cable portions formed between said first right cable-guiding units of said first sliding block and said first mounting member under tension one above another, said first sliding block being capable of being moved a first small distance in a predetermined direction so as to be adapted to move the door between said first left and right lower guiding members by a first large distance in the predetermined direction, wherein when the distance traveled by said first sliding block and the door are indicated by (Tb) and (Td), respectively, and the number of the first left upper horizontal cable portions is indicated by (N), the relationship between the distances traveled by said first sliding block and the door is designed by the equation:
• Td=Tb×N.