Patent ID: 7284407

Claim:
A reciprocating drive mechanism comprising: first and second motors serving as rotational driving sources; a first power transmission mechanism for converting a rotation of the first motor into a high-speed low-torque first rotational output and transmitting the first rotational output; a second power transmission mechanism for converting a rotation of the second motor into a low-speed high-torque second rotational output and transmitting the second rotational output; a conversion mechanism connected to the first and second motors respectively through the first and second power transmission mechanisms, the conversion mechanism converting the first and second rotational outputs into linear motions, the conversion mechanism including a nut member and a feed screw, one of which is screw-fed by the other, the nut member being rotatably supportable by a fixed frame; a drive target movable up and down by the linear motions from the conversion mechanism; and a co-rotation prevention mechanism having a first connecting part being defined on an end of the feed screw and a second connecting part being defined on the drive target, the first connecting part having a first friction surface, the second connecting part having a second friction surface, wherein: the feed screw and the nut member are coupled with the first power transmission mechanism and the second power transmission mechanism, respectively; the feed screw is supported in a screw hole of the nut member so as to be capable of screw-fed rotation; when the reciprocating drive mechanism is placed in an approach mode or in a return mode, a gap is formed between the first and second friction surfaces; and when the reciprocating drive mechanism is placed in a bending mode, the second friction surface is moved into contact with the first friction surface to eliminate the gap, so that a frictional braking force formed between the first and second friction surfaces prevents the feed screw from rotating.