Feed screw device

A nut drive mechanism having a feed screw for linearly and reciprocatively driving a nut over the length of a predetermined stroke so as to bring the nut into contact with a stopper for stopping movement thereof, said mechanism comprising:

• a shaft member rotatable in response to a driving force received from a driving unit;
• and
• deformation means for buffering the impact of the collision between the nut and the stopper when the nut is brought into contact with the stopper and for urging the nut to move in a reverse direction when the nut is at the end of the stroke, said deformation means comprising:
• a coil member disposed coaxially with and on the outer periphery of said shaft member;
• and
• fixing means for fixing an axially intermediate portion of said coil member on an intermediate portion of said shaft member such that an axial end of said coil member is elastically deformable in an axial direction of said shaft member when the nut is brought into contact with the stopper;
• wherein said nut is provided with engagement portions for engaging said coil member such that the nut moves along said shaft member in response to rotation of said shaft member.

A feed screw device for linearly and reciprocatively driving a nut over the length of a predetermined stroke so as to bring the nut into contact with a stopper for stopping the movement thereof, said feed screw device comprising:

• a shaft member that is formed with a portion for receiving a driving force from a driving unit and is rotatable in response to the driving force;
• deformation means for buffering the impact of the collision between the nut and the stopper and for urging the nut to move in a reverse direction when the nut is at the end of a stroke, said deformation means comprising:
• an elastically-deformable coil member disposed coaxially with and on the outer periphery of said shaft member;
• and
• fixing means provided between said coil member and said shaft member for fixing said coil member to said shaft such that said coil member is elastically deformable in the axial direction of the shaft member;
• whereby a rotating force is transmitted to said coil member through said fixing means when said shaft member receives the driving force thereby causing the reciprocative movement of the nut and a free end of said coil member is elastically deformed when the nut is brought into contact with the stopper thereby buffering the impact of collision between the nut and the stopper and urging the nut to move in a reverse direction.