Patent ID: 8733208

Claim:
A screw and nut assembly, comprising: a movable platform; a first screw and nut set comprising a first screw rod and a first screw nut, said first screw rod having two opposite ends thereof respectively affixed to a respective locating member, said first screw nut being pivotally mounted in said movable platform and threaded onto said first screw rod and movable along said first screw rod; a second screw and nut set comprising a second screw rod and a second screw nut, said second screw nut being pivotally mounted in said movable platform in such a manner that said second screw rod is threadable into said second screw nut and movable relative to said second screw nut; a driving mechanism adapted to drive said first screw nut and said second screw nut simultaneously for causing said first screw nut to create a first speed relative to said first screw rod and said second screw rod to create a second speed relative to said second screw nut, said first speed being greater than said second speed, the direction of said first speed being reversed to the direction of said second speed; and a first support and a second support respectively affixed to said second screw rod to support said first screw rod and to move with said second screw rod.