Screen unit

Abstract

A screen unit includes: a first frame and a second frame which extend in parallel with each other; a first roll provided in the first frame in such a manner as to be freely rotatable and having an urging force in the winding direction of the first roll; a second roll provided in the second frame in such a manner as to be freely rotatable and having an urging force in the winding direction of the second roll; and a screen which has one end fixed to the first roll and the other end fixed to the second roll, and is wound around the first roll and the second roll by the urging forces.

What is claimed is: 
     
         1 . A screen unit comprising:
 a first frame and a second frame which extend in parallel with each other;   a first roll provided in the first frame in such a manner as to be freely rotatable and having an urging force in the winding direction of the first roll;   a second roll provided in the second frame in such a manner as to be freely rotatable and having an urging force in the winding direction of the second roll; and   a screen which has one end fixed to the first roll and the other end fixed to the second roll.   
     
     
         2 . The screen unit according to  claim 1 , wherein the urging force of the first roll is different from the urging force of the second roll. 
     
     
         3 . The screen unit according to  claim 2 , wherein the strength ratio of the urging force of the first roll to the urging force of the second roll is set at approximately 9:1. 
     
     
         4 . The screen unit according to  claim 1 , wherein the roll diameter of the first roll is different from the roll diameter of the second roll.