Patent ID: 8199402

Claim:
A portable screen assembly comprising: a casing; a spring-biased roll rotatably mounted to the casing; a screen bonded at one end thereof to a top bar and wound around the spring-biased roll in storage and pulled out in an upward direction from the spring-biased roll against the elastic force of a spring mounted to the spring-biased roll and gravitational force when the top bar is pulled upward in use; and an expanding and contracting means having one end rotatably mounted to an mounting member mounted to the top bar and the other end rotatably mounted to the casing, wherein: the expanding and contracting means is a half-pantograph type expanding and contracting means having a first arm, a second arm, and a third arm arranged in an extended plane parallel to the extended screen, the second arm including two or more mutually parallel sub arms provided to be mutually parallel in the extended plane, the two or more sub arms being connected to the first arm and the third arm so as to form a parallel link; one end of the second arm of the expanding and contracting means is rotatably connected to a first connecting portion in which one end of the first arm is secured, and the other end of the second arm is rotatably connected to a second connecting portion in which one end of the third arm is secured, and one end of the sub arms are rotatably connected to the first connecting portion by separate connecting axes, respectively, and the other ends of the sub arms are rotatably connected to the second connecting portion by separate connecting axes, respectively; the first connecting portion includes a pair of first sandwiching plates parallel to each other for sandwiching both side surfaces of one end of the first arm, and the second connecting portion includes a pair of second sandwiching plates parallel to each other for sandwiching both side surfaces of one end of the third arm, when in rotating the sub arms, one end of the sub arms abut onto the sandwiching plates to generate a friction force; the expanding and contracting means has a height holding means engaged with a part of the expanding and contracting means; and the height holding means is a gas spring having one end engaged with the second arm and the other end engaged with the first arm and generating upward biasing force.