Apparatus for opening and closing a flexible screen in a greenhouse or the like

Claim 1

Apparatus for opening and closing a flexible screen of a greenhouse or the like of the type wherein an end edge of the flexible screen is fixed to a winding rod and wherein the screen is opened or closed by winding the screen onto the winding rod or unwinding the screen from the winding rod respectively, comprising: an elongated winding rod mounted for rotation about a fixed axis of rotation, said elongated winding rod having alternating large diameter and reduced diameter portions; an elongated flexible screen fixed at an end edge thereof to said winding rod and windable thereon to form a rolled screen; rolled screen supporting means for supporting the rolled screen wound on said winding rod including a casing defining an opening for receiving said rolled screen and a screen delivering slit, a plurality of rolled screen supporting rollers rotatably supported in said casing and arranged to support said rolled screen in said opening along the periphery thereof, and rollers provided in the region of said screen delivering slit for guiding said screen which passes therethrough; traction means operatively connected to the other end edge of said flexible screen for selectively pulling said flexible screen in either one of opening and closing directions, said traction means including an elongated driving shaft mounted for rotation about a fixed axis of rotation, second driving means for selectively rotating said driving shaft in either one of normal and reverse directions, elongated flexible members each of which has its two ends secured to said driving shaft with respective end portions thereof being coiled on said driving shaft opposite to each other, guide means for guiding two portions of each of said flexible members over a predetermined path of travel, and wherein each of said flexible members is operatively connected at one of said two portions thereof to said flexible screen; and first driving means for constantly applying a substantially constant restoring force to said winding rod tending to rotate the same about its fixed axis of rotation in a direction such that said flexible screen would be wound onto said winding rod, said first driving means including a casing, a constant-restoring-force spring housed in said casing, an output shaft rotatably supported in said casing, said spring being coiled thereon with an end of said spring being fixed to said output shaft, and a main shaft rotatably supported in said casing and having coiled thereon the other free end of said spring, and wherein at least one end of said winding rod is operatively connected to said output shaft.