System for rolling and unrolling a ground cover

A system for tightly rolling up a web covering a surface with one end of the web anchored to said surface, comprising a core about which the web is rolled,

• means for rolling up the web into a roll about said core from the other end thereof in the direction of said one end, and
• means for tightening the roll turns about one another during roll-up,
• said tightening means comprising a closed-ended tube of flexible and unstretchable material partially filled with a fluid,
• said tube having a length substantially equal to the width of said web,
• said tube underlying the roll for supporting the same above the web which covers the surface, and
• said tube being in an intitial position beneath the roll such that the central axis of the tube is spaced in said direction from the central axis of the roll, and
• said tube being in a normal position beneath the roll such that said central axes lie in a plane perpendicular to the web which covers the surface,
• whereby during a rolling up of the web said tube shifts by rolling on itself from said initial to said normal positions for causing said roll to slip to thereby tighten the web, whereafter said tube rolls on itself in said direction together with the roll and serves to maintain a tight web.