Apparatus for tensioning a cover sheet over an open-topped rectangular box or building

Claim 1

Apparatus for covering an open-topped rectangular box (10) having opposed pairs of vertical side (11, 12) and end (13, 14) walls, and means (23) defining a roof-shaping framework for said box, comprising (a) a rectangular cover sheet dimensioned to cover the box opening, said cover sheet having a width dimension that is greater than the width dimension of the box, one of the longer edges of said cover sheet being secured to one (11) of said side walls; (b) a roller (25) connected with the other longer edge of said cover sheet; (c) means (42, 41) for rotating said roller in a direction to wind said cover onto the roller and thereby uncover the box opening, said rotating means being operable in the opposite direction to unwind the cover sheet from the roller and to spread the cover sheet over the roof framework, said roller, when fully unwound, hanging from the adjacent marginal portion (38) of the cover sheet downwardly in spaced relation below the upper edge (19) of, and adjacent the external surface of, the other side wall (12); (d) stop means (S) connected with the outer surface of said other side wall (12) for locking said roller in a position in which the cover member extends over the box opening, said stop means including: (1) means (33) defining a downwardly facing horizontal stop surface extending laterally outwardly from said other side wall; and (2) means (35) defining an outwardly facing vertical stop surface orthogonally arranged relative to, and extending downwardly from, said first stop surface; (e) means (42, 45) maintaining said roller, when in an unrolled condition, in a locked condition in engagement with both of said horizontal and vertical stop surfaces, said stop means being so vertically spaced from said longitudinal edge (19) of said other wall that said cover sheet is maintained taut when said roller is in the locked condition; (f) a horizontal tubular open-ended housing (37) connected in spaced relation below said stop means; (g) an elastic cord (46) slidably mounted in said tubular housing; and (h) means rotatably connecting the ends of said cord with the ends of said roller, respectively, said roller having hub portions (39) of reduced diameter extending axially from the ends of the roller and projecting beyond the planes of the front and rear end walls, said connecting means including ring members (138) rotatably mounted on said hubs, respectively, and means (49) removably securing a respective end of said cord to each ring member, thereby to bias said roller toward the unwound position.