Abstract: A backstop to prevent contact between a spacer and a peripheral member includes a rear jib backstop for a crane, having an outer cylinder, an inner cylinder, a spacer, a spacer holder and a lock mechanism. The spacer holder supports the spacer pivotally and swingably about an axis thereof and allows the spacer to fit on the inner cylinder, to keep the rear jib backstop from contracting in accordance with a change in a posture of the rear jib backstop when a boom rises. The lock mechanism enables locking of the spacer in such a manner as to keep the spacer from swinging about a swing central axis in a state where the spacer is located away from an outer surface of the inner cylinder.

Abstract: A crane includes a jib posture retention device that retains a jib in a frontward tilt posture to a boom. The jib posture retention device includes a jib mast that holds a rope connection part at a tensioning position separate from a jib proximal end and a boom distal end backward thereof to render a jib-side support rope and a boom-side support rope linearly tensioned with the jib in the frontward tilt posture. The jib mast is shiftable to a tension form of holding the rope connection part at a tensioning position in an uprise posture and a looseness allowing form of locating the rope connection part at a looseness allowing position closer to the boom distal end than the tensioning position and closer to the jib proximal end than the tensioning position to allow the jib-side support rope and the boom-side support rope to be loosened.

Abstract: A sheet winding apparatus has a sheet, a winding axis to which one end of the sheet is fixed and having a cylindrical shape, a spring that is arranged in the winding axis and gives a biasing force to the winding axis in an opposite direction of drawing-out direction of the sheet, and a soundproof tube that is arranged between an outer periphery of the spring and inside the winding axis. The soundproof tube has first projected portions projecting outward from an outer periphery of the soundproof tube.

Abstract: A sheet winding apparatus has a sheet, a winding axis to which one end of the sheet is fixed and having a cylindrical shape, a spring that is arranged in the winding axis and gives a biasing force to the winding axis in an opposite direction of drawing-out direction of the sheet, and a soundproof tube that is arranged between an outer periphery of the spring and inside the winding axis. The soundproof tube has first projected portions projecting outward from an outer periphery of the soundproof tube.