Sheet member holding apparatus

A holding apparatus for a sheet member which has a density c and a thickness t, the apparatus comprising:

• (a) a rotary body having a radius r and an outer peripheral surface around which the sheet member can be wound, a coefficient of maximum rest friction between the sheet member and the outer peripheral surface being μ2;
• (b) a support attached to the outer peripheral surface of said rotary body;
• (c) an arm comprising two end portions and an arm portion supported by said support between said two end portions, said arm having a weight m per unit length in an axial direction of said rotary body, said arm being pivotable about a fulcrum at said arm portion, said arm having a clamp section provided at one of said end portions at a distance L1 from the fulcrum for applying pressure to the sheet member, which is disposed between said one end portion and the outer peripheral surface of said rotary body, a coefficient of maximum rest friction between said clamp section and the sheet member being μ1, and said arm having a center of gravity at a position between other of said end portions and the fulcrum at a distance L2 from the fulcrum and a distance αr from the center of said rotary body;
• and
• (d) a resiliently deformable element connected to said other end portion of said arm and which, when said support is attached to said rotary body, is resiliently deformed such that a pressure force T0 is applied at a pressure application point at said other end portion at a distance L3 from the fulcrum, said one end portion is pivoted toward the outer peripheral surface of said rotary body, and pressure on the sheet member is generated,
• wherein a tensioning force F acts to move the sheet member along a stretching direction along the outer peripheral surface of said rotary body, and the expression μ1{(L2/L1)mαrω2+(L3/L1)T0}>F>cr2tω2+μ2{(L2/L1)mαrω2+(L3/L1)T0} is satisfied, ω being angular velocity.