Arching mechanism

An arching mechanism, comprising:

• a structure having a pair of opposite members movable toward and away from one another and a pair of parallel flexible resilient pressure members anchored to said structure and adapted to flex upon displacement of said opposite members toward one another to form an arch having an apex;
• a multiplicity of elongated mutually parallel but mutually spaced apart transverse connection members spanning across said pressure members and forming ribs assuming a configuration of said arch;
• traction means including at least one traction element interconnecting said opposite members and extending generally parallel to and along a median line through said structure for selectively drawing said opposite members toward one another;
• and
• means forming a tension lock connected to said traction means and located between said opposite members and between said pressure members, said tension lock including
• means for actuating said traction element by application of arching force thereto to draw both said opposite members simultaneously toward said tension lock and enable both said opposite members to recede from said tension lock simultaneously, thereby selectively controlling convexity of said arch so that said apex remains substantially stationary for all convexities of said arch, and
• means for locking said traction means in selected positions to retain a selected convexity of the arch, said traction means comprising a respective traction rod connected to each of said opposite members, said means forming said tension lock comprising a rotatable member to which both of said rods are articulated, said means for actuating including means for rotating said rotatable member.