Longitudinal chamber profile preform and method

Apparatus comprising:

• a preform adapted to produce a longitudinal chamber profile element, including:
• an inner wall, wherein the inner wall
• is comprised of metal sheet,
• is bounded by two opposed inner wall short edges and two opposed inner wall long edges,
• an outer wall, wherein the outer wall
• is comprised of metal sheet,
• is bounded by two opposed outer wall short edges and two opposed outer wall long edges,
• wherein the outer wall and the inner wall
• are arranged with respective inner wall short edges and outer wall short edges in generally aligned relation and with respective inner wall long edges and outer wall long edges in generally aligned relation,
• are sealed in fluid tight relation by a respective short seal at each respective immediately adjacent inner wall short edge and outer wall short edge,
• are sealed in fluid tight relation by a respective long seal at each respective immediately adjacent inner wall long edge and outer wall long edge,
• wherein a fluid tight sealed internal gap extends intermediate of the inner wall and outer wall and intermediate of the short seals and the long seals,
• a valve, wherein the valve
• is positioned on one of the inner wall or the outer wall, and
• is adapted to enable the introduction of pressurized fluid to the gap,
• wherein the longitudinal chamber profile preform prior to the introduction of pressurized fluid in the gap is coiled such that each of the long seals in a side view has a shape that is an outward expanding spiral that extends through an angle of at least 900°.

A method comprising:

• a) providing a preform adapted to produce a longitudinal chamber profile element, that includes
• an inner wall, wherein the inner wall
• is comprised of metal sheet,
• includes two opposite inner wall short edges and two opposite inner wall long edges, wherein a respective inner wall short edge bounds a respective end of the inner wall,
• an outer wall, wherein the outer wall
• is comprised of metal sheet,
• includes two opposite outer wall short edges and two opposite outer wall long edges, wherein a respective outer wall short edge bounds a respective end of the outer wall,
• a pair of short seals,
• wherein each respective inner wall short edge is joined in sealed fluid tight relation with a respective outer wall short edge by a respective short seal,
• a pair of long seals,
• wherein each respective inner wall long edge is joined in sealed fluid tight relation with a respective outer wall long edge by a respective long seal,
• wherein a hermetic sealed internal gap extends intermediate of the inner wall and the outer wall and intermediate of the short seals and the long seals,
• a valve, wherein the valve
• is positioned on one of the inner wall or the outer wall, and
• is adapted to enable the introduction of pressurized fluid to the gap,
• wherein the preform prior to the introduction of pressurized fluid into the gap is coiled such that each of the long seals in a side view have a shape that is substantially an Archimedean spiral,
• b) delivering pressurized fluid into the gap through the valve and maintaining the fluid at a fluid pressure that is operative to cause each of the inner wall and the outer wall to deform and the shape of the spiral to uncoil.