US Patent 7556188 Clamping device for weld seam-backing member

A clamping device includes a backing member having an upper face pressing against two work pieces having a welding gap therebetween. A rod extends through the backing member and has an exposed upper portion extending through a narrower portion of the welding gap into a wider portion of the welding gap. An elastic element is mounted between a bottom face of the backing member and an abutting portion on a lower portion of the rod to bias the backing member to press against the work pieces. The upper portion includes a hooked section having a first width smaller than a width of the narrower portion and a second width perpendicular to and larger than the width of the narrower portion. The rod is turnable to a position in which the second width of the hooked section presses against the work pieces under the action of the elastic element.