Patent ID: 7360971

Claim:
A yieldable prop comprising: a first hollow conduit having a first end and an opposite second end; a second conduit having a first end and an opposite second end; a clamp assembly positioned on outer surface of the second conduit, the clamp assembly comprising a first side and an opposite second side, with the first side of the clamp assembly facing and spaced from the first end of the second conduit, and the second side of the clamp assembly facing and spaced from the second end of the second conduit, wherein the portion of the second conduit between the first end of the second conduit and the first side of the clamp assembly is slidably mounted in the first conduit through the second end of the first conduit; a bearing plate mounted on the second end of the second conduit; and a jack assembly comprising a base mounted on the bearing plate of the second conduit and a moveable clamp plate mounted on the base of the jack assembly and in engagement with the second side of the clamp assembly to move the first side of the clamp assembly against the second end of the first conduit to at least move a predetermined length of the portion of the second conduit between the first side of the clamp assembly and the first end of the second conduit out of the first conduit.