Locking power clamp

A vacuum loader truck containing a rear closure door with a peripheral seal member, said door and seal member generally being located at one end of a large vacuum chamber on said truck,

• wherein said vacuum loader truck contains a plurality of clamp assemblies to secure said door in a closed position,
• said clamp assemblies including:
• a clamp arm member having a clamping contact surface thereon,
• said clamp arm member being of elongated dimension and being capable of generally rotational movement, such that when the clamp assembly is opened, the clamp arm member will move in a generally perpendicular direction away from the plate of the closure door and will move in a radial direction away from a peripheral edge of the closure door,
• at least one frame member,
• at least two link arm members, each being of different length,
• a fluid operated piston and cylinder assembly, with a piston being connected to one of the link arm members, and a cylinder being connected to said frame member, and a rotator member secured to the frame member to support and assist proper movement of the clamp arm member, said rotator member having a central aperture for receiving said clamp arm in sliding rotation, said rotator member having a pair of outer rings for receiving said frame member in rotational relation.