A clamp for releasably clamping onto a sphere of an adapter includes a body having a sidewall and a cavity, a pivot member coupled to the body and defining a pivot axis, a cam cylinder positioned around the pivot member, a plunger coupled to the cam cylinder, and a lever coupled to the cam cylinder and being pivotable about the pivot axis. When the lever is pivoted in a first pivot direction from a unlocked position to a locked position, a cam surface cams the plunger in a first plunger direction such that the plunger engages the sphere and the sphere is held between the plunger and the sidewall thereby securing the sphere in the cavity. When the lever is pivoted in a second pivot direction from the locked position to the unlocked position, the cam surface cams the plunger in a second plunger direction such that the sphere is freely removable from the cavity.