Abstract: A mechanism for gripping an article including a housing, a piston slidably housed within the housing, a plunger slidably housed within the housing, wherein the plunger is at least partially extendable out from the housing, the plunger including a gripping surface, at least one spring operatively arranged between the piston and the plunger for relating a change of a position of the piston to the plunger, and a cam eccentrically rotatable about an axis and operatively engaged with the piston for setting the position of the piston.