Patent ID: 7191525

Claim:
A two-stage attachment, comprising: a plate; a first cam lever pivotally connected to the plate by a first master pivot and including a first convex arcuate cam surface; a first working member including a first concave arcuate surface and a first working surface, wherein the first convex arcuate surface is in sliding contact with the first concave arcuate surface while the first working member pivots around a first slave pivot, and wherein the first cam lever and the first working member are substantially in a common plane; a second working member opposite the first working member; a second cam lever, opposite the first cam lever, pivotally connected to the plate by a second master pivot and including a second convex arcuate cam surface; the second working member including a second concave arcuate cam surface and a second working surface, wherein the second convex arcuate cam surface is in sliding contact with the second concave arcuate surface while the second working member pivots around a second slave pivot, and wherein the second cam lever and the second working member are in a common plane; and a spring coupled to both cam levers and configured to pull the cam levers toward each other.