Retractable stop assembly

A power operated retractable stop assembly comprising:

• a body;
• a reciprocatable member extending into the body and being driveable between a first angular position and a second angular position;
• a rotary driving means connected to the reciprocatable member;
• a drive arm pivotally mounted to the body and drivingly connected to the reciprocatable member such that the drive arm is pivotable about a drive axis over a motion range between a pre-locked position and an unlocked position in response to movement of the reciprocatable member, the motion range including a locked position between the pre-locked position and the unlocked position, and the drive arm having a central axis passing through the drive axis to define a drive arm plane that pivots with the drive arm;
• and
• a stop arm pivotally mounted to the body such that the stop arm is pivotable about a stop axis, the stop arm having a front side for engaging a workpiece and a back side for engaging the drive arm, the stop arm being positioned to apply a reaction force to the drive arm in response to receiving a force exerted on the stop arm front side by a workpiece,
• wherein the stop arm back side is configured such that the reaction force has a component normal to the drive arm plane when the drive arm is between the pre-locked position and the locked position to urge the drive arm toward the locked position, and such that the reaction force is substantially coplanar with the drive arm plane when the drive arm is in the locked position to cause the drive arm to remain at the locked position with the stop arm held at a stop arm locked position.