Safe robotic tool changer

A robotic tool changer, comprising:

• a master unit including a coupling mechanism configured to place the master unit in one of a coupled state and a decoupled state, the coupling mechanism including
• a coupling piston movably mounted within the coupling mechanism, the coupling piston being moved toward a locked state by a first source of power to place the coupling mechanism in the coupled state, and being moved toward an unlocked state by a different second source of power to place the coupling mechanism in the decoupled state;
• a coupling ball displaced by the coupling piston in the locked state to cause the master unit to securely mechanically attach to a tool unit of the robotic tool changer if the tool unit is physically proximate the master unit, and allowed by the coupling piston to retract in the unlocked state to detach the master unit from the tool unit;
• a detent piston movably mounted within the coupling mechanism, the detent piston being biased toward a locked position and operative to assume the locked position when the coupling piston is in the unlocked state;
• and
• a detent ball, distinct from the coupling ball, displaced by the detent piston in the locked position to hold the coupling piston in the unlocked state;
• wherein the second source of power is received from a tool unit only when a robotic tool attached to the tool unit is disposed in a tool stand;
• and
• wherein the detent piston is moved to an unlocked position, against the bias, in response to physical contact with the tool unit;
• and
• a tool unit including
• a head configured to couple to the coupling mechanism of the master unit so as to apply mechanical force to the detent piston, moving the detent piston to the unlocked position to release the coupling piston from the unlocked state and allow it to couple to a tool unit;
• a fluid port configured to couple to a fluid receptacle of the master unit so as to apply the second source of power to the coupling mechanism.