Safe tool changer

A tool changer for safe changing of tools, the tool changer comprises:

• a master unit, comprising:
• a safety controller comprising at least two separate processing circuitries,
• a coupler comprising at least two valves,
• at least two coupling sensors,
• a tool unit, comprising:
• at least one tool unit sensor that detects if the tool unit is located in a tool stand,
• the at least one tool unit sensor provides two output signals and the output signals are sent to the safety controller when the tool unit is coupled to the master unit,
• the coupler being movable between a coupled state in which the tool unit is coupled to the master unit and a decoupled state in which the tool unit is decoupled from the master unit, wherein the coupler is moved from the coupled state to the decoupled state when both valves are actuated, and the at least two coupling sensors individually detect if the tool unit is coupled to the master unit by means of the coupler and the output signals from the coupling sensors are sent to the safety controller,
• wherein the two separate processing circuitries arranged, individually, to:
• receive a request to decouple the tool unit,
• receive the output from the at least two coupling sensors and the at least one tool unit sensor,
• determine whether the tool unit is coupled to the master unit by means of the coupler, based on the output from the at least two coupling sensors,
• determine whether the tool unit is in the tool stand, based on the output from the at least one tool unit sensor,
• send the result of the determinations to the other processing circuitry,
• receive a result of determinations from the other processing circuitry,
• a first of the two separate processing circuitries sends a decouple signal to actuate a first valve of the two valves and a second of the two separate processing circuitries sends the decouple signal to actuate a second valve of the two valves when the result of the determinations is the same as the received result of determinations and when the results of the determinations both indicate that:
• there is no tool unit coupled to the master unit, or
• the tool unit is coupled to the master unit and it is also in the tool stand, wherein the coupler is configured to move to a decoupled state when the at least two separate processing circuitries both send a decouple signal to decouple the tool unit.