Touch probe

A method of operating a coordinate positioning machine having an arm and a table movable relative to each other;

• a retaining module provided on the arm;
• a plurality of task modules, each releasably engageable with the retaining module;
• a magazine having a plurality of storage ports each of which retains a said task module, each storage port having a pair of jaws;
• the method comprising the steps of sequentially:
• engaging said task module with said retaining module, by magnetically urging said task module onto said retaining module;
• operating the machine to perform an operation with said task module;
• operating the machine to bring the task module into engagement with the jaws of a storage port;
• operating the machine to move the retaining module away from the storage port in a direction opposite to the direction of the magnetic attraction force between the retaining module and task module;
• wherein
• during said movement of the retaining module away from the storage port the jaws of the storage port apply a reaction force to said task module, equal and opposite to the said magnetic attraction force, thereby retaining the task module in the storage port and enabling disengagement of said retaining module from said task module by virtue of the movement of the movable arm and thus the retaining module.

A coordinate positioning machine comprising:

• a table;
• an arm supported by a support structure providing relative movement of the table and the arm;
• a probe supported on the arm, having a retaining module and a task module releasably connectable to the retaining module, the retaining module having means for detecting when a said task module becomes disconnected therefrom, and for generating an alarm signal accordingly to arrest said relative movement of said table and said arm;
• a magazine having a plurality of storage ports, each for retaining a said task module to enable exchange of one said task module on said retaining module for another;
• wherein sensing means are provided for sensing the presence of said retaining module in a predetermined spatial relationship with said magazine, and for emitting an inhibit signal accordingly to inhibit said alarm signal and thereby enable said relative movement during the course of an exchange operation.