Abstract: An electronic pen comprises a user-replaceable cartridge having a nib, a force sensor for sensing a nib force transmitted axially through the cartridge from the nib and a retraction mechanism for retracting the cartridge. The retraction mechanism comprises a barrel adapted for seating the cartridge in either an extended position or a retracted position, and a first biasing mechanism for biasing the cartridge towards the extended or retracted positions. A second biasing mechanism biases the barrel towards engagement with the force sensor.

Abstract: An electronic pen comprises a retractable cartridge having a nib, a force-actuable device that is actuated by a nib force transmitted axially through the cartridge from the nib, a retraction for retracting the cartridge, a button for actuating the retraction mechanism, and a decoupling mechanism for biasing the button away from coupled engagement with the retraction mechanism and thereby the force-actuable device.

Abstract: An electronic pen for interacting with a surface. The pen comprises a retractable cartridge having a nib, an automatic retraction mechanism for automatically retracting the cartridge, and a processor for controlling the automatic retraction mechanism. The processor is configured to automatically retract the cartridge in response to predetermined pen conditions.