US Patent 7334954 Retractable felt tip pen with air seal system

A retractable felt tip pen has a seal system that prevents air from drying out the felt between uses. The seal system can be actuated with one hand, and comprises two sealing devices that may be used in series in the pen or may be used alone. The first sealing device is a flexible self-sealing membrane, and the second is a specially-shaped and hinged cap. The membrane is actuated by extension and retraction of the felt itself. The cap may be actuated either by extension of the felt alone or by the push of a finger on the cap. Replacement of the cap is effected by snapping the cap over the end of the pen, again with one finger.