SELF-SEALING RETRACTABLE WRITING INSTRUMENT

摘要

This invention provides a retractable writing instrument (100) that substantially prevents writing fluid from evaporating through the tip (102) when the tip (102) is in a retracted position to eliminate the need for a cap. Within the writing instrument (100) is an enclosure member (300) that has a vapor chamber (306). In the retracted position, the tip (102) of the writing instrument (100) is within the vapor chamber (306) to substantially seal the tip (102) from ambient air so that writing fluid does not evaporate through the tip (102) The enclosure member (300) has a lip (302) that opens to allow the tip (102) to move forward and extend from the writing instrumen (100) so that writing fluid can be delivered to the writing surface for writing. When the tip (102) is moved back into the retracted position the lip (302) closes to substantially seal the tip (102) from the ambient air. An external compression may be made of a material that is durable so that the lip (302) does not wear out after many cycles of moving the tip (102) between the retracted and protracted positions, such as silicone, butyl rubber, and thermoplastic vulcanizate (TPV) material including butyl rubber cross-linked with polypropylene.