CPC B43K 5/03 (2013.01) [B43K 7/02 (2013.01)] | 17 Claims |
1. A refillable free ink writing instrument comprising a body having a rear end, a front end and an ink reservoir disposed between the rear end and the front end, a writing tip mounted on the front end and a plug mounted on the rear end, wherein the plug is configured to close an opening in fluid communication with the ink reservoir, the plug being configured to be removable from the rear end to refill the ink reservoir with water and concentrated ink refill, wherein the opening is provided with a sealing membrane having one or more cuts configured to allow elastic deformation of the sealing membrane when a predetermined pressure is applied thereto, and the sealing membrane is configured to adopt to states, a rest state in which the membrane prevents ink from flowing out of the ink reservoir and a working state in which the membrane allows introduction of water and of the concentrated ink refill into the ink reservoir.
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