Ball point pen cartridge with refill indicator
Publication Date: 2000-Oct-17
The IP.com Prior Art Database
The present invention is a ball point pen cartridge including a cartridge tube 110 having one end open, a metal tube 130 mounted in the other, a ball 150 rotatably mounted in the metal tube 130, a Marking fluid A 120 within the tube in contact with the ball, and a Marking fluid B 130 in contact with Marking fluid A 120. Marking fluid A 120 and Marking fluid B 130 are of two distinct colors. For example, Marking fluid A 120 might be black, and Marking fluid B 130 might be blue. During the normal life of the ballpoint cartridge, writing will appear in the color of Marking fluid A 120. Near the end of the life of the cartridge, the color of writing produced by the cartridge will change to the color of Marking fluid B 130, indicating it is time to replace the cartridge. In the example, the cartridge would be provided and labelled as a black ink cartridge. Near the end of its useful life, however, the writing produced by the pen in which the cartridge is installed will turn from black to blue. This indicates to the user that it is time to replace the cartridge, though the pen will continue to function for some period of time related to the amount of Marking fluid B 130 used in the cartridge.