Today all the major contemporary pen companies, American, Japanese, German, and Italian have or are producing demonstrator pens. The success of clear and durable plastics has made the production of great see-thru pens plentiful and common place.
The interest in how pens work is not a new phenomenon, pen manufacturers dating as far back as the 1920’s were eager to show off their unique filling systems, clip assemblies, nib and feed improvements and the ability to seal the nib inside the cap (safety pens). So all of the major manufacturers provided their sales representatives with hard rubber pens that were cut away to reveal the inner workings. This was the origin of the demonstrator pen.
Original functioning demonstrators
Parker demonstrating the button filler by incorporating a window in the side of the barrel allowing a view of the pressure bar compressing the bladder when that button is depressed. Sheaffer did the same with their lever filled pen. In the days of vacumatic pens, models were made using clear materials, thus maintaining the barrel so that the filling mechanism could be observed without cutting a hole in the barrel. Today, these pens are uncommon, rare and collectible, hence I decided to make my own cut away demonstrator.
I bought an Arnold lever filler pen and removed the side of the barrel, don’t worry it is a 21 cent pen that I paid $5 for….. hmmm, a sucker born ever minute. Anyway, I removed a bit too much but that oops provides a better view for us.
The sac is the largest component inside the barrel, it connects to the section near the nib and run the length of the barrel. Running parallel along the top of the sac under the lever is the pressure bar (aka J-bar). The lever is held in place by the snap ring, visible bisecting the center of the barrel.
The function of a lever filler pen is very basic, actually all fountain pens with an ink sac work with the same essential principle, a mechanism acts on a pressure bar which depresses the ink sac, when pressure bar is released, the sac expands to its original size and takes in ink.