Sheaffer’s second try at a converter for cartridge filled fountain pens was their pushbutton model. It is exactly the same size as their standard ink cartridge, so would fit in any pen that used their cartridge. Most other converter designs require more space than the corresponding cartridge, so sometimes have problems fitting into some pens.
I recently purchased a late 1960s Sheaffer Imperial cartridge-filling pen that happened to have a pushbutton converter inside. The converter did not work, so I decided to see if I could repair it, after all, what was there to lose?
Close examination showed that there are four tiny dents in the metal housing that lock the housing to the black plastic end cap. I used a number 61 drill bit in a pin vise to drill out each of the dents, then wiggled the end cap out of the housing.
NOTE: After publishing this article, I heard from reputable sources that it is often possible to extract the end cap from the housing without drilling out the dents. They use wire cutters, not to cut but to grasp the end cap just under the little flange at the end.
Inside, I found an ink sac and a miniature spring/pressure bar just like you would find in any button filler fountain pen – think Parker Duofold, for example. Pressing the button flexes the spring and squeezes the sac. Releasing the button allows the spring to flatten out and the sac to return to normal shape, sucking in ink.
In my case, the ink sac was nearly completely hardened and it tore into pieces as I extracted it with my tweezers. The spring/pressure bar was pristine. The button slid freely but wanted to stay in the housing, so, all I really needed to do was to fit a new ink sac.
I used a number 16 ink sac, cut to length to fit into the housing and shellacked it to the nipple on the end plug just as one would attach a sac to the nipple on a fountain pen section. After the shellac has set, I dusted the sac with talc and slipped the spring/pressure bar, and sac/end plug into the housing. There is a small notch in the side of the end plug that secures the end of the spring. The two ends of the spring are of slightly different lengths. The short end goes toward the button and the long end is captured in the notch. The flat side of the pressure bar goes toward the ink sac.
I found that the end plug seemed to stay in place just fine despite my having drilled out the dents that had secured it to the housing. If it were loose, I think some shellac would hold it just fine.
Once the assembly was complete, I tried a water test, pressing the button three times, pausing between presses, and the converter took up a small but acceptable volume of water. Reports are that these converters were not very effective, and I can believe that.
Below is an annotated picture of the disassembled converter for your reference.