An Interview with Francis Goossens
The pre-WWII period was charged with innovation in the fountain pen manufacturing world! Companies around the world were developing creative filling mechanisms and general design to address several common problems that fountain pen users experienced. One important innovation during this period was the piston filler by Pelikan in 1929. Montblanc had to match this reliable and efficient mechanism, and so a few years later it developed piston fillers too. But, with its tier-1 Meisterstück line of pens, Montblanc wanted to blow the competition out of the water. It created a piston - the teleskop füllmechanik, which claimed to almost double the ink capacity of its pens. This loved and revered filler was phased out by the late 1950s.
Question: Why is the telescopic piston so special to you?
Montblanc's telescopic system allows large ink intakes by its ingenious, clever design. Being myself a mechanical design engineer this design appeals greatly to me.
Question: Why do you think Montblanc stopped production of the telescopic piston?
Montblanc’s decision to stop making the telescopic fillers was probably triggered by two factors:
1) Fabrication cost: The system consists of many precision parts and is expensive to make and assemble.
2) Some specialists claim that at the end of the fifties and beginning of the sixties of the last century, Montblanc received a growing number of complaints from customers concerning blotting problems during aeroplane flights and temperature fluctuations. When the ink level was low in such a large capacity pen then expanding air due to pressure or heat would drive the ink out.
Question: How do you compare the modern Montblanc pistons to the telescopic ones?
Pros: large ink intake, beautiful design
Cons: expensive to make and assemble, not maintenance friendly, blotting risks at low ink levels.
2-Normal piston filler:
Pros: simple design
Cons: Low ink intake, the lead spindle is weak and easily warps when the pen is contaminated, spindle difficult to replace.
Question: I know that you are one of the very few people who can actually restore telescopic fillers. What makes them so difficult to repair?
The fillers are not maintenance friendly at all, in fact not designed for disassembling. Especially on the 13X range of pens, the telescopic filler is very difficult to repair. The filling knob on the 13X pens cannot be disassembled, one needs to cut the filler housing to get the filling knob off. The housing needs then to be rebuilt/restored afterwards. On the 14X & 64X pens, Montblanc improved the design allowing disassembling of the filling knob. However, dissembling the complete filler to replace/swap defective parts remains a very delicate and time-consuming task.
Question: According to you, which other piston filling mechanism or any filling mechanism comes close to the engineering of the telescopic piston?
The only “positive displacement” filling system which is comparable in view of ink intake and technical design is the Conid Bulk Filler. On these pens, an integrated ink shut-off valve eliminates the blotting risks inherent to large ink capacity fillers. A supplementary benefit is the exceptional flushing efficiency by turbulence triggered by the high volume displacement of the syringe. This is my honest opinion, but since I am the designer of the Bulkfiller, some will surely doubt it!
What inspired the design of the Bulkfiller and what are it’s key design features?
Being frustrated with the low ink intake of modern pens compared to my favourite system - the Montblanc telescopic filler - I started designing prototypes (pic below) of various filling systems:
1-Piston fillers: I tried to design piston fillers with a compact mechanism allowing the highest possible ink intake, but I wasn’t satisfied with the results - the filling system still took too much length thereby restricting the ink capacity. Another drawback was that I could not easily integrate an ink shut-off system, and so the inherent risks of blotting remained due to temperature or pressure fluctuations. Further, flushing/cleaning the pen took too much time.
2- Vacuum fillers: These allowed - at least theoretically- a higher ink intake, but not being a “positive displacement filling system” one can only fill 70% of the available barrel volume because of the vacuum release chamber length and the lack of efficiency of the system.
3- Pump fillers: basically an improved Parker vacumatic - allows a high ink intake, but doesn’t allow integration of an ink shut-off and emptying /flushing the pen is extremely difficult.
So I started my search for a system which would feature :
A- High ink intake
B- Allow the integration of an ink shut-off valve
C- Easy an efficient flushing in one or two actuation strokes.
D- Filling in one filling movement.
E- Postive displacement filling system
After a long - sometimes frustrating - journey I came up with the idea of a syringe filler on which the piston could be “parked” and latched positively after filling. After the piston is parked and axially/radially positively latched, one can unscrew the syringe rod from the piston and store the rod in the barrel. And, by providing an ‘O’ ring on the top of the syringe rod the barrel can safely shut off the ink in the barrel.
This worked well, but moving the piston down, after sitting stationary for a longer period, was sometimes very difficult due to "stick-slip” - when a piston seal sits stationary for a longer time the micro layer of fluid (ink) between the seal end the barrel wall is gradually pushed outwards resulting in a dry contact between the piston seal and the barrel wall. One can experience this phenomenon also on screw piston fillers - when starting to screw the piston down after being stationary for a longer time one initially feels a higher movement restriction i.e. the piston “sticks". But, after the piston moves a few millimetres it suddenly moves much more easily because wet contact is restored and the piston “slips”. To overcome this problem I came up with the “stick-slip breaker cam”. This is an axial cam which pushes the piston automatically 1mm forward when un-latching the parked piston, thereby completely eliminating the stick-slip problem!
Although our patent lawyers made a lot of investigations and did not find any patents on a similar system, we learned during the patent process a basically similar system was already patented in 1898! This system was however never produced and did not include the major and indispensable design features inherent to our Bulkfiller design, being :
- Positively axially and radially “latched" parking of the piston.
- The “stick-slip” breaker feature.
- The ink shut off valve
And these indispensable features logically became the basic elements of our “Bulkfiller” patent. The growing Bulkfiller sales figures and the enthusiastic feedback of the Conid customers shows us that we achieved our goal, mission accomplished!