Why Pistons, Not Syringes?

[thefenlander]

A simple question really. Why are there so many piston filling pens out there, while syringe fillers are a rarity? Both are positive displacement systems that need half the barrel length for the mechanism, but the piston filler requires much turning while the syringe is a quicker pull and push motion.

 

I can understand Pelikan and Montblanc being welded to the system for historical reasons, but why have recent manufacturers like TWSBI gone the same way? Just interested to know what people think.

[RMN]

A syringe has also a piston.

The difference is a screw-action system versus a push-pull system.

The danger of accidental displacement of the piston is much worse in the push-pull version.

 

D.ick

[Vendome]

To me syringes involve a lot of faffing about, as opposed to a piston or C/C filler. Quicker, easier and less messy to use.

[jar]

Experience has taught us that syringe systems are prone to catastrophic failure.

 

Now Plunger systems on the other hand are a great idea.

[BT-7274]

The vac-fill system on vintage Sheaffers more-or-less eliminated the need for the syringe filling system as well. More durable, and also 1-handable compared to the syringe.

[Doug C]

There are some out there like the Gate city Belmont, but I think of the main reasons is that they are longer than most pistons and so the pen has to be a certain length.

[Opooh]

As far as I know is the Fountainbel Bulkfiller the only modern pen using the syringe method

[rwilsonedn]

There are modern syringe-style converters that work just fine. I think the love of screw-driven pistons is mainly aesthetic, rather than practical: more parts to fabricate and assemble, more things to break. The only advantage I can see is that you don't have to remove the barrel or a long blind cap to use a screw-driven piston. So if you are making the pen from a soft material that is not likely to hold threads well, or a brittle material that could easily fracture at the threads, an internal piston might be a better choice.

ron

[proton007]

A problem with the syringe system is that its prone to overshoot, because the amount of movement is pretty high. You might end up damaging the piston if its stuck and then suddenly becomes loose.

 

The twisting mechanism reduces the amount of possible movement, and its much safer for the piston.

[hari317]

With a traditional syringe filler, the final pen barrel length has to be atleast double the "swept length" aka stroke of the syringe piston. In practice a little more to allow for some area to grip the syringe's end and also some more for the blind cap/cover over the syringe.

 

It is the same story as above with a traditional single stage piston filler as used in current Pelikans, MBs, etc.

 

However, the wondrous two stage telescopic piston filler developed by MB in 40s and used upto the end of the 50s occupied lesser than the half of the barrel length, this was due to the clever two stage telescopic piston shaft. Expensive to make, but such wonders did exist.

 

The latest innovation (patent protected, I believe) in this area is by Francis aka Fountainbel where he designed a syringe filler, but with the capability to "decouple" the syringe shaft from the syringe seal and park the shaft into the barrel of the pen when done. Since he used O rings as the piston seal and they typically suffer from higher stiction, thus leading to the sudden movement as the stiction is overcome(very familiar topic to engineers working in traction control systems etc...) etc described in posts above, he has cleverly designed a "stiction breaker" to avoid jerky piston movements as the user operates the filler.

[Seele]

Many second-tier Italian post-WWII pens were syringe fillers, along with a few others such as the Chinese-made Ta Tung 717; oddly enough its predecessor 707 was a proper piston filler. Of course the Noodler's Ahab is a syringe filler.

 

Ta Tung changed the filler mechanism design because the materials were somewhat brittle, when I tried to repair a 707 it cracked left right and centre, so it's understandable that they wanted to make things simpler, even though the piston mechanism works well when the piston makes its first move from a stationary position; users of Ahabs should know that quite well, as hari mentioned.

 

But another point is that a syringe mechanism actually takes up a fair bit of internal space: when the reservoir is filled the piston has to be pulled out all the way, meaning it sticks out at the back most. Within the barrel this length must be taken into account, thus making the syringe shorter than expected. The Conid system gets around this by making the piston disengageable from the piston shaft, so that the latter can be pushed back in, thus saving space inside the barrel. This might even hold more ink than a piston filler as the double-threaded piston mechanism can actually take up quite a bit of space inside the pen.

[tonybelding]

A syringe has also a piston.

The difference is a screw-action system versus a push-pull system.

The danger of accidental displacement of the piston is much worse in the push-pull version.

 

I don't get it. How is there going to be "accidental displacement" when you have a blind cap covering up the handle?

[tonybelding]

To me syringes involve a lot of faffing about, as opposed to a piston or C/C filler. Quicker, easier and less messy to use.

 

I don't get it. The syringe-filler is clearly much quicker and easier than piston or C/C. Push-and-pull, what could be easier?

[jar]

 

I don't get it. How is there going to be "accidental displacement" when you have a blind cap covering up the handle?

 

Drops, falls, gremlins, zombies.

[tonybelding]

Experience has taught us that syringe systems are prone to catastrophic failure.

 

Now Plunger systems on the other hand are a great idea.

 

I don't get it. What kind of "catastrophic failure" could a syringe mechanism possibly have? It's just like a piston-filler except with less parts and complexity. It would seem like there's less to fail in it. And why would a plunger-filler be any less prone to failure than a syringe-filler? (I say this as someone with two broken plunger-fillers fresh in my memory!)

[tonybelding]

There are some out there like the Gate city Belmont, but I think of the main reasons is that they are longer than most pistons and so the pen has to be a certain length.

 

I don't get it. The Belmont seems like Exhibit A showing that you can fit a syringe-filling mechanism into a normal (albeit, "full sized") pen and still have room for a large ink reservoir. It holds more ink than any of my piston fillers!

[jar]

 

I don't get it. What kind of "catastrophic failure" could a syringe mechanism possibly have? It's just like a piston-filler except with less parts and complexity. It would seem like there's less to fail in it. And why would a plunger-filler be any less prone to failure than a syringe-filler? (I say this as someone with two broken plunger-fillers fresh in my memory!)

 

A plunger filler has far less wasted space than a syringe system.

 

In fact, personally I'd rate the normal syringe filler as the most brain dead design ever.

 

In the normal syringe filler there is noting to stop the plunger from being pushed down.

[tonybelding]

 

A plunger filler has far less wasted space than a syringe system.

 

In fact, personally I'd rate the normal syringe filler as the most brain dead design ever.

 

In the normal syringe filler there is noting to stop the plunger from being pushed down.

 

Less wasted space, really? Well, let's look at the numbers... The TWSBI Vac 700 and the Belmont Pen are about the same size. According to my measurement, the Belmont draws about 1.7 cc of ink. A single stroke of the plunger on the Vac 700 gets about 1.2 cc. Isn't it odd that the pen with all that wasted space holds more ink? (Yes, if you go through the two-stroke trick with the Vac 700, you can get more ink into it, but that's not the way plunger-fillers were traditionally used, and it's tricky to do without the matching Vac 20 ink bottle.)

 

Nothing to stop the plunger from being pushed down? I assume you meant, nothing except the protective blind cap which keeps anything from bumping into the plunger...

[Vendome]

 

I don't get it. The syringe-filler is clearly much quicker and easier than piston or C/C. Push-and-pull, what could be easier?

 

Obviously, it's different strokes for different folks.

[jar]

 

Less wasted space, really? Well, let's look at the numbers... The TWSBI Vac 700 and the Belmont Pen are about the same size. According to my measurement, the Belmont draws about 1.7 cc of ink. A single stroke of the plunger on the Vac 700 gets about 1.2 cc. Isn't it odd that the pen with all that wasted space holds more ink? (Yes, if you go through the two-stroke trick with the Vac 700, you can get more ink into it, but that's not the way plunger-fillers were traditionally used, and it's tricky to do without the matching Vac 20 ink bottle.)

 

Nothing to stop the plunger from being pushed down? I assume you meant, nothing except the protective blind cap which keeps anything from bumping into the plunger...

 

The blind cap does little to keep a plunger from being pushed down.

 

And neither the TWISBI or Belmont are what I would consider as good designs.