Pen Mechanisms Revealed – 3. The Blackbird Topfillers

Laurence Oldfield

Introduction

The Blackbird Topfiller BT200 pen (Fig.1) was developed in the 1930’s to meet a growing requirement for a ‘high-tech’, classy llooking ink-visible fountain pen at a very affordable price. At 7s/6d it was a remarkable bargain compared with its upper class stable mate, the 25/- Swan Visofil VT.
The Blackbird matched the VT in style, operating efficiency and manufacturing quality, but it was 10mm shorter and it required a large blind cap to hide the filling mechanism. The filler worked on the same principles as the Visofil and is generally described by the same patents (WES Journal #65) plus Patent 514513 (Fig.2) published in 1939 two years after the pen entered production. However, none of the patents described the production pen in accurate detail. No repair manuals or drawings of these pens appear to exist, so I hope that this article will lead to a greater understanding of the Topfillers so that many of them can be restored and used again.

An advertisement dated September 1938 (Fig.3) claimed a ‘sacless’ pen with doubled ink capacity. It is interesting to note that Mabie Todd followed the Parker Vacumatic claim of a ‘sacless’ pen! Although the ink is contained directly in the barrel, the claim is misleading; the rubber sleeve does act more as a diaphragm than an ink container, but it certainly comes into contact with ink and deteriorates at the same rate as a conventional sac.

The pens came in black and clear, green gold and black, and blue gold and black, but they were sometimes marketed with black caps on coloured pens (Fig. 4). The large blind cap covers the filling system that is open to view rather than hidden within the barrel.

Like the Visofil, their future was determined by the Blitz of 1940. A recent discussion in this respect was published in the WES Journal #62. The article included a note sent out to repair customers that contained significant information on the technical history of the pens; it is reproduced here for convenience:

“In returning your Blackbird pen sent for repair we regret that, owing to the destruction of our Harlesden Factory by enemy action resulting in the loss of machinery and repair parts, we are unable to renew the original pump-filling action. We have, however fitted a simple filling device which efficiently fills the pen by a few depressions of the rubber sac, but if, when times are normal after the war, you wish to have the former filling action replaced, we shall do our best to carry out your instructions at a nominal net cost of 1/-“.

It appears then that the bulb fillers of this era (Fig. 5) resulted from the necessity to fulfil servicing requests for top-fill mechanisms rather than, perhaps, to cut costs. It also implies that servicing top fillers was not entirely straightforward and that parts (other than rubber sacs) were often required.

There is strong evidence that production of new bulb fillers took place after the Blitz. The pen shown in Fig.5 has been produced without the removable bush that held the early topfill mechanism in place (Figs.6,7a). The threaded portion was formed as part of the barrel and is there just as a means for attachment of the blind cap. However, the pen shown in Figs.7b,8 has the simplified barrel and a top-filler mechanism! It is a possibility that the pen design was modified in this way before the Blitz, but more likely, it shows that once the design had been changed following the introduction of the bulb filler, Mabie Todd were reluctant to revert to the old design which was almost certainly more expensive to produce. The evidence for this conclusion would be strengthened if a pen could be found that showed a response to the offer to restore, after the war, the top-fill mechanism to a pen with the original barrel design.

By now it will be clear that not all Blackbird Topfillers are of the same construction and that I may not have seen them all. The figures show the parts of pens that I have seen, and the operation and maintenance of these will be described.

Mode of operation

The Topfiller draws ink directly into the barrel, and as with the Visofil, a length of conventional sac compressed by a plunger against a return spring acts as the diaphragm to create the pressure difference necessary to fill the pen. Pressing the button causes air to be expelled down the breather tube, and when released, ink is drawn up the feed channel into the barrel of the pen. The bulb filler requires little explanation, but it is significant that a breather tube was retained (like the Visofil V) and thus it gained in ink capacity over earlier pens without this feature (for instance the Parker Streamline range).

Dismantling and renewal of seals

The first step is to extract the section from the barrel. Like the Visofil, the fit is usually very tight as a result of the ridged surfaces (not threaded) and the sealant used to prevent leakage. Careful use of hot air will reduce the risk of cracking the barrel. Using rubber nosed pliers, rotate the section to break the seal and then pull it out making sure to keep the force parallel to the axis of the pen. The next step depends on the version of the pen (not identifiable by the type number alone for the reasons given above).

a. Pens with a removable bush and topfill mechanism (Fig. 6)
The early pens had a threaded bush (like the Parker Vacumatic) that holds the filler mechanism, whereas on later ones the exposed thread is part of the barrel (Fig.7). If the bush is a separate part, it must be removed. The thread is an unusual one (13/32”, 36tpi), so to make a correctly threaded split nut to grip the bush an engineering lathe may be required. However, the M10, 0.75 thread is a sufficiently close approximation and taps are available for this. The filler components are quite delicate so care is necessary if they do not come out of the pen easily once the bush has been unscrewed. The hard rubber domed washer that provides seating for the diaphragm may have to be extracted with a toothpick or similar. It may be difficult to remove the brass ring that holds the other end of the diaphragm in place on the button. This ring may have to be filed off and replaced with a new one.
Once disassembled, it is very important to clean all components and to ensure that all sealing surfaces are undamaged. With all ink-view pens it is important to clean the inside of the barrel (a suitably sized bottle brush is useful for this).
A 31mm length of 17/64” pen sac is required to make the diaphragm. After pushing the diaphragm over the button and spring and through the retaining ring, the bush and the washer, it can be sealed against the domed washer using a little silicone grease. The bush can then be screwed home and the retaining ring used to seal the other end. Any excess rubber at the button end should be removed with a sharp blade.
When refitting the section, remember that the breather tube must lie within the small slot in the plunger nose so that it will not be fouled when the filler is operated. Gentle heat applied to the barrel end will help the section to fit correctly.

b. Pens with a removable bush and bulb filler mount (converted from topfiller)
On these pens the bush will have been reamed out with a taper to enable it to accept an adaptor for mounting the bulb. The adaptor joint can usually be parted following the application of a little hot air and/or soaking in water; a flat-ended 6mm diameter rod makes a convenient tool. It is not essential to remove the adaptor, but it does make cleaning the barrel easier. Some pens appear to have had the bush glued in, perhaps in the realisation that the pen could eventually be restored to topfill action by making a modification to the mechanism (Fig.7b). Replacement of the bulb is straightforward using a 17/64” sac end attached with shellac or other mild adhesive.

c. Pens with integral bush and bulb filler mount (Fig. 5)
These pens were produced during wartime to give a version that was consistent with the earlier pens that had a glued in bush following repair. Renovation of these is straightforward as described above.

d. Pens with a separate bush and improved topfill mechnism
These pens would be ones modified back to topfill after the war. They are identifiable by the fact that bushes were made from vulcanite. Has anyone come across one of these??

e. Pens with integral bush and improved topfill mechanism (Fig.7b,8)

These pens present a challenge because there appears to be no method to remove intact the glued plug that acts as an end seal and mount for the topfill mechanism. A dental x-ray machine had to be used to reveal the construction (Fig.9) - I have a friendly dentist!

First, the plunger knob must be unscrewed to allow removal of the plunger and spring. The diaphragm-retaining ring can then be picked out using a sharp piece of steel shim. If a lathe is available, the plug could be cut out and a new one made (as in Fig.8), but it may be possible to fit a new diaphragm without removing the plug. A stretching tool would be required to feed the end into the narrow groove provided and the retaining ring could then be pushed down over the diaphragm to secure it. The diaphragm is made from a 23mm length of sac, notably shorter than that used in the earlier mechanism.

Spare a thought for the next time the pen will need repair when the plug is glued back in, and do not use anything stronger than the traditional shellac. Following insertion of the plunger from the front of the pen, the spring and knob can be remounted and the diaphragm attached to the knob. These pens do not have the breather tube groove, so it does not matter about the orientation of the section with respect to the barrel.

Using the Blackbird Topfiller

These pens are a delight to use, despite their small size. They have style and, like most Mabie Todd pens, the nibs achieve the right balance of flexibility/durability. The manufacturers issued the following instructions for filling:

“Having removed the cap covering the nib, also unscrew the one from the other end of the pen so that exposing the depressor. With the nib completely immersed in the ink, fully press down and release the depressor several times until the pen is seen to be full. A lesser number of pumps will be required if a slight pause is made after each release, so that the ink can fully fill the vacuum created. Remember to replace the small cap when the pen is full.”

All the variations of filler manage a respectable quantity of ink. I have measured the volume for each of the pens that I have seen. In terms of the fluid volume that can be expelled from the full pen, the capacity of the early Topfiller is 1.78ml and the bulb filler 1.25ml. Each requires at least 10 cycles to fill the pen; compare this with the Parker 51 that requires 5 cycles to fill with 1.2ml. The only disadvantages of the Topfillers are the relative difficulty of repair and the tendency to flood due to temperature fluctuations (in common with all eyedroppers, Vacumatics and De La Rue piston fillers).

Happy hunting for the Blackbird Topfillers, they are worth the effort of restoration.
Please contact the author if you wish to purchase the bush remover or you would like the restoration done for you.

References

Pen mechanisms revealed (Visofil), WES Journal, vol. 65, p12, 2002
The evolution of Mabie Todd fountain pens and how they are made, WES Journal, vol.12, p9, 1985
A little piece of Mabie Todd, WES Journal, vol. 62, p51, 2001
Mabie Todd, Part 3, WES Journal, vol. 21, p13,1988
UK Patent No. 514513, November 1939

Acknowledgement

I am indebted to Steve Hull for his helpful comments and for finding the patents and the advertisement.