Parker 51 Vacumatic system reassessed
The Parker 51 Vacumatic fountain pen, introduced in 1941, was heralded as a revolution in fountain pen design but the filling system itself was not new at all. The 1928 patent was bought by Parker and used in the Parker Vacumatic from 1933 until 1948, when it ceased production as it could not compete with the Parker 51.
The only difference between the two vacumatic systems was that the aluminiumplunger in the Vacumatic was replaced with a plastic one in the 51 version. The diagram is from the Parker 51 repair manual:
The filler unit consists of a spring loaded plunger attached to the closed end of a short ink sac, or diaphragm which is folded back on itself and gripped againt the plunger collar as the pen is reassembled.
When the plunger is pushed the diaphragm extends, increasing in volume and pushing air out of the barrel. On release it returns to its original position under the actiion of the spring and ink is drawn into the barrel through the breather tube.
The Parker manual suggests that ten strokes of the plunger, sometimes twelve, are needed to fill the pen. Compared to a 'conventional' plunger system this seems excessive and does suggest some inherent inefficiency in the system.
That statement seems almost heretical, given the unquestioned expertise and knowledge of the Parker engineers and the spectacular success of the pen but the cold fact is that a dozen strokes of a plunger to fill a pen is less than optimum, Sheaffer touchdown models fill in just one stroke, albeit a much longer one.
The diagram above suggests that, as the plunger is pressed the diaphragm somehow expands to take on a bulbous shape and occupy a significant amount of space in order to expel the air from the barrel. At this point, however, the air pressure inside the diaphragm will be at normal atmospheric pressure, the plunger shaft is not an airtight seal in the collar. The pressure inside the barrel will be slightly elevated as air is being expelled through a small opening so the effect would be to flatten the diaphragm against the plunger. This would result in much less air being expelled than suggested in the diagram and consequently more cycles are needed to fill the pen.
Speaking pragmatically the much simpler and more efficient 'Aerometric' filler system that succeeded the Vacumatic filler in the '51' is a significant improvement but is the later version a 'better' pen?
Personally I don't think so. I'm a great fan of the Parker 51 and love the 'quirkiness' of the Vacumatic version and, perversely, enjoy the ritual of filling and using the original. In my collection I have a number of Vacumatics, Aerometrics, a Special Edition, and both 'New Parker 51s' but if I had to have only one it would be the Parker 51 Vacumatic in Cedar Blue.
