The leverless filling system was adopted by Swan in 1932 for the models of the same name, and its use was mainly dictated by aesthetic reasons. It is essentially a variant of the twist filler in which however the tank is realized with a rubber bag as in the ordinary lever loading and the comprehension torsion happens through an eccentric bar anchored to the bottom of the pen that in position of rest remains lateral, whose rotation involves a torsion applied laterally to the bag with the relative wringing.
Compared to twist filler the substantial innovation introduced by Swan was to allow only a limited rotation of the bottom, marked with arrows, and avoids excessive stress applied to the rubber of the bag. The system however had a limited success and has been used only by this company, having in substance the same problems of fragility of its analogue and a rather reduced filling capacity.
- Patent n° US-785654, of 1905-03-21, requested on 1904-12-21, of Claes W. Boman, Eagle. Fountain-pen.
- Patent n° GB-390585, of 1933-04-13, requested on 1932-01-07, of Edward Stephen Sears, Swan. Improvements in, or relating to, Fountain Pens.