A great many pianos used the Schulz action. It was not the first to make use of the pouch-pneumatic idea to raise the valve, rather than the conventional circle pouch diaphragm. The idea of the small inner, folded, pneumatic, dates back to the earliest player action design and was used by Melville Clark and early Sterling actions. However, Schulz applied the idea of the inner pneumatic with such perfect design, proportions and balance that it could achieve the classic claim of being the most perfectly-designed pneumatic action. There was no other that could out-perform it in repetition. responsiveness in pumping control, and tightness of great efficiency. Only the Gulbransen came close to eliminating the lag between the pedal stroke and the hammer action. Unfortunately and ironically both designs have suffered great discredit through ignorance or lack of understanding, when it comes to the fine points of restoration to equal original performance.
Below are illustrated the cross-section view of one of the three tiers of the stack. However, since this is not apparent without tearing it down, the more easy identification would be the lower pump assembly which was one continuous board as seen from the front, with the two pumps and two reservoirs on the back side, hidden from view. The reversing to rewind or play was accomplished through a simple double pneumatic operating linkage to the gate boxes.
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