Erard Double Escapement Action

In 1822, a French piano maker Sebastien Erard created the double escapement action. It became the favourite instrument of the nineteenth century composers for the expression of tone poems. Erard’s action was based on Cristofori’s model. His developed action would allow the hammer to speed up the repetition after initial strike. By comparing the Erard’s action with the English grand action, it showed a lighter action, faster repetition, as well as greater reliability. This action remains the basic model for today's grand pianoforte action.

Explanation on this action’s mechanism:
The structure of this action is mainly in one piece. The action is fixed above the key and the damper stops the strings vibration underneath. When the key is depressed, the action above the key will be pushed up. It therefore pulls back the hammer butt and makes it throw towards the strings. On the other hand, the damper releases from the strings because of gravity. After the hammer’s initial strike towards the strings, the check head will move forwards to receive the hammer, waiting for the hammer to make fast repetition if necessary. The hammer weight is also supported by the repetition spring. It enables the repeated sound of the note before the key finally returns to rest. This action will avoid the hammer from blocking or from double striking the strings.