Mechanical Principles › Complications › Striking Mechanisms › Clock Striking Mechanisms

STRIKING MECHANISM WITHOUT DELAY, TRIGGER-RELEASE TYPE

Origin and Principle

The trigger-release striking mechanism without delay is the oldest and simplest of the three principles: it already equipped movements fitted with a crown-wheel escapement, known as the verge escapement, associated with the foliot and later the balance, well before the widespread adoption of cam and rack systems. It therefore historically precedes these two more elaborate solutions, which would only appear in the 17th century and at the end of the 17th century, respectively. Like them, however, it relies on a striking train (wheel train) separate from the movement train (wheel train), driven by its own weight or mainspring, and connected to the latter solely through the release interface.

Components and Operation

Unlike the cap-and-hoop or rack striking mechanism, this mechanism includes no distinct preparation phase (delay): a detent is directly lifted by a pin carried by a locking wheel, which usually has two of them, as the hour passes. This contact is enough to instantly release the striking Train (wheel train), with no delay wheel or preliminary positioning step between the Release and the start of the blow count. The resulting strike is most often limited to the full hour, and, occasionally, to an intermediate blow at the half-hour, and its count remains, as with the cap-and-hoop striking mechanism, independent of the actual position of the hour Hand.

Use and limitations

This mechanical simplicity, which reduces the number of components, pivots and adjustments required, correspondingly lowers manufacturing cost and facilitates maintenance. It explains its persistence in robust and economical movements, such as Comtoise clocks and certain Alarm clocks, even as delay mechanisms, whether with hood or rack, became widespread in quality clockmaking. This economy of construction, however, comes at the cost of lower precision and finer adjustment than those offered by delay mechanisms.