Clock type · Domestic
Bulle Electric Clocks
Partially verifiedA French battery-powered domestic clock type, associated with the Bulle Clock company, using an electromagnetically impulsed pendulum rather than a mainspring or falling weight, distinct in principle from the master–slave electric clock systems used for synchronised public timekeeping.
Movement & mechanism
- A free pendulum carrying a small permanent magnet swings past a fixed coil, which both detects the pendulum's passage and, periodically, receives a battery-powered impulse to sustain the swing
- No mainspring, weight, or conventional escapement train is present; the pendulum itself is both the timekeeping element and, effectively, its own self-contained oscillator
- Hands are advanced from the pendulum's motion via a simple ratchet or similar mechanical counting arrangement
- Power drawn from a single dry or wet-cell battery, intended to run for an extended period, commonly cited by the maker as up to about a year, between replacements
Identification
- Absence of any visible mainspring winding arrangement or driving weight is a strong indicator of this or a related electrically impulsed clock type
- A coil and magnet assembly mounted near the base of the pendulum, rather than an anchor and escape wheel, distinguishes the mechanism internally
- Maker's name or 'Bulle' branding on the dial or movement supports specific attribution
Terminology
- Free pendulum — a pendulum that swings largely unconstrained by mechanical escapement, receiving only periodic electromagnetic impulses
- Master–slave clock — a related but functionally distinct system in which a single master clock periodically synchronises multiple simple slave dials, rather than each clock sustaining its own pendulum electrically
Known variations
- Mantel-cased Bulle clocks
- Longcase-format Bulle clocks
- Related, but mechanically distinct, early battery-driven pendulum clocks by other continental makers
Collecting notes
Bulle and comparable early battery-driven pendulum clocks are collected as a distinct step in the history of electrical timekeeping; because the coil, magnet and battery-contact assembly are specific to the type and can be lost or replaced, mechanical and electrical originality is a significant conservation consideration.
Related photographs
No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.
Sources & references
- Rawlings, A. L., The Science of Clocks and Watches
- Specific model ranges and precise production dates for Bulle clocks are not verified here.
Where sources disagree, the disagreement is stated rather than resolved silently.