= Gas flasher in a Dalén light
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Dalén's 1910 patent describes gas entering a diaphragm chamber. When its <pressure> overcomes a spring and magnetic restraint, a valve opens and the pilot ignites the burner. Escape of gas lowers the <pressure>, letting the valve close. A ratchet and cam alter an additional feed to create groups of flashes. This specification describes a pressure-driven flashing mechanism, rather than the <sun valve>'s daylight sensor.<Light-Signal Apparatus, US952420A by Gustaf Dalén>[Description, figures 1–4: diaphragm-pressure cycle, pilot flame and additional-feed grouping mechanism; published 15 March 1910]{ref}
The patent is evidence of the proposed mechanism, not an independent endurance or fuel-consumption test. For a simple original budget, suppose the pilot consumes gas at a steady rate $q_p$, the main burner consumes $q_m$ while lit, daylight shutoff permits operation for fraction $f$ of the day, and flashes occupy fraction $d$ of that permitted time. Then the daily mean consumption is
$$
\boxed{\overline q=q_p+fdq_m.}
$$
For stipulated $f=1/2$, $d=0.10$ and $q_p=0.02q_m$, this is $0.07q_m$, compared with $1.02q_m$ for a continuously lit main burner with the same pilot. The calculated saving is about $93.1\%$. The arithmetic explains the two independent opportunities for saving fuel; it does not establish those fractions or that performance for an actual lighthouse.
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