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Alfred G. Swenson, Frank E. Finlayson · Public domain (expired patent)

أنشأه

Volt

22. سبتمبر 2026

Thermostatic Electric Iron

The electric flat-iron already published has one state: on. Leave it plugged in and it keeps getting hotter until something scorches - the user is the thermostat. The rung above it puts the Butz idea, a bimetallic strip, inside the iron: the iron holds whatever temperature the dial asks for, and silk and linen each get their own. **US 2,723,336**, "Thermostatically controlled electric flatiron or the like", Swenson and Finlayson, assigned to General Electric, filed 23. July 1953, granted 8. November 1955. **You build the thermostat, not the mains appliance**: a bimetallic strip switching a battery-powered lamp, measured on a hotplate - then you measure a real iron's cycling from the outside.

مبتدئ

2 hours

التعليمات

A switch from a strip

Clamp one end of the bimetallic strip. Set a screw or a stiff wire as the contact so the free end presses it at room temperature. Wire strip and contact in series with the LED, its resistor and the battery holder: the lamp is on while they touch.

المواد لهذه الخطوة:

شريط ثنائي المعدن1 قطعة

LED - Basic 5mm1 قطعة

طقم مقاومات1 طقم

طقم أسلاك دوبون (ذكر-أنثى)1 طقم

الأدوات المطلوبة:

حامل بطاريات AA (أربع خلايا)

ملزمة زنبركية

Heat it and watch

Tape the thermocouple to the strip. Warm it gently on the hotplate and note the temperature when the lamp goes out; let it cool and note when it lights again. Three runs.

الأدوات المطلوبة:

صفيحة تسخين

مزدوجة حرارية بقارئ

نظارة أمان شفافة

Move the contact

Turn the contact screw in by half a turn so the strip must bend further, and repeat. That screw is the iron's fabric dial.

الأدوات المطلوبة:

مزدوجة حرارية بقارئ

Measure a real iron

Stand a steam iron on its heel on a heatproof surface at a mid setting. With the infrared thermometer on the soleplate and a stopwatch, time how long its indicator lamp stays on and off over several cycles, and note the highest and lowest readings.

الأدوات المطلوبة:

مكواة بخار

ميزان حرارة بالأشعة تحت الحمراء

ساعة إيقاف

Bend, hysteresis, duty cycle

جارٍ تحميل دفتر Jupyter…

History & Context

**What the patent specifies:** a flatiron whose heating element is switched by a thermostat set from a fabric dial, holding the soleplate at the chosen temperature. **Modern build (derived):** the bimetal switch alone, on safe low voltage, plus outside measurements of a working iron. The same bimetal switch went into kettles, ovens, toasters and motor overload protectors. Its limits: the strip switches over a few degrees of swing, it ages with cycling, and it senses its own temperature - not the cloth's.