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Oven: Insulated Electric Oven with Plug-In Grid Heaters and a Thermostat (Ogden, US 987,161, 1911)
An electric oven built to waste as little heat as possible: a double-walled, packed box with a packed door that seals like a strong-room door. Grid-shaped heating elements slide into grooves in the walls and plug into sockets at the back, and the food rests on them. A thermostat cuts the current when the set temperature is reached and switches it on again as the oven cools.
Result: an oven that bakes, roasts or dries at a set temperature with any number of heating grids.
Source: G. J. Ogden, US 987,161 (1911). Unknown: sizes, metals, packing and temperatures. Picture: the patent drawing.
Advanced
Unknown
Instructions
1
1
Build the insulated casing and door
Build the insulated casing and door
Make the oven chamber as a double-walled casing with packing between the walls, and grooves on the inner side walls to take the heating grids. Fit a door that closes like a fire-proof vault door, also packed, so the casing seals closely. Ours: mild steel sheet. Not given: sizes, the packing.
Materials for this step:
Mild Steel Sheet1 inner and outer walls, door
Unknown Insulating Material1 packingTools needed:
Tin Snips
Drill Press
Unknown Dimensions2
2
Make the plug-in heating grids
Make the plug-in heating grids
Make heating elements in the form of grids that slide into the grooves and on which the food can rest. Fix a porcelain plug to each, carrying spring fingers that push into a socket with matching spring fingers in the back wall. Wire the sockets so all the elements are in parallel; use as many as the temperature and amount of food need. Ours: nichrome wire. Not given: the element type.
Materials for this step:
Nichrome Wire1 heating grids
Unknown Material1 porcelain plugs and sockets
Spring Steel Wire1 spring fingers
Hook-Up Wire1 circuit wiringTools needed:
Soldering Iron3
3
Fit the thermostat control
Fit the thermostat control
Put a thermostat that bends with heat inside the oven, working a contact finger that plays between two contacts a few degrees above and below the set temperature. A switch-changing device, a small rotary motor, throws the main switch off and on as the finger touches one contact or the other. Mount a setting arm with a pointer over a scale marked in degrees, and a second pointer driven by the thermostat. Add a hand switch to turn the current on or off independently, and a lamp with its own switch to light the oven. Ours: a bimetal strip, toggle switches. Not given: temperatures.
Materials for this step:
Bimetallic Strip1 thermostat
Electric Motor1 switch-changing motor
Toggle Switch3 main, hand and lamp switches
Unknown Metal1 contacts, arm, scaleUnknown Material1 incandescent oven lampTools needed:
Soldering Iron
ThermometerMaterials
10- 1 inner and outer walls, doorPlaceholder
- 1 packingPlaceholder
- 1 heating gridsPlaceholder
- 1 incandescent oven lampPlaceholder
- 1 spring fingersPlaceholder
- Placeholder
- 1 thermostatPlaceholder
- 1 switch-changing motorPlaceholder
- Placeholder
- 1 contacts, arm, scalePlaceholder
Tools Required
5- Placeholder
- Placeholder
- Placeholder
- 2 vendors sell this, none ship to you yetPlaceholder
- Placeholder
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