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Water Bath: Copper Tank with Plug-In Heaters and an Air-Tube Thermostat (Lidberg, US 1,397,766, 1921)
An electric constant-temperature water bath for laboratory and bacteriological work. A copper tank sits in an insulated fibre-board box; two heater tubes and a thermostat tube are soldered through its wall so the heating coils and the switch plug in from outside. A switch adds extra coils to heat the water up quickly; then the thermostat alone holds the set temperature. Perforated trays on adjustable rods hold the tubes or flasks at the depth you choose.
Result: a thermostatic water bath that holds its water at a set temperature.
Source: T. Lidberg (Chicago Surgical & Electrical Co.), US 1,397,766 (1921). Unknown: sizes, the temperature range, the heater wire. Picture: the patent drawing.
Intermediate
Unknown
Instructions
1
1
Build the insulated tank
Build the insulated tank
Make a rectangular box of fibrous board on four short legs and line it with hair felt or cloth. Set a sheet copper tank inside, its walls a little taller than the box and turned over the top edge as a bead. Make perforated trays of several shelves, each with an upright rod hooked at the top for lifting, and on each rod a sliding clip with a set screw whose end rests on the tank edge, to set how deep the tray hangs. Not given: sizes.
Materials for this step:
Unknown Material1 fibrous board box, legs
Unknown Fabric1 hair felt or cloth lining
Copper Sheet1 tank
Perforated Screen Plate1 trays
Unknown Metal1 rods, clips
Machine Screws1 pieceTools needed:
Tin Snips
Soldering Iron
Unknown Dimensions2
2
Fit the heater tubes
Fit the heater tubes
Solder two watertight tubes across the tank, each closed at its inner end and open outside the wall, and a third for the thermostat. For each heater, wind two coils on a rod held in the tube by an insulating disk and an end head; join one end of each coil to the rod and the others to plates on the head, and cover the terminals with a cap plate. Slide each heater into its tube. Ours: nichrome wire. Not given: the coil ratings.
Materials for this step:
Copper Tube3 heater and thermostat tubes
Tin-Lead Solder1 as needed
Nichrome Wire1 four coilsUnknown Metal2 rods, plates, caps
Unknown Insulating Material1 disks, headsTools needed:
Soldering Iron
Hacksaw3
3
Make the air-tube thermostat
Make the air-tube thermostat
In the closed thermostat tube, mount on an insulating disk a strip carrying a thermostatic bar with a contact at its free end. Facing it, pivot an adjustable bar with its own contact on a bracket in the tube's insulating head, held by a spring against an adjusting screw with a knob outside: turning it sets the temperature at which the contacts open. Bridge the contacts with a condenser to stop sparking. The air in the tube takes the bath's temperature and bends the bar. Ours: a bimetallic strip.
Materials for this step:
Bimetallic Strip1 thermostatic barUnknown Metal1 strip, bar, bracket, contacts, screwUnknown Insulating Material1 disk, head
Compression Spring Set1 piece
Capacitor Kit1 spark condenserTools needed:
Screwdriver Set4
4
Wire and use it
Wire and use it
Wire one coil of each heater through the thermostat, and the other coil of each through a hand switch, with a lamp across the supply to show when current flows. To start, close the switch so all four coils heat the water up. Once it is at temperature, open the switch: the thermostat then switches its two coils on and off to hold the bath steady. Lower the trays of tubes or flasks to the depth wanted.
Materials for this step:
Toggle Switch1 piece
Lamp Socket1 piece
Light Bulb1 piece
Flexible Cord with Plug1 pieceTools needed:
Screwdriver SetMaterials
17- 1 fibrous board box, legsPlaceholder
- 1 hair felt or cloth liningPlaceholder
- 1 tankPlaceholder
- 1 traysPlaceholder
- 1 strip, bar, bracket, contacts, screwPlaceholder
- 1 piecePlaceholder
- 3 heater and thermostat tubesPlaceholder
- 1 as neededPlaceholder
- 1 four coilsPlaceholder
- 1 disk, headPlaceholder
- 1 thermostatic barPlaceholder
- 1 piecePlaceholder
- 1 spark condenserPlaceholder
- fromNOK 33.60
- 1 piecePlaceholder
- 1 piecePlaceholder
- 1 piecePlaceholder
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