Page 324 - Electromechanical Devices and Components Illustrated Sourcebook

286 Electromechanical Devices & Components Illustrated Sourcebook

Fuel Input between a pair of tips. When the tips are closed they form the
Connector secondary winding of a transformer. The primary winding is
connected to a bank of storage capacitors. The capacitors are
slowly charged with a small power supply. When the capacitors
reach full charge, they are switched into the primary coil cir-
cuit via an ignitron and they dump their entire power into the
Body Solenoid Coil transformer and, consequently, into the weld site. For more
information on transformers, see Chapter 5. For more infor-
mation on ignitrons, see Chapter 14.
Return Spring
Fuel Passage
Threads Poppet
Toasters
Seat
Valve Seat
One electromechnical device that we have all experienced is
Nozzle the ordinary bread toaster. These are clever devices that will
Figure 17-18 Electronic Fuel Injection Nozzle perfectly toast a slice of bread every time. Figure 17-20 shows
a schematic representation of a typical bread toaster. The
bread is placed into the slot and rests on a bread tray. When
the tray is lowered, it closes a limit switch and is latched into
Moving Jaw
place. As the heaters cook the bread, the coiled bimetal strip
Core
Pivot heats up and eventually pulls the latch open, allowing the
Primary Coil bread tray to pop up. By adjusting the preload on the coiled
bimetal strip, the down time can be adjusted and the brown-
Tips ness of the toast can be controlled.

Fixed Jaw
Ignitron Heating Element

Bread Tray
Power
Supply
Latch

Limit Switch
Treadle Bimetal Strip Light Dark
Switch Trigger
AC
Power
Capacitor Bank
Figure 17-19 Spot Welder Circuit Figure 17-20 Bread Toaster