Page 224 - Electromechanical Devices and Components Illustrated Sourcebook

186 Electromechanical Devices & Components Illustrated Sourcebook

Upper Alignment
Plate (PTFE)
High Voltage × ISO Flange

Flood with
Epoxy Glue
Two Pole
High Current
× 40 Series
NPT Bull Plug
Quick Flange
BNC × 25 Series
Quick Flange

Figure 10-60 High Vacuum Feedthroughs
Solid Wires

Counter Bore
High vacuum systems require a higher level of perfor-
mance than glue or potting compounds can provide. In these
PTFE cases, a combination of welding and soldering is generally
Alignment Base used. Figure 10-60 shows a few high vacuum feedthroughs.
The feedthrough is usually a connector or insulator assembly
that is welded into a standard flange.
The ceramic-to-metal joint is made with an indium solder
Figure 10-58 Bench Built High-Pressure Feedthrough
and provides an extremely clean and precise seal. Figure 10-61
shows a typical ceramic-to-metal soldered feedthrough. The
stainless steel skirt is provided so that the assembly can be
are placed into the holes and the plug is lowered into the
welded into a standard flange.
counter bore. The counter bore is intended to center the plug
around the conductors. The hole in the bull plug is flooded with
a two-part chemical set glue or potting material. Before the
glue sets, the upper alignment plate is set onto the conductors.
Solder Joints
After the glue sets, the plates are removed and the feedthrough
Stainless Steel Skirt Copper Electrical
is ready to be installed. It should be noted that PTFE plates are Head
used because the glue will not adhere to this type of plastic and
the fixtures can be easily removed and reused. Copper
Conductor
The same process can be used with a hose barb NPT fit-
ting, which allows an ordinary rubber hose to be used as the
Ceramic Insulator
cable jacket. Figure 10-59 shows a hose barb fitting and hose
assembly as a high-pressure feedthrough. Figure 10-61 Ceramic-to-Metal Solder Joint

Hose Barb × NPT Coupler W/Potted Wires
Conduit
Hose Clamp
Hose
Conduit is the pipe or tubing that electrical services are routed
through. Not normally used in homes, it is required by elec-
trical code in most commercial and industrial locations.
Conduit serves three basic functions, first it provides a
guide through which conductors can be conveniently pulled.
This makes installing large, convoluted distribution systems a
much easier proposition. The second function is to protect the
wires from being damaged from outside influences. Conduit
Figure 10-59 Water Tight Bench Built High-Pressure is called on to provide mechanical, chemical, and weather
Feedthrough and Cable protection. The third is to protect the outside world from the