k. Reed Valves. The reed valves control the intake and output of the
During the suction stroke, the following occurs:
(a) The intake is pulled down allowing the air to be drawn into the
(b) The exhaust or output valve is pulled closed to prevent drawing air
in from the tubing and storage tank.
During the compression stroke, the following occurs:
(a) The intake valve is pushed closed.
(b) The exhaust or output valve is pushed open.
(3) These valves are made of a spring steel that is appropriate for the
strength of the suction and pressure of this specific compressor.
l. Induction Motor. The induction motor requires two capacitors. These
capacitors create greater starting torque due to the phase shift.
THEORY OF OPERATION
The operation of the compressor consists of two cycles: the pumping cycle and
the purging cycle. During the pumping cycle, the compressor compresses intake air,
cools it, directs it through a drying chamber where a desiccant removes any water
vapor, and passes it into a storage tank (also called a pressure tank). Refer to figure
1-1. When the pressure in the storage tank reaches 80 psi, the compressor stops and
the purging cycle begins. During the purging cycle, a portion of the dry compressed air
in the storage tank is bled back through the drying tank to the atmosphere. This
expanded dry air reabsorbs any moisture from the desiccant and carries it out into the
atmosphere. When the pressure in the storage tank decreases to 60 psi, the
compressor again starts, and the pumping cycle begins. These two cycles continue to
automatically take place during operations of the compressor. Throughout both cycles,
the cooling coil fan runs continuously, and the dry compressed air in the storage tank is
supplied to the Dental Operating and Treatment Unit.
a. Pumping Cycle. Initially, with no pressure in the storage tank, the action of
the pressure switch closes the unloader valve and the pressure switch contacts that are
in series with the compressor motor. Refer to figure 1-3.