The balanced poppet selector valve has equal
consists of a group of conventional spring-loaded
poppet areas. The poppets will remain in the selected
poppets. The poppets are enclosed in a common
position during thermal expansion of working line
housing and interconnected by passageways to direct
fluid. For this reason, thermal relief valves are
the flow of fluid in the desired direction.
installed in working lines that incorporate balanced
Cams on a camshaft, as shown in figure 11-8,
poppet selector valves.
actuate the poppets. They are arranged so that rotation
Figure 11-7 shows a typical four-port poppet
of the shaft by its controlling lever will open the proper
selector valve. This is a manually operated valve, and
combination of poppets to direct the flow of hydraulic
fluid to the desired port of the actuating unit. At the
same time, fluid will be directed from the opposite port
of the actuating unit, through the selector valve, and
back to the reservoir.
All poppet-type selector valves are provided with a
stop for the camshaft. The stop is an integral part of the
shaft, and strikes against a stop pin in the body to
prevent overrunning. A poppet selector valve housing
usually contains poppets, poppet seats, poppet springs,
and a camshaft.
When the camshaft is rotated, either clockwise or
counterclockwise from neutral, the cam lobes unseat
the desired poppets and allow a fluid flow. One cam
Figure 11-7.--Poppet-type selector valve.
lobe operates the two pressure poppets, and the other
Figure 11-8.--Cutaway view of selector valve body.
11-9
