Page 433 - Mechatronics with Experiments

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JWST499-Cetinkunt
JWST499-c07
ELECTROHYDRAULIC MOTION CONTROL SYSTEMS 419
Pressure line
filter

Suction line
filter

(a) (b)

Return line
filter
Case drain
line filter
(c) (d)

Kidney loop

(e)
FIGURE 7.9: Filter locations in a hydraulic circuit: (a) filter in suction line, (b) filter in pressure
line at the pump output, (c) filter in return line to the tank, (d) filter in case drain line, (e) kidney
loop filtration. There is generally a by-pass check valve in parallel with the filter in order provide
a flow path in case the filter is clogged up.

moved by an operator. As the lever moves up, due to the pressure differences, check valve
1 opens and check valve 2 closes. Hence, the lever sucks the fluid from the reservoir. In the
down stroke, check valve 1 closes and check valve 2 opens. The pressure between the lever
side and cylinder side are almost equal. Hence, the force is multiplied by the area ratio,
while the speed of linear travel of the load and lever is divided by the same ratio. This is
the result of conservation of power.
Figure 7.10b shows a simple hydraulic system where the source of hydraulic power
is a fixed displacement gear type pump. Input mechanical power to the pump is provided
by an electric motor. An operator controls the flow to the cylinder by a manually actuated
valve. Notice that the valve is open-center type which means that the flow circulates from
pump port to tank port when the valve is in neutral position.