Figure 3-27.Operation of a sliding spool valve.
An accumulator is a pressure storage reservoir in
which hydraulic fluid is stored under pressure from an
external source. Accumulators have four major uses:
1. Store energy. Accumulators that store energy
are often used as boosters for systems with fixed
displacement pumps. The accumulator stores pressure
Figure 3-28.Single-acting ram-type actuating cylinder.
Figure 3-29.Double-acting ram-type actuating cylinder.
oil during slack periods and feeds it back into the system
during peak periods of oil usage.
2. Absorb shocks. Accumulators that absorb
shocks take in excess oil during peak pressures and let it
out again after the surge is past. This action reduces
vibrations and noise in the system. It also smoothes
operation during pressure delays, such as when a
variable displacement pump goes into stroke.
3. Build pressure gradually. Accumulators that
build pressure gradually are used to soften the working
stroke of a piston against a fixed load as in a hydraulic
4. Maintain constant pressure. Accumulators
that maintain constant pressure are always weight-
loaded types that place a fixed force on the oil in a closed