The diaphragm-type accumulator consists of a diaphragm secured in a shell and serving as an elastic barrier between the oil and the gas. The cross-sectional view of a diaphragm type accumulator is shown in Figure 7.18.
A shut off button which is secured at the base of the diaphragm, covers the inlet of the Hne connection when the diaphragm is fully stretched. This prevents the diaphragm from being pressed into the opening during the precharge period. On the gas side, the screw plug allows control of the charge pressure and the charging of the accumulator by means of a charging and testing device.
With the help of the following figures (Figures 7.19(a)-(f)), let us now see how exactly a diaphragm-type accumulator works.
Figure 7.19(a) shows the accumulator without the nitrogen charge in it or in other words in a precharged condition. The diaphragm can be seen in a non-pressurized condition.
Figure 7.19(b) shows the accumulator in charged condition. Here nitrogen is charged into the accumulator, to the precharged pressure.
Figure. 7.19(c) shows how the hydrauhc pump delivers oil to the accumulator and how this process leads to the deformation of the diaphragm.
As seen from Figure 7.19(d), when the fluid delivered reaches the maximum required pressure, the gas is compressed. This leads to a decrease in gas volume and subsequent storage of hydraulic energy.
Figure 7.19(e) shows the discharge of the oil back to the system when the system pressure drops, indicating requirement of oil to build back the system pressure.
Figure 7.19(f) shows the accumulator attaining its original precharged pressure condition.
The primary advantage of the diaphragm-type accumulator is the small weight-tovolume ratio, which makes it highly suitable for airborne applications.