Camozzi Pneumatics Manual

Fig. 16

3/2-way spool valves

The spool is a cylinder, typicallymetallic, with two different diameters, appropriately connected. Bymeans of its

axial movement inside the valve and due to the seals on the larger diameter, it connects the various passages

throughwhich the compressed air is channelled.

Figure 16

In this example, as illustrated in the drawing, there is no intermediate zone inwhich, during switching, all of the

internal passages are closed. One channel always remains open:

• it is the passage from the inlet 1 to the outlet 2

• or the passage from the outlet 2 to the exhaust 3.

Another difference is that at an equal flow rate of compressed air, the spool must perform a longer stroke; this

results in an increase in the response time and size (length of the valve).

The spool does have some advantages such as:

• it can functionwith any operating device

• the compressed air can be connected to any of the ports (inlet 1, outlet 2 and 4 and exhaust ports 3 and 5)

• the possibility to use any pressure value and even vacuum (themaximum values are given by themanufacturer).

Due to the flexibility of this type of valve, it is necessary to ensure that the operating device is supplied with the

necessary force.

The internal elements of the spool valve arenormally: spool, spacers and seals between spool andbody. The spool,

via the operating device, (which at present is not taken into consideration),moves along its axis inside the spacers

and seals and allows the separation of the various ports/channels due to the interference created by its larger

diameter being in contact with the seals..

This type of valvemay be used when themovement of the spool is operatedmechanically or manually, it can be

used inNCPos.

mode and inNOPos.

modemerely by reversing the inlet and exhaust port connections.

In these valves the pressure of the compressed air acts evenly on the entire surface of the spool, while in poppet

valves, the pressure of the compressed air tries to raise the sealing element, for this reason the spool valves are

defined as “balanced”.

CAMOZZI

VALVES