Camozzi Pneumatics Manual

CYLINDERS

Fig. 12

Acceleration phase of a double acting cylinder

We analyze the starting phase of a pneumatic cylinder.

Imagine replacing the cushioning seal with a simple seal with a circular section (commonly called “O-Ring”).

When the piston rod/piston reaches the end position the braking effect is similar to that seen in previous chapters,

in the starting phase the “dead space” and the volume of the chamber are pressurized, in proportion to the opening

of the cushion regulation screw.

This bottleneck delays the commonly called “acceleration” phase i.e. the pressurization of the chamber and the

subsequent start of the piston rod/pistonwhich in this areawould also have a non-linear movement.

To avoid this condition, seals with a particular profile are used.

Figure 12

Pos. 1

: the piston is against the cylinder head, the seal

is supportedwith its flat part against the side of the seat

on the cylinder head. On the opposite side, the rim is in contact with the cushioning sleeve.

Pos. 2

: with the arrival of the compressed air regardless of the position of the cushion regulation screw, the air flow

moves the seal

from its previous position towards the piston starting the filling of the volume phase of the chamber

Pos. 2a

: the compressedair passes through the cushion regulation screwand through the spacers on the seal, that

detach it from the supporting surface of the piston. In this way the filling takes placemore quickly.

Pos. 3

: in the chamber

of the cylinder we have the supplying pressure. The piston begins its movement only

when the generated thrust force overcomes the resistant force.

Pos. 4

: thepiston rod/piston ismoving, andwith the exit of the cushion sleeve from the seal wehave themaximum

flow of compressed air.

CAMOZZI

CYLINDERS