element 302 are kept to a minimum this is because the contact between its surface and the prongs 512 of the pusher 502 always occurs at very low velocities with a reasonably low degree of impact furthermore the central processing unit always has a precise confirmation of the position of the rod 103 owing to the sensor 42 and the signal to the solenoids 303 and 403 can therefore be suitably regulated by means of the control and monitoring probe 45 it should be noted that the position of the rod 103 of the actuator 3 can be regulated by means of the block 503 and similar the distance between the solenoids 303 403 can also be selected conveniently according to the travel required to actuate the pusher 502 fig4 shows a variant which provides an alternative to the system regulating the position of the rod 103 described above a chamber 933 maintains an equilibrium between the forces acting on the moving part when a pressurized fluid is present at the end of the rod 133 the said chamber 933 which is connected by means of a pipe 953 to the environment upstream of the corresponding valve makes it possible to cancel out the effect of a variation of pressure in the environment upstream of the valve in which is immersed the terminal part of the rod 133 in contact with the pusher because there.