Machine for manufacturing pre-stretched extendable film rolls

A machine for manufacturing pre-stretched extendable film rolls comprising a pre-stretch unit of the film (F) and a wrapping unit of the film into a roll provided with a series of rolls around which the advancing film is partially wrapped, wherein the pre-stretch unit comprises, in sequence, at least a first pre-stretching roll, a pre-stretching auxiliary roll acting against the first pre-stretching roll with the interposition of the film, and a second pre-stretching roll having a speed greater than the speed of the first pre-stretching roll to carry out the film pre-stretching, and wherein the wrapping unit comprises a wrapping roll for wrapping the pre-stretched film, the pre-stretch unit further comprising a detensioning roll arranged downstream said second pre-stretching roll and having a speed less than the speed of said second pre-stretching roll and greater than the speed of said wrapping roll, so as to obtain a first detensioning of the film having a first detensioning value after the pre-stretching operation and a second detensioning of the film having a second detensioning value before the wrapping operation,

• wherein the auxiliary roll is rotatably mounted at its ends on two arms that are pivoted at a fixed part of the machine, and actuating means are provided, so as to move said arms and consequently the auxiliary roll, between a position of the roll against the pre-stretching roll and a moved away position according to an arc-of-a-circle-shaped trajectory, and wherein means are provided, for adjusting the above-mentioned position of the auxiliary roll against the pre-stretching roll.