Machine and method for applying a tread to a tyre carcass

A method of applying a tread to a carcass of a tire, the method comprising:

• mounting the carcass onto a rotary drum;
• applying a first end of the tread to the carcass;
• feeding the tread to the carcass via a feed conveyor, while at the same time rotating the rotary drum;
• applying a pressure force on the tread by contacting the tread with a pressure roller spaced from the rotary drum and arranged between the rotary drum and the feed conveyor and at a given distance upstream from the rotary drum so that the pressure roller presses the tread upstream from the rotary drum;
• calculating an error variable as a difference between a length of a remaining portion of a circumference of the carcass and a length of a remaining portion of the tread;
• automatically adding a first constant quantity to the error variable to obtain a given overlap of two ends of the tread;
• and
• regulating an intensity of the force applied by the pressure roller as a function of the error variable with a proportional control block having a variable gain and by varying the gain of the proportional control block as a function of a value of the error variable,
• wherein:
• the gain of the proportional control block is maintained constant when the value of the error variable is above a first threshold in absolute value, and when a rate of change of the error variable is above a second threshold in absolute value;
• the gain of the proportional control block is increased when the value of the error variable is above the first threshold in absolute value, and when the rate of change of the error variable is below the second threshold in absolute value;
• the gain of the proportional control block is reduced when the value of the error variable is below the first threshold in absolute value, and when the rate of change of the error variable is above the second threshold in absolute value;
• and
• the gain of the proportional control block is maintained constant when the value of the error variable is below the first threshold in absolute value, and when the rate of change of the error variable is below the second threshold in absolute value.