Feeding and cutting device for a continuous web

A device for feeding and cutting a continuous web (11, 11') into cut pieces (120), having automatic reel change for a reel from which the web is unwound, including a cyclic cutting device (21) located at the confluence of two tracks (25) along which two continuous webs (11, 11') unwound from corresponding reels (10, 10') are fed, and control means (74, 74') generating a signal when an associated reel becomes empty;

• there being provided feed means (12, 20) for feeding said webs from the said reels (10) along each of the said tracks to the said cutting device (21), and the said feed means including, for each track, a pair of feed rollers (20) for feeding the associated web (11) to the said cutting device (21);
• the said device including a pulse generating unit (33, 34) for generating pulses which are phase related to the said cutting device (21) and a frequency of which is a function of a cutting frequency of the said device (21), and means (23) constituted by stepping motors controlled by the said pulse generating unit (33) for directly driving the said pair of rollers (20) in one direction for feeding said web and in a reverse direction for retracting said web;
• the said feed means (12, 20) comprising as well as the said pair of feed rollers (20) actuated by a first control circuit (23, 72), at least one pair of unwinding rollers (12) actuated by a second control circuit (13) to unwind the said web from a reel (10) towards the said feed rollers (20), the said second control circuit including means (16, 17) operable to maintain a substantially zero tension on the said web (11) at the said feed rollers (20) during the whole of the unwinding of the reel (10), the said stepping motor (23) being fed at each operating cycle by means of a control circuit (67, 47, 72) with a number of pulses (38) determining the passage of a cut piece of predetermined length between the said feed rollers (20), and including means (66) for selectively changing the predetermined length of the said cut piece, the said means varying the number of pulses (38) sent to the said stepping motor (23), the device further including reel change means (80, 88, 94, 86) actuated by the said means (74, 74') for detecting when a first web has been used up and, in a first operating cycle, simultaneously with the production of a piece cut from the said first web (11), controlling the arrival and stopping of the end of a second, replacement web (11') at the said cyclic cutting means (21), and in following operating cycles controlling the supply of only the said replacement web (11') to the said cyclic cutting means (21) to obtain pieces cut only from the said second web (11'), and including means (27, 27') for positioning the end of the said replacement web (11') at a predetermined distance from the said cyclic cutting means (21) during the unwinding of the first web (11), the said reel change means controlling the advancing movement of the said replacement web (11') in the operating cycle following that in which the said means (74) for detecting the end of the web being unwound are activated, and controlling a retraction of the end of the web (11) which is running out from the said cutting means (21) during the first operating cycle producing a piece (120) cut from the said second replacement web (11').