VORRICHTUNG ZUM STRECKEN VON EXTRUDIERTEN KUNSTSTOFFBÄNDERN, ZUM BEISPIEL AUS POLYPROPYLEN ODER POLYETHYLEN, ZUR HERSTELLUNG VON GURTEN, RAFFIA ODER ANDEREN BANDARTEN

The stretching oven (B), positioned between the upstream and downstream pulling groups (A, A'), is of a limited length, between 3000 and 4000 mm, for example about 3300 mm and is provided with suitable thermal insulation (32) against the exterior. Hot air is blown into the longitudinal treatment chamber (17) of said oven for plasticizing the strips that are to be stretched, with first opposite blowing mouths (25, 125) arranged at one end of the treatment chamber (17) of said oven, preferably at the door (16) where the strips to be treated enter, and with at least second opposite blowing mouths (27, 127) always operating in parallel flow in an intermediate portion of said treatment chamber, which at the other end, at the exit door (116), has two opposing pairs of suction mouths connected to fans (19, 119) which collect the hot air from said treatment chamber and send it to said blowing mouths (25, 125, 27, 127) through channels in which heating units (28, 128, 29, 129) are arranged, controlled selectively by suitable temperature sensors (30, 31, 130, 131) and by suitable regulating and controlling means.