GB910955A - Heat treatment of textiles - Google Patents

Abstract

<PICT:0910955/IV(a)/1> An apparatus for heating a longitudinally moving band of parallel filaments or threads, or lengths of permeable fabrics, comprises a closed circuit of air ducts incorporating in series a fan 1 driven by a motor 2, by means of which air is pumped through a duct 3, a thermostatically controlled air heater 4, and access for the band to cross said circuit so as to allow at least some of the air circulated to pass through the band, a duct 5 containing air flow levelling vanes 6, a thermo-couple 7 and a baffle 8 of perforated sheet metal or gauze, to the lower section 9 of a heat treatment chamber. In the heater, the heated air passes through the band of fibres 10, which is held, guided and stretched by two sets of nip rollers 11 and 12, to the upper section 13 of the heat treatment chamber and from thence through a duct 14, a dust extracting cyclone 15 (having a detachable dust collecting box 16), and a duct 17 to the inlet port 18 of the fan 1. The air temperature is controlled by setting an indicating pyrometer 19 to the required temperature. The pyrometer 19 receives a signal from the thermo-couple 7 and switches auxiliary electric heating elements in the heater 4 on or off, maintaining the temperature in the heat treatment chamber constant to within \sB1 DEG C. The heater 4 may be located in the circuit between the cyclone 15 and the fan inlet 18. The apparatus may be used for heat stretching or heat stabilizing a band of polyacrylonitrile threads and for drying or curing a finish which has been applied to a band of a permeable fabric. The fibres of the band are heated more uniformly in the above apparatus than by the conventional method of passing the band over and in contact with a hot plate.ALSO:<PICT:0910955/IV (b)/1> An apparatus for heating a longitudinally moving band of parallel filaments or threads, or lengths of permeable fabrics comprises a closed circuit or air ducts incorporating in series a fan 1 driven by a motor 2, by means of which air is pumped through a duct 3, a p thermostatically controlled air heater 4, and access for the band to cross said circuit so as to allow at least some of the air circulated to pass through the band, a duct 5 containing air flow levelling vanes 6, a thermocouple 7 and a baffle 8 of perforated sheet metal or gauze, to the lower section 9 of a heat treatment chamber. In the heater, the heated air passes through the band of fibres 10, which is held, guided and stretched by two sets of nip rollers 11 and 12, to the upper section 13 of the heat treatment chamber and from thence through a duct 14, a dust extracting cyclone 15 (having a detachable dust collecting box 16), and a duct 17 to the inlet port 18 of the fan 1. The air temperature is controlled by setting an indicating pyrometer 19 to the required temperature. The pyrometer 19 receives a signal from the thermo-couple 7 and switches auxiliary electric heating elements in the heater 4 on or off, maintaining the temperature in the heat treatment chamber constant to within \sB 1 DEG C. The heater 4 may be located in the circuit between the cyclone 15 and the fan inlet 18. The apparatus may be used for heat stretching or heat stabilizing a band of polyacrylonitrile threads and for drying or curing a finish which has been applied to a band of permeable fabric. The fibres of the band are heated more uniformly in the above apparatus than by the conventional method of passing the band over and in contact with a hot plate.