Patent GB-774339-A (GB)
Title: A process and apparatus for making fibres of thermoplastic materials
IPC: D01D5/08
Filed: 1955-06-13
Abstract: 774,339. Automatic control systems. OWENSCORNING FIBERGLAS CORPORATION. June 13, 1955 [June 14, 1954], No. 17003/55. Class 38 (4). In a process for making glass fibres, wherein plastic glass is contained in a temperature-controlled extruding bath from which continuous fibres are drawn, the speed of draw and the bath temperature are maintained in a constant relationship in order to maintain a constant fibre diameter. In Fig. 3, the temperature of the bath 11, as measured by a thermocouple 26, is compared with a reference signal derived from a circuit 27, the reference being progressively increased during a winding cycle. Any resulting error is applied to the control winding 30 of a saturable reactor 22 in series with a transformer 23, 24 supplying an electric heating element in the bath, whereby the heating current is varied so that the bath temperature progressively increases during winding to compensat for increases in the speed of draw due to increases in the diameter of the reel (not shown) on to which the fibres are wound. The reference circuit 27 may comprise a condenser 43, Fig. 4, initially charged to a comparatively low potential from a battery 40 due to the high conduction of a valve 31 connected in parallel across it through closed contacts 42, the valve being in effective diode connection since its grid and cathode are joined through these contacts. When a switch 28, associated with the reel traverse (not shown), is closed at the beginning of a winding cycle, a delay winding 46 is energized to open contacts 42. The condenser 43,is then charged to a gradually increasing voltage, whereby the decreasing valve grid voltage causes a gradual increase in the valve output to a D.C. amplifier 35 to provide an increasing reference during the winding cycle, the circuit components being chosen so as to give a time constant comparable with the time of wind. In an alternative reference circuit, Fig. 5, a D.C. reference is derived from a resistor 60 connected across the output of a bridge network comprising resistors 57, 58, 61, 62. The bridge is energized over a rectifier 68 from A.C. lines L5, L6, and the reference is progressively varied by the movement of a slider on resistor 58. A clock-type motor 67 actuates the slider through a clutch 55 energized over contacts 54 associated with the reel traverse. Adjustable tappings on resistors 57, 59 allow variation of the reference voltage characteristic which in some circumstances may be non-linear. In a modification, Fig. 7, for a constant bath temperature, the speed of draw is maintained constant by varying the speed of the D.C. reel winding motor 65 to compensate for increase in reel diameter during a wind. The D.C. motor field and armature are supplied from an A.C. source over rectifiers 76, 79 respectively. A speed signal from the armature is compared in a unit 78 with a varying reference from a unit 77, the output of unit 78 controlling the rectifier 79 to maintain a speed at the reference value. A current feedback 72 from rectifier 79 is provided for unit 77.