GB1390787A - Method and apparatus for controlling mould temperature - Google Patents

Abstract

1390787 Controls for cooling rotary press moulds OWENS-ILLINOIS Inc 23 May 1972 [24 May 1971] 24077/72 Heading C1M [Also in Division G3] Relates to the automatic temperature control of press moulds in an apparatus used for pressing and moulding hot glass articles, e.g. face plates for T.V. picture tubes, by controlling the flow of cooling fluid on to each mould in dependence upon temperature deviation from an individual required value for each mould. As shown, Fig. 1, a mould table 13 is rotated stepwise and carries a plurality of moulds 51 to (61) (not shown), presenting each mould successively to a plurality of stations 1 to 11. Molten glass is fed into the mould at station 1, is press moulded at station 3, and the article may be retained within the mould as it passes through cooling stations 5, 7, 9, 11, 2 and 4 and is subsequently removed at take-out station 6. The temperature of each mould is periodically sensed by a radiation pyrometer PH, PY at station 10 and correction is effected at a subsequent station. The period between successive corrections of the temperature of each mould is selectively adjustable, to allow one correction sufficient time to have effect before the next is applied, e.g. by skipping one or more corrections. A control circuit MTC causes a stepping motor SM to engage an adjustment means 31a of a plenum 31 to modify a known air slide mechanism 31b to adjust the flow of air from a duct 25 to the mould 51. Each mould 51 to 61 is arranged to receive cooling air from air plenums 31 to 41. In Fig. 2, the pyrometer output voltage signal is linearized by a logarithmic amplifier LOG and is fed to a summing junction SJ for comparison with an individual desired temperature signal value from a selector SS for the particular mould under test at station 10. This desired temperature signal is modified by a master target signal from a unit MS and which is proportional to the average of the desired temperatures of the eleven moulds. The resulting error signal produced by the summing junction is fed to a classiffier CLS for comparison therein with six limit values pre-set on relays DH, CH, BH, BL, CL, DL, defining seven correction ranges. An acceptable range is that between the settings of relays BL and BH. All other ranges call for correction by increasing or decreasing the cooling fluid flow rate. Excessively high or excessively low sensed temperature signals are detected by logic circuit encoder which operates warning devices only and effects no automatic correction. The controllable error signals, one for each range, are fed to a shift register SHR which is shifted in step with the table 13, stores information bits for a first zone magnitude correction (B) a second zone magnitude correction (C) and a direction correction (R) and has a section for each operation station 10, 1, 3 and 5. Correction information is read out when a particular mould reaches the adjustment station 5 and is used to cause the stepping motor SM to rotate by a corresponding predetermined number of steps and in the required direction. Depending upon the setting of a skip-switch SK2, temperature correction of a mould is made during each mould cycle, or only after a predetermined number of cycles. In an alternative arrangement, Fig. 5 (not shown), the temperature correction and temperature sensing are effected at the same station.