| 摘要 |
<p>924,691. Automatic temperature control. AJAX MAGNETHERMIC CORPORATION. Dec. 21, 1960, No. 43847/60. Class 38 (4). In order evenly to heat a metal billet to within a desired temperature range, e.g. in an induction furnace, the billet is heated in discrete stages which are automatically controlled in dependence upon the surface temperature and average temperature of the billet. As shown, curve 1 represents the average temperature of a billet being heated to a desired temperature of 1592‹ F., curve 2 represents the surface temperature, to be limited to 1675‹ F. during the heating process, curve 3 represents the temperature at the axial centre line of the billet, and curve 4 represents the position of a recording stylus (not shown) of a recording and contact making temperature responsive instrument. The billet initially heats up substantially linearly until its surface temperature reaches a point 2a on curve 2 representing the limit of 1675‹ F. This surface temperature is detected by the recording instrument which then acts to de-energize the heating circuit and to read the average temperature; if, as illustrated, the average temperature has not reached the desired 1592‹ F., the recording instrument, after a time delay, again reads the surface temperature. Assuming this to have fallen to a point 2b, below a lower control-point 1665‹ F., power is again turned on and the surface temperature rises from point 2b to point 2c-again at the upper limit of 1675‹ F. Power is again removed automatically, and the recording instrument is transferred to read average temperature. Assuming again that the average desired temperature has not been reached, the recording instrument returns to read surface temperature. If, as shown, this surface temperature is above the lower control value of 1665‹ F., power is only reapplied when the surface has cooled to the point 2d, representing 1665‹ F. The surface temperature then rises from point 2d to point 2e and power is removed. The recording instrument then reads the average temperature, now assumed to be above a low average control value of 1582‹ F.; after a fixed time period the recording instrument is transferred to read surface temperature, and cycles the heating periods to maintain the surface temperature and the average temperature between 1582 ‹ and 1592‹ F. An electrical circuit for effecting the method is described (Fig. 2, not shown), in which three thermocouples are used to measure the surface and average temperatures, and in which the recording instrument has contacts operating relay coils to control the heating cycle. Specifications 742,856 and 835,825 are referred to.</p> |
