| 摘要 |
1,142,252. Electrically heated platens. E. W. BLISS CO. 31 May, 1966 [17 June, 1965], No. 24150/66. Heading H5H. [Also in Divisions B3 and G1] A hot sizing press has upper and lower platens B, C, Fig. 1 (not shown), heated by resistance heaters arranged in series-connected pairs H1, H2, Fig. 4, and means 13, 14 are provided to test the heaters and identify any burned-out heater. The press which is actuated hydraulically, is of particular use in hot die pressing of high-alloy steel or titanium sheets used in aerospace work. The dies are mounted on carriages which move them between the press and ovens arranged on opposite sides thereof. For heating the platens, the pairs of resistance heaters are connected in star or preferably in delta across a three-phase supply R1, R2, R3, Fig. 5 (not shown). The heaters are connected individually to the contacts 13 of banks II, III of a stepping switch whose collectors 14 are automatically driven stepwise by a motor at about eight steps per second. A burned-out heater such as H1 will be detected by giving a no-voltage signal across its mating heater H3. A pair of counting tubes 36, 37 connected to further banks VI, VII of the stepping switch show which heaters are being tested and a defective heater causes the switch to be stopped with the heater identified on the tubes. Another embodiment is described, Fig. 6 (not shown), for checking up to ninetysix heaters using an eight-bank stepping switch. |
