| 摘要 |
508,218. Control systems for consumption apparatus. GENERAL ELECTRIC CO., Ltd. (Patent-Treuhand-Ges. f³r Elektrische Gl³hlampen) Jan. 3, 1938, No. 103. [Class 38 (iv)] [Also in Group XL] Switching control.-A discharge tube suitable for use as a limiting device in relay apparatus comprises a discharge path partly surrounded by a conductive sheath 2, Fig. 2, which is insulated from the electrodes 3 ; as the current through the tube is increased the voltage required to maintain the discharge undergoes a discontinuous change at a critical value of current. In use, the variable impedance element 4 may be the primary of a transformer with the load carrying the variable current to be switched off in the secondary ; or the variable voltage across the load may be supplied to the tube through switch 7, 4 being a contact breaking relay. By including a metal vapour in the filling the operation may be made dependent on temperature. Intermittent current may be generated by making the load 4 a temperature dependent resistance or a resistance-capacity combination. By connecting in parallel a number of positive-characteristic devices having different critical values, a constant-current device may be obtained, since any increase in current causes the tubes successively to switch themselves off. Specifications 378,672, 386,111, 420,522, and 450,925, [all in Group XL], are referred to. |
