| 摘要 |
438,172. Mercury switches; automatic circuit-breakers. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. Dec. 31, 1934, No. 37396. Convention date, Dec. 30, 1933. [Class 38 (v)] A mercury switch with a time-delayed action comprises a sealed envelope 22 formed with an internal shoulder 35 against which is clamped by means of a perforated plate 37 and bolt 39, a metal partition 36 which divides the envelope into two compartments, and which is formed with two tubes 40 and 41 provided with restricted orifices 42, 43. In one end of the envelope is a stem 45 terminating in a cup 46 at the bottom of which is an electrode 18 and towards the top of the cup is the exposed end of a second electrode 17 contained in an insulating sheath ending in a small cup 47. The envelope contains a quantity of conducting liquid such as mercury. The switch is described in its application for reclosing a solenoid controlled circuit breaker a predetermined number of times after it has been opened on overload. For this purpose the envelope is mounted on a bracket 25 pivoted on an axis 26 and is coupled by linkage to the operating lever of a circuit breaker (not shown), so that when the circuit breaker opens the envelope is tilted into a vertical position with the electrodes 17, 18 at the lower end. Mercury flows slowly through the orifice 42 and after a certain time the cup 46 is filled and electrodes 17 and 18 are connected to complete the circuit of the reclosing coil of the circuit breaker which closes and returns the mercury switch to the position shown in Fig. 2. The mercury is tipped out of cup 46 and starts to flow slowly through orifice 43. If the overload is removed the whole of the mercury is thus restored. If however the overload is sustained, the circuit breaker is immediately reopened and the switch again inverted leaving some of the mercury round the base of the stem 45. Any mercury which however remains in the other compartment flows through' orifice 42 to fill the cup 46 and cause reclosing. The number of times the circuit breaker is reclosed while the overload persists, depends on the quantity of mercury, and when this is all round the base of the stem 45 the circuit breaker remains open and must be reclosed by hand. In a modification, the orifice 42 is made wide so that all the mercury flows through quickly and the circuit-breaker is only reclosed once. |
