| 摘要 |
<p>An annular element (10) constituted by a bimetal laminate having a first layer (10a) of a noble material and a second layer (10b) of a non-noble metal such as nickel or an alloy thereof is disposed, in an electrically conductive relationship with the central electrode (4), around the portion of the central electrode (4) which projects from the insulating element (3a, 3) so that, in operation, the spark or sparks are struck between the annular element (10) and the earth electrode or electrodes (9). <IMAGE></p> |
