Abstract: A modified synthetic silica powder is produced by heating in vacuum an amorphous synthetic silica powder produced by a sol-gel process, and then cooling the heated silica powder in an atmosphere containing helium. When the modified synthetic silica powder is fused and vitrified in a process of crucible production, the resulting quartz glass crucible contains hardly any bubbles.

Abstract: A presser spring (43) is separately formed with a fuse body (33), and therefore may be formed of a material having a high spring characteristic. The presser spring (43) is attached to a portion of peripheral wall portions (41b) to which a back plate portion (41a) is opposed, so that a mating tab terminal (39), inserted in an engagement space (45), is pressed against the back plate portion (41a) by the presser spring (43).

Abstract: A rotating terminal (16) has a circumferential outer peripheral surface (21a, 24a) having its center disposed at an axis (13, 21b) of rotation of the rotating terminal, and has electrically conductive areas and non-electrically conductive areas alternately arranged on the outer peripheral surface in the circumferential direction. At least one pair of fixed terminals (17, 18) are fixed and disposed outwardly of a path of rotation of the outer peripheral surface of the rotating terminal. In accordance with a rotating position of the rotating terminal, the pair of fixed terminals can be switched between an electrically-conducting condition, in which the pair of fixed terminals are electrically connected together through the rotating terminal, and an interrupting condition in which the pair of fixed terminals are not electrically connected together through the rotating terminal.

Abstract: A load side terminal connected to a load portion, a power source side terminal connected to a power source portion and a sacrifice electric pole connected to the power source side terminal are fixed to an apparatus main body. A movable plug is provided movably to the apparatus main body. The sacrifice electrode is constituted by a sacrifice electric pole with resistor connected to the power source side terminal via a resistor and a through sacrifice electric pole directly connected to the power source side terminal and arranged to shift from each other such that in a procedure of moving a conductive portion of the movable plug from a circuit opened position to a circuit closed position. The conductive portion is firstly brought into contact with the load side terminal, successively brought into contact with the sacrifice electric pole and finally brought into contact with the power source side terminal.

Abstract: A presser spring (43) is separately formed with a fuse body (33), and therefore may be formed of a material having a high spring characteristic. The presser spring (43) is attached to a portion of peripheral wall portions (41b) to which a back plate portion (41a) is opposed, so that a mating tab terminal (39), inserted in an engagement space (45), is pressed against the back plate portion (41a) by the presser spring (43).