| 摘要 |
PURPOSE:To make it possible to adsorb the permanent expansion of the heat wire such as a creepy deformation to thereby improve safety by a method wherein a latch lever is prevented from holding a valve shaft when the heat wire is within a predetermined initial thermal expansion range. CONSTITUTION:The titled safety device operates such that the degree of expansion or contraction of the heat wire 1 taking place when the heat wire is heated by a gas flame 2 or when the heat wire is cooled due to the extinction of the flame 2 is increased by a drive lever 3 to make the latch lever 4 rotated to hold or release the valve shaft 5 at the valve opening position on the base of the friction clutch principle. In this case, the dimension of the heating section of the heat wire 1 is kept constant so as to allow the heat wire 1 a predetermined thermal expansion L1 and the valve shaft 5 is made to have sufficient play with respect to a latch hole 8 so that the latch lever 4 is prevented from holding the valve shaft 5 while the heat wire 1 is within the initial thermal expansion range L2 which is shorter than the predetermined thermal expansion L1. Further, a safety mechanism 13 is provided so as to drive the latch lever 4 in the valve shaft releasing direction when the expansion of the heat wire 1 reaches a predetermined value including its permanent expansion. |
