same as the first notch and therefore the description of the second notch will be described as the description of the first notch referring to fig2 c the supporting portion 165 is under the protrusion 143 a of the cap plate 143 and does not extend beyond the protrusion 143 a of the cap plate 143 that is when viewed in the plan view the bent lines 164 and the supporting portion 165 are inside the protrusion 143 a if the bent lines 164 are not inside the protrusion 143 a a portion of the supporting portion 165 positioned outside the protrusion 143 a blocks the passage to the exhaust port 143 b when the vent member 160 is opened since the bent lines 164 in the present embodiment are inside the protrusion 143 a the supporting portion 165 does not block the passage to the exhaust port 143 b and the first and second fracture pieces 167 and 168 guide the gas discharged through the opening 162 to the exhaust port 143 b as shown in fig3 and 4 when the maximum distance from the bent line 164 to the first notch 161 is referred to as a long width l 2 the long width l 2 of the first notch 161 according to the present illustrated embodiment may be formed of the same distance as the distance l 3 from the bent line 164 to the upper end of the exhaust.