| 摘要 |
A gas cartridge introduced into the housing of the invention is punctured by a pin moved by an arm designed to show through a series of windows whether the cartridge is full or empty. A pulling on a tab rotates the arm to action, in puncturing the cartridge and a spring then locks the visual displays in position. The pin is provided with a cone-shaped head which prevents any re-arming of the arm from changing the display to show that the cartridge is full, when in fact the cartridge has been spent. The amount of pull needed to activate the arm can be selectively controlled.
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