| 摘要 |
<p>A demand value for use in breathing apparatus, and comprising a housing 1 in which is mounted a diaphragm 2 such as to divide the interior of the housing into two separate chambers 3,4. Chamber 4 is vented to atmosphere through a hole 14; chamber 3 is connected via a pipe 13 to a gas outlet whereby breathing gas may be supplied to a face piece or mask for a user. Breathing air is supplied from a main gas supply channel 8 via a main valve 9,10 to a gas supply channel 6. A gas inlet channel 5 connects the supply channel 6 to the chamber 3 under the control of a needle valve 11 which closes an orifice 7. The head 11B of the needle valve is urged by a spring (not shown) into contact with the diaphragm 2 and thus the movement of the diaphragm controls the opening and closing of the needle valve. The diaphragm 2 is pivoted about spaced pivot members 15, and leaf springs 16 are used to maintain the diaphragm in contact with the pivot members 15. A leaf spring 17 acts to push the diaphragm about the pivot members in a direction such as to tend to close the needle valve 11. <IMAGE></p> |
