| 摘要 |
A pilot operated valve for a demand valve of breathing apparatus includes a valve body 1, a main valve having an apertured diaphragm main valve member 13 controlling fluid communication between an inlet port and an outlet port 3, a pilot valve 2 including a vent passage 10 sensing downstream pressure to open and close the main valve member as the sensed pressure is above or below a predetermined pressure, and selectively operable latchable override means to suspend pilot operation of the valve by occluding an aperture 39 in a diaphragm 38 in the vent passage 10. By depressing a plunger 40, a saddle 43 is urged by a latch spring 44 against the aperture 39. The latch is released in use by an intake of breath reducing the outlet pressure of the passage 10 displacing the diaphragm 38 and hence the saddle 43 and latch when a spring 41 returns the plunger to its initial position. <IMAGE> |
