| 摘要 |
PURPOSE:To prevent generation of external drain by providing a restriction mechanism in a first passage communicating a back chamber of a valve member and a secondary port and providing a check valve and switch means in a second passage communicating the back chamber and a primary port. CONSTITUTION:There are provided a first passage 9 communicating a back chamber 7 of a valve member 6 and a secondary port 2 and a second passage 10 communicating the back chamber 7 and a primary port 1. The first passage 9 is provided therein with a restriction mechanism 11, and the second passage 10 is provided therein a check valve 12 for permitting only the flow from the back chamber 7 to the primary port 1 and switch means 13. Therefore, switching operation of the switch means 13 permits a selection of free flow in the reverse direction from the secondary port 2 to the primary port 1, avoiding any generation of external drain.
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