| 摘要 |
A well drilling tool including a tubular member having a bore therethrough and adapted for connection in a drilling string to form a flow passage for drilling fluid and a full opening rotatable ball type bore closure means pivotally mounted with the tubular member in the bore of the tubular member for enabling desired flow down the bore of the drill string and which automatically rotates closed when incipient well pressure conditions indicate the direction of flow in the bore may be reversed. The drilling tool includes a means for releasably locking the ball in the open position in response to a predetermined directional pressure in the bore to render inoperative the automatic operation of the ball. The drilling tool may be employed by stabbing the tool in a drilling string having an upwardly flow in the bore of the drilling string to connect the tool with the drilling string for subsequently blocking the upwardly flow.
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