| 摘要 |
<p>An activating mechanism for controlling the operation of a downhole tool and which comprises: a hollow main body (11) adapted for mounting in a drill-string and through which fluid to the tool can be routed; an actuating sleeve (12) defining a through-flow passage and slidably mounted in the main body (11) for movement between positions corresponding to a through-flow mode and a by-pass mode of the mechanism; biasing means (15) acting on the sleeve (12) to urge it to its position corresponding to the through-flow mode of the mechanism; a seat (13) providing access to said passage in the through-flow mode of the mechanism; and a deformable activator (50) capable of being launched down the drill-string to engage the seat (13) and thereby cause pressure upstream of the seat to increase so that the activator (50) moves the sleeve (12) to its position corresponding to the by-pass mode of the mechanism; in which the activator (50) and the seat (13) are arranged to co-operate with each other, when the activator (50) engages the seat (13), in such a way that restricted flow of fluid through the sleeve (13) is maintained when the mechanism is in its by-pass mode.</p> |
