| 摘要 |
There is disclosed a downhole tool for generating a longitudinal mechanical load. In one embodiment, a downhole hammer (10) is disclosed which is activated by applying a load on the hammer and supplying pressurised fluid to the hammer. The hammer includes a shuttle valve (14) and a piston (16) that are moveable between first and further positions, seal faces (18, 20) of the shuttle valve (14) and piston (16) being released when the valve and the piston are in their respective further positions, to allow fluid flow through the tool. When the seal is released, the piston (16) impacts a remainder of the tool to generate a mechanical load. The mechanical load is cyclical by repeated movements of the shuttle valve (14) and piston (16).
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