| 摘要 |
A valve assembly for use in an inner tube member of a core barrel head assembly positionable within a drill string of a drilling apparatus. The valve assembly works using two separate surfaces A and B and a biasing element with a force FS. When hydrostatic pressure is present forces are created on these surfaces: FA and FB. These forces have a direct relationship with pressure, as an increase in pressure will increase the force and vice versa. The surface areas are designed such that: FA > FB + FS , which will maintain the valve closed while under a pre determined fluid pressure, indicating to the driller that the inner tube has landed. When the driller relieves the fluid pressure and the pressure decreases, the force difference between FA, FB and FS decreases until FA < FB + FS, thus opening the valve for drilling. |
