| 摘要 |
A sealing structure for a rock drill bit includes an elastomeric diaphragm (12) for installation in the drill bit (fig 3) to separate grease from drilling mud. The diaphragm (12) has an aperture (24) extending though it and a plug (14) disposed in the aperture (24) so as to form a mechanical seal with a wall (25) of the aperture (24). The plug (14) has a channel (36) therethrough which is normally sealed by a face (25) of the aperture (24) in the diaphragm (12). If the pressure of the grease exceeds the pressure of mud on the other side of the diaphragm (12) by more than a critical value, the diaphragm aperture (24) deforms and allows grease to move though the plug channel (36) and escape. The critical value can be varied by using, with the same diaphragm, plugs having different numbers, sizes and axial positions of plug channels. |
