| 摘要 |
1,213,598. Core drills. BROWN BOVERI & CO. Ltd. 3 June, 1969 [5 June, 1968], No. 27924/69. Addition to 1,201,585. Heading B3C. A core drill comprises a hollow shaft 3, hard metal cutter blades 35-38, secured in recesses 15-18, by clamps 20, 25, and arranged at different radial distances from the drill axis, and radially inwardly directed projections 91- 94 which will intercept uncut metal of the core 11 if the inside of a cutting edge of one of the blades is fractured, so that the drill is not damaged. External projections 98-101 are also provided, which protect the drill if the outside of a cutting edge is fractured. The drill is guided on the core 11 by studs 104-107 which are adjustably screwed into the hollow shaft 3 of the drill. In operation, if a cutter blade fractures, projections 91-94, or 98-101 abut the uncut portion of the workpiece and provide a sudden load increase on the drill, which increase causes a thermal trigger to switch off the drive motor of the machine. Oil under pressure in pockets 82 provides a hydrostatic cushion for the drill. |
