MANUFACTURE OF PISTON ROD INTO WHICH PERMANENT MAGNET IS BURIED AND RECIPROCATING PISTON TRANSMISSION MECHANISM, WHICH HAS PISTON TO WHICH PERMANENT MAGNET MADE THROUGH SAID METHOD IS BURIED AND IS USED PARTICULARLY FOR LONG WALL TYPE MININGAPPARATUS

摘要

A piston rod 10 for a hydraulic ram has a plurality of permanent magnets 13 embedded therein. Each magnet 13 is housed within a respective metallic bush 14 within a respective radial bore 15 in the piston rod 10. Each bush 14 is made of a stainless, acid-resistant, non-magnetic steel, and has a closed outer end surface 21 which lies flush with the cylindrical surface 20 of the piston rod 10. The cylindrical surface 20 of the piston rod 10 and the closed end surfaces 21 of the bushes 14 are covered by a uniform metallic coating. A sensor fixed to the cylinder of the ram can emit electrical signals in dependence upon the movement of the piston rod including the magnets. IMAGE