Abstract: A large electric dragline having a housing (35) and boom (37) is provided with spaced apart in-line sheaves (34) and (36) at boom point to separate hoist ropes (31) and (32) which are led to the front and rear of bucket (30) respectively. Differential hoist rope control allows accurate and continuous adjustment of the bucket carry angle during all modes of operation. Also described is a computer control system giving continuous accurate control of carry angle by differential hoist rope operation, with manual selection of mode of operation.

Abstract: A fluid drilling head has a plurality of nozzles (3, 4, 5, 6) in a rotatable nozzle assembly (2) to provide high pressure cutting jets (7). The head is provided with a gauging ring (10) having an annular clearance (11) to the rotatable nozzle assembly (2) to provide for the passage of rock particles eroded by the cutting action of the jets (7) while regulating the progress of the drilling head in the borehole and controlling drill stalling. A stepped rotatable nozzle assembly having a smaller diameter portion (8) and a larger diameter portion (9) to extend the cutting zone of a reaming jet closer to the outer diameter of the gauging ring (10) is also described and claimed.

Abstract: A method of controlling the dump position of a dragline (1) of the type where inclination of the bucket (4) is controlled by differential control of the front hoist rope (7) and the rear hoist rope (8), in order to control dumping too close to the dragline house (2) in a position where the bucket will not release all the load and where slackness in the front hoist rope can cause fouling and serious damage. The complex locus of rear hitch positions (14) that will result in an acceptable dump angle at the bucket when dumped, is empirically transposed to a locus of rear hitch positions (15) at a typical carry angle before dumping, which is in turn approximated by a vertical cylindrical envelope (16). Calculation of when the rear hitch position (13) reaches the envelope (16) may be easily performed by a computer in real time using available parameters such as rear rope inclination and payout values.