Abstract: A method and apparatus is provided for electromagnetically testing an elongate object such as a wire rope for cross-sectional area variations. The elongate object is magnetized over adjacent sections in opposing directions along a longitudinal axis of the elongate object. Variations in axial magnetic flux, which have been observed to be coincident with variations in the cross-sectional area of an elongate object, are measured by a plurality of non-inductive transducers. The transducers are interconnected to produce a composite signal. The composite signal is compared to a reference signal.

Abstract: A method and apparatus is provided for electromagnetically testing an elongate object such as a wire rope for cross-sectional area variations. The elongate object is magnetized over adjacent sections in opposing directions along a longitudinal axis of the elongate object. Variations in axial magnetic flux, which have been observed to be coincident with variations in the cross-sectional area of an elongate object, are measured by using saddle coils which are positioned adjacent the magnetized sections of the elongate object and which detect variations in radial flux. The saddle coils are positioned to have first half circumferential windings located where the magnetic flux density in the elongate object is at a maximum value and second half circumferential windings located where the magnetic flux density in the object is zero.

Abstract: A letdown valve for slurries under pressure is provided with a throttle 13 inside a housing 15 with interposed lubricant sealer and grooves 16 to accommodate any excess lubricant sealer. The throttle body 13 is held in place by a retaining ring 17 which is welded in position.

Abstract: A wire rope tester which can detect broken wires, area reductions, or wire contact irregularities. The tester includes two permanent magnetic stacks which produce axial adjacent and opposed DC magnetic fields which magnetize the rope. Broken wires are indicated by flux variations when the flux density is at saturation; area reductions are related to flux variations; also at saturation flux density; and wire contact pattern changes produce detachable eddy current flux variations when the flux density gradient is constant.

Abstract: A method of controlling a pair of hoist motors comprises delaying one about to raise a load while allowing the other to lower its load until a steady speed is reached, and then raising the load with the first motor. The regenerative current from the motor lowering its load at steady speed is offset against the drive current required for the motor raising its load.

Abstract: The level of a grinding charge in a grinding mill is monitored by comparing signals which are generated by means of two sensors which are located on opposed sides of an impact point of the material in the mill. A signal produced in the comparison step may be used to control the feeding of material to the mill.

Abstract: A base drive circuit for a transistor which includes a transformer with a primary winding and a secondary winding, a base drive source, and first and second diodes, the primary winding being connected to the source and to the collector of the transistor by means of the first diode, the secondary winding having a first terminal which is connected to the emitter of the transistor, a second terminal which is connected to the collector of the transistor by means of the second diode, and a tap which is connected to the base.

Abstract: High frequency welding apparatus which includes a transformer and four transistor switches. The switches and the primary winding of the transformer are connected in a self oscillating or free running bridge configuration the operation of which is load dependent. Component damage due to overload conditions is thereby prevented and the voltage rating of the components may be equal to the voltage supplied to the bridge.

Abstract: Welding apparatus and a method of producing source of welding current. Use is made of an inverter supplied with direct current from a source to pulse a center-tapped primary winding of a transformer at a frequency in excess of the audio range of frequencies, typically 10 KHz to 20 KHz. A secondary winding of the transformer has output terminals for electrical connection to an electrode and work to be welded. The operation of the inverter is controlled by means of a feedback signal derived from a winding inductively coupled to the transformer.The high operating frequency results in a significant reduction in the mass and dimensions of the welder compared to conventional welders which operate at mains frequencies.