Abstract: In the switchable magnet system disclosed herein, a central pole piece is backed by at least two permanent magnets having substantially different energies (Hc) so that one of the magnets is relatively switchable or reversible and the other is not. A magnetically permeable frame provides a peripheral pole face at least on either side of the central pole face and a backing plate bridging the central pole piece over the permanent magnets. A coil surrounds the first and second permanent magnets insde of the peripheral pole face. According, energization of the coil in one direction can reverse the polarization of the first magnet, thereby effectively short circuiting flux produced by the second magnet and terminating holding, while energization of the coil in the opposite direction can polarize the first magnet in parallel with the second magnet, thereby to effect holding.

Abstract: In the switchable magnet system disclosed herein, a central pole piece is backed by at least two permanent magnets having substantially different energies (H.sub.c) so that one of the magnets is relatively switchable or reversible and the other is not. A magnetically permeable frame provides a peripheral pole face at least on either side of the central pole face and a backing plate bridging the central pole piece over the permanent magnets. A coil surrounds the first and second permanent magnets inside of the peripheral pole face. According, energization of the coil in one direction can reverse the polarization of the first magnet, thereby effectively short circuiting flux produced by the second magnet and terminating holding, while energization of the coil in the opposite direction can polarize the first magnet in parallel with the second magnet, thereby to effect holding.

Abstract: In the magnetic chuck disclosed herein, a pair of elongate pole members are arranged to provide magnetic contact with a workpiece along parallel lines and thus are somewhat in the nature of rails. Preferably, the ends of the poles are segmented and provide for height adjustment to accommodate workpieces which are not entirely flat. The pole members extend along the sides of an elongate base plate with a space therebetween. Interposed between each pole member and the base member is a relatively thin layer of permanent magnetic material which resists de-magnetation. A switchable permeable magnet is provided between the pole members above the base plate and this latter permanent magnet is surrounded by a coil which allows the polarity of its magnetism to be switched so that it either aids or opposes the thin magnetic layer in polarizing the pole ends.

Abstract: In the ultrasonic bone testing apparatus disclosed herein, a pair of ultrasonic transducer assemblies are brought into contact with opposite sides of a patient's foot and each of the transducer assemblies includes, as an acoustic waveguide, a liquid filled bladder. The foot engaging end of each bladder is formed as a laterally projecting rounded cone so that, as the transducer assemblies are brought into contact with the foot, air is progressively and totally excluded from an enlarging area of contact. One or both of the transducer assemblies can be scanned with a small circular motion so that a variety of locations of the patient's foot can be sampled and the response can be analyzed.

Abstract: The eddy current separator apparatus disclosed herein employs first and second cylinders, each of which is provided with means for generating a circumferential series of radially directed magnetic poles of alternating polarity. The cylinders are mounted for rotation around parallel axes with an essentially vertical gap between them. A mixture of electrically conductive and non-conductive particles can be fed into the gap from one side. The cylinders are rotated synchronously in opposite directions with poles of opposite polarity facing across the gap, at a speed substantially higher than the speed of mixture feed. Electrically conductive non-magnetic particles are impelled by eddy currents generated by the magnetic flux projected across the gap by the faacing moving poles and can be received or collected separately from free falling non-conductive particles.

Abstract: The body member positioning apparatus disclosed herein operates to clamp a body member, such as a foot, in relation to a fixture, e.g. such as may be used for ultrasonic bone testing. A shell member is provided which conforms to the expected shape of the body member with a space therebetween, this space being filled with a compliant foam liner. An inflatable bladder or bellows operates between a stationary housing part and a movable housing part to which the shell member is attached so that, by inflating the bladder, a clamping pressure can be exerted against a body member positioned between the shell and the fixture.

Abstract: In the thread wrapping apparatus disclosed herein a binder spindle is driven by control circuit at a speed corresponding to the operating frequency of a variable oscillator. First, second and third sets of drafting rolls which draw and feed a sliver of fibers to the binder spindle are driven by respective stepper motors through control circuits which operate each of the motors at a respective speed which is an individually preselectable proportion of the speed of the spindle.

Abstract: In the magnetic chuck control disclosed herein, the chuck winding is selectively energized in one direction or the other through respective triggerable semiconductor current switching devices. Successively reducing current levels are applied in successive phases of operation, the polarity of the current being reversed in successive phases. During a first portion of each phase the device is triggered to apply a corresponding preselectable voltage. During a second portion of each phase the switching devices are triggered quite late to provide an average voltage which opposes the current flow which was induced during the first portion thereby to quickly reduce the level of current flowing in the winding.

Abstract: In the ion nitriding power supply disclosed herein, power to the discharge chamber is normally current-regulated by a pulse-width modulated current switching device effectively in series with a switching inverter which energizes the chamber, instantaneous current variations being smoothed by a series inductance which, together with the chamber, is shunted by a freewheeling diode. Incipient arcing is quickly extinguished by semiconductor switching devices incorporated in the inverter which, when energized simultaneously, shunt the chamber, instantaneous current limiting being provided by the series inductance. The shunt switching devices are triggered when the voltage across the discharge drops below a level indicative of the formation of an arc.

Abstract: The magnetic chuck disclosed herein is of the permanent magnet type in which both a top plate and a shiftable pack comprise alternating major pole pieces and magnets, the pack being shiftable so that its magnets either aid or oppose the magnets in the top plate, thereby to change between holding and release states. Improved holding for thin workpieces is obtained by providing a central region in the top plate in which the major pole pieces are thinner than the magnets and in which a plurality of floating minor pole pieces are positioned in the gaps between the major poles. While less flux is available through the thinner major pole pieces, the floating pole pieces provide an increased number of transitions for flux between top plate and workpiece so the total holding force for thin workpieces is improved.

Abstract: An electromagnet control apparatus having a remote control switch assembly switchable between a number of positions representing full, variable, residual and zero levels of magnetization. Means are provided for causing the electromagnet to be fully energized for several seconds before being dropped to the residual level of magnetization whenever the switch assembly is switched to a residual setting.

Abstract: In the lifting magnet system disclosed herein, demagnetization and releasing of a load are accomplished without switching inductively loaded d.c. power by employing a.c. energization, through respective bridge rectifiers, of entirely separate lifting and drop coils.

Abstract: Apparatus for the magnetically lifting and tilting an elongate load, e.g., a steel beam, is disclosed. The apparatus comprises a plurality of electromagnets supported in a corresponding plurality of yokes in a linear array along a beam structure. On each yoke, a stepping motor is coupled to the respective electromagnet for controllably rotating the electromagnet around a pivotal axis which is parallel to the axis of the array. The motors are synchronously operated, thereby enabling an elongate load to be lifted by the electromagnets together and tilted around the pivotal axis. In a preferred construction, each end of each yoke is suspended on a plurality of tie elements connected to a vertically compliant spring suspension system mounted on the beam structure. The tie elements are arranged to minimize swinging or misalignment of the several electromagnetic lifting elements.

Abstract: The magnetic chuck disclosed herein is of the interlocking finger type and substantial components thereof are fabricated by making parallel oblique cuts in conventional bar stock thereby to generate a succession of parallelogram-shaped pieces. A series of the parallelogram pieces are assembled with alternate pieces being reversed so that they overlap only over a common triangular area with adjacent parallelogram pieces being separated by interleaved triangular spacers. The projecting fingers provided by such an assembly may be then mated with other similar or half-similar pole-piece units to form an interlock magnetic chuck top plate.

Abstract: The integrating fluxmeter disclosed herein employs a second electronic integrator which operates during the intervals between test periods to adjust a compensating bias current, applied to the main integrator, to a value accurately canceling any residual drift. The integrating capacitor employed in this second electronic integrating circuit is of sufficient size so that the value of the compensating current does not vary significantly during a test period.