Abstract: An apparatus for erasing information recorded on a magnetic tape wound into a roll having a diameter. The apparatus comprises an erasing coil wound in the form of a solenoid defining a space therein. The space has a width shorter than the diameter of the magnetic tape roll and a length longer than the diameter of the magnetic tape roll. The magnetic tape roll is moved intermittently to different erasing positions in a predetermined sequence so that the magnetic tape roll has different portions placed in the space at the respective erasing positions. A ringing signal is applied to the erasing coil to provide a magnetic field in the space for erasing information recorded on the magnetic tape roll each time the magnetic tape roll is placed at one of the erasing positions.

Abstract: A closed-loop multi-sensor control system for controlling ship signatures positions away from local sensors used to direct local signatures controllers by controlling a field variable signature through local onboard sensors and active coil elements by determining a transfer matrix between discrete local and midrange field values, said determination being based upon virtual sources, M, and control parameters (coil currents) I wherein:M=(M.sub.X1,M.sub.Y.sup.1,M.sub.Z1,M.sub.Z2. . . M.sub.ZX) and I=(I.sub.1,I.sub.2, . . . I.sub.M),wherein local signatures H=A.sub.H I.sub.O +B.sub.H M and wherein midrange signatures K=A.sub.K I+B.sub.H M and wherein the ultimate solution for the coil currents for optimum degaussing is:I=-(A.sub.K.sup.T A.sub.K).sup.-1 A.sub.K.sup.T B.sub.K (B.sub.H.sup.T B.sub.H)..sup.1 B.sub.H.sup.T (H-A.sub.H I.sub.O)=G H.sub.

Abstract: A split core degaussing coil loop having a segmented and disassembled loop portion that is joined together to include an object to be demagnetized, in situ, as part of the assembled core loop and further having an inductor coil assembled with the loop that is selectively energized in one or more steps from a source of electrical power which generates a demagnetizing force directed to the object.

Abstract: A camera arranged to use a film having a magnetic storage part comprises a magnetic head which is arranged to demagnetize a signal pattern previously recorded in the magnetic storage part of the film; and a control circuit which causes the magnetic head to demagnetize the signal pattern previously recorded in the magnetic storage part with a predetermined demagnetization pattern of a frequency lower than the frequency of the signal pattern and to form information to be recorded in the magnetic storage part of the film in the shape of the demagnetization pattern.

Abstract: A compensating coil for a scanning electron beam display such as a color television tube reduces undesirable deflection of the electron beams due to ambient magnetic fields, in particular the geomagnetic field. A first coil section has at least one winding disposed to encircle the tube neck, perpendicular to the Z axis. Upper and lower coil sections are disposed above and below the first coil section, each inclined forwardly along the Z axis and having a loop encompassing an area extending in the X and Y directions generally following the surface of an internal magnetic shield. The coil sections are coupled in series. The upper and lower coil sections have a wider X axis dimension proceeding forwardly along the Z axis, being keystone shaped. Lateral lengths of the upper and lower coils sections connect to the first coil section at lateral sides, such that the compensating coil is a continuous winding. The first coil section may have two passes for each pass of the upper and lower coil sections.

Abstract: An apparatus for use with magnetically based electronic article surveillance systems employing certain types of markers includes a hollow core having a gap in its perimeter, a coil of wire wrapped around a portion of the core, and appropriate circuitry to drive the combination as an electromagnet. The gap configuration produces an external field of large intensity but limited range, such that the magnetizable portion of a marker is magnetized without affecting magnetic states of the article to which the marker is affixed. Depending on the nature of the circuit, the apparatus may be used as a desensitizer of such markers, or preferably as a resensitizer. The resensitizer incorporates a proportional-integral controller that keeps the level of the alternating current constant.

Abstract: Apparatus for characterizing the magnetic field of a device under test includes a device for nullifying the ambient magnetic field in a test environment area with a constant applied magnetic field, a device for rotating the device under test in the test environment area at least nearly through a complete circle, a device for sensing the magnetic field at a sensor location which is along the circumference of rotation as a function of the rotation angle for successive ones of a set of predetermined orientations of the device under test to obtain a profile of the magnetic field at the sensor location as a function of the rotation angle for each one of the predetermined orientations, a memory for storing the profiles, and a processor coupled to the memory for characterizing the magnetic field of the device from the magnetic field profiles thus obtained.

Abstract: A magnetic recording medium such as a magnetic recording tape or disk is demagnetized by applying a saturating magnetic field to the magnetic recording medium, then applying an unsaturating magnetic field to the magnetic recording medium in a direction opposite to the direction of the saturating magnetic field, and finally applying an alternating magnetic field to the magnetic recording medium to remove residual magnetism which has been produced on the magnetic recording medium by the unsaturating magnetic field. The saturating, unsaturating, and alternating magnetic fields are generated respectively by a first DC erasing head, a second DC erasing head, and an AC erasing head, which are arranged at spaced intervals in the order named in the direction in which the magnetic recording medium is continuously moved.

Abstract: Noise in the readback signal of a magnetic recording device resulting from spurious pulses in the readback signal produced by transitions of the magnetic remanent state of the yoke in the read/write transducer is eliminated by controlling the occurrence of the spurious pulses. Immediately following the completion of the write process, a decreasing amplitude alternating current is applied to the read/write coil of the transducer to drive the yoke remanent state to a stable or zero remanent state prior to the commencement of the read process.

Abstract: A magnetic recording medium such as a magnetic recording tape or disk is demagnetized by applying a saturating magnetic field to the magnetic recording medium, then applying an unsaturating magnetic field to the magnetic recording medium in a direction opposite to the direction of the saturating magnetic field, and finally applying an alternating magnetic field to the magnetic recording medium to remove residual magnetism which has been produced on the magnetic recording medium by the unsaturating magnetic field. The saturating, unsaturating, and alternating magnetic fields are generated respectively by a first DC erasing head, a second DC erasing head, and an AC erasing head, which are arranged at spaced intervals in the order named in the direction in which the magnetic recording medium is continuously moved.

Abstract: Auto transformer supplying current to the object to be demagnetized (chuck), this current controlled by an ON set of transformers, and a DEMAG set of transformers. Each set includes a pair of secondaries providing pulsating current for respective half cycles of AC, of opposite polarity. The opposite polarity of pulsating current is produced in intervals of decreasing time and voltage, until the magnetism in the object is at or near zero. The control transformer sets are controlled by a unit establishing selected values of voltage, that voltage controlling a cross-over unit which includes transistors, which in turn control the intervals of the control transformers. A CMOS oscillator circuit, with an oscillator chip, including NAND gates, effects alternate energization of the control transformers.

Abstract: A device for treatment of ferromagnetic materials comprising means for developing a magnetic field of a selected intensity, duration, and cycle, which field is passed through materials to be processed, such as cutting tools and drill bits that have been sharpened or resharpened and other parts that have internal stresses. The magnetic field through the material provides stress relief of the stresses from welding, forming, heating cooling or sharpening or loading. The treatment increases surface wear resistance, decreases the coefficient of friction on the surfaces that are so treated, and increases the strength and modulus of elasticity. In certain types of materials, an increase in the surface concentration of such alloying metals such as wolfram, molybdenum, and tungsten, as well as oxygen and carbon is achieved. The structure comprises a coil and a controlled source of electrical power that generates a magnetic field for achieving the desired results.

Abstract: An apparatus for demagnetizing parts after they have been subjected to the action of a magnetic field having coils (1,2) connected to an a-c power supply source and disposed one inside the other at one and the same angle with respect to a trough (3) extending through the inner coil. The coils (1,2) are mounted in such a manner that the angle (.alpha.) therebetween can be adjusted.

Abstract: A mechanically driven linkage causes a magnetic field acting on the object to be pulsed by alternately permitting and preventing a magnetic field from acting on the object during selected periods of time to relieve stress in the object or otherwise treat the object. Connections for applying a current through the object being treated are provided so that at the same the magnetic field is acting on the object a current added to affect the intermolecular structure of the object for various beneficial effects in treating. The current intensity and time cycle can be varied as desired and can be synchronized with the application of the magnetic field. Simple mechanical drives are used to selectively move the object or the magnetic field source, or to place a magnetic shield to block the field for selected periods of time, while permitting the magnetic field to act upon the object at other periods of time.

Abstract: First and second capacitors are charged prior to a degaussing interval. A first switch couples the first capacitor to a degaussing coil to initiate the degaussing interval. The first capacitor and the degaussing coil form a resonant circuit that resonates to generate a decaying degaussing current. During a predetermined portion of each cycle of the degaussing current, a second switch couples a precharged second capacitor in parallel with the first capacitor to form a charge transfer arrangement that transfers charge from the second to the first capacitor for replenishing energy losses in the first capacitor. The charge transfer arrangement increases the duration of the time it takes to the amplitude of the degaussing current to decay and, hence, the length of the degaussing interval.

Abstract: A magnetic material degausser in which the material to be degaussed is placed within the center of a degaussing coil. A capacitive discharge system is employed for energizing the degaussing coil. The capacitor is repeatedly discharged through the coil in such a way that for at least a portion of the degaussing cycle, the energy applied to the coil decreases with each energization. The magnetic material may be rotated within the coil as the degaussing cycle progresses. In one embodiment of the present invention, the energy discharged from the capacitor first increases and then decreases during the degaussing cycle with each energization of the coil. The rotational speed of the magnetic material within the coil may be related to the frequency at which the capacitor is discharged.

Abstract: The item to be demagnetized is placed in a chamber surrounded by electrical windings defining a pair of coils that are disposed in a mutually orthogonal configuration. Currents for the two coils are developed in a microprocessor-controlled inverter circuit and are applied through semiconductor switches in such a way that the resulting demagnetizing field is rotating and follows a predetermined amplitude variation in accordance with one or more profiles stored in the memory of the microprocessor.

Abstract: A dual-function circuit is provided which may be used to both magnetically bias and alternately, quickly degauss a magnetic device. The circuit may be magnetically coupled or directly connected electrically to a magnetic device, such as a magnetostrictive transducer, to magnetically bias the device by applying a d.c. current and alternately apply a selectively damped a.c. current to the device to degauss the device. The circuit is of particular value in many systems which use magnetostrictive transducers for ultrasonic transmission in different propagation modes over very short time periods.

Abstract: A demagnetizing power source for producing an attenuation alternating field to demagnetize a magnetized substance. This power source is provided with a memory circuit for sending actuating signals to a polarity changing-over circuit to change over the polarity of direct current supplied from a rectifying circuit to an exciting coil. In the memory circuit are stored a plurality of preset demagnetizing patterns. The polarity changing-over circuit changes over alternatively the polarity and gradually decreases the change-over cycle according to the selected demagnetizing pattern.

Abstract: An electronic current control device for energizing and de-energizing an electromagnet, such as a magnetic chuck, includes a DC power source preferably in the form of a phase-controlled SCR power unit. A conduction angle control signal is routed to positive or negative gates in the power unit to determine polarity and amplitude of direct current through the electromagnet windings. In the "on" mode an analog current feedback loop maintains a predetermined magnetizing level of current through the windings. In the demagnetize mode, a digital system decreases the current amplitude stepwise while alternating the polarity. When the sensed current attains the selected peak level for a given step, a digital count is decremented. The polarity is reversed according to the odd or even count, and a new peak reference level is established corresponding to the digital count.

Abstract: A process for demagnetizing components by subjecting them to the influences of the alternating magnetic field of a coil supplied by an oscillator circuit which includes a capacitor also includes providing a voltage supply to the oscillator at the resonant frequency and thereafter reducing the intensity of the alternating field acting on the components. This can be done in several ways, such as by varying the frequency of the supply voltage or by varying the capacitance connected in circuit with the coil. The process may also be used for calibrating permanent magnets.

Abstract: A demagnetizing device for a cassette tape player includes a cassette shell which defines a generally oval-shaped guide track extending around the interior of the shell. A magnet assembly is provided with shafts which fit within the guide track such that the magnet assembly is free to rotate within the guide track and to translate along the length of the guide track. The magnet assembly is rotated by a drive belt which in turn is driven by two hubs rotatably mounted in the cassette shell. An automatic shutoff lever is disclosed which acts automatically to shutoff a tape player equipped with automatic shutoff features when the magnet assembly reaches one of two predetermined positions on the guide track. By properly positioning the guide track, the single magnet assembly can be used to demagnetize multiple components of a tape player distributed around the cassette shell. For example, the single magnet assembly can be used to demagnetize two capstans and a tape head in a single operation.

Abstract: A pair of demagnetizing coils, or more than two, and the article to be demagnetized is put in the coils. The demagnetizing is done by reversing the polarity in a series of steps in a cycle, and the current reduced in successive steps, to a point at or near zero. The cycle can be varied as to time period, and the number of steps within a cycle varied. The applied initial voltage can be adjusted or predetermined as to maximum value, with corresponding current values, and the number of steps predetermined within the cycle independently of the maximum voltage. The apparatus can be set in manual mode, wherein the cycle timer period and number of steps can be independently set, and to automatic mode, wherein the cycle time and number of steps are directly correlated.

Abstract: A method for demagnetizing an automobile is disclosed in which the terrestrial magnetism is detected by a direction-detecting sensor and the running direction of the automobile is indicated in response to a signal produced from the direction-detecting sensor. The distortion of the magnetic field caused by the permanent magnetism of the magnetic materials of the whole body of the automobile is erased by placing the automobile in an AC magnetic field which gradually increases from zero to a predetermined intensity and then gradually decreases to zero, and thereafter the direction-detecting sensor is mounted at the magnetic center of the automobile.

Abstract: A nonelectric magnetizer and demagnetizer in the form of three flexible permanent magnets, approximately crescent U shaped, each having only one same magnetic pole on its main curved in surface and the opposite magnetic poles on their main curved out surfaces, with two of the flexible permanent magnets pliably mounted on one backing, having their curved in surfaces angularly facing each other, and the other magnet mounted on a separate backing manually movable so that the three magnets can form an adjustable air gap from substantially all directions within which a workpiece can be inserted and withdrawn to be magnetized, and the curved outside of the single magnet capable of demagnetizing various workpieces.

Abstract: An electromagnet for degaussing a magnetic head and which includes a yoke having a gap and one or more coils wound thereon is characterized by the middle portion of the yoke face, at and adjacent to said gap, being wider than the magnetic tape that passes by the magnetic head, and by the side portions of said yoke face, away from said gap, being narrower than the tape.

Abstract: A degaussing circuit for a color television receiver, in which the degaussing coil is in series with a PTC thermistor to which an NTC thermistor is thermally coupled and which is at the same time a protection resistance for a supply voltage circuit in the receiver.

Abstract: Demagnetizing methods and apparatus are provided in which a pipe, tube, rod, bar or other elongated part to be demagnetized is moved through the coil assembly to which pulses of current are applied to produce magnetic field pulses of alternating polarity and of substantially constant durations and magnitudes with a substantially constant repetition rate, each current pulse being effective to produce by the end thereof a reversal of the magnetic field in all portions of the part positioned within the confines of the coil assembly and immediately adjacent thereto, the part being moved longitudinally through the coil assembly at a velocity sufficiently low as to effect demagnetization of all portions of the part. The duration of each current pulse is at least 50 milliseconds and most preferably on the order of 0.5 seconds and the velocity of movement is preferably less than two feet per second.

Abstract: A magnetic bulk eraser for erasing a cassette magnetic recording tape. A pair of parallel magnetic disks have alternating magnetic poles around their peripheral surface. The disks are mounted facing each other, and are so aligned that the facing poles are similar, e.g. North faces North, and South faces South. A guide slot through which a cassette magnetic tape may be passed is provided between the magnet disks. A holder having a cassette magnetic tape to be erased moves linearly through the guide slot engaging a rack with pinions. When a handle is rotated manually, the magnetic disks rotate and provide an alternating magnetic flux in the guide slot through which a cassette magnetic tape passes, also driven by the manually operated handle.

Abstract: A demagnetizer for a magnetic head for a recording/reproducing device. The demagnetizer includes an electromagnet for producing an alternating magnetic field which gradually decreases in intensity. The demagnetizer is mounted in a case formed in the shape of a tape cassette. The electromagnet is resiliently held within the case adjacent to the opening for the magnetic head to be demagnetized. The electromagnet is energized by an oscillating drive circuit, the output of which is controlled by a capacitor.

Abstract: A process for thermally treating synthetic diamond grains to eliminate magnetism thereof and a diamond grain product obtained by the process, which is suitable for manufacturing electrodeposited diamond tools.