# US 8,345,402 B2 · Degaussing apparatus with highly uniform magnetic field > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,345,402 B2 - Document ID: US8345402B2 - Status: Granted - Kind: B2 - Application number: 12/707,951 - Filed: 2010-02-18 - Published: 2011-08-18 - Granted: 2013-01-01 - Earliest claimed: 2010-02-18 - Assignees: Data Security, Inc. - Inventors: Robert A. Schultz - Web page: https://patentgrep.com/patent/US8345402B2 ## CPC - G11B 5/0245: {Bulk erasing} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract Generation of an intense magnetic field to erase high coercivity magnetic media uses delivery of energy to a degaussing cavity. To conserve energy storage and delivery requirements and to obtain a desired magnetic strength generally uniformly within the cavity, strategic placement of supplemental turns at ends of the magnetic field generating coil wound around the cavity can promote uniformity. Construction of at least cavity ends from an adequate quantity of magnetically soft ferrous material can also promote uniformity. A combination of both approaches is possible. ## Claims ### Claim 1 An apparatus for applying a magnetic field to a data storage device, the apparatus comprising: a frame sized to accommodate a target device, the frame defining a first end and a second end; a coil comprising: a first layer extending between the first end and the second end, a second layer consisting of a first coil portion at least in part overlapping the first layer at the first end and a second coil portion at least in part overlapping the first layer at the second end; a first soft ferrous member disposed at least partially in the coil at the first end of the frame; a second soft ferrous member disposed at least partially in the coil at the second end of the frame. ### Claim 2 (depends on 1) The apparatus of claim 1 wherein the coil comprises a single wire. ### Claim 3 (depends on 1) The apparatus of claim 1 further comprising a tray configured to slidably engage the frame, wherein the tray comprises stainless steel bottom and sides and wherein the first soft ferrous member is disposed at a first end of the tray. ### Claim 4 (depends on 3) The apparatus of claim 3 comprising an actuation member connected to the tray and configured to engage a switch, the switch configured to allow electrical operation of the coil when engaged by the actuation member. ### Claim 5 (depends on 1) The apparatus of claim 1 wherein the first ferrous member and the second ferrous member comprise at least one of steel or stacked laminations of silicon steel. ### Claim 6 A method comprising: receiving a target device in a frame sized to accommodate the target device, the frame defining a first end and a second end; applying a current to a coil disposed around the frame, the coil comprising: a first layer extending between the first end and the second end, a second layer consisting of a first coil portion at least in part overlapping the first layer at the first end and a second coil portion at least in part overlapping the first layer at the second end; whereby the coil applies a substantially uniform magnetic field to the target device. ### Claim 7 (depends on 6) The method of claim 6 wherein a first soft ferrous member is disposed at least partially in the coil at the first end of the frame and a second soft ferrous member disposed at least partially in the coil at the second end of the frame such that the applying a current to the coil. ### Claim 8 An apparatus comprising: a means for receiving a target device in a frame sized to accommodate the target device, the frame defining a first end and a second end; a means for applying a current to a coil disposed around the frame, the coil comprising: a first layer extending between the first end and the second end, a second layer consisting of a first coil portion at least in part overlapping the first layer at the first end and a second coil portion at least in part overlapping the first layer at the second end. ### Claim 9 (depends on 8) The apparatus of claim 8 further comprising a first soft ferrous member disposed at least partially in the coil at the first end of the frame and a second soft ferrous member disposed at least partially in the coil at the second end of the frame. ### Claim 10 An apparatus for applying a magnetic field to a data storage device, the apparatus comprising: a frame sized to accommodate a target device, the frame defining a first end and a second end; a coil comprising a first layer extending between the first end and the second end, a first soft ferrous member disposed at least partially in the coil at the first end of the frame; a second soft ferrous member disposed at least partially in the coil at the second end of the frame. ### Claim 11 (depends on 10) The apparatus of claim 10 further comprising a tray configured to slidably engage the frame, wherein the tray comprises stainless steel bottom and sides and wherein the first soft ferrous member is disposed at a first end of the tray. ### Claim 12 (depends on 11) The apparatus of claim 11 further comprising an actuation member connected to the tray and configured to engage a switch, the switch configured to allow electrical operation of the coil when engaged by the actuation member. ### Claim 13 (depends on 10) The apparatus of claim 10 wherein the first ferrous member and the second ferrous member comprise at least one of steel or stacked laminations of silicon steel. ### Claim 14 An apparatus for applying a magnetic field to a data storage device, the apparatus comprising: a frame sized to accommodate a target device, the frame defining a first end and a second end; a coil comprising: a first layer extending between the first end and the second end, a second layer consisting of a first coil portion at least in part overlapping the first layer at the first end and a second coil portion at least in part overlapping the first layer at the second end. ### Claim 15 (depends on 14) The apparatus of claim 14 wherein the coil comprises a single wire. ### Claim 16 (depends on 14) The apparatus of claim 14 further comprising a tray configured to slidably engage the frame, wherein the tray comprises stainless steel bottom and sides. ### Claim 17 (depends on 16) The apparatus of claim 16 comprising an actuation member connected to the tray and configured to engage a switch, the switch configured to allow electrical operation of the coil when engaged by the actuation member.