Abstract: An optical disc is disclosed having a substrate in which data can be written on or read from, such optical disc has a transparent cover sheet which is held at a desired spacing from the substrate at least at an inner radius and an outer radius. In order to prevent the transparent cover sheet from deflecting due to pressure differences between the outside atmosphere and the air in the space between the substrate surface and the transparent cover sheet, a plurality of air passages in the transparent cover sheet are provided near an inflection point where on one lateral side of the point the transparent sheet will bulge and on the other lateral side it will be depressed due to centrifugal force acting upon air entrapped between the transparent cover sheet and the substrate surface during disc rotation in an optical disc drive. This arrangement equalizes the pressure in the air space between the transparent cover sheet and the substrate surface and the outside atmosphere.

Abstract: Apparatus for optically writing information on or reading information from a disc having tracks includes a carriage moveable in a radial direction relative to the disc tracks and at least first and second optical heads spaced and mounted on the carriage; the first and second optical heads being moveable with the carriage, and at least one of the heads being pivotally mounted; and the first head being adapted to write information on a track of the disc, the second head being adapted to read information and produce a signal representative of recorded data. The apparatus further includes a structure connected to the pivotally mounted head and adapted to pivot the optical head as the carriage is displaced in the radial direction so that both the first and second optical heads are spaced from each other but aligned on the same track within the tracking ability of the head, and an arrangement responsive to the read head signal to adjust operation of first head during writing to improve the recording of data.

Abstract: An optical disc having a substrate in which data can be written on or read from, such optical disc being adapted to be inserted and clamped onto a spindle in a disc drive and having a transparent cover sheet disposed over the substrate surface. The optical disc has a perimeter ring on the edge thereof and a spacer formed adjacent to a central opening in the disc. The perimeter ring is formed with a plurality of air passages leading from the space between the transparent cover sheet and the substrate surface to the outside atmosphere and the spacer is formed with a plurality of air passages leading from the outside atmosphere to the space between the transparent cover sheet and the substrate surface. Filters are provided in the air passages in the spacer and the perimeter ring to prevent contaminants from the atmosphere from entering into the space between the transparent cover sheet and the substrate surface.

Abstract: An optical disc is disclosed having a substrate in which data can be written on or read from, such optical disc being adapted to be inserted and clamped onto a spindle in a disc drive and having a transparent cover sheet disposed over the substrate surface. The cover sheet is held at inner and outer radii so that it is positioned to have a desired spacing from the substrate to prevent contaminants from passing to the substrate surface. A plurality of air passages are formed in the optical disc to prevent the transparent cover sheet from deflecting due to pressure differences between the outside atmosphere and the air in the space between the substrate surface and the transparent cover sheet.

Abstract: A focus/tracking actuator for controlling the respective focus and tracking positions of a lens used to direct a focused beam of radiation onto a desired data track on a moving recording element comprises a pair of moving coil-type linear motors. Each of the motors comprises a coil of wire disposed in a magnetic air gap and adapted to move therein in response to an applied current flow. According to the invention, the respective masses of the motor coils are optimized to achieve maximum acceleration with minimum power comsumption. Preferably, the coils have a combined mass substantially equal to the mass of the moving payload, which includes the lens assembly and its movable support.

Abstract: A focus/tracking actuator for an optical or magnetooptical disk drive includes a pair of moving-magnet type linear motors for simultaneously controlling the focus and tracking positions of an objective lens used to focus a write/read beam on a desired data track of a rotating data storage disk. Each motor includes a pair of selectively energizable focus and tracking coils, one coil being positioned within the other so that its respective windings are perpendicular to those of the other coil. Flux lines emanating from a permanent magnet secured to a movably mounted lens housing interact with the electromagnetic fields surrounding both coils, and a single steel plate or the like, positioned inside the windings of both coils, facilitates the return of magnetic flux to the magnet while preventing such flux from cutting portions of the coils which would act to exert an undesired forces on the lens housing. Preferably, the steel plate is composed of two segments to facilitate winding of the coils about the plate.

Abstract: An actuator of the type used in interacting with optical storage media includes a lens housing coupled to a stationary member by four X cross-section flexure arms. The lens housing has coupled thereto a coil assembly which, when current flows through at least one of the component coils of the coil assembly, interacts with a magnetic structure resulting in motion of the lens housing relative to the stationary member. The lens housing, the stationary member, and the flexure arms are fabricated from two identical members. The members have structure fabricated therein which permits the accurate positioning of the identical members during assembly. The flexure members have generally orthogonal thin regions which determines the motion of the lens housing relative to the stationary member. The coil assembly includes rectangular coils which are easily fabricated and conveniently assembled.

Abstract: In a disk player/recorder apparatus, a radial access mechanism is disclosed in which a first guide rod is positioned on a mounting plate accurately with respect to the information storage medium. A head assembly engages the first guide rod through bushings which provide stringent tolerance requirements. The position of the head assembly is accurately controlled by the position of the first guide rod and the tolerances on the bushings. A second guide rod coupled to the mounting plate and a single bushing also supports and guides the head assembly, however, the tolerances on the components associated with the second guide rod are less stringent. Coupled to each of the guide rods is a bracket with a permanent magnet coupled thereto. The permanent magnets interact with the coils of linear motors coupled to the head assembly. The linear motors are arranged to minimize torque on the head assembly. The brackets and the guide rods form magnetic circuits for the associated permanent magnets and linear motors.

Abstract: A magnetic field bushing has a movable member and stationary rod. The stationary rod has high permeability strips of magnetic material forming a portion of the surface. The stationary rod further includes at least two sets of coils, the magnetic field resulting from application of a current to each coil being coupled to a strip. The movable member is configured to encircle substantially the stationary rod. The movable member has regions of high permeability magnetic material which are positioned on the movable member to complete a magnetic circuit with related magnetic strips. The magnetic circuits are completed through air gaps between the movable member regions and the stationary rod strips. The magnetic field in the air gaps results in a force between the movable member regions and the stationary rod strips. Forces are generated between the movable member and the stationary rod, the forces being selected to prevent contact between the movable member and the stationary rod.

Abstract: A low-profile radial access mechanism for controlling the radial position of a read/write head relative to a rotating data storage disk (e.g. optical, magneto-optical and magnetic disks). Such mechanism has a carriage (10) which supports a plurality of bearings (11) on its opposing sides. The bearings engage a pair of space parallel rods (21, 31) to guide the carriage along a rectilinear path. Each rod is made of a ferromagnetic material and forms part of the flux-carrying structure of one of a pair of separate electromagnetic linear motors (20, 30). One of the two flux-carrying structures is movable relative to the other to preload the bearings against the guide rods. According to a preferred embodiment, the pair of linear motors share the windings of a single coil (22) carried by the carriage, such windings being physically distributed as to accommodate an exact constraint arrangement provided by the bearings.

Abstract: Disclosed herein is a linear actuator for controlling the movement of a payload along a linear trajectory. Such actuator is particularly useful, for example, in controlling the radial position of a write/read head in an optical or magnetic recorder/player. The actuator comprises a simple elongated ferromagnetic member, preferably having a substantially triangular cross-section. Such member is surrounded by a coil to which a payload-bearing carriage is rigidly connected. Bearing devices are provided for slidably mounting the carriage for movement on and along the ferromagnetic member. A plurality of magnets serve to establish a magnetic field through which the coil, upon applicaiton of a current, is advanced along the ferromagnetic member. The ferromagnetic member serves the dual function of conducting magnetic flux and guiding the payload along the linear trajectory.

Abstract: A stepper motor is disclosed which is comprised of planar elements. The motor comprises a disc-shaped rotor which includes a multipolar permanent magnet and generally planar stator coils mounted on opposite sides of the rotor. In order to provide a stepper motor which is efficient and is also relatively thin in the axial direction, generally planar pole plates having radially extending teeth are used to define the magnetic poles of the stator.

Abstract: Apparatus for controlling the radial position of a transducer (e.g. an optical, magneto-optic, or magnetic write/read head) relative to a spinning disk (e.g. a data storage disk) comprises a transducer-supporting radial access arm which is mounted via a rotary bearing for pivotal movement about a spinning support shaft. The continuous rotary movement of the support shaft dramatically reduces stick-slip friction in the bearings separating the support shaft and the access arm, thereby reducing start-up torque and enabling more precise positioning of the transducer relative to the disk. Moreover, it prolongs the life of the rotary bearing in that it eliminates so-called Brinelling (wearing of the bearing balls or rollers due to small oscillations about the same point).

Abstract: Radial access apparatus for controlling the coarse and fine radial position of a read/write head relative to a data storage disk (e.g. optical, magneto-optical and magnetic disks) comprises a radial access arm supported for movement about a virtual pivot point by a pair of converging flexure members. An electromagnetic motor is provided for controlling the position of the arm to position a read/write head, supported by such arm, opposite a desired data track on the disk.

Abstract: A radial access mechanism for translating, for example, the optical read/write head of an optical recording/playback apparatus relative to a rotating data storage disk to position such head adjacent a desired data track. Such mechanism basically comprises a stationary guide member defining a segment of a circular path, a roller having a head-supporting access arm rigidly coupled thereto, and means for causing the roller to roll, without slipping, on the inside of the circular path defined by the guide member. By virtue of its design, the mechanism inherently functions to translate the head along a hypotrochoidal trajectory.

Abstract: Map display apparatus for travelers and drivers presenting geographical regions (the world, continents, countries, states, cities, etc.) as a combination of sequential zones illustrated on pocket size cards with each zone repeated four times for North, East, West, and South (N E W S) orientation. It is supplemented by a set of accessories for tracing directions in an erasable or washable form with a provision for card's multiple usage and a portable holder for their storage.

Abstract: A method of manufacturing large gears by performing all steps required on a single vertical boring mill without removing the gear blank from the rotary table of the mill.