Disk recording device and method of fabrication

Abstract: A disk type of magnetic recording device (1) having a support plate (3) in which parts (11), normally separately fabricated and separately attached to the support in assembling the device, are simultaneously outsert molded on the support (3) by clamping the support (3) which has openings therethrough where parts (11) are to be secured, between upper and lower sections (M1, M2) of a mold, each mold section (M1, M2) having cavities (11b, 11c) defining part (11) configurations and/or attach flanges (11c), and thereafter outsert molding the parts (11) by injecting a fluid plastic material such as polycarbonate, into the mold, completely filling the cavities (11b, 11c). Indexing of the support plate (3) in the mold is accomplished, using as a reference at least that opening through the support whereat an actuator spindle or mount (7b) is to be secured, and preferably additionally referencing indexing an opening through the support plate used for mounting the disk spindle (5c). Preferably the disk spindle support plate opening and/or an actuator mount opening through the support plate are used for indexing the support plate in the mold. The support plate openings at the locations of the outsert molded parts may be circular, rectangular, or of any suitable configuration in planform, to secure the molded parts against angular displacement. The location of mold cavities (11b, 11c) for parts having a functional association with the actuator (7) is also necessarily referenced at least to that opening through the support plate whereat an actuator spindle (7b) or other actuator support is to be secured and preferably additionally referenced to an attach point of the disk spindle (5c) opening.

Description: Technical Field This invention relates to disk type recording devices and methods of fabrication thereof employing outsert molding. Background of the Invention Disk type recording devices, whether magnetic, magneto resistive or optical types, are high precision devices requiring the precise location and support of parts which interact in the positioning of a transducer head for recording or reading purposes. The recording devices are fabricated and assembled in a clean environment and require a clean environment in which to function. Fabrication techniques for both fabricating either a floppy disc drive or a hard disc drive usually involve the fabrication of individual parts, and in some instances pieces of parts, and thereafter their assembly in a clean environment upon a chassis, such as a base or a support plate. The use of fasteners, such as screws, rivets, swaged connections, etc., or adhesives, to join numerous parts, requires extreme care that location errors due to fabrication tolerances do not occur. These techniques can be seen in U.S. Patent 4,825,315 to Hirose, Sony patent EP-A-0,348,165, Fujitsu Patent EP-A-0,253,626, and Tokico (an abstract of an unexamined Japanese patent application Kokai-no.01-162,287). Sony patent EP-A-0,348,165 is to be considered the starting point for the present invention and the appended claims have been characterized in view of its teachings. The application of fasteners or adhesives to such parts and the use of tools on the fasteners, can damage the fasteners and/or the parts, or cause their mislocation. Particles form part and/or fastener damage, or adhesive contamination, may contaminate the clean environment and may be the cause of poor yields or the malfunction of the recording device at a later date. Fabrication and design techniques for improving recording devices with respect to performance, reliability, longevity and cost reduction have been under investigation since the introduction of these devices. Accuracy in recording and playback, or readback, and, in some applications, together with increasing recording density, have placed increasing and unyielding demands on precision in product fabrication using conventional assembly techniques. Summary of the Invention This invention presents a significant departure from practiced design and fabrication techniques in recording devices, achieving precision in repeatability of part fabrication and location, together with a reduction in part count, inventory, and assembly operations, to the end of obtaining an improved product which costs less to manufacture. Outsert molding techniques are employed in fabricating the improved recording device. To provide an explicit and enabling description of the present invention and to present the presently known best mode for its practice, the invention is described in connection with a rotary actuator type of magnetic disk memory drive or file. The invention's application to the fabrication of other types of recording devices has been noted hereinabove and will be readily apparent to those skilled in the design and fabrication of such devices. In recording devices, having a rotatably mounted disk or stack of disks, on which recordings are made in radially spaced tracks, which are either spiral or concentric, transducers for recording and/or reading, or playback, of disk recordings, and an actuator for radially moving and positioning the transducers over a recorded track, precision is required in the positioning of parts with respect, at least, to the axis of rotation of the disk(s). In accordance with the present invention, a support on which the disk(s), the actuator, and related parts are mounted, usually a base or a support plate, is fabricated. Openings are provided through the support plate in locations relative to the axis of rotation of the disk(s) and for securing parts such as those which function as actuator mounts, crash stops, for example. Printed circuit board mounts, electrical connector mounts and other parts not related to actuator movement and positioning are positioned in accordance with spatial availability in locations compatible with functional requirements. The support plate is indexed, secured and sealed between the bodies of a split mold which forms cavities on each side of the support for defining the configuration of the part on one or both sides of each opening in the support plate, when the mold material is injected, and for securing and sealing the part on the support through and in the opening. In particular, but without limitation, parts requiring high precision in location and configuration, and in repeatability in such requirements, are advantageously fabricated by this method. Crash stops configured to establish the limits of movement of the actuator and, hence, the transducer(s) between inner and outer radial limits on the disk, crash stop mounts for preloaded crash stops, actuator latch structures, actuator mounts for linear actuators, are typical examples of parts which can be formed by this technique. Other parts or features of lesser criticality with regard to configuration or location, include electrical connectors, filter pockets, flex circuit supports etc., are also advantageously outsert molded. All of the holes in the support plate used to secure the plastic parts or features are sealed on both sides of the support by the plastic base of a part on one face of the support and a flange on the opposite face or by the base of another integral part, such that mechanical security and an essentially airtight seal are created. This technique allows the low cost creation and attachment to a recorder device base or support of one or several plastic parts or features with one mold shot. Mounting hardware and/or sealing gaskets, or adhesives, are not required. Electrical connector plugs can be molded and sealed in openings in the support, separately or with other parts or features, to provide sealed electrical connections between the transducers and printed circuit boards on the bottom side of the support, thereby eliminating either the routing of flex circuits out of the recorder, or the gasket sealed screw mounting of a through connector. Very tight tolerances are achievable and repetitively maintainable in the configuration of parts and in their location and the base or support plate, since the support plates are of tight tolerance and can be accurately positioned in the mold assembly by the disk spindle hole and holes for mounting the actuator, or other jig holes referenced to such holes. These tight tolerances are critical with respect to molded parts associated with actuator movement such as crash stops, the actuator latch and the like. An example of a plastic material suitable for this application, particularly the high precision crash stops, a glass or carbon filled polycarbonate type of material which is a stiff and dimensionally stable, yet can yield a flexible and resilient structure in particular design configurations, to meet the requirements of the crash stop function for decelerating and precisely stopping an actuator in its limits of movement, yet being deflectable to permit actuator installation past the molded crash stop. This material is internally damped in a degree, in the crash stop configuration, to prevent ringing under actuator impact. Any material which has the characteristics of stiffness, damping, aging stability, dimensional stability, and the strength for this application and which is adaptable to outsert molding, may be used. Other presently known suitable materials include polyphenylene sulfide, polyetherimide, etc. In the present invention, a unique method of fabricating a support member for a disk drive is disclosed. The parts of the support member or the plate fabrication in the present invention are outsert molded on the support member through at least one opening provided at a predetermined location in the support member and preferably providing an air tight seal with the support at each opening. Brief Description of the Drawings A better understanding of this invention may be had from a study of the following specification when considered in conjunction with the accompanying drawings, in which: Figure 1 is an isometric view of a rotary actuator type of magnetic disk drive, embodying the principles of this invention, Figure 2 is an isometric view of outsert molded parts or features of a disk drive of the type of Fig. 1. Figure 3 is an isometric view similar to Fig. 2 showing a different outsert molded crash stop structure, and Figure 4 illustrates the mold arrangement. Best Mode for Carrying Out the Invention The best mode presently known to the applicants for practicing this invention, comprises its application in a rotary actuator type of magnetic disk drive, which is illustrated in Fig. 1. The principles of this invention, however, are also applicable in drives involving linear actuators and in drives or recorders involving magnetoresistive and optical principles in recording and playback or reading modes. The rotary disk memory drive 1 of Fig. 1 comprises a support 3 such as a base or support plate. An integrated disk stack 5 comprises axially spaced disks 5a. The disk stack 5 is mounted for rotation at constant speed by a motor (not shown), about an axis 5b of a disk spindle structure 5c securing the disk stack. A rotary actuator 7 comprises a bearing housing 7a which is rotatably mounted about an actuator spindle 7b. A plurality of arms 7c are mounted upon the bearing housing 7a in axially spaced positions in planes adjacent to the surface of the individual disks 5a. Load beams 7d, sometimes also referred to as flexures, attached to the free ends of the arms 7c at their extremities, mount individual magnetic heads 7e. These magnetic heads 7e are disposed in confronting relationship with adjacent surfaces of each of the disks. The actuator 7 is rotated about the actuator spindle 7b to move the magnetic heads 7e to different radial positions over the adjacent surface of a disk 5a for track seeking and track following modes of operation, as is well known, by means of an actuator motor 9. The coil structure 9a is attached to the bearing housing 7a and the center line of the coil is diametrically disposed with respect to the center line of the arms 7c on the opposite side of the axis of the actuator spindle 7b. In this position the coil structure 9a moves bidirectionally in an arc about the axis of the actuator spindle 7b. The coil structure 9a is disposed between a pair of two-pole permanent magnets, one above and one below the coil structure 9a. Only the lower permanent magnet 9b is shown in this illustration in the interest of clarity. The lower permanent 9b is disposed upon a steel, magnetic flux carrying motor base 9c which is attached to the support plate 3. Bidirectional movement of the coil 9a in its arc in the field of the permanent magnets is achieved, as is well known, by reversibly energizing the coil (not shown) of the coil structure 9a. The limits of angular mechanical movement of the rotary actuator 7 are determined by a crash stop 11, having a crash stop base 11a on the support plate 3, and circumferentially spaced arms 11b projecting upwardly therefrom, which arms are positioned on opposite sides of a pin 9d radially projecting from the end face of the coil structure 9a between the crash stop arms 11b. Engagement of the pin 9d with the respective crash stop arms 11b determines the opposite limits of angular movement of the actuator 7 and, hence, the inner and outer radial limits of movement of the individual magnetic heads 7e with respect to the surfaces of the respective disks 5a. As seen in Fig.1, the position of the left crash stop arm 11b determines the outermost radial position of the magnetic head 7e. This position is usually outside of the outermost data track 5e on the surface of the disk. The crash stop arm 11b on the right, as seen in Fig.1, determines the innermost position of the magnetic head 7e which is usually between the disk spindle 5c and the innermost track 5d on the surface of a magnetic disk 5a. The crash stop 11 has a lower base or flange llc on the bottom side of the support plate 3, as seen in Fig. 1, which is an integral part of the crash stop structure 11 by means of the integral connection extending through an opening 11d in the support plate 1. This opening 11d is of any configuration for the purpose of indexing and securing the crash stop against rotary movement. The opening 11d is in a predetermined position at least with respect to the axis 5b of the disk stack. The base of the disk spindle 5c and the actuator spindle 7b are secured in openings extending through the support plate 3. These openings in Figs. 2 and 3 are designated 5f and 7f, respectively, and are the openings which receive the bottom ends of the disk and actuator spindles 5c and 7b, respectively. In Fig. 4, showing the assembled mold, coaxial pins 5g and 5h projecting from opposite mold faces and coaxial pins 7g and 7h projecting from opposite mold faces fit into the respective openings 5f and 7f in the support plate 3. This precisely indexes the support plate 3 between the confronting faces of the mold sections M1 and M2, placing the opening 11d for the crash stop 11 at the location of the crash stop cavities in the mold sections M1 and M2. These crash stop cavities are precisely positioned with respect to the openings 5f and 7f, which receive the bases of the disk and actuator spindles 5c and 7b respectively. Thus, when the crash stop is formed by the injection of a fluid plastic material through an opening into the crash stop cavity, the crash stop is precisely positioned with respect to the axes of the disk and actuator spindles 5c and 7b, and this precision is repeatable. The locations of other cavities in this mold, having critical requirements as to location with respect to the disk spindle 5c and the actuator spindle 7b, may be similarly determined. It is believed that the illustration with respect to the crash stop as seen in Fig. 4 is sufficient in this respect. The two point indexing of the support plate between the two halves or sections M1 and M2 of the mold is preferred since it provides precise translational and angular positioning of the support plate 3 with respect to the cavities in the mold which are similarly precisely located with respect to such points. It is apparent however, that other holes or openings through the support plate 3 which are precisely related to the openings 5f and 7f may be used in place of the openings 5f and 7f to achieve the same results. In Fig. 1, additional openings are shown in the support plate 3. These include a rectangular opening 13 and two spaced circular openings 15a and 15b. These are provided for the purpose of mounting additional parts, such as the additional parts which are seen in Figs. 2 and 3. These parts include a molded outsert 16 and the crash stop 11. The crash stop 11 has been described. A connector plug 17, usually comprising a multiplicity of pin receptacles, is fitted through the opening 13 and secured and sealed within the confines of the molded outsert 16. The molded outsert 16 is secured to the support plate 3 by means of integral sections projecting through the openings 15a and 15b, providing an integral connection between the base section of the molded outsert 16 and a flange 16a on the bottom side of the support plate 3, as seen in dotted outline. Integral parts of the molded outsert 16 include a latch pivot pin 19 and snap pocket posts or supports 21 provided with bifurcated upper ends, for the purpose of receiving and securing a latch solenoid (not shown) which operates a latch arm (not shown) which is intended to be mounted on the latch pivot pin 19. These parts are not shown since they are not part of this molded outsert. The function of this latch is for the purpose of securing the actuator 7 in that angular position in which the magnetic head 7e is positioned radially inwardly of the innermost track 5d of the disk. This is known as the parked position of the magnetic head in the landing zone which is provided inboard of the innermost track 5d. In this parked position, the latch has an end portion which engages a catch 7g on the coil side of the coil structure 9a. The purpose of this latch is to lock the actuator against any possibility of angular movement when the disk drive is not being used and, for example, is being transported either separately or as a unit with the equipment in which the drive operates. Precision of casting of these parts as to repeatability and configuration and in location, is desirable to minimize the amount of radial disk space appropriated to guarantee that the actuator 7 always latches with the transducer 7e always clear of the innermost data tracks of the disk 5d. A variation of the crash stop 11 is illustrated in Fig. 3. The differently configured outsert molded crash stop structure is designated 23. It comprises an outsert molded base section 23a, as described hereinabove, and a clip-on spring loaded crash stop 23b. The base section 23a is provided with recesses 23c in its opposite side edges. The crash stop member 23b is of generally U-shaped configuration conforming to the configuration of the base section 23a and has end portions 23d on opposite sides conforming to the shape of the recesses 23c. Prior to installation, the end portions 23d of the spring crash stop 23b are spaced a lesser distance apart than the distance between the bases of the recesses 23c, to provide spring loading when installed. Thus the spring member 23b is conveniently clipped into position on the base section 23c with the end portions 23d engaged in the recesses 23c. Predetermined spring loading of the crash stop at the end portions 23d is provided by this arrangement for the purpose of restricting the angular limits of movement of the rotary actuator without exceeding the G limits on the magnetic heads 23e and their suspensions by which they are attached to the ends of the load beams 7d. The crash stop 11 need not be outsert molded as a single piece. The crash stop arms 11b may be molded on separate bases at individual holes through the support plate 3 with the same precision as with the single piece crash stop 11. Although a specific example of the structure of a recording device having parts fabricated according to the teachings of this invention has been described herein; it is apparent that the invention both as to its structure and to the method of fabrication of that structure is not limited to the type of device herein described and illustrated, but is rather of general application and applicable also, for Example to devices involving linear actuators and to devices involving different recording techniques such as magneto-resistive and magnetooptical techniques for recording and playback or reading.

Claims: A recording device, comprising: a support (3) having opposite faces; at least one disk (5a) having opposite faces on which recordings are made in radially spaced tracks in one surface thereof; means for mounting said disk (5a) on a first face of said opposite faces of said support (3) for rotation about an axis (5b); at least one transducer (7e) for making recordings on said disk (5a); a movable actuator (7) at a location on said first face of said support for supporting said at least one transducer (7e) adjacent to said one surface of said disk (5a) for movement to different radial portions on said disk (5a); motor means (9) for moving said actuator (7); said support (3) having an opening (11d) therethrough adjacent to said actuator (7); and characterized by: a single piece crash stop structure (11) outsert molded on said first face of said support (3), having a base (11a) and at least one crash stop projection (11b) disposed at a first predetermined distance from said location of said movable actuator (7) and at a second predetermined distance from said axis (5b), said at least one crash stop projection engaging said actuator (7) means in at least one of two mechanical extremes of movement of said actuator (7) means and having an integral portion extending through said opening (11d) and terminating in an enlarged portion (11c) on a second face of said support (3) opposite to said first face for securing and sealing said crash stop (11) to said support (3) at the location of said opening (11d). The device according to Claim 1 further characterized by the outsert molded part (11) being of a plastic material. The device according to Claim 2, further characterized by the outsert molded part (11) being of a polycarbonate plastic material. The device of any one of the preceding claims further characterized in that said outsert molded single piece crash stop structure (11) comprises two crash stop projections (11b) integral with said base (11a) for engaging said actuator (7) means in each of two mechanical extremes of movement. A method of fabricating the recording device of Claim 1, the method fabricating parts on opposite faces of said support and characterized by: providing a two section mold (M1, M2), each section having a spindle axis reference location (5g, 5h) and an actuator attachment reference location (7g, 7h), each of the mold sections (M1, M2) having a cavity (11b, 11c) defining an individual part having a surface at a location at respective predetermined distances from the spindle axis (5b) reference location and the actuator (7) attachment reference location; placing the support (3) between and in contact with said mold sections (M1, M2), indexing a spindle attachment location of the support (3) to the spindle axis reference location (5g, 5h) of each mold section and an actuator attachment location of said support (3) with the actuator attachment reference location (7g, 7h) of each mold section, and injecting a fluid molding material into each cavity (11b, 11c) in each mold section (M1, or M2) to mold a part having a portion seated on opposite faces of said support (3) at said opening and integrally connected through the opening (11d). A method of fabricating a support member (3) for the recording device of claim 1 having a disk spindle axis location (5f) and an actuator location (7f) on said support member (3), with openings (11d, 15a, 15b) through said support member, and characterized by at least one opening (11d) of said openings being referenced to both locations on said support member; and by outsert molding parts (11, 16) on said support member (3) through said openings (11d, 15a, 15b) at least one part of such outsert molded parts being a crash stop (11) and being at said one opening (11d).

Inventors: COLBERT RICHARD L, STRICKLER MIKE T, COLBERT, RICHARD L., STRICKLER, MIKE T.
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1991
Main classification: G11B25
IPC codes: G11B25, G11B33