AN HERMETICALLY SEALED DISK FILE

Abstract: In an hermetically sealed disk file, the longitudinal axis of a surrounding cylindrical housing (90) is transverse to the axis of rotation of the disk spindle (76) so that the cross-sectional diameter of the housing need be only slightly larger than that of the record disks (80) mounted on the spindle.

Description: This invention relates to an hermetically sealed disk file in which the disk or disks, a disk supporting spindle and drive motor and an associated disk file actuator are enclosed within a sealed housing. Hermetically sealed disk files have been known for some time; one such file is disclosed in US-A-4,367,503. The advantages of hermetically sealing a magnetic or optical disk file are several. First, the file can be operated in a low density, inert gas atmosphere such as helium which reduces the aerodynamic drag between the disks and their associated read-write heads by a factor of approximately 5 to 1 compared with operation in air. At the same time, the helium gas more effectively conducts away heat generated during operation of the disk file. A significant difficulty to be overcome when a disk file is hermetically sealed is to design the housing so that it will readily accommodate variations between its internal pressure and the ambient atmospheric pressure. Such variations can arise from normal temperature changes during operation, from changes in atmospheric pressure and, in an extreme instance, from extraordinary changes in ambient pressure during air shipment. In the latter case, a differential pressure of approximately 2.8 x 10⁴ Pascals (4 psi) can be experienced. Figure 1 of the drawings accompanying this description is a schematic elevation of a hermetically sealed disk file of the type disclosed in the US-A-4,367,503. The substantially circular base plate 10 has a stepped bore 12 located off-centre. On one side of plate 10 is attached a frusto-conical bearing support member 14 which supports on its inner diameter a pair of spindle bearings 16, 18. Within these bearings, a hollow spindle 20 is rotatably supported; and a spindle hub 22 is attached to the upper end of spindle 20. A plurality of disks 24, separated by spacing rings 26 and held in place on hub 22 by disk clamp 28, are provided for storage and retrieval of data. A quill shaft 30 extends through hollow spindle 20 to the opposite side of base plate 10 where it is operatively connected to the rotor 32 of a spindle drive motor 34. Rotor 32 is mounted for rotation in a pair of bearings 36, 38 supported within the stator assembly 40 of motor 34. Motor 34, as illustrated, is attached to the underside of base plate 10. As indicated schematically, a disk actuator assembly 42 is supported on base plate 10 next to the spindle and disk assembly so that its read-write heads 44 can be moved into position to receive or transmit data from or to the disks 24. A suitable actuator for such an application is disclosed in US-A-3,849,800. The previously described structure is enclosed within a deep drawn, corrugated sheet metal enclosure 46 which is closed at its upper end by a corrugated sheet metal cover 48. Enclosure 46 and cover 48 are hermetically joined to one another by a conventional double seamed viscoelastic seal 50 such as is commonly used in the canning industry. Typical materials for the viscoelastic material used in such seals are disclosed in US-A-4,367,503. A plurality of mounting brackets 52, each having a rounded end 54 are provided to engage an inwardly projecting, circumferentially extending corrugation 56 in enclosure 46. Within the enclosure, base plate 10 is secured to corrugation 56 by means of a clamping ring 58. Finally, power for motor 34 and disk file actuator 42 is brought into the sealed enclosure through an electrical feedthrough connector 60. As can be seen in Figure 1, a hermetically sealed disk file of the type disclosed in US-A-4,367,503 requires a cylindrical enclosure 46, 48 having an outer diameter approximately twice that of the enclosed disks 24. As a result of this, the end panels of the enclosure 46, 48 undergo relatively large deflections due to changes in pressure and temperature. The maximum deflection of a circular end panel can be shown to be a function of the diameter of the end panel raised to the fourth power. Thus a cylindrical enclosure having a diameter approximately twice the diameter of the disk file will deflect approximately 16 times more than would an enclosure having a diameter about equal to that of the disks. In the disk file shown in Figure 1, the amount of disk deflection can be reduced by increasing the thickness of the end panels; however, this also increases the weight of the disk file. The invention seeks to provide an improved hermetically sealed disk file in which the cylindrical housing of the disk file has a substantially reduced diameter, thereby reducing deflection of the end walls of the housing and minimising the weight of the housing. The housing disclosed herein has sufficient flexibility so that only minimal forces are applied to the enclosed support structure for the disk file, upon deflection of the housing due to temperature and pressure variations. An hermetically sealed disk file comprising at least one data storage disk mounted on a spindle rotatably mounted in at least one mounting plate, a cylindrical housing enclosing the disk, spindle and mounting plate, and means for attaching the housing to the mounting plate is characterised, according to the invention, by the cylindrical housing being so disposed that its longitudinal axis is transverse to the axis of the spindle. Because the axis of the cylindrical housing is transverse to the axis of the record disks, the housing can have a diameter which is only slightly larger than that of the disks. To provide a particularly secure mounting for the spindle, two mounting plates can be used with the spindle rotatably mounted therebetween. In such a case, the mounting plates are attached to the housing by a pair of end plates which bridge the support plates at the opposite ends of the housing and are attached to the housing. To provide rigidity against radial deflection but to allow some axial deflection due to differential pressure between the interior and exterior of the housing, the housing preferably comprises circumferentially extending corrugations. The drive motor for the spindle may be mounted on the opposite side of the mounting plate from the disks. How the invention can be carried out will now be described by way of example, with reference to Figures 2 and 3 of the accompanying drawings, in which:- Figure 2 is a partially schematic elevation of an hermetically sealed disk file embodying the present invention; and Figure 3 is a cross-section on line 3-3 of Figure 2. The disk file illustrated in Figures 2 and 3 comprises an upper mounting plate 62 and a lower mounting plate 64 secured to one another in substantially parallel, spaced relationship by a pair of end plates 66, 68 and a plurality of suitable cap screws 70. Although two mounting plates are preferred to provide a rigid support structure for the disk drive, a single mounting plate from which the spindle is cantilevered can alternatively be used. The mounting plates support a pair of spindle bearings 72, 74 within which a spindle 76 is mounted for rotation. A cylindrical spindle hub 78 is suitably attached to spindle 76 and one or more circular record disks 80 are attached to hub 78 in a similar manner to the disks in the disk file illustrated in Figure 1. At its upper end, spindle 76 is secured by a nut 82. At its lower end on the opposite side of mounting plate 64, spindle 76 is drivingly engaged with the rotor of a suitable drive motor 84 attached to the underside of mounting plate 64. Spindle 76 has an axis of rotation 86. The structure just described is enclosed within an elongate, substantially cylindrical and circumferentially corrugated housing 90. The housing 90 comprises a pair of complementary deep drawn and substantially cylindrical sheet metal containers 92, 94 which are hermetically joined at their lips by a double seamed viscoelastic seal 96. As can be seen in Figure 3, the inside diameter of housing 90 need be only slightly larger than the diameter of the disks 80. As a result of this configuration, the deflection of the end walls of the container is greatly reduced and the container may be made of relatively thin material to keep its weight to a minimum. The support frame comprised of mounting plates 62, 64 and end plates 66, 68 is attached to housing 90 at one end by means of cap screws 98 which extend through a base plate 100 of a carrying handle 102 to engage end plate 68. A circular C-seal 104 between housing 90 and end plate 68 prevents leakage past cap screws 98 into the interior of the housing. At the opposite end of the housing, a plurality of cap screws 106 extend through an annular clamping plate 108 to engage end plate 66. Clamping plate 108 surrounds an opening 110 provided through end plate 66 and housing 90. Within opening 110 is positioned an electrical connector 112. A pair of concentric C-seals 114, 116 prevent leakage past cap screws 106 and connector 112 on the inside of housing 90, while a further C-seal 118 prevents leakage past connector 112 on the outside of housing 90. A suitable disk actuator mechanism 120, illustrated in phantom in Figure 2, can be mounted between mounting plates 62, 64 or on one of end plates 66, 68, as desired, in a position to allow its read-write heads 122 to interact with disks 80 in the familiar manner. As can be seen clearly in Figure 2, the longitudinal axis 124 of housing 90 is transverse to the axis of rotation 86 of spindle 76. Preferably these axes are perpendicular to one another.

Claims: 1. An hermetically sealed disk file comprising at least one data storage disk (80) mounted on a spindle (76) rotatably mounted in at least one mounting plate (62,64), a cylindrical housing (90) enclosing the disk, spindle and mounting plate, and means (66, 68, 70, 98, 102) for attaching the housing to the mounting plate, characterised by the cylindrical housing being so disposed that its longitudinal axis is transverse to the axis of the spindle. 2. A disk filed as claimed in claim 1, wherein the housing has a substantially circular cross-section having a diameter only slightly larger than the diameter of the record disk. 3. A disk file as claimed in claim 1 or claim 2, wherein there are two of said mounting plates and the spindle is rotatably mounted therebetween; and the means for attaching the mounting plates to the housing comprises a pair of end plates (66,68) bridging the mounting plates at opposite ends of the housing and means (98, 102) for attaching the housing to the end plates. 4. A disk file as claimed in claim 3, wherein the spindle extends beyond one (64) of the mounting plates, and which further comprises a motor (84) mounted on the opposite side of said one mounting plate (64) and drivingly coupled to the spindle. 5. A disk file as claimed in any preceding claim, wherein the housing is provided with circumferentially extending corrugations to accommodate differential pressure between its interior and exterior.

Inventors: SAVARESE, THOMAS G., TRESEDER, ROBERT C.
Applicants: INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1985
Main classification: G11B23
IPC codes: G11B25, G11B19, G11B23, G11B33