ENCLOSED SELF-PURGING DISK PACK UNITS

Abstract: To provide a compact and efficient enclosed filtered disk pack unit, the enclosing shroud (10, 65) has planar inner surfaces (15, 66) close to and parallel with the outer surfaces of the disk pack (60, 61) and a passive filter system including a filter duct containing a filter element (40) formed externally to one such inner surface (15) and having a scooped (at 53) inlet and a flared outlet (56). The effective centres of the inlet and outlet are arcuately and radially displaced relative to the disk formation, the duct initially widening gradually and then rapidly just prior to the filter element (40). A barrier (68, 69) extends from the opposite inner surface (66) towards the flared outlet (56).

Description: ENCLOSED FILTERED DISK PACK UNITS The present invention relates to enclosed filtered disk pack units. The proper functioning of a disk file, in addition to the structural integrity and uninterrupted continuity of the storage medium, requires that no outside intervention interfere with the device operation. Since the read/write transducers operate using an air bearing clearance with respect to the disk surface of 10 to 15 micro inches it is imperative that no airborne particles have a dimension equivalent to or exceeding such clearance. The recognized need for atmospheric control within the disk enclosure has led to varying solutions, many of which result in a structure wherein more space is devoted to the filtering and air moving mechanisms than to the data storage, transducing and electronic support portions. The enlarged volume within such a device creates more opportunity for airborne particles to be present and often reduces the number of air changes per unit time and thereby limits the effectiveless of particle separation. In an attempt to improve matters, the present invention provides an enclosed filtered disk pack unit utilizing a passive filter system pumped by rotation of the disk pack comprises an enclosing shroud defining an internal annular cavity housing the disk pack with a pair of opposed planar inner surfaces close to and parallel with the outer surfaces of the disk pack and a filter duct housing a filter element communicating with the cavity through one of the said inner surfaces characterized in that the effective centres of the duct inlet and outlet are both radially and arcuately displaced with respect to the disk pack axis with the inlet effective centre being outboard and downstream relative to the outlet effective centre, the inlet being scooped and the outlet being lipped, and a counter barrier being provided on the other said inner surface opposite the outlet lipping. The result is a composite structure involving a combination of features enabling a compact structure and efficient operation to be realized. In one embodiment of the present invention disclosed hereinafter, a base casting and cover cooperate to form a sealed enclosure that surrounds the motor in addition to the disk media, transducers and supporting electronics. The base and cover present shrouding surfaces that closely confront each axial side of the multi disk media to limit the volume of air within that surrounds the operative portions of the device. The shrouding surfaces are separated from the disk.surface by a distance less than one-third the axial space between adjoining disks within the disk pack. The reduced volume causes a given level of filtered air to effect a greater number of air changes per unit time. A duct containing a filter is formed with inlet and outlet openings through a shroud surface and confronting the disk surface. Air flow is induced through the duct to produce a supply of filtered air at the duct outlet by the rotating disk surface with the effective central point of the duct inlet opening being a greater distance from the centre of rotation of the disk element than the effective centre of area of the duct outlet opening. The rotating disk thereby induces a higher pressure condition at the duct inlet opening and a reduced pressure at the duct outlet opening, A ##pple##ental aspirating effect is applied to air at the duct outlet by an "air foil like" deflector that is inclined from the shroud surface toward the disk surface to increase the velocity of air passing the duct outlet and cause entrainment of air leaving the duct. To prevent interference with air flow through the duct caused by turbulent flow, the duct width between the inlet and filter is configured to initially slowly increase and thereafter rapidly increase as the filter is approached. This prevents the circular whirlpool or eddy current motion that would impede flow. To equalize the involved forces and render more effective the air flow induced in the filter duct, a barrier ridge is formed on the shroud wall surface at the opposite axial end of the pack of disk elements that is axially aligned with the ridge of the deflector that adjoins the duct outlet. In, this provides for a sealed, mimimum volume disk pack enclosure using the air aspirating properties of the rotating disk elements to induce air flow through a filter duct that is a passive filter system. Limiting the enclosed volume enhances the air aspirating of the rotating disk media and increases the frequency of air changes. The duct configuration minimizes eddy currents in air flowing through such filter duct and avoids propagation of turbulent air currents near the disk surface that would adversely affect the flying characteristics of the magnetic transducers. The invention will be described further by way of example with reference to an embodiment thereof as illustrated in the accompanying drawings in which: FIG. 1 is an isometric view of the base member of one form of disk file according to the present invention with the filter duct formed as an integral part thereof; FIG. 2 is a plan of the base member of FIG. 1; FIG. 3 shows an exploded view of the cover and filter element that cooperates with the base member of FIGs. 1 and 2 to enclose the filter duct; FIG. 4 is an exploded section of the cover and filter element of FIG. 3 as seen in a section through the centre of the filter by a plane normal to the major surface of the cover; FIG. 5 is a section taken along line V-V of FIG. 3; FIG. 6 is a section taken along line VI-VI of FIG. 3; ; FIG. 7 is a section view of the base member taken along arcuate line VII-VII of FIG. 2 with the disks, duct cover, and file cover assembled thereto and shown in corresponding section; and FIG. 8 is a section of the file memory base member taken along line VIII-VIII of FIG. 2 with the disks, motor, duct cover and file cover assembled thereto and shown in corresponding section. The embodiment illustrated is an enclosed filtered disk pack unit utilizing a passive filter system pumped by rotation of the disk pack. The enclosure is formed, essentially, by a shroud formed by a base member 10 and a cover 65. FIGs. 1 and 2 show the base member 10 for the unit, the base member including a cylindrical wall surface portion 12 that surrounds the disks and a further cylindrical recess defined by wall surface 13 in which a concentric drive motor is received. The planar minor surface 15 confronts and shrouds the disk pack at one axial side. A cylindrical surface defined by wall 12 is interrupted between wall surfaces 16. This opening and the recesses in surface 15 defined by wall portions 17 provide space for mounting transducers and permitting such transducers to d#("##S the disk surface. The trajis ##'jer and the mounting structures therefore are not shown since they are not material to the present invention. A duct extending in a generally circular path about the disk axis of rotation is formed as a depression in the shroud surface 15. The duct that has an initial inclined surface 18 extending from shroud surface 15 to the duct floor 19 and a terminal incline surface 21 extending from duct floor surface 19 to shroud surface 15. The duct outer r.ldial elevation. surface 23 follows a generally circular path with a pair of projections 24 provided for mounting purposes. The radially inward duct sidewall 26 initially proceeds from the incline surface 18 in substantial parallelism to the outer wall 23 and thereafter rapidly diverges from the outer wall 23 to a terminal portion generally equidistant from the axis of rotation of the disk pack in the circular recess defined by the surface 12. A recessed surface 28 has a depth equal to the thickne-ss of a rover member 30 that defines the upper wall surface of the duc a.)3 provies an upper surface 31 that is coplanar with and a continuation of the shroud surface 15. The duct cover 30 shown in FIGs. 3 and 4 is installed with the lower surface 32 abutting the base member recess surface 28 and is secured in position by six fasteners that are received in six openings 33 and 34. The fasteners extending through openings 33 are secured in the base surface 28 while the fasteners extending through openings 34 are received in the upper surfaces of embossments 24 and 25. The circular opening 365 in cover 30 is received about boss 37. The upper surface of boss 37 is coplaner with the shroud surface 15. The filter element 40 is retained by a lower surface of cover 30, a flange 41 depending from and forming a part of the cover, and a retainer 42. The retainer 42 and cover 30 are bonded together with the filter positively retained by the marginal flanges 44 and 45 of cover 30 and retainer 42 respectively. The downwardly depending filter enclosure including cover 30 with flange 41 and retainer 42 extending from the duct cover is received in the recessed portions 47, 48 and 49 found respectively in duct wall surfaces 26, 19 and 23. A length of gasket material 80 seals the depending filtering closure within the duct and such gasket material is disposed in a continuous recess 50 found in the 3 recessed wall portions 47, 48 and 49. As seen in Fig. 5 an inclined surface 53 is formed in the cover 30 scooping the inlet to aid in deflecting air into the duct inlet. FIG. 6 illustrates the cover structure overlying the duct outlet. The surface 55 rises from the planar top surface 31 of the duct to the surface 56 which confronts the disk 60 in the assembled condition. The inclined lower surface 57 becomes a part of the duct outlet which extends to the plane of the shroud surface 15. Thus the formation defined by surfaces 55, 56, and 57 make the outlet lipped. FIG. 7 illustrates, in arcuate section, the base member of FIG. 2 with the duct cover 30, disks 60, 61 and cover 65 assembled thereto. The shroud surfaces 15 and 66 presented by base member 10 and cover 65 respectively are equidistant from the confronting disk surface and closely confining to minimize the enclosed air space. The spacing between the two disk elements 60 and 61 is slightly in excess of three times the spacing between the shroud surfaces 15 and 66 and the confronting surfaces of disks 60, 61. The inclined surface 55 terminates in the surface 56 confronting the disk 60 above the duct outlet and reduces the spacing between the planes of shroud surface 15 and disk 60 by about one-half above the surface 56. The cover 65 includes a barrier that is formed by inclined surfaces 68 extending from shroud surface 66 which terminate in a surface 69. The barrier reduces the clearance between shroud surface 66 and the surface of disk 61 by about one-third. FIG. 8 is a partial radial section of the base element 10 with the duct cover 30, filter 40, disks 60, 65, motor 70 and cover 65, some of which are in section, assembled thereto. With the enclosure formed by the base member 10 and cover 65 surrounding the disks 60, 61 in the assembled condition, the disks are rotated in the direction of arrow A in FIG. 7 or in a counterclockwise direction with respect to the base member as viewed in FIGs. 1 and 2. The rotating disks, although presenting a very smooth highly finished surface impart a force to the enclosed ambient air which causes a pressure gradient which increases as the distance from the centre of disk rotation increases and also induces a tangential motion of the air at any given point along the disk surface. The duct is basically a tubular structure having a varying rectangular cross section. The inlet opening overlying the inclined surface 18 has an area centre substantially further from the axis of rotation of the confronting disk that t}#e area centre of ti)# duct outlet opening overlying the inclined surface 21. Accordingly, the air pressure at tjit duct inlet is greater than the air pressure at the duct outlet during disk rotation, caused by the natural centrifa: pumping action, which induces an air flow through the duct and t5 filter disposed therein. In audition the air flow induced by the pressure differertial between duct inlet and duct outlet, positive aspiration assisted by the inlet scooping at 53 is provided to increase the air flow through the duct. The inclined surface 55 and the surface 56 confronting disk 60 function in the manner of an air foil to produce a venturi effect. As the clearance is reduced to that between disk 60 and surface 56 from the larger clearance between shroud surface 15 and disk 60, the speed increases and air is drawn fror the du:t and exhausted into the free air stream between the disk and shroud surface. A projection is formed on the upper shroud surface 66 with the inclined surfaces bQ terminating in a surface 69 which confronts the disk 61 and is axially aligned with the surface 56. This projection serves to equalize the pressure condition at each axial side of the disk pack. This is provided to introduce additional restriction to enhance aspiration and to avoid erratic disk rotation that might result from localized pressure variations occurring at one side of the disk pack. The combination of duct air flow inducing factors afforded by the pressure differential and the aspirating effect of the venturi type structure make the filtering action more effective. The closely confining shroud surfaces adjoining the disks not only increase the effectiveness of both the centrifugal pumping action and the aspiration of the venturi type structure, but reduction in enclosed volume causes the air flow through the filter to more frequently be the equivalent of a complete air change. The greater the number of air changes that occur per unit of time, the more secure the disk memory becomes with respect to airborne particulate matter that may be generated within the file or migrate into the file through imperfect sealing or filtering. The reduced volume or gas enclosed about the elements of the magnetic disk memory also renders less difficult the problems associated with totally sealing the device or the filtering of air introduced as a result of ambient temperature and/or pressure variation. It will be observed that the duct is initially of reduced continuous section with enlarlJement of the duct width occurring rapidly prior to the location of the filter element. Avoiding an enlarged duct cross sectional area for any significant distance prior to the filter location avoids the establishment of turbulent conditions that would cause a material pressure loss and reduce the effectiveness of the relatively small pressues that induce flow through the duct.

Claims: CLAIMS 1. An enclosed filtered disk pack unit utilizing a passive filter system pumped by rotation of thr disk pack comprises an enclosing shroud (10; 65) defining an internal annular cavity sousing the dis pack (60;61) with n pair of opposed planar inner surfaces (15; ;66) close to and parallel with the outer surfaces of the disk pack and a filter duct housing a filter element (40) communicating with the cavity through one of the said inner surfaces (15) characterized in that the effective centres of the duct inlet and outlet are both radially and arcuately displaced with respect to the disk pack axis with the inlet effective centre being outboard and downstream relative to the outlet effective centre, the inlet being scooped (at 53) and the outlet bfina lipped (at 56), and a courtier barrier (68;69) being provide on the other said inner surface opposite the outlet lipping. 2. A disk pack unit as claimed in claim 1 characterized in that the filter duct open gradually from the inlet towards the filter element, widening rapidly just prior to the filter element. 3. A disk pack unit as claimed in either preceding claim in which the axial separation of the disks of the disk pack exceeds the separation between the disk pack and the said inner surfaces. of the shroud.

Inventors: SIVERLING, MICHAEL MCHUGH, WHEELER, STEPHEN EDWARD
Applicants: INTERNATIONAL BUSINESS MACHINES CORPORATION
Application year: 1980
Main classification: G11B23
IPC codes: G11B33, G11B23