APPARATUS FOR COMMUNICATING AIR BETWEEN THE INTERIOR AND EXTERIOR OF A SEALED DISK DRIVE

Abstract: Apparatus for communicating air between the interior and exterior of a sealed disk drive while reducing ingress of water vapour into the drive has a vent outlet (30) mounted on the sealed disk drive and a passageway (42) communicating with the interior of the sealed disk drive. A vent cap (10) has a long, narrow passage (12) communicating between an inlet (14) communicating with the exterior and an outlet (16) communicating with the vent outlet (30) and forming an airtight seal between the exterior of the cap and the vent passageway except for the passage (12).

Description: This invention relates to apparatus for communicating air between the interior and exterior of sealed disk drives. EP-A-0174705 discloses a relatively long, narrow tube communicating between ambient or outside air and the interior of a sealed disk drive. The tube allows pressure equalisation between the inside and outside of a disk drive housing during operation, but also retards water vapour diffusion into the housing. Humidity increases friction, particularly static friction, between a head of the disk drive and a magnetic surface of the disk, which friction undesirably reduces disk/head life. According to the present invention there is provided apparatus for communicating air between the interior and exterior of a sealed disk drive while reducing ingress of water vapour into the drive comprising a vent outlet mounted on the sealed disk drive and having a passageway communicating with the interior of the sealed disk drive, and characterised by a vent cap having a long, narrow passage communicating between an inlet communicating with the exterior and an outlet communicating with the vent outlet and forming an airtight seal between the exterior of the cap and the vent passageway except for said passage. The apparatus may include sealing means, for example a gasket or double-sided adhesive tape, the vent cap having ridges forming said passage, said ridges and said gasket forming an airtight seal. Preferably the apparatus has an O-ring mounted about a central boss mounted on said cap, and a filter captured between the O-ring and the cap. The filter may be captured at an inner portion between the O-ring and the cap and at an outer portion between said double-­ sided adhesive tape and said disk drive. In a preferred embodiment the cap is circular and the passage follows the curvature of the cap. Said passage may include at least one elbow allowing at least two portions of the passage to follow the curvature of the cap. The invention is illustrated, merely by way of example, in the accompanying drawings, in which:- Figure 1 is a plan view of the interior of a vent cap of an apparatus according to the present invention for communicating air between the interior and exterior of a sealed disk drive; Figure 2 is a cross section of the cap along the line 2-2 of Figure 1; Figure 3 is a cross section of a vent outlet and filter of the sealed disk drive; and Figure 4 is a cross section illustrating another embodiment according to the present invention for communicating air between the interior and exterior of a sealed disk drive. Referring first to Figure 1 there is shown a vent cap 10 of an apparatus according to the present invention for communicating air between the interior and exterior of a sealed disk drive (not shown). The cap 10 includes ridges 20 which form a hollow passage or groove 12 communicating between an inlet 14 and an outlet 16. The groove 12 is semicircular in cross section as best seen in Figure 2. Mounted at the centre of the cap 10 is an attachment boss 18, which is preferably threaded, for attaching the cap 10 to a vent outlet 30 (Figure 3) of the sealed disk drive via a correspondingly threaded bore 40. When mounted on the vent outlet 30, the ridges 20 press against a gasket 32 mounted about a vent passageway 42 making an airtight seal therewith so that the only avenue for air to communicate between the exterior and the vent passageway 42 is through the inlet 14, the groove 12 and the outlet 16. Also shown in Figure 3 is a filter 44 for filtering dust out of the air which may enter the vent passageway 42. The vent passageway 42 communicates with the interior of the sealed disk drive. As can be seen from Figure 1, the groove 12 tracks the curvature of the circular cap 10 and doubles back on itself at an elbow 22. This provides for a long path relative to the narrow cross section of the path between the inlet 14 and the outlet 16. This long, narrow path provides for pressure equalisation during drive operation while retarding and reducing water vapour ingress. In a preferred embodiment, the cap 10 is 2.2cm (0.875 inch) in diameter. The groove 12 is 0.8mm (0.030 inch) in diameter, and when the ridges 20 are pressed against the gasket 32, the resulting passageway is approximately 0.39 sq.mm (0.0006 sq. inch) in cross section. The length of the groove is approximately 12.5cm (4.9 inch). It will be appreciated that a passage connecting the inlet 14 with the outlet 16 and formed entirely within the cap 10 is also within the scope of the present invention. Figure 4 shows an alternative embodiment of the present invention in which the cap 10 is mounted on a top cover 50 of a sealed disk drive about the opening of a breather vent comprised of a plurality of inlet holes 60. In this embodiment, the boss 18 is inserted into a corresponding bore in the top cover 50 and heat staked to form an expanded end 52 which holds the cap 10 on the circular cover 50. The airtight seal is maintained by circular double-sided adhesive tape 54, i.e. which has adhesive on both sides. The cap 10 presses against the tape, forcing the tape to press against the top cover. The groove 12 permits air ingress and egress. The tape 54 extends inwardly to cover an outer circumferential portion of a circular filter 58 and hold in against the top cover 50. The inner circumferential portion of this filter is held against the cap 10 at the boss 18 by an O-ring 56. By this arrangement, outside air reaching the interior of the cap 10 must pass through the filter 58 to reach the air inlet holes 60 of the breather vent.

Claims: 1. Apparatus for communicating air between the interior and exterior of a sealed disk drive while reducing ingress of water vapour in the drive comprising a vent outlet (30,60) mounted on the sealed disk drive and having a passageway (42) communicating with the interior of the sealed disk drive, and characterised by a vent cap (10) having a long, narrow passage (12) communicating between an inlet (14) communicating with the exterior and an outlet (16) communicating with the vent outlet (30,60) and forming an airtight seal between the exterior of the cap and the vent passageway except for said passage. 2. Apparatus as claimed in claim 1 characterised by sealing means (32,54) mounted about the passageway, the vent cap having ridges forming said passage (12), said ridges and said gasket forming an airtight seal. 3. Apparatus as claimed in claim 2 characterised in that said sealing means (32) is a gasket. 4. Apparatus as claimed in claim 2 characterised in that the sealing means (54) is double-sided adhesive tape. 5. Apparatus as claimed in any preceding claim characterised by an O-ring (56) mounted about a central boss (18) mounted on said cap (10) and a filter (58) captured between the O-ring and the cap. 6. Apparatus as claimed in claim 5 when dependent upon claim 4 characterised in that the filter (58) is captured at an inner portion between the O-ring (56) and the cap (10) and at an outer portion between said double-sided adhesive tape (54) and said disk drive. 7. Apparatus as claimed in any preceding claim characterised in that the cap (10) is circular and the passage (12) follows the curvature of the cap. 8. Apparatus as claimed in claim 7 characterised in that said passage (12) includes at least one elbow (22) allowing at least two portions of the passage to follow the curvature of the cap (10).

Inventors: BLANKS, JOHN BROCK
Applicants: MAGNETIC PERIPHERALS INC.
Application year: 1987
Main classification: G11B33
IPC codes: G11B25, G11B33