Disc drives are digital data storage devices which store and retrieve large amounts of user data in a fast and efficient manner. The data are magnetically recorded on the surfaces of one or more data storage discs affixed to a spindle motor for rotation at a constant high speed.
An array of vertically aligned data transducing heads are controllably positioned by an actuator to read data from and write data to tracks defined on the recording surfaces. An actuator motor rotates the actuator to move the heads across the disc surfaces. The heads are configured to be aerodynamically supported over these surfaces by fluidic (for example, air) currents established by the high speed rotation of the discs.
It is desirable to minimize the presence of fluid-borne particulate and vapor phase (gaseous) contamination within a data storage device housing, as such contamination can adversely affect data storage and transfer performance. Data storage housings are typically sealed using gaskets and similar features to prevent the ingress of contaminants from the external environment.
It has been found that a large pressure differential between the interior and exterior of a housing (such as by elevated temperatures or changes in altitude) can potentially lead to failure of the housing seal. Thus, instead of providing a completely sealed housing, designers typically provide a small diffusion path between the interior of the housing to the external environment to allow equalization of interior and exterior atmospheric pressures.
A typical diffusion path (diffusion tube) is formed through a housing wall and provides an elongated, narrow channel which permits fluidic flow while at the same time restricting passage of contaminants along the length of the channel.
Filters are further typically placed within the housing to remove contaminants from the internal recirculating fluidic currents established by rotation of the discs. Such filters typically include pass-through recirculation filters and chemical adsorbent filters.
A pass-through recirculation filter generally captures fluid-borne particulates as fluidic currents are directed through the filter. A typical construction includes pieces of filter media (such as polytetrafluoroethylene, PTFE) laminated to a nonwoven backing material or a fabric encapsulated, pillow-shaped filter containing electrostatic or other filter media.
A chemical adsorbent filter generally adsorbs gaseous and small diameter particulate contaminants as fluidic currents pass across a surface of the filter. A wide variety of constructions have been proposed including the use of activated carbon and silica based desiccant granules as an adsorbent media. The adsorbent media is typically melded into a contiguous block (brick) or is encapsulated within a semi-rigid permeable boundary layer of material.
Disc drive designers are constrained by a number of factors, including continually reduced form factors and internal clearance issues, to provide effective filtering and flow control. With the continued demand for higher performance data storage devices, there remains a continual need for improved approaches to directing and filtering recirculating fluidic currents within such devices. It is to such improvements that the claimed invention is directed.