PRESSURE DIFFERENTIAL LATCH FOR A DISK DRIVE

Abstract: A pressure differential actuator latching apparatus for a disk drive (10) includes a rotatable body portion (52), a rigid air vane portion (60), and a latching trap (62). When a data storage disk (20) does not rotate, the latching apparatus maintains a transducer actuator assembly (32, 34) of the disk drive in a locked position by engaging the actuator assembly in the latching trap (62). When the disk rotates, the transducer actuator assembly (32, 34) blocks the airflow generated on the surface of the disk creating an area of low pressure downstream. The latching apparatus is positioned so that the air vane portion (60) is between areas of low and ambient pressure. The pressure difference over the air vane portion (60) rotates the latching apparatus releasing the actuator assembly (32, 34) from the latching trap (62). When the disk stops, the air vane portion returns to its original position and the latching trap (62) locks the actuator assembly (32, 34).

Description: PRESSURE DIFFERENTIAL LATCH FOR A DISK DRIVE By A. David Michael Field ofthe Invention The present invention relates to an apparatus and method for releasably locking an transducer actuator assembly at a fixed position relative to a disk. More particularly, the present invention is related to an improved apparatus and method for releasably locking an actuator assembly using a rigid air vane positioned between high and low pressure zones existing in a spinning disk drive due to the transducer actuator assembly diverting airflow ofthe spinning disk. The rigid air vane can be deflected to an unlock position by the pressure difference integrated over an area ofthe air vane. Background ofthe Invention In conventional Winchester disk drives, a read/write head or transducer assembly "flies" upon an air bearing or cushion in very close proximity to the rotating surface ofthe data storage disk. The disk surface carries a thin film magnetic material having a multiplicity of magnetic storage domains that may be recorded and read back by the head. The transducer assembly, which can be any conventional, well-known combination of transducers, sliders and load beams, is positioned and supported proximate the surface ofthe data storage disk using an actuator. The combination ofthe transducer assembly and the actuator is commonly referred to as the transducer actuator assembly or actuator assembly. The actuator supports the load beams and sliders, and accurately positions the transducers above the surface ofthe disk to read and write data from/to the disk. The load beam typically applies a preload force to the slider to urge it toward the surface ofthe disk. This force is overcome by airflow generated during rotation, or spinning, ofthe disk, creating the air bearing upon which the transducer assembly flies. The actuator typically contains a driving mechanism for positioning of the transducer assembly, and a support mechanism, or carriage assembly, for connecting the driving mechanism to the transducer assembly. Typically, the driving mechanism is either a linear or rotary actuator motor which drives the support mechanism along a predetermined path to position the transducer assembly relative to the surface of the data storage disk. Typically, the actuator motor includes a voice coil operating within a closed loop head positioning servo, and is referred to as a voice coil actuator motor. When the data storage disk is spun or rotated, airflow is generated. The amount of airflow is known to be a function of the disk diameter and angular velocity, and the force ofthe airflow is greatest adjacent the peripheral edge ofthe rotating data storage disk. Additionally, the generated airflow produces the air cushion or bearing overcoming the preload force ofthe load beam, and enables the transducer assembly to fly in close proximity to the surface ofthe disk. When the disk rotation ceases, the air cushion dissipates, such that the transducer assembly is no longer supported above the surface of the disk. Typically, when power is removed from the spindle motor that rotates the disk, the transducers come to rest or "land" on the surface ofthe disk. Likewise, when spindle motor is powered up, the transducers "take off from the surface ofthe disk. This landing and taking off activity can lead to loss of data at best, and failure ofthe disk drive at worst, due to erosion or scarring ofthe magnetic film on the surface ofthe disk. To ensure that the transducers do not come to rest upon an area of useful data storage, the actuator positions the transducers over a head landing or parking zone on the surface of the disk, as power is removed from the disk drive. Conventionally, while the disk drive is not in operation, friction between the transducer assembly and the surface of the disk maintains the transducer actuator assembly at a fixed position in the landing zone. However, lateral shocks to the disk drive can cause the transducer assembly to move or slide radially across the surface ofthe disk. Such movements can cause damage to the surface ofthe disk, as well as damage to the sliders and transducers. Such damage can additionally result in loss of data and/or transducer malfunction which can render the disk drive inoperable. Consequently, disk drive designers have employed a variety of actuator latching devices to maintain the transducer actuator assembly in a locked position while the disk is not rotating. When the disk has attained a proper rotational velocity to produce a sufficient air bearing to support the transducer, the latching device releases the actuator, enabling it to operate through its predetermined path of travel relative to the surface of the disk. Generally, there are several well-known approaches to latching devices: solenoid style latches, magnetic capture latches, inertial latches, and air vane latches extending over or under the disk, or between the disks in the case of a multi-disk disk drive. Solenoid style latches typically have a pin, rod or shaft biased into engagement with a movable portion ofa transducer actuator assembly by a spring or by magnetic field attraction. When engaged, the pin immobilizes the transducer actuator assembly. A solenoid, attached to the pin, withdraws the pin from the transducer actuator assembly when the disk attains an appropriate rotational velocity to produce an air bearing or cushion. This approach requires a complex electro-mechanical latching apparatus which can add to the size, weight, cost and power consumption ofthe disk drive. Examples of solenoid style latches include U.S. Patent Nos. 4,881,139; 4,903,157; and 5,095,395. Magnetic capture latches typically have a small permanent magnet attached to a movable portion of a transducer actuator assembly, and a steel striking plate mounted at a fixed location on the housing ofthe disk drive. The permanent magnet and striking plate are positioned such that, when the transducers are positioned in the landing zone, the magnet attaches to the striking plate. The attractive latching force between the magnet and the striking plate immobilizes the transducer actuator assembly, latching the transducer actuator assembly in a locked position. When the disk drive is powered up, and the disk is spinning at a sufficient rotational velocity to produce an air bearing, the actuator motor overcomes the attractive latching force to move the transducer actuator assembly such that the magnet separates from the striking plate. U.S. Patent No. 5,025,335 discloses an example of a magnetic capture latch. A disadvantage of magnetic capture latches is that they require large actuator motors, which can add to the size, weight, cost and power consumption ofthe disk drive. While the magnetic capture latches are typically small in size, they require larger actuator motors than disk drives using other latching devices. This is because the actuator motor in a disk drive having a magnetic capture latch must be capable of overcoming the attractive latching force in addition to positioning the transducer. Another disadvantage of magnetic capture latches is that drives employing such latches are susceptible to damage from mechanical shocks having a force greater than the attractive latching force between the magnet and the striking plate. Additionally, a resultant magnetic field can add a deflection bias force to the actuator at the vicinity of innermost data tracks, thereby potentially interfering with, or adding complexity to, the head positioning servo loop. This bias force can be rmnimized by providing a shifting proximity magnetic capture latch, such as disclosed in U.S. Patent Nos. 5,003,422 and 5,341,259. Inertial latches, such as the one exemplified by U.S. Patent No. 5,404,257, typically include a biased inertial body capable of engaging a finger, or the like, on an actuator assembly. The inertial body is biased to an unlocked position when the computer is not being subjected to rotational forces, but in the presence of rotational shock forces, its moment of inertia overcomes the biasing force to latch the actuator assembly. A problem with such inertial latches is that they may prove to be unreliable in response to such rotational shock forces. The fourth type of known latching device, the air vane latch, typically includes an air vane latch mechanism that releasably engages a movable portion ofthe transducer actuator assembly when the disk is not being rotated. The conventional air vane latches include an air vane attached to or extending from the latch mechanism. The air vane is positioned to extend over the disk or between the disks ofthe disk drive, in close proximity to the surface ofthe disk(s). Such air vanes use kinetic energy ofthe generated airflow moving with the disk to move the air vane, overcoming a biasing force and causing the latch mechanism to release the transducer actuator assembly. Examples of such air vane latches are described in commonly assigned U.S. Patent Nos. 4,538,193; 4,647,997; 4,692,829; 5,319,511; and 5,452,161. However, the conventional air vane latching devices have several disadvantages. For example, such placement ofthe air vane proximate to the surface of the disk impedes the airflow thereby requiring additional airflow generators and increased power for generating airflow sufficient to produce a force necessary to overcome the biasing force. Additionally, the air vanes require an appropriate surface area for the airflow to move or deflect the air vane and cause release ofthe latch mechanism. Such surface area can require increased spacing between disks of a multi-disk drive and/or increased spacing between the surface ofthe disk and the housing enclosing the disk drive assembly. This increased spacing increases the size and cost of manufacturing the disk drives. Thus, there exists a need for an improved, simple and cost efficient latching apparatus which can effectively use the airflow generated by a spinning disk and which does not require increased power use, nor increased size ofthe disk drive assembly. Summary ofthe Invention The latching apparatus ofthe present invention satisfies these needs. A general object ofthe present invention is to provide a latching apparatus for a transducer actuator assembly of a disk drive assembly which overcomes the limitations and drawbacks of the prior art latching devices. A more specific object ofthe present invention is to provide a latching apparatus utilizing a single rigid air vane positioned away from the rotating data storage disks, which is deflected to release a transducer actuator assembly by diverted airflow within a disk drive assembly. A further specific object ofthe present invention is to provide a latching apparatus which positions a single rigid air vane between high and low pressure zones existing within a spinning disk drive assembly, to use the pressure difference for releasing a transducer actuator assembly from a locked state. Another object ofthe present invention is to provide a latching apparatus including a single rigid air vane, positioned away from the rotating data storage disk, responsive to airflow generated by the rotating data storage disk to deflect the air vane causing release of a transducer actuator assembly from a locked state. The latching apparatus is employed in a disk drive assembly contained within a housing including a base and integral sidewalls together defining an interior space. The disk drive typically includes a spindle motor fixedly attached to the housing, and which forms a spindle hub for at least one rotatable data storage disk. A voice coil actuator structure having either a linear or rotary-type actuator motor, is secured to the housing and positioned so that its movable support or carriage arm holding a transducer assembly extends over the surface ofthe data storage disk. The latching apparatus comprises a shaft fixedly attached to the base ofthe housing a predetermined distance from an edge ofthe data storage disk, and a latch member rotatably disposed on the shaft to have an axis of rotation about the shaft. The latch member includes a body portion disposed on the shaft, a rigid air vane portion extending radially from the body portion, and a latching trap extending from the body portion opposite the air vane portion. The rigid air vane portion has a surface oriented generally orthogonal to the surface ofthe disk, and extends radially from the body portion to within a predetermined distance from a sidewall ofthe housing. The air vane portion is disposed, away from the edge of the disk, between high and low pressure zones defined by the rotating disk, the transducer actuator assembly and the sidewalls of the housing. The air vane portion is deflected by the difference between the high and low pressure zones integrated over its surface, to rotate the latch member between a locked and unlocked position. The latching trap extends from a lower region ofthe body portion and is positioned to extend in a direction opposite to that ofthe air vane portion. When the latch member is in the locked position, the latching trap engages the transducer actuator assembly in a locked state to maintain the transducer assembly at a head landing or parking zone when the disk is not being rotated. The latch apparatus additionally includes a bias mechanism disposed between the shaft and the body portion ofthe latch member for biasing the latch member to the locked position in the absence of airflow. Preferably the bias mechanism is a spring mechanism. Preferably the latch member is formed ofa liquid crystal polymeric material. Preferably the latching trap defines a notch which is integrally formed with the body portion ofthe latch member. The latch apparatus further includes a stop fixedly attached to the base ofthe housing for preventing the air vane portion ofthe latch member from rotating into contact with the disk. The latch apparatus can further include an airflow blocking member positioned proximate to the surface ofthe rotating data storage disk for blocking the airflow generated incident to the rotation ofthe disk and for creating the low pressure zone downstream from the airflow blocking member. In operation, power is applied to the disk drive, enabling the spindle motor to rotate the data storage disk. Rotation ofthe data storage disk generates airflow in the direction of disk rotation, proximate to the surface ofthe disk. The transducer actuator assembly which is positioned over the surface ofthe disk blocks the airflow generated incident to the rotation ofthe disk. Alternatively, an airflow blocking member can be positioned over the surface of the disk to block the airflow. The airflow is diverted away from the disk and around the back ofthe transducer actuator assembly, or airflow blocking member. The blocked airflow creates a low pressure zone just down stream from the transducer actuator assembly, and a high pressure zone in a corner of the housing containing a bulkhead connector. The latch apparatus is disposed between the low and high pressure zones such that the pressure difference exerts a force against the air vane portion ofthe latch member, rotating the latch member to the unlocked position which releases the transducer actuator assembly from the latching trap. The carriage arm ofthe transducer actuator assembly is then free to move relative to the surface ofthe disk to position the transducer assembly for reading or writing data from/to the disk. When disk rotation ceases, the airflow consequently ceases such that the force exerted against the air vane portion ofthe latch member is eliminated. In the absence ofthe force, the latch member is biased to return to the locked position, and catches the transducer actuator assembly in the latching trap to secure the transducer actuator assembly in a locked state. Brief Description ofthe Drawings These and other objects, advantages and features ofthe present invention will be better understood and appreciated upon consideration ofthe following detailed description, appended claims and accompanying drawings of a preferred embodiment, where: Figure 1 a shows an enlarged diagrammatic top plan view of a disk drive showing a version ofthe latch apparatus ofthe present invention in the locked position. Figure lb shows a partial top plan view ofthe disk drive of Figure la, showing in detail the latching tooth engaged by the latching trap. Figure 2a shows a top plan view of a disk drive showing a version ofthe latch apparatus of the present invention in the unlocked position. Figure 2b shows a partial top plan view ofthe disk drive of Figure 2a, showing in detail the latching trap and the latching tooth. Figure 3 shows a side elevational view of an embodiment of the shaft and bias mechanism ofthe present invention. Figure 4a shows a side and top elevational view of an embodiment of a latch member ofthe present invention. Figure 4b shows a side and bottom elevational view ofthe latch member of Figure 4a. Detailed description of a Preferred Embodiment Referring to Figures la and 2a, a disk drive assembly 10 including an air vane latching mechanism 40 which incorporates principles ofthe present invention is shown. The disk drive 10 is contained within a housing 12 which includes a base 14, integrally connected sidewalls 16, and a cover (not shown). The combination ofthe base 14, sidewalls 16 and cover defines an interior space in which the disk drive 10 is disposed. The disk drive 10 includes a spindle or hub 18 having an axis of rotation, a data storage disk 20 rotatably mounted to the spindle 18, and a transducer actuator assembly 30. For simplicity, the following discussion describes operation of a disk drive 10 having a single data storage disk 20. However, as those skilled in the art will recognize, the present invention is capable of use in a disk drive 10 employing a plurality of data storage disks 20 which can be commonly mounted to the spindle 18. Typically, a brushless spindle motor 24 is coupled to the spindle 18 for rotating the data storage disk 20 at a predetermined angular velocity. The spindle motor 24 is typically integrated into the hub 18 that supports the data storage disk 20, such that the spindle motor 24 supports and directly rotates the storage disk 20. The data storage disk 20 is rotated in a counterclockwise direction, as indicated by arrow A, about the axis of rotation. The data storage disk 20 can have a single surface, or both an upper and lower surface, on which data is stored. Typically, the surface ofthe disk 20 is coated, plated or deposited with a suitable magnetic material, such as ferrous oxides. However, the storage medium can also be optical, magneto-optical, and the like. The transducer actuator assembly 30 is bidirectionally rotatably journalled to the base 14 of the housing 12 about an axis of rotation 25. The transducer actuator assembly 30 can rotate bidirectionally along a path of approximately 30 degrees, as indicated by the arrow B. The transducer actuator assembly 30 includes a transducer assembly 32, a carriage or support arm assembly 34, and an actuator voice coil motor 36. The transducer actuator assembly 30 can be a rotary or linear-type assembly. The transducer assembly 32 is attached to a first end ofthe carriage assembly 34 in a conventional manner, and the voice coil motor 36 is attached to a second end ofthe carriage assembly 34 by adhesive or by intergral molding thereto. The carriage assembly 34 is mounted to the base 14 by a journal 33 about which the transducer actuator assembly 30 rotates. The journal 33 is disposed adjacent to a peripheral edge 22 ofthe data storage disk 20 such that the carriage 34 and transducer assemblies extend over the the surface ofthe disk 20. Activation ofthe actuator voice coil motor 36 rotates the transducer actuator assembly 30 about the journal 33 and accurately positions the transducer assembly 32 over concentric data tracks on the surface ofthe data storage disk 20, to allow read/write transducers (not specifically shown) access to stored data. A conventional transducer assembly 32 includes a read/write transducer formed on an air bearing slider, and a load beam. The load beam is preloaded to bias the slider toward the surface ofthe disk 20 such that when the disk 20 is not rotating, the transducer rests on the surface ofthe disk 20. Alternatively, when the disk 20 is rotating, the slider-transducer overcomes the load beam preload force and "flies" just above the surface ofthe disk 20 on an air bearing or cushion in accordance with conventional Winchester disk principles. During flight, the transducer actuator assembly 30 rotates relative to the surface ofthe disk 20, as indicated by arrow B, to position the transducer over the necessary data tracks. When the actuator voice coil motor 36 is deactivated, the transducer assembly 32 must be positioned to a parking or landing zone 27 where they will not damage the surface ofthe disk 20. Typically, the landing zone 27 is an inner annular region ofthe disk 20 proximate to the spindle hub 18. The latching apparatus 40 of the present invention locks the transducer actuator assembly 30 as the transducer assembly 32 comes to rest in the landing zone 27. Additionally, the disk drive 10 typically includes an actuator crash stop 37 fixedly attached to the base 14. The crash stop 37 is located in a corner of the housing 12 between the peripheral edge 22 ofthe data storage disk 20, the transducer actuator assembly 30 and a bulkhead connector 38. The crash stop 37 provides a stop for an extension 31 of the transducer actuator assembly 30 to limit rotational movement ofthe transducer actuator assembly 30 on the disk. Additionally, a second crash stop 37a can be positioned such that a rear portion 39 of the transducer actuator assembly 30 will come to rest with the second crash stop 37a to prevent the transducer assembly 32 ofthe actuator assembly 30 from "crashing" into the spindle hub 18, which will destroy the read/write transducers ofthe transducer assembly 32. The second crash stop 37a can be constructed as part ofthe voice coil motor 36, or as a separate piece. The latching apparatus or mechanism 40 of the present invention generally comprises a shaft or post 42 fixed to the base 14 ofthe housing 12, with a latch member 50 rotatably disposed on the shaft 42. With reference to Figure 3, the shaft 42 has a cylindrical shape and includes a ledge portion 44 extending around its periphery proximate to a lower end 46 ofthe shaft 42. The shaft 42 is preferably fabricated out of stainless steel, or any other suitably strong, rigid material. In the illustrated embodiment ofthe present invention, the shaft 42 is sized to have a vertical height of approximately about 31 mm, with the ledge portion 44 disposed approximately about 6.4 mm from the lower end 46 ofthe shaft 42. The lower end 46 ofthe shaft 42 is sized to have a diameter of about 3.0 mm. Referring to Figures 4a and 4b, the latch member 50 comprises a body portion 52, a rigid air vane portion 60 and a latching trap 62. The latch member 50 is preferably formed from a liquid crystal polymer, or other suitably formable rigid, low friction material. The body portion 52 ofthe latch member 50 has a hollow cylindrical core 54 sized to accommodate the shaft 42 so that the shaft 42 engages the latch member 50 to enable rotation ofthe latch member 50. Additionally, the hollow cylindrical core 54 is sized to retain a bias mechanism 55 (partially shown) therein. Preferably, the bias mechanism 55 is a spring made of stainless steel, or any other suitably strong, corrosion resistant material. The spring 55 applies a reverse bias torque of approximately .70 N- mm to the latch member 50 to urge the latch member 50 to its locked position when the latch member 50 is positioned on the shaft 42. The body portion 52 ofthe latch member 50 is disposed on the shaft 42 and is rotatable about the shaft 42 in a bidirectional manner, as indicated by arrow C in Figures la and 2a. Preferably, the latch member 50 rotates bidirectionally in a limited range of movement of about 35 degrees, as measured from the locked position. As illustrated in Figures 4a and 4b, a version ofthe body portion 52 ofthe present invention includes a forward section 56 having a generally cylindrical shape and comprising the hollow core 54 in which the shaft 42 is disposed, and a rear section 58 extending from and integrally connected to the forward section 56. In the version ofthe latch member 50 shown in Figures 4a and 4b, the air vane portion 60 ofthe latch member 50 comprises a rectangular shaped plate extending from the forward section 56 of the body portion 52 in a direction opposite to that which the rear section 58 extends. The vane portion 60 is shaped and sized to have a surface area upon which the airflow induced pressure differential, generated by rotation ofthe data storage disk 20 acts. The action ofthe pressure differential upon the vane portion creates a force which acts at a distance to create a torque, causing the latch member 50 to be rotated about the shaft 42. The vane portion 60 extends to within a predetermined distance ofthe sidewall 16 ofthe housing 12, to miriimize diversion of airflow around the surface ofthe air vane portion 60. Preferably, the vane portion 60 extends to within about .2 to about .7 mm ofthe sidewall 16 ofthe housing 12. In an embodiment ofthe present latch apparatus 40 used in a disk drive 10 device with 3.5 inch diameter data storage disks 20, the air vane portion 60 preferably extends about 38 mm from the center ofthe core 54 ofthe body portion 52, has a vertical height of about 29 mm, and a width of about 0.63 mm. Referring to Figures 2b and 4b, the latching trap 62 is formed below the bottom ofthe rear section 58 ofthe body portion 52 ofthe latch member 50. The latching trap 62 comprises a tail 64 extending from the rear section 58 in a direction opposite to that of the air vane portion 60. and a notched indentation 66 defined by the tail 64 and the forward section 56 ofthe body portion 52. The latching trap tail 64 has a slightly arcuate face 65 against which the extension 31 of the actuator assembly 30 is positioned to guide the extension 31 into the notched indentation 66 which is capable of trapping and holding a latching tooth 35 on the extension 31 ofthe transducer actuator assembly 30. The body portion 52, air vane portion 60 and latching trap 62 ofthe latch member 50 can be integrally formed or molded as a single unit. Alternatively, the pieces can be fabricated separately and joined in any conventional manner, such as with adhesives or screws. The latch apparatus 40 ofthe present invention can additionally include a stop 70 as shown in Figures la, lb and 2a. The stop 70 is fixedly attached to the base 14 by a securing pin 75, screw, or the like (shown in Fig. lb), and disposed in a space between the peripheral edge 22 ofthe data storage disk 20 and the latch member 50. The stop 70 is shaped and sized to stop the deflected latch member 50 from rotating into contact with the data storage disk 20. In the illustrated version, the stop 70 comprises a main portion 72 having a vane stop 73 with which the air vane portion 60 of the latch member 50 makes contact, and a wall baffle portion 74, extending from the main portion. The wall baffle portion 74 is positioned such that when the actuator assembly 34 is positioned at the outer diameter, or proximate to the peripheral edge 22, ofthe data storage disk 20, the wall baffle portion 74 prevents low pressure air leakage. As illustrated in Figures 1 a, 1 b and 2a, the stop 70 is a separate piece disposed positioned apart from the latch member 50. However, those skilled in the art will recognize that the stop 70 could be realized as a member attached directly to the latch member 50 for limiting rotation ofthe latch member 50 to prevent the air vane portion 60 from crashing into the rotating disk 20. Additionally, in the embodiment shown, the stop 70 is formed or molded as an integral extension ofthe actuator crash stop 37. However, the stop 70 could be realized as a separate member from the actuator crash stop 37. To further understand the invention, operation ofthe latching mechanism 40 will now be discussed with reference to Figures la and 2b. Prior to the disk drive 10 being powered up, the transducer assembly 32 is parked in the landing zone 27 on the data storage disk 20, and the transducer actuator assembly 30 is latched in a locked state by the latching tooth 35 being trapped in the notched indentation 66 ofthe latching trap 62 ofthe latch member 50, which is in its undeflected locked position, as shown in Figure la. When power is applied to the spindle motor 24 ofthe disk drive 10, the data storage disk 20 is rotated in a counterclockwise direction as indicated by arrow A. As the rotating disk 20 reaches its optimum velocity of, for example, 6000 RPM, airflow is generated proximate to the surface ofthe disk 20 in a circular motion following the disk 20 rotation. However, the carriage arm 34 and transducer assembly 32 ofthe transducer actuator assembly 30 blocks the airflow from following its rotational path, thus creating a low pressure area 80 "downstream". The blocking effect ofthe actuator assembly 30 also diverts the airflow around a rear portion ofthe transducer actuator assembly 30, along a path defined by the sidewalls 16 ofthe housing 12 and into contact with the air vane portion 60 ofthe latch member 50, as indicated by the small directional arrows in Figure la. This obstruction ofthe generated airflow by the carriage arm 34 ofthe transducer actuator assembly 30 creates the area of low pressure 80 just downstream ofthe carriage arm 34, and an area of high pressure 85 in the corner ofthe housing 12 containing the bulkhead connector 38 for the disk drive device 10. Thus, anytime the fluid stream of 15 airflow is blocked by an obstruction, a low pressure zone or area is created downstream of the obstruction. When the latch member 50 is in the locked position, as shown in Figure la and detailed in Figure lb, the air vane portion 60 is disposed between the areas of low 80 and high pressure 85 such that the pressure difference integrated over the surface ofthe air vane portion 60 will generate a force, which will overcome the bias mechanism 55 of the latch member 50 and create a torque which will rotate the latch member 50 about the shaft 42 to its unlocked position, in the direction indicated by arrow C. The rotation of the latch member 50 causes the latching trap 62 to release the latching tooth 35 ofthe transducer actuator assembly 30 from the notched indentation 66 (Figure 2b), allowing the transducer actuator assembly 30 bidirectional rotation as indicated by arrow B in Figure 2a. This enables positioning ofthe transducer assembly 32 over various concentric data tracks on the surface ofthe disk 20. When the disk drive device 10 is powered down, back EMF energy from the spindle motor 24 is conventially applied to the voice coil motor 36 of the transducer actuator assembly 30 to return the transducer assembly 32 to the landing zone 27 ofthe disk 20. Once the disk 20 reaches some low angular velocity, the pressure difference from the diverted airflow fails to generate a force sufficient to overcome the bias mechanism 55, and the latch member 50 will rotate back to its locked position, re-engaging the latching tooth 35 ofthe transducer actuator assembly 30 in the latching trap 62 and thus securing the transducer actuator assembly 30 in the locked state. The latching mechanism 40 ofthe present invention provides several advantages over the prior art latching mechanisms. First, there is no need for extraneous electronic controls because the latching mechanism 40 is based on airflow principles which inherently exist within the disk drive device 10. This leads to a second advantage 16 of reduced power consumption over prior art vanes which do require such controls. A further advantage is that a disk drive device 10 employing the latching mechanism 40 of the present invention can be assembled in an easier and more cost efficient manner since there is no vane-to-disk merge operation. A still further advantage is that when the latching apparatus 40 ofthe present invention is employed in a disk drive device 10 containing multiple stacked disks 20, the number of disk surfaces in the disk drive device 10 can be increased without significantly increasing the height ofthe disk drive device 10, since the air vane structure is not disposed between the disks 20, eliminating the need for extra spacing between the disks 20. Thus, the present invention can provide an easy to assemble, reduced power, cost efficient disk drive device 10. Having thus described an embodiment ofthe invention, it will now be appreciated that the objects ofthe invention have been fully achieved, and it will be understood by those skilled in the art that many changes in construction and circuitry and widely differing embodiments and applications ofthe invention will suggest themselves without departure from the spirit and scope ofthe invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting. 17

Claims: What is claimed is: 1. A pressure differential latch apparatus for a disk drive assembly contained in a housing including a base and integral sidewalls defining an interior space, the disk drive assembly including at least one rotatable data storage disk having a surface for storing data and a transducer actuator assembly, disposed over the surface of the data storage disk, having a transducer assembly for accessing data on the data storage disk and an actuator motor for positioning the transducer assembly relative to concentric data track locations on the data storage disk and to and from a head parking position on the data storage disk, the latch apparatus comprising: a fixed shaft attached to the base ofthe housing a predetermined distance from an edge ofthe data storage disk; a rigid air vane member including a hollow body rotatably disposed on the shaft and an air vane portion extending radially from the hollow body, the air vane portion having a surface area disposed between an area of low pressure and high pressure resulting from airflow generated by rotation of the data storage disk being blocked by the transducer actuator assembly; and a latching trap extending from the hollow body ofthe air vane member in a direction opposite ofthe air vane portion, the latching trap for releasably engaging a latching tooth on the transducer actuator assembly to latch the transducer actuator assembly and maintain the transducer assembly at the head parking position when the disk is not being rotated, wherein a pressure differential acts upon the surface area ofthe air vane portion to create a force at a distance, rotating the vane member to an unlocked position thereby causing the latching trap to release the transducer actuator assembly, and wherein in an absence ofthe airflow, the air vane member is biased to rotate the vane portion to a locked position thereby causing the latching trap to engage the transducer actuator assembly. 2. The pressure differential latch apparatus of claim 1 further comprising a spring bias for retaining the air vane member in the locked position in the absence ofthe airflow. 3. The pressure differential latch apparatus of claim 1, wherein the air vane portion and the latching trap are integral extensions ofthe hollow body. 4. The pressure differential latch apparatus of claim 1 further comprising a stop fixedly attached to the base in a space between the edge ofthe data storage disk and the air vane member, the stop for preventing the air vane member from rotating into contact with the data storage disk. 5. A latch apparatus for a disk drive assembly contained in a housing including a base and integral sidewalls defining an interior space, the disk drive assembly including at least one rotatable data storage disk having a surface for storing data and a transducer actuator assembly, disposed over the surface ofthe data storage disk, having a transducer assembly for accessing data on the data storage disk and an actuator motor for positioning the transducer assembly relative to concentric data track locations on the data storage disk and to and from a head parking position on the data storage disk, the latch apparatus comprising: a shaft attached to the base a predetermined distance from a peripheral edge ofthe data storage disk; and a latch member rotatably disposed on the shaft, the latch member including: a body portion rotatable about the shaft, a rigid vane portion movably disposed in a space between the peripheral edge ofthe data storage disk and the sidewalls ofthe housing, the vane portion having a surface with a first end fixedly attached to the body portion, and a second end 19 extending radially from the body portion to within a predetermined distance from one of the sidewalls, the vane portion having a locked position and an unlocked position, and a latching trap for engaging the transducer actuator assembly in a locked state when the transducer assembly is located at the head parking position whenever the data storage disk is not being rotated, and for releasing the transducer actuator assembly from the locked state when the data storage disk is rotated, wherein rotation ofthe data storage disk generates airflow, proximate to the surface of the disk, which is blocked by the transducer actuator assembly, the blocked airflow creating a pressure differential which acts upon the surface ofthe vane portion, rotating the latch member to the unlocked position thereby causing the latching trap to release the transducer actuator assembly from the locked state, and wherein in an absence ofthe airflow, the shaft is biased to rotate the latch member to the locked position thereby causing the latching trap to engage the transducer actuator assembly. 6. The latch apparatus of claim 5, wherein the shaft further comprises a spring bias for retaining the air vane portion in the locked position in the absence ofthe airflow. 7. The latch apparatus of claim 6 further comprising a stop fixedly attached to the base in a space between the peripheral edge ofthe data storage disk and the air vane portion, the stop for preventing the air vane portion from rotating into contact with the data storage disk. 8. The latch apparatus of claim 7, wherein the stop comprises a main body and a wall baffle extending from the main body, wherein the latch member comes in contact with a point on the main body of the stop to prevent the air vane portion of the latch member from rotating into contact with the data storage disk, and the wall baffle is positioned such that the wall baffle prevents low pressure air leakage when the transducer actuator assembly is positioned proximate the edge ofthe data storage disk. 9. The latch apparatus of claim 5, wherein the second end ofthe rigid air vane portion extends to within about .2 to about .7 mm from one ofthe sidewalls of the housing. 10. The latch apparatus of claim 5, wherein the rigid air vane portion and the latching trap are integral extensions ofthe body portion. 11. The latch apparatus of claim 5, wherein the body portion of the latch member comprises a forward section having a hollow cylindrical core in which the shaft is disposed, and a rear section from which the latching trap extends. 12. The latch apparatus of claim 5 , wherein the latch member is formed of polymerized plastic resin. 13. A method for releasably latching a transducer actuator assembly of a rotatable disk drive device contained in a housing in order to maintain a transducer assembly at a landing zone on a surface ofa data storage disk when the data storage disk is not rotating, the method comprising the steps of: positioning a latch member a predetermined distance from an edge ofthe data storage disk, the latch member including a body portion rotatably attached to the housing, a rigid air vane portion having a planar surface which is disposed orthogonal to the surface of the data storage disk, and a trapping latch releasably engaging the transducer actuator assembly to maintain the transducer assembly at the landing zone, the latch member positioned to rotate without contacting the data storage disk; generating airflow proximate the surface ofthe data storage disk by 21 ET RULE 28 rotation ofthe data storage disk; blocking airflow over a portion of the surface ofthe disk upstream from the latch member thereby creating a low pressure area upstream from the air vane portion, a high pressure area in a space between the air vane portion and sidewalls ofthe housing, and a pressure differential force; rotating the rigid air vane portion toward the edge ofthe rotating disk by the pressure differential force; releasing the transducer actuator assembly from the latching trap upon rotation ofthe rigid air vane portion toward the edge ofthe rotating disk. 14. The method of claim 13 further comprising steps of: ceasing rotation ofthe data storage disk, causing dissipation ofthe airflow and thereby removing the pressure differential force; biasing the latch member to rotate the rigid air vane portion away from the edge of the disk; and re-engaging the transducer actuator assembly with the trapping latch, wherein the transducer assembly is repositioned at the landing zone when the data storage disk is no longer rotated. 22 T

Inventors: MICHAEL A DAVID, MICHAEL, A., DAVID
Applicants: QUANTUM CORP, QUANTUM CORPORATION
Application year: 1996
Main classification: G11B5
IPC codes: G11B21