Abstract:
A method and an apparatus for providing a highly repeatable loading/unloading pathway for a read/write head of a disk drive.

Description:
BACKGROUND 
     The present invention relates to a ramp motion mechanism used to load and unload a read-write head to and from a surface of a data storage medium. 
     Data storage is an important aspect of today&#39;s information technology. Great efforts have been made by the storage industry to increase the areal data density of a storage medium in order to meet the ever increasing demand for higher capacity storage devices. Various types of disks, including magnetic disks and optical disks, constitute recording media. 
     Magnetic storage devices such as fixed or removable magnetic disks and tapes are widely-used conventional storage devices. The state-of-art conventional magnetic hard drive systems can achieve extremely high linear bit densities, especially with the new MR and GMR magnetic heads. For example, the areal density of many hard disk drives is on the order of about one gigabits per square inch. 
     Optical storage devices are emerging as an alternative technology to the conventional magnetic technology because of their potential for high density data storage. The areal density of an optical storage device, in principle, is only limited by the diffraction limit of an illuminating optical beam for reading or writing. One type of commercial optical storage technology is based on magneto-optical materials. These materials can currently produce an areal data density of about one gigabits per square inch. 
     Generally, each data storage device includes a spindle motor for rotating one or more disks containing data, a head assembly for recording data onto and reproducing data from the disks, and an actuator for moving the head assembly. The actuator typically includes an electromagnetic coil motor, usually a voice coil motor, to move the actuator with the head assembly back and forth over a disk surface. 
     Data is generally stored in each disk in a series of concentric or spiral tracks. These tracks are accessed by one or more read/write heads in the head assembly. A head is mounted to an arm that is in turn mounted to the voice coil motor. During operation, it is necessary to move the head from a current position to a target track in an operation referred to as a “seek” operation. In such a seek operation, a command is provided to the data storage device to access a certain sector on the disk(s). If the head is not positioned over a target track containing the desired sector, a seek profile is determined. The seek profile contains various parameters associated with the head, including acceleration, deceleration, velocity and position information of the head. The seek profile is used to move the head from its current position to the target track by controlling the voice coil motor to move the head to the target track. Periodically, the actual position and velocity of the head are compared to the seek profile and adjustments are made by controlling the voice coil motor. 
     Once the head is positioned over the target track, the head is maintained over the target track&#39;s center line for accurate read/write operations in an operation known as track following. A position error signal (PES) is generated based on variations of the head from the center line of the target track. The PES is part of a closed-loop servo drive system which obtains actual head position information based on a servo pattern and compares the servo pattern to the desired head position information. When the PES identifies a variation, the servo control system provides correctional commands to the voice coil motor to accurately maintain the head over the center line of the target track. 
     In order to achieve improved mechanical stability and to reduce noise in positioning the head assembly, disk drives also typically employ an actuator mechanism to position the read/write head over the recording surface of the disk. 
     An actuator assembly designed for a disk contained in a removable shuttle or cartridge must be able to move the read/write head away from the recording disk into a “park position” in order to prevent damages to the head when the disk shuttle/cartridge is either inserted or removed from the drive. Similarly, the actuator assembly also needs to move the read/write head toward the surface of the recording disk into a work position., These are relatively large movements for the read/write head, and a ramped surface is needed to provide highly repeatable loading and unloading movements of the read/write head to maximize usable disk space. 
     Therefore, there is a need for an invention to provide a highly repeatable loading surface for loading and unloading a read/write head to and away from a surface of a recording medium. 
     SUMMARY 
     Advantages of the invention include one or more of the following. The invention provides a simple, low-cost and reliable system for loading and unloading the read-write head to and from the media inside a shuttle. One advantage is that the invention provides a highly repeatable loading/unloading surface for the read-write head. Another advantage of this device is the provision of reliable positioning and smooth transition of the head to and from the media, thus protecting the data stored in the media. 
     Because the design of this invention is simple, the aforementioned advantages are achieved without increasing the complexity of the drive, thereby increasing the performance and reliability of the entire disk drive system. 
     In general, in one aspect, the invention features a ramp motion mechanism for loading and unloading a read/write head positioned at an end of an actuator arm in a disk drive, wherein said read/write head accesses and records information upon a disk residing inside a shuttle removable from the disk drive. The ramp motion mechanism consists of a base fixedly mounted in the disk drive, and a nose slidably mounted on the base, the nose has a ramped surface, the surfaces guide the read/write head toward and away from a surface of the disk. 
     Implementation of the invention may include one or more of the following features. The base may have a protrusion adapted to engage a notch in the nose to lock the nose in an extended position. The base further may be affixed to a lever mounted on a base plate of the disk drive to lock the nose in a retracted position. A plurality of positional and angular orientations may be controlled by applying a force on the nose. They may have angular orientations with six degrees of positional and angular freedom in three dimensions. The force may be applied to a particular area on the nose resulting in a reaction force to the force located at a plurality of pads on the nose. 
     In another aspect, the invention is directed to a method for loading and unloading a read/write head to and from an edge of a disk surface. The method includes one or more of the following. Moving a ramped surface of a fork of a ramp motion mechanism movably affixed to a static base of the mechanism toward the edge of the disk surface to receive the read/write head. It engages a lifter attached to the read/write head to slide along the ramped surface, and it moves the ramped surface away from the edge of the disk to remove the read/write head away from the surface of the disk. 
     The method may control the fork in a plurality of angular and positional orientations by applying a force to the fork and obtaining a reaction force from a plurality of pads on the fork. The fork may have at least two fixed positions on the base. The base and the fork may be formed of plastic. 
     In yet another aspect, the invention is directed to a device for loading and unloading a read/write head to and from an edge of a disk surface. The device having a static ramp and a ramp nose, the ramp nose sliding in a channel formed on a top surface of the static ramp to provide precise, repeatable pathway for loading and unloading the read/write head. 
     In another aspect, the invention is directed to a method for loading and unloading a read/write head to and from an edge of a disk mounted in a disk drive. The method providing a ramp motion device including a static ramp and a ramp nose sliding in a channel formed on a top surface of the static ramp. The ramp nose providing a pathway for loading and unloading the read/write head, and controlling the ramp nose in angular and positional orientations by applying a force to the ramp nose. The ramp nose may have a plurality of pads which supplies a reaction force in response to the applied force. The method may provide a lever affixed to a base plate of the disk drive, and may apply the force to the ramp nose. 
     In another aspect, the invention is directed to a ramp motion device for loading a read/write head, having a movable nose adapted to engage the read/write head, a support base whereupon the movable nose moves between two positions in a channel on the support base to move toward and away from a surface of a disk, and a plate lever, fixedly mounted on a base plate of a disk drive and attached to the support base at a first end, to place the movable nose in the two positions. The nose and the support base may be plastic. The second end of the plate lever may be attached to a spring. The lever may be metallic. The read/write head may be attached to the distal end of an arm of an actuator of the disk drive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is an assembly diagram of an optical data storage device. 
     FIG. 2 is a perspective view of the actuator assembly and the ramp motion mechanism. 
     FIG. 3 is the top view of one embodiment of the ramp motion mechanism. 
     FIG. 4A is the perspective view of the ramp motion mechanism of FIG.  3 . 
     FIG. 4B is the top view of the ramp motion mechanism of FIG.  4 A. 
     FIG. 4C is the side view of the ramp motion mechanism of FIG.  4 A. 
     FIG. 5 is the top view of the ramp nose. 
     FIG. 6A shows the contact surfaces of the ramp motion mechanism. 
     FIG. 6B is the ramp motion mechanism in extended position with the actuator arm. 
     FIG. 6C is the ramp motion mechanism in retracted position with the actuator arm. 
     FIG. 7A shows the reaction pads on the first side of the ramp nose. 
     FIG. 7B shows the reaction pads on the second side of the ramp nose. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an exploded view of an optical data storage device is shown. A loader assembly  160  is positioned over the spindle motor  110  within the base plate  102 . The loader assembly  160  accepts a cartridge containing a shuttle with disk, and the disk cartridge is used to minimize contamination by keeping a disk out of reach of a user at all times. 
     In one implementation, the read/write head is a “flying” head which is suspended over an optical media by an air-bearing surface in a near-field recording configuration where the phasing between an exit facet of the flying head and a recording layer in the media is a fraction of a wavelength. The flying head includes a near-field lens with a high index of refraction and usually has a near-field condition. A focus beam with a spot size smaller than that obtainable from a conventional optical system is achieved due to the use of this high index solid immersion lens as the near-field lens. The optical read/write head of this embodiment is described in more detail in U.S. patent application Ser. No. 08/846,916, entitled “ELECTRO-OPTICAL STORAGE SYSTEM WITH FLYING HEAD OR NEAR-FIELD RECORDING AND READING,” filed on Apr. 29, 1997 and issued as U.S. Pat. No. 6,243,350, the disclosure of which is incorporated herewith by reference. 
     Referring back to FIG. 1, a data storage device base assembly  100  is shown. The assembly  100  has a base plate  102  which is adapted to receive a spindle motor  110 . The spindle motor  110  rotates one or more data storage media such as optical disks or platters (not shown). The spindle motor  110  is attached to the base plate  102 . 
     Also attached to the base plate  102  is the actuator assembly  150  with an actuator body  180 , arm  170 , and a “flying” head  178 . The flying head  178  is suspended over the optical media by an air-bearing surface in a near-field recording configuration. A rotary actuator is used as a coarse positioned for the data storage drive, although other positioning devices may also be used. An optics module containing the flying head is attached to an actuator arm  170  of the actuator assembly  150 . Any user data sector on the optical media may be addressed with a read/write beam by adjusting the rotary actuator and turning a galvo mirror (not shown). The actuator assembly  150  is described in more detail in U.S. patent application Ser. No. 09/205,350, entitled “Voice Coil Motor Assembly” filed on Dec. 3, 1998 and abandoned. 
     The flying head  178  accesses an optical media on a platter (not shown) which can be writable/erasable materials (i.e., write-many-read-many), write-once-read-many materials, and read-only materials. The writable/erasable materials are the magneto-optic type, including but not limited to, rare earth materials. 
     The ramp motion mechanism  200  is attached to base plate  102  to provide a pathway for loading and unloading flying head  178 . In one embodiment, the ramp motion mechanism  200  is made of plastic. 
     To complete the assembly  100 , a cover  190  is screwed into the base plate  102 . Further, a face plate assembly  195  is mounted to the front of the base plate  102  to provide data access information to the user through light-emitting diodes (LEDs). 
     FIG. 2 shows a detailed blown-up view of the actuator assembly  150  and the ramp motion mechanism  200 . The ramp motion mechanism  200  includes a stationary ramp, also called the static ramp or the support base,  210 , and a dynamic ramp nose, or fork,  220 . Actuator assembly  150  includes the actuator arm  170 , lifter  202 , and the read/write head  178 . Read/write head  178  is described as a flying head above, but it can be a number of other commercially available read/write heads. 
     In loading or unloading operations, lifter  202  contacts surface  680 , which is a part of the static ramp  210 , and surface  685 , which is a part of the nose  220 , as shown in FIG.  6 A. For dual read/write heads, the bottom surface  695  of the nose  220  and a corresponding part (not shown) of the static ramp  210  will also be used. 
     Referring to FIG. 3, the ramp motion mechanism  200  is shown in the top view, with ramp nose  220  in extended position. The ramp motion mechanism  200  has two stable positions, retracted and extended positions. These two positions are distinguished by the position of the ramp nose  220  relative to the static ramp  210 . Ramp nose  220  slides between the two ends of the channel  320  situated on the top surface of the static ramp  210 . At end  330  of channel  320 , the ramp nose  220  is in retracted position. At end  340  of channel  320 , the ramp  220  is in extended position. In the retracted position, the ramp nose  220  is inward on the static ramp  210 . In the retracted position, the ramp motion mechanism  200  provides maximum clearance for a disk cartridge to move into a loaded position. Channel end  330  stops the motion of the ramp nose  220 . In the extended position the ramp nose  220  is extended out from the static ramp  210 . The ramp motion mechanism  200  is held in this position to provide a pathway for the read/write head  178  to load smoothly onto the disk. 
     The accurate positioning and angular orientation of the ramp nose  220  are important because they control the landing site of the read/write head  178 . The ramp nose  220  is accurately controlled by the way it “docks” with the static ramp  210 . The surfaces and shapes of the static ramp  210  and ramp nose  220  are such that the position and angular orientation of the ramp nose are controlled completely in all six positional and angular degrees of freedom (the three axes and three angles). This is accomplished by means of the applied force and reaction forces that push on the ramp nose to be explained infra. 
     The ramp nose  220  is held in one of these two positions by the force exerted by lever  310 . Lever  310  in one implementation is attached to the base plate of the disk drive and is therefore also called plate lever. At the other end of lever  310  there is a spring torsion  320 . As lever  310  moves from end  330  to end  340 , or vice versa, spring  320  passes a center position, on either side of which spring  320  produces a force to push lever  310  until lever  310  is stopped by the ramp motion mechanism  200 . In one embodiment, lever  310  is made of metal. 
     FIGS.  4 A— 4 C show the perspective, top, and side views of the ramp motion mechanism  200  respectively. FIG. 5 shows the top view of the ramp nose  220 . Ramp nose  220  has loop  410 , which is where lever  310  applies a force. 
     FIG. 6A shows the contact surface  680 , which is a part of static ramp  210 , and contact surface  685 , which a part of nose  220 . In loading and unloading, lifter  202  contacts surfaces  680  and  685 . The distal end  690  of nose  220  is at a shallow angle of 20 degrees or less for loading and unloading a read/write head  178 . 
     FIG. 6B shows the ramp motion mechanism  200  in the extended position as it is ready to load into and unload from disk  610 . FIG. 6C shows the ramp motion mechanism  200  in the retracted position. 
     FIGS. 7A and 7B show a plurality of reaction pads present on the ramp nose  220  to provide reaction forces that push on the ramp nose  220  as it receives a force from lever  310  at location  710 . Reaction pads  720  and  715  are on one side of the nose  220 , and reaction pads  725 ,  730 ,  740 , and  745  are on the other side of the nose  220 . As lever  310  applies a force to nose  220  at location  710 , reaction forces to this applied force are located at the reaction pads on both sides of nose  220 . These pads dock the ramp nose  220  in the desired position and angular orientation. The ramp nose  220  is precisely controlled by the way it “docks” with static ramp  210 . The surfaces and shapes of the static ramp  210  and ramp nose  220  are such that the position and angular orientation of the ramp nose  220  are controlled completely in six degrees of freedom in three dimensions. Thus, the ramp motion mechanism  200  provides precise, repeatable pathway for loading and unloading read/write head  178  unto and from disk  610 . 
     Although the present invention has been described in detail with reference to the embodiments therein, one ordinarily skilled in the art to which this invention pertains will appreciate that various modifications and enhancements may be made without departing from the spirit and scope of the following claims. For example, the ramp motion mechanism can be used to engage two or more read/write head simultaneously attached to the actuator to access information of two or more recording disks.