Patent Publication Number: US-2022238137-A1

Title: Moveable ramp for data storage device

Description:
This application is a continuation-in-part of U.S. application Ser. No. 16/910,593, filed on Jun. 24, 2020, which published as U.S. publication number 2021/0407538 A1, on Dec. 30, 2021, the content of which is hereby incorporated by reference in its entirety. 
    
    
     SUMMARY 
     In one embodiment, a data storage device is provided. The data storage device includes a ramp configured to support at least one head in the data storage device, and a movement mechanism coupled to the ramp and configured to move the ramp from a first position to a second position by at least one of expansion or contraction of at least a portion of the movement mechanism. The data storage device further includes a ramp motion control module operably coupled to the movement mechanism. The ramp motion control module is configured to provide the movement mechanism with a first control signal that causes the movement mechanism to move the ramp from the first position to the second position. The data storage device additionally includes a latch configured to hold the ramp. 
     In another embodiment, a method of operating a ramp that is configured to support a head in a data storage device is provided. The method includes moving the ramp from a first position to a second position. The method also includes selectively releasing the ramp from the second position at different speeds corresponding to different operating conditions in the data storage device. 
     In yet another embodiment, a data storage system in provided. The data storage system includes a ramp configured to support at least one head in the data storage system. The ramp has a plurality of positions in the data storage system. The data storage system also includes a latch configured to hold the ramp in at least two of the plurality of positions. 
     Other features and benefits that characterize embodiments of the disclosure will be apparent upon reading the following detailed description and review of the associated drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  are schematic illustrations of a data storage device including data storage media, heads for reading data from and/or writing data to the data storage media, and a retractable ramp for supporting the heads in accordance with one embodiment. 
         FIG. 2  is a perspective view of an embodiment of an elevator for simultaneously moving the retractable ramp and a head stack assembly included in the data storage device of  FIGS. 1A-1C . 
         FIGS. 3A-3C  are diagrammatic illustrations of portions of a data storage device including discs that are vertically movable by a retractable ramp in accordance with one embodiment. 
         FIGS. 4A-4C  are diagrammatic illustrations of portions of a data storage device that employs a ramp retraction mechanism including one or more shape memory alloy (SMA) wires in accordance with one embodiment. 
         FIGS. 5A and 5B  and flowcharts of methods of operating a retractable ramp and a latch mechanism in different data storage device operating modes. 
         FIG. 6  is a flowchart of a method that may be carried out in a data storage device that includes a retractable ramp and an elevator for moving the ramp. 
         FIG. 7  is a diagrammatic illustration of a portion of a data storage device that employs a moveable ramp in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Embodiments of the disclosure relate to a moveable head-support ramp for use in a data storage device (e.g., a hard disc drive (HDD)). 
     In general, in order to keep read/write heads from landing on one or more discs in the HDD when, for example, power is removed from the HDD, and to prevent the heads from colliding with outer edges of the discs during load and unload operations, a head-support ramp is provided adjacent to an outer diameter (OD) of the disc or discs. In a traditional HDD, the ramp is placed over portions of the disc surfaces near the OD such that the heads can easily move on and off the discs straight from/onto the ramp. Such ramps, which remain stationary during HDD operation in traditional HDDs, take space on the discs and reduce the area for recording, thereby leading to loss of storage capacity per HDD, about 5% loss in capacity in some cases. 
     To address this above-noted problem, embodiments of the disclosure employ a retractable ramp that moves completely off the disc(s), or nearly off the disc(s), when the OD area is to be accessed, thereby enabling data recording to be carried out on substantially entire surfaces of the disc(s). Details regarding the different embodiments are provided below in connection with  FIGS. 1A-6 . 
       FIG. 1A  shows an illustrative operating environment in which certain embodiments disclosed herein may be incorporated. The operating environment shown in  FIG. 1A  is for illustration purposes only. Embodiments of the present disclosure are not limited to any particular operating environment such as the operating environment shown in  FIG. 1A . Embodiments of the present disclosure are illustratively practiced within any number of different types of operating environments. 
     It should be noted that the same reference numerals are used in different figures for same or similar elements. It should also be understood that the terminology used herein is for the purpose of describing embodiments, and the terminology is not intended to be limiting. Unless indicated otherwise, ordinal numbers (e.g., first, second, third, etc.) are used to distinguish or identify different elements or steps in a group of elements or steps, and do not supply a serial or numerical limitation on the elements or steps of the embodiments thereof. For example, “first,” “second,” and “third” elements or steps need not necessarily appear in that order, and the embodiments thereof need not necessarily be limited to three elements or steps. It should also be understood that, unless indicated otherwise, any labels such as “left,” “right,” “front,” “back,” “top,” “bottom,” “forward,” “reverse,” “clockwise,” “counter clockwise,” “up,” “down,” or other similar terms such as “upper,” “lower,” “aft,” “fore,” “vertical,” “horizontal,” “proximal,” “distal,” “intermediate” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or directions. It should also be understood that the singular forms of “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. 
     It will be understood that, when an element is referred to as being “connected,” “coupled,” or “attached” to another element, it can be directly connected, coupled or attached to the other element, or it can be indirectly connected, coupled, or attached to the other element where intervening or intermediate elements may be present. In contrast, if an element is referred to as being “directly connected,” “directly coupled” or “directly attached” to another element, there are no intervening elements present. Drawings illustrating direct connections, couplings or attachments between elements also include embodiments, in which the elements are indirectly connected, coupled or attached to each other. 
       FIG. 1A  is a schematic illustration of a data storage device  100  including data storage media, heads for reading data from and/or writing data to the data storage media and a retractable ramp for supporting the heads. In data storage device  100 , heads  102  may be positioned over storage media  104  to read data from and/or write data to the data storage media  104 . In the embodiment shown in  FIG. 1A , the data storage media  104  are rotatable data storage discs, with each disc  104  having opposing surfaces that serve as data storage surfaces. It should be noted that, in some embodiments, a single disc may be employed instead of multiple discs. For read and write operations, a spindle motor  106  (illustrated schematically) rotates the media  104  as illustrated by arrow  107  and an actuator mechanism  110  positions the heads  102  relative to data tracks  114  on the rotating media  104  between an inner diameter (ID)  108  and an outer diameter (OD)  109 . Both the spindle motor  106  and actuator mechanism  110  are connected to and operated through drive circuitry  112  (schematically shown). Each head  102  is coupled to the actuator mechanism  110  through a suspension assembly which includes a load beam  120  connected to an actuator arm  122  of the mechanism  110  for example through a swage connection. The actuator mechanism  110  is rotationally coupled to a frame or deck (not shown) through a bearing  124  to rotate about axis  126 . Rotation of the actuator mechanism  110  moves the heads  102  in a cross-track direction as illustrated by arrow  130 . Each of the heads  102  includes one or more transducer elements (not shown) coupled to head circuitry  132  through flex circuit  134 . 
     As indicated above, in general, in order to keep read/write heads  102  from landing on discs  104  in a data storage device  100  when, for example, power is removed from the data storage device  100 , and to prevent the heads  102  from colliding with outer edges of the discs  104  during load and unload operations, a head-support ramp  136  is provided adjacent to the OD  109  of the discs  104 . As can be seen in  FIG. 1A , ramp  136  includes tapers  144  that have edges  146  that are located over portions of the disc surfaces near the OD  109  to enable the heads  102  to easily move on/off the discs from/to main portions  148  of tapers  144  where lifts or lift tabs  149 , which extend beyond heads  102 , rest when the heads  102  are in a “parked” position. 
     When, for example, heads  102  are in the parked position and data storage device  100  receives a command from a host (not shown) to access one or more disc  104  surfaces, actuator mechanism  110  rotates about axis  126  to move the heads  102  toward the disc  104  surfaces. Such movement of the actuator mechanism  110  causes the lifts or lift tabs  149  to move towards the discs  104  by following surfaces of the tapers  144  towards the edges  146 . When the heads  102  reach the edges  146 , they establish bearings (e.g., air bearings) on the disc  104  surfaces and are then able to access the disc  104  surfaces for reading and/or writing to complete executing the command received from the host. 
     The process of moving the heads  102  from the ramp  136  to the disc  104  surfaces, which is referred to as a head load (or simply a load) operation, occurs smoothly when the edges  146  of the tapers  144  are located over portions of the disc surfaces near the OD  109 . Similarly, the process of moving the heads  102  from the disc  104  surfaces to the ramp  136 , which is referred to as a head unload (or simply an unload) operation, takes place smoothly when the when the edges  146  of the tapers  144  are located over portions of the disc surfaces near the OD  109 . The heads  102  may be unloaded when, for example, the data storage device  100  no longer needs to access the disc  104  surfaces. Portions of the disc  104  surfaces over which the edges  146  of the tapers  144  are positioned during head load and unload operations are referred to as load/unload zones and are denoted by reference numeral  150  in  FIG. 1A . 
     As indicated above, not recording data in the load/unload zones may amount to a loss of about 5% storage capacity of the data storage device  100 . To avoid such a loss in capacity, data storage device  100  employs a retraction mechanism (or movement mechanism)  152  that is attached to ramp  136  and is operable to retract ramp  136 , such that edges  146  of tapers  144  are withdrawn from the OD  109  region to no longer substantially overlap the load/unload zones  144  after the heads  102  are properly loaded and supported by, for example, the air bearings, thereby making the load/unload zones  150  accessible for data storage/retrieval.  FIG. 1B  shows ramp  136  in a retracted position and the load/unload region being accessed by the heads  102 . Details regarding example retraction mechanisms are provided further below. 
     In some embodiments, in addition to retracting ramp  136  to allow for recording data in load/unload zone  150  during operation of data storage as shown in  FIG. 1B , ramp  136  may also be retracted when the heads  102  are in the parked position on ramp  136 . The retraction of the ramp  136  when the heads  102  are in the parked position enables up and down movement of heads  102 . Reasons why up and down movement of the heads  102  is used is some embodiments and a description of one such embodiment are provided below. 
     In some embodiments, a number of heads  102  is less than a number of disc  104  surfaces. For example, data storage device  100  of  FIGS. 1A and 1B  includes 4 discs, with a total of 8 data storage surfaces, and 4 heads  102 . Each of the 4 heads  102  is coupled to the actuator mechanism  110  through a suspension assembly which includes load beam  120  connected to an actuator arm  122 . The actuator mechanism  110 , the load beams  120  and the actuator arms  122  with the heads  102  and lift tabs  149  are collectively referred to as a head stack assembly (HSA). The HSA, which is denoted by reference numeral  138 , may be moved along axis  126  between an upper position and a lower position with the help of an elevator  140 , which is schematically shown in  FIGS. 1A . In the upper position shown in  FIG. 1A and 1B , the 4 heads interact with data storage surfaces of discs  104 A and  104 B. In the lower position (not shown), the same 4 heads interact with data storage surfaces of discs  104 C and  104 D. 
     In order to enable the up/down movement of the HSA  138 , head-support ramp  136  is designed to be retractable away from the OD  109  to permit the upward/downward movement of the ramp and HSA  138  without contacting the data storage media  104 . In order to move the HSA  138  from either the upper position to the lower position or from the lower position to the upper position, the HSA  138  is first rotated about axis  126  until lift tabs  149  of the HSA  138  are supported on ramp  136  when the edges  146  of the tapers  144  are located over portions of the disc surfaces near the OD  109 . Then, the ramp  136 , with the lift tabs  149  of the HSA  138  thereon, is retracted away from the discs  104  by the retraction mechanism  152 . Once the ramp  136  supporting the heads  102  is retraced as shown in  FIG. 1C , the HSA  138  and the ramp  136  may be moved up/down in unison by the elevator  140 . In the position shown in  FIG. 1C , the HSA  138  and the ramp  136  may be moved down in unison for the heads  102  to be able to access data storage surfaces of discs  104 C and  104 D. Details regarding one embodiment of elevator  140  are provided below in connection with  FIG. 2 . 
       FIG. 2  illustrates an embodiment of an elevator  200  for the ramp  136  and the HSA  138 , allowing them to move in unison. Elevator  200  includes an upper portion  201  and a lower portion  202 . In one embodiment, each of portions  201  and  202  has a flexible first end  230  and a flexible second end  232 . In general, one or both portions  201  and  202  may be either flexible or floating. The HSA  138  and ramp  136  are positioned between the upper portion  201  and the lower portion  202  and are connected together via a base  220  of elevator  200 , thereby enabling the HSA  138  and the ramp  136  to be moved together. In one embodiment, the elevator base  220  may be driven up and down by a coil and a magnet (not shown) with hard stops at both ends that limit the extent of upward and downward movement of the HSA  138  and the ramp  136 . In general, any suitable driving mechanism may be used to move elevator  200  up and down. 
     In the embodiment illustrated in  FIG. 2 , the upper limit comprises a stopper  250  arranged with the ramp  136 . The flexible first end  230  of the upper portion  201  reaches the stopper  250  of the ramp  136  and halts the upward movement. In the downward direction, the movement may be stopped by the base  220  reaching the flexible first end  230  of the lower portion  202  which halts the progression of the downward movement. This arrangement may be pre-assembled before being placed into a form factor for a disc drive. 
     In some embodiments, when a number of heads  102  is less than a number of disc  104  surfaces, and the discs  104  are closely spaced, at least some of the discs  104  may be moved up/down by retractable ramp  136  to enable read/write operations to be carried out. Such an embodiment is shown in  FIGS. 3A-3C , which are described below. 
       FIGS. 3A-3C  illustrate an embodiment where a data storage device  300  may increase volumetric capacity (relative to a data storage device such as  100  of  FIG. 1A ) by allowing discs  104  to translate vertically, thereby permitting a decrease in relative disc spacing of at least some of the discs  104  to a distance that is small enough to be insufficient to accommodate an arm and head. In the embodiment of  FIGS. 3A-3C , one up head (e.g., a head that interacts with upper surfaces of discs  104 ) and one down head (e.g., a head that interacts with lower surface of discs  104 ) may be employed to interact with discs  104 A- 104 G. In the interest of simplification, the up and down heads are not shown in  FIGS. 3A-3C . For example, in order to accommodate the down head to carry out a read/write operation to the lower surface of disc  104 E, ramp  136  is first moved in a horizontal or X-direction as shown by arrow  302  in  FIG. 3A . Once the edge  146  of ramp  136  reaches the position below disc  104 E as shown in  FIG. 1A , disc  104 E may be moved in an upward direction along a Z-axis. Up/down movement along the Z-axis is denoted by reference numeral  304 , and the extent of upward movement by disc  104 E is denoted by reference numeral  306 . The upward movement may be carried out by, for example, elevator  140  shown in  FIG. 1A , which may lift the ramp  136 , which, in turn, lifts disc  104 E. Once disc  104 E is moved to the position shown in  FIG. 3B , the down head may be accommodated for a read/write operation to the lower surface of disc  104 E. After the down head is loaded, the ramp  136  may be retracted to the position shown in  FIG. 3C  (in direction  308 ) for the down head to be able to read/write from/to load/unload zone as described above in connection with  FIG. 1A . 
       FIGS. 4A-4C  are diagrammatic illustrations of portions of a data storage device  400  that employs a retractable ramp in accordance with one embodiment.  FIGS. 4A  is a top view of a portion of data storage device  400  without a ramp retraction control module of  FIG. 4B  installed, and  FIG. 4C  is a top view of the portion of the data storage device  400  with the ramp retraction control module of  FIG. 4B  installed. 
     Referring to  FIG. 4A , ramp  402  is shown in a retracted position where an edge  404  of the ramp  402  is only over a small portion of load/unload zone  150 . It should be noted that, in embodiments in which the ramp  402  is moved up/down in addition to being retractable, the edge  404  of ramp  402  is withdrawn past OD  109  to prevent the ramp  402  from contacting (or colliding with) the disc  104  during the up/down motion. As can be seen in  FIG. 4A , the ramp  402  is held in the retracted position by latch  406 . Latch  406  has a fixed end  408 , which may be attached to any suitable portion of the data storage device  400 , and a moveable end  410  that has a protrusion  412  that is configured to engage a corresponding protrusion  414  of the ramp  402  when the ramp  402  is retracted. 
     In the embodiment shown in  FIG. 4A , shape memory alloy (SMA) wires are employed to carry out the ramp  402  retraction. In general, a SMA wire may be in an expanded sate at room temperature (e.g., between about 15 degrees Celsius (° C.) and about 25° C.). To cause the SMA wire to contract, an electrical current may he supplied to the SMA wire to heat the wire. The heating of the wire above room temperature causes the wire to contract. It should be noted that SMA wires are only one example of a retraction/manipulation mechanism and other suitable retraction/manipulation mechanisms may be used in other embodiments. As can be seen in  FIG. 4A , a first end of a first SMA wire (or wires)  416  is connected to ramp  402 , and a first end of a second SMA wire (or wires)  418  is connected to latch mechanism  406  at moveable end  410 . More particularly, the first end of the second SMA wire  418  is connected to an outer portion of the moveable end  410  of the latch mechanism  406 , with the protrusion  414  being on the opposite (or inner) side of moveable end  410 . Second ends of SMA wires  416  and  418  are connected to pins  420 , with one of the pins  420  serving as a common (or ground) connection pin. Portions of the SMA wires  416  and  418  proximate to the pins  420  are hidden in  FIG. 4A . 
     Referring to  FIG. 4B , a ramp retraction control module (or ramp motion control module)  421  is shown. The ramp retraction control module  421  includes a control chip  422  and pads  424  that are coupled to the control chip  422 . The coupling between the control chip  422  and the pads  424  is hidden in  FIG. 4B . Control chip  422  is configured to selectively provide power (e.g., current) to SMA wires  416  and  418  when the ramp retraction control module  421  is installed in data storage device  400  in a manner shown in  FIG. 4C . Here, the pads  424  are in contact with the pins  420 . 
     To move the ramp  402  to the retracted position shown in  FIGS. 4A and 4B , control chip  422  supplies power (e.g., current) to SMA wire  416 , which responsively contracts as a result of a temperature rise caused by the current. The contraction of SMA wire  416  causes ramp  402  to retract. Withdrawal of the ramp  402  takes place until protrusion  412  on ramp  402  engages with corresponding protrusion  414  on latch  406 . In order to facilitate the engagement of  412  and  414 , control chip  422  may supply power (e.g., current) to SMA wire  418  substantially concurrently with current being supplied to SMA wire  416 . This causes SMA wire  418  to contract, which, in turn, causes the latch  406  to bend backwards near end  410 . The backward bending of the latch  406  brings protrusion  414  to a position where it is capable of engaging with protrusion  412  when latch  406  straightens from its bent position. Thus, with latch  406  in the retracted position, current supply to SMA wire  418  is terminated, which causes SMA wire  418  to expand. Expansion of the SMA wire  418  cause latch  406  to straighten, which, in turn, causes protrusion  414  to engage protrusion  412 . When protrusions  412  and  414  are engaged, supply of current to SMA wire  416  may be terminated by the control chip  422  because ramp  416  is now held in the retraced position by latch  406 . 
     To carry out a “quick release” of the ramp  402  from the retracted position to its non-retraced position (not shown in  FIGS. 4A-4C ), control chip  422  provides power (e.g., current) to SMA wire  418 , which responsively contracts. The contraction of SMA wire  418  causes the latch  406  to bend backwards, which, in turn, results in protrusion  414  disengaging from protrusion  412 , thereby causing ramp  402  to return back to its non-retracted position. The quick release may be carried out when an emergency condition occurs (e.g., a loss of main power supply) in the data storage device  400 . The quick release may be carried out using backup or residual power in the data storage device  400 . A normal release of the ramp  402  by the latch  406  may be carried out during normal operation of data storage device  400  under normal power supply conditions. Both normal and quick release operations are described below in connection with  FIGS. 5A and 5B . 
       FIGS. 5A and 5B  are flowcharts of methods of operating a retractable ramp and a latch mechanism in different data storage device operating modes.  FIG. 5A  is a flowchart of a basic retraction and latching method  500  when the data storage device is operating in a normal or standard mode. The normal or standard operation mode is denoted by reference numeral  502 . At  504 , a determination is made as to whether read/write operations are to be carried out in a load/unload zone of the data storage device. If no such operations are to be carried out, control returns to  502 . If read/operations are to be carried out in the load/unload zone, control passes to  506 . At  506 , power is provided to the retraction mechanism coupled to the ramp and to the latch (e.g., the retraction mechanism is energized). As described above in connection with  FIGS. 4A-4C , when power is supplied to the retraction mechanism coupled to the ramp (e.g., the SMA wire), the SMA wire contracts, thereby move the ramp to its retraced position. Supplying power to the SMA wire coupled to the latch causes the latch to bend backwards. Thus, the operations carried out at  506  cause the ramp to retract and the latch to bend backwards substantially simultaneously. At  508 , power to the latching mechanism is terminated (e.g., the SMA coupled to the latch no longer receives power or is de-energized). This results in the latch engaging the ramp, thereby causing the ramp to be held in the retracted position independently of whether power is provided to the SMA wire connected to the ramp. Thus, power to the SMA wire connected to the ramp is terminated at  510 . 
     At  512 , use of the load/unload zone for the read/write operations is monitored. Once it determined that load/unload zone is no longer to be used, control passes to  514 . At  514 , power is provided to the ramp retraction mechanism (e.g., power is provided to the SMA wire connected to the ramp). Thereafter, at  516 , power is provided to the latch mechanism (e.g., power is provided to the SMA coupled to the latch). This causes the latch to disengage from the ramp. At  518 , power to the ramp retraction mechanism is terminated (e.g., the power provided to the SMA wire connected to the ramp is terminated). This causes the SMA wire connected to the ramp to expand, thereby returning the ramp to its non-retracted position. After a predetermined wait period shown at  520 , the power to the latching mechanism is terminated (e.g., power is provided to the SMA coupled to the latch is terminated) at  522 , thereby returning the latch to the non-bent position. 
       FIG. 5B  is flowchart of a method  550  that adds emergency data storage device shutdown-related operations to method  500  of  FIG. 5A . In the interest of brevity, a description of  502 - 522  is not repeated in connection with  FIG. 5B . In method  550 , in addition to monitoring the use of the load/unload zone for the read/write operations at  512  when the ramp is in a retracted position, at  552 , monitoring is carried out for abnormal events taking place in the data storage device that may cause an emergency shutdown. Upon detection of an emergency shutdown (e.g., from a signal sent by a drive controller (not shown) to ramp retraction control module  421 ) at  552 , control passes to  554  where power is provided to the latch mechanism (e.g., power is provided to the SMA wire coupled to the latch). This results in a “quick release” of the ramp, thereby causing a rapid return of the ramp to its un-retracted position for the heads to be loaded onto the ramp. Once the heads are loaded onto the ramp, the data storage device may be safely shut down. 
       FIG. 6  is a flowchart of a method  600  that may be carried out in a data storage device that includes a retractable ramp and an elevator for moving the ramp along a z-axis direction. In the interest of brevity, a description of  502 - 522 ,  552  and  554  is not repeated. At  602 , a determination is made as to whether read/write operations are to be carried out at a different level (e.g., on one or more disc surfaces that may not be accessed without moving the head(s) in a z-direction to reach the surface(s) of interest). If it is determined, at  602 , that a level switch is to be carried out, the HSA is moved to the ramp at  604 . Thereafter, at  606 , a flag is set in a suitable memory within the data storage device to indicate that the HSA is to be moved to a different level. Thereafter, the ramp is retracted and latched in accordance with  506 - 510  described earlier in connection with  FIG. 5A . At  512 , use of the load/unload zone for the read/write operations is monitored. When it is determined, at  512 , that load/unload zone is no longer to be used, control passes to  608 . At  608 , a determination is made as to whether the switch level flag is set. If the switch level flag is found to be set, control passes to  610  where the elevator is operated to move the HSA and the ramp to the new level. The switch level flag is then reset at  612 . 
     It should be noted that the method embodiments described above may be carried out by drive circuitry  112 , head circuitry  132 , ramp  136 , latch mechanism  406 , retraction mechanism  152  (e.g., ramp retraction control module  421 ), elevator  140 , etc. Portions of drive circuitry  112 , head circuitry  132  and ramp retraction control module  421  may together constitute a controller that carries out at least some control operations in the method embodiments described above. 
     In the above-described embodiments, the retraction mechanism employs a SMA wire the contracts when it is energized. The SMA wire is only one example of an element that may be used to carry out the retraction of the ramp. In general, any retraction mechanism that moves the ramp between non-retracted and retracted positions by expansion and/or contraction may be employed. The expansion and/or contraction may act in a manner similar to a muscle that can change length by contracting and/or stretching. Thus, the ramp retraction mechanism may also be viewed as a muscle-based system. In general, any suitable expansion/contraction system may be employed in different embodiments. For example, some alternate embodiments may employ piezoelectric elements to enable the retraction of the ramp. 
     In the above-described embodiments, the movement of the ramp (e.g., ramp  402  of  FIGS. 4A-4C ) is described as taking place from a non-retracted position to a retracted position, and then back to the non-retracted position. Also, the description of  FIGS. 4A-4C  indicates that latch  406  is activated to hold the ramp  402  in the retracted position, and to release the ramp  402  to allow for movement of the ramp  402  back to the non-retracted position. However, in alternate embodiments, the latch  406  and other elements that enable latching may be configured to hold the ramp  402  in a number of different positions. One such embodiment is described below in connection with  FIG. 7 . 
       FIG. 7  is a diagrammatic illustration of a portion of a data storage device  700  that employs a moveable ramp  402  in accordance with one embodiment. In the interest of brevity, elements of  FIG. 7  that are similar to previously-described elements included in  FIGS. 4A-4C  are not described again in connection with  FIG. 7 . As can be seen in  FIG. 7 , multiple protrusions (e.g.,  412 A,  412 B and  412 C) are included on ramp  402  to selectively engage with protrusion  414  on latch  406 . In one embodiment, different levels of power (e.g., current) or times of power application or a combination of both may be provided by control chip  422  to SMA wire  416  to move the ramp  402  to different positions. For example, to move/bring ramp  402  to a first position, either no power (e.g., current) or a first level of power may be provided to SMA wire  416 . In the first position of the ramp  402 , latch  406  may be configured to engage with protrusion  412 A. To move ramp  402  to a second position, a second level of power (e.g., current), which may be higher than the first level of power, may be provided to SMA wire  416 . In the second position of the ramp  402 , latch  406  may be configured to engage with protrusion  412 B. To move ramp  402  to a third position, a third level of power (e.g., current), which may be higher than the first and second levels of power, may be provided to SMA wire  416 . In the third position of the ramp  402 , latch  406  may be configured to engage with protrusion  412 C. 
     As described above in connection with  FIGS. 4A-4C , control chip  422  may supply power (e.g., current) to SMA wire  418  to cause SMA wire  418  to contract, which, in turn, causes the latch  406  to bend backwards near end  410 . The backward bending of the latch  406  brings latch protrusion  414  to a position where it is capable of engaging with ramp protrusion  412 A,  412 B or  412 C when latch  406  straightens from its bent position. Thus, with latch  406  in the first, second or third positions, current supply to SMA wire  418  may be terminated, which causes SMA wire  418  to expand. Expansion of the SMA wire  418  causes latch  406  to straighten, which, in turn, causes latch protrusion  414  to engage ramp protrusion  412 A,  412 B or  412 C. When ramp protrusion  412 A,  412 B or  412 C and latch protrusion  414  are engaged, supply of current to the SMA wire  416  may be terminated by the control chip  422  because ramp  402  is now held in a suitable position by latch  406  engaging  412 A,  412 B or  412 C. The latch  406  may be released in any suitable manner (e.g., as described above in connection with  FIGS. 4A-6 ). 
     In different embodiments, latch  406  may be configured to hold the ramp  402  in a retracted position, a non-retracted position, one or more intermediate positions between the retracted and non-retracted positions, one or more rotary positions if the ramp  402  is rotatable, etc. In general, latch  406  may be configured to hold the ramp  402  in any suitable position. It should be noted that different types of latches may be employed in different embodiments. For example, in an alternate embodiment, the latch may be a clamp-like system where, rather than catching on a hook/protrusion, the latch holds/clamps on to the ramp  402  in an engaged position, and may be released from the engaged position. The latching mechanism may be SMR-based, piezo-based or may use any other suitable form of actuation including magnetic actuation. If magnetic actuation is employed for the latch, magnetic shielding may be utilized to protect the head from magnetic fields from the magnetic actuation system. 
     The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of apparatus and systems that utilize the structures or methods described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. Additionally, the illustrations are merely representational and may not be drawn to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be reduced. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive. 
     One or more embodiments of the disclosure may be referred to herein, individually and/or collectively, by the term “invention” merely for convenience and without intending to limit the scope of this application to any particular invention or inventive concept. Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description. 
     The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b) and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments employ more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. 
     The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.