Abstract:
A latch for locking a drive arm of a disk drive in a parking position comprising: a latch stop having a baffle moveable between an open position and a closed position; and a piezoelectric motor operable to move the baffle between the open and closed positions. When the drive arm is in the parking position it engages the baffle and is prevented from leaving the parking position when the baffle is in the closed position and is not prevented from leaving the parking position when the baffle is in the open position.

Description:
RELATED APPLICATIONS 
     The present application is a U.S. national application of PCT/IL98/00263, filed Jun. 4, 1998. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to data storage disk drives and in particular to latching a read/write arm that moves a read/write head over the surface of a magnetic data storage disk. 
     BACKGROUND OF THE INVENTION 
     Magnetic disk drives for data storage are an integral part of almost all computers. A conventional magnetic disk drive comprises at least one magnetic data disk on which data bits can be recorded by changing the state of magnetic domains on the surface of the disk. The disk drive also comprises a read/write head, hereinafter referred to as a “data head” for each of the at least one disk for “writing” or “reading” the domains on the disk surface. The data head for a disk is located at one end of a read/write arm, hereinafter referred to as a “drive arm”. A drive arm motor moves the drive arm so as to accurately position the data head over different regions of the surface of the disk used for data storage in order to read or write data to these regions. The disk drive comprises a drive frame to which the at least one data disk, drive arm and other parts of the disk drive are mounted. 
     When in use, the disk is rotated at high speed by a spindle motor. The rotation causes a cushion of air to form between the data head and the disk surface that keeps the data head a small (generally less than a micron), substantially constant, distance from the disk surface. The air cushion thereby prevents direct and possibly damaging contact between the data head and the surface of the disk while the data head moves over the surface of the disk. In effect, the data head glides “frictionless” over the surface of the disk on an air bearing. 
     When not in use the disk is stationary and the drive arm is rotated into a parking position so that the data head is positioned away from regions of the surface of the disk that are used for data storage. The drive arm is secured in the parking position by a latching device. The latching device prevents an external shock or blow delivered to the disk drive from dislodging the drive arm from the parking position and causing the data head to come into contact with the disk surface while the disk is stationary. 
     Among prior art latching devices, hereafter referred to as “latches”, used to secure a drive arm in a parking position are solenoid latches, magnetic capture latches, inertial latches and vane latches. 
     Solenoid latches use a solenoid or coil to produce a magnetic field that moves a locking pin or locking arm so as to engage and immobilize a drive arm in a parking position. Solenoid latches are often complicated, large and heavy, and their solenoids or coils must generally be shielded or distanced from the drive arm to prevent the magnetic fields of the solenoids or coils from affecting the operation of the drive arm motor. 
     Magnetic capture latches use a small permanent magnet and a strike plate formed from a ferromagnetic material to secure a drive arm in a parking position. Either one of the magnet or strike plate, is mounted on the drive arm and the other is mounted to the drive frame. When the drive arm enters the parking position the permanent magnet and strike plate come into contact and held together by the force of magnetic attraction between them. The drive arm is released from the parking position when the motor that moves the drive arm exerts sufficient force to pull the magnet and strike plate apart. Magnetic capture latches are often unreliable and release when the disk drive is subjected to a shock or blow that results in a force to the latch greater than the magnetic force binding the magnet and latch plate. Furthermore, the magnet must often be shielded to prevent its magnetic field from interfering with the motion of the drive arm. Also, the drive arm motor must be able to pull the magnet and strike plate apart in order to release the drive arm from the parking position. As a result, disk drives using magnetic capture latches often require drive arm motors that are stronger and heavier than drive arm motors used in disk drives operated with other types of latching devices. 
     An inertial latch uses the inertia of a drive arm and a locking element of the inertial latch to prevent the drive arm from dislodging from a parking position. When a shock or blow is delivered to a disk drive fitted with an inertial latch, the inertia of the locking element and drive arm cause the locking element and drive arm to move relative to each other in such a way that the locking element engages the drive arm and prevents the drive arm from leaving the parking position. Many inertial latches are unreliable and suffer from the fact that for certain directions of a shock or blow delivered to the disk drive, the inertial latch does not move so as to engage the drive arm. 
     With a vane latch, a drive arm is secured in a parking position by an air vane. The air vane is a thin generally rectangular sheet of material having two large planar surfaces. It is mounted in a disk drive close to and over a data disk of the disk drive with the large planar surfaces parallel to the plane of the data disk. When the drive arm is in the parking position a hole in the air vane engages a protuberance on the drive arm, thereby locking the drive arm in the parking position. When the disk rotates, air between the air vane and the disk is accelerated causing a Bernoulli effect to draw the air vane towards the disk and displace the hole in the air vane from the protuberance on the drive arm. The drive arm is thereby released from the parking position. Air vanes used in air vane latches are often large and air vane latches used in disk drives having multiple disks generally require more space between the disks than would be required using other types of latches. As a result, a disk drive using a vane latch must often be made larger and heavier than disk drives using other types of latches. 
     It would be desirable to have an improved latch for a disk drive, that is light weight and small that reliably secures a drive arm in a parking position and prevents it from being dislodged from the parking position when the disk drive is subjected to a shock or blow. 
     SUMMARY OF THE INVENTION 
     It is an object of one aspect of some preferred embodiments of the present invention to provide an improved latch for locking a drive arm of a disk drive in a parking position that is small and light weight. 
     It is an object of another aspect of some preferred embodiments of the present invention to provide a latch that has a locking action that is substantially unaffected by a blow or shock delivered to a disk drive in which the latch is installed. 
     According to another aspect of some preferred embodiments of the present invention, the latch has a locking action that is substantially unaffected by the direction of a blow or shock delivered to the disk drive. 
     According to another aspect of some preferred embodiments of the present invention the latch does not require a drive arm motor of the drive arm to provide force in order to release the locking action of the latch. 
     An object of yet another aspect of some preferred embodiments of the present invention is to provide a latch that does not produce a magnetic field that interferes with the operation of a disk drive in which the latch is installed. 
     Another aspect of some preferred embodiments of the present invention provides a latch, for locking a drive arm in a parking position, that has low power consumption and consumes power only when the drive arm is released from the locking position. 
     It is an object of yet another aspect of some preferred embodiments of the present invention to provide a latch operated by a piezoelectric micromotor. 
     A latch for locking a drive arm of a disk drive in a parking position, in accordance with a preferred embodiment of the present invention, comprises a latch stop and a latch hook. 
     The latch stop comprises a baffle that is moveable between an open and closed position. The latch hook is preferably mounted to the drive arm near or at the end of the drive arm distant from the data head. The latch hook moves with the drive arm and the latch hook and the baffle are so positioned that when the baffle is in the closed position the baffle protrudes into the path of motion traced out by the latch hook as the drive arm moves. As a result, when the baffle is in the closed position the latch hook cannot move from one side to the other side of the baffle without the latch hook colliding with the baffle. The baffle is normally in the closed position. 
     When the drive arm is in operation, the data head of the drive arm is over a data region of the data disk that is being read or written by the data head and the latch hook is on a first side, hereinafter referred to as an “operating side”, of the baffle. When the drive arm is in the parking position, the data head is over a region, a “parking region”, of the data disk that is not used to store data and the latch hook is on a second side, hereinafter referred to as a “parking side”, of the baffle. 
     The latch hook and baffle are constructed so that the latch hook can move from the operating side of the baffle to the parking side of the baffle when the baffle is in the closed position but cannot move from the parking side to the operating side of the baffle when the baffle is in the closed position. 
     Preferably, the latch hook is resiliently biased in a locking orientation. If the latch hook collides with the baffle from the parking side of the baffle, the latch hook is not displaced from the locking orientation and, the baffle blocks and stops the motion of the latch hook towards the operating side of the baffle. If the latch hook collides with the baffle from the operating side of the baffle, the latch hook displaces resiliently from the locking orientation so that the latch hook can pass to the parking side of the baffle. After the latch hook has passed to the parking side of the baffle, the latch hook snaps back to the locking orientation and cannot return to the operating side of the baffle unless the baffle is moved to the open position. The drive arm is thereby locked in the parking position. 
     The latch stop is moved back and forth between the open and closed positions by a piezoelectric motor. A small light weight piezoelectric motor suitable for moving a latch stop, in accordance with a preferred embodiment of the present invention, is described in the following documents which are incorporated herein by reference: U.S. Pat. Nos. 5,453,653, 5,616,980, 5,682,076, 5,714,833; EPO publication EP 0,755,054; Israel Patent 109,399; Israel Patent Applications 110,155, and 114,656 by some of the same applicants as the applicants of the present application; and PCT Application PCT/IL/98/00046 by some of the same applicants as the applicants of the present application. In some latches, in accordance with a preferred embodiment of the present invention, the piezoelectric motor is coupled directly to the body of the baffle in order to move the baffle between open and closed positions. In other preferred embodiments of the present invention the baffle is connected to the piezoelectric motor via a transmission. The piezoelectric motor is coupled to the transmission and “drives” the transmission in order to move the baffle between open and closed positions. 
     There is therefore provided in accordance with a preferred embodiment of the present invention a latch for a drive arm of a disk drive, wherein the drive arm has a parking position and an operating position and wherein the latch is operable to lock the drive arm in the parking position comprising: a latch stop comprising a baffle moveable between an open position and a closed position; and a piezoelectric motor operable to move the baffle between the open and closed positions, wherein the drive arm, in the parking position, engages the baffle and is prevented from leaving the parking position, when the baffle is in the closed position and is not prevented from leaving the parking position when the baffle is in the open position. 
     Preferably, the drive arm comprises a latch hook and when the drive arm is in the parking position and the baffle is in the closed position the latch hook engages the baffle and the drive arm is prevented from leaving the parking position, and when the baffle is in the open position the drive arm is not prevented from leaving the parking position. 
     Preferably, the baffle is resiliently biased in the closed position and as the drive arm moves from the operating position to the parking position the latch hook displaces the baffle from the closed position and when the drive arm reaches the parking position the baffle snaps back to the closed position. 
     Alternatively or additionally the latch hook is preferably resiliently biased in a locking orientation and as the drive arm moves from the operating position to the parking position the baffle displaces the latch hook from the locking orientation and when the drive arm reaches the parking position the latch hook snaps back to the locking orientation. 
     Alternatively or additionally, the baffle preferably comprises a coupling surface and the piezoelectric motor is resiliently pressed to the coupling surface and when the piezoelectric motor is activated, vibratory motion of the piezoelectric motor moves the baffle between open and closed positions. 
     In some preferred embodiments of the present invention the latch stop comprises a transmission having a coupling surface against which the piezoelectric motor is resiliently pressed, and the baffle is mounted to the transmission so that motion of the transmission moves the baffle between open and closed positions when the piezoelectric motor is activated. 
     Preferably, the transmission comprises a baffle arm and the baffle is mounted to the baffle arm. 
     The motion of the transmission preferably causes the baffle arm to rotate around a baffle arm axis to move the baffle between open and closed positions. 
     Preferably, the transmission comprises a coupling arm and the coupling surface is a surface of the coupling arm, and vibratory motion of the piezoelectric motor causes the coupling arm to rotate about a coupling arm axis which causes the baffle arm to rotate around the baffle arm axis. 
     The baffle arm axis and the coupling arm axis preferably coincide. 
     In some preferred embodiments of the present invention the coupling surface is a surface of the baffle arm and the baffle arm comprises a resilient stem having a fixed end, which resilient stem presses the coupling surface to the piezoelectric motor, and vibratory motion of the piezoelectric motor causes the coupling arm to rotate about the fixed end to move the baffle between open and closed positions. 
     Preferably the coupling surface is clad with a wear resistant material. Preferably, the piezoelectric motor comprises a friction nub and when the piezoelectric motor and the coupling surface are pressed together the friction nub contacts the coupling surface. 
     There is also provided a method of locking a drive of a disk drive in a parking position using a baffle having an open and a closed position, wherein when the drive arm is in the parking position and the baffle is in the closed position the drive arm engages the baffle and the drive arm is locked in the parking position, and when the baffle is in the open position the drive arm is free to leave the parking position, and moving the baffle between the open and closed positions using a piezoelectric motor, 
     The invention will be more clearly understood by reference to the following description of preferred embodiments thereof read in conjunction with the figures attached hereto. In the figures identical structures, elements or parts which appear in more than one figure are labeled with the same numeral in all the figures in which they appear. The figures are listed below and: 
    
    
     BRIEF DESCRIPTION OF FIGURES 
     FIG. 1 shows schematically and not to scale a rotary drive arm coupled to a latch with the latch stop of the latch in an open and closed position, in accordance with a preferred embodiment of the present invention; 
     FIG. 2 shows schematically and not to scale another latch in accordance with a preferred embodiment of the present invention; 
     FIG. 3 shows schematically and not to scale another latch in accordance with a preferred embodiment of the present invention; and 
     FIG. 4 shows schematically and not to scale yet another latch in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows schematically and not to scale a latch  20  in accordance with a preferred embodiment of the present invention used in a disk drive comprising a magnetic data disk  22  and a drive arm  24 . Drive arm  24  and parts mounted on drive arm  24  are shown in a parking position in solid lines and in a position for reading or writing to disk  22 , hereinafter referred to as an “operating position”, in dashed lines. Only those parts of the disk drive that are required to explain the invention are shown. 
     Data disk  22  is mounted to a drive frame (not shown) of the disk drive on a spindle that passes through a hole  26  in data disk  22 . A spindle motor (not shown) rotates the spindle and thereby data disk  22  at high speed about the axis of the spindle through hole  26 . The surface  30  of disk  22  comprises an “operating” region  32  outside of a circle  34  in which data is stored and a “parking” region  36  inside circle  34  where data is not stored. 
     Drive arm  24  has first and second ends  38  and  40  and is mounted to the drive frame on a shaft (not shown) through a hole  42  in drive arm  24 . Drive arm  24  is rotated back and forth between two limiting positions about the axis of the shaft preferably by a voice coil motor (not shown), as known in the art, mounted on first end  38  of drive arm  24  or by a piezoelectric motor. Second end  40  of drive arm  24  comprises a data head  42  used to read and write data to disk  22 . The axes about which disk  22  and drive arm  24  are rotated are parallel. 
     Data head  42  moves parallel to surface  30  of disk  22 , in a curved path substantially along a radius of disk  22 , back and forth between a minimum and maximum radial position on disk  22  as drive arm  24  rotates about its axis between it two limiting positions. The trajectory of data head  42  over surface  30  of disk  22  is represented by curved “double arrowed” line  44  and the minimum and maximum radial positions are represented by end points  46  and  48  of line  44 . When drive arm  24  is in a parking position, data head  42  is preferably at minimum radial position  46  and is over parking region  36 . When drive arm  24  is operating, data head  42  is over operating region  32 . 
     In a preferred embodiment of the present invention latch  20  comprises a latch hook  50  and a latch stop  52 . Latch hook  50  is preferably formed from a resilient material and preferably comprises a hook body  51 . Hook body  51  is preferably attached to end  38  of drive arm  24 . Latch stop  52  is mounted so that it is in a fixed position with respect to the axis of drive arm  24 . 
     Latch stop  52  preferably comprises a baffle  54  in the form of a thin rigid rectangular baffle plate having a top edge  56 . Baffle  54  is preferably clad in a protective wear resistant material such as Alumina. Baffle  56  is preferably mounted between at least one bushing  58  and a piezoelectric motor  60 . Piezoelectric motor  60  preferably comprises a thin rectangular ceramic vibrator  62  having a friction nub  64  mounted along a short edge  66  of vibrator  62  for coupling vibrator  62  to baffle  54 . Vibrator  62  is resiliently urged towards baffle  54  by means known in the art so that friction nub  64  presses baffle  56  to at least one bushing  58 . 
     Vibrator  62  is electrified so that friction nub  64  vibrates and transmits motion to baffle  54  in order to move baffle  54  back and forth between a closed and an open position along a preferably straight trajectory represented by double arrowed line  70 . Trajectory  70  is preferably parallel to a radius of disk  22 . Baffle  54  is normally in the closed position and is shown in the closed position in solid lines. Baffle  54  is shown in the open position in dashed lines. Baffle  54  has a parking side  72  and an operating side  74 . 
     Latch book  50  has a free end  84  visible in FIG. 1 in the operating position (dashed rendition) of drive arm  24  and a bottom surface  85 . When no force is applied to latch hook  50 , latch hook  50  is disposed in a “locking orientation” and extends away from hook body  51 , preferably with a moderate downward slope from hook body  51 . Latch hook  50  extends away from baffle  54  when latch hook  50  is on operating side  74  of baffle  54 . Free end  84  is preferably lower than top edge  56  of baffle  54 . Latch hook  50  is shown in the locking orientation in FIG.  1 . 
     Latch hook  50  can be resiliently displaced upwardly from the locking orientation by an applied force so that free end  84  is displaced towards hook body  51 . When the applied force is removed, latch hook  50  resiliently snaps back to the locking orientation. The trajectory that free end  84  traces out as hook arm  82  is forced upwards and then snaps back to the locking orientation is represented by double arrowed line  86 . 
     When drive arm  24  is in the parking position (solid lines) free end  84  is on parking side  72  of baffle  54 , latch hook  50  is in the locking orientation and free end  84  is below top edge  56  and hidden behind baffle  54  in the view of FIG.  1 . If a force acts to dislodge drive arm  24  from its parking position when baffle  54  is closed, free end  84  collides with baffle  54 . As a result of the direction and angle of latch hook  50  relative to the position and orientation of baffle  54 , the force of the collision is in a direction that does not displace hooking arm so as to raise free end  84  above top edge  56 . Therefore, as long as baffle  54  is closed (solid lines), free end  84  cannot move to the operating side of baffle  54  and drive arm  24  is securely locked in the parking position. 
     Whereas driving arm  24  cannot move from the parking position to an operating position with baffle  54  closed, in a preferred embodiment of the present invention it can move from an operating position to the parking position with baffle  54  closed. As drive arm  24  approaches the parking position with baffle  54  closed, top edge  56  of baffle  54  collides with latch hook  50 . However, unlike the situation when latch hook  50  collides with baffle  54  from parking side  72 , when latch hook  50  collides with baffle  54  from operating side  74 , free end  84  does not collide with baffle  54 . Instead, bottom surface  85  contacts top edge  56  of baffle  54 . The force between bottom surface  85  and top edge  56  operates in a direction to displace latch hook  50  upwards away from the locking position and towards hook body  51 , thus raising free end  84 . As drive arm  24  continues to advance towards the parking position, latch hook  50  continues to move upwards until free end  84  clears top edge  56  of baffle  54  and drive arm  24  reaches the parking position. When drive arm  24  reaches the parking position, latch hook  50  snaps back to the locking orientation, free end  84  is again below top edge  56  and locking drive arm  24  is locked in the parking position. 
     Inserts  90 ,  92  and  94  show schematic profiles of the relative positions of latch hook  50  and top edge  56  as drive arm  24  enters the parking position from an operating position. Inserts  90 ,  92  and  94  respectively show latch hook  50  in the locking orientation as it first contacts top edge  56 , maximally displaced upwards as free end  24  clears baffle  54  and snapped back to the locking orientation after drive arm  24  has reached the parking position. 
     FIG. 2 shows drive arm  24  and latch hook  50  as shown in FIG. 1 used with a different latch stop  100 , in accordance with another preferred embodiment of the present invention. Latch stop  100  comprises a baffle  102  mounted to a “baffle arm”  104  of a transmission  106 . Transmission  106  is attached to the drive frame so that it rotates in a plane parallel to the plane of disk  22 , about a shaft or pin through a hole  108 . A piezoelectric motor  110  having a friction nub  112  for coupling to a moveable element is resiliently pressed to transmission  106  so that friction nub  112  contacts, preferably, an edge surface  114  of transmission  106 . Edge surface  114  is preferably clad with a protective wear resistant material such as Alumina. Piezoelectric motor  110  is controlled to vibrate and transmit motion to transmission  106  in order to rotate baffle arm  104  back and forth about the shaft through hole  108  and move baffle  102  back and forth between open and closed positions. Transmission  106  and baffle  102  are shown in solid lines and dashed lines for baffle  102  in the closed and open positions respectively. 
     FIG. 3 shows drive arm  24  and latch hook  20  as shown in FIG. 1 with another latch stop  120  in accordance with another preferred embodiment of the present invention. Latch stop  120  comprises a baffle  122  and a two tiered transmission  124  comprising an upper baffle arm  126  and a lower “coupling arm”  128 . Baffle arm  126  and coupling arm  128  are preferably aligned one over the other. Transmission  124  rotates in a plane parallel to the plane of disk  22  about an appropriate shaft or pin (not shown) through a hole  130 . Baffle  122  is attached to baffle arm  126 . A piezoelectric motor  132  having a friction nub  134  is resiliently pressed, preferably, to an edge surface  136  of coupling arm  128  so that friction nub  134  contacts edge surface  136 . Edge surface  136  is preferably clad with a protective wear resistant material such as Alumina. Piezoelectric motor  132  is controlled to vibrate and transmit motion to rotate transmission  124  back and forth about the shaft through hole  130  and move baffle  122  back and forth between open and closed positions along a trajectory represented by double arrowed line  138 . 
     FIG. 4 shows yet another latch stop  140 , in accordance with a preferred embodiment of the present invention. Latch stop  140  comprises a baffle  142  and a transmission  144 . Transmission  144  preferably comprises an “L” shaped transmission frame  146 , and a baffle arm  150 . Baffle  142  is mounted to an end  151  of baffle arm  150 . 
     Transmission frame  146  has a short leg  152  and a long leg  154 . Baffle arm  150  has a resilient stem  156  and a coupling edge surface  158 . An end  160  of stem  156  is attached to short leg  152  of transmission frame  146 . Preferably, coupling edge surface  158  is clad with a protective wear resistant material such as Alumina. Stem  156  is preferably formed in the shape of a serpentine ribbon. 
     Preferably, transmission frame  146 , baffle arm  150  and baffle  142  are molded as a single piece from an appropriate plastic. 
     A piezoelectric motor  170  having a friction nub  172  is preferably rigidly mounted to long leg  154  of transmission frame  146  with brackets  174  so that friction nub  172  contacts coupling edge surface  158 . The serpentine ribbon shape of stem  156  provides a resilient force that keeps coupling edge surface  158  resiliently pressed to friction nub  172 . 
     Piezoelectric motor  170  is controlled to vibrate and transmit motion that causes baffle arm  150  to rotate about end  160  back and forth in a plane parallel to the plane of long leg  154 . The back and forth motion of baffle arm  150  moves baffle  142  back and forth between open and closed positions. The trajectories of the back and forth motion of baffle  142  is represented by double arrowed lines  180 . 
     Variations of the above-described preferred embodiments will occur to persons of the art. For example, it is possible to have a latch hook having a rigid hooking arm and a baffle that is resiliently displaced to allow the hooking arm to move to the parking side of the baffle. It is also possible to have both the hooking arm and the baffle resiliently displaceable when the hooking arm moves to the parking side of the baffle, but not displaceable for motion of the hooking arm from the parking side to the operating side of the baffle. In a yet another different variation of a latch, in accordance with a preferred embodiment of the present invention, neither the baffle nor the hooking arm are resiliently displaced when the hooking arm passes to the parking side of the baffle. Rather the baffle is opened when the drive arm enters the parking position to enable the hooking arm to pass to the parking side of the baffle. It is also possible to provide a latch hook in accordance with the present invention wherein the shapes and relative dispositions of the components are different from those shown in the figures and described in the text. Such variations in the construction of a latch hook in accordance with a preferred embodiment of the present invention will occur to persons of the art. The above detailed descriptions are provided by way of example and are not meant to limit the scope of the invention, which is limited only by the following claims.