GB2292000A

GB2292000A - A method and apparatus for launching and retracting the heads in a disk drive

Info

Publication number: GB2292000A
Application number: GB9514828A
Authority: GB
Inventors: Kai Chih-Kai Sun; Jack Duane Thorsen; Duncan Lee Pollock; Yee Cheok Low; Yin Yeow Choo; Kian Kok Lim
Original assignee: Syquest Technology Inc
Current assignee: Syquest Technology Inc
Priority date: 1994-07-27
Filing date: 1995-07-19
Publication date: 1996-02-07
Also published as: KR960005525A; JPH08171783A; ITRM950515A0; GB9514828D0; DE19527520A1; TW279974B; AU2721095A; IT1277876B1; FR2723244B1; ITRM950515A1; FR2723244A1

Description

2292000 METHOD AND APPARATUS FOR LAUNCHING AND RETRACTING READ-WRITE HEADS

FROM THE MEDIUM OF A DISK DRIVE ht

Field of the Invention

The present invention relates to a disk drive and in particular to a method and apparatus capable of launching and retracting the heads in the disk drive. This invention can be used with rigid or floppy disk drives using fixed or removable media.

Backaround Art

In the early and mid-1970s, almost all drives used removable media. Since the early 1980s, however, most drives use fixed media. In these fixed media drives, there has been little concern with removing the heads from the proximity of the media when access to data is unnecessary. Recently, there has been a trend back to removable media. This trend has resurrected the problem of launching and retracting the read-write heads.

Removable cartridge disk drives must be able to accurately,.smoothly, and efficiently load the read-write heads onto the media, which is generally protected in a disk cartridge.

Further, it is desirable to be able to remove the heads from the media both when the operator has voluntarily finished using the cartridge in the drive, and when the drive experiences an unexpected loss of power during use. If the read-write heads land on the surface of the disk when the motor spins down during power loss, this may cause the heads to stick to the disk if the heads are left -on the disk for a long period of time before power is restored to the driv6. This phenomenon is known as stiction.

Additional damage may occur during transportation of a disk drive when the read-write heads are left on a disk surface. It is thus desirable for the heads to be automatically removed from the cartridge without damaging the heads or the memory media in the process whenever power is removed from the drive.

In the past, various methods have been employed to control the power-on and power-off "retracting" of the heads off of the media. With many prior art drives, it is very difficult to remove a cartridge from the drive when power loss occurs, let alone to retract the read-write heads from the media, which is generally a prerequisite to being capable of removing the cartridge without risking damage to the recording media, read-write heads, or both, and concomitant loss of data.

In the past, various methods also have been used to control the "launching" of the heads in disk drives that employ removable disk cartridges. For example, U.S. Patent No.

4,870,518, issued September 26, 1989, and assigned to the assignee of the instant application, is directed to two different methods that may be used to control head launching speed in a removable cartridge disk drive. U.S. Patent No. 4,870,518 is incorporated by reference as though fully disclosed herein. one is the 2 of the methods disclosed in this patent employs a dash pot or air damper to contfol the launch velocity of the read-write heads. The use of precision air dampers, however, increases the cost of the drive, and these dampers do not remove the heads automatically during a loss of power.

Other prior art drives use velocity feedback based on back emf (electromotive force) or tachometer data from the head actuator assembly. Such drives monitor the velocity of the readwrite heads during the launching process. An example of controlling head launch velocity using back emf generated by the movement of the actuator.is described in U.S. Patent No. 4,864,437, which is owned by the assignee of the present invention and the disclosure of which is incorporated herein by reference. The use of these devices also increases the cost of the drive, and does not help remove the heads automatically after the drive loses power. It is also difficult to accurately detect back emf during low speed movement, such as during the loading of read- write heads.

Each of the prior art methods of controlling the launch velocity of the read-write heads are complex, which increases the potential for failure of the drive. In addition, these prior art devices are costly to incorporate into drives.

Therefore, there currently exists a need for a better method of controlling the velocity of the actuator during head 3 launch, of controlling the velocity of the actuator during head retraction, anct of storing sufficient energy for automatically retract the read-write.Aeads in the event of power failure.

Su1x of the Invention is Accordingly, a general object of the present invention is to provide in disk drives an improved method and apparatus for launching and retracting read-write heads, in which the abovedescribed problems and disadvantages have been considered and mitigated.

Another object of the present invention is to provide a read-write head launching apparatus that uses electromotive force (emf) produced in the coil of the actuator motor to incrementally balance the tension in a retraction spring and the friction on the guiding surfaces of the head unload arm to allow velocity control of the head arm assembly during launch.

A further object of the present invention is to provide a read-write head retraction apparatus that uses other than electrical energy to remove the read-write heads from the disk surface any time the drive experiences a loss of power.

A still further object of the present invention is to provide a readwrite head launching and retracting apparatus that is able to automatically retract the read-write heads if the drive experiences a loss of power, thereby lifting the heads away 4 from the disk surface without damaging either the read-write heads or disk,.or both. When the heads are thus lifted from the disk surface, the phenomena called stiction is also eliminated.

In order to achieve the above and other objects of the present invention, an apparatus is provided for launching the read-write head onto and for retracting the read-write heads from a disk within a disk drive. The disk may be mounted within a cartridge. The apparatus includes a read-write head attached to a head arm assembly, a pivotally- mounted retraction lever having a pressing end and a trappable end, wherein the retraction lever is positioned such that t-he pressing end is adjacent to a pressing surface of the head arm assembly, and a mechanical biasing member (e.g., a spring) that biases the pressing end of the retraction lever toward the pressing surface of the head arm assembly. In the preferred embodiment, a sleeve of energyabsorbing material is attached to the pressing end of the retraction lever. A retraction lever lock is provided to alternately trap and release the trappable end of the retraction lever, and a solenoid is attached to the retraction lever lock to position the retraction lever lock. A voice coil motor is operatively associated with the head arm assembly and is used both to launch the read- write heads and to position the readwrite heads for writing data to a disk or reading data from a disk. The apparatus also includes a head unload arm comprising a forked portion having an upper guiding surface and a lower guiding surface.

The invention will be further described by way of non-limitative example, with reference to the 5 accompanying drawings, in which:- Figures 1 to 8 are top elevational diagrammatic views of a preferred embodiment of the instant invention, showing the head launching and retracting apparatus at various points during operation of the apparatus; Figure 9 in an enlarged cross-sectional view of the forked portion of the head unload arm as referenced in Figures 3 and 16; Figure 10 is a three-dimensional view of the head arm assembly, voice coil motor, retraction lever, retraction spring, retraction lever lock, head unload arm and head unload arm guide; Figure 11 is an elevational view of the top of the retraction spring hook; Figure 12 in an elevational view of the side of the retraction spring hook, depicting the spring-retaining groove formed in the upright portion of the retraction spring hook; is Fig. 13 is an elevational view of the top of the retraction levoir; Fig. 14 is an elevational view of the side of the retraction lever depicted in Fig. 13; Fig. 15 is an elevational view of the front of the head unload arm used in the preferred embodiment of the present invention; Fig. 16 is an elevational view depicting the top of the head unload arm depicted in Fig. 15; Fig. 17 is an elevational view of the right end of the head unload arm depicted in Fig. 15; Fig. 18 is an elevational view of the top of the retraction lever lock; Fig. 19 is a cross-sectional view of the retraction lever lock depicted in Fig. 18; Fig. 20 is an elevational view of the bottom of the retraction lever lock depicted in Figs. 18 and 19; Fig. 21 is an elevational view of the side of the head unload assembly base in the direction referenced in Fig. 1; Fig. 22 is an elevational view of the top of the head unload arm guide; Fig. 23 is an elevational view of the end of the head unload arm guide depicted in Fig. 22; 7 Fig. 24 is an elevational view of the side of the solenoid from.he direction referenced in Fig. 1; Fig. 25 is the loading algorithm; Fig. 26 is a representation of the current applied to the voice coil motor (VCM) during the dithering stage of VCM operation; and Fig. 27 is a representation of the current applied to the VCM during the ramp-up stage of VCM operation.

Descrii)tion of the Prferred Embodiment In accordance with the present invention, a disk drive apparatus is provided for launching read-write heads onto disks and for retracting the read-write heads off of disks. In the preferred embodiment, one disk is contained within a cartridge.

The invention is not, however, so limited and may be applied to is multiple disks and to disks not mounted in cartridges. In the following description, when a component "A" is described as being on top of a component "BO that means component "A" is further away (in a direction out of the page in Figs. 1-8) from the drive base 10 (i.e., the bottom of the inside of the drive) than component "B".

Referring first to Figs. 1-8, the disk drive apparatus of the instant invention includes the following components. A head arm frame 13 is mounted to the drive base 10. A voice coil 8 motor (VCM) or head-arm-assembly-positioning motor is indicated generally at 1_C. A head arm assembly 19 is pivotally mounted to the head arm frame 13 for rotation about an axis 22. An inner crash stop 25 is mounted to the voice coil motor 16 and is positioned such that the stop pin bumper 28, which is made of energy absorbing rubber and is mounted on the base end 31 of the head arm assembly 19, impacts the stop pin 34 of the inner crash stop 25 when the head arm assembly 19 is rotated to its innermost position over the media 37. In this preferred embodiment, the stop pin 34 is threaded so that the location where it impacts the stop pin bumper 28 may be-adjusted.

Head arm assembly 19 comprises a bifurcated load beam 40, including an upper load beam 43 and a lower load beam 46 (Fig. 10). The head arm assembly 19 further comprises an upper flexure 49 attached to the upper load beam 43, and a lower flexure 52 attached to the lower load beam 46. A pair of transducers (read-write heads) 55, 58 are mounted on the free ends of the flexures 49, 52. The upper read-write head 55 is attached by a gimble (not shown) to the upper flexure 49. The lower read-write head 58 is attached by a gimble (not shown) to the lower flexure 52. These features are seen to best advantage in Fig. 10. In this preferred embodiment, a pressing surface 61 comprises part of a molded ratchet 64 mounted below the head arm 9 assembly 19 for rotation therewith. The teeth 67 depicted on the ratchet 64 are-not used in this preferred embodiment.

Referring next to Figs. 1-8, 11, and 12, a retraction spring and retraction spring hook will be described. The retraction spring hook 70 is mounted to the drive base 10 adjacent to the area of motion of the ratchet 64. The retraction spring hook 70 has a Slot 73 formed therein for adjusting the initial tension in the retraction spring 76. In the preferred embodiment of the present invention, retraction spring 76 has a spring rate of 16 ounces/inch. To adjust the initial tension in the retraction spring 76,- one may rotate the retraction spring hook 70 about a mounting screw 79. A second mounting screw 82 rides in the slot 73, thereby limiting the range of motion of the retraction spring hook 70. once the initial tension in the is retraction spring 76 has been adjusted, the retraction spring hook 70 is fixed to the drive base 10 by tightening mounting screws 79 and 82. The retraction spring hook 70 includes an upright portion 85 having a spring-retaining groove 88 formed therein (Fig. 12) - Referring next to Figs. 1-8, 13, and 14, the retraction lever 91 will be described. Retraction lever 91 is rotatably mounted to the drive base 10 for rotation about an axis 94. The retraction lever 91 is mounted on its axis 94 below the head arm assembly 19. This is indicated in Figs. 1-8 by depicting the hidden portions of the retraction lever 91 in phantom when they are covered by.-the head arm assembly 19. Retraction lever 91 includes a pressing end 97. The pressing end 97 of the retraction lever 91 impacts the pressing surface 61 of the ratchet 64 at various times during the operation of the disk drive.

A sleeve of damping material 100 (e.g., energy absorbing rubber) is mounted on the pressing end 97 of the retraction lever 91 in the preferred embodiment. This sleeve 100 mitigates any tendency of the read-write heads 55, 58 to crash against the disk 37 when the pressing end 97 of the retraction is lever 91 impacts the pres sing surface 61 of the head arm assembly 19 to drive the upper and lower flexures 49, 52 onto the upper and lower guiding surfaces 103, 106 of the forked portion 109 of the head unload arm 112. It is always important to keep the read-write heads 55, 58 from crashing into the media 37, particularly when the media exhibits a high data density. The head unload arm 112 is described further below and may be seen to best advantage in Figs. 9, 10, and 15-17.

Retraction lever 91 also has a trappable end 115. This trappable end 115 is locked or retained by the retraction lever lock 118 during normal operation of the disk drive. The retraction lever lock 118 is described more fully below and may be seen to best advantage in Figs. 18-20. The trappable end 115 11 of the retraction lever 91 has a sloped surface 121, which facilitates tht trapping action as further described below.

During a port'lon of the operation of the head launching apparatus of the instant invention, the retraction lever lock 118 presses against a wing 124 comprising part of the retraction lever 91. Specifically, a push pin 127 mounted to the bottom surface 130 of the retraction lever lock 118 may impact the wing 124 upon rotation of the retraction lever lock 118 depending upon the degree of rotation of the retraction lever 91. In particular, during the initial portion of the head-loading operation of the drive Mig. 2), the push pin 127 rotates the retraction lever 91 to create a gap between the pressing end 97 of the retraction lever 91 and the pressing surface 61 of the ratchet 64. The head-loading operation of the drive is discussed is more fully below. The retraction lever 91 includes a hole 133, which serves as an attachment point for the retraction spring 76.

Details concerning the components attached to the head load assembly base 136 will now be provided. Integrally formed with the head load assembly base 136 is an upward projection 139.

This upward projection 139 may be seen to best advantage in Fig.

21. Fig. 21 depicts an elevational view of the end of the head load assembly base 136 in the direction indicated by reference numeral 21 in Fig. 1. The upward projection 139 acts as a stop for the head unload arm 112. The upward projection 139 thereby 12 limits the most rearward travel of the head unload arm 112 as discussed more_7fully below. A first pin 142 and a second pin 145 are also mounted in the head load assembly base 136. The first is pin 142 acts as the axis of rotation for the retraction lever lock 118 and the head unload arm 112. The second pin 145 rides in a curved port 148 during rotation of the retraction lever lock 118. The curved port 148 thereby limits the range of permissible rotation of the retraction lever lock 118. The retraction lever lock is depicted to best,advantage in Figs. 18-20.

The retraction lever lock 118 is also connected to the solenoid 151. The solenc>.id 151, which may be seen in Figs. 1-8 and 24, is characterized by a spring return to the de-energized position. That is, when power to the solenoid 151 is turned off, the central shaft or plunger 154 of the solenoid 151 extends fully to its de-energized position. Fig. 24 represents a side view of the solenoid 151 from the direction indicated by reference number 24 in Fig. 1. The retraction lever lock 118 is swingably connected to the plunger 154 of the solenoid 151 with a connecting pin 157 (Fig. 24). The solenoid 151 generates the force that rotatably positions the retraction lever lock 118. The solenoid 151 thus provides the energy that activates the drive locking mechanism, which stores the mechanical energy that facilitates automatic retraction of the read-write heads 55, 58 when power is taken away from the disk drive. The retraction 13 lever lock 118 also includes a trap pin 160. The trap pin 160 projects from tle bottom surface 130 of the retraction lever lock 118. This pin 160 is u;ed to trap the trappable end 115 of the retraction lever 91 as further described below. Figs. 7 and 8 depict the trap pin 160 performing its trapping function.

Referring now to Figs. 9, 10, and 15-17, the head unload arm 112 will be described. The head unload arm 112, which may be manufactured from a suitable engineering plastic or other structural material, is mounted on top of the retraction lever lock 118 for rotation about the first pin 142 (pin 142 is depicted, for example, irr Figs. 1-8 and 21). In the preferred embodiment of the present invention, the material between the upper and lower guiding surfaces 103, 106 of head unload arm 112 has been removed to accommodate a disk 37 when it has been loaded into the drive. This may be seen to best advantage in Fig. 9. The head unload arm 112 thus includes a forked portion 109. As may best be seen in Figs. 9 and 10, each guiding surface 103, 106 of the forked portion 109 of the head unload arm 112 has the shape of a flat-taper ramp, with a knee between each ramped or tapered portion and its respective flat portion. Referring to Fig. 9 in particular, upper guiding surface 103 comprises ramped portion 104 and flat portion 105 separated by an upper knee 169. Similarly, lower guiding surface 106 comprises ramped portion 107 and flat portion 108 separated by a lower knee 170. This flat- 14 tapered designed effectively lifts each read-write head 55, 58 from its operat7ional position near the disk surface to its retracted position safely away from the disk surface. When the head arm assembly 19 is fully retracted, the upper and lower flexures 49, 52 of head arm assembly 19 are driven onto the upper and lower flat portions 105, 108, respectively. The flat portions 105, 108 help minimize the vertical motion of the flexures 49, 52 so that a cartridge may be loaded and also provide surfaces parallel to the plane of the flexures 49, 52 to minimize pressure upon the guiding surfaces 103, 106 when the read-write heads 55, 58 are fully parked on the flat portions 105, 108. The head unload arm 112 also includes a downward projection 163 and a bumper mount 166.

During any rotation of the head unload arm 112, the free end of the head unload arm 112 slidably rests on a head unload arm guide 172. This head unload arm guide 172, which like the head unload arm itself may be manufactured from a suitable material such as plastic, is depicted in Figs. 1-8, 10, 22, and 23. The guide 172 is rigidly mounted to the head load assembly base 136. A coil spring 175 (Fig. 10) biases the downward projection 163 of the head unload arm 112 against the stopping surface 178 of the head unload arm guide 172. The coil spring is mounted around the first pin 142, between the head unload arm 112 and the retraction lever lock 118. The distance between is is the stopping surface 178 of the head unload arm guide 172 and the upright projecjion 139 defines the full range of possible positions for the head unload arm 112.

A bumper 181 of energy absorbing material (e.g., energy-absorbing rubber) is mounted around the bumper mount 166. The bumper 181 is cylindrically shaped in the preferred embodiment, and helps mitigate any tendencies of the head arm assembly 19 to rebound when the read-write heads 55, 58 are retracted from the surface of the disk 37. The coil spring 175 further helps dampen the impact between the head arm assembly 19 and the head unload arm 112. The coil spring 175 and the bumper 181 mitigate any high-speed rebound problems occurring when the head arm assembly 19 is traveling to its retracted position under the influence of the retraction spring 76.

Figures 1-8 are arranged to show the progression of the head launch sequence, starting with a drive that has not yet been powered up (Fig. 1) and ending with a drive that has successfully launched the read-write heads 55, 58, achieving operational status. In the disclosed invention, one mechanism is used to both launch and later to retract the read-write heads 55, 58.

The launch sequence will be described first.

During the head launch sequence, the heads 55, 58 are positioned without position or velocity feedback. In other words, the instant invention describes an open-loop system.

16 During launch, a primary concern is to control the velocity of the upper and 176wer flexures 49, 52 as they leave their respective guiding surfaces 103, 106 so as to prevent the heads 55, 58 from crashing into the media 37. As the upper and lower flexures 49, 52 move along their respective guiding surfaces 103, 106, the resultant force acting on the head arm assembly 19 changes, particularly as the upper and lower flexures 49, 52 transition from the flat portions 105, 108 to the tapered portions 104, 107 of the upper and lower guiding surfaces 103, 106. As may be appreciated from considering Figs. 9 and 10, the read-write heads 55, 58 t-ravel toward each other and the media 37 as the flexures 49, 52 slide down the guiding surfaces 103, 106. If the heads 55, 58 approach each other too quickly as they travel down their respective guiding surfaces 103, 106, the heads is 55, 58 will crash into the media 37 upon leaving the head unload arm 112. If the read-write heads 55, 58 crash into the media 37, they can be damaged or data stored on the media 37 can be destroyed, particularly with high-density media 37. If, on the other hand, the read-write heads 55, 58 are traveling toward the media 37 too slowly as they leave the guiding surfaces 103, 106, of the head unload arm 112, the heads 55, 58 will not come off of the head unload arm 112 cleanly, and their transition to flight over the media 37 will be corrupted. This corruption is more 17 likely in a removable media device due to the increased vertical runout inheren in the interchange of media.

Referring now to Figs. 1-8 and 25-27, the step-by-step launching process will be described. Fig. 25 presents the algorithm for this process, wherein the values given are DAC constants. Figs. 26 and 27 show the current flow through the VCM during a portion of the launching process. In the preferred embodiment of the present invention, a neutral VCM has an 80H DAC value. Values greater than BOH apply force toward the inside diameter or "ID.11 Values less than BOH apply force toward the outside diameter or 110D."- The torque per DAC count is 7.32xlO'3 inch-ounce. Fig. I depicts the launching and retracting apparatus of the instant invention with a cartridge inserted in the drive. Upon command, the media 37 spins up. The launch is sequence is initiated when the media 37 reaches a specified rotational speed.

First, as depicted in Fig. 1, an OD force is generated to move the flexures 49, 52 to the top of the ramped portions 104, 107 of the upper and lower guiding surfaces 103, 106, respectively (step 1 in Fig. 25). Then, as depicted in Fig. 2, the solenoid 151 is activated (step 2 in Fig. 25). When the solenoid 151 is activated, the plunger 154 is retracted into the solenoid 151. As the plunger 154 retracts, it pulls on the retraction lever lock 118, thereby slightly rotating the is retraction lever lock 118 in a first direction (counterclockwise in Fig. 2). Tfiis rotation forces the push pin 127 against the wing 124 of the retract'lon lever 91. The force thus generated on the wing 124 causes the retraction lever 91 to rotate slightly about the axis 94 (clockwise in Fig. 2). This latter rotation of the retraction lever 91 creates a gap between the pressing end 97 of the retraction lever 91 and the pressing surface 61 of the molded ratchet 64.

The current in the voice coil motor 16 is then dithered (step 3 in Fig. 25; see also Fig. 26) to break any stiction between the flexures 49,.52 and the flat portions 105, 108 of the head unload arm 112, without excessively accelerating the flexures 49, 52 across the flat portions 105, 108. This dithering generates a net force that rotates thehead arm assembly counterclockwise in Fig. 2 until contact is reestablished between the pressing end 97 of the retraction lever 91 and the pressing surface 61. This places the apparatus in the position depicted in Fig. 3 without a gap between the retraction lever 91 and the pressing surface 61.

At this point, the upper and lower flexures 49, 52 have transitioned the respective knees 169, 170 of the upper and lower guiding surfaces 103, 106 (Figs. 3 and 9). The flexures 49, 52 are resting on the ramped portions 104, 107, respectively, of the head unload arm 112 at a "pause point" or pre-loading position.

19 At this pre-loading position, the spring force generated by the retraction spri-ng 76 (as determined by the position of the retraction lever 91, which is being rotated by the push pin 127 of the retraction lever lock 118, which is in turn being rotated by the solenoid 151 as described above) is greater than the net dithering torque generated by voice coil motor 16, so the flexures 49, 52 do not move off of the preloading position (although there may be some minor dithering motion about the preloading position). Therefore, the location of the pre-loading position is determined by the position of the retraction lever 91, which in turn depends-upon the settings of the solenoid 151. The solenoid 151 is adjus"ted such that the pre-loading position occurs just after the flexures 49, 52 are beyond the knee 169, 170 (Figs. 3 and 9). The duration of the dithering (presently is this is approximately 1.4 seconds) is established so that in the worst case (sticky friction), the flexures 49, 52 will arrive at the pre- loading position before the dithering stops.

Fig. 9 depicts an enlarged view showing the upper and lower flexures 49, 52 at this pre-loading position. In Fig. 9, one may clearly see the position of the flexures 49, 52 on the ramped portions 104, 107 of the upper and lower guiding surfaces 103, 106, respectively. Up to this point, the force generated by the retraction spring 76 on the retraction lever 91 has been balanced by the force generated by the solenoid 151 on the wing 124 via the puih pin.127 of the retraction lever lock lie.

After contact has been reestablished between the pressing end 97 of the retraction lever 91 and the pressing surface 61, the voice coil motor 16 begins to "take over" from the solenoid 151 the job of countering the force being generated by the stretched retraction spring 76. The head arm assembly 19, through the pressing surface 61 of-the molded ratchet 64, engages the retraction lever 91 and counters the force produced by the retraction spring 76. As the voice coil motor 16 is further energized, the head arm assembly 19, through the pressing surface 61 of the molded ratchet 64 pushes the retraction lever 91 and stretches the retractionspring 76. The emf in the voice coil motor 16 is incrementally increased through firmware so that the is upper and lower flexures 49, 52 begin to move on the ramped portions 104, 107 of the guiding surfaces 103, 106 of the head unload arm 112. The emf in the voice coil motor 16 is controllably increased or ramped up at a fixed rate of change, using techniques that would be apparent to anyone of ordinary skill in the art (see, e.g., step 4 in Fig. 25; see also Fig.

27). This ramp-up of the emf in the voice coil motor causes the retraction spring 76 to stretch until it equalizes the force produced by the motor 16. The head arm assembly 19 in turn moves at a controlled speed--equivalent to D'Arsonval movement--along 21 the ramped or sloped portions 104, 107 of the guiding surfaces 103,.106 and oilt over the disk surface.

If the voice-coil motor was simply energized from a fully parked position and rotated to move the flexures directly over the knee and down the ramp portions of the head unload arm, without stopping at the pre-loading position, control over the velocity of the heads would be much more difficult to achieve. This is because application of force sufficient to overcome friction and stiction between the flexures and the head unload arm guiding surfaces, coupled with the unknown loading dynamics caused by the flexures going over the knees of the head unload arm, would lead to acceleration of the flexures and loss of velocity control. By starting the voice coil motor current rampup after the flexures have reached the pre-loading position, is however, and thereafter controlling the current in the voice coil motor 16, the drive regulates the translational velocity of the read- write heads 55, 58 as the upper and lower flexures 49, 52 leave the upper and lower guiding surfaces 103, 106 of head unload arm 112. In this manner, as the read-write heads 55, 58 transition from resting on the forked portion 109 of the head unload arm 112 to "flying" over the spinning media 37, the velocity of the read- write heads 55, 58 is controlled as the heads approach each other and their respective disk surfaces.

22 During the loading process, the firmware in the microprocessor of the disk drive's electronic circuits looks for servo data that it ex0ects to find on the media 37 (step 4 in Fig. 25). If the read-write heads 55, Se begin to read servo data from the disk, they probably have been fully loaded. Up to a twelve-step ramp-up of the voice coil motor 16 is used in the preferred embodiment (step 4 in Fig. 25; see also Fig. 27), but the system is normally adjusted so that the heads 55, 58 should be off of the head unload arm 112 after the sixth ramp-up step.

To ensure that the read-write heads 55, 58 have actually cleared the head unload arm 112,-the disk drive firmware continues to drive the flexures 49, 52 from the head unload arm 112 after the read-write heads 55, 58 begin to read servo data from the disk (see step 5 in Fig. 25). This occurs even though the flexures 49, 52 may have fully cleared the head unload arm 112 as soon as the read-write heads 55, 58 began to read servo data.

Next, the solenoid 151 is de-activated (step 6 in Fig.

25), and its plunger 154 returns to its extended position (Fig.

4). When the plunger 154 returns to its extended position, the retraction lever lock 118 is rotated in a second direction (clockwise in Fig. 4) to a position that permits the trappable end 115 of the retraction lever 91 to eventually be rotated into a position to be trapped or locked by the trap pin 160 of the 23 retraction lever lock 118. This trapping action is more fully described belcy with reference to Figs. 6 and 7.

The current to the voice coil motor 16 is then further increased (step 7 in Fig. 25). Increasing the current to the voice coil motor 16 forces the head arm assembly 19 to make an initial run from the outer track of the media 37 to the innermost track (see, e.g. , Fig. 5). Fig. 6 depicts the head arm assembly 19 positioned beyond the inner-most track. When the head arm assembly 19 is thus positioned, the stop pin bumper 28 of energy absorbing material has impacted the stop pin 34. Also, when the head arm assembly 19 is at this position, the retraction spring 76 is at its maximum elongation, and the head arm assembly 19 has "cocked" the retraction lever 91, which is now ntrappablell by the retraction lever lock 118. This initial run of the head is arm assembly 19 from the outer track to the inner-most track of the media 37 increases the potential energy in the retraction spring 76, thus enabling the drive's automatic-head-retraction system, while placing the retraction lever 91 in "locking position" so that the spring energy may be "stored" by the retraction lever lock 118.

After a short delay (step 8 in Fig. 25), the solenoid 151 is again activated as depicted in Fig. 7. When the solenoid 151 is energized, the plunger 154 is drawn leftward in Fig. 7. This action rotates the retraction lever lock 118 in the first 24 is direction (counterclockwise in Fig. 7) to lock the retraction lever 91 in plice. 4hen the retraction lever 91 is positioned as shown in Fig. 7, and the solenoid 151 is energized, the retraction lever lock 118 traps the trappable end 115 of the retraction lever 91 behind the trap pin 160 attached to the bottom of the retraction lever lock 118, thereby holding the retraction spring 76 in a stretched configuration and storing the spring's potential energy. In particular, the trap pin 160, which may be seen to best advantage in Figs. 18-20, presses against the sloped surface 121 of the trappable end 115 of the retraction lever 91. This configuration, wherein the trap pin 160 has the retraction lever 91 trapped, may be seen in Figs. 7 and S. As long as the solenoid 151 is activated, the retraction lever 91 is held in a spring- loaded state.

As seen to best advantage in Fig. 8, when the retraction lever 91 is locked by the retraction lever lock 118, the retraction spring 76 no longer influences the motion of the head arm assembly 19. The pressing end 97 of the retraction lever 91 is not touching the pressing surface 61 of the molded ratchet 64, and the head arm assembly 19 can move freely over the media 37. The drive next goes into a calibration routine, which makes the drive ready to accept a command from a host computer and to perform any requested read-write operations.

is The retraction system of the instant invention is capable of retracting the read-write heads 55, 58 under normal conditions as well as under failure or loss of power conditions. During a normal retraction operation, the operator typically initiates the retraction sequence by pressing a button on the front of the disk drive. Alternatively, the sequence may be initiated through a sequence of interface commands. After initiation of the sequence, the read-write heads 55, 58 seek to the outer track. Then, the voice coil motor 16 provides sufficient force (60H DAC in the preferred embodiment) to lift or push the read-write heads55, 58 up the ramped portions 104, 107 (Fig. 9) of the guiding surfaces 103, 106 of the head unload arm 112 to a retracted location. The drive then spins down, and the solenoid 151 is subsequently de-activated, whereby the plunger 154 is driven rightward in Figs. 1-8. As the plunger 154 travels rightward, the retraction lever lock 118 is rotated in the second direction (clockwise in Fig. 8). When the retraction lever lock 118 thus releases the trappable end 115 of the retraction lever 91, the pressing end 97 of the retraction lever 91 is forced against the pressing surface 61. The retraction spring 76 thereby helps hold the read-write heads 55, S8 on the head unload arm 112 while, for example, a cartridge is removed from the drive. In a fixed drive, this feature may be engaged, for example, before the drive or the system containing it is moved.

26 The following paragraphs describe retraction of the read-write heaSi 55, 58 when the drive experiences an unexpected power loss.

In this s. ituation, the drive's automatic-head retraction system becomes operational. The energy that will be used for unloading the read-write heads 55, 58 in this situation is the energy stored in the stretched retraction spring 76.

In the instant invention, before a power loss occurs, the retraction lever lock 118 prevents the retraction lever 91 from influencing the operational movement of the head arm assembly 19. This locking action is fully described above. As is well known in the art,-the head arm assembly 19 can"then be used to access data from tracks on the media 37. When power is unexpectedly removed from the drive, the solenoid 151 eventually relaxes, releasing its plunger 154. The released plunger 154 travels rightward in Figs. 7 and 8, which rotates the retraction lever lock 118 in the second direction (clockwise in Figs. 1-8). With the retraction lever lock 118 thus rotated, trap pin 160 can no longer retain the trappable end 115 of the retraction lever 91. The stored energy of the retraction spring 76 is consequently released. The released spring energy is applied to the retraction lever 91 at the hole 133 in the retraction lever 91 where the retraction spring 76 is attached to the retraction lever 91. This in turn causes the retraction lever 91 to rotate counterclockwise in Figs. 1-8, eventually establishing contact 27 between the pressing end 97 of the retraction lever 91 and the pressing surfa6e 61 of the ratchet 64. The force against the pressing surface 61 by the pressing end 97 rotates the head arm assembly 19 clockwise in Figs. 1-8 and drives the head arm assembly 19 onto the head unload arm 112 by pushing the upper and lower flexures 49, 52 up the upper and lower guiding surfaces 103, 106, respectively. In this manner, the apparatus retracts the read-write heads 55, 58 independent of the location of the head arm assembly 19 over the media 37 when the drive losses power, placing the read-write heads 55, 58 safely away from the media 37.

When the head arm assembly 19 is near the outer track of the media 37 as depicted in Fig. 8, the gap between the pressing end 97 of the retraction lever 91 and the pressing surface 61 of the molded ratchet 64 is greatest. If the drive experiences an unexpected loss of power when the head arm assembly 19 is so positioned, the pressing end 97 has its greatest distance within which to accelerate towards the pressing surface 61. In this situation, the sleeve of damping material 100 helps mitigate any potential for rebound of the retraction lever 91 after its pressing end 97 impacts the pressing surface 61. As an alternative to the sleeve 100, the retraction lever 91 itself may be constructed from a material or in a shape that mitigates any potential for rebound. For example, the retraction 28 lever 91 itself could be formed from resilient material that would give rater than bounce when the pressing end 97 impacts the pressing surface 61.

The above-described invention provides many advantages over the prior art, including the following. It keeps the readwrite heads 55, 58 off of the media 37 any time the disk drive is without power, since the heads 55, 58 are always retracted from the media 37 using mechanical energy whenever the drive experiences a loss of power. Because the read-write heads 55, 58 are kept away from the disk surface when the disk drive is not powered, damage to the read-write heads 55, 58 is much less likely to occur during transportation of the drive with a disk loaded. The invention launches the read-write heads 55, 58 without employing devices like damping pots and tachometers or is other velocity sensors. The absence of these devices makes the drive less complex and less expense to build, while increasing the reliability of the drive.

While what has been described above is a preferred embodiment of this invention, it will be obvious to those skilled in the art that numerous changes may be made without departing from the spirit or scope of the invention. For example, a linear actuator may be used in place of the voice coil motor used in the preferred embodiment. It is intended that all matter contained in the above description or shown in the accompanying drawings

29 shall be interpreted as being illustrative only and not limiting.

The invention,.-therefore, is not to be limited except in i ' accordance with the below claims.

Claims

Claims

Ae- elraT-- 4 1. An apparaus in a disk drive, including at least one disk, for retracting from said at least one disk at least one read-write head attached to a head arm assembly, the apparatus comprising: a retraction lever having a pressing end, wherein said retraction lever is positioned such that said pressing end presses against a pressing surface of said head arm assembly during retraction of said at least one read-write head; a biasing member that mechanically biases said pressing end toward said pressing surface; and a retraction lever lock positioned to alternatively trap and release said retraction lever.
2. An apparatus as in claim 1 wherein said retraction lever further comprises a trappable end, said retraction lever lock alternatively trap and release said trappable end of said retraction lever.
3. An apparatus as in claim 1 further comprising a sleeve of energy absorbing material attached to said pressing end of said retraction lever.

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4. An apparatus as in claim 1, wherein a solenoid is swingably atta6hed to said retraction lever lock.
5. An apparatus as in claim 4, further comprising a head unload arm.
6. An apparatus as in claim 5, wherein said head unload arm is spring loaded and further wherein said head unload arm has a bumper of energy absorbing material attached to it.
7. An apparatus as in claim 6, wherein said head unload arm is mounted on a first pin such that said head unload arm can pivot between a forwardmost position and a rearward-most position, and further wherein said head unload arm rides on a head unload arm guide having a stopping surface defining said forward-most position of said head unload arm, and wherein said head unload arm is spring-loaded toward said forward-most position.
8. An apparatus as in claim 5, wherein said head unload arm comprises a forked portion in the shape of a flat taper ramp.

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9. A disk drive comprising:

(A) at least one disk; (B) a head arm assembly including (a) at least one flexible member, wherein said at least one flexible member supports at least one data transducer; and (b) a pressing surface; (C) a head unload arm having associated therewith a ramp surface for supporting each said at least one flexible member off said at least one disk, such that each said transducers is not in close proximity to said at least one disk; (D) a retraction lever for storing potential energy sufficient to move said head arm assembly so that each transducer is removed from said at least one disk by said ramp surface; and (E) a retraction lever lock that retains said retraction lever away from said head arm assembly during data access operations of the disk drive and which releases said retraction lever to remove said transducers from close proximity to said at least one disk by the pressing action of said retraction lever against said pressing surface of said head arm assembly.
lo. An apparatus as in claim 9, wherein said at least one disk consists of a single disk is contained within a cartridge.
11. A disk drive comprising:

(A) a head arm assembly including:

(a) a bifurcated load beam rotatably mounted to a first axis and having an upper load beam and a lower load beam; (b) an upper flexure mounted to said upper load beam, and a lower flexure mounted to said lower load beam; (c) an upper read-write head attached to said upper flexure, and a lower read-write head attached to said lower-flexure; and (d) a pressing surface; (B) a head load assembly base having the following associated therewith:

(a) an upward projection; (b) a first pin; (c) a second pin; (d) a head unload arm guide having a stopping surface; (e) a retraction lever lock rotatably mounted on said first pin, wherein said retraction lever lock includes a push pin, a trap pin, and a curved port in which said second pin rides; (f) a head unload arm rotatably mounted on said first pin above said retraction lever lock; 34 (9) a coil spring mounted between said retraction lever lock and said head unload arm, wherein said coil spring biases said head unload arm toward said stopping surface of said head unload arm guide; (C) a retraction lever rotatably mounted on a second axis, said retraction lever having a pressing end, a trappable end, and a wing; (D) a retraction spring connected between said retraction lever and a retraction spring hook; and (E) a solenoid having its central shaft or plunger swingably attached to said retraction lever lock.
12. A disk drive as in claim 11, wherein said head unload arm comprises a portion having an upper guiding surface and lower guiding surface, wherein each guiding surface has a flat-taper shape with a knee between a ramped portion and a flat portion.
13. An apparatus for launching and for subsequently retracting a readwrite head attached to a head arm assembly, the apparatus comprising a pivotally-mounted retraction lever having a pressing end and a trappable end, wherein said retraction lever is positioned such that said pressing end is adjacent to a pressing surface of said head arm issembly; a mechanical biasing member that biases said pressing end toward said pressing surface; a retraction lever lock positioned to alternatively trap and release said trappable end of said retraction lever; a voice coil motor operatively associated with said head arm assembly; and a head unload arm comprising an upper guiding surface and a lower guiding surface, wherein each guiding surface has a flattaper shape with a knee between a ramped portion and a flat portion.
14. An apparatus as in claim 13 further comprising a sleeve of energy absorbing material attached to said pressing end of said retraction lever, and wherein said mechanical biasing member is a spring.
15. An apparatus as in claim 14, wherein a solenoid is swingably attached to said retraction lever lock.
16. A method of launching an upper and a lower readwrite head onto a disk in a disk drive system, the disk drive system comprising a head arm assembly having a pressing surface 36 and an upper flexure and a lower flexure that support said upper and lower readlwrite.heads, respectively; a voice coil motor operatively associated ith the head arm assembly; a head unload arm comprising an upper guiding surface and a lower guiding surface upon which said flexures slide, each of said guiding surfaces having a flat-taper ramp design, including a knee between a flat portion and a tapered portion; a retraction lever; a retraction lever lock; a solenoid; and a biasing member; the method comprising the steps of: rotating the retraction lever to create a gap between the pressing end of the retraction lever and the pressing surface of the head arm assembly, driving the head arm assembly toward the inside diameter of the disk, until the pressing end of the retraction lever is adjacent to the pressing surface of the head arm assembly; controllably ramping the current in said voice coil motor to regulate the translational velocity of said read-write heads as said upper and lower flexures leave said upper and lower guiding surfaces, respectively, of said head unload arm; increasing the current in the voice coil motor until the head arm assembly impacts the inner crash stop; and trapping the trappable end of the retraction lever.

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17. The method of claim 16, wherein said driving step comprises dithiring the current in said voice coil motor to break any frictional forces between said upper and lower flexures and said upper and lower guiding surfaces, respectively, thereby rotating said head arm assembly toward the inside diameter of the disk until each of said flexures slides past the knees of said guiding surfaces upon which said flexures slide and are located on said tapered portions of said flat-taper ramps.
18. A method of launching a read-write head onto a disk in a disk drive system, the disk drive system comprising a head arm assembly having a pressing surface; a head-arm-assemblypositioning motor; a retraction lever having a wing, a pressing end, and a trappable end; a retraction lever lock having a push pin and a trap pin; a solenoid whose plunger is swingably attached to the retraction lever lock; and a biasing member attached to the retraction lever; the method comprising the steps of: activating the solenoid, thereby pressing the push pin of the retraction lever lock against the wing of the retraction lever to create a gap between the pressing end of the retraction lever and the pressing surface of the head arm assembly; 38 driving the head arm assembly toward the inside diameter of the disk, unt:Li the pressing end of the retraction lever is adjacent to the pressing surface of the head arm assembly; increasing the current in the motor until the pressing surface of the head arm assembly balances the force of the biasing member; de-activating the solenoid; increasing the current in the motor until the head arm assembly impacts the inner crash stop; and activating the solenoid, thereby trapping the trappable end of the retraction lever.-
19. The method of claim 18, wherein said step of driving the head arm assembly toward the inside diameter of disk comprises dithering the current in the voice coil motor
20. A method of using stored mechanical energy to retract disk drive read- write heads when the disk drive experiences a power loss while a disk is loaded in the drive, wherein the disk drive system comprises a head arm assembly having a pressing surface; a head-arm-assembly-positioning motor; a retraction lever having a pressing end and a trappable end; a retraction lever lock having a trap pin; a solenoid whose plunger is swingably attached to the retraction lever lock; a head unload 39 arm; and a mechanical biasing member attached to the retraction lever; the metiod comprising the steps of: using said head-arm-assembly- positioning motor to build up potential energy in said mechanical biasing member; storing said potential energy with said retraction lever lock; releasing said stored potential energy automatically when said disk drive experiences a loss of power; and applying said released energy to said retraction lever to retract said head arm assembly onto said head unload arm.
21. The method of claim 20, wherein said mechanical biasing member comprises a spring, and wherein said using step comprises activating said head-arm-assembly-positioning motor to rotate said head arm assembly toward a center of said disk, thereby driving said pressing surface of said head arm assembly into said pressing end of said retraction lever, thereby rotating said retraction lever and stretching said spring.
22. The method of claim 21, wherein said storing step includes activating said solenoid to rotate said retraction lever lock to thereby trap said trappable end of said retraction lever behind said trap pin of said retraction lever lock.
23. The method of claim 22, wherein said releasing step includes jelaxing said solenoid to rotate said retraction lever lock so as to release said trappable end of said retraction lever from behind said trap pin of said retraction lever lock.
24. The method of claim 23, wherein said method further comprises controlling a retraction velocity of the heads to be substantially constant, independent of a starting position of said heads over said disk.
25. A method af retracting read-write heads in a disk drive system, wherein the disk drive system comprises a head arm assembly having a pressing surface; a retraction lever having a pressing end and a trappable end; a retraction lever lock; a solenoid whose plunger is swingably attached to the retraction lever lock to rotate the retraction lever lock; a head unload arm; and a biasing member attached to the retraction lever; the method comprising the steps of: elongating the biasing member; activating the solenoid to rotate the retraction lever lock in a first direction; capturing the trappable end of the retraction lever with the retraction lever lock to store retraction energy in the elongated biasing member; 41 - 42 de-activating the solenoid to rotate the retraction lever lock in a second direction, thereby releasing the retraction lever, which releases the stored retraction energy; and using the released retraction energy to drive the pressing end of the retraction lever into the pressing surface of the head arm assembly until the head assembly comes to rest on the head unload arm.
26. The method of claim 25, wherein the biasing member comprises a spring connected between a retraction spring hook and the retraction lever, and said step of elongating the biasing m emb er comprises stretching the spring.
27. Apparatus for moving a head in a disk drive, the apparatus being constructed and arranged to operate substantially an hereinbefore described with reference to and as illustrated in the accompanying drawings.
28. A disc drive including apparatus according to claim 27.
29. A method of moving a head in a disk drive system, the method being substantially an hereinbefore described with reference to and an illustrated in the accompanying drawings.