FR2723244A1 - METHOD AND DEVICE FOR ADVANCING AND RETRACTING READ-WRITE HEADS RELATIVE TO THE RECORDING MEDIUM OF A DISK UNIT - Google Patents

Abstract

Magnetic recording disk drives. A unique mechanism which is used to advance and retract the read / write heads (55) relative to the disk (37) of a disk drive, includes a release lever. removal (91), a removal lever lock (118), a spring (76), and a voice coil motor (16). After the heads advance over the disc, the voice coil motor rotates the retract lever and increases the potential energy that is accumulated in the spring (76). In the event of a subsequent power failure, the mechanism automatically retracts the read-write heads relative to the disk (37), by releasing the stored mechanical energy. Application to data processing.

Description

The present invention relates to a disk drive and in particular a

  method and device capable of advancing and retracting the heads in the disk drive. The invention can be used with rigid or floppy disk drives using media

  fixed or removable recording.

  In the early and mid-1970s, most

  disk drives used recording media

  highly removable. However, since the early 1980s, most disk drives have used fixed recording media. In these units with fixed recording media, little attention has been paid to removing the heads in the vicinity of the recording medium when access to the data is unnecessary. He appeared

  recently a tendency to return to recording media

  highly removable. This trend has brought back the problem of advancing and retracting the read-write heads. Removable cartridge disk drives must be able to precisely, smoothly, and efficiently position the read-write heads on the recording medium, which is usually protected in a disk cartridge. In addition, it is desirable to be able to remove the heads from the recording medium both when the operator has voluntarily stopped using the cartridge in the disk drive, and when the latter experiences an unexpected power failure during use. If the read-write heads land on the surface of the disc while the engine is running slowing down during a power cut, this can cause the heads to adhere to the disc if left on the disc for a long time. time before power is restored to the disk drive. This phenomenon is called static friction. Additional damage may occur during transport of a disk drive, when the drive heads

  read-write are left on a disk surface.

  It is therefore desirable that the heads are automatic-

  removed from the cartridge without damaging the heads or the recording medium in the process, each time

  that the disk drive power is turned off.

  Various methods have been employed in the past to control the "removal" of the heads from the recording medium on and off. With many prior art disk drives, it is very difficult to remove a cartridge from the drive when a power failure occurs, not to mention the removal of the read-write heads from the media. recording, which is usually a prerequisite for being able to remove the cartridge without damaging the recording media, or read-write heads, or both

thereby data loss.

  In the past, various methods have also been used to control the advance of the heads in units

  that use removable disk cartridges

  wheat. For example, the U.S. patent No. 4,870,518, issued September 26, 1989 and assigned to the Applicant in this application, relates to two different processes which can be used to control the speed of advance

  heads in a removable cartridge disk drive.

  One of the methods which is described in this patent uses a fluid damper or an air damper to

  control the feed speed of the read heads -

  writing. However, the use of precision air dampers increases the cost of the disk drive, and these dampers do not automatically remove heads when

  moment of a power cut.

  Other prior art disk drives use speed feedback based on an fcem (counter electromotive force) or tachometer data from the head actuator structure. Such disk drives control the speed of the read-write heads during the advance process. An example

  for controlling the head feed speed by the user

  tion of an fcém generated by the movement of the actuator is described in the US patent. n 4 864 437, which

  belongs to the Applicant of the present invention.

  Using these devices also increases the cost of the disk drive, and does not help remove

  heads automatically after switching off the power supply

  tion of unity. It is also difficult to accurately detect an fcem during a low movement

  speed, as when loading read heads -

writing.

  Each of the prior art methods for

  control the feed speed of the read heads -

  writing is complex, which increases the risk of disk drive failure. In addition, the incorporation of these devices of the prior art in units of

disc is expensive.

  There is therefore currently a need for a better method for controlling the speed of the actuator during the advancement of the heads, for controlling the speed of the actuator during the removal of the heads, and for storing sufficient energy. to automatically retract the read-write heads in case of

power failure.

  A general object of the present invention is therefore to provide, in disk drives, an improved method and device for advancing and retracting read-write heads, in which the problems and

  the disadvantages described above have been taken into account

deration and mitigated.

  Another object of the present invention is to

  provide a read head advance device

  writing which uses an electromotive force (fem) produced in the coil of the actuator motor, to incrementally balance the tension in a withdrawal spring and the friction on the guide surfaces of the head unloading arm, to allow control speed of the head arm structure

during the advance of the heads.

  Another object of the present invention is to

  provide a read head removal device

  writing that uses energy other than electric power to remove the read-write heads from the surface of the disc, each time the disk drive

undergoes a power cut.

  Another additional object of the present invention is to provide a device for advancing and withdrawing read-write heads which is capable of automatically retracting the read-write heads if the disk drive undergoes a power failure, to lift the heads away from the surface of the disc without damaging the read-write heads or the

  disc, or both. When the heads are so lifted

  from the surface of the disc, the phenomenon called

  static friction is also eliminated.

  To achieve the goals set out above, as well as others, the present invention provides a device for advancing the read-write heads.

  to a disc and retract the read heads

  write from disk to a disk drive. The disc can be mounted in a cartridge. The device

  includes a read-write head attached to a structure

  head armature, a withdrawal lever so mounted

  swivel, having one pressure end and one end

  a restrainable miter, the withdrawal lever being positioned so that the pressure end is adjacent to a pressure surface of the head arm structure, and a mechanical biasing member (eg a spring) which biases the pressure end of the withdrawal lever towards the pressure surface

  of the head arm structure. In the embodiment

  preferred, a sleeve of energy absorbing material is attached to the pressure end of the withdrawal lever. A withdrawal lever lock is incorporated to alternately retain and release the end of the withdrawal lever which can be retained, and an electromagnet is attached to the withdrawal lever lock to position this

  latest. A voice coil motor is associated function-

  the head arm structure and it is

  used both to advance the read heads -

  write and to position the read-write heads to write data to a disc or read data from a disc. The device also includes a head unloading arm comprising a forked portion having an upper guide surface and a

lower guide surface.

  The invention will be better understood on reading

  the following description of an embodiment,

  given by way of nonlimiting example. Following the

  description refers to the accompanying drawings in which:

  Figures 1 to 8 are schematic representations, in top view, of a preferred embodiment of the present invention, showing the device for advancing and removing heads at various points during operation of the device; Figure 9 is an enlarged section of the part

  forked head unloading arm which is depicted

felt in Figures 3 and 16;

  Figure 10 is a three-dimensional representation

  the head arm structure, the voice coil motor, the withdrawal lever, the withdrawal spring, the withdrawal lever lock, the head unloading arm and the head unloading arm guide; Figure 11 is an elevational view of the upper portion of the withdrawal spring hook; Figure 12 is an elevational view of the side of the withdrawal spring hook, showing the spring retaining notch which is formed in the vertical portion of the withdrawal spring hook; Figure 13 is an elevational view of the upper part of the withdrawal lever; Figure 14 is an elevational view of the side of the withdrawal lever which is shown in Figure 13; Figure 15 is an elevational view of the front of the head unloading arm which is used in the preferred embodiment of the present invention;

  Figure 16 is an elevational view shown

  both the upper part of the head unloading arm which is represented in FIG. 15; Figure 17 is an elevational view of the right end of the head unloading arm which is shown in Figure 15; Figure 18 is an elevational view of the upper part of the withdrawal lever lock; Figure 19 is a section through the removal lever lock which is shown in Figure 18; Figure 20 is an elevational view of the bottom of the withdrawal lever lock which is shown in Figures 18 and 19; Figure 21 is an elevational view from the base side of the head unloading structure, in the direction which is designated in Figure 1; Figure 22 is an elevational view of the upper portion of the head unloading arm guide; Figure 23 is an elevational view of the end of the head unloading arm guide which is shown in Figure 22; Figure 24 is an elevational view from the side of the electromagnet, in the direction shown in Figure 1; FIG. 25 is a representation of the current which is applied to the voice coil motor (MBM) during the oscillation phase of the operation of the MBM; and FIG. 26 is a representation of the current which is applied to the MBM during the displacement phase in

  rising ramp of MBM operation.

  The present invention provides a device for a disk drive which is for advancing read / write heads to discs and retracting read / write heads from discs. In the mode of

  preferred realization, only one disc is contained inside

  laughing at a cartridge. The invention is however not limited to this case and it can be applied to multiple discs as well as to discs which are not mounted

  in cartridges. In the following description,

  that it is indicated that a component "A" is above a component "B", this means that the component "A" is more distant (in a direction which leaves the page on the

  Figures 1-8) of the base 10 of the disk drive (i.e.

  tell the bottom of the inside of the disk drive) that the

component "B".

  Referring first to Figures 1-8, it is noted that the device for a disk drive of the present invention comprises the following components. A head arm chassis 13 is mounted on the base 10 of the disk drive. A moving coil motor (MBM) or a head arm structure positioning motor is generally designated by the reference 16. A

  head arm structure 19 is pivotally mounted

  aunt on the head arm chassis 13 to rotate about an axis 22. An internal collision stop 25 is mounted on the voice coil motor 16, and it is positioned so that the stop buffer stop 28, which consists of energy absorbing rubber, and which is mounted on the base end 31 of the head arm structure 19, strikes the stop pad 34 of the inner crash stop 25, when the arm structure of head 19 is turned towards its innermost position

  on the recording medium 37. In this embodiment

  areciated, the tLpnd'arr 34 is threaded so that i can adjust the position at which it strikes the buffer stop

stop 28.

  The head arm structure 19 includes a forked loading bar 40, including a

  upper loading 43 and a lower loading bar

  lower 46 (figure 10). The head arm structure 19 further comprises an upper flexible element 49 fixed to the upper loading bar 43, and an element

  lower hose 52 fixed to the lower loading bar

  46. A pair of transducers (read heads-

  55), 58 are mounted on the free ends of the flexible elements 49, 52. The upper read-write head 55 is fixed by a cardan suspension (not shown) on the upper flexible element 49. The read head lower writing 58 is fixed by a cardan suspension (not shown) on the lower flexible element 52. These characteristics appear best in FIG. 10. In this preferred embodiment, a pressure surface 61 is constituted by a part d a ratchet wheel sector 64, which is mounted below the head arm structure 19, to rotate with it. The teeth 67 which are shown on the ratchet wheel sector 64 are not used

  in this preferred embodiment.

  Referring then to Figures 1-8, 11 and 12, a withdrawal spring and a withdrawal spring hook will be described. The withdrawal spring hook 70 is mounted on the base 10 of the disk drive, in position adjacent to the movement region of the ratchet wheel sector 64. A slot 73 is formed in the withdrawal spring hook 70, for adjusting the initial tension of the withdrawal spring 76. In the preferred embodiment of the present invention, the withdrawal spring 76 has a return constant of 1.75 N / cm. To adjust the initial tension of the withdrawal spring 76, the withdrawal spring hook 70 can be rotated around a mounting screw 79. A second mounting screw 82 moves in the slot 73, thereby limiting the range of movement of the withdrawal spring hook 70. Once the initial tension of the withdrawal spring 76 has been set, the withdrawal spring hook 70 is fixed to the base 10 of the disk drive by tightening the mounting screws 79 and 82. The withdrawal spring hook 70 comprises a vertical part 85 in which is formed a notch

  spring retainer 88 (see Figure 12).

  The removal lever 91 will be described with reference to

  Then going to Figures 1-8, 13 and 14. The withdrawal lever 91 is rotatably mounted on the base 10 of the disk drive, to rotate about an axis 94. The withdrawal lever 91 is mounted on its axis 94 below the head arm structure 19. This is indicated in FIGS. 1-8 by showing in dotted lines the parts

  hidden from the withdrawal lever 91, when covered

  green by the head arm structure 19. The lever

  withdrawal 91 includes a pressure end 97. The end

  pressure mate 97 of withdrawal lever 91 hits pressure surface 61 of ratchet wheel sector 64 at various times during operation of the

disk.

  A sleeve of shock absorbing material 100 (for example energy absorbing rubber) is mounted on the pressure end 97 of the withdrawal lever 91 in the preferred embodiment. This sleeve 100 mitigates any tendency of the read-write heads 55, 58 to come into

  collision with disc 37 when the end of pressure

  sion 97 of the withdrawal lever 91 strikes the pressure surface 61 of the head arm structure 19, to move the upper and lower flexible elements 49,

  52 up to the upper and lower guide surfaces

  103, 106 of the forked portion 109 of the head unloading arm 112. It is important to always prevent the read-write heads 55, 58 from colliding with the recording medium 37, in particular when this the latter has a high data density. The head unloading arm 112 is described below in more detail and can be

  see it best in Figures 9, 10 and 15-17.

  The withdrawal lever 91 also has an

  This retainable moth, 115. This retainable end, 115, is locked or retained by the removal lever lock 118 during normal operation of the disk drive. Removal lever lock 118 is described more fully below

  and we can see it best in Figures 18-20.

  The retainable end 115 of the withdrawal lever 91 has an inclined surface 121 which facilitates

  the restraining action, as will be described further below

  below. During part of the operation of the head advance device of the present invention, the withdrawal lever lock 118 exerts pressure against a wing 124 which is part of the withdrawal lever 91. More specifically, a pushing finger 127 which is mounted on the lower surface 130 of the withdrawal lever lock 118 can strike the wing 124 under the effect of the rotation of the withdrawal lever lock 118, depending on the degree of rotation of the withdrawal lever 91. In particular , during the initial part of the disk unit head loading operation (FIG. 2), the pushing finger 127 turns the withdrawal lever 91 to create a space between the pressing end 97 of the lever withdrawal 91 and the pressure surface 61 of the ratchet wheel sector 64. The operation of loading heads of the disk drive is considered below in a more complete manner. The withdrawal lever 91 includes a hole 133 which performs the function of an attachment point for the withdrawal spring 76. We will now indicate details of the components which are fixed to the head loading structure 136. A projection 139 directed upwards is formed integrally with the base of head loading structure 136. FIG. 21 best shows this projection 139 directed upwards. FIG. 21 shows an elevation view of the end of the head loading structure base 136, in the direction indicated by the reference 21 in FIG. 1. The projection 139 directed upwards fulfills the function of a stop for the head unloading arm 112. The

  projection 139 directed upwards limits the movement

  maximum rearward of the head unloading arm 112, as will be considered more fully below. A first finger 142 and a second finger 145 are also mounted on the base of head loading structure 136. The first finger 142 fulfills the function of the axis of rotation for the withdrawal lever lock 118 and the discharge arm of heads 112. The second finger moves in a curved opening 148 during the rotation of the withdrawal lever lock 118. The curved opening 148 thus limits the permissible range of rotation of the withdrawal lever lock 118. The lever lock

  shrinkage is best shown in Figures 18-20.

  The withdrawal lever lock 118 is also connected to the electromagnet 151. The electromagnet 151, which can be seen in FIGS. 1-8 and 24, is characterized by a spring return to the position de-energized. Thus, when the power supply to the electromagnet 151 is cut off, the central rod or plunger 154 of the electromagnet 151 extends completely to its de-energized position. FIG. 24 represents a side view of the electromagnet 151, in the direction which is indicated by the reference 24 in FIG. 1. The withdrawal lever lock 118 is

  pivotally coupled to the plunger 154 of the electro-

  magnet 151 by means of a coupling pin 157 (Figure 24). Electromagnet 151 produces the force that positions

  in rotation the withdrawal lever lock 118. The electro-

  magnet 151 therefore supplies the energy which activates the locking mechanism of the disk drive, having the function of storing mechanical energy which facilitates the automatic removal of the read-write heads 55, 58 at the time when the power supply disk drive is cut off. The withdrawal lever lock 118 also includes a retaining finger 160. The retaining finger 160 projects from the bottom surface 130 of the withdrawal lever lock 118. This finger 160 is used to retain the retaining end , 115, of the withdrawal lever 91, as will be described further below. Figures 7 and 8 show the retaining finger 160 in the condition in which it fulfills its retaining function. Referring now to Figures 9, 10 and

  -17, we will describe the head unloading arm 112.

  The head unloading arm 112, which can be

  made from a suitable technical plastic

  or other suitable structural material, is mounted on the upper part of the withdrawal lever lock 118, to rotate around the first finger 142 (finger 142 is shown for example in Figures 1-8 and 21). In the preferred embodiment of the present invention, the material between the upper and lower guide surfaces 103, 106 of the head unloading arm 112 has been removed to allow passage of a disc 37 which has been loaded in the disk drive. This can best be seen in Figure 9. The head unloading arm 112 therefore includes a forked portion 109. As can best be seen in Figures 9 and 10, each guide surface 103, 106 of the forked portion 109 of the head unloading arm 112 has a shape which includes a flat part and a part of

  ramp decreasing, with a change location-

  slope between each ramping or decreasing part, and its respective flat part. Referring in particular to FIG. 9, it is noted that the upper guide surface 103 comprises a ramp portion 104 and a flat portion 105 separated by an upper slope change location 169. Similarly, the lower guide surface 106 includes a part in

  ramp 107 and a flat part 108 separated by a place

  slope change 170. This configuration with a flat part and a decreasing part effectively lifts each read / write head 55, 58 from its functional position in the vicinity of the surface of the disc, towards its retracted position in safety , away from the surface of the disc. When the head arm structure 19 is fully retracted, the upper and lower flexible members 49, 52 of the head arm structure 19 are respectively brought

  on the upper and lower flat parts 105, 108.

  The flat parts 105, 108 help to minimize the vertical movement of the flexible elements 49, 52, so that a cartridge can be loaded, and they also provide surfaces parallel to the plane of the flexible elements 49, 52, to minimize the pressure which acts on the guide surfaces 103, 106 when the read-write heads 55, 58 are completely parked on the flat parts 105, 108. The head unloading arm 112 also includes a projection 163 directed downwards

and a buffer mount 166.

  During any rotation of the head unloading arm 112, the free end of the head unloading arm 112 slidably rests on a head unloading arm guide 172. This head unloading arm guide 172, which, as the head unloading arm itself, can be made from a suitable material, such as plastic, is shown in Figures 1-8, 10, 22 and 23. The guide 172 is mounted from rigidly based on

  head loading structure 136. A helical spring

  dal 175 (Figure 10) urges the downward projection 163 of the head unloading arm 112 against the stop surface 178 of the head unloading arm guide 172. The coil spring 175 is mounted around the first finger 142, between the head unloading arm 112 and the withdrawal lever lock 118. The distance

  between the stop surface 178 of the discharge arm guide-

  ment of heads 172 and the projection 139 directed upwards defines the total range of possible positions for the

  head unloading arm 112.

  A pad 181 of an energy absorbing material (such as energy absorbing rubber) is mounted around the pad mount 166. The pad 181 has a cylindrical shape in the preferred embodiment, and it helps to mitigate any tendency of the head arm structure 19 to rebound when the read-write heads 55, 58 are retracted from the surface of the disc 37. The coil spring 171 further contributes to absorbing the shock between the head arm structure 19 and the head unloading arm 112. The coil spring 175 and the buffer 181 attenuate

  rapid rebound problems that arise when

  as the head arm structure 19 moves toward the

  position retracted under the action of the withdrawal spring 76.

  Figures 1-8 are organized to show the progression of the head advance sequence, starting from a unit which has not yet been energized (Figure 1), and ending with a unit which has advanced with successfully the read-write heads 55, 58, thus reaching the operational state. In the invention which is described, a single mechanism is used at the same time for advancing and then for retracting the read-write heads 55, 58. We will first describe the

advance sequence.

  During the head-ahead sequence, the

  heads 55, 58 are positioned without position feedback

  tion or speed. In other words, the present invention

  tion describes an open loop system. During advance, a primary concern is to control the speed of the upper and lower flexible members 49, 52 as they leave their respective guide surfaces 103, 106, so as to prevent the heads

  , 58 do not collide with the recording medium

  very 37. As the upper and inner flexible elements 49, 52 move along their respective guide surfaces 103, 106, the resulting force which acts on the head arm structure 19 changes, particularly as the elements upper and lower hoses 49, 52 pass from the flat parts 105, 108 to the decreasing parts 104, 107 of the upper and lower guide surfaces 103, 106. As can be appreciated by considering FIGS. 9 and 10, the heads of read-write 55, 58 move towards each other and towards the recording medium 37 as the flexible elements 49, 52 slide down on the guide surfaces 103, 106. If the heads 55, 58 approach each other too quickly as they descend along their guide surfaces

  respective 103, 106, heads 55, 58 will collide

  sion with the recording medium 37 when they leave the head unloading arm 112. If the read-write heads 55, 58 collide with the recording medium 37, they may be damaged, or data recorded on the recording medium 37 can be destroyed, in particular with a recording medium 37 of the type to

  high density. If, on the contrary, the read heads

  writing 55, 58 move too slowly towards the recording medium 37 when they leave the guide surfaces 103, 106 of the head unloading arm 112, the heads 55, 58 will not leave the unloading arm clearly 112 heads, and

  their transition to flight on the recording medium

  ment 37 will be corrupted. This corruption is more likely to occur in the case of a removable recording medium, due to the increased value of the spurious variation of the vertical level during rotation, which

  is inherent in the change of recording medium.

  Referring now to Figures 1-8 and 25, 26, as well as the Appendix, we will describe the step-by-step process that is used for advancing the heads. The Annex presents the algorithm of this process, and the values

  data are digital converter constants-

  analog. Figures 25 and 26 show the current flowing through the voice coil motor during part of the head feed process. In the preferred embodiment of the present invention, a voice coil motor in a neutral condition has a digital to analog converter (DAC) value of 80H. Values greater than 80H apply a directed force

  towards the inside diameter or "DI". Lower values

  res at 80H apply a force directed towards the outside diameter or "DE". The torque by increment of the CNA is, 17 x 103 N.cm. Figure 1 shows the feed and take out device of the present invention with a cartridge inserted into the disk drive. Under the effect of an order, the recording medium 37 is rotated and accelerates. The advance sequence is triggered when the recording medium 37 reaches a speed

specified rotation.

  First, as shown in FIG. 1, a force directed towards the DE is produced to move the flexible elements 49, 52 towards the top of the ramp parts 104, 107 of the upper guide surfaces and

  respective 103, 106 (step 1 in the Appendix).

  Then, as shown in Figure 2, the electro-

  magnet 151 is activated (step 2 in the Appendix). When the electromagnet 151 is activated, the plunger 154 is retracted inside the electromagnet 151. When the plunger 154 retracts, it exerts traction on the withdrawal lever lock 118, which makes it rotate slightly. the removal lever lock 118 in a

  first direction (reverse clock direction in Figure 2).

  This rotation forcibly applies the pushing finger 127 against the wing 124 of the withdrawal lever 91. The force which is thus exerted on the wing 124 slightly turns the withdrawal lever 91 around the axis 94 (in direction d 'clock in figure 2). This last rotation of the withdrawal lever 91 creates a space between the pressure end 97 of the withdrawal lever 91 and the pressure surface 61 of the

  molded ratchet wheel sector 64.

  The current flowing in the voice coil motor 16 is then subjected to an oscillation (step 3 in the Appendix; see also FIG. 25), to break any static friction between the flexible elements 49, 52 and the flat parts 105, 108 of the head unloading arm 112, without excessively accelerating the elements of

  bending 49, 52 over the extent of the flat parts 105, 108.

  This oscillation generates a resulting force which rotates the head arm structure in a clockwise direction in Figure 2, until contact is restored between the pressure end 97 of the withdrawal lever 91 and the surface pressure 61. This places the device in the position shown in FIG. 3, with no space between the withdrawal lever 91 and the surface of

pressure 61.

  At this gint, the elements flible3 sprieir et infériir 49.52 srt passed on the places of chlangntrlt of penetrative resteives 169,170 of the surfaces of guide superior and inferior 103,106 (figures 3 and 9). The flexible elements 49, 52 rest on the respective ramped parts 104, 107 of the discharge arm of

  heads 112, at a "pause point", or pre-position

  loading. At this pre-loading position, the elastic force produced by the withdrawal spring 76 (which is determined by the position of the withdrawal lever 91, which has been turned by the thrust finger 127 of the withdrawal lever lock 118, which was in turn shot by

  the electromagnet 151, as described above) is above

  lower than the resulting oscillating torque generated by the voice coil motor 16, which means that the elements

  hoses 49, 52 do not leave the pre-

  loading (although there may be slight movement

  oscillation around the pre-loading position).

  Therefore, the location of the pre-

  loading is determined by the position of the withdrawal lever 91, which in turn depends on the settings of the electromagnet 151. The electromagnet 151 is adjusted so that the pre-loading position is immediately after the flexural elements 49, 52 have exceeded the slope change location 169, 170 (Figures 3 and 9). The duration of the oscillation (which is currently about 1.4 seconds) is established so that in the most unfavorable case (adherent friction), the flexible elements 49, 52 arrive at the preloading position.

before the oscillation stops.

  FIG. 9 shows an enlarged view showing the upper and lower flexible elements 49, 52 at this preloading position. In FIG. 9, one can clearly see the position of the flexible elements 49, 52 on the ramp parts 104, 107 of the respective upper and lower guide surfaces 103, 106. Up to this point, the force that the withdrawal spring 76 exerts on the withdrawal lever 91 has been balanced by the force that

  the electromagnet 151 exerts on the wing 124 by means of

  diary of the push finger 127 of the lever lever lock

withdrawal 118.

  After reestablishing contact between the pressure end 97 of the withdrawal lever 91 and the pressure surface 61, the voice coil motor 16 begins to "take over" from the electromagnet 151 with regard to the task which is to oppose the

  force which is produced by the tensioned withdrawal spring 76.

  The head arm structure 19 comes into contact with the withdrawal lever 91, via the pressure surface 61 of the ratchet wheel sector 64, and it opposes the force which is produced by the spring withdrawal 76. As the voice coil motor 16 becomes more energized, the head arm structure 19, acting through the pressure surface 61 of the ratchet wheel sector 64, pushes

  the withdrawal lever 91 and tightens the withdrawal spring 76.

  The fem in the voice coil motor 16 is increased incrementally by firmware, so that the

  upper and lower flexible elements 49, 52 start

  cent to move on the ramped parts 104, 107 of the guide surfaces 103, 106 of the head unloading arm 112. The fem in the voice coil motor 16 is increased in a controlled manner, or in a rising ramp, with

  a fixed speed of variation, using techniques

  which will be apparent to those skilled in the art (see for example step 4 in the Appendix; see also Figure 26). This variation in the rising ramp of the fem in the voice coil motor has the effect of tensioning the withdrawal spring 76, until it balances the force produced by the motor 16. The head arm structure 19 moves in turn at a controlled speed (in a manner equivalent to a D'Arsonval movement), along the ramped or inclined parts 104, 107 of the guide surfaces 103, 106, and it leaves these parts

  to move towards the surface of the disc.

  If the voice coil motor had simply been supplied from a fully parked position and had rotated to pass the flexible elements directly over the slope change location and to lower the ramped parts of the discharge arm from Without stopping them at the preload position, controlling the speed of the heads would have been much more difficult. This is because the application of sufficient force to overcome friction and static friction between the elements

  flexible and discharge arm guide surfaces-

  Heading, combined with the unknown dynamic load characteristics which are caused by the passage of the flexible elements on the change of slope locations of the head unloading arm, would have led to an acceleration of the flexible elements and a loss of system control. However, starting to change the current of the voice coil motor in a rising ramp after the flexible elements

  have reached the pre-loading position, and by ordering

  next to the current in the voice coil motor 16, the disk unit regulates the speed of translation of the read-write heads 55, 58 at the moment when the upper and lower flexible elements 49, 52 leave the upper guide surfaces and 103, 106 of the head unloading arm 112. In this way, at the moment when the read-write heads 55, 58 pass from the condition of rest on the forked part 109 of the head unloading arm 112, under the condition of "flight" on the recording medium 37 in rotation, the speed of the read-write heads 55, 58 is controlled at the moment when the heads approach one another and their

respective disc surfaces.

  During the charging process, the

  firmware in the microprocessor of the electrical circuits

  disk drive tronic looks for servo data it hopes to find on the recording medium 37 (step 4 in the Appendix). If the read-write heads 55, 58 begin to read servo data from the disk, they have probably been fully loaded. In the preferred embodiment, a rising ramp of the voice coil motor 16 comprising up to twelve steps is used (step 4 in the Appendix; see also Figure 26), but the system is normally adjusted so that the heads 55, 58 have left the head unloading arm 112 after the sixth upward ramp step. To ensure that the heads of

  read-write 55, 58 actually left the arm of the

  loading heads 112, the disk drive firmware continues to move flexible elements 49, 52 from the head unloading arm 112 after the read-write heads 55, 58 have started to read servo data on the disc (see step 5 in the Appendix). This occurs although the flexible members 49, 52 may have completely left the head unloading arm 112 as soon as the read-write heads 55, 58 have started to read servo data. Then, the electromagnet 151 is deactivated (step 6 in the Appendix) and its plunger 154 returns to its extended position (FIG. 4). When the plunger 154 returns to its extended position, the withdrawal lever lock 118 is turned in a second direction (clockwise in FIG. 4), towards a position which allows the end which can be retained, 115 , of the withdrawal lever 91, to be finally turned to a position in which it is retained or locked by the retaining finger 160 of the withdrawal lever lock 118. This retaining action is described below in more detail.

  complete in relation to Figures 6 and 7.

  The current which is directed to the voice coil motor 16 is then further increased (step 7 in the Appendix). The increase in current applied to the voice coil motor 16 forces the head arm structure 19 to make an initial movement from the outer track of the recording medium 37, towards the

  innermost track (see for example Figure 5).

  FIG. 6 represents the structure of head arms 19

  positioned beyond the innermost track. When-

  that the head arm structure 19 is thus positioned

  born, the stop buffer stopper 28 of absorbent material

  tion of energy has struck the stop buffer 34. In addition, when the head arm structure 19 is in this position, the withdrawal spring 76 is at its maximum elongation, and the head arm structure 19 has tilt the removal lever 91, which can now be

  retained by the withdrawal lever lock 118. This movement

  initial head arm structure 19 from the outer track to the innermost track

  of the recording medium 37 increases the potential energy

  in the withdrawal spring 76, which arms the automatic disk head removal system, while placing the withdrawal lever 91 in the "locked position" so that the energy of the spring can be "stored" by the lever lock

from withdrawal 118.

  After a short delay (step 8 in the Appendix),

  the electromagnet 151 is again excited, as shown

  felt in FIG. 7. When the electromagnet 151 is energized, the plunger 154 is pulled to the left in FIG. 7. This action turns the withdrawal lever lock 118 in the first direction (counter clockwise). in FIG. 7), in order to lock the withdrawal lever 91 in place. When the withdrawal lever 91 is positioned in the manner shown in FIG. 7, and the electromagnet 151 is energized, the lever lock withdrawal 118 retains the retainable end, 115, of the withdrawal lever 91 behind the retaining finger 160 which is fixed to the bottom of the withdrawal lever lock 118, which has the effect of holding the withdrawal spring 76 in a configuration of extension, and to store the potential energy of the spring. In particular, the retaining finger 160, which can best be seen in FIGS. 18-20, exerts pressure against the sloping surface 121 of the retrievable end 115 of the withdrawal lever 91. This configuration, in which the retaining finger 160 retains the withdrawal lever 91, can be seen in FIGS. 7 and 8. As long as the electromagnet 151 is energized, the withdrawal lever 91 is maintained in a state in which it is loaded by the spring. As best seen in Figure 8, when the withdrawal lever 91 is locked by the withdrawal lever lock 118, the withdrawal spring 76 no longer acts on the movement of the head arm structure 19. L pressure end 97 of withdrawal lever 91 does not touch the pressure surface 61 of the ratchet wheel sector 64, and the head arm structure

  19 can move freely on the recording medium

  37. The disk drive then goes to a sub-

  calibration program, which places the unit in a state in which it is ready to accept an order from a host computer and to perform the operations of

  any read-write that are requested.

  The removal system of the present invention is capable of retracting the read-write heads 55,

  58 under normal conditions as well as under

* power cut or failure. During a normal removal operation, the operator typically initiates the removal sequence by pressing

  on a button on the front of the disk drive.

  According to a variant, the sequence can be triggered by a sequence of interface orders. After the sequence has been triggered, the read-write heads 55, 58 head towards the outer track. Then, the voice coil motor 16 provides sufficient force (60H for the DAC in the preferred embodiment) to lift or push the read-write heads 55, 58 by making them mount on the ramped parts 104, 107 ( FIG. 9) of the guide surfaces 103, 106 of the head unloading arm 112, towards a retracted position. The disc unit then slows down the rotational movement of the disc, and the electromagnet 151 is then de-energized, so that the plunger 154 is driven to the right in Figures 1-8. As the plunger 154 moves to the right, the removal lever lock 118 is rotated

  in the second direction (clockwise in Figure 8).

  When the withdrawal lever lock 118 thus releases the retainable end 115 of the withdrawal lever 91, the pressing end 97 of the withdrawal lever 91 is forcibly applied against the pressing surface 61. The spring removal 76 thus helps to hold the read-write heads 55, 58 on the head unloading arm 112 while, for example, a cartridge is removed from the disk drive. In a fixed disk drive, this function can for example be implemented before the disk drive or the system that supports it

contains is not moved.

  The following paragraphs describe the removal of the write-read head 55, 58 when the disk drive experiences an unexpected power failure. In this situation, the system for automatically removing the heads from the disk drive comes into operation. Energy

  which will be used to unload the read heads -

  writing 55, 58 in this situation is the energy which is

  stored in the tensioned withdrawal spring 76.

  In the present invention, before a power failure occurs, the removal lever lock

  118 prevents withdrawal lever 91 from exerting influence

  this on the functional movement of the arm structure of

  heads 19. This locking action is described below.

  on it completely. As is well known in the art, the head arm structure 19 can then be used to access data on tracks of the recording medium 37. When the power of

  the disk drive unexpectedly shuts down, the power

  tro-magnet 151 ends up de-energizing itself, releasing its plunger 154. The released plunger 154 moves to the right in FIGS. 7 and 8, which turns the withdrawal lever lock 118 in the second direction (direction of clock in Figures 1-8). With this rotation of the withdrawal lever lock 118, the retaining finger 160 can no longer retain the retaining end,

  , of the withdrawal lever 91. The energy which is stored

  sine in the withdrawal spring 76 is therefore released.

  The energy of the spring which is released is applied to the withdrawal lever 91, to the hole 133 in the withdrawal lever 91 to which the withdrawal spring 76 is fixed to the withdrawal lever 91. This in turn rotates the withdrawal lever 91 in the opposite direction of the clock in FIGS. 1-8, which finally establishes contact between the pressure end 97 of the withdrawal lever 91 and the pressure surface 61 of the ratchet wheel sector 64. The force which acts against the pressure surface 61, under the action of the pressure end 97, rotates the head arm structure 19 in clockwise direction in FIGS. 1-8 and drives the head arm structure 19 towards the arm head discharge 112, by pushing the upper and lower flexible elements 49, 52 on the respective upper and lower guide surfaces 103, 106. In this way, the device retracts the read-write heads 55, 58 regardless of the position of the structure of head arms 19 on the recording medium 37 when the power supply to the disk drive is cut off, which has the effect of placing the read-write heads 55, 58 in a

  safety position, away from the recording medium 37.

  When the head arm structure 19 is close to the outer track of the recording medium 37, as shown in FIG. 8, the space between the pressure end 97 of the withdrawal lever 91 and the pressure surface 61 of the ratchet wheel sector 64 is the largest. If the disk drive experiences an unexpected power failure when the head arm structure 19 is positioned in this way, the end of

  pressure 97 has its greatest distance over which

  it can accelerate towards the pressure surface 61. In this situation, the material sleeve

  Amortization 100 helps to mitigate any risk of rebon-

  smoothing of the withdrawal lever 91 after its pressure end 97 has struck the pressure surface 61. As an alternative to the use of the sleeve 100, the withdrawal lever 91 itself can be made of a material or

  with a shape that mitigates any risk of rebound.

  For example, the withdrawal lever 91 itself could be formed from an elastic material which would fail rather than rebound when the pressure end 97

hits the pressure surface 61.

  The invention described above provides numerous advantages over the prior art, including the following. It maintains the heads of

  read-write 55, 58 distant from the recording medium

  ment 37 whenever the disk drive is not powered, since the heads 55, 58 are always retracted from the recording medium 37 using mechanical energy, whenever the drive disc experiences a power outage. Because the read-write heads 55, 58 are kept away from the surface of the disc when the disk drive is not receiving power, damage to the read-write heads 55, 58 is much less likely to occur during transport of the disk drive with a loaded disk. The invention advances the read-write heads 55, 58 without employing devices such as fluid dampers and tachometers or other speed sensors. The absence of these devices makes the disk drive less complex and less expensive to

  build, while increasing its reliability.

  Although a preferred embodiment of the invention has been described above, it will be apparent to those skilled in the art that many changes can be made without departing from the spirit or the scope

  of the invention. For example, you can use an action-

  linear motor in place of the voice coil motor which is used in the preferred embodiment. All that

  is contained in the foregoing description or is shown

  felt in the accompanying drawings is to be interpreted alone-

  in an illustrative sense, and not in a limited way

  tive. The invention is therefore only limited in accordance with

appended claims.

ANNEX

  1. Apply a force of 6EH, directed towards the outside diameter, to move the flexible elements 49, 52

  to the change of slope locations 169, 170.2. Activate the electromagnet 151 (225 ms).

  3. Move the flexible elements 49, 52 and their respective read / write heads 55, 58 to the preloading position on the ramped parts 104, 107, with the following sequence: 8CH for 2 ms 7EH for 5 ms Repeat 200 times 4. Slowly push the bending elements 49, 50 to make them descend the ramped parts 104, 107 while looking for servo data: Load X with 8DH Load Y with 8CH LOOP: Push with force X for 2 ms Push with force Y for 160 ms Search for servo data SQ800 Search for servo data SQ400 Search for servo data SQ2000 If servo data is found, go to 5

X = X + 1

Y = Y + 1

  If the loop counter indicates less than 12, go to LOOP

  Otherwise the loading of the heads failed.

  5. Continue on 3 additional steps to guarantee the release of the head unloading arm 112

X = X + 1

Push with X for 160 ms

X = X + 1

  Push with X for 160 ms X = X + i Push with X for 160 ms

  6. Deactivate the electromagnet 151.

  7. Push towards the inside diameter to tension the withdrawal spring 76 Push with X for 20 ms X = X + i Push with X for 20 ms

X = X + 1

continue until X = A1H

  8. Wait 50 ms (stabilization delay).

  Activate the electromagnet 151, which eliminates the influence

  this of the withdrawal spring 76 of the forces acting on

the head arm structure 19.

Wait for 225 ms.

9. Set 82H for 0.125 s.

  10. Head loading is complete.

Claims (26)

  1. Device incorporated in a disk drive, comprising at least one disk (37), intended to retract from this disk or these disks, at least one read-write head (55, 58) which is fixed to a structure of head arm (19), characterized in that it comprises: a withdrawal lever (91) having a pressure end (97), this withdrawal lever being positioned so that the pressure end (97) exerts a pressing against a pressure surface (61) of the head arm structure (19), during removal of the head or   read-write heads (55, 58); an element of stress   tation (76) which mechanically biases the pressure end (97) towards the pressure surface (61); and a withdrawal lever lock (118), positioned to alternately retain and release the withdrawal lever (91).   2. Device according to claim 1, character-   risé in that the withdrawal lever (91) further comprises a retainable end (115), the latch   removal lever (118) retaining and releasing alternative-   the retaining end (115) of the lever withdrawal (91).   3. Device according to claim 1, character-   laughed in that it further comprises a sleeve (100) of an energy absorbing material, fixed to the end of   pressure (97) of the withdrawal lever (91).   4. Device according to claim 1, character-   rised in that an electromagnet (151) is fixed so   pivotable to the withdrawal lever lock (118).   5. Device according to claim 4, character-   laughed in that it further comprises an unloading arm heads (112).   6. Device according to claim 5, character-   risé in that the head unloading arm (112) is biased by a spring, and further in that a stopper (181) of an energy absorbing material is fixed to the   head unloading arm (112).   7. Device according to claim 6, character-   risé in that the head unloading arm (112) is mounted on a first finger (142) so that this head unloading arm (112) can pivot between an extreme position towards the front and an extreme position towards the rear, and in addition to what the unloading arm of   heads (112) moves on a discharge arm guide-   ment of heads (172) having a stop surface (178) defining the extreme forward position of the head unloading arm (112), and in that the head unloading arm (112) is stressed by a spring   towards the extreme forward position.   8. Device according to claim 5, character-   risé in that the head unloading arm (112) comprises a forked part (109) having the shape of a   flat part associated with a decreasing part.   9. Disk unit, characterized in that it comprises: (A) at least one disk (37); (B) a head arm structure (19), comprising (a) at least one flexible element (49, 52), this or these flexible elements supporting at least one data transducer (55, 58); and (b) a pressure surface (61); (C) a head unloading arm (112) to which is associated a ramp surface which is intended to support each of the flexible elements (49, 52) in positions remote from the disc (s) (37), so that each of the transducers (55, 58) is not in the immediate vicinity of the disc (s) (37); (D)   a withdrawal lever (91) for storing energy   sufficient potential to move the head arm structure (19) so that each transducer (55, 58) is spaced from the disc or discs (37) by the ramped surface; and (E) a withdrawal lever lock (118) which   retains the withdrawal lever (91) away from the structure   ture of head arms (19) during operations of accessing data from the disk drive, and which releases the withdrawal lever (91) to move the transducers (55, 58) away from the immediate proximity of the one or more discs (37), by the pressure action of the withdrawal lever (91) against the pressure surface (61) of the arm structure of heads (19).   10. Device according to claim 9, charac-   terized in that the disc or discs consist of a single   disc (37) which is contained in a cartridge.   11. Disk drive, characterized in that it   includes: (A) a head arm structure (19) comprising   nant: (a) a forked loading bar (40) rotatably mounted on a first axis and having an upper loading bar (40) and a lower loading bar (46); (b) an upper flexible element (49) mounted on the upper loading bar (40), and a lower flexible element (52) mounted on the loading bar   lower load (46); (c) a read head   upper writing (55) fixed on the upper flexible element (49), and a lower read-write head (58) fixed on the lower flexible element (52); and (d) a pressure surface (61); (B) a head loading structure base (136) with which the following elements are associated: (a) an upwardly projecting projection (139); (b) a first finger (142); (c) a second finger (145); (d) a head unloading arm guide (172) having a stop surface (178); (e) a withdrawal lever lock (118) rotatably mounted on the first   finger (142), this withdrawal lever lock (118) includes   a pushing finger (127), a retaining finger (160) and a curved opening (148) in which the second finger (145) moves; (f) a head unloading arm (112) rotatably mounted on the first finger (142), above the withdrawal lever lock (118); (g) a helical spring (175) mounted between the withdrawal lever lock (118) and the head unloading arm (112), this helical spring (175) biasing the head unloading arm (112) towards the surface stopping (178) the head unloading arm guide (172); (C) a withdrawal lever (91) rotatably mounted on a second axis, this withdrawal lever having a pressing end (97), a retainable end (115) and a wing (124); (D) a withdrawal spring (76) connected between the withdrawal lever (91) and a withdrawal spring hook (70); and (E) an electromagnet (151) whose central bar or plunger (154) is fixed so   pivotable to the withdrawal lever lock (118).   12. Disk unit according to claim 11, characterized in that the head unloading arm (112) comprises a part having an upper guide surface (103) and a lower guide surface (106), and in that each guide surface has a flat / tapered shape, with a slope change location   (169, 170) between a ramped part and a flat part.   13. Device for advancing and then retracting a read-write head (55, 58) which is fixed to a head arm structure (19), characterized in that it comprises: a withdrawal lever (91) mounted pivotally, having a pressure end (97) and a retainable end (115), this withdrawal lever (91) being positioned so that the pressure end (97) is adjacent to a pressure surface of   the head arm structure (19); an element of stress   mechanical station (76) which urges the pressure end   sion (97) to the pressure surface (61); a withdrawal lever lock (118) positioned to alternately retain and release the retrievable end (115) of the withdrawal lever (91); a voice coil motor (16) operatively associated with the head arm structure (19); and a head unloading arm (112) comprising an upper guide surface (103) and a lower guide surface (106), each guide surface having a flat / tapered shape with a slope change location (169, 170 ) between a party in ramp and a flat part.   14. Device according to claim 13, charac-   terized in that it further comprises a sleeve (100) of an energy absorbing material fixed to the pressure end (97) of the withdrawal lever (91), and in that   the mechanical biasing element is a spring (76).   15. Device according to claim 14, charac-   terized in that an electromagnet (151) is fixed so   swivel on the withdrawal lever lock (118).   16. A method of advancing an upper read-write head (55) and a lower read-write head (58) over a disk (37) in a disk drive system, the disk drive system comprising a head arm structure (19) having a pressure surface (61) and an upper flexible member (49) and a   lower flexible element (52) which respectively support   the upper and lower read-write heads   higher (55, 58); a voice coil motor (16) operatively associated with the head arm structure (19); a head unloading arm (112) comprising an upper guide surface (103) and a lower guide surface (106) on which the flexible elements (49, 52) slide, each of these guide surfaces having a ramp configuration flat / tapered, including a slope change location between a flat portion and a tapering portion; a withdrawal lever (91); a withdrawal lever lock (118); an electromagnet (151); and a biasing member (76); characterized in that it comprises the following steps: the withdrawal lever (91) is rotated to form a space between a pressure end (97) of the release lever   shrinkage (91) and the pressure surface (61) of the structure   head armature; the head arm structure (19) is moved towards the inside diameter of the disc (37), until the pressure end (97) of the withdrawal lever (91) is adjacent to the pressure surface (61 ) of the head arm structure (19); the ramp current is varied, in a controlled manner, in the voice coil motor (16), to regulate the speed of translation of the read-write heads (55, 58), while the upper and lower bending elements ( 49, 52) respectively leave the upper and lower guide surfaces (103, 106) of the head unloading arm (112); increasing the current in the voice coil motor (16) until the head arm structure (19) hits an internal collision stop (25); and the retaining end (115) of the lever is retained withdrawal (91).   17. The method of claim 16, character-   rised in that the displacement step comprises the operation of oscillating the current in the voice coil motor (16) to overcome any friction forces between the upper and lower flexible elements (49, 52) and the upper and lower guide surfaces (103, 106), respectively, to thereby rotate the head arm structure (19) toward the inner diameter of the disc (37), until each   flexible elements (49, 52) slide beyond the locations   slope change cements (169, 170) of the guide surfaces on which the flexible elements (49, 52) slide, and is placed on the parts going   decreasing flat / tapered ramps.   18. A method of advancing a read / write head (55, 58) on a disk (37) in a disk drive system, said disk drive system comprising a head arm structure having a surface of pressure (61); a head arm structure positioning motor (16); a withdrawal lever (91) having a wing (124), a pressing end (97), and a retainable end (115); a withdrawal lever lock (118) having a pushing finger (127), and a retaining finger (160); an electromagnet (151) whose plunger (154) is pivotally attached to the withdrawal lever lock (118); and a biasing member (76) attached to the withdrawal lever (91); characterized in that this method comprises the following stages: the electromagnet (151) is excited, which has the effect of pressing the pushing finger (127) of the withdrawal lever lock (118) against the wing ( 124) of the withdrawal lever (91), to form a space between the pressure end (97) of the withdrawal lever (91) and the pressure surface (61) of the head arm structure (19); the head arm structure (19) is moved towards the inside diameter of the disc (37), until the pressure end (97) of the withdrawal lever (91) is adjacent to the pressure surface (61 ) of the head arm structure (19); increasing the current in the motor (16) until the pressure surface (61) of the head arm structure (19) balances the force of the biasing member (76); the electromagnet (151) is de-energized; the current in the motor (16) is increased until the head arm structure (19) hits an internal collision stop (25); and the electromagnet (151) is energized, thereby retaining the retaining end (115) of the lever withdrawal (91).   19. The method of claim 18, character-   risé in that the step of moving the head arm structure (19) to the inner diameter of the disc (37) includes the operation of oscillating the   current in the voice coil motor (16).   20. A method of using the stored mechanical energy to retract read-write heads (55, 58) of a disk drive, when the disk drive experiences a power failure while a disk ( 37) is loaded into the drive, wherein the disk drive system includes a head arm structure (19)   having a pressure surface (61); a position motor-   head arm structure (16); a withdrawal lever (91) having a pressing end (97) and a retainable end (115); a withdrawal lever lock (118) having a retaining finger (160); an electromagnet (151) whose plunger (154) is pivotally attached to the withdrawal lever lock (118); a head unloading arm (112); and a mechanical biasing member (76) attached to the withdrawal lever (91); this process being characterized in that it comprises   the following stages: the positioning motor is used   head arm structure (16) for accumulating potential energy in the mechanical biasing element (76); this potential energy is stored with the withdrawal lever lock (118); the potential energy stored is automatically released when the disk drive experiences a power failure; and applying the energy released to the withdrawal lever (91) to retract the head arm structure (19) on the arm head unloading (112).   21. The method of claim 20, character-   laughed in that the mechanical biasing element   includes a spring (76); and in that the use step   The engine includes activating the head arm structure positioning motor (16) to rotate the head arm structure (19) to a center of the disc (37), thereby to move the pressure surface (61 ) from the head arm structure (19) to the pressure end (97) of the withdrawal lever (91), thereby rotating the withdrawal lever (91) and tension the spring (76).   22. The method of claim 21, character-   rised in that the step of storing potential energy includes energizing the electromagnet (151) to rotate the withdrawal lever lock (118), thereby retaining the end capable of be retained (115) from the removal lever (91) behind the finger   retainer (160) of the withdrawal lever lock (118).   23. The method of claim 22, character-   laughed at in that the release stage includes de-excitation   tation of the electromagnet (151) to rotate the withdrawal lever lock (118), so as to release the retainable end (115) of the withdrawal lever (91) from the position it occupies behind the retaining finger (160) of the removal lever lock (118).   24. The method of claim 23, character-   laughed in that it further comprises controlling a speed of withdrawal of the heads (55, 58) so that it is practically constant, regardless of a position   of departure of the heads (55, 58) on the disc (37).   25. Method for removing read heads   writing (55, 58) to a disk drive system, wherein the disk drive system comprises a head arm structure (19) having a pressing surface (61); a withdrawal lever (91) having a pressing end (97) and a retainable end (115); a withdrawal lever lock (118); an electromagnet (151) whose plunger (154) is pivotally attached to the withdrawal lever lock (118) for rotating the withdrawal lever lock (118); a head unloading arm (112); and a biasing member (76) attached to the withdrawal lever (91); this process being characterized in that it comprises the following stages: one lengthens   the biasing element (76); we excite the electro-   magnet (151) to rotate in a first direction   the removal lever lock (118); capturing the retainable end (115) of the withdrawal lever (91), with the withdrawal lever lock (118), to store withdrawal energy in the elongate biasing member (76); the electromagnet (151) is de-energized to rotate the withdrawal lever lock (118) in a second direction, thereby releasing the withdrawal lever (91), which releases the stored withdrawal energy; and the release energy released is used to move the pressure end (97) of the withdrawal lever (91) to the pressure surface (61) of the   head arm structure (19), until the structure   head armature (19) come to rest on the arm of head unloading (112).   26. The method of claim 25, character-   risé in that the biasing element comprises a spring (76) fixed between a withdrawal spring hook (70) and the withdrawal lever (91), and in that the step of elongation of the element solicitation includes   the operation which consists in tensioning the spring (76).