WO2000063891A2

WO2000063891A2 - Actuator latch for disc drive

Info

Publication number: WO2000063891A2
Application number: PCT/US2000/010573
Authority: WO
Inventors: Erming Luo; Jackson W. Nichols; John D. Stricklin; Steve S. Eckerd; Roy L. Wood; Nigel F. Misso
Original assignee: Seagate Technology Llc
Priority date: 1999-04-21
Filing date: 2000-04-20
Publication date: 2000-10-26
Also published as: WO2000063891A3; CN1348584A; KR20020001835A; WO2000063891B1; GB2363670A; DE10084482T1; JP2002542556A; GB0124151D0

Abstract

A latch mechanism for latching the actuator assembly of a disc drive in a parked position. The latch mechanism includes a latch body having a pivot point rotatable upon a pivot pin integrally coupled to the disc drive, the latch body having a center of gravity substantially near the pivot point. The latch body having a moment of inertia, JL, which is approximately equal to the moment of inertia, JA, of the actuator multiplied by a gear ratio, GRL/A, between the latch body and the actuator. The latch body includes a pair of arms, which meet at the pivot point, and a latching section for latching with a latch member attached to one end of the actuator. The latch body also includes a plurality of ferro-magnetic balls attached to each arm. The latch mechanism also includes a magnet coupled to the disc drive, the magnet situated near the pair of arms to attract the ferro-magnetic balls and thus rotate the latch body.

Description

ACTUATOR LATCH FOR DISC DRIVE

Related Application

This application claims the benefit of U.S. Provisional Application Serial Number 60/130,280, filed April 21, 1999 under 35 U.S.C. 119(e).

Field of the Invention The present invention relates to the field of mass storage devices. More particularly, this invention relates to an apparatus and method for latching the actuator assembly of a disc drive.

Background of the Invention One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are an information storage disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc. The transducer is typically placed on a small ceramic block, also referred to as a slider, that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface ("ABS") which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider directed toward the disc surface. The various forces equilibrate so the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically the thickness of the air lubrication film. This film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.

Information representative of data is stored on the surface of the storage disc. Disc drive systems read and write information stored on tracks on storage discs. The transducers, in the form of read/write heads attached to the sliders, located on both sides of the storage disc, read and write information on the storage discs when the transducers are accurately positioned over one of the designated tracks on the surface of the storage disc. The transducer is also said to be moved to a target track. As the storage disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the storage disc. Similarly, reading data on a storage disc is accomplished by positioning the read/write head above a target track and reading the stored material on the storage disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disc drives, the tracks are a multiplicity of concentric circular tracks. In other disc drives, a continuous spiral is one track on one side of a disc drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information. The methods for positioning the transducers can generally be grouped into two categories. Disc drives with linear actuators move the transducer linearly generally along a radial line to position the transducers over the various tracks on the information storage disc. Disc drives also have rotary actuators which are mounted to the base of the disc drive for arcuate movement of the transducers across the tracks of the information storage disc. Rotary actuators position transducers by rotationally moving them to a specified location on an information recording disc. A rotary actuator positions the transducer quickly and precisely. Typically, a rotary actuator is rotatably attached to a shaft via a bearing cartridge which generally includes one or more sets of ball bearings. The shaft is attached to the base and may be attached to the top cover of the disc drive. A yoke is attached to the actuator. A voice coil is attached to the yoke at one end of the rotary actuator. The voice coil is part of a voice coil motor which is used to rotate the actuator and the attached transducer or transducers. A permanent magnet is attached to the base and cover of the disc drive. The voice coil motor which drives the rotary actuator comprises the voice coil and the permanent magnet. Since the voice coil sandwiched between the magnet and yoke assembly is subjected to magnetic fields, electricity can be applied to the voice coil to drive it so as to position the transducers at a target track.

When the power to the disc drive is turned off, the disc stops rotating. This means that the slider/head assembly stops flying and returns to the surface of the disc. Most disc drives have a specified landing zone on the disc surface for the slider to land on. The landing zone is typically on an outer or inner portion of the disc surface and is designed so that the head can contact the landing zone without causing damage to the surface of the disc. Once landed, the actuator is held in position so that the head stays or is "parked" in the landing zone. It is important to retain the head and actuator in the parked position since when the power to the disc drive is turned off, the voice coil motor no longer controls the actuator. Thus, if the disc drive is subject to a shock, the actuator arm can drift onto the disc. This can cause permanent damage to a disc. In the past, actuator latches such as the latch discussed in Patent 5,381,290 to Cheng have been used to hold an actuator in place after the power to the disc drive has been turned off.

However, as computers become smaller and more portable, disc drives also are becoming smaller and are being incorporated into the smaller computers. Such disc drives are being subject to greater rotational shocks, both because of their smaller size and because of the shocks they receive from being carried about. Moreover, as transducers are being designed to fly ever closer to the disc surface, even a slight flaw in the disc surface can cause permanent damage, since the transducer is more likely to hit the flaw and cause it to damage the disc. Thus, there is a need for actuator latches which can perform under high linear and rotational shock. It is also desirable that the latch mechanism be implemented with a minimal cost.

Thus, what is needed is a disc drive which includes an easily manufactured and assembled actuator latch which can hold the actuator even when subject to very high rotational shocks. This will decrease the risks of the transducer damaging the disc surface. Therefore, the resulting disc drive will be more reliable over the life of the drive.

Summary of the Invention The present invention provides a latch mechanism for latching the actuator assembly of a disc drive in a parked position. In one embodiment, the latch mechanism includes a latch body having a pivot point rotatable upon a pivot pin integrally coupled to the disc drive, the latch body having a center of gravity substantially near the pivot point. The latch body having a moment of inertia, J_L, which is approximately equal to the product of a moment of inertia of the actuator, J_A, multiplied by a gear ratio between the actuator and the latch body, GR_L/A. [J_L= J_A x GR_L/A.] In further embodiments, the latch body includes a pair of arms, which meet at the pivot point, and a latching section for latching with the actuator. In one embodiment, the present invention provides a disc drive having an actuator rotatably attached to its base. The actuator includes a latch member attached to one end and a transducer attached to the other end. The actuator having a moment of inertia, J_A. The disc drive also includes a latch mechanism for latching the actuator in a parked position. The latch mechanism includes a latch body having a pivot point rotatable upon a pivot pin integrally coupled to the base. The latch body having a center of gravity substantially near to the pivot point and a moment of inertia, J_L, approximately equal to J_A multiplied by a gear ratio, GR_L/A, between the actuator and the latch body.

Advantageously, the present invention provides a disc drive which includes an easily manufactured and assembled actuator latch which can hold the actuator in a parked position even when the disc drive is subject to very high rotational shocks and/or linear shocks. Thus, decreasing the risks of the transducer damaging the disc surface. Brief Description of the Drawings

FIG. 1 is an exploded view of a disc drive with a multiple disc stack. FIG. 2 is a top view of one embodiment of a disc drive assembly having an actuator latch according to the present invention. FIG. 3 is an isometric view of one embodiment of an actuator latch according to the present invention. FIG. 4 is a reverse isometric view of the actuator latch of FIG. 3. FIG. 5 is a schematic view of a computer system.

Description of the Preferred Embodiment In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

The invention described in this application is useful with all mechanical configurations of disc drives. In addition, the invention is also useful in all types of disc drives including hard disc drives, zip drives, floppy disc drives and any other type of drives where unloading the transducer from a surface and parking the transducer may be desirable. Figures 1-3 show an exemplary disc drive 100 having one embodiment of a latch mechanism 200. Disc drive 100 includes a housing or base 112, and a cover 114. Base 112 and cover 114 form a disc enclosure. Rotatably attached to base 112 on an actuator shaft 118 is an actuator assembly 120. Actuator assembly 120 includes an E-block or comb structure 122 having a plurality of arms 123. Attached to the separate arms 123 on comb 122 are load beams or load springs 124. Load beams or load springs are also referred to as suspensions. Attached at the end of each load spring 124 is a slider 126 which carries a magnetic transducer 150. Slider 126 with transducer 150 form what is many times called the head. It should be noted that many sliders have one transducer 150 and that is what is shown in the figures. It should also be noted that this invention is equally applicable to sliders having more than one transducer, such as what is referred to as an MR or magneto resistive head in which one transducer 150 is generally used for reading and another is generally used for writing. On the end of the actuator arm assembly 120 opposite the load springs 124 and sliders 126 is a voice coil 128.

Attached within base 112 is a first magnet 130 and a second magnet 131. As shown in FIG. 1, the second magnet 131 is associated with the cover 114. The first and second magnets 130, 131, and voice coil 128 are the key components of a voice coil motor which applies a force to actuator assembly 120 to rotate it about actuator shaft 118. Also mounted to base 112 is a spindle motor. The spindle motor includes a rotating portion called a spindle hub 133. In this particular disc drive, the spindle motor is within the hub. In FIG. 1, a number of discs 134 are attached to spindle hub 133. In other disc drives, a single disc or a different number of discs may be attached to the hub. The invention described herein is equally applicable to disc drives which have a plurality of discs as well as disc drives that have a single disc. The invention described herein is also equally applicable to disc drives with spindle motors which are within the hub 133 or under the hub.

Each of the arms 123 of the E block or comb assembly 122, except the arms 123 on the top and bottom of the E block 122, carry two load springs. In this particular disc drive 100, there is a slider for both the top and bottom fingers of the E block 122 have only one load spring 124 since these are used for the top surface of the top disc and the bottom surface of the bottom disc in the stack of discs 134. Attached to the load springs 124 are sliders 126 which include magnetic transducers which magnetize the surface of the disc 134 to represent and store desired data. As is well known in the art of disc drives, each of the discs has a series of concentric tracks onto which the magnetic information is recorded. Sliders 126 and the magnetic transducers incorporated therein are moved over the surface of a particular disc 134 so that a magnetic representation of data can be stored in any of the tracks on the disc 134. In this particular disc drive 100, the transducer movement is rotational and about actuator shaft 118. Rotating actuator arm assembly 120 causes slider 126 and the transducer therein to be repositioned over surface of disc 134.

Actuator assembly 120 has a pivot point 260 which rotates about shaft 118 during seeks where transducer 150 is moved from track to track on disc 134. Actuator 120 has a moment of inertia, J_A, about pivot point 260. Actuator 120 is driven by the voice coil motor during a seek. When power to disc drive 100 is removed, disc 134 stops rotating and transducer 150 returns to the disc surface. As is known in the art, back EMF (electro-motive force) from the spindle is commonly used to rotate the actuator so that when transducer 150 lands, it is located over the landing zone 234 of disc 134.

Actuator 120 also includes a latching member 270. Latching member 270 is generally located on an end of the actuator 120 opposite the end containing the transducer. Latching member 270 is for latching the actuator with latch mechanism 200 when the disc drive is powered down and the transducer is parked. Latch mechanism 200 exerts a latching force on latching member 270, thus preventing actuator assembly 120 from rotating onto the surface of disc 134 when disc drive 100 is subject to a shock.

Figures 2-4 show details of the exemplary embodiment of latch mechanism 200. Latch mechanism 200 includes a latch body 210. In the exemplary embodiment, latch body 210 is molded plastic member.

Alternatively, latch body 210 can have an inner metal core and an overmolded plastic exterior. In another embodiment of the present invention, latch body 210 can be a two-piece body having a core body and a weight member attached to the core body for providing a required center of gravity and moment of inertia for the body, as will be explained below.

In the exemplary embodiment, latch body 210 includes a pair of arms 305 and 306. Arms 305 and 306 extend from a central pivot point 219 of body 210. Pivot point 219 is the pivot upon which latch body 210 rotates about a pivot pin 220, which is attached to base 112 of disc drive 100. Generally centered between the arms 305 and 306 is a latch section 310. Latch section 310 is defined in part by a notch or wall 311 in arm 305 and a notch or wall 312 in arm 306. Latch section 310 is designed to matably match with latch member 270 of actuator 120. When actuator 120 is rotated to its parked position, latch member 270 matably latches into latch section 310, thus preventing rotation of the actuator until the latch is unlatched.

In the exemplary embodiment, arm 305 includes an attracting member such as a pair of ferro-magnetic or other magnetizable balls 320 and 321. Balls 320 and 321 are located towards one end of arm 305. Ferro-magnetic members 320 and 321 are attracted to a stopping member such as magnet 130 which is attached to base 112 of disc drive 100. In the exemplary embodiment, magnet 130 is a permanent magnet which is strong enough to attract balls 320 and 321 when they are slightly rotated towards it. This occurs when actuator 120 moves into a parked position since latching member 270 on the actuator mates within latching section 310 and applies a rotational force on latch body 210, thus rotating arm 305 slightly towards magnet 130 and thus allowing magnet 130 to exert an attracting force on balls 320 and 321. Arm 305 includes a member 323 for abutting against magnet 130 to provide a stopping position for the latch mechanism.

Arm 306 also includes an attracting member such as a ferro-magnetic ball 322. Ball 322 is attracted to a stopping member such as magnet 130. In the exemplary embodiment, the disc drive includes only a single magnet 130 for attracting the feπo-magnetic balls on each arm. Alternatively, there can be two or more separate magnets for applying the attracting force. Magnet 130 has a force great enough to attract ball 322 when ball 322 approaches within a predetermined distance to the magnet. Typically, this occurs when disc drive 100 is powered up and the voice coil motor starts rotating actuator 120, which in turn applies an opening rotating force on latch body 210. This attracting action rotates latch body 210 around pivot point 219 and then holds the latch in an open position. In various embodiments, other permutations of permanent magnets and/or electromagnets and attracting members such as magnetizable balls or other ferro-magnetic members are possible and within the scope of the present invention for opening and closing latch 200. The shape and design of latch body 210, including arms 305 and 306 and balls 320-322, is designed so that the center of gravity of latch body 210 is centered as closely as possible upon pivot point 219. This is so that any linear acceleration or shock upon the latch will not cause the body to rotate. For example, in Figure 2, a shock force 235 is applied to the disc drive. The force 235 will result in a linear acceleration component and an angular acceleration component on the latch body. As is known, the linear component of a force on a body acts through a body's center of gravity. Since body 210 is designed so that the center of gravity is at or near pivot point 219 the linear component of force 235 will have no rotational effect upon the body. This keeps the latch in a closed position and prevents actuator 120 from becoming unlatched.

The shape and mass of latch body 210 also give it a moment of inertia, J_L, around its pivot point 219. The moment of inertia of a body is a measure of the resistance of a body to rotate around a given axis. The moment of inertia of any body, such as latch mechanism 200 or actuator 120, is determined by integrating the distance squared of each particular mass away from the axis of rotation. Thus, the moment of inertia increases as the mass is moved away from the axis of rotation. In the present system, the moment of inertia of the latch body, J_L, is designed to be approximately equal to the product of the moment of inertia of the actuator, J_A, multiplied by a gear ratio between the actuator 120 and the latch body 210, GR_L/A. In other words, J_L ~ J_A x GR_L/A.

The gear ratio, GR_L/A, between two bodies denotes the relative amount of rotational movement between two connected and rotating members. It is defined as the ratio of the gear arm distance of latch body 210 divided by the gear arm distance of actuator 120. The gear arm distance of latch body 210 is the distance between its pivot point 219 and a point of contact 240 (see Figure 2) where latching member 270 contacts the latch body latching section 310. The actuator gear arm distance is the distance from the actuator pivot point 260 to the point 240 where the latching member contacts the latch body latching section. Thus, the gear ratio, GR_L/A, is the ratio of these two distances.

By designing latch body 210 so that J_L ~ J_A ^x GR_L/A, the actuator mechanism 200 of the present invention holds the actuator assembly 120 even when subject to very high rotational shocks in either direction. For example, referring to Figure 2, shock force 235 against the disc drive causes a rotational acceleration α in both the latch body 210 and the actuator 120. These are represented by arrows 236 and 237. These rotational accelerations lead to clockwise rotational torques on both bodies which are found from the well known equation: Torque = J x α. The clockwise torque on actuator 120 tends to rotate it onto the surface of disc 134. However, the actuator is held in place by latch mechanism 200. The rotational torque of actuator assembly 120 also means that the actuator assembly latch member 270 applies an opening force against latch body 210 at point 240. This force results in an opening torque on latch body 210 of T(open) = J_A ^χ a x GR_L/A. However, there is also a closing torque on the latch body 210 caused by its own moment of inertia. This closing torque is, T(close) = J_L . Those skilled in the art will see that to hold the latch closed, J_L ≥ J_A x GR_L/A. It is noted that magnet 130 also applies a closing torque on the latch body 210. However, at very high rotational accelerations, (i.e., when α is very high, for example, greater than 25 rad/s²), the magnet 130 by itself cannot overcome the opening torque applied to latch body 210 from the actuator 120.

If a different rotational shock is applied to disc drive 100 (force 238, for example, in Figure 2), then the rotational acceleration α of the latch and the actuator will be in a counterclockwise direction. In that situation, actuator assembly 120 will have a closing torque because of its moment of inertia of T(close) = J_A x α. At the same time, the latch body will apply an opening torque on actuator 120 of T(open) = J_L x α ÷ GR_L/A. As can be seen, in this case it is best if: J_L ≤ J_A x GR^. Thus, to design a latch so that it can withstand rotational shocks in both directions the inventors have discovered that it is best if: J_L = J_A ^χ GR_L/A.

Thus, advantageously, the mass of latch body 210 and the shape and design of arms 305 and 306 provides a moment of inertia J_L that balances the torque applied by the actuator arm in both rotational directions.

Another advantage of the present design is that although actuator latches need to hold actuators in a parked position when power is not applied, the latches must also be capable of releasing the actuator when power is reapplied to the disc drive. Thus, it is not desirable to increase the pure mechanical holding power of the latch, since it will then be difficult to open when desired. In the present invention, the closing force is supplied by the moment of inertia of the latch and thus requires no greater opening force to open than usual.

Advantageously, the present invention provides a disc drive which includes an easily manufactured and assembled actuator latch which can hold the actuator even when the disc drive is subject to very high rotational shocks and linear shocks and which is easily releasable when power to the drive is restored. Thus decreasing the risks of the transducer damaging the disc surface. Figure 5 is a schematic view of a computer system. Advantageously, the present invention is well-suited for use in a computer system 2000. The computer system 2000 may also be called an electronic system or an information handling system and includes a central processing unit, a memory and a system bus. The information handling system includes a central processing unit 2004, a random access memory 2032, and a system bus 2030 for communicatively coupling the central processing unit 2004 and the random access memory 2032. The information handling system 2002 includes a disc drive device which includes the ramp described above. The information handling system 2002 may also include an input/output bus 2010 and several devices peripheral devices, such as 2012, 2014, 2016, 2018, 2020, and 2022 may be attached to the input output bus 2010. Peripheral devices may include hard disc drives, magneto optical drives, floppy disc drives, monitors, keyboards and other such peripherals. Any type of disc drive may use the method for loading or unloading the slider onto the disc surface as described above. Conclusion

In conclusion, a latch mechanism 200 for latching the actuator assembly 120 of a disc drive 100 in a parked position. Latch mechanism 200 includes a latch body 210 having a pivot point 219 rotatable upon a pivot pin 220 integrally coupled to the disc drive 100, the latch body 210 having a center of gravity substantially near the pivot point 219, the latch body having a moment of inertia, J_L, which is approximately equal to the moment of inertia, J_A, of the actuator 120 multiplied by a gear ratio, GR_L/A, between the latch body 210 and the actuator 120. In further embodiments, the latch body 210 includes a pair of arms 305 and 306, which meet at the pivot point 219, and a latching section 310 for latching with the actuator 120.

In one embodiment, disc drive 100 including a base 112 and an actuator 120 rotatably attached to the base 112. The actuator 120 includes a latch member 270 attached to one end and a transducer 150 attached to the other end. Actuator 120 has a moment of inertia, J_A, about a pivot point 260. The disc drive 100 also includes a latch mechanism 200 for latching the actuator 120 in a parked position. The latch mechanism 200 includes a latch body 210 having a pivot point 219, the pivot point 219 rotatable upon a pivot pin 220 integrally coupled to the base 112. The latch body 210 having a center of gravity substantially near to the pivot point 219 and a moment of inertia, J_L, about a pivot point 219. J_L is approximately equal to J_A multiplied by a gear ratio, GR_L/A, between the actuator 120 and the latch body 210.

In one embodiment, a disc drive 100 includes an actuator 120 subject to a rotational shock and a latch 200 having means for counteracting an opening torque applied by the actuator 120 to the latch 200 when the actuator is subject to the rotational shock. It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

What is claimed is:

1. A latch mechanism for latching an actuator of a disc drive in a parked position, the latch mechanism comprising: a latch body having a pivot point rotatable upon a pivot pin integrally coupled to the disc drive, the latch body having a center of gravity substantially near the pivot point, the latch body having a moment of inertia approximately equal to a product of a moment of inertia of the actuator multiplied by a gear ratio between the latch body and the actuator.

2. The latch mechanism of claim 1 , wherein the latch body further comprises a pair of arms meeting at the pivot point.

3. The latch mechanism of claim 2, wherein the latch body includes a latching section for latching the actuator.

4. The latch mechanism of claim 1, further comprising a base, the pivot pin being coupled to the base.

5. The latch mechanism of claim 1 , wherein the latch body further comprises a pair of arms, the pair of arms meeting at the pivot point, each arm including a ferro-magnetic ball.

6. The latch mechanism of claim 5, further comprising a magnet coupled to the disc drive for attracting the ferro-magnetic balls.

7. The latch mechanism of claim 1, wherein the latch body includes a latching section for latching with the actuator, the gear ratio equal to a first distance from the latch body pivot point to the latching section divided by a second distance from a pivot point of the actuator to the latching section.

8. A disc drive comprising: a base; an actuator attached to the base at an actuator pivot point, the actuator having a first end and a second end, the actuator including a latch member attached to one of the first or second ends of the actuator and a transducer attached to the other of the first or second ends of the actuator, the actuator having a moment of inertia about the actuator pivot point; and a latch mechanism comprising a latch body having a latching section, the latching section adapted for mating with the actuator latching member, the latch body attached to the base at a latch body pivot point, the latch body having a center of gravity substantially near the latch body pivot point, the latch body having a moment of inertia about the latch body pivot point, the latch body moment of inertia being approximately equal to a product of the actuator moment of inertia multiplied by a gear ratio between the actuator and the latch body.

9. The disc drive of claim 8, wherein the latch body is a molded plastic material.

10. The disc drive of claim 8, wherein the latch body comprises a metal core overmolded with a plastic material.

11. The disc drive of claim 8, wherein the latch body comprises a pair of arms, wherein each of the pair of arms includes at least one ferro-magnetic member.

12. The disc drive of claim 11, further comprising a magnet coupled to the disc drive for attracting the ferro-magnetic members.

13. The disc drive of claim 12, wherein the latch body has a sickle shape.

14. The disc drive of claim 8, wherein the gear ratio is a latch gear arm distance divided by an actuator gear arm distance, wherein the actuator gear arm distance is a distance from the actuator pivot point to a point where the latching member contacts the latch body latching section, and wherein the latch body gear arm distance is a distance from the latch body pivot point to the point where the latching member contacts the latch body latching section.

15. The disc drive of claim 8, further comprising one or more stopping members coupled to the base for stopping the latch body.

16. The disc drive of claim 8, further comprising a pivot pin coupled to the base for rotating the latch body thereon.

17. The disc drive of claim 8, wherein the latch body includes a first arm and a second arm having the latch body pivot point therebetween.

18. The disc drive of claim 17, wherein the latch section of the latch body is located approximately between the first arm and the second arm.

19. A disc drive comprising: an actuator subject to a rotational shock; and a latch having a means for counteracting an opening torque applied by the actuator to the latch when the actuator is subject to the rotational shock.