Impact rebound type inertia latch for load/unload technology Y. Byun, J. Kang, J. Chang, V. Sharma, H. J. Lee 1 Introduction Various design mechanisms on latch in the hard disk drives have been introduced to help limit actuator from sudden uncontrolled motion [1, 2]. Magnetic type latch, which accounts for the majority of latches found in ex- isting disk drives, uses magnetic force to keep actuator in its home position. However, as the disk drive industry moves from contact start stop CSS) type drives to load/ unload L/UL) type drives for improving the mechanical reliability of HDD, inertia latch has become of greater importance in disk drive's non-operating shock perfor- mance. Despite its mechanical complexity, the actuator with an inertia latch can withstand higher and wider range of rotational shock that is otherwise not achievable by magnetic latch alone in L/UL drives. In this paper, single and dual lever inertia latches are explained and compared for their functionality. At Samsung, we developed a novel impact rebound IR) type inertia latch using a single lever, but showing the same functionality as dual lever inertia latch. Magnetic attraction mechanism applied to IR inertia latch in a prototype drive is also discussed. 2 Basic inertia latch Single lever type A single lever type inertia latch and actuator responding to rotational acceleration is shown in Fig. 1. The actuator and the inertia latch are both mass balanced on each pivot point so that there is no rotational motion due to linear shock. The inertia latch remains at its home position by a light bias force exerted in the clockwise direction Fig. 1a). When the clockwise rotational acceleration is exerted to the drive, the inertia latch and the actuator rotate in the counterclockwise direction with respect to the drive and thus the actuator gets engaged Fig. 1b). The timing of latch and actuator engagement is dependent on their rotational inertia, pivot friction, bias force and geometric con®guration hooking angles, lengths from the pivot, clearance) of barb and actuator tail. If the counterclock- wise shock is applied to the drive Fig. 1c), the latch and the actuator rotate in the clockwise direction with respect to the drive, then the latch stays in an open position. In this case, the actuator rebounds from the crash stop and cannot engage with the inertia latch. Dual lever type To solve this limitation during counter clockwise accel- eration of actuator with respect to the drive, a dual-lever type inertial latch was introduced as shown in Fig. 2 [1, 2]. The dual-lever type inertia latch consists of two levers in which large lever has great rotational inertia than the small one. The small lever is designed and aligned with respect to the large lever so that, in any rotational di- rection of the large lever, the small lever rotates toward the actuator for engagement. The large lever has two points of contact with the small lever where at one contact point the small lever is pulled at the back of its pivot during clockwise rotational motion of the drive, thus rotating in counter clockwise direction. Similarly, during counterclockwise motion of the base, the small lever is pushed by the large lever and rotates in the counter clockwise direction for engagement with the ac- tuator. Thus, unlike single lever inertial latch, the re- bound of the actuator in the clockwise motion does not cause any actuator escape for the dual-lever type inertia latch. For the bi-directional rotational shock, dual-lever type inertia latch is now commonly adopted in most of the conventional load/unload drives. 3 Single bi-directional Inertia latch As an alternative design to dual-lever type inertia latch, a single bi-directional inertia latch is developed. As shown in Fig. 3, this type of single bi-directional latch is con- ceptually designed to work in both directions during ro- tational shock. During clockwise rotational motion of the base, the inertia latch engages with the hook portion of the actuator. During counter clockwise rotational motion of the drive, the inertia latch moves in after actuator re- bounds from its crash stop. This type of latch has a steel piece attached at the back of the pivot to settle the latch to Microsystem Technologies 8 2002) 37±40 Ó Springer-Verlag 2002 DOI 10.1007/s00542-001-0118-x Received: 6 July 2001/Accepted: 27 September 2001 Y. Byun, J. Kang Samsung Advanced Institute of Technology SAIT), P.O. Box 111, Suwon, Korea 440±600 J. Chang &), V. Sharma, H. J. Lee Samsung Information Systems America, 75 West Plumeria Drive, San Jose, CA 95134, USA This paper is on load-unload technology used in magnetic rigid disk drives, which were solicited and edited by Dr. Mike Suk of IBM Storage Systems Products Division of San Jose, CA. Editor, Prof. B. Bhushan, acknowledges his efforts. 37