Strain relief for an actuator coil

Details Strain relief for an actuator coil Strain relief for an actuator coil

1998-10-30

2001-06-05

Tupper, Robert S. (Department: 2754)

Dynamic magnetic information storage or retrieval

Head mounting

For shifting head between tracks

Reexamination Certificate

active

06243239

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the field of disc drive data storage devices, and more particularly but not by way of limitation, to an apparatus and a method for providing a strain relief in support of the terminal end of an electrical wire used in the construction of the disc drive actuator coil.
BACKGROUND OF THE INVENTION
Modern disc drives are commonly used in a multitude of computer environments, ranging from super computers to notebook computers, to store large amounts of data in a form that is readily available to a user. Typically, a disc drive has one or more magnetic discs that are rotated by a spindle motor at a constant high speed. Each disc has a data storage surface divided into a series of generally concentric data tracks that are radially spaced across a band having an inner diameter and an outer diameter. The data is stored within the data tracks on the disc surfaces in the form of magnetic flux transitions. The flux transitions are induced by an array of read/write heads. Typically, each data track is divided into a number of data sectors where data is stored in fixed size data blocks.
The read/write head includes an interactive element such as a magnetic transducer. The interactive element senses the magnetic transitions on a selected data track to read the data stored on the track. Alternatively, the interactive element transmits an electrical signal that induces magnetic transitions on the selected data track to write data to the track.
Each of the read/write heads is mounted to a rotary actuator arm and is selectively positioned by the actuator arm over a pre-selected data track of the disc to either read data from or write data to the data track. The read/write head includes a slider assembly having an air bearing surface that, in response to air currents caused by rotation of the disc, causes the head to fly adjacent to the disc surface with a desired gap separating the read/write head and the corresponding disc.
Typically, multiple center-open discs and spacer rings are alternately stacked on a spindle motor hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively the discs, spacer rings and spindle motor hub define a disc pack assembly. The surfaces of the stacked discs are accessed by the read/write heads which are mounted on a complementary stack of actuator arms which form a part of an actuator assembly. The actuator assembly generally includes head wires which conduct electrical signals from the read/write heads to a flex circuit which, in turn, conducts the electrical signals to a flex circuit connector mounted to a disc drive base deck.
When the disc drive is not in use, the read/write heads are parked in a position separate from the data storage surfaces of the discs. Typically, a landing zone is provided on each of the disc surfaces where the read/write heads are positioned before the rotational velocity of the spinning discs decreases below a threshold velocity which sustains the air bearing. The landing zones are generally located near the inner diameter of the discs.
Generally, the actuator assembly has an actuator body that pivots about a pivot mechanism disposed in a medial portion thereof. A motor, such as a voice coil motor, selectively positions a proximal end of the actuator body. This positioning of the proximal end in cooperation with the pivot mechanism causes a distal end of the actuator body, which supports the read/write heads, to move radially across the face of the discs.
The voice coil motor involves an electrical coil and a magnet assembly that interact to produce an electro mechanical force that moves one with respect to the other. In some designs the magnet assembly is supported by the actuator assembly and thereby pivots with respect to a stationary electrical coil; conversely the electrical coil can be supported by the actuator assembly for pivoting relative to a stationary magnet assembly.
In either case, the electrical coil is produced from a very fine conductive wire which is wound to form a coiled portion. Both ends of the coiled wire are left extending from the coiled portion, these terminal ends thereby routed and connected to the flex circuit for connection to the control system. In this manner, the control system sends controlled currents to the electrical coil in order to effectuate movement of the actuator assembly.
The assembly process in manufacturing the disc drive, whether done manually or robotically, requires grasping the terminal ends and directing a distal portion thereof to the circuit board for electrical connection, such as by a suitable soldering process. These tensile forces tend to pull the wires loose from the electrical coil, and can lead to wire damage or breakage, or damage to the wire insulation.
There is a long-unresolved need in the industry for a method and accompanying apparatus to provide a strain relief support of the wires at a position medially disposed between the electrical coil and the distal portion of the terminal end. Such a strain relief could prevent expensive scrap and rework of actuator assemblies by absorbing tensile forces imparted to the terminal ends, and preventing the forces from reaching the windings of the electrical coil.
SUMMARY OF THE INVENTION
The present invention is directed to a strain relief apparatus and a method for routing the electrical leads of an actuator coil relative to the strain relief apparatus in order to prevent damage to the actuator coil during normal assembly operations involved in routing and electrically wiring the actuator assembly of a disc drive.
The strain relief apparatus has a base that supports one or two upstanding posts around which the terminal ends of the electrical wire are wrapped thereabout before routing the wires to a circuit board for electrical connection. Wrapping the wire about the strain relief post causes a frictional engagement between the wire and the post so that tension in the wire downstream of the strain relief, that is, between the post and the circuit board, is transmitted to the post and thereby not transmitted to the wire making up the windings of the actuator coil
The strain relief base is attached to the actuator assembly in a conventional manner, such as by an adhesive. A flange depends from the post to urge the wire onto the post and to retain the wire about the post during the routing and connection stages of electrically connecting the actuator coil to the disc drive control system.
With the strain relief supported by the actuator assembly, the terminal ends extending from the actuator coil are first wrapped around the posts of the strain relief and then routed to the circuit board for electrical connection. The advantages and features of the present invention will be apparent from the following description when read in conjunction with the drawings and appended claims.


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