Drive Mechanism Block Diagram; Optical Encoder; Rotary Positioner Assembly; Head Stack Assembly - Quantum Q2080 Product Description

1.2.1 DRIVE MECHANISM BLOCK DIAGRAM
FIGURE 1-2
MODEL Q2080 MECHANICAL LAYOUT
1.2.2 OPTICAL ENCODER
DC orAC
MOTOR
The optical encoder is mounted on a shaft that is pressed and bonded into the base casting. The assembly con-
sists of a housing, an infrared light emitting diode, an optical reticle, and a multi-cell photo diode matrix.
The infrared LED is mounted in the lower half of the housing. This allows the optical scale near the lower arm
of the head stack to move between the infrared LED and the upper half of the housing that contains the reticle and
photo cells. The reticle masks five photo cells so that each cell only receives light through a specific portion of the
moveable scale. Both the clearance and angular position of reticle and scale are precision adjustments that are made
when the drive is manufactured.
1.2.3 ROTARY POSITIONER ASSEMBLY
The positioner used in the Model Q2080 (a design proprietary to Quantum) consists of upper and lower magnet
plates, rotary single phase coil, head stack mounting hub, two magnet rings, and bearing shaft. The magnets are
composed of alternating poles bonded to the magnet plates that, in turn, are bolted to the base casting. The rotor
and hub are bonded together and the bearings and shaft are bonded into the hub. This entire bearing shaft assembly
is bonded into the base casting. The shaft/casting bond provides both mounting rigidity and an air-tight seal be-
tween the shaft and mounting bore. The bearing to shaft bond and bearing to hub bond are also rigid and air-tight.
This design allows the mass center of the head stack to be placed at the hub so that bearing wear and friction are
minimized and gravity forces cannot apply torques to the head stack that would have to be countered by rotor cur-
rent. This enables the drive to operate in any orientation. The crash stops, which prevent the heads from being
driven into the spindle or off the disk surface, are mounted to the upper magnet plate.
1.2.4 HEAD STACK ASSEMBLY
The head stack assembly consists of the heads, head arms, and counter balances. In addition, the optical scale is
bonded to the lower counter balance. The counter balances are castings whose shape and weight are designed to in-
sure that the mass center of the entire stack is at the center of the mounting hub. The lower counter balance is slightly
different than the others as it holds the rubber crash stop bumper and optical scale. The heads are Winchester slider
type mounted to spring steel flexures that are staked to the head arm. The head conductors are routed in plastic
guides and tacked in place with an adhesive. All head stack assemblies consist of an upper head arm assembly, a
lower head arm assembly, and three dual head arm assemblies.
REV A (01184)
1-2