One common basic disk drive design uses multiple, rigid, vertically spaced actuator arms or tips that extend outwardly from a common actuator body. This actuator body is rotatably or pivotably interconnected with the baseplate and/or cover of the disk drive by a pivot bearing or the like. Part of the disk drive's voice coil motor is also typically mounted on this actuator body in a position that is typically directly opposite the plurality of actuator arms.
A head gimbal assembly is attached to each actuator arm, and the resulting configuration is commonly referred to in the art as a head stack assembly. Each head gimbal assembly includes a flexible load beam or suspension and a head. One end of the suspension is mounted on an end portion of the actuator arm in an appropriate manner (e.g., using a gimbaled connection). The head (e.g., one or more transducers) is mounted on the opposite end of the suspension and exchanges signals with the corresponding recording media (e.g., a computer-readable storage disk) when installed in the drive.
Certain pairs of adjacent head gimbal assemblies may be biased toward each other. In any case, heads may be damaged by undesired contact prior to be installed in a hard disk assembly having a plurality of vertically spaced computer-readable storage disks. It is common practice in the disk drive industry to use a head stack assembly comb at various times throughout the overall assembly of a disk drive. One embodiment of such a head stack assembly comb is illustrated in FIG. 1.
The head stack assembly comb 110 of FIG. 1 is of integral or one-piece construction (e.g., an injection molded part) with no moving parts. That is, all portions of the comb 110 are in a fixed positional relation to each other. The comb 110 includes a comb body 114. A pivot pin 130 extends from a lower surface of the comb body 114 to provide an interface with a disk drive head stack assembly. Handling of the comb 110 may be enhanced by forming a handle 126 on an upper surface of the comb body 114.
The comb body 114 has a horizontal arm or arm-like structure 118, as well as a vertical arm or arm-like structure 122. A plurality of vertically spaced head separators 146 project outwardly from the vertical arm 122. A given head separator 146 may be disposed between an adjacent pair of head gimbal assemblies of a disk drive head stack assembly to attempt to maintain their corresponding heads in spaced relation. Typically each head separator 146 engages the flexible suspension of each relevant adjacent pair of head gimbal assemblies.
Installation of the head stack assembly comb 110 of FIG. 1 would initially entail disposing the pivot pin 130 within a hole formed in the actuator body of the disk drive head stack assembly or one or more of the actuator arms. An actuator arm catch 134 extends from the lower surface of the comb body 114 and would be disposed within a cut-out formed in the uppermost actuator arm of the head stack assembly at this time. Typically the horizontal arm 118 of the comb body 114 initially will be positioned relative to the disk drive head stack assembly so that the head separators 146 are initially disengaged from the head stack assembly. The head stack assembly comb 110 may then be pivoted so that one or more actuator arm supports 142 engage an upper surface of the uppermost actuator arm in the head stack assembly and so that the head separators 146 are disposed between an certain adjacent pairs of head gimbal assemblies. Typically the head separators 146 will be configured to facilitate this installation and will engage the suspensions of the relevant head gimbal assemblies. This pivotal motion will also dispose a leg 138 of the comb 110 under the uppermost actuator arm. This leg 138 extends from a lower surface of the comb body 114 and will be disposed in vertically spaced relation to the uppermost actuator arm when the comb 110 has been installed in the above-noted manner. The actuator arm catch 134 also receives or captures this same uppermost actuator arm, although typically these are in slightly spaced relation.
The head stack assembly comb 110 may be used in combination with a head protection fixture to ship a head stack assembly for installation in a corresponding hard disk assembly at another location. This head protection fixture facilitates securing the head stack assembly comb 110 to the disk drive head stack assembly. During a significant number of assembly and disassembly processes associated with the manufacture of the head stack assembly/hard disk assembly, the head protection fixture is not applicable and may not be installed. However, the head stack assembly comb 110 is still needed.
There are a number of problems associated with the head stack assembly comb 110 of FIG. 1. One problem is that the comb 110 is unstable when installed on a disk drive head stack assembly having an odd number of head gimbal assemblies. That is, the comb 110 will not sit flat on the upper surface of the uppermost actuator arm of the head stack assembly in this case. The comb 110 will then no longer control HGA alignment to the actuator body. HGA alignment is a critical component for ensuring a successful interface with head merge scissors, dynamic actuator tester ramps, and HSA tooling and the like.
Another problem with the head stack assembly comb 110 is that without the above-noted head protection fixture, the retention forces for maintaining the comb 110 on the head stack assembly are significantly reduced. Principally, the comb 110 is maintained relative to the head stack assembly at this time solely by the frictional interface between its head separators 146 and their corresponding pairs of head gimbal assemblies. Once again, certain adjacent pairs of head gimbal assemblies within the head stack assembly are biased toward each other, and a head separator 146 is disposed between each of such pairs. This is an insufficient retention force for many purposes.