Actuator Comb Stepped Bore Reduces Friction During Assembly
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Solution Overview
Problem
The existing methods for attaching an actuator comb to a pivot-bearing in hard disk drives face challenges such as torque shifts due to material mismatches with adhesives and the generation of debris particles when using tolerance rings, which complicates assembly and repair.
Innovation Solution
The implementation of an actuator comb with a stepped inner bore, where the upper portion has a larger diameter than the lower portion, reduces friction and debris generation during assembly by allowing a smooth fit until the pivot-bearing reaches the lower portion, and the use of multiple tolerance rings for a secure interference fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tolerance ring is used inside the bore of the actuator comb to provide an interference fit, then the coupling between comb and bearing cartridge is secured, but debris particles are generated when forcibly pressing the bearing cartridge into the comb
Solution Approach 1:
The inner bore is segmented into two distinct zones: an upper larger-diameter portion and a lower smaller-diameter portion. This segmentation allows the bearing cartridge to be pressed in with reduced friction in the upper zone, minimizing debris generation, while the lower zone provides the necessary interference fit for secure coupling.
Solution Approach 2:
Different portions of the inner bore are given different diameters to serve different functions. The upper portion has a larger diameter to reduce friction during assembly, while the lower portion has a smaller diameter to provide interference fit and secure coupling, thereby eliminating debris generation while maintaining coupling security.
2Ease of manufacture
If adhesive is used to adhere the comb to the bearing cartridge, then the assembly is formed, but torque shifts occur due to material mismatch during oven curing
Solution Approach 1:
The mechanical interference fit replacement eliminates the need for adhesive bonding. The stepped bore design provides a purely mechanical coupling through interference fit in the lower portion, replacing the chemical-mechanical adhesive system that caused torque shifts during curing.
3Ease of manufacture
If adhesive is used to attach the comb to the bearing cartridge, then the assembly is formed, but assembly time and oven space are consumed
Solution Approach 1:
The mechanical interference fit eliminates the adhesive curing process entirely. The bearing cartridge is simply pressed into the stepped bore, requiring no oven space or curing time, thereby dramatically reducing both assembly time and thermal processing requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution minimizes surface damage and debris particle generation, simplifies the assembly process, and reduces costs associated with large tolerance rings, while ensuring a secure coupling between the actuator comb and pivot-bearing.
Implementation Method 1
little resistance and friction is encountered when force fitting a pivot-bearing assembly into the stepped inner bore
Implementation Method 2
providing an interference fit between the comb and the bearing cartridge
Data Source
AI summary
A head stack assembly (HSA) having an actuator comb with a stepped inner bore may have an upper portion of the inner bore with a first diameter that is greater than the diameter of a lower portion of the inner bore. Therefore, little friction and resistance is encountered when force fitting a pivot-bearing assembly into the upper portion of the stepped inner bore, thereby avoiding surface damage and the generation of unwanted debris particles. The HSA may further comprise a plurality of tolerance rings to couple the actuator comb with the pivot-bearing assembly, such as one tolerance ring positioned below the step feature and one tolerance ring positioned above and seated on the step feature of the comb inner bore.