Split actuator with multiple head stack assemblies bonded to bearing sleeves

1. An apparatus, comprising:

at least one actuator shaft;

first and second head stack assemblies coaxially located on the at least one actuator shaft, the first and second head stack assemblies each comprising:

at least one bearing having an inner race coupled to an outer surface of the at least one actuator shaft;

a bearing sleeve surrounding an outer race of the at least one bearing;

an E-block surrounding the bearing sleeve;

an annular gap between the E-block and the outer race of the at least one bearing;

a ring of bonding material filling the annular gap;

an access gap providing a fluid path to the annular gap from at least one of a top and a bottom of the E-block; and

a groove fluidly coupled to the annular gap and facing away from the access gap, the groove encompassing a greater volume than that of the annular gap.

2. The apparatus of claim 1 , wherein the access gap facilitates inserting the bonding material into the annular gap.

3. The apparatus of claim 1 , wherein the bonding material reduces mechanical coupling between the first and second head stack assemblies.

4. The apparatus of claim 1 , wherein the bonding material has an elastic modulus at room temperature between 200 MPa and 1000 MPa.

5. The apparatus of claim 1 , wherein the at least one actuator shaft comprises top and bottom stacked actuator shafts, the first and second head stack assemblies located over the respective top and bottom stacked actuator shafts.

6. The apparatus of claim 5 , further comprising a damping material between the top and bottom stacked actuator shafts.

7. The apparatus of claim 5 , further comprising a damping material between the top actuator shaft and a cover.

8. The apparatus of claim 5 , further comprising a damping material between the bottom actuator shaft and a deck.

9. The apparatus of claim 1 , wherein the groove controls an adhesive joint geometry that affects a stiffness of the ring of bonding material.

10. An apparatus comprising:

at least one actuator shaft;

first and second head stack assemblies coaxially located on the at least one actuator shaft, the first and second head stack assemblies each comprising:

two bearings stacked on an outer surface of the at least one actuator shaft;

a bearing sleeve covering outer races of the two bearings;

an E-block surrounding the bearing sleeve, a central portion of the E-block slidably in contact with the bearing sleeve and separated from the bearing sleeve by first and second annular gaps away from the central portion;

first and second rings of bonding material filling the first and second annular gaps, the first and second rings of bonding material dampening mechanical coupling between the first and second head stack assemblies; and

first and second tapered access gaps providing fluid paths to the first and second annular gap from a top and a bottom of the E-block; and

first and second grooves fluidly coupled to the annular gap and facing away from the respective first and second tapered access gaps, first and second grooves each encompassing a greater volume than that of the annular gap.

11. The apparatus of claim 10 , wherein the access gaps facilitate inserting the bonding material into the first and second annular gaps.

12. The apparatus of claim 10 , wherein the bonding material reduces mechanical coupling between the first and second head stack assemblies.

13. The apparatus of claim 10 , wherein the bonding material has an elastic modulus at room temperature between 200 MPa and 1000 MPa.

14. The apparatus of claim 10 , wherein the at least one actuator shaft comprises top and bottom stacked actuator shafts, the first and second head stack assemblies located over the respective top and bottom stacked actuator shafts.

15. The apparatus of claim 14 , further comprising a damping material between the top and bottom stacked actuator shafts.

16. The apparatus of claim 14 , further comprising a damping material between the top actuator shaft and a cover.

17. The apparatus of claim 14 , further comprising a damping material between the bottom actuator shaft and a deck.

18. The apparatus of claim 10 , wherein the first and second grooves control an adhesive joint geometry that affects stiffnesses of the first and second rings of bonding material.