Cutting element assemblies comprising rotatable cutting elements
A cutting element assembly includes a sleeve, a rotatable cutting element disposed within the sleeve, and a retention element. The sleeve and rotatable cutting element each have frustoconical surfaces. In some embodiments, a rotatable cutting element defines a first generally cylindrical surface, a second generally cylindrical surface, and an axial bearing surface opposite the end cutting surface and intersecting each of the first generally cylindrical surface and the second generally cylindrical surface. A bearing element may be disposed between an upper surface of a sleeve and a bearing surface of the rotatable cutting element. Earth-boring tools having rotating cutting elements are also disclosed.
1. A cutting element assembly, comprising:
a sleeve defining a first internal groove and a first frustoconical surface longitudinally spaced from the first internal groove;
a rotatable cutting element disposed within the sleeve, the rotatable cutting element comprising a polycrystalline hard material and a supporting substrate, wherein the polycrystalline hard material has an end cutting surface, wherein the rotatable cutting element defines a second internal groove in a surface of the supporting substrate and a second frustoconical surface longitudinally spaced from the second internal groove;
wherein the first frustoconical surface and the second frustoconical surface are in direct sliding contact such that compressive loads are transferred substantially via a bearing interface at which the first frustoconical surface contacts the second frustoconical surface;
wherein the rotatable cutting element also defines an interior planar back surface parallel to the end cutting surface, and wherein a generally planar end surface of the sleeve and the interior planar back surface parallel to the end cutting surface define a void adjacent the interior planar back surface; and
a retention element disposed partially within the first internal groove and partially within the second groove such that the retention element provides sufficient force to retain the rotatable cutting element within the sleeve under normal operating conditions.
2. The cutting element assembly of claim 1 , wherein the sleeve further defines an interior cylindrical surface, wherein the supporting substrate of the rotatable cutting element comprises a cylindrical portion, and wherein the cylindrical portion of the supporting substrate is disposed within the interior cylindrical surface of the sleeve.
3. The cutting element assembly of claim 1 , wherein the retention element comprises an elastomeric material.
4. The cutting element assembly of claim 1 , wherein the retention element comprises a metal.
5. The cutting element assembly of claim 1 , wherein the retention element comprises at least one selected from the group consisting of an O-ring, a split ring, a beveled retaining ring, a bowed retaining ring, a spiral retaining ring, and a Belleville spring.
6. The cutting element assembly of claim 1 , wherein the supporting substrate defines the second groove and the second frustoconical surface.
7. A cutting element assembly, comprising:
a sleeve defining a first interior cylindrical surface, a second interior cylindrical surface, and a generally planar axial bearing surface between the first interior cylindrical surface and the second interior cylindrical surface, wherein the first interior cylindrical surface, the generally planar axial bearing surface, and the second interior cylindrical surface together at least partially define a cavity in the sleeve;
a rotatable cutting element disposed at least partially within the cavity, the rotatable cutting element comprising a polycrystalline hard material having an end cutting surface generally parallel to the axial bearing surface of the sleeve and mounted to a substrate, wherein the rotatable cutting element also defines an interior back surface parallel to the end cutting surface, and wherein a generally planar end surface of the sleeve and the interior back surface parallel to the end cutting surface define a void adjacent the interior back surface;
the substrate defining a first generally cylindrical surface, a second generally cylindrical surface, and an axial bearing surface opposite the end cutting surface and extending between the first generally cylindrical surface and the second generally cylindrical surface;
wherein the substrate is substantially disposed within and is in sliding contact with both an interior of each of the first interior cylindrical surface and the second interior cylindrical surface with the axial bearing surface of the rotatable cutting element in sliding contact with the axial bearing surface of the sleeve.
8. The cutting element assembly of claim 7 , wherein the substrate further defines a groove, and further comprising a retention element disposed at least partially within the groove and extending radially outward therefrom.
9. The cutting element assembly of claim 8 , wherein the retention element comprises at least one selected from the group consisting of a split ring, a beveled retaining ring, a bowed retaining ring, a spiral retaining ring, and a Belleville spring.
10. The cutting element assembly of claim 9 , wherein the sleeve defines another groove, and wherein the retention element is partially disposed within the another groove.
11. The cutting element assembly of claim 7 , wherein when a compressive longitudinal load is applied to the end cutting surface of the polycrystalline hard material of the rotatable cutting element, the compressive longitudinal load is transferred to the sleeve substantially via the axial bearing surface.