Friction Bearing for Deep Well Drilling Tools

This invention concerns a friction bearing for deep well drilling tools, especially drill bit direct drives.

In a known friction bearing for deep well drilling tools, a trace ring is provided (US Defensive Publication T102 901) having a ring-shaped bearing body of steel and prefabricated cylindrical bodies mounted in axial boreholes of the bearing body and having a bearing layer of polycrystalline diamond and a support layer of a sintered material. The molded bodies are placed in a ring-shaped arrangement in the trace ring with their diamond layer that is provided with a conical taper projecting above the surface of the supporting body and forming a sliding plane composed of adjacent ring-shaped sliding surfaces. The bearing ring in turn has cylindrical molded bodies provided with a polycrystalline diamond layer at the surface and set in a ring as bearing segments that are supported on the sliding surface of the trace ring.

Such a design is associated with load conditions that change constantly because the surfaces that are in mutual engagement change constantly and greatly during one complete revolution. A friction bearing with such a design of the trace ring is therefore limited in its load bearing capacity and is subject to a great deal of wear.

In another known friction bearing (German Patent No. 3,513,124), the trace ring has a cohesive ring-shaped slide way in the form of a seat of a sintered metal powder ceramic material or polycrystalline diamond material. Such a trace ring can withstand high loads and operates under uniform load conditions but is expensive to manufacture because the seat cannot be prefabricated but instead can only be manufactured by sintering it as a whole onto the support body in a separate operation.

This invention is based on the goal of creating a friction bearing that can withstand high loads, is subject to little wear and can be manufactured under favorable conditions.

With the friction bearing according to this invention, the surfaces of the molded bodies form an essentially closed ring channel with the result that the contact surface between the friction bodies of the bearing ring and the ring channel of the trace ring do not undergo any mentionable changes during one revolution of the bearing. Accordingly, the friction bearing can withstand high loads and also shows little wear due to the essentially uniform load conditions. Furthermore, the mosaic-like arrangement makes it possible to use molded bodies consisting of blanks of partially worn cutting elements of rotary drill bits. This is especially the case in one version where the surfaces of the molded bodies are bordered by arc sections, because such molded bodies can be cut from circular cutting elements which are preferred in rotary drill bits and are usually worn on one side.

Additional details and advantages derive from the following description and the figures showing schematic diagrams of two practical examples of the object of this invention. The figures show the following:

FIG. 1 shows a top view of one-half of the trace ring according to this invention.

FIG. 2 shows a cross-sectional diagram of FIG. 1.

FIG. 3 shows a top view like FIG. 1 of a trace ring of a modified design.

FIG. 4 shows a cross-sectional diagram to FIG. 3.

The friction bearing for deep well drilling tools, especially drill bit direct drives, includes a bearing ring 1 which is shown with dash-dot lines in the diagram in FIG. 4 and has bearing segments 2 plus a trace ring 3 (FIGS. 1 and 2) or 4 (FIGS. 3 and 4).

Trace ring 3 which is illustrated in FIGS. 1 and 2 includes a generally planar ring-shaped bearing body 5 that consists of a suitable matrix, e.g., a sintered metal. The ring-shaped sliding surface 6 of trace ring 3 is formed by a number of sintered molded bodies 7, 8 in the example according to FIG. 2 that are countersunk so they are flush with the surface 9 of bearing body 5 and arranged side by side in a mosaic pattern so with their surfaces together they define a ring channel with an essentially closed surface.

Surfaces of molded bodies 7, 8 of trace ring 3 are bordered with a straight line and are arranged in several radial ring groups 10, 11, 12 and 13 with a close mutual spacing. Molded bodies 7 have a cubic shape whereas molded bodies 8 have a rod prism shape. The cubic molded bodies 7 offer a surface that is always the same as wear advances, whereas the surface becomes smaller with progressive wear in the case of molded bodies 8.

With regard to the diagrams in FIGS. 1 and 2, it should be pointed out that only a few molded bodies 7 and 8 are shown in ring groups 10, 11 and 12. However, it is self-evident that ring groups 10, 11 and 12, like ring group 13, form a closed ring of molded bodies 7 and 8.

In the version according to FIGS. 3 and 4, the bearing body 14 which is likewise ring shaped is made of steel. This is provided with a ring groove 15 at its surface 9 with molded bodies 16, 17 arranged in it. Molded bodies 16, 17 have a layer 18 or 19 of polycrystalline diamond material at their surface and they include a supporting part 20, 21 which is made of a sintered material, e.g., tungsten carbide. These molded bodies 16, 17 have their surfaces flush with surface 9 of bearing body 14 and are secured by soldering in ring groove 15.

The surfaces of molded bodies 16, 17 are bordered by arc segment lines and abut seamlessly. Here again, molded bodies 16, 17 abut with radially adjacent ring groups 22, 23 where the molded bodies 16 or 17 provided with one ring group 22 or 23 have the same radial inner and outer bordering lines supplementing each other so each forms a common arc 24, 25 or 26.

The bordering lines of molded bodies 16, 17 of each ring group 22 and 23 as seen in the circumferential direction are formed by identical arc segment lines with a small radius of curvature so the approximately sickle-shaped molded bodies 16 and 17 are alternately intermeshed relatively far into each other in the circumferential direction. This design creates an especially stable load bearing assembly with a sliding face 27 which defines a completely closed ring channel.