A mechanical seal for use in a rotary rock bit comprises a leg seal ring positioned within a recessed portion of a leg forming a seal cavity. The leg seal comprises one surface partially engaged by a resilient material and an opposite surface comprising a first sealing surface. The mechanical seal also comprises cone seal ring positioned within a portion of a cone forming the seal cavity. The cone seal comprises one surface positioned within and attached to a recessed portion of the cone and another surface comprising a second sealing surface engaging the first sealing surface. The portion of the leg seal ring engaged by the resilient material engages a back face of the leg which includes a ramp, serving to urge the first sealing surface against the adjacent second sealing surface and create a sealing engagement. The first and second sealing surfaces are made from different hard materials each having a similar hardness of greater than 1000, and each material selected has a Knoop hardness difference of about 400 or less. The first and second sealing surfaces may be formed from materials the same as or different than materials forming the leg seal ring and cone seal ring, respectively.
A high pressure sensor is provided with a single-piece pressure port machined from stainless steel and has no internal gaskets or seals. A housing surrounds the pressure port along a portion of its axial length. The housing and pressure port have mating configurations that prevent axial rotation when the pressure port is inserted into the assembled position in the housing. A retaining ring locks the pressure port axially with respect to the housing and is fixed in place by a fixative, such as epoxy.
An earth-boring bit has a mechanical face seal assembly with PCD faces. The bit has a bearing shaft with a cone rotatably mounted on the bearing shaft. The seal locates between the bearing shaft and the cone for sealing lubricant therein. The seal includes at least one rigid seal ring having a carbide body and an annular PCD face located on it. The mating face may also be of a PCD material.
An earth-boring bit has a seal assembly with a seal face having a DLC coating. The seal assembly locates between a bearing pin and a cone of the bit. The seal assembly has at least one rigid ring that rotates against a mating surface. The DLC coating is diamond-like carbon that may be coated by different processes onto either the ring, the mating surface, or both.
A hydrostatic mechanical seal assembly includes a locally deployed pump for pressurizing a lubricant fluid between the opposing faces of a mating ring and a sealing ring. In one exemplary embodiment, such pressurization may be achieved via a device that converts the rotational motion of a drive shaft into fluid pressure. The locally deployed pump is intended to advantageously provide a stable positive pressure on the sealing interface between the mating and sealing rings, which may provide improved sealing characteristics, especially in demanding downhole environments.
An earth-boring bit has a mechanical face seal assembly with PCD faces. The bit has a bearing shaft with a cone rotatably mounted on the bearing shaft. The seal locates between the bearing shaft and the cone for sealing lubricant therein. The seal includes at least one rigid seal ring having a cemented carbide body and an annular PCD face located on it. The mating face may also be of a PCD material. The cemented carbide body contains a binder that migrates into the PCD face while the PCD face is being formed. A binder-free region is leached on the surface of the PCD face.
