An earth boring drill employing roller cutters is provided with a seal in a peripheral groove to inhibit ingress of detritus into the cutter bearing area and egress of lubricant therefrom. The shape of the seal is such that its cross section is not overly compressed or displaced when in operating position, thus preventing undue compression set, wear and heating of the seal. A preferred seal has a greater radial dimension than axial dimension by a ratio of at least one-and-one-half to one to conserve bearing space and to provide the necessary flexibility to accommodate the various movements of the cutter relative to the shaft upon which it is rotatably mounted. The roller cutter has a counterbore fitting over a short cylindrical boss from which the shaft extends on which the cutter is mounted. This provides a tortuous passage restricting ingress of detritus and substantially improved life of the drill bit.
A dynamic seal is disclosed for sealing between a rotating cutter and a drill bit journal in an underground formation drilling bit, which seal utilizes a static elastomeric seal ring abutting a metal seal ring having a dynamic sealing face.
A hyrodynamic lubricant sealing element for devices such as rotary cone rock bits, shaft seals and the like which is maintained under sufficient mechanical compression to effect a seal between relatively movable structures. The sealing element defines a sealing surface establishing a seal interface with a relatively movable circular sealing surface and forms a lubricant interface and a contaminant interface at opposite sides thereof. The lubricant interface is of such configuration as to induce a hydrodynamic lubricant wedging activity causing migration of lubricant film in the seal interface from the lubricant interface to the contaminant interface for flushing away any contaminant and for lubrication between the sealing element and sealing surface. The contaminant is of a configuration developing substantially no such hydrodynamic wedging activity at the contaminant interface and yet presenting a scraping edge to remove contaminant material from the sealing surface upon relative axial movement of the sealing surface and sealing element.
A seal assembly for a rotary drill bit of the type comprising a bearing journal constituting a first bearing member, and roller cutter having a blind end bore therein, constituting a second bearing member, receiving the journal and an annular recess at the open end of the bore, the annular recess and journal defining an annular cavity in the bit. The seal assembly is positioned in the cavity for holding lubricant in the bit and comprises a ring of relatively rigid material movable with respect to the journal and the roller cutter in the longitudinal axial direction thereof and having a sealing face. An elastomeric seal member sealingly engages the movable ring and one of the bearing members and biases the ring to a position in which the sealing face of the ring is in sealing engagement. A projection and recess arrangement on the ring and the stated one bearing member enables the ring to move along this bearing member, while holding it in predetermined angular position thereon, whereby the ring and this bearing member rotates together relative to the other bearing member, with the movable ring biased to its sealing position.
An improved sealing system for a rotary rock bit retains lubricant inside the bearing area of the bit and acts as a barrier to the pulverized cuttings and other materials in the borehole to prevent the materials from entering the bearing area through the cone mouth opening of the rolling cone cutter. An annular seal member located in the cone mouth opening has a hollow core filled with a fluid. The fluid will flow thru the hollow core when pressure is applied. During drilling with a rotary rock bit the lower or loaded side of the bearing has less clearance than the upper or unloaded side. The pressure on the loaded side of the bearing will force the fluid to the unloaded side of the seal member and cause that side of the seal member to expand and fill the clearance to maintain a seal.
A rotary cone drill bit for forming a borehole having a bit body with an upper end portion adapted for connection to a drill string. A number of angularly-spaced support arms formed to extend from the bit body. Each support arm has an inside surface with a spindle connected thereto and an outer shirttail surface. A number of cutter cones equal to the number of support arms are rotatably mounted on respective spindles. Each of the cutter cones includes an internal cylindrical cavity for receiving the respective spindle. A gap with a generally cylindrical portion is formed between the spindle and the cavity with a seal element disposed within the gap. The gap has an opening contiguous with the bottom edge of the shirttail surface and extending outwardly from the spindle. A shirttail ring is disposed on the exterior of each spindle between the cutter cone and the inside surface of the respective support arm with a portion of the shirttail ring extending from the respective shirttail surface. A seal ring may be disposed on the exterior of the spindle adjacent to the shirttail ring. The seal ring cooperates with the sealing element to form a fluid barrier between the spindle and the cavity.
