Patent Description:
Conventional roller cone drill bits include a body having two or more cutting arms. Each cutting arm defines an angular journal upon which a rotating disk or a roller cone is mounted. A roller cone drill bit, such as a "Tricone" drill bit for example, includes the body having three cutting arms defining three angular journals and three roller cones mounted on the three angular journals respectively. The roller cone may have multiple protrusions or teeth to cut through different rock formations. Further, the roller cone may be mounted on the angular journal with one or more bearing elements, such as, for example, ball bearings and rolling element bearings. The bearing elements facilitate rotation of the roller cone around an axis of the roller cone and the angular journal. During operation, an application of feed force and rotation to the body further enables the rotation of the roller cone by means of the ball bearings and the roller element bearings. The rotation of the teeth along with the rotation of the roller cone further enables the cutting of rocks.

Typically, the bearing elements in the roller cone drill bits are lubricated by means of a lubricant such as grease. However, grease as a lubricant may have limited flowability and may not lubricate different regions, such as crevices, edges, corners, and grooves, in and/or around different geometries of the bearing elements in an effective manner. As a result, a lifespan and performance of the roller cone drill bit may be affected over prolonged usage of the roller cone drill bit. Further, complex lubricant reservoirs with diaphragms and lubricant delivery systems may be needed in order to supply the grease to the bearing elements of the roller cone drill bits. In some instances, equalization of a pressure outside the roller cone drill bit and a pressure inside a lubricant reservoir of the roller cone drill bit may also be needed in order to squeeze the grease from the lubricant reservoir to the different regions in and/or around the bearing elements. The pressure equalization may further require additional parts and/or features in the roller cone drill bit to facilitate movement of the grease as desired.

In addition, the grease may also get contaminated with debris resulting from the cutting of the rocks. During operation, debris may accumulate around a lubricant seal provided between the roller cone and the angular journal of the roller cone drill bit. Continuous accumulation of the debris during operation results in wear and tear of the lubricant seal. The wear and tear may further result in seepage of the debris through annular spaces around the lubricant seal, and thereby result in the contamination of the grease lubricant. The contamination of grease further affects the lubrication of the bearing elements and hence, reduces the lifespan and performance of the roller cone drill bits.

<CIT> relates to a rock bit lubrication system having a pressurized air chamber and a central container of a lubricating liquid. Further, the rock bit lubrication system includes conduits that extend from an interior of the central container to an opening that allows air under pressure from the pressurized air chamber to entrain the lubricating liquid in measured amounts. The air under pressure also directs the lubricating liquid into openings leading to bearings formed between the roller cone and the journal. As is apparent, the rock bit lubrication system requires a complex arrangement of the central container, the pressurized air chamber, and the conduits to ensure sufficient circulation of the grease around the bearings. Further, debris from the rock cuttings may also seep through openings around the roller cone and contaminate the grease.

<CIT> describes a rotary drill bit having a body with three legs with conical cutters attached. A lubricant filler hole is connected to a main conduit which connects between a main reservoir at one end and a bore plug conduit at the other end.

In an aspect of the invention, as recited in claim <NUM>, a rotary drill bit comprising a body having an inlet and three cutting arms, each with a journal extending therefrom is disclosed. A rotary cutter is mounted on the journal by means of multiple bearings such that a clearance is defined between the rotary cutter and a base surface of the cutting arm from which the journal extends. The rotary drill bit also comprises an isolated lubrication system corresponding to each cutting arm. Each isolated lubrication system includes a reservoir in the body to contain a fluid lubricant that is isolated from communication outside the body. Further, the isolated lubrication system includes a plurality of conduits in the body having direct or indirect communication with the reservoir and with respect to each other. The conduits may facilitate lubrication between the journal and the rotary cutter, including the bearings, by means of at least one of a gravitational force and a centrifugal force acting on the fluid lubricant. The isolated lubrication system also includes a sealing system. The sealing system includes a sealing cap provided to the reservoir in the body to isolate the reservoir from communication outside the body, the sealing cap having an orifice and a retractable component provided in the orifice for the supply of fluid lubricant to.

the reservoir and a seal provided between the journal and the rotary cutter in the clearance. The sealing system also includes a stepped passageway extending from the seal to an opening provided between the cutting arm and the rotary cutter in the clearance, wherein a suction conduit is provided between the body inlet and each reservoir to facilitate suction of air from the reservoirs and a plug with a suction seal is provided in each of the suction conduits to isolate the reservoirs from communication outside the body after the vacuum is created.

In yet another aspect of the invention, as recited in claim <NUM>, a drilling machine comprising a power source, a feed unit in communication with the power source, and a drill bit as described above connected to the feed unit, is disclosed.

Reference will now be made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings.

Referring to <FIG>, an exemplary illustration of a rotary drill bit <NUM> is disclosed. An example of the rotary drill bit <NUM> includes, but is not limited to, a roller-cone bit, such as a tungsten carbide insert (TCI) drill bit or a milled-tooth drill bit. Another example of the rotary drill bit <NUM> includes, but is not limited to, a fixed-cutter bit, such as a polycrystalline diamond compact (PDC) drill bit, an impregnated drill bit, or a diamond drill bit. For sake of clarity and understanding, the rotary drill bit <NUM> that corresponds to the roller cone bit will be described herein. Further, the rotary drill bit <NUM> will herein be referred to as "roller cone bit <NUM>".

The roller cone bit <NUM> includes a body <NUM> that is capable of rotating about a central axis <NUM> of the roller cone bit <NUM>. The body <NUM> may include a first cutting arm <NUM> (see <FIG>), a second cutting arm <NUM> and a third cutting arm <NUM>. The first cutting arm <NUM>, the second cutting arm <NUM> and the third cutting arm <NUM> may be identical and equally spaced at an angle with respect to each other. The body <NUM> also includes a first rotary cutter <NUM>, a second rotary cutter <NUM>, and a third rotary cutter <NUM> affixed to the first cutting arm <NUM>, the second cutting arm <NUM> and the third cutting arm <NUM> respectively. The first cutting arm <NUM>, the second cutting arm <NUM> and the third cutting arm <NUM> are herein referred to as "cutting arms (<NUM>, <NUM>, <NUM>)" collectively. The first rotary cutter <NUM>, the second rotary cutter <NUM>, and the third rotary cutter <NUM> are herein referred to as "rotary cutters (<NUM>, <NUM>, <NUM>)" collectively. Further, the rotary cutters (<NUM>, <NUM>, <NUM>) maybe conical in shape and include inserts <NUM> such as, for example, tungsten carbide inserts, on respective peripheral surfaces in order to facilitate cutting of rock matter. In some embodiments, the rotary cutters (<NUM>, <NUM>, <NUM>) may include milled protruding teeth (not shown) in place of the inserts <NUM> to facilitate the cutting of the rock matter. The inserts <NUM> of different lengths and spacing arrangements on the peripheral surfaces of the rotary cutters (<NUM>, <NUM>, <NUM>) respectively may be used to cut the rock matter. The rotary cutters (<NUM>, <NUM>, <NUM>) may be affixed to the cutting arms (<NUM>, <NUM>, <NUM>) respectively such that the rotary cutters (<NUM>, <NUM>, <NUM>) with respective inserts <NUM> may face each other.

In addition, the body <NUM> also includes an isolated lubrication system <NUM> corresponding to the cutting arms (<NUM>, <NUM>, <NUM>) respectively. The isolated lubrication system <NUM> may be identical in the cutting arms (<NUM>, <NUM>, <NUM>) respectively. Accordingly, for sake of clarity and understanding, the first cutting arm <NUM> and the isolated lubrication system <NUM> corresponding to the first cutting arm <NUM> will be described herein in detail. Detailed explanation with respect to the second cutting arm <NUM>, the third cutting arm <NUM> and the corresponding isolated lubrication system <NUM> respectively will be omitted for brevity.

Referring to <FIG>, a cross-sectional view A - A of the roller cone bit <NUM> of <FIG> having the isolated system <NUM> is disclosed. The body <NUM> of the roller cone bit <NUM> includes an inlet <NUM>. The first cutting arm <NUM> includes a journal <NUM> extending from a base surface <NUM> of the first cutting arm <NUM>. The first rotary cutter <NUM> is mounted on the journal <NUM> by means of bearings (<NUM>, <NUM>). An example of the bearings (<NUM>, <NUM>) includes, but is not limited to, a ball bearing <NUM>, such as a single-row or deep-groove bearing, a double-row or thrust ball bearing, a double-row self-aligning ball bearing, or a single and double-row angular ball bearing. Another example of the bearings (<NUM>, <NUM>) includes, but is not limited to, a rolling element bearing <NUM>, such as a spherical roller bearing, a one-row or a two-row cylindrical bearing, conical tapered roller bearings, or a needle bearing. Additional examples of the bearings (<NUM>, <NUM>) include, but are not limited to, plain or sleeve bearings, friction bearings, jewel bearings, fluid bearings, magnetic bearings, flexure bearings, and composite bearings. The first rotary cutter <NUM> may be mounted on the journal <NUM> such that the first rotary cutter <NUM> rotates around an axis <NUM> of the first rotary cutter <NUM> and the journal <NUM> by means of the bearings (<NUM>, <NUM>). In some embodiments, additional bearings (not shown) may be provided between the journal <NUM> and the first rotary cutter <NUM> to facilitate load sharing along with the bearings (<NUM>, <NUM>) and also, to facilitate the rotation of the first rotary cutter <NUM>. A thrust bearing <NUM> may also be provided between the journal <NUM> and the first rotary cutter <NUM> so as to minimize friction between the journal <NUM> and the first rotary cutter <NUM> as the first rotary cutter <NUM> rotates.

The isolated lubrication system <NUM> of the roller cone bit <NUM> includes a reservoir <NUM> in the first cutting arm <NUM> of the body <NUM> to contain a fluid lubricant <NUM> such as, for example, oil. The reservoir <NUM> may be of different shapes and sizes. For example, the reservoir <NUM> may be a cylindrical or a rectangular slot in the first cutting arm <NUM> of the body <NUM>. A volume of the reservoir <NUM> may also vary depending on the shape and the size of the reservoir <NUM>. The reservoir <NUM> may have a reservoir opening <NUM> that extends to a peripheral surface <NUM> of the first cutting arm <NUM>. Prior to operation of the roller cone bit <NUM>, the isolated lubrication system <NUM> may need to be primed. The air from the reservoir <NUM> may need to be removed in order to create a vacuum and introduce the fluid lubricant <NUM> in the reservoir <NUM>. The vacuum created may facilitate uniform lubrication of the thrust bearing <NUM> and the bearings (<NUM>, <NUM>) when the reservoir <NUM> is filled with the fluid lubricant <NUM>.

The reservoir <NUM> may be in direct or indirect communication with multiple conduits (<NUM>, <NUM>, <NUM>) such that the conduits (<NUM>, <NUM>, <NUM>) facilitate a flow <NUM> (see <FIG>) of the fluid lubricant <NUM> in the isolated lubrication system <NUM>. The conduits (<NUM>, <NUM>, <NUM>) may also be in direct or indirect communication with respect to each other in order to facilitate the lubrication between the journal <NUM> and the first rotary cutter <NUM>, including the bearings (<NUM>, <NUM>). The conduits (<NUM>, <NUM>, <NUM>) may enable lubrication of multiple spaces, edges, corners, and crevices of different geometric shapes and sizes that may be formed around the bearings (<NUM>, <NUM>) and/or between the journal <NUM> and the first rotary cutter <NUM>.

The isolated lubrication system <NUM> may include a first conduit <NUM> in the first cutting arm <NUM> that is in direct communication with the reservoir <NUM> such that the fluid lubricant <NUM> from the reservoir <NUM> occupies the first conduit <NUM> by means of a gravitational force <NUM> (see <FIG>). The isolated lubrication system <NUM> may also include a second conduit <NUM> in the first cutting arm <NUM> that may be in direct communication with the first conduit <NUM> such that the fluid lubricant <NUM> from the first conduit <NUM> occupies the second conduit <NUM>. The fluid lubricant <NUM> in the second conduit <NUM> may lubricate the ball bearing <NUM> and/or the roller bearing <NUM> as a result of the vacuum created in the isolated lubrication system <NUM> and also by means of a centrifugal force <NUM> (see <FIG>) acting on the fluid lubricant <NUM> during operation. The rotation of the roller cone bit <NUM> around the central axis <NUM> may in turn result in the rotation of the first rotary cutter <NUM> around the axis <NUM> of the first rotary cutter <NUM>. The rotation of the roller cone bit <NUM> and the first rotary cutter <NUM> may result in the centrifugal force <NUM> acting on the fluid lubricant <NUM> in the second conduit <NUM> as shown in <FIG>. The fluid lubricant <NUM> in the second conduit <NUM> may lubricate the ball bearing <NUM> and/or the roller bearing <NUM> through annular spaces (<NUM>, <NUM>) (see <FIG>) formed between the journal <NUM> and the first rotary cutter <NUM>. In some embodiments, the second conduit <NUM> may be a through-hole provided across the first cutting arm <NUM> such that bearing balls in the ball bearing <NUM> may be introduced in the drill bit via the second conduit <NUM> and a pin <NUM> may be inserted in the second conduit <NUM> to hold the bearings balls of the ball bearing <NUM> in position. In some embodiments, the isolated lubrication system <NUM> may include additional conduits (<NUM>, <NUM>) (see <FIG>) that may be in direct communication with the second conduit <NUM> and with the ball bearing <NUM> in order to lubricate the thrust bearing <NUM>, the ball bearing <NUM> and/or the roller bearing <NUM>. In addition, the isolated lubrication system <NUM> may also include a third conduit <NUM> in the first cutting arm <NUM> that is in direct communication with the second conduit <NUM> and extends to an outlet <NUM> provided in the journal <NUM> of the first cutting arm <NUM>. The fluid lubricant <NUM> from the second conduit <NUM> may occupy the third conduit <NUM> by means of the gravitational force <NUM> and/or the centrifugal force <NUM> (see <FIG>) and exit from the outlet <NUM>. The fluid lubricant <NUM> exiting from the outlet <NUM> may lubricate the thrust bearing <NUM>, the ball bearing <NUM>, and/or the roller bearing <NUM> as a result of the vacuum created and also by means of the centrifugal force <NUM> (see <FIG>) acting on the fluid lubricant <NUM> during rotation of the roller cone bit <NUM> and the first rotary cutter <NUM>. The fluid lubricant <NUM> exiting from the outlet <NUM> may flow through annular spaces (<NUM>, <NUM>, <NUM>, <NUM>) (see <FIG>) formed between the journal <NUM> and the first rotary cutter <NUM> and lubricate the thrust bearing <NUM>, the ball bearing <NUM>, and/or the roller bearing <NUM> respectively. The conduits (<NUM>, <NUM>, <NUM>) may be cylindrical in shape and may be of same or different diameters. The second conduit <NUM> and the third conduit <NUM> may be in indirect communication with the reservoir <NUM> via the first conduit <NUM>. Similarly, the third conduit <NUM> may be in indirect communication with the reservoir <NUM> and the first conduit <NUM> via the second conduit <NUM>.

Referring to <FIG>, the isolated lubrication system <NUM> also includes a sealing system <NUM> to prevent leakage of the fluid lubricant <NUM> outside the body <NUM> of the roller cone bit <NUM>. The sealing system <NUM> also isolates the fluid lubricant <NUM> from communication outside the body <NUM>. The sealing system <NUM> includes a sealing cap <NUM> (also shown in <FIG>) that seals the reservoir opening <NUM> and thereby, isolates the reservoir <NUM> from communication outside the body <NUM>. The sealing cap <NUM> includes an orifice <NUM> and a retractable component <NUM> provided in the orifice <NUM>. The retractable component <NUM> may be retracted and removed from the orifice <NUM> to facilitate suction of air from the reservoir <NUM> and/or to supply the fluid lubricant <NUM> into the reservoir <NUM> via the orifice <NUM>. Examples of the retractable component <NUM> include, but are not limited to, a plug, a cap, a screw, or a nut and bolt assembly. A reservoir seal <NUM>, for example, an O-ring seal, may also be provided around the sealing cap <NUM>, to prevent seepage of the fluid lubricant <NUM> outside the reservoir <NUM> and to isolate the fluid lubricant <NUM> in the reservoir <NUM> from communication outside the body <NUM>.

Alternate embodiments to facilitate the suction of air from the reservoir <NUM> may also be contemplated. For example, with reference to <FIG>, a suction conduit <NUM> may be provided between the inlet <NUM> of the body <NUM> and the reservoir <NUM> to facilitate suction of air from the reservoir <NUM>. As a result, the suction of air from the suction conduit <NUM> and the supply of the fluid lubricant <NUM> into the reservoir <NUM> via the orifice <NUM> in the sealing cap <NUM> may be carried out independently. A plug <NUM> with a suction seal <NUM> may be provided in the suction conduit <NUM> after the suction of air in order to isolate the reservoir <NUM> from communication outside the body <NUM>. Alternatively, the suction conduit <NUM> may facilitate the supply of the fluid lubricant <NUM> into the reservoir <NUM> and the orifice <NUM> in the sealing cap <NUM> may facilitate the suction of air from the reservoir <NUM>.

Referring back to <FIG>, the sealing system <NUM> also includes the pin <NUM> inserted in the second conduit <NUM> to retain the ball bearing <NUM> in position and the fluid lubricant <NUM> in the second conduit <NUM>. A first end <NUM> of the pin <NUM> may retain the ball bearing <NUM> in position and a second end <NUM> of the pin <NUM> may facilitate the isolation of the fluid lubricant <NUM> from communication outside the body <NUM>. The second end <NUM> of the pin <NUM> may be welded in position in the second conduit <NUM> after the insertion in order to facilitate the isolation of the fluid lubricant <NUM>. The pin <NUM> may be a metal pin having an annular groove <NUM> provided between the first end <NUM> and the second end <NUM> of the pin <NUM>. The annular groove <NUM> may in turn facilitate the retention of the fluid lubricant <NUM> in the second conduit <NUM>. The fluid lubricant <NUM> in the second conduit <NUM> may pass through an annular space <NUM> around a periphery of the first end <NUM> of the pin <NUM> in the second conduit <NUM> and lubricate the thrust bearing <NUM>, the ball bearing <NUM>, and/or the roller bearing <NUM>. The lubrication may be facilitated as a result of the vacuum created in the isolated lubrication system <NUM> and also by means of the centrifugal force <NUM> (see <FIG>) acting on the fluid lubricant <NUM> during rotation of the roller cone bit <NUM> and the first rotary cutter <NUM>.

The first rotary cutter <NUM> may be mounted on the journal <NUM> such that a clearance <NUM> may be defined between the first rotary cutter <NUM> and a base surface <NUM> of the first cutting arm <NUM> from which the journal <NUM> extends. The sealing system <NUM> may also include a journal seal <NUM> (also shown in <FIG>) provided between the journal <NUM> and the first rotary cutter <NUM> in the clearance <NUM>.

Referring to <FIG>, the journal seal <NUM> may be a Duo-Cone ™ seal having two seal rings <NUM>, <NUM> for example, metal seal rings, that may be arranged coaxially with the journal <NUM> and in face-to-face sealing contact with respect to each other. The two seal rings <NUM>, <NUM> may be further supported by annular seals <NUM>, herein referred to as "torics", respectively. The torics <NUM> may be flexible and made of elastic material. Further, the torics <NUM> may enable the first rotary cutter <NUM> and the first cutting arm <NUM> to support the two seal rings <NUM>, <NUM> respectively. The seal ring <NUM> may be rotatable along with the first rotary cutter <NUM> and the seal ring <NUM> may be stationary supported by the first cutting arm <NUM>. The rotation of the first rotary cutter <NUM> along the axis <NUM>, during operation, may cause the torics <NUM> to perform a springing action that may push the two seal rings <NUM>, <NUM> further into the face-to-face sealing contact. As a result, the journal seal <NUM> may be capable of preventing the leakage of the fluid lubricant <NUM> (as shown in <FIG>) at varying speeds of the rotation of the first rotary cutter first <NUM>. The journal seal <NUM> may also facilitate the isolation of the fluid lubricant <NUM> from communication outside the body <NUM>. In addition, the journal seal <NUM> may also prevent seepage of debris and contamination of the fluid lubricant <NUM> in the isolated lubrication system <NUM> from outside the body <NUM> of the roller cone bit <NUM>.

Additional examples of the journal seal <NUM> include, but are not limited to, an O-ring seal, a T-seal, an inverted duo-cone seal, a tri-cone seal, a floating seal, a face seal, a heavy-duty seal, a lifetime seal, a Chevron-ring stack seal, a bonded seal, a helical-spring seal, an S-seal, a step seal, a wedge seal, a spring energized seal, a toric seal, or any other mechanical face seal. In some embodiments, a bushing (not shown) may also be provided between the journal <NUM> and the first rotary cutter <NUM> in place of the journal seal <NUM>.

Further, the sealing system <NUM> also includes a stepped passageway <NUM> or a labyrinth that extends from the journal seal <NUM> to an opening <NUM> provided between the first cutting arm <NUM> and the first rotary cutter <NUM> in the clearance <NUM>. The stepped passageway <NUM> may be defined by a combination of a continuous lip <NUM> provided on the base surface <NUM> in the first cutting arm <NUM> and a continuous groove <NUM> provided on an end surface <NUM> in the first rotary cutter <NUM> in the clearance <NUM>. The end surface <NUM> faces the base surface <NUM> of the cutting arm <NUM> in the clearance <NUM>. The continuous lip <NUM> and the continuous groove <NUM> may also be annular in shape. The continuous lip <NUM> may be accommodated in the continuous groove <NUM> such that the stepped passageway <NUM> is defined in the clearance <NUM>. The stepped passageway <NUM> may be "L", "S", or "Z" shaped or a combination of different shapes. The stepped passageway <NUM> may also include a portion of the clearance <NUM> defined between the base surface <NUM> and the end surface <NUM> at the opening <NUM>. In some embodiments, two or more continuous lips and continuous grooves similar to the continuous lip <NUM> and the continuous groove <NUM> respectively may be provided between the first cutting arm <NUM> and the first rotary cutter <NUM> such that the two or more continuous lips and continuous grooves may collectively define the stepped passageway <NUM>. The continuous lip <NUM> may be provided around the journal <NUM> on the base surface <NUM> of the cutting arm <NUM> from which the journal <NUM> extends. The continuous lip <NUM> may define side walls <NUM> that may be perpendicular to the base surface <NUM> of the first cutting arm <NUM>. In some embodiments, the continuous lip <NUM> and the continuous groove <NUM> may be provided adjacent to the journal seal <NUM>. An annular sealing groove <NUM> may also be provided adjacent to the continuous groove <NUM> in the first rotary cutter <NUM>. The annular sealing groove <NUM> and at least one side wall <NUM> of the side walls <NUM> may support the two seal rings <NUM>, <NUM> respectively via the torics <NUM>. The torics <NUM> may be compressed against the annular sealing groove <NUM> and the side wall <NUM> of the continuous lip <NUM> respectively in order to seal the fluid lubricant <NUM> (as shown in <FIG>) from communication outside the body <NUM>.

In an alternate embodiment, the continuous lip <NUM> may be provided on the end surface <NUM> of the first rotary cutter <NUM> and the continuous groove <NUM> may be provided in the base surface <NUM> of the first cutting arm <NUM> in order to define the stepped passageway <NUM>.

The stepped passageway <NUM> may impede a flow of debris of cut matter that may accumulate at the opening <NUM> during operation of the roller cone bit <NUM>. As a result, the stepped passageway <NUM> may prevent the journal seal <NUM> from abrasion due to the debris and improve a lifespan of the journal seal <NUM>. Consequently, the fluid lubricant <NUM> (as shown in <FIG>) contained by the journal seal <NUM> may also be prevented from contamination due to the debris.

In embodiments, for example, as shown in <FIG>, of the isolated lubrication system <NUM>, the sealing system <NUM> may also include the plug <NUM> with the suction seal <NUM> provided in the suction conduit <NUM> to isolate the reservoir <NUM> from the inlet <NUM> of the body <NUM>.

Referring to <FIG>, in some embodiments, the body <NUM> of the roller cone bit <NUM> may include multiple cutting arms of different shapes and sizes not described in the present disclosure. Accordingly, the isolated lubrication system <NUM> described in the present disclosure may also be applicable to the body <NUM> of the roller cone bit <NUM> having multiple cutting arms and multiple rotary cutters mounted on the multiple cutting arms respectively. The multiple cutting arms and the multiple rotary cutters may be of different shapes and sizes. Further, multiple conduits having different shapes and placed in different positions in the body <NUM> may also be provided to facilitate lubrication between the multiple cutting arms and the multiple rotary cutters, including the multiple bearings therein respectively. Further, alternate embodiments (as shown in <FIG> and <FIG>) of the shape, the size, and a position of the reservoir <NUM> in the body <NUM> may also be contemplated.

Referring to <FIG>, an alternate embodiment of the isolated lubrication system <NUM> of <FIG>, having a central reservoir <NUM> provided in the body <NUM> in place of the reservoir <NUM> is disclosed. In an embodiment, the central reservoir <NUM> (also shown in <FIG>) may be a cylindrical slot provided in the inlet <NUM>. The central reservoir <NUM> may be provided with a sealing cap <NUM> and sealed from the direct communication with the inlet <NUM> by means of a seal <NUM>, such as, for example, an O-ring seal and a seat ring <NUM>. The sealing cap <NUM> may include a central retractable component <NUM>. The central retractable component <NUM> may be retracted and removed to introduce the fluid lubricant <NUM> into the central reservoir <NUM>. Connecting conduits <NUM> may be provided between the central reservoir <NUM> and the cutting arms (<NUM>, <NUM>, <NUM>) respectively. For purposes of clarity and understanding, the central reservoir <NUM> in direct communication with the first cutting arm <NUM> via the connecting conduit <NUM> will be described herein in detail. The central reservoir <NUM> in direct communication with the connecting conduits <NUM> to the cutting arms <NUM> and <NUM> will be omitted for brevity.

The first conduit <NUM> in the first cutting arm <NUM> may be in direct communication with the connecting conduit <NUM> and in indirect communication with the central reservoir <NUM>. In an embodiment, the connecting conduit <NUM> may be perpendicular to the central reservoir <NUM>. In another embodiment, the connecting conduit <NUM> may be inclined at an angle with respect to the central reservoir <NUM>. The first conduit <NUM> may also extend to a cutting arm opening <NUM> provided on the peripheral surface <NUM> of the first cutting arm <NUM>. The cutting arm opening <NUM> may facilitate the suction of air from the isolated lubrication system <NUM>. The first conduit <NUM> may also be provided with a plug <NUM> and a conduit seal <NUM> in the cutting arm opening <NUM> to isolate the fluid lubricant <NUM> from communication outside the body <NUM> after the suction of air. In an alternate embodiment, the central retractable component <NUM> of the sealing cap <NUM> may be removed to facilitate the suction of the air from the central reservoir <NUM> and the fluid lubricant <NUM> may be introduced via the cutting arm opening <NUM> such that the central reservoir <NUM>, the connecting conduit <NUM>, and the conduits (<NUM>, <NUM>, <NUM>) are filled with the fluid lubricant <NUM>. The plug <NUM> and the conduit seal <NUM> may then be provided in the cutting arm opening <NUM> to isolate the fluid lubricant <NUM> from communication outside the body <NUM>.

Referring to <FIG>, a combination of the isolated lubrication system <NUM> of <FIG> and <FIG> is disclosed. The central reservoir <NUM> may be in communication with the reservoir <NUM> via the connecting conduit <NUM>. The first conduit <NUM> in the first cutting arm <NUM> may be in indirect communication with the connecting conduit <NUM> via the reservoir <NUM> and hence, in indirect communication with the central reservoir <NUM>. In one embodiment, the central retractable component <NUM> of the sealing cap <NUM> may be retracted and removed to facilitate the supply of the fluid lubricant <NUM> into the central reservoir <NUM>, the connecting conduit <NUM>, the reservoir <NUM>, and the conduits (<NUM>, <NUM>, <NUM>). Further, the retractable component <NUM> in the sealing cap <NUM> may be retracted and removed to facilitate the suction of the air from the reservoir <NUM> and the central reservoir <NUM> via the orifice <NUM>. Alternatively, the central retractable component <NUM> of the sealing cap <NUM> may be removed to facilitate the suction of the air from the central reservoir <NUM> and the reservoir <NUM>. The retractable component <NUM> in the sealing cap <NUM> may then be retracted and removed to facilitate the supply of the fluid lubricant <NUM> into the reservoir <NUM>, the conduits (<NUM>, <NUM>, <NUM>), the connecting conduit <NUM>, and the central reservoir <NUM>. The vacuum created as a result of the suction of the air and the gravitational force <NUM> may facilitate the lubrication of the bearings (<NUM>, <NUM>) and the thrust bearing (<NUM>) when the central reservoir <NUM> and the reservoir <NUM> are filled with the fluid lubricant <NUM>.

Referring to <FIG> and <FIG>, the body <NUM> of the roller cone bit <NUM> may be adapted to cut the rock matter and remove debris from a bore hole (not shown). The roller cone bit <NUM> may be connected to a drilling machine (not shown) via a feed unit (not shown). The feed unit may be connected to a power source (not shown) including a rotor (not shown) that provides the necessary rotation to the roller cone bit <NUM>. The feed unit may include a drill pipe having a drill string that may supply compressed air or fluids to flush the cut matter from the bore hole. Further, the feed unit may provide necessary feed force to facilitate the cutting of rock matter in the bore hole.

Prior to operation of the roller cone bit <NUM>, the isolated lubrication system <NUM> in the cutting arms (<NUM>, <NUM>, <NUM>) respectively may need to be primed. The air from the reservoir <NUM> may need to be removed in order to create a vacuum and introduce the fluid lubricant <NUM> in the reservoir <NUM>. In one embodiment, the retractable component <NUM> of the sealing cap <NUM> may be retracted and detached from the sealing cap <NUM> in order to facilitate suction of air. The fluid lubricant <NUM> may then be introduced into the reservoir <NUM>. The retractable component <NUM> may then be affixed to the sealing cap <NUM> to isolate the fluid lubricant <NUM> in the reservoir <NUM> from communication outside the body <NUM> of the roller cone bit <NUM>. In another embodiment, the air from the reservoir <NUM> may be removed via the suction conduit <NUM> (see <FIG>) and sealed by means of the plug <NUM> and the suction seal <NUM> provided in the suction conduit <NUM>. The fluid lubricant <NUM> may then be introduced into the reservoir <NUM> by detaching the retractable component <NUM> in the sealing cap <NUM> and re-attaching the retractable component <NUM> to isolate the fluid lubricant <NUM>. The fluid lubricant <NUM> may be introduced into the reservoir <NUM> such that the fluid lubricant <NUM> occupies the first conduit <NUM>, the second conduit <NUM>, and the third conduit <NUM>. The fluid lubricant <NUM> may also occupy the additional conduits <NUM> and <NUM> in communication with the second conduit <NUM>. In an embodiment, the fluid lubricant <NUM> may occupy <NUM> - <NUM> percent of the volume of the reservoir <NUM> such that the fluid lubricant <NUM> is contained in the reservoir <NUM> in an event of a thermal expansion of the fluid lubricant <NUM> during operation of the roller cone bit <NUM>. Further, in an embodiment, the fluid lubricant <NUM> may have a viscosity between <NUM> centistokes and <NUM> centistokes at an operating temperature of <NUM> degree Celsius. The flow <NUM> of the fluid lubricant <NUM> in the isolated lubrication system <NUM> may be due the gravitational force <NUM> and the centrifugal force <NUM> acting on the fluid lubricant <NUM> during operation of the roller cone bit <NUM>. The isolated lubrication system <NUM> may require no additional components or systems to facilitate the flow <NUM> of the fluid lubricant <NUM> in the isolated lubrication system <NUM>.

During operation of the roller cone bit <NUM>, the power source may facilitate the rotation of the roller cone bit <NUM> around the central axis <NUM> via the feed unit. The rotation of the roller cone bit <NUM> may in turn result in the rotation of the rotary cutters (<NUM>, <NUM>, <NUM>) mounted on the journals <NUM> of the cutting arms (<NUM>, <NUM>, <NUM>) respectively. The rotary cutters (<NUM>, <NUM>, <NUM>) may rotate around respective axes and the journals <NUM> in a direction opposite to the direction of rotation of the roller cone bit <NUM>. For example, the roller cone bit <NUM> may rotate in a clockwise direction and the rotary cutters (<NUM>, <NUM>, <NUM>) may rotate in an anti-clockwise direction.

For purposes of clarity and understanding, the flow <NUM> of the fluid lubricant <NUM> in the isolated lubrication system <NUM> of the first cutting arm <NUM> will be described herein in detail. The flow <NUM> of the fluid lubricant <NUM> in the isolated lubrication system <NUM> of the second cutting arm <NUM> and the third cutting arm <NUM> will be omitted for brevity.

The fluid lubricant <NUM> occupies the first conduit <NUM> by means of the gravitational force <NUM>. The rotation of the roller cone bit <NUM> and the first rotary cutter <NUM> also results in the centrifugal force <NUM> that acts on the fluid lubricant <NUM>. The centrifugal force <NUM> acting on the fluid lubricant <NUM> enables the fluid lubricant <NUM> to pass through an annular space <NUM> around the first end <NUM> of the pin <NUM> in the second conduit <NUM> and thereby, results in the lubrication of the ball bearing <NUM>. The fluid lubricant <NUM> may also seep through an annular space <NUM> between the ball bearing <NUM> and the roller bearing <NUM> and lubricate the roller bearing <NUM>. Further, the fluid lubricant <NUM> may then seep through an annular space <NUM> between the ball bearing <NUM> and the thrust bearing <NUM> and lubricate the thrust bearing <NUM>. Further, the fluid lubricant <NUM> occupies the third conduit <NUM> by means of the gravitational force <NUM>. The gravitational force <NUM> and/or the centrifugal force <NUM> acting on the fluid lubricant <NUM> due to rotation of the roller cone bit <NUM> and the first rotary cutter <NUM> enables the fluid lubricant <NUM> to exit the outlet <NUM> of the third conduit <NUM>. The fluid lubricant <NUM> from outlet <NUM> may then pass through annular spaces <NUM>, <NUM>, and <NUM> and thereby, lubricate the thrust bearing <NUM> and the ball bearing <NUM> respectively. The fluid lubricant <NUM> from the annular space <NUM> may also seep around ball bearing <NUM> and into the annular space <NUM> to lubricate the roller bearing <NUM>. The journal seal <NUM> may prevent further seepage of the fluid lubricant <NUM> around the roller bearing <NUM>.

The rotation of the first rotary cutter <NUM> also enables the inserts <NUM> provided on the first rotary cutter <NUM> to cut through the rock matter in the bore hole (not shown). The debris of cut matter may accumulate around the first rotary cutter <NUM> and may enter the clearance <NUM> via the opening <NUM>. The stepped passageway <NUM> provided in the clearance <NUM> may impede a flow of the debris from the opening <NUM> to the journal seal <NUM>. The stepped passageway <NUM> may thereby reduce the abrasion of the journal seal <NUM> and improve a lifespan of the journal seal <NUM>. As a result, the journal seal <NUM> may also prevent the debris from contaminating the fluid lubricant <NUM> around the bearings (<NUM>, <NUM>) and thereby, also improving a lifespan of the bearings (<NUM>, <NUM>) being lubricated.

Referring to <FIG>, prior to operation of the roller cone bit <NUM>, the air from the isolated lubrication system <NUM> may be removed by means of the cutting arm opening <NUM> and the cutting arm opening <NUM> may then be sealed by means of the plug <NUM> and the conduit seal <NUM>. The central retractable component <NUM> in the sealing cap <NUM> of the central reservoir <NUM> may then be retracted and removed in order to introduce the fluid lubricant <NUM> into the central reservoir <NUM> until the connecting conduit <NUM>, and the conduits (<NUM>, <NUM>, <NUM>) are occupied with the fluid lubricant <NUM>. For instances when the connecting conduit <NUM> is perpendicular to the central reservoir <NUM>, the vacuum created facilitates the flow <NUM> of the fluid lubricant <NUM> in the connecting conduit <NUM>. Further, for instances when the connecting conduit <NUM> is inclined at an angle with respect to the central reservoir <NUM>, the gravitational force <NUM> acting on the fluid lubricant <NUM>, in addition to the vacuum created, may facilitate the flow <NUM> of the fluid lubricant <NUM> in the connecting conduit <NUM>. The central retractable component <NUM> may then be affixed to the sealing cap <NUM> to isolate the fluid lubricant <NUM> in the central reservoir <NUM> from communication with the inlet <NUM> of the roller cone bit <NUM>. The vacuum created as a result of the removal of the air from the isolated lubrication system <NUM> and the gravitational force <NUM> facilitate in the lubrication of the thrust bearing <NUM>, the ball bearing <NUM>, and the rolling element bearing <NUM> as the fluid lubricant <NUM> is filled into the central reservoir <NUM>.

During operation, the fluid lubricant <NUM> from the central reservoir <NUM> may flow <NUM> through the connecting conduit <NUM> by means of the centrifugal force <NUM>. The fluid lubricant <NUM> may then flow <NUM> in the conduits (<NUM>, <NUM>, <NUM>) by means of the gravitational force <NUM> and/or the centrifugal force <NUM> and provide lubrication between the journal <NUM> and the first rotary cutter <NUM>, including the bearings (<NUM>, <NUM>).

Referring to <FIG>, prior to operation of the roller cone bit <NUM>, the air from the isolated lubrication system <NUM> may be removed via the orifice <NUM> of the sealing cap <NUM> by removing the retractable component <NUM>. The retractable component <NUM> may then be affixed to the sealing cap <NUM> such that a vacuum is created in the isolated lubrication system <NUM>. The central retractable component <NUM> in the sealing cap <NUM> of the central reservoir <NUM> may then be retracted and removed in order to introduce the fluid lubricant <NUM> into the central reservoir <NUM> until the connecting conduit <NUM>, the reservoir <NUM>, and the conduits (<NUM>, <NUM>, <NUM>) are occupied with the fluid lubricant <NUM> by means of the vacuum created and the gravitational force <NUM>. For instances when the connecting conduit <NUM> is perpendicular to the central reservoir <NUM>, the vacuum created facilitates the flow <NUM> of the fluid lubricant <NUM> in the connecting conduit <NUM>. Further, for instances when the connecting conduit <NUM> is inclined at an angle with respect to the central reservoir <NUM>, the gravitational force <NUM> acting on the fluid lubricant <NUM>, in addition to the vacuum created, may facilitate the flow <NUM> of the fluid lubricant <NUM> in the connecting conduit <NUM>. The central retractable component <NUM> may then be affixed to the sealing cap <NUM> to isolate the fluid lubricant <NUM> in the central reservoir <NUM> from communication with the inlet <NUM> of the roller cone bit <NUM>. The vacuum created as a result of the removal of the air from the isolated lubrication system <NUM> facilitates in the lubrication of the thrust bearing <NUM>, the ball bearing <NUM>, and the rolling element bearing <NUM> as the fluid lubricant <NUM> is filled into the reservoir <NUM>.

During operation, the fluid lubricant <NUM> from the central reservoir <NUM> may flow <NUM> through the connecting conduit <NUM> to the reservoir <NUM> by means of the gravitational force <NUM> and/or centrifugal force <NUM>. The fluid lubricant <NUM> may then flow <NUM> in the conduits (<NUM>, <NUM>, <NUM>) from the reservoir <NUM> by means of the gravitational force <NUM> and/or the centrifugal force <NUM> and provide lubrication between the journal <NUM> and the first rotary cutter <NUM>, including thrust bearing <NUM> and the bearings (<NUM>, <NUM>).

As is apparent, the isolated lubrication system <NUM> (as shown in <FIG>, <FIG>, and <FIG>) may improve a lifespan and performance of the first rotary cutter <NUM>, the bearings (<NUM>, <NUM>), and hence, the roller cone bit <NUM>.

Claim 1:
A rotary drill bit (<NUM>), comprising:
a body (<NUM>) having an inlet (<NUM>) and three cutting arms (<NUM>, <NUM>, <NUM>), each with a journal (<NUM>) extending therefrom and a rotary cutter (<NUM>, <NUM>, <NUM>) mounted on the journal (<NUM>) by means of a plurality of bearings (<NUM>, <NUM>, <NUM>) such that a clearance (<NUM>) is defined between the rotary cutter (<NUM>, <NUM>, <NUM>) and a base surface (<NUM>) of the cutting arm (<NUM>, <NUM>, <NUM>) from which the journal (<NUM>) extends; and
an isolated lubrication system (<NUM>) corresponding to each cutting arm (<NUM>, <NUM>, <NUM>), each including:
a reservoir (<NUM>) in the body (<NUM>) to contain a fluid lubricant (<NUM>), the fluid lubricant (<NUM>) being isolated from communication outside the body (<NUM>),
a plurality of conduits (<NUM>, <NUM>, <NUM>) in the body (<NUM>) having direct or indirect communication with the reservoir (<NUM>) and with respect to each other such that the plurality of conduits (<NUM>, <NUM>, <NUM>) facilitate lubrication between the journal (<NUM>) and the rotary cutter (<NUM>, <NUM>, <NUM>) and to the bearings (<NUM>, <NUM>, <NUM>) by means of at least one of a gravitational force and a centrifugal force acting on the fluid lubricant (<NUM>), and
a sealing system (<NUM>) including:
a sealing cap (<NUM>) provided to the reservoir (<NUM>) in the body (<NUM>) to isolate the reservoir (<NUM>) from communication outside the body (<NUM>), the sealing cap (<NUM>) having an orifice (<NUM>) and a retractable component (<NUM>) provided in the orifice (<NUM>) for the supply of fluid lubricant (<NUM>) to the reservoir (<NUM>),
a seal (<NUM>) provided between the journal (<NUM>) and the rotary cutter (<NUM>, <NUM>, <NUM>) in the clearance (<NUM>), and
a stepped passageway (<NUM>) extending from the seal (<NUM>) to an opening (<NUM>) in the clearance (<NUM>),
wherein a suction conduit (<NUM>) is provided between the body inlet (<NUM>) and each reservoir (<NUM>) to facilitate suction of air from the reservoirs (<NUM>) and a plug (<NUM>) with a suction seal (<NUM>) is provided in each of the suction conduits (<NUM>) to isolate the reservoirs (<NUM>) from communication outside the body (<NUM>) after the vacuum is created.