Patent Description:
This application also claims the benefit of priority to <CIT>.

This disclosure relates generally to earth-boring bits. This disclosure relates more particularly to earth-boring bits in which one or more cutting elements are attached using mechanical means. An example of such earth-boring bits is disclosed in document <CIT>.

<FIG> illustrates a portion of a known earth-boring bit. The earth-boring bit comprises blades, such as blade <NUM>. Each blade extends axially and radially from a body, which is not shown in <FIG>. In use, the body is coupled to a drill string and rotated around an axis in a direction indicated by arrow <NUM> in <FIG>. The blade <NUM> has a leading face <NUM>, which is the face of the blade <NUM> that is intended to lead when the body of the earth-boring bit is rotated, and a trailing face, which is the face of the blade <NUM> that is intended to trail when the body of the earth-boring bit is rotated. A surface spanning between the leading face <NUM> and trailing face is referred to herein as an edge <NUM> of the blade <NUM>.

The blade <NUM> has cavities formed in it, such as cavity <NUM>. Each cavity is shaped to receive a portion of a cutting element <NUM>. The cutting element <NUM> typically has a longitudinal axis <NUM> passing through its center, and a cross-section that is circular. The cutting element <NUM> typically includes an ultra-hard table <NUM> (e.g., made of sintered polycrystalline diamond) attached to a substrate <NUM> (e.g., made of sintered tungsten carbide). The ultra-hard table <NUM> has a cutting face <NUM> and a cutting edge <NUM>. Once introduced in the cavity <NUM>, the cutting element <NUM> protrudes from the cavity <NUM> through a first opening in the edge <NUM> of the blade <NUM> as well as through a second opening in the leading face <NUM> of the blade <NUM>. As such, a surface of the cutting element <NUM> is exposed so that the cutting element <NUM> can crush or shear the rock without the blade <NUM> rubbing excessively on the rock. However, the shape of the cavity <NUM> is not sufficient to retain the cutting element <NUM> inside the cavity <NUM>.

In order to retain the cutting element <NUM> inside the cavity <NUM>, the cutting element <NUM> is brazed to the blade <NUM> using a metal filler, which is shown disposed on a wall <NUM> of the cavity <NUM> in <FIG>. The cutting element <NUM> is positioned in the cavity <NUM> with the metal filler. The metal filler is melted in place, infiltrates the substrate <NUM> of the cutting element <NUM> and the blade <NUM>. Thus, the cutting element <NUM> and the blade <NUM> are subjected to a heating cycle when the cutting element <NUM> is attached to (or detached from) the blade <NUM>.

This heating cycle may damage the cutting element <NUM> and the blade <NUM>. As such, there is a continuing need in the art for alternative methods for attaching cutting elements to an earth-boring bit that preferably do no subject the cutting elements and the earth-boring bit to a heating cycle.

The disclosure describes an earth-boring bit, which comprises a body having a rotational axis, and a blade extending axially and radially from the body, the blade having a leading face and an edge. A cavity is formed in the blade. The cavity leads to a first opening in the edge of the blade and a second opening in the leading face of the blade.

In some embodiments, the cavity may be configured to receive a cutting element through the first opening. The cavity may be configured to receive a retainer through the first opening also, preferably after the cutting element is engaged with the portion of the wall of the cavity such that the retainer is capable of abutting the cutting element and a back wall of the cavity. The retainer may be releasably attached to the blade. For example, the retainer may comprise a shim releasably attached to the blade by using a screw, an adhesive, or brazing.

In some embodiments, the cutting element may have a cylindrical lateral surface and a flared lateral surface that points inwards in a direction toward a cutting face of the cutting element. A portion of a wall of the cavity may be complementary to the shape of the flared lateral surface of the cutting element. Furthermore, the cutting element is prevented from rotating inside the cavity after the flared lateral surface of the cutting element is engaged with the portion of the wall of the cavity.

In some embodiments, the cutting element may consist of a table of sintered polycrystalline diamond from which a transition metal used as a sintering catalyst is essentially entirely leached or otherwise removed from the pores of a polycrystalline diamond matrix that are connected to an outer surface of the table.

In some embodiments, the cutting element may have a rotational symmetry of order two or more around a longitudinal axis.

In some embodiments, the blade may include a fixed portion and a plate, the fixed portion being integral to the bit body, the plate being releasably attached to the fixed portion. A lateral surface of the plate may be at least partially forming the edge of the blade after the plate is releasably attached to the fixed portion. The cavity may be formed at least partially into the plate. The fixed portion of the blade may be abutting the cutting element.

In some embodiments, a first section of the cutting element that is perpendicular to the longitudinal axis may have a first contour line that includes a first line portion, a second line portion, a third line portion, and optionally a fourth line portion. The first line portion may have a first endpoint and a second endpoint that is offset from the first endpoint, the first endpoint of the first line portion being located at a first predetermined radius from the longitudinal axis, the first line portion being tangent to a circle centered on the longitudinal axis and having the first predetermined radius, the first line portion having curvatures that have a constant sign and magnitudes larger than the inverse of the first predetermined radius, the second endpoint of first line portion being located at a distance from the longitudinal axis that is shorter than the first predetermined radius. The second line portion may have a first endpoint and a second endpoint that is offset from the first endpoint, the first endpoint of the second line portion being co-located with the second endpoint of the first line portion, the second line portion being tangent to the first line portion, the second line portion being smooth, all points of the second line portion being located at distances from the longitudinal axis that are shorter than or equal to the first predetermined radius. The third line portion may have a first endpoint and a second endpoint that is offset from the first endpoint, the first endpoint of the third line portion being co-located with the second endpoint of the second line portion, the third line portion being tangent to the second line portion, the third line portion having curvatures that have a constant sign and magnitudes larger than the inverse of the first predetermined radius, the second endpoint of the third line portion being located at first the predetermined radius from the longitudinal axis, the third line portion being tangent to the circle centered on the longitudinal axis and having the first predetermined radius. The fourth line portion may have a first endpoint and a second endpoint that is offset from the first endpoint, the first endpoint of the fourth line portion being co-located with the second endpoint of the third line portion, the fourth line portion being an arc of the circle centered on the longitudinal axis and having the first predetermined radius. The first line portion may be adjacent to the wall of the cavity so that the cutting element is mechanically retained in the cavity formed in the blade. The third line portion and the fourth line portion may protrude from the first opening of the cavity so that a first surface of the cutting element is exposed.

In some embodiments, the cutting element may include an ultra-hard table attached to a substrate, the substrate having a lateral surface portion forming a keyseat, a lateral surface portion that is cylindrical, and a lateral surface including a concave depression. The concave depression may be surrounded by a corner. Optionally, an entirety of the ultra-hard table may have a circular perimeter. A portion of a wall of the cavity may be configured to form a complementary key such that the cutting element is prevented from rotating inside the cavity after the keyseat is engaged with the key. A through-hole may be formed in the substrate of the cutting element. The through-hole may lead to the concave depression.

In some embodiment, the earth-boring bit may comprise a retainer that is releasably attached to the blade, the retainer being positioned in the cavity and movable between a first position wherein the retainer is engaging a concave depression so that the cutting element is mechanically retained in the blade, and a second position wherein the retainer is offset from the concave depression so that the cutting element can be released from the blade. For example, the retainer can be moved from the first position to the second position with an elongated tool penetrating the through-hole. The retainer may comprise a ball or peg and a spring, the spring being disposed between the wall of the cavity and the ball or peg, or wherein the retainer comprises a threaded setscrew engaged with threads formed on the wall of the cavity.

In some embodiments, the cutting element may have a funneled lateral surface such that the cutting element includes a first longitudinal portion having a first central axis, and a second longitudinal portion having a second central axis. The second central axis may be parallel to and offset from, the first central axis such that a first section of the first longitudinal portion that is perpendicular to the first central axis has a first maximum width, a second section of the second longitudinal portion that is perpendicular to the second central axis has a second maximum width, and the second maximum width is smaller than the first maximum width. The first longitudinal portion of the cutting element may protrude from the cavity through the first opening and through the second opening. The second longitudinal portion of the cutting element may be entirely recessed into the blade.

For a more detailed description of the embodiments of the disclosure, reference will now be made to the accompanying drawings, wherein:.

It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention.

This disclosure describes methods for attaching cutting elements to an earth-boring bit that rely on keying the cutting elements inside cavities formed in the earth-boring bit, but may not rely on brazing. The attachment methods may involve specific shapes of the cutting elements and the cavities in which the cutting elements are received, and/or mechanical retainers.

<FIG> and <FIG> illustrate exemplary cross-sectional shapes of a cutting element usable for facilitating the retention of the cutting element in a cavity formed in the blade. When a cavity that is shaped for receiving the cutting element such as shown in these Figures is formed in the blade, the blade can be thicker around the opening in the edge of the blade than when the cavity is shaped for receiving a cutting element that has a circular cross-section. Accordingly, the cutting element such as shown in <FIG> or <FIG> may be mechanically retained in the cavity by the blade. Furthermore, the cutting element may not be excessively recessed below the edge of the blade so that the cutting element may still be sufficiently exposed to crush or shear rock.

In the example of <FIG>, a section <NUM> of a cutting element <NUM> has a rotational symmetry of order three around its longitudinal axis <NUM>. In the example of <FIG>, the section <NUM> of the cutting element <NUM> has a rotational symmetry of order two around its longitudinal axis <NUM>. In both Figures, the section <NUM> is taken perpendicularly to the longitudinal axis <NUM> of the cutting element <NUM>. The section <NUM> has a contour line <NUM>, which is described hereinafter.

The contour line <NUM> includes a first line portion <NUM> that has a first endpoint a and a second endpoint b, which is offset from the first endpoint a. The first endpoint a of the first line portion <NUM> is located at a predetermined radial distance R from the longitudinal axis <NUM>, which may be selected to optimize the drilling performance of the earth-boring bit as known. The second endpoint b of the first line portion <NUM> is located at a distance from the longitudinal axis <NUM> that is shorter than R. At its first endpoint a, the first line portion <NUM> is tangent to a circle <NUM> centered on the longitudinal axis <NUM> and having a radius equal to R. The first line portion <NUM> has a variable or constant curvature, and the first line portion <NUM> is more curved than the circle <NUM>. In other words, the curvature of the first line portion <NUM> has a sign that is constant, and a magnitude that is larger than the inverse of R. For example, the first line portion <NUM> may be a circular arc that has a radius smaller than R, or an elliptic arc that has a width and a height smaller than R.

The contour line <NUM> includes a second line portion <NUM> that has a first endpoint c and a second endpoint d, which is offset from the first endpoint c. The first endpoint c of the second portion <NUM> is co-located with the second endpoint b of the first line portion <NUM>. All points of the second line portion <NUM> are located at distances from the longitudinal axis <NUM> that are shorter than R. As such, at least a portion of the area between the second line portion <NUM> and the circle <NUM> may be filled with blade material (not shown in <FIG> and <FIG>), and thus, the blade may be thicker. At its first endpoint c, the second line portion <NUM> is tangent to the first line portion <NUM>. The second line portion <NUM> is smooth. For example, the second line portion <NUM> may be a circular arc, an elliptic arc, or a straight line. The second line portion <NUM> may be convex, such as shown in <FIG>, or concave, such as shown in <FIG>.

The contour line <NUM> includes a third line portion <NUM> that has a first endpoint e and a second endpoint f, which is offset from the first endpoint e. The first endpoint e of the third line portion <NUM> is co-located with the second endpoint d of the second line portion <NUM>. The second endpoint f of the third line portion <NUM> is located at a distance R from the longitudinal axis <NUM>. At its first endpoint e, the third line portion <NUM> is tangent to the second line portion <NUM>. At its second endpoint f, the third line portion <NUM> is tangent to the circle <NUM>. The third line portion <NUM> has a variable or constant curvature, and the third line portion <NUM> is more curved than the circle <NUM>. For example, the third line portion <NUM> may be a circular arc that has a radius smaller than R, or an elliptic arc that has a width and a height smaller than R.

The contour line <NUM> includes a fourth line portion <NUM> that has a first endpoint g and a second endpoint h, which is offset from the first endpoint g. The first endpoint g of the fourth line portion <NUM> is co-located with the second endpoint f of the third line portion. The fourth line portion <NUM> is an arc of the circle <NUM>.

The remainder of the contour line <NUM> is derived from the rotational symmetry of the cutting element <NUM>.

A cavity is formed in a blade for receiving a cutting element <NUM> such as shown in <FIG> or <FIG>. The cavity is shaped to receive a portion of a cutting element <NUM> such that the cutting element protrudes from the cavity through the first opening in the edge of the blade and through the second opening in the leading face of the blade. As such, the cutting edge and the cutting face of the cutting element <NUM> are exposed to rock.

A wall of the cavity includes a surface that is complementary of a portion of the lateral surface of the cutting element <NUM>. For example, the wall of the cavity includes a surface that is complementary of the portion of the lateral surface of the cutting element <NUM> shaped like the second line portion <NUM>. When the cutting element <NUM> is received in the cavity, this surface contacts the complementary portion of the lateral surface of the cutting element <NUM>. Because the portion of the contour line <NUM> contacted by the cavity wall is not entirely circular, the cutting element <NUM> is prevented from rotating around the longitudinal axis <NUM> inside the cavity. In other words, the portion of the contour line <NUM> contacted by the cavity wall provides a keyseat for the cavity wall, and the cavity wall provides a key for the portion of the lateral surface of the cutting element <NUM> contacted by the cavity wall.

When a cutting element having a cross-sectional shape such as shown in <FIG> or <FIG> is received in a cavity <NUM> formed in a blade <NUM>, the first line portion <NUM> is preferably adjacent to the wall <NUM> of the cavity <NUM> so that the cutting element <NUM> is mechanically retained in the cavity <NUM>. Furthermore, the third line portion <NUM> and the fourth line portion <NUM> preferably protrude from the first opening of the cavity <NUM> so that a surface of the cutting element <NUM> is sufficiently exposed.

In alternative embodiments, the fourth line portion may be omitted.

<FIG> illustrate cutting elements <NUM> that have cross-sectional shapes of a type disclosed in the description of <FIG> or <FIG>, and at least one lateral surface <NUM> that is flared and characterized by line portions <NUM>, <NUM>, and <NUM>. As shown in <FIG>, the lateral surface <NUM> is flared such that it points inwards in the direction toward the cutting face of the ultra-hard table <NUM>. In other words, the closer to the cutting face of the ultra-hard table <NUM> the cross-section of the cutting elements <NUM> is, the crossectional area of cutting element <NUM> becomes smaller. For example, the cutting elements <NUM> may have a first cross-section <NUM> and a second cross-section <NUM> that is offset from, and parallel to, the first section <NUM> and farther from the cutting face of ultra-hard table <NUM> of the cutting elements <NUM>. The first cross-section <NUM> may have a first contour line, and the second section <NUM> has a second contour line. All points of the second contour line are located at distances from the longitudinal axis <NUM> that are longer than or equal to a minimum eccentricity of the second contour line, and some points of the first contour line are located at distances from the longitudinal axis <NUM> that are shorter than the minimum eccentricity of the second contour line. A particular example is when the second contour line is a homogeneous dilatation of the first contour line, such as shown in <FIG>. For example, a flare angle may be determined experimentally to ensure sufficient mechanical retention and sufficient strength of the cutting element while drilling. The flare angle may be on the order of ten degrees. Another particular example is when the cutting elements <NUM> have a lateral surface <NUM> that is flared as well as a lateral surface <NUM> that is cylindrical, such as shown in <FIG>.

In the embodiments shown in <FIG>, the cutting element <NUM> includes a substrate <NUM> and an ultra-hard table <NUM>, and the lateral surface <NUM> that is flared is at least partially formed on the substrate <NUM>. However, when the cutting element <NUM> is mechanically attached, the substrate <NUM>, which is used for brazing the cutting element <NUM> to the blade <NUM>, may not be needed. Thus, in other embodiments, the size of the substrate <NUM> may be reduced, or the substrate <NUM> may even be omitted and the cutting element <NUM> may consist of an ultra-hard table <NUM> as illustrated in <FIG>. Accordingly, the cutting element <NUM> may consist of a table of sintered polycrystalline diamond where the transition metal used as the sintering catalyst, usually cobalt or nickel, is partially or essentially entirely leached or otherwise removed from the pores of the polycrystalline diamond matrix that are connected to the table surface. Nevertheless, a significant amount of transition metal may remain in the unconnected pores, and a residual amount of transition metal may remain in the connected pores. Such a cutting element <NUM> may be more heat resistant and durable than a cutting element <NUM> including a larger proportion of transition metal in the ultra-hard table <NUM>.

<FIG> illustrate a method for mounting a cutting element <NUM> of a type disclosed in the description of <FIG>. In certain embodiments related to the methods shown in Figres 7A-7E, cutting element <NUM> has a crossectional shape at section <NUM> as shown in <FIG>. The cavity <NUM> is longer than the cutting element <NUM>. The back of the opening in the edge <NUM> of the blade is larger than its front so that the cutting element <NUM> can be introduced into the cavity <NUM> through the back of the opening in the edge <NUM> of the blade. The cutting element <NUM> is then advanced toward the leading face <NUM> of the blade until it engages a portion of the wall <NUM> of the cavity <NUM> that is complementary to the shape of a portion of the lateral surfaces <NUM> and <NUM>. Preferably, after moving the cutting element <NUM> in the forward direction, a substantial portion of the lateral surface <NUM> that is flared is contacted by the wall <NUM> of the cavity. Further and as described above, surfaces of cutting element <NUM> engage within cavity <NUM> by the contact of surfaces characterized by line portions <NUM>, <NUM>, <NUM>, and/or <NUM> (as shown in <FIG>) with the complementary surfaces in cavity <NUM>. Additionally, while moving cutting element <NUM> within cavity <NUM> toward leading face <NUM>, first cross-section <NUM> is advanced through cavity <NUM> and cutting element <NUM> is then constrained from additional forward movement within cavity <NUM> upon the larger cross sectional area of cutting element <NUM> at second cross-section <NUM> engaging or interfering with wall <NUM> of cavity <NUM>.

A retainer <NUM> is then introduced through the back of the opening in the edge <NUM> of the blade. The retainer <NUM> comprises a shim and in a fastener. For example, the shim may be made from several types of material such as steel or metal carbide. When positioned, the shim abuts the cutting element <NUM> and a back surface <NUM> of the wall <NUM>. As such, the cutting compression forces applied in the direction of the longitudinal axis <NUM> are substantially transmitted to the back surface <NUM> of the wall <NUM>. The shim is then releasably attached to the blade using the fastener, such as by using a screw, an adhesive, or brazing. The fastener prevents the shim from falling off through the first opening in the edge <NUM> of the blade <NUM>; however, the fastener is not required to resist the cutting compression forces applied in the direction of the longitudinal axis <NUM>.

Because the shape of the lateral surface <NUM> is not cylindrical and due to the engagement of complementary surfaces among the cutting element <NUM> and cavity <NUM> described above, the cutting element <NUM> is prevented from rotating under cutting forces applied the cutting element <NUM> by the rock, such fixation as would be otherwise be provided by brazing in the prior art. In other words, a substantial portion of the lateral surface <NUM> provides a keyseat for the cavity wall, and the cavity wall provides a key for the portion of the lateral portion <NUM> of the cutting element <NUM> contacted by the cavity wall.

The wall <NUM> or a portion of the wall <NUM> of the cavity <NUM> is also flared such that it points inward in the direction toward the leading face <NUM> of the blade <NUM>. The wall <NUM> of the cavity <NUM> is shaped to engage the lateral surfaces <NUM> and/or <NUM> of the cutting element <NUM> (shown in <FIG>). As such, the blade <NUM> can be thicker around the second opening in the leading face <NUM> of the blade than when the cavity is formed for receiving a cutting element having a straight cross-section. Thus, the cutting element <NUM> may be mechanically retained in the cavity <NUM> by the blade <NUM> and may not fall off through from the second opening in the leading face <NUM> of the blade <NUM>.

The cutting element <NUM> may or may not include a substrate <NUM> attached to an ultra-hard table <NUM>, and may thus consist of an ultra-hard table <NUM> in some embodiments.

<FIG> differ from <FIG> at least by the shape of the retainer <NUM>. In <FIG>, the retainer <NUM> has a cross-sectional shape of a rectangle combined with a semicircle. In <FIG>, the retainer <NUM> has a cross-sectional shape of a circle.

<FIG> illustrates an alternative method for mounting a cutting element <NUM> of a type disclosed in the description of <FIG>. The blade <NUM> includes a fixed portion <NUM>, which may be integral to the bit body, and a plate <NUM>, which may be releasably attached to the fixed portion <NUM>. Before the plate <NUM> is attached to the fixed portion <NUM>, the cutting element <NUM> is introduced into the cavities <NUM> that is formed into the plate <NUM> from a back (i.e., opposite the leading face <NUM>) opening of the cavity. The cutting element <NUM> is then advanced until it engages the wall of the cavity <NUM>. The plate <NUM> is then attached to the fixed portion <NUM>, such as by using a screw. Other means for attaching the plate <NUM> to the fixed portion <NUM> may include a dovetail joint, an adhesive, or other known means capable of attaching the plate <NUM> to the fixed portion <NUM> during drilling. The fixed portion <NUM> of the blade <NUM> abuts the cutting element <NUM>. After attachment of the plate <NUM>, a central surface of the plate <NUM> forms at least a portion of the leading face <NUM> and a lateral surface of the plate <NUM> forms at least a portion of the edge <NUM> of the blade <NUM>. The cutting element <NUM> may or may not include a substrate <NUM> attached to an ultra-hard table <NUM>, and may thus consist of an ultra-hard table <NUM> in some embodiments.

<FIG> illustrate cutting elements <NUM> that have cross-sectional shapes of a type disclosed in the description of <FIG> or <FIG>, and a lateral surface <NUM> that neither flares out nor contracts. In contrast with the cutting elements <NUM> illustrated in <FIG>, which have a lateral surface that is flared, the cutting elements <NUM> illustrated in <FIG> could slide inside the cavity <NUM>, and fall off the earth-boring bit through the opening in the leading face <NUM> of the blade <NUM>. In order to avoid the cutting elements <NUM> from falling off, the lateral surface <NUM> of the cutting elements <NUM> include one or more concave depressions <NUM>, wherein each of the concave depressions <NUM> is surrounded by a corner <NUM> formed at the interface between the concave depression <NUM> and the remainder of the lateral surface <NUM>. The number of depressions <NUM> preferably depends on the order of symmetry of the cutting elements <NUM>, for example, three depressions <NUM> are shown in <FIG> and two depressions <NUM> are shown in <FIG>. Furthermore, one or more through-holes <NUM> are formed in the substrate <NUM> of the cutting element <NUM> such that one through-hole <NUM> leads to each of the concave depression <NUM>. The through-holes <NUM> are sized for introducing an elongated tool in them. The elongated tool is used as described hereinafter.

<FIG> illustrate a method of retaining cutting elements <NUM> of a type illustrated in <FIG> inside cavities <NUM> in the blade <NUM>. A retainer <NUM> is positioned and can remain in the cavity <NUM>. For example, the retainer <NUM> illustrated in <FIG> comprises a ball and a spring, wherein the spring is disposed between the wall <NUM> of the cavity <NUM> and the ball. In other embodiments, the retainer <NUM> can comprise a peg and a spring, wherein the spring is disposed between the wall <NUM> of the cavity <NUM> and the peg, such as illustrated in <FIG>. In other embodiments, the retainer <NUM> can comprise a threaded setscrew engaged with threads formed on the wall <NUM> of the cavity <NUM>, such as illustrated in <FIG>. The retainer <NUM> is movable between a first position, as shown in <FIG>, and a second position, as shown in <FIG>. In the first position, the retainer <NUM> is engaging the concave depression <NUM>. The corner <NUM> is sufficiently sharp so that the retainer <NUM> essentially remains in the first position when the cutting element <NUM> applies a side force to the retainer <NUM>. The positioning of the retainer <NUM> in the first position, combined with the cross-sectional shapes of a type disclosed in the description of <FIG> or <FIG>, completely retains the cutting element <NUM> in the blade <NUM> mechanically. In the second position, the retainer <NUM> is offset from the lateral surface <NUM> of the substrate <NUM> so that the cutting element <NUM> can be released from the blade <NUM>. For example, the retainer <NUM> may be pushed from the first position into the second position with an elongated tool (shown in ghost line in <FIG>), that has been introduced in the through-hole <NUM>. Alternatively, the retainer <NUM> may be unscrewed with an elongated tool that has been introduced in the through-hole <NUM>, until the retainer <NUM> reaches a second position, wherein the retainer <NUM> is offset from the lateral surface <NUM> of the cutting element <NUM> so that the cutting element <NUM> can be released from the blade <NUM>.

The rotational symmetry of the cutting elements <NUM> of a type illustrated in <FIG> or <FIG> may be utilized to expose a second, sharp cutting surface of the cutting elements <NUM> once a first cutting surface of the cutting elements <NUM> is worn. Accordingly, a method of using these cutting elements may involve the steps of using an earth-boring bit whereby the first surface of the cutting element <NUM> wears, releasing the cutting element <NUM> from the blade <NUM>, turning the cutting element <NUM> around the longitudinal axis <NUM>, and retaining the cutting element <NUM> in the blade <NUM> in a position such that a second surface of the cutting element <NUM> that is not worn is exposed.

<FIG> illustrate a cutting element <NUM> that has a lateral surface <NUM> that is shaped like a funnel, so that the blade can be thicker behind the opening in the edge <NUM> of the blade <NUM> than when the cavity is formed for receiving a cutting element having a cylindrical lateral surface. Accordingly, the cutting element may be mechanically retained in the cavity by the blade. The cutting element <NUM> may or may not include a substrate <NUM> attached to an ultra-hard table <NUM>, and may thus consist of an ultra-hard table <NUM> in some embodiments.

The cutting element <NUM> includes a first longitudinal portion <NUM> and a second longitudinal portion <NUM>. For example, the first longitudinal portion <NUM> and/or the second longitudinal portion <NUM> may be cylindrical, such as shown. The first longitudinal portion <NUM> may be adjacent to the second longitudinal portion <NUM>, such as shown, or a transitional portion (not shown) may be provided between the first longitudinal portion <NUM> and the second longitudinal portion <NUM>. The first longitudinal portion <NUM> has a first central axis <NUM>, and the second longitudinal portion <NUM> has a second central axis <NUM> that is parallel to, and offset from, the first central axis <NUM>. As shown in <FIG>, the first longitudinal portion of the cutting element protrudes from the cavity <NUM> through the opening in the edge <NUM> of the blade <NUM>.

<FIG> illustrates the cutting element <NUM> shown in <FIG> after it is positioned and retained in a cavity <NUM> of the blade <NUM>. A first section of the first longitudinal portion <NUM> that is perpendicular to the first central axis <NUM> has a first maximum width. The first maximum width is such that the first longitudinal portion <NUM> of the cutting element <NUM> protrudes from the cavity <NUM> through the first opening in the edge <NUM> of the blade <NUM> and provide sufficient exposure for the cutting element <NUM> to crush or shear rock. A second section of the second longitudinal portion <NUM> that is perpendicular to the second central axis <NUM> has a second maximum width that is smaller than the first maximum width. The first maximum width and the offset are such that the second longitudinal portion <NUM> of the cutting element is entirely recessed into the blade <NUM>, thus increasing the thickness of the blade <NUM> behind the first opening in the edge <NUM> of the blade <NUM>. Furthermore, the direction of the offset of the second central axis <NUM> relative to the first central axis <NUM>, illustrated downward in <FIG>, is such that the blade <NUM> behind the first opening in the edge <NUM> of the blade <NUM> is thicker than with other directions of the offset, for example, an upward direction.

<FIG> also illustrates a method of retaining cutting elements <NUM> of a type illustrated in <FIG> inside cavities <NUM> in the blade <NUM>. A through-hole <NUM> is formed in the blade <NUM> instead of in the substrate <NUM> as shown in <FIG>, and leads to a retainer <NUM>. In the example of <FIG>, the retainer <NUM> comprises a threaded setscrew engaged with threads formed on the wall <NUM> of the cavity <NUM>.

As shown in <FIG>, the retainer <NUM> is in a first position wherein the retainer <NUM> engages a concave depression <NUM> so that the cutting element <NUM> is mechanically retained in the blade <NUM>. Similarly to <FIG>, a concave depression <NUM> is formed in the lateral surface of the cutting element <NUM> and is surrounded by a corner <NUM>. In order to release the cutting element <NUM> from the blade <NUM>, the retainer <NUM> may be unscrewed with an elongated tool that has been introduced in the through-hole <NUM>, until the retainer <NUM> reaches a second position, wherein the retainer <NUM> is offset from the lateral surface <NUM> of the cutting element <NUM> so that the cutting element <NUM> can be released from the blade <NUM>.

In other embodiments, cutting elements <NUM> of a type illustrated in <FIG> may alternatively be retained inside cavities <NUM> in the blade <NUM> using the retainer <NUM> illustrated in <FIG>. In these embodiments, the substrate of the cutting elements <NUM> would include a through-hole leading to the concave depression <NUM>, and the through-hole <NUM> formed in the blade <NUM> would be omitted.

While <FIG> illustrates a method of retaining cutting elements <NUM> of a type illustrated in <FIG> inside cavities <NUM> in the blade <NUM>, it should be appreciated that a similar method may be used to retain cutting elements of a type described in <FIG>. In such embodiments, the through-hole <NUM> formed in the substrate of the cuttings elements <NUM>, as illustrated in <FIG>, would again be omitted.

<FIG> illustrate a cutting element <NUM> that has a rotational symmetry of order eight. <FIG> illustrates a portion of the cutting element <NUM> shown in <FIG>. As best seen in <FIG>, the cutting element <NUM> has a section that is perpendicular to its longitudinal axis having a contour line that includes a first line portion <NUM>, a second line portion <NUM>, a third line portion <NUM>, and a fourth line portion <NUM>, as previously described in <FIG>. The remainder of the contour line <NUM> is derived from the rotational symmetry of the cutting element <NUM>. As best seen in <FIG>, the cutting elements <NUM> has a plurality (eight in this embodiment) of lateral surfaces <NUM> that are flared as well as a lateral surface <NUM> that is cylindrical, in a way similar to the lateral surfaces previously described in <FIG>. The cutting element <NUM> may or may not include a substrate <NUM> attached to an ultra-hard table <NUM>, and may thus consist of an ultra-hard table <NUM> in some embodiments.

The cutting element <NUM> can be received in a cavity is formed in a blade. The wall or a portion of the wall of the cavity is also flared such that it has a plurality of surfaces (e.g., eight or six surfaces in this embodiment) that point inward in the direction toward the leading face of the blade. The wall of the cavity is shaped to engage the lateral surfaces <NUM> and/or <NUM> of the cutting element <NUM>. As such, the blade can have a plurality of regions that are thicker around the opening in the leading face of the blade than when the cavity is formed for receiving a cutting element having a straight cross-section. The regions that are thicker around the opening in the leading face <NUM> of the blade <NUM> engage a corresponding number of lateral surfaces <NUM> of the cutting element <NUM>. Thus, the cutting element <NUM> may be mechanically retained in the cavity by the blade.

While the embodiment of <FIG> illustrates a cutting element <NUM> that has a rotational symmetry of order eight, in other embodiments, the cutting element <NUM> may have another order of symmetry, such as two as shown in <FIG>, or more.

<FIG> illustrate a cutting element <NUM> that has a rotational symmetry of order two. As best seen in <FIG>, the cutting element <NUM> has a section that is perpendicular to its longitudinal axis having a contour line that includes a first line portion <NUM>, a second line portion <NUM>, a third line portion <NUM>, and a fourth line portion <NUM>, similar to the line portions previously described in <FIG>. In this embodiment, the second line portion <NUM> has two intervals 66a and 66b which have a rotational symmetry of <NUM> degrees in this example. Thus, the cutting elements <NUM> has four lateral surfaces <NUM> that are flared as well as a lateral surface <NUM> that is cylindrical. In addition, some points of the second line portion <NUM> are located at distances from the longitudinal axis <NUM> that are equal to R. Furthermore, the second line portion <NUM> is only partially concave, because it has a middle portion that is convex, and to end portions that are concave. For example, the middle and end portions of the second line portion <NUM> may be circular arcs, elliptic arcs, or combinations of circular and elliptic arcs. The cutting element <NUM> may or may not include a substrate <NUM> attached to an ultra-hard table <NUM>, and may thus consist of an ultra-hard table <NUM> in some embodiments.

The cutting element <NUM> shown in <FIG> can be mounted, for example, in the blade <NUM> shown in <FIG>. The blade <NUM> shown in <FIG> is similar to the blade <NUM> previously described in <FIG>, and includes a plate <NUM> and a fixed portion <NUM>. The wall <NUM> or a portion of the wall <NUM> of the cavity <NUM> is also flared such that it has two surfaces 64a and 64b that point inward in the direction toward the leading face <NUM> of the blade <NUM>. The two surfaces 64a and 64b engage only two of the four lateral surfaces <NUM> of the cutting element <NUM> such that the cutting element <NUM> can be mechanically retained in the cavity <NUM>. In other words, each of the two surfaces 64a and 64b provides a key for one of the lateral surfaces <NUM> of the cutting element <NUM>, and each of the lateral surfaces <NUM> provides a keyseat for the cavity wall.

The rotational symmetry of the cutting elements <NUM> of a type illustrated in <FIG> cooperates with the rotational symmetry of the second line portion <NUM> to expose any of the two cutting surfaces <NUM> when the cutting elements <NUM> is mounted in the blade <NUM> as illustrated in <FIG>, and any of the two cutting surfaces <NUM> when the cutting elements <NUM> is mounted in the blade <NUM> as illustrated in <FIG>. As such, the cutting elements <NUM> has four positions that expose a different cutting surface.

While the embodiment of <FIG> illustrates a cutting element <NUM> that has a section having a contour line in which the second line portion <NUM> has two intervals 66a and 66b which have a rotational symmetry of <NUM> degrees, in other embodiments, the second line portion <NUM> may have more than two intervals that have a rotational symmetry. Furthermore, the rotational symmetry may be of an angle that differs from <NUM> degrees.

While the embodiment of <FIG> illustrates a method of mounting a cutting element of a type illustrated in <FIG> in a blade <NUM> that includes a fixed portion <NUM> and a plate <NUM> that is releasably attached to the fixed portion, in other embodiments, a cutting element of a type illustrated in <FIG> may alternatively be mounted in a blade in a way illustrated in <FIG>, that is, using a releasable retainer received through an opening in the edge <NUM> of the blade <NUM> after the cutting element <NUM> is engaged with the wall <NUM> of the cavity <NUM>.

<FIG> and <FIG> illustrate cutting elements <NUM> that have a rotational symmetry of order two. The cutting elements <NUM> have cross-sectional shapes of a type disclosed in the description of <FIG>. The cutting elements <NUM> have at least one lateral surface <NUM> that is contained only in the substrate <NUM> and does not reach the ultra-hard table <NUM>, and a lateral surface <NUM> that is cylindrical. Thus, the cutting elements <NUM> shown in <FIG> and <FIG> are such that at least the cutting face of the ultra-hard table <NUM>, and optionally an entirety of the ultra-hard table <NUM>, has a circular perimeter. However, the cutting face of the ultra-hard table <NUM>, and optionally an entirety of the ultra-hard table <NUM> may have a non-circular perimeter, which may not be dictated by the shape of the lateral surface <NUM>. The lateral surface <NUM> has a longitudinal portion <NUM> that is parallel to a longitudinal axis <NUM> of the cutting element <NUM>; however, the lateral surface <NUM> can alternatively be flared such that it points inwards in the direction away from the cutting face of the ultra-hard table <NUM>. The lateral surface <NUM> provides a keyseat for the wall of the cavity <NUM>.

In other embodiments, a cutting elements similar to the cutting element shown in <FIG> and <FIG> may not have a rotational symmetry of order <NUM> or more. For example, the lateral surfaces <NUM>, which are ilustrated in <FIG> and <FIG> at <NUM> deg. appart may instead be symmetrically opposed at an angle of less than <NUM> deg. appart (e.g., <NUM> deg. In such embodiments, it may not be possible to turn the cutting element around the longitudinal axis in a position such that a surface of the cutting element that is not worn is exposed. However, the blade can be thicker around the opening in the edge of the blade than when the cavity is shaped for receiving a cutting element that his cylindrical.

Like the cutting elements <NUM> illustrated in <FIG>, the cutting elements <NUM> illustrated in <FIG> and <FIG> could fall off the earth-boring bit through the opening in the leading face <NUM> of the blade <NUM>. In order to avoid the cutting elements <NUM> from falling off, the cutting elements <NUM> shown in <FIG> and <FIG> include one or more depressions <NUM>, wherein each of the depressions <NUM> is surrounded by a corner <NUM> formed at the interface between the depression <NUM> and the remainder of the lateral surface <NUM> or <NUM>. Furthermore, a through-hole <NUM> is formed in the substrate <NUM> of the cutting element <NUM> such that the through-hole <NUM> joins the depressions <NUM>. In <FIG>, a width of the through-hole <NUM> is smaller than a width of the corners <NUM> so that each depression <NUM> includes a shoulder <NUM>. In <FIG>, the width of the through-hole <NUM> is equal to the width of the corner <NUM> so that the depressions <NUM> extend the through-hole <NUM>.

<FIG> illustrate the cutting elements <NUM> shown in <FIG>, and a retainer <NUM> that is positioned in the cavity <NUM>. The retainer <NUM> illustrated in <FIG> comprises a peg and a spring, wherein the spring is disposed between the wall <NUM> of the cavity <NUM> and the peg. The retainer <NUM> illustrated in <FIG> comprises a threaded setscrew engaged with threads formed on the wall <NUM> of the cavity <NUM>. Like in <FIG>, the retainer <NUM> is movable between a first position, wherein the retainer <NUM> is engaging the concave depression <NUM>, and a second position, wherein the retainer <NUM> is offset from the lateral surface <NUM> of the substrate <NUM> so that the cutting element <NUM> can be released from the blade <NUM>. For example, the retainer <NUM> may be pushed from the first position into the second position with an elongated tool that has been introduced in the through-hole <NUM>. Alternatively, the retainer <NUM> may be screwed with an elongated tool that has been introduced in the through-hole <NUM>. Regardless of whether the retainer <NUM> is pushed or screwed, the retainer <NUM> allows a quick assembly and disassembly of the cutting element <NUM>, such that repair of a worn cutting element is easy and fast. Because the width of the through-hole <NUM> is smaller than the width of the corners <NUM>, the retainer <NUM> can remain entirely trapped in the concave depression <NUM>, even after failure. Accordingly, portions of the retainer <NUM> may not fall in the well being drilled where these portions could cause damage to the bit or other drilling components.

<FIG> illustrates the cutting elements <NUM> shown in <FIG>, and a retainer <NUM> that is positioned against the shoulder <NUM> and attached to (e.g., threaded into) the blade <NUM>. Unlike the retainer shown in <FIG> and <FIG>, the retainer <NUM> needs to be removed from the cavity <NUM> so that the cutting element <NUM> can be released from the blade <NUM>. Unlike the retainer shown in <FIG>, after the failure of the retainer <NUM>, portions of the retainer <NUM> may fall in the well being drilled.

<FIG> illustrate the cutting elements <NUM> shown in <FIG>, and a retainer <NUM> that is attached to (e.g., threaded into) the blade <NUM>. Again, the retainer <NUM> needs to be removed from the cavity <NUM> so that the cutting element <NUM> can be released from the blade <NUM>. To allow the positioning of the retainer <NUM>, the width of the through-hole <NUM> is dimensioned to be larger than the width of the retainer <NUM>. Therefore, to receive a retainer <NUM> having a similar width as the retainer shown in <FIG>, the width of the through-hole <NUM> located in the substrate <NUM> of the cutting elements <NUM> is larger than the width of the cutting elements <NUM> shown in <FIG>, which may weaken the cutting elements <NUM> compared to other designs. However, the risk of failure of the retainer <NUM> may be lower compared to other designs.

Claim 1:
An earth-boring bit comprising:
a body having a rotational axis;
a blade (<NUM>, <NUM>) extending axially and radially from the body, the blade having a leading face (<NUM>) and an edge (<NUM>);
a cavity (<NUM>) formed in the blade, the cavity leading to a first opening in the edge of the blade, the cavity leading to a second opening in the leading face of the blade;
the cavity being configured to receive a cutting element (<NUM>) and a retainer (<NUM>, <NUM>) through the first opening, the cutting element having a cylindrical lateral surface (<NUM>) and a flared lateral surface (<NUM>) that points inwards in a direction toward a cutting face of the cutting element, a portion of a wall (<NUM>) of the cavity being complementary to a shape of the flared lateral surface of the cutting element;
wherein the cutting element is prevented from rotating inside the cavity after the flared lateral surface of the cutting element is engaged with the portion of the wall of the cavity;
wherein the cavity is configured to receive the retainer after the cutting element is engaged with the portion of the wall of the cavity such that the retainer is capable of abutting the cutting element and a back wall (<NUM>) of the cavity; and
wherein the retainer is releasably attached to the blade.