MXPA01008834A - Roller cone bit with improved seal gland design - Google Patents

Abstract

In the seal gland in a rotating cone drill bit, the O-ring is initially compressed between the journal and a central portion of the gland which has a cross-section parallel to the journal. These two concentric surfaces provide a minimum amount of contact pressure for a given amount of squeeze than other configurations. Chamfers connect the central portion to the sidewalls of the gland, so that after the seal has worn in use, it will ride up onto the chamfers, where additional squeeze will be applied to the seal. This allows the seal to operate in a standard regime during the first part of its lifetime and to automatically shift to a more compressed mode as the seal wears.

Description

ROTATING CONE BARRENA WITH CLOSURE NECK DESIGN Background and synthesis of the invention The present invention relates to the design of a neck closure, especially but not exclusively with the design of a neck for a rotary closure in a remote environment.

Background: Closings of Co inete In applications in which relative movement is necessary, one of several types of bearings is used, such as ball bearings, bearing bearings, and more simply the bearings. A closure, such as an elastomeric seal, that is typically used between the bearings and the outside environment to hold the lubricant around the bearings and to keep contamination out. In a rotating closure, where one surface rotates around the other, some special considerations are important in the design of both the closure itself and the neck in which it is seated. For example, the elastomeric seal must be under compression tension (never tension), and although there must be sufficient pressure between the closure and the rotating surface to prevent dripping, the pressure must be minimized to reduce friction and wear.

Additionally, there should be sufficient space in the neck to allow expansion under changing conditions but not excessive space that could allow the closure to writhe or buckle.

Additional information regarding closures can be found in Practical Closure Design, by Leonard J.

Martini (1984) and in the Closed and Closing Manual, fourth edition, M. Brown (1995), both of which are incorporated herein by reference.

Background: Drills One side of the important types for rotary drills in the petroleum business is the rotary cone bit, seen in FIG. 6. In such drill bits, the rotary cones 42, the teeth 44 on their outer surface are mounted on an arm 46 of the body of the drill. Figure 7 shows a drill rig, which includes a drill bit and an auger string, which include sections of tubes which transfer the rotating force of the drill bit and which convey drilling fluid to the bottom of the borehole, where it washes to outside the rubble. While the drill rotates, the applied forces of weight on the drill ("WOB") the teeth pointing down the rotating cones in the formation that is being drilled. Therefore the tips of the teeth apply a compression tension which exceeds the tension yield of the formation, and this induces the fracture. The resulting fragments are ejected away from the cutting face by an upper flow of drilling fluid, referred to as "mud".

Although improvements have been made to the rotary cone type drill bits over the years, improvements have continued to be a necessity in the closures which protect the bearings. The constraints on the closures used in these applications are different from those of other low-speed closure applications in several aspects. First, everything in a drill, which operates very deep in the earth, must be extremely strong to withstand the pressure and eccentric movement to which the bits are held. Additionally, the closures by themselves are exposed to abrasive materials from two sources: not only the drilling fluid near the cutting face includes a heavy load of abrasive material (which is moving very turbulently at very high speeds), but the same bearings, while wearing down, may tend to produce metal particles, and these metal particles by themselves can be abrasive to a soft seal. Therefore, both sides of the closures should ideally be protected from these abrasive effects. Additionally, the drill is operating in a remote environment from which it can take hours to recover for replacement, so it is very desirable to have the drill operating as long as possible.

For closing in a rock drill, an O-ring, or a ring-0 derivative, are typically used. A problem with this closure is that, while the drill is operating, the closure will inevitably wear out, so a less compressive force is applied against the moving surface, with the risk of a leak developing through of the closing.

A prior neck design can be seen in the United States Patent No. 4,372,624 issued to Neilson and this reproduced in Figure 8. In this patent it can be seen that a ring in 0 of circular cross section is confined within a pair of complementary and symmetrical V-shaped surfaces having rounded corners, a V-shaped surface is formed in a journal within the body of a rock drill, the other V-shaped surface in the cone cutter mounted in the journal . In this design, it allows the O-ring to move axially in response to the differential pressure through the closure, with movement in er direction causing an increase in the closure narrowing. An opposite narrowing is provided if and only if necessary.

Another type of neck design can be seen in U.S. Patent No. 5,129,471 issued to Maurstad et al., And this reproduced in Figure 9. In this neck, two walls are in the moving cone, while the other two are part of the stationary stump. The closure is transported between the surfaces 45 and 46 having flat cross sections, with a skirt or protuberance 48 for pushing the ring at 0 away from the wall 49 and preventing wear.

Improved Closure Neck Design for Low Speed Swivel Application The present inventors have noted that for a given amount of constriction in the closure, the contact pressure through the closure surface is minimal when the closure is compressed between two surfaces whose cross section is flat, as compared to a surface in V or any other surface with a radius. This means that while the neck of Figure 8 provides advantages in the anterior portions of the closure life time, it does not provide an optimum closure in the part at the beginning of the use of the closure.

The present application describes a neck of closure whose shape provides two modes of operation: in the first part of its life, the closure is seated in a part of the base of the neck, which is concentric with the surface and closure of the stump, for that works analogously with a normal elastomeric closure, providing an adequate, pressure as it is installed; but while the closing element wears out and the contact pressure is loosened (resulting in more axial movements with er cone vibration or a small differential pressure), the axial movement of the closure causes it to be additionally compressed by a bevel inside the neck. Unlike previous attempts to solve this problem, this solution seeks to optimize the function of the closure while minimizing wear in both parts of its useful life.

In some embodiments, the present application describes a closure having a cross section which is approximately circular, but with a recess in the side in which the movement occurs, so that the lubricant can be provided therein.

In some additions, this application also describes preventive measures to protect the seal and lubricant from contamination. A gutter trap can be placed circumferentially on the cone or in the bearing of the arm or on the surfaces of the protrusion of the closure. This trap collects and stores bearing wear materials that are generated during rotation of the cone, keeping them out of the sealing surfaces.

In some embodiments, this application also describes a filter on both sides of the closure surface to avoid both the bearing and cutting materials that contaminate the closure surface. This filter takes the form of another ring of a softer elastomeric material, which can inherently wear out more slowly than the closure itself.

The innovations described, in several embodiments, provide one or more of at least the following advantages: * The total life of the closure is improved; Y * The correct amount of pressure is maintained in the closure during its total life.

Brief Description of the Drawings The described inventions may be described with reference to the appended drawings, which show important sample additions of the invention and which are incorporated in the embodiment herein by reference, wherein: Figure 1 shows a sectional view of a cone drill, showing the described neck and closure.

Figure 2 shows a cross-sectional view of the closure surfaces of an embodiment of this invention.

Figure 3 shows an embodiment of the invention in which a channel is designed on the surface of the bearing.

Figure 4 shows a closure having two annular surfaces of contact between the moving surface and the storage of lubricant.

Figure 5 shows placing filter materials on both sides of the closure.

Figure 6 shows a cone drill which can be used on the neck and the closure described.

Figure 7 shows a drill rig which can be used in the described lock / neck combination.

Figure 8 is a closure collar of the prior art which offers increased narrowing if axial change occurs.

Figure 9 is a closing collar of the prior art which pushes the O-ring inwards.

Figure 10 is an analysis of the finite element of output showing the distribution of pressure in the closure after its installation.

Figure 11 is an analysis of the finite output element showing the pressure distribution in the compressed closure once it has been changed in the bevel, causing an increased contact.

In Figures 12 to 15 are finite element analyzes of alternate incorporations of necks having a filter / sleeve on the side of the closure opposite the core.

Detailed Description of Preferred Additions The numerous innovative teachings of the present application may be described with particular reference to the current preferred embodiment (by way of example, and not limitation).

Truncated cone-shaped neck Seen in Figure 1 is a sectional view of a part of a rotary drill. Seen in outline is an outer surface of the rotating cone 10, while the journal 12 with the rotary bearing journals 14 and the ball bearings 16 are viewed while adjusting in the cone. The closure 20 and the neck 22, which rest within the cone while rotating around the stump, are seen in section which show their cross sections.

Figure 2 shows a cross-sectional view of the closure surfaces of an embodiment of this invention, with the journal on the left and the rotating cone on the right (the closure itself is not shown). In this embodiment, the closing collar is seen as a chute formed in the lower part of the cone. The cross section of the neck shows a central planar area 24 attached to both sides of the chamfers 26 which connect the flat area to the side walls 28. The trunnion forms an additional wall 29 of the neck. It can be understood that the two surfaces in this drawing between which the closure is compressed (for example 24 and 29) are actually concentric cylindrical walls.

The dimensions of the neck have been determined by finite element analysis (FEA), a computer-assisted technique which helps predict the response of physical systems to the external load. Using this technique, it has been determined that the angle of the chamfers to the flat area (and 0), in the current preferred embodiment, are in the range of 110 to 150 degrees. The central section, in the current preferred embodiment, has a width, which is approximately 40 to 60% of the diameter of the cross section of the closure. When the O-ring is seated in the neck, it will be under light compression forces which force the closure to sit in the deepest part of the neck, for example, against the flat central part 28. Figure 10, shows a finite element analysis of the closure after the cone is joined in the stump. In the axial direction, there is a slight groove, so that the closure is not compressed in this direction. It is worth noting that although the cone is the moving part of the bit, the closure moves with the cone, so that the moving surface is between the closure and the wall 29. After that a significant part of its The useful life has passed, the closure may show enough wear that the pressure that holds it in place is loosened. Small differential pressures between the bearing lubricant and the external environment may cause the seal to be changed axially in the chamfers. This causes an additional narrowing to be applied to the closure, compensating for wear. Figure 11 which is a finite element analysis of the closure once it has changed in the bevel.

Alternate Incorporation: Bevel on One Side In an alternate embodiment, the neck has a larger flat area, which extends from the upstream side to the differential pressure of a bevel on only one side of the flat area. This incorporation is not optimal for use in a drill, where small differential pressures can occur in any direction, but for applications where differential pressure is in one direction only, this is a viable alternative.

Alternate Incorporation: Bevel in the Stump In a less preferred embodiment, the chamfers are formed in the stump instead of, or in addition to, the rotating cone. This is less desirable, since the movement in the chamfers may then result in an additional contact area on the dynamic surface, which increases wear.

Alternate Incorporation: Bevel Angles That Differ Although the angles o; and 0 may generally be the same, this is not necessary for the practice of the invention. If it is known that a higher pressure can be applied in one direction than in the other, the two angles can be adequately measured to provide different amounts of narrowing in the O-ring.

Alternate Incorporation: Bianular Closure In an alternate embodiment, the cross section of the elastomeric closure is observed in Figure 4. In this embodiment, in the portion of the closure 20 'which contacts the die has a layered shape so that the closure (in the section transverse) touch the stump in only two points which are axially separated. This is the contrast with the most common form (or derivative) ring at 0, in which a segment of the circumference of the closure is compressed against the stump. The two-point contact effectively acts as two separate closures, while the inner, concave part of the closure provides storage for a lubricant 35. Both the same two-point contact and the lubricant carried by the closure reduce the friction noted on this surface and it improves the life of the closing.

Alternate Incorporation: Canaleta Trap In an alternate embodiment of the invention, a circumferential trough is provided either in the stump or in the cone between the journal and the closure. Figure 3 shows such channel 30 positioned on the surface of the stump. This gutter, which opens into the space which separates the stump from the cone, provides a place where the bearing material is carried by the lubricant, can be deposited outside before reaching the closure, and can be designed in either the stump or in the cone.

Alternate Incorporation: Aggregate Filter In another aspect of the invention, the "filters" can be placed along the side walls of the closure neck. These filters are rings made of an elastomer softer than the closure itself, ensuring that they wear less than the closure. The filters act to trap bearing wear material that migrates from the wax sums on one side to a highly abrasive drilling mud trap on the other side of the seal. An example of a locking collar having two filters 32 as shown in Figure 5.

Alternate Incorporations: Other Forms / Filter Locations As can be seen in figures 12 and 15, there are the analysis of finite element analysis, the closure using alternative incorporations for the shape and location of the filter. Note that in these embodiments, the shape of the neck is modified to accommodate an elastomeric filter / sleeve 34 in the wall of the neck opposite the core, with the sleeve filling the groove between the core and the cone where this groove is exposed to the drilling mud. . When the closure is armed, the O-ring 20 finds its stable seating position between the stump and the filter material.

Figures 12, 13, and 14 each show a sleeve with slightly different geometries, while Figure 15 shows an elastomeric sleeve with a polymer / metal material around it.

Alternate Incorporation: Spare Ring In an alternate embodiment, a spare ring, formed of a material more rigid than the 0-ring, can be added to provide lateral support.

Alternate Incorporation: Belleville Ring In an alternate embodiment, a Belleville can be added to apply a lateral preload inside the neck.

Alternate Incorporation: Other Types of Closures In an alternate embodiment, the described closure and neck can be used in other types of closure applications, such as a front closure.

Definitions What follows are short definitions of the usual meanings of some technical terms which are used in the present application. (However, those with ordinary ability will be able to recognize whether the context requires a different meaning). Additional definitions can be found in journals and in standard technical dictionaries.

Neck: a box or cavity to accommodate sealing rings or compression gaskets.

Closure: a device for closing (sealing) a groove and / or making it fluid-tight.

Rotary drill: a drill made of two, three, or four cones, or cutters, which are mounted on extremely resistant bearings. Also called drill bits for rock.

Narrowing: deformation of a closure produced when it is armed with an interference fit; Note that a narrowing of excessive should be avoided as this can over stress the material and cause premature aging.

According to a described class of innovative embodiments, there is provided: a structure, comprising: an elastomeric closure element positioned at a position at the base, between two concentric surfaces, to operate stably while providing a closure at said base position; and a mechanical structure, positioned to apply a compression to said closure element after said closure element is sufficiently worn to change out of said base position under pressure.

According to another described class of innovative embodiments, there is provided: a closure structure, comprising: a trough having a cross section which is substantially rectangular with at least one chamfered corner; an elastomeric closure which fits in said channel, providing a closure with a closing force which opposes said channel in such a way that during a first substantially phase of its life, said elastomeric closure is not substantially compressed by said chamfered corner, but during a subsequent substantial phase of its life, said elastomeric closure is compressed by said chamfered corner; so the longevity of said closure is improved.

According to another class described in innovative embodiments, there is provided: a rotary closure for use under a known maximum working pressure differential, comprising: a neck in a first element for a rotary joint; a closure surface on a second element of said rotary joint, said closure surface being smooth and positioned in the vicinity of said neck; and a compression sealing element interposed between said neck and said closing surface; wherein said neck includes not only side walls, but also a basic seating position between said side walls, and a bevel between said basic seating position and a first of said side walls; and wherein said closure element, said neck and said closure surface have relative dimensions such that for a first substantial part of the operating life of said closure element, said closure element is compressed, between said basic and said closing surface, sufficient to support said expected pressure differential, and after the dimensions of said closing element are changed by the wear, said closing element can automatically be changed by said expected pressure differential in said bevel within said neck, to provide an increase in compression to said closure element against said closure surface.

According to another described class of innovative incorporations, there is provided: a rotating closure, comprising: a closing surface in a first element of a rotary joint; a neck in a second element of said rotary joint, said neck has a first surface which is concentric with said closing surface, the side walls which are axially spaced from said first surface, and a bevel which connects said first surface to one of said side walls; a compression closure element interposed between said neck and said closing surface.

According to another described class of innovative embodiments, there is provided: a rotating drill, comprising: a rotating cutting element mounted on an arm of said rotating drill; a channel in said cutting element, having a cross section which is substantially rectangular with at least one chamfered corner; an elastomeric closure which fits in said gutter, which provides a closure with a closing force which opposes said gutter in such a way that during a first substantial phase of its life, said elastomeric closure is not substantially compressed by said chamfered corner, but during a subsequent substantial phase of its life, said elastomeric closure is compressed by said chamfered corner.

According to another described class of innovative incorporations, there is provided: a drilling rig, comprising: an auger string which is mounted on a rotating drill, said rotating drill containing a channel having a cross section which is substantially rectangular with at least one chamfered corner; an elastomeric closure which fits in said channel, which provides a closure with a closing surface which opposes said channel in such a way that during a first substantial phase of its life, said elastomeric closure is not substantially compressed by said chamfered corner, but during a subsequent substantial phase of its life, said elastomeric closure is compressed by said corner to chamfered.

According to another described class of innovative embodiments, there is provided: a method for operating a closure, comprising in the steps of: (a) during a first part of the life of a closing element being compressed, the compression of said closing element between two concentric surfaces; (b) then, that additional compression of a mechanical element is provided which compensates for wear on said compression closure element.

According to another described class of innovative embodiments, there is provided: a method of protecting a journal, comprising the steps of: (a) installing a closure element between two cylindrical surfaces with sufficient initial elastic load to provide a closure between said bearing and an external environment; (b) providing an additional surface on which said closure element can move only after wear degrades said closure element, said additional surface providing sufficient elastic load to maintain said initial elastic load.

Modifications and Variations As will be recognized by those with a skill in the art, the innovative concepts described in the present application can be modified and varied over a tremendous range of applications, and therefore the scope of the patented subject is not limited by any of the teachings specific specimens given.

Claims (22)

R E I V I N D I C A C I O N S

1. A sealing structure comprising: an elastomeric sealing element positioned in a base position, between two concentric surfaces, to operate stably while providing a seal in said base position; Y a mechanical structure, positioned to apply pressure to said sealing element after said sealing element has worn out enough to shift outward from the base position under pressure.

2. The sealing structure as claimed in clause 1, characterized in that the width of one of said two concentric surfaces is 40-60% of the cross-sectional diameter of said elastomeric seal.

3. The sealing structure as claimed in clause 1, characterized in that said mechanical structure is a bevel that connects one of said two concentric surfaces to a third surface which is normal to said concentric surfaces.

4. A sealing structure comprising: a groove having a cross section which is essentially rectangular with at least one bevelled corner; an elastomeric seal which fits within said groove, providing a seal with a sealing surface which opposes said groove in such a manner that during a first substantial phase of its life time, said elastomeric seal is not essentially compressed by said bevelled corner , but during a subsequent substantial phase of its life time, said elastomeric seal is compressed by said bevelled corner; so the longevity of said seal is improved.

5. The seal as claimed in clause 4, characterized in that said elastomeric seal is separated from a side wall of said neck by a ring of material which is softer than the material of said compressible sealing element.

6. The seal as claimed in clause 4, characterized in that said elastomeric seal makes contact with the sealing surface in two places which are axially separated from each other.

7. A rotary seal for use under a known maximum working pressure difference, comprising a neck in a first element of a rotary joint; a sealing surface in a second element of said rotary joint, said sealing surface being smooth and being positioned in proximity to said neck; Y a compressible sealing element interposed between said neck and said sealing surface; wherein said neck includes not only the side walls, but also a basic sitting position between said side walls, and a bevel between said basic seating position and a first of said side walls; Y wherein said sealing element, said neck and said sealing surface have relative dimensions, so that for a first substantial part of the operating life of said sealing element, said sealing element is compressed between said basic seating position and said sealing surface, sufficiently to support said expected pressure difference, and then the dimensions of said sealing element are changed by wear, said sealing element can automatically be changed by an expected pressure difference on said bevel inside said neck to provide an increased compression of said sealing element against said sealing surface.

8. The seal as claimed in clause 7, characterized in that said compressible sealing element is separated from a side wall of said neck by a ring of a material which is softer than the material of said compressible sealing element.

9. The seal as claimed in clause 7, characterized in that said elastomeric sealing element makes contact with said sealing surface in two places which are axially separated from each other.

10. The seal as claimed in clause 7, characterized in that the angle formed by said bevel and said -position of basic settlement is 110-150 degrees.

11. The seal as claimed in clause 7, characterized in that the width of said base seating position is 40-60% of the cross-sectional diameter of said compressible sealing element.

12. A rotating seal that includes: a sealing surface in a first element of a rotary joint; a neck in a second element of said rotary joint, said neck having a first surface which is concentric with said sealing surface, side walls which are axially spaced from said first surface, and a bevel which connects said first surface to a of said side walls; a compressible sealing element interposed between said neck and said sealing surface.

13. The rotary seal as claimed in clause 12, characterized in that said compressible sealing element is separated from a side wall of said neck by a ring of material which is softer than the material of said compressible sealing element.

14. The seal as claimed in clause 12, characterized in that said compressible sealing element makes contact with said sealing surface in two places which are axially separated from each other.

15. The seal as claimed in clause 12, characterized in that the angle formed by said bevel and said first surface is 110-150 degrees.

16. A rotating cone drill that includes: a cutting element rotatably mounted on an arm of said rotating cone drill; a groove in said cutter element, having a cross section which is essentially rectangular with at least one beveled corner; an elastomeric seal which fits within said groove providing a seal with the sealing surface opposing said groove such that during a first substantial phase of its life, said elastomeric seal is not essentially compressed by said beveled corner, but during a subsequent substantial phase of its life, said elastomeric seal is compressed by said beveled corner.

17. A drilling rig comprising: a drill string on which a rotating cone drill is mounted, said rotating cone drill contains a groove having a cross section which is essentially rectangular with at least one bevelled corner; an elastomeric seal which fits within said groove, providing a seal with a sealing surface to which it opposes said groove in such a manner that during a first substantial phase of its life, said elastomeric seal is essentially not compressed by said corner beveled, but during a subsequent substantial phase of its life, said elastomeric seal is compressed by said bevelled corner.

18. A method for operating a seal, comprising the steps of: (a) during a first part of the life of a compressible sealing element, compressing said sealing element between two concentric surfaces; (b) later, providing additional compression from a mechanical element which compensates for wear on said compressible sealing element.

19. The method as claimed in clause 18, characterized in that said two concentric surfaces are a journal and a cone respectively of a rotating cone drill.

20. The method as claimed in clause 18, characterized in that the additional compression is provided by a bevel on which the sealing element moves after wear.

21. A method for protecting a bearing comprising the steps of: (a) installing a sealing element between two cylindrical surfaces with an initial elastic load sufficient to provide a seal between said bearing and an external environment; (b) providing an additional surface on which said sealing element can move only after wear degrades said sealing element, said additional surface providing a sufficient elastic load to maintain said initial elastic load.

22. The method as claimed in clause 21, characterized in that the bearing is part of a rotating cone drill. SUMMARY In the closing collar on a rotating cone drill, the O-ring is initially compressed between the stump and a central part of the neck which has a cross section parallel to the stump. These two concentric surfaces provide a minimum amount of contact pressure for a given amount of tightening than other configurations. The bevels are connected to the central part of the side walls of the neck, so that after the closure has worn out in use, it will run over the bevels, where the additional tightening will be applied to the closure. This allows the seal to operate in a normal mode during the first part of its life and to automatically switch to a more compressed mode when the seal or seal is worn out.