DRILL BIT
The proposed device relates to roller drill bits with air drilling capability and can be used for drilling of rocks of high hardness. The drill bit includes a body and rock-destroying elements with cutting equipment mounted on the body one inside the other by means of bearing supports, wherein the inner element is located at an angle relatively to the axis of the drill bit, and the outer element is located in the opposite direction of the axis. The device provides for an increase of the service life, high efficiency, and interchangeability due to a special design, which envisages the cutting equipment formed as replaceable jet nozzles made of hardwearing material and provided with arm insertions, preferably made of wolframite-cobalt based alloy, wherein the bearing support of each rock-destroying element is furnished with a unit adjusting the axial play value of the rock-destroying elements.
This application is a U.S. national stage application of a PCT application PCT/UA2010/000054 filed on 2 Sep. 2010, published as WO/2011/028193, whose disclosure is incorporated herein in its entirety by reference, which PCT application claims priority of a Ukrainian application UA a2009 09105 filed on 4 Sep. 2009.
FIELD OF THE INVENTIONThe invention relates to a rock-destroying tool, more specifically to roller drill bits with air drilling ability. The tool can be used for drilling rocks of a high and highest hardness by an open-cut method during wellbore drilling operations in the mining and metal mining industries.
BACKGROUND OF THE INVENTIONKnown roller drill bits are typically supplied with roller cutters mounted on the leg axles by means of a retaining ball bearing and two roller bearings, wherein both roller bearings are tapered and a retaining ball bearing is located between them. (USSR Certificate of Inventorship No 1229297, MIIK4 E 21 B 10/22, publ. 7 May 1986, Bulletin No 17).
Such a drill bit has the following disadvantages:
1) The widespread disadvantage of modern drill bits with tapered roller cutters, especially those that are aimed at drilling of hard rocks, is considered to be insufficient weight-supporting capacity of drill bit legs. It is known that the bearing support of one section (leg) of a common tricone roller drill bit is manufactured according to one of the following arrangements: “roller-ball-roller” or “roller-sliding ball”. Even the companies that are famous world leaders in the industry manufacture such drill bits, in which the allowed load onto the drill bit legs is equal only to 60-70% of the size, which is taken to be optimal for the effective drilling of hard rocks. As known, the main reason of failures of drill bits is a breakage or locking of the leg of one of the roller cutters (it makes more than 80% of the failures). For example, in 2007 at the drilling of rocks in Krivoy Rog iron ore basin, the average drilling depth was 166 meters (rocks with the rigidity factor f=16-19 according to Protodyakonov scale). With that the service life of hard-alloy cutting structure of a drill bit several times exceeds the service life of the drill bit legs.
2) The bearing support of one section (leg) of a tricone drill bit with tapered roller cutters takes up approximately one-third of the load applied onto the drill bit. Since the axle of each leg extends at an angle of about 37-39° to the horizontal, the total load applied onto one leg can be represented as having radial and axial components. The radial component of the load applied onto the support is sustained only by the end and peripheral roller bearings and is distributed between them in the ratio of 35 and 65% accordingly (see e.g. Drill Bits. Digest. Publication 3. Palyi P. A. Korneev K. E. “Depths”. 1971, page 446). Each bearing of the support, in particular, the bearing race on the axle, bears the load at the limit of metal capacity of the axle, rollers and roller cutters.
3) The difference in design of the legs, bearing assemblies and roller cutters of the drill bits aimed at drilling of soft rocks, rocks of middle hardness and hard rocks, is so significant that the possibility of standardization of compounding elements even for drill bits of the same size is absolutely impossible. This is exactly the reason why roller drill bits are expensive.
4) The axial component of the load applied onto the bearing support is a variable and negative value, which has no influence on rock destroying characteristics of the drill bit. It is directed along the axis of the axle and it makes more than 60% of the total load onto one support. The thrust load in the traditional “roller-ball-roller” support is taken up by a double-direction retaining ball bearing. It holds the thrust loads, which are directed, both in the direction of the end bearing and in the opposite direction, i.e. in the direction of base of the axle. Double-sided loads lead to a fast wearing-out of the retaining ball bearing and cause a large axial play. It is known that when there is a play of 3-5 mm in the support, a skew of cylindrical rollers respectively to the bearing races occurs and the seizure of the supports takes place, wherein a load area angle of the tapered roller bearings is dramatically lowering.
There is known a drill bit open bearing support, which has a leg with an axle, a roller cutter, a peripheral retaining tapered roller bearing mounted close to the base of the axle, and an end tapered roller bearing, on which the roller cutter is arranged. Herewith, the peripheral bearing is fixed on the axle and in the body of the roller cutter by means of spring rings. The end bearing is mounted on the axle so as to be freely axially (longitudinally) rotatable and it thrusts against the axle's shoulder through a belleville spring. In this variant, the support comprises a tapered roller bearing, a cylindrical roller bearing and a roller thrust bearing. (International PCT application No WO 2005/021923 A1, MIIK7: E 21 B 10/22. Date of international publication: Mar. 10, 2005).
The above described drill bit has the following disadvantages:
1) It does not include the traditional double-direction retaining ball bearing of the support, but, instead an (imaginary) function of the retaining bearing has been centered on the peripheral tapered roller bearing, though it is known that the latter is capable to take up only one-sided thrust load. The support design concept of such a drill bit (FIG. 1, 2 of the drawings attached to PCT application No WO 2005/021923) includes images of typical single-row tapered roller bearings of type 7000. Type 7000 is the principal one according to GOST 333-71(R. D. Beyzelman, B. V. Tsypkin, L. Ya. Perel. Bearings. Digest. Publication b, M. “Mechanical Engineering”, 1975, p. 52-53. Further referred to as the Digest). The contact angle of 7000 type bearings is α=10-17°. Also, the single-row tapered roller bearings are capable to deal only with one-sided thrust load. The allowed thrust load applied onto the 7000 type bearings cannot exceed 70% of the allowed radial load that was not used. As mentioned above, the end roller bearing of the traditional tricone roller drill bit holds about 35% of the radial load on the support. This value balances upon the material strength limit of the bearing races and the bearing rollers. The additional thrust load, the value of which by 2-2.5 times exceeds the allowed radial component of the end bearing load, may become a reason for fatal failure of the end bearing and locking of the roller cutter leg.
2) The inner ring of the end bearing of the analogue of the drill bit is mounted on the axle so as to be randomly (spontaneously) rotatable along the axis of the axle, which comprises a cylindrical shoulder from the side of the peripheral bearing. The belleville spring being provided between the shoulder and the inner ring of the end bearing assumes to ensure the preliminary axial tension and the power closure of the elements of both roller bearings, which allegedly eliminates the possibility of axial play (backlash) in the support.
However, kinetostatic analysis over the interaction of components of the support of the foregoing drill bit has shown the following:
a) When roller cutter body is immovable by convention (the body of the roller cutter is supported by an absolutely rigid surface), the radial component of the load applied onto the axle (leg) is distributed between two roller bearings (FIG. 1 of PCT application No WO 2005/021923). Through the cylindrical shoulder on the axle, the thrust load comes at full on the belleville spring and deforms it deeply. Since all the elements of the end roller bearing are already closed between each other and with the roller cutter body, the only available direction for the movements in the support is longitudinal rotation of the axle through the inner ring hole of the end bearing in the direction of the top of the roller cutter. In this respect, the inner ring of the peripheral tapered roller bearing together with the tapered rollers, the retainer and the axle will move in the direction of the roller cutter's top. The imaginary retaining peripheral roller bearing opens up consequently, since the rollers located above the axis of the axle are not capable any more to come in contact with the outer ring. Therewith the radial play exceeds the allowed specified value by several times (Digest, p. 168, table 14). As a result, the load area angle of the bearing is dramatically lowering (down to a value of 60-90° instead of an optimal value of 170-180°), and the pressure applied to the elements of the bearing may exceed marginally the allowed value.
b) When the axle is immovable by convention, the axial component of the load onto the roller cutter is directed along the axis of the axle in the direction of its base. Through the roller cutter's body, the outer ring, rollers and the inner ring of the end bearing, the thrust load comes at full on the belleville spring and deforms it deeply. With that, the body of the roller cutter, the end bearing, the belleville spring, and the outer ring of the (imaginary) retaining peripheral tapered roller bearing will move in the direction of the axle base by a value equal to the size of deformation of the belleville spring. The (imaginary retaining) peripheral roller bearing opens up again, its radial play grows quickly and the load area angle of the bearing lowers dramatically. Taking into account the fact that when operating the loads applied onto the supports of the roller cutters of the drill bit are drilling and repeating in any case, the additional axial and radial vibrations in the supports will have an extremely negative influence on the service life of the drill bit. That's exactly why the radial and axial plays in any support are aimed to be minimal and strictly limited. The main disadvantage of the support design of the aforesaid drill bit is that the imaginary peripheral retaining tapered roller bearing in reality doesn't have any influence on the value of the axial play in this support.
3) Another type of the bearing support of another drill bit (FIG. 2 of PCT application No WO 2005/021923) known in the related art, comprising one single-row tapered roller bearing, one roller bearing with cylindrical rollers, and one thrust ball bearing, doesn't comply with the simple rules of use of tapered and thrust bearings, in particular:
a) Single-row tapered roller bearings should build at least one pair in the support (Digest, p. 53 paragraph 2; p. 169, FIG. 3-b, 3-d).
b) Thrust bearings have some peculiarities as to how their thrust rings should be mounted on the shaft and in the body. For example, it is required to mount one thrust ring on the shaft firmly, with the standard level of tightness, while the other thrust ring should be assembled with the standard level of looseness, which is equal to 0.2-0.4 mm. The looseness is ensured in that the inner diameter of the second thrust ring is wider by 0.2-0.4 mm than the shaft diameter. The diameter of the groove in the body dedicated to mount the second ring should be by 0.5-1 mm wider than the outer diameter of the thrust bearing. On the top of that GOST contains the compulsory requirements as to minimal allowed width of the thrust surface separately from the pair “ring-shaft” and the pair “ring-body” (Digest, p. 520-523 table 19). The design of the foregoing drill bit has ignored all these requirements (see drawings of PCT No WO 2005/021923, FIG. 2). For instance, one thrust ring mounted on the axle with the radial play (rotatable mounting) and the other ring and rolling elements mounted together with the retainer are arranged outside the axle. Having ignored the required width of the thrust surfaces for the rings of the thrust ball bearings, the design has used the belleville spring end (linear contact) as the thrust surface of the thrust ring.
c) The imaginary peripheral retaining tapered roller bearing is arranged in the body of the roller cutter by means of a threaded bush, though the threaded couplings are not aimed at sustaining the dynamical radial loads. For this purpose, if required, cylindrical liners, cups, etc. are used with the radial tightness of the cylindrical joint surfaces, which liners, cups, etc. are to be firmly mounted together with the bearing in the main body (for example: Digest, p. 380 FIG. 2 and p. 381 FIG. 3).
The supports represented on FIGS. 1 and 2 (PCT application No WO 2005/021923) don't meet the simple requirements as to the design of drill bit supports, since no principle elements ensuring the limitation of the axial play value are provided.
The closest prior art device, herein called a prototype, is considered to be a drill bit comprising a body and rock-destroying elements with an equipment, wherein the rock-destroying elements are mounted on the body one inside the other by means of bearing supports, wherein the one, inwardly assembled, is located at an angle relatively to the axis of the drill bit, and the outer one is located in the opposite direction in relation to the axis of the drill bit (USSR Certificate of Inventorship No 512282, MIIK2: E 21 B 9/08, publ. 30 Apr. 1976, Bulletin No 16).
The prototype drill bit has the following disadvantages:
1) The bearing supports of the drill bit are introduced as all-in-one-piece, and in the same way as they are presented in tricone drill bits, they are furnished with retaining ball bearings, which are mounted in the supports by means of access holes and ball plugs. Such retaining bearings don't provide any possibility for a preliminary or current control over the value of axial play.
2) The techniques of the production of the bearing races on the body in the cavity of the roller cutters are very complicated and time-consuming, just like the techniques the tricone drill bits are based on.
3) Like in other drill bits, the duration of the service life of the main components of the drill bit prototype (i.e. the body, bearing supports, and roller cutter equipment) differs greatly. For instance, at the test operations of the drill bit samples from the trial batch it was determined that for the first time ever the service life of the bearing supports has several times overgrown the service life of the wolframite-cobalt rock-destroying elements. This became possible because the angle of the bearing load zone in the support of the drill bit prototype is equal to 360°, but it makes not more than 160-175° in the tricone drill bits right after the run-in test.
When wearing-out of the operating surfaces of the rock-destroying elements of the drill-bit prototype provided with hard-alloy cutters was already 100%, the wearing-out of the drill bit body was not more than 25% and the wearing-out of the bearing supports was 35%. Such drill bits that are worn out in half, are not subject to repairing as the design of the drill bit prototype doesn't provide the possibility of changing or recovering the components that are worn-out.
BRIEF DESCRIPTION OF THE INVENTIONTherefore, the goal of the present invention is to sufficiently increase the service life of the drill bits, their efficiency and interchangeability.
The aforesaid goal is achieved due to the inventive design of the drill bit. Accordingly, the drill bit comprises: a body and rock-destroying elements with cutting equipment, said rock-destroying elements include an inner element and an outer element mounted on the body one inside the other by means of bearing supports, wherein the inner element is located at an angle relatively to the axis of the drill bit, and the outer element is located in the opposite direction of the axis of the drill bit, and, in accordance with the invention, the cutting equipment is formed as replaceable jet nozzles (matrices) made of a predetermined hardwearing material and provided with arm insertions made of a predetermined firm material, wherein the bearing support of each rock-destroying element is furnished with an adjustment unit to adjust the axial play value (or preliminary tightness).
The inventive design of the drill bit offers the following advantages:
the use of replaceable jet nozzles (matrices) that are quickly removable and exposed to wear allows maintaining reliable operation of the drill bit until the complete wearing out of all elements (body, roller cutters and bearing supports) takes place;
the use of replaceable jet nozzles, i.e. the removable equipment of the roller cutters, which, if desired, might be different in quantity, size and shape of hard-alloy cutters, including those that are diamond-tipped, ensures standardization of the drill bit. With that being said the drill bits of one definite size, aimed at drilling of soft rocks, rocks of middle hardness, hard rocks and rocks of the highest hardness, might be different only in material and geometrical shape of the cutters of the replaceable jet nozzles equipment.
replaceable jet nozzles allow using cheaper material for the body of the drill bit and body parts of the rock-destroying elements, wherein the replaceable jet nozzles can be made of high-hardness steel and alloys having special properties of hardness, abrasion resistance, etc.;
equipment of rock-destroying elements resistant to wearing out together with the solid bearing supports that are taking up only useful one-sided thrust load and having the angle of the load of 3600, allow increasing the operational life of the drill bit by 3-5 times, wherein only costs for manufacturing of the spare units of the equipment are required.
the units for adjusting the axial play or preliminary tightness in the supports of the rock-destroying elements allow avoiding the world's common practices of selective grouping of rolling elements depending on the actual diameter of the bearing races on the axle and in the cavity of the roller cutters, which are unique for each section of the drill bit.
as a result of the aforesaid, it is possible to standardize the manufacturing of some parts of the drill bit: legs, roller cutters, bearings or rolling elements, and retainers. Due to these measures, the manufacturing and assembling of the drill bits are sufficiently simplified and cheapened.
Three possible variants (preferred embodiments) to manufacture the drill bit are described by means of accompanying drawings, i.e.:
While the invention may be susceptible to embodiment in different forms, there are described in detail herein below, specific embodiments of the present invention, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein.
In a preferred embodiment, the inventive drill bit (shown on
The upper thrust ball bearing of the support of the rock-destroying element 3 is provided with a retaining ring 10 and an adjusting unit 11 to adjust the axial play value in the support realized, for example, in the form of an end plate and a bolt. In its turn, the ball bearing support 5 of the outer rock-destroying element 4 is provided with a retaining ring 12 and a threaded-type cap 13 for adjusting the axial play value in the support. The cap has a seal ring.
In another preferred embodiment, the inventive drill bit, shown further on
Yet, in another preferred embodiment, the inventive drill bit (shown on
The rock-destroying elements are provided with the replaceable jet nozzles made of hardwearing material. The operating parts of the jet nozzles are equipped with cutters 9 made of a suitable known firm material, for example, of wolframite-cobalt based alloy or an extra-hard composite formed on the basis of synthetic and natural diamonds. The ends of the cutters can be diamond-tipped.
The inventive drill bit operates as follows. The body of the drill bit is connected to a drillpipe of the drilling machine. The rotating drill bit with the axial play being set is brought to the downhole. Simultaneously the air is delivered under the pressure through the scavenge channels 2. As far as the cutters 9 are deepened in the surface of the downhole, the rock-destroying elements come in contact with the rock and roll over the downhole due to rotation of the body 1 of the drill bit. The zones of contacts of the rock-destroying elements are located on the opposite sides relatively to the axis of the downhole, which eliminates the possibility of radial vibrations of the drill bit relatively to the axis of the well. The movement path of each cutter 9 of the jet nozzles 7 and 8 can be described as a waveform type. Herewith cutters 9 cut the local parts of the downhole in a sequential order, by destroying and grinding a predetermined layer of the rock. Currents of the compressed air blow away the drilling mud from the downhole surface and deliver it onto the ground surface within an annular space. The cone shape of the outer rock-destroying element minimizes the possibility of its contact with the hole walls. Thanks to that, the working torque of the motor on the shaft is reduced and heating of the drill bit parts is minimal.
The bench tests and tests in natural conditions of the trial models of the drill bits (for example, shown on
an increase of the mechanical speed of the drilling by 2-2.5 times thanks to the possibility to grow the load on the drill bit;
a decrease of the value of the required torque of the motor by 2-3 times;
enhancement of the service life of the drill bit bearing supports by 10-45 times as a result of increasing the angle of the bearing load zone in the support up to 360°;
an increase of the service life of hard-alloy cutting equipment of the rock-destroying elements by 3-5 times due to changing their movement paths and angles of cutters entering the rock;
an increase of the service life of the drill bit itself by 4-5 times thanks to introduction of replaceable assemblies of the equipment.
Claims
1. A drill bit having an axis, and comprising: a body and rock-destroying elements supplied with cutting equipment, said rock-destroying elements include an inner element and an outer element mounted on the body one inside the other by means of bearing supports, said inner element is located at an angle relatively to the axis, and said outer element is located at the opposite direction of the axis;
- wherein the cutting equipment is formed as replaceable jet nozzles made of a predetermined hardwearing material and provided with arm insertions made of a predetermined firm material, wherein each said bearing support is furnished with a means for adjusting an axial play value of said rock-destroying elements.
Type: Application
Filed: Sep 2, 2010
Publication Date: Jun 14, 2012
Inventors: Leonid Borisovich Dobrolyubov (Dnepropetrovsk), Irina Grigorievna Dobrolyubova (Dnepropetrovsk), Vyacheslav Victorovich Snegovoi (s. Bogdanovka), Anatolyi Ivanovych Stepaniuk (Dnepropetrovsk), Yuryi Anatolyevich Stepaniuk (Dnepropetrovsk)
Application Number: 13/390,780
International Classification: E21B 10/36 (20060101);
