RU2515361C2 - Multi-row crown bit - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to rock crushing tool. Proposed crown bit comprises several rows of cutters located at different spacing from well work face. Cutters, their holders and shanks made integral with the latter feature cylindrical shape and common rotational axis located at mid diameter of bit body or shifted towards larger bit body diameter on one side of cutters and towards smaller diameter on opposite part of cutters. Cylindrical shanks of holders with groove making the top and bottom ring ledges along with thrust bearing resting thereon and compression ring pack fit in blind holes from the bit body end parallel with its axis. Compression force of springs in every row complies with axial load of rock crushing for given row to be crushed thereby. Note here that every next superlying row is intended for higher-hardness rocks compared with previous underlying row while first row cutters stay in permanent contact therewith in drilling. Cutter holders of all moving rows along, apart from the top one, with pre-contracted packs of springs are retained in place due to thrust of cylinder shank flat groove top ledge against top face of thrust ring welded of two halves, fitted in ring groove made at bit body outer surface. while shanks of top row are retained by steel ball fitted via bit body side bore in ring groove made at shank lower end.

EFFECT: longer life, higher mechanical rate, lower power input, fast round-trip.

4 dwg

Description

The invention relates to a rock cutting tool designed for exploration drilling in often alternating physical and mechanical properties of rocks, mainly using double core pipes, including with a removable core receiver.

In such difficult drilling conditions, it is difficult to ensure the efficiency of the drill bit, since a significant difference in rock hardness, abrasiveness and fracture and their frequent intermittency require appropriate and fundamentally excellent weapons, which cannot be combined in one standard drill bit. This leads to a significant investment of time in tripping operations in order to replace the drill bit with the corresponding physical and mechanical properties of the rock.

At the same time, on the one hand, the desire to maximize the crown resource gradually led to excessive saturation of its end with rock-breaking elements to the detriment of the washing elements and, accordingly, to an increase in energy consumption and a decrease in the mechanical drilling speed. On the other hand, reserves to increase the durability of the drill bit due to increased armament are practically exhausted, since, for example, the possibility of further increasing the matrix height achieved in a modern diamond impregnated crown is limited by the resource of cutting tools.

Recent studies have established (see Superhard materials in a geological exploration tool / Collective of authors: R.K. Bogdanov, A.P. Zakora, AMIsonkin et al. Yekaterinburg: Publishing House of the Ural State Geological Administration, 2003, 138 pp.), Which, upon optimization structures of drill bits, it is necessary to strive to reduce the length of the diamond sectors and the number of carbide cutters, while maintaining a uniform load on their end. So, in diamond crowns with a diameter of 76 mm, with a decrease in the length of the end sector from 13 to 8 mm, their resource increased by 64%, and a decrease in the number of cutters of carbide crowns of the same diameter from 8 to 3 led to a twofold increase in mechanical speed.

A well-known diamond drill bit (AS No. 1689581, authors Belov AM and others) with an additional body bearing its own set of cutters and connected to the main one through rivets that are cut by axial force after operation of the cutters located on the additional case, due to which the cutters of the main body of the crown enter the work.

Also known as a closer analogue, a two-tiered drill bit (AS No. 161008, authors L. Lachinyan and others), adopted as a prototype, the cutters of the upper fixed tier of which are mounted directly on the crown body, and the lower (temporarily fixed ) are also installed on the crown body, but on temporary supports with shock absorbing filler. First, the lower tier cutters work on this crown, upon which, after the blunting of the cutters, they create an excessive axial force, as a result of which the cutters of this tier cut the temporary support and, pressing into the crown body through the shock-absorbing filler, provide drilling with the upper tier cutters.

Such a crown, as / and mentioned above, has a higher resource in comparison with the usual one, it allows to significantly reduce the energy consumption of the drilling process and increase its mechanical speed. However, the possibility of linking the armament of such a crown with the frequently changing physicomechanical properties of the rocks encountered is limited, since after the triggering of the first tier of the incisors, it is not restored to meet the newly changed rock, i.e. has a single use.

The objective of the invention is to increase the efficiency of the drill bit, on the one hand, by supplying it with a universal set of weapons and in ensuring prompt inclusion in the work of the group of minimum necessary weapons that most fully corresponds to the physicomechanical properties of rocks passing at a given time at an unlimited frequency their intermittency, and on the other - by increasing its armament with cutters that process the walls of the well and core.

To solve this problem, in the drill bit, which includes several tiers of cutters located at different distances from the bottom of the well, the cutters, toolholders firmly connected with them, and also the shanks made in parallel with the toolholders have a cylindrical shape and a common axis of rotation, which is located on the average diameter of the end face the crown housing or is shifted at one part of the incisors of this tier towards the larger diameter of the housing, and at the other towards the smaller, moreover cylindrical shanks of the holders having a groove forming the upper and lower circles oic ledge in abutting together with them and the thrust bearing package compression springs, are also a minimum clearance and rotatable around its axis in the blind holes made from the end crowns of the body parallel to its axis.

The compression force of the spring pack of each tier corresponds to the axial load of rock destruction, for drilling of which this tier of cutters is intended. Moreover, each subsequent upstream tier of the cutters, counting from the bottom, is intended for rocks of greater hardness than for rocks of the previous lower tier, and the cutters of the first tier from the bottom are in constant contact with the latter during drilling.

At the same time, the tool holder shanks of the cutters of all tiers, except the upper one, together with the pre-pressed thrust bearings and spring packs, are prevented from falling out of their holes due to the stop by the upper ring step of the tool holder shanks into the upper face of the support ring welded from two halves, with a minimum clearance in diameter installed in the corresponding annular groove made on the outer surface of the crown body, and the shanks of the holders of the upper tier of the incisors - thanks to the steel ball installed through a side opening in the body of the crown at its end in the annular groove formed at the lower end of the shank.

When creating an axial load on the face that exceeds the limit for the cutters of the first tier from the bottom, the spring package of this tier is compressed and simultaneously the cutters of the second tier come into operation with its cutters.

With a further increase in the load on the face to a value exceeding the total ultimate load of the first and second tier of the incisors, the shanks of the holders of the first from the bottom of the tier of the incisors, abutting their lower annular ledge against the lower face of the mentioned support ring, raise the incisors of the second from the bottom of the incisor, thereby ensuring work incisors of the subsequent, third from the bottom, tier along with incisors of the first. And, on the contrary, in the case of reducing the load on the face in the reverse sequence, they enter into the work, also in the reverse sequence, first together the cutters of the second and first tier and then only the cutters of the first.

The invention is illustrated by drawings, where Figures 1 and 2 schematically depict a three-tier and four-tier diamond drill bit, the axis of rotation of the cutters of which is located on the average diameter of the end face of its body. To simplify the drawings and their greater visibility, washing windows, slurry grooves and sealing elements are not shown. Tier numbering begins with the one closest to the face.

Shown here:

figure 1 - three-tiered drill bit with four tool holders on each tier;

figure 2 - four-tiered drill bit with three tool holders on each tier;

figure 3 presents a view along aa (see figure 1) of a three-tiered drill bit, and figure 4 - its scan (view of the outer diameter) with a local section along its average diameter.

The three-tiered drill bit (see Figs. 3 and 4) is characterized in that the cutters 1, the toolholders 2, which are firmly connected with them, and the shanks 3, which are integral with the toolholders, have a cylindrical shape and a common axis of rotation located on the average diameter of the end face of the crown body. Cylindrical shanks 3 of the holders having a groove forming the upper 4 and lower annular ledge 5, together with the thrust bearing 6, the fifth 15 and packages of compression springs 7 resting on them, also enter with a minimum clearance and the possibility of rotation around their axis into blind holes 8, made from the end face of the body of the crown 16 parallel to its axis.

The compression force of the spring pack of each tier corresponds to the axial load of rock destruction, for drilling of which this tier of cutters is intended. Moreover, each subsequent upstream tier of the cutters, counting from the bottom, is intended for rocks of greater hardness than for rocks of the previous lower tier, and the cutters of the first tier from the bottom are in constant contact with the latter during drilling.

The shanks of the toolholders of the cutters of all tiers, except the upper one, together with the pre-pressed thrust bearing 6 and the spring packs 7, are prevented from falling out of their holes due to the stop by the upper ring step 4 of the grooves of the tool shanks into the upper face 9 of the support ring 10 welded from two halves, s the minimum gap in diameter installed in the corresponding annular groove 11, made on the outer surface of the body of the crown. The shanks of the upper tier holders are kept from falling out of their holes due to the steel ball 12 installed through the hole in the body of the crown at its end into an annular groove made at the lower end of the shank (Fig. 4).

The annular groove together with the support ring is protected from external influences by a metal or plastic casing 13 (not shown in Fig. 4).

When creating an axial load on the face that exceeds the limit for the cutters of the first tier from the bottom, the spring package of this tier is compressed, and simultaneously the cutters of the second tier come into operation, and with a further increase in the load on the face to a value exceeding the total maximum load of the first and the second tier of the incisors, the cylindrical shanks of the holders of the first tier of the incisors from the bottom, abutting their lower annular ledge 5 of the groove of the shanks to the lower face 14 of the aforementioned support ring 10, raise the incisors of the second from Aboy of the tier, thereby ensuring the work of the incisors of the subsequent, third from the bottom, tier along with the cutters of the first, and, conversely, in the case of reducing the load on the face in the reverse sequence, they also enter the work, in the reverse sequence, first together the cutters of the second and first tier and then only the incisors of the first.

The inventive design of a multi-tiered drill bit allows you to solve the problem.

Indeed, the cutters of the first tier from the bottom face destroy the rock, provided that the axial load on the face corresponds to the compressive force of the spring package of this tier. When a harder rock is encountered and, as a result, an axial load on the face is exceeded that exceeds the limit for the cutters of this tier, the packs of its springs are compressed and the cutters of the second tier come along with the cutters of the first tier. In this case, the cutters are destroyed by the incisors of the second tier, and the incisors of the first work in self-sharpening mode. When meeting even harder rock and further increasing the load on the face to a value exceeding the total ultimate load of the first and second tier of the incisors, the cylindrical shanks of the holders of the first from the bottom of the tier of the incisors, abutting their lower annular step 5 of the groove of the shank 3 in the lower face 14 of the support ring 10 (Figs. 3 and 4), raise the incisors of the second tier from the bottom of the bottom, thereby ensuring the operation of the incisors of the next, third from the bottom, tier along with the cutters of the first.

In this case, the cutters are destroyed by the incisors of the third tier, and the incisors of the first are also in the self-sharpening mode. When changing the hardness of the rocks and, accordingly, the load on the face in the reverse sequence, they also enter the work, in the reverse sequence, first together the cutters of the second and first tier and then only the cutters of the first.

Thus, the use of the proposed multi-tiered drill bit, due to the versatility of the weapon kit and the possibility of including the minimum necessary weapon group that most closely matches the physicomechanical properties of the rocks passed at any given time at an unlimited frequency of their alternation, can significantly increase the efficiency of the process drilling by reducing the energy intensity of the process, increasing the mechanical speed, resource of the crown and saving time on its deputy well, particularly when drilling with a removable core receiver. Cutters have the ability to rotate around its axis.

In this case (see Fig. 1), the axes of the incisors are located on the average diameter of the end face of the crown body and the adhesion of each incisor to the wall of the well causes it to rotate counterclockwise, and the adhesion to the core, on the contrary, clockwise. But, since the torque of rotation of the points of the cutter relative to the axis of the crown in the outer diameter is greater, then, in the end, the cutter must turn counterclockwise. At the same time, as a result of the engagement of the cutter with the central part of the annular face under the action of axial load, the cutter slips along with the rotation and conditions are created for almost all types of rock destruction - abrasion, cutting, chipping, crushing and crushing in various combinations depending on their physico-mechanical properties and the applicable drilling modes.

In the case of the location of 2 incisors of each tier closer to the outer diameter of the crown, and 2 others to the inner, then, since they are in contact only with the wall of the well, or only with the core, taking into account their contact with the central part of the face , the degree of slipping of the incisors will be much less, and, as a result, the most effective type of rock destruction — crushing and crushing — will prevail (see Sulakshin S.S. Exploration well drilling: Reference manual. - M .: Nedra, 1991. - 334 p.: Ill.)

The rotation of the incisors around its axis provides higher armament of the crown with scoring incisors. The matrix, for example, of a conventional diamond drill bit can be represented as a set of square-shaped posts with side “a” equal to the width of the matrix. In each such headquarters, cutting diamonds can only be placed on the inside and outside of the square, i.e. on the length of 2a. In the proposed crown, the racks are made of cylindrical shape with a diameter of the same value “a”, and the cutting diamonds are located along the entire circumference of the racks, i.e. over a length of 3.14a, and therefore the armament with cutting diamonds in a cylindrical head is 1.57 times higher (3.14a: 2a = 1.57). Considering that cylindrical cutters are installed with a gap and their total face area is therefore slightly less than that of a conventional one, the advantage in arming with cutting diamonds is not 1.57 but 1.5 times higher. Therefore, ceteris paribus, the durability of such a crown in comparison with the usual is also 1.5 times higher.

The presence of shock absorbers in the form of compression spring packs dramatically reduces the effect of shock loads resulting from longitudinal and transverse vibrations of the drill string and leading to chipping of the cutters, especially diamond ones, as the most fragile ones, and, therefore, shock-absorbing springs contribute to increasing the drill bit durability .

An example implementation of the proposed multi-tiered drill bit.

As an example, we take a three-tier impregnated diamond crown with an outer and inner diameter of 75.31 and 47.62 mm, respectively. corresponding to overall dimensions, a WLN-sized bit according to ISO 10097-1: 1999 (E) for drilling with a removable core receiver. The thickness of the crown matrix according to this standard is 13.8 mm. In these overall parameters, all the structural elements of the three-tiered diamond crown shown in Figs. 1, 3 and 4 are placed. Considering that the resource of the cutting tools of the proposed crown is 1.5 times higher in comparison with the usual one, we also increase the matrix height by 1.5 times, which provides a corresponding increase in durability.

The diameter of the shank groove forming the upper and lower circular ledge is 4 mm. A ball with a diameter of 6 mm according to GOST 3722-81 with a fifth is adopted as a thrust bearing.

Drilling is carried out using a shell with a removable core receiver in rocks of V-X drillability categories, including longline cutters: the first - V-VI, the second - VI-VIII, the third - VIII-X drillability categories. Rotational speed - up to 1500 rpm.

The specific axial load is taken in accordance with the recommendations for diamond drilling (see Drilling exploratory wells. Textbook for universities / N.V. Soloviev and others; under the general editorship of N.V. Soloviev. - M.: Higher school ., - 2007, 904 s .; ill.) Depending on the rock category according to drillability, respectively, for cutters of 3 tiers (kN / cm ² ): V-VI - 0.4-0.6; VI-VIII - 0.6-0.8 and VIII-X - 0.8-1.0. In total, there are 12 incisors, including 4 incisors in each tier. Accordingly, the area of the working surface of the cutters, taking into account the washing windows and slurry grooves, is 2.1 cm ² per cutter and, therefore, 8.4 cm ² in each tier. According to these parameters, the axial loads on the cutters of each tier will be (kN): 1st tier - 3.8-5.2 (for one cutter 0.8-1.3); 2nd tier - 5.2-6.8 (for one incisor 1.3-1.7) and 3rd tier - 6.8-8.4 (for one incisor 1.7-2.1).

Crown incisors are represented by diamond-bearing pads soldered to the holders of all tiers of incisors, and, as conventionally shown in the schematic drawings, the higher the hardness of the rocks, the finer the diamonds. In this case, the maximum deformation (stroke) of the spring package of the cutters of the first tier is h ₁ = 9 mm, of the second - h ₂ = 6 mm, of the third - h ₃ = 3 mm (see figure 5).

As the axial load increases, the cutters of the first tier, choosing the first 2 mm of their stroke, destroy the rocks of the V category and, then, within the course of the springs of 1 mm, together with the cutters of the 2nd tier that come into operation, destroy the rocks of the VI category. With a further increase in axial load, the incisors of the 2nd tier, within the range of their springs of 3 mm, first destroy the rock VII and, then, together with the incisors of the third tier, the rock of the VIII category. Further, the cylindrical shanks of the holders of the cutters of the 1st tier, which entered the self-sharpening mode, after a stroke of 6 mm, under the action of increased axial force, abutting their lower annular step 5 against the lower face 14 of the support ring 10, tear off the cutters of the 2nd tier from the face , opening up the possibility of continued work of the 3rd tier cutters for the destruction of rocks of VIII-X drillability categories with a load on the cutter of 1.7-2.1 kN or with a total crown load of 6.8-8.4 kN.

Thus, when the axial load on the crown changes in one direction or another, in any sequence and at any value within the specified boundaries, cutters are designed to break the rock corresponding to the given load. Obviously, this basic scheme of the crown can be used with rocks that are not only hard, but also fractured or abrasive. In this case, the armament of the crown cutters should correspond to these physical and mechanical properties of the rocks according to the purpose of each tier of the cutters.

To ensure the self-sharpening mode and to avoid polishing diamonds of the cutters of the 1st tier of the crown, the hardness of the material of the matrix of their beads is selected in accordance with the abrasiveness of the rocks intended for destruction by the cutters of the 2nd and 3rd tier, i.e., in this case, VII-X categories of drillability.

In addition, since the cutters of the first tier are in constant contact with the bottom of the well, they can be reinforced with scoring inserts made of composite material of the Twesal type, which are located directly in the diamond-bearing staff with the overlapping end layer, so that the latter can only wear out after the wear of the inserts. Taking into account the significant axial loads acting on the cutters of the moving tiers, we choose packages of Belleville springs according to GOST 3057-90 for their perception. Given the thickness of the body wall of the crown body (12.8 mm), we take spring No. 020 with an outer diameter of 8 mm, the force of which at maximum deformation is F ₃ = 400 N. The nominal diameter of the holes and cylindrical shanks of the holders is 8.3 mm.

We calculate the number of springs for the first tier of the incisors. It is represented by two groups of springs: parallel and sequential assembly. With a working strain of 0.8 F ₃ = 341 N and in accordance with the maximum axial load on the cutter of the first tier (1300 N), the required number of springs of parallel assembly will be

n ₁ = 1300: 341 = 3.80,

accept n ₁ = 4 pcs.

The maximum deformation of a group of springs of parallel assembly will be

S _par . S = S ₃ = 0.17 mm,

where S ₁ - maximum deformation of the spring №020.

Since the total stroke of the spring pack of the cutter of the first tier is taken equal to h ₁ = 9 mm (see figure 5), the maximum deformation of the group of springs of sequential assembly will be

S _post.s = 9-0.17 = 8.83 mm

The number of sequential assembly springs in the package is

n = 8.83: 0.17 = 51.94,

accept n = 52 pcs.

Height of a group of springs of parallel assembly in a package in a free state

$$L_{P\mathrm{but}R.\mathrm{from}}=I_{\mathrm{about}}+(n_{\mathrm{one}}-\mathrm{one})t,(\mathrm{one})$$

Where

I _about - the height of the spring, mm;

t is the thickness of the spring, mm

L _par . _S = 0.67 + (4-1) 0.5 = 2.17 mm.

Free spring group height

L _pos.s = I _o × n = 0.67 × 52 = 34.84 mm.

Total height of the spring pack in the free state

2.17 + 34.84 = 37.0 mm.

The total height of the spring pack of the cutter of the first tier with a preliminary deformation of 0.2 F ₃ (with preload during installation) will be

37.0-37.0 × 0.2 = 29.6 mm.

Similarly, for the cutter of the second tier we get the required number of springs of parallel assembly n ₁ = 1700: 341 = 4.98; accept n ₁ = 5 pcs.; S _par. S = 0.17 mm; since the maximum deformation of the spring package is taken equal to h ₂ = 6 mm (see Fig. 5), the total stroke of the group of springs of sequential assembly will be equal to S _pos = 6-0.17 = 5.83 mm; then n = 5.83: 0.17 = 34.29, take n = 34 pcs.;

L _par.s = 0.67 + (5-1) 0.5 = 2.67 mm; L _pos.s = 0.67 × 34 = 22.78 mm; the total height of the spring pack of the cutter of the second tier in the free state is 22.78 + 2.67 = 25.45 mm; the same with preliminary deformation of 0.2 F ₃ will be 25.45-25.45 × 0.2 = 20.36 mm.

For incisors of the third tier, we also obtain the required number of springs of parallel assembly n 1 = 2100: 341 = 6.16; accept n ₁ = 6 pcs.; S _par. S = 0.17 mm; since the maximum deformation of the spring package is taken equal to h ₃ = 3 mm (see Fig. 5), the total stroke of the group of springs of sequential assembly will be equal to S _pos = 3-0.17 = 2.83 mm; then n = 2.83: 0.17 = 16.64, take n = 17 pcs.

L _par . _S = 0.67 + (6-1) 0.5 = 3.17 mm; L _pos.s = 0.67 × 17 = 11.39 mm; the total height of the spring pack of the cutter of the third tier in the free state is 3.17 + 11.39 = 14.56 mm. The same with preliminary deformation of 0.2 F ₃ will be 14.5-14.56 × 0.2 = 11.65 mm.

We check the strength of the body of the crown, which, at the junctions of the cylindrical shank of the holder of the movable cutter with the wall of the hole, experiences shear stress from the action of the peripheral rotation force when the rock is destroyed at the bottom. As the material for the body of the crown we take steel 35 with a yield strength of 294 N / mm ² .

The maximum stresses occur in the holes of the third tier of the cutters, in which the maximum axial force at the bottom is 8.4 kN. First, we determine the power consumption for the rotation of a conventional diamond core from the following relationship (see the Manual of an engineer for drilling exploration wells: In 2 volumes / Under the general editorship of Prof. EA Kozlovsky. - Volume 2. - M .: Nedra, 1984 , 437 p.):

$$N=0.81\times {10}^{-8}P\times n_{\mathrm{at}R}(D_n+D_{\mathrm{at}}),(2)$$

Where

P - axial load on the crown, N;

n _BP - crown rotation frequency, rpm;

D _n - the outer diameter of the crown, mm;

D _in - the inner diameter of the crown, mm

Since P = 8400 N; n _BP = 1500 rpm; D _n = 75.31 mm; D _in = 47.62 mm, we have

N = 0.81 × 10 ^-8 × 6000 × 1500 (75.31 + 47.62) = 12.6 kW.

Of the 12 incisors, only 4 are involved in the work, i.e. 33% of the total area of the end face of a conventional crown, and, consequently, the cost of power will be

12.6 × 0.33 = 4.16 kW.

Then the torque on the crown

M _cr = 9552 × 4.16: 1500 = 26.5 Nm.

Given that the radius of the drill bit is

R = 75.31: 2: 1000 = 0.0376 m

and that 4 cutters work simultaneously, we find the calculated circumferential force per one cutter

q _res.r = M _cr : R: 4 = 26.5: 0.0376: 4 = 176 N.

The area S from the inner surface of the hole with a diameter of d = 8.3 mm, perceiving the lateral load of collapse, will be equal to:

$$S_{\mathrm{about}t}=3.14\times d\times h:2(3)$$

where h is the mating height of the cylindrical shank with the lower edge of the inner surface of the hole associated with its bias, the value of which depends on the gap between the hole and the cylindrical shaft of the holder. Given that the cylindrical shank enters the hole with a minimum clearance (for example, along a sliding fit), we take the value h = 0.2 mm. Then

S _from = 3.14 × 8.3 × 0.2: 2 = 2.60 mm ² ,

and the crushing stress will be equal

176: 2.60 = 67.7 N / mm ² .

With a shear load, the permissible stress for steel 35 will be 294 × 2.25 = 662 N / mm ² , where 294 is the yield strength of steel 35, N / mm ² , and the margin of safety of the body of the crown body for shearing will be equal to

662: 67.7 = 9.8,

which is enough.

We check for crushing the material of the support ring and the annular ledge of the groove of the cylindrical shank of the holder of the cutter of the first tier from the action of the axial load on the face. The maximum load occurs in the conjugation of these two elements of the crown during the joint work of the first and third tiers of the incisors, when the load on the incisor of the first tier is the total load of the incisor of the first and second tiers, i.e.

1.3 + 1.7 = 3 kN = 3000 H.

The supporting area of the annular ledge formed by a groove with a diameter of 4 mm of a cylindrical shank with a diameter of 8.3 mm, at the contact with the face of the supporting ring is (see Fig. 4) 25% of the total area of the annular ledge of the shank:

S _op = (8.3 ² -4 ² ) × 0.785 × 0.25 = 10.4 mm ² .

The shear stress of the annular ledge of the cylindrical shank and the mating surface of the support ring will be

3000: 10.4 = 288 N / mm ² ,

and the margin of safety, taking into account the permissible stress for steel 35, will be equal to

662: 288 = 2.3,

which is enough.

We check the strength of the supporting surface of the thrust bearing, which is a ball with a diameter of 6 mm and a fifth. According to GOST 3722-81, the ball hardness is not less than 62HRC, the breaking strength is 16170 N (1650 kg).

The margin of safety is determined for the heel and the working end of the shank, the segment surface of which, in conjunction with the ball, is determined by the following dependence:

$$S=3.14\times d\times H,(\mathrm{four})$$

Where

d is the diameter of the ball;

H is the height of the segmented surface at the contact of the ball with the fifth or working end of the shank.

For d = 6 mm and H = 2 mm, we have

S = 3.14 × 6 × 2 = 37.68 mm ² .

Maximum collapse stress in the bearing (on the working surface of the heel or shank):

3000 N: 37.68 = 79.6 N / mm ² .

Safety margin, with a permissible stress on the collapse of 662 N / mm ²

662: 79.6 = 8.4,

which is enough.

To ensure high wear resistance of the working surfaces of the heel and shank, we subject them to carbonitration, which increases the hardness of these surfaces to 56 HRC and brings them closer to the hardness of the ball surface.

The given example of the implementation of the proposed design of a multi-tiered drill bit with optimal parameters of the drilling mode and taking into account the real loads perceived by the most critical structural elements during the destruction of the face showed its performance and high strength according to its purpose. The use of such a drill bit will allow, ceteris paribus, to increase its resource by 1.5 times, increase the mechanical speed, reduce the energy consumption of the drilling process and significantly reduce the time required for tripping to replace it.

Claims (1)

A multi-tiered drill bit, including several tiers of cutters located at different distances from the bottom of the well, characterized in that the cutters, toolholders firmly connected with them, and also the shanks made in parallel with the toolholders have a cylindrical shape and a common axis of rotation, which is located on the average diameter of the end face the crown body or is displaced at one part of the incisors of this tier towards the larger diameter of the housing, and at the other - towards the smaller, with cylindrical shanks of the holders having a bore forming the upper and The lower circular ledge, together with the thrust bearing and the compression spring package resting on them, also enter, with a minimum clearance and the possibility of rotation around its axis, into blind holes made from the end face of the crown body parallel to its axis, and the compression force of the spring package of each tier corresponds to the axial load destruction of the rock, for drilling of which this tier of cutters is intended, and in this case, each subsequent upstream tier of cutters, counting from the bottom, is intended for rocks of greater hardness than for rocks of the previous lower and the cutters of the first tier from the bottom are in constant contact with the latter during drilling, at the same time, the shanks of the toolholders of the cutters of all tiers, except the upper one, together with the pre-pressed thrust bearing and the spring pack are prevented from falling out of their holes due to the stop the upper ledge of the circular groove of the cylindrical shanks of the holders in the upper face of the support ring welded from two halves, with a minimum clearance in diameter installed in the corresponding annular groove made on the outer surface the body of the crown, and the shanks of the holders of the upper tier of the incisors - thanks to the steel ball installed through the side hole in the body of the crown at its end in an annular groove made at the lower end of the shank, and when creating an axial load on the face that exceeds the limit for the incisors of the first from the bottom tier, the spring pack of this tier is compressed, and simultaneously with its cutters, the cutters of the second tier come into operation, and with a further increase in the load on the face to a value exceeding the total ultimate load of the first and W horny tier of incisors, cylindrical shanks of the holders of the first tier of incisors from the bottom, abutting their lower annular ledge to the lower face of the mentioned support ring, raise and lower the incisors of the second from the bottom of the tier into the body of the crown end face, thereby ensuring the operation of the incisors of the next, third from the bottom, tier together with the incisors of the first, and, conversely, in the case of reducing the load on the face in the reverse order, they also come into operation, also in the reverse order, first together the incisors of the second and first tier, and then ko cutters first.

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