RU2090734C1 - Drill bit for rotary drilling - Google Patents

Abstract

FIELD: rock-cutting tools, in particular, drill bits for rotary drilling. SUBSTANCE: drill bit has body with shank and wings on which main and peripheral inserts are installed. Inserts form nonrectilinear continuous cutting-gaging blade. Main inserts have negative rake whose value reduces for each, subsequent from drill bit axis insert and depends on relation between drill bit radius and distance from drill bit axis to the most distant cutting blade of main insert. EFFECT: higher efficiency. 5 dwg, 2 tbl

Description

 The invention relates to the mining industry, namely to a rock cutting tool, and can be used in a bit for rotary drilling.

 A bit for rotary drilling is known, comprising a body with blades and incisors mounted on the blades, the front angles of which vary from positive in the central part of the bit to negative at the periphery (AS USSR N 395559, class E 21 B 10/42, 1971) .

 The disadvantage of this bit is its low resistance (especially when drilling hard rocks), due to the rapid wear of the cutting blades. This type of wear is explained by the large steepness (the radius of curvature decreases) of the trajectory of movement of the central and middle cutters relative to the bottom of the well, which leads to an increase in the loads on the cutting blades of the cutters, the strength of the blades of which decreases as the rake angle changes from negative to positive.

 Also known is a bit for rotary drilling, comprising a housing with blades and interchangeable unified cutters mounted on blades with a negative rake angle (AS USSR N 1456546, class E 21 B 10/46, 1985).

 The disadvantages of this bit include the same value of negative rake angles for all incisors. The specific value of these angles is not indicated, however, at small values of the angles, the bit resistance decreases due to the rapid cleavage of the cutting blades at the cutters located closer to the axis of the bit, and at large values the drilling speed decreases. In addition, the cutters of the specified bit form an intermittent cutting edge along its radius, which contributes to the appearance of undisturbed sections in the form of concentric scallops on the bottom of the well. With this pattern of destruction of the bottom of the well, the rock is in a blocked state, that is, 1.5-2 times stronger than the destruction, which reduces the efficiency of the bit.

 The closest technical solution to the proposed one is a bit for rotary drilling, comprising a body with a shank, blades rigidly connected to the body of the blade and interchangeable unified cutters mounted on the blades, forming a non-linear continuous cutting gauge blade (AS USSR N 1502797, class E 21 B 10/42, 1986).

 In this bit, a solid blade eliminates the presence on the bottom of the well sections with a blocked state of the rock, which facilitates the process of its destruction.

 The disadvantage of this bit is that all the cutters have the same rake angle equal to zero, while the cutters located closer to the periphery of the bit are subject to more intense wear than the cutters located closer to the axis of the bit.

 The invention is aimed at increasing the wear resistance of the bit, more uniform wear of the cutting blades of the cutters and increase the drilling speed. This is achieved by the fact that the main cutters are made with a negative rake angle, and the rake angle decreases from the center to the periphery of the bit.

,
где γ_i передний угол i-го резца;
R_д радиус долота;
R_i расстояние от оси долота до наиболее удаленного от нее конца режущего лезвия i-го основного резца.The value of the rake angle for each cutter is determined in accordance with the expression:

,
where γ _{i is the} rake angle of the i-th cutter;
R _d radius of the bit;
R _{i the} distance from the axis of the bit to the farthest end of the cutting blade of the i-th main cutter.

 This embodiment of the bit allows to increase its wear resistance, to achieve more uniform wear of the cutters located at different distances from the axis of the bit, and allows to increase the drilling speed.

 In FIG. 4 shows a general view of the bit, in FIG. 2 section AA of FIG. 1, in FIG. C section BB in FIG. one; in FIG. 4, section BB in FIG. one; in FIG. 5 is a section GG in FIG. one.

,
где γ_i передний угол i-го резца;
R_д радиус долота;
R_i расстояние от оси до наиболее удаленного от нее конца режущего лезвия i-го основного резца.The bit contains a housing 1 with a shank 2 and blades 3 rigidly connected to the housing, on which the main 4, 5 and 6 and peripheral 7 cutters are installed, forming a non-linear continuous cutting-calibrating blade. The main incisors have a negative rake angle, the value of which decreases from the axis of the bit to its periphery and is determined in accordance with the expression:

,
where γ _{i is the} rake angle of the i-th cutter;
R _d radius of the bit;
R _{i the} distance from the axis to the end of the cutting blade of the i-th main cutter farthest from it.

 The bit works as follows.

 During drilling, the axial load and torque are transmitted to the bit, under the influence of which the main 4, 5 and 6 cutters destroy the rock, forming a well bore of the required diameter. Peripheral cutters 7 give stability to the bit, improving its centering at the bottom, and maintain the required diameter of the well by calibrating its walls.

 The optimality of the proposed ratio for determining the values of the front angles of the main incisors depending on the size of the front angle of the peripheral cutter and their distance from the axis of the bit is confirmed by the test results of seven experimental bits with a diameter of 160 mm, differing in the value of the front negative angle.

Distinctive parameters of the experimental bits are given in table. one
Tests of experimental bits were carried out while drilling limestone with a coefficient of strength of 8-10 on the scale of prof. M.Protodyakonova machines SVB-2M with a feed force of up to 20 kN and a rotational speed of 2 s ^-1 . The test results are given in table. 2.

 From the table. 2 it follows that the best performance indicators have experimental bits with a variable rake angle of the cutters, the value of which is determined by the proposed ratio.

Claims (1)

A bit for rotary drilling, comprising a body with a shank and blades, unified interchangeable main and peripheral cutters mounted on the blades, forming a non-linear cutting blade, characterized in that the main cutters have a negative rake angle, the value of which decreases from each subsequent from the axis of the bit of the cutter and is determined according to the expression

where γ _i is the rake angle of the i-th cutter;
R _d radius of the bit;
R _{i the} distance from the axis of the bit to the farthest end of the cutting blade of the i-th main cutter.

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