A drill pipe and a connection mechanism suitable for a drill pipe joint.

Abstract

This invention discloses a connection mechanism suitable for drill pipe joints, including a first joint and a second joint. The first joint has an external thread, comprising a first external thread segment, a second external thread segment, and a third external thread segment connected in sequence. The second joint has an internal thread, comprising a first internal thread segment, a second internal thread segment, and a third internal thread segment connected in sequence. During the threaded connection and tightening of the first and second joints, due to the relationship between the pitches of the thread segments, the second external thread segment experiences a large displacement relative to the first and third external thread segments, thereby increasing the contact pressure of the second external thread segment and reducing the contact pressure on the bearing surfaces of the first and third external thread segments, avoiding stress concentration and improving the connection structure strength of the drill pipe joint. Simultaneously, this invention also provides a drill pipe, which utilizes the first and second joints to threadly connect with adjacent drill pipes, improving the operational reliability of the drill pipe.

Description

Technical Field

[0001] This invention relates to the technical field of drilling construction equipment and its peripheral supporting facilities, and in particular to a drill pipe and a connection mechanism suitable for drill pipe joints. Background Technology

[0002] Existing drill pipe products mainly include oil drill pipe and geological drill pipe. They adopt a rotating shoulder thread structure, similar to the bolt and nut tightening structure. As a variable cross-section heterogeneous body, the geometric characteristics of the threaded connection lead to concentrated stress distribution and complex stress, making it a weak link in the drill pipe string.

[0003] As the two drill pipes are tightened, a pair of interaction forces are generated between the joint shoulder surface and the thread teeth due to structural constraints. These forces increase with the tightening of the joint. The presence of this force ensures a tight fit between the shoulder surfaces and the preload between the thread teeth, which is essential for achieving the joint's sealing performance and reducing the amplitude of alternating stress on the threads under external forces. For a fixed screw-in angle, the axial movement distance of each thread relative to the shoulder surface is basically the same. This results in a phenomenon where the strain of the pipe section between the thread cross-section and the shoulder surface is greater the closer to the shoulder surface, meaning the axial force is greater. For double-shoulder threads (both the main and auxiliary shoulders are in contact), the force distribution of each thread is "large at both ends and small in the middle." For single-shoulder threads (only the main shoulder is in contact), the force distribution of each thread is "large at one end and small at the other." This phenomenon exacerbates the complexity of the thread stress and increases fatigue failure during operation.

[0004] For ultra-deep hole drilling, under the action of the top torque or the service working torque, the axial tensile force on each thread of the drill pipe joint is very uneven, with greater stress at the ends. Under heavy loads, this uneven internal stress distribution of the drill pipe joint will become more prominent, seriously affecting the safe and stable service capability of the drill pipe. This is especially true for ultra-deep hole wireline coring drill pipes, which, due to their thin-walled characteristics, have a greater impact on the overall strength of the drill pipe joint due to uneven stress distribution, reducing the overall strength of the drill pipe joint and affecting drilling safety.

[0005] Therefore, how to change the current situation where uneven stress distribution in drill pipe joints reduces the strength of drill pipe connections has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a drill pipe and a connection mechanism suitable for drill pipe joints, so as to solve the problems existing in the prior art, avoid stress concentration in drill pipe joints, and improve the strength of drill pipe connection structure.

[0007] To achieve the above objectives, the present invention provides the following solution: The present invention provides a connection mechanism suitable for drill pipe joints, comprising:

[0008] A first connector has an external thread, the external thread comprising a first external thread segment, a second external thread segment, and a third external thread segment connected in sequence, the third external thread segment being located at the end of the first connector, and the first external thread segment, the second external thread segment, and the third external thread segment forming a continuous curved surface;

[0009] The second connector has an internal thread, which includes a first internal thread segment, a second internal thread segment, and a third internal thread segment connected in sequence. The first internal thread segment is located at the end of the second connector, and the first internal thread segment, the second internal thread segment, and the third internal thread segment form a continuous curved surface.

[0010] The first connector and the second connector are threadedly connected. The first external thread segment is adapted to the first internal thread segment, and both have a pitch of P1. The second external thread segment is adapted to the second internal thread segment, and both have a pitch of P2. The third external thread segment is adapted to the third internal thread segment, and both have a pitch of P3, where P2 > P3 > P1.

[0011] Preferably, the first connector further has a first shoulder surface, and the second connector further has a second shoulder surface, wherein the first shoulder surface and the end face of the second connector form a main shoulder, and the second shoulder surface and the end face of the first connector form a secondary shoulder.

[0012] The relationship between P1, P2, and P3 is as follows:

[0013] P1=P2-360L×Δσ1 / E / θ Equation 1

[0014] P3=P2-360L×Δσ2 / E / θ Equation 2

[0015] In Equation 1, L is the distance between the midpoint of the axial length of the first external thread segment and the midpoint of the axial length of the second external thread segment; in Equation 2, L is the distance between the midpoint of the axial length of the third external thread segment and the midpoint of the axial length of the second external thread segment.

[0016] The main shoulder is in contact with the bearing surfaces of the external and internal threads, while the secondary shoulder is not in contact. At this time, the first and second joints are in a connected state. After the first and second joints continue to rotate relative to each other by an angle θ along the tightening direction, the connecting mechanism is tightened to the recommended tightening torque value. At this time, the first and second joints are in a tightened state. Δσ1 is the change in stress on the bearing surfaces of the first external thread segment and the first internal thread segment when the first and second joints change from a connected state to a tightened state. Δσ2 is the change in stress on the bearing surfaces of the second external thread segment and the second internal thread segment when the first and second joints change from a connected state to a tightened state. E is the elastic modulus of the materials of the first and second joints.

[0017] Preferably, when the first connector and the second connector change from a connected state to a tightened state, the first external thread segment generates an axial displacement s1 relative to the first internal thread segment, the second external thread segment generates an axial displacement s2 relative to the second internal thread segment, and the third external thread segment generates an axial displacement s3 relative to the third internal thread segment. Then:

[0018] s1=P1×θ / (2π)

[0019] s² = P² × θ / (2π)

[0020] s3 = P3 × θ / (2π).

[0021] Preferably, the number of thread turns in the first external thread segment is n1, the number of thread turns in the second external thread segment is n2, and the number of thread turns in the third external thread segment is n3. Then:

[0022] In Equation 1, L = (n1 × P1 + n2 × P2) / 2;

[0023] In Equation 2, L = (n3 × P3 + n2 × P2) / 2.

[0024] Preferably, when the first connector and the second connector change from a connected state to a tightened state, the relative displacement between the second external thread segment and the first external thread segment is ΔL, where ΔL = (P2 - P1) × θ / 360;

[0025] Then, Δσ1=Eε1=E×ΔL / L=E×(P2-P1)×θ / 360 / L

[0026] Δσ2=E×(P2-P3)×θ / 360 / L.

[0027] Preferably, when the first connector and the second connector are in a connected state, the secondary shoulder has a gap of 0.1mm to 0.2mm.

[0028] Preferably, the value of θ ranges from 10° to 30°.

[0029] The present invention also provides a drill pipe, utilizing the above-described connection mechanism suitable for drill pipe joints, wherein the drill pipe includes a first joint and a second joint, and the drill pipe can be threadedly connected to an adjacent drill pipe using the first joint and the second joint.

[0030] The present invention achieves the following technical effects compared to the prior art:

[0031] The present invention relates to a connection mechanism for drill pipe joints. During the threaded connection and tightening of the first and second joints, due to the relationship between the pitches of each thread segment, the second external thread segment experiences a large displacement relative to the first and third external thread segments. This increases the contact pressure of the second external thread segment, thereby reducing the contact pressure on the bearing surfaces of the first and third external thread segments, avoiding stress concentration, and improving the structural strength of the drill pipe joint connection. Furthermore, the first, second, and third external thread segments form a continuous curved surface, as do the first, second, and third internal thread segments, further preventing stress concentration. Simultaneously, the present invention also provides a drill pipe, which utilizes the first and second joints for threaded connection with adjacent drill pipes, improving the reliability of drill pipe operation and ensuring smooth drilling operations. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the connection mechanism of the present invention applicable to drill pipe joints;

[0034] Figure 2 This is an enlarged schematic diagram of a portion of the connection mechanism applicable to drill pipe joints according to the present invention;

[0035] Figure 3 This is a disassembled structural diagram of the connection mechanism applicable to drill pipe joints according to the present invention.

[0036] Among them, 100 is a connection mechanism applicable to drill pipe joints;

[0037] 1 is the first connector, 101 is the first external thread segment, 102 is the second external thread segment, 103 is the third external thread segment, and 104 is the first shoulder surface;

[0038] 2 is the second connector, 201 is the first internal thread section, 202 is the second internal thread section, 203 is the third internal thread section, and 204 is the second shoulder surface. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] The purpose of this invention is to provide a drill pipe and a connection mechanism suitable for drill pipe joints, so as to solve the problems existing in the prior art, avoid stress concentration in drill pipe joints, and improve the strength of drill pipe connection structure.

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] This invention provides a connection mechanism 100 suitable for drill pipe joints, including a first joint 1 and a second joint 2. The first joint 1 has an external thread, which includes a first external thread segment 101, a second external thread segment 102, and a third external thread segment 103 connected in sequence. The third external thread segment 103 is located at the end of the first joint 1, and the first external thread segment 101, the second external thread segment 102, and the third external thread segment 103 form a continuous curved surface. The second joint 2 has an internal thread, which includes a first internal thread segment 201, a second internal thread segment 202, and a third internal thread segment 103 connected in sequence. The threaded section 203, the first internal threaded section 201 is located at the end of the second connector 2, and the first internal threaded section 201, the second internal threaded section 202 and the third internal threaded section 203 form a continuous curved surface; the first connector 1 and the second connector 2 are threadedly connected, the first external threaded section 101 is adapted to the first internal threaded section 201 and both have a pitch of P1, the second external threaded section 102 is adapted to the second internal threaded section 202 and both have a pitch of P2, the third external threaded section 103 is adapted to the third internal threaded section 203 and both have a pitch of P3, P2>P3>P1.

[0043] The connection mechanism 100 of the present invention, applicable to drill pipe joints, during the threaded connection and tightening process of the first joint 1 and the second joint 2, results in a large displacement of the second external thread segment 102 relative to the first external thread segment 101 and the third external thread segment 103 due to the relationship of the thread pitch of each thread segment. This increases the contact pressure of the second external thread segment 102, thereby reducing the contact pressure on the bearing surfaces of the first external thread segment 101 and the third external thread segment 103, avoiding stress concentration, and improving the connection structure strength of the drill pipe joint. Furthermore, the first external thread segment 101, the second external thread segment 102, and the third external thread segment 103 form a continuous curved surface, as do the first internal thread segment 201, the second internal thread segment 202, and the third internal thread segment 203, further preventing stress concentration. Please refer to [reference needed]. Figure 1 and Figure 2 The third external thread segment 103 is located at the end of the first connector 1, and the first internal thread segment 201 is located at the end of the second connector 2. During the threaded connection and tightening of the first connector 1 and the second connector 2, the first external thread segment 101, the second external thread segment 102, and the third external thread segment 103 all undergo axial displacement. Since P2 > P3 > P1, the second external thread segment 102 displaces to the right relative to the first external thread segment 101 and the third external thread segment 103, causing the first external thread segment 101 to be subjected to a rightward tensile force and the third external thread segment 103 to be subjected to a rightward thrust force. This reduces the contact pressure on the bearing surfaces of the first external thread segment 101 and the third external thread segment 103, while increasing the rightward contact pressure on the second external thread segment 102, thereby alleviating the problem of stress concentration on the thread bearing surface and improving the connection structure strength of the drill pipe joint.

[0044] More specifically, the first connector 1 also has a first shoulder surface 104, and the second connector 2 also has a second shoulder surface 204. The first shoulder surface 104 and the end face of the second connector 2 form a main shoulder, and the second shoulder surface 204 and the end face of the first connector 1 form a secondary shoulder.

[0045] The relationship between P1, P2, and P3 is as follows:

[0046] P1=P2-360L×Δσ1 / E / θ Equation 1

[0047] P3=P2-360L×Δσ2 / E / θ Equation 2

[0048] In Equation 1, L is the distance between the midpoint of the axial length of the first external thread segment 101 and the midpoint of the axial length of the second external thread segment 102; in Equation 2, L is the distance between the midpoint of the axial length of the third external thread segment 103 and the midpoint of the axial length of the second external thread segment 102.

[0049] The main shoulder is in contact with the bearing surfaces of both the external and internal threads, while the secondary shoulder is not in contact. At this time, the first connector 1 and the second connector 2 are in a connected state. After the first connector 1 and the second connector 2 continue to rotate relative to each other by an angle θ along the tightening direction, the connecting mechanism 100 is tightened to the recommended tightening torque value (the recommended tightening torque value of the drill pipe is common knowledge to those skilled in the art). At this time, the first connector 1 and the second connector 2 are in a tightened state. Δσ1 is the change in stress on the bearing surface of the first external thread segment 101 and the first internal thread segment 201 when the first connector 1 and the second connector 2 change from a connected state to a tightened state. Δσ2 is the change in stress on the bearing surface of the second external thread segment 102 and the second internal thread segment 202 when the first connector 1 and the second connector 2 change from a connected state to a tightened state. E is the elastic modulus of the materials of the first connector 1 and the second connector 2.

[0050] Before determining the relationship between P1, P2, and P3, first consider the displacement of each thread segment during the connection and tightening process of the first connector 1 and the second connector 2. When the first connector 1 and the second connector 2 change from the connected state to the tightened state, the first external thread segment 101 generates an axial displacement s1 relative to the first internal thread segment 201, the second external thread segment 102 generates an axial displacement s2 relative to the second internal thread segment 202, and the third external thread segment 103 generates an axial displacement s3 relative to the third internal thread segment 203. Then:

[0051] s1=P1×θ / (2π)

[0052] s² = P² × θ / (2π)

[0053] s3 = P3 × θ / (2π)

[0054] Based on P2>P3>P1, we can deduce that s2>s3>s1.

[0055] When the first connector 1 and the second connector 2 change from the connected state to the tightened state, the axial displacement of the second external thread section 102 is θ / 360×P2, and the corresponding axial displacement of the first external thread section 101 is θ / 360×P1. Thus, the relative displacement ΔL between the second external thread section 102 and the first external thread section 101 is obtained, ΔL=(P2-P1)×θ / 360;

[0056] The number of thread turns in the first external thread segment 101 is n1, the number of thread turns in the second external thread segment 102 is n2, and the number of thread turns in the third external thread segment 103 is n3. In actual machining, the width of the thread teeth can be appropriately reduced to ensure that the threads with unequal pitches do not interfere with each other before the shoulder surfaces contact during manual screwing. Let L be the distance between the midpoint of the axial length of the first external thread segment 101 and the midpoint of the axial length of the second external thread segment 102, or the distance between the midpoint of the axial length of the third external thread segment 103 and the midpoint of the axial length of the second external thread segment 102. Then:

[0057] In Equation 1, L = (n1 × P1 + n2 × P2) / 2;

[0058] In Equation 2, L = (n3 × P3 + n2 × P2) / 2;

[0059] In this specific embodiment, the value of L in Equation 1 and Equation 2 is equal.

[0060] Then, Δσ1=Eε1=E×ΔL / L=E×(P2-P1)×θ / 360 / L

[0061] Accordingly, Δσ2=E×(P2-P3)×θ / 360 / L, and based on Δσ1 and Δσ2, the relationship between P1, P2 and P3 can be derived.

[0062] In practical applications, when the first connector 1 and the second connector 2 are connected, the secondary shoulder has a gap of 0.1mm to 0.2mm. The gap of the secondary shoulder is also adjusted according to the specifications of the first connector 1 and the second connector 2 and the specific working conditions.

[0063] It should also be noted that the value of θ ranges from 10° to 30°. In practical applications, an appropriate value can be selected according to the specific working conditions to improve the flexibility and adaptability of the connecting mechanism 100.

[0064] Furthermore, the present invention also provides a drill rod, which utilizes the above-mentioned connection mechanism 100 suitable for drill rod joints. The drill rod includes a first joint 1 and a second joint 2. The drill rod can be threadedly connected to adjacent drill rods using the first joint 1 and the second joint 2, thereby avoiding stress concentration problems, improving the working reliability of the drill rod, and providing a guarantee for the smooth progress of drilling operations.

[0065] The following specific embodiments will further explain the connection mechanism 100 of the present invention applicable to drill pipe joints.

[0066] Example 1

[0067] The second external thread segment 102 has 4 thread turns, while the first external thread segment 101 and the third external thread segment 103 both have 3 thread turns. The pitch of the second external thread segment 102 is P2 = 10mm. During machining, the thread width is appropriately reduced to ensure that the threads with unequal pitches do not interfere with each other before the shoulder surfaces contact during manual screwing. After the main shoulder surfaces contact and the bearing surface is under force, the thread is screwed in circumferentially by 20° around the tightening direction to achieve tightening. This 20° screwing corresponds to an axial displacement of 20 / 360 × P2, i.e., P2 / 18, and a corresponding displacement of P1 / 18 for the first external thread segment 101. Therefore, the second external thread segment 102 and the first external thread segment 101... The relative displacement is ΔL = (P2 - P1) / 18. Taking the distance L between the midpoints of each thread segment as the research object, L = (3 × P1 + 4 × P2) / 2 ≈ 35. Then, the stress that reduces the bearing surface of the first external thread segment 101 due to the rightward pulling force generated by the second external thread segment 102 on the first external thread segment 101 is Δσ1 = Eε1 = E × ΔL / L = 206000 × (P2 - P1) / 18 / 35 ≈ 327(P2 - P1). Similarly, the stress that reduces the bearing surface of the third external thread segment 103 due to the rightward thrust generated by the second external thread segment 102 on the third external thread segment 103 is Δσ2 ≈ 327(P2 - P3). Next, we will determine P1 and P3. It is known that in existing conventional equal-pitch joints, the contact stress on the bearing surface of the left thread (3 turns) is 600 MPa, the contact stress on the bearing surface of the middle thread (4 turns) is 200 MPa, and the contact stress on the bearing surface of the right thread is 500 MPa. When the middle thread increases by 100 MPa, the corresponding stress on the left and right threads decreases by 100 × 4 / 3 MPa. When the middle thread increases the contact stress on the bearing surface of the left thread by 150 MPa due to the pulling force on the left thread, the stress on the left thread decreases by 200 MPa. When the middle thread pushes the right thread forward... When the contact stress on the bearing surface increases by 75 MPa, the stress on the right thread decreases by 100 MPa. At this time, the contact stress on the bearing surface of the left thread is 600 - 200 = 400 MPa, the contact stress on the bearing surface of the middle thread is 200 + 150 + 75 = 425 MPa, and the contact stress on the bearing surface of the right thread is 500 - 100 = 400 MPa. Thus, the contact stress distribution of the left, middle, and right threads changes from (600, 200, 500) MPa to (400, 425, 400) MPa, thereby alleviating the stress concentration problem. Based on the above example, Δσ1 = 150 MPa and Δσ2 = 100 MPa can be obtained. Therefore, according to Δσ1≈327(P2-P1) and Δσ2≈327(P2-P3), P1 = 9.54 mm and P3 = 9.69 mm can be calculated.

[0068] The connecting mechanism 100 of the present invention, applicable to drill pipe joints, adopts a segmented unequal pitch method to alleviate the stress concentration problem of the threaded pair of drill pipe joints, improve the overall structural strength of the drill pipe joint, and the external and internal threads of the present invention are both continuous helical surfaces, further avoiding stress concentration. It is suitable for thin-walled wireline coring drill pipe joints, improving the adaptability of the connecting mechanism 100.

[0069] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A connection mechanism suitable for use in a drill pipe joint, characterized in that, The utility model relates to a kind of threaded connection mechanism, including: First joint, the first joint has outer thread, the outer thread includes sequentially connected first outer thread section, second outer thread section and third outer thread section, the third outer thread section is located at the end of the first joint, the first outer thread section, the second outer thread section and the third outer thread section form continuous curved surface; Second joint, the second joint has inner thread, the inner thread includes sequentially connected first inner thread section, second inner thread section and third inner thread section, the first inner thread section is located at the end of the second joint, the first inner thread section, the second inner thread section and the third inner thread section form continuous curved surface; The first joint is connected with the second joint by thread, the first outer thread section is adapted with the first inner thread section, and the pitch of both is P1, the second outer thread section is adapted with the second inner thread section, and the pitch of both is P2, the third outer thread section is adapted with the third inner thread section, and the pitch of both is P3, P2>P3>P1; The first joint also has first shoulder surface, the second joint also has second shoulder surface, the first shoulder surface forms main shoulder with the end surface of the second joint, and the second shoulder surface forms auxiliary shoulder with the end surface of the first joint; The relationship between P1, P2, P3 is as follows: P1=P2-360L×Δσ1 / E / θ formula one P3=P2-360L×Δσ2 / E / θ formula two Wherein, in formula one, L is the distance between the midpoint of the axial length of the first outer thread section and the midpoint of the axial length of the second outer thread section;In formula two, L is the distance between the midpoint of the axial length of the third outer thread section and the midpoint of the axial length of the second outer thread section; The main shoulder is in contact state with the load bearing surface of the outer thread and the inner thread, and the auxiliary shoulder is in non-contact state, at this time, the first joint and the second joint are in connected state, after the first joint and the second joint continue to rotate relative angle θ in tightening direction, the connection mechanism is tightened to recommended make-up torque value, at this time, the first joint and the second joint are in tightening state;Δσ1 is the change value of the stress of the load bearing surface of the first outer thread section and the first inner thread section when the first joint and the second joint are converted from connected state to tightening state;Δσ2 is the change value of the stress of the load bearing surface of the second outer thread section and the second inner thread section when the first joint and the second joint are converted from connected state to tightening state;E is the elastic modulus of the material of the first joint and the second joint.

2. A connection mechanism suitable for use in a drill pipe joint according to claim 1, characterized in that: When the first joint and the second joint are converted from connected state to tightening state, the first outer thread section produces axial displacement s1 relative to the first inner thread section, the second outer thread section produces axial displacement s2 relative to the second inner thread section, and the third outer thread section produces axial displacement s3 relative to the third inner thread section, then: s1=P1×θ / (2π) s2=P2×θ / (2π) s3=P3×θ / (2π).

3. A connection mechanism suitable for use in a tool joint according to claim 2, characterized in that: The first external thread segment has a thread number of n1, the second external thread segment has a thread number of n2, and the third external thread segment has a thread number of n3, and thus: In Formula I, L=(n1×P1+n2×P2) / 2; In Formula II, L=(n3×P3+n2×P2) / 2.

4. A connection mechanism suitable for use in a tool joint according to claim 3, characterized in that: When the first joint and the second joint are switched from a connected state to a screwed state, the relative displacement between the second external thread segment and the first external thread segment is ΔL, and ΔL=(P2-P1)×θ / 360; Thus, Δσ1=Eε1=E×ΔL / L=E×(P2-P1)×θ / 360 / L Δσ2=E×(P2-P3)×θ / 360 / L.

5. A connection mechanism suitable for use in a tool joint according to claim 1, characterized in that: When the first joint and the second joint are in a connected state, the sub-shoulder has a gap of 0.1mm-0.2mm.

6. A connection mechanism suitable for use in a tool joint according to claim 1, characterized in that: The value of θ is in the range of 10°-30°.

7. A drill pipe using the connection mechanism for a drill pipe joint according to any one of claims 1 to 6, characterized by: The drill pipe comprises the first joint and the second joint, and the drill pipe can be connected with adjacent drill pipes by the first joint and the second joint.

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