CN112096904B

CN112096904B - Telescopic frictionless ball valve driven by disc type motor and face cam

Info

Publication number: CN112096904B
Application number: CN202010733776.XA
Authority: CN
Inventors: 田中山; 常清; 杨昌群; 王波; 牛道东; 王虎斌; 石保虎; 张梅
Original assignee: Xian Aerospace Yuanzheng Fluid Control Co Ltd; China Oil and Gas Pipeline Network Corp South China Branch
Current assignee: Xian Aerospace Yuanzheng Fluid Control Co Ltd
Priority date: 2020-07-27
Filing date: 2020-07-27
Publication date: 2022-06-10
Anticipated expiration: 2040-07-27
Also published as: CN112096904A

Abstract

The invention relates to the field of friction-free ball valves, in particular to a telescopic friction-free ball valve driven by a disc motor and a face cam, which comprises an upper disc motor stator, a lower disc motor stator and a disc motor rotor, wherein the disc motor rotor is fixedly connected with an output shaft; the tail end of the transmission cylinder is fixedly connected with the valve core shaft through a pin shaft; the hollow spherical valve body is fixedly connected to the lower end of the transmission mechanism mounting frame, the bottom of the valve core shaft is inserted into a square hole in the center of the upper top surface of the square valve core, and a threaded release bolt at the lower end of the upper end optical axis is inserted into a round hole in the lower bottom surface of the valve core. The invention adopts the disc type motor with the characteristics of low rotating speed and large torque as a power source, is suitable for the working principle of the frictionless ball valve, directly drives the transmission mechanism and the valve core without a speed reducing mechanism, and has higher control precision and higher response speed.

Description

Telescopic frictionless ball valve driven by disc type motor and face cam

Technical Field

The invention relates to the field of friction-free ball valves, in particular to a telescopic friction-free ball valve driven by a disc type motor and a face cam.

Background

As a large country for petroleum transportation and consumption, the total length of pipelines for petroleum transportation exceeds 2 kilometers, and the pipelines are in an increasing trend year by year. Ball valves are widely used in oil and gas transportation pipelines as important parts for regulating the flow of pipelines. The ball valve has the characteristics of small fluid resistance, high opening and closing speed, simplicity in operation and the like, so that the ball valve is widely applied to industries such as petroleum, chemical engineering, power stations and the like. The sealing of the ball valve is formed by the pre-set pre-tightening force between the ball body and the valve seat and the acting force of the liquid pressure on the sealing surface of the valve seat.

The following defects generally exist in the traditional ball valve: firstly, in the opening and closing process of the valve, the ball body is always tightly attached to the valve seat, the friction force is large during rotation, and the ball body and the valve seat are seriously abraded after long-term repeated use. Secondly, after long-term frequent operation, the valve core is abraded, so that the valve can generate poor conditions such as leakage and the like in a conducting or closing state, and the service life is short. And thirdly, the opening and closing operation is very laborious and is often limited by the use environment including the flow cut-off temperature and the pressure. The driving device of the large ball valve is not perfect, the reducer and other parts have larger volumes, the use performance of the large ball valve is influenced by the problems of being not beneficial to installation and the like, and the requirements of modern industrial production are difficult to meet.

The frictionless ball valves currently available in the market can be divided into two broad categories. One type is an offset type friction-free ball valve, a valve core is shifted through an eccentric shifting rod to generate offset along the central axis of the bottom, and the valve core is separated from a valve seat to further ensure that no friction exists in the process of opening and closing the valve; the other type is a track type frictionless ball valve, the valve core part of the frictionless ball valve is mostly a wedge-shaped valve core, and valve core valve clacks are separately manufactured and mutually matched to move, so that the vertical displacement from top to bottom can be converted into the horizontal displacement of the valve clacks, and then the frictionless effect is achieved. The two types of frictionless ball valves also have the defects that the design of a transmission mechanism is complicated, and the offset frictionless accidental sealing effect has larger defects, so that the two types of frictionless ball valves cannot be used in key pipelines.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a telescopic frictionless ball valve driven by a disc type motor in cooperation with a face cam, and the idea that a special motor, a face cam transmission mechanism and a valve clack can be telescopically separated from a valve body is applied to the design of the traditional ball valve, so that the power element is accurately controlled, the transmission structure is simple, the efficiency is high, and the valve core and the valve clack are separated from a valve seat in the rotating process so as to achieve the aim of frictionless movement.

The technical scheme for realizing the functions is as follows: the utility model provides a telescopic frictionless ball valve of disk motor cooperation face cam drive which characterized in that:

the disc type motor rotor is fixedly connected with an output shaft, and a round roller is fixedly connected with the lower half section of the output shaft;

the lower side of the lower stator of the disc type motor is fixedly connected with a transmission mechanism mounting frame, a first pin hole, a second pin hole, a third pin hole and a fourth pin hole are formed in the transmission mechanism mounting frame, and a first electric push rod, a second electric push rod, a third electric push rod and a fourth electric push rod are respectively arranged on the outer sides of the first pin hole, the second pin hole, the third pin hole and the fourth pin hole;

the transmission mechanism comprises a transmission mechanism mounting frame, a circular roller and a transmission cylinder, wherein the transmission cylinder is mounted inside the transmission mechanism mounting frame; the tail end of the transmission cylinder is fixedly connected with the valve core shaft through a pin shaft;

the hollow spherical valve body is fixedly connected to the lower end of the transmission mechanism mounting frame, and a square valve core is mounted inside the hollow spherical valve body; four grooves are formed in four horizontal planes of the square valve core and are respectively as follows: the first groove, the second groove, the third groove and the fourth groove; the first groove is opposite to the second groove, the two closing valve flaps are installed, the third groove is opposite to the fourth groove, and the two opening valve flaps are installed;

the bottom of the valve core shaft is inserted into a square hole in the center of the upper top surface of the square valve core, a first rectangular slide way, a second rectangular slide way, a third rectangular slide way and a fourth rectangular slide way are respectively arranged on four sides of the upper top surface of the square valve core, and a first slide block, a second slide block, a third slide way and a fourth slide way are respectively arranged in the first slide way, the second slide way, the third slide way and the fourth slide way; the front ends of the first sliding block and the second sliding block are fixedly connected with the back surface of the closing valve clack, and the front ends of the third sliding block and the fourth sliding block are fixedly connected with the back surface of the opening valve clack; the other end of the sliding block is respectively connected with the valve plug shaft through a first crank, a second crank and a third crank;

the center of the lower bottom surface of the valve core is provided with a round hole, the round hole is inserted with the upper semi-optical axis section of the upper end optical axis lower end threaded release bolt, and the lower semi-optical section of the upper end optical axis lower end threaded release bolt is fixedly connected with the hollow spherical valve body for sealing.

Furthermore, a first pin hole, a second pin hole, a third pin hole and a fourth pin hole are uniformly distributed on the circumference of the transmission mechanism mounting frame.

Further, the lower half thread section of the upper end optical axis lower end thread type release bolt is fixedly connected and sealed with the hollow spherical valve body through threads.

The invention has the advantages that:

1. the disc type motor with the characteristics of low rotating speed and large torque is used as a power source, the disc type motor is suitable for the working principle of the friction-free ball valve, the transmission mechanism and the valve core are directly driven without a speed reducing mechanism, the control precision is higher, and the response speed is higher;

2. the transmission mechanism has fewer components, overcomes the defects of complex structure and low transmission precision of the traditional track type friction-free ball valve transmission track, and has higher transmission efficiency and higher transmission precision;

3. the valve body part of the invention adopts the structure that the valve core is provided with the valve clack, and the valve clack can stretch out and draw back, so that the valve clack can be separated from the valve body, and further, the friction does not exist in the working process of the valve, the problem that the friction still exists in the upward moving process of the conventional wedge-shaped valve core is solved, and the service life of the valve body is greatly prolonged;

4. the valve clack realizes the horizontal displacement of the valve clack by a crank connecting rod mechanism, and the motion requirement is met without another redundant power mechanism, so that the design space is saved;

5. the groove at the bottom of the valve core is matched with a special discharge bolt design, so that the supporting and guiding effects of the valve core in the rotating process can be achieved, and after the valve state is switched, the discharge bolt is screwed out, so that residual liquid in the switching process can be discharged.

Drawings

FIG. 1 is a cross-sectional view of an embodiment of the present invention with the ball valve fully closed;

FIG. 2 is a sectional view of the embodiment of the present invention when the ball valve is fully opened;

FIG. 3 is a cross-sectional view of the first pin hole 41 at the height of the center of the circle;

FIG. 4 is a view showing the construction of a transmission cylinder 5, which is a key part in the present invention;

FIG. 5 is another directional view of FIG. 4;

FIG. 6 is an isometric view of the overall construction of a portion of the telescoping valve cartridge of the present invention;

FIG. 7 is an axial side view of the valve cartridge 9 of the present invention;

FIG. 8 is a view of the construction of the opening flap 16 of the present invention;

FIG. 9 is a structural diagram of the closing valve flap 7 of the present invention;

fig. 10 is an isometric view of the component valve plug shaft 12 of the present invention.

In the figure: 1. an upper stator of the disc motor; 2. a disc motor rotor; 3. a lower stator of the disc motor; 4. a transmission mechanism mounting frame; 41. a first pin hole; 42. a second pin hole; 43. a third pin hole; 44. a fourth pin hole; 45. a first electric push rod; 46. a second electric push rod; 47. a third electric push rod; 48 fourth electric push rod; 5. a transmission cylinder; 51. a U-shaped guide groove; 52. an I-shaped guide groove; 53. an arc-shaped slot; 6. a hollow spherical valve body; 7. a closing valve clack; 8. the upper end optical axis and the lower end of the screw thread type relief bolt are arranged on the upper end of the screw thread type relief bolt; 9. a square valve core; 91. a first slideway; 92. a second slideway; 93. a third slide way, 94, a fourth slide way; 95. a square hole; 96. a circular hole; 97. a first groove; 98. a second groove; 99. a third groove; 910. a fourth groove; 101. a first slider; 102. a second slider; 103. a third slider; 104. a fourth slider; 111. a first crank; 112. a second crank; 113. a third crank; 114. a fourth crank; 12. a spool shaft; 13. a pin shaft; 14. a roller; 15. an output shaft; 16. an opening flap.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention.

As shown in fig. 1 to 10, a telescopic frictionless ball valve driven by a disc motor and a face cam is provided, which includes an upper stator 1 of the disc motor, the upper stator 1 of the disc motor is fixedly connected with a lower stator 3 of the disc motor, a rotor 2 of the disc motor is mounted inside the upper stator 1 of the disc motor and the lower stator 3 of the disc motor, the rotor 2 of the disc motor is fixedly connected with an output shaft 15, and a circular roller 14 is fixedly connected with the lower half section of the output shaft 15. The transmission mechanism mounting frame 4 is fixedly connected to the lower side of the disc type motor lower stator 3, a first pin hole 41, a second pin hole 42, a third pin hole 43 and a fourth pin hole 44 are uniformly distributed on the transmission mechanism mounting frame 4, and a first electric push rod 45, a second electric push rod 46, a third electric push rod 47 and a fourth electric push rod 48 are respectively mounted on the outer sides of the first pin hole 41, the second pin hole 42, the third pin hole 43 and the fourth pin hole 44. The transmission cylinder 5 is installed inside the transmission mechanism mounting frame 4, the upper half part of the transmission cylinder 5 is provided with an arc-shaped groove 53, a circular roller 14 is embedded in the arc-shaped groove 53, and the lower half part of the transmission cylinder 5 is provided with a U-shaped guide groove 51 and an I-shaped guide groove 52 respectively. The tail end of the transmission cylinder 5 is fixedly connected with the valve core shaft 12 through a pin shaft 13. The hollow spherical valve body 6 is fixedly connected with the lower end of the transmission mechanism mounting frame 4. The hollow spherical valve body 6 is internally provided with a square valve core 9. Four grooves, namely a first groove 97, a second groove 98, a third groove 99 and a fourth groove 910 are formed in four horizontal planes of the square valve core 9. Wherein the first groove 97 and the second groove 98 are opposite to each other, and two closing valve clacks 7 are arranged. The third groove 99 and the fourth groove 910 are opposite to each other, and two opening flaps 16 are installed. The bottom of the valve core shaft 12 is inserted into a square hole 95 in the center of the top surface of the square valve core 9. The rectangular first slideway 91, second slideway 92, third slideway 93 and fourth slideway 94 are respectively arranged on four sides of the upper top surface of the square valve core 9. A first slider 101, a second slider 102, a third slider 103 and a fourth slider 104 are respectively mounted inside the first slideway 91, the second slideway 92, the third slideway 93 and the fourth slideway 94. The front ends of the first slider 101 and the second slider 102 are fixedly connected to the back of the closing valve flap 7, and the front ends of the third slider 103 and the fourth slider 104 are fixedly connected to the back of the opening valve flap 16. The other end of the slide block is respectively connected with the valve plug shaft 12 through a first crank 111, a second crank 112, a third crank 113 and a fourth crank 114. A round hole 96 is formed in the center of the lower bottom surface of the valve core 9, an upper semi-optical axis section of the upper optical axis lower end threaded release bolt 8 is inserted into the round hole 96, and the lower semi-optical axis section of the upper optical axis lower end threaded release bolt 8 is fixedly connected and sealed with the hollow spherical valve body 6 through threads.

In fig. 1, which is a sectional view of the closed state of the ball valve, the roller 14 is at the highest position of the arc-shaped groove 53, the upper end of the vertical side of the U-shaped guide groove 51, which is not opposite to the I-shaped guide groove, is at a position completely coinciding with the first pin hole 41, and the I-shaped guide groove 52 is on the opposite side of the sectional view, and the upper end thereof is completely coinciding with the third pin hole 43, which is not visible in the sectional view. When the transmission mechanism is in the position, the valve core shaft 12 is at the lowest point of the vertical height, the square shaft section at the tail end is inserted into the bottommost part of the square hole 95 in the center of the top surface of the square valve core 9, the first sliding block 101 and the second sliding block 102 are respectively ejected out through the first crank 111 and the second crank 112 to be positioned at the outermost ends of the respective slide ways, the closing valve clack 7 is in an ejection state, fluid is blocked, and the valve is closed.

Fig. 2 shows the valve in the open state, and compared with the closed state of the valve in fig. 1, the entire transmission mechanism and the entire structure of the square valve core 9 have rotated 90 °, at this time, the other vertical edge of the U-shaped guide groove 51 is located at the position where the highest point completely coincides with the pin hole 41, the I-shaped guide groove 52 appears in the cross section after rotating 90 ° counterclockwise, the highest point completely coincides with the pin hole 42, and the lowest section of the arc-shaped groove 53 is located at the position where the cross section is visible. The open valve flap 16 ejects out of the fitting flow channel and the valve is opened.

Referring to fig. 4 and 5, the vertical height variation of the arc-shaped groove 53 is the ascending or descending displacement of the valve plug shaft 12. In the positions of the 4 slide ways on the top surface of the square valve core 9 shown in fig. 6 and 7, the left and right surfaces of each slide way are provided with convex edges which are matched with grooves on the side surfaces of the 4 sliding blocks, so that the 4 sliding blocks are limited from leaving the slide ways in the vertical direction. Fig. 10 shows the valve plug shaft 12 as a 4-segment stepped shaft. The pin hole opened at the uppermost end is used for installing a transmission pin shaft 13, the secondary does not have a function, one section of the secondary is a square cylinder, 4 surfaces are provided with a first crank 111, a second crank 112, a third crank 113 and a fourth crank 114, and the square cylinder section at the bottommost section is inserted into a square hole 95 in the center of the top surface of the square valve core 9 and is used for transmitting the motion of rotating by 90 degrees.

The working principle of the invention is as follows:

1. the process of switching the valve from closing to opening is as follows: the first electric push rod 45 outside the first pin hole 41 extends out and is inserted into the top of the vertical edge of the U-shaped guide groove 51 on the transmission cylinder 5 until the top passes through, the upper stator 1 of the disc motor and the lower stator 3 of the disc motor are electrified, the rotor 2 of the disc motor and the output shaft 15 are driven to rotate anticlockwise, and the roller 14 rotates anticlockwise together. Because the first electric push rod 45 inserted into the first pin hole 41 is located on the vertical edge of the U-shaped guide groove 51 at the moment, the transmission cylinder 5 cannot rotate, when the roller 14 rotates along the arc-shaped groove 53, because of the downward oblique shape of the arc-shaped groove 53, the transmission cylinder cannot rotate along with the roller 14, the rotation is converted into the vertical upward movement along the vertical edge of the U-shaped guide groove 51, the roller 14 rotates to the lowest end of the arc-shaped groove 53, and at the moment, the transmission cylinder 5 integrally ascends to the bottom edge of the U-shaped guide groove 51 and is consistent with the height of the first pin hole 41. The bottom of the transmission cylinder 5 drives the valve core shaft 12 to vertically ascend through the pin shaft 13, the valve core shaft 12 ascends to drive the tail ends of the first crank 111, the second crank 112, the third crank 113 and the fourth crank 114 to ascend, and then the first slide block 101, the second slide block 102, the third slide block 103 and the fourth slide block 104 are pulled to move towards the center direction along respective slide ways, so that the closing valve clack 7 is driven to move towards the center direction, and at the moment, the spherical surface of the closing valve clack 7 is separated from the inner cavity of the hollow spherical valve body 6. When the lifting motion is completed, the output shaft 15 continues to rotate, the roller 14 is already positioned at the lowest end of the arc-shaped groove 53, the transmission cylinder 5 is pushed to rotate counterclockwise by 90 degrees together, and the first electric push rod 45 inserted into the first pin hole 41 is positioned at the bottom of the other vertical side of the U-shaped guide groove 51 at the moment. The I-shaped guide groove 52 rotates to a position where the bottom end of the I-shaped guide groove completely coincides with the second pin hole 42, and at this time, the second electric push rod 46 outside the second pin hole 42 extends until the inside of the I-shaped guide groove 52, and the first electric push rod 45 retracts. The transmission cylinder 5 rotates 90 degrees and transmits the rotation to the valve core shaft 12 through the pin shaft 13, and the square column body section at the bottommost part is still positioned in the square hole 95 at the center of the top surface of the valve core 9 after rising, so that the valve core 9 can be driven to rotate 90 degrees anticlockwise to the open valve clack 16, and the through hole is parallel to the pipeline. Then the motor rotates reversely, at this time, the output shaft 15 rotates clockwise, the second electric push rod 46 newly inserted from the outside of the second pin hole 42 extends into the bottom end of the I-shaped guide groove 52, the roller 14 moves along the arc-shaped groove 53 in the opposite direction, and the transmission cylinder 5 can only move vertically downwards due to the limitation of the push rod inserted into the I-shaped guide groove 52. The transmission cylinder 5 drives the valve core shaft 12 to move downwards, and further drives the first crank 111, the second crank 112, the third crank 113 and the fourth crank 114 to move downwards, so as to push the respective connected sliders to move outwards, further push the open valve flap 16 to move outwards until the spherical surface is completely attached to the inner cavity of the hollow spherical valve body 6, and at the moment, fluid flows through the open valve flap 16, so that the valve is opened.

2. The process of switching the valve from opening to closing is as follows: the closing process and the opening process of the valve are basically the same, namely the valve core shaft 12 moves vertically upwards to make the valve clack be separated from contact, then the valve core shaft rotates 90 degrees, then the valve core shaft 12 moves vertically downwards to push out the crank and the sliding block, and the closing valve clack 7 is further pushed to be completely attached to the inner cavity of the hollow spherical valve body 6. In this process, the U-shaped guide groove 51 has already rotated 90 ° compared to the previous process, so that when the pin hole on the transmission mechanism mounting bracket 4 is used, the third electric push rod 47 and the fourth electric push rod 48 outside the third pin hole 43 and the fourth pin hole 44 are changed to perform the same operation as the previous process one after another.

3. The invention discloses a process for discharging residual liquid after the state of a valve is switched: the upper end optical axis part of the upper end optical axis lower end thread type discharge bolt 8 plays a role in guiding and limiting the movement of the conical valve core in the two processes. After the state switching is finished, the external part rotates out of the bottom of the hollow spherical valve body 6, the upper end optical axis lower end thread type discharge bolt 8 is separated from the bottom of the hollow spherical valve body, and residual liquid in the cavity can be discharged.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures or equivalent processes performed by the present specification and the accompanying drawings, or directly or indirectly applied to other related system fields, are included in the scope of the present invention.

Claims

1. The utility model provides a telescopic frictionless ball valve of disk motor cooperation face cam drive which characterized in that:

the disc type motor rotor structure comprises a disc type motor upper stator (1), wherein the disc type motor upper stator (1) is fixedly connected with a disc type motor lower stator (3), a disc type motor rotor (2) is arranged inside the disc type motor upper stator (1) and the disc type motor lower stator (3), the disc type motor rotor (2) is fixedly connected with an output shaft (15), and a round roller (14) is fixedly connected with the lower half section of the output shaft (15);

a transmission mechanism mounting frame (4) is fixedly connected to the lower side of the disc type motor lower stator (3), a first pin hole (41), a second pin hole (42), a third pin hole (43) and a fourth pin hole (44) are formed in the transmission mechanism mounting frame (4), and a first electric push rod (45), a second electric push rod (46), a third electric push rod (47) and a fourth electric push rod (48) are respectively mounted on the outer sides of the first pin hole (41), the second pin hole (42), the third pin hole (43) and the fourth pin hole (44);

the roller type roller chain transmission mechanism is characterized by further comprising a transmission cylinder (5), wherein the transmission cylinder (5) is installed inside the transmission mechanism installation frame (4), an arc-shaped groove (53) is formed in the upper half portion of the transmission cylinder (5), the circular roller (14) extends into the arc-shaped groove (53), and a U-shaped guide groove (51) and an I-shaped guide groove (52) are respectively formed in the lower half portion of the transmission cylinder (5); the tail end of the transmission cylinder (5) is fixedly connected with the valve core shaft (12) through a pin shaft (13);

the hollow spherical valve body (6) is fixedly connected to the lower end of the transmission mechanism mounting frame (4), and a square valve core (9) is installed inside the hollow spherical valve body (6); four grooves are formed in four side faces of the square valve core (9) and are respectively as follows: a first groove (97), a second groove (98), a third groove (99), a fourth groove (910); wherein the first groove (97) is opposite to the second groove (98) and is provided with two closing valve flaps (7), the third groove (99) is opposite to the fourth groove (910) and is provided with two opening valve flaps (16);

the bottom of the valve core shaft (12) is inserted into a square hole (95) in the center of the upper top surface of the square valve core (9), a first rectangular slide way (91), a second rectangular slide way (92), a third rectangular slide way (93) and a fourth rectangular slide way (94) are respectively arranged on four sides of the upper top surface of the square valve core (9), and a first slide block (101), a second slide block (102), a third slide block (103) and a fourth slide block (104) are respectively arranged in the first slide way (91), the second slide way (92), the third slide way (93) and the fourth slide way (94); the front ends of the first sliding block (101) and the second sliding block (102) are fixedly connected with the back surface of the closing valve clack (7), and the front ends of the third sliding block (103) and the fourth sliding block (104) are fixedly connected with the back surface of the opening valve clack (16); the other end of the sliding block is respectively connected with the valve core shaft (12) through a first crank (111), a second crank (112) and a third crank (113), and a fourth crank (114);

a round hole (96) is formed in the center of the lower bottom surface of the valve core (9), an upper semi-optical axis section of the upper-end optical axis lower-end threaded release bolt (8) is inserted into the round hole (96), and the lower semi-threaded section of the upper-end optical axis lower-end threaded release bolt (8) is fixedly connected with the hollow spherical valve body (6) in a sealing mode.

2. The disc motor and face cam driven telescopic frictionless ball valve of claim 1, wherein:

a first pin hole (41), a second pin hole (42), a third pin hole (43) and a fourth pin hole (44) are uniformly distributed on the circumference of the transmission mechanism mounting frame (4).

3. A disc motor and face cam driven telescopic frictionless ball valve according to claim 1 or 2, wherein:

and the lower half thread section of the upper end optical axis lower end thread type relief bolt (8) is fixedly connected and sealed with the hollow spherical valve body (6) through threads.