A stretching device for the production of bio-based nylon yarn

Abstract

This invention discloses a stretching device for the production of bio-based nylon yarn, comprising two chains, with multiple base plates fixedly disposed between the two chains. A clamping assembly is disposed on the outer side of each base plate for clamping the yarn and moving it along the chains. A limiting component is disposed between the clamping assembly and the clamping plate. A first magnetic block is disposed between the two chains. When the clamping assembly rotates with the chains to the first magnetic block, the attraction force of the first magnetic block on the limiting component causes it to move away from the clamping assembly. Through the cooperation of multiple sliding plates, the yarn can be clamped between adjacent sliding plates. Since the yarn length between adjacent sliding plates is limited, the yarn is subjected to more uniform force. Furthermore, the rotation of the sliding plates driven by the chains allows for repeated and continuous clamping of the yarn, avoiding the problems of large equipment size or uneven force distribution caused by long yarns.

Description

Technical Field

[0001] This invention relates to the field of yarn processing technology, and in particular to a stretching device for the production of bio-based nylon yarn. Background Technology

[0002] In the fabric production process, the stretching process utilizes the plasticity of fibers such as cellulose, silk, and wool under humid conditions to gradually widen the fabric width to the specified size and then perform a drying and stabilization process, which can reduce the deformation of the fabric during use.

[0003] Chinese patent CN217052700U discloses a fabric stretching device, including a mounting base, a fixed base on one side of the mounting base, a first clamping mechanism on the upper end of the fixed base, a linear mechanism on the surface of the mounting base, a movable base at the sliding end of the linear mechanism, a second clamping mechanism on the upper end of the movable base, a side of the movable base connected to the upper end of a handle, and an adjustment mechanism on the side of the mounting base for limiting the horizontal displacement of the lower end of the handle. The advantages of this solution are: by providing a handle and a corresponding adjustment mechanism on the movable base and mounting base respectively, and by locking the lower end of the handle to the adjustment mechanism to control the distance between the movable base and the fixed base, the operator can fine-tune the stretching amplitude according to the fabric length or material properties, which is beneficial to improving the fabric setting quality.

[0004] The above-mentioned device pulls the yarn through the first clamping mechanism and the second clamping mechanism. However, in actual use, when the yarn is long, the overall volume of the device will increase accordingly, and the force on the yarn is not uniform when it is pulled. If a long section of yarn is stretched in segments, the first clamping mechanism and the second clamping mechanism need to be operated repeatedly to clamp the yarn. In summary, the above-mentioned device still has room for improvement.

[0005] Therefore, it is necessary to provide a stretching device for the production of bio-based nylon yarn to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to provide a stretching device for the production of bio-based nylon yarn, in order to solve the problem mentioned in the background art that the existing device stretches the yarn by setting a first clamping mechanism and a second clamping structure, but in actual use, when the yarn is long, the overall volume of the device will increase accordingly, and the force on the yarn is not uniform when it is stretched.

[0007] Based on the above ideas, the present invention provides the following technical solution: a stretching device for the production of bio-based nylon yarn, comprising two chains, a plurality of base plates fixedly disposed between the two chains, a clamping component disposed on the outer side of the base plate for clamping the yarn and driving it to move with the chain, and a limit component disposed between the clamping component and the clamping plate.

[0008] A first magnetic block is provided between the two chains. When the clamping component rotates with the chain to the first magnetic block, the attraction force of the first magnetic block on the limiting component causes it to move away from the clamping component, thereby separating the substrate from the clamping component. The clamping component moves downward relative to the substrate. During this process, the yarn between two adjacent clamping components can be stretched.

[0009] As a further embodiment of the present invention: the clamping assembly includes a connecting plate connected to the substrate, a sliding plate fixedly connected to the outer side of the connecting plate, a groove is provided on the outer surface of the sliding plate, pressure blocks are provided at both ends of the groove, a plurality of clamping plates are slidably arranged between the two pressure blocks, a screw is provided at the sliding plate, the screw passes through the pressure block and is threadedly connected to it, both ends of the screw pass through the sliding plate and are fixedly fitted with gears, and a first rack and a second rack that cooperate with the gears are respectively provided on both sides of the chain.

[0010] As a further aspect of the present invention: the limiting component includes a locking block elastically connected to the substrate, and a locking groove that cooperates with the locking block is provided on the side of the connecting plate near the substrate. A connecting rod is fixedly provided at the end of the locking block away from the connecting plate, and a second magnetic block that cooperates with the first magnetic block is fixedly provided at one end of the connecting rod. The sides of the first magnetic block and the second magnetic block opposite each other have different magnetic poles. A support rod is fixedly connected between the two second racks, and a stop block is elastically provided at both ends of the support rod. A first inclined surface is provided at the end of the stop block near the chain. When the chain drives the slide plate to move downward, it will contact the first inclined surface on the stop block.

[0011] As a further aspect of the present invention: a crossbar is provided on one side of the chain, and a plurality of through holes are evenly provided on the crossbar.

[0012] As a further aspect of the present invention: baffles are provided on the outer side of the first rack and the inner side of the second rack. When the gear is meshed with the first rack or the second rack, the slide plate is in contact with the baffle.

[0013] As a further aspect of the present invention: a sliding groove is provided on the side of the substrate near the connecting plate, a protrusion that slides with the sliding groove is fixedly connected to the connecting plate, a vertical shaft is fixedly connected inside the sliding groove, and the vertical shaft passes through the protrusion and is slidably connected to it.

[0014] As a further embodiment of the present invention: a through circular hole is provided on the substrate, the card block and the second magnetic block are slidably disposed inside the circular hole, a baffle is fixedly connected inside the circular hole, the connecting rod passes through the baffle and is slidably connected to it, and a third spring is sleeved on the outside of the connecting rod, the third spring being located between the baffle and the card block.

[0015] As a further embodiment of the present invention: a side plate is provided on the outer side of the chain, and sliders are rotatably provided at both ends of the crossbar. A sliding rod is fixedly connected to the outer side of the slider, and a fixing block that cooperates with the sliding rod is fixedly connected to the side plate. The sliding rod passes through the fixing block and is slidably connected to it. A second spring is sleeved on the outer side of the sliding rod. The second spring is located between the fixing block and the slider, and a second inclined surface is provided at the bottom of the slider.

[0016] As a further embodiment of the present invention: mounting holes are provided on the opposite sides of two adjacent clamping plates, and a limit spring is fixedly provided between the two adjacent clamping plates at the mounting holes.

[0017] As a further aspect of the present invention: the outer side of the screw is provided with two sections of external threads with opposite directions.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: When the substrate moves to the first magnetic block along the chain, the attraction between the first magnetic block and the second magnetic block can drive the locking block to move towards the chain and separate from the connecting plate, thereby allowing the connecting plate and the sliding plate to slide downward relative to the substrate, while the adjacent and above sliding plate is in a state of being locked with the substrate. At this time, under the gravity of the connecting plate and the sliding plate, a section of yarn between the two sliding plates will be stretched. This device uses the cooperation of multiple sliding plates to clamp the yarn between two adjacent sliding plates. Since the length of the yarn between two adjacent sliding plates is limited, the yarn is subjected to more uniform force. Furthermore, by driving the sliding plates to rotate through the chain, the yarn can be clamped repeatedly and continuously, avoiding the problem of the device being large or the force being uneven due to the long yarn. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 This is a distribution diagram of the clamping components of the present invention;

[0022] Figure 3 This is a schematic diagram showing the distribution of the first rack, the second rack, and the baffle of the present invention.

[0023] Figure 4 This is a schematic diagram of the substrate, connecting plate, and sliding plate structure of the present invention;

[0024] Figure 5 This is a schematic diagram of the sliding fit between the connecting plate and the substrate of the present invention;

[0025] Figure 6 This is a schematic diagram of the elastic connection structure between the card block and the substrate of the present invention;

[0026] Figure 7 This is a schematic diagram of the pressure block and clamping plate structure of the present invention;

[0027] Figure 8 This is the present invention. Figure 1 A magnified structural diagram at point A;

[0028] Figure 9 This is the present invention. Figure 2 A magnified structural diagram at point B;

[0029] Figure 10 This is the present invention. Figure 3 A magnified structural diagram at point C.

[0030] In the diagram: 1. Side plate; 2. Rotating shaft; 3. Chain; 4. Connecting plate; 5. Slide plate; 6. Clamping plate; 7. Baffle; 8. Second rack; 9. Support rod; 10. Slider; 11. First rack; 12. Gear; 13. First magnet; 14. Stop block; 15. Connecting shaft; 16. Second magnet; 17. Base plate; 18. First spring; 19. Guide post; 20. First inclined surface; 21. Wire hole; 22. Crossbar; 23. Second inclined surface; 24. Second spring; 25. Slide rod; 26. Vertical shaft; 27. Protrusion; 28. Slot; 29. ​​Connecting rod; 30. Third spring; 31. Locking block; 32. Screw; 33. External thread; 34. Limiting spring; 35. Pressure block. Detailed Implementation

[0031] like Figure 1-3 As shown, a stretching device for producing bio-based nylon yarn includes two chains 3, with a plurality of base plates 17 fixedly disposed between the two chains 3. A clamping component is disposed on the outer side of the base plate 17 for clamping the yarn and driving it to move with the chain 3. A limit component is disposed between the clamping component and the clamping plate 6 to facilitate the interlocking of the base plate 17 and the clamping component.

[0032] Furthermore, a first magnetic block 13 is provided between the two chains 3, and the first magnetic block 13 is located on the side of the chain 3 away from the substrate 17. When the clamping component rotates with the chain 3 to the first magnetic block 13, the attraction force of the first magnetic block 13 on the limiting component causes it to move away from the clamping component, thereby separating the substrate 17 from the clamping component. The clamping component moves downward relative to the substrate 17. During this process, the yarn between two adjacent clamping components can be stretched. The multiple sets of clamping components facilitate continuous yarn stretching and restrict the yarn to be stretched between two adjacent clamping components, avoiding the problem of uneven force during stretching due to excessive yarn length. It also avoids the problem of large equipment size due to long yarn. At the same time, the continuous operation of the device is enhanced because the chain 3 drives the clamping component to rotate.

[0033] like Figure 1-4 8-10 The above-mentioned clamping assembly includes a connecting plate 4 connected to the substrate 17. The connecting plate 4 can slide relative to the substrate 17, and a sliding plate 5 is fixedly connected to the outer side of the connecting plate 4. Specifically, a groove is provided on the outer side of the sliding plate 5, and pressure blocks 35 are provided at both ends inside the groove. Multiple clamping plates 6 are slidably arranged between the two pressure blocks 35. Specifically, a screw 32 is provided at the sliding plate 5. The screw 32 passes through the pressure block 35 and is threadedly connected to it. The clamping plate 6 is provided with a through hole that cooperates with the screw 32.

[0034] Furthermore, both ends of the screw 32 extend through the slide plate 5 and are rotatably connected to it. A gear 12 is fixedly sleeved on one end of the screw 32 outside the slide plate 5. A first rack 11 and a second rack 8 that cooperate with the gear 12 are respectively provided on both sides of the chain 3. Specifically, the first rack 11 is located outside the gear 12, while the second rack 8 is located inside the gear 12. This allows the chain 3 to drive the slide plate 5 to move, and through the meshing of the first rack 11, the second rack 8 and the gear 12, the gear 12 can be driven to rotate in different directions. In turn, the screw 32 drives the two pressure blocks 35 to move closer and further apart.

[0035] The limiting component includes a locking block 31 that is elastically connected to the substrate 17, and a locking groove 28 that cooperates with the locking block 31 is provided on the side of the connecting plate 4 near the substrate 17. A connecting rod 29 is fixedly provided at the end of the locking block 31 away from the connecting plate 4, and a second magnetic block 16 that cooperates with the first magnetic block 13 is fixedly provided at the end of the connecting rod 29 away from the locking block 31. The sides of the first magnetic block 13 and the second magnetic block 16 opposite to each other have different magnetic poles.

[0036] In addition, a support rod 9 is fixedly connected between the two second racks 8. A stop block 14 is elastically provided at both ends of the support rod 9. The top of the stop block 14 near the chain 3 is set as a first inclined surface 20. When the chain 3 drives the slide plate 5 to move downward, it will contact the first inclined surface 20 on the stop block 14.

[0037] In actual use, a crossbar 22 is provided on one side of the chain 3. The crossbar 22 is evenly provided with multiple through holes 21. Specifically, one end of the yarn is passed through the through hole 21 and located between two adjacent clamping plates 6. The chain 3 is driven to rotate by an external device. The chain 3 can drive the clamping plates 6 to rotate, and then drive the slide plate 5 to move through the base plate 17. When the gear 12 meshes with the first rack 11, it can drive the screw 32 to rotate in the forward direction, thereby driving the two pressure blocks 35 to move closer to each other. During this process, the two pressure blocks 35 that move closer to each other will squeeze the clamping plates 6, so that the two adjacent clamping plates 6 clamp the yarn. After the gear 12 passes the first rack 11, the clamping plates 6 remain stable. Through this structure, the yarn can be continuously clamped between the two adjacent slide plates 5 in the vertical direction.

[0038] When the substrate 17 moves to the first magnetic block 13 along with the chain 3, the attraction between the first magnetic block 13 and the second magnetic block 16 can drive the locking block 31 to move in the direction of the chain 3 and separate from the connecting plate 4, thereby allowing the connecting plate 4 and the sliding plate 5 to slide downward relative to the substrate 17, while the adjacent and above the substrate 17 is in a locked state with the substrate 17. At this time, under the gravity of the connecting plate 4 and the sliding plate 5, a section of yarn between the two sliding plates 5 will be stretched.

[0039] After the stretching continues for a period of time, the chain 3 continues to rotate. As the slide plate 5 continues to move with the chain 3, it will contact the first inclined surface 20 on the stop block 14. The stop block 14 limits the slide plate 5 so that it can temporarily stop moving. At this time, the base plate 17 continues to move with the chain 3. When the first magnetic block 13 and the second magnetic block 16 are misaligned, the locking block 31 will return to its initial state. When the base plate 17 moves to the state where the locking block 31 is aligned with the slot 28, the locking block 31 can be inserted into the slot 28 again, so that the connecting plate 4 and the base plate 17 are locked together again. At this time, the chain 3 can drive the base plate 17, the connecting plate 4 and the slide plate 5 to move synchronously. During this process, the slide plate 5 will exert a large pressure on the stop block 14 and cause the stop block 14 to slide outward.

[0040] When the gear 12 on the slide plate 5 moves to the second rack 8, the meshing of the second rack 8 and the gear 12 drives the screw 32 to rotate in the opposite direction, thereby causing the two pressure blocks 35 to move away from each other. At this time, the multiple clamping plates 6 also separate and release the pressure on the yarn, allowing the operator to remove the stretched yarn from between the multiple clamping plates 6. Subsequently, when the interconnected base plate 17, connecting plate 4, and slide plate 5 move to the crossbar 22, they will continue to clamp new yarn. By repeating the above steps, the yarn can be clamped between two adjacent slide plates 5 using the cooperation of multiple slide plates 5. Since the yarn length between two adjacent slide plates 5 is limited, the yarn is subjected to more uniform force. Furthermore, the chain 3 drives the slide plate 5 to rotate, which can repeatedly and continuously clamp the yarn, avoiding the problem of a large equipment size or uneven force due to the long yarn.

[0041] like Figure 1-2 As shown, sprockets are provided at both ends of the chain 3, so that the chain 3 can be fitted onto the outside of the sprockets. In addition, a side plate 1 is provided on the outside of the chain 3, and a rotating shaft 2 is provided between the two side plates 1. Specifically, the rotating shaft 2 passes through the sprocket and is fixedly connected to it, and the rotating shaft 2 passes through the side plate 1 and is rotatably connected to it, thereby driving the sprocket to rotate. A motor is fixedly installed on the side plate 1, and the output shaft of the motor is connected to the rotating shaft 2 to drive the sprocket to rotate, thereby driving the chain 3 to rotate. In actual use, the operation of the chain 3 is controlled by starting and stopping the motor, so that the slide plate 5 cooperates with the first magnetic block 13.

[0042] In actual use, multiple sets of connecting shafts 15 are fixedly installed between the two chains 3, with two connecting shafts in each set. The connecting shafts 15 penetrate the base plate 17. In actual application, the connecting shafts 15 can be rotatably engaged with the base plate 17, or they can be fixed to each other by welding. The chain 3 is specifically composed of chain links and pins between adjacent chain links. The connecting shaft 15 can be connected to the pin, or a clamp can be pre-fixed on the pin, and the connecting shaft 15 is fixedly connected to the clamp. Of course, installing a rigid component between the two chains 3 is a mature technical means in the mechanical field, which will not be elaborated here.

[0043] A bracket is fixedly installed on the outside of side plate 1 to facilitate its installation.

[0044] like Figure 3-4 As shown, in order to improve the stability of gear 12 when meshing with the first rack 11 or the second rack 8, baffles 7 are provided on the outer side of the first rack 11 and the inner side of the second rack 8. When gear 12 is meshing with the first rack 11 or the second rack 8, the slide plate 5 is in contact with the baffles 7, thereby preventing gear 12 from disengaging from the first gear 11 or the second rack 8.

[0045] The outer surfaces of the baffle 7, the first rack 11, and the second rack 8 are all fixedly connected with protrusions, which fix the baffle 7, the first rack 11, and the second rack 8 to the side plate 1.

[0046] A fixing rod is fixedly provided between the first magnetic block 13 and the side plate 1 to install the first magnetic block 13.

[0047] like Figure 5-7 As shown, a groove is provided on the side of the substrate 17 near the connecting plate 4, and a protrusion 27 that slides and engages with the groove is fixedly connected to the connecting plate 4. A vertical shaft 26 is also fixedly connected in the groove, and the vertical shaft 26 passes through the protrusion 27 and is slidably connected to it.

[0048] A through circular hole is provided on the substrate 17. The locking block 31 and the second magnetic block 16 are slidably disposed inside the circular hole. A baffle is fixedly connected inside the circular hole. The baffle is located between the second magnetic block 16 and the locking block 31. The connecting rod 29 passes through the baffle and is slidably connected to it. A third spring 30 is sleeved on the outside of the connecting rod 29. The third spring 30 is located between the baffle and the locking block 31 to realize the elastic connection between the locking block 31 and the substrate 17. When the first magnetic block 13 and the second magnetic block 16 are misaligned, the locking block 31 can be inserted into the slot 28 by the force of the third spring 30.

[0049] The stop block 14 passes through the support rod 9 and is slidably connected to it. A boss is fixedly connected to the end of the stop block 14 away from the chain 3. A guide post 19 is fixedly connected to the outer surface of the support rod 9. The guide post 19 passes through the boss and is slidably connected to it. A retaining ring is fixedly connected to the end of the guide post 19 that passes through the boss. A first spring 18 is sleeved on the outer side of the guide post 19. The first spring 18 is located between the retaining ring and the boss. The pressure of the first spring 18 allows the stop block 14 to move towards the chain 3.

[0050] Both ends of the crossbar 22 are rotatably equipped with sliders 10. A sliding rod 25 is fixedly connected to the outer side of the slider 10, and a fixing block that cooperates with the sliding rod 25 is fixedly connected to the side plate 1, so that the sliding rod 25 passes through the fixing block and slides with it. A second spring 24 is sleeved on the outer side of the sliding rod 25. The second spring 24 is located between the fixing block and the slider 10. A second inclined surface 23 is provided at the bottom of the slider 10. In actual use, when the slide plate 5 moves to the crossbar 22 with the chain 3, the slide plate 5 will contact the second inclined surface 23 on the slider 10, thereby squeezing the slider 10 to slide outward, and thus driving the crossbar 22 to move upward. After the slide plate 5 passes the slider 10, the slider 10 and the crossbar 22 will return to their original positions. During this process, the yarn passing through the thread hole 21 will be placed between the two adjacent clamping plates 6, which is conducive to the clamping plates 6 clamping the yarn.

[0051] like Figure 7 As shown, the screw 32 has two external threads 33 with opposite directions on its outer side, which allows the screw 32 to drive the two pressure blocks 35 to move closer or further apart. The middle and both ends of the screw 32 are made of smooth rods, which allows the clamping plate 6 to slide relative to the screw 32, and the screw 32 can be rotatably connected to the slide plate 5.

[0052] A guide shaft is fixedly connected in the groove. The guide shaft passes through the pressure block 35 and the clamping plate 6 and is slidably connected to both. Each of the two adjacent clamping plates 6 has a mounting hole on its opposite side. A limit spring 34 is fixedly installed between the two adjacent clamping plates 6 at the mounting hole. In actual use, the limit spring 34 is located at the bottom of the groove. When the two pressure blocks 35 move away from each other, the pressure of the limit spring 34 causes the multiple clamping plates 6 to separate, thereby removing the pressure between the clamping plates 6 and the yarn.

[0053] In actual use, the clamp 6 can be made of materials such as rubber to increase the friction between it and the yarn.

Claims

1. A stretching device for producing bio-based nylon yarn, comprising two chains, wherein a plurality of base plates are fixedly disposed between the two chains, characterized in that: A clamping assembly is provided on the outer side of the substrate for clamping the yarn and driving it to move with the chain. A limit component is provided between the clamping assembly and the clamping plate. A first magnetic block is provided between the two chains. When the clamping component rotates with the chain to the first magnetic block, the attraction force of the first magnetic block on the limiting component causes it to move away from the clamping component, thereby separating the substrate from the clamping component. The clamping component moves downward relative to the substrate. During this process, the yarn between two adjacent clamping components can be stretched. The clamping assembly includes a connecting plate connected to the base plate, a sliding plate fixedly connected to the outer side of the connecting plate, a groove opened on the outer surface of the sliding plate, a pressure block provided at both ends of the groove, a plurality of clamping plates slidably arranged between the two pressure blocks, a screw provided at the sliding plate, the screw passing through the pressure block and threadedly connected to it, both ends of the screw passing through the sliding plate and fixedly fitted with gears, and a first rack and a second rack that cooperate with the gears respectively provided on both sides of the chain; The limiting component includes a locking block that is elastically connected to the substrate. The connecting plate has a locking groove on the side near the substrate that cooperates with the locking block. A connecting rod is fixedly installed at the end of the locking block away from the connecting plate. A second magnetic block that cooperates with the first magnetic block is fixedly installed at one end of the connecting rod. The sides of the first magnetic block and the second magnetic block opposite each other have different magnetic poles. A support rod is fixedly connected between the two second racks. A stop block is elastically installed at both ends of the support rod. A first inclined surface is provided at the end of the stop block near the chain. When the chain drives the slide plate to move downward, it will contact the first inclined surface on the stop block.

2. The stretching equipment for producing bio-based nylon yarn according to claim 1, characterized in that: A crossbar is provided on one side of the chain, and multiple through holes are evenly distributed on the crossbar.

3. The stretching equipment for producing bio-based nylon yarn according to claim 1, characterized in that: A baffle is provided on the outer side of the first rack and the inner side of the second rack. When the gear is meshed with the first rack or the second rack, the slide plate is in contact with the baffle.

4. The stretching equipment for producing bio-based nylon yarn according to claim 1, characterized in that: A groove is provided on the side of the substrate near the connecting plate. A protrusion that slides with the groove is fixedly connected to the connecting plate. A vertical shaft is fixedly connected inside the groove, and the vertical shaft passes through the protrusion and is slidably connected to it.

5. A stretching device for producing bio-based nylon yarn according to claim 1, characterized in that: The substrate has a through circular hole. The card block and the second magnetic block are slidably disposed inside the circular hole. A baffle is fixedly connected inside the circular hole. The connecting rod passes through the baffle and is slidably connected to it. A third spring is sleeved on the outside of the connecting rod. The third spring is located between the baffle and the card block.

6. A stretching device for producing bio-based nylon yarn according to claim 2, characterized in that: A side plate is provided on the outer side of the chain, and sliders are rotatably provided at both ends of the crossbar. A sliding rod is fixedly connected to the outer side of the slider, and a fixed block that cooperates with the sliding rod is fixedly connected to the side plate. The sliding rod passes through the fixed block and is slidably connected to it. A second spring is sleeved on the outer side of the sliding rod. The second spring is located between the fixed block and the slider, and a second inclined surface is provided at the bottom of the slider.

7. A stretching device for producing bio-based nylon yarn according to claim 1, characterized in that: Mounting holes are provided on the opposite sides of two adjacent clamping plates, and a limit spring is fixedly installed between the two adjacent clamping plates at the mounting holes.

8. A stretching device for producing bio-based nylon yarn according to claim 1, characterized in that: The screw has two external threads with opposite directions on its outer side.

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