A bead wire fracture detection device

Abstract

The present invention relates to the technical field of tire bead wire testing, and specifically to a tire bead wire fracture detection device, comprising: a bracket and four positioning wheels rotating on the outer wall thereof, the four positioning wheels forming a rectangular distribution; two test wheels slidably mounted on the outer wall of the bracket, the two test wheels being located within the range of the rectangular distribution, a test object being sleeved on the outer walls of the positioning wheels and the test wheels to form an I-shaped alignment; a driver for controlling the two test wheels to approach each other is mounted on the outer wall of the bracket; a welding part S of the test object may be located at the top or bottom center of the I-shaped alignment, two limiters and two baffles are slidably mounted on the bracket, the two limiters need to be adjusted to the two sides of the welding part S respectively, and the limiters can penetrate into the rubber layer of the test object to complete locking, and the baffles limit the displacement of the limiters. The present invention realizes the fracture performance detection of the tire bead wire welding part, and also detects the rubber hanging ability of the tire bead wire.

Description

Technical Field

[0001] The invention relates to the technical field of tire bead wire testing, and in particular to a tire bead wire fracture detection device. Background Art

[0002] The bead wire is the main part that connects the tire to the rim. It can withstand the tensile force caused by internal pressure and overcome the lateral force exerted on the tire when turning.

[0003] During the production process of the tire bead wire, a welding machine is required to weld the head and tail ends of the tire bead wire, and then the welding part is allowed to cool naturally or through intervention cooling, and finally the welding part is cleaned, so that the tire bead wire can be continuously transported and connected to the head and tail rolls during the production process. However, during the process of performing fracture detection on the tire bead wire, the steel wire is usually tested for fracture, and the fracture performance of the welding part of the tire bead wire is not tested, which may result in bad spots or weak spots in the tire bead wire.

[0004] The above welding steps can be referred to the Chinese patent for a welding machine for bead wire production, announcement number:

[0005] CN114083295B. Summary of the invention

[0006] The present invention provides a tire bead wire fracture detection device, which can detect the fracture performance of a tire bead wire welding portion and also detect the rubber attachment ability of the tire bead wire.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A bead wire fracture detection device, comprising:

[0009] A bracket and four positioning wheels rotating on the outer wall thereof, wherein the four positioning wheels are arranged in a rectangular shape;

[0010] Two test wheels are slidably mounted on the outer wall of the bracket, the two test wheels are located in a rectangular distribution range, and the test object is sleeved on the outer wall of the positioning wheel and the test wheel to form an I-shaped routing;

[0011] The outer wall of the bracket is provided with a driver for controlling the two test wheels to approach each other;

[0012] The welding position S of the test object can be located at the top or bottom center of the I-type trace.

[0013] Optionally, two limiters and two baffles are slidably installed on the bracket, and the two limiters need to be adjusted to the two sides of the welding position S respectively, and the limiters can penetrate the rubber layer of the test object to complete the locking, and the baffles are fixedly installed on the bracket, and the test object can freely shuttle through the outer wall of the baffle, and the baffle limits the displacement of the limiter.

[0014] Optionally, a sleeve is fixedly mounted on the baffle, and the limiter includes a limit plate slidably mounted inside the sleeve, two molds are symmetrically slidably mounted on the limit plate, and the opposing surfaces of the two molds are designed with arc-shaped grooves, and puncture parts are arrayed inside the arc-shaped grooves, and the puncture parts have a blade surface and a right-angle surface, and the right-angle surface limits the escape of the test object, and a transmission device is also designed inside the sleeve to bring the two molds close to each other and lock them, and a temporary connector is also designed on the sleeve to lock the limit plate.

[0015] Optionally, the transmission device includes a driving block slidably mounted on the inner wall of the sleeve, the driving block can approach the baffle and the mold, the ends of the driving block and the mold close to each other are designed to be inclined surfaces, and the inclined surfaces are matched for transmission. Limiting holes are designed on the outer walls of the sleeve, the driving block and the mold. When the driving block slides to a preset position that can lock the two molds, the three limiting holes are interconnected, and interference pins can be placed in the limiting holes. The limiting holes on the sleeve do not interfere with the movement of the interference pins.

[0016] Optionally, the temporary connector includes a plurality of shear pins passing through the outer wall of the sleeve, wherein the plurality of shear pins are located between the limiting plate and the baffle, and one end of the shear pins extends into the interior of the sleeve and blocks the displacement of the limiting plate.

[0017] Optionally, an assembly groove is penetrated through the outer wall of the bracket, two assembly blocks are slidably installed inside the assembly groove, the two test wheels are rotatably installed on the two assembly blocks respectively, a ring is rotatably installed on the outer wall of the assembly block, an assembly box is installed on the outer wall of the bracket, a tension sensor is slidably installed inside the assembly box, a regulator for controlling the position of the tension sensor is installed in the assembly box, a transmission rope is fixedly connected between the tension end of the tension sensor and the outer wall of the ring, and a digital display screen is installed on the outside of the assembly box.

[0018] Optionally, the regulator includes a screw rod penetrating into the interior of the assembly box, the screw rod is threadedly connected to the penetration portion, and an end of the screw rod is rotatably connected to the housing of the tension sensor.

[0019] Optionally, the driver includes a connecting rod hinged on the outer walls of the two assembly blocks, the ends of the two connecting rods away from the assembly blocks are jointly hinged to the limit seat, the two connecting rods are distributed in a V shape, and the driver includes an external power source, which can control the limit seat to move in the vertical direction.

[0020] Optionally, a laser transmitter and a laser receiver are respectively mounted on the outer walls of the two opposite surfaces of the assembly blocks, the laser receiver and the laser transmitter are located on the same plane, and the laser receiver can receive light emitted from the laser transmitter.

[0021] Optionally, also include:

[0022] A position corrector, wherein the position corrector is designed on the positioning wheel;

[0023] The positioner comprises two clamping plates slidably mounted on the roller wall of the positioning wheel, a wire clamping gap is formed between the two clamping plates, and an elastic member is fixedly mounted between the outer wall of the clamping plate away from the wire clamping gap and the inner wall of the positioning wheel.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The test object is restricted by four positioning wheels, and then the test object is tightened by the relative displacement of two test wheels, so that the test object can be in a testable state. At this time, the welding part S of the test object is adjusted to the top or bottom center of the I-type alignment by rotating the positioning wheel or the test wheel, and then the two test wheels are moved away from each other to stretch the test object, so as to perform fracture detection on the welding part S of the test object and test the pressure bearing capacity of the welding part S.

[0026] 2. After completing the fracture detection of the welding part S, the limiters located on both sides of the welding part S can prevent the test object from detaching from the test wheel. By continuing to bring the two test wheels closer to each other, a conflict occurs between the limiter and the baffle, so that the test object can be tightened again. Then, the two test wheels are continued to be controlled to approach each other, so that the rubber layer of the test object is locked by the penetration of the limiter, thereby detecting the adhesion between the rubber layer and the test object. When the rubber layer is detached from the test object, the glue hanging ability of the test object can be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the front three-dimensional structure of the present invention;

[0028] Figure 2 For the present invention Figure 1 Right view of;

[0029] Figure 3 For the present invention Figure 2 Sectional view at AA in the middle;

[0030] Figure 4 It is a schematic diagram of the back three-dimensional structure of the present invention;

[0031] Figure 5It is a structural schematic diagram of the limiter in the present invention;

[0032] Figure 6 For the present invention Figure 5 Right view of;

[0033] Figure 7 For the present invention Figure 6 A schematic diagram of the structure cut away at the middle edge BB;

[0034] Figure 8 It is a schematic diagram of the disassembly of the parts of the limiter in the present invention;

[0035] Fig. 9 It is a partial structural schematic diagram of the regulator and digital pressure display in the present invention;

[0036] Fig.10 For the present invention Fig. 9 An internal cross-sectional view of

[0037] Fig.11 It is a schematic diagram of the structure of the position corrector in the present invention.

[0038] In the figure: 1. bracket; 2. positioning wheel; 3. test wheel; 4. baffle; 5. sleeve; 6. mold; 7. drive block; 8. limit plate; 9. shear nail; 11. puncture part; 12. assembly box; 13. tension sensor; 14. transmission rope; 15. screw; 16. collar; 17. assembly block; 18. connecting rod; 19. limit seat; 20. assembly groove; 21. laser transmitter; 22. laser receiver; 23. splint; 24. elastic member. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] See also Figures 1 to 11 The present invention provides a technical solution: a bead wire fracture detection device, comprising:

[0041] A bracket 1 and four positioning wheels 2 rotating on its outer wall, the four positioning wheels 2 form a rectangular distribution; two test wheels 3 slidably mounted on the outer wall of the bracket 1, the two test wheels 3 are located within the range of the rectangular distribution, and a test object is sleeved on the outer walls of the positioning wheels 2 and the test wheels 3 to form an I-type alignment; a driver is installed on the outer wall of the bracket 1 to control the two test wheels 3 to approach each other; a welding part S of the test object can be located at the top or bottom center of the I-type alignment.

[0042] In the prior art, some tire bead wires need to be welded by welding equipment after rubber coating production. Secondly, during the production process of the tire bead wire, in order to make the production line output continuously, the front and rear rolled wires are connected end to end by welding equipment. In both cases, the tire bead wire will have a welding part S. In the present invention, the test object is restricted by four positioning wheels 2, and then the test object is tightened by the relative displacement of two test wheels 3, so that the test object can be in a testable state. At this time, by rotating the positioning wheel 2 or the test wheel 3, the welding part S of the test object is adjusted to the top or bottom center of the I-type alignment, and then the two test wheels 3 are moved away from each other to stretch the test object, so as to perform fracture detection on the welding part S of the test object and test the pressure bearing capacity of the welding part S.

[0043] Among the more preferred embodiments, two stoppers and two baffles 4 are slidably mounted on the bracket 1. The two stoppers need to be adjusted to the two sides of the welding position S respectively, and the stoppers can penetrate the rubber layer of the test object to complete the locking. The baffle 4 is fixedly mounted on the bracket 1, and the test object can freely shuttle through the outer wall of the baffle 4. The baffle 4 limits the displacement of the stopper. In addition to the breaking tensile performance of the test object, its glue hanging ability needs to be tested to ensure that the test object has sufficient adhesion with the wheel rim rubber. In this embodiment, please refer to Figure 1 and Figure 3 Before testing the fracture performance of the welding part S, it is necessary to adjust the welding part S to the middle point of the two limiters, and then limit and lock the limiters and the rubber layer of the test object. When the welding part S of the test object breaks during the stretching process, the limiters on both sides of the welding part S can prevent the test object from detaching from the test wheel 3. At the same time, by continuing to bring the two test wheels 3 closer to each other, a conflict occurs between the limiter and the baffle 4, so that the test object can be tightened again, and then the two test wheels 3 are continued to be controlled to approach each other, so that the rubber layer of the test object is locked by the penetration of the limiter, so as to detect the adhesion between the rubber layer and the test object. When the rubber layer is separated from the test object, the glue hanging ability of the test object can be tested.

[0044] On the basis of an embodiment of detecting the glue hanging ability of a test object, a sleeve 5 is fixedly mounted on the baffle 4, and the limiter comprises a limit plate 8 slidably mounted inside the sleeve 5, and two molds 6 are symmetrically slidably mounted on the limit plate 8, and arc-shaped grooves are designed on opposite surfaces of the two molds 6, and a puncture portion 11 is arrayed inside the arc-shaped groove, and the puncture portion 11 has a blade surface and a right-angle surface, and the right-angle surface limits the escape of the test object, and a transmission device is also designed inside the sleeve 5 to bring the two molds 6 close to each other and lock them, and a temporary connector for locking the limit plate 8 is also designed on the sleeve 5.

[0045] Please refer to Figures 5 to 8 In this embodiment, the limit plate 8 can be temporarily locked and limited by a temporary connector. When the limiter needs to be combined with the test object, the transmission device is driven to allow the two molds 6 to approach each other, so that the dense puncture portion 11 can puncture the rubber layer. Secondly, the mutual approach of the two molds 6 will also apply pressure to the rubber layer to increase friction. At this time, the limiter can be locked with the rubber layer. After the fracture performance test of the welding part S is completed, the restriction of the temporary connector on the limit plate 8 can be released, so that the limit plate 8, the limiter and the transmission device can be displaced synchronously. When the two test wheels 3 approach each other, the limiter will conflict and block with the baffle 4, so that the test object is in a tight state again. Then the two test wheels 3 are controlled to approach each other, so that the test object can be disengaged from the baffle 4. Since the rubber layer and the limiter are blocked by the baffle 4, the test object needs to be out of the restriction of the rubber layer to escape. In this way, the cooperation between the limiter and the baffle 4 can be used to test the adhesion of the test object.

[0046] Second, see Figure 8 In the enlarged detail diagram, by designing the right-angle surface of the puncture portion 11, the right-angle surface can be made perpendicular to the rubber layer of the puncture portion, which can increase the locking ability of the limiter on the rubber layer.

[0047] Furthermore, the transmission device includes a driving block 7 slidably mounted on the inner wall of the sleeve 5. The driving block 7 can approach the baffle 4 and the mold 6. The ends of the driving block 7 and the mold 6 that are close to each other are designed as inclined surfaces. The inclined surfaces are transmission-matched. Limiting holes are designed on the outer walls of the sleeve 5, the driving block 7 and the mold 6. When the driving block 7 slides to a preset position that can lock the two molds 6, the three limiting holes are interconnected, and interference pins can be placed in the limiting holes. The limiting holes on the sleeve 5 do not interfere with the movement of the interference pins. Please refer to Figure 7 and Figure 8 In this embodiment, the driving block 7 is matched with the inclined surface at the end of the mold 6. When the driving block 7 is inserted into the sleeve 5, the two molds 6 can be brought close to each other to lock the rubber layer of the test object. Secondly, when the driving block 7 is inserted into the preset position, the three limiting holes will be connected to each other. At this time, the interference pin can be inserted through the limiting hole on the sleeve 5 to complete the integration between the driving block 7 and the mold 6, so that the mold 6 can always keep the rubber layer locked. After the interference pin is inserted, there will be no association between the interference pin and the limiting hole on the sleeve 5 to avoid mutual interference. The interference pin is configured with a design that is easy to pull out.

[0048] Furthermore, the temporary connector includes a plurality of shear pins 9 which are passed through the outer wall of the sleeve 5, and the plurality of shear pins 9 are located between the limit plate 8 and the baffle 4. One end of the shear pins 9 extends into the interior of the sleeve 5 and blocks the displacement of the limit plate 8. By designing the shear pins 9, when the limiter completes the puncture and locking of the rubber layer, the shear pins 9 can be pulled out to release the blocking of the limit plate 8 and the limiter.

[0049] Among the more preferred embodiments, the outer wall of the bracket 1 is penetrated with an assembly groove 20, and two assembly blocks 17 are slidably installed inside the assembly groove 20. The two test wheels 3 are rotatably installed on the two assembly blocks 17, and the outer wall of the assembly block 17 is rotatably installed with a collar 16. The outer wall of the bracket 1 is installed with an assembly box 12, and a tension sensor 13 is slidably installed inside the assembly box 12. A regulator for controlling the position of the tension sensor 13 is installed in the assembly box 12. A transmission cable 14 is fixedly connected between the tension end of the tension sensor 13 and the outer wall of the collar 16. A digital display screen is installed on the outside of the assembly box 12. Please refer to Fig. 9 and Fig.10 In this embodiment, the two test wheels 3 can be horizontally limited by the cooperation of the assembly groove 20 and the assembly block 17. By designing the regulator, the position of the tension sensor 13 can be controlled. When the two test wheels 3 are brought close to each other to tighten the test object, the digital tension of the tension sensor 13 needs to be zero, and the regulator can control the position of the tension sensor 13 to adjust the tension digital display. Secondly, when performing adhesion testing, the tension sensor 13 also needs to be reset to zero again, and the regulator will also be used at this time. Therefore, this embodiment can adjust the position of the tension sensor 13 in real time to ensure that the test is carried out normally.

[0050] Furthermore, the regulator includes a screw 15 that penetrates into the interior of the assembly box 12, the screw 15 is threadedly connected to the penetration point, and the end of the screw 15 is rotatably connected to the outer shell of the tension sensor 13. By designing the matching relationship between the screw 15 and the assembly box 12, the position of the tension sensor 13 can be adjusted by rotating the screw 15, so that the digital display of the tension sensor 13 returns to zero.

[0051] Further, the driver includes a connecting rod 18 hinged on the outer wall of the two assembly blocks 17, and the ends of the two connecting rods 18 away from the assembly blocks 17 are hinged together to the limit seat 19, and the two connecting rods 18 are distributed in a V shape. The driver includes an external power source, and the external power source can control the limit seat 19 to move in the vertical direction. Please refer to Figure 4 , Fig. 9 and Fig.10Since the assembly groove 20 limits the horizontal position of the assembly block 17, and there is an articulated relationship between the limit seat 19 and the assembly groove 20 through the connecting rod 18, when the limit seat 19 is displaced in the vertical direction, the two assembly blocks 17 can be relatively displaced, thereby controlling the two test wheels 3 to be relatively displaced.

[0052] Furthermore, a laser emitter 21 and a laser receiver 22 are respectively installed on the outer walls of the opposite surfaces of the two assembly blocks 17. The laser receiver 22 and the laser emitter 21 are located on the same plane. The laser receiver 22 can receive the light emitted from the laser emitter 21. When detecting the fracture performance of the welding part S of the test object, the tensile pressure and the total deformation elongation of the test object are also recorded. In the tensile test, the ratio of the total elongation of the test object at fracture to the original gauge length is the total elongation at fracture. In this embodiment, since the two assembly blocks 17 remain horizontal and displaced from each other, the laser receiver 22 can always receive the ranging light emitted from the laser emitter 21. By real-time recording of the displacement between the laser emitter 21 and the laser receiver 22, the total elongation of the test object can be accurately inferred.

[0053] Furthermore, the bead wire fracture detection device further comprises:

[0054] Positioner, the positioner is designed on the positioning wheel 2; the positioner includes two clamping plates 23 slidably mounted on the roller wall of the positioning wheel 2, a clamping gap is formed between the two clamping plates 23, and an elastic member 24 is fixedly installed between the outer wall of the clamping plate 23 away from the clamping gap and the inner wall of the positioning wheel 2. For details, please refer to Fig.11 In this embodiment, since the clamping plates 23 are slidably mounted on the roller wall of the positioning wheel 2, the two clamping plates 23 can maintain the same distance on the circumferential surface of the roller wall to ensure consistent friction pressure on the outer layer of the test object. At the same time, the elastic action of the elastic member 24 can enable the two clamping plates 23 to be in symmetrical positions to ensure that the test object is limited to the center of the roller wall of the positioning wheel 2. Through the cooperation of the four positioning wheels 2 and the positioner, the test object can be centered when it is socketed, and it can also adapt to test objects of different diameter specifications.

[0055] The positioner can also be applied to the test wheel 3.

[0056] Through the cooperation of the above structures, the fracture performance test of the bead wire welding part is realized, and the glue hanging ability of the bead wire is also tested.

[0057] Working principle: The test object is sleeved on the positioning wheel 2 and the test wheel 3, and the test wheel 3 is used to tighten the test object and adjust the position of the welding part S. The driver controls the two test wheels 3 to move away from each other to complete the fracture performance test at the welding part S. Secondly, before detecting the adhesion between the test object and the rubber, the test object in the tightened state is locked by the limiter. First, the shear nails 9 are inserted to limit the displacement of the limit plate 8, which is beneficial to the assembly of the drive block 7 and the mold 6 to complete the penetration of the rubber layer. Then the shear nails 9 can be extracted to release the blocking of the limit plate 8 and its upper limiter, so that the limiter can be blocked by the baffle 4. At this time, the adhesion between the test object and the rubber can be detected by moving the test wheels 3 away from each other.

[0058] The standard parts used in this embodiment can be purchased directly from the market, and the non-standard structural components recorded in the specification and the drawings can also be directly processed according to the existing technical common sense without any doubt. At the same time, the connection method of each component adopts the mature conventional means in the prior art, and the machinery, parts and equipment all adopt the conventional models in the prior art, so no specific description will be given here.

[0059] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A bead wire fracture detection device, characterized in that: include: A bracket (1) and four positioning wheels (2) rotating on the outer wall thereof, wherein the four positioning wheels (2) are arranged in a rectangular shape; Two test wheels (3) are slidably mounted on the outer wall of the bracket (1), the two test wheels (3) are located in a rectangular distribution range, and the test object is sleeved on the outer walls of the positioning wheel (2) and the test wheel (3) to form an I-shaped routing; The outer wall of the bracket (1) is provided with a driver for controlling the two test wheels (3) to approach each other; The welding position S of the test object is located at the top or bottom center of the I-type wiring; Two stoppers and two baffles (4) are slidably mounted on the bracket (1), the two stoppers need to be adjusted to the two sides of the welding position S respectively, and the stoppers can penetrate the rubber layer of the test object to complete the locking, the baffles (4) are fixedly mounted on the bracket (1), the test object can freely shuttle through the outer wall of the baffles (4), and the baffles (4) limit the displacement of the stoppers; The baffle (4) is fixedly mounted with a sleeve (5), the limiter comprises a limit plate (8) slidably mounted inside the sleeve (5), two moulds (6) are symmetrically slidably mounted on the limit plate (8), the opposite surfaces of the two moulds (6) are designed with arc-shaped grooves, and the arc-shaped grooves are arrayed with puncture parts (11), and the sleeve (5) is also designed with a temporary clamp for locking the limit plate (8); An assembly groove (20) is formed through the outer wall of the bracket (1), two assembly blocks (17) are slidably mounted inside the assembly groove (20), the two test wheels (3) are rotatably mounted on the two assembly blocks (17), a collar (16) is rotatably mounted on the outer wall of the assembly block (17), an assembly box (12) is mounted on the outer wall of the bracket (1), a tension sensor (13) is slidably mounted inside the assembly box (12), a regulator for controlling the position of the tension sensor (13) is mounted inside the assembly box (12), and a transmission cable (14) is fixedly connected between the tension end of the tension sensor (13) and the outer wall of the collar (16); The driver comprises a connecting rod (18) hinged on the outer walls of two assembly blocks (17), the ends of the two connecting rods (18) away from the assembly blocks (17) are jointly hinged to a limit seat (19), and the two connecting rods (18) are distributed in a V shape. The driver comprises an external power source, and the external power source can control the limit seat (19) to move in a vertical direction.

2. The bead wire fracture detection device according to claim 1, characterized in that: The sleeve (5) is also provided with a transmission device inside thereof for bringing the two moulds (6) closer to each other and locking them. The transmission device comprises a driving block (7) slidably mounted on the inner wall of the sleeve (5). The driving block (7) can approach the baffle (4) and the mould (6). The ends of the driving block (7) and the mould (6) that are closer to each other are both designed as inclined surfaces. The inclined surfaces are transmission-matched. Limiting holes are provided on the outer walls of the sleeve (5), the driving block (7) and the mould (6). When the driving block (7) slides to a preset position for locking the two moulds (6), the three limiting holes are interconnected. Interference pins can be placed in the limiting holes. The limiting holes on the sleeve (5) do not interfere with the movement of the interference pins.

3. The bead wire fracture detection device according to claim 2, characterized in that: The temporary connector comprises a plurality of shear pins (9) which are inserted through the outer wall of the sleeve (5); the plurality of shear pins (9) are located between the limiting plate (8) and the baffle (4); one end of the shear pins (9) extends into the interior of the sleeve (5) and blocks the displacement of the limiting plate (8).

4. The bead wire fracture detection device according to any one of claims 1 to 3, characterized in that: Also includes: A position corrector, wherein the position corrector is designed on the positioning wheel (2); The positioner comprises two clamping plates (23) slidably mounted on the roller wall of the positioning wheel (2), a wire clamping gap being formed between the two clamping plates (23), and an elastic member (24) being fixedly mounted between the outer wall of the clamping plate (23) away from the wire clamping gap and the inner wall of the positioning wheel (2).

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