A feeding mechanism for fine blanking punch processing

Abstract

This utility model belongs to the technical field of punch production equipment, and particularly relates to a feeding mechanism for fine punch processing, including a frame, chuck, guide frame, drive assembly, and adsorption assembly; the adsorption assembly includes a cylinder connected to the output end of the drive assembly, a sleeve slidably sleeved on one end of the cylinder, a drive component and a trigger component installed inside the cylinder, and a compression spring disposed between the cylinder and the sleeve; the end of the sleeve is provided with a sliding hole that slides with the fine punch, and the trigger component slides axially with the sleeve to control the action state of the drive component; automatic linkage is achieved through mechanical contact reaction force to complete the adsorption, pulling into the sliding hole, and ejection feeding action of the fine punch. The structure is simple, avoids the problem of clamp interference, and improves feeding stability and production efficiency.

Description

Technical Field

[0001] This utility model belongs to the technical field of punch production equipment, and particularly relates to a feeding mechanism for fine punching punch processing. Background Technology

[0002] Fine blanking punches are the core mold components that determine the final head shape, dimensional accuracy, and surface quality of bolts and screws. They typically include Phillips head punches and internal hexagonal head punches, and are generally manufactured using metals such as high-speed steel.

[0003] When finishing the fine blanking punch, an automatic feeding method is usually used to feed the roughly formed fine blanking punch. Traditional feeding methods usually use chucks, but because the chucks interfere with the end face of the chuck, the fine blanking punch is not properly fed into the chuck along the axial direction. An additional independent pushing mechanism is required to complete the feeding action, which is complex. Some feeding methods use magnetic attraction, but magnetic attraction usually only attracts the end face of the fine blanking punch. When the feeding mechanism moves, it is easy to shift or even fall off, resulting in low feeding accuracy, which in turn affects product quality and production efficiency. Utility Model Content

[0004] The purpose of this utility model is to address the aforementioned technical problems by providing a feeding mechanism for fine blanking punch processing, which achieves the effects of simple feeding structure, no interference from the grippers, and high stability of the fine blanking punch during movement.

[0005] In view of this, the present invention provides a feeding mechanism for fine blanking punch processing, including a frame and a chuck mounted on the frame. The feeding mechanism includes a guide frame, a drive assembly, and an adsorption assembly mounted on the frame. The guide frame is used for guiding and conveying the fine blanking punch. The adsorption assembly is installed at the output end of the drive assembly and is used to grab the fine blanking punch from the guide frame and convey it to the chuck. The adsorption assembly includes: The cylinder is connected to the output end of the drive component; A sleeve is coaxially arranged with the cylinder body and slidably sleeved on the end of the cylinder body away from the drive assembly, and a sliding hole is provided at the end away from the cylinder body for sliding engagement of the fine punch. The driving component, installed inside the cylinder, is used to attract and drive the fine punch to slide within the sliding hole; A trigger element, installed between the cylinder and the sleeve, and sliding in conjunction with the sleeve, is used to switch the driving direction of the driving element; A compression spring is installed between the cylinder and the sleeve to drive the sleeve to return to its original position away from the cylinder.

[0006] In the above technical solution, the driving component further includes: The sliding column is slidably connected to the cylinder, and one end of it extends axially out of the cylinder and is slidably connected to the sleeve. A permanent magnet is installed at one end of the slide column near the sleeve to attract the fine punch. An annular protrusion is installed at the end of the sliding column away from the permanent magnet; The tension spring is installed inside the cylinder and located on the side of the annular protrusion near the sleeve, with its two ends connected to the annular protrusion and the inner wall of the cylinder, respectively. A magnetically conductive metal sheet is installed on the side of the annular protrusion away from the tension spring; An electromagnet, installed inside the cylinder and controlled by a trigger, is used to attract and de-attract magnetic metal sheets. When the electromagnet is energized, the attraction force on the magnetic metal sheet is greater than the restoring force of the tension spring.

[0007] In the above technical solution, further: The cylinder surface has a groove along the axial direction, and the sleeve is equipped with a slider that slides in cooperation with the groove to limit the sliding distance of the sleeve along the cylinder axis.

[0008] In the above technical solution, further: An arc-shaped groove is provided at the axial end of the slide column near the permanent magnet, and the arc-shaped groove is set in accordance with the axis of the slide column.

[0009] In the above technical solution, further: A first annular groove is provided at the axial end of the sliding column near the permanent magnet, and the first annular groove is used for the embedded installation of the permanent magnet.

[0010] In the above technical solution, further: The inner walls of the cylinder and sleeve that are slidably connected to the sliding column are provided with a second annular groove, and an elastic ring is installed in the second annular groove to provide damping force for the sliding column. The damping force is less than the restoring force of the tension spring, and the sum of the damping force and the restoring force of the tension spring is less than the attraction force of the electromagnet on the magnetic metal sheet when it is energized.

[0011] In the above technical solution, the trigger element further includes: The first conductive ring is mounted on the sleeve and connected in series in the power supply circuit of the electromagnet; The second conductive ring is installed on the cylinder and connected in series in the power supply circuit of the electromagnet; When the compression spring is compressed, the first conductive ring separates from the second conductive ring, disconnecting the power supply circuit of the electromagnet; when the compression spring returns to its original state, the first conductive ring contacts the second conductive ring, turning on the power supply circuit of the electromagnet.

[0012] In the above technical solution, further: The inner wall of the sleeve is provided with a third annular groove for installing the first conductive ring; The surface of the cylinder is provided with a fourth annular groove for installing the second conductive ring.

[0013] The beneficial effects of this utility model are as follows: 1. Align the fine blanking punch with the sliding hole on the sleeve. Then, the movement of the sleeve triggers the trigger, which in turn drives the drive to attract the fine blanking punch. After the sleeve returns to its original position, it pulls most of the fine blanking punch into the sliding hole. The attraction between the sliding hole and the drive ensures the stability of the fine blanking punch during movement, preventing it from shifting or even falling off. At the same time, after the fine blanking punch is aligned with the clamping hole of the chuck, the drive pushes the fine blanking punch to slide outward along the sliding hole, ensuring that the material is properly loaded. This effectively guarantees the processing accuracy and production efficiency.

[0014] 2. Automatic linkage is achieved through the contact reaction force between the sleeve and the guide frame and chuck. The electromagnet is directly controlled to turn on and off through the conductive ring. There is no need to configure an independent pushing mechanism and a complex sensor control system, which helps to reduce manufacturing costs and operating failure rate.

[0015] 3. By setting the slide block stroke limit, elastic ring damping buffer, and conductive ring built-in sealing protection structure, the sleeve can be prevented from falling off, the impact wear between parts can be reduced, and the coolant can be prevented from corroding electrical components, which helps to extend the overall service life of the mechanism. Attached Figure Description

[0016] Figure 1 This is a structural schematic diagram of the application of this utility model; Figure 2 This is a schematic diagram of the structure of this utility model; Figure 3 This is a bottom view of the present invention; Figure 4 This is a utility model Figure 3 Sectional view at point AA; Figure 5 This is a utility model Figure 4 Enlarged view of point B in the middle; The markings in the diagram represent: 1. Frame; 2. Chuck; 3. Guide frame; 4. Drive assembly; 5. Cylinder; 6. Sleeve; 7. Sliding hole; 8. Drive component; 80. Sliding column; 81. Permanent magnet; 82. Annular protrusion; 83. Tension spring; 84. Magnetic conductive metal sheet; 85. Electromagnet; 9. Trigger; 90. First conductive ring; 91. Second conductive ring; 10. Compression spring; 11. Slide groove; 12. Slider; 13. Arc-shaped groove; 14. First annular groove; 15. Second annular groove; 16. Elastic ring; 17. Third annular groove; 18. Fourth annular groove; 19. Fine blanking punch. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0018] Example 1:

[0019] This embodiment provides a feeding mechanism for processing a fine blanking punch 19, including a frame 1 and a chuck 2 mounted on the frame 1. The feeding mechanism includes a guide frame 3, a drive assembly 4, and an adsorption assembly mounted on the frame 1. The guide frame 3 is used for guiding and conveying the fine blanking punch 19. The adsorption assembly is mounted on the output end of the drive assembly 4 and is used to grab the fine blanking punch 19 from the guide frame 3 and convey it to the chuck 2. The adsorption assembly includes: Cylinder 5 is connected to the output end of drive component 4; Sleeve 6 is coaxially arranged with cylinder 5 and slidably sleeved on the end of cylinder 5 away from drive assembly 4, and has a sliding hole 7 at the end away from cylinder 5 for sliding engagement with fine punch 19. The driving component 8 is installed inside the cylinder 5 and is used to adsorb and drive the fine punch 19 to slide within the sliding hole 7. Trigger 9 is installed between cylinder 5 and sleeve 6 and is linked to the sliding of sleeve 6 to switch the driving direction of drive component 8; A compression spring 10 is installed between the cylinder 5 and the sleeve 6 to drive the sleeve 6 to return to its original position away from the cylinder 5; The specific structures of the frame 1, chuck 2, drive assembly 4 and guide frame 3 are all existing mature technologies. The guide frame 3 is also connected to the vibrating feed plate, and the frame 1 also includes a lathe tool, which are all conventional structures of traditional fine stamping punch 19 processing equipment. These are all known to those skilled in the art from traditional equipment and will not be described in detail here.

[0020] As can be seen in this embodiment, the cylinder 5 approaches the fine blanking punch 19 under the drive of the drive component 4, and after the fine blanking punch 19 is aligned with the sliding hole 7, the head of the fine blanking punch 19 extends into the sliding hole 7. As the drive component 4 continues to move, the sleeve 6 is restricted by the guide frame 3 and moves closer to one side of the cylinder 5. The trigger 9 switches the direction of the drive component 8 and moves it closer to the fine blanking punch 19, and then adsorbs the fine blanking punch 19. After the drive component 4 moves the adsorption component away from the guide frame 3, the sleeve 6 is reset under the action of the compression spring 10, and the trigger 9 switches the direction of the drive component 8 and moves it with the fine blanking punch 19 towards the inside of the sliding hole 7, thereby completing the adsorption and gripping of the fine blanking punch 19. Most of the axial direction of the fine blanking punch 19 is located in the sliding hole 7, and one axial end is adsorbed by the drive component 8, thereby effectively improving the stability of the fine blanking punch 19 during movement and making it less prone to displacement and detachment. Subsequently, driven by the drive component 4, the sleeve 6 aligns with the clamping hole of the chuck 2 and moves closer to the chuck 2. The end of the fine blanking punch 19 enters the clamping hole, while the sleeve 6, restricted by the chuck 2, moves closer to the side of the cylinder 5. The trigger 9 switches the direction of the drive component 8 again, causing it to move outward of the sliding hole 7 and push the fine blanking punch 19 further out of the sliding hole 7 until it is fully loaded into the clamping block of the chuck 2. Then, the chuck 2 clamps the fine blanking punch 19, and the drive component 4 drives the adsorption component away from the fine blanking punch 19. Since the fine blanking punch 19 is clamped, the drive component 8 releases the adsorption of the fine blanking punch 19 during movement, thus completing the loading of the fine blanking punch 19. The structure is simple and does not interfere with the gripper. Furthermore, under the push of the drive component 8, it can ensure that the fine blanking punch 19 is fully loaded, effectively ensuring the processing accuracy and production efficiency.

[0021] Example 2:

[0022] This embodiment provides a feeding mechanism for fine blanking punch 19. In addition to the technical solution of the above embodiment, it also has the following technical features: the driving component 8 includes: The sliding column 80 is slidably connected to the cylinder 5, and one end of it extends axially out of the cylinder 5 and is slidably connected to the sleeve 6. A permanent magnet 81 is installed at one end of the slide column 80 near the sleeve 6 to attract the fine punch 19; An annular protrusion 82 is installed at the end of the sliding column 80 away from the permanent magnet 81; The tension spring 83 is installed inside the cylinder 5 and is located on the side of the annular protrusion 82 near the sleeve 6, with its two ends connected to the annular protrusion 82 and the inner wall of the cylinder 5, respectively. A magnetically conductive metal sheet 84 is installed on the side of the annular protrusion 82 away from the tension spring 83; An electromagnet 85 is installed inside the cylinder 5 and is controlled to open and close by a trigger 9. It is used to attract and de-attract the magnetic metal sheet 84. When the electromagnet 85 is energized, the attraction force on the magnetic metal sheet 84 is greater than the restoring force of the tension spring 83. Meanwhile, the specific structure of the electromagnet 85 and the specific materials of the permanent magnet 81 and the magnetic conductive metal sheet 84 are all existing mature technologies, which can be selected and applied by those skilled in the art from the traditional electromagnet 85, permanent magnet 81 and magnetic conductive metal sheet 84, and will not be elaborated here.

[0023] As can be seen in this embodiment, the sliding of the fine blanking punch 19 within the sliding hole 7 is achieved by the movement of the sliding column 80. Specifically, when the sleeve 6 approaches the cylinder 5 due to its contact with the guide frame 3, the trigger 9 controls the electromagnet 85 to be de-energized. The electromagnet 85 releases its attraction to the magnetic metal sheet 84. Therefore, under the restoring force of the tension spring 83, the sliding column 80 will move outward within the sliding hole 7, causing the permanent magnet 81 to contact the fine blanking punch 19 and simultaneously perform magnetic attraction. Subsequently, the cylinder 5 moves away from the guide frame. The frame 3 and sleeve 6 are reset under the action of the compression spring 10. After reset, the trigger 9 controls the electromagnet 85 to be energized. The electromagnet 85 attracts the magnetic metal sheet 84, which then drives the slide column 80 to move inward in the slide hole 7, and drives the fine blanking punch 19 so that most of the fine blanking punch 19 is pulled into the slide hole 7. This effectively ensures the stability of the fine blanking punch 19 after it is attracted and moved to the chuck 2, and avoids the fine blanking punch 19 from shifting or even falling off during the movement. The structure is also simple.

[0024] Example 3:

[0025] This embodiment provides a feeding mechanism for fine blanking punch 19, which, in addition to the technical solution of the above embodiment, also has the following technical features: The surface of the cylinder 5 is provided with a sliding groove 11 along the axial direction, and the sleeve 6 is equipped with a slider 12 that slides in cooperation with the sliding groove 11 to limit the sliding distance of the sleeve 6 along the axial direction of the cylinder 5.

[0026] As can be seen from this embodiment, by setting the groove 11 and the slider 12, the sliding distance of the sleeve 6 relative to the cylinder 5 is limited, thereby preventing the sleeve 6 from slipping off the cylinder 5 and ensuring the structural stability of the adsorption assembly.

[0027] Example 4:

[0028] This embodiment provides a feeding mechanism for fine blanking punch 19, which, in addition to the technical solution of the above embodiment, also has the following technical features: An arc-shaped groove 13 is provided at the axial end of the sliding column 80 near the permanent magnet 81, and the arc-shaped groove 13 is arranged corresponding to the axis of the sliding column 80.

[0029] As can be seen from this embodiment, by opening an arc-shaped groove 13 at the axial end of the slide column 80 near the permanent magnet 81, interference between the permanent magnet 81 on the slide column 80 and the cross protrusion on the fine punch 19 can be avoided when the permanent magnet 81 on the slide column 80 attracts the fine punch 19, thus ensuring the stability of the magnetic attraction of the permanent magnet 81 to the fine punch 19.

[0030] Example 5:

[0031] This embodiment provides a feeding mechanism for fine blanking punch 19, which, in addition to the technical solution of the above embodiment, also has the following technical features: The sliding column 80 has a first annular groove 14 at its axial end near the permanent magnet 81, and the first annular groove 14 is used for the embedded installation of the permanent magnet 81.

[0032] As can be seen from this embodiment, the opening of the first annular groove 14 effectively improves the installation stability of the permanent magnet 81 on the sliding column 80 and ensures the service life of the permanent magnet 81.

[0033] Example 6:

[0034] This embodiment provides a feeding mechanism for fine blanking punch 19, which, in addition to the technical solution of the above embodiment, also has the following technical features: The inner walls of the cylinder 5 and sleeve 6, which are slidably connected to the sliding column 80, are provided with a second annular groove 15, and an elastic ring 16 is installed in the second annular groove 15 to provide damping force for the sliding column 80. The damping force is less than the restoring force of the tension spring 83, and the sum of the damping force and the restoring force of the tension spring 83 is less than the attraction force of the electromagnet 85 on the magnetic metal sheet 84 when the electromagnet is energized. The elastic ring 16 can be made of rubber. In order to avoid excessive initial damping force, the interference of the elastic ring 16 can be appropriately reduced, or a small amount of lubricating oil can be applied to the surface of the rubber ring. These are all conventional operations for those skilled in the art to set the damping force provided by the elastic ring 16 to be less than the reset force of the tension spring 83, and will not be described in detail in this application.

[0035] As can be seen from this embodiment, by opening the second annular groove 15 and setting the elastic ring 16 in the annular groove, a certain damping force is provided for the sliding of the slide column 80, thereby effectively avoiding excessive impact when the tension spring 83 drives the slide column 80 to move, slowing down the speed of the slide column 80, ensuring the stability of the movement, avoiding excessive impact between the permanent magnet 81 and the fine punch 19, and further extending the service life of the permanent magnet 81.

[0036] Example 7:

[0037] This embodiment provides a feeding mechanism for fine blanking punch 19. In addition to the technical solution of the above embodiment, it also has the following technical features: the trigger 9 includes: The first conductive ring 90 is mounted on the sleeve 6 and connected in series in the power supply circuit of the electromagnet 85; The second conductive ring 91 is installed on the cylinder 5 and connected in series in the power supply circuit of the electromagnet 85; When the compression spring 10 is compressed, the first conductive ring 90 separates from the second conductive ring 91, thus disconnecting the power supply circuit of the electromagnet 85; when the compression spring 10 returns to its original state, the first conductive ring 90 contacts the second conductive ring 91, thus turning on the power supply circuit of the electromagnet 85. Meanwhile, both the first conductive ring 90 and the second conductive ring 91 can be made of copper.

[0038] As can be seen from this embodiment, by setting the first conductive ring 90 and the second conductive ring 91 and connecting them in series in the power supply circuit of the electromagnet 85, they can be used as an on / off switch in the power supply circuit. When the first conductive ring 90 and the second conductive ring 91 are in contact, the power supply circuit is turned on, and the electromagnet 85 generates a magnetic attraction force to attract the magnetic metal sheet 84, thereby driving the slide column 80 to move against the force of the tension spring 83. Conversely, when the first conductive ring 90 and the second conductive ring 91 are separated, the power supply circuit is turned off, and the electromagnet 85 loses its magnetic attraction force on the magnetic metal sheet 84. The restoring force of the tension spring 83 drives the slide column 80 to move in the opposite direction.

[0039] Example 8:

[0040] This embodiment provides a feeding mechanism for fine blanking punch 19, which, in addition to the technical solution of the above embodiment, also has the following technical features: The inner wall of the sleeve 6 is provided with a third annular groove 17 for installing the first conductive ring 90; The surface of the cylinder 5 is provided with a fourth annular groove 18 for installing the second conductive ring 91; A fifth annular groove is provided between the cylinder 5 and the sleeve 6, and a rubber sealing ring is installed in the fifth annular groove to prevent coolant and other liquids from seeping in and corroding the first conductive ring 90 and the second conductive ring 91 after long-term use, thus ensuring the power-on and power-off control of the electromagnet 85 and its service life.

[0041] As can be seen from this embodiment, by opening the third annular groove 17 and the fourth annular groove 18, the installation stability of the first conductive ring 90 and the second conductive ring 91 can be improved. Furthermore, by placing both the first conductive ring 90 and the second conductive ring 91 between the sleeve 6 and the cylinder 5, the first conductive ring 90 and the second conductive ring 91 are both internally installed, which provides a certain degree of protection for the first conductive ring 90 and the second conductive ring 91 and extends their service life.

[0042] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A feeding mechanism for fine blanking punch processing, comprising a frame (1) and a chuck (2) mounted on the frame (1), the feeding mechanism comprising a guide frame (3), a drive assembly (4), and an adsorption assembly mounted on the frame (1), the guide frame (3) being used for guiding and conveying fine blanking punches (19), and the adsorption assembly being mounted at the output end of the drive assembly (4) for gripping the fine blanking punches (19) from the guide frame (3) and conveying them to the chuck (2), characterized in that, The adsorption component includes: The cylinder (5) is connected to the output end of the drive assembly (4); The sleeve (6) is coaxially arranged with the cylinder (5) and is slidably sleeved on the end of the cylinder (5) away from the drive assembly (4), and a sliding hole (7) for sliding engagement with the fine punch (19) is provided at the end away from the cylinder (5). The driving component (8) is installed inside the cylinder (5) and is used to adsorb and drive the fine punch (19) to slide in the sliding hole (7); The trigger (9) is installed between the cylinder (5) and the sleeve (6) and is in sliding linkage with the sleeve (6) to switch the driving direction of the drive (8); A compression spring (10) is installed between the cylinder (5) and the sleeve (6) to drive the sleeve (6) to return to its original position away from the cylinder (5).

2. The feeding mechanism for fine stamping punch processing according to claim 1, characterized in that, The driving component (8) includes: The sliding column (80) is slidably connected to the cylinder (5), and one end of the axial part extends out of the cylinder (5) and is slidably connected to the sleeve (6); A permanent magnet (81) is installed at one end of the slide column (80) near the sleeve (6) to attract the fine punch (19); An annular protrusion (82) is installed at the end of the sliding column (80) away from the permanent magnet (81); The tension spring (83) is installed inside the cylinder (5) and located on the side of the annular protrusion (82) near the sleeve (6), with its two ends connected to the annular protrusion (82) and the inner wall of the cylinder (5) respectively. A magnetically conductive metal sheet (84) is installed on the side of the annular protrusion (82) away from the tension spring (83); An electromagnet (85) is installed inside the cylinder (5) and is controlled to open and close by a trigger (9) for adsorbing and de-adsorbing the magnetic metal sheet (84). When the electromagnet (85) is energized, the attraction force on the magnetic metal sheet (84) is greater than the restoring force of the tension spring (83).

3. The feeding mechanism for fine stamping punch processing according to claim 2, characterized in that: The surface of the cylinder (5) is provided with a sliding groove (11) along the axial direction, and the sleeve (6) is equipped with a slider (12) that slides in cooperation with the sliding groove (11) to limit the sliding distance of the sleeve (6) along the axial direction of the cylinder (5).

4. The feeding mechanism for fine stamping punch processing according to claim 2, characterized in that: The sliding column (80) has an arc-shaped groove (13) at its axial end near the permanent magnet (81), and the arc-shaped groove (13) is arranged corresponding to the axis of the sliding column (80).

5. The feeding mechanism for fine stamping punch processing according to claim 2, characterized in that: The sliding column (80) has a first annular groove (14) at its axial end near the permanent magnet (81), and the first annular groove (14) is used for the embedded installation of the permanent magnet (81).

6. The feeding mechanism for fine stamping punch processing according to claim 2, characterized in that: The inner walls of the cylinder (5) and sleeve (6) that are slidably connected to the sliding column (80) are provided with a second annular groove (15), and an elastic ring (16) is installed in the second annular groove (15) to provide damping force for the sliding of the sliding column (80). The damping force is less than the restoring force of the tension spring (83), and the sum of the damping force and the restoring force of the tension spring (83) is less than the attraction force of the electromagnet (85) on the magnetic metal sheet (84) when the electromagnet (85) is energized.

7. The feeding mechanism for fine stamping punch processing according to claim 2, characterized in that, The trigger (9) includes: The first conductive ring (90) is mounted on the sleeve (6) and connected in series in the power supply circuit of the electromagnet (85); The second conductive ring (91) is installed on the cylinder (5) and connected in series in the power supply circuit of the electromagnet (85); When the compression spring (10) is compressed, the first conductive ring (90) separates from the second conductive ring (91), thus disconnecting the power supply circuit of the electromagnet (85); when the compression spring (10) is restored, the first conductive ring (90) contacts the second conductive ring (91), thus turning on the power supply circuit of the electromagnet (85).

8. The feeding mechanism for fine stamping punch processing according to claim 7, characterized in that: The inner wall of the sleeve (6) is provided with a third annular groove (17) for installing the first conductive ring (90). The surface of the cylinder (5) is provided with a fourth annular groove (18) for installing the second conductive ring (91).

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