In-place automatic carbon brush polishing device

Abstract

The utility model discloses an in-place automatic carbon brush polishing device which comprises a brush holder formed by a brush box and a constant-pressure spring in a matched mode, a carbon brush is installed in the brush box through the constant-pressure spring, and a polishing mechanism is detachably arranged on the brush box. The polishing mechanism comprises fixing mechanisms arranged in pairs, the fixing mechanisms are detachably and fixedly matched with the left side and the right side of the brush box respectively, each fixing mechanism is provided with a moving mechanism and a clamping mechanism, the clamping mechanisms are matched with the corresponding moving mechanisms in a linkage mode, and a tensioned abrasive paper belt is clamped between the clamping mechanisms on the two sides in a matched mode. The polishing surface of the abrasive paper belt is tightly attached to the to-be-polished end of the carbon brush, the polishing surface of the abrasive paper belt and the to-be-polished end of the carbon brush form reciprocating polishing cooperation through alternate operation of the two moving mechanisms, in-place polishing of the carbon brush installed on the brush holder is facilitated, the carbon brush does not need to be disassembled and transferred, and the motor maintenance efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of motor repair, in particular to an on-site automatic carbon brush grinding device. Background Art

[0002] Carbon brushes are an important sliding contact part in the excitation system of large hydro-generators and are installed on the brush holder. Carbon brushes are in contact with the collector rings for a long time and are easily worn and consumed, so they need to be regularly maintained and replaced. The contact area between the new carbon brush and the collector ring must be greater than or equal to 3 / 4. The new carbon brush is in the shape of a rectangular parallelepiped and has a surface contact with the collector ring, so it needs to be polished into an arc surface to meet the contact requirements. At present, there are the following problems in maintenance and replacement:

[0003] (1) The traditional grinding method currently relies on manual grinding. When the contact area with the collector ring after grinding does not meet the requirements, uneven current distribution, sparking, overheating and other phenomena will occur, affecting the safe and stable operation of the generator set;

[0004] (2) In actual situations, the carbon brushes are not always directly facing the collector rings. There may be a slight error. In addition, the collector rings have a swing problem and are eccentric. Based on this, the position of each carbon brush is actually unique. Only in-situ grinding can play a role. Nowadays, most of them are off-site grinding, that is, they are disassembled and transferred, and then polished on the grinding device before installation. The practicality on site is relatively poor. Utility Model Content

[0005] The utility model provides an on-site automatic carbon brush grinding device, aiming to solve the problems of possible mismatching of the carbon brush grinding and poor on-site practicability caused by off-site grinding.

[0006] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0007] An in-situ automatic carbon brush grinding device comprises a brush holder formed by a brush box and a constant pressure spring, a carbon brush is installed in the brush box through the constant pressure spring, and a grinding mechanism is detachably provided on the brush box;

[0008] The grinding mechanism includes fixed mechanisms arranged in pairs, and the fixed mechanisms are detachably fixed to the left and right sides of the brush box respectively, and each fixed mechanism is provided with a moving mechanism and a clamping mechanism, and the clamping mechanism cooperates with the corresponding moving mechanism in a linkage manner, and a tensioned sandpaper belt is clamped and cooperated between the clamping mechanisms on both sides, and the grinding surface of the sandpaper belt is tightly attached to the end to be polished of the carbon brush, and the grinding surface of the sandpaper belt and the end to be polished of the carbon brush form a reciprocating grinding cooperation through the alternating operation of the two moving mechanisms.

[0009] Preferably, the fixing mechanism, the moving mechanism and the clamping mechanism arranged in pairs are all symmetrical about the middle position of the brush box.

[0010] As a more preferred embodiment, the fixing mechanisms include an L-shaped fixing block, which fits with the right-angled edge of the brush box on the left or right side close to the constant pressure spring, and limit blocks are provided on both sides of the L-shaped fixing block, and the limit blocks are symmetrical about the L-shaped fixing block. The L-shaped fixing block and the two limit blocks cooperate to form a fixing groove, and one end of the brush box on the left or right side close to the constant pressure spring is wrapped by the fixing groove to form a fixed fit.

[0011] Furthermore, one right-angled side of the L-shaped fixing block is in close contact with the outer wall of the left or right side of the brush box, and the right-angled side is in close contact with the brush box through a clamping screw, and the other right-angled side of the L-shaped fixing block is in close contact with the open side of the brush box close to the constant pressure spring, and the two limit blocks are respectively in close contact with the top surface and the side surface of the brush box, and the limit blocks are both in close contact with the brush box through a clamping screw.

[0012] Furthermore, a support block is provided on the outer side of the right-angled side of the L-shaped fixing block tightly attached to the outer wall of the left or right side of the brush box, and the support block is parallel to the right-angled side on the other side of the L-shaped fixing block, and a mounting block is provided at one end of the support block away from the L-shaped fixing block, the mounting block is perpendicular to the support block and extends toward the side away from the constant pressure spring, and a moving mechanism is provided on the side of the mounting block away from the L-shaped fixing block.

[0013] Specifically, the L-shaped fixing block, the supporting block, the mounting block and the two limiting blocks are integrally formed.

[0014] More specifically, the moving mechanism includes a slide rail arranged on a side of the mounting block away from the L-shaped fixed block, a slider is installed in the slide rail for limited sliding, a mounting plate is provided on the side of the slider away from the mounting block, and the mounting plate is parallel to the mounting block, a clamping mechanism is provided on the side of the mounting plate away from the slider, and an electric telescopic rod is provided on the mounting block close to the constant pressure spring, and the output end of the electric telescopic rod cooperates with the slider.

[0015] In detail, the electric telescopic rod is installed on the mounting block on the same side of the slide rail through fasteners. The direction of the slide rail is the same as the direction in which the carbon brush is embedded in the brush box. The direction of the electric telescopic rod is the same as the direction of the slide rail, and the electric telescopic rods on both sides run alternately. The output end of the electric telescopic rod forms a linkage with the slider through a coupling seat and fasteners.

[0016] In more detail, the clamping mechanism includes a sandpaper clamp, one side of which is detachably fixed to the mounting plate, and the clamping opening of the sandpaper clamp faces the side of the end of the carbon brush to be polished, one end of the sandpaper belt is clamped and fitted with the clamping opening of the sandpaper clamp on one side, and the other end of the sandpaper belt is tightly passed around the end of the carbon brush to be polished and then clamped and fitted with the clamping opening of the sandpaper clamp on the other side.

[0017] Preferably, the sandpaper belt is located between the end to be polished of the carbon brush and the collector ring.

[0018] Beneficial effects of the utility model:

[0019] (1) The utility model directly installs a grinding device on the brush holder to perform in-situ grinding, which can grind the position of the collector ring and the carbon brush at this time, thereby improving the fit effect after grinding;

[0020] (2) Grinding is achieved automatically through the alternating moving mechanism, saving manpower and material resources;

[0021] (3) The grinding devices are designed for a single carbon brush and operate independently of each other. They can grind multiple carbon brushes synchronously to improve the efficiency of maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a three-dimensional schematic diagram of the utility model close to one side of the constant pressure spring;

[0023] Figure 2 It is a three-dimensional schematic diagram of the utility model away from the side of the constant pressure spring;

[0024] Figure 3 It is a three-dimensional schematic diagram of the single-side grinding mechanism of the utility model close to the constant pressure spring side;

[0025] Figure 4 It is a three-dimensional schematic diagram of the single-side grinding mechanism of the utility model, which is away from the constant pressure spring;

[0026] Figure 5 This is a schematic diagram of the installation of the utility model at the collector ring;

[0027] In the figure: 1. Brush box; 2. Constant pressure spring; 3. Carbon brush;

[0028] 4. Fixing mechanism; 401. L-shaped fixing block; 402. Limiting block; 403. Pressing screw; 405. Support block; 406. Mounting block;

[0029] 5. Moving mechanism; 501. Slide rail; 502. Sliding block; 503. Mounting plate; 504. Coupling seat; 505. Electric telescopic rod;

[0030] 6. Clamping mechanism; 601. Sandpaper clamp;

[0031] 7. Sandpaper belt. DETAILED DESCRIPTION

[0032] As follows, embodiments are further described with reference to the accompanying drawings.

[0033] like Figure 1~Figure 5As shown, as a preferred embodiment 1, an in-situ automatic carbon brush grinding device comprises a brush holder formed by a brush box 1 and a constant pressure spring 2, a carbon brush 3 is installed in the brush box 1 through the constant pressure spring 2, and a grinding mechanism is detachably provided on the brush box 1;

[0034] The grinding mechanism includes a pair of fixed mechanisms 4, which are detachably fixed to the left and right sides of the brush box 1, and each fixed mechanism 4 is provided with a moving mechanism 5 and a clamping mechanism 6, which are linked with the corresponding moving mechanism 5, and a tensioned sandpaper belt 7 is clamped between the clamping mechanisms 6 on both sides, and the grinding surface of the sandpaper belt 7 is in close contact with the end to be polished of the carbon brush 3, and the grinding surface of the sandpaper belt 7 and the end to be polished of the carbon brush 3 form a reciprocating grinding cooperation through the alternating operation of the two moving mechanisms 5.

[0035] Embodiment 1 provides an on-site automatic carbon brush grinding device, which is directly installed on the brush box 1 of the brush holder. There is no need to disassemble the carbon brush for off-site grinding. In-situ grinding is performed directly on the brush box 1 at the collector ring, which can directly match the collector ring after grinding to the greatest extent. At the same time, the maintenance efficiency is improved. The device is respectively installed on both sides of the brush box 1 through paired fixing mechanisms 4, which can avoid grinding causing conflicts with the supporting device at the bottom of the brush box 1 and the constant pressure spring 2 at the tail, and a moving mechanism 5 and a clamping mechanism 6 are provided on the fixing mechanism 4. The clamping mechanism 6 is used to tighten and fix the sandpaper belt 7 so that the grinding surface of the sandpaper belt 7 is tightly attached to the end to be ground of the carbon brush 3, and the grinding surface of the sandpaper belt 7 is tightly attached to the end to be ground of the carbon brush 3 through the alternating movement of the moving mechanisms 5 on both sides. The sandpaper belt 7 is moved toward the side of the retracted moving mechanism 5, and when the moving mechanisms 5 reach a certain degree and change the output direction, the sandpaper belt 7 also changes direction and moves in the opposite direction, thereby forming a reciprocating grinding on the end of the carbon brush 3 to be polished, and the constant pressure spring 2 continuously applies a force to the carbon brush 3, so that the carbon brush 3 is tightly attached to the collector ring during the grinding process, and the sandpaper belt 7 is clamped between the grinding end of the carbon brush 3 and the collector ring, so as to ensure the grinding shape, so that the sandpaper belt 7 is pulled out after the grinding is completed, and the carbon brush 3 can also keep the shape matching with the collector ring, and the automatic grinding improves the grinding efficiency and realizes the in-situ grinding.

[0036] As a preferred embodiment 2, the fixing mechanism 4, the moving mechanism 5 and the clamping mechanism 6 arranged in pairs are all symmetrical about the middle position of the brush box 1, so as to ensure the stability of installation and use.

[0037] As a preferred embodiment 3, the fixing mechanism 4 includes an L-shaped fixing block 401, which fits with the right-angle edge of the left or right side of the brush box 1 close to the constant pressure spring 2, and limit blocks 402 are provided on both sides of the L-shaped fixing block 401, and the limit blocks 402 are symmetrical about the L-shaped fixing block 401. The L-shaped fixing block 401 and the two limit blocks 402 cooperate to form a fixing groove, and one end of the left or right side of the brush box 1 close to the constant pressure spring 2 is wrapped by the fixing groove and forms a fixed fit.

[0038] As a preferred embodiment 4, one right-angled side of the L-shaped fixing block 401 is tightly attached to the outer wall of the left or right side of the brush box 1, and the right-angled side is pressed together with the brush box 1 through a clamping screw 403, and the other right-angled side of the L-shaped fixing block 401 is tightly attached to the open side of the brush box 1 close to the constant pressure spring 2. The two limit blocks 402 are respectively tightly attached to the top surface and the side surface of the brush box 1, and the limit blocks 402 are both pressed together with the brush box 1 through a clamping screw 403.

[0039] Embodiment 3 and embodiment 4 respectively provide the basic structure of the fixing mechanism 4 and the fixing method with the brush box 1. When in use, it is only necessary to clamp the L-shaped fixing block 401 with the right-angle edge on the left or right side of the brush box 1 close to the constant pressure spring 2. At this time, the limit block 402 just fits with the top and bottom surfaces of the brush box 1 to form a limit fixation. The fixing groove is not only convenient for fixed installation, but also for limiting. There is no need to consider the adjustment problem during installation. As long as it is installed, the position is automatically determined. The tightening screw 403 further ensures the degree of fixation and ensures the overall stability of the device during grinding.

[0040] As a preferred embodiment 5, the right-angle side of the L-shaped fixing block 401 close to the constant pressure spring 2 is shorter and does not exceed the thickness of the brush box 1 to avoid conflict with the constant pressure spring 2;

[0041] The right-angled side of the L-shaped fixing block 401 away from the constant pressure spring 2 is longer, which is convenient for arranging the supporting block 405 and the clamping screw 403 .

[0042] As a preferred embodiment 6, a support block 405 is provided on the outer side of the right-angled side of the L-shaped fixing block 401 that is tightly attached to the outer wall of the left or right side of the brush box 1, and the support block 405 is parallel to the right-angled side on the other side of the L-shaped fixing block 401, and a mounting block 406 is provided at one end of the support block 405 away from the L-shaped fixing block 401, the mounting block 406 is perpendicular to the support block 405 and extends toward the side away from the constant pressure spring 2, and a moving mechanism 5 is provided on the side of the mounting block 406 away from the L-shaped fixing block 401.

[0043] On the one hand, the support block 405 ensures the stable arrangement of the mounting block 406, and on the other hand, leaves a buffer space for the installation of the mounting block 406, widens the width of the device after installation, facilitates the subsequent arrangement of the sandpaper belt 7, and avoids the sandpaper belt 7 from directly contacting the brush box 1 during grinding, causing wear of the brush box 1.

[0044] As a preferred embodiment 7, the L-shaped fixing block 401, the supporting block 405, the mounting block 406 and the two limiting blocks 402 are integrally formed, which is convenient for installation and use, and also convenient for carrying and assembly during maintenance.

[0045] As a preferred embodiment 8, the moving mechanism 5 includes a slide rail 501 arranged on the side of the mounting block 406 away from the L-shaped fixed block 401, and a slider 502 is installed in the slide rail 501 for limited sliding. A mounting plate 503 is provided on the side of the slider 502 away from the mounting block 406, and the mounting plate 503 is parallel to the mounting block 406. A clamping mechanism 6 is provided on the side of the mounting plate 503 away from the slider 502, and an electric telescopic rod 505 is provided on the mounting block 406 close to the constant pressure spring 2, and the output end of the electric telescopic rod 505 is linked to the slider 502.

[0046] Example 8 provides a specific structure of the moving mechanism 5, which realizes reciprocating motion by providing driving force through the alternating electric telescopic rods 505. The movement directions of the electric telescopic rods 505 on both sides are opposite, and the telescopic speeds of the electric telescopic rods 505 are the same. When one side contracts, the other side outputs until the limit distance of contraction and output is reached, and then reverse operation begins. The cycle is repeated until the grinding is completed. During the process, the electric telescopic rod 505 drives the corresponding slider 502 to move synchronously along the slide rail 501, thereby driving the clamping mechanism 6 on the corresponding mounting plate 503 to move synchronously, thereby realizing the control of the sandpaper belt 7.

[0047] As a preferred embodiment 9, the electric telescopic rod 505 is connected to an external control mechanism, such as a PLC controller, to facilitate control of the movement. When stopping and starting grinding, the electric telescopic rod 505 stops at half of the moving distance, which is convenient for the installation of the sandpaper belt 7.

[0048] As a preferred embodiment 10, a dust suction pipe may be arranged on the side of the mounting block 406 away from the moving mechanism 5, and the dust suction pipe is connected to an external suction device to absorb dust generated during the grinding process.

[0049] As a preferred embodiment 11, the electric telescopic rod 505 is installed on the mounting block 406 on the same side as the slide rail 501 through fasteners, the direction of the slide rail 501 is the same as the direction in which the carbon brush 3 is embedded in the brush box 1, the direction of the electric telescopic rod 505 is the same as the direction of the slide rail 501, and the electric telescopic rods 505 on both sides operate alternately, and the output end of the electric telescopic rod 505 forms a linkage with the slider 502 through the coupling seat 504 and the fasteners. Ensure the effect of horizontal grinding and avoid conflicts between grinding and installation.

[0050] As a preferred embodiment 12, the clamping mechanism 6 includes a sandpaper clamp 601, one side of the sandpaper clamp 601 is detachably fixedly matched with the mounting plate 503, and the clamping opening of the sandpaper clamp 601 faces the side of the end to be polished of the carbon brush 3, one end of the sandpaper belt 7 is clamped and matched with the clamping opening of the sandpaper clamp 601 on one side, and the other end of the sandpaper belt 7 is tightly passed around the end to be polished of the carbon brush 3 and then clamped and matched with the clamping opening of the sandpaper clamp 601 on the other side. The polishing effect is ensured.

[0051] As a preferred embodiment 13, the sandpaper belt 7 is located between the end of the carbon brush 3 to be polished and the collector ring, so as to facilitate continuous application of force through the constant pressure spring 2 to match the carbon brush 3 with the collector ring after polishing.

[0052] The working principle of this utility model:

[0053] The utility model provides an on-site automatic carbon brush grinding device, which is directly installed on the brush box 1 of the brush holder. The carbon brush does not need to be disassembled for off-site grinding. The on-site grinding is directly performed on the brush box 1 at the collector ring, which can directly match the collector ring after grinding to the greatest extent, and at the same time, improve the maintenance efficiency;

[0054] The device is respectively installed on both sides of the brush box 1 through the fixed mechanisms 4 arranged in pairs, so as to realize grinding in the horizontal direction, avoid the grinding causing conflict to the support device at the bottom of the brush box 1 and the constant pressure spring 2 at the tail, and the moving mechanism 5 and the clamping mechanism 6 are arranged on the fixed mechanism 4, the clamping mechanism 6 is used to tighten and fix the sandpaper belt 7, so that the grinding surface of the sandpaper belt 7 is in close contact with the end to be polished of the carbon brush 3, and reciprocating grinding is formed by the alternating operation of the moving mechanisms 5 on both sides. When the moving mechanism 5 on one side contracts, the moving mechanism 5 on the other side outputs, and the moving speeds of the two sides are the same, and the sandpaper belt 7 moves toward the side of the contracted moving mechanism 5. When the moving mechanisms 5 reach a certain degree and change the output direction, the sandpaper belt 7 also changes direction and moves in the opposite direction, thereby forming reciprocating grinding of the end to be polished of the carbon brush 3;

[0055] The constant pressure spring 2 continuously applies force to the carbon brush 3, so that the carbon brush 3 and the collector ring are closely attached during the grinding process, and the sandpaper belt 7 is clamped between the grinding end of the carbon brush 3 and the collector ring, thereby ensuring the grinding shape, so that the sandpaper belt 7 can be pulled out after the grinding is completed, and the carbon brush 3 can also keep the shape matching with the collector ring, and the automatic grinding improves the grinding efficiency and realizes the in-situ grinding;

[0056] At the same time, the device automatically grinds after installation. During the grinding process, another carbon brush 3 that needs to be polished can be installed. Multiple grinding devices operate independently of each other for a single carbon brush, which can improve the efficiency of maintenance. There is no need to grind them one by one, and multiple brushes can be polished at the same time.

Claims

1. An in-situ automatic carbon brush grinding device, comprising a brush holder formed by a brush box (1) and a constant pressure spring (2), wherein a carbon brush (3) is installed in the brush box (1) via the constant pressure spring (2), characterized in that: The brush box (1) is detachably provided with a grinding mechanism; The grinding mechanism comprises a pair of fixed mechanisms (4), the fixed mechanisms (4) being respectively fixedly matched with the left and right sides of the brush box (1) in a detachable manner, and each fixed mechanism (4) is provided with a moving mechanism (5) and a clamping mechanism (6), the clamping mechanism (6) being linked with the corresponding moving mechanism (5), a tensioned sandpaper belt (7) being clamped between the clamping mechanisms (6) on both sides, the grinding surface of the sandpaper belt (7) being in close contact with the end to be ground of the carbon brush (3), and the grinding surface of the sandpaper belt (7) and the end to be ground of the carbon brush (3) being formed into a reciprocating grinding match through the alternating operation of the two moving mechanisms (5).

2. The on-site automatic carbon brush grinding device according to claim 1, characterized in that: The fixing mechanism (4), the moving mechanism (5) and the clamping mechanism (6) arranged in pairs are all symmetrical about the middle position of the brush box (1).

3. The on-site automatic carbon brush grinding device according to claim 2, characterized in that: The fixing mechanisms (4) all comprise an L-shaped fixing block (401), the L-shaped fixing block (401) being matched with a right-angled edge on the left or right side of the brush box (1) close to the constant-pressure spring (2), both sides of the L-shaped fixing block (401) being provided with a limit block (402), and the limit blocks (402) being symmetrical with respect to the L-shaped fixing block (401), the L-shaped fixing block (401) and the two limit blocks (402) being matched to form a fixing groove, and one end of the left or right side of the brush box (1) close to the constant-pressure spring (2) is wrapped by the fixing groove and forms a fixed match.

4. The on-site automatic carbon brush grinding device according to claim 3 is characterized in that: One right-angled side of the L-shaped fixing block (401) is in close contact with the outer wall of the left or right side of the brush box (1), and the right-angled side is in close contact with the brush box (1) via a clamping screw (403). The other right-angled side of the L-shaped fixing block (401) is in close contact with the open side of the brush box (1) close to the constant pressure spring (2). The two limit blocks (402) are in close contact with the top surface and the side surface of the brush box (1), respectively, and the limit blocks (402) are in close contact with the brush box (1) via a clamping screw (403).

5. The on-site automatic carbon brush grinding device according to claim 4, characterized in that: A support block (405) is provided on the outer side of a right angle side of the L-shaped fixing block (401) which is in close contact with the outer wall of the left or right side of the brush box (1), and the support block (405) is parallel to the right angle side of the other side of the L-shaped fixing block (401). A mounting block (406) is provided at one end of the support block (405) away from the L-shaped fixing block (401), the mounting block (406) is perpendicular to the support block (405) and extends toward a side away from the constant pressure spring (2), and a moving mechanism (5) is provided on a side of the mounting block (406) away from the L-shaped fixing block (401).

6. The on-site automatic carbon brush grinding device according to claim 5, characterized in that: The L-shaped fixing block (401), the supporting block (405), the mounting block (406) and the two limiting blocks (402) are integrally formed.

7. The on-site automatic carbon brush grinding device according to claim 6, characterized in that: The moving mechanism (5) comprises a slide rail (501) arranged on a side of the mounting block (406) away from the L-shaped fixed block (401); a slider (502) is installed in the slide rail (501) in a limited sliding manner; a mounting plate (503) is provided on the side of the slider (502) away from the mounting block (406); the mounting plate (503) is parallel to the mounting block (406); a clamping mechanism (6) is provided on the side of the mounting plate (503) away from the slider (502); an electric telescopic rod (505) is provided on the mounting block (406) close to the constant pressure spring (2); and an output end of the electric telescopic rod (505) is linked to the slider (502).

8. The on-site automatic carbon brush grinding device according to claim 7, characterized in that: The electric telescopic rod (505) is mounted on a mounting block (406) on the same side as the slide rail (501) via a fastener; the direction of the slide rail (501) is the same as the direction in which the carbon brush (3) is embedded in the brush box (1); the direction of the electric telescopic rod (505) is the same as the direction of the slide rail (501); the electric telescopic rods (505) on both sides operate alternately; the output end of the electric telescopic rod (505) forms a linkage with the slider (502) via a coupling seat (504) and a fastener.

9. The on-site automatic carbon brush grinding device according to claim 8, characterized in that: The clamping mechanism (6) comprises a sandpaper clamp (601), one side of the sandpaper clamp (601) is detachably fixedly matched with the mounting plate (503), and the clamping opening of the sandpaper clamp (601) faces the side of the end to be polished of the carbon brush (3), one end of the sandpaper belt (7) is clamped and matched with the clamping opening of the sandpaper clamp (601) on one side, and the other end of the sandpaper belt (7) is tightly passed around the end to be polished of the carbon brush (3) and is clamped and matched with the clamping opening of the sandpaper clamp (601) on the other side.

10. The on-site automatic carbon brush grinding device according to claim 9, characterized in that: The sandpaper belt (7) is located between the end of the carbon brush (3) to be polished and the collector ring.

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