Laser cladding device for repairing rolling mill roll bearing housings

Abstract

This invention discloses a laser cladding device for repairing bearing housings of rolling mill rolls, belonging to the field of laser cladding technology. It includes a base plate, on which a rotating platform and a multi-axis laser cladding module are mounted. Symmetrically distributed fixed frames are fixedly connected to the base plate, and these symmetrically distributed fixed frames are slidably connected to a sliding frame. Each of the symmetrically distributed fixed frames and the base plate is rotatably connected to a threaded shaft, which is threadedly connected to the sliding frame. A shielding cylinder is rotatably connected to the sliding frame, and the shielding cylinder has a notch that exposes the bearing housing repair area. This invention, through the notch design of the shielding cylinder, exposes a localized area of ​​the bearing housing to be repaired, achieving large-scale physical isolation of the non-repairable inner wall, reducing the area where cladding slag spatter adheres, and thus reducing the area requiring subsequent additional grinding of the non-repairable area, improving the effectiveness of bearing housing cladding repair.

Description

Technical Field

[0001] This invention relates to the field of laser cladding technology, and more particularly to a laser cladding device for repairing bearing seats of rolling mill rolls. Background Technology

[0002] The bearing housing of a steel rolling mill roll is a key load-bearing component in the roller conveyor system of a heating furnace. It is usually installed at both ends of the roll to support the roll shaft and bear the high load transmitted during the rolling process. Since the rolling force is basically constant, the contact stress between the rolling elements and the inner wall of the bearing housing is mainly concentrated in the load-bearing area of ​​about 120° of the lower half circumference. Under long-term alternating loads, this area is prone to contact fatigue damage, which manifests as wear forms such as pitting, spalling or dents. The non-load-bearing area usually remains intact. Given the high manufacturing cost and long replacement cycle of large bearing housings, laser cladding technology is commonly used in industry for remanufacturing and repair.

[0003] Laser cladding is an advanced surface modification and repair process. It uses a high-energy laser beam to form a tiny molten pool on the substrate surface, simultaneously feeding in alloy powder to achieve a strong metallurgical bond between the cladding layer and the substrate. This restores dimensions and improves surface properties. However, existing laser cladding equipment has significant shortcomings when repairing the inner wall of bearing housings: it lacks an effective spatter isolation and protection mechanism. During the cladding process, fluctuations in process parameters, surface oil contamination, or oxides can easily cause metal spatter in the molten pool, forming high-temperature liquid weld slag. This slag disperses at high speed, randomly adhering to the non-repaired areas of the inner wall and firmly adhering to the inner wall of the bearing housing, forming metal protrusions. Since the non-repaired areas of the bearing housing originally maintained their original machining precision, the presence of weld slag forces workers to perform additional grinding on these areas after the inner wall repair is completed. This easily damages the original dimensional accuracy and surface quality of the non-repaired areas, significantly reducing the expected benefits of bearing housing cladding repair. Summary of the Invention

[0004] In order to overcome the shortcomings mentioned in the background art, the present invention provides a laser cladding device for repairing rolling mill roll bearing housings.

[0005] The technical solution of the present invention is: a laser cladding device for repairing bearing seats of rolling mill rolls, comprising a base plate, a rotating platform for driving the bearing seat to rotate on the base plate, a multi-axis laser cladding module for laser repair of the inner wall of the bearing seat on the base plate, symmetrically distributed fixed frames fixedly connected to the base plate, the symmetrically distributed fixed frames being slidably connected to a sliding frame, threaded shafts rotatably connected between the symmetrically distributed fixed frames and the base plate, the symmetrically distributed threaded shafts being threadedly connected to the sliding frame, symmetrically distributed drive modules on the base plate for driving adjacent threaded shafts to rotate, a shielding cylinder rotatably connected to the sliding frame, the shielding cylinder having a notch exposing the bearing seat repair position, and a rotating component for driving the shielding cylinder to rotate on the sliding frame.

[0006] More preferably, the rotating assembly includes a gear ring, which is fixedly connected to the top of the shielding cylinder, and the sliding frame is fixedly connected to a driving member. The output shaft of the driving member is fixedly connected to a spur gear, which meshes with the gear ring.

[0007] More preferably, the central angle of the notch in the shielding cylinder is α, and the value of α is in the range of 120°≤α≤150°.

[0008] More preferably, the shielding cylinder is fixedly connected to a negative pressure pipe, the negative pressure pipe is located above the opening of the shielding cylinder, and the negative pressure pipe is fixedly connected to and communicates with a connecting pipe.

[0009] More preferably, the outer wall of the shielding cylinder is provided with several pairs of vertically distributed sliding arc plates, and two vertically adjacent sliding arc plates are in contact with each other, and the sliding arc plates are used to seal the opening of the shielding cylinder.

[0010] More preferably, a fixing bolt is threadedly connected to the side of the sliding arc plate away from the notch of the shielding cylinder, and the fixing bolt is used to press the shielding cylinder to lock the adjacent sliding arc plate.

[0011] More preferably, the shielding cylinder is fixedly connected with the same number of slide rails as the sliding arc plates, the sliding arc plates are provided with grooves, and the slide rails slide within the grooves corresponding to the sliding arc plates.

[0012] More preferably, the groove is located in the middle of the outer wall of the sliding arc plate.

[0013] More preferably, the arc length of the groove is less than the arc length of the corresponding sliding arc plate, and the groove penetrates the side of the corresponding sliding arc plate away from the notch of the shielding cylinder.

[0014] More preferably, a supporting arc rod is fixedly connected to the bottom of the shielding cylinder, and the supporting arc rod slides in contact with a pair of adjacent sliding arc plates, the supporting arc rod being used to provide stable support for the sliding arc plates.

[0015] The present invention has the following advantages: 1. The present invention exposes the local area to be repaired of the bearing housing through the notch design of the shielding cylinder, thereby achieving a large-scale physical isolation of the non-repaired inner wall, reducing the area where cladding slag spatter adheres, and thus reducing the area that needs to be additionally ground in the non-repaired area, thereby improving the effect of cladding repair of the bearing housing.

[0016] 2. Through the adjustable design of several sliding arc plates, the staff can flexibly adjust the distribution of each set of sliding arc plates according to the actual range and location of the damage to the inner wall of the bearing housing, and accurately control the opening size of the shielding cylinder notch. This achieves precise positioning and exposure of the area to be repaired, while maximizing the shielding area of ​​the non-repairable inner wall, reducing the area where molten weld slag adheres, and significantly reducing the probability of accidental damage to other parts of the bearing housing.

[0017] 3. By hiding the groove between the sliding arc plate and the inner wall of the bearing, the shielding surface exposed to the welding slag spatter environment remains smooth and continuous, reducing structural dead corners where welding slag easily accumulates, such as groove gaps, and allowing welding slag to adhere to the smooth surface, which greatly shortens the equipment cleaning and maintenance time and improves the convenience and turnover efficiency of continuous operation of the device. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0019] Figure 2 This is a three-dimensional structural diagram of the sliding frame of the present invention;

[0020] Figure 3 This is a three-dimensional structural diagram of the negative pressure pipeline of the present invention;

[0021] Figure 4 This is a bottom view of the three-dimensional structure of the shielding cylinder of the present invention;

[0022] Figure 5 This is a three-dimensional structural diagram of the sliding arc plate of the present invention;

[0023] Figure 6 for Figure 5 Enlarged schematic diagram of the three-dimensional structure at point A;

[0024] Figure 7 This is a three-dimensional structural diagram of the slide rail of the present invention;

[0025] Figure 8 This is a three-dimensional structural diagram of the supporting arc rod of the present invention.

[0026] In the attached diagram, the following are the reference numerals: 1-base plate, 2-rotating platform, 3-multi-axis laser cladding module, 4-fixed frame, 5-sliding frame, 6-threaded shaft, 7-drive module, 8-shielding cylinder, 201-gear ring, 202-drive component, 203-spur gear, 301-negative pressure pipe, 302-connecting pipe, 401-sliding arc plate, 402-fixing bolt, 501-slide rail, 502-groove, 503-support arc rod. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only one of the preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in the present invention without creative effort should be covered within the protection scope of the present invention.

[0028] Existing laser cladding equipment lacks effective spatter protection. During cladding, high-temperature welding slag can easily splash onto the non-repair area of ​​the bearing housing inner wall, causing local thermal shock, resulting in residual stress, structural distortion or microcracks, leading to inner wall deformation, damaging geometric accuracy, affecting assembly and service reliability, and weakening the repair effect.

[0029] Example 1

[0030] This embodiment provides a laser cladding device for repairing rolling mill roll bearing housings, used to protect undamaged areas of the bearing housing's inner wall.

[0031] Combination Figures 1-4As shown, the system includes a base plate 1, on which a rotating platform 2 for driving the bearing housing to rotate is mounted. The rotating platform 2 is equipped with a positioning module (not shown in the figure) to ensure that the central axis of the bearing housing hole is collinear with the rotation axis of the rotating platform 2 and to fix them relatively. The rotating platform 2 supports the steel rolling furnace roll bearing housing and drives it to rotate precisely around its own axis (hereafter, the bearing housing will be used as the reference). A multi-axis laser cladding module 3 for laser repair of the inner wall of the bearing housing is mounted on the base plate 1. The multi-axis laser cladding module 3 consists of a multi-axis mechanical device, a laser welding gun, a feeding device, and a camera. Two symmetrically distributed fixing frames 4 are fixedly connected to the base plate 1, located on opposite sides of the rotating platform 2. The two symmetrically distributed fixing frames 4 are slidably connected to a sliding frame 5. Both symmetrically distributed fixing frames 4 and the base plate 1 are rotatably connected by threaded shafts 6. Both symmetrically distributed threaded shafts 6 are threadedly connected to the sliding frame 5. A symmetrically distributed drive module is mounted on the base plate 1. Block 7, the drive module 7 consists of a servo motor and two transmission gears. The servo motor is fixedly connected to the base plate 1, and the two transmission gears are respectively fixedly connected to the output shaft of the servo motor and the adjacent threaded shaft 6. The two transmission gears mesh with each other. The drive module 7 is used to drive the adjacent threaded shaft 6 to rotate. The sliding frame 5 is rotatably connected to the shielding cylinder 8. In this embodiment, after the shielding cylinder 8 enters the bearing seat hole, the outer wall of the shielding cylinder 8 is in a close fit with the inner wall of the bearing seat. However, this is limited to this embodiment. The inner wall of the shielding cylinder 8 is used to shield the welding slag sputtered during the bearing seat repair. The shielding cylinder 8 is provided with a notch that exposes the bearing seat repair position. The central angle of the notch of the shielding cylinder 8 is α. The value of α is in the range of 120°≤α≤150°. This angle design is based on the local distribution characteristics of bearing seat damage (usually about 120° in the load-bearing area). It can fully expose the area to be repaired and maximize the shielding of the non-repaired inner wall. The sliding frame 5 is provided with a rotating component for driving the shielding cylinder 8 to rotate.

[0032] Combination Figure 2 and Figure 3 As shown, the rotating assembly includes a gear ring 201, which is fixedly connected to the top of the shielding cylinder 8. A driving component 202 is fixedly connected to the upper side of the sliding frame 5. The driving component 202 is a servo motor. A spur gear 203 is fixedly connected to the output shaft of the driving component 202. The spur gear 203 meshes with the gear ring 201. The driving component 202 can drive the shielding cylinder 8 to rotate through the spur gear 203 and the gear ring 201, thereby enabling the notch on the shielding cylinder 8 to follow the damaged position of the bearing seat. A negative pressure pipe 301 is fixedly connected to the shielding cylinder 8. The negative pressure pipe 301 is located above the notch on the shielding cylinder 8. The negative pressure pipe 301 is used to adsorb and collect the exhaust gas generated during the repair of the bearing seat. The negative pressure pipe 301 is fixedly connected to and connected to a connecting pipe 302, which is connected to an external negative pressure extraction device.

[0033] Working principle: When it is necessary to repair the bearing housing of the rolling mill roll, the operator places the bearing housing on the rotating platform 2 and makes the central axis of the bearing housing hole coincide with the central axis of the rotating platform 2 and the central axis of the shielding cylinder 8. Then the operator turns on the two drive modules 7, so that the two drive modules 7 drive the adjacent threaded shafts 6 to rotate. The two threaded shafts 6 together drive the sliding frame 5 to slide down along the two fixed frames 4. The sliding frame 5 drives the shielding cylinder 8 on it to enter the hole of the bearing housing and shield part of the inner wall of the bearing housing. This continues until the bottom of the shielding cylinder 8 is in contact with the upper side of the rotating platform 2. Then the two drive modules 7 are turned off.

[0034] After the shielding cylinder 8 enters the hole in the bearing housing, the multi-axis laser cladding module 3 drives the laser welding gun on it into the shielding cylinder 8 and stops at the repair position. At this time, the camera on the multi-axis laser cladding module 3 observes whether the damaged position of the bearing housing is located in the middle of the notch in the shielding cylinder 8 and whether the damaged position of the bearing housing is located in the repair position of the laser welding gun of the multi-axis laser cladding module 3. If the damaged position of the bearing housing is not aligned with the middle of the notch in the shielding cylinder 8 and the repair position of the laser welding gun of the multi-axis laser cladding module 3, the following operation is performed: the rotating platform 2 is operated to drive the bearing housing to rotate, and the damaged position on the inner wall of the bearing housing is rotated to the repair position of the laser welding gun of the multi-axis laser cladding module 3. At the same time, the drive component 202 is turned on, so that the output shaft of the drive component 202 drives the shielding cylinder 8 to rotate through the spur gear 203 and the gear ring 201. The rotation of the shielding cylinder 8 drives the notch on it to rotate synchronously, so that the repair position of the bearing housing is located in the middle of the notch in the shielding cylinder 8. At this moment, the preparation work for the repair of the bearing housing is completed.

[0035] Once the preparation work for the bearing housing repair is completed, the multi-axis laser cladding module 3 begins to repair the damaged area of ​​the bearing housing. During this process, the rotating platform 2 drives the bearing housing to rotate, thereby changing the circumferential repair position of the multi-axis laser cladding module 3 on the inner wall of the bearing housing. At the same time, the drive component 202 drives the shielding cylinder 8 to rotate through the spur gear 203 and the gear ring 201, so that the shielding cylinder 8 and the notch on it rotate synchronously with the bearing housing. This ensures that the damaged area is always located in the middle of the notch of the shielding cylinder 8, reducing the probability that the weld slag sputtered during the repair of the inner wall of the bearing housing will adhere to other parts of the bearing housing. At the same time, the external negative pressure extraction device is turned on, so that the fumes generated during the repair of the bearing housing are collected along the negative pressure pipe 301 and the connecting pipe 302, reducing the harm to the workers. This continues until the repair of the inner wall of the bearing housing is completed.

[0036] After the inner wall of the bearing housing is repaired, the staff turns off the external negative pressure extraction device, rotating platform 2 and drive component 202. Then, the multi-axis laser cladding module 3 controls the laser welding gun on it to return to the initial position. At the same time, the two drive modules 7 drive the sliding frame 5 to return to the initial position through the adjacent threaded shaft 6, so that the sliding frame 5 drives the shielding cylinder 8 to return to the initial state. Then, the repaired bearing housing is removed from the rotating platform 2. When the bearing housing needs to be repaired again, the above steps are repeated.

[0037] Example 2

[0038] This embodiment provides a laser cladding device for repairing rolling mill roll bearing housings, which is a further improvement on embodiment 1.

[0039] Combination Figure 3 , Figure 5 and Figure 6 As shown, the outer wall of the shielding cylinder 8 is provided with several vertically distributed sets of sliding arc plates 401. In this embodiment, the shielding cylinder 8 and the pair of sliding arc plates 401 at the top are in a limiting sliding connection, and two adjacent sliding arc plates 401 are mutually limiting sliding connections. The sliding arc plates 401 and the shielding cylinder 8 are in a fitting relationship, but this is limited to this embodiment. The two vertically adjacent sliding arc plates 401 are mutually fitting, and several sliding arc plates 401 together block the opening of the shielding cylinder 8. In this embodiment, after the shielding cylinder 8 drives the sliding arc plates 401 on it into the hole of the bearing seat, the outer surface of the sliding arc plates 401... It will fit against the inner wall of the bearing housing, while there is a gap between the shielding cylinder 8 and the inner wall support of the bearing housing. By changing the state of several sliding arc plates 401 according to the location and range of damage to the inner wall of the bearing housing, the opening position and range of the notch of the shielding cylinder 8 can be adjusted to accurately expose the damaged location of the inner wall of the bearing housing. The side of the sliding arc plate 401 away from the notch of the shielding cylinder 8 is threaded with a fixing bolt 402. The fixing bolt 402 is used to press the shielding cylinder 8 to lock the adjacent sliding arc plate 401, ensuring that when the shielding cylinder 8 drives the sliding arc plate 401 on it to rotate, the shielding cylinder 8 and the sliding arc plate 401 will not rotate relative to each other.

[0040] Working principle: Before the shielding cylinder 8 enters the hole of the bearing housing, the operator rotates the fixing bolts 402 on several sliding arc plates 401 in sequence. The fixing bolts 402 release the pressure on the shielding cylinder 8, allowing the sliding arc plates 401 to slide freely against the outer wall of the shielding cylinder 8. Then, the operator changes the position of all sliding arc plates 401 according to the location and extent of damage inside the bearing housing. Taking a pair of sliding arc plates 401 as a reference, the operator slides the two sliding arc plates 401 in opposite directions according to the extent of the damage corresponding to the two sliding arc plates 401 on the bearing housing, thus blocking the notch area on the shielding cylinder 8. Gradually open the slides until the area between the two sliding arc plates 401 is sufficient to cover the corresponding damaged location on the bearing housing. Then stop sliding the two sliding arc plates 401 and rotate the corresponding fixing bolts 402 to press the blocking cylinder 8 to lock the adjacent sliding arc plates 401. After the remaining sets of sliding arc plates 401 are adjusted one by one according to the above steps, the two drive modules 7 then operate the blocking cylinder 8 to enter the hole in the bearing housing. By adjusting the distribution of the several sets of sliding arc plates 401 according to the damage range of the inner wall of the bearing housing, the blocking area of ​​the inner wall of the bearing housing is further increased, reducing the probability of damage to other parts of the bearing housing.

[0041] Example 3

[0042] This embodiment provides a laser cladding device for repairing rolling mill roll bearing housings, which is a further improvement on embodiment 2.

[0043] Combination Figure 5 , Figure 7 and Figure 8 As shown, the shielding cylinder 8 is fixedly connected with the same number of slide rails 501 as the sliding arc plates 401. The sliding arc plates 401 are provided with grooves 502. The slide rails 501 slide within the grooves 502 of the corresponding sliding arc plates 401. The sliding arc plates 401 can slide stably along the corresponding slide rails 501. In this embodiment, two adjacent sliding arc plates 401 slide only in contact. The grooves 502 are located in the middle of the outer wall of the corresponding sliding arc plates 401. The arc length of the grooves 502 is less than the arc length of the corresponding sliding arc plates 401, and the grooves 502 penetrate through the corresponding sliding arc plates 401 away from the notch of the shielding cylinder 8. On the side, that is, the side of the groove 502 on the two sliding arc plates 401 near the opening of the shielding cylinder 8 is in a blocked state, so that the inner wall, side wall and top and bottom surfaces (i.e. the shielding surface for welding slag) of the sliding arc plate 401 are completely smooth and without gaps or depressions. The bottom of the shielding cylinder 8 is fixedly connected to the support arc rod 503. The support arc rod 503 slides in contact with the pair of sliding arc plates 401 on the lower side. The support arc rod 503 is used to provide stable support for the sliding arc plate 401, reduce the probability of the sliding arc plate 401 and the slide rail 501 sagging due to gravity, and ensure the sealing degree of the shielding of the opening of the shielding cylinder 8.

[0044] Working principle: During the process of adjusting the sliding arc plate 401 to slide along the shielding cylinder 8, since the groove 502 is located on the outer wall of the sliding arc plate 401 and the groove 502 is in a blocked state on the side near the opening of the shielding cylinder 8, after the shielding cylinder 8 and several sliding arc plates 401 on it enter the hole of the bearing seat, the outer wall of the sliding arc plate 401 will fit with the inner wall of the bearing seat, hiding the groove 502 for the sliding arc plate 401 to slide on the shielding cylinder 8. That is, when repairing the inner wall of the bearing seat, the areas where several sliding arc plates 401 and shielding cylinder 8 leave welding slag on the outside are all smooth curved surfaces, which greatly improves the subsequent cleaning efficiency of welding slag adhering to the sliding arc plate 401 and shielding cylinder 8.

[0045] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A laser cladding device for repairing bearing seats of rolling mill rolls, comprising a base plate (1), a rotating platform (2) for driving the bearing seat to rotate on the base plate (1), and a multi-axis laser cladding module (3) for laser repair of the inner wall of the bearing seat, characterized in that: It also includes symmetrically distributed fixed frames (4), all of which are fixedly connected to the base plate (1). The symmetrically distributed fixed frames (4) are slidably connected to a sliding frame (5). The symmetrically distributed fixed frames (4) and the base plate (1) are rotatably connected to threaded shafts (6). The symmetrically distributed threaded shafts (6) are threadedly connected to the sliding frame (5). The base plate (1) is provided with symmetrically distributed drive modules (7). The drive modules (7) are used to drive the adjacent threaded shafts (6) to rotate. The sliding frame (5) is rotatably connected to a shielding cylinder (8). The shielding cylinder (8) is provided with a notch that exposes the bearing seat repair position. The sliding frame (5) is provided with a rotating component for driving the shielding cylinder (8) to rotate.

2. The laser cladding device for repairing rolling mill roll bearing seats according to claim 1, characterized in that, The rotating assembly includes a gear ring (201) which is fixedly connected to the top of the shielding cylinder (8). The sliding frame (5) is fixedly connected to a driving member (202). The output shaft of the driving member (202) is fixedly connected to a spur gear (203), which meshes with the gear ring (201).

3. The laser cladding device for repairing rolling mill roll bearing seats according to claim 1, characterized in that, The central angle of the notch in the shielding cylinder (8) is α, and the value of α is in the range of 120°≤α≤150°.

4. The laser cladding device for repairing rolling mill roll bearing seats according to claim 3, characterized in that, The shielding cylinder (8) is fixedly connected to a negative pressure pipe (301), the negative pressure pipe (301) is located above the opening of the shielding cylinder (8), and the negative pressure pipe (301) is fixedly connected to and connected to a connecting pipe (302).

5. The laser cladding device for repairing rolling mill roll bearing seats according to claim 4, characterized in that, The outer wall of the shielding cylinder (8) is provided with several pairs of vertically distributed sliding arc plates (401), and two vertically adjacent sliding arc plates (401) are in contact with each other. The sliding arc plates (401) are used to block the opening of the shielding cylinder (8).

6. The laser cladding device for repairing rolling mill roll bearing seats according to claim 5, characterized in that, The sliding arc plate (401) is threaded with a fixing bolt (402) on the side away from the notch of the shielding cylinder (8). The fixing bolt (402) is used to press the shielding cylinder (8) to lock the adjacent sliding arc plate (401).

7. The laser cladding device for repairing rolling mill roll bearing seats according to claim 6, characterized in that, The shielding cylinder (8) is fixedly connected with the same number of slide rails (501) as the sliding arc plate (401). The sliding arc plate (401) is provided with a groove (502). The slide rail (501) slides within the groove (502) corresponding to the sliding arc plate (401).

8. The laser cladding device for repairing rolling mill roll bearing seats according to claim 7, characterized in that, The groove (502) is located in the middle of the outer wall of the corresponding sliding arc plate (401).

9. The laser cladding device for repairing rolling mill roll bearing seats according to claim 8, characterized in that, The arc length of the groove (502) is less than the arc length of the corresponding sliding arc plate (401), and the groove (502) penetrates the side of the corresponding sliding arc plate (401) away from the notch of the shielding cylinder (8).

10. The laser cladding device for repairing rolling mill roll bearing seats according to claim 9, characterized in that, The bottom of the shielding cylinder (8) is fixedly connected to a support arc rod (503), which slides in contact with a pair of adjacent sliding arc plates (401). The support arc rod (503) is used to provide stable support for the sliding arc plates (401).

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