A kind of auxiliary tool for adjusting concentricity of rotating pipe mating surface and metal end

Abstract

This utility model relates to the field of glass tube forming rotary tube assembly technology, and particularly to an auxiliary tooling for adjusting the concentricity of the mating surface of the rotary tube and the metal end. It aims to solve the technical problem in related technologies where the concentricity of the rotary tube and the metal end around the rotation axis cannot be guaranteed during grinding, leading to increased concentricity error of the mating conical surface and thus easy displacement of the rotary tube and the metal end. This auxiliary tooling for adjusting the concentricity of the mating surface of the rotary tube and the metal end uses a rolling element abutting against the outer wall of the rotary tube to determine the rotation axis coaxial with the rotary tube. Then, by rotating the adjusting screw, the metal end is driven to become coaxial with the rotary tube, completing the coaxial fit of the metal end, the rotary tube, and the rotation axis. This overcomes the technical problem in existing rotary tube assembly methods where the concentricity of the rotary tube and the metal end around the rotation axis cannot be guaranteed during grinding, leading to increased concentricity error of the mating conical surface and thus easy displacement of the rotary tube and the metal end.

Description

Technical Field

[0001] This utility model relates to the field of glass tube forming and rotating tube assembly technology, and in particular to an auxiliary tooling for adjusting the concentricity of the rotating tube mating surface and the metal end. Background Technology

[0002] In the glass tube manufacturing process, the rotating tube and the metal end are installed and fitted together via a pre-machined conical surface. The contact area and concentricity of this conical fit are extremely critical. The current method involves first inserting the rotating tube laterally onto a mandrel, then screwing the metal end onto the front end of the mandrel, followed by a gentle rotation of the rotating tube for grinding. However, during grinding, the concentricity of the rotating tube and the metal end around the rotation axis cannot be guaranteed, resulting in concentricity errors between the ground conical surface and the metal end. This makes the rotating tube and the metal end prone to displacement during subsequent use.

[0003] The existing rotary tube assembly method has a technical problem: it cannot guarantee the concentricity of the rotary tube and the metal end around the rotation axis during the grinding process, which leads to an increase in the concentricity error of the mating conical surface, making the rotary tube and the metal end prone to displacement. Utility Model Content

[0004] The purpose of this utility model is to provide an auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end, so as to overcome the technical problem in the related technology that the concentricity of the mating conical surface is increased due to the inability to guarantee the concentricity of the rotating tube and the metal end around the rotation axis during the grinding process, which makes the rotating tube and the metal end easy to shift.

[0005] To solve the above-mentioned technical problems, the technical solution provided by this utility model is as follows:

[0006] The auxiliary tooling provided by this utility model for adjusting the concentricity of the mating surface of a rotating tube and the metal end includes:

[0007] The fixture includes a support frame, a locking element, and a fixed-axis assembly. The support frame comprises a main frame and multiple extension arms. The main frame is connected to a metal end via the locking element, and the metal end abuts against a mating surface at one end of a rotating tube. The extension arms extend from the main frame towards the other end of the rotating tube, and the fixed-axis assembly is mounted on the extension arms. The fixed-axis assembly includes multiple adjusting units evenly distributed around the axis of the rotating tube. Each adjusting unit includes a rolling element and adjusting elements respectively adjusted and connected to each of the extension arms. The rolling element is rotatably connected to the adjusting element and abuts against the rotating tube.

[0008] Specifically, the rolling element is a ball bearing, and the adjusting element is an adjusting screw. The fixed-axis assembly also includes a ball bearing seat, which is mounted on the end of the adjusting screw near the rotating tube. The ball bearing is embedded in and rolls within the ball bearing seat. The adjusting screw is threadedly connected to the extension arm, and the rotation of the adjusting screw around its own axis drives the ball bearing to move radially along the metal end to push the rotating tube, thereby adjusting the concentricity of the metal end and the rotating tube.

[0009] Specifically, the rolling element is configured as a roller, and the adjusting component is configured as an adjusting screw. The fixed-axis assembly also includes a rotating frame, to which the roller is rotatably connected. The rotating frame is provided with limit plates and a U-shaped groove. The two limit plates are respectively clamped on both sides of the extension arm to limit the relative rotation of the roller and the extension arm. The U-shaped groove is located on the side of the rotating frame away from the roller. The adjusting screw has an annular groove at one end near the rotating tube, which engages with the U-shaped groove. The adjusting screw is threadedly connected to the extension arm, and the rotation of the adjusting screw around its own axis drives the roller to move radially along the metal end to push the rotating tube, thereby adjusting the concentricity of the metal end and the rotating tube.

[0010] Specifically, the opening direction of the U-shaped groove is not parallel to the extension direction of the extension arm, which is used to ensure the engagement stability of the annular groove and the U-shaped groove and to prevent the rotating frame from disengaging from the adjusting screw.

[0011] Specifically, in the length direction of the adjusting screw, the length of the threaded section of the adjusting screw is greater than the sum of the length of the limiting plate and the thickness of the extension arm.

[0012] Specifically, the tooling bracket also includes a support ring, which is sleeved on the rotating tube and connected to each of the extension arms to assist in supporting each of the extension arms.

[0013] Specifically, the plurality of support rings and the plurality of fixed-axis assemblies are arranged alternately along the length of the rotating tube.

[0014] Specifically, the locking element is a locking screw sleeve. A stepped boss is provided at the center of the main frame, and a center hole is provided on the metal end, with the center hole of the metal end fitting onto the stepped boss. The locking screw sleeve is threadedly connected to the stepped boss, thereby fixing the metal end to the main frame.

[0015] Specifically, the fixed-axis assembly also includes an adjustment handle, which is installed at the end of the adjustment member away from the rotating tube, and is used to drive the adjustment member to rotate around its own axis.

[0016] Specifically, the tooling bracket also includes reinforcing ribs, which are disposed between the main frame and the extension arms to assist in supporting each of the extension arms.

[0017] Based on the above technical solutions, the beneficial effects of this utility model are analyzed as follows:

[0018] This utility model provides an auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end, comprising:

[0019] The fixture includes a support frame, a locking element, and a fixed-axis assembly. The support frame comprises a main frame and multiple extension arms. The main frame is connected to a metal end via the locking element, and the metal end abuts against a mating surface at one end of a rotating tube. The extension arms extend from the main frame towards the other end of the rotating tube, and the fixed-axis assembly is mounted on the extension arms. The fixed-axis assembly includes multiple adjusting units evenly distributed around the axis of the rotating tube. Each adjusting unit includes a rolling element and adjusting elements respectively adjusted and connected to each of the extension arms. The rolling element is rotatably connected to the adjusting element and abuts against the rotating tube.

[0020] In practical application, the rolling elements are mounted on the extension arm via the adjusting members, and the metal end is connected to the main frame as a single unit via the locking members. The metal end is placed inside the vertical rotating tube, abutting against the mating surface of the rotating tube. Rotating the adjusting members causes the rolling elements to abut against the outer wall of the rotating tube. At this point, the rotating shaft and the rotating tube are coaxial. The adjusting members are further adjusted to adjust the concentricity of the metal end and the rotating tube, thereby making the metal end coaxial with the rotating shaft. Rotating the tooling bracket and the metal end causes the metal end and the rotating tube to rotate relative to each other by means of the rolling elements rolling on the outer wall of the rotating tube, thus grinding the contact surfaces.

[0021] As can be seen, compared with the prior art, this auxiliary tooling for adjusting the concentricity of the rotating tube mating surface and the metal end determines the rotating axis coaxial with the rotating tube by the rolling element abutting against the outer wall of the rotating tube. Then, the rotation of the adjusting component drives the metal end to be coaxial with the rotating tube, thus completing the coaxial mating of the metal end, the rotating tube, and the rotating axis. This overcomes the technical problem of existing rotating tube assembly methods, where the concentricity of the rotating tube and the metal end around the rotating axis cannot be guaranteed during the grinding process, leading to increased concentricity error of the mating conical surface and making the rotating tube and the metal end prone to displacement. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 A schematic diagram of the combined structure of the auxiliary tooling for adjusting the concentricity of the rotating tube mating surface and the metal end provided in an embodiment of this utility model;

[0024] Figure 2 Schematic diagram of the cross-sectional structure of the auxiliary tooling used for adjusting the concentricity of the rotating tube mating surface and the metal end. Figure 1 ;

[0025] Figure 3 This is an exploded view of the auxiliary tooling used to adjust the concentricity between the mating surface of the rotating tube and the metal end.

[0026] Figure 4 Schematic diagram of the cross-sectional structure of the auxiliary tooling used for adjusting the concentricity of the rotating tube mating surface and the metal end. Figure 2 ;

[0027] Figure 5 This is a schematic diagram of the auxiliary tooling used to adjust the concentricity between the mating surface of the rotating tube and the metal end.

[0028] Figure 6 A cross-sectional diagram of the adjustment unit when ball bearings are used;

[0029] Figure 7 A cross-sectional view of the adjustment unit when rollers are used;

[0030] Figure 8 An exploded view of the adjustment unit using rollers.

[0031] icon:

[0032] 001. Metal end; 002. Rotating tube;

[0033] 100. Tooling bracket; 110. Main frame; 101. Stepped boss; 120. Extension arm; 130. Support ring; 140. Reinforcing rib;

[0034] 200. Locking component; 210. Locking nut sleeve;

[0035] 300. Fixed shaft assembly; 310. Rolling element; 311. Ball; 312. Roller; 320. Adjusting component; 321. Adjusting screw; 303. Annular groove; 330. Ball bearing seat; 340. Rotating frame; 301. Limiting plate; 302. U-shaped groove; 350. Adjusting handle. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0038] The following detailed description, in conjunction with the accompanying drawings, outlines some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0039] The existing rotary tube assembly method has a technical problem: it cannot guarantee the concentricity of the rotary tube and the metal end around the rotation axis during the grinding process, which leads to an increase in the concentricity error of the mating conical surface, making the rotary tube and the metal end prone to displacement.

[0040] In view of this, the present invention provides an auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end, comprising:

[0041] The fixture bracket 100, locking element 200, and fixed axis assembly 300 are included. The fixture bracket 100 includes a main frame 110 and multiple extension arms 120. The main frame 110 is connected to a metal end 001 via the locking element 200. The metal end 001 abuts against a mating surface at one end of the rotating tube 002. The extension arms 120 extend from the main frame 110 along the length direction to the other end of the rotating tube 002. The fixed axis assembly 300 is mounted on the extension arms 120. The fixed axis assembly 300 includes multiple adjusting units evenly distributed around the axis of the rotating tube 002. Each adjusting unit includes a rolling element 310 and adjusting elements 320 that are respectively adjusted and connected to each extension arm 120. The rolling element 310 is rotatably connected to the adjusting element 320 and abuts against the rotating tube 002.

[0042] In summary, the auxiliary tooling provided by this utility model for adjusting the concentricity of the mating surface of a rotating tube and the metal end can achieve the following technical effects:

[0043] The auxiliary tooling used for adjusting the concentricity of the mating surface of the rotating tube 002 and the metal end 001 determines the rotating shaft coaxial with the rotating tube 002 by the rolling element 310 abutting against the outer wall of the rotating tube 002. Then, the rotation of the adjusting component 320 drives the metal end 001 to be coaxial with the rotating tube 002, thus completing the coaxial mating of the metal end 001, the rotating tube 002, and the rotating shaft. This overcomes the technical problem of existing rotating tube 002 assembly methods, where the concentricity of the rotating tube 002 and the metal end 001 around the rotating shaft cannot be guaranteed during the grinding process, resulting in increased concentricity error of the mating conical surface and making the rotating tube 002 and the metal end 001 prone to displacement.

[0044] The following combination Figures 1 to 8 The structure and shape of the auxiliary tooling provided in this embodiment for adjusting the concentricity of the rotating tube mating surface and the metal end are described in detail:

[0045] In an optional embodiment, the rolling element 310 is configured as a ball bearing 311, and the adjusting element 320 is configured as an adjusting screw 321. The fixed-axis assembly 300 also includes a ball bearing seat 330, which is mounted on the end of the adjusting screw 321 near the rotating tube 002. The ball bearing 311 is embedded in and rolls within the ball bearing seat 330. The adjusting screw 321 is threadedly connected to the extension arm 120. The rotation of the adjusting screw 321 around its own axis drives the ball bearing 311 to move radially along the metal end 001 to push the rotating tube 002, thereby adjusting the concentricity of the metal end 001 and the rotating tube 002.

[0046] In this embodiment, the rolling element 310 is configured as a roller 312, and the adjusting element 320 is configured as an adjusting screw 321. The fixed-axis assembly 300 also includes a rotating frame 340, to which the roller 312 is rotatably connected. The rotating frame 340 is provided with a limiting plate 301 and a U-shaped groove 302. The two limiting plates 301 are respectively clamped on both sides of the extension arm 120 to limit the relative rotation between the roller 312 and the extension arm 120. The U-shaped groove 302 is located on the side of the rotating frame 340 away from the roller 312. The adjusting screw 321 has an annular groove 303 at the end near the rotating tube 002, which engages with the U-shaped groove 302. The adjusting screw 321 is threaded to the extension arm 120. The rotation of the adjusting screw 321 around its own axis is used to drive the roller 312 to move radially along the metal end 001 to push the rotating tube 002, thereby adjusting the concentricity of the metal end 001 and the rotating tube 002.

[0047] Regarding how the adjusting screw 321 prevents the annular groove 303 from sliding out along the U-shaped groove 302 and disengaging from the rotating frame 340, specifically:

[0048] Two limiting plates 301 are respectively clamped on both sides of the extension arm 120, allowing the rotating frame 340 to slide along the extension direction of the extension arm 120. The engagement of the annular groove 303 and the U-shaped groove 302 allows the rotating frame 340 to slide along the opening direction of the U-shaped groove 302. Since the opening direction of the U-shaped groove 302 is not parallel to the extension direction of the extension arm 120, the sliding directions conflict with each other, preventing the rotating frame 340 from sliding in either direction, thereby achieving precise positioning and ensuring the stability of the engagement between the annular groove 303 and the U-shaped groove 302, preventing the rotating frame 340 from disengaging from the adjusting screw 321.

[0049] In this embodiment, the length of the threaded section of the adjusting screw 321 is greater than the sum of the length of the limiting plate 301 and the thickness of the extension arm 120. Rotating the adjusting screw 321 moves the rotating frame 340 towards the roller 312. When the limiting plate 301 disengages from the extension arm 120, the annular groove 303 slides out along the U-shaped groove 302, thus separating from the U-shaped groove 302, thereby separating the rotating frame 340 from the adjusting screw 321.

[0050] To facilitate the operation of the adjusting screw 321, in this embodiment, the fixed-axis assembly 300 further includes an adjusting handle 350. The adjusting handle 350 is installed at the end of the adjusting screw 321 away from the rotating tube 002, and is used to drive the adjusting screw 321 to rotate around its own axis. The connection method between the adjusting handle 350 and the adjusting screw 321 can be set as snap-fit, welding, or pin connection, etc.

[0051] To enhance the rigidity of each extension arm 120 and thus improve the positioning accuracy of the fixed-axis assembly 300, in this embodiment, the tooling bracket 100 further includes a support ring 130. The support ring 130 is sleeved on the rotating tube 002 and connected to each extension arm 120 to assist in supporting each extension arm 120. The connection method between the support ring 130 and the extension arm 120 can be snap-fit, welded, or bolted.

[0052] To further improve the stability of each extension arm 120 and limit the positioning deviation between the fixed axis assembly 300 and the rotating tube 002 caused by the deformation of the extension arm 120, in this embodiment, multiple support rings 130 and multiple fixed axis assemblies 300 are arranged alternately along the length direction of the rotating tube 002.

[0053] Regarding how the main frame 110 is connected to the metal end 001 as a whole, specifically:

[0054] The locking element 200 is a locking nut 210. A stepped boss 101 is located at the center of the main frame 110, and a metal end 001 has a central hole. The central hole of the metal end 001 is fitted onto the stepped boss 101. The locking nut 210 is threaded onto the stepped boss 101. The stepped boss 101, the metal end 001, and the locking nut 210 abut against each other in sequence, thereby fixing the metal end 001 to the main frame 110.

[0055] To further improve the connection stability between the extension arm 120 and the main frame 110, in this embodiment, the tooling bracket 100 also includes a reinforcing rib 140, which is disposed between the main frame 110 and the extension arm 120 to assist in supporting each extension arm 120.

[0056] In summary, the specific working process of the auxiliary tooling provided in this embodiment for adjusting the concentricity of the rotating tube mating surface and the metal end is as follows:

[0057] Taking the rolling element 310 as an example, which uses roller 312.

[0058] After the stepped boss 101 passes through the center hole of the metal end 001, it is threadedly connected to the locking nut 210. The stepped boss 101, the metal end 001 and the locking nut 210 abut against each other in sequence, and the metal end 001 is fixedly connected to the main frame 110 as a whole.

[0059] The metal end 001 is placed inside the vertical rotating tube 002, abutting against the mating surface of the rotating tube 002. Rotating the adjusting screws 321 clockwise causes the rollers 312 to abut against the outer wall of the rotating tube 002. At this point, the rotating shaft and the rotating tube 002 are coaxial. The adjusting screws 321 are further adjusted to regulate the concentricity of the metal end 001 and the rotating tube 002, ensuring that the metal end 001 is coaxial with the rotating shaft. Rotating the tooling bracket 100 and the metal end 001 causes relative rotation between the metal end 001 and the rotating tube 002 via the rolling of the rollers 312 on the outer wall of the rotating tube 002, thus grinding the contact surfaces.

[0060] The installation steps for the rotating bracket 340 and the adjusting screw 321 are as follows:

[0061] By rotating the adjusting handle 350 forward, the adjusting screw 321 is screwed inward into the tooling bracket 100 until the length of the adjusting screw 321 extending out of the extension arm 120 is greater than the length of the limiting plate 301. The U-shaped groove 302 of the rotating frame 340 is slid along the annular groove 303, so that the annular groove 303 and the U-shaped groove 302 are engaged. By rotating the adjusting handle 350 in reverse, the adjusting screw 321 and the rotating frame 340 are moved towards the extension arm 120 and abut against the extension arm 120. At this time, the two limiting plates 301 are clamped on both sides of the extension arm 120 to form a limit, completing the installation of the rotating frame 340 and the adjusting screw 321.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. An auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube with a metal end, characterized in that, include: The tooling bracket (100), locking element (200) and fixed axis assembly (300) are provided, wherein the tooling bracket (100) includes a main frame (110) and multiple extension arms (120); The main frame (110) is connected to the metal end (001) through the locking member (200), the metal end (001) abuts against the mating surface of one end of the rotating tube (002), the extension arm (120) extends from the main frame (110) to the other end of the rotating tube (002) in the length direction, and the fixed axis assembly (300) is installed on the extension arm (120); The fixed-axis assembly (300) includes a plurality of adjustment units evenly distributed around the axis of the rotating tube (002). Each adjustment unit includes a rolling element (310) and an adjustment member (320) respectively adjusted and connected to each of the extension arms (120). The rolling element (310) is rotatably connected to the adjustment member (320) and abuts against the rotating tube (002).

2. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 1, characterized in that: The rolling element (310) is configured as a ball (311), and the adjusting element (320) is configured as an adjusting screw (321); The fixed axis assembly (300) also includes a ball seat (330), which is mounted on one end of the adjusting screw (321) near the rotating tube (002), and the ball (311) is embedded in and rolls in the ball seat (330); The adjusting screw (321) is threaded to the extension arm (120). The rotation of the adjusting screw (321) around its own axis is used to drive the ball (311) to move radially along the metal end (001) to push the rotating tube (002) thereby adjusting the concentricity of the metal end (001) and the rotating tube (002).

3. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 1, characterized in that: The rolling element (310) is configured as a roller (312), and the adjusting element (320) is configured as an adjusting screw (321); The fixed-axis assembly (300) further includes a rotating frame (340), and the roller (312) is rotatably connected to the rotating frame (340); The rotating frame (340) is provided with a limiting plate (301) and a U-shaped groove (302). The two limiting plates (301) are respectively clamped on both sides of the extension arm (120) to restrict the relative rotation of the roller (312) and the extension arm (120). The U-shaped groove (302) is disposed on the side of the rotating frame (340) away from the roller (312); The adjusting screw (321) has an annular groove (303) at one end near the rotating tube (002), and the annular groove (303) is engaged with the U-shaped groove (302); The adjusting screw (321) is threaded to the extension arm (120). The rotation of the adjusting screw (321) around its own axis is used to drive the roller (312) to move radially along the metal end (001) to push the rotating tube (002) thereby adjusting the concentricity of the metal end (001) and the rotating tube (002).

4. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 3, characterized in that: The opening direction of the U-shaped groove (302) is not parallel to the extension direction of the extension arm (120), which is used to ensure the engagement stability of the ring groove (303) and the U-shaped groove (302) and to prevent the rotating frame (340) from disengaging from the adjusting screw (321).

5. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 4, characterized in that: In the length direction of the adjusting screw (321), the length of the threaded section of the adjusting screw (321) is greater than the sum of the length of the limiting plate (301) and the thickness of the extension arm (120).

6. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 1, characterized in that: The tooling bracket (100) also includes a support ring (130), which is sleeved on the rotating tube (002) and connected to each of the extension arms (120) to assist in supporting each of the extension arms (120).

7. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 6, characterized in that: The plurality of support rings (130) and the plurality of fixed-axis assemblies (300) are staggered along the length of the rotating tube (002).

8. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 1, characterized in that: The locking element (200) is configured as a locking screw sleeve (210); The main frame (110) is provided with a stepped boss (101) at the center, and the metal end (001) is provided with a central hole. The central hole of the metal end (001) is sleeved on the stepped boss (101). The locking nut (210) is threaded onto the stepped boss (101), thereby fixing the metal end (001) to the main frame (110).

9. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 1, characterized in that: The fixed-axis assembly (300) also includes an adjustment handle (350), which is installed at the end of the adjustment member (320) away from the rotating tube (002) and is used to drive the adjustment member (320) to rotate around its own axis.

10. The auxiliary tooling for adjusting the concentricity of the mating surface of a rotating tube and the metal end according to claim 1, characterized in that: The tooling bracket (100) also includes a reinforcing rib (140), which is disposed between the main frame (110) and the extension arm (120) to assist in supporting each of the extension arms (120).

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