Tooling board rotation support structure

Abstract

The utility model provides a kind of tooling bottom plate rotary support structure, comprising: machine table, its both ends are oppositely provided with the driving end and driven end that can rotate around coaxial;Bottom plate, its both ends are fixedly connected driving end and driven end;Rotary drive structure, it is set in driving end, for driving bottom plate rotation;Support adjusting mechanism, between driving end and driven end, including rotating seat and rotating block, the rotating seat is fixed on machine table, the outer periphery of the rotating block is equipped with arc rotating part, the rotating part, driving end and driven end coaxial line rotation;Rotating block is equipped with placing groove, for carrying bottom plate;Clamping mechanism and horizontal adjusting mechanism are equipped on the placing groove.Provide a kind of tooling bottom plate rotary support structure, solve the problem that when existing tooling bottom plate is longer, conventional support structure cannot adapt rotation, and there is no support structure to cause middle subsidence.

Description

Technical Field

[0001] This utility model relates to the field of tooling fixtures, specifically to a tooling base plate rotation support structure. Background Technology

[0002] In industrial fields such as machining, assembly, and testing, the tooling base plate, as a core component supporting the workpiece, directly affects operational accuracy and efficiency due to its stability and functionality. To adapt to the needs of multi-station machining, multi-angle assembly, or omnidirectional testing, the tooling base plate often needs to have the function of rotating around its axis, thus giving rise to various tooling base plate rotation support structures. In existing technologies, conventional tooling base plate rotation support structures mostly adopt a "two-end support" mode, that is, the base plate is fixed and rotated by a drive end and a driven end set opposite to each other at both ends of the machine tool—the drive end is connected to a rotation drive structure to provide rotational power, and the driven end rotates synchronously and coaxially with the drive end, thereby driving the tooling base plate fixed between the two ends to complete the rotation action. When dealing with short-sized tooling base plates, this structure can meet the rotational stability requirements due to the high rigidity of the base plate itself, and the structural deformation problem is not easily caused. It is widely used in the machining and assembly of small and medium-sized workpieces. However, with the increasing demand for processing large and long workpieces in industrial production, the length of the tooling base plate has increased significantly. The drawbacks of the traditional "two-end support" rotating structure have become increasingly apparent, mainly due to the following core problems: First, the problem of central sinking in long base plates is prominent. When the length of the tooling base plate increases to a certain extent, its own weight and the weight of the workpiece will cause significant bending stress in the middle of the base plate. Because the traditional structure relies only on the driving and driven ends for support, the middle lacks an effective support point, making it prone to central sinking and deformation during long-term use. This sinking not only leads to excessive deviations in the base plate's levelness, affecting the installation and processing accuracy of the workpiece, but in severe cases, it can also cause permanent structural damage to the base plate, shortening the equipment's service life. Second, the contradiction between support and rotation compatibility is difficult to resolve. To address the issue of central sinking in long base plates, a fixed support structure is added between the driving and driven ends. However, traditional fixed supports cannot adapt to the rotational movement of the base plate, resulting in rigid friction with it. This not only hinders the rotation process and causes jamming, but also exacerbates wear on the base plate and support structure, further reducing equipment reliability. Thirdly, the coordination between base plate fixing and horizontal adjustment is insufficient. While some long base plate rotating structures attempt to add a central support, the lack of an effective clamping and fixing mechanism leads to relative sliding between the base plate and the support structure, preventing synchronous rotation and significantly reducing the anti-sinking effect of the central support. Furthermore, due to the susceptibility to horizontal errors during the processing and installation of long base plates, most existing structures lack targeted horizontal adjustment components, making it impossible to accurately correct central sinking or localized horizontal deviations, further limiting the improvement of operational accuracy. In summary, existing technologies struggle to simultaneously address the core contradiction of "preventing sinking of the central support" and "unimpeded rotational adaptation" for the rotational support requirements of long tooling base plates. Furthermore, they exhibit significant shortcomings in terms of fixation stability, horizontal adjustment accuracy, and structural load-bearing capacity. Therefore, there is an urgent need for a novel tooling base plate rotational support structure that can balance support strength, rotational adaptability, and adjustment functionality. Utility Model Content

[0003] The problem this utility model aims to solve is to provide a rotating support structure for tooling base plates, which addresses the issue that conventional support structures cannot adapt to rotation when tooling base plates are long, and the lack of a support structure leads to the sinking of the middle section.

[0004] The technical solution adopted by this utility model to solve the above problems is as follows: a tooling base plate rotating support structure, comprising: a machine base, with a driving end and a driven end that can rotate around a coaxial axis at both ends; a base plate, with the driving end and the driven end fixedly connected at both ends respectively; a rotation driving structure, disposed at the driving end, for driving the base plate to rotate; a support adjustment mechanism, located between the driving end and the driven end, comprising a rotating seat and a rotating block, wherein the rotating seat is fixed on the machine base, and the outer periphery of the rotating block is provided with an arc-shaped rotating part, and the rotating part, the driving end and the driven end rotate coaxially; the rotating block is provided with a placement groove for supporting the base plate; the placement groove is provided with a clamping mechanism and a horizontal adjustment mechanism.

[0005] By incorporating a support and adjustment mechanism between the driving and driven ends, the placement slot of the rotating block supports the middle of the base plate, filling the support gap in the middle of the long base plate and structurally preventing sagging. Simultaneously, the arc-shaped rotating part of the rotating block is designed coaxially with the driving and driven ends, allowing the rotating block to rotate synchronously and coaxially with the base plate during rotation, providing support without hindering rotation. The horizontal adjustment mechanism can specifically adjust the height of the middle of the base plate; even with slight sagging or horizontal errors during installation, the base plate can be restored to a level state through adjustment. The clamping mechanism is used to fix the base plate in the placement slot. This solves the contradiction of long tooling base plates sagging due to lack of support during rotation, and the inability to adapt to rotation even with support.

[0006] Furthermore, an auxiliary wheel is rotatably connected inside the rotating seat. The auxiliary wheel is symmetrically arranged on both sides of the rotating part. The outer circumference of the auxiliary wheel is in rolling connection with the rotating part, and the distance between the contact point of the auxiliary wheel and the rotating part is smaller than the diameter of the rotating part.

[0007] By using auxiliary wheels that are symmetrically arranged on both sides of the rotating part and rotatably connected inside the rotating seat, the outer circumference of the auxiliary wheels is rolled to the rotating part and the contact point distance is smaller than the diameter of the rotating part; this achieves symmetrical clamping rolling support for the rotating part, improving the coaxiality and stability of the rotating part during rotation; it solves the problem that the long base plate is prone to radial displacement and rotation jamming when relying solely on the cooperation between the rotating part and the rotating seat, while strengthening the stability of the central support to further suppress sagging.

[0008] Furthermore, the rotating seat includes two limiting plates, which are respectively disposed on both sides of the axial direction of the rotating part, and the gap between the two limiting plates is greater than the thickness of the rotating part.

[0009] By using two limiting plates on both sides of the rotating part on the rotating seat, the gap between the two limiting plates is greater than the thickness of the rotating part; thus, the axial limiting of the rotating part is achieved, preventing axial movement of the rotating block when it rotates with the base plate; this solves the rotational offset caused by the lack of axial restraint in the central support structure, ensures the accuracy of the three-point coaxial support, and prevents the base plate from becoming unstable or sinking due to axial movement.

[0010] Furthermore, the rotating seat is fixed to the machine base by support legs, which include: a clamping part that connects two limiting plates; and a fixing extension part that extends to both sides of the long side of the base plate and is fixed to the machine base.

[0011] The rotating seat is fixed to the machine tool by means of a clamping part that connects the two limiting plates and a fixed extension part that extends to both sides of the long side of the base plate and is fixed to the machine tool; a large-area stable connection between the rotating seat and the machine tool is achieved, and the force on the central support is distributed; the problem of the rotating seat being easy to loosen and the support failing due to the concentrated force at the central support point of the long base plate is solved, and the load-bearing capacity of the central support is strengthened to resist sinking.

[0012] Furthermore, the clamping mechanism includes a lower pressure block and a locking screw. The locking screw passes vertically through the lower pressure block and the base plate and is threadedly connected to the bottom of the placement groove. By tightening the locking screw, the lower pressure block presses against the base plate.

[0013] The clamping mechanism consists of a lower pressure block and a locking screw that passes vertically through the lower pressure block and the base plate and is threaded to the bottom of the placement slot. Tightening the locking screw makes the lower pressure block press against the base plate, thus achieving a firm fixation between the base plate and the rotating block, ensuring that the two rotate synchronously and fit tightly. This solves the problem of asynchronous rotation and failure of the central support caused by a loose connection between the base plate and the central support structure, which in turn leads to sinking or rotation jamming.

[0014] Furthermore, the bottom surface of the placement groove extends horizontally at both ends to form extensions. The horizontal adjustment mechanism is located at the four corners of the extensions and includes: an adjustment block embedded in the adjustment hole of the extension; and an adjustment screw threaded upwards to the bottom of the adjustment hole. Rotating the adjustment screw pushes the adjustment block against the base plate. By using the adjustment blocks (embedded in the adjustment holes of the extension) located at the four corners of the extension at both ends of the placement groove bottom surface and the adjustment screw threaded upwards to the bottom of the adjustment hole, rotating the adjustment screw pushes the adjustment block against the base plate; achieving precise height adjustment at different points in the middle of the base plate; solving the problem of localized sinking and level deviation caused by the weight or installation error of the long base plate, and ensuring operational accuracy. Attached Figure Description

[0015] Figure 1 This is a perspective view of the entire utility model; Figure 2 This is a cross-sectional view of the present invention.

[0016] Diagram: 1. Machine base; 1.1. Rotary drive structure; 1.2. Drive end; 1.3. Driven end; 1.4. Rotating seat; 1.4.1. Auxiliary wheel; 1.4.11. Chip removal groove; 1.4.2. Limiting plate; 1.4.3. Support leg; 1.4.3.1. Clamping part; 1.4.3.2. Fixed support part; 1.5. Rotating block; 1.5.1. Rotating part; 1.5.2. Placement groove; 1.5.2.1. Extension part; 1.5.3. Lowering block; 1.5.4. Locking screw; 1.5.4.1. Locking nut; 1.5.4.2. Locking screw; 1.5.5. Adjusting block; 1.5.6. Adjusting screw; 1.5.7. Adjusting hole; 2. Base plate. Detailed Implementation

[0017] Before describing any embodiment of this invention in detail, it should be understood that the invention is not limited in its application to the details of the construction and arrangement of the components set forth in the following description or illustrated in the following figures. The invention is capable of other embodiments and can be practiced or carried out in various ways. Furthermore, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered limiting. The use of “comprising” or “having” and variations thereof herein is intended to cover the items set forth below and their equivalents, as well as any additional items. Unless otherwise specified or limited, the terms “installation,” “connection,” “support,” and “linkage,” and variations thereof are used broadly and cover both direct and indirect installation, connection, support, and linking. Moreover, “connection” and “linkage” are not limited to physical or mechanical connections or links.

[0018] Furthermore, firstly, in the disclosure of this utility model, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as a limitation on this utility model. Secondly, the term "a" should be understood as "at least one" or "one or more," that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple. The term "a" should not be construed as a limitation on the quantity.

[0019] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functions and structural principles of the present invention have been shown and explained in the embodiments. Without departing from the stated principles, the implementation of the present invention may have any variations or modifications.

[0020] The embodiments of this utility model will be further described below with reference to the accompanying drawings.

[0021] Please see Figures 1 to 2 A tooling base plate rotation support structure includes a machine base 1, a base plate 2, a rotation drive structure 1.1, and a support adjustment mechanism. The specific structure and connection relationship of each part are as follows: The machine base 1 has a drive end 1.2 and a driven end 1.3 that can rotate around a coaxial axis at both ends. The two ends of the base plate 2 are fixedly connected to the drive end 1.2 and the driven end 1.3, respectively. The rotation drive structure 1.1 (a common existing technology, not shown in the figure) can be powered by a servo motor or a stepper motor, which has the characteristics of stable output torque and adjustable speed. It can meet the rotation speed requirements of the base plate under different working conditions (such as low-speed precise positioning or uniform rotation). The encoder built into the motor can achieve precise control of the rotation angle, ensuring the accuracy of the base plate's rotation position. The transmission component is used to transmit the motor's power to the drive end. Common forms include a combination of a gearbox and a coupling: the gearbox can reduce the motor's output speed and increase the torque according to the actual load requirements, avoiding insufficient power due to excessive weight of the base plate and the workpiece; the coupling connects the output shaft of the gearbox and the rotating shaft of the drive end, compensating for the installation coaxiality error between the two shafts and reducing vibration and noise during transmission. The connecting component directly fixes the transmission assembly to the drive end 1.3 using a threaded fastening method to ensure no relative slippage during power transmission. This ensures that the drive end 1.2 can rotate synchronously with the transmission assembly, thereby driving the fixed base plate and driven end to rotate together. A support adjustment mechanism is located at the drive end 1.2 to drive the base plate 2 to rotate. It includes a rotating seat 1.4 and a rotating block 1.5, situated between the drive end 1.2 and the driven end 1.3. The rotating seat 1.4 is fixed to the machine base 1. The outer periphery of the rotating block 1.5 has an arc-shaped rotating part 1.5.1. This rotating part 1.5.1 shares a common axis of rotation with the drive end 1.2 and the driven end 1.3, and the rotating part 1.5.1 forms a rolling fit with the rotating seat 1.4. Specifically, an auxiliary wheel 1.4.1 is rotatably connected inside the rotating seat 1.4. The auxiliary wheel 1.4.1 is symmetrically arranged on both sides of the rotating part 1.5.1. The outer periphery of the auxiliary wheel 1.4.1 forms a rolling connection with the rotating part 1.5.1, and the distance between the contact points of the auxiliary wheel 1.4.1 and the rotating part 1.5.1 is smaller than the diameter of the rotating part 1.5.1. A chip removal groove 1.4.11 is formed around the outer periphery of the middle part of the auxiliary wheel 1.4.1. The bottom surface of the chip removal groove 1.4.11 is 0.5-1mm lower than the outer periphery of the auxiliary wheel 1.4.1. The rotating base 1.4 includes limiting plates 1.4.2 respectively disposed on both sides of the rotating part 1.5.1 along the rotation axis of the rotating part 1.5.1. The gap between the two limiting plates 1.4.2 is greater than the thickness of the rotating part 1.5.1. The rotating base 1.4 is fixedly connected to the machine base 1 via support legs 1.4.3. There are two support legs 1.4.3. The upper part of the support leg 1.4.3 is a clamping part 1.4.3.1. Both clamping parts 1.4.3.1 are disposed between the two limiting plates 1.4.2. The two limiting plates 1.4.2 are connected to each other through the clamping parts 1.4.3.1. The lower part of the support leg 1.4.3 is a fixed support part 1.4.3.2 extending toward both sides of the long side of the base plate 2. The fixed support part 1.4.3.2 is fixedly connected to the machine base 1.

[0022] The rotating block 1.5 is provided with a placement groove 1.5.2 for supporting the base plate 2. The placement groove 1.5.2 is provided with a clamping mechanism for fixing the base plate 2 in the placement groove 1.5.2 and a horizontal adjustment mechanism for adjusting the levelness of the base plate 2. The clamping mechanism includes a lower pressure block 1.5.3 and a locking screw 1.5.4. The locking screw 1.5.4 includes a locking screw rod 1.5.42 and a locking nut 1.5.41 located at the top of one end of the locking screw rod 1.5.42. The diameter of the locking nut 1.5.41 is larger than that of the locking screw rod 1.5.42. The locking screw rod 1.5.42 passes vertically downward through the lower pressure block 1.5.3 and the base plate 2 in sequence and is threaded to the bottom of the placement groove 1.5.2. By rotating the locking nut 1.5.41, the locking nut 1.5.41 moves downward, causing the lower pressure block 1.5.3 to press the base plate 2 against the bottom surface of the placement groove 1.5.2.

[0023] The bottom surface of the placement groove 1.5.2 extends horizontally at both ends along the axial direction to form an extension 1.5.2.1. The extension 1.5.2.1 increases the contact area with the middle of the base plate 2. A horizontal adjustment mechanism is provided on the extension 1.5.2.1. At least four sets of horizontal adjustment mechanisms are provided, respectively located at the four horizontal corners of the extension 1.5.2.1. The mechanisms include an adjustment block 1.5.5, an adjustment screw 1.5.6, and an adjustment hole 1.5.7 opened at the upper end face of the extension 1.5.2.1. The adjustment hole 1.5.7 is a non-penetrating hole. The adjustment block 1.5.5 is placed in the adjustment hole 1.5.7. The adjustment screw 1.5.6 is vertically threaded upward to the non-penetrating part at the bottom of the adjustment hole 1.5.7. By rotating the adjustment screw 1.5.6, the adjustment block 1.5.5 is pushed vertically up and down to abut against the bottom surface of the base plate 2, thereby adjusting the levelness of the base plate 2.

[0024] Working principle: First, fix both ends of the base plate 2 to the drive end 1.2 and driven end 1.3 of the machine base 1 respectively, ensuring the coaxiality of the base plate 2 with the drive end 1.2 and driven end 1.3. Then, place the middle part of the base plate 2 into the placement groove 1.5.2 of the rotating block 1.5. At this time, the bottom surface of the base plate 2 is initially in contact with the extension 1.5.2.1 of the placement groove 1.5.2. Next, operate the clamping mechanism: rotate the locking nut 1.5.41 of the locking screw 1.5.4, so that the locking screw 1.5.42 is screwed downward along the threaded hole at the bottom of the placement groove 1.5.2, driving the lower pressure block 1.5.3 to move downward synchronously until the lower pressure block 1.5.3 tightly presses against the upper surface of the base plate 2, firmly fixing the base plate 2 in the placement groove 1.5.2, and preventing the base plate 2 from shifting or shaking during rotation.

[0025] After the base plate 2 is fixed, its levelness needs to be calibrated using a leveling mechanism to ensure the machining accuracy or placement stability of the workpiece during subsequent rotation. A leveling tool (such as a level) is used to check the levelness of the base plate 2 and determine the areas requiring adjustment. For locations with out-of-tolerance levels, the leveling mechanisms at the four corners of the extension 1.5.2.1 are operated accordingly: If a certain area of ​​the base plate 2 is too high, the adjusting screw 1.5.6 at that location is rotated in the opposite direction, causing it to retract downwards along the bottom thread of the adjusting hole 1.5.7. The adjusting block 1.5.5, under the weight of the base plate 2, moves downwards synchronously with the adjusting screw 1.5.6, releasing the supporting force on the base plate 2 and causing that area of ​​the base plate 2 to sink. If a certain area of ​​the base plate 2 is too low, the adjusting screw 1.5.6 is rotated in the forward direction, causing it to push the adjusting block 1.5.5 upwards along the threaded hole. The adjusting block 1.5.5 then abuts against the bottom surface of the base plate 2 and pushes that area of ​​the base plate 2 upwards. Adjust the four sets of leveling mechanisms point by point until the leveling tool shows that the base plate 2 is level enough, and the leveling calibration is completed.

[0026] After horizontal calibration, the rotation drive structure 1.1 is activated, and the tooling base plate rotation support structure enters the rotation working state. The rotation drive structure 1.1 generates power and transmits it to the drive end 1.2 of the machine tool 1. The drive end 1.2 rotates around its own axis. Since the two ends of the base plate 2 are fixedly connected to the drive end 1.2 and the driven end 1.3, the drive end 1.2 drives the base plate 2 to rotate synchronously through a rigid connection. The driven end 1.3 passively rotates around the same axis as the base plate 2, ensuring that the base plate 2 always rotates along a fixed axis. During this process, the base plate 2 drives the rotating block 1.5 to rotate synchronously. The arc-shaped rotating part 1.5.1 on the outer periphery of the rotating block 1.5 forms a rolling fit with the auxiliary wheel 1.4.1 inside the rotating seat 1.4, converting sliding friction into rolling friction, greatly reducing rotational resistance and ensuring the smooth rotation of the base plate 2.

[0027] During rotation, the rotating connection assembly of the support and adjustment mechanism simultaneously provides support and protection, ensuring rotational stability and extending the service life of the tooling base plate's rotating support structure. On one hand, the rotating seat 1.4 is firmly connected to the machine base 1 via support legs 1.4.3. Its internal auxiliary wheels 1.4.1 symmetrically clamp the rotating part 1.5.1 of the rotating block 1.5, providing radial support for the rotating block 1.5 and axially limiting the rotating part 1.5.1 via the limiting plate 1.4.2, effectively preventing radial offset or axial movement during base plate 2 rotation. On the other hand, the chip removal groove 1.4.11 in the middle of the auxiliary wheel 1.4.1 can promptly collect chips, dust, and other impurities generated during rotation, preventing impurities from accumulating on the contact surface between the auxiliary wheel 1.4.1 and the rotating part 1.5.1. Simultaneously, the bottom surface of the chip removal groove 1.4.11 is 0.5-1mm lower than the outer circumference of the auxiliary wheel 1.4.1, preventing impurities from scratching the surface of the rotating part 1.5.1 and ensuring the stability of the rolling fit.

[0028] The above description only illustrates the preferred embodiment of this utility model and should not be construed as limiting the claims. This utility model is not limited to the above embodiments, and variations in its specific structure are permitted. All changes made within the scope of the independent claims of this utility model are also within the scope of protection of this utility model.

Claims

1. A rotating support structure for a tooling base plate, characterized in that, include: The machine base (1) has a drive end (1.2) and a driven end (1.3) that can rotate around the same axis at both ends; The base plate (2) has a drive end (1.2) and a driven end (1.3) fixedly connected to its two ends respectively; A rotation drive structure (1.1) is provided at the drive end (1.2) for driving the base plate (2) to rotate; The support adjustment mechanism is located between the driving end (1.2) and the driven end (1.3), and includes a rotating seat (1.4) and a rotating block (1.5). The rotating seat (1.4) is fixed on the machine base (1), and the outer periphery of the rotating block (1.5) is provided with an arc-shaped rotating part (1.5.1). The rotating part (1.5.1), the driving end (1.2) and the driven end (1.3) rotate on the same axis. The rotating block (1.5) is provided with a placement groove (1.5.2) for supporting the base plate (2); The placement slot (1.5.2) is equipped with a clamping mechanism and a horizontal adjustment mechanism.

2. The tooling base plate rotation support structure according to claim 1, characterized in that: An auxiliary wheel (1.4.1) is rotatably connected inside the rotating seat (1.4). The auxiliary wheel (1.4.1) is symmetrically arranged on both sides of the rotating part (1.5.1). The outer circumference of the auxiliary wheel (1.4.1) is in rolling connection with the rotating part (1.5.1), and the distance between the contact points of the auxiliary wheel (1.4.1) and the rotating part (1.5.1) is smaller than the diameter of the rotating part (1.5.1).

3. The tooling base plate rotation support structure according to claim 2, characterized in that: The rotating seat (1.4) includes two limiting plates (1.4.2), which are respectively disposed on both sides of the rotating part (1.5.1) axially, and the gap between the two limiting plates (1.4.2) is greater than the thickness of the rotating part (1.5.1).

4. The tooling base plate rotation support structure according to claim 3, characterized in that: The rotating base (1.4) is fixed to the machine base (1) by a support leg (1.4.3), the support leg (1.4.3) comprising: The clamping part (1.4.3.1) connects to the two limiting plates (1.4.2); the fixed support part (1.4.3.2) extends to both sides of the long side of the base plate (2) and is fixed to the machine base (1).

5. The tooling base plate rotation support structure according to claim 1, characterized in that: The clamping mechanism includes a lower pressure block (1.5.3) and a locking screw (1.5.4). The locking screw (1.5.4) passes vertically through the lower pressure block (1.5.3) and the base plate (2) and is threaded to the bottom of the placement groove (1.5.2). By tightening the locking screw (1.5.4), the lower pressure block (1.5.3) presses the base plate (2) together.

6. The tooling base plate rotation support structure according to claim 1, characterized in that: The bottom surface of the placement groove (1.5.2) extends horizontally at both ends to form an extension (1.5.2.1). The horizontal adjustment mechanism is located at the four corners of the extension (1.5.2.1) and includes: an adjustment block (1.5.5) embedded in the adjustment hole (1.5.7) of the extension (1.5.2.1); and an adjustment screw (1.5.6) threaded upward to the bottom of the adjustment hole (1.5.7). By rotating the adjustment screw (1.5.6), the adjustment block (1.5.5) is pushed to abut against the base plate (2).

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