Tapered roller end face circle run-out measuring instrument

Abstract

The invention discloses a conical roller end face circle run-out measuring instrument, which belongs to the technical field of conical roller measurement, and is characterized in that the angles of two cross beams are adjusted, the cross beam angle is the same as the roller angle, the height of a material supporting assembly does not need to be adjusted, and the cross beams rotate relatively and can be unfolded or combined; the angles of the supporting points on the two cross beams relative to the axis of the roller are ensured to be symmetrical, so that the vertical line of the axial line of the roller is just positioned on the central line of the movable measuring point assembly and the fixed measuring point assembly, and the circle center of a radial circle formed by the supporting points is positioned on the axis of the roller and is vertical to the axis of the roller; the height of the first sliding rod and the height of the second sliding rod are adjusted according to the diameter of the rolling body, so that the movable measuring point pointer and the fixed measuring point pointer are located at the measuring positions of the roller, and the roller can be rotated for measurement, so that the measurement requirements of rollers with different angles, diameters and lengths are met, and efficient and stable measurement of the end face of the tapered roller is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of tapered roller measurement, in particular to a tapered roller end face circular runout measuring instrument. Background Art

[0002] With the rapid development of modern industry, various machines have higher and higher requirements on the accuracy and service life of bearings; thus, the requirements for various tests on bearings are becoming more and more stringent; the accuracy of the circular runout (symbol "SDw") of the large end of the tapered roller against the outer surface directly affects the rotation accuracy and service life of the tapered bearing; therefore, the detection of "SDw" is indispensable. According to the GB / T25767 standard, the definition of "SDw" is the difference between the maximum and minimum axial distances of each point on the circumference of a radial plane at a distance of 1.2 times the maximum chamfer of the roller and with the center of the circle on the axis of rotation of the bearing; and according to the GB / T25767 standard, the measurement requirements of "SDw" are: place the roller on a V-shaped block (rack), rotate the roller one circle, and 1 / 2 of the maximum difference shown by the indicator is "SDw".

[0003] Since the tapered roller is a cone-shaped roller with different diameters at both ends, keeping the roller axis horizontal will result in different heights of the fulcrums at both ends. In addition, due to the different sizes of tapered bearings and different usage environments, rollers with different diameters, lengths, and angles will be designed. If different V-shaped frames are made, a lot of tooling costs will be incurred. As the number of types of tapered bearings processed by the factory increases, greater management costs will also be incurred. When debugging the equipment, it will be time-consuming and laborious to find and use them. If fulcrum support is used, four fulcrums are required. According to standard requirements, it is very laborious to adjust the height and position of the fulcrums. At the same time, it is necessary to ensure that the measuring point is on the vertical line of the axis centerline. Without a clear measuring device, it is difficult to adjust the height of the four fulcrums, which is not conducive to efficient and stable measurement of the end face of the tapered roller. Summary of the invention

[0004] In order to overcome the above-mentioned defects, the present invention provides a tapered roller end face circular runout measuring instrument, which solves the problem that due to the different sizes of tapered bearings and different usage environments, rollers with different diameters, lengths and angles will be designed. If different V-shaped frames are made, a large amount of tooling costs will be generated. As the number of types of tapered bearings processed by the factory increases, large management costs will also be generated. In addition, when debugging the equipment, it is time-consuming and laborious to search and obtain them. If fulcrum support is adopted, four fulcrums are required. According to standard requirements, it is very laborious to adjust the height and position of the fulcrums. At the same time, it is necessary to ensure that the measuring point is on the vertical line of the axis centerline. Without a clear measuring device, it is relatively difficult to adjust the height of the four fulcrums, which is not conducive to the efficient and stable measurement of the tapered roller end face.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a tapered roller end face circular runout measuring instrument, comprising a base, one side of the base is fixedly connected to two columns, a support assembly is installed on the top of the column, a fixing assembly is installed through one side of the support assembly, the same limit assembly is installed at the bottom of the two fixing assemblies, the bottom end of the limit assembly is fixed to the base, the limit assembly overlaps the two support assemblies, and an adjustment assembly is installed on the side of the two support assemblies away from the columns; Two material supporting assemblies are installed in the supporting assembly, a slideway is provided in the middle of the base, two slide seats are slidably connected in the slideway, the slide seats are connected to the slideway through threaded nails, and a movable measuring point assembly and a fixed measuring point assembly are fixedly connected to the two slide seats respectively, the tops of the movable measuring point assembly and the fixed measuring point assembly are located between the two supporting assemblies, and locking screws are respectively installed on one side of the movable measuring point assembly and the fixed measuring point assembly.

[0006] As a further solution of the present invention: the support assembly includes a crossbeam, a pin is installed at one end of the crossbeam, the top of the column is hinged to the end of the crossbeam through the pin, a sliding groove is inclined on one side of the crossbeam, a plurality of clamping holes are opened on the inner wall of the sliding groove, the sliding groove is T-shaped, and the support assembly is slidably connected in the sliding groove, and the end of the support assembly is clamped in the clamping hole.

[0007] As a further solution of the present invention: the fixing assembly includes a screw rod, the screw rod is arranged through the supporting assembly, the external thread of the screw rod is connected with a fixing slider, the fixing slider is fixed to the bottom of the supporting assembly, and the fixing slider is arranged on the limiting assembly.

[0008] As a further solution of the present invention: the limiting assembly includes a support plate, which is overlapped with the bottom of the two supporting assemblies, and the two sides of the bottom of the support plate are respectively fixedly connected with vertical poles, and the bottom ends of the vertical poles are fixed to the base. Two slide grooves are provided on the support plate, and the slide grooves are arc-shaped and connected to each other. The fixed slider is slidably connected in the slide groove, and the cross-sectional shape of the fixed slider and the slide groove is T-shaped.

[0009] As a further solution of the present invention: the adjustment assembly includes a bidirectional screw rod, and nuts are respectively threaded on both sides of the outside of the bidirectional screw rod, a connecting shaft is fixed to the bottom of the nut, a bearing seat is installed at the bottom end of the connecting shaft, two bearing seats are respectively fixed on two supporting assemblies, and one end of the bidirectional screw rod is fixedly connected to a turning handle.

[0010] As a further solution of the present invention: the material support assembly includes a movable seat, the cross-sectional shape of the movable seat is T-shaped, the movable seat is slidably connected in the sliding groove, a pull rod is provided through the movable seat, one end of the pull rod is clamped in the clamping hole, a spring is connected to the outer sleeve of the pull rod, and the two ends of the spring are respectively fixed to the movable seat and the end of the pull rod.

[0011] As a further solution of the present invention: the movable measuring point assembly includes a first set of rods, a first sliding rod is slidably connected inside the first set of rods, a measuring table is installed on the top of the first sliding rod, a dynamic measuring point pointer is provided on the measuring table, and the dynamic measuring point pointer is installed through the top of the first sliding rod.

[0012] As a further solution of the present invention: the fixed measuring point assembly includes a second set of rods, a second sliding rod is slidably connected inside the second set of rods, and a fixed measuring point pointer is installed on the top of the second sliding rod.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. In the present invention, the bidirectional screw is driven to rotate by rotating the handle. Since the two nuts are respectively located on both sides outside the bidirectional screw, the two nuts can move relatively. The nut drives the crossbeam to rotate around the pin at the end through the connecting shaft and the bearing seat, so that the two crossbeams can rotate relatively and form an angle. During this process, the nut drives the connecting shaft to rotate in the bearing seat to ensure the relative angle between the nut and the bidirectional screw, and does not affect the normal adjustment of the position of the nut by the bidirectional screw. When placing the roller, the support assembly is slid in the sliding groove so that it can be adjusted according to the length of the roller, so that multiple support assemblies support the roller. Because the angle of the crossbeam is the same as the angle of the roller, there is no need to adjust the height of the support assembly. The slide seat at the bottom of the movable measuring point assembly and the fixed measuring point assembly can be on the slideway of the base The movable measuring point assembly and the fixed measuring point assembly are located on the center line of the roller, and the center line of the radial circle formed by the supporting points is determined to be on the roller axis and perpendicular to the roller axis. The heights of the first slide bar and the second slide bar are adjusted according to the diameter of the rolling element, so that the movable measuring point pointer and the fixed measuring point pointer are located at the measuring position of the roller. The roller can be rotated to perform measurement. Therefore, the measuring instrument can adjust the roller angle, diameter and length to meet the measurement requirements of rollers with different angles, diameters and lengths, and is conducive to efficient and stable measurement of the end face of the tapered roller.

[0014] After the angle of the beam is adjusted, the screw is rotated to make it pass through the fixed slider and fit closely with the inner wall of the slide groove, so as to prevent the angle of the beam from changing during the measurement process and causing inaccurate measurement, thereby improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a three-dimensional structural schematic diagram of the present invention; Figure 2 It is a schematic diagram of the structure of the present invention from a top view; Figure 3 It is a structural schematic diagram of the regulating assembly of the present invention; Figure 4 It is a schematic diagram of the structure of the support assembly of the present invention; Figure 5 It is a structural schematic diagram of the movable measuring point assembly and the fixed measuring point assembly of the present invention; Figure 6 It is a schematic diagram of the structure of the connection between the crossbeam and the fixing assembly of the present invention; Figure 7 It is a structural schematic diagram of the support assembly of the present invention; In the figure: 1, base; 2, column; 3, support assembly; 301, crossbeam; 302, pin; 303, sliding groove; 304, clamping hole; 4, fixing assembly; 401, screw rod; 402, fixed slider; 5, limit assembly; 501, support plate; 502, column; 503, sliding groove; 6, adjustment assembly; 601, two-way screw rod; 602, nut; 603, connecting shaft; 604, bearing seat; 605, turning handle; 7, material support assembly; 701, moving seat; 702, pull rod; 703, spring; 8, slideway; 9, movable measuring point assembly; 901, first set of rods; 902, first slide bar; 903, measuring table; 904, dynamic measuring point pointer; 10, fixed measuring point assembly; 101, second set of rods; 102, second slide bar; 103, fixed measuring point pointer; 11, slide seat; 12, locking screw. DETAILED DESCRIPTION

[0016] The technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0017] like Figure 1-7 As shown, the present invention provides a technical solution: a tapered roller end face circular runout measuring instrument, comprising a base 1, one side of the base 1 is fixedly connected with two columns 2, the top of the column 2 is installed with a support assembly 3, the support assembly 3 comprises a crossbeam 301, one end of the crossbeam 301 is installed with a pin 302, the top of the column 2 is hinged with the end of the crossbeam 301 through the pin 302, one side of the crossbeam 301 is inclinedly provided with a sliding groove 303, the inner wall of the sliding groove 303 is provided with a plurality of clamping holes 304, the sliding groove 303 is T-shaped, and the support assembly 7 is slidably connected in the sliding groove 303, the end of the support assembly 7 is clamped in the clamping hole 304, the crossbeam 301 rotates around the pin 302 at the end, so that the two crossbeams 301 can rotate relative to each other and form an angle, ensuring that the angles of the support points on the two crossbeams 301 to the roller axis are symmetrical, and the angle of the crossbeam 301 is the same as the angle of the roller, so there is no need to adjust the height of the support assembly 7; A fixing assembly 4 is installed through one side of the support assembly 3. The fixing assembly 4 includes a screw rod 401. The screw rod 401 is arranged through the support assembly 3. The screw rod 401 is externally threaded with a fixing slider 402. The fixing slider 402 is fixed to the bottom of the support assembly 3. The fixing slider 402 is arranged on the limiting assembly 5. The screw rod 401 is rotated to pass through the fixing slider 402 and fit closely with the inner wall of the slide groove 503, so as to prevent the angle of the beam 301 from changing during the measurement process, resulting in inaccurate measurement. The same limiting assembly 5 is installed at the bottom of the two fixing assemblies 4, and the bottom end of the limiting assembly 5 is fixed to the base 1. The limiting assembly 5 includes a support plate 501, and the support plate 501 is overlapped with the bottom of the two supporting assemblies 3. The two sides of the bottom of the support plate 501 are respectively fixedly connected with vertical rods 502, and the bottom ends of the vertical rods 502 are fixed to the base 1. Two slide grooves 503 are provided on the support plate 501. The slide grooves 503 are arc-shaped, and the two slide grooves 503 are connected. The fixed slider 402 is slidably connected in the slide groove 503. The cross-sectional shape of the fixed slider 402 and the slide groove 503 is T-shaped. The cross beam 301 can drive the fixed slider 402 to slide in the slide groove 503 on the support plate 501 through the screw 401. With the use of the support plate 501, the cross beam 301 is supported and limited to prevent the tail end of the cross beam 301 from sagging. The limit assembly 5 is overlapped with the two supporting assemblies 3. An adjustment assembly 6 is installed on the side of the two supporting assemblies 3 away from the column 2. The adjustment assembly 6 includes a bidirectional screw rod 601. The two sides outside the bidirectional screw rod 601 are respectively threadedly connected with nuts 602. A connecting shaft 603 is fixed to the bottom of the nut 602. A bearing seat 604 is installed at the bottom end of the connecting shaft 603. The two bearing seats 604 are respectively fixed on the two supporting assemblies 3. One end of the bidirectional screw rod 601 is fixedly connected with a rotating handle 605. The bidirectional screw rod 601 is driven to rotate by rotating the rotating handle 605. Since the two nuts 602 are respectively located on the two sides outside the bidirectional screw rod 601, the two nuts 602 can move relatively, so as to synchronously adjust the angles of the two beams 301. Two supporting components 7 are installed in the supporting component 3, and the supporting component 7 includes a moving seat 701. The cross-sectional shape of the moving seat 701 is T-shaped. The moving seat 701 is slidably connected in the sliding groove 303. A pull rod 702 is provided on the moving seat 701. One end of the pull rod 702 is clamped in the clamping hole 304. A spring 703 is connected to the outer sleeve of the pull rod 702. The two ends of the spring 703 are respectively fixed to the ends of the moving seat 701 and the pull rod 702. The position of the moving seat 701 is adjusted according to the length of the roller. After the adjustment is completed, the pull rod 702 is slowly released. The pull force of the spring 703 drives the pull rod 702 to move, so that the bottom of the pull rod 702 is clamped in the clamping hole 304, and the locking work of the moving seat 701 can be completed, thereby facilitating the stable adjustment of the position of the moving seat 701 and improving the convenience of operation. A slideway 8 is provided in the middle of the base 1, and two slide seats 11 are slidably connected in the slideway 8. The slide seats 11 are connected to the slideway 8 by screw nails. A movable measuring point assembly 9 and a fixed measuring point assembly 10 are respectively fixedly connected to the two slide seats 11. The movable measuring point assembly 9 includes a first set of rods 901, and a first slide bar 902 is slidably connected in the first set of rods 901. A measuring table 903 is installed on the top of the first slide bar 902. A dynamic measuring point pointer 904 is provided on the measuring table 903, and the dynamic measuring point pointer 904 is installed through the top of the first slide bar 902; the fixed measuring point assembly 10 includes a second set of rods 101, and a second slide bar 102 is slidably connected in the second set of rods 101. A fixed measuring point pointer 103 is installed on the top of the second slide bar 102. The top of the movable measuring point assembly 9 and the fixed measuring point assembly 10 are located between the two supporting assemblies 3. Locking screws 12 are respectively installed on one side of the movable measuring point assembly 9 and the fixed measuring point assembly 10. The height of the first slide bar 902 and the second slide bar 102 are adjusted according to the diameter of the rolling body. The first slide bar 902 and the second slide bar 102 are locked by the locking screw 12, so that the movable measuring point pointer 904 and the fixed measuring point pointer 103 are in the measuring position of the roller, meeting the requirements for measuring rollers of multiple specifications.

[0018] The working principle of the present invention is: The two-way screw rod 601 is driven to rotate by rotating the handle 605, so that the two nuts 602 can move relatively, and the nut 602 drives the beam 301 to rotate around the pin 302 at the end through the connecting shaft 603 and the bearing seat 604, so that the two beams 301 can rotate relatively and form an angle. During this process, the nut 602 will drive the connecting shaft 603 to rotate in the bearing seat 604 to ensure the relative angle between the nut 602 and the two-way screw rod 601. When adjusting the angle of the beam 301, the beam 301 can drive the fixed slider 402 to slide in the slide groove 503 on the support plate 501 through the screw rod 401, and cooperate with the use of the support plate 501 to play a role. The crossbeam 301 is supported and limited. After the angle adjustment of the crossbeam 301 is completed, the screw 401 is rotated to make it pass through the fixed slider 402 and fit tightly with the inner wall of the slide groove 503. When adjusting the position of the supporting component 7, the pull rod 702 is pulled to make it slide in the movable seat 701, so that its end is separated from the clamping hole 304 in the sliding groove 303. At this time, the movable seat 701 is in a free movable state and can slide in the sliding groove 303. The position of the movable seat 701 is adjusted according to the length of the roller. After the adjustment is completed, the pull rod 702 is slowly released, and the pull force of the spring 703 drives the pull rod 702 to move, so that the bottom of the pull rod 702 is clamped into the clamping hole. 304, the locking work of the movable seat 701 can be completed, the slide seat 11 at the bottom of the movable measuring point assembly 9 and the fixed measuring point assembly 10 can slide in the slideway 8 on the base 1, and the slide seat 11 is locked by a screw, the axis of the slideway 8 coincides with the center line between the two beams 301, and because the beams 301 are relatively rotatable and can be unfolded or merged, it is ensured that the angles of the supporting points on the two beams 301 to the roller axis are symmetrical, so the vertical line of the roller axis line will be exactly on the center line of the movable measuring point assembly 9 and the fixed measuring point assembly 10, and the center of the radial circle formed by the supporting point is determined to be on the roller axis and perpendicular to the roller axis. According to the size of the rolling body diameter, adjust the height of the first slide bar 902 and the second slide bar 102, and lock the first slide bar 902 and the second slide bar 102 by locking screw 12, so that the dynamic measuring point pointer 904 and the fixed measuring point pointer 103 are in the measuring position of the roller, apply red oil on the roller, rotate the roller to check whether they are in the same radial circle, if not, adjust the angle of the beam 301 to be in the same circle, and then readjust the height of the dynamic measuring point pointer 904 and the fixed measuring point pointer 103 so that the two points are on the circle required for roller measurement. After completing all adjustments, rotate the roller for one circle and read the measurement data according to the requirements of GB / T25767 standard.

[0019] In the description of the present invention, it is necessary to understand that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0020] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0021] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] In the present invention, unless otherwise clearly specified and limited, the first feature "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, the description with reference to the terms "one scheme", "some schemes", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the scheme or example are included in at least one scheme or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same scheme or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more schemes or examples in a suitable manner.

Claims

1. Tapered roller end face circular runout measuring instrument, including base (1), Features: One side of the base (1) is fixedly connected to two upright posts (2); a support assembly (3) is installed on the top of the upright post (2); a fixing assembly (4) is installed through one side of the support assembly (3); the bottoms of the two fixing assemblies (4) are installed with a same limiting assembly (5); the bottom ends of the limiting assemblies (5) are fixed to the base (1); the limiting assembly (5) overlaps the two supporting assemblies (3); and an adjustment assembly (6) is installed on the two supporting assemblies (3) on the sides away from the upright posts (2); Two material support assemblies (7) are installed in the support assembly (3), a slideway (8) is provided in the middle of the base (1), two slide seats (11) are slidably connected in the slideway (8), the slide seats (11) are connected to the slideway (8) via screws, and a movable measuring point assembly (9) and a fixed measuring point assembly (10) are fixedly connected to the two slide seats (11), respectively, the tops of the movable measuring point assembly (9) and the fixed measuring point assembly (10) are located between the two support assemblies (3), and locking screws (12) are respectively installed on one side of the movable measuring point assembly (9) and the fixed measuring point assembly (10).

2. The tapered roller end face circular runout measuring instrument according to claim 1, Features: The support assembly (3) comprises a crossbeam (301), one end of which is mounted with a pin (302), the top end of the column (2) being hinged to the end of the crossbeam (301) via the pin (302), a sliding groove (303) being obliquely provided on one side of the crossbeam (301), a plurality of clamping holes (304) being provided on the inner wall of the sliding groove (303), the sliding groove (303) being of T-shaped design, the support assembly (7) being slidably connected in the sliding groove (303), and the end of the support assembly (7) being clamped in the clamping hole (304).

3. The tapered roller end face circular runout measuring instrument according to claim 1, Features: The fixing assembly (4) comprises a screw rod (401), the screw rod (401) is arranged to penetrate the supporting assembly (3), the screw rod (401) is externally threadedly connected to a fixing slider (402), the fixing slider (402) is fixed to the bottom of the supporting assembly (3), and the fixing slider (402) is arranged on the limiting assembly (5).

4. The tapered roller end face circular runout measuring instrument according to claim 3, Features: The limiting assembly (5) comprises a support plate (501), the support plate (501) is overlapped with the bottom of the two supporting assemblies (3), two sides of the bottom of the support plate (501) are respectively fixedly connected with vertical rods (502), the bottom ends of the vertical rods (502) are fixed to the base (1), the support plate (501) is provided with two slide grooves (503), the slide grooves (503) are of arc-shaped design, and the two slide grooves (503) are connected, the fixed slider (402) is slidably connected in the slide groove (503), and the cross-sectional shape of the fixed slider (402) and the slide groove (503) is T-shaped.

5. The tapered roller end face circular runout measuring instrument according to claim 1, Features: The adjustment assembly (6) comprises a bidirectional screw rod (601), and nuts (602) are respectively threadedly connected on two sides of the bidirectional screw rod (601), a connecting shaft (603) is fixed to the bottom of the nut (602), a bearing seat (604) is installed at the bottom end of the connecting shaft (603), and the two bearing seats (604) are respectively fixed on the two supporting assemblies (3), and one end of the bidirectional screw rod (601) is fixedly connected to a rotating handle (605).

6. The tapered roller end face circular runout measuring instrument according to claim 2, Features: The support assembly (7) comprises a movable seat (701), the cross-sectional shape of the movable seat (701) is T-shaped, the movable seat (701) is slidably connected in the sliding groove (303), a pull rod (702) is provided through the movable seat (701), one end of the pull rod (702) is clamped in the clamping hole (304), a spring (703) is connected to the outer sleeve of the pull rod (702), and the two ends of the spring (703) are respectively fixed to the ends of the movable seat (701) and the pull rod (702).

7. The tapered roller end face circular runout measuring instrument according to claim 1, Features: The movable measuring point assembly (9) comprises a first set of rods (901), a first sliding rod (902) being slidably connected inside the first set of rods (901), a measuring table (903) being installed at the top end of the first sliding rod (902), a movable measuring point pointer (904) being provided on the measuring table (903), and the movable measuring point pointer (904) being installed through the top end of the first sliding rod (902).

8. The tapered roller end face circular runout measuring instrument according to claim 1, Features: The fixed measuring point assembly (10) comprises a second set of rods (101), a second sliding rod (102) is slidably connected inside the second set of rods (101), and a fixed measuring point pointer (103) is installed at the top end of the second sliding rod (102).

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