Laser digital display measuring tape

Abstract

A laser digital display tape provided by the present invention comprises a tape core seat, a laser ranging module, a calibration detection unit and a corner measurement unit which are installed in a shell, one side of the tape core seat is fixedly connected with a roller, and the other side of the roller is connected with a tape core cover; the center of one side of the ruler core cover is fixedly connected with a rotating shaft, and one end of the rotating shaft is connected with a corner measuring unit; a ruler strip is tightly wound on the outer side of the roller through a ruler spring, and black and white stripes are printed on the ruler strip in a silk-screen mode. The measuring tape is compact in overall structure, does not occupy space, is integrated with the laser ranging module, solves the problem that the measuring length of the measuring tape is limited, can achieve high-precision distance measurement within the range of dozens of meters or even hundreds of meters, enables a laser line to be close to the tape strip as much as possible, brings convenience to a user for measuring the same target object through the measuring tape and laser, and improves the measuring efficiency. The use convenience of a common measuring tape is improved, direct reading by a user is facilitated, the measuring distance is prolonged, and long-distance linear measurement is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of laser digital display tape measure, and more specifically, particularly relates to a laser digital display tape measure. Background Art

[0002] The tape measure is a common tool in daily life and is widely used in the construction and decoration industries. The tape measure is mainly composed of a ruler, a ruler spring (disc spring), and a tape measure shell. The so-called disc spring is like the spring in an old-fashioned winding clock. When the ruler is pulled out, the disc spring is wound up, generating a force to roll back. When the tension of the ruler is released, the ruler is pulled back by the tension of the disc spring. The distance measurement of the tape measure is measured along the ground using a rolled-up strip ruler, which is a direct distance measurement. Laser distance measurement is an electronic physical distance measurement that uses an instrument to emit and receive modulated light waves between two points, and determines the distance according to its propagation speed and time. Laser distance measurement is an indirect distance measurement, but the reading of the tape measure is inconvenient, and the user needs to read the scale on the ruler with the naked eye, and it cannot be digitized. The user must use other calculation tools to calculate volume, area, diameter, unit conversion, etc. Household tape measures are usually less than 5m, and cannot measure long distances in one go. Laser distance measurement has blind spots at close range, so the closest measurement range is usually more than 50mm, and cannot measure smaller distances. In addition, laser distance meters are greatly affected by target board material, target board color, ambient temperature and humidity, ambient light intensity, etc., and often fail to achieve the nominal accuracy parameters during measurement, causing a lot of trouble for users.

[0003] In order to realize the digital display of the tape measure, some manufacturers add a grating roller or a mechanical encoder roller including a grating disk and a transmission roller, and connect the tape measure between the rollers. The tape measure drives the transmission roller to rotate. This method not only requires the addition of an additional rotating roller, but also requires a spring to compress the tape measure and the transmission roller to increase the friction force to drive the rotation of the roller. This method has a complex structure and is prone to measurement errors caused by factors such as friction and slippage. In addition, additional rollers need to be added to the structure, which will also cause the problem of a larger volume of the tape measure. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a laser digital tape measure, which aims to solve the technical problems in the prior art that the tape measure is inconvenient to read, the laser distance measurement cannot measure a small distance, and the additional rotating roller makes the tape measure larger in size.

[0005] The technical scheme of the present invention is as follows: a laser digital display tape measure comprises a ruler core seat, a laser distance measurement module, and a calibration detection unit; further comprising a roller, a ruler core cover, a rotating shaft, an angle measurement unit, and a ruler strip; the front end of the ruler core seat is fixedly connected to the roller; the front end of the roller is snap-connected to the ruler core cover; the front end of the ruler core cover is fixedly connected to the rotating shaft; the front end of the rotating shaft is fixedly connected to the angle measurement unit; the outer side of the roller is tightly wound with a ruler strip through a ruler spring; the ruler core seat, the laser distance measurement module, the calibration detection unit, the roller, the ruler core cover, the rotating shaft, the angle measurement unit, and the ruler strip; The ruler strips are installed in the shell; a ruler hook engaged with the shell is arranged at the end of the ruler strip; the roller includes a drum; an L-shaped clamping block distributed in an annular manner with equal intervals is fixedly connected to the front end of the drum; a limiting protrusion is fixedly connected to the inner side of the L-shaped clamping block; an open groove is provided on the outer surface of the drum; the ruler core cover includes a cover plate; a through groove distributed in an annular manner with equal intervals is provided on the cover plate; a limiting clamping block corresponding to the through groove is fixedly connected to the rear end of the cover plate; a positioning protrusion corresponding to the open groove is fixedly connected to the rear end of the cover plate; the L-shaped clamping block and the limiting clamping block are engaged; black and white stripes are silk-screened on the ruler strip.

[0006] Preferably, when in use, the ruler is pulled outward to drive the roller and the shaft to rotate, and the angle measurement unit on the outside of the shaft rotates synchronously to detect the rotation angle of the magnetic field pole. It is necessary to perform circumference compensation in the software algorithm. The mathematical model of the curve of the ruler winding can be represented by an Archimedean spiral. Since the thickness, total length and center axis diameter of the ruler are known, the actual stretched length of the ruler can be calculated by the software algorithm. Since the length of the ruler is indirectly calculated by measuring the rotation angle of the roller, in actual measurement, since the ruler is not completely tightly wound, the outer diameter change of the ruler is related to the user's stretching force. The error will be accumulated and amplified as the ruler is stretched. If the calibration method is not added, the measurement error is large. Therefore, calibration points and calibration measurement units are added to the ruler. The calibration points on the ruler are distributed on the ruler at a fixed interval. Each time the calibration point passes through the calibration measurement unit, it notifies the system that the ruler has been stretched by a fixed length. Combined with the stretching direction of the magnetic field measurement, the stretched length of the ruler can be accurately obtained. The calibration points are set on the front and back of the ruler. A black dot is set at an interval of 2 inches by screen printing. When the calibration When a point passes through the calibration detection unit, the reflective photoelectric detector inside the calibration detection unit will receive a pulse signal, which indicates that the ruler is stretched exactly 2 inches, so the length is calibrated once every 2 inches. In the above measurement, each time the measurement starts, the ruler needs to be returned to zero position to measure correctly, otherwise only the relative result of the starting point and the current position can be obtained, because neither the angle measurement nor the calibration point can reflect the absolute position of the ruler. For this reason, the calibration stripes are set to fixed incremental absolute position encoding, and each stripe is distributed in a regular manner of increasing 1 / 8 inch, such as the first and second points The spacing is 1 inch, the second and third points are 1 + 1 / 8 inches, the third and fourth points are 1 + 2 / 8 inches, and the fourth and fifth points are 1 + 3 / 8 inches. By analogy, when two calibration points are detected passing through the calibration detection unit, the absolute position of the current ruler can be obtained by calculating the increment between the two points. Therefore, this encoding does not require the ruler to be reset to zero. It only needs to move a certain distance to calculate the current absolute position of the ruler. At the same time, the laser ranging module emits a laser and measures together with the ruler.

[0007] Preferably, a display screen and buttons are installed on the shell, and the functions of the laser digital tape measure include but are not limited to: circumference-diameter conversion, area / volume calculation, trigonometric relationship calculation, unit conversion, and voice broadcast.

[0008] Preferably, the rotation angle measuring unit is arranged outside the rotating shaft via an external rolling wheel or a gear.

[0009] Preferably, the rotation angle measurement unit adopts magnetic pole measurement, grating measurement or mechanical encoder measurement; when magnetic pole measurement is adopted, a magnet is fixedly arranged on the rotating shaft.

[0010] Preferably, the black and white stripes on the ruler are distributed at the same interval.

[0011] Preferably, the black and white stripes on the ruler are distributed in an absolute value coding or incremental coding manner, and each stripe is distributed in a regular pattern of increasing by 1 / 8 inch.

[0012] Preferably, the laser emitted by the laser ranging module is parallel to the stretching direction of the ruler, and the laser ranging module is installed on the side of the same plane as the ruler.

[0013] Preferably, the laser ranging module is installed at the upper end of the center of the ruler; a 45° reflector installed in the shell is arranged below the laser ranging module; the laser of the laser ranging module is parallel to the stretching direction of the ruler after being refracted by the 45° reflector.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The overall structure of the present invention is compact, does not take up space, integrates a laser distance measurement module, solves the problem of limited measuring length of a tape measure, can achieve high-precision distance measurement within a range of tens of meters or even hundreds of meters, and brings the laser line and the ruler bar as close as possible. The laser line can be placed on the side of the ruler bar and in the same plane as the ruler bar, or the laser line can be placed above or below the center of the ruler bar. This makes it convenient for users to use a tape measure and a laser to measure the same target object, improves the convenience of using an ordinary tape measure, facilitates users to read directly, extends the measuring distance, and achieves long-distance straight-line measurement. The measurement results can be used to calculate the diameter and circumference of a circle, as well as the volume, area, and trigonometric relationship of space; 2. Calibration points and calibration measurement units with fixed intervals are set on the ruler. When the calibration point passes through the calibration measurement unit, a calibration signal will be generated to prompt the system to calibrate the measured length, which can improve the measurement error and avoid the accumulation of errors caused by indirect angle measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the first three-dimensional structure of the laser digital display tape measure embodiment 1 of the present invention; Figure 2 It is another three-dimensional structural schematic diagram of the laser digital display tape measure embodiment 1 of the present invention; Figure 3 It is a schematic diagram of the three-dimensional structure of the roller in the laser digital display tape measure of the present invention; Figure 4 It is a schematic diagram of the three-dimensional structure of the core cover of the middle length of the laser digital display tape measure of the present invention; Figure 5 It is a schematic diagram of the magnetic pole detection method in the laser digital display tape measure of the present invention; Figure 6 A fixed-spacing calibration point diagram is added to the ruler of the laser digital display tape measure of the present invention; Figure 7 An absolute position coding calibration point diagram is added to the ruler of the laser digital display measuring tape of the present invention; Figure 8 This is a schematic diagram of the three-dimensional structure of Example 2 of the laser digital display tape measure of the present invention.

[0016] In the figure, the corresponding relationship between the component names and the figure numbers is as follows: 1. Ruler core seat; 2. Laser distance measurement module; 3. 45° reflector; 4. Calibration detection unit; 5. Roller; 51. Roller; 52. L-shaped block; 53. Limiting protrusion; 54. Opening slot; 6. Ruler core cover; 61. Cover plate; 62. Through slot; 63. Limiting block; 64. Positioning protrusion; 7. Rotating shaft; 8. Rotation angle measurement unit; 9. Ruler bar. DETAILED DESCRIPTION

[0017] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0018] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0019] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" 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 or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Embodiment 1:

[0020] See also Figure 1-7The present invention provides a laser digital display tape measure, comprising a ruler core seat 1, a laser distance measuring module 2, and a calibration detection unit 4; further comprising a roller 5, a ruler core cover 6, a rotating shaft 7, an angle measuring unit 8 and a ruler strip 9; the front end of the ruler core seat 1 is fixedly connected with the roller 5; the front end of the roller 5 is engaged with the ruler core cover 6; the front end of the ruler core cover 6 is fixedly connected with the rotating shaft 7; the front end of the rotating shaft 7 is fixedly connected with the angle measuring unit 8; the outer side of the roller 5 is tightly wound with a ruler strip 9 through a ruler spring; the ruler core seat 1, the laser distance measuring module 2, the calibration detection unit 4, the roller 5, the ruler core cover 6, the rotating shaft 7, the angle measuring unit 8 and the ruler strip 9 are all installed in a shell (not shown); a ruler hook engaged with the shell is arranged at the end of the ruler strip 9; the roller 5 comprises a roller 51; the front end of the roller 51 is fixedly connected with an L-shaped clamping block 52 distributed in an annular manner at equal intervals; the inner side of the L-shaped clamping block 52 is fixedly connected with a limiting protrusion 53; the outer surface of the roller 51 is provided with The ruler core cover 6 comprises a cover plate 61; the cover plate 61 is provided with annular through grooves 62 which are evenly distributed; a limit block 63 which corresponds to the through grooves 62 is fixedly connected to the rear end of the cover plate 61; a positioning protrusion 64 which corresponds to the opening groove 54 is fixedly connected to the rear end of the cover plate 61; the L-shaped block 52 and the limit block 63 are snap-fitted; black and white stripes are silk-screened on the ruler bar 9; a display screen and buttons (not shown) are installed on the shell, and the functions of the laser digital display tape measure include but are not limited to: circumference-diameter conversion, area / volume calculation, trigonometric relationship calculation, unit conversion, and voice broadcast; the angle measurement unit 8 adopts magnetic pole measurement, and a magnet is fixedly arranged on the rotating shaft 7; the laser distance measuring module 2 is installed at the upper end of the center of the ruler bar 9; a 45° reflector 3 installed in the shell is arranged below the laser distance measuring module 2; the laser of the laser distance measuring module 2 is refracted by the 45° reflector 3 and is parallel to the stretching direction of the ruler bar 9.

[0021] When working, the ruler 9 is pulled outward to drive the roller 5 and the rotating shaft 7 to rotate. The angle measuring unit 8 outside the rotating shaft 7 rotates synchronously to detect the rotation angle of the magnetic field pole. It is necessary to perform circumference compensation in the software algorithm. The mathematical model of the curve of the ruler 9 winding can be represented by an Archimedean spiral. Since the thickness, total length and center axis diameter of the ruler 9 are known, the actual stretched length of the ruler 9 can be calculated through the software algorithm. Since the length of the ruler is indirectly calculated by measuring the rotation angle of the roller, in actual measurement, since the ruler 9 is not completely tightly wound, the ruler 9 The change in the outer diameter is related to the user's stretching strength. The error will be accumulated and amplified as the ruler 9 is stretched. If the calibration method is not added, the measurement error will be large. Therefore, calibration points and calibration measurement units 4 are added to the ruler 9. The calibration points on the ruler 9 are distributed on the ruler at fixed intervals. Each time the calibration point passes through the calibration measurement unit 4, it notifies the system that the ruler 9 is stretched by a fixed length. Combined with the stretching direction measured by the magnetic field, the stretching length of the ruler 9 can be accurately obtained. The calibration points are set on the front and back sides of the ruler 9. A black dot is set every 2 inches by screen printing. When the calibration point When passing through the calibration detection unit 4, the reflective photoelectric detector inside the calibration detection unit 4 will receive a pulse signal, which indicates that the ruler is stretched exactly 2 inches, so the length is calibrated once every 2 inches. In the above measurement, each time the measurement starts, the ruler 9 needs to be returned to the zero position to measure correctly, otherwise only the relative result of the starting point and the current position can be obtained, because neither the angle measurement nor the calibration point can reflect the absolute position of the ruler 9. For this reason, the calibration stripes are set to fixed incremental absolute position encoding, and each stripe is increased by 1 / 8 inch. Regular distribution, such as the first two points spacing is 1 inch, the second three points spacing is 1 + 1 / 8 inch, the third four points spacing is 1 + 2 / 8 inch, the fourth five points spacing is 1 + 3 / 8 inch, and so on. When two correction points are detected through the calibration detection unit 4, the absolute position of the current ruler 9 can be obtained by calculating the increment between the two points. Therefore, the encoding does not need to reset the ruler 9. It only needs to move a certain distance to calculate the current absolute position of the ruler 9. At the same time, the laser ranging module 2 emits a laser, which is refracted by the 45° reflector 3 and then measured together with the ruler 9. Embodiment 2:

[0022] See also Figure 3-8The present invention provides a laser digital display tape measure, comprising a ruler core seat 1, a laser distance measuring module 2, and a calibration detection unit 4; further comprising a roller 5, a ruler core cover 6, a rotating shaft 7, an angle measuring unit 8 and a ruler strip 9; the front end of the ruler core seat 1 is fixedly connected to the roller 5; the front end of the roller 5 is snap-connected to the ruler core cover 6; the front end of the ruler core cover 6 is fixedly connected to the rotating shaft 7; the front end of the rotating shaft 7 is fixedly connected to the angle measuring unit 8; the outer side of the roller 5 is tightly wound with a ruler strip 9 through a ruler spring; the ruler core seat 1, the laser distance measuring module 2, the calibration detection unit 4, the roller 5, the ruler core cover 6, the rotating shaft 7, the angle measuring unit 8 and the ruler strip 9 are all installed in a shell (not shown); a ruler hook snap-fitted with the shell is arranged at the end of the ruler strip 9; the roller 5 comprises a roller 51; the front end of the roller 51 is fixedly connected to an L-shaped clamping block 52 distributed in an annular manner and at equal intervals; the inner side of the L-shaped clamping block 52 is fixedly connected A limiting protrusion 53; an opening groove 54 is provided on the outer surface of the roller 51; the ruler core cover 6 includes a cover plate 61; the cover plate 61 is provided with annular through grooves 62 that are equidistantly distributed; a limiting block 63 corresponding to the through grooves 62 is fixedly connected to the rear end of the cover plate 61; a positioning protrusion 64 corresponding to the opening groove 54 is fixedly connected to the rear end of the cover plate 61; the L-shaped block 52 and the limiting block 63 are snap-fitted; black and white stripes are silk-screened on the ruler 9; a display screen and buttons (not shown) are installed on the shell, and the functions of the laser digital display tape measure include but are not limited to: circumference-diameter conversion, area / volume calculation, trigonometric relationship calculation, unit conversion, and voice broadcast; the angle measurement unit 8 adopts magnetic pole measurement, and a magnet is fixedly arranged on the rotating shaft 7; the laser emitted by the laser distance measuring module 2 is parallel to the stretching direction of the ruler 9, and the laser distance measuring module 2 is installed on the side of the same plane as the ruler 9.

[0023] Through the above steps, when in use, the ruler 9 is pulled outward to drive the roller 5 and the rotating shaft 7 to rotate, and the angle measurement unit 8 outside the rotating shaft 7 rotates synchronously to detect the rotation angle of the magnetic field pole. It is necessary to perform circumference compensation in the software algorithm. The mathematical model of the curve of the ruler 9 winding can be represented by an Archimedean spiral. Since the thickness, total length and center axis diameter of the ruler 9 are known, the actual stretched length of the ruler 9 can be calculated through the software algorithm. Since the length of the ruler is indirectly calculated by measuring the rotation angle of the roller, in actual measurement, since the ruler 9 is not completely tightly wound, The change in the outer diameter of the ruler 9 is related to the user's stretching force. The error will be accumulated and amplified as the ruler 9 is stretched. If the calibration method is not added, the measurement error will be large. Therefore, calibration points and calibration measurement units 4 are added to the ruler 9. The calibration points on the ruler 9 are distributed on the ruler at a fixed interval. Each time the calibration point passes through the calibration measurement unit 4, it notifies the system that the ruler 9 is stretched by a fixed length. Combined with the stretching direction measured by the magnetic field, the stretching length of the ruler 9 can be accurately obtained. The calibration points are set on the front and back sides of the ruler 9. A black dot is set at an interval of 2 inches by screen printing. When the calibration point passes through the calibration detection unit 4, the reflective photodetector inside the calibration detection unit 4 will obtain a pulse signal, which indicates that the ruler is stretched by a distance of 2 inches, so that the length is calibrated once every 2 inches. In the above measurement, each time the measurement starts, the ruler 9 needs to be returned to the zero position to measure correctly. Otherwise, only the relative result of the starting point and the current position can be obtained. Because neither the angle measurement nor the calibration point can reflect the absolute position of the ruler 9, for this reason, the calibration stripes are set to fixed incremental absolute position encoding, and each strip The patterns are distributed in a regular pattern of increasing by 1 / 8 inch, such as the first two points are 1 inch apart, the second and third points are 1+1 / 8 inch apart, the third and fourth points are 1+2 / 8 inch apart, the fourth and fifth points are 1+3 / 8 inch apart, and so on. When two correction points are detected through the calibration detection unit 4, the absolute position of the current ruler 9 can be obtained by calculating the increment between the two points. Therefore, the code does not need to reset the ruler 9. It only needs to move a certain distance to calculate the current absolute position of the ruler 9. At the same time, the laser ranging module 2 emits a laser and measures together with the ruler 9.

[0024] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

Claims

1. A laser digital tape measure, comprising a tape core seat (1) installed inside a housing, a laser distance measurement module (2), a calibration detection unit (4) and an angle measurement unit (8), characterized in that: A roller (5) is fixedly connected to one side of the ruler core seat (1), and a ruler core cover (6) is connected to the other side of the roller (5); a rotating shaft (7) is fixedly connected to the center of one side of the ruler core cover (6), and one end of the rotating shaft (7) is connected to an angle measuring unit (8); a ruler strip (9) is tightly wound around the outer side of the roller (5) via a ruler spring, and black and white stripes are silk-screened on the ruler strip (9), and a detection port of the calibration detection unit (4) faces the side of the ruler strip (9) on which the black and white stripes are silk-screened.

2. The laser digital measuring tape according to claim 1, characterized in that: A display screen and buttons are installed on the shell, and the functions of the laser digital tape measure include but are not limited to: circumference-diameter conversion, area / volume calculation, trigonometric relationship calculation, unit conversion, and voice broadcast.

3. The laser digital measuring tape according to claim 1, characterized in that: The rotation angle measuring unit (8) is arranged outside the rotating shaft (7) via an external rolling wheel or a gear.

4. The laser digital measuring tape according to claim 1, characterized in that: The rotation angle measurement unit (8) adopts magnetic pole measurement, grating measurement or mechanical encoder measurement; when magnetic pole measurement is adopted, a magnet is fixedly arranged on the rotating shaft (7).

5. The laser digital measuring tape according to claim 1, characterized in that: The black and white stripes on the ruler (9) are distributed at the same interval.

6. The laser digital measuring tape according to claim 1, characterized in that: The black and white stripes on the ruler (9) are distributed in an absolute value coding or incremental coding manner, and each stripe is distributed in a regular pattern of increasing by 1 / 8 inch.

7. The laser digital measuring tape according to claim 1, characterized in that: The laser emitted by the laser distance measuring module (2) is parallel to the stretching direction of the ruler (9), and the laser distance measuring module (2) is installed on the side of the same plane as the ruler (9).

8. The laser digital measuring tape according to claim 1, characterized in that: The laser distance measuring module (2) is mounted on the upper end of the center of the ruler (9), and a 45° reflector (3) mounted in the housing is arranged below the laser distance measuring module (2). The laser light of the laser distance measuring module (2) is refracted by the 45° reflector (3) and is parallel to the stretching direction of the ruler (9).

9. The laser digital measuring tape according to claim 1, characterized in that: The end of the ruler (9) is provided with a ruler hook which engages with the housing.

10. The laser digital measuring tape according to claim 1, characterized in that: The roller (5) comprises a roller (51), the front end of which is fixedly connected to an L-shaped clamping block (52) distributed in an annular manner with equal spacing; the inner side of the L-shaped clamping block (52) is fixedly connected to a limiting protrusion (53), and the outer surface of the roller (51) is provided with an opening groove (54); the ruler core cover (6) comprises a cover plate (61), the cover plate (61) is provided with through grooves (62) distributed in an annular manner with equal spacing, the rear end of the cover plate (61) is fixedly connected to a limiting clamping block (63) corresponding to the through grooves (62), and the rear end of the cover plate (61) is fixedly connected to a positioning protrusion (64) corresponding to the opening groove (54); the L-shaped clamping block (52) and the limiting clamping block (63) are connected in a snap-fit ​​manner.

Images