Arc radius gauge

Abstract

The present application relates to a kind of arc radius measuring tools for measuring the radius of bent pipe after machining in chemical industry, boiler and other metal pipe industry, comprising measuring body, two fixed measuring claws are arranged on the upper part of measuring body, which are close to the arc surface of the inner arc of workpiece bent pipe during working, the distance between the two fixed measuring claws is the chord length of the arc line to be measured;A slide is provided in the middle of measuring body, a measuring rod is installed in the slide, which can freely slide and stretch out, and the upper end of the measuring rod is on the middle point of the arc line to be measured after stretching out, the chord height of the arc line to be measured is measured by the measuring rod, a measuring cam is installed in the U-shaped groove of the lower part of measuring body, which can freely rotate around the pin shaft, the profile line of the measuring cam is in contact with the lower end of the measuring rod;A dial is fixed on the measuring cam by rivet, and the dial rotates together with the measuring cam when dial is actuated, the measuring rod is pushed to slide and stretch out to measure the arc, which has the advantages of fast, convenient and accurate measurement of the bent pipe.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of arc radius measuring tool for measuring the radius of elbow pipe after elbow pipe machining in chemical industry, boiler and other industries. BACKGROUND

[0002] In heat exchange equipment, a large number of heat exchange tubes are often used for medium heat exchange. In order to reduce the number of joints and reduce the probability of welding defects, the heat exchange tubes need to be bent. On some compact equipment, the bending radius of the heat exchange tubes is strictly required. Therefore, it is necessary to quickly, conveniently and accurately measure the bending radius of the bent pipe. The bending angle of the general heat exchange tube is less than 180°, and since the chord length of the arc is not linearly related to the radius, the direct measurement of the arc bending radius is difficult. Therefore, the existing measuring tools cannot directly measure the R arc radius. However, the mathematical principle of determining the arc size by three points can be used to analyze the functional relationship between the arc length and the radius, and the nonlinear relationship between the arc chord height and the radius can be converted into a linear relationship between the angle (or length) and the measured arc radius. Then, a measuring tool is designed according to this linear relationship to directly measure the arc radius. SUMMARY

[0003] The present application aims to overcome the deficiencies in the prior art and provide an arc radius measuring tool that can quickly, conveniently and accurately measure the bending radius of the bent pipe.

[0004] The present application is achieved by an arc radius measuring tool, which includes a measuring body. Two fixed measuring jaws are arranged on the upper part of the measuring body and are in close contact with the arc surface of the inner arc of the workpiece elbow pipe during work. The distance between the two fixed measuring jaws is the chord length of the measured arc. A sliding channel is arranged in the middle of the measuring body. A measuring rod is installed in the sliding channel and can freely slide and extend along the sliding channel. The upper end of the measuring rod is in contact with the middle point of the measured arc when it is extended. The chord height of the measured arc is measured by the measuring rod. A measuring cam is installed in the U-shaped groove at the lower part of the measuring body through a pin shaft and can freely rotate around the pin shaft. The profile line of the measuring cam is in contact with the lower end of the measuring rod. A scale dial is fixed to the measuring cam by a rivet and becomes an integral part of the measuring cam. When the scale dial is rotated, the scale dial and the measuring cam rotate together, and the measuring rod is pushed to slide and extend for arc measurement.

[0005] The upper end and the lower end of the measuring rod are designed as sharp corners, and the sharp corners have a small R arc.

[0006] A stop pin is fixedly installed on the measuring rod in the transverse position along the extension direction of the measuring rod. A sliding groove is formed in the measuring body, and the head of the stop pin extends out of the measuring body through the sliding groove.

[0007] The sector window with the scale disc exposed is provided on the upper end of the measuring ruler, and the sector window has a taper surface, and the secondary scale line is engraved on the taper surface of the sector window.

[0008] The material of each part is tool steel, and quenching treatment is performed.

[0009] The circumferential scale line is provided on the circumference of the scale disc, and the circumferential scale line corresponds to different profile radii of the measuring cam, and the corresponding arc radius values are marked on the scale line.

[0010] The scale disc protrudes from the lower end of the measuring ruler.

[0011] The profile line of the measuring cam is made according to the method.

[0012] The relationship between the radius R of the inner arc circle of the workpiece to be measured, the half chord length A and the chord height H is

[0013] R 2 =A 2 +B 2 R=H+B

[0014] After mathematical derivation, the relationship between the radius R of the inner arc circle, the half chord length A and the chord height H is

[0015] R=1 / 2*(A 2 / H+H)

[0016] If the chord length 2A is a fixed value, then the radius R of the circle has a unique corresponding relationship with the chord height H, the working part of the measuring cam is equally divided according to the circumference, and the radius H of each equal part of the measuring cam is determined according to the relationship between R and H, and the profile line of the measuring cam is made according to the method.

[0017] Grooves are provided on both sides of the measuring ruler for hand clamping during measurement.

[0018] The present application has the following positive effects:

[0019] 1. The present application has the advantages of fast, convenient and accurate measurement of the bent pipe.

[0020] 2. The measurement principle of the present application refers to the working principle of the vernier caliper and the universal angle ruler, which improves the accuracy of the circumferential direction measurement, and converts the angle measurement function of the universal angle ruler into the measurement of the extended length through the cam.

[0021] 3. The working principle of a vernier caliper is as follows: Taking a vernier caliper with an accuracy of 0.05 mm as an example, the vernier scale has 20 equally divided graduations, with a total length of 19 mm. During measurement, if the 11th graduation line on the vernier scale aligns with the main scale, the decimal part reading is 11 / 20 mm = 0.55 mm; if the 12th graduation line aligns with the main scale, the decimal part reading is 12 / 20 mm = 0.60 mm. Generally, the vernier scale has n equally divided graduations, and their total length is equal to the total length of (n-1) equally divided graduations on the main scale. If the smallest graduation on the vernier scale is x, and the smallest graduation on the main scale is y, then nx = (n-1)y, x = y - (y / n). The difference between the smallest graduations on the main scale and the vernier scale is Δx = y - x = y / ny / n, which is called the accuracy of the vernier caliper, and it determines the number of decimal places in the reading. As can be seen from the formula, improving the measurement accuracy of a vernier caliper involves increasing the number of graduations on the vernier scale or decreasing the minimum graduation value on the main scale. Generally, y is 1 mm, and n takes values ​​of 10, 20, and 50, corresponding to accuracies of 0.1, 0.05, and 0.02 mm, respectively.

[0022] The reading mechanism of a universal protractor is based on the vernier principle. Each division on the main scale represents 1°. The vernier scale is formed by dividing 29° of the main scale into 30 divisions. Therefore, the vernier division is 29° / 30, meaning the difference between one division on the main scale and one on the vernier scale is 2'. This indicates that the universal protractor has a reading accuracy of 2'. In addition, it is available in 5' and 10' precision versions. The reading method is exactly the same as that of a vernier caliper.

[0023] 4. In this invention, the dial and cam are fixed together, and the circumferential scale lines of the dial correspond to different cam radii. The scale of the dial is equivalent to the main scale graduations of a universal protractor, with each division representing 1°. The graduations of the sector-shaped window of the measuring instrument are equivalent to the vernier graduations. The vernier graduations can be divided into 30 divisions, taking 29° of the main scale. Therefore, the vernier graduation angle is 29° / 30, meaning the difference between one division of the main scale and the vernier is 2', which means the reading accuracy of the universal protractor is 2'. If lower measurement accuracy is required, the graduations of the measuring instrument window can be divided into 6 divisions, taking 5° of the main scale. Therefore, the vernier graduation angle is 5° / 6, meaning the difference between one division of the main scale and the vernier is 10', which means the reading accuracy of the universal protractor is 10'. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the R-arc radius measuring tool of the present invention.

[0025] Figure 2 This is a measurement schematic diagram of the R-arc radius measuring tool of the present invention.

[0026] Figure 3 This is the front view of the specific quantity of the present invention, 4.

[0027] Figure 4This is a left sectional view of the specific part 4 of the present invention.

[0028] Figure 5 This is a front view of the riveted assembly of the measuring cam 5 and the dial 7 of the present invention.

[0029] Figure 6 This is a cross-sectional view of the riveted assembly of the measuring cam 5 and the dial 7 of the present invention.

[0030] Figure 7 This is an assembly diagram of the measuring rod 3 and the stop pin 8 of the present invention.

[0031] Figure 8 This is a graph showing the relationship between the radius R of the circle in this invention and the half-chord length A and chord height H.

[0032] In the diagram: 1. Inner arc of the bend, 2. Radius gauge, 3. Measuring rod, 4. Measuring body, 5. Measuring cam, 6. Pin, 7. Dial, 8. Stop pin. Detailed Implementation

[0033] like Figure 1 , 2 As shown, a circular arc radius measuring tool includes a measuring body 4. Fixed measuring jaws are provided on both sides of the upper part of the measuring body 4, which adhere to the arc surface of the inner arc 1 of the workpiece bend during operation. The distance between the two fixed measuring jaws is the chord length of the measured arc. A slide is provided in the middle of the measuring body 4, in which a measuring rod 3 is installed. This rod can slide and extend freely along the slide, and its upper end probe rests on the midpoint of the measured arc after extension. The chord height of the measured arc is measured through the measuring rod 3. A measuring cam 5 is installed in the U-shaped groove at the lower part of the measuring body 4 via a pin 6. The measuring cam 5 can rotate freely around the pin 6, and its outline contacts the lower end of the measuring rod 3. A scale 7, integrally formed with the measuring cam 5, is fixed to the measuring cam 5 by rivets. When the scale 7 is turned, the scale 7 rotates together with the measuring cam 5, pushing the measuring rod 3 to slide out of the measuring body 4 and perform circular arc measurement. The upper probe and lower end of the measuring rod 3 are both designed with sharp angles, each with a small radius (R).

[0034] A stop pin 8 is fixedly installed on the measuring rod 3 at a lateral position along its extension direction. A corresponding sliding groove is provided on the measuring body 4, and the head of the stop pin 8 extends out of the measuring body 4 through the sliding groove.

[0035] Figure 1 This is a schematic diagram of the structural principle of the present invention. The upper two sides of the measuring body 4 are fixed measuring jaws, which, during operation, adhere to the arc surface of the inner arc 1 of the workpiece bend, effectively determining the chord length of the measured arc. The measuring rod 3 has sharp corners at both ends (with a small radius to reduce friction and wear, and improve service life) and is mounted on a slide rail in the middle of the measuring body 4. It can slide and extend freely along the slide rail. After extension, its upper end (probe) can rest against the midpoint of the measured arc, effectively measuring the chord height of the measured arc.

[0036] The measuring cam 5 is mounted in the U-shaped slot of the measuring body 4 by a pin shaft 6, and can rotate freely around the pin shaft 6. The profile line of the measuring cam 5 is in contact with the lower end of the measuring rod 3. When the measuring cam 5 rotates, the measuring rod 3 is pushed to move out along the slide.

[0037] As shown in Figure 5 , Figure 6 , the dial 7 is fixed with the measuring cam 5 by rivets, and the circumferential scale line on the circumference of the dial 7 corresponds to different profile radii of the measuring cam 5. The corresponding arc radius values are marked on the scale line.

[0038] A sector window for reading the measured data of the dial 7 is provided on the upper surface of the measuring body 4, and the sector window has a tapered surface. A secondary scale line is marked on the tapered surface of the sector window, and the secondary scale line is a circumferential equal division line.

[0039] A circumferential scale line is provided on the circumference of the dial 7, and the circumferential scale line corresponds to different profile radii of the measuring cam 5. The corresponding arc radius values are marked on the scale line. The outer edge of the dial 7 protrudes from the lower end of the measuring body 4. Grooves are provided on both sides of the measuring body 4 for easy hand holding during measurement.

[0040] Figure 8 The figure is a graph of the relationship between the radius R of the circle and the half-chord length A and the chord height H. The parameter relationship in the figure is

[0041] R 2 = A 2 +B 2

[0042] R = H + B

[0043] After mathematical derivation, the relationship between the radius R of the circle and the half-chord length A and the chord height H is

[0044] R = 1 / 2*(A 2 / H + H)

[0045] If the chord length 2A is a fixed value, then the radius R of the circle and the chord height H have a unique corresponding relationship. The working part of the measuring cam 5 is equally divided according to the circumference, and the radius (H) of each equal part of the measuring cam 5 is determined according to the relationship between R and H above. The profile line of the measuring cam 5 is made according to this method. The rotation angle of the measuring cam 5 made according to the above method has a corresponding linear relationship with the measured arc radius R.

[0046] Figure 2 is a schematic diagram of the measurement of the R arc radius gauge. Figure 3 、 Figure 4The structure of the measuring instrument 4 is shown in the figure. The upper part of the measuring instrument 4 is provided with a sector window for reading the measured data. In order to improve the measuring display precision, referring to the scale value display principle of the vernier caliper, according to the measuring precision requirement, the circumferential division lines, i.e. the secondary scale lines, are marked on the conical surface of the sector window. The division angle value of the sector arc division line (secondary scale line) can be 0.5, 0.8 or 0.9 times of the division line, i.e. the primary scale line angle value on the dial 7, so that the primary scale measuring display precision can be improved by 2, 5 or 10 times respectively.

[0047] The dial 7 also has the function of manual dialing. When the outer edge of the dial 7 is manually dialled, the dial 7 rotates together with the measuring cam 5, pushes the measuring rod 3 to slide and extend, and performs the arc measurement. Figure 2 As can be seen, the outer edge of the dial 7 protrudes from the lower end of the measuring instrument 4. The outer edge of the dial 7 is manually dialled, the dial 7 rotates together with the measuring cam 5, pushes the measuring rod 3 to slide and extend, and performs the arc measurement.

[0048] The measuring rod 3 is provided with a stop pin 8. The stop pin 8 can prevent the measuring rod 3 from sliding out of the slide of the measuring instrument 4, and can also be manually moved to help the measuring rod 3 to retract.

[0049] The grooves on both sides of the measuring instrument 4 are designed to facilitate hand clamping during measurement.

[0050] The upper part of the measuring instrument 4 is provided with fixed measuring claws which are tightly attached to the arc surface of the inner arc 1 of the workpiece elbow during work. The measuring rod 3 is installed in the slide in the middle of the measuring instrument 4 and can freely slide and extend along the slide. The upper end (measuring head) of the measuring rod 3 can be abutted against the middle point of the measured arc line after extension. The measuring cam 5 is installed in the U-shaped groove at the lower part of the measuring instrument 4 through the pin shaft 6 and can freely rotate around the pin shaft 6. The profile line of the measuring cam 5 is in contact with the lower end sharp corner of the measuring rod 3. When the measuring cam 5 rotates, the measuring rod 3 is pushed to extend along the slide. The dial 7 is fixed together with the measuring cam 5 by rivets. The dial 7 also has the function of manual dialing. When the outer edge of the dial 7 is manually dialled, the dial 7 rotates together with the measuring cam 5, pushes the measuring rod 3 to slide and extend, and performs the arc measurement. The measuring rod 3 is provided with a stop pin 8. The stop pin 8 can prevent the measuring rod 3 from sliding out of the slide of the measuring instrument 4, and can also be manually moved to help the measuring rod 3 to retract.

[0051] In order to improve the service life of the measuring instrument, tool steel is selected for the materials of the parts, and quenching treatment is performed. After the measuring instrument is assembled, the measuring rod 3 slides, and the riveted parts of the measuring cam 5 and the dial 7 rotate flexibly.

[0052] Before use, the dial 7 is dialled, and the stop pin 8 is moved to make the measuring rod 3 retract to the lowest position in the measuring instrument 4.

[0053] As shown in the figure, Figure 1 , Figure 2As shown, when in use, the measuring element 4 is held by hands, the measuring element 4 is placed in the inner arc position of the measured arc, and the two sides of the measuring element 4 are fixed to the arc surface of the workpiece. The dial 7 is actuated, the dial 7 drives the measuring cam 5 to rotate, the lower end of the measuring rod 3 is in contact with the outer contour of the measuring cam 5, the measuring rod 3 is pushed out along the sliding groove under the driving of the measuring cam 5, when the upper end (the measuring head) of the measuring rod 3 contacts the measured arc surface of the workpiece, the rotation of the dial 7 is stopped. The R arc radius size displayed by the scale of the sector window of the measuring element 4 is read, and the measurement of the R arc radius size is completed.

[0054] The display principle of the measuring element is to convert the linear scale display principle of the vernier caliper into the circumferential scale display. When reading the value, the number of the main scale before the 0 line of the secondary scale is read first, for example, 62, and then the number of the secondary scale aligned with the main scale is read, for example, 8, and the measured arc radius is 62.8mm.

[0055] When measuring, firstly, the two sides of the measuring element 4 should be fixed to the arc surface of the workpiece, and cannot be fixed to the straight line segment, otherwise the true data of the arc radius cannot be measured; secondly, in order to improve the measurement accuracy, the force should be moderate, and the workpiece and the measuring element can be reliably attached.

[0056] The dial 7 and the cam 5 are fixed together, and the circumferential scale line of the dial 7 corresponds to different cam radii. The scale of the dial 7 is equivalent to the main scale line of the universal angle ruler, and each grid is 1°. The scale line of the sector window of the measuring element 4 is equivalent to the vernier scale line, and the scale line of the vernier can be divided into 30 grids by 29° of the main scale, so that the angle grid of the vernier scale line is 29° / 30, that is, the difference between the main scale and the vernier is 2', that is, the reading accuracy of the universal angle ruler is 2'. If the measurement accuracy requirement is low, the scale line of the window of the measuring element 4 can be divided into 6 grids by 5° of the main scale, so that the angle grid of the vernier scale line is 5° / 6, that is, the difference between the main scale and the vernier is 10', that is, the reading accuracy of the universal angle ruler is 10'.

Claims

1. A circular arc radius gauge comprising a gauge body (4), characterized in that: The upper part of the measuring body (4) is provided with two fixed measuring claws which are close to the inner arc (1) of the workpiece elbow pipe during work, and the distance between the two fixed measuring claws is the chord length of the measured arc; a slide is arranged in the middle of the measuring body (4), and a measuring rod (3) capable of freely sliding and extending in the slide is arranged on the slide, the upper end of the measuring rod (3) is located on the middle point of the measured arc, the chord height of the measured arc is measured through the measuring rod (3), a measuring cam (5) is arranged in the U-shaped groove at the lower part of the measuring body (4) through a pin shaft (6), the measuring cam (5) is capable of freely rotating around the pin shaft (6), the profile line of the measuring cam (5) is in contact with the lower end of the measuring rod (3), and a scale disc (7) is fixed on the measuring cam (5) by a rivet, the scale disc (7) rotates together with the measuring cam (5) when the scale disc (7) is rotated, the measuring rod (3) is pushed to slide and extend out of the measuring body (4) to perform arc measurement; The upper end and the lower end of the measuring rod (3) are designed as sharp corners, and the sharp corners are provided with small R arcs; a stop pin (8) is fixedly arranged on the measuring rod (3) in the transverse position of the extension direction of the measuring rod (3), a sliding groove is arranged on the measuring body (4) in correspondence, and the head of the stop pin (8) extends out of the measuring body (4) through the sliding groove; recesses are arranged on the two sides of the measuring body (4) for hand clamping during measurement; A sector window is arranged on the upper surface of the measuring body (4) for reading the measured data of the scale disc (7), the sector window is provided with a conical surface, a secondary scale line is arranged on the conical surface of the sector window, and the secondary scale line is a circumferential division line; a circumferential scale line is arranged on the circumference of the scale disc (7), the circumferential scale line corresponds to different profile radii of the measuring cam (5), and the corresponding arc radius values are marked on the scale line; The profile line of the measuring cam (5) is made according to the method: The relationship between the radius R of the inner arc circle of the workpiece elbow pipe, the half chord length A and the chord height H is R 2 =A 2 +B 2 R=H+B After mathematical derivation, the relationship between the radius R of the inner arc circle, the half chord length A and the chord height H is R = 1 / 2 * (A 2 / H + H) The chord length 2A is set as a fixed value, and the radius R of the circle and the chord height H have a unique corresponding relationship, the working part of the measuring cam (5) is equally divided according to the circumference, the radius H of each equal part of the measuring cam (5) is determined according to the relationship between R and H, and the profile line of the measuring cam (5) is made according to the method.

2. A circular arc radius gauge according to claim 1, characterized in that: The materials of the parts are tool steels, and the tool steels are subjected to quenching treatment.

3. A circular arc radius gauge according to claim 1, wherein: The lower end of the scale disc (7) protrudes out of the lower end of the measuring body (4).

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