Vernier caliper capable of being transformed without damage and method for measuring bottom wall thickness of narrow cavity by using vernier caliper

Abstract

The invention discloses a non-destructive modified vernier caliper and a method for measuring the bottom wall thickness of a narrow cavity, relates to the technical field of mechanical measurement tools, and aims to solve the problem of measurement of the bottom wall thickness of a narrow cavity of a spaceflight large shell section part. The caliper comprises a vernier caliper body, cylindrical ball top contacts are fixed at the lower ends of two caliper feet, a supporting block is slidably arranged on a main caliper, a positioning block is fixed on an auxiliary caliper, and a dial indicator is mounted on the positioning block; a clamping pin lengthening block can be connected between the clamping pin and the contact, all the components are connected through plug-in screws with soft copper pads, key components are made of 45 # steel which is blued after quenching, and the overall precision reaches 0.01 mm. The invention also discloses a measuring method, which comprises the following steps of: after zero calibration of the standard gauge block, extending the long contact into the cavity, arranging the short contact outside, and calculating the wall thickness according to a formula. The device can go deep into a narrow cavity for measurement, has the advantages of high precision, low cost, convenient operation and no damage, and is suitable for high-precision measurement requirements in the fields of spaceflight and the like.

Description

Technical Field

[0001] This invention relates to the field of mechanical measuring tools, specifically to a non-destructive modification of a vernier caliper and a method for measuring the wall thickness of a narrow cavity bottom, which is particularly suitable for measuring the wall thickness of narrow cavities on complex components such as large shell sections for aerospace applications. Background Technology

[0002] Large shell-shaped components for aerospace applications are core load-bearing parts of launch vehicles, and their structural performance directly determines the rocket's flight safety and launch reliability. To achieve lightweight design of the rocket body, the inner surface of these components is usually machined with a large number of cavity structures of varying depths and specifications. The thickness of the bottom wall of the cavity is a key parameter affecting the overall strength of the shell-shaped component and must be strictly controlled within the design precision range.

[0003] Currently, the measurement of cavity bottom wall thickness faces significant technical bottlenecks: On the one hand, due to the large size of the parts and the depth of the cavities, traditional measuring tools such as vernier calipers and outside micrometers have limited measuring ranges and cannot reach the bottom of the cavity, making it difficult to complete the measurement. On the other hand, although the ultrasonic thickness gauges commonly used in the industry can achieve non-contact measurement, they have many inherent defects: First, before measurement, thick and thin test blocks with the same material as the part being measured need to be prepared for sound velocity calibration, which is cumbersome and the test blocks are expensive. Second, for cavities with arc-shaped surfaces, if the probe does not fit tightly with the measuring surface, large measurement errors are likely to occur. Third, for deep cavities with narrow spaces, the probe size is limited and cannot reach the bottom, resulting in a measurement blind zone. Fourth, ultrasonic thickness gauges are expensive to purchase and take a long time to measure, which is not suitable for the high-efficiency testing needs of mass production.

[0004] Therefore, developing a tool that is simple in structure, low in cost, easy to operate, and can accurately measure the wall thickness of narrow cavities has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for measuring the wall thickness of narrow cavity bottoms using a vernier caliper without causing damage. It aims to solve the problems of insufficient measurement range of traditional measuring tools and the complex operation and high cost of ultrasonic thickness gauges, achieving efficient, high-precision, and low-cost measurement of the wall thickness of narrow cavity bottoms.

[0006] To achieve the above objectives, the present invention employs the following technical solutions: A non-destructive modification vernier caliper includes a vernier caliper body (1). The lower ends of the two caliper feet (2) of the vernier caliper body (1) are fixedly connected to cylindrical ball-shaped contact heads (3). Specifically, the cylindrical ball-shaped contact head (3) is a contact piece with a spherical end on the end of a cylindrical rod. The actual working length of the cylindrical ball-shaped contact head (3) is greater than the height of the side wall of the cavity to be measured, ensuring that it can penetrate deep into the bottom of the cavity to contact the measurement point. A support block (5) is slidably set on the main scale (4) of the vernier caliper body (1) to support and position the dial indicator (8). A positioning block (7) is fixedly connected on the secondary scale (6) of the vernier caliper body (1). A dial indicator (8) is fixedly installed on the positioning block (7). Through the high-precision reading of the dial indicator (8) and the sliding adjustment of the vernier caliper, micron-level precision measurement can be achieved.

[0007] To further optimize and adapt to the measurement needs of cavities of different depths, the caliper body (1) is detachably and fixedly connected to the caliper foot (2) and the cylindrical ball-shaped contact (3). The two ends of the caliper foot extension block (9) are respectively provided with connection holes that match the lower end of the caliper foot (2) and the upper end of the cylindrical ball-shaped contact (3). A reliable connection is achieved by inserting screws (10). The caliper foot extension block (9) can be flexibly added or removed or replaced with a caliper foot extension block (9) of different lengths according to the cavity depth.

[0008] Further optimization involves using two cylindrical dome contacts (3) with different lengths. The working length of the longer cylindrical dome contact (3) is defined as the actual working length. The cylindrical dome contact outside the cavity is not blocked by the height of the side wall and does not need to be too long, which reduces weight and avoids unnecessary waste.

[0009] Further optimization is needed to improve the structural strength, wear resistance and corrosion resistance of the components. The extended foot block (9), cylindrical dome contact (3), support block (5) and positioning block (7) are all made of 45# steel and are subjected to quenching and bluing treatment in sequence. The quenching treatment makes the component hardness reach HRC40-45, which meets the requirements of high strength measurement. The bluing treatment forms an oxide film with a thickness of 0.5-1μm on the surface of the component, which effectively improves its corrosion resistance and extends its service life.

[0010] To further optimize the connection and ensure its reliability, the clamp (2) and the clamp extension block (9), the clamp extension block (9) and the cylindrical dome contact (3), the vernier scale (6) and the positioning block (7), and the positioning block (7) and the dial indicator (8) are all connected by insert screws (10). Soft copper pads (11) with a thickness of 0.3-0.5 mm are provided at the contact points between the insert screws (10) and the dial indicator (8) and between the insert screws (10) and the vernier caliper body (1). The soft copper pads (11) can effectively buffer the screw pressure and avoid causing indentations or scratches on the surface of precision parts.

[0011] Further optimization, by reasonably matching the accuracy of the vernier caliper body (1) with the indication accuracy of the dial indicator (8), the overall measurement accuracy of this non-destructive modified vernier caliper can reach 0.01mm, which fully meets the high-precision measurement requirements of aerospace parts.

[0012] This invention also discloses a method for measuring the wall thickness of a narrow cavity using a vernier caliper that has been modified without causing damage, the specific steps of which are as follows: S1. Zero the dial indicator (8) using a standard gauge block (12) to ensure accurate measurement reference: S11. Based on the design drawings or estimated dimensions of the bottom wall thickness of the cavity to be measured, select a standard gauge block (12) with matching specifications. The accuracy grade of the standard gauge block (12) shall not be lower than grade 0. S12. Make the top of the two cylindrical ball-shaped contacts (3) fit tightly against the measuring surface of the standard gauge block (12) to ensure no gap; move the support block (5) on the main scale (4) so ​​that the probe of the dial indicator (8) is in full contact with the upper working surface of the positioning block (7), and slowly push the support block (5) to compress the probe of the dial indicator (8) to the 1mm range, that is, the small pointer of the dial indicator (8) accurately points to the "1" scale line; use a screwdriver to gently rotate the zeroing knob of the dial indicator (8) to adjust the long pointer to the zero scale line; use the insert screw (10) to fasten the support block (5) to the current position of the main scale (4) to prevent the support block (5) from sliding; finally, loosen the clamping foot (2) of the vernier caliper body (1), remove the standard gauge block (12), and complete the zeroing operation.

[0013] S2. Perform the measurement and calculate the results: S21. After zeroing, keep the dial indicator (8) and support block (5) fixed. Loosen the brake screw of the vernier caliper body (1). Slide the auxiliary scale (6) to move the positioning block (7) and dial indicator (8) back to the preset position. The preset position must meet the following conditions: the relative distance between the auxiliary scale (6) and the main scale (4) is greater than the sum of the total length of the two cylindrical dome contacts (3), the height of the cavity sidewall, and the estimated thickness of the cavity bottom wall by more than 5mm, to ensure that the caliper feet ( 2) The cylindrical ball-shaped contact (3) can smoothly pass over the side wall of the cavity; slowly insert the longer cylindrical ball-shaped contact (3) into the cavity, and place the shorter cylindrical ball-shaped contact (3) on the surface of the part outside the cavity; adjust the position of the caliper so that the ball tips of the two cylindrical ball-shaped contacts (3) are accurately aligned with the preset measurement point, and slowly move them inward toward the caliper foot (2) until both contacts are in close contact with the measurement surface. After stabilization, read the long pointer value of the dial indicator (8).

[0014] S22. Calculate the cavity bottom wall thickness according to the measurement formula “actual thickness = standard gauge block (12) specification + (1mm - dial indicator (8) reading)” and record the data. During the measurement process, pay attention to the following: if the dial indicator (8) points to “1” and the long pointer is aligned with the zero mark, it indicates that the actual thickness is equal to the standard gauge block (12) specification; if the vernier scale (6) moves the positioning block (7) forward, the actual thickness is less than the standard gauge block (12) specification, the dial indicator (8) probe shortens, and the reading is greater than 1mm; if the vernier scale (6) moves the positioning block (7) backward, the actual thickness is greater than the standard gauge block (12) specification, the dial indicator (8) probe extends, and the reading is less than 1mm.

[0015] The present invention has the following advantages: 1. Breaking through measurement space limitations: Through the design of replaceable cylindrical dome contact (3) and clamping foot extension block (9), it can reach the bottom of narrow cavity that traditional measuring tools cannot reach, effectively eliminating measurement blind spots and adapting to the measurement needs of cavities of different depths and specifications.

[0016] II. High and stable measurement accuracy: The dual precision guarantee structure of dial indicator (8) and vernier caliper is adopted. With the zeroing process of standard gauge block (12), the measurement accuracy can reach 0.01mm. Moreover, it does not need to rely on material test block for calibration, avoiding the fit error and sound velocity error of ultrasonic thickness gauge, and the measurement results are more stable and reliable.

[0017] 3. Low cost and easy to promote: Based on the modification of ordinary vernier calipers, the core components only include simple structural parts such as cylindrical dome contact (3) and support block (5). The material cost is low and the processing technology is simple. Compared with ultrasonic thickness gauges, the equipment investment cost is reduced by more than 80%, and it is easy to promote and apply in industries such as machinery manufacturing and aerospace.

[0018] IV. Convenient and efficient operation: The zeroing process is simple, and the measurement process only requires sliding the auxiliary scale and aligning the contact head. A single measurement takes no more than 30 seconds, which is more than 5 times more efficient than ultrasonic thickness gauges and is suitable for high-efficiency testing in mass production.

[0019] V. Non-damage protection design: The soft copper pad (11) buffers the connection parts to avoid damage to the vernier caliper body (1) and dial indicator (8); the cylindrical ball contact (3) has a ball design that reduces the contact stress with the cavity surface, prevents scratches on the measured parts, and achieves dual protection for the measuring tool and the measured parts. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a vernier caliper structure that can be modified without damage.

[0021] Figure 2 This is a schematic diagram of the structure when using a non-destructive modified vernier caliper to measure a workpiece.

[0022] Figure 3 This is a partial structural diagram of a vernier caliper without the installation of the caliper foot extension block, which is modified without damage.

[0023] Figure 4 This is a partial structural diagram of a vernier caliper with extended feet installed using a non-destructive modification method.

[0024] In the diagram: 1-Vernier caliper body, 2-Caliper foot, 3-Cylindrical dome contact, 4-Main scale, 5-Support block, 6-Vernier scale, 7-Positioning block, 8-Dial indicator, 9-Caliper foot extension block, 10-Insertion screw, 11-Soft copper pad, 13-Measured cavity part. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example 1; like Figure 3 As shown, the thickness of the bottom wall of a narrow cavity on a large aerospace shell section was measured. The designed sidewall height is 100mm, the cavity bottom wall thickness is 5mm, and the distance from the measurement point to the edge of the part is 15mm (i.e., less than the length of the clamping foot). Component assembly: Select a vernier caliper with a range of 0-500mm and an accuracy of 0.02mm as the vernier caliper body (1). Connect cylindrical ball-shaped contacts (3) with lengths of 110mm and 120mm respectively to the lower ends of the two feet (2) by insert screws (10). There is no need to install the foot extension block (9). Fix the positioning block (7) on the auxiliary scale (6) by insert screws (10). Install a dial indicator (8) with a range of 0-5mm and an accuracy of 0.02mm on the positioning block (7). Put soft copper pads (11) on each connection part. Install the support block (5) on the main scale (4).

[0028] Zeroing operation: Select a 5mm grade 0 standard gauge block (12), put the two cylindrical ball-top contacts (3) into contact with the standard gauge block (12), move the support block (5) to compress the dial indicator (8) probe by 1mm (small dial indicator 1), adjust the zero long pointer and then tighten the support block (5).

[0029] Measurement process: Slide the auxiliary scale (6) to move the part back to a position of about 110mm+120mm+100mm+5mm=335mm, insert the 120mm long cylindrical dome contact (3) into the cavity, place the short contact on the outside, align it with the measuring point and bring it close to the clamp foot (2), and read the dial indicator (8) reading as 1.05mm.

[0030] Calculation result: Actual thickness = 5mm + (1mm - 1.05mm) = 4.95mm.

[0031] Example 2; like Figures 1-2 and Figure 4 As shown, the thickness of the bottom wall of a narrow cavity on a large aerospace shell section was measured. The designed sidewall height is 100mm, the cavity bottom wall thickness is 5mm, and the distance from the measurement point to the edge of the part is 65mm (i.e., greater than the length of the clamping foot). Component assembly: Select a vernier caliper with a range of 0-500mm and an accuracy of 0.02mm as the vernier caliper body (1). Install caliper extension blocks (9) and cylindrical ball-shaped contacts (3) with connection lengths of 110mm and 120mm respectively at the lower ends of the two caliper feet (2) by insert screws (10). Fix a positioning block (7) on the auxiliary scale (6) by insert screws (10). Install a dial indicator (8) with a range of 0-5mm and an accuracy of 0.02mm on the positioning block (7). Put soft copper pads (11) on each connection part. Install a support block (5) on the main scale (4).

[0032] Zeroing operation: Select a 5mm grade 0 standard gauge block (12), put the two cylindrical ball-top contacts (3) into contact with the standard gauge block (12), move the support block (5) to compress the dial indicator (8) probe by 1mm (small dial indicator 1), adjust the zero long pointer and then tighten the support block (5).

[0033] Measurement process: Slide the auxiliary scale (6) to move the part back to a position of about 110mm+120mm+100mm+5mm=335mm, insert the 120mm long cylindrical dome contact (3) into the cavity, place the short contact on the outside, align it with the measuring point and bring it close to the clamp foot (2), and read the dial indicator (8) reading as 0.95mm.

[0034] Calculation result: Actual thickness = 5mm + (1mm - 0.95mm) = 5.10mm.

[0035] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A vernier caliper that can be modified without damage, characterized in that: The vernier caliper body (1) includes a cylindrical ball-shaped contact (3) fixedly connected to the lower ends of the two feet (2) of the vernier caliper body (1). The actual working length of the cylindrical ball-shaped contact (3) is greater than the height of the side wall of the cavity to be measured. A support block (5) is slidably arranged on the main scale (4) of the vernier caliper body (1). The support block (5) is set to apply a predetermined pre-pressure stroke to the dial indicator (8) when zeroing and keep the stroke unchanged during measurement. A positioning block (7) is fixedly connected to the secondary scale (6) of the vernier caliper body (1). A dial indicator (8) is fixedly installed on the positioning block (7).

2. The vernier caliper with non-destructive modification according to claim 1, characterized in that: The caliper body (1) has a detachable and fixed connection between the caliper foot (2) and the cylindrical ball-shaped contact (3). The two ends of the caliper foot extension block (9) are respectively adapted to the caliper foot (2) and the cylindrical ball-shaped contact (3).

3. The vernier caliper with non-destructive modification according to claim 1, characterized in that: The two cylindrical dome contacts (3) have different length specifications, and the working length of the longer cylindrical dome contact (3) is defined as the actual working length.

4. The vernier caliper with non-destructive modification according to claim 2, characterized in that: The materials of the extended foot block (9), cylindrical dome contact (3), support block (5) and positioning block (7) are all 45# steel, and the surfaces of the above components are all subjected to quenching and bluing treatment in sequence.

5. A vernier caliper with non-destructive modification according to claim 2, characterized in that: The clamping foot (2) and the clamping foot extension block (9), the clamping foot extension block (9) and the cylindrical ball head contact (3), the vernier scale (6) and the positioning block (7), and the positioning block (7) and the dial indicator (8) are all connected by insert screws (10); the contact parts of the insert screws (10) and the dial indicator (8) and the contact parts of the insert screws (10) and the vernier caliper body (1) are all padded with soft copper pads (11).

6. The vernier caliper with non-destructive modification according to claim 1, characterized in that: The graduation value of the dial indicator (8) is 0.01 mm, and the accuracy of the vernier caliper body (1) is 0.02 mm or 0.05 mm.

7. A method for measuring the wall thickness of a narrow cavity bottom using a vernier caliper with non-destructive modification as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Zero the dial indicator (8) using a standard gauge block (12): S11. Select standard gauge blocks (12) of the corresponding specifications based on the estimated size of the bottom wall thickness of the cavity to be measured. S12. Make the two cylindrical dome contacts (3) come into close contact with the measuring surface of the standard gauge block (12), move the support block (5) on the main scale (4) so ​​that the contact of the dial indicator (8) contacts the working surface of the positioning block (7) and is compressed to the 1mm range, that is, the small pointer of the dial indicator (8) points to the "1" scale line. Then adjust the long pointer of the dial indicator (8) to the zero scale line, and fasten the support block (5) to the current position of the main scale (4) by inserting the screw (10). Loosen the clamp (2) and remove the standard gauge block (12) to complete the zeroing. S2. Perform measurements and calculate results: S21. Keep the dial indicator (8) in a fixed position, slide the auxiliary scale (6) to drive the positioning block (7) and the dial indicator (8) to move back to the preset position. The distance of the preset position is greater than the sum of the estimated dimensions of the total length of the two cylindrical ball-shaped contacts (3), the height of the cavity sidewall and the thickness of the cavity bottom wall by more than 5 mm. Insert the longer cylindrical ball-shaped contact (3) into the cavity and place the shorter cylindrical ball-shaped contact (3) outside the cavity. After aligning the two cylindrical ball-shaped contacts (3) with the measurement point, move them inward toward the locking foot (2) and read the value of the dial indicator (8). S22. Calculate the cavity bottom wall thickness according to the formula "actual thickness = standard gauge block (12) specification + (1mm - dial gauge (8) reading)" and record the data.

Images