Method for measuring the tooth width of a negative angle trapezoidal thread and device therefor

Abstract

The application discloses a negative angle trapezoidal thread tooth width measuring method and device, comprising the following steps: 1) confirming the design parameters of thread tooth profile; 2) producing a tooth width standard sample according to the design parameters in step 1); 3) producing a tooth width instrument according to the tooth width standard sample in step 2); 4) zeroing the tooth width instrument with the tooth width standard sample as a reference; 5) measuring the tooth width data of the thread tooth profile by using the tooth width instrument; and 6) converting the measured tooth width data into actual tooth width S. The application realizes quick and accurate negative angle trapezoidal thread tooth width parameter measurement, and operation will be more convenient, quick and accurate.

Description

Technical Field

[0001] This invention relates to threaded connection measurement technology in oil pipeline engineering, and more specifically, to a method and apparatus for measuring the tooth width of a negative angle trapezoidal thread. Background Technology

[0002] In the oil and gas extraction process, pipelines are used to transport underground oil and gas to the surface. These pipelines are generally composed of steel pipes connected by threads, which are called oil casing threaded joints. With technological advancements, the types of oil casing threaded joints are increasing, among which negative angle trapezoidal threads are increasingly used in special thread products. Negative angle trapezoidal threads have strong load-bearing capacity and are more likely to ensure stable joint performance under high tensile and bending loads, avoiding joint slippage and failure.

[0003] During thread machining, it is typically necessary to measure various thread parameters to ensure the thread meets requirements. For conventional threads, parameters such as tooth height, pitch, and tooth width need to be measured. However, for negative angle threads, existing tooth width tables are affected by the shape characteristics of negative angles, such as… Figure 1 As shown, thread parameters such as tooth width cannot be accurately measured. However, for oil casing threaded joints with very high safety performance requirements, thread parameters such as tooth width are very important, so accurate measurement is necessary; especially for special threaded joint products with double-thread quick-connect features and high-speed engagement characteristics, tooth width error will directly affect the thread engagement state.

[0004] Existing patent applications, such as Chinese Patent 201610710359.7, describe a method for measuring the geometric parameters of the thread profile in online machining of large-diameter multi-start thread ring gauges. This method involves locking the machining equipment and adjusting the part's measurement reference; using an internal micrometer to measure the minor diameter D1 of the composite thread to determine the minor diameter D1 (measurement); acquiring thread profile data via laser scanning; fitting and calculating the measured values ​​P (measurement) of the thread pitch P and θ (measurement) of the thread profile angle θ; selecting a suitable diameter steel ball to calibrate the side head through theoretical thread profile size calculation; measuring the thread by marking points to determine the machining allowance d and calculating the machining amount; measuring the actual pitch diameter of the thread by marking points to obtain all geometric parameters of the thread profile of the large-diameter multi-start internal thread ring gauge. Using the measurement method of this invention, the thread profile parameters of the ring gauge can be checked on-site during ring gauge machining, providing the parameters to machining personnel for high-precision machining, ensuring the ring gauge yield, and providing high detection accuracy. This method is applicable to all specifications of large-diameter multi-start internal thread ring gauges.

[0005] Chinese Patent No. 201711236551.8 discloses a method for measuring the tooth thickness of gears based on line structured light, belonging to the fields of precision testing technology and instruments, and gear detection technology. After installing the measured gear, the center of the coordinate system is calibrated with a line laser probe. The design datum of the measured gear is selected as the measurement datum, and more than 4 teeth evenly distributed on the gear are selected according to the gear parameters, and 3 evenly distributed cross-sections are taken for each tooth as the measurement positions. Obtaining data: Calculate the parameters required for installing the two probes and the relationships between the parameters according to the parameters of the measured gear, establish the coordinate systems of the two line structured light probes, and start obtaining the data of the two sides of the tooth. Establish the spatial coordinate transformation formula for obtaining data based on the installation parameters and measurement data, and transform the measurement values of each group in the probe coordinate system to the gear design center. Establish a mathematical model of tooth thickness deviation, and then achieve high-precision measurement of tooth thickness deviation, chord tooth thickness, and average deviation of single tooth thickness.

[0006] Chinese Patent No. 202021603841.9 introduces a measuring instrument for the tooth thickness of the buttress thread of oil pipes. The device body is provided with a profiling groove, and an indicating gauge, a lever mechanism, and a reset device are sequentially arranged in the profiling groove in a "C" shape. The indicating gauge, the lever mechanism, and the reset device are located in the profiling groove and connected to the body; the body is provided with an installation groove for installing a limiting device, and the installation groove of the limiting device and the installation groove of the reset device are arranged in a "one" shape, and there is a gap between the two installation grooves; a bottom plate is fixedly installed on one side of the installation grooves of the reset device and the limiting device of the body, a fixed probe is fixedly connected to the bottom plate, and the measuring probe and the limiting contact of the limiting device are respectively located on both sides of the fixed probe; the measuring probe and the limiting contact respectively extend out from the measuring hole and the limiting hole of the bottom plate, and the measuring probe, the fixed probe, and the limiting contact are in a straight line. Its beneficial effects are reasonable design, convenient operation, high work efficiency, and can ensure the accuracy of the tooth thickness measurement of the buttress thread.

[0007] Chinese Patent No. 202020856123.6 discloses a tooth thickness measuring tool for an internal gear ring, including a measuring caliper arranged inside the internal gear ring body. The two sides of the bottom of the measuring caliper are respectively fixedly connected with a first fixing plate and a second fixing plate. One side of the bottoms of the first fixing plate and the second fixing plate are both slidably connected with telescopic rods, and a reset spring is installed at the center of each of the two chutes. The inner sides of the first fixing plate and the second fixing plate are both slidably connected with measuring plates, and two fixed shafts are fixedly connected to the inner walls of the first fixing plate and the second fixing plate respectively. The outer walls of the plurality of fixed shafts are sleeved with telescopic springs. In the present utility model, the tooth thickness measuring tool for the internal gear ring not only has a quick positioning mechanism but also has an elastic measuring mechanism, which can not only quickly position according to the size of the internal gear ring but also quickly measure the tooth thickness of the internal gear ring, thereby greatly improving its work efficiency and being worthy of strong promotion.

[0008] Chinese Patent 201120247457.4 discloses a tooth thickness measuring tool, particularly relating to a tooth thickness measuring tool for small-angle variable-tooth-thickness gears. A fixed jaw is fixed to the left end of the main scale, and a fixed probe is located inside the lower end of the fixed jaw. A sliding jaw is slidably engaged with the main scale at the other end of the main scale, and a movable probe is located inside the lower end of the sliding jaw. A height gauge sliding frame is slidably engaged with the main scale. One end of an extension rod is fixed to the height gauge sliding frame, and a height gauge slider is fitted onto the other end of the extension rod. A height gauge is mounted on the height gauge slider. This tool can not only measure the tooth thickness of small-angle variable-tooth-thickness gears with arbitrary cross-sections but also conveniently solves problems in any situation.

[0009] Chinese Patent 202021007837.6 describes a tooth measuring device for measuring tooth width. Addressing the problems of existing tooth width measuring devices having limited functionality, being inconvenient for measuring teeth with large curvatures, and having large measurement errors, the following solution is proposed: It includes a measuring base, a gear on one side of which multiple teeth are fixedly connected; a mounting hole on one side of the measuring base, in which a fixing plate is fixedly installed; a measuring hole on one side of the fixing plate; and a sliding hole on one side of the measuring base, in which a sliding plate is slidably installed; a measuring ruler is fixedly installed on one side of the sliding plate and slidably installed within the measuring hole. This utility model has a reasonable structure, is easy to operate, and offers comprehensive functionality, facilitating the measurement of teeth with different inclinations, with minimal measurement error.

[0010] Although these patents use different methods to measure thread width, they still have limitations in the following two cases when measuring the width of negative angle trapezoidal threads:

[0011] In scenario one, most of these measurement methods and devices measure from a direction perpendicular to the thread. While this facilitates direct reading of tooth width data, it is easily affected by direction and angle. When the measurement direction deviates from the perpendicular direction to the thread, it will cause measurement errors, especially for tooth profiles with a helix angle, where the impact will be particularly significant. Figure 1 As shown;

[0012] In the second scenario, a negative angle tooth surface can interfere with the measuring device, affecting the tooth width measurement results. Figure 2 As shown. Summary of the Invention

[0013] In view of the above-mentioned defects in the existing technology, the purpose of this invention is to provide a method and device for measuring the tooth width of a negative angle trapezoidal thread, so as to realize the measurement of the tooth width parameter of a negative angle trapezoidal thread quickly and accurately, and the operation will be more convenient, faster and more accurate.

[0014] To achieve the above objectives, the present invention adopts the following technical solution:

[0015] On the one hand, a method for measuring the tooth width of a negative angle trapezoidal thread includes the following steps:

[0016] 1) Confirm the design parameters of the thread tooth profile;

[0017] 2) Fabricate a standard tooth width sample block according to the design parameters described in step 1);

[0018] 3) Fabricate a tooth width instrument based on the tooth width standard sample block described in step 2);

[0019] 4) Zero the tooth width instrument using the tooth width standard sample block as a reference;

[0020] 5) Use the aforementioned tooth width gauge to measure the tooth width data of the thread profile;

[0021] 6) Convert the measured tooth width data into the actual tooth width S.

[0022] Preferably, in step 1), the design parameters include tooth height h, pitch p, guide surface tooth profile angle α, bearing surface tooth profile angle β, and tooth root width t.

[0023] Preferably, in step 3), the tooth width instrument has a spherical measuring contact;

[0024] The diameter d of the measuring contact must satisfy:

[0025]

[0026] Preferably, in step 5), the relative amount δ of the measuring contact relative to the tooth width standard sample block also needs to be confirmed.

[0027] Preferably, in step 6), the actual tooth width S is converted as follows:

[0028] S = (tanα - tanβ) * δ.

[0029] On the other hand, a negative angle trapezoidal thread tooth width measuring device includes a tooth width gauge;

[0030] The tooth width instrument includes a dial, a connecting rod, a base, and a measuring contact.

[0031] The dial is located above the base, the measuring contact is located below the base, and the connecting rod is arranged perpendicular to the base and passes through the base;

[0032] The upper end of the connecting rod is connected to the dial, and the lower end is connected to the measuring contact.

[0033] The tooth width instrument is manufactured by performing steps 1) to 3) of the negative angle trapezoidal thread tooth width measurement method.

[0034] The tooth width gauge is used to measure the tooth width data of the thread tooth profile;

[0035] The tooth width data obtained from the tooth width gauge is converted into the actual tooth width S.

[0036] Preferably, the cross-section of the connecting rod is circular;

[0037] The measuring contact is spherical.

[0038] Preferably, the cross-sectional diameter of the connecting rod is smaller than the diameter of the measuring contact.

[0039] The present invention provides a method and apparatus for measuring the tooth width of a trapezoidal thread with a negative angle, which avoids the problem of difficulty in measuring trapezoidal threads with a negative angle and improves the accuracy and efficiency of measurement. Because this patent uses a spherical contact, there is no difference in the circumferential direction, avoiding the limitation of existing measurement methods that have high requirements for directionality, making the measurement simpler and easier, while solving the problem of difficulty in measuring negative angles. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of scenario one in the prior art;

[0041] Figure 2 This is a schematic diagram of scenario two in the prior art;

[0042] Figure 3 This is a flowchart illustrating the negative angle trapezoidal thread tooth width measurement method of the present invention;

[0043] Figure 4 This is a schematic diagram of the design parameters in step 1) of the negative angle trapezoidal thread tooth width measurement method of the present invention;

[0044] Figure 5 This is a schematic diagram of step 3) tooth width measurement using a tooth width instrument in the negative angle trapezoidal thread tooth width measurement method of the present invention;

[0045] Figure 6 This is a schematic diagram of the negative angle trapezoidal thread width measuring device of the present invention. Detailed Implementation

[0046] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0047] Combination Figure 3 As shown, the present invention provides a method for measuring the tooth width of a negative angle trapezoidal thread. By improving the thread tooth width measurement method, the measurement is changed from the tooth width direction to the tooth height direction, thus realizing the tooth width measurement of a negative angle trapezoidal thread. Specifically, the method includes the following steps:

[0048] 1) Confirm the design parameters of the thread tooth profile. These parameters include tooth height h, pitch p, guide surface tooth profile angle α, bearing surface tooth profile angle β, and tooth root width t, etc. Figure 4 As shown;

[0049] 2) Fabricate a standard tooth width sample block according to the design parameters in step 1) to serve as a measurement reference;

[0050] 3) Construct a tooth width gauge based on the tooth width standard sample block from step 2), wherein: the tooth width gauge has a spherical measuring contact 4. To avoid the measuring contact 4 contacting the tooth root and thus affecting the measurement result, the diameter d of the measuring contact 4 must satisfy:

[0051] like Figure 5 As shown;

[0052] 4) Zero the tooth width instrument using the tooth width standard sample block as a reference;

[0053] 5) Use a tooth width meter to measure the tooth width data of the thread tooth profile and confirm the relative amount δ of the measuring contact relative to the tooth width standard sample;

[0054] 6) Convert the measured tooth width data into the actual tooth width S. The conversion formula is as follows:

[0055] S = (tanα - tanβ) * δ.

[0056] Combination Figure 6 As shown, a negative angle trapezoidal thread tooth width measuring device includes the tooth width instrument in the negative angle trapezoidal thread tooth width measuring method of the present invention.

[0057] The tooth width instrument includes a dial 1, a connecting rod 2, a base 3, and a measuring contact 4.

[0058] The dial 1 is located above the base 3, the measuring contact 4 is located below the base 3, and the connecting rod 2 is set perpendicular to the base 3 and passes through the base 3.

[0059] The upper end of the connecting rod 2 is connected to the dial 1, and the lower end is connected to the measuring contact 4.

[0060] The cross-section of connecting rod 2 is circular, and the measuring contact 4 is spherical. The diameter of the cross-section of connecting rod 2 is smaller than the diameter of the measuring contact 4 to avoid interference between connecting rod 2 and the negative angle bearing surface.

[0061] During use, the base 3 rests against the top of the thread or sample block tooth for measurement or calibration. The measuring contact 4 contacts the tooth surfaces on both sides (guide surface and bearing surface) for measurement, and the measurement results are fed back to the dial 1 through the connecting rod 2. Finally, the data is read through the dial 1.

[0062] Example

[0063] The tooth width parameter of a double-start thread was measured. The thread design parameters are as follows:

[0064] Tooth height h = 2.0 mm;

[0065] Pitch p = 6.35 mm;

[0066] The guide surface tooth profile angle α = 60°;

[0067] The tooth profile angle β on the bearing surface is 5.71°;

[0068] Tooth root width t = 1.44 mm.

[0069] Based on the above thread parameters, a standard sample block for tooth width and a tooth width instrument were developed, in which the diameter of measuring contact 4 was selected as d = 2.2 mm and the diameter of connecting rod 2 was < 1.5 mm.

[0070] After zeroing the tooth width instrument with the tooth width standard sample block, the reading displayed on dial 1 after measurement is 0.03mm, so the actual tooth width measurement result is 0.049mm.

[0071] After zeroing the tooth width instrument with the tooth width standard sample block, the reading displayed on dial 1 after measurement is -0.02mm, so the actual tooth width measurement result is -0.033mm.

[0072] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method of measuring the width of a negative angle trapezoidal thread, characterized by, The negative angle trapezoidal thread tooth width measurement method is based on a negative angle trapezoidal thread tooth width measurement device, which comprises a tooth width instrument, the tooth width instrument comprising a dial, a connecting rod, a base and a measurement contact head; The dial is located above the base, the measurement contact head is located below the base, and the connecting rod is arranged perpendicularly to the base and passes through the base; The upper end of the connecting rod is connected to the dial, and the lower end is connected to the measurement contact head, The negative angle trapezoidal thread tooth width measurement method comprises the following steps: 1) confirming the design parameters of the thread tooth profile, the design parameters comprising tooth height h, pitch p, guide surface tooth profile angle α, load surface tooth profile angle β and tooth bottom width t; 2) producing a tooth width standard block according to the design parameters in step 1) for use as a measurement reference; 3) producing a tooth width instrument according to the tooth width standard block in step 2), the tooth width instrument having a spherical measurement contact head thereon; The diameter d of the measurement contact head needs to meet: ； 4) zeroing the tooth width instrument with the tooth width standard block as the reference; 5) measuring the tooth width data of the thread tooth profile using the tooth width instrument and confirming the relative amount δ of the measurement contact head relative to the tooth width standard block; 6) converting the measured tooth width data into actual tooth width S according to the following conversion formula: ， The tooth width instrument is produced by performing steps 1) to 3), The tooth width instrument is used to measure the tooth width data of the thread tooth profile; The tooth width data measured by the tooth width instrument is converted into actual tooth width S.

2. The method of measuring the width of a negative trapezoidal thread flank according to claim 1, wherein: The cross section of the connecting rod is circular; The measurement contact head is spherical.

3. The method of measuring the width of a negative trapezoidal thread flank according to claim 2, wherein: The cross section diameter of the connecting rod is smaller than the diameter of the measurement contact head.

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