A measuring device for measuring the radius of an incomplete concave arc and a method for using the same

Abstract

The present invention discloses a measuring device for the radius size of an incomplete concave circular arc and a method for using the same. The present invention comprises a positioning sleeve, wherein an inner hole is provided in the positioning sleeve, and an opening is provided at the top of the right end of the positioning sleeve; at the opening section of the right end of the positioning sleeve, a through end D5 inner hole is provided at the bottom of the right end, and a stop end D4 inner hole is provided next to the through end D5 inner hole; a measuring rod is inserted at the right end of the inner hole, and a D6 inner hole is provided vertically in the middle of the measuring rod, and a D7 through hole is provided horizontally, and a measuring head is provided in the D6 inner hole, and a waist-shaped groove is provided on the measuring head; the present invention also comprises a pin, which is inserted into the D7 through hole and the end of which is provided in the waist-shaped groove. The present invention has high measurement accuracy, is simple and convenient to use and store on site, has strong operability, low cost, and high measurement efficiency, and well solves the problem that the radius of an incomplete circular arc cannot be measured.

Description

Technical Field

[0001] The present invention relates to a technique for measuring the radius size of an incomplete concave arc, and in particular to a device for measuring the radius size of a concave arc of a shell part and other parts in the field of aviation engine machinery manufacturing, and a method for using the device. Background Art

[0002] With the continuous development of the company's military, civilian and foreign trade products, the inner wall of the shell part cavity needs to be processed with incomplete concave arcs of different sizes due to assembly requirements (processing space without interfering with assembly) (see attached Figure 1 As shown in the figure), the arc length of the concave arc processed is less than 1 / 2 of the entire arc circumference, and some shell parts have cavities (see the attached Figure 1 As shown in the figure, the size of the incomplete concave arc is relatively small, so the use of general measuring tools (such as: internal diameter gauge) and three-coordinate measuring machines cannot measure the radius of the incomplete concave arc (the incomplete concave arc has no symmetric surface and cannot be measured by the internal diameter gauge; the measuring probe of the three-coordinate measuring machine is too large to enter the cavity of the shell part). Even if the three-coordinate measuring machine can measure the radius of the incomplete concave arc with a large cavity size of the shell part, if the three-coordinate measuring machine is equipped to measure each part on site, not only will the processing cost be high and the operability be poor, but the arc length will be too short, and the error after the measured size fitting will be large, which will pose certain quality risks.

[0003] In order to ensure product quality and production delivery nodes, a measuring device for the radius size of incomplete concave arcs has been designed and manufactured by consulting relevant information and combining the structure and use of related parts. This measuring device not only has high measurement accuracy, is easy to use and store, but also can greatly save production costs, better ensure product quality and production nodes, and also fill the technical gap in measuring the radius size of incomplete concave arcs on the inner wall of the shell part cavity. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a device for measuring the radius size of an incomplete concave arc and a method for using the device.

[0005] The technical solution of the present invention is: a measuring device for the radius size of an incomplete concave arc and a method of using the same, comprising a positioning sleeve, wherein an inner hole is provided through the positioning sleeve, and an opening is provided at the top of the right end of the positioning sleeve; at the opening section of the right end of the positioning sleeve, a through end D5 inner hole is provided at the bottom of the right end, and a stop end D4 inner hole is provided next to the through end D5 inner hole; a measuring rod is inserted into the right end of the inner hole, an inner hole D6 is provided vertically in the middle of the measuring rod, a through hole D7 is provided horizontally, a measuring head is provided in the inner hole D6, and a waist-shaped groove is provided on the measuring head; and a pin is also provided, the pin is passed through the through hole D7 and the end of the pin is provided in the waist-shaped groove.

[0006] In the aforementioned measuring device for the radius size of an incomplete concave arc and the method for using the same, the left portion of the positioning sleeve is provided with an outer circle d1, the middle portion is provided with an outer circle d2, and the outer wall of the outer circle d2 is a conical surface 1.

[0007] In the aforementioned measuring device for the radius size of an incomplete concave arc and its use method, the inner hole at the outer circle d2 is the inner hole D3, and the fitting clearance between the inner hole D3 and the outer circle d3 on the left side of the measuring rod is 0.003 to 0.008; the fitting clearance between the inner hole D6 and the outer circle d6 of the measuring head is 0.003 to 0.008.

[0008] In the aforementioned measuring device for the radius size of an incomplete concave arc and the method for using the same, the inner hole of the through end D5 and the inner hole of the stop end D4 are transitioned through two conical surfaces.

[0009] In the aforementioned incomplete concave arc radius measuring device and its use method, the lengths of the inner holes of the through end D5 and the stop end D4 are each 1 / 2 of the length of the incomplete arc; the radius difference between the inner holes of the through end D5 and the stop end D4 is equal to the incomplete concave arc radius tolerance value.

[0010] In the aforementioned measuring device for the radius size of an incomplete concave arc and its using method, the pin and the D7 through hole are interference fit, and the interference amount is 0.01 to 0.02; the width groove E of the waist groove is 0.2 larger than the outer circle size of the pin d7.

[0011] In the aforementioned measuring device for the radius size of an incomplete concave arc and the use method thereof, the two ends of the measuring head are designed to be spherical.

[0012] In the aforementioned measuring device for the radius of an incomplete concave arc and its use method, the length H of the measuring head is equal to half of the inner hole size of the through end D5 plus the minimum value of the radius of the incomplete concave arc to be measured; the tolerance of H is ±0.01.

[0013] In the aforementioned measuring device for the radius of an incomplete concave arc and its use method, the length dimension K of the pin is smaller than the outer diameter dimension d3 of the measuring rod, and cannot protrude from the outer surface of the measuring rod after assembly.

[0014] A method for using a device for measuring the radius size of an incomplete concave arc comprises the following steps: firstly, a positioning sleeve is installed into a part hole of a part to be measured from the opposite side of the center hole of the incomplete arc to be measured until it abuts against the incomplete arc, and an opening on the positioning sleeve is aligned with the incomplete arc to be measured; a measuring rod assembly composed of a measuring rod, a measuring head and a pin is installed into the positioning sleeve from the right open end of the inner hole of the positioning sleeve, and the measuring head is placed into the inner hole of the through end D5; a knurled handle arranged at the right end of the measuring rod is held by hand and rotated back and forth in the radial direction within the effective arc length of the incomplete arc, and at the same time, the measuring rod is rotated in the axial direction. Move the measuring rod back and forth. If the radial rotation and axial movement are flexible, that is, the inner hole of the through end D5 can pass through, and then move the measuring head to 1 / 2 of the opening of the positioning sleeve, if the measuring head can no longer move axially and cannot rotate radially, that is, the measuring head cannot pass through the inner hole of the stop end D4 of the positioning sleeve, then the incomplete arc radius size of the measured part is judged to be qualified; on the contrary, if the measuring head can continue to move axially to the stop at the opening of the positioning sleeve and can also rotate radially, then the incomplete arc radius size of the measured part is judged to be unqualified.

[0015] Beneficial Effects

[0016] 1. It has been proved through use that the measuring device can measure the radius of incomplete arcs with high measurement accuracy, simple and convenient on-site use and storage, strong operability, low cost, high measurement efficiency, and well solves the problem of incomplete arc radius measurement, filling a technical gap in measurement for our company and even the same industry. The invention has been promoted and applied internally in the processing of various parts with incomplete arcs in the company, and the on-site use effect is excellent, and the satisfaction of production branches and customers has been greatly improved. With the continuous development of our company's products, the invention has great promotion and application value.

[0017] 2. The present invention has a simple structure, reasonable design and the following characteristics:

[0018] (1) According to the characteristic that the positioning hole of the housing is a stepped hole structure, the present invention adopts the method of positioning the outer circle with a small taper (eliminating the gap) and positioning the outer circle with a small gap cylinder (ensuring the positioning accuracy) to design the positioning sleeve. The designed positioning sleeve has the characteristics of simultaneous positioning of the outer circle and the conical surface, thereby eliminating the gap and ensuring the positioning accuracy.

[0019] (2) The present invention provides the size requirement of the inner hole D3 within the length of the conical surface 1 on the positioning sleeve. The hole is used to install the measuring rod. The clearance between the inner hole D3 and the outer circle of the measuring rod d3 is set to 0.003-0.008, and the coaxiality between the conical surface 1 and the outer circle d1 is φ0.02. In this way, when the positioning sleeve and the measuring rod are matched, the measurement accuracy can be guaranteed while the flexibility of installing the measuring rod can be guaranteed.

[0020] (3) The present invention provides two sizes of the through end (with the largest radius of the incomplete concave arc) D5 inner hole and the stop end (with the smallest radius of the incomplete concave arc) D4 inner hole and the conical surface within the length range corresponding to the incomplete concave arc to be measured on the positioning sleeve. The lengths of the D5 inner hole and the D4 inner hole each account for approximately 1 / 2 of the length of the incomplete concave arc. In this way, the incomplete concave arc to be measured of the shell part can be accurately measured.

[0021] (4) The coaxiality between the inner hole of the through end D5 and the inner hole of the stop end D4 and the outer circle of d1 is φ0.02. A small taper surface 2 should be designed between the inner hole of the through end D5 and the inner hole of the stop end D4 for transition, which can ensure that the measuring head can move back and forth freely along the axial direction.

[0022] (5) The present invention cuts the inner hole of the through end D5 and the inner hole of the stop end D4 within the length range of the incomplete concave arc of the shell part to be measured, and the section A must be set to pass through the center. This is convenient for processing and can better ensure the size and shape and position tolerance requirements of the inner hole D5 and the inner hole D4. On the other hand, the measuring head needs to move in and out during measurement, which also makes it convenient to observe the radial rotation, axial movement and position of the measuring head during measurement.

[0023] (6) When designing the locating sleeve, the present invention has determined that the clearance between the outer circle size of d3 and the inner hole of the locating sleeve D3 is 0.003 to 0.008; the L size is required to ensure that the measuring head can be in full contact with the inner hole of the locating sleeve D3 when moving axially when measuring the incomplete concave arc of the shell part.

[0024] (7) The clearance between the inner hole D6 of the present invention and the outer circle of the measuring head d6 is determined to be 0.003-0.008, which can ensure both the measurement accuracy and the flexibility of installing the measuring head.

[0025] (8) The through hole D7 of the present invention and the outer circle of the pin d7 are designed to be interference fit, and the interference is determined by 0.01 to 0.02. In this way, the structure of the present invention is firm and the pin is not easy to fall out.

[0026] (9) The present invention designs the two ends of the measuring head to be spherical, which ensures that the measuring head is in effective contact with the incomplete concave arc of the shell part to be measured and the generatrix of the inner hole of the through end D5 and the inner hole of the stop end D4 of the positioning sleeve, so that the measurement result is accurate.

[0027] (10) A waist-shaped groove is designed on the measuring head of the present invention to ensure flexible movement of the measuring head.

[0028] (11) The design of the measuring head of the present invention ensures that the clearance between the outer circle d6 and the hole D6 of the measuring rod is within the range of 0.003 to 0.008; the size of the groove E should be 0.2 larger than the outer circle size of the pin d7; the sizes of H1 and H2 should ensure that the measuring head can move freely in the inner hole of the measuring rod 2D6 with sufficient travel without being able to escape from the measuring rod; the size H is equal to half of the basic size of the inner hole D5 of the positioning sleeve plus the minimum value of the radius of the incomplete concave arc of the measured shell part; considering the measurement requirements and the economy of measuring tool manufacturing, the size tolerance of H is given as ±0.01.

[0029] (12) The length dimension K of the pin of the present invention should be smaller than the outer diameter dimension of the measuring rod d3 and should not protrude from the outer surface of the measuring rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0031] Figure 1 is a schematic diagram of the shell part to be tested; the upper left figure in the figure is a front view of the shell to be tested, the upper right figure is a side view of the shell to be tested, and the lower right figure is a cross-sectional view of AA in the upper right figure;

[0032] Figure 2 is a schematic diagram of the measuring device of the present invention;

[0033] Figure 3 It is a schematic diagram of the positioning hole and incomplete arc of the shell parts;

[0034] Figure 4 It is a schematic diagram of the structure of the positioning sleeve;

[0035] Figure 5 It is a schematic diagram of the structure of the measuring rod;

[0036] Figure 6 It is a schematic diagram of the structure of the measuring head;

[0037] Figure 7 It is a schematic diagram of the structure of the pin;

[0038] Figure 8 It is a schematic diagram of the structure of the measuring device when measuring parts;

[0039] The markings in the attached drawings are: 1-positioning sleeve; 2-measuring rod; 3-measuring head; 4-pin; 5-edge of the housing part cavity; 6-incomplete concave arc; 7-conical surface one; 8-conical surface two; 9-opening; 10-stop hole; 11-through hole; 11-; a-axial movement; b-radial rotation; c-clearance (0.003-0.008). DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0041] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0042] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0043] In addition, the terms "installed", "set", "provided with", "connected", "connected", and "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0044] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0045] Embodiment. A device for measuring the radius of an incomplete concave arc, the structure of which is as follows: Figure 2-8As shown, it includes a positioning sleeve 1, in which an inner hole is set through, and an opening is provided at the top of the right end of the positioning sleeve 1; at the opening section of the right end of the positioning sleeve 1, a through end D5 inner hole is provided at the bottom of the right end, and a stop end D4 inner hole is provided next to the through end D5 inner hole; a measuring rod 2 is inserted into the right end of the inner hole, and a D6 inner hole is vertically provided in the middle of the measuring rod 2, and a D7 through hole is horizontally provided, a measuring head 3 is provided in the D6 inner hole, and a waist-shaped groove is provided on the measuring head 3; it also includes a pin 4, which is penetrated in the D7 through hole and the end of which is arranged in the waist-shaped groove.

[0046] The unit of dimensions involved in this embodiment is: mm.

[0047] The positioning sleeve 1, measuring rod 2, measuring head 3 and pin 4 in this embodiment are specifically designed as follows

[0048] 1. Design of positioning sleeve 1

[0049] The design of the positioning sleeve 1 is shown in the attached Figure 4 Since the inner hole of the shell part to be tested is a stepped hole (see attached Figure 3 As shown in the figure, and each hole ring is very narrow, so the inner hole D1 farthest from the measured incomplete concave arc R and the inner hole D2 closest to the measured incomplete concave arc R are selected as simultaneous positioning holes. The inner hole D1 farthest from the measured R is positioned by a small gap with the outer circle of d1, and the inner hole D2 closest to the measured R is positioned by using the outer circle of d2 as a cone surface 1. The simultaneous positioning of the outer circle of d1 and the cone surface 1 can eliminate the gap and ensure the positioning accuracy. The coaxiality of the cone surface 1 and the outer circle of d1 is φ0.02.

[0050] The dimension requirement of the inner hole D3 is given within the length of the conical surface on the positioning sleeve 1. This hole is used to install the measuring rod 2. In order to ensure the measurement accuracy, the flexibility of installing the measuring rod 2 must be ensured. The inner hole D3 and the outer circle of the measuring rod 2d3 (see attached Figure 5 (As shown) The fit clearance is generally determined as 0.003~0.008, and the coaxiality with the outer circle of d1 is φ0.02.

[0051] The through end (with the largest radius of the incomplete concave arc) D5 inner hole and the stop end (with the smallest radius of the incomplete concave arc) D4 inner hole and the dimensions of the tapered surface 2 are given on the positioning sleeve 1 within the length range corresponding to the incomplete concave arc of the shell part being measured. The lengths of the D5 inner hole and the D4 inner hole are approximately 1 / 2 of the length of the incomplete concave arc. Since the tolerance of the incomplete concave arc of the shell part being measured is generally large, the manufacturing tolerances of the D4 inner hole and the D5 inner hole are given according to the H7 tolerance. The difference between the values ​​is equal to the tolerance value of the radius of the incomplete concave arc of the shell part being measured, which is expressed by the formula:

[0052] (D5-D4) / 2=ρ

[0053] Where: D5 - basic size of through hole

[0054] D4 ----- Basic size of stop hole

[0055] ρ ----- Tolerance of the radius R of the incomplete concave arc of the part

[0056] The coaxiality between the inner hole of the through end D5 and the inner hole of the stop end D4 and the outer circle of d1 is φ0.02. A small taper should be designed between the inner hole of the through end D5 and the inner hole of the stop end D4 to ensure that the measuring head 3 (see attached Figure 6 The inner hole of the through end D5 and the inner hole of the stop end D4 are cut within the length range of the incomplete concave arc of the measured shell part. The cut surface A must pass through the center. On the one hand, it is convenient to better ensure the size and shape and position tolerance requirements of the inner hole of D5 and the inner hole of D4 during processing. On the other hand, the measuring head 3 needs to move in and out during measurement, which is also convenient for observing the radial rotation, axial movement and position of the measuring head 3 during measurement.

[0057] 2. Design of measuring rod 2

[0058] The design of measuring rod 2 is attached Figure 5 When designing the positioning sleeve 1, the outer diameter of d3 and the inner hole of the positioning sleeve 1D3 (see attached Figure 4 The clearance is 0.003~0.008; the L dimension should ensure that the measuring head 3 is in full contact with the inner hole of the positioning sleeve 1D3 when measuring the incomplete concave arc of the shell part; in order to ensure the measurement accuracy and the flexibility of the measuring head 3, the inner hole of D6 and the outer circle of the measuring head 3d6 (see the attached Figure 6 The clearance is generally determined as 0.003 to 0.008. To ensure that the structure is firm and the pin 4 is not easy to fall out, the D7 through hole and the outer circle of the pin 4d7 (see the attached Figure 7 The design is an interference fit, and the interference amount is generally determined as 0.01 to 0.02.

[0059] 3. Design of measuring head 3

[0060] The design of measuring head 3 is attached Figure 6 In order to ensure that the measuring head 3 is in effective contact with the incomplete concave arc of the shell part and the inner hole of the through end D5 and the inner hole of the stop end D4 of the positioning sleeve 1, so as to make the measurement result accurate, the two ends of the measuring head 3 are designed to be spherical; the outer circle d6 is in contact with the hole D6 of the measuring rod 2 (see attached Figure 5 The clearance should be within 0.003~0.008; the size of slot E should be larger than the outer circle of pin 4d7 (see attached Figure 7 The size of H1 and H2 should be 0.2 larger than that of the measuring rod 2D6; the size of H1 and H2 should be able to ensure that the measuring head 3 can move freely in the inner hole of the measuring rod 2D6 with sufficient travel without slipping out of the measuring rod 2; the size of H is equal to half of the basic size of the inner hole of the through end D5 of the positioning sleeve 1 plus the minimum value of the radius of the incomplete concave arc of the measured shell part, which can be expressed by the formula:

[0061] H=D5 / 2+Rmin.

[0062] Where: H ----- basic dimension of total length of measuring head 3

[0063] D5 ----- Basic size of through hole

[0064] Rmin ----- minimum value of the radius R of the incomplete concave arc of the part

[0065] In order to meet the measurement requirements and the economy of measuring tool manufacturing, the H dimension tolerance is given as ±0.01.

[0066] 4. Pin 4 design

[0067] See attached for the design of pin 4 Figure 7 When designing the measuring rod 2, the outer circle of d7 and the inner hole of the measuring rod 2D7 have been determined (see attached Figure 5 (as shown) is an interference fit with an interference amount of 0.01 to 0.02; the length dimension K should be smaller than the outer diameter dimension of the measuring rod 2d3 and cannot protrude from the outer surface of the measuring rod 2.

[0068] 5. Assembly of the measuring device

[0069] As attached Figure 2 As shown. The measuring head 3 is installed into the small hole of the measuring rod 2, the waist groove on the measuring head 3 must be aligned with the pin hole on the measuring rod 2, and the pin 4 is pressed from the pin hole to pass through the waist groove on the measuring head 3. After assembly, it must be ensured that the measuring head 3 moves flexibly along the waist groove without any jamming phenomenon; the assembled measuring rod 2 assembly is combined with the positioning sleeve 1, and the measuring device required by the present invention is obtained.

[0070] The method of using the measuring device for the radius size of the incomplete concave arc is as follows: Figure 8As shown, first install the positioning sleeve 1 from the opposite side of the center hole at the incomplete arc to be measured into the part hole of the part to be measured until it touches the top, and align the opening on the positioning sleeve 1 with the incomplete arc to be measured; install the assembled measuring rod 2 composed of the measuring rod 2, the measuring head 3 and the pin 4 into the positioning sleeve 1 from the right open end of the inner hole of the positioning sleeve 1, and put the measuring head 3 into the inner hole of the through end D5, hold the knurled handle set at the right end of the measuring rod 2 and rotate it back and forth in the radial direction within the effective arc length of the incomplete arc, and move the measuring rod 2 back and forth along the axial direction at the same time. If the radial rotation If the measuring head 3 can move axially and flexibly (through end), that is, the inner hole of the through end D5 can pass through, and then the measuring head 3 is moved to the 1 / 2 of the opening of the positioning sleeve 1, if the measuring head 3 can no longer move axially and can not rotate radially, that is, the measuring head 3 can not pass through the inner hole of the stop end D4 of the positioning sleeve 1 (the stop end does not pass), then the incomplete arc radius size of the measured part is judged to be qualified; on the contrary, if the measuring head 3 can continue to move axially to the stop at the opening of the positioning sleeve 1 and can also rotate radially, then the incomplete arc radius size of the measured part is judged to be unqualified. After being judged as unqualified, the radius size of the incomplete arc is too large, and the processing parameters should be adjusted to reduce the radius size of the incomplete arc.

[0071] The above is only a preferred specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent substitutions or changes according to the technical solution and concept of the present application within the technical scope disclosed in the present application, which should be covered by the protection scope of the present application.

Claims

1. A method for using a device for measuring the radius of an incomplete concave arc, characterized in that: The measuring device for the radius size of an incomplete concave arc comprises a positioning sleeve (1), wherein an inner hole is provided in the positioning sleeve (1), and an opening is provided at the top of the right end of the positioning sleeve (1); at the opening section of the right end of the positioning sleeve (1), a through end D5 inner hole is provided at the bottom of the right end, and a stop end D4 inner hole is provided next to the through end D5 inner hole; a measuring rod (2) is inserted into the right end of the inner hole, a D6 inner hole is provided vertically in the middle of the measuring rod (2), a D7 through hole is provided horizontally, a measuring head (3) is provided in the D6 inner hole, and a waist-shaped groove is provided on the measuring head (3); and a pin (4) is also provided, the pin (4) is inserted into the D7 through hole and the end portion is provided in the waist-shaped groove; the two ends of the measuring head (3) are designed to be spherical; The method for using the incomplete concave arc radius measuring device is as follows: first, the positioning sleeve (1) is installed into the part hole of the part to be measured from the opposite side of the center hole of the incomplete arc to be measured until it abuts against the incomplete arc to be measured, and the opening on the positioning sleeve (1) is aligned with the incomplete arc to be measured; the assembled measuring rod (2) assembly consisting of the measuring rod (2), the measuring head (3) and the pin (4) is installed into the positioning sleeve (1) from the right open end of the inner hole of the positioning sleeve (1), and the measuring head (3) is placed into the inner hole of the through end D5; the knurled handle provided at the right end of the measuring rod (2) is held by hand and rotated back and forth in the radial direction within the effective arc length of the incomplete arc, and the measuring rod (2) is rotated back and forth in the radial direction at the same time. When the measuring rod (2) is moved back and forth along the axial direction, if the radial rotation and axial movement are flexible, that is, the inner hole of the through end D5 can pass through, and then the measuring head (3) is moved to 1 / 2 of the opening of the positioning sleeve (1), if the measuring head (3) can no longer move along the axial direction and can no longer rotate along the radial direction, that is, the measuring head (3) can no longer pass through the inner hole of the stop end D4 of the positioning sleeve (1), then it is determined that the incomplete arc radius size of the measured part is qualified; on the contrary, if the measuring head (3) can continue to move along the axial direction to the stopper at the opening of the positioning sleeve (1) and can also rotate along the radial direction, then it is determined that the incomplete arc radius size of the measured part is unqualified.

2. The method for using the device for measuring the radius of an incomplete concave arc according to claim 1, characterized in that: The left portion of the positioning sleeve (1) is provided with an outer circle d1, the middle portion is provided with an outer circle d2, and the outer wall of the outer circle d2 is a conical surface 1.

3. The method for using the device for measuring the radius of an incomplete concave arc according to claim 2, characterized in that: The inner hole at the outer circle of d2 is the inner hole of D3, and the fitting clearance between the inner hole of D3 and the outer circle of d3 on the left side of the measuring rod (2) is 0.003-0.008; the fitting clearance between the inner hole of D6 and the outer circle of d6 of the measuring head is 0.003-0.

008.

4. The method for using the device for measuring the radius of an incomplete concave arc according to claim 1, characterized in that: The inner hole of the through end D5 and the inner hole of the stop end D4 are transitioned through a second conical surface.

5. The method for using the device for measuring the radius of an incomplete concave arc according to claim 1, characterized in that: The lengths of the inner holes of the through end D5 and the stop end D4 are respectively 1 / 2 of the length of the incomplete arc; the radius difference between the inner holes of the through end D5 and the stop end D4 is equal to the radius tolerance value of the incomplete concave arc.

6. The method for using the device for measuring the radius of an incomplete concave arc according to claim 1, characterized in that: The pin (4) and the D7 through hole are interference fit, and the interference amount is 0.01 to 0.02; the width groove E of the waist-shaped groove is 0.2 larger than the outer circle size d7 of the pin (4).

7. The method for using the device for measuring the radius of an incomplete concave arc according to claim 1, characterized in that: The length H of the measuring head (3) is equal to half the inner hole size of the through end D5 plus the minimum radius of the incomplete concave arc to be measured; the tolerance of H is ±0.

01.

8. The method for using the device for measuring the radius of an incomplete concave arc according to claim 1, characterized in that: The length dimension K of the pin (4) is smaller than the outer diameter dimension d3 of the measuring rod (2), and cannot protrude from the outer surface of the measuring rod (2) after assembly.

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