Internal thread measuring instrument for small hole long nut

Abstract

The utility model discloses a kind of internal thread measuring instrument suitable for small hole long nut in thread detection technical field, including main shaft module, confocal laser sensor and electric sliding table, confocal laser sensor is fixed in the bottom of electric sliding table by holder, holder includes the longer pipe than nut, wedge piece located in pipe and inner tube, pipe tail portion is equipped with internal thread, internal thread is equipped with cap inside, the confocal laser sensor is located in pipe, the wedge piece is located between the outer wall of confocal laser sensor and the inner wall of pipe, inner tube is located between the tail portion of wedge piece and cap, the cap is inwards to push inner tube, inner tube is tightly pressed between the outer wall of confocal laser sensor and the inner wall of pipe with wedge piece.This utility model installs confocal laser sensor in a pipe, so that confocal laser sensor has longer moving range, can be inserted into small hole long nut inside, satisfy the measurement demand of planetary roller screw pair nut.

Description

Technical Field

[0001] This utility model relates to the field of thread detection technology, and in particular to an internal thread measuring instrument suitable for long nuts with small holes. Background Technology

[0002] Planetary roller screw nuts are characterized by small pitch P ≥ 0.4 mm, small inner diameter D ≥ 12 mm, and some nuts also have a large length-to-diameter ratio L / D(max) = 7. Currently, the main method for inspecting internal threads is to use the stylus of a contact profilometer. However, this method is time-consuming, and the stylus may scratch the thread being measured, leading to rapid wear and increased replacement costs.

[0003] Currently, there are also some non-contact measurement methods, such as the internal thread parameter detection method and system disclosed in CN115900585A, which utilizes laser point cloud analysis technology. This system uses a line-scanning laser profilometer that rotates at a constant speed for over 360 degrees while simultaneously acquiring profile data. Through a registration algorithm, the system automatically filters out valid data within the 360-degree range and converts it into polar coordinate point cloud data. In subsequent processing, the system performs outlier removal, cylindrical fitting, and sawtooth wave fitting steps to accurately calculate parameters such as the major diameter, minor diameter, pitch diameter, pitch, and thread angle of the internal thread. Although this patent enables rapid measurement of internal threads, its design uses a nut for fixation, and the method of scanning the thread with a reflector limits its application in measuring the nut of planetary roller screw pairs with small inner holes and long nuts. Another invention patent, CN113375550A, introduces a non-contact internal thread detection device. This device utilizes an axially emitted spectral confocal laser sensor to measure the internal thread through a reflector. However, due to its structural characteristics, this device is also not suitable for measuring the nuts of planetary roller screw pairs with small inner bores and long nuts. Utility Model Content

[0004] To overcome the above-mentioned shortcomings of existing internal thread measurement methods, the technical problem to be solved by this utility model is to provide an internal thread measuring instrument suitable for long nuts with small holes.

[0005] The technical solution adopted by this utility model to solve its technical problem is:

[0006] An internal thread measuring instrument for small-hole long nuts includes a spindle module for vertically fixing and rotating the nut around its axis, a confocal laser sensor for detecting internal threads, and an electric slide for mounting and moving the confocal laser sensor along the nut's axis and radial direction. The confocal laser sensor is fixed to the bottom of the electric slide by a clamp. The clamp includes a circular tube longer than the nut, a wedge-shaped plate inside the circular tube, and an inner tube. The end of the circular tube has an internal thread, and a nut is installed inside the internal thread. The confocal laser sensor is located inside the circular tube. The wedge-shaped plate is located between the outer wall of the confocal laser sensor and the inner wall of the circular tube. The inner tube is located between the end of the wedge-shaped plate and the nut. The nut pushes the inner tube inward, and the inner tube presses the wedge-shaped plate against the outer wall of the confocal laser sensor and the inner wall of the circular tube, thus fixing the confocal laser sensor to the circular tube.

[0007] Furthermore, the spindle module includes a support base located at the bottom of the frame, a pneumatic chuck rotatably mounted on the top of the support base, and a spindle motor that drives the pneumatic chuck to rotate at the bottom of the support base.

[0008] Furthermore, the electric slide table includes a vertical slide table and a horizontal slide table. The vertical slide table is slidably mounted on the frame in a vertical direction via a vertical drive mechanism, and the horizontal slide table is slidably mounted at the bottom of the vertical slide table in a horizontal direction via a horizontal drive mechanism. The clamp is installed at the bottom of the horizontal slide table.

[0009] Furthermore, the sidewall of the circular tube has a strip-shaped opening along its length for the side where the confocal laser sensor detection head is located to be exposed.

[0010] Furthermore, a groove is provided on the inner wall of the side of the circular tube opposite to the strip opening, from the head to the middle, and the wedge-shaped plate is slidably disposed in the groove.

[0011] Furthermore, the middle part of the circular tube has an elongated waist-shaped hole on the side wall corresponding to the groove, and the tail of the wedge-shaped piece is located in the area of ​​the elongated waist-shaped hole, and the tail of the wedge-shaped piece has a small hole.

[0012] Furthermore, the clamp is fixed to the electric slide by a probe mounting base. The probe mounting base has a channel in the middle for the round tube to pass through, and a mounting cavity in the middle of the channel. A locking block is provided in the mounting cavity. A locking screw is provided on the side wall of the probe mounting base. The locking screw pushes the locking block inward to fix the round tube in the probe mounting base.

[0013] Furthermore, the measuring rod mounting base is provided with a guide screw on each side of the locking screw. A compression spring is provided between the head of the guide screw and the outer wall of the measuring rod mounting base. The two guide screws pass through the through hole on the measuring rod mounting base and are threadedly connected to the threaded holes at the upper and lower ends of the locking block, respectively.

[0014] Furthermore, an adapter plate is provided between the probe mounting base and the electric slide table. The probe mounting base and the adapter plate are connected by three connecting screws that are symmetrically arranged about their axes. The probe mounting base is provided with three set screws that are symmetrically arranged about their axes, and the upper end of the set screws abuts against the bottom of the adapter plate.

[0015] Furthermore, a three-dimensional force sensor is also provided between the adapter plate and the electric slide table. The controller for controlling the movement of the electric slide table is electrically connected to the three-dimensional force sensor and is configured to stop the movement of the electric slide table when the three-dimensional force sensor shows a change in force during the movement of the electric slide table.

[0016] The beneficial effects of this utility model are: by installing the confocal laser sensor inside a circular tube, the confocal laser sensor has a longer range of motion and can extend into the interior of a small-hole long nut, thus meeting the measurement requirements of the planetary roller screw pair nut; compared with the existing indirect measurement method through a reflector, this solution allows the measuring head of the confocal laser sensor to be directly close to the thread teeth, thereby improving measurement accuracy and reducing interference from outlier data. Attached Figure Description

[0017] Figure 1 This is a side view of the present invention;

[0018] Figure 2 This is a cross-sectional view of the clamp of this utility model;

[0019] Figure 3 This is a cross-sectional view of the clamp of this utility model;

[0020] Figure 4 This is a schematic diagram of the structure of the measuring rod mounting base of this utility model.

[0021] The diagram is labeled as follows: 1- Spindle module, 2- Confocal laser sensor, 3- Electric slide, 4- Nut, 5- Clamp, 6- Frame, 7- Probe mounting base, 8- Adapter plate, 9- Three-dimensional force sensor, 11- Pneumatic chuck, 12- Spindle motor, 13- Support base, 31- Vertical slide, 32- Horizontal slide, 51- Round tube, 52- Wedge plate, 53- Inner tube, 54- Nut, 55- Strip opening, 56- Groove, 57- Elongated oblong hole, 58- Small hole, 61- Vertical drive mechanism, 62- Horizontal drive mechanism, 71- Channel, 72- Mounting cavity, 73- Locking block, 74- Locking screw, 75- Guide screw, 76- Compression spring, 77- Threaded hole, 81- Connecting screw, 82- Set screw. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings.

[0023] It should be noted that if this utility model contains directional indicators such as up, down, left, right, front, and back, these terms are used to describe the relative positional relationships between components and are not specific references to the absolute positions of the components or the relationships between them. They are only used to explain the relative positional relationships and movement of the components in a specific posture. If the specific posture changes, the directional indicator will also change accordingly. If this utility model contains terms related to quantity such as "many," "multiple," or "several," these terms specifically refer to two or more.

[0024] like Figure 1-3 As shown, the present invention provides an internal thread measuring instrument suitable for small-hole long nuts, including a main spindle module 1 for vertically fixing and driving the nut 4 to rotate around its axis, a confocal laser sensor 2 for detecting internal threads, and an electric slide 3 for mounting and driving the confocal laser sensor 2 to move along the axis and radial direction of the nut 4. The confocal laser sensor 2 is fixed to the bottom of the electric slide 3 by a clamp 5, the clamp 5 including a circular tube 51 longer than the nut 4 and a wedge-shaped plate located inside the circular tube 51. The confocal laser sensor 2 is located inside the confocal laser sensor 2. The wedge-shaped plate 52 is located between the outer wall of the confocal laser sensor 2 and the inner wall of the confocal laser sensor 2. The inner tube 53 is located between the tail of the wedge-shaped plate 52 and the nut 54. The nut 54 pushes the inner tube 53 inward, and the inner tube 53 presses the wedge-shaped plate 52 against the outer wall of the confocal laser sensor 2 and the inner wall of the confocal laser sensor 2, thereby fixing the confocal laser sensor 2 and the confocal laser sensor 51.

[0025] The specific method for measuring threads using the confocal laser sensor 2 is existing technology. This application mainly involves hardware modifications and does not involve algorithms and control software during the measurement process. The spindle module 1 includes a support base 13 located at the bottom of the frame 6. A pneumatic chuck 11 is rotatably mounted on the top of the support base 13, and a spindle motor 12, which drives the pneumatic chuck 11, is located at the bottom of the support base 13. The electric slide table 3 includes a vertical slide table 31 and a horizontal slide table 32. The vertical slide table 31 is slidably mounted on the frame 6 in a vertical direction via a vertical drive mechanism 61. The horizontal slide table 32 is slidably mounted at the bottom of the vertical slide table 31 in a horizontal direction via a horizontal drive mechanism 62. The clamp 5 is installed at the bottom of the horizontal slide table 32. The vertical drive mechanism 61 and the horizontal drive mechanism 62 can be linear motors or lead screw and nut transmission mechanisms.

[0026] For small-hole long nuts like planetary roller screw nut, the main problem in the testing process is that the length of commonly available small confocal laser sensors is only about 80mm, while the length of some planetary roller screw nuts is over 150mm. Therefore, in order to extend the confocal laser sensor 2 into the nut 4, an extended tooling is needed to extend the movement range of the confocal laser sensor 2. Based on the existing structure of the confocal laser sensor 2, it is not possible to directly add an extension rod at the rear. Furthermore, considering the small inner diameter of the nut 4, it is difficult to balance structural strength and installation compactness. The solution adopted in this invention is to use a circular tube 51 with an inner diameter slightly larger than the outer diameter of the confocal laser sensor 2 as the main body of the clamp 5, for example, a difference of 1-2mm, to ensure structural strength. A wedge-shaped piece 52 is used to wed the sidewall of the confocal laser sensor 2 tightly within the circular tube 51, ensuring structural compactness and installation stability. The specific installation process is as follows: First, insert the confocal laser sensor 2 into one end of the circular tube 51, bringing the head of the confocal laser sensor 2 close to the head of the circular tube 51. Then, insert the wedge-shaped piece 52 into the gap between the circular tube 51 and the confocal laser sensor 2 from the tail end of the circular tube 51. Next, insert the inner tube 53 from the tail end of the circular tube 51. Finally, screw in the nut 54 and push the inner tube 53 inward. During this process, the confocal laser sensor 2 can be held in place by hand to prevent it from sliding. Ultimately, the inner tube 53 presses the wedge-shaped piece 52 against the outer wall of the confocal laser sensor 2 and the inner wall of the circular tube 51, thus fixing the confocal laser sensor 2 to the circular tube 51. When installing and debugging the equipment, the moving path of the horizontal slide 32 should pass through the center of the pneumatic chuck 11, and the direction of laser emission from the confocal laser sensor 2 should be parallel to the moving direction of the horizontal slide 32.

[0027] The main measurement process of this utility model is as follows: First, the nut 4 whose thread needs to be measured is fixed on the pneumatic chuck 11. Then, the vertical slide 31 drives the clamp 5 to move downward and insert it into the thread hole of the nut 4 until the part of the confocal laser sensor 2 emitting laser light on the side of the head passes through the bottom of the nut 4. Then, the horizontal slide 32 is used to bring the confocal laser sensor 2 close to the inner wall of the nut 4 and accurately focus the light spot on the thread profile of the nut 4. Then, the confocal laser sensor 2 is moved vertically to measure one thread profile section. After that, the spindle motor 12 rotates the nut 4 to measure the next section. At the same time, the confocal laser sensor 2 moves synchronously in the vertical direction until the thread measurement of the entire nut 4 is completed.

[0028] Because the measurement range of the confocal laser sensor 2 is limited, typically only one or two millimeters, to avoid the thickness of the circular tube 51 occupying the measurement range, such as Figure 2 , Figure 3As shown, a strip-shaped opening 55 is provided along the length of the side wall of the circular tube 51, exposing the side where the detection head of the confocal laser sensor 2 is located. The width of the strip-shaped opening 55 is preferably such that the detection head extends beyond the outer wall of the circular tube 51, allowing the confocal laser sensor 2 to approach the thread profile before the circular tube 51. The length of the strip-shaped opening 55 is preferably not less than the length of the confocal laser sensor 2. During installation, the wedge-shaped piece 52 is placed on the side opposite to the strip-shaped opening 55, and the confocal laser sensor 2 is pressed against the strip-shaped opening 55. This provides positioning for the confocal laser sensor 2 and increases the contact area between the confocal laser sensor 2 and the circular tube 51, improving the stability of the confocal laser sensor 2 installation.

[0029] Furthermore, to facilitate the placement of the wedge-shaped piece 52 on the side opposite to the strip opening 55, a groove 56 is provided on the inner wall of the circular tube 51 on the side opposite to the strip opening 55, extending from the head to the middle. The wedge-shaped piece 52 is slidably disposed within the groove 56. The length of the groove 56 must be greater than the length of the confocal laser sensor 2. It can be a flat groove or a wedge-shaped groove, with a wedge-shaped groove being preferred. The inclined surface of the groove matches the inclined surface of the wedge-shaped piece 52, so that the side of the wedge-shaped piece 52 closest to the confocal laser sensor 2 is parallel to the inner wall of the circular tube 51. This allows the wedge-shaped piece 52 to fully contact the outer wall of the confocal laser sensor 2, improving the installation accuracy and stability.

[0030] To facilitate disassembly in case of a malfunction of the confocal laser sensor 2, an elongated oblong hole 57 is provided on the side wall of the central section of the circular tube 51 corresponding to the groove 56. The tail of the wedge-shaped plate 52 is located within the area of ​​the elongated oblong hole 57, and a small hole 58 is provided at the tail of the wedge-shaped plate 52. The width of the elongated oblong hole 57 is preferably smaller than the width of the wedge-shaped plate 52 to prevent the tail of the wedge-shaped plate 52 from bending at the elongated oblong hole 57 during the pushing process of the inner tube 53. When it is necessary to disassemble the confocal laser sensor 2, first loosen the nut 54 at the tail of the circular tube 51, then remove the inner tube 53, and finally use a needle or other tool to insert into the small hole 58 through the elongated oblong hole 57, and then push the wedge-shaped plate 52 towards the tail of the circular tube 51 to remove the wedge-shaped plate 52 and the confocal laser sensor 2.

[0031] Regarding the installation method of the clamp 5 and the electric slide 3, the solution adopted by this utility model is as follows: Figure 4As shown, the clamp 5 is fixed to the electric slide table 3 via the probe mounting base 7. The probe mounting base 7 has a channel 71 in the middle for the round tube 51 to pass through. The channel 71 has a mounting cavity 72 in the middle, and a locking block 73 is provided in the mounting cavity 72. A locking screw 74 is provided on the side wall of the probe mounting base 7. The locking screw 74 pushes the locking block 73 inward to fix the round tube 51 in the probe mounting base 7. During installation, first, the locking block 73 is placed into the mounting cavity 72, then the tail of the round tube 51 is inserted into the channel 71, and finally the locking block 73 is pushed inward by the locking screw 74 to fix the round tube 51 in the probe mounting base 7.

[0032] To prevent the locking block 73 from rotating or sliding in the mounting cavity when the locking screw 74 is tightened, a guide screw 75 is provided on the upper and lower sides of the locking screw 74 on the probe mounting base 7. A compression spring 76 is provided between the head of the guide screw 75 and the outer wall of the probe mounting base 7. The two guide screws 75 pass through the through hole on the probe mounting base 7 and are threaded to the threaded holes 77 at the upper and lower ends of the locking block 73, respectively. During installation, first place the locking block 73 into the mounting cavity 72. Then, pass two guide screws 75 through the through holes on the measuring rod mounting base 7, ensuring their ends are threaded into the threaded holes 77 on the locking block 73. During installation, ensure the ends of the guide screws 75 do not extend beyond the threaded holes 77. Next, insert the tail of the round tube 51 into the channel 71. Finally, use the locking screws 74 to push the locking block 73 inward to fix the round tube 51. During this process, the guide screws 75 provide support and prevent rotation of the locking block 73, while the compressed spring 76 provides cushioning, preventing excessive compression damage to the round tube 51 by the locking screws 74. Furthermore, when the locking screws 74 are loosened, the locking block 73 can quickly detach from the round tube 51 under the restoring force of the spring 76, facilitating the removal of the clamp 5. Additionally, to increase the contact area, an arc-shaped surface matching the round tube 51 can be provided on the inner side of the locking block 73.

[0033] Due to manufacturing and installation errors, the axis of the confocal laser sensor 2 may not be vertical. Therefore, to allow for subsequent adjustment of the angle of the confocal laser sensor 2, an adapter plate 8 is provided between the probe mounting base 7 and the electric slide table 3. The probe mounting base 7 and the adapter plate 8 are connected by three connecting screws 81 that are symmetrically arranged about their axes. The probe mounting base 7 is provided with three set screws 82 that are symmetrically arranged about their axes, with the upper ends of the set screws 82 abutting against the bottom of the adapter plate 8. The connecting screws 81 and the set screws 82 are spaced apart. During installation, the connecting screws 81 are first used to initially connect the probe mounting base 7 and the adapter plate 8. Then, the three set screws 82 are adjusted to ensure that the axis of the confocal laser sensor 2 is vertical. Finally, the connecting screws 81 are tightened to fix the probe mounting base 7 onto the adapter plate 8.

[0034] During the measurement process, incorrect parameters may be input due to operational errors, causing the round tube 51 to collide with the nut 4. Therefore, in order to avoid equipment damage, a three-dimensional force sensor 9 is also provided between the adapter plate 8 and the electric slide table 3. The controller used to control the movement of the electric slide table 3 is electrically connected to the three-dimensional force sensor 9 and is configured to stop the movement of the electric slide table 3 when the three-dimensional force sensor 9 experiences a change in force during the movement of the electric slide table 3.

[0035] In summary, this utility model, by installing the confocal laser sensor 2 inside a circular tube 51, enables the confocal laser sensor 2 to have a long range of motion, allowing it to extend into the interior of a small-hole long nut, thus meeting the measurement requirements of the planetary roller screw pair nut; and by fixing the circular tube 51 with the measuring rod mounting seat 7, adjusting the angle of the circular tube 51 with the adapter plate 8, and protecting the equipment with the three-dimensional force sensor 9, can ensure the installation accuracy and stability of the confocal laser sensor 2, as well as the safety of operation during the measurement process.

Claims

1. An internal thread measuring instrument for small-hole long nuts, comprising a spindle module (1) for vertically fixing and driving the nut (4) to rotate about its axis, a confocal laser sensor (2) for detecting internal threads, and an electric slide (3) for mounting and driving the confocal laser sensor (2) to move along the axis and radial direction of the nut (4), characterized in that: The confocal laser sensor (2) is fixed to the bottom of the electric slide table (3) by a clamp (5). The clamp (5) includes a round tube (51) longer than the nut (4), a wedge (52) located inside the round tube (51), and an inner tube (53). The end of the round tube (51) is provided with an internal thread, and a nut (54) is provided inside the internal thread. The confocal laser sensor (2) is located inside the round tube (51). The wedge (52) is located between the outer wall of the confocal laser sensor (2) and the inner wall of the round tube (51). The inner tube (53) is located between the end of the wedge (52) and the nut (54). The nut (54) pushes the inner tube (53) inward. The inner tube (53) presses the wedge (52) against the inner wall of the confocal laser sensor (2) and the inner wall of the round tube (51), thereby fixing the confocal laser sensor (2) and the round tube (51).

2. The internal thread measuring instrument for small-hole long nuts as described in claim 1, characterized in that: The spindle module (1) includes a support base (13) located at the bottom of the frame (6), a pneumatic chuck (11) is rotatably mounted on the top of the support base (13), and a spindle motor (12) that drives the pneumatic chuck (11) to rotate is located at the bottom of the support base (13).

3. The internal thread measuring instrument for small-hole long nuts as described in claim 2, characterized in that: The electric slide (3) includes a vertical slide (31) and a horizontal slide (32). The vertical slide (31) is slidably mounted on the frame (6) in the vertical direction by means of a vertical drive mechanism (61). The horizontal slide (32) is slidably mounted at the bottom of the vertical slide (31) in the horizontal direction by means of a horizontal drive mechanism (62). The clamp (5) is installed at the bottom of the horizontal slide (32).

4. The internal thread measuring instrument for small-hole long nuts as described in claim 1, characterized in that: The side wall of the circular tube (51) is provided with a strip-shaped opening (55) along its length direction for the detection head of the confocal laser sensor (2) to be exposed on the side.

5. The internal thread measuring instrument for small-hole long nuts as described in claim 4, characterized in that: On the inner wall of the circular tube (51) opposite to the strip opening (55), there is a groove (56) from the head to the middle, and the wedge-shaped piece (52) is slidably disposed in the groove (56).

6. The internal thread measuring instrument for small-hole long nuts as described in claim 5, characterized in that: The middle part of the round tube (51) is provided with an elongated waist-shaped hole (57) on the side wall corresponding to the groove (56). The tail of the wedge (52) is located in the area where the elongated waist-shaped hole (57) is located. The tail of the wedge (52) is provided with a small hole (58).

7. The internal thread measuring instrument for small-hole long nuts as described in any one of claims 1-6, characterized in that: The clamp (5) is fixed on the electric slide table (3) by the probe mounting base (7). The probe mounting base (7) has a channel (71) in the middle for the round tube (51) to pass through. The channel (71) has a mounting cavity (72) in the middle. The mounting cavity (72) has a locking block (73). The side wall of the probe mounting base (7) has a locking screw (74). The locking screw (74) pushes the locking block (73) inward to fix the round tube (51) in the probe mounting base (7).

8. The internal thread measuring instrument for small-hole long nuts as described in claim 7, characterized in that: The probe mounting base (7) is provided with a guide screw (75) on each side above and below the locking screw (74). A compression spring (76) is provided between the head of the guide screw (75) and the outer wall of the probe mounting base (7). The two guide screws (75) pass through the through hole on the probe mounting base (7) and are threaded to the threaded holes (77) at the upper and lower ends of the locking block (73).

9. The internal thread measuring instrument for small-hole long nuts as described in claim 7, characterized in that: A transition plate (8) is provided between the probe mounting base (7) and the electric slide (3). The probe mounting base (7) and the transition plate (8) are connected by three connecting screws (81) that are symmetrically arranged about their axes. The probe mounting base (7) is provided with three set screws (82) that are symmetrically arranged about their axes. The upper end of the set screws (82) abuts against the bottom of the transition plate (8).

10. The internal thread measuring instrument for small-hole long nuts as described in claim 9, characterized in that: A three-dimensional force sensor (9) is also provided between the adapter plate (8) and the electric slide (3). The controller for controlling the movement of the electric slide (3) is electrically connected to the three-dimensional force sensor (9) and is configured to stop moving when the three-dimensional force sensor (9) experiences a change in force during the movement of the electric slide (3).

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