A method and device for detecting outer diameter of PVC pipe

Abstract

The invention relates to the technical field of pipe outer diameter detection, and discloses a method and device for detecting the outer diameter of a PVC pipe. A channel is formed between an upper shell and a lower shell, and the upper shell is connected to the lower shell so as to be movable up and down, and a negative pressure environment is formed in the channel, and the negative pressure value in the channel is detected at the same time. When the PVC pipe passes through the channel, if the outer diameter of the PVC pipe is larger than the standard outer diameter, the PVC pipe will lift the upper shell, so that the gap between the upper shell and the lower shell becomes larger, and the negative pressure value detected in the channel becomes smaller; if the outer diameter of the PVC pipe is smaller than the standard outer diameter, the gap between the upper shell and the lower shell becomes smaller, and the negative pressure value detected in the channel becomes larger; therefore, the method and device of the invention only need to detect the negative pressure in the channel to know whether the outer diameter of the PVC pipe is too large or too small, without manual observation, reducing labor intensity, improving efficiency, and can detect all produced pipes and the outer diameters of various parts of the pipes to achieve full inspection.

Description

Technical Field

[0001] The invention relates to the technical field of pipe outer diameter detection, and in particular to a method and a device for detecting the outer diameter of a PVC pipe. Background Art

[0002] PVC pipes are widely used. For PVC pipe production lines connected to automatic packaging machines, the outer diameter of PVC pipes needs to be tested to prevent unqualified products from entering the market. At present, the outer diameter of PVC pipes is mainly tested manually using a vernier caliper. This measurement method is cumbersome and has a long measurement cycle, which seriously affects production efficiency and cannot meet the requirements of the current fast production rhythm. In addition, it is impossible to measure specific values ​​one by one, and only random inspections can be carried out, which makes it easy for unqualified products to enter the market.

[0003] Chinese utility model CN206347952U (published on July 21, 2017) discloses a synchronous detection tool for inner and outer diameters of steel pipes, including an inner diameter inspection rod, an outer diameter inspection sleeve, a handle, a spring and a fixing nut. The left end of the handle is fixedly connected to the inner diameter inspection rod, and the inner diameter inspection rod and the left end of the handle are both sleeved in the outer diameter inspection sleeve. The right end of the handle can movably pass through the outer diameter inspection sleeve. The fixing nut is screwed on the handle outside the outer diameter inspection sleeve. The spring is sleeved on the handle between the outer diameter inspection sleeve and the fixing nut. The inner diameter inspection rod detects the inner diameter of the steel pipe to be inspected, and the outer diameter inspection sleeve detects the outer diameter of the steel pipe to be inspected. This patent requires manual observation of whether the top of the steel pipe is between point A and point B of the outer diameter inspection sleeve and whether the outer diameter inspection sleeve is retreated. The labor intensity is high, and there is a certain error rate in manual observation. In addition, the patent requires the steel pipe to be stationary and then the outer diameter inspection sleeve is placed on one end of the steel pipe for inspection. The patented tool cannot be directly set at the end of the pipe production line for use. Moreover, the patented tool can only detect the outer diameters at both ends of the pipe and cannot detect unqualified pipes with larger or smaller outer diameters in the middle. Summary of the invention

[0004] The purpose of the present invention is to provide a PVC pipe outer diameter detection method and device which are accurate, efficient and can fully detect all pipes and the outer diameters of each pipe at all locations.

[0005] In order to achieve the above object, the present invention provides a method for detecting the outer diameter of a PVC pipe, comprising the following steps:

[0006] The upper shell is connected to the lower shell so that it can move up and down, and a passage for the PVC pipe to pass through is formed between the upper shell and the lower shell;

[0007] The channel is evacuated to form a negative pressure in the channel;

[0008] A PVC pipe with a standard outer diameter is passed through the channel, and the negative pressure value in the channel when the PVC pipe passes through is detected, and the detected negative pressure value is used as the standard value;

[0009] When the PVC pipe to be tested passes through the channel, the negative pressure value in the channel is detected, and the detected air pressure value is compared with the standard value. If the detected negative pressure value is less than the standard value, the outer diameter of the PVC pipe to be tested is greater than the standard outer diameter of the PVC pipe; if the detected negative pressure value is greater than the standard value, the outer diameter of the PVC pipe to be tested is smaller than the standard outer diameter of the PVC pipe.

[0010] The present invention also provides a PVC pipe outer diameter detection device, including a bracket, an upper shell, a lower shell, a negative pressure device and a negative pressure detection device, the upper shell and the lower shell both have a groove, the lower shell is connected to the bracket, the upper shell can be connected to the bracket movably up and down, the upper shell and the lower shell are arranged up and down to form a channel for the PVC pipe to pass through between the upper shell and the lower shell, and the negative pressure device and the negative pressure detection device are both connected to the channel.

[0011] As a preferred solution, the diameter of the middle portion of the channel is larger than the diameters of its two ends, and the negative pressure device and the negative pressure detection device are connected to the middle portion of the channel.

[0012] As a preferred embodiment, the upper shell and the lower shell both include a shell plate, a front baffle, a rear baffle and two connecting plates, the shell plate is semi-cylindrical, the front baffle and the rear baffle are semi-annular, the front baffle and the rear baffle are respectively connected to the two ends of the shell plate, the two connecting plates are both rectangular plates and are respectively connected to the two sides of the shell plate, one side of the connecting plate is located in the shell plate and its two ends are respectively connected to the front baffle and the rear baffle, the other side of the connecting plate extends from the shell plate, and the upper shell and the lower shell are respectively connected to the bracket through their respective connecting plates.

[0013] As a preferred embodiment, the bracket includes a mounting plate and two support beams, the mounting plate is provided with a through hole for the PVC pipe to pass through, the two support beams are vertically connected to the mounting plate and are located on both sides of the through hole, the support beams are provided with connecting columns perpendicular to them, the connecting plates of the upper shell and the lower shell are provided with connecting holes, the connecting plates are plug-connected to the connecting columns through the connecting holes, and the connecting plate of the lower shell is located below the connecting plate of the upper shell.

[0014] As a preferred solution, it also includes a pressure wheel and a pressure wheel bracket, both ends of the upper shell and the lower shell are connected to the pressure wheel bracket, and the pressure wheel is rotatably connected to the pressure bracket.

[0015] As a preferred solution, a circle of grooves is provided on the wheel surface of the pressure wheel, and the grooves are V-shaped grooves.

[0016] As a preferred solution, the angle between the rotation axis of the pressure wheel and the vertical direction forms an acute angle.

[0017] As a preferred solution, the diameter of the front port of the channel gradually decreases from front to back.

[0018] As a preferred solution, it also includes an alarm and a controller, and the negative pressure detection device and the alarm are respectively communicatively connected with the controller.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The method and device of the present invention form a channel between the upper shell and the lower shell, and connect the upper shell to the lower shell so that it can move up and down, and form a negative pressure environment in the channel, and detect the negative pressure value in the channel at the same time. When the PVC pipe passes through the channel, if the outer diameter of the PVC pipe is larger than the standard outer diameter, the PVC pipe will lift the upper shell, so that the gap between the upper shell and the lower shell becomes larger, and the contact between the channel and the external environment is increased, resulting in the balance of the external atmospheric pressure and the negative pressure of the channel, thereby reducing the negative pressure value detected in the channel; if the outer diameter of the PVC pipe is smaller than the standard outer diameter, the upper shell will drop to contact with the PVC pipe, so that the gap between the upper shell and the lower shell becomes smaller, reducing the contact between the inside of the channel and the external environment The contact between the outside atmospheric pressure and the negative pressure in the channel is less balanced, thereby increasing the negative pressure value detected in the channel; therefore, the method and device of the present invention only need to detect the negative pressure in the channel to know whether the outer diameter of the PVC pipe is too large or too small, without manual observation, reducing labor intensity and improving efficiency; in addition, the device of the present invention can be directly arranged at the end of the pipe production line, and the pipes output by the production line continuously pass through the channel between the upper shell and the lower shell, without the need for stationary pipes, and all produced pipes can be inspected to achieve full inspection, and when the pipe passes through the channel, the outer diameter of each part of the pipe can be detected, and unqualified pipes with larger or smaller outer diameters in the middle can be found, thereby reducing the unqualified rate of pipes entering the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of a method for detecting the outer diameter of a PVC pipe according to a first embodiment of the present invention.

[0022] Figure 2 It is a structural schematic diagram of a PVC pipe outer diameter detection device according to the second embodiment of the present invention.

[0023] Figure 3 It is a side view of a PVC pipe outer diameter detection device according to a second embodiment of the present invention.

[0024] Figure 4It is a front view of a PVC pipe outer diameter detection device according to a second embodiment of the present invention.

[0025] Figure 5 yes Figure 4 Section view at AA.

[0026] In the figure, 1-upper shell; 2-lower shell; 3-negative pressure device; 4-negative pressure detection device; 5-channel; 6-shell plate; 7-front baffle; 8-rear baffle; 9-connecting plate; 10-mounting plate; 11-support beam; 12-through hole; 13-connecting column; 14-counterweight cylinder; 15-pressure wheel; 16-pressure wheel bracket; 17-card slot; 18-alarm; 19-controller; 20-touch screen. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0028] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Embodiment 1

[0031] like Figure 1 As shown, a method for detecting the outer diameter of a PVC pipe according to a preferred embodiment of the present invention comprises the following steps:

[0032] The upper shell is connected to the lower shell so that it can move up and down, and a passage for the PVC pipe to pass through is formed between the upper shell and the lower shell;

[0033] The channel is evacuated to form a negative pressure in the channel;

[0034] A PVC pipe with a standard outer diameter is passed through the channel, and the negative pressure value in the channel when the PVC pipe passes through is detected, and the detected negative pressure value is used as the standard value;

[0035] When the PVC pipe to be tested passes through the channel, the negative pressure value in the channel is detected, and the detected air pressure value is compared with the standard value. If the detected negative pressure value is less than the standard value, the outer diameter of the PVC pipe to be tested is greater than the standard outer diameter of the PVC pipe; if the detected negative pressure value is greater than the standard value, the outer diameter of the PVC pipe to be tested is smaller than the standard outer diameter of the PVC pipe.

[0036] The PVC pipe outer diameter detection method of the present embodiment only needs to detect the negative pressure in the channel when the pipe passes through, and then compare it with the negative pressure in the channel when the standard outer diameter pipe passes through, so as to determine whether the outer diameter of the PVC pipe is too large or too small. The detection is accurate and efficient, and the passing pipes can be fully inspected, and unqualified pipes with too large or too small outer diameter in the middle of the pipe body can be found, thereby improving the comprehensiveness of the detection.

[0037] Embodiment 2

[0038] like Figures 2 to 5As shown, a preferred embodiment of the present invention is a PVC pipe outer diameter detection device, including a bracket, an upper shell 1, a lower shell 2, a negative pressure device 3 and a negative pressure detection device 4, the upper shell 1 and the lower shell 2 both have grooves, the lower shell 2 is connected to the bracket, the upper shell 1 is connected to the bracket movably up and down, the upper shell 1 and the lower shell 2 are arranged up and down, so that a channel 5 for the PVC pipe to pass through is formed between the upper shell 1 and the lower shell 2, and the negative pressure device 3 and the negative pressure detection device 4 are both connected to the channel 5. The device of this embodiment forms a channel 5 between the upper shell 1 and the lower shell 2, and connects the upper shell 1 to the lower shell 2 so that it can move up and down, and forms a negative pressure environment in the channel 5, and detects the negative pressure value in the channel 5 at the same time. When the PVC pipe passes through the channel 5, if the outer diameter of the PVC pipe is larger than the standard outer diameter, the PVC pipe will lift the upper shell 1, so that the gap between the upper shell 1 and the lower shell 2 becomes larger, and the contact between the channel 5 and the external environment is increased, resulting in the balance of the external atmospheric pressure and the negative pressure of the channel 5, thereby reducing the negative pressure value detected in the channel 5; if the outer diameter of the PVC pipe is smaller than the standard outer diameter, the upper shell 1 will drop to contact with the PVC pipe, so that the gap between the upper shell 1 and the lower shell 2 becomes smaller, reducing the negative pressure value inside the channel 5. The contact with the external environment makes the balance between the external atmospheric pressure and the negative pressure in the channel 5 less, so that the negative pressure value detected in the channel 5 becomes larger; therefore, the device of this embodiment only needs to detect the negative pressure in the channel 5 to know whether the outer diameter of the PVC pipe is too large or too small, without manual observation, reducing labor intensity and improving efficiency; in addition, the device of this embodiment can be directly set at the end of the pipe production line, and the pipes output by the production line continuously pass through the channel 5 between the upper shell 1 and the lower shell 2, without the need for stationary pipes, and can detect all produced pipes to achieve full inspection, and when the pipe passes through the channel 5, the outer diameter of each part of the pipe can be detected, and unqualified pipes with larger or smaller outer diameters in the middle can be found, reducing the unqualified rate of pipes entering the market. The negative pressure device 3 of this embodiment is a vacuum air source, and the negative pressure detection device 4 is a negative pressure sensor.

[0039] Furthermore, the diameter of the middle part of the channel 5 of this embodiment is larger than the diameter of its two ends, and the negative pressure device 3 and the negative pressure detection device 4 are connected to the middle part of the channel 5. When the PCV pipe passes through the channel 5, due to the larger diameter of the middle part of the channel 5, a cavity is formed between the pipe and the upper shell 1 and the lower shell 2, which is relatively closed and can form a larger negative pressure. When the outer diameter of the PVC pipe passing through changes, the detection value of the negative pressure detection device 4 changes more significantly, thereby improving the detection accuracy.

[0040] In this embodiment, the upper shell 1 and the lower shell 2 both include a shell plate 6, a front baffle plate 7, a rear baffle plate 8 and two connecting plates 9. The shell plate 6 is semi-cylindrical, the front baffle plate 7 and the rear baffle plate 8 are semi-circular, the front baffle plate 7 and the rear baffle plate 8 are respectively connected to the two ends of the shell plate 6, the two connecting plates 9 are both rectangular plates and are respectively connected to the two sides of the shell plate 6, one side of the connecting plate 9 is located in the shell plate 6 and its two ends are respectively connected to the front baffle plate 7 and the rear baffle plate 8, the other side of the connecting plate 9 extends from the shell plate 6, and the upper shell 1 and the lower shell 2 are respectively connected to the bracket through their respective connecting plates 9. Through the connection of the shell plate 6, the front baffle plate 7, the rear baffle plate 8 and the connecting plate 9, the middle diameter of the formed channel 5 is larger than the diameter of the two ends, that is, the front port of the channel 5 formed by the upper shell 1 and the lower shell 2 is formed by the depression of the respective front baffle plate 7, and the rear port is formed by the depression of the respective rear baffle plate 8, and the middle of the channel 5 is the space between the shell plate 6 of the upper shell 1 and the shell plate 6 of the lower shell 2. The gap between the upper shell 1 and the lower shell 2 is the distance in the vertical direction between the connecting plate 9 of the upper shell 1 and the connecting plate 9 of the lower shell 2 .

[0041] The bracket of this embodiment includes a mounting plate 10 and two support beams 11. The mounting plate 10 is provided with a through hole 12 for the PVC pipe to pass through. The two support beams 11 are vertically connected to the mounting plate 10 and are located on both sides of the through hole 12. The support beams 11 are provided with connecting columns 13 vertical thereto. The connecting plates 9 of the upper shell 1 and the lower shell 2 are provided with connecting holes. The connecting plates 9 are plug-connected with the connecting columns 13 through the connecting holes. The connecting plates 9 of the lower shell 2 are located below the connecting plates 9 of the upper shell 1. The connecting plates 9 of the upper shell 1 and the lower shell 2 protrude from the shell plate 6 and overlap the support beams 11, which is convenient for installation and disassembly, and the connecting columns 13 can guide the upper shell 1 to move up and down. In addition, the device of this embodiment also includes a counterweight cylinder 14, which is sleeved on the connecting column 13 and is located above the connecting plate 9 of the upper shell 1. Under the gravity of the counterweight cylinder 14, the upper shell 1 descends and can be attached to the passing PVC pipe, making the detection more accurate and avoiding the upper shell 1 being stuck and unable to descend after being lifted up by the PVC pipe or descending too slowly to cause missed detection.

[0042] In addition, the device of this embodiment also includes a pressure wheel 15 and a pressure wheel bracket 16. The pressure wheel bracket 16 is connected to both ends of the upper shell 1 and the lower shell 2. The pressure wheel 15 is rotatably connected to the pressure bracket 16, which is conducive to the smooth entry and passage of the PVC pipe between the upper shell 1 and the lower shell 2. A circle of card grooves 17 are provided on the wheel surface of the pressure wheel 15 of this embodiment. The card groove 17 is a V-shaped groove, so that the pressure wheel 15 can fit the outer wall of PVC pipes of various outer diameters. In addition, the rotation axis of the pressure wheel 15 of this embodiment forms an acute angle with the vertical direction, so that the pressure wheel 15 is tilted, the number of pressure wheels 15 is increased, and the pressure wheels 15 can be symmetrically arranged to prevent the PVC pipe from moving unsteadily. In this embodiment, two pressure wheels 15 are connected to both ends of the upper shell 1 and the lower shell 2, that is, four pressure wheels 15 are provided at one end, and the four pressure wheels 15 at this end are symmetrically arranged. The diameter of the front port of the channel 5 of this embodiment gradually decreases from front to back, so that the diameter of the end of the channel 5 close to the mounting plate 10 is larger, making it easier for the PVC pipe to enter the channel 5. The front port of the channel 5 of this embodiment is formed by the depressions of the front baffle 7 of the upper shell 1 and the front baffle 7 of the lower shell 2, that is, the mouths of the front baffle 7 of the upper shell 1 and the front baffle 7 of the lower shell 2 are bell mouths.

[0043] The device of this embodiment also includes an alarm 18 and a controller 19. The negative pressure detection device 4 and the alarm 18 are respectively connected to the controller 19 for communication. The negative pressure detection device 4 sends a detection signal to the controller 19. The controller 19 compares the detection value with the negative pressure value when the standard PVC pipe passes through. If it exceeds a certain range, the controller 19 sends a signal to the alarm 18 to alarm and notify the staff to take out the unqualified products to separate the qualified pipes from the unqualified pipes. In this embodiment, the negative pressure value in the channel 5 when multiple standard pipes pass through is obtained, the obtained data is analyzed, a maximum negative pressure value and a minimum negative pressure value are set, and the qualified range is set between the maximum negative pressure value and the minimum negative pressure value. If it is higher than the maximum negative pressure value or lower than the minimum negative pressure value, it is judged as unqualified. The alarm 19 of this embodiment is an audible and visual alarm, and the controller 19 is a PLC system. In addition, the device of this embodiment also includes a touch screen 20, which is connected to the controller 19 for communication, and the human-computer interaction with the controller 19 can be realized through the touch screen 20.

[0044] The working process of the present invention is as follows: the upper shell 1 and the lower shell 2 are installed at the end of the PVC pipe production line. The end of the PVC pipe production line will continuously pass through the pipes one by one, so the pipes will pass through the channel 5 between the upper shell 1 and the lower shell 2. If the outer diameter of the PVC pipe is larger than the outer diameter of the standard pipe, when passing through, the pipe will lift the upper shell 1, so that the gap between the upper shell 1 and the lower shell 2 becomes larger, so that the atmospheric pressure inside the channel 5 and the atmospheric pressure of the external environment are balanced, resulting in a smaller negative pressure value in the channel 5; if the outer diameter of the PVC pipe is smaller than the outer diameter of the standard pipe, when passing through, the upper shell 1 is not supported and falls to the point where it is close to the PVC pipe passing through, so that the gap between the upper shell 1 and the lower shell 2 becomes smaller, reducing the contact between the inside of the channel 5 and the external environment, making it more closed, resulting in a larger negative pressure value in the channel 5. Therefore, by detecting the negative pressure value in the channel 5 when the pipe passes through, and then comparing it with the negative pressure value when the standard pipe passes through, it can be known whether the outer diameter is qualified.

[0045] In summary, the embodiments of the present invention provide a method and device for detecting the outer diameter of a PVC pipe, which forms a channel 5 between an upper shell 1 and a lower shell 2, and connects the upper shell 1 to the lower shell 2 so that it can move up and down, and forms a negative pressure environment in the channel 5, and detects the negative pressure value in the channel 5 at the same time. When the PVC pipe passes through the channel 5, if the outer diameter of the PVC pipe is larger than the standard outer diameter, the PVC pipe will lift the upper shell 1, so that the gap between the upper shell 1 and the lower shell 2 becomes larger, and the contact between the channel 5 and the external environment is increased, resulting in the balance of the external atmospheric pressure and the negative pressure of the channel 5, thereby reducing the negative pressure value detected in the channel 5; if the outer diameter of the PVC pipe is smaller than the standard outer diameter, the upper shell 1 will drop to contact the PVC pipe, so that the gap between the upper shell 1 and the lower shell 2 The negative pressure in the channel 5 is reduced, which reduces the contact between the inside of the channel 5 and the external environment. The balance between the external atmospheric pressure and the negative pressure in the channel 5 is less, so that the negative pressure value detected in the channel 5 becomes larger; therefore, the device of this embodiment only needs to detect the negative pressure in the channel 5 to know whether the outer diameter of the PVC pipe is too large or too small, without manual observation, reducing labor intensity and improving efficiency; in addition, the device of this embodiment can be directly set at the end of the pipe production line, and the pipes output by the production line continuously pass through the channel 5 between the upper shell 1 and the lower shell 2. There is no need to stationary pipes, and all produced pipes can be tested to achieve full inspection. When the pipe passes through the channel 5, the outer diameter of each part of the pipe can be detected, and unqualified pipes with larger or smaller outer diameters in the middle can be found, reducing the unqualified rate of pipes entering the market. .

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting the outer diameter of a PVC pipe, characterized in that: A PVC pipe outer diameter detection device is used, the PVC pipe outer diameter detection device comprising a bracket, an upper shell (1), a lower shell (2), a negative pressure device (3) and a negative pressure detection device (4), the upper shell (1) and the lower shell (2) both having a groove, the lower shell (2) being connected to the bracket, the upper shell (1) being connected to the bracket in a manner of moving up and down, the upper shell (1) and the lower shell (2) being arranged up and down, so that a space for PV to pass through is formed between the upper shell (1) and the lower shell (2). The negative pressure device (3) and the negative pressure detection device (4) are both connected to the channel (5); the upper shell (1) and the lower shell (2) each comprise a shell plate (6), a front baffle plate (7), a rear baffle plate (8) and two connecting plates (9); the shell plate (6) is semi-cylindrical, the front baffle plate (7) and the rear baffle plate (8) are semi-annular, the front baffle plate (7) and the rear baffle plate (8) are respectively connected to the two ends of the shell plate (6), and the two connecting plates (9) are The connecting plate (9) is a rectangular plate and is respectively connected to both sides of the shell plate (6); one side of the connecting plate (9) is located in the shell plate (6) and its two ends are respectively connected to the front baffle (7) and the rear baffle (8); the other side of the connecting plate (9) extends out from the shell plate (6); the upper shell (1) and the lower shell (2) are respectively connected to the bracket through their respective connecting plates (9); the bracket comprises a mounting plate (10) and two support beams (11); the mounting plate (10) is provided with a PVC pipe The two support beams (11) are vertically connected to the mounting plate (10) and are located on both sides of the through hole (12); the support beams (11) are provided with connecting columns (13) vertical thereto; the connecting plates (9) of the upper shell (1) and the lower shell (2) are provided with connecting holes; the connecting plates (9) are plug-connected to the connecting columns (13) through the connecting holes; and the connecting plates (9) of the lower shell (2) are located below the connecting plates (9) of the upper shell (1); The method comprises the following steps: The upper shell is connected to the lower shell in an upward and downward manner, and a passage is formed between the upper shell and the lower shell for the PVC pipe to pass through; The channel is evacuated to form a negative pressure in the channel; A PVC pipe with a standard outer diameter is passed through the channel, and the negative pressure value in the channel when the PVC pipe passes through is detected, and the detected negative pressure value is used as the standard value; When the PVC pipe to be tested passes through the channel, the negative pressure value in the channel is detected, and the detected air pressure value is compared with the standard value. If the detected negative pressure value is less than the standard value, the outer diameter of the PVC pipe to be tested is greater than the standard outer diameter of the PVC pipe; if the detected negative pressure value is greater than the standard value, the outer diameter of the PVC pipe to be tested is smaller than the standard outer diameter of the PVC pipe.

2. A PVC pipe outer diameter detection device, characterized in that: The invention comprises a bracket, an upper shell (1), a lower shell (2), a negative pressure device (3) and a negative pressure detection device (4), wherein the upper shell (1) and the lower shell (2) both have a groove, the lower shell (2) is connected to the bracket, the upper shell (1) is connected to the bracket in an upward and downward movable manner, the upper shell (1) and the lower shell (2) are arranged vertically so that a channel (5) capable of allowing a PVC pipe to pass through is formed between the upper shell (1) and the lower shell (2), and the negative pressure device (3) and the negative pressure detection device (4) are both connected to the channel (5); the invention also comprises a pressure wheel (15) and a pressure wheel bracket (16), both ends of the upper shell (1) and the lower shell (2) are connected to the pressure wheel bracket (16), and the pressure wheel (15) is rotatably connected to the pressure wheel bracket (16); the diameter of the front end of the channel (5) gradually decreases from front to back.

3. The PVC pipe outer diameter detection device according to claim 2, characterized in that: The diameter of the middle portion of the channel (5) is greater than the diameters of its two ends, and the negative pressure device (3) and the negative pressure detection device (4) are connected to the middle portion of the channel (5).

4. The PVC pipe outer diameter detection device according to claim 3, characterized in that: The upper shell (1) and the lower shell (2) both comprise a shell plate (6), a front baffle (7), a rear baffle (8) and two connecting plates (9); the shell plate (6) is semi-cylindrical, the front baffle (7) and the rear baffle (8) are semi-annular, the front baffle (7) and the rear baffle (8) are respectively connected to the two ends of the shell plate (6); the two connecting plates (9) are both rectangular plates and are respectively connected to the two sides of the shell plate (6); one side of the connecting plate (9) is located in the shell plate (6) and its two ends are respectively connected to the front baffle (7) and the rear baffle (8); the other side of the connecting plate (9) extends from the shell plate (6); the upper shell (1) and the lower shell (2) are respectively connected to the bracket via their respective connecting plates (9).

5. The PVC pipe outer diameter detection device according to claim 4, characterized in that: The bracket comprises a mounting plate (10) and two support beams (11); the mounting plate (10) is provided with a through hole (12) capable of allowing a PVC pipe to pass through; the two support beams (11) are vertically connected to the mounting plate (10) and are located on both sides of the through hole (12); the support beams (11) are provided with connecting columns (13) vertical thereto; the connecting plates (9) of the upper shell (1) and the lower shell (2) are provided with connecting holes; the connecting plates (9) are plug-connected to the connecting columns (13) through the connecting holes; and the connecting plates (9) of the lower shell (2) are located below the connecting plates (9) of the upper shell (1).

6. The PVC pipe outer diameter detection device according to claim 2, characterized in that: A circle of clamping grooves (17) is provided on the wheel surface of the pressing wheel (15), and the clamping grooves (17) are V-shaped grooves.

7. The PVC pipe outer diameter detection device according to claim 2, characterized in that: The angle between the rotation axis of the pressing wheel (15) and the vertical direction forms an acute angle.

8. The PVC pipe outer diameter detection device according to claim 2, characterized in that: It also includes an alarm (18) and a controller (19), wherein the negative pressure detection device (4) and the alarm (18) are respectively communicatively connected to the controller (19).

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