Pipe positioning device of pipe cutting machine

Abstract

The utility model discloses a pipe positioning device of a pipe cutting machine, which relates to the technical field of pipe cutting machines and comprises a plurality of servo spiral positioning devices arranged along the same direction. Each servo spiral positioning device comprises a main body frame, a first transmission part capable of rotating relative to the main body frame, and a second transmission part which is in transmission connection with the first transmission part and can do reciprocating motion in the extension direction of the rotation axis of the first transmission part; and the driving device comprises a driving motor and a transmission shaft in transmission connection with the driving motor, and the transmission shaft is in transmission connection with the first transmission parts of the servo spiral positioning devices so as to drive the second transmission parts of the servo spiral positioning devices to synchronously reciprocate relative to the first transmission parts. The multiple servo spiral positioning devices can act synchronously, the equipment cost for arranging multiple independent power sources is saved, the action synchronism is higher, the situation that the machining precision is affected by deformation of the pipe due to asynchronous actions can be avoided, and the cutting machining precision of the pipe is guaranteed advantageously.

Description

Technical Field

[0001] The utility model relates to the technical field of pipe cutting machines, in particular to a pipe material positioning device for a pipe cutting machine. Background Art

[0002] With the development of society and the improvement of living standards, the pursuit of social production capacity has also been continuously improved. Therefore, various equipment that can improve social production capacity and production efficiency have been continuously designed and manufactured. For example, the emergence of pipe cutting machines has greatly improved the ability and efficiency of pipe processing, making it easier to meet the needs of various production fields in society for pipes.

[0003] The common pipe cutting machines in the existing market usually only use the conventional clamping and centering mechanism to center the pipe to be cut during the feeding process so that the rotation center of the pipe is aligned with the center of the chuck that clamps the pipe, thereby facilitating the laser cutting head to perform precise cutting to ensure the processing accuracy of the pipe. However, this centering method can only ensure that the center of the pipe is aligned with the rotation center of the chuck at the beginning of cutting. As the processing proceeds, changes in the structure and weight of the pipe and the impact of the rotation of the pipe will cause the center of the pipe to deviate from the rotation center of the chuck, which will have an adverse effect on the processing accuracy.

[0004] Moreover, for slender pipes and heavy pipes, due to structural limitations, the pipes are prone to flexural deformation during the cutting process with long-span support, which causes the center of the pipe to seriously deviate from the rotation center of the chuck. In the prior art, multiple servo rollers are provided to provide auxiliary support for the pipes, but each servo roller usually uses a separate servo motor as a power source to drive the roller to support the pipe for lifting and centering, and the separately provided servo motors usually cannot achieve precise synchronous movement, which also leads to the inability of multiple rollers to support the pipe to achieve precise synchronization. The different supporting forces of multiple rollers on the pipe cause the pipe to flexibly deform, which in turn causes the pipe to shake more violently when rotating, and cannot continuously meet the cutting accuracy requirements during the entire processing process. Utility Model Content

[0005] The utility model aims to provide a pipe positioning device for a pipe cutting machine, so as to solve the problem that each servo roller device in the existing pipe cutting machine is provided with a servo motor to realize the movement of the roller, resulting in the rollers being unable to move accurately and synchronously, causing different supporting forces in different directions of the pipe, thereby resulting in low pipe cutting accuracy.

[0006] To achieve the above-mentioned purpose, the utility model provides a pipe positioning device for a pipe cutting machine, comprising a plurality of servo screw positioning devices arranged along the same direction, each of the servo screw positioning devices comprising a main frame, a first transmission member arranged on the main frame and capable of rotating relative to the main frame, and a second transmission member that is transmission-connected to the first transmission member and capable of reciprocating along the extension direction of the rotation axis of the first transmission member;

[0007] It also includes a driving device, which includes a driving motor and a transmission shaft drivingly connected to the driving motor, and the transmission shaft is drivingly connected to the first transmission member of each servo screw positioning device to drive the second transmission member of each servo screw positioning device to reciprocate synchronously relative to each first transmission member.

[0008] In the scheme of the present application, the second transmission members of each servo screw positioning device can be driven to achieve synchronous action through a driving motor and a transmission shaft, so that multiple servo screw positioning devices can be enabled to synchronously support the pipe. Compared with the existing auxiliary support structures such as rollers with independent power, the deformation of the pipe caused by the asynchronous action of the second transmission members can be avoided, which affects the processing accuracy. This is beneficial to further ensure the cutting processing accuracy of the pipe and also saves the equipment cost of setting up multiple independent power sources.

[0009] In addition, the present application can play a role in assisting positioning and improving the efficiency of pipe feeding during the pipe feeding process by setting up multiple servo screw positioning devices arranged in the same direction, and can also continuously provide auxiliary positioning during the pipe cutting process. At the same time, the servo screw positioning device can also play a role in assisting support during the entire cutting process. For pipes that are arranged and supported for cutting with long spans, the support of the servo screw positioning device can effectively avoid or reduce the influence of the flexible deformation of the pipe on the pipe cutting processing accuracy, and it is also beneficial to improve the overall load-bearing capacity of the equipment.

[0010] In a preferred implementation of a pipe positioning device for a pipe cutting machine, along the extension direction of the rotation axis of the first transmission member, the first transmission member is provided with a driving portion that penetrates the first transmission member, and the second transmission member is provided with a mating portion that cooperates with the driving portion in transmission.

[0011] Through the cooperation of the driving part and the matching part, the transmission connection between the first transmission member and the second transmission member is realized. On the one hand, it can simplify the structure of the servo screw positioning device in the present application, and the arrangement of the driving part running through the first transmission member can effectively reduce the installation space occupied by the matching structure of the first transmission member and the second transmission member, so as to better adapt to the limited installation space of the pipe cutting machine; on the other hand, the above-mentioned matching structure and matching method are simple, the processing and use costs are low, and good economic benefits can be obtained.

[0012] In a preferred implementation of a pipe positioning device for a pipe cutting machine, the driving portion is a driving hole, and an internal thread is arranged on the inner wall of the driving hole; the matching portion is a threaded portion arranged on the second transmission member along the extension direction of the rotation axis of the first transmission member, and the threaded portion is provided with an external thread meshing with the internal thread.

[0013] The connection through the meshing of internal and external threads can realize both the structural connection and the transmission relationship connection, which is conducive to simplifying the structure, reducing the number of parts, and is convenient, practical and easy to maintain. At the same time, the threaded connection method itself also has good structural stability, which is conducive to ensuring the stability of the connection structure between the first transmission member and the second transmission member and the stability of the relative movement between the two.

[0014] In a preferred implementation of a tube positioning device for a tube cutting machine, the first transmission member is a gear, the second transmission member is a lead screw, the axial hole of the gear is the driving hole and is provided with the internal thread, and the threaded portion of the lead screw is the mating portion and is provided with the external thread.

[0015] Gears and lead screws are common parts in the field of mechanical equipment. They are easy to obtain and have low usage and maintenance costs. They also have good working stability. During long-term use, they are conducive to ensuring the stable operation of the servo spiral positioning device and even the entire pipe cutting machine pipe positioning device.

[0016] In a preferred implementation of a pipe positioning device for a pipe cutting machine, each of the servo screw positioning devices also includes a circumferential limit assembly, which is respectively connected to the second transmission member and the main frame to limit the rotation of the second transmission member around the rotation axis of the first transmission member.

[0017] By setting the circumferential limit assembly, it can be ensured that the second transmission member only reciprocates along the extension direction of the rotation axis of the first transmission member during operation, thereby preventing the second transmission member from rotating with the first transmission member, resulting in the second transmission member being unable to complete the reciprocating movement or causing the second transmission reciprocating movement rate to decrease, thereby affecting the positioning and centering accuracy of the pipe. This is beneficial to ensuring that the servo spiral positioning device can stably perform its servo positioning function and ensure the pipe processing accuracy.

[0018] In a preferred implementation of a pipe positioning device for a pipe cutting machine, the circumferential limit assembly includes a connecting plate and a limit rod, and the two ends of the connecting plate are respectively connected to the second transmission member and the limit rod; the main frame is provided with a limit hole for the limit rod to pass through in a direction parallel to the rotation axis of the first transmission member, and the limit rod is inserted into the limit hole and can move axially relative to the limit hole.

[0019] The second transmission member is limited circumferentially by the connecting plate and the limiting rod, which has a simple structure and is easy to set up. While the limiting rod limits the second transmission member circumferentially, it can also guide the reciprocating movement of the second transmission member by cooperating with the limiting hole, thereby further ensuring the arrival rate of the second transmission member and the positioning and centering accuracy of the pipe, thereby improving the processing accuracy of the pipe.

[0020] In a preferred implementation of a pipe positioning device for a pipe cutting machine, it also includes an axial limiting component, which is connected to the second transmission member of at least one of the servo screw positioning devices, and can cooperate with the first transmission member and / or the main frame of at least one of the servo screw positioning devices to limit the second transmission member from being separated from the transmission connection with the first transmission member along the extension direction of the rotation axis of the first transmission member.

[0021] The setting of the axial limit assembly can effectively prevent the second transmission member from exceeding the action stroke during the reciprocating movement relative to the first transmission member, causing the second transmission member to disengage from the first transmission member, affecting the normal operation of the servo spiral positioning device and even the entire pipe cutting machine pipe positioning device.

[0022] In a preferred implementation of a tube positioning device for a tube cutting machine, the axial limiting assembly includes a limiting block arranged at the end of the second transmission member along the extension direction of the rotation axis of the first transmission member.

[0023] In a preferred implementation of a pipe positioning device for a pipe cutting machine, at least one or more of the servo screw positioning devices are also provided with a distance monitoring device, and the distance monitoring device is connected to the second transmission member to monitor the movement distance of the second transmission member relative to the first transmission member.

[0024] In a preferred implementation of a pipe positioning device for a pipe cutting machine, the distance monitoring device includes a photoelectric sensing element connected to the second transmission element and a photoelectric emitting element arranged on the main frame and / or the first transmission element.

[0025] By setting the above-mentioned distance monitoring device, the action distance of the second transmission member can be monitored in real time during the entire processing process, which is convenient for real-time adjustment of the working condition of the servo screw positioning device according to the diameter of the pipe, thereby facilitating the alignment of the center of the pipe and the center of the chuck during the entire processing process, thereby better ensuring the processing accuracy of the pipe.

[0026] In a preferred implementation of a tube positioning device for a tube cutting machine, the tube positioning device for a tube cutting machine is installed on a bed of the tube cutting machine, and the bed includes a bed frame and a bed cover plate arranged on an upper portion of the bed frame;

[0027] The bed cover plate and the bed frame enclose an installation space, the pipe positioning device of the pipe cutting machine is arranged in the installation space, and the bed cover plate is provided with an opening through which the second transmission member can pass. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0029] Figure 1 This is a schematic structural diagram of a servo screw positioning device in one embodiment of the utility model;

[0030] Figure 2 is a schematic diagram of the structure of a single servo screw positioning device in an example;

[0031] Figure 3 for Figure 2 A schematic diagram of the structure of a single servo screw positioning device from another perspective;

[0032] Figure 4 It is a schematic diagram of the matching structure of the pipe positioning device of a pipe cutting machine and the pipe cutting machine bed in one embodiment of the utility model.

[0033] List of parts and reference numerals:

[0034] 1-driving motor; 2-transmission shaft; 3-servo screw positioning device, 31-first transmission member, 32-second transmission member, 33-main frame, 341-connecting plate, 342-limiting rod; 4-limiting block; 51-photoelectric sensing element, 52-photoelectric emitting element; 6-bed, 61-bed frame, 62-bed cover, 621-opening. DETAILED DESCRIPTION

[0035] In order to more clearly illustrate the overall concept of the present invention, a detailed description is given below in combination with the accompanying drawings by way of examples.

[0036] It should be noted that many specific details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific implementation methods disclosed below.

[0037] like Figures 1 to 3As shown, the utility model provides a tube positioning device for a tube cutting machine, including a plurality of servo screw positioning devices 3 arranged along the same direction, such as the axial direction of the bed 6 and / or the axial direction of the tube, each servo screw positioning device 3 includes a main frame 33, a first transmission member 31 arranged on the main frame 33 and capable of rotating relative to the main frame 33, and a second transmission member 32 that is transmission-connected to the first transmission member 31 and capable of reciprocating along the extension direction of the rotation axis of the first transmission member 31; it also includes a driving device, the driving device includes a driving motor 1 and a transmission shaft 2 that is transmission-connected to the driving motor 1, the transmission shaft 2 is transmission-connected to the first transmission member 31 of each servo screw positioning device 3, so as to drive the second transmission member 32 of each servo screw positioning device 3 to synchronously reciprocate relative to each first transmission member 31. Preferably, referring to Figure 1 As shown, the transmission shaft 2 has multiple sections, and the multiple sections are connected by couplings. Compared with a single long shaft, this arrangement can prevent the long shaft from being deformed flexibly due to a large aspect ratio and affecting its rotational stability, which is conducive to ensuring the synchronization of the actions of each second transmission member 32. At the same time, when a single section fails, some sections can still maintain normal operation, and the replacement and maintenance of a single section is more convenient, avoiding the phenomenon that a single long shaft failure causes the whole machine to stop and the processing efficiency to be seriously reduced.

[0038] In the scheme of the present application, the second transmission members of each servo screw positioning device can be driven to achieve synchronous action through a driving motor and a transmission shaft, so that multiple servo screw positioning devices can be enabled to synchronously support the pipe. Compared with the existing auxiliary support structures such as rollers with independent power, the deformation of the pipe caused by the asynchronous action of the second transmission members can be avoided, which affects the processing accuracy. This is beneficial to further ensure the cutting processing accuracy of the pipe and also saves the equipment cost of setting up multiple independent power sources.

[0039] As a preferred embodiment of the present application, refer to Figure 4 As shown, the pipe positioning device of the pipe cutting machine is installed on the bed 6 of the pipe cutting machine, and the bed 6 includes a bed frame 61 and a bed cover plate 62 arranged on the upper part of the bed frame 61; the bed cover plate 62 and the bed frame 61 surround an installation space, and the pipe positioning device of the pipe cutting machine is arranged in the installation space, and the bed cover plate 62 is provided with an opening 621 for the second transmission member to pass through. A plurality of pipe positioning devices of the pipe cutting machine are arranged along the axial direction of the bed 6.

[0040] The present application can play a role in assisting positioning and improving the efficiency of pipe feeding during the pipe feeding process by setting up multiple servo screw positioning devices arranged in the same direction, and can also continuously provide auxiliary positioning during the pipe cutting process. At the same time, the servo screw positioning device can also play a role in assisting support during the entire cutting process. For pipes that are arranged and supported for cutting with long spans, the support of the servo screw positioning device can effectively avoid or reduce the influence of the flexible deformation of the pipe on the pipe cutting accuracy, and it is also beneficial to improve the overall load-bearing capacity of the equipment.

[0041] Further, refer to Figure 2 and Figure 3 As shown, along the extension direction of the rotation axis of the first transmission member 31, the first transmission member 31 is provided with a driving part that penetrates the first transmission member 31, the second transmission member 32 is provided in the driving part and the second transmission member 32 has a matching part that matches with the driving part; the first transmission member 31 and the second transmission member 32 realize transmission connection through the matching between the driving part and the matching part.

[0042] Through the cooperation of the driving part and the matching part, the transmission connection between the first transmission member 31 and the second transmission member 32 is realized. On the one hand, it can simplify the structure of the servo screw positioning device 3 in the present application, and the arrangement of the driving part running through the first transmission member 31 can effectively reduce the installation space occupied by the matching structure of the first transmission member 31 and the second transmission member 32, so as to better adapt to the limited installation space in the pipe cutting machine body 6; on the other hand, the above-mentioned matching structure and matching method are simple, the processing and use costs are low, and good economic benefits can be obtained.

[0043] It should be noted that the present application does not specifically limit the structures of the driving part and the matching part and the transmission matching method therebetween, and the following embodiments may be adopted:

[0044] Implementation method 1: Figure 2 and Figure 3 As shown, in this embodiment, the driving part is a driving hole, and an internal thread is provided on the inner wall of the driving hole; the matching part is a threaded part provided on the second transmission member 32 along the extension direction of the rotation axis of the first transmission member 31, and the threaded part is provided with an external thread engaged with the internal thread. The connection through the engagement of internal and external threads can simultaneously achieve the structural connection and the connection in the transmission relationship, which is conducive to simplifying the structure, reducing the number of parts, and is convenient, practical and easy to maintain. At the same time, the threaded connection method itself also has good structural stability, which is conducive to ensuring the stability of the connection structure between the first transmission member 31 and the second transmission member 32 and the stability of the relative movement between the two.

[0045] Of course, it is also possible to adopt more different solutions other than this embodiment.

[0046] It should be further explained that the present application does not specifically limit the structures of the first transmission member 31 and the second transmission member 32, and adopts the scheme in the following embodiments:

[0047] Example 1: Continue to refer to Figure 2 As shown, the first transmission member 31 is a gear, the second transmission member 32 is a lead screw, the shaft hole of the gear is a driving hole and is provided with an internal thread, and the threaded portion of the lead screw is a matching portion and is provided with an external thread.

[0048] Gears and lead screws are common parts in the field of mechanical equipment, which are easy to obtain and have low use and maintenance costs, and have good working stability. During long-term use, they are conducive to ensuring the stable operation of the servo screw positioning device 3 and even the entire pipe cutting machine equipment.

[0049] Of course, it is also possible to adopt more different solutions other than this embodiment.

[0050] As a preferred embodiment of the present application, refer to Figure 2 and Figure 3 As shown, each servo screw positioning device 3 also includes a circumferential limit assembly, which is respectively connected to the second transmission member 32, the main frame 33 and / or the bed 6 to limit the second transmission member 32 from rotating around the rotation axis of the first transmission member 31.

[0051] By setting the circumferential limit assembly, it can be ensured that the second transmission member 32 only reciprocates along the extension direction of the rotation axis of the first transmission member 31 during operation, thereby preventing the second transmission member 32 from rotating with the first transmission member 31, resulting in the second transmission member 32 being unable to complete the reciprocating movement or causing the second transmission reciprocating movement rate to decrease, thereby affecting the positioning and centering accuracy of the pipe. This is beneficial to ensuring that the servo spiral positioning device 3 stably performs its servo positioning function and ensures the pipe processing accuracy.

[0052] It should be noted here that the present application does not specifically limit the structure of the axial limit assembly and the coordination method and coordination structure between it and other components of the servo screw positioning device 3 such as the second transmission member 32, and it can adopt the scheme in the following embodiments.

[0053] Example 1: Reference Figure 2 and Figure 3 As shown, the circumferential limit assembly includes a connecting plate 341 and a limit rod 342, and the two ends of the connecting plate 341 are respectively connected to the second transmission member 32 and the limit rod 342; a limit hole for the limit rod 342 to pass through is opened on the main frame 33 along a direction parallel to the rotation axis of the first transmission member 31, and the limit rod 342 penetrates into the limit hole and can move axially relative to the limit hole.

[0054] The second transmission member 32 is limited circumferentially by the connecting plate 341 and the limiting rod 342, which has a simple structure and is easy to set up. While the limiting rod 342 limits the second transmission member 32 circumferentially, it can also guide the reciprocating movement of the second transmission member 32 by cooperating with the limiting hole, thereby further ensuring the arrival rate of the second transmission member 32 and the positioning and centering accuracy of the pipe, thereby improving the processing accuracy of the pipe.

[0055] Of course, it is also possible to adopt more different solutions other than this embodiment.

[0056] As a preferred embodiment of the present application, refer to Figure 2 and Figure 3 As shown, the pipe positioning device of the pipe cutting machine in the present application also includes an axial limiting component, which is connected to the second transmission member 32 of at least one servo screw positioning device 3, and can be limitedly cooperated with the bed 6 or the first transmission member 31 and / or the main frame 33 of at least one servo screw positioning device 3 to limit the second transmission member 32 from being separated from the transmission connection with the first transmission member 31 along the extension direction of the rotation axis of the first transmission member 31.

[0057] The setting of the axial limit assembly can effectively prevent the second transmission member 32 from exceeding the action stroke during the reciprocating movement relative to the first transmission member 31, causing the second transmission member 32 to separate from the first transmission member 31, affecting the normal operation of the servo screw positioning device 3 and even the entire pipe cutting machine pipe positioning device.

[0058] It should be noted that the present application does not specifically limit the structure of the axial limit assembly and the connection structure and connection method between the servo screw positioning device 3 and the bed 6, and the following embodiments may be adopted:

[0059] Example 1: Reference Figure 2 As shown, the axial limiting assembly includes a limiting block 4 arranged at the end of the second transmission member 32 along the extension direction of the rotation axis of the first transmission member 31. This setting method of using the limiting block 4 for limiting is simple, reliable, low-cost and easy to maintain.

[0060] Of course, it is also possible to adopt more different solutions other than this embodiment.

[0061] As a preferred embodiment of the present application, at least one or more than two servo screw positioning devices 3 are further provided with a distance monitoring device, which is connected with the second transmission member 32 to monitor the moving distance of the second transmission member 32 relative to the first transmission member 31. In a preferred example, referring to Figure 1 , 2As shown in FIG. 3 , each servo screw positioning device 3 is provided with a distance monitoring device, which includes a photoelectric sensing element 51 connected to the second transmission element 32 and a photoelectric emitting element 52 arranged on the main frame 33 .

[0062] By setting the above-mentioned distance monitoring device, the action distance of the second transmission member 32 can be monitored in real time during the entire processing process, and the working condition of the servo spiral positioning device 3 can be adjusted in real time according to the diameter of the pipe, which is conducive to keeping the center of the pipe and the center of the chuck aligned during the entire processing process, and better ensuring the processing accuracy of the pipe. In addition, since the second transmission member 32 of each servo spiral positioning device 3 in the present application synchronously reciprocates relative to each first transmission member 31, the distance monitoring device in the present application can be set only on one or a few spiral servo positioning devices, thereby saving equipment costs.

[0063] It should be noted here that the above examples of distance monitoring devices are only preferred examples of the present application, and other more different setting schemes may also be adopted, and the present application does not make specific limitations on this.

[0064] The technical solution protected by the present utility model is not limited to the above-mentioned embodiments. It should be pointed out that the combination of the technical solution of any embodiment with the technical solution of one or more other embodiments is within the protection scope of the present utility model. Although the present utility model has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to it based on the present utility model. Therefore, these modifications or improvements made without departing from the spirit of the present utility model are within the scope of protection claimed by the present utility model.

Claims

1. A pipe positioning device for a pipe cutting machine, characterized in that: It comprises a plurality of servo screw positioning devices arranged in the same direction, each of which comprises a main frame, a first transmission member arranged on the main frame and capable of rotating relative to the main frame, and a second transmission member which is transmission-connected to the first transmission member and capable of reciprocating along the extension direction of the rotation axis of the first transmission member; It also includes a driving device, which includes a driving motor and a transmission shaft drivingly connected to the driving motor, and the transmission shaft is drivingly connected to the first transmission member of each servo screw positioning device to drive the second transmission member of each servo screw positioning device to reciprocate synchronously relative to each first transmission member.

2. A pipe positioning device for a pipe cutting machine according to claim 1, characterized in that: Along the extension direction of the rotation axis of the first transmission member, the first transmission member is provided with a driving portion penetrating the first transmission member, and the second transmission member is provided with a matching portion for transmission matching with the driving portion.

3. A pipe positioning device for a pipe cutting machine according to claim 2, characterized in that: The driving portion is a driving hole, and an internal thread is arranged on the inner wall of the driving hole; the matching portion is a threaded portion arranged on the second transmission member along the extension direction of the rotation axis of the first transmission member, and the threaded portion is provided with an external thread meshing with the internal thread.

4. A pipe positioning device for a pipe cutting machine according to claim 3, characterized in that: The first transmission member is a gear, the second transmission member is a lead screw, the axial hole of the gear is the driving hole and is provided with the internal thread, and the threaded portion of the lead screw is the matching portion and is provided with the external thread.

5. The pipe positioning device for a pipe cutting machine according to claim 1, characterized in that: Each of the servo screw positioning devices further comprises a circumferential limit assembly, and the circumferential limit assembly is respectively connected to the second transmission member and the main frame to limit the second transmission member from rotating around the rotation axis of the first transmission member.

6. A pipe positioning device for a pipe cutting machine according to claim 5, characterized in that: The circumferential limit assembly includes a connecting plate and a limit rod, and the two ends of the connecting plate are respectively connected to the second transmission member and the limit rod; the main frame is provided with a limit hole for the limit rod to pass through in a direction parallel to the rotation axis of the first transmission member, and the limit rod is inserted into the limit hole and can move axially relative to the limit hole.

7. A pipe positioning device for a pipe cutting machine according to claim 1, characterized in that: It also includes an axial limiting component, which is connected to the second transmission member of at least one of the servo screw positioning devices, and can cooperate with the first transmission member and / or the main frame of at least one of the servo screw positioning devices to limit the second transmission member from being separated from the transmission connection with the first transmission member along the extension direction of the rotation axis of the first transmission member.

8. A pipe positioning device for a pipe cutting machine according to claim 7, characterized in that: The axial limiting assembly includes a limiting block arranged at the end of the second transmission member along the extending direction of the rotation axis of the first transmission member.

9. A pipe positioning device for a pipe cutting machine according to claim 1, characterized in that: At least one or more than two of the servo screw positioning devices are also provided with a distance monitoring device, and the distance monitoring device is cooperatively connected with the second transmission member to monitor the moving distance of the second transmission member relative to the first transmission member.

10. A pipe positioning device for a pipe cutting machine according to claim 9, characterized in that: The distance monitoring device comprises a photoelectric sensing element connected to the second transmission element and a photoelectric emitting element arranged on the main frame and / or the first transmission element.

11. A pipe positioning device for a pipe cutting machine according to any one of claims 1 to 10, characterized in that: The pipe positioning device of the pipe cutting machine is installed on the bed of the pipe cutting machine, and the bed includes a bed frame and a bed cover plate arranged on the upper part of the bed frame; The bed cover plate and the bed frame enclose an installation space, the pipe positioning device of the pipe cutting machine is arranged in the installation space, and the bed cover plate is provided with an opening through which the second transmission member can pass.

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