CN112475074A

CN112475074A - Necking method of thin-wall pipe fitting and necking equipment applying same

Info

Publication number: CN112475074A
Application number: CN202011413554.6A
Authority: CN
Inventors: 黄伟; 林爱素
Original assignee: Ningbo Tianxin Metal Hose Co ltd
Current assignee: Ningbo Tianxin Metal Hose Co ltd
Priority date: 2020-12-04
Filing date: 2020-12-04
Publication date: 2021-03-12
Anticipated expiration: 2040-12-04
Also published as: CN112475074B

Abstract

The invention relates to a necking method of a thin-wall pipe fitting and necking equipment applying the method, wherein the necking method comprises the following steps: firstly, determining the necking length of the pipe fitting; secondly, clamping the pipe fitting through a pipe clamping machine, extruding the joint of a necking section and a non-necking section of the pipe fitting from outside to inside through a clamp, and simultaneously rotating the clamp until the pipe wall of the pipe fitting forms an inwards concave annular groove; and finally, keeping the clamp rotating, and controlling the pipe clamping machine to drive the pipe fitting to axially move until the necking section is formed, thus completing pipe fitting necking. The necking equipment mainly comprises a necking clamp, a pipe clamping machine and a first power cylinder, wherein the pipe clamping machine is used for clamping a pipe, the first power cylinder drives the pipe clamping machine to move along the axial direction of the pipe, and the necking clamp mainly comprises a clamp capable of achieving the processing of the annular groove and a mechanism for driving the clamp to form clamping and rotating. The invention has the advantages of high necking forming efficiency, good size precision and convenient adjustment of the necking caliber, and is particularly suitable for necking the thin-wall pipe fitting with the wall thickness dimension smaller than 0.25 mm.

Description

Necking method of thin-wall pipe fitting and necking equipment applying same

Technical Field

The invention relates to the field of pipe fitting processing, in particular to a necking method of a thin-wall pipe fitting and necking equipment applying the method.

Background

The necking process is a forming process for reducing the mouth of a preformed pipe fitting or pipe blank to a required size through a necking die holder. The existing necking process is generally suitable for pipe fittings with the wall thickness of more than 0.25MM, and the requirements of the thin-wall pipe fittings are difficult to meet, mainly because the thin-wall pipe fittings are easy to wrinkle when being subjected to necking in a necking die seat, so that the quality is unqualified. In the prior art, as published in the patent application publication No. CN107745051A published in chinese patent literature, published in 2018, 3 and 2, the invention application name is "a die and a method for reducing a thin-wall metal tube, which includes a reducing die body provided with a central reducing through hole, the central reducing through hole sequentially includes, from front to back: the diameter of the tail end straight line section is larger than that of the middle straight line section, a plurality of fan-shaped cutting grooves which take the central shaft of the middle straight line section as the axis are uniformly distributed on the cone forming section and the middle straight line section, and the intersection positions of every two of the fan-shaped cutting grooves, the cone forming section and the middle straight line section are all in circular arc transition. Although the structure can realize thin-wall necking, the precision size requirement of the die is high, the investment cost is high, and the necking machining size is not easy to adjust, so that the large-batch industrial machining is difficult to realize. Therefore, the existing thin-wall pipe necking method and equipment are to be improved.

Disclosure of Invention

In order to overcome the defects, the invention aims to provide a method for necking a thin-wall pipe fitting and necking equipment applying the method for necking the thin-wall pipe fitting in the field, so that the technical problems that the existing similar necking method or equipment is high in input cost, difficult in adjustment of necking size and difficult to meet the requirement of large-scale industrial processing and use are solved. The purpose is realized by the following technical scheme.

The necking method of the thin-wall pipe fitting comprises the following steps:

determining the length of a necking of the pipe fitting, and determining the joint position of a necking section and a non-necking section of the pipe fitting according to the length of the necking.

And step two, clamping the pipe fitting through a pipe clamping machine, extruding the joint position of the pipe fitting in the step one from outside to inside through a clamp, and simultaneously rotating the clamp until the pipe wall of the pipe fitting forms an inwards concave annular groove, wherein the outer diameter of the groove bottom of the annular groove is the outer diameter of the necking section of the pipe fitting.

And step three, keeping the clamp to rotate, and controlling the pipe clamping machine to drive the pipe fitting to axially move until the necking section is formed, so that the pipe fitting necking is finished.

The method utilizes the modes of reducing the diameter in the pipe and then stretching the reducing, thereby not only effectively ensuring the caliber size of the reducing, but also ensuring the reducing quality because the pipe fitting is not easy to wrinkle or damage and deform during stretching the reducing.

And in the second step and the third step, the contact position of the pipe fitting and the clamp is lubricated and cooled. By the method, the quality of necking forming is further ensured.

And in the second step and the third step, a positioning mold core is inserted into the end opening of the to-be-reduced section of the pipe fitting, the outer diameter of the positioning mold core is matched with the inner diameter of the pipe fitting, the positioning mold core is fixed relative to the clamp, and the positioning mold core and the pipe fitting reduced section are kept to be formed without interference. By the method, the stability of necking operation is improved, and the necking quality is favorably ensured.

And lubricating between the positioning mold core and the inner wall of the pipe fitting. The method is beneficial to improving the rotating stability of the pipe fitting and further ensuring the quality of necking forming.

In the second step and the third step, the rotation of the pipe fitting is changed into the rotation, and the rotation of the clamp relative to the axis of the pipe fitting is changed into the static state. The method can replace the original working condition and also achieve the same purpose.

A throat apparatus to employ the above-mentioned thin-walled tube necking method, the throat apparatus includes the throat clamp, the tube holder used for clamping the tube, drive the tube holder to move axially along the tube, the first power cylinder to fix the stander of the first power cylinder; the structure is characterized in that the necking clamp comprises a clamp body and a clamping rotating mechanism, wherein the front section of the clamp body is an elastic clamping section, the rear section of the clamp body is a cylindrical guide section, the elastic clamping section forms at least two parts which are uniformly distributed along the circumferential direction, deformation gaps are arranged between the circumferential direction of each part, the outer circumferential surface of the elastic clamping section is a conical surface with the outer diameter size from the front end to the rear section being gradually reduced, a working cavity matched with the length of the necking section of the pipe fitting is arranged inside the elastic clamping section, and the front end of the elastic clamping section is provided with a clamping part which clamps the pipe fitting within the range of the deformation gaps and forms the annular groove; the clamping and rotating mechanism comprises a rotating seat, a fixed seat, a second power cylinder and a motor, the rotating seat is positioned and rotated relative to the fixed seat, the fixed seat is fixed on the rack, a belt wheel A is integrated on the outer peripheral surface of the rotating seat, the belt wheel A is connected with a driving wheel of the motor through transmission of a transmission belt, and the motor is fixed on the rack; the rotary seat is internally provided with a working guide hole which is sleeved with the conical surface of the elastic clamping section and is in butt contact with the conical surface of the elastic clamping section, and a cylindrical guide hole which is axially matched with the guide section in a sliding manner and drives the guide section to synchronously rotate, the rear end of the guide section of the clamp body in the rotary seat is movably connected with a piston rod of a second power cylinder which drives the clamp body to axially move, the second power cylinder is fixed on the rack, and when the clamp body moves towards the rear end direction along with the second power cylinder, the conical surface of the clamp body is extruded by the working guide hole of the rotary seat, so that the clamping part of the clamp body forms clamping; the movable connection means that the guide section is axially connected relative to the end of the piston rod and simultaneously forms relative rotation. By adopting the necking equipment, the structure is simple, the necking size is easy to adjust, the automatic necking operation can be realized, and the necking forming quality is ensured.

The clamping part of the clamp body is detachably connected with the elastic clamping section. Through this structure, conveniently change clamping part to be applicable to different throat operating modes.

The necking equipment comprises a necking clamp, a pipe clamping machine, a first power cylinder and a rack, wherein the pipe clamping machine is used for clamping the pipe; the necking clamp is structurally characterized by comprising a clamp, a clamping mechanism, a fixed seat and a motor, wherein the clamp comprises at least two clamping heads which are distributed in the circumferential direction relative to a pipe fitting, and a clamping rotating seat which clamps the clamping heads towards the pipe fitting to form a guide, the clamping rotating seat is positioned and rotated relative to the fixed seat, the fixed seat is fixed on a rack, a belt wheel B is integrated on the outer circumferential surface of the clamping rotating seat, the belt wheel B is connected with a driving wheel of the motor through a transmission belt, and the motor is fixed on the rack; the front end of the clamping rotary seat is provided with a cavity matched with the length of the necking section of the pipe fitting, the cavity of the clamping rotary seat is circumferentially provided with a guide hole matched with the expansion of the chuck, one end of the chuck extends into the cavity and is provided with a clamping part for extruding the pipe fitting and forming the annular groove, the other end of the chuck extends out of the guide hole and is provided with a guide block limited on the outer side of the guide hole, and a reset spring sleeved on the chuck is arranged between the guide block and the outer end of the guide hole; the clamping mechanism comprises a guide push rod and a second power cylinder, the second power cylinder is fixed on the rack, the clamping rotary seat is provided with a guide sliding hole matched with the guide push rod to slide in a telescopic mode, one end of the guide push rod extends out of the guide sliding hole to be in contact with a guide block at the outer end of the chuck, the other end of the guide push rod extends out of the guide sliding hole to be movably connected with a piston rod of the second power cylinder, and when the guide push rod moves along with the second power cylinder, the guide push rod pushes the guide block and enables the chuck to move towards the cavity of the clamping rotary seat, namely, the clamping part of the chuck reaches the position where the pipe fitting is clamped and the annular groove is; the movable connection means that the guide push rod is axially connected relative to the piston rod of the second power cylinder and simultaneously forms relative rotation. By adopting the necking equipment, the same structure is simpler, the necking size is easy to adjust, the automatic necking operation can be realized, and the necking forming quality is ensured.

One of the contact parts of the guide push rod and the guide block of the clamp is a rod, and the other contact part is an inclined plane. The axial motion of the guide push rod is linked with the guide block to drive the chuck to move in a telescopic way through force transmission formed by matching the rod and the inclined plane, and the clamping operation of the chuck on the pipe fitting is realized.

The first power cylinder and the second power cylinder are any one of an air cylinder, a hydraulic cylinder or an electric cylinder. The axial force can be provided, and the purpose of pushing and pulling is achieved.

The invention has the advantages that: the necking forming efficiency is high, the size precision is good, the necking caliber is convenient to adjust, the requirement of large-scale industrial processing production is met, and the method is particularly suitable for necking the thin-wall pipe fitting with the wall thickness dimension smaller than 0.25mm or improving the similar necking method.

Drawings

Fig. 1 is a schematic structural diagram of the necking operation state of the present invention.

Fig. 2 is a schematic structural diagram of the two working states of the necking device of the present invention.

Fig. 3 is a schematic diagram of three structures of the necking working state of the invention.

Fig. 4 is a schematic diagram of the four structures of the necking operation state of the present invention.

Fig. 5 is a schematic structural view of a version of the necking apparatus of the present invention, partially sectioned and framed.

Fig. 6 is an enlarged schematic view of the framing portion of fig. 5.

Fig. 7 is a schematic view of the end face structure of the clamp body in fig. 5.

Fig. 8 is a perspective view of the clamp body in fig. 5 in a disassembled state.

Fig. 9 is a schematic structural view of a second embodiment of the necking apparatus of the present invention, partially sectioned and framed.

Fig. 10 is an enlarged schematic view of the framing portion of fig. 9.

Fig. 11 is a schematic view of the structure of the clamp of fig. 9.

Fig. 12 is a schematic perspective view of fig. 11.

The sequence numbers and names in the figure are: 1. the pipe fitting comprises a pipe fitting body, a pipe clamping machine, 101, an annular groove, 2, a clamp, 201, a clamping head, 202, a clamping part, 203, a guide block, 3, a pipe clamping machine, 4, a first power cylinder, 5, a frame, 6, a motor, 7, a clamp body, 701, an elastic clamping section, 702, a guide section, 703, a conical surface, 704, a working cavity, 705, a clamping part, 706, a deformation gap, 8, a rotating seat, 801, a working guide hole, 802, a cylindrical guide hole, 803, a belt pulley A, 9, a fixed seat, 10, a second power cylinder, 11, a thrust bearing, 12, a clamping rotating seat, 1201, a cavity, 1202, a guide hole, 1203, a guide sliding hole, 1204, a belt pulley B, 13, a return spring, 14, a positioning mold core, 15 and a guide push rod.

Detailed Description

The invention will now be further described with reference to the accompanying drawings.

As shown in fig. 1-4, the method for necking the thin-wall pipe fitting mainly comprises the following steps:

step one, determining the necking length of the pipe fitting 1, and determining the joint position of a necking section and a non-necking section of the pipe fitting according to the necking length.

And step two, clamping the pipe fitting through a pipe clamping machine 3, extruding the joint position of the pipe fitting in the step one from outside to inside through a clamp 2, and simultaneously rotating the clamp until the pipe wall of the pipe fitting forms an inwards concave annular groove 101, wherein the outer diameter of the groove bottom of the annular groove is the outer diameter of the necking section of the pipe fitting.

In order to further ensure the stability of the necking process and the necking quality. And in the second step and the third step, the contact position of the pipe fitting 1 and the clamp 2 is lubricated and cooled. And step two, inserting a positioning mold core 14 into the end opening of the to-be-reduced section of the pipe fitting in step three, matching the outer diameter of the positioning mold core with the inner diameter of the pipe fitting, fixing the positioning mold core relative to the clamp, and keeping the positioning mold core and the pipe fitting reduced section from being formed without interference. And lubricating between the positioning mold core and the inner wall of the pipe fitting.

In the second step and the third step, the pipe fitting can be still and changed into rotation, the clamp can be still relative to the rotation of the axis of the pipe fitting, and the necking forming of the pipe fitting can be realized.

According to the pipe fitting necking method, the invention also discloses two necking devices, which are as follows.

A first necking apparatus, as shown in fig. 5 to 8, includes a necking clamp, a pipe clamping machine 3 for clamping a pipe 1, a first power cylinder 4 for driving the pipe clamping machine to move axially along the pipe, and a frame 5 for fixing the first power cylinder. The necking clamp comprises a clamp body 7 and a clamping rotating mechanism, wherein the front section of the clamp body is an elastic clamping section 701, the rear section is a cylindrical guide section 702, the elastic clamping section forms at least two parts which are uniformly distributed along the circumferential direction, deformation gaps 706 are formed between the circumferential directions of the parts, the outer circumferential surface of the elastic clamping section is a conical surface 703 with the outer diameter size from the front end to the rear section gradually reduced, a working cavity 704 matched with the length of the necking section of the pipe fitting is arranged inside the elastic clamping section, and a clamping part 705 which clamps the pipe fitting 1 in the deformation gap range and forms the annular groove 101 is arranged at the front end of the elastic clamping section. The clamping and rotating mechanism comprises a rotating seat 8, a fixed seat 9, a second power cylinder 10 and a motor 6, the rotating seat is positioned and rotated relative to the fixed seat, the fixed seat is fixed on the rack, a belt wheel A803 is integrally arranged on the outer peripheral surface of the rotating seat, the belt wheel A is connected with a driving wheel of the motor through transmission of a transmission belt, and the motor is fixed on the rack 5. The rotary base is internally provided with a working guide hole 801 which is sleeved with a conical surface of the elastic clamping section and is in contact with the conical surface in an offsetting way, and a cylindrical guide hole 802 which is axially matched with the guide section in a sliding way and drives the guide section to synchronously rotate, for example, the guide section is a polygonal column, the working guide hole is a polygonal hole, or the outer diameter of the guide section is provided with a sliding groove, and a convex rib which is matched with the sliding groove in a sliding way is arranged corresponding to the inner diameter of the working guide hole. The rear end of the guide section of the fixture body in the rotary seat is movably connected with a piston rod of a second power cylinder which drives the fixture body to move axially, the second power cylinder is fixed on the rack, and when the fixture body moves towards the rear end direction along with the second power cylinder, the conical surface of the fixture body is extruded by the working guide hole of the rotary seat, so that the clamping part of the fixture body forms clamping. The movable connection means that the guide section can rotate freely relative to the end part of the piston rod when being axially connected, and the specific structure adopts that the rear end of the clamp body and the two sides of the shaft connection of the piston rod are provided with the thrust bearings 11 or the angular contact bearings for positioning, so that the purpose of relative rotation can be achieved while the shaft connection is realized.

In order to facilitate the adaptation to necking processes of different sizes, the clamping portion 705 of the clamp body 7 is detachably connected to the elastic clamping section 701, and as shown in fig. 7, a bolt is used to fix the clamping portion and the end face of the elastic clamping section. Therefore, the size of the necking can be adjusted by replacing the clamping part, and the adjustment is convenient.

As shown in fig. 9-12, another necking apparatus comprises a necking clamp, a pipe clamping machine 3 for clamping a pipe, a first power cylinder 4 for driving the pipe clamping machine to move along the axial direction of the pipe, and a frame 5 for fixing the first power cylinder. The necking clamp comprises a clamp 2, a clamping mechanism, a fixed seat 9 and a motor 6, the clamp comprises at least two chucks 201 which are distributed circumferentially relative to a pipe fitting 1, and a clamping rotating seat 12 which clamps the chucks towards the pipe fitting direction to form a guide, the clamping rotating seat is positioned and rotated relative to the fixed seat, and the fixed seat is fixed on a rack. The periphery of the clamping rotary seat is integrally provided with a belt wheel B1204, the belt wheel B is connected with a driving wheel of a motor through a transmission belt, and the motor is fixed on the frame. The front end of the clamping rotary seat is provided with a cavity 1201 matched with the length of the necking section of the pipe fitting, the circumference of the cavity of the clamping rotary seat is provided with a guide hole 1202 matched with the expansion of a chuck, one end of the chuck extends into the cavity and is provided with a clamping part 202 for extruding the pipe fitting and forming an annular groove 101, the other end of the chuck extends out of the guide hole and is provided with a guide block 203 limited on the outer side of the guide hole, and a reset spring 13 sleeved on the chuck is arranged between the guide block and the outer end. The clamping mechanism comprises a guide push rod 15 and a second power cylinder 10, the second power cylinder is fixed on the rack, a clamping rotating seat is provided with a guide sliding hole 1203 matched with the guide push rod to slide in a telescopic mode, one end of the guide push rod extends out of the guide sliding hole to be in contact with an inclined plane of a guide block at the outer end of the chuck, the other end of the guide push rod extends out of the guide sliding hole to be movably connected with a piston rod of the second power cylinder, and when the guide push rod moves along with the second power cylinder, the guide push rod pushes the guide block, the chuck moves towards the cavity of the clamping rotating seat, namely, the clamping portion of the chuck reaches the position where. The movable connection means that the rear end of the guide push rod is axially connected relative to the end part of the piston rod and simultaneously freely rotates, the rear end of the guide push rod is integrally provided with a push block 1501 which is coaxial with the clamping rotating seat, the middle part of the push block is in shaft connection with the piston rod, and two sides of the shaft connection are provided with thrust bearings 11 or angular contact bearings for positioning, so that the purpose of relative rotation of the shaft connection can be achieved.

In the two necking devices, the first power cylinder 4 and the second power cylinder 10 are any one of an air cylinder, an oil cylinder or an electric cylinder, and the same purpose can be achieved.

The working process of the first necking equipment comprises the following steps: firstly, a steel pipe 1 to be necked is clamped and fixed on a pipe clamping machine 3, then a first power cylinder 4 is controlled to drive the pipe clamping machine to enable the end to be necked of the steel pipe to extend into a working cavity 704 of a clamp body 7, then a motor 6 is started to drive a rotary seat 8 and the clamp body to rotate, a second power cylinder 10 is controlled at the same time, the clamp body is slowly pulled by the second power cylinder, a clamping portion 705 of the clamp body slowly clamps the steel pipe, inward extrusion is formed on the pipe wall of the steel pipe until a set depth is reached, and at the moment, an annular groove 101 with a required concave size is formed on the outer wall of the steel pipe in a machining. And then, controlling the first power cylinder to slowly pull the pipe clamping machine to enable the pipe clamping machine to drive the pipe fitting to axially move towards the non-necking end until the necking end of the steel pipe is separated from the clamp body, namely completing one-time necking operation of the steel pipe, and resetting the necking equipment after the necking operation is completed so as to prepare for the next necking operation.

The operation of the second necking device is substantially similar to that of the first necking device, and only the clamping process of the clamp 2 is different, mainly in that the clamping head 201 of the clamp forms clamping when the guide push rod 15 is pushed by the second power cylinder 10, and vice versa releases clamping.

The above description is intended to illustrate the technical means of the present invention, and not to limit the technical scope of the present invention. Obvious modifications or alterations to the present invention in combination with the prior art knowledge will be apparent to those skilled in the art and fall within the scope of the appended claims.

Claims

1. A necking method of a thin-wall pipe fitting is characterized by comprising the following steps:

determining the length of a necking of the pipe fitting (1), and determining the joint position of a necking section and a non-necking section of the pipe fitting according to the length of the necking;

step two, clamping the pipe fitting through a pipe clamping machine (3), extruding the joint position of the pipe fitting in the step one from outside to inside through a clamp (2), and simultaneously rotating the clamp until the pipe wall of the pipe fitting forms an inwards concave annular groove (101), wherein the outer diameter of the bottom of the annular groove is the outer diameter of a necking section of the pipe fitting;

2. The method for necking the thin-walled tube according to claim 1, wherein the contact position of the tube (1) and the clamp (2) in the second step and the third step is lubricated and cooled.

3. The method for necking the thin-wall pipe fitting according to claim 1, wherein in the second step and the third step, a positioning mold core (14) is inserted into the end of the section to be necked of the pipe fitting (1), the outer diameter of the positioning mold core is matched with the inner diameter of the pipe fitting, the positioning mold core is fixed relative to the clamp (2), and the positioning mold core is kept from interfering with the forming of the pipe fitting necking section.

4. A method according to claim 3, characterized in that a lubricating treatment is carried out between the positioning die core (14) and the inner wall of the tube (1).

5. The method for necking the thin-walled tube according to claim 1, wherein in the second step and the third step, the tube (1) is changed from stationary to rotating, and the clamp (2) is changed from rotating relative to the axis of the tube to stationary.

6. A necking apparatus applying the thin-walled tube necking method of claim 1, the necking apparatus comprising a necking jig, a tube clamping machine (3) for clamping the tube (1), a first power cylinder (4) for driving the tube clamping machine to move axially along the tube, and a frame (5) for fixing the first power cylinder; the necking fixture is characterized by comprising a fixture body (7) and a clamping rotating mechanism, wherein the front section of the fixture body is an elastic clamping section (701), the rear section of the fixture body is a cylindrical guide section (702), the elastic clamping section forms at least two parts which are uniformly distributed along the circumferential direction, deformation gaps (706) are formed among the circumferential directions of the parts, the peripheral surface of the elastic clamping section is a conical surface (703) with the gradually-reduced outer diameter size from the front end to the rear section, a working cavity (704) matched with the length of the necking section of the pipe fitting is arranged in the elastic clamping section, and the front end of the elastic clamping section is provided with a clamping part (705) which clamps the pipe fitting (1) in the deformation gap range and forms the annular groove (101); the clamping and rotating mechanism comprises a rotating seat (8), a fixed seat (9), a second power cylinder (10) and a motor (6), the rotating seat is positioned and rotated relative to the fixed seat, the fixed seat is fixed on the rack, a belt wheel A (803) is integrated on the outer peripheral surface of the rotating seat, the belt wheel A is connected with a driving wheel of the motor through transmission of a transmission belt, and the motor is fixed on the rack (5); a working guide hole (801) which is sleeved with the conical surface of the elastic clamping section and is in contact with the conical surface of the elastic clamping section in an abutting mode and a cylindrical guide hole (802) which is in axial sliding fit with the guide section and drives the guide section to rotate synchronously are arranged in the rotary seat, the rear end of the guide section of the clamp body in the rotary seat is movably connected with a piston rod of the second power cylinder which drives the clamp body to move axially, the second power cylinder is fixed on the rack, and when the clamp body moves towards the rear end direction along with the second power cylinder, the conical surface of the clamp body is extruded by the working guide hole of the rotary seat, so that the clamping part of the clamp body forms clamping; the movable connection means that the guide section is axially connected relative to the end of the piston rod and simultaneously forms relative rotation.

7. A necking apparatus according to claim 6, wherein the clamping portion (705) of the clamp body (7) is removably connected with respect to the elastic clamping section (701).

8. A necking apparatus for applying the necking method of the thin-walled tube member according to claim 1, the necking apparatus comprising a necking jig, a tube clamping machine (3) for clamping the tube member, a first power cylinder (4) for driving the tube clamping machine to move axially along the tube member, and a frame (5) for fixing the first power cylinder; the necking fixture is characterized by comprising a fixture (2), a clamping mechanism, a fixed seat (9) and a motor (6), wherein the fixture comprises at least two clamping heads (201) which are circumferentially distributed relative to the pipe fitting (1) and a clamping rotating seat (12) which clamps the clamping heads towards the direction of the pipe fitting to form a guide, the clamping rotating seat is positioned and rotated relative to the fixed seat, the fixed seat is fixed on the rack (5), a belt wheel B (1204) is integrally arranged on the outer peripheral surface of the clamping rotating seat, the belt wheel B is connected with a driving wheel of the motor through a transmission belt in a transmission mode, and the motor is; the front end of the clamping rotary seat is provided with a cavity (1201) matched with the length of the necking section of the pipe fitting, the cavity of the clamping rotary seat is circumferentially provided with a guide hole (1202) matched with the extension of the chuck, one end of the chuck extends into the cavity and is provided with a clamping part (202) for extruding the pipe fitting and forming the annular groove (101), the other end of the chuck extends out of the guide hole and is provided with a guide block (203) limited on the outer side of the guide hole, and a reset spring (13) sleeved on the chuck is arranged between the guide block and the outer end of the guide hole; the clamping mechanism comprises a guide push rod (15) and a second power cylinder (10), the second power cylinder is fixed on the rack, the clamping rotating seat is provided with a guide sliding hole (1203) matched with the guide push rod to slide in a telescopic mode, one end of the guide push rod extends out of the guide sliding hole to be in contact with a guide block at the outer end of the chuck, the other end of the guide push rod extends out of the guide sliding hole to be movably connected with a piston rod of the second power cylinder, and when the guide push rod moves along with the pushing action of the second power cylinder, the guide push rod pushes the guide block and enables the chuck to move towards the cavity of the clamping rotating seat, namely, the clamping part of the chuck reaches the position where the pipe fitting is; the movable connection means that the guide push rod is axially connected relative to the piston rod of the second power cylinder and simultaneously forms relative rotation.

9. A necking apparatus according to claim 8, wherein one of the contact points of said guide pusher (15) and said guide block (203) of said gripper (2) is a rod and the other is a ramp.

10. The necking apparatus of claim 6 or 8, wherein the first power cylinder (4) and the second power cylinder (10) are both any one of a pneumatic cylinder, a hydraulic cylinder or an electric cylinder.