CN211599845U

CN211599845U - Joint capable of providing movable steering of protective pipe

Info

Publication number: CN211599845U
Application number: CN201922352205.7U
Authority: CN
Inventors: 林泰源
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-12-24
Filing date: 2019-12-24
Publication date: 2020-09-29
Anticipated expiration: 2029-12-24

Abstract

A joint for movably steering a protection tube comprises a body unit and a limiting unit. The body unit is used for inserting the protection pipe along an axis and comprises a first inner end face, a second inner end face opposite to the first inner end face along the axis and an inner peripheral face, and the first inner end face, the second inner end face and the inner peripheral face define a setting space together. The limiting unit is used for being connected with the protection pipe and limited in the setting space, the limiting unit comprises a first outer end face adjacent to the first inner end face, a second outer end face adjacent to the second inner end face and an outer peripheral face adjacent to the inner peripheral face, the distance between the first outer end face and the second outer end face is smaller than the distance between the first inner end face and the second inner end face, and the diameter of the outer peripheral face is smaller than that of the inner peripheral face, so that the limiting unit can rotate around the axis relative to the body unit, and the connection position of the protection pipe and the joint can be flexibly rotated.

Description

Joint capable of providing movable steering of protective pipe

Technical Field

The utility model relates to a connect, especially relate to a can supply joint that protection tube activity turned to.

Background

One conventional wave tube quick waterproof joint disclosed in taiwan patent No. M296536, for example, comprises a hollow joint body, a waterproof fixing member set, and a fastening member. The joint body comprises a second joint part with external threads and a convex abutting edge protruding from the middle section of the interior. The waterproof fixing piece set comprises a soft waterproof seat and a ring buckle ring, wherein the soft waterproof seat is hollow and is provided with a second joint part inserted into the joint body and a lip edge leaning against the convex abutting edge, and a concave bearing part opposite to the lip edge and leaning against the end surface of the second joint part, the ring buckle ring is inserted into the concave bearing part of the soft waterproof seat and is provided with a plurality of elastic buckle pieces arranged on the inner ring and a plurality of clamping edges arranged at the free ends of the elastic buckle pieces. The packing piece is provided with a socket for a wave pipe to penetrate, an internal thread section locked on the second joint part of the joint body, and a pushing surface which is positioned on the inner edge of the socket and pushes against the ring buckle ring.

When the quick waterproof connector is used, one end part of the corrugated pipe is inserted into the socket opening of the packing piece, inserted into the waterproof fixing piece group and clamped with the clamping edge of the ring buckle ring to be fixed on the quick waterproof connector of the corrugated pipe, so that the corrugated pipe can be connected to a fixed object through the quick waterproof connector of the corrugated pipe.

However, the wave tube is mainly used for the electric wire of the machine platform to penetrate through so as to protect the electric wire, and the electric wire can move along with the movement of the machine platform, at this time, because the end part of the wave tube is firmly pressed on the quick waterproof joint of the wave tube, the electric wire and the wave tube are limited and can not freely rotate along with the movement of the machine platform, especially, the mechanical arms above three axes are very common nowadays, four-axis and five-axis mechanical arms are widely applied in the manufacturing industry, and the mechanical arms teach flexibility and accuracy of movement, but the electric wire of the mechanical arm is limited by the quick waterproof joint of the wave tube, so that the mechanical arm is pulled in the operation process to influence the accuracy of movement.

In addition, if this wavy pipe receives great revolving force and when rotating for this latch ring, also can cause this wavy pipe to receive this latch ring the card edge cuts and decreases for this wavy pipe is by this joint drops, makes inside electric wire expose, cuts this wavy pipe even when, also cuts inside electric wire.

Disclosure of Invention

An object of the utility model is to provide a can supply the joint that the protection tube activity turned to.

The utility model discloses a can supply joint that protection tube activity turned to contains body unit, reaches spacing unit. The body unit is hollow and is used for inserting the protection tube along an axis, the body unit comprises a first inner end surface, a second inner end surface opposite to the first inner end surface along the axis, and an inner peripheral surface extending between the first inner end surface and the second inner end surface, and the first inner end surface, the second inner end surface and the inner peripheral surface jointly define a setting space for inserting the protection tube. The limiting unit is used for being connected with the protection tube and limited in the arrangement space and comprises a first outer end face adjacent to the first inner end face, a second outer end face opposite to the first outer end face along the axis and adjacent to the second inner end face, and an outer peripheral face extending between the first outer end face and the second outer end face and adjacent to the inner peripheral face, wherein the distance between the first outer end face and the second outer end face is smaller than the distance between the first inner end face and the second inner end face, and the diameter of the outer peripheral face is smaller than that of the inner peripheral face, so that the limiting unit can rotate around the axis relative to the body unit.

The utility model discloses a can supply joint that protection tube activity turned to, this body unit is still including connecting the body, and the rigid coupling is in the external member of this tip that connects the body, this tip that should connect the body has the terminal surface, this terminal surface constitutes this first interior terminal surface, this external member is used for supplying this protection tube to wear to establish and has the interior terminal surface relative with this joint body, and connect this interior terminal surface and connect the interior terminal surface that should connect the body, terminal surface constitutes this second interior terminal surface in this, this interior terminal surface constitutes this inner peripheral surface.

The utility model discloses a can supply joint that protection tube activity turned to, the surface of this protection tube forms a plurality of rings forms and each other looks spaced depressed part, and this spacing unit still includes the locating part that is C shape around this axis, and this locating part has the outer loop that is used for the cover to locate this protection tube, and at least one connects this outer loop and hinders the portion towards the inside protruding card that stretches of this axis, and this outer loop has two opposite terminal surfaces along this axis, connects the outer anchor ring of terminal surface, and on the contrary in the inner loop of this outer anchor ring, this locating part the terminal surface is adjacent this first interior terminal surface and this second interior terminal surface respectively to constitute this first outer terminal surface and this second outer terminal surface respectively, this outer anchor ring of this locating part then constitutes this outer peripheral face, and this card hinders the portion and is used for the card to hinder and is positioned one of them depressed part of this protection tube.

The utility model discloses a can supply joint that protection tube activity turned to, this locating part of this spacing unit have a plurality of block portions that set up around this axis interval, and each block portion of hindering is connected in this interior anchor ring of this outer ring portion and is the jack catch form of utensil elasticity, the block is used for blocking one of them depressed part of locating at this protection tube to only supply this protection tube to pass through by the direction of this first interior anchor ring of this second face.

The utility model discloses a can supply the joint that the protection tube activity turned to, this card of this locating part of this spacing unit hinders portion quantity and is one, and this card hinders portion and extends around this axis to by this inner ring face of this outer ring portion towards this axis radial extension.

The utility model discloses a can supply the joint that the protection tube activity turned to, this inner peripheral surface of this body unit has first inside diameter section, and second inside diameter section, and this outer peripheral face of this spacing unit has the first outside diameter section that corresponds to this first inside diameter section, and corresponds the second outside diameter section of this second inside diameter section, and the diameter of this first outside diameter section is less than the diameter of this first inside diameter section, and the diameter of this second outside diameter section is less than the diameter of this second inside diameter section.

The utility model discloses a joint that can supply protection tube activity to turn to, this tip of this joint body of this body unit is the tubulose, and this tip still has the interior pipe surface of the inner edge of this terminal surface of connection self, and the shoulder surface that the outer fringe is connected this interior pipe surface and is kept away from this terminal surface, this interior pipe surface constitutes this first internal diameter section, this shoulder surface constitutes this first internal end surface, this internal ring surface of this external member does not connect this joint body's part constitutes this second internal diameter section, this spacing unit still includes adjacent this first internal end surface and is used for the setting element of rigid coupling in the tip of protection tube, and be located this setting element and this second internal end surface and be used for the backing ring of cover locating this protection tube, this setting element has the outer cover portion that is located between this first internal end surface and this backing ring and is used for the cover to locate the tip of this protection tube, and connect the inner edge of this outer cover portion and be used for inserting the locking part of this protection tube, the outer cover part is provided with an end face adjacent to the first inner end face, an outer ring face which is connected with the outer edge of the end face of the outer cover part and extends towards the backing ring, the end face of the positioning element forms the first outer end face, the outer ring face of the positioning element forms the first outer diameter section, the backing ring is provided with two abutting faces which are opposite along the axis, and an outer ring face which is connected with the outer edge of the abutting face, the abutting faces are respectively adjacent to the positioning element and the second inner end face, the abutting face adjacent to the second inner end face forms the second outer end face, and the outer ring face of the backing ring forms the second outer diameter section.

The beneficial effects of the utility model reside in that: the distance between the first outer end face and the second outer end face of the limiting unit is smaller than the distance between the first inner end face and the second inner end face of the body unit, and the diameter of the outer peripheral face of the limiting unit is smaller than the diameter of the inner peripheral face of the body unit, so that the limiting unit can rotate around the axis in the setting space along with the protection tube, and the connection part of the protection tube and the joint can flexibly rotate.

Drawings

Other features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments with reference to the accompanying drawings, in which:

fig. 1 is an exploded perspective view of a first embodiment of a joint of the present invention for movably steering a protective pipe;

FIG. 2 is a cross-sectional view of the first embodiment;

fig. 3 is an exploded perspective view of a second embodiment of the joint of the present invention for movably steering the protective tube;

FIG. 4 is a cross-sectional view of the second embodiment;

fig. 5 is an exploded perspective view of a third embodiment of the joint of the present invention for movably steering the protective tube; and

fig. 6 is a cross-sectional view of the third embodiment.

Detailed Description

Before the present invention is described in detail, it should be noted that in the following description, similar components are denoted by the same reference numerals.

Referring to fig. 1 and 2, the first embodiment of the joint for movably turning the protection tube of the present invention is suitable for connecting a protection tube 9, in this embodiment, an outer surface 91 of the protection tube 9 forms a plurality of annular recesses 911 spaced from each other. The joint for protecting the movable steering of the pipe comprises a body unit 1 and a limiting unit 2.

The body unit 1 is hollow and is used for inserting the protection pipe 9 along an axis L. The body unit 1 includes a first inner end surface 11, a second inner end surface 12 opposite to the first inner end surface 11 along the axis L, and an inner peripheral surface 13 extending between the first inner end surface 11 and the second inner end surface 12, and the first inner end surface 11, the second inner end surface 12, and the inner peripheral surface 13 together define a setting space 14 into which the protection pipe 9 is inserted.

In this embodiment, the body unit 1 further includes a connector body 15, and a sleeve 16 sleeved and screwed on an end 150 of the connector body 15, wherein the connector body 15 and the sleeve 16 define the installation space 14. The end portion 150 of the joint body 15 is tubular and has an end surface 151, and the end surface 151 constitutes the first inner end surface 11. The sleeve member 16 is used for the protection tube 9 to pass through and has an inner end surface 161 opposite to the joint body 15 and an inner ring surface 162 connected to the inner end surface 161 and locked to the joint body 15, the inner end surface 161 forms the second inner end surface 12, and the inner ring surface 162 forms the inner circumferential surface 13.

The limiting unit 2 is used for connecting the protection tube 9 and is limited in the setting space 14, and the limiting unit 2 includes a first outer end surface 21 adjacent to the first inner end surface 11, a second outer end surface 22 opposite to the first outer end surface 21 and adjacent to the second inner end surface 12 along the axis L, and an outer peripheral surface 23 extending between the first outer end surface 21 and the second outer end surface 22 and adjacent to the inner peripheral surface 13. The first outer end surface 21 and the second outer end surface 22 are limited by the inner end surface 11 and the second inner end surface 12 of the body unit 1, respectively, in the direction in which the axis L extends, so that the limiting unit 2 is limited in the setting space 14. The distance L2 between the first outer end surface 21 and the second outer end surface 22 is smaller than the distance L1 between the first inner end surface 11 and the second inner end surface 12, and the diameter d2 of the outer peripheral surface 23 is smaller than the diameter d1 of the inner peripheral surface 13, so that the limiting unit 2 can rotate around the axis L relative to the body unit 1.

In the present embodiment, the limiting unit 2 further includes a limiting member 24 having a C-shape around the axis L. The limiting member 24 has an outer ring portion 241 for being sleeved on the protection tube 9, and at least one blocking portion 242 connected to the outer ring portion 241 and protruding inward toward the axis L. The outer ring portion 241 has two opposite end surfaces 243 along the axis L, an outer ring surface 244 connecting the end surfaces 243, and an inner ring surface 245 opposite to the outer ring surface 244, wherein the end surfaces 243 are respectively adjacent to the first inner end surface 11 and the second inner end surface 12, the end surface 243 adjacent to the first inner end surface 11 forms the first outer end surface 21, the other end surface 243 forms the second outer end surface 22, and the outer ring surface 244 forms the outer circumferential surface 23. In this embodiment, the position-limiting member 24 has a plurality of blocking portions 242 spaced around the axis L, each blocking portion 242 is connected to the inner ring surface 245 and is in the shape of an elastic claw, the blocking portion 242 is used for blocking one of the recessed portions 911 of the protection tube 9, and only the protection tube 911 passes through the second inner end surface 12 toward the first inner end surface 11.

In this embodiment, the joint body 15, the sleeve 16, the limiting member 24 and the protection tube 9 can be made of plastic material, and the materials of the components are not limited thereto.

During assembly, the limiting member 24 can be first placed in the sleeve member 16, the sleeve member 16 is then locked with the end portion 150 of the joint body 15, the protection tube 9 is then inserted into the installation space 14 along the axis L from the sleeve member 16 toward the joint body 15, during the insertion process, the limiting member 24 can be deformed by a pushing force to allow the protection tube 9 to pass through, until the protection tube 9 is inserted into a sufficient length, the blocking portion 242 of the limiting member 24 is blocked and positioned with one of the recessed portions 911 of the protection tube 9, and the protection tube 9 cannot be pulled out along the axis L toward a direction away from the joint body 15, thereby completing the assembly. However, the assembling method of the present embodiment is not limited thereto.

When in use, because the distance L2 between the first outer end surface 21 and the second outer end surface 22 of the spacing unit 2 is smaller than the distance L1 between the first inner end surface 11 and the second inner end surface 12 of the body unit 11, and the diameter d2 of the outer peripheral surface 23 of the spacing unit 2 is smaller than the diameter d1 of the inner peripheral surface 13 of the body unit 1 (at this time, the connector body 15 and the sleeve 16 are locked with each other), when the protection tube 9 rotates around the axis L under external force, the spacing unit 2 can rotate around the axis L with the protection tube 9 in the installation space 14, so as to allow the connection between the protection tube 9 and the connector for movably steering the protection tube to flexibly rotate, so that when the embodiment is used for the wire penetration of a general machine, the wire can be freely rotated with the action of the machine, especially when the wire penetration of a mechanical arm with more than three axes is performed, the power supply wire can smoothly rotate to avoid the influence on the action accuracy of the mechanical arm caused by the blockage and the pulling of the wire.

In addition, since the limiting member 24 can rotate freely in the installation space 14, the limiting member 24 can be prevented from being clamped in the installation space 14 and rotating relative to the protection tube 9, so that the stopping portion 242 of the limiting member 24 cuts the protection tube 9.

Referring to fig. 3 and 4, the second embodiment of the joint for movably steering the protection pipe of the present invention is similar to the first embodiment, and the difference is:

the number of the blocking portions 242 of the limiting member 24 of the limiting unit 2 is one, and the blocking portion 242 extends around the axis L and radially extends from the inner ring surface 245 of the outer ring portion 241 toward the axis L, and the blocking portion 242 is used for blocking one of the recessed portions 911 of the protection tube 9.

In the present embodiment, since the structure of the position-limiting member 24 is simple, the thickness of the outer ring portion 241 can be increased, and the structural strength of the position-limiting member 24 can be improved, so that the position-limiting member is not easily deformed and can be firmly connected to the protection tube 9, thereby enabling the present embodiment to be suitable for connecting protection tubes 9 with larger size.

In this embodiment, during assembly, the external member 16 is firstly sleeved on the protection tube 9, then the limiting member 24 is pulled open and sleeved and clamped on the end of the protection tube 9, and finally the connector body 15 and the external member 16 are locked.

Since the present embodiment has a structure similar to that of the first embodiment, the same purpose and effect as the first embodiment can be achieved.

Referring to fig. 5 and 6, the third embodiment of the joint for movably steering the protection pipe of the present invention is similar to the first embodiment, and the difference is:

an inner surface 92 of the protection tube 9 to which the joint for movably turning the protection tube is applied is formed with a recess 921 in a spiral shape. The inner circumferential surface 13 of the body unit 1 of the joint for protecting the pipe from moving has a first inner diameter section 131 and a second inner diameter section 132 having a different diameter from the first inner diameter section 131. The outer circumferential surface 23 of the stopper unit 2 has a first outer diameter section 231 corresponding in position and diameter to the first inner diameter section 131, and a second outer diameter section 232 corresponding in position and diameter to the second inner diameter section 132. The diameter d2 'of the first outer diameter section 231 is less than the diameter d 1' of the first inner diameter section 131, and the diameter d2 "of the second outer diameter section 232 is less than the diameter d 1" of the second inner diameter section 132.

The end portion 150 of the joint body 15 of the body unit 1 further has an inner tube surface 152 connected to the inner edge of the end surface 151, and a shoulder surface 153 having an outer edge connected to the inner tube surface 152 and far away from the end surface 151, the inner tube surface 152 forms the first inner diameter section 131, the shoulder surface 153 forms the first inner end surface 11, and the portion of the inner ring surface 162 of the sleeve 16 not connected to the joint body 15 forms the second inner diameter section 132.

The limiting unit 2 includes the first outer end surface 21, the second outer end surface 22, the outer peripheral surface 23, a positioning element 25 adjacent to the first inner end surface 11 and used for being fixedly connected to the end portion of the protection tube 9, and a cushion ring 26 located between the positioning element 25 and the second inner end surface 12 and used for being sleeved on the protection tube 9. The positioning member 25 has an outer cover portion 251 located between the first inner end surface 11 and the backing ring 26 and used for being sleeved on the end portion of the protection tube 9, and a locking portion 252 connected to the inner edge of the outer cover portion 251. The outer cover portion 251 has an end surface 253 adjacent to the first inner end surface 11, and an outer ring surface 254 connecting the outer edge of the end surface 253 and extending toward the backing ring 26, the end surface 253 constituting the first outer end surface 21, and the outer ring surface 254 constituting the first outer diameter section 231. The locking portion 252 is inserted into an end portion of the protection tube 9 and is screwed to the inner surface 92 of the protection tube 9. The backing ring 26 has two abutting surfaces 261 opposite to each other along the axis L, and an outer ring surface 262 connecting the outer edges of the abutting surfaces 261, the abutting surfaces 261 are respectively adjacent to the positioning element 25 and the second inner end surface 12, the abutting surfaces 261 adjacent to the second inner end surface 12 form the second outer end surface 22, and the outer ring surface 262 forms the second outer diameter section 232.

In this embodiment, the positioning element 25 can be made of metal, the backing ring 26 can be made of rubber, and the protection tube 9 can be made of metal and covered with rubber layer, but the materials of the components are not limited thereto.

In the present embodiment, during assembly, the sleeve member 16 can be firstly sleeved on the protection tube 9, then the backing ring 26 is sleeved on the end portion of the protection tube 9, the locking portion 252 of the positioning member 25 is inserted into the end portion of the protection tube 9 and is screwed on the inner surface 92 of the protection tube 9, at this time, the backing ring 26 is located between the positioning member 25 and the sleeve member 16, and finally the connector body 15 and the sleeve member 16 are locked.

In use, the distance l2 between the first outer end surface 21 and the second outer end surface 22 is smaller than the distance l1 between the first inner end surface 11 and the second inner end surface 12 (when the positioning member 25 abuts against the backing ring 26), and the diameter d2 'of the first outer diameter section 231 is smaller than the diameter d 1' of the first inner diameter section 131, and the diameter d2 "of the second outer diameter section 232 is smaller than the diameter d 1" of the second inner diameter section 132, so that the limiting unit 2 can rotate with the protection tube 9 in the installation space 14, and the same purpose and effect as the first embodiment can be achieved.

To sum up, the utility model discloses can supply the joint that the protection tube activity turned to, interval L2 through this first outer terminal surface 21 of this spacing unit 2 and this second outer terminal surface 22 is less than interval L1 of this first inner terminal surface 11 of this body unit 1 and this second inner terminal surface 12, and the diameter d2 of this outer peripheral face 23 of this spacing unit 2 is less than the diameter d1 of this inner peripheral surface 13 of this body unit 1, make this spacing unit 2 can rotate around this axis L along with this protection tube 9 in this setting space 14, in order to allow this protection tube 9 and this can supply the flexible rotation of the articulate department that the protection tube activity turned to, and then ensure that the action of inside electric wire and board is smooth and easy, and can avoid this protection tube 9 and this spacing unit 2 relative rotation and impaired, so can reach the purpose of the utility model with low costs really.

The above description is only an example of the present invention, and the scope of the present invention should not be limited thereby, and all the simple equivalent changes and modifications made according to the claims and the description of the present invention are still within the scope of the present invention.

Claims

1. The utility model provides a can supply joint that protection tube activity turned to which characterized in that: comprises the following steps:

the body unit is hollow and is used for inserting the protection pipe along an axis, the body unit comprises a first inner end surface, a second inner end surface opposite to the first inner end surface along the axis, and an inner peripheral surface extending between the first inner end surface and the second inner end surface, and the first inner end surface, the second inner end surface and the inner peripheral surface jointly define a setting space for inserting the protection pipe; and

and the limiting unit is used for connecting the protection pipe and limited in the setting space, and comprises a first outer end surface adjacent to the first inner end surface, a second outer end surface opposite to the first outer end surface along the axis and adjacent to the second inner end surface, and an outer peripheral surface extending between the first outer end surface and the second outer end surface and adjacent to the inner peripheral surface, wherein the distance between the first outer end surface and the second outer end surface is smaller than the distance between the first inner end surface and the second inner end surface, and the diameter of the outer peripheral surface is smaller than that of the inner peripheral surface, so that the limiting unit can rotate around the axis relative to the body unit.

2. The joint for movably steering a protective tube according to claim 1, wherein: the body unit further comprises a joint body and a sleeve piece fixedly connected to the end portion of the joint body, the end portion of the joint body is provided with an end face, the end face forms the first inner end face, the sleeve piece is used for enabling the protection tube to penetrate through and is provided with an inner end face opposite to the joint body, an inner ring face connected with the inner end face and connected with the joint body, the inner end face forms the second inner end face, and the inner ring face forms the inner peripheral face.

3. The joint for movably steering a protective tube according to claim 2, wherein: the outer surface of the protection tube forms a plurality of annular recessed portions spaced from each other, wherein the limiting unit further comprises a limiting member in a C shape around the axis, the limiting member is provided with an outer ring portion for being sleeved on the protection tube, and at least one blocking portion connected with the outer ring portion and protruding inwards towards the axis, the outer ring portion is provided with two end faces opposite to each other along the axis, an outer ring face connected with the end faces, and an inner ring face opposite to the outer ring face, the end faces of the limiting member are respectively adjacent to the first inner end face and the second inner end face and respectively form the first outer end face and the second outer end face, the outer ring face of the limiting member forms the outer peripheral face, and the blocking portion is used for blocking one of the recessed portions located in the protection tube.

4. The joint for movably steering a protective tube according to claim 3, wherein: the limiting part of the limiting unit is provided with a plurality of blocking parts which are arranged at intervals around the axis, each blocking part is connected to the inner ring surface of the outer ring part and is in an elastic claw shape, and the blocking parts are used for blocking one of the concave parts positioned on the protection pipe and only allowing the protection pipe to pass through from the second inner end surface to the first inner end surface.

5. The joint for movably steering a protective tube according to claim 3, wherein: the number of the blocking parts of the limiting part of the limiting unit is one, and the blocking parts extend around the axis and radially extend from the inner ring surface of the outer ring part towards the axis.

6. The joint for movably steering a protective tube according to claim 2, wherein: the inner peripheral surface of the body unit is provided with a first inner diameter section and a second inner diameter section, the outer peripheral surface of the limiting unit is provided with a first outer diameter section corresponding to the first inner diameter section and a second outer diameter section corresponding to the second inner diameter section, the diameter of the first outer diameter section is smaller than that of the first inner diameter section, and the diameter of the second outer diameter section is smaller than that of the second inner diameter section.

7. The joint for movably steering a protective tube according to claim 6, wherein: the end part of the joint body of the body unit is tubular, the end part is also provided with an inner tube surface connected with the inner edge of the end surface of the end part, the outer edge is connected with the inner tube surface and is far away from the shoulder surface of the end surface, the inner tube surface forms a first inner diameter section, the shoulder surface forms a first inner end surface, the part of the inner ring surface of the sleeve part, which is not connected with the joint body, forms a second inner diameter section, the limiting unit also comprises a positioning part which is adjacent to the first inner end surface and is used for being fixedly connected with the end part of a protection tube, and a backing ring which is positioned between the positioning part and the second inner end surface and is used for being sleeved on the protection tube, the positioning part is provided with an outer cover part which is positioned between the first inner end surface and the backing ring and is used for being sleeved on the end part of the protection tube, and a locking part which is connected with the inner edge of the outer cover part and is used for being inserted into the protection tube, the outer ring surface is connected with the outer edge of the end surface of the outer cover part and extends towards the backing ring, the end surface of the positioning element forms the first outer end surface, the outer ring surface of the positioning element forms the first outer diameter section, the backing ring is provided with two abutting surfaces which are opposite along the axis, and the outer ring surface is connected with the outer edge of the abutting surface, the abutting surfaces are respectively adjacent to the positioning element and the second inner end surface, the abutting surface adjacent to the second inner end surface forms the second outer end surface, and the outer ring surface of the backing ring forms the second outer diameter section.