CN218158431U

CN218158431U - SFP optical module structure

Info

Publication number: CN218158431U
Application number: CN202221836380.9U
Authority: CN
Inventors: 何超; 朱巨艳; 陈丽琼; 黄文娟
Original assignee: Wuhan Huagong Genuine Optics Tech Co Ltd
Current assignee: Wuhan Huagong Genuine Optics Tech Co Ltd
Priority date: 2022-07-14
Filing date: 2022-07-14
Publication date: 2022-12-27
Anticipated expiration: 2032-07-14

Abstract

The utility model relates to an optical module technical field, in particular to SFP optical module structure, including the casing and install light emission device, optic fibre adapter, light receiving device and PCBA in the casing, the casing is equipped with the light mouth along length direction's one end, and the other end is equipped with the electricity mouth, the casing is including dismantling and form the installation cavity between base and upper cover and the base and the upper cover of connection, installed in the installation cavity PCBA, set firmly along one side of casing width direction in the installation cavity light receiving device and optic fibre adapter are close to the light mouth, the opposite side set firmly light emission device, be connected with first optic fibre between light emission device and the light receiving device, be connected with the second optic fibre between light receiving device and the optic fibre adapter. The utility model provides a SFP optical module structure can encapsulate TOSA, optical fiber adapter, light receiving device and PCBA in the optical module structure well through improving structural design, can satisfy the in-service use requirement better.

Description

SFP optical module structure

Technical Field

The utility model relates to an optical module technical field, in particular to SFP optical module structure.

Background

With the development of communication technology, optical modules with special structures are needed in some special occasions, the conventional single-fiber bidirectional LC optical port optical module structure can be designed within the size range required by the MSA protocol only by packaging a TOSA (light emitting device), a light receiving device and a PCBA, but some single-fiber bidirectional LC optical port optical modules with special function requirements need to be packaged in a structural component, namely the TOSA (light emitting device), the optical fiber adapter, the light receiving device and the PCBA, and the conventional SFP packaged optical module structure cannot meet the requirements. In view of the above-mentioned shortcomings, the present invention provides an improvement.

SUMMERY OF THE UTILITY MODEL

In order to overcome the not enough of background art, the utility model provides a SFP optical module structure can be well encapsulation TOSA, fiber adapter, light receiving device and PCBA in optical module structure through improving structural design, can satisfy the in-service use requirement better.

The utility model adopts the technical proposal that: the utility model provides a SFP optical module structure, includes the casing and installs light emitting device, optic fibre adapter, light receiving device and PCBA in the casing, the casing is equipped with the light mouth along length direction's one end, and the other end is equipped with the electricity mouth, the casing is including dismantling to form the installation cavity between base and the upper cover of connection, install in the installation cavity PCBA, and one side along casing width direction in the installation cavity has set firmly light receiving device and optic fibre adapter are close to the light mouth, and the opposite side has set firmly light emitting device, be connected with first optic fibre between light emitting device and the light receiving device, be connected with the second optic fibre between light receiving device and the optic fibre adapter.

Preferably, be equipped with first spacing draw-in groove and the spacing draw-in groove of second on the base, on cover and be equipped with the spacing draw-in groove of third and the spacing draw-in groove of fourth, first spacing draw-in groove, the spacing draw-in groove of third with the spacing flange adaptation of optic fibre adapter, the spacing draw-in groove of second, the spacing draw-in groove of fourth with the spacing flange adaptation of light emission device, the light mouth is located one side of casing tip and the light mouth is just right first spacing draw-in groove.

Preferably, the base is provided with a fiber winding boss, two arc-shaped fiber winding surfaces are respectively arranged on two sides of the fiber winding boss, and the first optical fiber is wound on the fiber winding boss.

Preferably, a fiber coiling groove is formed between one end of the fiber coiling boss close to the base and the end of the fiber coiling boss and the base, and the first optical fiber is clamped into the fiber coiling groove and then fixed by adhesive dispensing.

Preferably, PCBA includes PCB, be equipped with the installation in the base PCB's supporting seat, the top of supporting seat is equipped with the reference column, PCB be equipped with the installation locating hole of reference column adaptation still is equipped with first installation breach and second installation breach on the PCB, first installation breach with light receiving device adaptation, second installation breach with light emitting device adaptation.

Preferably, one side of the light receiving device is covered with a dust cover, the dust cover is arranged on the PCB, and the dust cover is provided with a fiber passing groove.

Preferably, one side of the light receiving device, which is far away from the dust cover, is provided with a tungsten copper block, and the tungsten copper block is provided with a mounting groove matched with the light receiving device.

Preferably, the electric port is located on one side of the end portion of the shell, and the golden finger end of the PCBA is installed in the electric port.

Preferably, still include the sliding lock subassembly, the sliding lock subassembly includes slider, spring, pull ring and gland, be equipped with on the base with the spout of slider adaptation, still be equipped with on the base with the pull ring mounting hole of pull ring adaptation, the bottom of slider be equipped with the arc recess of spring adaptation, the joint has on the base gland and gland are right one side of slider is carried on spacingly, the one end of slider is equipped with atress portion, and the other end is equipped with unlocking portion, be equipped with on the pull ring contradict in the application of force arch of atress portion.

Preferably, the upper cover is fixed on the base through threaded connection, a step groove matched with the top of the base is formed in the outer side of the bottom of the upper cover, and a scrap edge is formed on one side of the step groove.

To sum up, the utility model discloses beneficial effect does:

1. the optical fiber adapter is close to an optical port and can be conveniently connected with an external optical fiber accessed from the optical port, and the TOSA, the optical fiber adapter, the optical receiver device and the PCBA can be well packaged in the optical module structural member by adopting the structural design, so that the actual use requirement can be better met.

2. The fiber winding boss is additionally arranged on the base, so that the fiber winding radius of the first optical fiber is guaranteed, fiber breakage caused by shaking of the first optical fiber in the module structure can be prevented, a round angle larger than the minimum bending radius of the optical fiber is formed on an arc-shaped fiber winding surface on the fiber winding boss, the situation that the use of the first optical fiber is influenced due to the fact that the bending radius is too small when the first optical fiber is coiled is guaranteed, the internal fiber winding of the optical module structure can be well achieved by adopting the structural design, and the actual requirements can be better met;

3. the light receiving device is located the first installation breach on the PCB, can play dustproof effect well through set up the dust cover in one side of light receiving device, sets up on the dust cover and has crossed the fine groove and can be convenient for pass optic fibre, can satisfy actual demand better.

The present invention will be further explained with reference to the accompanying drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

FIG. 1 is a top schematic view of the overall structure of the present invention;

FIG. 2 is a schematic view of the bottom side of the overall structure of the present invention;

fig. 3 is an exploded view of the present invention;

FIG. 4 is a schematic view of the internal structure of the present invention with the upper cover removed;

FIG. 5 is a schematic view of the internal structure of the base of the present invention;

fig. 6 is a schematic structural view of the upper cover of the present invention;

fig. 7 is a schematic structural view of the dust cover of the present invention;

fig. 8 is a schematic structural view of the slider of the present invention;

fig. 9 is a schematic structural view of the gland of the present invention;

fig. 10 is a partial schematic view of the present invention illustrating the mounting of a light receiving device;

FIG. 11 is an enlarged view of a portion of FIG. 2 at A;

the mark in the figure is: 1-a light emitting device, 2-a fiber optic adapter, 3-a light receiving device, 4-PCBA, 5-a light port, 6-an electrical port, 7-a base, 8-a top cover, 9-a first fiber, 10-a second fiber, 11-a first limit clamp slot, 12-a second limit clamp slot, 13-a third limit clamp slot, 14-a fourth limit clamp slot, 15-a first limit flange, 16-a second limit flange, 17-a fiber-wound boss, 18-an arc-shaped fiber-wound surface, 19-a fiber-wound groove, 20-PCB, 21-a support base, 22-a positioning post, 23-an installation positioning hole, 24-a first installation notch, 25-a second installation notch, 26-a third installation notch, 27-a dust cover, 28-a fiber-wound groove, 29-a post, 30-a tungsten copper block, 31-a gold finger end, 32-a slider, 33-a spring, 34-a press cover, 35-a press cover, 36-a sliding slot, 37-an installation hole, 38-an arc-a pull ring groove, 39-a pull ring stress-relief portion, 40-a movable tab, 40-a movable finger end, 42-a movable finger end, 32-a slider, 33-a spring, a tab-tab, a tab, 45-tab, a tab, and a tab, 48-tab, and a tab.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to fig. 1 to 11 in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments obtained by a person skilled in the art based on the embodiments of the present invention without any creative work belong to the protection scope of the present invention.

In order to make the purpose, technical solution and advantages of the present invention clearer, the attached drawings in the embodiments of the present invention will be combined below to carry out more detailed description on the technical solution in the embodiments of the present invention.

As shown in fig. 1 to 11, the SFP optical module structure disclosed in this embodiment includes a housing, and a light emitting device 1, an optical fiber adapter 2, a light receiving device 3, and a PCBA4 installed in the housing, where one end of the housing along a length direction is provided with an optical port 5, the other end is provided with an electrical port 6, the housing includes a base 7 and an upper cover 8 detachably connected, and an installation cavity is formed between the base 7 and the upper cover 8, the PCBA4 is installed in the installation cavity, the light receiving device 3 and the optical fiber adapter 2 are fixedly installed in the installation cavity along one side of the housing in a width direction, and the optical fiber adapter 2 is close to the optical port 5, the light emitting device 1 is fixedly installed on the other side, a first optical fiber 9 is connected between the light emitting device 1 and the light receiving device 3, and a second optical fiber 10 is connected between the light receiving device 3 and the optical fiber adapter 2. In the above technical solution, the optical port 5 disposed at one end of the housing along the length direction can facilitate connection of optical fibers, the electrical port 6 disposed at the other end can facilitate electrical connection with the outside, the light emitting device 1 and the light receiving device 3 are respectively disposed at two sides of the mounting cavity along the width direction, the first optical fiber 9 can be conveniently connected between the light emitting device 1 and the light receiving device 3, the light receiving device 3 and the optical fiber adapter 2 are disposed at the same side of the mounting cavity along the width direction, the second optical fiber 10 can be conveniently connected between the light receiving device 3 and the optical fiber adapter 2, the optical fiber adapter 2 is close to the optical port 5 and can facilitate connection of external optical fibers accessed from the optical port 5, and thus it can be known that the TOSA, the optical fiber adapter 2, the light receiving device 3 and the PCBA4 can be well packaged in the optical module structure by using the above technical solution, and the actual use requirements can be better satisfied. In this embodiment, an optical port 5 is disposed at one end of the base 7, and an electrical port 6 is disposed at the other end of the base, where the optical port 5 is an LC optical port 5.

As an optimal technical scheme, be equipped with first spacing draw-in groove 11 and second spacing draw-in groove 12 on the base 7, be equipped with third spacing draw-in groove 13 and fourth spacing draw-in groove 14 on the upper cover 8, first spacing draw-in groove 11, third spacing draw-in groove 13 with the spacing flange adaptation of optical fiber adapter 2, second spacing draw-in groove 12, fourth spacing draw-in groove 14 with the spacing flange adaptation of light emission device 1, light mouth 5 is located one side of shell end portion and light mouth 5 just right first spacing draw-in groove 11. In this embodiment, set up the limiting flange on the optical fiber adapter 2 and be used for confirming the agreement size of optical port 5, also can be convenient for fixed mounting optical fiber adapter 2, it can be convenient for fixed mounting optical transmission device 1 to set up the limiting flange on the optical transmission device 1, this embodiment is called first limiting flange 15 with the limiting flange of optical fiber adapter 2, the limiting flange of optical transmission device 1 is called second limiting flange 16, during the installation, optical fiber adapter 2 blocks into first limiting card slot 11 through first limiting flange 15, optical transmission device 1 blocks into second limiting card slot 12 through second limiting flange 16, when fixing upper cover 8 on base 7, first limiting flange 15 still blocks into third limiting card slot 13, second limiting flange 16 still blocks into fourth limiting card slot 14, namely first limiting flange 15 blocks between first limiting card slot 11 and third limiting card slot 13, second limiting flange 16 blocks between second limiting card slot 12 and fourth limiting card slot 14, thus optical fiber adapter 2 and optical transmission device 1 are just fixed inside the casing well by the location respectively, optical fiber adapter 2 is fixed in first limiting card slot 11, optical fiber adapter is just over to optical port 5, so optical fiber adapter is just over optical port 5, so optical fiber adapter can also be convenient for external connection from optical fiber card slot 2. In specific implementation, the mounted light receiving device 3 is opposite to the first limiting clamping groove 11, so that the light receiving device 3 is opposite to the optical fiber adapter 2, and the second optical fiber 10 can be conveniently connected between the light receiving device 3 and the optical fiber adapter 2.

As a preferred technical solution, a fiber winding boss 17 is provided on the base 7, two sides of the fiber winding boss 17 are respectively provided with an arc-shaped fiber winding surface 18, and the first optical fiber 9 is wound on the fiber winding boss 17. In this embodiment, the optical receiver 3 includes FA (Fiber Array), connect optical transmitter 1 and FA through first optic fibre 9, this embodiment is through increasing around fine boss 17 on base 7, both guaranteed the fine radius of winding of first optic fibre 9, can also prevent that first optic fibre 9 from rocking in modular structure and causing disconnected fine, it has formed the fillet that is greater than the minimum bend radius of optic fibre to wind the fine face 18 around the arc on fine boss 17, it can not influence the use because of the bend radius undersize when having guaranteed that first optic fibre 9 coils, adopt above-mentioned structural design can realize optical module structure's inside well around fine, can satisfy actual demand better.

As a preferable technical solution, a fiber winding groove 19 is formed between the fiber winding boss 17 and the end of the base 7 at one end of the fiber winding boss 17 close to the base 7, and the first optical fiber 9 is fixed by dispensing after being clamped into the fiber winding groove 19. In this embodiment, the first optical fiber 9 is wound on the winding boss 17 and then clamped into the fiber winding groove 19, and the first optical fiber 9 can be well fixed in the fiber winding groove 19 by applying glue to points in the fiber winding groove 19, so that the phenomenon of fiber breakage caused by shaking of the optical fiber in the use process can be prevented.

As a preferred technical solution, the PCBA4 includes a PCB20, a supporting seat 21 for mounting the PCB20 is disposed in the base 7, a positioning column 22 is disposed at the top of the supporting seat 21, a mounting positioning hole 23 adapted to the positioning column 22 is disposed on the PCB20, a first mounting notch 24 and a second mounting notch 25 are further disposed on the PCBA 20, the first mounting notch 24 is adapted to the light receiving device 3, and the second mounting notch 25 is adapted to the light emitting device 1. In this embodiment, a plurality of supporting seats 21 for mounting the PCB20 are disposed in the base 7, and the mounting PCB20 can be well supported, wherein the top of two supporting seats 21 are disposed with semi-cylindrical positioning posts 22, the PCBA 20 is disposed with semi-circular mounting positioning holes 23, the two positioning posts 22 are just clipped into the two mounting positioning holes 23 on the PCB20 during mounting, the mounting positioning holes 23 on the PCB20 can be used to ensure the protocol size of the golden finger end 31 on the PCBA4, the first mounting notch 24 on the PCB20 can better arrange and mount the light receiving device 3 in the mounting cavity, the second mounting notch 25 on the PCB20 can better arrange and mount the light emitting device 1 in the mounting cavity, and the structure inside the light module structure can be more compact by arranging the mounting notches. In an embodiment, the PCB20 is further provided with a third installation notch 26 for facilitating installation of the fiber optic adapter 2.

Preferably, a dust cover 27 is covered on one side of the light receiving device 3, the dust cover 27 is mounted on the PCB20, and a fiber passing groove 28 is formed on the dust cover 27. In this embodiment, the light receiving device 3 is located in the first mounting notch 24, a dust-proof function can be well achieved by arranging the dust-proof cover 27 on one side of the light receiving device 3, the fiber groove 28 is arranged on the dust-proof cover 27 to facilitate the first optical fiber 9 and the second optical fiber 10 to pass through, in particular, the bottom of the dust-proof cover 27 is provided with the post 29, the pcba 20 is provided with the mounting waist hole matched with the post 29, the post 29 of the dust-proof cover 27 is inserted into the mounting waist hole on the PCB20, and then the dust-proof cover 27 is compressed by fixedly mounting the upper cover 8 on the base 7, so that the dust-proof cover 27 is well fixed.

Preferably, a tungsten copper block 30 is arranged on one side of the light receiving device 3 away from the dust cover 27, and an installation groove adapted to the light receiving device 3 is arranged on the tungsten copper block 30. In this embodiment, the tungsten copper block 30 is fixedly disposed at the bottom of the PCB20, the mounting groove of the tungsten copper block 30 is aligned to the first mounting notch 24 of the PCB20, the light receiving device 3 can be well mounted in the mounting groove of the tungsten copper block 30, and the light receiving device 3 can be well cooled by the tungsten copper block 30, so as to better meet the actual requirement.

Preferably, the electric port 6 is located on one side of the end of the housing, and the gold finger end 31 of the PCBA4 is installed in the electric port 6. In this embodiment, electrical port 6 on the side of the end of the housing facilitates the installation of gold finger tip 31 of PCBA4, and electrical port 6 meets the protocol size requirements of the SFP package, and the design of biasing electrical port 6 to one side is for better routing of PCBA 4. The light emitting device 1 after installation is just right electric port 6 during this embodiment concrete implementation, and is rationally distributed, can be convenient for PCBA4 to walk the line better.

As a preferred technical scheme, still include the sliding lock subassembly, the sliding lock subassembly includes slider 32, spring 33, pull ring 34 and gland 35, be equipped with on base 7 with the spout 36 of slider 32 adaptation still be equipped with on the base 7 with the pull ring mounting hole 37 of pull ring 34 adaptation, the bottom of slider 32 be equipped with the arc recess 38 of spring 33 adaptation, the joint has on the base 7 gland 35 and gland 35 are right one side of slider 32 is spacing, the one end of slider 32 is equipped with atress portion 39, and the other end is equipped with unlocking portion 40, be equipped with on the pull ring 34 contradict in the application of force arch 41 of atress portion 39. In this embodiment, during installation, the spring 33 is first placed in the arc-shaped groove 38 at the bottom of the slider 32, the spring 33 and the slider 32 are then installed in the sliding groove 36 of the base 7 together, the pull ring 34 is then installed in the pull ring installation hole 37 of the base 7, and finally the press cover 35 is installed on the base 7, so that after the press cover 35 is covered, one side of the slider 32 can be well limited, and the slider 32 can well slide in the sliding groove 36. In the specific implementation of this embodiment, an inwardly concave movable opening 42 is disposed on one side of the middle portion of the gland 35, the movable opening 42 is adapted to the stressed portion 39 on the slider 32, a protruding tab 43 is formed by protruding the other side of the middle portion of the gland 35 outward, two limiting bosses 44 respectively located on two sides of the chute 36 are disposed on the base 7, the protruding tab 43 on the gland 35 can be just clipped into the spacing slot between the two limiting bosses 44, the bottoms of one sides of the two limiting bosses 44 away from the spacing slot are both provided with a clipping groove 45, a clipping sheet 46 adapted to the clipping groove 45 is disposed on the gland 35, a downward folded hem 47 is further disposed on one side of the gland 35 away from the protruding tab 43, the hem 47 has certain elasticity, so that the gland 35 can be conveniently clipped and mounted on the base 7, the clipping sheet 46 on the gland 35 is pressed into the clipping groove 45 after the gland 35 is covered, so that the gland 35 is fixed, the assembly manner of the above-mentioned slide lock assembly is simple and low in cost, and can well meet the actual requirements.

As a preferable technical solution, the upper cover 8 is fixed on the base 7 through threaded connection, a step groove 48 adapted to the top of the base 7 is arranged on the outer side of the bottom of the upper cover 8, and a ledge 49 is formed on one side of the step groove 48. In this embodiment, the upper cover 8 is fixed on the base 7 through the screw 50, the base 7 is provided with a plurality of threaded holes adapted to the screw 50, the upper cover 8 is provided with a plurality of through holes adapted to the screw 50, three sides of the bottom of the upper cover 8 are provided with the step grooves 48, the top of the base 7 can be correspondingly clamped into the step grooves 48 when the upper cover 8 and the base 7 are fixed together through the screw 50, the upper cover 8 and the base 7 can be better connected through the step grooves 48 and the overlap edges 49, and the gap between the upper cover 8 and the base 7 can be favorably reduced.

In specific implementation, after the sliding lock assembly is assembled on the base 7, the TOSA, the optical receiving device, the optical fiber adapter 2, the PCBA4 and the dust cover 27 are assembled in the base 7, then the upper cover 8 is covered, finally, the screw 50 is screwed, and the optical module structure is assembled, so that the assembly is convenient and can be used in practice.

The fixing manner or the fixing connection manner not described in the embodiment may adopt a connection manner in the prior art according to a specific position, and is not specifically described herein.

The parts not referred to in the present embodiment are the same as or can be implemented by the prior art, and will not be further described here.

The skilled person should understand that: although the present invention has been described in terms of the above embodiments, the inventive concept is not limited to this embodiment, and any modification that utilizes the inventive concept is intended to be within the scope of the present patent application.

Claims

1. An SFP optical module structure, comprising: including the casing and install light emission device, optical fiber adapter, light receiving device and PCBA in the casing, the casing is equipped with the light mouth along length direction's one end, and the other end is equipped with the electricity mouth, the casing forms the installation cavity including the base and the upper cover that can dismantle the connection and between base and the upper cover, install in the installation cavity PCBA, one side along casing width direction in the installation cavity has set firmly light receiving device and optical fiber adapter are close to the light mouth, the opposite side has set firmly light emission device, be connected with first optic fibre between light emission device and the light receiving device, be connected with the second optic fibre between light receiving device and the optical fiber adapter.

2. The SFP optical module structure of claim 1, wherein: be equipped with first spacing draw-in groove and the spacing draw-in groove of second on the base, on cover and be equipped with the spacing draw-in groove of third and the spacing draw-in groove of fourth, first spacing draw-in groove, the spacing draw-in groove of third with the spacing flange adaptation of optic fibre adapter, second spacing draw-in groove, the spacing draw-in groove of fourth with the spacing flange adaptation of light emission device, it is just right that light mouth is located one side and the light mouth of shell end portion first spacing draw-in groove.

3. The SFP optical module structure of claim 1, wherein: the optical fiber winding device is characterized in that a fiber winding boss is arranged on the base, two arc-shaped fiber winding surfaces are respectively arranged on two sides of the fiber winding boss, and the first optical fiber is wound on the fiber winding boss.

4. An SFP optical module structure as claimed in claim 3, wherein: and a fiber winding groove is formed between one end of the fiber winding boss close to the base and the end part of the fiber winding boss and the base, and the first optical fiber is clamped into the fiber winding groove and then fixed by adhesive dispensing.

5. The SFP optical module structure of claim 1, wherein: PCBA includes PCB, be equipped with the installation in the base PCB's supporting seat, the top of supporting seat is equipped with the reference column, be equipped with on the PCB with the installation locating hole of reference column adaptation still is equipped with first installation breach and second installation breach on the PCB, first installation breach with light receiving device adaptation, second installation breach with light emitting device adaptation.

6. An SFP optical module structure according to claim 5, wherein: and one side of the light receiving device is covered with a dust cover, the dust cover is arranged on the PCB, and the dust cover is provided with a fiber passing groove.

7. The SFP optical module structure of claim 6, wherein: and a tungsten copper block is arranged on one side, away from the dust cover, of the light receiving device, and a mounting groove matched with the light receiving device is formed in the tungsten copper block.

8. The SFP optical module structure of claim 1, wherein: the electric port is located one side of casing tip, PCBA's golden finger end is installed in the electric port.

9. The SFP optical module structure of claim 1, wherein: still include the sliding lock subassembly, the sliding lock subassembly includes slider, spring, pull ring and gland, be equipped with on the base with the spout of slider adaptation, still be equipped with on the base with the pull ring mounting hole of pull ring adaptation, the bottom of slider be equipped with the arc recess of spring adaptation, the joint has on the base gland and gland are right one side of slider is carried on spacingly, the one end of slider is equipped with atress portion, and the other end is equipped with unlocking portion, be equipped with on the pull ring contradict in the application of force arch of atress portion.

10. The SFP optical module structure of claim 1, wherein: the upper cover is fixed on the base through threaded connection, a step groove matched with the top of the base is formed in the outer side of the bottom of the upper cover, and a scrap edge is formed on one side of the step groove.