CN214706180U

CN214706180U - Negative pole post subassembly and secondary cell top cap thereof

Info

Publication number: CN214706180U
Application number: CN202120186509.5U
Authority: CN
Inventors: 邓平华; 王雷
Original assignee: Jiangxi Baisili New Energy Technology Co ltd
Current assignee: Jiangxi Baisili New Energy Technology Co ltd
Priority date: 2021-01-22
Filing date: 2021-01-22
Publication date: 2021-11-12
Anticipated expiration: 2031-01-22

Abstract

The utility model provides a negative pole post subassembly and secondary battery top cap thereof, wherein the negative pole post subassembly includes negative pole utmost point post, be fixed in the connecting piece on the top cap piece, the embedding piece, the sealing member, upset piece and the injection molding of enclosing locating negative pole utmost point post, the embedding piece is fixed in connecting piece and embedding injection molding, negative pole utmost point post is including exposing out in the output of injection molding and holding in the connecting portion of injection molding, the upper portion butt of sealing member in the lower part of output, the lower part of sealing member is fixed with the connecting piece joint, the connecting member is equipped with the first perforating hole that is located the output below and is located the second perforating hole of connecting portion below, the upset piece is fixed in the second perforating hole and is located the below of negative pole utmost point post, when battery internal pressure surpasss the default, the upset piece is ordered about upwards upset and contact connection portion and is connected top cap piece and negative pole utmost point post electricity by atmospheric pressure. The output part of the cathode pole is provided with a sealing element, and the connecting part does not need to be sealed by the sealing element and does not need to bear pulling force, so that the sensitivity and the accuracy of the action of the cathode pole and the overturning sheet can be improved.

Description

Negative pole post subassembly and secondary cell top cap thereof

Technical Field

The utility model relates to an energy storage apparatus field especially relates to a negative pole post subassembly and secondary battery top cap thereof.

Background

In modern society, driving power sources for more and more electric tools and new energy vehicles are developed in a direction of high capacity and high safety, and batteries are widely used in electric tools and new energy vehicles due to their excellent characteristics such as high capacity. These batteries should have good safety in addition to high capacity to meet the standards of use and to meet the needs of people.

General secondary battery, the negative pole end needs to satisfy with the electrical insulation of top cap and casing, therefore can set up numerous insulating column subassembly, if go up plastic part with negative pole post and top cap insulation, arrange the sealing washer that carries out electrical insulation and sealed in the negative pole perforating hole in, and carry out electrical insulation's lower plastic part with negative pole connection piece and top cap, these post subassemblies are when carrying out the installation of top cap piece negative pole end, for its gas tightness of strict control, the required precision of its installation is very high, both carry out the pre-compaction to the sealing washer, clearance between each part of will strictly controlling again, therefore with high costs and yields are low. Simultaneously in order to guarantee secondary battery's security, some batteries among the prior art install the upset piece in the negative pole end of top cap, and set up resistance electricity through the positive pole end and connect anodal and top cap piece, thereby when the battery leads to secondary battery inside atmospheric pressure to rise because of accidents such as overcharge or electrolyte emergence reaction, the upset piece overturns and forms outer electric current between anodal and the negative pole, stop overcharging, slowly overflow the heat dissipation through resistance and release the inside energy of secondary battery, thereby can not take place overcharge, fire, dangers such as explosion, thereby improve secondary battery's security performance. When the turnover piece is arranged, the isolation between the turnover piece and the cathode pole and the firm welding between the turnover piece and the top cover piece are guaranteed, and the assembling and processing difficulty of the top cover structure is undoubtedly increased.

Accordingly, it is desirable to provide a new roof structure or method of producing a roof that addresses the aforementioned assembly and processing problems of roof structures.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a negative pole post subassembly to prior art not enough, its simple structure, need not loaded down with trivial details sealed and assembly process, therefore easy to produce and yields are high.

In order to achieve the above object, the present invention provides a negative electrode pillar assembly, which is installed on a top cover plate, and comprises a negative electrode pillar, a connecting member fixed on the top cover plate, an insert, a sealing member, a flip piece, and an injection molding member surrounding the negative electrode pillar, wherein the insert is fixed on the connecting member and embedded in the injection molding member, the negative electrode pillar comprises an output portion exposed out of the injection molding member and a connecting portion accommodated in the injection molding member, an upper portion of the sealing member abuts against a lower portion of the output portion, a lower portion of the sealing member is fixed to the connecting member in a snap-fit manner, the connecting member is provided with a first through hole located below the output portion and a second through hole located below the connecting portion, the flip piece is fixed to the second through hole and located below the negative electrode pillar, when the internal pressure of a battery exceeds a preset value, the overturning sheet is driven by air pressure to overturn upwards and contact the connecting part so as to electrically connect the top cover sheet with the negative pole post.

The utility model discloses a negative pole post subassembly only needs to fix connecting piece and top cap piece, can accomplish the assembly of negative pole post and top cap piece, and its process is simple, need not loaded down with trivial details sealed and assembly process, can improve production efficiency through setting up of negative pole post subassembly, and the negative pole post subassembly is applicable in multiple top cap piece, and its suitability is high. And the cathode pole component has a simple structure, the cathode pole, the embedded part and the connecting part can be fixed through the injection molding part, and the formation of the injection molding part is very easy to realize. Meanwhile, the embedded part is embedded into the injection molding part, so that the cathode pole can be prevented from driving the injection molding part to move due to looseness in the use process of the battery, and the firmness is better. The upper portion butt of sealing member is in the lower part of output portion, and the lower part is fixed with the connecting piece joint, therefore can improve the sealing performance of sealing member, and in addition, the sealing member only seals in the output portion below of negative pole utmost point post, and the connecting portion suspension of negative pole utmost point post is in the top of second perforating hole, and it need not adopt the sealing member to seal and also need not bear the pulling force, so can improve sensitivity and the degree of accuracy with the upset piece effect. The turning sheet is fixed in the second through hole of the connecting piece and is arranged below the cathode pole, so that the turning sheet and other parts of the cathode end can be integrated into a cathode pole assembly, and additional assembling and processing procedures are omitted.

Preferably, the negative electrode pole further comprises a connection part between the output part and the connection part, and the output part, the connection part and the connection part can be integrally formed. Furthermore, the embedding part is a cavity which is provided with a hollow structure and is formed by enclosing, one side of the cavity is provided with a notch, the connecting part penetrates through the notch, and the injection molding part, the embedding part and the negative pole post are stronger in connectivity through the structure. Furthermore, the output part is provided with a first step and a second step along the vertical direction, the injection molding piece wraps the first step, and the upper surface of the injection molding piece is flush with the platform of the second step. The injection molding wraps the first step to enable the injection molding to be more firmly embedded with the output part, the upper surface of the injection molding is flush with the platform of the second step to enable the output part to be more conveniently installed and connected with external parts, and the output part is enabled to be surrounded by the injection molding except for the part electrically connected with the outside, so that the safety of the secondary battery is improved.

Preferably, the peripheral wall of the cavity is provided with a plurality of through holes for accommodating the injection molding part, and the arrangement of the through holes can improve the connection firmness of the injection molding part and the embedded part in the horizontal direction. Furthermore, the top of cavity to hollow direction extension forms joint portion, the embedding part borrows by joint portion joint in the injection molding, the setting of joint portion can improve injection molding and embedding in the firm nature of being connected of vertical side.

Preferably, the sealing element has a main body abutting against the output portion and a protrusion extending from a side of the main body away from the output portion, the protrusion is clamped to the connector, the connection reliability between the sealing element and the connector can be improved by clamping, and the sealing element can be made of an electrically insulating material made of rubber or plastic with certain elasticity, preferably a rubber material.

Preferably, the connecting piece is provided with a first annular groove and a second annular groove in sequence around the first through hole, the lower part of the sealing piece is clamped in the first annular groove, and the lower part of the embedding piece is clamped in the second annular groove.

Preferably, the connecting piece is concave in the second through hole to form a first step part, the turnover piece is provided with a welding part, the welding part is welded and fixed on the first step part, and a boss embedded into the injection molding piece is arranged above the second through hole of the connecting piece. The turnover sheet is welded in the first step part of the connecting piece, so that the overall height of the negative pole column assembly can be reduced, and the height of the whole secondary battery top cover is reduced.

The utility model discloses another aspect provides a secondary battery top cap for seal the casing that holds electric core, including the top cap piece with set up in the positive pole post subassembly and the aforementioned negative pole post subassembly of top cap piece, the top cap piece is equipped with the negative pole mounting hole, the negative pole post subassembly install in the negative pole mounting hole, the positive pole post subassembly with the top cap piece electricity is connected.

The utility model discloses a secondary battery top cap only needs to fix negative pole post subassembly and top cap piece, can accomplish the assembly of utmost point post and top cap piece, and its process is simple, need not loaded down with trivial details sealed and assembly process.

Preferably, the positive pole post assembly comprises a positive pole post, a conducting strip and a positive connecting piece, wherein the conducting strip and the positive connecting piece are sequentially sleeved on the positive pole post from top to bottom, the positive connecting piece and the positive pole post are isolated in the horizontal direction by a sealing piece, and the positive pole post assembly is fixed on the top cover plate by the positive connecting piece. Only need fix anodal connecting piece and top cap piece, can accomplish the assembly of anodal utmost point post and top cap piece, its process is simple, need not loaded down with trivial details sealed and assembly process, therefore can improve production efficiency through setting up of anodal post subassembly, and anodal post subassembly is applicable in multiple top cap piece, and its suitability is high.

Drawings

Fig. 1 is a plan view of an embodiment of a secondary battery top cap according to the present invention.

Fig. 2 is a bottom view of an embodiment of a secondary battery top cap according to the present invention.

Fig. 3 is an exploded view of the secondary battery top cap according to the present invention in one direction.

Fig. 4 is an exploded view of the secondary battery top cover according to the present invention in the other direction.

Fig. 5 is a sectional view taken in the direction a-a of fig. 1.

Fig. 6 is an enlarged view of a portion indicated by a in fig. 5.

Fig. 7 is a top view of an embodiment of a negative electrode pillar assembly of the present invention.

Fig. 8 is a bottom view of an embodiment of a negative electrode pillar assembly of the present invention.

Fig. 9 is a sectional view in the direction B-B in fig. 7.

Fig. 10 is an exploded view of the negative electrode pillar assembly of the present invention in one direction.

Fig. 11 is an exploded view of the negative electrode pillar assembly of the present invention in another direction.

Fig. 12 is an enlarged view of a portion indicated by B in fig. 5.

Fig. 13 is a top view of an embodiment of a positive post assembly of the present invention.

Fig. 14 is a bottom view of an embodiment of a positive electrode pillar assembly according to the present invention.

Fig. 15 is a cross-sectional view in the direction of C-C in fig. 13.

Fig. 16 is an exploded view of the positive post assembly of the present invention in one direction.

Fig. 17 is an exploded view of the positive post assembly of the present invention in another direction.

Description of the element reference numerals

100-secondary battery top cover; 10-a top cover sheet; 11-a negative mounting hole; 13-positive mounting holes; 15-explosion-proof valve mounting holes; 20-a positive post assembly; 21-positive pole column; 211-pole fitting hole; 22-a conductive sheet; 221-upper projection; 223-lower bulge; 23-positive electrode connection; 231-connector fitting holes; 24-positive seal; 25-a soldering tab; 26-positive electrode lower insulation member; 30-a negative post assembly; 31-a negative electrode post; 311-a connecting part; 313-a junction; 315-output section; 32-an insert; 321-cavity, 323-gap; 325-a via hole; 327-a snap-in portion; 33-a connector; 331-second through hole; 332-first through-hole; 333-boss; 334-a first annular groove; 335-a second annular groove; 336-a first step; 34-a seal; 341-body portion; 343-a boss; 35-injection molding; 36-turning over the sheet; 361-a turning part; 363-a weld; 365-upper boss; 40-an explosion-proof valve assembly; 41-explosion-proof valve; 43-explosion-proof valve protection plate; 50-liquid injection hole; 60-lower insulation;

Detailed Description

In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the accompanying drawings. The preferred embodiments of the present invention are shown in the drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. It should be noted that, in general, the secondary battery is placed vertically, one side of the secondary battery top cover, where the pole extends out and is connected with the outside, is an upper side, and the other side is a lower side.

The utility model discloses a secondary battery top cap can be used to the sealed casing and prepares secondary battery, and the secondary battery top cap can weld with the casing and seal. Referring to fig. 1 to 5, a secondary battery top cap 100 has a top cap sheet 10, and a positive electrode post assembly 20 and a negative electrode post assembly 30 provided on the top cap sheet 10, the top cap sheet 10 is provided with an explosion-proof valve assembly 40 and a liquid injection hole 50, and a lower insulator 60 is provided under the top cap sheet 10 for electrically insulating the top cap sheet 10 from a cell in a case (not shown in the drawings). Top cap piece 10 is equipped with negative pole mounting hole 11, anodal mounting hole 13 and explosion-proof valve mounting hole 15, and anodal post subassembly 20 and negative pole post subassembly 30 are fixed in anodal mounting hole 13 and negative pole mounting hole 11 respectively, and anodal post subassembly 20 is connected with top cap piece 10 electricity, and negative pole post subassembly 30 and top cap piece 10 electricity are insulating. The explosion-proof valve assembly 40 includes an explosion-proof valve 41 fixed to the explosion-proof valve mounting hole 15 and an explosion-proof valve protection sheet 43 covering the upper side of the explosion-proof valve 41 for protection.

First, referring to fig. 6 to 11, describing the structure of the negative pole post assembly 30, the negative pole post assembly 30 includes a negative pole post 31, a connecting member 33 fixed on the top cover plate 10, an insert 32, a sealing member 34, an inversion sheet 36 and an injection molding member 35 surrounding the negative pole post 31, the insert 32 is fixed on the connecting member 33 and is embedded in the injection molding member 35, the negative pole post 31 includes an output portion 315 exposed out of the injection molding member 35 and a connecting portion 311 accommodated in the injection molding member 35, an upper portion of the sealing member 34 abuts against a lower portion of the output portion 315, a lower portion of the sealing member 34 is fixed to the connecting member 33 in a snap-fit manner, the connecting member 33 is provided with a first through hole 332 located below the output portion 315 and a second through hole 331 located below the connecting portion 311, the inversion sheet 34 is fixed to the second through hole 331 and located below the negative pole post 31, when the internal pressure of the battery exceeds a predetermined value, the inversion sheet 34 is driven to be inverted upwards by the air pressure and contacts the connecting portion 311 to electrically connect the top cover plate 10 and the negative pole post 31, thereby electrically conducting the negative electrode post 31, the positive electrode post assembly 20 and the top cap piece 10 to form an external short circuit to ensure the safety of the secondary battery.

With continued reference to fig. 9-11, the negative electrode terminal 31 further includes a connection portion 313 located between the output portion 315 and the connection portion 311, the output portion 315, the connection portion 311, and the connection portion 313 may be integrally formed, and in practical applications, a lower portion of the output portion 315 may be welded and fixed to a connection piece for connecting a negative electrode of the battery cell. The output portion 315 is provided with a first step (not shown) and a second step along the vertical direction, the injection molding 35 wraps the first step, and the upper surface of the injection molding 35 is flush with the platform of the second step. The injection molding 35 wraps the first step, so that the injection molding 35 and the output part 315 are more firmly embedded, the upper surface of the injection molding 35 is flush with the platform of the second step, so that the output part 315 is more convenient to mount and connect with external parts, and the rest parts of the output part 315 except the part electrically connected with the outside are surrounded by the injection molding 35, so that the safety of the secondary battery is improved.

The insert 32 is a cavity 321 which has a hollow structure and is formed by enclosing, a notch 323 is arranged on one side of the cavity 321, the connecting part 313 of the cathode post 31 penetrates through the notch 323, and the injection molding part 35, the insert 32 and the cathode post 31 can be stronger in connectivity through the structure. The peripheral wall of the cavity 321 is provided with a plurality of through holes 325 for accommodating the injection molding part 35, and the arrangement of the through holes 325 can improve the connection firmness of the injection molding part 35 and the embedded part 32 in the horizontal direction. The top of cavity 321 extends to hollow direction and forms joint portion 327, and insert 32 borrows to be passed through joint portion 327 and connects in injection molding 35, and the setting of joint portion 327 can improve injection molding 35 and insert 32 in the firm nature of being connected of vertical direction.

The inversion sheet 36 includes an inversion portion 361 which is inverted by the air pressure, an upper boss 365 at the middle portion, and a welding portion 363 at the edge of the inversion portion 361. The connecting member 33 is provided with a first annular groove 334 and a second annular groove 335 in this order around the first through hole 332, the lower portion of the sealing member 34 is engaged with the first annular groove 334, and the lower portion of the insert member 32 is engaged with the second annular groove 335. The connecting piece 33 is recessed in the second through hole 331 to form a first step portion 336, the welding portion 363 of the flip piece 36 is welded and fixed to the first step portion 336, and a boss 333 embedded in the injection molding 35 is arranged above the second through hole 331 of the connecting piece 33. The welding of the inversion sheet 36 into the first stepped portion 336 of the connection member 33 may reduce the overall height of the negative electrode tab assembly 30, thereby reducing the height of the entire secondary battery top cap 100.

The sealing member 34 has a main body 341 abutting against the output portion 315 and a protrusion 343 formed by extending from a side of the main body 341 away from the output portion 316, the protrusion 343 is clamped to the connector 33, the fastening between the sealing member 34 and the connector 33 can be improved by clamping, and the sealing member 34 can be an electrically insulating material made of rubber or plastic with certain elasticity, preferably a rubber material.

Next, the structure of the positive electrode post assembly 20 will be described with reference to the drawings, and the positive electrode post assembly 20 may have various structures, which only need to be electrically connected to the top lid sheet 10. For convenience of assembly, the positive post assembly 20 may have a structure as shown in fig. 12 to 17, the positive post assembly 20 includes a positive post 21, a conductive sheet 22 and a positive connector 23 sequentially sleeved on the positive post 21 from top to bottom, the positive connector 23 and the positive post 21 are separated by a sealing member 24 in a horizontal direction, and the positive post assembly 20 is fixed to the top cover 10 by the positive connector 23. Therefore, only need to fix anodal connecting piece 20 and top cap piece 10, can accomplish the assembly of anodal utmost point post 21 and top cap piece 10, its process is simple, need not loaded down with trivial details sealed and assembly process, therefore can improve production efficiency through setting up of anodal post subassembly 20, and anodal post subassembly 20 is applicable in multiple top cap piece 10, and its suitability is high. In order to ensure that the connection among the components is firmer and prevent dislocation and rotation, the positive pole post 21 and the conducting strip 22, and the conducting strip 22 and the positive connecting piece 23 can be clamped and fixed, specifically, the positive pole post 21 is provided with a post embedding hole 211, and the conducting strip 22 is provided with an upper protrusion 221 in clamping fit with the post embedding hole 211. The positive electrode connector 23 is provided with a connector fitting hole 231, and the conductive plate 22 is provided with a lower protrusion 223 which is snap-fitted into the connector fitting hole 231. In order to facilitate the welding and fixing with the positive plate of the battery core, a welding plate 25 is fixed on the lower part of the positive pole post 21, and a positive lower insulation 26 is arranged between the welding plate 25 and the positive connecting piece 23.

The utility model discloses a negative pole post subassembly 30 only needs to fix connecting piece 33 and top cap piece 10, can accomplish the assembly of negative pole post 31 and top cap piece 10, and its process is simple, need not loaded down with trivial details sealed and assembly process, can improve production efficiency through setting up of negative pole post subassembly 30, and negative pole post subassembly 30 is applicable in multiple top cap piece, and its suitability is high. The cathode post assembly 30 is simple in structure, the cathode post 31, the embedded part 32 and the connecting part 33 can be fixed through the injection molding part 35, and the injection molding part 35 is easy to form. Meanwhile, the embedded part 32 is embedded into the injection molding part 35, so that the cathode pole 31 can be prevented from driving the injection molding part 35 to move due to looseness in the use process of the battery, and the firmness is better. The upper portion of the sealing member 34 abuts on the lower portion of the output portion 315, and the lower portion is fixed by being engaged with the connector 33, so that the sealing performance of the sealing member 34 can be improved, and the sealing member 34 is sealed only below the output portion 315 of the negative electrode terminal 31, and the connecting portion 311 of the negative electrode terminal 31 is suspended above the second through hole 331, so that it is not necessary to seal with the sealing member 34 and to receive a tensile force, and therefore, the sensitivity and accuracy of the action with the inverting piece 36 can be improved. The inverted piece 36 is fixed to the second through hole 331 of the connection member 33 and disposed under the negative electrode tab 31, so that it can be integrated with other components of the negative electrode terminal into one negative electrode tab assembly 30, thereby eliminating additional assembly and processing steps.

It should be noted that the above-mentioned embodiments illustrate rather than limit the scope of the invention, and that modifications of various equivalent forms of the invention, which may occur to those skilled in the art after reading the present application, fall within the scope of the appended claims.

Claims

1. A negative pole post assembly (30) is mounted on a top cover plate (10) and is characterized by comprising a negative pole post (31), a connecting piece (33) fixed on the top cover plate (10), an embedded piece (32), a sealing piece (34), an overturning piece (36) and an injection molding piece (35) enclosed in the negative pole post (31), wherein the embedded piece (32) is fixed on the connecting piece (33) and embedded in the injection molding piece (35), the negative pole post (31) comprises an output part (315) exposed out of the injection molding piece (35) and a connecting part (311) accommodated in the injection molding piece (35), the upper part of the sealing piece (34) is abutted against the lower part of the output part (315), the lower part of the sealing piece (34) is clamped and fixed with the connecting piece (33), the connecting piece (33) is provided with a first through hole (332) positioned below the output part (315) and a second through hole (331) positioned below the connecting part (311), the overturning sheet (36) is fixed to the second through hole (331) and located below the negative electrode post (31), and when the internal pressure of the battery exceeds a preset value, the overturning sheet (36) is driven by air pressure to overturn upwards and contact the connecting portion (311) so as to electrically connect the top cover sheet (10) and the negative electrode post (31).

2. The negative electrode post assembly (30) according to claim 1, wherein the negative electrode post (31) further comprises an interface portion (313) between the output portion (315) and the connection portion (311).

3. The negative pole post assembly (30) of claim 2, wherein the insert (32) is a hollow cavity (321) enclosed therein, one side of the cavity (321) is provided with a notch (323), and the connection portion (313) penetrates through the notch (323).

4. The negative electrode pillar assembly (30) according to claim 3, wherein the peripheral wall of the cavity (321) is provided with a number of through holes (325) that receive the injection molded part (35).

5. The negative electrode pillar assembly (30) of claim 3, wherein the top of the cavity (321) extends to the hollow direction to form a clamping portion (327), and the insert (32) is clamped to the injection molding part (35) by the clamping portion (327).

6. The negative electrode column assembly (30) according to claim 1, wherein the sealing member (34) has a body portion (341) abutting against the output portion (315) and a protrusion portion (343) formed to extend from a side of the body portion (341) away from the output portion (315), and the protrusion portion (343) is engaged with the connecting member (33).

7. The negative electrode pillar assembly (30) according to claim 1, wherein the connecting member (33) is provided with a first annular groove (334) and a second annular groove (335) in sequence around the first through hole (332), a lower portion of the sealing member (34) is caught in the first annular groove (334), and a lower portion of the insert member (32) is caught in the second annular groove (335).

8. The negative column assembly (30) according to claim 1, wherein the connecting member (33) is recessed in the second through hole (331) to form a first step portion (336), the flip piece (36) has a welding portion (363), the welding portion (363) is welded and fixed to the first step portion (336), and the connecting member (33) is provided with a boss (333) embedded in the injection molding member (35) above the second through hole (331).

9. A secondary battery top cover (100) used for sealing a shell containing an electric core is characterized by comprising a top cover plate (10), a positive pole column assembly (20) arranged on the top cover plate (10) and a negative pole column assembly (30) according to any one of claims 1 to 8, wherein the top cover plate (10) is provided with a negative pole mounting hole (11), the negative pole column assembly (30) is mounted in the negative pole mounting hole (11), and the positive pole column assembly (20) is electrically connected with the top cover plate (10).

10. The secondary battery top cover (100) according to claim 9, wherein the positive pole assembly (20) comprises a positive pole column (21), a conductive sheet (22) and a positive pole connecting piece (23) which are sequentially sleeved on the positive pole column (21) from top to bottom, the positive pole connecting piece (23) and the positive pole column (21) are separated by a positive pole sealing piece (24) in the horizontal direction, and the positive pole column assembly (20) is fixed on the top cover plate (10) by the positive pole connecting piece (23).