CN217062233U

CN217062233U - Winding battery

Info

Publication number: CN217062233U
Application number: CN202123124589.0U
Authority: CN
Inventors: 闫天昊; 何宏; 石小利
Original assignee: Yunshan New Energy Material Technology Shenzhen Co ltd
Current assignee: Yunshan New Energy Material Technology Shenzhen Co ltd
Priority date: 2021-12-13
Filing date: 2021-12-13
Publication date: 2022-07-26
Anticipated expiration: 2031-12-13

Abstract

The utility model provides a winding battery, which comprises a winding core, wherein the winding core is wound along a winding direction after being compounded by a pole piece and a diaphragm to form a multilayer structure with a core shaft, the pole piece comprises a pole lug, the pole piece has a winding state and an unfolding state, and a soldering tin layer is arranged on the pole lug; when the pole piece is in a winding state, a spacing space is formed between two adjacent layers of pole lugs, one side of the pole lug close to the mandrel is defined as the inner side, one side opposite to the inner side is defined as the outer side, the soldering tin layer is positioned in the spacing space, and a gap is formed between the soldering tin layer and the outer side of the pole lug of the adjacent layer on the inner side, or a gap is formed between the soldering tin layer and the inner side of the pole lug of the adjacent layer on the outer side. The winding battery effectively solves the problem that the tab is easy to break movably due to thin material; a gap is reserved between the soldering tin layer and one side of the lug, and the infiltration effect of the electrolyte is guaranteed.

Description

Winding battery

Technical Field

The present disclosure relates to the field of battery technology, and more particularly, to a wound battery.

Background

The wound battery has characteristics of ultra-strong high-rate discharge capability, stable high output voltage, ultra-long service life and the like, is increasingly widely used, and is generally applied to the fields of instruments, medical instruments, power transmission equipment, automobiles and the like.

The existing cylindrical full-lug or multi-lug winding type battery mainly comprises two methods for forming a flat plane on the surface of a lug group, wherein the first method is to directly rub and flatten the lug after winding and press the lug under the action of ultrasound or external force to form a plane on the uppermost layer of a vertical lug; the second is to cut the pole ear in narrow gap, divide the pole ear into several small pole ears separated from the upper part, and then bend and flatten the cut small pole ears to form a plane. The adoption kneads flat mode can make utmost point ear because of receiving external force to push down and the friction produces the metal fillings and enter into the battery inside can't clear away, causes the battery self discharge easily to arouse the potential safety hazard, simultaneously because utmost point ear root bending degree is different, has the cracked risk of utmost point ear, and kneads flatly between the back utmost point ear more closely, is unfavorable for electrolyte to soak. And the mode of bending and flattening is adopted, so that the formed plane is not a complete plane easily, uneven and unstable gaps exist in the flattened surface after pressing down, the welding connection is unstable, the current density is uneven or insufficient welding is generated, and the point discharge or self-discharge of the battery is caused.

SUMMERY OF THE UTILITY MODEL

The present disclosure provides a wound battery to solve at least the above technical problems occurring in the prior art.

The winding battery comprises a winding core, wherein the winding core is wound along a winding direction after a pole piece and a diaphragm are compounded to form a multilayer structure with a core shaft, the pole piece comprises a pole lug, the pole piece is in a winding state and an unfolding state, and a soldering tin layer is arranged on the pole lug; when the pole pieces are in the winding state, a spacing space is formed between two adjacent layers of the pole lugs, one side, close to the core shaft, of the pole lug is defined as an inner side, the side, opposite to the inner side, of the pole lug is defined as an outer side, the soldering tin layer is located in the spacing space, a gap is formed between the soldering tin layer and the outer side of the pole lug of the adjacent layer, or a gap is formed between the soldering tin layer and the inner side of the pole lug of the adjacent layer.

In an embodiment, the tab is defined as being placed in a forward direction when the tab is located at the top end of the whole pole piece, and the tab has a first section welded to the solder layer and a second section exceeding the upper edge of the solder layer when the pole piece is in the unfolded state.

In one embodiment, when the pole piece is in the wound state, the second section is bent to be in contact with the upper edge of the solder layer and to form a half-wrapped space which is half-wrapped on the solder layer with the first section.

In one embodiment, the solder layers have the same cross-sectional shape on the cross-section of the core.

In one embodiment, the electrode sheet includes a positive electrode sheet and a negative electrode sheet, a surface of the solder layer connected to the tab is defined as a contact surface, a farthest point of the solder layer in a direction perpendicular to the electrode sheet is defined as a first point, a perpendicular distance between an extending direction of the contact surface and the first point is defined as a thickness of the solder layer, and the thickness of the solder layer on the positive electrode sheet is expressed by a formula: h is a total of ₁ (a + b +2c-m)/2, wherein h ₁ The thickness of the soldering tin layer on the positive plate is shown as a, the thickness of the positive plate is shown as b, the thickness of the negative plate is shown as c, and the thickness of the positive plate foil is shown as m.

In one embodiment, the electrode sheet includes a positive electrode sheet and a negative electrode sheet, a surface of the solder layer connected to the tab is defined as a contact surface, a farthest point of the solder layer in a direction perpendicular to the electrode sheet is defined as a first point, a perpendicular distance between an extending direction of the contact surface and the first point is defined as a thickness of the solder layer, and the thickness of the solder layer on the negative electrode sheet is expressed by a formula: h is ₂ (a + b +2c-n)/2, wherein h ₂ The solder layer on the negative plateA is the thickness of the positive plate, b is the thickness of the negative plate, c is the thickness of the diaphragm, and n is the thickness of the negative plate foil.

In an embodiment, the pole piece includes a start end and a stop end, the tab is a full tab, when the pole piece is in the unfolded state, the soldering tin layer extends from the start end to the stop end, and the soldering tin layer is parallel to the top end of the pole piece.

In an embodiment, the solder layer is disposed on the inner side, and when the pole piece is in the wound state, a gap is formed between the two solder layers on the two tabs on the two innermost layers of the winding core.

In an implementation mode, the pole piece comprises a starting end and a terminating end, the pole lug is a full pole lug, and when the pole piece is in the unfolded state, the soldering tin layer begins to extend from any position between the starting end and the terminating end; or every interval sets up a distance, every section the soldering tin layer with the pole piece top is parallel, and the top edge of soldering tin layer to the distance of pole piece top is the same.

In an embodiment, the pole piece includes a start end and a stop end, the tab is a multi-tab, and when the pole piece is in the unfolded state, the soldering tin layer starts to be continuously arranged from any one of the multi-tab between the start end and the stop end; or the multiple tabs are arranged at intervals of different numbers, the soldering tin layer is parallel to the top end of the pole piece, and the distances from the upper edge of the soldering tin layer to the top end of the pole piece are the same.

In the disclosure, as the soldering tin layer arranged on the tab has certain strength and hardness, the tab above the soldering tin layer can be supported in strength, so that a stable plane is formed on the surface of the tab group and is not easy to deform, the problem that the tab is easy to move and break due to thin material is effectively solved, and the tab and the bus bar piece are favorably welded; the soldering tin layer is arranged on one side between two adjacent layers of the tabs, and a gap is reserved between the soldering tin layer and the other side, so that electrolyte can conveniently enter the space between the tab layers through the gap, and the infiltration effect of the electrolyte is ensured; by adopting the non-kneading and flattening process, metal scraps generated in the kneading and flattening mode are effectively eliminated, the production processes and steps are reduced, the generation of self-discharge can be reduced, the potential safety hazard is eliminated, the production efficiency is improved, and the production quality is ensured.

It should be understood that the statements in this section do not necessarily identify key or critical features of the embodiments of the present disclosure, nor do they limit the scope of the present disclosure. Other features of the present disclosure will become apparent from the following description.

Drawings

The above and other objects, features and advantages of exemplary embodiments of the present disclosure will become readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. Several embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

in the drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

Fig. 1 shows a schematic cross-sectional structure of a wound battery according to an exemplary embodiment of the present disclosure;

fig. 2 shows a schematic cross-sectional structure of another exemplary embodiment of a rolled battery of the present disclosure;

fig. 3 shows an expanded schematic view of a full tab pole piece when a solder layer is uniformly distributed according to an embodiment of the disclosure;

FIG. 4 is an expanded schematic view of a multi-tab pole piece with evenly distributed solder layers according to an embodiment of the disclosure;

fig. 5 shows an expansion schematic diagram of a multi-tab pole piece when solder layers are non-uniformly distributed according to an embodiment of the disclosure.

The numbering in the figures illustrates: 1. a tab; 2. a solder layer; 3. an intervening space; 4. a coating zone; 11. an inner side; 12. an outer side; 13. a first stage; 14. a second section; 15. a starting end; 16. and a terminating end.

Detailed Description

In order to make the objects, features and advantages of the present disclosure more apparent and understandable, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure, and it is apparent that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

Referring to fig. 1 to 3, in the wound battery according to one embodiment of the present disclosure, a pole piece and a diaphragm are combined and then wound in a winding direction to form a multilayer structure having a core shaft, the pole piece includes a tab 1 and a coating area 4, the coating area 4 is covered with an active material, a soldering tin layer 2 is welded on the tab 1, and when the pole piece is in a winding state, a space 3 is formed between every two adjacent layers of tabs 1. The side of the tab 1 close to the mandrel is defined as the inner side 11, the other side is defined as the outer side 12, and the solder layer 2 can be arranged on the inner side 11 or the outer side 12, but not both. The soldering tin layer 2 is positioned in the spacing space 3, and when the soldering tin layer 2 is arranged on the inner side 11 of the tab 1, a gap is formed between the soldering tin layer 2 and the outer side 12 of the tab 1 of the adjacent layer; when the solder layer 2 is disposed on the outer side 12 of the tab 1, there is a gap between the solder layer 2 and the inner side 11 of the tab 1 adjacent thereto.

In the present embodiment, the surface shown in fig. 3 is defined as a first surface, the surface opposite to the first surface and not shown is defined as a second surface, and taking the first surface of the pole piece as an example, the solder layer 2 is arranged on the first surface of the pole piece, the solder wire is welded with the pole ear 1 to form the solder layer 2, after the solder layer 2 is formed on the pole ear 1, the pole piece is wound from the starting end 15 to the terminating end 16, after winding, the first surface is wrapped on the inner side 11, and the solder layer 2 is also positioned on the inner side 11 of the pole ear 1 after winding; or the welding process of the solder wire and the tab 1 is synchronously carried out with the winding of the pole piece, the pole piece starts to be wound when the solder wire is welded on the tab 1 to form the solder layer 2, and the welding mechanism can be integrated on the winding equipment in order to realize the synchronous welding and winding, so that the production efficiency of the battery can be effectively improved.

Similarly, when the soldering tin layer 2 is arranged on the second surface of the pole piece, the soldering tin wire is welded with the pole lug 1 to form the soldering tin layer 2, after the soldering tin layer 2 is formed on the pole lug 1, the pole piece is wound from the starting end 15 to the ending end 16, the first surface is wrapped on the inner side 11 after winding, and the soldering tin layer 2 is positioned on the outer side 12 of the pole lug 1 after winding; or the process of welding the soldering tin wire and the tab 1 is synchronously performed with the winding of the pole piece, the pole piece starts to be wound when the soldering tin wire forms the soldering tin layer 2 on one section of the tab 1, and the soldering tin layer 2 is arranged on the second surface of the pole piece and is the same as the winding core forming mode arranged on the first surface, so that the description of the soldering tin layer is omitted, and in addition, the soldering tin wire can also be other metal wires capable of forming hard layers.

In this disclosure, because the soldering tin layer 2 that sets up on utmost point ear 1 has certain intensity and hardness, can make utmost point ear 1 more than soldering tin layer 2 obtain the intensity and support, make utmost point ear crowd surface form stable plane non-deformable, effectively solved because of utmost point ear 1 material is thinner, easy activity fracture's problem helps the welding between utmost point ear 1 and the busbar. Furthermore, the soldering tin layer 2 is arranged on one side between the two adjacent layers of the lugs 1, and a gap is reserved between the soldering tin layer and the other side, so that electrolyte can conveniently enter the space between the lug layers through the gap, and the infiltration effect of the electrolyte is ensured. Moreover, the non-kneading process effectively eliminates metal scraps generated in the kneading mode, reduces the production processes and steps, can also reduce the generation of self-discharge, eliminates potential safety hazards, improves the production efficiency and ensures the production quality.

In an embodiment, the tab 1 is defined to be placed in a forward direction when being positioned at the top end of the whole pole piece, the tab 1 is provided with a first section 13 welded with the soldering tin layer 2 and a second section 14 exceeding the upper edge of the soldering tin layer 2, and the second section 14 of the tab 1 can be welded with the confluence plate in a vertical mode (refer to fig. 2) without any treatment after a winding core is formed; or after the winding core is formed, the second section 14 of the tab 1 is bent to be connected with the upper edge of the soldering tin layer 2, and forms a half-wrapping space which covers the soldering tin layer 2 with the first section 13, wherein the connection mode of the second section 14 of the tab 1 and the upper edge of the soldering tin layer 2 can be welding, or the second section 14 can be directly folded to the upper edge of the soldering tin layer 2 (refer to fig. 1).

In the above embodiment, since the soldering tin layer 2 is effectively combined with the first section 13, the tab 1 exceeds the second section 14 of the soldering tin layer 2, and the upper end of the second section 14 can form a rigid plane under the support of the soldering tin layer 2, thereby solving the problem that the tab 1 is easy to move and break due to the thin material of the tab, and being beneficial to the welding between the tab 1 and the bus bar. And the second section 14 is bent to form a half-wrapping space with the first section 13, so that a flat surface is further formed at the upper end of the tab group, the subsequent welding of the tab 1 and the confluence piece is facilitated, the effective welding area is ensured, and the overcurrent capacity is improved.

In any of the above embodiments, the cross-sectional shape of the solder layers 2 is the same on the cross section of the winding core, so that after the solder wires are welded to the tabs 1, the solder layers 2 are on the same straight line, and the flat surface of the upper end of the tab group is ensured.

In one embodiment, the pole piece comprises a positive pole piece and a negative pole piece, the surface of the solder layer 2 connected with the pole lug 1 is defined as a contact surface, the farthest point of the solder layer 2 in the direction perpendicular to the pole piece is a first point, the vertical distance from the extending direction of the contact surface to the first point is the thickness of the solder layer 2, and the thickness of the solder layer 2 on the positive pole piece is designed and expressed by the formula:

h ₁ ＝(a+b+2c-m)/2

the thickness of the solder layer 2 on the positive plate is designed and expressed by the formula:

h ₂ ＝(a+b+2c-n)/2

in the above two formulae, h ₁ Thickness of solder layer 2 on positive electrode plate, h ₂ The thickness of the solder layer 2 on the negative plate, a is the thickness of the positive plate, b is the thickness of the negative plate, c is the thickness of the diaphragm, m is the thickness of the foil of the positive plate, and n is the thickness of the foil of the negative plate.

The thickness of the soldering tin layer 2 is designed to be the recommended optimal thickness, that is, the thickness of the soldering tin layer 2 occupies half of the spacing space 3 formed between two adjacent layers of the tabs 1, but is not limited to the thickness, and in a specific application, the thickness of the soldering tin wire does not fill the spacing space 3.

In the embodiment, the thickness of the soldering tin layer 2 accounts for half of the space 3 formed between two adjacent layers of the polar lugs 1, so that electrolyte can conveniently enter the space between the polar lug layers through the gap, and the infiltration effect of the electrolyte can be well ensured.

In an embodiment, the tab 1 of the pole piece is a full tab, and on the one hand, the solder layer 2 can be continuously and uniformly disposed on the tab 1 from the starting end 15 of the pole piece, and the solder layer 2 is parallel to the top end of the pole piece (see fig. 3). Specifically, after the core is rolled up in full utmost point ear pole piece formation, guarantee to roll up and have the clearance between the soldering tin layer 2 on the core innermost two-layer utmost point ear 1, this clearance is recommended to be set up according to the one third in clearance between two utmost point ears 1, but not be limited to this size, as long as guarantee that soldering tin layer 2 does not fill up interval space 3. On the other hand (refer to fig. 4), the solder layers 2 can be continuously arranged from any position between the starting end 15 and the ending end 16 of the pole piece, or arranged at the same or different intervals, as long as each segment of the solder layer 2 is parallel to the top end of the pole piece, and the distance from the upper edge of the solder layer 2 to the top end of the pole piece is the same. After the full tab is cut in the narrow gap, the second section 14 can be bent to connect with the solder layer 2, so that the top of the tab group forms a plane.

Referring to fig. 5, in an embodiment, the tab 1 of the pole piece is a multi-tab, and the solder layer 2 may be continuously disposed from any multi-tab between the start end 15 and the end 16 of the pole piece, or disposed at the same or different intervals, as long as it is ensured that each solder layer 2 is parallel to the top end of the pole piece and the distance from the top edge of the solder layer 2 to the top end of the pole piece is the same.

By combining the above embodiments, when the soldering tin layer 2 is continuously and uniformly arranged on the tab 1, the soldering tin layer 2 is uniformly distributed on the section of the winding core, at this time, the supporting effect achieved by the soldering tin layer 2 is the best, the plane formed at the top end of the tab 1 has better strength support, and when the tab 1 and the bus bar are welded in a resistance welding or laser welding manner, the deformation of welding stress is not easy to occur; and when the soldering tin layer 2 is arranged at a certain distance or the tab 1, the soldering tin layer 2 is unevenly distributed on the section of the winding core, so that the supporting effect is weakened to some extent. During actual production, a corresponding mode can be selected for production according to production requirements.

In the description of the present disclosure, it is to be understood that the orientation or positional relationship indicated by the orientation terms is generally based on the orientation or positional relationship shown in the drawings, and is for convenience only to facilitate the description of the present disclosure and to simplify the description, and in the case of not having been stated to the contrary, these orientation terms are not intended to indicate and imply that the device or element being referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore should not be taken as limiting the scope of the present disclosure; the terms "inner" and "outer" refer to the interior and exterior of the respective components as they relate to their own contours.

Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe the spatial relationship of one or more components or features shown in the figures to other components or features. It is to be understood that the spatially relative terms are intended to encompass not only the orientation of the component as depicted in the figures, but also different orientations of the component in use or operation. For example, if an element in the figures is turned over in its entirety, elements "above" or "over" other elements or features would include elements "below" or "beneath" other elements or features. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". Further, these components or features may also be oriented at other different angles (e.g., rotated 90 degrees or other angles) and all such are intended to be included herein.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, elements, components, and/or combinations thereof, unless the context clearly indicates otherwise.

It should be noted that the terms "first," "second," and the like in the description and claims of the present disclosure and in the above-described drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the disclosure described herein are capable of operation in other sequences than those illustrated or described herein.

The present disclosure has been illustrated by the above-described embodiments, but it should be understood that the above-described embodiments are for purposes of illustration and description only and are not intended to limit the present disclosure to the described embodiments. Furthermore, it will be understood by those skilled in the art that the present disclosure is not limited to the embodiments described above, and that many variations and modifications may be made in light of the teaching of the present disclosure, all of which fall within the scope of the claimed disclosure. The scope of the disclosure is defined by the appended claims and equivalents thereof.

Claims

1. A winding battery comprises a winding core, wherein the winding core is wound along a winding direction after being compounded by a pole piece and a diaphragm to form a multilayer structure with a core shaft, the pole piece comprises a pole lug (1), and the pole piece has a winding state and an unfolding state, and is characterized in that a soldering tin layer (2) is arranged on the pole lug (1); when the pole piece is in the winding state, a spacing space (3) is formed between two adjacent layers of the pole lugs (1), one side, close to the core shaft, of the pole lug (1) is defined as an inner side (11), one side, opposite to the inner side (11), of the pole lug (1) is defined as an outer side (12), the soldering tin layer (2) is located in the spacing space (3), a gap is formed between the soldering tin layer (2) arranged on the inner side (11) and the outer side (12) of the pole lug (1) of the adjacent layer, or a gap is formed between the soldering tin layer (2) arranged on the outer side (12) and the inner side (11) of the pole lug (1) of the adjacent layer.

2. The wound battery according to claim 1, characterized in that the tab (1) is defined as being placed in the forward direction when it is positioned on the top end of the pole piece as a whole, the tab (1) having a first section (13) welded to the layer of solder (2) and a second section (14) beyond the upper edge of the layer of solder (2).

3. The wound battery according to claim 2, characterized in that the second section (14) is bent to meet the upper edge of the solder layer (2) and to form a half-envelope space with the first section (13) half-enveloping the solder layer (2) when the pole pieces are in the wound state.

4. The wound battery according to any one of claims 1 to 3, wherein the solder layers (2) have the same cross-sectional shape in the cross-section of the winding core.

5. The wound battery according to claim 1, characterized in that the pole piece comprises a positive pole piece and a negative pole piece, the surface of the solder layer (2) connected with the pole lug (1) is defined as a contact surface, the farthest point of the solder layer (2) in the direction perpendicular to the pole piece is a first point, the perpendicular distance from the extending direction of the contact surface to the first point is the thickness of the solder layer (2), and the thickness of the solder layer (2) on the positive pole piece is expressed by the formula:

h ₁ ＝(a+b+2c-m)/2 ①

wherein h is ₁ The thickness of the soldering tin layer (2) on the positive plate is shown as a, the thickness of the positive plate is shown as b, the thickness of the negative plate is shown as c, and the thickness of the positive plate foil is shown as m.

6. The wound battery according to claim 1, characterized in that the pole piece comprises a positive pole piece and a negative pole piece, the surface of the solder layer (2) connected with the pole ear (1) is defined as a contact surface, the farthest point of the solder layer (2) in the direction perpendicular to the pole piece is a first point, the perpendicular distance from the extending direction of the contact surface to the first point is the thickness of the solder layer (2), and the thickness of the solder layer (2) on the negative pole piece is expressed by the formula:

h ₂ ＝(a+b+2c-n)/2 ②

wherein h is ₂ The thickness of the soldering tin layer (2) on the negative plate is shown in the specification, and a is the thickness of the positive plateThe thickness of the negative plate is b, the thickness of the diaphragm is c, and the thickness of the negative plate foil is n.

7. The wound battery according to claim 1, characterized in that the pole piece comprises a starting end (15) and a terminating end (16), the tab (1) is a full tab, the solder layer (2) extends from the starting end (15) to the terminating end (16) when the pole piece is in the unfolded state, and the solder layer (2) is parallel to the top end of the pole piece.

8. The wound battery according to claim 7, characterized in that the solder layers (2) are arranged on the inner side (11), and a gap is provided between the two solder layers (2) on the tab (1) of the innermost two layers of the winding core when the pole pieces are in the wound state.

9. The winding battery according to claim 1, characterized in that the pole piece comprises a starting end (15) and a terminating end (16), the tab (1) is a full tab, and when the pole piece is in the unfolded state, the solder layer (2) begins to extend from any position between the starting end (15) to the terminating end (16); or the soldering tin layers (2) are arranged at intervals, each section of soldering tin layer is parallel to the top end of the pole piece, and the distances from the upper edge of the soldering tin layer (2) to the top end of the pole piece are the same.

10. The winding battery according to claim 1, characterized in that the pole piece comprises a starting end (15) and a terminating end (16), the pole tab (1) is a multi-pole tab, and the soldering tin layer (2) is continuously arranged from any one of the multi-pole tab between the starting end (15) and the terminating end (16) when the pole piece is in the unfolded state; or the multiple tabs are arranged at intervals of different numbers, the soldering tin layer (2) is parallel to the top end of the pole piece, and the distances from the upper edge of the soldering tin layer (2) to the top end of the pole piece are the same.