Description:TECHNICAL FIELD
[001] The embodiments herein generally relate to a cylindrical battery cell and more particularly to a jelly roll with a flexible reinforcement assembly for reinforcing the jelly roll of the cylindrical battery cell.
BACKGROUND
[002] Generally, a cylindrical battery cell includes a cylindrical metal can, usually made of steel or aluminum, which serves as both the container and one of the electrodes (typically the negative terminal) of the cylindrical battery cell. An electrode assembly in the form of a jelly-roll configuration is formed by tightly winding the positive and negative electrodes (anode and cathode) with a separator in between, is placed inside the cylindrical metal can. An electrolyte is introduced in the jelly roll, which enables the movement of ions between the electrodes during charge and discharge cycles. The separator which is made from a microporous polymer keeps the two electrodes from touching while allowing the flow of ions. The cylindrical battery cell further includes current collectors which are connected to the electrodes to ensure efficient electron flow in and out of the cylindrical battery cell.
[003] Generally, in cylindrical battery cells, over a period of use, mechanical or thermal stress may affect a core of the electrode assembly, particularly the innermost layers of the jelly roll. The stress may arise during various stages of the battery’s life cycle, including manufacturing, charging, discharging, or from external factors like temperature fluctuations. The inner layers of the jelly roll tend to experience greater pressure compared to the outer layers due to the winding tension during assembly and the expansion of materials inside the cell during operation. Over time, this pressure can deform the separator, compromise the insulation between the electrodes, or cause the electrodes to come into contact. This internal short circuit can result in localized heating, degradation of cell materials, and in extreme cases, thermal runaway, where the battery heats uncontrollably, leading to possible rupture or even explosion. The deformation of the jelly roll at the core is further intensified under high power operations, rapid charging, or discharging, where the thermal stress is significantly higher, further straining the inner components.
[004] Further, the deformation of the jelly roll at the core is also called core collapse which compromises the safety, performance, and longevity of the battery. One of the primary problems is thermal instability, where increased internal resistance due to the impingement of the core causes localized heating, which can initiate further thermal breakdown of the electrolyte. This not only reduces the battery's efficiency but also poses significant safety risks. Another issue is capacity fade, where the battery’s ability to hold a charge diminishes over time as the impingement of the core leads to irreversible chemical changes in the electrodes. Mechanical deformation of the internal layers can also cause premature aging of the cell, increasing the likelihood of electrical shorts and reducing the overall lifespan of the battery. In high-energy applications like electric vehicles or grid storage systems, core impingement can lead to costly failures, necessitating more frequent battery replacements or complex battery management systems (BMS) to monitor and mitigate such risks.
[005] Conventional solutions for mitigating core impingement includes modifying the winding tension during the jelly roll assembly to reduce the mechanical stress on the inner layers. While this can alleviate the issue to some extent, it often results in a trade-off between energy density and mechanical stability. Another solution is the use of advanced separators with higher thermal and mechanical durability, which can withstand the internal pressures and prevent shorts even under severe conditions. However, these separators tend to be more expensive and may still degrade over time, particularly in high-temperature environments. Some cells use pressure-relief mechanisms, such as vents or tabs that release excess pressure before it can cause internal damage. While this is effective in preventing catastrophic failure, these pressure-relief mechanisms are ineffective in mitigating core impingement and may lead to reduced energy efficiency or increased complexity in battery design.
[006] Therefore, there exists a need for a reinforced battery cell jelly roll which obviates the aforementioned drawbacks.
OBJECTS
[007] The principal object of embodiments herein is to provide a jelly roll with a flexible reinforcement assembly for reinforcing the jelly roll of a cylindrical battery cell.
[008] Another object of embodiments herein is to prevent deformation of the jelly roll in a direction towards a core of the jelly roll.
[009] Another object of embodiments herein is to provide a self-adjustable reinforcement assembly for the jelly roll which accommodates a change in size of the core of the jelly roll in accordance with expansion and contraction of the jelly roll during charging and discharging cycles of the cylindrical battery cell respectively.
[0010] Another object of embodiments herein is to easily insert the reinforcement assembly into the core of the jelly roll without causing any damage to separator of the jelly roll.
[0011] Another object of embodiments herein is to provide the jelly roll with the flexible reinforcement assembly having high stiffness for reinforcing the core of the jelly roll.
[0012] Another object of embodiments herein is to enhance the performance and lifetime of the jelly roll.
[0013] Another object of embodiments herein is to provide the jelly roll which is durable and is easy to manufacture.
[0014] Another object of embodiments herein is to increase the safety of the jelly roll.
[0015] These and other objects of embodiments herein will be better appreciated and understood when considered in conjunction with following description and accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF DRAWINGS
[0016] The embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0017] Fig. 1 depicts an exploded view of a jelly roll with a reinforcement assembly for a cylindrical battery cell, according to embodiments as disclosed herein;
[0018] Fig. 2 depicts a sectional view of the jelly roll, according to embodiments as disclosed herein;
[0019] Fig. 3 depicts a perspective view of the reinforcement assembly, according to embodiments as disclosed herein;
[0020] Fig. 4 depicts a top view of the reinforcement assembly, according to embodiments as disclosed herein; and
[0021] Fig. 5 depicts a flowchart indicating steps of a method of inserting the reinforcement assembly into a core of the jelly roll of the cylindrical battery cell, according to embodiments as disclosed herein.

DETAILED DESCRIPTION
[0022] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0023] The embodiments herein achieve a jelly roll with a reinforcement assembly for reinforcing the jelly roll of a cylindrical battery cell thereby preventing deformation of the jelly roll in a direction towards its core. Further embodiments herein achieve a self-adjustable reinforcement assembly for the jelly roll which accommodates a change in size of the core of the jelly roll in accordance with expansion and contraction of the jelly roll during charging and discharging cycles of the cylindrical battery cell respectively. Referring now to Figs. 1 to 5, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0024] Fig. 1 depicts an exploded view of a jelly roll (10) with a reinforcement assembly (100) for a cylindrical battery cell, according to embodiments as disclosed herein. Fig. 2 depicts sectional view of the jelly roll (10), according to embodiments as disclosed herein. In an embodiment, the jelly roll (10) includes a reinforcement assembly (100), at least one positive electrode (200) (cathode), at least one negative electrode (300) (anode) and at least one separator (400). For the purpose of this description and ease of understanding, the jelly roll (10) is explained herein with below reference to be provided in the cylindrical battery cell. The separator (400) is disposed between the positive electrode (200) and the negative electrode (300). The positive electrode (200), the negative electrode (300) and the separator (400) are stacked upon each other and wounded to form a core (10C) extending along an axial direction of the jelly roll (10).
[0025] Figs. 3 and 4 illustrates the reinforcement assembly (100) of the jelly roll (10), according to embodiments as disclosed herein. In an embodiment, the reinforcement assembly (100) is adapted to reinforce the jelly roll (10) thereby preventing deformation of the jelly roll (10) in the direction towards its core (10C). In an embodiment, the reinforcement assembly (100) includes a first flexible reinforcement member (102) and a second flexible reinforcement member (104). In an embodiment, the second flexible reinforcement member (104) is configured to be temporarily deformed to reduce an outer diameter of the first flexible reinforcement member (102) thereby facilitating insertion of the first and second flexible reinforcement members (102, 104) into the core (10C) of the jelly roll (10). Further, in an embodiment, the reinforcement assembly (100) is configured to self-adjust with respect to the core (10C) of the jelly roll (10) to accommodate a change in a size of the core (10C) of the jelly roll (10) in accordance with expansion and contraction of the jelly roll (10) during charging and discharging cycles of the cylindrical battery cell respectively. The reinforcement assembly (100) is adapted to be disposed inside the core (10C) of the battery cell jelly roll (10). The second flexible reinforcement member (104) is adapted to be co-axially positioned inside the first reinforcement member (102) to which the second flexible reinforcement member (104) is connected thereto. A space is provided between the first and second flexible reinforcement members (102, 104). The first and second flexible reinforcement members (102, 104) are adapted to be disposed inside the core (10C) of the jelly roll (10). The first and second flexible reinforcement members (102, 104) are adapted to extend along the axial direction between a first end (10F) and a second end (10S) (as shown in fig. 2) of the jelly roll (10). The first and second flexible reinforcement members (102, 104) are adapted to reinforce the jelly roll (10) thereby restricting deformation of the battery cell jelly roll (10) in the direction towards its core (10C).
[0026] In an embodiment, the first flexible reinforcement member (102) includes a hollow body (102A) and a slit (102B) (as shown in fig. 4) extending along a lengthwise direction of the hollow body (102A) at its corresponding side. Further, in an embodiment, the second flexible reinforcement member (104) includes a hollow body (104A), a reinforcing protrusion (104B), a slit (104C), a first connecting arm (104D) and a second connecting arm (104E) (as shown in fig. 4). The reinforcing protrusion (104B) of the first flexible reinforcement member (102) is adapted to extend outward from the hollow body (104A) in a direction towards the first flexible reinforcement member (102) along a lengthwise direction of the hollow body (104A) at its first side. The reinforcing protrusion (104B) of the second flexible reinforcement member (104) is adapted to be received by the slit (102B) of the first flexible reinforcement member (102) thereby reinforcing the jelly roll (10) in vicinity of the slit (102B). The slit (104C) of the second flexible reinforcement member (104) is adapted to extend along a lengthwise direction of the hollow body (104A) at its second side. The slit (104C) of the second flexible reinforcement member (104) is defined between the first and second connecting arms (104D, 104E). The first connecting arm (104D) of the second flexible reinforcement member (104) is adapted to extend outward from the hollow body (104A) in a direction towards the first reinforcement member (102) along a lengthwise direction of the hollow body (104A) at its second side. The second connecting arm (104E) of the second flexible reinforcement member (104) is adapted to extend outward from the hollow body (104A) in a direction towards the first reinforcement member (102) along the lengthwise direction of the hollow body (104A) at its second side. The second connecting arm (104E) is parallel and spaced apart from the first connecting arm (104D). The first and second connecting arms (104D, 104E) are adapted to connect the second flexible reinforcement member (104) with the first flexible reinforcement member (102). Each of the first and second connecting arms (104D, 104E) is tapered in a direction towards the inner surface of the first flexible reinforcement member (102).
[0027] Further, in an embodiment, the first flexible reinforcement member (102) includes a pair of curved arms (102C) (as shown in fig. 4) extending from the hollow body (102A) in a direction towards the reinforcing protrusion (104B) and the hollow body (104A) of the second flexible reinforcement member (104). A clearance is defined between the curved arms (102C) and the hollow body (104A) and the reinforcing protrusion (104B) of the second flexible reinforcing member (104). The slit (102B) of the first flexible reinforcement member (102) is defined between the curved arms (102C). The curved arms (102C) of the first flexible reinforcement member (102) are adapted to push the second flexible reinforcement member (104) in a direction towards a central axis of the reinforcement assembly (100) to reduce the outer diameter of the first flexible reinforcement member (102) thereby compressing the reinforcement assembly (100) to accommodate contraction of the core (10C) of the jelly roll (10) when a pressure is acting on the hollow body (102A) of the first reinforcement member (102) during contraction of the jelly roll (10). Further, the reinforcement assembly (100) is configured to move outwards with respect to the core (10C) for accommodating expansion of the core (10C) of the jelly roll (10) during expansion of the jelly roll (10).
[0028] Furthermore, in an embodiment, each of the first and second flexible reinforcements members (102, 104) include a plurality of slots (102AS, 104AS) (as shown in fig. 3) adapted to allow electrolyte flow therethrough to facilitate uniform distribution of electrolyte to the core of the jelly roll (10) during an electrolyte filling process. The slots (102AS, 104AS) are provided on the hollow body (102A, 104A) of the flexible reinforcement member (102, 104). Each of the flexible reinforcement member (102, 104) is made of non-metallic material selected from one of a first group consisting of polypropylene, polyethylene, polyethylene terephthalate and polyimide, and a second group consisting of low density polyethylene and polypropylene.
[0029] For the purpose of this description and ease of understanding, the jelly roll (10) and the sizes of the components of the jelly roll (10) is considered herein with respect to a large format cylindrical battery cell such as 4680 battery. However, it is also within the scope of the invention to consider the jelly roll (10) to be provided in any other sizes and configurations of the cylindrical battery cell. A length of each of the first and second flexible reinforcement member (102, 104) is in the range of 70 mm to 80 mm. An outer diameter of the first flexible reinforcement member (102) is in the range of 5 mm to 7 mm. An inner diameter of the first flexible reinforcement member (102) is in the range of 4.5 mm to 6.5 mm. An outer diameter of the second flexible reinforcement member (104) is in the range of 3.5 mm to 5.5 mm. An inner diameter of the second flexible reinforcement member (104) is in the range of 3 mm to 4 mm. A thickness of the each of the first and second flexible reinforcement member (102A, 102B) is in the range of 0.3 mm to 0.7 mm. A distance between an inner diameter of the second flexible reinforcement member (104) and an outer surface of the reinforcing protrusion (104B) is 0.95 mm. A thickness of the each of the first and second connecting arms (104D, 104E) is 0.15 mm.
[0030] Fig. 5 depicts a flowchart indicating steps of a method (20) of inserting the reinforcement assembly (100) into the core (10C) of the jelly roll (10) of the cylindrical battery cell, according to embodiments as disclosed herein. At step (22), the method (20) includes providing the reinforcement assembly (100) with the first flexible reinforcement member (102) and the second flexible reinforcement member (104) co-axially positioned inside the first flexible reinforcement member (102) to which the second flexible reinforcement member (104) is connected thereto. At step (24), the method (20) includes temporarily deforming the second flexible reinforcement member (104) for reducing an outer diameter of the first flexible reinforcement member (102). At step (26), the method (20) includes inserting the first and second flexible reinforcement member (102, 104) inside the core (10C) of the jelly roll (10) upon reducing the outer diameter of the first flexible reinforcement member (102).
[0031] In an embodiment, the method step (24) includes pushing the reinforcing protrusion (104B) of the second flexible reinforcement member (104) in a direction towards a central axis of the reinforcement assembly (100) thereby moving the reinforcing protrusion (104B) of the second flexible reinforcement member (104) away from the slit (102B) defined on corresponding side of the first flexible reinforcement member (102) for reducing the outer diameter of the first flexible reinforcement member (102).
[0032] Further, in another embodiment, the method step (26) includes pushing, by rods (not shown), the first and second connecting arms (104C) of the second flexible reinforcement member (104) to move corresponding ends of the first and second connecting arms (104C) of the second flexible reinforcement member (104) in a direction towards each other thereby moving the reinforcing protrusion (104B) of the second flexible reinforcement member (104) away from the slit (102B) defined on corresponding side of the first flexible reinforcement member (102) reducing the outer diameter of the first flexible reinforcement member (102).
[0033] The technical advantages of the battery cell jelly roll (10) are as follows. The jelly roll (10) with the reinforcement assembly (100) prevents deformation of the jelly roll (10) in a direction towards the core (10C) of the jelly roll (10). The self-adjustable reinforcement assembly (100) is used accommodate a change in size of the core (10C) of the jelly roll (10) in accordance with expansion and contraction of the jelly roll (10) during charging and discharging cycles of the cylindrical battery cell respectively. The flexible reinforcement assembly (100) is easy to manufacture and is easy to insert inside the core (10C) of the jelly roll (10) without causing any damage to separator of the jelly roll (10). The reinforcement assembly (100) is flexible and at the same time, the reinforcement assembly (100) has high stiffness for reinforcing the core (10C) of the jelly roll (10). The reinforcement assembly (100) enhances the performance and lifetime of the jelly roll (10) as well as increases the safety of the jelly roll (10).
[0034] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the spirit and scope of the embodiments as described herein.
, Claims:We claim:
1. A jelly roll (10) for a cylindrical battery cell, the jelly roll (100) comprising:
at least one positive electrode (200);
at least one negative electrode (300);
at least one separator (400) disposed between the positive electrode (200) and the negative electrode (300), wherein the positive electrode (200), the negative electrode (300) and the separator (400) are stacked upon each other and wounded to form a core (10C) extending along an axial direction of the jelly roll (10); and
a reinforcement assembly (100) having:
a first flexible reinforcement member (102); and
a second flexible reinforcement member (104) adapted to be co-axially positioned inside the first reinforcement member (102) to which the second flexible reinforcement member (104) is connected thereto,
wherein
the first and second flexible reinforcement members (102, 104) are adapted to be disposed inside the core (10C) of the jelly roll (10); and
the first and second flexible reinforcement members (102, 104) are adapted to reinforce the jelly roll (10).
2. The jelly roll (10) as claimed in claim 1, wherein the first and second flexible reinforcement members (102, 104) are adapted to extend along the axial direction between a first end (10F) and a second end (10S) of the jelly roll (10);
a space is provided between the first and second flexible reinforcement members (102, 104); and
the reinforcement assembly (100) is configured to self-adjust with respect to the core (10C) of the jelly roll (10) to accommodate a change in a size of the core (10C) of the jelly roll (10) in accordance with expansion and contraction of the jelly roll (10) during charging and discharging cycles of the cylindrical battery cell respectively.

3. The jelly roll (10) as claimed in claim 2, wherein the second flexible reinforcement member (104) is configured to be temporarily deformed to reduce an outer diameter of the first flexible reinforcement member (102) thereby facilitating insertion of the first and second flexible reinforcement members (102, 104) into the core (10C) of the jelly roll (10).
4. The jelly roll (10) as claimed in claim 1, wherein the first flexible reinforcement member (102) includes:
a hollow body (102A); and
a slit (102B) extending along a lengthwise direction of the hollow body (102A) at its corresponding side,
wherein
the second flexible reinforcement member (104) includes:
a hollow body (104A);
a reinforcing protrusion (104B) extending outward from the hollow body (104A) in a direction towards the first flexible reinforcement member (102) along a lengthwise direction of the hollow body (104A) at its first side, wherein the reinforcing protrusion (104B) is adapted to be received by the slit (102B) of the first flexible reinforcement member (102);
a slit (104C) extending along a lengthwise direction of the hollow body (104A) at its second side;
a first connecting arm (104D) extending outward from the hollow body (104A) in a direction towards the first reinforcement member (102) along a lengthwise direction of the hollow body (104A) at its second side; and
a second connecting arm (104E) extending outward from the hollow body (104A) in a direction towards the first reinforcement member (102) along the lengthwise direction of the hollow body (104A) at its second side.
5. The jelly roll (10) as claimed in claim 4, wherein the second connecting arm (104E) is parallel and spaced apart from the first connecting arm (104D);
the first and second connecting arms (104D, 104E) are adapted to connect the second flexible reinforcement member (104) with the first flexible reinforcement member (102);
the slit (104C) is defined between the first and second connecting arms (104D, 104E);
a distance between an inner diameter of the second flexible reinforcement member (104) and an outer surface of the reinforcing protrusion (104B) is 0.95 mm;
each of the first and second connecting arms (104D, 104E) is tapered in a direction towards the inner surface of the first flexible reinforcement member (102); and
a thickness of the each of the first and second connecting arms (104D, 104E) is 0.15 mm.
6. The jelly roll (10) as claimed in claim 5, wherein the first flexible reinforcement member (102) includes:
a pair of curved arms (102C) extending from the hollow body (102A) in a direction towards the reinforcing protrusion (104B) and the hollow body (104A) of the second flexible reinforcement member (104),
wherein
a clearance is defined between the curved arms (102C) and the hollow body (104A) and the reinforcing protrusion (104B) of the second flexible reinforcing member (104); and
the slit (102B) of the first flexible reinforcement member (102) is defined between the curved arms (102C).
7. The jelly roll (10) as claimed in claim 6, wherein the curved arms (102C) of the first flexible reinforcement member (102) are adapted to push the second flexible reinforcement member (104) in a direction towards a central axis of the reinforcement assembly (100) to reduce the outer diameter of the first flexible reinforcement member (102) thereby compressing the reinforcement assembly (100) to accommodate contraction of the core (10C) of the jelly roll (10) when a pressure is acting on the hollow body (102A) of the first reinforcement member (102) during contraction of the jelly roll (10); and
the reinforcement assembly (100) is configured to move outwards with respect to the core (10C) for accommodating expansion of the core (10C) of the jelly roll (10) during expansion of the jelly roll (10).

8. The jelly roll (10) as claimed in claim 4, wherein each of the first and second flexible reinforcements members (102, 104) include a plurality of slots (102AS, 104AS) adapted to allow electrolyte flow therethrough to facilitate uniform distribution of electrolyte to the core of the jelly roll (10) during electrolyte filling process;
the first and second flexible reinforcement members (102, 104) are adapted to be restrict deformation of the battery cell jelly roll (10) in a direction towards its core (10C); and
the slots (102AS, 104AS) are provided on the hollow body (102A, 104A) of the flexible reinforcement member (102, 104).
9. The jelly roll (10) as claimed in claim 1, wherein each of the flexible reinforcement member (102, 104) is made of non-metallic material selected from one of a first group consisting of polypropylene, polyethylene, polyethylene terephthalate and polyimide, and a second group consisting of low density polyethylene and polypropylene;
a length of each of the first and second flexible reinforcement member (102, 104) is in the range of 70 mm to 80 mm;
an outer diameter of the first flexible reinforcement member (102) is in the range of 5 mm to 7 mm;
an inner diameter of the first flexible reinforcement member (102) is in the range of 4.5 mm to 6.5 mm;
an outer diameter of the second flexible reinforcement member (104) is in the range of 3.5 mm to 5.5 mm;
an inner diameter of the second flexible reinforcement member (104) is in the range of 3 mm to 4 mm; and
a thickness of the each of the first and second flexible reinforcement member (102A, 102B) is in the range of 0.3 mm to 0.7 mm.

10. A method (20) of inserting a reinforcement assembly (100) into a core (10C) of a jelly roll (10) of a cylindrical battery cell, the method (20) comprising:
providing the reinforcement assembly (100) with a first flexible reinforcement member (102) and a second flexible reinforcement member (104) co-axially positioned inside the first flexible reinforcement member (102) to which the second flexible reinforcement member (104) is connected thereto;
temporarily deforming the second flexible reinforcement member (104) for reducing an outer diameter of the first flexible reinforcement member (102); and
inserting the first and second flexible reinforcement member (102, 104) inside the core (10C) of the jelly roll (10) upon reducing the outer diameter of the first flexible reinforcement member (102).

11. The method (20) as claimed in claim 10, wherein said temporarily deforming the second flexible reinforcement member (104) for reducing the outer diameter of the first flexible reinforcement member (102) includes:
pushing a reinforcing protrusion (104B) of the second flexible reinforcement member (104) in a direction towards a central axis of the reinforcement assembly (100) thereby moving the reinforcing protrusion (104B) of the second flexible reinforcement member (104) away from a slit (102B) defined on corresponding side of the first flexible reinforcement member (102) for reducing the outer diameter of the first flexible reinforcement member (102).

12. The method (20) as claimed in claim 10, wherein said temporarily deforming the second flexible reinforcement member (104) for reducing the outer diameter of the first flexible reinforcement member (102) includes:
pushing a first and second connecting arms (104C) of the second flexible reinforcement member (104) to move corresponding ends of the first and second connecting arms (104C) of the second flexible reinforcement member (104) in a direction towards each other thereby moving the reinforcing protrusion (104B) of the second flexible reinforcement member (104) away from a slit (102B) defined on corresponding side of the first flexible reinforcement member (102) reducing the outer diameter of the first flexible reinforcement member (102).