Clamping band for an electrical stack assembly

Abstract

A clamping band (1) for maintaining a compression of an electrical stack assembly, particularly fuel cell stack assembly, comprising at least an elongated band element (2) having a first end (4) and a second end, and at least one fastening element (6), wherein the at least one fastening element (6) includes at least one bolt portion (8) configured to be attachable to a part of the electrical stack assembly (2), wherein the fastening element (6) comprises at least one marker (14) that marks a position and / or an orientation of the fastening element (6).

Description

[0001] Clamping band for an electrical stack assembly

[0002] Description:

[0003] The present invention relates to an electric cell stack assembly.

[0004] Usually, an electric cell stack assembly, such as a fuel cell stack, comprises a stack body including a plurality of unit cells which are stack in a stacking direction. Each of the unit cells comprises at least two plates, so called flow field plates, which are placed on top of each other and have a flow field for the reactants at one side and a flow field for a cooling fluid on the other side. Thus, the flow fields of the adjacent plates form channels through which the respective fluids stream.

[0005] To avoid any fluid leaks and to achieve fluid tightness of the electric cell stack, the stack body is compressed in the stacking direction with the aid of a compression element. Usually, a stack body of the electrical stack assembly is sandwiched between two end plates. To maintain a compression of the electrical stack assembly, a clamping band could be fixed to a part of the electric cell stack and / or wrapped around the stack. The clamping band may comprise a band element having a determined length for defining and maintaining the pressure of the stack and a fastening element for attaching the clamping band to the stack. Thereby, the fastening element may be a separate element which can be permanently attached to the band element.

[0006] However, due to the tension that is necessary to maintain the compression on the stack, the band element and / or the fastening element are subjected to strain and / or stress such as shear forces. These forces can lead to deterioration and / or wearing of the connection between band element and fastening element and finally to a loss of compression and therefore fluid leaks. It is therefore object of the present invention to provide a clamping band having an improved service life and stability.

[0007] This object is solved by the clamping band according to claim 1.

[0008] In the following, a clamping band for maintaining a compression of an electrical stack assembly, particularly fuel cell stack assembly, is provided. The clamping band comprises at least an elongated band element having a first end and a second end, and at least one fastening element for fastening the band element (4) to the electric stack assembly, wherein the fastening element is a separate element, which has been permanently attached to the band element. For example, the fasting element may be welded, glued, and / or rivetted to the base element.

[0009] For ensuring that the attachment of the fastening element and the band element remains permanent, also over a long service life and high forces, it is necessary to ensure that a seam between the fastening element and the band element is not subjected to excess shear forces. For that it is suggested to provide the fastening element with at least one an alignment feature for defining an attachment orientation for the fastening element in relation to the band element so that that the fastening element is attached to the band element in a predefined position and / or at a predefined orientation.

[0010] The electric cell stack assembly, particularly fuel cell stack assembly, may comprises at least an electric energy generating cell stack body with a plurality of unit cells stacked in a stacking direction, wherein preferably each unit cell is a unit fuel cell comprising a bipolar plate and a membrane electrode assembly. The stack assembly may also include a first and second endplate sandwiching the electric energy generating cell stack body. For example, at least one of the end plates may have an opening in a side face configured to receive the at least the a portion of the fastening element. Preferably, the at least one fastening element is arranged at the first and / or second end of the band element. The fastening element may protrude perpendicular from the band element such that is insertable in an opening provided in a part of the stack assembly, such as a side face of an end plate. This has the advantage that an over-compression of the stack assembly can be avoided during the assembly process. More particularly, the stack is compressed during the assembly process at most to a height of the finished stack assembly such that the fastening element can be inserted into the corresponding opening. Thus, the risk of damaging parts of the stack body is reduced.

[0011] Preferably, the band element has a predetermined length. Preferably, the length is adapted to provide the desired pressure of the stack assembly under operation condition. This allows to determine the applied pressure. For example, the at least one compression element may be made of sheet metal.

[0012] As mentioned above, for providing a clamping band having an improved service life and stability, it is preferred to attach the fastening element to the band element in a predefined spatial orientation. The alignment feature for providing the predetermined spatial orientation is preferably at least one marker that marks a position and / or an orientation of the fastening element. The at least one marker may be a geometrical and / or optical feature of at least a part of the fastening element. For example, the at least one marker may be an optical feature that can be detected visually and / or with a camera device such as one or more lines, one or more dots, one or more symbols, which might be painted on or scratched into the fastening element. The marker can also be a groove, a notch, a protrusion. If the fastening element has a rounded surface area and / or shape, the at least one marker may be a flat area, and / or if the fastening element has a flat surface area, the at least one marker may be a rounded area.

[0013] According to a further preferred embodiment, the fasting element has a base portion and a bolt portion, wherein the base portion is attached to the band element and the bolt portion is attachable to the electric stack assembly. Preferably, the bolt portion may have a circular, rectangular, oval, triangular, or polygonal cross-section, and / or a block, conical, frustoconical, or pyramidal shape, and / or at least one chamfered edge. Furthermore, an opening formed in part of the stack assembly that is configured to receive the bolt portion may have a shape that is complementary to the bolt portion. This has the advantage that a position of the bolt portion can be defined within the opening. Furthermore, a contact area between the opening and the bolt portion can be increased which can lead to an increased friction between the opening and the bolt portion such that the position of the bolt portion in the opening is secured.

[0014] Furthermore, the fastening element may comprise at least one position securing element configured to secure a position of the fastening element in relation to the stack. This reduces the risk that the fastening element disengages from the stack assembly due to vibrations and / or other external forces. Preferably, the fastening element and / or bolt portion may include a through hole, wherein the through hole is adapted to accommodate and / or interact with the position securing element. This allows to insert the position securing element through the through hole.

[0015] According to a further embodiment, the at least one fastening element further includes a base portion and a bolt portion as mentioned above, wherein the at least one marker is arranged on the bolt portion and / or the base portion. Since the marker indicates the predefined position and / or orientation of the fastening element it may also indicate a preferred installation situation of the clamping band itself. This allows to ensure that the clamping band can be installed in such way that strain and / or shear forces acting on the fastening element and / or the band element are reduced.

[0016] Moreover, since the base portion is permanently fixed to the band element a height of the stack assembly can be maintained over a life span of the stack assembly. For example, the base portion may be welded, glued, and / or rivetted to the band element. According to a preferred embodiment, the at least the band element and the base portion are made from metal, and the base portion is welded to the band element. For example, the base portion may be welded to the band element using resistance welding. Welding allows for a robust connection between the band element and the base portion. However, weld seams are prone to detachment in case of excess shear forces. Therefore, the spatial orientation of fastening element in relation to the band element is highly important, which can be ensured by the alignment feature.

[0017] According to a further embodiment, the base portion comprises at least one weld protrusion for welding the base portion to the band element, wherein the at least one marker is configured to mark a position of the at least one weld protrusion. The at least one weld protrusion may have an arc-shape. Weld protrusions may be used to automatically weld the base portion to the band element. Also, the at least one weld protrusion allows to ensure the use of consistent and / or reliable welding parameters. This has the advantage that a shear strength of the weld may be more consistent.

[0018] Furthermore, by using the at least one marker to mark the at least one weld protrusion it is possible to ensure that the at least one weld protrusion is positioned in a predefined position even if the welding is performed automatically. Thus, a consistency of the alignment of the weld protrusion with respect to the band element, particularly a longitudinal direction of the band element, can be improved.

[0019] Preferably, the at least one weld protrusion is arranged such that it is at least partially aligned with a load direction of the clamping band. This may improve a shear strength of the weld.

[0020] Preferably the base portion comprises two or more distinct weld protrusions. For example, the base portion may have four weld protrusions. Distinct weld protrusions may have the advantage of focusing the welding current, which may allow for a more efficient welding process.

[0021] According to a further embodiment, the plurality of weld protrusion is arranged in such a way that in areas that experience a higher load more weld protrusion are provided than in areas that experience less load.

[0022] Further preferred embodiments are defined in the dependent claims as well as in the description and the figures. Thereby, elements described or shown in combination with other elements may be present alone or in combination with other elements without departing from the scope of protection.

[0023] In the following, preferred embodiments of the invention are described in relation to the drawings, wherein the drawings are exemplarily only, and are not intended to limit the scope of protection. The scope of protection is defined by the accompanied claims, only.

[0024] The figures show:

[0025] Fig. 1 : a perspective view of a clamping band according to an embodiment, and Fig. 2: a top view of the clamping band of Fig. 1 .

[0026] In the following same or similar functioning elements are indicated with the same reference numerals.

[0027] Fig. 1 and 2 show a clamping band 1 for maintaining a compression of an electrical stack assembly, particularly fuel cell stack assembly. The clamping band 1 comprises at least an elongated band element 2 having a first end 4 and a second end (not shown), and an fastening element 6. The fastening element 6 includes a bolt portion 8, configured to be attachable to a part of the electrical stack assembly, and a base potion 10 with which the fastening element may be permanently attached to the band element 6. The fastening element 6 is arranged at the first end 4 of the band element 2 such that the bolt portion 8 of the fastening element 6 protrudes perpendicular from the band element 2. The bolt potion 8 is insertable in an opening provided in a part of the stack assembly, such as a side face of an end plate.

[0028] In the embodiment shown in Fig. 1, the bolt portion 8 has essentially a cylindrical shape, and the base portion 10 has a circular shape. However, the bolt portion 8 and / or the base portion may have any other possible shape and / or cross section. Furthermore, the fastening element 6 includes a through hole 12 which is adapted to accommodate and / or interact with a position securing element (not shown) configured to secure a position of the fastening element 6 in relation to the electric stack. For example, the position securing element may be a screw.

[0029] To fix the base portion 10 to the band element 2, the base portion 10 comprises a plurality of weld protrusion 16 at the side of the base portion 10 that faces the band element 2. The clamping band 1 of the shown embodiment has four weld protrusions. Alternatively, the clamping band 1 may have two, three, five, six, or even more weld protrusions. The weld protrusions 16 may have an arc shape and are arranged distinct from another around a circumference of the base portion 10. Preferably, the shape of the weld protrusion is similar to a circumference shape of the base portion. Preferably, each weld protrusion 16 may have the same length. However, the length of the weld protrusion 16 can also differ from another.

[0030] In the shown embodiment, the weld protrusion 16 are equally distanced from each other. However, it may also be possible to have more weld protrusions e.g. in areas that experience a higher load than in areas that experience less load. For the shown clamping band 1 , the load is usually applied along the longitudinal direction of the band element 2 between the first and second end. As can be seen in Fig. 2, three of the four weld protrusion 16, namely 16-1 , 16-2, 16-3 are arranged such that they lie directly in the line of a load acting in the longitudinal direction of the band element 2 (see arrow). Preferably, the fastening element 6 is automatically welded to the band element 2. Thus, in order to ensure that the weld protrusions 16 are arranged such that they lie directly in the line of a load acting in the longitudinal direction of the band element 2, it is necessary to provide a marker 14 which is configured to mark a position and / or an orientation of the fastening element 6 and thereby of the weld protrusion 16, in relation to the band element 2.

[0031] In the shown embodiment, the marker 14 is a flat area located at the curved surface of the cylindrical bolt portion 8. However, the marker can be any other geometrical and / or optical feature that can be detected visually and / or with a camera device. For example, the marker may be one or more painted or scratched lines, dots, or symbols, and / or a groove, a notch, an / or a protrusion. In addition or alternatively, the marker 14 may arranged on the base portion 10.

[0032] In summary, the described clamping band 1 has an improved service life and stability. More particularly, by using the at least one marker 14 to mark a position and / orientation of the fastening element 6 and / or a weld protrusion 16 with which the fastening element 6 is connected to the band element 2 of the clamping band 1 , it is possible to ensure that the at least one weld protrusion 16 is positioned in a predefined position even if the welding is performed automatically. Thus, a consistency of the alignment of the weld protrusion 16 with respect to the band element 2, particularly a longitudinal direction of the band element 2, can be improved.

[0033] Reference numerals

[0034] 1 clamping band

[0035] 2 band element

[0036] 4 first end

[0037] 6 fastening element

[0038] 8 bolt portion

[0039] 10 base portion

[0040] 12 through hole

[0041] 14 marker

[0042] 16 weld protrusion

Claims

Clamping band for an electrical stack assemblyClaims:

1. Clamping band (1 ) for maintaining a compression of an electrical stack assembly, particularly fuel cell stack assembly, comprising at least an elongated band element (2) having a first end (4) and a second end, and at least one fastening element (6) for fixing the band element (4) to the electric stack assembly, wherein the fastening element is a separate element, which has been permanently attached to the band element (2), characterized in that the fastening element (6) has an alignment feature (14) for defining an attachment orientation for the fastening element (6) in relation to the band element (2) so that that the fastening element (6) is attached to the band element (2) in a predefined position and / or at a predefined orientation.

2. Clamping band (1 ) according to claim 1 , wherein the alignment feature is a marker (14) that marks a position and / or an orientation of the fastening element (6) in relation to the band element (2).

3. Clamping band (1) according to claim 1 or 2, wherein the at least one marker (14) is a geometrical and / or optical feature of at least a part of the fastening element (6).

4. Clamping band (1 ) according to any one of the preceding claims, wherein the at least one fastening element (6) further includes a base portion (10) and a bolt portion (8), wherein the base portion (10) is configured to be attached to the band element (2) and the bolt portion is configured to be attached to the electric stack assembly, wherein the at least one marker (14) is arranged on the bolt portion (8) and / or the base portion (10).

5. Clamping band (1 ) according to claim 4, wherein at least the band element (2) and the base portion (10) are made from metal, and wherein the base portion (10) is welded to the band element (2).

6. Clamping band (1) according to claim 5, wherein the base portion (10) comprises at least one weld protrusion (16) for welding the base portion (10) to the band element (2), wherein the at least one marker (14) is configured to mark a position of the at least one weld protrusion (16).

7. Clamping band (1) according to claim 6, wherein the at least one weld protrusion (16) is arranged such that it is at least partially aligned with a load direction of the clamping band (1).

8. Clamping band (1) according to claim 6 or 7, wherein the base portion (10) comprises a plurality of distinct weld protrusions (16).

9. Clamping band according to claim 8, wherein the plurality of weld protrusion is arranged in such a way that in areas that experience a higher load more weld protrusions are provided than in areas that experience less load.