Clamping band for an electrical stack assembly

Abstract

A clamping band (1) for maintaining a compression of an electrical stack assembly (2), particularly fuel cell stack assembly, comprising at least an elongated band el- ement (4) having a first end and a second end (6), wherein the band element (4) is at least partially made from an electrically insulating material.

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 band element could be fixed to each of the end plates and / or wrapped around the stack.

[0006] However, there is a risk, particularly in case of taller stack assemblies, that mechanical instabilities of the stack assembly may become an issue that can lead to damages to the electric stack assembly.

[0007] It is therefore object of the present invention to provide a clamping band that reduces the risk of damaging the electric cell stack assembly.

[0008] This object is solved by the electric cell stack assembly according to claim 1 .

[0009] In the following a clamping band for maintaining a compression of an electrical stack assembly, particularly fuel cell stack assembly, is provided, which comprises at least an elongated band element having a first end and a second end. The electrical stack assembly may comprise an electric energy generating cell stack body with a plurality of unit cells stacked in a stacking direction. For example, each unit cell may be 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.

[0010] The first end and / or a second end of the band element may be directly or indirectly attached to at least a part of the stack assembly, for example at least one of the end plates. For example, the first and / or second end may be provided with an attaching element configured to be attached to at least one of the end plates. The attaching elements may be formed integrally with the band element and / or are attached to the band element in a permanent or detachable manner. Alternatively, the first and second of the elongated band element may be connected to each other.

[0011] To reduce the risk of damaging the electric cell stack assembly and avoiding any short circuits caused by a contact of the clamping band with the electrical stack, the band element is at least partially made from an electrically insulating material.

[0012] According to a preferred embodiment, the band element may be entirely made from an electrically insulating material, e.g from a plastic material. Most preferred a fiber reinforced plastic material such as fiber reinforced PEEK, PPS or PA may be used. These materials provide sufficient strength for maintaining the compression of the stack and simultaneously are electrically isolating.

[0013] According to a further preferred embodiment, the band element comprises a support structure. Preferably, the support structure is made from metal, e.g. sheet metal. Alternatively, the support structure may be made from a reinforced plastic material. The support structure further comprises a first layer of an electrically insulating material.

[0014] Thereby it is preferred that the first layer made from an electrically insulating material is arranged on the side of the support structure that faces the electrical stack assembly. For example, the support structure may be coated with the electrically insulating material, e.g. by dip coating or by powder coating and / or the electrically insulating material may be connected to the band element, e.g. by glue. It is further possible to use a shrinking tube e.g. made from plastic, e.g. rubber, which is pulled over the support structure and then heated until the plastic is securely attached to the support structure. The electrically isolating material can be any kind of electrically isolating material e.g. PEEK, PPS, PA or rubber.

[0015] By making the band element from the electrically insulating material and / or by providing a first layer made from an electrically insulating material on a support structure, a short circuit can be prevented in case that the cells of the stack assembly come in contact with the clamping band.

[0016] 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.

[0017] According to a further embodiment, the support structure comprises at least one further layer. This layer may be arranged between the support structure and the first layer, but can also be arranged otherwise.

[0018] In particular, the first and the at least one further layer may form a sandwich structure that is arranged between the support structure and the stack assembly.

[0019] Preferably, the at least one further layer is a dampening layer which is made from a material configured to dampen impacts that act on the electrical stack assembly. For example, the material may be a compressible material, in particular a reversibly compressible material such as a soft foam or a memory foam, e.g. rubber foam or polyurethane. This allows to support the cells of the stack assembly in case of impact such that the risk of damaging the stack assembly is further reduced.

[0020] According to a further embodiment, the at least one further layer is a stiffening layer configured to stiffen the band element as such. For example, the stiffening layer may be made from a rigid material such as hard plastics and / or rigid foam. Providing a stiffening layer may have the advantage of mitigating or even preventing the band element from bending.

[0021] Preferably, the stiffening layer is arranged between two dampening layers. This may allow to stabilize the clamping band, while at the same time reduce the risk that impacts may damage the cells of the stack assembly.

[0022] To further stabilize the stack assembly, the support structure may further comprise a reinforcement element. The reinforcement element may be configured to increase a rigidity of the support structure and thereby of the band element as such so that the band element is less prone to bending.

[0023] Preferably, the reinforcement element is at least one reinforcement rib extending from the support structure in a direction perpendicular to a longitudinal direction of the support structure and the band element, respectively. For example, the at least one reinforcement rib may be arranged such that it extends from an edge of the support structure and the band element, respectively. Alternatively or additionally, the at least one reinforcement rib may protrude from a side face and / or an edge of the support structure reps, the band element, perpendicular to the side face of the support structure resp. the band element.

[0024] For example, the support structure and the band element, respectively, may be II- shaped such that the support structure resp. the band element, is configured to receive at least partially the first layer and / or the at least one further layer. This allows both to increase a rigidity of the band element due to the legs of the II- shaped support structure that can function as reinforcement ribs and to confine the first and / or second layer.

[0025] Preferably, the at least one first layer and / or the at least one second layer protrudes over the legs of the U-shape. This allows to prevent the legs from contacting the stack assembly. 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.

[0026] 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.

[0027] The figures show:

[0028] Fig. 1 : a schematic side view of a part of a clamping band for maintaining a compression of an electrical stack assembly according to a first embodiment, Fig. 2: a schematic side view of a part of a clamping band for maintaining a compression of an electrical stack assembly according to a second embodiment, Fig. 3: a schematic side view of a part of a clamping band for maintaining a compression of an electrical stack assembly according to a third embodiment, Fig. 4: a perspective view of a part of a clamping band for maintaining a compression of an electrical stack assembly according to a fourth embodiment, Fig. 5: a perspective view of a part of a clamping band for maintaining a compression of an electrical stack assembly according to a fifth embodiment, and Fig. 6: a schematic top view of an electrical stack assembly with the clamping band of Fig. 5.

[0029] In the following same or similar functioning elements are indicated with the same reference numerals.

[0030] Fig. 1 shows a schematic side view of a clamping band 1 for maintaining a compression of an electrical stack assembly 2 according to a first embodiment. The clamping band 1 has an elongated band element 3 with a first end 6 (Fig. 4, 5) and a second end (not shown).

[0031] As can be seen from Fig. 1 , the longitudinal direction of the band element 4 is parallel to a stacking direction 7 of the electric cell stack assembly 2. The electric cell stack assembly 2 may be a fuel cell stack assembly. The electric cell stack assembly 2 comprises an electric energy generating cell stack body with a plurality of unit cells stacked in a stacking direction 7. For example, each unit cell may be a unit fuel cell comprising a bipolar plate 8 and a membrane electrode assembly 10. The stack assembly 2 may also include a first and second endplate sandwiching the electric energy generating cell stack body.

[0032] The band element 3 has a predetermined length, wherein the first end and / or a second end of the band element 3 may be directly or indirectly attached to at least a part of the stack assembly 2, for example one of the end plates. For example, the first and / or second end 6 may be provided with an attaching element 12 (Fig. 4, 5) configured to be attached to at least one of the end plates. Alternatively, the first and second of the elongated band element may be connected to each other.

[0033] In order to reduce the risk of damaging the electric cell stack assembly 2 or causing short circuits when the clamping band accidentally are contacting the electric stack, the band element 3 comprises a support structure 4, which is made from metal and a first layer 14 made from an electrically insulating material such as plastic, which is arranged on the side of the support structure 4 that faces the electric stack assembly 2. According to the illustrated embodiment, the band element 3 further comprise a second layer 16 arranged between the support structure 4 and the first layer 14. In particular, the first and second layer 14, 16 form a sandwich structure that is arranged between the support structure 4 and the stack assembly 2. In Fig. 1 , the second layer 16 is a rigid foam that allows to further stiffen the band element 4 such that a bending of the band element 4 can at least be mitigated or even prevented.

[0034] The first and second layer may be fixed to another and / or to the support structure 4. For example, the first layer 14 may be glued to the second layer 16, and the second layer 16 may be glued to the support structure 4.

[0035] Fig. 2 shows a schematic side view of a part of a clamping band 1 for maintaining a compression of an electrical stack assembly 2 according to a second embodiment. In Fig. 2, the first layer 14 is made from an electrically insulating compressible foam, which is configured to dampen impacts that act on the electrical stack assembly 2. In this way, any impact that act of the stack assembly 2 can be absorbed. This allows the elements of the stack assembly like the bipolar plates 8 and / or the membrane electrode assemblies 10 to compress the first layer 14, when contacting the first layer 14. The second layer 16 in Fig. 2 is a rigid foam that acts as a stiffening element which is configured to mitigate any bending of the band element 3.

[0036] Fig. 3 shows a schematic side view of a part of a clamping band 1 for maintaining a compression of an electrical stack assembly 2 according to a third embodiment. In contrast to Fig. 2, the clamping band 1 shown in Fig. 3 comprises a first layer 14 made from an electrically insulating rigid foam, that is configured to act as a stiffening means, while the second layer 16 is made from a compressible foam that acts as a dampening element which is configured to mitigate any impacts that act on stack assembly 2. Alternatively, it may also be possible to place a rigid layer between two compressible layers.

[0037] Fig. 4 shows a perspective view of a part of a clamping band 1 for maintaining a compression of an electrical stack assembly according to a fourth embodiment. The clamping band 1 of Fig. 4 comprise a reinforcement element 18 that is configured to increase a rigidity of the support structure 4 such that the band element 3 is less prone to bending.

[0038] For the sake of simplicity, in the illustrated view of Fig. 4 to 6, only one layer of material which is supported by the support structure 4 is seen and referenced by reference number 14. This can be the first layer 14, but also any kind of sandwiched layer structure.

[0039] As can be further seen from Fig. 4, the reinforcement element 18 is a rib that extends from a side edge 20 of the support structure 4 perpendicular to the longitudinal direction of the support structure 4 resp. the band element 3. For example, the at least one reinforcement rib 18 may be arranged such that it extends from an edge of the support structure 4. Fig. 5 and 6 show a perspective view of a clamping band 1 according to a fifth embodiment, wherein the support structure 4 is provided with two reinforcement elements 18 that are arrange on both side edges 20 of the support structure 4, The reinforcement elements 18 are bend in such a way that the support structure 4 has a U-shape when viewed from above, wherein the two reinforcement elements 18 form the legs of the U-shape.

[0040] As can be seen from Fig. 6, the U-shape is dimensioned such that the band element 4 is configured to receive the first layer 14 or the sandwiched layer structure. This allows both to increase a rigidity of the band element 3 due to the legs of the U-shaped support structure 4 that can function as reinforcement ribs and to confine the first and / or second layer.

[0041] To avoid that the legs of the U-shaped support structure 4 contact the stack assembly 2 and cause a short circuit, the first layer 14 or the sandwiched layer structure protrudes over the legs of the U-shaped support structure 4.

[0042] In summary, the described clamping band 1 has the advantage that is reduces the risks that the electrical stack assembly is damaged due to mechanical instabilities that may be caused due to a height of the stack assembly such as tilting and / or bending of the stack assembly which may lead to short circuits and / or damages to the stack assembly as parts of the stack may contact the clamping band itself and / or an housing which enclosures the stack.

[0043] Furthermore, by providing additional layers that are configured to dampen impacts acting of the stack assembly and / or stiffening the clamping band to increase to rigidity of the stack assembly, the risk that the stack assembly is damaged can be further reduced. Reference numerals

[0044] 1 clamping band

[0045] 2 electrical stack generating cell stack body

[0046] 3 band element

[0047] 4 support structure

[0048] 6 first end

[0049] 7 Stacking direction

[0050] 8 bipolar plate

[0051] 10 membrane electrode assembly

[0052] 12 attaching element

[0053] 14 first layer

[0054] 16 second layer

[0055] 18 reinforcement element

Claims

Clamping band for an electrical stack assemblyClaims:1 . Clamping band (1 ) for maintaining a compression of an electrical stack assembly (2), particularly fuel cell stack assembly, comprising at least an elongated band element (3) having a first end and a second end (6), characterized in that the band element (3) is at least partially made from an electrically insulating material.

2. Clamping band (1 ) according to claim 1 , wherein the band element (3) is made from a plastic material, particularly from a fiber reinforced plastic material.

3. Clamping band (1 ) according to claim 1 or 2, wherein the band element (3) comprises a support structure (4), which is made from metal or from a reinforced plastic material, and wherein at at least one side of the support structure (4) a first layer (14) made from an electrically insulating material is arranged.

4. Clamping band (1 ) according to claim 3, wherein the at least one first layer (14) is arranged on the side of the support structure (4) that faces the electrical stack assembly (2).

5. Clamping band (1 ) according to any one of the previous claims, wherein the band element (3) further comprises at least on further layer (16).

6. Clamping band (1 ) according to claim 5, wherein the second layer (16) is arranged between the support structure (4) and the at least one first layer (14).

7. Clamping band (1 ) according to claim 5 or 6, wherein at least one of the further layers (16) is a dampening layer configured to dampen impacts that act on the stack assembly (2).

8. Clamping band (1 ) according to any one of the claims 5 to 7, wherein at least one of the further layers (16) is a stiffening layer configured to stiffen the at least one clamping band (1 ).

9. Clamping band (1 ) according to claim 8, wherein the stiffening layer is arranged between two dampening layers.

10. Clamping band (1 ) according to any one of the previous claims, wherein the support structure (4) further comprises at least one reinforcement element (18).11 . Clamping band (1 ) according to claim 10, wherein the reinforcement element (18) is a reinforcement rib extending from the support structure (4) in a direction perpendicular to a longitudinal direction of the band element (3).

12. Clamping band (1 ) according to any one of the previous claims, wherein the support structure (4) is U-shaped such that the support structure (4) encompasses at least partially a side face of the at least one first layer (14) and / or of the at least one further layer (16).

13. Clamping band (1 ) according to claim 12, wherein the at least one first layer (14) and / or of the at least one further layer (16) protrudes over legs of the U- shape.