Plate processing

A method of processing a linked series of metallic plates, in which each plate (9) is connected to an adjacent plate along adjoining edges (8), the method comprising: providing the series of plates as a first fan-folded stack of plates (1); drawing the plates in sequence from the stack; applying a surface treatment to one or more of the plates; and stacking the plates in reverse order to form a second fan-folded stack of plates (5).

RELATED APPLICATION

This application claims the full Paris Convention Priority from, and is a U.S. National Stage entry of PCT/GB2010/002052 filed Nov. 9, 2010; which is based upon GB 0920100.5, filed Nov. 17, 2009, the contents of which are incorporated by reference, each as if fully set forth herein in its entirety.

FIELD

The invention relates to processing metallic plates, for example, for use in manufacturing fuel cell electrode plates.

BACKGROUND

Electrode or separator plates for fuel cells, i.e. in the form of anode or cathode plates, need to meet stringent requirements to avoid or remove any contamination, and typically require a series of different processing steps to be applied before the plates can be assembled into a fuel cell stack. Various types of coatings and other surface treatments may be required, which may need to be carried out in an enclosed chamber, for example in a vapour or ion deposition process. To prevent the risk of non-adherence of coatings, the surfaces of the plates to be coated must first be free of organic contaminants such as grease or oil. The preceding stamping operations used for applying surface features to the plates cannot however be generally assumed to be clean processes, which results in a significant risk of cross-contamination. The raw material, which may be in the form of a sheet metal roll, also cannot be assumed to be clean. Given that volume production of fuel cell parts requires a large number of such plates to be handled in rapid succession, a solution that enables continuous feeding of metallic plates through a batch type process is ideally required.

Current known processes for applying surface treatments to electrode plates include handling of individual plates and applying various surface treatments to the plates individually, as for example disclosed in US 2005/0241732, in which pressed plates are treated with a passivating solution followed by rinsing and drying steps.

A problem with existing processes is that automated handling of individual plates involves complex machinery.

A further problem, in particular in relation to fuel cell electrode or separator plates, is that such plates are thin and may be prone to damage by being handled individually.

A further problem is, on a mass-production scale where hundreds of thousands of plates are to be processed, how to handle batches of plates between processes, some of which may require a break in a production line.

A further problem is how to minimise on use of resources such as solutions for surface treatment and to reduce energy usage for applying other treatments such as surface deposited layers.

A further problem is how to minimise the space required for surface treatment apparatus configured to handle many thousands of plates in rapid succession.

It is an object of the invention to address one or more of the above mentioned problems.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided a method of processing a linked series of metallic plates, in which each plate is connected to an adjacent plate along adjoining edges, the method comprising: providing the series of plates as a first fan-folded stack of plates; drawing the plates in sequence from the stack; applying a surface treatment to one or more of the plates; and, stacking the plates in reverse order to form a second fan-folded stack of plates.

By processing the metallic plates as a fan-folded stack, problems relating to handling of individual plates are substantially reduced, since the plates only need to be handled in the form of readily transported batches of plates. Such batches would be provided in the form of cartridges containing large numbers of plates in a highly compact form.

In preferred embodiments, a plurality of the metallic plates in at least the second fan-fold stack comprise one or more fuel cell electrode plates. As applied to the production of fuel cell electrode plates, the invention has substantial advantages over existing techniques, not least because the problems associated with applying the various different surface processing treatments required for such types of plates are substantially reduced.

In order to increase the efficiency of the process further, each plate may comprise a regular array of fuel cell electrode plates.

The surface treatment applied to the plates may comprise one or more of a cleaning, stamping, spraying, moulding and heat treatment process.

In an exemplary cleaning process, the first fan-folded stack of plates may be at least partially immersed in a cleaning solvent. The amount of solvent used during the process is minimised by immersing the stack, rather than each individual plate, in the cleaning solvent.

Each plate may be connected to an adjacent plate along a line of weakened material joining the plates. Such a join, typically referred to as a ‘living hinge’ can be designed to withstand repeated folding and unfolding steps, sufficient to subject a stack of plates to a series of processing steps, before separating each plate in a final step before assembly of the plates into a fuel cell stack.

The line of weakened material may be provided by a series of perforations. This type of fold can be applied, for example, during a stamping process as the stack of plates is prepared from a raw sheet metal reel.

Alternatively, each plate may be connected to an adjacent plate by a hinge, which may be in the form of a temporary joining piece that is removed once the processing steps are completed. The hinge may comprise one or more corresponding tab and slot connections joining adjacent plates together. This type of join may be suitable where individual plates are stamped from a starting material, for example a larger sheet of metal, followed by a process that joins the plates together to form a stack.

According to a second aspect of the invention there is provided a cartridge of metallic plates for a surface treatment process, the cartridge comprising a linked series of metallic plates, in which each plate is connected to an adjacent plate along adjoining edges forming a fan-folded stack.

According to a third aspect of the invention there is provided an apparatus for applying a surface treatment to a series of metallic plates, the apparatus comprising: a first cradle configured to receive a first fan-folded stack of metallic plates; a first rotatable transfer spool assembly configured to draw the metallic plates from cradle in sequence; and a second cradle configured to receive in reverse order a second fan-folded stack of the plates drawn by the first transfer spool from the first fan-folded stack.

The first rotatable transfer spool assembly preferably comprises a series of arms equally spaced around the assembly, the spacing corresponding with the width of the plates in the stack.

The apparatus may comprise a second rotatable transfer spool configured to receive plates drawn from the first cradle by the first transfer spool and to transfer the plates into the second cradle.

FIG. 1illustrates a schematic overview of the process according to the invention, as embodiment by an apparatus10for applying a surface treatment to a series of metallic plates. A first fan-folded stack of plates1is held in a first cradle2. The plates in the stack1are drawn out sequentially, for example using a rotatable transfer spool assembly3having a series of arms4equally spaced around the assembly, the spacing between the arms4corresponding with the width of the plates in the stack1. As the assembly3rotates in the direction indicated by arrow7, the arms4connect with adjoining edges8of adjacent plates9, drawing further plates from the stack1. The same, or a second similar, assembly3can be used to re-stack the series of plates to form a second fan-folded stack of plates5in a second cradle6.

Processing of fan-folded stacks of paper is a well-known method for printing, in particular for printing large quantities of computer-generated forms. One example is that disclosed in U.S. Pat. No. 3,683,756, in which a first fan-folded stack of paper is fed into an address printer, which outputs the paper to create a second fan-folded stack of paper having address details printed on each sheet. Such a method would not, however, be suitable for processing metallic plates as shown inFIG. 1, particularly if such plates have stamped surface features as applied to fuel cell electrode plates, because such plates could not be fed using such a system without the plates being permanently distorted.

The assembly10shown inFIG. 1illustrates a basic version of the process according to the invention, in which a single transfer spool assembly3is used to unstack and re-stack in reverse order the series of plates. Further steps may be incorporated while remaining within the scope of the invention, for example by having the assembly3feed the plates from the first stack into a conveyor system, with a further similar assembly arranged to extract the plates from the conveyor system to re-stack the plates into the second cradle6. The use of a transfer spool prevents the plates from being distorted during de-stacking and re-stacking.

The plates in the first stack1may be interconnected in various ways, for example via tabs connecting adjacent plates, the tabs being configured to yield when the plates are being stacked and re-stacked. Adjacent plates may alternatively be connected by tabs engaging with corresponding slots or by the use of additional temporary hinge components. Examples of different types of hinges are illustrated inFIGS. 2a, 2b, 3a, 3band 4a,4b.

FIG. 2ashows a pair of plates21,22connected along adjoining edges by means of a first type of hinge23. The hinge23in this embodiment is an additional component in the form of a hinged connecting piece formed from a polymeric material. The hinged connecting piece23preferably has a uniform cross-section, which makes the component suitable for being formed by an extrusion process. The slots28,29are provided along opposing long edges of the hinge23, into which the edges of the plates21,22are fitted. Flexibility of the hinge23is allowed by the use of two living hinges25,26, as shown more clearly inFIG. 2b, which shows an expanded view of the region24outlined inFIG. 2a. The living hinges25,26are provided along either side of a connecting piece27, the combination of which allows the plates21,22to be folded flat. The thickness of the hinge component23also allows the plates21,22to have features formed out of the plane of the plates, for example as a result of stamping operations for forming flow channels in the plates, while still allowing the plates21,22to be stacked flat and parallel to each other. The width of the connecting piece27can therefore be designed to match the thickness of the plates21,22after any such stamping operations.

FIG. 3ashows a pair of plates21,22connected along adjoining edges by means of a second type of hinge33. The hinge33in this embodiment is formed by a series of perforations along adjoining edges of the plates21,22, which results in the join between the plates being weakened sufficiently to allow the join to be repeatedly folded and unfolded. The hinge33is illustrated in more detail inFIG. 3b, which shows a magnified view of the region34indicated inFIG. 3a. This second type of hinge has an advantage over the first type of hinge in that no further components are required. The hinge33does not, however, allow for an unlimited number of folding and unfolding operations to be carried out, as the hinge33will eventually weaken and break due to metal fatigue. The hinge33also does not accommodate increases in the thickness of the plates as a result of stamping operations or from other components being joined to the surface of the plates21,22. This type of hinge is therefore more suitable for use during operations where the plates are in a planar form without any raised surface features, and for use with a small number of folding and unfolding operations.

FIG. 4ashows a pair of plates21,22connected along adjoining edges by means of a third type of hinge43. The hinge43in this embodiment is formed by a series of tabs and corresponding slots along adjacent edges of adjoining plates21,22. The tabs are each inserted through a corresponding slot and bent to form an interlocking hinge. A magnified view of the hinge43is shown inFIG. 4b, which illustrates the region44indicated inFIG. 4a. This third type of hinge has similar advantages to the first type of hinge, in that an unlimited number of folding and unfolding operations are possible, and the hinge can allow for the plates to be increased in thickness through stamping operations or by addition of components on a surface, while avoiding the need for the hinge to be formed from an additional component, thereby potentially reducing complexity and cost. This third type of hinge does, however, require an additional processing step for forming the hinge between each pair of adjoining plates that is more complex than the simple punching operation required to form the second type of hinge.

A combination of the second type of hinge with the first type of hinge is possible, for example using the second type for initial cleaning operations on the plates followed by the use of the first type of hinge for subsequent operations. This may in some circumstances be necessary, for example if the cleaning operations involve high temperatures that the hinge component23(FIG. 2a, 2b) would not be able to withstand.

A typical fan-folded stack of plates1may for example comprise flat rectangular plates that each contain a regular array of components. A 12×12 array of components in each plate, with an series of such plates formed into a stack containing 100 such plates, results in one stack containing 14400 individual components. The process thereby provides an efficient way of handling large numbers of components.

The process of de-stacking to re-stacking is space efficient and could be totally contained within an environment that may be dictated by the process, for example in a sealed vacuum chamber of a PVD (Physical Vapour Deposition) magnetron.

In processes where the surface treatment is a cleaning process, the first (or dispensing) stack could be partially or fully immersed in a cleaning solution, with the transfer spool indexing the plates across an air stripper.

The fan-folded stack can provide a common format suitable for many types of processing that may be required during the manufacture of fuel cell electrode plates. One type of processing that would be particularly suitable for the invention is that of multi-cavity injection moulding, in which components are moulded on to the plates as they are indexed through a moulding tool. The invention is therefore particularly suited for automated handling, both within the processing stage and between different processes.

An exemplary embodiment of an assembly for processing a stack of fan-folded plates in accordance with the invention is illustrated inFIG. 5. The assembly50comprises first and second rotatable transfer spools3a,3bsituated either side of a moulding press51. Each spool3a,3bis of the form illustrated inFIG. 1, as described above. Plates from a first stack1in a first cradle2are drawn out over the first spool3a, through the moulding press51between opposing platens52and over the second spool3bbefore being folded into a second stack5in a second cradle6. Each cradle2,6may be removable from the assembly50to allow a new stack of plates to be introduced and fed through the press51.

The plates9are passed through the press51sequentially by means of a stepper motor53linked to one or more teeth that engage with corresponding tractor holes provided along one or more edges of the plates9. The stepper motor53and press51are configured to be operated such that the plates are moved while the platens52are separated and maintained stationary while the press51operates. The press51is operated by actuating a hydraulic ram54. The press51could alternatively be configured to operate as a stamping press for embossing or punching features on to the plates9.

Other embodiments are intentionally within the scope of the invention as defined by the appended claims.