FUEL CELL ASSEMBLIES AND CORRESPONDING METHODS OF ASSEMBLING
The present disclosure relates to the field of fuel cell plate assemblies and methods of
assembling fuel cell plate assemblies, and in particular, although not exclusively, to fuel
cell plate assemblies that can be put together to form a fuel cell stack and methods of
assembling a fuel cell stack.
Conventional electrochemical fuel cells convert fuel and oxidant, generally both in the
form of gaseous streams, into electrical energy and a reaction product. A common type
of electrochemical fuel cell for reacting hydrogen and oxygen comprises a polymeric ion
(proton) transfer membrane, with fuel and air being passed over respective sides of the
membrane. Protons (i.e. hydrogen ions) are conducted through the membrane,
balanced by electrons conducted through a circuit connecting the anode and cathode of
the fuel cell. To increase the available voltage, a stack may be formed comprising a
number of such membranes arranged with separate anode and cathode fluid flow paths.
Such a stack is typically in the form of a block comprising numerous individual fuel cell
plates held together by end plates at either end of the stack.
Because the reaction of fuel and oxidant generates heat as well as electrical power, a
fuel cell stack requires cooling once an operating temperature has been reached.
Cooling may be achieved by forcing air through the cathode fluid flow paths. In an open
cathode stack, the oxidant flow path and the coolant path are the same, i.e. forcing air
through the stack both supplies oxidant to the cathodes and cools the stack.
According to a first aspect of the invention, there is provided a method of assembling a
fuel cell plate assembly, the method comprising:
placing a bipolar plate on a build point platform;
optionally lowering the build point platform;
placing a prefabricated first fluid diffusion layer on, and in alignment with, the
bipolar plate;
optionally lowering the build point platform;
dispensing a first track of adhesive adjacent both the bipolar plate and a
peripheral edge of the first fluid diffusion layer;
placing a prefabricated MEA and second fluid diffusion layer in sealing
engagement with the first track of adhesive and thereby forming a seal between the
bipolar plate, the peripheral edge of the first fluid diffusion layer and the MEA and second
fluid diffusion layer; and
optionally lowering the build point platform;
wherein the method comprises lowering the build point platform before and/or
after any or all of the placing or dispensing steps.
Such a method enables convenient and efficient assembly at a single build point, and
does not require a significant amount of human intervention. Also, it is advantageous to
provide a consistent assembly plateau by lowering the build point platform between
component placement operations.
The method may be automated.
The method may further comprise placing the prefabricated MEA and the second fluid
diffusion layer onto, and in sealing engagement with, the first track of adhesive such that
a face of the prefabricated MEA and second fluid diffusion layer is in sealing engagement
with the first track of adhesive.
Dispensing an adhesive may comprise screen printing the adhesive and/or placing a
semi-fluid adhesive in a desired location using transfer tape.
There may be provided a method of assembling a fuel cell stack, the method comprising:
placing a first end plate on a build point platform;
lowering the build point platform;
repeatedly performing any method of assembling a fuel cell plate assembly, and
lowering the build point platform in order to assemble a plurality of fuel cell plate
assemblies on the first end plate;
placing a second end plate on the plurality of fuel cell plate assemblies.
The method may further comprise compressing the first end plate, plurality of fuel cell
plate assemblies and second end plate. Advantageously, this compressing can be
performed at the build point on the build point platform.
The method may further comprise securing the first end plate, plurality of fuel cell plate
assemblies and second end plate in the compressed state. Advantageously, this
securing can be performed at the build point on the build point platform.
The bipolar plates may have a first and/or a second port. The method of assembling a
fuel cell plate assembly may further comprise:
dispensing a second track of adhesive as a loop around the first port of the
bipolar plate; and/or
dispensing a third track of adhesive as a loop around the second port of the
bipolar plate.
The second and third tracks of adhesive may provide seals between respective ports of
adjacent bipolar plates in the fuel cell stack. In this way, a fluid communication gallery
can be provided through the thickness of the fuel cell stack in order to provide fluid to
each of the fuel cell plate assemblies.
The method may further comprise exposing the one or more tracks of adhesive to ultra¬
violet light to cure the adhesive. It can be advantageous to cure the adhesive after the
fuel cell stack has been assembled so as not to take up valuable time at the build point.
This can improve the time of manufacture per fuel cell stack and provide an increase
throughput for the method of assembly.
According to a further aspect of the invention, there is provided a fuel cell plate assembly
comprising:
a bipolar plate;
a prefabricated first fluid diffusion layer located on, and in alignment with, the
bipolar plate;
a first track of adhesive located adjacent both the bipolar plate and a peripheral
edge of the first fluid diffusion layer; and
a prefabricated and second fluid diffusion layer in sealing engagement with
the first track of adhesive and thereby forming a seal between the bipolar plate, the
peripheral edge of the first fluid diffusion layer and the MEA.
There may be provided a fuel cell stack comprising:
a first end plate;
a plurality of fuel cell plate assemblies as disclosed herein located on the first end
plate; and
a second end plate located on the plurality of fuel cell plate assemblies.
The bipolar plates may have a first and/or a second port. The fuel cell plate assemblies
may further comprise:
a second track of adhesive configured to provide a loop around the first port of
the bipolar plate; and/or
a third track of adhesive configured to provide a loop around the second port of
the bipolar plate.
The second and third tracks of adhesive may be configured to provide seals between
respective ports of adjacent bipolar plates in the fuel cell stack.
A description is now given, by way of example only, with reference to the accompanying
drawings, in which:
Figures 1 to 4 show schematically how a fuel cell plate assembly according to an
embodiment of the invention can be built up;
Figure 5 shows a section view of a second bipolar plate positioned on top of the
fuel cell plate assembly of Figure 4;
Figures 6 to 12 illustrate schematically how a fuel cell plate assembly can be
constructed according to an embodiment of the invention;
Figure 13 illustrates schematically how a fuel cell stack can be put together
according to an embodiment of the invention;
Figure 14 illustrates schematically how a fuel cell stack can be put together
according to an alternative embodiment of the invention;
Figure 5 illustrates a fuel cell stack according to an embodiment of the invention;
and
Figure 16 illustrates a method according to an embodiment of the invention.
One or more embodiments disclosed herein relate to a method of assembling a fuel cell
plate assembly and a fuel cell stack at a single build point on a build point platform. The
method can be automated and can provide an efficient and convenient method for
assembly that does not require significant, or any, human intervention. Advantageously
the build point platform can be lowered after component placement operation in order to
provide a consistent location.
Figures 1 to 4 show how a fuel cell plate assembly according to an embodiment of the
invention can be built up. Figure 1 shows a bipolar plate 102. Figure 2 shows a
prefabricated first fluid diffusion layer 210 placed over the bipolar plate. Figure 3 shows
adhesive 314, 316 dispensed over the bipolar plate 102 and prefabricated first fluid
diffusion layer 210. Figure 4 shows a laminate layer 418, which includes a membrane
electrode assembly and a second fluid diffusion layer, placed over the prefabricated first
fluid diffusion layer and adhesive 316. Further details are provided below.
Figure 1 shows one end of a bipolar plate 102 that can provide part of a fuel cell plate
assembly according to an embodiment of the invention. The end of the bipolar plate 102
that is shown in Figure 1 has a port 104. It will be appreciated that the other end of the
bipolar plate 102 can also have a port, as shown in Figure 6. The port 104 is for
receiving a fluid, such as hydrogen, that is to be provided to an active area of an
electrode. The footprint of the active area of an electrode is shown with reference 105 in
Figure 1, even though the electrode itself is not shown. The electrode is described in
more detail below with reference to Figure 4.
The active area 105 can be considered as the footprint/area of the gas diffusion layers
(GDLs) that are in contact with the electrode surfaces such that the electrodes are
provided with the necessary reactant gasses to promote proton exchange through the
membrane.
The port 104 receives the fluid in a direction that is through the thickness of the bipolar
plate 102. In addition to providing the fluid to the electrode, the port 104 also passes the
fluid to an adjacent fuel cell assembly in a fuel cell stack as the ports of the bipolar plates
are aligned when the stack is constructed.
In this example, the bipolar plate 102 has a plurality of fluid flow channels 06, which are
discontinuous and extend across a lateral width of the bipolar plate 102. In this way, the
fluid can be laterally dispersed across the width of the active area 105 when the fluid
enters the fluid flow channels 106.
As will be discussed in more detail below, the fluid passes along the longitudinal length
of the bipolar plate 102 through a gas diffusion layer. However, one or more optional
port channels 108 can provide a fluid connection between the port 04 and the active
area 105. The port channels 108 can be provided as grooves in the bipolar plate 102.
The relationship between the port channels 108 and the fluid diffusion layer will be
described in more detail below with reference to Figure 2.
In addition, one or more optional connecting channels 107 can also transport the fluid
between successive fluid flow channels 06 along the length of the bipolar plate 102.
Such connecting channels 107 can also be provided as grooves in the bipolar plate 102.
The connecting channels 107 may alternate between connecting different ends of the
fluid flow channels 106 so as to provide a winding or inter-digitized path along the
longitudinal length of the bipolar plate 102. This can encourage the fluid to penetrate a
large proportion of the fluid diffusion layer so that it is presented evenly to the electrode.
Figure 2 shows a prefabricated first fluid diffusion layer 210 located on the bipolar plate
102 of Figure 1. The fluid diffusion layer is typically known as a gas diffusion layer
(GDL), and in this example will be referred to as an anode GDL 2 0 as it provides gas to
the active area of the anode side of the electrode.
The anode GDL 210 has an extending region 212 that extends between the port 104 of
the bipolar plate 102 and the active area 105. The tab 212 is outside the footprint of the
active area 105. The extending region will be referred to as a tab 212. The tab 212
extends from the main body of the anode GDL 210, which in this example is generally
co-located with the active area 105. The tab 212 of the anode GDL can communicate
the hydrogen received at the port 104 to the active area 105. As identified above, the
port channels 108 shown in Figure 1 can also communicate the hydrogen from the port
104 to the active area 105. However, it will be appreciated that these port channels 108
are optional as the transport of hydrogen can take place solely through the anode GDL
210. Similarly, the connecting channels 107 of Figure 1 are also optional as the anode
GDL 210 can be the sole means for communicating the hydrogen between the fluid flow
channels 106.
In other embodiments, the tab 212 can be considered as optional because the port
channels 108 can be used to communicate fluid between the port 104 and the active
area 105.
Figure 3 shows two tracks of adhesive 314, 316 deposited on the bipolar plate 102 and
anode GDL 210 of Figure 2. A second track of adhesive 314 provides a continuous loop
around the port 104 and passes over the tab 212 of the anode GDL 210. A first track of
adhesive 316 is deposited on the bipolar plate 102 around the outside of the anode GDL
210, which also passes over the tab 212 of the anode GDL 210. In this way, the first
track of adhesive 316 is positioned so that it provides a seal around the anode GDL 210
when the membrane electrode assembly is located on the partial fuel cell plate
assembly. The first track of adhesive 316 is located adjacent both the bipolar plate 102
and a peripheral edge of the anode GDL 210.
The adhesive is selected such that penetration of the adhesive into the tab 212 of the
anode GDL 210 is minimal, thereby not significantly impeding fluid transport through the
anode GDL 210.
Figure 4 shows a fuel cell plate assembly 400 in which a laminate layer 418 has been
added to the partial fuel cell plate assembly of Figure 3. The laminate layer is a 4-layer
membrane electrode assembly (MEA) and comprises a cathode fluid diffusion layer, a
first layer of catalyst, an electrode membrane and a second layer of catalyst. The two
catalyst layers and the electrode membrane can be referred to together as a membrane
electrode assembly comprising the electrode, or alternatively a prefabricated MEA and
second fluid diffusion layer.
The 4-layer MEA 418 is positioned over the first track of adhesive 316. It can be seen
from Figure 4 that the first track of adhesive 316 has been displaced and spread out
such that it abuts the second track of adhesive 314 thereby providing a seal around the
tab 2 2 of the anode GDL 210 that is outside the port 104. Also, the two displaced
adhesive tracks 314, 316 meet over the surface of the tab 212 thereby completing the
anode enclosure and providing a global anode seal for the cell.
In this way the prefabricated MEA and second fluid diffusion layer 418 is placed in
sealing engagement with the dispensed adhesive 316 and thereby forms a seal between
the bipolar plate102, the peripheral edge of the first fluid diffusion layer 210 and the MEA
and second fluid diffusion layer 418. In some examples, a bottom face of the
prefabricated MEA and second fluid diffusion layer 418 can be in sealing engagement
with the dispensed adhesive 316.
The active area is defined within the periphery of the 4-layer MEA 418 as an outer band
of the 4-layer MEA 418 is positioned over the adhesive 316, which prevents the transport
of the anode gas (hydrogen) to the electrode. It will be appreciated that the placement of
the adhesive can be controlled so as to minimise the displacement of the adhesive into
the intended active area 105.
Figure 5 shows a section view of a second bipolar plate 502 positioned on top of the fuel
cell plate assembly 400 of Figure 4. As is known in the art, a plurality of fuel cell plate
assemblies 400 can be built up to form a fuel cell stack.
As shown, in Figure 5, when the second bipolar plate 502 is positioned on top of the fuel
cell assembly 400 it contacts the second track of adhesive 314 around the port 104 of
the first bipolar plate 102. This second track of adhesive 314 therefore creates a seal
around the ports of the two bipolar plates, underneath which the tab 212 of the anode
GDL 210 passes. If the bipolar plate 102 includes port channels (as shown in Figure 1
with reference 108), then the tab 212 of the anode GDL 210 can be rigid enough to
prevent slumping into the grooves of the port channels. This can be in contrast to prior
art fuel cells, whereby a sub-gasket associated with the electrode is located above the
grooves, and can sag into the grooves.
Figures 6 to 12 illustrate schematically how a fuel cell plate assembly can be constructed
on a build point platform (not shown in the figures) according to an embodiment of the
invention. The build point platform can be lowered after components are added to the
fuel cell plate assembly so that the build point is at substantially the same height during
the construction process.
Figure 6 illustrates a strip of bipolar plates 102 that are provided to the build point. It can
be seen that the bipolar plates 102 in this example have two ports 104, 622. The first
port 104 is an inlet as discussed in detail above. The second port 622 can be an outlet
or an inlet. In some embodiments, the stoichiometric efficiency of the reaction with the
hydrogen in the fuel cell is greater than one, and therefore the second port 622 should be
used as an outlet in order to provide a through flow for product water management. In
other embodiments, the second port 622 can also be an inlet if the stoichiometric
efficiency and/or water management techniques permit.
The bipolar plates may comprise a separate anode sheet 602a and a cathode sheet
602b that are only joined together, for example resistance, laser or adhesive bonded
together shortly before the bipolar plate 102 enters the build point. This is shown in
Figure 6 as the anode sheets 602a and cathode sheets 602b are initially supplied
separately.
Located on either side of the build point are a stack of anode GDLs 210 and a stack of 4-
layer MEAs 18.
Figure 7 shows that a prefabricated first fluid diffusion layer, which will be referred to as
an anode GDL 210, has been taken from the stack ready for positioning on the bipolar
plate in the same way as shown in Figure 2 . It will be appreciated that this operation,
and the operations that follow, can be automated. Figure 8 shows the anode GDL 210
located in position on, and in alignment with, the bipolar plate 102.
Figure 9 shows an adhesive dispenser 930 in position above the anode GDL 210 and
bipolar plate 102.
Figure 10 shows three tracks of adhesive 314, 316, 1040 that have been dispensed by
the adhesive dispenser 930. The first track 316 is dispensed to a location that is
adjacent both the bipolar plate and a peripheral edge of the anode GDL. The second
track 314 provides a continuous loop around the first port 104. The first track 316 and
second track 314 are the same as those described with reference to Figure 3. Also
shown in Figure 10 is a third track of adhesive 1040 that provides a continuous loop
around the second port 622. This is in the same way that the second track of adhesive
314 provides a continuous loop around the first port 104.
Figure 1 1 shows that a prefabricated 4-layer MEA and second diffusion layer 418 has
been taken from the stack ready for positioning on the bipolar plate 102 and anode GDL
210 in the same way as shown in Figure 4. Figure 12 shows the 4-layer MEA and
second diffusion layer 418 located in position on the bipolar plate 102 and anode GDL
210.
It will be appreciated that each of the construction steps illustrated by Figures 6 to 12 can
be performed on the same build point platform as it is lowered in between placement
operations.
Figure 13 develops the method of construction illustrated by Figure 6 to 12 such that a
fuel cell stack can be put together on a build point platform (not shown). Figure 13
illustrates a strip of bipolar plates 102, a stack of anode GDLs 210 and a stack of 4-layer
MEAs 418 that are the same as those illustrated in Figures 6 to 12. In addition, Figure
13 shows two stacks of components 1350, 1352 for a top/second end plate of the fuel
cell stack and two stacks of components 1354, 1356 for a bottom/first end plate of the
fuel cell stack. Plates from the stacks 1354, 1356 for the bottom end plate are placed on
the build point platform before the construction of the fuel cell plate assemblies is begun.
Plates from the stacks 350, 1352 for the top end plate are placed on top of the fuel cell
plate assemblies at the build point when the fuel cell stack has been built to the desired
size. The fuel cell stack can then be moved from the build point platform to a position
shown with reference 1362 in Figure 13.
The first end plate 1354, 1356, the plurality of fuel cell plate assemblies and the second
end plate 1350, 1352 can be compressed at the build point or elsewhere in order to
compress the components to a working dimension. Alternatively, the components may
be compressed to a dimension that is slightly smaller than the working dimension so that
clips 1358, 1360 can conveniently be attached to the plates to secure the fuel cell
assembly together.
Clips 1358, 1360 can be attached to each side of the fuel cell stack 1362 to keep the fuel
cell plate assemblies together at the intended working dimension in order to provide a
completed fuel cell stack 1361. The clips 1358, 1360 can be attached to the fuel cell
stack 1362 before or after it is moved from its original build point.
In some examples, the dispensed adhesive can be exposed to a curing environment
either during or after the fuel cell stack is assembled. A suitable curing environment may
be provided by exposing the fuel cell stack to ultraviolet light and/or a suitable curing
temperature. The structure of the fuel cell plates of this embodiment can be well suited
to exposure to ultraviolet light as a least a portion of each track of adhesive can be
exposed from between the stacked fuel cell plate assemblies.
Figure 14 illustrates an alternative method for constructing a fuel cell stack according to
an embodiment of the invention. In this example, the anode GDL, 4-layer MEAs and
components for the end plates are strip supplied and segmented just before a pick and
place process.
Figure 5 illustrates a fuel cell stack 1500 according to an embodiment of the invention.
The top end plate 1570 of the fuel cell stack includes two apertures 1572, 1574 that are
respectively in fluid connection with the ports (not shown in Figure 15) at each end of the
fuel cell plate assemblies. It will be appreciated that similar apertures may be provided in
the bottom end plate 1576 if required.
Figure 16 illustrates a method of assembling a fuel cell plate assembly according to an
embodiment of the invention.
The method begins at step 1602 by placing a bipolar plate on a build point platform. The
build platform can then be lowered at step 1604 in some embodiments, for example such
that the top of the bipolar plate is at the same height as the original height of the build
platform. That is, the build platform may be lowered by a distance equal to the thickness
of the bipolar plate.
At step 1606, the method of assembly continues by placing a prefabricated first fluid
diffusion layer on, and in alignment with, the bipolar plate. The build platform can then
be lowered at step 1608, for example such that the top of the prefabricated first fluid
diffusion layer is at the same height as the original height of the build platform. That is,
the build platform may be lowered by a distance equal to the thickness of the
prefabricated first fluid diffusion layer.
At step 1610, the method continues by dispensing a first track of adhesive adjacent both
the bipolar plate and a peripheral edge of the first fluid diffusion layer. In some
examples, method step 1610 may also involve dispensing a second track of adhesive as
a loop around a first port of the bipolar plate and/or dispensing a third track of adhesive
as a loop around a second port of the bipolar plate.
The adhesive can be dispensed by screen printing a liquid adhesive or placing a semi
fluid adhesive in the desired location using transfer tape.
At step 1612, the method continues by placing a prefabricated and second fluid
diffusion layer in sealing engagement with the first track of adhesive. This can form a
seal between the bipolar plate, the peripheral edge of the first fluid diffusion layer and the
and second fluid diffusion layer.
It will be appreciated that in some examples the build point platform can be, but need not
necessarily be, lowered before or after any or all of the placing and dispensing steps
1602, 1606, 1610, 1612. The specific increment that the build point platform is lowered
can be different for different lowering operations. The specific increment that the build
point platform is lowered does not necessarily need to be related to every component
placed.
The method of Figure 16 can be repeated in order to assemble a fuel cell stack. In such
examples, the second and third tracks of adhesive can provide seals around the
respective first and second ports of adjacent bipolar plates.
Any "prefabricated" layers disclosed herein may be considered as unitary, selfsupporting,
layers that can be provided to a build point as a single component.
CLAIMS
. A method of assembling a fuel cell plate assembly, the method comprising:
placing a bipolar plate on a build point platform;
placing a prefabricated first fluid diffusion layer on, and in alignment with, the
bipolar plate;
dispensing a first track of adhesive adjacent both the bipolar plate and a
peripheral edge of the first fluid diffusion layer; and
placing a prefabricated MEA and second fluid diffusion layer in sealing
engagement with the first track of adhesive and thereby forming a seal between the
bipolar plate, the peripheral edge of the first fluid diffusion layer and the MEA and second
fluid diffusion layer;
wherein the method comprises lowering the build point platform before or after
any or all of the placing and dispensing steps.
2. The method of claim 1, comprising lowering the build point platform after placing
the bipolar plate on the build point platform.
3. The method of claim 1 or claim 2, comprising lowering the build point platform
after placing the prefabricated first fluid diffusion layer on, and in alignment with, the
bipolar plate.
4. The method of any preceding claim, comprising lowering the build point platform
after placing the prefabricated MEA and second fluid diffusion layer in sealing
engagement with the first track of adhesive.
5. The method of any preceding claim, wherein the method is automated.
6. The method of any preceding claim, comprising:
placing the prefabricated MEA and the second fluid diffusion layer onto, and in
sealing engagement with, the first track of adhesive such that a face of the prefabricated
MEA and second fluid diffusion layer is in sealing engagement with the first track of
adhesive.
7. The method of any preceding claim, wherein dispensing an adhesive comprises
screen printing the adhesive.
8. The method of any one of claims 1 to 6, wherein dispensing an adhesive
comprises placing a semi-fluid adhesive in a desired location using transfer tape.
9. A method of assembling a fuel cell stack, the method comprising:
placing a first end plate on a build point platform;
lowering the build point platform;
repeatedly performing the method of any one of claims 1 to 8 and lowering the
build point platform in order to assemble a plurality of fuel cell plate assemblies on the
first end plate;
placing a second end plate on the plurality of fuel cell plate assemblies.
10. The method of claim 9, further comprising:
compressing the first end plate, plurality of fuel cell plate assemblies and second
end plate; and
securing the first end plate, plurality of fuel cell plate assemblies and second end
plate in the compressed state.
1 . The method of claim 9 or claim 10, wherein the bipolar plates have a first and a
second port, and the method of assembling a fuel cell plate assembly further comprises:
dispensing a second track of adhesive as a loop around the first port of the
bipolar plate; and
dispensing a third track of adhesive as a loop around the second port of the
bipolar plate;
such that the second and third tracks of adhesive provide seals between respective ports
of adjacent bipolar plates in the fuel cell stack.
12. The method of any preceding claim, further comprising exposing the one or more
tracks of adhesive to ultra-violet light to cure the adhesive.
13. A fuel cell plate assembly comprising:
a bipolar plate;
a prefabricated first fluid diffusion layer located on, and in alignment with, the
bipolar plate;
a first track of adhesive located adjacent both the bipolar plate and a peripheral
edge of the first fluid diffusion layer; and
a prefabricated MEA and second fluid diffusion layer in sealing engagement with
the first track of adhesive and thereby forming a seal between the bipolar plate, the
peripheral edge of the first fluid diffusion layer and the MEA.
14. A fuel cell stack comprising:
a first end plate;
a plurality of fuel cell plate assemblies according to claim 3 located on the first
end plate; and
a second end plate located on the plurality of fuel cell plate assemblies.
15. The fuel cell stack of claim 14, wherein the bipolar plates have a first and a
second port, the fuel cell plate assemblies further comprise:
a second track of adhesive configured to provide a loop around the first port of
the bipolar plate; and
a third track of adhesive configured to provide a loop around the second port of
the bipolar plate;
wherein the second and third tracks of adhesive are configured to provide seals between
respective ports of adjacent bipolar plates in the fuel cell stack.
16. A method substantially as described herein, and as illustrated in the
accompanying drawings.
17. A fuel cell plate assembly substantially as described herein, and as illustrated in
the accompanying drawings.
18. A fuel cell plate stack substantially as described herein, and as illustrated in the
accompanying drawings.