U.S. patent application number 10/115556 was filed with the patent office on 2003-10-09 for apparatus and method for singulating porous fuel cell layers using adhesive tape pick head.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Eaton, Warren David, Mlinar, John Russell, Schukar, Gary William.
Application Number | 20030190226 10/115556 |
Document ID | / |
Family ID | 28673798 |
Filed Date | 2003-10-09 |
United States Patent
Application |
20030190226 |
Kind Code |
A1 |
Eaton, Warren David ; et
al. |
October 9, 2003 |
Apparatus and method for singulating porous fuel cell layers using
adhesive tape pick head
Abstract
An apparatus and method provide for singulating thin and
substantially porous material layers arranged in a stack. A pick
head is positioned above the stack of material layers. An adhesive
tape is stabilized against the pick head through use of a vacuum
between the adhesive tape and the pick head. Contact is effected
between the stabilized adhesive tape and the top material layer.
The pick head is moved to move the top material layer from the
stack to a predetermined location. While at the predetermined
location, the adhesive tape is detached from the top material
layer. The singulation apparatus and method are particularly well
suited for destacking individual porous fluid transport layers
(FTLs) from a magazine of FTLs during automated fuel cell
assembly.
Inventors: |
Eaton, Warren David; (White
Bear Township, MN) ; Schukar, Gary William; (North
Oaks, MN) ; Mlinar, John Russell; (Coon Rapids,
MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
28673798 |
Appl. No.: |
10/115556 |
Filed: |
April 3, 2002 |
Current U.S.
Class: |
414/796.4 ;
414/796.9; 414/797 |
Current CPC
Class: |
Y10T 156/19 20150115;
B65H 2553/30 20130101; H01M 8/0297 20130101; B65H 3/0816 20130101;
Y10T 156/1785 20150115; H01M 8/24 20130101; Y10T 156/1778 20150115;
Y02E 60/50 20130101; B65H 2511/22 20130101; B65H 2701/1718
20130101; Y10S 156/934 20130101; B65H 2511/22 20130101; B65H
2220/02 20130101 |
Class at
Publication: |
414/796.4 ;
414/796.9; 414/797 |
International
Class: |
B65H 003/08; B65H
003/00 |
Claims
What is claimed is:
1. A method of singulating a plurality of porous fuel cell fluid
transport layers (FTLs) arranged in a stack (FTL stack), the FTL
stack comprising a top FTL, the method comprising: positioning a
pick head above the FTL stack; stabilizing an adhesive tape against
the pick head through use of a vacuum between the adhesive tape and
the pick head; effecting contact between the stabilized adhesive
tape and the top FTL; moving the pick head to move the top FTL from
the FTL stack to a predetermined location; detaching, while at the
predetermined location, the adhesive tape from the top FTL; and
repeating the positioning, stabilizing, effecting, moving, and
detaching processes for subsequent top FTLs.
2. The method of claim 1, further comprising determining a distance
between the pick head and the top FTL, wherein effecting contact
further comprises moving the pick head by at least the determined
distance such that the adhesive tape contacts the top FTL.
3. The method of claim 2, wherein determining the distance
comprises ultrasonically determining the distance between the pick
head and the top FTL.
4. The method of claim 1, wherein detaching the adhesive tape
comprises extending a stripper mechanism of the pick head to effect
detachment of the adhesive tape from the top FTL.
5. The method of claim 4, wherein detaching the adhesive tape
further comprises retracting the stripper mechanism after detaching
the adhesive tape from the top FTL.
6. The method of claim 1, further comprising advancing the adhesive
tape to present unused adhesive proximate the pick head after
detaching the adhesive tape from the top FTL.
7. The method of claim 6, further comprising removing the vacuum
between the adhesive tape and the pick head after detaching the
adhesive tape from the top FTL and prior to advancing the adhesive
tape.
8. The method of claim 1, wherein the FTL stack is stationary, and
effecting contact comprises moving the pick head so that the
adhesive tape contacts the top FTL.
9. The method of claim 1, wherein effecting contact comprises
displacing the pick head vertically so that the adhesive tape
contacts the top FTL, and moving the pick head comprises moving the
pick head horizontally to move the top FTL to the predetermined
location.
10. The method of claim 1, further comprising detecting presence or
absence of the adhesive tape at the pick head.
11. The method of claim 1, wherein detaching the adhesive tape from
the top FTL comprises detaching the adhesive tape from the top FTL
at the predetermined location with a positional tolerance ranging
between about 0.01 inches and about 0.02 inches.
12. A method of singulating a plurality of thin and substantially
porous material layers arranged in a stack, the stack of material
layers comprising a top material layer, the method comprising:
positioning a pick head above the stack of material layers;
stabilizing an adhesive tape against the pick head through use of a
vacuum between the adhesive tape and the pick head; effecting
contact between the stabilized adhesive tape and the top material
layer; moving the pick head to move the top material layer from the
stack to a predetermined location; detaching, while at the
predetermined location, the adhesive tape from the top material
layer; and repeating the positioning, stabilizing, effecting,
moving, and detaching processes for subsequent top material
layers.
13. The method of claim 12, further comprising determining a
distance between the pick head and the top material layer, wherein
effecting contact further comprises moving the pick head by at
least the determined distance such that the adhesive tape contacts
the top material layer.
14. The method of claim 12, wherein determining the distance
comprises ultrasonically determining the distance between the pick
head and the top material layer.
15. The method of claim 12, wherein detaching the adhesive tape
comprises extending a stripper mechanism of the pick head to effect
detachment of the adhesive tape from the top material layer.
16. The method of claim 15, wherein detaching the adhesive tape
further comprises retracting the stripper mechanism after detaching
the adhesive tape from the top material layer.
17. The method of claim 12, further comprising advancing the
adhesive tape to present unused adhesive proximate the pick head
after detaching the adhesive tape from the top material layer.
18. The method of claim 17, further comprising removing the vacuum
between the adhesive tape and the pick head after detaching the
adhesive tape from the top material layer and prior to advancing
the adhesive tape.
19. The method of claim 12, wherein the stack of material layers is
stationary, and effecting contact comprises moving the pick head so
that the adhesive tape contacts the top material layer.
20. The method of claim 12, wherein effecting contact comprises
displacing the pick head vertically so that the adhesive tape
contacts the top material layer, and moving the pick head comprises
moving the pick head horizontally to move the top material layer to
the predetermined location.
21. The method of claim 12, further comprising detecting presence
or absence of the adhesive tape at the pick head.
22. The method of claim 12, wherein detaching the adhesive tape
from the top material layer comprises detaching the adhesive tape
from the top material layer at the predetermined location with a
positional tolerance ranging between about 0.01 inches and about
0.02 inches.
23. An apparatus for singulating a plurality of porous fuel cell
fluid transport layers (FTLs) arranged in a stack (FTL stack), the
FTL stack comprising a top FTL, the apparatus comprising: a pick
head comprising a pick region, a stripper mechanism situated
proximate the pick region, and a vacuum port located at the pick
region, the vacuum port adapted for coupling to a vacuum system; a
tape drive mechanism, the tape drive mechanism controlling movement
of an adhesive tape proximate the vacuum port at the pick region; a
positioning system that supports the pick head, the positioning
system controllable to move the pick head vertically and
horizontally; and a controller, the controller programmed to
control the positioning system to move the pick head so that the
adhesive tape contacts the top FTL, the adhesive tape stabilized at
the pick region by a vacuum between the adhesive tape and the pick
region, the controller programmed to further control the
positioning system to move the pick head to a predetermined
location, the stripper mechanism actuating to detach the top FTL
from the adhesive tape at the predetermined location.
24. The apparatus of claim 23, wherein the controller is programmed
to effect repeated singulation of FTLs from the FTL stack.
25. The apparatus of claim 23, wherein the tape drive mechanism is
connected to the pick head.
26. The apparatus of claim 23, wherein the tape drive mechanism is
separate from the pick head.
27. The apparatus of claim 23, wherein the tape drive mechanism
comprises a wind-up mechanism and an unwind mechanism, the wind-up
and; unwind mechanisms cooperating to move the adhesive tape so
that unused adhesive of the adhesive tape is presented at the pick
region.
28. The apparatus of claim 27, wherein the wind-up and unwind
mechanisms each comprise a roll, and the adhesive tape is unwound
from the roll of the unwind mechanism and wound on the roll of the
wind-up mechanism.
29. The apparatus of claim 27, wherein the wind-up mechanism
comprises a roller clutch needle bearing and a brake, the roller
clutch needle bearing and brake cooperating to index the adhesive
tape in a forward direction from the unwind mechanism to the
wind-up mechanism.
30. The apparatus of claim 27, wherein the pick head comprises a
pneumatic cylinder and a linkage, the pneumatic cylinder and
linkage cooperating to advance the adhesive tape between the unwind
mechanism and the wind-up mechanism.
31. The apparatus of claim 23, wherein the pick head comprises a
pneumatic cylinder and a linkage, the pneumatic cylinder and
linkage cooperating to actuate the stripper mechanism.
32. The apparatus of claim 31, wherein the controller is programmed
to control the pneumatic cylinder so that the stripper mechanism is
actuated at the predetermined location to detach the top FTL from
the adhesive tape.
33. The apparatus of claim 23, wherein the stripper mechanism
comprises stripper feet.
34. The apparatus of claim 23, further comprising a distance sensor
at the pick head, the distance sensor determining a distance
between the pick head and the top FTL.
35. The apparatus of claim 34, wherein the distance sensor
comprises an ultrasonic sensor.
36. The apparatus of claim 23, further comprising a sensor that
senses presence or absence of the adhesive tape proximate the pick
region.
37. The apparatus of claim 23, wherein the pick head comprises one
or more springs mounted to provide counter-balance for weight of
the pick head.
38. The apparatus of claim 23, wherein the pick head and tape drive
mechanism define a unitary pick head unit, and a plurality of pick
head units are supported by the positioning system.
39. The apparatus of claim 23, wherein the positioning system
comprises a vertical servomotor for moving the pick head
vertically, and a horizontal servomotor for moving the pick head
horizontally.
40. The apparatus of claim 39, wherein the pick head comprises
vertical linear slides to allow for slight over travel of the
vertical servomotor to ensure adequate contact between the adhesive
tape and the top FTL.
41. The apparatus of claim 39, wherein the vertical servomotor is
coupled to a rack and pinion arrangement, and the horizontal
servomotor is coupled to a ball screw assembly.
42. The apparatus of claim 23, wherein the apparatus includes a
pair of the pick heads comprising a first pick head and a second
pick head, and the tape drive mechanism comprises an unwind
mechanism mounted proximate the first pick head and a wind-up
mechanism proximate the second pick head, the unwind and wind-up
mechanisms cooperating to control movement of the adhesive tape
proximate the vacuum port at the pick region of the first and
second pick heads, respectively.
43. The apparatus of claim 42, wherein the first and second pick
heads define a unitary pick head assembly.
44. The apparatus of claim 42, wherein the first and second pick
heads define separate pick head assemblies.
45. The apparatus of claim 23, wherein the positioning system
detaches the top FTL from the adhesive tape at the predetermined
location with a positional tolerance ranging between about 0.01
inches and about 0.02 inches.
46. An apparatus for singulating a plurality of porous material
layers arranged in a stack, the stack comprising a top porous
material layer, the apparatus comprising: a pick head comprising a
pick region, a stripper mechanism situated proximate the pick
region, and a vacuum port located at the pick region, the vacuum
port adapted for coupling to a vacuum system; a tape drive
mechanism, the tape drive mechanism controlling movement of an
adhesive tape proximate the vacuum port at the pick region; a
positioning system that supports the pick head, the positioning
system controllable to move the pick head vertically and
horizontally; and a controller, the controller programmed to
control the positioning system to move the pick head so that the
adhesive tape contacts the top porous material layer, the adhesive
tape stabilized at the pick region by a vacuum between the adhesive
tape and the pick region, the controller programmed to further
control the positioning system to move the pick head to a
predetermined location, the stripper mechanism actuating to detach
the top porous material layer from the adhesive tape at the
predetermined location.
47. The apparatus of claim 46, wherein the controller is programmed
to effect repeated singulation of the porous material layers from
the stack.
48. The apparatus of claim 46, wherein the tape drive mechanism is
connected to the pick head.
49. The apparatus of claim 46, wherein the tape drive mechanism is
separate from the pick head.
50. The apparatus of claim 46, wherein the tape drive mechanism
comprises a wind-up mechanism and an unwind mechanism, the wind-up
and unwind mechanisms cooperating to move the adhesive tape so that
unused adhesive of the adhesive tape is presented at the pick
region.
51. The apparatus of claim 46, wherein the stripper mechanism
comprises stripper feet.
52. The apparatus of claim 46, further comprising a distance sensor
at the pick head, the distance sensor determining a distance
between the pick head and the top porous material layer.
53. The apparatus of claim 52, wherein the distance sensor
comprises an ultrasonic sensor.
54. The apparatus of claim 46, further comprising a sensor that
senses presence or absence of the adhesive tape proximate the pick
region.
55. The apparatus of claim 46, wherein the pick head comprises one
or more springs mounted to provide counter-balance for weight of
the pick head.
56. The apparatus of claim 46, wherein the pick head and tape drive
mechanism define a unitary pick head unit, and a plurality of pick
head units are supported by the positioning system.
57. The apparatus of claim 46, wherein the positioning system
comprises a vertical servomotor for moving the pick head
vertically, and a horizontal servomotor for moving the pick head
horizontally.
58. The apparatus of claim 57, wherein the pick head comprises
vertical linear slides to allow for slight over travel of the
vertical servomotor to ensure adequate contact between the adhesive
tape and the top porous material layer.
59. The apparatus of claim 57, wherein the vertical servomotor is
coupled to a rack and pinion arrangement, and the horizontal
servomotor is coupled to a ball screw assembly.
60. The apparatus of claim 46, wherein the apparatus includes a
pair of the pick heads comprising a first pick head and a second
pick head, and the tape drive mechanism comprises an unwind
mechanism mounted proximate the first pick head and a wind-up
mechanism proximate the second pick head, the unwind and wind-up
mechanisms cooperating to control movement of the adhesive tape
proximate the vacuum port at the pick region of the first and
second pick heads, respectively.
61. The apparatus of claim 60, wherein the first and second pick
heads define a unitary pick head assembly.
62. The apparatus of claim 60, wherein the first and second pick
heads define separate pick head assemblies.
63. The apparatus of claim 46, wherein the positioning system
detaches the top porous material layer from the adhesive tape at
the predetermined location with a positional tolerance ranging
between about 0.01 inches and about 0.02 inches.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to manufacturing
pick and place devices and, more particularly, to an apparatus and
method for singulating porous layers of a fuel cell using an
adhesive tape pick head assembly.
BACKGROUND OF THE INVENTION
[0002] Various apparatuses have been developed to destack items
from a magazine of such items in an automated fashion. Conventional
destacking apparatuses typically employ suction cups or a vacuum to
releasably engage and transport layers of a given material during a
destacking operation. Although such conventional arrangements may
be satisfactory in certain applications, implementing known
approaches for destacking relatively thin materials having varying
porosity renders conventional arrangements unworkable.
[0003] Moreover, it is often desirable to automate, either
partially or completely, a number of processes of a destacking
operation. Many conventional material handling and destacking
apparatuses and methods are not well suited for a high degree of
automation, particularly destacking processes which have tight
positional tolerance requirements.
[0004] There is a need for improved material layer destacking
apparatuses and methodologies. There is a further need for such
apparatuses and methodologies that can safely and precisely
position destacked material layers of varying porosity in an
automated assembly environment, such as in an automated fuel cell
assembly plant. The present invention fulfills these and other
needs.
SUMMARY OF THE INVENTION
[0005] The present invention is directed to an apparatus and method
of singulating thin and substantially porous material layers
arranged in a stack. According to a method of the present
invention, a pick head is positioned above the stack of material
layers. An adhesive tape is stabilized against the pick head
through use of a vacuum between the adhesive tape and the pick
head. Contact is effected between the stabilized adhesive tape and
the top material layer of the stack. The pick head is moved so as
to move the top material layer from the stack to a predetermined
location. While at the predetermined location, the adhesive tape is
detached from the top material layer.
[0006] An apparatus of the present invention provides for
singulating porous material layers arranged in a stack. The
apparatus includes a pick head comprising a pick region, a stripper
mechanism situated proximate the pick region, and a vacuum port
located at the pick region. The vacuum port is adapted for coupling
to a vacuum system. A tape drive mechanism is employed to control
movement of an adhesive tape proximate the vacuum port at the pick
region. A positioning system supports the pick head, and is
controllable to move the pick head vertically and horizontally.
[0007] A controller is programmed to control the positioning system
to move the pick head so that the adhesive tape contacts the top
porous material layer. The adhesive tape is stabilized at the pick
region by a vacuum between the adhesive tape and the pick region.
The controller is programmed to further control the positioning
system to move the pick head to a predetermined location. At the
predetermined location, the stripper mechanism actuates to detach
the top porous material layer from the adhesive tape. The
controller is programmed to effect repeated singulation of the
porous material layers from the stack. The singulation processes
are repeated for subsequent material layers at the top of the
stack. The singulation apparatus and method are particularly well
suited for destacking individual porous fluid transport layers
(FTLs) from a magazine of FTLs during automated fuel cell
assembly.
[0008] The above summary of the present invention is not intended
to describe each embodiment or every implementation of the present
invention. Advantages and attainments, together with a more
complete understanding of the invention, will become apparent and
appreciated by referring to the following detailed description and
claims taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is an illustration of a fuel cell and its constituent
layers;
[0010] FIG. 2 is a perspective view of a pick head assembly mounted
on a robot in accordance with an embodiment of the present
invention, the robot controllable to move the pick head assembly
vertically and horizontally;
[0011] FIG. 3 is a perspective view of a pick head assembly
comprising a pair of pick heads and a common tape drive mechanism
that presents an adhesive tape across each of the pick heads in
accordance with an embodiment of the present invention;
[0012] FIG. 4a is a top view of the wind-up mechanism shown in FIG.
3, the view of FIG. 4a showing a portion of a linkage assembly of
the wind-up mechanism;
[0013] FIG. 4b is a front view of the wind-up mechanism shown in
FIG. 3;
[0014] FIG. 4c is a side view of the linkage assembly partially
shown in FIG. 4a;
[0015] FIG. 4d is a rear view of the linkage assembly partially
shown in FIG. 4a;
[0016] FIG. 5a is a top view of the unwind mechanism shown in FIG.
3, the view of FIG. 5a showing a portion of an unwind assembly of
the unwind mechanism;
[0017] FIG. 5b is a front view of the unwind mechanism shown in
FIG. 3;
[0018] FIG. 5c is a side view of the unwind assembly partially
shown in FIG. 5a; and
[0019] FIG. 5d is a rear view of the unwind assembly partially
shown in FIG. 5a.
[0020] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It is to
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the scope of the invention as defined
by the appended claims.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0021] In the following description of the illustrated embodiments,
reference is made to the accompanying drawings which form a part
hereof, and in which is shown by way of illustration, various
embodiments in which the invention may be practiced. It is to be
understood that the embodiments may be utilized and structural
changes may be made without departing from the scope of the present
invention.
[0022] A singulation apparatus and methodology of the present
invention can be employed to singulate individual layers of
relatively thin material and to move singulated thin material
layers to a predetermined location with high precision. In
particular, a singulation apparatus and methodology of the present
invention is well suited for destacking individual thin material
layers which are substantially porous. For example, certain
material layers used to construct a fuel cell can have a thickness
of one or two thousandths of an inch (e.g., about 0.001 inches).
These material layers can be porous and, in addition, may be
brittle. One skilled in the art will readily appreciate that
destacking and transporting relatively thin layers of material,
particularly porous and brittle material layers, both accurately
and safely is a significant challenge. These challenges are
presently facing those attempting to automate the process of
fabricating fuel cells.
[0023] A singulation apparatus and methodology of the present
invention provides for the safe and precise singulation of thin,
porous material layers during automated processing of such material
layers. Moreover, principles of the present invention may also be
applied to singulate and accurately position non-porous material
layers during automated processing of such material layers.
[0024] As indicated above, a singulation apparatus and methodology
of the present invention can be employed to facilitate automated
singulation and positioning of material layers defining a fuel cell
or a portion of a fuel cell. A fuel cell is an electrochemical
device that combines hydrogen fuel and oxygen from the air to
produce electricity, heat, and water. Fuel cells do not utilize
combustion, and as such, fuel cells produce little if any hazardous
effluents. Fuel cells convert hydrogen fuel and oxygen directly
into electricity, and can be operated at much higher efficiencies
than internal combustion electric generators, for example.
[0025] A typical fuel cell is depicted in FIG. 1. The fuel cell 10
shown in FIG. 1 includes a first fluid transport layer 12 adjacent
an anode 14. Adjacent the anode 14 is an electrolyte membrane 16. A
cathode 18 is situated adjacent the electrolyte membrane 16, and a
second fluid transport layer 19 is situated adjacent the cathode
18. In operation, hydrogen fuel is introduced into the anode
portion of the fuel cell 10, passing through the first fluid
transport layer 12 and over the anode 14. At the anode 14, the
hydrogen fuel is separated into hydrogen ions (H.sup.+) and
electrons (e.sup.-).
[0026] The electrolyte membrane 16 permits only the hydrogen ions
or protons to pass through the electrolyte membrane 16 to the
cathode portion of the fuel cell 10. The electrons cannot pass
through the electrolyte membrane 16 and, instead, flow through an
external electrical circuit in the form of electric current. This
current can power an electric load 17, such as an electric motor,
or be directed to an energy storage device, such as a rechargeable
battery.
[0027] Oxygen flows into the cathode side of the fuel cell 10 via
the second fluid transport layer 19. As the oxygen passes over the
cathode 18, oxygen, protons, and electrons combine to produce water
and heat.
[0028] Individual fuel cells, such as that shown in FIG. 1, can be
combined with a number of other fuel cells to form a fuel cell
stack. The number of fuel cells within the stack determines the
total voltage of the stack, and the surface area of each of the
cells determines the total current. The total electrical power
generated by a given fuel cell stack can be determined by
multiplying the total stack voltage by total current.
[0029] A singulation apparatus and methodology of the present
invention can be employed to facilitate automated destacking and
positioning of material layers in the construction of fuel cells of
varying technologies. For example, a singulation apparatus and
methodology of the present invention can be employed to singulate
material layers used to construct proton exchange membrane (PEM)
fuel cells. PEM fuel cells operate at relatively low temperatures
(about 175 degrees F.), have high power density, can vary their
output quickly to meet shifts in power demand, and are well suited
for applications where quick startup is required, such as in
automobiles for example.
[0030] The proton exchange membrane used in a PEM fuel cell is a
thin plastic sheet that allows hydrogen ions to pass through it.
The membrane is coated on both sides with highly dispersed metal or
metal alloy particles (e.g., platinum or platinum/ruthenium) that
are active catalysts. The electrolyte used is typically a solid
organic polymer poly-perfluorosulfonic acid. Use of a solid
electrolyte is advantageous because it reduces corrosion and
management problems.
[0031] Hydrogen is fed to the anode side of the fuel cell where the
catalyst encourages the hydrogen ions to release electrons and
become hydrogen ions (protons). The electrons travel in the form of
an electric current that can be utilized before it returns to the
cathode side of the fuel cell where oxygen has been introduced. At
the same time, the protons diffuse through the membrane to the
cathode, where the hydrogen ions are recombined and reacted with
oxygen to produce water.
[0032] According to one PEM fuel cell construction, a PEM layer is
sandwiched between a pair of fluid transport layers, such as
diffuse current collectors or gas diffusion layers for example. An
anode is situated between a first FTL and the membrane, and a
cathode is situated between the membrane and a second FTL. In one
configuration, a PEM layer is fabricated to include an anode
catalyst coating on one surface and a cathode catalyst coating on
the other surface. According to another configuration, the first
and second FTLs are fabricated to include an anode and cathode
catalyst coating, respectively. In yet another configuration, an
anode catalyst coating can be disposed partially on the first FTL
and partially on one surface of the PEM, and a cathode catalyst
coating can be disposed partially on the second FTL and partially
on the other surface of the PEM. The five layer construct defined
by the first FTL/anode/PEM/cathode/second FTL is referred to as a
membrane electrode assembly (MEA).
[0033] The FTLs are typically fabricated from a carbon fiber paper
or non-woven material. Depending on the product construction, the
FTLs can have carbon particle coatings on one side. The FTLs, as
discussed above, can be fabricated to include or exclude a catalyst
coating. The FTLs, according to this product construction, are both
porous and brittle. A singulation apparatus and methodology
consistent with the principles of the present invention is
particularly well suited for destacking and positioning thin fuel
cell layers, such as PEM layers and FTLs for example, during
automated fuel cell assembly.
[0034] Direct methanol fuel cells (DMFC) are similar to PEM cells
in that they both use a polymer membrane as the electrolyte. In a
DMFC, however, the anode catalyst itself draws the hydrogen from
liquid methanol fuel, eliminating the need for a fuel reformer.
DMFCs typically operate at a temperature between 120-190 degrees
F.
[0035] Molten carbonate fuel cells (MCFC) use a liquid solution of
lithium, sodium and/or potassium carbonates, soaked in a matrix for
an electrolyte. MCFCs operate at about 1,200 degrees F. The high
operating temperature is needed to achieve sufficient conductivity
of the electrolyte. Because of this high temperature, noble metal
catalysts are not required for the cell's electrochemical oxidation
and reduction processes. MCFCs are typically operated on hydrogen,
carbon monoxide, natural gas, propane, landfill gas, marine diesel,
and simulated coal gasification products.
[0036] A solid oxide fuel cell (SOFC) typically employs a hard
ceramic material of solid zirconium oxide and a small amount of
ytrria, instead of a liquid electrolyte, allowing operating
temperatures to reach 1,800 degrees F.
[0037] In regenerative fuel cells, water is separated into hydrogen
and oxygen by a solar-powered electrolyser. The hydrogen and oxygen
are fed into the regenerative fuel cell which generates
electricity, heat, and water. The water is then recirculated back
to the solar-powered electrolyser and the process is repeated.
[0038] A protonic ceramic fuel cell (PCFC) employs a ceramic
electrolyte material that exhibits high protonic conductivity at
elevated temperatures. PCFCs operate at about 1,300 degrees F.
PCFCs can operate at high temperatures and electrochemically
oxidize fossil fuels directly to the anode. Gaseous molecules of
the hydrocarbon fuel are absorbed on the surface of the anode in
the presence of water vapor, and hydrogen ions are efficiently
stripped off to be absorbed into the electrolyte, with carbon
dioxide as the primary reaction product. These and other fuel cell
technologies can be constructed from material layers singulated and
positioned by use of a singulation apparatus and methodology in
accordance with the present invention.
[0039] In accordance with one application, a singulation apparatus
and methodology of the present invention are employed to pick a
single fluid transport layer (FTL), such as a gas diffusion layer
or diffuse current collector, off the top of a stack of FTLs and
place the singulated FTL in an precise location for inclusion
within a fuel cell membrane electrode assembly, such as a PEM type
MEA. In MEA construction, for example, picking and placing of FTLs
needs to be accomplished carefully and precisely. There are
typically very tight locational tolerances when constructing an MEA
stack (e.g., positional tolerances ranging between about 0.01
inches and about 0.02 inches). FTLs are porous and typically
brittle. Use of conventional vacuum techniques to destack an FTL
from a magazine of FTLs would result in picking up several FTLs. An
apparatus and methodology of the present invention advantageously
provides for the singulation of an FTL from a stack of FTLs, and
further provides for the placement of singulated FTLs at a
preestablished location with high precision.
[0040] According to an embodiment of the present invention, one,
two, or more adhesive tape pick heads are used in conjunction with
a servomotor driven robot to singulate FTLs or other thin porous
material layers and to transport individual FTLs to a desired
location with high accuracy. The robot is preferably controllable
to move the pick heads in horizontal and vertical directions. A
horizontal servomotor of the robot employs a rack and pinion system
with linear bearing to precisely locate the pick heads in the
horizontal direction. A vertical servomotor of the robot employs a
ball screw assembly with linear bearing to locate the pick heads in
the vertical direction.
[0041] Because the product to be handled in accordance with this
embodiment is porous and must be picked out of a magazine, an
adhesive tape system is employed in the pick head assembly to
destack the product. The pick head assembly incorporates wind and
unwind mechanisms to index an adhesive tape by a small amount after
each pick cycle, thereby maintaining the needed adhesion capability
of the pick head assembly. A distance sensor, such as an ultrasonic
sensor, is used to determine stack height and the vertical travel
needed to engage the adhesive tape with the product. A stripping
mechanism, such as stripper feet, is used to separate the product
from the adhesive tape at the predetermined destination
location.
[0042] Due to the brittle nature of the product according to this
application, one or more springs are preferably used to counter the
weight of the pick heads. A web break sensor detects if the
adhesive tape breaks or the unwind mechanism dispenses all of the
available adhesive tape. Vacuum is advantageously used at the pick
head to stabilize the adhesive tape and prevent the adhesive tape
and FTL from moving relative to the pick head. The incorporation of
vacuum to control the adhesive tape at the pick head, and therefore
maintain precise locational control of the FTL adhered thereto,
combined with servomotor positioning of the robot provides for a
high precision pick and place apparatus.
[0043] Turning now to FIG. 2, there is illustrated an adhesive tape
pick head assembly 40 in accordance with an embodiment of the
present invention. According to this embodiment, the pick head
assembly 40 comprises two pairs of pick heads for a total of four
pick heads that operate in conjunction to pick and place thin
porous material layers, such as FTLs, during an automated
destacking and placement operation. The pick head assembly 40 is
shown mounted via mounts 41 to a support 34 extending from support
arms 32 of a robot 30.
[0044] Movement of the robot 30, and therefore the pick head
assembly 40, is effected by a positioning system 31 under control
of a controller 35. Controller 35 is a programmable device, such as
a processor, that executes program instructions to coordinate the
activities of various elements of the robot 30. The controller 35
may be an on-board device or may be located remotely of the robot
30. If located remotely, the controller 35 is coupled to the robot
30 using an appropriate hardwired or wireless connection.
[0045] The positioning system 31 includes a vertical positioning
system and a horizontal positioning system. The vertical
positioning system includes a vertical servomotor 37 which
cooperates with a ball screw assembly (not shown) to controllably
move the pick head assembly 40 in the vertical direction. The
horizontal positioning system includes a horizontal servomotor 39
which cooperates with a rack and pinion system (not shown) to
controllably move the pick head assembly 40 in the horizontal
direction.
[0046] FIG. 3 is a perspective view of a pick head assembly 40
comprising a pair of pick heads 50 and a common tape drive
mechanism 43 that advances an adhesive tape 65 across each of the
pick heads 50 in accordance with an embodiment of the present
invention. As shown in FIG. 3, and as described below, the pick
head assembly 40 includes a first pick head assembly 40A and a
second pick head assembly 40B. It is understood that a pick head
assembly 40 of the present invention may include a single pick head
50 or greater than two pick heads 50. For example, FIG. 2 shows
four pick heads 50 arranged on the robot 30 to operate
cooperatively.
[0047] In the case of pick head assembly 40 in which a single pick
head 50 is employed, it is understood that both the unwind and
wind-up sections of the tape drive mechanism 43 are typically
integrated within the single pick head assembly 40. Moreover, and
in accordance with another embodiment, the tape drive mechanism 43
need not be mounted directly to the pick head assembly 40, but may
instead be supported by an external support system, such that
adhesive tape 65 is fed to the pick head assembly 40 to present
fresh adhesive at the pick head 50 for each pickup cycle.
[0048] The first pick head assembly 40A and second pick head
assembly 40B shown in FIG. 3 each incorporate a pick head 50 which
includes a vacuum port 52 at a distal end and an inlet 72 at a
proximal end of the pick head 50. A chamber of the pick head 50
extends between the inlet 72 and the vacuum port 52. The inlet 72
is adapted to connect with a vacuum system (not shown) which is
controlled to selectively provide a vacuum between the vacuum port
52 situated at a pick region of the pick head 50 and a portion of
the adhesive tape 65 moved into proximity with the vacuum port
52.
[0049] Stripper feet 54 are situated on each of two sides of the
vacuum port 52. The stripper feet 54 are shown in a retracted
configuration in FIG. 3, and remain in the retracted configuration
until after the product has been picked from the product magazine
and moved to its intended destination location. When the pick head
50 is properly positioned at the destination location, the stripper
feet 54 are extended beyond a plane of the vacuum port 52, which
cause the adhesive tape 65 to separate from the product without
disturbing the orientation of the product.
[0050] A distance sensor 60 is situated on the pick head assembly
40 and is used to determine the height of the product stack. The
distance sensor 60 cooperates with the controller 35 or other
processor to compute the vertical travel needed to effect
engagement between the adhesive tape 65 presented at the vacuum
port 52 and the top product of the product stack. The distance
sensor 60 is preferably an ultrasonic sensor, but may also be an
optical sensor.
[0051] In the embodiment depicted in FIG. 3, the first pick head
assembly 40A incorporates a wind-up mechanism 42 and the second
pick head assembly 40B incorporates an unwind mechanism 44. The
wind-up mechanism 42 of the first pick head assembly 40A shown in
FIG. 3 will now be described in greater detail with reference to
FIGS. 4a-4d. FIG. 4a is a top view of the first pick head assembly
40A shown in FIG. 3. FIG. 4b is a front view showing of the wind-up
mechanism 42 shown in FIG. 3. FIG. 4c is a side view of a linkage
assembly 74 partially shown in the top view of FIG. 4a. FIG. 4d is
a rear view of the linkage assembly 74 shown in FIG. 4c.
[0052] The wind-up mechanism 42 includes a wind-up roll 45 that
receives spent adhesive tape 65 fed to the pick head 50 via an
idler roll 46. The idler roll 46 of the wind-up mechanism 42,
according to this embodiment, receives adhesive tape 65 from an
idler roll 47 and unwind roll 48 of the unwind mechanism 44. The
wind-up mechanism 42 employs a roller clutch needle bearing 71
which cooperates with a brake 78 to index the adhesive tape 65 in a
forward direction from the unwind roll 48 to the wind-up roll 45. A
pneumatic cylinder 77 cooperates with a 6-bar linkage 76 to advance
the core of the wind-up roll 45. In one configuration, the
pneumatic cylinder 77 cooperates with a 6-bar linkage 76 to advance
the core of the wind-up roll 45 and concurrently actuates the
stripper feet 54 to move to their extended configuration to strip
the product off the pick head 50.
[0053] As previously discussed, vacuum is applied at the vacuum
port 52 via chamber 72 to stabilize the adhesive tape 65 presented
proximate the vacuum port 52. Stabilizing the adhesive tape 65 at
the pick head 50 when engaging a porous product increases the
precision by which such product can be destacked and
repositioned.
[0054] A spring 49 is employed between a vertical portion of the
mount 41 and the first pick head assembly 40A to counter balance
the weight of the first pick head assembly 40A. This weight counter
balancing mechanism significantly reduces or prevents damage to
brittle product, such as fluid transport layers of a fuel cell,
when the pick head 50 is brought into contact with the product. The
first pick head assembly 40A is compliant vertically, through use
of vertical shafts comprising slides 51 and linear bearings 53, to
allow for slight over travel of the robot's vertical servomotor 37
to ensure sufficient contact between the pick head 50 and the
product.
[0055] The unwind mechanism 44 of the second pick head assembly 40B
shown in FIG. 3 will now be described in greater detail with
reference to FIGS. 5a-5d. FIG. 5a is a top view of the second pick
head assembly 40B shown in FIG. 3, and provides a partial showing
of a portion of an unwind assembly 80 of the unwind mechanism 44.
FIG. 5b is a front view of the unwind mechanism 44 shown in FIG.
5a. FIG. 5c is a side view of the unwind assembly 80 partially
shown in FIG. 5a. FIG. 5d is a rear view of the unwind assembly 80
shown in FIG. 5c.
[0056] The unwind mechanism 44 includes an unwind roll 48 that
provides unused adhesive tape 65 to the pick head 50. The partially
used adhesive tape 65 advances from the pick head 50, to the idler
roll 47, and to the idler roll 46 of the wind-up mechanism 42. The
wind-up mechanism 42, according to this embodiment, receives
adhesive tape 65 from the idler roll 47 and unwind roll 48 of the
unwind mechanism 44.
[0057] In one configuration, the length of the adhesive tape 65
between the pick heads 50 of the first and second pick head
assemblies 40A, 40B is selected so that sections of the adhesive
tape 65 used by the pick head 50 of the first pick head assembly
40A skip past the pick head 50 of the second pick head assembly
40B. In this configuration, fresh adhesive is presented at the
vacuum ports 52 of the first and second pick head assemblies 40A,
40B. In another configuration, the adhesive tape 65 employs an
adhesive that provides sufficient adhesion for two or more picking
cycles, in which case the section of the adhesive tape used by the
first pick head 50 is simply advanced for use by each subsequent
pick head 50.
[0058] The unwind mechanism 44 preferably uses the same vacuum
system as the wind-up mechanism 42 to stabilize the adhesive tape
65 via a vacuum at the vacuum port 52 of the pick head 50. The
unwind mechanism 44 employs a brake 85 to control the tension in
the adhesive tape 65. A pneumatic cylinder 86 is used to extend the
stripper feet 54 to strip the product off the pick head 50 when the
product reaches its intended destination location.
[0059] A tape break detection system is provided at the unwind
mechanism 44. In one configuration, a tape sensor 62, which may be
a proximity switch operating in cooperation with flags 84, senses
when a break occurs in the adhesive tape 65 or when the all of the
adhesive tape 65 has been dispensed from the unwind roll 48.
[0060] A spring 49 is employed between a vertical portion of the
mount 41 and the second pick head assembly 40B to counter balance
the weight of the second pick head assembly 40B to prevent damage
to brittle product when the pick head 50 is brought into contact
with the product. The second pick head assembly 40B is compliant
vertically, through use of vertical shafts comprising slides 51 and
linear bearings 53, to allow for slight over travel of the robot's
vertical servomotor 37 to ensure sufficient contact between the
pick head 50 and the product.
[0061] A process of singulating an FTL according to an embodiment
of the present invention will now be described. It is understood
that two to four pick heads 50 are typically employed to pick and
place FTLs from an FTL stack to a desired position, although a
single pick head may be used. Initially, the pick heads 50 are
positioned above a magazine containing a stack of FTLs. At this
stage, the stripper feet 54 are retracted and vacuum at the vacuum
ports 52 are actively stabilizing adhesive tape 65 against the
respective pick heads 50. The distance sensor 60 determines the
distance to the top FTL of the stack of FTLs. The vertical
servomotor 37 of the robot 30 lowers the pick heads 50 by the
determined distance plus a small additional amount to ensure
capture of the top FTL by the pick heads 50. As was discussed
above, the pick heads 50 have vertical compliance built in to
handle over travel.
[0062] After the adhesive tape 65 stabilized at the pick region of
the respective pick heads 50 engages the top FTL, the vertical
servomotor 37 of the robot 30 moves the top FTL upward and the
robot's horizontal servomotor 39 moves the top FTL to the desired
position. The stripper feet 54 of the respective pick heads 50 are
extended to strip the top FTL from the pick heads 50 at the desired
position. Extending the stripper feet 54 also rotates the wind-up
mechanism's indexing arm back. The vertical servomotor 37 then
lifts the pick heads 50 away from the top FTL. The vacuum at the
vacuum ports 52 is turned off of the adhesive tape 65, and the
stripper feet 54 are retracted. This movement also advances the
adhesive tape 65 forward. Vacuum is once again turned on to
stabilize the adhesive tape 65, and the horizontal servomotor 39
returns to the magazine in a ready state to handle the next top FTL
of the FTL stack.
[0063] The foregoing description of the various embodiments of the
invention has been presented for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed. Many modifications and
variations are possible in light of the above teaching. It is
intended that the scope of the invention be limited not by this
detailed description, but rather by the claims appended hereto.
* * * * *