U.S. patent application number 14/391722 was filed with the patent office on 2015-04-16 for automated percussive riveting system.
The applicant listed for this patent is Ryerson University. Invention is credited to David Dakdouk, Brien East, Mohamed Helal, Yu Lin, Fengfeng (Jeff) Xi.
Application Number | 20150101175 14/391722 |
Document ID | / |
Family ID | 49326976 |
Filed Date | 2015-04-16 |
United States Patent
Application |
20150101175 |
Kind Code |
A1 |
Xi; Fengfeng (Jeff) ; et
al. |
April 16, 2015 |
AUTOMATED PERCUSSIVE RIVETING SYSTEM
Abstract
A fastener carrier for fasteners for use in a riveting system,
said carrier comprising at least one holding zone and at least one
release zone, wherein said holding zone holds a fastener in a
stored position and said release zone releases said fastener from
said carrier, said holding zone having a diameter smaller than said
release zone.
Inventors: |
Xi; Fengfeng (Jeff);
(Toronto, CA) ; Lin; Yu; (Toronto, CA) ;
Dakdouk; David; (Etobicoke, CA) ; Helal; Mohamed;
(Toronto, CA) ; East; Brien; (Toronto,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ryerson University |
Toronto |
|
CA |
|
|
Family ID: |
49326976 |
Appl. No.: |
14/391722 |
Filed: |
April 15, 2013 |
PCT Filed: |
April 15, 2013 |
PCT NO: |
PCT/CA2013/000357 |
371 Date: |
October 10, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61623925 |
Apr 13, 2012 |
|
|
|
Current U.S.
Class: |
29/525.06 ;
29/243.54 |
Current CPC
Class: |
B21J 15/28 20130101;
B21J 15/16 20130101; B21J 15/10 20130101; Y10T 29/53774 20150115;
B21J 15/323 20130101; Y10T 29/49956 20150115; B21J 15/30 20130101;
B21J 15/025 20130101 |
Class at
Publication: |
29/525.06 ;
29/243.54 |
International
Class: |
B21J 15/30 20060101
B21J015/30; B21J 15/16 20060101 B21J015/16; B21J 15/28 20060101
B21J015/28 |
Claims
1. A fastener carrier for fasteners for use in a riveting system,
said carrier comprising at least one holding zone and at least one
release zone, wherein said holding zone holds a fastener in a
stored position and said release zone releases said fastener from
said carrier, said holding zone having a diameter smaller than said
release.
2. The fastener carrier of claim 1 wherein said holding zone and
said release zone are proximate each other, further said holding
zone comprises an aperture of a first diameter and said release
zone comprises an aperture of a second diameter greater than said
first diameter, further said holding zone and said release zone are
interconnected.
3. The fastener carrier of claim 2 further comprising a plurality
of holding zones and release zones wherein each pair of said
holding zone and release zone are evenly spaced on the fastener
carrier.
4. The fastener carrier of claim 3 wherein the carrier is a tape,
the fastener is a rivet having a stem and a head, while the
diameter of the holding zone is substantially equal to the diameter
of the rivet stem and the diameter of the release zone is at least
larger than the rivet head.
5. The fastener carrier of claim 4 further comprising a plurality
of holding zone and release zone pairs.
6. The fastener carrier of claim 1 further comprising a fastener
feeding system, wherein said fastener feeding system comprises: a
holder for the fastener carrier, an opening to receive a hammer to
fasten a fastener, an advancing unit for movement of said fastener
carrier to said opening, a controller for controlling the position
of the fastener carrier.
7. The system of claim 6 wherein said controller further controls
the speed and direction of motion of said fastener carrier.
8. The fastener feeding system of claim 6, further comprising: a
support system for supporting a fastening device, wherein said
support system is selected from the group consisting of handheld
systems, stationary systems and robot supported systems; preferably
said fastening device is selected from a pressure or percussion
device,
9. The fastener feeding system of claim 8 wherein said fastening
device is a percussive riveting device comprising a plunger.
10. The fastener feeding system of claim 9, further comprising a
control system comprising a software program, wherein said program
receives data input, such as material properties and fasteners
positions, and generates instructions to said fastener application
system.
11. The fastener feeding system of claim 8 further comprising a
backing system, said backing system comprising a mobile gantry,
controlled by CNC control to provide a hitting surface for the
fastening device.
12. The backing system of claim 11 further utilized as a jig for
mounting and holding members to be fastened.
13. The backing system of claim 11 wherein said system has at least
two degrees of freedom.
14. The backing system of claim 13 wherein said system has at least
3 degrees of freedom.
15. The backing system of claim 14 wherein said system has at least
5 degrees of freedom.
16. The fastener feeding system of claim 9, further comprising a
microprocessor system comprising a software program and a backing
system, the software program controlling and synchronizing the
fastener feeding system and the backing system to perform fastening
of pre-drilled members by rivets.
17. The system of claim 8 configured to perform percussive riveting
fastening by a repetitive cycle of operations as follows: moving a
fastener application system by a support system to a riveting
position; moving a mobile gantry to a riveting position; feeding a
rivet into the fastener application system; forwarding fastener
application system to insert rivet; energizing fastening device to
rivet; retracting support system; and retracting mobile gantry.
18. A method of fastening by percussive riveting of two or more
predrilled members comprising the following steps: positioning a
rivet in front of a percussive plunger, setting the rivet inside a
predrilled hole of the predrilled members by the means of a support
system, forwarding a fastener carrier to the operational position
in which the head of the rivet is positioned proximate the center
of a release zone of the fastener carrier, setting a backing system
in an operating position, actuating a percussive plunger in order
to fasten the predrilled members by the means of pressing the rivet
between a hitting surface and the percussive plunger thus
plastically deforming said rivet.
19. The method of claim 18 controlled by a microprocessor
system.
20. (canceled)
21. A fastener application system, for introducing a fastener for
attachment of two or more predrilled members, said system
comprising: a robotic support system for supporting a percussive
fastening device comprising a plunger, and a fastener feeding
system; said fastener feeding system comprises a feeding channel to
support the fastener carrier in front of the plunger of the
percussive fastening device, an aperture in the feeding channel for
passing the plunger of the fastening device, a forwarding mechanism
to forward the fastener carrier through the feeding channel, a
fastener feeding control system to control the position of the
fastener and the fastener carrier in the fastener application
system.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a fastener carrier such as a tape
for carrying and releasing fastening members, a tool for receiving
said tape and the use of said tool for riveting operations, and the
use thereof in a percussive riveting system, preferably in an
automated percussive riveting system.
[0002] The term "fastening members" or "fasteners" used herein
shall include rivets, and other fastening devices. Preferably
rivets, more preferably percussion rivets.
[0003] The term "fastening machine" or "fastener application
system", used herein shall refer to fastening machines or systems
comprising a riveting mechanism, preferably a percussive riveting
mechanism with a rivet feeding mechanism, such as a robot arm
equipped with a rivet feeding mechanism and a pneumatic percussion
gun, but shall not be limited to such machines.
[0004] The term "stem" of a fastener used herein shall also include
a "shank" or a leg of a fastener.
BACKGROUND OF THE INVENTION
[0005] Riveting and welding represent two primary joining methods
for assembly of structural components that require strong joint
strength. Compared to welding that is mainly a fusion method,
riveting as a mechanical method causes no thermal deformation and
hence is widely used for joining high thermal conductive materials
such as aluminum sheet metals in aircraft assembly. There are
hundreds of thousands of rivets in a regional aircraft and millions
in a large aircraft. Overall, the operation of aircraft assembly is
divided into three stages: subcomponent assembly, component
assembly, and line assembly. The subcomponent assembly is the first
step to construct the base components for four major sections,
namely, fuselage, wing, cockpit and empennage. The component
assembly is the middle step to join the subcomponents to form an
individual major section. The line assembly is the last step to
assemble a whole aircraft by connecting the four major sections
together.
[0006] The current riveting processes in aerospace manufacturing
entail a mix of manual riveting, semi-automated riveting, and
automated riveting. The use of semi-automated and automated
riveting machines is becoming popular in North America and Europe.
However, these machines are limited to component assembly, such as
large wing skin panels and fuselage skin panels. Subcomponent
assembly and line assembly are still done manually. The labour
required producing these subassemblies and assemblies accounts for
as much as fifty percent of the total cost. Manual riveting
operations are tedious, repetitious, prone to error, and may lead
to health and ergonomic problems.
[0007] In principle, there are two riveting methods, the first
being called squeezing (or one-shot) riveting, where a large
upsetting force is applied to deform a rivet instantly. This method
requires a large riveter operating under high pressure beyond the
yield strength of aluminum rivets in a range over 5 Kpsi,
illustrated in FIG. 1A. This type of riveter is made of either a
hydraulic cylinder or an electromagnetic piston, which can be very
heavy and in some instances heavier than 50 lb, bulky having a
length of more than 24'' and usually requiring a lifting assisted
device if used for manual operation.
[0008] The automated and semi-automated riveting machines employ
this type of riveter, and hence are significant in size and thus
limited to riveting large, simple and relatively flat
components.
[0009] The second riveting method is called percussive (or
hammering) riveting, where a small impulsive force is applied to
deform a rivet accumulatively by a series of hits. This method
employs a rivet gun, having the size of a regular hand-held power
tool, illustrated in FIG. 1B, being very compact typically having a
length less than 10'' and light (weighting less than 5 lb),
operating under much lower pressure (in a range less than 100 psi),
very safe and energy efficient. Manual riveting is mainly based on
this method.
[0010] Historically, research on robotic riveting has been mainly
centered on squeezing riveting that employs heavy-duty industrial
robots of large size (>100 Kgs payload). In the automotive
industry, squeezing robotic riveting systems have been fully
developed and commercialized to join metal parts. This technology
is called robotic self-piercing riveting, in which a C-frame
tooling (illustrated in FIG. 1C), is designed to have a squeezing
riveter mounted on one end of the C-frame as a punch and the other
end of the C-frame serving as a hitting base. This system has been
widely used for automotive chassis assembly. The application of
robotic technology in aerospace manufacturing has been
significantly slower than that in automotive manufacturing. Though
not commercially available, squeezing robotic riveting systems have
been researched in the past by Boeing and recently by EADS in
Germany affiliated with AirBus. In addition, a robotic system has
been implemented at Bombardier in Montreal, Quebec that uses two
giant Kuka robots to hold large panels to be riveted on a C-frame
squeezing riveting machine.
[0011] Though adhesives are used to bond composites, riveting is
adopted as a primary method for joining composite panels to provide
strong joint strength and prevent laminate de-bonding. Automated
squeezing riveting systems have been developed by AirBus and Boeing
for riveting composite panels of fuselages and wings. As composites
are being introduced to replace steels for fabrication of
automotive structural parts, robotic riveting will probably take
over welding as a primary joining method for the future of
automotive industry. By comparison, percussive robotic riveting is
much more compact. Not only a much smaller riveting gun is used but
also a light/medium-duty industrial robot of small size (<50 Kgs
payload) can be applied.
[0012] The overall compactness of a percussive robotic riveting
system offers a great advantage since a percussive robotic riveting
system can access tight and awkward areas that a squeezing robotic
riveting system is not able to access. Therefore there is a need to
develop a percussive riveting robot assisted system for the
aerospace industry. U.S. Pat. No. 6108896 ("Gignac et al.")
entitled "Process and Tool Assembly for Riveting Parts", discloses
a tool assembly to be used with two robots or with a C-frame as a
method for performing percussive riveting.
[0013] It should be noted that the robots are only general-purpose
motion devices. The success of applying robots to a particular
application requires specific research on the application itself
with issues pertinent to robotics. This is similar to machine tool
research vs. machining research. The complete development of a
percussive robotic riveting system calls for systematic research
pertinent to hardware integration and software advancement, which
has not been conducted before.
[0014] U.S. Pat. No. 4,615,475 ("Fuhrmeister") discloses a feeder
for headed fasteners, where the fasteners, carried by a tape, are
sequentially advanced into alignment with the punch and die
assembly of a fastening machine by an oscillating actuator, which
is timed by the plunger holding the punch, the actuator releasable
engaging the heads of the fasteners to advance the fasteners.
[0015] U.S. Pat. No. 6,089,437 ("Fuhrmeister et al.") discloses a
pressure actuated rivet feeding system for constrained locations.
However the system disclosed relates to a pressure actuated feeding
system which requires a significant amount of pressure (5
Kpsi).
[0016] Furthermore as best seen in FIG. 13, the system disclosed by
Fuhrmeister et al. requires the use of a C-frame in order to
function. The use of a C-frame is limited in terms of size of
materials that are to be fastened. Though claimed to function in
confined areas, it would be cumbersome to rivet very large panels,
like aircraft panels, which would require a large arced C-frame in
order to accommodate large panels to fit in (for example large
aircraft panels). The use of a large arced C-frame lacks
convenience and depending on the situation, the system may require
C-frames of varying sizes. This may lead to increased costs and
lengthened down time in production due to the need to remove a
certain sized C-frame with another sixed C-frame to accommodate the
requirements of the job.
[0017] Furthermore, the tape carrier of Fuhrmeister et al was
designed for a squeezing riveting gun. The tape carrier includes a
single hole for each rivet carried. In use, the rivet may be
punched through the tape during the riveting process, because the
force used in squeezing riveting is large, compared to percussion
riveting.
[0018] There is a need for a system for feeding rivets for
percussive riveting systems for use in locations that are difficult
to reach with a C-frame.
[0019] There is also a need for an improved robotic system for
riveting operation.
[0020] There is also a need for a fastener carrier useful in
percussive riveting systems.
SUMMARY OF THE INVENTION
[0021] The current invention provides an improved fastening
apparatus and method for fastening two or more members with a
fastener such as a rivet. Furthermore, the current invention
provides an improvement to a rivet feeding system. In addition, the
current invention provides a computer system controlling the
fastening apparatus, and feeding apparatus along with a backing
system synchronized with the fastening apparatus.
[0022] The current invention is primarily directed to percussive
riveting. However, it can be also employed with other types of
riveting or fastening systems.
[0023] According to one aspect of the invention, there is provided
a riveting system comprising two parts: hardware and software. The
hardware is designed according to actual aircraft assembly setting
for manual riveting normally requiring two workers. The hardware
system comprises three subsystems: a support system, preferably an
automated support system, preferably controlled by a controller
system, most preferably a 6 degree of freedom (DOF) robot to
replace a first worker, and for holding/moving a percussive rivet
gun; a gantry system, preferably a 5-axis computer numerical
control (CNC) gantry system to replace a second worker, for
holding/moving a bucking bar or damper; and a programmable logic
control (PLC), to control the operation of the support and gantry
systems; a rivet feeder, attached to a rivet gun, for feeding and
positioning said rivets automatically.
[0024] Preferably, the gantry system also serves as a jig for
mounting sheet metals or other parts to be fastened.
[0025] According to another aspect of the invention, there is
provided software for robotic riveting planning and control
computer program for all three controllers of the aforementioned
subsystems. Preferably, the three subsystems are substantially
synchronized to perform riveting according to a planned rivet
pattern and sequence, allowing a user to perform planning,
simulation and execution all through a computer and/or
microprocessor.
[0026] According to yet another aspect of the present invention
there is provided an improved rivet/fastener feeding system for a
fastening system enabling its use in confined spaces.
[0027] According to yet another aspect of the invention there is
provided an improved fastener carrier, preferably in the form of a
tape, for use in a percussive riveting system.
[0028] Preferably the fastener carrier comprises two apertures
proximate each other, preferably each aperture being of different
diameter, wherein the first diameter allows for the snug fit of a
fastener, preferably a rivet, preferably the stem of the rivet, and
the second diameter allows the fastener, preferably a rivet, most
preferably the head of the rivet to pass freely from the fastener
carrier to allow for fastening of said members, preferably by said
rivet.
[0029] According to yet another aspect of the invention, there is
provided a fastener carrier, preferably in the form of a fastener
tape, wherein each fastener, preferably a rivet, may be released
from the carrier, by positioning the rivet snugly fit on said
carrier proximate an aperture for receiving said fastener,
preferably said aperture is a predrilled aperture on a member to be
fastened, and further moving said carrier, such that said second
diameter is in alignment with said predrilled aperture to allow
said fastener, preferably a rivet, to be released from said
fastener carrier, preferably a fastener tape.
[0030] According to yet another aspect of the invention there is
provided advancing means on the fastener feeding system to advance
the fastener carrier resulting in the positioning of the fastener
on said fastener carrier in alignment with a fastener receiving
hole, preferably preformed, on the members to be
attached/fastened.
[0031] Preferably, said fastener on said fastener carrier feeder is
further prevented from tilting or becoming misaligned with the
holes of the members to be attached/fastened.
[0032] According to yet another aspect of the invention, there is
provided a fastener feeding system as described herein further
comprising a percussive riveting tool, preferably synchronized with
a corresponding bucking or gantry system, as described herein.
[0033] Preferably the subsystems as described herein are
substantially automated, preferably through a robotic control
system.
[0034] According to another aspect of the invention, there is
provided a fastener carrier, preferably in the form of a tape,
comprising: [0035] a substantially planar web, preferably made of
plastic or other flexible material; [0036] a plurality of
substantially equally spaced hole pairs formed in the web for
receiving a fastener, said fastener comprising a head and a stem;
[0037] wherein each pair comprises a hole with a small diameter and
one hole with a large diameter; [0038] the fastener, preferably the
stem of the fastener is releasably engageable on said fastener
carrier, in the hole with a small diameter and the fastener,
preferably the head of the fastener is releasable from the hole
with a large diameter of the web fastener carrier when said
fastener is pushed or urged in a direction substantially
perpendicular to the fastener carrier towards a member to be
riveted.
[0039] According to another aspect of the invention, there is
provided a fastener feeding system for a fastening apparatus
comprising: [0040] a feeder head attached to a plunger having a
punch; [0041] an aperture in the feeder head accessible by the
punch; [0042] a fastener guide path to receive a fastener carrier,
preferably said fastener guide path is in substantial alignment
with the punch; [0043] fastener carrier drive means to push or pull
the carrier through the fastener guide path; and [0044]
controllers, or indexing means allowing the carrier to be
selectively advanced for accurate positioning of a fastener on said
fastener carrier in front of the punch, and further movement of
said carrier for release of the fastener from the fastener carrier,
so that on descent of the punch, the punch will urge the fastener
against the backing system described herein.
[0045] In operation, the controllers or indexing means allow
positioning of the fastener in front of a percussion tool, such
that when the percussion tool is aimed in front of a hole extending
through the members to be fastened, the stem of the fastener is
inserted into the hole while the stem is snugly fit in said
fastener carrier, the controller or indexing means, preferably a
forwarding mechanism, forwards the fastener carrier in order to
align the hole of larger diameter with the head of the fastener,
allowing for the release of said fastener, followed by a percussive
action of the percussion tool the fastening device in the hole
extending through the members to be fastened against the backing
system.
[0046] In a preferred embodiment, the present invention further
comprises an inlet guide passage or tube to guide the fastener
carrier, preferably in the form of a tape, from a source, such as a
spool, to the fastener guide path. Preferably, a similar outlet
guide passage guides the empty fastener carrier from the fastener
guide path once the fastener is released from said fastener
carrier. Preferably, the inlet and outlet guide passages are
parallel to each other. Most preferably, the fastener carrier is
further guided via rollers, wheels or sprockets as the fastener
carrier changes directions entering and leaving the fastener
guiding path.
[0047] Preferably, fastener head and/or stem stop means may be
provided in the fastener guide path to index the advance of the
fastener into alignment with the hammer/punch and the fastener
inlet guide passage.
[0048] Preferably, sensor means such as a limit switch, proximity
sensor, light switch or the like may be provided in the fastener
feeding system to sense when the fastener is aligned with the
hammer and hole of the members to be attached, to shut off the
advancing fastener carrier drive, and to initiate percussive
movement of the punch towards the fastener.
[0049] According to yet another aspect of the invention, there is
provided a rivet feeding system positioned on a robot arm, wherein
said robot arm is paired with a percussive riveting gun.
[0050] The rivet feeding system preferably has a storage zone for a
rivet carrier, a path way for said rivet carrier, a percussive
hammer opening, an emptied rivet carrier storage zone, and a rivet
carrier forwarding mechanism. The feeding system further comprises
at least one sensor to ensure the correct positioning of the rivet
between the hammer and the hole in the members to be fastened.
[0051] According to yet another aspect of the invention, there is
provided a backing bar on a gantry system to provide support and a
hitting base on the side of the members to be fastened opposite of
the hammer.
[0052] According to yet another aspect of the invention there is
provided a computer system controlling a robotic arm with a
percussive riveting tool to aim said robotic arm toward a hole of a
member to be fastened with a rivet. Further, there is provided a
computer system correspondingly controlling a gantry system to be
synchronized with the operation of the percussive riveting tool,
resulting in controlled attachment of the members by riveting.
[0053] According to yet another aspect of the invention, there is a
robot controller. Preferably, the robot controller serves as a
central controller to communicate with the controllers of the other
two subsystems. In a preferred embodiment, all three subsystems are
programmed by their respective controllers and then amalgamated
into a master program that may be executed by the robot controller
through signal handshaking.
[0054] In a preferred embodiment the three subsystems are
synchronized.
[0055] According to another embodiment of the invention, there is
provided a robotic riveting process, preferably a percussive
robotic riveting process incorporating the system and components of
the present invention described herein. Preferably, the robotic
riveting process is a repetitive cycle, comprising the following
operations: place members, preferably to be fastened in gantry,
ensuring each hole in members are aligned move robotic riveting arm
to position.fwdarw.move gantry to position.fwdarw.feed
rivet.fwdarw.forward robotic riveting arm to insert rivet in
hole.fwdarw.energize riveting gun to rivet.fwdarw.perform rivet
action retract robotic riveting arm.fwdarw.retract gantry.
Preferably, all the riveting points are computer generated
according to given materials such as sheet metals and riveting
pattern, however manual inputs are also possible.
[0056] In yet another embodiment of the invention there is provided
a three dimensional (3D) laser scanner applied and mounted on the
robot, preferably the robot's end-effector to perform high-speed
inspection after the completion of the required riveting. The
measurement data from the 3D laser scanner are 3D dimensional
points, from which the diameter and height of the rivet upon
completion of the riveting action, is computed and checked against
specified inspection values. The laser scanner will be used to scan
three tooling bars for the determination of an alignment
transformation matrix.
[0057] The percussive riveting system of the present invention
incorporates a smaller tool, and not a C-frame tool of the prior
art, therefore making the system more compact than the systems of
the prior art. The hitting end of the C-frame tool, is replaced by
a separate bucking-bar system, preferably synchronized with the
smaller percussive riveting tool of the present invention described
herein. In this manner, the rivet tool is more compact than the
prior art C-frame tool, and remains compact regardless of the size
of sheet metals panels. Thus allowing for versatile use of the
percussive riveting system in constrained areas without the need of
two users or a bulky C-frame riveting tool of the prior art.
[0058] Furthermore, the fastener carrier of the present invention
is unique in it comprises a fastener storing and feeding zone and a
fastener releasing zone. Preferably the zones are comprised of two
holes or apertures, a small one for storing and feeding a fastener,
preferably a rivet and a large one for releasing or pushing the
rivet through the carrier into the members to be fastened. This
design of the fastener facilitates a percussive rivet gun as the
force from a percussive riveting gun is much smaller than that of a
squeezing riveting gun as discussed above. This design eliminates
the need for punching the gun through the carrier, further it
substantially eliminates the possibility of any carrier material
remaining between the rivet head and the fastened members, which is
not preferred in the aerospace industry due to safety
considerations in manufacturing.
[0059] In one embodiment of the invention there is provided a
tooling system on the automated riveting machine that is designed
to have both drill and riveter together this embodiment results in
a relatively large attachment to the robot arm.
[0060] In the preferred embodiment a separate drill tooling is
designed solely for hole drilling. This design follows the manual
operation procedure, that is: drill all the holes first and rivet
them afterwards. As a result, each tool can remain compact,
providing each tool with high accessibility to the entire riveting
process.
[0061] A quick tool change subsystem is preferred for the robot to
switch tools between drilling, riveting, possibly inspection and
even sealing. Though general-purpose robotic tool changers are
available, for example from ATI, extra design is required in order
to meet specific tooling requirement with respect to mechanical,
electronic, electrical and pneumatic connections.
[0062] According to one aspect of the invention, there is provided
a fastener carrier for fasteners for use in a riveting system, said
carrier comprising at least one holding zone and at least one
release zone, wherein said holding zone holds a fastener in a
stored position and said release zone releases said fastener from
said carrier, said holding zone having a diameter smaller than said
release.
[0063] Preferably, said holding zone and said release zone are
proximate each other, further said holding zone comprises an
aperture of a first diameter and said release zone comprises an
aperture of a second diameter greater than said first diameter,
further said holding zone and said release zone are
interconnected.
[0064] In a preferred embodiment, said fastener carrier further
comprising a plurality of holding zones and release zones wherein
each pair of said holding zone and release zone are evenly spaced
on the fastener carrier.
[0065] In a preferred embodiment, the carrier is a tape, the
fastener is a rivet having a stem and a head, while the diameter of
the holding zone is substantially equal to the diameter of the
rivet stem and the diameter of the release zone is at least larger
than the rivet head.
[0066] Preferably, the fastener carrier further comprising a
plurality of holding zone and release zone pairs.
[0067] According to another aspect of the invention, there is
provided a fastener feeding system, wherein said fastener feeding
system comprises: [0068] A holder for the fastener carrier
described herein, [0069] an opening to receive a hammer to fasten
said fastener, [0070] an advancing unit for movement of said
fastener carrier to said opening, [0071] a controller for
controlling the position of the fastener carrier.
[0072] Preferably, said controller further controls the speed and
direction of motion of said fastener carrier.
[0073] According to another aspect of the invention, there is
provided a fastener application system, for securing two or more
members by fasteners, said system comprising: a support system for
supporting a fastening device, and a fastener feeding system
described herein, wherein said support system is selected from the
group consisting of handheld systems, stationary systems and robot
supported systems; preferably said fastening device is selected
from a pressure or percussion device,
[0074] Preferably, said fastening device is a percussive riveting
device comprising a plunger.
[0075] According to another aspect of the invention, there is
provided a control system comprising a software program for
controlling the system described herein, wherein said program
receives data input, such as material properties and fasteners
positions, and generates instructions to said fastener application
system.
[0076] According to another aspect of the invention, there is
provided a backing system for use with the fastener application
system described herein said backing system comprising a mobile
gantry, controlled by CNC control to provide a hitting surface for
the fastening device.
[0077] Preferably, said backing system is further utilized as a jig
for mounting and holding members to be fastened.
[0078] Preferably, said backing system has at least two degrees of
freedom, more preferably, said system has at least three degrees of
freedom, most preferably, said system has at least five degrees of
freedom.
[0079] According to another aspect of the invention, there is
provided a microprocessor system comprising a software program
controlling and synchronizing, the fastening application system and
backing system described herein to perform fastening of pre-drilled
members by rivets.
[0080] According to another aspect of the invention, there is
provided a process of percussive riveting fastening performed by
the systems described herein comprising a repetitive cycle of
operations as follows: [0081] moving a fastener application system
by a support system to a riveting position; [0082] moving a mobile
gantry to a riveting position; [0083] feeding a rivet into the
fastener application system; [0084] forwarding said fastener
application system to insert rivet; [0085] energizing a fastening
device to rivet; [0086] retracting mobile gantry; and [0087]
retracting said support system.
[0088] According to another aspect of the invention, there is
provided a method of fastening by percussive riveting of two or
more predrilled members comprising the following steps: [0089]
positioning a rivet in front of a percussive plunger by the means
of the feeding system described herein, [0090] setting the rivet
inside the predrilled hole of the predrilled members by the means
of a the support system, [0091] forwarding the fastener carrier to
the operational position in which the head of the rivet is
positioned proximate the center of the release zone of the fastener
carrier, [0092] setting the backing system described herein in an
operating position, [0093] actuating the percussive plunger in
order to fasten the predrilled members by the means of pressing the
rivet between the hitting surface and the percussive plunger thus
plastically deforming said rivet; [0094] Repeating the above listed
steps as necessary.
[0095] Preferably, the method is controlled by the microprocessor
system described herein.
[0096] According to another aspect of the invention, there is
provided a riveting control system comprising the fastener feeding
system, the fastener application system and backing system
described herein.
[0097] According to another aspect of the invention, there is
provided a fastener application system, for introducing a fastener
for attachment of two or more predrilled members, said system
comprising: a robotic support system for supporting a percussive
fastening device comprising a plunger, and a fastener feeding
system; said fastener feeding system comprises a feeding channel to
support the fastener carrier in front of the plunger of the
percussive fastening device, an aperture in the feeding channel for
passing the plunger of the fastening device, a forwarding mechanism
to forward the fastener carrier through the feeding channel, a
fastener feeding control system to control the position of the
fastener and the fastener carrier in the fastener application
system.
[0098] Further aspects of the invention will be apparent from the
provided illustrations, description and the claims.
BRIEF DESCRIPTION OF THE FIGURES
[0099] FIGS. 1A-1C illustrate an example of prior art tools used in
riveting industry.
[0100] FIGS. 2A-2F illustrate the components of the current
invention in a preferred embodiment, namely the riveting robot and
associated arm, the bucking system, the rivet feeder and their
respective controllers.
[0101] FIGS. 3A-3C illustrate simulation of the percussive riveting
system and the software application associated therewith of the
current invention in a preferred embodiment.
[0102] FIGS. 4A-4 C illustrate the comparison between a percussive
rivet gun and a squeezing rivet gun and the respective mean values
of performance indices.
[0103] FIGS. 5A-5C illustrate a typical setup of the current
invention and the results of a percussive riveting study
implementing a preferred embodiment of the current invention.
[0104] FIGS. 6A-6C further illustrate the results of a rivet
deformation study.
[0105] FIGS. 7A-7B illustrate the system used to rivet samples of
Examples 1 and 2 of the present invention, in a preferred
embodiment.
[0106] FIGS. 8A-8C illustrate the fastener carrier with a fastener
on said carrier.
[0107] FIG. 9 illustrates a top view of the percussive
apparatus/hammer with a rivet feeding system of the present
invention.
[0108] FIG. 10 illustrates an elevated side view of the rivet
feeding system of the present invention.
[0109] FIG. 11 illustrates a top view of the rivet feeding system
during alignment of the rivet with the hole of the members to be
attached.
[0110] FIG. 12 illustrates the elevated side view of the rivet
feeding system, with a rivet positioned in front of the percussive
hammer prior to insertion into the hole of the members to be
attached.
[0111] FIG. 13 illustrates a side view of a preferred embodiment of
the fastener carrier advancing system of the present invention.
[0112] FIG. 14 illustrates the side view of a bucking system used
with the system of the present invention.
[0113] FIG. 15 illustrates the percussive system and the bucking
system in synchronized positions during riveting operation of the
members to be attached.
[0114] FIG. 16 illustrates a preferred embodiment of the flow chart
of the percussive riveting system of the present invention.
[0115] FIGS. 17A-17C illustrate the test samples and stress/strain
relationship of the samples of Example 3.
DETAILED DESCRIPTION OF THE INVENTION:
[0116] As discussed in the Background of the Invention, the prior
art systems comprise the tools depicted in FIGS. 1A-1C. In
particular, FIG. 1A depicts a pressure riveting gun, FIG. 1B
depicts a percussive riveting gun and FIG. 1C depicts a C-frame
riveting system with a gun and a backing component.
[0117] Referring now to FIGS. 2A-2F and 9-15, the percussive
riveting system of the current invention comprises a robot arm 19,
controlled by controller 19A, the robot arm 19 being equipped with
a percussive gun 30 and a rivet feeding system 20. The rivet
feeding system 20 allows the positioning of at least one rivet R
between the percussive gun plunger (or hammer) 32 and the holes 51
in the members to be fastened 50. FIG. 2C depicts the backing
system 40 to be used in conjunction with the robot arm 19 during
the percussive riveting operation. The backing system 40 comprises
a hard hitting surface or bucking bar 41 that assists in the
percussive riveting process known in the art. FIG. 2D is the
controller 41A for the backing system 40.
[0118] FIG. 2E provides the rivet feeding system 20 in association
with a percussive rivet gun 30. The rivet feeding system 20
comprises a substantially horseshoe like rivet guide path 10' to
guide the fastener carrier 10 during the riveting process. FIG. 2F
depicts the controller 20A for the rivet feeding system 20.
[0119] The rivet feeding system 20 receives at least one rivet R
carrier by a fastener carrier 10. In this embodiment, the fastener
carrier 10 is a flexible web/belt or tape. At least one rivet R,
preferably a plurality of rivets R are attached to the fastener
carrier 10 during storage, and released from the fastener carrier
10 immediately prior to the percussive attaching operation by the
action of the percussive gun 30 on the rivet R in the hole 51 of
the members 50 to be fastened (see FIGS. 10, 11 and 12).
[0120] Different riveting methods bring up different issues in
tooling design. In squeezing robotic riveting, a large static force
is applied, thus the main concern is the robot rigidity to
withstand said static force. In percussive robotic riveting,
however, a series of impulsive (relatively small) forces are
applied, thus the main concern becoming robot vibration. In
arriving at the present invention, our research results have led to
a new design method for percussive riveting that follows the
general guidance of robot tooling design including lightweight,
compact size and large holding force against vibrations. The
results are provided in FIGS. 4A-4C
[0121] Three new indices have been introduced to evaluate the
influence of the tooling system on the overall robot system
dynamics. The first one, w.sub.1, is kinetic energy ratio,
measuring the energy consumption due to the robot's motion relative
to the total (robot+tooling) kinetic energy (addressing the issue
of lightweight). The second one, w.sub.2, is the robot vibration
ratio, evaluating the influence of the tooling system on the robot
natural frequency (addressing the issue of vibration). The third
one, w.sub.3, is the dynamic manipulability ellipsoid, measuring
the acceleration capability of the tool tip (addressing the issue
of compact size). According to our research, our percussive tooling
design FIG. 4A has yielded better dynamic performance than the
C-frame tooling FIG. 4B used for squeezing robotic riveting see
FIG. 4C.
[0122] FIG. 4C shows the mean values of dynamic performance indices
compared for the two riveting tools, percussive in FIG. 4A and
squeezing in FIG. 4B.
[0123] First, the kinetic energy ratio .eta..sub.min and
.eta..sub.max is a performance index to measure the energy
consumption to drive the tooling system's motion. The kinetic
energy ratio is defined by the ratio of the kinetic energies of the
robot and the whole system. A low ratio represents that a large
part of the energy generated by the actuators is consumed to drive
the tooling system, which is undesirable. Thus, a tooling system
with low .eta..sub.min should be avoided. It has been found that
the percussive tooling system can consume 27%, while the squeezing
tooling system can consume as high as 65% of the total kinetic
energy.
[0124] Second, the joint vibration ratio is used to evaluate the
influence of the tooling system on the natural frequencies. e.sub.v
is a robot vibration ratio of the fundamental natural frequency of
the system with the tool to that without the tooling. The joint
vibration ratio is defined as the ratio between the fundamental
natural frequencies with and without the tooling system. Higher
joint vibration ratio means less influence on the nature
frequencies of robot. With a squeezing tool, the fundamental
frequency decreases about 21%, but with a percussive tool, the
frequency decreases only 6%. It means that percussive tooling
reducing the nature frequency less, which is more desirable.
[0125] Third, the product of the singular values w.sub.1 reflects
the overall acceleration capability. Index w.sub.2 measures the
isotropy characteristics of the tool tip's acceleration. If w.sub.2
is close to 1, the tool tip has similar acceleration capability in
different directions. Index w.sub.3 represents the tool tip's
weakest acceleration capability. In the overall acceleration
performance with the percussive tool is much higher than that with
the squeezing tool by the comparison of their w.sub.i. Although the
squeezing tool can provide more isotropic accelerations than the
percussive tool from w.sub.2, its weakest acceleration capability
represented by W.sub.3 is still 15% lower than the one with
percussive tool.
[0126] Based on the comparison of these indices for the two tooling
systems, it can be seen that the squeezing tool has stronger
effects on the dynamic behavior and the percussive tool consumes
less energy, provides higher natural frequencies, and has better
acceleration performance.
[0127] Furthermore, a part feature-based method has been developed
by the research team to map sheet metal part features onto tool
approach directions (TAD) for detail study and improvement of tool
feasibility.
[0128] Software advancement is meant for the development and
integration of riveting planning and control program into a
commercial robot motion simulation and control package. The key
issue for this aspect of research was the determination of the
riveting time needed for each riveting. In a percussive robotic
riveting, the robot is tasked to follow a path specified according
to a given rivet pattern and move from spot-to-spot to perform
riveting at each spot. The riveting time is needed in order to plan
and control the duration for the robot to stay at each riveting
spot. The applicant has developed a complete method for modeling
the percussive riveting process.
[0129] The following explanation relates to a study illustrated in
FIGS. 5A-C and 6A-C .In percussive riveting, a rivet R is placed
between a rivet gun 30 and a bucking bar 43 to be subject to
repetitive impulses from the hammer 32 of the gun 30. Due to these
impacts, the rivet R is deformed plastically to join the two pieces
of sheet metals 50 together. In our molding, first impact dynamics
was applied to compute the energy transferred from the pressure
supply of the gun piston P to the initial speed of the rivet R. An
empirical relation was established through experiment between the
gun hitting frequency and the gun pressure. Then, a bilinear model
based on plastics theory was applied to determine the rivet
deformation each time hitting the bucking bar. Since the final
deformation of a rivet can be predetermined based on rivet
requirement, the needed number of hits may be determined using our
method and then divided by the hitting frequency corresponding to
the operating pressure to determine the required riveting time.
[0130] In FIG. 5B, the gun shown in FIG. 1B is tested for the
relation between the triggering frequency (both at 12 Hz and 24 Hz)
and the supplied pressure. A pneumatic regulator is used to adjust
the pressure for providing a testing range from 172 kPa (25 psi) to
310 kPa (45 psi). An accelerometer is used to measure the gun
hammer acceleration. The top figure is the time history of the
measured hammer acceleration and the bottom figure is the
corresponding amplitude spectrum.
[0131] Extensive experiment has been carried out to validate this
model as best seen in FIGS. 6A-C.
[0132] FIG. 6A
[0133] This Figure shows the result of the simulation developed
in-house. The straight cylinder on the left represents a rivet with
S.sub.F as the free surface and S.sub.c as the contact surface.
[0134] Under simulation, the free surface is subject to a series of
gun hits to drive the contact surface to hit the wall (bucking
bar). The deformed cylinder on the right represents the rivet after
a series of hits.
[0135] FIG. 6B
[0136] This Figure shows the bilinear model used for the rivet
deformation simulation. For example, the first hit causes the rivet
to deform elastically from A to B, and then plastically to C, once
the hit is gone, back to D. When the second hit comes, the rivet
will continue to deform elastically from E straight up and then
plastically in a similar fashion to the first hit, but with further
plastic deformation. This pattern will continue till all hits are
finished. The resulting effect is the accumulated plastic
deformation as illustrated in FIG. 6A.
[0137] FIG. 6C
[0138] This Figure shows the simulation results that the rivet
deformation in percussive riveting is accumulated from a series of
hammer hits and comparison with the experiment. The ratio between
deformed and undeformed length is plotted against the riveting
time, under pressure 93.6 kPa. It is found from that the standoff
distance (d) can strongly influence the rivet deformation. The
deformation becomes less as the standoff distance increases.
[0139] The final rivet deformation in percussive riveting is
accumulated from a series of hammer hits. The ratios between
deformed and undeformed lengths during riveting are drawn in FIGS.
6C for input pressures of 93.6 kPa. It is shown that the
accumulated length deformation can be as high as 35-40% after 12 s.
It is found from our studies that the standoff distance (d) can
strongly influence the rivet deformation. The deformation becomes
less as the standoff distance increases. The reason behind this is
that the retaining spring also stretches more, which consumes more
hammer kinetic energy. Finally, the simulation results are compared
to the experimental data in FIGS. 6C. We can see that the
simulation provides a reasonable prediction of the variation in
rivet length with riveting time under different pressures.
[0140] FIGS. 8A-C depict a rivet R on a rivet carrier 10 also
referred to as a fastener carrier, according to the present
invention.
[0141] In this embodiment, the fastener carrier is a flexible tape
10, comprising a plurality of paired apertures. The paired
apertures are formed by two holes having different diameters and
being positioned proximate to each other, preferably
interconnected. As illustrated in FIG. 8A, the aperture 12 has a
larger diameter than the aperture 11. It is preferred that the
aperture 11 is adapted such that snugly fits the stem 13 of the
rivet R fits snugly in aperture 11, as illustrated in FIG. 8B. The
rivet R is positioned along the tape 10 and may be stored on the
tape 10 prior to the fastening operation. FIG. 8C shows that the
aperture 12 has a sufficiently larger diameter compared to aperture
11, to allow the head 14 of the rivet R to freely pass through
aperture 12. The sufficient diameter of aperture 12 ensures no
piece of the tape or carrier material 10 will be trapped between
the head 14 of the rivet R and the members 50 to be fastened; thus
ensuring proper and clean attachment of the members 50 to be
fastened.
[0142] The percussive system 30 may be selected from a handheld gun
unit as illustrated in FIGS. 9, 10 and 11 and may also be adapted
to receive specially manufactured plunger systems or systems
readily available on the market; the plunger is preferably operated
by pressurized air, or by other suitable means. In alternative
embodiments, the percussive plunger may be replaced by a pressure
plunger.
[0143] The tape 10 may be made of plastic, fabric, metal or polymer
materials, or any suitable material for use in riveting, and in
particular percussive riveting to allow for secure storage of the
rivet in the first aperture 11 and release of the rivet from the
second aperture 12. The apertures 11 and 12 may have same or
different forms, further they do not have to be round, but may be
oval, square or any other suitable form such as star shape,
allowing the retention of the rivet in the first aperture during
the storage and supply, and easy release of the rivet from the
second aperture during the fastening operation. The tape is
preferably flat; it may be color-coded, marked, and adapted to the
forwarding system of the rivet feeding unit. The distances between
the pairs of apertures may be selected by the design requirement of
the feeding system.
[0144] The apertures of the rivet carrier or tape 10 may be punched
manually or automatically through a punch machine. The pitch
distance between rivets along the rivet carrier or tape is
important for rivet insertion. To increase the insertion speed thus
the overall riveting rate, a punch machine has been designed and
constructed so that rivet tapes will be punched under computer
control with high accuracy of rivet pitches.
[0145] FIGS. 9, 10, 11 and 12 illustrate the feeding apparatus 20
receiving the tape 10 carrying rivets R. The feeding apparatus 20
having a holder for the fastener carrier or tape 10, here an
aligning horseshoe member 21, tape holder roll 29, tape forwarding
apparatus/mechanism 23, controller 26 and a plunger/hammer window
22 to allow the plunger/hammer 32 access to the rivet R on the
carrier 10 during attachment of the members 50. The aligning
horseshoe member 21 comprises a first railing 27 for the aligned
movement of the tape 10, which also prevents any unwanted bending
of the tape 10. As best illustrated in FIG. 2E and FIG. 10, the
first railing 27 is made in such a way that stem 13 of the rivet R
is able to extend outside of the railing walls 27'. The first
railing 27 extends up to the plunger window 22. Beyond the plunger
window 22, there is a second Railing 28, which is closed see FIG.
2E. This provides not only a mechanism to prevent jamming of the
rivet R in the tape forwarding mechanism 23, but also receives and
guides the empty tape 10 once the rivet R is released
therefrom.
[0146] The holder for rivet carrier 21, as best illustrated in
FIGS. 9 and 11, is exemplified as being of generally U-shaped, but
it can be manufactured in other forms such as V-shaped,
oval-shaped, trapezoidal or any other form, allowing easy access
into confined spaces, requiring fastening, while allowing for
facile movement of the tape 10 during riveting operation.
Preferably the railings 27 and 28 of the aligning member 21 are
adapted to receive the tape 10, and also to occupy as little space
as possible to allow use of the system in confined spaces.
[0147] As best seen in FIGS. 10 and 11, sensor 26 senses the
presence of the rivet R by optical, magnetic, mechanical or other
means and sends control signals to the tape forwarding mechanism 23
for proper alignment and synchronization with hammer 32.
[0148] The tape forwarding mechanism 23 carries the tape with the
rivet R towards the plunger window 22 as illustrated in FIG. 11 and
FIG. 12. At this position, the robot arm 19 aligns the rivet stem
13 with the predrilled hole 51 of the members 50 to be fastened. At
the moment when the rivet stem 13 is inserted into the hole 51, the
forwarding mechanism 23 receives a signal to release the rivet R
from the tape 10 and forward the tape 10 until the rivet head 14 is
aligned with the aperture 12 on the tape 10. Then the fastening
apparatus performs the percussive fastening operation by the
plunger 32 of the percussion tool 30.
[0149] FIG. 12 illustrates the rivet stem 13 positioned in the tape
aperture 11 in front of the plunger window 22 proximate the plunger
32 aligned with the hole 51 in the member 50 just prior to the
insertion of said rivet R in said hole 51 and the movement of said
tape 10 releasing rivet R in aperture 12
[0150] FIG. 13 illustrates one embodiment of the tape forwarding
system 23 comprising a first roller 24 and a second roller 25
capable of gripping and pulling the tape 10. The rollers 24 and 25
may have teeth, ribs, pins or other means for grabbing the tape 10.
In an alternative embodiment the use of friction, pressure or
pulling to forward the tape 10 is also available. Preferably, the
forwarding system 23 is controlled by at least one sensor 26 of the
feeding system and/or by the computer controlling system.
[0151] In one embodiment, tape 10 is advanced via a pair of gears
24 and 25 (see FIG. 13). Preferably the surfaces of the gears 24
and 25 are knurled surfaces advancing said tape 10 via friction.
Alternatively the surface of gears 24 and 25 may comprise teeth, or
be replaced with other friction or mechanical means to engage said
tape 10 during advancement thereof. A preferred design has been
completed to advance the tapes by engaging a number of teeth inside
a series of guiding holes on the tape. However other means of
advancing the tape may be utilized.
[0152] FIGS. 14 and 15 illustrate the backing system 40 positioned
on the opposite side of the members to be fastened 50 and provide a
hitting surface 41 for the percussion tool 30 to allow the rivet R
to be deformed upon completion of the percussion tool 30 fastening
the rivet R in place. The backing system 40 is positioned on a
gantry system 40'as shown in
[0153] FIG. 15. The gantry system 40'allows the motion of the
backing system 40 from one position to another and thus eliminates
the use of a second robot/or worker compensating for the operation
of the robot arm 19.
[0154] The gantry system 40 freely moves in at least two
dimensions, preferably in at least three dimensions, to allow
movement and synchronization of the backing head 41 to the members
50 to be fastened by a rivet R. Preferably this gantry system may
be provided with additional degrees of freedom to allow riveting of
members with complicated shapes and forms.
[0155] Preferably there is a computer system capable of operating
the riveting system, the rivet feeding system and the backing
system simultaneously by receiving instructions from the operator,
computer or sensor. The instruction may include the type of the
material, position of the rivets and the distance between the
rivets.
[0156] In order to facilitate the operation of the fastening
system, a control program with a set of instructions is further
provided as part of this invention. An example of the flow chart of
such a control program is provided in FIG. 16.
[0157] The following procedures are referenced in FIG. 16.
[0158] R-R8(Robot) refer to robot arm 19 equipped with a riveting
gun 30 and riveting feeder 20.
[0159] F1-F6(Feeder) refer to a fastener feeder system of a
riveting gun 30 and rivet feeding mechanism 20
[0160] G1-G6(Gantry) refer to a gantry system 40
[0161] Power on of the entire system
[0162] R1--Robot moves to the home position.
[0163] F1--Feeder moves rivet tape to the home position.
[0164] G1--Gantry moves to the home position.
[0165] R2--Robot moves the rivet gun to a desired position of rivet
hole with a standoff distance, and then sends a hand-shaking signal
of "Gun position ok" to Feeder and Gantry.
[0166] F2--Upon receiving the signal of "Gun position ok" from
Robot, Feeder feeds a rivet, and then sends a signal of "Rivet
feeding ok" to Robot.
[0167] G2--Upon receiving the signal of "Gun position ok" from
Robot, Gantry moves the Bucking Bar (BB) to the corresponding
position of the rivet hole, and then sends a signal of "BB position
ok" to Robot.
[0168] R3--Upon receiving the signals of "Rivet feeding ok" from
Feeder and "BB position ok" from Gantry, Robot moves the rivet gun
forward to place the rivet into the hole, and then sends a signal
of "Rivet in the hole" to Feeder and Gantry.
[0169] F3--Upon receiving the signal of "Rivet in the hole" from
Robot, Feeder releases the rivet by dragging the tape from a
carrying aperture 11 to a releasing aperture 12, and then sends a
signal of "Rivet released" to Robot.
[0170] G3--Upon receiving the signal of "Rivet in the hole" from
Robot, Gantry loads the BB by extending the piston pneumatically,
and then sends a signal of "BB ready" to Robot.
[0171] R4--Upon receiving the signals of "Rivet released" from
Feeder and "BB ready" from Gantry, Robot sends a command of
riveting to Feeder, and then waits for the "Riveting Done"
feedback
[0172] F4--Upon receiving the signal of "Riveting Command" from
Robot, Feeder starts the riveting by triggering the rivet gun for a
period of setting time, and then sends a signal of "Riveting Done"
to Robot.
[0173] R5--Upon receiving the signal of "Riveting Done" from
Feeder, Robot sends a signal of "Riveting Done" to Gantry.
[0174] G4--Upon receiving the signal of "Riveting Done" from Robot,
Gantry unloads the BB by retracting the piston pneumatically, and
then sends a signal of "BB unloaded" to Robot.
[0175] R6--Upon receiving the signal of "BB unloaded" from Gantry,
Robot moves the gun backward.
[0176] R7--Robot checks if the whole process is finished? In other
words, if all the holes are riveted? If yes, Robot sends a signal
of "Finished" to Feeder and Gantry, and then stops. If not, Robot
goes back to step R2.
[0177] F5--If receives a signal of "Finished" from Robot, Feeder
stops. If not, Feeder goes back to step F2.
[0178] G5--If receives a signal of "Finished" from Robot, Gantry
stops. If not, Gantry goes back to step G2.
[0179] R8--Robot stops
[0180] F6--Feeder stops
[0181] G6--Gantry stops
EXAMPLE 1
Test of the System
[0182] A 6-DOF ABB IRB4400 industrial robot was set up and running
with a rivet gun mounted. A programmable logic control (PLC)
automatic rivet feeder was developed and set up. The conventional
vibratory rivet feeder used in the aerospace manufacturing has to
be fixed horizontally due to the way of vibratory spiral feeding.
As a result, this type of feeder cannot be directly attached to the
robot's end-effect or because it rotates in different directions.
The existing way used in squeezing riveting is to feed rivets by
blowing them one by one through a tube from the vibratory feeder to
the gun tip. However, rivets often jam inside the tube. Our design
applies a rivet tape. It not only solves the jamming problem but
also makes the entire feeder very compact and light.
[0183] Also, a computer numeric control (CNC) bucking bar gantry
system has been developed and setup. This is a five-axis CNC
system, with three linear translation axes for flat panel riveting
and two rotational axes for curved panel riveting. The action of
the bucking bar is provided through a pneumatic piston attached to
the top of the five-axis CNC gantry.
[0184] The entire system was installed inside a safety fence
forming a single robotic assembly cell, as shown in FIG. 3A. The
current setup has been used to conduct basic percussive riveting
tests. The entire system is being synchronized with the ABB robot.
Furthermore, a riveting planning package through integration with
ABB RobotStudio has been completed. FIG. 3B shows a snapshot of the
software package. The results of using the system on various
materials are discussed below.
EXAMPLE 2
Test of the System
[0185] In the tested system, the holes in the members are
predrilled, according to which the gun on the robot and the bucking
bar on the gantry are programmed. To enable riveting at different
angles, the rivet tapes are created by the research team that can
be controlled to feed rivets one-by-one through the rivet feeder.
Extensive tests have been carried out on the synchronization of the
three subsystems to follow the required riveting sequence.
Afterwards, a series of tests were performed using the standard
aircraft rivets to rivet aluminum sheet metals of different
thickness. FIG. 7A shows one of test setups. Key process parameters
have also been investigated with respect to riveting quality. It
has been found that the stand-off distance from the gun tip to the
outer surface of sheet metals is the most critical factor. FIG. 7B
shows a test sample (I) with the front (II), back (IV) and side
(III) views. After riveting, these rivets have been checked by a
set of the standard rivet gauges for diameter and height.
Inspection results have clearly demonstrated that the developed
system of the present invention produces consistent good riveting
quality.
EXAMPLE 3
Composite Riveting
[0186] The developed robotic riveting system of the present
invention has been utilized for joining of laminate strips made of
composites materials such as Carbon-Fiber-Reinforced-Polymer
(CFRP). Multiple sets of samples were successfully fastened using
the system. The samples have been tested by tensile loading to find
out the joints' ultimate tensile strength.
[0187] Though rivet patterns are available for metallic sheet
metals, the direct application of these patterns for composite
sheets may not be applicable. For this reason, a series of tests
were conducted to study the joint strength in order to determine
appropriate rivet patterns.
[0188] The first step in determining the rivet pattern formula
produced using the percussive riveting system was to conduct a
design of experiment and find the optimal parameters. The Taguchi
method was used in order to reduce the number of tests performed
while at the same time determining the optimal solution. Due to the
fact that the rivet pattern design has 4 factors affecting quality
(ultimate tensile strength) and 3 levels were desired per factor,
an L9 orthogonal array was used. Each of the factors and its
corresponding level can be seen in the Table 1. Table 2 describes
the design of experiments using the L9 orthogonal array. Three
samples were prepared for each experiment. Table 3 shows the
tooling for the experiments. The mechanical properties of composite
and rivets are shown in Table 4. Table 5 illustrates the dimensions
of specimens, while rivet pitch is a minimum distance between the
rivets in the rows and edge refers to a minimal distance from the
edge of the specimen.
TABLE-US-00001 TABLE 1 Factors and levels for the design of
experiments Levels Factors L1 L2 L3 A: (T--sheet thickness) 2
layers of 3 layers of 4 layers of fiber fiber fiber B: (D/T--rivet
diameter/sheet 2 3 4 thickness) C: (.DELTA./D--rivet pitch/rivet 3
4 5 diameter) D: (R--rows of rivets) S--single D--double T--triple
row rows rows O (Fiber orientations)* .+-.45.degree. 0/90.degree.
*Not considered in the current stage. Fiber orientations are
relative to the specimen axes. In the tensile loading cases, the
behavior of specimens with 0/90.degree. fiber orientation is fiber
dominated, while that with .+-.45.degree. is very much matrix
dominated [1].
[0189] Other Riveting Parameters:
TABLE-US-00002 1) Edge distance is 2*D D/T Edge Distance 2 4T 3 6T
4 8T 2) Rivet length - 2*T + 1.5*D, assuming two sheets have
identical thickness of T. D/T Rivet Length 2 5T 3 6.5T 4 8T
TABLE-US-00003 TABLE 2 Design of experiments based on the Taguchi
method using L9 orthogonal arrays Factors and Levels Ultimate
Tensile Strength Experiments T D/T .DELTA./D R TSi1 TSi2 TSi3 1 1 1
1 1 TS11 TS12 TS13 2 1 2 2 2 TS21 TS22 TS23 3 1 3 3 3 TS31 TS32
TS33 4 2 1 2 3 TS41 TS42 TS43 5 2 2 3 1 TS51 TS52 TS53 6 2 3 1 2
TS61 TS62 TS63 7 3 1 3 2 TS71 TS72 TS73 8 3 2 1 3 TS81 TS82 TS83 9
3 3 2 1 TS91 TS92 TS93
TABLE-US-00004 TABLE 3 Tooling and set-ups for experiments
Pneumatic Rivet Gun frequen- Ex- cy Pres- peri- Rivet Drill (Blow/
sure Time ments Rivets Sets bits Model min) (psi) (s) 1 AD-3-4
AN470- #40 P/N 2160 80 1 (D- 3/32'', 3/32'' 3x, 1/4''-Length) 2
AD-4-4 AN470 - #30 P/N 2160 80 1.5 (D-1/8'', 1/8'' 3x 1/4''-Length)
3 AD-6-5 AN470- #11 P/N 2160 80 3 (D- 3/16'', 3/16'' 3x
5/16''-Length) 4 AD-4-5 AN470- #30 P/N 2160 80 1.5 (D-1/8'', 1/8''
3x 5/16''-Length) 5 AD-6-6 AN470- #11 P/N 2160 80 5 (D- 3/16'',
3/16'' 3x 3/8''-Length) 6 AD-8-8 AN470- F P/N 1740 80 3 (D-1/4'',
1/4'' 4x 1/2''-Length) 7 AD-6-6 AN470- #11 P/N 2160 80 5 (D-
3/16'', 3/16'' 3x 3/8''-Length) 8 AD-8-8 AN470- F P/N 1740 80 3
(D-1/4'', 1/4'' 4x 1/2''-Length) 9 AD-10-10 AN470- P P/N 1740 80 6
(D- 5/16'', 1/4'' 4x 5/8''-Length)
TABLE-US-00005 TABLE 4 Material mechanical characteristics of
composite and rivets Fiber Rivets Tensile Shear Tensile Materials
strength Resins Materials strength strength 10.9 oz x 500,000 MVS
Epoxy 2117 26,000 38,000 60'' 8HS psi 410 + aluminum PSI PSI Carbon
Hardener heat treated Fiber 462/464 to the T4 (5:1) condition
TABLE-US-00006 TABLE 5 Dimensions of specimens of the experiments
Factors and Levels D .DELTA. R Edge T (rivet (rivet (rows of 2D
Experiments (thickness) diameter) pitch) rivets) Width Length [in]
1 2 layers 2T 3D single 0.65625'' 12.5'' 0.1875''
(.apprxeq.0.03937'') ( 3/32'') (.apprxeq.0.28125'') row 2 2 layers
3T 4D double 1'' 12.5'' 0.25'' (.apprxeq.0.03937'') (1/8'')
(.apprxeq.0.5'') rows 3 2 layers 4T 5D triple 1.6875'' 12.5''
0.375'' (.apprxeq.0.03937'') ( 3/16'') (.apprxeq.0.9375'') rows 4 3
layers 2T 4D triple 1'' 12.5'' 0.25'' (.apprxeq.0.059055'') (1/8'')
(.apprxeq.0.5'') rows 5 3 layers 3T 5D single 1.6875'' 12.5''
0.375'' (.apprxeq.0.059055'') ( 3/16'') (.apprxeq.0.9375'') row 6 3
layers 4T 3D double 1.75'' 12.5'' 0.5'' (.apprxeq.0.059055'')
(1/4'') (.apprxeq.0.75'') rows 7 4 layers 2T 5D double 1.6875''
12.5'' 0.375'' (.apprxeq.0.07874'') ( 3/16'') (.apprxeq.0.9375'')
rows 8 4 layers 3T 3D triple 1.75'' 12.5'' 0.5''
(.apprxeq.0.07874'') (1/4'') (.apprxeq.0.75'') rows 9 4 layers 4T
4D single 2.5'' 12.5'' 0.625'' (.apprxeq.0.07874'') ( 5/16'')
(.apprxeq.1.25'') row As an example, the specimens of experiment #4
before and after failure are depicted in FIG. 17 A-B. The curve of
strain-stress is shown in FIG. 17C. The maximum load was 2190 Lbs.
The ultimate tensile strength was 33692 psi.
EXAMPLE 4
Three Point Consecutive Riveting
[0190] The synchronization of the riveting system has been tested
and validated by riveting three rivets into three consecutive holes
in the automated mode, as opposed to the manual mode. It follows
the procedure that was described in the flowcharts of FIG. 16.
[0191] Preferably, the complex of riveting device and backing
system are working in generally vertical plane to save space on the
work floor, however, those systems can be reoriented in any
dimension.
[0192] Although preferred embodiments of the invention have been
described in the foregoing description and the illustrated
drawings, it will be understood that the invention is not limited
to the embodiments disclosed, but is capable of modifications
without departing from the spirit of the invention.
* * * * *