U.S. patent application number 13/829030 was filed with the patent office on 2013-10-10 for automated fastener setting tool.
The applicant listed for this patent is NEWFREY LLC. Invention is credited to Zachary S. Stoian.
Application Number | 20130263433 13/829030 |
Document ID | / |
Family ID | 48092680 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130263433 |
Kind Code |
A1 |
Stoian; Zachary S. |
October 10, 2013 |
Automated Fastener Setting Tool
Abstract
A fastener setting device includes a monitoring circuit having
circuitry to receive a feed status signal from a first sensor
within the feed system. The circuitry receives a robotic arm status
signal from a second sensor within the robotic arm and receives a
rivet set status signal from a third sensor within the setting
tool. The circuit determines if a fault condition occurs; and
initiates a rivet clearing procedure if a fault condition is
detected.
Inventors: |
Stoian; Zachary S.;
(Rochester Hills, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEWFREY LLC |
Newark |
DE |
US |
|
|
Family ID: |
48092680 |
Appl. No.: |
13/829030 |
Filed: |
March 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61615562 |
Mar 26, 2012 |
|
|
|
Current U.S.
Class: |
29/525.06 ;
29/243.53 |
Current CPC
Class: |
B21J 15/10 20130101;
B21J 15/28 20130101; B21J 15/32 20130101; Y10T 29/49956 20150115;
Y10T 29/5377 20150115; B21J 15/025 20130101; B21J 15/02
20130101 |
Class at
Publication: |
29/525.06 ;
29/243.53 |
International
Class: |
B21J 15/02 20060101
B21J015/02; B21J 15/10 20060101 B21J015/10 |
Claims
1. A system for setting a self-piercing rivet, said system
comprising: a self-piercing rivet setting tool, said tool including
a rivet engaging assembly, an axially movable piston assembly
operatively coupled to said rivet for driving said rivet, a housing
annularly disposed about said piston; a monitoring circuit, having
circuitry to: (a) receive a feed status signal from a first sensor
within the feed system; (b) receive a robotic arm status signal
from a second sensor within the robotic arm; (c) receive a rivet
set status signal from a third sensor within the setting tool; (d)
determine if a fault condition is detected; and (e) initiate a
rivet clearing procedure if a fault condition is detected.
2. The system for setting a self-piercing rivet of claim 1 wherein
said monitoring circuit further includes circuitry to: produce from
a series of feed status signals and a measured rivet set status
dataset; scan said measured rivet set status dataset to determine a
first local feed value; scan an example rivet set status dataset to
determine a second local feed value; and determine if the first
local feed value and the second local feed value are within one of
a predetermined time tolerance band, or within a predetermined feed
tolerance band.
3. The system of claim 1 wherein the first sensor is configured to
measure feed of a fastener along an axial direction.
4. The system for setting a self-piercing rivet of claim 1 further
including an indicator operatively connected to said monitoring
circuit for signaling to an operator the acceptability of a
fastener feed based on said comparison of said feed output/
predetermined value pairs.
5. The system of claim 1 wherein said first sensor is a
micro-strain sensor.
6. The system of claim 1 wherein the housing comprises a C-shaped
structure.
7. The system of claim 1 wherein the first sensor is positioned on
an exterior surface of the feed system.
8. The system according to claim 1 wherein the body defines a
sensor mounting location, said sensor mounting location being at a
point on the feed system which experiences deformation during a
rivet feed event.
9. A method of setting a fastener with a setting tool having an
axially movable piston assembly operatively coupled to an engaging
assembly for driving said fastener in response to the application
of pressurized hydraulic fluid to said piston assembly, said method
including the steps of: (a) monitoring the feed status of a feed
system during a rivet setting process and producing a series of
measured feed/time signals related thereto; (b) defining an set of
example feed/time signals; (c) aligning the measured feed/time
signals to the example feed/time signals; and (d) identifying the
occurrence of an improper feed during the rivet setting process
from the feed/time signal based upon misalignment of signals.
10. The method of claim 9 further including the steps of: producing
a rivet set status dataset based on a series of measured force
signal; scanning said force signal to determine the point in time
during the rivet setting process when the highest value of force
occurs; and using said determined point to identify the rivet
setpoint.
11. A system for setting a self-piercing fastener and evaluating
the acceptability of the set, said system comprising: a rivet
setting tool, said tool including a C-shaped support body, a feed
system, and a rivet engaging assembly configured to drive said
fastener; a first transducer configured to measure a rivet feed
within the feed system during a rivet setting process and producing
feed status signal related thereto; a circuit, configured to: (a)
receive a series of feed status signals and assign an associated
time thereto during the rivet setting process; (b) identify the
occurrence during the rivet setting process of the last local feed
signal; (c) use the occurrence of the last local feed signal to
identify the movement of the fastener; (d) determine the total time
of said rivet feed process; (e) compare said total time with a
predetermined desired value; and (f) compare said feed timing at
the last local maximum with a predetermined value.
12. A method of setting a self-piercing rivet with a setting tool
having a support body and an axially movable piston assembly
operative for driving said rivet, said method including the steps
of: (a) monitoring an axial fastener feed during a rivet setting
process and producing a series of feed signals related thereto; (b)
monitoring the time of said rivet setting process and producing a
series of time signals related thereto; (c) identifying the
occurrence during the rivet setting process of an improper feed;
(d) using the occurrence of the improper feed to identify a fault;
and (e) initiate a rivet cleaning process should the fault be
detected.
13. The method of claim 12 further including the steps of:
producing a rivet feed status waveform based on said series of feed
signals and said series of time signals produced over a rivet
feeding process; scanning said rivet feed status waveform to
identify the location of a feed peak in said waveform; and using
the location of the feed peak to identify the total time of the
rivet feed event.
14. The method for setting a self-piercing rivet according to claim
13 including comparing the rivet feed status waveform with an
example rivet feed status waveform to determine if the rivet feed
is acceptable.
15. An electronic control system for use in a riveting process, the
system comprising: an electronic control unit; a drive connected to
the electronic control unit; a feed sensor connected to the
electronic control unit and the drive, the feed sensor being
operable to indicate changes in feed status within the feed system
during the rivet feeding process; and wherein the electronic
control unit is configured to compare the changes in feed system
with a predetermined value to determine if a rivet feed status is
acceptable.
16. The system of claim 15 further comprising a rivet wherein the
drive is a hydraulic drive.
17. The system of claim 16 further comprising: a rivet feeder
having an actuator connected to the electronic control unit; and a
feed tube sensor connected to the electronic control unit; wherein
the electronic control unit operably controls feeding of the rivet
by the feeder during the riveting process and the feed tube sensor
sends a signal to the electronic control unit indicative of the
presence of the rivet.
18. The system of claim 15 further comprising a punch and a piston,
the piston being operable to convert hydraulic pressure to linear
motion driving the punch.
19. The system of claim 18 wherein the piston is operable to
convert pneumatic pressure to linear motion.
20. The system of claim 15 further comprising a second sensor being
operable to measure one of: (a) torque of an electric motor, (b)
speed of the drive, (c) a power characteristic of an electric
motor, (d) a punch location, (e) rivet size.
21. The system of claim 15 wherein the system comprises a second
sensor configured to measure a workpiece thickness.
22. The system of claim 15 wherein the second sensor is a load cell
operably indicating a linearly moving member force.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/615,562, filed on Mar. 26, 2012. The entire
disclosure of the above application is incorporated herein by
reference.
FIELD
[0002] The present disclosure relates to rivet setting devices and,
more particularly, to a control system and method for a rivet
setting device which will clear a fastener from a feed mechanism
upon detection of a fault condition.
BACKGROUND
[0003] The background description provided herein is for the
purpose of generally presenting the context of the disclosure. Work
of the presently named inventors, to the extent it is described in
this background section, as well as aspects of the description that
may not otherwise qualify as prior art at the time of filing, are
neither expressly nor impliedly admitted as prior art against the
present disclosure.
[0004] Fastener setting devices are often coupled to robotic arms
and include mechanisms that apply forces to a fastener to
plastically deform the fastener to couple two outputs together.
Often, the fastener setting device has an associated fastener
feeding device to feed fasteners into the device. The robotic arms
can be configured to equally position the rivet setting device in
specific locations along an assembly to couple various rivets onto
a structure.
[0005] Unfortunately, failures in the robotic or the fastener
feeding system can cause the system to stop unexpectedly. When this
happens, undeformed or unset fasteners located within the feeding
system or within the fastener setting machine must be removed
before the fastener setting system can be restarted. To remove the
fasteners, the feed system and setting tool must be disassembled,
thus increasing costs and delaying production.
SUMMARY
[0006] A system for setting a fastener includes a mode control
module, a robot control module, and a fastener set module. The
fastener set module selectively sets a fastener feed mode, a
fastener set mode, and a fastener clear mode. In response to a
fastener set error signal, the module transfers from one of the
fastener set mode and fastener feed mode to the fastener clear
mode.
[0007] The robot control module operates a fastener set clear mode
during a fastener clear cycle. To accomplish this, the control
module operates a mandrel clear mode during a first robotic cycle,
and operates a drive coupled to a mandrel actuator. The first
robotic cycle moves the fastener set mechanism to a fastener feed
discharge station a fixed distance from the workpiece. At the
discharge station, the fastener is set into a dummy workpiece, thus
clearing the feed mechanism.
[0008] A method for setting a fastener using a fastener setting
device includes selectively moving from a status check mode for a
fastener setting apparatus to one of a feeding mode, a setting
mode, and a clearing mode. In response to an error signal from one
of the feeding mode or the setting mode to the clearing mode,
during a first system cycle operating a mandrel actuator in a
fastener setting mode, and operating the robotic arm into a second
system cycle.
[0009] A system for setting a self-piercing rivet is disclosed. The
system has a self-piercing rivet setting tool. The tool includes a
rivet engaging assembly, an axially movable piston assembly
operatively coupled to said rivet for driving the rivet. The system
includes a monitoring circuit, having circuitry to: receive a feed
status signal from a first sensor within the feed system; receive a
robotic arm status signal from a second sensor within the robotic
arm; receive a rivet set status signal from a third sensor within
the setting tool; determine if a fault condition occurs; and to
initiate a rivet clearing procedure if a fault condition is
detected.
[0010] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
DRAWINGS
[0011] The drawings described herein are for illustrative purposes
only of selected embodiments and not all possible implementations,
and are not intended to limit the scope of the present
disclosure.
[0012] FIG. 1 is a diagrammatic view showing a preferred embodiment
of a riveting system according to the present teachings;
[0013] FIG. 2 is a partially diagrammatic, partially elevational
view according to the present teachings;
[0014] FIG. 3 is a perspective view showing a riveting tool
according to the present teachings;
[0015] FIG. 4 is an exploded perspective view showing the nut and
spindle mechanism, punch assembly, and clamp according to the
present teachings;
[0016] FIG. 5 is a cross sectional view, taken along line 5 of FIG.
3, showing the riveting tool according to the present
teachings;
[0017] FIG. 6 is an exploded perspective view showing a receiving
head according to the present teachings;
[0018] FIG. 7 is a cross sectional view showing the receiving head
according to the present teachings;
[0019] FIG. 8 is a partially fragmented perspective view showing a
rivet feed tube according to the present teachings;
[0020] FIG. 9 is an exploded perspective view showing a feeder
according to the present teachings;
[0021] FIGS. 10A-10H are a series of cross sectional views, showing
the self-piercing riveting sequence according to the present
teachings;
[0022] FIGS. 11A-11E are a series of diagrammatic and enlarged
views, similar to those of FIG. 10, showing the self-piercing
riveting sequence according to the present teachings;
[0023] FIG. 12 is a diagrammatic view showing the control system
according to the present teachings;
[0024] FIG. 13 is a graph showing sense versus distance riveting
characteristics according to the present teachings;
[0025] FIGS. 14A-14D are diagrams of example fastener setting
systems according to the present disclosure in an example flowchart
depicting an example method of controlling a fastener setting
device for a transition from a fastener set mode to a fastener
clearing set mode according to the present teachings;
[0026] FIG. 15 is a partially diagrammatic, partially side
elevational view showing another embodiment of a riveting system
according to the present teachings; and
[0027] FIGS. 16A-16C represent a rivet clearing station and its
interaction with the fastener setting tool according to the present
teachings, where corresponding reference numerals indicate
corresponding parts throughout the several views of the
drawings.
DETAILED DESCRIPTION
[0028] The following description of the preferred embodiments is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses. Generally speaking, the system
sets a fastener for joining parts. The system is configured to
confirm the quality of the setting process and of the resultant set
as well as the status of the feed system. The system uses a rivet
setting machine 23 having a first member configured to apply a
setting force to a fastener to set the fastener. A coupling
structure is provided which is configured to apply reaction forces
to the first member in response to the setting force. Sensors of a
plurality of sensors attached to the feed mechanism's structure
individually sense changes in physical parameters within the feed
system induced by a moving or stationary fastener.
[0029] A sensor 34 is configured to measure the presence of a
fastener at a location which is a predetermined location within the
feed system. As described below, the sensor 34 is located at a
location on the feed tube which is susceptible to strains induced
by moments caused by the movement of the fastener. Because of its
location, the sensor 34 is capable of being calibrated to indicate
changes in physical parameters that can be displayed in comparative
terms. Further, because of its location, sensor 34 need not be
calibrated after routine maintenance such as the changing of dies
or punch components. Optionally, the sensor 34 can be optical,
magnetic, or magneto restrictive.
[0030] A first member or plunger 31 applies the setting force along
an axis to a first side of the fastener and the setting force is
resisted by a second member which applies a reaction force
generally parallel to the setting force. This reaction force is
caused by elastic deformation in the coupling structure. These
forces can be used to detect the quality of a rivet set and can be
used to set a default code. At this point, the system can determine
if an additional fastener is located within the feed system that
needs to be cleared.
[0031] Referring to FIGS. 1 and 2, a joining device for punch
rivets, hereinafter known as a riveting system 21, includes a
riveting machine or tool 23, a main electronic control unit 25, a
plurality of feed sensors 34 and 34', a rivet feeder 27, and
associated robotic movement mechanism and controls. Riveting tool
23 further has a drive mechanism which can be either hydraulic (not
shown) or electric. The electric drive has an electric motor 29, a
transmission unit, a plunger 31, a clamp 33, and a die or anvil 35.
The hydraulic drive, when used, can utilize hydraulic fluid driven
by a fluid initiated piston. The fluid initiated piston can be
driven by either hydraulic or pneumatic fluid. While not needed for
a blind fastener, the die 35 is preferably attached to a C-shaped
frame 37 or the like. Frame 37 also couples the advancing portion
of riveting tool 23 to a set of linear slides 39 which are, in
turn, coupled to an articulated robot mounted to a factory floor. A
linear slide control unit 41 and an electronic robot control unit
43 are electrically connected to linear slides 39 and main
electronic control unit 25, respectively. The slides 39 are
actuated by a pneumatic or hydraulic pressure source 45.
[0032] The transmission unit of riveting tool 23 can include a
reduction gear unit 51 and a spindle drive mechanism 53. Plunger
31, also known as a punch assembly, includes a punch holder and
punch, as will be described in further detail hereinafter. A data
monitoring unit 61 may be part of the electronic control unit 25,
as shown in FIG. 2, or can be a separate microprocessing unit, as
shown in FIG. 1, to assist in monitoring signals from the various
system monitoring sensors. As will be described in detail below,
the system also utilizes feed sensors, force sensors, and strain
sensors.
[0033] Referring to FIGS. 3, 5, and 6, the main electronic control
unit 25 contains a microprocessor, a display screen, indicator
lights, and input buttons. The main electronic control unit 25 is
also electrically connected to the feed sensor 34 and other
proximity switch sensors located in riveting tool 23. Electric
motor 29 can be of a brushless, three-phase alternating current
type. Energizing electric motor 29 serves to rotate an armature
shaft which, in turn, rotates an output gear 73. Electric motor 29
and output gear 73 are disposed within one or more cylindrical
outer casings.
[0034] Reduction gear unit 51 includes gear housings 75 and 77
within which are disposed two different diameter spur gears 79 and
81. Various other ball bearings 83 and washers are located within
housings 75 and 77. Additionally, removable plates 85 are bolted
onto housing 75 to allow for lubrication. Spur gear 79 is coaxially
aligned and driven by output gear 73, thus causing rotation of spur
gear 81. Adapters 87 and 89 are also stationarily mounted to
housing 77.
[0035] Referring to FIG. 4 and again to FIGS. 1-3, when the system
is associated with a self-piercing rivet, a nut housing 101 is
directly connected to a central shaft of spur gear 79, therefore
rotation of spur gear 79 causes a concurrent rotation of nut
housing 101. Nut housing 101 is configured with a hollow and
generally cylindrical proximal segment and a generally enlarged,
cylindrical distal segment. A load cell 103 is concentrically
positioned around a proximal segment of nut housing 101. Load cell
103 is electrically connected to a load cell interface 105 (see
FIG. 1) which, in turn, is electrically connected to monitoring
unit 61. Load cell 103 preferably has a direct current bridge
wherein the mechanical input force causes a change in resistance
which generates a signal. Alternately, the load cell may be of a
piezo-electric type.
[0036] A rotatable nut 111, also known as a ball, is directly
received and coupled with a distal segment of nut housing 101 such
that rotation of nut housing 101 causes a simultaneously
corresponding rotation of nut 111. Ball bearing members 113 are
disposed around nut housing 101. A spindle 115 has a set of
external threads which are enmeshed with a set of internal threads
of nut 111. Hence, rotation of nut 111 causes linear advancing and
retracting movement of spindle 115 along a longitudinal axis. A
proximal end of a rod-like punch holder 121 is bolted to an end of
spindle 115 for corresponding linear translation along the
longitudinal axis. A rod-like punch 123 is longitudinally and
coaxially fastened to a distal end of punch holder 121 for
simultaneous movement therewith.
[0037] An outwardly flanged section 125 of punch holder 121 abuts
against a spring cup 127. This causes compression of a relatively
soft compression spring 128 (approximately 100-300 newtons of
biasing force), which serves to drive a rivet out of the receiver
and into an initial loaded position for engagement by a distal end
of punch 123. A stronger compression spring 141 (approximately
8,000-15,000 newtons of biasing force) is subsequently compressed
by the advancing movement of punch holder 121. The biasing action
of strong compression spring 141 serves to later retract a clamp
143 and nose piece back toward gear reduction unit 51 and away from
the workpieces.
[0038] A main housing 145 has a proximal hollow and cylindrical
segment for receiving the nut and spindle assembly. Main housing
145 further has a pair of longitudinally elongated slots 147. A
sleeve 149 is firmly secured to punch holder 121 and has
transversely extending sets of rollers 151 or other such structures
bolted thereto. Rollers 151 ride within slots 147 of main housing
145. Longitudinally elongated slots 153 of clamp 143 engage
bushings 155 also bolted to sleeve 149. Thus, rollers 151 and slots
147 of main housing 145 serve to maintain the desired linear
alignment of both punch holder 121 and clamp 143, as well as
predominantly prevent rotation of these members. Additional
external covers 157 are also provided. All of the moving parts are
preferably made from steel.
[0039] Referring to FIGS. 3, 5, 8 and 12, one of the feed sensors
34 can be positioned either on the C-shaped support frame 37 or
within the nose housing of the punch. A spindle position proximity
switch sensor 201 is mounted within riveting tool 23. A
spring-biased upper die and self-locking nut assembly 203 serve to
actuate spindle position proximity switch sensor 201 upon the
spindle assembly reaching a fully retracted, home position. A plate
thickness proximity switch sensor 205 is also mounted within
riveting tool 23. An upper die-type thickness measurement actuator
and self-locking nut assembly 207 indicate the positioning of clamp
143 and thereby serve to actuate proximity switch sensor 205.
Additional proximity switch sensors 34 and 34' are located in a
feed tube for indicating the presence of a rivet therein in a
position acceptable for subsequent insertion into the receiver of
riveting tool 23. These proximity switch sensors 201, 205, 34 and
34' are all electrically connected to main electronic control unit
25 via a module 601. Furthermore, a resolver-type sensor 211 is
connected to electric motor 29 or a member rotated therewith.
Resolver sensor 211 serves to sense actuator torque, actuator
speed, and/or transmission torque. The signal is then sent by the
resolver to main electronic control unit 25. An additional sensor
(not shown) connected to electric motor 29 is operable to sense and
indicate power consumption or other electrical characteristics of
the motor which indicate the performance characteristics of the
motor; such a sensed reading is then sent to main electronic
control unit 25.
[0040] FIGS. 6 and 7 best illustrate a receiver 241 attached to a
distal end or head of riveting tool 23 adjacent punch 123. It is
envisioned that the receiver 241 can incorporate a feed sensor, as
previously described. An upper housing 243 is affixed to a lower
housing 245 by way of a pair of quick disconnect fasteners 247. A
clamp/nose piece portion 249 of the clamp assembly is screwed into
lower housing 245 and serves to retain a slotted feed channel 251,
compressibly held by an elastomeric O-ring 253. A pair of flexible
fingers 255 pivot relative to housings 243 and 245 and act to
temporarily locate a rivet 261 in a desired position aligned with
punch 123 prior to insertion into the workpieces. Compression
springs 262 serve to inwardly bias flexible fingers 255 toward the
advancing axis of punch 123. Furthermore, a catch stop 263 is
mounted to upper housing 243 by a pivot pin. Catch stop 263 is
downwardly biased from upper housing 243 by way of a compression
spring 265.
[0041] FIGS. 7 and 8 illustrate a feed tube 271 having end
connectors 273 and 275 and associated sensors 34 and 34'. End
connector 273 is secured to receiver 241 (see FIG. 8) and end
connector 275 is secured to feeder 27 (see FIG. 2). Feed tube 271
further includes a cylindrical outer protective tube 277 and an
inner rivet carrying tube 279. Inner rivet carrying tube 279 has a
T-shaped inside profile corresponding to an outside shape of the
rivet fed therethrough. Feed tube 271 is semi-flexible. Entry and
exit proximity switch sensors 36 and 36', respectively, monitor the
passage of each rivet through feed tube 271 and individually send
an indicating signal to main electronic control unit 25 (see FIGS.
2 and 15). The rivets are pneumatically supplied from feeder 27 to
receiver 241 through feed tube 271.
[0042] FIG. 9 shows the internal construction of the feeder 27. The
feeder 27 can have a stamped metal casing 301, upper cover 303, and
face plate 305. Feeder 27 is intended to be stationarily mounted to
the factory floor. A storage bunker 307 is attached to an internal
surface of face plate 305 and serves to retain the rivets prior to
feeding. A rotary bowl or drum 309 is externally mounted to face
plate 305. It is rotated by way of a rotary drive unit 311 and
associated shafts. A pneumatic cylinder 313 actuates drive unit 311
and is controlled by a set of pneumatic valves 315 internally
disposed within casing 301. An electrical connector 317 and
associated wiring electrically connect feeder 27 to main electronic
control unit 25 by way of module 601 (see FIGS. 2 and 12).
[0043] A pneumatically driven, sliding escapement mechanism 319 is
also mounted to face plate 305 and is accessible to drum 309. A
proximity switch sensor 34'' is mounted to escapement mechanism 319
for indicating passage of each rivet from escapement mechanism 319.
Proximity switch sensor 34'' sends the appropriate signal to the
main electronic control unit through module 601 (shown in FIG. 12).
Rotation of drum 309 causes rivets to pass through a slotted
raceway 323 for feeding into escapement mechanism 319, which aligns
the rivets and sends them into feed tube 271 (see FIG. 8).
[0044] According to a preferred embodiment, FIGS. 10A-10F and FIGS.
11A-11E show the riveting process steps employing the system of the
present invention. The preferred rivet employed is of a
self-piercing and hollow type which does not fully pierce through
the die-side workpiece. First, FIGS. 10A and 11A show the
clamp/nose piece portion 249 and punch 123 starting from retracted
positions relative to workpieces 50, 50' and moving thereto.
Workpieces 50, 50' are preferably stamped sheet metal body panels
of an automotive vehicle, such as will be found on a conventional
pinch weld flange adjacent a door and window openings. The robot
and linear slides will position the riveting tool adjacent the
sheet metal flanges such that clamp/nose piece portion 249 and die
35 sandwich workpieces 50, 50' therebetween at a target joint
location. It is alternately envisioned that a manually
(non-robotic) moved riveting tool or a stationary riveting tool can
also be used with the present invention.
[0045] FIG. 10B shows clamp/nose piece portion 249 clamping and
compressing workpieces 50, 50' against die 35. Punch 123 has not
yet begun to advance rivet 261 toward workpieces 50, 50'. At this
point, the plate thickness proximity switch senses the thickness of
the workpieces through location of the clamp assembly until the 4kn
clamp spring is fully compressed; the plate thickness switch sends
the appropriate signal to the main controller. Next, punch 123
advances rivet 261 to a point approximately 1 millimeter above the
punch-side workpiece 50. This is shown in FIGS. 10C and 11B. If the
workpiece thickness dimension is determined to be within an
acceptable range by the main electronic control unit, then the
electric motor further advances punch 123 to insert rivet 261 into
punch-side workpiece 50, as shown in FIG. 11C, and then
continuously advances the rivet into the die-side workpiece 50', as
shown in FIGS. 10D and 11D. Die 35 serves to outwardly deform and
diverge the distal end of rivet 261 opposite punch 123.
[0046] FIG. 10E shows the system measuring the plate thickness of
the workpieces 50, 50'. Finally, punch 123 and clamp/nose piece
portion 249 are fully engaged to bring the fastener into engagement
with the workpieces 50, 50'. This allows the system to measure the
size of the fastener to determine if a fastener has been missfed.
Subsequently, the punch 123 and clamp/nose piece portion 249 are
fully removed from the workpieces 50, 50' to be separated and
removed from die 35 if an acceptable riveted joint is determined by
the main electronic control unit based on sensed joint
characteristics. As shown in FIG. 11E, an acceptable riveted joint
has an external head surface of rivet 261 positioned flush and
co-planar with an exterior surface of punch-side workpiece 50'.
Also, in an acceptable joint, the diverging distal end of rivet 261
has been sufficiently expanded to engage workpiece 50' without
piercing completely through the exterior surface of die-side
workpiece 50.
[0047] A simplified electrical diagram of a preferred embodiment
riveting system is shown in FIG. 12. Main electronic control unit
25, such as a high-speed industrial microprocessor computer, having
a cycle time of about 0.02 milliseconds has been found to be
satisfactory. A separate second microprocessor controller 61 is
connected to main electronic control unit 25 by way of an analog
input/output line 602 and an Encoder2 input 604 which measures the
position of the spindle through a digital signal. Second
microprocessor controller 61 receives an electric motor signal and
a resolver signal. The load cell force signal is sent directly from
the tool to the main electronic control unit 25 while the proximity
switch signals (from the feeder, feed tube, and spindle home
position sensors) are sent from the tool through an input/output
delivery microprocessor module 601 and then to main electronic
control unit 25. Input/output delivery microprocessor module 601
actuates error message indication lamps 603, receives a riveting
start signal from an operator activatable switch 605, and relays
control signals to feeder 27 from main electronic control unit 25.
An IBS/CAN gateway transmits data from main electronic control unit
25 to a host system which displays and records trends in data such
as joint quality, workpiece thickness, and the like.
[0048] FIG. 13 is a feed/distance (displacement) graph showing a
sequence of a single riveting operation or cycle and is directed
with continuing reference to FIGS. 5-7 and 10A-10H. The first
spiral spring distance range is indicative of the force and
displacement of punch 123 due to light spring 128. The next
displacement range entitled hold-down spring is indicative of the
force and displacement generated by heavy spring 141, clamp 143,
and the associated clamp/nose piece portion 249. As described above
in the description of FIGS. 10A-10H, measurement of the sheet
metal/workpiece thickness occurs at a predetermined point within
this range by way of load cell 103 interacting with main electronic
control unit 25. In the next rivet length range, the rivet length
is sensed and determined through load cell 103 and main electronic
control unit 25. In the distance range between 25 and 30 mm, the
middle line shown is the actual rivet signature sensed, while the
upper line shown is the maximum tolerance band, and the lower line
shown is the minimum tolerance band of an acceptable rivet length
for use in the joining operation. If an out-of-tolerance rivet is
received and indicated, the software will discontinue or "break
off" the riveting process and send the appropriate error
message.
[0049] The plunger, and optionally the clamp, can also be movable
from a predeterminable rest position that can be changed through
the computer software. The rest position of the plunger, and
optionally of the clamp, is selected as a function of the design of
the parts to be joined. If the parts to be joined are smooth metal
plates, the distance between a riveting unit which comprises the
plunger and the clamp and a die can be slightly greater than the
thickness of the superimposed parts to be joined. If a part to be
joined has a ridge, as viewed in the feed direction of the part to
be joined, the rest position of the riveting unit is selected such
that the ridge can be guided between the riveting unit and the die.
Therefore, it is not necessary for the riveting unit always to be
moved into its maximum possible end or home position.
[0050] A force or a characteristic corresponding to the force of
the plunger, and optionally of the clamp, can be measured as a
function of a change in strain within the rivet setting apparatus.
This produces a measured level. This is compared with a desired
level. If comparison shows that the measured level deviates from
the desired level by a predetermined limit value in at least one
predetermined range, a signal is triggered. This process control
advantageously permits qualitative monitoring of the formation of a
punch connection.
[0051] The feeder system includes the monitoring circuit configured
to receive feed startup signals from a first sensor 34' in the feed
system. The robot arm has a second sensor 42', while the setting
tool has a third sensor 42'. The monitoring circuit is configured
to monitor these sensors to determine if a fault condition is
detected. Should a fault condition be detected, the monitoring
system initiates a rivet clearing procedure.
[0052] The monitoring circuit can measure the feed of a fastener
along an axial path of the feed tube 271. In this regard, the
monitoring circuit measures the time between pulses and compares
these pulses, as well as the timing of the pulses, to predetermined
values. Should these values be out-of-tolerance, an error is issued
and an improper feed signal can be provided. The signals can be
compared to an associated test set of signals. This way, the
monitoring circuit can determine if a fastener feed has been
properly completed.
[0053] FIGS. 14A-14D show a flow chart of the computer software
used in the main electronic control unit 25 for the preferred
embodiment riveting system of the present invention. The beginning
of the riveting cycle is started through an operator actuated
switch, whereafter the system waits for the spindle to return to a
home position. From a prestored memory location, a rivet joint
number is read in order to determine the prestored characteristics
for that specific joint in the automotive vehicle or other
workpiece (e.g., joint number 16 out of 25 total). Thus, the
workpiece thickness, rivet length, rivet quality, and force versus
distance curves are recalled for comparison purposes for the joint
to be riveted.
[0054] Next, the software determines if a rivet is present in the
head based upon a proximity switch 34' signal. If not, the feeder
27 is energized to cause a rivet to be fed into the head. The
spindle is then moved and the workpiece is clamped. The plate or
workpiece thickness is then determined based on the load cell
signals and compared against the recalled memory information
setting forth the acceptable range. If the plate thickness is
determined to be out of tolerance, then the riveting process is
broken off or stopped. If the plate thickness is acceptable for
that specific joint, then the rivet length is determined based on
input signals from the load cell. If the punch force is too large,
too soon in the stroke, then the rivet length is larger than an
acceptable size, and vice versa for a small rivet. The riveting
process is discontinued if the rivet length is out-of-tolerance. At
any of these faults, the system will determine if a rivet is within
the feed mechanism and initiate a clearing mode.
[0055] The spindle is then retracted after the joint is completed.
As described below, the system will monitor the output of the feed
sensor 34 to determine if a rivet set is acceptable. After the
spindle is opened or retracted to the programmed home position,
which may be different than the true and final home position,
indicator signals are activated to indicate if the riveted joint
setting is acceptable (if the riveting cycle is complete) and is
ready for the next rivet setting cycle. It should also be
appreciated that various resolver signals and motor power
consumption signals can also be used by second microprocessor 61 to
indicate other quality characteristics of the joint, although they
are not shown in these flow diagrams. However, such sensor readings
would be compared against prestored memory values to determine
whether to continue the riveting process or discontinue the
riveting process and send an error signal. Motor sensor readings
can also be used to store and display cycle-to-cycle trends in data
to an output device such as a CRT screen or printout.
[0056] Shown is a separate software subroutine of error messages if
the riveting process is broken off or discontinued. For example, if
the plate thickness is unacceptable, then an error message will be
sent, stating that the setting is not okay, with a specific error
code. Similarly, if the rivet length was not acceptable, then a not
okay setting signal will be sent with a specific error code. If
another type of riveting fault has been determined, then another
rivet setting not okay signal will be sent and a unique error code
will be displayed. In this event, a rivet clearing routine is
initiated.
[0057] Also represented are methodologies to determine if a rivet
has been improperly set and if it has initiated the rivet clear
module. The statistically significant feed and time or distance
coordinates from these subsequent self-piercing rivet settings are
monitored and collated. An exemplary set of data is formed from
these feed verse time data. Tolerance bands are constructed based
on the statistically significant sets of training data. There are
various conditions that may exist in the setting of self-piercing
rivets and these will be described separately.
[0058] To generate a baseline to compare the quality of rivets, a
baseline rivet feed curve is generated. FIG. 14A represents the
system performance after a rivet clear mode has been initiated.
FIGS. 14B-14D represent the detection of a plurality of rivets by
comparing detected sensor signal curves to curves which are used to
generate average feed or presence versus time curves to be used by
the system. Specifically, the detection of a fastener having a
length which is too long, too short, or not to spec. Optionally,
statistical techniques can be employed related to strains in the
rivet setting system to determine if a sample load versus time
curve is close enough to the meeting curve to determine if the
specific curve is usable in formulating the meeting curve. Once the
baseline curve is developed a pulse curve (FIG. 13), the system 21'
tracks the feed or pressure versus time data of each rivet set to
determine if the system has created a potentially defective
set.
[0059] Should a defective set be detected, the system (see FIG.
14A) issues a warning and initiates the fastener clearing module.
In this case, the robotic arm is instructed to move the fastener
setting mechanism to a clearing station (see FIGS. 16A-16C). At the
clearing station, a plate having a dummy hole allows for the
mechanism to set the fastener, thus clearing the feed mechanism.
The system then checks to determine if a fault code still
exists.
[0060] In this system, all portions of the medium curve have the
specific fixed-size tolerance band defined around them. The system
then tracks the feed timing or sensing versus time data or curve of
an individual rivet set to determine whether it falls outside of
the tolerance band. In case the rivet does fall outside of the
specific tolerance band, an alarm or warning is presented to the
line operator.
[0061] FIGS. 14B and 14C represent the feeding of an incorrect
rivet. In this regard, the flow chart describes the detection of a
fastener being too short or too long. Specifically, it should be
noted that the varying tolerance heights depend on the portion of
each curve. Should a defective set be detected, the system issues a
warning and initiates the fastener clearing module (see FIG. 14A).
In this case, the robotic arm is instructed to move the fastener
setting mechanism to the clearing station. At the clearing station,
a plate having a dummy hole allows for the mechanism to set the
fastener, thus clearing the feed mechanism. Optionally, the system
monitors the feeding system and identifies the length of time T1
needed to feed the rivet. T1 is compared to an example Time Te to
determine if an acceptable rivet set occurs.
[0062] The system for setting a fastener includes a mode control
module, a robot control module, and a fastener set module. The
fastener set module selectively sets a fastener feed mode, a
fastener set mode, and a fastener clear mode. In response to the
fastener set signal, the module transfers from one of the set mode
and feed mode to the clear mode.
[0063] Optionally, as shown in FIG. 14A, if a defect is detected
the robot control module operates a fastener set mechanism clear
mode during a fastener clear cycle. The system then operates a
mandrel clear mode during a first robotic cycle and operates a
drive coupled to a mandrel actuator. During the feeder clear
operation, the fastener setting mechanism is moved by the robotic
arm to the clearing station. The rivet is then fed into the setting
mechanism which is actuated to set the fastener into a dummy
location.
[0064] A method for clearing a fastener setting device according to
the present teachings includes selectively setting a fastening mode
for a fastener setting apparatus to one of a feeding mode, a
setting mode, and a clearing mode. In response to one of the
feeding mode or the setting mode, in the clearing mode during a
first system cycle a mandrel actuator operates in a fastener
setting mode.
[0065] The system has a monitoring circuit or module which has
circuitry to receive a feed status signal from the sensor within
the feed system. The system also is configured to receive a robotic
arm status signal from a sensor within the robotic control system
and a rivet set status signal from the sensor within the feed
system. An example set of output/time signals is formed and used to
initiate a rivet clearing procedure if the feed status signal is
positive, and should a fault condition be detected. An operator is
optionally prompted to initiate the clearing procedure.
[0066] The monitoring circuit further includes circuitry to
produce, from a series of feed status signals, a measured rivet set
status dataset. The circuit scans the measured rivet set status
dataset to determine a first last local feed value. The example
rivet set status dataset is scanned to determine a second last
local feed value. At this point, the system determines if the first
last local feed value and the second local feed values are within
one of a predetermined time tolerance band or within a
predetermined feed size tolerance band. The feed sensor is
configured to measure feed in an axial direction. Should a fault
condition be detected, an operator is prompted to initiate the
clearing procedure.
[0067] The system further includes an indicator operatively
connected to the measurement circuit for signaling to an operator
the acceptability of the set based on the comparison of the feed
output/predetermined value pairs. The first transducer can be a
micro-strain sensor, a metal detector, or an optical sensor.
[0068] Optionally, the method of producing a rivet set status
dataset is based on a series of measured feed signals and scanning
the feed-versus-time dataset to determine the point in time during
the rivet setting process when the highest value of feed occurred.
The method can include the steps of monitoring the axial feed of a
fastener during a rivet setting process and producing a series of
feed signals related thereto. Then, the system monitors the time of
the rivet setting process and producing a series of time signals
related thereto and identifies the occurrence during the rivet
setting process of an improper feed or set. This information is
used to identify the occurrence of the initiation of the rivet
setting process and to determine if an improper feed occurred to
identify a fault. Upon the detection of a fault, the system, upon
clearance by an operator, initiates a rivet feed mode. This mode
includes moving the fastener setting head to a location a distance
away from the workpiece and setting the fastener into a "dummy"
plate. The system will then again check the status of the feed
sensors to determine if a fastener is within the feed system.
[0069] The system produces a rivet feed status waveform based on
the series of feed signals and the series of time signals produced
over the rivet setting process. The rivet feed status waveform is
used to identify the location of a feed peak in the waveform; and
the system uses the location of the feed peak to identify the total
time of the rivet feed event. The system then compares the rivet
set status waveform with an example rivet set status waveform to
determine if the rivet set is acceptable.
[0070] It is envisioned (see FIG. 15) that two separate rivet
feeders 27 and 27' can be employed. Rivet feeders 27 and 27' are of
the same general construction as that disclosed above; however, the
rivet length employed in the feeders 27, 27' can vary. Each feeder
27 and 27' transmits the specific length rivets to a selector
junction device 40 by way of separate input feed tubes 30 and 30'.
Selector device 40 has a pneumatically actuated reciprocating slide
mechanism which is electrically controlled by a main electronic
control unit 47. When main electronic control unit 47 recalls the
specific joint to be worked on, it then sends a signal to selector
device 40 as to which rivet length is needed. Selector device 40
subsequently mechanically feeds the correct rivet through a single
exit feed tube 44 which is connected to a receiver 38 of riveting
tool 23. It is envisioned sensors 36 and 34' can be used to monitor
the feed system.
[0071] Thus, a single riveting tool can be used to rivet multiple
joints having rivets of differing selected sizes or material
characteristics without the need for complicated mechanical
variations or multiple riveting tool set ups. The software program
within main electronic control unit 47 can easily cause differing
rivets to be sent to the single riveting tool 23, and changes can
be easily made by reprogramming the main electronic control unit.
This saves space on the crowded assembly plant line, reduces
mechanical complexity, and reduces potential failure modes.
[0072] Referring to FIGS. 16A-16C and again to FIG. 3, a discharge
station 815 is provided according to the present teachings.
Discharge station 815 includes a dummy plate 816 and an associated
collection container 817. Optionally, the discharge station 815 can
provide plate 816 of a predetermined thickness having a hole
defined therein. When the fastener setting mechanism 23 is moved to
the discharge station, the feeder 27 is engaged to feed the
fastener to the setting mechanism 23. A sensor 818 is disposed at
the discharge station. Sensor 818 issues a signal when the fastener
has left the upper housing 243 of receiver 241. The electronic
control unit 25 upon receipt of the signal from sensor 818 actuates
the fastener setting mechanism 23. After being positioned, the
fastener is then set into the dummy plate 816. Optionally, the
detection system will then recheck the feeder mechanism to
determine if a second fastener has been fed. Electronic control
unit 25 confirms if a second fastener is detected, the fastener
setting mechanism 23 leaves the discharge station, and the feeder
27 will feed the second fastener to the fastener setting mechanism
23 for removal.
[0073] FIG. 16C represents the retraction of the fastener setting
tool 23 with the discharge station. It is envisioned the dummy
plate can have an aperture which is oversized to facilitate the
disposal of blind or self-piercing rivets. Optionally, the dummy
plate can be indexable and capture the discarded fasteners
therein.
[0074] The accuracy of riveting, as well as measurements in the
preferred embodiment, is insured by use of the highly accurate
electric servo motor and rotary-to-linear drive mechanism employed.
For example, the rivet can be inserted into the workpieces with one
tenth of a millimeter of accuracy. The control system of the
present invention also provides a real time quality indication of
the joint characteristics, rather than the traditional random
sampling conducted after many hundreds of parts were improperly
processed. Thus, the present invention achieves higher quality,
greater consistency, and lower cost riveted joints as compared to
conventional constructions.
[0075] It should be noted that depending on the type of fastener or
fastener setting equipment used, different shaped quality and feed
curves are equally possible. As described below, while the time
duration and magnitude of portions of these curves can vary by
specific amounts, large deviations of these curves represent either
a failure of the rivet set or a failure of the structure. As the
system utilizes an average of "good" sets histories to set an
acceptable median feed profile, the profile generated by the system
is relatively independent of the orientation of the sensor 34 on
feed system 27 or the specific manufacturing environment of the
C-shaped frame 37. This is opposed to other systems which use load
cell versus stroke length to perform an interpretation of an
independent load stroke curve.
[0076] The foregoing description is merely illustrative in nature
and is in no way intended to limit the disclosure, its application,
or uses. The broad teachings of the disclosure can be implemented
in a variety of forms. Therefore, while this disclosure includes
particular examples, the true scope of the disclosure should not be
so limited since other modifications will become apparent upon a
study of the drawings, the specification, and the following claims.
For purposes of clarity, the same reference numbers will be used in
the drawings to identify similar elements. As used herein, the
phrase at least one of A, B, and C should be construed to mean a
logical (A or B or C), using a non-exclusive logical OR. It should
be understood that one or more steps within a method may be
executed in different order (or concurrently) without altering the
principles of the present disclosure.
[0077] Example embodiments are provided so that this disclosure
will be thorough, and will fully convey the scope to those who are
skilled in the art. Numerous specific details are set forth such as
examples of specific components, devices, and methods, to provide a
thorough understanding of embodiments of the present disclosure. It
will be apparent to those skilled in the art that specific details
need not be employed, that example embodiments may be embodied in
many different forms and that neither should be construed to limit
the scope of the disclosure. In some example embodiments,
well-known processes, well-known device structures, and well-known
technologies are not described in detail.
[0078] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a," "an," and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. The
method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the
particular order discussed or illustrated, unless specifically
identified as an order of performance. It is also to be understood
that additional or alternative steps may be employed.
[0079] When an element or layer is referred to as being "on,"
"engaged to," "connected to," or "coupled to" another element or
layer, it may be directly on, engaged, connected or coupled to the
other element or layer, or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly engaged to," "directly connected to," or
"directly coupled to" another element or layer, there may be no
intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0080] Although the terms first, second, third, etc. may be used
herein to describe various elements, components, regions, layers
and/or sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the example embodiments.
[0081] Spatially relative terms, such as "inner," "outer,"
"beneath," "below," "lower," "above," "upper," and the like, may be
used herein for ease of description to describe one element or
feature's relationship to another element(s) or feature(s) as
illustrated in the figures. Spatially relative terms may be
intended to encompass different orientations of the device in use
or operation in addition to the orientation depicted in the
figures. For example, if the device in the figures is turned over,
elements described as "below" or "beneath" other elements or
features would then be oriented "above" the other elements or
features. Thus, the example term "below" can encompass both an
orientation of above and below. The device may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
spatially relative descriptors used herein interpreted
accordingly.
[0082] As used herein, the term module may refer to, be part of, or
include an Application Specific Integrated Circuit (ASIC); an
electronic circuit; a combinational logic circuit; a field
programmable gate array (FPGA); a processor (shared, dedicated, or
group) that executes code; other suitable hardware components that
provide the described functionality; or a combination of some or
all of the above, such as in a system-on-chip. The term module may
include memory (shared, dedicated, or group) that stores code
executed by the processor.
[0083] The term code, as used above, may include software,
firmware, and/or microcode, and may refer to programs, routines,
functions, classes, and/or objects. The term shared, as used above,
means that some or all code from multiple modules may be executed
using a single (shared) processor. In addition, some or all code
from multiple modules may be stored by a single (shared) memory.
The term group, as used above, means that some or all code from a
single module may be executed using a group of processors. In
addition, some or all code from a single module may be stored using
a group of memories.
[0084] The apparatuses and methods described herein may be
implemented by one or more computer programs executed by one or
more processors. The computer programs include processor-executable
instructions that are stored on a non-transitory tangible computer
readable medium. The computer programs may also include stored
data. Non-limiting examples of the non-transitory tangible computer
readable medium are nonvolatile memory, magnetic storage, and
optical storage.
* * * * *