Note: Descriptions are shown in the official language in which they were submitted.
2~6904~
C-4311
G-4593
SYSTEM FOR PERFORMING RELATED OPERATIONS
ON WORKPIECES _
Cross Reference To Related Application
This application is related to applicant's
copending U.S. application Serial No. 07/660,761 filed
simultaneously herewith, entitled "System For
Performing Work on Workpieces."
Field of the Invention
This invention relates to a sy~tem for
performing related operations on workpieces and, more
particularly, to an apparatus and method for applying
coatings onto predetermined portions of circuit boards
and then curing the coatings.
Background of the Invention
In fabricating circuit boards, a coating is
usually applied to certain portions thereof either to
mask them temporarily during subsequent processing or
to protect them permanently.
Temporary masking is typically effected by
selectively coating the concerned portions of the
circuit board with a maskant-type coating material that
is stripped from the board at a later fabrication
stage. Permanent protection is typically effected by
coating the concerned portions of the circuit board
with a conformal type coating material that conforms to
the surface configuration of the board to seal
20~9~45
therewithin pertinent circuit components of various
shapes and heights on the board that are to be
protected. In both cases, the coating is usually
subjected to curing to impart structural integrity
thereto.
U.S. Patent No. 4,254,163 tPiazza) shows a
thermographic printing method for making a given type
printed circuit on a metal clad substrate. Resin
powder is dusted onto a pattern of non-dryable,
hydrophobic and heat non-spreadable, liquid ink on the
substrate, the powder adhering only to the ink. Heat
fusing the powder to the ink forms a strippable mask
which is stripped to form the circuit after etching the
ink-free substrate areas.
U.S. Patent No. 4,287,226 (Pirvics et al.)
shows the curing of an ultraviolet (UV) light curable
resin to form a protective coating on a given type
circuit element-containing substrate. The resin is
exposed to UV light through a silk screen having opaque
areas that mask the UV light from corresponding areas
of the resin that are not to be cured. Assumably, the
non-cured resin areas of the coating are thereafter
stripped.
U.S. Patent No. 4,826,705 (Drain et al.)
shows the mechanical stripping of a laminated portion
of a conventionally cured conformal coating and
underlying ultraviolet light cured temporary mask that
cover an edge connection area on a given type printed
circuit board, thereby exposing the area. The cured
mask is readily stripped in one piece in the manner of
adhesive tape.
20~9~
U.S. Patent No. 4,830,922 (Sparrowhawk
et al.) shows use of a solvent removable coating of
glass microspheres in a grease as a temporary
protective conformal coating for ~elective components
of various shapes and heights on a given type circuit
board.
U.S. Patent ~o. 4,623,559 (Hudock) show6 an
assembly line conveyor for dipping a given type
thermistor ir~ a bath of ultraviolet (UV) light curable
coating material, and then passing each thermistor
under UV light to cure the coating.
U.S. Patent No. 4,695,482 (Weiswurm) shows an
assembly line conveyor for programmed top and bottom
side coating and curing of two different types of
circuit boards horizontally clipped thereto. At a ~ole
station, a sensor stops the conveyor on sensing a
board, and the appropriate one of two identifiers
determines the type board sensed. This causes the
appropriate one of two types of upper nozzle sets to
descend to the board for selectively spray coating its
top side. At the same time, its bottom side is grossly
coated by an underlying wave coating unit. The nozzle
set is then raised and the conveyor restarted for
sensing and spraying the next board in time-consuming
sequential tandem steps at the sole station. The
coated boards continue on the conveyor for intermittent
travel through an oven for curing.
U.S. Patent No. 3,836,388 (Fowler) shows a
manually operated batch apparatus for applying a
silicone rubber coating on a given type
circuit-containing substrate, in sets of four
2 ~ A 5
substrates at a time. Each set of coated substrates is
then transferred by the operator to the next available
one of a plurality of cam actuated vacuum degassing
chambers on an adjacent manually operated rotary table
(dial), after the operator removes a previously
degassed set of coated substrates from that chamber for
curing elsewhere.
U.S~ Patent No. 4,661,368 (Rohde et al.)
shows a program controlled spray nozæle movable to
apply adhesive dots to a ~iven type circuit board for
holding later added components.
U.S. Patent No. 4,560,584 (Henninger) shows a
program controlled spray nozzle movable to apply
individual dots of liquid solder resist material onto
selected portions of a given type circuit board to mask
such portions and prevent them from being coated in a
subsequent wave soldering step. The resist material is
then removed in a cleaning step.
U.S. Patent Nos. 4,753,819 and 4,880,663
(Shimada) commonly show a program controlled spray
nozzle movable to apply a flowable, e.g., conformal,
coating material selectively onto predetermined
portions of a circuit board having circuit components
of various shapes and heights. Airless spraying
technique is used to coat such portions without
overspraying onto adjacent board portions not intended
to be coated.
Nordson Corporation (Nordson Electronics
Business Group, Amherst, OH), Product Data Sheet
306-18-857, issued 2/89, shows a local or an in-line,
program controlled, spray nozzle conformal coating
206~
system for selectively coating a given type circuit
board by a robotic unit available in 4-axis and 5-axis
configurations.
Integrated Technologies, Inc. (Acushnet, MA),
Product Data Sheet~, Series S5000 and CL7000, also show
program controlled spray nozzle conformal coating
systems for selectively coating a given type circuit
board by robotic units.
None of these prior art teachings involves
the uninterrupted performing of respective sequential
operations simultaneously at successive stations of a
multiple station assembly line, selectively on randomly
differing types of workpiece& in individually differing
orientation, respectively at the stations.
It is desirable to provide a system for
performing related operations on workpieces of
different types in random order in assembly line
fashion, wherein the system is flexible in that it
enables work to be performed selectively on each
workpiece, regardless of its type, orientation or
assembly line order, without interrupting on-line
processing to adjust the system to each type workpiece,
and wherein the system is also synchronous in that it
enables related operations to be performed in sequence
"in-line," i.e., while keeping up with on-line
production speed.
Summary_of the Invention
In accordance with the present invention, a
system is provided for performing related operations on
workpieces of different types in random order in
- 5
2 ~ 4 ~
assembly line fashion. The ~ystem contemplates an
apparatus and method for performing the related
operations, including initial and 6ubsequent work, such
as the selective masking or conformal coating of
irradiation curable, flowable coating material onto
predetermined portions of circuit boards, followed by
irradiation curing of the coating.
The system is flexible in that the related
operations are performed "in line," i.e., without
interrupting the assembly line operation to adjust it
to each of the individual types of workpieces or their
individually differing orientation, even though they
vary randomly in order. The system is synchronous in
that the related operations are performed in sequence
"in-line," i.e., while keeping up with on-line
production speed.
The apparatus in accordance with the
invention contemplates a rotary table comprising
circumferentially spaced-apart table sections, and
having rotating means for rotating the table stepwise
to move each section in cycles successively at
selective intervals from a load-unload ~tation to a
sensing station, next to an initial work station, then
to a subsequent work station, and in turn back to the
load-unload station.
A plurality of at least two different types
of carriers are receivable in random order respectively
on the table sections. Each type carrier is
distinctive for carrying an associated type of
workpiece different from that of each of the other
types of carriers, and has holder means for holding its
206~
associated type workpiece in at least two different
alternative orientations to perform work on
respectively predetermined portion6 thereof in each
orientation.
Sensing means are provided for sens~ng the
type and orientation of a workpiece held on a carrier
on a respective table section at the sensing station.
Initial work performing means are provided to
perform initial work selectively on such predetermined
portions of a workpiece held in a given said
orientation on a respective section at the initial work
station. The initial work performing means are
operated in dependence upon the workpiece type and
orientation previously sensed at the sensing station.
Subsequent work performing means are provided
to perform subsequent work on a workpiece held in the
said orientation on a respective table section at the
subsequent work station, the subsequent work being
related to the initial work performed thereon
previously at the initial work station. The subsequent
work performing means are operated in dependence upon
the workpiece type and orientation previously sensed at
the sensing station for the corresponding workpiece.
Control means are used for c~ntrolling the
rotating means, sensing means, initial work performing
means and subsequent work performing means for
selective interval stepwise operation, to permit
loading and unloading of the carriers in random order
respectively onto and from the table sections at the
load-unload station, workpiece type and orientation
sensing at the sensing station, predetermined portion
205~04~
workpiece initial work per~orming at the initial work
station and related subsequent work performing on the
corresponding workpiece at the subsequent work station,
between stepwise movements of the 6ections.
Each table section suitably has receiving
means to receive a respective carrier thereon.
Indicator means may be associated with each carrier to
indicate the associated type workpiece, the indicator
means being arranged for sensing by the sensing means
when the carrier is on a section at the sensing
station.
Each carrier holder means may comprise a
first holder to hold an associated type workpiece in a
first orientation for performing initial and subseguent
work on predetermined first portions thereof, and a
second holder to hold an associated type workpiece in a
second orientation for performing initial and
subsequent work on predetermined second portions
thereof. The first holder may be arranged to hold the
workpiece such that a portion thereof occupies a first
region relative to the carrier, and the second holder
may be arranged to hold the workpiece such that a
portion thereof occupies a second region relative to
the carrier which is distinct from the first region.
The sensing means may comprise signal beam
projecting means for projecting a first beam along a
first sensing path intersecting the first region when
the workpiece is in the given said first orientation on
the carrier on a table section at the sensing station,
and for projecting a second beam along a second sensing
path intersecting the second region when the workpiece
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is in a given said second orientation on the carrier
thereat. In this way, a workpiece in a said
orientation on an associated carrier at the sen6ing
station interrupts the corresponding beam for sensing
S its orientation.
The initial work performing means may include
dispensing means comprising a movable nozzle to
dispense a flow of irradiation curable coating
material, and moving means. The moving means move the
nozzle along a first predetermined coating path to coat
the dispensed coating material selectively onto
predetermined first portions of a workpiece in a first
said orientation on an associated carrier on a table
section at the initial work station, and alternatively
along a second predetermined coating path to coat the
dispensed coating material selectively onto
predetermined second portions of the workpiece in a
second said orientation on the carrier on a table
section at the initial work station, in dependence upon
the workpiece type and orientation previously sensed at
the sensing station.
The subsequent work performing means may
include irradiation means for supplying radiation at
the subsequent work station for curing thereat the
coating of coating material previously coated onto
predetermined portions of a corresponding workpiece at
the initial work station. The subsequent work
performing means may also include irradiation operating
means for initiating and terminating the supply of
radiation from the irradiation means.
The control means control the dispensing
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means, moving means and irradiation operating means for
selective interval stepwise operation to permit
predeterminecl portion workpiece coating at the initial
work station and corresponding workpiece curing at the
subsequent work station, between stepwise movements of
the table sections.
Typically, the workpieces are circuit boards
each having first and second sides, and each holder is
arranged to hold an associated type circuit board in a
first orientation such that the first side of the
circuit board is exposed for selectively initially
coating and subsequently irradiating predetermined
first portions thereof, and alternatively in a second
orientation such that its second side is exposed for
selectively initially coating and subsequently
irradiating predetermined second portions thereof.
The moving means are arranged to move the
nozzle in a generally horizontal linear first
direction, in a generally horizontal linear second
direction crosswise of the first direction, and in a
generally vertical linear third direction. The moving
means desirably also move the nozzle in a rotational
fourth direction about a generally vertical axis and in
a rotational fifth direction about a generally
horizontal axis.
The apparatus of the invention favorably
contemplates automatic operation. Specifically, the
control means are arranged to control the rotating
means, sensing means, initial work performing means and
subsequent work performing means for selective interval
stepwise automatic operation, to permit loading and
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unloading of the carriers in random order respectively
onto and from the table section6 at the load-unload
station, automatic workpiece type and orientation
sensing at the sensing station, and automatic
predetermined portion workpiece initial work performing
at the initial work station and automatic related
subsequent work performing on the corresponding
workpiece at the subsequent work 6tation, between
automatic stepwise movements of the table sections.
The method in accordance with the invention
contemplates performing related work operations on
workpieces of different types in random order in
assembly line fashion, by a series of related steps.
These include rotating the table stepwise at
selective intervals to move each section stepwise in
cycles successively from the load-unload station to the
sensing station, next to the initial work station, then
to the subsequent work station and in turn back to the
load-unload station, and providing the plurality of
different types of carriers, each distinctive for
carrying its type workpiece and capable of holding such
a workpiece in at least two different alternative
orientations to perform work on respectively
predetermined portions thereof in each orientation, as
well as providing such a workpiece on each carrier in a
said orientation.
Then, the following steps are carried out
therewith, between stepwise movements of the table
sections:
(1) loading in random order a carrier holding
an associated type workpiece in a said orientation onto
11
20690~
each section, on stepwise movement of the respective
section to the load-unload station,
(2~ sensing the type and orientation of the
workpiece, on stepwise movement of the respective
section to the sensing ~tation,
(3) performing initial work selectively on
said predetermined portions of the workpiece in the
said orientation, on stepwise movement of the
respective section to the initial work station, the
initial work being performed in dependence upon the
type and orientation of the workpiece previously sensed
at the sensing station,
(4) performing subsequent work selectively on
said predetermined portions of the workpiece in the
said orientation, on stepwise movement of the
respective table section to the subsequent work
station, the subsequent work being related to the
initial work performed thereon previously at the
initial work station, the subsequent work being
performed in dependence upon the type and orientation
of the workpiece previously sensed at the sensing
station for the corresponding workpiece,
(5) selectively either changing the workpiece
from the said orientation to another said orientation
on the associated carrier, or alternatively unloading
such carrier and loading in random order another
carrier holding an associated type workpiece in a said
orientation, on stepwise movement of the respective
section to the load-unload station to complete a cycle,
and
(6) repeating said steps sufficiently to
12
~06904~
complete at least one further cycle.
Desirably, the steps are effected 6uch that
at least one of the cycles includes the selective step
of changing of a workpiece from the said orientation to
S another said orientation on an associated carrier, and
the repeating of the steps sufficiently to complete at
least one further cycle.
The step of performing initial work
advantageously comprises coating an irradiation
curable, flowable coating material selectively onto
such predetermined portions of the workpiece in the
given said orientation. The step of performing
subsequent work advantageously compri~es irradiating
the coating of coating material previously coated on
lS the corresponding workpiece, for curing the coating.
The irradiating is conveniently effected with
ultraviolet (UV) light.
Thus, where the workpieces have first and
second sides, each workpiece may be held on the
associated carrier either in a first orientation such
that the first side of the workpiece is exposed for
selectively initially coating and subsequently
irradiating predetermined first portions thereof, or
alternatively in a second orientation such that the
second side thereof is exposed for selectively
initially coating and subsequently irradiating
predetermined second portions thereof.
In particular, the workpieces comprise
circuit bGards each having a different pattern of
circuit components on its first and second sides. The
coating material may be an irradiation curable masking
13
206904~
material for masking selectively circuit component# on
a corresponding side of the circuit bo~rd, or an
irradiation curable conformal coating material for
sealing the circuit components on a corresponding side
thereof. The workpieces typically have opposed first
and second sides, and the selective step of changing
the workpiece from the said orientation to another said
orientation is effected by turning over the workpiece
to expose its other corresponding side.
Typically, carrier loading and the step of
selectively either changing the workpiece or
alternatively unloading such carrier is effected
manually, and the steps of sensing the workpiece type
and orientation, performing initial and related
subsequent work on the predetermined portions of the
workpiece, and rotating the table stepwise at selective
intervals, are effected automatically. The table
conveniently comprises four sections and is rotated to
move each section stepwise successively from the
load-unload station to the sensing station, next to the
initial work station, then to the subse~uent work
station and in turn back to the load-unload station.
According to a further method embodiment, a
carrier holding an associated type workpiece in a said
orientation is provided on each table section, for said
steps of sensing and performing initial and subsequent
work, after which the workpiece is selectively either
changed to another said orientation on the same
carrier, or alternatively unloaded and another
associated type workpiece loaded on the same carrier in
a said orientation thereon. The steps may be effected
14
20690~5
such that at least one of the cycles includes the
selective step of changing a first workpiece from the
said (first) orientation to another ~second) said
orientation on an associated carrier, and the further
step of loadinq on the same carrier a second associated
type workpiece in the said (first) orientation thereon,
and the repeating of the steps sufficiently to complete
at least one further cycle in which the type and
orientation of each said workpiece are sensed and
initial and subsequent work are performed on both said
workpieces in dependence upon such sensing.
The invention will be better understood from
the following more detailed description taken with the
accompanying drawings.
Brief Description of the Drawings
FIG. 1 is a perspective view of an apparatus
according to the invention, showing a rotary table with
four different types of workpieces held by carriers
received on respective table sections at the
load-unload station for sensing at the sensing station
and undergoing initial work at the initial work station
and related subsequent work at the subsequent work
station;
FIG. 2 is a schematic view of control means
for operating the apparatus of FIG. 1;
FIG. 3 is a top view of the apparatus of FIG.
l;
FIG. 4 is a side view, partially in section,
of the apparatus as shown in FIG. 3;
FIG. 5 is a top view of the portion of the
:
2069045
apparatus of FIG. 3 at the load-unload station showing
a first type workpiece;
FIG. 6 is an e~ploded view ~howing the manner
of loading and unloading a carrier onto and from a
table section at the load-unload station as indicated
in FIG. 5;
FI~. 7 is an elevational view showing the
manner of changing the orientation of a workpiece on a
carrier at the load-unload station a6 indicated in FIG.
5;
FIG. 8 is a top view of the portion of the
apparatus of FIG. 3 at the sensing station 6howing a
second type workpiece;
FIG. 9 is a side view showing the manner of
sensing a workpiece at the sensing station as indicated
in FIG. 8;
~IG. 10 is an elevational view, partially in
section, showing details at the sensing station as
indicated in FIG. 8;
FIG. 11 is a top view of the portion of the
apparatus of FIG. 3 at the initial work station showing
a third type workpiece;
FIG. 12 is an elevational view showing the
manner of performing initial work on a workpiece at the
initial work station as indicated in FIG. 11;
FIG. 13 is a side view of the arrangement
shown in FIG. 12;
FIG. 14 is a top view of the portion of the
apparatus of FIG. 3 at the subsequent work station,
showing a fourth type workpiece on which initial work
has been performed at the initial work station;
16
206904~
FIG~ 15 is a sectional side view of the
portion of the apparatus shown in FIG. 14, with the
subsequent work performing means in inactive ~tate;
FIG. 16 is a sectional side view
corresponding to FIG. 15, but with the subsequent work
performing means in active state;
FIG. 17 is a sectional side view of a portion
of a modified form of the apparatus of FIG. 14, with
the subsequent work performin~ means in inactive state;
FIG. 18 is a sectional partial view of the
apparatus of FIG. 17, with the subsequent work
performing means in active state;
FIG. 19 is a top view of a fifth type
workpiece usable in the apparatus of FIG. l;
FIG. 20 is an elevational view of the
workpiece of FIG. 19;
FIG. 21 is a side view of the workpiece shown
in FIG. 19;
FIG. 22 is a top view of a sixth type
workpiece usable in the apparatus of FIG. l;
FIG. 23 is an elevational view of the
workpiece of FIG. 22;
FIG. 24 is a side view of the workpiece of
FIG. 22;
FIG. 25 is a top view of a seventh type
workpiece usable in the apparatus of FIG. l;
FIG. 26 is an elevational view of the
workpiece of FIG. 25;
FIG. 27 is a side view of the workpiece shown
in FIG. 25;
FIG. 28 is a top view of the top side of
17
2069045
lB
another type carrier holding two as60ciated type
workpieces;
FIG. 29 is a top view of the bottom side of
the reversed carrier of FIG. 28; and
FIG. 30 is a sectional view of the
arrangement of FIG. 28.
FIG. 31 illustrates "focused ultraviolet
light."
FIG. 32 illustrates "semi-focused ultraviolet
light."
FIG. 33 illustrates "diffused ultraviolet
light."
FIG. 34 illustrates a dispensing sun
according to the present invention.
It is to be noted that the drawings are not
to scale, some portions being exaggerated to make them
easier to understand.
Detailed Description
FIG. 1 is a perspective view of an apparatus
30 according to the invention, with a rotary table 31
having four table sections 32 whose receiving means 40
respectively receive four different types of carriers
80 correspondingly holding four different types of
workpieces 81. Table 31 is mounted on a support 50 for
rotation by a motor 70 as rotating means to move the
sections 32 from a load unload station 36 to a sensing
station 37 for sensing by sensing means 100, next to an
initial work station 38 to perform initial work on the
workpieces 81 by initial work performing means 130
formed of a coating material spray gun 131 and moving
18
2069045
means 133, then to a subsequent work station 39 to
perform related subsequent work on the workpieces 81 by
subsequent work performing means 300 formed of an oven
301 having an ultraviolet (UV) light source 310 as
irradiation means and shutters 314 as irradiation
operating means, and back to the load-unload station
36, under control of control means 170.
FIG. 2 is a diagram of control means 170
showing a computer processor 176 connected to a manual
control panel 171, the motor 70, a set of workpiece
orientation sensors 102 and 103, a set of workpiece
type sensors 101, moving means 133, a valve (not shown)
in the spray gun 131, a coating material heater 156,
spray gun light screen ~eans 180, operator light screen
means 190, the UV source 310, a set of shutter
solenoids 315 and 316, and an alternative microwave
switch 318 (in dashed line). FIGS. 3 and 4 are top and
side views, respectively, of apparatus 30.
FIGS. 5, 6 and 7 are top, exploded and
elevational views, respectively, of the portion of
apparatus 30 at load-unload station 36 per FIG. 3, with
a first type carrier 80 as a pallet 801 holding a first
type workpiece 81 as a circuit board 811. FIGS. 8, 9
and 10 are top, side and elevational views,
respectively, of the portion of apparatus 30 at sensing
station 37 per FIG. 3, with a second type carrier 80 as
a pallet 802 holding a second type workpiece 81 as a
circuit board 812. FIGS. 11, 12 and 13 are top,
elevational and side views, respectively, of the
portion of apparatus 30 at initial work station 38 per
FIG. 3, with a third type carrier 80 as a pallet 803
lg
20690~5
holding a third type workpiece 81 as a circuit board
813. FIG. 14 is a top view of the portion of apparatus
30 at subsequent work station 39 per FIG. 3, with a
fourth type carrier 80 as a pallet 804 holding a fourth
type workpiece 81 as a circuit board 814 on which
initial work has been performed at initial work station
38. FIGS. 15 and 16 are sectional side views of the
arrangement shown in FIG. 14, respectively illustrating
the inactive and active states of subsequent work
performing means 300. FIGS. 17 and 18 are schematic
views of a modified form of the arrangement of FIG. 14,
with side doors 333 for subsequent work performing
means 300.
FIGS. 19, 20 and 21 are top, elevational and
side views, respectively, of a fifth type workpiece 81
as a circuit board 820. FIGS. 22, 23 and 24 are top,
elevational and side views, respectively, of a sixth
type workpiece 81 as a circuit board 830. FIGS. 25, 26
and 27 are top, elevational and side views,
respectively, of a seventh type workpiece 81 as a
circuit board 840. FIGS. 28, 29 and 30 are top side,
bottom side and sectional views, respectively, of a
reversible pallet 901 having aperture~ 902 and 903
holding two further associated type circuit boards 805
via clips 904 and ledges 905.
Referring now to FIGS. 1, 3 and 4, apparatus
30 is used for performing work on workpieces 81 of
different types in random order in assembly line
fashion, such as four different types of circuit boards
811, 812, 813 and 814 having circuit components 86 in
various patterns denoted as~predetermined portions 87.
206904~i
Rotary table 31 of apparatus 30 forms a
turntable or dial having, e.g., four, circumferentially
spaced-apart table sections 32. Table 31 i~ mounted on
support 50 for stepwise (cam indexed) rotation by motor
70 as rotating means. Motor 70 comprises a
conventional indexer that rotates table 31 to move each
section 32 in cycles successively at selective
intervals from load-unload station 36 to sensing
station 37 for sensing the type and orientation of the
workpieces 81 by sensing means 100 thereat, next to
initial work station 38 for performing initial work on
the workpieces 81 by initial work performing means 130
thereat, then to subsequent work station 39 for
performing related subsequent work on the workpieces 81
by subsequent work performing means 300 thereat, and in
turn back to load-unload station 36, all under the
control of control means 170.
A plurality of different types of carriers
80, such as four different types of pallets 801, 802,
803 and 804, are receivable in random order
respectively by receiving means 40 on sections 32.
Each type carrier 80 is distinctive (dedicated) for
carrying an associated type of workpiece 81 different
from that of each of the other types of carriers 80,
and has holder means (fixtures) such as a right side
holder 82 and a left side holder 83 for holding its
associated type workpiece 81 in two alternative
(positional or spatial) orientations.
As shown in FIG. 3, workpieces 81 may be
circuit boards 811, 812, 813 and 814 having circuit
components 86 on one side or face (e.g., top side or
21
20690~
component side) and component solder site6 on the
opposite side or face (e.g., bottom side or solder
side). Each board may be held by the respective right
holder 82 in a right side orientation, e.g., with its
component side up and solder side down (shown in solid
line), or alternatively by the respective left holder
83 in a left side orientation, e.g., with its component
side down and solder side up (shown in dashed line),
for performing initial work (applying an irradiation
curable coating) and related subsequent work
(irradiating the coating) on respectively predetermined
portions 87 thereof in each orientation.
Table 31 is conveniently provided in
horizontal orientation, for rotation about a generally
vertical axis, and constitutes a circular ring-shaped
member having a central aperture 34 and a periphery 35.
Table 31 is divided typically into four quadrant-like
(angularly rotationally spaced-apart) sections 32
separated by UV light shielding radial dividing walls
33, e.g., of glass or metal, so that the sections 32
are correspondingly adjacent the load-unload station
36, sensing station 37, initial work station 38 and
subsequent work station 39, between intervals of
successive stepwise movement of table 31 by motor 70.
As is clear from FIGS. 3 and 4, aperture 34
is provided with a formation defining a driven gear 45
that is engaged by a driving gear 72 on the drive shaft
71 of motor 70. Motor 70 is powered via a conduit 73
from control means 170 to rotate (index) table 31
stepwise at selective intervals. Motor 70 is mounted
on a bracket 53 on the underside of support 50 so that
22
206904S
drive shaft 71 extends upwardly through an opening 54
in support 50 to position drive gear 72 in engagement
with driven gear 45.
Support 50 is maintained at desired height by
legs 51 and has a bearing 52, such as a roller bearing
race, on its upper side that acts a~ a thrust bearing
for rotatably carrying table 31 thereon. The underside
of table 31 defines a journal 44 that coacts with
bearing 52 on the upper side of support 50 so as to
mount table 31 rotatably on support 50 for stepwise
rotation.
As sensing means 100 and related components
are conveniently mounted centrally of table 31 to
conserve space, yet must remain stationary when table
31 rotates, a shelf 55 is provided on support 50 to
carry sensing means 100 above table 31. Shelf 55 has a
hollow hub 56 on its underside that seats in a well 57
in support 50 that has a well bore 58 through which the
common power conduit 110 from sensing means 100 extends
for connection to control means 170. Because of this
arrangement, table 31 must be accommodated rotationally
in a manner not interfering with the supporting
structure for shelf 55, yet with the load of table 31
being transmitted to support 50 in any movement
position thereof.
Use of a bearing 52 on the upper side of
support 50 to engage the underside of table 31, in
conjunction with the coaction of drive gear 72 of motor
70 and driven gear 45 of table 31, is only one means
for providing rotational support of table 31 for
stepwise movement under the action of motor 70, without
23
- 206904~
24
interfering with the disposition of shelf 55 and
sensing means 100. Any other arrangement of the~e
parts may be employed to provide the same functions and
purposes, as means for mounting rotary tables for
stepwise (indexed) rotation are well known.
For instance, driven ~ear 45 may instead be
formed as a peripheral gear on the exterior of a hub
(not shown) downwardly extending from aperture 34 for
engaging drive gear 72.
Motor 70 is controlled by control means 170
for rapid stepwise rotation (dialing) of table 31 at
operator selective predetermined intervals, typically
indexing table 31 (i.e., rotating table 31 stepwise) a
precise 90 increment in about 2 seconds, and executing
a complete cycle (revolution of a given section 32),
including interim sensing and work performing between
movement increments, in about 48-168 seconds, depending
on the work, as explained below. Motor 70 moves (cam
indexes) each section 32 to the same precise position
at each station, so that all sections 32 successively
occupy the same common area at load-unload station 36,
at sensing station 37, at initial work station 3~ and
at subsequent work station 39.
An overload clutch mechanism (not shown) may
be provided, e.g., on drive shaft 71, to disengage
drive gear 72 of motor 70 from driven gear 45 of table
31, should jamming occur during stepwise incremental
rotation of table 31.
Referring now to FIG. 6, receiving means 40
may comprise a set of cooperating iatches 41, stops 42
and bosses 43 on each section 32 of table 31 for
24
20690~
releasably stationarily receiving a respective carrier
80 thereon, i.e., at load-unload station 36. All
carriers 80 may be of common shape and size, enabling
them to be received interchangeably by the set of
latches 41, stops 42 and bosses 43 forming receiving
means 40 on each section 32. Receiving means 40 are
identically positioned on each section 32 to position
each carrier 80 at the same location thereon. Thus, as
motor 70 moves each section 32 to the same position at
each station, all carriers 80 will successively occupy
the same common area at load-unload station 36, at
sensing station 37, at initial work station 38 and at
subsequent work station 39.
~eferring now to FIGS. 5, 8, 11 and 14, each
carrier 80 constitutes a fixture (pallet) that has a
right side holder 82 and a left side holder 83 that are
distinctive for holding its associated type of
workpiece 81. Holders 82 and 83 may each be formed of
a set of cooperating latches 84 and stops 85 on the
given carrier 80 that is specifically arranged for
releasably stationarily holding its type workpiece 81
only. The set of latches 84 and stops 85 of the right
holder 82 of a given carrier ~0 may be in side-by-side
arrangement with the set of latches 84 and stops 85 of
its left holder 83, so that its workpiece 81 is
positioned on the right holder 82 in mirror image
fashion to the position of such workpiece 81 when held
on the left holder 83.
Each set of holders 82 and 83 is identical in
arrangement on carriers 80 of the same type but differs
in arrangement from those sets on carriers 80 of the
206904~
other types, in dependence upon the shape and size of
the associated type wor~piece 81 to which the set of
holders 82 and 83 is dedicated. However, all sets of
holders 82 and 83 occupy essentially the same
corresponding areas on all carriers 80. Thus, as motor
70 moves each section 32 to the same position at each
station r all sets of holders 82 and 83 successively
occupy the same common areas at load-unload station 36,
at sensing station 37, at initial work station 38 and
at subsequent work station 39.
As shown in FIG. 5, each pallet 801 has a
right holder 82 as a set of latches 84 and stops 85
dedicated for holding a circuit board 811 with its
component side facing up, and a left holder 83 as a set
lS of latches 84 and stops 85 dedicated for holding a
circuit board 811 with its component side facing down,
i.e., in mirror image to its position on the right
holder 82.
As shown in FIG. 8, each pallet 802 has a
right holder 82 as a set of latches 84 and stops 85
dedicated for holding a circuit board 812 with its
component side facing up, and a left holder 83 as a set
of latches 84 and stops 85 dedicated for holding a
circuit board 812 with its component side facing down,
i.e., in mirror image to its position on the right
holder 82.
As shown in FIG. 11, each pallet 803 has a
right holder 82 as a set of latches 84 and stops 85
dedicated for holding a circuit board 813 with its
component side facing up, and a left holder 83 as a set
of latches 84 and stops 85 dedicated for holding a
26
206904~
circuit board 813 with its component side facing down,
i.e., in mirror image to its position on the right
holder 82.
As shown in FIG. 14, each pallet 804 has a
right holder 82 as a set of latches 84 and stops ~5
dedicated for holding a circuit board 814 with its
component side facing up, and h left holder 83 as a set
of latches 84 and stops 85 dedicated for holding a
circuit board 814 with its component side facing down,
i.e., in mirror image to its position on the right
holder 82.
Referring now to FIG. 7, this releasable
holding arrangement enables a given workpiece 81 to be
switched from the right holder 82 of its associated
carrier 80 to the left holder 83 thereof, e.g., by
manually lifting the workpiece 81 from the right holder
82, turning or flipping it over to reverse its
orientation, as indicated by the arrow 91 (shown in
dashed line), and placing it on the left holder 83.
However, as all such carriers 80 (pallets~ are of
common shape and size, they may be received by the
receivinq means 40 at each section 32 in random order.
Any other receiving means 40 than latches 41,
stops 42 and bosses 43 may be used to receive carriers
80 on the respective sections 32, and any other holder
means than latches 84 and stops 85 as right holders 82
and left holders 83 may be used to hold the associated
type workpieces 81 on their dedicated carriers 80, so
long as the above functions and purposes are attained.
Edge connector areas 92 often occupy local
portions on both sides of a circuit board 813 (see FIG.
27
20690~
28
11). Accordingly, both sides of the circuit board 813
must first be masked by a masking typ0 coating material
if the board is to be conformal coated. This i8 one
reason for providing each carrier 80 with two board
positions or orientations. In the first position on
right holder 82, one side, e.g., the top ~ide (face),
o~ the board is coated in a first cycle of table 31.
On completing the first cycle, the circuit board 813 is
flipped over and placed in the second position on left
holder 83 so that its opposite side, e.g., the bottom
side (face) can be coated in a second cycle of table
31.
Referring now to FIGS. 9 and 10, and also to
FIGS. 1, 3 and 8, it is seen that sensing means 100
includes a series of, e.g., five, side-by-side
conventional workpiece type identifying sensors 101,
e.g., photoelectric cells, and a pair of conventional
workpiece orientation identifying sensors, e.g.,
photoelectric cells, positioned side by side as a right
side orientation sensor 102 and a left side orientation
sensGr 103.
Workpiece type identifying sensors 101 are
arranged on 6helf 55 to overlie the radially inner edge
portion of each carrier 80 at sensing station 37. Type
sensors 101 cooperate with indicator means such as a
series of up to four code holes 88 in any of five code
positions at the radially inner edge of the carrier 80
that register with the corresponding type sensors 101
and that are unique to and distinguish the particular
type carrier 80 from the other types of carriers 80.
Each type sensor 101 senses (reads) when a hole 88 is
28
2069045
absent from its registering position on the carrier flO,
and the five type sensors 101 collectively sense the
type carrier 80 (and thus its type workpiece 81) then
at sensing station 37 and send this sensed information
to control means 170.
As shown in FIGS. 8 and 10, type sensors 101
are photoelectric signal beam projectors, each
projecting a beam 89 aimed at a corresponding position
on the carrier 80 at censing station 37 at which a hole
88 is either present (shown in solid line) or absent
(shown in dashed line), issuing a response signal to
control means 170 only if a hole 88 is absent. The
beam 89 is interrupted by and thereby senses the
surface of the carrier 80 at the blank (non-hole) code
position.
As is clear from FIG. 5, showing the section
32 at load-unload station 36, pallet 801 has a hole 88
at the first and fifth positions of the series, but
lacks a hole 88 at the second, third and fourth
positions (denoted by dashed line), thereby indicating
that pallet 801 is dedicated to circuit boards 811.
As is clear from FIG. 8, showing the section
32 at sensing station 37, pallet 802 has a hole 88 at
the first, second and fifth positions of the series,
but lacks a hole 88 at the third and fourth positions
(denoted by dashed line), thereby indicating that
pallet 802 is dedicated to circuit boards 812.
As is clear from FIG. ll, showing the section
32 at work station 38, p~llet 803 has a hole 88 at the
second, third and fourth positions of the series, but
lacks a hole 88 at the first and fifth positions
29
2069~4S
(denoted by dashed line), thereby indicating that
pallet 803 is dedicated to circuit boards 813.
As is clear from FIG. 14, showing the section
32 at subsequent work station 39, pallet 804 has a hole
88 at each of the first four positions of the serie~,
but lacks a hole 88 at the fifth position (denoted by
dashed line), thereby indicating that pallet 804 is
dedicated to circuit boards 814.
Type sensors 101 operate in known manner to
sense the absence of holes 88 at the code positions of
a carrier 8Q, and the response signals that identify
the type workpiece 81, i.e., by identifying its
dedicated associated type carrier 80 in terms of the
number and location of holes 88 (and blanks) thereon,
are fed via the corresponding conduits 108 ( FIG. 3) and
common conduit 110 ( FIG. 4) to control means 170.
As shown in FIGS. 3, 8 and 9, right workpiece
orientation sensor 102 and left workpiece orientation
sensor 103 are photoelectric signal beam projectors
that project a right beam 104 and a left beam 105,
respectively (indicated by dashed lines). Orientation
sensors 102 and 103 cooperate with a pair of
correspondingly aligned side-by-side conventional
retro-reflectors, denoted as right retro-reflector 106
and left retro-reflector 107, respectively, on support
50 radially outwardly of the carrier 80 at sensing
station 37 to determine the presence or absence of a
workpiece 81 on each of the right holder 82 and left
holder 83 of the carrier 80.
Or~entation sensors 102 and 103 are "parts
presence sensors" in that they each sense the presence
206904S
(or absence) of a workpiece 81. At the same tlme, they
are "orientation sensors" in that if a part (workpiece)
is present, not only is its presence sensed but also
its orientation automatically as well, becau~e the part
must be in a corresponding orientation, i.e., on its
right holder 82 or left holder 83, as the case may be.
If a workpiece 81 is present on the right
holder 82, so as to occupy a first (right) region
relative to its carrier 80, right beam 104 projected by
right orientation sensor 102 is interrupted by the
workpiece 81 (FIG. 9) and not reflected back thereto by
right retro-reflector 106. Right orientation sensor
102 senses (reads) the presence of a workpiece 81 on
the right holder 82 and inherently its orientation
(component side up, solder side down), issuing a signal
fed as information (workpiece presence and orientation)
to control means 170. If no workpiece 81 is positioned
on the right holder 82, the right beam 104 is reflected
back to right orientation sensor 102 by right
retro-reflector 106. In this case, the absence of a
workpiece 81 on the right holder 82 is sensed (read),
and no signal is sent to control means 170 (thereby
indicating workpiece absence).
If a workpiece 81 is present on the left
holder 83, so as to occupy a second (left) region
relative to its carrier 80 and which is distinct from
the first region, left beam 105 projected by left
orientation sensor 103 is interrupted by the workpiece
81 and not reflected back thereto by left
retro-reflector 107. Left orientation sensor 103
senses (reads) the presence of a workpiece on the left
31
20690~
32
holder 83 and inherently its orientation (component
side down, solder side up), issuing a signal fed as
information (workpiece presence and orientation) to
control means 170. If no workpiece 81 is positioned on
the left holder 83, the left beam 107 is reflected back
to left orientation sensor 103 by left retro-reflector
107. In this case, the absence of a workpiece 81 on
the left holder 83 is sensed (read), and no signal is
sent to control means 170 (thereby indicating workpiece
absence).
Orientation sensors 102 and 103 operate in
known manner to sense the presence or absence of a
workpiece 81 at either the right or left holder
position on a carrier 80, and the signals are fed as
information via the corresponding conduits 109 (FIG. 3)
and common conduit 110 (FIG. 4) to control means 170.
This information is used when the carrier 80
is next moved to initial work station 38, to program
initial work performing means 130 to perform initial
work on a previously sensed workpiece 81 present on its
right holder 82, or alternatively to perform initial
work on a previously sensed workpiece 81 present on its
left holder 83. If no workpiece 81 had been previously
sensed on either the holder 82 or holder 83 of that
carrier 80, then initial work performing means 130 is
programmed not to operate, and the empty carrier 80
indexes to subsequent work station 39 as is, on the
next stepwise movement of table 31.
This information is also used when the
carrier 80 then moves to subsequent work station 39, to
program subsequent work performing means 300 to perform
32
20690~
subsequent work on a previously sensed workpiece 81 on
right holder 82, or alternatlvely to perform 6ubseguent
work on a previously sensed workpiece 81 on left holder
83. If no workpiece 81 had been previously sensed on
either the holder 82 or holder 83 of that carrier 80,
then subsequent work performing means 300 is programmed
not to operate, and the empty carrier 80 indexes to
load-unload station 36 as is, on the next stepwise
movement of table 31.
As may be seen from FIGS. 1, 3 and 4, initial
work performing means 130 may be a conventional robotic
arrangement of dispensing means formed of spray gun 131
and its spray nozzle 132, moved by moving means 133
(e.g., a robot) along a predetermined spray path. This
arrangement is usable for selectively applying an
irradiation curable, flowable coating material 149 onto
predetermined portions 87 of a workpiece 81, i.e.,
corresponding to a pattern of components 86 thereon, at
initial work station 38, denoting a coating station.
Such arrangement is operated in dependence upon the
type and orientation of the workpiece 81 previously
sensed at sensing station 37.
Moving means 133 may be formed of a base 134
supporting a vertical spindle 135 that pivotally mounts
a cantilever arm 136 rotatable thereon in the back and
forth directions of the arrow 137. A floating arm 138
is pivotally mounted on the outer end of cantilever arm
136 and is rotatable thereon in the back and forth
directions of the arrow 139. The outer end of floating
arm 138 operatively mounts a vertical shaft 140 for
vertical movement in the up and down directions of the
33
206904~
arrow 141 and independently for rotation in the back
and forth directions of the arrow 142. The lower end
of shaft 140 pivotally carries a wrist member 143 that
is tiltable about the horizontal pivot 144 in the up
and down pivotal directions of the arrow 145.
As is clear from FIG. 1, coordinated conjoint
rotation of cantilever arm 136 and floating arm 138,
i.e., in the manner of a swivel stand, permits spray
gun 131 to move in a horizontal linear first direction,
corresponding to movement along the X axis between the
right and left sides of a carrier 80 on the section 32
at initial work station 38, as well as in a horizontal
linear second direction, corresponding to movement
along the Y axis, i.e., crosswise of the X axis,
between the radially outer or front end (adjacent base
134) and radially inner or back end (adjacent shelf 55
of the given carrier 80 thereat. Thus, spray gun 131
may be moved along any area portions of a workpiece 81
on a given right holder 82 or left holder 83 of the
carrier 80.
At the same time, vertical movement of shaft
140 relative to floating arm 138 permits spray gun 131
to move in a vertical linear third direction,
corresponding to movement along the Z axis, i.e.,
crosswise of the X axis and of the Y axis. ~his
enables spray gun 131 to move to any height above a
given workpiece 81 on a carrier 80 at initial work
station 38.
Also, coordinated conjoint rotation of
vertical shaft 140 relative to floating arm 138 and of
wrist member 143 relative to vertical shaft 140 permits
34
206904~
spray gun 131 to move in a rotational fourth direction,
corresponding to rotation about the vertical rotational
R axis, as well as in a rotational fifth dir~ction,
corresponding to tilting rotation about the horizontal
tilting ~ axis, i.e., crosswise of the R axis. Thus,
spray gun 131 may be positioned in any spatial
orientation relative to any portions of a given
workpiece 81 on a carrier 80 at initial work station
3~.
By suitable coordination of these movements,
e.g., predetermined by appropriate programming o~ the
operation of moving means 133, spray gun 131 may be
moved in the directions of the five axes X, Y, Z, R and
T, independently or collectively, to place spray gun
131 at any desired horizontal and vertical location and
spatial orientation relative to a workpiece 81 or its
components 86, on a carrier 80 at initial work station
38.
Referring now to FIGS. 12 and 13, and also to
FIGS. 1, 3, 4 and 11, it is seen that this 5-axis
movement of spray gun 131 permits spray nozzle 132 to
direct flowable coating material 149 to all local sites
of a workpiece 81 at initial work station 38 to assure
precise coating of all pertinent predetermined portions
87, including components 86, regardless of their
individual shape and height relative to the circuit
board surface.
For example, moving means 133 is
automatically programmed consequent sensing o~ a pallet
803 and thereby its type circuit board 813, and the
orientation (and thus presence) of the latter on its
206904~
36
riqht holder 82 (or on its left holder 83, as the case
may be), when the pallet is first moved (indexed) to
sensing station 37 rom load-unload station 36. When
that pallet 803 is next moved (indexed) to initial work
station 38, moving means 133 moves ~pray gun 131 in
desired manner to place spray nozzle 132 in the range
of the predetermined portions 87 of circuit board 813
to be coated in dependence upon that previous sensing.
At initial work station 38, spray gun 131 is
accordingly moved along a predetermined path relative
to the first side of circuit board 813 on right holder
82 (or relative to the second or opposite side of
circuit board 813 on left holder 83, as the case may
be), in a conventionally programmed manner to apply
coating material 149 to its predetermined portions 87
to form a coating 90 (FIG. 14).
As is clear from FIGS. 3 and 4, moving means
133 is powered in conventional manner via control
conduit 146 that is connected to control means 170.
Coating material 149 is supplied to spray gun 131 via
feed line 147, and the solenoid valve (not shown) for
operating spray gun 131 is actuated via valve control
conduit 148. In this way, coating material 149 may be
sprayed in precise dosage onto predetermined portions
87 of a workpiece 81 at initial work station 38 to form
the given coating gO.
For instance, moving means 133 may be
programmed to move spray gun 131 from a retracted
position remote from table 31 to a proximate position
adjacent table 31 and overlying the particular
workpiece 81 either on the right holder 82 or left
36
206904~
holder 83 of the carrier 80 thereat. Then, valve
control conduit 148 under the control of control means
170 actuates the spray gun valve (not shown~ to spray
coating material 149 from spray nozzle 132 onto the
predetermined portions 87 of the workpiece 81, as
programmed by control means 170 in dependence upon the
information previously received for that workpiece 81
when it was sensed at sensing station 37 by ~ensing
means 100.
This information from sensing means 100 is
fed to previously stored information in control means
170 for operating moving means 133 and spray gun 131
(denoting a robotic coating arm and coating dispenser
unit). The stored information includes X, Y and Z axis
coordinates of the predetermined portions 87 to be
coated, and concordant R and T axis information used in
conjunction therewith in operating spray gun 131.
On completion of the spraying of the
pertinent predetermined portions 87, valve control
conduit 14~, under the control of control means 170,
actuates the spray gun valve (not shown) to stop the
spraying operation. In turn, moving means 133, also
under the control of control means 170, stops further
movement of spray gun 131 and then retracts it from
table 31.
In order to obtain a uniform coating
efficiently, typically spray gun 131 accelerates to
coating speed, moves to a location close to the surface
of the circuit board, and only then starts ejection of
coating material 149 from spray nozzle 132. It is
important to maintain ejection or spraying of coating
37
2069045
38
material 149 at a continuous and uniform rate, and to
move spray nozzle 132 at a continuous and uniform speed
until a coated strip of desired configuration and
length is obtained on the board. When a sufficient
length of the desired configuration coating strip has
been provided, ejection of coating material 149 from
spray nozzle 132 is discontinued, and only then is
movement of spray gun 131 slowed to a stop.
Preferably, for maximizing efficiency, spray
gun 131 is simultaneously withdrawn from the circuit
board to its retracted position during the time it is
being slowed to a stop.
As may be seen from FIGS. 3 and 11, if
maskant-type coating material is to be applied by a
spray gun 131 having 3-axis movement, i.e., for
coordinated movement relative to the X, Y and Z axes as
shown in FIG. 1, it may be readily applied to an edge
connection area 92, as a predetermined portion 87 on a
circuit board. In particular, if the edge connection
area 92 does not have electrical components on its
opposite ends, i.e., that would occupy a raised height
relative to the edge connector area 92 so as to
interfere with the path of travel of the spray gun 131,
then spray nozzle 132 can be lowered initially into
sliding engagement with the circuit board surface to
apply the coating.
Thereafter, spray nozzle 132 can be
accelerated laterally to coating velocity along the
board, and coating material 149 dispensed when spray
nozzle 132 reaches the first part of the edge connector
area 92 that is to be masked. When spray nozzle 132
38
:,
2~69045
39
finishes passing over the last part of the edge
connector area 92 to be masked, dispensing from 6pray
nozzle 132 can be stopped, and spray nozzle 132 can
then be decelerated to zero velocity and withdrawn from
the board.
If the given &pray gun 131 is arranged for
5-axis movement, i.e., for coordinated movement
relative to the X, Y, Z, R and T axes as shown in FIG.
1, its acceleration and deceleration can occur while
spray nozzle 132 is being brought toward the board to
dispense coating material 149 and while it is being
removed from the board after dispensing has been
completed.
~pray gun 131 is desirably provided as a
conventional airless spray gun that dispenses coating
material 149 from spray nozzle 132 as pressure atomized
liquid particles for precise delivery to the pertinent
predetermined portions 87 without overspraying coating
material 149 onto adjacent portions of the workpiece 81
that are not intended to be sprayed. On the other
hand, airspray type spray guns, that use air to
dispense the coating material, are not as desirable for
the purposes of the invention, as they cannot be
closely controlled and tend to overspray the coating
material onto such adjacent portions.
Feed line 147 is supplied with irradiation
curable coating material 149 from a supply means such
as a reservoir pot 150 in a pressure tank 151, sealed
~y a removable cover 152, and kept under selective
delivery pressure by an automatically controlled air
pump 153, e.q., connected by a conduit (not shown) to
39
2069045
control means 170, and communicating via a pressure
line 154 with tank 151. Tank 151 may have an air bleed
valve (not shown) to reduce its pressure. Feed line
147 is connected to a supply tube 155 immersed in the
coating material 149 in pot 150. A supply indicator
(not shown~, e.g., connected to control means 17Q, may
be used to indirate the level of coating material 149
in pot 150.
The pressure generated in tank 151 by pump
153 feeds coating material 149 upwardly ~hrough supply
tube 155 and feed line 147 to spray gun 131 for
spraying from nozzle 132 under the control of valve
conduit 148. Coating material 149 is brought to
selective spraying temperature by an electric heater
156 at the entrance of feed line 147 into spray gun
131. Heater 156 is energized by a power conduit 157
connected to control means 170.
As disclosed in applicant~s said related
copending application, which does not contemplate
performing subsequent work such as curing of a coating
on a workpiece 81 coated at a previous coating station,
the carriers 80 holding the coated workpieces 81
removed from table 31 at load-unload station 36 are
sent to an off-line curing site for conventional curing
(i.e., heating) of the coatings 90. Coating material
149, whether of masking or conformal type, must
normally be cured. Such off-line site curing is
effected, e.g., by heating in an elevated temperature
curing oven or by exposure to UV light in an
ultraviolet light oven, depending on the coating
material.
2069045
However, according to the invention, curing
of the coatings 90 applied to the circuit boards is
effected on-line, while the workpieces B1 (circuit
boards) are on sections 32 of table 31 and during the
normal processing cycle of carriers 80, in synchronous
assembly line fashion. To this end, subsequent work
performing means 300 at subsequent work station 39,
denoting a curing station, ha~ the oven 301 with the UV
source 310 as irradiation means and pair of shutters
314 as irradiation operating means.
Referring now to FIGS. 15 and 16, and also to
FIGS. 1, 3, 4 and 14, oven 301 is formed as a UV light
shielding, shell-shaped housing, e.g., of glass or
metal. Oven 301 has a radially adjacent inner wall 302
mounted on shelf 55, a roof 303 connected at its
radially adjacent portion to inner wall 302, a radially
remote outer wall 304 depending from the radially
remote portion of roof 303, and a pair of opposed
radial side walls 305 depending from the opposed side
portions of roof 303. Outer wall 304 is arranged to
provide a very slight clearance with periphery 35 of
table 31, and the bottom edges of side walls 305 are
arranged to provide a very slight clearance with the
top edges of radial walls 33, for unhindered rotation
of table 31 while inhibiting escape of radiation from
oven 301. Side walls 305 are located to register
precisely radially with the corresponding radial walls
33 delimiting each section 32, when moved to subsequent
work station 39, for essentially closing the openings
formed in the sides of oven 301 below side walls 305.
Outer wall 304 may be mounted on the adjacent portion
41
20690~
42
of support 50 for further support of oven 301.
UV source 310 includes one or more
conventional UV lamps 311, such as mercury vapor lamps,
mounted at the underside of roof 303, and having a
reflector 312 to focus the radiation 320 (shown in
dashed line in FIG. 16), emitted by UV lamps 311, in
desired manner to cover a ~elective area of the
workpiece 81 on a carrier 80 at a selective distance
therebelow at subsequent work station 39. UV lamps 311
are energized by a UV power conduit 313 connected to
control means 170. The two shutters 314 are mounted at
the underside of roof 303 to enelose UV lamps 311, and
are operated by the opposed sets of conjoint solenoids
315 and 316, respectively arranged at the sides of oven
301 for simultaneous actuation, to effect selectively
timed opening (FIG. 16) and closing (FIG. 15) of
shutters 314. This controls the exposure time of the
coating 90 on a circuit board on a section 32 at
subsequent work station 39. Shutters 314, and
solenoids 315 and 316, are csnventional, and the
respective sets of solenoids 315 and 316 are energized
by the respective solenoid power conduits 317 connected
to control means 170.
UV lamps 311 may be medium pressure mercury
vapor lamps that utilize voltage excitation for
operation. As these lamps take about two minutes to
warm up, it is impractical to turn them on and off each
time a workpiece 81 is to be irradiated. Instead,
shutters 314 are used to shield the workpiece 81, e.g.,
2 circuit board, from excessive radiation, except
during the precise period of desired exposure. When in
42
206904~
warmed-up condition, the desired degree of irradiation
is emitted by UV lamps 311 during the time shutters 314
are open. To conserve energy, control means 170, which
controls the closing and opening of ~hutters 314, may
be arranged to reduce automatically the wattage of UV
lamps 311 instantaneously to a minimum, idle level
simultaneously with the closing of shutters 314, and to
increase automatically such wattage instantaneously to
proper curing level simultaneously with the opening of
shutters 314. This wattage control concordant with the
closing and opening of shutters 314 greatly reduces the
heat generated by UV lamps 311.
As noted below, UV lamps 311, such as Union
Carbide Corp. medium pressure mercury vapor lamps
utilizing voltage excitation, may be used in an
interfocused manner.
UV power conduit 313 and solenoid power
conduits 317 may be combined with conduits 108 and 109
of sensing means 100 to form common conduit 110 that
passes via bore 58 in support 50 to control means 170
(FIGS. 3 and 4).
Alternatively, UV lamps 311 may be actuated
by microwave energy to turn them on and off
instantaneously. In this case, a~ shown in FIG. 4, a
microwave switch 318 (indicated by dashed line) is used
as radiation operating means to control UV lamp
exposure time, and shutters 314 and solenoids 315 and
316 are omitted. As microwave switch 318 turns UV
lamps 311 on and off instantaneously, control of the
irradiation exposure time is achieved without the need
for shutters 314.
43
20690~5
44
Shutter solenoids 315 and 316 are programmed
to open and close shutters 314 at selective timed
intervals by control means 170, in dependence upon the
information previously sensed as to the type and
orientation of the particular workpiece 81 by ~ensing
means 100, in relation to the nature of the coating
material 14g, and the exposure time and level of curing
energy needed to cure the coating 90. At the same
time, control means 170 is programmed to operate UV
lamps 311 at high curing level and at minimum, idle
level simultaneously with the concordant opening and
closing of shutters 314.
Alternatively, microwave switch 318 is
programmed to turn UV lamps 311 on and off at selective
timed intervals by control means 170, in dependence
upon such information previously sensed by sensing
means 100 for the particular workpiece 81, in relation
to the nature of the coating material 149, and the
exposure time and level of curing energy needed to cure
the coating 90~
Oven 301 may have a conventional blower 319
to exhaust noxious gases, including ozone, generated
during UV irradiating ~or curing a coating 90 on a
workpiece 81 at subsequent work station 39. Blower 319
is connected, e.g., by a power conduit (not shown), to
control means 170 to control blower operation.
Oven 301 and attendant parts are kept cool in
known manner, such as by associated cooling means (not
shown). In particular, workpieces 81 (circuit boards)
are kept at a temperature below about 212F (100C)
during normal operation, such as by providing oven 301
44
:
2~690~
with a temperature limit switch (not shown) to maintain
its operating temperature adjustably between about
100-300F (38-149C). Shielding of per#onnel from UV
liqht at oven 301 may be provided by UV light shielding
means in conventional manner.
Alternatively, oven 301 may be provided as a
conventional separate unit (not shown) mounted on
support 50 or on a separate support, for movement
between a retracted position remote from table 31 and a
proximate position in resting contact with table 31 to
seal therewithin the section 32 then at subsequent work
station 39. This separate oven unit can be programmed
to operate under the control of control means 170 in a
manner analogous to the robotic movement of spray gun
131 at initial work station 38. If such separate oven
unit is used, radial walls 33 are omitted.
Referring now to FIGS. 17 and 18, a modified
form of oven 301 is shown in which each side wall 305
is replaced by a door 333 riding in a pair of opposed
tracks 334 at each end of inner wall 302 and outer wall
304. Each door 333 is connected to a solenoid 335,
mounted by a bracket 336 on roof 303 and energized by a
conduit 337 connected to control means 170, to raise
and lower the door to open and close the corresponding
side of oven 301. Doors 333 are normally in raised
open position, and are only lowered to closed position
during curing. They are made of UV light shielding
material such as glass or metal, and seal oven 301 from
the exterior to prevent escape of UV radiation. Thus,
radial walls 33 are omitted when oven 301 has doors
333.
20~904~
46
When doors 333 are included, control means
170 is programmed to energize solenoids 335 via thelr
conduits 337 to lower and raise doors 333
simultaneously with the concordant opening and closing
of shutters 314, or alternately with the turning on and
off of UV lamps 311 by microwave switch 318.
The radiation emitted by UV lamps 311 when
shutters 314 are open, or when the lamps are kept on by
microwave switch 318, is controlled so that autogenous
heat from the lamps does not cause the workpiece 81 to
reach an elevated temperature higher than about 185F
(85C). Blower 319 aids this temperature control by
removing the heat with the air it exhausts from oven
301.
UV lamps 311 are preferably medium pressure
mercury vapor lamps, in which the mercury in liquid
state is encased in a glass bulb filled with inert gas
such as argon. On applying a voltage of about 2300
volts to the bulb, the mercury becomes excited enough
to emit photons, i.e., the mercury radiates light. As
is known, the higher the voltage, i.e., energy, applied
to the bulb, the lower the percentage of UV energy
radiated. For example, at 100 watts/in2 of applied
energy, 26% UV light or 26 watts of UV energy is
radiated from the bulb. In turn, at 200 watts/in2 of
applied energy, only 22% UV liqht or 22 watts of UV
energy is radiated, while at 300 watts/in2 of applied
energy, only 18% UV light or 18 watts of UV energy is
radiated, therefrom.
Optimization of the irradiated UV light is
important, especially in irradiating circuit boards, as
46
2069045
47
the radiating energy or light that is not in the form
of UV light is in the form of heat. This undesirably
heats the surface of the circuit boards, making them
extremely hot, so that they cannot be stacked,
particularly in the case of rigid printed circuit
boards. This heat is also prone to damage flex stock,
flex printed circuit boards, overlays, membrane
switches, etc., during curing.
From an efficiency standpoint, it is
preferable to use a larger number of low watt lamps
than a smaller number of high watt lamps in an
irradiation bank of UV lamps 311 to cure the coatings
90, considering that the total UV light radiated is the
product of the number of lamps times the watts of UV
light. For example, seven 100 watt lamps radiate 182
watts of UV energy (7 x 26 watts as noted above) and a
remainder of 518 watts of infrared or visible light
energy (total 700 watts), whereas three 300 watt lamps
radiate only 162 watts of UV energy 13 x 54 watts as
noted above~ and a remainder of 738 watts of infrared
or visible light energy (total 900 watts). The
remainder energy represents heat that adversely heats
the substrate (circuit board).
Hence, oven 301 is desirably operated with a
larger number of UV lamps 311 of lower wattage rather
than a smaller number of UV lamps 311 of greater
wattage, to provide the UV light energy for irradiating
and curing the coatings 90 on the workpieces 81, as
this reduces the remainder energy, left over as heat,
to which the workpieces (circuit boards) are exposed
during irradiation.
47
20690~5
48
~ s to the actual curing of the coatings 90 on
the workpieces 81 in oven 301, the amount of cure is
the product of the rate of cure times the time, the
rate of cure being proportional to the ~quare root of
the radiation flux, where the square root of the flux
density is the energy/unit area. The amount of energy
is proportional to the product of the square root of
the flux times the time, the time being proportional to
the distance of the UV lamps 311 from the surface of
the coatings 90. These energy delivery parameters are
used in conjunction with the optical system for
focusing the irradiated UV light on the coatings 90.
Reflector 312 may be formed as a prefocused
system to direct the UV light from each UV lamp 311 to
a single focal point at a selective distance
representing the coating 90 to be cured. However,
varying the UV lamp position in this arrangement will
not expand the flux to a desired optimum range.
Instead, the irradiated surface will have a theoretical
instantaneous surface temperature of about 1800CF
(982C). The instantaneous surface temperature is
defined as the temperature the product would reach if
it were a perfect insulator and radiated as a black
body to dissipate from its surface all of the UV,
visible and infrared ener~y delivered to the product in
the zone of irradiation.
For this reason, reflector 312 is preferably
formed as an interfocused or expanded flux system to
direct the UV light from the bank of UV lamps 311 in an
adjustable interfocused or expanded manner. This
interfocused arrangement is more versatile and
48
20690~5
49
efficient than the prefocused arrangement, as it can
adapt readily to vary selectively the distance
separating the individual UV lamps 311 and the distance
therefrom of the coating 90 to be cured, enabling the
theoretical instantaneous surface temperature to be
reduced to about 120-500F (49-260C).
It is desirable to ~perate W lamps 311 to
cure coatings 90, using less energy for a longer period
of irradiating time (area), as this is more efficient
than using more energy for a shorter period of time.
Compared to use of a flux (i.e., energy/limited area of
coatings 90) of 1 unit (more energy) for an exposure
time of 1 second (shorter time), to obtain a
proportional amount of cure of 1 unit (i.e., the square
root of 1 unit of flux times 1 second), use of a flux
of only 0.5 unit (less energy) for an exposure time of
2 seconds (longer time), leads to a proportional amount
of cure of 1.41 units (i.e., the square root of 0.5, or
0.707, times 2 seconds). Thus, slightly extending the
exposure time and lowering the amount of energy
irradiated (i.e., the square root of the flux), yields
a 41% increase in UV energy cure amount (1.41 units
less 1 unit).
UV lamps 311 are typically adjustable from
100 to 300 watts per inch of flux density energy, e.g.,
in increments of a maximum of about 50 watts, and are
typically maintained at a minimum of ~" from table 31.
Oven 301 is typically provided with a minimum of three
different cure (irradiation exposure) times, e.g.,
adjustable between 10, 15 and 40 second time periods,
depending on the nature and extent of the coating
49
206904S
so
material 149 used.
Accordingly, assuming the same exposure time
at oven 301 for all four sections 32, each will require
a 10, 15 or 40 second residence time thereat, for a
corresponding total processing time of 40, 60 or 160
seconds per cycle (revolution) of table 31. If table
31 takes about 2 seconds to index from one station to
the next, for a total of about 8 seconds per cycle, the
total time per cycle will be about 48 seconds at a 10
second exposure time per section 32 at oven 301, about
68 seconds at a 15 second exposure time per section 32
at oven 301, or about 168 seconds at a 40 second
exposure time per section 32 at oven 301.
The time for sensing the workpieces 81 at
sensing station 37 is essentially instantaneous. As
moving means 133 and spray gun 131 typicalIy form
elements of a programmable robotic unit operating at
high speed, the time for coating the workpieces 81 at
initial work station 38 may be about 10-15 seconds,
depending on the extent of the predetermined portions
87 to be coated. The time ~or unloading and reloading
carriers 80, or turning over a workpiece 81, at
load-unload station 36 may be about 8-15 seconds, given
the releasable nature of receiving means 40 and of
holders 82 and 83, and the simple manual tasks
involved.
Significant to the development, use and
operation of the system for performing related
operations on workpieces as disclosed and claimed
herein, is the discovery that a conformal coating or
mask coating could be developed that would cure in a
206904~
51
stationary position by diffused ultraviolet light.
Heretofore, focused ultraviolet l~ght was used to cure
conformal coatings or mask coatings. Focused
ultraviolet light must be moved relative to the coated
circuit board or vice versa. If focused ultraviolet
light is directed onto a stationary coated circuit
board, the light will damage the coating, burn a hole
through the circuit board and reflow of soldex, thus
destroying the workpiece.
Figures 31 - 33 do not accurately depict the
shapes of actual reflectors used to produoe focused
light, semi-focused light or diffused light and are for
illustration purposes only. Figure 31 illustrates
"focused ultraviolet light" produced by an ultraviolet
lamp 1000 that emits light that reflects off of a
reflector 1001 to a single focused line of points
having a width of about one inch or less. Focused
light is directed to a single point or line of points
thus necessitating the movement of the light relative
to the circuit board or vice versa to cure the coating
over an extended area of the circuit board. Figure 32
illustrates "semi-focused ultraviolet light" produced
by an ultraviolet lamp 1000 that emits light that
reflects off of a reflector 1002 to focus the light on
a "band" which is about three to five inches in width.
Figure 33 illustrates "diffused ultraviolet
light" produced by an ultraviolet lamp 1000 that emits
light that reflects off of a reflector 1003 so that the
light is scattered in all directions to create a wide
curing area. Unlike focused or semi-focused light,
diffused light provides a uniform ultraviolet light
51
2069045
intensity and heat intensity over a very wide work
envelope. The diffused ultraviolet light not only
allows for the curing of a conformal coating on a
stationary board but also provides for curing of at
least a portion of the coating under components due to
the scattering of the light.
The invention includes the combination of a
conformal coating or mask coating that can be easily
and accurately dispensed onto a circuit board and the
use of diffused ultraviolet light to cure the coating
while the circuit board is in a stationary position.
The requirements of and structure of the dispensing
means of the present invention are described elsewhere
in this application and Applicant's copending
application U.S. Serial No. 07/660,761, the written
descriptions of which are hereby incorporated by
reference. Briefly, the material must be precisely
heated to about 160 F. ~ 2 F. to control the
viscosity of the material. The material is heated in
the dispensing gun just prior to dispensing. Heating
the material reservoir is likely to degrade the
material. However, it is possible to heat the hose
from the reservoir to about 100 F. and gradually
increase the temperature of the materials in the
delivery line to near the actual dispensing
temperature. The material is heated 50 that it has a
viscosity sufficient to dispense the material. Figure
34 illustrates a dispensing gun 1100 according to the
invention which includes a dispensing nozzle 1102, a
coating inlet 1104, a valve 1106 for selectively
dispensing the coating, and a heating plate 1108 to
52
20690~S
accurately heat the coating material to the desired
temperature just prior to dispensing. A coating
conduit 1110 is formed in the heating plate. The gun
includes a means for controlling the heat generated
from the heating plate, and means for actuating the
valve in a manner known in the art.
Heretofore, 100 percent solid materials had
never been dispensed from a nozzle apparatus to coat a
circuit board with a conformal coating or mask coating.
In prior methods, solvents had to be added to reduce
the viscosity of such coatings to a dispensable level.
The discovery of the above-described combination
eliminates the need to remove the circuit board from
the assembly line for coating in expensive, isolated,
production floor consuming dip tanks. Many, but not
all, dip tank coating compositions have high volatile
organic compound (VOC) emissions that must be isolated
from the rest of the production facilities due to
pollution problems and the potential for explosions.
Further, the dipping process is extremely long, messy
and requires an operator to remove the circuit board
from the dipping apparatus. Still further, the dip
coating process wastes enormous amounts of coating
material because all dip processes have a drop off
region or section. A large amount of material drips
off immediately after the material emerges from the dip
tank use is not recoverable. Further, a large amount
of material drips off in the oven from the underside of
the circuit board. Finally, in the dip coating process
it is difficult to maintain process control due to the
uncontrollable variables associated with a large open
53
206904~
54
vat of material.
The discovery of the above-described
combination eliminated the need to use conveyor belt
type focused ultraviolet light ovens which consume
large amounts of production floor space and require the
circuit board to be passed through the oven twice in
order to cure the coating on both ~ides of the circuit
board. In the prior art processes, the circuit board
is usually coated on both sides and then sent to the
curing operation. This prior art proce~s causes
serious dewetting on the side of the circuit board that
is not cured first. Further, when the coated circuit
board is placed on the conveyor belt of the oven,
sometimes the parts must be propped up to prevent the
coating on the side not being cured from sticking to
the belt thus removing a portion of the coating from
the circuit board and causing production problems. The
propping up of the circuit board is labor intensive and
time consuming. Most importantly, the conveyor belt
2~ mechanisms of the prior focused ultraviolet light
curing conformal and mask coating processes were not
amenable or suitable for use in a "dial" proce~sing
apparatus.
The present invention includes the discovery
or realization that conveyor belt focused ultraviolet
light ovens are not required to cure conformal or mask
coatings. Further, the present invention includes the
discovery or realization that a conformal or mask
coating could be developed that could be cured by
diffused ultraviolet light in a stationary position and
the discovery or realization that such would make the
54
206904~
step of curing conformal or mask coatings amenable or
suitable to use in a "dial" proces6ing apparatus.
Still further, the present invention includes the
discovery, realization and development of conformal and
mask coatings which can be cured by diffused
ultraviolet light in a stationary position. The
present invention was arrived at by a multitude of
nonobvious conceptual leaps in directions opposite that
of the prior processes using physically isolated dip
tanks and conveyor belt focused ultraviolet light
ovens.
The dial apparatus of the present invention
is placed directly in the production line consuming
little floor space and so that continuous,
uninterrupted, synchronous flow of the circuit board
through the production line is provided. In the
present invention, the conformal coating is accurately
deposited on the circuit board at one station and cured
in a stationary position at another station. Then the
circuit board is flipped over and the process repeated
to coat and cure the other side of the circuit board.
The process of the present invention is fast, clean and
accurate. By way of example, a circuit board can ~e
conformal coated and cured on both sides using a
solvent based, dip coating system and cured in a
conveyor belt heat cured oven in 45-50 minutes,
compared to the present system which wil~ be able to
coat and cure a conformal coating on a circuit board in
about two minutes or less. The present invention
eliminates the extensive and time consuming masking
steps needed for dip coating processes.
20690~
The residence time of each
section 32 at each station is normally determined by
the curing time at sub6equent work station 39, a6 it
generally eqllals or exceeds the times needed to
complete the operations at the other stations. Thu~,
the total time per cycle of table 31 is typically
determined by the total of the four succe6sive curing
operations.
A unique feature of apparatus 30 according to
the invention is that all four operations at all four
stations are effected simultaneously between intervals
of stepwise movement of table 31. Thus, a workpiece 81
on each section 32 is successively moved in assembly
line fashion from one station to the next for
sequential operation at each station, while respective
cognate operations are being performed simultaneously
at each of the other stations. The total processing
time per cycle is thereby reduced to a minimum, with no
additional cycle time being needed to accomplish any of
the contemplated individual operations, even though the
workpieces 81 may differ in type and orientation in
random order on the four sections 32.
Operation of apparatus 30 may be controlled
manually by an operator at load-unload station 36 using
a conventional local control panel 171 on a swivel
stand 172 mounted on shelf 55, and also connected via
conduit 173 with sensing means 100, such that conduits
108 and 109 of sensing means 100, UV lamp conduit 313,
solenoid conduits 317, and conduit 173 of control panel
171 form the common conduit 110 that passes via bore 58
in support 50 to control means 170. As shown in FIG.
56
206904~
57
4, control means 170 has a suitable display (readout)
174, a main control and programming panel 175, and a
conventional computer processor 176 (shown in dashed
line). Manual operation of local control panel 171
overrides the control of control means 170.
As shown in FIGS. 3 and 4, to insure safe
operation of apparatus 30 at initial work station 38,
spray gun light screen means 180 are provided. Screen
means 180 include a vertical photoelectric curtain beam
emitter 181 and a vertical photoelectric curtain beam
receiver 182, plus three vertical beam reflecting
mirrors 183, to provide a vertical light curtain beam
184 ~shown in dashed line). Beam emitter 181 and beam
receiver 182 are mounted at right angles to each other
on support 50 by a bracket 185. The three mirrors 183
are mounted on support 50 by the respective brackets
186, 187 and 188 at right angles to each other. The
first and third mirrors 183 are also mounted at a 45
angle to beam emitter 181 and beam reflector 182,
respectively.
Brackets 185, 186, 187 and 188 are arranged
on platform 50 at the four corners of a rectangular
space enclosing the range of movement envelope of work
performing means 130, to provide beam emitter 181, beam
receiver 182 and the three mirrors 183 in optical
alignment to form a personnel safety net. Beam emitter
181 and beam receiver 182 are conventional and operate
in known manner. On disturbing the signal beam emitted
by beam emitter 181 and reflected by the three mirrors
183 to beam receiver 182, an interruption signal issues
that is sent to control means 170.
57
20690~5
58
Beam emitter 181 is aimed to emit curtain
beam 184 to the fir6t mirror 183 on bracket 186, which
is arranged at a 45 angle thereto, to reflect it to
the second mirror 183 on bracket 187. The ~econd
mirror 183 is arranged on bracket 187 at a 90 angle to
the first mirror 183, to reflect curtain beam lB4 to
the third mirror 183 on bracket 188. The third mirror
183 is arranged on bracket 188 at a 90 angle to the
second mirror 183, and at a 45 angle to beam receiver
182, to reflect curtain beam 184 back to beam receiver
182 to complete the enclosing safety net. Beam emitter
181 and beam receiver 182 are connected to control
means 170 by common control conduit 189. If curtain
beam 184 is interrupted by any personnel, on receiving
such interruption signal, control means 170 is
programmed to stop apparatus 30.
As shown in FIGS. 3 and 4, for operator
safety and optional operator controlled operation of
apparatus 30, operator light screen means 190, like
spray gun light screen means 180, are provided at
load-unload station 36. Screen means 190 include a
vertical photoelectric curtain beam emitter 191 and a
vertical photoelectric curtain beam receiver 192 to
provide a vertical light curtain beam 193 (shown in
dashed line in FIG. 3). Beam emitter 191 and beam
receiver 192 are mounted in facing alignment on support
50 by brackets 194 and 195, respectively, on the left
and right sides of the operator area at load-unload
station 36. Beam emitter 191 and beam receiver 192
position curtain beam 193 between periphery 35 of table
31 and the operator zone radially outwardly thereof.
5`8
206904~
59
Beam emitter 191 and beam receiver 192 are conventional
and operate in known manner. On disturbing the signal
beam emitted by beam emitter 191, an interruption
signal issues that is sent to control means 170.
Beam emitter 191 and beam receiver 192 are
connected to control means 170 by their respective
control conduits 196 and 197 that are combined in
common control conduit 198. If curtain beam 193 is
interrupted, on receiving such interruption signal,
control means 170 stops apparatus 30 or keeps it from
starting if it is already stopped. This insures
operator safety, and optionally enables the operator to
start the next indexing lincremental stepwise movement)
of table 31 upon completing the operator tasks at
load-unload station 36, i.e., by programming control
means 170 to start and stop movement of table 31 by the
operator interrupting and ceasing to interrupt curtain
beam 193.
Referring now to FIG. 2, control means 170 is
shown with its computer processor 176 connected to the
various control conduits of the elements of apparatus
30 that are automatically operated. Processor 176 is
programmed to control apparatus 30 under the overriding
manual control of local control panel 171, for
automatic operation of motor 70, workpiece orientation
sensors 102 and 103, workpiece type sensors 101, moving
means 133 for moving spray gun 131, the spray gun valve
for nozzle 132, coating material heater 155, spray gun
light screen means 180, operator light screen means
190, UV source 310, and shutter solenoids 315 and 316,
or alternatively microwave switch 318.
59
~ 20690~
As is clear from FIGS. 1, 3, 5, 6 and 7, the
operator at load-unload station 36 may operate
apparatus 30 via local control panel 171 for selective
timed sequence stepwise rotation of table 31 to move
each section 32, so that a processed workpiece 81
arriving at load-unload station 36 may be manually
unloaded by removing its carrier 80 from the receiving
means 40 (FIG. 6) and placing that carrier on the
adjacent conveyor 200 (FIG. 1), or on a separate
conveyor (not shown), followed by the replacing of the
removed carrier 80 on the same receiving means 40 with
another carrier 80 delivered thereto in random sequence
by conveyor 200.
Where both sides of the workpiece 81 are to
be processed, after being coated and cured on one side
on right holder 82 and arriving at load-unload station
36 at the end of a first cycle, the operator can
efficiently remove the workpiece 81 from right holder
82, turn it over ~flip it 180) to expose its other,
mirror image, side and place it in that reverse side
orientation on left holder 83 (FIG. 7). The workpiece
81 will then repeat the cycle to coat and cure the
reverse side at initial and subsequent work ctations 38
and 39, respectively, after being sensed in it~ changed
orientation at sensing station 37. When the workpiece
81 again arrives at load-unload station 36, its carrier
80 can be unloaded and replaced by another carrier 80.
Referring now to FIGS. 19, 20 and 21, a fifth
type circuit board 820 is shown, with many different
components of a variety of shapes and heights relative
thereto, some of which must be coated by a masking
206904~
61
coating and others by a conformal coating. These
include circuit elements 821, product connectors B22,
integrated circuits 823, pin connectors 824, lamp
sockets 825, edge connectors 826 and right angle intake
connectors 827.
Heretofore, circuit board 820 was conformal
coated by dipping it in a coating bath to the full
depth D to coat elements 821 and integrated circuits
823, and then curing the coating. As product
connectors B22, pin connectors 824, lamp sockets 825,
edge connectors 826 and intake connectors 827 must be
protected from contact with the bath, a masking coating
was first applied to such parts, and then cured. After
applying the conformal coating to the masked circuit
board 820, and curing the conformal coating, the
underlying masking coating was stripped.
This cumbersome operation is avoided by the
invention, as a circuit board 820 may be loaded,
sensed, coated, cured and unloaded at rapid rate under
precise conditions using apparatus 30, operated by
suitably programmed control means 170. Only
predetermined portions 87 requiring a coating 90 are
coated, eliminating the separate masking process needed
in the past to pre-mask those areas not to be coated
with a conformal coating.
Referring now to FIGS. 22, 23 and 24, a sixth
type circuit board 830 is shown, with many different
components of a variety of shapes and heights relative
thereto, some of which must be coated by a masking
coating and others by a conformal coating. These
include a display 831, circuit elements 832, integrated
61
20690~
62
circuits 833, tooling holes 834, lamp sockets 835, key
pads 836 and pins 837 (FIG. 23).
Heretofore, circuit board 830 was conformal
coated by dipping it in a coating bath to the partial
depth DD to coat elements 832, integrated circuits 833
and pins 837, and then curing the coating. As display
831, tooling holes 834, lamp sockets 835 and key pads
836 must be protected from contact with the bath, a
separate masking coating was first applied to such
parts, and then cured. After applying the conformal
coating to the masked circuit board 830, and curing the
conformal coating, the underlying the masking coating
was stripped.
This equally cumbersome operation is avoided
by coating and curing a circuit board 830 according to
the invention.
Referring now to FIGS. 25, 26 and 27, a
seventh type circuit board 840 is shown, with many
different components of a variety of shapes and heights
relative thereto, some of which must be coated by a
masking coating and others by a conformal coating.
These include a display 841, a pin connector 842, an
integrated circuit 843, circuit elements 844, tooling
holes 845, lamp sockets 846, key pads 847 and pins 848
(FIG. 25). Integrated circuit 843, elements 844 and
pins 848 must be conformal coated, whereas display 841,
pin connectors 842, tooling holes 845, lamp sockets 846
and key pads 847 must not be conformal coated.
Due to its intricate component arrangement,
circuit board 840 cannot be dip coated as a practical
matter. Heretofore, it was conformal coated manually
62
2~6904~
with a paint brush, to avoid the difficult masking of
the components that must not be coated.
This previously manually brush coated-type
circuit board 840, in particular, i6 efficiently coated
selectively with a conformal coating, without the need
for a preliminary masking coating, and then cured,
using apparatus 30 per the invention.
In all cases, according to the invention, the
circuit board may be coated selectively and cured to
provide a uniform cured coating on predetermined
portions 87 of one side when it is located on right
holder 82 of its carrier 80 in a first cycle. Upon
being turned over to locate it on left holder 83 of its
carrier 80 at load-unload station 36 (FIG. 7), it may
be coated selectively and cured to provide a uniform
cured coating on predetermined portions 87 of the
opposite side in a second cycle. This eliminates a
separate masking process step prior to a conformal
coating dipping step, or use of manual brush coating.
Where a conformal coating is used, the
material in pot 150 may be a viscous, irradiation
curable (UV curable) silicone liquid material, such as
"100% Solids Silicone Conformal Coating, RTV Silicone
product type, Formula No. X-125457" (Loctite Corp.,
Newington, CT), containing 95-100% polysiloxane, 0.1-1%
photoinitiator: CAS No. 6175-45-7, 0.1-1~
photoinitiator: CAS No. 7473-98-5, and 0.1-1~ titanium
derivative: CAS No. 546-68-9.
Typically, at a delivery pressure of up to
200 psig in tank 151, a pattern width of 0.20" of
conformal coating material can be applied by spray gun
63
20690~
64
131 onto predetermined portions ~7 of the circuit board
where spray nozzle 132 is spaced no more than 4" from
the circuit board, and the flow rate is 0.03 gal/min.
or 0.04 gal/min., depending on the nozzle 132 used.
Where a masking coating is used, the material
in pot 150 may be a water insoluble, irradiation
curable (UV curable) silicone oil material, such as
"Dow Corning (R) X3-6228 UV Masking Material" (Dow
Corning Corp., Midland, MI).
Using a 1/2" width spray nozzle 13~ to
provide a 1/2" width and 3/32" thickness material
ribbon, at a robot (moving means 133) dispense speed of
15"/sec, controlled by a delivery pressure of about 200
psig in tank 151, a flow rate of 0.703125 in3/sec or
about 10.96 gal/hr of masking material can be dispensed
by spray gun 131. Using a 1/8" width spray nozzle 132
under such conditions, the flow rate can be about 2.74
gal/hr.
In these cases, the temperature of heater 156
is typically kept at about 100-300F (38-149C).
In one preferred embodiment, spray nozzle 132
is provided with a variable ejection opening capable of
dispensing coating material 149 at a viscosity of about
50-300 CPS in a ribbon width variable from about 1/4"
to 1", e.g., at an accuracy of about ~ 0.0~0", or in an
even smaller ribbon width of about 1/16", e.g., at that
same accuracy, such as by providing the nozzle with a
vertical distance adjustment. For such purposes, the
delivery pressure in tank 151 is correspondingly
adjustable between about 0-30 PSIG, and the temperature
of heater 156 is correspondingly adjustable between
64
20690~5
about 70-120F (21-49C).
Maskant material for conformal coating i6
usually extremely viscous and dries to a very rubbery
texture of considerable cohesive strength. This
characteristic is desired for easy removal of the
maskant material after the protective conformal coating
has been applied. Ideally, ~he maskant material should
come off in one manual pull when stripping the maskant
coating to separate it from the circuit board.
If it is applied to all the irregular areas
of the board that contain circuit components of various
shapes and heights, i.e., over nooks and crannies on
the board, it is usually applied in a thickness of
approximately 1/8". On curing, this gives the maskant
coating sufficient cohesive strength. Thus, once one
starts pulling on the maskant material, i.e., after the
conformal coating has been applied and cured, the
masking material will readily pull away and peel from
the board and its contained components in one single
piece, even from the nooks and crannies. This is
desirable for minimizing production costs, and ic
achievable with apparatus 30 according to the
invention.
On the other hand, if an essentially flat
surface on the board is to be coated, a coating of only
about 1/16" may be needed according to the invention to
provide sufficient cohesive strength for it to be
pulled away in one piece from the board.
A typical spray gun 131 is the "Aro Flow Gun,
Part No. 407444" (Aro Corp., Bryan, OH), e.g., with a
spray nozzle 132 of 0.3 mm (0.012"), 0.5 mm (0.020") or
2069~
0.7 mm (0.02~") diameter size. The nozzle size is
usually selected at least in part in relation to the
viscosity of the coating material being spray
dispensed. Spray gun 131 is desirably provided with a
quick disconnect mounting, enabling one size or type
spray gun to be readily exchanged for another. Spray
nozzle 132 is desirably interchangeable with others of
different size and shape openin~s.
A typical 5-axis robotic moving means 133
(robot) is the "AdeptOne Manipulator" (Adept
Technolo~y, Inc., San Jose, CA).
A typical motor 70 moving means arrangement
(table indexer) is the "Camco Indexer, #902 ROM
4H32-330" (CAMCO, Wheeling, IL), having a lHP motor
(permanent magnet DC type) and a "R250" reducer (@ 50:1
reduction), and a "Camco #7.8D" overload clutch.
Typical type sensors 101 are "Banner Photo
Cells, micro switch type proximity sensor
#923AA3W-A7T-L" (Banner Engineering Corp., Minneapolis,
MN). Typical orientation sensors 102, 103 and
retro-reflectors 106, 107 are "Banner Photo Cells,
mini-beam sensor #SM 312 LV" and "Banner
Retro-reflectors #3RT 2."
Typical light curtain screen means 180 and
light curtain screen means 190 are those designated
"Light Curtains" (Scientific Technologies, Inc.,
Mountainview, CA).
A typical UV curing oven unit is available
from Union Carbide Corp.
As an example of the sequence of operations
of apparatus 30 with four sections (quadrants) 32 on
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67
table 31 successively moved in intervalfi (indexed) by
motor 70 to each of load-unload station 36, sen~ing
station 37, initial work station 38 and subsequent work
station 39, e.g., for conformal coating and curing of
circuit boards on dedicated pallets, the following
steps are effected.
The operator at load-unload station 36
(operator station, 0 index) loads and unloads circuit
boards on dedicated pallets in random order onto the
respective sections 32.
If the operator is clear of curtain beam 193,
table 31 indexes each section 32 successively to
sensing station 37 (pallet read station, 90 index),
for sensing (reading) pallet type and circuit board
presence, and circuit board type and orientation, and
transmitting the "read" information to the programmable
dispense system constituted by control means 170 and
initial work performing means 130, and also to the
programmable curing system constituted by control means
170 and subsequent work performing means 300.
If the operator is clear of curtain beam 193,
table 31 next indexes each section 32 successively to
initial work station 38 (automatic programmable
coat/mask dispense or coating station, 180 index), for
dispensing the coating material on the corresponding
circuit board, based on the information previously
sensed at sensing station 37.
If the operator is clear of curtain beam 193,
table 31 then indexes each section 32 to subsequent
work station 39 (automatic programmable UV oven curing
station, 270 index), for curing the coating of coating
67
2069~
68
material, based on the information previoucly ~ensed at
sensing station 37.
If the operator is clear of curtain beam 193,
table 31 in turn indexes back to load-unload station
36, for unloading and loading, or turning over the
given circuit board, as earlier discussed.
The cycle time of table 31 will vary due to
the fact that it will not index (automatically) until
all stations are in "home" position, i.e., until all
operations at each station are completed, spray gun 131
is retracted and the operator hafi finished pallet
unloading and reloading, or turning over of a circuit
board from one of holders 82 and 83 to the other.
The above routine is effectively carried out
with a 4-stop drive ~e.g., DC) indexed motor 70
arrangement, preferably having cam switches (not shown)
for precise control of the 90 increments of stepwise
movement of table 31 (e.g., of about 48" diameter) in
relation to its four quadrant sections 32, to rotate
table 31 rapidly, e.g., in a maximum of 2 seconds for
each 90 increment. Receiving means 40 are accurately
located on each section 32, and holders 82 and 83 are
accurately located on each pallet, to assure that each
circuit board is properly aligned for sensing at
sensing station 37, coating at initial work station 38,
and irradiation curing at subsequent work station 39.
Apparatus 30 constitutes a compact automatic
masking or conformal coating and related curing machine
that occupies a minimum of floor area in a workplace,
thus reducing capital and other costs. At the same
time, it represents an assembly line installation for
6~
206904~
69
performing work in-line on workpieces, such as the
coating and related curing of circuit boards, in random
order, due to the specific rotary table and station
arrangement. An essentially reject-free, high
S throughput product fabrication is achievable because of
the operation of such arranqement in conjunction with
programmable control means under operator attendant
overriding control.
Apparatus 30 is flexible in that it is usable
to coat and cure all types of circuit boards. Separate
machines are not needed to coat and cure separate types
of circuit boards, as in the past. It is also flexible
in that it can accommodate a different type circuit
board at each station, so that several different types
of circuit boards can be processed at the same time.
Apparatus 30 is synchronous in that it may be
used to coat and concurrently cure all types of circuit
boards without intervening interruptions for off-line
steps. One machine does not have to be used to coat
the circuit boards and another machine to cure the
circuit boards in separate, assembly line-unrelated
operations, as in the past.
Separate operations are simultaneously
conducted at load-unload station 36, sensing ~tation
37, initial work station 38 and subsequent work station
39 of apparatus 30, rather than in time-consuming
sequential tandem steps at a sole station, and/or at
different, unrelated processing sites. One board may
be loaded, while a second is being sensed, a third
undergoing initial work, and a fourth undergoing
subsequent work, with each being either the same or a
69
206904~
different type relative to the others, as well as in
the same or a different orientation (component side
up/solder side down, or solder side up/component side
down) from each of the others. The6e features are
attained in uninterrupted flexible and synchronous
on-line operation of apparatus 30, with no change in
setting needed to switch from one product (board) to
another, yet keeping up with assembly line speed.
Apparatus 30 permits a diversity of circuit
board products (parts) to be coated and cured
automatically, after they are manually loaded and the
machine activated, including the coating and curing of
a variety of components of differing shapes and heights
relative to the board surface, such as edge board
connectors, both male and female connectors, mounting
holes, display glass, and the like.
The versatility of the kind of work that can
be performed on the workpieces 81 by apparatus 30, as
typified above, enables the arrangement to be
positioned in a desired spatial orientation for further
conserving floor space in the workplace. For instance,
by way of modification, table 31 can be mounted for
rotation about a horizontal axis (akin to an amusement
park ferris wheel), or about an axis at an angle to the
vertical, rather than about a vertical axis as depicted
in FIG. 1.
In such modification, load-unload station 36
can be located at operator (floor) level, sensing
station 37 and subsequent work station 39 at a common
raised level, and initial work station 38 at a still
higher raised level, to conserve even more floor space
- 206904~
71
by use of otherwise unused height. While the floor
space of a workplace is usually at a premium, its
height is normally not fully exploited. This
modification exploits the height more fully and
simultaneously conserves floor space. The conserved
space may be used to place a conveyor 200 more
compactly thereat.
While table 31 is shown with a circular
shape, it may have any other suitable shape, such as a
polygonal, e.g., pentagonal, hexagonal, etc., shape, so
long as its periphery 35 does not interfere with
sensing means 100, initial work performing means 170,
subsequent work performing means 300, or the free
movement of any attending operator. Also, while
support 50 is shown carrying table 31, initial work
performing means 130, and subsequent work performing
means 30, initial work performing means 130 may be on a
separate support adjacent support 50 at initial work
station 38, and subsequent work performing means 300
may be on a separate support at subsequent work station
39.
Instead of holes 88 on each carrier 80, other
indicator means can be used for sensing by type sensors
101, such as bar code labels (not shown) as used on
retail product items, specific pattern shapes (not
shown), etc., that are readable by sensors 101. For
instance, a bar code label may be located in the same
area occupied by holes 88 on each carrier 80, or each
type carrier 80 may be provided with an edge portion in
that same area having a specific pattern shape
indigenous to that type carrier.
71
206904~
These alternative forms of indicator means
can also be located instead in suitable positions on
the workpiece 81 itself, rather than on its associated
carrier 80. Specifically, a bar code label indigenous
to the given type circuit board may be located on an
edge portion on each side of the board that is aligned
with the beams of appropriately aimed type sensors 101
when the board is in the corresponding right or left
orientation on its carrier 80, where that edge portion
is otherwise unused and does not interfere with the
work being performed, e.g., the spray coating
operationO Also, that edge portion of the given type
circuit board may have a specific pattern shape
indigenous to that type circuit board that can serve as
indicator means.
In all these cases, the same result is
achieved, to wit, identifying at sensing station 37 the
particular type workpiece 81 and calling up the proper
program in control means 170 for performing the
contemplated work thereon at initial work station 38
and then at subsequent work station 39.
Carriers 80 may have conventional adjustment
means and adapters as used to convert a commercial
universal type carrier (pallet) to a dedicated or
distinctive form corresponding to any of pallets 801,
802, 803 or 804. Such adjustment means and adapters
may be used to adjust and adapt the latches 84 and
stops 85 of the right holder 82 and left holder 83 of a
universal type carrier to hold a given one of the
different type circuit boards 811, 812, 813 or 814 as a
thereby adjusted dedicated pallet 801, 802, 803 or 804.
72
~ 2069045
Instead of holes 88, the universal type carrier ~0 may
have other indicator means such as a bar code label, or
the indicator means may be on the workpiece 81, as
noted above.
Apparatus 30 is advantageously usable to
apply selectively a coating to predetermined portions
87 (areas) of a circuit board, such as a curable
viscous maskant material, and cure the coating, just
prior to the blanket coating of the board with a
conformal coat. It is equally usable to apply
selectively and cure a conformal coat on an electronic
circuit board, without prior masking of pertinent
components, due to the precise manner in which the
coating material 149 can be sprayed onto the
predetermined portions 87 without overspraying adjacent
portions (areas) not to be coated.
A critical aspect of the invention is that it
provides a flexible machine unit (apparatus 30) that
can be installed in-line, e.g., in a circuit board
manufacturing area, without taking up much floor space.
It is "flexible" in that workpieces 81 are
automatically processed on a dial machine ~table 31) in
random order, despite their individually differing
types, because of the use of automatic sensing means
100 in conjunction with automatic work performing means
130 and 300 programmed by control means 170 to operate
on the random order workpieces 81 in dependence upon
the workpiece sensing previously effected by sensing
means 100.
At the same time, the flexible machine unit
(apparatus 30) is advantageously selective in that it
73
2069045
74
can be used not only to apply a ma6kant type coating
for after-applied conformal coating~, but also to apply
the conformal coatin~ itself.
Moreover, the flexible machine unit
(apparatus 30) is "synchronous" in its ability to
perform simultaneously two individual, related
operations, e.g., coating and then curing, while the
workpieces 81 keep up with assembly line speed.
In one commonly used procedure, when the
entire solder side of the workpiece 81 (circuit board)
must be coated, while only selective portions of its
component side are to be coated, it is first placed on
the left holder 83 (solder side up, component side
down) and completely coated and cured in a first cycle
of table 31. Then, the workpiece 81 is flipped over
and placed on the right holder 82 (component side up,
solder side down) and selectively coated on
predetermined portions 87 thereof and cured in a
further cycle.
It Will be apparent that apparatus 30 may be
used to perform other kinds of work on workpieces 81
than the coating and curing of circuit ~oards, such as
the spray painting, embossing, stamping, etc., and
curing or irradiation drying, of other products, e.g.,
automotive or other parts, in random order.
It will also be apparent that each carrier 80
can have more than two holders, for holding its type
workpiece 81 in additional orientations. For instance,
in addition to holders 82 and 83 that respectively hold
a horizontally positioned, generally two-dimensional
mono-planar workpiece 81 (circuit board) in top and
74
~ 2069045
bottom side orientations, each carrier 80 may have one
or more further holders to hold such mono-planar
workpiece 81 in vertical position to present one or
more edge portions thereof to an appropr~ately
programmed spray nozzle 132 at initial work station 38
after sensing the respective further orientation by
appropriately arranged sensing means 100 at sensing
station 37, to irradiate such edge portions at
subsequent work station 39.
Also, carriers 80 can have more than two
holders to hold a generally three-dimensional
multi-planar shaped workpiece 81, such as an automobile
hood, fender, trunk lid, bumper, etc., in more than two
orientations to present different portions thereof
respectively to an appropriately programmed spray
nozzle 132 at initial work station 38, and to curing in
oven 301 at subsequent work station 39, after ~ensing
the respective orientation by appropriately arranged
sensing means 100 at sensing station 37, in ~uccessive
cycles of table 31. Thus, a first portion of the
multi-planar workpiece 81 may be processed in a first
cycle, a second (different) portion thereof processed
in a second cycle, a third (still different) portion
processed in a third cycle, etc.
For large, bulky product, workpieces 81,
several operators may be needed to manipulate them at
load-unload station 36. Whether the workpiece 81 is
manually manipulatable by one operator or requires
several operators, conventional automatic programmable
robotic means may be used at load-unload station 36 to
effect such manipulation, under operator guidance.
~ 206904~
76
Initial work performing means 130 and
subsequent work performing means 300 may be programmed
by sensing means 100 and control mean6 170 to perform
work on two workpieces 81 in side-by-side arrangement
on holders 82 and 83 on a carrier 80 during their
common stay at initial work st~tion 38, and then at
subsequent work station 39, in one cycle.
Alternatively, two separate initial work
performing means 130 may be provided at initial work
station 38 to perform initial work respectively on two
workpieces 81 in side-by-side arrangement on holders 82
and 83 on a carrier 80 during their common stay at
initial work station 38 in one cycle. For instance,
two moving means 133 correspondingly moving two spray
guns 131 for respectively coating two circuit boards
simultaneously, may be arranged at initial work station
38. Each moving means 133 will be pro~rammed by
sensing meàns 100 and control means 170 to move its
spray gun 131 only in the area adjacent its
corresponding circuit board, so that the two spray guns
131 do not interfere with each other, yet precisely
coat the desired predetermined portions 87 on their
respective boards.
If work is performed on both sides ~faces) of
the two side-by-side workpieces 81, they may be
relatively switched on holders 82 and 83 after the
first cycle, for second cycle processing.
Referring now to FIGS. 28, 29 and 30, the
carriers 80 may be formed as a reversible pallet 901
with two side-by-side through apertures such as a right
aperture 902 and a left aperture 903 as right and left
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77
holding means, shaped and ~ized to contain two
side-by-side associated type workpieces 81 formed as
circuit boards 850, held by top side releasable clips
904 and reverse side ledges 905. As shown in FIG. 28,
the top sides of circuit boards 850 having components
86 are exposed when the top ~ide of pallet 901 faces
upwardly on the receiving means of a table section 32,
for processing in one cycle. Pallet 901 is then
flipped over (front to back) on the receiving means to
expose its reverse side, as shown in FIG. 29, to
process the bottom sides of circuit boards 850 in a
further cycle. Pallet 901 has a first (inner edge)
series of holes 88 for sensing when its top side is
exposed, and a second (outer edge) different series of
holes 88 for sensing when its reverse side is exposed.
As shown in FIG. 30, the circuit boards 850
may be more or less flush with the adjacent surfaces of
pallet 901 at the edges of apertures 902 and 903, and
stationarily held from below by ledges 905 when in
face-up (first) orientation (FIG. 28) and by clips 904
when in face-down (second) orientation (FIG. 29).
Pallet 901 is used to process one side of
both circuit boards 850 in one cycle or both sides of
both circuit boards in two cycles per intervening
reversal of pallet 901 on its section 32 of table 31.
Each pallet 901 is dedicated to its associated type
circuit board 850 by its apertures 902 and 903 that are
complemental to the circuit board shape and size.
In a random mixture operation embodiment,
using apparatus 30 with carriers 80, formed of pallets
801, 802, 803 and 804, having holders 82 and 83 to hold
77
2 Q 69 ~ ~ 5
workpieces 81, formed of circuit boards 811, 812, 813
and 814, in two alternative orientations, e.g., one
face up (component side up, solder side down) on left
holder 83 and one face down (solder side up, component
side down) on right holder 82, the sensing and
processing operations may be effected r~ndomly, with a
matching preset random mixture supply, e.g., via
conveyors, of preloaded pallets and of circuit boards
alone.
Assuming that a pallet 801 with a processed
circuit board 811 has just reached load-unload station
36, the operator may remove only the circuit board 811
from the pallet 801 and replace it with a fresh circuit
board 811 on either right holder 82 or left holder 83
of that same pallet 801 for sensing and processing in
the next cycle. If both sides of the fresh circuit
board 811 are to be processed, at the end of the next
cycle the fresh circuit board 811 may be flipped over
and switched to the other of holders 82 and 83 of the
same pallet 801 for sensing and processing in a further
cycle. This circuit board loading and unloading, and
intervening switching from one to the other holder, of
a pallet that remains in place on table 31, may be
performed by the operator for each pallet as it arrives
at load-unload station 36. The operator may instead
unload the pallet and its processed circuit board, and
load another pallet holding a circuit board for sensing
and processing in the usual way.
As the sensing and processing steps are
automatic, using apparatus 30 as above described, the
operator may be guided by the next delivered matching
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, 20690g5
79
preset random mixture supply item as to whether to
unload the pallet and its processed circuit board and
load in its place on table 31 the next random order
pallet holding a fre~h cirCuit board to be processed,
or to unload only the processed circuit board and load
in its place the next of the same type on the pallet
which remains in place on table 31.
This random mixture operation may also be
used to process two circuit boards at the same time,
when side by side on the holders 82 and 83 of a pallet.
For instance, in a preliminary step, after a first
cycle in which a single, first circuit board on holder
82 of the pallet is processed on one side, it is
flipped over and switched to holder 83 and a fresh,
second circuit board loaded on holder 82, while the
pallet remains in place on table 31. In a full step,
after the second cycle, the first circuit board is
removed from holder 83, the second circuit board
flipped over and switched to holder 83, and a fresh,
third circuit board loaded on holder 82, while the
pallet remains on table 31. A~ter the third cycle, the
full step can be repeated.
This incremental loading and unloading
procedure for side-by-side circuit board processing on
the same pallet at the same time, may be individually
performed by the operator for each pallet as it
randomly arrives at load-unload station 36. In each
case, the operator may instead unload the pallet and
its processed circuit board as it arrives at
load-unload station 36 and load another random order
pallet holding a circuit board, or side-by-side circuit
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20690~
boards, for processing as above described.
Accordingly, it can be appreciated that the
specific embodiments described are merely illustrative
of the general principles of the invention. Various
modifications may be provided consistent with the
principles set forth.
