Note: Descriptions are shown in the official language in which they were submitted.
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END EFFECTOR FOR ROBOTIC EQUIPMENT
TECHNICAL FIELD
The present invention pertains to -the field of robotic
equipment, and more particularly to robotic systems employ-
ing end effector devices.
EACKGROUND OF THE INVENTION
Robotic equipment is commonly employed in many indus-
trial applications. In one important application, robotic
equipment inserts electronic components into predetermined
locations on printed circuit boards. Commonly~ the boards
are passed along an assembly line on a conveyor. At sepa-
rate stations along the line, insertion machines insert
components of the same type. The robotic equipment of the
prior art are generally unable to handle more than one size
or shape of components without changing or modifying the
machine to accommodate the different part. Thus, a differ-
ent machine station may typically be employed to insert each
diffarent sized or shaped component. This~ of course,
greatly increases the capital equipment cost of the product
insertion line, and increases the physical space needed to
house and support the assembly line. For components which
have nonstandard shapes and siæes and/or for which small
quantities are used in the circuit, hand labor is typically
employad to finish the insertion process for each board,
thus further reducin~ the speed and efficiency by which the
boards may be assembled.
The typical prior robotic equ.ipment employs a robot
arm which ~s adapted to be moved through a predetermined
~equence o~ motions. An end effector i~ connected to the
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robotic arm and comprises a gripper unit which is adapted to
grip each component when the robot arm moves to the compo~
nent supply location, hold the component while the robot arm
traverses from the supply location to the circuit board, and
then to release the component when its leads have been
inserted through the formed holes in the cixcuit board.
Typically, once all the components have been inserted in the
board, ~ither by machine or by hand, the board is moved to a
soldering station where the components are soldered to the
board.
The prior art robotic equipment known to applicant is
unable to handle components of significantly varying si~es
and shapes. Thus, a different end effector may typically be
required for each different type o~ component. Moreover,
such equipment may typically have problems handling compo-
nents of the same type, due to variations in the component
body from the nominal size and relative to the leads. Since
many components are formed from a molded or dipped material,
substantial size and shape variations may be encountered, as
well as variations of body to lead relationships. Thus,
when substantial variations from nominal dimensions are
encountered, automatic insertion may not be accomplished and
xejection of the component may occur, even though the
component is electrically acceptable. Such rejection of
elec~ricall~ acceptable components increases the cost of
assembling the board.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention
to provide a robot system adapted to ~andle components of
var~ing sizes.
Another object of the inven$ion is to provide an end
effector adapted to handle nonstandard electrical components
whose relationship between component body and component
leads varies ~rom component to component
;
It is yet another object of the present invention to
provide a robot arm end effector adapted to compensate for
variations in body-to-lead orientation to permit a component
to be precisely placed without damaging the component body
or bending its leads.
A further object of the invention is to provide a
robotic system adapted to precisely place components on a
circuit board in closely spaced relationship to other
components.
These and other objects are accomplished by the
present inv~ntion as disclosed in the following detailed
description. The present invention comprises an end
effector adapted for use with programmable servo robot
systems. The end effector comprises a component gripping
mechanism coupled to the robot arm by a compliance mecha-
nism. The gripping mechanism comprises two gripper jaw
members and is pneumaticall~ actuated for opening and
closing the grip. The compliance mechanism is adapted to
operate in two states. The first is a floating state
wherein the gripping means is freely movable through a
predetermined range of movement with respect to the mounting
plate of the robot arm on which the effector is mounted. In
the second state, the gripping means is fixedly held in
relation to the mounting plate. Actuating means are pro-
vided to selectively operate the compliance m~chanism in its
two states.
~ he insertion cycle of the robotic system of the
invention comprises the steps of ~1) with the gripping
mechanism opened and the compliance mechanism in the first
state, positioning the end effector over the component
pick-up station and the component to be picked up, (2)
closing the gripping mechanism on the component, with the
compliance mechanism in its first state to allow the compo-
nent to be gripped without preloading or deorming the
component or it~ leadsr t3) actuatin~ the compliance
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mechanism to assume its second, fixed state, also without
preloading or deforming the component or its leads, (4)
releasing the component lead from the supply station, (5~
moving the robot arm to the circuit board and inserting the
component at its predetermined location, and (6) releasing
the gripping mechanism and withdrawing the arm.
Other features and improvements are disclosed.
BRIEF DESC;~IPTION OF THE DRAWINGS
~ he various objects, features and advantages of the
disclosed invention will be readily appreciated by those
skilled in th~ art from the following detailed disclosure
when read in conjunction with the drawings, wherein:
Fiyure 1 is a perspective view illustrating a robotic
sys-tem employing the preferred embodiment.
Figure 2 is a broken away side view of the end
effector unit of the preferred embodiment, taken in the
direction of arrow 2 of Figure 1 with the cylindrical cover
of khe effector broken away.
Figure 3 is a bottom view of the end effector of the
preferred embodiment.
Figure 4 is a cross-sect:;onal top view of the end
effector of the preferred embodiment, taken along line 4-4
of Figure 2.
Figure 5 is a side cross-sectional view of the end
è~ector of ~he preferred embodiment, taken along line 5-S
of Figure 2, and a broken-away view of the air cylinder of
the gripper assembly.
Figure 6 is a cross-sectional view, taken along line
6-6 of Figure 5 and illustrating the linkage connected upper
and lower split-ball-and-socket assemblies as employed in
the preferred embodiment.
~ igure 7 is a cross-sectional view of the lower
split-ball- and-socket assembly, taken along line 7-7 of
Figure 5.
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Figure 8 is a cross-sectional view illustratin~ the
dual air cylinder/piston arrangement employed in the pre-
ferred embodiment to actuate the split-ball-and-socket
assembly.
F.igure 9 is a cross-sectional view, taken along line
9-9 of Figure 5, of the air cylinder actuati.ng the gripper
mechanism as employed in the preferred embodiment of the
invention with the air piston assembly in the expanded
position.
Figure 10 is a cross-sectional view illustrating the
gripper mechanism air piston assembly in a compressed
position.
Figure 11 is a function block diagram illustrating the
pneumatic and electrical systems of the robot system of the
preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention comprises a nove:L robotic system
and end effector particularly adaptad for handling nonstan-
dard components. The following description of the preferred
embodiment is provided to enable any person skilled in the
art to maXe and use the invention. Various modifications ~o
the disclosed embodiment will be readily apparent. The
invention is not intended to be limited to the embodiment
shown, but is to be accorded the widest scope consistent
with the principles and novel features of the invention.
Referring now to Figure 1~ a perspective view is shown
of components o:E a robotic system in accordance with the
present invention. In the preferred embodiment, robot 10
comprises a model RT-3000 robot marketad by Seiko Instru-
ments USA Inc. This robot is a programmable, 4 axis DC
servo robot with nominal positional repeatability of i.001
inches. Robot arm 15 extends ~rom the robot body 20 along
axis 25. The arm is selectively extensible and retractable
along axis 25, and is rotatable about the center axis 30 of
the robot body 20. The body 20 is alsa selectively
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extensible and retractable along axis 30 to raise and lower
the arm 15.
rrhe robo-t 10 also includes a central controller and a
keyboard interface (not illustrated in Figure 1) which
allows the system operator to interface with the central
controller. As is well known to those skilled in the art,
the system controller is programmed to carry out prede~
termined movements and operational sequences. Thus, the
controller is progral~m~d to relate the known position of the
leads of the component held at a pickup station to the known
locatlon on the circult board at which the component is to
be inserted.
The end effector is attached to the extensible end of
arm 15. As is well known to those skilled in the art, the
end effector is employed to interface with the components to
be handled by the robotic system. The components 60 are
deliv~recl to a pick-up station 70 The rohot controller is
programmed to cause the robot arm to move the end effector
to above the pick-up station 70, and then to lower ~he end
effector so as to grip the next component in the conveyor
line.
The pick-up station employs a pneumatically operated
component lead clamping vise 600, which clamps the component
leads to fix the component at the predeterm~ned pick-up
point. Thus, the position of the leads of the component at
the pick up station is a known parameter. The end effector
grips the component by its body, not by its leads and,
therefoxe, any dimensional variation in the component body
by the end effector will, for the pr~or art effector devices
known to applicant, be translated into either a preload
tensioning on the component leads, or bending o-f the leads.
~he result may be a failure to insert the component by the
robotic sy~tem, since the leads may be offset from their
nominal position a suffiaient amount to prevent insertion.
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The end effector in accordance with the present
invention alleviates this problem. The end effector grip
ping mechanism is coupled to the robot arm mounting plate by
a novel compliance mechanism, which allows the gripping
mechanism to move through a predetermined range of movement
relative to the mounting plate while the component is
gripped and the gripping mechanism settles to a clamping
equilibrium position on the component. The compliance
mechanism is then fixed in the equilibrium position while
the component is inserted in the board. The no~el end
effector thus provides a means for maintaining a component
lead to robot mounting flange relationship, allowing accu-
ratQ placement of the component leads.
The novel end effector 100 is shown in greater detail
in Figures 2-10. Figure 2 is a side view taken in the
direction of arrcw 2 shown in Figure 1, with the cylindrical
shroud 105 broken away to illustrate various aspects of the
device. As shown in Figure 2, the efector comprises a
circular ~nterface plate llO which is fastened to the robot
arm mounting flange 22 by threaded fasteners 112. Shroud
105 is formed with an inwardly turned lip 107. The lip 107
fits between flange 22 and interface plate 110 and is held
in compression therebetween by fasteners 112 to secure the
shroud in place~
~ he effector also comprises circular lower pla~e 120.
Three counter balance springs 130 are coupled between the
interface plate ~10 and the lower plate 120, and are dis-
posed at 120 spacings around the peripheries of plates
110,120. Springs 130 take up some of the weight of the
gripping mechanism 400, lower plate 120 and lower assembly
300 to reduce the insertio~ force exerted by the effector
device on the components and to reduce friction to allow the
gripping mechanism ~00 ~o more freely "~loat" when the
compliance mechanism is ln its flrst or floatiny state.
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Upper split ball-and-socket assembly 200 is fastened
to the lower surface o~ inter~ace plate 110. Lower split-
ball-and-socket assembly 300 is fastened to the upper
surface of lower plate 120. Assemblies 200,300 are coupled
together by connecting link 150.
Gripping mechanism 400 is fastened to the lower
surface of plate 120. Also shown in the effector bottom
view, Figure 3, the gripping mechanism comprises fixed grip
jaw and movable grip jaw 420, which translates linearly
along a slot formed in the lower surface of plate 120,
actuated by double acting air cylinder 430.
It will be apparent from Figure 2 that bottom plate
120 is allowed some range of movement without contacting the
inner surface o~ shroud 105. As will be described in more
detail below, the upper and lower assemblies 200,300 are
adapted to allow, when the compliance mechanism is in a
~irst state, a freedom of movement of lower plate 120 with
respect to upper plate 110 throughout a predetermined range.
Referring now to Figure 5, a cross-sectional view of
the end effector 110 is shown, taken along line 5-5 of
Figure 2, which further shows the air cylinder 430 with its
outer shroud partially broken away. Upper ball-and-socket
assembly 2Q0 comprises fixed ball socket 205 7 floating ball
socket 210, and split ball members 215,220. Fixed ball
socket 220 is secured to the bottom surface of interface
plate 110 by threadad fasteners 207. Tension bolt 225 is
passed through aligned bores formed in sockets 205,210,
split ball members 215,220 and connecting link 150. Nut 230
secures bolt 225 in the assembled position. Bolt 225 closes
ball sockets 205,210 on the ball members 215,220 when
actuated by lever 230, shown in cross-section in Figure 5.
Lower assembly 300 corresponds to assembly 200. Thus,
fixed socket 305 is secured to the upper surace o~ lower
plate 120 by threaded fasteners 307. Tension bolt 325 is
~itted ~hrou~h ali~ned bores formed in floating ball socket
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310, split ball members 315 r 320, fixed socket 305 and a slot
155 formed in connecting link 1500 Nut 330 secures tension
bolt 325 in the assembled position. Actuating lever 335
tensions bolt 325 to close the ball sockets on the split
ball members and the connecting link 150.
Further details of the upper and lower assemblies
200,300 are shown in Figures 6-8. The cross-sectional view
of Figure 6 shows the connecting link 150 with bore 157 for
xeceiving tension bolt 225 of upper assembly 200, and
elongated slot 155 for receiving tension bolt 325 of lower
assembly 300. Slot 155 allows assembly 300 to move in
vertical relationship with assembly 200 along the length of
slot 155. The purpose of this additional freedom of move-
ment will be discussed below.
Figure 7 is a cross-sectional view taken along lower
assembly 300, illustrating the actuating mechanism of the
a~sembly. The lower assembly 300 is also shown in the
cross-sectional view of Figure 4. The actuating lever 335
is held in position by tension bolt 325, with end 336 held
against wear block 340. In the preferred embodiment, the
split socket members are fabricated of aluminum, and a steel
wear block is used to reduce wear caused by the repetitive
contacting of the socket member 310 by lever arm end 336.
At the opposite end 338 of the lever arm, a pin 350 pro-
trudes from socket 310 and fits into slot 355 formed in
lever 335 ~see Figure 2) to further constrain the lever arm.
A pair of threaded retaining bolts 345,350 pass
through bores in socket member 310 and are threadingly
engaged in threaded bores formed in fixed socket member 305.
Bolts 345,350 are not tightened down so that adjacent
surfaces of sockets 305,310 are in constrained contact, but
rather allow movement of the adjacent surfaces away from
each other.
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Referring to Figures 7 and 8, a pair of air cylinders
are fitted into floating ball socket 310. Rods 364,384
extend respectively from air pistons 362,382, which are in
turn carried in cylindrical bores 374,394 formed in floating
socket member 310. Air lines 370,390 are respectively
brought in to fixtures 368,388 which communicate with bores
374,394 by passages 372,392. To minimize air leakage
between the pistons 362,382 and the bore walls, each piston
is fitted with O-ring gaskets seals 366 and 386, respec-
tively.
By pressurizing lines 370 and 390, the resulting air
pressure forces the respective pistons 366,386 to move away
from passages 372,392 so that rods 364,384 contact end 338
of actuating lever 335 to push it away from socket member
310. Tens:ion bolt 325 provides a fulcrum point, causing a
force to be applied by lever end 335 against wear block 340,
and also by nut 330 against socket 305. These forces
against the two socket members are translated into opposing
forces against split ball members 315,320, thereby fixing
the ball members in relation to the socket members.
The split ball members ar2 adapted so that surfaces
316 of ball member 315 contact acljacent sur~aces 321 of ball
member 320 when levar 335 is actuated. The split ball
members are further constructed so that there is a cl.earance
of about .0005 inches between connecting link 150 and the
adjacent surfaces of the split ball members, so that even
with lever 335 actuated, the connecting link may slide
reely with respect to the ball-and-socket assembly 300
along the extent of slot 155 in link 150.
In the preferred embodiment, a valve is provided to
switch lines 370,39G between a source of air pressure to fi~
or lock the assembly 300, and a source of vacuum to withdraw
the air plstons 36~,382 and release the assembly 30Q from
lts ~ixed position. The vacuum overcomes khe friction
resistance to piston withdrawal caused by the O-ring seals.
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Other suitable means for overcoming the resistance, such as
springs, will be readily apparent to those skilled in the
art.
Upper assembly 200 operates in a manner similar to
that described with respect to lower assembly 300 except
that substantial vertical movement of the link 150 in
relation to the assembly 200 is not provided, since there is
no slot but rather a bore formed in the link through which
the tension bolt is fitted.
The double acting air cylinder which actuates the
gripping mechanism is illustrated in the broken-away view of
Figure 5 and the cross-sectional view of Figure 5 and the
cross-sectional views of Figures 9 and 10. Air cylinder 430
comprises a piston assembly 450 mounted at one end of rod
435. Rod 435 fits through an opening ormed in fixed
gripper jaw 410. Sliding gripper jaw 420 is fastened to the
other end of rod 435.
Figure 9 is a cross-sectional view of the compound
piston assemhly 450. The assembly comprises a first piston
member 455 which is integrally formed with rod 435O The
piston 450 includes a complaint U-seal 456 with tensioning
spring 457 fitted therein. Spring 457 urges auter lip 458
of seal 456 outwardly into contact with the inner periphery
of cylinder 430.
Second piston member 460 is slidably secured to the
end of piston 435 by button screw 480 and washer 481. Screw
480 is secured in a threaded bore formed in the end of rod
435. Bore 462 is formed in piston 460. Movement of piston
460 on rod 435 is constrained in one direction by screw 480
and washer 481. A pair of washer wave springs 470 and 475
are concentrically mounted on rod 435 between first piston
455 and second pist.on 460, Springs 470,475 urge second
piston 460 to the separated location shown in Figure 9, with
piston ~60 full~ ext~nded in abutting relationship with 481~
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Air cylinder 430 is a double acting cylinder, with
pressurized air being coupled through air passages 492,494
to either the cap end 440 of the cylinder in the direction
of arxow 490, or into the rod end of the cylinder in the
direction of arrow 485. To close the gripping mechanism,
pressurized air is admitted into the rod end of the cylin-
der, causing rod 435 and ~ripper jaw 420 to move in the
direction of arrow 485 until jaw 420 closes against a
component or fixed jaw 410~ Because O-ring seals 465 exert
a greater frictional drag on piston 460 than the frictional
drag exerted by U-cup seal 456 on piston 455 or the spring
force exerted by the two wave springs 470,475, the wave
springs will be compressed through the compound movement
stroke indicated in Figure 9 as distance "C" to the com-
pressed configuration shown in Figure 10.
Compound piston assembly 450 provides a novel gripper
release means. One of the problems inherent in known
effector gripper apparatus is that when air pressure to the
pneumatic gripper assembly is released to release the
component from the ef~ector after insertion, frictional drag
on the component may be sufficient such that the component
is carried away or perturbed from its inserted position as
the effector is lifted away. If the gripping mechanism is
opened after insertion, before the effector is lifted away,
the grip jaw as it moves through its opening stroke may
contact other components on the board, and thereby cause
damage and/or dislocation of such components. For densely
populated circuit boards, the gripper jaw may not be moved
to a fully opened position.
The compound piston assembly 450 solves this problem.
When air pressure is released from the rod end of the
cylinder, the compressed wave springs axe released, exerting
an expansive force against pistons 455 and 460. Since the
frictional drag exerted on piston 455 by U-cup seal 456 is
less than the drag exerted by O-ring seals 465 on piston
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460, piston 460 remains substantially stationary while
piston 455, rod 435 and gripper jaw 420 move in the direc
tion of arrow 490 a distance substantially equal to distance
"C." With the jaw mechanism opening by distance "C" there
is no long~r any drag to be exerted on the component as the
gripper mechanism is lifted away from the inserted compo-
nent, yet the opening movement has been relatively small,
protecting adjacent components. Once the gripping mechanism
has been lifted away from the circuit board, pressurized air
may be admitted to the cap end of the air cylinder 430 to
fully open the gripper jaws 410~420. In the preferred
embodiment, this feature allows insertion of components to
within .05 inches of ad~acent components.
A pair of vent holes (not shown) are formed in second
piston 460 such that the cap end of the air cylinder commu-
nicates with the space between the first and second pistons.
The vent holes prevent this space from becoming pressurized,
and preventing compression of the two pistons.
Referring now to Figure 5, an insertion fault sensor
580 is provided on socket member 210, and is adapted to
sense the presence of socket mem~er 310 of the lower assem-
bly 300. Sensor 580 comprises a spring-loaded plunger 5~2
which fits into counterbore 584 formed in socket member 210
The plunger acts as the target for sensor 580~
The purpose of the sensor is to sense the failure to
insert a component into the board. Since ~he leads are not
inserted into the pre-formed holes in the board during such
a failure, the leads contact the surface o~ the board. As
the effector is lowered, the component, the lower assembl~
300, lower plate 120 and the gripping mechanism will remain
stationary, with assembly 200 and link 150 descending along
the extent of slot 155. As upper assembly 200 is lowered,
the plung~r of the proximity sensox contacts the upper,
adjacent surface o~ socket member 310 and is forced
upwardly. In the preferxed embodiment, .07 inches of
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upwardly travel of the plunger will trigger proximity sensor
580, indicating that a failure to insert the component has
occurred. The robot controller may then either determine
whether to make another attempt to insert the. component, or
to jettison that component and pick up a new componentO
Referring now to Figure 5, a second proximity sensor -
585 is attached to lower plate 120 and is adapted to sense
the condition of failure to pick up a componentO The sensor
is adapted to be triggered when the grip jaws 410,420 are
fully closed~ TriggQring of the second proximity sensor
provides an indication to the robot controller that the
gripping mechanism is not gripping a component, so that a
decision can be made to pick up another component.
Referring now to Figure 11, a function block diagram
illustrative of the interconnection of the electrical and
pneumatic systems of the preferred embodiment is
illustrated. Robot controller 600 is adapted to control the
pneumatic system via a plurality of electrically actuated
pneumatic valves. The controller 600 receives input data
from the several sensor transducers which are provided in
the system. As is well known to those skilled in the art,
the robot controller is progra~nable for causing the robot
to operate in accordance with a predetermined sequence of
steps and movements. The program will depend upon the
particular controller and the application.
Pressurized air which has been regulated and filtered
is supplied to the system via line 505. Pneumatic vacuum
generator 510 is driven by the pressurized air via line 506.
In the preferred embodiment, generator 510 comprises a model
M16 generator, marketed by PIAB USA Incorporated, 65 Sharp
Street, Hingham, Massachusetts 02043. This device develops
a vacuum on line 512, which is coupled to valve 545. Arrow
511 indicates a pneumatic exhaust outlet for generator 510.
It is to be understood that such arrows are generally
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employed throughout Figure 11 to indicate pneumatic exhaust
outlets.
The pressurized air is provided from line 505 to
valves 515, 520, 525, ~30, 535 and 5~0. Valve 515 is a five
port, two-way valve which is adapted to operate the double
acting air piston of the pick up station lead clamping vise
600. Electrical line 516 is coupled between the electric
actuator valve 515 and the output section of controller 500.
The valve 515 has two high pressure output por*s to supply
the ends of the air piston 602 of clamp 600 via air lines
517, 518. Two ports of the valve 515 are connected to a
pneumatic exhaust outlet. Thus, in dependence upon elec-
trical control signals from controller 600, the component
lead clamp vise is opened or closed.
The pick up station further comprises component lead
sensor 590 which is adapted to sense the presence of the
leads of the component at the lead clamping vise 600. In
the preferred embodiment, sensor 590 comprises a model
52005-3LED photoelectric sensor marketed by Skan-A-Matic
Corp., P.O. Box S, Elbridge, New York 13060. The sensor
comprises a LED which generates light which is transmi~ted
coaxially to the target through an outer diameter of fiber
optic fibers. Light is reflected by the component leads
back through an inner fiber optic bundle to a phototransis-
tor transducer. The sensor 590 output is coupled to the
controller 600 via electrical line 591 to provide a signal
indicative of the presence of a component lead in the vise.
rThe pick up station also includes a "vise open" sensor
adapted to provide a signal to the controller to indicate
the "vise open" condition. This sensor compxises a Hall
effect proximity sensor, model 37XL31-003, marketed by the
Microswitch Division of Honeywell Corporation, Marlborough,
Massachusetts.
It will be readily apparent to those skilled in the
art that~ with the ~n~ormation provided by sensors 590, 595,
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the controller may cause the vise to grip the leads of a
component which has been delivered to the vise along a
conveyor or other conventiona] means, and thereafter to
release the component leads.
Pneumatic valves 520, 525, 530, and 535 comprise three
port valves marketed by SMC Pneumatics, Inc., 5538 W.
Raymond Street, Indianapolis, Indiana 46241, as model
NVS4114-00520. Each valve is supplied with pressurized air
via line 505, and each valve also comprises a port which is
coupled to a pneumatic exhaust outlet. The high pressure
output port of valve 520 is coupled to one input port of
valve 545; the output of vacuum generator 510 is coupled to
the other input port of valve 545. The output o-E valve 525
is coupled to to the pilot or control port of valve 545.
Valve 545 comprises a model VA125A valve marketed by
~Iumphrey Products, P.O. Box 2008/ Kalamazoo, Michigan 49003.
It operates to switch output line 546 between the high
pressure source and the vacuum source, in dependence upon
the pressure at the valve pilot port. Pneumatic line 546 is
coupled to the four single-acting air cylinders provided in
upper and lower assemblies 200,300. Thus, the controller
may cause either pressurized air or a vacuum to be applied
~o the air cylinders which actuate the assemblies 200,300 by
controlling valves 525 and 545.
Insertion fault SenSQr 580, as described above, is
disposed in floating socket member 210. In the preferred
embodiment, this sensor comprises a model FYGE/M10-0 prox-
imity sensor marketed by the Microswitch Division o
Honeywell Corporation. Its output signal is provided to
controller 500 via electrical line 581 to provide a sensor
signal which indicates an insertion fault, as described
above.
The gripping mechanism alr cylinder 430 is actuated by
valves 530, 535, 540, 570 and 575. The outputs o~ valves
530,535 are respectively passed through pressure regulators
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550,55~ and check valves 560,565 to valve 570. Re~ulators
550,555 may be separately adjusted to provide separate air
pressure levels (e.g. 10 or 10 psi) to valve 570. The
purpose of using two regulators is to allow the controller
the capability o~ selecting between two grip pressures. The
controller is adapted to select the grip pressure by actuat-
in~ valve 570, which in the preferred embodiment comprises a
model 3E1 valve marketed by Humphrey Products.
The output of valve 570 is passed through quick
exhaust valve 575 to the rod end o~ air cylinder 430. Valve
575 comprises a model SQE valve marketed by Humphrey
Products, and is adapted to rapidly vent the pressurized air
provided to it ~s the air pressure from valve 570 begins to
drop. Valve 575 increases the system cycle time.
Valve 540 comprises the robot output valve (internal
to the Sei]co RT-3000 robot) whose output is coupled to the
cap end o~ double acting air cylinder 430.
~ alves 570,5~0 are actuated simultaneously by control-
ler 500 to actuate cylinder 430. Thus, to close the ~rip,
valve 570 is opened and valve 5~0 closed. To fully open the
grip, valve 540 is opened and valve 570 closed. To release
a component, valves 570 are closed, thereby removing the
pressurized air supply ~rom both the cap and rod ends of air
cylinder 530.
Sensor 585 is provided to sense the "jaws closed"
position o~ the gripper assembly. In the pre~erred embodi-
ment sensor 580 is a proximity sensor, model FYGE/M10-0,
marketed by the Microswitch Division of Honeywell Corpora-
tion.
As will be apparent to those skilled in the art, other
electrical and/or pneumatic system layouts may be employed
to implement the invention. Additional lead clamping vises
and pick up stations may be readily incorporated into the
system to increase the system capacity. The types o~ valves
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and sensors may be readily changed to suit the particular
applicationO
From the foregoing description, it will be a.pparent
that the compliance mechanism of the preferred embodiment is
adapted to allow the connecting link 150 to move through a
predetermined range of movement with respect to upper
ball-and-socket assembly 200 when the compliance mechanism
is in the first floating state. The range of movement is
generally about the tension bolt 225, and is defined by the
amount of the clearances between the link and adjacent
surfaces of the socket members ~05,210, and between the
tension bolt 225 and the bores through which it is inserted
in split ball members 215,220 and socket members 205,210.
The re~uisite range of movement for the application of the
preferred embodiment is relatively small, and indeed the
respective clearances shown in the Figures are somewhat
exaggerated for illustrative purposes. The actual required
range of movement is a function of the particular applica-
tion.
The compliance mechanism is further adapted to allow
the lower plate 120 and lower assembly 300 to move through apredetermined range of movement with respect to the connect-
ing link when the compliance mechanism is in the first
state, The range of mo~ement is generally about tension
bolt 330, and is also defined by the clearances between the
link and adjacent surfaces of the socket members 305, 310,
and between the tension bolt and the bores through which it
is inserted in split ~all members 315,320 and socke,t members
305,310. An additional degree of freedom is provided by
slot 155 formed in link 150, which allows vertical movemPnt
of the ass~mbly 300 with respect to the link 150 along the
extent of the slot 155,
The multiple ran~es of movement provided by the
compliance mechanism is one novel feature of the invention.
With the compllance mechanism in its first state, the
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gripping mechanism is allowed to Eind a clamping e~uilibrium
position on the component which is held in the clamping vise
at the pick up station. This equilibrium point may deviate
from a nominal clamping point, due to variations in the body
or body-to-lead relationship of the component. Because of
the degrees of movement of the compliance mechanism, the
lower plate may, for example, shift slightly from a horizon-
tal position to a slightly cocked position, or the ~ripping
jaws ma~ be offset slightly from the effector center axis.
The ability to allow the effector to freely find this
clamping equilibrium means that the compliance mechanism
accommodates the offsets or deviations in the component
size. Without the compliance mechanism, the offset would be
translated into a preload force on the leads, which would
either bend the leads or, once the component leads are
released from the pick-up station, be translated into an
offset in the position of the leads relative to the robot
arm.
After a predetermined "float time" sufficlent to allow
the clamping equilibrium position to be found, the compli-
ance mechanism is actuated into the second or fixed state.
In this state, the lateral position of the gripping mecha-
nism with respect to the robot mounting flange is fixed;
upward vertical movement is still possible due to the slot
155 in link 150, as discussed above. With the compliance
mechanism in the fixed state, the component may be released
from the lead clamping vise at the pick-up station, and the
robot arm moved from the pick-up station to a point above
the predetermined location on the circuit board where the
component is to be inserted. The robot arm is then lowered
to insert the leads of the component in pre-formed holes in
the board.
To urther ~acilitate the insertion process, the robot
controller may be programmed to cause the robot arm to lower
the ~omponent above its board position a predetQrmined
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distance, usually until the leads contact the board, and
then cause the robot arm to oscillate or dither. The
oscillatory motion moves the leads back and forth across the
respective board holes to facilitate lead insertion. The
arm then finishes its downward stroke.
The degree of oscillation or dithering will be depen-
dent upon the requirements for the particular application.
In the preferred embodiment, the oscillatory, i~eO, lateral,
movements range in size from .002 inches to .02 inches~
The typical insertion cycle time of the robotic s~stem
in accordance with the preferred embodiment is about 2.5
seconds. Of this cycle time, the compliance mechanism
"float" time, i~e., the time in which the compliance mecha-
nism is in the first state, after the grippin~ mechanism has
closed on the component, is typically less than 50 milli-
seconds. The cycle time and float time may obviously be
varied in accordance with the particular application.
A typical insertion cycle comprises the followin~
steps. The component to be inserted is positioned at a
predetermined pick up point and fixed in position at that
point, for example, by a pneumatic clamping vise. The robot
arm is brought to a point above the component to be picked
up. With the compliance mechanism in its ~irst, floating
state, and the gripping mechanism fully opened, ~he gripper
jaws are lowered to a point so that ~he jaws are disposed on
opposing sides of the component. Typically, the arm is
lowered with the fixed jaw disposed about 1/32 inch from the
adjacent side of the component. The arm is then moved
laterall~ to bring the fixed jaw up against the side of the
component, and the gripping mechanism is actuated to close
the movable jaw up against the opposing side of the compo-
nent to ~rip the component.
Since the compliance mechanism is in the first float-
ing state, the component is gripped without preloading or
bending its leads.
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After the predetermined float time has elapsed, the
compliance mechanism is actuated to the second, fixed state
to lock the compliance mechanism. This actuation causes
substantially no preload force to be applied to the compo-
nent leads. The pneumatic clamp of the pick up station is
then actuated to release the component from its grip.
The robot arm then lifts the component, moves it to a
location above its predetermined board location, and com-
mences its downward insertion stroke. During the insertion
stroke, the oscillation described above may be employed.
Once the component has been inserted in the board, air
pxessure to the gripper air cylinder is released, allowing
the rod o~ the gripper air cylinder to withdraw through its
expansion stroke to release the component. The robot arm is
then lifted and the gripper jaws fully opened. With the
robot arm moved back to its position above the component
pick up point, the system is ready to commence another
cycle.
The above-described invention may be used to insert
standard as well as nonstandard components. By way of
example only, the invention may be employed in applications
wherein a dozen or more different types of components, both
standard and nonstandard, are inserted in a closely packed
relationship on a printed circuit board. With the compli-
ance mechanism of the invention, the system adapts to each
type and size of component. With the novel release mecha-
nism of the invention, the system is capable of insertion in
a closely packed relationship.
It is understood that the above-described embodiment
is merely illustrative o~ the many possible speci~ic embodi-
ments which can represent principles of the present inven-
tion. Numerous and varied other arran~ements can be raadily
devised in accordance with these principles by those skilled
in the art withou-t departin~ from the spirit and scope of
the invention.
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