U.S. patent number RE32,794 [Application Number 06/508,076] was granted by the patent office on 1988-12-06 for programmable automatic assembly system.
This patent grant is currently assigned to Unimation, Inc.. Invention is credited to Maurice J. Dunne, Joseph F. Engelberger, Horace L. Gardener, deceased, Torsten H. Lindbom, William Perzley, Wilbur N. Roberts.
United States Patent |
RE32,794 |
Engelberger , et
al. |
December 6, 1988 |
Programmable automatic assembly system
Abstract
A programmable automatic assembly system is provided which may
be employed to assemble small parts. Each assembly station includes
cooperating manipulator arms which are programmable to assemble
parts on a centrally located work table. Improved facilities are
provided for teaching the manipulator arms at each station, these
facilities including a computer which assists the teaching operator
in setting up the programs required for assembly of small parts to
close tolerances. Each manipulator arm includes closed loop teach
facilities for maintaining the arm at a previously located position
during the teaching mode of operation. The computer is employed as
a teach assist facility in performing a number of tasks during the
teaching operation which are extremely difficult for the operator
to perform manually. All of the assembly stations may be controlled
during playback from a common disc storage facility so that the
control circuitry and memory storage facilities at each manipulator
are minimized.
Inventors: |
Engelberger; Joseph F.
(Newtown, CT), Lindbom; Torsten H. (Brookfield, CT),
Dunne; Maurice J. (Newtown, CT), Perzley; William
(Weston, CT), Roberts; Wilbur N. (Newtown, CT), Gardener,
deceased; Horace L. (late of Ridgefield, CT) |
Assignee: |
Unimation, Inc. (Danbury,
CT)
|
Family
ID: |
26707279 |
Appl.
No.: |
06/508,076 |
Filed: |
June 24, 1983 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
31463 |
Apr 19, 1979 |
04275986 |
Jun 30, 1981 |
|
|
Current U.S.
Class: |
414/730; 414/4;
414/732; 414/739; 901/15; 901/22; 901/26; 901/3; 901/30; 901/8;
901/9 |
Current CPC
Class: |
B25J
9/046 (20130101) |
Current International
Class: |
B25J
9/04 (20060101); B25J 9/02 (20060101); B25J
009/00 () |
Field of
Search: |
;414/618,733,730,732,735,738,740,742,744R,1,5 ;29/270
;901/14,15,23,25,26 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Paperner; Leslie J.
Attorney, Agent or Firm: Hawranko; G.
Claims
What is claimed as new and desired to be secured by Letters Patent
of the United States is: .[.1. In a programmable manipulator, the
combination of, a base member mounted for rotation about a vertical
axis, a first arm portion pivotally mounted on said base member for
rotation about a first horizontal axis, a second arm portion
mounted on the upper end of said first arm portion for movement
about a second horizontal axis, a manipulator hand mounted on the
outer end of said second arm portion and movable about a wrist bend
axis which is perpendicular to the longitudinal axis of said second
arm portion, said hand having a swivel portion on the outer end
thereof which is rotatable about a wrist swivel axis which is
perpendicular to said wrist bend axis, means for rotating said
first and second arm portions about their respective axes, and
drive means for said hand and swivel portions mounted on said first
arm portion and movable therewith..]. .[.2. The combination of
claim 1, wherein said drive means for said first arm portion
includes a housing pivotally mounted in said base member, an
hydraulic motor mounted in said housing, a ball-screw linear
actuator mounted in said housing and including a nut movable along
the length of said screw as the same is rotated, gear means
interconnecting said motor and said screw, a flange projecting
outwardly from the upper end of said first arm portion, and means
interconnecting said nut and said flange so that extension and
retraction of said actuator is effective to pivot said first arm
portion about said first horizontal axis..]. .[.3. The combination
of claim 1, wherein said drive means for said second arm portion
includes a housing pivotally mounted in said first arm portion, an
hydraulic motor mounted in said housing, a ball-screw linear
actuator mounted in said housing and including a nut movable along
the length of said screw as the same is rotated, gear means
interconnecting said motor and said screw, a flange extending
rearwardly from said second arm portion, and means interconnecting
said nut and said flange so that extension and retraction of said
actuator is effective to pivot said second arm portion about said
second horizontal axis..]. .[.4. The combination of claim 1, which
includes a work head connected to said swivel hand portion and
including a pneumatic work chamber, and means for supplying air to
said chamber through said swivel hand portion..]. .[.5. The
combination of claim 1, which includes a support, means rotatably
mounted said base member on said support, a housing pivotally
connected to said support, an hydraulic motor mounted in said
housing, a ball-screw linear actuator mounted in said housing and
including a nut movable along the length of said screw as the same
is rotated, gear means interconnecting said motor and said screw,
and means interconnecting said nut and a point on said base member
which is offset from the central rotary axis thereof so that
extension and retraction of said actuator is effective to move said
base member through a predetermined limited arc about said central
axis..]. .[.6. The combination of claim 5, wherein said limited arc
is approximately 110.degree...]. .[.7. The combination of claim 1,
wherein said drive means includes a first motor for said hand and a
second motor for said swivel portion, said first and second motors
being positioned relatively close to the central axis of said first
arm portion and having the drive shafts thereof extending generally
parallel to said central axis, thereby to limit the rotational
inertia of said first arm
portion..]. 8. The combination of claim .[.7, .]. .Iadd.19
.Iaddend.which includes a pair of beveled ring gears independently
mounted for rotation about said second horizontal axis, means
interconnecting said first and second motors with said pair of
beveled ring gears to rotate the same, means including first gear
means interconnecting one of said beveled ring gears and said hand,
thereby to move said hand about said wrist bend axis, and means
including second gear means interconnecting the other of said
beveled ring gears with said swivel portion to move the same about
said
wrist swivel axis. 9. The combination of claim 8, which includes
wrist bend encoder means and wrist swivel encoder means each having
an input shaft, means including a first beveled gear in engagement
with one of said pair of beveled ring gears for driving one of said
input shafts, and means including a second beveled gear in
engagement with the other of said pair of beveled ring gears for
driving the other one of said input shafts. .[.10. The combination
of claim 1, which includes a housing mounted on the end of said
second arm portion, an input shaft rotatably mounted in said
housing, a motor mounted on said first arm portion, means
connecting the output shaft of said motor to said input shaft, a
ring gear mounted on said hand, a shaft rotatably mounted in said
housing, a gear in said shaft and in engagement with said ring
gear, gear means interconnecting said shaft and said input shaft,
and antibacklash means for continuously exerting a biasing force on
said shaft in the direction to hold said gear
in engagement with said ring gear..]. 11. The combination of claim
.[.10.]. .Iadd.20 .Iaddend.wherein said biasing force is exerted by
a
plurality of Belleville washers which are under compression. 12.
The combination of claim 11, wherein said Belleville washers are
compressed to a point at which the force exerted thereby remains
relatively constant as the deflection of said washers varies due to
wear and the like. .[.13. The combination of claim 1, wherein said
second arm portion includes an elbow arm portion mounted for
rotation about said second horizontal axis, and a forearm portion
positioned concentric with said elbow arm portion and rotatable
with respect thereto, said manipulator hand being mounted on
the
outer end of said forearm portion. .]. 14. The combination of claim
.[.13.]. .Iadd.21.Iaddend., which includes a work head connected to
said swivel hand portion and including a pneumatic work chamber,
means for supplying air to said elbow arm portion, air conduit
means in said rotatable forearm portion and connected to said air
supply, and means connecting said air conduit means to said air
chamber through said swivel
hand portion. 15. The combination of claim .[.13.].
.Iadd.21.Iaddend., which includes drive means for said forearm
portion and includes a .[.third.]. motor positioned relatively
close to the central axis of said first arm portion with the
driveshaft thereof extending generally parallel
to said central axis. 16. The combination of claim 15, wherein said
forearm portion includes a sleeve portion rotatably mounted in said
elbow arm portion, a ring gear mounted within said sleeve portion,
and means
interconnecting said third motor and said ring gear. 17. The
combination of claim 16, which includes a beveled ring gear mounted
for rotation about said second horizontal axis, means connected to
the driveshaft of said third motor for rotating said beveled ring
gear, and gear means interconnecting said beveled ring gear and
said sleeve mounted ring gear.
8. The combination of claim 17, which includes forearm encoder
means having an input shaft, and means including a beveled gear in
engagement
with said beveled ring gear for driving said input shaft. .Iadd.19.
In a programmable manipulator, the combination of, a base member
mounted for rotation about a vertical axis, a first arm portion
pivotally mounted on said base member for rotation about a first
horizontal axis, a second arm portion mounted on the upper end of
said first arm portion for movement about a second horizontal axis,
a manipulator hand mounted on the outer end of said second arm
portion and movable about a wrist bend axis which is perpendicular
to the longitudinal axis of said second arm portion, said hand
having a swivel portion on the outer end thereof which is rotatable
about a wrist swivel axis which is perpendicular to said wrist bend
axis, means for rotating said first and second arm portions about
their respective axes, a first drive motor for said hand, and a
second drive motor for said swivel portion, said first and second
motors being mounted on and positioned relatively close to the
central axis of said first arm portion and having the drive shafts
thereof extending generally parallel to said central axis, thereby
to limit the rotational inertia of said first arm portion.
.Iaddend. .Iadd.20. In a programmable manipulator, the combination
of, a base member mounted for rotation about a vertical axis, a
first arm portion pivotally mounted on said base member for
rotation about a first horizontal axis, a second arm portion
mounted on the upper end of said first arm portion for movement
about a second horizontal axis, a manipulator hand mounted on the
outer end of said second arm portion and movable about a wrist bend
axis which is perpendicular to the longitudinal axis of said second
arm portion, said hand having a swivel portion on the outer end
thereof which is rotatable about a wrist swivel axis which is
perpendicular to said wrist bend axis, means for rotating said
first and second arm portions about their respective axes, drive
means for said hand and swivel portions mounted on said first arm
portion and movable therewith, a housing mounted on the end of said
second arm portion, an input shaft rotatably mounted in said
housing, including said drive means, a motor mounted on said first
arm portion, means connecting the output shaft of said motor to
said input shaft, a ring gear mounted on said hand, a shaft
rotatably mounted in said housing, a gear in said shaft and in
engagement with said ring gear, gear means interconnecting said
shaft and said input shaft, and antibacklash means for continuously
exerting a biasing force on said shaft in the direction to hold
said gear in engagement with said ring gear. .Iaddend. .Iadd.21. In
a programmable manipulator, the combination of, a base member
mounted for rotation about a vertical axis, a first arm portion
pivotally mounted on said base member for rotation about a first
horizontal axis, a second arm portion mounted on the upper end of
said first arm portion for movement about a second horizontal axis,
a manipulator hand mounted on the outer end of said second arm
portion and movable about a wrist bend axis which is perpendicular
to the longitudinal axis of said second arm portion, said hand
having a swivel portion on the outer end thereof which is rotatable
about a wrist swivel axis which is perpendicular to said wrist bend
axis, means for rotating said first and second arm portions about
their respective axes, drive means for said hand and swivel
portions mounted on said first arm portion and movable therewith,
said second arm portion including an elbow arm portion mounted for
rotation about said second horizontal axis, and a forearm portion
positioned concentric with said elbow arm portion and rotatable
with respect thereto, said manipulator hand being mounted on the
outer end of said forearm portion. .Iaddend.
Description
.[.This is a division of copending application Ser. No. 625,932,
filed Oct. 28, 1975, now U.S. Pat. No. 4,163,183..]. .Iadd.This is
a reissue of U.S. Pat. No. 4,275,986 dated June 30, 1981.
.Iaddend.
The present invention relates to programmable manipulator
apparatus, and, more particularly, to a programmable automatic
assembly system which is capable of assembling small parts by
virtue of the programmed coordinated movement between two
manipulator arms, the article gripping hands of which are arranged
to cooperate in assembling small parts at a centrally located work
station.
Programmable manipulators have been employed in various industries
for some time to transport articles from one location to another
and to perform certain patterned operations such as welding, paint
spraying or the like. Such programmable manipulators are shown, for
example, in Devol U.S. Pat. No. 3,306,471 dated Feb. 28, 1967;
Devol U.S. Pat. No. 3,543,947 dated Dec. 1, 1970; Dunne et al U.S.
Pat. No. 3,661,051 dated May 9, 1972; Engelberger et al U.S. Pat.
No. 3,744,032 dated July 3, 1973; Engelberger et al U.S. Pat. No.
3,885,295 dated May 27, 1975; Devol et al U.S. Pat. No. 3,890,552
dated June 17, 1975 and British Pat. No. 781,465. While these
programmable manipulators are generally suitable for their intended
purpose, they have not generally been employed in assembly line
operations where numerous small parts must be assembled into larger
subassemblies and the packing density of labor is highest. For
example, in the automotive industry we see personnel shoulder to
shoulder assembling heating and air conditioning units, dashboards,
carburetors, brakes, power steering, pumps, windshield wipers,
etc.
One reason why programmable manipulators or industrial robots have
not been employed in assembly line operations is that heretofore it
has been considered necessary to provide some sort of robot eye, in
the form of a television monitoring camera or the like, and to
provide suitable hand-to-eye coordination so that the robot can
interpret the visual scene and provide the correct hand orientation
to pick up the article and assemble it to another part. Most, if
not all of these arrangements have considered that the robot eye is
essential. However, hand-to-eye coordination is extremely difficult
and expensive to achieve even in the simplest of assembly
operations.
A further reason why programmable manipulators have not heretofore
been employed in assembly line operations lies in the basic concept
of assembly line production which is to reduce individual acts to
the simplest acts practical, on the theory that if the job is
simple a worker can be trained quickly and can be made highly adept
at a simple task. Further his skill is not a bargaining asset and
management is little distressed by personnel turnover. This
assembly line concept is carried over into transfer machine
automation wherein each station on the line performs only one
peculiar function. According to this line of thinking replacement
of each of the multitude of workers on an assembly line by an
expensive programmable robot is not economically justifiable.
Furthermore, in industries outside the automotive industry where
relatively low volumes of assembly are required, special purpose
assembly machines cannot be economically justified on any basis. In
addition, the existing programmable manipulators have not been able
to provide the necessary speed and accuracy of positioning which
would be required to replace the assembly of parts by human beings.
For example, simply to place two mating parts together and assembly
them with screws requires a high degree of coordination and
cooperation between different manipulator arms if they are to
accomplish this operation automatically.
Another reason why existing programmable manipulators have not been
employed to perform parts assembly on the assembly line basis is
that the teaching or initial programming of each of the
manipulators to perform a series of intricate tasks, many of which
involve movement in oblique angles and planes, is very laborious
and time consuming particularly when it is realized that assembly
of parts may be required to a high degree of precision and
accuracy. This is particularly true in those situations where the
manipulator arm must have at least six independent degrees of
freedom in order to permit the article gripping member, i.e. the
hand of the manipulator, to have the range of movement necessary to
accomplish small part assembly operations. In such instances the
requirement for simultaneous movement in a number of different axes
during the teaching operation, in order to effect desired movement
of the manipulator hand along a particular line, becomes almost
impossible for a human operator to perform. For example, if it is
required that a pin be inserted into an opening in another part, it
is extremely difficult for a human operator to choose just the
right velocity components in all axes in which movement is required
to give the desired resultant straight line motion along the axis
of said opening, particularly where the axis of the opening is not
aligned with any axis of movement of the manipulator arm.
The task of initially programming or teaching the manipulator is
further complicated by the fact that facilities must be provided
for supplying large numbers of unassembled parts to the assembly
station where they can be picked up by the manipulator during the
assembly operation. Some small parts may be supplied to a fixed
pickup point by vibrator bowls or similar apparatus. However, many
parts, due to their size, shape, or weight, cannot be fed to a
given pickup point but instead are supplied to the assembly station
on pallets, each pallet containing a fixed number of parts at
different locations on the pallet. The manipulator arm then has to
be programmed or taught the position of each part on the pallet so
that during successive assembly operations the same type of part
will be picked up from different locations on the pallet.
Accordingly, the teaching of the manipulator apparatus is further
complicated when palletized parts are employed during the assembly
operation.
It is also important in situations where small parts are being
assembled by means of two cooperating manipulator arms, as for
example, when an arm inserts a spring in an opening and holds the
spring down while a keeper is placed over the spring by the other
arm, that the position of one arm does not move while the other arm
is being programmed or taught its desired movement. In prior art
arrangements, the manipulator arm may be moved to a desired
position during the teaching operation and this position recorded
as a program in memory storage for use on playback, but no
facilities were provided for ensuring that the arm would remain
fixedly at that position for any length of time. Accordingly, the
arm could be moved accidentally by the operator in adjusting a part
in the area of the manipulator hand. Also, the arm would droop, due
to leakage in the controlling hydraulic valves if the arm were left
in a particular position for an extended period of time.
It is, therefore, a primary object of the present invention to
provide a programmable automatic assembly system wherein one or
more of the above-mentioned disadvantages of prior art arrangements
is eliminated.
It is another object of the present invention to provide a new and
improved programmable automatic assembly system whereby the
assembly of small parts is achieved by programmed coordinated
movement between two cooperating manipulator arms.
It is a further object of the present invention to provide a new
and improved programmable automatic assembly system wherein
coordination between two closely-spaced programmable manipulators
is employed to assemble parts on a centrally located work table and
improved facilities are provided for initially teaching the two
manipulators to perform the desired assembly operations.
It is another object of the present invention to provide a new and
improved programmable manipulator which is particularly adapted by
virtue of its speed and accuracy of positioning to be employed in
the assembly of small parts at a work station adjacent to the
manipulator.
It is a further object of the present invention to provide a new
and improved programmable manipulator arrangement wherein
facilities are provided for assisting the teaching or programming
of the manipulator arm so that the article gripping hand may be
moved in a particular direction and to a desired end point along
that line automatically.
It is a still further object of the present invention to provide a
new and improved programmable manipulator arrangement wherein a
computer is employed during the initial teaching or programming of
the manipulator arm to calculate the points along a desired
straight line path and record these points as program steps in the
manipulator memory, these steps on playback causing the manipulator
hand to move along the desired straight line.
It is another object of the present invention to provide a new and
improved programmable manipulator arrangement in which a computer
may be used during the initial teaching or programming of the
manipulator arm to perform various tasks and calculations and
facilities are provided for storing the data generated by the
computer at the correct program step in the manipulator memory,
thereby to control movement of the manipulator arm or playback in
accordance with data generated by the computer during the teaching
operation.
It is another object of the present invention to provide a new and
improved programmable manipulator arrangement for removing parts
from or placing parts on predetermined locations on a pallet
wherein a computer is employed during the initial teaching or
programming of the manipulator arm to calculate from data fed into
the computer regarding certain locations where the manipulator arm
picks up or places parts on the pallet, the program steps necessary
to move that manipulator arm to all other locations of parts on the
pallet during successive playback cycles, and to record these
program steps in the manipulator memory automatically.
It is still another object of the present invention to provide a
new and improved programmable automatic assembly station wherein
two programmable manipulator arms cooperate with a centrally
located work table to assemble a plurality of parts on the table
while occupying a minimum of floor space for the overall assembly
station.
It is a further object of the present invention to provide a new
and improved programmable automatic assembly system wherein a
number of assembly stations each employing a pair of cooperating
manipulator arms are employed and facilities are provided for
operating these assembly stations in out of phase relationship so
that a single human operator can perform certain manual tasks at
each assembly station in sequence.
It is another object of the present invention to provide a new and
improved programmable automatic assembly station wherein two
programmable manipulator arms cooperate with a centrally located
work table to assemble a plurality of parts on the table and
facilities are provided during the initial teaching or programming
of each manipulator arm for holding either arm in its most recently
taught position while the other arm is moved to its next desired
position.
It is still another object of the present invention to provide a
new and improved programmable manipulator arrangement, wherein
facilities are provided during the initial teaching operation for
temporarily recording the position of the manipulator arm and
employing each temporarily recorded position to control the
position of the arm during the teaching operation until the arm is
moved to a different position.
It is a further object of the present invention to provide a new
and improved programmable automatic assembly system wherein a
plurality of automatic assembly stations are provided each having a
pair of programmable manipulator arms which cooperate in the
assembly of a desired group of parts, computer storage facilities
common to said stations are employed for storing a series of
program steps suitable for moving each of the manipulator arms at a
particular station in accordance with a desired series of
movements, and control means are provided for supplying the stored
program steps to the manipulator arms in each of the assembly
stations as required to permit the simultaneous assembly of groups
of parts at said stations.
Briefly, in accordance with one aspect of the invention, a series
of programmable automatic assembly stations are provided, each of
these stations including a pair of small, highly maneuverable
articulated manipulator arms which can cooperate in the assembly of
small parts at a centrally located work table between the
manipulator arms. All of the necessary parts to complete a given
assembly are positioned in predetermined locations at each assembly
station and in such position that they may be grasped by one of the
manipulator arms and assembled to or with other parts.
Furthermore, each assembly station includes a number of
interchangeable manipulator hands so that grippers of different
types, screwdrivers and other tools may be selectively connected to
either manipulator arm so that a wide variety of assembly tasks can
be performed at each station. Also, each of the manipulator arms at
each assembly station is capable of being moved at relatively high
speed and with a high degree of accuracy so that the assembly of
small parts to precise tolerances can be accomplished in a minimum
amount of time.
With such an assembly station concept a large number of assembly
operations are performed at each assembly station which requires
only a small amount of floor space as compared to a conventional
assembly line in which a large number of personnel are employed,
one for each assembly operation. Furthermore, since the assembly of
parts is being performed simultaneously at different assembly
stations, if a breakdown occurs at one assembly station, the entire
production is not halted, but instead, only the production at a
particular assembly station is lost. For example, in an assembly
system employing twenty assembly stations, if a downtime incident
occurs every twenty hours there would be a loss of production of
only one-twentieth the amount if a common conveyor system were
employed for the same amount of downtime.
In accordance with a further aspect of the invention, the
manipulator arms at one of the assembly stations can be taught or
programmed in any desired sequence of steps and the taught series
of program steps may be stored in a mass memory, such as a disc
file of large capacity, which is common to all of the assembly
stations. If the assembly of parts is not critical in positioning
of the manipulator arms, the taught series of program steps may be
employed to control the manipulator arms at the other assembly
stations so that identical groups of parts may be simultaneously
assembled at each station. This may be accomplished by providing
only storage facilities for one or two program steps at each
assembly station and sequentially transferring the common stored
program steps to each assembly station to effect the desired series
of assembly steps at each station. Such an arrangement eliminates
the requirement of large capacity, separate program storage
facilities in connection with each programmed manipulator arm, as
was required in past arrangements. Even if the assembly tolerances
are such that the manipulator arms at each assembly station have to
be separately programmed, due to manufacturing tolerances and other
differences between individual manipulator arms, the provision of a
large capacity central storage facility for the program steps
required by each assembly station is generally more economical than
providing separate storage facilities for each manipulator arm, as
has been done in the past.
In accordance with a further aspect of the invention a teaching
assist arrangement is provided wherein a computer may be interfaced
with the control circuitry of a particular manipulator arm and may
be employed to calculate the successive positions required to move
the manipulator arm in a desired direction. The complex
interrelated movements in the various axes of the manipulator arm
to produce resultant movement in a desired direction require
extensive calculations which are quite time consuming even for the
computer to accomplish. However, by performing these calculations
during the teaching operation, which is usually accomplished by
moving the manipulator arm quite slowly to a desired position, and
then recording the positions which have been calculated, sufficient
time is provided for the computer to perform its calculations. Once
these calculations have been made and the computed positions stored
as program steps in the memory, they may be used as command signals
during playback without requiring the assistance of the computer.
This is particularly important because the computer would not be
capable of carrying out these complex calculations during each
playback or repeat cycle and move the manipulator arm at a
sufficiently high rate of speed to be useful in assembling parts on
a mass production basis.
With the specific arrangement of the present invention, the
manipulator hand can be aimed in any desired direction and a
desired distance along that direction may be designated by the
teaching operator. The computer than performs all of the necessary
calculations to accomplish straight line motion of the hand in that
particular direction and to the desired distance so that insertion
of one part within another, taking parts from a pallet, and other
complex teaching jobs are substantially simplified. In accordance
with another aspect of the invention, the calculations performed by
the computer are substantially simplified by making the assumption
that the outer three axes of the manipulator arm, which control
orientation of the manipulator hand, all move in parallel straight
line motion in the particular desired direction. This assumption
introduces only very slight errors if movement from one program
point to the next is kept quite small, and the time required for
the computer to perform the necessary calculations is substantially
reduced by making this assumption.
In accordance with another phase of the invention, the computer may
be employed during the teaching operation to assist the teaching
operator in recording a series of program steps which are required
when the manipulator arm picks up parts from, or places parts on, a
pallet. Specifically the operator may move the manipulator arm to
three points on the pallet at which parts are to be picked up, such
as the parts at three corners of the pallet, and data regarding
these three positions are fed into the computer along with data as
to the number and spacing of parts on the pallet. The computer than
calculates the required position of the manipulator arm to pick up
all other parts on the pallet and record the calculated positions
as program steps which will be used on playback to pick up
successive parts from the pallet during successive playback
cycles.
In accordance with another aspect of the invention, facilities are
provided for moving the manipulator hand in a straight line path
between two programmed end points. This arrangement substantially
reduces the number of program steps which must be recorded to
accomplish a desired series of movements, particularly when these
movements involve complex curved paths, and the like. To effect
such straight line motion, the distance to be moved in each axis is
divided into a number of equal increments and artificial command
signals are generated at equally spaced intervals which are
employed to move the manipulator arm at a constant velocity in each
axis proportional to the distance to be moved in that axis. During
the teaching operation a computer may be employed to calculate the
number of increments and the rate of generation of said increments
necessary to providde a predetermined velocity on playback and
these calculations are stored at the appropriate program step in
the manipulator memory for use during playback.
In accordance with a further aspect of the invention facilities are
provided for the inclusion of one or more manually performed
assembly steps at each assembly station in timed relationship so
that a single human operator can perform the same manual assembly
steps at all of the assembly stations. For example, if a limp
O-ring is to be inserted at a particular point in an assembly
operation, this operation being performed more readily by hand than
by the programmed manipulator, the assembly operations at each
assembly station are coordinated so as to permit a human operator
to perform the manual assembly step at a particular assembly
station and then move on to the next assembly station and perform
the same manual step at that station. As a result, a single human
operator may serve a large number of assembly stations each of
which is simultaneously assembling a group of parts.
The invention, both as to its organization and method of operation,
together with further objects and advantages thereof, will best be
understood by reference to the following specification taken in
connection with the accompanying drawings in which:
FIGS. 1 to 3, inclusive, are perspective views of the programmable
automatic assembly station of the present invention;
FIG. 4 is a diagrammatic plan view of the assembly station to FIG.
1 showing the motions in various axes thereof;
FIG. 5 is a diagrammatic right side view of the assembly station of
FIG. 4;
FIG. 6 is a fragmentary, front elevational view, partly in section,
of one of the manipulators of the assembly station of FIG. 1;
FIG. 7 is a fragmentary view similar to FIG. 6 and showing the base
drive portion of the manipulator of FIG. 6;
FIG. 8 is a fragmentary, plan view of the manipulator base portion
of FIG. 7;
FIG. 9 is a fragmentary sectional view taken along line 9--9 of
FIG. 6;
FIG. 10 is a fragmentary rear view of the manipulator of FIG.
6;
FIG. 11 is a sectional view of the forearm portion of the
manipulator of FIG. 6 taken along the forearm twist axis
thereof;
FIG. 12 is a sectional view taken along the line 12--12 of FIG.
11;
FIG. 13 is a fragmentary plan view of the manipulator forearm
portion of FIG. 11;
FIG. 14 is a rear view of the gear drive portion of FIG. 11 taken
on a somewhat larger scale;
FIG. 15 is a sectional view taken along the line 15--15 of FIG.
14;
FIG. 16 is a sectional view taken along the line 16--16 of FIG.
15;
FIG. 17 is a fragmentary side elevational view similar to FIG. 11
but taken on a somewhat larger scale;
FIG. 18 is a sectional view taken along the line 18--18 of FIG.
17;
FIG. 19 is a sectional plan view of the manipulator hand portion of
the manipulator shown in FIG. 11;
FIG. 20 is a sectional view of one of the differential drive units
of FIG. 19 taken on a larger scale;
FIG. 21 is a diagrammatic view of the gear drive trains of the
manipulator of FIG. 6;
Referring now to the drawings, and more particularly to FIGS. 1 to
21, inclusive thereof, the programmable assembly system of the
present invention comprises a plurality of automatic assembly
stations one of which is shown in FIGS. 1, 2 and 3, it being
understood that a number of similar automatic assembly stations are
provided in the overall system and are arranged to be controlled by
a common computer arrangement or common storage facilities as will
be described in more detail hereinafter.
Each of the automatic assembly stations shown in FIGS. 1 to 3,
inclusive, includes a pair of programmable manipulator arms,
indicated generally at 50 and 52 which are positioned on opposite
sides of a centrally located rotatable work table. The table 54
includes a vertically extending work plate 56 on which parts may be
positioned for assembly with other parts thereon to provide a
completed subassembly of parts.
In accordance with an important aspect of the invention, the
manipulator arms 50 and 52 are capable of moving at high speed and
may be positioned with a high degree of accuracy so that the
assembly of small parts to precise tolerances can be achieved.
Furthermore, each of the manipulator arms 50, 52 is provided with
six degrees of angular motion and is comparable in its flexibility
and versatility to the human arm so that individual parts which are
positioned in predetermined locations on work pallets 58, 60, 62
and 64 may be grasped by the article gripping hand of one of the
manipulator arms, removed from the pallet and assembled on the work
plate 56 in the desired sequence to effect a particular assembly of
parts on the work table 54. Also nested around the working area of
the manipulator arms 50, 52 are a series of vibrator bowls 66, 68,
which may contain various small parts such as springs, washers, and
the like, and are positioned so that the article gripping
manipulator hand may grasp one of these items at a predetermined
location and insert it in the desired sequence during the assembly
operation.
In order that a wide variety of parts may be grasped and assembled
with other parts, each of the manipulator arms 50, 52 is provided
with a series of interchangeable manipulator hands, such as the
manipulator hands 70 and 72 associated with the manipulator arm 50,
the hands 70 and 72 being held in a bracket 74 when not in use in
such position that they may be automatically inserted into a
cooperating socket in the end of the manipulator arm.
Also, to facilitate the insertion of one part within another at
tolerances which are more precise than the positioning accuracy of
the manipulator arms 50, 52, the work table 54 is arranged to be
vibrated by a vibrator 76 which is mechanically connected to the
base of the work table 54. In addition, the work table may be
rotated to different indexed positions to facilitate the insertion
of parts on the work plate 56 by the arms 50, 52.
Considering now the mechanical arrangement of the manipulator arms
50, 52 which permits the rapid assembly of parts at high
accuracies, each of the manipulator arms, such as the manipulator
arm 50, includes a rotary platform 80 which is movable about a
vertical axis and is supported by the main base member 82 of the
manipulator 50. A shoulder arm portion 84 is pivotally mounted on a
horizontal shoulder joint or axis 86 by means of a pair of
upstanding ear portions 88 and 89 on the platform 80. An elbow arm
portion 90 is pivotally mounted on the upper end of the shoulder
arm portion 84 and is connected to the arm portion 84 by means of a
horizontal elbow joint or axis 92. A forearm portion 94 which is
coaxial with the elbow arm portion 90 is rotatable about the axis
of the elbow arm portion 90 to effect a so-called forearm twist
motion. The outer end of the manipulator hand 96 is provided with a
socket adapted to receive one of the manipulator hands 70, 72 and
may be rotated about a wrist bend axis 98 at the end of the forearm
portion 94. The outer end portion 96 of the manipulator hand may
also be rotated in a wrist swivel axis which is perpendicular to
and intersects the wrist bend axis 98.
In accordance with an important aspect of the invention, movement
of each of the manipulator arms 50, 52 in the above described six
different axes is arranged so that the different manipulator hands
attached to the end of each manipulator arm may be employed to
accomplish a wide variety of assembly operations with respect to
the centrally located work area. Thus, referring to FIGS. 4 and 5,
the area of the rotatable work table 54, indicated generally by the
circle 100 in FIG. 4, is positioned somewhat ahead of and spaced
between the two waist or rotary motion axes 102 and 104 of the
manipulator arms 50 and 52, respectively. Furthermore, the rotary
motion of each manipulator arm in the waist axes 102, 104 is
limited to 110 degrees as indicated by the arc 106 for the
manipulator arm 52, a similar but mirror image motion being
provided for the manipulator arm 50. Motion about the shoulder axis
86 (FIG. 5) is limited to 80 degrees, as indicated by the arc 108
in FIG. 5. Movement in the elbow axis 92 may be approximately 130
degrees, as indicated by the arc 110 in FIG. 5. Movement in the
major axes, i.e. the waist, shoulder and elbow axes, is limited in
the manner described above so that motor driven precision
ball-screw linear actuators may be employed to drive the indicated
arm portions over these limited ranges of movement and position the
same with a high degree of accuracy while moving these relatively
heavy portions of the manipulator at a high rate of speed, as will
be described in more detail hereinafter.
In order to provide drive means for the outer three axes, i.e. the
forearm twist, the wrist bend and wrist swivel axes, which will
permit more extensive movement of the outer end of the manipulator
arm, while avoiding rotational inertia effects which become
increasingly important at high speeds, the drive means for these
three outer axes are all located within the shoulder arm portion 84
of each manipulator arm and each drive means is directly connected
by gearing to the outer end of the manipulator arm through
coaxially arranged beveled gear drive systems arranged along the
elbow axis 92, as will be described in more detail hereinafter.
Accordingly, the manipulator hand portion 96 can be moved in the
wrist bend axis 98 through an arc of approximately 240 degrees as
shown by the arrow 112 in FIG. 4. The forearm twist portion 94 of
each manipulator arm may be rotated through an arc of approximately
300 degrees as indicated by the arrow 114 in FIG. 4 and the
manipulator hand portion 96 may be rotated continuously through 360
degrees in the wrist swivel axis as indicated by the arrow 116 in
FIG. 4. As a result, each of the manipulator arms 50, 52 may be
moved so that its wrist bend axis follows the center line indicated
at 118 in FIG. 4 for the manipulator 50, with respect to the waist
axis 102. The wrist bend axis 98 is also movable along the center
line indicated at 120 in FIG. 5 as the elbow arm portion 90 is
moved about the elbow axis 92 from the position shown in full lines
to the position shown in dotted lines in FIG. 5 and as the shoulder
portion 84 is moved from the position shown in full lines to the
position shown in dotted lines in FIG. 5 the axis 98 is movable
along the center line 121. It will thus be seen that complete
coverage of the work area around the work table 54 is provided by
the cooperating manipulator arms 50, 52 while at the same time
providing an arrangement whereby each manipulator hand may be moved
at a high rate of speed and accurately positioned to accomplish the
desired assembly operations in a minimum amount of time.
Considering now the manner in which each manipulator arm is moved
in the three major axes, i.e. the waist, shoulder and elbow axes,
consideration will first be given to the manner in which the elbow
arm portion 90 is moved about the elbow axis 92. Thus, referring to
FIGS. 6, 11 and 13 the elbow arm portion 90 is provided with a pair
of rearwardly extending ear portions 130 and 132 which support a
pivot pin 134 therebetween and the shoulder arm portion 84 is
provided with a pair of rearwardly extending flange portions 136
and 138 which support a pin 140 therebetween. A motor driven
precision ball screw linear actuator indicated generally at 142, is
positioned between the pins 134 and 140 so that when the actuator
142 is extended or retracted, the elbow arm 90 is pivoted around
the elbow axis 92 with respect to the shoulder arm portion 84 of
the manipulator. More particularly, a main housing 144 is pivotally
mounted on the pin 140 and supports an hydraulic drive motor 146
the output shaft 148 of which carries a gear 150. The gear 150 is
in mesh with an idler gear 152 which is mounted on the stub shaft
154 carried by the housing 144 and the idler gear 152 in turn
meshes with a gear 156 on the end of the shaft portion 158 of a
ball screw 160, the shaft portion 158 being mounted in the bearings
162 and 164 in the housing 144. Preferably, the idler gear 152 is
offset from the gears 150 and 156 and is movable so that it can be
adjusted for zero blacklash.
A ball nut 166 is mounted on the ball screw 160 so that it will be
advanced along the length of the screw 160 as this screw is rotated
in response to energization of the motor 146, it being understood
that suitable balls are provided between the threads of the ball
screw 160 and internal races within the ball nut 166 so that the
ball nut 166 is advanced as the screw 160 is rotated. An actuator
sleeve 168 is slidably mounted within an outer sleeve portion 170
of the housing 144, the inner end of the sleeve 168 being secured
to a portion 172 of the ball nut 166 which rides on the inner
surface of the housing sleeve 170, and the upper end of the
actuator sleeve 164 is provided with a cap portion 174 which is
pivotally mounted on the pin 134. The upper end of the ball screw
160 is rotatably mounted within the actuator sleeve 168 by means of
the bearing 176 and a pair of stop collars 178 and 180 are provided
at the opposite ends of the ball screw 160 which cooperate with
shoulders 182 and 184, respectively, on the ball nut 166 to limit
travel of the ball nut 166 in either direction. When either of the
shoulders 182 or 184 is engaged by the ball nut 166 the hydraulic
motor 146 ceases to rotate the elbow arm portion 90, thereby
defining the limits of the arcuate movement 110 (FIG. 5).
In order to pivot the shoulder arm portion 84 about the horizontal
shoulder axis 86, the upper end of the shoulder arm portion 84 is
provided with the upwardly and rearwardly extending ear portions
186 (FIG. 6) which support a pivot pin 188 therebetween and the
rotary platform 80 is provided with a pair of upstanding ear
portions 190 which support a pivot pin 192 therebetween. A motor
driven precision ball screw linear actuator indicated generally at
194 (FIG. 6) is positioned between the pivot pin 188 on the
shoulder portion 84 and the pivot pin 192 on the platform 80 so
that as the actuator sleeve portion 196 of the actuator unit 194 is
extended the shoulder arm portion 84 is tilted through an arc about
the vertical axis as indicated at 108 in FIG. 5. The linear
actuator 194 includes a main housing 198 which mounts hydraulic
motor 200, similar to the motor 146. In other respects the linear
actuator 194 is substantially identical to the linear actuator 142
described in detail heretofore. Accordingly, it will be understood
that when the motor 200 is energized the actuator sleeve 196 is
extended or retracted so as to pivot the shoulder arm portion 84
about the axis 86.
Considering now the manner in which the rotary platform 80 is moved
about the vertical waist axis, the main base member 82 of the
manipulator arm is employed as a support for an annular casting 202
which is provided with upper and lower tapered bearings 204 and 206
which in turn mounts an internal sleeve casting 208 which is
secured to the rotary platform 80 by means of the cap screws 210.
The member 208 is provided with a downwardly depending offset ear
portion 212 and a pivot pin 214 is mounted in this offset portion
of the member 208, another pivot pin 216 being mounted in a pair of
spaced ear portions 218 and 220 formed in the base member 82 at the
end thereof remote from the platform 80. A motor driven precision
ball screw linear actuator unit indicated generally at 222 is
mounted between the pivot pins 214 and 216, this actuator unit 222
including an hydraulic motor 224 and being in other respects
similar to the actuator unit 142 described in detail heretofore.
Accordingly, when the actuator sleeve 226 of the unit 222 is
extended and retracted the platform 80 is rotated about the waist
axis 228 through a range of 110 degrees, as shown in FIG. 4 and 8.
A removable cover 230 is provided for the base member 82 in the
vicinity of the actuator unit 222 so as to permit service and
repair on this unit. In this connection it will be noted that by
limiting movement in the waist or rotary axis to 110 degrees, the
safety of personnel working near the assembly station is enhanced
since the manipulator arm cannot be moved outside this arc.
However, this arc of rotary motion may be adjusted as desired
relative to the base of the manipulator, by adjustment of the
platform 80 before it is clamped to the member 208.
Considering now the drive means provided for the three outer axes,
i.e. the forearm twist axis, and the wrist bend and wrist swivel
axes, three hydraulic motors, two of which are shown in FIG. 6 at
232 and 234 are mounted within the shoulder arm portion 84. More
specifically, these hydraulic motors are mounted on a plate 236
which is secured to the underside of a transverse partition 240
provided intermediate the height of the shoulder arm 84, these
three hydraulic motors being mounted so that their axes intersect
the elbow axis 92 at spaced points along this axis. These motors
are controlled by the servo valves 233 (FIG. 10) and are supplied
with hydraulic fluid through the main rotary joint 235, which
permits rotary movement of the platform 80, and the pressure line
rotating joint 237 and returns line rotary joint 239, which permit
movement about the shoulder axis 86, the three hydraulic motors
being connecting to different sections of the joints 237 and
239.
In order to limit movement of the manipulator hand in the twist,
bend and swivel axes while providing an arrangement whereby each of
the motors 232, 234 is directly connected to control a particular
axis of movement of the hand, each motor, such as the motor 232 is
provided with a flexible coupling 242 connected to the end of the
motor, this flexible coupling being connected to a screw 244 (FIG.
10) along which rides a stop nut 246, the stop nut 246 being
restrained from rotation by means of a transversely extending lug
portion 248 (FIG. 9) having a bifurcated end portion which rides in
the edge of a plate 250 mounted within the shoulder arm portion 84.
Similar stop nuts 252 and 254 are provided for the other two axes,
the stop nut 252 having a lug portion 256 which engages the other
edge of the plate 250 and the stop nut 254 having a similar lug
portion 260 which engages a transversely extending plate 258 which
is secured to the plate 250 intermediate its edges. A pair of stop
collars, such as the stop collars 262 and 264, (FIG. 10), are
secured to each of the three screws 244, these stop collars being
provided with shoulders which engage cooperating shoulders on each
stop nut, such as stop nut 246 shown in FIG. 10 to limit rotation
in each axis to the amount of angular movement required in each
axis, as described in detail heretofore in connection with FIGS. 4
and 5.
Considering now the manner in which the elbow arm portion 90 is
pivotally mounted on the upper end of the shoulder arm 84 for
pivotal movement about the elbow axis 92 and also the arrangement
whereby suitable qearing is provided along the axis 92 for
interconnection of the hydraulic motors 232, 234 etc. to the
respective control axes for the manipulator hand portion 96, the
elbow arm portion 90 includes a cylindrical outer housing 270 (FIG.
11) which is mounted between a pair of spaced ear portions 272 and
274 (FIG. 12) provided at the upper end of the shoulder arm portion
94. The forward wall 276 of the shoulder portion 84 is shaped to
define a cylindrical trough portion 288 (FIG. 6) which permits the
housing 270 to be tilted about the axis 92 to the position shown in
dotted lines at 290 in FIG. 11. With such an arrangement, when the
elbow arm 90 is lowered and the shoulder arm portion 84 is tilted
forwardly the manipulator hand portion 96 may be moved relatively
close to the rotary platform 80 of the manipulator, as shown by the
portion 292 of the trajectory 294 shown in FIG. 5 which represents
movement of the outer end of the article gripper attached to the
hand portion 96. In order to permit such movement of the housing
270 around the axis 92, the bottom portion thereof is open in the
area shown at 296 in FIG. 11 so as to provide clearance for the
gearing associated with the rotatable shafts 244 which extend
upwardly through an opening 298 in the shoulder arm portion 84.
The housing 270 is provided with a pair of sidewardly extending
stub shafts 300 and 302 (FIG. 12) which are secured to the housing
270 at either side thereof by means of the bolts 304, the stub
shafts 300 and 302 being mounted in the bearings 306 and 308
provided in ear portions 272 and 274, respectively, so that the
housing 274 is pivotally mounted for movement along the elbow axis
92 at the upper end of the shoulder arm portion 84. The stub shafts
300 and 302 are also provided with inwardly opening recesses 310
and 312 (FIG. 12) which act as support bearings for the
independently movable gearing indicated generally at 314, which is
associated with the shafts 244 extending upwardly through the
opening 298 in the shoulder arm portion 84, the gearing 314 being
shown in more detail in FIGS. 14 to 16, inclusive. A retaining nut
316 is provided for each of the stub shafts 300 and 302, and end
caps 318, which cover the ends of the stub shafts 300 and 302, are
secured to the ear portions 272 and 274 by means of the bolts 320.
Accordingly, the housing 270 is accurately mounted for pivotal
movement about the elbow axis 92 while permitting independent
movement of the gearing 314 about the axis 92 so that movement for
the three outer axes may be transmitted through this gearing and
through the housing 270 to the forearm twist portion 94 and the
manipulator hand 96.
Considering now in more detail the gearing 314, a shaft 322 (FIG.
15) is provided with end rings 324 and 326 which are positioned
within the recess 310 and 312 of the stub shafts 300 and 302 (FIG.
12) and a series of three beveled ring gears 328, 330 and 332,
having teeth on both sides thereof, are rotatably mounted on the
shaft 322 by means of the bearings 334, 336 and 338. A first
casting member 340 is provided with a downwardly and rearwardly
extending ear portion 342 which is fixed to the upper end of the
shoulder arm portion 84 by means of a pin 344 (FIG. 12) which
passes through an opening 346 (FIG. 14) in the ear portion 342 so
that the casting 340 is fixed to and moves with the shoulder arm
portion 84. The casting 340 acts as a support for a plurality of
rotatable input shafts 348, 350 and 352 which are connected to the
upper ends of the screw shafts 244 by means of the universal
couplings 354 (FIG. 6). The input shaft 348, 350 and 352 carry
input beveled pinions 356, 358 and 360 which are in engagement with
the beveled teeth on one side of the ring gears 328, 330 and 332. A
second casting 362 is also rotatably mounted on the shaft 322 and
is provided with an ear portion 364 which is secured to the elbow
housing 270 by means of a pin 366 (FIG. 12) so that the casting 362
is fixed to and moves with the housing 270 as this housing is
pivoted around the elbow axis 92. The casting 362 acts as a support
for a plurality of rotatable output shafts 368, 370 and 372 which
carry beveled gears in engagement with the teeth on the opposite
side of the beveled ring gears 328, 330 and 332. Accordingly, when
any one of the input shafts 348, 350 or 352 is rotated, the
corresponding output shaft 368, 370 or 372 is rotated through the
intermediate double-sided beveled ring gear 328, 330 or 332, while
at the same time the output shafts may be rotated on the shaft 322
with respect to the input shafts as the housing 70 is pivoted
around the elbow axis 92.
Considering now the manner in which the input shaft 350 is employed
to rotate the forearm portion 94 about the axis of the elbow arm
portion 90 to effect the so-called forearm twist motion referred to
previously, the output shaft 370, which is interconnected with the
input shaft 350 through the ring gear 330, carries a drive pinion
374 (FIG. 17) which is in mesh with a gear 376 which is carried by
a shaft 378 which is rotatably mounted in a boss portion 380 of the
housing 270 by means of the bearings 382 and 384. The shaft 378 has
formed in the end thereof another pinion gear 386 which is in mesh
with an idler gear 388 secured to the end of a shaft 390 which is
rotatably mounted in a member 392 which is secured to the housing
270 by means of the bolts 394 (FIG. 18), the shaft 390 being
mounted within the member 392 by means of the bearings 396 and 398.
The forearm portion 94 comprises a generally cylindrical hollow
portion 400 (FIG. 1) which is rotatably mounted within the housing
270 by means of the bearings 402 and 404, the forearm portion 94
including a tapered outer portion 406 which terminates in a
transverse end plate 408 to which the hand gearing mechanism
indicated generally at 410 is secured. The elbow arm housing 270
includes an end ring 412 which is secured to the end of the housing
270 by means of the bolts 414, the ring 412 defining an air
passageway 416 (FIG. 11) between the ring 412 and the forearm
portion 94, a pair of O rings 418 and 420 being employed to provide
an airtight fit between the ring 412 and the forearm housing 400,
406 so that the forearm housing may be rotated with respect to the
ring 412 while maintaining an airtight seal. Compressed air may
then be supplied through the fitting 422 (FIG. 13) to the ring 412
and is supplied through a passageway 424 in the conical portion 406
of the forearm housing 94 to an air fitting 426 secured to the
exterior of this housing. Compressed air for actuating the gripper
members in the manipulator hand is thus conducted through the
rotatable forearm portion 94, it being understood that air from a
suitable compressed air supply is supplied to the fitting 422
through a flexible hose 428.
Referring again to the manner in which the forearm portion 94 is
rotated with respect to the elbow portion 90, the cylindrical
housing portion 400 is provided with an internal ring gear 430
(FIGS. 11 and 17) which is in mesh with the idler gear 388, the
gear 388 being carried by the housing 270, as described heretofore.
Accordingly, when the output shaft 370 of the gearing 314 is
rotated, the forearm housing portion 400 is rotated through the
gears 374, 376, 386, 388 and 430.
Considering now the manner in which the other two output shafts 368
and 372 of the gearing 314 are employed to effect the wrist bend
and wrist swivel actions described generally heretofore, it is
pointed out that all three of the output shafts of the gearig 314
extend through an opening 432 (FIG. 11) in the elbow housing 270
and the output shafts 368 and 372 (FIG. 15) are connected through
universal couplings 434, shafts 436 and universal couplings 438,
within the interior of the tapered forearm housing 400, 406 to two
splined shafts 440 and 442 (FIG. 19) which are mounted in the end
plate 408 of the forearm portion 94. The hand gearing mechanism 410
is mounted to the end plate 408 by means of the bolts 444 so that
this mechanism rotates with the forearm portion 94. Since the two
shafts 440 and 442 are offset from the central axis of the forearm
portion 94 the portions of the universal couplings 438 are provided
with splined end portions mating with the splined shafts 440 and
442 so as to permit a limited movement of the universal couplings
438 along the length of the shafts 440 and 442 as the forearm
portion 94 is rotated through 300 degrees in the forearm twist
axis.
The hand gearing mechanism 410 is shown in FIG. 19 and is
illustrated diagrammatically in FIG. 21. A beveled gear 446, which
is connected to the splined shaft 440, engages a mating beveled
gear 448 carried on the end of a transverse shaft 450. A gear 452
is positioned on the other end of the shaft 450 which is in mesh
with an adjustable idler gear 454 rotatably mounted on an idler
shaft 456. The idler gear 454 is connected to the input gear 458 of
a planetary drive unit 460 which is rotatably mounted in the
bearings 462 and includes an offset shaft 464 on which is mounted a
gear 466 in engagement with a fixed internal toothed ring gear 468
and a second gear 470 which is in engagement with an internal
toothed ring gear 472 which is connected to the wrist bend ouput
member 474. The output member 474 is rotatably mounted in the main
housing 476 of the hand gearing mechanism 410 by means of the
bearings 478 and 480 so that the member 474 may be rotated about
the wrist bend axis 98. Accordingly, when the output shaft 368 of
the main gearing 314 is rotated, the wrist bend output member 474
is rotated so that the outer end portion 482 thereof is pivotally
moved around the forward edge of the housing 476 along the bend
axis 98.
Considering now the manner in which rotation of the output shaft
372 is employed to effect the wrist swivel movement, the splined
shaft 442 has a drive pinion 490 on the end thereof which is in
mesh with an idler gear 492 rotatably mounted on an idler shaft
494. The idler gear 492 is in engagement with a gear 496 mounted on
one end of a shaft 498 which is rotatably mounted in a sleeve 500
by means of the bearings 502 and carries a beveled gear 504 on the
other end thereof. The beveled gear 504 is in mesh with a beveled
gear 506 formed on one end of a transverse sleeve 508 which is
rotatably mounted on a transverse shaft 510, the shaft 510 being in
turn rotatably supported at one end thereof within the housing 476
by means of the bearing 512 and is connected at the other end
thereof to a bore 514 formed in the bend output member 474 so that
the shaft 510 is aligned with the bend axis 98 and the member 474
may be rotated about this axis while at the same time permitting
the sleeve 504 to be independently driven through the swivel
gearing described heretofore.
A beveled gear 516 is formed in the other end of the sleeve 508 and
engages a beveled input gear 518 of a planetary gear drive unit 520
which is rotatably mounted in the member 474 by means of the
bearing 522 and includes an offset shaft 524 on which are mounted a
first gear 526 in engagement with an internal toothed ring gear 528
which is connected to the bend output member 474, and a gear 530
which is in engagement with an internal toothed ring gear 532
secured in one end of a wrist swivel output member 534. The member
534 is rotatably mounted in the outer end portion 482 of the bend
member 474 by means of the bearings 536 and 538. The wrist swivel
output member 534 is provided with a socket 540 adapted to receive
any one of a number of interchangeable article gripping members, or
other tools, and is provided with passageways 542 and 544 by means
of which compressed air can be supplied to the groove 546 and may
be employed to actuate the article gripping hand which is placed in
the socket 540, as will be readily understood by those skilled in
the art. The passageway 542 communicates with a groove 548 formed
in the periphery of the wrist bend output member 534, the groove
548 in turn communicating with an opening 550 in the outer portion
482 of the bend output member 474 so that compressed air may be
supplied by way of the conduit 552 (FIG. 13), through the rotating
joint 554 which is positioned on the wrist bend axis 98 and is
attached to one side of the hand gearing 410, and through the
output conduit 556 to the opening 550. Accordingly, compressed air
is supplied to the groove 546 for actuation of the article gripping
fingers while permitting movement in the above described wrist bend
and wrist swivel axes.
As stated generally heretofore, it is an important aspect of the
invention to provide a programmable manipulator arm arrangement
which is highly versatile and may be moved at high speed and
positioned accurately so as to accomplish assembly of parts to
close tolerances in a minimum amount of time. The above described
ball-screw drives for the three major axes accomplish these
objectives since they are powerful enough to rotate and tilt the
relatively massive shoulder arm portion 84 and pivot the elbow arm
portion 90. Furthermore, these ball screw linear actuators provide
a substantial step down ratio so that a relatively stiff drive
means is provided for positioning these relatively massive portions
of the manipulator arm to the desired accuracy. However, with
regard to motion in the three outer axes, these motions are
obtained by direct gearing as described in detail heretofore and it
is highly essential that all backlash be removed from the gear
trains associated with each of these axes. Furthermore, it is
important that an arrangement be provided in which backlash will
not be introduced upon wear of the parts so that continuous usage
of the manipulator without substantial downtime is provided.
Elimination of backlash is particularly important in the complex
hand gearing mechanism 410 since the article gripping fingers must
be precisely positioned in order to accomplish assembly of small
parts. To this end, each of the planetary drive units 460 and 520
is provided with a backlash eliminating arrangement which is
maintained despite wear of the intermeshing parts. More
particularly, with respect to the planetary unit 520 shown in FIG.
20, the main housing 506 thereof is provided with a pair of
transverse bores 562 and 564 which communicate with the ends of the
shaft 524, these end portions of the shaft 524 being provided with
bores 566 and 568 which receive transversely extending pins 565 and
567. The pins 565 and 567 are adapted to receive a plurality of
stacks of Belleville spring washers 570, each stack consisting of 8
or 9 spring and alternate stacks of springs being opposite
oriented, as shown in FIG. 20. The springs 570 may be held under
pressure by means of a cap 572, which is held in place by a nut
threaded into the threaded bore 574, so that side thrust is exerted
on both ends of the shaft 524. The shaft 524 is mounted in the
bearings 576 and 578 between end faces 580 and 582 of the housing
560 so that the entire assembly including the gears 526, 530 and
the bearings 576 and 578 may be urged laterally under the force of
the Belleville springs 570. Accordingly, when the planetary unit
520 is mounted in the hand mechanism 410, as shown in FIG. 19, the
teeth of the gears 526 and 530 are urged respectively into
engagement with the ring gears 528 and 532 so as to remove all
backlash in the planetary gear system. Preferably, the Belleville
washers 570 provide approximately 300 pounds of side thrust and are
operated over a portion of the force/deflection characteristic of
the springs in which the force remains relatively constant with
variation in deflection of the spring. Accordingly, when the moving
parts become worn and the deflection of the Belleville springs 570
changes slightly, the force exerted by these springs will still be
relatively constant so as to provide an automatic adjustment for
wear which continuously eliminates backlash. Furthermore, with the
disclosed arrangement it is not necessary to disassemble the hand
gearing mechanism 410 in order to compensate for changes in
backlash due to wear, or the like.
In connection with the automatic assembly station apparatus
described thus far, it should be pointed out that the speed and
accuracy with which the manipulator arms 50 and 52 are moved in
assembling parts on a mass production basis must be considerably
greater than that presently available in industrial robots if the
automatic assembly station is to be economically feasible.
Preferably, the speed and accuracy with which parts are assembled
should be one and one-half times that of a human being to justify
the use of such assembly stations. Such requirements for speed and
accuracy demands not only a stiffer supporting structure and drive
mechanism but also a lightweight design which will give the
manipulator arm a high enough natural frequency so that it can
respond to the desired control signals in a minimum amount of time.
With the arrangement of the present invention, the hydraulically
driven ball screws and high reduction ratio gear boxes provide the
necessary stiffness in structure which is considerably superior to
the hydraulic cylinder actuator type of drive employed previously
for moving the controlled axes of a manipulator apparatus. While
the hydraulic cylinder actuator is superior in response to a
pneumatic one, the oil column in the cylinder is compressible and
reflects the condition of all load changes and variations and hence
is too soft and spongy to be used for rapid assembly of parts.
The hydraulically driven ball screw drive arrangements described in
detail heretofore provide a stiffness which is several orders of
magnitude better than the hydraulic vane motor type of drive
arrangement. In this connection it is also pointed out that the
amount of stiffness required is related to the inertia of the mass
that is to be driven. For the wrist bend and wrist swivel motions,
less stiffness is required than for the major arm articulations.
Thus, if stiffness is plotted against moment of inertia, a diagonal
line across the plot will represent a constant natural frequency
and the wrist articulations and major arm articulations will lie on
a constant frequency line, the larger inertia major articulations
requiring a larger angular stiffness along this line. The
arrangement of the present invention provides an increase in
natural frequency of approximately one order of magnitude which
results in a speed increase of a factor of two for short motions
and a five-fold increase in accuracy. The arrangement of the
present invention also provides hand gear trains which are
relatively small so that the manipulator hands may be programmed to
assemble small parts and at the same time provides the above
described planetary gear systems which provide approximately
sixteen to one reduction, which when combined with the two to one
input gear reduction provides an overall thirty-two to one ratio
which provides the desired output speed in relative to conventional
motor speeds. It is also pointed out that the inertia forces of the
high speed elements in the manipulator arm are minimized in
accordance with the present invention by selecting a ball screw
with a relatively coarse pitch. Thus, the ball screw such as the
ball screw 160 provided in the actuating unit 142, preferably has a
pitch of one thread per inch so that when driven at a maximum speed
of 1500 inches per minute the inertial forces of the drive elements
do not become excessive.
While there have been illustrated and described various embodiments
of the present invention, it will be apparent that various changes
and modifications thereof will occur to those skilled in the art.
It is intended in the appended claims to cover all such changes and
modifications as fall within the true spirit and scope of the
present invention.
* * * * *