Note: Descriptions are shown in the official language in which they were submitted.
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WRIST TENDON ACTUATOR
BACKGROUND GF THE I~NENTION
1. Field of the Invention.
The present invention relates generally to
05 mechanical joints and in particular relates to a
mechanical joint for a robot wrist.
2. Description of the Prior Art.
Interest in robotics and the use of robots
in industrial applications has greatly increased in
recent years. One area in which the use of robots
has become important is the replacement of humans in
tasks that involve manual work, such as welding,
material handling, paint spraying, and assembly.
Many of these tasks require working in cramped spaces
or performing complex maneuvers. To perform such
tasks, a robot arm or wrist should be able to
rotationally move in a range similar to a human wrist
and at a dwell time acceptable for the particular
task involved.
One article reviewing the development of
robot arms and wrists is entitled, "Robot Wrist
Actuators," Robotics Age, ~ovember/December 1982,
pp. 15-22, and was wxitten by the applicant of the
present application. In the article, several
characteristics are described that make robot wrists
attractive. One characteri6tic is that a mechanical
arm or wrist can be safely used in areas where there
is a danger of explosion if the wri t is driven by
hydraulic actuators~ However, there are several
disadvantages with the prior art robot arms and
wrists. Some of the disadvantages are also
enumerated in the above-mentioned article and include
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large and bulky mechanical joints, slow dwell time in
some rotational directions and low mechanical
efficiency.
A number of well known universal joints are
05 illustrated and described on pages 16 and 11 of the
Pictorial Handbook of Technical Devices by Pete
Grafstein and 0. Schwarz, published by the Chemical
Publishing Company, Inc. of New York, 1971. Although
rotational motion can be transmitted through the
universal joints illustrated on pages 16 and 17, the
universal ~oints cannot be used in operations for
tran6mitting pitch, yaw and roll motion to an
implement or tool member.
A rotary actuator mechanism is described in
the Higuchi et al U.S. Patent 4,009,644. However,
the rotary actuator of the Higuchi et al Patent is
not very useful for the transmission of pitch, yaw
and roll motion to a tool or implement member.
A number of robot joints are illustrated in
the Vykukal U.S. Patent 3,405,406 and the Vykukal et
al U.S. Patent 4,046,262. The Vykukal patents
describe hard-type space suits that permit the user
inside the space suit to move around somewhat
unrestricted.
The Bolner U.S. Patent 3,912,172 describes a
back-drivable, direct drive, hydraulically-actuated
pitch and roll actuator.
The Rosheim U.S. Patents 4,194,437 and
4,296,681, which were issued to the applicant of the
present application, describe hydraulic
servomechanisms which impart rotary movements to a
device to be driven.
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The Stackhouse U.S. Patent 4,068,536
describes a remotely-driven, mechanical m~nipulator.
The manipulator is controlled by three concentric
drive shafts which terminate in a spherically-3paced
05 wrist mechanism.
The Totsuka U.S. Patent 3,739,g23 and the
Niitu et al U.S. Patent 3,784,031 describe a manipu-
lator arm having two parallel rotating drive shafts
in a beveled gear system which translates the drive
shaft's rotating motion to a bending pitch motion and
rotary roll motion in a tool member.
A mechanical wrist is described in German
Patent 2,752,236 that includes three electric motors,
providing pitch, yaw, and roll, which are mounted on
the outside of a housing with the inside of the
housing being hollow. The wrist is used for holding
welding tongs and the hollow inside housing permits
electrical power lines to be fed through the wrist.
The Molaug U.S. Patent 4,107,948 describes a
flexible robot arm that is composed of a number of
mutually connected rigid links being connected at one
end to a drive mPans and at the other end to a tool
member that is to be rotated. Another robot arm is
illustrated in the Wells U.S. Patent 3,631,737. The
robot arm of the Wells Patent includes a plurality of
rigid tubular sections joined end-to-end by flexible
joints to form an articulated arm. The rigid
sections are manipulated by slender control cables
which are attached to the respective sections and
selectively extend and retract.
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SUMMARY OF THE INVENTION
The present invention is a ball and socket
mechanical joint having pitch, yaw and compound
pitch-yaw movement, particularly adaptable ~or
05 anthropomorphic joint design including hand ~nuckles
and personal robots. The mechanical joint is
singularity-free and back-drivable for walk-through
programming~ The mechanical joint is a simple and
ru~ged economical design and is easily miniaturized.
The mechanical joint includes a spherical
member having a pair of grooves in i~s outer surface,
each groove e~tending circumferentially about the
spherical member and disposed approximately 90 from
each other. A housing means has a concave spherical
socket for receiving the spherical member. The
housing means includes a pair o~ slots located
proximately at an equatorial plane of the spherical
member. A frame means is fixedly secured to the
spherical member at the intersection of the first and
second groove opposite the housing means. A first
ribbon means, slidable wi~hin the first groove, is
attached to pivot pins in the slots of the housing
means and is looped around a first pulley within the
frame means. A second ribbon means slidable within
the second groove, is attached to pivot pins mounted
in the housing means at the approximate midpoints
between the slots of the housing means. The second
ribbon means is attached to a second pulley within
the housing means. An output means is fixedly
connected to the housing means. A first and second
drive means provide selective movement of the first
and second ribbon means.
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In a first alternate embodiment, an integral
passageway for fluid iB provided in the mechanical
joint of the present invention. In a second
alternate embodiment, a pair of sleeve assemblies
Q5 teaches roll movement for the wrist actuator combined
with the pitch and yaw movements.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of the
apparatus of the present invention, with portions
broken away for clarity.
Figure 2 is a sectional view taken along
line 2~2 of Figure 1.
Figure 3 is a sectional view taken along
line 3-3 of Figure 1.
Figure 4 is a ssctional view taken along
line 4-4 of Fig. 3 illustrating a ball of the present
invention.
Figure 5 is an alternate embodiment of the
present invention illustrating an internal fluid
passageway.
Figure 6 i9 a detailed view of the
embodiment of Fig. 5 showing the port in a pivot pin.
Figure 7 is an alternate embodiment of the
pre~ent invention showing a roll axis and a pair of
slidable sleeve assemblies.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The mechanical joint or wrist actuator
generally indicated at 10 of the present invention is
illu~trated in Figure 1. Throughout the figures and
the embodiments, like reference characters are used
to indicate like elements.
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A ball or spherical member 20 i8 $ixedly
connected to a frame member 32. The ball 20 includes
a pair of grooves 22 and 24 cut circumferentially and
approximately 90 apart from each other in the outer
05 surface of the ball 20.
The frame member 32 is preferably an
elongated hollow and generally rectangular frame.
The ~rame 32 is connected to the ball 20 at a point
where the grooves 22 and 24 intersect. A shaft or
rod 30 is fixedly mounted inside the ball 20 and
extends into the open central portion of the frame
member 32.
A housing 40 receives the ball 20 and
includes a concave spherical socket or cavity for
receiving the ball 20. The housing 40 slides over
the outer surface of the ball 20 in a manner similar
to a ball-and-socket joint. The housing 40 includes
a pair of rectangular slots 41 and 42 as best seen in
Figure 4. The slots 41 and 42 are disposed at
proximate an equatorial plane of the ball 20. The
slots 41 and 42 are diametrically opposed to each
other. A retaining flange 43 is secured to the
housing by screws 44A and 44F.
The housing includes an output shaft 45
secured by a nut 46. If desired, the output shaft
may be integral with the housing 40, as illustrated
in Figures 5 and 7. It is to be understood that the
output shaft 45 in the Figures is representative of
any desired tool implement, such as a disk, grippers,
and the like.
A pair of tendons or ribbons 52 and 54 are
wrapped around the ball and disposed within the
.
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grooves 22 and 24 respectively. Each ribbon 52 and
54 is movable within its respective groove as will be
described subsequently. The ribbons are made o~ a
flexible, yet strong ma~erial, such as a reinforced
05 fabric.
As illustrated in Figure 3, the ribbon 52
has a first end 52A which is inserted over a first
flanged pin 56 and a second end which is inserted
over a second flanged pin 58. The pins 56 and 58
along with the ribbon ends 52A and 52B slide in the
groove 22. The ribbon 52 extends along the groove 22
of the ball 20 and through the frame member, between
the rod 30 and the frame member 32 and exits the
frame member 32 at an opening 34. An idler 36
rotatably secured into the frame 32 reduces slack in
the ribbon 52 as it exits the opening 34. The ribbon
52 loops around a pulley 70 and passes over a pulley
38. The pulley 38 i5 mounted within the frame member
32 by pin 39 attached to the frame member at a point
where the shaft 30 terminates. The ribbon 52 extends
back through the opening 34 inside the frame member
32 and extends upwardly between the rod 30 and the
frame member 32 into the groove 22 of the ball 20 up
to pin 56. The pins 56 and 58 are extended into and
slidably engage slots 41 and 42, respectively, of the
housing 40.
As illustrated in Figure 2, the ribbon 54
extends into the groove 24 and held at an end 54A by
a ~langed pin 60 and at an end 54B by a flanged pin
30 62. The pins 60 and 62 along with the ribbon ends
54A and 54B slide in the groove 24. I~e pin 60 and
62 rotatably engage bearings 61 and 63,
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respectively. The b0arings 61 and 62 are mounted to
the housing and are disposed about the equatorial
plane of the ball 20 at midpoints between slots 41
and 42. Thus, the pins 60 and 62 are approximately
05 180 from one another. The ribbon 54 extends
downwardly from the ball 20, through the frame member
32 and is looped around a pulley 74. The pulley 74
is located proximate a bottom end of the frame member
32.
The pully 70 is mounted to an ou~put shaft
71 of a motor 72. The ribbon 52 is looped over the
pulley 70 and moved by the motor 72 as best
illustrated in Figure 1. The pulley 74 is mounted to
an output shaft 75 of a motor 76 by a snap ring 77.
Ribbon 54 is looped over pulley 74 and activated by
motor 76. Any desirable means of connecting ribbons
52 and 54 to a driven shaft is includable within the
present invention. It i~ preferred that the motors
be bidirectional, that is capable of driving ribbons
52 and 54 in two directions.
Figure 4 is a sectional view taken along the
equatorial plane of the ball 20. The ball 20 and
grooves 22 and 24 travel intact and the housing 40 is
shown in section. The grooves 22 and 24 extend
circumferentially around an outer surface of the ball
and intersect at the ball's top. The ribbon 52 is
connected to the pins 56 and 52 which slide within
slots 41 and 42, respectively. The ribbon 54 is
connected to pins 60 and 62 which rotate within the
bearings 61 and 63, respectively.
As the housing is rotated in pitch, yaw or
compound pitch-yaw movement on the ball 20, the
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ribbons 52 and 54 slide within their respectlve slots
and move about their respective pulleys. Simple
pitch movement of the wrist actuator 10 is
accomplished by pivoting the housing 40 about pins 56
05 and 580 In this manner, ribbon 54 travels and slides
within groove 24. Simple movement about the yaw axis
occurs when the housing 40 pivots about pin~ 60 and
62, causing ribbon 52 to slide within groove 22. In
compound pitch-yaw movement, pins 56 and 58 slide
within their respective slots 41 and 42 as the
housing 40 rotates and pivots about pins 56, 58, 60
and 62~
The wrist actuator 10 of the present
invention can be adapted to provide a fluid channel
or passayeway ~0 as illustrated in Figures 5 and 6.
In the embodiment in Figures 5 and 6, the rod 30 and
the ball 20 are shown as an integral structure.
Additionally, the housing 40 and the output shaft 43
are shown as an integral structure. An internal bore
20 82 is provided in the rod 30 and ball 20. The bore
82 leads to an interior fluid chamber 84 defined by
the housing 40 and the ball 20. The chamber 84 is
sealed by a ring liner 86 which is positioned and
slides within groove 24. The ring liner 86 includes
25 a pair of flanged pins 87 and 88 that replace pins 60
and 62 of the embodiment shown in Figures 1-4. In
addition, ring liner 86 includes a seal 89 to contain
the fluid in the chamber 84.
A detailed section view of the ring liner 86
and pin 88 is illustrated in Figure 6. An internal
port 90 is provided along the longitudinal axis of
pin 88 from the flange portion to a desired position
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on the ou~er surface. The port 90 allows fluid to
flow from the interior fluid chambex 84 to an
internal bore 92 that extends through the housing and
the output shaft. A pair of 0-rings 94 and 96 are
05 pxovided on the pin 8>3 on opposite sides of the
housing bore 92 to prevent leaXage from the port 90~
The ring liner 86 is secured to the housing 40 by
pins 87 and 88 and slides with the housing 40 over
the ball 20. The ribbon 54 is held in place by pins
87 and 88 in a manner similar to th~ embodiment of
Figures 1-4.
An alternate embodiment of the present
invention having a roll axis is depicted in Figure
7. A pair of sleeve assemblies 110 and 150 are
slidably connected to the frame member 32. The first
sleeve assembly 110 includes an inner sleeve 112 and
an outer sleeve 114. A peg 113 projecting ~rom the
inner sleeve 112 is inserted into the ribbon 54. As
the inner sleeve 112 slides along the longitudinal
axis of the frame member 32, the pegs travel within
the borders of a slot 115 of the frame member 32,
causing the ribbon to move through the frame member
and about the pulley 38.
The outer sleeve 114 is decoupled ~rom the
inner sleeve 112 by a pair of ring bearings 118 and
120. The ring bearings permit the outer sleeve 114
to rotate about the inner sleeve 112. A linearally-
actuated rod 124 is fixedly connected to the outer
sleeve 114. Any suitable drive means, such as an
electric motor or hydraulic cylinder, can be used to
actuate the drive rod 124 along the arrow~ 126 and
128. Linear movement of the rod 124 is transmitted
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to the wrist actuator 10 by the ribbon 52 to provide
yaw movement.
In a similar manner to the first sleeve
assembly 110, a second sleeve assembly 150 is
05 slidable along the longitudinal axis of the frame
member 32. An inner sleeve 152 is connected to the
ribbon 52 by a peg 153. As the inner sleeve 153
travels along the longitudinal axis of the frame
member 32, the ribbon 52 is rotated inside the frame
member 32 about pulley 74 mounted on pin 79.
The outer sleeve 154 is decoupled from the
inner sleeve 152 by a pair of ring bearings 156 and
158. A rod 160 is fixedly connected to the outer
sleeve 154. Any suitable drive means for actuating
the rod 160 along arrows 161 and 162 may be utilized
and provide pitch movement to the wrist actuator 10.
A drive shaft 180 is fixedly connected to an
end of the frame member 32 oppo~ite the ball 20. As
the drive shaft rotates, sleeve assemblies 110 and
150 decouple the rods 124 and 160 from the frame
member 32. Thus, roll movement may be transmitted to
the output shaft 45 simultaneously with pitch and yaw
movement through the actuation rods 124 and 160.
The wrist actuator of the present invention
is simple to operate and economical to manufacture.
The ball 20 is constructed of any lightweight
material capable of being formed to the
specifications described. Plastics and other like
materials such as sold by E. I. DuPont under the mark
DELRIN are suitable for the ball 20. The wrist
actuator 10 is singularity-free and back-drivable for
walk-through programming. The wrist acutator 10 has
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up to 100 degrees of pitch motion and 100 degrees of
yaw motion about a common center point, thereby
avoiding gimbal locX in compound pitch~yaw motion.
Although the present inve~tion has been
05 described with reference to preferred embodiments,
workers skilled in the art will recogni~e that
changes may be made in form and detail without
departing from the spirit and scope of the invention.
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