U.S. patent number 4,690,012 [Application Number 06/859,239] was granted by the patent office on 1987-09-01 for robot wrist.
This patent grant is currently assigned to ASEA Aktiebolag. Invention is credited to H.ang.kan Dahlquist, Herbert Kaufmann.
United States Patent |
4,690,012 |
Dahlquist , et al. |
September 1, 1987 |
Robot wrist
Abstract
A wrist for an industrial robot with a large orientation
capacity comprising first, second , third and fourth turnable wrist
parts arranged in series with each other. The first wrist part is
rotatable about a first axis. The second wrist part is journalled
in the first wrist part and is rotatable about a second axis which
intersects the first axis. The third wrist part is journalled in
the second wrist part and is rotatable about a third axis which
intersects the second axis. A tool attachment is rotatably
journalled in the third wrist part about a fourth axis which
intersects the third axis.
Inventors: |
Dahlquist; H.ang.kan
(Vaster.ang.s, SE), Kaufmann; Herbert (Vaster.ang.s,
SE) |
Assignee: |
ASEA Aktiebolag (Vaster.ang.s,
SE)
|
Family
ID: |
20352365 |
Appl.
No.: |
06/859,239 |
Filed: |
May 7, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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645686 |
Aug 30, 1984 |
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Foreign Application Priority Data
Current U.S.
Class: |
74/490.06;
74/417; 901/26; 901/29 |
Current CPC
Class: |
B25J
17/0291 (20130101); Y10T 74/20335 (20150115); Y10T
74/19665 (20150115) |
Current International
Class: |
B25J
17/02 (20060101); G25J 017/02 () |
Field of
Search: |
;414/735
;901/14,15,26,28,29,38 ;74/665C,417,479 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Spar; Robert J.
Assistant Examiner: Underwood; Donald W.
Attorney, Agent or Firm: Watson, Cole, Grindle &
Watson
Parent Case Text
This application is a continuation of application Ser. No. 645,686,
filed Aug. 30, 1984, now abandoned.
Claims
What is claimed is:
1. A wrist mechanism which can be attached to the arm of a robot
and which can support a working tool, said wrist mechanism
comprising
a first tubular wrist part which defines a first central axis
therethrough and which has a first end and a second end, said first
end being mountable on said robot arm so as to be rotatable about
said first central axis and said second end having an oblique
orientation relative to said first central axis, said first central
axis defining a first rotation axis of said wrist mechanism,
a second tubular wrist part which defines a second central axis
therethrough and which has a first end and a second end, each of
said first and second ends having an oblique orientation relative
to said second central axis,
first journal means for mounting the first end of said second
tubular wrist part to the second end of said first tubular wrist
part and to enable said second tubular wrist part to rotate
relative to said first tubular wrist part about a second rotation
axis which intersects said first central axis,
a third tubular wrist part which defines a third central axis
therethrough and which has a first end and a second end, said first
end having an oblique orientation relative to said third central
axis,
second journal means for mounting the first end of said third
tubular wrist part to the second end of said second tubular wrist
part and to enable said third tubular wrist part to rotate relative
to said second tubular wrist part about a third rotation axis which
intersects said third central axis,
bevel gear means interconnecting the second end of said first
tubular wrist part with the first end of said third tubular wrist
part so as to cause coordinated rotation therebetween,
a tool attachment means, and
a third journal means for mounting said tool attachment means on
the second end of said third tubular wrist part and to enable said
tool attachment means to rotate relative to said third journal
means about a fourth rotation axis which intersects said third
rotation axis,
said first, second and third tubular wrist parts allowing a cable
to be extended therethrough.
2. The wrist mechanism according to claim 1, wherein the robot arm
to which said wrist mechanism is attachable includes first and
second drive means, wherein the first end of said first tubular
wrist part is connectable to said first drive means such that said
first drive means can cause said first tubular wrist part to rotate
about said first rotation axis, and wherein the first end of said
second tubular wrist part includes a first gear wheel means which
is engageable with said second drive means such that said second
drive means can cause said second tubular wrist part to rotate
about said second rotation axis.
3. The wrist mechanism according to claim 2, wherein said first
gear wheel means comprises an annular bevel gear pinion.
4. The wrist mechanism according to claim 3, wherein the robot arm
to which said wrist mechanism is attachable includes a third drive
means, wherein a second gear wheel means is rotatably journalled
within said second tubular wrist part, and wherein said tool
attachment means includes a third gear wheel means, said second
gear wheel means being engaged with said third gear wheel means and
engageable with said third drive means such that said third drive
means can cause said second gear wheel means to rotate and said
tool attachment means to rotate about said fourth rotation
axis.
5. The wrist mechanism according to claim 4, wherein said second
gear wheel means comprises a first pair of interconnected annular
bevel gear pinons which are rotatably journalled within the first
end of said second tubular wrist part, a second pair of
interconnected annular bevel gear pinions which are rotatably
journalled within the second end of said tubular wrist part, and a
hollow sleeve rotatably journalled within said second tubular wrist
part and engaged with both said first pair and said second pair of
annular bevel gear pinions, said first pair of annular gear pinions
being also engageable with said third drive means, and said second
pair of annular gear pinions being also engaged with said third
gear wheel means.
6. The wrist mechanism according to claim 5, wherein said third
gear wheel means comprises an annular bevel gear pinion.
7. The wrist mechanism according to claim 3, including drive motor
means mounted in said second tubular wrist part and connection
means extending between said drive motor means and said tool
attachment means to rotate said tool attachment means about said
fourth rotation axis.
8. The wrist mechanism according to claim 3, including drive motor
means mounted in said third tubular wrist part and connection means
extending between said drive motor means and said tool attachment
to rotate said tool attachment means about said fourth rotation
axis.
Description
BACKGROUND OF THE INVENTION
This invention relates to a robot wrist and to a robot provided
with a robot wrist. In particular, the invention is concerned with
a robot wrist having a high orientation capacity, .theta.. (In this
connection the term "orientation capacity" refers to that ratio of
the surface area of a sphere of given radius, centered on the point
of articulation of the wrist, to the surface area of the spherical
or part spherical surface of the same radius which can be reached
by a member articulated by the wrist. Thus the orientation capacity
.theta. ranges from 0 to 1, a high value for .theta., e.g.
.theta.=0.8, indicating that the wrist has a high degree of
orientation about its point of articulation).
For operations such as arc welding, glueing, puttying, burring, and
so on, involving the use of industrial robots operable within
confined spaces, e.g., inside box-shaped objects such as the
insides of car bodies, heavy demands are placed on the industrial
robots used. In order to perform such operations the robot should
have at least six axes of movement to enable a tool carried by the
robot to be positioned, aligned and adjusted at any desired
location within its operating range. Three such axes are normally
provided in the robot itself and the other three axes provided in
the robot wrist.
The robot arm and the robot wrist should also be hollow to
accommodate a channel for cables and other wires in the robot arm
and robot wrist. This channel should have a large radius of
curvature and be otherwise so shaped as not to damage the cables
and wire during operation of the robot, for example when the robot
has a bent wrist.
To move a tool or a welding tip with a constant angle towards a
working surface in a box, an orientation capacity of .theta.=0.8 is
required. This means that the wrist should be capable of being
deflected at least 135.degree. from the central axis of the robot
arm carrying the wrist and be capable of adopting any angular
position around the central axis of the robot arm.
The present invention aims to provide a robot wrist with a large
orientation capacity and with three axes of movement.
A further aim of the invention is to provide a channel through the
wrist for the passage of wires, cables or conduits for operating a
tool carried by the wrist.
SUMMARY OF THE INVENTION
According to the invention, the wrist is formed with a plurality of
rotatable parts arranged in series with each other, these parts
each being rotatable around a different axis. A first wrist part is
rotatable around a firt axis. A second wrist part is journalled in
the first wrist part and is rotatable around a second axis which
intersects the first axis. A third wrist part is journalled in the
second wrist part and is rotatable around a third axis intersecting
the second axis. In a third part of the wrist a tool attachment is
rotatably arranged around a fourth axis intersecting the third axis
of the robot arm.
Conveniently, the first and third wrist parts are provided with
gear pinions for interconnecting the parts. These gear pinions may
cooperate directly with each other, or possibly cooperate with
intermediate gear pinions.
Suitably the second wrist part is connected to drive means via a
drive shaft in the robot arm and bevel gear pinions on the drive
shaft and on the second wrist part. The tool attachment means in
the third wrist part is suitably connected to drive means in the
robot via a drive shaft in the robot arm and an intermediate gear
unit with a number of gear pinions, arranged in series, in the
second wrist part. These gear pinions are suitably annular, thus
obtaining a through-going opening or channel in the wrist, in which
cables and other wires may be extended to a tool, for example a
welding tool. It is also possible to arrange a drive motor for the
tool attachment in the wrist.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described by way of
example, with reference to the accompanying drawings, in which
FIG. 1 is a side view of a computer-controlled industrial robot
provided with a wrist according to the invention,
FIGS. 2 and 3 are sectional views of a wrist according tc the
invention with an extreme axis of the wrist oriented so as to
coincide with the axis of the outer arm of the robot and making a
maximum angle with this axis, respectively, and
FIGS. 4 and 5 are sectional views of a wrist having a driving motor
inside the wrist for the rotary movement of the tool carrier
means.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, reference numeral 1 designates an industrial robot
having six axes, three of which are in the robot itself and three
in the wrist of the robot. The robot 1 comprises a base plate 2 on
which is mounted a column 3 journalled for rotation about an axis
A--A. A first arm 4 is mounted on the column 3 for rotary movement
about an axis B and, at the end or upper part of this first arm 4,
a second arm 5 is rotatably journalled for angular movement about
an axis C. The column 3 is operated by drive means (not shown), the
arm 4 is operated by a drive device 6 and the arm 5 is operated by
a drive device 7, the main part of which is concealed by the drive
device 6. A drive device 8 is mounted on one end of the arm 5 for
driving a wrist 10 provided at the free end of the arm 5.
As can be seen in FIGS. 2 and 3, the wrist 10 comprises first,
second and third parts 11, 12 and 13, respectively, arranged one
after the other and rotatable or turnable with respect to each
other. The first wrist part 11 is rotatable around an axis D--D,
the second part 12 is rotatable around an axis E--E, and the third
part 13 is rotatable around an axis F--F. The whole wrist 10
constitutes a readily replaceable unit since the first wrist part
11 is formed so as to be connectible to a tubular drive shaft 15
journalled in a bearing 14 in the robot arm 5.
The wrist part 11 comprises a tubular sleeve 16 having one end
which is cut-off perpendicular to the axis D--D and which is formed
with a threaded flange 17 and another end which is obliquely
cut-off perpendicular to the axis E--E and which is formed with a
seat for a bearing 23. A ring 20 is joined to the sleeve 16 by
bolts 18 and forms the seat for bearings 21 and 22. The wrist 10 is
joined to the drive shaft 15 by means of the threaded flange 17 and
a threaded ring 25, applied on the flange 24 of the drive shaft,
and a locking pin 26 for fixing the parts in mutually correct
angular positions. An annular bevel gear pinion 27 is joined to the
obliquely cut-off end of the sleeve 16 by means of bolts 28 and
forms a fixing ring for a bearing 23.
The second wrist part 12 comprises a tubular sleeve 30 which is cut
off obliquely at both its ends. The sleeve 30 is formed with seats
for the bearing 23, a corresponding bearing 31 and the bearings 32,
33, 34, 35. Mounted on the sleeve 30 are an annular bevel gear
pinion 37, which is joined to the tube sleeve 30 by means of bolts
38 and forms a fixing ring for the bearings 23 and 32, a ring 40
which is joined to the tubular sleeve 30 by bolts 41 and forms a
fixing ring for bearings 31 and 33, and protection means 42 which
is joined to the tube sleeve 30 by fastening devices 43. The bevel
gear pinion 37 meshes with a bevel gear pinion 44 on a sleeve 45
which is journalled in the ring 20 by bearings 21 and 22 and
axially fixed by the ring 48. The sleeve 45 is provided with
external splines for interengagement with internal splines on a
tube drive shaft 50. This drive shaft 50 is journalled in a bearing
51 inside the drive shaft 15.
The third part 13 of the wrist 10 comprises a part 52 of truncated
cone form. The part 52 is obliquely cut off at its base where it
provides a seat for the bearing 31 and is perpendicularly cut off
at its top, in relation to an axis G--G, where it provides seats
for bearings 53 and 54. An annular bevel gear pinion 55 is joined
to the part 52 by means of bolts 56 and constitutes a fixing ring
for bearing 31. The gear pinion 55 cooperates with the gear pinion
27 in the first wrist part 11 and thus connects the wrist parts 11
and 13 together. Upon rotation of wrist part 11 around the axis
D--D, the wrist part 13 will rotate around the axis F--F.
A tool attachment 57 is mounted in the third wrist part 13 for
rotation about the axis G--G. This attachment 57 includes a sleeve
58, which is journalled in bearings 53 and 54 and at its axially
inner end is formed with a bevel gear pinion 60, and fixing ring
61, axially displaceable on the sleeve 58, for supporting a tool
(not shown). A wedge 62 and a locking ring 63 are also provided for
fixing the sleeve 58 in bearings 53, 54 and the fixing ring 61 on
the sleeve 58.
The second wrist part 12 includes annular bevel gear pinions 68 and
69 which are mounted so as to be rotatably journalled within the
bevel gear pinion 37 by means of the bearing 32 and annular bevel
gear pinions 73 and 74 which are mounted so as to be rotatably
journalled within the tubular sleeve 30 by means of the bearing 33.
An externally threaded ring 78 retains the gear pinions 73 and 74
in position, the threaded part of the ring 78 cooperating with an
internally threaded part of the annular gear pinion 73. An
externally threaded ring 80 retains the gear pinions 68 and 69 in
position, the threaded part of the ring 80 cooperating with an
internally threaded part of the annular gear pinion 69. A sleeve 70
is rotatably mounted inside the tubular sleeve 30 by means of
bearings 34 and 35, the sleeve 30 being prevented from axial
movement by a locking ring 79. The sleeve 30 has bevel gear pinions
71 and 72 formed at its opposite axial ends, the pinion 71 meshing
with pinion 69 and the pinion 72 meshing with bevel gear pinion
73.
A shaft 65 is journalled in the drive shaft 50 by means of a
bearing 64 and is provided with internal splines which key with
external splines provided on a sleeve 66. The sleeve 66 is
journalled in the sleeve 45 by bearings 75 and 76 and axially fixed
by the threaded ring 77. the sleeve 66 has a bevel gear pinion 67
thereon which meshes with the gear pinion 68. Drive from the shaft
65 is thus transmitted directly to the sleeve 66 and from the gear
pinion 67 on the latter to the gear pinion 68. Drive is transmitted
from the gear pinion 68 to the gear pinion 69 which rotates with
the gear pinion 68. Drive is then transmitted to the sleeve 70 by
virtue of the meshing gear pinions 69 and 71 and from the sleeve 70
to the gear pinions 73 and 74 by virtue of the gear pinion 72
meshing with the gear pinion 73. Finally, drive is transmitted to
the tool attachment 57 by meshing of the pinion 74 with the bevel
gear pinion 60.
In the position of the wrist parts shown in FIG. 2, the wrist axes
D--D and G'G and a center axis H--H of the wrist part 12 coincide.
The angles .gamma. and .gamma. between axes D--D and E--E and
between axes E--E and H--H, respectively, are the same and the
angles .alpha. and .alpha. between axes H--H and F--F and between
axes F--F and G--G, respectively, are also the same. Thus
.alpha.=.alpha.'=.gamma.=.gamma.'. angle .beta. between axes E--E
and F--F becomes 180-(.alpha.+.gamma.). However since
.alpha.=.gamma., .beta.=180 -2.alpha.. With regard to FIG. 3, with
.alpha.=.alpha.'=.gamma.=.gamma.'=35 .degree., .eta., the angle
between axes D--D and G--G becomes equal to 140.degree., which
provides the wrist extremely good accessibility which is very
valuable, particularly when welding inside box-shaped
structures.
The size of the angles mentioned above results in a very practical
wrist with a versatile field of use, but the size of the angles may
be selected within wide limits and may be different from those
referred to above.
It is possible to drive the tool attachment 57 by means of a
separate drive motor positioned in the wrist 10. This drive motor
may be applied, for example, in the second or third wrist part, 12
or 13. The drive shaft 65 and the transmission shown between the
shaft 65 and the tool attachment 57 are then omitted, which results
in a significant simplification of the design of the wrist. It is
also possible to replace the gear pinion 74 with a tool attachment.
Further, it is possible, for simpler applications, to utilize the
conical sleeve 52 of the third wrist part 13 as a tool attachment.
Also in that case, the drive shaft 65 and the subsequently
positioned transmission are eliminated.
As will be clear from the description and the drawings, the wrist
is hollow so that cables and protective gas conduits and wires for
tools, for example a welding bar, can be passed through the robot
arm and further through the wrist to a working station. A
particular advantage with the wrist according to the invention is
that the channel, formed by the openings through the annular gear
pinions 68, 69, 71, 72, 73, 74 when bending the wrist, has a
relatively great radius of curvature. This radius of curvature is
greater than at the corresponding channels in prior art wrists. The
diameter of the channel is great in relation to the outer diameter
of the wrist. Another important advantage is that, during rotation
of the tool, the tubular shaft 65 and all the elements surrounding
a cable assembly through the shaft 65 and in the robot wrist rotate
in the same direction. Twisting of the cable assembly is eliminated
and the wear is insignificant. The shape of the wrist 10 also means
that the bending moment is absorbed in a favourable manner by
bearings and gear pinions. The wrist has great rigidity and can be
positioned with great precision.
In the alternative embodiment of FIG. 4, the rotary movement of the
sleeve 58 of the attachment 57 is achieved by means of a motor 100,
preferably an electric motor, in the wrist part 52 of the wrist 10.
The motor 100 is secured to the wrist part 52 by means of bolts
101. The rotor 103 is journalled in the motor housing 104 by
bearings 105 and 106. The shaft 107 carries a gear pinion 108. This
pinion 108 is in mesh with the internal gear 109 of the ring 110
journalled in the housing 52 by a bearing 111. A shaft 112 is
journalled in the housing 52 by bearings 113 and 114 and carries
intermediate gear wheels 115 and 116 in mesh with the gear ring 110
and the gear 117 of the sleeve 58.
In the alternative embodiment of FIG. 5, the rotary movement of the
sleeve 58 of the attachment member 57 is achieved by means of a
motor 120 in the sleeve 30 of the second wrist part 12. The motor
120 is secured to the sleeve 30 by means of bolts 121. The rotor
123 is journalled in the motor housing 124 by bearings 125 and 126.
The shaft 127 carries a gear pinion 128. This pinion 128 is in mesh
with the internal gear 129 of the ring 130, journalled in the
sleeve 30 by means of a bearing 131. The ring 130 is also provided
with a bevel gear 132 in mesh with the annular gear pinion 73.
* * * * *