Machine element or mechanism – Control lever and linkage systems – Multiple controlling elements for single controlled element
Reexamination Certificate
1997-06-19
2001-05-15
Bucci, David A. (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Multiple controlling elements for single controlled element
C074S490100, C901S041000, C414S680000
Reexamination Certificate
active
06230580
ABSTRACT:
BACKGROUND OF THE INVENTION
1. (Field of the Invention)
The present invention relates to an industrial manipulator, particularly a manipulator wrist structure, and a method of controlling the manipulator.
2. (Description of the Prior Art)
Industrial manipulators are currently employed in various industries. Although manipulators are many in type, most of the manipulators largely employed to accomplish factory automation are of a type resembling a human hand, an example of which is shown in
FIGS. 4
to
5
C for discussion of the prior art to which the present invention pertains.
Referring particularly to
FIG. 4
, the prior art manipulator arm shown therein comprises a first tubular shell (a first driving articulate element)
31
, a second tubular shell (a second driving articulate element)
35
a
, an intermediate tubular shell (a driven articulate element)
35
b
positioned between the first tubular shell
31
and the second tubular shell
35
a
and a third tubular shell (a third driving articulate element)
39
positioned adjacent one of the opposite ends of the second tubular shell
35
a
remote from the intermediate tubular shell
35
b.
The first tubular shell
31
includes a first reduction gear unit
32
incorporated therein and having a first drive axis
33
, and a first drive motor
34
housed within the first tubular shell
31
and drivingly coupled with an input side of the first reduction gear unit
32
. The intermediate tubular shell
35
b
has one end coupled with an output side of the first reduction gear unit
32
and the opposite end coupled with the second tubular shell
35
a.
The second tubular shell
35
a
includes a second reduction gear unit
36
incorporated therein and having a second drive axis
37
, and a second drive motor
38
housed within the second tubular shell
35
a
and adapted to drive an input side of the second reduction gear unit
36
through a drive transmission element. On the other hand, the third tubular shell
39
includes a third reduction gear unit
40
incorporated therein and having a third drive axis
41
, a third drive motor
42
housed within the second tubular shell
35
a
and drivingly coupled with an input side of the third reduction gear unit
40
through a drive transmission element.
The third tubular shell
39
has a safety holder
14
fixedly coupled with an output side of the third reduction gear unit
40
for carrying a welding torch
13
which can revolve together with the safety holder
14
about the third drive axis
41
. The welding torch
13
is connected with a cable
15
having an electric power line, a conduit and a gas hose bundled together.
In order for the manipulator arm to allow the welding torch
13
to gain access to a workpiece of a relatively complicated shape during a welding operation without interfering with a manipulator wrist, the second and third tubular shells
35
a
and
39
must have a size as small as possible and, particularly, the dimension L
3
shown in
FIGS. 5B and 5C
affects the accessibility of the welding torch
13
to the workpiece. Accordingly, how small the dimension L
3
is designed is one of the factors determinative of the range of application in which the welding manipulator can be effectively utilized to accomplish an intended job. For this reason, the prior art manipulator is so designed and so configured that the first and second drive axes
33
and
37
lie perpendicular to each other; the second and third drive axes
37
and
41
lie perpendicular to each other; and both of the second and third drive motors
38
and
42
are housed within the second tubular shell
35
.
The operation of the prior art manipulator arm of the structure discussed above will now be described with reference to FIG.
4
.
When the first drive motor
34
drives the input side of the first reduction gear unit
32
accommodated within the first tubular shell
31
, the second and intermediate tubular shells
35
a
and
35
b
rotate about the first drive axis
33
in one of the opposite directions shown by &thgr;1. The third tubular shell
39
can rotate about the second drive axis
37
in one of the opposite directions shown by &thgr;2 when the second drive motor
38
drives the input side of the second reduction gear unit
36
, accommodated within the second tubular shell
35
a
, through the drive transmission element. On the other hand, when the third drive motor
42
drives the input side of the third reduction gear unit
40
, accommodated within the third tubular shell
39
, through the drive transmission element, the safety holder
14
carrying the welding torch
13
rotates about the third drive axis
41
in one of the opposite directions shown by &thgr;3.
Accordingly, it is theoretically possible for the welding torch
13
to assume any position and/or orientation relative to the workpiece by suitably selecting and/or combining directions of movement &thgr;1, &thgr;2 and &thgr;3.
However, in the prior art manipulator arm of the type discussed above, and so long as the freedom of movement in either of the opposite directions &thgr;3 is concerned, the angle through which the safety holder
14
carrying the welding torch
13
can rotate relative to the third tubular shell
39
is limited and, thus, the prior art manipulator arm is necessarily incapable of continuously assuming an arbitrarily chosen orientation. This is because, in the case of the welding manipulator such as discussed above or a paint applying manipulator, the cable
15
extending outwardly from the welding torch
13
interferes with the second tubular shell
35
a
when the safety holder
14
rotates in one of the opposite directions &thgr;3 about the third drive axis
41
.
Considering that all of the second reduction gear unit
36
, the second drive motor
38
, the third drive motor
42
, the drive transmission element connecting the second reduction gear unit
36
and the second drive motor
38
together and the drive transmission element connecting the third reduction gear unit
40
and the third drive motor
42
together are housed within the second tubular shell
35
a
, the second tubular shell
35
a
necessarily has a square outer appearance, that is, a generally rectangular sectioned shape, as shown in FIG.
5
C. Accordingly, when the cable
15
interferes with the second tubular shell
35
a
, the cable
15
is considerably bent with its outer sheath
15
a
damaged and, consequently, weld padding tends to be considerably adversely affected.
By way of example, where a welding line along which welding is desired to be effected at the workpiece lies at a location shown by B in
FIG. 4
, the cable
15
when moved to a position shown by
13
b
about the third drive axis
41
interferes with the second tubular shell
35
a
and, accordingly no beautiful weld padding can be obtained. Thus, the prior art welding manipulator has a problem in that the position and/or orientation of the workpiece to be welded relative to the welding manipulator have been limited.
Moreover, when it comes to effecting a fillet welding continuously along a circular welding line
19
defined between a cylindrical workpiece
17
and a base plate
18
as shown in
FIG. 6
to eventually form a circular fillet joint by which the cylindrical workpiece
17
is rigidly connected to the base plate
18
, the welding torch
13
has to be revolved so as to follow the circular welding line
19
. In this instance, even though the workpiece is disposed in an optimum layout, interference between the cable
15
and the second tubular shell
35
a
necessarily takes place and, consequently, no beautiful weld padding that continues along the circular welding line
19
can be obtained.
The foregoing problems discussed in connection with the welding manipulator are equally found in the paint applying manipulator.
In view of the foregoing, it is suggested to position the cable at a location distant from the second drive axis
37
and towards the third drive axis
41
. However, to position the cable at a location distant from the second drive axis
37
may result in enhancement
Iwai Seiji
Matsumoto Kazunori
Mukai Yasushi
Bucci David A.
Hansen Colby
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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