Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
2002-04-23
2004-01-06
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S254000, C700S260000, C700S261000, C700S262000, C901S042000, C901S014000, C901S015000, C901S016000, C362S423000, C362S424000, C362S259000, C219S121780, C414S696000, C414S751100
Reexamination Certificate
active
06675069
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an arm operation mechanism for moving a workpiece vertically and/or horizontally. The present invention also relates to an industrial robot including such an arm operation mechanism.
2. Description of the Related Art
A typical prior art industrial robot includes a plurality of arms pivotally connected to each other for vertically or horizontally moving a workpiece or processing tool held by one of the arms. Such a robot is often referred to as “articulated robot”. An example of articulated robot is disclosed in JP-A-2000-24966 for example. For the convenience of description, the articulated robot disclosed in this Japanese document is illustrated in
FIG. 6
of the accompanying drawings.
As shown in
FIG. 6
, the prior art industrial robot includes a machine base
90
, a first arm
91
having a base end and a tip end, a second arm
92
having a base end and a tip end, a first parallel link
94
a
, a second parallel link
94
b
, and a link base
95
. The base end of the first arm
91
is pivotally supported on the machine base
90
, whereas the base end of the second arm
92
is pivotally connected to the tip end of the first arm
91
via a coupler
93
. The tip end of the second arm
92
is provided with a workpiece holder
96
for holding a workpiece (not shown). the workpiece holder
96
is integrally pivotable with a lever
97
.
The first arm
91
is driven by a motor M
1
for rotation about a fixed axis
97
. The base end of the second arm
92
is provided with a gear
80
a
which is connected, via a shaft
81
, to a gear
80
b
which is rotated by the motor M
1
. The opposite ends of the shaft
81
are provided with bevel gears
82
a
,
82
b
for meshing with the gears
80
a
,
80
b
, respectively.
One parallel link
94
a
is pivotally connected to the machine base
90
and to the link base
95
, respectively. The other parallel link
94
b
is pivotally connected to the link base
95
and to the lever
97
of the workpiece holder
96
.
With the above-described structure, when the first arm
91
is rotated about the axis
97
in the arrow Na directions, the second arm
92
rotates about the coupler
93
in the arrow Nb directions. Thus, the tip end of the second arm
92
and the workpiece holder
96
move up and down in the arrow Nc directions.
However, the above-described prior art robot has the following drawbacks. In the prior art robot, the rotational force of the gear
80
b
driven by the motor M
1
is transmitted to the gear
80
a
via the shaft
81
for rotating the second arm
92
based on the rotation of the first arm
91
. Therefore, the shaft
81
needs to be substantially equal, in length, to the first arm
91
. Further, though not illustrated, the first arm
91
need be provided with a support mechanism, which may include a bearing for example, for supporting the shaft
81
. Thus, the provision of the shaft
81
and the support mechanism in the arm
91
increases the size of the first arm
91
, which leads to an increase in the overall size of the robot. Further, the provision of the shaft
81
and the support mechanism, which may be relatively large in weight, also increases the inertia of the first arm
91
during the rotation. Therefore, it may often be difficult to make the first arm
91
move quickly unless the motor M
1
is high-powered.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an arm operation mechanism which operates suitably while having a simple structure and relatively small size and weight.
Another object of the present invention is to provide an industrial robot incorporating such an arm operation mechanism.
According to a first aspect of the present invention, there is provided an arm operation mechanism which comprises a support, a first arm, a second arm, a link base, a parallel link, and a conversion mechanism. The first arm has a tip end and a base end, and the base end of the first arm is pivotally connected to the support for rotation relative to the support. The second arm has a base end pivotally connected to the tip end of the first arm for rotation relative to the first arm. The link base is pivotally connected to the first arm for rotation relative to the first arm. The parallel link keeps a constant posture of the link base upon the rotation of the first arm. The conversion mechanism converts the rotation of the link base relative to the first arm into the rotation of the second arm relative to the link base.
Preferably, when the first arm rotates relative to the support in one direction through a first angle, the conversion mechanism causes the second arm to rotate relative to the first arm in an opposite direction through a second angle which is twice the first angle.
Preferably, the conversion mechanism comprises a first gear fixedly mounted to the link base, and a second gear rotatably mounted to the first arm in mesh with the first gear and operatively connected to the base end of the second arm.
Preferably, the conversion mechanism further comprises a third gear coaxial and integrally rotatable with the second gear, and a fourth gear fixedly connected to the second arm in mesh with the third gear. In this case, the fourth gear is fixedly connected to the base end of the second arm via a sleeve on which the first gear is coaxially and rotatably fitted. Further, the first gear and the second gear have a gear ratio of 1:1 while the third gear and the fourth gear have a gear ratio of 2:1. Moreover, the first arm may be hollow to accommodate all of the first through the fourth gears.
According to a second aspect of the present invention, there is provided an industrial robot comprising a holder and an arm operation mechanism for movably supporting the holder. The arm operation mechanism comprises a support, a first arm, a second arm, a link base, a parallel link, and a conversion mechanism. The first arm has a tip end and a base end, and the base end of the first arm is pivotally connected to the support for rotation relative to the support. The second arm has a base end pivotally connected to the tip end of the first arm for rotation relative to the first arm. The link base is pivotally connected to the first arm for rotation relative to the first arm. The parallel link keeps a constant posture of the link base upon the rotation of the first arm. The conversion mechanism converts the rotation of the link base relative to the first arm into the rotation of the second arm relative to the link base.
Preferably, the arm operation mechanism causes the tip end of the second arm to move vertically, and the holder includes a hand for supporting and moving a workpiece horizontally. The hand may be rotatable about a vertical axis. Further, the holder may also include a holder support pivotally connected to the tip end of the second arm, and the arm operation mechanism additionally includes a second parallel link pivotally connected to the link base and the holder support for constantly keeping the hand in a horizontal posture.
Other features and advantages of the present invention will become clearer from the detailed description given below with reference to the accompanying drawings.
REFERENCES:
patent: 4534694 (1985-08-01), Tuda
patent: 4953822 (1990-09-01), Sharber et al.
patent: 5678979 (1997-10-01), Kovacs
patent: 6068704 (2000-05-01), Saeki et al.
patent: 6450757 (2002-09-01), Saeki et al.
patent: 2000-024966 (2000-01-01), None
Nenchev, PARA-Arm Singularity Perturbed Design of a Planar 2 DOF Parallel Manipulator, 1996, IEEE, pp. 1234-1240.*
FANUC, News of Mar. 1998, Internet, pp. 1-2.*
Nobuji et al., INtroducing linear servo motor system, 1998, Internet, pp. 1-6.
Cuchlinski Jr. William A.
Daihen Corporation
Marc McDieunel
Merchant & Gould P.C.
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