An electrically driven explosion-proof painting robot comprises a base having a first pressurized chamber, a rotary base having a second pressurized chamber, an inner arm having a third pressurized chamber and an outer arm having a fourth pressurized chamber. Each pressurized chamber is hermetically sealed and independently formed, can contain an electric motor connected with cables and is not in fluid communication with one another. Each pressurized chamber is supplied with pressurized air respectively by respective air pipes extending through the respective walls of the chambers. Each air pipe is made detectable its pressure respectively. An explosion-proof cable bundle housing cables and is shielded by a steel tube extend from the robot controller to the wall of the first pressurized chamber and from the first pressurized chamber other explosion-proof cable bundles extend in between the rest chambers through the respective walls of the rest chambers, to feed electric powers into the motors contained therein.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electrically driven explosion-proof 
painting robot for use in a painting booth having an environment 
containing inflammable gases, in particular, the robot has pressurized 
chambers which may contain ignitable electric motors, cables and other 
electric equipments. 
2. Description of Related Art 
U.S. Pat. No. 4,984,745 and 5,421,218 disclose an electrically driven 
explosion-proof painting robot having pressurized chambers which are in 
fluid communication with one another and may contain ignitable electric 
motors and cables, therein. Non-explosion-proof cables housed in a 
shielding steel air pipe and supplied with pressurized air, supply 
electric power to the robot motors. U.S. Pat. No. 5,212,432 discloses an 
electrically driven explosion-proof painting robot having explosion-proof 
containers containing hollow electric motors. The motor containers are 
supplied with pressurized air independently via respective input ports and 
purged via respective output ports through respective pressurized hoses. 
Further, the '432 patent proposes a robot which houses these hoses inside 
the robot. 
However, in the '745 and '218 patents, the cables extending via an opening 
between the neighboring pressurized chambers are likely to be affected by 
abrupt bendings and twistings in a short portion around the opening 
arising out of relative movement of the neighboring chambers which may 
damage the cables. Further, it also may take a long time to purge gases or 
air from all pressurized chambers, and when any one of the pressurized 
chambers leaks, it may not be possible to detect at once the chamber which 
has leaked. Further; supply of air pressure to the pressurized chambers 
drops, it may take too long a time to purge air from the pressurized 
chambers. In the '432 patent, the hollow electric motors are expensive and 
the respective pressurized supplying and purging hoses are exposed outside 
the robot body. Consequently additional installation floor space is 
required and friction between the exposed hoses and operating robot arms 
or painting apparatuses is liable to cause damage to the hoses. Further, 
the robot which houses these hoses inside the robot has a drawback in that 
it may damage the hoses through friction therebetween. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an 
electrically driven explosion-proof painting robot wherein the cables 
extending between the pressurized chambers are not likely to be effected 
abrupt bendings and twistings thereby eliminating a damage of the cables, 
further, purging gases or airs in all pressurized chambers can be made in 
a shorter time. 
It is another object of the present invention to provide an electrically 
driven explosion-proof painting robot wherein it is possible to detect a 
leaked pressurized chamber at once when it caused a leakage, further, when 
the supply air pressure to the pressurized chambers drop, it is possible 
to detect it to take necessary measures. 
It is further object of the present invention to provide an electrically 
driven explosion-proof painting robot wherein respective pressurized 
horses and purging horses are substantially not exposed outside the robot 
body and are not made liable to be damaged through friction between the 
exposed horses and operating robot arms or painting apparatuses. 
According to the present invention, there is provided an electrically 
driven explosion-proof painting robot comprising a base having a first 
pressurized chamber, a rotary base supported rotatably relative to the 
base around a vertical axis and having a second pressurized chamber, an 
inner arm the lower end of which is supported rotatably relative to the 
rotary base around a first horizontal axis and having a third pressurized 
chamber, and an outer arm one end of which is supported rotatably relative 
to the inner arm around a second horizontal axis and having a fourth 
pressurized chamber. Each pressurized chamber is hermetically sealed and 
independently formed and not in fluid communication with one another, can 
contain an electric motor connected with cables. The first pressurized 
chamber is supplied with a pressurized air via an air pipe connected to a 
manifold disposed therein having one output port communicating therewith, 
and then from the manifold three divided pressurized air pipes extend 
through the wall of the first pressurized chamber into a hazardous 
environment and from there, respectively extends into the second, third 
and fourth chambers through the respective walls of the second, third and 
fourth chambers, to feed pressurized airs into the chambers respectively. 
Each air pipe do not contain cables and the air pressures and purge air 
flow rates of the respective pressurized chambers are made detectable 
respectively. An explosion-proof cable bundle housing cables and is 
shielded by a steel tube the inside of the steel tube is injected with 
sealing material to prevent the entry of the air, and is not supplied with 
pressurized air extend from the robot controller to the wall of the first 
pressurized chamber and from the first pressurized chamber other 
explosion-proof cable bundles extend in between the second, third and 
fourth chambers through the respective walls of the chambers, to feed 
electric powers into the motors contained therein. 
By such an arrangement, since respective explosion-proof cable bundles are 
supported by each partition walls through joints attached thereto, the 
robot of the present invention is possible that the cables extending via 
an opening between the neighboring pressurized chambers are not made 
likely to be effected abrupt bendings and twistings in a short portion 
around the opening between the neighboring chambers arising out of 
relative movement thereof resulting that it eliminates a damage of the 
cables, further, since each pressurized chamber is supplied with 
pressurized air respectively, each chamber is possible to be supplied with 
pressurized air quickly so that the robot can be started faster, moreover, 
since the four pressure switches detect a leakage in the four pressurized 
chambers respectively, it is possible to detect a leakage in any one of 
the pressurized chambers at once when it caused the leakage, further, when 
the supply air pressure to the pressurized chambers drops, the purge air 
flow rates detect it to take necessary measures. And further, since the 
explosion-proof cable bundles and air pipes are very little or 
substantially not exposed outside the robot body resulting that they are 
not made liable to be damaged through friction between the exposed horses 
and operating robot arms or painting apparatuses thereby a longer life of 
the robot can be attained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
This invention will be described in further detail by way of example with 
reference to the attached drawings. As shown in FIGS. 1(a), 1(b), 2(a) and 
2(b) an electrically driven explosion-proof painting robot 1 is installed 
in a painting booth having a hazardous environment or an environment 
containing inflammable gases in an area divided by an explosion-proof wall 
26. A robot controller 28 and an air unit 118 are located in an area 
having a non-hazardous environment or an environment not containing 
inflammable gases. An explosion-proof cable bundle 30 extends from the 
robot controller 28 through the wall 26 to the wall of the robot 1. An air 
pipe 44 made of nylon, the inside of which does not house cables extends 
from the air unit 118 through the wall 26 to the robot 1 and supplies 
pressurized air to the robot 1. The robot 1 is controlled by the robot 
controller 28 through the explosion-proof cable bundle 30. 
The electrically driven robot has a fixed base 16 having a first 
pressurized chamber 101. A rotary base 12 is supported rotatably relative 
to the base 16 around a vertical axis 501 (FIG. 5), and has a second 
pressurized chamber 102. As best seen in FIG. 5, the first pressurized 
chamber 101 is sealed by its metal wall, an outer lower metal wall of the 
rotary base 12, a sealed cover 301 and a circular oil seal 111, whereas 
the second pressurized chamber 102 is sealed by its metal wall. The oil 
seal 111 is disposed to keep the first pressurized chamber 101 
hermetically sealed from the air or the hazardous environment. The first 
and second pressurized chambers 101 and 102 are not in fluid communication 
with each other. A space 120 provided between the first and second 
pressurized chambers and communicating with air or the hazardous 
environment has therein only a cover 122 for preventing external damage to 
an explosion-proof cable bundle 821 and air supply pipes 400 which are 
very little or substantially not exposed from the robot 1. The sealed 
cover 301 is a fixed sealing wall made detachable through bolts(not shown) 
and a seal 110 for maintenance and support of the explosion-proof cable 
bundle 821 through a sealing joint attached thereto. 
The rotary base 12 is driven by an electric motor 861 disposed within the 
second pressurized chamber 102. A reduction gear unit 166 of the motor 861 
is housed in the first pressurized chamber 101. An arm assembly comprises 
an inner arm 20 the lower end of which is supported rotatably around a 
first horizontal axis 502 (FIG. 5) relative to the rotary base 12, and an 
outer arm 22 one end of which is supported rotatably around a second 
horizontal axis 503 (FIG. 7(a)) relative to the inner arm 20. The inner 
arm 20 is driven by an electric motor 862 disposed within the second 
pressurized chamber 102, while the outer arm 22 is driven by an electric 
motor 863 provided within a third pressurized chamber 103 formed within 
the inner arm 20 (FIG. 7(a)). The third pressurized chamber 103 is sealed 
by its metal wall, rotatable sealed walls 302 and 303, and oil seals 112 
and 113, whereas the fourth pressurized chamber 104 is sealed by its metal 
wall and a fixed sealed cover 304. The rotatable sealed walls 302 and 303 
rotatable around the first and second horizontal axes 502 and 503(FIG. 
7(a)) respectively are supported by bearings 332 and 333 and seals 112 and 
113 in the inner arm wall. The rotatable sealed walls 302 and 303 support 
explosion-proof cable bundles 824 and 826 and air pipes 443 and 444 
through sealing joints attached thereto(FIG. 7(a)). The second, third and 
fourth pressurized chambers 102, 103 and 104 are not in fluid 
communication with one another, rather, they are out of contact with one 
another through spaces 120 and 121 communicating with the air or the 
hazardous environment. A wrist 24 is rotatably mounted on the free end of 
the outer arm 22, and is driven by electric motors 864 provided within the 
fourth pressurized chamber 104 formed within the outer arm 22 and supports 
a painting gun (not shown). 
The electric motors 861, 862, 863 and 864 each constituting the drive 
mechanism for the rotary base 12, the inner arm 20, the outer arm 22 and 
the wrist 24, are located in the three pressurized chambers 102, 103 and 
104. Specifically, the first pressurized chamber 101 of the base 16 has 
the reduction gear unit 166 but has no electric motor for the drive 
mechanism of the rotary base 12. The second pressurized chamber 102 of the 
rotary base 12 has not only the electric motor 861 of the first drive 
mechanism for rotating the rotary base 12 around the vertical axis 501 
(FIG. 5) relative to the base 16, but also the electric motor 862 of the 
second drive mechanism for driving the inner arm 20 back and forth around 
the horizontal axis 502 (FIG. 5) relative to the rotary base 12. The third 
pressurized chamber 103 provided within the inner arm 20 has the electric 
motor 863 of the third drive mechanism for driving the outer arm 22 up and 
down around the horizontal axis 503 (FIG. 7 (a)) relative to the inner arm 
20. The fourth pressurized chamber 104 of the outer arm 22 has electric 
motors 864 of the fourth drive mechanism for driving the wrist around the 
three axes (not shown). 
Explosion-proof cable bundles 30, 821, 824 and 826 each house cables 82 and 
are shielded by a steel tube. Further, the inside of each steel tube 
between the tube and the cables 82 is injected with sealing material 822, 
825 and 827 to prevent the entry of air, and is not supplied with 
pressurized air. The explosion-proof cable bundle 30 extends from the 
robot controller 28 through the wall 26 provided between the non-hazardous 
environment and the hazardous environment to the wall of the first 
pressurized chamber 101 of the base 16. Cables 82 are electrically 
connected to a terminal strip 161 in the first pressurized chamber 101. 
The explosion-proof cable bundles 821, 824 and 826 extend respectively 
from the sealed cover 301 of the first pressurized chamber 101 to the 
lower wall of the second pressurized chamber 102, from the upper wall of 
the second pressurized chamber 102 to the rotatable sealed wall 302 of the 
third pressurized chamber 103, and from the rotatable sealed wall 303 of 
the third pressurized chamber 103 to the sealed cover 304 of the fourth 
pressurized chamber 104. Cables 82 are electrically connected to a 
terminal strip 162 in the second pressurized chamber 102 and to the 
respective motors 861, 862, 863 and 864. 
The four pressurized chambers 101, 102, 103 and 104 each have individual 
air supply pipes 44, 442, 443 and 444 the inside of which do not house 
cables, so that four air systems including four flow 54, four pressure 
switches 48 and four exhaust valves 49 (FIG. 4) are necessarily provided 
and are located outside of the first pressurized chamber 101. The air pipe 
44 made of nylon the inside of which does not house cables supplies 
pressurized air from the air unit 118 located in the area having the 
environment containing non-inflammable gases to the first airtight or 
pressurized chamber 101 through the wall 26 and to a manifold 6 disposed 
therein having one output port communicating with the chamber 101. From 
the manifold 6 the three divided pressurized air pipes 442, 443 and 444 
made of nylon the insides of which do not house cables extend through the 
wall 301 of the first airtight chamber 101 into the hazardous environment 
120 and from there, respectively extends into the second, third and fourth 
chambers through the respective walls 302, 303 and 304 of the chambers, to 
feed pressurized air into the chambers 102, 103 and 104. Four air vent 
pipes (partly shown and the insides of which do not house cables) are 
provided from the pressurized chambers 101, 102,103 and 104 to a vent 
manifold 66 located outside of the first pressurized chamber 101 and to 
the four flow switches 54 fixed on the vent manifold 66, in parallel with 
the air supply pipes 400, 442, 443 and 444. One relief valve 60 located 
outside of the first pressurized chamber 101 is connected to the manifold 
6. The four flow switches 54 respectively communicate with the four 
pressure switches 48 detecting the pressures of the respective chambers 
101, 102, 103 and 104 and further are connected to the four exhaust valves 
49 all located outside of the first pressurized chamber 101 and then 
exhausted into air. The exhaust valves 49 are adapted to operate by a 
preset pressure or an electric signal. Further, when the supply of air 
pressure from the air unit 118 to the pressurized chambers drops, the four 
flow switches 54 detect the drop and necessary measures are taken 
including raising the supply of; air pressure. Joints capable of keeping 
air tightness between the explosion-proof cable bundles 821, 824 and 826, 
air pipes 442, 443 and 444 and the pressurized chambers are used in each 
of the partition walls 301, 302, 303 and 304. 
In operation, before the robot 1 is energized, pressurized air is supplied 
from the air unit 118 to the respective four pressurized chambers through 
the air pipe 44, the manifold 6 and the air pipes 400, 442, 443 and 444. 
Return air from the respective four pressurized chambers is exhausted into 
the air in the four air vent pipes, to the vent manifold 66, the four flow 
switches 54, the pressure switches 48 and to the exhaust valves 49. When 
the pressures detected by the respective pressure switches 48 all reach a 
preset pressure, the four exhaust valves 49 open to purge the air in the 
respective pressure chambers. After respective measured amounts of 
pressurized air, which are respectively computed to be a predetermined 
percentage of the volume of the respective pressurized chambers, are 
purged, the respective exhaust valves 49 are closed. The robot is then 
energized. During the time the robot is energized, each the pressure in 
each of the pressurized chambers is kept above the predetermined air 
pressure set by the pressure switches 48. When the air pressure in any one 
of the four pressurized chambers falls below the predetermined air 
pressure set by the pressure switches 48, one of the pressure switches 48 
or flow switches 54 acts to stop the supply of electric power to the robot 
1.