Explosion-proof industrial robot

An industrial robot for use in an atmosphere containing an inflammable or explosive gas, comprising:

• a stationary base unit having therein a first airtight chamber;
• a swiveling body unit rotatably connected to said stationary base unit through a first hollow shaft for rotation about a first axis and having therein a second airtight chamber which is communicated with said first airtight chamber through the interior of said first hollow shaft;
• an upper arm rotatably connected to said swiveling body unit through a second hollow shaft fixed to said upper arm for rotation about a second axis perpendicular to said first axis and having therein a third airtight chamber which is communicated with said second airtight chamber through the interior of said second hollow shaft;
• a forearm rotatably connected to said upper arm for rotation about a third axis parallel to said second axis and for supporting thereon a three-axis wrist assembly having three degrees of motion;
• a first group of three electric drive motors, for driving said swiveling robot body unit, said upper arm and said forearm, respectively, said electric drive motors being located in said second airtight chamber;
• a second group of three electric drive motors, for driving said wrist assembly, said second group of electric drive motors being located in said third airtight chamber;
• a first group of electric cables connected to said first group of three electric motors in said second airtight chamber and extending from the interior of said second airtight chamber into a fixed pipe fixedly connected to said stationary base unit through said first hollow shaft and further into said first airtight chamber;
• a second group of electric cables connected to said second group of three electric motors in said third airtight chambers and extending from the interior of said third airtight chambers into said fixed pipe through said second hollow shaft, said second airtight chamber, said first hollow shaft and into said first airtight chamber;
• and,
• an air supply pipe connected to said stationary base unit for supplying pressurized air to said first, second and third airtight chambers to maintain the interior of said airtight chambers at a predetermined pressure higher than atmospheric pressure outside said airtight chambers and thus prevent seepage of said inflammable or explosive gas into said airtight chamber.