Rotary Joint
Data- Power Rotary Joint

Instruments lowerd down to the ocean bed are not easy to control. Besides underwater modems the main control option is still based on wire connections. Instruments mounted on a frame (e.g. tripods) are connected to a distribution box and data and power are controlled via a submersible cable. This cable acts as a connection between the submerged frame and a floating buoy were the data can be send via radio modems. A battery source inside the buoy is powering up the instrument at the submerged frame.

The weakest link of this system is the cable itself. Tides, wind and other events are pulling, pushing and twisting on the cable, and the cable will eventually break. The biggest stress on the cable is the torgue generated by twisting against a fixed support. A decoupling piece is neccessary to reduce the torque and the risk of breaking the cable.

To minimize the risk of cable breakage ARGUS developed a novel DATA-POWER-SWIVEL (DPS) which resists a load of 4...15 tons. The rotary joint contains an optical data unit. The data transfer is 115.2 kb/s. The serial data in- and output can be configurated as RS 485, 422, 232. The cable can be as long as  1.300 m depending on the cable quality (twisted pair). Another interesting feature is the possibility of powering up instruments or charging batteries mounted on a submerged frame. The swivel contain a DC/DC converter which transforms power through an air gap (water gap). Thus the swivel galvanically isolates the floating system from the submerged one galvanically.   


Technical data:

    tensil strength:       4 to 15 tons (4000...15,000 kg)
    material:                stainless steel,(optional: marine bronze, titanium)
    cable length:          500 m max. for 60 watt, wire: AWG12
    pressure:              80 m maximum deployment depth
    dimensions:          620 mm length, 90 mm diameter
    weight:                  7 kg (4 tons version)

    data transfer:         serial: ext. rs 485, 422, 232 int. optical (115.2 kb/s)

    power transfer:      DC/DC fly back converter
    efficiency :             80 % max.
    power over gap:    60 watt, (optional: 1 watt to run data link only)
    voltage:                 11...30 vdc
    current:                 2.5 amps. max (applicable) (option 0.040 amps.
    additional:              battery charger on board
                                 energy management on board

All moving parts utilize water-lubricated ceramic ball bearings for axial force and plain bearings made of teflon and delrin for radial force. These parts can be easily replaced if worn down. Therefore the unit contain no o-ring seals on the runner side and runs oil-free.
Special cable mouldings are available on request.


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