A clamshell bucket

A grab or mechanical grab is a mechanical device with two or more jaws (sometime clamshell-shaped), used to pick things up or to capture things. Some types include:

  • Roundnose grab
  • Clamshell grab
  • Orange-peel grab
    • in Dutch and German they are called poliep grijpers/ Polypengreifer = "polyp grabs".

There are different ways of open/close the grabs:

  • electro-hydraulic / diesel-hydraulic
  • mechanical by rope(s) (1-rope, 2-ropes, 3-ropes, 4-ropes)

Grabs can be used for:

  • dredging
  • bulk handling (e.g. loading/unloading ships)
  • salvage (e.g. ship-wrecks, oil)
  • seabed sampling[1]

History

The mechanical grab,[2]: 21  specifically the clamshell grab,[3] was invented by the Persian Banu Musa brothers and described in their Book of Ingenious Devices in the 9th century. It was an original innovation by the Banu Musa that does not appear in any earlier Greek works.[2]: 21  The grab described by the Banu Musa was used to extract objects from underwater,[2]: 44  and recover objects from the beds of streams.[3]

See also

References

  1. ↑ Baker, D. James; Rechnitzer, Andreas B. "Undersea exploration". Encyclopedia Britannica. Retrieved 29 December 2022.
  2. 1 2 3 Banu Musa (1979), The book of ingenious devices (Kitāb al-ḥiyal), translated by Donald Routledge Hill, Springer, ISBN 90-277-0833-9
  3. 1 2 Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, p. 64-69

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