Hi Beatriz,

the following link should give you a better explanation:

http://drum-handlers.liftomatic.com/item/dde/portable-drum-d...
The model TD-850 DrumVertor is modular design for lifting, dumping and transporting drums of liquid or dry materials. Standard 55 gallon steel drum is held in a round cradle and secured by toggle clamp. A hydraulic jack with foot pedals offers 63" lift dumping height and a hand crank worm-gear reducer allows operator to mix drum contents and control pouring rotation at any angle along 360 degree path. An optional retaining clamp bar for fiber or plastic drums is available upon request.

you can also have a look here: http://schlumpf-inc.com/

and hereunder other links self-explanatory:

http://www.genkinger-hubtex.com/english/warehouse-equipment/...
High lift truck with cradle

http://www.motorola.com/Business/US-EN/Business Product and ...
This cradle is made specifically for fork-lift applications

http://www.google.com/patents/US5090842
A lift apparatus has a load member, a lift cradle and a lifting arrangement. The load member has a rail or track portion which provides a path when raising and lowering the lift cradle. The load member also has a mounting portion for mounting the load member to an adjacent structure such as a dock, a pier or a wall. The mounting portion has a web, which stands off mounting hardware, such as a mounting plate, from the rail portion. The lift cradle has **bearings (=cuscinetti) for sliding along the rail portion**. The bearings have a gap, which allow the bearings to slide along the rail portion without interference from the web. When the bearings are free of the web, the lift cradle can rotate, to deposit the load onto a dock. The lifting arrangement is rotatively coupled to the upper end of the load member, so as to rotate with the lift cradle. A lift system utilizes the lift apparatus and a wheeled cart. The load is located on the cart, which couples to the lift cradle. As the lift cradle is lifted,...


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Note added at 5 ore (2012-12-17 14:17:53 GMT)
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I did your same search on IATE:
IATE search
Dominio: Metallurgia e siderurgia, elettronica e elettrotecnica
language: en
abbreviazione: rocker
language: it culla
commento relativo al termine: part o fan arc furnace

and I had a look at the other outcomes therein but, IMHO, no one seems to fit this context.

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Note added at 5 ore (2012-12-17 14:20:12 GMT)
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sorry typo pls read: part of an arc furnace

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Note added at 6 giorni (2012-12-23 12:53:58 GMT) Post-grading
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Thanks Beatriz. Season's greetings.