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(11) | EP 1 593 645 A3 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | Hydraulic lifting device for a telescopically extendable fork lift truck mast |
(57) Device at fork truck where in a telescopically extendable mast in the outermost or
uppermost mast section is arranged a movement journaling of movement of the forks
over the major part of the height of the uppermost mast section, and where lifting
movements are achieved hydraulically by means of one or several hydraulic pistons
(4) for the lifting of the mast sections and one or several other hydraulic pistons
(3) for the lifting of the forks (8) in relation to the uppermost mast section (5).
In the feed conduits to the hydraulic cylinders proportional valves 1, 2 are arranged
in order to, at the transition shift between low lift movement and high lift movement
and vice versa successively control the oil flow to and from the cylinders of the
different systems respectively so that an unnoticeable transition and constant speed
is obtained.
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