Rack jack

Rack jack for hoisting, lowering and/or supporting containers, cabins, shelters, exchangeable superstructures or the like, having upper and lower corner fittings, said rack jack comprising an upwardly extending jack shaft (13), means for moving said jack shaft upwardly, an upper arm (22) mounted on the jack shaft and having an engaging part (26) at its outer end for engaging an adjacent upper corner fitting, a lower arm (28) mounted on the jack shaft and having an engaging part (34) at its outer end for engaging an adjacent lower corner fitting, each of said arms comprising a pair of supporting rods of different length connected at their inner ends to the jack shaft and at their outer ends to the engaging parts, the engaging part (26) for the upper corner fitting being adjustable substantially parallel to the axis of the jack shaft and substantially transversely to the jack shaft axis, and the engaging part (34) for the lower corner fitting being adjustable substantially perpendicularly with reference to the jack shaft axis, characterized in that the two rods (29, 30) of the lower arm (28) that is associated with a lower corner fitting (11) are articulatedly connected respectively with the jack shaft (13) and the engaging part (34), and in that the longer rod (29) in the working position runs obliquely against the jack shaft (13), the jack shaft is provided with a plurality of mutually spaced articulation points (36) in the upper half thereof to which the inner end of the longer rod (29) may be connected, and in that the total length of the two rods, (29, 30) of the lower arm (28) does not exceed, or does not substantially exceed, the height of the jack shaft (13).