the application in which the compressed air cylinder is to be used a space whose magnitude volume depends on the piston 39 s position in the compressed air cylinder is formed in the cavity on each side of the piston 12 in fig1 and 2 one space is designated v 1 and the space on the opposite side of the piston is designated v 2 as previously mentioned the volume of these spaces depends on the piston 39 s axial position in the cavity in the embodiment depicted in fig1 the piston and the spindle connected to it are movable between two different positions at the respective ends of the cavity whereas the piston in the embodiment of the compressed air cylinder depicted in fig2 is movable between three different positions at each end of the compressed air cylinder a compressed air hose 14 with associated compressed air valve 30 is connected to the cavity near to the respective end wall in such a way that one hose leads into the space v 1 and the other hose leads into the space v 2 on the opposite side of the piston the respective compressed air hoses 14 are connected to a compressed air source 31 which constantly supplies them with compressed air the piston and hence the spindle connected to it can be moved in desired directions between the two positions by opening the valve and thereby connecting the compressed air and pressurising the respective spaces v 1 and v 2 fig2 depicts a second embodiment of a compressed air cylinder 20.