Heavy duty lifting devices

A jack construction comprising, in combination,

• a substantially rectangular base plate,
• an elongate post of rectangular cross-section fixed at one end thereof to the base plate and extending substantially normal thereto,
• an elongate sleeve of rectangular cross-section congruent to the cross-sectional shape of the post having one open end and one closed end mounted on and movable along and with respect to said post,
• the length of the sleeve substantially that of the post,
• the closed end of the sleeve positioned away from the base plate, there being a flat end plate closing the end of said sleeve which is adapted to receive work loads thereon,
• first lug means on the base plate adjacent to one side of the post which is adapted to receive and engage one end of a hydraulic cylinder,
• the said end plate of the sleeve having an extending, substantially rectangular lip projecting outwardly past the wall of the sleeve next the side of the post adjacent to said lug means,
• means on the upper portion of the sleeve and on the side thereof next to the said first lug means forming a pair of horizontal slideways of a size and configuration equal to one another, said slideways positioned one above the other and below said lip,
• two slides removably insertable in the said slideways, one slide into each slideway, one of said slides having second lug means thereon for engagement with the piston rod of the hydraulic cylinder,
• and means cooperating between the post and the sleeve for fixing an extended position of the sleeve with respect to the post once the sleeve is extended thereon by action of the hydraulic cylinder.