Telescopic load transfer device

A stacker crane tray mechanism comprising a tray and movable support means therefor, said support means comprising a plurality of pairs of telescopically articulated beams;

• one beam pair being attached to said tray and one other beam pair being relatively fixed and with respect to which fixed beam pair all other beam pairs are telescopically movable;
• the beam pairs intermediate said fixed beam pair and the beam pair attached to said tray having guide channels at one face thereof and guide rollers at the other face thereof;
• wherein all said beam pairs are telescopically connected by rollers of beam pairs extending into guide channels of immediately adjacent beam pairs;
• drive plates in superimposed array and secured to respective beam pairs for effecting telescopic movement thereof and having central nested channels;
• drive chain means and said drive plates being sequentially coupled by said drive chain means so that driven movement of a first of said drive plates effects progressively extended movement of the remainder of said drive plates and the respective beam pairs, to drive said tray;
• said drive plates being reversibly movable;
• and hydraulic drive means comprising a plurality of double acting hydraulic cylinders secured in pairs, one pair being connected to another pair by connection of a piston rod of each of said pairs to each other;
• the cylinders of each pair being connected to each other and the respective rods thereof extending in opposite directions and;
• said cylinders and pistons being disposed in the lowermost drive plate channel;
• means whereby the other piston rod of one of said pairs has an end relatively fixed with respect to said relatively fixed beam pair and the other piston rod of the other of said pairs is drivingly connected to said first drive plate;
• whereby selective pressurization of said cylinders effects motion of one or both of said piston rods to actuate said first drive plate to a selective extent and in a direction dependent upon direction of pressurization of said cylinders.