1314072 Fluid operated positioning apparatus INTERNATIONAL BUSINESS MACHINES CORP 12 May 1970 [14 May 1969] 22930/70 Heading F1P An assembly of piston and cylinder units 15, Fig. 21, of differing strokes connected together for positioning a load are supplied with hydraulic fluid through respective pilot operated valves (not shown) fed from a line 47, 51, 52, Fig. 2B, the line containing a flow sensing system 23 which sends fluid signals to a logic unit 20, which unit 20 causes inter alia unlocking of the load and an increase in the throttling effect of a valve 17, Fig. 21, in the lines 141, 142 between the units 15 and the pilot operated valves. With the load locked in an adjusted position, opening of a different selection of the pilot operated valves first causes some units 15 to extend while others contract, the load remaining stationary. Because the load itself is not moved this operation (termed "exchange") is performed at high speed, the logic unit 20 automatically arranging for the flow sensing unit 23 and the valve 17 to allow a high flow rate to the units 15. Thus logic unit 20 causes pressurization of a line 38 and consequential opening of a valve 40. This allows pressure from a supply system described in Specification 1314075 .Fig. 2C, (not shown) and connected to the line 47, to flow through parallel paths 49, 42 to the line 51, 52 leading via the pilot operated valves to the lines 141, 142 (depending on the positions of the pilot operated valves) and thence through the valve 17 to the units 15. During "exchange" the throttling effect of the valve 17 is low. When "exchange" is completed fluid no longer flows through orifices 50 in spring loaded pistons 35, 36 in the respective parallel flow paths 49, 42 and the pistons 35, 36 are moved to the positions shown. Thus the previous connection of lines 24, 25 to a return 46 is momentarily closed. The logic unit 20 detects closure of the line 25 and acts to unlock the load and to de-pressurize lines 38, 94. The release of pressure in the line 94 allows a spring to force a spool 143 of the valve 17 to increase its throttling of the hydraulic fluid which then commences to flow to those units 15 required to move the load. The release of pressure from the line 38 allows the valve 40 to close so that the flow rate to the units 15 is reduced by having to flow only through the path 49. The units 15 are connected to a movement damping device, Fig. 2J, (not shown) as described in Specification 1314071 the device being arranged to be returned and held in a central position after re-positioning of the load. An air reader Fig. 2D, (not shown) as described in Specification 1314073 has a perforated tape advanced in steps to cause the pneumatic re-positioning of pilot valves controlling the said pilot operated valves which control the individual units.