intersection 44 through a conduit 45 opening outside hydraulic unit 1 through orifice t 12 and on the other side through a conduit 46 opening through orifice t 13 during operation these supplementary conduits 45 and 46 are connected by a distribution connector 14 to securing devices 15 16 respectively for secured cylinders 9 and 10 this arrangement of supplementary outlet conduits 45 and 46 is easy to construct and represent however either one these supplementary outlet conduits 45 46 may be connected to any point on connecting conduit 33 or to any point on first inlet conduit 32 that is located before balance valve 21 when first inlet conduit 32 has one alternatively hydraulic unit 1 may contain only a single supplementary outlet conduit joined to connecting conduit 33 or to inlet conduit 32 while the two connections 14 required for operation of the securing devices for the secured cylinders may be interconnected outside hydraulic unit 1 for example in the preferred embodiment shown in fig9 each of the outlets on hydraulic unit 1 is advantageously duplicated by another equivalent outlet located on another surface of the unit inlet conduit 41 is thus divided into two conduits 47 and 48 opening through orifices a 1 and a 2 respectively inlet conduit 32 is also divided into.