GB838627A - Improvements in jacking mechanisms for portable marine platforms - Google Patents

Abstract

838,627. Piles; marine platforms. DE LONG CORPORATION. July 16, 1956 [July 20, 1955], No. 21981/56. Class 68(2) In jacking-mechanism for raising or lowering a floatable platform, e.g. a barge, on legs which are forced into the sea bed, the upper and lower means for engaging the legs are positively locked to the legs by sliding bolts which engage longitudinal series of holes in the sides of the legs; the jacking-mechanism is secured to the barge deck by means which cushion shocks both in the upward and downward directions; and automatic means are provided for controlling the various relative movements of the barge and the legs. Means are provided to relieve the sliding bolts of the weight of the barge whilst they are disengaged from the holes in the legs, so that the holes and the bolts are not damaged by attrition. A jacking- mechanism 26 is secured around each well 'in the barge through which a leg 22 is vertically movable, the leg having at each side a channel member 28 with a longitudinal series of holes 32 for engagement with upper and lower sliding bolts 74, 76. The bolts 76 are each slidable in a bottom cross-piece 92 of a slider 42 in which an hydraulic cylinder 86 is held, the piston rod 96 being locked at 100 in a bearing member 46 for the bolt 74, the member 46 being the cross member of a jack-supporting frame having spaced vertical members 44 formed with guides for the slider 42. The members 44 are bolted at the bottom to an abutment plate 48 which receives the downward jacking forces, a concave-convex resilient buffer 132, 134 cushioning the forces on the barge deck and allowing a slight departure of the leg from the vertical. Upward forces are taken resiliently by a cushioning assembly 126 arranged between the plate 48 and an abutment 118 which spans plates 114, 116 welded to the barge deck to keep the jack assembly in position. The load is relieved from the pins 74, 76 before retraction thereof by a pivotal lever 146 having a nose 150 which engages a hole 32 and takes the load when the toggles 166 are slightly beyond the dead centre and are against the stop 168, so that they are selflocking. The hydraulic cylinder 156 contains a coil spring which is compressed by the piston as it descends to force the toggles over the dead centre. If pressure is exhausted from the cylinder, the coil spring brings the toggles back to the dead centre and the spring 154 effects a rapid disengagement of the nose 150 from the hole 32. The legs may be of triangular section with three sets of longitudinal holes and three jacking-sets working in unison. The hydraulic means for projecting and withdrawing the bolts 74, 76; for altering the vertical distance between the bolts 74, 76, and for operating the release means 146, 150, are controlled by solenoid actuated valves, the current supply to the solenoids being under manual control or under automatic control, the latter being of different sequences according to the nature of the operation required, i.e. raising barge, lowering barge, raising legs, lowering legs. A sequence of operations in the automatic control is selected by plugging into a switchboard, one of a number of wiring-strips which provides a circuit according to the particular operation to be performed, limit switches LS1, LS2 operated by the hydraulic means 80, 82 for the bolts 74, 76, and another limit switch operated by the slide 42 taking part in the control of the solenoid valves. The whole of the jacks on all the legs may act in unison, or each leg may be worked on separately. Means are provided for compensating for Dolts being out of alignment with holes 32. Specification 838,628 is referred to.