POWER CONVERTER FOR DRIVING A HYDRAULIC SUBMERGED TOOL

Abstract: Method for driving a hydraulic submerged tool whereby the hydraulic pressure energy is generated in a submerged power converter, being driven by pressurised surrounding water which after the energy transfer is exhausted into the surrounding water, said power converter consis­ ting of one or more work cylinders (1,2), each by means of a floating piston (3, 4) being divided in a space (5, 6) filled with the pressurised surrounding water and a space (7, 8), filled with a hydraulic work medium, switching means (17, 18) being provided, for alternately connecting said space (5, 6) either to a feed conduct (13) for pressurised surrounding water, or to an exhaust (14).

Description: The invention relates to a power converter comprising at least one pair of workcylinders, each by means of a floating piston being divided into a first space to which a pressurized medium can be supplied and a second space filled with a hydraulic medium which can be used for driving a tool, switching means being present which are activated each time that a floating piston reaches the end of its work stroke as a result of which the first space of the one cylinder is connected to either a feed conduct for pressurized medium or to an exhaust and the first space of the other cylinder to either said exhaust or to said conduct, said second space being connected to the tool via a first one way valve for supplying hydraulic work medium to said tool and via a second one way valve for the return flow of hydraulic medium from said tool towards said power converter. Such a power converter is known by GB-A-1 470 956. The object of this known converter is only to raise the pressure of a hydraulic fluid to a higher level. Now the object of the invention is to enlarge the usefullness of such a converter and to that end it is provided, that the respective work cylinders of each pair are located in line, the pistons in said cylinders are connected by a link movable in the longitudinal direction of the cylinders through a wall adjacent to the respective spaces of said cylinders which are filled with the hydraulic medium and wherein, the power converter having been lowered by hoisting means under water for driving a submerged tool, the pressurized medium is formed by pressurising surrounding water and the exhaust is free to said surrounding water. In this way pressurized surrounding water can be supplied to the power converter by means of a hose and a hydraulic medium can be used for driving the tool. The water used by the power converter can be passed directly to the surrounding water. In order to compensate changes in the volume of the hydraulic medium or small losses in said circuit and to promote the removal of water out of a work cylinder at the end of the work stroke the power converter according to the invention can be provided with at least one store cylinder in which an over pressure with respect to the surrounding is present and which is partly filled with the hydraulic work medium and is connected to the return conduct of the tool. The over pressure in said store cylinder can be realized in a simple way by providing said cylinder with a floating piston on which spring means are working such as for instance a pressurized gas. A simple embodiment can be obtained when according to the invention one pair of work cylinders is located within said store cylinder. It will be prefered that the power converter is forming one unit with the tool. By this the number of elements can be decreased and limited connecting lines between said power converter and the tool are obtained. Further the supply conduct for the pressurized surrounding water can be combined with the hoisting means. This in particular will be applied in case of drilling ships in which the drilling pipe which is composed of sections may also serve as supply conduct for the pressurized surrounding water. The invention now will be further elucidated on hand of the drawings in which some examples of embodiments of the invention are shown. Figure 1 schematically shows a vertical cross section through an embodiment of the power converter according to the invention, but for a correct understanding of the invention only; Figure 2 schematically shows another embodiment of the power convert in cross section, the hydraulic scheme being left out. Figure 3 schematically shows the preferred embodiment of the power converter according to the invention in longitudinal cross section. The power converter shown in Fig. 1 consists of two work cylinders 1 and 2 which each by a floating piston 3 and 4 resp. are divided in a variable space 5 and 6 resp. which can be filled with pressurized surrounding water, and a variable space 7 and 8 resp., which is filled with the hydraulic work medium with which the tool is driven and which spaces via one way valves 9 and 10 are connected to a pressure conduct 11 to a not further shown tool. By means of switching means the pressurized water spaces 5 and 6 can alternately be connected either to a supply conduct 13 of pressurized surrounding water, or to a free exhaust 14 toward the surroundings. The switching means consist in approach switches located near the end positions of the work stroke of the floating piston or sensors, which, each time the floating piston 3, 4, reaches the end of its work stroke in a work cylinder 1, 2 give a switching, which controls the switching valve 17 or 18 of the related cylinder. The mentioned approach switches can be mounted as well at the end of the side wall of the spaces 7, 8 as in the end wall of the spaces 7, 8. The switching command may be mechanical, hydraulical or electrical. The switching valve 17, 18 can in stead of a 3/2 valve, as shown in Fig. 1 also be a 3-positions valve with three connections, or two valves switching independently from each other, a switching position being present in which the conduct 13 is immediately switched on the exhaust 14 for a free pass way. The power converter shown in Fig. 1 is further provided with a store cylinder 19, which by means of a floating piston 20 is divided in a space 21, which is filled with the hydraulic work medium and via a conduct 23 can be connected to the return conduct of a tool not further shown, and a space 22 in which a gas is present having a higher pressure than the surroundings The conduct 23 is also connected to the spaces 7, 8 of the work cylinders 1, 2, filled with the hydraulic work medium via one way valves 24 and 25. In Fig. 1 the pressurized surrounding water is connected to the pressurized water space 5 of the work cylinder 1 via the switching valve 17. As a consequence of this the floating piston 3 carries out a work stroke and presses the hydraulic work medium to the tool via the one way valve 9 and the pressure conduct 11. During this work stroke of the work cylinder 1 the valve 18 has been switched in such a way, that the pressurized water space 6 of work cylinder 2 is connected to the free exhaust 14 toward the surroundings. The pressurized water now can be pressed out of the space 6 by the floating piston 4 under influence of the low pressure return flow from the tool and/or the hydraulic work medium which is present in the space 21 of the store cylinder 19 and has an over pressure with respect to the surroundings. Herewith via de conduct 23 and the one way valve 25 the space 8 is again filled with the hydraulic work medium. At the end of the work stroke of the floating piston 3 an approach switch is activated, by reason of which valves 17 and 18 are reversed. Now the floating piston 4 in the work cylinder 2 carries out a work stroke, whereas the space 7 in the work cylinder 1 is filled with the hydraulic work medium via the one way valve 24 during the intake stroke. At the end of this work stroke the valves 17 and 18 are reversed by an approach switch mounted in the work cylinder 2. In this manner a continuous fluctuating or not fluctuating flow of hydraulic work medium is obtained. By the application of more than two work cylinders and/or having the work strokes overlapping the fluctuations can be reduced. In the pressure conduct 11 and the return conduct 23 an accumulator 26, 27 can be located for absorbing pressure variations or strong variations of liquid flows. In the scheme the further components such as safety valves, coolers, filters and so on have been left out because they are not of principal interest for the invention. It is conceivable to use only one work cylinder in combination with a sufficiently large dimensioned high pressure accumulator. The power converter according Fig. 2 consists of two work cylinders 1, 2 which are located inside the store cylinder 19. Fig. 3 shows an embodiment of the power converter in which two work cylinders 34 and 35 are located in line with each other, whereas the combination is surrounded by a coaxial store cylinder 36. In this embodiment the two floating pistons 37 and 38 are coupled by a link 39. The spaces 40 and 41 can be alternately connected either to a supply conduct of pressurized surrounding water or a free exhaust toward the surroundings, by means of switching means. The spaces 42 and 43 are alternately filled with the hydraulic work medium which during the work stroke of the related piston 37, 38 is pressed under high pressure via one way valves 44 and 45 resp. toward the tool. The mechanical coupling between both pistons 37 and 38 causes that during a work stroke of for instance piston 37 the piston 38 is carrying out an intake stroke during which while the space 43 is filled with hydraulic work medium from the space 48 of the store cylinder 36 via the one way valve 46. In the space 49 above the space 48 a medium, for instance a gas, is present with an over pressure with respect to the surroundings. During the reversed strake the space 42 filled with hydraulic medium via the one way valve 47. It will be obvious that the invention is not restricted to the embodiments described in the above, which within the scope of the invention as defined in the appended claims can be varied in different manners.

Claims: 1. Power converter comprising at least one pair of workcylinders (1,2,34,35), each by means of a floating piston (3,4,37,38) being divided into a first space (5,6,40,41) to which a pressurized medium can be supplied and a second space (7,8,42,43) filled with a hydraulic medium which can be used for driving a tool, switching means (17,18) being present which are activated each time that a floating piston reaches the end of its work stroke as a result of which the first space (5, 6,40,41) of the one cylinder is connected to either a feed conduct (13) for pressurized medium or to an exhaust (14) and the first space of the other cylinder to either said exhaust (14) or to said conduct (13), said second space (7,8,42,43) being connected to the tool via a first one way valve (9,10,44,45) for supplying hydraulic work medium to said tool and via a second one way valve (24,25,46,47) for the return flow of hydraulic medium from said tool towards said power converter, characterized in that the respective work cylinders (34,35) of each pair are located in line, the pistons (37,38) in said cylinders are connected by a link (39) movable in the longitudinal direction of the cylinders through a wall adjacent to the respective spaces (42,43) of said cylinders which are filled with the hydraulic work medium and wherein, the power converter having been lowered by hoisting means under water for driving a submerged tool, the pressurized medium is formed by pressurising surrounding water and the exhaust (14) is free to said surrounding water. 2. Power converter according to claim 1, characterized in that it is provided with at least one store cylinder (19,36) in which an over pressure with respect to the surrounding water is present and which is partly filled with the hydraulic work medium and is connected to the return conduct (23) of the tool. 3. Power converter according to claim 2, characterized in that said store cylinder (19,36) is provided with a floating piston (20) on which spring means are working such as for instance a pressurized gas. 4. Power converter according to claim 2 or 3, characterized in that one pair of work cylinders (34,35) is located within said store cylinder (36). 5. Power converter according to one of the preceding claims, characterized in that said converter forms one unit with the tool. 6. Power converter according to one of the preceding claims, characterized in that the supply conduct (13) for the pressurized surrounding water is combined with the hoisting means.

Inventors: ARENTSEN, DIK
Applicants: IHC HOLLAND N.V.
Application year: 1989
Main classification: E02D7
IPC codes: F04B9, E02D7