Compensating device for maintaining specifiable target positions of a hoisted load

Abstract

A compensating device (200) maintains specifiable target positions of a load (206) handled using a cable hoist (202) and attached to a cable (216) of the cable hoist. The respective specifiable target position of the load may change unintentionally to an actual position deviating from the target position. The compensating device has a sensor device (240, 242) for detecting the respective actual position of the load (206). A rotational drive (226, 228, 230) specifies a cable length of the cable hoist (202). A controller (244) changes the cable length after the respective actual position has been detected until the load (206) re-assumes its target position. The respective drive (226, 228,230) can be controlled at least partly by a hydraulic motor (226, 228, 230) with opposite rotational directions. The motor is connected to an actuating device (246) having at least two separate pressure chambers (250, 252) with pressure levels that differ during operation, thereby forming a drive section (248) for the respective hydraulic motor (226, 228, 230), and which can be actuated by the controller (244).

Claims

1. A compensating device for maintaining specifiable target positions of a load that is subject to manipulation by a cable hoist, that is attached to a cable of the cable hoist and that unintentionally changes a respective specifiable target position into an actual position deviating from the specifiable target position due to interference factors, the compensating device comprising: a sensor capable of directly or indirectly acquiring the actual position of the load; a rotatory drive capable of setting an effective length of a cable of the cable hoist; a control capable of changing an effective length of the cable returning the load to the specifiable target position of the load; a first hydraulic motor controlling the rotary drive in opposite first and second rotational directions, the hydraulic motor having a first fluid connection; and an actuator being connected in fluid communication to the first fluid connection and forming an actuator drive for the first hydraulic motor, the actuator drive having first and second pressure chambers separated from each other and having different pressure levels in operation, the actuator being operably controlled by the control, the actuator driving having a third pressure chamber being separated from the first and second pressure chambers and being operated in a higher pressure mode relative to the first and second pressure chambers, the second pressure chamber being permanently connected in fluid communication to a low-pressure store, the lower-pressure store being a hydraulic accumulator.

2. A compensating device according to claim 1 wherein the actuator drive is operable by a drive actuator; the first and second pressure chambers each have a fluid-conducting connection to the first hydraulic motor, with the first pressure chamber driving the hydraulic motor in the first rotational direction while the second pressure chamber receives fluid discharged from the first hydraulic motor to be subsequently discharged therefrom, the second pressure chamber driving the first hydraulic motor in the second rotational direction while the first pressure chamber receives fluid discharged from the first hydraulic motor to be subsequently discharged therefrom.

3. A compensating device according to claim 2 wherein the control comprises a valve in fluid communication with and controlling the drive actuator to rotate the first hydraulic motor in the first or second rotational direction using an operating pressure from a supply source connected in fluid communication with the first hydraulic motor.

4. A compensating device according to claim 1 wherein the sensor comprises at least one of a gyroscope, an inertia-based sensor or a satellite-based navigation device.

5. A compensating device according to claim 2 wherein each of the actuator drive and the drive actuator comprises a piston being guided for movement inside a common housing of the actuator and being connected to each other via a coupling.

6. A compensating device according to claim 5 wherein the coupling device comprises a piston rod extending between the pistons.

7. A compensating device according to claim 6 wherein the piston rod is fixedly connected to said pistons for simultaneous movement thereof.

8. A compensating device according to claim 1 wherein The actuator comprises first, second and third pistons connected by a piston rod and guided for movement inside a common housing, walls of said housing and the piston defining the first, second and third pressure chambers and defining fourth, fifth and sixth pressure chambers, each of the pressure chambers having at least partially varying pressure levels and volumes and being assigned directly to the actuator drive and the drive actuator.

9. A compensating device according to claim 8 wherein each of the pistons has an equal outer diameter.

10. A compensating device according to claim 2 wherein the third pressure chamber and a fourth pressure chamber form the hydraulic accumulator for the actuator drive and the drive actuator.

11. A compensating device according to claim 2 wherein the actuator has a position sensor acquiring a position of the actuator drive and/or the actuator drive; and the control controls the drive actuator based on the position acquired by the position sensor by a processor.

12. A compensating device according to claim 1 wherein the first hydraulic motor is accelerated and decelerated in both of the first and second rotational positions by a hydraulic driver and brake superimposed upon pressure applied by the respective one of the first and second pressure chambers.

13. A compensating device according to claim 1 wherein the cable hoist is fixedly mounted on a dock or a floating transport subjected to the interference factors.

14. A compensating device for maintaining specifiable target positions of a load that is subject to manipulation by a cable hoist, that is attached to a cable of the cable hoist and that unintentionally changes a respective specifiable target position into an actual position deviating from the specifiable target position due to interference factors, the compensating device comprising: a sensor capable of directly or indirectly acquiring the actual position of the load; a rotatory drive capable of setting an effective length of a cable of the cable hoist; a control capable of changing an effective length of the cable returning the load to the specifiable target position of the load; a first hydraulic motor controlling the rotary drive in opposite first and second rotational directions, the hydraulic motor having a first fluid connection; and an actuator being connected in fluid communication to the first fluid connection and forming an actuator drive for the first hydraulic motor, the actuator drive having first and second pressure chambers separated from each other and having different pressure levels in operation, the actuator being operably controlled by the control, the actuator drive is operable by a drive actuator, the first and second pressure chambers each having a fluid-conducting connection to the first hydraulic motor, with the first pressure chamber driving the hydraulic motor in the first rotational direction while the second pressure chamber receives fluid discharged from the first hydraulic motor to be subsequently discharged therefrom, the second pressure chamber driving the first hydraulic motor in the second rotational direction while the first pressure chamber receives fluid discharged from the first hydraulic motor to be subsequently discharged therefrom.

15. A compensating device according to claim 14 wherein the control comprises a valve in fluid communication with and controlling the drive actuator to rotate the first hydraulic motor in the first or second rotational direction using an operating pressure from a supply source connected in fluid communication with the first hydraulic motor.

16. A compensating device according to claim 14 wherein each of the actuator drive and the drive actuator comprises a piston being guided for movement inside a common housing of the actuator and being connected to each other via a coupling.

17. A compensating device according to claim 16 wherein the coupling device comprises a piston rod extending between the pistons.

18. A compensating device according to claim 17 wherein the piston rod is fixedly connected to said pistons for simultaneous movement thereof.

19. A compensating device for maintaining specifiable target positions of a load that is subject to manipulation by a cable hoist, that is attached to a cable of the cable hoist and that unintentionally changes a respective specifiable target position into an actual position deviating from the specifiable target position due to interference factors, the compensating device comprising: a sensor capable of directly or indirectly acquiring the actual position of the load; a rotatory drive capable of setting an effective length of a cable of the cable hoist; a control capable of changing an effective length of the cable returning the load to the specifiable target position of the load; a first hydraulic motor controlling the rotary drive in opposite first and second rotational directions, the hydraulic motor having a first fluid connection; an actuator being connected in fluid communication to the first fluid connection and forming an actuator drive for the first hydraulic motor, the actuator drive having first and second pressure chambers separated from each other and having different pressure levels in operation, the actuator being operably controlled by the control, the actuator including first, second and third pistons connected by a piston rod and guided for inside a common housing, walls of said housing and the piston defining the first, second and third pressure chambers and defining fourth, fifth and six pressure chambers, each of the pressure chambers having at least partially varying pressure levels and volumes and being assigned directly to the actuator drive and the drive actuator.

20. A compensating device according to claim 19 wherein each of the pistons has an equal outer diameter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Referring to the drawings that form a part of this disclosure that are schematic and not to scale:

(2) FIG. 1 is a schematic side view of a prior art compensating device, which comprises a hydraulic power cylinder with a guide pulley at the end to guide a cable; and

(3) FIG. 2 a schematic hydraulic circuit diagram of a compensating device according to an exemplary embodiment of the invention, as part of a cable hoist on a cargo ship.

DETAILED DESCRIPTION OF THE INVENTION

(4) A section of a prior art compensating device 100 is depicted in FIG. 1. That device is usually disposed in a cable hoist 102 between a cable winch 104 and a load 106 to be lifted. The compensating device 100 comprises a piston/cylinder unit 108. A guide pulley 114 is attached at the free end 110 of the piston rod 112. With this compensating device 100, it is possible to deflect the cable 116 by a certain amount upwards or downwards through the traversing path of the piston rod 112. Pulleys 118 for the cable 116 are disposed before and after the piston/cylinder unit 108. By suitably controlling the piston/cylinder unit 108, the effective length of the cable 116 can be reduced after the compensating device 100 through extending the piston rod 112. The cable length can be extended again through retracting the piston rod 112. This device makes it possible to compensate to a limited extent for any interference factors, which may be caused by wind loads or wave action, although a relatively large expense for equipment and controls is required, not to mention wear and tear on the cable 116.

(5) FIG. 2 depicts a compensating device 200 according to the invention that is improved compared to the above-described prior art compensation device 100. The compensating device 200 is provided to maintain specifiable target positions of a load 206 that is manipulated by a cable hoist 202 and a cable 216 attached to the load 206. Interference factors unintentionally change the specifiable target position of the load 206 into an actual position that deviates from the target position.

(6) In this example, the cable hoist 202 is part of an installation location 220 that is subject to interference factors, in particular a floating transport in form of a ship that is subject to wave action. The cable hoist 202 is provided as part of the structure of the ship 220 and serves for the lifting and lowering of the load 206 from/to the sea floor 222. The cable hoist 202 is provided with a cable winch 204 onto which the cable 216 can be wound on and off again. Starting from the cable winch 204, the cable 216 extends via a pulley 224 to the load 206. As is common practice, multiple pulleys and booms as well as hooks or other coupling devices may be provided as part of the cable hoist 202, which have not been included in this schematic hydraulic circuit diagram for reasons of simplification.

(7) The cable winch 204 may be operated with a hydraulic motor 226, 228, 230 in one rotational direction and in the opposite rotational direction. As an example, FIG. 2 depicts three hydraulic motors 226, 228, 230 in total. Of these at least one is always provided to drive the cable winch 204. The hydraulic motors 226, 228, 230 differ from each other in their displacement. The hydraulic motor 228, depicted in the centre of the diagram, has a fixed displacement. The hydraulic motor 226 shown on the left has a graduated displacement. The hydraulic motor 230 on the right has an infinitely variable displacement. Each of the hydraulic motors 226, 228, 230 is connected via two fluid lines 232, 234 to a hydraulic pump 236, which is operated in four-quadrant mode. A safety device 238 may be connected in the fluid lines 232, 234 between the hydraulic pump 236 and the respective hydraulic motor 226, 228, 230, which is provided with valves and/or sensors for the reliable control of the cable hoist 202.

(8) The raising and lowering of the load 206 is possible with the cable hoist 202 described so far. The problem is, however, that the position and orientation of the cargo ship 220 can change due to wave action or wind loads. The changed orientation or position would be transferred via the cable hoist 202 to the load 206, so that the load also constantly changes its position and in particular its height above the sea floor 222. Thus, the precise dropping of a load 206 to the sea floor 222 is made very difficult, if not impossible.

(9) To remedy this problem, the compensating device 200 according to the invention is provided. The compensating device 200 comprises a sensor device or sensor 240, 242 for the direct or indirect acquisition of the respective actual position of load 206. The rotatory drive in form of the cable winch 204 is driven by the respective hydraulic motor 226, 228, 230, for paying out an effective cable length of the cable hoist 202. A control device or control 244, after acquisition of the respective actual position of the load, changes the effective cable length until the load 206 has regained its specified target position again. According to the invention, the rotatory drive may be controlled by a contra-rotating hydraulic motor 226, 228, 230, each having a fluid connection to an actuating device or actuator 246. While forming a drive means or drive 248 for the respective hydraulic motor 226, 228, 230, the actuating device or actuator 246 comprises at least two pressure chambers 250, 252 being separated from each other with different pressure levels when in operation, and being controlled by the control device 244.

(10) The actuating device 246 is connected parallel to hydraulic pump 236 via corresponding fluid lines 254, 256 to the hydraulic motor 226, 228, 230, depending on which one will come into operation. The respective hydraulic motor 226, 228, 230 may be accelerated or decelerated, respectively, in both contra-rotating directions, superimposed by the pressure applied from the respective pressure chamber 250, 252 of drive means or actuator drive 248 and by a hydraulic driving and braking unit in form of a hydraulic pump 236 of the cable hoist 202.

(11) The actuating device 246 is implemented as a triple-piston with a drive means 248 and an actuator or drive actuator 258. The actuating device 246 is subdivided overall into three sections 260, 262, 264 of which in the drawing the upper section 260 is called the high-pressure section, the centre section 262 is called the low-pressure section and the lower section 264 is the actuator section. Each section 260-264 is provided with a piston 266, 268, 270 within a common, pressure-resistant housing 272. The pistons 266, 268, 270 are connected and separated from each other by a common piston rod 274. The sections 260-264 are separated from each other leak-proof through the separating walls 276, 278. The piston rod 274 passes through the separating walls 276, 278. The drive means 248 and the actuator 258 each are then provided with a piston 266, 268, 270 that is guided in the common housing 272 of the actuating device 246. The adjacent pistons 266, 268, 270 are in operative connection with each other via a coupling device in form of the piston rod 274. The coupling device 274 in form of the piston rod forms, together with the respective pistons 266, 268, 270 that are guided inside housing 272 of the actuating device 246, the piston rod unit 280 as a whole. The pistons 266, 268, 270 of the piston rod unit 280 subdivide, preferably with the same outside diameter, the housing 272 of the actuating device 246 into a total of six pressure chambers 250, 252, 282, 284, 286, 288.

(12) Two of the separated pressure chambers 250, 252 of the actuating device 246 each have a fluid connection to the associable hydraulic motors 226, 228, 230 in such a way that either the one or the other of the pressure chambers 250, 252 serves to drive the respective hydraulic motor 226, 228, 230 in the one direction or the other contra-rotating direction. The pressure chamber 250, 252 that is not engaged in driving the respective hydraulic motor 226, 228, 230 takes up the fluid, which was displaced by this driving process, for a subsequent discharge process. The additional pressure chamber 282 of the drive means 248 of the actuating device 246 is preloaded by an energy store 290 in form of a container and biases the piston rod unit 280 with the actuator 258 to move into a specifiable movement direction. To this end the pressure chamber 282 and the energy store 290 are filled with an operating gas in form of nitrogen (N.sub.2) with specified preloading. The additional pressure chamber 282 of the actuating device 246 can then be operated in a kind of high-pressure mode. In contrast another additional pressure chamber 284 of the drive means 248 is operated in a kind of low-pressure mode and is open to the environment U. A low-pressure store 292 is connected permanently to pressure chamber 252. This low-pressure store 292 has the purpose to maintain a sufficiently high pressure level in pressure chamber 252 and in the fluid line 254 and to prevent possible cavitation.

(13) The drive means 248 of the actuating device 246 may be operated by the actuator 258. A control device 244 with a valve device 294 or valve is provided for controlling the actuator 258. With valve device 294 a supply pressure of a supply unit 296 can be applied to the actuator 258 in opposite movement directions. The supply unit 296 comprises a hydraulic pump 298, which draws hydraulic fluid from a tank 300. A hydro-pneumatic pressure store 302 is inserted between the hydraulic pump 298 and the valve device 294 as equalisation buffer. The valve device 294 takes the form of a 4/3-way proportional valve. In the left switch position of the valve device 294, as shown in the drawing, the hydraulic pump 298 feeds fluid into a rod-side pressure chamber 286 of the actuator 258, while fluid is able to flow away from the opposite, piston-side pressure chamber 288 in the direction of the tank 300. In this left side switch position, the piston rod unit 280 is lowered inside the housing. In the right switch position, both pressure chambers 286, 288 of the actuator 258 are supplied with hydraulic fluid. Due to the pressure-active area at the rod-side 304 of piston 270 of the actuator 258, this leads to a lifting of the piston rod unit 280. In the central neutral position, both pressure chambers 286, 288 of the actuator 258 have a fluid connection to each other via a restrictors 305 as well as with the tank 300 via a restrictor 305. The actuator 258 is inactive in this switch position. The valve piston 306 of the valve device 294 is centred in its middle neutral position via springs 308 provided at the valve piston ends. In order to set the required switch positions of the valve piston 306 with the control device 244, an electromagnetic operating device 310 is provided.

(14) A safety device 312 is additionally installed in the fluid lines 314, 316 between the valve device 294 and the actuator 258. The safety device is provided with further sensors and/or valves for controlling the actuator 258.

(15) The control device 244 is coupled to the two sensor devices 240, 242. The one or first sensor device 240 comprises a gyroscope or inertia-based sensor, in particular an acceleration sensor as well as, where necessary, an additional satellite-based position acquisition device. This sensing facility makes it possible to determine the position and orientation of the cable hoist 202, and thus, indirectly the actual position of the load 206. The actuating device 246 comprises a further or second sensing device 242 in form of a position sensing device 242 with which the position of the piston rod unit 280 within the actuator 258 and that of the drive means 248 can be determined. By a processor unit or processor 318, the control device 244 controls the actuator 258 under consideration of the position and orientation data.

(16) The compensating device 200 according to the invention acts in parallel to the hydraulic pump 236 of the cable hoist 202 of the respective hydraulic motor 226, 228, 230 of the cable winch 204. The hydraulic fluid of a hydraulic circuit 320 of the cable hoist 202 may be fed into a corresponding pressure chamber 250, 252 of the drive means 248 of the actuating device 246 of the compensating device 200. Its pressure-based energy may be stored temporarily in the corresponding energy store 290, 292. In the opposite operating direction, the energy may be released from the energy stores 290, 292 from the actuating device 246 in order to decelerate and accelerate the respective hydraulic motor 226, 228, 230 of the cable hoist 202. Moreover, the drive means 248 of the actuating device 246 may be operated by the actuator 258 so as to selectively control the deceleration or acceleration of the hydraulic motor 226, 228, 230 of the cable hoist 202 to compensate for the interference factors. The actuator 258 is controlled by the control device 244 in conjunction with the position and orientation information of the cable hoist 202 and the piston rod unit 280 inside the actuating device 246, which has been acquired with the sensor devices 240, 242.

(17) The solution according to the invention proposes a modern hydraulic motor drive concept for the directly drivable cable winch 204 of the cable hoist 202 with small quantities of operating or drive fluid, which exhibits a greater degree of efficiency than the drive concepts using hydraulic power cylinders 108 as per the prior art. Since the respective hydraulic motor does not have its own cable guide, for example, the above-described guide pulley 114 on power cylinder 108, but rather acts directly on the rotatory drive 226, 228, 230 of the cable winch 204 of the cable hoist 202, for example by a hydraulic clutch, or forms its drive module entirely, it is possible to achieve a low-wearing cable guidance solely through the already necessary cable winch 204. By using a correspondingly large winch diameter, the cable friction may be further reduced so as to minimise wear in particular on cable 216.

(18) While one embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the claims.