WO2010049594A1

WO2010049594A1 - Method and arrangement for the storing of energy

Info

Publication number: WO2010049594A1
Application number: PCT/FI2009/050879
Authority: WO
Inventors: Pekka Tapani GRÖHN
Original assignee: Mantsinen Group Ltd Oy
Priority date: 2008-10-30
Filing date: 2009-10-30
Publication date: 2010-05-06
Also published as: FI20086027A0

Abstract

The object of the invention is a method and an arrangement for storing energy, such as potential energy, and for using the stored energy in a fluid system, such as a hydraulic or pneumatic system, which fluid system comprises a fluid cylinder (5, 7), such as a hydraulic or pneumatic cylinder, consisting of a cylinder and a piston arrangement movably mounted in the cylinder, and actuators for moving the fluid cylinder's (5, 7) piston arrangement in the cylinder.

Description

METHOD AND ARRANGEMENT FOR THE STORING OF ENERGY

Background of the Invention

The object of the invention is the method according to the preamble of Claim 1 for the storing of energy and for using the stored energy in a fluid system, such as a hydraulic or pneumatic system, said fluid system comprising a fluid cylinder, such as a hydraulic or pneumatic cylinder, and actuators for moving a piston arrangement of the fluid cylinder in the cylinder.

The method, that is the object of the invention, can be appropriately applied in devices and arrangements, in which movement by means of the fluid cylinder is performed against an external force. Typically, and most frequently, the force is the force of gravity, at least in hoisting devices, but it can also be some other force, like flow resistance, force of inertia, or the wind. The method constituting the object of the invention can preferably be applied in various material handling equipment and hoisting devices, like boom cranes and other cranes, not excluding other devices for material handling.

A prior art arrangement, wherein a circuit comprising an operating cylinder, an auxiliary cylinder, separate from the operating cylinder, and a hydraulic pressure accumulator are being used for the balancing of a boom of a device for material handling. The arrangement also comprises required loading valves, filters and other peripheral devices. Such a solution is presented in the publications JP 2004116674 and JP 1 199002.

A prior art system is also one, wherein a closed circuit pump is used for an actuator, said pump being located in the system between a pressure accumulator and the actuator. Such a solution is presented in the publication EP 1 092 097.

In hydraulically driven machines, the overall efficiency is often low. Typically, the energy of the work performed by the cylinder in the return movement against the force disappears as loss in the system. For instance, in load handling machines with a boom, the potential energy of the boom structure or the load cannot, in most cases, be utilized. In arrangements, where an operating cylinder and separate auxiliary cylinders are being used, the introduction of additional actuators to the boom structure and the frame frequently cause problems. In particular, troublesome situations occur in connection with retrofitting.

Brief Description of the Invention

The objective of the invention is the solving of at least part of the aforementioned problems.

The objective of the invention is achieved by the method according to the independent patent claim 1.

An object of the invention is also the arrangement according to the independent patent claim 7.

The preferable embodiments of the invention are presented in the dependent patent claims.

The invention is based on connecting to the fluid cylinder, such as a hydraulic or pneumatic cylinder, in addition to a fluid circuit belonging to a fluid system, such as a hydraulic or pneumatic system, at least one fluid circuit, separate from the fluid system, which separate fluid circuit is functionally connected to the fluid cylinder such, that the movement of the piston arrangement in the cylinder causes a fluid flow in said at least one separate fluid circuit. Said separate fluid circuit comprises an energy storing system for storing the energy of the fluid flow. The motion of the piston arrangement in the cylinder is partly caused, in some stage of the work cycle, by the force of gravity or some other force external to the fluid cylinder. The piston arrangement of the fluid cylinder is moved as in the normal case in the cylinder by means of the actuators of the fluid system, but by means of the arrangement according to the invention, a fluid flow is additionally achieved in said at least one separate fluid circuit and the energy of this fluid flow is stored by means of the energy storing arrangement. Subsequently, when the piston arrangement of the fluid cylinder is moved in the cylinder by means of the actuators of the fluid system, the stored energy can be released for use from the energy storing arrangement into the separate fluid circuit connected to the fluid cylinder for assisting the movement of the piston arrangement in the cylinder and/or for implementing the movement of the fluid cylinder.

In the energy storing arrangement, preferably in a pressure store, such as, for instance, a pressure accumulator, energy is stored in a compressible gas. The gas storing the energy can be precompressed. There may be one or more energy storing arrangements, such as pressure accumulators. The arrangement further comprises a fluid duct, like a hydraulic or pneumatic tube, by means of which the fluid cylinder is connected to the energy storing arrangement. Naturally, one or more fluid duct can extend from the fluid cylinder to the energy storing arrangement, preferably a pressure accumulator. The arrangement preferably comprises a device, by means of which a minimum operating pressure of the system is maintained by means of an external fluid pressure. The arrangement further preferably comprises a device, by means of which the maximum operating pressure of the system is being limited. Some other energy recovery arrangement, for example a mass, like a counterweight hanging from the cylinder storing energy in the form of potential energy, can also serve as the energy storing arrangement.

According to a preferable embodiment of the invention, the fluid cylinder contains two or more cavities, the force caused by the pressure of which act in the same direction in the cylinder. The cylinder always contains at least one cavity for the fluid circuit comprising the storing arrangement separate from the fluid arrangement. This said at least one separate fluid circuit is connected to the cylinder to the at least one cavity. Preferably the pressure produced by the fluid circuit separate from the fluid arrangement will be connected together with the pressure produced by the fluid circuit belonging to the fluid system to separate cavities in the same cylinder, which mutually act in the same direction. The pressure produced by said at least one fluid circuit separate from the fluid system can affect more than one cavity. Further, cavities in several fluid cylinders can be connected to the same fluid circuit. According to a preferable embodiment of the invention, the pressure produced by the separate fluid circuit can be recovered by means of valve arrangements and be used in different cavities of the fluid cylinder or just within a certain range of motion or even in different fluid cylinders. According to still another preferable embodiment of the invention, the cavity of the fluid cylinder can, itself, serve as a pressure accumulator. Then energy is accumulated into compressible gas in one cavity, which gas may be precompressed. According to an embodiment of the invention a fluid cylinder is arranged in a device, which typically lifts a boom and/or a load against the force of gravity. Then, at least part of the lifting force is produced by an energy storing arrangement, which preferably can be a pressure accumulator. There may be one or more energy storing arrangements, such as pressure accumulators. According to a preferable embodiment of the invention, the fluid cylinder in the arrangement is hinged to the pivot mechanism between an upper carriage of the crane and a first boom. When the first boom is at the topmost position of its path, the length of the fluid cylinder is at its maximum. Then, the piston shaft in the piston arrangement of the fluid cylinder is at its outer extreme position. As the first boom moves from a high position to a low position the piston shaft in the piston arrangement of the fluid cylinder is foreshortened until, as the said boom is at the lowest extreme position of its path, the length of the fluid cylinder is at its minimum. Then, the piston shaft in the piston arrangement of the fluid cylinder is inside the cylinder and the pressure, which used to be in the fluid cylinder, is stored in the pressure accumulator. As the boom moves again from its lowest position upwards, stored energy is released from the pressure accumulator in order to aid the movement of the piston arrangement.

An advantage achieved by means of a preferable embodiment of the invention is, that energy is saved by storing potential energy in the at least one pressure accumulator and by subsequently utilizing that energy. An advantage is also the fact, that the structure of the device is simplified while the efficiency stays the same, and the number of components is decreased, which implies easier retrofitting. Generally, a solution according to the invention enables energy recovery and energy utilization in devices, in which that previously has not been economically viable or even possible.

List of Figures

Below, some preferable embodiments of the invention are presented in more detail with reference to the accompanying figures, of which

Figure 1 shows a boom crane, in the fluid cylinders if which a solution according to the invention can be used, Figure 2 shows, in a different position, the same boom crane as the one in Figure 1 ,

Figure 3 shows a hydraulic cylinder with three cavities, and an energy storing arrangement, and

Figure 4 shows a hydraulic cylinder with four cavities, and an energy storing arrangement.

Detailed Description of the Invention

The object of the invention is a method and an arrangement for storing energy, e.g. potential energy, and for using the stored energy in a fluid system, such as a hydraulic or pneumatic system, which fluid system comprises a fluid cylinder 5, 7, such as a hydraulic or pneumatic cylinder, consisting of a cylinder and a piston arrangement movably installed in the cylinder, and actuators for moving the fluid cylinder's 5, 7 piston arrangement in the cylinder.

Figure 1 shows a boom crane 1 , including an upper carriage 2, a first boom 3, a final boom, i.e. a folding boom 4, and fluid cylinders 5, 7. The fluid cylinder 5 in the system is hinged to a pivot mechanism 6 between the crane's upper carriage 2 and the first boom 3. A fluid cylinder 7 is also provided between the first boom 3 and the folding boom 4, which cylinder also could be called a folding cylinder. When the first boom 3 is positioned at the top of its path, the length of the fluid cylinder 5 is at its maximum.

Figure 2 shows the boom crane 1 having the first boom 3 at the lowest extreme position of its path. When the boom 3 is at the lowest extreme position, the length of the fluid cylinder 5 is at its minimum. In the Figure, the folding boom 4 is also at an extreme position of its path, and the length of the folding cylinder 7 is then at its minimum.

As shown in Figure 1, when the first boom 3 is located at the topmost position of its path, the length of the fluid cylinder 5 is at its maximum. Then the position of the piston shaft in the fluid cylinder's 5 piston arrangement is at its outward extreme position. As the first boom 3 moves from the top position, shown in Figure 1 , to the bottom position, shown in Figure 2, the piston shaft in the fluid cylinder's 5 piston arrangement is foreshortened until, as the said boom 3 is at the lowest extreme position of its path, the length of the fluid cylinder 5 is at its minimum. Then, the piston shaft in the fluid cylinder^'s 5 piston arrangement is in the cylinder, and the pressure having been present in the fluid cylinder is stored in the pressure accumulator. As the boom 3 again moves from the low position upwards, stored energy is released from the pressure accumulator in order to aid the movement of the piston arrangement.

Figure 3 shows a fluid cylinder with three cavities, here a hydraulic cylinder 5, 7, having the cavities 10, 11, and 12. The hydraulic cylinder 5, 7 is connected to a pressure accumulator 14. The energy created through the motion of the hydraulic cylider's 5, 7 piston arrangement is stored in the at least one pressure accumulator 14. Not all the parts of a fluid system, such as a hydraulic or pneumatic system, which parts are obvious to a person skilled in the art, are shown in connection with the hydraulic cylinder 5, 7, but, rather, the focus is on the most important ones regarding the description of the invention.

Figure 4 shows a fluid cylinder with four cavities, here a hydraulic cylinder 5, 7, having the cavities 10, 11, 12 and 13. Pressure accumulators 14 and 15 are connected to the hydraulic cylinder 5, 7. Not all the parts of a fluid system, such as a hydraulic or pneumatic system, which parts are obvious to a person skilled in the art, are shown in connection with the hydraulic cylinder 5, 7, but, rather, the focus is on the most important ones regarding the description of the invention.

In Figure 4, in addition to of the hydraulic system's own fluid circuit, at least one separate fluid circuit is connected to the hydraulic cylinder 5, 7, in which separate fluid circuit the movement of the piston arrangement is arranged to cause a fluid flow in said at least one separate fluid circuit. For storing the energy of the fluid flow, the fluid circuit is provided with the pressure accumulators 14 and 15 as an energy storing arrangement. The pressure accumulators 14 and 15 are situated in separate fluid circuits enabling energy recovery and utilization, respectively, in both directions of motion. This would be the case, for instance, in an arrangement, in which the effective direction of the force of gravity is switched in the course of the cylinder's motion.

When the boom 3 of the crane 1 , shown in Figure 1 , is lowered, partly caused by the force of gravity and/or partly caused by the fluid cylinder 5, the fluid cylinder 5 is foreshortened. Thus the fluid cylinder's 5 piston arrangement moves in said fluid cylinder 5 by means of the actuators of the fluid system and, partly, also influenced by the force of gravity, and a fluid flow is induced in the fluid circuit of the fluid cylinder 5. The energy of this fluid flow can be stored by means of the energy storing arrangement. The folding cylinder 7 between the first boom 3 and the folding boom 4 can operate in a similar manner.

When the boom 3 of the crane 1, shown in Figure 2, is lifted upwards against the force of gravity, the piston shaft in the fluid cylinder's 5 piston arrangement moves outwards in the fluid cylinder 5, and then the portion of the piston shaft outside the piston arrangement of the fluid cylinder extends in length. Thus the fluid cylinder's 5 piston arrangement moves in said fluid cylinder 5 by means of the actuators of the fluid system while stored energy from the energy storing arrangement is being released for use in order to aid the movement of the piston arrangement in said fluid cylinder 5 and/or to implement the movement of the fluid cylinder 5. The folding cylinder 7 between the first boom 3 and the folding boom 4 can operate in a similar manner.

To a person skilled in the art, it is obvious, that, along with the technical development, the basic idea of the invention can be implemented in many different ways. Thus, the invention and its embodiments are not limited to the examples described above, but they can vary within the scope of the patent claims.

Claims

Patent Claims

1. A method for the storing of energy, such as potential energy, and for using the stored energy in a fluid system, such as a hydraulic or pneumatic system, which fluid system comprises a fluid cylinder (5, 7), such as a hydraulic or pneumatic cylinder, consisting of a cylinder and a piston arrangement movably mounted in the cylinder, and actuators for moving the fluid cylinder's (5, 7) piston arrangement in the cylinder, characterized in, that to the fluid cylinder (5, 7) is connected, in addition to a fluid circuit in the fluid system, an at least one fluid circuit separate from the fluid system, which separate fluid circuit is functionally connected to the fluid cylinder (5, 7) such, that the movement of the piston arrangement in the cylinder causes a fluid flow in said at least one separate fluid circuit and which said separate fluid circuit comprises an energy storing arrangement (14) for storing the energy of the fluid flow, that the fluid cylinder's (5, 7) piston arrangement is moved in the cylinder by means of the actuators of the fluid system and the fluid flow is produced in said at least one separate fluid circuit and the energy of the fluid flow is stored in the energy storing arrangement (14), and that the fluid cylinder's (5,7) piston arrangement is moved in the cylinder by means of the actuators of the fluid system and, at the same time, the stored energy is released from the energy storing arrangement (14) into the separate fluid circuit connected to the fluid cylinder (5, 7) for aiding the movement of the piston arrangement in the cylinder and/or for implementing the movement of the fluid cylinder.

2. Method according to Claim 1 , characterized in, that at least one cavity (10, 11, 12, 13) is formed in the cylinder (5, 7) for the fluid circuit separate from the fluid system, and that said at least one separate fluid circuit is connected to the cylinder to at least one cavity (10, 11, 12, 13).

3. Method according to Claim 1 or 2, characterized in, that at least one pressure accumulator operates as the energy storing arrangement (14).

4. Method according to any one of the Claims 1 - 3, characterized in, that the movement of the piston arrangement in the cylinder (5, 7) is achieved at least partly by means of the force of gravity or some other force external to the fluid cylinder.

5. Method according to any one of Claims 1 - 4, characterized in, that, in the energy storing arrangement, the energy is stored in compressible gas.

6. Method according to Claim 5, characterized in, that the gas storing the energy is precompressed.

7. An arrangement for storing energy, such as potential energy, and for using the stored energy in a fluid system, such as a hydraulic or pneumatic system, which fluid system comprises a fluid cylinder (5, 7), such as a hydraulic or a pneumatic cylinder, consisting of a cylinder and a piston arrangement movably mounted in the cylinder, and actuators for moving the fluid cylinder's (5, 7) piston arrangement in the cylinder, characterized in, that to the fluid cylinder (5, 7) is connected, in addition to its own fluid circuit in the fluid system, an at least one fluid circuit separate from the fluid system, which separate fluid circuit is functionally connected to the fluid cylinder (5, 7) such, that the movement of the piston arrangement in the cylinder is arranged to cause a fluid flow in said at least one separate fluid circuit, and that said separate fluid circuit contains an energy storing arrangement (14), into which the energy of the fluid flow can be stored and from which energy storing arrangement (14) stored energy can be released into the fluid circuit connected to the fluid cylinder (5, 7) in order to aid the movement of the piston arrangement in the cylinder.

8. Arrangement according to Claim 7, characterized in, that, in the cylinder (5, 7), there is formed at least one cavity (10, 1 1 , 12, 13) for the fluid circuit separate from the fluid system, and that said at least one separate fluid circuit is connected to the cylinder (5, 7) to at least one cavity (10, 1 1, 12, 13).

9. Arrangement according to Claim 7 or 8, characterized in, that there is at least one pressure accumulator in the energy storing arrangement (14).

10. Use of the method according to any one of Claims 1 - 6 and of the arrangement according to any one of Claims 7 - 9, characterized in, that it is used in material handling devices and/or hoisting devices.