Device for the direct recovery of hydraulic energy by means of a single-acting hydraulic cylinder

Abstract

The invention concerns a device for the direct recovery of hydraulic energy in a machine, comprising at least one single-acting storage cylinder-piston device with a storage cylinder, a storage cylinder-piston and a storage cylinder chamber, with at least one differential cylinder-piston device with a differential cylinder comprising a separate rod side and base side, and with at least one hydraulic accumulator, which may be connected to the storage cylinder-piston device and/or the differential cylinder-piston device, wherein the potential energy of the storage cylinder-piston device, which retracts under a compressive load, may be at least partially stored in the hydraulic accumulator.

Claims

1. A device for direct recovery of hydraulic energy in a machine comprising: a single-acting storage cylinder-piston device comprising a storage cylinder, a storage cylinder piston, and a storage cylinder chamber, wherein the storage cylinder includes only one hydraulic connection; a differential cylinder-piston device comprising a differential cylinder with a separated rod side and a base side; a hydraulic accumulator hydraulically connected to the single-acting storage cylinder-piston device and the differential cylinder-piston device, wherein only one valve is positioned in a flow pathway between the single-acting storage cylinder-piston device and the hydraulic accumulator; and an operating pump driven by a drive motor of the machine, where a further valve is positioned between the operating pump and the base side of the differential cylinder; wherein a potential energy of the single-acting storage cylinder-piston device is stored at least partially in the hydraulic accumulator; wherein the single-acting storage cylinder-piston device retracts under a compressive load; and wherein the device for direct recovery of hydraulic energy in the machine further comprises a tank, and wherein flow from the rod side of the differential cylinder is fed back into the tank via the further valve.

2. The device according to claim 1, wherein a ratio of a retracting and extending movement of the single-acting storage cylinder-piston device to the differential cylinder-piston device to each other is predetermined at a forced ratio through their mechanical attachment.

3. The device according to claim 1, wherein the storage cylinder-piston device and the differential cylinder-piston device are arranged to each other for parallel operation.

4. The device according to claim 1, wherein the operating pump is provided to operate at least one of the single-acting storage cylinder-piston device and the differential cylinder-piston device.

5. The device according to claim 1, further comprising a differential cylinder brake valve, wherein the differential cylinder brake valve shuts off the base side of the differential cylinder.

6. The device according to claim 5, wherein the only one valve positioned in the flow pathway between the single-acting storage cylinder-piston device and the hydraulic accumulator is a storage valve, and wherein the storage valve shuts off the hydraulic accumulator.

7. The device according to claim 1, further comprising a storage cylinder brake valve, wherein the storage cylinder brake valve shuts off the storage cylinder chamber of the single-acting storage cylinder-piston device from the tank.

8. The device according to claim 1, wherein a connection valve is provided to connect the base side of the differential cylinder to the storage cylinder chamber of the single-acting storage cylinder-piston device.

9. The machine according to claim 1, wherein the machine is configured such that it is able to operate when the device for direct recovery of hydraulic energy fails.

10. The device according to claim 1, wherein the further valve positioned between the operating pump and the base side of the differential cylinder is a slide valve, and wherein the slide valve controls at least one of the single-acting storage cylinder-piston device and the differential cylinder-piston device.

11. The device according to claim 1, wherein the only one valve positioned in the flow pathway between the single-acting storage cylinder-piston device and the hydraulic accumulator is a storage valve, and wherein the storage valve shuts off the hydraulic accumulator.

12. The device according to claim 1, wherein the rod side of the differential cylinder includes a rod side hydraulic connection and the base side of the differential cylinder includes a base side hydraulic connection.

13. The device according to claim 1, wherein the further valve positioned between the operating pump and the base side of the differential cylinder is the only valve positioned between the operating pump and the base side of the differential cylinder.

14. The device according to claim 1, wherein the single-acting storage cylinder-piston device and the differential cylinder-piston device are arranged for simultaneous retraction and extension in a same direction.

15. The device of claim 1, wherein the single-acting storage cylinder-piston device is directly coupled to a three-way junction.

16. The device of claim 1, wherein a connection valve is positioned between the single-acting storage cylinder-piston device and the further valve.

17. The device of claim 16, wherein a storage cylinder brake valve is positioned between the single-acting storage cylinder-piston device and the further valve.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 depicts an embodiment of a device for the direct recovery of hydraulic energy.

DETAILED DESCRIPTION

(2) When taking the machine in operation, the corresponding preload pressure may be present in the high-pressure accumulator 20. If the storage process is to be started, an external force has to be present on the differential cylinder 7 and on the storage cylinder 1, which leads to a retraction. Differential cylinder 7 and storage cylinder 1 are part of the respective differential cylinder-piston device 700 and the storage cylinder-piston device 100. Where this description refers to cylinders or differential cylinders, those skilled in the art know that, depending on context, this may also mean the corresponding cylinder-piston device.

(3) As the respective pistons retract, pressure builds up at the base side 9 of the differential cylinder 7 and in the cylinder chamber 3 of the storage cylinder 1, which defines the present potential energy. Said potential energy is to be absorbed by the hydraulic accumulator 20. At the start of the lowering process the differential cylinder brake valve 10 of the differential cylinder 7 and the storage valve 19 of the storage cylinder 1 are opened. Through the differential cylinder brake valve 10 of the differential cylinder 7 a portion of the flow passes from the base side 9 of the differential cylinder 7 at a preload pressure, which is determined by the preload valve 12, through the non-return valve 11 to the rod side 8 of the differential cylinder 7. This prevents a lack of oil volume at the rod side 8 of the differential cylinder 7 during the retraction movement. The flow that is not absorbed by the rod side 8 of the differential cylinder 7 from the base side 9 of the differential cylinder 7 reaches the tank 13 via the preload valve 12. The oil volume displaced through the retracting movement of the storage cylinder piston 2 of the storage cylinder 1 from the storage cylinder chamber 3 of the storage cylinder 1 flows through the storage valve 19 into the hydraulic accumulator 20. Due to the volume absorption of the hydraulic accumulator 20 from the storage cylinder chamber 3 of the storage cylinder 1, the pressure in hydraulic accumulator 20 rises. Through proportional control of the differential cylinder brake valve 10 of the differential cylinder 7 and the storage valve 19, the retracting speed of the drive, consisting of differential cylinder 7 and storage cylinder 1, may be adjusted.

(4) If the retracting movement of the differential cylinder 7 and storage cylinder 1 is to be stopped, the differential cylinder brake valve 10 of the differential cylinder 7 and the storage valve 19 will be closed. The hydraulic accumulator 20 now contains the pressurised oil volume, which was displaced during the retracting movement of the storage cylinder 1 by the storage cylinder piston 2 from the storage cylinder chamber 3 of the storage cylinder 1.

(5) For the reutilisation of the hydraulic energy from the hydraulic accumulator 20 in an extension movement of storage cylinder 1 and differential cylinder 7, a connection is established by way of the storage valve 19 between hydraulic accumulator 20 and storage cylinder chamber 3 of storage cylinder 1. The operating pump 14, which is driven via the transfer gearbox 16 by drive motor 15, generates a flow which passes via a corresponding control system of slide valve 17 into the base side 9 of differential cylinder 7. The flow exiting from the rod side 8 of differential cylinder 7 is fed back into the tank 13 via the slide valve 17. Depending upon the hydraulic energy available in hydraulic accumulator 20, only the corresponding difference necessary for the extension of the differential cylinder 7 and the storage cylinder 1 has to be generated by the operating pump 14.

(6) Depending on the size of the hydraulic accumulator 20, storage of the potential energy is possible either from the entire stroke or only part of the stroke of storage cylinder 1.

(7) If the hydraulic accumulator 20 is designed for only part of the stroke of storage cylinder 1, and the retraction movement of storage cylinder 1 is to be greater than the design of the hydraulic accumulator 20 permits, a brake valve circuit is activated. Said circuit comprises a storage cylinder brake valve 18 of storage cylinder 1, which is connected to the storage cylinder chamber 3 of storage cylinder 1. The storage cylinder brake valve 18 may in this instance be designed as a 1-way valve. Through proportional control of the storage cylinder brake valve 18, the flow from the storage cylinder chamber 3 of the storage cylinder 1 is passed through storage cylinder brake valve 18 into tank 13. This allows for the retraction speed to be set. Control of the differential cylinder brake valve 10 of the differential cylinder 7 occurs parallel to the control of storage cylinder brake valve 18 of storage cylinder 1. Said control action also takes place in a desired retraction movement of storage cylinder 1 and differential cylinder 7 with a defective storage facility, wherein the hydraulic accumulator 20 and/or the storage valve 19 may be defective.

(8) Depending on the charge state and design of the hydraulic accumulator 20 it may be necessary to implement an extension movement of the storage cylinder 1 and of the differential cylinder 7 with the aid of the operating pump 14. To achieve this, the storage valve 19 is kept closed and the connection valve 4 is opened. Through a corresponding control action of the slide valve 17 the flow is directed from the operating pump 14 to the base side 9 of the differential cylinder 7 and via the connection valve 4 into the storage cylinder chamber 3 of storage cylinder 1. The flow coming from the rod side 9 of the differential cylinder 7 is directed via the slide valve 17 back into the tank 13. Said control action may also take place in a desired extension movement of storage cylinder 1 and differential cylinder 7 with a defective storage facility, wherein the hydraulic accumulator 20 and/or the storage valve 19 may be defective.

(9) If a retraction movement of the differential cylinder 7 is intended in the machine cycle, in which the flow of the operating pump 14 is to be directed to the rod side 8 of the differential cylinder 7 through a corresponding control action of the slide valve 17, the storage cylinder brake valve 18 of the storage cylinder 1 is kept open. The discharge flow from the storage cylinder chamber 3 of storage cylinder 1 is directed in this manner via storage cylinder brake valve 18 of the storage cylinder 1 into the tank 13. The discharged flow from the base side 9 of the differential cylinder 7 is directed back into tank 13 via the slide valve 17.

(10) The invention comprises at least one differential cylinder 7 or at least one differential cylinder-piston device 700. Further differential cylinders 7 may be integrated into the system at the rod side connection 6 and the base side connection 5 of the differential cylinder 7. The circuit may be provided with at least one operating pump 14 and at least one slide valve 17. The hydraulic accumulator 20 may be chosen from all different kinds of hydraulic accumulators 20 with varying energy storage media such as, for example, nitrogen. Feasible are designs in form of bladder accumulators, piston accumulators, membrane accumulators and/or spring accumulators as well as different combinations of accumulator designs.

(11) The depicted valves may be individual 2/2-way valves or they may be provided as a valve combination in form of a rod assembly. The control of said valves may be proportional or switched.

(12) The invention is characterised by an arrangement of at least one hydraulic differential cylinder and at least one single-acting hydraulic cylinder. The single-acting hydraulic cylinder does not have a rod side chamber that would require refilling in a retracting movement. The ratio of the retraction and extension movement of the cylinders to each other is predetermined by their mechanical attachment in a forced ratio to each other. Said combination of hydraulic cylinders and their mechanical attachment will in the following be called a hydraulic linear drive.

(13) The invention is characterised in that potential energy present during the retracting movement of the hydraulic linear drive under compressive load can be stored to a large degree with the aid of one or more hydraulic accumulator(s).

(14) The invention is further characterised in that at least one single-acting hydraulic cylinder is used inside the hydraulic linear drive for the purpose of energy storage and energy release.

(15) The invention is characterised in that the stored hydraulic energy may be fed directly back into the linear drive without energy conversion.

(16) The invention is further characterised in that the hydraulic linear drive can be retracted and extended without activating the one or more hydraulic accumulator(s) and hydraulic valves for storing the potential energy. This is achieved inside the hydraulic circuit through a corresponding parallel connection of the hydraulic linear drive.

(17) The invention is characterised in that the stored energy from the retraction process of the hydraulic linear drive can be released by the one or more single-acting cylinders during the extension process of the hydraulic linear drive. This is achieved through a corresponding connection of the one or more hydraulic accumulator(s) with corresponding valves.

(18) The invention is further characterised in that the energy storage and release by means of the hydraulic linear drive is possible over the entire travel path or only over part of the possible travel path.

(19) The invention is also characterised in that it can be integrated into the drive train of a machine without influencing the function of the drive train in such a way that the entire functionality of the machine is dependent on the invention. This means that the machine may be operated flawlessly even without the correct functioning of the invention.