The invention relates to excavators and to machines for material transfer comprising an element movable via at least one hydraulic cylinder.
With excavators and machines for material transfer such as excavators, wheel-mounted loaders and similar plant, a boom and/or a shaft are moved e.g. via two parallel hydraulic cylinder pairs. In the case of an excavator, an attachment tool is then attached to the shaft and the good to be loaded is transferred with it. Both the boom and the shaft and the attachment tools naturally have masses. This means that only a small part of the energy used for the lifting work benefits the lifting of the load. The much greater part must be used for the lifting of the equipment and of the attachment tool.
A detail of an excavator and of machines for material transfer in accordance with the prior art is shown by way of example in
Some first efforts have already been made to recover the energy expended in the lifting work of the equipment and of the attachment tool in an energy recovering system. For this purpose, it was attempted, for example in DE 102 56 442 A1 and DE 103 15 071 A1, to feed hydraulically stored energy into the main hydraulic circuit. However, this is only successful with limitations since the infeed pressure must always be larger than the system pressure in the main circuit.
It is therefore the object of the present invention to provide an excavator or a machine for material transfer in accordance with the element movable via at least one hydraulic cylinder in which a large part of the energy expended for the lifting of the equipment and attachment tool can, where possible, be stored for successive work cycles.
This object is solved in accordance with the invention in that, in addition to the at least one hydraulic cylinder present for the movement of the movable elements, one or more additional hydraulic cylinders are hinged to the element to be moved, with the additional cylinder(s) being connected to one or more hydraulic accumulators of their own. These additional hydraulic cylinders can be arranged parallel to the already present at least one hydraulic cylinder, but can also be attached at a different position. In accordance with the invention, the additional hydraulic cylinders do not engage in the hydraulic system, but are connected on the piston side with a hydraulic accumulator which can consist of a piston accumulator or a bladder accumulator.
Advantageous aspects of the present invention result from the description herein.
The element to be moved can accordingly be a boom or a shaft of the excavator or of the machine for material transfer.
The additional hydraulic cylinder(s) can be arranged between two hydraulic cylinders which serve to move the element, i.e. the boom or the shaft.
In accordance with the invention, the accumulator is loaded on the downward movement of the equipment. The stored energy then in turn supports the upward movement of the equipment. The equipment weight can hereby be compensated at least partly. The same work is carried out via the, for example, three cylinders now present instead of the two previously present as was previously carried out by the two hydraulic cylinders connected in the hydraulic circuit.
In accordance with a particularly advantageous embodiment of the invention, the additional hydraulic cylinder(s) can be connectable to the main hydraulic circuit of the excavator or machine for material transfer via a switchable valve. For example, for the case that the storage system breaks down, the third cylinder can thus be switched into the main hydraulic circuit via a valve so that the machine is not down and can carry out its work without a problem.
Furthermore, with a multi-element equipment and on the provision of more than one additional hydraulic cylinder, the number of additional hydraulic cylinders can advantageously be connected among one another. For example, on the downward movement of the boom, the additional hydraulic cylinder of the shaft can thus be fed such that the shaft is supported on extension and vice versa.
The solution of the initially presented object in accordance with the invention results in a series of advantages: The previously used main hydraulic cylinders can thus be dimensioned smaller. Less energy from the diesel engine is necessary overall for the lifting. Higher working speeds are possible. The engine can theoretically have less power or, if it has a higher power, it can work in the part load range. Less energy has to be removed via the radiator overall. The machine efficiency can be considerably increased. The fuel consumption can thus be lowered. This in turn results in a lowering of operating costs.
Moreover, the bearing strains of the hydraulic cylinders can also be distributed onto six bearing positions instead of the usual four. Due to the provision of accumulator(s) of its/their own for the additional hydraulic cylinder(s), an active feeding into the main hydraulic circuit is not necessary. No complex hydraulic connections are thereby necessary.
The processes of feeding energy into the additional hydraulic cylinder(s) are possible at any pressure level. No consideration has to be made of the pressure level of the main hydraulic circuit here. Finally, system redundancy is given by switching the additional hydraulic cylinder(s) over to the main hydraulic circuit.
Further features, details and advantages of the invention result from the embodiments shown in the drawing. There are shown:
A detail of a hydraulic excavator is shown with reference to
As can be seen from the hydraulic circuit in accordance with
In the hydraulic circuit diagram in accordance with
Number | Date | Country | Kind |
---|---|---|---|
10 2004 032 868 | Jul 2004 | DE | national |
Number | Name | Date | Kind |
---|---|---|---|
6918247 | Warner | Jul 2005 | B1 |
20020001516 | Cook et al. | Jan 2002 | A1 |
Number | Date | Country |
---|---|---|
10315071 | Nov 2003 | DE |
10256442 | Dec 2003 | DE |
2238811 | Feb 1975 | FR |
60-250128 | Dec 1985 | JP |
3-036333 | Feb 1991 | JP |
4-120324 | Apr 1992 | JP |
5-163745 | Jun 1993 | JP |
09-310379 | Dec 1997 | JP |
2004-116675 | Apr 2004 | JP |
2004-116676 | Apr 2004 | JP |
2004-125094 | Apr 2004 | JP |
9311363 | Jun 1993 | WO |
9833989 | Aug 1998 | WO |
Number | Date | Country | |
---|---|---|---|
20060053666 A1 | Mar 2006 | US |