NO320025B1 - Device at an excavator - Google Patents

Description

The present invention relates to the use of a combined cylinder for hydraulics and gas, for operating an excavator's lifting boom.

Today's excavators usually use a diesel engine to operate the machine and to drive hydraulic pressure cylinders on the excavator. When loading, the excavator's boom is often eased twice a minute in normal use. This means that a lot of fuel is used in the various work cycles. For a large excavator, for example of 40 tonnes, with an engine of 300-400 hp, it goes without saying that the fuel consumption will be high during a working day, and not least during a year. By using the present invention, one will not only save large amounts, due to reduced fuel consumption, but emissions of harmful gases will consequently also be reduced considerably. So that by using the invention both an economic and an environmental benefit is achieved.

US Patent No. 4,393,607 and No. 6,663,089 describe a combi cylinder for use in vehicles. US Patent No. 5,016,911 describes an embodiment of a combi cylinder.

The purpose of the present invention is to produce a system that makes the excavator's lifting boom, i.e. the digging aggregate, as weightless as possible. To achieve this, a combi cylinder with a gas lift function can be fitted in connection with the excavator's lifting boom. Advantages of this are, among other things, that energy (fuel) is saved. When lifting, as mentioned, the boom is eased approx. 2 times a minute. The bigger the machine, the bigger the boom to be lifted, and the more diesel can be saved.

This purpose is solved by the present invention, as defined in claim 1, in which the combi cylinder comprises an active part to drive the lifting boom and a passive part to produce a counter force corresponding to the weight of the lifting boom, and in that one or more of the cylinders for lifting and lowering the lifting boom consists of a combined cylinder for hydraulics and gas, where the gas part of the combined cylinder is designed to produce a counterforce that is roughly equivalent to the lifting boom's downward force vector.

Preferred applications of the invention are characterized by the independent claims 2-6.

The invention will now be described in more detail with the help of the attached drawings, in which: Figure 1 shows an excavator comprising a combi cylinder according to the present invention. Figure 2 shows a section of an embodiment of a combi cylinder, according to the invention. Figure 3 shows a section of another embodiment of a combi cylinder, according to the invention. Figure 4 shows a section of another further embodiment of a combi cylinder, according to the invention. Figure 5 shows a section of another further embodiment of a combi cylinder, according to the invention. Figure 1 shows an excavator 10 according to the invention, comprising a lower part 12 with a driving mechanism, such as caterpillar feet or wheels, and an upper part 14. The upper part 14 may comprise an engine and optionally also a cab 16.

In this description, the terms vertical and horizontal are used. By this is meant a normal plane which is respectively vertical and horizontal in relation to the excavator, and does not depend on the position of the excavator itself in the terrain.

A lifting boom is connected to the upper part 14 which comprises a lifting arm 18 which is vertically pivotable connected to the upper part 14, optionally the lifting arm can also be pivotable about a vertical axis. The lifting arm is hinged to an intermediate arm, such as a digging arm 20, where the lifting arm and the digging arm work together to lift and move a drawer 22, or other equipment, to the desired position by means of mounted cylinders, such as, for example, a first cylinder 24, a second cylinder 26 and a third cylinder 28.

The pressure cylinders 26 and 28 are mounted in a manner well known to a person skilled in the art, and will therefore not be discussed further. One or more cylinders 24 in the form of a combi cylinder can be mounted between an outer point on the lifting arm 18 and a central area on the upper part 14, where this area can be centered around the upper part's middle part or center of gravity. Preferably, one or more combi cylinders 24 should be mounted in a conventional manner, i.e. between an inner point on the lifting arm and a front point on the upper part (as shown in Figure 1). A combi cylinder 24 can be used on one or both sides of the lifting boom or a combi cylinder 24 that is centrally located in the lifting boom can be used.

To lift and move the lifting boom, i.e. the lifting arm, the digging arm and the bucket, the combi cylinders 24 are used as mentioned. The purpose of the combi cylinder 24 is to make the lifting boom, i.e. the lifting arm and digging arm, as "weightless" as possible. Fuel consumption is reduced because the cylinders, which are normally hydraulically driven, do not have to lift the weight of the boom. When lifting, the boom is lightened in normal use by approx. 2 times a minute. So that the bigger the machine, the bigger the lifting boom has to be lifted, and the more fuel can be saved.

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The combination cylinder 24 essentially consists of a cylinder comprising a number of working chambers for both hydraulics and gas, and must function as a counterweight to the lifting boom.

The system also gives the machine extra strong boom lifting, as the machine's forces are not used to lift the boom itself.

In what follows, various examples of a combi cylinder 24 will be described.

An embodiment of a combi cylinder 24 is shown in figure 2. This embodiment comprises three working chambers 1, 2 and 3, for gas and hydraulics respectively. The combination cylinder 24 comprises an outer cylinder 150 and an inner cylinder 140, where a piston rod 14 4 with a piston 142 is arranged in the inner cylinder 140. Working chamber 3 is made up mainly of the interior of the inner cylinder 140, but also of an area adjacent to a first end 130 of the combi cylinder, which is produced now that the inner cylinder 140 is moved out of the outer cylinder 150. Working chamber 1 is arranged for the supply of gas under pressure and will thus contribute to the lifting of the lifting boom. The gas can be supplied/evacuated via one or more channels 132 in the first end 130 from/to an accumulator (not shown) arranged adjacent to the combi cylinder 24, or the accumulator can be arranged centrally on the excavator for supply to all the combi cylinders, if more than one.

Working chambers 2 and 3 are arranged to be controlled by hydraulic oil, for lifting and lowering the lifting boom. Preferably, working chamber 2 is used for lifting the lifting boom, and the chamber is supplied/evacuated with hydraulic oil via one or more channels 134 adjacent to the other end of the combi cylinder. Working chamber 3 is preferably used to lower the lifting boom, and supply/evacuation of hydraulic oil can be carried out via one or more channels 136.

Figure 3 shows a section of a combi cylinder according to the invention. The cylinder, or cylinders, can be mounted as described above. The combination cylinder comprises a first cylinder 40, in which a movable piston 42 which is fixedly arranged to a piston rod 44 can be moved vertically in the cylinder 40. The piston defines two working chambers 1 and 2 in the first cylinder 40. In the lower part of the cylinder 40 is an inlet /outlet opening to regulate the supply/evacuation of pressure medium in working chamber 2.

For the supply/evacuation of pressure medium to the first working chamber 1, in the upper part of the first cylinder 40, the piston rod 44 comprises a longitudinal, internal channel, which extends from an outer end of the piston rod 44, adjacent to a fastening means such as a " eye", to an inner end of the piston rod. The combination cylinder includes, as the drawings show, an "eye" at each opposite end, for attachment to machinery.

It should be noted that designations such as "upper" and "lower" only refer to the combi cylinder as shown in the drawing and not to the actual position of use. Furthermore, the terms "upper" and "lower", when it comes to the definition of working chambers, refer to the part of the cylinder that is above the piston, respectively below the piston, and/or any delimiting edge parts, as shown in the drawings. For example, the piston may be driven at the bottom of the first cylinder so that working chamber 1 comprises the main part of the cylinder, yet the term "upper" in the cylinder refers to the part of the chamber that is above the piston.

The upper, outer part of the first cylinder 40 can function as a piston 62 in the second cylinder 50. Figure 3 shows a combi cylinder with four working chambers, here alternatively the upper, outer end of the first cylinder 40 can comprise a protruding, circular edge portion 52 which is similarly arranged to connect the inner surface of the second cylinder 50 in a sealing manner. Common seals in the form of gaskets such as piston rings, for example o-rings, or other sealing rings which are suitable for use in piston/cylinder constructions can be used as seals in the combi cylinder. The sealing means can be arranged around the piston 42, around the upper end of the first cylinder and possibly also in or near the lower end of the second cylinder. The piston rod 44 is movable in the first cylinder 40, so that sealing means can also be arranged in a bore in the upper end of the first cylinder, through which the piston rod is movable.

Figure 3 shows a principle sketch for a combined cylinder with four working chambers that combines hydraulic oil and gas. Hydraulic oil can be supplied/evacuated to working chamber 2 via the longitudinal inner channel 60, or the cavity, in the piston rod 44. Hydraulic oil is supplied/evacuated to working chamber 3 via the outlet/inlet opening 47 at the lower part of the first cylinder 40. Working chamber 1 can be filled with gas under pressure, where the gas can be in communication with an expansion tank, or accumulator, via opening 48. The cylinder is thus controlled in the usual way with hydraulic oil in working chambers 2 and 3, while the gas supplied to working chamber 1 contributes to the cylinder is given an additional expansion force, i.e. that a "free" lift is produced by means of the combi cylinder without, for example, the excavator's engine power being affected. Working chamber 4 can in this case be controlled with hydraulic oil.

The combi cylinder (shown in Figure 3) can take up several working positions starting from the supply/evacuation of hydraulics and gas; an extended position where working chambers 2 and 4 are mainly evacuated of pressure medium, an intermediate position where pressure is applied in all chambers and an almost compressed position where working chambers 1 and 3 are mainly evacuated of pressure medium.

Other working positions that the combi cylinder can take from the supply/evacuation of hydraulics and gas oil; is that oil is supplied to working chamber 4 so that gas is forced out from working chamber 1. This means that the extra expansion force is no longer present, and the combi cylinder can be used as an ordinary cylinder, where piston rod 44 becomes the visible piston rod.

The combination cylinder can also be used as a pure gas cylinder. Working chambers 1 and 3 can then, for example, be filled with gas, while chamber 2 is controlled with hydraulic oil to remove gas from chamber 3 and, correspondingly, chamber 4 can be filled with hydraulic oil to remove gas in chamber 1. Alternatively, all the working chambers can be filled with gas.

Figure 4 shows an alternative design of a combi cylinder, where a cylinder with four working chambers is shown, with a combined cylinder for hydraulics and gas. In this embodiment, the inner first cylinder 40 at its upper end, adjacent to a piston 62, is equipped with one or more continuous openings 64 towards working chamber 4. Chambers 2 and 4 can be controlled with hydraulic oil, while working chambers 1 and 3 are controlled with gas , possibly hydraulics and/or gas respectively.

The combination cylinder shown in figure 4 will normally be constructed with more gaskets than the arrangements shown in figures 2-3. The purpose of the opening 64, or openings, is that due to working chamber 4 and the flow between chambers 2 and 4, a larger pressure surface is produced, whereby a larger downward pressure is achieved. The advantage of this is that the necessary force is achieved when the excavator's boom is pushed down to lift the undercarriage or the machine. There is thus no need for a channel in the piston rod 44 for supplying hydraulic oil/pressure medium to working chamber 2.

Figure 5 shows another alternative embodiment which comprises three working chambers. In this embodiment, working chamber 4 is omitted, as well as the circular projecting edge portion of the inner cylinder and the circular inward projecting edge portion at the lower part of the second cylinder. Working chamber 3 will normally be controlled with hydraulic oil via the opening 48, and working chamber 2 will normally be controlled with hydraulic oil via the channel 60 in the piston rod 44, while working chamber 1 may contain gas under pressure. Working chamber 1 is controlled by filling/evacuating gas via the opening 46. Such a cylinder construction is simple and can be constructed with a few extra gaskets. It will normally have a relatively small force impact directed downwards and will therefore be best suited for equipment where such a downward force is not necessary, such as a wheel loader or the like.

Claims (5)

1. Application of a combined cylinder (24) for hydraulics and gas, for operating an excavator's (10) lifting boom, in which the combined cylinder comprises an active part to drive the lifting boom and a passive part to produce a counter force corresponding to the weight of the lifting boom, in that the combi cylinder (24) comprises one or more working chambers (2,3) for receiving/evacuating hydraulic oil for said operation of the lifting boom, and at least one gas-filled working chamber (1) to produce said counterforce. 2. Application in accordance with claim 1, in which said at least one working chamber (1) for gas is connected to an accumulator or an expansion tank for receiving/evacuating gas. 3. Application in accordance with claim 2, in which the combi cylinder (24) comprises three working chambers, with two working chambers (2,3) for receiving/evacuating hydraulic oil, and a working chamber (1) for receiving/evacuating gas. 4. Application in accordance with claim 2, in which the combi cylinder (24) comprises four working chambers, with one or more working chambers (2,3) for receiving/evacuating hydraulic oil, and one or more working chambers (1,3) for receiving/evacuating gas. 5. Application in accordance with one or more of the preceding claims, in which one or more combi cylinders (24) are arranged between a front part of an upper part (14) of the excavator and an inner part of the lifting arm (18).