Load lifting / lowering system with energy recovery circuit

Abstract

The invention is a system for lifting / lowering a load, comprising a lifting device (30, 300, 300'), a feed pump (10), a distributor (11), a hydraulic lifting line (21, 211, 213) through which pressurized oil is conveyed from said pump (10) to said lifting device (30, 300, 300') via said distributor (11) to lift a load, a hydraulic lowering line (22) through which the oil is conveyed from said motor of the winch (30) to said distributor (11) and then to a tank, an overcenter control valve (40) positioned on said hydraulic lifting line (21, 211, 213), and an energy recovery circuit (50).

Description

[0001] TITLE

[0002] LOAD LIFTING / LOWERING SYSTEM WITH ENERGY RECOVERY CIRCUIT DESCRIPTION

[0003] The present patent concerns load lifting / lowering systems, and more specifically it concerns a new load lifting / lowering system equipped with a hydraulic energy recovery circuit.

[0004] Mechanical equipment involving the lifting and lowering of a load is known, such as the known drilling machines, in which a load slides along a mast with alternating motion by means of a powered hydraulic winch.

[0005] The lowering motion, in particular, cannot be obtained using gravity alone, for obvious safety reasons, but is controlled by means of systems intended to control the lowering movement of the load, in our case we consider the following hydraulic system, which comprises said winch, at least one brake and at least one control valve, known as overcenter or counterbalance valve.

[0006] More specifically, a pump is used to supply pressurized oil to the motor in order to lift the load. The increase in oil pressure causes the winch brake to open through a selector valve or an electronic system, wherein a pressure transducer senses the pressure increase in the hydraulic lifting line of the winch and activates a solenoid valve, thus providing pressure to release the brake. At this point the load is lifted and the oil flowing out of the motor returns to the tank.

[0007] In the case where, due to a malfunction in the pump or the hydraulic circuit, the lifing pressure should suddenly drop, the overcenter valve blocks the outflow of oil, keeping the winch motor full of oil. In this way, the load is prevented from falling and simultaneously, before the oil trapped between the overcenter valve and the motor is drained into the tank, the brake is closed and the load secured.

[0008] During the lowering of the load, the pump supplies pressurized oil to the winch motor. The winch brake opens due to the pressure detected by the selector valve or by the electronic system, as described above with reference to the lifting movement, and the load can be lowered. The lowering movement is controlled by the overcenter control valve which, if it detects sufficient pressure in the hydraulic lowering line, opens and allows the oil to flow into the tank and thus the load to be lowered in a controlled manner. Therefore, it is always necessary to use a certain amount of energy not only to lift the load, but also to lower it.

[0009] In addition, during the lowering of the load, since the overcenter valve controls the hydraulic motor of the winch, a pressure that is a function of the weight is generated in the line connecting these two components; once having passed through the overcenter valve, the oil flow pressure takes on the value of the discharge pressure, thus wasting energy.

[0010] Figure 1 shows an example diagram of a hydraulic lifting / lowering system of the known type, in which an overcenter control valve is installed.

[0011] The subject of the present patent is a new system for lifting / lowering a load with an integrated energy recovery circuit.

[0012] The main object of the present invention is to recover part of the energy produced by the control system during the load lowering operation.

[0013] In particular, the recovered energy can be used to power a generator or the motor of a lifting / lowering winch, or to help save energy in any other equipment.

[0014] According to the invention, said energy recovery takes place thanks to the presence of the known safety systems used in load lifting / lowering systems equipped with overcenter valves which are not sensitive to back pressure and can continue to operate with the same effectiveness and efficiency.

[0015] The system can be applied essentially in the same way independently of whether the load is lifted / lowered by means of a powered winch or by means of a cylinder or other element. The characteristics of the new system are better clarified in the following description, making reference to the drawings, which are attached by way of nonlimiting example.

[0016] Figures 2 to 6 show examples of embodiment of the new system, in which, according to a preferred solution, the lifting / lowering device is a powered winch (30).

[0017] Figure 2 shows a diagram illustrating the operation of the new load lifting / lowering system equipped with an energy recovery circuit according to a first embodiment, in which the recovered energy is used to operate an electric generator unit.

[0018] Figure 3 shows a diagram of the new system, in which, instead, the recovered energy is used to re-power the motor of the lifting / lowering device.

[0019] Figure 3 a shows a diagram of the new system, in which electronic pressure control devices are used, as better described and claimed below.

[0020] Figures 7 and 8 show the same diagram as the one shown in Figure 3a, in which the winch (30) is replaced by a hydraulic cylinder (300, 300').

[0021] Figure 4 shows a diagram of the system, in a solution similar to the one shown in Figure 3, in which the energy recovery circuit is made with a block, that is, an integrated circuit, where there are no valves connected to one another by means of tubes, but the connections are made by drilling a metal block, thus obtaining a circuit made up of cartridges joined together by means of holes, based on the layout to be carried out.

[0022] Figure 4a shows a diagram of the system, in a solution similar to the one shown in Figure 3a, in which the energy recovery circuit is carried out as a block.

[0023] Figure 5 shows a diagram of the system according to an alternative solution, in which the pressurized oil is drawn upstream of the overcenter control valve and the recovered energy is used to power the motor of the lifting / lowering device. This lowers the safety level of the system, because the overcenter valve is excluded and another / other component / s is / are responsible for the safety of the system.

[0024] Finally, Figure 6 shows a diagram of the system according to a further alternative solution, in which the pressurized oil is drawn upstream of the overcenter control valve and the recovered energy is used to power an electric generator unit. This lowers the safety level of the system, because the overcenter valve is excluded and another / other component / s is / are responsible for the safety of the system.

[0025] With reference to Figure 1, a known hydraulic system for lifting / lowering loads comprises, for example, a powered winch (30), a delivery pump (10), a distributor (11), a hydraulic lifting line (21) through which pressurized oil is conveyed from the pump (10) to the winch motor (30) via the distributor (11) to cause a load to be lifted, a hydraulic lowering line (22) through which pressurized oil is conveyed from the winch motor (30) to the distributor (11) and then to the tank to cause the load to be lowered, a selector valve (23) that is positioned between the two lifting and lowering lines (21, 22), connected to the brake (31) of the winch (30) and designed to open the brake (31) based on the oil pressure, an overcenter control valve (40) positioned on said hydraulic lifting line (21).

[0026] During the load lifting operation, the oil, pumped into the hydraulic lifting line (21), flows through the one-way valve of the control valve (40) and reaches the motor of the winch (30). The selector valve (23) detects the pressure in the hydraulic lifting line (21) and opens the brake (31), thus allowing the winch to lift the load. The control valve (40) prevents the uncontrolled return of the oil from the hydraulic lifting line (21) in case of malfunction or breakage.

[0027] During the load lowering operation, instead, the oil is pumped into the hydraulic lowering line (22) and reaches the motor of the winch (30). The selector valve (23) detects the pressure in the hydraulic lowering line (22) and opens the brake (31), thus allowing the winch to lower the load. The oil flows out of the motor and through the control valve (40) which, via the pilot circuit (41), senses the pressure in the hydraulic lowering line (22) together with the pressure at the exit of the motor of the winch (30). The delivery pressure + the pressure generated by the load + the piloting ratio of the overcenter valve activate the latter, allowing the oil to flow from the hydraulic lifting line (21) towards the distributor (11) and the tank, and thus the load to be lowered in a controlled manner.

[0028] The control valve is usually set to a pressure equal to the pressure generated by the maximum permissible load for lifting, increased, for example, by 30%.

[0029] In the event of any pressure change, for example and particularly in the event of malfunctions or breakages, the control valve (40) closes, preventing the oil from flowing out and thus the load from being lowered. For maximum safety, also the brake closes when it senses any pressure drop.

[0030] With reference to Figure 2, the new system differs from the known systems in that it is also equipped with an energy recovery circuit (50) comprising

[0031] - said overcenter control valve (40) insensitive to back pressure, which controls the lowering movement of the load;

[0032] - a valve suited to make the oil available for energy recovery, which may for example be a sequence valve (53) and which hereinafter is referred to as sequence valve (53) for the sake of simplicity; said sequence valve (53) is mounted on said hydraulic lifting line (21) and serves to limit the oil flow while the load is being lowered, essentially acting as an element that interrupts the oil flow or throttle, so that the oil in the first section (211) of said hydraulic lifting line (21) included between said sequence valve (53) and said control valve (40) has a certain pressure and can be used to activate one or more devices (60) connected to a first pipe (51) which in turn is connected to said first section (211) through a second valve (52);

[0033] - said second valve (52) on said first pipe (51); when said second valve (52) is working, it activates the energy recovery system by connecting said first section (211) to said first pipe (51) and allowing the oil to reach the devices (60); - precisely sized openings (55) which serve to set said sequence valve (53) to a pressure lower than or equal to the pressure generated in a second section (213) of the hydraulic lifting line (21) or at a point included between said motor of the winch (30) and said control valve (40). Said second section (213) may actually be absent, if the control valve (40) is directly flange-mounted on the motor.

[0034] Said precisely sized openings (55) are connected to said sequence valve (53) through a second pipe (54) and, upstream of said control valve (40), through a third pipe (212), thus obtaining a hydraulic pilot circuit.

[0035] As shown in the example of Figure 2, said second valve (52), when working, activates the energy recovery system by connecting said first section (211) of the hydraulic lifting line (21) to said first pipe (51).

[0036] In this way, the oil is drawn from the winch (30) through said first section (211) of the hydraulic lifting line (21) and then conveyed to a device (60) through said first pipe (51). As shown in the example of Figure 2, said device (60) can be an electric generator unit or, as shown in Figure 3, it can be the motor of the winch (30) itself, via a regenerative pipe (51').

[0037] With reference to Figure 2, during the load lifting operation, thanks to the electric energy stored in an accumulator it is also possible to use the electric motor (61) of the generator unit (60), which acted as a generator during the energy recovery cycle. More specifically, said electric motor (61), through the hydraulic motor (62) coupled with it, which for this purpose becomes a pump, conveys the oil to the motor of the winch (30) through said first drawing pipe (51) and said first section (211) of said hydraulic lifting line (21), by means of the control valve (40). It is thus possible to facilitate the load lifting operation, while part of the oil is still supplied by said pump (10).

[0038] The control valve (40) used in the new system, which is the subject of the present patent is an overcenter valve insensitive to back pressure The diagram in Figure 3 shows how the recovery circuit (501) is fed with the oil coming from said first section (211) of the hydraulic lifting line (21), during the lowering of the load, and conveys it to the motor of the winch (30) through said regenerative pipe (51 ’) and the related valve (52’), and through a flow control valve (56) and a one-way valve (80).

[0039] This makes it possible to interrupt the oil supply from the distributor (11) almost completely and to use it only to compensate for the drained oil.

[0040] To reduce the load lowering speed, it is possible to reduce the flow rate of the oil being supplied to the motor of the winch (30) by means of said flow control valve (56) connected to the tank through a dedicated line (57).

[0041] The diagram in Figure 3 a shows how electronic controls can be used instead of the hydraulic pilot circuit (54) and the precisely sized openings (55) (shown in Figure 2), which are replaced by a valve suited to set said sequence valve (53), which can be, for example, an electro-proportional valve or an electro-proportional pressure relief valve (85), or another suitable device controlled by a suitable electronic system.

[0042] In greater detail, the energy recovery circuit (502) comprises the following pressure transducers: at least one first transducer (581) upstream of said control valve (40), on said second section (213) or point of the hydraulic lifting line (21), at least one second transducer (582) at the first section (211) of the hydraulic lifting line (21), at least one third transducer (583) on the hydraulic lowering line (22) at the spill of the selector valve (23), at least one fourth transducer (584) on the brake line (31) of the winch (30).

[0043] Based on the measured pressure values, said sequence valve (53) is controlled by means of said electro-proportional pressure relief valve (85), in such a way as to maintain the upstream pressure, measured by said second transducer (582), lower than or equal to the pressure generated by the load being handled by the winch, measured by said first transducer (581).

[0044] The same system can also be applied if other lifting devices are used instead of the powered winch (30), for example hydraulic cylinders (300, 300'), as schematically shown in Figures 7 and 8. According to the diagram shown in Figure 5 and Figure 6, the pressurized oil to be conveyed to the recovery circuit (503, 504) can be taken directly from said second section (213) or point of the hydraulic lifting line (213) upstream of the control valve (40) and conveyed to the motor of the winch (30) or to a device such as said generator unit (60). This lowers the safety level of the system, because the overcenter valve is excluded and another / other component / s is / are responsible for the safety of the system.

[0045] In this configuration, the part of the system comprising the sequence valve (53), the precisely sized openings (55) and said second and third pipes (54, 212) or the electronic controls is not needed. The load lifting / lowering system as described above can be usefully installed in an earth drilling machine.

[0046] Therefore, with reference to the above description and the attached drawings, the following claims are made.

Claims

CLAIMS1. System for lifting / lowering a load, comprising a lifting device (30, 300, 300‘), a feed pump (10), a distributor (11), a hydraulic lifting line (21, 211, 213) through which pressurized oil is conveyed from said pump (10) to said lifting device (30, 300, 300’) via said distributor (11) to lift a load, a hydraulic lowering line (22) through which the oil is conveyed from said motor of the winch (30) to said distributor (11) and then to a tank, an overcenter control valve (40) positioned on said hydraulic lifting line (21, 211, 213), characterized in that it also comprises an energy recovery circuit (50) comprising: said overcenter control valve (40) of the type insensitive to back pressure; a valve (53) mounted on said hydraulic lifting line (21), defining a first section (211) of said hydraulic lifting line (21) included between said valve (53) and said control valve (40); a first pipe (5L, 51’) connecting said first section (211) of the hydraulic lifting line (21) to one or more devices (60, 30, 300, 300'); means for setting said valve (53) in such a way that the latter remains closed when the oil pressure in said first section (211) is lower than or equal to the oil pressure in a second section (213) or point of said hydraulic lifting line (21) included between said control valve (40) and said lifting device (30, 300, 300').

2. Lifting system according to claim 1, characterized in that it comprises a second valve (52, 52’) mounted on said first pipe (51, 51’).

3. Lifting system according to claim 1 or 2, characterized in that said means for setting said valve (53) comprise precisely sized openings (55) connected to said valve (53) through a second pipe (54) and to said second section (213) or point of the hydraulic lifting line (21) through a third pipe (212), thus obtaining the hydraulic pilot circuit.

4. Lifting system according to claim 1 or 2, characterized in that said means for setting said valve (53) comprise at least the following pressure transducers: at least one first transducer (581) on said second section (213) or point of the hydraulic lifting line (21), at least one second transducer (582) on said first section (211) of the hydraulic lifting line (21), at least one third transducer (583) on said hydraulic lowering line (22), at the drawing pipe of a selector valve (23) between said hydraulic lifting line (21) and said hydraulic lowering (22) line, at least one fourth transducer (584) on the brake line (31) of said winch (30), and wherein said sequence valve (53) is controlled through an electronic system by means of a setting valve, for example an electro-proportional pressure relief valve (85), based on the pressure values measured by said transducers, in such a way as to maintain the upstream pressure, measured by said second transducer (582), lower than or equal to the pressure generated by the load being handled by the lifting device (30, 300, 300’), measured by said first transducer (581).

5. Lifting system according to one of the claims from 1 to 4, characterized in that said device (60) is an electric generator unit (61) which during the load lifting operation becomes a motor and which also comprises a hydraulic motor (62) which is coupled with it and becomes a pump to convey the oil to said lifting device (30, 300, 300') through said first pipe (51) and said second valve (52), to said first section (211) of said hydraulic lifing line (21) through said control valve (40) and through said second section (213) or point of said hydraulic lifting line (21) to facilitate the load lifting operation.

6. Lifting system according to one of the claims from 1 to 4, characterized in that said device is said lifting device (30, 300, 300‘) and wherein, during the load lowering operation, the oil in said hydraulic lifting line (213, 211) is conveyed tosaid lifting device (30, 300, 300’) through said first pipe, or regenerative pipe (51 ‘), with the related second valve (52’), and through a one-way valve (80) with flow control valve (56).

7. Lifting system according to any of the preceding claims, characterized in that said lifting device is a powered winch (30).

8. Lifting system according to any of the preceding claims, characterized in that said lifting device is a hydraulic cylinder (300, 300’).

9. Drilling machine characterized in that it comprises a lifting system according to one or more of the preceding claims.

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