WO2008143584A1 - Hydraulic crane and a method for regulating the maximum allowed working pressure in such a crane - Google Patents

Hydraulic crane and a method for regulating the maximum allowed working pressure in such a crane Download PDF

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Publication number
WO2008143584A1
WO2008143584A1 PCT/SE2008/050588 SE2008050588W WO2008143584A1 WO 2008143584 A1 WO2008143584 A1 WO 2008143584A1 SE 2008050588 W SE2008050588 W SE 2008050588W WO 2008143584 A1 WO2008143584 A1 WO 2008143584A1
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WO
WIPO (PCT)
Prior art keywords
crane
crane boom
hydraulic cylinder
boom
hydraulic
Prior art date
Application number
PCT/SE2008/050588
Other languages
French (fr)
Inventor
Lars Rydahl
Per Gustafsson
Lars Andersson
Bengt SÖDERHOLM
Sten SIRÉN
Lennart Andersson
Original Assignee
Cargotec Patenter Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cargotec Patenter Ab filed Critical Cargotec Patenter Ab
Publication of WO2008143584A1 publication Critical patent/WO2008143584A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C23/00—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
    • B66C23/62—Constructional features or details
    • B66C23/82—Luffing gear
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C23/00—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
    • B66C23/88—Safety gear
    • B66C23/90—Devices for indicating or limiting lifting moment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C23/00—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
    • B66C23/88—Safety gear
    • B66C23/90—Devices for indicating or limiting lifting moment
    • B66C23/905—Devices for indicating or limiting lifting moment electrical

Definitions

  • Hydraulic crane and a method for regulating the maximum allowed working pressure in such a crane
  • the present invention relates to a hydraulic crane, preferably in the form of a lorry crane, which comprises at least:
  • the invention also relates to a method for regulating the maximum allowed working pressure in such a hydraulic crane.
  • a hydraulic crane of the above-mentioned type normally has a constant value on the maximum allowed working pressure for said first hydraulic cylinder, which constitutes the so-called lifting cylinder of the crane, and for said second hydraulic cylinder, which constitutes the so-called outer boom cylinder of the crane, whereby the working pressure for the respective cylinder has to be limited to a value that takes into account the position of the crane which, with respect to strength, is the most critical one among the allowed positions for the crane boom system of the crane, which in its turn entails that the true lifting capacity of the crane will be underutilized in the other allowed positions for the crane boom system.
  • the object of the present invention is to provide a new and favourable manner for regulating the maximum allowed working pressure in a hydraulic crane.
  • said object is achieved by means of a hydraulic crane having the features defined in claim 1 and a method having the features defined in claim 8.
  • the hydraulic crane according to the present invention comprises at least: - a liftable and lowerable first crane boom, which is articulately fastened to a column, - a first hydraulic cylinder for lifting and lowering the first crane boom in relation to the column,
  • a second hydraulic cylinder for lifting and lowering the second crane boom in relation to he first crane boom
  • a regulating unit which is adapted to regulate the maximum allowed working pressure for the first hydraulic cylinder, i.e. the maximum allowed hydrau ic pressure or differential pressure in the first hydraulic cylinder , in dependence on values of variables defining the prevailing position of the crane booms of the crane, these variables comprising at least a variable representing the swing-out angle of the fi st crane boom and a variable repre- senting the swing-out ang e of the second crane boom.
  • the prevailing load on the crane depends on the prevailing posi- tion of the crane booms of the crane and the weight of the load carried in the load suspension point.
  • the crane may in all positions of the crane boom system formed by the crane booms be utilized optimally with re- spect to the strength of the steel structure of the crane boom system and possibly the stability of the frame of the crane.
  • Fig 1 a lateral view of a hydraulic crane provided with a bucket
  • Fig 2 an outline diagram of the crane according to Fig 1 ,
  • Fig 3 a lateral view of a hydraulic crane provided with a jib
  • Fig 4 an outline diagram of the crane according to Fig 3,
  • Fig 5 a schematic perspective view of a manoeuvring unit with a number of manoeuvring members for controlling different crane functions
  • Fig 6 a schematic illustration of an embodiment of the invention.
  • liftable and lowerable crane boom refers to a crane boom which can be turned in a vertical plane so as to thereby perform liftings and lowerings of a load carried by the crane.
  • hydraulic cylinder for lifting and lowering the crane boom here refers to the hydraulic cylinder which is associated with the liftable and lowerable crane boom and which carries out the turning thereof in a vertical plane.
  • Fig 1 shows a hydraulic crane 1 mounted on a frame 2, which for instance can be connected to a lorry chassis.
  • the frame is provided with adjustable support legs 3 for supporting the crane 1 .
  • the crane 1 comprises:
  • the hydraulic cylinder 6 comprises a cylinder part 6a, which is articulately fastened to the column 4, and a piston, which is received in this cylinder part and dis- placeable in relation to it, the piston being provided with a piston rod 6b which is articulated fastened to the first crane boom 5.
  • the hydraulic cylinder 8 comprises a cylinder part 8a, which is articulately fastened to the first crane boom 5, and a piston, which is received in this cylinder part and displaceable in rela- tion to it, the piston being provided with a piston rod 8b which is articulately fastened to the second crane boom 7.
  • the second crane boom 7 comprises two crane boom sections 7a, 7b which are mutually displaceable in the longitudinal direction of the second crane boom for adjustment of the extension length L of this second crane boom.
  • the second crane boom could also comprise three or more crane boom sections which are mutually displaceable in the longitudinal direction of the second crane boom for adjustment of the extension length of the second crane boom.
  • the crane boom sections 7a, 7b are displaceable in relation to each other by means of a hydraulic cylinder 9 carried by the second crane boom 7, which hydraulic cylinder in the illustrated example comprises a cylinder part 9a, which is fastened to the first crane boom section 7a, and a piston, which is received in this cylinder part and displaceable in relation to it, the piston being provided with a piston rod 9b which is fastened to the second crane boom section 7b.
  • a rotator 10 is articulately fastened to the outer end of the second crane boom, which rotator in its turn carries a hydraulic grab tool in the form of a bucket 1 1 .
  • the crane 1 is equipped for performing excavations.
  • the rotator 10 and the bucket 1 1 can be removed and replaced by a lifting hook.
  • the rotator 10 may possibly be retained, in which case the bucket 1 1 is re- placed by a lifting hook.
  • the rotator 10 and the bucket 1 1 can be replaced by a liftable and lowerable third crane boom 12 in the form of a so-called jib, as illustrated in Fig 3.
  • the third crane boom 12 is articulately fastened to the second crane boom 7 in such a manner that it is turnable in relation to the second crane boom about an essentially horizontal axis of rotation A4.
  • a hy- draulic cylinder 13 is arranged for lifting and lowering the third crane boom 12 in relation to the second crane boom 7.
  • the hydraulic cylinder 13 comprises a cylinder part 13a, which is articulately fastened to the third crane boom 12, and a piston, which is received in this cylinder part and displaceable in relation to it, the piston being provided with a piston rod 13b which is articulately fastened to the second crane boom 7.
  • the third crane boom 12 comprises two crane boom sections 12a, 12b which are mutually displaceable in the longitudinal direction of the third crane boom for adjustment of the extension length Lj of the third crane boom.
  • the third crane boom could also comprise three or more crane boom sections, which are mutually displaceable in the longitudinal direction of the third crane boom for adjustment of the extension length of the third crane boom.
  • the crane boom sections 12a, 12b are displaceable in relation to each other by means of a hy- draulic cylinder 14 carried by the third crane boom 12, which hydraulic cylinder in the illustrated example comprises a cylinder part 14a, which is fastened to the first crane boom part 12a, and a piston, which is received in this cylinder part and displaceable in relation to it, the piston being provided with a piston rod which is fastened to the second crane boom part 12b.
  • the control system for controlling the different crane functions i.e. lifting/lowering by means of the hydraulic cylinder 6, tilting by means of the hydraulic cylinder 8, extension/retraction by means of the hydraulic cylinder 9 etc, comprises a pump 20, which pumps hydraulic fluid from a reservoir 21 to a directional- control-valve block 22.
  • the directional-control-valve block 22 comprises a directional-control-valve section 23 for each of the hydraulic cylinders 6, 8 and 9 of the crane boom system, to which hydraulic cylinders hydraulic fluid is supplied in a conventional manner in dependence on the setting position of the slide member in the respective directional-control-valve section 23.
  • the setting position of the slide members in the directional-control-valve sections 23 is controlled either via a number of manoeuvring members, for instance in the form of manoeuvring levers, each of which being connected to its own slide member, or by remote control via a manoeuvring unit 25 (see Fig 5) comprising a manoeuvring member S1 -S6 for each slide member.
  • control signals are transmitted via cable or a wireless connection from the manoeuvring unit 25 to an electronic control unit, for instance in the form of a microprocessor, which in its turn controls the setting position of the slide members in the valve sections 23 of the directional-control- valve block 22 in dependence on the magnitude of the respective control signal from the manoeuvring unit 25.
  • an electronic control unit for instance in the form of a microprocessor, which in its turn controls the setting position of the slide members in the valve sections 23 of the directional-control- valve block 22 in dependence on the magnitude of the respective control signal from the manoeuvring unit 25.
  • Each individual directional-control-valve section 23 consequently controls the magnitude and the direction of the flow of hydraulic fluid to a specific hydraulic cylinder and thereby controls a specific crane function.
  • Fig 3 For the sake of clarity, only the directional-control-valve section 23 for the hydraulic cylinder 6 is illustrated in Fig 3.
  • the directional-control-valve block 22 further comprises a shunt valve 26, which pumps excessive hydraulic fluid back to the res- ervoir 21 , and an electrically controlled dump valve 27, which can be made to return the entire hydraulic flow from the pump 20 directly back to the reservoir 21.
  • the directional-control-valve block 22 is of load-sensing and pressure-compensating type, which implies that the magnitude of the hydraulic flow supplied to a hydraulic cylinder is always proportional to the position of the slide member in the corresponding directional-control-valve section 23, i.e. proportional to the setting position of the manoeuvring lever 24.
  • the directional-control-valve section 23 comprises a pressure limiter 28, a pressure compensator 29 and a directional-control-valve 30.
  • Directional-control-valve blocks and directional-control-valve sections of this type are known and available on the market. Also other types of valve devices then the one here described may of course be used in a crane according to the present invention.
  • a load holding valve 31 is arranged between the respective hydraulic cylinder and the associated directional-control-valve section 23, which load holding valve makes sure that the load will remain hanging when the hydraulic system runs out of pressure when the dump valve 27 is made to return the entire hydraulic flow from the pump 20 directly back to the reservoir 21.
  • the crane 1 further comprises an electronic regulating unit 40, for instance in the form of a microprocessor, which is adapted to regulate the maximum allowed working pressure for the hydraulic cylinder 6 in dependence on values of variables defining the prevailing position of the crane booms of the crane.
  • an electronic regulating unit 40 for instance in the form of a microprocessor, which is adapted to regulate the maximum allowed working pressure for the hydraulic cylinder 6 in dependence on values of variables defining the prevailing position of the crane booms of the crane.
  • said variables comprise:
  • the regulating unit 40 is suitably also adapted to establish the maximum allowed working pressure for the hydraulic cylinder 8 in dependence on the values of these variables ⁇ , ⁇ , L, ⁇ .
  • the swing-out angle ⁇ , the swing-out angle ⁇ , the extension length L and the slewing angle ⁇ together define, in an unambiguous manner, the exact position of the crane boom system and the load suspension point P of the crane according to Figs 1 and 2, and these variables will consequently provide complete information about the prevailing position of the crane boom system and the crane booms 5, 7 included therein.
  • the swing-out angle ⁇ of the first crane boom 5 is established by means of a sensor 41 which continuously senses the position of the piston rod 6b in relation to the cylinder part 6a of the hydraulic cylinder 6, whereas the swing-out angle ⁇ of the second crane boom 7 is established by means of a sensor 42 which continuously senses the position of the piston rod 8b in relation to the cylinder part 8a of the hydraulic cylinder 8.
  • the swing-out angle ⁇ is a function of the extension position of the piston rod 6b
  • the swing-out angle ⁇ is a function of the extension position of the piston rod 8b.
  • these swing-out angles ⁇ , ⁇ could be established by means of suitable angle sensors, which directly sense the respective swing-out angle.
  • the extension length L of the second crane boom 7 can for instance be established by means of a sensor 43 which continuously senses the position of the piston rod 9b in relation to the cylinder part 9a of the hydraulic cylinder 9.
  • the extension length L could be established by means of a measuring device comprising an ultrasonic transmitter and an ultrasonic receiver of the type described in US 5 877 693 A or by means of any other suitable measuring device.
  • the slewing angle ⁇ of the column 4 is established by means of a not shown sensor which continuously senses the slewing position of the column.
  • the regulating unit 40 is connected to said sensors in order to receive measuring signals from these sensors related to the swing-out angle ⁇ , the swing-out angle ⁇ , the extension length L and the slewing angle ⁇ .
  • said variables comprise: - a variable ⁇ representing the swing-out angle of the first crane boom 5,
  • variable ⁇ representing the swing-out angle of the second crane boom 7
  • variable L representing the extension length of the second crane boom 7
  • the regulating unit 40 is suitably also adapted to establish the maximum allowed working pressure for the hydraulic cylinder 8 and the maximum allowed working pressure for the hydraulic cylinder 13 in dependence on the values of these variables ⁇ , ⁇ , L, y, Lj, ⁇ .
  • the swing-out angle ⁇ , the swing-out angle ⁇ , the extension length L, the swing-out angle y, the extension length Lj and the slewing angle ⁇ together define, in an unambiguous manner, the exact position of the crane system and the load suspension point P of the crane according to Figs 3 and 4, and these variables will consequently provide complete information about the prevailing position of the crane boom system and the crane booms 5, 7, 12 included therein.
  • the swing-out angle ⁇ of the first crane boom 5, the swing-out angle ⁇ and the extension length L of the second crane boom 7 and the slewing angle ⁇ of the column are established by means of sensors in the above-mentioned manner.
  • the swing-out angle Y of the third crane boom 12 is established by means of a sensor (not shown) which is connected to the regulating unit and which continuously senses the position of the piston rod 13b in relation to the cylinder part 13a of the hydraulic cylinder 13.
  • the swing-out angle ⁇ is a function of the extension length of the piston rod 13b.
  • this swing-out angle Y could be established by means of an angle sensor which directly senses this swing-out angle.
  • the extension length Lj of the third crane boom 12 can for instance be established by means of a sensor (not shown) which is connected to the regulating unit and which continuously senses the position of the piston rod in relation to the cylinder part 14a of the hydraulic cylinder 14.
  • the extension length Lj could be established by means of a measuring device comprising an ultrasonic transmitter and an ultrasonic receiver of the type described in US 5 877 693 A or by means of any other suitable measuring device.
  • the swing-out angle ⁇ of the first crane boom 5 is defined as the angle between the longitudinal axis of the first crane boom and the horizontal plane
  • - the swing-out angle ⁇ of the second crane boom 7 is defined as the angle between the longitudinal axis of the second crane boom and the longitudinal axis of the first crane boom
  • - the swing-out angle y of the third crane boom 12 is defined as the angle between the longitudinal axis of the third crane boom and the longitudinal axis of the second crane boom.
  • the regulating unit 40 can be adapted to establish the maximum allowed working pressure for the respective hydraulic cylinder without taking the slewing angle ⁇ of the column into account.
  • the regulating unit 40 is suitably adapted to establish the maximum allowed working pressure for the respective hydraulic cylinder 6, 8, 13 by means of a suitable calculation model, which can be stored as an algorithm in a memory of the regulating unit.
  • the crane further comprises pressure sensors 32, which are arranged to measure the hydraulic pressure on the piston side of the hydraulic cylinders 6, 8 and 13. For the sake of clarity, only the pressure sensor 32 for the hydraulic cylinder 6 is illustrated in Fig 6.
  • the regulating unit 40 is connected to the pressure sensors 32 in order to receive measuring signals from these sensors related to said hydraulic pressures.
  • the regulating unit 40 continuously reads the output signals from the pressure sensors 32 and compares the output signal from the respective pressure sensor with the established value of the maximum allowed working pressure for the hydraulic cylinder associated with the pressure sensor 32. If the pressure sensed by any of the pressure sensors 32 exceeds the estab- lished maximum allowed working pressure for the associated hydraulic cylinder, the regulating unit 40 delivers a signal to the dump valve 27, which dumps the hydraulic flow directly to the reservoir 21 , which results in that the hydraulic system runs out of pressure and that the load is held by means of the load hold- ing valve 31. In this situation, the control system is adapted to allow only moment reducing crane movements.
  • the regulating unit 40 is adapted to let the maximum allowed working pressure for a hy- draulic cylinder 6, 8, 13 represent the maximum allowed hydraulic pressure on the piston side of the hydraulic cylinder.
  • the regulating unit 40 could alternatively be adapted to let the maximum allowed working pressure for a hydraulic cylinder 6, 8, 13 represent the maximum allowed differential pressure in the hydraulic cylinder.
  • This differential pressure is defined as the hydraulic pressure on the piston side of the hydraulic cylinder minus the hydraulic pressure on its piston rod side divided by the cylinder ratio.
  • the regulating unit 40 is also arranged to receive measuring signals from pres- sure sensors 33 which measure the hydraulic pressure on the piston rod side of the hydraulic cylinders 6, 8, 13 so as to thereby be able to establish the prevailing differential pressure of the respective hydraulic cylinder and compare this differential pressure with the established value of the maximum allowed working pressure for the hydraulic cylinder in question.
  • control system of the crane may for instance have another design than the control system which is illustrated in Fig 6 and described above.
  • the crane boom system of the crane could have another design than the crane boom systems which are illustrated in Figs 1 -4 and described above.
  • the first crane boom 5 could for instance comprise two or more crane boom sections which are mutually displaceable in the longitudinal direction of the first crane boom for adjustment of the extension length of the first crane boom, in which case the regulating unit 40 could be adapted to take also this extension length into account in the regulation of the maximum allowed working pressure for the first hydraulic cylinder 6, the second hydraulic cylinder 8 and the third hydraulic cylinder 13.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Jib Cranes (AREA)

Abstract

The invention relates to a hydraulic crane (1 ) comprising at least: - a liftable and lowerable first crane boom (5), which is articulately fastened to a column (4), - a first hydraulic cylinder (6) for lifting and lowering the first crane boom in relation to the column, - a liftable and lowerable second crane boom (7), which is articulately fastened to the first crane boom, and - a second hydraulic cylinder (8) for lifting and lowering the second crane boom in relation to the first crane boom, - a regulating unit (40), which is adapted to regulate the maximum allowed working pressure for the first hydraulic cylinder in dependence on values of variables defining the prevailing position of the crane booms of the crane, these variables comprising at least a variable (α) representing the swing-out angle of the first crane boom and a variable (β) representing the swing-out angle of the second crane boom. The invention also relates to a method for regulating the maximum allowed working pressure in a hydraulic crane.

Description

Hydraulic crane and a method for regulating the maximum allowed working pressure in such a crane
FIELD OF THE INVENTION AND PRIOR ART
The present invention relates to a hydraulic crane, preferably in the form of a lorry crane, which comprises at least:
- a liftable and lowerable first crane boom which is articulately fastened to a column,
- a first hydraulic cylinder for lifting and lowering the first crane boom in relation to the column,
- a liftable and lowerable second crane boom, which is articulately fastened to the first crane boom, and
- a second hydraulic cylinder for lifting and lowering the second crane boom in relation to the first crane boom. The invention also relates to a method for regulating the maximum allowed working pressure in such a hydraulic crane.
At the present time, a hydraulic crane of the above-mentioned type normally has a constant value on the maximum allowed working pressure for said first hydraulic cylinder, which constitutes the so-called lifting cylinder of the crane, and for said second hydraulic cylinder, which constitutes the so-called outer boom cylinder of the crane, whereby the working pressure for the respective cylinder has to be limited to a value that takes into account the position of the crane which, with respect to strength, is the most critical one among the allowed positions for the crane boom system of the crane, which in its turn entails that the true lifting capacity of the crane will be underutilized in the other allowed positions for the crane boom system. OBJECT OF THE INVENTION
The object of the present invention is to provide a new and favourable manner for regulating the maximum allowed working pressure in a hydraulic crane.
SUMMARY OF THE INVENTION
According to the present invention, said object is achieved by means of a hydraulic crane having the features defined in claim 1 and a method having the features defined in claim 8.
The hydraulic crane according to the present invention comprises at least: - a liftable and lowerable first crane boom, which is articulately fastened to a column, - a first hydraulic cylinder for lifting and lowering the first crane boom in relation to the column,
- a liftable and lowerable second crane boom, which is articu- lately fastened to the first crane boom,
- a second hydraulic cylinder for lifting and lowering the second crane boom in relation to he first crane boom, and - a regulating unit, which is adapted to regulate the maximum allowed working pressure for the first hydraulic cylinder, i.e. the maximum allowed hydrau ic pressure or differential pressure in the first hydraulic cylinder , in dependence on values of variables defining the prevailing position of the crane booms of the crane, these variables comprising at least a variable representing the swing-out angle of the fi st crane boom and a variable repre- senting the swing-out ang e of the second crane boom.
The prevailing load on the crane depends on the prevailing posi- tion of the crane booms of the crane and the weight of the load carried in the load suspension point. By allowing the maximum allowed working pressure to vary in dependence on values of variables defining the prevailing position of the crane booms, it will be possible to optimize the lifting capacity of the crane with good accuracy while maintaining a proper safety against overloading of the crane. With the aid of the solution according to the invention, the crane may in all positions of the crane boom system formed by the crane booms be utilized optimally with re- spect to the strength of the steel structure of the crane boom system and possibly the stability of the frame of the crane.
Preferred embodiments of the invention will appear from the dependent claims and the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will in the following be more closely described by means of embodiment examples, with reference to the appended drawings. It is shown in:
Fig 1 a lateral view of a hydraulic crane provided with a bucket,
Fig 2 an outline diagram of the crane according to Fig 1 ,
Fig 3 a lateral view of a hydraulic crane provided with a jib,
Fig 4 an outline diagram of the crane according to Fig 3,
Fig 5 a schematic perspective view of a manoeuvring unit with a number of manoeuvring members for controlling different crane functions, and
Fig 6 a schematic illustration of an embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In this description and the following claims, the expression "liftable and lowerable crane boom" refers to a crane boom which can be turned in a vertical plane so as to thereby perform liftings and lowerings of a load carried by the crane. The expression "hydraulic cylinder for lifting and lowering the crane boom" here refers to the hydraulic cylinder which is associated with the liftable and lowerable crane boom and which carries out the turning thereof in a vertical plane.
Fig 1 shows a hydraulic crane 1 mounted on a frame 2, which for instance can be connected to a lorry chassis. The frame is provided with adjustable support legs 3 for supporting the crane 1 .
The crane 1 comprises:
- a column 4, which is rotatable in relation to the frame 2 about an essentially vertical axis of rotation A1 by means of a not shown rotating device;
- a liftable and lowerable first crane boom 5, which is articulately fastened to the column 4 in such a manner that it is turnable in relation to the column about an essentially horizontal axis of rotation A2; - a hydraulic cylinder 6 for lifting and lowering the first crane boom 5 in relation to the column 4;
- a liftable and lowerable second crane boom 7, which is articulately fastened to the first crane boom 5 in such a manner that it is turnable in relation to the first crane boom about an essen- tially horizontal axis of rotation A3, and
- a hydraulic cylinder 8 for lifting and lowering the second crane boom 7 in relation to the first crane boom 5.
In the illustrated example, the hydraulic cylinder 6 comprises a cylinder part 6a, which is articulately fastened to the column 4, and a piston, which is received in this cylinder part and dis- placeable in relation to it, the piston being provided with a piston rod 6b which is articulated fastened to the first crane boom 5. The hydraulic cylinder 8 comprises a cylinder part 8a, which is articulately fastened to the first crane boom 5, and a piston, which is received in this cylinder part and displaceable in rela- tion to it, the piston being provided with a piston rod 8b which is articulately fastened to the second crane boom 7.
In the example illustrated in Figs 1 and 2, the second crane boom 7 comprises two crane boom sections 7a, 7b which are mutually displaceable in the longitudinal direction of the second crane boom for adjustment of the extension length L of this second crane boom. In a crane of the type here in question, the second crane boom could also comprise three or more crane boom sections which are mutually displaceable in the longitudinal direction of the second crane boom for adjustment of the extension length of the second crane boom. The crane boom sections 7a, 7b are displaceable in relation to each other by means of a hydraulic cylinder 9 carried by the second crane boom 7, which hydraulic cylinder in the illustrated example comprises a cylinder part 9a, which is fastened to the first crane boom section 7a, and a piston, which is received in this cylinder part and displaceable in relation to it, the piston being provided with a piston rod 9b which is fastened to the second crane boom section 7b.
In the example illustrated in Fig 1 , a rotator 10 is articulately fastened to the outer end of the second crane boom, which rotator in its turn carries a hydraulic grab tool in the form of a bucket 1 1 . In the example shown in Fig 1 , the crane 1 is equipped for performing excavations. When the crane 1 is to be used for proper lifting operations, the rotator 10 and the bucket 1 1 can be removed and replaced by a lifting hook. The rotator 10 may possibly be retained, in which case the bucket 1 1 is re- placed by a lifting hook. In order to perform lifting operations requiring a great range, the rotator 10 and the bucket 1 1 can be replaced by a liftable and lowerable third crane boom 12 in the form of a so-called jib, as illustrated in Fig 3. The third crane boom 12 is articulately fastened to the second crane boom 7 in such a manner that it is turnable in relation to the second crane boom about an essentially horizontal axis of rotation A4. A hy- draulic cylinder 13 is arranged for lifting and lowering the third crane boom 12 in relation to the second crane boom 7. In the illustrated example, the hydraulic cylinder 13 comprises a cylinder part 13a, which is articulately fastened to the third crane boom 12, and a piston, which is received in this cylinder part and displaceable in relation to it, the piston being provided with a piston rod 13b which is articulately fastened to the second crane boom 7.
In the example illustrated in Figs 3 and 4, the third crane boom 12 comprises two crane boom sections 12a, 12b which are mutually displaceable in the longitudinal direction of the third crane boom for adjustment of the extension length Lj of the third crane boom. In a crane of the type here in question, the third crane boom could also comprise three or more crane boom sections, which are mutually displaceable in the longitudinal direction of the third crane boom for adjustment of the extension length of the third crane boom. The crane boom sections 12a, 12b are displaceable in relation to each other by means of a hy- draulic cylinder 14 carried by the third crane boom 12, which hydraulic cylinder in the illustrated example comprises a cylinder part 14a, which is fastened to the first crane boom part 12a, and a piston, which is received in this cylinder part and displaceable in relation to it, the piston being provided with a piston rod which is fastened to the second crane boom part 12b.
The control system for controlling the different crane functions, i.e. lifting/lowering by means of the hydraulic cylinder 6, tilting by means of the hydraulic cylinder 8, extension/retraction by means of the hydraulic cylinder 9 etc, comprises a pump 20, which pumps hydraulic fluid from a reservoir 21 to a directional- control-valve block 22. The directional-control-valve block 22 comprises a directional-control-valve section 23 for each of the hydraulic cylinders 6, 8 and 9 of the crane boom system, to which hydraulic cylinders hydraulic fluid is supplied in a conventional manner in dependence on the setting position of the slide member in the respective directional-control-valve section 23. The setting position of the slide members in the directional-control-valve sections 23 is controlled either via a number of manoeuvring members, for instance in the form of manoeuvring levers, each of which being connected to its own slide member, or by remote control via a manoeuvring unit 25 (see Fig 5) comprising a manoeuvring member S1 -S6 for each slide member. In the case of remote control, the control signals are transmitted via cable or a wireless connection from the manoeuvring unit 25 to an electronic control unit, for instance in the form of a microprocessor, which in its turn controls the setting position of the slide members in the valve sections 23 of the directional-control- valve block 22 in dependence on the magnitude of the respective control signal from the manoeuvring unit 25.
Each individual directional-control-valve section 23 consequently controls the magnitude and the direction of the flow of hydraulic fluid to a specific hydraulic cylinder and thereby controls a specific crane function. For the sake of clarity, only the directional-control-valve section 23 for the hydraulic cylinder 6 is illustrated in Fig 3.
The directional-control-valve block 22 further comprises a shunt valve 26, which pumps excessive hydraulic fluid back to the res- ervoir 21 , and an electrically controlled dump valve 27, which can be made to return the entire hydraulic flow from the pump 20 directly back to the reservoir 21.
In the shown embodiment example, the directional-control-valve block 22 is of load-sensing and pressure-compensating type, which implies that the magnitude of the hydraulic flow supplied to a hydraulic cylinder is always proportional to the position of the slide member in the corresponding directional-control-valve section 23, i.e. proportional to the setting position of the manoeuvring lever 24. The directional-control-valve section 23 comprises a pressure limiter 28, a pressure compensator 29 and a directional-control-valve 30. Directional-control-valve blocks and directional-control-valve sections of this type are known and available on the market. Also other types of valve devices then the one here described may of course be used in a crane according to the present invention.
A load holding valve 31 is arranged between the respective hydraulic cylinder and the associated directional-control-valve section 23, which load holding valve makes sure that the load will remain hanging when the hydraulic system runs out of pressure when the dump valve 27 is made to return the entire hydraulic flow from the pump 20 directly back to the reservoir 21.
The crane 1 further comprises an electronic regulating unit 40, for instance in the form of a microprocessor, which is adapted to regulate the maximum allowed working pressure for the hydraulic cylinder 6 in dependence on values of variables defining the prevailing position of the crane booms of the crane.
In a crane 1 with the configuration illustrated in Figs 1 and 2, said variables comprise:
- a variable α representing the swing-out angle of the first crane boom 5,
- a variable β representing the swing-out angle of the second crane boom 7,
- a variable L representing the extension length of the second crane boom 7, and
- a variable θ representing the slewing angle of the column 4.
In this case, the regulating unit 40 is suitably also adapted to establish the maximum allowed working pressure for the hydraulic cylinder 8 in dependence on the values of these variables α, β, L, θ.
The swing-out angle α, the swing-out angle β, the extension length L and the slewing angle θ together define, in an unambiguous manner, the exact position of the crane boom system and the load suspension point P of the crane according to Figs 1 and 2, and these variables will consequently provide complete information about the prevailing position of the crane boom system and the crane booms 5, 7 included therein.
In the example illustrated in Fig 6, the swing-out angle α of the first crane boom 5 is established by means of a sensor 41 which continuously senses the position of the piston rod 6b in relation to the cylinder part 6a of the hydraulic cylinder 6, whereas the swing-out angle β of the second crane boom 7 is established by means of a sensor 42 which continuously senses the position of the piston rod 8b in relation to the cylinder part 8a of the hydraulic cylinder 8. The swing-out angle α is a function of the extension position of the piston rod 6b, and the swing-out angle β is a function of the extension position of the piston rod 8b. Alternatively, these swing-out angles α, β could be established by means of suitable angle sensors, which directly sense the respective swing-out angle. The extension length L of the second crane boom 7 can for instance be established by means of a sensor 43 which continuously senses the position of the piston rod 9b in relation to the cylinder part 9a of the hydraulic cylinder 9. Alternatively, the extension length L could be established by means of a measuring device comprising an ultrasonic transmitter and an ultrasonic receiver of the type described in US 5 877 693 A or by means of any other suitable measuring device. The slewing angle θ of the column 4 is established by means of a not shown sensor which continuously senses the slewing position of the column. The regulating unit 40 is connected to said sensors in order to receive measuring signals from these sensors related to the swing-out angle α, the swing-out angle β, the extension length L and the slewing angle θ.
In a crane 1 of the configuration illustrated in Figs 3 and 4, said variables comprise: - a variable α representing the swing-out angle of the first crane boom 5,
- a variable β representing the swing-out angle of the second crane boom 7, - a variable L representing the extension length of the second crane boom 7,
- a variable y representing the swing-out angle of the third crane boom 12,
- a variable Lj representing the extension length of the third crane boom 12, and
- a variable θ representing the slewing angle of the column 4.
In this case, the regulating unit 40 is suitably also adapted to establish the maximum allowed working pressure for the hydraulic cylinder 8 and the maximum allowed working pressure for the hydraulic cylinder 13 in dependence on the values of these variables α, β, L, y, Lj, θ.
The swing-out angle α, the swing-out angle β, the extension length L, the swing-out angle y, the extension length Lj and the slewing angle θ together define, in an unambiguous manner, the exact position of the crane system and the load suspension point P of the crane according to Figs 3 and 4, and these variables will consequently provide complete information about the prevailing position of the crane boom system and the crane booms 5, 7, 12 included therein.
In a crane 1 with the configuration illustrated in Figs 3 and 4, the swing-out angle α of the first crane boom 5, the swing-out angle β and the extension length L of the second crane boom 7 and the slewing angle θ of the column are established by means of sensors in the above-mentioned manner. The swing-out angle Y of the third crane boom 12 is established by means of a sensor (not shown) which is connected to the regulating unit and which continuously senses the position of the piston rod 13b in relation to the cylinder part 13a of the hydraulic cylinder 13. The swing-out angle γ is a function of the extension length of the piston rod 13b. Alternatively, this swing-out angle Y could be established by means of an angle sensor which directly senses this swing-out angle. The extension length Lj of the third crane boom 12 can for instance be established by means of a sensor (not shown) which is connected to the regulating unit and which continuously senses the position of the piston rod in relation to the cylinder part 14a of the hydraulic cylinder 14. Alternatively, the extension length Lj could be established by means of a measuring device comprising an ultrasonic transmitter and an ultrasonic receiver of the type described in US 5 877 693 A or by means of any other suitable measuring device.
In the example illustrated in Figs 2 and 4:
- the swing-out angle α of the first crane boom 5 is defined as the angle between the longitudinal axis of the first crane boom and the horizontal plane,
- the swing-out angle β of the second crane boom 7 is defined as the angle between the longitudinal axis of the second crane boom and the longitudinal axis of the first crane boom, and - the swing-out angle y of the third crane boom 12 is defined as the angle between the longitudinal axis of the third crane boom and the longitudinal axis of the second crane boom.
In the case when the crane 1 is mounted in such a manner that it has the same stability in all slewing position of the column 4, the regulating unit 40 can be adapted to establish the maximum allowed working pressure for the respective hydraulic cylinder without taking the slewing angle θ of the column into account.
The regulating unit 40 is suitably adapted to establish the maximum allowed working pressure for the respective hydraulic cylinder 6, 8, 13 by means of a suitable calculation model, which can be stored as an algorithm in a memory of the regulating unit. The crane further comprises pressure sensors 32, which are arranged to measure the hydraulic pressure on the piston side of the hydraulic cylinders 6, 8 and 13. For the sake of clarity, only the pressure sensor 32 for the hydraulic cylinder 6 is illustrated in Fig 6. The regulating unit 40 is connected to the pressure sensors 32 in order to receive measuring signals from these sensors related to said hydraulic pressures.
The regulating unit 40 continuously reads the output signals from the pressure sensors 32 and compares the output signal from the respective pressure sensor with the established value of the maximum allowed working pressure for the hydraulic cylinder associated with the pressure sensor 32. If the pressure sensed by any of the pressure sensors 32 exceeds the estab- lished maximum allowed working pressure for the associated hydraulic cylinder, the regulating unit 40 delivers a signal to the dump valve 27, which dumps the hydraulic flow directly to the reservoir 21 , which results in that the hydraulic system runs out of pressure and that the load is held by means of the load hold- ing valve 31. In this situation, the control system is adapted to allow only moment reducing crane movements.
In the example described above, the regulating unit 40 is adapted to let the maximum allowed working pressure for a hy- draulic cylinder 6, 8, 13 represent the maximum allowed hydraulic pressure on the piston side of the hydraulic cylinder. However, the regulating unit 40 could alternatively be adapted to let the maximum allowed working pressure for a hydraulic cylinder 6, 8, 13 represent the maximum allowed differential pressure in the hydraulic cylinder. This differential pressure is defined as the hydraulic pressure on the piston side of the hydraulic cylinder minus the hydraulic pressure on its piston rod side divided by the cylinder ratio. In the last-mentioned case, the regulating unit 40 is also arranged to receive measuring signals from pres- sure sensors 33 which measure the hydraulic pressure on the piston rod side of the hydraulic cylinders 6, 8, 13 so as to thereby be able to establish the prevailing differential pressure of the respective hydraulic cylinder and compare this differential pressure with the established value of the maximum allowed working pressure for the hydraulic cylinder in question. The ex- pression "working pressure" as used in this description and the following claims, consequently refers either to the hydraulic pressure on the piston side of a hydraulic cylinder or the differential pressure in a hydraulic cylinder.
The invention is of course not in any way limited to the embodiments described above. On the contrary, several possibilities to modifications thereof should be apparent to a person skilled in the art without thereby deviating from the basic idea of the invention as defined in the appended claims. The control system of the crane may for instance have another design than the control system which is illustrated in Fig 6 and described above. Furthermore, the crane boom system of the crane could have another design than the crane boom systems which are illustrated in Figs 1 -4 and described above. The first crane boom 5 could for instance comprise two or more crane boom sections which are mutually displaceable in the longitudinal direction of the first crane boom for adjustment of the extension length of the first crane boom, in which case the regulating unit 40 could be adapted to take also this extension length into account in the regulation of the maximum allowed working pressure for the first hydraulic cylinder 6, the second hydraulic cylinder 8 and the third hydraulic cylinder 13.

Claims

1. A hydraulic crane comprising at least: - a liftable and lowerable first crane boom (5), which is articulately fastened to a column (4),
- a first hydraulic cylinder (6) for lifting and lowering the first crane boom (5) in relation to the column (4),
- a liftable and lowerable second crane boom (7), which is ar- ticulately fastened to the first crane boom (5), and
- a second hydraulic cylinder (8) for lifting and lowering the second crane boom (7) in relation to the first crane boom (5), characterized in that the crane (1 ) comprises a regulating unit (40), which is adapted to regulate the maximum allowed working pressure for the first hydraulic cylinder (6) in dependence on values of variables defining the prevailing position of the crane booms of the crane, these variables comprising at least a variable (α) representing the swing-out angle of the first crane boom (5) and a variable (β) representing the swing-out angle of the second crane boom (7).
2. A hydraulic crane according to claim 1 , characterized in:
- that the second crane boom (7) comprises two or more crane boom sections (7a, 7b) which are mutually displaceable in the longitudinal direction of the second crane boom for adjustment of the extension length of the second crane boom, and
- that said variables also comprises a variable (L) representing the extension length of the second crane boom (7).
3. A hydraulic crane according to claim 1 or 2, characterized in
- that the column (4) is rotatable about an essentially vertical axis, and
- that said variables also comprises a variable (θ) representing the slewing angle of the column (4).
4. A hydraulic crane according to any of claims 1-3, characterized in
- that the crane (1 ) comprises a liftable and lowerable third crane boom (12), which is articulately fastened to the second crane boom (7), and a third hydraulic cylinder (13) for lifting and lowering the third crane boom (12) in relation to the second crane boom (7), and
- that said variables also comprises a variable (Y) representing the swing-out angle of the third crane boom (12).
5. A hydraulic crane according to claim 4, characterized in
- that the third crane boom (12) comprises two or more crane boom sections (12a, 12b) which are mutually displaceable in the longitudinal direction of the third crane boom for adjustment of the extension length of the third crane boom, and
- that said variables also comprises a variable (Lj) representing the extension length of the third crane boom (12).
6. A hydraulic crane according to claim 4 or 5, characterized in that the regulating unit (40) also is adapted to regulate the maximum allowed working pressure for the third hydraulic cylinder (13) in dependence on said variables.
7. A hydraulic crane according to any of claims 1 -6, charac- terized in that the regulating unit (40) also is adapted to regulate the maximum allowed working pressure for the second hydraulic cylinder (8) in dependence on the values of said variables.
8. A method for regulating the maximum allowed working pressure of a hydraulic crane (1 ) which comprises at least:
- a liftable and lowerable first crane boom (5), which is articulately fastened to a column (4),
- a first hydraulic cylinder (6) for lifting and lowering the first crane boom (5) in relation to the column (4), - a liftable and lowerable second crane boom (7), which is articulately fastened to the first crane boom (5), and
- a second hydraulic cylinder (8) for lifting and lowering the second crane boom (7) in relation to the first crane boom (5), characterized in that the maximum allowed working pressure for the first hydraulic cylinder (6) is regulated in dependence on values of variables defining the prevailing position of the crane booms of the crane, these variables comprising at least a variable (α) representing the swing-out angle of the first crane boom (5) and a variable (β) representing the swing-out angle of the second crane boom (7).
9. A method according to claim 8, the second crane boom (7) comprising two or more crane boom sections (7a, 7b) which are mutually displaceable in the longitudinal direction of the second crane boom for adjustment of the extension length of the second crane boom, characterized in that also a variable (L) representing the extension length of the second crane boom (7) is taken into account in the regulation of the maximum allowed working pressure for the first hydraulic cylinder (6).
10. A method according to claim 8 or 9, the column (4) being rotatable about an essentially vertical axis, characterized in that also a variable (θ) representing the slewing angle of the column (4) is taken into account in the regulation of the maximum allowed working pressure for the first hydraulic cylinder (6).
1 1. A method according to any of claims 8-10, the crane (1 ) comprising a liftable and lowerable third crane boom (12), which is articulately fastened to the second crane boom (7), and a third hydraulic cylinder (13) for lifting and lowering the third crane boom (12) in relation to the second crane boom (7), characterized in that also a variable (y) representing the swing- out angle of the third crane boom (12) is taken into account in the regulation of the maximum allowed working pressure for the first hydraulic cylinder (6).
12. A method according to claim 1 1 , the third crane boom (12) comprising two or more crane boom sections (12a, 12b) which are mutually displaceable in the longitudinal direction of the third crane boom for adjustment of the extension length of the third crane boom, characterized in that also a variable (Lj) representing the extension length of the third crane boom (12) is taken into account in the regulation of the maximum allowed working pressure for the first hydraulic cylinder (6).
13. A method according to claim 1 1 or 12, characterized in that also the maximum allowed working pressure for the third hy- draulic cylinder (13) is regulated in dependence on the values of said variables.
14. A method according to any of claims 8-13, characterized in that also the maximum allowed working pressure for the second hydraulic cylinder (8) is regulated in dependence on the values of said variables.
PCT/SE2008/050588 2007-05-23 2008-05-20 Hydraulic crane and a method for regulating the maximum allowed working pressure in such a crane WO2008143584A1 (en)

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EP3415460A1 (en) * 2017-06-15 2018-12-19 Cargotec Patenter AB Load handling crane with high seat and portable manoeuvring unit
US10494234B2 (en) 2015-06-24 2019-12-03 Palfinger Ag Crane controller

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CN103170963A (en) * 2013-03-20 2013-06-26 辽宁威跃集团机械制造有限公司 Two-arm manipulator
US10494234B2 (en) 2015-06-24 2019-12-03 Palfinger Ag Crane controller
EP3313771B1 (en) 2015-06-24 2021-12-08 Palfinger AG Crane controller
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EP3239092A1 (en) * 2016-04-25 2017-11-01 Cargotec Patenter AB Hydraulic crane
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EP3549899A1 (en) * 2016-04-25 2019-10-09 Cargotec Patenter AB Hydraulic crane
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EP3415460A1 (en) * 2017-06-15 2018-12-19 Cargotec Patenter AB Load handling crane with high seat and portable manoeuvring unit
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