US3841605A - Moving apparatus for a load - Google Patents

Moving apparatus for a load Download PDF

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Publication number
US3841605A
US3841605A US00317773A US31777372A US3841605A US 3841605 A US3841605 A US 3841605A US 00317773 A US00317773 A US 00317773A US 31777372 A US31777372 A US 31777372A US 3841605 A US3841605 A US 3841605A
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Prior art keywords
load
moving
speed
motor
current
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Expired - Lifetime
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US00317773A
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English (en)
Inventor
S Kawano
M Joraku
S Yomekura
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Hitachi Ltd
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Hitachi Ltd
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    • 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
    • B66C23/005—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 with balanced jib, e.g. pantograph arrangement, the jib being moved manually
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C13/00—Other constructional features or details
    • B66C13/18—Control systems or devices
    • B66C13/22—Control systems or devices for electric drives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
    • B66C13/00—Other constructional features or details
    • B66C13/18—Control systems or devices
    • B66C13/22—Control systems or devices for electric drives
    • B66C13/23—Circuits for controlling the lowering of the load
    • B66C13/24—Circuits for controlling the lowering of the load by dc motors

Definitions

  • This invention relates to a moving apparatus for a load and, particularly, to an apparatus for moving a load to a desired place in a certain space with a small external force.
  • a conventional moving apparatus lifts a load in response to an on or off operation of a switch.
  • the lifted load cannot be moved by a man directly, since the control means of the conventional moving apparatus operates so as to add force in an opposite direction to the external force.
  • the control means When the designated speed is zero speed, the control means operates so as to keep the load at a constant position. If an external force tending to lift the load is applied to the load, a motor produces a force in the opposite direction in response to an out put from the control means in order to keep the load in position. If the operator wants to move the load, he must operate the switch or a speed designating circuit.
  • the load cannot be moved directly by hand, the operator cannot move the load precisely to the desired position and cannot stop it precisely at the desired level.
  • a conventional moving apparatus is used for lifting heavy parts which are used to assemble a machine. The parts must be stopped at certain positions for assembling the machine without colliding with each other. This operation is very difficult. As a result, it is desirable to move the load by hand directly as if the load were located in a gravity-free state.
  • the primary object of the invention is to provide an apparatus for moving a load precisely without much power.
  • the second object of the invention is to provide an apparatus for moving a load in a certain space as if a load were located in a gravity-free state.
  • the third object of the invention is to provide a moving apparatus having a very small frictional resistance.
  • the moving apparatus of the present invention has force control means and speed control means, the force control means storing the weight of a load and maintaining the generation of a desired force which is needed to lift the load, and the speed control means maintaining the speed for moving the load at an appointed value.
  • the force control means stores the weight of the load and generates a force needed for suspending or lifting the load. If an external force having a tendency to move the load is applied to the load, the speed control means operates to generate a force which acts on the load in the opposite direction to the external force in order to stop the movement of the load in response to the value of the appointed speed.
  • the operation of the speed control means is stopped in order that the speed of the load can become independent of the appointed speed. Since the force control means stores the weight of the load, the load is lifted or suspended with a certain force. If a man applies the same force for moving the load, the load can be moved with some speed. Namely, since the force produced in response to an output from the control means is equal to the weight of the load, all of the force provided by the man is used for moving the load where it is assumed that the mechanical friction of the moving apparatus is neglected.
  • the load When the load is moving to a position with some appointed speed in response to an output from the speed control means, if the operation of the speed control means is stopped, the load maintains its movement with the appointed speed until an external force is applied to the load.
  • the apparatus of the present invention has a compensating means for mechanical friction in order to move the load with a small force. Namely, the compensating means operates so as to apply to the load a force corresponding to the frictional force, but in the opposite direction.
  • the force control means stores the real weight value of the load and the compensating means compensates only for the mechanical friction.
  • the force control means stores the real weight value of the load and the mechanical friction force.
  • the compensating means calculates the needed compensating value from the value of the real mechanical friction and the value of the stored mechanical friction force.
  • FIG. I is a side view of a mechanism in accordance with one embodiment of the invention.
  • FIG. 2 is a plane view of the mechanism of FIG. 1.
  • FIG. 3 is a schematic block diagram of a control means in accordance with an ambodiment of the invention.
  • FIG. 4 is a detailed circuit diagram of the force control system and the speed control system of the control means of FIG. 3. r
  • FIG. 5 is a schematic circuit diagram of a voltage supply circuit for the motor and the control means of FIG. 3.
  • FIG. 6 is a schematic circuit diagram of a relay circuit for operating the circuits of FIG. 4 and FIG. 5.
  • FIGS. through 7c are schematic diagrams for explaining the mechanical friction when a load is lifted up.-
  • FIGS. 8a through 8c are schematic diagrams for explaining the mechanical friction when a load is lowered down.
  • FIGS. 9a through 90 are detailed circuit diagrams of compensating circuits for mechanical friction force.
  • FIG. is a detailed circuit diagram of a compensating circuit for a dynamic frictional force.
  • a lifting assembly includes four arms 1, 2, 3 and 4, pivotally connected at 5, 6, 7 and 8 to form a parallelogram linkage.
  • the connection point 8 is supported movably by a first supporting pole 20.
  • a load 10 is lifted by an end of the arm 2.
  • the lifting assembly is balanced by applying to an end 11 of the arm 1 a force corresponding to the weight of the load 10.
  • the end 9 of the arm 2 can be moved in a certain space defined by points a, b, c and (1, since the ratio of the distance between the connected points 8 and 11 and the distance between the connection points 8 and 9 is always constant.
  • the end 11 of arm 1 is pulled by chain 12 which is wound on a sprocket 16 fixed on a shaft of a motor 13.
  • a guide wheel 14 fixed on the end of the arm 1 moves up or down along guides 15.
  • a frame 17- having wheels 18 is free to move along a guide 19 which is rotatably fixed on the first supporting pole 20 and a second supporting pole 21.
  • the first and second supporting poles 20 and 21 are supported by a base 23 through a main pole 22.
  • an output corresponding to a designated speed from a speed designating circuit 301 is compared with feed back information from a speed detector 311 at a summing point 302 and is applied to an operational amplifier 304.
  • An output from the operational amplifier 304 and an output from a current detector 307 are applied to each input terminal of an operational amplifier 305.
  • a current converter 306 controls the current supplied to a motor 316 in response to the output from the operational amplifier 305.
  • a load 310 lifted by a chain 312 is moved by a moving body 313, such as a sprocket or a pulley,'which is fixed on a shaft of the motor 316.
  • the value of the current drawn by the motor 316 is fed back to the operational amplifier 305 through the current detector 307.
  • the value of the speed of the motor 316 is applied to the summing point 302 through the speed detector 311.
  • the load 310 When the output from the speed designating circuit 301 has a high value, the load 310 is lifted up. While, if the output from the speed designating circuit 301 is of small value, the load 310 goes down. When the output is represented by an intermediate value, the load is stopped. Namely, when the output from the speed designating circuit represents zero speed, the load is stopped at its position. In this case the output of the operational amplifier 304 represents zero speed. The value of current corresponding to the torque of the motor 316 needed for lifting the load 310 flows into the motor 316 and is stored in the operational amplifier 305. In order to keep the value of the motor current constant. the output of the current detector representing the motor current value is fed back to the operational amplifier.
  • the power control means consisting of the operational amplifier 305, the current converter 306 and the current detector generates the output corresponding to the weight of the load 310. Namely, in order to control the load 310 as if it were balanced with an imaginary load 314 of equal weight to the weight of the load 310, the motor applies power to the sprocket 313 in response to the output from the power control means.
  • the speed control means consisting of the speed designating circuit 301, the speed detector 311, the summing point 302 and the operational amplifier 304 generates an output power of the motor representing all that is used for moving the load, upward or downward,
  • the speed of the motor is fed back as an information through the speed detector 311, the speed of the motor is kept at a designated value by the operation of the speed control means.
  • terminals 401 and 402 of the variable resistor 403 are connected to terminals 520 and 521 of a voltage control circuit 516, respectively.
  • A. sliding contact having a terminal 408 is connected to a summing point 405 through a resistor 404.
  • a terminal of a generator 407 having a terminal 409 is connected to the summing point 405 through a resistor 406 and a contactor B
  • a command signal from the variable resistor 403 is compared with the instantaneous voltage from the generator 407. The result of this comparison, an output of the summing point 405 representing anerror, is applied to input terminal 410 of an operational amplifier 414.
  • Another input terminal 411 of the amplifier 414 is grounded through a resistor 415.
  • Terminals 416 and 417 are connected to the terminals 520 and 521 of the voltage control circuit 516.
  • a series circuit of a resistor 412 and a capacitor 413 is connected between the terminal 410 and an output terminal 418 of the amplifier 414.
  • variable resistor 403 The system consisting of the variable resistor 403, the
  • the summing point 405, the generator 407 and the amplifier 414 operates as the speed control means.
  • the output of the speed control means is applied to an input terminal 421 of an operational amplifier 427, which has a capacitor 425 and resistor 426 for storing the power of a motor 506 needed for lifting a load.
  • Another input terminal 422 is connected to a terminal 541 (FIG. 5) of a rectifier circuit 540 through a resistor 440 and terminal 441.
  • An output terminal 430 is connected to bases of transistors 463 and 463A through resistors 462 and 462A, respectively.
  • a bidirectional Zener diode 435 is connected between the terminal 430 of the operational amplifier 427 and ground.
  • Terminals 445 and 445A are connected to the terminal 520 of the voltage control circuit 516 and terminals 446 and 446A are connected to the terminal 521.
  • Terminals 450 and 450A are connected to terminals 511 and 512, respectively.
  • current through a resistor 454 flows to the terminal 511 through the terminal 450, a resistor 451 and a diode 453.
  • the charged voltage of the capacitor 452 is zero value. Since the voltage of the terminal 511 is increased, the base current of a transistor 456 through a diode 455 is increased.
  • the transistor 456 is turned on and the base voltage of the transistor is lowered through a resistor 457.
  • the collector current of the transistor 459 flows through a resistor 460 in response to the value of the base current of the transistor 459 flowing through a resistor 450.
  • the collector voltage of the transistor 459 is applied to the base of a transistor 463 through a resistor 461.
  • a high potential is applied to the base of the transistor 463, and then the transistor 463 is turned on.
  • the output of the operational amplifier 427 is also applied to the base of the transistor 463. Since the potential of the collector of the transistor 459 is increased along a certain characteristic curve, the time of the turning on operation of the transistor 463 is changed by the potential at the output terminal 430 of the operational amplifier 427. Namely, when the potential of the output terminal 430 has a negative value, the time of the turning on operation lags and the position potential advances the time of the turning on operation.
  • emitter of the transistor 463 connected to the resistor 464 is connected tothe base of a transistor 468 through diodes 465 and 467.
  • the base and collector of the transistor 460 are connected to the terminal 445 through a resistor 46b and a resistor 470, respectively.
  • the base and collector of the transistor 469 are connected re spectively to the collector of transistor 460 and terminal 511 through a diode 472, a resistor 471, and terminal 473.
  • the increasing potential of the terminal 511 is stored by a capacitor 475.
  • the charge on the capacitor 475 flows in a circuit consisting of the transistor 469, ground and a primary winding of the transformer 476, so as to cause a pulse voltage between terminals 477 and 478 and terminals 479 and 430 for turning on a thyristor 530, 531, 532 and 533.
  • the base of a transistor 456A is connected to the terminal 521 through diodes 453A and 455A connected to a resistor 454A, a resistor 451A connected to 21 capacitor 452A and terminal 450A.
  • a collector of the transistor 4556A is connected to the terminal 445A through resistors 457A and 450A connected to the base of a transistor 459A.
  • the collector of the transis tor 459A is connected to the base of a transistor 463A and a negative voltage supply 521 at terminal 446A through a resistor 46IA and a resistor 460A, respectively.
  • the base of the transistor 463A is connected to the collector of the transistor 459A and the output terminal 430 of the operational amplifier 427.
  • the emitter of the transistor 463A is connected to the base of a transistor 468A through diodes 465A and 467A connected to a resistor 466A and to the terminal 446A.
  • the collector of the transistor 468A is connected to the base of a transistor 469A and the terminal 445A through a resistor 470A.
  • the collector of the transistor 469A is connected to the terminal 512 through a resistor 471A, diode 472A and terminal 473A and to a primary winding of a transformer 476A through a capacitor 475A.
  • Terminals 477A, 478A, 479A, 480A are connected to the gates of the thyristors 532 and 531.
  • Terminals 501 and 502 are connected to an external voltage supply, and alternating voltage is applied to a transformer 510, a second winding of which having two terminals 5 ll and 512 is connected to the voltage control circuit having terminals 520 and 521 through a rectifier circuit 515.
  • a motor 506 is connected to the terminals 501 and 502 through the thyristors for controlling motor current, a current transformer 504 and a contact A
  • a field winding 505 of the motor is connected to the terminals 501 and 502 through a rectifier circuit 503.
  • the relay circuit of FIG. 6 is connected between the terminals 520 and 521.
  • a timer relay When switches S and 8;, are actuated, a timer relay is energized. Then, after a certain time, a contact TM is turned on. Since relay C is energized, a contact C is turned on and a contact C is turned off. Since the relay B is opened, the contacts Bi, and B are disconnected. Since the output from the summing point 405 is stopped, in response to the charge level of the capacitor 425 of the operational amplifier 427, the output of the force control means is regulated. Then, the motor 506 generates a force which is equal to weight of the load. Since the operation of the speed control means is stopped by opening the contacts B and B the load is independent .of its speed and position.
  • an operational amplifier 903 for compensating for the frictional force is connected to resistors 902, 904, 905, 906 and terminals 901, 915 and 916, the terminal 901 being connected to the terminal 418 of FIG. 4.
  • a switching circuit has resistors 907, 908, 909 and 910, contacts GS, GR, D,, D F and F and terminals 111 and 112, the terminal 111 being connected to the terminal 422 of FIG. 4 and the terminal 112 being connected to the terminal 421 of FIG. 4.
  • the contacts GR and GS are operated by the circuit of'FIG. 9(b).
  • An operational amplifier 925 has resistors 921, 928, 930 and 924, diodes 922 and 923, a capacitor 929, terminals 920, 926 and 927 and contact C
  • the relay circuit of FIG. 9(b) has two relays D and F resistors 936, 939, 940 and 938, diodes 935, 937, 947 and 948, capacitors 941 and 942 and terminals 950 and 951.
  • the output of the operational amplifier 925 is of positive value, which is transmitted to the transistor 943 through the diode 935. Then, the contacts D, and D are closed by energizing the transistors 943 and 946.
  • an operational amplifier 925C has resistors 921C, 924C, 928C and 930C, diodes 922C and 923C, a capacitor 929C, terminals 920C, 926C, and 927C and contact B
  • a relay circuit has one relay having two coils GR and GS, resistors 936C, 939C, 940C and 938C, diodes 935C and 937C and two diodes connected to the relay coils, capacitors 941C and 942C, transistors 943C, 944C, 945C, 946C, and terminals 950C, 951C.
  • the output of the speed designating signal is transmitted to the input terminals of the operational amplifier 925C through the terminals 408 and 920C, contact B and the resistor 921C.
  • the coil GR connected to the terminal 520 of FIG. 5 is energized by turning on the transistors 943 and 946.
  • the relay of FIG. 9(0) is a relay having the following characteristics. When the coil GS connected to the. terminal 521 is energized, the contact GS is turned on until the coil GR is energized even if the contact is opened.
  • FIG. 10 is a circuit for compensating for the dynamic friction having one operational amplifier 1010, resistors 1002, 1015, 1016, 1012, 1020, 1026, 1027, 1040, 1050, 1056 and 1057, two transistors 1025 and 1055, two diodes 1021 and 1051, five terminals 1001, 1013, 1014, 1030 and 1060, and a contact C
  • the terminal 1001 is connected to the terminal 410 of the generator 407 and terminals 1030 and 1060 are connected to the terminals 421 and 422, respectively.
  • the transistor 1025 When the output of the generator 407 has a positive value, the transistor 1025 is conductive, since the operational amplifier 1010 generates a negative voltage.
  • the collector current of the transistor 1025 is controlled by the value of the input voltage from the terminal 410.
  • the dynamic friction compensating means generates an output tending to decrease the speed of the load.
  • a moving apparatus for moving a load comprising lifting means including a motor for lifting a load,
  • force control means for controlling the force applied from said motor to said lifting means to correspond to the weight of-the load
  • first means for selectively stopping the operation of said speed control means.
  • a moving apparatus for moving a load according to claim 1, wherein the force control means includes memory means for storing a signal value equal to the force needed for lifting the load.
  • a moving apparatus for moving a load wherein said speed control means includes speed detecting means for detecting the speed of the motor, said force control means including force detecting means for detecting the force produced by said mo- 10!.
  • a moving apparatus for moving a load according to claim 3, wherein said speed control means includes speed designating means for providing a signal designating the speed of movement for said load.
  • a moving apparatus for moving a load wherein said compensating means includes second means for detecting the moving direction of the load to determine the acting direction of the mechanical friction of said lifting means and third means for detecting the moving direction of the load before said first means is operated.
  • said compensating means includes transistor switching circuit means for switching the output of the compensating means in response to the outputs of said second and third means.
  • a moving apparatus for moving a load according to claim further including dynamic friction compensating means for generating a force tending to decrease the moving speed of the load when said first means is operated.
  • a moving apparatus for moving a load comprismg:
  • speed detecting means for detecting the rotating speed of the motor;
  • speed designating means for providing a signal designating a desired rotating speed for the motor;
  • comparing means for comparing the output of the speed detecting means with the signal from the speed designating means
  • a current control means for controlling said current supply means to regulate the current applied to the motor in response to the outputs of said current detectin g means and said comparing means;
  • said speed designating means, said speed detecting means, and said comparing means comprising a speed control means for controlling the rotating speed of the motor in accordance with the signal generated by the speed designating means;
  • first means for selectively stopping the operation of said speed control means.
  • a moving apparatus for moving a load wherein said comparing means comprises a summing point and a first operational amplifier, said signals from said speed designating means and said 10 speed detecting means being applied to respective inputs of said summing point.
  • a moving apparatus for moving a load according to claim M, wherein said current control means further includes limiting means between said second operational amplifier and said current converter, said limiting means preventing an analog value of the output of said second operational amplifier from exceeding a certain range.
  • a moving apparatus for moving a load wherein said second operational amplifier has at least two input terminals, one terminal being connected to the output of said first input terminal and another being connected to said current detecting means, and a first capacitor provided between the one input terminal and the output terminal of said second operational amplifier.
  • a moving apparatus for moving a load wherein said lifting means includes four arms, one end of said first arm being adapted to receive a load to be hoisted, one end of said second arm being connected to another end of said first arm, another end of said second arm being mechanically connected to said motor and being moved by the motor force in the vertical direction, one end of said third arm being connected to a point between the one and other ends of said first arm and the other end of said third arm being connected to a base, one end of said fourth means being connected to a point between the one and other ends of said second arm, the other end of said fourth arm being connected to the base, said first and fourth arms being always arranged in parallel, said second and third arms being always arranged in parallel, and said motor being supported on said base for movement in the horizontal direction.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Position Or Direction (AREA)
  • Control Of Direct Current Motors (AREA)
US00317773A 1971-12-22 1972-12-22 Moving apparatus for a load Expired - Lifetime US3841605A (en)

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JP46104818A JPS5226015B2 (sv) 1971-12-22 1971-12-22

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3916279A (en) * 1973-08-20 1975-10-28 Hitachi Ltd Friction compensating apparatus for load moving machines
US4378652A (en) * 1980-08-25 1983-04-05 Lindgren Peter B Motor driven fishing reel
US5004181A (en) * 1989-10-27 1991-04-02 Fowles Arthur D Cordless electric fishing reel
WO2001005697A1 (en) * 1999-07-20 2001-01-25 Comoco, Inc. Method and apparatus for a high-performance hoist
US20040118639A1 (en) * 2001-04-30 2004-06-24 Michael Skovgaard Method for operating a lifting apparatus and lifting apparatus
US6974044B1 (en) * 1999-02-11 2005-12-13 Gerd Munnekehoff System and device for controlling a load lifting device
US20120186380A1 (en) * 2009-07-15 2012-07-26 Yasuyuki Yamada Load-compensation device
CN104261258A (zh) * 2014-08-12 2015-01-07 北京天拓四方科技有限公司 一种起重机重物下放时的控制方法及控制系统
US11136226B2 (en) * 2016-03-31 2021-10-05 Nhlo Holding B.V. Apparatus comprising a pivotable arm and a configurable spring

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5536598B2 (sv) * 1972-07-04 1980-09-22
JPS5536600B2 (sv) * 1972-08-02 1980-09-22
JPS5539520B2 (sv) * 1972-11-14 1980-10-11
JPS5516946Y2 (sv) * 1975-02-14 1980-04-19
FR2344492A2 (fr) * 1976-03-18 1977-10-14 Potain Sa Perfectionnements aux treuils pour la commande d'appareils de levage du genre des grues, ponts-roulants ou analogues
DE3711472A1 (de) * 1986-12-19 1988-06-30 Phb Weserhuette Ag Geschwindigkeitsregelung bei doppellenker-wippkranen
DE4415029A1 (de) * 1994-04-29 1995-11-02 Hafentechnik Eberswalde Gmbh Steuerung des Lastenaufnahmepunktes K eines Kranes oder Baggers

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3533524A (en) * 1968-10-28 1970-10-13 Bucyrus Erie Co Counterweight removal arrangement for hydraulic excavators or the like
US3713544A (en) * 1971-10-21 1973-01-30 Araneida Inc System for controlling a boom

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3533524A (en) * 1968-10-28 1970-10-13 Bucyrus Erie Co Counterweight removal arrangement for hydraulic excavators or the like
US3713544A (en) * 1971-10-21 1973-01-30 Araneida Inc System for controlling a boom

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3916279A (en) * 1973-08-20 1975-10-28 Hitachi Ltd Friction compensating apparatus for load moving machines
US4378652A (en) * 1980-08-25 1983-04-05 Lindgren Peter B Motor driven fishing reel
US5004181A (en) * 1989-10-27 1991-04-02 Fowles Arthur D Cordless electric fishing reel
US6974044B1 (en) * 1999-02-11 2005-12-13 Gerd Munnekehoff System and device for controlling a load lifting device
WO2001005697A1 (en) * 1999-07-20 2001-01-25 Comoco, Inc. Method and apparatus for a high-performance hoist
US6241462B1 (en) * 1999-07-20 2001-06-05 Collaborative Motion Control, Inc. Method and apparatus for a high-performance hoist
US20040118639A1 (en) * 2001-04-30 2004-06-24 Michael Skovgaard Method for operating a lifting apparatus and lifting apparatus
US7021427B2 (en) * 2001-04-30 2006-04-04 V. Guldmann A/S Lifting apparatus and method
US20120186380A1 (en) * 2009-07-15 2012-07-26 Yasuyuki Yamada Load-compensation device
US9132557B2 (en) * 2009-07-15 2015-09-15 Keio University Load-compensation device
CN104261258A (zh) * 2014-08-12 2015-01-07 北京天拓四方科技有限公司 一种起重机重物下放时的控制方法及控制系统
US11136226B2 (en) * 2016-03-31 2021-10-05 Nhlo Holding B.V. Apparatus comprising a pivotable arm and a configurable spring

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Publication number Publication date
DE2262800A1 (de) 1973-06-28
JPS4869246A (sv) 1973-09-20
JPS5226015B2 (sv) 1977-07-12

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