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
  • B66C23/84—Slewing gear
  • B66C23/86—Slewing gear hydraulically actuated
• • 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
  • B66C13/04—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack
  • B66C13/06—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack for minimising or preventing longitudinal or transverse swinging of loads
• • 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
  • B66C13/04—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack
  • B66C13/06—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack for minimising or preventing longitudinal or transverse swinging of loads
  • B66C13/063—Auxiliary devices for controlling movements of suspended loads, or preventing cable slack for minimising or preventing longitudinal or transverse swinging of loads electrical
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/60—Circuit components or control therefor
  • F15B2211/63—Electronic controllers
  • F15B2211/6303—Electronic controllers using input signals
  • F15B2211/6306—Electronic controllers using input signals representing a pressure
  • F15B2211/6313—Electronic controllers using input signals representing a pressure the pressure being a load pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B2211/00—Circuits for servomotor systems
  • F15B2211/80—Other types of control related to particular problems or conditions
  • F15B2211/86—Control during or prevention of abnormal conditions
  • F15B2211/8616—Control during or prevention of abnormal conditions the abnormal condition being noise or vibration

Definitions

• This invention relates to a device for damping undesirab oscillations in an arm or other member of a crane that is pivo- tally movable by hydraulic means. It is concerned with a system having at least one hydraulic motor in a hydraulic circuit in which there is a restriction. When a circuit-closing device or function is operated to stop the main motion, this restriction converts energy inherent in the system (deformation energy and kinetic energy) to heat in the hydraulic fluid that still flows as a result of oscillation. The heat dissipates that energy to damp or suppress any oscillations of said member.
• Thi crane arm 1 is mounted on a post 2 having a coaxial gear wheel 3, which engages a toothed rack 4 connected at opposite ends to motors in the form of two linear hydraulic actuators. These hav cylinders 5, 5' in which pistons 6, 6' define two operating chambers 7, 7'. These two hydraulic actuators are part of a hyd raulic circuit, generally designated 8, in which is also inclu ⁇ ded a directional valve 9. This is operable to direct oil from pump 10 to either one of the cylinders 5, 5' through main con ⁇ duits 8a, 8b, while exhaust oil flows to a tank 11.
• the tip of the crane arm swing or deflect between positions of the order of 2 metres apart and it can be 15 to 20 seconds before the tip and accordingly the load are stopped.
• Such oscillations are especially troublesome where the load is at the end of a lengthy rope hanging down from the tip of the crane arm.
• the crane arm tip oscillates to and fr at the same time as the load oscillates relative to the tip through the rope.
• Such oscillations may also occur during the slewing of the crane arm tip between two desired positions. The may happen, for example, if the hydraulic flows to the respec ⁇ tive cylinders 5, 5' are disrupted, as a consequence of sharp lever movements at the directional valve 9 perhaps or as a con ⁇ sequence of the load or the crane arm hitting obstacles.
• a damping unit which is installed in a branch or interme- diate conduit bridging the main conduits between the directiona valve and the hydraulic cylinders.
• the damping unit is in the form of a restriction associated with a co-operating shut-off device.
• this shut-off device consists of a pis- ton captive in a cylinder and freely movable between opposite end positions, the piston shutting off the oil flow through the restriction when it reaches either end position. When the oil passes the restriction a turbulent flow in the oil is generated which converts the energy inherent in the system to heat.
• the duration of the oscillations of the crane arm is reduce to a significant extent. Assuming the crane arm is suddenly stopped from the full velocity of slewing, the duration of oscillatory motions (to when the arm is finally still) can be reduced from 15 to 20 seconds to 3 to 5 seconds.
• the present invention aims to alleviate the problem stil left by SE 9101544-6 and provide a damping device which, during the damping operation, promotes regular or even movements of th crane arm and at the same time makes sure that the arm will sto in a reliable manner and in a desired position after slewing.
• a basic object of the invention is to provide a damping device which is capable of being activated whenever an oscillation tends to occur due to an expected or unexpected ex ⁇ ternal influence on the hydraulic system, such as intentional o unintentional lever movements or collisions against obstacles.
• Another object is to provide a damping device which, after the arm has stopped moving, will ensure that any flow of hydraulic fluid through the damping restriction will cease and so prevent uncontrolled movements of the crane arm.
• Fig 1 is a schematic illustration of a hydraulic system of the type previously mentioned, in which a schematically shown damping device according to the invention is included. More particularly figure 1 shows a first, preferred embo ⁇ diment having control means including a microcomputer or similar control unit.
• Fig 2 is a schematic illustration of a second embodiment of a damping device according to the invention, in which the control means is of a mechanical and automatically opera ⁇ ting nature.
• a restriction symbolically indicated at 13 is arranged in a branch or intermediate conduit 12 between the main conduits 8a, 8b.
• this restriction may consist of a fixed restric- tion in the form of an annular insert or shoulder of reduced diameter located in the conduit 12.
• the conduit may be a tube o a drilled bore in a block.
• a shut-off valve generally designa ⁇ ted 14, and in the form of a magnetic valve of the on-off-type for example, co-operates with this fixed restriction 13.
• the conduit 12 may either be comple tely blocked, whereby oil flow through the restriction 13 is rendered impossible, or opened in order to allow oil to flow through the restriction.
• This opening and closing of the valve is controlled by a control unit 15 which in practice advanta ⁇ geously, but not necessarily, may consist of a microcomputer.
• input data to this control unit are obtai ned by means of two sensors 16, 16' in the form of pressure or flow sensors. These may be connected as shown to the interme- diate conduit 12, or they may be connected to the conduits 8a, 8b, on either side of the restriction 13 and the magnetic valve 14.
• sensors 16, 16' The purpose of these sensors 16, 16' is to detect signifi ⁇ cant conditions and/or changes of conditions in the hydraulic oil in the circuit. It is preferred in practice to use sensors which are capable of detecting significant pressures and/or changes of pressure which occur in the two actuators 5, 5' when the crane arm 1 starts to oscillate.
• the control unit 15 When the control unit 15 receives information from the sensors 16, 16' that pressures and/or pressure changes of a certain magnitude have arisen in the system, the unit will provide a signal to the magnetic valv 14 to open, whereby the valve will allow oil to flow through th restriction 13. In other words the restriction is activated, an a turbulent flow is created in the oil passing to and fro through it.
• the varying deformation energy and the kinetic energy in the system is converted, in a manner known per se, to heat in the oil, and the oscillatory motions of the crane arm are damped.
• the control unit 15 provide a signal to the magnetic valve 14 to close. Any further flow of oil through the restriction 8 is thus blocked.
• the directional valve 9 is kept closed all the time during this damping operation. Therefore, when the valve 14 is shut off even a minimum flow of oil between the two cylinders 5 5' is rendered impossible. This ensures that the crane arm 1 is reliably maintained in its given, desired position.
• the damping device of figure 1 makes possible a comp letely, reliably and positively controlled closure of the inter mediate conduit 12 when the crane arm is arrested.
• a basi advantage of the invention is that it provides a reliable and positive adjustment of the crane arm to the desired position while the duration of the resultant oscillations is substan ⁇ tially reduced in comparison with such cranes that lack damping devices.
• Another advantage in comparison with SE 9101544-6 is that the restriction - and accordingly the damping - can be con trolled in a positive and efficacious manner.
• the control unit 15 when it is a microcomputer, may be programmed in such a man ner that the magnetic valve 14, which is normally closed, will be opened not only when the crane arm has finished slewing (whe the lever of the directional valve 9 is moved to the neutral position) but also at any moment during slewing.
• a sequence of oscillations irrespective of whether it occurs after the basic crane arm movement has stopped or during slewing, manifests it ⁇ self in a harmonic function the condition of which is read by the microcomputer by means of the sensors.
• the computer On a given condition existing the computer may send a signal to the magnetic valve t either open or close.
• the freely movable or floa ⁇ ting piston in the damping cylinder according to SE 9101544-6 cannot be acted on at all from outside in any controllable man ⁇ ner.
• FIG 2 illustrates a crane slewing system as described but with a damping device pro ⁇ vided with mechanical control means.
• the device includes a fixed restriction 13 in an intermediate conduit 12.
• pressure limiting valves 17, 17' are installed at either side of the restriction, said valves being of the type which opens only at certain minimum pressure.
• the two valves 17, 17' are arranged t co-operate with a common piston-cylinder mechanism, generally designated 18, which includes a cylinder 19 and a piston 20 having opposed piston rods 21, 21'.
• Each piston rod 21, 21' is connected to an associated valve 17, 17' by.way of a mechanical spring 22, 22'.
• These springs are for increasing the pressure drop across the pressure limiting valves 17 and 17' and accor ⁇ dingly for increasing the resistance to movement of the piston towards a valve-closing position. They operate alternatively an successively to decrease the flow of oil through the associated valve until the valve completely closes the intermediate condui 12.
• the springs 22, 22' ensure - by increasing the pressure drop across the valve i question - that the piston 20 moves in a smoothly decelerating movement towards the end position without giving rise to abrupt pressure shocks. Moreover, the pressure limiting valves 17, 17' prevent any flow of oil through the restriction 13 as soon as the oscillations have been damped. Unintentional creeping move ⁇ ments of the crane arm after the damping has stopped are thereb avoided.
• the invention is not merely limited to the embodiments disclosed above and in the drawings.
• the embodiment of figure 1 includes a fixed restriction and a magnetic valve separate from the restriction.
• a check valve serving bot as a variable restriction, and for completely shutting-off the hydraulic conduit.
• a single fixed restriction in practice in the form of an insert or a shoulder having a small percolation aperture
• two or more restric ⁇ tions having wider apertures.
• pressure sensors it is also possible to use either flow sensors in the hydraulic cir- cuit or position sensors which instantaneously detect the posi ⁇ tion of the crane member to be damped.
• the damping device of the invention may also be used for other members for ⁇ ming parts of a crane, such as the inner boom and the outer boom, in order to damp oscillations in other planes, such as vertical.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Control And Safety Of Cranes (AREA)
• Vibration Prevention Devices (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20393744

Family Applications (1)

Country Status (6)

Cited By (1)

Families Citing this family (1)

Citations (4)

• 1994
  • 1994-04-22 SE SE9401369A patent/SE505698C2/sv not_active IP Right Cessation
• 1995
  • 1995-04-07 WO PCT/SE1995/000375 patent/WO1995029118A1/en active IP Right Grant
  • 1995-04-07 DE DE69521423T patent/DE69521423T2/de not_active Expired - Lifetime
  • 1995-04-07 EP EP95917527A patent/EP0756574B1/de not_active Expired - Lifetime
  • 1995-04-07 AU AU23543/95A patent/AU2354395A/en not_active Abandoned
  • 1995-04-07 AT AT95917527T patent/ATE202324T1/de not_active IP Right Cessation

Patent Citations (4)

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