WO2020100145A1 - Luffing crane featuring tipping over balance - Google Patents

Luffing crane featuring tipping over balance Download PDF

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Publication number
WO2020100145A1
WO2020100145A1 PCT/IL2019/051252 IL2019051252W WO2020100145A1 WO 2020100145 A1 WO2020100145 A1 WO 2020100145A1 IL 2019051252 W IL2019051252 W IL 2019051252W WO 2020100145 A1 WO2020100145 A1 WO 2020100145A1
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WO
WIPO (PCT)
Prior art keywords
luffing
jib
crane
swing
counterweight
Prior art date
Application number
PCT/IL2019/051252
Other languages
French (fr)
Inventor
Aviv Carmel
Original Assignee
Sky-Line Cranes & Technologies Ltd.
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 Sky-Line Cranes & Technologies Ltd. filed Critical Sky-Line Cranes & Technologies Ltd.
Priority to CA3120433A priority Critical patent/CA3120433A1/en
Publication of WO2020100145A1 publication Critical patent/WO2020100145A1/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
    • B66C23/72—Counterweights or supports for balancing lifting couples

Definitions

  • the present invention relates generally to luffing cranes, and in particular to coping with tipping over due to luffing or wind.
  • Luffing cranes feature a working arm in the form of a luffing boom or jib, which changes its tilt while lifting and moving loads, the loads are usually hoisted while hanging from the distal tip of the luffing jib or boom.
  • the working arm of a tower crane is usually mounted atop a mast and is rotated by virtue of a swing bearing such as a slewing unit.
  • a luffing jib may be tiltably mounted at the distal frontal tip of a main boom, which may be a horizontal main boom of the working arm (e.g., a luffing tower crane) or directly to a mobile vehicle (e.g., truck mounted crane or a crawler crane), which often feature a main pivotal boom which changes it tilt, in a manner similar to the tilting of the luffing jib, such that the working arm is a compound arm featuring two tilting sections coupled in a series (as is common with mobile cranes).
  • Another variate is the level luffing crane.
  • the term "luffing jib" will be used herein to describe all types of luffing arms, booms and jibs.
  • the luffing jib changes its tilt, the combined weight moment of the luffing jib and its hoisted load is changed.
  • the sum of all moments about the base of the crane e.g., it may be the location where luffing boom is mounted such as the mast
  • the safety margin the maximal magnitude of load which is permitted to be lifted (the "rated load"), is some value less than the load that will cause the crane to tip, and depends on the balance of weights inflicted about the base of the crane.
  • counter measures are installed over the crane to prevent tipping over, such as a heavy base, and for a tower cranes - a counter weight disposed at a short horizontal machinery arm (usually at its distal rear for greater moment).
  • a sliding counterweight trolley is runs along the machinery arm is moved to compensate for the changing moment of the luffing jib (with its load).
  • a luffing crane including a luffing jib pivotable about a jib pivot axis at a front side of the luffing crane, and a tip-over balance including a movable counterweight.
  • the movable counterweight is configured to move toward the front side of the luffing crane when the luffing jib pivots upwards toward a stalling posture, and further configured to move away from the front side of the luffing crane when the luffing jib pivots downwards away from the stalling posture to assume a forwardly headed position, so as to prevent tipping over of the crane during its operation.
  • the tip-over balance may further include a static counterweight, located to the rear of the jib pivot axis, such that the movable counterweight balances the luffing crane against the static counterweight when the luffing jib is near or at a stalling posture.
  • the movable counterweight may be gradually moved toward the front side of the luffing crane when the luffing jib pivots upward toward a stalling posture, and the movable counterweight may be gradually moved away from the front side of the luffing crane when the luffing jib pivots downwards away from the stalling posture to assume a forwardly headed position.
  • the movable counterweight may be configured to move beyond the jib pivot axis, such that when the luffing jib is nearing or at complete stall, the movable counterweight is positioned to the front of the jib pivot axis.
  • the movable counterweight may be mounted on a movable- counterweight swing, rotatable in a vertical plane about a counterweight swing axis.
  • the counterweight swing axis and the jib pivot axis may be a common axis.
  • the swing may further include a swing frame pivotable about and extending from the swing axis, and the movable counterweight may be disposed on the swing frame, such that when the swing rotates, the movable counterweight swings below the swing axis.
  • the movable counterweight may be configured to pivot below the swing axis when the luffing jib pivots above the jib pivot axis, such that the horizontal movements and displacements of the luffing jib and the movable counterweight are opposed.
  • the movable counterweight may be configured to pivot from an uppermost rearmost location, through an interim lowermost location below the swing axis, and toward a frontmost location in front of the swing axis above the interim lowermost location, when the luffing jib pivots from a lowermost forwardmost horizontal posture and pivots upwards toward an uppermost rearmost posture at or nearing a stalling posture.
  • the luffing crane may further include a coupling, configured to couple the luffing jib and the swing to synchronize directional rotations that accompany opposed horizontal movements of the luffing jib and the swing.
  • the coupling may include a mechanical coupling; and/or a controlled drive for moving one of the luffing jib and the swing synchronously.
  • the coupling may include a mechanical movement transfer member, such as a rod or a rope.
  • the swing frame may include an upwardly extending upper swing ear, where the movement transfer member connects the front head of the luffing jib and the upper swing ear.
  • the movable counterweight may be disposed below the axis, and the upper swing ear may protrudes above the swing, and when the movable counterweight moves forward, the upper swing ear pivots rearward, together with the upward movement of the luffing jib, and when the movable counterweight moves rearward, the upper swing ear pivots forward, together with the downward movement of the luffing jib.
  • a drive of the luffing jib may be conveyed via the swing.
  • the drive may include a piston coupled to the swing frame.
  • the piston may be coupled at one end to a rearwardly extending machinery arm of the crane, and at another end to a forwardly extending girder of the frame, where an extension or a contraction of the piston moves the swing frame to pull, release to drop, or push the head of the luffing jib via the movement transfer member.
  • the luffing crane may further include a crane hoisting hook hanging on a rope from the head of the luffing jib, where the crane hoisting hook is releasably secured to the movable counterweight when the luffing jib is nearing or at a stalling posture, and the movable counterweight is positioned to the front of the jib pivot axis.
  • the tip-over balance may include at least one side-panel whose sidewind moment increases the sidewind moment of the luffing jib as the luffing jib rises, and decreases the sidewind moment of the luffing jib as the luffing jib descends, to compensate for the changing sidewind drag- profile of the luffing jib.
  • the side-panel may include the side surface-area of a movable counterweight; a swing, a swing frame, and/or a retractably expandable side-panel.
  • the retractably expandable side-panel may include at least one side panel which is fanned out as the luffing jib rises, to form a differential surface area facing sidewind which expands as the luffing jib is pivoted upwards, and retracts as the luffing jib is pivoted downwards.
  • a method for preventing tipping over of a luffing crane includes the procedures of: providing a luffing jib of the luffing crane, the luffing jib pivotable about a jib pivot axis at the front side of the luffing crane, and providing a tip-over balance of the luffing crane, the tip-over balance comprising a movable counterweight.
  • the method further includes the procedures of: moving the movable counterweight toward a front side of the luffing crane, when the luffing jib pivots upwards toward a stalling posture, and moving the movable counterweight away from the front side of the luffing crane, when the luffing jib pivots downwards to assume a forwardly headed position.
  • the tip-over balance may further include a static counterweight, located to the rear of the jib pivot axis, such that the movable counterweight balances the luffing crane against the static counterweight when the luffing jib is near or at a stalling posture.
  • the movable counterweight may be configured to move beyond the jib pivot axis, such that when the luffing jib is nearing or at complete stall, the movable counterweight is positioned to the front of the jib pivot axis.
  • the movable counterweight may be mounted on a movable-counterweight swing, rotatable in a vertical plane about a counterweight swing axis.
  • the swing may further include a swing frame pivotable about and extending from the swing axis, and the movable counterweight may be disposed on the swing frame, such that when the swing rotates, the movable counterweight swings below the swing axis.
  • the luffing crane may further include a coupling, configured to couple the luffing jib and the swing to synchronize directional rotations that accompany opposed horizontal movements of the luffing jib and the swing.
  • the luffing crane may further include a crane hoisting hook hanging on a rope from the head of the luffing jib, where the crane hoisting hook is releasably secured to the movable counterweight when the luffing jib is nearing or at a stalling posture, and the movable counterweight is positioned to the front of the jib pivot axis.
  • the tip-over balance may include at least one side-panel whose sidewind moment increases the sidewind moment of the luffing jib as the luffing jib rises, and decreases the sidewind moment of the luffing jib as the luffing jib descends, to compensate for the changing sidewind drag-profile of the luffing jib.
  • the tip-over balance may include a retractably expandable side-panel which includes at least one side panel which is fanned out as the luffing jib rises, to form a differential surface area facing sidewind which expands as the luffing jib is pivoted upwards, and retracts as the luffing jib is pivoted downwards.
  • Figure 1 is a schematic side view illustration of a luffing crane having a counterweight swing for anti-back tipping, constructed and operative in accordance with an embodiment of the present invention
  • Figure 2 is a schematic side view illustration of the luffing crane of Figure 1 illustrating division of rotational movements about a central axis into quadrants;
  • Figure 3 is a is a schematic side view illustration of a luffing crane featuring two exemplary gradually deployable side panel arrangements which are spontaneously fanned out as the luffing jib rises to form a differential surface area facing sidewind, constructed and operative in accordance with an embodiment of the present invention
  • Figure 4A is a schematic side view illustration of a luffing crane having a movable counterweight and a static counterweight with the luffing jib in a forwardly headed position, constructed and operative in accordance with an embodiment of the present invention
  • Figure 4B is a schematic side view illustration of the luffing crane of Figure 4A with the luffing jib nearing a stalling posture, constructed and operative in accordance with an embodiment of the present invention
  • Figure 4C is a side view illustration of a luffing crane having a movable counterweight but no static counterweight, constructed and operative in accordance with an embodiment of the present invention.
  • a luffing crane includes a working jib, which pivots about some pivot axis. By virtue of such pivoting, the gravitational moment and the wind drag profile of the jib, including its load (which is usually hanging from the remote jib head) is changed, which thereby may cause tipping over of the crane.
  • the gravitational moment change is explained above.
  • the wind drag profile which affects wind moments inflicted on the crane is altered as well, with respect to two horizontal wind directions relative to the jib positioning (i.e., its front head direction).
  • the jib profile surface area facing a "frontal-wind” i.e., wind facing the head of the jib
  • a "back-wind” or “rear-wind” i.e., wind facing the rear of the crane away from the jib
  • the wind drag moment is maximal when the jib is pivoted to rise into an erect stance, up to a stall (or its closest allowed raised position nearing a stall), as the (almost) entire length of the jib profile faces the rear/front wind and builds up a large moment about the pivot axis of the jib or the entire crane.
  • a counterweight is often disposed at the rear of the crane, it is usually a front wind which is more prone to tip over the crane toward the back.
  • the jib surface area facing a side-wind i.e., wind facing the side of the jib
  • a side-wind i.e., wind facing the side of the jib
  • cranes are often designed to freely rotate in windy and stormy conditions.
  • Such cranes are allowed to freely rotate in a horizontal plane about the swing bearing, such as the slewing unit, such that the wind rotates the crane in a manner similar to weathervanes.
  • the side-wind drag profile of the frontal working arm (e.g., the front jib) should be significantly greater than that of the rear, machinery arm, for example twice as big, to ensure that the side-wind will always turn the crane to point with its jib head toward the wind.
  • the side-wind moment inflicted by the jib profile about the axis of horizontal rotation of the crane (e.g., the rotation axis of the slewing unit) is also changed.
  • the side-wind horizontal rotation moment is maximal when the jib is lowered to a horizontal stance because the average radius away from the horizontal crane rotation axis is maximal.
  • the side-wind horizontal rotation moment is minimal when the jib is tilted to rise toward a vertical stall, because the average radius away from the horizontal crane rotation axis is minimal (and null when the jib is at a complete stall).
  • the present invention provides for countermeasures that cancel out, at least to an effective extent, the altered moments. For simplicity, it assumed herein that the horizontal posture of a jib tilt is designed to best meet the optimal required moments of the crane.
  • a movable counterweight is maneuvered to move toward the front of the luffing crane as the jib is tilted or pivoted to rise upwards, where the counterweight is allowed to move beyond the jib pivot axis, such that when the jib is nearing or at a complete stall, the counterweight is disposed below or to the front of the jib pivot axis.
  • the movable counterweight negates the jib gravitational moment, and as the jib approaches a stall and loses moment, so does the movable counterweight.
  • Moving the counterweight towards the front and beyond the tilt axis is particularly effective when an additional counterweight, which is fixed, is disposed at the rear machinery arm to allow tilting of the jib near a stall (where the jib gravitational moment is almost null) as the movable counterweight balances the crane against the fixed counterweight.
  • Enabling tilting of the jib into an almost erect posture is of particular significance for allowing safe hoisting and moving of a load near the axis or tilt (e.g., close to the mast of a tower crane), which is nowadays dramatically limited to relatively light loads due to the danger of topple down as the jib loses most of its moment upon approaching a stall.
  • a further effect of this movable counterweight arrangement is the appropriate balancing of weights between the front and back, which can better confront the front wind moment inflicted by the raised jib. Without the movable counterweight located at the front, all of the crane's balancing weight resides with the fixed counterweight at the rear and a front wind gust hitting the erect jib may cause back topple down of the crane.
  • the luffing crane of the present invention includes a luffing jib, tiltable or pivotable about a jib pivot axis at a front side of the crane.
  • the luffing crane further includes a tip-over balance, which includes at least a movable counterweight, configured to move toward the front side of the crane as the luffing jib pivots upwards toward a stalling posture, and configured to move away from the front side of the crane as the luffing jib pivots downwards away from stalling and toward assuming a forwardly- headed position.
  • the movable counterweight is rotatable in a vertical plane about a counterweight swing axis, which may optionally be common with the jib tilt pivot axis.
  • the luffing crane may further include a static counterweight, which may be disposed on a rear machinery arm.
  • Figure 1 is a schematic side view illustration of a luffing crane, denoted 100, having a counterweight swing, denoted 102, for anti-back tipping, constructed and operative in accordance with an embodiment of the present invention.
  • Figure 2 is a schematic side view illustration of the luffing crane of Figure 1 illustrating division of rotational movements about a central axis into quadrants.
  • "Quadrant I" represents an upper front quadrant
  • quaddrant II represents an upper rear quadrant
  • quaddrant III represents a lower rear quadrant
  • quadrant IV represents a lower front quadrant.
  • the quadrants are divided by the straight perforated bold lines and are defined respective of vertical rotation along the round perforated line on the plane of the drawing sheet or in parallel thereto, about an axis of rotation denoted 106.
  • luffing crane 100 includes a luffing jib 104, which is tiltable or pivotable in the upper front quadrant I at the front side of crane 100, about a jib pivot axis 106.
  • Luffing crane 100 further includes a tip-over balance in the form of counterweight swing 102, wherein the balance is gradually deployed, as luffing jib 104 pivots upward toward a stalling posture (posture 1 12), and retracts, as luffing jib 104 tilts down away from a stalling posture and toward a forwardly-headed horizontal position.
  • Luffing crane 100 usually includes a static counterweight 152, which may be disposed on a rear machinery arm 132.
  • Swing 102 includes a movable counterweight 108, also referred to herein as a "swinging-counterweight” 108, which is disposed on swing frame 1 10 extending from swing axis 106 to displace swinging- counterweight 108 with respective of axis 106, such that when swing 102 rotates, swinging-counterweight 108 swings below swing axis 106, dwelling in the lower rear quadrant III and lower front quadrants IV of the vertical plane of rotation.
  • a movable counterweight 108 also referred to herein as a "swinging-counterweight” 108, which is disposed on swing frame 1 10 extending from swing axis 106 to displace swinging- counterweight 108 with respective of axis 106, such that when swing 102 rotates, swinging-counterweight 108 swings below swing axis 106, dwelling in the lower rear quadrant III and lower front quadrants IV of the vertical plane of rotation.
  • Swing frame 1 10 and luffing jib 104 rotate vertically in similar rotational directions, namely in parallel rotational directions (depicted by the round perforated bold line in Figure 2) or in common directions in parallel or common vertical plane(s), when considered from a side point of view.
  • pivot axis 106 is shown as a common axis for swing 102 and luffing jib 104, the axis for each of these two rotating elements 102 and 104 may be separately spaced, distanced upwards, frontally or rearwardly, relative to the other axis, and the determination of the positioning of swing 102 and jib 104 (i.e., quadrant, above/below/rearward/forward with respect to an axis is taken only with relation to the respective axis (of swing 102 or of jib 104).
  • swinging-counterweight 108 While luffing jib 104 always rotates above its tilt pivot axis 106, swinging-counterweight 108 always rotates below its swing axis 106, such that the horizontal movements and displacements of jib 104 and swinging-counterweight 108 are always opposed (taken along a line extending from the front at the right of the drawing sheet to the rear at the left of the drawing sheet).
  • swinging-counterweight 108 rotates from its uppermost rearmost location (similar to the one shown in Figure 1 ), through its interim lowermost location right below swing axis 106 toward its frontmost location in front of swing axis 106, denoted by perforated line 1 14, somewhat above its interim lowermost location (where frame 1 10 assumes the posture denoted by perforated lines 1 15).
  • Coupling of these similar directional rotations may be provided by a mechanical coupling of luffing jib 104 and swing 102, or by otherwise-controlled movement that synchronizes the rotations of one of swing 102 and jib 104, with the rotation of the other.
  • a mechanical coupling may be provided by coupling swing 102 and jib 104 with a movement transfer member, such as a rod or a rope.
  • member 1 16 may provide such a mechanical coupling, where member 1 16 can connect between the tip of luffing jib 104 front head (extending to the right of the drawing) and an upwardly extending upper swing ear of swing frame 1 10, such as upper swing ear 1 18, at joint 120.
  • swinging-counterweight 108 While swinging-counterweight 108 is disposed below swing axis 106, upper swing ear 1 18 protrudes above swing axis 106. Therefore, when swinging- counterweight 108 rotates forward, upper swing ear 118 rotates rearward (arrow 122), together with the rearward (and upward) movement (of the head) of luffing jib 104 (arrow 124). Conversely, when swinging- counterweight 108 rotates rearward, upper swing ear 1 18 rotates forward, together with the forward (and downward) movement of luffing jib 104.
  • Luffing jib 104 is usually heavier than swing 102 (including the weight of swinging- counterweight 108), and the jib tilt is usually dictated by a jib tilt drive, e.g., for the sake of hoisting an moving a load hanging on the jib head.
  • the movement transfer member 1 16 pulls swing 102 by swing upper ear 1 18 when luffing jib 104 descends toward a horizontal posture, and releases swing 102 to drop, or pushes swing 102 by swing upper ear 1 18 when luffing jib 104 ascends toward an erect posture 1 12.
  • a rigid rod must be utilized as the movement transfer member 1 16 for moving swing weight 108 toward the front because a rope would not push swing 108 beyond its lowermost position below swing axis 106.
  • a rope (a guyline, tension member, or cable tautly stretched between swing upper- ear 1 18 and the head of luffing jib 104) may be used when the drive of jib 104 is conveyed via swing 102, because the rope would remain tautly stretched as luffing jib 104 never passes over the fulcrum of the jib rotation (jib pivotal axis 106).
  • a drive such as piston 126 is coupled to swing frame 1 10, e.g., at joint 128 disposed in a forwardly extending girder 130 and thus swing frame 1 10 pulls or releases to drop (pushes only via a rod 1 16) the head of luffing jib 104 via linking member 1 16 (a rod or a rope).
  • the drive may feature other means for swinging counterweight swing 102, and thereby to pivot luffing jib 104.
  • Piston 126 may be hinged at joint 128 to girder 130 at one end and to a rearwardly extending machinery arm 132 at another end 134.
  • Frame 1 10 may further feature support struts or girders that strengthen the frame to withstand the inflicted forces, such as strut 136 which connects ear 1 18 and girder 130 with arm 138 on which counterweight 108 is mounted.
  • a further measure may take advantage of the forward disposition 1 14 of movable counterweight 108 which is convenient for securing crane hook 140 which hangs from the almost erect luffing jib 104 and thereby prevent tipping back of the erect jib 104, at perforated positioning 1 12 (even when mast 142 or other part of crane 100 remain intact) upon impact of a front wind gust.
  • movement transfer member 1 16 is positioned along perforated line 144, and the load hoist rope along perforated line 146.
  • the hoist rope is shown hanging along perforated line 148 with its hook denoted as 150.
  • swinging counterweight 108 When swinging counterweight 108 is maneuvered to move toward the front as jib 104 is pivoted upwards, swinging counterweight 108 is allowed to move beyond jib pivot axis 106, such that when jib 104 is nearing or at a complete stall (posture 1 12), counterweight 108 is disposed below or to the front of tilt axis 106. Swinging counterweight 108 negates the jib gravitational moment, and as jib 104 approaches a stall (posture 1 12) and loses moment, so does swinging counterweight 108.
  • Moving swinging counterweight 108 toward the front and beyond tilt axis 106 is particularly effective when fixed counterweight 152 is disposed at the rear of machinery arm 132, to allow tilting of jib 104 near a stall (posture 1 12, where the gravitational moment of jib 104 is almost null) as swinging counterweight 108 at posture 1 14 balances crane 100 against fixed counterweight 152.
  • Enabling the pivoting of jib 104 into an almost erect posture 1 12 is of particular significance for allowing safe hoisting and moving of a load near axis 106 of tilt, e.g., close to mast 142 of a tower crane (or slewing unit 143), represented by the hoist rope at position 148 and the hook at position 150, which is nowadays dramatically limited for conventional cranes to relatively light loads due to the danger of topple down as jib 104 loses most of its moment upon approaching a stall.
  • a further effect of this movable counterweight arrangement is the appropriate balancing of weights between the front and back, which can better confront the front wind moment inflicted by the raised jib 104.
  • the tip-over balance may include at least one side-panel whose sidewind moment increases the sidewind moment of luffing jib 104 as luffing jib 104 rises, and decreases the sidewind moment of luffing jib 104 as luffing jib 104 descends, to thereby compensate for the changing sidewind drag-profile of the luffing jib.
  • the side-panel may feature the side surface-area of a movable object the moves from the rear to the front and back in a counter-correlation to the rearward and forward movements of luffing jib 104.
  • One location changing side panel may be provided by the side surface area of the moving components of the embodiment of Figure 1.
  • the side surface area of a movable counterweight such as counterweight 108, a counterweight-swing such swing 102 or counterweight swing frame 1 10.
  • Swing 102 or frame 1 10 may be fully or partially covered or shielded by a panel facing the sidewind.
  • the tip over balance measure includes at least one side panel which is fanned out as the luffing jib rises, to form a differential surface area facing sidewind which expands as the jib is tilted up, and thereby change the sidewind drag- profile of the jib.
  • FIG. 3 is a schematic side view illustration of a luffing crane, denoted 200, featuring two exemplary gradually deployable side panel arrangements, denoted 250 and 251 , which are spontaneously fanned out as the luffing jib rises to form a differential surface area facing sidewind, constructed and operative in accordance with an embodiment of the present invention.
  • Luffing crane 200 includes mast 242, slewing unit 243, machinery arm 232, static counterweight 252, and luffing jib 204.
  • Side panels 250 and 251 are fanned out as luffing jib 204 rises, to form a differential surface area facing sidewind which expands as jib 204 is tilted up, and thereby change the sidewind drag- profile of jib 204.
  • Jib 204 is shown in three different postures: a low, almost horizontal, posture denoted 204, an interim posture denoted 204', and a raised, almost erect, posture denoted 204".
  • Fanning out side panels in the context of the invention may feature sail-like foldable stretchable fabric spanning above a horizontal "sail" boom.
  • the sail like may be polygonal (e.g., triangular, rectangular, or trapezoidal) or feature vertically stacked, card-like panels, which are spontaneously (by virtue of gravitational force) and gradually fanned out as luffing jib 204 rises, to form a differential surface area facing sidewind and thereby changing the drag-profile of the tilting jib 204 according to its angle of tilt.
  • a panel arrangement may feature commonly hinged cards or moved about a hinge at a common lowermost corner or location point. A multiplicity of such panel arrangements may be distributed along the jib.
  • panel arrangement 250 is disposed near the frontal remote head of jib 204, and panel arrangement 251 is disposed at some medial location over jib 204.
  • a respective guyline panel cord 254, 255 is anchored to a common anchoring location 256 which is fixed respective of the upper section of crane 200, rearward and above the jib pivot axis 258 (e.g., mounted at the top of strut 260), and is pulleyed at jib 204 at overhead respective locations 262, 263 right above the respective remote side of panel arrangements 250, 251 to connect to a remote side 259 of the panel arrangement 250 or 251.
  • Panel arrangements 250, 251 include vertically stacked card-like panels.
  • Arrangement 250 includes a lowermost card 264 and an uppermost card 266.
  • Arrangement 251 includes a lowermost card 265 and an uppermost card 267.
  • An expanded illustration of arrangement 250 is shown with greater detail in balloon 272.
  • Panel cards 264 and 266 of arrangement 250 and the cards in between are commonly hinged at a common lower rear corner 274 to jib 204.
  • Panel cards 268 and 270 of arrangement 251 and the cards in between are similarly commonly hinged at another respective common lower rear corner to jib 204.
  • the distancing between pulleys 262, 263 head and fixed anchoring location 256 gradually changes as jib 204 rotates, from the longest when jib is lowered to assume a horizontal posture (204) to the shortest when jib 204 is tilted up to assumes a stall or a near stall in an almost erect posture 204".
  • cord 254 or 255 When cord 254 or 255 is tautly stretched between the respective panels (264 to 266, or 268 to 270), which are allowed to rotate about their common hinge (274, or the respective hinge of arrangement 251 ), the difference in cord (254, 255) length (or any fracture thereof, as can be apportioned by an adequate pulley assembly) is conveyed to the portion of the cord 254, 255 stretched between the pulley at location 262, 263 and the lowest card 264, 268, which drops to remain in a horizontal posture despite the tilt of jib 204 (when jib 204 is horizontal, lowest card 264, 286 silhouette is fully contained within the side profile silhouette of jib 204), and thereby add its side panel area to the general side surface area of jib 204.
  • each arrangement 250, 251 The steeper the tilt of jib 204, the larger the surface area of the panel which is exposed to add to that of jib 204 side profile.
  • the other cards in the stack of each arrangement 250, 251 are fanned out by a partial rotation dictated by mechanical limiter (not shown) allowing each card to move within limits respective of a neighboring card or by merely passing the respective cord 254, 255 through upper remote corners 276 (for arrangement 250) of the cards, which force gradual rotation per order of the cards due to frictional forces or the shortest track of cord 254, 255, which is closest to its round winding.
  • the luffing crane tip-over balance features at least a movable counterweight to stabilize the crane and prevent it from tipping over due to scenarios such as a frontal wind gust or the pivoting of the luffing jib toward an erect posture.
  • the tip-over balance may further include an optional static counterweight to provide further stabilization of the luffing crane in such scenarios.
  • Figures 4A, 4B and 4C Figure 4A is a schematic side view illustration of a luffing crane, generally referenced 300, having a movable counterweight and a static counterweight with the luffing jib in a forwardly headed position, constructed and operative in accordance with an embodiment of the present invention.
  • Figure 4B is a schematic side view illustration of the luffing crane of Figure 4A with the luffing jib nearing a stalling posture, constructed and operative in accordance with an embodiment of the present invention.
  • Figure 4C is a side view illustration of a luffing crane, generally referenced 330, having a movable counterweight but no static counterweight, constructed and operative in accordance with an embodiment of the present invention.
  • luffing crane 300 includes a central mast 312 and a luffing jib 314, which is pivotable about a jib pivot axis 316, and which carries a load 318.
  • Luffing crane 300 further includes a movable counterweight, referenced 320, situated on a horizontally aligned arm 322 coupled with crane mast 312.
  • Luffing crane 300 further includes a fixed or static counterweight, referenced 324, situated on a horizontally aligned arm 326 coupled with crane mast.
  • fixed counterweight, 324 and arm 326 is configured above movable counterweight 320 and arm 322, although the relative positions may alternatively be reversed.
  • luffing jib 314 is aligned at a forwardly headed position, and movable counterweight is disposed at the rear edge of horizontal arm 322, behind (rearward) of jib pivot axis 316, such that crane 300 is stabilized by both movable counterweight 320 and fixed counterweight 324, both of which are rearward of jib pivot axis 316, while load 318 is hanging from the end of jib 314.
  • luffing jib 314 is aligned at an erect posture, at or nearing a stalling posture, and movable counterweight 320 is moved toward the front edge of horizontal arm 322, in front of (frontward) of jib pivot axis 316, such that crane 300 is stabilized by load 318 and movable counterweight 320 (both of which are frontward of jib pivot axis) and fixed counterweight 324 (which is rearward of jib pivot axis 316).
  • luffing crane 330 includes a central mast 332 and a luffing jib 334, which is pivotable about a jib pivot axis 336, and which carries a load 338.
  • Luffing crane 330 further includes a movable counterweight, referenced 340, situated on a horizontally aligned arm 342 coupled with crane mast 332.
  • luffing crane 330 does not include a fixed or static counterweight.
  • movable counterweight 340 When luffing jib 334 is aligned at an erect posture (depicted by solid lines), movable counterweight 340 is moved toward the front edge of horizontal arm 342, near but not in front of jib pivot axis 336, such that crane 300 is stabilized by load 338 (at the end of jib 314 frontward of jib pivot axis 336) and movable counterweight 340 near jib pivot axis 336).
  • movable counterweight 340 When luffing jib 334 is aligned at a forwardly headed position (depicted by dashed lines), movable counterweight 340 is disposed at the rear edge of horizontal arm 342, rearward of jib pivot axis 316, such that crane 330 is stabilized by load 338 (at the end of jib 314 frontward of jib pivot axis 336) and movable counterweight 340 (at the rear end of arm 344 rearward of jib pivot axis 336).

Abstract

A luffing crane which includes a luffing jib pivotable about a pivot axis in a front side of the crane and a tip-over balance that includes at least a movable counterweight. The movable counterweight is configured to move toward the front side of the crane when the jib pivots upwards toward a stalling posture, and further configured to move away from the front side of the crane when the jib pivots downwards to assume a forwardly headed horizontal position, so as to prevent the crane from tipping over when operating. The movable counterweight may move beyond the jib pivot axis such that when the luffing jib is nearing or at complete stall, the movable counterweight is positioned to the front of the jib pivot axis. The tip-over balance may further include a static counterweight located to the rear of the jib pivot axis, to provide further stabilization.

Description

LUFFING CRANE FEATURING TIPPING OVER BALANCE
FIELD OF THE INVENTION
The present invention relates generally to luffing cranes, and in particular to coping with tipping over due to luffing or wind.
BACKGROUND OF THE INVENTION
Luffing cranes feature a working arm in the form of a luffing boom or jib, which changes its tilt while lifting and moving loads, the loads are usually hoisted while hanging from the distal tip of the luffing jib or boom. The working arm of a tower crane is usually mounted atop a mast and is rotated by virtue of a swing bearing such as a slewing unit. A luffing jib may be tiltably mounted at the distal frontal tip of a main boom, which may be a horizontal main boom of the working arm (e.g., a luffing tower crane) or directly to a mobile vehicle (e.g., truck mounted crane or a crawler crane), which often feature a main pivotal boom which changes it tilt, in a manner similar to the tilting of the luffing jib, such that the working arm is a compound arm featuring two tilting sections coupled in a series (as is common with mobile cranes). Another variate is the level luffing crane. For the sake of simplicity, the term "luffing jib" will be used herein to describe all types of luffing arms, booms and jibs. As the luffing jib changes its tilt, the combined weight moment of the luffing jib and its hoisted load is changed. For stability, the sum of all moments about the base of the crane (e.g., it may be the location where luffing boom is mounted such as the mast), should be close to zero so that the crane does not tip over, or over overturn. The safety margin the maximal magnitude of load which is permitted to be lifted (the "rated load"), is some value less than the load that will cause the crane to tip, and depends on the balance of weights inflicted about the base of the crane. Accordingly, counter measures are installed over the crane to prevent tipping over, such as a heavy base, and for a tower cranes - a counter weight disposed at a short horizontal machinery arm (usually at its distal rear for greater moment). For balancing the changing moment of the luffing arm as it changes its tilt, sometimes a sliding counterweight trolley is runs along the machinery arm is moved to compensate for the changing moment of the luffing jib (with its load).
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is thus provided a luffing crane including a luffing jib pivotable about a jib pivot axis at a front side of the luffing crane, and a tip-over balance including a movable counterweight. The movable counterweight is configured to move toward the front side of the luffing crane when the luffing jib pivots upwards toward a stalling posture, and further configured to move away from the front side of the luffing crane when the luffing jib pivots downwards away from the stalling posture to assume a forwardly headed position, so as to prevent tipping over of the crane during its operation. The tip-over balance may further include a static counterweight, located to the rear of the jib pivot axis, such that the movable counterweight balances the luffing crane against the static counterweight when the luffing jib is near or at a stalling posture. The movable counterweight may be gradually moved toward the front side of the luffing crane when the luffing jib pivots upward toward a stalling posture, and the movable counterweight may be gradually moved away from the front side of the luffing crane when the luffing jib pivots downwards away from the stalling posture to assume a forwardly headed position. The movable counterweight may be configured to move beyond the jib pivot axis, such that when the luffing jib is nearing or at complete stall, the movable counterweight is positioned to the front of the jib pivot axis. The movable counterweight may be mounted on a movable- counterweight swing, rotatable in a vertical plane about a counterweight swing axis. The counterweight swing axis and the jib pivot axis may be a common axis. The swing may further include a swing frame pivotable about and extending from the swing axis, and the movable counterweight may be disposed on the swing frame, such that when the swing rotates, the movable counterweight swings below the swing axis. The movable counterweight may be configured to pivot below the swing axis when the luffing jib pivots above the jib pivot axis, such that the horizontal movements and displacements of the luffing jib and the movable counterweight are opposed. The movable counterweight may be configured to pivot from an uppermost rearmost location, through an interim lowermost location below the swing axis, and toward a frontmost location in front of the swing axis above the interim lowermost location, when the luffing jib pivots from a lowermost forwardmost horizontal posture and pivots upwards toward an uppermost rearmost posture at or nearing a stalling posture. The luffing crane may further include a coupling, configured to couple the luffing jib and the swing to synchronize directional rotations that accompany opposed horizontal movements of the luffing jib and the swing. The coupling may include a mechanical coupling; and/or a controlled drive for moving one of the luffing jib and the swing synchronously. The coupling may include a mechanical movement transfer member, such as a rod or a rope. The swing frame may include an upwardly extending upper swing ear, where the movement transfer member connects the front head of the luffing jib and the upper swing ear. The movable counterweight may be disposed below the axis, and the upper swing ear may protrudes above the swing, and when the movable counterweight moves forward, the upper swing ear pivots rearward, together with the upward movement of the luffing jib, and when the movable counterweight moves rearward, the upper swing ear pivots forward, together with the downward movement of the luffing jib. A drive of the luffing jib may be conveyed via the swing. The drive may include a piston coupled to the swing frame. The piston may be coupled at one end to a rearwardly extending machinery arm of the crane, and at another end to a forwardly extending girder of the frame, where an extension or a contraction of the piston moves the swing frame to pull, release to drop, or push the head of the luffing jib via the movement transfer member. The luffing crane may further include a crane hoisting hook hanging on a rope from the head of the luffing jib, where the crane hoisting hook is releasably secured to the movable counterweight when the luffing jib is nearing or at a stalling posture, and the movable counterweight is positioned to the front of the jib pivot axis. The tip-over balance may include at least one side-panel whose sidewind moment increases the sidewind moment of the luffing jib as the luffing jib rises, and decreases the sidewind moment of the luffing jib as the luffing jib descends, to compensate for the changing sidewind drag- profile of the luffing jib. The side-panel may include the side surface-area of a movable counterweight; a swing, a swing frame, and/or a retractably expandable side-panel. The retractably expandable side-panel may include at least one side panel which is fanned out as the luffing jib rises, to form a differential surface area facing sidewind which expands as the luffing jib is pivoted upwards, and retracts as the luffing jib is pivoted downwards.
In accordance with another aspect of the present invention, there is thus provided a method for preventing tipping over of a luffing crane. The method includes the procedures of: providing a luffing jib of the luffing crane, the luffing jib pivotable about a jib pivot axis at the front side of the luffing crane, and providing a tip-over balance of the luffing crane, the tip-over balance comprising a movable counterweight. The method further includes the procedures of: moving the movable counterweight toward a front side of the luffing crane, when the luffing jib pivots upwards toward a stalling posture, and moving the movable counterweight away from the front side of the luffing crane, when the luffing jib pivots downwards to assume a forwardly headed position. The tip-over balance may further include a static counterweight, located to the rear of the jib pivot axis, such that the movable counterweight balances the luffing crane against the static counterweight when the luffing jib is near or at a stalling posture. The movable counterweight may be configured to move beyond the jib pivot axis, such that when the luffing jib is nearing or at complete stall, the movable counterweight is positioned to the front of the jib pivot axis. The movable counterweight may be mounted on a movable-counterweight swing, rotatable in a vertical plane about a counterweight swing axis. The swing may further include a swing frame pivotable about and extending from the swing axis, and the movable counterweight may be disposed on the swing frame, such that when the swing rotates, the movable counterweight swings below the swing axis. The luffing crane may further include a coupling, configured to couple the luffing jib and the swing to synchronize directional rotations that accompany opposed horizontal movements of the luffing jib and the swing. The luffing crane may further include a crane hoisting hook hanging on a rope from the head of the luffing jib, where the crane hoisting hook is releasably secured to the movable counterweight when the luffing jib is nearing or at a stalling posture, and the movable counterweight is positioned to the front of the jib pivot axis. The tip-over balance may include at least one side-panel whose sidewind moment increases the sidewind moment of the luffing jib as the luffing jib rises, and decreases the sidewind moment of the luffing jib as the luffing jib descends, to compensate for the changing sidewind drag-profile of the luffing jib. The tip-over balance may include a retractably expandable side-panel which includes at least one side panel which is fanned out as the luffing jib rises, to form a differential surface area facing sidewind which expands as the luffing jib is pivoted upwards, and retracts as the luffing jib is pivoted downwards.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:
Figure 1 is a schematic side view illustration of a luffing crane having a counterweight swing for anti-back tipping, constructed and operative in accordance with an embodiment of the present invention;
Figure 2 is a schematic side view illustration of the luffing crane of Figure 1 illustrating division of rotational movements about a central axis into quadrants;
Figure 3 is a is a schematic side view illustration of a luffing crane featuring two exemplary gradually deployable side panel arrangements which are spontaneously fanned out as the luffing jib rises to form a differential surface area facing sidewind, constructed and operative in accordance with an embodiment of the present invention;
Figure 4A is a schematic side view illustration of a luffing crane having a movable counterweight and a static counterweight with the luffing jib in a forwardly headed position, constructed and operative in accordance with an embodiment of the present invention;
Figure 4B is a schematic side view illustration of the luffing crane of Figure 4A with the luffing jib nearing a stalling posture, constructed and operative in accordance with an embodiment of the present invention; and Figure 4C is a side view illustration of a luffing crane having a movable counterweight but no static counterweight, constructed and operative in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
In its broadest aspects the present invention discloses features with are directed at preventing the tipping over of a luffing crane. A luffing crane includes a working jib, which pivots about some pivot axis. By virtue of such pivoting, the gravitational moment and the wind drag profile of the jib, including its load (which is usually hanging from the remote jib head) is changed, which thereby may cause tipping over of the crane. The gravitational moment change is explained above. As the jib is pivoted to change stance or posture, e.g., raised or lowered, the wind drag profile which affects wind moments inflicted on the crane is altered as well, with respect to two horizontal wind directions relative to the jib positioning (i.e., its front head direction).
According to one aspect of the present invention, the jib profile surface area facing a "frontal-wind" (i.e., wind facing the head of the jib) or a "back-wind" or "rear-wind" (i.e., wind facing the rear of the crane away from the jib) is minimal when the jib is lowered to a horizontal stance pointing toward the front-wind (or away from the back-wind) and therefore front/back wind drag moment is minimal. The wind drag moment is maximal when the jib is pivoted to rise into an erect stance, up to a stall (or its closest allowed raised position nearing a stall), as the (almost) entire length of the jib profile faces the rear/front wind and builds up a large moment about the pivot axis of the jib or the entire crane. As a counterweight is often disposed at the rear of the crane, it is usually a front wind which is more prone to tip over the crane toward the back.
According to another aspect of the present invention, the jib surface area facing a side-wind (i.e., wind facing the side of the jib) inflicts another moment effect. To avoid tipping over to the side due to the large side surface area profile of cranes (e.g., formed by the jib and rear machinery arm with its counterweight), cranes are often designed to freely rotate in windy and stormy conditions. Such cranes are allowed to freely rotate in a horizontal plane about the swing bearing, such as the slewing unit, such that the wind rotates the crane in a manner similar to weathervanes. To achieve this, the side-wind drag profile of the frontal working arm (e.g., the front jib) should be significantly greater than that of the rear, machinery arm, for example twice as big, to ensure that the side-wind will always turn the crane to point with its jib head toward the wind. However, as the jib changes its tilt stance, the side-wind moment inflicted by the jib profile about the axis of horizontal rotation of the crane (e.g., the rotation axis of the slewing unit) is also changed. The side-wind horizontal rotation moment is maximal when the jib is lowered to a horizontal stance because the average radius away from the horizontal crane rotation axis is maximal. The side-wind horizontal rotation moment is minimal when the jib is tilted to rise toward a vertical stall, because the average radius away from the horizontal crane rotation axis is minimal (and null when the jib is at a complete stall). In order to avoid tipping over of the crane due to changing gravitational and wind-inflicted moments, and a luffing jib alters its tilt stance, the present invention provides for countermeasures that cancel out, at least to an effective extent, the altered moments. For simplicity, it assumed herein that the horizontal posture of a jib tilt is designed to best meet the optimal required moments of the crane.
According to one aspect of the present invention, a movable counterweight is maneuvered to move toward the front of the luffing crane as the jib is tilted or pivoted to rise upwards, where the counterweight is allowed to move beyond the jib pivot axis, such that when the jib is nearing or at a complete stall, the counterweight is disposed below or to the front of the jib pivot axis. The movable counterweight negates the jib gravitational moment, and as the jib approaches a stall and loses moment, so does the movable counterweight. Moving the counterweight towards the front and beyond the tilt axis, is particularly effective when an additional counterweight, which is fixed, is disposed at the rear machinery arm to allow tilting of the jib near a stall (where the jib gravitational moment is almost null) as the movable counterweight balances the crane against the fixed counterweight. Enabling tilting of the jib into an almost erect posture (i.e., in a raised and almost fully vertical position) is of particular significance for allowing safe hoisting and moving of a load near the axis or tilt (e.g., close to the mast of a tower crane), which is nowadays dramatically limited to relatively light loads due to the danger of topple down as the jib loses most of its moment upon approaching a stall. A further effect of this movable counterweight arrangement is the appropriate balancing of weights between the front and back, which can better confront the front wind moment inflicted by the raised jib. Without the movable counterweight located at the front, all of the crane's balancing weight resides with the fixed counterweight at the rear and a front wind gust hitting the erect jib may cause back topple down of the crane.
The luffing crane of the present invention includes a luffing jib, tiltable or pivotable about a jib pivot axis at a front side of the crane. The luffing crane further includes a tip-over balance, which includes at least a movable counterweight, configured to move toward the front side of the crane as the luffing jib pivots upwards toward a stalling posture, and configured to move away from the front side of the crane as the luffing jib pivots downwards away from stalling and toward assuming a forwardly- headed position. The movable counterweight is rotatable in a vertical plane about a counterweight swing axis, which may optionally be common with the jib tilt pivot axis. The luffing crane may further include a static counterweight, which may be disposed on a rear machinery arm.
Reference is now made to Figures 1 and 2. Figure 1 is a schematic side view illustration of a luffing crane, denoted 100, having a counterweight swing, denoted 102, for anti-back tipping, constructed and operative in accordance with an embodiment of the present invention. Figure 2 is a schematic side view illustration of the luffing crane of Figure 1 illustrating division of rotational movements about a central axis into quadrants. "Quadrant I" represents an upper front quadrant, "quadrant II" represents an upper rear quadrant, "quadrant III" represents a lower rear quadrant, and "quadrant IV" represents a lower front quadrant. The quadrants are divided by the straight perforated bold lines and are defined respective of vertical rotation along the round perforated line on the plane of the drawing sheet or in parallel thereto, about an axis of rotation denoted 106.
Referring to Figures 1 and 2, luffing crane 100 includes a luffing jib 104, which is tiltable or pivotable in the upper front quadrant I at the front side of crane 100, about a jib pivot axis 106. Luffing crane 100 further includes a tip-over balance in the form of counterweight swing 102, wherein the balance is gradually deployed, as luffing jib 104 pivots upward toward a stalling posture (posture 1 12), and retracts, as luffing jib 104 tilts down away from a stalling posture and toward a forwardly-headed horizontal position. Luffing crane 100 usually includes a static counterweight 152, which may be disposed on a rear machinery arm 132.
Swing 102 includes a movable counterweight 108, also referred to herein as a "swinging-counterweight" 108, which is disposed on swing frame 1 10 extending from swing axis 106 to displace swinging- counterweight 108 with respective of axis 106, such that when swing 102 rotates, swinging-counterweight 108 swings below swing axis 106, dwelling in the lower rear quadrant III and lower front quadrants IV of the vertical plane of rotation.
Swing frame 1 10 and luffing jib 104 rotate vertically in similar rotational directions, namely in parallel rotational directions (depicted by the round perforated bold line in Figure 2) or in common directions in parallel or common vertical plane(s), when considered from a side point of view. It is noted, however, that although the pivot axis 106 is shown as a common axis for swing 102 and luffing jib 104, the axis for each of these two rotating elements 102 and 104 may be separately spaced, distanced upwards, frontally or rearwardly, relative to the other axis, and the determination of the positioning of swing 102 and jib 104 (i.e., quadrant, above/below/rearward/forward with respect to an axis is taken only with relation to the respective axis (of swing 102 or of jib 104). While luffing jib 104 always rotates above its tilt pivot axis 106, swinging-counterweight 108 always rotates below its swing axis 106, such that the horizontal movements and displacements of jib 104 and swinging-counterweight 108 are always opposed (taken along a line extending from the front at the right of the drawing sheet to the rear at the left of the drawing sheet). Accordingly, when luffing jib 104 rotates from its lowermost forwardmost horizontal posture (similar to the one shown in Figure 1 ) and tilts upwards toward its uppermost rearmost posture (i.e., a stall), denoted by perforated line 1 12, swinging-counterweight 108 rotates from its uppermost rearmost location (similar to the one shown in Figure 1 ), through its interim lowermost location right below swing axis 106 toward its frontmost location in front of swing axis 106, denoted by perforated line 1 14, somewhat above its interim lowermost location (where frame 1 10 assumes the posture denoted by perforated lines 1 15).
Coupling of these similar directional rotations (that accompany opposed horizontal movements) may be provided by a mechanical coupling of luffing jib 104 and swing 102, or by otherwise-controlled movement that synchronizes the rotations of one of swing 102 and jib 104, with the rotation of the other. A mechanical coupling may be provided by coupling swing 102 and jib 104 with a movement transfer member, such as a rod or a rope. For example, member 1 16 may provide such a mechanical coupling, where member 1 16 can connect between the tip of luffing jib 104 front head (extending to the right of the drawing) and an upwardly extending upper swing ear of swing frame 1 10, such as upper swing ear 1 18, at joint 120. While swinging-counterweight 108 is disposed below swing axis 106, upper swing ear 1 18 protrudes above swing axis 106. Therefore, when swinging- counterweight 108 rotates forward, upper swing ear 118 rotates rearward (arrow 122), together with the rearward (and upward) movement (of the head) of luffing jib 104 (arrow 124). Conversely, when swinging- counterweight 108 rotates rearward, upper swing ear 1 18 rotates forward, together with the forward (and downward) movement of luffing jib 104. Luffing jib 104 is usually heavier than swing 102 (including the weight of swinging- counterweight 108), and the jib tilt is usually dictated by a jib tilt drive, e.g., for the sake of hoisting an moving a load hanging on the jib head. The movement transfer member 1 16 pulls swing 102 by swing upper ear 1 18 when luffing jib 104 descends toward a horizontal posture, and releases swing 102 to drop, or pushes swing 102 by swing upper ear 1 18 when luffing jib 104 ascends toward an erect posture 1 12. In such a case a rigid rod must be utilized as the movement transfer member 1 16 for moving swing weight 108 toward the front because a rope would not push swing 108 beyond its lowermost position below swing axis 106. However, a rope (a guyline, tension member, or cable tautly stretched between swing upper- ear 1 18 and the head of luffing jib 104) may be used when the drive of jib 104 is conveyed via swing 102, because the rope would remain tautly stretched as luffing jib 104 never passes over the fulcrum of the jib rotation (jib pivotal axis 106). In this case a drive, such as piston 126 is coupled to swing frame 1 10, e.g., at joint 128 disposed in a forwardly extending girder 130 and thus swing frame 1 10 pulls or releases to drop (pushes only via a rod 1 16) the head of luffing jib 104 via linking member 1 16 (a rod or a rope). The drive may feature other means for swinging counterweight swing 102, and thereby to pivot luffing jib 104. Piston 126 may be hinged at joint 128 to girder 130 at one end and to a rearwardly extending machinery arm 132 at another end 134. Frame 1 10 may further feature support struts or girders that strengthen the frame to withstand the inflicted forces, such as strut 136 which connects ear 1 18 and girder 130 with arm 138 on which counterweight 108 is mounted. A further measure may take advantage of the forward disposition 1 14 of movable counterweight 108 which is convenient for securing crane hook 140 which hangs from the almost erect luffing jib 104 and thereby prevent tipping back of the erect jib 104, at perforated positioning 1 12 (even when mast 142 or other part of crane 100 remain intact) upon impact of a front wind gust. In this posture, movement transfer member 1 16 is positioned along perforated line 144, and the load hoist rope along perforated line 146. When jib 104 is further erected or closer to a full stall, the hoist rope is shown hanging along perforated line 148 with its hook denoted as 150.
When swinging counterweight 108 is maneuvered to move toward the front as jib 104 is pivoted upwards, swinging counterweight 108 is allowed to move beyond jib pivot axis 106, such that when jib 104 is nearing or at a complete stall (posture 1 12), counterweight 108 is disposed below or to the front of tilt axis 106. Swinging counterweight 108 negates the jib gravitational moment, and as jib 104 approaches a stall (posture 1 12) and loses moment, so does swinging counterweight 108. Moving swinging counterweight 108 toward the front and beyond tilt axis 106, is particularly effective when fixed counterweight 152 is disposed at the rear of machinery arm 132, to allow tilting of jib 104 near a stall (posture 1 12, where the gravitational moment of jib 104 is almost null) as swinging counterweight 108 at posture 1 14 balances crane 100 against fixed counterweight 152. Enabling the pivoting of jib 104 into an almost erect posture 1 12 is of particular significance for allowing safe hoisting and moving of a load near axis 106 of tilt, e.g., close to mast 142 of a tower crane (or slewing unit 143), represented by the hoist rope at position 148 and the hook at position 150, which is nowadays dramatically limited for conventional cranes to relatively light loads due to the danger of topple down as jib 104 loses most of its moment upon approaching a stall. A further effect of this movable counterweight arrangement is the appropriate balancing of weights between the front and back, which can better confront the front wind moment inflicted by the raised jib 104. Without the movable counterweight 108 located at the front at position 1 14, the entire balancing weight of crane 100 resides with fixed counterweight 152 at the rear, and a front wind gust hitting the erect jib 104 may cause back topple down of crane 100.
According to another aspect of the invention, a differential side wind drag altering measure is applied. For example, the tip-over balance may include at least one side-panel whose sidewind moment increases the sidewind moment of luffing jib 104 as luffing jib 104 rises, and decreases the sidewind moment of luffing jib 104 as luffing jib 104 descends, to thereby compensate for the changing sidewind drag-profile of the luffing jib. The side-panel may feature the side surface-area of a movable object the moves from the rear to the front and back in a counter-correlation to the rearward and forward movements of luffing jib 104. One location changing side panel may be provided by the side surface area of the moving components of the embodiment of Figure 1. For example, the side surface area of a movable counterweight such as counterweight 108, a counterweight-swing such swing 102 or counterweight swing frame 1 10. Swing 102 or frame 1 10 may be fully or partially covered or shielded by a panel facing the sidewind.
Another such side panel that changes the sidewind moment may feature a retractably expandable side-panel. In one embodiment, the tip over balance measure includes at least one side panel which is fanned out as the luffing jib rises, to form a differential surface area facing sidewind which expands as the jib is tilted up, and thereby change the sidewind drag- profile of the jib. Reference is now made to Figure 3, which is a schematic side view illustration of a luffing crane, denoted 200, featuring two exemplary gradually deployable side panel arrangements, denoted 250 and 251 , which are spontaneously fanned out as the luffing jib rises to form a differential surface area facing sidewind, constructed and operative in accordance with an embodiment of the present invention. Luffing crane 200 includes mast 242, slewing unit 243, machinery arm 232, static counterweight 252, and luffing jib 204. Side panels 250 and 251 are fanned out as luffing jib 204 rises, to form a differential surface area facing sidewind which expands as jib 204 is tilted up, and thereby change the sidewind drag- profile of jib 204. Jib 204 is shown in three different postures: a low, almost horizontal, posture denoted 204, an interim posture denoted 204', and a raised, almost erect, posture denoted 204".
Fanning out side panels in the context of the invention may feature sail-like foldable stretchable fabric spanning above a horizontal "sail" boom. The sail like may be polygonal (e.g., triangular, rectangular, or trapezoidal) or feature vertically stacked, card-like panels, which are spontaneously (by virtue of gravitational force) and gradually fanned out as luffing jib 204 rises, to form a differential surface area facing sidewind and thereby changing the drag-profile of the tilting jib 204 according to its angle of tilt. A panel arrangement may feature commonly hinged cards or moved about a hinge at a common lowermost corner or location point. A multiplicity of such panel arrangements may be distributed along the jib. With reference to Figure 3, panel arrangement 250 is disposed near the frontal remote head of jib 204, and panel arrangement 251 is disposed at some medial location over jib 204. For each arrangement, 250, 251 , a respective guyline panel cord 254, 255 is anchored to a common anchoring location 256 which is fixed respective of the upper section of crane 200, rearward and above the jib pivot axis 258 (e.g., mounted at the top of strut 260), and is pulleyed at jib 204 at overhead respective locations 262, 263 right above the respective remote side of panel arrangements 250, 251 to connect to a remote side 259 of the panel arrangement 250 or 251. Panel arrangements 250, 251 include vertically stacked card-like panels. Arrangement 250 includes a lowermost card 264 and an uppermost card 266. Arrangement 251 includes a lowermost card 265 and an uppermost card 267. An expanded illustration of arrangement 250 is shown with greater detail in balloon 272. Panel cards 264 and 266 of arrangement 250 and the cards in between are commonly hinged at a common lower rear corner 274 to jib 204. Panel cards 268 and 270 of arrangement 251 and the cards in between are similarly commonly hinged at another respective common lower rear corner to jib 204. The distancing between pulleys 262, 263 head and fixed anchoring location 256 gradually changes as jib 204 rotates, from the longest when jib is lowered to assume a horizontal posture (204) to the shortest when jib 204 is tilted up to assumes a stall or a near stall in an almost erect posture 204". When cord 254 or 255 is tautly stretched between the respective panels (264 to 266, or 268 to 270), which are allowed to rotate about their common hinge (274, or the respective hinge of arrangement 251 ), the difference in cord (254, 255) length (or any fracture thereof, as can be apportioned by an adequate pulley assembly) is conveyed to the portion of the cord 254, 255 stretched between the pulley at location 262, 263 and the lowest card 264, 268, which drops to remain in a horizontal posture despite the tilt of jib 204 (when jib 204 is horizontal, lowest card 264, 286 silhouette is fully contained within the side profile silhouette of jib 204), and thereby add its side panel area to the general side surface area of jib 204. The steeper the tilt of jib 204, the larger the surface area of the panel which is exposed to add to that of jib 204 side profile. The other cards in the stack of each arrangement 250, 251 are fanned out by a partial rotation dictated by mechanical limiter (not shown) allowing each card to move within limits respective of a neighboring card or by merely passing the respective cord 254, 255 through upper remote corners 276 (for arrangement 250) of the cards, which force gradual rotation per order of the cards due to frictional forces or the shortest track of cord 254, 255, which is closest to its round winding.
In general, the luffing crane tip-over balance features at least a movable counterweight to stabilize the crane and prevent it from tipping over due to scenarios such as a frontal wind gust or the pivoting of the luffing jib toward an erect posture. The tip-over balance may further include an optional static counterweight to provide further stabilization of the luffing crane in such scenarios. Reference is made to Figures 4A, 4B and 4C. Figure 4A is a schematic side view illustration of a luffing crane, generally referenced 300, having a movable counterweight and a static counterweight with the luffing jib in a forwardly headed position, constructed and operative in accordance with an embodiment of the present invention. Figure 4B is a schematic side view illustration of the luffing crane of Figure 4A with the luffing jib nearing a stalling posture, constructed and operative in accordance with an embodiment of the present invention. Figure 4C is a side view illustration of a luffing crane, generally referenced 330, having a movable counterweight but no static counterweight, constructed and operative in accordance with an embodiment of the present invention. Referring to Figures 4A and 4B, luffing crane 300 includes a central mast 312 and a luffing jib 314, which is pivotable about a jib pivot axis 316, and which carries a load 318. Luffing crane 300 further includes a movable counterweight, referenced 320, situated on a horizontally aligned arm 322 coupled with crane mast 312. Luffing crane 300 further includes a fixed or static counterweight, referenced 324, situated on a horizontally aligned arm 326 coupled with crane mast. In the example provided, fixed counterweight, 324 and arm 326 is configured above movable counterweight 320 and arm 322, although the relative positions may alternatively be reversed. In the configuration of Figure 4A, luffing jib 314 is aligned at a forwardly headed position, and movable counterweight is disposed at the rear edge of horizontal arm 322, behind (rearward) of jib pivot axis 316, such that crane 300 is stabilized by both movable counterweight 320 and fixed counterweight 324, both of which are rearward of jib pivot axis 316, while load 318 is hanging from the end of jib 314. In the configuration of Figure 4B, luffing jib 314 is aligned at an erect posture, at or nearing a stalling posture, and movable counterweight 320 is moved toward the front edge of horizontal arm 322, in front of (frontward) of jib pivot axis 316, such that crane 300 is stabilized by load 318 and movable counterweight 320 (both of which are frontward of jib pivot axis) and fixed counterweight 324 (which is rearward of jib pivot axis 316). Referring to Figure 4C, luffing crane 330 includes a central mast 332 and a luffing jib 334, which is pivotable about a jib pivot axis 336, and which carries a load 338. Luffing crane 330 further includes a movable counterweight, referenced 340, situated on a horizontally aligned arm 342 coupled with crane mast 332. However luffing crane 330 does not include a fixed or static counterweight. When luffing jib 334 is aligned at an erect posture (depicted by solid lines), movable counterweight 340 is moved toward the front edge of horizontal arm 342, near but not in front of jib pivot axis 336, such that crane 300 is stabilized by load 338 (at the end of jib 314 frontward of jib pivot axis 336) and movable counterweight 340 near jib pivot axis 336). When luffing jib 334 is aligned at a forwardly headed position (depicted by dashed lines), movable counterweight 340 is disposed at the rear edge of horizontal arm 342, rearward of jib pivot axis 316, such that crane 330 is stabilized by load 338 (at the end of jib 314 frontward of jib pivot axis 336) and movable counterweight 340 (at the rear end of arm 344 rearward of jib pivot axis 336).
While certain embodiments of the disclosed subject matter have been described, so as to enable one of skill in the art to practice the present invention, the preceding description is intended to be exemplary only. It should not be used to limit the scope of the disclosed subject matter, which should be determined by reference to the following claims.

Claims

1. Luffing crane comprising:
a luffing jib pivotable about a jib pivot axis at a front side of the luffing crane; and
a tip-over balance, comprising a movable counterweight, wherein the movable counterweight is configured to move toward the front side of the luffing crane when said luffing jib pivots upwards toward a stalling posture, and wherein the movable counterweight is further configured to move away from the front side of the luffing crane when the luffing jib pivots downwards away from the stalling posture to assume a forwardly headed position, so as to prevent tipping over of the crane during its operation.
2. The luffing crane of claim 1 , wherein the tip-over balance further comprises a static counterweight, located to the rear of the jib pivot axis, such that the movable counterweight balances the luffing crane against the static counterweight when the luffing jib is near or at a stalling posture.
3. The luffing crane of claim 1 , wherein the movable counterweight is gradually moved toward the front side of the luffing crane when the luffing jib pivots upward toward a stalling posture, and wherein the movable counterweight is gradually moved away from the front side of the luffing crane when the luffing jib pivots downwards away from the stalling posture to assume a forwardly headed position.
4. The luffing crane of claim 1 , wherein the movable counterweight is configured to move beyond the jib pivot axis, such that when the luffing jib is nearing or at complete stall, the movable counterweight is positioned to the front of the jib pivot axis.
5. The luffing crane of claim 1 , wherein the movable counterweight is mounted on a movable counterweight swing, rotatable in a vertical plane about a counterweight swing axis.
6. The luffing crane of claim 5, wherein the counterweight swing axis and the jib pivot axis comprise a common axis.
7. The luffing crane of claim 5, wherein the swing further comprises a swing frame pivotable about and extending from the swing axis, and wherein the movable counterweight is disposed on the swing frame, such that when the swing rotates, the movable counterweight swings below the swing axis.
8. The luffing crane of claim 5, wherein the movable counterweight is configured to pivot below the swing axis when the luffing jib pivots above the jib pivot axis, such that the horizontal movements and displacements of the luffing jib and the movable counterweight are opposed.
9. The luffing crane of claim 8, wherein the movable counterweight is configured to pivot from an uppermost rearmost location, through an interim lowermost location below the swing axis, and toward a frontmost location in front of the swing axis above the interim lowermost location, when the luffing jib pivots from a lowermost forwardmost horizontal posture and pivots upwards toward an uppermost rearmost posture at or nearing a stalling posture.
10.. The luffing crane of claim 5, further comprising a coupling, configured to couple the luffing jib and the swing and to synchronize the directional rotations that accompany opposed horizontal movements of the luffing jib and the swing.
1 1. The luffing crane of claim 10, wherein the coupling comprises at least one of: a mechanical coupling; and a controlled drive for moving one of the luffing jib and the swing synchronously.
12. The luffing crane of claim 10, wherein the coupling comprises a mechanical movement transfer member.
13. The luffing crane of claim 12, wherein the swing frame comprises an upwardly extending upper swing ear, and wherein the movement transfer member connects the front head of the luffing jib and the upper swing ear.
14. The luffing crane of claim 13, wherein the movable counterweight is disposed below the axis, and the upper swing ear protrudes above the swing, and when the movable counterweight moves forward, the upper swing ear pivots rearward, together with the upward movement of the luffing jib, and when the movable counterweight moves rearward, the upper swing ear pivots forward, together with the downward movement of the luffing jib.
15. The luffing crane of claim 12, wherein a drive of the luffing jib is conveyed via the swing.
16. The luffing crane of claim 15, wherein the drive comprises a piston coupled to the swing frame.
17. The luffing crane of claim 16, wherein the piston is coupled at one end to a rearwardly extending machinery arm of the crane, and at another end to a forwardly extending girder of the frame, wherein an extension or a contraction of the piston moves the swing frame to pull, release to drop, or push the head of the luffing jib via the movement transfer member.
18. The luffing crane of claim 1 , further comprising a crane hoisting hook hanging on a rope from the head of the luffing jib, the crane hoisting hook releasably secured to the movable counterweight when the luffing jib is nearing or at a stalling posture, and the movable counterweight is positioned to the front of the jib pivot axis.
19. The luffing crane of claim 1 , wherein the tip-over balance comprises at least one side-panel whose sidewind moment increases the sidewind moment of the luffing jib as the luffing jib rises, and decreases the sidewind moment of the luffing jib as the luffing jib descends, to compensate for the changing sidewind drag-profile of the luffing jib.
20. The luffing crane of claim 19, wherein the side-panel comprises the side surface-area of at least one selected from the group consisting of: a movable counterweight as of claim 4; a swing as of claim 5; a swing frame as of claim 7; and a retractably expandable side-panel.
21. The luffing crane of claim 20, wherein the retractably expandable side- panel comprises at least one side panel which is fanned out as the luffing jib rises, to form a differential surface area facing a sidewind which expands as the luffing jib is pivoted upwards, and retracts as the luffing jib is pivoted downwards.
22. A method for preventing tipping over of a luffing crane, the method comprising the procedures of:
providing a luffing jib of the luffing crane, the luffing jib pivotable about a jib pivot axis at the front side of the luffing crane;
providing a tip-over balance of the luffing crane, the tip-over balance comprising a movable counterweight;
moving the movable counterweight toward a front side of the luffing crane, when the luffing jib pivots upwards toward a stalling posture; and
moving the movable counterweight away from the front side of the luffing crane, when the luffing jib pivots downwards to assume a forwardly headed position.
23. The method of claim 22, wherein the tip-over balance further comprises a static counterweight, located to the rear of the jib pivot axis, such that the movable counterweight balances the luffing crane against the static counterweight when the luffing jib is near or at a stalling posture.
24. The method of claim 22, wherein the movable counterweight is configured to move beyond the jib pivot axis, such that when the luffing jib is nearing or at complete stall, the movable counterweight is positioned to the front of the jib pivot axis.
25. The method of claim 22, wherein the movable counterweight is mounted on a movable counterweight swing, rotatable in a vertical plane about a counterweight swing axis.
26. The method of claim 25, wherein the swing further comprises a swing frame pivotable about and extending from the swing axis, and wherein the movable counterweight is disposed on the swing frame, such that when the swing rotates, the movable counterweight swings below the swing axis.
27. The method of claim 25, further comprising a coupling, configured to couple the luffing jib and the swing and to synchronize the directional rotations that accompany opposed horizontal movements of the luffing jib and the swing.
28. The method of claim 22, further comprising a crane hoisting hook hanging on a rope from the head of the luffing jib, the crane hoisting hook releasably secured to the movable counterweight when the luffing jib is nearing or at a stalling posture, and the movable counterweight is positioned to the front of the jib pivot axis.
29. The method of claim 22, wherein the tip-over balance comprises at least one side-panel whose sidewind moment increases the sidewind moment of the luffing jib as the luffing jib rises, and decreases the sidewind moment of the luffing jib as the luffing jib descends, to compensate for the changing sidewind drag-profile of the luffing jib.
30. The method of claim 29, wherein the tip-over balance comprises a retractably expandable side-panel comprising at least one side panel which is fanned out as the luffing jib rises, to form a differential surface area facing a sidewind which expands as the luffing jib is pivoted upwards, and retracts as the luffing jib is pivoted downwards.
PCT/IL2019/051252 2018-11-18 2019-11-17 Luffing crane featuring tipping over balance WO2020100145A1 (en)

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FR3106129A1 (en) * 2020-01-14 2021-07-16 Manitowoc Crane Group France Luffing jib tower crane equipped with an adjustable wind grip system
DE102020107417A1 (en) 2020-03-18 2021-09-23 Liebherr-Werk Biberach Gmbh Tower crane with adjustable counter ballast

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CN2725255Y (en) * 2004-09-16 2005-09-14 赵元黎 Rigid driving arm frame system variable amplitude crane
DE60113546T2 (en) * 2000-07-11 2006-06-29 Jean-Marc Yerly CRANE WITH KRANARM CONSISTING OF MEMBERS
CN102303821A (en) * 2011-08-24 2012-01-04 江运金 Luffing tower crane with balanced type suspension arm based on traction luffing of steel rope

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US970773A (en) * 1910-01-29 1910-09-20 Hamilton Neil Wylie Jib-crane.
JPH05201694A (en) * 1992-01-24 1993-08-10 Hitachi Koki Co Ltd Controller for suspending machine
DE60113546T2 (en) * 2000-07-11 2006-06-29 Jean-Marc Yerly CRANE WITH KRANARM CONSISTING OF MEMBERS
CN2725255Y (en) * 2004-09-16 2005-09-14 赵元黎 Rigid driving arm frame system variable amplitude crane
CN102303821A (en) * 2011-08-24 2012-01-04 江运金 Luffing tower crane with balanced type suspension arm based on traction luffing of steel rope

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3106129A1 (en) * 2020-01-14 2021-07-16 Manitowoc Crane Group France Luffing jib tower crane equipped with an adjustable wind grip system
EP3851405A1 (en) * 2020-01-14 2021-07-21 Manitowoc Crane Group France Lifting boom tower crane provided with an adjustable wind load system
US11673776B2 (en) 2020-01-14 2023-06-13 Manitowoc Crane Group France Luffing boom tower crane equipped with an adjustable wind load system
DE102020107417A1 (en) 2020-03-18 2021-09-23 Liebherr-Werk Biberach Gmbh Tower crane with adjustable counter ballast

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