US3767061A - Tower crane with load limiting apparatus - Google Patents

Tower crane with load limiting apparatus Download PDF

Info

Publication number
US3767061A
US3767061A US00220609A US3767061DA US3767061A US 3767061 A US3767061 A US 3767061A US 00220609 A US00220609 A US 00220609A US 3767061D A US3767061D A US 3767061DA US 3767061 A US3767061 A US 3767061A
Authority
US
United States
Prior art keywords
load
boom
tower crane
lmax
amax
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
US00220609A
Other languages
English (en)
Inventor
H Tax
R Franke
K Hosler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Application granted granted Critical
Publication of US3767061A publication Critical patent/US3767061A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • B66C23/88—Safety gear
    • B66C23/90—Devices for indicating or limiting lifting moment

Definitions

  • ABSTRACT The load limiting apparatus of a tower crane, which inactivates the load lifting winch when a predetermined load is exceeded, is controlled in such a manner that the maximum permissible load L,,,,, varies with the angle a between the boom and the horizontal, and the corresponding horizontal spacing a between the projections of the boom pivot and of the depending load carrying cable in a manner to satisfy the equation L,,,,,,, L k,a wherein L is thevalue of L when a is at a minimum, and k is a proportionality factor and constant for all practical purposes. Under these conditions the maximum tensile stress developed in the boom is constant, at least for an optimum boom length, while a varies between a,,,,,, and a and the structural strength of the material can be fully utilized under all conditions.
  • SHEET 30F 7 SNOl 'uvow oaiuwaad WW RADIAL RANGE (m Fig. 3
  • This invention relates to tower cranes, and particularly to tower cranes equipped with an improved load limiting apparatus.
  • a tower crane may safely be loaded to a maximum load L,,,',;, determined by the equation ,...r L4 i wherein L is the permissible maximum load when a is a,,,,,,, that is, the spacing between the load and the pivot of the boom, projected into a common horizontal plane, is at the smallest available value, and k is proportionality factor which is practically constant.
  • L is the permissible maximum load when a is a,,,,,, that is, the spacing between the load and the pivot of the boom, projected into a common horizontal plane, is at the smallest available value
  • k proportionality factor which is practically constant.
  • the boom employed is preferably loaded in compression only and free from bending stresses other than those caused by its own weight.
  • FIG. 1 shows a tower crane equipped with the load limiting device of the invention
  • FIG. 2 shows a portion of the tower crane of FIG. 1 including the load limiting device of the invention.
  • FIG. 3 is a diagram illustrating the relationship of the maximum permissible load L and the horizontal spacing a of the load from the tower for'booms of different length in a tower crane equipped with a conventional load limiting device;
  • FIG. 4 illustrates the relationship of permissible load L and the horizontal spacing of the load from the tower for a tower crane equipped with a protection device of the invention, but otherwise analogous to the crane referred to in FIG. 3;
  • FIG. 5 shows the improvement of the load bearing capacity of the crane of the invention as compared to an otherwise analogous crane as a function of the angle of inclination of two booms of different length;
  • FIG. 6 illustrates the maximum tensile stresses in booms of different length in a crane equipped with the conventional load limiting device as a function of the inclination of the boom;
  • FIG. 7 shows the corresponding maximum tensile stresses in a crane according to the invention.
  • the tower crane of the invention illustrated in FIG. 1 has'a base structure 10 including a vehicular lower part 12 whose center portion 14 provides a bearing for a turntable 16.
  • the tower proper 18 of the crane is mounted on the'turntable l6 and is a vertical column having an obliquely inclined head portion 20.
  • the boom 22 of the crane is a compression member, not subjected to significant bending stresses, and one of its ends is secured to the upper end of the column 18 by a pivot 24.
  • the boom 22 is angularly adjusted on the pivot 24 by a cable or cable system 26 which is operated by a winch 28 on the turntable 1 6 and, passing over guide pulleys 30, 34 on a rearwardly extending jib 32 and on the head portion 20, it is attached to the boom 22 near its front or free end by a suitable fastener 36.
  • One end of the jib 32 is suspended from the head portion 20 by a cable 33.
  • a load may be raised or lowered by a lifting cable 38 operated by a winch 40 on the turntable 16.
  • the cable 38 is trained over guide pulleys 42, 44, 46 respectively mounted on the jib 32, the head portion 20, and the front end of the boom 22, and a reversing pulley on a hook 48 to be fastened to an attachment 50 on the boom 22 near the free end of the latter.
  • the tower column 18 has upright front and rear frames 52, 54 which are connected by oblique braces 53 and by horizontal struts 3 of which one, of U-shaped cross section, is shown in FIG. 2.
  • the end of the jib 32 remote from the cable 33 is fastened to the illustrated strut 3 by a pivot 4.
  • the guide pulley 42 is mounted on a bracket 56 attached to the jib 32 by a pivot pin 58.
  • a switch actuating abutment 60 is mounted on the bracket 56 adjacenta switch 62 arranged on a post 63 which is fixedly mounted on the jib 32.
  • the abutment 60 is normally held out of engagement with the switch 62, as shown in FIG. 2, by a helical compression spring 64 coiled about a pin 68.
  • the two axial ends of the spring 64 respectively abut against a guide sleeve 66 pivotally mounted on the bracket 56 and slidably receiving the pin 68, and against a collar 70 on the pin'68.
  • a rod 72 coaxially attached to the pin 68 is secured to the boom 22 by a pivot pin 74.
  • the pivot pin which attaches the sleeve 66 to the bracket 56 may be shifted between several bearing openings in the bracket 56 for adapting the load limiting device to dif ferent boom lengths.
  • the tension in the load lifting cable 38 tends to pivot the bracket 56 clockwise as viewed in FIG. 2.
  • the switch 62 operates a relay circuit in a control box 76 in a conventional manner and stops the winch 40. A load exceeding the maximum load determined by the limiting device thus cannot be lifted.
  • FIG. 3 illustrates the relationship between the maximum permissible load L and the effective horizontal spacing a of 'the'load from a crane tower equipped with conventional load limiting devices.
  • the full length of the boom is assumed to be 45 meters, and separate curves are shown for operation at full boom length (100 percent) and with booms shortened in steps of one-eighth to 87.5 percent, 75 percent, and 62.5 percent respectively.
  • the abscissa indicates the distance a (see FIG. 1) between the pivot 24 and the load hook 48 projected into a horizontal plane, and it varies for a boom of a given length with the angle a of boom inclination.
  • the ordinate is calibrated in metric tons.
  • the curves representing the relationship between maximal permissible load and horizontal spacing of the load from the pivot 24 of the boom 22 on the tower 18 are curves whose concave faces are directed toward higher loads. They are characteristic of tower cranes equipped with conventional load limiting devices.
  • L is the maximum load capacity to be determined, and L is the maximum load permissible for minimum effective horizontal spacing a.
  • the smallest available, horizontal spacing a of the hook 48 and the pivot 24 is 12.9 meters; k is a constant proportinality factor.
  • equation (I) may be rewritten as mnr orna: 1 cos a
  • the force exerted on the guide pulley 42 by the load lifting cable 38 is directly proportional to the load supported by the cable.
  • the corresponding effective force R exerted by the cable on the pulley reaches the value and I k L k k lcos a (IV)
  • FIG. 5 illustrates the percentage increase in load bearing capacity as a function of the angle of boom inclination when the conventional load limiting device is replaced by that of the invention.
  • FIG. 5 has been derived from the values of FIGS. 3 and 4 for efi'ective boom lengths of 100 percent and 87.5 percent. It is evident that the maximum permissible load L is greatly increased for values of a which are intermediate the maximum and minimum.
  • FIG. 6 illustrates the variation in the maximum tensile stress in the boom 22 when the crane is equipped with the known load limiting device which is characterized by the curves of FIG. 3.
  • the actual stresses are well below the permissible stress in the curve illustrating the condition of the boom of full length (100 percent), and the stresses are even lower in shorter booms, the permissible stress having a value of 2,400 kp/mm in this instance.
  • FIG. 7 shows the maximum tensile stresses generated in booms of different lengths with the load limiting device of the invention whose characteristics are illustrated by FIG. 4.
  • the actual stresses generated in the boom of 100 percent length when the crane is operated at the full load tolerated by the limiting device differ from the design load over the entire range of boom inclination by not more than 5 percent so that the material of the boom is utilized to best advantage.
  • k was considered to be absolutely constant, yet, many of the advantages of this invention are available when k, is at least substantially constant, but varies due to secondary factors, not considered above, to let the values of L differ by not more than 10 percent, and preferably not more than 5 percent from the values of L defined by Equation (I) when k is absolutely constant while a varies between a the horizontal spacing of the lifting cable 38 and the pivot 34 when the boom is as close to a horizontal position as the crane permits, and a the horizontal spacing of the cable 38 and the pivot 24 when the boom is as close to a vertical position as is possible.
  • the material of construction of the boom (and of the column 18) is used to best advantage if the load carried by the cable 38 is limited in such a manner that the maximum tensile stress at permitted maximal loading of the cable is precisely constant and equal to the maximum design load. It would not be economical under most conditions to design a tower crane to such a precise performance, and the major advantages of this invention are available if the tensile stress in the boom differs by not more than plus/minus 10 percent, and preferably plus/minus 5 percent from a constant value while the spacing a varies between a and a v I
  • the load limiting device of the invention illustrated in FIG. 2 is, in effect, a mechanical comparator.
  • the stress V in the spring 64 is generated in response to the angle of inclination a of the boom, or the spacing a between the pivot 24 and the depending cable 38, as projected into a horizontal plane.
  • the cable 38 and the pulley 42 generate another force R in response to the magnitude of the load supported by the cable.
  • the two forces V and R are both applied to the bracket 56 in such a manner as to oppose each other, and the bracket transmits the two forces, or their resultant force to the switch actuating abutment 60 which inactivates the winch 40 when the relationship of the forces V and R exceeds a predetermined value set, at least in part, by shifting the pivot axis of the bracket 56.
  • a tower crane comprising:
  • adjusting means for varying the angular position of said boom in said plane
  • winch means for longitudinally raising and lowering said tension member and a load attached thereto; and a h. load limiting means for inactivating said winch means when a load attached to said tension member exceeds a predetermined value
  • said load limiting means including means for varying said predetermined value as a function of said projected spacing during said variation of the angular position of said boom to satisfy the equation ina: orna: l
  • L is predetermined value of said attached load
  • a is said projected spacing
  • L is the value of L, when a a a, being minimum value of said projected spacing
  • k is a proportionality factor and substantially constant.
  • said load limiting means include means responsive to said spacing a for generating a first force, means responsive to said attached load for generating a second force, and comparator means for generating an inactivating signal when the relationship of said forces exceeds a predetermined value, said winch means responding to said signal.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Jib Cranes (AREA)
US00220609A 1971-02-02 1972-01-25 Tower crane with load limiting apparatus Expired - Lifetime US3767061A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2104800A DE2104800C3 (de) 1971-02-02 1971-02-02 Überlastsicherung

Publications (1)

Publication Number Publication Date
US3767061A true US3767061A (en) 1973-10-23

Family

ID=5797606

Family Applications (1)

Application Number Title Priority Date Filing Date
US00220609A Expired - Lifetime US3767061A (en) 1971-02-02 1972-01-25 Tower crane with load limiting apparatus

Country Status (6)

Country Link
US (1) US3767061A (fr)
BE (1) BE778348A (fr)
DE (1) DE2104800C3 (fr)
FR (1) FR2124244B1 (fr)
NL (1) NL171882C (fr)
SE (1) SE396357B (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3990584A (en) * 1974-06-03 1976-11-09 Strawson Hydraulics (Consultants) Limited Electrical safety control device for a variable radius crane
US4053060A (en) * 1976-02-13 1977-10-11 Wilson Virgil D Crane
US4270663A (en) * 1978-10-17 1981-06-02 Fmc Corporation Stop for crane boom
US6508372B1 (en) * 1998-10-20 2003-01-21 Mammoet Holding B.V. Method for using a revolver crane, and a revolver crane
ES2343768A1 (es) * 2007-08-03 2010-08-09 Linden Comansa, S.L Sistema de control de carga para gruas de pluma abatible.
CN105347211A (zh) * 2015-11-17 2016-02-24 山东聊建集团有限公司 塔式起重机全景可视、可控、智能监测与防护集成系统
US10410124B1 (en) * 2013-01-21 2019-09-10 Link-Belt Cranes, L.P., Lllp Display for displaying lifting capacity of a lifting machine and related methods
US20230008800A1 (en) * 2021-07-06 2023-01-12 Manitowoc Crane Group France Crane drive method for selecting and applying a preferential load curve according to the inclination of a jib structural element

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE20876C (de) * D. H. CAMPBELL in Pawtucket (Rhode Island, V. St. A.) Pechfaden-Nähmaschine
US3037641A (en) * 1961-02-27 1962-06-05 American Hoist & Derrick Co Tower crane attachment
US3072264A (en) * 1960-05-12 1963-01-08 Westinghouse Bremsen Gmbh Overload safety control apparatus for hoisting equipment
GB1060089A (en) * 1964-10-22 1967-02-22 Star Cranes Ltd Safe load indicator for cranes

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB380108A (en) * 1931-06-02 1932-09-02 Hamilton Neil Wylie Improvements in cranes and like lifting appliances
DE976872C (de) * 1953-12-08 1964-07-02 Hans Liebherr Kippsicherung fuer leichte Turmdrehkrane
FR1392141A (fr) * 1963-05-20 1965-03-12 Alltools Ltd Dispositif avertisseur de surcharge pour grue
CH407467A (de) * 1964-03-13 1966-02-15 Haechler Walter Vorrichtung zur Begrenzung des Lastmomentes von Kranen
DE1209709B (de) * 1964-12-24 1966-01-27 Beteiligungs & Patentverw Gmbh Turmkran

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE20876C (de) * D. H. CAMPBELL in Pawtucket (Rhode Island, V. St. A.) Pechfaden-Nähmaschine
US3072264A (en) * 1960-05-12 1963-01-08 Westinghouse Bremsen Gmbh Overload safety control apparatus for hoisting equipment
US3037641A (en) * 1961-02-27 1962-06-05 American Hoist & Derrick Co Tower crane attachment
GB1060089A (en) * 1964-10-22 1967-02-22 Star Cranes Ltd Safe load indicator for cranes

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3990584A (en) * 1974-06-03 1976-11-09 Strawson Hydraulics (Consultants) Limited Electrical safety control device for a variable radius crane
US4053060A (en) * 1976-02-13 1977-10-11 Wilson Virgil D Crane
US4270663A (en) * 1978-10-17 1981-06-02 Fmc Corporation Stop for crane boom
US6508372B1 (en) * 1998-10-20 2003-01-21 Mammoet Holding B.V. Method for using a revolver crane, and a revolver crane
ES2343768A1 (es) * 2007-08-03 2010-08-09 Linden Comansa, S.L Sistema de control de carga para gruas de pluma abatible.
US10410124B1 (en) * 2013-01-21 2019-09-10 Link-Belt Cranes, L.P., Lllp Display for displaying lifting capacity of a lifting machine and related methods
CN105347211A (zh) * 2015-11-17 2016-02-24 山东聊建集团有限公司 塔式起重机全景可视、可控、智能监测与防护集成系统
CN105347211B (zh) * 2015-11-17 2017-07-28 山东聊建集团有限公司 塔式起重机全景可视、可控、智能监测与防护集成系统
US20230008800A1 (en) * 2021-07-06 2023-01-12 Manitowoc Crane Group France Crane drive method for selecting and applying a preferential load curve according to the inclination of a jib structural element
US11999598B2 (en) * 2021-07-06 2024-06-04 Manitowoc Crane Group France Crane drive method for selecting and applying a preferential load curve according to the inclination of a jib structural element

Also Published As

Publication number Publication date
SE396357B (sv) 1977-09-19
DE2104800A1 (de) 1972-08-17
DE2104800B2 (de) 1979-08-23
NL171882C (nl) 1983-06-01
FR2124244A1 (fr) 1972-09-22
DE2104800C3 (de) 1980-05-14
FR2124244B1 (fr) 1978-03-03
NL171882B (nl) 1983-01-03
NL7201230A (fr) 1972-08-04
BE778348A (fr) 1972-05-16

Similar Documents

Publication Publication Date Title
US5799807A (en) Mobile crane
US3767061A (en) Tower crane with load limiting apparatus
US11186467B2 (en) Crane with hoisting cable load-dependent load torque equalization
US3265360A (en) Tower crane with auxiliary hoist
JPS61502254A (ja) ジブクレ−ンの監視・制御装置
US4168781A (en) Crane
US3072265A (en) Boom rigging
US4172529A (en) Crane
US6669038B1 (en) Self-propelled crane
US3486635A (en) Jib crane
US3176854A (en) Boom suspension system
US4047617A (en) Luffing crane with overload protection mechanism
US3612294A (en) Load control apparatus for cranes
US2572336A (en) Loading boom construction
US4169535A (en) Crane
US2378915A (en) Suspension for crane booms
US3339652A (en) Load weight indicator installation for cranes, derricks and the like
NO140626B (no) Svingbar kran med bom.
US3191779A (en) Anti-pendulum crane rigging
US3062384A (en) Boom and jib assembly
US2015957A (en) Safety device for the prevention of overloading cranes and the like
US2948512A (en) Constant tension device for boat falls
KR890003879B1 (ko) 선박용 데릭 크레인
WO1984000151A1 (fr) Fleche supportee par une pantoire avec des parties de la pantoire fixes et mobiles
US726325A (en) Log hauling and loading machine.