Traversing hoists – Having random condition sensor combined with an indicator or... – Means determining overloading produced by load
Patent
1996-05-07
1998-01-27
Brahan, Thomas J.
Traversing hoists
Having random condition sensor combined with an indicator or...
Means determining overloading produced by load
212277, 212300, 212231, B66C 1500
Patent
active
057114404
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a suspension load and tipping moment detecting apparatus for a mobile crane, and more particularly, to a suspension load and tipping moment determining apparatus for a mobile crane capable of reducing an error produced at the time of calculating a suspension load and a tipping moment.
BACKGROUND ART
In a conventional mobile crane, a telescopic boom is mounted to a chassis so that the boom can turn and can swing upwardly and downwardly, and the boom is pointed to a predetermined direction by a turning motor and is raised by a derricking cylinder to a state in which it stands substantially upright. A jib of a truss construction type is mounted to the tip of the telescopic boom, and heavy equipment is lifted and moved by a suspension hook which is moved upwardly and downwardly from the tip of the jib. In contrast with such mobile crane, a crane truck has been recently proposed in which a telescopic boom is mounted in place of the jib so as to impart a function of a tower crane thereto. According to such crane truck, a first boom, raised in a substantially upright state on a turn table of a chassis by the derricking cylinder, is extended to a desired height; a second boom, mounted to the tip of the first boom, is extended while being set to a substantially horizontal state by its own derricking cylinder; and the suspension hook hanging from the tip of the second boom is lowered toward the ground so as to perform operations.
Incidentally, according to the mobile crane to which a function of the tower crane is imparted, since the second boom is horizontally extended at a high lift position, it is important to determine a suspension load and a tipping moment associated therewith from a viewpoint of a safety operation so as to prevent an excessive load. For this type of excessive load prevention, a suspension load has been conventionally calculated from a balance equation of a moment due to the suspension load, a boom self-weight, and a resistance moment due to an axle weight applied to the derricking cylinder of the first boom, and the value thereof has been determined so as to calculate the tipping moment.
However, according to the conventional method, the suspension load and the tipping moment are calculated from the axle weight applied to a main cylinder which derricks the first boom. Thus, in the event that the first boom is operated to increase a tilt angle from the vertical position thereof so that operating radius is increased, the effect of the piston frictional force within the main cylinder on the axle weight is increased, whereby a value smaller than the actual suspension load may be outputted. More particularly, in the event that the second boom is extended, the effect of the frictional force cannot be ignored because the position of the center of gravity of the entire boom moves farther away from a base point of the main cylinder. For this reason, according to a conventional excessive load prevention system, a safety factor is forced to be set high so as to be determined on the side of safety, and therefore, there is a drawback in that the system can be operated only within a range which is smaller than the actually possible operation range. In addition, when calculating the tipping moment, the conventional system is one in which the operating radius is calculated by a geometrical operation in which a boom is a rigid body, although the boom is deflected by the suspension load and the self-weight thereof. Thus, there is a problem in that the actual operating radius is not reflected to the excessive load prevention system correctly.
SUMMARY OF THE INVENTION
The present invention has been made to solve the drawbacks of the prior art, and particularly has its object to provide a suspension load and tipping moment determining apparatus for a mobile crane capable of determining the suspension load and the tipping moment with high accuracy, thereby making effective use of an excessive load prevention system while ensuring safety.
A suspension load dete
REFERENCES:
patent: 3883130 (1975-05-01), Gardes et al.
patent: 4052602 (1977-10-01), Horn et al.
patent: 4178591 (1979-12-01), Geppert
patent: 4241837 (1980-12-01), Suverkrop
patent: 4752012 (1988-06-01), Juergens
Brahan Thomas J.
Komatsu Ltd.
Komatsu Mec Kabushiki Kaisha
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