Traversing hoists – Having random condition sensor combined with an indicator or... – Means determining overloading produced by load
Patent
1996-06-18
1998-03-31
Brahan, Thomas J.
Traversing hoists
Having random condition sensor combined with an indicator or...
Means determining overloading produced by load
340685, B66C 1506
Patent
active
057328358
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for controlling the boom hoisting angle and the length of a wind-up rope such that the working radius of the crane or its lift have desired fixed values.
BACKGROUND ART
When a crane is performing a so-called ground-departing operation, it is desirable that the crane is operated such that the working radius indicating the horizontal distance from the rotation center of the crane to the tip of the boom is a desired fixed value.
However, when departing from the ground, the load acting on the boom increases as the hook on which the load is suspended is raised, causing the boom to flex and thereby increasing the working radius. Conversely, when performing an operation such as pouring fresh concrete, the suspended load decreases, thus decreasing the boom load and so decreasing the working radius.
Accordingly, when performing operations in which the flexure of the boom fluctuates as described above, the exercise of control such as to maintain the working radius at a fixed value is desirable from the standpoint of increasing ease of working by improving the accuracy of tracking and also from the standpoint of improving safety by preventing accidents involving contact due to flow of the load.
In some cases, cranes are used to perform horizontal movement operations in which the suspended load is shifted in the horizontal direction while maintaining the lift indicating the vertical distance from the ground to the hook at a fixed value.
In such cases also, the amount of boom flexure fluctuates with the horizontal movement of the suspended load, so exercise of control such as to keep the lift fixed irrespective of such fluctuations in the flexure of the boom is desirable both to improve ease of working as mentioned above and to improve safety.
Conventionally therefore arrangements have been made to compensate for fluctuation in the working radius produced by fluctuation in boom flexure by calculating the amount of flexure produced in the boom and by varying the boom hoisting angle in accordance with the results of this calculation (Japanese Patent Publication Sho.59-26599, Laid-Open Japanese Patent Application Hei. 1-256496, and Laid-Open Japanese Patent Application Hei.3-284598, etc).
However, although the prior art, in which only the boom hoisting angle was changed in order to remove fluctuations of the working radius, did indeed succeed in removing fluctuations of the working radius itself it tended to produce concurrent fluctuations in lift, sometimes resulting in the dangerous condition that the suspended load might spring up abruptly in combination with raising of the boom.
Also, similar problems regarding safety were produced when the prior art was applied to performing operations in which the lift must be kept at a fixed value.
The present invention was made after considering the above circumstances, and its object is to perform in a safe manner an operation that advances by varying the lift while keeping the working radius constant or an operation that advances by varying the working radius while keeping the lift constant.
DISCLOSURE OF THE INVENTION
Accordingly, the present invention comprises boom drive means for changing a boom hoisting angle in response to an input drive instruction; winch drive means for changing a rope length of the wind-up rope from a tip of the boom to a hook in response to the input drive instruction; and control means for outputting drive instructions respectively to the boom drive means and winch drive means such as to effect a prescribed operation in which a lift, indicating the vertical distance from the ground to the hook, is varied, while maintaining the working radius, indicating the horizontal distance from the rotation center of the crane to the boom tip, at a fixed value.
Also, the present invention comprises boom drive means for changing the boom hoisting angle in response to an input drive instruction; winch drive means for changing the rope length of the wind-up rope from the boom tip to the hook in response
REFERENCES:
patent: 4185280 (1980-01-01), Wilhelm
patent: 4532595 (1985-07-01), Wilhelm
patent: 4752012 (1988-06-01), Juergens
patent: 5160056 (1992-11-01), Yoshimatsu et al.
patent: 5217126 (1993-06-01), Hayashi et al.
patent: 5282136 (1994-01-01), Zui et al.
Mizui Seiichi
Morita Tadashi
Brahan Thomas J.
Komatsu Ltd.
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