Boots – shoes – and leggings
Patent
1996-06-20
1998-03-24
Trammell, James P.
Boots, shoes, and leggings
364506, 36442407, 212347, 212348, 212350, B66C 2300
Patent
active
057319871
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an operating system for the telescopic movement of a telescopic boom for a crane, particularly a boom having one non-telescopically moveable section and three or more telescoping sections.
2. Description of Related Art
In conventional telescopic booms having multiple telescoping sections the extension and retraction of the boom is normally controlled by the operator using multiple control switches, or levers, each of which controls the extension and retraction of one, or possibly two, telescoping sections. With such an arrangement, when the boom is under load, there is a significant risk that the operator might inadvertently exceed the load capacity of the boom. There is also a risk that the operator might telescope the boom into a configuration which renders the boom and the structure to which the boom is mounted, such as a vehicle, for example, unstable, whether by over-extending the boom or by telescoping the boom sections into an inappropriate configuration for a particular overall boom length.
For these reasons, when it is necessary to extend or retract a multiple section boom in order, for example, to vary the reach of a crane, it may be necessary to do this when the boom is not under load.
U.S. Pat. No. 4,589,076 discloses a method of operating a telescopic boom so as to switch the telescopic movement between successive boom sections with accurate timing and so as to account for errors in the measurement of the overall boom length.
In order to optimise the lifting capacity of the crane, it is common to operate a multiple section telescopic boom in two modes of operation. The first mode of operation is with at least one of the innermost telescoping boom sections held in the fully retracted position, hereinafter referred to as the first mode of operation of the boom. The second mode of operation is by extending or retracting all of the telescoping sections in a prescribed manner, hereinafter referred to as the second mode of operation. In order to switch between the first and second modes it is first necessary with conventional boom operating systems fully to retract the boom, and this can be a lengthy procedure.
SUMMARY OF THE INVENTION
It is an object of the present invention to facilitate the telescoping of a crane boom having a plurality of telescoping sections whilst optimising the load capacity of the boom and/or the stability of the crane for any given overall boom length.
It is a further object of the present invention to provide an operating system for a multiple section telescopic boom which minimises the time required to switch between the first and second modes of operation.
A further object of the invention is to reduce the time taken to change the overall length of the boom.
A still further object of the present invention is to simplify the procedure to be undertaken by an operator in order to change the overall boom length.
A method of operating the telescopic boom of a crane in accordance with the invention comprises calculating, for each of a number of overall boom-lengths, the lengths of extension of the respective boom sections which optimise the load capacity and/or the stability of the crane when the boom is under load at the said overall boom lengths, and programming the calculated boom section extension lengths into processing means which, in response to a signal input by an operator to extend or retract the boom between two operating boom lengths, determine the optimum sequence of movements of the respective sections as the boom length increases/decreases so that at any boom length intermediate two said overall boom lengths the load capacity and/or the stability of the crane is/are optimised and produce corresponding output signals to means for moving the respective sections.
With such an arrangement an operator may telescope the boom from the fully retracted position to the fully extended position or to any intermediate position or vice versa, in a predetermined and safe sequence, in a fully au
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patent: 4205308 (1980-05-01), Haley et al.
patent: 4456093 (1984-06-01), Finley et al.
patent: 4468166 (1984-08-01), Jameson
patent: 4906981 (1990-03-01), Nield
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Clark Peter
Harrison Nigel
Strong John
Watson Christopher
Kidde Industries, Inc.
Smith Demetra R.
Trammell James P.
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