Traversing hoists – Boom or mast – Extensible by sliding sections
Patent
1996-09-26
1998-09-29
Brahan, Thomas J.
Traversing hoists
Boom or mast
Extensible by sliding sections
212296, B66C 2304
Patent
active
058135529
DESCRIPTION:
BRIEF SUMMARY
For the purpose of extending and retracting telescopic booms, e.g. booms of cranes and excavators, telescopic, i.e. multistage, hydraulic cylinders are frequently used. Each subsection of the telescopic boom, i.e. each so-called telemember, has normally associated therewith one unit of the multistage telescopic hydraulic cylinder. During operation, the hydraulic cylinder is acted upon by bending forces, said bending forces increasing in proportion to the increase in the length of the hydraulic cylinder and resulting from the unloaded weight of the hydraulic cylinder as well as from the loads to be lifted. These bending forces may cause buckling of the hydraulic cylinder.
Up to now, attempts have been made to prevent such buckling by providing the cylinder walls with adequately strong dimensions. However, this strong dimensioning of the hydraulic cylinder walls results in an increase of the unloaded weight of the hydraulic cylinder, and this has the effect that the maximum load which can be lifted is reduced accordingly.
It is therefore the object of the present invention to construct a telescopic boom with a multistage hydraulic cylinder in such a way that, without a buckling-proof dimensioning of the hydraulic cylinder, buckling of the hydraulic cylinder need not be feared under any operating conditions.
This object is achieved by the invention disclosed in claim 1. The technical progress which can be achieved by means of the present invention results primarily from the fact that measures have been taken with the aid of which the hydraulic cylinder is supported throughout its whole length or through selected subsections thereof by the telemembers of the boom which are constructed as buckle-proof members from the very beginning. A particular advantage results from the fact that, thanks to the present invention, protection against buckling of the hydraulic cylinder exists not only in the final stages of the boom extension process but also in all intermediate stages and even during the transition from one stage of the boom extension process to the next one.
Another advantage of the present invention must be seen in the fact that the individual hydraulic cylinder units are prevented from rotating relative to one another, since the supporting means according to the present invention guarantee that a rotational displacement of individual hydraulic cylinder units relative to one another cannot occur.
The invention will be described in detail in the following on the basis of an embodiment and with reference to the drawing, in which:
FIG. 1 is a schematic representation of a boom comprising five telemembers and a five-stage hydraulic cylinder, in the fully extended state;
FIG. 2 shows the boom according to FIG. 1, in which, however, only two telemembers and only two units of the hydraulic cylinder are extended;
FIG. 3 shows the boom according to FIGS. 1 and 2, in which, however, only one telemember and only one unit of the hydraulic cylinder are extended;
FIG. 4 shows the boom according to FIGS. 1 to 3 in the fully retracted state;
FIG. 5 shows a view of the hydraulic cylinder in the fully retracted state;
FIG. 6 is a representation of the way in which the components of the buckling protection device cooperate;
FIG. 7 is a representation substantially corresponding to FIG. 1, in which, however, the tie rods are tied in a preferred manner;
FIG. 8 shows the boom illustrated in FIG. 7 in the fully extended state, under an incorrect operative situation; and
FIG. 9 shows the boom illustrated in FIG. 7 in another incorrect operative position.
According to FIG. 1, the telescopic boom as shown comprises a non-telescopic basic member GK as well as five telescopic members A to E, which will be referred to as telemembers hereinbelow. From the basic member GK up to telemember E, which is extended furthest and which has the smallest dimension as far as the diameter is concerned, the diameters and the base areas of the telemembers decrease in a manner known per se.
For extending the telemembers A to E from the basic member GK a
REFERENCES:
patent: 3353686 (1967-11-01), Cowan
patent: 3792555 (1974-02-01), Sung
patent: 3836011 (1974-09-01), Sakamoto et al.
patent: 3837502 (1974-09-01), Hornagold
patent: 4358915 (1982-11-01), Pantalone
patent: 4408424 (1983-10-01), Sutter
patent: 5584645 (1996-12-01), Kaspar
Brahan Thomas J.
EC Engineering & Consulting Spezial-maschinen GmbH
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