Traversing hoists – Boom or mast – Extensible by sliding sections
Patent
1993-06-04
1996-05-21
Bucci, David A.
Traversing hoists
Boom or mast
Extensible by sliding sections
212230, B66C 2306
Patent
active
055181295
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a loading crane that can be attached to a truck and that has a boom including several telescopic arms, wherein one hydraulic unit, comprising piston and cylinder, it arranged between each pair of successive arms. Upon telescoping an arm, a stop attached to the preceding arm actuates a valve which is moved along with the telescoped arm and which releases the hydraulic supply for the subsequent arm.
Sequence controls for loading cranes have the purpose of ensuring that the individual arms of a telescopic boom are telescoped or retracted in a specific, usually fixed order of sequence. This is achieved either by means of an electro-hydraulic controller (DE-PS 26 48 608) or by avoiding electric components with significant mechanical complexity (DE-OS 34 13 443). Correspondingly, the loading cranes used in the past by the Palfinger Aktiengesellschaft company are equipped with a mechanically simple sequence control of the type defined above and which has, however, the drawback that only that arm of the telescopic boom that is braced directly against the folding arm enveloping the preceding arm is automatically telescoped first. The other parts of the telescopic boom are, in contrast, not fixed with respect to the order of sequence at which they are telescoped.
In the case of the cranes, in prior public use, of the Palfinger Aktiengesellschaft, the valve which is actuated by means of the stop attached to the folding arm is on the piston-sided end of the hydraulic cylinder that actuates the first arm, such end being directed toward the folding arm. Not until this first arm is totally telescoped does the valve designed as a non-return valve release the throughflow of hydraulic fluid to the cylinders of the other telescopic arms.
SUMMARY OF THE INVENTION
The object of the invention is to provide a device of the type described above in such a manner that it can be used to control the sequence of several telescopic arms. Therefore, merely the multiple use of the device in prior public use would not be a suitable solution for this problem, because the lines leading from the stop-actuated valve to the hydraulic unit supplied by such valve, in addition to the plurality of hydraulic units, valves and stops, no longer can be housed on the outside of the folding arm. The invention makes these pipelines superfluous by arranging the valve, which upon telescoping an arm releases the oil supply to the following arm, not on the telescoped arm but rather on the following arm. Thus, it is provided according to the invention that the valve is disposed on the closed end of the hydraulic cylinder of the arm following the telescoped arm.
The invention makes it possible not only to avoid disturbing pipelines, but also primarily a very compact construction of the valves that are integrated virtually in the floor of the hydraulic unit. As will be explained in detail below, it correspondingly is provided in an advantageous manner that the valve is a spring-loaded slide valve which is flanged directly to the cylinder and whose slide rod interacts with the stop.
According to the prior art, the stop-controlled valve is a simple non-return valve. Thus, it can be achieved that the first telescopic arm is necessarily telescoped first, but not retracted last. To ensure that the first telescopic arm retracts last, it is well known to provide the piston of the suitable hydraulic unit with a mandrel which actuates a non-return valve attached to the floor of the hydraulic unit when the piston is totally driven in. The invention makes it possible to combine the two measures and thus to arrive as a simple sequence control to telescope and retract even several telescopic arms in that the valve is a shutoff valve, to which a non-return valve is connected in parallel that is opened in the well known manner when the piston is totally pushed in.
BRIEF DESCRIPTION OF THE DRAWINGS
Details of the invention are explained in the following with reference to the accompanying drawings, wherein:
FIG. 1 is a
REFERENCES:
patent: 3657969 (1972-04-01), Wirkus
patent: 3658189 (1972-04-01), Brown et al.
patent: 3809248 (1974-05-01), Ohniwa et al.
patent: 3841494 (1974-10-01), Chalupsky et al.
patent: 4125974 (1978-11-01), Kay et al.
patent: 4490951 (1985-01-01), Mentzer et al.
Brahan Thomas J.
Bucci David A.
Palfinger Aktiengesellschaft
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