| 摘要 |
The invention relates to a vacuum hoisting device of the kind having a vertically suspended lifting tube (4), which is extensible and contractible in dependence on the air pressure in the lifting tube, and which at its lower part is provided with a suction device (6) in the shape of one or more suction cups. Up to now a valve at the suction device is used for manoeuvering the suction device, which valve when closed brings a vacuum source (7, 20) to work with a constant suction capacity to decrease the pressure in the lifting tube such that an object (32) to be lifted is attached by the suction after which the lifting tube is contracted such that the object is lifted. To limit the lifting height and to lower and release the object it has been necessary to partially open the valve and permit a restricted inlet of air and at last completely open the valve resulting in a large comsumption of air. According to the invention there is instead a valve (14, 23) arranged to control the suction capacity of the vacuum source in direct dependence of the desired air pressure in the lifting tube (4).
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