Main Catalogue - VUOTOTECNICA - #20

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19 SPECIAL CASES OF LIFTING All those cases where: - The gripping plane of the cups is vertical; - The acceleration or deceleration of the load to be handled is over 10 m/s2; - The gripping surface is very rough or uneven; - The load to be held is porous; The safety factor value is to be increased in each of these cases. Please contact our technical department for its calculation. POWER REQUIREMENT AT VARIOUS VACUUM levels As we have noticed in the previous chapters, whenever a vacuum is produced inside a vacuum cup layed on a surface, the surrounding atmospheric pressure will exert a force on it that is proportional to the reached vacuum level. The lifting force is proportional to the gripping surface and to the vacuum level. If the vacuum level goes from 60% to 90%, the lifting force will increase by 1.5 times, while the required energy will increase, according to Boyle’s law, by 10 times. To reduce energy consumption, it is advisable to limit the vacuum level and, when possible, increase the gripping surface of the cup. CHOOSING THE CONFORMATION OF THE VACUUM CUPS Vacuum cups come in various conformations, each meeting the various requirements that arise during the design phase, and when handling objects and loads with various shapes. Cups must be chosen according to their features, listed below: Traditional cups Bellow cup Flat, circular and rectangular cups These are the most common cups, used in most industries for handling plastic objects, cardboard boxes, wooden panels, thin metal or glass sheets, etc., featuring a reduced weight and rough or uneven surfaces. They are available with diameters ranging from 4 mm to 100 mm. They are not recommended for vertical handling of heavy loads. The particular shape of these cups allows them to quickly crumple up, as soon as they come into contact with the load to be held and in presence of a vacuum, thus lifting the load a few centimetres, independently from the movements of the automatism. This rapid movement prevents the load underneath from remaining attached to the lifted load. For this particular feature, Bellow cups are recommended for handling paper or cardboard sheets, thin metal sheets, wooden panels, glass sheets, etc. Thanks to their great flexibility, they can also be used for compensating flatness errors or for gripping on inclined surfaces. However, they are not suited for vertical handling of heavy loads. These cups are suited for vertical or horizontal handling of heavy loads, such as metal sheets with a large thickness, as well as of marble, granite, glass sheets, etc.