Pneumatic And Hydraulic Equipment Page 548

Product Features Flat and bellows options for a variety of lifting surfaces Durabletear-resistant vinyl material Threaded or 'slip-fit' mounting options available Lifting Force (lbs.) Safety Factor = 1 Dimensions Part No. Price Style Mounting 10" Hg 15" Hg 20" Hg 27" Hg A B C D F Cleats VG2100 $58.91 Bellows .375" FNPT 42 63 84 114 3.31 2.38 2.18 2.38 0.375 No VG2101 $111.10 Flat .375" FNPT 87 130 174 235 4.75 1.18 1 1.62 0.375 Yes The material of the object being moved will also affect cup diameter. For example, to lift very porous materials such as corrugated cartons or denim material you should use smaller diameter cups. Larger cups may result in leakage. You can, however, use larger cups if you are using a high-flow pump because the greater flow capabilities will compensate for the inherent leakage of larger cups. The type of material being moved can also affect the number of cups used. With thin metal plates, for example, you need six or eight evenly-distributed cups instead of just two or three needed to lift the actual weight of the plates. This prevents damage to the sheet metal from bowing during lifting. The configuration of the workpiece is also important. An irregularly- shaped object can be lifted, but care must be taken to select proper diameter cups. Plus, the cups must be distributed so that the object is balanced around the center of gravity during lifting. Items with curved surfaces may even require bellows cups so that the cup conforms to the curves. Selecting and Sizing Vacuum Cups One of the keys to getting the most performance out of vacuum pumps and generators is selecting the right size, number and type of vacuum cups. Cup diameters are generally selected based on the weight of the object to be lifted. Use the following formula to calculate the theoretical lifting force of any size vacuum cup: W = Force in lbs. C = Area of cup (in 2 ) P = Vacuum level - in Hg F = Safety Factor W = CXPX14.7 FX29.92 The key word here, of course, is theoretical. While the chart and formula will get you in the ball park, selecting the right size cup means taking several variables into consideration. Try to use the largest cup possible to ease the requirements on your vacuum pump. It's far easier and more economical to get an adequately- sized vacuum cup than to overwork your vacuum pump. This helps ensure long pump life. It is also much more economical. High levels of vacuum increase energy requirements dramatically. Going from 60% to 90% of vacuum (18 in. Hg vs. 27 in. Hg) may increase vacuum force by a factor of 1.5, but the energy needed to produce that force increases by a factor of 10. Choosing a slightly larger cup also adds safety to your system. A safety factor should always be used in actual cup sizing, too, even though cup diameter increases about 10% during use. If the object is to be lifted vertically, a safety factor of four (4x) should be used. For horizontal movement a safety factor of two (2x) is recommended. Acceleration during the lift is another important factor to consider when sizing vacuum cups. Formulas exist to calculate the affect of acceleration, but they are very difficult to work with. It is easiest and perhaps best to use a higher safety factor and carefully test cups in these applications. VACUUM CUPS Gast (314) 427-0600 800-444-0522 (FAX) 314-427-3502 www. j JHF Catalog [ Volume 7 ] 548 Prices Subject to Change Without Notice John Henry Foster pneumatic and hydraulic equipment

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