. The Bell System technical journal . e is much larger than necessary since approximately 8inches of cushioning thickness is supplied to accommodate 2 inches ofdisplacement. The Tension-Spring Package (Class B)The tension spring package is useful when the allowable Gm is so smalland height of drop so great that a large displacement (say dm > severalinches) is required. The decision as to whether or not a tension springpackage is indicated may be made on the basis of a preliminary estimateof displacement based on the linear case. Suppose the height of drop isto be 60 inches and the allow
. The Bell System technical journal . e is much larger than necessary since approximately 8inches of cushioning thickness is supplied to accommodate 2 inches ofdisplacement. The Tension-Spring Package (Class B)The tension spring package is useful when the allowable Gm is so smalland height of drop so great that a large displacement (say dm > severalinches) is required. The decision as to whether or not a tension springpackage is indicated may be made on the basis of a preliminary estimateof displacement based on the linear case. Suppose the height of drop isto be 60 inches and the allowable acceleration for the packaged item is 370 BELL SYSTEM TECHNICAL JOURNAL 20g. Then, from Equation , the approximate displacement that willbe required is , 2 X 60 ^ . , dm = —r^r— = 6 mched () The actual maximum displacement in a tension spring package will proveto be somewhat more than 6 inches, but the preliminary calculation showsthe displacement to be large enough to warrant the use of this type ofcushioning. H G. Q B Fig. —Schematic diagram of a tension spring package. A schematic diagram of a typical tension spring package is shown in and a photograph of one design is given in Fig. The packageditem is suspended on eight identical helical tension springs which divergeto the outer frame. The analysis and design procedures described in thisand the following section apply equally well if the springs converge from thepackaged item to the outer frame. With a slight modification, indicatedin the next section, the procedure also applies if four of the springs (say,BJ, DL, EM, OG in Fig. ) are omitted. In all cases, however, we shall consider only systems having reflectedsymmetry about each of three mutually perpendicular planes through thecenter of gravity of the packaged article. DYNAMICS OF PACKAGE CUSHIONING 371
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