Illustrated Sourcebook of Mechanical Components Part 6 pps

Washers 11-7 Tube crimped Gefol /lot wosher of end Rubber flof woshersv - VOCUl - Rubber Ball f/of wusher ‘Adhesive bond ‘Adhesive bond ‘Ploslic chamber 4 Compression ball seat 5 Hose bib retainer , Connec fion 8 Protective bumper 9 Expansion isolator 11-8 Take Another Look at Serrated- Washers They're a stock item and come in a variety of sizes. With a little thought they can do a variety of iobs. Here are just eight. Robert 0. Parrnley Washers 11-9 11-10 Dished Washers Get Busy Robert 0. Parmley A 0 HEIGHT ADJUSTMENT Jam nuf Dished washer3 1 20 GUIDE WHEEL Add rubber befwsen wosbers for gr@power To remove pi?? Refahing ring I COIL SPRING STABlLlZEA 10 SIMPLE VALVE Washers 11-1 1 Let these ideas spur your own design creativity. Sometimes commercial Belleville washers will suit; other wise you can easily dish your own. Washers Section A-A Workpiece Section A-A Base 3 ALIGNING BUTTONS 0 will rotate if holding screw is shouldered here for non-slipp;ng non-s//p arrangement/ 4, V-BELT PULLEY Rubber sur face adhesive. A Alternate: Profecf corners and ,Lock washer I I tope on bevels Sbc Washers / 7ff I 7111 I c 7. END AND CORNER PROTECTION 11 FLARED SPOOL-FLANGES Sho f fs Beflevil/e sprjng washers Enlarged \I Jam ffufs / Work area 12 0 CORRUGATING ROLLERS FOR PAPER OR CARDBOARD 11-12 Design Problems Solved with Belleville Spring Washers Robert 0. Parmley Pulley assembly Mounting spring stabilizer (Nut and washer Force Retain tapered coil spring Knurled adjustment Washers 11-13 ~elleviIle springs are a versatile component that offer a wide range of applications. There are many places where these components can be used and their availability as a stock item should be considered when confronted with a design problem that requires a fast solution. Secure anchor bolt Clamp fixture spring , Belleville ._ r Lock retainer Lock mechanism Machine leg spring mounts I spring disc A €5 C 11-14 HOW to Increase Energy Capacity of Belleville,Spring Washers New equations give stress-energy relationships and lead to the unusual arrangement of nesting Bellevilles one inside the other. H. P. Swieskowski INCE 1867, when Mien F. Belfeville was issued a S patent in Paris for the invention, Belleville springs have never ceased to find wide application. Now, more and more, they are being used to absorb high impact energies. With the arrangements and new design equations given here, you can easily design for maximum energy-absorbing capacity. Also called conical disk springs, Belleville springs are actually no more than conical washers. They are very compact, which leads to first of several advantages: @They can absorb a large amount of energy at high loads and with a comparatively short working stroke. They can return to the system practically all the energy they absorb during the compression or impact stroke. With ring springs, in contrast, approximately 50% of the input energy is dissipated as heat. Their load-deflection characteristics can be altered simply by adding or removing individual washers, by stacking washers in various parallel-series combinations, 1 . . Four arrangements of Belleville springs. The nested design and by nesting them inside larger washers, Fig 1. Generally speaking, Belleville springs are better suited than helical compression springs where longitudinal space is limited, in other words, where space for solid height is limited and where a helical spring would result in a small index (the ratio of the mean coil diameter to the wire diameter). Design recommendations You don’t need a maze of nomographs and tables to calculate the impact load a Belleville spring must absorb. With these new design equations, given below, you can predict the amount of induced stress directly. But first, some important findings: Nested springs-ne washer inside another-require no more space than single springs and reduce the maxi- mum stress by 14%. One-parallel-series arrangements of Belleville springs are more efficient energy absorbers than two- or three-parallel TWO-PARAiLEL SERIES THREE-PARALLEL SERlES has highest efficiency for absorbing energy. Contrary to popular opinion, the one-parallel design is more efficient than the two- or three-parallcl designs Washers 11-15 series - contrary to some popular misconceptions. 0 Final working stress is directly proportional to the square root of the energy capacity and inversely propor- tional to the outside diameter and square root of the solid height. Oneparallel-series equations To simplify analysis, it is assumed that the minimum working height is equal to the solid height and that there is no precompression for assembly. Thus the total deflec- tion is Fs = HF - Hs For symbols, see Box on page 93. The height-thickness ratio, B = h/t, determines the shape of the load-deflection curve. By varying the B values, it is possible to obtain a wide variety of load- deflection curves, Fig 2. The curves are plotted against the deflection in terms of height as the spring washers are com- NESTED ARRANGEMENT I for most ratios of dish height (deflec- tion to flat) to metal thickness. Bel!eville springs .Preload nut Buffer mechanism with Belleville springs for high-impact energy absorption. 11-16 pressed from free height to solid height. ville springs are Load The conventional load and stress formulas for Belle- where the constants C,, C, and Y are given by the equa- t;ons 2.c 1 .E l.E 1.4 1.2 a" 1.c 2 0 D 3 0.E c U 0 Of 01 0; ( 3 (A - 1) Ga = T In A The constants can be iuickly approximated by means of Fig 3. The stress equation, Eq 2, givcs the value of the com- pressive stress which occurs on the convex side at the inner diamzter. The stress h2s a maximum value when fi = h. Hen-e the maximum (final) stress from Eq 2 is The energy stored in one washer compresszd from 0 2h 0 4h 0 6h Deflection in terms of height, h 0.8h h 2 . . LOAQ-DEFLECTION CURVES. The hcight-thicknebs ratio, S, dclci-iniiics thc shape of tl~c CUI'VC. [...]... that = 2R (15) 66 Solid height, in 1 .65 I 65 Total travel, in B g 30 1 .65 4.95 Final stress, psi 21 8,000 21 8,000 Number of washers I Therefore, Eq 1 is rewritten as 4 L A graph of the stress ratios for one and two-parallel series arrangements are shown in Fig 7 Note that in 1), the one-parallel series the practical range -of B, ( B is more efficient &an the two-parallel series This is particularly... Table III 26 Outside diameter, in In combination with Eq 7, and the fact that both assemblies have equal strokes, it follows that the ratio of stresses of one-parallel to three-parallel design is THREE-PARALLEL SERIES 1.7 1.7 Height 0.034 0.055 Thickness, in 0.085 0.0 46 Height-thickness ratio, 0.4 1.2 Stroke, in 0.884 0.884 Solid height, in 2.21 2.21 Energy capacity, in.-lb 60 0 60 0 Number of individual... familiar with the uye of ietaining rings in product asscmbly Applications for this type of fastening device range from miniature clectronic asscmblics to heavy cluty equipment In spite of this widespread use, many opportunities for taking advantage of these versatile fastening components oftcn arc ovcrlooked However, when a value enginecring approach is talccn and thc basic function of retaining rings... the energy of a 4000-lb force Cycles to failure traveling through a foot of stroke 100 times The number o f cycles t o failure influences total amount of energy absorption c ( Retaining Rings A = Deflection at Point A P = Load at Point B R = Radius of Ring E G = Shear Modulus J = Cross-Section Polar Moment of Inertia I = Cross-Section Polar Moment of Inertia About Neutral Axis = Modulus of Elasticity... A 6 2.0 Therefore, we recommend that the diameter ratio should be kept within the range of 1.5 to 2 0 Note also from Fig 4 that in the favorable diameter ratio range the final stress increases with increasing values of B This condition is true except for the height-thickness ratio of B = 3, for in the range of A = 1.5 to A = 2.0, the final stress for B = 3 is less thm that for smaller B values (of. .. between the final stress of the single springs to that of the nested spring is obtained from Eq S, 9 and 12 as Ss = 1. 168 s" (13) Therefore, the percentage reduction in final stress, AS, + TABLE I SINGLE VS NESTED ARRANGEMENTS NESTEO ARRANGEMENT ONE-PARALLEL ARRANGEMENT OUTER SPRING INNER SPRING Thickness, in 0.055 0.051 0.030 Dish height, in 0.01 1 0.0102 0.0 06 Number of washers 37 40 68 Diameter ratio... 0.312 Height-thickness ratio 0.20 0.20 0.20 Stroke, in 0.407 0.408 0.408 Solid height, in 2.035 2.040 2.040 Energy capacity, in.-lb 100 74 26 Material, AIS1 61 50 61 50 61 50 191,000 191,000 Final stress, psi 222,000 11-19 11-20 that is gained by the substitution of a nested arrangement for a single spring is values for energy capacity, stroke, solid height, diameter ratio, material, and outside diameter... values For one-parallel series Variation index of final stress Energy capacity and final stress of inner spring in nested design, in.-lb, psi Energy capacity and final stress of E. . 0.20 0.408 2.040 74 61 50 191,000 0.030 0.0 06 68 1.7 0.530 0.312 0.20 0.408 2.040 26 61 50 191,000 11 -20 that is gained by the substitution of a nested arrange- ment. ONE-PARALLEL SERIES 26 1.87 1.10 1.7 0.034 0.085 0.4 0.884 2.21 60 0 305,000 THREE-PARALLEL SERIES 48 1.87 1.10 1.7 0.055 0.0 46 1.2 0.884 2.21 60 0 266 .000 Washers 11 -23. 61 50 SPRING B 2.300 1.1 50 0.075 0.025 3.0 2.0 66 I .65 4.95 21 8,000 342 61 50 11-21 11 -22 Similarly, the ha1 stress of the three-parallel series (shown in Fig 1) is