| 摘要 |
Piston assemblies for rocking piston compressors, diaphragm compressors and vacuum pumps are provided wherein the overall mass of each piston assembly is identical to that of the other assembly despite having rod tops, retainers and diaphragms of different diameters and therefore different capacities. Each piston assembly includes a connecting rod connected to a rod top that supports a cup seal and a retainer or retainer plate. The mass of each rod is equal to that of the other rod despite the differing geometries. The mass of each retainer is the same as that of the other retainer despite the differing geometries. The overall length and stroke length of each piston assembly is the same. As a result, centers of gravity of the piston assemblies are continuously balanced on either side of the drive shaft in terms of distance from the drive shaft and in absolute value. Alternatively, in embodiments where the first and second piston assemblies have unequal stroke lengths, and/or the first and second connecting rods having different masses, and/or the first and second retainers having different masses, balance is achieve by equalizing a product of an acceleration of the first piston assembly and combined masses of the first retainer and the first connecting rod with a product of an acceleration of the second piston assembly and combined masses of the second retainer and the second connecting rod according to the equation: <?in-line-formulae description="In-line Formulae" end="lead"?>(Mretainer1+Mrod1).Aside1=(Mretainer2+Mrod2).Aside2.<?in-line-formulae description="In-line Formulae" end="tail"?>
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