Verbesserung der genauigkeit und laufgüte sechsglierdriger koppel-schwingrastgetriebe

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In order to produce dwell-rise-dwell motions cam mechanisms can be designed much simpler than linkages. Because of the many advantages of linkages, more attention should be spent to their design and at first to the six-linked structures which fulfill the given problem by smallest expense. The six-bar coupler linkage is discussed here. It realizes the dwells by approximation of the coupler-curve to a circle which is represented by the length of an additional coupler link. Many investigations have been made to meet this problem best. So the circle point curve (Burmester-curve) represents a four-fold coincidence of coupler-curve and circle. If a dwell at the end of an oscillating motion is ordered, the curvature of coupler-curve must show an extremum value. If, in addition, two end-dwells are asked for the classic Burmester Theory never can solve this problem. Now the computer-aided design is able to give new ideas as follows: The major size of coupler-curves is well-known by tables like Hrones and Nelson's atlas and also the ranges usable for dwell-motions. Such four-bars are computer-programmed to find maximum values of curvature automatically. Deviations of the transmitting link from radius of maximum curvature enlarge the duration of dwell but increase the errors during the dwell period. In each case a four-fold coincidence is realized. The computer automatically finds all extremum curvature point and there are no difficulties in finding a second end-dwell. Using special four-bars with equal lengths of coupler, output link and coupler point distance, symmetrical coupler curves are produced in which extremum curvatures correspond to crank displacements of 180°. If non-symmetrical motions are wanted, four-bars with general dimensions have to be computer-investigated. It should be stated that by the method explained eight precision points of coupler curve have been found when the maximum of them is nine. For each problem a certain number of usable four-bars can be found. The computer cam then be ordered to find that one having smallest maximum acceleration. Further investigations in this direction should be started in order to find the limits of six-linked mechanisms and to learn exactly for which requirements linkages of higher order have to be used, i.e. how to produce longer dwells and those ones with higher accuracy, also how to produce two dwells having a larger difference in back and forth motion between dwells and finally how to design linkages for more than two dwells.