Change (construction theory)
Link exchange , change of form , change of position , speed change and change of grip are systematic ways of working in the Engineering Design . They are mainly used in the construction of machines and devices , especially their moving mechanisms ( gears ).
The change takes place between two or more possibilities of a basic technical principle. The systematic approach consists primarily of taking into account all possible options. Starting from a first or already existing construction, modifications are made by changing to another option. After several solutions have been worked out, an optimal one is selected for use.
Examples
Link change :
With a multi- link gear mechanism ( kinematic chain ), each link can be a frame , a driven link or another link with a specific function. The change of link that takes place in the process creates a large number of basic linkage gears , each of which is suitable for a specific task area.
In the case of simpler mechanisms such as ratchets or tensioning mechanisms (no closed link chain), the link changes result in construction variants for a constant function that can only be found in manufacture, use and the like. differentiate.
This type of modification called already Franz Reuleaux link exchange .
Change of shape :
A shadow pointer ( line or point ) is usually used as the pointer of a sundial . By changing the shape of the shadow-casting object from a rod or a small ball to a slot or a hole , a light pointer is created. The light pointer is used less often because the slot or hole has to be readjusted against the direction of the sun over the course of the day.
For the mechanisms, the term is used more narrowly and is also called pair reversal . The components forming a joint between two links (e.g. a shaft in a bearing ring ) are connected to the two links in reverse.
Change of position :
The use of the term change of position is closely linked to mechanisms, whereby one speaks of internal and external position . An example is guiding a roller through a curve, the curve being the outer shape (outer layer) of the corresponding link, or being designed as a curved groove surrounding the roller (inner layer) . A change of position also takes place when a change between external and internal toothing takes place on one of the two wheels of a gear pair .
Change of numbers :
In mechanisms, a change of number is often understood as a change to a parallel arrangement of two identical links between the other links. A change of numbers as well as a change of limbs can also be used in the case of measuring instruments in which many pointers (moving scale) move against a single point on the scale (stationary scale).
Handle change :
From change of grip to be discussed by mechanisms that are operated manually as most chip works. In principle, any link can be used for actuation, but this is not always practical. The case is eliminated in which the "handle" is not hinged to the frame and a "higher" movement is to be introduced into it. An example is the swing top on a bottle. The force relationships would also be a practical obstacle if you wanted to create the closure by moving the bracket leading to the lid or the lid itself.
Individual evidence
- ↑ a b c d e f Willibald Lichtenheldt : The importance of construction theory for precision mechanics , Scientific Journal of the Technical University of Dresden, 3 (1953/54) Issue 2, pages 211 to 214
- ^ Siegfried Hildebrand : Feinmechanisch Baulemente , 1968, p. 763
- ↑ This can also show that the first or previous solution was the optimal one.
- ↑ Willibald Lichtenheldt : Konstruktionslehre der Getriebe , 1970, p. 8
- ↑ Kurt Luck, Karl-Heinz Modler: Transmission technology: analysis synthesis optimization . 1st edition. Springer, 1990, ISBN 978-3-7091-3890-8 , pp. 12 - 13 , Figure 2.11 ( limited preview in Google Book search).
- ↑ Examples are sundials with several shadow hands that fall on a single scale mark / point. See Siegfried Wetzel: A multi-rod sundial and a multi-mode sundial .