Vestibule (clock)

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Simple vestibule with worm gear (music box)

A windscreen also wind blades or wind vane controller called, is a machine element that the air resistance to control the speed of a mechanism used.

function

Simple vestibule resiliently mounted on the shaft (table clock)
Speed-dependent vestibule with return spring (table clock)
Simple vestibule with ratchet (tower clock)

According to the laws of flow physics , the flow resistance of a plate perpendicular to the direction of flow increases by the square of the flow velocity. Wind vane controllers are based on this physical law. Their resistance is speed-dependent and increases with increasing speed. Wind vane regulators have a very simple structure and are quiet. They should reach the rated speed quickly and therefore must have a low moment of inertia. The metal sheets from which the wings are made should be as thin as possible. Wind vane regulators are available in two versions:

Simple regulator

If the speed increases, the flow resistance of the wind blades increases and the controller shaft brakes the driving drive. Due to the falling drive speed, the flow resistance drops and the speed levels off at a fluctuating mean value .

Speed-dependent controller

The speed-dependent flow resistance can be increased by using centrifugal governors with speed-dependent blade positions instead of unchangeable wind blades . They spread with increasing centrifugal force and slow down the drive more effectively at increasing speeds. Their control effect is more constant and adjustable. Nevertheless, here too the speed fluctuates around an average value. The porch with movable wings corresponds better to the conditions of rapid approach than the simple one. The start-up time can be selected by tensioning the return springs to different degrees.

application

The vestibule is used as a regulator for the flow of such drives, in which no absolutely uniform, but fast movement is desired. Therefore, such arrangements cannot be used to display the time.

  • In music boxes , the playback speed is regulated by means of a wind vane controller. Usually a worm is attached directly to the windscreen. This arrangement is at the same time a rare example of a worm gear with a speed ratio.
  • In clocks as flow regulators in striking mechanisms . In the early console and tower clocks , the vestibule was often arranged outside the bearing bands; in the case of the Renaissance watches, it was integrated between the bearing strips or plates in the gear train . The vestibule was resilient or connected to the shaft by a ratchet , so that when the wheels are at a standstill, their torque is slowed down slowly and not abruptly absorbed by the gears. In early small watches, instead of a vestibule, a start-up mass was attached to the last shaft, which slowed the process down due to its moment of inertia.

literature

  • Friedrich Assmus: Technical drives including clocks ; Springer-Verlag Berlin, Göttingen, Heidelberg 1958; P. 192f
  • Günter Krug: mechanical clocks ; VEB Verlag Technology; Berlin 1987; ISBN 3-341-00356-8 ; P. 178f
  • Richard Reutebuch: The watchmaker: A textbook f. every watchmaker,…. ; Wilhelm Kempter Verlag, Ulm (Donau) 1951; P. 490f

See also

Web links

Commons : Windfang  - collection of images, videos and audio files

Individual evidence

  1. ↑ Fritz von Osterhausen: Callweys lexicon . Munich 1999, ISBN 3-7667-1353-1 ; P. 360
  2. ↑ vestibule . In: Heinrich August Pierer , Julius Löbe (Hrsg.): Universal Lexicon of the Present and the Past . 4th edition. tape 19 . Altenburg 1865, p. 255 ( zeno.org ).
  3. ↑ porch in UhrenLexion
  4. ↑ Lukas Stolberg: Lexicon of the pocket watch ; Carinthia Verlag; Klagenfurt 1995; ISBN 3-85378-423-2 ; P. 256
  5. ↑ Rudi Koch (Ed.): BI-Lexikon - Clocks and Time Measurement , VEB Leipzig, 1986, ISBN 3-323-00100-1 ; P. 242f.