Pawl
A pawl , even locking lever called, is part of a form guide - locking mechanism or ratchet gear . It prevents the backward movement of a component , e.g. B. turning a wheel backwards (see adjacent figure). The forward movement is approximately unhindered.
Function and types
Characteristic are the serrations with one steep and one flat flank on the component (generalized technical term: locking piece ). Over the flat edge of the tip of the pawl can (generalized technical concept: blocker ) during forward turning slide away, while it meets with attempted reverse rotation against the steep flank, one with its form-fitting forms, and stops the rotation.
The pawl tip is frictionally perpendicular to the direction of movement of the locking piece (eg. With spring force held) against the locking piece.
We distinguish between pressure ratchet (see illustration above, tip presses against tooth flank on the locking pieces) and Zugsperrklinke (hooks rather than peak, the locking piece now steeper opposite flank retains).
The pawl can be movable in a pin swivel joint or have a simple spring joint .
Pawls with a pin swivel joint can be swiveled around in order to lock in the opposite direction of movement if the tooth shape is designed accordingly.
Applications
Lock with z. B. Pawls are used wherever uncontrolled reverse rotation is to be prevented. Examples are winches , lashing straps , vehicles with free-wheeling , scraper floor drives , handcuffs and mechanical watches . In the latter the turning back of the ratchet wheel in the barrel or the cable drum is prevented. The pawl is called the locking cone and the locking mechanism is called the ratchet .
A double-acting locking mechanism can be found e.g. As in the screwing gun . The teeth are symmetrical, and one of two oppositely directed pawls is optionally lifted out of the teeth.
A cable tie has one or more elastically yielding pawls in its head. Most of the time, the elastic yielding of the teeth on the tie strap is also taken into account so that the pawls can jump over them when the tie is closed. In the case of reusable cable ties, the latch is manually lifted out of the teeth to release.
Other names and demarcation
The term ratchet is also used colloquially for this type of locking mechanism, because when it is operated, a similar noise occurs as with real ratchets , which are used exclusively to generate noise.
See also
Web links
- Ralph Steiner: Mechanical Principles (1930) , YouTube of September 13, 2009
Individual evidence
- ^ A b Siegfried Hildebrand : Feinmechanische Bauelemente, Hanser 1968, p. 671, Fig. 3.611.
- ^ Siegfried Hildebrand : Feinmechanische Bauelemente, Hanser 1968, p. 686
- ^ A b Siegfried Hildebrand : Feinmechanische Bauelemente, Hanser 1968, p. 670
- ^ Helmut Kahlert , Richard Mühe , Gisbert L. Brunner : Wristwatches: 100 years of development history. Callwey, Munich 1983; 5th edition, ibid. 1996, ISBN 3-7667-1241-1 , p. 48.