Claw coupling
A claw coupling is a design of a machine element for the transmission of rotary movements or torques . It represents one of the simplest types of coupling and is therefore very widespread. Colloquially, an elastomer coupling is often referred to as a claw coupling.
The term has also become known for the use of manual transmissions in railways, see TAG transmissions . A construction similar to the claw coupling is often used as a connecting element, for example in closures or connectors (fire hose). This plug-and-turn mechanism is called a bayonet lock.
Working principle
The claw coupling belongs to the group of form-locking couplings. Its name is derived from the gripping function of a claw in the animal kingdom.
Similarly, in a claw coupling, two or more extensions engage on one of the two shafts behind corresponding thickenings on the opposite shaft end and enable torque to be transmitted by turning.
Claw clutches can be designed to be switchable. In most cases, when the machine is at a standstill, the “claw” is simply pulled off the opposite end of the shaft. The shifting of the relevant gears in vehicles with mechanical power transmission was already practiced very early in rail vehicles due to the larger loads to be transmitted and the reduction in gear wheel wear when shifting. Even the benzene railcars of the Spandau-West – Hennigsdorfer Kleinbahn had mechanical gears with dog gears and constantly engaged transmission gears when they were commissioned in 1923. Since the claws cannot synchronize the speeds of the motor and output shaft smoothly, such gears also require a single-disk dry clutch . The claws are usually controlled using compressed air . This type of dog clutches are still used today in reversing gears , in which the transmission gears are also constantly in mesh and which are only switched at a standstill.
Another possibility of the claw coupling is to bevel the non-force-transmitting rear side. As a result, the clutch is disengaged when the driven shaft moves faster. It is a kind of freewheeling , formerly at starting handles of engines was used.
Both sides of the coupling can also be designed symmetrically.
application
The force at the connection between screwdriver and screw is transmitted according to the principle of the claw coupling, with the screw head of a slotted screw acting as a claw. In most vehicle transmissions, gear pairs are alternately disengaged or non-rotatably connected to the shafts via claw clutches when shifting, depending on the gear position. Well-known applications were the NAG railcar transmission , the TAG transmission or the Mylius transmission in railcar construction. Since the engine driver was distracted from observing the route during the switching operations, this type of gearbox was later replaced by automatic gearboxes .
Depending on the special design, the claw coupling compensates for axial misalignment and dampens rotary movements, especially shock loads and vibrations .
Highly dynamic intermediate axes, combined with claw couplings, are increasingly used in the entire machine and plant construction. Important areas of application are, for example, screw jacks , linear guides , palletizing or packaging systems.
As soon as the claw flanks have a bevel different from 90 °, a slip clutch can be implemented via a defined axial preload in cooperation with the coefficient of friction of the contact surfaces , which interrupts the power transmission above a certain torque.
See also
literature
- Wilhelmdaughtermann, Ferdinand Bodenstein: construction elements of mechanical engineering ..., part 2: elements of the rotating and the linear movement, elements for the transmission of uniform rotating movements. 9. verb. Springer edition, Berlin 1979, ISBN 3-540-09265-X , p. 100ff. and 112ff.
Individual evidence
- ↑ K. R. Repetzki diesel locomotives in Glaser annals 1895-1936 , Trans Press reprint, Berlin 1987, ISBN 3-344-00127-2 , page 47