Benutzer:Dielsdorftuermli/Self-synchronising clutch

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The self-synchronising clutch,also called overrunning clutch, (common abbreviation SSS clutch), is a Freewheel in which the torque transmission is carried out with the help of a gear coupling, which is engaged by a built-in pawl freewheel (ratchet mechansism). It is suitable for transmitting higher torques than with a classic freewheel and is, for example used in ships and power plants.

Construction

The self-synchronising clutch consists of gear coupling, ratchet mechanism with pawls and sliding piece, which is steered by a helical gear system for automatic engagement and disengagement. The internal gear system is designed so that finally the gear coupling is transmitting the full torque, while the ratchet mechanism and pawls are de-loaded. This enables the high torque transmission capability of self-synchronising clutches.

Function

When engaging, the two toothed parts of the gear coupling are screwed into one another by the drive torque guided by the helical gear.When disengaging, the sliding piece is automatically pushed out of the gear coupling again by the higher speed of the output. In disengaged state, the pawls are ratcheting on the sliding pieceand hold it in disengaged position, which is called freewheeling or pawl freewheel.

Engaging

As soon as the input shaft overruns the output shaft, the pawls engage with the ratchet wheel of the sliding piece and move the entire sliding piece guided by the helical gear axially into the coupling position, and the gear coupling engages. In fully engaged position, the pawls are no longer engaged, and the power from the drive is completely transmitted by the gear coupling. On large couplings, some oil dampers, which dampen the engagement, are integrated in the end stop of the sliding piece.

Disengaging

If the drive is slowed down compared to the output, the resulting braking torque causes a tooth flank change in the gear coupling. The sliding piece is screwed back by the thread, so that the gear coupling is opened and the pawls slide over the ratchet wheel toothing. If the speed difference is very high, the pawls are lifted as a result of centrifugal force and hydrodynamic effects, which is desirable to reduce wear.

Manufacturer

There are only a few manufacturers of self-synchronising clutches. The most important are:

• SSS Clutch Company, USA and SSS Gears Limited, England
• RENK-MAAG GmbH, Switzerland, subsidiary of Renk AG

Application

Self-synchronising clutches are used in drive trains with multiple drivers (e.g. turbines, diesels, electric motors, expanders) with the target of optimum drive train efficiency, flexibility and safety. The most important applications of self-synchronising clutches are listed below.

Air defence destroyer County-Class,on which an SSS clutch was used for the first time.

Shipbuilding

Self-synchronising cclutches are used for the following applications in Shipbuilding:

• Coupling of several driving machines to a common shaft train that drives the Propeller
• Coupling of energy recovery machines to the main drive train

Power plants

Shaft train of Huntorf power plant in which two SSS clutchess are installed one for 300 MW and one for 80 MW.

Self-synchronising clutches are used for the following applications in power plants :

• Coupling of the steam turbine to the drive train in combined cycle power plants that are designed as single-shaft systems
• Coupling of low pressure steam turbine to the high pressure drive train in cogeneration also called combined heat and power plants
• Coupling of two gas turbines to a common generator
• Coupling between generator motor and turbine or compressor in an compressed-air energy storage power plant
• Coupling between gas turbine and generator, so that the generator can be used as a phase shifter without being driven by the gas turbine (synchronous condensing operation to support grid stability).

Other

Self-synchronising clutches are also used for the following applications:

• Coupling a power-independent emergency drive to electric pumps
• Coupling two redundant prime movers to a work machine
• Coupling of energy recovery turbines or expanders to the compressor drive train (e.g. steel production)

History

The first commercial application of a self-synchronizing coupling took place in COSAG-Drive of the County-Class-destroyer In the Royal Navy at the end of the 1950s. In 1964, the clutch was used in power plants for the first time so that a gas turbine generator could work in phase shifter mode. In 1978, the most powerful SSS coupling was put into operation at the Huntorf power plant it can transmit an output of 300 MW.

Literature

• M. Klocke, St. Kulig, G. Zimmer: Modeling and Simulation of a Sychnronising Selfshifting Clutch in Single Shaft Cogeneration Plants. In: Electromechanical drive systems: Innovations, trends, mechatronics; Conference proceedings; 6th - 7th October, 2004 ,in Fulda. 2004, ISBN 978-3-8007-2852-7, S. 5055 (Google Buch). 

Weblinks

• Patent AT206234: Self-shifting synchronous clutch. Published 10 November 1959. Inventor: Harold Sinclair, SSS Gears Ltd
• Patent US2986249: Synchronous self-shifting clutches (SSS). Published 30 April 1961. Inventor: Arthur Clements, SSS Gears Ltd.
• Patent CH390007: Self-engaging synchronous toothed coupling. Veröffentlicht am 19. November 1964.‌
• SSS Clutch engagement during high speed rotation. SSS Gears Ltd., 8. Februar 2010, abgerufen am 13. September 2015 (englisch). 
• Synchronous Clutch Coupling. RENK-MAAG GmbH, abgerufen am 19. April 2021.