A slip clutch is an automatic torque-switching safety clutch that protects parts of the system from damage.
Definition and demarcation
- A slip clutch in the narrower sense is used when, in addition to the introductory definition, the safety clutch is based on a friction clutch, i.e. there is a frictional connection .
- A slip clutch is also present in the opposite normal case, i.e. when the clutch does not disengage but closes when a defined torque is applied.
However, there is still the same aspect (torque-switching safety clutch)
- Locking body couplings ( form fit ) → e.g. B. spring-loaded balls, bolts or claws , which slip reversibly out of corresponding grooves or when a limit torque is reached
- Shear pin couplings (form fit) → pins break irreversibly when the limit torque is reached
- hydrodynamic or electrodynamic couplings
See the main article: Coupling
The slip clutch as a component (the mechanics ) is arranged between two shafts . When a defined torque is reached , the clutch disconnects or connects without external (external) influence. In addition to synchronous operation, the shafts can also run at different speeds up to a standstill of one shaft.
In principle, all friction clutches are also slip clutches. For the necessary aspect of the safety clutch, an (adjustable) clutch force and, as a result, the defined torque already introduced at the beginning is important. A flat force characteristic (of the clutch) is functionally sensible so that when the clutch wears, there is no excessive deviation in the torque to be secured. In addition, the slip clutch should be checked and secured for slippage in normal operation (closed).
Depending on the application, single, double or multi-plate (multi-plate) clutches are used as the design.
The magnetic coupling is a special form , which can be implemented both as a disk coupling and as a magnetic particle coupling.
Applications and examples
In principle, slip clutches are used where (due to the system separation through the clutch) overloading of machine elements or injuries to people should be avoided.
One example is their use as a material or occupational safety measure in which they slip when a part of the body, an item of clothing or (generally) gentle material gets into a machine. However, this function can only be used in areas where the working torque is so low that the clutch does not slip during normal operation.
In industrial use, slip clutches are usually combined with a control system via electromechanical or electronic switches (sensor-controlled), which stops the drive when the drive comes to a standstill or when the speed falls below the target speed on the output side (clutch slips).
Slipping clutches are also used in motor vehicles :
- with electric window regulators as the simplest mechanical anti-trap protection
- the clutch is designed as a slip clutch in the broadest sense: (engine / gearbox output train wheels)
- as an anti-hopping clutch in motorcycles
- In the case of special designs (e.g. off-road, racing) as variable locking differentials in order to provide (mostly variable) torques on a spinning shaft or to divert them to the other axle (multi-disc locking differential).
In the case of the tape recorder , the slip clutch on the right tape plate only ensures that the tape is easily wound up, while the actual tape drive takes place via the capstan and pressure roller . As a result, the belt speed always remains the same despite the variable winding diameter.
In the case of the automatic watch , the slip clutch prevents the mainspring from being overturned by the rotor.
In a radio-controlled model car with an electric drive, the slip clutch ("slipper") is not only used to protect the drive, but primarily to improve the acceleration and controllability of the model on slippery surfaces. The effect of the slip clutch and thus the maximum torque that can be transmitted is set via the preload of a compression spring. Plastic disks built into the slip clutch are designed in such a way that they expand when the clutch slips, so that the torque that can be transmitted increases sharply with increasing slip time, i.e. H. the clutch grabs.