Electromagnetic Particle Clutch and Brake  
Basic Design and Operation Basic Construction 
Examples of installation & Application


Chain Tail' s powder-type clutch and brake units utilize electromagnetic powder to transmit torque. This offers the advantages of more streamlined and softer clutch operation and greater effectiveness during engagement of clutch friction surfaces.
Chain Tail produces a diverse range for clutches and is widely experienced in their application.
The company has accumulated extensive technology and know-how and can meet the needs of any client. The many products available are used to control winding machines used in producing paper, fiber, wire and cable and plastic items, and are indispensable parts of any production line.
These units can also be used in low-impact start and drive applications and to prevent overload during operations as torque.

 

 
Easy, wide-ranging controls
  The close correlation between magnetic current and torque makes it easy to control transmitted torque over a very broad range.
   

Enables seamless, continuous operation
  The use of magnetic powder makes it possible to maintain continuous operation with no effect on turning speeds, with stable torque levels over long periods.
   

Steady torque
  The work surfaces and the cuved shape contribute to proper operation of the magnetic powder, and a steady level of torque is available even when power is repeatedly turned on and off.
   

No chirping
  The design avoids the development of slick spots on tricition surfaces which can cause squeaks and chirping, resulting in ultra-quiet operation.
   

Extra heat capacity
  This design avoids the development of slick spots on friction surfaces which can cause squeaks and chirping, resulting in qltra-quiet operation.
   

Smooth engagement and transmission
  The static and dynamic friction rates for this model are virtually identical, which means very little vibration when contact is made. Acceleration and speed reduction to meet torque demands are also smoothly accomplished.
 
 Motion characteristics

This section describes desired control of start-up times as well as the actions necessary when performing repeated high frequency operations.
Figure 3 depicts how the powder clutch functions during engagement and release. When voltage is delivered to the coil, the energizing current changes and exhibits numerical increases in accordance with the time factor (T = L/R). This time factor is determined by the basic resistance R of the coil and the induction index L. The increase in torque is only slightly slower than the rise in magnetic current and has nothing to do with the slip between the  driver and driven sides; it will continue to rise until it reaches a set level. The torque also causes the load level to rise steadily.
In other words, although the driver and driven sides are not directly connected, the desired level of torque can still be achieved. This feature is connected to the large heat capacity of the clutch and offers several advantages where low-impact starts and stops or high-speed starts and stops are concerned.
This feature is helpful when emergency connection and drive are needed. Low resistance can be added into the coil to reduce the time factor; and when torque start-up causes two the three times the rated voltage to flow in, resulting in excessive magnetism, torque build-up is accelerated. When the rated voltage is applied, the coil time factor T may rise to 4~5 T, which will cause torque to build up fully. On the other hand, when the magnetism is cut off and all torque is gone, about one T of time will be needed.
Consult the various specification charts for time factors for coils.
 

 
 Allowable sustained slip rates
Although powder clutches and brakes can be used with sustained slip, the heat generated by slip will be confined to a rise in the temperature of the powder in the firs clutch and brake. Thus the allowable continuous slip rate for each type of machine must be determined, and the machine must be maintained within the set range during operation.

In addition, natural and forced-air cooling can also change the continuous slip rate. Although this rage is generally shown on the case of the unit, natural cooling and the input turning speed may cause variations in the rate.

 
 Allowable engagement workloads
When a clutch or brake endures an abnormal load during start-up or drive, the powder and the work surface may slip and generate frictional heat, This heat can cause the temperature in the first clutch and brake to rise.

When frictional heat becomes excessive the temperature of the affected parts will rise significantly. To prevent this from happening each machine must have its particular allowable contact workload determined, and this range must be observed during operation.

 
 No-load torque
Even when the magnetic current is completely shut off, the residual magnetism in the powder, lubricating oil in the bearings, linings and other sources of friction can cause mechanical loss, a feature called no-load torque.
No-load torque varies from machine to machine, and if the acceleration rate become excessive, mechanical losses in the accelerating portion may keep the torque form reaching proper levels.
 
 Test run
During shipment the powder in a clutch or brake may be lost or displaced, thus it is necessary to carry out test run of the parts before engaging in full use.
 
 Under forced-air cooling
Under forced-air cooling
  Their used for compressed air cooling should be free from water and oil, and a filter system with complete oil removal should be installed to remove vapors and deliver dry, clean air. (If moist air is used with a compressed air blower it will make the machinery damp, and decrease the efficiency of the system).
   
If the blower system uses hoses that are long or complex, ensure that a sufficient flow of air is being delivered.
 
 Heat blocks and heat cooling coils
Even when blowers are installed, they may lose their capacity and ability to dissipate heat, causing a drop in the operating efficiency of machines. A generous amount of space should be reserved around blower fans, especially in more adverse environments. The blades of blower fans can pick up impurities from the air and should be thoroughly cleaned on a regular basis.
   
A heat sensor should be fitted to the outside of the unit with a thermostatic switch and a warning system, which must be regularly checked.
 
 Options
Rated torque levels should not be exceeded even if they lie within the range of acceptable operating efficiencies.
   
When the tension control range is too broad, several different clutches may be installed and used interchangeably. In such cases the clutches must be isolated from each other to ensure that clutches that are not engaged will not run freely.
 
 Abnormal torque on start-up
Some types of operation(*) may cause torque levels to exceed specifications during start-up (this will not adversely affect normal operations unless the powder in the units is damp). This possibility can be minimized by carrying out a proper test run on installation and applying low levels of magnetism even when the system is stopped. (* applying input after or at the same time the unit is magnetized.)