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Servo couplingsDimensioning

c) according to the shaf t diameter: After selecting the coupling type, it must be checked whether the requested shaft diameter corresponds with the allowed diameter (D
min / D
max ) of the hub bores. Another coupling type or size must be chosen, if the shaft diameter is overdimensioned in relation to the torque, which means it is larger than D
max of the hub. Note: e) Max. load: Hub bores which are smaller than “D
min ”. are possible; but an optimal transfer of the nominal torque can not be guaranteed in this case, so a reduction of TKM is necessary. d) Useful life of the coupling - durability: The durability of JAKOB compensating couplings is basically determined by the peak torque and the existing shaft displacement or misalignment. If the admissible maximum values for the axial, lateral and angular displacement are not exceeded, and if the operating torque at the same time is below the coupling nominal torque TKN, then the coupling is within the range of prolonged alternating-stress strength limit. An infinite number of start - stop - cycles or acceleration and deceleration can be carried out without having to expect a break - down of the coupling during operation.

Fatigue lifeof coupling

torque permanentdistortionendurance strength(endurance failure) TT maxKN 7 load change cyclesprolonged alternating-stress strength2 10 In special cases, the couplings (metal bellow, membrane, elastomer spider) can be overloaded for a short time with twice the nominal torque (2 x T
KN ) . The hub-bore-connection, however, must be calculated seperately then.
Misalignment f) Bearing loads:
lateralaxialangular g) Operating temperatures: Due to the flexibility of the compensating couplings in all directions, considerable bearing loads are prevented, in spite of possible axial, lateral or angular displacement from the drive shaft to the output shaft. Therefore, an early breakdown or higher wear of the rolling bearing can be prevented. This means less difficult and expensive repairing. Metal bellow and membrane couplings are, as whole metal couplings, extremely insensitive to temperature and can be used at temperatures up to 300° C without limitation. The temperature limit of the elastomer spider is at 90° C (98 Sh-A) resp. 120° C (72 Sh-D). At high operating temperatures, an appropriate correction factor needs to be applied. h) S peeds: Due to precision machining and the rotation symmetrical design resp. the additional balance pin, the compensating couplings are generally suitable for high speeds up to 20,000 min
-1 even without additional balancing. The standard balancing quality are approx. Q 6.3 to Q 16. Couplings with conical hubs or hubs with tapered ring can be operated with speeds over 25,000 min
-1 (please further consultation). The low moment of inertia also has a positive effect. i) Maintenance and wear: Compensation couplings are maintenance and wear free under normal conditions. The polyurethan spiders of the elastomer couplings should be changed in suitable periods, if critical operation parameters are given.
Servocouplings www.jakobantriebstechnik.de Tel. 06022 2208-0 Fax 06022 220822

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