Technical Data  Coupling  Sizing and procedure

To view selection procedures and precautions, please proceed to the following.

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Jaw-flex Couplings 　LN Series 　Selection

To ensure that LN Series Jaw-Flex Couplings provide backlash-free operation over a long period, selected products must have a sufficient margin of safety for the spider’s normal-use torque.

Accordingly, use the procedure below to select products. Spiders are consumable parts, so must be replaced periodically to maintain backlash-free operation.

  • 1. Apply the drive’s transmitted power P [kW] and the coupling’s operating rotation speed n [r/min] to the formula below to calculate the torque T [N·m] that will be applied to the coupling.

    T = 9550・P/n

  • 2. Use the operation conditions to determine the service factors St and Sd, and calculate the correction torque Tr [N·m] that will be applied to the coupling.

    Tr = T・St・Sd

    • St：Temperature coefficient
    • Sd：Torsional stiffness factor

    Select a product size that will result in the coupling’s normal-use torque Tn being greater than or equal to the correction torque Tr.

    Tn ≧ Tr

    Temperature coefficient
    Operating temperature ℃ Temperature coefficient St
    -30 ～ +30 1.0
      ～ +40 1.2
      ～ +60 1.4
      ～ +80 1.8
    Torsional stiffness factor
    Application Torsional stiffness factor Sd
    Machine tool spindle 2 ～ 5
    Positioning 3 ～ 8
    Encoder 10 or more
  • 3. Check that the maximum torque Ts [N·m] generated from the drive, load, or both the drive and load will be less than or equal to the coupling’s normal-use torque Tn.
    • Maximum torque from drive ：Ts = Tas・Ma・Sa
    • Maximum torque from load ：Ts = Tℓs・Mℓ・Sℓ
    • Tn ≧ Ts・St・Sd
    • Tas：Maximum drive torque (N・m)
    • Tℓs：Maximum load torque (N・m)
    • Ma：Drive’s moment of inertia ratio Ma = Jℓ/ (Ja + Jℓ)
    • Mℓ：Load’s moment of inertia ratio Mℓ = Ja/ (Ja + Jℓ)
    • Sa：Shock load factor (drive )
    • Sℓ：Shock load factor (load )
    • Ja：Drive’s moment of inertia
    • Jℓ：Load’s moment of inertia
    Shock load factor
    Load characteristics Shock load factor Sa(Sℓ)
    Uniform load 1.0
    Low fluctuation 1.4
    High fluctuation 1.8
  • 4. Check that the shafts to be mounted are within the coupling’s range of mountable shaft diameters.
    The shaft coupling torque varies according to the shaft diameter, so may be lower than the spider’s normal-use torque in some cases.
    Check that the shaft coupling torque for the selected coupling size is greater than or equal to the maximum torque Ts applied to the coupling.