Eltra elastic couplings

Elastic couplings allow the encoder shaft to be connected to another device’s shaft. It minimize shifts and can absorb radial and axial shaft play.


  1. Encoder flexible couplings by EltraEltra flexible elastic couplings image
  2. Eltra standard couplings
  3. Eltra special application couplings

Encoder flexible couplings by Eltra

Presented devices are very important part of motion transmitting to the encoder shaft. They connect with the moving shafts of other devices and transmit displacement to encoder.

Such device avoids the following problems:

  • stiffness during rotation;
  • small distortions of the shaft;
  • axial clearance.

The company produces couplings with cylindrical housing. On the main body, there is a special spiral groove.

Eltra s.p.a. produces couplings for both standard and special applications.

Eltra standard couplings

Standard couplings belong to the G series (precision elastic coupling). They are available in three basic outer diameter sizes:

  • 20 mm;
  • 25 mm;
  • 30 mm.

It is also possible to make couplings with other sizes on order. All of them are included in the shaft fixing with grub screw category (A - Eltra marking).

Standard models include the following Eltra coupling models:

  1. G 20 A 6Eltra standard elastic coupling scheme image
  2. G 20 A 8
  3. G 20 A 9
  4. G 25 A 9
  5. G 25 A 10
  6. G 30 A 10

G 20 A 6 has an outer diameter of 20mm and internal Ø6H7. The tolerance for the difference in internal diameters at the inlet and outlet is +0.012mm. Device length is also equal to 20 mm. It has an internal thread M3 and is designed to work with shafts Ø7 mm.

G 25 A 8 has an outer diameter of 25mm. Internal diameters are 8H7 and have a tolerance of +0.015. Such couplings have an M4 thread and is designed to work with shafts Ø8mm.

G 25 A 9 has almost identical parameters with the previous model, but the internal diameter is 9.52H7.

G 25 A 10 has the same characteristics however the internal diameter here is 10H7.

G 30 A 10 has an outer diameter of 30mm and internal 10H7. The device is most compatible with 9mm shafts. The housing has an internal thread M4.

All standard models are made of aluminum. They are available in many variants of internal diameters. For example, G 25 A 6/8 will have d1 = 6mm and d2 = 8mm.

Eltra special application couplings

In addition to standard ones, the Italian company also produces special couplings. They are intended for extraordinary cases. This means high torques, axial and radial play etc.

The manufacturer produces the following series of special application couplings:

  1. GS-DAEltra specialized elastic flexible couplings GS series
  2. GS-EA
  3. GS-EP
  4. GS-M
  5. GS-O
  6. GS-S

GS-DA elastic coupling is a thermally and electrically insulated double-circuit coupling made of plastic. It has medium stiffness and low restoring forces. Device has good resistance to shock and vibration. This coupling is able to provide a smooth ride. It also successfully reduces radial, lateral and angular displacements.

GS-EA elastic couplings are specifically designed for heavy-duty conditions. They can be used for multipurpose operations. Such unit has high torsional stiffness and medium restoring forces. GS-EA is made from a single piece with clamping hubs installed.

Due to its design, such couplings have anti-vibration properties and optimum compensation for distortions.

GS-EP is a series of low-cost couplings that have medium torsional stiffness and low restoring forces. They are made by injection molding. Metal inserts provide a reliable connection with the shaft. Such couplings have free slot area.

GS-M has an excellent transmission of rotational motion without backlash and a high level of vibration suppression. They have low torsional stiffness and low restoring forces. The design has a high level of robust, as it has no moving parts. It can be used for the most various purposes where reliability is necessary.

GS-O have a central disk in its design which slides on the hubs tenons under the influence of a controlled load. This helps to avoid shaft play. The main advantages of such couplings are excellent radial compensation and ease of maintenance.

GS-S are flexible couplings that have very high torsional stiffness and low restoring forces. They differ in quite strong design. Reliability is ensured with stainless steel bellows. The shaft is connected using clamping sleeves, which avoids damage to it.

Specialized models can also have different sizes.

Conclusion: Eltra S.r.o. Company releases a wide range of couplings for transmitting motion to the encoder shaft. Standard versions allow to quickly putting device into operation, and specialized ones help to improve quality of work and avoid some problems.

On our website eltra-encoder.eu you can find the full catalog of G20A, G25A, G30A, GS elastic couplings by Eltra and all another series for request.

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