quality products for mechanical & fluid power: www.jbj.co.uk

quality products for mechanical & fluid power: www.jbj.co.uk

Torsionally Flexible Claw Couplings

N-EUPEX® rated torque: up to 85,000 Nm, ATEX compliant.

Complies with the current ATEX Directive for:
II 2G Ex h IIC T6 ... T4 Gb X
II 2D Ex h IIIC T85 °C ... 110 °C Db X
I M2 Ex h Mb X
jbj Techniques Limited, official UK partner for the complete Flender coupling range.
ATEX compliant torsionally flexible claw couplings, N-Eupex

N-EUPEX as overload holding, fail-safe series

N-EUPEX as overload holding, fail-safe series
The elements of the N-EUPEX coupling are subjected to compression.
If the elements are irreparably damaged, the hub parts come into contact metal to metal. This emergency operation capability, fail-safe characteristic is required for instance, in the case of fire pump drives as an example.
ATEX compliant torsionally flexible claw couplings, N-Eupex DS

N-EUPEX DS as overload shedding, non-fail-safe series

N-EUPEX DS as overload shedding, non-fail-safe series
The elements of the N-EUPEX DS series are subjected to compression and bending forces.
If the elements are irreparably damaged, the metal parts turn against one another without contact, and the power transmission is separated. Fitting new elements will make the coupling usable again. The capacity of the N-EUPEX DS series to shed overloads is especially necessary for highly sensitive machines.
For details of materials and shore hardness values please see page 2 of the technical specification catalogue.
N-EUPEX and N-EUPEX DS flexible shaft couplings connect machines and compensate for shaft misalignment, generating only low restorative forces. The torque is transmitted through elastomer elements, so the coupling has typically flexible rubber properties.
» Torque up to 85,000 Nm.

» Speeds up to 7,500 rpm. dependent on model

» ATEX compliance (details below)

» NEW TYPE: N-EUPEX DK, added to the modular principle of N-EUPEX and the performance & bore capacity of all types increased. (details below)
Large stocks for quick delivery and in-house machine shop for exact fit to your application machinery.

Telephone: +44 (0)1737 767493 or email: info@jbj.co.uk
N-EUPEX® flexible shaft couplings are designed on a modular principle and have a very simple construction. N-EUPEX types are made up of sub-assemblies to suit requirements. The couplings are assembled by simply fitting the coupling halves together. Wear is restricted to the elastomer elements, which must be replaced at the end of their service life. Depending on type, the elastomer elements can be changed without moving the coupled machines. The coupling parts are readily available from stock and are mostly finish-machined, i.e. with finished bore, keyway, set screw and balancing. Please note that if the couplings are finished machined / bored and keyed in the jbj Techniques machine shop, the couplings will be supplied un-balanced, unless specifically requested.

The N-EUPEX coupling is available as a catalogue standard in 23 sizes with a rated torque up to 85,000 Nm. The coupling is suitable for use at ambient temperatures of between -30°C and +80°C. By using alternative elastomer elements, the permissible ambient temperature range can be extended to between -50°C and +100°C. Generally, the coupling is used to connect the motor to the gear unit input shaft. The coupling is especially suitable for drives with uniform to average dynamic loads.

Additional variations:
» Adapters and hubs: Grey cast iron EN-GJL-250
» Brake disks: EN-GJS-400 spheroidal graphite cast iron or S355J2G3 steel
» Brake drums: Grey cast iron EN-GJL-250
» Low-temperature application: Shock loads in the drive caused by e.g. starting of drives with large masses to be accelerated (e.g. in fan drives) result in high component loads, particularly at low temperatures. For such applications a particularly robust coupling series must be selected.

Note about ATEX compliance

Both series are ATEX certificated, but importantly it must be noted that the N-Eupex coupling is ATEX compliant as long as the coupling is operated in accordance with the installation, operation and maintenance manual. More importantly the maintenance aspect, replacing the elastomers prior to failure. This is due to the fail-safe design allowing torque transmission should the elastomers fail.

If complete ATEX safety is required, without needing to adhere to the N-Eupex maintenance requirements, then the N-Eupex DS is the coupling to use.
Coupling suitable for use in potentially explosive atmospheres.
Complies with the current ATEX Directive for:
II 2G Ex h IIC T6 ... T4 Gb X
II 2D Ex h IIIC T85 °C ... 110 °C Db X
I M2 Ex h Mb X

A new type, N-EUPEX DK, added to the modular principle of N-EUPEX and the performance & bore capacity of all types increased.

Double-cardanic system.
With the new double-cardanic design, the coupling compensates for not only a greater range of shaft angle offsets, but also a considerably greater radial offset so that shaft ends can be connected in a manner that offers the drive greater protection. With this two-joint version, compensation for radial offset that occurs between the shaft ends is enabled by a corresponding angle of inclination in the elastomer joints. This increases the range of possible radial offset by more than a multiple of four. Especially with pump applications, shaft ends that are not 100% in alignment present a significant problem. In this case, the N-EUPEX DK provides a solution for many problems because, depending on the coupling length and size, it enables compensation  for  a  radial  offset  of  up  to  3  millimetres. Furthermore, in contrast to the previous N-EUPEX, the new coupling type "DK" makes use of not just one, but two series of elastomer elements, which guarantees increased damping over the entire drive train. In addition, due to the double-cardanic design, significantly lower restoring forces are generated. The high ratio of shaft and joint clearance also decreases the restoring forces. Depending on size, offset and installation dimensions, the restoring forces decrease by more than half. The result is a lower load on the shafts along with a lower load on the bearings. This is advantageous especially with thinner shafts, which can be damaged due to the wrong coupling design or improper installation, even up to the breakage point. The spacer, made of aluminum with a joined pocket part made of gray cast iron, comes in standard increments for shaft spacing from 100 mm to 250 mm, so its length can be adapted to the customer's design.
Double cardanic system of the new N-Eupex DK mechanical power transmission coupling
Cutaway of double cardanic system of the new N-Eupex DK
Performance data for type N-Eupex DK (two-joint coupling)Performance data for type N-Eupex (single-joint coupling)
For coupling fatigue torque: TKW = 0.15 x TKN, where TN > TW must be adhered to.
FLENDER has succeeded in increasing both the performance and the bore capacity of the entire N-EUPEX series by nearly one-third. As a result, users benefit from greater torque, higher rotation speeds and a change in size. The N-EUPEX series has proven itself for decades as a standard solution, and it has now been elevated to a new level of connector technology.


The name "EUPEX" comes from ancient Greek and means "well connected." These couplings by Flender GmbH are as durable as the ancient Greek name is old. The manufacturer of gear units, couplings, generators and complete drive systems has been producing the EUPEX coupling for about one hundred years, ever since the company's founder, Alfred Friedrich Flender, had this name entered as a trademark in the registry of the Patent Office of the German Reich on December 22, 1923.

The successor to these couplings, N-EUPEX®, has been manufactured since 1967 and there are millions of them all over the world in every industrial sector. To continue to meet the high expectations for the product in the coming decades as well, the development team has made some changes to the series. New types were added to the modular principle of N-EUPEX. Couplings with a torque limiter, with a clamping element as well as with a short double-cardanic design will now be added to the existing short and long types. In addition, elastomers made of TPU are offered. Moreover, both the performance and the bore capacity were increased for all types in the series in 2020.

The pages via this » link « contain detailed information and the advantages regarding these changes and here below, in brief, are a few notes
N-Eupex ERN with torque limiter

Torque limiter for more safety in the drivetrain

The new N-EUPEX ERN coupling is equipped with a torque limiter, which provides even more security in the drivetrain in many applications. Users can specify a maximum torque and thus protect machines and systems from overload. The coupling never transmits torques that are critical for the motor or output machine.

Clamping elements as a practical shaft-hub connection

The main advantage of this shaft-hub connection becomes especially apparent in the course of service work, for example during assembly or when replacing worn elastomers, which can be carried out more easily. With this type of connection, in contrast to the feather key connection, the usual heating of the hub parts before tightening is not required. The hubs are also very easy to remove during disassembly after the clamping screws of the clamping elements have been loosened, thus restoring sufficient play in the connection between the shaft and coupling. No connecting machine components have to be moved, which reduces the time required and also the machine downtime.
N-EUPEX DKS, double-cardanic coupling as “short version”

Double-cardanic coupling as “short version”

The benefit for users is mainly the shortened overall length of this type including reduced costs, while the advantages of a double-cardanic coupling connection can still be utilized. Thus, it is possible to replace single-joint couplings with the double-cardanic design in problematic drives. In short: the new and inexpensive  N-EUPEX DKS  can  be  used even  more  universally  than  its  "big  role  model"  N-EUPEX DK.
Technical specification of new N-EUPEX DK couplings found in this on-line » catalogue « link

Mechanical power transmission couplings . . .

1) What is your application?

2) Which power transmission coupling would best serve your purpose?

3) Which size & specification of coupling will safely and cost effectively fulfill your requirements?

Selection of the correct coupling type

There are a range of factors when selecting the most suitable coupling for your application.

Contacting jbj Techniques for helpful, friendly advice is definitely a good idea. Before doing so why not be prepared with some useful information first.

The range of Flender couplings showing the different types in a selection criteria, quick reference grid.

Pages 1 to 17 cover many considerations in the selection of the right coupling for mechanical power transmission.
The drop down menu marked 'links to FLENDER couplings info' will then direct you to the relevant technical specification catalogue in order to then select the correct model and size. Should you require assistance in coupling selection we are here to help so please contact the technical office telephone: +44 (0)1737 767493 or email: info@jbj.co.uk
Driver to driven shaft detail diagram
To connect the driver to the driven safely, proficiently and cost effectively full details of how to select the correct coupling type and coupling size for your application start at here « link.

jbj Techniques Limited
for friendly help and advice
telephone: +44 (0)1737 767493
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