New Safety Couplings Protect Against Dangers And Loss Of Production

One hundred percent security and continuous availability are increasingly becoming a decision criterion for the operation of plants. Couplings for encoder attachments must therefore meet very special requirements. On the one hand, they have to be flexible enough to compensate for any mounting inaccuracies without overloading the ball bearings of the attached encoder, on the other hand, they have to be strong enough to withstand even extreme operating conditions.

Permanent design is mandatory

The requirements for the design of safety couplings are defined in the IEC standard 61800-5-2. It specifies in detail which fault models for the mechanical connection of safety components, such as. B. sensors for functional safety may be used and with which safety factors the design must be carried out. According to the standard, a permanent design is mandatory for safety couplings.

When it came to proving the fatigue strength of the new HKS Safety couplings, the Hübner-Giessen designers also opted for maximum safety: in addition to the prescribed calculations, extensive trials and tests were also carried out. These included shock tests, endurance tests, flexural strength tests and a 96-hour salt spray test to demonstrate corrosion resistance. In contrast to operational clutches, whose lifespan is limited to a certain number of load changes, durable safety clutches are designed for an infinite number of load changes and had to complete more than 106 load changes in the test series without errors.

Additional safety claws ensure further availability

Even if the spring washers made of high-strength special steel are unlikely to break in the event of an overload, additional safety claws ensure further availability. They take on a “driver function” and ensure that the clutch and encoder continue to rotate in this worst-case scenario and that there is no unplanned downtime.

The HKS series includes both single-joint couplings for correcting angular errors in flange attachments and double-joint couplings that can be used to compensate for shaft misalignments in foot attachments. For the attachment of encoders to converter-controlled drives, Johannes Hübner Giessen recommends the optionally available coupling variants with insulation made of glass fiber reinforced plastic. This effectively interrupts shaft currents and prevents damage to ball bearings.

Robust design

Thanks to their robust design and tested safety, HKS safety couplings are suitable for use under extreme conditions. HKS and HKDS safety couplings operate between -50 ° C to max. 120 ° C flawless, the insulated HKSI or HKDSI product variant works perfectly between -25 ° C to 85 ° C. This is made possible, among other things, by a shock resistance of 10 g (briefly max. 100 g) tested in accordance with DIN EN 60068-2-27 and a vibration resistance (DIN EN 60068-2-6) of 3 g (briefly max. 20 g). A maximum torque of 3 Nm can be transmitted up to the permissible maximum speed of 6000 rpm.

The HKS series comprises various couplings with total lengths between 36 mm and 120 mm and bore diameters up to 22 mm. From this, the coupling variant that is optimally suited to the respective application can be selected. With each HKS safety coupling, Johannes Hübner Giessen provides a declaration of conformity, in which the exclusion of errors is guaranteed if the operating and installation conditions are observed. This means that the couplings can also be used for safety applications up to SIL 3 (Safety Integrity Level 3) / PL e (Performance Level e) and can be classified as a component with error exclusion in the risk analysis. (jv)