High-speed Backstops Equipped With Carbon Friction Pads

According to the company's own information, the development engineers at Ringspann have succeeded in doubling the load capacity of the new backstops while maintaining or reducing the previous outer diameter (330 mm to 975 mm) with the new high-speed backstops of type FXRW and FXRU. This was achieved through the use of carbon fiber friction linings, which should offer high surface pressures with good wear resistance. In relation to the sizes, this should enable high slip torques to be achieved - in extreme cases of up to 140,000 Nm. The maximum slip torque (MR) is - in addition to the expected maximum return torque - the decisive parameter for the design of a torque-limited backstop in multiple drives. It saysAt what maximum load a backstop limits and its effect to protect people and machine technology unfolds.

More freedom in construction

According to Ringspann, the backstops FXRW and FXRU are high-tech components for applications in gearboxes for multi-motor drives. During idle operation, the centrifugal forces generated during the rotation are used to enable the sprags to be lifted off the outer raceway and allow wear-free operation. The backstops should be suitable, for example, for securing high-speed transmission input shafts in the first and second gear stages. Like all freewheels of the Ringspann FXR family, they have integrated torque limiters as standard. Ringspann sees particular advantages for designers of multiple drive systems: Since the new backstops provide extremely high slip torques with relatively compact dimensions,The safety level of the drive systems should be able to be increased significantly without taking up more installation space. There is also freedom in the design - for example with regard to the collision problem with neighboring shafts or a cheaper design of the gearbox.

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Housing freewheel

Ringspann realizes the largest housing freewheel so far in record time

Sliding hub

Maximum constancy up to 60,000 Nm

In the FXRU variant, the backstops are available in all sizes with a simple mechanical release device. With this patented release mechanism, the use of leakage-prone hydraulic release systems is to be dispensed with, which simplifies operation and lowers maintenance costs.

Due to the simple release device and its overall very robust design, the high-speed backstops should also be suitable for dirty and dusty operating environments. A typical area of ​​application is therefore the multiple drive systems in the conveyor systems of the bulk goods, mining and heavy industry. Here, the backstops protect the gearboxes installed at various points in the system from overload damage due to the usually very uneven distribution of the load that occurs during a reverse rotation - for example in the event of a stop or a sudden emergency stop. They are also intended to protect the entire drive train from dynamic torque peaks.

Additional information on the topic Why torque limitation?

The high relevance of the torque limiter in the FXR ring tension backstops should be particularly evident in the multiple drive systems of continuous conveyors. If one were to use backstops without torque limitation, each gearbox and its backstops would have to be designed for safety reasons so that it could absorb the entire back torque of the conveyor system. That would be very expensive and would amount to oversizing. The ring tension backstops with torque limitation are supposed to solve this problem. Because the integrated limiter slips briefly when the set torque is exceeded - until the other backstops gradually take action. This ensures that the entire reverse torque of the system can be distributed among the individual backstops and gearboxes.At the same time, the dynamic torque peaks of the locking process are reduced, which is intended to protect the transmission from harmful torque peaks. In addition, the gear units should be able to be made smaller with the aid of the ring tension backstops with torque limitation.

Supplementary on What is a backstop?

Backstops belong to the family of freewheels and are indispensable machine elements for the implementation of safe drive systems. They are always used when a rotational movement (eg a drive shaft) against the direction of rotation is to be prevented. This is the case with many machines and systems for safety or functional reasons. For the operation of conveyor systems, for example, there are legal regulations that require such a mechanical safety device. A backstop with centrifugal lift-off sprags runs idle in normal operation without wear, and the lock is carried out by the engagement of sprags at the moment of torque transmission.At the customer's request, Ringspann can deliver its backstops with torque limitation with factory-set slip torque.

Detailed simulations in advance

The development of the new backstops FXRW and FXRU was preceded by detailed torque simulations with analysis tools and intensive customer surveys. Among other things, this led to an optimized calculation model and the realization that the wishes of users for robust and easy-to-use backstops with high slip torques could best be met by using carbon friction linings. The new backstops are currently available in a total of 20 variants for slip torques from 3300 Nm to 107,000 Nm. (sh)