Efficient Emergency Stops in the Woodworking Industry: RINGFEDER® Friction Springs for Block Band Saws

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In addition to the steel industry with its harsh environments and high temperatures, wood processing is another industry that benefits from our RINGFEDER® friction springs. 

Regardless of whether steel slabs, coils or entire tree trunks are being moved - high masses generate large amounts of energy. Our dampers with friction springs reduce these to a level that is tolerable for the neighbouring components and structures. The case shown here involves an emergency stop on a log band saw. This is a wood saw with a mostly horizontal bandsaw blade guide, which is used to saw logs lengthways.

The saw is fed with the help of clamping carriages, which are used to clamp and manipulate the logs to be processed. The EW2 model from Esterer EWD is moved to and from the saw by means of a cable drive with a 24 mm thick cable. With a maximum total weight of 16 tonnes when fully loaded, the clamping carriage is accelerated to a speed of v = 200 m/min = 3.33 m/s. If the cable should break unexpectedly, an emergency stop must be available to absorb the unbraked impact of the trolley or the forces and energies that occur, thus preventing damage to the system. This should be realised by 2 buffers per wagon side.

With the given data, the energy W to be absorbed is calculated to be around 90.000 Joules. Divided over 2 buffers, this results in a rounded figure of 44.400 J per buffer.

As not all the boundary conditions had been fully clarified at the start of the project planning, a double spring in a parallel arrangement was initially considered as a possible solution. It consisted of the standard types 16600 with 56 elements and 12400 with 80 elements. As there were no special requirements regarding the ambient temperature, the use of RINGFEDER® standard grease F-S1 was planned. This would have resulted in a preload force FV = 53 kN and an operating force FB = 490 kN with an operating spring travel  sB = 164 mm per buffer. The buffer itself would have had an installation length of approx. 1270 mm.

This proposed solution had to be discarded as new requirements had arisen. Instead of just one wagon, it should also be possible to stop two wagons attached to each other if necessary. This meant that an energy absorption of 90.000 Joules per buffer had to be possible in this load case. In addition, the installation length was limited to 620 mm for space reasons.

This resulted in a triple spring combination consisting of the special type 24201 with 20 elements and the standard types 19600 and 14000 with 24 and 34 elements respectively, which have the following operating values.

Bei einem Wagen:
FV = 160 kN, FB = 1267 kN bei sB = 63 mm pro Puffer

For one carriage:
FV = 160 kN, FB = 1267 kN with sB = 63 mm pro Puffer 


Image 1: Force-displacement diagram

The requirement for the maximum overall length of 620 mm could not be met. It is 690 mm. The Esterer company was able to compensate for this with design measures, so that this solution was ultimately used.


Image 2: RINGFEDER® buffers in the wood industry 

In this application, the buffers serve as double safety and prevent damage to the carriage and building structure if the steel cable breaks.


Image 3: Side view of emergency stop buffer

Due to the enormous moving masses and the harsh conditions in wood processing, RINGFEDER® friction spring products are perfectly suited for use in the wood industry. Whether as an emergency stop for log band saws or as overload protection for clamping carriages, the applications are diverse and crucial for the safety and efficiency of your systems. Contact us for customised solutions!

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