Spring shafts – technical information

Keroll Kerger spring shaft

Useful information
Roller shutters and folding grilles fitted with spring shafts can only be operated with the least possible manual force if the traction of the springs has been calibrated precisely to the curtain weight. For this reason, we incorporate springs of varying widths, material thickness, length and tractive power (e.g. 10, 20 or 30 kg) into our housing. In order to ensure that the spring design is precisely calibrated with your gate it is therefore essential to determine curtain dimensions and weights accurately without estimating.

For manual operation of gates using spring shafts, roller shutter-/ folding grille curtains should be as light as possible. It is therefore recommended to use aluminium instead of steel and to use a lower material thickness (e.g. 1.00 mm) in preference to a larger thickness (e.g. 1.25 mm) (this applies especially to steel gates). Please also be aware that the manufacturers’ information concerning the m² weights of the folding grille- or roller shutter profiles is sometimes inaccurate. Please also take into account the weight of the end pieces (do not use any steel end pieces), the end rail (do not use any that are too heavy) and the lock. In order to determine the exact weight, weighing the curtain is recommended (e.g. on a set of personal scales). Please also indicate whether a single or double-walled curtain is being used. Double-walled profiles always run with greater difficulty in comparison with single-walled roller shutter curtains, despite being of the same size or weight. In the case of double-walled profiles in particular, the permissible manual strength values can be exceeded quickly.

The guide rails should, where possible, be designed in steel and without PVC inserts. This applies especially to curtain weights above 50 kg. The clear opening of the guide rail should be approx. 2mm greater than the profile thickness. If there is too much clearance, the profiles will tilt when raised; if there is insufficient clearance, the curtain will jam when operated. If the PVC insert cannot be dispensed with, the material used should be as hard as possible. The curtain dimensions are decisive when assembling the spring shafts – not the clear opening dimensions! The curtain height above the shaft centre must not exceed 150 mm when opened out. Otherwise the chuck key to be used cannot be inserted correctly. Information regarding aluminium roller shutters: Steel bars should not be used as a suspension rail. Individual suspension hooks (max. suspension hook width: 120 mm) are ideal for fastening to the housings. Screwing the upper bar directly onto the spring housing is not recommended, except in the case of double-walled gates.

According to DIN EN 12604:2000, the manual force required for operating gates in domestic areas should not exceed 15 kg and in commercial areas 26 kg. The permissible manual strength in the end positions may briefly be exceeded by up to 50 % according to DIN EN 12453:2000. When moving out of the end positions, single-walled curtains weighing more than 100 kg and double-walled curtains weighing more than 80 kg may exceed the permissible manual strength of 15 or 26 kg. If it is anticipated that the 15/26 kg manual force required will be exceeded due to the weight of the curtain, please seek the customer’s approval before ordering. In general, the following applies: It is essential that the curtain weight is indicated as accurately as possible. For heavy curtains especially, incorrect information can quickly lead to the spring shaft becoming completely unusable for the particular gate.

Further information: It is essential that the lower third part of the guide rails are greased. Even in the case of wider gates, two handles must not be installed. A single handle, installed exactly in the middle of the curtain, is sufficient.

Assembly
Pay attention to span direction! Tensioning should only be carried out using the chuck key supplied by us and not with a pipe wrench or similar tools. Count the tensioned rotations of the spring. The springs should be tensioned approx. ½ rotation more than the winding number of the curtain: 1 rotation = 6 holes of spring pin. The springs will reach their maximum traction after approx. 5 rotations. Additional tensioning will not increase the tractive power, but only the lifting height, so that the curtain strikes the lintel too forcefully.

Problem solution
1. Problem:

Springs too weak The curtain can only be lifted with difficulty (up to approx. ½ lifting height) and strikes the lintel forcefully. The curtain must be pulled vigorously upwards from the lintel and falls to the ground with force. The problem cannot be resolved on-site. The problem can only be resolved by changing the springs. 2. Problem:

Springs too strong The curtain already starts rising from the ground while being tensioned and must be held at the bottom. The curtain cannot reach the lintel because the springs cannot be brought to the required number of rotations due to their strong tractive power. The problem can be resolved by tensioning the springs. This involves tensioning the springs up to the end, which will cause them to become softer. 3. Problem:

End rails tilt when raised Problem solution: Rivet a flat bar approx. 200 mm in length onto the end rail.

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