General Felt Information
Advantages of the Technology provided by Dostal Maschinenbau for the Felt Industry
Krafft Göbel, the founder of Krafft Göbel Maschinenfabrik GmbH in Alsfeld improved and modified the technology in the felt industry. By his inventions the manufacturing of felt became more economic and last but not least it was possible to produce a high-quality of felt.
The Krafft Göbel Maschinenfabrik was taken over by us, the Dostal Maschinenbau GmbH by the 1st of April 2006. The Dostal Maschinenbau GmbH produces and sells worldwide felt manufacturing machines in different executions. The cooperation with felt factories all over the world allows us adapting the machines to the actual technical standards and to the requirements of our customers.
In the following we want to give you a short presentation of the machines produced by Dostal Maschinenbau:
1. The Pilgrim Step Roller Fulling Machine
In the thirties of last century Krafft Göbel developed the so-called Gatterwalke machine. This was the first flat working fulling machine for the felt industry. By a sensible arrangement of rows of shaft-shaped wooden rods the felt was processed after hardening. This machine proved worthwhile in the felt industry and was sold with success.
In the fifties of last century the Pilgrim Step Roller Fulling Machine was developed – similar to the multiroller in the hat industry – but with a roller width of 2,40 m and a roller diameter of more than 130 mm. The felt was flat fulled from the beginning of the fulling up to the end of fulling. The fulling rollers do not rotate continuously round but swinging forward and backward. The backward motion is less than the forward motion.
A reasonable drive mechanism with hydraulically controlled couplings allows a speed rate adjustment between inlet and outlet. Whereas the forward swinging of the fulling rollers is always constant the backward swinging is gradually adjustable from inlet to outlet. If the backward movement is increased the running speed becomes minor and the felt is compressed.
Hundreds of Pilgrim Step Roller Fulling Machines are working worldwide in the felt industry. They were continuously improved and modified and were designed bigger, stronger and with a longer life time. With this machine all kinds of felts can be fulled. Moreover it has a re-hardening effect, i.e., badly hardened material can be fulled.
Whereas in the Hammer Fulling Mill or the Cylinder Mill an excellent and even hardening is required, the Pilgrim Step Roller Fulling Machine is a machine in which less hardened material can be fulled to a high quality felt. Thin and thick felts, shaped and conical felts as hammer head felts can be fulled on the Pilgrim Step Roller Fulling Machine, obtained specific weights of up to 0,58 g/cm3.
This machine allows admixtures of synthetic fibres in felt lengths up of to 70 %, i.e., by using the Pilgrim Step Roller Fulling Machine essential savings of material are obtained. The abrasives–loss of material during fulling process is much less than in the Hammer Fulling Mill or Cylinder Mill.
However, it is difficult to indicate exact performance data, as there are differences in the used raw material, the required density and specific weight, and the ability of fulling the wool varied.
The Roller Hardener works differently. Hardening is affected during the passage, i.e., the felt is moved and pressed in lines between the rollers. Between the two pressure lines the fibres can orientate themselves newly and a better strengthening is obtained, already during the first process operation. Whereas with thinner felt lengths specific weights of 0,14 to 0,16 g/ccm are obtained in the plate hardener, specific weights of 0,20 g/ccm can be obtained in the roller hardener by multiple treatment. Consequently many thinner wardrobe felts do not need a fulling process after hardening. The material is then washed, dyed and dried. Less wool and more synthetics can be used for felt manufacturing.
In the roller hardening machine the intermediate cloth is brought back to feeding position by forward and backward running. The standstills of the machine are minimized.
The compensation between pressure and movement is important for an even fulling. We succeeded in reaching this aim by the new shape of hammers and troughs. The application of modern proven material is the guarantee for a long life time of these machines. Big flywheels increase the force of impact and thus the high capacity.
Felts manufactured in the Pilgrim Step Roller Fulling Machine, the Hammer Fulling Mill or the Cylinder Mill are often reduced at the edges. Moreover all felts are impregnated with acid that must be removed after fulling. In the Re-Fulling Machine felt-plates, discs, blocks and felt lengths can be processed.
The edges become sharp after treatment in the Re-Fulling Machine. Felt lengths are treated between strips screwed on the table and at the same time become more even in width. Felts treated in a Cylinder Mill showing folds and swellings are equalized in the Re-Fulling Machine.
The problem of dewatering can be solved by squeezing or centrifuging. Whereas squeezing may cause damages on the felt by strong pressing, a gentle dewatering is guaranteed by the horizontally working centrifuge. The felt is winded up a drum, secured with belts and dried. A good dewatering is ensured.
We constructed those centrifuges not only for felt lengths but also for plates and discs. The felts are packed in cages made of stainless steel and are dewatered by centrifugal force, as well.
All machines delivered by Dostal Maschinenbau GmbH for the felt industry have proven worthwhile. The machines are sturdily constructed and have a long life time. We offer servicing and deliver spare parts for machines older than 20 years. Our service manuals allow solving troubles with delivered spare parts that are no longer available. They will replaced by new modern parts which can be applied by means of adapters.
Here you find our felt making machines