PROTECTIVE FLAP FOR THE SEAM IN NEEDLE-FELTS FOR INDUSTRIAL USE

Abstract: Drying felts have since many years been provided with a seam (2) in order to facilitate the mounting in the paper machine and during the last three years also the press felts have been provided with such a seam. In order to prevent that the paper web is marked by the seam, the seam is covered by a wadding flap, which is a continuation of the wadding layer which is fastened to the felt. The wadding flap is worn in different ways when the felt is used in the paper machine and its firm­ ness will therefore decide the limit for the effective life­ time of the felt and marking in the web will occur due to the wearing of the wadding flap. In order to decrease the wear on it, so that a better felt is obtained and also a safer production of paper, the protective flap includes at least one layer (6), the fibers, the yarns or filaments of which are mainly placed in the moving direction of the felt in the machine.

Description: This invention concerns a felt, press felt, drying felt, conveyor belt or -felt, which is made endless by a releasable seam, said seam being covered by a protective flap having one or several layers whereby the uppermost layer is of wadding. Endless felts are used in paper machines in order to convey and support the wet and weak web through the presses and the press section. Felts are also used in the drying section - specifically in marking sensitive positions - in order to convey the web through the drying section, whereby the web is pressed by the flet against heated cylinder. One of the most important requirements of the felts is that they may not give impressions on the wet web. Such felts have therefore earlier been furnished endless even if this has made it more difficult to mount them in the paper machine. Drying felts have since many years been provided with a seam in order to facilitate the mounting in the paper machine and during the last three years also the press felts have been provided with such a seam. In order to prevent that the paper web is marked by the seam, the seam is covered by a wadding flap, which is a continuation of the wadding layer which is fastened to the felt, see EP-A-0 108 733. The wadding flap is worn in different ways when the felt is used in the paper machine and its firmness will therefore decide the limit for the effective lifetime of the felt and marking in the web will occur due to the wearing of the wadding flap. Felts which are provided with the above-mentioned seams are so called needle-felts which have a substrate on which a fibrous web, a layer of wadding is fastened. The layer of wadding is usually produced from carded fibrous web, which is placed transversely by an operating means with a breadth, which is in accordance with that of the substrate. The wadding layer is fastened to the substrate by several needless having downwardly directed hooks which penetrate the wadding layer and the substrate so that the fibers of the wadding layer are drawn downwardly between the yarns of the substrate and are fastened. By this way of covering the substrate by wadding the fibers of the wadding layer and of the so formed wadding flap over the seam are given a direction, which mainly is transverse to the longitudinal direction of the felts or the moving direction in the machines. In the wadding flap where fibers are not needled into the substrate but only penetrated so that the fibers are wound around and tied to each other, the strength in the operating direction will be very low. Fibers get very often loose by strains in the paper machine and the wadding flap can after a certain time not fulfil its function as a cover over the seam for preventing marking of the web. The connection between the wadding flap, the paper machine and the web will be discussed in the following. A bad or weard out wadding flap in the press section will result in: a risk of marking, breakage of the web, disturbing of the operation of the press, disturbing of the vacuum system and the fiber passage. The elements in the press section which are wearing the wadding flap are: suction boxes, HT- strips, press cylinders and guiding rollers. A wadding flap which is bad or weared out in the drying section will result in: risk of marking, breakage of the web and air leakage at so called ejector blowing boxes. Matters which have influence on the strength of the wadding flap in the drying section are: wear of the cylinders and the guiding rollers, chemical degradation and hydrolys and air blowing for cleaning. The object of the invention is to provide a protective flap, which is so formed that the wear on it is decreased, so that a better felt is obtained and a safer production of paper. The invention is thereby characterized in that the protective flap includes at least one layer, the fibers, the yarns or filaments of which are oriented in the moving direction of the felt in the machine. An embodiment of the invention will now be described with reference to the drawings. Fig. 1 is a schematic longitudinal view of a known felt having layers of wadding and a protective flap. Fig. 2 is a similar view of a felt but according to the invention. Fig. 3 is a similar view as Fig. 2 but showing a second embodiment of the invention. Fig. 4 is a schematic view of the protective flap formed in order to be able to fasten by needling. The felt according to Fig. 1 includes a substrate 1, which has a transversal seam 2, which consists of usual locking loops and locking thread. The layer 3 of wadding having transversal fibers is needled to the upper side of the substrate. The so called protective flap 4 is placed in the area above the seam. Fig. 2 shows an embodiment of the invention, whereby the felt includes substrate 1 and the seam 2. A layer 5 of wadding having transversal fibers is placed upon the substrate. A layer 6 of wadding having longitudinal fibers is placed upon the layer 5. The layers themselves may include several layers. The layer having longitudinal fibers does not need to pass around the entire felt but it is necessary that the layer is placed within the area closest to the seam 2. A modified embodiment is shown in Fig. 3. On the substrate 1 there is the layer 5 of wadding having transversal fibers. A loose woven fabric "scrim" or a non-woven fabric (e.g. "spunbond") is placed on this layer, the woven fabric or the nonwoven fabric has hereby the main part of the fiber material oriented in the longitudinal direction. A further layer 8 of wadding having its fibers in transversal direction or in longitudinal direction is then placed on the woven fabric 7. It should be noted that alternatively the fibers in the layer having the fibers in the longitudinal direction may partly or completely be exchanged to other fibers than those which are included in wadding. The exchanged fibers may be such which are stronger or have a better chemical or heat resistance. Fibers having greater length may also be used and also e.g. multifilament. By using longitudinal fibers in order to reinforce at least one of the layers of wadding above the seam,a further possibility is achieved to improve the seam with a flap of wadding. The felt is normally produced by that the layer of wadding is needled to the substrate, the ends of which are joined with a locked seam. The flap is cut after being needled in the way as shown in Fig. 4. Thus, an oblique cut is made in the direction to the seam along the dashed line 9. When there is a reinforced upper layer having longitudinal fibers it is possible to disengage this from the underlaying layers in a point 10, which lies a certain distance after the seam when seen in the moving direction of the web. The disengaged flap of wadding has sufficient strength so that the structure is maintained when the felt is being mounted in the paper machine. After that the felt has been mounted in the machine and the seam 2 has been locked the felt is placed in the right position over the seam and is fastened on the same place as it was disengaged by needling down into the felt with a portable needling machine having a certain amount of needles. There is a smaller risk for damages and wear on this needled flap than when the flap is free. The invention is not limited to needle felts in paper machines but can be adopted for needle felts, which have lockable seams and are used endless as e.g. conveyor belts and -felts.

Claims: Felt, press felt. drying felt, conveyor belt or -felt, which is made endless by a releasable seam, said seam being covered by a protective flap having one or several layers whereby the uppermost layer is of wadding, characterized in that the flap (4) includes at least one layer (6), the fibers, the yarns or the filament of which being oriented in the moving direction of the felt in the machine. Felt according to claim 1, characterized in that the layer (6) is a wadding. Felt according to claim 1, characterized in that the flap includes several layers, one of the lower layers (7) consisting of filaments oriented in the moving direction of the web. Felt according to claim 1, characterized in that the flap includes several layers, one of the lower layers (7) consisting of a woven fabric having longitudinal yarns orientated in the moving direction of the felt. Felt according to claim 1, characterized in that the flap includes several layers, one of the lower layers (7) consiting of a non-woven fabric with the fiber material orientated in the moving direction of the web. Felt according to any of the preceding claims, characterized in that the joining edge of the flap is oblique in the transverse direction, and that the length of the flap in the direction opposite to the moving direction of the felt is so long on the upper side that the flap after being placed gown above the seam can be fixed to the pulling strand by a needling procedure.

Inventors: JOHANSSON, JOERGEN, NOHLGREN, GOERAN, NYHOLM, ERIK, Johansson, Jörgen, Nohlgren, Göran
Applicants: SCANDIAFELT AB
Application year: 1986
Main classification: D21F7
IPC codes: D21F7, D04H1