Papermaker's felt

Details Papermaker's felt Papermaker's felt

2001-08-20

2004-03-02

Griffin, Steven P. (Department: 1731)

Paper making and fiber liberation

Apparatus

Running or indefinite length product forming and/or treating...

C162S900000, C139S3830AA, C442S192000, C442S270000

Reexamination Certificate

active

06699367

ABSTRACT:

CLAIM FOR PRIORITY AND CROSS-REFERENCE TO OTHER APPLICATIONS
This application claims priority to German Application No. 100 40 828.1, filed Aug. 21, 2000, the disclosure of which is hereby incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a seamed felt such as is variously employed in paper machines as a press felt to remove water from a web of paper.
For this purpose, in the paper machine the web of paper is pressed between two felts or between a felt and a roller, so that the water is removed.
BACKGROUND OF THE INVENTION
For reasons of operating safety and to shorten the time during which the machine must be stopped for installation of the felts, seamed felts are increasingly being used on the paper machine in the lower and intermediate speed range and for papers with relatively low quality requirements. As a rule, these felts are composed of a woven backing fabric of coarse monofils in the longitudinal and transverse directions, with a monofil diameter in the range 0.35 mm to 0.5 mm. Onto this fabric fibres are needled in the conventional manner to form a felt-like structure.
The disadvantage of this backing-fabric concept lies in the poor anchoring of the fibres and the increased frictional wear and tear of the press felt, the tendency of the coarse backing fabric to leave marks on sensitive papers, and the low damping capacity of the felt on vibration-sensitive press positions.
In order to eliminate the problem of poor fibre anchoring, in the past attempts have been made to use curled yarns, as is described for example in the patent EP 0 502 638 A1. However, the curling of such yarns makes it difficult to work with them. Furthermore, it is difficult to produce and maintain a specific and reproducible curling of the yarns, in particular when different kinds of fibre materials are used.
A similar attempt to eliminate the above-mentioned disadvantages is disclosed in DE 39 30 315, which describes felts with braided yarns in the long direction with respect to the direction of movement of the endless band in the paper machine. Here, however, it has proved disadvantageous that on one hand the manufacture of braided yarns is elaborate and expensive, whereas on the other hand the felts made with these braided yarns show a declining elasticity and/or an impermanent or temporally unspecified stability.
The patent U.S. Pat. No. 5,514,438 describes felts for use in a paper machine, in which wound yarns are employed in the long direction with respect to the direction of movement of the endless band in the paper machine. These wound yarns consist of monofils surrounded by a layer or several layers of multifils. This embodiment, too, has so far proved to be suboptimal, because the construction of the wound yarns is very complex and hence they are complicated and expensive to manufacture.
SUMMARY OF THE INVENTION
The objective of the invention is thus to make available felts in which the fibre anchoring is improved in comparison to the known state of the art and which have a lower tendency to leave marks as well as a higher damping potential in comparison to the known state of the art.
For this purpose the invention includes the essential idea of improving the seamed felts previously used in paper machines by using structured fibres not only as the longitudinal threads of a basic textile area used as backing fabric, i.e. those aligned with the direction of movement, but also as the transverse or weft threads, which run substantially in the perpendicular direction. It further includes the idea of providing a twisted structure in which monofils, each of which in itself has a helical construction, are entwined with one another.
It has proved advantageous for the twisted structure to have a substantially round cross section. Surprisingly, it has been found particularly advantageous for this cross-sectional shape to be formed by entwining three monofils with one another, because when three monofils are used, an approximately homogeneous and substantially circular cross section is achieved over the entire length of the twisted structure. Another substantial advantage of the use of three monofils to produce the twisted structure lies in the fact that it is easy to handle threads that are not too thin, whereas the overall diameter of the twisted structure must not become too large, and this is enabled by the use of several monofils. Furthermore, three monofils provide adequate stability, so that an optimal combination of stability and flexibility is achieved.
In contrast, a twisted structure made of only two monofils has a cross section in the shape of two circles side by side, while a twisted structure made of four monofils has a substantially four-cornered shape with rounded corners. Furthermore, the diameter of the twisted structure as a whole increases, the more monofils are incorporated therein, so that the twisted structure in itself becomes more rigid and hence more difficult to work with. In principle, however, twisted threads made of five or more individual monofils are possible, in which case the diameter of each individual strand is made smaller.
The textile backing elements are constructed in at least two-ply form. This minimally two-ply backing element (see FIG.
1
=duplex design) forms the basis for combinations with one or more woven fabrics which, laid over or under the backing fabric, can be connected thereto by means of needles. For special applications it is also possible to place two seamed backing fabrics (see FIG.
2
=laminate) one over the other and join them together by needling or adhesive technology to form a backing element. Such backing elements make it possible to dispose between the woven layers other layers of fibres suitable for forming a felt-like structure.
According to another advantageous design, it is likewise possible to provide between the layers of the textile backing element special damping layers that have a suitable structure and are made of a material suited to the particular application.
Preferably when the textile backing element is constructed in several-ply form, at least one upper ply of longitudinal threads is connected to a lower ply, in which case the seam loop can be formed between upper and middle, upper and lower or middle and lower ply. The advantage of this and similar constructions lies in the greater thickness, lower tendency to leave marks and better damping in comparison to a two-ply or a laminated backing element. Owing to the inclusion of an additional ply of longitudinal threads by weaving technology, the textile backing element gains stability.
This stabilizing effect on the felt, combined with preservation of its mobility, in particular in the region of rollers over which the felt passes during operation of the paper machine, is reinforced by the twisted structure of the transverse threads. The twisting of the monofils makes it possible for the threads used to produce the felt to penetrate into and/or through the twisted structure between the monofils, and thus to be optimally anchored in the backing fabric. When plain monofils are used instead of a twisted structure, such anchoring is impossible.
This kind of anchoring is just as impossible when braided or curled yarns are used, because these have an elastic component and therefore with respect to their structure exhibit a distinctly weaker cohesion of the threads. Fibres needed to produce a felt cannot become securely attached to these curled or braided yarns and/or to monofils that have been worked into such yarns, so that under load a migration of the fibres out of the structure formed by curled or braided yarns is practically unavoidable.
In contrast, felts manufactured with a twisted structure in their textile backing fabric exhibit a distinctly improved long-term stability because here, as a result of the firm intertwining or twisting together of the monofils, once the fibres have penetrated into the twisted structure they are permanently anchored there; outward migration is hardly possible and practically never occurs.
Accordi

Affiliated with

Also associated with

Rating

Papermaker's felt does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Papermaker's felt, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Papermaker's felt will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3254399