This application claims priority from and incorporates by reference German Patent Application DE 10 2022 117 304.6 filed on Jul. 12, 2022.
The invention relates to a fabric tape, in particular a forming fabric tape for a machine configured to produce and/or process for forming a fiber web.
A generic fabric tape is already known from DE 10 2013 218 465 A1. This fabric tape provides satisfactory fiber support through the upper fabric layer and sufficient dimensional stability through the lower fabric layer and is characterized in that the first groups and the second groups in the pattern repeat improve support of the upper longitudinal threads by the lower longitudinal threads compared to known fabric tapes which have already included more lower longitudinal threads than upper longitudinal threads. The improved support of the upper longitudinal threads causes fewer depressions in the upper fabric layer which reduces the propensity for undesirable visible hydraulic markings in the fiber material web.
Though the fabric tape known from the printed document DE 10 2013 218 465 A1 already delivers good results flatness of the upper fabric layer can still be improved in order to further reduce the propensity to cause undesirable visible markings.
The object is achieved by the features of a forming fabric tape for a machine for producing or processing a fiber web, the forming fabric tape including an upper fabric layer including upper longitudinal threads and upper transversal threads woven with the upper longitudinal threads; and a lower fabric layer including lower longitudinal threads and lower transversal threads woven with the lower longitudinal threads, wherein the upper fabric layer and the lower fabric layer are arranged above one another so that the upper fabric layer is oriented towards the fiber material web and the lower fabric layer is oriented away from the fiber web, wherein the upper fabric layer is connected with the lower fabric layer by binding threads running in a transversal direction of the fabric tape, wherein a weaving pattern of the forming fabric tape is repeated in pattern repeats, wherein the pattern repeats are formed from plural longitudinal thread supergroups respectively including the upper longitudinal threads and the lower longitudinal threads, wherein each of the longitudinal thread super groups includes two first groups and a second group, wherein each first group is formed respectively from an upper longitudinal thread and a lower longitudinal thread arranged below the upper longitudinal thread and each second group is formed respectively from an upper longitudinal thread and two lower longitudinal threads arranged below the upper longitudinal thread, wherein each binding thread in the pattern repeat forms at least one multiple binding with the upper transversal threads in the pattern repeat, and wherein the pattern repeat includes at least six longitudinal thread super groups that include the upper longitudinal threads and the lower longitudinal threads.
Advantageous improvements include at least one or more of the following:
The pattern repeat (R) may include exactly six longitudinal threads super groups (WE) including the upper longitudinal threads (O1-O3) and the lower longitudinal threads (U1-U4). The upper fabric layer may be connected with the lower fabric layer in the pattern repeat (R) exclusively by multiple bindings of the binding threads (B1, B2) with the upper longitudinal threads (O1-O3). A first binding thread (B1) in the pattern repeat (R) may form two double bindings with the upper longitudinal threads, and a second binding thread (B2) forms a double binding and a triple binding with the upper longitudinal threads (O1-O3). The binding threads (B1, B2) may be always arranged in binding thread pairs, and the two binding threads (B1, B2) of a respective binding thread pair are woven in an alternating pattern with the upper longitudinal threads (O1-O3) and the lower longitudinal threads (U1-U4) and intersect in intersection points when switching from being woven with the upper longitudinal threads (O1-O3) to being woven with the lower longitudinal threads (U1-U4). The binding threads (B1-B2) form a plain weave of the upper fabric layer with the upper transversal threads (OQF) and the upper longitudinal threads (O1-O3). The lower fabric layer may include a 6-shaft repeat binding of the lower longitudinal threads (U1-U4) or a 8-shaft repeat binding of the lower longitudinal threads (U1-U4) or a 12-shaft repeat binding of the lower longitudinal threads (U1-U4). A lower transversal thread (UQF) may only switch over one or at the most two directly adjacent lower longitudinal threads (U1-U4) and otherwise floats below the remaining lower longitudinal threads (U1-U4) per shaft repeat of the lower longitudinal threads (U1-U4). The upper longitudinal threads (O1-O3) and the lower longitudinal threads (U1-U4) in each group (I, II) need not be offset relative to each other in an orthogonal view of the fabric layers or only slightly offset relative to each other in the orthogonal view of the fabric layers so that a clear space of half a diameter of an upper longitudinal thread (O1-O3) is formed at the most between the upper longitudinal threads and the lower longitudinal threads of each group or there is no free space. A diameter of the lower longitudinal threads (U1-U4) may be greater than a diameter of the upper longitudinal threads (O1-O3). There may be more upper transversal threads (OQF) than lower transversal threads (UQF) or 1.5 times an amount of upper longitudinal threads compared to an amount of lower transversal threads (UQF).
The term “multiple binding” means that a binding thread that transits from the lower fabric layer into the upper fabric layer runs at least over a first upper longitudinal thread, under a second upper longitudinal thread that is directly adjacent to the first upper longitudinal thread and over a third upper longitudinal thread that is directly adjacent to the second upper longitudinal thread before it switches from the upper fabric layer into the lower fabric layer again. Put differently, the binding thread that switches from the lower fabric layer into the upper fabric layer runs over at least two not directly adjacent upper longitudinal threads before it transitions back into the lower fabric layer. However, this can also apply to three or more upper longitudinal threads that are not directly adjacent to one another. When these are exactly two upper longitudinal threads, this is called “double binding” or a “2-binding segment” and when these are exactly three threads is called a “triple binding” or also a “3-binding segment”, etc.
The inventors have found that flatness of the upper fabric layer deteriorates when single bindings are used in the pattern repeat exclusively, this means that each binding thread that switches from the lower fabric layer into the upper fabric layer only runs over one upper longitudinal thread before it switches back into the lower fabric layer again. This has the effect that the upper longitudinal thread over which the binding thread is run is pulled down in a relatively sharp turn so that an undesirable depression is formed at this spot in the upper fabric layer. This effect of forming depressions is reduced compared to single binding when using multiple binding.
Additionally, the inventors have found that it is advantageous for low marking properties of a fabric tape when the pattern repeat is made from at least six longitudinal thread super groups which are made in turn from a second group and two first groups like in the instant embodiment. The at least six longitudinal thread super groups which respectively include three upper longitudinal threads and four lower longitudinal threads facilitate to use the binding threads in the fabric as binding thread pairs which continue a plain weave of the upper fabric layer together with the upper longitudinal threads and the upper transversal threads even when each binding thread in the pattern repeat forms at least one multiple binding with the upper transversal threads in the pattern repeat. The plain weave of the upper fabric layer provides good fiber support which advantageously impacts the marking properties of the fabric tape. Theoretically this would also be possible for fewer than six longitudinal thread super groups, namely four longitudinal thread super groups with 12 upper longitudinal threads and 16 lower longitudinal threads. However, it has come as a surprise that fabric tapes of this type have the disadvantage of being relatively thick. This may be caused by the fact that a 16-shaft binding is used for the upper longitudinal threads for the 16 lower longitudinal threads which then causes a rather long floatation of the lower transversal threads, typically to floatation below at least 12 lower longitudinal threads. This, however, means: the longer the floatation the thicker the fabric tape and the thicker the fabric tape the greater the clear volume of the screen and thus the amount of undesirable transported water and required repulsion power etc.
In order not to make the production of the fabric tape according to the invention more complicated than necessary, the upper longitudinal threads and the lower longitudinal threads of the pattern repeat include exactly six longitudinal thread supergroups. The six longitudinal thread super groups have the effect that the pattern repeat includes 18 upper longitudinal threads and 24 lower longitudinal threads, thus in total 42 longitudinal threads. Since the fabric tapes, in particular the forming fabric tapes are typically woven flat, the longitudinal threads correspond to the warp threads, whereas the transversal threads correspond to the weft threads in the weaving process. A pattern repeat with 42 warp threads provides plenty freedom for the design. For example, 3-, 4-, 6-, 8-, or 12-, shaft repeats can be used for the lower fabric layer and 2- or 3-shaft repeats can be used for the upper fabric layer, which already facilitates 10 (=5×2) different designs with respect to the number of shafts of the base binding. The 24 lower longitudinal threads would also facilitate a 24-shaft binding, however this is not advantageous since this leads to very long flotations of the lower longitudinal threads below at least 12 lower longitudinal threads and thus to an undesirable thickness of the fabric tape.
In order to have the least amount of depressions in the upper fabric layer it is advantageous that the upper fabric layer is connected with the lower fabric layer in the pattern repeat exclusively by multiple bindings of the binding threads with the upper longitudinal threads.
In a pattern repeat with six previously described longitudinal thread groups, thus with 18 upper longitudinal threads the upper fabric layer becomes particularly flat when a binding thread pair forms a quadruple binding and the other binding threads of the binding thread pair forms a quintuple binding with the upper longitudinal threads. However, this can cause the undesirable effect that the upper fabric layer and the lower fabric layer are not bonded together with sufficient strength due to the resulting small number of binding points between the upper fabric layer and the lower fabric layer which can lead to an increased inner abrasion of the binding threads at the binding points. In the extreme the two fabric layers can separate from each other. Therefore it is particularly advantageous, in particular when the upper longitudinal threads and the lower longitudinal threads are made exactly from six longitudinal thread super groups and the binding threads configured as binding thread pair continue a plain weave of the upper fabric layer so that a first binding thread of a binding thread pair in the pattern repeat forms two double bindings with the upper longitudinal threads whereas a second binding thread of the binding thread pair forms a double binding and a triple binding with the upper longitudinal threads. This achieves an acceptable flatness of the upper fabric layer and a typically completely sufficient stability of the binding of the upper fabric layer with the lower fabric layer.
As stated supra it is advantageous to always arrange the binding threads in binding thread pairs, wherein the two binding threads of the respective binding thread pair are woven with the upper and lower longitudinal threads in an alternating pattern and intersect in intersection points when alternating between being woven with the upper longitudinal threads in order to be woven with the lower longitudinal threads and vice versa. Thus, the two binding threads of a binding thread pair advantageously correspond to an upper transversal thread in the weaving pattern of the upper fabric layer.
Furthermore, it is advantageous for good fiber material support on the upper fabric layer when the binding threads form a plain weave of the upper fabric layer together with the upper transversal threads and the upper longitudinal threads as stated supra.
Though it is possible to use, for example, 3-shaft or 4-shaft repeat binding for the lower fabric layer, it has proven particularly advantageous in practical applications when the lower fabric layer includes 6-shaft repeat binding or 8-shaft repeat binding or 12-shaft repeat binding with respect to the lower longitudinal threads. In order to provide a maximum wear volume through the lower transversal threads on the machine side of the fabric tape it is advantageous when a lower transversal thread only switches over one or at the most two directly adjacent lower longitudinal threads per shaft repeat and is otherwise floated below the remaining lower longitudinal threads. In particular with 6-shaft repeat binding or 8-shaft repeat binding a lower transversal thread can only be run over one longitudinal thread per shaft repeat, whereas it is also possible for a 12-shaft repeat binding that a lower transversal thread runs over two directly adjacent lower longitudinal threads per shaft repeat.
With respect to flatness of the upper fabric layer it is advantageous when the upper and lower longitudinal threads are not offset at all or only slightly offset relative to each other in each group in an orthogonal view of the fabric layer so that a clear space of a half diameter of an upper longitudinal thread is formed between the upper longitudinal threads and the lower longitudinal threads of a group at the most, advantageously there is no free space at all. Thus, the upper longitudinal threads can be supported by the lower longitudinal threads sufficiently well. Reference is made in this respect to the printed document DE 10 2013 218 465 A1 recited supra.
Advantageously the diameter of the lower longitudinal threads is greater than the diameter of the upper longitudinal threads. The diameter of the lower longitudinal threads can advantageously be in a range of 0.13 mm to 0.35 mm, whereas the upper longitudinal threads have a diameter of 50% to 90% advantageously 60% to 80% of the diameter of the lower longitudinal threads. This provides a fabric tape with a particularly fine upper fabric layer and a lower fabric layer that is sufficiently stable to provide a high wear volume and/or high dimensional stability.
In order to obtain a sufficiently dense upper fabric layer, even when the fabric tape includes fewer upper longitudinal threads than lower longitudinal threads it is advantageous when the fabric tape simultaneously includes a relatively large number of upper transversal threads, in particular more upper transversal threads than lower transversal threads, particularly advantageously 1.5 times or two times the upper transversal threads compared to the lower transversal threads. In this context also binding thread pairs which jointly complete the weave of the upper fabric layer with the upper transversal threads and the upper longitudinal threads, in particular to form a plain weave, shall be counted among the upper transversal threads as well. In this case a binding thread pair would count among the upper longitudinal threads.
The invention is subsequently described based on advantageous embodiments with reference to drawing figures, wherein:
The schematic representation of
The fabric tape includes a weaving pattern that is repeated in pattern repeats R according to the invention. The pattern repeat R is formed from at least six longitudinal threads super groups with respect to the upper longitudinal threads and the lower longitudinal threads of the fabric tape. In particular, the pattern repeat can be formed from precisely six longitudinal thread super groups WE as schematically illustrated in
Since the pattern repeat R includes at least six, advantageously exactly six longitudinal thread super groups WE, each binding thread B1, B2 according to the invention can form at least one multiple binding with the upper longitudinal threads in the pattern repeat R and the binding threads B1, B2 can continue a plain weave of the upper fabric layer in pairs without rendering the fabric tape too thick. Corresponding embodiments for the path of the binding threads B1-B2 are schematically illustrated in
However, this embodiment is not necessarily optimum with regard to strength of the connection of the upper fabric layer with the lower fabric layer through the binding threads B1, B2. This is caused by the fact that this embodiment provides only very few switches of the binding threads B1, B2 from the upper fabric layer into the lower fabric layer in the pattern repeat R.
In order to increase strength of the connection between the two fabric layers it is advantageous to let the binding threads B1, B2 switch in the pattern repeat from the upper fabric layer into the lower fabric layer more often. The second embodiment according to
The embodiment according to
Three different variants of the third embodiment illustrated in
In the second variant according to
In the third variant according to
Number | Date | Country | Kind |
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DE102022117304.6 | Jul 2022 | DE | national |