Jointing of fabric ends to form an endless structure

(54) Name: Splice for woven material webs, preferably paper machine wires and method for producing such a splice

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The present invention relates to a joint for woven material webs, preferably paper machine wires and the like webs, wherein each web end is formed with a plurality of loops which are spaced at regular intervals in the width direction of the web and are formed by reversing the ends of some of the web warp threads. the loops at a web end are arranged to push in between the loops at the adjacent web end, and at least one connecting wire is inserted through the loops of both web ends to connect the web ends with each other.

It is well known to connect the ends of a wiper blanket to a paper machine by means of a so-called strap lock, which comprises groups of thread loops that are attached to the ends to be joined to each other, the loops extending in the longitudinal direction of the felt and alternately disposed with a locking thread. is passed through the overlapping portions of all loops to connect the ends. The wire loops are usually substantially unformed and the parallel legs have different lengths and are provided with an inward-facing tooth or hook at their free end for engagement with the blanket or a band connected to the blanket. A belt lock of this kind is described in British Patent Specification 1,040-694.

In a further development of this strap lock, two locking wires are used which are located next to each other in the loops, which are elongated to accommodate both locking wires. The locking wires are kept when used in

7510836-5 roller contact when the blanket is bent, for example when it passes over rollers, due to the tension in the felt. A belt lock with two locking wires arranged next to each other is shown in British Patent Specification 1,114,602.

It is also known to use the warp threads in a woven felt as an alternative to the thread loops in the above-described strap locks, thereby removing some weft threads in the woven blanket to provide a narrow band parallel to the end of the felt and is at some distance from the dehha and has only warp threads, after which the end is folded around a line in the middle of the band, so that a large number of loops lying next to each other are formed. A helical member is attached to the felt by partially inserting its individual turns into the spaces between adjacent warp threads in the weft-free band, whereupon a thread or corresponding locking member is inserted axially into the portion of the helical member under the blanket. Then, the end of the blanket is folded around a line in the middle of the wrap-free band to lock the thread between the inner periphery of the warp holes and the inner periphery of the helical member, and finally, the folded end of the felt is attached to the main body of the felt by sewing or otherwise. Such a joint is described in Austrian patent specification 288 14 ?.

As an alternative to the joint according to the aforementioned Austrian patent, full engagement can be achieved between the helical member and the warp threads of the weft-free band in the web, whereby the helical member is attached to the web by folding the end of the web around a line at the middle of the web. the opposite direction to the insertion directions of the helical member. Such a joint is disclosed in British Patent Specification 1 J48 098.

The joints described above are considered fully acceptable, but they do not give entirely satisfactory results when it comes to jointing a single layer synthetic paper machine wire for making paper and paperboard. For these, two main requirements are set, namely that the joint must not be thicker than the main part of the fabric or the fabric and that the permeability of water should be substantially equal for the fabric and for the joint. If any of these requirements are not fully met, the joint will adversely affect the quality of the product produced.

The state of the art is such that in order to fulfill both of the above requirements, a single-layered weave must be joined to an endless weave either by hand weaving the two ends together or by weaving an endless weave. This means that the paper machine must be so constructed that an endless fabric can be used, which means that

7510836-5 The paper machine must be partially dismantled in some way, so that the fabric can be mounted in the machine.

The main object of the present invention is to provide a joint and a method for making such a joint for, for example, single-layer synthetic paper machine wires, which eliminate the need to render the fabric endless before being mounted in the machine. This is achieved in accordance with the invention by means of a joint of the type indicated initially, which is mainly characterized in that the folded end of each warp thread forming a loop is inserted into the web and arranged in line with and close to the end of a nearby warp wire which is cut at a distance from the end of the web, the shrinkage pattern in the end portion of the web generally corresponds to the shrinkage pattern in the main body of the fabric and the warp coverage before is in excess of 80%.

The invention is based on the principle that the thickness of the fabric should be approximately equal to or greater than three times the diameter of the warp threads in order for the thickness of the joint to be substantially equal to the thickness of the fabric. A single-layered fabric of normal structure has less thickness than three times the diameter of the warp threads, which is due to the shrinkage to which the threads are exposed. For example, a single-layer fabric of normal construction may have warp yarns of a diameter of 0.22 mm and weft yarns of a diameter of 0.25 mm. If such a fabric is built up as a 1 and 3 broken keypad, the total thickness becomes 0.55 mm, ie. 2 times the diameter of the warp threads.

It has been found possible to maintain the material thickness at a value corresponding to the thickness of a joint with warp holes by appropriate choice of tissue pattern and thread diameter.

Warp coverage means the sum of the diameter of the warp threads in% of the width of the fabric. If the weft yarns and warp yarns have substantially the same diameter and the warp coverage is considerably less than $ 80, the weft yarns may have some shrinkage and material thickness will be reduced. If this happens, the loops will protrude above the surface of the material and the required relationship between the material thickness and the joint thickness cannot be achieved.

A free warp wire end which has been folded back around the shaft in the loops to be provided can be positioned in line with the adjacent severed warp wire end, but preferably it is placed in line with a further away cut warp wire end by displacing sideways a distance corresponding to three warp thread ends.

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The invention is described in more detail below with reference to the accompanying drawings, in which Fig. 1 schematically shows the required dimension of a loop; Fig. 2 is a perspective view of a known web, the shrinkage of the wires being shown; Fig. 3 is a schematic perspective view of a web. suitable for use with the present invention; 4 is a plan view of a joint according to a first embodiment of the invention, wherein free warp wire ends are folded back and positioned in line with the adjacent warp wire end, FIG. 5 is a plan view of the end of a web of loops formed in accordance with another embodiment of the invention, wherein a free throw wire end which is folded back is in line with a distant warp wire end, and Figure 6 shows a joint made in accordance with Figure 5.

Fig. 1 shows a side view of a warp wire loop formed at the end of a paper machine wire. As shown in the figure, the total height of the loop corresponds to at least twice the wire diameter plus the diameter of the connecting wire to be inserted through the loop. In FIG. 2 a perspective view of a light wire of known kind is shown, and it will be seen that the total thickness of the weave due to the shrinkage of the incoming wires becomes between the sum of the warp threads and weft thread diameters and the sum of twice the warp thread diameter and the weft thread diameter, and the total thickness becomes the closer the lower value the larger shrinkage to which the weft threads are exposed.

In Fig. 3, a tissue pattern is shown which, with sufficient thread coverage, has a thickness corresponding to three times the thread diameter and can therefore be used in conjunction with the invention, thereby obtaining correspondence between the height of the loop and the thickness of the fabric as required by the invention. The tissue shown is a broken twill.

As shown in Fig. 4 of the drawing, loops 11 at the end 12 of a fabric 13 are formed by removing weft threads from the end portion of the fabric, after which the ends of selected warp threads 14a are cut off and the remaining free warp thread ends 14b and 14b 'are folded back warp wire end is in line with adjacent cut warp wire end 14a.

Of the folded warp wire ends 14b and 14b ', each other, namely the warp wire ends 14b, is folded about an axis determined by the axis of the loops 11 to be provided, while the other free warp wire ends 14b are folded around an axis located closer to the body portion of the web, the folding shafts correspond to the distance a between the weft threads.

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It is important that the shrinkage pattern when folding back the free warp thread ends 14b and 14b 'is the same as in the main body of the tissue, and therefore the tissue pattern must be selected appropriately. In the embodiment shown in Fig. J, a broken 2 and 2 bends are used, and when reversing each other free warp wire end about an axis spaced from the folding axis of intermediate warp wire ends, the shrinkage pattern is maintained, allowing easy re-insertion of the weft threads. The weft threads are reinserted into the fabric in accordance with the shrinkage pattern to provide a loom with loops at its end portion.

In order to provide a joint, the ends to be joined together are arranged with the loops 11 at one end positioned between the loops 11 'at the other end, after which a connecting wire 15 is inserted through the loops.

In another embodiment shown in Figures 5 and 6, the warp wire ends are cut in pairs, leaving two adjacent free warp wire ends 24b and 24b 'between each pair of cut warp wire ends 24a and 24a'. When reversing the free warp wire ends in each pair, one, namely the warp wire end 24b, is placed i. in line with the adjacent cut warp wire end 24a, while the second free warp wire end 24b, which is intended to form a loop 21, is folded back in alignment with the second cut end 24a ', moving in the transverse direction of the web a distance b corresponding to the distance b warp yarns. As in the previously described embodiment, the ends to be connected to each other with the loops 21 and 21 'are placed alternately with one another, after which the loops are connected by inserting a connecting wire 25 through all the loops.

A significant advantage of the present invention is that it allows to achieve a very satisfactory joint with the same thickness as the fabric, thereby avoiding making marks on a paper web produced on the fabric. Such a splice is possible to achieve with the embodiments shown in Figs. 5 and 6.

Another significant advantage is that the permeability of the web in the area of ​​the joint does not differ significantly from the permeability of the main body of the web, which means that a paper web of uniform quality can be produced, and this is especially true with regard to the de-embodiment shown in Figs. 5 and 6.

The invention cannot be used in conjunction with all tissue patterns since it is required that the shrinkage pattern in the body of the tissue be recreated with the shrinkage present in the warp thread ends which are folded back and re-woven into the end portion. The invention can therefore advantageously be used only on a fabric with a tissue pattern where the warp threads' shrinkage pattern

7510836-5 is symmetrical in such a way that the folded back warp ends which are in line with cut warp ends transmit tear a shrinkage pattern corresponding to the shrinkage pattern of the cut warp yarns.

Usually, the position in the longitudinal direction of the fabric, at which the folded free warp thread ends meet the cut warp threads will vary over the width of the fabric.

The invention has been described above in connection with simple threads, but of course it is not limited to this but can also be used in connection with threads consisting of a plurality of fibers.

In order to allow sufficient bending of the warp yarns to form a loop within the thickness of the fabric, it may be desirable to use warp yarns smaller than the weft yarns, and the difference may thus vary between 10% and 50% of the warp yarns diameter.