EP2729611B1 - Thermally unfixed flat structure for a spiral link fabric, and method for producing a spiral link fabric - Google Patents

Description

The invention relates to a thermally unfixed fabric for a spiral wire with a plurality of juxtaposed and adjacent intermeshing spirals, and with a plurality of plug wires, which are inserted for connecting the spirals with each other in overlapping spiral sections of the adjacent spirals, wherein in the assembled state of the spirals in the region of each spiral a free cross-section is provided, and a method of manufacturing a spiral screen having a plurality of spirals which are joined together in overlapping manner, with a plurality of plug-in wires, which are inserted into overlapping regions of adjacent spirals and thus connect the spirals to a sheet together, and with a plurality of packing, the be introduced into free cross sections of the spirals of the fabric, wherein before or after the introduction of the filling body, the sheet undergoes a thermofixing process.

Thermally unfixed fabrics which are used for the production of spiral fabrics, in particular for use in paper machines, are generally known. Such fabrics are composed of several juxtaposed spirals, each made of a plastic monofilament endless. The helical spirals are dimensioned identically to each other and overlap each other with lateral spiral turn portions inserted in the adjacent spiral turn portions of the laterally succeeding spirals. The adjacent spirals are preferably designed alternately clockwise and counterclockwise. In order to connect the adjacent spirals with each other, plug wires are provided, which are preferably also made of a plastic monofilament. The plug wires are inserted in superimposed spiral sections of two adjacent spirals in the longitudinal direction of the spirals, whereby the adjacent spirals are connected to each other. After joining the sheet of a corresponding number of spirals and pigtails, the sheet is subjected to a heat setting process, in which the sheet is brought to a predetermined calender tension and due to the effect of temperature shrinkage in the material itself builds up tension, whereby the thickness of the Sheet is reduced. In order to reduce the air permeability of the fabric and of the spiral wire, filler particles are introduced into the free cross sections of the spirals from one end face, which fill the free cross section of each spiral largely. After the manufacture of the fabric by the combination of spirals and pigtails, a heat-setting of the fabric takes place. The fillers can be introduced before or after thermosetting - depending on the embodiment.

Examples of corresponding prior art fabrics are from the documents EP 0 666 366 A1 and US 5,364,692 known.

The object of the invention is to provide a thermally unfixed sheet for a spiral wire and a method for producing a spiral wire through which a lower basis weight for the spiral wire and an improved contact surface to the transported goods are achieved.

This object is achieved for the thermally unfixed sheet, characterized in that an extending in the plane of the sheet clear width of each free cross-section is greater than a lying between top and bottom spiral turns each spiral clear height of each free cross-section. The solution according to the invention results in a lower air permeability of spiral screens provided with packing elements. Because the fact that the spirals in relation to their height have a significantly greater width than known spirals, less plug wires and less connecting areas are required per area, so inevitably fewer air passage openings are available. The reduced number of plug wires to create the spiral composite and thus the fabric additionally ensures a lower basis weight than conventional fabrics for spiral fabrics. The larger width of the spirals of the fabric also ensures an improved contact surface to the transported product, in particular to paper webs. This ensures that used as drying screens for the paper webs spiral screens for the paper industry cause fewer marks in the paper, which increases the paper quality. The increased contact surface also increases the heat flow from the spiral screen to the drying medium. This allows an increase in the drying rate and thus also an increase in the production speed. At constant speed would result in energy savings compared to known spiral screens in the paper industry. Because the drying process could be reduced in time.

In an embodiment of the invention, the ratio of the clear width to the clear height of each free cross section of the spirals of the sheet is in a range between 1.01 and 2.50. Particularly advantageous are width / height ratios between 1.30 and 1.80.

In a further embodiment of the invention, the spirals are made of round or flat wires. Both round and flat wires are plastic wires. The use of flat wires further increases the contact area for the goods to be transported.

In a further embodiment of the invention, the round or flat wires are designed as plastic monofilaments. As a result, a quick and easy production of round or flat wires, in particular in an extrusion process, possible.

In a further embodiment of the invention, the spirals have an outer width in the range between 6.50 and 8.60 mm and an overall height in the range between 2.50 and 3.50 mm. Preferably, the round wires have a diameter ranging from 0.40 mm to 0.70 mm. The flat wires and / or the plug wires are preferably provided with cross-sectional dimensions between 0.40 and 0.80 mm. These dimensions are particularly advantageous for improving the solution according to the invention.

For the method of the type mentioned above for producing a spiral wire, the object underlying the invention is achieved in that the spirals are joined together to form the sheet that before the thermofixing for the free cross sections of the fabric interconnected spirals one in the Plane of the sheet seen width, which is greater than a clear height of the free Cross section of each spiral. By this method, the same advantages are achieved as they have already been described for the inventive thermally unfixed sheet and the spiral wire produced therefrom. It is particularly advantageous for the method as well as for the thermally unfixed fabric that even before the thermofixing process, the free cross sections of the fabric in the area of the spirals have a greater width than height. As a result, packing can already be inserted into the unfixed sheet and are held so securely by the design of the free cross sections in unfixed state between the spiral turns of the fabric that in a subsequent heat setting no unwanted twist or twist of the packing, which are also referred to as cored wires , can occur. This results in a high quality finished spiral screen is achieved.

Fig. 1a und 1b

zeigen ein bekanntes Flächengebilde für ein bekanntes Spiralsieb,

Fig. 2a und 2b

in gleichem Maßstab wie die Fig. 1 a und 1b eine Ausführungsform eines erfindungsgemäßen Flächengebildes für ein Spiralsieb, wobei die Gegenüberstellung der Fig. 1 a und 1 b sowie 2a und 2b die unterschiedlichen Dimensionierungen verdeutlicht,

Fig. 3

in vergrößerter Darstellung schematisch einen Querschnitt durch das Flächengebilde gemäß Fig. 2b entsprechend 2a, jedoch mit zwei Füllkörpern und

Fig. 4

in anderem Maßstab eine Draufsicht auf das Flächengebilde nach Fig. 3.

Further advantages and features of the invention will become apparent from the claims and from the following description of a preferred embodiment of the invention, which is explained with reference to the drawings.

Fig. 1a and 1b

show a known sheet for a known spiral wire,

Fig. 2a and 2b

on the same scale as the Fig. 1 a and 1b an embodiment of a fabric according to the invention for a spiral wire, wherein the juxtaposition of Fig. 1 a and 1b and 2a and 2b illustrate the different dimensions,

Fig. 3

in an enlarged view schematically a cross section through the fabric according to Fig. 2b 2a, but with two packing and

Fig. 4

on a different scale a plan view of the fabric after Fig. 3 ,

A thermally unfixed fabric 1 after the Fig. 2a to 4 is intended for a spiral screen used in the paper industry. The thermally unfixed sheet 1, which is described in more detail below, still undergoes a thermofixing process, is cut to length for the desired surface dimensioning and straightened and fixed at its marginal edges, in particular by a welding process. The sheet 1 consists of a plurality of spirals 2, which are dimensioned identical to each other. Each spiral 2 is wound endlessly from a plastic monofilament, which can be designed as a round wire or as a flat wire. As with the cross-sectional views of the Fig. 2a and 3 can be seen, each spiral has an oval-like cross-section. To create the sheet, the individual spirals 2 are brought into juxtaposition with each other alternately in each reversed winding direction and inserted with the side edge regions of their turns between corresponding side edge regions of the turns of the adjacent spiral 2. As based on the Fig. 2b and 4 can be seen, this results in the adjacent spirals two each winding-wise alternately overlapping spiral sections. Based on Fig. 2a and 3 It can be seen that, as seen through this superimposition of the spiral sections of the adjacent spirals 2 in the longitudinal direction of the spirals 2, channel sections respectively are pushed or pulled through the plug wires 3 in the longitudinal direction so as to connect the adjacent spirals 2 to one another. The plug wires 3 are also made of plastic and designed in the illustrated embodiment as a monofilament. The plug wires 3 are designed in a straight line. The so-formed composite of spirals 2 and 3 wires defines the fabric 1, which is needed for the production of the spiral wire.

As based on the Fig. 2a and 3 can be seen, continuous cross-section 4 are created after preparation of the composite of spirals 2 and 3 plug wires in the region of each spiral 4 in the longitudinal direction of the fabric 1, ie in the longitudinal direction of the plug wires 3. The free cross sections 4 are towards their sides, ie seen in the plane of the sheet 1, bounded by corresponding outer edge regions of the spiral sections of the left and right adjacent spirals 2. Upwards and downwards, the free cross-sections 4 are bounded respectively by upper and lower winding sections of the respective spiral 2, which at the same time also define an upper and a lower contact surface of the fabric 1 and thus of the later spiral wire.

A basically identical construction has a sheet 1 'according to the Fig. 1 a and 1 b, as known in the art. There are spirals 2 'via plug wires 3' joined together to form a composite. Significant difference in the known from the prior art sheet 1 'is that in contrast to the inventive sheet 1, the spirals 2' have a much smaller width in relation to their height than in the inventive sheet 1 according to the Fig. 2a to 4 , The spirals 2 with respect to the spirals 2 'greater width according to Fig. 2a to 4 are combined with the plug wires 3, which are dimensioned identically to the plug wires 3 'in the prior art. This results in a free cross-section 4, whose width B (for the inventive sheet 1 in the region of each spiral. Fig. 3 ) is larger than its height H. With corresponding free cross sections, which result in the fabric 1 'according to the prior art, the corresponding dimensions are reversed. This means that in the prior art, the width of the free cross sections is less than the height of the free cross sections in the region of the spirals 2 'of the known sheet 1'.

It should be emphasized that these explanations apply both to the known fabric 1 'and to the fabric 1 according to the invention Fig. 2a to 4 refer to the thermally unfixed fabric, ie before going through a heat setting process. Because in a thermofixing process, the fabrics are thermally stressed in addition to an extension and thereby shrink to a smaller thickness with simultaneously increased width extension.

As based on the Fig. 3 1, the width B of each free cross-section 4 corresponds to the clear distance between opposite side edge regions of the spiral sections of the adjacent spirals 2. The clear height H of the free cross-section 4 is defined by the size spacing between upper and lower turn sections of the respective spiral 2. In the illustrated embodiment, this largest distance in the middle of the respective free cross-section 4 is provided. Based on Fig. 3 is still an outer width A and a total height G of each spiral 2 defined. Particularly preferred dimensions of the spirals 2 of a fabric 1 according to the invention after the Fig. 2a to 4 have a total height G in the range between 2.50 mm and 3.50 mm and a preferred outer width A in the range of 6.50 mm to 8.60 mm. Particularly advantageous spirals 2 are provided with a ratio of outer width A to total height G of 6.75 mm x 2.90 mm, 7.00 mm x 3.00 mm and 8.40 mm x 3.40 mm. The plastic monofilament for Preparation of the spirals 2 is preferably made of polyethylene terephthalate (PET) and is preferably carried out either as a flat wire with cross-sectional dimensions of 0.43 mm x 0.70 mm or as round wire with a diameter of 0.60 mm or 0.70 mm. The plug wires 3 are also made of PET and designed as plastic monofilaments. They are preferably designed as round wires with a preferred diameter of 0.70 mm. The tolerances in the outer width A and the total height G of the spirals 2 may preferably differ within a tolerance range of ± 0.20 mm.

With an outer width A of about 6.70 mm and a total height of the spiral 2 of about 2.90 mm results in the composite for the fabric 1 for each free cross-section 4 a clear width B of about 3.50 mm and a clear height H. of about 2.12 mm. This results in such an embodiment, a width / height ratio B: H for each free cross-section 4 of 1.65: 1.

Bone-shaped filling bodies F, which are adapted to a large extent to the cross-sectional dimensions of the respective free cross-section 4, can be introduced into the free cross-sections 4 thus formed in the longitudinal direction Fig. 3 and 4 is recognizable. The packing F can also be made of plastic as rectilinear cored wires with a cross-section according to Fig. 3 be executed. Seen in the plan view of the sheet 1 remain after introduction of the filler F only small air passage openings L, which are based on the Fig. 4 can be seen and are between the lateral edges of the filler body F and the plug wires 3 and the corresponding superimposed spiral sections of the adjacent spirals 2.

The packing F are also in the illustrated embodiment, before the heat-setting of the fabric 1 in the free cross sections 4 of the composite of spirals 2 and 3 plug wires inserted. This is followed by a thermofixing process, which is basically known for the production of spiral screens, in which the fabric 1 is exposed to a specific stress in the longitudinal direction in addition to thermal stress. In addition, the sheet 1 by self-shrinkage of the plastic spirals 2 itself builds tension, so that the sheet 1 is stretched and thereby reduces the thickness and it is thermally fixed in this flatter state.

Claims (8)

1. Non-thermoset sheet-like structure (1) for a spiral sieve having a plurality of spirals (2) which are located next to one another and mutually engage with adjacent spirals, and having a plurality of pintle wires (3) which are inserted into mutually overlapping spiral portions of the adjacent spirals (2) for connecting the spirals (2) to one another, a void cross section being provided in the region of each spiral (2) in the assembled state of the spirals (2), characterized in that a clear width (B), extending in the plane of the sheet-like structure (1), of each void cross section (4) is greater than a clear height (H), extending between spiral whorls lying on the top and on the bottom of each spiral (2), of each void cross section (4).
2. Non-thermoset sheet-like structure according to claim 1, characterized in that the ratio of clear width (B) to clear height (H) of each void cross section (4) of the spirals (2) of the sheet-like structure (1) lies in a range between 1.01 and 2.0.
3. Non-thermoset sheet-like structure according to claim 1 or 2, characterized in that the spirals (2) are manufactured from round wires or flat wires.
4. Non-thermoset sheet-like structure according to claim 3, characterized in that the round wires or flat wires are configured as monofilaments.
5. Non-thermoset sheet-like structure according to at least one of the preceding claims, characterized in that the spirals (2) have an external width (A) in the range between 6.50 and 8.60 mm and an overall height (G) in the range between 2.50 and 3.50 mm.
6. Non-thermoset sheet-like structure according to claim 3 or 4, characterized in that the round wires have a diameter from within a range of 0.40 mm to 0.70 mm.
7. Non-thermoset sheet-like structure according to at least one of the preceding claims, characterized in that the flat wires and/or the pintle wires (3) have cross-sectional dimensions between 0.40 and 0.80 mm.
8. Method for manufacturing a spiral sieve having a plurality of spirals (2) which are joined together in an overlapping manner, having a plurality of pintle wires (3) which are inserted into overlapping regions of adjacent spirals (2) and which in this way connect the spirals (2) to one another to form a sheet-like structure (1), having a plurality of filler bodies (F) which are introduced into void cross sections of the spirals (2), the sheet-like structure (1) undergoing a thermosetting process before or after introducing the filler bodies (F), characterized in that the spirals (2) are joined together to form the sheet-like structure (1) in such a manner that, prior to the thermosetting process, a clear width (B) is resulting for the void cross sections (4) of the spirals (2) interconnected to the sheet-like structure (1), when viewed in a plane of the sheet-like structure (1), which is greater than a clear height (H) of the void cross section (4) of each spiral (2).

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