WO1996013374A1

WO1996013374A1 - Processing band for compacting bulk materials

Info

Publication number: WO1996013374A1
Application number: PCT/CH1995/000253
Authority: WO
Inventors: Hans-Rudolf Gubler; Sibylle Schunk
Original assignee: Habasit Ag
Priority date: 1994-10-31
Filing date: 1995-10-30
Publication date: 1996-05-09

Abstract

A processing band for compacting bulk materials has three mutually spaced fabric layers (4, 8, 12) interconnected by intermediate layers (5, 6, 7, 9, 10, 11). Depending on their use, the fabric layers are provided with additional intermediate layers (2, 3, 13, 14) or with covering layers (1, 15). The middle fabric layer (8) has warp threads with a particularly high modulus of elasticity and is preferably made of aramide materials. Both outer fabric layers (4, 12) have a modulus of elasticity in the longitudinal direction of the processing band that is significantly lower than that of the middle fabric layer (8).

Description

Process belt for the compression of bulk materials

The invention relates to a process belt for pre-compressing bulk materials.

Tapes of this type are used, inter alia, in the woodworking industry, especially for producing the generally known wood chipboard and fiberboard.

Comparable process belts are also used for the compression of other materials, e.g. in the production of panels from mineral materials.

The precompression of the materials mentioned usually takes place in a continuous manner, namely between an overhead and an underlying process belt.

In the course of such a pre-compression it may be necessary to remove the air between chips in a suitable form.

After pre-compression has been carried out, a finished press cycle is usually carried out in a downstream press, under the influence of higher temperature and high pressure.

The process belts are endless and are guided or driven via associated deflection drums.

It goes without saying that process belts of this type must meet special mechanical and chemical requirements in order to supply a pre-pressed chip cake or pressed material mats with a uniform structure on the output side. It is particularly important that the effect of tensile stress on the chip cakes or pressed material mats is strictly limited, as otherwise cracks could form in them. This is one of the main reasons that a suitable minimum mechanical stability must be required for a process belt.

Because of the adhesives added to the wood chips, a process belt must have sufficient chemical resistance; at the same time, it is required that all components of a pre-pressed chip cake can be easily and largely completely removed from the process belt.

Furthermore, care must be taken to ensure that, when such a process belt is operated, there are no electrostatic charges which would give rise to malfunctions, such as the deposition of wood dust on the belt.

It is also of particular importance that the physical properties of the tape remain largely constant over the entire length of the tape, so that, in particular at a joint or seam of the tape, major changes (or even discontinuities) of locally determinable characteristic values are reduced to a minimum or entirely be avoided.

On the other hand, in order to achieve high productivity in the production of chipboard, fiberboard or the like, it is preferred to use production belts that are as wide as possible.

The realization of these partially contradicting requirements could only be solved unsatisfactorily by pressing systems with conventional process belts, such as those specified in DE 40 31 171.

REPLACEMENT LEAF In the cited document, a process belt is designed as a ventilation press belt, which has at least four layers of a polyester fabric. Coatings made of highly cross-linked polyurethane are provided between and outside these fabric layers.

To vent a chip cake, vent holes of a suitable size and spacing are made. Furthermore, the ventilation press belt described is antistatically equipped.

Due to the thickness of the strip material used, drive drums or deflection drums with a comparatively large diameter are required to operate such a strip. This is based on the fact that such strips have only a low flexibility in the longitudinal direction due to their material thickness and a minimum bending radius must not be undercut.

The material thickness of the tapes mentioned is not only necessary for reasons of a necessary compressive strength during the pre-pressing process. Due to a relatively low modulus of elasticity of the known process belt materials, a certain minimum thickness must also be provided in order to keep the elongation of the belt in the longitudinal direction as low as possible under all load conditions.

Due to the large number of fabric layers or layers used in conventional process belts, it is still difficult to achieve a controlled tension distribution within the belt, especially in the area of the wrap around a deflection drum.

Overall, it is preferred in conventional belts to make an end connection by gluing individual layers of the belt to one another in order to achieve the desired running properties to achieve. This adhesive process when installing a tape is usually complex.

The technical difficulties mentioned, which are to be mastered in the operation of conventional process belts, therefore also limit its width, which can be specified in a constructively sensible manner.

The process tapes known so far cannot therefore be described as satisfactory overall due to the aforementioned disadvantages.

It is therefore an object of the invention to provide a process belt for chips, fibers, granules or the like made of wood, annual plants, mineral or ceramic materials or for comparable fields of application and to specify processes for its production which, in addition to being highly loadable, also include has a high modulus of elasticity in the longitudinal direction of the tape, yet has a high degree of flexibility in the longitudinal direction with high rigidity in the transverse direction of the tape, has uniform material properties throughout, particularly at joints or end connections to be fitted, in particular with regard to the elasticity module in the longitudinal direction of the tape; is simple, inexpensive, can be produced in any length and as wide as possible, can be assembled into an endless band at the installation site with as little effort as possible, has the best possible adhesion of the individual components or layers (fabric layers, plastic layers) to one another, Dimensional stability with high line and surface pressure and problem-free thermal behavior up to 50 ° C and finally has good so-called antistatic properties overall or at least on one of the surfaces.

In addition, the tape to be provided should have further specific requirements for the surface properties, which are determined on the traction side (rear side) by a sufficiently large coefficient of static friction, and on the transport side (chip or granule side) in addition to a high abrasion and scratch resistance with generally good non-stick properties, sufficient chemical stability with regard to adhesive - or have binder components of the pressed material, such as formaldehyde resins, resins or glue materials of a natural or synthetic nature.

This object is achieved in that the process belt according to the invention has a layered structure according to the characterizing part of claim 1.

The invention is based on the knowledge that a process belt with the required properties can be realized if the number of fabric layers of such a belt is reduced and, in particular, only three layers are implemented without sacrificing the strength values of such a belt must be taken.

According to the invention it is provided to use a medium fabric layer for the process belt, which has a particularly high modulus of elasticity and is connected to surrounding fabric layers by means of suitable plastic layers.

Accordingly, such a process belt preferably has a layer structure that is symmetrical about the central fabric layer.

The required mechanical characteristic values can be achieved by the fact that in particular the warp threads of a middle fabric layer consist of either aramid, glass fiber, plastic-bound carbon fiber, aluminum, steel or ramie fiber and have the highest possible modulus of elasticity. In contrast, the weft threads of the middle fabric layer, also referred to below as the backing layer, can consist of, for example, polyester material.

The modulus of elasticity of the outer fabric layers deviates from that of the middle fabric layer and has comparatively low values, so that these fabric layers are characterized by a certain flexibility.

A further measure to achieve the required properties is to combine the band into an endlessly circulating band by means of a special end connection, as a result of which a finger-shaped or interlocking connection is created. This makes a significant contribution to realizing an almost homogeneous characteristic of mechanical parameters for the process belt. The necessary precise shaping of the tooth, finger or step-shaped ends of the strip starting material is carried out by means of punching or cutting devices provided for this purpose.

Process belts can be created that are 4 meters wide and more.

The choice of the plastic layers according to the invention between and outside the fabric layers ensures that the local characteristic values of the strip for tensile strength and modulus of elasticity have practically no discontinuity, but are maintained in an almost continuous manner.

In addition, the plastic layers provided according to the invention bring about a connection of the fabric layers with particularly favorable adhesive properties. The invention is explained in more detail below, in a preferred embodiment with possible modifications, using the attached schematic drawings and tables.

Show it :

1 shows a layer structure of a process belt according to the invention;

2 shows a preferred layer structure of a process belt according to the invention;

3 - 5 further structures of a layer structure for process tapes according to the invention;

6 shows an end connection (joint) for a process belt according to the invention;

Table 1 is a list of preferred materials for the individual layers or fabric layers of the embodiments of a process belt and

Table 2 a compilation of the layer sequence or the layer structure of further embodiments of a process belt according to the invention.

1 shows an essentially symmetrically arranged layer sequence for a process belt according to the invention. This consists of the three fabric layers 4, 8 and 12, with respective weft threads 41, 81 and 121, which are not drawn to scale. Of the three fabric layers mentioned, the layer (or layer) 8 has the highest modulus of elasticity in the indicated running direction L.

The remaining layers, beginning with layer 1 and ending with layer 15, each consist of different plastics. Layer 1 represents a cover layer (for the plastic layer 2 below) which consists of cross-linked! Polyurethane material (PU), for example also consists of high-solid polyurethane material and is preferred, but not necessarily antistatic or has a certain conductivity.

A typical layer thickness for layer 1 is <0.2 mm.

Layer 1 is firmly bonded to layer 2. Layer 2, which is generally thicker than layer 1, preferably consists of thermoplastic polyurethane or an associated co-polymer or alloy with materials such as e.g. Polyester or polyether.

Layer 2 can also consist of the material PEBAX based on polyether block amide.

In the absence of the top layer 1 layer 2 coming for example wahl¬ materials on Fluoropolymerbasis, polyolefin, Hytrel ^® (thermoplastic base), polyamide-based, PVC materials, TPE (thermaplastische elastomers) or NBR (nitrile butadiene rubber) into consideration.

Layer 3 consists of a material with adhesion-promoting properties and is of comparatively small thickness. With this material, the underlying fabric layer 4 already mentioned is firmly connected to the layer 2. The adhesion promoters are commercially available products which, depending on the intended A combination of layers 2 and 4 can be specified so that maximum adhesion between these layers is achieved.

The fabric layer or fabric layer 4 already mentioned has warp threads made of polyester (PES) or polyamide (PA) in the running direction of the belt, optionally made monofilament or multifilament. Alternatively, natural fibers, in particular made of cotton or ramie, are also provided for the fabric layer 4.

The weft threads 41 of the layer 4 likewise consist of chemical or natural fibers from the materials just mentioned.

The weft threads can have a significantly greater thickness or diameter than that of the warp threads. Since they are oriented essentially transversely to the running direction, they do not impair the favorable bending characteristics or flexibility of the treadmill.

Fabric layer 4 is connected to fabric layer 8 by means of the adhesion-promoting and comparatively thin layers 5 and 7 and the plastic layer 6 lying between them.

The combination of materials provided according to the invention results in a particularly good adhesive bond between the fabric layers 4 and 8.

Preferably, one of the materials already mentioned for layer 2 is provided for layer 6, but the use of the materials PA (polyamide) and NBR is of less importance.

The thickness of the layer 6 is typically 0.7 to 1.4 mm.

The fabric layer 8 is located in the neutral bending plane of the process belt or in its immediate vicinity. This layer 8 is also referred to as a carrier fabric, and consists in warp and weft of clearly different materials. In order to achieve the above-mentioned mechanical properties with low elasticity (ie high modulus of elasticity) in the longitudinal or running direction of the process belt, the fibers of the warp threads of this layer 8 consist of aramid, glass, carbon (in particular plastic-coated carbon), aluminum, Steel or Ramie.

Since 8 fibers with a very high modulus of elasticity, which is at least 20 kN / mm ² and preferably have values of 250 kN / mm ² and more, are provided for the warp threads of this fabric layer, the base fabric is given a correspondingly high modulus of elasticity in the running direction.

A multifilament embodiment is preferably provided for these warp threads of layer 8, which are aligned in the running direction of the process belt.

Monofilament or multifilament polyester threads, glass fibers or ramie fibers are provided for the weft threads of the carrier fabric layer 8.

These can also have a significantly greater thickness or diameter in comparison to the values of the warp threads of this layer. Since they are oriented essentially transversely to the running direction, they do not impair the favorable bending parameters or flexibility of the treadmill.

The layers 9 to 11 largely correspond to the layers 7 to 5 in structure. If necessary, a material already mentioned for layer 2 is specified for layer 10. PVDF (polyvinylidene fluoride), for example, is suitable as the fluoropolymer material for layer 10. The layer thicknesses of layers 9 to 11 also compare with those of layers 7 to 5, in particular in the case of a fully symmetrical layer structure of a process belt.

Likewise, the same materials for warp threads and weft threads are available for the construction of the fabric layer 12 as already mentioned for the fabric layer 4.

The same applies to the adhesion-promoting layer 13, which corresponds to layer 3.

The subsequent layers 14 and 15 are correspondingly comparable to layers 2 and 1. Materials are selected for these which have already been mentioned for the corresponding layers.

2 shows the layer structure of a particularly preferred exemplary embodiment. This largely corresponds to the exemplary embodiment according to FIG. 1, but is not completely symmetrical since layer 15 is omitted, so that special and advantageous contact properties of the process belt with associated drive or deflection rollers result.

The preferred materials for the individual layers of this embodiment are shown in Table 1, which also shows the material properties for warp and weft threads of the individual fabric layers.

While the layers 2, 6, 10 and 14 preferably consist of a uniform material, it is advantageous to choose a similar material composition for the adhesion-promoting layers 7 and 9, but adapted to the specific purpose as for adhesion-promoting layers 3, 5, 11 and 13. 3 shows the layer structure of a further exemplary embodiment according to the invention.

This process belt has a layer structure similar to that shown in FIG. 2.

Instead of the adhesion-promoting layer 3, however, a cover layer 1 is provided, which covers the fabric layer 4 with respect to the material to be pressed.

Because of its relatively small thickness, this layer (as in the aforementioned cases) is called the top coat and consists of highly cross-linked polyurethane material. It is preferably provided with an antistatic treatment by adding conductive substances and advantageously has a surface conductivity.

The other layers correspond to those from FIGS. 1 and 2.

The layer structure of a further exemplary embodiment according to FIG. 4 is similar to that of the previous figures.

In comparison to FIG. 3, layer 1 is omitted here, so that the belt has an open fabric on the side of the material to be pressed, which supports a ventilation function of the process belt.

5 shows the layer structure of a further exemplary embodiment with a structure similar to that shown in FIGS. 3 and 4.

Instead of an adhesion-promoting layer 3, a cover layer 1 is provided from one of the materials already mentioned for such a layer. However, the opposite surface of this band has an open fabric layer 12, which consists of the materials already described for such a fabric layer.

Such a construction is advantageous if the process belt has a perforation that is regular or statistically distributed according to predetermined parameters, so that air to be removed is passed through the perforation and through the fabric layer 12. Such a perforation can be introduced by means of high-energy laser radiation.

Another embodiment (not shown) provides channel-like structures for air to be discharged by providing the surface on the material to be pressed with suitable grooves or grooves.

6 shows the top view of a transverse end connection of a process belt according to the invention. This splicing, which interlocks like a finger or tooth, enables the endless assembly of wide process belts.

To join a band into a finished product, the ends of a precisely cut amount of roll material are precisely contoured using a punch. In a subsequent process step, the ends contoured in this way are placed in a special, inexpensive heating and pressing device and welded to form an endless belt, the weldability of the thermoplastic layers 2, 6, 10, 14 being used in particular.

In this way it can be achieved that the local mechanical parameters of such a strip do not have any particularly pronounced fluctuations or even discontinuities, so that overall a joint (end connection) of excellent gender continuity, especially for strength values.

It goes without saying that instead of tapering contours of the end sections of a band, rounded cutting lines, for example according to a sine function, can also be provided for an end connection of this type.

Furthermore, the band can alternatively or additionally be carried out in such a way that its layers at the two ends of a cut piece are exposed stepwise over the band thickness and then connected to one another. In this way it is possible to provide a step-like as well as finger-shaped end connection.

Further information on material combinations of individual layers of a process belt according to the invention are shown in Table 1.

The layers denoted by consecutive numbers 1 to 15 correspond to those in accordance with FIGS. 1-5. For tissue layers 4, 8 and 12, sub-indices .1 and .2 respectively indicate whether they are in the running direction of the ribbon oriented warp threads or weft threads perpendicular to them.

The preferred solution corresponds to FIG. 2.

The material combination in Table 1 according to the column to the right of the preferred solution corresponds to the layer structure according to FIG. 1.

Depending on the intended application for a process belt according to the invention, one of the materials specified in the respective associated line is specified for the individual layers 1 to 15. so that, despite a uniform underlying structure, a sufficient variability is made available by specifying the layer area and the materials of the individual layers.

In this way the usability of the process belt for compacting wood chips and other materials such as e.g. mineral or ceramic masses guaranteed.

Table 2 shows the layer structure of preferred embodiments, specifically for variants 1 to 9, of which variants 1, 2, 5, 6 and 8 have already been described by FIGS. 1, 2, 3, 4 and 5, respectively.

Variant 3 is similar to variant 2; however, the top layer (top coat) 1 is omitted.

Variant 4 is similar to variant 5, but has an additional top line (reference number 15 in FIG. 1) on the back.

Variant 7 is similar to variant 8, but lacks the backstroke (reference numeral 15 in FIG. 5).

Variant 9 denotes a special embodiment, which is characterized by fabric layers exposed on both sides, corresponding to fabric layers 4, 8 and 12 in FIG. 1).

Claims

claims

1. Multi-layered process belt for compacting bulk materials, in particular for use in wood-processing machines, consisting of several layers or layers of a fabric coated with an elastic material, characterized in that the process belt (20) has three layers, one between the other, by intermediate layers has spaced fabric layers (4, 8, 12), of which the middle fabric layer (8), the warp threads of which have a modulus of elasticity of at least 20 kN / mm ² , is arranged in or near the neutral bending plane of the process belt and the two Outer fabric layers (4, 12) have a modulus of elasticity in the longitudinal direction of the process belt, which is significantly lower than that of the middle fabric layer (8), the process belt layers or intermediate layers (2, 3, 5, 6, 7, 9, 10 , 11, 13, 14) and in some cases additional cover layers (1, 15), each of which is o which are connected to a fabric layer (4, 8, 12) and which consist of a total of at least two elastic materials.

2. Process belt according to claim 1, characterized in that the arrangement of the fabric layers (4, 8, 12) and the interposed elastic intermediate layers (5, 6, 7, 9, 10, 11) with respect to a middle or a neutral bending level of the process belt is essentially symmetrical.

3. Process belt according to claim 1 or 2, characterized in that the material of a cover layer (1, 15) differs from that of an intermediate layer (2, 3, 5, 6, 7, 9, 10, 11, 13, 14 ) differs.

4. Process belt according to one of claims 1 to 3, characterized in that each tissue layer (4, 8, 12) warp threads and weft threads (41, 81, 121), which are each made of different materials.

5. Process belt according to one of claims 1 to 3, characterized in that at least one of the fabric layers (4, 8, 12) has warp threads and weft threads (41, 81, 121), which are each made of different materials.

6. Process belt according to one of claims 1 to 5, characterized in that the middle fabric layer (8) warp threads made of one or more of the materials aramid, polyester, polyamide, steel or carbon fibers and weft threads made of one or more of the materials polyester, polyamide or aramid.

7. Process belt according to one of claims 1 to 6, characterized in that an outer fabric layer (4, 12) monofilament or multifilament warp threads made of one or more of the materials polyester, polyamide or natural fiber and monofilament weft threads made of one or more of the materials polyester, steel, aluminum, glass, polyvinyl alcohol, polyethylene, polypropylene or multifilament fibers impregnated with carbon made of carbon.

8. Process belt according to one of claims 1 to 7, characterized in that the warp threads of the middle fabric layer (8) consist of aramide and are composed of single fibers in a multifilament manner and the modulus of elasticity of a single fiber or a warp thread has a value of more as

20 kN / mm ² .

9. Process belt according to one of claims 1 to 8, characterized in that the weft threads of the fabric layers (4, 8, 12) are mostly monofilament and fibers or Have wires with a single diameter of 0.05 mm to 1 mm.

10. Process belt according to one of claims 1 to 9, characterized in that at least two of the elastic intermediate layers (5, 6, 7, 9, 10, 11) consist of a polyurethane material, at least one of these intermediate layers consisting of a thermoplastic There is a polyurethane material and at least one other of these intermediate layers consists of a crosslinked polyurethane material.

11. Process belt according to one of claims 1 to 10, characterized in that at least one elastic intermediate layer is present, which consists of a thermoplastic or cross-linked adhesion promoter, in particular of a polyurethane material.

12. Process belt according to one of claims 1 to 11, characterized in that an elastic intermediate layer (2, 3, 5, 6, 7, 9, 10, 11, 13, 14) or cover layer (1, 15) either made of polyurethane, Polyvinyl chloride, polyamide, polyolefin, thermoplastic elastomer, nitrile butadiene rubber, Hytrel ^® , Pebax ^® or a mixture of these materials.

13. Process belt according to one of claims 1 to 12, characterized in that it is antistatically equipped and has conductive areas or a surface conductivity.

14. Process belt according to one of claims 1 to 13, characterized in that it is perforated or that the side of the process belt facing the bulk material or a pressed material has a structured surface with ventilation grooves or ventilation channels.

15. Process belt according to one of claims 1 to 14, characterized in that it has a smooth structure on one or both surfaces.

16. Process belt according to one of claims 1 to 15, with a total thickness of 2 to 15 millimeters and with a total width between 400 and 10000 millimeters.

17. Process belt according to one of claims 1 to 16, characterized in that the structure of the belt is not symmetrical with respect to a middle fabric layer, or that one of the surfaces of the process belt is formed by a fabric layer made of polyamide, polyester, steel or aluminum that is exposed on one side becomes.