WO2009092174A1

WO2009092174A1 - Conveyor device having antistatic conveyor belt

Info

Publication number: WO2009092174A1
Application number: PCT/CH2009/000020
Authority: WO
Inventors: Edgar Von Gellhorn
Original assignee: Habasit Ag
Priority date: 2008-01-23
Filing date: 2009-01-20
Publication date: 2009-07-30

Abstract

A conveyor device is described, which comprises a metal detector and an endless antistatic conveyor belt, wherein the antistatic property of the conveyor belt is caused by an adhesive layer (61, 62, 65, 91, 92, 95, 111), comprising an electrically conductive particulate material dispersed therein. The conveyor belt of the conveyor device is made endless by means of a step connection and/or comprises only a single adhesive layer having a particulate electrically conductive material dispersed therein. If the conveyor belt comprises only a single such adhesive layer, preferred end connections are a graduated connection or finger end connection.

Description

Conveying device with antistatic conveyor belt

The present invention relates to metal detector conveyors comprising an endless antistatic conveyor belt.

Endless conveyor belts are made antistatic in the art because the contact of the circulating belt with the underlying rollers would otherwise give rise to considerable static charges which, when discharged by sparking, could result in a fire or explosion. A conveyor belt is considered to be antistatic according to the EN 12882 standard if, during its operation, its charge at the surface of the belt (surface potential) does not exceed 500 volts with respect to ground (earth). To achieve such an antistatic property, a plurality of antistatic adhesive layers are generally provided in the conveyor belt, which contain an electrically conductive material, and which connect the traction element or bodies contained in the conveyor belt (typically a fabric) with the adjacent layers. Such conveyor belts have useful low surface potentials of the order of 10 to 200 volts.

A common end connection of conveyor belts is the so-called finger-end connection. In this case, the two ends are serrated, in such a way that the teeth of the two ends can interlock form-fitting and interlocking. After the so-described joining of the two ends, the ends are welded together, whereby the conveyor belt is endless. A desirable field of use for such endless antistatic conveyor belts would be conveyor systems with metal detectors in which a good is examined for the presence of metallic or metal-containing objects in the product itself or as admixture mixed with the product. Hitherto, however, it has been shown that the finger end connection, which makes the conveyor belt endless, as it passes through the metal detector triggers an interference signal, which is often stronger than the signal that would trigger the metallic or metal-containing objects to be detected. The passage of the finger end connection through the metal detector thus often triggered a false alarm. As a result, conveyor belts with antistatic adhesive layers have hitherto been considered unsuitable for use in conveyor systems with metal detectors.

Conveyor belts intended for use in conveyor systems with metal detectors are currently not being antistaticized with antistatic adhesive layers, but by embedding antistatic filaments or yarns longitudinally in at least one of the layers of the conveyor belt. In this type of antistatic conveyor belts, the spurious signals which are triggered by the detector when passing the finger-end connection are lower than in the case of the conveyor belts with antistatic adhesive layers. However, this type of antistatic equipment of conveyor belts is more expensive and expensive, and the antistatic properties of these conveyor belts are inadequate because surface potentials of up to 1000 volts can occur during their operation. In addition, the surface potential can vary widely from one location of the belt surface to another. The applicant of the present application distributed at the time of filing the present application under the name "3TPF" a sol- suitable for use in conveyor systems with metal detectors antistatic conveyor belt with three tensile bodies and a suede upper layer, wherein the upper layer contained antistatic yarns.

In treadmills known as a step connection end connection is known. In the step connection, the ends are not cut finger-shaped as in the finger-end connection, but stepped (i.e., with a step-shaped profile, when viewing any cross-section through the end parallel to the flanks of the conveyor belt). The steps are in the form of a step with a flat face.

The object of the present invention is to provide an improved conveying device with a metal detector comprising an endless antistatic conveyor belt with low surface potential.

The object is achieved according to the invention by a conveying device for a product to be conveyed, comprising: a) an endless conveyor belt on which the product to be conveyed is conveyed, wherein the conveyor belt comprises: a) a thermoplastic first layer having a top side and a bottom side, a2 ) a first tensile body having a first textile layer which is arranged on the underside of the thermoplastic first layer, a3) if desired, a layer composite comprising one or more layers which consist of one or more further tensile bodies each having a textile layer and one or more further Layers selected a4) an adhesive layer having a particulate electrically conductive material dispersed therein, by means of which the first tensile body adheres or the composite layer adheres to the upper side or two of the layers adhere to one another within the composite layer with the proviso that the conveyor belt is made endless by means of a step connection and / or there is only a single adhesive layer in the conveyor belt with a particulate electrically conductive material dispersed therein; and b) a metal detector capable of detecting metallic or metal-containing objects in the goods being conveyed or on the conveyor belt.

Preferred embodiments of the invention will become apparent from the dependent claims.

It has surprisingly been found that conveyor belts comprising an antistatic adhesive layer containing a particulate conductive material are, contrary to the conventional wisdom, suitable for use in metal detection systems, provided the end connection is a step connection and / or only a single one in the conveyor belt antistatic adhesive layer is present. These conveyor belts show only a small interference signal when the end connection passes through the metal detector, are easy to produce and at the same time have a low surface potential.

The conveyor belt of the conveying device according to the invention tion initially has a thermoplastic endless first layer. It contains for this purpose a thermoplastic polymer (ie a thermoplastic). Examples of thermoplastics usable in the thermoplastic first layer are: PA such as PA 6, PA 11, PA 12, PA 66, PA 69, PA 610, PA 612, PA 6T, PA 6-3-T, PA MXD6, TPE A such as PEBA (polyether block amides, in particular poly (poly {tetramethylene ethylene glycol} -b-poly {ω-laurinlactam}), poly (poly {tetramethylene ethylene glycol} -b-poly { ^' ε-caprolactam}), poly (polyethylene oxide) b-poly {ω-laurolactam}) and poly (polyethylene oxide-b-poly {ε-caprolactam}); PE such as PET or PBT; TPE-E such as poly (poly {tetradecakis [oxytetramethylene] oxyterephthaloyl} -b - Poly {oxytetramethylenoxyterephthaloyl}); suitable for the production of flexible foams TPU; TPE-U, in particular copolymers of polyester diols or polyether diols with

Diisocyanates, or TPE-U based on polycarbonate. The polyester diol may be formed from adipic acid and butanediol, the polyether diol may be about a polyaddition adduct of ethylene oxide and / or propylene oxide, and the diisocyanate may in particular be diphenylmethane-4,4'-diisocyanate. The TPE-U can also be a TPE-U based on polycarbonate. Further examples of thermoplastics are TPO such as polyethylenes and copolymers of ethylene with another olefinic monomer consisting of (C ₃ -C ₁₂ ) -α-olefin (here preferably C ₈ -α-01efin), vinyl acetate , Styrene, acrylic acid (C 1 -C ₄ ) -alkyl esters and methacrylic acid (Cχ-C ₄ ) -alkyl esters; and PVC. Also suitable as "thermoplastic" are blends (ie mixtures) of the said thermoplastics, insofar as they are chemically compatible and miscible with one another in the molten state. Particularly preferred are TPU, TPO and PVC. The thermoplastics which can be used in the thermoplastic first layer can be uncrosslinked or partially crosslinked. The term "partially crosslinked" is to be understood as meaning that the degree of crosslinking is only so strong that the thermoplastic can nevertheless be melted without decomposition. Preferably, the Thermo ^¬ plast is uncrosslinked. The usable thermoplastics are therefore not elastomers or thermosets. If desired, conventional plasticizers can be added to the thermoplastics.

The thermoplastic first layer preferably comprises at least 50 weight percent, more preferably at least 75 weight percent, even more preferably at least 90 weight percent and most preferably at least 95 weight percent, based on the layer, of a thermoplastic as exemplified above. The remaining portions in the layer are optional further additives. Such additives include:

a) Auxiliaries for improving the properties of the finished products, such as temperature stabilizers; Flame retardants; Colorant; antibacterial or antifungal additives; and

b) fillers as extenders to save plastics and thereby to reduce costs and / or to change the dimensional accuracy and / or to reduce the thermal expansion. In particular, elongated or fibrous additives increase the strength.

The conveyor belt of the conveyor device according to the invention has a first tensile body, which is arranged on the underside of the thermoplastic first layer. Of the first tensile body contains a textile fabric or consists of this. This textile fabric can be, for example, a woven fabric or a knitted fabric (eg a knitted fabric or a knitted fabric); alternatively, it may also be a nonwoven fabric such as a nonwoven or a scrim. Preferably, the first tensile body contains a tissue or consists of this. As the fabric, in turn, woven or twill weave fabrics are preferred, more preferably plain weave fabrics. For the warp yarns of the fabric, it is preferred that it has multifilaments of about 200 to 3300 dtex, more preferably about 500 to 1200 dtex. The weft threads may also be exemplified in a preferred embodiment also multifilaments as in the warp threads; In another preferred embodiment, they are monofilaments, typically having a diameter of about 0.15 to 0.6 mm, more preferably about 0.25 to 0.4 mm. Rather preferably, the weft threads are monofilaments. The material of the threads, yarns, fibers or ropes of the textile fabrics which can be used in the first tensile body preferably contains or consists of polyester, polyamide, cotton, polyolefin or polyethylene naphthalate; it may also contain or consist of a cotton / polyamide or cotton / polyester blend or a ternary cotton / polyamide / polyester blend. The fabric of the first tensile body may be embedded or cast in a plastic (such as a rubber or a thermoplastic as exemplified above for the thermoplastic first layer). The thickness of the first tensile body is preferably about 0.2 to 0.8 mm.

The conveyor belt of the device according to the invention optionally comprises, but preferably a layer composite which is arranged on top of the first thermoplastic layer. This layer composite may comprise one or more further layers which are one or more further tensile bodies and / or further, in particular thermoplastic, layers. In the simplest form, this one can

Layer composite consist only straight from a second tensile body or a top layer. In a first preferred embodiment, however, the layer composite comprises a second tensile body and a top layer, wherein the layer composite is arranged on the first thermoplastic layer such that the second tensile body comes to rest on the first thermoplastic layer, ie points to its top side.

The statements made above regarding the first tensile body can also be applied to the second and all other possible tensile bodies of the composite layer. If the layer composite itself contains two or more tensile bodies, then it is preferred that in each case two tensile bodies are not in direct contact with one another, but rather by a different type of position, a position lying between them

are separated.

The statements made above for the first thermoplastic layer are also applicable to other thermoplastic layers of the laminate. The plastic for the upper layer may preferably be a TPU.

The layer composite can have an uppermost layer on which the material to be examined for metal-containing material is conveyed. The uppermost layer may be the above-mentioned upper layer; it can also be an additional covering layer arranged on the upper layer. The first tensile body may adhere to the underside of the thermoplastic first layer via a first adhesive layer; Likewise, the said layer composite can adhere to the upper side of the thermoplastic layer by means of a second adhesive layer. Likewise, within the

Layer composite itself, if it consists of two or more layers, be provided further adhesive layers by means of which two layers adhere to each other. If two layers are adjacent to one another, which are not tensile bodies but, for example, thermoplastic layers; it is preferred if no adhesive layer is present between these two layers.

The adhesive layer (s) comprises an adhesive. Suitable adhesives are all thermoplastic, thermoplastic or two-component adhesives which are suitable for bonding the material of the first tensile body to the underside of the first layer (adhesive of the first adhesive layer) or for bonding the material of the second tensile body to the top of the first layer ( Adhesive of the second adhesive layer) are suitable. If a tensile body consists only of a flat fabric, the adhesive must be able to adhere the material of this fabric to the first layer. If desired, the textile fabric may be embedded or cast in a plastic other than the fabric of the fabric. In this way, under certain circumstances, a material pairing tensile body / first layer can be achieved, which can be glued with a given adhesive better than the material combination textile fabric / first layer.

Examples of adhesives are about thermosetting (Crosslinkable) polyurethanes, rubber, rubber compounds and phenol-formaldehyde resin. Also suitable are thermoplastic hot melt adhesives, such as polyvinyl acetate, poly (ethylene vinyl acetate) or polyamide. A preferred example of the adhesive is thermosetting polyurethanes.

In the conveyor belt of the device according to the invention, at least one adhesive layer is present which also comprises a particulate electrically conductive material dispersed therein.

In the above-mentioned first preferred

Embodiment of the conveyor belt of the device according to the invention with first traction element, first thermoplastic layer and a layer composite comprising a second traction element and a top layer, wherein the layer composite is arranged on the first thermoplastic layer such that the second traction element comes to rest on the first thermoplastic layer, For example, it is preferable that a first adhesive layer is disposed between the first tensile body and the first thermoplastic layer; in that a second adhesive layer is arranged between the first thermoplastic layer and the second tensile body, and that a third adhesive layer is arranged between the second tensile body and the upper layer. Here then either a) only in the first adhesive layer, b) only in the second adhesive layer, c) only in the third adhesive layer, d) both in the first adhesive layer and the second adhesive layer, e) both in the first adhesive layer and in the third adhesive layer, f) both in the second adhesive layer and in the third adhesive layer, and g) in the first, second and third adhesive layers, a particulate electrically conductive material dispersed therein to be available.

As "electrically conductive material" is preferably understood a material in the context of the present application, which has a resistivity of at most 10 ¹⁰ ohm-m at 2O ⁰ C; more preferably, it has a resistivity of at most 10 ⁶ Ωm. A generally accepted minimum value of the resistivity, the resistivity of metallic silver at 20 ⁰ C can be. The "particulate electrically conductive material" is in a fixed aggregate state. For example, the particulate material may be in the form of flakes, flakes, chips, fibers or fibrids, or in the form of a powder or granules. The particle size (mass median aerodynamic diameter MMAD) of the particulate material preferably ranges from about 0.1 to about 100 microns, preferably from about 1 to about 20 microns.

In a particularly preferred embodiment, the first particulate electrically conductive material is a powder or in particular span shaped metallic conductor having a resistivity at 20 ⁰ C in the range of preferably about 1.7 x 10 ^"8 ohm-m to about 110 x ^{10" 8} Ωm. Examples of these are metals, such as Cu, Ag, Fe, Co, Al, Sn, Zn, Au, Ni and their alloys.

In a particularly preferred second embodiment, the particulate electrically conductive material is an especially powdery, fibrous, fibrid, flake or flake-shaped electrically conductive organic polymer, such as Polyacetylene, polyphenylene, polyphenylvinylene, polyfuran, polythiophene or polypyrrole. Since the electrically conductive organic polymer is preferably present only in one of the adhesive layers, ie in the interior of the conveyor belt according to the invention, it is largely protected from moisture and atmospheric oxygen and can therefore, if desired, also be used in doped form in the conveyor belts according to the invention (the doping reduces the specific resistance of the polymer by many orders of magnitude). For doping electron donors (eg alkali metals) or

Electron acceptors (eg J ₂ , SbC ₅ or FeCl ₃ ) can be used.

In a particularly preferred third embodiment, the particulate electrically conductive material is selected from di er forms of electrically conductive, preferably pulverulent carbon, such as coal, graphite, carbon black, activated carbon and anthracite.

The most preferred electrically conductive carbon black or graphite powder is a particulate electrically conductive material.

The particulate electroconductive material of the adhesive layer (s) is preferably not in the form of antistatic yarns. The particulate electroconductive material is also preferably not present in the form of antistatic filaments. Rather preferably, it is not present in the form of antistatic yarns nor in the form of antistatic filaments.

The adhesive layer having dispersed therein Particulate material is located in a first preferred embodiment between the first thermoplastic layer and first tensile body. In two further preferred embodiments, in which a layer composite having at least one second tensile body and a top layer is arranged on the upper side of the first thermoplastic layer, the tensile body pointing towards the top side of the first layer, on the one hand being located only between the second tensile body and the first thermoplastic one Layer such an adhesive layer, or on the other hand is located both between the first thermoplastic layer and first tensile body and between the second tensile body and the first thermoplastic layer, such an adhesive layer. In a fourth preferred embodiment, which has the same layer composite, such an adhesive layer is located only just between the upper layer and the second tensile body.

When an adhesive layer contains a particulate electroconductive material dispersed therein, its content is preferably in the range of about 10 to 30% by weight, based on the adhesive layer, which content may be determined by the desired resistivity of the final adhesive layer. Preferably, the particulate electrically conductive material is homogeneously dispersed in the adhesive layer.

In a preferred variant of the conveyor belt in the conveyor device according to the invention, apart from the particulate electrically conductive material in the adhesive layer or the adhesive layers, no further electrically conductive material is present. In another preferred variant, in addition to the particulate electrically conductive material in the adhesive layer or the adhesive layers also in the fabric which is present in the first tensile body and / or in the second tensile body (or from which sheet the first and / or the second tensile body consist), in the longitudinal or transverse direction, preferably the longitudinal direction of the conveyor belt running antistatic threads or antistatic yarns incorporated. If this textile fabric is a woven fabric, the antistatic threads or yarns thus form at least part of the warp threads (if they run in the longitudinal direction) and / or a part of the weft threads (if they run in the transverse direction). The antistatic threads preferably form at least part of the warp threads. Rather, it is preferred in this other variant, if only the second tensile body has such a fabric with antistatic threads or yarns or consists of such a textile fabric.

The adhesive layers can be made for example by means of a solid hot melt adhesive. The hotmelt adhesive can be uniformly sprinkled in about powdered form on one of the layers to be bonded and used for bonding. This process is also known in the art as "powder lamination". If the adhesive layer is to contain a particulate electrically conductive material, the

Melt adhesives are either previously mixed with the particulate electrically conductive material, or the hot melt adhesive and the particulate electrically conductive material can be uniformly aufgerieselt separately on one of the layers to be bonded in a suitable mixing ratio. In a second variant, the actual adhesive are dissolved in a suitable solvent; if a particulate electroconductive material is to be included, it may be suspended in the solution. This adhesive suspension can be applied to one of the layers to be bonded by means of suitable nozzles or doctor blades. Prior to bonding, the solvent is evaporated so that a film of uncured adhesive with optional particulate electrically conductive material is formed on the solution-coated layer. This adhesive layer can then be cured. These

Variant is particularly useful when thin adhesive layers are to be formed and the solution of the actual adhesive and the particulate electrically conductive material have similar or nearly equal densities, so that negligible sedimentation of the particulate electrically conductive material takes place in the solution. In a third variant, a hotmelt adhesive, which optionally contains particulate electrically conductive material, can be calendered beforehand into a compact layer or film, and with this layer or film, the layers to be bonded are again glued together under calendering.

The surfaces of those layers to be bonded together by means of an adhesive layer, such as the surfaces of the first and second tensile members, and the front and bottom surfaces of the thermoplastic first layer may, if desired, be pretreated before bonding to improve the adhesion of the adhesive. Examples of such pretreatments include treatment with oxidizing agents such as chromic acid, persulfate, hypochlorite or ozone; or the treatment in a plasma or by means of a Corona.

The thickness of the thermoplastic first layer and / or the upper layer, which is preferably present in the layer composite, is preferably in the range of about 0.1 to 1.0 mm. If one of these layers is unfoamed, the thickness is more preferably in the range of about 0.2 to 0.4 mm; when foamed (see below), the thickness is more preferably in the range of about 0.2 to 1.0 mm.

The thicknesses of the individual layers of the conveyor belt of the conveyor device according to the invention can be determined either on the conveyor belt itself or after its separation into the individual layers (slicing, milling or delamination of layers). However, it may happen that one of the layers does not have enough geometrically clear shape. In that case, instead of the geometric thickness, the thickness h can be determined as the quotient of the basis weight of the layer, G _Lr (kg / m ² ) and the mass-average density of all the materials in the first tensile body, p, (kg / m ³ ) :

where πii is the mass fraction of the i-th material of the situation and where the summation goes over all N materials that occur in the situation.

The thermoplastic first layer and / or the above-mentioned upper layer may preferably be foamed. If the top layer is foamed, then it is preferably also thermoplastic. For foaming, known physical or chemical blowing agents or expandable microspheres can be used; The latter is preferred.

When the thermoplastic first layer and / or the topsheet are foamed, it is preferred that the foam contained therein has a degree of foaming of from about 5 to about 60 percent, preferably from about 10 to about 40 percent on ^¬. In the context of the present invention, the "degree of foaming" defines the volume fraction of the gas bubbles in the total volume of the foam. The degree of foaming can be determined very simply by measuring the densities of the thermoplastic material of the first layer in the foamed and unfoamed state:

In this formula, r denotes the degree of foaming in percent, p _u denotes the density of the unfoamed material as a homogeneous mixture with all other optional additives such as dyes, and p _g denotes the density of an equal amount of the same material in the foamed state.

When both the thermoplastic first layer and the topsheet are foamed, the foams contained therein may be the same or different.

The joining of thermoplastic first layer and first and second tensile body and the optional further layers can be achieved by means of calendering, extrusion coating or Laminating done. All of these methods are familiar to the person skilled in the art.

The conveyor belt of the conveyor device according to the invention is endless. To obtain this endless treadmill, a laminate which already has all the necessary layers and tensile members (as described above) is first cut to a suitable length, if necessary, and the ends thus obtained are re-joined using a suitable end connection. This end compound is arbitrary in cases where only an antistatic adhesive layer is present; it is preferably a finger end connection or a step connection here. However, if two or more antistatic adhesive layers are present, a step connection is used according to the invention.

In a variant according to the invention, the step connection can be of the type mentioned above with plane end faces. Such step connections are referred to below as "simple step connections". In another variant, each step runs in a plurality of points pointing in the direction of the tape spikes, which like a finger end connection, the prongs of one stage of one end can positively engage in the teeth of a step of the other end. This type of step connection is hereinafter referred to as a "serrated step connection". The distance d, by which the two end faces of the one step of one end are offset from each other, may, if it is not zero, typically be in the range of about 5 to 200 mm; it is preferably about 30 to 80 mm.

For a simple step connection, it is more likely given when the step height is at the level of half the strip thickness, so that the ends with an additional overlap x (in addition to the distance d) in the longitudinal direction of the laminated body can overlap and yet can be joined together without joints. This additional distance x, when different from zero, may typically be in the range of about 2 to 200 mm; preferably it is in the range of about 2 to 10 mm. The four end faces, which are required for a stepped connection (two end faces per end, of which one end face is stepped back by the said distance d relative to the other end face), are preferably all flat and parallel to one another. The surface normals of these four flat end faces are preferably inclined at an angle of inclination α to the longitudinal direction of the layer composite, this angle of inclination lying in the plane of the underside of the foamed first layer. This inclination angle α is typically in the range of about 10 to 50 degrees, preferably about 20 to 40 degrees. In a serrated step connection, the ends are preferably joined together without additional overlap.

If the conveyor belt of the conveying device according to the invention contains only an adhesive layer which contains a particulate electrically conductive material dispersed therein, then either the finger-end connection or the step connection (single or serrated) can be used with preference. In this embodiment, the conveying device is capable of detecting metal or metal-containing objects which have a significantly smaller volume than a standard iron ball of 2 mm diameter. However, if the conveyor belt has two or more adhesive layers with a particulate electrically conductive material, then the step Connection (simple or jagged) used. In this embodiment, the device according to the invention is also capable of detecting small metallic or metal-containing objects which typically have a volume which is smaller than the volume of a standard iron ball of 2 mm diameter.

The remaining components of the conveyor device according to the invention, i. such as the metal detector, the drive, etc., are conventional and need no explanation. Examples of manufacturers who sold metal detectors or conventional metal detector conveyors at the time of filing the present application include Cassel or S + S metal detectors (Germany); Goring Kerr (Germany, USA, Canada, New Zealand) and Cintex (England, USA, Canada).

The conveying device according to the invention can be used in all fields in which a good is examined for the presence of metallic or metal-containing particles by means of a metal detector. Exemplary, but not exhaustive, applications include: a) the pharmaceutical industry, where drug packages are tested for metallic contaminants; b) the food industry, where food is analyzed for metal fragments; (c) the wood industry where parts of wood need to be examined for nails; and (d) airports where items of luggage are inspected for weapons or other dangerous metallic objects.

In the following, the conveyor belt of the conveyor device according to the invention and its production will be referred to to the attached figures with reference to embodiments described in more detail. Show it:

Figure 1 shows a cross section through a conveyor belt with two tensile bodies, as is preferred for the inventive conveyor device;

Figure 2 is a perspective view, seen from below, of a similar conveyor belt as in Figure 1;

Figure 3 shows schematically the production of such a conveyor belt by calendering;

Figures 4, 5 details the ends of the conveyor belt and their assembly into a simple step connection; and

Figure 6 is a plan view of the two ends of a not yet endless conveyor belt, these ends are designed for the production of a serrated step connection.

The conveyor belt of Figure 1 shown as a sectional drawing has a first tensile body 41 which is arranged on the underside of a thermoplastic first layer 11; and has a layer composite which is arranged on the upper side of the first layer 11 and comprises a second tensile body 71 and a top layer 101. The thermoplastic first Layer 11 is not foamed and consists of TPU. Its thickness is about 0.6 mm. The first tensile body 41 consists of a plain weave fabric, the warp yarns being multifilaments and the weft yarns being monofilaments. The fiber material of the first tensile body 41 is made of a PET suitable for fibers; the warp threads are 1100 dtex; the weft threads are 0.25 mm in diameter. The thickness of the first tensile body 41 is about 0.5 mm. Thermoplastic first layer 11 and first tensile body 41 are bonded together by means of a first adhesive layer 61 comprising a thermosetting adhesive (cross-linked polyurethane). The second pulling body 71 is constructed the same as the first pulling body 41. Second tensile body 71 and thermoplastic first layer 11 are bonded together by means of a second adhesive layer 91 of the same composition as first adhesive layer 61. The topsheet 101 is free of electrically conductive materials. The thickness of the upper layer 101 is about 0.6 mm; its upper side represents the conveying surface of the conveyor belt. The upper layer 101 is attached to the second pulling body 71 by an adhesive layer 111 comprising a thermosetting adhesive (crosslinked polyurethane). The conveyor belt of this embodiment may be either a) only in the first adhesive layer 61, b) only in the second adhesive layer 91, c) only in the third adhesive layer 111, d) in both the first adhesive layer 61 and the second adhesive layer 91, e) in both the first adhesion layer 61 and the third adhesion layer 111, f) in both the second adhesion layer 91 and the third adhesion layer 111 and g) in the first adhesion layer 61, the second adhesion layer 91 and the third adhesion layer 111 comprising particulate electrically conductive material dispersed therein. The electrically conductive material is preferably electrically conductive soot in all cases an amount of about 16% by weight, based on the respective adhesive layer 61, 91 or 111.

The conveyor belt of Figure 2 shown below is similar to the conveyor belt of Figure 1. This conveyor belt comprises a thermoplastic non-foamed first layer 12 having a bottom 32, a first tensile member 42 and a laminate comprising a second tensile member 72, a topsheet 102 and a Covering layer 112, on. First tensile body 42 and thermoplastic first layer 12 are by means of a first adhesive layer 62 having the same composition as the

Adhesive layer 61 of Figure 1 glued together. Second draw ^¬ body 72 and thermoplastic first layer 12 are bonded together by means of a second adhesive layer 92 having the same composition as the second adhesive layer 91 of Figure 1. Both adhesive layers 62, 92 comprise conductive carbon black powder in an amount of about 16% by weight, based on the adhesive layer. The thicknesses and materials of the first thermoplastic layer 12, the first tensile body 42 and the second tensile body 72 are the same as the corresponding layers of FIG. 1. The upper layer 102 consists of a foamed TPU with a degree of foaming of about 20%, wherein the foaming can be expanded with ^¬ expandable Microspheres was effected. Its thickness is about 0.6 mm. There is an additional cover layer 112 consisting of a non-foamed hard TPU; its thickness is about 0.2 mm. Cover layer 102 and second tensile body 72 on the one hand and covering layer 112 and top layer 102 on the other hand are connected to one another without an adhesive layer, for example by direct calendering. Upper layer 102 and cover layer 112 are free of electrically conductive materials. FIG. 3 schematically shows the production of a conveyor belt as used in the conveyor device according to the invention by calendering two tensile bodies 43 and 73 onto the lower side 33 or the upper side 23 of a thermoplastic first layer 13. The first layer 13 can be unfoamed or be foamed. When foamed, the foaming is preferably effected with expandable microspheres. It is first aufkalandriert to the bottom 33 of the first layer 13 of the first train 43. The optionally used first adhesive layer may be formed by sprinkling an adhesive 1000 in the form of a powdery resin and, if desired, a particulate electrically conductive material 1001 onto the first tensile member 43; The puffed powdery layer combines in the calender rolls with melting to the first adhesive layer, which adheres the thermoplastic first layer 13 and the first tensile body 43 together. The optional particulate electrically conductive material 1001 could also have previously been admixed with the adhesive 1000. Immediately thereafter, a second tensile body 73 is aufkalandriert on the top 23 of the thermoplastic first layer 13. The second adhesive layer, if desired, required for bonding, is formed analogously by preliminary trickling of an adhesive 1002 in the form of a powdered resin to which a particulate electrically conductive material 1003 can be admixed. The particulate electrically conductive material 1003 could also have previously been admixed with the adhesive 1002. It is further shown with the thick dashed arrow that the conveyor belt obtained could, if desired, be coated with additional layers, so that a

Conveyor belt is formed with a layer composite arranged on the first layer 13 with two or more layers: From the right Then, instead of the first pulling member 43, the already existing conveyor belt would be fed to the calender, from the left instead of the second pulling member 73 the questionable further layer would be fed. Here, too, a renewed trickle of powdered resin (1002), if desired with the addition of particulate electrically conductive material (1003), could form a further, third adhesive layer. At least one of the adhesive layers should contain the particulate electrically conductive material.

Figures 4 and 5 illustrate the endless making of a finished but not yet endless conveyor belt by means of a simple step connection comprising a thermoplastic first layer 14, a first tensile body 45 and a second tensile body 74. In particular, above the second tensile body 74, further layers could be present, but these are not shown in FIGS. 4 and 5.

The conveyor belt, which is not yet endless from above (FIG. 4), is initially cut to a desired length so that a flat first end face 131 is formed at one end and a flat second end face 134 at the other end. These two end faces 131, 134 are chamfered such that their surface normals (drawn as short dashed arrows) are parallel to the lower side of the thermoplastic first layer 14 by an angle α of approximately 30 ° with respect to the longitudinal direction of the laminate (indicated by long dashed arrows). ie in the sheet plane) are angled. The layer composite is then separated at the two ends to a distance d in the longitudinal direction, such as with a knife, such that the thermoplastic first layer 14 is cut through at half the strip thickness, under Forming a first separation surface 281 and a second separation surface 282 (Figure 5). At the end shown on the left, the second traction element 74 (as well as any layers located above the second traction element, not shown in FIGS. 4 and 5) and the thermoplastic first one becomes

Layer 14 offset by a distance d relative to the end face 131 and cut perpendicularly, such that a first recessed face 132 is formed, which is parallel to the first end face 131 and opposite to this by a distance d stepped back. At the other end, the thermoplastic first layer 14 and the first traction element 45 are set back by the same distance d from the end face 134 and cut perpendicularly, such that a second retarded end face 133 is formed, which runs parallel to the second end face 134 and about a second Distance d is stepped back. The second set back end face 133 is drawn in dashed lines in Figure 4, since it is covered in the plan view of the second tension member 74. The left-hand end has a step formed by first recessed face 132, first parting surface 281 and first end face 131; The end shown on the right has a step formed by second end surface 134, second separation surface 282 and second retarded end surface 133. The two ends are then overlapped by an additional distance x of about 5 mm (FIG. 5). The so superimposed ends are welded by means of a hot press. The thermoplastic material on the first parting surface 281 merges with the thermoplastic material on the second parting surface 282. By this fusion becomes an endless thermoplastic first. Layer 14 and thus obtained an endless conveyor belt. Figure 6 shows an embodiment of the two ends of the conveyor belt, which are suitable for obtaining a serrated step connection. The preparation of a serrated step connection mentioned above is analogous to the production of a simple step connection, with the exception that the steps of the ends not to form flat end faces 131, 132, 133 and 134 as shown in Figure 4, but with the formation of tapered prongs 141, 142, 143 and 144, respectively. The jagged patterns shown here run obliquely over the sides at an angle of about 15 °

Strip surface; but they could also just walk over it. The tips 142 are set back by the distance d from the tips 141, and the tips 143 are also set back from the tips 144 by the distance d. The reversed tips 143 are covered by the overlying second traction body 76, so they are drawn only by dashed lines. In a cross section through the band ends, which runs parallel to the flanks of the conveyor belt, i. which would be perpendicular to the plane of the page on the line AA ', the same image would result as in Figure 5. To connect the ends of the end shown in Figure 6 right is placed on the left end shown in such a way that the points A, B and C, D of the right end come to lie on the points A ', B' and C, D 'of the left end.

Example: Measurement of the metal detector signal at

Passage of the end connections of conveyor belts with adhesive layers comprising a particulate conductive material

The test system used was a SHARK BD 450 x 150 detector with a metal detector and a conveyor belt. det, wherein on the conveyor belt patterns of a conveyor belt were passed through the metal detector. The metal detector was mounted at a height of 30 mm above the conveyor belt and was operated in AC mode with an operating frequency of 300 kHz. The speed of the conveyor belt was set to 340 mm / s. Thus, a conveyor device according to the invention is simulated with this test system.

The dimensions of the belt samples to be tested were 3000 mm in the theoretical running direction of the belt and 400 mm across. For a test, a band pattern was cut into two pieces so that the cut was from one 3000 mm long flank to the other 3000 mm long flank and parallel to the 400 mm long flanks, and the parts thus obtained were fitted with suitable end connections (step connection or Fingerendverbindung) again connected. After the end connection, a band pattern was placed on the conveyor belt of the test system in such a way that it was transported through the metal detector tunnel of the test system in the direction of the 3000 mm wide flank, ie in its theoretical direction. The signal amplitude was measured during the passage of the end connection of the band pattern through the detector.

The tested band patterns all had a layer structure according to FIG.

In a first variant, the tested band patterns in all three adhesive layers 61, 91 and 1.11 according to variant g) in the description of FIG. 1 had a particulate conductive material (electrically conductive carbon black powder). In this first variant, 8 band patterns were added after the Cut to obtain a simple step connection with d = 45 mm and additional overlap x = 5 mm. In this first variant, values were measured according to the following Table 1:

Table 1

In a second variant, the band patterns had only in the third adhesive layer 111 according to variant c) in the description of Figure 1, a particulate conductive material (electrically conductive carbon black powder). In this second variant, 2 first band patterns were after the said

Cutting to obtain a simple step connection with d = 45 mm and additional overlap x = 5 mm end connected; Two further tape samples were finally bonded after said cutting to obtain a perpendicular to the tape running direction Fingerendverbindung with prongs of 80 mm in length and 10 mm wide. In this second variant, values according to the following Tables 2 and 3 were obtained:

Table 2

Table 3

When instead of one of the band patterns an iron ball of 2 mm diameter was passed through the metal detector, a signal amplitude of 1030 mV was measured.

All band patterns tested above, especially those of the second variant with single step connection, showed much smaller signal amplitudes when passing through the metal detector than the iron sphere.

The suitability of conveyor belts with adhesive layers comprising a particulate conductive material for metal detection systems is thus proved.

Claims

claims

A conveying device for a product to be conveyed, comprising: a) an endless conveyor belt on which the product to be conveyed is conveyed, the conveyor belt comprising: a) a thermoplastic first layer (11, 12, 13, 14) having a top side ( 23) and a lower side (32, 33), a2) has a first tensile body (41, 42, 43, 45) with a first textile layer which on the underside (32, 33) of the thermoplastic first layer (11, 12, 13 , 14), a3) if desired, a layer composite comprising one or more layers, which consists of one or more further tensile bodies (71, 72, 73, 74) each having a textile layer and one or more further layers (101, 102). wherein the layer composite is arranged on the upper side (23) of the thermoplastic first layer (11, 12, 13, 14), a4) an adhesive layer (61, 62, 65, 91, 92, 95, 111) with one therein dispersed particulate electrically conductive material, by means of which the first tensile body (41 , 42, 43, 45) adheres to the underside (32, 33) or the layer composite adheres to the upper side (23) or two of the layers adhere to one another within the layer composite; with the proviso that the conveyor belt is made endless by means of a step connection and / or in the conveyor belt only a single adhesive layer with a particulate electrically conductive material dispersed therein is present, and b) a metal detector capable of detecting metallic or metal-containing objects in the material to be conveyed or on the conveyor belt.

2. Conveying device according to claim 1, characterized in that a layer composite with a second tensile body (71, 72, 73, 74) and an upper layer (101, 102) is present, and arranged the layer composite on the upper side (23) in that the second pulling body (71, 72, 73, 74) faces the upper side (23).

3. Conveying device according to claim 2, characterized in that the upper layer (101, 102) is foamed.

4. Conveying device according to claim 2 or 3, characterized in that the composite layer adheres by means of a second adhesive layer (91, 92, 95) having a dispersed therein particulate electrically conductive material on the upper side (23).

5. Conveying device according to one of claims 2 to 4, characterized in that the upper layer (101, 102) with a third adhesive layer (111) having dispersed therein a particulate electrically conductive material on the second tensile body (71, 72, 73, 74) liable.

6. Conveying device according to one of claims 1 to 5, characterized in that the first pull member (41, 42, 43, 45) by means of a first adhesive layer (61, 62, 65) having dispersed therein a particulate electrically conductive ma- ^■ TERIAL to the underside (32, 33) adheres.

7. Conveyor device according to claim 1, characterized in that the conveyor belt comprises only one adhesive layer (61, 62, 65, 91, 92, 95, 111) with a particulate electrically conductive material dispersed therein.

8. Conveyor device according to claim 7, characterized in that the conveyor belt is made endless by means of a step connection or a finger end connection.

9. Conveying device according to claim 2 or 3, characterized in that the first pulling body (41, 42, 43, 45) by means of a first Haftsσhicht (61, 62, 65) having dispersed therein a particulate electrically conductive material on the underside (32, 33) and that the laminate adheres to the top surface (23) by means of a second adhesive layer (91, 92, 95) having a particulate electroconductive material dispersed therein, and the conveyor belt is made endless by means of a step connection.

10. Conveying device according to claim 2 or 3, characterized in that the first tensile body (41, 42, 43, 45) by means of a first adhesive layer (61, 62, 65) having dispersed therein a particulate electrically conductive material on the underside (32, 33) adheres to the layer composite adhering to the upper side (23) by means of a second adhesive layer (91, 92, 95) having a particulate electrically conductive material dispersed therein, the upper layer (101, 102) being provided with a third adhesive layer (111 ) is adhered to the second tensile body (71, 72, 73, 74) dispersed therein with a particulate electrically conductive material and that the conveyor belt is made endless by means of a step connection.

11. Conveying device according to one of claims 1 to 10, characterized in that the particulate electrically conductive material of the adhesive layer (s) (61, 62, 65, 91, 92, 95, 111) in the form of flakes, flakes, chips , Fibers, fibrids or in the form of a powder or granules.

12. Conveying device according to one of claims 1 to 10, characterized in that the particulate electrically conductive material of the adhesive layer (s) (61, 62, 65, 91, 92, 95, 111) is electrically conductive carbon black or graphite.

13. Conveying device according to one of claims 1 to

12, characterized in that the thermoplastic first layer (11, 12, 13, 14) comprises TPU, TPO or PVC.

14. Conveyor device according to one of claims 1 to

13, characterized in that the thermoplastic first layer (11, 12, 13, 14) is foamed.

15. Conveying device according to one of claims 1, 6, 7 or 8, characterized in that the textile

Sheet of the first tensile body (41, 42, 43, 45) in the longitudinal or transverse direction, preferably the longitudinal direction of the conveyor belt extending antistatic threads or antistatic yarns comprises.

16. Conveying device according to one of claims 2 to 5, 9 or 10, characterized in that the textile Fabric of the second tensile body (71, 72, 73, 74) in the longitudinal or transverse direction, preferably the longitudinal direction of the conveyor belt extending antistatic threads or antistatic yarns comprises.