EP2311576B1 - Surface coating of product-transporting assembly parts of weighing devices - Google Patents

Description

The present invention relates to a method for surface coating of weighing devices and correspondingly coated components of weighing devices. Furthermore, the present invention relates to a method for surface coating of feeders for feeding weighing devices and corresponding coated components thereof. Furthermore, the invention relates to surface coatings of collection devices and transition systems downstream of the weighing devices and correspondingly coated components thereof.

More particularly, the invention relates to an improved surface coating process using a fluoropolymer coating material and corresponding coated components.

In order to transport a product, for example, in a weighing device along a transport direction, the product-carrying system parts are partially inclined, so that the product is moved by the gravitational force. In this case, the product-carrying part of the plant can additionally be vibrated to enable or accelerate the movement of the product.

When transporting a product through these fixed or moving product-guided plant components, adhesion and frictional forces occur at the contact surfaces between the product surface and the product-carrying surface of the respective plant component Transport direction difficult. Depending on the consistency and surface condition of the product, the adhesion and frictional forces that occur are different. High adhesion and frictional forces between the product and the product-carrying part of the system often lead to product parts adhering to the surface. The adherent products, in turn, create additional obstacles that hinder the movement of other products and, in turn, create starting points for the attachment of other products. In order to allow the product to be transported as evenly as possible in the automatic weighing machines, the product-carrying parts of the system must therefore be cleaned frequently.

The cleaning of the product-carrying system parts of adhering, often dried product residues is difficult and requires great time, personnel and technical effort. Furthermore, there is a risk that the product-carrying system parts of the weighing machine are attacked by the aggressive cleaning agents and cleaning processes used.

Weighing equipment, in particular combination trolleys, are used, inter alia, in the food industry and the pharmaceutical industry for the production and packaging of weighed quantities of the respective product. Depending on the application, therefore, there are considerable differences in the consistency and the surface quality of the products to be transported and weighed. This is illustrated, for example, by the different consistency and the surface texture of meat pieces, salad, packaged candies, sugar, gummy bears, etc.

Depending on the area of use of the weighing device, ie depending on the product to be weighed, the product-carrying surfaces of the weighing device must be optimized to this effect be that the lowest possible adhesion and friction between the product-carrying surfaces and the bearing surface of the product occur. Depending on the consistency and surface condition of the product, different product-carrying surfaces are generally used. The product-carrying equipment parts of a weighing device are usually removable, on the one hand so that a cleaning of these parts is facilitated, and on the other hand, so that a replacement of the product-carrying system parts is possible.

Traditionally, to optimize product bearing surfaces of a weighing equipment, particularly in the food industry, coating of the product carrying surfaces with fluoropolymers such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA) such as perfluoroalkoxytetrafluoroethylene, or perfluoroethylene propylene (FEP) such as tetrafluoroethylene hexafluoropropylene, which has been applied to a substrate be applied. These are known to have good hydrophobic and non-stick properties and have high chemical and thermal resistance.

Since the fluoropolymers do not form an atomic bond to, and adhere poorly to, the most metallic substrate, prior to coating with the fluoroplastics, a layer of a specific primer is first applied to the substrate, and then the fluoropolymer is applied to this substrate.

These fluoropolymer coatings have several disadvantages. Fluoropolymers do not have sufficient mechanical strength, so in practice, they are often subject to rapidly progressive wear, which in many cases results in unacceptable premature failure of the coating. Especially Due to the low mechanical strength of the fluoropolymer material, due to the still necessary cleaning processes of these product-carrying surfaces, damage to the coating regularly occurs. Since the adhesion of this coating on the substrate is very limited, partial detachment of the coatings occur at such points of damage, so that here the coating flakes over a large area. This is particularly problematic in the food industry, as these detached parts can get into the product to be weighed.

To address this problem, the document fails WO 2006/117512 To use the coating of components with one or more layers of a mixture of polyetheretherketones and fluoropolymers instead of a coating material of fluoropolymers. These materials have similar good hydrophobic and non-stick properties with equivalent temperature and chemical resistance. However, they have a higher mechanical strength and are thus more resistant to wear.

Again, it is problematic that it may come through in the slowed down but still existing wear that the coating flakes off large areas of damage and it comes to contamination of the product. Therefore, in certain areas of the food industry, in particular, where contamination of the product with chipped coating components is not allowed, the use of coated surfaces is not possible.

US 2003/0049485 describes a durable corrosion resistant coating for metal substrates. For this purpose, a first layer of molten particles is applied to the substrate. The first layer is then covered with a second layer consisting of a polymer mixture, which may contain fluoropolymers and PEEK. The first layer and / or the substrate can be roughened by means of abrasion.

It is the object of the invention to solve the above-mentioned problems of the prior art. In particular, it is the object of the invention to provide a process for surface coating per se of product-carrying equipment, as well as providing a surface coating per se that are more durable and durable than in the prior art.

The object is achieved by a method according to claim 1 and by a device according to claim 10. Advantageous developments are the subject of the dependent claims.

Disclosed is a coating method of a substrate having a substrate surface, comprising the steps of: applying a bond coat by applying glowing particles of bond coat material to the substrate surface; Applying a slip coating of at least one layer of a lubricious coating material to the adhesive coating, the lubricious coating material including at least one type of polyaryletherketone (PAEK) and at least one type of fluoropolymers (FP).

Thereby, a coated member is provided which comprises a substrate having a substrate surface, an adhesive coating of an adhesive coating material, and a slip coating of at least one layer of a lubricious coating material. Here, the adhesive coating material is applied to the substrate surface by thermal spraying, and a first interface layer is formed between the substrate and the adhesive coating. Further, in this case, the lubricious coating material is applied to the adhesive coating and a second interface layer is formed between the adhesive coating and the lubricious coating. In this case, the lubricious coating material contains at least one type of polyaryl ether ketones and at least one type of fluoropolymers.

A polyaryletherketone (PAEK) is a polymer having the general structure:

Such polymers include u. A polyether ketone (PEK) with X = y = 1, polyetheretherketone (PEEK) with X = 2 and y = 1 or polyether ketone ketone (PEKK) with X = 1 and y = 2. In the context of the invention, the preferred use of polyetheretherketone (PEEK) achieved particularly good adhesion and distribution results.

The effect of the invention is achieved here by the fact that the adhesive coating applied by means of thermal spraying between a substrate and a lubricious coating adheres much better to the substrate than a conventional slide coating applied directly to the substrate. The rough second interface layer provided by the adhesive coating allows the wear resistant sliding coating of PAEK and FP to be much better anchored. The combination of this improved anchorage and the use of the more durable slip coating material will prevent the flake coating from flaking off even if wear of the slip coating progresses. This follows in particular from the fact that the wear of the lubricious coating is substantially terminated as soon as the lubricious coating has worn away so far that the tips of the underlying adhesive coating are exposed.

By roughening the substrate surface of the substrate prior to application of the adhesive coating, a rough first interface layer is provided, thereby improving adhesion of the adhesive coating to the substrate surface.

Characterized in that a thermal spraying is applied, are generated in which only glowing stick coating material particles, preferably of stainless steel with a grain size of 25-50 microns and deposited onto the substrate surface, a second interface layer is formed that had a mean roughness R _a of 25-50 microns , preferably 30 microns, whereby the subsequent adhesion of the lubricious coating is improved to the adhesive coating.

By using a stainless steel having a chromium weight fraction of more than the usual 18%, preferably from 25% to 35% or optionally an increased nickel weight fraction of 8% to 15%, in particular rust formation on an aluminum substrate can be reduced.

By using a blend of polyaryletherketones and fluoropolymers as a lubricious coating matrix, a hydrophobic, non-stick, lubricious coating having high durability is obtained, particularly when the weight fraction of the fluoropolymer is less than 30%. The polyaryletherketone used is preferably a polyetherketone (PEK) or polyetheretherketone (PEEK) and as the fluoropolymer a polytetrafluoroethylene (PTFE), a perfluoroalkoxylalkane (PFA) such as perfluoroalkoxytetrafluoroethylene, or a perfluoroethylenepropylene (FEP) such as tetrafluoroethylenehexafluoropropylene.

The advantages explained above can be achieved, in particular, if one or more of the product-carrying system parts a weighing device, in particular a combination weigher, such a coated product-carrying surface has / have. Such coated product-carrying equipment parts may in particular be a central distribution device, such as a distribution plate, a conveyor trough, a flap of a supply container or a weighing container for discharging product from the respective container, a chute or a hopper of a weighing device. The same applies to product-carrying system parts of feeders for feeding weighing devices, which are connected upstream of the weighing device. The same also applies to collection devices and transfer systems, which are connected downstream of the weighing device. Collecting devices are in particular devices which serve to temporarily store products after weighing. Transfer systems are in particular systems that transfer products to downstream plant components after weighing.

In the following an embodiment of the invention will be described with reference to FIGS.

FIG. 1 shows a side view of a combination weigher of the embodiment.

FIG. 2 shows a front view of a conveyor trough the combination weigher.

FIG. 3 shows a schematic cross-sectional view of a substrate on which the coating is applied.

FIG. 4 shows a schematic cross-sectional view of the substrate to which a thermal spray method is applied.

FIG. 5 shows a schematic cross-sectional view of the substrate, were applied to the stainless steel particles.

FIG. 6 shows a schematic cross-sectional view of the substrate with applied lubricious coating.

The following embodiment is an inventively implemented combination weigher.

In Fig. 1 a combination weigher 2 is shown. The following section explains the product-carrying system components. These have surfaces that come into contact with the weighing or with the weighed product.

The product is transferred from a product delivery device 4 to a central distribution device, which in Fig. 1 shown as distribution plate 6, promoted. The distribution plate 6 has a peripheral edge 8 around which a plurality of conveyor troughs 10 are arranged. Each of the conveyor troughs 10 is arranged on a vibration drive 12. At each conveyor trough 10, a supply container 14 is disposed below the outer end. Below each staging container 14, in turn, a weighing container 16 is arranged.

Both the supply container 14 and the weighing container 16 each have two flaps 18. The flaps 18 are pivotally mounted to the respective container 14, 16. The flaps 18 of each pair of flaps are each disposed opposite each other and can be opened to skip the product. A (not shown) control of the combination weigher is used to control the opening and closing of the flaps 18 in response to a weighing result of the respective weighing container 16. The product is from the corresponding weighing containers 16 omitted and passes through chutes 20 in a hopper 22 which is disposed below the plurality of weighing containers 16. The weighed product is discharged from the outlet port 23 of the hopper 22. This outlet opening 23 is arranged, for example, above a packaging machine (not shown), which subsequently packages the weighed product.

Accordingly, the product to be weighed is transported from the product feeder 4 to the distribution plate 6, from which it is subsequently distributed to the plurality of conveyance channels 10. From the conveyor troughs 10, the product is then conveyed into the respective supply container 14. By opening the flaps 18 of the staging container 14, the product is then conveyed into the weighing container 16 and weighed therein. The control (not shown) of the combination weigher then determines a combination of weighing bins 16 based on the respective measured weights of the batches in the weighing bins 16 and outputs a control signal for opening the respective flaps 18. The weighed product is discharged via chutes 20 into the hopper 22 and then leaves the combination weigher 2 through the outlet opening 23 of the hopper 22.

Accordingly, the product supply device 4, the distribution plate 6, the conveyor troughs 10, the supply container 14, the weighing container 16, the flaps 18, the slides 20 and the hopper 22 product-carrying parts of the combination weigher 2, each having product-carrying surfaces. In order to achieve the advantageous transport properties according to the invention and to prevent sticking of product parts, in such a combination weigher one or preferably several of the product-carrying plant parts have a product-carrying surface according to the present invention. Preferably, at least the surface portions of the product-carrying equipment parts coming into contact with the product are formed with a product-carrying surface according to the present invention.

In Fig. 2 For example, a conveyor trough 10 is shown as a product-carrying system part of the combination weigher. The conveyor trough 10 has a central channel 24 which extends in a transport direction 26 to an opening 28 of the conveyor trough 10. On both sides of the channel 24 obliquely upwardly inclined side walls 30, 32 are arranged, which direct the product in the direction of the central channel 24. On the opposite side of the opening 28, a raised wall 34 may be formed, which prevents the product from being transported beyond the opening 28 in the transporting direction.

Preferably, in the conveyor trough 10, the central trough 24 and at least a central portion of the laterally inclined walls 30, 32 are formed with a product-carrying surface according to the present invention.

The product-carrying plant part has a substrate on which the coating according to the invention is applied, and a coating. Substrates are usually made of stainless steel sheets.

FIG. 3 shows a schematic cross-sectional view of a substrate 40 on which the coating is to be applied.

The substrate 40 has a substrate surface to which an adhesion coating 41 is to be applied so that the substrate surface forms a first interface layer 42.

In a first step, the substrate surface is roughened. This is preferably done in the embodiment by sandblasting, which allows a quick implementation of the roughening.

By this step, a substrate surface and, accordingly, a first interface layer 42 are provided in the embodiment.

FIG. 4 shows a schematic cross-sectional view of the substrate 40, to which a thermal spraying method is applied.

Thermal spraying in the context of the invention is a coating method for applying a firmly adherent layer of adhesive coating material, in particular a stainless steel, to the substrate surface. Here, in the context of the invention, the adhesive coating material is heated by heating in a glowing, in the embodiment incandescent state. Further, the thus obtained incandescent adhesive coating material particles 43 are accelerated toward the substrate 40 so as to strike the substrate 40, adhere thereto, and form the adhesive coating 41. It is irrelevant whether the acceleration takes place before, after or at the same time as the heating. Alternatively, the adhesive coating material in powder, string, rod or wire form is caused to liquefy and sputtered by heating so that adhesive coating material particles 43 have become incandescent before being impacted on the substrate.

In the exemplary embodiment, flame spraying is used as the thermal spraying process. Flame spraying in the context of the invention is a form of thermal spraying in which the adhesive coating material is ignited by means of a flame of an ignited gas-oxygen mixture is heated. By the gas-oxygen mixture or by supplying additional compressed air, the adhesive coating material is accelerated and sprayed onto the substrate.

Alternatively, plasma spraying can be used as thermal spraying. Plasma spraying in the context of the invention is a form of thermal spraying in which a highly heated plasma is generated by means of an arc from a gas stream. Adhesive coating material is introduced into this stream and heated. As a result of this current, the adhesion-promoting material is accelerated and sprayed onto the substrate 40 as incandescent adhesive coating material particles 43.

Further alternatively, all known thermal spraying methods can be used with the proviso that glowing stainless steel particles are produced.

• einen Eisengewichtsanteil von mehr als 35%,
• einen Chromgewichtsanteil von 15%-35%,
• einen Nickelgewichtsanteil von 8%-15%,
• einen Kohlenstoffgewichtsanteil von 0,1% und weniger,
• einen Mangangewichtsanteil von 2% und weniger,
• einen Siliziumgewichtsanteil von 0,4% und weniger.

As a bonding coating material, a stainless steel is used in the embodiment. Usable is any common stainless steel. In particular, a steel is usable which has the following constituents:

• an iron content of more than 35%,
• a chromium weight fraction of 15% -35%,
• a nickel weight fraction of 8% -15%,
• a carbon weight fraction of 0.1% and less,
• a manganese content of 2% and less,
• a silicon weight fraction of 0.4% and less.

Due to the high proportion of chromium or, optionally, the increased proportion of nickel, it is possible in certain cases to reduce the formation of rust.

FIG. 5 shows a schematic cross-sectional view of the substrate 40, were applied to the adhesive coating material particles 43.

After the incandescent adhesive coating material particles 43 are applied to the substrate 40, they cool on the substrate surface to form the adhesive coating 41. Here, the adhesive coating material particles cover 50% -85% of the substrate surface. The fact that the adhesive coating material particles 43 were merely put in an incandescent state and were not completely liquefied results in an adhesive coating surface with a pronounced relief. On this adhesive coating surface is a sliding coating 45 (see Fig. 6 ) so that the bond coat surface and the still exposed portions of the substrate surface form a second interface layer 44.

FIG. 6 FIG. 12 shows a schematic cross-sectional view of substrate 40 with applied adhesive coating 41 and applied lubricious coating 45.

In a next step, the sliding coating 45 is applied. Here, a sliding coating material is used, which consists of a mixture of polyaryletherketones (PAEK) and fluoropolymers (FP). In this embodiment, a polyether ether ketone (PEEK) is used as the polyaryletherketone. Alternatively, a polyether ketone (PEK) can be used. The fluoropolymer used is a polytetrafluoroethylene (PTFE), alternatively perfluoroalkoxyalkane (PFA), in particular perfluoroalkoxytetrafluoroethylene, or a perfluoroethylene-propylene (FEP), in particular tetrafluoroethylene-hexafluoro-propylene, wherein its weight fraction is 30% or less.

The liquid lubricious coating material is applied to the second interface layer 44.

In a next step, the drying of the liquid lubricious coating material takes place. This is preferably done at a temperature of 120 ° C - 150 ° C.

In a subsequent step, the curing of the slide coating material succeed. This is preferably done at a temperature of 200 ° C - 450 ° C, and more preferably at a temperature of 340 ° C - 390 ° C.

Of the slip coating 45, one or more layers may be present. The slip coating 45 has a thickness of 50-200 μm, the thickness being measured perpendicular to a slide coating surface.

The present invention is not limited to the above-described embodiments. As will be apparent from the introductory part of the description, the invention may also be applied to product-carrying equipment parts of feeding devices for feeding weighing devices upstream of the weighing device. The same also applies to product-carrying system parts of collection devices and transfer systems, which are connected downstream of the weighing device.

The junk "and" is used here in a meaning that is based on the logical conjunction. The punctuation mark "or" is used in a meaning similar to the logical disjunction (often referred to as "and / or"). Of the Junktor "either ... or" is used in a meaning that is based on the logical contravalence.

Claims (16)

1. Method for coating a substrate (40) with a substrate surface of a member to be coated, which is a product carrying machine part of a weighing device, particularly of a combination scale (2), of a feeding device, of a collecting device, or of a transition system, comprising the steps:

   depositing an adherent coating (41) by coating of glowing, non-liquid particles (42) made of adherent coating material to the substrate surface, for creating an adherent layer with a roughness on the substrate surface,

   depositing a slide coating (45) made of at least one layer of a slide coating material onto the adherent coating (41), wherein the slide coating material includes at least one type of polyaryletherketones and at least one type of fluoropolymers.
2. Method for coating according to claim 1, wherein in advance to the depositing the adherent coating (41) a roughening of the substrate surface is performed.
3. Method for coating according to one of claims 1 - 2, wherein the depositing of the adherent coating comprises the steps:

   heating an adherent coating material such that adherent coating material particles are created having a temperature of 1.200°C - 1.600°C,

   accelerating the adherent coating material particles, and

   impacting the adherent coating material particles on the substrate surface.
4. Method for coating according to one of claims 1 - 3, wherein the depositing of glowing adherent coating material particles is carried out by thermal spraying, particularly by flame spraying or plasma spraying.
5. Method for coating according to one of claims 1 - 4, wherein the adherent coating material is a stainless steel and comprises a weight component of chrome of 35% or less and preferably 15% and more.
6. Method for coating according to one of claims 1 - 5, wherein the adherent coating material is a stainless steel and comprises a weight component of nickel of 15% and less and preferably 8% and more.
7. Method for coating according to one of claims 1 - 6, wherein the depositing of the slide coating comprises the steps:

   depositing a liquid slide coating material,

   drying the liquid slide coating material, preferably at a temperature of 120°C - 150°C,

   hardening the slide coating material, preferably at a temperature of 200°C - 450°C, in particular preferably at a temperature of 340°C - 390°C.
8. Method for coating according to one of claims 1 - 7, wherein the slide coating material comprises a weight component of fluoropolymer of 30% or less.
9. Method for coating according to one of claims 1 - 8, wherein the slide coating material includes as polyaryletherketone polyetheretherketone and as fluoropolymer polytetrafluoroethylene or a perfluoroalkoxylalkane.
10. Coated element, wherein the coated element is a product carrying machine part of a weighing device, particularly of a combination scale (2), of a feeding device, of a collecting device or of a transition system, comprising:

    a substrate (40) with a substrate surface,

    an adherent coating (41) made of an adherent coating material, wherein

    the adherent coating material is deposited on the substrate surface by thermal spraying and

    having a first interface layer (42) formed between the substrate (40) and the adherent coating (41) and

    a slide coating (45) made of at least one layer of a slide coating material, wherein

    the slide coating material includes at least one type of polyaryletherketones and at least one type of fluoropolymers, and

    the slide coating material being deposited on the adherent coating, and

    a second interface layer (44) being formed with a roughness between the adherent coating (41) and the slide coating (45).
11. Coated element according to claim 10, wherein the adherent coating material is a stainless steel and comprises a weight component of chrome of 35% or less and (preferably) 15% and more.
12. Coated element according to one of claims 10 - 11, wherein the adherent coating material is a stainless steel and comprises a weight component of nickel of 15% and less and (preferably) 8% and more.
13. Coated element according to one of claims 10 - 12, wherein the slide coating material comprises a weight component of fluoropolymer of 30% or less.
14. Coated element according to one of claims 10 - 13, wherein the slide coating material includes as a polyaryletherketone polyetheretherketone and as fluoropolymer polytetrafluoroethylene or a perfluoroalkoxylalkane.
15. Coated element according to one of claims 10 - 14, wherein the slide coating (45) comprises a thickness of 50 - 200 µm.
16. Coated element according to one of claims 10 - 15, wherein the second interface layer (44) comprises a mean roughness R_a of 25 - 50 µm, preferably 30 µm.

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