EP0524710A2 - Metallic cutlery - Google Patents

Abstract

The invention relates to integral metallic cutlery manufactured by powder metallurgy. The cutlery concerned is primarily that for table use and can be produced in the conventional shape or in a hitherto unusual configuration and the composition of the alloy used for it can be adjusted to match its function since the cutlery is manufactured from sintered metal. The cutlery is manufactured by methods known from powder metallurgy. <IMAGE>

Description

The invention relates to one-piece cutlery parts made of metal, in particular tableware, such as knives, forks, spoons.

The high-quality cutlery parts made of steel or nickel silver, in particular made of rust-free chrome-nickel steel or nickel silver, which have become known and are on the market, have to be produced by complex manufacturing processes. The manufacturing processes for the production of cutlery made of nickel silver, which are silvered, and for cutlery made of chrome-nickel steel are roughly the same.

Fork and spoon cutlery are cut in one piece from sheet steel. These pre-cuts, called brandeln, have to be deburred and rolled. The brandeln for the production of spoon cutlery parts must be rolled down to a smaller material thickness in the area of the bowl to be formed later. Afterwards fork and spoon brandies have to be cut to size according to the model. Washing and glowing operations follow before the cutlery parts get their shape and decor through the embossing process.

The embossing process creates an inevitable burr on the "high edge" of the cutlery. This burr has to be sanded, only then can the grinding and polishing operations for leveling the surface and for producing the gloss on the surface take place. A The washing process then completes the steps for the manufacture of cutlery items made of chrome-nickel steel. With silver-plated cutlery, silvering follows.

This list alone shows how complex it is to manufacture. The problems with the individual work steps largely prevent mechanization when producing cutlery, which is why high-quality cutlery is relatively expensive to manufacture. The many work steps also result in a long lead time in production.
In order to be able to decorate cutlery parts in the same way as the associated spoons and forks, they must be made in several parts. The knife booklet is welded together from two half-shells that were previously formed from a sheet metal strip. The blade is fastened in the hollow knife handle part, preferably by welding or cementing. With this type of knife, the handle is made from a surface-finishable chrome-nickel steel. The blade is made of hardened, elastic, stainless steel.

In order to avoid this complex manufacturing process, the manufacture of monoblock knives is known. In this manufacturing process, a one-piece knife is produced from a hardenable chrome-nickel steel by rolling and / or forging.

The different requirements, for example regarding mechanical strength and scratch resistance for the magazine and on the other hand the cutting ability and elasticity for the Blade blade, but can not be optimally fulfilled when using a single sheet quality.

The forging process cannot achieve the same or similar decors as an embossing process. The forging process is also very complex, especially because the surface has to be polished afterwards. Fine decors cannot be achieved here. These introduced during forging would be ground down again during the grinding operation. Monoblock knives can therefore only be provided with very simple decors. The matching spoons and forks, derived from them, can only be given simple decors.

In the manufacture of knives, forks and spoons, the manufacturing process is therefore very limited in the selection of shapes and decors.

The usual cutlery for picking up and transporting food from the plate to the mouth has hardly changed in the last hundreds of years. This is due to the fact that the manufacturing processes did not allow other shapes to be produced inexpensively.

However, there is actually a need to design cutlery items in such a way that the dishes can be more easily taken from the plate and can be more safely fed to the mouth. There is also a need to adapt the bowl to the mouth better than before and to shape the handles of the cutlery so that they fit better in the hand.
In addition, there is a desire to be able to produce cutlery with rich decors and distinctive designs in industrial production.

The object of the invention is to provide cutlery parts made of stainless steel, which are manufactured by powder metallurgy, allow a simple and economical production method and, in addition to the usual simple designs, require little or no restrictions with regard to their shape and type of design options.

The invention relates to new cutlery items of the type characterized in the characterizing part of claim 1 and having advantageous and / or expedient refinements specified in subclaims 2 to 17.

The cutlery parts according to the invention are comparatively less technically complex to manufacture, extremely variable in shape and allow - with unchanged good, partly improved usage properties - any new cutlery designs which are advantageous and expedient for increasingly internationalized eating habits. Cutlery parts according to the invention give every possibility for fashionable innovations and progressive designs.

Known powder metallurgy processes are used for the manufacture of cutlery parts according to the invention for other purposes. As is known, there are a number of methods for obtaining the sintered metal material from metal powders by pressing and sintering and for producing workpieces using powder metallurgy. The cutlery parts according to the invention can be produced and shaped using these methods.

Known working methods are, for example, hot forging metal powders or metal powder mixtures filled in sheet metal capsules, isostatic compression, explosion compacting of metal powders or metal powder mixtures and Mold casting or extrusion or injection molding of metal powder mixtures pasted or kneaded with temporary binders and subsequent removal of the binder from the "green body" and sintering of the green body.

For example, the metal powders can be introduced into sheet metal capsules designed in accordance with the cutlery parts to be produced, these can be evacuated, the powder mixture mechanically compacted and then sintered in the closed capsules. Special tools are used to compact metal powders, in particular in the form of slender structures such as cutlery items; e.g. can be ensured by spring force, hydraulic and / or pneumatic cylinder, a safe positioning of the die, and it can be controlled the die speed during the upsetting process in relation to the movable punch so that the slim moves the die at a predetermined speed when the upper punch goes down . The metal powder mixture in the sheet metal capsules can also be subjected to a forging and sintering process in special forging machines or compacted by rolling and then removed from the mold. The sheet metal capsule material can be reused.

It can be cold isostatically or hot isostatically (so-called HIP process) pressed.

The so-called MIM method (metal injection molding) is also advantageous for the production of cutlery parts according to the invention with a complicated shape, for example, for example, a special decorative design of the cutlery handles or the formation of particularly “exotic” cutlery shapes. The metal powder is plasticized Binder or binder mixture is mixed, e.g. kneaded or slurried, the kneading compound or slurry (slip) is degassed and brought into a shape corresponding to the cutlery to be manufactured, for example poured into a die or by extrusion or injection molding (so-called PM injection molding) Shaped appropriately trained injection mold, then the binder is removed from the green body, this is sintered and / or compacted and the finished cutlery is obtained.

The starting materials for cutlery items according to the invention are commercially available. Metal powders of different types of metal are available on the market in different particle sizes and grain shapes, in particular in spherical and speckled grain shapes with relatively small particle sizes. In particular, such metal powders with the small particle sizes up to about 60 μm are well usable for cutlery items according to the invention. Metal powders with particle sizes up to 20 µm are especially recommended for the manufacture of cutlery items according to the invention by the injection molding process. The special composition of the starting metal powder for the production of cutlery parts according to the invention depends on the properties specifically desired for the finished cutlery parts. Unlike with conventional sheet metal material, it is possible with metal powder mixtures as the starting material to achieve alloys that cannot be produced in the normal melting process and thus to achieve material properties of the cutlery parts according to the invention that are adapted to the intended uses.

The cutlery part properties for cutlery parts according to the invention can be influenced in a comparatively wide range by the composition of the metal powder mixtures used for the production. The metal composition is no longer restricted to alloy phases. Largely variable chemical compositions can be formed by powder metallurgy, and the shape, size and mixing ratio of differently shaped powder particles can influence the properties in the finished cutlery during its manufacture.
One-piece cutlery parts according to the invention can have two or more different alloy compositions over their longitudinal extent. One-piece knife-cutlery parts according to the invention are particularly advantageous, the blade parts of which have a higher hardness than their shaft part.

Depending on the composition of the metal powder starting mixtures and the specific manufacturing conditions chosen, cutlery items according to the invention can also have a partially desired porosity and have a decorative coating, at least partially, for example on the handle portion. Cutlery parts according to the invention can have plastic functional and / or decorative elements that cannot be produced by sheet metal technology using industrial manufacturing methods at any point on the cutlery surface. And they can be surface-treated in a manner known per se, for example provided with a detector by painting or enamelling. The surfaces of cutlery items according to the invention can advantageously be partially decorated in accordance with the process described in DE-PS 12 98 384 by the applicant.
You can silver in a manner known per se. Cutlery parts according to the invention require a small amount of material in their production because, in contrast to sheet metal production, there is practically no waste in the course of processing.

example 1

An atomized pre-alloyed metal powder made of stainless Cr-Ni steel with the following composition (in% by weight) and particle size distribution was used: C. 0.05 Mesh size <0.150 -> 0.075 Cr 17.32 " <0.075 -> 0.045 Ni 9.2 " <0.045 Fe rest " <0.045

The powder mixture was filled into a spoon-shaped press mold and pressed on both sides by means of a press pressure of approx. 6500 bar. Spoon green body was obtained, which was sintered in a hydrogen atmosphere at a sintering temperature of 1300 ^° C. for three hours. The density after sintering was 92% of the theoretical density. It was then densified with the original molding pressure and again sintered for two hours at 1300 ^o C in a hydrogen atmosphere. This gave a sintered metal spoon with a density of 96% of the theoretical density. The sintered metal spoon obtained in this way was degreased with acetone to remove surface contamination, dried at 80 ^° C., washed with ammonia water and dried in vacuo at 150 ^° C. It was then mechanically finished.

The spoon thus obtained had excellent usage properties, was scratch-resistant and corrosion-resistant.

Example 2

A metal powder mixture of the following composition and particle size distribution was used to produce a spoon: 18 parts of ferrochrome Grain size 10 - 30 µm 6% Cr, 0.2% C, 0.05% Si, balance Fe 9 parts of carbonyl nickel Grain size 0.5 - 10 µm 73 parts of carbonyl iron Grain size 0.5 - 10 µm.

2.5% by volume of polyethylene oxide as dispersion aid and 50% by volume of xylene as suspending agent were incorporated into the powder in a ball mill. A well-pasted, viscous powder metal mass was obtained. Polyethylene in granular form was used as the binder. A tandem extruder system was used, as is known for the production of foam sheets and is described, for example, in the trade magazine "Plastverarbeiter" 32, 1981, No. 8, page 948. The homogenizing extruder of the tandem system was designed with two feed openings arranged at a distance of 20 D (screw diameter). Binder granules were continuously fed into the first feed opening and melted in the screw. Powder metal suspension was fed continuously into the second feed opening and mixed into the binder melt. The melting and homogenization process is controlled by the speed of the screw. The mixing length, ie the screw length of the homogenizing extruder, calculated from the powder metal mass feed opening, was 12 D. The homogenized powder-binder melt then went into the cooling extruder, which had a degassing device by means of which the solvent present in the melt was removed. In the snail's head was the solvent freed molding compound compressed and extruded through the nozzle into a spoon shape. The binder was then heated from the demolded spoon body (green body), which consisted of 63% by volume powder metal and 37% by volume binder and was practically non-porous. For this, the green compact was placed in a continuous furnace with a heating rate of 15 ^o C / min. heated to a temperature of 350 ^o C and held at this temperature for 5 hours. The resulting degradation products (essentially water, CO₂ and small amounts of cracked products) were continuously removed from the furnace chamber by diffusion.
The binder-free spoon body was then sintered in a sintering furnace for 10 hours under a pressure of 0.01 mb at 1260 ^° C. and then slowly cooled to room temperature.
The spoon obtained in this way could be finished with conventional mechanical post-processing and had an excellent appearance and very good usage properties.

Fig. 1

eine Draufsicht auf eine Ausführungsform eines Löffel-Besteckteils,

Fig. 2

eine Seitenansicht des Löffel-Besteckteils der Fig. 1,

Fig. 3

einen Schnitt nach I-I der Fig. 1,

Fig. 4

einen Schnitt nach II-II der Fig. 1,

Fig. 5

eine Draufsicht auf eine andere Ausführungsform eines Löffel-Besteckteils,

Fig. 6

eine Draufsicht auf eine weitere Ausführungsform eines Löffel-Besteckteils,

Fig. 7

im Querschnitt eine Laffe-Gestaltung eines Löffel-Besteckteils,

Fig. 8

im Längsschnitt eine andere Laffe-Gestaltung eines Löffel-Besteckteils,

Fig. 9

im Querschnitt eine weitere Laffe-Gestaltung eines Löffel-Besteckteils, und

Fig. 10

im Längsschnitt eine Laffe-Stiel-Gestaltung an einem Löffel-Besteckteil.

Cutlery parts according to the invention are illustrated, for example, in the accompanying drawing. Show it:

Fig. 1

a plan view of an embodiment of a spoon cutlery part,

Fig. 2

2 shows a side view of the spoon cutlery part of FIG. 1,

Fig. 3

2 shows a section according to II of FIG. 1,

Fig. 4

2 shows a section according to II-II of FIG. 1,

Fig. 5

a plan view of another embodiment of a spoon cutlery part,

Fig. 6

a plan view of a further embodiment of a spoon cutlery part,

Fig. 7

in cross-section a spoon cutlery part,

Fig. 8

in longitudinal section another bowl design of a spoon cutlery part,

Fig. 9

in cross-section another bowl design of a spoon cutlery part, and

Fig. 10

Longitudinal section of a spoon-shaped handle on a piece of cutlery.

1 to 4 illustrate an inventive spoon 1 made of sintered metal and consisting of a cup 2 and a stem 3 made of stainless steel. The spoon is made using powder metallurgy. The bowl 2 is - as can be seen from FIGS. 1 and 2 - asymmetrical to the longitudinal and transverse axes. The contour edge 4 of the bowl 2 forms a curve which has cracks. This curve consists of a total of three individual curves that do not continuously adjoin each other. The bowl 2 has depressions 5 on its front side. As can be seen from FIG. 3, the dimensions of one recess 5a are larger than the other recess 5b. In addition, as can be clearly seen in FIG. 3, the thickness distribution of the bowl is discontinuous. In the recess 5b, the bowl near the contour edge 4 is thicker than in the recess part running towards the center of the bowl, and in the recess 5a, the material thickness at the contour edge 4 is weaker than in the center of the bowl. The bowl 2, as shown in FIG. 1, also has an engraving 6 on its front, which serves for decorative design, but at the same time also contributes to the identification of the different recesses 5 of the bowl 2.
The different thickness of the spoon improves the usability of the spoon. Due to the different, delimited recesses 5a and 5b, it is possible to separate dishes on this spoon, so that dishes in the spoon can be stripped separately from the lips, for example liquids and solids.

In the area of the transition from cup 2 to stem 3, a three-leaf opening 7 is provided in the spoon 1. This breakthrough is for decorative purposes. However, it can also be used to allow liquid to drain from the spoon 2 in the particular handling position of the spoon. This opening 7 is harmoniously followed on the one hand by the engraving 8 and on the other hand by the curved lines of the stem neck 9. The stem 3 offers an all-round view. It is designed on all sides with merging structured elements. From the stem neck 9, the stem 3 extends in a tapered profile 10 to the handle part 11. The profile 10, as illustrated in FIG. 4, has a shape in its cut surface which is irregularly formed by various curves and undercuts. Both the cross-section and the shape of the profile 10 change over the length of the profile. Approximately in the middle of the handle 3, it thickens in several jumps to the handle part 11. The handle part 11 increases discontinuously in its cross-section up to the handle end 13. The profile 12 of the handle part 11 results up to the stem end 13, beveled by a cut running at an angle to the longitudinal axis of the stem. As illustrated in FIG. 2, oval openings 14 are provided in the grip part 11.

The spoon 15 shown in FIG. 5 consists in one piece of a bowl 16 and a handle 17 and, according to the material, of sintered metal made of stainless steel. It was manufactured using powder metallurgy. The bowl 16 is formed on one side with a straight edge 18. With such a spoon according to the invention, dishes, especially liquids, can advantageously be taken from a plate. The material distribution in the cross section of the bowl 16 is discontinuous. The thickness of the bowl is thinner on the straight edge 18 than on the opposite side. With this type of material distribution, the spoon is also suitable for being able to share food more easily.

FIG. 6 shows a spoon cutlery part 19 made of stainless sintered steel in one piece and made of a bowl 20 and a handle 21 in a conical bowl shape with roundings on the bowl tip 22. In this cup 20 there are approximately straight side edges 23a and 23b on both sides, which bring about the same use effect as previously described in connection with the design according to FIG. 5.

Further novel creative bowl shapes which could not be produced industrially with conventional spoon cutlery parts are shown in FIGS. 7 to 10.

The bowls 24, 26 and 29 shown in FIGS. 7, 8 and 9 have an advantageously thin bowl material, as a result of which very light cutlery items are created. The required stability in use is ensured according to the embodiments of FIGS. 7 and 8 by edge reinforcements 25 and 27, so that the cutlery parts according to the invention thus formed are stable in use despite the thin material thickness of the bowl due to the thickened and rounded rim of the bowl. In the embodiment of FIG. 8, the bowl 26 is designed to be pulled up laterally on one side. The rim of the cup 28 does not run in one plane, which also has an advantageous effect on the properties of use. The light-weight cup 29 made of very thin material shown in FIG. 9 has an unreinforced, but angled cup edge 30 which ensures the required stability in use and is not unpleasant to handle and use.

FIG. 10 shows a spoon shape of a cutlery part according to the invention made of sintered metal, which is made in one piece from the bowl 31 and the handle 33, the handle 33 already starting at the side edge 32 of the bowl and / or the bowl 34 increasing in thickness and continuously in its part 34 facing the handle turns into a thickened stem neck. Through this Measure increases the bending strength of the cutlery at the critical point of the stem neck, a particularly stable embodiment.

The design features illustrated in the drawing for spoon cutlery parts can of course be realized in a comparable manner to fork and knife cutlery parts according to the invention.

It is also possible and advantageous in terms of material and manufacture to provide cutlery parts, such as a spoon, fork or knife, in a conventional design, but consisting in one piece of sintered metal according to the invention.

Cutlery items according to the invention, which are manufactured by powder metallurgy, can be finished by a polishing operation in such a way that they have the same surface quality as a previously customary cutlery item, which was manufactured and polished from sheet metal material.

Claims (17)

One-piece cutlery, in particular flatware, made of metal, characterized in that it is made by powder metallurgy and consists in one piece of sintered metal. Cutlery part according to claim 1, characterized in that it consists of at least two different alloy compositions over its longitudinal extent. Cutlery part according to claim 2, characterized in that one of the alloy compositions has a higher hardness in comparison. Cutlery part according to any one of claims 2 or 3, characterized in that one of the alloy compositions is hardenable. Cutlery part according to any one of claims 1 to 4, characterized in that it has been produced by means of die pressing of the metal powder and sintering. Cutlery part according to any one of claims 1 to 4, characterized in that it has been produced by cold or hot isostatic pressing of the metal powder and sintering. Cutlery part according to any one of claims 1 to 4, characterized in that it has been produced by introducing the metal powder into molded capsules, presses and / or rollers and sintering. Cutlery part according to any one of claims 1 to 4, characterized in that it has been produced by means of powder metal injection molding. Cutlery part according to claim 8, characterized in that at any point on the cutlery part surface there are plastic functional and / or decorative elements that cannot be produced by sheet metal technology using industrial production methods. Cutlery part according to any one of claims 1 to 9, characterized in that it is at least partially surface-treated and / or decorated in a manner known per se. Cutlery part according to claim 10, characterized in that it is at least partially enamelled. Spoon cutlery part according to any one of claims 1 to 11, characterized in that the bowl (16) has a straight edge (18) on one side. Spoon cutlery part according to any one of claims 1 to 11, characterized in that it has a conical tapered shape (20) with rounded portions on the tip of the trough (22) and side edges (23a and 23b) which are partially straight on both sides. Spoon cutlery part according to any one of claims 1 to 13, characterized in that the bowl edge has a reinforcement. Spoon cutlery part according to any one of claims 1 to 14, characterized in that the rim of the bowl, at least on one side of the bowl, has a curved, curved shape. Spoon and fork cutlery part according to any one of claims 1 to 15, characterized in that the thickness of the bowl continuously changes into a thickened stem neck. Spoon and fork cutlery part according to any one of claims 1 to 16, characterized in that the thickness of the bowl, viewed in cross section, is asymmetrical, decreasing from one side to the other.

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